chapter 3basic data communication technology

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1、Chapter3BasicDataCommunicationTechnologyBusinessImpactofModemTechnologyModemsDataCompressionCommunicationErrorsBusinessImpactofModemTechnologyFasterEfficientReliableSecureFasterNewimprovedmodelDigitaltransmissionBenefitsofDigitalTransmissionBetterdatai

2、ntegrity(detect&correcterror)Highercapacitycables(fiber-optic)Easierintegration(voice,data,video,etc.)Bettersecurityandprivacy(encryptdata)Lowercost(large-scaleintegratedcircuitry)EfficientDatacompressionBackwardcompatibilityReliableErrorpreventionError

3、detectionErrorcorrectionErrorcontrolstandardFlowcontrolLine-failurebackupSecureAccesscontrolLogical:password,callbackPhysicalEncryptionModemsStandardFunctionsInterfacesHandshakingTypesSelectionCriteriaStandardsV.byITU-T(InternationalTelecommunicationsUn

4、ion-TelephonySector)V.bis&V.terMNPstandard(Microcomnetworkingprotocols)Modemstandard:V.34(28.8Kbps)Datacompressionstandard:V.42bis&MNP5Errorcontrolstandard:V.42&MNP4ModemFunctionsConvertsignalsReversechannelforsignaloneanotherAutodial/autoanswerModemdia

5、gnosticsforaccuracycheckingV.34TechnicalInnovationMultiplebaudrates/carrierGreaterbaudrateAuxiliarymanagementchannelAsymmetrictransmit/receivespeedAdaptivelineprobingPrecodingandnonlinearencodingFallback/fallforwardTrellis-codedmodulationV.8trainingspec

6、ificationModemInterfacesBetweenmodemandlineTwo-tofour-wirecableRJ-11plugBetweenDTEandmodemRS-232interfaceSoftwareHayesATcommandsetModems-HandshakingExchangesignalsbetweenmodemsTestthecharacteristicsofcircuitandqualitydeterminebaudrate,modulationtechniqu

7、eanderrorcontrolModemTypes-ISimplex,half-duplex,full-duplextransmissionmodemsAsynchronousorsynchronoustransmissionmodemsAcousticallycoupledmodems(portable)Limiteddistancemodems/shorthaulmodems(lessthan20miles)Modemeliminators/nullmodems(cablelessthansev

8、eralthousandfeet)ModemTypes-IIFacsimilemodemsErrorcorrectionanddatacompressionModemforfiber-opticscircuitsDigital-electricaltodigital-opticalCablemodemsDTEtocabletelevisionsystemcableInternetandcabletelevisionsystemproblemsCellul