動態(tài)頻譜共享系統(tǒng)中頻譜切換機制的研究的中期報告

動態(tài)頻譜共享系統(tǒng)中頻譜切換機制的研究的中期報告摘要本中期報告介紹了動態(tài)頻譜共享系統(tǒng)中頻譜切換機制的研究進展。首先簡要介紹了動態(tài)頻譜共享系統(tǒng)的概念和結(jié)構(gòu)，然后對其中涉及的若干關(guān)鍵技術(shù)進行了討論，包括頻譜感知、頻譜控制、頻譜切換等。接著重點介紹了頻譜切換機制的設(shè)計和實現(xiàn)，包括選頻策略、切換決策、切換時間等。最后，對當(dāng)前研究的不足和需要進一步探討的方向進行了總結(jié)。關(guān)鍵詞：動態(tài)頻譜共享；頻譜感知；頻譜控制；頻譜切換；切換機制；IntroductionDynamicspectrumsharingisaneffectivewaytoimprovespectrumutilizationandalleviatespectrumscarcityproblem.Indynamicspectrumsharingsystems,multipleuserscansharethesamespectrumresourcebasedontime,frequencyorspacedivision.Spectrumsensingandcontrolaretwokeytechnologiesfordynamicspectrumsharingsystems.Spectrumsensingistodetecttheunusedoridlespectrumresourcesinagivenfrequencyband,whilespectrumcontrolistoallocateandmanagethespectrumresourcesamongmultipleusersaccordingtotheservicerequirementsandqualityofservice(QoS)constraints.Spectrumswitchingisanothercriticaltechnology,whichistoenabletheuserstoswitchfromonefrequencybandtoanotherwhenthequalityoravailabilityofthecurrentbandisdegradedorunavailable.Inthisreport,wefocusonthedesignandimplementationofspectrumswitchingmechanismindynamicspectrumsharingsystems.Therestofthereportisorganizedasfollows:Section2brieflyintroducestheconceptandarchitectureofdynamicspectrumsharingsystems,anddiscussessomekeytechnologiesinvolved.Section3highlightsthedesignandimplementationofspectrumswitchingmechanism,includingfrequencyselectionstrategy,switchingdecision,andswitchingtime.Section4concludesthereportandpointsoutthefutureresearchdirections.DynamicSpectrumSharingSystemsDynamicspectrumsharingsystemsallowmultipleuserstosharethesamespectrumresourcebasedontime,frequencyorspacedivision.Theuserscanbeclassifiedintotwocategories:primaryusers(PUs)andsecondaryusers(SUs).PUshavetheprimaryrighttousethespectrumresource,whileSUscanaccesstheunusedoridlespectrumresourcesafterobtainingthepermissionfromPUs.Themaincomponentsofdynamicspectrumsharingsystemsincludespectrumsensing,spectrumcontrol,andspectrumswitching,asshowninFigure1.Figure1.ArchitectureofaDynamicSpectrumSharingSystemSpectrumsensingistodetecttheunusedoridlespectrumresourcesinagivenfrequencyband.Therearetwotypesofspectrumsensingmethods:cooperativespectrumsensingandnon-cooperativespectrumsensing.CooperativespectrumsensingrequiresthecollaborationamongmultipleSUstoimprovethedetectionaccuracyandreliability.Non-cooperativespectrumsensingistoperformindividualspectrumsensingwithoutanycoordinationorcollaboration.Bothmethodshavetheiradvantagesanddrawbacks,andtheselectionofspectrumsensingmethoddependsonthenetworkenvironmentandsystemrequirements.SpectrumcontrolistoallocateandmanagethespectrumresourcesamongmultipleusersaccordingtotheservicerequirementsandQoSconstraints.Spectrumcontrolincludestwosub-modules:spectrumallocationandspectrummanagement.SpectrumallocationistoallocatetheavailablespectrumresourcestoSUsbasedontheirservicerequirementsandpriority.Spectrummanagementistomonitorandadjustthespectrumusageandperformancebasedonthedynamicnetworkconditionsanduserbehaviors.Spectrumswitchingistoenabletheuserstoswitchfromonefrequencybandtoanotherwhenthequalityoravailabilityofthecurrentbandisdegradedorunavailable.Spectrumswitchingcanbetriggeredbyvariousreasons,suchasinterference,congestion,orspectrumhandoff.Spectrumswitchingincludestwophases:frequencyselectionandswitchingdecision.Frequencyselectionistoselectthemostsuitablefrequencybandbasedonthespectrumavailabilityandquality.Switchingdecisionistodeterminewhethertoswitchornot,basedonthecost-benefitanalysisandthetrade-offbetweenspectrumutilizationanduserexperience.SpectrumSwitchingMechanismSpectrumswitchingmechanismisacrucialcomponentindynamicspectrumsharingsystems.Themainobjectivesofspectrumswitchingmechanismaretoimprovethespectrumutilizationandenhancetheuserexperience.Spectrumswitchingcanbeclassifiedintotwotypes:reactivespectrumswitchingandproactivespectrumswitching.Reactivespectrumswitchingistoswitchtoalternativefrequencybandwhenthecurrentbandisentirelyoccupiedorsignificantlydegraded.Proactivespectrumswitchingistopre-emptivelyswitchtoabetterfrequencybandbeforethecurrentbandisdegraded.FrequencySelectionStrategyFrequencyselectionstrategyistodeterminethemostsuitablefrequencybandforspectrumswitching.Theselectioncriteriaincludethespectrumavailability,latency,throughput,interference,transmissionpower,andenergyconsumption.Themostchallengingissueinfrequencyselectionistobalancethetrade-offbetweenspectrumutilizationanduserexperience.Ononehand,thefrequencybandwithhigheravailabilityandlessinterferencecanimprovethespectrumutilizationandreducethecollisionprobability.Ontheotherhand,thefrequencybandwithhigherthroughputandlowerlatencycanenhancetheuserexperienceandsatisfaction.SwitchingDecisionSwitchingdecisionistodeterminewhethertoswitchornotbasedonthecost-benefitanalysisandthetrade-offbetweenspectrumutilizationanduserexperience.Theswitchingdecisiondependsonseveralfactors,suchasspectrumavailability,spectrumquality,requestpriority,userlocation,andcommunicationhistory.Themostcommonswitchingdecisionalgorithmsarebasedonthethresholdorpolicy-basedrules.Thethreshold-basedalgorithmrequiresthecomparisonbetweenthecurrentandthresholdvaluesoftheswitchingcriteria.Thepolicy-basedalgorithmrequiresthepredefinedrulesorstrategiestodecidewhethertoswitchornot.SwitchingTimeSwitchingtimeisthedurationoftheswitchingprocess,includingthefrequencyscanning,channelreservation,anddatatransmissionpause.Theswitchingtimeshouldbeasshortaspossibletominimizethedisruptionoftheongoingcommunicationandensurethecontinuityoftheservice.Theswitchingtimedependsonthenetworkenvironmentandthecomplexityoftheswitchingmechanism.Themostsignificantfactorsaffectingswitchingtimearethefrequencyscanningtimeandthechannelaccesstime.Thefrequencyscanningtimeistodetecttheavailablefrequencybandsandestimatethequalityofthefrequencyband,whichmaytakeseveralmillisecondstoseveralseconds.Thechannelaccesstimeisto