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1、1.Inmodernsocietymorehighdependenceandtherequirementsofcommunication,communicationsystemandthedesignanddevelopmentofhighefficiencyhasbecometheconstantpursuitofcommunicationengineering.Theefficiencyofthecommunicationsystem,inthefinalanalysisisthespectrumutilizationandpowereff
2、iciency.Especiallyinwirelesscommunicationscenarios,therequirementsofthesetwoindicatorsmoreoften,especiallyinspectrumefficiency.Becauseofthespaceavailablespectrumresourcesarelimited,andwirelessapplicationsaremoreandmore,makinguseofwirelessspectrumofstrictmanagementbygovernmen
3、tsandunifiedplanning.Thus,awidevarietyofcommunicationtechnologyhashighspectrumefficiencycontinuestobedeveloped,OFDM(OrthogonalFrequencyDivisionMultiplexing)isknownspectralefficiencyofacommunicationsystemisthehighest,thedigitalmodulation,digitalsignalprocessing,multicarriertr
4、ansmissiontechnologycombinetogether,makeitinthesystemspectrumutilizationrate,powerutilization,systemcomplexitieshasverystrongcompetitivepower,issupportforfuturemobilecommunicationespeciallyisoneofthemaintechnologyofmobilemultimediacommunications.OFDMisamulticarriertransmissi
5、ontechnology,theNsubcarrierchannelisdividedintoNsubchannel,Nsubchannelparalleltransmission.OFDMsystemhasmanyremarkableadvantages.First,OFDMhasveryhighspectrumutilization.ThecommonFDMsystemtosignalfromeachsubchannel,needtosettheprotectionintervalintheadjacentchannel(band),sot
6、hatthereceivercanusetheband-passfiltertoisolatesignalscorrespondingtosubchannels,whichnotonlyprotectthesubbandwaste.OFDMsystemspectrumresourcesbetweenchannels,andbetweenadjacentchannelsThemainlobesignalspectrumisoverlapping(seeFigure1.5),butthespectrumofeachsubchannelsignali
7、sorthogonaltoeachotherinthefrequencydomain,eachsubcarrierisorthogonalintimedomain,separatingeachsubchannelsignalsoftheOFDMsystem(demodulation)bytheorthogonalitytocomplete.Inaddition,subchannelOFDMcanalsobeusedM-arymodulation(suchashighspectrumefficiency,QAM)tofurtherimprovet
8、hespectrumefficiencyofOFDMsystem.Second,relativelysimpletoachieve.Whenthech
