Ch1 Introduction to Wireless Communications & Networks Reading materials:Overview of wireless communications移动通讯词汇（中英）
Outline • Part 1 Introduction to Wireless Communication & Networks • Part 2 Applications of Wireless Networks
Part 1 Introduction to Wireless Communication & Networks • The Wireless Vision • Technical Challenges • Current Wireless Systems • Emerging Wireless Systems • Spectrum Regulation • Standards
Wireless History First Mobile Radio Telephone 1924
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
The Cellular Concept • Basic Principles Frequency Reuse Cell Splitting First proposed by D. H. Ring at Bell Laboratories in 1947
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
BS BS BS MTSO MTSO Cellular Phone Networks San Francisco Internet New York PSTN
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
World Telecom Statistics Crossover has happened in May 2002!
World Cellular Subscribers by Technology as of June 2006 2.41 Billion Cellular Customers Worldwide GSM/UMTS Totals 82.3%
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
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
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
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.
Global Satellite Suburban Urban In-Building Picocell Microcell Macrocell Basic Terminal PDA Terminal Audio/Visual Terminal 3G: ITU-Developed IMT-2000
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
Current Wireless Systems • Cellular Systems • Wireless LANs • Satellite Systems • Paging Systems • Bluetooth • Ultrawideband radios • Zigbee radios
Cellular Systems 3GPP • 3GPP(LTE, Long Term Evolution ) and 3GPP2 are currently developing evolutionary revolutionary systems beyond 3G.
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)
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
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
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
How the Inmarsat System Works • The satellites are controlled from the Satellite Control Centre (SCC) at Inmarsat HQ in London. • Four tracking, telemetry and control (TT&C) stations located at Fucino, Italy; Beijing in China; Lake Cowichan, western Canada; and Pennant Point, eastern Canada. There are also back-up stations at Eik in Norway and Aukland, New Zealand. • A call from an Inmarsat mobile terminal goes directly to the satellite overhead, which routes it back down to a land earth station (LES). • The flow of communications traffic through the Inmarsat network is monitored and managed by the Network Operations Centre (NOC) at Inmarsat HQ. • The NOC is supported by network co-ordination stations (NCS).
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
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
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
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