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1、1172IEEETRANSACTIONSONCOMMUNICATIONS,VOL.50,NO.7,JULY2002BlindMultiuserDetectionviaInterferenceIdentificationGiuseppeRicci,Member,IEEE,MaheshK.Varanasi,SeniorMember,IEEE,andAntonioDeMaioAbstract—Previousresultsonblindmultiuserdetectionapplyinreceiverscanbeachievedbyadoptingstrictpo
2、wercontrolandsituationswherethesignalparametersoftheusersofinterestarelargevaluesofpower,andtheratioofspreadingfactortotheknown,andthoseoftheinterferersareunknown.Inthispaper,numberofusers(cf.[5]).weconsiderthenewparadigmofan-usersystem,inwhichAmuchbetterwaytoovercomethenear–farpro
3、blemistousersareactive,andtheproblemistodetectusersofinterestoutofthoseactiveuserswhenthesignalparameters(codes,ampli-resorttomultiuserreceivers[6],[7],namely,todetectionstrate-tudes)oftheusersofinterestareknown,asarethecodesofallgieswhichaccountforthepresenceofotherinterferersinth
4、eusers.Whatisnotknownatthereceiver,however,is,thechannel(without[7]orwithpowercontrol[8]).Inaseminalnumberofactiveinterferers,andtheidentityoftheseinterferers.Apaper[9],itwasshownthatitisthethermalnoiseandnotsolutiontosuchaproblemcouldbetoignoretheknowledgeofthethemultiaccessinterf
5、erence(MAI)whichdeterminestheulti-remainingcodes,andapplyknownblindmultiuserdetec-torsbasedonstochasticapproximationorsubspacetrackingtech-mateperformancelevelsattainableinaCDMAcommunicationniques.However,itisshownherethattheadditionalknowledgesystem.Althoughtheoptimummultiuserrece
6、iverentailsanex-ofthosecodescanbeusedtoobtainaninterference-identification-ponentialcomplexityinthenumberofactiveusers,itispos-basedblindmultiuserreceiverthathasmuchfasterconvergencesibletoresorttosuboptimummultiuserreceiversoflowercom-properties.Weillustratetheunderlyingprinciplei
7、nthecontextplexity,asthedecorrelatingandtheminimummeansquareerrorofblindgroupdetectioninsynchronousdirect-sequence/code-di-visionmultiple-access(DS/CDMA)systemsoperatinginchannels(MMSE)detectorswhichachieveoptimumresistanceagainstthatexhibitfrequency-selectivefading.thenear–farprob
8、lem,albeitatthepriceofanin