Td corrigé Title: WiMAX ? Broadband Wireless Access Technology - Read pdf

Title: WiMAX ? Broadband Wireless Access Technology - Read

Higher-order modulation (e.g., 64 ?Quartered Amplitude Modulation? or QAM provides high ...... by the underlying technology, in formal exercises to define acceptable and/or ...... wireless technology, much like the Chinese are doing with TD-SCDMA. ...... Gaussian filtered Minimum Shift Keying; a refinement of FSK which ...




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GEREF _Toc120990652 \h 27
 HYPERLINK \l "_Toc120990653" What is Broadband?  PAGEREF _Toc120990653 \h 30
 HYPERLINK \l "_Toc120990658" Broadband Technologies  PAGEREF _Toc120990658 \h 34
 HYPERLINK \l "_Toc120990667" Broadband Demand  PAGEREF _Toc120990667 \h 45
 HYPERLINK \l "_Toc120990670" Economics of Broadband  PAGEREF _Toc120990670 \h 50
 HYPERLINK \l "_Toc120990672" Broadband Connectivity Solutions  PAGEREF _Toc120990672 \h 53
 HYPERLINK \l "_Toc120990677" Designing Broadband Solution  PAGEREF _Toc120990677 \h 59
 HYPERLINK \l "_Toc120990692" Mobile & Wireless Access  PAGEREF _Toc120990692 \h 68
 HYPERLINK \l "_Toc120990693" Appeal of Wireless  PAGEREF _Toc120990693 \h 70
 HYPERLINK \l "_Toc120990698" WLAN  PAGEREF _Toc120990698 \h 72
 HYPERLINK \l "_Toc120990702" Wireless Broadband - The Communications Revolution  PAGEREF _Toc120990702 \h 79
 HYPERLINK \l "_Toc120990703" Attraction of Wireless Broadband  PAGEREF _Toc120990703 \h 80
 HYPERLINK \l "_Toc120990704" Need for Wireless Broadband  PAGEREF _Toc120990704 \h 81
 HYPERLINK \l "_Toc120990705" Broadband Wireless Access  PAGEREF _Toc120990705 \h 82
 HYPERLINK \l "_Toc120990707" Broadband Wireless Networks  PAGEREF _Toc120990707 \h 85
 HYPERLINK \l "_Toc120990712" Broadband Wireless Technologies  PAGEREF _Toc120990712 \h 89
 HYPERLINK \l "_Toc120990718" WiMAX - Broadband for Masses  PAGEREF _Toc120990718 \h 96
 HYPERLINK \l "_Toc120990720" Chapter 2  PAGEREF _Toc120990720 \h 99
 HYPERLINK \l "_Toc120990721" WiMAX – The Disruptive Technology  PAGEREF _Toc120990721 \h 99
 HYPERLINK \l "_Toc120990722" Impact of Disruption  PAGEREF _Toc120990722 \h 102
 HYPERLINK \l "_Toc120990723" Technology Life Cycle  PAGEREF _Toc120990723 \h 105
 HYPERLINK \l "_Toc120990724" Disruption  PAGEREF _Toc120990724 \h 106
 HYPERLINK \l "_Toc120990725" Dominant Design  PAGEREF _Toc120990725 \h 107
 HYPERLINK \l "_Toc120990726" Disruption and New Market  PAGEREF _Toc120990726 \h 108
 HYPERLINK \l "_Toc120990727" Innovation for Disruption  PAGEREF _Toc120990727 \h 109
 HYPERLINK \l "_Toc120990728" Technology Strategy  PAGEREF _Toc120990728 \h 112
 HYPERLINK \l "_Toc120990729" Emerging & Established Technologies  PAGEREF _Toc120990729 \h 113
 HYPERLINK \l "_Toc120990730" Technology Uncertainty  PAGEREF _Toc120990730 \h 114
 HYPERLINK \l "_Toc120990731" Diffusion of Innovation  PAGEREF _Toc120990731 \h 115
 HYPERLINK \l "_Toc120990732" Technology Adoption  PAGEREF _Toc120990732 \h 116
 HYPERLINK \l "_Toc120990733" Broadband Wireless - Technology Advancements  PAGEREF _Toc120990733 \h 120
 HYPERLINK \l "_Toc120990734" WiMAX – The Biggest Disruption  PAGEREF _Toc120990734 \h 125
 HYPERLINK \l "_Toc120990735" It’s Different  PAGEREF _Toc120990735 \h 127
 HYPERLINK \l "_Toc120990736" WiMAX - Disruptive Capabilities  PAGEREF _Toc120990736 \h 130
 HYPERLINK \l "_Toc120990737" What is WiMAX?  PAGEREF _Toc120990737 \h 131
 HYPERLINK \l "_Toc120990738" Why WiMAX  PAGEREF _Toc120990738 \h 133
 HYPERLINK \l "_Toc120990744" WiMAX Hype or Reality  PAGEREF _Toc120990744 \h 135
 HYPERLINK \l "_Toc120990745" Chapter 3  PAGEREF _Toc120990745 \h 137
 HYPERLINK \l "_Toc120990746" How WiMAX Works  PAGEREF _Toc120990746 \h 137
 HYPERLINK \l "_Toc120990747" Robust Technology  PAGEREF _Toc120990747 \h 140
 HYPERLINK \l "_Toc120990748" Channel Characteristics  PAGEREF _Toc120990748 \h 141
 HYPERLINK \l "_Toc120990755" RF and Hardware Considerations  PAGEREF _Toc120990755 \h 144
 HYPERLINK \l "_Toc120990760" Flexible Tradeoffs  PAGEREF _Toc120990760 \h 146
 HYPERLINK \l "_Toc120990761" WiMAX Networks  PAGEREF _Toc120990761 \h 147
 HYPERLINK \l "_Toc120990762" WiMAX Types  PAGEREF _Toc120990762 \h 150
 HYPERLINK \l "_Toc120990765" Building Blocks of WiMAX  PAGEREF _Toc120990765 \h 153
 HYPERLINK \l "_Toc120990766" WiMAX Base Station  PAGEREF _Toc120990766 \h 156
 HYPERLINK \l "_Toc120990771" WiMAX Receiver  PAGEREF _Toc120990771 \h 167
 HYPERLINK \l "_Toc120990772" Backhaul  PAGEREF _Toc120990772 \h 168
 HYPERLINK \l "_Toc120990773" Working Mechanism  PAGEREF _Toc120990773 \h 169
 HYPERLINK \l "_Toc120990774" Operational  PAGEREF _Toc120990774 \h 173
 HYPERLINK \l "_Toc120990775" Architecture  PAGEREF _Toc120990775 \h 173
 HYPERLINK \l "_Toc120990776" Network Topology  PAGEREF _Toc120990776 \h 175
 HYPERLINK \l "_Toc120990777" Point to Point  PAGEREF _Toc120990777 \h 175
 HYPERLINK \l "_Toc120990778" Point to Multi Point  PAGEREF _Toc120990778 \h 176
 HYPERLINK \l "_Toc120990779" Mesh  PAGEREF _Toc120990779 \h 178
 HYPERLINK \l "_Toc120990786" Section 2  PAGEREF _Toc120990786 \h 187
 HYPERLINK \l "_Toc120990787" WiMAX - Cutting Edge  PAGEREF _Toc120990787 \h 187
 HYPERLINK \l "_Toc120990788" Chapter 4  PAGEREF _Toc120990788 \h 188
 HYPERLINK \l "_Toc120990789" WiMAX – Specification  PAGEREF _Toc120990789 \h 188
 HYPERLINK \l "_Toc120990790" Basic Profiles  PAGEREF _Toc120990790 \h 192
 HYPERLINK \l "_Toc120990796" Medium Access Control (MAC) Layer  PAGEREF _Toc120990796 \h 203
 HYPERLINK \l "_Toc120990815" Physical (PHY) Layer  PAGEREF _Toc120990815 \h 225
 HYPERLINK \l "_Toc120990816" Mobile WiMAX  PAGEREF _Toc120990816 \h 228
 HYPERLINK \l "_Toc120990819" RF System  PAGEREF _Toc120990819 \h 234
 HYPERLINK \l "_Toc120990823" Chapter 5  PAGEREF _Toc120990823 \h 237
 HYPERLINK \l "_Toc120990824" WiMAX – State of the Art Technologies  PAGEREF _Toc120990824 \h 237
 HYPERLINK \l "_Toc120990825" Learning from The Past  PAGEREF _Toc120990825 \h 237
 HYPERLINK \l "_Toc120990826" Technology of WiMAX  PAGEREF _Toc120990826 \h 243
 HYPERLINK \l "_Toc120990827" Dynamic Burst Mode TDMA MAC  PAGEREF _Toc120990827 \h 243
 HYPERLINK \l "_Toc120990828" Quality of Service  PAGEREF _Toc120990828 \h 243
 HYPERLINK \l "_Toc120990829" Link Adaptation  PAGEREF _Toc120990829 \h 244
 HYPERLINK \l "_Toc120990830" Non Line Of Sight (NLoS) Support  PAGEREF _Toc120990830 \h 245
 HYPERLINK \l "_Toc120990831" Highly Efficient Spectrum Utilization  PAGEREF _Toc120990831 \h 247
 HYPERLINK \l "_Toc120990832" Flexible Channel Bandwidth  PAGEREF _Toc120990832 \h 250
 HYPERLINK \l "_Toc120990833" Smart Antenna Support  PAGEREF _Toc120990833 \h 251
 HYPERLINK \l "_Toc120990836" Error Correction Techniques  PAGEREF _Toc120990836 \h 256
 HYPERLINK \l "_Toc120990837" Power Control  PAGEREF _Toc120990837 \h 257
 HYPERLINK \l "_Toc120990838" Data Security  PAGEREF _Toc120990838 \h 258
 HYPERLINK \l "_Toc120990839" WiMAX Radio  PAGEREF _Toc120990839 \h 260
 HYPERLINK \l "_Toc120990840" Multiplexing Technology  PAGEREF _Toc120990840 \h 260
 HYPERLINK \l "_Toc120990844" Modulating Technology  PAGEREF _Toc120990844 \h 265
 HYPERLINK \l "_Toc120990846" Duplexing Technology  PAGEREF _Toc120990846 \h 270
 HYPERLINK \l "_Toc120990847" WiMAX Silicon  PAGEREF _Toc120990847 \h 273
 HYPERLINK \l "_Toc120990848" Radio on Silicon  PAGEREF _Toc120990848 \h 273
 HYPERLINK \l "_Toc120990849" System on Chip (SoC)  PAGEREF _Toc120990849 \h 276
 HYPERLINK \l "_Toc120990850" Chapter 6  PAGEREF _Toc120990850 \h 278
 HYPERLINK \l "_Toc120990851" WiMAX Proposition  PAGEREF _Toc120990851 \h 278
 HYPERLINK \l "_Toc120990852" Features of Substance  PAGEREF _Toc120990852 \h 279
 HYPERLINK \l "_Toc120990863" Value Creation  PAGEREF _Toc120990863 \h 285
 HYPERLINK \l "_Toc120990868" Drivers  PAGEREF _Toc120990868 \h 291
 HYPERLINK \l "_Toc120990869" Throughput & Coverage  PAGEREF _Toc120990869 \h 291
 HYPERLINK \l "_Toc120990870" Flexibility & Scalability  PAGEREF _Toc120990870 \h 292
 HYPERLINK \l "_Toc120990871" Cost Effectiveness  PAGEREF _Toc120990871 \h 294
 HYPERLINK \l "_Toc120990872" Emergence of Standards  PAGEREF _Toc120990872 \h 294
 HYPERLINK \l "_Toc120990873" Backing of Intel  PAGEREF _Toc120990873 \h 296
 HYPERLINK \l "_Toc120990874" Challenges  PAGEREF _Toc120990874 \h 298
 HYPERLINK \l "_Toc120990875" RF Interference  PAGEREF _Toc120990875 \h 298
 HYPERLINK \l "_Toc120990877" Infrastructure Placement  PAGEREF _Toc120990877 \h 299
 HYPERLINK \l "_Toc120990879" Roll out Cost  PAGEREF _Toc120990879 \h 302
 HYPERLINK \l "_Toc120990880" Incomplete Standards  PAGEREF _Toc120990880 \h 302
 HYPERLINK \l "_Toc120990881" Chipset Availability  PAGEREF _Toc120990881 \h 304
 HYPERLINK \l "_Toc120990882" Interoperability Testing and Market Feel  PAGEREF _Toc120990882 \h 304
 HYPERLINK \l "_Toc120990883" Uncertain Economics  PAGEREF _Toc120990883 \h 305
 HYPERLINK \l "_Toc120990884" Spectrum  PAGEREF _Toc120990884 \h 307
 HYPERLINK \l "_Toc120990885" Competition  PAGEREF _Toc120990885 \h 311
 HYPERLINK \l "_Toc120990886" Wireline  PAGEREF _Toc120990886 \h 315
 HYPERLINK \l "_Toc120990888" Wireless  PAGEREF _Toc120990888 \h 317
 HYPERLINK \l "_Toc120990898" Section 3  PAGEREF _Toc120990898 \h 332
 HYPERLINK \l "_Toc120990899" WiMAX – Roll Out  PAGEREF _Toc120990899 \h 332
 HYPERLINK \l "_Toc120990900" Chapter 7  PAGEREF _Toc120990900 \h 334
 HYPERLINK \l "_Toc120990901" WiMAX Standard  PAGEREF _Toc120990901 \h 334
 HYPERLINK \l "_Toc120990902" Why Standards  PAGEREF _Toc120990902 \h 334
 HYPERLINK \l "_Toc120990903" IEEE 802.16 Standards Family  PAGEREF _Toc120990903 \h 338
 HYPERLINK \l "_Toc120990905" IEEE 802.16  PAGEREF _Toc120990905 \h 345
 HYPERLINK \l "_Toc120990907" Mobile Broadband Wireless Access (MBWA)  PAGEREF _Toc120990907 \h 361
 HYPERLINK \l "_Toc120990908" MBWA Technology Issues  PAGEREF _Toc120990908 \h 363
 HYPERLINK \l "_Toc120990909" Power Consumption Reduction  PAGEREF _Toc120990909 \h 364
 HYPERLINK \l "_Toc120990910" IEEE 802.20 - Alternate MBWA  PAGEREF _Toc120990910 \h 366
 HYPERLINK \l "_Toc120990911" Chapter 8  PAGEREF _Toc120990911 \h 369
 HYPERLINK \l "_Toc120990912" WiMAX Certification  PAGEREF _Toc120990912 \h 369
 HYPERLINK \l "_Toc120990913" WiMAX TM & IEEE 802.16  PAGEREF _Toc120990913 \h 370
 HYPERLINK \l "_Toc120990914" WiMAX Forum  PAGEREF _Toc120990914 \h 371
 HYPERLINK \l "_Toc120990916" Global Harmonization  PAGEREF _Toc120990916 \h 374
 HYPERLINK \l "_Toc120990917" Why Certification  PAGEREF _Toc120990917 \h 377
 HYPERLINK \l "_Toc120990921" Conformance vs. Interoperability  PAGEREF _Toc120990921 \h 386
 HYPERLINK \l "_Toc120990922" Certification Process  PAGEREF _Toc120990922 \h 387
 HYPERLINK \l "_Toc120990923" Conformance Testing  PAGEREF _Toc120990923 \h 387
 HYPERLINK \l "_Toc120990924" Interoperability Testing  PAGEREF _Toc120990924 \h 389
 HYPERLINK \l "_Toc120990925" Abstract Test Suite Process  PAGEREF _Toc120990925 \h 392
 HYPERLINK \l "_Toc120990926" Chapter 9  PAGEREF _Toc120990926 \h 394
 HYPERLINK \l "_Toc120990927" WiMAX Regulation  PAGEREF _Toc120990927 \h 394
 HYPERLINK \l "_Toc120990928" Regulating Broadband  PAGEREF _Toc120990928 \h 394
 HYPERLINK \l "_Toc120990929" Broadband for Unserved  PAGEREF _Toc120990929 \h 396
 HYPERLINK \l "_Toc120990930" Wireless Regulation  PAGEREF _Toc120990930 \h 398
 HYPERLINK \l "_Toc120990931" Regulatory Framework and Convergence  PAGEREF _Toc120990931 \h 401
 HYPERLINK \l "_Toc120990933" Deregulation  PAGEREF _Toc120990933 \h 404
 HYPERLINK \l "_Toc120990934" Spectrum  PAGEREF _Toc120990934 \h 410
 HYPERLINK \l "_Toc120990936" Licensed and Unlicensed Spectrum  PAGEREF _Toc120990936 \h 412
 HYPERLINK \l "_Toc120990942" Spectrum for WiMAX Mobility  PAGEREF _Toc120990942 \h 420
 HYPERLINK \l "_Toc120990943" The Spectrum Picture  PAGEREF _Toc120990943 \h 423
 HYPERLINK \l "_Toc120990950" New Bands of Interest  PAGEREF _Toc120990950 \h 428
 HYPERLINK \l "_Toc120990951" Section 4  PAGEREF _Toc120990951 \h 430
 HYPERLINK \l "_Toc120990952" WiMAX - Planning  PAGEREF _Toc120990952 \h 430
 HYPERLINK \l "_Toc120990953" Chapter 10  PAGEREF _Toc120990953 \h 431
 HYPERLINK \l "_Toc120990954" WiMAX Business  PAGEREF _Toc120990954 \h 431
 HYPERLINK \l "_Toc120990955" WiMAX Markets  PAGEREF _Toc120990955 \h 433
 HYPERLINK \l "_Toc120990960" WiMAX and Demographics  PAGEREF _Toc120990960 \h 435
 HYPERLINK \l "_Toc120990964" WiMAX Applications  PAGEREF _Toc120990964 \h 438
 HYPERLINK \l "_Toc120990965" Metropolitan-Area Networks (MANs)  PAGEREF _Toc120990965 \h 441
 HYPERLINK \l "_Toc120990966" Last Mile High Speed Internet Access or Wireless DSL  PAGEREF _Toc120990966 \h 444
 HYPERLINK \l "_Toc120990972" Backhaul  PAGEREF _Toc120990972 \h 448
 HYPERLINK \l "_Toc120990975" Other Applications  PAGEREF _Toc120990975 \h 450
 HYPERLINK \l "_Toc120990986" WiMAX Business Models  PAGEREF _Toc120990986 \h 457
 HYPERLINK \l "_Toc120990987" Last Mile  PAGEREF _Toc120990987 \h 458
 HYPERLINK \l "_Toc120990990" WiMAX Opportunity  PAGEREF _Toc120990990 \h 465
 HYPERLINK \l "_Toc120990991" Strategy to Succeed  PAGEREF _Toc120990991 \h 468
 HYPERLINK \l "_Toc120990992" Decision Making for Success  PAGEREF _Toc120990992 \h 469
 HYPERLINK \l "_Toc120990993" Technology Forecasting  PAGEREF _Toc120990993 \h 470
 HYPERLINK \l "_Toc120990996" Service Providers  PAGEREF _Toc120990996 \h 472
 HYPERLINK \l "_Toc120990997" Public Sector  PAGEREF _Toc120990997 \h 474
 HYPERLINK \l "_Toc120990998" Regulators  PAGEREF _Toc120990998 \h 476
 HYPERLINK \l "_Toc120991001" Equipment Vendors  PAGEREF _Toc120991001 \h 480
 HYPERLINK \l "_Toc120991002" Investor  PAGEREF _Toc120991002 \h 483
 HYPERLINK \l "_Toc120991003" Chapter 11  PAGEREF _Toc120991003 \h 484
 HYPERLINK \l "_Toc120991004" WiMAX Deployment  PAGEREF _Toc120991004 \h 484
 HYPERLINK \l "_Toc120991008" WiMax Business Planning  PAGEREF _Toc120991008 \h 487
 HYPERLINK \l "_Toc120991010" Provision of Service  PAGEREF _Toc120991010 \h 490
 HYPERLINK \l "_Toc120991011" Deployment Best Practices  PAGEREF _Toc120991011 \h 491
 HYPERLINK \l "_Toc120991015" Deployment Stages  PAGEREF _Toc120991015 \h 495
 HYPERLINK \l "_Toc120991016" Deployment Type  PAGEREF _Toc120991016 \h 496
 HYPERLINK \l "_Toc120991023" Designing WiMAX Solution  PAGEREF _Toc120991023 \h 506
 HYPERLINK \l "_Toc120991024" System Components  PAGEREF _Toc120991024 \h 506
 HYPERLINK \l "_Toc120991025" WiMAX Network Planning  PAGEREF _Toc120991025 \h 507
 HYPERLINK \l "_Toc120991030" Need for Scalability  PAGEREF _Toc120991030 \h 513
 HYPERLINK \l "_Toc120991032" Hardware Platform  PAGEREF _Toc120991032 \h 520
 HYPERLINK \l "_Toc120991037" System on Chip (SoC)  PAGEREF _Toc120991037 \h 521
 HYPERLINK \l "_Toc120991039" Choosing the Best SoC  PAGEREF _Toc120991039 \h 523
 HYPERLINK \l "_Toc120991040" WiBro – The WiMAX Sibling  PAGEREF _Toc120991040 \h 526
 HYPERLINK \l "_Toc120991041" Chapter 12  PAGEREF _Toc120991041 \h 530
 HYPERLINK \l "_Toc120991042" Conclusion & The Way Forward  PAGEREF _Toc120991042 \h 530
 HYPERLINK \l "_Toc120991043" Expectations  PAGEREF _Toc120991043 \h 532
 HYPERLINK \l "_Toc120991044" Early Movers  PAGEREF _Toc120991044 \h 533
 HYPERLINK \l "_Toc120991045" Road Ahead  PAGEREF _Toc120991045 \h 535
 HYPERLINK \l "_Toc120991046" Next Generation Networks  PAGEREF _Toc120991046 \h 536
 HYPERLINK \l "_Toc120991047" What Future Holds  PAGEREF _Toc120991047 \h 538
 HYPERLINK \l "_Toc120991051" IP Multimedia Subsystem (IMS)  PAGEREF _Toc120991051 \h 548
 HYPERLINK \l "_Toc120991052" IMS Definition  PAGEREF _Toc120991052 \h 548
 HYPERLINK \l "_Toc120991054" IMS Applications  PAGEREF _Toc120991054 \h 552
 HYPERLINK \l "_Toc120991056" IP UTRAN  PAGEREF _Toc120991056 \h 555
 HYPERLINK \l "_Toc120991057" 4th Generation  PAGEREF _Toc120991057 \h 555
 HYPERLINK \l "_Toc120991058" Appendix  PAGEREF _Toc120991058 \h 559
 HYPERLINK \l "_Toc120991070" Appendix 1  PAGEREF _Toc120991070 \h 560
 HYPERLINK \l "_Toc120991059" Wireless Standards  PAGEREF _Toc120991059 \h 560
 HYPERLINK \l "_Toc120991070" Appendix 2  PAGEREF _Toc120991070 \h 567
 HYPERLINK \l "_Toc120991071" WLAN - Wi-Fi, IEEE 802.11  PAGEREF _Toc120991071 \h 567
 HYPERLINK \l "_Toc120991073" WiFi – Standards  PAGEREF _Toc120991073 \h 572
 HYPERLINK \l "_Toc120991081" Appendix 3  PAGEREF _Toc120991081 \h 579
 HYPERLINK \l "_Toc120991082" WPAN – Bluetooth, Ultra Wideband and ZigBee  PAGEREF _Toc120991082 \h 579
 HYPERLINK \l "_Toc120991094" Appendix 4  PAGEREF _Toc120991094 \h 590
 HYPERLINK \l "_Toc120991095" WWAN - Cellular Technology  PAGEREF _Toc120991095 \h 590
 HYPERLINK \l "_Toc120991103" Appendix 5  PAGEREF _Toc120991103 \h 599
 HYPERLINK \l "_Toc120991104" Proprietary BWA Systems  PAGEREF _Toc120991104 \h 599
 HYPERLINK \l "_Toc120991109" Appendix 6  PAGEREF _Toc120991109 \h 603
 HYPERLINK \l "_Toc120991110" Trends & Projections  PAGEREF _Toc120991110 \h 603
 HYPERLINK \l "_Toc120991114" BIBLIOGRAPHY  PAGEREF _Toc120991114 \h 610
 HYPERLINK \l "_Toc120991115" ABBREVIATIONS AND GLOSSARY  PAGEREF _Toc120991115 \h 616
 HYPERLINK \l "_Toc120991116" ABOUT AUTHOR  PAGEREF _Toc120991116 \h 660

Table of Figures
 TOC \h \z \c "Figure"  HYPERLINK \l "_Toc120991145" Figure 1 - Broadband Evolution  PAGEREF _Toc120991145 \h 28
 HYPERLINK \l "_Toc120991146" Figure 2 - Applications of High Speed Internet  PAGEREF _Toc120991146 \h 34
 HYPERLINK \l "_Toc120991147" Figure 3 - Access Technologies and Speeds  PAGEREF _Toc120991147 \h 38
 HYPERLINK \l "_Toc120991148" Figure 4 - Internet Access Technologies  PAGEREF _Toc120991148 \h 40
 HYPERLINK \l "_Toc120991149" Figure 5 - Broadband Subscribers Projection - USA  PAGEREF _Toc120991149 \h 46
 HYPERLINK \l "_Toc120991150" Figure 6 - Residential Broadband Penetration Trends & Forecast - Europe  PAGEREF _Toc120991150 \h 49
 HYPERLINK \l "_Toc120991151" Figure 7 - Total Utility Curve for Broadband  PAGEREF _Toc120991151 \h 51
 HYPERLINK \l "_Toc120991152" Figure 8 - Marginal Utility Curve for Broadband  PAGEREF _Toc120991152 \h 52
 HYPERLINK \l "_Toc120991153" Figure 9 - OSI Model  PAGEREF _Toc120991153 \h 62
 HYPERLINK \l "_Toc120991154" Figure 10 - Voice Service Subscribers - Fixed Vs Mobile  PAGEREF _Toc120991154 \h 69
 HYPERLINK \l "_Toc120991155" Figure 11 - Worldwide Subscriber Base for Wireless Broadband Services  PAGEREF _Toc120991155 \h 70
 HYPERLINK \l "_Toc120991156" Figure 12 - Use of Mobile Data  PAGEREF _Toc120991156 \h 80
 HYPERLINK \l "_Toc120991157" Figure 13 - Wireless Network Types  PAGEREF _Toc120991157 \h 86
 HYPERLINK \l "_Toc120991158" Figure 14 - Various BWA Technology  PAGEREF _Toc120991158 \h 89
 HYPERLINK \l "_Toc120991159" Figure 15 - Cellular Wireless Technology Evolution  PAGEREF _Toc120991159 \h 92
 HYPERLINK \l "_Toc120991160" Figure 16 - Future of Broadband - Multi Technology Access  PAGEREF _Toc120991160 \h 96
 HYPERLINK \l "_Toc120991161" Figure 17 - Disruptive Technology Performance Curve  PAGEREF _Toc120991161 \h 102
 HYPERLINK \l "_Toc120991162" Figure 18 - Technology Life Cycle  PAGEREF _Toc120991162 \h 106
 HYPERLINK \l "_Toc120991163" Figure 19 - Sustaining and Disruptive Technology Cycle  PAGEREF _Toc120991163 \h 107
 HYPERLINK \l "_Toc120991164" Figure 20 - Sustained Innovations for Disruption  PAGEREF _Toc120991164 \h 111
 HYPERLINK \l "_Toc120991165" Figure 21 - WiMAX Adoption and Acceptance  PAGEREF _Toc120991165 \h 116
 HYPERLINK \l "_Toc120991166" Figure 22 - Technology Adoption Chasm  PAGEREF _Toc120991166 \h 118
 HYPERLINK \l "_Toc120991167" Figure 23 – WiMAX: One Solution for Multiple Needs  PAGEREF _Toc120991167 \h 140
 HYPERLINK \l "_Toc120991168" Figure 24 - WiMAX Wireless Complete Ethernet Solution  PAGEREF _Toc120991168 \h 141
 HYPERLINK \l "_Toc120991169" Figure 25 - WiMAX Coverage With Different SS Types  PAGEREF _Toc120991169 \h 150
 HYPERLINK \l "_Toc120991170" Figure 26 - WiMAX Types  PAGEREF _Toc120991170 \h 152
 HYPERLINK \l "_Toc120991171" Figure 27 - WiMAX PHY Architecture  PAGEREF _Toc120991171 \h 167
 HYPERLINK \l "_Toc120991172" Figure 28 - WiMAX Point to Multi Point Deployment  PAGEREF _Toc120991172 \h 178
 HYPERLINK \l "_Toc120991173" Figure 29 - Mesh Network  PAGEREF _Toc120991173 \h 179
 HYPERLINK \l "_Toc120991174" Figure 30 - Multi-stake Holder Relationships for WiMAX Standard  PAGEREF _Toc120991174 \h 192
 HYPERLINK \l "_Toc120991175" Figure 31 - Scope of WiMAX Specification  PAGEREF _Toc120991175 \h 193
 HYPERLINK \l "_Toc120991176" Figure 32 - Layers of the 802.16 Protocol  PAGEREF _Toc120991176 \h 197
 HYPERLINK \l "_Toc120991177" Figure 33 - 10-66 GHZ TDD Frame for 1mS,  PAGEREF _Toc120991177 \h 198
 HYPERLINK \l "_Toc120991178" Figure 34 - 802.16 MAC PDU Format  PAGEREF _Toc120991178 \h 205
 HYPERLINK \l "_Toc120991179" Figure 35 - PSDU Transport Stages  PAGEREF _Toc120991179 \h 208
 HYPERLINK \l "_Toc120991180" Figure 36 - Burst FDD - With Scheduling Flexibility  PAGEREF _Toc120991180 \h 225
 HYPERLINK \l "_Toc120991181" Figure 37 - Working of Smart Antennas  PAGEREF _Toc120991181 \h 254
 HYPERLINK \l "_Toc120991182" Figure 38 - Power Control Using Sleep Mode  PAGEREF _Toc120991182 \h 258
 HYPERLINK \l "_Toc120991183" Figure 39 - OFDM Wave Form  PAGEREF _Toc120991183 \h 260
 HYPERLINK \l "_Toc120991184" Figure 40 - OFDM Channel  PAGEREF _Toc120991184 \h 263
 HYPERLINK \l "_Toc120991185" Figure 41 - Adaptive Modulation  PAGEREF _Toc120991185 \h 268
 HYPERLINK \l "_Toc120991186" Figure 42 - Radio on Silicon  PAGEREF _Toc120991186 \h 273
 HYPERLINK \l "_Toc120991187" Figure 43 - WiMAX SoC  PAGEREF _Toc120991187 \h 276
 HYPERLINK \l "_Toc120991188" Figure 44 - Coverage Vs Throughput  PAGEREF _Toc120991188 \h 291
 HYPERLINK \l "_Toc120991189" Figure 45 - Cost Advantage of WiMAX  PAGEREF _Toc120991189 \h 294
 HYPERLINK \l "_Toc120991190" Figure 46 - WiMAX OpEx Break-up  PAGEREF _Toc120991190 \h 301
 HYPERLINK \l "_Toc120991191" Figure 47 – WiMAX Network Coverage Cost Vs Frequency Curves, Rural, Suburban and Urban  PAGEREF _Toc120991191 \h 307
 HYPERLINK \l "_Toc120991192" Figure 48 - Path Length & Capacity Curve for Different Frequency Bands in Line of Sight Deployments  PAGEREF _Toc120991192 \h 308
 HYPERLINK \l "_Toc120991193" Figure 49 - Value Analysis, 3G, WLAN (Wi-Fi) and WiMAX  PAGEREF _Toc120991193 \h 317
 HYPERLINK \l "_Toc120991194" Figure 50 - 3G Time Line  PAGEREF _Toc120991194 \h 329
 HYPERLINK \l "_Toc120991195" Figure 51 - Impact of Standards  PAGEREF _Toc120991195 \h 336
 HYPERLINK \l "_Toc120991196" Figure 52- WiMAX Standard Evolution  PAGEREF _Toc120991196 \h 342
 HYPERLINK \l "_Toc120991197" Figure 53 - L2.5 Label Routing for 802.16e  PAGEREF _Toc120991197 \h 366
 HYPERLINK \l "_Toc120991198" Figure 54 - WiMAX Forum Defined Interoperability  PAGEREF _Toc120991198 \h 389
 HYPERLINK \l "_Toc120991199" Figure 55 - Certification Process  PAGEREF _Toc120991199 \h 390
 HYPERLINK \l "_Toc120991200" Figure 56 - Abstract Test Suite Development Process  PAGEREF _Toc120991200 \h 392
 HYPERLINK \l "_Toc120991201" Figure 57 - Collaborative Technology Environment  PAGEREF _Toc120991201 \h 401
 HYPERLINK \l "_Toc120991202" Figure 58 - Average Modelled Downlink Capacity for WiMAX in 3.5GHz Band  PAGEREF _Toc120991202 \h 412
 HYPERLINK \l "_Toc120991203" Figure 59 - Global Licensed & Un Licensed Band Allocations  PAGEREF _Toc120991203 \h 423
 HYPERLINK \l "_Toc120991204" Figure 60 - Spectrum Picture for WiMAX  PAGEREF _Toc120991204 \h 424
 HYPERLINK \l "_Toc120991205" Figure 61- WiMAX Applications  PAGEREF _Toc120991205 \h 438
 HYPERLINK \l "_Toc120991206" Figure 62 - Metropolitan-Area Networks (MANs)  PAGEREF _Toc120991206 \h 440
 HYPERLINK \l "_Toc120991207" Figure 63 - Cellular Backhaul  PAGEREF _Toc120991207 \h 448
 HYPERLINK \l "_Toc120991208" Figure 64 - Diverse WiMAX Applications  PAGEREF _Toc120991208 \h 450
 HYPERLINK \l "_Toc120991209" Figure 65 - Personal Broadband  PAGEREF _Toc120991209 \h 459
 HYPERLINK \l "_Toc120991210" Figure 66 - Opportunity for WiMAX  PAGEREF _Toc120991210 \h 467
 HYPERLINK \l "_Toc120991211" Figure 67 - Business Risks of WiMAX  PAGEREF _Toc120991211 \h 469
 HYPERLINK \l "_Toc120991212" Figure 68 - Technology Evaluation  PAGEREF _Toc120991212 \h 487
 HYPERLINK \l "_Toc120991213" Figure 69 - WiMAX Roll Out Stages  PAGEREF _Toc120991213 \h 495
 HYPERLINK \l "_Toc120991214" Figure 70 - WiMAX Deployment  PAGEREF _Toc120991214 \h 516
 HYPERLINK \l "_Toc120991215" Figure 71 - WiBro Spectrum  PAGEREF _Toc120991215 \h 526
 HYPERLINK \l "_Toc120991216" Figure 72 - WiBro Speed Vs Mobility  PAGEREF _Toc120991216 \h 527
 HYPERLINK \l "_Toc120991217" Figure 73 - WiBro Value Analysis  PAGEREF _Toc120991217 \h 528
 HYPERLINK \l "_Toc120991218" Figure 74 - WiBro Functional Model  PAGEREF _Toc120991218 \h 529
 HYPERLINK \l "_Toc120991219" Figure 75 - WiMAX Future Evolution  PAGEREF _Toc120991219 \h 536
 HYPERLINK \l "_Toc120991220" Figure 76 - Next Generation Network Architecture  PAGEREF _Toc120991220 \h 543
 HYPERLINK \l "_Toc120991221" Figure 77 - Next Generation Network with RAN, PCN and IMS  PAGEREF _Toc120991221 \h 552
 HYPERLINK \l "_Toc120991222" Figure 78 - SIP in VoIP Service  PAGEREF _Toc120991222 \h 554
 HYPERLINK \l "_Toc120991223" Figure 79 - Worldwide Broadband Subscribers - According to Technology Used  PAGEREF _Toc120991223 \h 604
 HYPERLINK \l "_Toc120991224" Figure 80 - Fixed BWA Users – World Wide  PAGEREF _Toc120991224 \h 605
 HYPERLINK \l "_Toc120991225" Figure 81 - WiFi Client Units – World Wide  PAGEREF _Toc120991225 \h 606
 HYPERLINK \l "_Toc120991226" Figure 82 - World Wide WiMAX Subscribers by Standards  PAGEREF _Toc120991226 \h 607
 HYPERLINK \l "_Toc120991227" Figure 83 - World Wide WiMAX Subscribers by Segment  PAGEREF _Toc120991227 \h 608
 HYPERLINK \l "_Toc120991228" Figure 84 - World Wide 802.16a & Proprietary < 11GHz Subscribers & Equipment Revenue  PAGEREF _Toc120991228 \h 609
 Table of Tables
 TOC \h \z \c "Table"  HYPERLINK \l "_Toc120991117" Table 1 - Broadband Throughput as a Function of Delivery and Time  PAGEREF _Toc120991117 \h 45
 HYPERLINK \l "_Toc120991118" Table 2 - Features of Wireless Networking Standards  PAGEREF _Toc120991118 \h 76
 HYPERLINK \l "_Toc120991119" Table 3 - Wireless Personal Area Network (WPAN) Technologies  PAGEREF _Toc120991119 \h 88
 HYPERLINK \l "_Toc120991120" Table 4 - Sustaining Technology Vs Disruptive Technology  PAGEREF _Toc120991120 \h 104
 HYPERLINK \l "_Toc120991121" Table 5 - 802.16 MAC Features  PAGEREF _Toc120991121 \h 164
 HYPERLINK \l "_Toc120991122" Table 6 - 802.16 PHY Features  PAGEREF _Toc120991122 \h 166
 HYPERLINK \l "_Toc120991123" Table 7 - Working Mechanism for WiMAX Connection  PAGEREF _Toc120991123 \h 173
 HYPERLINK \l "_Toc120991124" Table 8 - BWA Evolution  PAGEREF _Toc120991124 \h 242
 HYPERLINK \l "_Toc120991125" Table 9 - QoS for WiMAX  PAGEREF _Toc120991125 \h 282
 HYPERLINK \l "_Toc120991126" Table 10 - Spectrum used for Broadband Wireless in the US  PAGEREF _Toc120991126 \h 310
 HYPERLINK \l "_Toc120991127" Table 11 - Present and Future of Broadband Technologies - DSL, Cable, BWA/WiMAX  PAGEREF _Toc120991127 \h 315
 HYPERLINK \l "_Toc120991128" Table 12 - Relationship between IEEE 802.16 and IEEE 802.11  PAGEREF _Toc120991128 \h 321
 HYPERLINK \l "_Toc120991129" Table 13 - Capabilities of WiMAX and various 3 G Technologies  PAGEREF _Toc120991129 \h 331
 HYPERLINK \l "_Toc120991130" Table 14 - Characteristics of Key IEEE 802.16 Standards  PAGEREF _Toc120991130 \h 338
 HYPERLINK \l "_Toc120991131" Table 15 - IEEE 802.16 Family of Standard  PAGEREF _Toc120991131 \h 345
 HYPERLINK \l "_Toc120991132" Table 16 - 802.16a PHY Features  PAGEREF _Toc120991132 \h 352
 HYPERLINK \l "_Toc120991133" Table 17 - Comparison between FBWA and MBWA  PAGEREF _Toc120991133 \h 356
 HYPERLINK \l "_Toc120991134" Table 18 - Comparison between IEEE 802.20 and IEEE 802.16e  PAGEREF _Toc120991134 \h 368
 HYPERLINK \l "_Toc120991135" Table 19- WiMAX Forum Mission & Principles  PAGEREF _Toc120991135 \h 374
 HYPERLINK \l "_Toc120991136" Table 20 - Bands and frequencies available for WiMAX  PAGEREF _Toc120991136 \h 386
 HYPERLINK \l "_Toc120991137" Table 21 - Key Advantages & Disadvantages - Converged Regulators  PAGEREF _Toc120991137 \h 404
 HYPERLINK \l "_Toc120991138" Table 22 - Regulatory Environment for Wireless - Europe & US  PAGEREF _Toc120991138 \h 410
 HYPERLINK \l "_Toc120991139" Table 23 - List of First Stage System Profiles  PAGEREF _Toc120991139 \h 414
 HYPERLINK \l "_Toc120991140" Table 24- Matrix of Opportunity by Demography  PAGEREF _Toc120991140 \h 466
 HYPERLINK \l "_Toc120991141" Table 25 - Matrix of Opportunity by Sector  PAGEREF _Toc120991141 \h 467
 HYPERLINK \l "_Toc120991142" Table 26 - WiMAX Multiple Antenna Schemes  PAGEREF _Toc120991142 \h 512
 HYPERLINK \l "_Toc120991143" Table 27 - IMS Evolution  PAGEREF _Toc120991143 \h 551
 HYPERLINK \l "_Toc120991144" Table 28 - WPAN - Technology Comparison  PAGEREF _Toc120991144 \h 589

Preface
Modern disruptive technologies are revolutionising the way we work, play, and interact. It won’t be an exaggeration if we suggest these technologies are altering the way we live. More interesting to note is that with every passing day these disruptions are becoming more rapid. This trend has created new competitive threats as well as new opportunities in each walk of our lives.
One such technology, which will have profound impact on future of our world, is WiMAX. This groundbreaking development in Broadband Wireless Access technology landscape is an evolving standard for point-to-multipoint wireless networking, works for the "last mile" in the same way that WiFi "hotspots" work for the last one hundred feet of networking.
Think of the possibilities that this affordable broadband wireless access technology offer to wide range of users like you and me. These advancements on WiMAX technology front can save life of millions of people living in remote underdeveloped part of the globe by providing remote health care services, emergency or distress information regarding possible typhoons, floods or may be the Tsunamis. An under served poor kid living in sub-Sahara can read details of latest experiments in space science or biotechnology conducted in California or Oxford.
Potential of WiMAX is phenomenal.
The challenge, then, is how to turn these possibilities into a reality.
“WiMAX – Broadband Wireless Access Technology” is a book which is a step in the direction to demystify WiMAX. The key idea behind the book is
“To pin down the technical details that make WiMAX actually work”
In WiMAX – Broadband Wireless Access Technology, Deepak Pareek an expert in the field dissects critical issues of compatibility, internetworking, standardization and certification, providing audience an in-depth understanding of the field.
The book is divided in four sections each covering an important aspect of subject. The centrepiece of the book is in-depth exploration of the “Disruptive Technology Innovations of WiMAX, WiMAX Deployment Planning and Successful Solution Strategies for all the stake holders”.
SECTION 1 - WiMAX - Overview
WiMAX, or the IEEE 802.16 standard for broadband wireless access, is increasingly gaining in popularity as a technology with significant market potential. This section as the name suggest provides an overview of WiMAX while putting forward concept of “Disruptive Technology”.
SECTION 2 - WiMAX - Cutting Edge
WiMAX is not one technology but a aggregation of many technology innovations bound together by IEEE 802.16 standards effort. This section, as the name suggest provides an overview of WiMAX technology and associated characteristics.
SECTION 3 - WiMAX – Roll Out
This section provides understanding about issues related to WiMAX deployment, which includes discussions about standards, certification and regulation.
SECTION 4 - WiMAX - Planning
This section, the last one of this book, deals with some of the major aspects of planning a successful WiMAX solution. The section deals with three major areas of business planning, deployment planning and future strategy.
The book also incorporates some detailed readings on different topics which have been touched upon in main text but were not covered for sake of larger audience. Annexure provides an overview of these topics.
WiMAX – Bigger than the Biggest Disruption

Section 1
WiMAX - Overview
WiMAX, or the IEEE 802.16 standard for broadband wireless access, is increasingly gaining in popularity as a technology with significant market potential. This section as the name suggest provides an overview of WiMAX while putting forward concept of “Disruptive Technology”. The section consists of three chapters.
Chapter 1 – Introduction
This chapter provides background information on developments in area of Broadband, Wireless and Mobile Broadband including WiMAX.
Chapter 2 – WiMAX: The Disruptive Technology
This chapter, as evident by the name, provides an in-depth understanding about factors making WiMAX a disruption and discusses in detail the concept of “Technology Disruption”.
Chapter 3 – How WiMAX Works
This chapter takes a close look at all the pieces of WiMAX puzzle, including its component i.e. Base Station, Subscriber Station and Backhaul. It also discusses the WiMAX architecture and provides insight about various network related issues including Network Topologies. The PHY and MAC layers as well as RF Interface of a typical WiMAX system are then described.
Chapter 1
Introduction
The swift emergence of a global information society is changing the way people live, learn, work, and relate. An explosion in the free flow of information and ideas has brought knowledge and its myriad applications to millions of people across the globe, creating new choices and opportunities in some of the most vital realms of human endeavour.
Modern societies are currently undergoing a number of fundamental transformations caused by the growing impact of the new ICTs on all aspects of human life. But this revolution brought about by the new technologies has to confront a major challenge, namely the extreme disparities of access between the industrialized countries and the developing countries and those in transition, as well as within societies themselves.
Even though there has been a substantial increase in telecom investment not to forget technology advancements in the past decade, there are still enormous gaps in accessibility. There is still an average tele-density in decimals in the poorest countries while in some advance countries it is touching saturation levels. The gaps are even greater between urban and non-urban areas.
Affordable access, connectivity, and the skills to utilise increasingly advanced but essential services remain the central public interest issues in the area of information and communication technologies across the globe. This is true for all countries, but particularly for developing countries.
There are many reasons behind polarization of today's knowledge society on basis of access to connectivity hence information. Some of the vital issues extensively responsible for “digital divide” across the globe are lack of resources, scarce infrastructure, widespread illiteracy, inadequate technology, biased policies, apathetic governance, political instability and deep rooted corruption. Technology though is considered undeniably important, in comparison with other causes it is rated less important than policy, funding, and geo-political issues to name a few.
All these issues are interrelated and have technology as insignificant component. But in recent past advancement of information and communication technology had revolutionary impact on these obstacles, though indirectly. These radical developments were based on a wave of concurrent technological innovations, coined as Disruptive Technologies, underpinned by a number of externalities (network externalities, knowledge-sharing effects, innovative business modelling) never experienced in the past.
Broadband Age
The history of modern-day communications technology can be said to have started when Samuel Morse invented the wireline telegraph in 1832. However, it was Alexander Graham Bell's invention of the telephone, in 1874, that led to the development of our present day communications technology. The former had simply created a way for humans to extend their ability to transfer information – instantly – over long distances, while later gave the ability to have the most personal and intimate form of communication over distances – the use of our voices.

Figure  SEQ Figure \* ARABIC 1 - Broadband Evolution
The concept of the telephone was so strong that most communication technology during the past century was developed to support an efficient voice communication network. From 1874 to 1980, communication networks around the world were constructed to facilitate the efficient and economical transmission of voice conversations. Multiplexing and digital transmission systems were developed to "cram" more voice conversations into the existing copper wire communication facilities.
The Internet, first developed in 1973 initiated a profound change in the future development of communications networks and technologies. Originally called the Arpanet, which linked several Universities, and research laboratories it evolved into the World Wide Web (WWW). The advent of the networked computer was truly revolutionary in terms of information processing, data sharing and data storage. In the ‘90s, the Internet was even more revolutionary in terms of communications and furthering the progress of data sharing, from the personal level to the global enterprise level.
It wasn't until 2004 that major telecommunication carriers announced the need to develop, and support, a network designed for the purpose of transporting high-speed digital data instead of voice centric networks. While the 1970s and 1980s will be remembered as the “Information Age,” and the 1990s will undoubtedly be singled out in history as the beginning of the “Internet Age,” the first decades of the 21st Century may become the “Broadband Age”.
Today, broadband sources such as fibre-optic, wireless access and cable modems provide very high-speed access to information and media of all types via corporate networks and the World Wide Web, creating an “always-on” environment. The result will eventually be a widespread convergence of entertainment, telephony and computerized information: data, voice and video, delivered to a rapidly evolving array of Internet appliances, PDAs, wireless devices (including cellular telephones) and desktop computers.
Broadband access networks are much faster than traditional dial-up connections. Broadband networks are fast enough to deliver a variety of simultaneous services, such as file transfer, streaming media (sound or video) and, most important, voice.
What is Broadband?
There are various definitions of broadband, and it is worth noting that working definitions have changed and are changing with both time and place. A simple notion is anything perceptibly better than a basic ISDN line. This implies a rate around or exceeding 256 kbps, although customers may accept less if this is the best available to them. A common current understanding is “a service that is always on, and can scale up to at least 2 Mbps”.
Some broadband access technology platforms have a dedicated channel to each user (for example ADSL and fibre-to-the-user), while others have a shared channel that goes to many users. A feature of this second type of system is contention for the bandwidth, because it is shared. In this type of system the maximum instantaneous bandwidth obtainable exceeds by a large margin the average bandwidth a user enjoys.
Irrespective of however it is defined and technology platform it use, what is important and hence useful to examine, is the user services that become possible with “broadband”. As it is these services, and not theoretical technical definitions, that drive consumer demand the stress must always be on applications.
The number of applications enabled by broadband services is unbounded, and each has its own peculiar technical requirements. While for one throughput is vital then for another low latency (this is time delay to respond, and is typical of satellite links because of the long distance the signals must travel) is critical. Nonetheless, it possible in broad terms to identify a trail of application types such that the most basic broadband service supports only the first while the highest offering supports them all. In the interests of cost, availability and financial realism, a user group or a community may decide what it can afford and what it cannot. Some of the most prevalent applications and services are
Type 1: Messaging Services
These include simple e-mail, instant text messaging, remote login, simple web and Internet access, electronic shopping and business, electronic government and chat. These services can operate at the lowest bandwidths such as 256 or 512 kbps, although they are considerably more convenient and enjoyable when enriched by higher bandwidths. Most users receive more data than they send, so these services are compatible with asymmetric broadband (higher downstream than upstream capacity). These services can tolerate latency.
Type 2: Large File Transfer Services
These services are similar to messaging, but the messages contain larger quantities of data, perhaps 100’s kilobytes or megabytes as opposed to the tens of kilobytes envisaged for simple messaging. They may be extended simple messaging services, for example rich-content Internet surfing, electronic catalogue shopping, remote healthcare, home working, remote working and business virtual private networks (VPNs). Large-scale file transfer services include downloading of games, software, educational material, films and other entertainment content. These services ideally require 1-2 Mbps or higher, if the user is not to be kept waiting too long. As with Type 1, Type 2 services are compatible with asymmetric links and can tolerate latency.
Type 3: Unidirectional Real Time Services
These are mainly broadcast services such as audio and video streaming, and radio and television broadcasting. These services typically require high (at least 1.5 Mbps for video) or very high bandwidths, and are inherently asymmetric. They can tolerate high latency, as the data flow is one way only.
Type 4: Interactive Real Time Messaging Services
These messaging services operate between users who are interacting one with another, such bi-directional real time services include, video-conferencing, interactive video, interactive gaming, integrated business telecommunications, tele-education and tele-presence services supplied over a broadband link and wide area networks. These services ideally require 1-2 Mbps or higher, need to be symmetric and cannot tolerate latency.
The promises of broadband technologies have generated much interest all around. However in reality, a lot needs to be done for broadband to deliver as per its promises. The key is to identify ways to unleash the potential of broadband networks.
Today's broadband solutions are quite complex and require semiconductor manufacturers to integrate a wide variety of innovative technologies to offer low-power, cost-effective system solutions that address the needs of original equipment manufacturers (OEMs), service providers, and end users. This tutorial provides an overview of various broadband infrastructure, access, and home networking technologies and examines the essential technology building blocks required to deliver end-to-end broadband connectivity from the infrastructure to endpoint devices.

Figure  SEQ Figure \* ARABIC 2 - Applications of High Speed Internet
Broadband Technologies
There are multiple transmission media or technologies that can be used to provide broadband access. Each technology has its respective advantages and disadvantages, and will likely compete with each other based on performance, price, quality of service, geography, user friendliness, and other factors.
Cable and DSL are currently the most widely used technologies for providing broadband access. Both require the modification of an existing physical infrastructure that is already connected to the home.
Cable
The same cable network that currently provides television service to consumers is being modified to provide broadband access with maximum download speeds as much as 6 Mbps. As an alternative to existing copper phone wires, cable companies have been providing broadband access using their cable plant to carry data and voice services in addition to traditional video services.
A cable-modem termination system (CMTS) communicates with cable modems located at the customer premises to provide broadband access services. The cable modem typically provides an Ethernet interface to a PC or to a small router when multiple PCs are connected. However, network sharing has also led to security concerns and fears that hackers might be able to eavesdrop on a neighbour’s Internet connection.
Today's cable networks generally deliver data with download speeds roughly between 500 kbps and 6 Mbps and upstream speeds of 128 kbps. As users share cable networks, access speeds can decrease when many customers are sharing bandwidth at the same time.
Newer-generation cable-modem technologies will significantly increase the available bandwidth to further enable interactive applications such as videoconferencing and high-end on-line video. Internet protocol (IP) telephony is one of the services that can be delivered over coaxial cable. For the cable operators, IP telephony enables them to offer voice services that, to date, have been the domain of the telephone companies.
Digital Subscriber Line (DSL) & ADSL
DSL is a modem technology that converts existing copper telephone lines into two-way high-speed data conduits. Data transmission speeds typically range up to 3 Mbps for downloading and 768 kbps for uploading. Speeds can depend on the condition of the telephone wire and the distance between the home and the telephone company’s central office.
DSL technology is a copper-loop transmission technology for transmitting high-speed data over ordinary telephone wires. A DSL modem is installed at the customer premises and at the central office (CO). Different variants of DSL exist to address different technology trade-offs that can be made regarding different network environments and applications. One of the key trade-offs is distance (referred to as reach) from the CO and data rate.
Asymmetrical DSL, or ADSL, is primarily used for residential services. ADSL takes advantage of the fact that there is more cross talk interference at the CO end of a copper pair than at the subscriber end due to the large bundles of cabling entering the CO. ADSL can provide data rates up to 8 Mbps from the network to the subscriber direction, and up to 1 Mbps from the subscriber to the network direction. The asymmetry of ADSL works well for today's home applications where the majority of bandwidth is consumed in the network to user direction.
As ADSL uses frequencies much higher than those used for voice communication, both voice and data can be sent over the same telephone line. Thus, customers can talk on their telephone while they are online, and voice service will continue even if the ADSL service goes down. Like cable broadband technology, an ADSL line is “always on” with no dial-up required. Unlike cable, however, ADSL has the advantage of being unshared between the customer and the central office. Thus, data transmission speeds will not necessarily decrease during periods of heavy local Internet use.
A disadvantage relative to cable is that ADSL deployment is constrained by the distance between the subscriber and the central office. ADSL technology over a copper wire only works within 18,000 feet (about three miles) of a central office facility. However, providers are deploying technology to further increase deployment range.
Symmetrical DSL, or SDSL, is a cost-effective solution for small and medium enterprises, offering a competitive alternative to T1 and E1 lines. The International Telecommunication Union-Telecommunications Standardization Sector (ITU-T) standard G.991.2, also known as G.shdsl, is a replacement standard for proprietary SDSL. G.shdsl offers data rates from 192 kbps to 2.3 Mbps while providing a 30% longer reach than SDSL.
Very-high-data-rate DSL, or VDSL, can support symmetrical or asymmetrical services. Asymmetrical VDSL is capable of providing data rates to the user of up to 52 Mbps, making it suitable for transporting high-speed applications such as real-time video streaming. The trade-off for this high speed is restricted reach. This requires that the customer be located close to the CO or that the infrastructure access gateway resides outside the CO (and closer to the customers) in a remote terminal (RT).

Figure  SEQ Figure \* ARABIC 3 - Access Technologies and Speeds
Satellite
Satellite broadband Internet service like cable, is a shared medium, meaning that privacy may be compromised and performance speeds may vary depending upon the volume of simultaneous use. Another disadvantage of Internet - over-satellite is its susceptibility to disruption in bad weather. On the other hand, the big advantage of satellite is its universal availability. This makes satellite Internet access a possible solution for rural or remote areas not served by other technologies.
Powerline Communication (PLC)
Power utilities around the world are recognising the natural competitive advantage they have in telecommunications. This comes from the use of infrastructure they have in place (ducting, building access, poles), their systems (billing, call centres), a strong relationship with and an understanding of a large customer base, and a core competency in network management and maintenance. It is a natural extension of business activity for a power company to enter into telecommunications.
New developments in Powerline Communication (PLC) are making it possible for these utilities to enter the more lucrative broadband market. Over the years a large number of utilities have entered the telecommunications market. Some started to look at core electricity applications such as Automated Meter Reading (AMR) others started to exploit their internal telecom networks and offered access to their infrastructure on a wholesale basis.
Others made poles and towers available for new telcos to string their own telecom infrastructure. Increasingly however, we are starting to see electricity utilities taking a higher-level strategic interest in the telco market, based on the development of broadband. Power utilities around the world are recognising the natural competitive.

Figure  SEQ Figure \* ARABIC 4 - Internet Access Technologies
HomePlug-AV – Keep an Eye on Power
HomePlug-AV is gaining interest as with characteristics capable of supporting multiple High Definition TV streams simultaneously using a single A/C power outlet are essentially impressive.
In a recent demo, a pioneer customer electronics manufacturer showed video streams being sent simultaneously between A/C power outlets common in any home or office. They were using a prototype version of an emerging standard for high-speed audio/video applications over the 110v powerline with speeds up to 170 Mbps and with full QoS support.
Its performance becomes more compelling as well as incredulous when one considers the “noise” injected by electric motors, fluorescent lights, and air conditioners.
Powerline Repeaters - To Extend Wireless Range
Even if the available bandwidth varies at different outlets or fluctuates over time, powerline still makes a good backbone for extending the range of wireless networks. Similar to mesh networks that let adjacent PCs extend the range and function as wireless signal repeaters, repeaters are also feasible for power line networks, and can also work on other wired networks like coaxial cables. Coax can also be a backbone for extending range.
The Multimedia over Coax Alliance (MoCA) is working on solutions designed to let TV programs, data, and voice applications share the same coax cabling.
Wireless – Radio Access
In the last 15 years radio access networks have transitioned from analog to digital technologies and moved on from voice-only services. Today’s WiMAX, Wi-Fi and WCDMA networks are pushing the performance of the wireless interface to a completely different level and this development is expected to continue for the foreseeable future.
Cellular Wireless
When GSM started in the early nineties radio services took off: literally.
Next-generation cellular is providing high-speed data capabilities in addition to traditional voice. Current 2G cellular services only offer data service rates on the order of 9.6 kbps. The emerging 2.5G services will boost available bandwidth to the user and facilitate always-on data services. For 2.5G networks, there are two primary technologies: general packet radio service (GPRS) and enhanced data rates for GSM and TDMA (IS-136) evolution (EDGE). Third-generation (3G) wireless communication technologies support even higher data rates. The packet switching is IP-based, making for efficient routing of data from the Internet through the carrier's gateway. The higher bandwidth should allow for better integration of voice, data, and video signals. Delivery of data services over cellular offers the promise of ubiquitous high-speed data access, including while in moving vehicles.
Cellular evolution however, after driving bit rates up from 384 kbps just a year back to today’s figure of 2 Mbps, is not stopping at 3G. Industry is moving towards 200 Mbps in 3.9G and eventually above 1 Gbps in 4G.
HSPA (High Speed Packet Access) services are coming on stream and the long term evolution of WCDMA (sometimes referred to as 3.9G) is already being discussed in 3GPP. This may become the most advanced wide area network solution that mobile operators can deploy; only time can tell weather this initiative will succeed in the next few years.
In addition, the cost efficiency of networks will increase over time.
After that what is in pipeline is 4G, a generic term used to refer to a new radio access network technology that has not been defined. 4G is still in the research stage though performance target speculated today by vendors is above 1 Gbps and that the chosen technology should be a global standard.
Wireless Ethernet
In addition to cellular-based wireless data services, wireless Ethernet, traditionally a home and enterprise networking technology, is being used for broadband access in public areas such as airports, hotels, sports arenas, convention centres, and coffee shops. This allows users to take their laptop and PDA devices with them and to use a common access technology to deliver high-speed Internet services in their office, home, and while on the road.
Fibre
For new infrastructure build out, where copper wires are not currently present, the installation of fibre is being employed. Fibre-optic technology, through local access network architectures such as fibre-to-the-home/building (FTTH/B), fibre-to-the-cabinet (FTTCab), and fibre-to-the-curb (FTTC) offers a mechanism to enable sufficient network bandwidth for the delivery of new services and applications.
Fibre-to-the-Premise [FTTP] extends fibre connections from the central office to the “curb” (fibre to the curb or FTTC) and into customer's houses or places of business. Dedicated fibre connections provide extremely high bandwidth and make possible movies-on-demand and online multimedia presentations would arrive without noticeable delay. Fibre-optic technology delivers Internet, voice and video at speeds from 2Mbps to 100Mbps and beyond. On a fibre optic network, data is transmitted as light impulses along thin strands of silica glass.
Unlike copper cabling, optical fibre is not subject to electromagnetic interference because it uses light, not electricity. Moreover, fibre optics can transmit data over much longer distances; 6.2 to 49.6 miles over single-mode fibre-optic cabling vs. a few thousand feet for copper cabling.
“Broadband – Present & Future”Delivery Type200020032004 20052008Wireline512 kbps1 Mbps2 Mbps4 Mbps144 MbpsFixed Wireless #70 kbps500 kbps1 Mbps2.8 Mbps70 MbpsMobile Wireless9.4 kbps300 kbps600 kbps2.4 Mbps16 MbpsTable  SEQ Table \* ARABIC 1 - Broadband Throughput as a Function of Delivery and Time
# Fixed Wireless also includes Satellite
Broadband Demand
The broadband is a dynamic sector as the competitive landscape and consumer demand for new communication services continue to evolve. Driven by the need to find new sources of revenue, service providers are looking for ‘killer applications’.
A killer application is service or software that is so innovative and impressive that consumers are willing to pay to use them and adopt them quickly. Killer applications can be games or applications, operating systems or multimedia platforms. Some examples are Windows, Doom, and Napster.
It is not difficult to understand that unless there is clear value proposition customers are reluctant to spend money on premium products. Napster’s value was that paying for DSL/cable modem cost less than buying music. Lower pricing plans for SMS led to its adoption over voice.
Killer applications in the wireless space will be a function of how mobile the person is. Consumers and businesses that depend on mobility are the most likely to find value in wireless broadband, and some business applications are more obviously suited to broadband wireless, such as metering. As the technology proliferates the not-so-obvious ‘killer’ applications will become clearer.

Figure  SEQ Figure \* ARABIC 5 - Broadband Subscribers Projection - USA
After years of use, Internet customers are very much aware of what the Internet can do for them. Some people use it for banking; others for research. Game playing is another popular application, but many more people use it for very personal purposes, based on their hobbies, work or lifestyle. These users are becoming frustrated with the fact that they constantly have to dial up to check their e-mails or to have quick access to information. What should be a 5-minute search can easily turn into a 15-minute source of frustration. These users are more than ready for broadband. Always-on, high-speed Internet access will be the initial ‘killer application’ for broadband.
However, there will not be one killer application that will suddenly turn mass markets on. Numerous niche market applications, packaged in the right way will be the way to go. In a sense, during the mid-1990s, the email became the killer application of Internet that everybody had been waiting for since the early 1980s.
There are many areas, which will stimulate the use of broadband, some of them are:
High-speed Internet access
Multi access services including Voice, Data and Video
Tele-working, Tele-education, Tele-medicine
Gambling, Games, Adult Entertainment
VoIP and IPTV
Broadband Everywhere
In recent years, Broadband technology has rapidly become an established, global commodity required by a high percentage of the population. In the past four years alone, the demand has risen rapidly, with worldwide installed base of 57 million lines in 2002 rising to an estimated 200 million mark by end of 2006. This healthy growth curve is expected to continue steadily over the next few years. The broadband market, which initially focused their deployments efforts on densely-populated urban and metropolitan areas in developed economies, are now challenged to provide broadband services in suburban and rural areas of these developed economies as well as most parts of the developing world, where new markets are quickly taking root. Governments are prioritising broadband as a key political objective for all citizens to overcome the “broadband gap” also known as the “digital divide”.
Broadband the Development Catalyst
Telecommunication plays a vital role in any nation’s economy and is widely accepted as an important change agent. In developed as well as underdeveloped economies, telecommunication services are applicable to a wide range of economic production and distribution activities, delivery of social services and government administration.
Globally, the telecommunications sector has converged into an information and communication technology (ICT) sector. The Industrial Revolution and thereafter mastering of the mechanical industry and of electricity production and their use have granted prosperity and political clout to some countries in the past. The Digital Revolution and thereafter mastering the capability to control the technologies of information and communication is a unique opportunity to earn economical and political rewards for the 21st Century.

Figure  SEQ Figure \* ARABIC 6 - Residential Broadband Penetration Trends & Forecast - Europe
Telecommunication infrastructure supporting broadband access serves as the medium for the flow of information in all forms encompassing voice, data and video. Broadband is an enabler and an important precursor for economic development. It is occupying an increasingly important role in society and to the economy. It is widely acknowledged to be a crucial driver of business growth and development, which in turn has the potential to influence other spheres – job creation, infrastructure, healthcare, education, etc.
In developing markets, high-speed and low-cost bandwidth, which the developed world can take for granted, is still almost non-existent. It is almost like the bandwidth revolution has bypassed the developing markets, even as the LANs have kept pace with the rest of the world. This is not to say that things aren't changing: DSL, Fibre, Fixed Wireless and Cable solutions are promising to usher in broadband. But impact of these initiatives, is not as wide spread as desired.
However, what is certain is that in near future broadband will be seen in its full advent, building upon a universal access to two-way multimedia information (data, sound, living images,).
Economics of Broadband
Broadband services must be less costly to provide, making it affordable for subscribers. At the same time, voice service being a necessity, subscribers won’t drop existing POTS usage. To encourage mass subscriber adoption of broadband services, it must be available at a cost comparable to existing lifeline POTS service charges. Further, voice services must be provided bundled to broadband without any additional cost to the subscriber, or traditional POT services must be provided, preferably at a lower service cost than today, without any impact on quality. However, the service fee must also enable the carriers to realize an appreciable return on investment, a portion of which can be reinvested for continuous service enhancements and to meet increase in bandwidth demands.
As carriers have deployed broadband and DSL services from the local loop, they have typically deployed a separate logical and sometimes physical network to separate and carry the voice and data traffic, placing a significant burden on the local loop infrastructure. This costly solution has limited carriers’ ability to service subscribers profitably and slowed the rollout of broadband services.

Figure  SEQ Figure \* ARABIC 7 - Total Utility Curve for Broadband

Figure  SEQ Figure \* ARABIC 8 - Marginal Utility Curve for Broadband
Broadband Puzzle
Broadband to the remote and un-served areas is in a quagmire. Wireline providers are not too keen to pursue these prospects due to very high spending requirement in order to create a digital plant. Horror stories abound on installations botched by company bureaucracy or incompetence, especially with DSL installed by ILECs.
In spite of all the promises of broadband the reality is much different than the practice. Getting a truck roll is a major barrier in these markets. Thus, the quagmire is a market cycle between poor installation performance, high end user total cost, and lack of compelling user scenarios.
With limited network resources and many competing demands from different segments of users, satisfying the demands of one segment means taking resources away from another. This problem, along with the over-subscription model of the Internet possesses great challenges for network operators.
How to break the cycle?
This is not a problem easily addressed because of its complexity and the fact that it spans many aspects of the value chain in a broadband network. There have been many significant developments that hold promise for addressing this complex equation, the current barriers to greater broadband deployment. Ultimately how this intricate and intriguing cycle will be broken rests on with various factors, with three key areas being:
Technology improvements
Market developments
Policy pragmatism
Improved technology holds the promise of overcoming many of the barriers currently preventing more widespread deployment and use of broadband. The history of broadband technology has been one of ever-greater innovation, increasing capabilities, and decreasing costs. Broadband service providers are thus optimistic about reaching a position sooner than later, where they can ensure fair allocation of network resources between potentially competing uses of the network. In doing so they may need tools that give them visibility and control of the traffic that traverses their network, while they allocate resources between subscribers, applications, and content providers to derive maximum utility from the network, hence realizing satisfactory overall subscriber experience.
Broadband Connectivity Solutions
Broadband connectivity is extended from the core infrastructure to end users' devices such as PCs, personal digital assistants (PDAs), telephones, television sets, and digital cameras. Infrastructure gateway equipment provides broadband access to the packet-based infrastructure. Customer premises equipment (CPE) access gateways extend broadband access connectivity to end-user devices via one or more technologies.
Broadband Building Blocks
Broadband communications consists of the technologies and equipment required to deliver packet-based digital voice, video, and data services to end-users. Broadband offers users high-speed, always-on Internet access, while offering service providers increased revenue from new, value-added services. Broadband solutions residing within today's broadband communications equipment are complex and require semiconductor manufacturers to integrate a wide variety of innovative technologies to offer low-power, cost-effective system solutions that address the needs of OEMs, service providers, and end users.
The challenge of the semiconductor manufacturer is to design silicon and software with a complete solution focus and not just chips or chipsets. Customers have many needs that require a multitude of core competencies for semiconductor manufacturers to satisfy. First of all, customers desire flexible solutions that can accommodate a range of densities to meet requirements scaling from endpoint devices to CPE to carrier-class equipment. Flexibility dictates the need for programmable architecture that can facilitate quick and easy software upgrades to address new features, interoperability issues, performance, and evolving standards.
For broadband technologies, high-performance digital signal processors (DSPs) are required to implement the various signal-processing algorithms necessary to perform functions such as modulation, voice compression, and video processing. The industry has moved beyond general-purpose DSPs to specialised silicon/software solutions optimised for a particular vertical application. These solutions include the following:
DSP and RISC processor cores
Networking interfaces, including Ethernet, Utopia, PCI, USB, 1394, etc.
Software with well-defined application programming interfaces (APIs), including signal-processing algorithms, protocol stacks, device drivers, real-time operating system pre-ports, network management, and application software
High-performance analogue components, including data converter and amplifiers
Power management solutions, including power supply control and battery management
Digital modem technologies for broadband communications
Radio frequency (RF) wireless technologies for wireless devices
Voice over packet (VoP) technologies, including voice compression, echo cancellation, tone processing, dial modem, Group 3 facsimile, and telephony signalling
Networking technologies, including routing, switching, filtering, encryption and quality of service (QoS)
These solutions must be very low power to allow battery or line-powered operation for endpoint devices or to scale in an infrastructure environment where equipment is limited by power consumption and heat dissipation.
Cost is always a concern. Customers want semiconductor providers to provide them with the lowest-cost solution, and this is for the entire customer's solution, not just the semiconductor manufacturer's portion. Thus, the semiconductor manufacturer must understand the total build of materials (BOM) cost of the equipment and work at reducing the total BOM. This includes integrating more functionality into the silicon solution and eliminating the need for "glue" logic. It also includes reducing manufacturing costs by making the solution easy to build by minimizing the number of printed-circuit board layers, making the chip package easy to mount and signals easy to route on the printed-circuit board. There is a constant need for cost reduction for mass-market deployment.
Customers want to know that the semiconductor's roadmap will offer significant cost reduction for subsequent customer refreshes of the product. The key to facilitating continued cost reduction is to have high-volume manufacturing facilities with leading-edge process technologies coupled with strong system-integration capabilities.
To speed customer time to market, semiconductor manufacturers must offer the customers hardware reference platforms that are integrated with software, fully system tested for conformance to industry standards, interoperable with other vendors, and product hardened under real-world conditions.
Infrastructure Equipment
Broadband infrastructure gateway equipment is responsible for interconnecting broadband access services to the optical core network infrastructure. For multiservice gateways, multicore DSP platforms facilitate the ability to support multiple broadband access technologies as well as traditional voice-grade services. Communications processors containing high-speed processing engines and networking interfaces perform protocol processing and network-management functions. High-speed aggregation logic is required for performing packet processing while providing QoS functions.
Infrastructure gateway equipment providing broadband access is driven by the need to support a large number of end-user connections in a concentrated area while being constrained on the total power (heat) dissipation. The concept of solution density has been developed to help service providers and OEMs more clearly understand the technical requirements for implementing high-density products. From a system-engineering perspective, a solution must be evaluated on how the combination of system elements delivers a complete solution with the lowest power and smallest area without compromising quality and features. Solution density refers to the optimisation of the overall system architecture, taking into account the following critical elements:
Power of the solution expressed in mill watts (mW) per end-user channel
Density of the solution expressed in end-user channels per square inch
System partitioning, including packet aggregation and routing
Software features that define the functionality of the product
Network capabilities to address high availability and accountability
To engineer an optimal solution, cost, power, and area must be evaluated on a total system basis and must be a function of the features and capabilities supported.
Premises Access Gateway Equipment
Premises access gateway equipment is responsible for terminating a broadband access pipe from a service provider and making that pipe available to the home or home-office network. Communications processors containing high-speed processing engines and networking interfaces perform protocol processing such as bridging, routing, packet filtering, and firewall operation. Typically, a premises access gateway provides connection to a single broadband access medium e.g., cable, DSL, or broadband wireless, but may support multiple LAN interfaces such as wired Ethernet, wireless Ethernet, and Bluetooth. VoP technologies are required for derived voice services.
Broadband endpoint devices
Broadband endpoint devices come in many forms, such as PDAs, digital cameras, MP3 players, digital television, and IP phones. DSPs perform multimedia processing such as MP3 audio, MPEG-4, and JPEG imaging. High-quality analogue components are essential for performing analogue to digital (A/D) and digital to analogue (A/D) processing. These consumer devices must be extremely low cost. Devices that are portable handheld devices must be very low power to ensure long battery life. Also, devices that are line powered, e.g., from the infrastructure, Ethernet, or universal serial bus (USB) interface, must adhere to the power constraints of that interface. Thus, low-power devices coupled with power-management technologies are essential.
Designing Broadband Solution
Fundamental premises on which an ideal broadband solution, that can further the technical and business goal of provision of cost effective broadband services, must be conceived are:
Simple Design is Better
Greater simplicity reduces ongoing operational and management costs to lower the cost of delivering services.
Edge Aggregation is More Efficient
All voice and data streams should be aggregated at the remote terminal. This makes service provision more efficient for the longest local loop to meet the growing demand for broadband services.
Common Protocol for All Traffic
All traffic should be controlled and routed through a common protocol. Today the leading protocols from the point of scalability, cost and reliability are the Internet Protocol (IP) and ATM.
Standards Based Provides More Value
Standardised solutions are cheaper to acquire, operate and manage. At the same time proprietary solutions trap carriers and limit their flexibility in transitioning their networks to newer, more cost effective technologies.
Scalability is the Key
In-view of cost involved, any equipment deployed in a carrier’s network should have a substantial lifespan. However, over the next few years the demand for broadband service is expected to explode, requiring a network that can scale easily to meet this growing demand.
Smooth Network Transition
Unless a new solution can integrate seamlessly into a carrier’s existing network infrastructure, it will be cost-prohibitive regardless of how effective it may be. New solution must be capable of transition from the current network to a fully converged access network at a carrier’s own pace
Meet Critical Technology Challenges
Must meet a number of critical technology challenges, including enabling converged networks, removing bandwidth bottlenecks, and improving a carrier’s ability to provision and manage services.
Architecture to Technology Challenges
The broadband solution must be designed carefully to meet a number of critical technology challenges thrown open by unrelenting expectation growth and tricky market dynamic, including promotion and enabling broadband adoption in underserved markets. Some other challenges are removing bandwidth bottlenecks, and improving a carrier’s ability to provision and manage services. These challenges without doubt are central, however many more exist and many more would be created in coming day. A robust solution must be able to resolve these existing issues and must be prepared to handle new once.

Figure  SEQ Figure \* ARABIC 9 - OSI Model
Enabling Converged Networks
Any equipment deployed in a carrier network in the 21st century must further the technical and business goal of supporting a single network for voice and data traffic. A series of key architectural innovations, which can be considered a substantial forward move in the direction, are:
Terminate services on one port
Convergence must begin at the edge of the carrier network. Innovative products available today terminate all copper and wireless local loops on a single port served by a programmable DSP. Each DSP reads the entire frequency spectrum of the copper wire or wireless and directs the traffic appropriately. Common termination makes it possible to turn up services remotely via software. In the future, we may see subscriber interfaces served by universal DSPs that can deliver any voice or broadband service.
Convert to a common protocol
A fully converged solution enables a carrier to create a high-performance, packet-based local distribution network that is similar to a carrier’s core network.
Some products wrongly referred as “Next Generation DLCs’’ sometimes combine TDM and ATM switching into a single platform. While this appears to be a converged architecture, in reality these platforms promote continued reliance on circuit switched voice connections and a separate overlay ATM network to support broadband traffic. Such solutions can be a stopgap arrangement but defiantly are not capable to become a generation.
A converged network is capable to operate successfully delivering optimum results only when all voice and data traffic are controlled by a common protocol. The idea to have a solution, which uses IP as its common protocol, has a substantial value. We have seen the pros and cons as well as interest generated by Voice over IP (VoIP). VoIP work on principal, where streams of voice traffic is converted to uncompressed individual data virtual circuits and are terminated and aggregated into a broader IP data stream.
Quality of Service
Increasing demand from multiple market segments, with varied needs and price points, for data and voice services has impacted carriers operations in a big way. For carriers to succeed they need to provide different services depending on quality to different segments, while charging differential tariff from customers. Broadband solutions must be able to classify all traffic and apply a guaranteed quality of service.
Enterprise and high end individual user data streams need higher reliability and committed quality, unlike retail customer which cannot or don’t want to pay for reliability and are satisfied with low cost ‘best effort’ basis services. This need for variable Quality of Services in same network leads to need for prioritisation of traffic for transport across the local distribution loop either by data type, user or service.
Traffic engineering and bandwidth management
Further bandwidth demand may also differ with users, as enterprise may ask for 10s of MBs and individuals 100s of KBs. To serve these clients bandwidth needs to be segmented. Also with bandwidth for voice traffic during peak traffic loads reserved and guaranteed, it can then be reallocated for data during low traffic loads. This provides carriers with a much more effective use of available bandwidth that does not require significant.
Processing power and capacity
As more functionality is moved to the edge of the network, local loop devices will need to be able to support a broader range of functions from data prioritisation to encryption, for a small number of users with common access rights to a large number of specialized subscription based-services. Present day devices must be provided with advanced network processors having capacity to process packets at a rate of multiple gigabits per second and includes enough memory on board. These devices must be capable to classify and track services for individual data flows.
Eliminating Bandwidth Bottlenecks
If creating a converged network is the first technological step, the second is to remove any bandwidth bottlenecks in the equipment installed in the local distribution network – that part of the carrier network from the remote edge to the central office.
High capacity switching core
Broadband solution must be designed with a high capacity switching core that can provide non-blocking, line speed throughput without buffering and geared towards the future, enabling scaling to greater capacities without impacting the passive back plane or feature cards.
Ability to Provision and Manage Services
The final challenge for carriers is to deploy platforms that improve their ability to provision and manage the infrastructure and services. This can be made possible with features like
Easy integration with existing Systems
Design for broadband solution must make provision for a broad range of interfaces for carriers of different size and capabilities to use in integrating into their existing systems like OSS or into next-generation OSS platforms. From a simple command line interface and browser based-GUI configuration, to a traditional TL1 or future XML interface. Further they should support automated provisioning and management.
Provisioning for instant remote activation
The ultimate goal for broadband services is pass-through provisioning, where a subscriber or a customer service representative simply enters an order and the service is turned up. For this to occur, the edge equipment must support software provisioning of each and every port – where a new or existing service can be defined and brought on-line within minutes, not weeks.
Multiple transition paths
One of the key challenges for carrier equipment is its ability to fit into the existing infrastructure while ensuring a path to the future. These devices must be designed for transition, from its size to its protocol support in multiple scenarios, from sub-tending into existing legacy infrastructure to a true green-field deployment utilizing state of the art technologies.
Management and Support from Central Office
Broadband solutions must be capable to reduce loop management cost, which can be achieved by providing line testing functionality that can be performed before or after service deployment from a centralized operations centre. Line lengths, quality of the line and other performance attributes should be measured, viewed, and analysed remotely.
Mobile & Wireless Access
In 1894, when Italian Guglielmo Marconi invented a system, which could send messages through the air, only few people were impressed. After all, Marconi's crude prototype could only send signals a hundred yards -- hardly a match for the increasingly popular telephone. The Italian government even turned down his offer of first rights because they saw no use for the technology.
Who would have known such a weak transmission method would pave the way for so many disruptions in following centuries? Everything from television to cellular phones, even now 100 years later, wireless is still opening up new markets and changing the way individuals, governments and businesses communicate and operate.
Marconi's wireless invention truly represents what some people call "disruptive technologies." Wireless local area networks (WLANs), are a so-called disruptive technology that will have the same impact on the networking industry that wireless phones did to the telecommunications industry.

Figure  SEQ Figure \* ARABIC 10 - Voice Service Subscribers - Fixed Vs Mobile
The main factor behind this tremendous growth has been wireless medium’s ability to satisfy substantially two “any” component of the three that comprise the ultimate goal of telecommunications: “Any information, any time, any place”. Wireless communication system provides anytime, anywhere communications.
The future of wireless lies in faster, more reliable methods of transferring data and, to a lesser extent, increased use of voice commands and audio improvements. In today’s world wireless communication is no longer just about cell phones, instead it is the direction that telecommunications seems to be heading to provide all possible ways to keep information place-independent to a lesser or a greater extent.
 EMBED MSPhotoEd.3 
Figure  SEQ Figure \* ARABIC 11 - Worldwide Subscriber Base for Wireless Broadband Services
Appeal of Wireless
Some of the inherent characteristics of Wireless communications system, which make it attractive for users, are
Mobility Wireless enables better communication, enhances productivity and enables better customer service. A Wireless communications system allows user to access information beyond their desk, and conduct business from anywhere.
Reach Wireless communication systems means people are better connected, and are reachable where ever they are.
Simplicity Wireless communications system is faster and easier to deploy than cabled networks. Installation can take place without hassles and ensuring minimum disruption.
Flexibility Wireless communications system provides flexibility as a subscriber can have full control of his communication. Customer is always accessible irrespective of his location, activity or time of the day, provided he is willing.
Cost
The initial costs of implementing a Wireless communications system compares favourably to traditional wireline or cable system. Communications can reach where wiring is infeasible or costly, e.g. rural areas, old buildings, battlefield, vehicles etc. Further wireless service pricing is rapidly approaching wireline service pricing due to falling service provision cost.
Global Accessibility
Roaming makes dream of global accessibility a reality, as today most parts of the globe are well covered by one wireless services provider or other. Also roaming service provided by service providers allow flexibility to stay connected anywhere.
Smart Service Capability
Wireless communications system due to its fundamental feature of intelligent terminal device, which is capable of processing data, is capable to deliver various smart services like SMS, MMS, M-Banking, etc. However, sophistication and quality of service varies substantially depending upon capability of service providers as well as customer side device.
Cultural
Wireless communications system is a personal device, whereas wireline is more of a location device i.e. office or residence. There are many more cultural positives of wireless, not to deny negatives as well, but we will limit this discussion, leaving it for obvious reason of keeping focus on topic at hand.
WLAN
WLAN is an acronym for wireless local-area network, also referred to as local-area wireless network (LAWN). It is a type of local-area network that uses high-frequency radio waves rather than wires to communicate between nodes. Wireless LANs are slowly but surely starting to take hold in homes, small businesses and corporations as well. When you compare cost of WLAN interface cards and access point with that to the cost of wiring up a cubicle and the inflexibility of that wired connection, it is easy to see why people are gravitating towards wireless LANs.
Performance ranges from standard Ethernet performance down to perhaps 2 Mbps if there is significant interference or if the user strays too far away from an Access Point. If the Network Interface Card (NIC) and Access Point support roaming, a user can wander around a building or campus and the NIC will automatically switch between Access Points based on the strength of the beacon signal it receives from nearby Access Points. The strongest signal wins.
Growth in WLANs can be traced to the creation and adoption of 802.11, the IEEE technical standard that enabled high-speed mobile interconnectivity. After sustained efforts by the WLAN Standards Working Group, the IEEE ratified a new rate standard for WLANs, viz. 802.11b, also known as Wi-Fi (Wireless Fidelity). Some other WLAN technologies are WiMAX, Bluetooth, HomeRF and Open Air.
Wireless Networking Standards
There are a plenty of new wireless networking standards, as is the case with wireless technologies. The table below provides some quick information on most of them and can also help to differentiate between the available wireless networking standards. One can also find further information on wireless networking standards in  REF A1 \h  \* MERGEFORMAT Appendix 1
at the end of this book.
StandardData RateModulationSecurityIEEE 802.11 Up to 2Mbps in the 2.4GHz band FHSS or DSSS WEP & WPA IEEE 802.11a
(Wi-Fi) Up to 54Mbps in the 5GHz band OFDM WEP & WPA IEEE 802.11b
(Wi-Fi) Up to 11Mbps in the 2.4GHz band DSSS with CCK WEP & WPA IEEE 802.11g
(Wi-Fi) Up to 54Mbps in the 2.4GHz band OFDM above 20Mbps, DSSS with CCK below 20Mbps WEP & WPA IEEE 802.16
(WiMAX)Specifies WiMAX in the 10 to 66 GHz rangeOFDMDES3 and AESIEEE 802.16 a
(WiMAX)Added support for the 2 to 11 GHz range.OFDMDES3 and AESBluetooth Up to 2Mbps in the 2.45GHz band FHSS PPTP, SSL or VPN HomeRF Up to 10Mbps in the 2.4GHZ band FHSS Independent network IP addresses for each network. Data is sent with a 56-bit encryption algorithm. HiperLAN/1 (Europe) Up to 20Mbps in the 5GHz band CSMA/CA Per-session encryption and individual authentication. HiperLAN/2 (Europe) Up to 54Mbps in the 5GHz band OFDM Strong security features with support for individual authentication and per-session encryption keys. OpenAirPre-802.11 protocol, using Frequency Hopping and 0.8 and 1.6 Mb/s bit rate CSMA/CA with MAC retransmissionsOpenAir doesn't implement any encryption at the MAC layer, but generates Network ID based on a password (Security ID)Table  SEQ Table \* ARABIC 2 - Features of Wireless Networking Standards
WLANs’ Working
Wireless LANs (WLANs) use electromagnetic radio waves to transport data between computers in a Local Area Network (LAN), without the limitations set by hard wired network cable or phone wire connection.  Whilst simple optical links are commercially available, radio is presently more useful since it is not strictly restricted to line-of-sight paths.
Radio Networks
Radio waves are often called radio carriers when they are used to carry information. The data to be transported is superimposed on the radio carrier by various modulation techniques, which allow the data to be faithfully reconstructed at the receiving end. Once data is superimposed (modulated) onto the radio carrier, this combined "radio signal" now occupies more than a single frequency since the frequency components or spectra of the modulating data add frequency bandwidth to the basic carrier (in direct proportion to its information content or bit rate).
The frequency range, which is needed to accommodate a radio, signal with any given modulation bandwidth is called a channel. Radio receiver techniques can select one radio channel while efficiently rejecting signals on other frequencies. Many radio signals to and from many users can thereby co-exist in the same place and time without interfering with each other if the radio waves are transmitted at minimum necessary power within different radio channels.
In a typical commercial WLAN configuration a radio transmitter/receiver (transceiver) called a Wireless Access Point (WAP), connects to a wired network from a fixed location using a standard Ethernet (IEEE 802.3) cable connection. WAP typically consists of an antenna (can be internal or external) attached with electronics connected to a co-axial cable fed.
At a minimum, the access point receives, buffers, and transmits data between the WLAN and the wired network infrastructure. The Wireless Access Point (WAP) is usually mounted high and may be mounted essentially anywhere that is practical as long as the desired radio coverage is obtained.
A single commercial wireless access point, depending on technology used, can support a group of simultaneous users typically at a range of not more than a couple of hundred metres (with specification IEEE 802.11) in free space and much less via obstructions at the very restricted non interfering power levels therein specified for licence free users.
Considering case of Wi-Fi WLAN in 2.4GHz band, practical and inexpensive improvements to the antenna systems alone can enhance distant up to 25 Km (18 miles) line-of-sight distance. Much better performance (over obstructed paths) may be had with (sector directional) gain antenna systems and licensed power amplification. Further, access points can extend the range of independent WLANs by acting as a repeater, effectively doubling the distance between wireless users.
End users access the WLAN through WLAN Adapters, which are implemented as PCIMCIA cards in notebook computers, or use ISA or PCI adapters in desktop computers or fully integrated devices within hand-held computers. WLAN adapters provide an interface between the client network operating system (NOS) and the airwaves (via an antenna). The nature of the wireless connection is transparent to the NOS.
Wireless Broadband - The Communications Revolution
We are at the dawn of a communications revolution. Concepts that once resided in the realm of science fiction are now being transformed into the reality of everyday experience. Wireless technologies are one of the major drivers of this revolution. These networks are largely invisible to consumers, yet powerful enough to transform their lives. Wireless broadband offers consumers a new freedom – the ability to communicate and connect with the world anytime, anywhere:
Freedom to access
Consumers using wireless broadband technologies have the freedom to access the high speed Internet from coffee shops, on moving trains, and in their own backyards.
One device now opens up the world.
Consumers can access the Internet using a single device – to make phone calls, pay bills electronically, and access entertainment and data – all with a seamless high-speed wireless connection

Figure  SEQ Figure \* ARABIC 12 - Use of Mobile Data
Attraction of Wireless Broadband
Wireless is a unique broadband solution for several reasons. These include providing both mobility and portability, efficiently connecting devices within short distances, and bridging longer distances more efficiently than wireline and cable technologies. This combination of mobility and portability can make broadband access both seamless and ubiquitous.
Just as wireless voice technologies have enabled users to move through their daily lives without having to worry about being accessible, they are always connected irrespective to how and where they are. Similarly wireless broadband technologies can free them from troubles of gaining access to information while on move.
Wireless technologies also can be more efficient and in addition, wireless technologies have the ability to reach remote geographic areas, particularly rural and underserved areas that often cannot be efficiently served by other technologies. Because the deployment of wireless technologies does not require running copper, cable, or fibre lines to individual homes, the costs of deployment often are lower than those associated with these technologies.
Further, wireless technologies frequently are a more cost effective solution for serving areas with less dense populations, and provide rural and remote regions new ways to connect to critical health, safety, and educational services.
Need for Wireless Broadband
One unique characteristic that distinguishes wireless broadband from other broadband technologies is its ability to provide both portability and mobility. These attributes enable the kinds of seamless connectivity – at both short and long distances – that people seek. In addition, wireless broadband plays a critical role in ensuring that broadband reaches underserved areas, where it often is the most efficient means of delivering these services. Many applications are today possible because of wireless broadband. The applications include:
Hotspots and hotzones (e.g., stores, airports, city, localities),
Community networks (e.g., municipalities, counties, government),
En route (e.g., on trains, highways and ferries)
Public safety applications (e.g., integrating police in the field with their departments, enabling quicker communications of emergency information)
Surveillance applications (e.g., ensuring building security, securing military bases, improving transportation monitoring, preventing theft in shopping centres)
Personalized mobile access to music and video entertainment
Educational applications (e.g., creating a “wireless campus” that connects students with school networks).
These examples are but a few of the wireless broadband applications that exist today. Tomorrow promises even greater growth and innovation.
Broadband Wireless Access
Today’s wireless world is, at an increasing pace, being enriched or assailed - depending on the point of view - by new technologies of every sort. First came Wi-Fi and raised a discussion whether or to what extent this new technology would substitute for or supplement 3G technology. Recently, WiMAX and Mobile-Fi have gained much attention raising similar discussions as to their disruptiveness. Some see these technologies as being disruptive, while others focus on their complementarities with other access technologies.
There’s no doubt the world is going wireless faster and more broadly than anyone might have expected. Present day reality is that billions of people will gain broadband Internet access wirelessly within next few years. Broadband wireless presents the most viable opportunity to improve communications for more than one and a half billion people that currently enjoy Internet access and to newly connect the next few billion users.
Not since the early days of the Internet era have there been so many new opportunities. So much momentum is being generated around broadband wireless access, making some of the top industry leaders including the author believe that “Broadband Wireless” will eventually displace Internet as biggest disruption.
It will require a virtual plethora of solutions, technologies, components, platforms, infrastructure and services to meet this demand. “Broadband wireless” is a continuum of co-existing, overlapping technologies that enable wireless high-speed communications. Different BWA technologies like Wi-Fi, WiMAX, 3G and Ultra-Wideband (UWB) can deliver high-speed communications and Internet access.
The transition to wireless broadband, which started as trivial initiatives, to conceive radio enabled exchange mechanism for electronic data, in research labs and sustained by nothing but zeal and enthusiasm of researchers and academicians has covered a lot of ground since then. Today the thrust for the broadband wireless revolution is not coming from academicians, as was the case in 1990s, but from consumers and businesses worldwide who increasingly expect to enjoy wireless computing and communications anytime, anywhere.
BWA makes business sense
Providing cost effective, affordable wireless bandwidth (almost) everywhere is one of the key success factors for future wireless systems. There are quite a few benefits that make the implementation of wireless solutions very attractive. Some substantial benefits of using wireless technologies are:
BWA technologies have implicit advantages such as an ability to serve the customer everywhere and offer right capacity at right cost and remain connected on the move.
BWA is scalable in capacity and coverage, an imperative as requested services evolve towards increasingly bandwidth hungry applications. BWA promises high-speed data, voice and video services.
BWA offers last-mile connection, as many customers are outside the range of DSL's or broadband cable reach, so with wireless broadband these barriers can be lifted and new customers can be captured.
BWA offers faster time to market, and lower Total Cost of Ownership. Further it is faster to deploy, and more flexible, thus it gives an alternative service to customers who are not satisfied by their wired broadband.
BWA will enable information flow across geographical areas that are unreasonable in terms of distance, cost, access, and/or time. The inherent nature of wireless is that it doesn't require wires or lines to accommodate the data/voice/video pipeline.
Businesses can generate revenue in less time through the deployment of wireless solutions because a wireless system can be assembled and brought online in as little as two to three hours.
Wireless technologies play a key role in quickly and reliably extending the reach of cable, fibre, and DSL markets, while also providing a competitive alternative to broadband wire line.
A lot of things are happening in this space, with constantly evolving applications, technologies, business models and regulatory environment BWA promises an exciting journey to the future.
Broadband Wireless Networks
Wireless networking technologies range from global voice and data networks, to infrared light and radio frequency technologies optimised for short-range wireless connections. Devices commonly used for wireless networking include portable computers, desktop computers, hand-held computers, personal digital assistants (PDAs), cellular phones, pen-based computers, and pagers. Wireless technologies have evolved substantially over the past few years and depending on their range can be classified as

Figure  SEQ Figure \* ARABIC 13 - Wireless Network Types
Wireless Wide Area Network (WWAN)
Designed to enable users to access the Internet via a wireless wide area network (WWAN) access card and a personal digital assistant (PDA) or laptop. While data speeds are very fast compared with mobile telecommunication technology data rates, their range is also on higher side. Cellular and mobile networks based on CDMA and GSM are good examples of WWAN.
Wireless Local Area Network (WLAN)
Designed to enable users to access the Internet in localized ‘hotspots’ via a wireless local area network (WLAN) access card and a personal digital assistant (PDA) or laptop. While data speeds are relatively fast compared with mobile telecommunication technology data rates, their range is short. Among the WLAN solutions Wi-Fi can be safely termed most widespread and most popular.
Wireless Personal Area Network (WPAN)
Designed to enable users to access the Internet via a wireless personal area network (WPAN) access card and a personal digital assistant (PDA) or laptop. While data speeds are very fast compared with mobile telecommunication technology data rates, their range is very short.
TechnologyMax SpeedAvailableAdvantagesDisadvantagesBottom-lineBluetooth723.2Kbps2001Low costInterference, securityReplace cablesInfrared115KbpsIn useVery low costLOSReplaced by Bluetooth802.15.1723.2Kbps2002Low costInterference, securityFormalized Bluetooth802.15.3 High rate>20Mbps2003High data ratesExpensive, not backwards compatibleCase not proven yetTime Modulated Ultra Wideband (UWB)>20Mbps2006High data rates, no dedicated frequencyNot approved, expensiveUnder hyped. Potentially revolutionary technology.Table  SEQ Table \* ARABIC 3 - Wireless Personal Area Network (WPAN) Technologies
Wireless Region Area Network (WRAN)
Designed to enable users to access the Internet and Multimedia Streaming services via a Wireless Region Area Network (WRAN). While data speeds are very fast compared with mobile telecommunication technology data rates as well as other wireless network technology, their range is also quite substantial. Specific charter of WRAN working group is to "develop a standard for a cognitive radio-based air interface for use by license-exempt devices on a non-interfering basis in spectrum that is allocated to the TV Broadcast Service." WRAN, which is presently in its infant stage, is most recent addition to a growing list of wireless access network acronyms defined by coverage area. Due to relevance to the subject in hand we will deal with two flavours of wireless networks WLAN and WWAN.

Figure  SEQ Figure \* ARABIC 14 - Various BWA Technology
Broadband Wireless Technologies
The huge explosion of wireless technology over the last decade has captured the imagination and innovativeness of technologist around the world. The need for mobility in an ever-changing environment is of paramount importance. From mobiles to laptops and PDAs (Personal Digital Assistance), the list of wireless technological devices is endless. The BWA technology though in its early stage has the ability to mature into a very capable, integrated technology. These technologies are
Fixed Wireless Access (FWA)
As the name suggest FWA provides fixed wireless broadband access. Such networks are known as "fixed wireless" since the receivers are in fixed locations. Some vendors have coined the phrase "wireless DSL" to refer to their service offering because they are able to provide fairly high-speed connections, similar to various flavours of DSL, at reasonable prices.
There are basically two types of FWA systems based on their network topology referred as point-to-point (P-P) and point-to-multipoint (P-MP). Again as the name suggests P-P is the one in which a carrier’s base station can provide wireless broadband access to a single subscriber. While in case of P-MP base station can provide wireless broadband access to multiple subscribers.
The race to become the last mile access method of choice (referred to as local loop) is becoming fierce, this makes wireless a viable alternative to (wired) DSL, cable, and fibre optic for reaching into a home or office. Today, there are technologies emerging that take advantage of line of site transmission capabilities long thought out of date. Whereas line of site technology was more often than not "point to point," today's advances allow for point to multipoint, providing a much more cost effective service to be available. Some of these technologies can even support obstructed transmission paths, more common to typical communities.
Point-to-point (P-P): Current FWA and local service implemented with duplex point-to-point (P-P) microwave and millimetre wave systems include fixed versions of mobile cellular systems, competitive local exchange carrier (CLEC) provided Broadband Wireless Access up to 155MB/s capacity from business premises to long distance carriers and satellite terminals, private industrial and local government networks, and very small aperture terminals (VSAT) links. Future millimetre wave point-to-point systems will include a greater variety of narrowband and broadband links from fibre network terminations to CLEC subscribers, and private networks.
Point-to-multipoint (P-MP): Current FWA systems like LMDS or MMDS include simplex broadcast entertainment distribution, simplex educational television, and simplex wireless for television distribution.
Local Multipoint Distribution Service LMDS: LMDS is a high bandwidth wireless networking service in the 28-31 GHz range of the frequency spectrum and has sufficient bandwidth to broadcast all the channels of direct broadcast satellite TV, all of the local over-the-air channels, and high speed full duplex data service. Average distance between LMDS transmitters is approximately one mile apart.
Multichannel Multipoint Distribution Service MMDS: MMDS operates at lower frequencies, in the 2 GHz licensed frequency bands. MMDS has wider coverage than LMDS, up to 35 miles, but has lower throughput rates. Future P-MP fixed services will include the duplex MMDS and 28/31 GHz.

Figure  SEQ Figure \* ARABIC 15 - Cellular Wireless Technology Evolution
3G
3G Cellular is long range, mobile, reliable, plug-n-play, secure, private, and manageable data solution based on UMTS – Universal Mobile Telecommunication System.
Wideband Code Division Multiple Access (WCDMA) is the access scheme used in UMTS. Frequently, WCDMA is used as a synonym for UMTS. It was developed in order to create a global standard for real-time wireless multimedia services that ensures international roaming. A specific allocation was made in the 2 GHz band for 3G telecom systems with the support of ITU (International Telecommunication Union). The work was later taken over by the 3GPP (3rd Generation Partnership Project), which is the present WCDMA specification body with participants around the world.
Wi-Fi
Wi-Fi stands for Wireless Fidelity and is based on the IEEE 802.11 standard. We have seen Wi-Fi deployment over the last years, privately in companies as well as homes, and also in public areas such as hotels, airports and cafes, providing easy access to the Internet. Wi-Fi is a local area network technology that was originally thought to replace the thousands of miles of LAN (Local Area Network) cables that run across all offices, universities and homes. Instead of using a cable to connect to the local network, with Wi-Fi, it is possible to connect wirelessly with the use of a wireless card on the PC and the network access point.
The 802.11b is still currently the most popular Wi-Fi standard, giving transmission rates of up to 11Mbps. The newer 802.11g standard, which allows for transmission of up to 54Mbps, is gaining in popularity and is fully backward compatible with the earlier 802.11b version. These two operate in the 2.4GHz frequency spectrum. The 802.11a standard gives up to 54Mbps at 5GHz.
WiMAX
Work on the WiMAX or the IEEE 802.16 standard started in 1999. It is a broadband wireless access standard that was originally positioned as a complement to Wireless Fidelity (Wi-Fi). While Wi-Fi was seen mainly as a cable replacement technology for the numerous cables and wires required for LAN connectivity, WiMAX was seen as more of a Metropolitan Area Network (MAN) technology providing a much larger coverage. WiMAX, in fact, comes in two forms, a so-called ‘fixed WiMAX’ and a ‘mobile WiMAX’. Mobile WiMAX is a relatively new revision of the 802.16 standard and has not been standardised as yet. In 2004, both these standards were combined into the 802.16 rev.2004. The mobility option is of interest to many players in the mobile market. New potential operators see this as a technology possibility that could be deployed as an alternative to 3G networks. Existing 3G or other cellular network operators could see this as a potential threat or as a complement to their cellular product.
As it is nowadays, wire line operators find it more and more expensive and not profitable to deploy fibre to far away office clusters and residential areas. WiMAX is seen as a possible alternative to expensive cable and fibre deployment. WiMAX, being a wireless broadband access standard, will be able to provide broadband services, on par with fibre or cable access. It is faster to deploy and less expensive than wire line deployments of fibre and cable and it also offers operators more flexibility in terms of deployment time frame and possible installation areas.
Mobile-Fi
Another broadband wireless access technology is Mobile-Fi or MBWA, based on the IEEE 802.20 standard. This is the newest of the IEEE wireless standards and will operate in the licensed bands below 3.5GHz and have broadband Internet access speeds exceeding that of today’s DSL and cable access options. The IEEE introduced the 802.20 and its goal was to address the optimisation of IP data transportation at over 1 Mbps per user and in a mobile environment of up to 250km/h.
Specifications for this standard are still in their early stages and it will take some time before this standard will take off. However, some people have come to view Mobile-Fi as being a competitor to 3G because of its built-in mobility option that was planned from the beginning of its conception. If Mobile-Fi is able to support mobility of users as well as providing a broadband connection, it is likely that 3G will lose revenue to this technology. It is thus worrying for all those parties involved in 3G deployments such as network operators and equipment manufacturers. Further information on wireless broadband standards is provided in  REF A1 \h  \* MERGEFORMAT Appendix 1

Figure  SEQ Figure \* ARABIC 16 - Future of Broadband - Multi Technology Access
WiMAX - Broadband for Masses
Wireless broadband access to the Internet has recently witnessed explosive growth. Much of this growth has come from the rise of wireless networks. Wireless networks today are being widely used in markets such as education, healthcare, manufacturing, retail, hospitality, government, and transportation.
A new wireless network transition is gathering momentum in the shadows of the accelerating trend in wired broadband. The rapid growth of wireless infrastructure has generated an interesting set of problems for operators, users, and regulators. Traditional operators have been forced to consider multiple business models to generate viable revenue streams.
Some of these models are similar to traditional ISP-type models that marked the spread of dial-up Internet access. Committed individuals, community-based networks, and public networks, on the other hand, are taking a radically different approach by seeking to provide free wireless access.
Irrespective of whatever model is taken for bringing benefits to masses the basic service vision must have three key characteristics -
High Throughput & Reach
Ubiquitous & Predictable
Affordable & Reliable
WiMAX have throughput of 75MBps and range of 31 miles, future versions will be ubiquitous and without second thoughts they will be affordable. Having had a few false starts in an earlier incarnation as purely fixed service, and having been catalysed by fundamental advances in wireless technology, the concept of true broadband, wide-area wireless is once again coming to the fore. Many industry players believe a new class of networks and services will be rolled out very broadly over the next several years. Leading indicators from recent commercial network deployments suggest the prospects are indeed exciting.
Affordable Broadband
Once WiMAX certified equipment is available from a number of suppliers, increased competition can occur, and with volumes of units shipped, more attractive price points can be reached. If WiMAX continues to gain more support from the industry, it can also provide broadband access in remote regions and developing parts of the world where basic voice or broadband access using fixed line service is not economically feasible. As the WiMAX will be available as System on Chip it will provide benefits of extraordinary cost and future innovation based on Moore’s law.
WiMAX will bring broadband to the masses.


Chapter 2
WiMAX – The Disruptive Technology
A disruptive technology is a new technological innovation, product, or service that eventually overturns the incumbent dominant technology in the market, despite the fact that the disruptive technology is both radically different from the leading technology and that it often initially performs worse than the leading technology according to existing measures of performance.
Disruptive technologies are technologies that not only create new industries, but also eventually change the world. A disruptive technology comes to dominate an existing market by either filling a role in a new market that the older technology could not fill (as more expensive, lower capacity but smaller-sized hard disks did for newly developed notebook computers in the 1980s) or by successively moving up-market through performance improvements until finally displacing the market incumbents (as digital photography has come to replace film photography).
Disruptive technologies often come from outside the mainstream. The light bulb was not invented by the candle industry looking to improve output. Owners of established technologies tend to focus on making successive incremental improvements to performance of their own products, referred as sustaining technology, avoiding the potential threat to their own businesses. Those who profit by bringing innovation to their customers must keep track of movements outside established markets. Something such as the personal computer or the Internet is always just around the corner.
Disruptive technologies are not disruptive to customers, and often take a long time before they are significantly disruptive to other manufacturers, so they are often difficult to recognize. It is often entirely rational for incumbent companies to ignore disruptive technologies, since they compare so badly to existing approaches, and the initial markets for a disruptive technology are often very small compared to the main existing market for the technology. Even if a disruptive technology is recognized, existing businesses are often reluctant to take advantage of it, since it would involve competing with their existing (and more profitable) technological approach.
One could see a disruptive technology as one that introduces technological qualities that are overwhelmingly better than the original product and thus disrupts the market of the original product. A disruption can be a new market disruption or a low-end disruption. As the name implies, a new market disruption is one that targets a market that was not addressed before. For example, if a product was originally only addressing retail urban clients, a product that addressed rural or bulk sale clients, in this case, could represent a new market disruption. A low-end disruption, on the other hand, addresses segments of the population that could not afford the original product or saw no use for such advanced technology that came with the original product. A low-end disruption makes available to users products they once could not afford or did not see the point to buying.
A technology must have certain characteristics for being considered as disruptive. Experiences from the past have shown that 6Cs differentiate disruptive technologies from others. These 6Cs, which can also be classified as characteristics of disruptive technologies, are:
Comfortable (To use)
Cheap (To acquire and deploy)
Capable (To target masses)
Competitive (Against established products)
Commercialised (In emerging market)
Collaborative (In technological progress)

Figure  SEQ Figure \* ARABIC 17 - Disruptive Technology Performance Curve
Impact of Disruption
Generally any market is made up of incumbent companies and new market entrants. While the incumbents are those, already present in the market and have built up their customer bases from past dealings with clients over a period of time, the new market entrants do not have any existing customer bases to build up from. The incumbents address the old market, while the new entrants address a new (unformed) market.
Substantial cost is what drives the incumbent’s profitability southwards hence lower return on investment, while new entrants due to efficiency and new technology are able to work with low costs and hence better returns. Another interesting aspect is that the incumbents due to their monopolistic approach and complacency are not flexible, while the new entrants are flexible and are able to adapt in any way the market causes them to.
What this means is that the incumbents would lose a lot if they decided to move down the value chain for tapping less profitable market, while new entrants would have nothing (or almost nothing) to lose if they addressed a new (non-existent) market. A new disruptive technology would impact this equation a lot, for simple reason that it will lower the barrier to entry, hence increase competition, as well as will put substantial pressure on margins.
Sustaining Technology”!Disruptive TechnologyIncremental improvements Technology qualitiesSimpler, more reliable, more convenient Predictable - can be modelled and forecast MarketUnknown & orders of magnitude larger than "expected" Quantified, accurate estimates InformationPure speculation - none exists Business as usual Management perceptionDistraction from business as usual Addresses important customer needs Customer needsNiche needs at best Positive impact ProfitNegative Impact "Wait until market is large enough to be interesting" Management
TendenciesEntrepreneurial High dependence on existing resources, supply chains, & products DependenciesNone or very few dependencies "Fits" within existing Value networkTotally different and usually not obvious or apparent Completely identified Application and usesNot apparent or foreseen Table  SEQ Table \* ARABIC 4 - Sustaining Technology Vs Disruptive Technology
Technology Life Cycle
Most of the technology tends to follow an evolutionary cycle. Understanding its nature can help us predict the timing of radical change, which is needed for continuous improvement of performance. In general the cycle begins with a technological discontinuity or blur, which represents a new possibility.
Each technology has its own life cycle.
The beginning of any technology cycle is marked with a high rate of innovation. Generally when a new technology disruption takes place, many different versions of the new technology are introduced. However, variation ceases as one of the designs becomes dominant or after the establishment of an industry standard. Market forces leads to acceptance of one such version, which is accepted by the industry as a standard, this is termed as “Dominant Design” by Abernathy and Utterback.
This starts a retention state for the product, a period marked by incremental change as well as architectural innovation with involvement of industry players, who join hands and continues the technology improvement, which may also lead to taking the same product to the different markets. This phase is termed as the stable and mature stage. The innovation focus shifts from the product to the production thus fostering process innovations. Finally, the whole cycle starts over with a discovery of another technological discontinuity. What awaits then is for the entire cycle to repeat with the new disruptive innovation.

Figure  SEQ Figure \* ARABIC 18 - Technology Life Cycle
Disruption
Sustaining technologies and disruptive technologies take different technology development paths in the same industry. Initially sustaining technologies are the mainstream technology (those technologies which are wildly used at any given point of time). However after a point in time, the performance of the mainstream technology exceeds the performance that is demanded by the low-end market users, which could be due to various factors. At this point a disruptive technological innovation results in a new option being added where the initial performance of the new product is lower than that of the original product.
The new disruptive product will first be able to cater to the requirements of the low end of the market but as the technology improves, it is soon able to address the needs of the high-end market as well. As the disruptive technology grows, it slowly starts to serve the needs of the high-end market and takes over the old product. And this will continue until a new disruptive technology enters the market and the cycle is repeated.

Figure  SEQ Figure \* ARABIC 19 - Sustaining and Disruptive Technology Cycle
Dominant Design
However, a disruptive technology doesn’t become the dominant design on its own right. The dominant design is the culmination of the development of the disruption and this is what is seen by and accepted by the market. It is only through improvements and development on the disruption that a dominant design will emerge. Therefore, for a dominant design to occur, it is usually preceded by first a disruptive technological change, followed by several rounds of incremental and sustaining changes to the original disruption before a true dominant product design can occur.
A dominant design usually means that the industry has come to a consensus on the new technology and a ‘standard’ has been achieved. After the emergence of a dominant product design, the industry will engage in sustaining and incremental technological innovations that result in better attributes of the product. The focus for companies, at this stage, changes from performance enhancing innovations to methods of cost efficiency and differentiation of the product from other similar ones in the market.
Disruption and New Market
The fact that disruptive technologies lead to new markets has caused much interest in industries throughout the years. Whether a technology becomes a sustaining one or a disruptive one really depends very much on individual firms and their reactions to these technologies.
One could say that the whole point of the theory on disruptiveness is to empower company executives in their strategic approaches to new technologies. The purpose is not, as it is most often used, to put ‘labels’ on technologies regarding their sustainability of disruptiveness.
The strategy of a firm in coping with new emerging technologies will steer them towards a disruption or a sustaining change. It is never easy to look at a set of different upcoming technologies or innovations and to decide which of them will be sustaining and which of them will be disruptive to the existing market.
When a firm faces a new technology, it often has the means to react to it, either to treat it as a threat or to treat it as something that would be complementary to its current technology. And, if the new technology proves to be disruptive to them, it is probably because they did not foresee the consequences of their business strategy and, therefore, failed to react to the emerging technology when it first appeared.
This could then be interpreted as a market disruption. But on the other hand, if the strategy had been to adopt and to see the technology as a complement or as one that could work with (instead of against) the existing technology, then the technology could likely be sustaining to the existing market. A technology only becomes a market disruption if a threatened firm does not change its strategy to encompass the new technology.
Innovation for Disruption
The displacement of telegraphy by telephony offers insights into a process of innovation and product market competition that lies at the heart of the next wave of growth in wireless. Growing faster than the market requires that company to win over new, and typically more demanding, customers. This drives companies to work hard to “catch up” with the needs of these more demanding market tiers.
Sustaining innovations are what enable organizations to appeal to more demanding customer segments, and hence to grow. Sustaining innovations can be incremental, year-by-year improvements, or they can be leapfrog-the-competition breakthroughs. Either way, as companies move along their sustaining trajectories, they inevitably “overshoot” at least some and sometimes much of the market, and as a result leave behind those segments whose needs can be satisfied with lower performing and even inferior products.
It is this overshoot that makes disruption possible. Disruptive innovations introduce products that are inferior to currently available products — at least in terms of traditional performance measures. However, they do offer other benefits. In general, disruptive innovations are simpler and more convenient to use, and less expensive than the products and services that tend to dominate mainstream markets.

Figure  SEQ Figure \* ARABIC 20 - Sustained Innovations for Disruption

Technology Strategy
A technological innovation always has some degree of benefit or advantage for its potential adopters, even if it is not very clear or impressive from their point of view. One reason for this is that the technology’s superiority compared to its predecessor is seldom obvious.
Possible advantage however provides motivation for learning more about innovation leading to further reduced uncertainty and finally decision concerning adoption or rejection. Therefore, the innovation-decision process can be seen as an information-seeking and information-processing activity aimed at reducing individual’s uncertainty concerning the advantages and disadvantages of the innovation.
Any product development strategy must be adapted according to both market uncertainty and technology uncertainty. Some cases highlighting the same are
In case of Incremental innovations are for example product changes or improvement. The technology is mature and the customers well defined. An appropriate strategy is straightforward by its nature. Hence process or quantitative-based approach is most suitable.
In case of evolutionary technology innovation, the market conditions are known but the technology unrefined. Therefore the strategy should be learning and technology-based, as immature technology requires long periods of research and development. Evolutionary market innovation, on the other hand, has high market but low technology uncertainties. New market should be studied, thus learning or market-based strategy should be applied.
In case of Radical innovation is the most extreme form of a new product. Neither is the market understood nor the product stable. Experimenting is an essential component in such a situation and the strategy should be focused on learning.
Emerging & Established Technologies
The difference between emerging and established technologies lies in the technological uncertainties, ambiguous market signals and embryonic competitive structure.
These characteristics lead on to the competence destroying nature of emerging technology while it makes obsolete the current knowledge and skills associated with the established technology. New technologies often demand acquiring or developing totally radical new competencies.
However, with several competitive technologies and the constraint on limited resources, the choice of strategically correct technology becomes increasingly difficult. Failure may occur because of technology’s poor performance, inability to scale it to commercially viable production rate, superseding technology becoming available or on the other hand technology being ahead of its time.
Technology Uncertainty
Technology is a means of uncertainty reduction that is made possible by the information about cause-effect relationships on which the technology is based.
Uncertainty means not knowing which issues, trends, decision, and events will make up tomorrow or it is the degree to which a number of alternatives are perceived with respect to occurrence of an event and the relative probability of these alternatives. It is also associated with a lack of predictability, structure and information.
Uncertain of future circumstances results in uncertainty about the whole outcome. Major difficulty in forecast of the future is different interpretation of the present. This leads to a situation in which we have many pasts, several presents and large varieties of possible futures.
Technological uncertainty refers to the extent to which product form, performance and cost are understood. Main questions concerning product are its technical feasibility, defining product’s costs and volume, product’s performance features and their evolvement over time. Other aspects of uncertainty refer to specifying the manufacturing process and clarifying development times and costs.
Diffusion of Innovation
Diffusion is “the process by which an innovation is communicated through certain channels over time among the members of a social system”. Diffusion can be perceived as a special type of communication in which new ideas equate to messages. The term “diffusion” generally includes both planned and spontaneous spread of new ideas. The newness of an idea also means that there is some uncertainty involved.
Financial situation affects innovativeness as well as the attitude toward the innovation. Also the speed of diffusion of a new product is affected by the firm’s innovation strategy. The main determinant factors of the innovation strategy are the technological strategic choices and the entry-strategy choices.
The technology aspect encompasses particularly the product compatibility decisions and competence-enhancing or competence-destroying technological choices. Both of these are usually influenced by such environmental factors as technological change and network externalities.
The main issues of the entry strategy aspect are market segmentation and target selection, the order of entry as whether to be the first to market, the pre-announcement decisions, the market-entry commitment, and the distribution.

Figure  SEQ Figure \* ARABIC 21 - WiMAX Adoption and Acceptance
Technology Adoption
Adopter categories can be classified in five groups:
Innovators
Innovators are eager to try new ideas, but they also have the ability to cope with the uncertainty involved in an innovation as well as to understand complex technical knowledge.
Early Adopters
Early adopters are individuals whose judgement on innovations is valued by their social system. Being not too far ahead of the average individual in innovativeness, early adopters serve as role models for other members of community and are looked to for advice and information.
Early Majority
Early majority has a relatively longer innovation-decision period than the previous two groups. Although willingly adopting new ideas, early majority deliberates for some time before the adoption occurs.
Late Majority
Late majority, on the other hand, is sceptical and cautious toward innovations. Adoption may rather be a result from an economic necessity or increasing network pressure than actual willingness.
Laggards
Laggards typically have scarce social networks and therefore the main point of reference is the past, which offers little incentive for adoption of new ideas. From the business point of view the laggards are rarely an appropriate target segment as they do not contribute to the spread of information, are usually more expensive to service and maintain, and have no loyalty to particular brand.

Figure  SEQ Figure \* ARABIC 22 - Technology Adoption Chasm
Rapidly adopted innovations are usually perceived by individuals as having greater relative advantage, compatibility, trialability, observablity and less complexity. Different rate of adoption can further be explained through the characteristics of innovations, as perceived by individuals. Such characteristics include:
Relative Advantage
Relative advantage is the advantage perceived by the individual compared to the one of the previous idea. It may be due to economic factors, social-prestige factors, convenience or satisfaction.
Compatibility
Compatibility is consistency with the existing values, past experiences and needs of potential adopters.
Complexity
Complexity is the degree of perceived difficulty of using and understanding an innovation.
Trialability
Trialability refers to possibility of trying an innovation on a limited basis, thus reducing uncertainty and enabling learning by doing.
Observablity
Observablity is the general visibility of the results of an innovation.
Broadband Wireless - Technology Advancements
Wireless broadband technologies are helping to fuel the engines of our economy. Indeed, the impact of wireless technologies is magnified by their ability to be coupled with other communications technologies, including wireline, cable, and broadband over power line, and satellite technologies, in ways that enable endless combinations of mixing and matching of technologies to suit the needs of different applications.
Enhancements to current wireless broadband technologies, as well as the burgeoning development of new technologies, are continuing to improve and expand the deployment of wireless broadband. From wireless broadband networks ranging short, medium, or long distances – e.g., those that span from a few feet or yards, to 300 feet, to several miles, or even nationwide – we are witnessing significant technological advances, growth in users, and expansion of portable fixed and mobile applications.
Advances in short-range wireless communications networks
Wireless broadband networks that use unlicensed devices for connecting short distances (e.g., a few feet or yards) among mobile devices (including laptops, PDAs, pagers, televisions, and mobile telephones) and desktop devices are often described as Personal Area Networks (WPANs). These wireless networks increasingly serve as a desirable replacement for wires and cables, and provide seamless interconnectivity among a wide range of devices and the data they can access. We expect significant advances in the coming years in these broadband technologies (e.g., Bluetooth, ultra-wide band) – both in terms of data rates and range of coverage – under the evolving Institute of Electrical and Electronics Engineers (IEEE) 802.15 family of standards and related standards.
Advances in medium-range wireless communications networks
Wireless broadband networks that use unlicensed devices for point-to-multipoint transmissions of distances of fewer than 300 feet, or for point-to-point Internet connectivity using networks that span greater distances (e.g., distances that can reach a few miles) can be described as Wireless Local Area Networks (WLANs). These networks generally involve equipment manufactured in accordance with the IEEE 802.11 family of standards for unlicensed wireless devices, commonly known as “Wi-Fi” (an abbreviation for Wireless Fidelity).
These networks have met with tremendous success, and increasingly have been used by Wireless Internet Service Providers (WISPs) to provide a facilities-based alternative to wireline (e.g., DSL) and cable services to millions over networks that may range in size from small communities, to multiple counties, to multi-regional geographic areas or even larger.
Over the last several years, the number of wireless “hot spots” using Wi-Fi technologies has grown exponentially. In addition, several mobile service providers recently have begun using Wi-Fi hot spots to complement their licensed mobile cellular services. Significant advances are expected in the IEEE 802.11 family of standards, thus enabling further improvements in the broadband data rates, coverage, and performance.
Advances in longer-range wireless networks
Wireless broadband networks that involve point-to-point or point-to-multipoint networks with individual network links that can provide last mile connectivity in metropolitan environments or can span distances of up to 30 miles are often referenced as Wireless Metropolitan Area Networks (WMANs).
Devices deployed in these networks are manufactured in accordance with vendor-specific proprietary equipment or with the IEEE 802.16 family of standards. The IEEE 802.16 standard, first developed in 2001 for fixed wireless systems (e.g., backhaul) operating in the 11-16 GHz frequency range of licensed “upper” bands, continues to evolve. In 2003, IEEE 802.16a – commonly referred to as WiMAX – was developed for operations in lower frequencies in the 2-11 GHz range, including licensed bands as well as bands that permit use of unlicensed wireless devices. More recently, the IEEE 802.16a standard has been extended to include 802.16d, which is also for fixed wireless broadband applications. In addition, the IEEE currently is working to finalize the 802.16e standard, a mobile wireless extension.
In sum, the evolving 802.16 standard holds great promise for future developments in wireless broadband because it can be used for applications in both licensed and unlicensed spectrum, allows communications without the need for line-of-site connections, enables interoperability with different equipment using the same standard, and, in the near future, will encompass both fixed and mobile wireless applications.
Advances in mobile technologies
Over the past year months, wireless carriers have begun to deploy broadband technologies on their mobile cellular networks operating on licensed spectrum, and many have announced plans to launch or expand these technologies in the near future. Using new technologies – such as CDMA 1x EV-DO (EV-DO), Wideband CDMA (WCDMA) (also known as UMTS), UMTS/HSDPA (High Speed Downlink Packet Access), and Flash-OFDM (Orthogonal Frequency Division Multiplexing) – carriers are now, or later this year will be, providing wireless broadband services to millions of Americans at speeds ranging from 300 kbps to close to one Mbps. It is expected, for instance, that networks using EV-DO technologies will cover as many as 150 million Americans by the end of 2005.
Advances in the development of mesh networks
Additional technological advances, such as those associated with mesh networks, may also enable further expansion in the delivery of wireless broadband services. Mesh networks are a relatively new and evolving type of network that will have wireless broadband applications. Unlike more traditional wireless networks, in which each node in the network communicates only with a central antenna or base station, each node in a mesh network can function as an access point and transmit data to nodes in close proximity.
Advances in the development of applications
Along with the advances in wireless broadband technologies, came a host of new and exciting applications. These applications continue to proliferate and empower people. They provide people with more ways to be “more connected” and simplify their communications with work, home, and friends.
While wireless broadband currently represents only a small share of the total market for broadband services substantial growth is anticipated. Growing numbers of people use wireless, future developments such as technological advances, enhancement of features, and the increasing convergence and integration of wireless broadband with other new applications such as video and VoIP will also stimulate significant growth in wireless broadband over both the near and longer term.
WiMAX – The Biggest Disruption
The prospect of broadband Internet access anywhere, at any time, seemed a distant dream, far from the reality for the vast majority of PC, laptops and handheld users. But with WiMAX all set to change the situation sooner than later, watch out if it becomes something users can't live without. WiMAX is one of the hottest wireless technologies around today.
WiMAX development globally is very much in its infancy. Products are only beginning to appear in the market and some trial networks have been deployed. WiMAX systems are expected to deliver broadband access services to residential and enterprise customers in an economical way. Although it has one name, WiMAX is going to be two different market technologies. The first is for fixed wireless and falls under the IEEE 802.16-2004 standard approved last year. The second, for mobile applications, will be under the 802.16e specification expected to be finalized this year.
As of now, fixed WiMAX is capable to become a replacement for DSL or cable or for network backhaul. In the future, WiMAX will transform the world of mobile broadband by enabling the cost effective deployment of metropolitan area networks based on the IEEE 802.16e standard to support notebook PC and mobile users on move.
WiMAX has been marketed by supporters as a cable replacement technology and also as last mile solutions to areas where it is expensive to deploy wired infrastructure. Its aim is to be an alternative to cable technologies such as ADSL or even fibre. In the less developed countries, it is unlikely that wired infrastructure is in place today. Therefore, if the economy permits and if demand exists, a possible alternative to wired technology is to use WiMAX. This is also the case for countries with rugged terrain and where it is not feasible to put in wired infrastructure. WiMAX presents a good alternative to this.
There are still several unanswered questions to the future development of WiMAX. One of these questions is whether to use the unlicensed spectrum or licensed spectrum below 11GHz or from 10 to 66 GHz. Both have advantages and disadvantages and this also is indicative of the quality of service issues and costs of operations. Another question is how WiMAX can be used effectively in a world already filled with so many communication choices. The third question is how operators will react to WiMAX once cheap equipment and handsets become available. It is difficult to predict the road that WiMAX will follow. But it is worth following the progress it makes.
When it was first introduced to the industry, many thought of WiMAX as a possible disruptive technology to traditional mobile technologies such as GSM or 3G. Today, the specifications for the mobile form of WiMAX are still being studied and defined and are expected to be ready by end of 2005. Equipment for the fixed WiMAX solution is expected to hit the market in 3rd quarter of 2005.
There are many advantages of systems based on 802.16, the ability to provide service, even in areas that are hard for wired infrastructure to reach and the ability to overcome the physical limitations of traditional wired infrastructure. The standard will offer wireless connectivity of up to 30 miles. The major capabilities of the standard are its widespread reach because of which it can be used to set-up a metropolitan area network and its data capacity of 75 mbps.
This High-speed wireless broadband technology promises to open new, economically viable market opportunities for operators, wireless Internet service providers, and equipment manufacturers. The flexibility of wireless technology, combined with high throughput, scalability and long range features of the IEEE 802.16 standard help fill the broadband coverage gaps and reach millions of new residential and business customers worldwide.
It’s Different
WiMAX is different from what ever we have seen so far in communication. These technologies play a unique role in bringing broadband to everyone, everywhere, at any time. Unlike other broadband technologies, WiMAX gives you “broadband on the go.” Its uniqueness lies in its combined mobility and portability. Either on a freestanding basis, or when combined with other broadband networks, wireless broadband imparts new freedom to users, providing the kinds of seamless interconnectivity that users increasingly seek.
A very important characteristic of the WiMAX standard, which defines and suggests key profiles for the MAC layer, providing excellent applicability qualities is that it generates predefined standardized profiles while at the same time also allows for vendor customization.
This is very important for WiMAX (or most of the communications technologies) success as it provides benefits of standardization, like cost benefits and competitive advantage, at the same time provides enough flexibility to meet specific or localized market needs, or to allow the vendor to differentiate products with value-added features.
WiMAX will plays a critical role in bringing the benefits of broadband to rural and underserved areas in the country, where it often is the most efficient means of delivering these services.
Unlike narrowband wireless:
WiMAX-certified broadband access, unlike existing narrowband wireless solutions, will enable high-bandwidth metro area networks for enterprise, small business and home users. Further it will act as remote area communication facilitator providing backhaul networks for cellular services and LAN connections. WiMAX is
Multi-Mbps, not limited to a few 100 kbps
Always on, bandwidth on demand, not circuit oriented
Unlike proprietary broadband wireless:
WiMAX-certified broadband access, unlike existing proprietary broadband wireless solutions, will cost much less. Further, unlike more affordable proprietary broadband wireless solutions it won’t have restrictions of LOS. WiMAX can work satisfactorily in
Fading, interference, multipath, NLOS and OLOS conditions
Unlike broadband wireline:
WiMAX-certified broadband access, unlike existing wireline broadband solutions, will serve remote areas eliminating need for truck rolls. Installation and device costs for WiMAX-certified subscriber stations are expected to be much lower than the existing customer premise equipments stations used in broadband wireline deployments. WiMAX can provide
Low cost alternate to wireline solution
Opportunity to cherry pick customers from large geographical areas
Unlike WLAN:
WiMAX though is very much influenced by Wi-Fi efforts, especially standardization and certification, however unlike existing WLAN solutions, will serve more customers spread across greater areas at higher throughput in more secured conditions. It is
Scalable to hundreds of users
Spectral efficient
Support Quality of Service requirements – not just best effort
Special Attributes of Wireless Broadband
WiMAX - Disruptive Capabilities
In recent years, broadband data communications has seen an enormous demand and growth. Wireless Broadband access is a fast-growing telecommunication market globally and has a huge market potential. WiMAX the high-performance wireless access technology is being sought for its disruptive capabilities, enabling it to reach new untapped markets and provide additional value to existing market. Some of these capabilities are:
WiMAX is optimised for NLOS and self-installing systems, which mean users don’t need extra skills to make this system work.
WiMAX is aided by SoCs, RFICs, interoperability and volume, which will drive system costs down to levels unseen in the past. Further doesn’t need truck rolls for installation.
WiMAX provides optimum price-performance for Broadband Wireless Access Large wireless MAN deployments with hundreds of customers per base station and large ranges.
WiMAX more spectrally efficient, offers carrier grade QOS, prioritisation of voice/video and data and higher network capacity.
WiMAX is viable to deploy in markets where wired broadband is not cost effective i.e. under served and developing world, allows spread of broadband more quickly, allows higher speeds farther away.
WiMAX forms basis for future evolution to mobile broadband wireless access, the next generation mobile WiMAX standard (802.16e), Mobile WIMAX will be available starting mid-2006 in trials, commercial deployments in 2007.
What is WiMAX?
Commonly referred to as WiMAX or less commonly as WirelessMAN"! or the Air Interface Standard, IEEE 802.16 is a specification for fixed broadband wireless metropolitan access networks (MANs) that use a point-to-multipoint architecture. Published on April 8, 2002, the standard defines the use of bandwidth between the licensed 10GHz and 66GHz and between the 2GHZ and 11GHz (licensed and unlicensed) frequency ranges and defines a MAC layer that supports multiple physical layer specifications customized for the frequency band of use and their associated regulations. 802.16 supports very high bit rates in both uploading to and downloading from a base station up to a distance of 30 miles to handle such services as VoIP, IP connectivity and TDM voice and data.
Loosely, WiMAX is a standardized wireless version of Ethernet intended primarily as an alternative to wire technologies (such as cable modems, DSL, and T1/E1 links) to provide broadband access to customer premises. This application is often called wireless last/first-mile broadband because the transmission distances involved are typically of this order and the engineering problem is to bridge the final gap between the customer premises and the telco’s or service provider’s main network. The technology is specified by the Institute of Electrical and Electronics Engineers Inc. (IEEE), as the IEEE 802.16 standard.
More strictly, WiMAX is the Worldwide Microwave Interoperability Forum, a non-profit industry body dedicated to promoting the adoption of this technology and ensuring that different vendors’ products will interoperate. WiMAX will do this through developing conformance and interoperability test plans, selecting certification laboratories, and hosting interoperability events for 802.16 equipment vendors. But WiMAX is such a convenient term that people tend to use it for the 802.16 standards and technology themselves, although strictly it applies only to systems that meet specific conformance criteria laid down by the WiMAX Forum.
The 802.16 standard is large, complicated, and evolving, and offers many options and extensions, so interoperability is a major issue that must be addressed. In particular, one extension known as 802.16a became the focus of a lot of industry attention because it should be the easiest and most useful to implement. So it is likely that when people talk loosely of WiMAX they are referring to the technology for fixed wireless specified by 802.16a and its later version 802.16d.
802.16 is one of a family of technologies being standardized by the IEEE (with other bodies, such as the European Telecommunications Standards Institute (ETSI), whose Hiperman standard is harmonized with 802.16) to create wireless versions of Ethernet that can operate over distances from a few meters to tens of kilometres -- from personal area networks (PANs), through local area networks (LANs) and metropolitan area networks (MANs), to wide area networks (WANs). 802.16 is the MANs member of the family.
Why WiMAX
WiMAX can satisfy a variety of access needs. Potential applications include extending broadband capabilities to bring them closer to subscribers, filling gaps in cable, DSL and T1 services, Wi-Fi and cellular backhaul, providing “last 100-meter” access from fibre to the curb and giving service providers another cost-effective option for supporting broadband services.
As WiMAX can support very high bandwidth solutions where large spectrum deployments (i.e. > 10 MHz) are desired it can leverage existing infrastructure, keeping costs down, while delivering the bandwidth needed to support a full range of high-value, multimedia services. Further, WiMAX can help service providers meet many of the challenges they face due to increasing customer demands without discarding there existing infrastructure investments because it has the ability to seamlessly inter-operate across various network types.
WiMAX can provide wide area coverage and quality of service capabilities for applications ranging from real-time delay sensitive Voice-over-IP (VoIP) to real-time streaming video and non-real-time downloads ensuring that subscribers get the performance they expect for all types of communications.
WiMAX, which is an IP-based wireless broadband technology, can be integrated into both wide-area third-generation (3G) mobile and wireless & wireline networks, allowing it to become part of a seamless anytime, anywhere broadband access solution. WiMAX also looks very appealing due to some impressive characteristics it boasts of as mentioned below –
Key Features
Centrally Coordinated Architecture
High-end Security, Encryption, and Service Authentication
No Ad-hoc PP Client Communication is possible
Robust Radio Interface that works in NLOS Conditions
OFDM PHY supports Indoor, self-installation by end users.
High Speed IP Services
Optimised to deliver 110 Mbit/s (net) services (in 3.5 MHz)
Up to 3550 Mbit/s (net) with large channels (1420 MHz)
2nd Generation IP QoS
Hierarchical QoS supports Real-time and Grant based service delivery (Not just Best Effort!)
A Low Delay Radio Interface
Enables Latency and Jitter sensitive applications (VoIP, Internet Gaming etc…)
WiMAX Hype or Reality
What excites the industry is the combination of potential low cost and flexibility that WiMAX promises. In principle, WiMAX broadband networks can be built quickly and (compared to wireline systems) relatively cheaply by installing just a few wireless base stations mounted on buildings or poles to provide coverage to the surrounding area.
The use of wireless eliminates the costly trenching and cabling of new wire/fibre networks, and Ethernet itself has a long history of achieving lower equipment costs than competing technologies. And WiMAX networks should scale well, as extra channels and base stations can be added incrementally as bandwidth demand grows.
With WiMAX users could really cut free from today’s Internet access arrangements and be able to go online at broadband speeds almost wherever they like from within a "MetroZone."
“So keep watching - - - - - WiMAX is coming for real”
Chapter 3
How WiMAX Works
WiMAX has been designed to address challenges associated with traditional wired & wireless access deployments. A WiMAX network has a number of base stations and associated antennas communicating by wireless to a much larger number of client devices (or subscriber stations).
WiMAX works pretty much like a WLAN (or Wi-Fi), which is just an Ethernet local area network (LAN) that uses wireless instead of wires to connect. However WiMAX eliminates range and capacity constraints of WLAN because it is designed to work over distances of up to 50 km and to create wireless metropolitan area networks (WMANs). So unlike WLAN, it’s intended to work outdoors and over fairly long distances, although the distances used in practice will be much less than the maximum. This means it is a more complex technology and has to handle issues of importance to carriers and service providers, such as quality-of-service (QOS) guarantees and carrier-class reliability.
A WiMAX network has a number of base stations and associated antennas communicating by wireless to a much larger number of client devices (or subscriber stations). The WiMAX MAN is schematically similar to the point-to-multipoint layout of a cellular network. It revolves around strategically positioned, highly elevated base stations that beam signals to CPE within their radii. The original 802.16 specification paved the way for fixed wireless-access coverage, which requires a mounted outdoor antenna at the customer’s access point. However, this fixed coverage will soon evolve to incorporate indoor antennas before altogether segueing into an even more significant development: the 802.16e “mobility” extension. Where fixed wireless-access coverage CPE can only communicate to their respective base station, this revision would enable seamless communication from station to station.
A WiMAX base station is connected to public networks using optical fibre, cable, microwave link or any other high-speed point-to-point connectivity referred as a backhaul. WiMAX base stations are either directly wired to the Internet or use WiMAX links to other base stations that are so connected. In few cases like mesh networks, point-to-multipoint WiMAX link to other base stations is used as a backhaul. Ideally WiMAX should use point-to-point antennas as a backhaul to connect aggregate subscriber sites to each other and to base stations across long distances.
Each base station serves Subscriber Stations (also called Customer Premise Equipment for obvious reasons) using non-line-of-sight or line-of-sight point-to-multipoint connectivity referred as “Last mile”. Base station provides wireless coverage over an area called a cell. The maximum radius of a cell is theoretically 50 km (depending on the frequency band chosen), however, typical deployments will use cells of radii from 3 to 10 km. Ideally WiMAX should use non-line-of-sight point-to-multipoint antennas to connect residential or business subscribers to the base station.
As with conventional cellular mobile networks, the base-station antennas can be omni directional, giving a circular cell shape, or directional to give a range of linear or sectoral shapes for point-to-point use or for increasing the network’s capacity by effectively dividing large cells into several smaller sectoral areas.
Subscriber Station typically serves a building (business or residence) using wired or wireless LAN. Subscriber Stations initially are generally small, building-mounted antenna/transceiver systems to which in-building LANs (such as WLANs) are connected. But future clients depending on the frequency bands used will often be integrated into end-user devices, such as notebook PCs and, eventually, mobile devices, such as PDAs and smart phones.

Figure  SEQ Figure \* ARABIC 23 – WiMAX: One Solution for Multiple Needs
Robust Technology
A lot of effort has gone into making the wireless technology very robust and flexible so it will work well in a range of different environments around the world. This was a major area of work in the development of the 802.16a version. For example, it can withstand the effects of multiple radio reflections (or echoes) from buildings and other obstacles in the transmission path, a major problem in built-up environments.
Different channel sizes and methods of providing two-way communications are supported so that the technology can accommodate different national regulatory and technical requirements. And, importantly, WiMAX supports smart antenna systems, which are rapidly becoming less expensive and are very effective in reducing the effects of radio interference and the wireless power needed. This is done by using four antennas at the base station instead of just one. Each of the four antennas transmits and receives the same data signal, but at slightly different times. By clever signal processing, the best signal can always be extracted. To get the same performance with a single antenna, vastly more wireless power would be needed, increasing costs and the problems of interference and cell planning.
A further bonus of WiMAX is that it supports mesh networks. This means that Enabled-enabled devices can act as relays, passing signals from one device to another until they reach a WiMAX base station from which they can enter the wired Internet. Relaying like this greatly extends the potential range of an access point, and allows networks to grow in an organic fashion.

Figure  SEQ Figure \* ARABIC 24 - WiMAX Wireless Complete Ethernet Solution
Channel Characteristics
Channel characteristics also influence the broadband wireless system performance hence the design. Some of the key channel characteristics having substantial impact are channel dispersion, Ricean K-factor, Doppler, cross-polarisation discrimination, antenna correlation, and condition number.
Channel Dispersion
An important channel characteristic that influences a system performance is channel dispersion due to reflections from close in and far away objects. The dispersion is often quantified by the RMS delay spread, which increases with distance, and changes with environment, antenna beamwidth, and antenna height. Typical values are in the 0.1–5 µs range.
K-Factor
The fading signal magnitude follows a Rice distribution, which can be characterized by two parameters: the power Pc of constant channel components and the power Ps from scatter channel components. The ratio of these two (Pc/Ps) is called the Ricean K-factor. The worst case fading occurs when Pc = 0 and the distribution is regarded as Rayleigh distribution (K = 0).
The K-factor is an important parameter since it relates to the probability of a fade of certain depth. Both fixed and mobile communications systems have to be designed for the most severe fading conditions for reliable operation (i.e., Rayleigh fading).
Doppler
The fixed wireless channel Doppler spectrum differs from the mobile channel Doppler spectrum. For fixed wireless channels, the Doppler is in the 0.1–2 Hz frequency range and has close to exponential or rounded spectrum shape. For mobile wireless channels, the Doppler can be on the order of 100 Hz.
Cross-Polarization Discrimination
The cross-polarization discrimination (XPD) is defined as the ratio of the co-polarized average received power Pll to the cross-polarized average received power, P¥". XPD quantifies the separation between two transmission channels that use different polarization orientations. The larger the XPD, the less energy is coupled between the cross-polarized channels. The XPD values decrease with increasing distance.
Antenna Correlation
Antenna correlation plays a very important role in single-input multi-output (SIMO), multi-input single-output (MISO), and MIMO systems. If the complex correlation coefficient is high (e.g., greater than 0.7), diversity and multiplexing gains can be significantly reduced (or completely diminished in the case of correlation of 1). Generally, it was found that the complex correlation coefficients are low, in the 0.1–0.5 range for properly selected base station and receiver antenna configurations.
Condition Number
The condition number is defined as a ratio of the maximum and minimum eigenvalues of the channel matrix. Large capacity gains from spatial multiplexing operation are possible when the statistical distributions of condition numbers have mostly low values. LOS conditions often create undesirable matrix conditions (i.e., high condition numbers) that can be mitigated using dual-polarized antennas.
RF and Hardware Considerations
In addition to the wireless channel characteristics, the practical hardware (HW) limitations of low-cost RF and mixed signal devices need to be considered when designing a broadband wireless data system. Moreover, since wireless systems must coexist with other co-channel and adjacent-channel services, the system must meet emission specifications at the transmitter (masks, max EIRP, etc.) and must be able to tolerate specified levels of undesired interfering signals at the receiver.
The distortion effects from the HW will add to the degradation effects from the channel to yield the overall link performance. Moreover, under good channel conditions the HW distortion will ultimately determine the maximum performance of the link. There exist a large number of sources of distortion at both the transmit and receive ends of a broadband wireless system, but the most significant are:
Digital–analog and analog–digital converters (DAC/ADC)
Digital–analog and analog–digital converters, mixed signal devices, generate distortion through saturation, quantization noise, and spurs. For high-performance broadband wireless applications with adequate level control, 10 effective bits with minimal over sampling are typically enough not to degrade the overall SDR.
DAC/ADC Clocks
The sampling instants at both transmitter and receiver will not be uniform spaced and will have slightly different rates. Even with timing tracking loops at the receiver to account for clock drifts, the residual timing phase noise or jitter will cause residual SDR.
Up/Down Converter Oscillators
The frequency converters will introduce frequency drift and add phase noise. Even with phase tracking loops, the integral of the phase noise will cause residual SDR.
Linearity and Dynamic Range
All HW components introduce noise and have a limited range over which the signal can be processed without significantly distorting it. Thus, the signal levels must be carefully controlled with a combination of power control and automatic gain control (AGC) to maximize the signal level relative to the HW noise without saturating the device. OFDM signals have slightly higher peak to average ratios (PARs) than other high-performance modulations, and extra care is required.
The dynamic range and linearity requirements of OFDM can be made comparable to single-carrier modulation with PAR reduction algorithms.
Flexible Tradeoffs
WiMAX provides great flexibility to service providers, as one can fine-tune multiple parameter to deliver appropriate service depending on customer need. For example, the flexibilities that comes from trading off range and throughput.
WiMAX operates at a range of up to 30 miles and provides a data rate of up to 70 Mbps, but not at the same time. A wireless subscriber unit near a base station and receiving a strong signal can use an efficient modulation scheme, such as 64QAM, and get the highest possible data rate. A unit farther away, however, might require a more robust scheme like 16QAM, which, being less efficient, will provide a lower rate, but at least keep the unit connected.
Furthermore, the modulation method can change in real time, from user to user and even from second to second for a single user. An 802.16a system thus can continually provide the highest data rates for the conditions that exist.
WiMAX also provides useful tradeoffs between channel width and number of users. Unlike the fixed-width, 20 MHz channels of Wi-Fi, WiMAX channels can vary in width from 1.5 to 20 MHz. Wireless operators with few subscribers in an area can start with a narrow channel and then add channels or use a wider channel as they acquire additional customers. Similarly, they can use a narrow channel to provide broadband wireless access to a few rural customers and a wide channel to provide the equivalent of a T1 connection to multiple business customers simultaneously.
Flexible channel widths offer other advantages, too, among them the ability to meet requirements of regulatory agencies in different countries. For example, a wireless operator in Europe with 14 MHz of bandwidth in the 3.5 GHz band might want equipment that provides 7 or 3.5 MHz channel bandwidths, which 802.16a allows. Also, in licensed bands (WiMAX has spectrum in both licensed and unlicensed bands), flexible channel widths prevent waste of purchased bandwidth. An operator that has paid for 14 MHz of bandwidth will not want a system that requires channel widths of, say, 6 MHz, which would waste spectrum.
WiMAX Networks
802.16 was originally designed to provide a flexible, cost effective, standards-based last-mile broadband connectivity to fill in the broadband coverage gaps that are not currently served by “wired” solutions such as cables or DSL, the evolved versions of the standard are aiming to create new forms of broadband services both with high-speed and mobility.
Worldwide Interoperability of Microwave Access (WiMAX) is a technology based on the IEEE 802.16 specifications to enable the delivery of last mile wireless broadband access as an alternative to cable and DSL. WiMAX will provide fixed, nomadic, portable and eventually mobile wireless broadband connectivity without the need for direct line-of-sight with a base station. The design of WiMAX network is based on the following major principles:
Spectrum – Able to be deployed in both licensed and unlicensed spectra.
Topology – Support different Radio Access Network (RAN) topologies.
Interworking – Independent RAN architecture to enable seamless integration and interworking with Wi-Fi, 3GPP and 3GPP2 networks and existing IP operator core network (e.g., DSL, cable, 3G) via IP-based interfaces which are not operator-domain specific.
IP connectivity – Support a mix of IPv4 and IPv6 network interconnects in clients and application servers.
Mobility Management – Possibility to extend the fixed access to mobility and broadband multimedia services delivery.
WiMAX created the 10-66 GHz technical working group for testing mission in the IEEE. WiMAX has defined two MAC system profiles, which are basic ATM system MAC profile and basic IP system MAC profile. Also they have defined two primary PHY system profiles which are 25 MHz wide channel for (typically for U.S. deployments) use in the 10-66 GHz range and 28 MHz wide channel for (typically European deployments) use in the 10-66 GHz.
WiMAX expanded their working to include the 802.16a standard in terms of addressing testing and conformance issues .the 2-11 GHz technical working group has the mandate of creating testing and conformance documents as contributions to IEEE and ETSI standards bodies in support of the IEEE 802.16a and ETSI HiperMan standards.
The WiMAX technical working group is defining MAC and PHY system profiles for IEEE 802.16a and HiperMan standards. The MAC profile include IP based version for both Wireless MAN (Licensed) and Wireless HUMAN (License-exempt).
IEEE Standard 802.16 was designed to evolve as a set of air interfaces standard for WMAN based on a common MAC protocol but with physical layer specifications dependent on the spectrum of use and the associated regulations. The IEEE 802.16 Working Group designed a flexible medium access control layer (MAC) and accompanying physical layer (PHY) for 10-66 GHz.

Figure  SEQ Figure \* ARABIC 25 - WiMAX Coverage With Different SS Types
WiMAX Types
The WiMAX family of standards address two types of usage models: a fixed usage model (IEEE 802.16-2004) and a portable usage model (802.16 REV E, scheduled for ratification in current year). Before we discuss more about these distinct types of WiMAX it is important to understand and appreciate key differences between the mobile, nomadic and fixed wireless access systems.
Basic feature, which differentiate these system, is the ground speed at which the systems are designed to operate. Based on mobility wireless access can be divided into four classes i.e. stationary (0 km/h), pedestrian (up to 10 km/h), vehicular (sub classified as typical up to 100 km/h, and high-speed up to 500 km/h).
Mobile wireless access system is the one that can address the vehicular class, while the fixed on other hand is referred to the stationary and even pedestrian. This raises the question about nomadic wireless access system, which is refereed to as a system that works as a fixed wireless access system but subscriber can change its location, within as well as outside its cell. Example being that a subscriber of WiMAX system operates from one location i.e. office during day time, and moves to other location i.e. residence in the evening, if the wireless access system he is using works at both the location it can be referred to as “nomadic”.
Fixed
Service and consumer usage of 802.16 for fixed access is expected to mirror that of fixed wireline service with many of the standards-based requirements being confined to the air interface. Because communication takes place via wireless links from customer premises equipment to remote Non Line of Sight (NLOS) base station requirements for link security are increased beyond those needed for wireline service. The security mechanisms within the IEEE 802.16 standards are adequate for fixed access service.
An additional challenge for the fixed access air interface is the need to establish high-performance radio links capable of data rates comparable to wired broadband service, using equipment that can be self installed indoors by users, as is the case for DSL and cable modems. IEEE 802.16 standards provide advanced Physical (PHY) layer techniques to achieve link margins capable of supporting high throughput in NLOS environments. The 802.16a extension, ratified in January 2003, uses a lower frequency of 2–11GHz, enabling non line-of-sight connections.

Figure  SEQ Figure \* ARABIC 26 - WiMAX Types
Portable or Mobile
IEEE 802.16e will add mobility and portability to applications like notebooks and PDAs. Both licensed and unlicensed spectrums will be utilized in these deployments. 802.16e is tentatively scheduled to be approved in the second half of this year.
The latest 802.16e task group is capitalizing on the new capabilities this provides by working on developing a specification to enable mobile 802.16 clients. These clients will be able to hand-off between 802.16 base stations, enabling users to roam between service areas.
There can be two cases of portability full mobility or limited mobility. The simplest case of portable service (referred to as Nomadicity) involves a user transporting an 802.16 modem to a different location. Provided this visited location is served by wireless broadband service, in this scenario, the user re-authenticates and manually re-establishes new IP connections and is afforded broadband service at the visited location.
In the fully mobile scenario, user expectations for connectivity are comparable to those experienced in 3G voice/data systems. Users may be moving while simultaneously engaging in a broadband data access or multimedia streaming session.
Building Blocks of WiMAX
The core components of a WiMAX system are the subscriber station (SS) otherwise known as the CPE and the base station (BS). A BS and one or more SSs can form a cell with a point-to-multipoint (P2MP) structure. On air, the BS controls activity within the cell, including access to the medium by SSs, allocations to achieve quality of service (QoS) and admission to the network based on network security mechanisms.
An 802.16-based system often uses fixed antenna at the subscriber station site. The antenna is mounted to the roof or an eave. Provisions such as adaptive-antenna systems (AAS) and sub-channelisation are also supported optionally by the standard for enhanced link budget required for in-door installation. IEEE 802.16e sub-committee is currently working on extension to the standard required for mobility and support for the power limited SS terminals.
A BS typically uses either sectored/directional or omni-directional antennas. A fixed SS typically uses directional antenna while mobile or portable SS usually uses an omni-directional antenna. Multiple BSs can be configured to form a cellular wireless network. When orthogonal frequency division multiplexing (OFDM) is used, the cell radius can ideally reach up to 30 miles, however this requires a favourable channel environment and only the lowest data rate can be achieved.
Practical cell sizes usually have a small radius of around 5 miles or less. The 802.16 standard also can be used in a point-to-point (P2P) or mesh topology, using pairs of directional antennas. This can be used to increase the effective range of the system relative to what can be achieved in P2MP mode.
WiMAX supports both time division duplex (TDD) and frequency division duplex (FDD) modes of operation on air, along with a range of channel bandwidths. The OFDM PHY mode, which is also known WirelessMAN-OFDM, is specified for use between 2 and 11 GHz.
The 802.16 MAC controls access of the BS and SSs to the air through a rich set of features. The on-air timing is based on consecutive frames that are divided into slots. The size of frames and the size of individual slots within the frames can be varied on a frame-by-frame basis, under the control of a scheduler in the BS. This allows effective allocation of on air resources to meet the demands of the active connections with their granted QoS properties.
The 802.16 MAC provides a connection-oriented service to upper layers of the protocol stack. Connections have QoS characteristics that are granted and maintained by the MAC. The SS making requests to the BS to change them while a connection is maintained can vary the QoS parameters for a connection.
QoS service in the 802.16 MAC service takes one of four forms: constant bit rate grant, real time polling, non-real-time polling, and best effort. Media access control packet data units (MPDUs) are transmitted in on-air PHY slots. Within these MPDUs, MAC service data units (MSDUs) are transmitted. MSDUs are the packets transferred between the top of the MAC and the layer above. MPDUs are the packets transferred between the bottom of the MAC and the PHY layer below.
Across MPDUs, MSDUs can be fragmented. Within MPDUs, MSDUs can be packed (aggregated). Fragments of MSDUs can be packed within a single packed MPDU. Automatic retransmission request (ARQ) can be used to request the retransmission of un-fragmented MSDUs and fragments of MSDUs.
Typically, a WiMAX system consists of three parts a WiMAX base station and a WiMAX Receiver (also referred as customer premise equipment (CPE). While the backhaul connects the system to the core network it is not the integrated part of WiMAX system as such.
WiMAX Base Station
A WiMAX base station consists of indoor electronics and a WiMAX tower. Typically, a base station can cover up to 6 miles radius (Theoretically, a base station can cover up to 50 kilo meter radius or 30 miles, however practical considerations limit it to about 10 km or 6 miles). Any wireless node within the coverage area would be able to access the Internet.
The WiMAX base stations would use the Media Access Control layer defined in the standard—a common interface that makes the networks interoperable—and would allocate uplink and downlink bandwidth to subscribers according to their needs, on an essentially real-time basis.
Each base station provides wireless coverage over an area called a cell. The maximum radius of a cell is theoretically 50 km (depending on the frequency band chosen), however typical deployments will use cells of radii from 3 to 10 km.
As with conventional cellular mobile networks, the base-station antennas can be omni directional, giving a circular cell shape, or directional to give a range of linear or sectoral shapes for point-to-point use or for increasing the network’s capacity by effectively dividing large cells into several smaller sectoral areas.
WiMAX base stations can range from units that support only a few subscriber stations to elaborate equipment that supports thousands of subscriber stations and provides many carrier-class features. Whatever number of subscriber stations a base station supports, the latter must manage a variety of functions that are not required in subscriber equipment. Some base stations must support sophisticated antenna capabilities and implement efficient frequency reuse.
As a result, WiMAX base stations will have many different configurations. They will likely range from simple stand-alone units that support a few users to redundant, rack mounted systems and server blades that operate alongside wireline networking equipment. On the hardware side, this equipment will typically use off-the-shelf microprocessors and discrete radio-frequency (RF) components.
Initially, form factors will be very similar to those of the proprietary broadband wireless systems of today. Base-station sectors will be perhaps the size of three or four notebook computers stacked end to end, and weigh of the order of 40 to 60 pounds.
Types of Base Stations
There is likely to be a lot of variation in base-station equipment, tailored to the deployment scenario. Base-station designs vary in cost, performance, and physical size, but can be broadly divided into two categories: Micro and macro.
Micro base stations support only a single radio and have the lowest cost and performance. Costing as little as $2,000, they can be fixed-configuration, or "pizza-box," designs. Because they lack expansion capabilities, they are best suited to commercial point-to-point links or networks with a small number of subscriber stations. Micro base stations generally integrate either all or a portion of the radio, while antennas are external for outdoor mounting. As with CPE, 10/100 Ethernet is the typical connection to the infrastructure network. These low cost solutions will be for rural, campus, indoor, and fill-in deployments. They will use a single RF carrier, and support micro and pico cells.
Macro base stations resemble those used in cellular networks and cost tens of thousands of dollars. To support higher capacities, these designs use multiple sectors. Because they operate independently, every sector requires a dedicated radio, base band, and MAC. To support expansion, macro base stations use chassis-based designs. Radios may be mounted in a tower some distance away, in which case the macro base station integrates only digital functions such as the MAC/base band. These cellular-style base stations will be for urban, suburban, high user density, business and residential deployments.
Power Control
In any WiMAX network, power levels and control for both transmit and receive are important for system efficiency. To ensure successful communication, the levels must be actively managed. Power control algorithms are used to improve the overall performance of the system, it is implemented by the base station sending power control information to each of the CPEs to regulate the transmit power level so that the level received at the base station is at a pre-determined level.
The power control reduces the overall power consumption of the CPE and the potential interference with other co-located base stations. For LOS the transmit power of the CPE is approximately proportional to its distance from the base station, for NLOS it is also heavily dependant on the clearance and obstructions. In a dynamical changing fading environment this pre-determined performance level means that the CPE only transmits enough power to meet this requirement. The converse would be that the CPE transmit level is based on worst-case conditions.
Power levels are dynamically adjusted on a per-subscriber basis, depending on the profile and distance from the base station. For the base-station transmitter, the actual transmitted power will depend on the subscriber distance, propagation characteristics, channel bandwidth, and modulation scheme (BPSK, QPSK, 16QAM, or 64QAM). The least data-efficient method is BPSK. Because it is employed where the subscriber station is farthest from the base, BPSK requires additional transmit power. 64QAM offers high data efficiency, which is best when the subscriber station is closer to the base station.
MAC Layer Overview
The IEEE 802.16 MAC was designed for point-to-multipoint broadband wireless access applications. The MAC was developed by Task Group 1 along with the original 10-66 GHz PHY. The 802.16 MAC designed for is based on Collision Sense Multiple Access with Collision Avoidance (CSMA/CA). The 802.16 AP MAC manages UL and DL resources including Transmit and Receive scheduling. The original design of MAC was flexible enough to support, with extension all other project of the IEEE 802.16.
The design addresses the need for very high bit rates, both uplink and downlink. The MAC must accommodate both continuous and burst traffic to support a variety of services that required by multiple end users. These services are varied in their nature and include legacy time-division multiplex (TDM) voice and data, Internet Protocol (IP) connectivity, and packetised voice over IP (VoIP).
The 802.16 MAC provides the option of allowing a smart subscriber station to manage its bandwidth allocation among its users, and this is due to MAC characteristic that offers the choice of conceding bandwidth to a subscriber station rather than to the individual connection it supports.
The 802.16 MAC is adaptable and flexible, and it supports several multiplexing and duplexing schemes. The MAC consists of three sublayers: the Service Specific Convergence Sublayer (SSCS), the MAC Common Part Sublayer and the (CPS) and Privacy Sublayer. In the 802.16 MAC protocol convergence sublayers are used to map the transport-layer-specific traffic to a MAC that is flexible enough to efficiently carry and traffic type.
The main focus of the MAC layer is to manage the resources of the air link in an efficient manner. The MAC layer of WiMAX provides grant/request access, in contrast to Wi-Fi's contention-based access. In case of WiMAX data from users seeking access doesn't collide with the data from other users which means bandwidth is not wasted due to the necessity of data retransmission. The overhead added by contention-based access is relatively small only when the number of users is small, less than about ten per access point. When the average network loading becomes more than 25% or so, the number of retransmissions caused by collisions becomes unacceptable. WiMAX avoids that difficulty simply by avoiding collisions.
The MAC layer consists of three sub-layers. Service specific convergence sub-layer (SSCS) provides an interface to the upper layer entities through a CS service access point (SAP).
The MAC common part sub-layer (CPS) provides the core MAC functions, including uplink scheduling, bandwidth request and grant, connection control, and automatic repeat request (ARQ). Privacy sub-layer (PS) provides authentication and data encryption functions.
The tasks performed by the 802.16 MAC protocol can also be partitioned in a different way into two categories: periodic (per-frame) “fast path” activities, and non-periodic “slow path” activities. Fast path activities (such as scheduling, packing, fragmentation, and ARQ) must be performed at the granularity of single frames, and they are subject to hard real-time deadlines. They must complete in time for transmission of the frame they are associated with. In contrast, slow path activities typically execute according to timers that are not associated with a specific frame or the frame period and as such do not have stringent deadlines.
FeatureBenefitsTDM/TDMA Scheduled Uplink/Downlink frames. • Efficient bandwidth usage Scalable from 1 to hundreds of subscribers • Allows cost effective deployments by supporting enough subs to deliver a robust business case Connection-oriented • Per Connection QoS • Faster packet routing and forwarding QoS support Continuous Grant Real Time Variable Bit Rate Non Real Time Variable Bit Rate Best Effort • Low latency for delay sensitive services (TDM Voice, VoIP) • Optimal transport for VBR traffic (e.g., video)· Data prioritisation Automatic Retransmission request (ARQ) • Improves end-to-end performance by hiding RF layer induced errors from upper layer protocols Support for adaptive modulation • Enables highest data rates allowed by channel conditions, improving system capacity Security and encryption (Triple DES) • Protects user privacy Automatic Power control • Enables cellular deployments by minimizing self interference Table  SEQ Table \* ARABIC 5 - 802.16 MAC Features
PHY Layer Overview
The 10-66 GHz PHY assumes line-of-sight propagation with no considerable concern over multipath propagation. The PHY layer contains several forms of modulation and multiplexing to support different frequency range and application.
The IEEE 802.16 standard was originally written to support several physical medium interfaces and it is expected that it will continue to develop and extend to support other PHY specifications. Hence, the modular nature of the standard is helpful in this aspect. For example, the very first version of the standard only supported single carrier modulation. Since that time, Orthogonal Frequency Division Multiplexing (OFDM) has been added.
Because of its superior performance in multipath fading wireless channels, orthogonal frequency division multiplexing (OFDM) signalling is recommended in OFDM and WirelessMAN OFDMA PHY layer modes of the 802.16 standard for operation in sub 11 GHz non-line of sight (NLOS) applications. OFDM technology has also been recommended in other wireless standards such as digital video broadcasting (DVB) and wireless local area networking (WLAN).
Apart from the usual functions such as randomisation, forward error correction (FEC), interleaving, and mapping to QPSK and QAM symbols, the standard also specifies optional multiple antenna techniques. This includes space-time coding (STC), beam forming using adaptive antennas schemes, and multiple input multiple output (MIMO) techniques, which achieve higher data rates. The OFDM modulation/demodulation is usually implemented by performing fast Fourier transform (FFT) and inverse FFT on the data signal. Although not specified in the standards, other advanced signal processing techniques such as crest factor reduction (CFR) and digital pre-distortion (DPD) are also usually implemented in the forward path, to improve the efficiency of the power amplifiers used in the base stations.
FeatureBenefits256 point FFT OFDM waveform • Built in support for addressing multipath in outdoor LOS and NLOS environments Adaptive Modulation and variable error correction encoding per RF burst • Ensures a robust RF link while maximizing the number of bits/ second for each subscriber unit. TDD and FDD duplexing support • Address varying worldwide regulations where one or both may be allowed Flexible Channel sizes (e.g. 3.5MHz, 5MHz, 10MHz, etc) • Provides the flexibility necessary to operate in many different frequency bands with varying channel requirements around the world. Designed to support smart antenna systems • Smart antennas are fast becoming more affordable, and as these costs come down their ability to suppress interference and increase system gain will become important to BWA deployments. Table  SEQ Table \* ARABIC 6 - 802.16 PHY Features

Figure  SEQ Figure \* ARABIC 27 - WiMAX PHY Architecture
WiMAX Receiver
A WiMAX receiver, which is also referred as customer premise equipment (CPE), may have a separate antenna (i.e. receiver electronics and antenna are separate modules) or could be a stand-alone box or a PCMCIA card that sits in your laptop or computer. Access to WiMAX base station is similar to accessing a Wireless Access Point in a Wi-Fi network, but the coverage is more.
So far one of the biggest deterrents to the widespread acceptance of BWA has been the cost of customer premise equipment (CPE). This is not only the cost of the CPE itself, but also the installation costs. Historically proprietary BWA systems have been predominantly Line of Site, requiring highly skilled labour and a truck role to install and "turn up" a customer. The concept of a self-installed CPE has been the Holy Grail for BWA from the beginning. With the advent of WiMAX this issue seems to be getting resolved.
Depending on the end-user needs WiMAX can have provision of three different types of CPEs.
A modem attached to an external rooftop antenna
A modem with an indoor antenna
Integrated antenna since as further integration into silicon by major chip suppliers takes hold, CPEs can be integrated into laptops, phones and other devices.
A generic WiMAX subscriber system includes a control processor, MAC unit, base band processor (BBP), and analogue RF front end. That front end places 802.16X into a specific licensed or unlicensed band.
Wish List for WiMAX CPE
Lower cost
Plug-and play
Greater throughput
Quality of Service (QoS) for value-added services
Ship it soon ;-)
Backhaul
Backhaul refers both to the connection from the Access Point back to the provider and to the connection from the provider to the core network. A backhaul can deploy any technology and media provided it connects the system to the backbone. In most of the WiMAX deployment scenarios, it is also possible to connect several base stations with one another by use of high-speed backhaul microwave links. This would also allow for roaming by a WiMAX subscriber from one base station coverage area to another base station coverage area, similar to roaming enabled by Cellular phone companies.
Working Mechanism
The basic mechanism of connection between Subscriber and Base Station in a WiMAX network is as below.
SS – Subscriber Station BS – Base StationSSSS “enters” BS service areaBSDL-MAP Broadcast: Phy Synchronisation field, Operator ID, Sector ID, MAP message length,SSSS Scans for DL Channel: DL SynchedSSObtain UL Parameters BSDCD broadcast: BS Power, PHY type, DL burst profile, Modulation type, FEC, Phy synchronisation,BSBSID + UCD broadcast: PHY synchronisation field, BSID, Phy specifications,SSRanging and Adjust ParametersBSRange-Request: requested DL burst profile, SS MAC address, Ranging anomalies, SS broadcast capabilitiesBSRange-Response: Timing adjust, Power level adjust, Freq offset adjustment, ranging status, DL freq override, UL freq override, burst profile, SS Mac address, CID,SSNegotiate Basic CapabilitiesBSSS BC-Request: CID, PHY parameters supported, Bandwidth allocations supported,BSSS BC-Response: CID, PHY parameters supported, Bandwidth allocations supported,SSRegister with BSBSRegistration-Request: CID, Hashed Message Auth Code, IP version, Vendor ID, CS capability, ARQ parametersBSRegistration-Response: CID, Ok/Not, HMAC tuple, IP version, Vendor ID, CS capability, ARQ parametersSSEstablish IP ConnectivityBSDHCP-Request: H/W type = Ethernet, MAC address, Parameters requested: Subnet mask, Time offset,BSRouter option, Timeserver option, Vendor class identifierSSEstablish ToDBSDHCP-Request: IP Address, TFTP provisioning server name, Time offset, List of routers,BSToD Request/ResponseSSTransfer Operational ParametersBSTFTP Configuration File (Download SS binary Configuration File)BSTFTP Complete: CIDBSTFTP RSP: CID, OK/NotSSEstablish Provisioned ConnectionsBSDSA-Request (SS or BS initiated): Service flow parameters, CS parameter encodings (802.3, 802.1p, 1q, ATM)BSDSA-Response): CID, Transaction ID, Confirmation Code, Service flow parameters, CS parameters encodings, Service flow error set,OperationalTable  SEQ Table \* ARABIC 7 - Working Mechanism for WiMAX Connection
Architecture
The architecture and usage of WiMAX is a two-stage evolution: initially combining fixed access with portability and scaling up to evolve to full mobility. The framework is based on several core principles:
Support for different Radio Access Network (RAN) topologies.
Well-defined interfaces to enable 802.16 RAN architecture independence while enabling seamless integration and interworking with Wi-Fi, 3GPP3 and 3GPP2 networks.
Leverage open, Internet Engineering Task Force (IETF)-defined IP technologies to build scalable all- IP 802.16 access networks using Common Off the Shelf (COTS) equipment.
Support for IPv4 and IPv6 clients and application servers; recommending use of IPv6 in the infrastructure.
Functional extensibility to support future migration to full mobility and delivery of rich broadband multimedia.
The architecture framework is based on the following requirements:
Applicability
The architecture shall be applicable to licensed and license-exempt 802.16 deployments.
Service Provider Categories: The architecture, especially the RAN, shall be suitable for adoption by all incumbent operator types, examples of which were listed earlier. Harmonization/Interworking: The architecture shall lend itself to integration with an existing IP operator core network (e.g., DSL, cable, or 3G) via interfaces that are IP-based and not operator-domain specific. This permits reuse of mobile client software across operator domains.
Provisioning and Management
The architecture shall accommodate a variety of online and offline client provisioning, enrolment, and management schemes based on open, broadly deployable Industry standards.
IP Connectivity & Services
The architecture shall support a mix of IPv4 and IPv6 network interconnects and communication endpoints and a variety of standard IP context management schemes. The architecture shall support a broad range of TCP and UDP real-time and non-real-time applications.
Security
The architecture shall support Subscriber Station (SS) authorization, strong bilateral user authentication based on a variety of authentication mechanisms such as username/password, X.509 certificates, Subscriber Identity Module (SIM), Universal SIM (USIM), Removable User Identity Module (RUIM), and provide services such as data integrity, data replay protection, data confidentiality, and non-repudiation using the maximum key lengths permissible under global export regulations.
Mobility Management
The architecture shall scale from fixed access to fully mobile operation scenarios with scalable infrastructure evolution, eventually supporting low latency (< 100 msec) and virtually zero packet loss handovers at mobility speeds of 120 km/hr or higher.
Network Topology
WiMAX network deployment can be done based on three topologies.
Point to Point
Point-to-point fixed wireless networks are commonly deployed to offer high-speed dedicated links between high-density nodes in a network. Such systems are cost effective and can be deployed easily. Moreover, as a large part of a wireless network’s cost is not incurred until the customer premises equipment (CPE) is installed, the network service operator can time capital expenditures to coincide with the signing of new customers.
Point-to-point (P-P) systems provide an effective last-mile solution for the incumbent service provider and can be used by competitive service providers to deliver services directly to end-users. Benefits can be summarized as follows:
Lower entry and deployment costs
Ease and speed of deployment (systems can be deployed rapidly with minimal disruption to the community and the environment)
Fast realization of revenue (as a result of rapid deployment)
Demand-based build-out (scalable architecture employing open industry standards ensuring services and coverage areas can be easily expanded as customer demand warrants)
Cost shift from fixed to variable components
No stranded capital when customers churn
Cost-effective network maintenance, management, and operating costs
Point to Multi Point
Point-to-multipoint is a concept in which multiple subscribers can access the same radio platform, utilizing both a multiplexing method and queuing. More recent advances in a point-to-multipoint technology offer service providers a method of providing high-capacity local access that is less capital-intensive than a wireline solution, faster to deploy than wireline, and able to offer a combination of applications.
Point-to-multipoint (P-MP) implementations are emerging in several bands above 20 GHz, up to about 40 GHz. These consist of a complex time division multiplex (TDM) hub or base station using sectoral antennas and time division multiple access (TDMA) subscriber stations using parabolic antennas.
Most P-MP systems use a simple modulation method, e.g. QPSK, but higher-level modulation methods are also used in some systems, e.g. 64 QAM (quadrature amplitude modulation). There is a trade-off between modulation method, interference tolerance and link length. More advanced P-MP system capabilities, including even higher-level modulation methods.

Figure  SEQ Figure \* ARABIC 28 - WiMAX Point to Multi Point Deployment
Mesh
Mesh Routing is a new, self-adjusting and self-healing topology that extends range, reduces interference, improves security and performance, and lowers costs by requiring fewer access points. Each device only transmits enough power to reach adjacent devices instead ones far away. Performance is improved because there’s less attenuation over distance, and security is improved since signals don’t transmit as far.
An ad hoc (peer-to-peer) network is an independent local area network not connected to a wired infrastructure and where all stations are connected directly to one another (called a mesh topology). Configuring WiMAX base stations in ad hoc mode is used to establish a network where wireless infrastructure does not exist. As base stations themselves acts as backhaul this is popular application provided the number of user are substantial.
Mesh topologies provide a flexible, effective, reliable, economical, and portable architecture that can move data between nodes efficiently while maintaining balanced traffic along the network.
Mesh also has promise in deploying wide area wireless networks. An electric utility can install access points on light poles and have them share one broadband connection, with the poles providing height and electric power. The access points could even be solar powered, so no wired infrastructure is needed beyond the first broadband connection – a great solution for developing countries.
Figure  SEQ Figure \* ARABIC 29 - Mesh Network
Mesh Networks
Mesh networks are wireless data networks composed of two or more autonomous, self-organizing nodes. The nodes are similar to traditional wireless transmitter receivers (akin to a base station or wireless network card) but have additional intelligence built in that enables them to act as mini-routers for the network. The nodes are installed throughout a large area (such as a colony or a school campus). Each node then transmits a low power signal capable of reaching neighbouring nodes, each of which in turn transmits the signal to the next node, with the process being repeated until the data arrives at its destination. By adding the capacity for each node to route packets to other nodes in the network, meshes can extend the range of wireless technologies like WiMAX or Wi-Fi and can provide low-cost coverage of a geographic area using minimum available backhaul infrastructure.
Connections between nodes are made on-demand and packets are routed across the network either using predetermined routing tables (proactive routing) or using routes generated on demand by the network (reactive routing). Properly configured mesh networks should be self-healing – if a node goes down, the remaining nodes in the network can reconfigure their routes to work around the failure.
Mesh networks also scale up and out in very small size increments – a project can start with a few nodes and then scale up a single node at a time. Mesh network is based on multi-hop topology, which has many advantages as well as few disadvantages.
Multi-hop Topology
Up to this point, wireless systems have been discussed as consisting of base stations or access points that feed a collection of end systems. But more complex wireless systems make good sense as well. For example, a simple case would consist of an 802.16 wireless-access system with rooftop antenna wired to an 802.11 access point (AP) inside the building with which end systems communicate.
In a more complex example instead of feeding an 802.16 base station directly with a fibre, a link from another 802.16 base station can be used as a feed. A multi-hop 802.16 system, mentioned above warrants careful channel selection so that the feeder signal from the first base station does not interfere with the distribution signal sent from the end base station, nevertheless such a system might avoid considerable construction of fibre links when serving sparsely populated areas.
A multi-hop is a better topology then single-hop and directional last-mile alternatives. It is more robust than single-hop networks because they are not dependent on the performance of a single node for operation. In a single-hop network, if the node goes down, so does the network. In mesh-network architecture, if the nearest node goes down or if localized interference occurs, the network continues to operate; data is simply routed along an alternate path.
Also multi-hop networks use available bandwidth efficiently. In single hop network devices must share a node, due to which several devices attempt to access the network at once, a traffic jam occurs and the system slows. By contrast, in a multi-hop network, many devices can connect to the network at the same time through different nodes, without necessarily degrading system performance. The shorter transmission ranges in a multi-hop network limit interference, allowing simultaneous, spatially separated data flows. To deploy a multi-hop network cost effectively, however, service providers need a large initial subscriber base.
Technical considerations like network latency seen by the end systems, which keeps escalating with increase in the number of hops, may limit the effectiveness of this approach by adversely impacting some applications such as voice. In designing multi-hop links that will carry latency sensitive traffic, one needs to define an acceptable latency budget and then compute the latency added for each relay point. Generally, a few hops can be tolerated without unacceptable degradation to voice traffic (i.e., latencies worse than what is experienced by cell users or general VoIP users today). The specific limits will depend on the specifications of the actual equipment, however.
Another limiter to multi-hop deployments is that the traffic from outlying base stations will fan in eventually to a common link to the high-performance fibre backbone, and the total capacity of the common links can eventually limit total system performance.
Mesh Design
An even more complex system architecture that may be appropriate for some deployments is the one with a mesh design. Such designs are still in the research stage today but will likely be incorporated into future standards. In a mesh design, all or at least very many, end-point nodes also act as relay points to other end-point nodes. Essentially traffic to many users is carried through radios at their neighbours’ homes. This reduces the number of explicit base stations that are needed by turning every end point into a sort of mini-base station. For cases where the end points to be served are very sparse, this may reduce deployment costs by eliminating central base stations in favour of adding small incremental costs to many user stations. For more dense deployments, mesh systems can increase reliability and capacity because there may be many traffic paths back to the Internet.
Mesh networks are a highly innovative extension of wireless networking technology. Most deployments and commercial efforts to date focus on military and emergency services applications, but the potential exists for mesh networks to be used to extend the reach of broadband Internet connections.
Mesh Types
There are two types of mesh networks, which are based on network topology, referred as "Full mesh and Partial mesh".
In Full mesh networks, every node has a circuit connecting it to every other node in the entire network. This type of network can be expensive to build, but offers the greatest degree of network redundancy.
In Partial mesh networks, only some nodes operate in a full mesh arrangement, and other nodes connect to perhaps just one or two others in the network. This type of network is less expensive to implement, but offer incomplete redundancy for the network.
Mesh Advantage
An advantage of Mesh topology is the ability for the deployment to navigate around a large obstacle, such as a mountain or tall buildings. Such obstacles can block a subscriber from reaching a base station. In a mesh network, blocked subscribers can get to the base station indirectly by going through other nodes. Even a small amount of meshing can greatly improve a base station’s coverage if sufficient small nodes are in place.
Mesh networks unlike direct line-of-sight implementations can adapt to changes in network making them more effective. In this topology nodes can be readily added or removed, and their location changed. As people become more mobile and wireless capabilities are included in new classes of devices, future business and home networks need to adapt or self-configure to these changes.
Mesh networks provide greater redundancy and can be used for traffic balancing. In dense networks, such as crowded offices or apartments, each device can have many neighbours creating multiple paths between two communicating devices. In the presence of localized interference, a multi-hop network can route data along an alternate path. If only one node requires a large amount of bandwidth, then the network can dynamically route traffic to other network nodes, avoiding the congested node.
Mesh Drawbacks
Mesh networks do not conform to standards at this time. IEEE has begun work on a mesh standard for both WiMAX and Wi-Fi technologies but full, approved standards aren't expected until late 2006 or early 2007. Current back-end implementations of mesh infrastructures are based on proprietary solutions.
Mesh networks can be slow as latency (the time it takes for a packet of information to cross a network connection from sender to receiver) increases with each network hop.
Mesh networks are also inherently noisy, due to the fact that wireless mesh network links are multi-directional broadcasters and can pick up extraneous signals.
Mesh networks can have scalability issue, since mesh networks involve a high degree of information routing between nodes.



Section 2
WiMAX - Cutting Edge
WiMAX is not one technology but a aggregation of many technology innovations bound together by IEEE 802.16 standards effort. This section, as the name suggest provides an overview of WiMAX technology and associated characteristics. This section consists of three chapters.
Chapter 4 – WiMAX – Specifications
This chapter provides detailed understanding of WiMAX specifications and provides insight about basic idea of WiMAX technology
Chapter 5 – WiMAX – State of the Art Technologies
This chapter provides overview of key technological advancements, which made WiMAX a reality, also discussed, is evolution of these innovations.
Chapter 6 - WiMAX Proposition
This chapter takes a look at the perception and hype surrounding the WiMAX and verifies the reasons and issues behind this hype.
Chapter 4
WiMAX – Specification
The IEEE 802.16 Air Interface Standard is truly a state-of-the-art specification for broadband wireless access systems employing a point-to-multipoint (PMP) architecture. The initial version was developed with the goal of meeting the requirements of a vast array of deployment scenarios for BWA systems operating between 10 and 66 GHz. As a result, only a subset of the functionality is needed for typical deployments directed at specific markets.
IEEE 802.16 Air Interface Specification is a very capable, while complex, specification. There are allowances for a number of physical layers for different frequency bands and region-by-region frequency regulatory rules. There are features that allow an IP centric system or an ATM centric system depending upon the needs of customers. The specification is designed to cover application to diverse markets from very high bandwidth businesses to SOHO and residential users.
The IEEE process stops short of providing conformance standards and test specifications. In order to ensure interoperability between vendors equipment, the WiMAX technical working groups have completed the work for 10 to 66 GHz and has started work for the sub 11 GHz part of the standard. Due to the wealth of options made available by these specifications, an implementer currently faces a tough decision.
To address this issue WiMAX undertaken the development of System Profiles. The working groups develop a set of system profiles, Protocol Implementation Conformance Statement Performa, Test Suite Structure & Test Purposes, and Abstract Test Suite specifications for 10 to 66 GHz and sub 11 GHz, all according to the ISO/IEC 9464 series (equivalent to ITU-T x.290 series) of conformance testing standards.
The broadband wireless market was dominated by proprietary systems targeted at wireless back haul and point-to-point microwave link applications for a long period. There was pressure within the industry for standardisation to take place in order to increase market growth and reduce costs, and this ultimately led to the IEEE 802.16 standardisation efforts.
Initially, the first 802.16 specifications concentrated on the needs of backhaul, however over time, through the work of the IEEE working groups, the standard developed to address customer demand for a system that was capable of providing high-speed data services to fixed, and later increasingly mobile user terminal equipment. It also evolved to address some of the issues apparent in the recently deployed Wi-Fi (IEEE802.11a, b, g, h) systems. These largely related to increasing the service range of high-speed wireless access, and mitigating the degradation of QoS caused by the environmental effects. Some salient features supported by WiMAX specification are:
The 802.16 specification uses a 256-point orthogonal frequency division multiplexed (OFDM) carrier technology, giving it greater range than wireless LANs, which are based on 64-point OFDM.
The 802.16 supports ATM, IPv4, IPv6, Ethernet, and VLAN services thus offering a rich choice of service possibilities to voice and data carriers. This is achieved by dividing different services into specific sub layers of the MAC. Convergence sublayers at the top of the MAC enable Ethernet, ATM, TDM voice and IP (Internet Protocol) services to be offered.
The 802.16 standard can be used to deliver broadband voice and data into cells that may have a wide range of properties. This includes a wide range of population densities, a wide range of cell radii and a wide range of propagation environments. This is achieved through the use of flexible PHY modulation and coding options, flexible frame and slot allocations, flexible QoS mechanisms, packing, fragmentation and ARQ.
The 802.16 has a well thought out security with authentication being handled as part of the common part sub layer with (PKI) X.509 digital certificates. All 802.16a compliant devices will incorporate two unique certificates, one specific to the unit and one specific to the manufacturer of the unit thus promoting a secure and efficient way of authenticating upstream. The 802.16 MAC has a privacy sublayer than performs authentication, key exchange and encryption of Media access control packet data units (MPDUs).
The 802.16 supports both time division duplex (TDD) and frequency division duplex (FDD) modes of operation on air, along with a range of channel bandwidths. The OFDM PHY mode, which is also known WirelessMAN-OFDM, is specified for use between 2 and 11 GHz.
The 802.16 use time slots, allowing greater spectral efficiency for quality of service capabilities. The maximum data rate for 802.16 is higher than that of 802.11a/b, mainly because it gets nearly twice the number of bits per second from a single Hertz of frequency.

Figure  SEQ Figure \* ARABIC 30 - Multi-stake Holder Relationships for WiMAX Standard
Basic Profiles
WiMAX defines interoperable system profiles targeted for common licensed and unlicensed bands used around the world. This enables 802.16-based equipment to be used in diverse spectrum allocations around the world.
WiMAX system profiles consist of one of the two basic MAC profiles, P2MP or Mesh and one of the six PHY profiles. Three bandwidth sizes 1.75, 3.5 and 7 MHz are primarily considered for 3.5GHz ETSI band, 3 and 5.5 MHz channelisation are considered for MMDS band, while the 10 MHz channelisation can be used for unlicensed bands.

Figure  SEQ Figure \* ARABIC 31 - Scope of WiMAX Specification
802.16 – Supported Features
The core components of a WiMAX system are the subscriber station (SS) otherwise known as the Customer Premise Equipment (CPE) and the base station (BS). A BS and one or more SSs can form a cell with a point-to-multipoint (P2MP) structure.
The IEEE 802.16 standard was designed to be as flexible as possible and has evolved as a set of air interfaces, where each physical layer specification is governed by the spectrum used and the associated regulations – but most importantly all have a common MAC layer.
802.16 Medium Access Control (MAC)
The IEEE 802.16 MAC protocol addresses the need for very high bit rates, both uplink and downlink. Access and bandwidth allocation algorithms must accommodate hundreds of terminals per channel, with terminals that may be shared by multiple end users. The services required by these end users are varied in their nature and include legacy time-division multiplex (TDM) voice and data, Internet Protocol (IP) connectivity, and packetised voice over IP (VoIP).
Along with the fundamental task of allocating bandwidth and transporting data, the MAC includes a privacy sublayer that provides authentication of network access and connection establishment to avoid theft of service, and it provides key exchange and encryption for data privacy.
To accommodate the more demanding physical environment and different service requirements of the frequencies between 2 and 11 GHz, the 802.16a project is upgrading the MAC to provide automatic repeat request (ARQ) and support for mesh, rather than only point-to-multipoint, network architectures.
The 802.16 MAC controls access of the BS and SSs to the air through a rich set of features. The on-air timing is based on consecutive frames that are divided into slots. The size of frames and the size of individual slots within the frames can be varied on a frame-by-frame basis, under the control of a scheduler in the BS. This allows effective allocation of on air resources to meet the demands of the active connections with their granted QoS properties.
The 802.16 MAC provides a connection-oriented service to upper layers of the protocol stack. Connections have QoS characteristics that are granted and maintained by the MAC. The QoS parameters for a connection can be varied by the SS making requests to the BS to change them while a connection is maintained. QoS service in the 802.16 MAC service takes one of four forms: constant bit rate grant, real time polling, non-real-time polling, and best effort.
To support this variety of services 802.16 MAC must accommodate both continuous and bursty traffic. Additionally, these services expect to be assigned QoS in keeping with the traffic types. The 802.16 MAC provides a wide range of service types analogous to the classic asynchronous transfer mode (ATM) service categories as well as newer categories such as guaranteed frame rate (GFR).
The 802.16 MAC protocol must also support a variety of backhaul requirements, including both asynchronous transfer mode (ATM) and packet-based protocols. Convergence sublayers are used to map the transport-layer-specific traffic to a MAC that is flexible enough to efficiently carry any traffic type. Through such features as payload header suppression, packing, and fragmentation, the convergence sublayers and MAC work together to carry traffic in a form that is often more efficient than the original transport mechanism.
Issues of transport efficiency are also addressed at the interface between the MAC and the physical layer (PHY). The MAC can make use of bandwidth-efficient burst profiles under favourable link conditions but shift to more reliable, although less efficient, alternatives as required to support the planned 99.999 percent link availability.
The request-grant mechanism is designed to be scalable, efficient, and self-correcting. The 802.16 access system does not lose efficiency when presented with multiple connections per terminal, multiple QoS levels per terminal, and a large number of statistically multiplexed users. It takes advantage of a wide variety of request mechanisms, balancing the stability of contentionless access with the efficiency of contention-oriented access.
While extensive bandwidth allocation and QoS mechanisms are provided, the details of scheduling and reservation management are left unstandardised and provide an important mechanism for vendors to differentiate their equipment. Media access control packet data units (MPDUs) are transmitted in on-air PHY slots. Within these MPDUs, MAC service data units (MSDUs) are transmitted. MSDUs are the packets transferred between the top of the MAC and the layer above. MPDUs are the packets transferred between the bottom of the MAC and the PHY layer below. Across MPDUs, MSDUs can be fragmented. Within MPDUs, MSDUs can be packed (aggregated). Fragments of MSDUs can be packed within a single packed MPDU. Automatic retransmission request (ARQ) can be used to request the retransmission of unfragmented MSDUs and fragments of MSDUs.
 INCLUDEPICTURE "http://img.cmpnet.com/commsdesign/csd/2004/jan04/intel-fig1.jpg" \* MERGEFORMATINET 
Figure  SEQ Figure \* ARABIC 32 - Layers of the 802.16 Protocol
802.16 Physical (PHY)
In the design of the PHY specification for 10–66 GHz, line-of-sight propagation was deemed a practical necessity. With this condition assumed, single-carrier modulation was easily selected; the air interface is designated “WirelessMAN-SC.” Many fundamental design challenges remained, however. Because of the point-to-multipoint architecture, the BS basically transmits a TDM signal, with individual subscriber stations allocated time slots serially. Access in the uplink direction is by time-division multiple access (TDMA).
While extensive bandwidth allocation and QoS mechanisms are provided, the details of scheduling and reservation management are left un-standardised and provide an important mechanism for vendors to differentiate their equipment. The PHY specification defined for 10–66 GHz uses burst single-carrier modulation with adaptive burst profiling in which transmission parameters, including the modulation and codling schemes, my be adjusted individually to each subscriber station on a frame-by-frame basis. Both TDD and burst FDD variants are defined.

Figure  SEQ Figure \* ARABIC 33 - 10-66 GHZ TDD Frame for 1mS,
Selected burst design allows both time-division duplexing (TDD), in which the uplink and downlink share a channel but do not transmit simultaneously, and frequency-division duplexing (FDD), in which the uplink and downlink operate on separate channels, sometimes simultaneously. This burst design allows both TDD and FDD to be handled in a similar fashion. Support for half-duplex FDD subscriber stations, which may be less expensive since they do not simultaneously transmit and receive, was added at the expense of some slight complexity. Both TDD and FDD alternatives support adaptive burst profiles in which modulation and coding options may be dynamically assigned on a burst-by-burst basis.
The 2–11 GHz bands, both licensed and license-exempt are addressed in IEEE Project 802.16a. The standard is in ballot but is not yet complete. The draft currently specifies that compliant systems implement one of three air interface specifications, each of which provides for interoperability. Design of the 2–11 GHz physical layer is driven by the need for non-line-of-sight (NLOS) operation. Because residential applications are expected, rooftops may be too low for a clear sight line to a BS antenna, possibly due to obstruction by trees. Therefore, significant multipath propagation must be expected. Furthermore, outdoor-mounted antennas are expensive due to both hardware and installation costs.
The three 2–11 GHz air interface specifications in 802.16a Draft 3 are:
WirelessMAN-SC2: This uses a single-carrier modulation format.
WirelessMAN-OFDM: This uses orthogonal frequency-division multiplexing with a 256point transform. Access is by TDMA. This air interface is mandatory for license-exempt bands.
WirelessMAN-OFDMA: This uses orthogonal frequency-division multiple access with a 2048-point transform. In this system, addressing a subset of the multiple carriers to individual receivers provides multiple accesses.
The OFDM PHY
The OFDM signalling format was selected in preference to competing formats such as single-carrier (SC) and CDMA due to its superior non line-of-sight (NLOS) performance, which permits significant equalizer design simplification to support operation in multipath propagation environments. Reel-Solomon and convolutional coding are mandatory forward-error correction techniques that must be used when implementing the WirelessMAN OFDM PHY.
Orthogonal Frequency Division Multiplexing is one of the radio interface techniques that has gained attraction recently. The key issue in OFDM is the division of the frequency-selective transmission channel into several subchannels, which can be characterized as flat fading channels. Another significant property of the OFDM is the IDFT / DFT pair. All signal processing is made in the frequency domain and before transmission the signal is transformed to the time domain. OFDM is very tolerant to ISI and it is spectrally efficient. On the other hand, OFDM is very susceptible to phase and frequency offsets.
Orthogonal Frequency Division Multiplexing has become an attractive technique and gained more popularity recently. Many new communication systems have selected OFDM because its good properties, e.g. tolerance to inter-symbol interference (ISI) and good spectral efficiency. It becomes more attractive proposition with falling prices of integrated circuits and the ever increasing new possibilities of using fast Fourier-transform. At the moment OFDM is used in both wireline and wireless communications.
In WirelessMAN OFDM, the Fast Fourier transform (FFT) size is 256. In this 256 block, 55 sub-carriers (28 low and 27 high) are set aside for guard band and 8 sub-carriers are used for pilot signal. Fixing the number of used sub-carriers to 192, the system uses different over-sampling rates of higher than 1, 8/7 and 7/6, to maximize the achieved throughput while meeting spectral masks of different regulatory requirements. The WirelessMAN OFDM supports a wide range of guard time sizes relative to the OFDM symbol period. At the maximum, 25% guard time can be considered while the minimum value of 3% can be used in relatively benign channel condition.
IEEE 802.16 also considers optional sub-channelisation in uplink. This feature is particularly useful when a power-limited platform such as a laptop is considered in the subscriber station in an indoor portable or mobile environment. With a sub-channelisation factor of 1/16, a 12-dB link budget enhancement can be achieved. Sixteen sets of 12 sub-carriers each are defined, where one, two, four, eight or all sets can be assigned to a subscriber station in uplink. The eight pilot carriers are used when more than one set of sub-channels are allocated.
To support and handle time variation in the channel, the 802.16 standard provisions optional, more frequent repetition of preambles. In the uplink path, short preambles, called mid-ambles for this purpose, can be repeated with a programmable repetition period.
In the downlink direction, a short preamble can be optionally inserted at the beginning of all downlink bursts in addition to the long preamble that is presented by default at the beginning of the frame. A proper implementation of base station scheduler guarantees minimum required repetition interval for channel estimation.
Framing and Media Access
In 802.16, the PHY part of the specification is responsible for the on air framing, media access, and slot allocation. The MAC itself is concerned with performing the mapping from MSDUs to the MPDUs carried in the on air transmissions. This places the division of labour between the PHY and MAC slightly higher in the stack than is common. On air transmission time is divided into frames. In the case of an FDD system, there are uplinks (SS to BS) and downlink (BS to SS) sub frames that are time aligned on separate uplink and downlink channels. In the case of a TDD system, each frame is divided up into a downlink sub frame and an uplink sub frame.
In both TDD and FDD modes, the length of the frame can vary (under the control of the BS scheduler) per frame. In TDD mode, the division point between uplink and downlink can also vary per frame, allowing asymmetric allocation of on airtime between uplink and downlink if required.
Medium Access Control (MAC) Layer
A successful broadband wireless access system must have an efficient co-designed medium access control (MAC) layer for reliable link performance over the lossy wireless channel. The MAC must be designed so that the TCP/IP layers see a high-quality link that it expects. This is achieved by an automatic retransmission and fragmentation mechanism (automatic repeat request, ARQ), wherein the transmitter breaks up packets received from higher layers into smaller sub packets, which are transmitted sequentially. If a sub packet is receiver incorrectly, the transmitter is requested to retransmit it. ARQ can be seen as a mechanism for introducing time diversity into the system due to its capability to recover from noise, interference, and fades.
The MAC includes service-specific convergence sublayers that interface to higher layers, above the core MAC common part sublayer that carries out the key MAC functions. Below the common part sublayer is the privacy sublayer. In an 802.16 system, the MAC communicates using MAC protocol data units (MPDUs) that are carried by the PHY.
The generic MAC header (GMH) contains details of the MPDU. Principally the connection ID (CID) that defines the connection that this packet is servicing, the length of the frame and bits to qualify the presence of the CRC, sub headers and whether or not the payload is encrypted and if so, with which key.
A 32-bit CCITT standard CRC of the entire MPDU may be appended to the frame if required. The payload can contain either a management message or transport data. Specific connections are set-aside as management connections and these carry management messages and not anything else. All other channels are transport channels that do not carry management messages.
A payload in a transport connection can contain a MAC service data unit (MSDU), fragments of MSDUs, aggregates of MSDUs, aggregates of fragments of MSDUs, bandwidth requests or retransmission requests according to the MAC rules on bandwidth requesting, fragmentation, packing and ARQ.
Classification
Classification is the process by which a MAC SDU is mapped onto a particular connection for transmission between MAC peers. The mapping process associates a MAC SDU with a connection, which also creates an association with the service flow characteristics of that connection.
A classifier is a set of matching criteria applied to each packet entering to the 802.16 network. It consists of some protocol, specific matching criteria (i.e. destination IP address), a classifier priority and a reference to a CID.
Classifiers based on Layer 2, Layer 3 and Layer 4 criteria, i.e. by:
MAC address destination/source
VLAN destination/source
IP address destination/source
TOS
Port

Figure  SEQ Figure \* ARABIC 34 - 802.16 MAC PDU Format
MAC PDU Formats
The MAC PDU is the data unit exchanged between the MAC layers of the BS and its SSs. A MAC PDU consists of a fixed-length MAC header, a variable-length payload, and an optional cyclic redundancy check (CRC). Two header formats, are defined: the generic header and the bandwidth request header. Except for bandwidth request MAC PDUs, which contain no payload, MAC PDUs contain either MAC management messages or convergence sublayer data.
Three types of MAC sub header may be present.
The grant management sub header is used by an SS to convey bandwidth management needs to its BS.
The fragmentation sub header contains information that indicates the presence and orientation in the payload of any fragments of SDUs.
The packing sub header is used to indicate the packing of multiple SDUs into a single PDU.
The grant management and fragmentation sub headers may be inserted in MAC PDUs immediately following the generic header if so indicated by the Type field. The packing sub-header may be inserted before each MAC SDU if so indicated by the Type field.
The IEEE 802.16 MAC supports various higher-layer protocols such as ATM or IP. Incoming MAC SDUs from corresponding convergence sublayers are formatted according to the MAC PDU format, possibly with fragmentation and/or packing, before being conveyed over one or more connections in accordance with the MAC protocol. After traversing the airlink, MAC PDUs are reconstructed back into the original MAC SDUs so that the format modifications performed by the MAC layer protocol are transparent to the receiving entity.
IEEE 802.16 takes advantage of incorporating the packing and fragmentation processes with the bandwidth allocation process to maximize the flexibility, efficiency, and effectiveness of both. Fragmentation is the process in which a MAC SDU is divided into one or more MAC SDU fragments. Packing is the process in which multiple MAC SDUs are packed into a single MAC PDU payload. Both processes may be initiated by either a BS for a downlink connection or an SS for an uplink connection. IEEE 802.16 allows simultaneous fragmentation and packing for efficient use of the bandwidth.

Figure  SEQ Figure \* ARABIC 35 - PSDU Transport Stages
Service Specific Convergence Sublayer (SSCS)
IEEE Standard 802.16 defines two general service-specific convergence sublayers for mapping services to and from 802.16 MAC connections. The ATM convergence sublayer is defined for ATM services, and the packet convergence sublayer is defined for mapping packet services such as IPv4, IPv6, Ethernet, and virtual local area network (VLAN).
The SSCS interface to higher layers provides any transformation or mapping of external network data, received through the SSCS service access point (SAP), into MAC Service Data Unit SDUs received by the MAC CPS through the MAC SAP. For mapping service to and from 802.16 MAC connections, the SSCS is providing in two convergence sublayers, the ATM convergence sublayer and Packet convergence sublayer, to allow integration with both ATM and packet based networks.
The primary task of the sublayer is to classify service data units (SDUs) to the proper MAC connection, preserve or enable QoS, and enable bandwidth allocation. The mapping takes various forms depending on the type of service.
In addition to these basic functions, the convergence sublayers can also perform more sophisticated functions such as payload header suppression and reconstruction to enhance airlink efficiency.
The ATM convergence Sublayer (ATM CS)
The ATM CS is defined for ATM services, and it is a logical interface that associates different ATM services with the MAC CPS SAP. The ATM CS accepts ATM cells from the ATM layer, performs classification and, if provisioned, payload header suppression (PHS), and delivers CS PDUs to the appropriate MAC SAP.
The Packet convergence Sublayer (Packet CS)
The packet CS is used for mapping all packet-based protocols such as Ethernet, point-to-point protocol (PPP) and both IPv4 and IPv6 Internet protocols.
MAC Common Part Sublayer MAC (CPS)
The MAC CPS is the nucleus of the standard. It provides the core MAC rules and mechanisms for system access, bandwidth allocation, and connection maintenance. The MAC CPS receives data from the different CSs through the MAC SAP, classified to particular MAC connections. Also within the MAC CPS QoS decisions for transmission scheduling are performed.
In general, the 802.16 MAC is designed to support a point-to-multipoint architecture with a central BS handling multiple independent sectors simultaneously. On the downlink, data to SSs are multiplexed in TDM fashion. The uplink is shared between SSs in TDMA fashion.
The 802.16 MAC is connection-oriented. All services, including inherently connectionless services, are mapped to a connection. This provides a mechanism for requesting bandwidth, associating QoS and traffic parameters, transporting and routing data to the appropriate convergence sub-layer, and all other actions associated with the contractual terms of the service. Connections are referenced with 16-bit connection identifiers (CIDs) and may require continuously granted bandwidth or bandwidth on demand. As will be described, both are accommodated.
Each SS has a standard 48-bit MAC address, but this serves mainly as an equipment identifier, since the primary addresses used during operation are the CIDs. Upon entering the network, the SS is assigned three management connections in each direction. These three connections reflect the three different QoS requirements used by different management levels.
The first of these is the basic connection, which is used for the transfer of short, time-critical MAC and radio link control (RLC) messages. The primary management connection is used to transfer longer, more delay-tolerant messages such as those used for authentication and connection set-up.
The secondary management connection is used for the transfer of standards-based management messages such as Dynamic Host Configuration Protocol (DHCP), Trivial File Transfer Protocol (TFTP), and Simple Network Management Protocol (SNMP). In addition to these management connections, SSs are allocated transport connections for the contracted services. Transport connections are unidirectional to facilitate different uplink and downlink QoS and traffic parameters; they are typically assigned to services in pairs.
The MAC reserves additional connections for other purposes. One connection is reserved for contention-based initial access. Another is reserved for broadcast transmissions in the downlink as well as for signalling broadcast contention-based polling of SS bandwidth needs. Additional connections are reserved for multicast, rather than broadcast, contention-based polling. SSs may be instructed to join multicast polling groups associated with these multicast polling connections.
PHY Support and Frame Structure
The IEEE 802.16 MAC supports both TDD and FDD. In FDD, both continuous and burst downlinks are supported. Continuous downlinks allow for certain robustness enhancement techniques, such as interleaving. Burst downlinks (either FDD or TDD) allow the use of more advanced robustness and capacity enhancement techniques, such as subscriber-level adaptive burst profiling and advanced antenna systems.
Radio Link Control
The advanced technology of the 802.16 PHY requires equally advanced radio link control (RLC), particularly the capability of the PHY to transition from one burst profile to another. The RLC must control this capability as well as the traditional RLC functions of power control and ranging.
RLC begins with periodic BS broadcast of the burst profiles that have been chosen for the uplink and downlink. The particular burst profiles used on a channel are chosen based on a number of factors, such as rain region and equipment capabilities. Burst profiles for the downlink are each tagged with a Downlink Interval Usage.
After initial determination of uplink and downlink burst profiles between the BS and a particular SS, RLC continues to monitor and control the burst profiles. Harsher environmental conditions, such as rain fades, can force the SS to request a more robust burst profile.
Alternatively, exceptionally good weather may allow an SS to temporarily operate with a more efficient burst profile. The RLC continues to adapt the SS’s current UL and DL burst profiles, ever striving to achieve a balance between robustness and efficiency. Because the BS is in control and directly monitors the uplink signal quality, the protocol for changing the uplink burst profile for an SS is simple: the BS merely specifies the pro-file’s associated UIUC whenever granting the SS bandwidth in a frame. This eliminates the need for an acknowledgment, since the SS will always receive either both the UIUC and the grant or neither. Hence, no chance of uplink burst profile mismatch between the BS and SS exists.
In the downlink, the SS is the entity that monitors the quality of the receive signal and therefore knows when its downlink burst profile should change. The BS, however, is the entity in control of the change. There are two methods available to the SS to request a change in downlink burst profile, depending on whether the SS operates in the grant per connection (GPC) or grant per SS (GPSS).
Service Flows
Service Flow is a MAC transport service that provides unidirectional transport of packets either to uplink packets transmitted by the SS or to downlink packets transmitted by the BS. A Service Flow is characterized by a set of QoS parameters such as latency, jitter, and throughput assurance.
Uplink Scheduling Services
Each connection in the uplink direction is mapped to a scheduling service. Each scheduling service is associated with a set of rules imposed on the BS scheduler responsible for allocating the uplink capacity and the request-grant protocol between the SS and the BS. The detailed specification of the rules and the scheduling service used for a particular uplink connection is negotiated at connection set-up time. The scheduling services in IEEE 802.16 are based on those defined for cable modems in the DOCSIS standard.
Unsolicited grant service (UGS) is tailored for carrying services that generate fixed units of data periodically. Here the BS schedules regularly, in a pre-emptive manner, grants of the size negotiated at connection set-up, without an explicit request from the SS. This eliminates the overhead and latency of bandwidth requests in order to meet the delay and delay jitter requirements of the underlying service. A practical limit on the delay jitter is set by the frame duration. If more stringent jitter requirements are to be met, output buffering is needed. Services that typically would be carried on a connection with UGS service include ATM constant bit rate (CBR) and E1/T1 over ATM.
The real-time polling service is designed to meet the needs of services that are dynamic in nature, but offers periodic dedicated request opportunities to meet real-time requirements. Because the SS issues explicit requests, the protocol overhead and latency is increased, but this capacity is granted only according to the real need of the connection. The real-time polling service is well suited for connections carrying services such as VoIP or streaming video or audio.
The non-real-time polling service is almost identical to the real-time polling service except that connections may utilize random access transmit opportunities for sending bandwidth requests. Typically, services carried on these connections tolerate longer delays and are rather insensitive to delay jitter. The non-real-time polling service is suitable for Internet access with a minimum guaranteed rate and for ATM GFR connections.
A best effort service has also been defined. Neither throughput nor delay guarantees are provided. The SS sends requests for bandwidth in either random access slots or dedicated transmission opportunities. The occurrence of dedicated opportunities is subject to network load, and the SS cannot rely on their presence.
Bandwidth Requests and Grants
The IEEE 802.16 MAC accommodates two classes of SS, differentiated by their ability to accept bandwidth grants simply for a connection or for the SS as a whole. Both classes of SS request bandwidth per connection to allow the BS uplink scheduling algorithm to properly consider QoS when allocating bandwidth. With the grant per connection (GPC) class of SS, bandwidth is granted explicitly to a connection, and the SS uses the grant only for that connection. RLC and other management protocols use bandwidth explicitly allocated to the management connections.
With the grant per SS (GPSS) class, SSs are granted bandwidth aggregated into a single grant to the SS itself. The GPSS SS needs to be more intelligent in it’s handling of QoS. It will typically use the bandwidth for the connection that requested it, but need not. For instance, if the QoS situation at the SS has changed since the last request, the SS has the option of sending the higher QoS data along with a request to replace this bandwidth stolen from a lower QoS connection. The SS could also use some of the bandwidth to react more quickly to changing environmental conditions by sending message.
The two classes of SS allow a trade-off between simplicity and efficiency. The need to explicitly grant extra bandwidth for RLC and requests, coupled with the likelihood of more than one entry per SS, makes GPC less efficient and scalable than GPSS. Additionally, the ability of the GPSS SS to react more quickly to the needs of the PHY and those of connections enhances system performance. GPSS is the only class of SS allowed with the 10–66 GHz PHY.
With both classes of grants, the IEEE 802.16 MAC uses a self-correcting protocol rather than an acknowledged protocol. This method uses less bandwidth. Furthermore, acknowledged protocols can take additional time, potentially adding delay.
There are a number of reasons the bandwidth requested by an SS for a connection may not be available, in the self-correcting protocol, all of these anomalies are treated the same. After a timeout appropriate for the QoS of the connection (or immediately, if the bandwidth was stolen by the SS for another purpose), the SS simply requests again. For efficiency, most bandwidth requests are incremental; that is, the SS asks for more bandwidth for a connection. However, for the self-correcting bandwidth request/grant mechanism to work correctly the bandwidth requests must occasionally be aggregate; that is, the SS informs the BS of its total current bandwidth needs for a connection.
This allows the BS to reset its perception of the SS’s needs without a complicated protocol acknowledging the use of granted bandwidth. The SS has a plethora of ways to request bandwidth, combining the determinism of unicast polling with the responsiveness of contention-based requests and the efficiency of unsolicited bandwidth. For continuous bandwidth demand, such as with CBR T1/E1 data, the SS need not request bandwidth; the BS grants it unsolicited.
To short-circuit the normal polling cycle, any SS with a connection running UGS can use the poll-me bit in the grant management sub header to let the BS know it needs to be polled for bandwidth needs on another connection. The BS may choose to save bandwidth by polling SSs that have unsolicited grant services only when they have set the poll-me bit.
A more conventional way to request bandwidth is to send a bandwidth request MAC PDU that consists of simply the bandwidth request header and no payload. GPSS SSs can send this in any bandwidth allocation they receive. GPC terminals can send it in either a request interval or a data grant interval allocated to their basic connection. A closely related method of requesting data is to use a grant management sub header to piggyback a request for additional bandwidth for the same connection within a MAC PDU.
In addition to polling individual SSs, the BS may issue a broadcast poll by allocating a request interval to the broadcast CID. Similarly, the standard provides a protocol for forming multicast groups to give finer control to contention-based polling. Due to the non-deterministic delay that can be caused by collisions and retries, contention-based requests are allowed only for certain lower QoS classes of service.
In general, service flows in IEEE 802.16 are pre-provisioned, and set-up of the service flows is initiated by the BS during SS initialisation. However, service flows can also be dynamically established by either the BS or the SS.
Channel Acquisition
The MAC protocol includes an initialisation procedure designed to eliminate the need for manual configuration. Upon installation, an SS begins scanning its frequency list to find an operating channel. It may be programmed to register with a specified BS, referring to a programmable BS ID broadcast by each. This feature is useful in dense deployments where the SS might hear a secondary BS due to selective fading or when the SS picks up a side-lobe of a nearby BS antenna.
After deciding on which channel or channel pair to attempt communication, the SS tries to synchronize to the downlink transmission by detecting the periodic frame preambles. Once the physical layer is synchronized, the SS will look for the periodically broadcast DCD and UCD messages that enable the SS to learn the modulation and FEC schemes used on the carrier.
Initial Ranging and Negotiation of SS Capabilities — Upon learning what parameters to use for its initial ranging transmissions, the SS will look for initial ranging opportunities by scanning the UL-MAP messages present in every frame. The SS uses a truncated exponential back off algorithm to determine which initial ranging slot it will use to send a ranging request message. The SS will send the burst using the minimum power setting and will try again with increasingly higher transmission power if it does not receive a ranging response.
Based on the arrival time of the initial ranging request and the measured power of the signal, the BS commands a timing advance and a power adjustment to the SS in the ranging response. The response also provides the SS with the basic and primary management CIDs. Once the timing advance of the SS transmissions has been correctly determined, the ranging procedure for fine-tuning the power can be performed using invited transmissions.
All transmissions up to this point are made using the most robust, and thus least efficient, burst profile. To avoid wasting capacity, the SS next reports its PHY capabilities, including the modulation and coding schemes it supports and whether, in an FDD system, it is half-duplex or full duplex. The BS, in its response, can deny the use of any capability reported by the SS.
SS Authentication and Registration
Each SS contains both a manufacturer-issued factory-installed X.509 digital certificate and the certificate of the manufacturer. These certificates, which establish a link between the 48bit MAC address of the SS and its public RSA key, are sent to the BS by the SS in the Authorization Request and Authentication Information messages. The network is able to verify the identity of the SS by checking the certificates and can subsequently check the level of authorization of the SS. If the SS is authorized to join the network, the BS will respond to its request with an Authorization Reply containing an Authorization Key (AK) encrypted with the SS’s public key and used to secure further transactions.
Upon successful authorization, the SS will register with the network. This will establish the secondary management connection of the SS and determine capabilities related to connection set-up and MAC operation. The version of IP used on the secondary management connection is also determined during registration.
IP Connectivity
After registration, the SS attains an IP address via DHCP and establishes the time of day via the Internet Time Protocol. The DHCP server also provides the address of the TFTP server from which the SS can request a configuration file. This file provides a standard interface for providing vendor-specific configuration information.
Connection Set-up
IEEE 802.16 uses the concept of service flows to define unidirectional transport of packets on either downlink or uplink. Service flows are characterized by a set of QoS parameters such as latency and jitter. To most efficiently utilize network resources such as bandwidth and memory, 802.16 adopts a two-phase activation model in which resources assigned to a particular admitted service flow may not be actually committed until the service flow is activated. Each admitted or active service flow is mapped to a MAC connection with a unique CID.
In general, service flows in IEEE 802.16 are pre-provisioned, and set-up of the service flows is initiated by the BS during SS initialisation. However, service flows can also be dynamically established by either the BS or the SS. The SS typically initiates service flows only if there is a dynamically signalled connection, such as a switched virtual connection (SVC) from an ATM network. The establishment of service flows is performed via a three-way handshaking protocol in which the request for service flow establishment is responded to and the response acknowledged.
In addition to dynamic service establishment, IEEE 802.16 also supports dynamic service changes in which service flow parameters are renegotiated. Like dynamic service flow establishment, service flow changes also follow a similar three-way handshaking protocol.
Privacy Sublayer
The Privacy Sublayer lies between the MAC CPS and the PHY layer. It provides subscribers with privacy across the fixed broadband wireless network. It does this by encrypting connections between SS and BS. Further more, Privacy is used for authentication and secure key exchange.
IEEE 802.16’s privacy protocol is based on the Privacy Key Management (PKM) protocol of the DOCSIS BPI+ specification but has been enhanced to fit seamlessly into the IEEE 802.16 MAC protocol and to better accommodate stronger cryptographic methods, such as the recently approved Advanced Encryption Standard.
Security Associations
PKM is built around the concept of security associations (SAs). The SA is a set of cryptographic methods and the associated keying material; that is, it contains the information about which algorithms to apply, which key to use, and so on. Every SS establishes at least one SA during initialisation. Each connection, with the exception of the basic and primary management connections, is mapped to an SA either at connection set-up time or dynamically during operation.
Cryptographic Methods
Currently, the PKM protocol uses X.509 digital certificates with RSA public key encryption for SS authentication and authorization key exchange. For traffic encryption, the Data Encryption Standard (DES) running in the cipher block chaining (CBC) mode with 56-bit keys is currently mandated. The CBC initialisation vector is dependent on the frame counter and differs from frame to frame. To reduce the number of computationally intensive public key operations during normal operation, the transmission encryption keys are exchanged using 3DES with a key exchange key derived from the authorization key.
The PKM protocol messages themselves are authenticated using the Hashed Message Authentication Code (HMAC) protocol with SHA-1. In addition, message authentication in vital MAC functions, such as the connection set-up, is provided by the PKM protocol.
The MAC incorporates several features suitable for a broad range of applications at different mobility rates, such as the following:
Four service classes are Unsolicited Grant Service (UGS), real-time Polling Service (rtPS), non-real time Polling Service (nrtPS), and Best Effort (BE).
Header suppression, packing, and fragmentation for efficient use of spectrum.
Privacy Key Management (PKM) for MAC layer security. PKM version 2 incorporates support for Extensible Authentication Protocol (EAP).
Broadcast and Multicast support.
Manageability primitives.
High-speed handover and mobility management primitives.
Three power management levels: Normal Operation, Sleep, and Idle (with paging support).
These features combined with the inherent benefits of scalable OFDMA make 802.16 suitable for high-speed data and bursty or isochronous IP multimedia applications.
Physical (PHY) Layer
The PHY specification defined for 10–66 GHz uses burst single-carrier modulation with adaptive burst profiling in which transmission parameters, including the modulation and coding schemes, may be adjusted individually to each subscriber station (SS) on a frame-by-frame basis. Both TDD and burst FDD variants are defined.
Channel bandwidths of 20 or 25 MHz (typical U.S. allocation) or 28 MHz (typical European allocation) are specified, along with Nyquist square-root raised-cosine pulse shaping with a rolloff factor of 0.25. Randomisation is performed for spectral shaping and to ensure bit transitions for clock recovery.

Figure  SEQ Figure \* ARABIC 36 - Burst FDD - With Scheduling Flexibility
The forward error correction (FEC) used is Reed-Solomon GF(256), with variable block size and error correction capabilities. This is paired with an inner block convolutional code to robustly transmit critical data, such as frame control and initial accesses. The FEC options are paired with quadrature phase shift keying (QPSK), 16state quadrature amplitude modulation (16QAM), and 64-state QAM (64-QAM) to form burst profiles of varying robustness and efficiency. If the last FEC block is not filled, that block may be shortened. Shortening in both the uplink and downlink is controlled by the BS and is implicitly communicated in the uplink map (ULMAP) and downlink map (DL-MAP).
The system uses a frame of 0.5, 1, or 2 ms and is divided into physical slots for the purpose of bandwidth allocation and identification of PHY transitions. A physical slot is defined to be 4 QAM symbols. In the TDD variant of the PHY, the uplink sub frame follows the downlink sub frame on the same carrier frequency. In the FDD variant, the uplink and downlink sub frames are coincident in time but are carried on separate frequencies.
The downlink sub frame starts with a frame control section that contains the DL-MAP for the current downlink frame as well as the ULMAP for a specified time in the future. The downlink map specifies when physical layer transitions (modulation and FEC changes) occur within the downlink sub frame. The downlink sub frame typically contains a TDM portion immediately following the frame control section. Downlink data are transmitted to each SS using a negotiated burst profile. The data are transmitted in order of decreasing robustness to allow SSs to receive their data before being presented with a burst profile that could cause them to lose synchronization with the downlink.
In FDD systems, the TDM portion may be followed by a TDMA segment that includes an extra preamble at the start of each new burst profile. This feature allows better support of half-duplex SSs. In an efficiently scheduled FDD system with many half-duplex SSs, some may need to transmit earlier in the frame than they receive. Due to their half-duplex nature, these SSs lose synchronization with the downlink. The TDMA preamble allows them to regain synchronization.
Due to the dynamics of bandwidth demand for the variety of services that may be active, the mixture and duration of burst profiles and the presence or absence of a TDMA portion vary dynamically from frame to frame. Since the recipient SS is implicitly indicated in the MAC headers rather than in the DL-MAP, SSs listen to all portions of the downlink sub frame they are capable of receiving. For full-duplex SSs, this means receiving all burst profiles of equal or greater robustness than they have negotiated with the BS.
Unlike the downlink, the UL-MAP grants bandwidth to specific SSs. The SSs transmit in their assigned allocation using the burst profile specified by the Uplink Interval Usage Code (UIUC) in the UL-MAP entry granting them bandwidth. The uplink sub-frame may also contain contention-based allocations for initial system access and broadcast or multicast bandwidth requests. The access opportunities for initial system access are sized to allow extra guard time for SSs that have not resolved the transmit time advance necessary to offset the round-trip delay to the BS.
Between the PHY and MAC is a transmission convergence (TC) sublayer. This layer performs the transformation of variable length MAC protocol data units (PDUs) into the fixed length FEC blocks (plus possibly a shortened block at the end) of each burst. The TC layer has a PDU sized to fit in the FEC block currently being filled. It starts with a pointer indicating where the next MAC PDU header starts within the FEC block. The TC PDU format allows resynchronisation to the next MAC PDU in the event that the previous FEC block had irrecoverable errors. Without the TC layer, a receiving SS or BS would potentially lose the entire remainder of a burst when an irrecoverable bit error occurred.
Mobile WiMAX
Universal acceptance of 802.16 for portable and mobile use is contingent on the Industry’s development, acceptance, and conformance to two complementary aspects of the IEEE 802.16 air interface standards work:
Development and adoption of an open and extensible end-to-end architecture framework and specification that is agnostic to incumbent operator backend networks
Means for ensuring specification compliant and vendor interoperable equipment to support cost-effective deployments and give users the capability to roam across networks established by different network operators.
A common architecture framework and standardized compliance testing mechanisms based on a suite of PHY and MAC profiles will enable multivendor interoperability supporting different deployment and use case scenarios.
IEEE 802.16 specifications are evolving to target a broader market opportunity for mobile, high-speed broadband applications. The promise of realizing a low-cost, broadly interoperable wide-area data network that supports portable and mobile usage could have significant end-user benefits. Notably, this network can complement and extend the Wi-Fi hotspot usage model to provide broader Internet Protocol (IP) data service coverage and roaming that has so far eluded current 3G systems, due to system cost and complexity.
Further to the 802.16-2004 standard published last year, which supersedes all previous versions as the base standard and specifies networks for the current fixed access market segment, the soon to be finalized 802.16e amendment and the 802.16f and 802.16g task groups will update the base specification to enable not just fixed, but also portable and mobile operation in frequency bands below 6 GHz.
802.16 is optimized to deliver high, bursty data rates to Subscriber Stations (SS) but the sophisticated Medium Access Control (MAC) architecture can simultaneously support real-time multimedia and isochronous applications such as Voice Over IP (VoIP) as well. This means that IEEE 802.16 is uniquely positioned to extend broadband wireless beyond the limits of today’s Wi-Fi systems, both in distance and in the ability to support applications requiring advanced Quality of Service (QoS) such as VoIP, streaming video, and on-line gaming.
The technology is expected to be adopted by different incumbent operator types–for example, Wireless Internet Service Providers (WISPs), cellular operators (CDMA and WCDMA), and wireline broadband providers. Each of these operators will approach the market with different models. As a result, 802.16 network deployments face the challenging task of needing to adapt to different network architectures while still supporting standardized components and interfaces for multivendor interoperability.
Migration towards Mobility
To support the incremental functionality beyond fixed access deployment, there are required enhancements to both the air interface and network infrastructure. Both of these enhancements must also be standardized before interoperable services meeting end user demands can be realized. Usage expectations will play a prime role in development of future system as well as success of present systems in future.
Taking a cue from the past wireless and mobile technology evolution, some basic system capabilities which will be required and must be driven into the end-to-end architecture, interfaces, and network features are:
Support for different Radio Access Network (RAN) topologies
Well-defined interfaces to enable 802.16 RAN architecture independence
Interfaces capable of seamless integration and interworking with Wi-Fi, 3GPP3 and 3GPP2 networks
Scalable all-IP 802.16 access network using Common Off The Shelf (COTS) equipment
Support for IPv4 and IPv6 clients and application servers
Functional extensibility to support future migration to full mobility and delivery of rich broadband multimedia
The 802.16 standard provides an excellent framework upon which systems can be built to satisfy the broad spectrum of usage models. Of the three PHY layers supported in the standard, scalable OFDMA is the most versatile and the one preferred for operation across channel widths ranging from 1.75 MHz to 20 MHz.
Single Carrier Access (SCa) will likely be considered for backhaul links while OFDM with 256point Fast Fourier Transform (FFT) is best suited for Fixed Access in up to 10 MHz channel widths. Scalable OFDMA supports features (enhanced over OFDM) that are especially suited for high-speed mobile operation such as Downlink (DL) and Uplink (UL) sub-channelization, fixed sub carrier spacing (by maintaining constant ratio of FFT size to channel width), and reduced overhead for Cyclic Prefix (CP) by keeping its duration constant at 1/8th the OFDMA symbol duration.
The 802.16 MAC is designed for Point-to-Multipoint (PMP) applications and is based on Collision Sense Multiple Access with Collision Avoidance (CSMA/CA). The 802.16 AP MAC manages UL and DL resources including Transmit and Receive scheduling. The MAC incorporates several features suitable for a broad range of applications at different mobility rates, such as four service classes, header suppression, packing, and fragmentation for efficient use of spectrum, privacy Key Management (PKM) for MAC layer security, high-speed handover and mobility management primitives. These features combined with the inherent benefits of scalable OFDMA make 802.16 suitable for high-speed data and bursty or isochronous IP multimedia applications.
Network Enhancement
As 802.16 evolves to address portable and mobile service, the feature requirements of the air interface and RAN network, interoperability demands, and interworking with other dissimilar networks like Wi-Fi and 3G also need to simultaneously evolve. The simple fact that mobile clients can dynamically associate and perform handover across base stations crossing large, possibly discontinuous geographic regions and operator domains, drives the need for a number of network-related enhancements.
The nomadic service usage needs enhancement over fixed access as in such case the user tries to log on from different locations in coverage area. This requires enhancements to security such as strong mutual authentication between the user/client device and the network base station supporting a flexible choice of credential types. Portable and mobile devices need a means for authenticating trusted base station and detecting rogue base station. Such mutual authentication is not present in the fixed access standard. Also a common centralized mechanism for user authentication is needed as users may move between different base stations within an IP prefix or subnet, or across base stations in different subnets, or even roam to other service providers in different locales.
The next stage, portability with simple mobility, describes a more automated management of IP connections with session persistence or automatic re-establishment following transitions between base stations. This incremental enhancement allows for more user transparent mobility and is suitable for latency tolerant applications such as TCP it does not provide adequate handover performance for delay and packet loss sensitive real-time applications such as VoIP.
In the fully mobile scenario, user expectations for connectivity are comparable to those experienced in 3G voice/data systems. Users may be moving while simultaneously engaging in a broadband data access or multimedia streaming session. The need to support low latency and low packet loss handovers of data streams as users transition from one AP to another is clearly a challenging task. For mobile data services, users will not easily adapt their service expectations because of environmental limitations that are technically challenging but not directly relevant to the user (such as being stationary or moving). For these reasons, the network and air interface must be designed up front to anticipate these user expectations and deliver accordingly.
RF System
There are three main blocks for a radio: synthesizer, power amplifier, and filter.
Synthesizer
The synthesizer generates the LO that mixes with the incoming RF to create a lower frequency signal that can be digitized and processed by the Baseband IC. The WiMAX specifications call for a high-performance synthesizer. The synthesizer block takes up a large part of the RFIC die area and is therefore a costly component of the RFIC. The Integrated Phase Noise is 99.9 percent reliability), high peak data rates (>2 Mb/s), and high spectrum efficiency (>4 b/s/Hz/sector).
Some of the key developments having direct bearing on commercial acceptance of system functionality are described below.
Dynamic Burst Mode TDMA MAC
Provides High Bandwidth
802.16 is optimised to deliver high, bursty data rates to Subscriber Stations. This means that IEEE 802.16 is uniquely positioned to extend broadband wireless beyond the limits of today's systems, both in distance and in the ability to support applications
Quality of Service
Provides carrier class service
Voice capability is extremely important, especially in underserved international markets. For this reason the IEEE 802.16a standard includes Quality of Service features that enable services including voice and video that require a low-latency network.
The grant/request characteristics of the 802.16 Media Access Controller (MAC) enables an operator to simultaneously provide premium guaranteed levels of service to businesses, such as T1-level service, and high-volume “best-effort” service to homes, similar to cable-level service, all within the same base station service area cell.
Link Adaptation
Provides high reliability
Adaptive modulation and coding - subscriber-by-subscriber, burst by burst, uplink and downlink. Transmission adaptation with help of modulation depending on channel condition provides high reliability to the system.
Keeps more users connected by virtue of its flexible channel widths and adaptive modulation. Because it uses channels narrower than the fixed 20-MHz channels used in 802.11, the 802.16-2004 standards can serve lower data- rate subscribers without wasting bandwidth. When subscribers encounter noisy conditions or low signal strength, the adaptive modulation scheme keeps them connected when they might otherwise be dropped.
Further this feature imparts differential service provision to the system making it economically more appealing to operators. Dynamic adaptive modulation allows the base station to tradeoff throughput for range. For example, if the base station cannot establish a robust link to a distant subscriber using the highest order modulation scheme, 64 QAM (Quadrature Amplitude Modulation), the modulation order is reduced to 16 QAM or QPSK (Quadrature Phase Shift Keying), which reduces throughput and increases effective range.
Non Line Of Sight (NLoS) Support
Provides wider market and lower costs
LoS service points a fixed antenna on the roof of a home or business at a wireless connectivity enabled tower with a strong and stable connection capable of sending high amounts of data with little loss or errors. LOS transmissions use higher frequencies as high as 60-100 GHz that features low interference and a lot of bandwidth. Most of the past and existing wireless broadband Solutions like LMDS suffered this restriction, limiting there market by enhancing installation and maintenance cost.
WiMAX solves or mitigates the problems resulting from NLOS conditions by using: Multiple frequency allocation support from 2-11 GHz - OFDM and OFDMA for NLoS applications (licensed and license-exempt spectrum), Sub-Channelisation, Directional antennas, Transmit and receive diversity, Adaptive modulation, Error correction techniques, and Power control.
NLOS service is one, as in case of proven and popular Wi-Fi, by which a small computer-based antenna links with a tower using a frequency range from 2 to 11 GHz. Longer-wavelength transmissions are not as easily disrupted by physical obstructions and can bend around obstacles.
WiMAX provides both LoS and NLoS options, this characteristic make available, wider client base to WiMAX. However the range and throughput is higher in case of LoS. WiFi-style access will be limited to a four to six mile radius (perhaps 25 square miles or 65 square km of coverage). On the other hand, the WiMAX LoS transmitting station sends data to WiMAX-enabled computers or routers in the transmitter's 30-mile radius (perhaps 3,600 square miles or 9,300 square km of coverage). A move from LoS to NLoS means that the RF challenges mount so do the costs of the Radio. For WiMAX to be successful the cost vs. performance equation has to be balanced carefully.
Two extreme examples of this cost and performance equation are on one hand we have a Single In Single Out (SISO) system requiring Line of Sight (LOS) radios while on the other hand, a Multiple In Multiple Out (MIMO) radio with NLOS capability, a 3x2 system (three receive and two transmit chains) support link margins of 165 dB that could penetrate inside homes in multipath environments against SISO’s link margins of typically 145 dB.
LOS radios result in truck rollouts utilizing experienced technicians to set the equipment up. However the cost of the radio is low due to its simplicity. In general, the SISO radio requires expensive installation and reliability is poor. MIMO radio with the NLoS ability, do not suffer from issue of costly truck rollouts, however, the cost of the multiple radio chains becomes a deterrent.
But with changing environment in which Radio Frequency Integrated Circuit (RFIC) integration is improving, costs will head down. WiMAX, through the use of integration and advanced techniques to increase link margins, should be able to achieve reliable wireless systems at a reasonable cost.
Highly Efficient Spectrum Utilization
Provides high efficiency
MAC designed for efficient use of spectrum, incorporates techniques for efficient frequency reuse, deriving a more efficient spectrum usage of the access system. WiMAX is amongst most spectral efficient systems developed so far.
Spectral Efficiency, which can be defined as information delivered per unit of spectrum and is measured in bits/second/Hertz/cell, is effected by various factors including but not limited to:
Multiple access method
Modulation methods
Channel organization
Resource reuse (code, timeslot, carrier,)
Spectral efficiency plays an important role in deciding technology, topology, specification and other design parameters of a broadband wireless network (even other narrowband or voice wireless networks). As the primary spectral efficiency limitation in generally is self-interference (interference from other base station of the same network), isolated base station spectral efficiency results does not represent real-world situation which is very different and complex. This has made derivation of per cell spectral efficiency vital for design consideration.
Spectrum efficiency is critical to network planners and operators as it directly affects network cost structure for a given service and grade of service. These parameters are basis of consumer pricing, hence value proposition of overall service and its affordability.
Some important cost implications depending on efficiency of spectrum use are
Amount of spectrum required (CapEx)
Number of sites, base stations and associated maintenance (CapEx, OpEx)
WIMAX which have many capabilities aiding in enhanced resource utilisation at the same time minimise losses due to factors like interference. It would not be an exaggeration, to say that WiMAX is designing for spectral efficiency. Some of the “Spectral (Temporal) and Spatial” tools (all to minimize interference) imbibed in WiMAX are:
Spectral Tools
Optimization Based on traffic characteristics
Multiple access
Data compression
Optimization Based on link qualities
Modulation
Channel coding
Equalization
Spatial Tools
Cellularisation - mitigate co-channel interference by separating co-channel users
Sectorisation - mitigate co-channel interference through static directivity
Power control - use minimum power necessary for successful communications
Flexible Channel Bandwidth
Provides bandwidth on demand, and scalability
As the distance between a subscriber and the base station (or AP) increases, or as the subscriber starts to move by walking or driving in a car, it becomes more of a challenge for that subscriber to transmit successfully back to the base station at a given power level. For power-sensitive platforms such as laptop computers or handheld devices, it’s often not possible for them to transmit to the base station over long distances if the channel bandwidth is wide.
The IEEE 802.16-2004 and IEEE 802.16e standards have flexible channel bandwidths between 1.5 and 20 MHz to facilitate transmission over longer ranges and to different types of subscriber platforms. In addition, this flexibility of channel bandwidth is also crucial for cell planning, especially in the licensed spectrum. For scalability, an operator with 14 MHz of available spectrum, for example, may divide that spectrum into four sectors of 3.5 MHz to have multiple sectors (transmit/receive pairs) on the same base station. With a dedicated antenna, each sector has the potential to reach users with more throughputs over longer ranges than can an omni-directional antenna. Net-to-net, flexible channel bandwidth is imperative for cell planning.
Smart Antenna Support
Provides better throughput to range relationship
The challenge faced by broadband wireless access technologies and solutions like WiMAX lies in not only provision of extremely high throughput but also in providing a comparable quality of service (QoS) for similar cost as competing wireline technologies.
The target frequency band for this system is 2–5 GHz due to favourable propagation characteristics and low radio frequency (RF) equipment cost. The broadband channel is typically non-LOS channel and includes impairments such as time-selective fading, frequency-selective fading and hence fall in spectral density.
Smart antennas are being used to increase the spectral density (that is, the number of bits that can be communicated over a given channel in a given time) and to increase the signal-to-noise ratio (SNR) for both WiMAX solutions (can be used for other wireless technologies like Wi-Fi). While smarter antennas extend Range, conserve Power, and improve Security. Smart antennas greatly improve range and bandwidth capacity, sometimes extending more than 100 times farther than omnidirectional antennas.
Smart antennas are derivatives of the directional antenna concept. Where omnidirectional antennas radiate energy in a 3600 pattern directional antennas focus that energy more narrowly like a megaphone that focuses voice and helps it reach longer distances. Directional 1800 antennas are useful on the outside walls of buildings when aimed inward, and 900 antennas are good for corners. Even more narrowly focused models are good between two buildings.
Smart antennas can be described as narrowly focused directional antennas that can “spin” around electronically and aim at each user in turn. Some of them can also adjust transmit power as they spin conserving power and improve security. They use digital signal processing and an array of two or more antennas to adjust the focus and shape of transmissions.
Smart or Adaptive Antennas are systems comprising of multiple antenna elements (antenna arrays) with capability of coherent processing and strategies that can adapt to environment. In these antenna systems each antenna element signals are processed adaptively, are controlled by DSP and adapts to the RF environments. While providing gain and interference mitigation to improve signal quality and spectral efficiency. Overall smart antennas lead to improved coexistence behaviour. In case of the most advanced smart antenna systems, applied approach is one of using variety of DSP algorithms to dynamically minimize interference and maximise intended signal reception quality.
The 802.16-2004 standards, due to performance and technology, support several adaptive smart antenna types as discussed below.
Receive spatial diversity antennas: Entails more than one antenna receiving the signal. The antennas need to be placed at least half a wavelength apart to operate effectively, where wavelength can be derived by taking the inverse of the frequency. For example, for a 2.5-GHz carrier the wavelength would be 0.13 meters hence the distance between antennas would be 0.065 meter or approx 2.5 inches. Maintaining this minimum distance ensures that the antennas are incoherent, that is, they will be impacted differently by the additive/subtractive effects of signals arriving by means of multiple paths.
Simple diversity antennas: Detect the signal strength of the multiple (two or more) antennas attached and switch that antenna into the receiver. The likelihood of getting a strong signal depends on number of incoherent antennas to choose from.
Beam-steering antennas: Shape the antenna array pattern to produce high gains in the useful signal direction or notches that reject interference. High antenna gain increases the signal, noise and rate. The directional pattern attenuates the interference out of the main beam. Selective fading can be mitigated if multi-path components arrive with a sufficient angular separation.
Beam-forming antennas: Allow the area around a base station to be divided into sectors, allowing additional frequency reuse among sectors. The number of sectors can range from as few as four to as many as 24. Base stations that intelligently manage sectors have been used for a long time in mobile-service base stations.

Figure  SEQ Figure \* ARABIC 37 - Working of Smart Antennas
Using smart antenna systems is like talking to someone close by for one millisecond and then talking to someone far away for the next millisecond, without the need to shout or increase pitch. Irrespective of distance in between only whispers are sufficient to communicate clearly as others cannot hear.
Working of these systems start when the signal processing steers the radiation beam towards a desired wireless user. On locking the user, the beam follows the user as he moves. At the same time, it minimises the interference arising from other users by interference cancellation or nulling. This smartness seen in these systems come from the intelligent signal processor, the one which use a complex and intensive computational algorithm, incorporated in these systems.
Mechanisms
Functions performed by smart antennas during transmission and reception are:
Direction of arrival (DoA) is estimated for all incoming signals, including the interfering and multipath signals
The desired user signal is identified
The beam is steered in the direction of the desired signal
The user is tracked while he moves
Nulls are placed in the interfering signal direction
One must note that some of the traditional strategies of radio planning have to be modified while using smart antenna, as it is much more efficient to position the base stations at specific locations for better exploitation of the spatial dimension, for example base stations must be placed away from the road or railways, if mobile subscribers travelling on them are intended to be covered by the service.
MIMO – Coming Soon to Networks Near You
Increasing demand for high-performance broadband wireless access at throughputs in range of tens of Mbps can be enabled by the use of multiple antennas at both base station and subscriber ends. Multiple antenna technologies enable high capacities suited for Internet and multimedia services, and also dramatically increase range and reliability. In future such multiple-input multiple-output OFDM wireless communication systems will increase capacity, coverage, and reliability of future broadband wireless access technologies including 4G and may be “Beyond 4G”.
Multiple antennas at the transmitter and receiver provide diversity in a Non LoS fading environment providing high throughput and desired QoS. By employing multiple antennas, multiple spatial channels are created, and it is unlikely all the channels will fade simultaneously.
Error Correction Techniques
Provides better overall performance
Error correction techniques have been incorporated into WiMAX to reduce the system signal to noise ratio requirements. Forward Error Correction, Convolutional encoding and interleaving algorithms are used to detect and correct errors to improve throughput. These robust error correction techniques help to recover erroneous frames that may have been lost due to frequency selective fading or burst errors. Automatic repeat request (ARQ) is used to correct errors that cannot be corrected by the FEC, by having the erroneous information resent. This significantly improves the bit error rate (BER) performance for a similar threshold level.
Power Control
Provides better power efficiency and coexistence
Power control algorithms are used to improve the overall performance of the system, it is implemented by the base station sending power control information to each of the CPEs to regulate the transmit power level so that the level received at the base station is at a pre-determined level. In a dynamical changing fading environment this pre-determined performance level means that the CPE only transmits enough power to meet this requirement. The converse would be that the CPE transmit level is based on worst-case conditions. The power control reduces the overall power consumption of the CPE and the potential interference with other co-located base stations. For LOS the transmit power of the CPE is approximately proportional to its distance from the base station, for NLOS it is also heavily dependant on the clearance and obstructions.

Figure  SEQ Figure \* ARABIC 38 - Power Control Using Sleep Mode
Data Security
Provides secured communication
WiMAX proposes the full range of security features to ensure secured data exchange: terminal authentication by exchanging certificates to prevent rogue devices, user authentication using the Extensible Authentication Protocol (EAP), data encryption using the Data Encryption Standard (DES) or Advanced Encryption Standard (AES), both much more robust than the Wireless Equivalent Privacy (WEP) initially used by WLAN. Furthermore, each service is encrypted with its own security association and private keys.
Since its early days IEEE 802.16 standards have seen a lot of changes. Even today it continues to innovate and evolve with every passing day, and technology advancements. Security concern for wide range connectivity is always there. The security features of the standard are being worked on so that when its time for the product release to market, the technology will be more secure.

WiMAX Radio
Multiplexing Technology
WiMAX uses OFDM (Orthogonal Frequency Division Multiplexing), a multicarrier technique that allows broadband transmission in a mobile environment with fewer multipath effects than a single signal with broad bandwidth modulation.

Figure  SEQ Figure \* ARABIC 39 - OFDM Wave Form
A key feature of the 802.16 standard is that it is based on Orthogonal Frequency Division Multiplexing (OFDM). OFDM is chosen over a single-carrier solution due to lower complexity of equalizers for high delay spread channels or high data rates. A broadband signal is broken down into multiple narrowband carriers (tones), where each carrier is more robust to multipath.
OFDM transmits data in a parallel manner by distributing it over a large number of carriers (tones). In order to maintain orthogonality among tones, these tones are separated by a precise frequency. A cyclic prefix is added that has length greater than the expected delay spread. Tones with proper coding and interleaving across frequencies, are orthogonal to each other over the OFDM symbol duration while multipath turns into an OFDM system, having advantage of frequency diversity.
OFDM can be implemented efficiently by using fast Fourier transforms (FFTs) at the transmitter and receiver. At the receiver, FFT reduces the channel response into a multiplicative constant on a tone-by-tone basis. With MIMO, the channel response becomes a matrix. Since each tone can be equalized independently, the complexity of space-time equalizers is avoided. Multipath remains an advantage since frequency selectivity caused by multipath improves the rank distribution of the channel matrices across frequency tones, thereby increasing capacity.
Simultaneous modulation / demodulation of data over these carriers is done efficiently by IFFT / FFT, which is implemented using high-speed digital signal processors (DSPs).
Orthogonal Frequency Division Multiplexing (OFDM)
Orthogonal frequency division multiplexing (OFDM) is a multi-carrier transmission technique that has been recently recognized as an excellent method for high-speed bi-directional wireless data communication. Its history dates back to the 1960s, but it has recently become popular because economical integrated circuits that can perform the high-speed digital operations necessary have become available. Today other than WiMAX, the technology is also used in such systems as asymmetric digital subscriber line (ADSL) as well as wireless systems IEEE 802.11a/g (Wi-Fi). It is also used for wireless digital audio and video broadcasting.
Orthogonal frequency division multiple access (OFDMA) allows some sub-carriers to be assigned to different users. These groups of sub-carriers are known as sub-channels. Scalable OFDMA allows smaller FFT sizes to improve performance (efficiency) for lower bandwidth channels. This applies to IEEE 802.16-2004, which can now reduce the FFT size from 2048 to 128 to handle channel bandwidths ranging from 1.25–20 MHz. This allows sub-carrier spacing to remain constant independent of bandwidth, which reduces complexity while also allowing larger FFT for increased performance with wide channels.
OFDM and FDM
OFDM is similar to FDM. OFDM is based on frequency division multiplexing (FDM) but much more spectrally efficient. FDM is a technology that uses multiple frequencies to simultaneously transmit multiple signals in parallel. Each signal has its own frequency range (sub carrier), which is then modulated by data. Each sub-carrier is separated by a guard band to ensure that they do not overlap. These sub-carriers are then demodulated at the receiver by using filters to separate the bands.
OFDM is much more spectrally efficient than FDM achieved by spacing the sub-channels much closer together (until they are actually overlapping). This is done by finding frequencies that are orthogonal, which means that they are perpendicular in a mathematical sense, allowing the spectrum of each sub-channel to overlap another without interfering with it. The effect of this is seen as the required bandwidth is greatly reduced by removing guard bands and allowing signals to overlap. In order to demodulate the signal, a discrete Fourier transform (DFT) is needed. Fast Fourier transform (FFT) chips are commercially available, making this a relatively easy operation.

Figure  SEQ Figure \* ARABIC 40 - OFDM Channel
Why OFDM
The choice of OFDM as the multiple access technology is based both on physical layer considerations and on MAC, link and network layer requirements. OFDM enables the creation of a flexible system architecture that can be used efficiently for a wide range of services, including both voice and data.
OFDM efficiently combat against frequency selective fading by dividing channel into smaller subchannels. Narrow subchannel bandwidths make each of these subchannels to experience flat channel fading in the transmission medium.
The major advantage of using OFDM is that, due to orthogonality, the system is free from inter carrier interference (ICI) and inter symbol interference (ISI). OFDM effectively squeezes multiple modulated carriers tightly together, reducing the required bandwidth but keeping the modulated signals orthogonal so they do not interfere with each other. Users are allocated capacity in one or more groups of tones, each having a definite number of tones. The tones in each group can be either contiguous or can be spread over the entire band of operation in a pseudo random fashion. When they are contiguous, feedback-based beam forming can help improve throughput.
On the other hand, when they are random, the group of tones allotted to a user is hopped. This will average the interference from adjacent cells, and also exploit frequency diversity. Tones are allocated for different users using two methods i.e. pseudo random fashion or contiguous.
Another advantage of OFDM is its resilience to multipath, which is the effect of multiple reflected signals hitting the receiver. This results in interference and frequency-selective fading which OFDM is able to overcome by utilizing its parallel, slower bandwidth nature. This makes OFDM ideal to handle the harsh conditions of the mobile wireless environment, while OFDM’s high spectral efficiency make it an extremely suitable technology to meet the demands of wireless data traffic.
These unmatched characteristics of OFDM based systems including the simplicity of implementation, robustness to channel impairments and narrowband interference, along with the possibility of using advanced antenna techniques have made OFDM not only ideal for such new technologies like WiMAX or MBWA but also is currently one of the prime technologies being considered for use in future fourth generation (4G) networks.
Modulating Technology
A WiMAX provider can appeal to a wide variety of needs by means of a single distribution point by providing flexible service and rate structures to its customers. Depending upon specific demand, it is possible for providers to offer a wide variety of standard and custom service offerings. This is possible because of inherent modulation technique used in IEEE 802.16. These modulation techniques are also the basis of communications for systems like cable modems, DSL modems, CDMA, 3G, Wi-Fi* (IEEE 802.11) and futuristic 4G.
Modulation is the process by which a carrier wave is able to carry the message or digital signal (series of ones and zeroes). There are three basic methods to this: Amplitude shift keying (ASK), Frequency shift keying (FSK), Phase shift keying (PSK). Higher orders of modulation allow us to encode more bits per symbol or period (time).
In case of WiMAX ASK and PSK can be combined to create QAM where both the phase and amplitude are changed. The receiver then receives this modulated signal, detects the shifts and demodulates the signal back into the original data stream.
The modulation scheme is dynamically assigned by the base station, depending on the distance to the client, as well as weather, signal interference, and other transitory factors. This flexibility further enables service providers to tailor the reach of the technology to the needs of individual distribution areas, allowing WiMAX service to be profitable in a wide variety of geographic and demographic areas.
802.16 supports “adaptive modulation”, this allows it to automatically increase effective range, where necessary, at the cost of decreasing throughput. Higher-order modulation (e.g., 64 “Quartered Amplitude Modulation” or QAM provides high throughput at sub-maximum range, while lower-order modulation (e.g., 16 QAM) provides lower throughput at higher range, from the same base station.

Figure  SEQ Figure \* ARABIC 4141 - Adaptive Modulation
Adaptive Modulation
Adaptive modulation and coding, the key feature of the WiMAX physical layer design allows different data rates to be assigned to different users depending on their channel conditions. Since the channel conditions vary over time, the receiver collects a set of channel statistics which are used both by the transmitter and receiver to optimize system parameters such as modulation and coding, signal bandwidth, signal power, training period, channel estimation filters, automatic gain control, and so on.
The use of adaptive modulation allows a wireless system to choose the highest order modulation depending on the channel conditions. In case of WiMAX either phase shift keying (PSK) or quadrature amplitude modulation (QAM) is typically employed to increase the data throughput. These systems have a link adaptation algorithm (LA) that tracks channel variations and adapts transmission parameters to perform optimally under prevailing conditions.
Different order modulations allow sending more bits per symbol and thus achieving higher throughputs or better spectral efficiencies. However, it must also be noted that when using a modulation technique such as 64-QAM, better signal-to-noise ratios (SNRs) are needed to overcome any interference and maintain a certain bit error ratio (BER).
As the range is increased, modulation is lowered (in other words, BPSK), but when range reduces, higher order modulations like QAM can be utilized for increasing throughput. In addition, adaptive modulation allows the system to overcome fading and other interference. The modulated signals are then demodulated at the receiver where the original digital message can be recovered.
Both QAM and QPSK are modulation techniques used in IEEE 802.16 (WiMAX), they are also used in IEEE 802.11 (Wi-Fi), and 3G (WCDMA/HSDPA) wireless technologies. The use of adaptive modulation allows wireless technologies to optimise throughput, yielding higher throughputs while also covering long distances.
Duplexing Technology
Duplexing refers to the process of creating bi-directional channels for uplink and downlink data transmission.
Time division duplexing (TDD) and frequency division duplexing (FDD) are both supported by the 802.16-2004 standards. FDD unlike TDD requires two channel pairs that are separated to minimize interference, one for transmission and one for reception. Most FDD bands are allocated to voice, because the bi-directional architecture of FDD allows voice to be handled with minimal delays while TDD is more efficient for IP or Data.
FDD, however, adds additional components to the system and therefore increases costs. FDD is also used in third-generation wireless (3G) networks, which operate at a known frequency and are designed for voice applications. FDD have limitations for data throughput. As network traffic increases or decreases, the geographical area covered by the transmitter may shrink or grow, a phenomenon called “cell breathing”.
IEEE 802.16 specifies both FDD and TDD options:
FDD
Support for legacy services
Symmetrical traffic only
Not as flexible to deploy
Lower efficiency (esp. HD-FDD)
It’s necessary to have a guard band
TDD
Efficient for IP based systems
Symmetrical and asymmetrical
Flexibility – single band required
Highly efficient, twice the BW
Adaptability with advance signal processing (i.e. AAS)
Both FDD and TDD systems can coexist
For example in adjacent bands
Recommendations are provided in IEEE, ETSI and CEPT documents
Coexistence proved on the field in many deployment cases
WiMAX Silicon

Figure  SEQ Figure \* ARABIC 4242 - Radio on Silicon
Radio on Silicon
Before the advent of digital processing, radios were designed entirely of analogue circuitry. As advances with the cost and scale of CMOS technology provided digital processing power, digital signal processing (DSP) began to play a major role in overall communication system designs. Ever-improving DSP techniques have enabled improvements in communications consistent with the predictions of Moore’s Law.
Today, we are experiencing the power of DSP techniques through many wireless radio frequency (RF) communication applications. Wireless wide area networks (WWAN, or cell phones), Wireless Local Area Networks (WLAN), and Wireless Personal Area Networks (WPAN) all employ sophisticated communication techniques. Some of these techniques include complex modulation schemes, powerful new error correcting codes, and decoding algorithms to combat the effects of channel fading, and so on.
All these techniques are being enabled, cost-effectively, by the increasing capabilities of digital processing. At the same time, CMOS technology and the effects of Moore’s Law have enabled digital devices to be produced in high volumes, again in a cost-effective manner, enabling larger markets.
Until recently, high-frequency wireless communications applications have used technology processes such as Gallium-Arsenide (GaAs) to obtain the performance needed from the RF Analogue Front End (AFE) circuits. Although these processes provide the functional performance required by radios today, they do not support the same cost/scalability economics of standard CMOS that is reflected by Moore’s Law.
The higher switching speeds that result from the smaller geometries being developed in CMOS are enabling the design of analogue circuits at very high frequencies, with very good gain and linearity. This new capability will allow analogue circuit designs to scale with the digital capabilities predicted by Moore’s Law. Analogue solutions implemented in CMOS will achieve high performance, functionality, and bandwidth while maintaining low cost, small size, high quality, and robust architecture across the wireless market.
PC industry has always enjoyed the 18 month half-life trend a corollary of Moore’s law, unlike in communications. For example, PC prices have decreased by half every 18 months, but our communication costs have remained relatively the same over this period. Typically the “half-life” of communication prices has been 5 years. Thankfully, all of that is about to change due to convergence. As the new convergence industry takes advantage of traditional PC architectures example being
CPUs (e.g. Motorola PowerPC and Intel’s Pentium)
Bus (e.g. PCI, Universal Serial Bus [USB] and IEEE 1394 - Firewire)
Then the same “price erosion trends” will be observed, and Moore’s law will apply to convergence networks as well. As routers evolve to multiservice, and proprietary hardware migrates to PC based hardware implementations, and as corporate networking solutions move to the commodity market, the benefits will be reaped by the end user. With the communications industry opening up to new providers, the market will become increasingly more competitive. Consumers will soon enjoy this cost cutting, and competitively aggressive market in our communication hardware and software.

Figure  SEQ Figure \* ARABIC 4343 - WiMAX SoC
System on Chip (SoC)
The future digital life style, which can be best summarized as anytime, anywhere, any device and any content—has raised the need of the development of system with broadband connectivity and smaller, portable device with low power consumption, wireless connectivity and low cost.
Such demand requires highly integrated and multi-functional personal devices or Consumer Electronics (CE), so called ‘embedded system’ in consumer space. While SoC technology is fast rising as the most essential technology of future Consumer Electronics, the nature of CE industry demands the change of SoC R&D paradigm.
These devices are multifunctional converged equipments, consisting of various components including modem, video, 3D, CPU/DSP, bus and software. Ignoring other facets like digital camera, video etc; these devices are capable of using multiple technologies for broadband wireless access.
It is composed of a network layer, I/O (Input/Output) layer and a processor. What previously were separate components are now merging into one chip thanks to the SoC technology. A processor platform consists of a CPU (Central Processing Unit), DSP (Digital Signal Processor), accelerator, SoC bus, and memory (which will not be discussed in this context).
With the growing demand for the processor platform to support multiple communication standards (such as CDMA, W-CDMA, GSM/GPRS, WLAN 802.11/16/20, and UWB) at a single terminal and provide standard OS (Operating System) support, a combination of an efficient processor architecture, high performance bus and low power consumption is necessary. Thus, the adoption of a programmable, configurable ‘CPU + DSP + accelerator’ architecture is increasingly becoming favourable.

Chapter 6
WiMAX Proposition
WiMAX can satisfy a variety of access needs. Potential applications include extending broadband capabilities to bring them closer to subscribers, filling gaps in cable, DSL and T1 services, Wi-Fi and cellular backhaul, providing “last 100-meter” access from fibre to the curb and giving service providers another cost-effective option for supporting broadband services.
As WiMAX can support very high bandwidth solutions where large spectrum deployments (i.e. > 10 MHz) are desired it can leverage existing infrastructure, keeping costs down, while delivering the bandwidth needed to support a full range of high-value, multimedia services. Further, WiMAX can help service providers meet many of the challenges they face due to increasing customer demands without discarding there existing infrastructure investments because it has the ability to seamlessly inter-operate across various network types.
WiMAX can provide wide area coverage and quality of service capabilities for applications ranging from real-time delay sensitive Voice-over-IP (VoIP) to real-time streaming video and non-real-time downloads ensuring that subscribers get the performance they expect for all types of communications.
WiMAX, which is an IP-based wireless broadband technology, can be integrated into both wide-area third-generation (3G) mobile and wireless & wireline networks, allowing it to become part of a seamless anytime, anywhere broadband access solution.
Ultimately, WiMAX is intended to serve as the next step in the evolution of 3G mobile phones, via a potential combination of WiMAX and CDMA standards called 4G. Developed markets such as South Korea and Japan, where tele-density is over 100%, are leading the charge in deploying this next generation of broadband wireless technologies.
Features of Substance
To support a profitable business model, operators and service providers need to sustain subscriber satisfaction, wide base of subscribers, broad reach and multiple revenue streams. WiMAX unlike its predecessors can fulfil all these and many more service requirements. Some of the characteristics of WiMAX, which differentiate it to other existing wireless broadband solutions, are explained below.
Throughput
By using a robust modulation scheme, IEEE 802.16a delivers high throughput at long ranges with a high level of spectral efficiency that is tolerant of signal ref lections. The base station can also trade throughput for range. For example, if a robust link cannot be established using 64QAM, changing to 16QAM can increase effective range.
Scalability
The standard has been designed to scale up to hundreds or even thousands of users within one RF channel. To accommodate easy cell planning in both licensed and license-exempt spectrum worldwide, 802.16 supports flexible channel bandwidths. Operators can re-allocate spectrum through sectoring as the number of subscribers grows. If an operator is assigned 20MHz of spectrum, that operator can divide it into two sectors of 10MHz each. Scalability
Coverage
In addition to supporting a robust and dynamic modulation scheme, the 802.16a standard supports technologies that increase coverage, including mesh topology and “smart antenna” techniques.
Quality of service (QoS)
QoS refers to the ability of the network to provide better service to selected network traffic over various technologies. The goal of QoS technologies is to provide priority (including dedicated bandwidth to control jitter and latency) that is required by some real-time and interactive traffic, while making sure that in so doing the traffic on the other paths does not fail. The standard includes QoS features that enable services that require a low-latency network, such as voice and video. The 802.16a voice service can either be VoIP or the traditional time-division multiplexed voice.
QoS ClassType of trafficSchedulingParametersUnsolicited Grant Service (UGS)Real-time data services with fixed size data and period transmissions. E.g: T1/E1/VoIP w/o silence suppressionBS grants service periodically SS contention and piggyback requests prohibited.Unsolicited grant size, Grants per interval, Nominal grant interval, Tolerated grant jitterReal-time Polling Services (rtPS)Real time data with variable sized packets and with periodic transmission. E.g: MPEGPeriodic unicast request opportunities granted to SS. Contention/piggyback requests prohibitedNominal polling interval, tolerated poll jitter, minimum reserved traffic rateNon-real-time polling services (nrtPS)Delay tolerant with variable packet size and aperiodic transmission. E.g.: FTPPeriodic unicast request opportunities granted to SS farther apart. Contention/piggyback requests allowedNominal polling interval, minimum reserved traffic rate, traffic priorityBest Effort (BE)Handled on a space available basisContention/piggyback requests from SS to BSMinimum reserved traffic rate, traffic priorityTable  SEQ Table \* ARABIC 9 - QoS for WiMAX
Security
Security is about trust, privacy is about perception, and technology either makes us feel better or causes more concern, in case of WiMAX it is the former than the latter. Privacy and encryption features are included in the 802.16a standard to support secure transmissions, authentication and data encryption.
Differentiated Service Levels
The standard support differentiated service levels. 802.16a systems can cater to a mix of subscribers having diverse service needs i.e. a mix of business customers and residential subscribers. For example, a base station could simultaneously support more than 60 businesses with T1-level connectivity and hundreds of homes with DSL-rate connectivity.
Wider access scope
WiMAX adopts the orthogonal frequency division multiplexing non-line-of-sight propagation technology to provide broadband access for residents or enterprises for a surrounding area of more than 10 miles. In areas where wired resources are scarce and of poor quality, the advantage of WiMAX access is particularly apparent. Cost effectiveness
Flexibility
A wireless medium enables deployment of an access solution over long distances across a variety of terrains in different countries.
Standard-based
WiMAX products are based on the 802.16 standards and have to pass the consistency certification conducted by the WiMAX Forum to ensure the interconnection and interoperability of equipment of different manufacturers. The WiMAX Forum also helps in making 802.16 standards more popular, hence more user, more operators, more technology providers and faster development of new features.
Competitive costs
WiMAX is a wireless access technology, operators do not need to invest in cable installation, the construction period is short and capacity expansion and removal is flexible and convenient. All these factors allow operators to cut capital investment, quicken capital turnover and recovery, protect investments already made and cut business risks. This means
Lower Cost of Ownership
Quicker profitability
Value Creation
WiMAX has become one of the most talked-about and eagerly anticipated developments throughout the world. The reason is straightforward: WiMAX responds to the real challenges faced by various sections of the society, from government to masses, from service providers to equipment vendors all can reap benefits of the revolution called WiMAX.
However, the value proposition in the wireless broadband marketplace will be very difficult to create because consumers’ expectations have already been set by their current Internet experience, and consumers are reluctant to pay for wireless broadband services solely on basis of convenience.
WiMAX will provide attractive benefits to all players in the industry value chain – from chip set providers, to equipment vendors to network operators to end-users. Adoption of the WiMAX standard, and the WiMAX Forum"! s efforts to ensure its success, will greatly encourage the growth of broadband wireless markets worldwide. Eventually, WiMAX will eliminate the remaining barrier to providing broadband access to millions of potential users in under-served markets across the globe.
Governments
Today, political leaders at all levels of government are working to strengthen economic development, bridge the Digital Divide, streamline the delivery of government services and improve the quality of citizens’ lives within their communities. To accomplish these goals, local officials are embracing a vision for Digital Cities, a term used to describe communities where access technology like WiMAX is applied to make universal broadband access a reality hence promote economic development and community enhancement. Specifically, this will benefit society as
Broadband telecommunications for businesses, residents and government agencies is universally-available and affordably-priced hence its positive impact on economic development and community enhancement
Solutions deployed to create more efficient and responsive government while easing citizen-to-government interaction in areas such as Public Safety, Transportation, Education, E-Government, Healthcare and Public Works
A formal process for cooperation between local governments and private technology and telecommunications companies means more effective technologies will come out with these segments as a target
More the technology investment and programs to bring technology products, services and training to lower-income or disadvantaged areas of the community, helping to bridge the Digital Divide.
Consumers
Though market demand is not clear but technology development is driving the value for customers currently getting DSL as well as those who don’t. Customers currently getting DSL get far more features including new application and flexibility. While the prospective customers not having access to DSL will get new hope to be connected in a broad way. Some key benefits for customers are
More broadband access choices, especially in areas where there are gaps: worldwide urban centres where building access is difficult; in suburban areas where the subscriber is too far from the central office; and in rural and low population density areas where infrastructure is poor.
Easy and Low cost method to get connected for billions not even having a basic telephone line forget the broadband Internet.
More choices for broadband access will create competition, which will result in lower monthly subscription prices.
Pay for what you use, possibility of differential service levels makes optimum utility possible as service variables like quality, speed etc can be selected depending upon the user need.
More applications and flexibility with mobile version of WiMAX expected latter. Potential additional value the mobile WiMAX might bring users are more than simply replacing what they have today, e.g.; increased mobility, same provider at home and on the go, VoIP/Skype on a PDA
Component & Equipment Makers
WiMAX promises many strategic opportunities to Component & Equipment Makers, not just as a backhaul solution for Wi-Fi, delivering additional bandwidth to hotspots, but potentially for 3G networks too. WiMAX may also become a viable DSL/cable broadband replacement technology for consumers, and may even offer nomadic or portable wireless Internet access for consumers and enterprise users. WiMAX will be an important mobile networking technology following the ratification of the 802.16e standard and the availability of WiMAX clients’ devices in 2007-2008. Operators could also use it to carry VoIP services. What does this entire means for Component & Equipment Makers?
The steady growth of outdoor wireless equipment. as of now and indoor wireless equipment later.
A common platform opens the door for volume component suppliers, which drives down the cost of equipment also creates a volume opportunity for silicon suppliers
Innovate more rapidly because there exists a standards-based, stable platform upon which to rapidly add new capabilities. A common platform allows faster innovation and accelerates price/performance improvements unachievable by proprietary approaches.
The $$ amount of risk is reduced because of the economies of scale enabled by the standard. No longer need to develop every piece of the end-to-end solution
Service Providers and Network Operators
WiMAX can give service providers and network operators another cost-effective way to offer new high-value services like multimedia to their subscribers. With the potential to deliver high data rates, along with mobility, it can support the sophisticated “lifestyle” services that are increasingly in demand among consumers, along with the feature-rich voice and data services that enterprise customers require. Because it is an IP-based solution, it can be integrated with both wireline and 3G mobile networks. This versatility opens up cost-effective new opportunities for extending bandwidth to customers in a wide range of locations and for delivering new revenue generating service such as wireless voice over IP and video streaming.
Other benefits WiMAX can offer operators
A common platform which drives down the cost of equipment and accelerates price/performance improvements unachievable with proprietary approaches
Generate revenue by filling broadband access gaps, provision of services providing true broadband speeds, delivering > 1 Mbps per user
NLOS Operations providing strong multipath protection (indoor self install)
High Link Budget enabling >150-160 dB of link budget, High Number of Simultaneous Sessions offering 100’s simultaneous sessions per channel
Quickly provision T1 / E1 level and "on demand" high margin broadband services
Reduce the risk associated with deployment as scalability allows investment as per demand growth, also equipment will be less expensive due to economies of scale
No longer be locked into a single vendor since base stations will interoperate with multiple vendors' CPEs.
Drivers
Stronger business case WiMAX is designed to cover wide geographical areas serving large numbers of users at low cost and provides a wireless alternative to wired backhaul and last mile deployments that use Data Over Cable Service Interface Specification (DOCSIS) cable modems, Digital Subscriber Line technologies (xDSL), T-carrier and E-carrier (T-x/E-x) systems, and Optical Carrier Level (OC-x) technologies. WiMAX is considered one of the best solutions for “last mile” distribution due to extraordinary performance characteristics.

Figure  SEQ Figure \* ARABIC 4444 - Coverage Vs Throughput
Throughput & Coverage
WiMAX technology can reach a theoretical 30-mile coverage radius and achieve data rates up to 75 Mbps, although at extremely long range, throughput is closer to the 1.5 Mbps performance of typical broadband services (equivalent to a T-1 line). Dynamic adaptive modulation allows the base station to tradeoff throughput for range so service providers can provision rates based on a tiered pricing approach, similar to that used for wired broadband services.
WiMAX 802.16 equipment certified by the forum support shared throughput of up to 75 Mbits/sec and has a coverage radius of 5 to 8 km (licence exempt), depends on terrain and population density. By using a robust modulation scheme, IEEE 802.16 delivers high throughput at long ranges with a high level of spectral efficiency that is also tolerant of signal reflections.
In addition to supporting a robust and dynamic modulation scheme, the IEEE 802.16 standard also supports technologies that increase coverage, including mesh topology and “smart antenna” techniques. As radio technology improves and costs drop, the ability to increase coverage and throughput by using multiple antennas to create “transmit” and/or “receive diversity” will greatly enhance coverage in extreme environments.
Flexibility & Scalability
The 802.16-2004 standard supports flexible radio frequency (RF) channel bandwidths and reuse of these frequency channels as a way to increase network capacity. The standard also specifies support for Transmit Power Control (TPC) and channel quality measurements as additional tools to support efficient spectrum use.
Easy addition of new sectors supported with flexible channels maximizes cell capacity, allowing operators to scale the network as the customer base grows. Flexible channel bandwidths accommodate spectrum allocations for both licensed and unlicensed spectrum.
The standard has been designed to scale up to hundreds or even thousands of users within one RF channel. Operators can re-allocate spectrum through sectoring as the number of subscribers grows. Support for multiple channels enables equipment makers to provide a means to address the range of spectrum use and allocation regulations faced by operators in diverse international markets.
802.16 standard provides an important flexibility advantage to new businesses or businesses that move their operations frequently, like a construction company with offices at each building site. Unlike T1 or DSL line, wireless broadband access can be quickly and easily set up at new and temporary sites.

Figure  SEQ Figure \* ARABIC 4545 - Cost Advantage of WiMAX
Cost Effectiveness
The wireless medium used by WiMAX enables service providers to circumvent costs associated with deploying wires, such as time and labour. Interoperable equipment lets operators purchase WiMAX Certified"! equipment from more than one vendor. A stable, standards-based platform improves OpEx by sparking innovation at every layer, Network Management, antennas, and more.
Emergence of Standards
The lack of standardization is one of the major challenges for the present Wireless Broadband Access (WBA) technologies. This is especially relevant for the point to multipoint radio technologies. Within the Wi-Fi area (802.11x) the technology has been standardized with a price/performance curve, as we know from the PC-component industry. The standardization work related to WiMAX is expected to create a similar price/performance curve. WiMAX is based on the 802.16e (OFDMA) industry standard and can be implemented without the costly, proprietary interfaces and royalties found in 3G networks.
The development of WiMAX industry standards (802.16) will significantly improve the economics for both network equipment and CPE. Major manufacturers like Intel, Motorola, Fujitsu, Siemens and Alcatel are already committed to development in accordance with these new standards. There focus is on bringing scale to the market.
Nearly all laptops and a large number of PDA’s and cell phones are already Wi-Fi enabled. It is expected that chipset manufacturers like Intel will target standardizing and embedding WiMAX chipsets in laptops and other mobile devices within 2006.
The manufacturers of WBA equipment are also always interested in less expensive chipsets. A standardization of WBA technologies will result in interoperability, which in turn will bring plug-and-play products. That should imply that in the years to come WiMAX vendors no longer have to provide end-to-end solutions in a complete network.
They can specialize on different components like base stations or wireless modems. Such specialization will result in competitive pricing and value-added innovations. The standardization of the WBA technologies will also most likely provide easier upgrade paths to future technologies, without the costly need to dispatch technicians or physically run wires.
Backing of Intel
Intel is actively participating in WiMAX industry efforts to help reduce investment risks for operators and service providers while enabling them to more cost effectively take advantage of the tremendous market potential of wireless broadband access. The 802.16 wireless standard will provide a flexible, cost-effective means of filling existing gaps in broadband coverage, and creating new forms of broadband services, not thought of in a wired world. With Intel, Fujitsu & Nokia backing this wireless technology and standards, 802.16 and its variants will find many takers in the product arena.
Researchers are creating on-chip smart radio circuits with built-in, re-configurable wireless network hook ups that offer always-on connections, plus the ability to switch automatically and transparently between wired and wireless networks. It’s just one illustration of a basic principle: the principles of Moore’s Law to benefit entirely new arenas and enable expanded capabilities and performance.
Challenges
The performance of a broadband wireless system is generally measured by four key metrics: capacity, coverage, spectrum efficiency, and reliability. The first two metrics determine the cost of the system, while later two are vital in successful service business creation.
Good coverage and capacity being primary requirement are important initially when need to attract subscribers is the sole aim, as few base stations are installed other issues are not that vital. As spectrum efficiency defines how many users can be supported per unit of spectrum over the long-term, higher spectrum efficiency can be a crucial success element. Further, as reliability determines the quality of service a customer receives, and correspondingly long-term customer satisfaction.
Some of the challenges faced by WiMAX in achieving desired results and performance explained above are discussed below.
RF Interference
An interfering RF source disrupts a transmission and decreases performance by making it difficult for a receiving station to interpret a signal. Forms of RF interference frequently encountered are multipath interference and attenuation. Multipath interference is caused by signals reflected off objects resulting in reception distortion. Attenuation occurs when an RF signal passes through a solid object, such as a tree, reducing the strength of the signal and subsequently its range. Overlapping interference from an adjacent base station can generate random noise.
License-exempt solutions have to contend with more interference then licensed solutions, including intra-network interference caused by the service provider’s own equipment operating in close proximity, and external network interference. Licensed solutions must only contend with inter-network interference. For license-exempt solutions, RF interference is a more serious issue in networks with centralized control than in a shared network because the base station coordinates all traffic and bandwidth allocation.
Addressing Issues with Interference
Interference is the disruption or degradation of a transmitted signal by extraneous RF energy. Interference impedes the ability of an RF receiver to distinguish between the transmitted signal and the background RF energy that exists at that specific point in time. Causes of extraneous RF energy include noise, direct spectrum overlap by identified and unidentified sources.
Extraneous RF energy can be addressed by sub-channelisation and adaptive modulation, proper network design, filtering, shielding, synchronization of signals and using power amplifiers and antenna technologies.
Infrastructure Placement
Infrastructure location refers to the physical location of infrastructure elements. Infrastructure placement can be an issue for both licensed and license-exempt solutions. However, infrastructure placement presents some special considerations for license-exempt solutions. Service providers are quickly deploying solutions in specific areas to stake out territory with high subscriber density and spectrum efficiency. Such areas include higher ground, densely populated or population growth areas, and areas with a less crowded RF spectrum. In addition, the physical structure that houses or supports the base station must be RF compatible, A metal farm silo, for example, may distort signals, or a tree swaying in the wind may change signal strength.
Addressing Issues with Infrastructure Placement
Infrastructure placement establishes the foundation for the service provider’s network. When choosing a location for deployment, a service provider must ensure that it can obtain 24/7 access to the site, that the building or location does not contain physical material that is not RF friendly, and that the infrastructure provides protection against weather-related elements, such as wind and lightning. Obstacles such as trees and buildings frequently block signal paths in urban areas and some rural areas. NLOS performance is greatly improved with 802.16-2004 due to its improved resistance to multipath interference. Even with no direct line-of-sight (LOS) between the base station and the subscriber station, signals can be received after they reflect off buildings or other obstructions. Factors such as these make a preliminary site survey indispensable. Infrastructure placement provides a solid market advantage for incumbents. The cost and time involved in obtaining building permits, leases, and roof space present significant barriers to those without an already established infrastructure. Infrastructure placement provides a solid market advantage for incumbents. The cost and time involved in obtaining building permits, leases, and roof space present significant barriers to those without an already established infrastructure.

Figure  SEQ Figure \* ARABIC 4646 - WiMAX OpEx Break-up
Roll out Cost
The increased number of cell sites, as a result of using higher frequency bands, raises site acquisition/leasing and construction costs, regardless of the technology being deployed. The cost to acquire a site in North America can easily reach $25,000, plus ongoing lease costs, while an operator may have to spend up to $75,000 on construction costs to get the site up and running - assuming the operator starts from scratch. Further, the logistical challenges of getting enough sites to deploy a ubiquitous mobile network can pose a tremendous challenge, regardless of the cost factor.
That said, WiMAX will likely have a lower cost structure with respect to the core network, or the portion of the network that is "behind" the base stations. Specifically, WiMAX uses an all-IP core, which means it is scalable and can therefore support a higher level of user traffic for a given amount of network resources.
Additionally, WiMAX makes use of off-the-shelf routers versus a combination of circuit switches and other network components, that, although are similar to off the- shelf routers, have been specially customized for use in a cellular network. It is important to point out, however, that 3G is also transitioning to an all-IP core at which point it will greatly reduce its own cost structure and achieve higher scalability than possible today.
Incomplete Standards
The 802.16e standard only addresses the physical (PHY) and medium access control (MAC) layers, leaving it to the WiMAX Forum to tackle issues such as call control, session management, security, the network architecture, roaming, etc. To put things in perspective, as the standard is currently written, each WiMAX base station is virtually oblivious of its surrounding base stations while the MAC layer only has placeholders for the messaging traffic associated with implementing a handover. As a consequence, the notion of seamless mobility doesn't exist while power management issues could result in reduced performance, in particular for users at the cell edge (25-35% of the network) where inter-cell interference would be the most evident.
The WiMAX Forum created a network architecture working group in late 2004 to address some of these unresolved issues, but it is unrealistic to expect all of them to be solved, let alone tested and verified, in a few months. As it stands now, the first revision of the networking specification is scheduled to be completed by the end of the year. As an interim step, the WiMAX Forum is moving to first implement a portable solution that lacks some of the network intelligence required to support higher vehicular speeds (up to 120km/h) and seamless handoffs.
In lieu of applications and services, such as voice, that require seamless handoffs and in the absence of widespread coverage, a portable broadband connection should more than adequately meet the needs of high bandwidth data users.
Chipset Availability
Another major uncertainty is the availability of chipsets. In addition to Intel and Fujitsu, several private companies are also promising very compelling .16e chipset solutions and they may, in fact, beat the larger silicon suppliers to the market. Regardless of who is first to market, it will be challenging to have silicon available for sampling anytime soon. For one, the mobile standard won't be finished until later in 2005 and the initial profiles have not been selected yet, meaning that while some work can currently be done, the fine technical details cannot be implemented until after the standard is fully ratified. Equally important, the major semiconductor companies who are important to the success of WiMAX are not necessarily first-to-market suppliers of wireless chipsets (Wi-Fi and cellular technologies are two examples). Given some of the requirements for the mobile WiMAX solution, it could take more than one die spin to manufacture a chipset that supports the initial WiMAX profiles and does so with adequate performance (size, power requirements, etc.).
Interoperability Testing and Market Feel
While the 802.16e standard could be completed in late 2005, it does not necessarily suggest that the technology will then be ready for commercial deployment. Even for the 802.16d standard, multivendor interoperability testing, commonly referred to as "Plugfests," has yet to occur, although it is expected to begin later this year.
Interoperability testing always takes longer than anticipated, in particular if an entirely new standard is being tested and if companies not normally accustomed to this type of activity are involved. Assuming that interoperability testing is successful and that commercially-viable solutions (e.g., data cards) are available, potential operators could then take months conducting field trials before moving to a market trial and then potentially a broader-scale commercial rollout.
It is interesting to note that current plans for WiMAX "plugfests" are to certify equipment against one of the many WiMAX targeted profiles. Since the Forum targets multiple profiles for different regions and applications, many interoperability activities will be required. Additionally, end-to-end "plugfests" cannot be a reality until WiMAX base stations and WiMAX CPEs are available. If history is a guide, the WiMAX base stations will be ready for interoperability testing well before the CPEs will be ready.
Uncertain Economics
Like with other wireless technologies, the economics of using WiMAX to offer fixed wireless services in regions of the world where wireline deployments have not taken place or where there is little competition are attractive. By eliminating the need to deploy copper or fibre, an operator can significantly reduce its upfront capital expenditures while at the same time reduce the risk of service disruption, brought on by vandalism or by theft of the buried cabling.
Once consumers can self-install the CPE, the deployment costs become even more compelling. It isn't clear if the same can be said for other market opportunities, especially when the network operator is designing its network to support seamless mobility and voice - far more base stations are required, regardless of the air interface that is used. However, if the operator deploys its WiMAX network in select, albeit geographically large, areas where portable/mobile broadband data traffic is highest and if the operator doesn't attempt to deliver ubiquitous coverage within that area, its cost structure will be reduced.
Put simply, deploying a mobile network is not an inexpensive proposition and with an abundance of mobile operators in most countries, these regions may not be able to support another Greenfield mobile operator. These regions could, however, support a service that differentiated itself by offering higher data rates with the tradeoff coming in the form of reduced coverage and lower quality of service - seamless handoffs, high-speed vehicular support, etc.

Figure  SEQ Figure \* ARABIC 4747 – WiMAX Network Coverage Cost Vs Frequency Curves, Rural, Suburban and Urban
Spectrum
WiMAX, as in case of most of the wireless technologies has to operate within spectrum constraints and contend with issues caused by multipath, the composition of a primary signal plus duplicate or echoed signal caused by reflections off objects between transmitter and receiver. These radio characteristics play a vital role in the way the spectrum is physically used.
Signals with longer wavelengths (lower frequencies) are more robust (i.e. improved performance in atmospheric noise) whereas signals with increasingly short wavelengths become directional and focused. Examining uses at the two extremes of the RF spectrum helps to explain these properties further.
Very low frequency (VLF) transmitters, operating in the 3KHz to 30KHz range, are used in submarine communications because signals of these frequencies are best able to bend and propagate across very large areas and are resilient to most noise under the surface of the water.

Figure  SEQ Figure \* ARABIC 4848 - Path Length & Capacity Curve for Different Frequency Bands in Line of Sight Deployments
At the other extreme, products that can beam RF signals in the 70GHz to 80GHz range between line-of-sight targets, such as distributed office buildings that are about a mile away. The focused, narrow RF beam allows the delivery of very concentrated RF energy from point-to-point.
Band Designation Abbreviation WLAN WWAN MMDS U-NII LMDS Frequency (GHz) 2.4 2.4 2.5 5.8 28 P2P Throughput (Mbps) 1-11 11/11 44/44 100-1,000 155/155 P2MP Throughput (Mbps) 1-11 3/3 22/18 54+ 45/10 Bandwidth (MHz) 83.5 83.5 186 300 1300 Range: Line of sight P2P 400 ft 25 mi 25 mi 20 mi 3 mi Range: NLOS P2P N/A N/A 7 mi 7 mi N/A Range: P2MP 400 ft 6 mi 5 mi 4 mi 2 mi Affected by Rain No No No No Yes Over the Air Protocol IP IP IP ATM & IP ATM Approximate Cost Per Link $0.3k $1k $8k $3k $200k Licensed No No Yes No Yes Table  SEQ Table \* ARABIC 10 - Spectrum used for Broadband Wireless in the US

Competition
The primary performance criteria for broadband are:
Coverage
Price, including up front, device, recurring, and roaming costs and contracts
Range, including roaming and interoperability
Security
Speed
DSL PresentFutureLow density ADSL focused DSLAMs installed in central offices in late 90’s. Rush by CLECs to offer DSL.
2000-2001 slower builds due to capital constraints – urban deployment continues. Rural areas ignored.
2002-2003 digital loop carriers begin to be upgraded. National DSL availability moves from 45% to 65% - stands at around 70% today.
Low density, CO based DSLAMs giving way to environmentally harden remote cabinet DSLAMs.
Average throughput is 500 Kbps downstream, 100 Kbps.
Upgrade of DSL in outside plant will be completed.
Likely to cover 90% of addressable market nationally.
Will include high-income rural locations.
G.SHDSL can offer 2.3 Mbps symmetric. ADSL2+ can deliver 10 to 20 Mbps within 10K feet.
ADSL2+ can be bonded for more bandwidth.
Micro DSLAMs will allow small line powered DSL devices to cherry pick attractive, yet remote end-users.

Cable ModemToday FuturePlant upgraded in the late 90’s and fibre pushed deeper into the network for higher capacity
Mainly a consumer grade “best effort” data service.
Downstream speeds up to 5 Mbps for consumers and businesses, but upstream speeds limited to less than 1 Mbps.
Tiered best effort services for SMBs, but do not meet the criteria of the dedicated T1+ market unless using fibre.
New standards allow operators to prioritise traffic such as VoIP and dedicate bandwidth for business applications, but only providing consumer VoIP so far.
Next generation network architecture will combine the voice, video, and data networks, allowing them to forge services and applications across these three areas.
Network enhancements (DOCSIS 2.0, splitting fibre nodes) will allow them to increase upstream and downstream speeds of their services.
Expand SMB offerings by using their ability to prioritise traffic and reserve bandwidth to create better business class services. Likely to try to introduce symmetrical T1 type services.
Will use QoS mechanisms to create new multimedia services that keep broadband from becoming a commodity service/pipe.Broadband Wireless Access/WiMAXToday FutureOnly proprietary technologies today.
Fixed and portable/mobile broadband wireless products exist.
Throughput varies depending on spectrum used. Unlicensed 5 GHz spectrum provides the ability to offer T1+ services, but must be line of sight or near line of sight.
Using licensed 2.5 GHz spectrum or unlicensed 900 MHz allows for non-line of sight operation.
Unlicensed and licensed spectrum can also be used to provide point-to-point links with capacity greater the 50 Mbps.


Availability of standards-based equipment will drive down prices, especially of customer premise equipment (CPE).
WiMAX enhances the QoS capabilities of broadband wireless access products, enabling a higher level of support for VoIP and other latency sensitive applications.
Initial fixed WiMAX products (802.16-2004) will require outdoor mounted antennas.
The second generation of the standard (802.16e), will allow for indoor antennas, and will be portable/mobile.
The customer premise equipment will also go from a modem product, to a PCMCIA card, to being embedded in devices.Table  SEQ Table \* ARABIC 11 - Present and Future of Broadband Technologies - DSL, Cable, BWA/WiMAX
Wireline
WiMAX is a wireless version of Ethernet and an alternative to wire technologies (such as cable modems, DSL, and T1/E1 links) to provide broadband access to customer premises.
DSL & Cable
The WiMAX deployment as the last mile not only serves the residential and enterprise users but it can also be deployed as a backhaul for Wi-Fi hotspots and backhaul between the conventional cell towers. There are different opinions of whether BWA will be successful as a last mile. Our study lays the groundwork for deploying future BWA systems based on WiMAX certified products. There are challenges in deploying WiMAX, but it has the huge potential to compete on a cost-per-megabyte level with cable and DSL, if both engineering and economics are carefully applied.
We mainly focus on backhauling and tower leasing, by exploring several opportunities for significant cost savings like aggregating the backhaul traffic and optimal use of tower space. WiMAX is all about delivering broadband wireless access to the masses. It represents an inexpensive alternative to digital subscriber lines (DSL) and cable broadband access. The installation costs for a wireless infrastructure based on 802.16 is far less than today's wired solutions, which often require laying cables and ripping up buildings and streets.
For this reason, WiMAX makes an attractive solution for providing the last mile connection in wireless metropolitan area networks. Many countries in Europe have long-established copper networks where up to 40 percent of the fixed-line subscribers cannot benefit from DSL because of distance limitations or the use of pair-gain technology (using network amplifier systems to increase the strength of signals on paired wires).

Figure  SEQ Figure \* ARABIC 4949 - Value Analysis, 3G, WLAN (Wi-Fi) and WiMAX
Wireless
WiMAX have 3G and Wi-Fi as its closest rivals in race for broadband. WiMAX wireless Metropolitan Area Networks (MANs), based on the IEEE 802.16 family of standards is a solution that can offer wireless Broadband Internet access to residences and businesses at relatively low cost. The standard supports shared transfer rates up to 75Mbps from a single base station, which can offer broadband access without requiring a physical 'last-mile' connection from the end user to a service provider. Service delivery to end clients is likely to be roughly 300Kbps for residences and 2Mbps for businesses.
Among the promises of WiMAX is that it could offer the solution to what's sometimes called the "last-mile" problem, referring to the expense and time needed to connect individual homes and offices to trunk lines for communications. WiMAX promises a wireless access range of up to 31 miles, compared with Wi-Fi’s 300 feet and Bluetooth's 30 feet.
To appreciate what WiMAX brings to the table we need to understand what additional features it provides over existing technologies. Existing broadband wireless access technologies, which are closest to WiMAX with respect to service features, are Wi-Fi, and 3rd Generation Mobile. Let us first examine these three closely.
Wi-Fi
Wi-Fi has risen to become one of the most popular forms of wireless local area networking thanks to its open standard, high speed, and ability to handle network interference. Still, Wi-Fi’s popularity has exposed its number one limitation, the range. The wireless technology can only serve signals in a "hot spot" with a typical reach of about 1,000 ft. (300m) outside or 328 ft. (100m) indoors, due to interference.
Whether WiMAX will complement or clash with Wi-Fi technologies remains to be seen. For a while, at least, it will certainly be complementary to 802.11a, enabling Wi-Fi users to dramatically extend their distance from wired networks. As 802.11 needs backhaul, and WiMAX will emerge as a perfect way to do that. However, WiMAX systems eventually can replace Wi-Fi counterparts.
While Wi-Fi typically provides local network access for around a few hundred feet with speeds of up to 54 megabits per second, a single WiMAX antenna is expected to have a range of up to 40 miles with speeds of 70 megabits per second or more. WiMAX may not be designed to replace 802.11 and it may be the last-mile piece while 802.11 is the last 100 feet, but the fact remains that WiMAX is similar to Wi-Fi on a much larger scale and at faster speeds.
Accessing WiMAX via Wi-Fi would entail an unnecessary step, and Wi-Fi, as it now exists, lacks many WiMAX capabilities, such as long range and the ability to handle voice and video applications. Wi-Fi is addressing the low-latency requirements necessary for voice and video with proposed standard 802.11e, but current efforts are headed only toward improving latency with prioritisation, not toward a guaranteed QoS. Also Wi-Fi still doesn't solve the contention problem and that's the core of 802.11. Further a mobile/nomadic version would keep Enabled-enabled devices connected over large areas much like today's cell phones. Wi-Fi won’t provide ubiquitous broadband while WiMAX will.
Though Wi-Fi hot spots will need to remain in place, but until there are WiMAX-based networks to replace them.
 802.11802.16Technical DifferenceRangeSub-300 feet. (Add access points for greater coverage.)Up to 30 miles. Typical cell size of 4-6 miles.802.16 PHY tolerates greater multipath delay spread (reflections) via implementation of a 256 FFT vs. 64 FFT for 802.11.CoverageOptimised for indoor performance, short range.Outdoor NLOS performance. Standard support for advanced antenna techniques.802.16 systems have an overall higher system gain, delivering greater penetration through obstacles at longer ranges.ScalabilityIntended for LAN applications. Users scale from one to tens with one subscriber for each CPE device.Designed to efficiently support from one to hundreds of CPEs, with unlimited subscribers behind each CPE. Flexible channel sizes from 1.5 MHz to 20 MHz.The MAC protocol used in 802.11 uses a CSMA/CA protocol, while 802.16 employs Dynamic TDMA. 802.11 can only be used in license-exempt spectrum; limited number of channels. 802.16 can use all available frequencies; multiple channels support cellular deployment.Bit Rate2.7 bps/Hz peak. Up to 54 Mbps in 20 MHz channel.5 bps/Hz peak. Up to 100 Mbps in a 20 MHz channel.Higher modulations coupled with flexible error correction results in more efficient use of spectrum.QoSNo QoS support.QoS built into MAC; voice/video and differentiated service levels.802.11: Contention-based MAC (CSMA/CA), basically wireless Ethernet. 802.16: Dynamic TDMA-based MAC with on-demand bandwidth allocation.Table  SEQ Table \* ARABIC 12 - Relationship between IEEE 802.16 and IEEE 802.11
3 G Technologies
3G Cellular is long range, mobile, reliable, plug-n-play, secure, private, and manageable data rates, but data applications are too expensive, as much as 10 times the cost of using similar wireline services. Also biggest problem with 3G Cellular is the usage cost, which due to factors like totally revamping the infrastructure for high-speed access and high license fees. 3 G cellular access is possible in multiple flavours.
UMTS – Universal Mobile Telecommunication System
Wideband Code Division Multiple Access (WCDMA) is the access scheme used in UMTS. Frequently, WCDMA is used as a synonym for UMTS. It was developed in order to create a global standard for real-time wireless multimedia services that ensures international roaming. A specific allocation was made in the 2 GHz band for 3G telecom systems with the support of ITU (International Telecommunication Union). The work was later taken over by the 3GPP (3rd Generation Partnership Project), which is the present WCDMA specification body with participants around the world.
The WCDMA architecture is such that the core network of GSM is shared and the GSM Base Station is replaced with WCDMA radio access network (RAN). WCDMA uses code division multiple access (CDMA) instead of the classical time division multiple access (TDMA) as the multiple access technique. Users are separated by unique codes allowing all users to transmit at the same band. Since the same frequency band is used in all cells, the re-use is 1/11. However, it uses a wide band of 5 MHz per carrier with a chip rate of 3.84 Mcps (Mega Cycle per Second), and a frame size of 10 ms. This high bandwidth and spreading factor increases the processing gain and multi-path resolution, and thereby improves coverage and combats fading, particularly for low bit-rate services (such as voice).
WCDMA – features
WCDMA supports highly variable user data-rates based on a rate matching procedure, where data-rates among users can change from frame to frame. In both uplink (UL) and downlink (DL), it supports a peak data-rate of 2 Mbps using QPSK modulation. WCDMA provides service to the users in all environments (vehicular, pedestrian and indoor), and for all kinds of traffic using the following RAN functionalities:
Power control regulates the terminal and base station transmitter power, resulting in less interference by updating the power at 1500 Hz.
Inter cell interference especially at the borders is mitigated with soft / softer hand over in which the mobile station (MS) is connected to different/same base station (BS) respectively. This helps to maintain continuity and quality of connection while moving from one cell to another.
Handover to GSM (inter system handover) is supported to enable deployment of WCDMA in a phased manner in the existing GSM network. This is also useful in handover of the subscribers to the WCDMA network, when the number of subscribers in the GSM network is close to the capacity limit in one area.
Multiple carriers can be used within a cell or sector. Hard handover (Inter frequency or intra system handover) is supported to handover between WCDMA carriers.
Channel-type switching to move subscribers between the common and the dedicated channels, depending on the amount of information to be transmitted.
Admission control to avoid system overload and to provide planned coverage.
Congestion control to deal with the movement of users between cells.
Synchronization by a mechanism where the handset, when needed, measures the synchronization offset between the cells and reports this to the network. In addition, there is also an option of using external source, such as GPS, for synchronizing the BS.
HSDPA – High-speed downlink packet access
HSDPA is an evolution of WCDMA in the DL for packet data communications. Compared to the WCDMA architecture, HSPDA introduces a shorter transmission time interval (TTI) of 2 ms, adaptive modulation and coding (AMC), multi-code transmission, fast physical layer hybrid automatic repeat request (HARQ), and a high speed packet scheduler. HSDPA consists of a new forward link data channel called high-speed downlink shared channel (HSDSCH). This is based on shared-channel transmission, which means that some channel codes and the transmission power in a cell are seen as a common resource. This is dynamically shared between users in the time and code domains.
Shared channel transmission results in more efficient use of available codes and power resources compared to the current use of a dedicated channel in WCDMA. The shared code resource onto which the HSDSCH is mapped consists of up to 15 codes. The actual number employed depends on the number of codes supported by the terminal / system, operator settings, and desired system capacity. The spreading factor (SF) is fixed at 16, and the frame duration is only 2 ms.
Fast link adaptation is done using adaptive modulation and coding based on the channel quality indicator (CQI) feedback, instead of power control as in WCDMA. The highest possible data-rate on a given link is ensured by link adaptation for both near (high coding rate) and far users (low coding rate). While connected, HSDPA user equipment (UE) periodically sends a CQI to the BS indicating the data-rate, coding and modulation scheme to be used, and the number of multi-codes the UE can support under its current radio conditions. The CQI also contains the information about the power level to be used.
Fast retransmission is done using Hybrid ARQ with incremental redundancy and soft (chase) combining. Fast scheduling is done at the BS rather than at the radio network controller (RNC) as in WCDMA. This is done based on information on the channel quality, terminal capability, and quality of service (QoS) class and power / code availability. This channel-sensitive opportunistic scheduling obtains multi-user diversity gain by preferentially transmitting to users with better channel conditions.
Enhanced uplink (EUL), an evolution of WCDMA for uplink is also emerging and may support a peak data-rate of 5 Mbps with QPSK modulation, and also an increased average sector throughput in the UL.
CDMA 1x-EVDO (CDMA-HDR or IS-856) – Single RF carrier Evolution to Data Only
This is a broadband wireless packet data system. Qualcomm is the driving force behind this standard. The channel bandwidth (1.25 MHz) and the chip rate (1.2288 Mcps) are same as that of the CDMA2000. The forward and reverse links are separated in frequency. CDMA is the multiple access technique in the UL, and CDM or TDM in the DL. Improved code-rates and higher-order modulation such as 8-PSK and 16-QAM for large packets provide higher spectral efficiency in terms of b/s/Hz.
The DL peak data-rate is 2.4 Mbps (may be evolved to 3.1 Mbps) and the UL peak data-rate is 153.6 kbps (may be evolved to 1.8 Mbps). Users close to the base station can be assigned higher-order modulation and high code-rate. Users close to the cell boundary, or users at a deep fade, need to use the more robust BPSK or QPSK modulation, and low coding rates. The mobile terminal performs channel quality measurements and reports the index to the network using physical layer signalling, which in turn transmit the requested configuration. Also, there is flexibility in the choice of payload size and data-rate combinations. The payload may have 1 to 16 slots.
Economic Analysis
WiMAX is the first widely backed wireless standard that is both technically capable and has sufficient industry support to disrupt telecommunication landscape. It is potent enough to turn on its head connectivity stranglehold of incumbent telecommunication operators.
WiMAX provides an economically viable broadband wireless access technology and provides extraordinary value to service providers as well end-users. It serves new entrants as well as dominant national incumbent operators with access & backbone infrastructure.
Let us first examine economic cases of existing broadband wireless access technologies, which are closest to WiMAX with respect to service features. Comparative economic differentiation between Wi-Fi, WiMAX, and 3 Generation Mobile is as below.
Wi-Fi
Attractive Unit Economics
Customer Premise Equipment: Per unit cost $60
Access Points or Base Station: $ 500
Unattractive Network Economics
Range: Limited means many cells, many backhaul links, for 1 Sq KM carpet coverage need of 100 + Access Points
Backhaul determines user experience and cost. Backhaul Pricing inelastic, Backhaul typically 1.5 Mbps cost $500/mo, while 11 Mbps may cost $3000/month
Attractive Services Economics
Inexpensive, sometimes free, site lease

Figure  SEQ Figure \* ARABIC 5050 - 3G Time Line
3G
Unattractive Unit Economics
Spectrum Cost: At 10% penetration, $450/sub
Access Points or Base Station: $ 50000 - 100000
Comparatively Attractive Network Economics
Range: Licensed spectrum permits large cells
Base station, backhaul costs amortized over many users
Unattractive Services Economics
Very expensive, Low data rate, Designed for voice
WiMAX
Attractive Unit Economics
Customer Premise Equipment: Per unit expected cost of a WiMAX CPE would be
About $230 in 2005
About $100 in 2008
Spectrum Cost: Free license exempt also available, low for licensed spectrum
Access Points or Base Station: $ 500
Attractive Network Economics
Range: Large cells
Base station, backhaul costs amortized over many users as well as over 1000 subscribers which one base station and back haul can service
Attractive Services Economics
Differential services provision can cater to need of wide customer range without need for further investment on Infrastructure.
Technology Bandwidth MHz Re-use NDR UL -NDR DL
(Mbps) ST-DL (Mbps) Spectral Efficiency
(b/s/Hz) HSDPA 5 1/1 2.0 - 14.4 2.4-3.6 0.48-0.72 1x-EVDO 1.25 1/1 0.1535 - 2.40.6525-1.125 0.522-0.9 1x-EVDV 1.25 1/1 1.8-3.1 1 0.8 WiMAX 20 1/1 75 --Flash OFDM 1.25 1/1 1.5 - 3 1.5 1.2 UL - Uplink
DL - Downlink
NDR - Net Data-Rate
System Spectral Efficiency = (Sector throughput / System bandwidth) * Re-use factor Table  SEQ Table \* ARABIC 13 - Capabilities of WiMAX and various 3 G Technologies


Section 3
WiMAX – Roll Out
This section provides understanding about issues related to WiMAX deployment, which includes discussions about standards, certification and regulation. The section consists of three chapters.
Chapter 7 – WiMAX Standard
This chapter will examine the overall importance of building a standard, as well as provide a brief overview of the evolution of the IEEE 802.16 family of standards for broadband wireless and how it will benefit technology adoption as well as their key differences.
Chapter 8 - WiMAX Certification
This chapter discuss the concept of Certification for Conformance and Interoperability. It also introduces WiMAX Forum and its role in growth and development of WiMAX. Also described is process of certification and related documentation.
Chapter 9 - WiMAX Regulation
This chapter takes a look at the regulatory environment and regulatory perception as of now as well as that which need to developed for growth of WiMAX globally.

Chapter 7
WiMAX Standard
As with any technology, the development of an industry standard is the critical turning point for widespread adoption. The broadband wireless arena is no exception. As such, considerable efforts have been made on the part of the IEEE (Institute of Electrical and Electronics Engineers) Standards Association Working Group, the WiMAX Forum"! and vendors to adopt a standard for technology that will allow for interoperability and pave the way for future deployment.
There have been a number of ill-fated efforts to make data services come to life over broadband wireless links. From LMDS to MMDS to proprietary approaches, designers have struggled to make broadband wireless a true competitor to DSL and cable modem connections until now. New work being conducted at the 802.16 committee has breathed new life into developing systems that delivery data services over broadband wireless links. And, with the development of the 802.16 specification (also known as WiMAX), the IEEE is providing a technology platform for developing low-cost radios that can make broadband wireless soar.
Why Standards
Developing an accepted industry standard is critical along with ongoing product development and user acceptance for any technology to thrive and become successful.
Standards bodies are created to:
Bridge the gap between research ideals, technology theory and reality
Provide a unified voice for the underlying knowledge and potential of technology to resolve a business issue or problem
Serve as a public policy arena where competing stakeholders interests and values are drawn together
Help define telecommunication and data communication system outcomes for public accountability purposes
Establish a structured decision making process to determine points for further decision making within the regulatory, vendor and user communities.

Figure  SEQ Figure \* ARABIC 5151 - Impact of Standards
Some time back, standard setting was primarily of interest to industry specialists, academicians and regulators. Now they are also engaging end user organizations, vendors, technology providers, and other stakeholders impacted by the underlying technology, in formal exercises to define acceptable and/or desirable levels of performance for communication networks and systems. This allows the standards setting process to be viewed from a number of widely varying perspectives. The process can be viewed as a crucial intersection point, where research theory meets the “real world”.
Standards consensus, or lack thereof, can make or break a communications technology. By way of example, it is only recently that we witnessed the battle between Wi-Fi"! and Home RF for supremacy in the wireless LAN market. Wi-Fi"! succeeded because of the speed at which the wireless LAN industry coalesced around the standard and decided upon what elements they would and would not use to build interoperable products.
This is the same challenge now faced by the WiMAX Forum member companies as they work on deciding the test and interoperability criteria that will lead to truly interoperable 802.16a compliant and WiMAX certified wireless WAN products.
 802.16802.16a802.16eCompletedDecember 2001January 2003Estimate mid '04Spectrum10-66 GHz
 :