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Ch1 Introduction to Wireless Communications & Networks

Ch1 Introduction to Wireless Communications & Networks. Reading materials : [1]Overview of wireless communications [2] 移动通讯词汇（中英）. Outline. Part 1 Introduction to Wireless Communication & Networks Part 2 Applications of Wireless Networks.

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Ch1 Introduction to Wireless Communications & Networks

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  1. Ch1 Introduction to Wireless Communications & Networks Reading materials:[1]Overview of wireless communications[2]移动通讯词汇（中英）

  2. Outline • Part 1 Introduction to Wireless Communication & Networks • Part 2 Applications of Wireless Networks

  3. Part 1 Introduction to Wireless Communication & Networks • The Wireless Vision • Technical Challenges • Current Wireless Systems • Emerging Wireless Systems • Spectrum Regulation • Standards

  4. Wireless History First Mobile Radio Telephone 1924

  5. Pre-Cellular Wireless • One highly-elevated antenna in a large service area • Small number of channels • Very low capacity • Examples: MJ and MK systems in the United States

  6. The Cellular Concept • Basic Principles Frequency Reuse Cell Splitting First proposed by D. H. Ring at Bell Laboratories in 1947

  7. Cellular - Implementation

  8. Cellular - Implementation

  9. BASE STATION Cellular Systems:Reuse channels to maximize capacity • Geographic region divided into cells • Frequencies/timeslots/codes reused at spatially-separated locations. • Co-channel interference between same color cells. • Base stations/MTSOs coordinate handoff and control functions • Shrinking cell size increases capacity, as well as networking burden MTSO

  10. GSM System Architecture

  11. BS BS BS MTSO MTSO Cellular Phone Networks San Francisco Internet New York PSTN

  12. The Wireless Revolution • Cellular is the fastest growing sector of communication industry (exponential growth since 1982, with over 2 billion users worldwide today) • Three generations of wireless • First Generation (1G): Analog 25 or 30 KHz FM, voice only, mostly vehicular communication • Second Generation (2G): Narrowband TDMA and CDMA, voice and low bit-rate data, portable units. 2.5G increased data transmission capabilities • Third Generation (3G): Wideband TDMA and CDMA, voice and high bit-rate data, portable units

  13. World Telecom Statistics Crossover has happened in May 2002!

  14. World Cellular Subscribers by Technology as of June 2006 2.41 Billion Cellular Customers Worldwide GSM/UMTS Totals 82.3%

  15. World Cellular Subscriber Distribution as of June 2006

  16. GSM Growth - 1993 to June 2006

  17. Exciting Developments • Internet and laptop use exploding • 2G/3G wireless LANs growing rapidly • Huge cell phone popularity worldwide • Emerging systems such as Bluetooth, UWB, Zigbee, and WiMAX opening new doors • Military and security wireless needs • Important interdisciplinary applications

  18. Future Wireless Networks Ubiquitous Communication Among People and Devices Wireless Internet access Nth generation Cellular Wireless Ad Hoc Networks Sensor Networks Wireless Entertainment Smart Homes/Spaces Automated Highways All this and more… • Hard Delay Constraints • Hard Energy Constraints

  19. Design Challenges • Wireless channels are a difficult and capacity-limited broadcast communications medium • Traffic patterns, user locations, and network conditions are constantly changing • Traffic is nonstationary, both in space and in time • Energy and delay constraints change design principles across all layers of the protocol stack

  20. Evolution of Current Systems • Wireless systems today • 2G Cellular: ~30-70 Kbps. • WLANs: ~10 Mbps. • Next Generation • 3G Cellular: ~300 Kbps. • WLANs: ~70 Mbps. • Technology Enhancements • Hardware: Better batteries. Better circuits/processors. • Link: Antennas, modulation, coding, adaptivity, DSP, BW. • Network: Dynamic resource allocation. Mobility support.

  21. Migration to 3G

  22. Global Satellite Suburban Urban In-Building Picocell Microcell Macrocell Basic Terminal PDA Terminal Audio/Visual Terminal 3G: ITU-Developed IMT-2000

  23. 4G 3G 2G Future Generations Other Tradeoffs: Rate vs. Coverage Rate vs. Delay Rate vs. Cost Rate vs. Energy Rate 802.11b WLAN 2G Cellular Mobility Fundamental Design Breakthroughs Needed

  24. Current Wireless Systems • Cellular Systems • Wireless LANs • Satellite Systems • Paging Systems • Bluetooth • Ultrawideband radios • Zigbee radios

  25. Cellular Systems －1G

  26. Cellular Systems －2G

  27. Cellular Systems 2G－D-AMPS

  28. Cellular Systems 2G－GSM

  29. Cellular Systems 2G－CDMA

  30. Cellular Systems--2.5G

  31. Cellular Systems--3G

  32. Cellular Systems 3G—IMT-2000

  33. Cellular Systems 3G—UMTS

  34. Cellular Systems--4G

  35. Cellular Systems--4G(续)

  36. WLAN

  37. Wireless Local Area Networks (WLANs) 1011 0101 01011011 Internet Access Point • WLANs connect “local” computers (100m range) • Breaks data into packets • Channel access is shared (random access) • Backbone Internet provides best-effort service • Poor performance in some apps (e.g. video)

  38. In 200?, all WLAN cards will have all 3 standards Wireless LAN Standards • 802.11b (Current Generation) • Standard for 2.4GHz ISM band (80 MHz) • Frequency hopped spread spectrum • 1.6-10 Mbps, 500 ft range • 802.11a (Emerging Generation) • Standard for 5GHz NII band (300 MHz) • OFDM with time division • 20-70 Mbps, variable range • Similar to HiperLAN in Europe • 802.11g (New Standard) • Standard in 2.4 GHz and 5 GHz bands • OFDM • Speeds up to 54 Mbps

  39. WPAN

  40. Satellite Systems • Cover very large areas • Different orbit heights • GEOs (39000 Km) versus LEOs (2000 Km) • Optimized for one-way transmission • Radio (XM, DAB) and movie (SatTV) broadcasting • Most two-way systems struggling or bankrupt • Expensive alternative to terrestrial system • A few ambitious systems on the horizon

  41. Inmarsat System (海事卫星) Inmarsat Satellite Inmarsat NCS NOC OCC AERO TT&C SCC LES RESCUE COORDINATION CENTRE MARITIME National & International Telecom Network voice data fax telex LAND

  42. Inmarsat 卫星覆盖图

  43. 车载卫星导航系统

  44. 军用卫星指挥系统

  45. 中国卫星概况 • 1970年4月24日，第一颗人造卫星“东方红一号”发射成功，使中国成为世界上第五个独立研制和发射人造地球卫星的国家 • 1975年11月26日，首次发射回收了返回式遥感卫星 使中国成为世界上第三个掌握卫星返回技术的国家 • 1984年4月8日发射成功第一颗“东方红二号”地球静止轨道通信卫星 4月16日定点于东经125赤道上空，使中国成为世界上第五个独立研制和发射静止轨道卫星的国家

  46. 中国卫星系列 • 返回式遥感卫星系列 • “东方红”通信广播卫星系列 • “风云”气象卫星系列 • “实践”科学探测与技术试验卫星系列 • “资源”地球资源卫星系列 • “北斗”导航定位卫星系列

  47. Paging Systems • Broad coverage for short messaging • Message broadcast from all base stations • Simple terminals • Optimized for 1-way transmission • Answer-back hard • Overtaken by cellular

  48. Bluetooth • Cable replacement RF technology (low cost) • Short range (10m, extendable to 100m) • 2.4 GHz band (crowded) • 1 Data (700 Kbps) and 3 voice channels • Widely supported by telecommunications, PC, and consumer electronics companies • Few applications beyond cable replacement 8C32810.61-Cimini-7/98

  49. Ultrawideband Radio (UWB) • UWB is an impulse radio: sends pulses of tens of picoseconds(10-12) to nanoseconds (10-9) • Duty cycle of only a fraction of a percent • A carrier is not necessarily needed • Uses a lot of bandwidth (GHz) • Low probability of detection • Excellent ranging capability • Multipath highly resolvable: good and bad • Can use OFDM to get around multipath problem.

  50. Why is UWB Interesting? • Unique Location and Positioning properties • 1 cm accuracy possible • Low Power CMOS transmitters • 100 times lower than Bluetooth for same range/data rate • Very high data rates possible • 500 Mbps at ~10 feet under current regulations • 7.5 Ghz of “free spectrum” in the U.S. • FCC recently legalized UWB for commercial use • Spectrum allocation overlays existing users, but its allowed power level is very low to minimize interference • “Moore’s Law Radio” • Data rate scales with the shorter pulse widths made possible with ever faster CMOS circuits

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