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全双工

全双工

wxy911
2014-04-30 0人阅读 举报 0 0 暂无简介

简介:本文档为《全双工pdf》,可适用于IT/计算机领域

AnalogandDigitalSelfinterferenceCancellationinFullDuplexMIMOOFDMTransceiverswithLimitedResolutioninADConversionTaneliRiihonenandRistoWichmanAaltoUniversitySchoolofElectricalEngineering,FinlandSpecialSessionMAb“FullDuplexMIMOCommunications,”Nov,thAsilomarConferenceonSignals,SystemsandComputersIntroductionTaneliRiihonenFullDuplexMIMOOFDMTransceivers–AsilomarTheCradleofFullDuplexWirelessTaneliRiihonenFullDuplexMIMOOFDMTransceivers–TRiihonen,RWichman,andJHa¨ma¨la¨inen:“Cophasingfullduplexrelaylinkwithnonidealfeedbackinformation”wasunsuccessful,presentedlateratIEEEISWCSTRiihonen,SWerner,JCousseau,andRWichman:“DesignofcophasingallpassfiltersforfullduplexOFDMrelays”TRiihonen,SWerner,andRWichman:“SpatialloopinterferencesuppressioninfullduplexMIMOrelays”MDuarteandASabharwal:“Fullduplexwirelesscommunicationsusingofftheshelfradios:Feasibilityandfirstresults”PLioliou,MViberg,MColdrey,andFAthley:“SelfinterferencesuppressioninfullduplexMIMOrelays”TRiihonen,SWerner,andRWichman:“ResidualselfinterferenceinfullduplexMIMOrelaysafterspaceprojectionandcancellation”BPDay,DWBliss,ARMargetts,andPSchniter:“FullduplexbidirectionalMIMO:Achievableratesunderlimiteddynamicrange”EEverett,MDuarte,CDick,andASabharwal:“Empoweringfullduplexwirelesscommunicationbyexploitingdirectionaldiversity”TRiihonen,SWerner,andRWichman:“Transmitpoweroptimizationformultiantennadecodeandforwardrelayswithloopbackselfinterferencefromfullduplexoperation”Twospecialsessionsandtenpapers!Theultimatebreakthroughforthisresearchtopiclenovo铅笔lenovo铅笔lenovo铅笔FullDuplexWireless:WhatWhyWhenTaneliRiihonenFullDuplexMIMOOFDMTransceivers–•“Fullduplex”wirelesscommunication=systemswheresomenode(s)maytransmit(Tx)andreceive(Rx)simultaneouslyonasinglefrequencyband•Progressivephysicallinklayerfrequencyreuseconcept=uptodoublespectralefficiencyatsystemlevel,ifthesignificanttechnicalproblemofselfinterferenceistackled•Temporalsymmetryisneededtomakethemostoffullduplex=TxandRxshouldusethebandforthesameamountoftime−(a)symmetryoftrafficpattern,ie,requestedratesinthetwosimultaneousdirections−(a)symmetryofchannelquality,ie,achievedratesinthetwosimultaneousdirectionslenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔FullDuplexCommunicationScenariosTaneliRiihonenFullDuplexMIMOOFDMTransceivers–SourceDestinationDownlinkuserUplinkuserRelayTerminalTerminalAccesspoint)Multihoprelaylink•Symmetrictraffic•Asymmetricchannels•Directlinkmaybeuseful)Bidirectionalcommunicationlinkbetweentwoterminals•Asymmetrictraffic(maybe)•Symmetricchannels(roughly))Simultaneousdownanduplinkfortwohalfduplexusers•Asymmetrictraffic•Asymmetricchannels•Interuserinterference!lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔GenericFullDuplexMIMOTransceiversTaneliRiihonenFullDuplexMIMOOFDMTransceivers–FullduplextransceiverFullduplextransceiverFullduplextransceiverFullduplextransceiverThebasicbuildingblockformorecomplexnetworks•Thebenefitsgobeyondthephysicallayer!•WillsinglearrayfullduplextransceiversbeviablesomedayInthiswork:OFDMsignallimitedRxdynamicrange(=realisticADconversion)⊲bbitquantization⊲adaptivegaincontrolanalogvsdigitaldomainselfinterferencecancellationlenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔MainPracticalProblem:LimitedDynamicRangeTaneliRiihonenFullDuplexMIMOOFDMTransceivers–multipathselfinterferencechannelADCDACdecoderencoderOFDMdemodulatorOFDMmodulatorcentralprocessingunit•Selfinterferencemaybemuchstrongerthanthesignalofinterest•Severeriskofsaturatinganalogtodigitalconverters(ADCs)⊲Quantizationnoiseduetolimitedresolution⊲ClippingnoisewhichispronouncedwithOFDM⊲Biasinadaptivegaincontrol(AGC)balancingaboveeffectslenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔DigitalCancellation(DC)TaneliRiihonenFullDuplexMIMOOFDMTransceivers–multipathselfinterferencechanneldigitalfilterADCDACdecoderencoderOFDMdemodulatorOFDMmodulatorcentralprocessingunit•Interferencecancellationisastraightforwardtaskindigitaldomain⊲Theresponseofadigitalcancellationfiltercanbeadaptedtomatchthefrequencyselectiveselfinterferencechannel•Butnothingcanbedoneatthisstageanymoreifthesignalofinterestisalreadydrownedinclippingplusquantizationnoiselenovo铅笔lenovo铅笔lenovo铅笔ExampleonQuantizationNoise(b=)TaneliRiihonenFullDuplexMIMOOFDMTransceivers–SignalofinterestInterferencesignalSumsignal•∼bitresolutionforthesignalofinterestbeforeADCafterADCafterdigitalcancellationandscaling•∼bitresolutionforthesignalofinterestlenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔ExampleonClippingNoise(b=)TaneliRiihonenFullDuplexMIMOOFDMTransceivers–SignalofinterestInterferencesignalSumsignal•∼bitclippedresolutionforthesignalofinterestbeforeADCafterADCafterdigitalcancellationandscaling•∼bitresolutionforthesignalofinterestlenovo铅笔lenovo铅笔AnalogCancellation(AC)TaneliRiihonenFullDuplexMIMOOFDMTransceivers–multipathselfinterferencechannelanalogfilterADCDACdecoderencoderOFDMdemodulatorOFDMmodulatorcentralprocessingunit•ItwouldbedesirabletoeliminateinterferencebeforeADCs•ButitisdifficultandexpensivetoadapttheresponseofananalogfiltertomatchthetimeandfrequencyselectiveMIMOchannel⊲Typicalimplementation,simplephaseshiftandamplificationineachbranch,leavessignificantresidualinterferencelenovo铅笔lenovo铅笔lenovo铅笔CombinedAnalogDigitalCancellation(ACDC)TaneliRiihonenFullDuplexMIMOOFDMTransceivers–multipathselfinterferencechannelanalogfilterdigitalfilterADCDACdecoderencoderOFDMdemodulatorOFDMmodulatorcentralprocessingunit•Theobviouscombinationofanaloganddigitaldomainprocessing⊲IfanalogcancellationcouldsufficientlysuppresstheselfinterferencesuchthatADCsaturationisavoided,⊲thendigitalcancellationwouldbeabletoefficientlyeliminatetheremainingselfinterferencelenovo铅笔lenovo铅笔HybridAnalogDigitalCancellation(ACDC)TaneliRiihonenFullDuplexMIMOOFDMTransceivers–multipathselfinterferencechanneldigitalfilterADCDACDACdecoderencoderOFDMdemodulatorOFDMmodulatorcentralprocessingunit•Smartdesigna`laDuarteandSabharwal(Asilomar)⊲Pros:CircumventsthedrawbacksofbothACandDC⊲Cons:Extratransmitterchainpereachreceiveantenna•ChannelestimationerrorsandTxnonlinearitieslimitperformancelenovo铅笔lenovo铅笔SystemModelTaneliRiihonenFullDuplexMIMOOFDMTransceivers–TransmittedSignalsTaneliRiihonenFullDuplexMIMOOFDMTransceivers–HkCakCdkADCDACxdixaiOFDMdemodulatorOFDMmodulator•Thefullduplextransceivertriestoreceivethesignalofinterestfromadistanttransmitter•whilesimultaneouslytransmittingsignalxi∈CNt×toitsowndesignateddestination⊲Digitaltoanalogconverters(DACs)arenowideal:xai≃xdi•GaussianlikeOFDMsignalsareassumedthroughoutthisstudylenovo铅笔lenovo铅笔lenovo铅笔ReceivedSignalsTaneliRiihonenFullDuplexMIMOOFDMTransceivers–HkCakCdkADCxiyaiyˆaizaiOFDMdemodulatorOFDMmodulator•Receivedanalogcompositesignal:yai=yˆaizai∈CNr×⊲thesignalofinterestisgivenbyyˆai∈CNr×andPS=E{|{yˆai}m|}denotesitspoweratthemthantenna⊲interferencesignalisgivenbyzai=∑∞k=Hkxi−k∈CNr×andPI=E{|{zai}m|}denotesitspoweratthemthantenna•Multipathselfinterferencechannel:Hk∈CNr×Nt,k=,,lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔AnalogCancellation(AC)TaneliRiihonenFullDuplexMIMOOFDMTransceivers–HkCakCdkADCxiyaiy˜aiOFDMdemodulatorOFDMmodulator•Afteranalogcancellation:y˜ai=yˆaiz˜ai⊲thesignalofinterestyˆaiisnotaffected⊲residualinterferencesignalbecomesz˜ai=∑∞k=(HkCak)xi−k•Analogcancellationfilter:Cak∈CNr×Nt,k=,,⊲forexample{Cak}m,n={−{Hk}m,n,ifk=argmaxk′|{Hk′}m,n|,otherwiselenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔AnalogtoDigitalConversion(ADC)TaneliRiihonenFullDuplexMIMOOFDMTransceivers–HkCakCdkADCy˜aiydiOFDMdemodulatorOFDMmodulator•×NrADCs:Re({ydi}m)=Q(√gmRe({y˜ai}m))Im({ydi}m)=Q(√gmIm({y˜ai}m))⊲AGCtunesvariablegainamplifier(VGA)settinggmtokeepsignallevelwithinthefixedrangeofquantizationblockQ(·)•Thetheoryofnonlinearmemorylessdevices:ydi=Ay˜aini⊲clippingplusquantizationnoisepowerisPN=E{|{ni}m|}lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔DigitalCancellation(DC)TaneliRiihonenFullDuplexMIMOOFDMTransceivers–HkCakCdkADCxiydiy˜diOFDMdemodulatorOFDMmodulator•Afterdigitalcancellation:y˜di=Ayˆaiz˜dini⊲interferencesignalistransformedfromzdi=Az˜aitoz˜di=∑∞k=(A(HkCak)Cdk)xi−k⊲clippingplusquantizationnoisetermniisnotsuppressed!•Digitalcancellationfilter:Cdk∈CNr×Nt,k=,,⊲ideallyCdk=−A(HkCak)ifthereisnoestimationerrorlenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔CompleteSignalModelTaneliRiihonenFullDuplexMIMOOFDMTransceivers–HkCakCdkADCxiy˜diyˆaiOFDMdemodulatorOFDMmodulator•Afterputtingeverythingtogether:y˜di=Ayˆai∑∞k=(A(HkCak)Cdk)xi−kni•Powersofsignalcomponentsatthemthantenna:E{|{y˜di}m|}=αPSE{|{z˜di}m|}PNwhereα={A}m,m•SINRcanbeformulatedaftercalculatingE{|{z˜di}m|}lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔AnalyticalResultsTaneliRiihonenFullDuplexMIMOOFDMTransceivers–SignaltoInterferenceandNoiseRatio(SINR)TaneliRiihonenFullDuplexMIMOOFDMTransceivers–•Theratioofdesiredsignalpowertoresidualinterferenceandclippingplusquantizationnoisepowerbecomesγ=ρPSPI∆aρ∆d·PSPI∆awhereρ=α(PSPI∆a)PN⊲interferencesuppressionduetocancellation:∆a=E{|{zai}m|}E{|{z˜ai}m|}fromAC∆d=E{|{zdi}m|}E{|{z˜di}m|}fromDC⊲signaltointerferenceratio(SIR):PSPIwithoutcancellation∆aPSPIafterAC∆a∆dPSPIafterDC•ADconversionaffectsSINRonlythroughρ=ρ(α,PN,PSPI∆a)⊲γ→∆a∆dPSPIifdynamicrangeisnotthelimitingfactor(ρ→∞)lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔SNRwithLimitedADCResolutionTaneliRiihonenFullDuplexMIMOOFDMTransceivers–•TheratioofsignalpowertoclippingplusquantizationnoisepowerafterADC,ie,dynamicrange:ρ=α(PSPI∆a)PN=αpgPN⊲AGCtunesVGAsettinggsuchthatnormalizedinputpowertothequantizationblockisconstantlyp=g(PSPI∆a)•SINRismonotonicallyincreasingintermsofdynamicrangeρ:γ=ρPSPI∆aρ∆d·PSPI∆a≤∆a∆dPSPI⊲Thus,systemdesignshouldalwaysaimatmaximizingρirrespectiveofPS,PI,∆aand∆d(astheydonotaffectρ)⊲Signaltype,ADCpropertiesandpdefineρviaαgandPN−OFDMtransmission−Uniformquantization−ADCresolution−AGCbiaslenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔DynamicRangeforUniformQuantizationTaneliRiihonenFullDuplexMIMOOFDMTransceivers–•Input–outputrelationforuniformbbitquantization(Q=b):Q(y)=,ifQ−Q−<yq−Q−−,ifq−Q−−<y≤q−Q−−−,ify≤−QQ−•AftercalculatingαgandPNforOFDMsignal:ρ=piΦ(√p−QQ−)∑Q−q=(q−Q−−)Φ(√p(q−Q−−))−Φ(√p(q−Q−−))e−p(−QQ−)∑Q−q=(q−Q−−)e−p(q−Q−−)−e−p(q−Q−−)−−whereΦ(·)istheCDFofthestandardnormaldistribution•ρ=ρ(b,p):TheADCaffectsachieveddynamicrange(andSINR)onlythroughitsresolutionandVGAsetting(orAGCbias)lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔NumericalResultsTaneliRiihonenFullDuplexMIMOOFDMTransceivers–DynamicRangevsVGASettingTaneliRiihonenFullDuplexMIMOOFDMTransceivers–•DynamicrangecanbemaximizedbyproperAGC:ρ∗(b)=maxp′ρ(b,p′)⊲resultsinmaximalSINRwithanyPS,PI,∆aand∆d•OptimalVGAsettingyieldsp=p∗(b)=argmaxp′ρ(b,p′)•AGCbias:⊲whenp<p∗(b),quantizationdominates⊲whenp>p∗(b),clippingdominates−−−−−−−−−−pdBρdBb=ρintermsofpρ∗forb=lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔OptimalVGASettingvsADCResolutionTaneliRiihonenFullDuplexMIMOOFDMTransceivers–•ρ∗(b)increasesintermsofb⊲HigherADCresolutionallowstotradeoffquantizationnoiselevelforlowerclippingprobability•p∗(b)decreasesintermsofb⊲AGCshouldbedesignedbychoosingVGAsettingbasedonADCresolution⊲ConstantVGAsettingwouldinevitablyresultinsignificantAGCbiasandlossofdynamicrange−−−−−−−−−−pdBρdBb=,,,ρintermsofpρ∗intermsofblenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔DynamicRangevsADCResolutionTaneliRiihonenFullDuplexMIMOOFDMTransceivers–bρdB·b·b−ρ∗(numericaloptimization)ρwhenp=−dBρwhenp=−dB•Leastsquaresfitatb=,,,showsalmostlinearrelation:ρ∗(b)≃·b−dB•Theclassicruleofthumb,·bdB,istoooptimistic⊲NotintendedforOFDMsignals,eg,clippingneglectedlenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔LossofDynamicRangefromAGCBiasTaneliRiihonenFullDuplexMIMOOFDMTransceivers–−−−−−pp∗dBρ∗ρdBb=,,,•ThelossofdynamicrangeduetoAGCbiasisincreasedwhentheADCresolutionisincreased⊲AGCbiasmayeatawaythebenefitofusingbetterADC•LowVGAsettingisasafechoice:linearlossintermsofAGCbias•ToohighVGAsettingcausesADCsaturationduetoclippinglenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔SINRvsDynamicRange()TaneliRiihonenFullDuplexMIMOOFDMTransceivers–•Signaltointerferenceandnoiseratio(SINR)versusdynamicrangeρ:γ=ρPSPI∆aρ∆d·PSPI∆a•Ontheright:Examplewhen⊲SIRbeforeACPSPI=−dB•Tightboundsif∆aPSPI<:γ≤ρPSPI∆a·PSPI∆a≤ρ·PSPI∆aγ≤ρρ∆d·PSPI∆a≤∆d·PSPI∆a−−ρdBγdB∆a→∞∆a=dB,∆d→∞∆a=dB,∆d=dB∆a=dB,∆d=dB•Thus,γ≈min{ρ,∆d}·∆aPSPIisagoodapproximationinpracticalsituationswithlimiteddynamicrange(imperfectAC)lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔SINRvsDynamicRange()TaneliRiihonenFullDuplexMIMOOFDMTransceivers–•Signaltointerferenceandnoiseratio(SINR)versusdynamicrangeρ:γ=ρPSPI∆aρ∆d·PSPI∆a•Ontheright:Examplewhen⊲SIRbeforeACPSPI=−dB•Tightboundsif∆aPSPI>:γ≤ρPSPI∆aρ∆d·PSPI∆a≤ργ≤ρPSPI∆aρ∆d·PSPI∆a≤∆d·PSPI∆a−−ρdBγdB∆a→∞∆a=dB,∆d→∞∆a=dB,∆d=dB∆a=dB,∆d=dB•Thus,γ≈min{ρ,∆a∆dPSPI}isagoodapproximationwhenanalogcancellationworksalmostperfectlylenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔SINRvsDigitalCancellationTaneliRiihonenFullDuplexMIMOOFDMTransceivers–•Signaltointerferenceandnoiseratio(SINR)versusdigitalsuppression∆d:γ=ρPSPI∆aρ∆d·PSPI∆a•Ontheright:Examplewhen⊲dynamicrangeρ=dB,eg,bitADCresolutionwithsmallAGCbias(dBlossofdynamicrange)−∆ddBγdBPSPI∆a=−dB,−dB,,dB•SINRincreaseslinearlyintermsofdigitalsuppressionuntilperformanceislimitedbytheADCdynamicrangeorimperfectanalogcancellationlenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔SuppressionRequirementsTaneliRiihonenFullDuplexMIMOOFDMTransceivers–•Minimaldigitalsuppressionneededtoachieveγ≥γt:∆d≥ρPSPI∆a(ργt−)−•Ontheright:Examplewhen⊲dynamicrangeρ=dB⊲targetSINRγt=dB•DigitalcancellationisefficientiftargetSINRγt≪ρ(obviously)andSIRafterAC∆aPSPI≥γtρ•Thenrequirementforcombinedanaloganddigitalsuppressionbecomessimply∆a∆d≥γtPSPI∆adB∆ddBPSPI=dB,−dB,,−dBlenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔ConclusionTaneliRiihonenFullDuplexMIMOOFDMTransceivers–ConclusionTaneliRiihonenFullDuplexMIMOOFDMTransceivers–•Wirelessfullduplex:Aprogressivefrequencyreuseconcept!⊲GenericMIMOOFDMtransceiversconsideredherein•Challengingimplementation:strongselfinterferencecombinedwithlimiteddynamicrange,ie,practicalADconversion⊲Residualselfinterferenceduetononidealcancellation⊲QuantizationnoiseduetolimitedbbitADCresolution⊲Clippingnoiseduetohighpeaktoaveragepowerratio•Analyticalexpressionsfordesiredsignalpowertoresidualinterferenceandclippingplusquantizationnoisepowerratio⊲Optimaladaptivegaincontrolformaximaldynamicrange⊲Biasinvariablegainamplifiersetting⊲Analogvsdigitalcancellationlenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔lenovo铅笔TaneliRiihonenFullDuplexMIMOOFDMTranscei

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