移动通信课件4

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1、Chapter4:WirelessTelecommunicationSystems•GSM–Mobileservices/Newdataservices–Systemarchitecture–Radiointerface–Protocols–Localizationandcalling–Handover–Security•UMTS/IMT-20001GSM:MobileServicesGSMoffers•voiceanddataservicesandtheinterworkingwithexistingnetworksThreeca

2、tegoriesofservices•BearerServices•TeleServices•SupplementaryServicesbearerservicesMStransitsource/TEMTGSM-PLMNnetworkdestinationTER,SU(PSTN,ISDN)network(U,S,R)mteleservices2BearerServices•Specificationofservicesuptotheterminalinterface(OSIlayers1-3)•Differentdataratesf

3、orvoiceanddata(originalstandard)•dataservice(circuitswitched)–synchronous:2.4,4.8or9.6kbit/s–asynchronous:300-1200bit/s•dataservice(packetswitched)–synchronous:2.4,4.8or9.6kbit/s–asynchronous:300-9600bit/s3TeleServices•GSMmainlyfocusesonvoice-orientedteleservices—encry

4、ptedvoicetransmission,messageservicesandbasicdatacommunicationwithterminals•Offeredservices•telephony——primarygoalofGSMwastoprovidehigh-qualitydigitalvoicetransmission,offeringthetypicalbandwidthof3.1kHzofanalogphonesystems•Emergencynumber——commonnumberthroughoutEurope

5、(112);mandatoryforallserviceproviders;freeofcharge;connectionwiththehighestpriority(pre-emptingotherconnectionspossible)4TeleServicesAdditionalservices•Non-Voice-Teleservices–ShortMessageService(SMS)alphanumericdatatransmissionto/fromthemobileterminalusingthesignalling

6、channel,thusallowingsimultaneoususeofbasicservicesandSMS–EnhancedMessageService–MultimediaMessageService–group3fax5Supplementaryservices•Servicesinadditiontothebasicservices,cannotbeofferedstand-alone•SimilartoISDNservicesbesideslowerbandwidthduetotheradiolink•Maydiffe

7、rbetweendifferentserviceproviders,countriesandprotocolversions•Importantservices–Useridentification–Callredirectionorforwardingofongoingcalls–Closedusergroupsandmultipartycommunication6ArchitectureoftheGSMsystemcomprisingmanyentities,interfaces,andacronyms(缩略语)•subsyst

8、ems–RSS(radiosubsystem):coversallradioaspects–NSS(networkandswitchingsubsystem):callforwarding,handover,switching–OSS