会议presentation-PPT

PNCodeAcquisitionMethodwithEnhancedSensitivityPerformance22AbstractNon-coherentintegration（非相干积分）canenhancetheperformanceofacquisitionsensitivityinspreadspectrumcommunicationsystemwithhighbitrate,butitcannotmeettherequirementsinlowSNRenvironmentduetothelargelossofSNR.Inthispaper,anovelmethodisproposedforPNcode（伪码）acquisition.Sincethecoherentintegrationtimeisextendedbypre-judgingthedatasign,thelossofnon-coherentintegrationisdecreased.Bypre-processingthecoherentintegrationresultsbeforenon-coherentintegration,thismethodcangetanachievablesensitivitygain,i.e.about2dBcomparedwithdirectnon-coherentintegrationmethods.Thus,theproposedmethodoffersaneffectivewaytoimprovetheacquisitionsensitivityperformance.233Contents2Methods4Conclusions1Introduction3Results1.1Researchscope1.2Presentmethods1.3Myresearch2.1Signalmodel2.2Acquiremethod2.3Performanceanalysis3441Introduction•SynchronizationofPNcode1.Coretechnologyofspreadspectrumcommunication2.Requirethereceiverstogeneratealocalsequencewhichisidenticalwiththereceivedsignals3.Twosteps:acquisitionandtracking.Onlyacquisitiontechnologyisconsidered1.1ResearchScope4551Introduction5ExtendcoherentintegrationtimewithassistancesystemHighrateofdatatransmissionisnoteasilyimplementedPresentmethodsNon-coherentintegrationLargelossofSNR.Differentialnon-coherentintegrationOnlybeusedinlowratecondition1.2Presentmethods661IntroductionNovelenhancedmethod•Expandcoherentintegrationtimebypre-judgingsignalsign•Enhancedacquisitionsensitivityperformancecomparedwithdirectcoherentintegration.61.3MyResearch772Methods•Spreadspectrumcommunicationsystemwithhighbitrate,asignalmodelwithonebitperiodcontainingonePNcodecycle•Afterpassingthroughaband-passfilterwithbandwidth()2cos2()iStPdtCtftnt()2cos()cos2...2sin()sin2iiqiStPdtCtntftPdtCtntft72CT2.1Signalmodel82MethodsCoherentIntegrationCoherentIntegrationCombineMcoherentintegrationresultsinsequenceCombineMcoherentintegrationresultsinsequence()iYi()qYi2()2()MaxValuble22IQZ2Q2INon-coherentIntegrationComparewiththresholdkZ'kZ2.2AcquiremethodFig.3.Acquisitionscheme12M992Methods2.3Performanceanalysis•InhighSNRChosencombination:correspondstotherealsituationPerformance:equaltocoherentintegration•InlowSNRChosencombination:notalwaystheresultssupposedtobePerformance:weakenergyofsignalanddeterioratedperformance910102Methods•Missettobe2forsimplicity.Theerrorprobabilitycanbecomputedas:22222211PIQIQ2222121212122cos()2sin()22IIQQIIQQPPPnnnnLnnLnn2121212124422cos()()22sin()()20IIQQIIQQPnnnnLPnnLPnnLP1011112MethodsFig.4.therelationshipbetweenprobabilityoferrorandCNRprobility11•WhenCNRisequalto40dB,theacquisitionperformancewillbedeteriorated•Addacomparinglogic12122Methods•Provingtheassumptionthatthevaluedistributingofisdifferentbetweenthetrueandfalsechoosing.ProbilityProbilitytrueflaseFig.5.thedistributingofwhentruechoosinganderrorchoosing,0/PNequalsto40dB'kZ'kZ13132Methods13•Thetruechoosing:non-centralchi-squareddistribution•Thefalsechoosing:centralchi-squareddistribution•Thethreshold:adaptiveandvaried'kZTh'kZThadoptthenon-coherentintegrationmethodchosecombiningmodeintegration14143Results14•Acquisitiontimes:1000•NoresidualDoppler（残余多普勒）•Noresidualcodephaseerrors•Constantfalsedetectingprobability:0.01•Totalintegrationtime:12codecycles•DifferentcombinationsofMandN,12MNSimulationconditions15153Results40414243444546474849500.40.50.60.70.80.91P/N0dB检测概率非相干累加M=2,N=6M=3,N=4M=4,N=3M=6,N=2ProbilityNCFig.6.theperformancecomparingbetweenthenewmethodandnon-coherentintegrationmethod16163Results•2dBbetterthandirectnon-coherentintegrationwhenSNRislow.•ChoseM=2,N=6forthesimplicityofimplementing17174Conclusions•Thedirectnon-coherentintegrationhasadisadvantageofSNRloss.SothenewmethodispresentedtoimprovetheperformanceofPNcodeacquisition.•Thecoherentintegrationresultispre-processedbeforeimplementingthenon-coherentintegration.•Thismethodcangetasensitivityperformanceimprovementofabout2dB.Andtheimplementingissimple.Sothenewmethodisvaluableinrealwork.171818Acknowledgment•WegratefullyacknowledgetheSatelliteNavigationLabinBeijingInstituteofTechnologyforthehardwaresupportandtheassistanceofdatacollecting.181919References[1]DeokWonLim,SangJeongLee.DesignofanAssistedGPSReceiveranditsPerformanceAnalysis,IEEEInternationalSymposiumon27-30May2007:1742–1745.[2]A.SchmidandA.Neubauer,”ComparisonoftheSensitivityLimitsforGPSandGalileoReceiversinMultipathScenarios,”Proc.IEEEPositionLocationandNavigation,April2004.[3]RethnakaranPulikkoonattu,MarkusAntweiler.AnalysisofDifferentialNonCoherentDetectionSchemeforCDMAPseudoRandom(PN)codeAcquisition,2004IEEEEighthInternationalSymposiumon30Aug.-2Sep.2004:212–217.[4]M.H.ZarrabizadehandE.S.Sousa.ADifferentiallyCoherentPNCodeAcquisitionReceiverforCDMASystems.IEEETransactionsonCommunications,45(11):1456–1465,Nov1997.[5]VladanM.JovanoviC,AnalysisofNon-CoherentCorrelationinDS/BPSKSpreadSpectrumAcquisition,IEEETRANSACTIONSONCOMMUNICATIONS,VOL.43,NO.2/3/4,FEBRUARY/MARCH