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1、The31stAnnualIEEEInternationalConferenceonComputerCommunications:Mini-ConferenceMIMODownlinkSchedulinginLTEsystemsHonghaiZhang,NarayanPrasad,SampathRangarajanNECLaboratoriesAmerica{honghai,prasad,sampath}@nec-labs.comAbstractSchedulingplaysavitalroleinLTEdownlink
2、sys-whereLeeetal.consideredthecommonMIMOoperationaltemswithMultipleInputandMultipleOutput(MIMO)antennas.mode(transmitdiversityorspatialmultiplexing),althoughWeconsidertheMIMOdownlinkschedulingproblematthebaseonlyonefixedprecodingmatrixisassumed.Moreover,theystatio
3、n(BS)inLTEnetworksunderseveralpracticalconstraintsdidnotconsidertheconstraintofone-MCS-per-codeword.mandatedbythe3GPPstandards.WeDefineanewconstructcalledtransmissionmode,whichdenotesaparticularchoiceofInthiswork,weconsiderallaforementionedpracticalcon-MIMOoperati
4、onalmode,precodingmatrix,transmissionrank,straintsimposedbyLTEstandardsandaddresstheschedulingaswellasthemodulationandcodingschemes(MCSs)ofuptoprobleminpracticalLTEsystemsundertwotrafficmodels:twocodewordsandshowthatbothLTEsystemsrequirethateachbackloggedmodelandfi
5、nitequeuemodel.Ourmajorcontri-scheduleduserbeservedusingonlyonetransmissionmodeineverysubframe.Weprovethattheresultingschedulingproblemsbutionsaretwofold.First,wedefineanewconstructcalledareNP-hardunderbothbackloggedandfinitequeuetrafficmod-transmissionmode,whichden
6、otesaparticularchoiceofaels,andthendevelopaunifiedlow-complexitygreedyalgorithmMIMOoperationalmode,precodingmatrix,transmissionrank,thatyieldssolutionsguaranteedtobewithin1/2oftherespectiveandMCS(s)fortheallocatedcodeword(s),andshowthatLTEoptima.Extensiveperforman
7、ceevaluationinrealisticsettingsrequiresusingacommontransmissionmodeonallRBsallo-revealsnear-optimalperformanceofourproposedalgorithmandthatitsignificantlyoutperformsthestateoftheart,especiallycatedtoaparticularuser.Withthenewconstruct,weformulateunderthemorepracti
8、cal,finitequeuemodel.theproblemofweightedsumratemaximizationundertheseconstraintsasinteger-programmingproblemsandprovetheI.INTRODUCTIONNP-hardnessoftheproblemsu