現(xiàn)代通信原理課件ChaerOne

現(xiàn)代通信原理課件ChapterOne1IntroductionChapterOneWhy?InformationAgeInformationSuperhighway2Applicationmilitaryapplication;commonapplication;

ChapterOne3Whatisacommunicationsystem?Communicationsystemsisusedtotransmitinformation.1.1Introduction4Keyconceptionsorwords(1)Information;(2)Message;(3)Signal;(4)Waveforms1.1Introduction51JimesC.Maxwell（1864）2HeinrichHertz（1887）ClaudeE.Shannon(1948)4.Winner1.1Introduction6PerspectiveofcommunicationWireoptic-fiberandnetworkswireless1G->2G->3G->B3GWLAN;MIMOandMIMO-OFDM,UWB,optic–wirelesscommunication1.1Introduction7Whatmustbeconsideredwhenyoudesignacommunicationsystem?1.Selectionoftheinformation-bearingwaveform2.Bandwidthandpowerofthewaveform3.Effectofsystemnoiseonthereceivedinformation4.Costofthesystem1.1Introduction81.2DigitalandAnalogsourceandsystemThegenerationofcommunicationsystem9signalprocessorInanalogsystemitmaybeananaloglow-passfilter;Inhybridone,itmaybeanalog-to-digitalconverter(ADC)2)Functionofsignal-processingblockinhybridoneSourcecodingChannelcoding(addingparityandothers)3)FunctionofCarrierCircuitsmodulationFunctionoftransmitter101）

Classification:wireandwirelessWirechannelincludingtwisted-pairtelephoneline/Coaxialcables,waveguidesandfiber-opticcables

Wirelesschannelhavingair,vacuumandseawater2)Note:Thegeneralprinciplesofdigitalandanalogmodulationapplytoalltypesofchannels,althoughchannelcharacteristicsmayimposeconstraintsthatfavoraparticulartypeofsignalingChannel11Thereceivertakesthecorruptedsignalatthechanneloutputandconvertsittoabasebandsignalthatcanbehandledbythereceiverbasebandprocessor,andthenthereceiverbasebandprocessorestimatethesourceinformationandoutputtheestimationresultReceiver12Thegoalistodesigncommunicationsystemthattransmitinformationtothereceiverwithaslittledeteriorationaspossiblewhilesatisfyingdesignconstrainssuchasallowabletransmittedenergy,allowablesignalbandwidthandcost.Indigitalsystemmeasureofdeteriorationistakentobebiterrorrate(BER),whileinanalogsystemtheperformancemeasureisusuallytakentobethesignal-to-noiseratio(SNR)atthereceiveroutput.Summary131.2DigitalandAnalogsourceandsystemModelofanalogcommunicationsystem141.2DigitalandAnalogsourceandsystem

(modelofdigitalcommunicationsystem)151）Relativelyinexpensivedigitalcircuitsmaybeused2）Privacyispreservedbyusingdataencryption3）Greaterdynamicrangeispossible4）Datafromdifferentsourcesmybetransmittedoveracommondigitaltransmissionsystem2theadvantageofdigitalsystem1.2DigitalandAnalogsourceandsystem165）Noisedoesnotaccumulateinlong-distancesystemsbyrepeater6）Errorindetecteddatamaybesmall,eveninlargeamountofnoiseonthereceivedsignal7）Errormayoftenbecorrectedbytheuseofcoding2theadvantageofdigitalsystem1.2DigitalandAnalogsourceandsystem171)Morebandwidthisrequiredgenerally2)Sychronizationisrequired3.DisadvantagesofDigitalcommunication1.2DigitalandAnalogsourceandsystem181.2DigitalandAnalogsourceandsystem

(classificationofcommunicationsystem)accordingtophysicalpropertiesofinformation:Telephone/data/imageandsoon

accordingtofrequency:basebandtransmitting/bandpasstransmittingsystem

accordingtotransmittingmedium:wire/wireless

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