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1、AdaptiveTimeDelayandFrequencyEstimationforDigitalSignalSynchronizationinCDMASystemsSaulR.DooleyandAsokeK.NandiDepartmentofElectronicandElectricalEngineering,UniversityofStrathclyde,Glasgow,G11XW,UK.e-mail:a.nandi@eee.strath.ac.ukAbstracttiontosynchro
2、nizationmethodswhicharecomputationallyinexpensiveandthuscanbeimplementedinrealtime.TheproblemofsynchronizationofdigitalnarrowbandSynchronizationofXkandYkiscomprisedoftwoparts:signalsispresented.Fornon-stationarycommunicationestimationofandcompensatio
3、nfortheTDOAT(delaysyn-channels,accurateadaptivetimedelayandcarrierfre-chronization)andFDOAv(frequencysynchronization).Aquencyofsetestimationisrequired.Modificationstoawell-knowntechniquefortheestimationofdelaysisthewell-knowntimedelayestimationmethod
4、(theexplicittimeexplicittimedelayestimator(ETDE)algorithm[2],whichdelayestimator),includinganovelfrequencyadjustmentel-usestheLMSalgorithm[3].However,ifYisnonzero,theement,areproposedwhichareshownthroughsimulationsignalsarenotfrequencysynchronizedand
5、delaysynchro-toenablesignificantlylowestimationbius,evenattheverynizationbythismethodisimpossible.Hence,compensa-shortfilterlengthsdesirableinthisapplication.tionfortheFDOAmustoccurbeforedelaysynchronizationispossible.Forfrequencysynchronization,onem
6、ustmod-ulateYkby-v,andtodothis,onemustestimatevfirst.Short-timeFourierTransformandothertime-fi-equencydis-1.Introductiontributiontechniquescouldbeused(seee.g.[4])butareei-therhigh-resolutionandcomputationallyveryexpensiveorRecently,therehasbeengrowin
7、ginterestinpostdigitallowresolutionandrequiresubsequentinterpolation,possi-conversiondemodulation(tobaseband)inCDMAcarrierblyyieldingabiasedsolution.Itshouldbenotedanybiassystems,inordertoexploitthepowerofefficientdigitalintheFDOAestimateimpliesthesi
8、gnalsarenotfrequencysignalprocessingalgorithmstomovefurthertowardserror-synchronizedandreliableTDOAestimationisstillimpos-freecommunication.Signalsynchronizationiscriticaltosible.coherentdemodulation,andaccuratephaseandfrequencyInthiswork,thecarrierf
