Chapter 1 Introduction to Wireless Communication Systems. School of Information Science and Engineering, SDU

Transcription

1 Chapter 1 Introduction to Wireless Communication Systems School of Information Science and Engineering, SDU

2 Outline Wireless History The Wireless Vision Technical Challenges Wireless definitions Classification of Wireless Systems Modern Wireless Systems and Trends

3 Wireless History Ancient Systems: Smoke Signals, Carrier Pigeons, Radio invented in the 1880s by Marconi Many sophisticated military radio systems were developed during and after WW2 Cellular has enjoyed exponential growth since 1988 Ignited the wireless revolution Voice, data, and multimedia becoming ubiquitous Use in third world countries growing rapidly Wifi also enjoying tremendous success and growth Wide area networks (e.g. Wimax) Short-range systems: Bluetooth, UWB,

4 The Wireless Vision Next-generation Cellular Wireless Internet Access Wireless Multimedia Sensor Networks Smart Homes/Spaces Automated Highways In-Body Networks Internet of things All this and more

5 Technical Challenges Network Challenges Scarce spectrum Demanding/diverse applications Reliability Ubiquitous coverage Seamless indoor/outdoor operation Device Challenges Size, Power, Cost Multiple Antennas in Silicon Multi-radio Integration Coexistence

6 Wireless System Definitions Mobile Station A station in the cellular radio service intended for use while in motion at unspecified locations. They can be either handheld personal units (portables) or installed on vehicles (mobiles) Base station A fixed station in a mobile radio system used for radio communication with the mobile stations. Base stations are located at the center or edge of a coverage region. They consists of radio channels and transmitter and receiver antennas mounted on top of a tower.

7 Wireless System Definitions Mobile Switching Center Switching center which coordinates the routing of calls in a large service area. In a cellular radio system, the MSC connections the cellular base stations and the mobiles to the PSTN (telephone network). It is also called Mobile Telephone Switching Office (MTSO) Subscriber A user who pays subscription charges for using a mobile communication system Transceiver A device capable of simultaneously transmitting and receiving radio signals

8 Wireless System Definitions Control Channel Radio channel used for transmission of call setup, call request, call initiation and other beacon and control purposes. Forward Channel Radio channel used for transmission of information from the base station to the mobile Reverse Channel Radio channel used for transmission of information from mobile to base station

9 Wireless System Definitions Simplex Systems Communication systems which provide only one-way communication Half Duplex Systems Communication Systems which allow two-way communication by using the same radio channel for both transmission and reception. At any given time, the user can either transmit or receive information. Full Duplex Systems Communication systems which allow simultaneous two-way communication. Transmission and reception is typically on two different channels (FDD).

10 Wireless System Definitions Handoff The process of transferring a mobile station from one channel or base station to an other. Roamer Page A mobile station which operates in a service area (market) other than that from which service has been subscribed. A brief message which is broadcast over the entire service area, usually in simulcast fashion by many base stations at the same time.

11 Wireless Systems Paging Messaging Systems Cordless Telephones Satellite Based Mobile Systems Cellular Telephony (High-tier) Wide Area Wireless Data Systems (High-tier) High Speed Local and Personal Area Networks 3G Systems

12 Major Mobile Radio Standards USA 300 DQPSK TDMA/FDMA 1994 Cordless/PCS PACS 200 GMSK TDMA 1994 PCS DCS-1900 (GSM) 15 4-FSK Several Simplex 1993 Paging FLEX 1250 QPSK/BPSK CDMA 1993 Cellular/PCS IS GMSK FH/Packet 1993 Cellular CDPD 30 DQPSK TDMA 1991 Cellular USDC 30 FM FDMA 1983 Cellular AMPS Channel BW (KHz) Modulation Frequency Band (MHz) Multiple Access Year Intro Type Standard

13 Major Mobile Radio Standards - Europe 100 GFSK FDMA 1989 Cordless CT2 200 GMSK TDMA 1993 Cordless/PCS DCS GFSK TDMA 1993 Cordless DECT 25 4-FSK Several FDMA Paging ERMES FM FDMA 1985 Cellular C KHz GMSK TDMA 1990 Cellular/PCS GSM 12.5 FM FDMA 1986 Cellular NMT FM 900 FDMA 1985 Cellular ETACS Channel BW (KHz) Modulation Frequency Band (MHz) Multiple Access Year Intro Type Standard

14 Paging Systems One-way messaging (asymmetric communication) Wide-area coverage Low complexity, very low-power pager (receiver) devices

15 Wide-Area Paging System City 1 Terrestrial Link Paging Terminal Telephone Base station City 2 PSTN Paging Control Center Terrestrial Link Paging Terminal Base station Satellite City N Satellite Link Paging Terminal Base station pager

16 Cordless Telephone Systems Low mobility (in terms of range and speed) Low power consumption/ Short transmission range Two-way wireless voice communication High circuit quality Low cost equipment, small form factor and long talk-time No handoffs between base units At homes or public places where cordless phone base units are available

17 Cordless Telephone Systems Cordless Phone Base unit PSTN Telephone Network

18 Satellite Communication Systems Two-way (or one-way) limited quality voice or data transmission Very wide range and coverage Large regions Sometimes global coverage Very useful in sparsely populated areas: rural areas, sea, mountains, etc. Target: Vehicles and/or other stationary/mobile uses Expensive base station (satellites) systems

19 Satellite communication systems Very large coverage Low overall system capacity Expensive service Proposed Satellite Systems LEOS: Low-earth orbit satellite systems satellites/system High overall system capacity, low delay Many but comparably less expensive satellites MEOS: Medium-earth satellite systems GEOS: Geostationary or Geosynchronous Orbit Systems Fewer than 10 satellites/system Low overall system capacity, high end-to-end delay (~0.5sec) Very expensive satellites Iridium, Globalstar, Teledesic, Inmarsat are some example systems

20 Cellular Telephone Systems High mobility provision Wide-range Two-way wireless voice communication Handoff and roaming support Integrated with sophisticated public switched telephone network (PSTN) High transmit power requires at the handsets (~2W)

21 Cellular Telephone Systems Radio tower PSTN Telephone Network Mobile Switching Center

22 Cellular Telephone Systems Mobile users and handsets Very complex circuitry and design Base stations Provides gateway functionality between wireless and wireline links Mobile switching centers Connect cellular system to the terrestrial telephone network

23 Modern Wireless Systems Cellular Networks Wireless Local Loop (WLL) and LMDS High-Speed Wireless LANs Wireless Body Area Networks

24 Cellular Networks First Generation Analog Systems Analog Modulation, mostly FM AMPS Voice Traffic FDMA/FDD multiple access Second Generation (2G) Digital Systems Digital Modulation Voice Traffic TDMA/FDD and CDMA/FDD multiple access 2.5G Digital Systems Voice + Low-datarate Data Third Generation Digital Voice + High-datarate Data Multimedia Transmission also

25 2G Technologies cdmaone (IS-95) GSM, DCS-1900 IS-54/IS-136 PDC Uplink Frequencies (MHz) (Cellular) (US PCS) MHz (Eurpe) (US PCS) 800 MHz, 1500 Mhz (Japan) (US PCS) Downlink Frequencies MHz (US Cellular) MHz (US PCS) (Europa) (US PCS) MHz (Cellular) (US PCS) 800 MHz, 1500 MHz (Japan) Deplexing FDD FDD FDD Multiple Access CDMA TDMA TDMA Modulation BPSK with Quadrature Spreading GMSK with BT=0.3 p/4 DQPSK Carrier Seperation 1.25 MHz 200 KHz 30 KHz (IS-136) (25 KHz PDC) Channel Data Rate Mchips/sec Kbps 48.6 Kbps (IS-136) 42 Kbps (PDC) Voice Channels per carrier Speech Coding CELP at 13Kbps EVRC at 8Kbps RPE-LTP at 13 Kbps VSELP at 7.95 Kbps

26 2G and Data 2G is developed for voice communications You can send data over 2G channels by using modem Provides adat rates in the order of ~9.6 Kbps Increased data rates are requires for internet application This requires evolution towards new systems: 2.5 G

27 2.5G Technologies Evolution of TDMA Systems HSCSD for 2.5G GSM Up to 57.6 Kbps data-rate GPRS for GSM and IS-136 Up to Kbps data-rate EDGE for 2.5G GSM and IS-136 Up to 384 Kbps data-rate Evolution of CDMA Systems IS-95B Up to 64 Kbps

28 3G Systems Goals Voice and Data Transmission Simultanous voice and data access Multi-megabit Internet access Interactive web sessions Voice-activated calls Multimedia Content Live music CDMA2000, WCDMA, TD-SCDMA

29 3G Systems Evolution of Systems CDMA sysystem evaolved to CDMA2000 CDMA2000-1xRTT: Upto 307 Kbps CDMA2000-1xEV: CDMA2000-1xEVDO: upto 2.4 Mbps CDMA2000-1xEVDV: 144 Kbps datarate GSM, IS-136 and PDC evolved to W-CDMA (Wideband CDMA) (also called UMTS) Up to Mbps data-rates Future systems 8Mbps Expected to be fully deployed by New spectrum is allocated for these technologies

30 Upgrade Paths for 2G Technologies IS-95 GSM IS-136 PDC 2G IS-95B HSCSD GPRS EDGE 2.5G cdma200-1xrtt cdma2000-1xev,dv,do cdma200-3xrtt W-CDMA TD-SCDMA EDGE 3G

31 WLL and LMDS

32 WLL and LMDS

33 High-Speed Wireless LANs (WLAN) Characterized by Low mobility (not for vehicular use) High speed data transmission Confined regions buildings and campuses Coverage: 100m 300m per base station Speed: 2-11Mbps, 20Mbps Uses ISM bands MHz MHz MHz Uses FHSS or DSSS spectrum usage techniques

34 WLAN Standards Bitrate Frequency Band Range IEEE b Mbps 2.4 GHz ~100m IEEE a 54 Mbps 5 Ghz ~100m HiperLAN 20Mbps 5 GHz ~50m (Europe) HiperLAN/2 54 Mbps 5 GHz ~50m

35 Personal Area Networks (PANs) Bluetooth 2.5GHz ISM band 10m range, 1mW transmit power 100m range, requires increase in transmit power 1 Mbps data rate shared between 7 devices FHSS spread spectrum use TDD duplex scheme Polling based multiple access Retricted start topology 1 master connects to 7 slaves

36 Personal Area Networks (PANs)