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1、_●■東北大學碩士學位論文AbstractResearchandSimulationofWirelessChannelModelBasedonNeuralNetworkAbstractInthemobilecommunicationsystem,thereceivesignalshavebeeninevitablyaffectedbymultipathfadingandtheeffectofshadowingwhenmobileusersaremoving.Whendesigningthecommuncations
2、ystem,thepropagationcharacteristicsofwirelesschannelarethemostimportantfactor,whichdirectlyinfluencethequalityofcommunicationserviceandthestablityofthecommunicationsystem.Andtherefore,theresearchesofthecharacteristicsofradiopropagationandwirelessmobilechannelm
3、odelsarenecessarytodevelopanddesignanexcellentwirelesscommunicationsystem.Wirelesschannelmodelingandsimulationaremainlystudiedinthisthesis.Themaincontentofthethesisisdevidedintotwoparts:theexistingflatfadingchannelmodelingandsimulationmethodsarestudiedinthefir
4、stpart,andtheirownadvantagesanddisadvantagesbysimulatoinsarealsoanalyzed.Andoneofmodelingmethodsisappliedtothefrequencyselectivefadingchannelsimulation,andthesimulationresultsaregiven.Thewirelesschannelcanberegardedasanonlineartransimissionsystem,andtheneuraln
5、etworkhasfitlyfavorableperformanceinsimulatingnonlinearsystem.Soamodelingmethodofwirelesschannelbasedonneuralnetworkisproposedinthesecondpartofthispaper.Inthispart,thenewchannelmodelisstudiedanddevelopedfromtheshallowtothedeep:anAdditiveWhiteGaussianNoise(AWGN
6、)channelmodelbasedonBPneuralnetworkiscreatedfirstly,andissimulatedbybasicBPalgorithmandimprovedBPalgorithmrespectively.ThesimulationresultsshowthatBPneuralnetworkhasacertainapproachcapacity,buttheconvergencerateofBPalgorithmistooslow,withexistenceoflocalminimu
7、mvalueinobjectivefunction;theimprovedBPalgorithmenhancestheconvergencerate,butthereisstillacertainerrorbetweenactualoutputanddesiredoutput,withinaptitudeinselectinghiddenlayerneuronsnumbers.AsRadialBasisFunction(RBF)neuralnetworkcanapproachanynonlinearfunction
8、witharbitraryprecisionandhasafastlearningspeed,nolocalminimumvalue,anAWGNchannelmodelbasedonRBFneuralnetworkisproposed.Andthenewmodelingmethodisextendedtotheflatfadingchannelandfre