Chapter 1
Introduction to Wireless
Communication Systems
School of Information Science
and Engineering, SDU
Outline
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Wireless History
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The Wireless Vision
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Technical Challenges
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Wireless definitions
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Classification of Wireless Systems
Wireless History
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Ancient Systems: Smoke Signals, Carrier Pigeons, …
lRadio invented in the 1880s by Marconi
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Many sophisticated military radio systems were
developed during and after WW2
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Cellular has enjoyed exponential growth since 1988
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Ignited the wireless revolution
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Voice, data, and multimedia becoming ubiquitous
lUse in third world countries growing rapidly
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Wifi also enjoying tremendous success and growth
lWide area networks (e.g. Wimax)
The Wireless Vision
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Next-generation Cellular
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Wireless Internet Access
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Wireless Multimedia
lSensor Networks
lSmart Homes/Spaces
lAutomated Highways
lIn-Body Networks
lInternet of things
lAll this and more
Technical Challenges
lNetwork Challenges
lScarce spectrum
lDemanding/diverse applications
lReliability
lUbiquitous coverage
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Seamless indoor/outdoor operation
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Device Challenges
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Size, Power, Cost
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Multiple Antennas in Silicon
lMulti-radio Integration
Wireless System Definitions
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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)
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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 Definitions
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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)
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Subscriber
§ A user who pays subscription charges for using a mobile communication system
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Transceiver
§ A device capable of simultaneously transmitting and receiving radio signals
Wireless System Definitions
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Control Channel
§ Radio channel used for transmission of call setup, call request, call initiation and other beacon and control purposes.
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Forward Channel
§ Radio channel used for transmission of information from the base station to the mobile
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Reverse Channel
§ Radio channel used for transmission of information from mobile to base station
Wireless System Definitions
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Simplex Systems
§ Communication systems which provide only one-way communication
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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.
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Full Duplex Systems
§ Communication systems which allow simultaneous two-way communication. Transmission and reception is typically on two different channels (FDD).
Wireless System Definitions
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Handoff
§ The process of transferring a mobile station from one channel or base station to an other.
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Roamer
§ A mobile station which operates in a service area (market) other than that from which service has been subscribed.
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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
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Paging Messaging Systems
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Cordless Telephones
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Satellite Based Mobile Systems
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Cellular Telephony (High-tier)
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Wide Area Wireless Data Systems (High-tier)
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High Speed Local and Personal Area
Networks
Major Mobile Radio Standards
USA
300 DQPSK 1850-1990 TDMA/FDMA 1994 Cordless/PCS PACS 200 GMSK 1850-1990 TDMA 1994 PCS DCS-1900 (GSM) 15 4-FSK Several Simplex 1993 Paging FLEX 1250 QPSK/BPSK 824-894 1800-2000 CDMA 1993 Cellular/PCS IS-95 30 GMSK 824-894 FH/Packet 1993 Cellular CDPD 30 DQPSK 824-894 TDMA 1991 Cellular USDC 30 FM 824-894 FDMA 1983 Cellular AMPS Channel BW (KHz) Modulation Frequency Band (MHz) Multiple Access Year Intro Type StandardMajor Mobile Radio Standards
-Europe
100 GFSK 864-868 FDMA 1989 Cordless CT2 200 GMSK 1710-1880 TDMA 1993 Cordless/PCS DCS-1800 1728 GFSK 1880-1900 TDMA 1993 Cordless DECT 25 4-FSK Several FDMA4 1993 Paging ERMES 20-10 FM 450-465 FDMA 1985 Cellular C-450 200KHz GMSK 890-960 TDMA 1990 Cellular/PCS GSM 12.5 FM 890-960 FDMA 1986 Cellular NMT-900 25 FM 900 FDMA 1985 Cellular ETACS Channel BW (KHz) Modulation Frequency Band (MHz) Multiple Access Year Intro Type StandardPaging Systems
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One-way messaging (asymmetric communication)
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Wide-area coverage
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Low complexity, very low-power pager (receiver)
Wide-Area Paging System
PSTN Base station Telephone Paging Terminal Paging Terminal Paging Terminal Base station Base station pager Satellite Paging Control Center Terrestrial Link Terrestrial Link Satellite Link City 1 City 2 City NCordless Telephone Systems
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Low mobility (in terms of range and speed)
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Low power consumption/ Short transmission range
lTwo-way wireless voice communication
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High circuit quality
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Low cost equipment, small form factor and long talk-time
lNo handoffs between base units
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At homes or public places where cordless phone base
Cordless Telephone Systems
Cordless Phone Base unit PSTN Telephone NetworkSatellite Communication
Systems
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Two-way (or one-way) limited quality voice or data
transmission
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Very wide range and coverage
§ Large regions
§ Sometimes global coverage
§ Very useful in sparsely populated areas: rural areas, sea, mountains, etc.
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Target: Vehicles and/or other stationary/mobile
uses
Satellite communication
systems
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Very large coverage
l Low overall system capacity
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Expensive service
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Proposed Satellite Systems
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LEOS: Low-earth orbit satellite systems
§ 10-100 satellites/system
§ High overall system capacity, low delay
§ Many but comparably less expensive satellites
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MEOS: Medium-earth satellite systems
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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
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Iridium, Globalstar, Teledesic, Inmarsat are some example
Cellular Telephone Systems
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High mobility provision
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Wide-range
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Two-way wireless voice communication
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Handoff and roaming support
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Integrated with sophisticated public switched
telephone network (PSTN)
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High transmit power requires at the handsets
Cellular Telephone Systems
Radio tower PSTN Telephone Network Mobile Switching CenterCellular Telephone Systems
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Mobile users and handsets
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Very complex circuitry and design
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Base stations
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Provides gateway functionality between wireless
and wireline links
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Mobile switching centers
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Connect cellular system to the terrestrial
Modern Wireless Systems
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Cellular Networks
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Wireless Local Loop (WLL) and LMDS
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High-Speed Wireless LANs
Cellular Networks
l First Generation
l Analog Systems
l Analog Modulation, mostly FM
l AMPS
l Voice Traffic
l FDMA/FDD multiple access
l Second Generation (2G)
l Digital Systems l Digital Modulation
l Voice Traffic
l TDMA/FDD and CDMA/FDD multiple access
l 2.5G
l Digital Systems
l Voice + Low-datarate Data
l Third Generation
l Digital
l Voice + High-datarate Data
2G Technologies
VSELP at 7.95 Kbps RPE-LTP at 13 Kbps CELP at 13Kbps EVRC at 8Kbps Speech Coding 3 8 64 Voice Channels percarrier
48.6 Kbps (IS-136) 42 Kbps (PDC) 270.833 Kbps
1.2288 Mchips/sec Channel Data Rate
30 KHz (IS-136) (25 KHz PDC) 200 KHz 1.25 MHz Carrier Seperation π/4 DQPSK GMSK with BT=0.3 BPSK with Quadrature Spreading Modulation TDMA TDMA CDMA Multiple Access FDD FDD FDD Deplexing 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-136 PDC GSM, DCS-1900 cdmaOne (IS-95)
2G and Data
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2G is developed for voice communications
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You can send data over 2G channels by
using modem
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Provides adat rates in the order of ~9.6 Kbps
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Increased data rates are requires for internet
application
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This requires evolution towards new systems:
2.5G Technologies
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Evolution of TDMA Systems
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HSCSD
for 2.5G GSM
§ Up to 57.6 Kbps data-rate
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GPRS for GSM and IS-136
§ Up to 171.2 Kbps data-rate
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EDGE for 2.5G GSM and IS-136
§ Up to 384 Kbps data-rate
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Evolution of CDMA Systems
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IS-95B
3G Systems
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Goals
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Voice and Data Transmission
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Simultanous voice and data access
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Multi-megabit Internet access
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Interactive web sessions
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Voice-activated calls
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Multimedia Content
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Live music
3G Systems
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Evolution of Systems
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CDMA sysystem evaolved to CDMA2000
§ CDMA2000-1xRTT: Upto 307 Kbps
§ CDMA2000-1xEV:
§ CDMA2000-1xEVDO: upto 2.4 Mbps
§ CDMA2000-1xEVDV: 144 Kbps datarate
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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
Upgrade Paths for 2G
Technologies
IS-136 PDC GSM IS-95 IS-95B HSCSD GPRS EDGE W-CDMA EDGE TD-SCDMA cdma200-1xRTT cdma2000-1xEV,DV,DO cdma200-3xRTT 2G 2.5G 3GHigh-Speed Wireless LANs (WLAN)
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Characterized by
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Low mobility (not for vehicular use)
lHigh speed data transmission
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Confined regions – buildings and campuses
lCoverage: 100m – 300m per base station
lSpeed: 2-11Mbps, 20Mbps
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Uses ISM bands
§ 902-928 MHz
§ 2400-2483.5 MHz § 5725-5850 MHz
WLAN Standards
5 GHz 5 GHz 5 Ghz 2.4 GHz Frequency Band ~50m ~50m ~100m ~100m Range 20Mbps HiperLAN (Europe) 54 Mbps HiperLAN/2 54 Mbps IEEE 802.11a 5.5 – 11Mbps IEEE 802.11b BitratePersonal Area Networks
(PANs)
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Bluetooth
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2.5GHz ISM band
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10m range, 1mW transmit power
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100m range, requires increase in transmit power
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1 Mbps data rate shared between 7 devices
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FHSS spread spectrum use
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TDD duplex scheme
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Polling based multiple access
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