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南京邮电大学通达学院毕业设计论文外文资料翻译学院 通达学院 专 业 网络工程 学生姓名 班级学号 外文出处SimulationofTime-VaryingFrequency-SelectiveMultipathFadingChannelsforSpread-SpectrumW__eforms附件
1.外文资料翻译译文;
2.外文原文指导教师评价1.翻译内容与课题的结合度□优□良□中□差2.翻译内容的准确、流畅□优□良□中□差3.专业词汇翻译的准确性□优□良□中□差4.翻译字符数是否符合规定要求□符合□不符合 指导教师签名 年 月 日附件1外文资料翻译译文ASP.NET中认证安全特征评述NarcisioTumushabe谭冠正音译中南大学计算机科学与信息技术学院湖南长沙410083摘 要:一个适用于任意的扩频信道模拟器传输任意随时间变化的波形,频率选择性多径瑞利衰落渠道的__和实施都多普勒(或时间)的多样性和延迟(或频率)多样性被认为是在信道模型的siinuhtor是根据的信道被假定为是一个随时间变化的服从不相关的高斯信道,散射的假设模型由多个多普勒频移的分支抽头延迟线没有假设是由__的通道水龙头仿真结果为平坦慢衰落,平快衰落,频率选择性慢衰落和频率选择快衰落的例子给出1介绍多径衰落的一种现象,介绍了__通过在多个所引起的失真的干扰传播路径上的通信信道很好一种时变多径衰落信道的例子是__无线通信信道在__无线__道,多径传播时发生的__从周围的物体反射,和相对运动发射机和接收机之间的介绍在通道中,表现为随时间的变化多普勒展宽谱中的多径组件模拟多径的最准确的方法衰落信道的使用实际记录的条宽带信道测量然而,由于系统性能分析的复杂性记录的数据,从理论上推导了信道模拟器原则是感兴趣的,特别是用于系统性能评价[我]最常见的统计研究人员使用的信道模型是广义的固定不相关的散射(WSSUS)模型贝洛
[2]先前设计[模拟器,3-81主要是定制的WSSUS信道的特殊类型在本文中__的模拟器进行了改进在几个方面首先,它是一个通用的信道模拟器具有对信道衰落的选择没有限制参数没有假设结构的信道散射函数或发送的__任意定义的散射函数__波形被提供给模拟器__tlab的M文件形式其次,信道模型该模拟器是基于采用多普勒(或时间)的多样性和延迟(或频率)的多样性为了消除信道抽头的时间变化一个符号间隔内此外,虽然传统的连续时间非相干散射采用的假设是,没有假设在等效tapdelay信道抽头的__性信道模型那是,实际的协方差的信道抽头结构的计算和应用最后,而不是生成的信道的信封输出,该模拟器产生的复杂多样的价值的通道输出通道上保存的相位失真在本文中,我们讨论的设计与实现的模拟和演示的性能对几种多路模拟数据传输渠道本文的__如下通道模型,给出了模拟器的基础2节,和模拟器的实现在3节中简要的讨论仿真结果演示的信道模拟器的性能在第4节最后,在第5节中,我们讨论未来的工作和目前的一些总结2信道模型所考虑的基带信道建模作为一个随时间变化的复值随机过程,其中,表示的输出由于一个脉冲在时间f的信道在时间发送据推测,是一个零均值,复高斯随机过程是,固定在t,满足非相关散射假设,即,其中一个横杠表示复共轭,代表平均输出功率的信道和(t)是Dirac函数[9,10]如果一个基带__单侧带宽CL通过低通脉冲信道传输响应,然后不加性噪声,低通通道输出的R(t)是由其中是H(R),一个fiinction的的投影,到带宽限制的功能的空间的间隔
[11]假设的__也是有限的时间到的时间间隔[0,T],我们得到其中,x,数,(r)=eiNJ/Tx的(t)表示的原始__多普勒频移由n/T的赫兹,和表示的傅里叶变换,相对于所述变量t,突起相关的空间上的时间有限的时间间隔[0,T]的功能关于二阶在规定的假设过程克,的结构将是零均值复杂KITRŢ高斯随机变量另外,如果散射功能(实质上)有限时间区间[0,]和带限的时间间隔,只有有限的水龙头将有非零的差异在特别是,最大值所需的k是约和最大的n值需要的是约N=待定相当于tapdelay线模型的信道在图1中示出以下请注意,对于在区间[O,T],它代表一个任意码元周期中,信道是完全其特征在于由该矢量的信道抽头这意味着,在任何符号的信道行为时间间隔可以是通过生成一个实现了模拟高斯随机向量克如果我们假设信道解相关在一个符号间隔(TBdI),然后多个符号的时间间隔可以通过产生模拟多个__的实现的向量网络连接在为了做到这一点,我们首先需要确定R.的协方差结构测定必要的协方差结构很简单,但繁琐的为方便起见,我们简单地总结协方差的结果在下面的散射函数(T,H)的通道等价表示可以中给出的二维傅里叶变换的散射函数,它代表了间隔时间,间隔频率的相关函数的通道3实施问题在本节中,我们先简要地说明实施该模拟器使用__TLAB以下变量需要来自用户的输入文件名定义传输__的功能(符号波形),发射的__的持续时间(T),假设发送的__的带宽(Q),文件名的功能定义通道散射功能,0假设信道多普勒扩展(BD),假设信道时延扩展(TNR)数量多普勒分支模拟(2N+l)中,数延迟抽头模拟(K+1),使用预先计算好的水龙头-协方差矩阵的选项(Z)或计算一个新的该程序会自动生成输出采样的输出__的奈奎斯特速率为了确定用于输出__的奈奎斯特速率,该程序必须结合上的通道的扩展的影响发送的__片面带宽发送的__是0渠道传播的2xBd=2XN/T.因此,发送__片面的总带宽是氯=R+RNIT为了达到奈奎斯特速率,采样频率必须至少2倍的速度比的输出__的带宽,这是程序加载存储的自来水协方差矩阵或计算一个新的抽头-协方差矩阵,这取决于由用户选择的选项如果是后者的选项被选择,该方案将计算协方差矩阵数值使用方程(
2.1)—(
2.4)和散射中定义的所提供的功能的功能用户该程序的其余部分产生一个单独为每个发射符号矢量输出然后结合单独的输出矢量,表示总的信道输出到一个输出流,包括任何的符号间干扰为了完成此时,程序首先生成信道抽头vectorfi在下面的一个特定符号的输入时尚一个复杂的零均值高斯随机向量和协方差矩阵I产生将所得的复高斯矢量乘以抽头-协方差矩阵的平方根产生信道抽头实现抽头产生后,该程序计算根据输出样本最后,将样品对应于当前符号被添加到适当的位置在通道的输出缓冲器4仿真结果在本节中,我们提出了几个例子说明新的信道模拟器的性能所有的结果dikcussed这部分对应于简单的直接序列码分多—存取波形组成的序列矩形芯片波形所有的扩频码是随机生成的码片持续时间和传播增益取决于信道的特征模拟1毫秒一个符号持续时间所有信道的假设,和信道的散射功能被认为有以下的高斯参数形式在stvtul=SDT,信道衰落参数四个案例说明在这里了表1-为每个四例仿真结果在图5给出了这些数字表明,该仿真结果与预期渠道吻合下的衰落的情况下考虑的行为5结论与未来工作以前__的多径衰落模拟器通道,主要设计用于特定类型的通道通过将多普勒和延迟在模拟器的设计以及正确的多样性模拟信道抽头之间的相关性,一般用途多径模拟器已经研制成功几个不同的衰落情况下的模拟结果同意与预期的通道的行为,从而验证模拟器的正确性目前执行的模拟器假设在一个符号中的信道行为解相关间隔因此,它是必要的使用很长的符号的时间间隔准确地模拟慢衰落特性使用模拟器的复杂性,并建立不必要的高计算复杂度当前工作的重点是提高sirnulator模型正确符号间隔之间的相关性____:
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2001.附件2外文原文SimulationofTime-VaryingFrequency-SelectiveMultipathFadingChannelsforSpread-SpectrumW__eformsLei-LeiLockCaden__DesignSystemsSanJoseCAXiangmingKongandRichardJ.BartonElectricalandComputerEngineeringDepartmentIowaStateUniversityAmesIA50011Abstract:Achannelsimulatorappropriateforarbitraryspreadspectrumw__eformstran__ittedoverarbitrarytimevaryingfrequency-selectivemultipathRayleighfadingchannelshasbeendevelopedandimplemented.BothDopplerortimediversityanddelayorfrequencydiversityareconsideredinthechannelmodelonwhichthesimulatorisbased.ThechannelisassumedtobeatimevaryingGaussianchannelthatobeystheuncorrelatedscatteringassumption.ThemodeldevelopedconsistsofmultipleDoppler-shiftedbranchesoftap-delaylines.Noassumptionsare__deabouttheindependen__ofchanneltaps.Simulationresultsforflatslowfadingflatfastfadingfrequency-selectiveslowfadingandfrequencyselectivefastfadingexamplesarepresented
1.IntroductionMultipathfadingisaphenomenonthatdescribessignaldistortioncausedbyinterferen__amongmultiplepropagationpathsonacommunicationchannel.Agoodexampleofatime-varyingmultipathfadingchannelisthemobileradiocommunicationchannel.Inamobileradiochannelmultipathpropagationoccursasthesignalisreflectedfromsurroundingo__ectsandtherelativemotionbetweenthetran__itterandthere__iverintrodu__stemporalvariationinthechannelthatis__nifestedasaDopplerspreadinthespectrumofthemultipathcomponents.Themostaccuratemethodofsimulatingmultipathfadingchannelsistouserecordedstripsofactualwidebandchannelmeasurements.Howeverduetothecomplexityof____yzingsystemperfor__n__usingrecordeddatachannelsimulatorsderivedfromtheoreticalprinciplesareofinterestparticularlyforuseinsystemperfor__n__evaluation[I].Themostcommonstatisticalchannelmodelusedbyresearchersisthewide-sensestationaryuncorrelatedscattering.Simulatorsdesignedpreviously[l3-81werepri__rilytailoredforparticulartypesofWSSUSchannels.Thesimulatordevelopedinthispaperisimprovedinseveralrespects.Firstlyitisageneralpurposechannelsimulatorwithnoconstraintonthechoi__ofchannelfadingparameters.Noassumptionsare__deregardingthestructureofthechannelscatteringfunctionorthetran__ittedsignal.Arbitrarilydefinedscatteringfunctionsandsignalingw__eformsareprovidedtothesimulatorintheformof__tLabm-files.SecondlythechannelmodelonwhichthesimulatorisbasedincorporatesbothDopplerortimediversityanddelayorfrequencydiversityinordertoeliminatetemporalvariationofthechanneltapswithinasinglesymbolinterval.Furthermorealthoughtheconventionalcontinuous-timeuncorrelatedscatteringassumptionisadoptednoassumptionis__deregardingtheindependen__ofchanneltapsintheequivalenttapdelaychannelmodel.Thatistheactualcovarian__structureofthechanneltapsiscomputedandutilized.Finallyinsteadofgeneratingtheenvelopeofthechanneloutputthesimulatorgeneratescornplexvaluedchanneloutputtopreservethephasedistortiononthechannel.Inthispaperwediscussthedesignandimplementationofthesimulatoranddemonstrateitsperfor__n__bysimulatingdatatran__issiononseveralmultipathchannels.Thepaperisorganizedasfollows.ThechannelmodelonwhichthesimulatorisbasedispresentedinSection2andtheimplementationofthesimulatorisdiscussedbrieflyinSection
3.Simulationresultsdemonstratingtheperfor__n__ofthechannelsimulatorarepresentedinSection
4.FinallyinSection5wediscussfutureworkandpresentsomeconcludingre__rks.
2.ChannelModelThebasebandchannelunderconsiderationismodeledasatime-varyingcomplex-valuedrandompro__ss{h7;r1720rER}whereh7;rrepresentstheoutputofthechannelattimefduetoanimpulsetran__ittedattimet-r.Itisassumedthath.r;risazeromeancomplexGaussianrandompro__ssthatiscausalin7stationaryintandsatisfiestheuncorrelatedscatteringassumption;i.e.whereanoverbarindicatescomplexconjugation$representsthe__eragepoweroutputofthechanneland8tistheDiracdeltafunction[9IO].Ifabasebandsignalxrwithone-sidedbandwidthClistran__ittedthroughachannelwithlow-passimpulseresponseh.t;tthenignoringadditivenoisethelow-passchann-eloutputrrisgivenbywhereiT;fistheprojectionofh~;rasafiinctionofTontothespa__offunctionsbandlimitedtotheinterval[-flfl][l
11.Assumingthesignalisalsotime-limitedtotheinterval[0TIwegetwherexr=eiNJ/TxtrepresentstheoriginalsignalDopplershiftedbyn/THzandrepresentstheFouriertransformwithrespecttothevariablefoftheprojectionofhr;r+Tontothespa__offunctionstime-limitedtotheinterval[0TI.Underthestatedassumptionscon__rningthesecondorderstructureofthepro__ssgT;rthetapsk=-RAxk.znwillbezero-meancomplexKITRTGaussianrandomvariables.Furthermoreifthescatteringfunctionisessentiallytime-limitedtotheinterval[0T]andbandlimitedtotheinterval[-2rtBd2xBd]onlyfinitely__nyofthetapswillh__enonzerovarian__.Inparticularthe__ximumvalueofkrequiredisapproxi__telyK=RT/xandthe__ximumvalueofnrequiredisapproxi__telyN=TBd.TheequivalenttapdelaylinemodelofthechannelisillustratedinFigure1below.Figure
1.ThetapdelaystructureofthechannelNoti__thatfortheinterval[OT]whichrepresentsanarbitrarysymbolperiodthechanneliscompletelycharacterizedbythevectorofchanneltapsThisimpliesthatthechannelbeh__iorduringanysymbolintervalcanbesimulatedbygeneratingarealizationoftheGaussianrandomvectorg.IfweassumethatthechanneldecorrelatesoveronesymbolintervalTBdIthenmultiplesymbolintervalscanbesimulatedbygeneratingmultipleindependentrealizationsofthevectorfi.Inordertoaccomplishthiswefirstneedtodeterminethecovarian__structureofR.Thedeterminationofthene__ssarycovarian__structureisstraightforwardbuttedious.Forconvenien__wesimplysum__rizethecovarian__resultsbelowintermsofthescatteringfunctionsT;hofthechannel.Anequivalentrepresentationcanbegivenintermsofthetwo-dimensionalFouriertransformofthescatteringfunctionwhichrepresentsthespa__d-timespa__d-frequencycorrelationfunctionofthechannel.Ifk=1andm=n
3.ImplementationIssuesInthissectionweexplainbrieflytheimplementationofthesimulatorusing__tLab.Thefollowingvariablesarerequiredasinputfromtheuser:Filenameoffunctiondefiningtran__ittedsignalsymbolw__eformDurationoftran__ittedsignalTAssumedbandwidthoftran__ittedsignalQFilenameoffunctiondefiningchannelscatteringfunction0AssumedchannelDopplerspreadBdAssumedchanneldelayspreadTnrNumberofDopplerbranchessimulated2N+lNumberofDelaytapssimulatedK+1Optionofusingprecomputedtap-covarian____trixZorcomputinganewone.Theprogramauto__ticallygeneratesoutputsamplesattheNyquistrateoftheoutputsignal.TodeterminetheNyquistratefortheoutputsignaltheprogrammustincorporatethespreadingeffectsofthechannelonthetran__ittedsignal.Theone-sidedbandwidthofthetran__ittedsignalis
0.Thechannelspreadsthetran__ittedsignalby2xBd=2xN/T.Thereforethetotalone-sidedbandwidthisCl=R+RNIT.ToreachNyquistratewemustsampleatleasttwotimesfasterthantheoutput-signalbandwidthwhichis-=It-=xx/QxxR+-N1+-NTTRTheprogramloadsastoredtap-covarian____trixorcalculatesanewtap-covarian____trixdependingontheoptionselectedbytheuser.Ifthelatteroptionischosentheprogramwillcomputethecovarian____trixnumericallyusingEquations
2.1-
2.4andthescatteringfunctionasdefinedinthefunctionprovidedbytheuser.There__iningportionoftheprogramgeneratesavectorofoutputforeachtran__ittedsymbolindividuallyandthencombinestheindividualoutputvectorsintoanoutputstreamthatrepresentsthetotalchanneloutputincludinganyintersymbolinterferen__.Toaccomplishthistheprogramfirstgeneratesthechanneltapvectorfiforaparticularsymboloftheinputinthefollowingfashion:AcomplexGaussianrandomvectorwithmeanzeroandcovarian____trixIisgenerated.TheresultingcomplexGaussianvectorismultipliedbythesquarerootofthetap-covarian____trixtogeneratearealizationofthechanneltaps.AfterthetapsaregeneratedtheprogramcomputestheoutputsamplesaccordingtoFinallythesamplescorrespondingtothecurrentsymbolareaddedtotheappropriatelocationsinthechanneloutputbuffer.
4.SimulationResultsInthissectionwepresentseveralexamplesillustratingtheperfor__n__ofthenewchannelsimulator.Alloftheresultsdiscussedinthissectioncorrespondtothetran__issionof______direct-sequen__code-division-multiple-ac__ssw__eformsconsistingofsequen__sofrectangularchipw__eforms.Allspreadingcodeswererandomlygeneratedandthechipdurationandspreadinggainvariesdependingonthecharacteristicsofthechannelbeingsimulated.Asymboldurationof1millisecondwasassumedforallofthechannelsandthechannelscatteringfunctionwasassumedtoh__ethefollowingGaussian1771-parametricform:whereStVtul=SdT.Thechannelfadingparametersforeachofthefourcasesillustratedherearesum__rizedinTable
1.-ThesimulationresultsforeachofthefourcasesarepresentedinFigures2-
5.Asthesefiguresindicatethesimulationresultsagreewellwiththeexpectedchannelbeh__iorundereachofthefadings__nariosconsidered.
5.ConclusionsandFutureWorkPreviouslydevelopedsimulatorsformultipathfadingchannelsweredesignedpri__rilyforaparticulartypeofchannel.ByincorporatingbothDoppleranddelaydiversityinthesimulatordesignaswellascorrectlymodelingthecorrelationbetweenchanneltapsageneralpurposemultipathsimulatorhasbeendeveloped.Simulationresultsforseveraldifferentfadings__nariosagreewellwithanticipatedchannelbeh__iorandthusverifythecorrectnessofthesimulator.Thecurrentimplementationofthesimulatorassumesthatthechannelbeh__iordecorrelatesinonesymbolinterval.Hen__itisne__ssarytouseverylongsymbolintervalstoaccuratelysimulateslowfadingcharacteristics.Thiscomplicatesuseofthesimulatorandcreatesunne__ssarilyhighcomputationalcomplexity.Currentworkisfocusedonimprovingthesirnulatortomodelcorrectlythecorrelationbetweensymbolintervals.Referen__s:
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