通信工程专业外文翻译--码分多址.doc

外文原文
Codedivisionmultipleaccess
Codedivisionmultipleaccess(CDMA)isaHYPERLINK"http://en.wikipedia.org/wiki/Channel_access_method"\o"Channelaccessmethod"channelaccessmethodusedbyvariousradiocommunicationtechnologies.ItshouldnotbeconfusedwiththeHYPERLINK"http://en.wikipedia.org/wiki/List_of_mobile_phone_standards"\o"Listofmobilephonestandards"mobilephonestandardscalledHYPERLINK"http://en.wikipedia.org/wiki/IS-95"\o"IS-95"cdmaOne,HYPERLINK"http://en.wikipedia.org/wiki/CDMA2000"\o"CDMA2000"CDMA2000(theHYPERLINK"http://en.wikipedia.org/wiki/3G"\o"3G"3GevolutionofcdmaOne)andHYPERLINK"http://en.wikipedia.org/wiki/WCDMA"\o"WCDMA"WCDMA(the3GstandardusedbyHYPERLINK"http://en.wikipedia.org/wiki/GSM"\o"GSM"GSMcarriers),whichareoftenreferredtoassimplyCDMA,anduseCDMAasanunderlyingchannelaccessmethod.
Oneoftheconceptsindatacommunicationistheideaofallowingseveraltransmitterstosendinformationsimultaneouslyoverasinglecommunicationchannel.Thisallowsseveraluserstoshareabandoffrequencies(seeHYPERLINK"http://en.wikipedia.org/wiki/Bandwidth_(signal_processing)"\o"Bandwidth(signalprocessing)"bandwidth).ThisconceptiscalledHYPERLINK"http://en.wikipedia.org/wiki/Multiple_access"\o"Multipleaccess"multipleaccess.CDMAemploysHYPERLINK"http://en.wikipedia.org/wiki/Spread-spectrum"\o"Spread-spectrum"spread-spectrumtechnologyandaspecialcodingscheme(whereeachtransmitterisassignedacode)toallowmultipleuserstobemultiplexedoverthesamephysicalchannel.Bycontrast,HYPERLINK"http://en.wikipedia.org/wiki/Time_division_multiple_access"\o"Timedivisionmultipleaccess"timedivisionmultipleaccess(TDMA)dividesaccessbyHYPERLINK"http://en.wikipedia.org/wiki/Time"\o"Time"time,whileHYPERLINK"http://en.wikipedia.org/wiki/Frequency-division_multiple_access"\o"Frequency-divisionmultipleaccess"frequency-divisionmultipleaccess(FDMA)dividesitbyHYPERLINK"http://en.wikipedia.org/wiki/Frequency"\o"Frequency"frequency.CDMAisaformofHYPERLINK"http://en.wikipedia.org/wiki/Spread_spectrum"\o"Sp