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1、扩频码分多址通信的关键技术ThekeytechnologiesforthespreadofmultiplexcommunicationThespreadcodedivisionmultipleaccess(DS/CDMA)isacombinationofcommunicationaddressesandinformationformanyusersInalimitedband,apointofcommunicationisformedatasinglefrequencypoint.Becauseoftheu
2、seofamplifabletechnology,Italsohascertainanti-jammingability.Thecodedivisionmultipleaccessisusedtospreadthetechnology,themaincharacteristicofthespreadsignalthatcarriesinformationistheirbandwidthwidthWIt'smuchbiggerthanthespeedofinformation.Thespreadinforma
3、tioncontainsalargenumberoffrequencybandredundancyforovercomingthewirelesschanneltransmissionTheinterferencethatisencountered,ineludingmultipleaddressinterference・ThecodedivisionmultipleaccessUSESthebroadbandtransmission,thepowerspectrumdensityislow,allowin
4、gmultipleuserstosimultaneouslyinthesamebroadbandchannelTransmitinformation.Itcanbeseenasawayofmultiplexingwiththebandatthesametime,andtheyhavethefollowingmainfeaturesItis.(1)broadbandtransmission,theresistancetomulti-diameterisstrong・Itssignalfrequencyband
5、isgreaterthanthechanneTscoherencebandwidthThecomponentscanbeseparated,andthuscanbeusedtoreceivethetechnology.(2)lowpowerspectraldensitytransmissionandaddresscodeselectioninformation,anti-interferenceperformanceandconfidentiality・(3Capacityhassoftlimits・Inf
6、requencydivisionandtimedivisionmultipleaccess,thecapacityofthesystemisspecifiedinthedesign,cannotchangeChange,theextrausercannotgetthecircuit・Inthecodedivisionmultipleaccess,thedeterminationofthecircuitcapacityisdeterminedbytheallowednoiseRatio.Therefore,i
7、ncreasingtheuseronlyreducesthesignal-to-noiseratioandreducesthecommunicationquality・Inordertorealizetheimprovementofthemultipleaccesscommunication,wealsoneedtounderstandandgraspthekeytechnologiesanddifficultiesofthecodedivisionmultipleaccessPoints,inordert
8、ofacilitatetheuseandresolutionofthedifficultiesencounteredinthecodedivisionmultipleaccesscommunication.ItinvoIvesthecodedivisionmultipleaccessThekeytechnologiescanbeextendedsequenceandmodulation,channelcoding
