通信系统绪论课件.ppt

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1、CommunicationSystems（FourthEdition）SimonHaykin1ContentsCH0:BackgroundandPreviewCH1:RandomProcessesCH2:Continuous-WaveModulationCH3:PulseModulationCH4:BasebandPulseTransmissionCH5:Signal-SpaceAnalysisCH6:PassbandDataTransmissionCH7:Spread-SpectrumModulationCH8:

2、MultiuserRadioCommunicationsCH9:FundamentalLimitsinInformationTheoryCH10:Error-ControlCoding2Ch.0BackgroundandPreviewTheCommunicationProcessPrimaryCommunicationResourcesSourcesofInformationCommunicationNetworksCommunicationChannelsModulationProcessAnalogandDig

3、italTypesofCommunicationShannon’sInformationCapacityTheoremADigitalCommunicationsProblemHistoricalNotes30.1TheCommunicationProcessFig.1.Elementsofacommunicationsystem.4TheCommunicationProcess(cont’d)ThreebasicelementstoeverycommunicationsystemTransmitter:tocon

4、vertthemessagesignalproducedbythesourceofinformationintoaformsuitablefortransmissionoverthechannelChannel:introducesdistortionandnoiseReceiver:toreconstructtheoriginalmessagesignalfromthereceivedsignal5TheCommunicationProcess(cont’d)Twobasicmodesofcommunicatio

5、nBroadcastingOne-to-manycommunicationUsuallyonedirectionalflowofsignalsE.g.radioandtelevisionPoint-to-pointcommunicationOne-to-onecommunicationUsuallybidirectionalflowofsignalsE.g.telephoneandsatellitecommunicationOnecommonfeatureofcommunicationprocess:Statist

6、icalinnature60.2PrimaryCommunicationResourcesTransmittedpower:theaveragepowerofthetransmittedsignalChannelbandwidth:thebandoffrequenciesallocatedforthetransmissionofthemessagesignalTwotypesofcommunicationchannels:Powerlimited:e.g.satellitechannelBandlimited:e.

7、g.telephonecircuitNoiseUnwantedandunavoidableThesignal-to-noiseratio(SNR)Usuallyexpressedindecibels(dBs),SNRdB=10log10(SNR)70.3SourcesofInformationFourimportantsourcesofinformation:Speech:Usingthe300–3100HzbandMusic:upto15kHzPicturesCanbedynamic(e.g.television

8、)orstatic(e.g.facsimile)ThescanningprocessWidebandsignalsComputerdataTheAmericanStandardCodeforInformationInterchange(ASCII)WidebandsignalsBurstinessCompression(losslessandlossy)80