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安徽工程科技学院毕业设计（论文）-I-CDMA系统的研究与MATLAB仿真摘要CDMA(CodeDivisionMultipleAccess)是在扩频通信的基础上发展起来的。所谓扩频，是将原信号频谱扩展到宽带中进行传输的一种技术。它主要利用相互正交(或尽可能正交)的不同随机码区分用户，实现多用户同时使用同一频率接入系统和网络。经过几种网络的实现和发展，CDMA已经逐渐成熟起来。我国的CDMA发展十分迅速，网络构架已初具规模。预计在将来，CDMA将与GSM一样，在整个通信业起到举足轻重的作用。仿真是一个系统应用于实际生活前的模拟，能有效的发现问题、纠正问题，而MATLAB是最具影响力、最有活力的软件之一，在科学运算、自动控制、通信仿真等领域有着广泛地应用。本课题利用MATLAB对DS-CDMA系统进行仿真。在研究DS-CDMA系统理论的基础上，利用SIMULINK对其进行仿真，根据系统功能和指标要求，对信道、扩频/解扩、QPSK(QuadratureReferencePhaseShiftKeying，四相相移键控)调制/解调等模块进行了设计，并设置了相对应的参数，最后给出系统仿真的整个框图。通过波形、频谱图、相位等结果，对系统进行了性能分析，并作了进一步改进与调试。仿真结果证明了整个设计系统的正确性。由频谱特性可以看出，信源信号的频谱被大大展宽，验证了扩频的实现；由误码率分析表明，系统对加性高斯噪声等具有一定的抗干扰能力等。可以看出，MATLAB在系统动态仿真中具有较大优越性和重要作用。关键词：直扩系统；CDMA；PN扩频；QPSK调制解调；simulink仿真单活辉：CDMA系统的研究与MATLAB仿真-II-CDMAsystemresearchandsimulationbyMATLABAbstractCDMA(CodeDivisionMultipleAccess)isabranchtechnologywhichbasedonthespectrum-spreadofthedigitalcommunication.Thespectrumspreadisakindoftechnologythatexpandstheoriginalsignalfrequencyspectrumtoawidebandinthetransmission.Itdiscriminatesdifferentusersmainlybythedifferentmutualorthogonal(orasfaraspossibleorthogonal)randomcode.Itcanrealizethecommunicationwhichmulti-usersutilizethesamefrequencytoconnecttothesystemandthenetwork.CDMAbecomemoreandmorematurethroughthedevelopmentsofseveralnetworks.ThedevelopmentofCDMAisveryquickinChinanowadays.ThenetworkconfigurationofCDMAisbasicallyself-contained.CDMAwillexertimportantfunctionsincommunicationfieldasGSMinthefuture,buttheamalgamationofCDMAandGSMisanotherdirection.Thesimulationisthebaseofasystembeforeitisusedinthelife,throughwhichwecanfindtheproblemsandcorrectthem.Matlabisoneofthemostpopularandvigoroussoftwaremassivelyappliedinscienceoperation,automaticcontrol,sciencecartographyandcorrespondencesimulation.Inmydesign,afterstudyingtheDS-CDMAsystemtheory,taketheMatlabtosimulateit,mainlycontainingthePNcodewidefrequencydesign,theQPSK(QuadratureReferencePhaseShiftKeying)modulationanddemodulationcircuitdesign,thechanneldeclineanalysisandsoon;finallycontrastandanalyzetheresults.Thesimulationresultsindicatethatthesystemdesignisrightoverall.Fromfrequencyspectrumpicture,wecanknowthatthesourcesignal’sfrequencyspectrumisgreatlystretched;theerrorrateanalysisindicatedthatthesystemhasstrongabilitytoresisttheadditiveGaussnoise.MATLAB’scorrespondencedynamicsimulationsuperioritycanbeseeninthissimulation.Wecanpredicttheresultquicklyfromthesimulation.Keywords:DSsystem;CDMA;PNspectrum-spread;QPSKmodulationanddemodulation;simulinksimulation安徽工程科技学院毕业设计（论文）-III-目录引言............................................................................................................................................1第1章绪论..............................................................................................................................21.1课题的背景和研究意义.....................................................................................................21.2课题的发展概况及存在的问题.........................................................................................21.3本文的主要研究内容.........................................................................................................3第2章CDMA系统理论.........................................................................................................42.1数字通信系统......................................................................................................................42.2扩频通信基础......................................................................................................................52.3CDMA系统概述.................................................................................................................62.4IS-95CDMA.........................................................................................................................82.4.1PN码的生成..............................................................................................................92.4.2扩频与调制..............................................................................................................102.4.3信道..........................................................................................................................112.4.4其他关键技术.........................................................................................................11第3章DS-CDMA系统的MATLAB仿真与调试.............................................................133.1MATLAB介绍...................................................................................................................133.1.1概述.........................................................................................................................133.1.2SIMULINK...............................................................................................................133.1.3通信工具箱.............................................................................................................133.2通信仿真............................................................................................................................143.3DS-CDMA系统各模块设计...................................................