Introduction to Wireless and Mobile Systems, 3rd ed

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Introduction toWireless andMobileSystems, 3rd EditionDharma Prakash AgrawalQing-An Zeng

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C H A P T E R

1 Introduction

1.1 History of Cellular SystemsLong-distance communication began with the introduction of telegraphs and sim-ple coded pulses, which were used to transmit short messages. Since then, numerousadvances have rendered reliable transfer of information both easier and quicker.There is a long history of how the field has evolved and how telephony has intro-duced a convenient way of conversing by transmitting audio signals. Hardwareconnections and electronic switches have made transfer of digital data feasible. Theuse of the Internet has added another dimension to the wireline communicationfield, and both voice and data are being processed extensively. In parallel to wire-line communication, radio transmission has progressed substantially. Feasibility ofwireless transmission has brought drastic changes in the way people live and com-municate. New innovations in radio communication have brought about the use ofthis technology in new application areas [1.1]. A chronological evolution of radiocommunication is given in Table 1.1, with specific events that occurred in differentyears clearly marked [1.2]. Table 1.2 on page 3 lists how, for different applications,radio frequency (RF) bands have been allocated [1.3].

Wireless systems have been around for quite some time, and their obvious usein garage-door openers and cordless telephones has gone unnoticed until recently.The introduction of affordably priced wireless telephones has made them attractivefor the general population. Their main usefulness is their capability to maintainthe same contact number even if the user moves from one location to another,and this is illustrated in Figure 1.1 on page 6. Wireless systems have evolvedover time, and the chronological development of first-generation (1G) and second-generation (2G) cellular systems (known as mobile systems outside North America)is given in Tables 1.3 and 1.4 on pages 6 and 7, respectively.

The first-generation wireless systems were primarily developed for voice com-munication using frequency division multiplexing. To have efficient use of com-munication channels, time division multiplexing was used in the second-generationsystems so that data could be also processed. The third-generation systems evolveddue to the need for transmitting integrated voice, data, and multimedia traffic.The channel capacity is still limited, and attempts are being made to compress theamount of information without compromising the quality of received signals.

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2 Chapter 1 Introduction

Table 1.1: �History and StartFrom: Mobile Communications Engineering: Theory and Applications by Lee. Copyright 1997 by MCGRAW-HILLCOMPANIES, INC.—BOOKS. Reproduced with permission of MCGRAW-HILL COMPANIES, INC.—BOOKS in the formatTextbook via Copyright Clearance Center. (continued on next page)

Year Event and Characteristics

1860 Maxwell’s equation relating electric and magnetic fields

1880 Hertz—Initial demonstration of practical radio communication

1897 Marconi—Radio transmission to a tugboat over an 18-mile path

1921 Detroit Police Department—Police car radio dispatch (2 MHz frequency band)

1933 FCC (Federal Communications Commission)—Authorized four channels in the 30 to 40 MHz range

1938 FCC—Ruled for regular service

1946 Bell Telephone Laboratories—152 MHz (simplex)

1956 FCC—450 MHz (simplex)

1959 Bell Telephone Laboratories—Suggested 32 MHz band for high-capacity mobile radio communication

1964 FCC—152 MHz (full duplex)

1964 Bell Telephone Laboratories—Active research at 800 MHz

1969 FCC—450 MHz (full duplex)

1974 FCC—40 MHz bandwidth allocation in the 800 to 900 MHz range

1981 FCC—Release of cellular land mobile phone service in the 40 MHz bandwidth in the 800 to 900 MHz range for commercialoperation

1981 AT&T and RCC (radio common carrier) reach an agreement to split 40 MHz spectrum into two 20 MHz bands. Band Abelongs to nonwireline operators (RCC), and band B belongs to wireline operators (telephone companies). Each markethas two operators

1982 AT&T is divested, and seven RBOCs (regional Bell operating companies) are formed to manage the cellular operations

1982 MFJ (modified final judgment) is issued by the U.S. Department of Justice. All the operators were prohibited to (1) operatelong-distance business, (2) provide information services, and (3) do manufacturing business

1983 Ameritech system in operation in Chicago

1984 Most RBOC markets in operation

1986 FCC allocates 5 MHz in extended band

1987 FCC makes lottery on the small metropolitan service area and all rural service area licenses

1988 TDMA (time division multiple access) voted as a digital cellular standard in North America

1992 GSM (global system for mobile communications) operable in Germany D2 system

1993 CDMA (code division multiple access) voted as another digital cellular standard in North America

1994 American TDMA operable in Seattle, Washington

1994 PDC (personal digital cellular) operable in Tokyo, Japan

1994 Two of six broadband PCS (personal communication services) license bands in auction

1995 CDMA operable in Hong Kong

1996 U.S. Congress passes Telecommunication Reform Act Bill


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Section 1.1 History of Cellular Systems 3

Table 1.1: �History and StartFrom: Mobile Communications Engineering: Theory and Applications by Lee. Copyright 1997 by MCGRAW-HILLCOMPANIES, INC.–BOOKS. Reproduced with permission of MCGRAW-HILL COMPANIES, INC.–BOOKS in the formatTextbook via Copyright Clearance Center. (Continued)

Year Event and Characteristics

1996 The auction money for six broadband PCS licensed bands (120 MHz) almost reaches 20 billion U.S. dollars

1997 Broadband CDMA considered as one of the third-generation mobile communication technologies for UMTS (universalmobile telecommunication systems) during the UMTS workshop conference held in Korea

1999 ITU (International Telecommunication Union) decides the next generation mobile communication systems (e.g.,W-CDMA (wideband-CDMA), cdma2000, TD-SCDMA (time division synchronous CDMA))

2001 W-CDMA commercial service beginning from October in Japan

2002 FCC approves additional frequency band for Ultra-Wideband (UWB)

Table 1.2: �Selected U.S. Frequency Allocations (3 kHz ∼ 300 GHz) (continued on next page)(Entries have been extracted from "FCC Online Table of Frequency Allocations," 47 C.F.R. § 2.106, Revised on Jan-uary 25, 2010, http://www.fcc.gov/oet/spectrum/,http;//www.ntia.doc.gov/osmhome/allochrt.pdf, http://en.wikipedia.org/wiki/Ultra_high_frequency and Thomas W. Hazlett, “Optimal Abolition of FCC Spectrum Allocation,” Journal ofEconomic Perspectives—Volume 22, Number 1—Winter 2008 —Pages 103–128)

Application Frequency Band Unit

AeronauticalMobile

200∼285, 325∼415 kHz

2.85∼3.155, 3.4∼3.5, 4.65∼4.75, 5.45∼5.73, 6.525∼6.765, 8.815∼9.040, 10.005∼10.1, 11.175∼11.4,13.2∼13.36, 15.10∼15.10, 17.9∼18.03, 21.924∼22.0, 23.2∼23.35, 117.975∼137.0, 849∼851, 894∼896

MHz

AeronauticalMobile Satellite

1545∼1559 (Space to Earth) MHz

Aeronautical RadioNavigation

190∼285, 285∼405 (Radio beacon), 415∼495, 510∼535 (Radio beacon) kHz

74.8∼75.2, 108.0∼117.975, 328.6∼335.4, 980∼1215, 1300∼1350, 2700∼2900 MHz

3.5∼3.65 (Ground), 4.2∼4.4, 5.0∼5.15, 5.35∼5.46, 9.0∼9.2, 13.25∼13.4, 15.4∼15.7 GHz

Amateur 1800∼1900 kHz

3.5∼4.0, 7.0∼7.3, 10.01∼10.05, 14.0∼14.35, 18.068∼18.168, 21.0∼21.45, 24.89∼24.99, 28.0∼29.7,50.0∼54.0, 144.0∼148.0, 216.0∼220.0, 222.0∼225.0, 420.0∼450.0, 902.0∼928.0, 1240∼1300,2300∼2310, 2390∼2450

MHz

3.3∼3.5, 5.56∼5.925, 10.0∼10.5, 24.0∼24.05, 47.0∼47.2, 75.5∼81.0, 119.98∼120.02, 142.0∼149.0,241.0∼250.0

GHz

Amateur Satellite 7.0∼7.1, 14.0∼.14.25, 18.068∼18.168, 21.0∼21.45, 24.89∼24.99, 28.0∼29.7, 144.0∼146.0 MHz

5.83∼5.85, 10.45∼10.5, 24.0∼24.05, 47.0∼47.2, 75.5∼76.0, 77.0∼81.0, 142.0∼149.0, 241.0∼250.0 GHz

Broadcasting 535∼1705 (AM Radio) kHz

5.90∼6.2, 7.3∼7.35, 9.4∼9.9, 11.6∼12.10, 13.57∼13.87, 15.10∼15.8, 17.48∼17.9, 18.9∼19.02,21.45∼21.85, 25.67∼26.1, 54.0∼72.0 (TV Channel 2-4), 76.0∼88.0 (TV Channel 5-6), 88.0∼108.0(FM Radio), 174.0∼216.0 (TV Channel 7-13), 470.0∼512.0 (TV Channel 14-20), 512.0∼608.0 (TVChannel 21-36), 614.0∼698 (TV Broadcasting), 698∼764, 776∼794, 40.5∼42.5, 84.0∼86.0

MHz


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Table 1.2: �Selected U.S. Frequency Allocations (3 kHz ∼ 300 GHz) (continued on next page)


BroadcastingSatellite

2310∼2360, 2655∼2690 MHz

12.2∼12.7, 17.3∼17.7, 40.05∼42.5, 84.0∼86.0 GHz

EarthExplorationSatellite

2025∼2110, 2200∼2290, 2655∼2700 MHz

8.025∼8.4, 10.6∼10.7, 31.3∼31.8, 36.0∼37.0, 40.0∼40.5, 50.2∼50.4, 52.6∼59.3, 65.0∼66.0, 86.0∼92.0,100.0∼102.0, 105.0∼126.0, 150.0∼151.0, 164.0∼168.0, 174.0∼176.0, 182.0∼-185.0, 200.0∼202.0,217.0∼231.0, 235.0∼238.0, 250.0∼252.0

GHz

Fixed 14.0∼19.95, 20.05∼59.0, 61.0∼90.0, 110.0∼190.0, 1705.0∼1800.0, 2000.0∼2065.0, 2107.0∼2170.0,2194.0∼2495.0, 2505.0∼2850.0

kHz

3.155∼3.4, 4.0∼4.063, 4.438∼4.65, 4.75∼4.995, 5.005∼5.45, 5.73∼5.95, 6.765∼7.0, 7.3∼8.195,9.040∼9.5, 9.9∼9.995, 10.15∼11.175, 11.4∼11.65, 12.05∼12.23, 13.41∼13.6, 13.8∼14.0,14.35∼14.990, 15.6∼16.36, 17.41∼17.55, 18.03∼18.068, 18.168∼18.78, 18.9∼19.68, 19.80∼19.990,20.010∼21.0, 21.85∼21.924, 22.855∼23.2, 23.35∼24.89, 25.33∼25.55, 26.48∼26.96, 27.32∼28.0,29.8∼37.0, 38.0∼39.0, 40.0∼43.69, 46.6∼47.0, 49.6∼50.0, 72.0∼73.0, 74.6∼74.8, 75.2∼76.0,138.0∼144.0, 148.0∼149.9, 150.05∼152.855, 154.0∼156.2475, 157.45∼161.575, 162.0125∼174.0,216.0∼222.0, 225.0∼328.6, 335.4∼399.9, 406.1∼420.0, 454.0∼455.0, 456.0∼462.5375,462.7375∼467.5375, 467.7375∼512.0, 698.0∼821.0, 824.0∼849.0, 851.0∼866.0, 869.0∼894.0,896.0∼902.0, 928.0∼960.0, 1350.0∼1395.0, 1427.0∼1435.0, 1670.0∼1675.0, 1700.0∼2000.0,2020.0∼2025.0, 2110.0∼2180.0, 2200.0∼2300.0, 2305.0∼2390.0, 2450.0∼2483.5, 2500.0∼2690.0

MHz

3.65∼4.2, 4.4∼4.99, 5.925∼6.425, 6.525∼8.5, 10.55∼10.68, 10.7∼11.7, 12.2∼13.25, 14.4∼15.35,17.7∼18.3, 19.3∼19.7, 21.2∼23.6, 24.25∼24.45, 25.05∼29.5, 31.0∼31.3, 36.0∼40.0, 40.543.5, 46.9∼47.0,47.2∼50.2, 50.4∼52.6, 55.78∼66.0, 71.0∼75.5, 81.086.0, 92.095.0, 102.0∼105.0, 116.0∼134.0, 149.0164.0,168.0∼182.0, 185.0∼190.0, 200∼217.0, 231.0∼241.0, 265.0∼300.0

GHz

Fixed Satellite 1390∼1392, 1430∼1432, 2500∼2690 MHz

3.6∼4.2, 4.5∼4.8, 5.15∼5.25, 5.85∼7.075, 7.25∼7.75, 7.90∼8.4, 10.7∼12.2, 12.7∼13.25, 13.75∼14.5,15.43∼15.63, 17.3∼21.2, 24.75∼25.25, 27.5∼31.0, 37.6∼41.0, 42.5∼45.5, 47.2∼50.2, 50.4∼51.4,71.0∼75.5, 81.0∼84.0, 92.0∼95.0, 102.0∼105.0, 149.0∼150.0, 151.0∼164.0, 202.0∼217.0, 231.0∼241.0,265.0∼275.0

GHz

Inter-Satellite 22.55∼23.55, 24.45∼24.75, 25.25∼27.5, 32.0∼33.0, 54.25∼58.2, 59.071.0, 116.0∼134.0, 170.0∼182.0,185.0∼190.0

GHz

Land Mobile 2107∼2170, 2194∼2495, 2505∼2850 kHz

25.01∼25.07, 25.21∼25.33, 26.175∼26.48, 27.41∼27.54, 29.7∼29.8, 30.56∼32.0, 33.0∼34.0, 35.0∼36.0,37.0∼38.0, 39.0∼40.0, 42.0∼46.6, 47.0∼49.6, 150.8∼156.2475, 157.1875∼161.575, 161.625∼162.0125,173.2∼173.4, 220.0∼222.2, 450.0∼512.0, 806.0∼849.0, 851.0∼894.0, 896.0∼901.0, 931.0∼932.0,935.0∼941.0, 1395.0∼1400.0, 1427.0∼1432.0

MHz

Land MobileSatellite

14.0∼14.5 GHz

Maritime Mobile 14∼19.95, 20.05∼59.0, 61.0∼90.0, 110.0∼190.0, 415.0∼495.0, 505.0∼525.0, 2000.0∼2065.0,2065.0∼2107.0 (telephone), 2107.0∼2170.0, 2170.0∼2173.0 (telephone), 2190.0∼2194.0 (telephone),2194.0∼2495.0, 2505.0∼2850.0

kHz

4.0∼4.438, 6.2∼6.525, 8.1∼8.815, 12.23∼13.2, 16.36∼17.41, 18.78∼18.9, 19.68∼19.80, 22.0∼22.855,25.07∼25.21, 26.1∼26.175, 156.2475∼157.1875, 161.575∼161.625, 161.775∼162.0125

MHz

Maritime MobileSatellite

1530.0∼1544.0 MHz


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Table 1.2: �Selected U.S. Frequency Allocations (3 kHz ∼ 300 GHz) (continued on next page)


Maritime RadioNavigation

275∼335 kHz

3.0∼3.1, 9.2∼9.3 GHz

MeteorologicalAids

400.15∼406.0, 1668.4∼1670.0, 1675.0∼1700.0, 2700.0∼2900.0 MHz

5.6∼5.65, 9.3∼9.5 GHz

MeteorologicalSatellite

400.15∼403.0, 460.0∼470.0, 1675∼1710 MHz

7.45∼7.55, 8.175∼8.215 GHz

Mobile 495∼505, 525∼535, 1605∼1615, 1705∼1800, 2000∼2065, 2107∼2170, 2173.5∼2190.5, 2194∼2495,2505∼2850

kHz

3.155∼3.4, 4.438∼4.65, 4.75∼4.995, 5.065∼5.45, 5.73∼5.95, 6.765∼7.0, 7.3∼8.1, 10.15∼11.175,13.41∼13.6, 13.8∼14.0, 14.35∼14.990, 18.168∼18.78, 20.010∼21.0, 23.0∼23.2, 23.35∼24.89,25.33∼25.55, 26.48∼26.95, 26.96∼27.41, 27.54∼28.0, 29.89∼29.91, 30.0∼30.56, 32.0∼33.0, 34.0∼35.0,36.0∼37.0, 38.0∼39.0, 40.0∼42.0, 46.6∼47.0, 49.6∼50.0, 72.0∼73.0, 74.6∼74.8, 75.2∼76.0, 138.0∼144.0,148.0∼149.9, 150.05∼150.8, 162.0125∼173.2, 173.4∼174.0, 216.0∼220.0, 225.0∼328.6, 335.4∼399.9,406.1∼410.0, 698∼806, 901∼902, 930∼931, 1350∼1395, 1432∼1535, 1670∼1675, 1710∼2000,2020∼∼2155, 2160∼2180, 2290∼2390

MHz

3.65∼3.7, 4.4∼4.99, 6.425∼6525, 6.875∼7.125, 11.7∼12.2, 127∼15.35, 21.2∼23.6, 25.25∼29.5,31.0∼31.3, 36.0∼40.0, 40.5∼43.5, 45.5∼47.0, 47.2∼50.2, 50.4∼52.6, 55.78∼75.5, 81.0∼86.0, 92.0∼100.0,116.0∼142.0, 149.0∼151.0, 168.0∼182.0, 185.0∼217.0, 231.0∼241.0, 252.0∼300.0

GHz

Mobile Satellite 137.0∼138.0, 148.0∼150.05, 235.0∼322.0, 335.4∼400.05, 400.15∼401.0, 406.0∼406.1, 1525∼1558.5,1610.0∼1660.5, 2000.0∼2020.0, 2180.0∼2200.0, 2483.5∼2500.0

MHz

7.25∼7.75, 7.90∼8.4, 19.7∼21.2, 29.5∼31.0, 39.5∼40.5, 43.5∼47.0, 50.4∼51.4, 66.0∼74.0, 81.0∼84.0,95.0∼100.0, 134.0∼142.0, 190.0∼200.0, 252.0∼265.0

GHz

RadioAstronomy

13.38∼13.41, 25.55∼25.67, 37.5∼38.25, 73.0∼74.6, 149.9∼150.05, 406.1∼410.0, 608.0∼614.0,1400.0∼1427.0, 1610.6∼1613.8, 1660.0∼1670.0, 2655.0∼2700.0

MHz

4.99∼5.0, 10.6∼10.7, 15.35∼15.4, 22.21∼22.5, 23.6∼24.0, 31.3∼31.8, 42.5∼43.5, 86.0∼92.0,105.0∼116.0, 164.0∼168.0, 182.0∼185.0, 217.0∼231.0, 265.0∼275.0

GHz

RadioDeterminationSatellite

1610.0∼1626.5, 2483.5∼2500.0 MHz

Radio Location 70.0∼90.0, 110.0∼130.0, 1705.0∼1800.0, 1900.0∼2000.0 kHz

3.230∼3.4, 216.0∼225.0, 420.0∼450.0, 902.0∼928.0, 1215.0∼1390.0, 2305.0∼2385.0, 2417.0‘2483.5,2700.0∼3000.0

MHz

3.0∼3.65, 5.25∼5.85, 8.5∼10.55, 13.4∼14.0, 15.7∼17.7, 24.05∼24.25, 33.4∼36.0, 59.0∼64.0, 76.0∼81.0,92.0∼100.0, 126.0∼142.0, 144.0∼149.0, 231.0∼235.0, 238.0∼248.0

GHz

Radio LocationSatellite

24.65∼24.75 GHz

RadioNavigation

9∼14, 90∼110, 405∼415 kHz

5.46∼5.47, 9.3∼9.5, 14.0∼14.2, 24.45∼24.65, 24.75∼25.05, 31.8∼32.0, 32.0∼32.3, 32.3∼33.0,33.0∼33.4, 66.0∼71.0, 95.0∼100.0, 134.0∼142.0, 190.0∼200.0, 252.0∼265.0

GHz


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Table 1.2: �Selected U.S. Frequency Allocations (3 kHz ∼ 300 GHz) (Continued)


RadioNavigationSatellite

149.0∼150.05, 399.9∼400.05, 1215.0∼1240.0, 1559.0∼1610.0 MHz

45.5∼47.0, 66.0∼71.0, 95.0∼100.0, 134.0∼142.0, 190.0∼200.0, 252.0∼265.0 GHz

Space Operation 137.0∼138.0, 400.15∼402.0, 2025.0∼2110.0, 2200.0∼2290.0 MHz

Space Research 2.501∼2.505, 5.003∼5.005, 10.003∼10.005, 15.005∼15.010, 19.990∼19.995, 20.005∼20.010,25.005∼25.01, 137.0∼138.0, 400.15∼401.0, 410.0∼420.0, 1400.0∼1427.0, 1660.5∼1668.4,2025.0∼2110.0, 2200.0∼2300.0, 2655.0∼2700.0

MHz

4.99∼5.0, 7.19∼7.235, 8.4∼8.5, 10.6∼10.7, 12.75∼14.2, 14.5∼15.4, 16.6∼17.1, 17.2∼17.3, 18.6∼18.8,21.2∼21.4, 22.21∼22.5, 23.6∼24.0, 31.332.3, 36.0∼38.0, 40.0∼40.5, 50.2∼50.4, 52.6∼59.3, 65.0∼66.0,86.0∼92.0, 100.0∼102.0, 105.0∼126.0, 150.0∼151.0, 164.0∼168.0, 174.0∼176.5, 182.0∼185.0,200.0∼202.0, 217.0∼231.0, 235.0∼238.0, 250.0∼252.0

GHz

StandardFrequency andTime SignalSatellite

19.95∼20.05, 95.0∼61.0, 2495.0∼2505.0 kHz

4.995∼5.005, 9.995∼10.005, 14.990∼15.010, 19.990∼20.010, 24.99∼25.01, 400.05∼400.15 MHz

13.4∼14.0, 20.2∼21.2, 25.25∼27.0, 30.0∼31.3 GHz

Figure 1.1Maintaining thetelephone numberin a wireless andmobile system.

Cincinnati, OH

Washington, DC

Table 1.3: �First-Generation Wireless Systems and Services

Year Events

1970s Developments of radio and computer technologies for 800/900 MHz mobile communication

1976 WARC (world administrative radio conference) allocates spectrum for cellular radio

1979 NTT (Nippon Telephone & Telegraph) introduces the first cellular system in Japan

1981 NMT (Nordic Mobile Telephone) 900 system introduced by Ericsson Radio System AB and deployed in Scandinavia

1984 AMPS (advanced mobile phone service) introduced by AT&T in North America


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Table 1.4: �Second-Generation Wireless Systems and Services

Year Events

1982 CEPT (Conference European des Post of Telecommunications) establishes GSM (global special mobile) todefine future Pan-European cellular radio standards

1990 Interim Standard IS-54 (USDC: United States digital cellular) adopted by TIA (TelecommunicationsIndustry Association)

1990 Interim Standard IS-19B (NAMPS: narrowband AMPS) adopted by TIA

1991 Japanese PDC system standardized by the MPT (Ministry of Posts and Telecommunications)

1992 Phase I GSM system is operational

1993 Interim Standard IS-95 (CDMA) adopted by TIA

1994 Interim Standard IS-136 adopted by TIA

1995 PCS Licenses issued in North America

1996 Phase II GSM is operational

1997 North American PCS deploys GSM, IS-54, IS-95

1999 IS-54: used in North America; IS-95: used in North America, Hong Kong, Israel, Japan, South Korea, andChina; GSM: used in 110 countries

The second-generation wireless systems have been designed for both indoorand vehicular environments with an emphasis on voice communication. Anincreased acceptance of mobile communication networks for conventional serviceshas led to demands for high bandwidth wireless multimedia services. These ever-growing demands require a new generation of high-speed mobile infrastructurenetworks that can provide the capacity needed for high traffic volumes as well asflexibility in communication bandwidth or services. There is a need for frequentInternet access and multimedia data transfer, both of which may also involve theuse of satellite communication. Thus, the third-generation (3G) systems (IMT-2000:International Mobile Telecommunications 2000) need to support real-time datacommunication while maintaining compatibility with second-generation systems.There are two schools of thought on the third-generation systems. In the UnitedStates, people are inclined to use cdma2000 as the basic technology, while in Europeand Japan, W-CDMA is being considered as the future scheme. In principle, boththese schemes are similar, but there are differences in their implementations. Theseare basically design issues, and anticipated characteristics are identified in Table 1.5.There are subtle differences between wireless and mobile systems—for example, asystem could be immobile but wireless, or a system could be mobile but not wireless.For the purpose of this text, we do not differentiate between the two and use theseterms interchangeably.


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Table 1.5: �Third-Generation Wireless Systems and Services

IMT-2000 - Fulfill one’s dream of anywhere, anytime communication

- High degree of commonality of design worldwide

- Compatibility of services within IMT-2000 and with the fixed networks

Key Features - High quality

- Small terminal for worldwide use

- Worldwide roaming capability

- Capability for multimedia applications and a wide range of services and terminals

- 2 Mbps for fixed environment

Important Component - 384 kbps for indoor/outdoor and pedestrian environment

- 144 kbps for vehicular environment

Standardization Work - In progress (see Table 1.6)

Scheduled Service - Started in October 2001 in Japan (W-CDMA)

- Started in December 2001 in Europe

- Started in January 2002 in South Korea

- Started in October 2003 in USA

Table 1.6: �3GPP Release Dates and Contents [1.20, 1.21] (continued on next page)

3GPP Release Release Date Summary

3GPP Release 99 1999 First release of the UMTS standard

3GPP Release 4 2001 This release was originally referred to as Release 2000 and added featuresincluding an all-IP core network.

3GPP Release 5 2002 This release introduced the IP multimedia subsystem, IMS (IP multimediasubsystem), and high-speed packet downlink access, HSDPA (high-speeddownlink packet access).

3GPP Release 6 2004 This release integrated the operation of UMTS with wireless LAN net-works and added enhancements to IMS (including Push to talk overcellular), and GAN (generic access network). It also added high speedpacket uplink access, HSUPA (high-speed uplink packet access).

3GPP Release 7 2007 This release detailed improvements to QoS (Quality of Service) for appli-cations such VoIP (Voice over IP). It also detailed upgrades for high-speedpacket access evolution, HSPA+ (high-speed packet access), as well aschanges for EDGE (enhanced data rates for GSM evolution) evolutionand also provided interfaces to enable operation with NFC (near fieldcommunication) technology.


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Table 1.6: �3GPP Release Dates and Contents [1.20, 1.21] (Continued)

3GPP Release Release Date Summary

3GPP Release 8 2008 This release provided the details of the LTE (long-term evolution) systemarchitecture evolution (SAE), and an all-IP network architecture providingthe capacity and low latency required for LTE and future evolutions.

3GPP Release 9 End 2009 This release added further enhancements to the SAE as well as allow-ing for WiMAX (worldwide interoperability for microwave access) andLTE/UMTS interoperability.

3GPP Release 10 Estimated 2010 This release detailed the 4G LTE-Advanced technology.

Wireless telephones are not only convenient but are also providing flexibilityand versatility. Thus, there has been a growing number of wireless phone ser-vice providers as well as subscribers. Past numbers and future projections aregiven in Figure 1.2. It is expected that third-generation wireless systems will havemany subsystems, with different requirements, characteristics, and coverage areas(Figure 1.3). The term cell basically represents the area that can be covered bya transmitting station, usually called a base station (BS), and pico, micro, macro,and so on primarily indicate the relative size of the area that can be covered. Thetransmission capacity as a function of support for mobility in different radio accesssystems is illustrated in Figure 1.4. To cater to the different needs, different wirelesstechnologies have been developed and are discussed next.

Figure 1.2Subscriber growthfor wireless phones.

3G Subscribers

2G Digital-only Subscribers

1G Analog-only Subscribers

Sub

scri

bers

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

Year

Different size cells are primarily needed due to the fact that in some areas,such as downtown or a big office complex, a large number of wireless telephoneusers may be present and served by a smaller size cell. This enables having a larger


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Figure 1.3Coverage aspect ofthird-generationwirelesscommunicationssystems.

Picocell Microcell Macrocell Global

In-building

Urban

Suburban

Global

Satellite

Figure 1.4Transmission capacityas a function ofmobility in someradio access systems.

Broadband Radio

Glo

bal S

yste

m f

or M

obile

Com

mun

icat

ions

0.01 0.1 1 10 100

Mob

ility

Universal MobileTelecommunicationsSystem

Mobile Broadband SystemMobile Broadband System

Broadband Satellite Multimedia

Local Multipoint Distribution System

Satellite Universal Mobile Telecommunications System Broadband Satellite Multimedia

Local Multipoint Distribution System

Satellite Universal MobileTelecommunicationsSystem

Data Rate (Mb/s)

Stationary

Pedestrian

Vehicular

number of channels allocated to each cell, which is assumed to be the same or inde-pendent of the cell size. The idea is to maintain the same number of channels percustomer and try to have a similar quality of service in all areas.

1.2 Characteristics of Cellular SystemsThe network characteristics largely depend on the type of applications beingexplored, and a brief account is given in Table 1.7 [1.1]. One major partition ofrequirements is based on whether it is being envisioned for the home-based orindustrial system versus the commercial and private environment (Table 1.8 onpage 12). In a house, a central access point (AP) is expected to communicate withvarious appliances and control them using localized wireless mode. This would notonly enable close coordination among appliances, but also enable control froma remote location to the house AP using voice or a short message. A similar


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Section 1.2 Characteristics of Cellular Systems 11

Table 1.7: �Wireless Technologies and Associated CharacteristicsFrom: L. Malladi and D.P. Agrawal, “Current and Future Applications of Mobile and Wireless Networks”Communications of the ACM, 45:10, October 2002, pp. 144–146. (c) 2004 ACM, Inc. Reprinted by permission.

Technology Services or Features Coverage Area Limitations Examples

Cellular Voice and data throughhandheld phones

Continuous coveragelimited to metropolitanregions

Available bandwidth isvery low for most dataintensive applications

Cellular phones,personal digitalassistant

Wireless local areanetwork (LAN)

Traditional LANextended with wirelessinterface

Used only in localenvironments

Limited range NCR’s Wavelan,Motorola’s ALTAIR,Proxim’s range LAN,Telesystem’s ARLAN

GPS Helps to determine thethree-dimensionalposition, velocity, andtime

Any place on thesurface of earth

It is still not affordableby everyone

GNSS, NAVSTAR,GLONASS

Satellite-based PCS Applications mainly forvoice paging andmessaging

Almost any place onearth

It is costly Iridium, Teledesic

Ricochet High-speed, securemobile access to thedesktop (data) fromoutside the office

Some major cities,airports, and someuniversity areas

Has a transmissionlimitation.Environmentalconditions affect qualityof service

MicroCellular DataNetwork (MCDN)

Home networking To connect differentPCs in the house toshare files and devicessuch as printers

Anywhere in the house Limited to a home Netgear Phoneline 10X,Intel AnyPointPhoneline HomeNetwork, 3Com HomeConnect HomeNetwork Phoneline

Ad hoc networks Group of people cometogether for a shorttime to share data

Equal to that of localarea network, butwithout fixedinfrastructure

Limited range Defense applications

WPAN (Bluetooth) All digital devices canbe connected withoutany cable

Private ad hocgroupings away fromfixed networkinfrastructures

Range is limited due tothe short-range radiolink used

Home devices

Sensor networks A large number of tinysensors with wirelesscapabilities

Relatively small terrain Very limited range Defense and civilianapplications


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Table 1.8: �Characteristics of Wireless and Mobile Systems

Public Sphere Traffic information system, personal security, disaster information system

Business Sphere Mobile videophone, video conferencing, database e-mail

Private Sphere Information services, music on demand portable TV, interactive TV, interactive games,video on demand, electronic newspapers and books, shopping, home schooling system,information service for pagers, news, weather forecasts, financial information

mechanism could be used to control devices in an industrial floor as well. To pro-vide such wireless control, a consortium of companies are pursuing the Bluetoothproject. For example, a system like this could support a bracelet, which wouldconstantly monitor various body functions/parameters and take corrective action(like informing a family physician about a health problem). Substantial efforts areneeded to make such a system fully operational. To design such a generic systemwith plug-and-play capability requires standardization and necessary infrastructurefor Internet access, audio/video editing, and distributed decision-making software.Wireless communication has become very popular in major fields such as commerce,medicine, education, and military defense. A simple example is when doctors arediagnosing a patient and can receive advice from medical specialists located in anypart of the world (Figure 1.5).

Figure 1.5An example ofmedical and healthapplication.

Wireless remoteconsultation

ATM backbonenetwork

Possibility for remote consulting(including audio-visual communication)

ATM switch

ATM switch

Remotedatabases

In-hospitalphysician

Ambulance

In a commercial environment there are many issues involved, like the rangeof the system, the number of Access Points (APs) as distribution infrastructuresthat are installed, and the number of users for each AP. For a department store,each floor may have one AP, while in a factory there is a need for several uni-formly spaced APs per floor so that users are connected to an AP at all times.Thus channel bandwidth requirements and coordination of channels between APs


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Section 1.2 Characteristics of Cellular Systems 13

govern the complexity. Communication can be either by a voice or a data packet, ora combination of both. The corresponding data loss is unacceptable in connection-oriented as well as connectionless wireless switching schemes; therefore correctnessof transmitted and received data is important in all such applications. A new high-speed technology (WiMAX [Worldwide Interoperability for Microwave Access]) isbeing introduced to cover larger areas, possibly large metropolitan areas.

In a defense application, effective communication could be achieved using aninfrastructure system or could be supported by a decentralized ad hoc networkformed with close-by mobile users or wireless devices, and we use a generic termmobile stations (MSs) to indicate the presence of any such mobile device with wire-less radio. It may also involve satellite systems. In ad hoc networks, informationtransfer is achieved in peer-to-peer mode, and there is a tradeoff between cover-age area and power consumption. Other issues include channel allocation basedon address and type of traffic (voice, video, audio, or data), utilization, routingtechniques, and mobility pattern (e.g., moving speed, moving direction, etc.). It isalso not clear how to optimize power usage, routing table size, and sustainabilityof path during each transmission session and diversity for unicasting and multicas-ting. Issues like handling of congestion, overloading of resources, adaptations ofprotocols, and queue length need to be considered carefully.

In all these systems, security, both in terms of authentication and encryption, iscritical. This is fairly expensive in terms of hardware and software resources, andit affects channel capacity and information contents. Often, many levels of secu-rity may be useful and desirable. In all these systems, mobility is an integral factorand can be characterized by personal, terminal, and service mobilities. The effect ofhandoff needs to be viewed in various layers, and changing of radio resources needsto be minimized as much as possible. In order to minimize handoff and switching,the use of a macrocellular infrastructure (a larger coverage area per cell) has beenadvocated, and multilevel overlapped schemes have also been proposed to serviceusers with different mobility patterns. In actual practice, however, a typical user onaverage utilizes a mobile phone one minute per day. A tradeoff between cost andperformance encourages the use of smaller-size cells. The idea is to have a largenumber of small cells, with each cell effectively covering users located in that area.

A wireless system is expected to provide “anytime anywhere” type of service,and this characteristic has made it a very attractive technology. This kind of featureis essential for military and defense areas as well as to a limited class of potentiallylife-threatening applications like nuclear power, aviation, and medical emergencies.Different wireless features and their potential application areas are summarizedin Table 1.9. However, for most day-to-day operations, the “anytime anywhere”feature may not be needed. Therefore, a “many time” or “many where” attributemay be adequate for Internet access, wherein you wait for resources to pass by; oryou wait until you are close to a resource access point to have wireless or Internetaccess [1.4]. Also, there is no need to wait for completion of a transaction or datatransfer completely for a MS as long as the remaining part could be made available(automatically routed) to an AP that the unit will be reaching along the path withinthe synchronized time constraints. In addition, emphasis should be on a scalablecommunication paradigm to reach multiple destinations and to support a query in


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Table 1.9: �Potential Applications of Different Services

Wireless Features Electronic Mail WMAN/WLAN(Wireless MAN/LAN)

GPS Satellite-BasedPCS

ApplicationAreas

-Field Service-Sales Force-TransportationIndustry

-Vending-Public Safety-Stock Trading-AirlineActivities

-Bill Paying-Field Audit

-Retail-Warehouses-Manufacturing-Students-Telediagnostics-Hospitality-General Office-Health Care

-Surveying-Car Rental Agency-Toll Collection-Sports

-Iridium-Teledesic

a distributed fashion. Transfer of data at the right time is also guided by associatedcost.Therefore, efficient design of a protocol is a challenge, as users may not alwaysbe connected ubiquitously.

1.3 Fundamentals of Cellular SystemsAs discussed earlier, there are many ways of providing wireless and mobile com-munications, and each has relative advantages and disadvantages. For example, acordless telephone used at home also employs wireless technology, except that it hasa transmitter with a small amount of power and hence has a very limited coveragearea. In fact, such range makes all users use more or less the same frequency rangewithout many interferences among users. The same principle of frequency interfer-ence avoidance is used in cellular systems with a much more powerful transmittingstation, or base station (BS). All users in the cell are served by the BS. Under idealradio environments, the shape of the cell can be circular around the microwavetransmitting tower. The radius of the circle is equal to the reachable range of thetransmitted signal. It means that if the BS is located at the center of the cell, thecell area and periphery are determined by the signal strength within the region,which in turn depends on many factors, such as the contour of the terrain; heightof the transmitting antenna; presence of hills, valleys, and tall buildings; and atmo-spheric conditions. Therefore, the actual shape of the cell, indicating a true coveragearea, may be of a zigzag shape. However, for all practical purposes, the cell isapproximated by a hexagon (Figure 1.6).

The hexagon is a good approximation of a circular region. Moreover, it allowsa larger region to be divided into nonoverlapping hexagonal subregions of equalsize, with each one representing a cell area. The square is another alternative shape


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Section 1.3 Fundamentals of Cellular Systems 15

Figure 1.6Illustration of a cellwith a BS and MSs.

BS

MS

Cell

Cell area used inmost models

Ideal cell area(2–10 km radius)

Alternativeshape of a cell

MS

that can be used to represent the cell area. The triangle is another less frequentlyused coverage area. Octagons and decagons do represent shapes closer to a circulararea as compared to a hexagon. However, as explained in Chapter 5, they are notused to model a cell as it is not possible to divide a larger area into non-overlappingsubareas of the same shape. One practical example of a hex-based building block isthat of hives made by bees; hives are three-dimensional hexagons in nature.

In each cell area, multiple users or wireless subscribers are served by a singleBS. If the coverage area is to be increased, then additional BSs are placed to takecare of the added area. Moreover, only a limited amount of bandwidth is allo-cated for the wireless service. Therefore, to increase the effectiveness of the overallsystem, some kind of multiplexing technique needs to be employed. Four basic mul-tiplexing techniques that are employed are primarily known as frequency divisionmultiple access (FDMA), time division multiple access (TDMA), code division mul-tiple access (CDMA), and orthogonal frequency division multiplexing (OFDM).A new technique of space division multiple access (SDMA) is also being exploredusing specialized microwave antennas. In FDMA, the allocated frequency band isdivided into a number of subbands, called channels, and one channel is allocated bythe BS to each user (as illustrated in Figures 1.7, 1.8, and 1.9). FDMA is used in allfirst-generation cellular systems.

Figure 1.7Frequency divisionmultiple access(FDMA).

User 1

User 2

User

…

Time

Frequency

Figure 1.8FDMA bandwidthstructure. Total bandwidth

1 2 3 … nFrequency

4


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Figure 1.9Illustration of FDMAchannel allocation.

Frequency 1 User 1

Frequency 2 User 2

Frequency n User n

Base Station

… …

Mobile Stations

In TDMA, one channel is used by several users, with BS assigning time slotsfor different users, and each user is served in a round-robin method. This fixed timeslot scheme is shown in Figures 1.10, 1.11, and 1.12. Most second-generation cellularsystems are based on TDMA.

Figure 1.10Time division multipleaccess (TDMA).

Use

r 1

Use

r 2

Use

r n

…

Time

Frequency

Figure 1.11TDMA frame structure.

1 2 3 … nTime

Frame

4

Figure 1.12TDMA frameillustration by multipleusers.

Time 1

Time 2

Time n……

Base Station

User 1

User 2

User n

…

Mobile Stations

The third and most promising CDMA technique utilizes a wider frequency bandfor each user. As the transmission frequency is distributed over the allocated spec-trum, this technique is also known as spread spectrum. This scheme (Figure 1.13)is totally different from FDMA or TDMA. In this technique, one unique code isassigned by the BS to each user and distinct codes are used for different users. Thiscode is employed by a user to mix with each bit of information before it is transmit-ted. The same code (or key) is used to decode these encoded bits, and any variationof the code interprets the received information simply as noise. This is illustratedfor a 10-bit codeword in Figure 1.14. The orthogonality of the codes (described inChapter 7 in more detail) enables transmission of data from multiple subscribers


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Section 1.3 Fundamentals of Cellular Systems 17

Figure 1.13Code division multipleaccess (CDMA).

Use

r 1

Time

Frequency

Use

r 2

Use

r n

Code

...

Figure 1.14Transmitted andreceived code in aCDMA system.

Information bits

Code attransmitting end

Transmitted signal

Received signal

Code atreceiving end

Decoded signalat the receiver

simultaneously using the full frequency band assigned for a BS. Each receiver isprovided the corresponding code so that it can decode the data it is expected toreceive. The number of users being serviced simultaneously is determined by thenumber of possible orthogonal codes that could be generated. The encoding stepin the transmitter and the corresponding decoding at the receiver make the sys-tem design robust but complex. Some second-generation and most third-generationcellular systems employ CDMA. The frequency ranges used by FDMA, TDMA andCDMA in the United States are shown in Table 1.10.

One of the newest and upcoming modulation techniques, known as OFDM,has recently been introduced, allowing parallel data transmission using multiplefrequency channels. In radio communications, reflection and diffractions cause thetransmitted signal to arrive at the receiver traversing different path lengths. Sincethere are many objects such as buildings, automobiles, trees, etc., which can serveas obstacles, the radio signals are affected and scattered throughout the area. Thus,in general, multipath signals arrive at the receiver with intersymbol interference(ISI). Therefore, it is relatively harder to extract the original signal. One approachto decrease the ISI is to use multicarrier transmission techniques, which requiresconverting a high-speed data stream to slow transmission of parallel bit streams


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Table 1.10: �Frequency Range Used in Different Systems (an Example)

Systems BS Transmitting Range/MSReceiving Range

BS Receiving Range/MSTransmitting Range

RFChannel

FDMA (AMPS) 870–890 MHz 825–845 MHz 0.03 MHz

TDMA (GSM 900) 935–960 MHz 890–915 MHz 0.20 MHz

TDMA (GSM 1800) 1805–1880 MHz 1710–1785 MHz 0.20 MHz

CDMA (IS-95) 869–894 MHz 824–849 MHz 1.25 MHz

and employing several channels. Therefore, OFDM provides super quality signalswith decreased ISI. OFDM is different from FDMA systems. In FDMA, the totalbandwidth is divided into non-overlapping frequency subbands, which are usedto eliminate the interference between adjacent channels and do not contribute toenhance the bandwidth utilization. In OFDM, the chosen subcarrier frequencies arespaced apart by the inverse of the symbol time, and the spectrum of each subchan-nel may overlap to fully utilize the available bandwidth. Figure 1.15 illustrates thetwo different multicarrier techniques.

Figure 1.15Two differentmulticarriertechniques.

(a) Conventional multicarrier modulation used in FDMA

Frequency

Frequency

(b) Orthogonal multicarrier modulation used in OFDM

OFDM is a broadband multicarrier modulation method that offers supe-rior performance and benefits over traditional single-carrier modulation methods.OFDM allows only one user on the channel at any given time. For supporting mul-tiple users simultaneously, a strictly OFDM system must employ TDMA or FDMA.Of course, in order to accommodate multiple users, an extended OFDM technique,Orthogonal frequency division multiple access (OFDMA) is proposed. OFDMAallows multiple users to access the same channel at the same time. Current WLANssuch as IEEE 802.11a/g/n and IEEE 802.16d (fixed service) are based on OFDM,while WiMAX such as IEEE 802.16e (mobile service) uses OFDMA.


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Section 1.4 Cellular System Infrastructure 19

There are several variants and combinations of FDMA, TDMA, CDMA, andOFDM schemes based on specific systems. A detailed comparison is beyond thescope of this book. However, one noted exception is the frequency hopping, whichcan be defined as a combination of FDMA and TDMA in terms of the frequencyuse and time multiplexing. Basically, one user employs one channel for a pre-specified time period and then changes to another channel for transmission. Thiskind of frequency hopping is illustrated in Figure 1.16. The receiver can tune intothe transmitter provided that it also knows the frequency hopping sequence. Ofcourse, the sequence is repeated after all channels to be used in the sequence havebeen exhausted. For multiple users, different frequency hopping sequences can beused for transmitting information as long as, at any given time, one channel is usedby only one user. The frequency hopping technique was primarily introduced fordefense purposes wherein messages could still be transmitted even if strong enemysignals were present at one particular frequency band and is widely known as the“jamming” effect.

Figure 1.16Illustration offrequency hopping. Time

Frequency

f1

f2

f3

f4

f5

Frame Slot

1.4 Cellular System InfrastructureEarly wireless systems had a high-power transmitter, covering the entire servicearea. This required a huge amount of power and was not suitable for many practicalreasons. The cellular system replaced a large zone with a number of smaller hexago-nal cells with a single BS covering a fraction of the area. Evolution of such a cellularsystem is shown in Figures 1.17 and 1.18, with all wireless receivers located in a cellbeing served by a BS.

Wireless devices need to be supported for different types of services. The wire-less device could be a wireless telephone, personal digital assistant (PDA), PalmPilotTM, laptop with wireless card, or Web-enabled phone. For simplicity, it couldbe called an MS. The only underlying requirement is to maintain connectivity withthe world while moving, irrespective of the technology used to obtain ubiquitous


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Figure 1.17Early wireless system:large zone.

BS

Service area(Zone)

Figure 1.18Cellular system: smallzone.

Service areaBS BS

BSBSBS

BS BS

access. In a cellular structure, a MS needs to communicate with the BS of the cellwhere the MS is currently located (Figure 1.6), and the BS acts as a gateway to therest of the world. Therefore, to provide a link, the MS needs to be in the area ofone of the cells (and hence a BS) so that mobility of the MS can be supported. Sev-eral BSs are connected through hard-wires and are controlled by a BS controller(BSC), which in turn is connected to a mobile switching center (MSC). SeveralMSCs are interconnected to a PSTN (public switched telephone network) and theATM (asynchronous transfer mode) backbone. To provide a better perspective ofwireless communication technology, simplified system infrastructure for a cellularsystem is shown in Figure 1.19.

Figure 1.19Cellular systeminfrastructure.

Home phone

PSTN

MSC

BSC …

BS

…

…

MS

…

BS MS

BSC

BS MS

…

BS MS

BSC

BS MS

…

BS MS

BSC

BS MS

…

BS MS

MSC

A BS consists of a base transceiver system (BTS) and a BSC. Both tower andantenna are a part of the BTS, while all associated electronics are contained in theBSC. The home location register (HLR) and visitor location register (VLR) aretwo sets of pointers that support mobility and enable the use of the same telephonenumbers worldwide. HLR is located at the MSC where the MS is registered andwhere the initial home location for billing and access information is maintained. Insimple words, any incoming call, based on the called number, is directed to HLR of


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Section 1.4 Cellular System Infrastructure 21

the home MSC and then HLR redirects the call to the MSC (and the BS) where theMS is currently located. VLR basically contains information about all visiting MSsin that particular MSC area.

In any cellular (mobile) scheme, four simplex channels are needed to exchangesynchronization and data between BS and MS, and such a simplified arrangement isshown in Figure 1.20. The control links are used to exchange control messages (suchas authentication, subscriber information, call parameter negotiations) between theBS and MS, while traffic (or information) channels are used to transfer actualdata between the two. The channels from BS to MS are known as forward chan-nels (called downlinks outside the United States), and the term reverse channels(uplinks) is used for communication from MS to BS. Control information needsto be exchanged before actual data information transfer can take place. Simplifiedhandshake steps for call setup using control channels are illustrated in Figure 1.21.

Figure 1.20Four simplex channelsbetween BS and MSin a cell. Base Station

Forward

(downlin

k) contro

l channel

Mobile Station

Reverse (

uplink) c

ontrol c

hannel

Forward

(downlin

k) traff

ic channel

Reverse (

uplink) tr

affic

channel

Figure 1.21Handshake steps for acall setup between MSand BS using controlchannels.

BS MS1. Need to establish path

2. Frequency/time slot/code assigned

(FDMA/TDMA/CDMA)3. Control information acknowledgment

4. Start communication on assigned traffic channel

(a) Steps for a call setup from MS to BS

BS MS

2. Ready to establish a path

3. Use frequency/time slot/code

(FDMA/TDMA/CDMA)4. Ready for communication

5. Start communication on assigned traffic channel

(b) Steps for a call setup from BS to MS

1. Call for MS # pending


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The control channels are used for a short duration for exchanging control infor-mation between the BS and each MS needing any service. Therefore, all MSs usejust a few control channels to achieve this and hence have to compete for suchaccess in shared mode. On the other hand, traffic channels are exclusively allocatedto each MS by the BS, and a large number of channels are used for the traffic. Forthis reason, handing of control and traffic channels must be considered in differentways, and more details on control channel access are provided in Chapter 6. Vari-ous alternative techniques for traffic channel assignments are covered in Chapter 7.The total number of channels that could be allocated for both control and trafficchannels is influenced by the cell design and is discussed in Chapter 5.

There are many issues involved in wireless communication, and extensive signalprocessing is required before any signals are transmitted. The major steps are shownin Figure 1.22. Many of the signal processing operations are beyond the scope ofthis book, and we will concentrate primarily on the system aspect of wireless datacommunication.

Figure 1.22A simplified wirelesscommunicationsystem representation.

Information tobe transmitted(Voice/Data)

Coding Modulator Transmitter

Information to be received

(Voice/Data) Decoding Demodulator Receiver

Air

Antenna

Antenna

Carrier

Carrier

1.5 Satellite SystemsSatellite systems have been in use for several decades. Satellites, which are far awayfrom the surface of the earth, can cover a wider area, with several satellite beamsbeing controlled and operated by one satellite [1.5]. Large areas can be covered dueto the rotation of satellites around the earth. The information transmitted usingsatellites should be correctly received from one of the earth stations (ESs). Thus,only “line of sight (LOS)” communication is possible. There is a long history ofthe development of satellite systems from a communications point of view, andimportant events are shown in Table 1.11. Possible application areas are outlinedin Table 1.12. A more detailed discussion on satellite systems is given in Chapter 12.


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Section 1.6 Network Protocols 23

Table 1.11: �History of Satellite Systems

1945 Arthur C. Clarke publishes an essay titled “Extra Terrestrial Relays”

1957 First satellite, SPUTNIK

1960 First reflecting communication satellite, ECHO

1963 First geostationary satellite, SYNCOM

1965 First commercial geostationary satellite, “Early Bird” (INTEKSAT I): 240 duplex telephone channels or1 TV channel, 1.5 years lifetime

1976 Three MARISAT satellites for maritime communication

1982 First mobile satellite telephone system, INMARSAT-A

1988 First satellite system for mobile phones and data communication, INMARSAT-C

1993 First digital satellite telephone system

1998 Global satellite systems for small mobile phones

Table 1.12: �Application Areas of Satellite Systems

Traditionally -Weather satellites

-Radio and TV broadcast satellites

-Military satellites

-Satellites for navigation and localization (e.g., GPS)

Telecommunication -Global telephone connections

-Backbone for global networks

-Connections for communication in remote places orunderdeveloped areas

-Global mobile communication

1.6 Network ProtocolsProtocols are a basic set of rules that are followed to provide systematic signalingsteps for information exchange. Such interfaces for smooth transfer in networksare covered in Chapter 9. Most systems evolve over a period of time. We explainearly signaling systems and compare them with current systems. Separate signal-ing approaches are taken for narrowband and broadband transmissions and arebased on some simple concepts. We introduce the concepts of OSI (Open SystemsInterconnection), TCP/IP (Transmission Control Protocol/Internet Protocol), IPv4(Internet Protocol version 4), and IPv6 (Internet Protocol version 6) protocols inChapter 9.


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1.7 Ad Hoc NetworksAn ad hoc (also written ad-hoc or adhoc) network is a local network with wire-less or temporary plug-in connection, in which mobile or portable devices are partof the network only while they are in close proximity. Future military applicationsfor ad hoc networks, which include a group of soldiers in close proximity sharinginformation on their notebook computers using RF signals, along with numerouscommercial applications, are now being explored.

A mobile ad hoc network (MANET) is an autonomous system of mobilenodes, mobile hosts (MHs), or MSs (also serving as routers) connected by wire-less links, the union of which forms a network modeled in the form of an arbitrarycommunication graph. The routers are free to move at any speed in any direc-tion and organize themselves randomly. Thus, the network’s wireless topology maydynamically change in an unpredictable manner. There is no fixed infrastructure,and information is forwarded in peer-to-peer (p2p) mode using multihop routing.According to [1.6], “an ad hoc network is a collection of wireless MHs forming atemporary network without the aid of any centralized administration or standardsupport services regularly available on the wide area network to which the hostsmay normally be connected.”

MANETs are basically peer-to-peer (p2p) multihop mobile wireless networkswhere information packets are transmitted in a store-and-forward method fromsource to destination, via intermediate nodes, as shown in Figure 1.23. As the nodesmove, the resulting change in network topology must be made known to the othernodes so that prior topology information can be updated. Such a network may oper-ate in a stand-alone fashion, or with just a few selected routers communicating withan infrastructure network.

Figure 1.23Illustration of aMANET.

Source

Destination

MANET consists of mobile platforms, known as nodes (MSs), which are freeto move around arbitrarily. Very small device-based nodes may be located insideairplanes, ships, trucks, cars, and perhaps within the human body. The system mayoperate in isolation or may have gateways to a fixed network. When it is communi-cating with hosts in a wired network, it is typically envisioned to operate as a “stub”network connected to a fixed internetwork. Stub networks carry traffic originatingat and/or destined for internal nodes but do not permit exogenous traffic to “transit”through the stub network.

Each node is equipped with a wireless transmitter and a receiver with appropri-ate antenna, which may be omnidirectional, highly directional (point to point) [1.7],


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Section 1.8 Sensor Networks 25

possibly steerable, or some combination thereof. At a given point in time, depend-ing on the nodes’ positions and their transmitter and receiver coverage patterns,transmission power levels, and cochannel interference levels, a wireless connectiv-ity in the form of a random, multihop graph or ad hoc network exists between thenodes. This MANET topology may change with time as the nodes move or adjusttheir transmission and reception parameters.

1.8 Sensor NetworksMANETs are finding an increased use as a Vehicular Area Network (VANET). Thisis especially true in urban areas where presence of an internet on streets is impos-sible and needed assistance and other useful information can be shared withusers using MANETs among vehicles on the road. These issues are consid-ered in Chapter 13.

Sensor networks [1.8, 1.9, 1.10, 1.11] are the newest members of one specialclass of wireless ad hoc networks wherein a large number of tiny immobile sensorsare planted on an ad hoc basis to sense and transmit some physical characteris-tics of the environment. An associated BS collects the information gathered by thesensors on a data-centric basis. Although tiny sensors are yet to be produced ona large scale, people are exploring their usefulness in many application areas. Onesuch example—sensing the cloud of smoke—is shown in Figure 1.24, with sensornodes being deployed in the area of interest. One of the most quoted examplesis the battlefield surveillance of enemy territory, wherein a large number of sen-sors are dropped from an airplane so that activities on the ground can be detectedand communicated. Other potential commercial fields include machinery prognosis,biosensing [1.12], and environmental monitoring [1.13].

Figure 1.24An example of awireless sensornetwork.

Path of the response

Radio range

Data collection andmonitoring agency

Cloud of smoke

Predicted position forthe cloud of smoke

Sensor


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In all these applications, a large volume of data is generated by sensors, and it isdesirable to aggregate data so as to reduce the amount of data to be communicated.In addition, because of sensors, associated operating systems need to be designedcarefully, and underlying security needs to be examined in detail. These are studiedin Chapter 14.

1.9 Wireless LANs, MANs, and PANsWireless and mobile networking is finding extensive applications in different facetsof our life. Cellular telephones comprise a significant portion of household andbusiness voice services, and wireless pagers have made inroads into major com-mercial sectors. Plans are also underway to enable efficient transfer of data usingwireless devices. It is also anticipated that wireless multimedia support is forth-coming. Wireless devices are also influencing both office operations and the homeenvironment. A citywide access is now feasible using a wireless MAN (WMAN)and is being named as WiMAX. A special class of wireless local area and personalarea networks (wireless LANs [WLANs] or Wireless PANs [WPANs]) can coversmaller areas with low power transmission (especially in the ISM [industrial, sci-entific, and medical] band) and have become increasingly important for both officeand home. Noteworthy techniques include the use of the IEEE 802.11 (IEEE standsfor Institute of Electronics and Electrical Engineering) [1.14], Bluetooth network[1.15, 1.16], HomeRF [1.17], and HiperLAN [1.18, 1.19]. Characteristics of thesenetworks are given in Table 1.13, and more information is presented in Chapter 15.

Table 1.13: �Noteworthy Wireless LANs and PANs Techniques

Type of Network Range of Node Primary Function Deployed Locations

IEEE 802.11 30 meters A standard for wireless nodes Any peer-to-peer connection

HiperLAN 30 meters High-speed indoor connectivity Airports, warehouses

Ad Hoc Networks ≥500 meters Mobile, wireless, similar to wired connectivity Battlefields, disaster locations

Sensor Networks 2 meters Monitor inhospitable or inaccessible terraincheaply

Nuclear & chemical plants,ocean, etc.

HomeRF 30 meters Share resources, connect devices Homes

Ricochet 30 meters High-speed wireless Internet access (128 Kbps) Airports, office

Bluetooth Networks 10 meters Avoid wire clutter, provide low mobility Offices

1.10 Recent AdvancesResearch on wireless and mobile systems is moving at a much faster pace thananyone would expect. There have been many important developments, and it israther hard to select a subset of topics of recent interest. The introduction of theFremto cell is generating interest because of its potential to bring good cell phoneconnectivity to homes that have poor signal strength. An ultrawideband—basedscheme is attracting attention for its low-power technology. Sending short messages


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Section 1.12 References 27

by cell phone has become a de facto wireless practice for message transfer. RFIDis being increasingly used for numerous applications in daily life. Intelligent useof the spectrum employing cognitive techniques seems to offer many advantages.Multimedia traffic has various requirements that should be examined. As multiplewireless resources have become available in some areas, it is important to select theappropriate technology based on the applicable specifications and requirements.

Managing resources in connection with mobile systems creates a unique chal-lenge. Multicast in ad hoc networks has become very useful. Directional antennasbasically extend transmission range and reduce potential interference. WiMAX isallowing much wider coverage, and various efforts at standardization should beexamined. Given that many wireless devices have only limited energy available tothem, low-power design techniques are used in their construction. Graphical trans-fer of information, accomplished using XML, calls for special consideration. Finally,distributed DoS must be identified and eliminated. All these recent advances inwireless and mobile systems are discussed in Chapter 16.

1.11 Outline of the BookWe introduce probability, statistics, queuing, and traffic theories in Chapter 2 andwireless and mobile radio propagation in Chapter 3. We discuss ways of codingchannels in Chapter 4 and cellular concepts in Chapter 5. Multiple radio accesstechniques, multiple division techniques and modulation techniques, and differentchannel allocation techniques are covered in Chapters 6, 7, and 8, respectively. Con-cepts of several network protocols are introduced in Chapter 9. A summary ofexisting systems is included in Chapter 10. Satellite systems are becoming increas-ingly important because of their effective support for GPS capabilities. They arediscussed in Chapter 11. Design of mobile communication systems is included inChapter 12. Ad hoc and sensor networks have also become increasingly impor-tant and are discussed in Chapter 13 and Chapter 14, respectively. Wireless MANs,LANs, and PANs are described in Chapter 15. Many recent advances in technolo-gies have emerged, and we provide a brief overview in Chapter 16. An adequatenumber of problems are provided to reinforce the ideas covered in the text as well asto test the knowledge gained in specific subject matter. Each chapter is also followedby important relevant references.

1.12 References[1.1] R. Malladi and D. P. Agrawal, “Applications of Mobile and Wireless

Networks: Current and Future,” Communications of the ACM, Vol. 45,No. 10, pp. 144–146, October 2002.

[1.2] W. C. Y. Lee, Mobile Communications Engineering: Theory and Applica-tions, 2nd edition, McGraw-Hill, 1997.

[1.3] http://www.rfm.com/corp/new868dat/fccchart.pdf.


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[1.4] D. P. Agrawal, “Future Directions in Mobile Computing and Network-ing Systems,” Report on NSF Sponsored Workshop Held at the Universityof Cincinnati, June 13-14, 1999, Mobile Computing and CommunicationsReview, October 1999, Vol. 3, No. 4, pp. 13–18, also available at http://www.ececs.uc.edu/˜dpa/ tc-ds-article.pdf.

[1.5] R. Bajaj, S. L. Ranaweera, and D. P. Agrawal, “GPS: Location Technology,”IEEE Computer, pp. 115–117, April 2002.

[1.6] D. B. Johnson and D. A. Maltz. “The Dynamic Source Routing Pro-tocol in Ad Hoc Networks,” Mobile Computing, T. Imielinski andH. Korth, eds., Culwer, pp. 152–181, 1996. http://www.ics.uci.edu/atm/adhoc/papercollection/johnson-dsr.pdf.

[1.7] S. Jain and D. P. Agrawal, “Community Wireless Networks for SparselyPopulated Areas,” IEEE Computer, Vol. 36, No. 8, pp. 90–92, August 2003.

[1.8] D. Estrin et al., “Next Century Challenges: Scalable Coordination in SensorNetworks,” ACM Mobicom, 1999.

[1.9] J. M. Kahn et al., “Next Century Challenges: Mobile Networking for SmartDust,” ACM Mobicom, 1999.

[1.10] “The Ultra Low Power Wireless Sensors Project,” http://www-mtl.mit.edu.

[1.11] A. Manjeshwar, “Energy Efficient Routing Protocols with ComprehensiveInformation Retrieval for Wireless Sensor Networks,” M.S. Degree Thesis,University of Cincinnati, Cincinnati, May 2001.

[1.12] L. A. Roy and D. P. Agrawal, “Wearable Networks: Present and Future,”IEEE Computer, Vol. 36, No. 11, pp. 31–39, November 2003.

[1.13] D. P. Agrawal, M. Lu, T. C. Keener, M. Dong, and V. Kumar, “Exploiting theUse of Wireless Sensor Networks for Environmental Monitoring,” Journalof Environmental Management, pp. 35–41, August 2004.

[1.14] “Wireless WAN Medium Access Control (MAC) and Physical Layer (PHY)Specification: Higher Speed Physical Layer (PHY) Extension in the 2.4 GHzBand,” IEEE, 1999.

[1.15] “Baseband Specifications,” The Bluetooth Special Interest Group, http://www.bluetooth.com.

[1.16] J. Haartsen, “The Bluetooth Radio System,” IEEE Personal Communica-tions, pp. 28–36, February 2000.

[1.17] K. Negus, A. Stephens, and J. Lansford, “HomeRF: Wireless Network-ing for the Connected Home,” IEEE Personal Communications, pp. 20–27,February 2000.

[1.18] M. Johnson, “HiperLAN/2—The Broadband Radio Transmission Technol-ogy Operating in the 5 GHz Frequency Band,” http://www.hiperlan2.com/site/specific/whitepaper.exe.

[1.19] L. Taylor, “HIPERLAN Type 1—Technology Overview,” http://www.hiperlan.com/hiper_white.pdf.

[1.20] http://www.3gpp.org/releases.

[1.21] http://www.radio-electronics.com/info/cellulartelecomms/umts/3g-history.php.


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Section 1.13 Problems 29

1.13 ProblemsP1.1. Why do you need wireless services when adequate wired infrastructure exists in

most parts of the United States?

P1.2. What are the challenges for wireless networking?

P1.3. What are the unconventional applications of wireless networks?

P1.4. What are the household applications that use wireless schemes?

P1.5. How many cellular service providers are present in your area? Which of the mul-tiple access techniques is supported by each system? What are the cell size andtransmitting power level? What is the number of subscribers in your area?

P1.6. How is an ad hoc network different from a cellular network?

P1.7. List some prospective application areas for sensor networks.

P1.8. Look at your favorite Web site and find what is meant by “Web-in-the-sky.”

P1.9. What are the advantages of different wireless service providers in an area? Explainclearly.

P1.10. Can a network be wireless, but not mobile? Explain your answer carefully.

P1.11. What are the limitations if a network is mobile with no wireless support?

P1.12. Why is “anytime anywhere” access not required for all applications? Explain clearly.

P1.13. What are the pros and cons of having different-size cells for wireless networking?

P1.14. Why do you have difficulty in using your cell phone inside an elevator?

P1.15. What phenomenon do you observe when a cell phone is used while traveling a longmetallic bridge?

P1.16. How do you compare a cell phone with a satellite phone?

P1.17. In an airplane in flight, what happens if you use(a) A walkie-talkie?(b) A satellite phone?(c) A cell phone?

P1.18. What are the similarities between frequency hopping and TDMA?

P1.19. If a total of 33 MHz of bandwidth is allocated to a particular cellular telephonesystem that uses two 25 kHz simplex channels to provide full duplex voice chan-nels, compute the number of simultaneous calls that can be supported per cell if asystem uses(a) FDMA(b) TDMA with 8-way time multiplexing

Assume that additional bandwidth is reserved for the control channels.

P1.20. Many types of sensors are commercially available. Looking at different Web sites,can you prepare their cost-size-performance tradeoff?


Documents

Introduction to Wireless and Mobile Systems, 3rd ed