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1、外文资料原文Spectralefficiencyofasingle-cellmulti-carrierDS-CDMAsysteminRayleighfadingP.Varzakas,G.S.TombrasLaboratoryofElectronics,DepartmentofPhysics,UniversityofAthens,GR-15784Athens,GreeceReceived8June2005;receivedinrevisedform12September2005;accepted11Ma
2、rch2006Abstract:Thespectralefficiencyofamulti-camerdirect-sequencecode-divisionmultiple-access(MC/DSCDMA)systemoperatinginaRayleighfadingenvironmentisinvestigatedandevaluatedintermsofthetheoreticallyachievablechannelcapacity(intheShannonsense)peruser,es
3、timatedinanaveragesense,oThisshortpapercoversoperationoftheconsideredsystemoverbroadcastcommunicationrandomlytime-varyingchannelsasapplicabletowirelessradionetworksandsingle-cellindoormobilesystemsandleadstothederivationofaclosed・fbnYiexpressionfortheac
4、hievedspectralefficiency.Furthermore,therelationbetweenthenumberoftheemployedsub-carriersandtheachievedspectralefficiencyisrevealed.Keywords:Spectralefficiency;Channelcapacity;Multi-carriermodulation;Code-divisionmultipleaccess;Rayleighfading;1.Introduc
5、tionBasedonorthogonalfrequency-divisionmultiplexing(OFDM),multi-carrierdirectsequencecode-divisionmultiplc-acccss(MC/DS・CDMA)hasbeenproposedandinvestigatedinthecontextofhighdataratecommunicationovertime-variantchannels[1].InsuchaMC/DS-CDMAsystem,thedata
6、sequence,multipliedbyaspreadingsequence,modulatesasetofNorthogonalfrequencyearnersratherthanasingleone,asitisthecaseinconventionalDS-CDMA・Inthispaper,weconsidertheoperationofasingle-cellMC/DS-CDMAsysteminaRayleighfadingenvironmentandevaluateitsspectrale
7、fficiencyintermsofthetheoreticallyachievablechannelcapacity(intheShannonsense)peruser,ontheconditionthatthisisestimatedinanaveragesense・Suchanapproachisjustifiedbythefactthatthespectralefficiencyachievedbyanymultipleaccesscommunicationsystemdependsonthe
8、physicalmodelofthefadingradioenvironment,i.e.,onwhatisknownabouttheparticularfadingchannels・Forexample,ifnothingisknownforthefadingstatisticsofachannelthenitscountablecapacity(inbits/s)willbedictatedbytheminimumfadesignal-to-nois
