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1、Today’sAgendaFinishM-arySystemsQAMFSK,MSK,GMSKSystemComparisonsIntroductiontoCodingandInformationTheory(15.1)Ref:Sklar,DigitalCommunicationsEE422Lecture261J.DickersonCopyright2002QuadratureAmplitudeModulation(QAM)Amplitude-phaseshiftkeying(APK)riqiEE422Lecture262J.Dickerso
2、nCopyright2002QAMPerformanceAnalysisiscomplexandiscoveredinsection14.3QAM-16UpperBoundforgeneralQAMdependsonspectralefficiencyrelativetobipolarsignals,EE422Lecture263J.DickersonCopyright2002ComparingSystems:ErrorProbabilityPlaneErrorProbabilityPlane(Pbvs.Eb/N)Showstrade-of
3、fs1:Pbvs.Eb/N,BWfixed2:Pbvs.BW,Eb/Nfixed3:Eb/Nvs.BW,PbfixedChangesalong2and3requiremodulationandcodingchangesEb/N(dB)Pb123EE422Lecture264J.DickersonCopyright2002ComparingSystems:BandwidthEfficiencyPlaneBandwidthEfficiencyPlane(R/Bvs.Eb/N)Showstrade-offs1:Pbvs.Eb/N,R/Bfixed
4、2:Pbvs.R/B,Eb/Nfixed3:Eb/Nvs.R/B,PbfixedChangesalong2and3requiremodulationandcodingchangesEb/N(dB)2Rb/B123R>CR=CCapacityboundaryPower-limitedregionBW-limitedregion1½1/4EE422Lecture265J.DickersonCopyright2002EE422Lecture266J.DickersonCopyright2002QAMCommentsVerypowerefficie
5、ntforhighsignalconfigurations,butrequiresalotofpowerCangiveinconsistentresultsfordifferentbitconfigurationsEE422Lecture267J.DickersonCopyright2002ChannelCapacity:Shannon’sTheoremShannon'sTheoremgivesanupperboundtolinkcapacityinbitspersecond(bps)C:achievablechannelcapacity,
6、W:bandwidthofthelineS/Nsignal-to-noiseratio,usuallyindB10*log10(S/N)EE422Lecture268J.DickersonCopyright2002ChannelCapacityCanbeputintermsofEb/NC/WEb/N(dB)PracticalSystemsUnattainableRegionEE422Lecture269J.DickersonCopyright2002ExamplesofShannon’sTheoremModemForatypicaltele
7、phonelinewithasignal-to-noiseratioof30dBandanaudiobandwidthof3kHz,wegetamaximumdatarateof:C=3000*log2(1001),alittlelessthan30kbps.SatelliteTVChannelForasatelliteTVchannelwithasignal-tonoiseratioof20dBandavideobandwidthof10MHz,wegetamaximumdatarateof:C=10,000,000*log2(101)w
8、hichisabout66Mbps.Source:http://www.cs.ncl.ac.uk/modules/1996-97/csc210/shannon.htmlEE422
