简介:在无线局域网(WLAN)势头正劲之际,最近又出现了无线城域网(MAN)技术。与为无线局域网制定802.11标准一样,IEEE为无线城域网推出了802.16标准,同时业界也成立了类似WiFi联盟的WiMAX论坛。无线城域网技术为何会紧跟WLAN之
简介:Themediumaccesscontrol(MAC)protocolforindoorvisiblelightcommunication(VLC)withenergyharvestingisexploredinthispaper.Theunfairnessofthroughputexistsamongdevicesduetothesignificantdifferenceoftheirenergyharvestingrateswhichchangeswithdistance,acceptanceangleandtheobstructionprobability.Weproposeanenergyharvestingmodel,anewobstructionprobabilitymodelandanenergyadaptivecontentionalgorithmtoovercometheunfairnessproblem.Thisdevicecanadjustitscontentionwindowaccordingtotheenergyharvestingrate.Asaresult,thedevicewithlowerenergyharvestingratecangetshortercontentionwindowtoimproveitstransmissionopportunity.SimulationresultsshowthatourMACprotocolcanachieveahigherdegreeoffairness.
简介:Backoffmechanismisakeycomponentofcontention-basedmediumaccesscontrol(MAC)layerprotocol.IthasbeenshownthatthebackoffmechanismofIEEE802.11standardmaybeveryinefficientespeciallywhenthenetworkiscongested.Numbersofmethodshavebeenproposedtotunethecontentionwindow(CW)withtheaimtoachievetheoptimalthroughputinIEEE802.11WLANs.However,themechanismsdonotspecificallyaddresspropersettingsforthevariablepacketlengthinfluenceandCWdivergingproblem.Thispaperproposesanovelfour-wayhandshakingfull-feedbackbackoffalgorithmnamedadoptivecontentionwindowbackoff(ACWB)toovercomethesedrawbacks.Theperformanceoftheproposedalgorithmisinvestigatedthroughanalysisandsimulation.SimulationresultsdemonstratethattheACWBalgorithmprovidesaremarkableperformanceimprovementintermsofshort-termfairness,packetdelayanddelayjitter,whilemaintaininganoptimalthroughputclosetothetheoreticalthroughputlimitoftheIEEE802.11distributedcoordinationfunction(DCF)accessscheme.
简介:Coexistenceandinteroperabilitybetween20MHzand40MHzdeviceandmodesofop-erationsarestressedinstandardIEEE802.11nsystem.Itismandatetoreportthebothsub-channelsstatestoMediumAccessControl(MAC)atreceiver,sincefor40MHzdevice,itshouldservenotonly20MHzbutalso40MHzsignalsreceiving.Bothenergydetectionandcarriersenseareemployedtodetectchannelstate.Inthecaseof20/40Mmode,thepowerdifferencebetweenthetwosub-channelsisalsodetectedinordertoreportthechannelstateaccurately.Thesimulationresultsdemonstratethattheperformanceoftheproposedmethodsaremuchbetterthanthemethodswhichjustemployenergydetection.Besides,thesimulationresultsshowthattheproposedmethodsensurethatthechannelsensingisnotaroadblockofIEEE802.11nsystemdesign.
简介:27-30September2011,Chengdu,Chinahttp://www.icsgce.com/2011IEEEInternationalConferenceonSmartGridandCleanEnergyTechnologies(IEEEICSGCE2011)willbeheldinSeptember27-30,2011inChengdu,China.IEEEICSGCE2011issponsoredbytheInstituteofElectricalandElectronicEngineers(IEEE),Journal
简介:AnovellinkadaptationschemeusinglinearAutoRegressive(AR)modelchannelestimationalgorithmtoenhancetheperformanceofautorateselectionmechanisminIEEE802.11gisproposed.ThisschemecanovercomethelowefficiencycausedbytimeintervalbetweenthetimewhenReceivedSignalStrength(RSS)ismeasuredandthetimewhenrateisselected.Thebestrateisselectedbasedondatapayloadlength,frameretrycountandtheestimatedRSS,whichisestimatedfromrecordedRSSs.Simulationresultsshowthattheproposedschemeenhancesmeanthroughputperformanceupto7%,insaturationstate,andupto24%infiniteloadstatecomparedwiththosenon-estimationschemes,performanceenhancementsinaveragedroprateandaveragenumberoftransmissionattemptsperdataframedeliveryalsovalidatetheeffectivenessoftheproposedscheme.
简介:IEEE802.16d通讯标准使用直角的频率部门multiplexing(OFDM)。在广泛地使用的OFDM系统,快Fourier变换(快速傅里叶变换)和反的快Fourier变换对被用来调制并且使解调副载波上的数据星座。在这份报纸,为OFDM调节的人和解调器的高效快速傅里叶变换的高级实现被介绍。设计在Verilog被编码了并且指向了可编程的门数组进XilinxSpartan3地。Radix-22算法被建议并且为OFDM通讯系统使用了。FFT的设计被实现并且适用于固定WiMAXIEEE802.16dcommuni-阳离子标准。结果被公布,硬件参数被比较。建议体系结构在使用的multipliers的数字是最少的,到在蝮蛇的数字的最少的存储器尺寸,和秒使用。