通信技术专业外文翻译--关于cdma2000的发射分集方案-豆柴文库

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英文原文：
TransmitDiversitySchemesforcdma-2000
DineshRajan，StevenD.Gray

Abstract-Transmitdiversityoffersanadvantageintheforwardlinkofthecdma2000systembybalancingthespectrumefficiencyintheuplinkanddownlink.Threeschemesforperformingtransmitdiversityareexaminedinthispaper–orthogonaltransmitdiversity,timeswitchedtransmitdiversity,andselectiontransmitdiversityforvehicular,indoor-outdoorpedestrianandindoorofficeenvironments.Alsoconsideredaresomeissuesrelatedtoimplementationcomplexityinthemobilehandset.Undercertainchannelconditions,weshowthatlowratefeedbackofantennaselectionandnoforwardlinkpowercontroloffersperformanceadvantagesovertransmitdiversityschemeswithforwardlinkpowercontrolandnoantennaselection.
I.INTRODUCTION
ThirdGenerationcellularsystemsareexpectedtoprovideincreasedthroughput,bothforvoiceandpacketdatatransmission.Toachievethisgoal,wemustovercomethelimitationsinherentinawirelesschannel.Oneofthebiggesthurdlesofmobilecellularcommunicationsisthatofmultipathfading,implyingthat,multiplecopiesofthetransmittedsignalarereceivedwithvaryingamountsofattenuationanddelay.
Diversitytechniquesareusuallyemployedateitherthetransmitterand/orreceivertoovercometheproblemoffading.Therearemanytechniquesforprovidingdiversityincludingtemporal,frequencyandspatial.
Inacdma2000systemthebottleneckincapacityoccursintheforwardlink.ThisisduetothefactthatthereverselinkemploystwoantennasattheBaseStation(BS)andmaximal-ratio-combiningofthereceivedsignals.Asaresult,transmitdiversityschemesaidinbalancingtheforwardandreverselinks.
ThreeschemesfortransmitdiversityareOrthogonalTransmitDiversity(OTD)[1],Time-SwitchedTransmitDiversity(TSTD)[4],andSelectionTransmitDiversity(STD)[3].Itisunclearastowhichoftheseschemesachievesthebesttradeofperformanceimprovementvsimplementationcomplexity.Inthispaperwepresenttheresultsofsimulationsoftheaboveschemesunderthecontextofacdma20003xphysicallayer.Theremainderofthepaperisorganizedasfollows.Section2givesadescriptionofthetransmitterandreceiverforthethreediversityschemes.T