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页数:51页
时间:2020-10-03
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1、ABriefHistoryofCommunicationDavidTseCommunicationSystemsWhatgoesintotheengineeringofthesesystems?KeyIngredientsSoftwareHardwareCommunicationarchitecture,withcodingandsignalprocessingalgorithmsCommunicationchannelscanbeverynasty!Channeldistortion,noise,interference……Howdowecommunicatere
2、liablyoversuchchannels?CommunicationhasalonghistorySmokesignals,telegraph,telephone…1895:inventionoftheradiobyMarconi1901:trans-atlanticcommunicationStateofaffairs:Early20thcenturyMostcommunicationsystemsareanalog.Engineeringdesignsaread-hoc,tailoredforeachspecificapplication.BigQues
3、tionsIsthereageneralmethodologyfordesigningcommunicationsystems?Istherealimittohowfastonecancommunicate?HarryNyquist(1928)AnalogsignalsofbandwidthWcanberepresentedby2Wsamples/sChannelsofbandwidthWsupporttransmissionof2Wsymbols/sFromCTtoDTNyquistconvertedthecontinuous-timeproblemtoadisc
4、rete-timeproblem.Buthashereallysolvedthecommunicationproblem?No.Youcancommunicateinfinitenumberofbitsinonecontinuous-valuedsymbol!ClaudeShannon(1948)Hisinformationtheoryaddressedallthebigquestionsinasinglestroke.RandomnessShannonthoughtofbothinformationsourcesandchannelsasrandomandused
5、probabilitymodelsforthem.encodersourcechanneldecoderEverythingisbitsShannonshowedtheuniversalityofadigitalinterfacebetweenthesourceandthechannel.sourceSourceEncoderChannelencoderchannelBitstreamInformationislikefluidEverysourcehasanentropyrateHbitspersecond.EverychannelhasacapacityCbit
6、spersecondReliablecommunicationispossibleifandonlyifH7、heday.Hedidn’treallytellpeopleexactlyhowtodesignoptimalcommunicationsystems.50yearslater….Ourcommunicationinfrastructureisgoingfullydigital.MostmoderncommunicationsystemsaredesignedaccordingtotheprincipleslaiddownbyShannon.InternetSDLessonsforUsThinkdifferentThinkbigThinksimpleMobili
7、heday.Hedidn’treallytellpeopleexactlyhowtodesignoptimalcommunicationsystems.50yearslater….Ourcommunicationinfrastructureisgoingfullydigital.MostmoderncommunicationsystemsaredesignedaccordingtotheprincipleslaiddownbyShannon.InternetSDLessonsforUsThinkdifferentThinkbigThinksimpleMobili
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