通信工程专业外语-unit13原文与翻译

Unit13与之比较Comparison betweenGSM andCDMA GSMCDMAUsing CDMA/FDD technology,subscribers of CDMA cellular mobile communication system cantransmittheir informationsimultaneously throughthe same channel.On theother hand,the GSMsystemadopts TDMA/FDD methodto transmitand distinguishinformation from different GSMmobilestations.In addition,in favorof QCELP arithmetic,RAKE receiver,power controland softswitchingetc.,CDMA showsmore advantagesin itssystem performancethan theGSM,such asgreateranti-interference capability,bigger systemcapacity,higher successfulconnection ratio,fewer off-linechances,low probabilityof interceptLPI,and soon.运用码分多址/频分双工技术，用户的蜂窝移动通信系统的传输信息的同时，通过同样的渠道另一方面，该系统采纳时分多址/频分双工传输的方法和识别信息从不同的移动台此外，有利于中国电信集团广州研发中心算术，耙式接收器，功率限制和软开关等，显示出更多的优势在码分多址系统性能比，如更高的抗干扰实力，更大的系统容量，连接胜利率较高,离线的机会少，低截获概率低截获概率，等功率限制和瑞克接收机1,Power Controland RAKEReceiverWhen differentsubscribers sendtheir informationto the same BSbase station,different signalpowercaused bydifferent transmittingdistances willconsequentially causeinterference witheach other,especially forthose MSsmobile station beingfar awayfrom BSwill beseriously disturbedbecause oftheiralmost submergedsignals bysignals of the close-to-BS MSs.

[2]pllOIn orderto solvethis problemand keephigh system performance,power control technique isintroducedin CDMAcommunication system,which can effectively overcomethis cross-disturbance.As one of thecore techniquesin CDMAcellular mobile communication system,power controlcanmake the signal powerfrom allsubscribers to the BSequivalent throughadjusting thetransmittingpower fromeach subscriber.为解决这一问题，保持较高的系统性能，功率限制技术介绍了码分多址通信系统，它可以有效地克服这作为一个核心技术在蜂窝移动通信系统的功率限制,可以使信号功率cross-disturbance从全部用户的学士学位相当于通过调整放射功率，从每个用户Power controlcan benot onlydivided toopen-loop controland closed-loop control,but alsotoforward downpower controland backwardup power control.For open-loop controlmethod,subscriber adjustsemitting poweraccording to the measuredframe errorprobability,while for theclosed-loop power control,basestationmeasures thesignal-to-noise ratioof receivedsignals and thenadjust thetransmitting powerof correspondingMS.功率限制不仅可以分为开环限制和闭环限制，而且还提出了下功率限制和反向功率限制上开环限制方法，用户调整放射功率依据测量帧错误概率，同时为闭环功率限制，基站测量接收信号的信噪比，然后调整放射功率相应的女士The backwardpowercontrolin CDMA system can be dividedinto twokinds ofcontroltechnique,the open-loop backwardpowercontrolonly usedby mobilestation,and theclosed-loop backwardpowercontrol thatcan beadopted byboth basestation andmobilestation.On theother hand,theforward powercontrol isjust usedto reduce the disturbancefrom smalladjacent districts.反向功率限制系统可分为开环限制技术，反向功率限制用的移动站，以及闭环反向功率限制,可以通过基站和移动站另一方面，正向功率限制是用来降低干扰小旁边的地区RAKE ReceptionTechnique（瑞克接收技术）Fading anddistortion areinevitable forsignals transmittedin mobilecommunication channelbecauseof theunideal characteristicsof channel,and thenmake badinfluence onsystem performance.变形是不行避开的衰落和信号传输的移动通信信道因为不志向的信道特性，进而会影响系统的性能The basictheory of RAKE reception technique is:by meansof collectingall transmittedsignals frommulti-path anduniting them,the receivedsignal powercan obtain aneffectiveenhancement,which canimprovethe outputSNR andsystemperformance.

[3]pllOThree,four RAKE receivers arerespectively setin eachMS,BS in CDMA systemin ordertoreceive thearriving branchsignal of the sameoriginal fromdifferent transmittingroutes,and thencombinethem toget anincrescent outputSNR aftertheir respectivelyindependent demodulation.Thus,in favorofRAKEreceptiontechnique,the disadvantageous factor thatsignal transmittedin multi-pathbecause anadvantageousfactorin CDMAcellular mobilecommunication system.三，四的耙式接收器分别设置于每一毫秒，在码分多址系统，以便接收到信号相同的原始分支从不同的传播途径，并结合他们得到一个增大的输出信噪比后分别独立解调因此，有利于瑞克接收方法，发送信号的不利因素，因为一个有利因素在多径码分多址蜂窝移动通信系统性能更好的码分多址2Better Performanceof CDMA更大的抗干扰实力Greater Anti-interference CapabilityBecauseof spread spectrum modulation,bandwidth ofusers signalis extremelybroadened by theassigned uniquepseudo-random sequence,thus themodulated broad band signalowns spectralpropertiesclose toGaussian whitenoise.Receiving thiskind ofspread spectrumsignal,all the CDMAreceivers tryto demodulateit usingPN sequencecreated locally,but onlyone receiverwith thesamelocal PN sequence asthat inthe receivedsignal canconvert thebroad bandnoise-like signalinto narrowbanduseful signal,while otherreceiver isstill theinsignificant broadbandnoise exceptthe relativedemodulatorwith theunique localPN sequence.由于扩频调制，带宽用户的信号是特别扩大的安排独特的伪随机序列，从而调制的宽带信号拥有光谱性能接近高斯白噪声接受这种扩频信号，全部的码分多址接收机尝试运用伪随机序列解调本地创建，但只有一个接收相同的本地伪码序列，在接收信号可以转换成宽带类噪声信号为窄带有用信号，而其他接收器仍旧是微乎其微的宽带噪声，除了相关解调器与当地独特的伪随机序列In addition,as faras thenarrow bandmeaningless signaladditive tothe receivedsignal by therelative receiverwith thesame uniquepseudo-random sequence,it ismodulated intobroad band signalwith extremelylessened power spectral density.Thus,the relativereceiver canfilter thebroad bandsignal from otherusers andmajority of the meaninglesssignal outofthe filter bandwidthjust throughanarrowband filter.Therefore,reservation inwithin thereceiver onlyconsists ofthe narrowbandusefulsignal andlittle meaninglesssignal withinthefilterbandwidth.As aconsequent result,the outputsignal-to-noise ratiois improvedlargely,that willnecessarily leads to greatersystem anti-interferencecapability.此外，至于窄带毫无意义的信号添加剂的接收信号的相对接收相同的独特的伪随机序列，它是调制成宽带信号的功率谱密度特别削减因此，相对接收器可以过滤宽带信号从其他用户和广阔的毫无意义的信号进行滤波器的带宽是通过窄带滤波器因此，保留在接收由窄带有用信号和小无意义的信号在滤波器的带宽作为一个必定结果，输出信噪比有较大的提高，这必定会导致更大的系统的抗干扰实力It can be provedthat the more highvalue ofBn/Bb,themoregreat systemanti-interferencecapability.由于扩频调制，带宽用户的信号是特别扩大的安排独特的伪随机序列，从而调制可以证明更高价值的更大的系统的抗干扰实力Bn/Bb,Bigger SystemCapacity andHigher SuccessfulAccess Ratio更大的系统容量和更高的接入胜利率Unlike theTDMA multi-access modein GSMmobilecommunication system,signal ofeachCDMA subscriberis distinguishedbytheassigned uniquePNsequencebased on theCDMAtechnology.Thus,each signalofCDMAsubscriber canbe transmittedsynchronously occupyingthe entiresub-channel bandwidthdivided from the FDDmethod.So underthe equalfrequency resourcecondition,in otherword,for thesamechannelbandwidth,capacity ofCDMA systemis4〜5times largerthan thatofGSM system.不同的是时分多址接入模式在移动通信系统中，信号的每个用户的特点是独特的伪随机序列的安排基于码分多址技术因此，每一个信号，用户可同步传输信道带宽占整个分从故障诊断方法所以在同等频率资源条件，换句话说，在同一信道带宽，码分多址系统容量为〜倍以上的系统45In thenature ofthings,a communicationsystem withbig capacitymust havehigh successfulaccessratio.在事物的性质，通信系统容量大，必需具备较高的接入胜利率In addition,using CELP Code ExcitedLinear Predictive arithmetic forvoice code,audio signalinCDMAsystem canbetransmitted withvariable speed,with themaximum CELPcoded audiosignaltransmitting velocityis

9.6kbit/s whilethe subscriberis talking,andtheminimum velocityof

1.2kbit/sfor theconversation pause.This techniquecalled VoiceActivation canreducethebackgrounddisturbance amongsubscribers communicatingon onechannel atthesametime,and enhancesthe systemcapacity.For GSMsystem,this VoiceActivation techniquecannot beused becauseofthesignaltransmitting delayat conversationpause.此外，利用线性预料码激励线性预料算法的语音编码，音频信号在码分多址系统可以传播速度可变，以最大线性预料编码的音频信号传输速率为比特每秒而用户说话，和最低速度的比特每

9.

61.2秒的谈话暂停这种技术称为语音激活能降低背景干扰用户间的通信在一个频道在同一时间，并提高了系统容量全球移动通讯系统，该语音激活技术无法运用，由于信号传输延迟谈话停顿更好的声音质量Better VoiceQualityUsing advancedCELPCodeExcited linearPredictivearithmeticfor itsdigital audiosignal code,and3RAKEreceiversinahandset toreceive signalsfromdifferentdirections simultaneously,it ismadeextremely abundantand dimensionalfor audiosignal spectrumfrom CDMAhandset.Furthermore,vocoder basedontheCELParithmeticinCDMAsystemcanadjust itstransmitting velocityand choosecorrespondingsending powerlevel automaticallyto reducethe disturbanceof noise.Thus,even underthecircumstance withloud noise,we canmake conversationof goodquality withoutany cacophony.采纳先进的线性预料码激励线性预料算法的数字音频信号的代码，在手机和接收机接收来自不3同方向的信号的同时:它是极其丰富和三维音频信号频谱从手机此外，声码器的线性预料算法在码分多址系统可以调整其传输速度和选择相应的发送功率电平自动削减噪声的干扰因此，即使在状况下的声音，我们可以把会话质量好无杂音下可能拦截低截获概率Lower Probablyof InterceptLPIIt isnecessary foreavesdropping somebodysconversion thatthe transmittedconversion informationmust be capturedand thendecoded.For CDMAsystem,signal withusers informationmustbespreadspectrum modulatedbefore senttothecommon channelwith extremelyspread spectrumand verylowpower spectraldensity.Thus it is toodifficult todetect thiskind ofCDMA signalfor thelistener-inbecause itspowerspectraldensity iseven lowerthan ambientnoise,and itsalmost impossiblefor himtodistinguish thesignalfrombackground noise.这是必要的窃听别人的转换，传输转换信息必需捕获和解码用于码分多址系统的信号，用户的信息必需发送扩频调制前的共同渠道极扩频和特别低的功率谱密度因此，这是很难检测到这种信号的收听者因为其功率谱密度甚至低于环境噪声，它几乎不行能为他区分信号从背景噪音Moreover,even ifthesignalis captured,what thelistener-in canget onlybroadbandnoise ofinsignificancefrom hisdemodulator becauseof hisinaccurate localpseudo-random sequence.Theprobability ofright PNsequence patternnecessary forspreadspectrumdemodulation isoneofmore thanonethousand billion!What alow probabilityfor listener-in toeavesdrop othersconversation throughCDMAcellularmobilecommunicationsystem!此外，即使信号捕获的听众，仅能获得宽带噪声微乎其微从解调器因为他的不精确的本地伪随机序列概率的正确的序列模式所必需的扩频解调是超过一千个亿！什么是低概率的听众偷听别人的谈话通过蜂窝移动通信系统！离线的机会较少Fewer Off-line chancesBecauseofthesoft-switching technique,which meansuconnect-before-break,z,its overcomeforCDMA thatthe frequentoccurrence ofoff-time.由于软开关技术，即・，它克服了码分多址，频繁发生的时间“connect before-break”In mobilecommunicationsystem,BS isthe guaranteefor conversation.When subscribersduringconversation moving close toedge ofthe BSdemesne,the BSshould maintainthe communicationthroughits activeswitching,otherwise theprocess willbe interrupted.During switchingperiod,BSsdominion shouldshift fromdemesne ofthe localBS suchas Ato demesne of Aand itsneighboringBSB todemesne ofB,andsignalfromthe moving mobilestation willautomaticallyswitch toa relativelyidle neighboringBS.Thus,only whenitisapproved thatthe movingMS hasmovedtothedemesneofB,can theconnection betweenthemovingMS andits originalBSA beswitchedoff.So itis noteasy fora CDMAconversation to be interruptedby off-line.在移动通信系统，基站是保证谈话当用户在会话移动接近边缘的学士学位的私有化，如要保持通信通过其主动开关，否则程序中断在切换期间，英国的主权应当从“私有的地方本科如”到“私有和邻近基站乙”到“私有”，和信号从移动台移动会自动切换到一个相对空闲周边基站因此，只有当它是批准移动质谱已移到“私有”，可连接之间的移动和原来的学士学位一关闭所以它是不简单的码分多址的谈话被打断了离线Unlike theabove soft-switching inCDMA,hard-switching methodadopted inGMS systemexecutesswitching processas break-before-connect,which happentobethe reversedprocessing sequencewiththat ofCDMA.That isto say,when aGSM subscriberduring conversationmovingcloseto edgeofBSs demesne,the localBSA cutoff connectionwith theMS atfirst,then theMS setnewconnection with the neighboringBSB onceagain.Thus,communication duringthis switchingwillhave tobe interrupted,that consequentlyleadstoa highoff-line ratio.抽样频率Sample FrequencyLayoutCDMA subscribersare distinguishedbytheassigned uniquepseudo-random sequence,so neighboringchannelscanbeused forsignals transmittingwiththesame carrierfrequency.Thus,its quiteflexible toprogramthe systemfrequency layout,and soforthesystem expansion.与上面的软开关在CDMA,硬开关方法采纳GMS系统执行开关过程中为“break-before-connect”,恰巧相反的处理序列与CDMA也就是说，当一个GSM订户在谈话期间移动接近边缘的废话的私有，当地BS⑸切断了连接和多发性硬化症的在第一,然后设置新连接女士与周边BSB又一次因此,沟通在这个开关将不得不被打断,因此引起很高的离线比率采样频率的布局CDMA用户区分由指定的独特的伪随机序列,所以邻近频道可以用于信号传输载波频率相同因此,这是相当敏捷的程序系统频率的布局,那么对系统扩张。