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1、DEDICATIoNThisthesisisdedicated’tomybel-ovedparentsLateDr．MosesBesongandFridaBesongJortheirendlessloveandsupport．2ABSTRACTOrthogonalFrequencyDivisionMultiplexing(OFDM)iSacommunicationstechniquethatdividesacommunicationschannelintoanumberofequallyspacedfr
2、equencybands．AsubcarriercarryingaportionoftheuserinformationiStransmittedIneachband．EachsubcarrieriSorthogonalfindependentofeachother)witheveryothersubcarrier．Itwasinventedover40yearago，andhasbeenadoptedinmanytechnologiessuchasAsymmetricDigitalSubscriber
3、line(ADSL)services，IEEE802．11a／g，IEEE802．16a，DigitalVideoBroadcast(DVB)，DigitalTerrestriaITelevisionAudioBroadcast，4G，IEEE802．11n，IEEE802．16．a(chǎn)ndIEEE802．20．OFDMiSamulti—carriermodulationtechniquethatiSunlikeothermodulationtechniques．InOFDM．thecarriershave
4、substantialoverlap．Foreachsinglehighfrequencycarrierused，OFDMtransmitsmultiplehighdataratessignalsconcurrentlyusingsubcarriers．Thesub—carriersareorthogonalwitheachotherandhencedonotinterferewitheachother．OFDMiScurrentlythenextchoicefornextgenerationmobil
5、ecommunications，primarilybecauseitoffershighbandwidthefficiencyduetooverlappingofspectra，itsrobustnesstofrequencyselectivefadingchannelsanditsefficientimplementation．DespitetheadvantagesofusingOFDM，oneofitsmaindrawbacksisthehighPeak—to—AveragePowerratio(
6、PAPR)，whichcouldlimittransmissionefficiencyande仟icientuseofHPA．InthisthesisweshalIpresenttwonewPAPRreductionschemeswithimprovedperformanceandreasonablecomplexity．Inthefirstscheme．a(chǎn)modifiedtonereservationschemeforPAPRreductionusingFFTiterationstogeneratet
7、hetones；thereservetonesaredesignedtobothcancelpeaksandslightlyincreasetheaveragepowertoinduceabetterPAPRreduction．Thetonesaregeneratedbymeansof2FFToperationsandtheprocessiSsometimesiteratedtoachievebetterPAPRreductions．ThisschemeachievesasignificantPAPRr
8、eductionofatleast4．6dBwhenabout4％ofthecarriersareusedasreservetonesandwithevenlesseriterationswhensimulatedinanOFDMsystem．Inthesecondtechnique，wecombinebothtonereservationandSLM(SelectedMappingTechnique)toachieveabetterPAP
