TD-SCDMA系统中III型HARQ性能仿真分析-豆柴文库

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TD-SCDMA系统中III型HARQ性能仿真分析
I.Introduction
HighlyEfficientAdaptiveRetransmissionRequest(HARQ)isanessentialfeatureinmodernwirelesscommunicationsystemsthathelpstoimprovethecommunicationqualityandreliability.Inthispaper,wepresentasimulationanalysisoftheperformanceoftheIII-typeHARQinTimeDivision-SynchronousCodeDivisionMultipleAccess(TD-SCDMA)system.
II.III-typeHARQinTD-SCDMA
TheIII-typeHARQschemeisbasedontheincrementalredundancytechnique.Inthisscheme,thereceiversendsanegativeacknowledge(NACK)messagetothetransmitterindicatingthatthereceiveddatawasnotdecodedcorrectly.UponreceivingtheNACKmessage,thetransmitterretransmitsonlythemissingbitsorsymbols,thusminimizingtheamountofredundantdatatransmitted.Thereceivercombinestheoriginalandretransmitteddatatorecovertheoriginalmessage.Ifthereceiverstillcannotdecodethemessagecorrectlyafterapredefinednumberofretransmissions,thecommunicationisconsideredtohavefailed.
InTD-SCDMA,theIII-typeHARQschemeisusedforbothuplinkanddownlinktransmissions.TheuplinkHARQprocessistriggeredbytheNodeBuponthereceptionofadatapacketfromtheUserEquipment(UE).Ifthereceptionissuccessful,theUEsendsanacknowledgment(ACK)messagetotheNodeB.Ifthereceptionisunsuccessful,theUEsendsaNACKmessagetotheNodeB,triggeringtheretransmissionofthemissingdata.Inthedownlinkdirection,theUEsendstheACK/NACKmessagetotheNodeBbasedonthesuccessfulorunsuccessfulreceptionofthedatapacket.
III.SimulationModel
ToevaluatetheperformanceoftheIII-typeHARQinTD-SCDMA,weimplementedasimulationmodelusingMATLAB.Thesimulationmodelconsistsofasingle-cellTD-SCDMAnetworkwithoneNodeBandmultipleUEs.TheNodeBisequippedwitheightantennas,andeachUEisequippedwithtwoantennas.
Thesimulationparametersareasfollows:
-Carrierfrequency:2GHz
-Bandwidth:5MHz
-Frameduration:10ms
-Subframeduration:1ms
-Modulationscheme:QPSK
-Channelmodel:Rayleighfading
Wesimulatedthedownlinktransmissionintheabsenceofinterferencefromothercells.Wevariedthesignal-to-noiseratio(SNR)from0dBto30dBinstepsof5dB.ForeachSNRvalue,wesimulatedthetransmissionof10