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PrimaryUserAuthenticationof CognitiveRadioNetworkusing UnderlayWaveform Rohit Chakravarthy,Kaiyu Huang,LinZhangandZhiqiang Wu Outline 1. 2. 3. 4. 5. 6. 7. 8. SpectrumCongestion CognitiveRadio PrimaryUsers&SecondaryUsers PrimaryUserEmulationAttack Currentresearch&limitations PUAuthenticationSystemModel Results Conclusions SpectrumCongestionProblem • Overcrowdingofspectrumduetoanincreasednumberofusers, increasednumberofspectrumbaseddevices,andhigher frequencies/datarates • Realproblemcomesdowntoinefficientusageofthespectrumrather thanalackofspectrumitself UnusedSpectrum Overcrowded CognitiveRadio Anintelligentradioorsystemthatsensesthespectrumandisawareof itsoperationalenvironmentandcanbetrainedtodynamicallyand autonomouslyadjustitsradiooperatingparametersaccordingly PrimaryUsers&SecondaryUsers • PrimaryUser(PU) ØTheintendeduserinaCRnetwork ØPrincipalaccesstothespectrum • SecondaryUser(SU) ØOpportunisticuserusingthespectrumonanoninterferencebasisbutincooperationwiththePU ØCanonlyusethespectrumwhenPUgrantsaccessornot present PrimaryUsers&SecondaryUsers(cont.) PrimaryUsersEmulationAttack • “Intruder”whotriestointerfereandoccupythevacant spectrumofthePUintendedforSU • ImpersonatesPUbymimickingdistinctivecharacteristics andfeatures • SUassumesPUisstilloccupyingthespectrumwhenin realityPUEAttackisoccurring • CRleftvulnerabletoPUEattackthuslosingspectrumto intruder • Poorspectrumutilization PrimaryUsersEmulationAttack(cont.) PU PU PU + UL SU PUE PUE PU PU PU + UL CurrentPUEresearchandlimitations 1. 2. 3. 4. Energy&Cyclostationarymethods Locationbasedapproaches Cooperativesensing Cryptography AbovemethodsareineffectivetoidentifyPUEattacksorrequirehigh computationalcomplexity PUSensingMethodsinliterature • EnergyDetection ØUsageofanenergydetectorinsignaldetectiontoidentifythepresenceof aPU ØProblem– Justdetectionofenergylevelsisnotsufficientenoughto differentiatePUfromPUE • Match-filterdetection ØCorrelatesashiftedversionofthePUwaveformandcomparestheoutput ofthefilterwiththepredeterminedsignal ØProblem– requiresperfectknowledgeofPU,andmoreoveraPUEcanjust usearepeatertoimitatePU • CyclostationarySignalProcessing(CSP)Detection ØExtractsdistinctfeaturesofPUsignalandperformsdetectionbasedon thosespecialfeatures ØCandistinguishPUfromnoise ØExtractionoffeaturesstillpossibleundervaryingSignaltoNoiseRatio (SNR)usingembeddedinformationinPUsignalthatarenon-existentin noise ØProblem– highcomputationalcomplexity WhatisCyclostationarySignal Processing? CyclostationarySignalProcessing(CSP)isa statisticalsignalprocessingtechniquewhich exploitstheinherentfeaturesandpropertiesofa modulatedsignalsuchasmodulation,symbol rate,chiprate,etc. SpectralCorrelationFunction BPSK - AWGN QAM BPSK - Fading DS-CDMA PUAuthenticationSystemModel PrimaryUser PrimaryUser Emulator PrimaryUser +Underlay C H A N N E L SUSensing (Receiver) Cyclostationary SignalProcessing Feature Extractionto AuthenticatePU (BitRate) PUAuthenticationSystemModel GenerationofPUSignalinTimeDomain: PUAuthenticationSystemModel PUvs.PU+UnderlayinTimeDomain PUAuthenticationSystemModel ResultsofCSPforPU&PU+Underlay PUAuthenticationSystemModel PUAuthenticationAlgorithmfeaturingPUSignalCancellationtechnique: Received Signal MaskFunction: PUMessage datacancellation Feature Extraction Integration Subtraction: PUHeaderdata cancellation ApplyCSP Amplitude Amplitude Amplitude Results Amplitude Amplitude Amplitude Results:VaryingSNRsforUnderlay Amplitude Amplitude Amplitude UnderlaySNR=10dB UnderlaySNR=-10dB Amplitude Amplitude Amplitude Results:VaryingSNRsforUnderlay Amplitude Amplitude Amplitude UnderlaySNR=-20dB UnderlaySNR=-40dB Fb=7000 Conclusions • Superimpositionofcovertunderlaywaveformwasessentialto authenticatePUfromPUE • PresenceofunderlaywaveformwasnotvisibleinbothtimeandCSP domain • Knowledgeofunderlaywaveformincombinationwithnovel techniquetoextractunderlaywaveformwaskey • Post-CSPIntegrationallowedclearidentificationofbitfrequencyto authenticatePU Novelties&Contributions • SuperimpositionofUnderlaywaveformontoPrimaryUserHeader • CreatingaCSPbasedalgorithmfeaturingPUSignalCancellationto extractunderlayandauthenticatePU Questions?
