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1、RayleighFadingMulti-AntennaChannelsAlexGrantInstituteforTelecommunicationsResearchUniversityofSouthAustraliaMawsonLakesBoulevardMawsonLakesSA5095Australiaalex.grant@unisa.edu.auSubmittedtoEURASIPSpecialIssueonSpace-TimeCodingMay29,2001AbstractInformationtheoreticp
2、ropertiesof°atfadingchannelswithmultipleantennasareinvestigated.Perfectchannelknowledgeatthereceiverisassumed.Expressionsformaximuminformationratesandoutageprobabilitiesarederived.Theadvan-tagesoftransmitterchannelknowledgearedeterminedandacriticalthresholdisfound
3、beyondwhichsuchchannelknowledgegainsverylittle.Asymptoticexpres-sionsfortheerrorexponentarefound.Forthecaseoftransmitdiversityclosedformexpressionsfortheerrorexponentandcuto?ratearegiven.Theuseoforthogonalmodulatingsignalsisshowntobeasymptoticallyoptimalintermsofi
4、nformationrate.Keywords:Space-TimeChannels,TransmitDiversity,InformationTheory,ErrorExponents11IntroductionWirelessaccesstodatanetworkssuchastheInternetisexpectedtobeanareaofrapidgrowthformobilecommunications.Highuserdensitieswillrequireveryhighspeedlowdelaylinksi
5、nordertosupportemergingInternetapplicationssuchasvoiceandvideo.Eveninthelowmobilityindoorenvironment,thedeleteriouse?ectsoffadingandtheneedforverylowtransmitpowercombinetocauseproblemsforradiotransmissions.Regardlessofadvancedcodingtechniquessuchasturbo-codes[1],c
6、hannelcapacityre-mainsanunmovablebarrier(withoutyetconsideringine±cienciesintroducedbyhigherlayernetworkoverheads).Withoutchangingthechannelitselfnotmuchcanbedone.Fortunately,increasingthenumberofantennasatboththebaseandmobilestationsac-complishesexactlythat,resul
7、tinginchannelswithhighercapacity.Suchsystemscantheoreticallyincreasecapacitybyuptoafactorequalingthenumberoftransmitandreceiveantennasinthearray[2{6].Spatialdiversityhasbeenproposedforsupportofveryhighratedatauserswithinthirdgenerationwide-bandCode-DivisionMultipl
8、eAccess(CDMA)systemssuchascdma2000[7].Usingmultipleantennas,thesesystemsachievegainsinlinkqualityandthereforecapacity.Classically,diversityhasbeenexploi
