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GSMEDGE上行链路中信道估计和均衡的设计实现.docx

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GSMEDGE上行链路中信道估计和均衡的设计实现 Introduction TheuplinkofaGSM/EDGEnetworkisthetransmissionpathfromthemobiledevicetothebasestation.Thispathischaracterizedbyseveralchallenges,suchasinterference,fading,andnoise,whichcandegradethequalityofthetransmittedsignal. Toovercomethesechallengesandensurereliablecommunication,theuplinkchannel'sestimationandequalizationareofcrucialimportance.ThispaperdiscussesthedesignandimplementationofchannelestimationandequalizationtechniquesfortheuplinkchannelinGSM/EDGEnetworks. ChannelEstimation Channelestimationistheprocessofestimatingthecommunicationchannel'sparameters,includingthechannel'simpulseresponse,carrierfrequencyoffset,andphaseoffset.Channelestimationisperformedatthereceiverendofthecommunicationsystembyexploitingknowntrainingsequencestransmittedbythetransmitter. InGSM/EDGEnetworks,channelestimationisperformedusingtwotypesoftrainingsequences:thetrainingsequencefortheinitialchannelestimationandthetrainingsequenceforthecontinuouschannelestimation.Theinitialchannelestimationisperformedoncepercall,whilethecontinuouschannelestimationisperformedperiodicallyduringthecalltotrackanychangeinthechannel'sparameters. Theinitialchannelestimationisperformedusingatrainingsequencetransmittedbythemobiledevice.Thetrainingsequenceisapseudo-randomsequencewithaknownstructure.Thereceivercorrelatesthereceivedsignalwithalocallygeneratedcopyofthetrainingsequencetoestimatethechannel'sparameters. Thecontinuouschannelestimationisperformedusingthemidamblesequence,whichisashortsequenceinsertedbetweenthetrafficburstsintheuplinktransmission.Themidamblesequencehasaknownstructure,andthereceiverusesittoestimateandtrackthechannel'sparameters. Equalization Equalizationistheprocessofcompensatingforthedistortionintroducedbythetransmissionchannel.IntheuplinkofaGSM/EDGEnetwork,equalizationisperformedatthereceiverendtomitigatetheeffectsofmultipathfadingandinterference. TwoequalizationtechniquesarecommonlyusedinGSM/EDGEnetworks:zero-forcingequalizationandminimummeansquareerror(MMSE)eq