简介：LDPC码是纠错码,在信道编码中,与RS码和Turbo码相比,其纠错能力是最好的,因此,对LDPC码的研究有很大的价值和意义。目前,已经广泛应用于深空通信、光纤通信和卫星数字视频等领域。

简介：基于Watterson短波信道模型，构建了Turbo码在短波信道下的设计和仿真方法。在高信噪比区域中，推导出了不同信道条件下Turbo码的性能界公式；在低信噪比区域中，用Matlab仿真了短波信道下不同的信道条件及Turbo码的主要设计参数对其性能的影响，并给出了Turbo码在短波信道下的设计参数，为实际工程中的应用提供参考。

简介：低密度奇偶校验（LDPC）码具有译码简单、抗衰落性能好的特点，成为未来宽带移动通信的信道编码研究热点之一。一类π旋转LDPC码利用双对角线校验矩阵克服了以往LDPC码编码复杂度高的缺点；同时由于LDPC码的随机性，码长越长，其等效交织效果越明显。为了提高信道频带利用率，本文利用准规则π旋转LDPC码设计了一种不采用交织的高阶编码调制方案。

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。

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简介：ThispaperpresentsapragmaticadaptiveschemeforTuCMoverslowlyfadingchannels.Theadaptiveschemeemploysasingleturbocodedmodulatorcomposedofavariable-rateturboencoderandavariable-ratevariable-powerMQAMforallfadingregions,soithasanacceptablecomplexitytoimplement.TheoptimaladaptiveTuCMschemeisdeterminedsubjecttovarioussystemconstraints.Simulationshavebeenperformedtomeasuretheperformanceoftheschemefordifferentparameters.Itisshownthatadoptingboththeturbocodedmodulatorandthetransmitpowerachievesaperformancewithin2.5dBofthefadingchannelcapacity.

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：介绍了基于turbo码的联合编码调制技术,结合turbo码、网格编码调制（TCM）、连续相位调制技术（CPM）,提出TurboTCM-8CPFSK的硬件实现方案,并将其应用于军用移动通信系统中以提高频谱利用率和抗干扰性能。

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：设计的一条改进欧几里德几何学的几何学途径伪周期(质量管理)有高率、低的错误地板的低密度的同等值检查(LDPC)代码被论述。构造QC-LDPC代码与高率比原来的代码有更低的错误地板。最小的重量codeword的分发被分析，并且最小的重量codeword的一个足够的存在条件被发现。很多QC-LDPC与更低的错误地板编码的模拟表演能被减少最小的重量codewords的数字设计令人满意这个足够的条件。

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：随着太空资源的研究与开发,深空通信技术受到越来越广泛的重视.空间数据系统咨询委员会（CCSDS）逐步为深空通信中遥控遥测及高级在轨系统（AOS）制定了一系列推荐性标准.介绍了深空通信信道研究的意义,其信道特点决定了低信噪比条件下信道码对深空通信可靠性的重要作用.分析了该标准中各类信道码技术,探讨了信道码性能,为该标准的工程应用提供参考.

简介：ThemultilevelmodulationtechniquesofM-DifferentialAmplitudePhaseShiftKeying(DAPSK)havebeenproposedincombinationwithTurbocodeschemefordigitalradiobroadcastingbandsbelow30MHzradiochannel.ComparisonofthismodulationmethodwithchannelcodinginanAdditiveWhiteGaussianNoise(AWGN)andmulti-pathfadingchannelshasbeenpresented.TheanalysisprovidesaniterativedecodingoftheTurbocode.

简介：短波战术数据链在现代战争中发挥着重要作用.针对短波时变多径信道特性,提出了一种基于信道估计的Turbo均衡算法.该算法在初次迭代时根据训练序列的自相关特性,采用快速相关信道估计算法估计信道初始状态,并进行基于线性最小均方误差（MMSE）的Turbo均衡;然后利用译码器反馈的软信息,采用最小均方（LMS）迭代信道估计算法优化信道估计值,并进行迭代均衡.仿真结果表明,该算法的误码率性能逼近于假定信道状态已知的Turbo均衡算法,对Turbo均衡在数据链中实际应用具有借鉴意义.