Peak-to-Average Power Control in峰值平均控制率

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1、RenaldiWinotoEE229BProjectPeak-to-AveragePowerControlinOFDMSystemsI.IntroductionHighPeak-to-AveragePowerRatio(PAPR)hasbeenrecognizedasoneofthemajorpracticalprobleminvolvingOFDMmodulation.HighPAPRresultsfromthenatureofthemodulationitselfwheremultiplesubcarriers/

2、sinusoidsareaddedtogethertoformthesignaltobetransmitted.WhenNsinusoidsadd,thepeakmagnitudewouldhaveavalueofN,wherethe(rms)averagemightbequitelowduetodestructiveinterferencebetweenthesinusoids.HighPAPRsignalsareusuallyundesirableforitusuallystrainstheanalogcircu

3、itry.HighPAPRsignalswouldrequirealargerangeofdynamiclinearityfromtheanalogcircuits,whichusuallyresultsinexpensivedevices,andhigherpowerconsumption/lowerefficiency(forexample,poweramplifierhastooperatewithlargerbackofftomaintainlinearity).It’squitestraightforwar

4、dtoobservethatinanOFDMsystems,someinputsequenceswouldresultinhigherPAPRthanothers.Forexample,aninputsequencethatrequiresallsubcarrierstotransmittheirmaximumamplitudeswouldcertainlyresultinahighoutputPAPR.Thusbylimitingthepossibleinputsequencestoasmallestsubset,

5、itshouldbepossibletoobtainoutputsignalswithaguaranteedlowoutputPAPR.Atthesametime,bylimitinginputsequencestoasmallersubsetwealsoprovidethesystemwithmoreresiliencyinthepresenceofnoise–thisideaiscentralintheareaoferror-controlcodes.Thusthequestioniscanwesetupafra

6、meworksuchthatwecanjointlyoptimizetheselectionofcodewordsbasedonboththeirPAPRandminimumdistanceperformance.InthisprojectwewillconductaliteraturesurveyofthevarioustechniquesproposedtoestablishPAPRcontrolinOFDMmodulation.Theemphasiswillcertainlybeonthosetechnique

7、swhichusescodesdesignedtohavebothlowPAPRalongwithgooderror-correctioncapabilities.Wewillalsobrieflymentionothermethodsthathavebeenproposedintheliterature.Thesemethodsalsoindirectlytakeadvantageoftheredundancyaffordedbyerror-controlcodingperformedontheinputdatas

8、equences–inthatthePAPRreductionsystemisallowedtoalterthetransmittedsignalalittlebit(introducebiterror)withthehopeofoptimizingforPAPR.Inmostofthemainresultspresentedhere,theg