chapter 1-introduction to wireless communication...
TRANSCRIPT
Chapter 1Introduction to Wireless Communication Systems
School of Information Science and Engineering, SDU
Outline
l Wireless Historyl The Wireless Vision l Technical Challengesl Wireless definitionsl Classification of Wireless Systemsl Modern Wireless Systems and Trends
Wireless History
l Ancient Systems: Smoke Signals, Carrier Pigeons, …l Radio invented in the 1880s by Marconi l Many sophisticated military radio systems were
developed during and after WW2 l Cellular has enjoyed exponential growth since 1988l Ignited the wireless revolution l Voice, data, and multimedia becoming ubiquitous l Use in third world countries growing rapidly
l Wifi also enjoying tremendous success and growth l Wide area networks (e.g. Wimax) l Short-range systems: Bluetooth, UWB, …
The Wireless Vision
l Next-generation Cellular l Wireless Internet Access l Wireless Multimedia l Sensor Networks l Smart Homes/Spaces l Automated Highways l In-Body Networks l Internet of thingsl All this and more
Technical Challengesl Network Challenges l Scarce spectrum l Demanding/diverse applications l Reliability l Ubiquitous coverage l Seamless indoor/outdoor operation
l Device Challengesl Size, Power, Cost l Multiple Antennas in Silicon l Multi-radio Integration l Coexistence
Wireless System Definitionsl Mobile Station
§ A station in the cellular radio service intended for use while in motion at unspecified locations. They can be either hand-held personal units (portables) or installed on vehicles (mobiles)
l 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.
Wireless System Definitionsl 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)
l Subscriber§ A user who pays subscription charges for using a mobile
communication system
l Transceiver§ A device capable of simultaneously transmitting and
receiving radio signals
Wireless System Definitionsl Control Channel
§ Radio channel used for transmission of call setup, call request, call initiation and other beacon and control purposes.
l Forward Channel§ Radio channel used for transmission of information from the
base station to the mobile
l Reverse Channel§ Radio channel used for transmission of information from
mobile to base station
Wireless System Definitionsl Simplex Systems
§ Communication systems which provide only one-way communication
l 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.
l Full Duplex Systems§ Communication systems which allow simultaneous two-way
communication. Transmission and reception is typically on two different channels (FDD).
Wireless System Definitionsl Handoff
§ The process of transferring a mobile station from one channel or base station to an other.
l Roamer§ A mobile station which operates in a service area (market)
other than that from which service has been subscribed.
l Page§ A brief message which is broadcast over the entire service
area, usually in simulcast fashion by many base stations at the same time.
Wireless Systems
l Paging Messaging Systems l Cordless Telephonesl Satellite Based Mobile Systemsl Cellular Telephony (High-tier)l Wide Area Wireless Data Systems (High-tier)l High Speed Local and Personal Area
Networksl 3G Systems
Major Mobile Radio Standards USA
300DQPSK1850-1990TDMA/FDMA1994Cordless/PCSPACS
200GMSK1850-1990TDMA1994PCSDCS-1900 (GSM)
154-FSKSeveralSimplex1993PagingFLEX
1250QPSK/BPSK824-8941800-2000
CDMA1993Cellular/PCSIS-95
30GMSK824-894FH/Packet1993CellularCDPD
30DQPSK824-894TDMA1991CellularUSDC
30FM824-894FDMA1983CellularAMPS
Channel BW(KHz)
ModulationFrequency Band(MHz)
MultipleAccess
Year Intro
TypeStandard
Major Mobile Radio Standards -Europe
100GFSK864-868FDMA1989CordlessCT2
200GMSK1710-1880TDMA1993Cordless/PCSDCS-1800
1728GFSK1880-1900TDMA1993CordlessDECT
254-FSKSeveralFDMA41993PagingERMES
20-10FM450-465FDMA1985CellularC-450
200KHzGMSK890-960TDMA1990Cellular/PCSGSM
12.5FM890-960FDMA1986CellularNMT-900
25FM900FDMA1985CellularETACS
Channel BW(KHz)
ModulationFrequency Band(MHz)
MultipleAccess
Year Intro
TypeStandard
Paging Systems
l One-way messaging (asymmetric communication)l Wide-area coveragel Low complexity, very low-power pager (receiver)
devices
Wide-Area Paging System
PSTN
Base stationTelephone
PagingTerminal
PagingTerminal
PagingTerminal
Base station
Base station
pager
Satellite
Paging Control Center
Terrestrial Link
Terrestrial Link
Satellite Link
City 1
City 2
City N
Cordless Telephone Systems
l Low mobility (in terms of range and speed)l Low power consumption/ Short transmission rangel Two-way wireless voice communicationl High circuit qualityl Low cost equipment, small form factor and long talk-timel No handoffs between base unitsl At homes or public places where cordless phone base
units are available
Cordless Telephone Systems
CordlessPhone
Base unit
PSTN TelephoneNetwork
Satellite Communication Systemsl Two-way (or one-way) limited quality voice or data
transmissionl Very wide range and coverage
§ Large regions§ Sometimes global coverage§ Very useful in sparsely populated areas: rural areas, sea,
mountains, etc.
l Target: Vehicles and/or other stationary/mobile uses
l Expensive base station (satellites) systems
Satellite communication systemsl Very large coverage
l Low overall system capacityl Expensive servicel Proposed Satellite Systemsl LEOS: Low-earth orbit satellite systems
§ 10-100 satellites/system§ High overall system capacity, low delay§ Many but comparably less expensive satellites
l MEOS: Medium-earth satellite systemsl 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
l Iridium, Globalstar, Teledesic, Inmarsat are some example systems
Cellular Telephone Systems
l High mobility provisionl Wide-rangel Two-way wireless voice communicationl Handoff and roaming supportl Integrated with sophisticated public switched
telephone network (PSTN)l High transmit power requires at the handsets
(~2W)
Cellular Telephone Systems
Radio tower
PSTNTelephoneNetwork
Mobile SwitchingCenter
Cellular Telephone Systems
l Mobile users and handsetsl Very complex circuitry and design
l Base stationsl Provides gateway functionality between wireless
and wireline linksl Mobile switching centersl Connect cellular system to the terrestrial
telephone network
Modern Wireless Systems
l Cellular Networksl Wireless Local Loop (WLL) and LMDSl High-Speed Wireless LANsl Wireless Body Area Networks
Cellular Networksl First Generation
l Analog Systemsl Analog Modulation, mostly FM l AMPSl Voice Trafficl FDMA/FDD multiple access
l Second Generation (2G)l Digital Systemsl Digital Modulationl Voice Trafficl TDMA/FDD and CDMA/FDD multiple access
l 2.5Gl Digital Systemsl Voice + Low-datarate Data
l Third Generationl Digitall Voice + High-datarate Data l Multimedia Transmission also
2G Technologies
VSELP at 7.95 KbpsRPE-LTP at 13 KbpsCELP at 13KbpsEVRC at 8Kbps
Speech Coding
3864Voice Channels per carrier
48.6 Kbps (IS-136)42 Kbps (PDC)
270.833 Kbps1.2288 Mchips/secChannel Data Rate
30 KHz (IS-136)(25 KHz PDC)
200 KHz1.25 MHzCarrier Seperation
π/4 DQPSKGMSK with BT=0.3BPSK with Quadrature Spreading
Modulation
TDMATDMACDMAMultiple Access
FDDFDDFDDDeplexing
869-894 MHz (Cellular)1930-1990 (US PCS)800 MHz, 1500 MHz (Japan)
935-960 (Europa)1930-1990 (US PCS)
869-894 MHz (US Cellular)1930-1990 MHz (US PCS)
Downlink Frequencies
800 MHz, 1500 Mhz (Japan)1850-1910 (US PCS)
890-915 MHz (Eurpe)1850-1910 (US PCS)
824-849 (Cellular)1850-1910 (US PCS)
Uplink Frequencies (MHz)
IS-54/IS-136PDC
GSM, DCS-1900cdmaOne (IS-95)
2G and Data
l 2G is developed for voice communicationsl You can send data over 2G channels by
using modeml Provides adat rates in the order of ~9.6 Kbpsl Increased data rates are requires for internet
applicationl This requires evolution towards new systems:
2.5 G
2.5G Technologies
l Evolution of TDMA Systemsl HSCSD for 2.5G GSM
§ Up to 57.6 Kbps data-rate
l GPRS for GSM and IS-136§ Up to 171.2 Kbps data-rate
l EDGE for 2.5G GSM and IS-136§ Up to 384 Kbps data-rate
l Evolution of CDMA Systemsl IS-95B
§ Up to 64 Kbps
3G Systems
l Goalsl Voice and Data Transmissionl Simultanous voice and data access
l Multi-megabit Internet accessl Interactive web sessions
l Voice-activated callsl Multimedia Contentl Live music
l CDMA2000, WCDMA, TD-SCDMA
3G Systemsl Evolution of Systems
l CDMA sysystem evaolved to CDMA2000§ CDMA2000-1xRTT: Upto 307 Kbps§ CDMA2000-1xEV:§ CDMA2000-1xEVDO: upto 2.4 Mbps§ CDMA2000-1xEVDV: 144 Kbps datarate
l GSM, IS-136 and PDC evolved to W-CDMA (Wideband CDMA) (also called UMTS) § Up to 2.048 Mbps data-rates§ Future systems 8Mbps§ Expected to be fully deployed by 2010-2015
l New spectrum is allocated for these technologies
Upgrade Paths for 2G Technologies
IS-136PDCGSMIS-95
IS-95B HSCSDGPRS
EDGE
W-CDMAEDGE
TD-SCDMA
cdma200-1xRTT
cdma2000-1xEV,DV,DO
cdma200-3xRTT
2G
2.5G
3G
WLL and LMDS
WLL and LMDS
High-Speed Wireless LANs (WLAN)
l Characterized byl Low mobility (not for vehicular use)l High speed data transmissionl Confined regions – buildings and campusesl Coverage: 100m – 300m per base stationl Speed: 2-11Mbps, 20Mbpsl Uses ISM bands
§ 902-928 MHz§ 2400-2483.5 MHz§ 5725-5850 MHz
l Uses FHSS or DSSS spectrum usage techniques
WLAN Standards
5 GHz
5 GHz
5 Ghz
2.4 GHz
Frequency Band
~50m
~50m
~100m
~100m
Range
20MbpsHiperLAN(Europe)
54 MbpsHiperLAN/2
54 MbpsIEEE 802.11a
5.5 – 11MbpsIEEE 802.11b
Bitrate
Personal Area Networks (PANs)l Bluetoothl 2.5GHz ISM bandl 10m range, 1mW transmit powerl 100m range, requires increase in transmit power l 1 Mbps data rate shared between 7 devicesl FHSS spread spectrum usel TDD duplex schemel Polling based multiple accessl Retricted start topology
§ 1 master connects to 7 slaves
Personal Area Networks (PANs)