资源描述：
《外文翻译---蜂窝无线通信系统的研究》由会员上传分享，免费在线阅读，更多相关内容在学术论文-天天文库。
1、附录Ⅰ外文翻译(原文)RESEARCHOFCELLULARWIRELESSCOMMUNATIONSYSTEMAbstract1897,Marconidemonstratesthefirstpracticalapplicationofthemobileradiocommunication,openingupaprecedentofmobilecommunication,wirelesscommunicationinthemodernsensewasborn.Fromthatdayonwards,thewirelessco
2、mmunicationtechnologyiscommittedtoachievingbettercommunicationquality,lowerpowerconsumption,smallersizeandcheaperprice.Inthenext60years,anumberoflandmarktechnologicalbreakthroughstopromotethefurtherdevelopmentofmobilecommunications.Knowtheearly1980s,withtheestab
3、lishmentofacellularmobilecommunicationsystems,mobilecommunicationsystemhasnowenteredaperiodofprosperityanddevelopment.Thecellularsystemhasexperiencedrapidexponentialgrowth,clearlyshowingthatwirelesscommunicationhasabrightfuture.Cellularcommunicationsystemsallowa
4、largenumberofmobileuserstoseamlesslyandsimultaneouslycommunicatetowirelessmodemsatfixedbasestationsusingalimitedamountofradiofrequency(RF)spectrum.TheRFtransmissionsreceivedatthebasestationsfromeachmobilearetranslatedtobaseband,ortoawidebandmicrowavelink,andrela
5、yedtomobileswitchingcenters(MSC),whichconnectthemobiletransmissionswiththePublicSwitchedTelephoneNetwork(PSTN).Similarly,communicationsfromthePSTNaresenttothebasestation,wheretheyaretransmittedtothemobile.Cellularsystemsemployeitherfrequencydivisionmultipleacces
6、s(FDMA),timedivisionmultipleaccess(TDMA),codedivisionmultipleaccess(CDMA),orspatialdivisionmultipleaccess(SDMA).1IntroductionAwidevarietyofwirelesscommunicationsystemshavebeendevelopedtoprovideaccesstothecommunicationsinfrastructureformobileorfixedusersinamyriad
7、ofoperatingenvironments.CellularmobilecommunicationsystembytheexchangeofNetworkSubsystem(NSS),thewirelessbasestationsubsystem(BSS)andmobilestation(MS)hasthreemajorcomponents.Switchednetworksubsystem(NSS)completionoftheexchangefunctionalandcustomerdata,andmobilit
8、ymanagement,securitymanagementdatabasefunctionalityMostoftoday’swirelesssystemsarebasedonthecellularradioconcept.Cellularcommunicationsystemsallowalargenumberofmobile
