认知无线电技术原理介绍

1CADENCEDESIGNSYSTEMS,INC.CognitiveRadioEmergesfromObscurityJohnNotorJanuary23,2004Rev22Focus•Togiveanoverviewofcurrentcognitiveradioinitiativesandapplications:–Regulatory:FederalCommunicationsCommission(FCC)–Standards:IEEE802Wireless•Tokeepthediscussionlimitedtothenearterm,not“pieintheskybyandby”.•Tofocusprimarilyonunlicensedapplications.3WhatisCognitiveRadio?•ThetermCognitiveRadiomeansdifferentthingstodifferentaudiences:•Mitola,addressingthebroadissueofwirelesspersonaldigitalassistantsinhisdissertation,says1:“Thetermcognitiveradioidentifiesthepointatwhichwirelesspersonaldigitalassistants(PDAs)andtherelatednetworksaresufficientlycomputationallyintelligentaboutradioresourcesandrelatedcomputer-to-computercommunicationsto:(a)detectusercommunicationsneedsasafunctionofusecontext,and(b)toprovideradioresourcesandwirelessservicesmostappropriatetothoseneeds.”1.Dr.JosephMitolaIII,CognitiveRadioAnIntegratedAgentArchitectureforSoftwareDefinedRadioDissertation,p.1,para1.1,RoyalInstituteofTechnology,May8,2000.4WhatisCognitiveRadio?•Mitolacontinues2:“Cognitiveradioincreasestheawarenessthatcomputationalentitiesinradioshaveoftheirlocations,users,networks,andthelargerenvironment.”•Mitolaincludestheconceptofmachinelearningasapropertyofcognitiveradio3.•Mitola’sapproachincludesahighlevelofawarenessandautonomy4:“Cognitiontasksthatmightbeperformedrangeindifficultyfromthegoal-drivenchoiceofRFband,airinterface,orprotocoltohigher-leveltasksofplanning,learning,andevolvingnewprotocols.”2.Ibidp.13,para2.33.Ibidp.47,para4.24.Ibidp.49,para4.35WhatisCognitiveRadio?•TheFCC5viewofcognitiveradio6:“Acognitiveradio(CR)isaradiothatcanchangeitstransmitterparametersbasedoninteractionwiththeenvironmentinwhichisoperates.”•TheFCCreferstoaSoftwareDefinedRadio(SDR)as7:“atransmitterinwhichtheoperatingparameters…canbealteredbymakingachangeinsoftwarethatcontrolstheoperationofthedevicewithout…changesinthehardwarecomponentsthataffecttheradiofrequencyemissions.”•AccordingtotheFCC8:“ThemajorityofcognitiveradioswillprobablybeSDRs,butneitherhavingsoftwarenorbeingfieldreprogrammablearerequirementsofacognitiveradio.”5.FederalCommunicationsCommission6.FCC03-322,NoticeofProposedRulemakingonCognitiveRadio,p.5,para107.Ibidp.4,para98.Ibidp.5,para106WhatisCognitiveRadio?SDRAdaptstoNetworkEnvironmentCognitiveRadioAdaptstoSpectrumEnvironment•Notor’sSimplifiedView•Mitolaaddsanotherlevel:device/networkintelligencewhichadaptstouseractivity.•TheFCCseemsprimarilyconcernedwitharegulatoryfriendlyview,focusedontransmitterbehaviorforthemoment.7WhatisCognitiveRadio?•Afullycognitiveradioshouldhavetheabilitytodothefollowing9:1.Tunetoanyavailablechannelinthetargetband.2.Establishnetworkcommunicationsandoperateinallorpartofthechannel.3.Implementchannelsharingandpowercontrolprotocolswhichadapttospectrumoccupiedbymultipleheterogeneousnetworks.4.Implementadaptivetransmissionbandwidths,datarates,anderrorcorrectionschemestoobtainthebestthroughputpossible.5.Implementadaptiveantennasteeringtofocustransmitterpowerinthedirectionrequiredtooptimizereceivedsignalstrength.9.AdaptedfromthepresentationbyJohnNotor,RadioArchitecturesforUnlicensedReuseofBroadcastTVChannels,CommunicationsDesignConference,September,2003.8EvidenceofPrimitiveCognitiveRadioLifeForms•Inthecommercialnetworkingarena,thecognitiveradiolandscapeisprimitiveatbest.–Limitedbythecurrentregulatoryframeworktooperationwithinagivenfrequencyband.•SomeexamplesofcognitiveradiocitedbytheFCCintheircognitiveradioNPRM:–Cordlesstelephonesinthe43.71-44.49MHzbandavoidchannelsoccupiedbyprivatelandmobilesystemsusingpassivescanningtechniquestoautomaticallyselectunoccupiedchannels.–U-NIIbanddevicesoperatinginthe5.25-5.35GHzand5.47-5.725GHzbandsarerequiredtousesimilartechniquestoavoidinterferencewithFederalGovernmentoperations.9EvidenceofPrimitiveCognitiveRadioLifeForms•Twoprotocolshaveemergedasearlycognitiveradiobehavior:–DynamicFrequencySelection(DFS):–Originallyusedtodescribeatechniquetoavoidradarsignalsby802.11anetworkswhichoperateinthe5GHzU-NIIband.–Nowgeneralizedtorefertoanautomaticfrequencyselectionprocessintendedtoachievesomespecificobjective(likeavoidingharmfulinterferencetoaradiosystemwithahigherregulatorypriority).–TransmitPowerControl(TPC):–Originallyamechanismfor802.11anetworkstoloweraggregatetransmitpowerby3dBfromthemaximumregulatorylimittoprotectESSS(EarthExplorationSatelliteSystems)operations.–Nowgeneralizedtoamechanismthatadaptivelysetstransmitterpowerbasedonthespectrumorregulatoryenvironment.10EvidenceofPrimitiveCognitiveRadioLifeForms•AnotherkeycognitiveradiobehaviorisIncumbentProfileDetection10(IPD).•IPDistheabilitytodetectanincumbentuser(onewithregulatorypriority)basedonaspecificspectrumsignature.–DFSrequiresanIPDprotocolidentifyunoccupied,orlightlyusedfrequencies.–IPDincludesdetectionschemesfocusedonthecharacteristicsofthespecificincumbentsintheband,orbands,thatthecognitiveradioisdesignedtosupport.–IPDeliminatestheneedforgeolocationtechniques(GPS,etc.)todeterminethelocationoftheradioand,usingadatabase,identifyunusedchannels.10.J