简介:针对低密度校验码(LDPC)的硬判决位翻转(Bit—Flipping,BF)译码性能不佳的问题,文中在BF算法的基础上提出了一种新的判据计算方法,通过将BF算法中的判据加入迭代过程,改善了译码性能。计算机仿真结果显示,与BF算法相比,修改的IterateF-BF算法对低列重LDPC码有明显的译码改善。
简介:Anovelschemeemployinglow-densityparity-check(LDPC)codesinatmosphericopticalcommunicationsystemisproposed.Wedeploycoherentdetectionatthereceivingsideintheproposedscheme.Toreducebiterrorrate(BER)andenhancethesystemperformance,LDPCcodesareexploitedandcoherentreceiverisusedtoimprovethereceivingsensitivity.Experimentsareimplementedtoevaluatetheperformanceofthetransmissionsystem.Theatmosphericchannelattenuationsaresetto20-30dB/km.ThecoherentdetectionwithLDPCcodescanreducethereceivedpowerrequirementby~4dBmattheBERof10-9.
简介:Thesingle-carrierblocktransmission(SCBT),a.k.a.,single-carrierfrequency-domainequalization(SC-FDE),isbeingconsideredasanoptiontechniqueforthewirelesspersonalareanetwork(WPAN)operatingat60GHz.Itisfoundthatforresidentialenvironment,innon-line-of-sight(NLOS)multi-pathchannels,theSCBTismuchmoreeffectivetocombattheinter-symbolinterference(ISI)comparedwithorthogonalfrequencydivisionmultiplexing(OFDM).Low-densityparity-check(LDPC)codesareaclassoflinearblockcodeswhichprovidenearcapacityperformanceonalargecollectionofdatatransmissionandstoragechannelswhilesimultaneouslyadmittingimplementabledecoders.TofacilitateusingLDPCcodesforSCBTsystem,anewlog-likelihoodratio(LLR)calculationmethodisproposedbasedonpilotsymbols(PS).GolaySequenceswhosesumautocorrelationhasauniquepeakandzerosidelobeareusedforcreatingthePS.ThepositionandlengthofthePSarenotfixedinthedatablocks.ThesimulationresultsshowthattheproposedmethodcansignificantlyimprovetheLDPCdecodingperformanceinSCBTsystem.Thisisverypromisingtosupportultrahigh-data-ratewirelesstransmission.
简介:AclassofQuasi-SystematicBlock-CirculantLow-DensityParity-Check(QSBC-LDPC)codesisproposed.Block-circulantLDPCcodeshavebeenstudiedalotrecently,becausethesimplestructuresoftheirparity-checkmatricesareveryhelpfultoreducetheimplementationcomplexities.QSBC-LDPCcodesarespecialblock-circulantLDPCcodeswithquasi-systematicparity-checkma-trices.ThememoriesforencodersofQSBC-LDPCcodesarelimited,andtheencodingprocesscanbecarriedoutinasimplerecursivewaywithlowcomplexities.ResearchesshowthattheQSBC-LDPCcodescanprovideremarkableperformanceswithlowencodingcomplexities.
简介:ThislettergivesarandomconstructionforLowDensityParityCheck(LDPC)codes,whichusesaniterativealgorithmtoavoidshortcyclesintheTannergraph.TheconstructionmethodhasgreatflexiblechoiceinLDPCcode'sparametersincludingcodelength,coderate,theleastgirthofthegraph,theweightofcolumnandrowintheparitycheckmatrix.ThemethodcanbeappliedtotheirregularLDPCcodesandstrictregularLDPCcodes.Systemiccodeshavemanyapplicationsindigitalcommunication,sothisletterproposesaconstructionofthegeneratormatrixofsystemicLDPCcodesfromtheparitycheckmatrix.Simulationsshowthatthemethodperformswellwithiterativedecoding.
简介:ThispaperproposestheLowDensityParityCheck(LDPC)codedFilteredMultiTone(FMT)systemswithhigh-ordermodulationforthehighdataratereliabletransmissionoverfrequencyselectivefadingchannel.ForthepurposeofaccomplishingsoftinputsoftoutputiterativedecodingofLDPCcodes,anewsoftdecisionmetricgenerationmethodisproposed,whichobviatestheneedofthenoisevarianceestimation,forM-PSK/M-QAM-typehigh-ordermodulationoverfrequencyselectivefadingchannel.Computersimulationindicatesthat,thereisnoperformancelosswithournewmetric,butthecomplexityofimplementationisreduced,andthattheLDPCcodesareeffectivetoimprovetheBitErrorRate(BER)ofFMTinfrequencyselectivefadingchannel.
简介:Aconstructionmethodbasedonthep-planetodesignhigh-girthquasi-cycliclow-densityparity-check(QC-LDPC)codesisproposed.Firstlythegoodpointsineverylineofthep-planecanbeascertainedthroughfilteringthebadpoints,becausethedesignedparity-checkmatrixesusingthesepointshavetheshortcyclesinTannergraphofcodes.Thenoneofthebestpointsfromtheresidualgoodpointsofeverylineinthep-planewillbefound,respectively.Theoptimalpointisalsosingledoutaccordingtothebiterrorrate(BER)performanceoftheQC-LDPCcodesatlast.ExplicitnecessaryandsufficientconditionsfortheQC-LDPCcodestohavenoshortcyclesarepresentedwhichareinfavorofremovingthebadpointsinthep-plane.Sincepreventingtheshortcyclesalsopreventsthesmallstoppingsets,theproposedconstructionmethodalsoleadstoQC-LDPCcodeswithahigherstoppingdistance.
简介:InordertoimprovethevideotransmissionperformanceinMultiple-InputMultiple-OutputOrthogonalFrequencyDivisionMultiplexing(MIMO-OFDM)system,anewscheme,whichintegratesMultipleDescriptionCoding(MDC),LowDensityParityCheck(LDPC)codingandhybridspacetimecoding,isproposedinthisletter.Inparticular,ahybridspacetimecodingalgorithmiscombinedwithLDPCcodestoperformUnequalErrorProtection(UEP)ofMDCencodedvideostreams.ComparingwiththeUEPtransmissionwithonlyLDPCcodes,theproposedschemeachievesmorethan1dBgainintermsofSignaltoNoiseRatio(SNR)whenthePeakSignaltoNoiseRatio(PSNR)ofreconstructedvideoisabove30dB.
简介:Inordertomeettheneedsofhigh-speeddevelopmentofopticalcommunicationsystem,aconstructionmethodofquasi-cycliclow-densityparity-check(QC-LDPC)codesbasedonmultiplicativegroupoffinitefieldisproposed.TheTannergraphofparitycheckmatrixofthecodeconstructedbythismethodhasnocycleoflength4,anditcanmakesurethattheobtainedcodecangetagooddistanceproperty.Simulationresultsshowthatwhenthebiterrorrate(BER)is10-6,inthesamesimulationenvironment,thenetcodinggain(NCG)oftheproposedQC-LDPC(3780,3540)codewiththecoderateof93.7%inthispaperisimprovedby2.18dBand1.6dBrespectivelycomparedwiththoseoftheRS(255,239)codeinITU-TG.975andtheLDPC(32640,30592)codeinITU-TG.975.1.Inaddition,theNCGoftheproposedQC-LDPC(3780,3540)codeisrespectively0.2dBand0.4dBhighercomparedwiththoseoftheSG-QC-LDPC(3780,3540)codebasedonthetwodifferentsubgroupsinfinitefieldandtheAS-QC-LDPC(3780,3540)codebasedonthetwoarbitrarysetsofafinitefield.Thus,theproposedQC-LDPC(3780,3540)codeinthispapercanbewellappliedinopticalcommunicationsystems.
简介:鉴于伪周期的低密度的同等值检查(QC-LDPC)的编码复杂性编码的问题,高,最小的距离不足够大它导致错误修正表演的降级,基于完成式,周期的差别设置的新不规则的type-IIQC-LDPC代码(CDS)被构造。这些type-IIQC-LDPC代码的同等值检查矩阵与0的重量由零个矩阵组成,有1的重量的circulant排列矩阵(CPM)和有2的重量(W2CMs)的circulant矩阵。在同等值检查矩阵的W2CMs的介绍使完成能改进错误的更大的最小的距离可能--代码的修正性能。这些代码的更黝黑的图没有girth-4,因此,他们有优秀译码集中特征。另外,因为同等值检查矩阵有伪双的斜结构,快编码算法能有效地减少编码复杂性。新type-IIQC-LDPC编码的模拟结果表演能完成更优秀的错误修正表演并且没在添加剂白人Gaussian噪音(AWGN)上有错误地板现象有和产品算法(矿泉)的隧道反复的译码。
简介:在这份报纸,我们比较了联合网络隧道编码的表演(JNCC)为多点传送当独占时,用低密度同等值支票(LDPC)的继电器网络作为隧道代码编码,Convolutional编码或(XOR)编码的网络在中间的继电器节点使用了。多点传送继电器传播是二个固定继电器节点在第二在作出贡献的传播计划的一种类型在基础收发器车站(BTS)和一双活动车站之间的端对端的传播跳跃。我们认为一个方法和二个方法多点传送评估位错误率(BER)和产量性能的情形。是否使用XOR网络在中间的继电器节点编码,被看了那,一样的传播因此在更少的时间槽变得可能产量性能能被改进。而且我们也在建议系统模型,差异和multiplexing获得在被考虑了讨论了二种可能的情形。它值得通知那BER和产量为LDPC代码完成了比对讨论的所有计划的Convolutional代码好。
简介:Low-DensityParity-Check(LDPC)codeisoneofthemostexcitingtopicsamongthecodingtheorycommunity.Itisofgreatimportanceinboththeoryandpracticalcommunicationsovernoisychannels.ThemostadvantageofLDPCcodesistheirrelativelylowerdecodingcomplexitycomparedwithturbocodes,whilethedisadvantageisitshigherencodingcomplexity.Inthispaper,anewap-proachisfirstproposedtoconstructhighperformanceirregularsystematicLDPCcodesbasedonsparsegeneratormatrix,whichcansignificantlyreducetheencodingcomplexityunderthesamede-codingcomplexityasthatofregularorirregularLDPCcodesdefinedbytraditionalsparseparity-checkmatrix.Then,theproposedgenerator-basedsystematicirregularLDPCcodesareadoptedascon-stituentblockcodesinrowsandcolumnstodesignanewkindofproductcodesfamily,whichalsocanbeinterpretedasirregularLDPCcodescharacterizedbygraphandthusdecodediteratively.Finally,theperformanceofthegenerator-basedLDPCcodesandtheresultantproductcodesisinvestigatedoveranAdditiveWhiteGaussianNoise(AWGN)andalsocomparedwiththeconventionalLDPCcodesunderthesameconditionsofdecodingcomplexityandchannelnoise.