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1、TELECOMMUNICATIONSATTHESTARTOFTHENEWMILLENNIUMEXTENDINGTHECAPACITYOFMULTIPLEACCESSCHANNELSHikmetSari,AlcatelResearch&TechnologyFrederikVanhaverbekeandMarcMoeneclaey,UniversityofGhentABSTRACTthatcanbeaccommodatedonagivenchannel,multipleaccesstechniquescanbeseparatedintoMult
2、ipleaccesstechniqueswhichallowatwobasiccategorieswithdistinctoperatingprin-communicationmediumtobesharedbetweenciples:Thefirstcategory,whichcanbereferreddifferentusersrepresentoneofthemostchal-toasorthogonal-waveformmultipleaccesslengingtopicsindigitalcommunications.In(OWM
3、A),includesFDMA,TDMA,CDMAtermsofthenumberofusersthatcanbeaccom-withorthogonalspreadingsequences(calledmodatedonagivenchannel,therearetwodis-orthogonalCDMA,orOCDMA),OFDMA,andtinctclassesofmultipleaccesstechniques.Theanyothermultipleaccessschemewhichassignsfirstclassincludes
4、thewell-knownFDMA,orthogonalsignalwaveforms.OnachannelTDMA,andOCDMA.OnachannelwhosewhosebandwidthisNtimesthebandwidthofbandwidthisNtimesthebandwidthoftheindi-theindividualusersignals,thesetechniquescanvidualusersignals,thesetechniquescanaccom-accommodateNuserswithoutanymut
5、ualinter-modateNuserswithoutanymutualinterference,ference,butNappearsasahardlimitwhichbutnotasingleadditionalusercanbesupportedcannotbeexceededwithoutreducinguserbitbeyondthislimitingnumber.Thesecondclassrates.TheothercategoryincludesCDMAwithincludesCDMAwithpseudo-noisespr
6、eadingpseudonoise(PN)spreadingsequences(PN-sequences(whichwerefertoasPN-CDMA)andCDMA)andmultipleaccesstechniquesbasedsomeotherrelatedschemes.PN-CDMAdoesonfrequencyhopping.Here,wewillignorefre-nothaveahardlimitonthenumberofusersquencyhoppingandfocusonPN-CDMA.Inthisthatcanbe
7、accommodated,butissubjecttotechnique,differentusersignalsinterferewithmulti-userinterferencewhichgrowslinearlywitheachother,andtheamountofinterferencethenumberofusers.Inthisarticle,afterreview-growslinearlywiththenumberofsimultaneousingthecapacitylimitsofexistingmultipleac
8、cessusers.Consequently,thecapacityofPN-CDMAtechniques,wedescribesomenewlyintroducedisnota
