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1、446IEEETRANSACTIONSONWIRELESSCOMMUNICATIONS,VOL.5,NO.2,FEBRUARY2006OptimalandSuboptimalPacketSchedulingoverCorrelatedTimeVaryingFlatFadingChannelsAshokK.Karmokar,StudentMember,IEEE,DejanV.Djonin,andVijayK.Bhargava,Fellow,IEEEAbstractWeaddresstheissue
2、ofoptimalpacketschedulingovercorrelatedfadingchannelswhichtradesoffbetweenmin-imizationofthreegoals:averagetransmissionpower,averagedelayandaveragepacketdroppingprobability.WeshowthattheproblemformsaweaklycommunicatingMarkovdecisionprocessandformulat
3、etheproblemasbothunconstrainedandconstrainedproblem.Relativevalueiteration(RVI)algorithmisusedtofindoptimaldeterministicpolicyforunconstrainedprob-lem,whileoptimalrandomizedpolicyforconstrainedproblemisobtainedusinglinearprogramming(LP)technique.Where
4、aswithRVIonlyafinitenumberofschedulingpoliciescanbeobtainedoverthefeasibledelayregion,LPcanproducepoliciesforallfeasibledelayswithafixeddroppingprobabilityandiscomputationallyfasterthantheRVI.WeshowthestructureofFig.1.Schematicsofthesystemandchannelmod
5、el.optimaldeterministicpolicyintermsofthechannelandbufferstateandformasimplelogfunctionalsuboptimalschedulerthatapproximatelyfollowstheoptimalstructure.PerformanceresultsaregivenforbothconstantandburstyPoissonarrivals,andthemoreefficientutilizationofb
6、atteryenergyandhencelongerproposedsuboptimalscheduleriscomparedwiththeoptimalandbatterylifeofmobiledevices.Weconsiderthesituationchannelthresholdscheduler.OursuboptimalschedulerperformsclosetotheoptimalschedulerforeveryfeasibledelayandisdepictedinFig
7、.1(a)wherepacketsarrivefromsomehigherrobusttodifferentchannelparameters,numberofactionsandlayerapplicationandareplacedintoafinitetransmissionincomingtrafficdistributions.buffer.Periodically,aschedulertakessomeofthepacketsIndexTermsPacketscheduling,Mark
8、ovdecisionprocess,fromthebuffer,encodesthem,andtransmitstheencodedwirelesscorrelatedfadingchannel,suboptimalscheduling.packetsoveracorrelatedfadingchannel.Weassumethatcurrentchannelstateinformation(CSI)andbufferstateareavailableatthetransmitter.Bydel