基于Kalman滤波的WCDMA上行链路衰落信道跟踪-豆柴文库

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基于Kalman滤波的WCDMA上行链路衰落信道跟踪
Introduction
Inwirelesscommunication,signalpropagationisaffectedbyvariousfadingconditions.Fadingconditionsrefertothelossofsignalpowerandsignaldistortionthatoccurwhenaradiosignalpropagatesthroughthecommunicationchannel.Thefadingconditionisamajorreasonforsignaldistortioninwirelesscommunication,whicheventuallyleadstoadecreaseinthequalityofservicethattheuserexperiences.Fadingsignalscanbeclassifiedintotwotypes,namelymultipathfadingandshadowfading.Inthispaper,wefocusonthemultipathfadingcondition,whichcausesfluctuationsinsignalstrengthovertimeanddelayspread.
KalmanFilter
Kalmanfilterisawidelyusedtoolforestimationandpredictioninuncertainandtime-varyingsystems.Thisfilterisamathematicalmodelthatusesaseriesofmeasurementsobservedovertimetoestimateunknownvariables.TheprimaryobjectiveoftheKalmanfilteristoremovenoisefromthemeasurementdataandprovideamoreaccurateestimateofthesystemstate.Itisarecursivefilterthatupdatestheestimateeachtimeanewmeasurementisreceived.
WCDMAUplinkChannel
TheWCDMA(WidebandCodeDivisionMultipleAccess)isacommunicationstandardusedin3Gwirelesscommunicationsystems.TheuplinkchannelinWCDMAissubjecttomultipathfading,whichaffectsthequalityofthereceivedsignalatthebasestation.Theuplinkchannelhasatime-varyingnature,whichmeansthatthetransmittedsignalexperiencesdifferentdelaysandphasesduetothereflectionsfromnearbyobstacles.Toovercometheeffectsofmultipathfading,channelestimationisnecessarytoadaptthemodulationandcodingschemesaccordingtothechannelstate.TheestimationoftheuplinkchannelisakeyproblemthatneedstobeaddressedinWCDMAsystems.
KalmanFilter-basedChannelEstimation
TheKalmanfilterhasbeenwidelyusedforchannelestimationinwirelesscommunicationsystems.TheKalmanfilter-basedchannelestimationmethodisbasedontheassumptionthatthechannelisalinearandtime-varyingsystem.Thefilterconsidersthecurrentstateofthechannelandthepreviousstatetoestimatethecurrentstateofthechannel.Theprocessofchannelestimationinvolvestwomainsteps,namelypredictionandupdate.
Prediction
The