The Mobile Communications Handbook.pdf

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Frontmatter
Mobile Communications Contents
PARTIBasicPrinciples
1 Complex Envelope Representations for Modulated Signals Leon W. Couch, II
2 Sampling Hwei P. Hsu
3 Pulse Code Modulation Leon W. Couch, II
4 Baseband Signalling and Pulse Shaping Michael L. Honig and Melbourne Barton
5 Channel Equalization John G. Proakis
6 Line Coding Joseph L. LoCicero and Bhasker P. Patel
7 Echo Cancellation Giovanni Cherubini
8 Pseudonoise Sequences Tor Helleseth and P. Vijay Kumar
9 Optimum Receivers Geoffrey C. Orsak
10 Forward Error Correction Coding V.K. Bhargava and I.J. Fair
11 Spread Spectrum Communications Laurence B. Milstein and Marvin K. Simon
12 Diversity Arogyaswami J. Paulraj
13 Digital Communication System Performance Bernard Sklar
14 Telecommunications Standardization Spiros Dimolitsas and Michael Onufry
PARTIIWireless
15 Wireless Personal Communications: A Perspective Donald C. Cox
16 Modulation Methods Gordon L. Stuber
17 Access Methods Bernd-Peter Paris
18 Rayleigh Fading Channels Bernard Sklar
19 Space-Time Processing Arogyaswami J. Paulraj
20 Location Strategies for Personal Communications Services Ravi Jain, Yi-Bing Lin, and
Seshadri Mohan 1
21 Cell Design Principles Michel Daoud Yacoub
22 Microcellular Radio Communications Raymond Steele
23 Fixed and Dynamic Channel Assignment Bijan Jabbari
24 Radiolocation Techniques Gordon L. Stuber and James J. Caffery, Jr.
25 Power Control Roman Pichna and Qiang Wang
26 Enhancements in Second Generation Systems Marc Delprat and Vinod Kumar
27 The Pan-European Cellular System Lajos Hanzo
28 Speech and Channel Coding for North American TDMA Cellular Systems Paul
Mermelstein
29 The British Cordless Telephone Standard: CT-2 Lajos Hanzo
30 Half-Rate Standards Wai-Yip Chan, Ira Gerson, and Toshio Miki
31 Wireless Video Communications Madhukar Budagavi and Raj Talluri
32 Wireless LANs Suresh Singh
33 Wireless Data Allen H. Levesque and Kaveh Pahlavan
34 Wireless ATM: Interworking Aspects Melbourne Barton, Matthew Cheng, and Li Fung
Chang
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1999 by CRC Press LLC
35 Wireless ATM: QoS and Mobility Management Bala Rajagopalan and Daniel Reininger
36 An Overview of cdma2000, WCDMA, and EDGE Tero Ojanpera and Steven D. Gray
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1999 by CRC Press LLC
Couch, II, L.W. “Complex Envelope Representations for Modulated Signals”
Mobile Communications Handbook
Ed. Suthan S. Suthersan
Boca Raton: CRC Press LLC, 1999
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1999byCRCPressLLC
ComplexEnvelopeRepresentations
forModulatedSignals 1
LeonW.Couch,II
UniversityofFlorida
1.1 Introduction
Whatisageneralrepresentationforbandpassdigitalandanalogsignals?Howdowerepresenta
modulatedsignal ? Howdoweevaluatethespectrumandthepowerofthesesignals?Thesearesome
ofthequestionsthatareansweredinthischapter.
A baseband waveformhasaspectralmagnitudethatisnonzeroforfrequenciesinthevicinityof
theorigin(i.e.,
f D
f D f c
(where
f c
0),
andthespectralmagnitudeisnegligibleelsewhere.
f c
iscalledthe carrierfrequency. Thevalueof
maybearbitrarilyassignedformathematicalconvenienceinsomeproblems.Inothers,namely,
modulation p roblems,
isthefrequencyofanoscillatorysignalinthetransmittercircuitandisthe
assignedfrequencyofthetransmitter,suchas850kHzforanAMbroadcastingstation.
Incommunicationproblems,theinformationsourcesignalisusuallyabasebandsignal—for
example,atransistor-transistorlogic(TTL)waveformfromadigitalcircuitoranaudio(analog)
signalfromamicrophone.Thecommunicationengineerhasthejobofbuildingasystemthatwill
transfertheinformationfromthissourcesignaltothedesireddestination.AsshowninFig. 1.1 ,this
f c
1 Source: Couch,LeonW.,II.1997. DigitalandAnalogCommunicationSystems, 5thed.,PrenticeHall,UpperSaddleRiver,
NJ.
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1999byCRCPressLLC
0)andnegligibleelsewhere.A bandpass waveformhasaspectralmagnitudethat
isnonzeroforfrequenciesinsomebandconcentratedaboutafrequency
f c
23661909.001.png
usuallyrequirestheuseofabandpasssignal,
s.t/
,whichhasabandpassspectrumthatisconcentrated
at
f c
where
f c
isselectedsothat
s.t/
willpropagateacrossthecommunicationchannel(eithera
wireorawirelesschannel).
FIGURE1.1:Bandpasscommunicationsystem. Source: Couch,L.W.,II.1997. DigitalandAnalog
CommunicationSystems, 5thed.,PrenticeHall,UpperSaddleRiver,NJ,p.227.Withpermission.
Modulation istheprocessofimpartingthesourceinformationontoabandpasssignalwithacarrier
frequency
f c
s.t/
,andthebasebandsourcesignaliscalledthe modulating signal
.Examplesofexactlyhowmodulationisaccomplishedaregivenlaterinthischapter.This
definitionindicatesthatmodulationmaybevisualizedasamappingoperationthatmapsthesource
informationontothebandpasssignal
thatwillbetransmittedoverthechannel.
Asthemodulatedsignalpassesthroughthechannel,noisecorruptsit.Theresultisabandpass
signal-plus-noisewaveformthatisavailableatthereceiverinput,
s.t/
,asillustratedinFig. 1.1 .The
receiverhasthejoboftryingtorecovertheinformationthatwassentfromthesource;
r.t/
Q m
denotesthe
corruptedversionof
m
.
1.2 ComplexEnvelopeRepresentation
All bandpasswaveforms,whethertheyarisefromamodulatedsignal,interferingsignals,ornoise,
mayberepresentedinaconvenientformgivenbythefollowingtheorem.
v.t/
willbeusedtodenote
th e bandpasswaveform ca nonically.Thatis,
v.t/
canrepresentthesignalwhen
s.t/ v.t/
,the
noisewhen
n.t/ v.t/
,thefilteredsignalplusnoiseatthechanneloutputwhen
r.t/ v.t/
,orany
othertypeofbandpasswaveform 2 .
THEOREM1.1 Anyphysicalbandpasswaveformcanberepresentedby
v.t/ D
Re g.t/e j! c t
(1.1a)
Re
fg
denotestherealpartof
fg
g.t/
iscalledthecomplexenvelopeof
v.t/
,and
f c
istheassociated
carrierfrequency(hertz)where
! c D
2
f c .Furthermore,twootherequivalentrepresentationsare
2 Thesymbol
denotesanequivalenceandthesymbol D
denotesadefinition.
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1999byCRCPressLLC
bytheintroductionofamplitudeand/orphaseperturbations.Thisbandpasssignal
iscalledthe modulated signal
m.t/
.
23661909.002.png

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