简介:在已有矿井MIMO信道模型的基础上,提出了一种基于Nakagami衰落的矿井MIMO空间相关信道建模方法。基于Nakagami衰落的非相关MIMO信道,通过计算收发天线间的空间相关性生成MIMO空间相关信道。对所建信道模型的空间相关性及信道容量进行仿真分析。仿真结果证明:MIMO信道的空间相关性随收发端天线单元间距的增大而减小;MIMO信道容量与信道空间相关性以及收发端天线数目有关;减小信道的空间相关性或者增加天线数目,可增加MIMO信道容量。基于Nakagami衰落的矿井MIMO空间相关信道模型适用于矿井无线通信系统。
简介:摘要近年来,OFDM技术由于其频谱使用率较高与抗频率择选性薄弱的特征,现已成为将来宽带无线通讯互联网重点技术的优选方案,其能提供宽带化、快速化、个性化的服务。本文将主要围绕OFDM基础原理展开分析,并着重探究OFDM通信网络中的无线定位技术。
简介:Orthogonalfrequencydivisionmultiplexing(OFDM)isanattractivemodulationcandidateforCognitiveRadio(CR)networks.EffectiveandreliablesubcarrierpowerallocationinOFDM-basedCognitiveRadio(CR)networksisachallengingproblem.ThispaperfocusesonthepowerallocationforOFDM-basedCognitiveRadio(CR)networks.OurobjectiveistomaximizethetotaltransmissionratesofSecondaryUsers(SU)byadjustingthepowerofsubcarrierwhiletheinterferenceintroducedtothePrimaryUser(PU)iswithinacertainrangeandthetotalpowerofsubcarrierisnotbeyondthetotalpowerconstraint.WeinvestigatetheoptimalpowerallocationalgorithmforOFDM-basedCog-nitiveRadio(CR)basedonconvexoptimizationtheory.Then,becauseofhighcomplexityoftheop-timalpowerallocationalgorithm,weproposeaneffectivesuboptimalpowerloadingscheme.Theoryanalysisandsimulationresultsshowthattheperformanceofthesuboptimalpowerallocationalgorithmisclosetotheperformanceoftheoptimalpowerallocationalgorithm,whilethecomplexityofthesuboptimalpowerallocationalgorithmismuchlower.
简介:Aimingattheproblemofthepeaktoaveragepowerratio(PAPR)incoherentopticalorthogonalfrequencydivisionmultiplexing(CO-OFDM),ahybridPAPRreductiontechniqueoftheCO-OFDMsystembycombiningiterativepartialtransmitsequence(IPTS)schemewithmodifiedclippingandfiltering(MCF)isproposed.Thesimulationresultsshowthatatthecomplementarycumulativedistributionfunction(CCDF)of104,thePAPRofproposedschemeisoptimizedby1.86dBand2.13dBcomparedwiththoseofIPTSandCFschemes,respectively.Meanwhile,whenthebiterrorrate(BER)is10^-3,theopticalsignaltonoiseratio(OSNR)areoptimizedby1.57dBand0.66dBcomparedwiththoseofCFandIPTS-CFschemes,respectively.
简介:这份报纸求婚最大化率(先生)连接配对的副载波(SP)并且驱动分配(PA)(MR-SP&PA),为最大化与decode-and-forward(DF)中继系统的orthogonal-frequency-divisionmultiplexing(OFDM)的加权的和率的一个新奇计划继电器。MR-SP&PA与全部的力量限制基于SP和力量分配的联合优化,并且在纸作为一个混合整数编程问题提出了。编程问题然后被使用连续松驰转变到一个凸的优化问题,并且在Lagrangian双领域解决了。模拟结果证明MR-SP&PA能在全部的力量限制下面最大化加权的和率并且超过相等的力量分配(EPA)和比例力量分配(PCG)。
简介:Anovelarchitectureforthecolorlessopticalnetworkunit(ONU)isproposedandexperimentallydemonstratedwithdirect-detectionopticalorthogonalfrequencydivisionmultiplexing(DDO-OFDM).Inthisarchitecture,polarization-divisionmultiplexingisusedtoreducethecostatONU.Inopticallineterminal(OLT),quadratureamplitudemodulation(QAM)intensity-modulatedOFDMsignalwithx-polarizationat10Gbit/sistransmittedasdownstream.AteachONU,theopticalOFDMsignalisdemodulatedwithdirectdetection,andy-polarizationsignalismodulatedforupstreamon-offkeying(OOK)dataat5Gbit/s.SimulationresultsshowthatthepowerpenaltyisnegligibleforbothopticalOFDMdownstreamandtheon-offkeyingupstreamsignalsafterover50kmsingle-modefiber(SMF)transmission.
简介:Gettingalongwiththeimprovementofgreencommunications,theenergyefficiency(EE)ofwirelessnetworkbecomesmoreandmoreimportant.However,inmulti-relay-assistedsystems,therelatedworkobviouslydependsontheend-to-endperformance,whereasEEofrelayshasnotattractedenoughattention.Theauthorsproposeanorthogonalfrequencydivisionmultiplexing(OFDM)multi-relaysystembasedonamplifyandforward(AF)mode.TakingincorporatingEEandremainingenergyasfactor,decisioncriteriaofattendingcooperationisdesigned.TheEEbasedasynchronouspoweriterationmethodispresented,andtheexistenceandconvergenceofnashequilibrium(NE)isproven.Furthermore,ajointalgorithminsubcarrierpairing,relayselectionandpowerallocationisgiven.Geneticalgorithm(GA)anditerationmethodareintegratedtoimprovetheconvergencespeedadditionally.SimulationdemonstratestheobviousimprovementofEE,decreaseofpowerconsumptionandincreaseoflifetimeinrelaysofthisalgorithmwiththeconstraintofminimumdatatransmissionrate.
简介:Weproposeajointnonlinearelectricalequalizationapproachincoherentopticaldiscrete-Fourier-transformspreadorthogonal-frequency-division-multiplexing(DFT-spread-OFDM)systemswithpolarizationdivisionmultiplexing(PDM).ThismethodisbasedonanadaptiveVolterraseriesexpansionfornonlineardistortionsoftwoorthogonalpolarizations.Thenonlinearelectricalequalizationisvalidatedthroughnumericalsimulationof100-Gb/squadraturephaseshiftkeyingand200-Gb/s16quadratureamplitudemodulationPDMDFT-spread-OFDMsystems.
简介:H-infinityestimatorisgenerallyimplementedintimevariantstate-spacemodels,butitleadstohighcomplexitywhenthemodelisusedformultipleinputmultipleoutputwithorthogonalfrequencydivisionmultiplexing(MIMO-OFDM)systems.Thus,anH-infinityestimatorovertime-invariantsystemmodelsisproposed,whichmodifiestheKreinspaceaccordingly.InordertoavoidthelargematrixinversionandmultiplicationrequiredineachOFDMsymbolfromdifferenttransmitantennas,expectationmaximization(EM)isdevelopedtoreducethehighcomputationalload.JointestimationovermultipleOFDMsymbolsisusedtoresistthehighpilotoverheadgeneratedbytheincreasingnumberoftransmitantennas.Finally,theperformanceoftheproposedestimatorisenhancedviaanangle-domainprocess.Throughperformanceanalysisandsimulationexperiments,itisindicatedthattheproposedalgorithmhasabettermeansquareerror(MSE)andbiterrorrate(BER)performancethantheoptimalleastsquare(LS)estimator.JointestimationovermultipleOFDMsymbolscannotonlyreducethepilotoverheadbutalsopromotethechannelperformance.Whatismore,anobviousimprovementcanbeobtainedbyusingtheangle-domainfilter.
简介:以Matlab7.0为平台,结合IEEE802.11a协议,对OFDM系统进行建模仿真,主要包括发射机,无线信道模型以及接收机三部分。本文分析了不同传输模式及参数选择对OFDM系统性能的影响,比较仿真结果,可知系统的误比特率与传输的调制方式、编码速率有关。