2023學(xué)年完整公開課版Diversitytechnology

DiversityTechnologyMobileCommunicationTechnologyLecturer：WeiDeng010203KnowledgeIntroductionDiversityTechnologyCONTENTSummary01KnowledgeIntroductionPARTONEKnowledgeIntroductionThereareseriousinterferenceandfadingphenomenainmobilecommunication,therefore,necessarymeasuresmustbetakentocombatanti-interferenceandanti-fading.ElectromagneticsignalBasicMobilechannelTelephoneAttenuationInterferencesNoise

Interferenceandfadingarethemainfactorsthataffectthequalityofcommunication.KnowledgeIntroductionDiversityisaneffectiveanti-fadingtechnology.Theso-calleddiversityreceptionmeansthatthereceivercarriesoutspecificprocessingonthesignalswithindependentfadingcharacteristics(carryingthesameinformation)receivedbythereceiverinordertoreducetheelectricalfluctuationofthesignal.02DiversityTechnologyPARTTWODiversityTechnologyImprovesignalstability

Thereceivercarriesoutspecificprocessingonthesignalsreceivedbyitwhichareindependentofeachother(carryingthesameinformation)inordertoreducethesignallevelfluctuation.DefinitionActionImplementDecentralizedtransmissionandcentralizedprocessingDiversityTechnology321TypesDividedby"points"Dividedby"set"MaximumratiocombinationTimediversitySpatialdiversitySelectivemergerEqualgaincombinationFrequencydiversityPrinciple:anytwodifferentlocationsreceivethesamesignal,aslongasthedistancebetweenthetwolocationsislargetoacertainextent,thefadingofthetworeceivedsignalsisnotrelated.Spatialdiversity

Distanceselection:thedistancedisrelatedtotheworkingwavelength,groundfigureandantennaheight.

Urbanarea

d=0.5λSuburbd=0.8λDiversityTechnologyDiversityTechnologyPrinciple:sincethefadingoftwosignalswhosefrequencyintervalisgreaterthanthecorrelationbandwidthcanbeconsideredtobeunrelated,thesameinformationcanbetransmittedatmorethantwodifferentfrequenciestoachievefrequencydiversity.Frequencydiversity

Frequencyinterval>correlationbandwidth

Principle:fastfadingnotonlyhasspatialandfrequencyindependence,butalsohastimeindependence,thatis,thesamesignalisretransmittedmanytimesindifferenttimeintervals,aslongasthetimeintervalofeachtransmissionislargeenough.thenthefadingofeachtransmittedsignalwillbeindependentofeachother,andthereceiverwillcombinethesamesignalreceivedrepeatedly,whichcanreducetheimpactoffading.TimediversityCondition:

theretransmissionintervalofthedigitalsignalislargerthanthecoherenttime.DiversityTechnologySupposetheMinputsignalvoltageisr1(t),r2(t),.

For,rM(t),theoutputvoltager(t)ofthecombineris:MergediversitymodeIntheformula,akistheweightingcoefficientofthekthsignal.DiversityTechnology1SelectivemergerSelectthesignalofthebranchwiththehighestsignal-to-noiseratio.2MaximumratiocombinationThecontributionofthebranchwithstrongsignalismore,andthesignalwithweaksignaliswellsuppressed.3EqualgaincombinationThesignalsofeachbranchareaddedwithequalgain.DiversityTechnology03SummaryPARTTHREESummaryWhatisthewaytoreceivediversitysignals?Whatisthewaytooutputfromthediversitysignal?DiversitymodeMergermodeDiversitytechnologyDiversity+merging21Spatialdiversity:thereceivedsignalsofdifferentantennasareindependentofeachother.

Frequencydiversity:receivedsignalsofdifferentfrequenciesareindependentofeachother.Timediversity:receivedsignalsatdifferenttimesareindependentofeachother.

Selectivemerging:selectthebestbranchastheoutput,anddiscardtheotherbranches.

Equalgaincombination:adjustthephaseofthemaindiameterofeachbranchinthesamephase,andaddtheequalgain.Maximumratiocombination:adjustthephaseof