基于Matlab的CDMA通信系统的仿真与实现毕业论文.doc

基于Matlab的CDMA通信 系统的仿真 北方工业大学 本科毕业论文 摘 要 CDMA(Code Division Multiple Access)又称码分多址，是在无线通信上的使用技术，更是第三代移动通信的核心技术。 CDMA技术早在第二次世界大战期间因战争的需要而研究开发，但长期以来一直被用于军事领域，直到近些年才开始用于民用领域，在中国，也就是近几年刚开始盛行。 目前，实现第三代蜂窝网（通称3G）目标的方案主要有3种，即欧洲提出的W-CDMA，美国提出的CDMA2000，和我国提出的TD-SCDMA。它们的共同特点是都采用了码分多址（CDMA）技术。 码分多址包含两种基本技术：一是码分技术，其基础是扩频技术；二是多址技术。扩频技术优点很多，比如能够提高抗窄带干扰的能力、将信号藏在噪声中，防窃听、能使多个用户共用同一频带等等。 在我国，CDMA正处于刚刚盛行阶段,市场前景非常广阔，因此，CDMA是一个非常有研究价值的课题。通过使用Matlab仿真CDMA了解其原理，为以后继续学习CDMA或从事相关职业打下坚实的基础。 本课题主要研究内容包括：将两路信号扩频后混合在一起，调制解调，加入噪声，最后通过一定方法将两路信号分离出来，使误码率尽量小，通过波形、频谱图等，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。 关键词： CDMA；扩频；matlab仿真  The analysis and simulation of communication system based on Matlab Abstract A technology in wireless communication was called Code Division Multiple Access(Referred to CDMA) and it is the Core technology in 3G. CDMA technology was developed During World War II for the need of war. But it has been used in the military areas for a long time and was used in civilian areas until resent years. In china, it is in a few years that this technology began to thrive. At present, there are three methods to implement CDMA technology: W-CDMA put forward by Europe, CDMA2000 put forward by America and TD-SCDMA put forward by China. The common feature of these three technologies is CDMA. In fact, CDMA is composed of two technologies: CD and MA. The former is based on spread spectrum which has many advantages such as the ability to improve the suppression of narrowband interference, hiding signals in the background noise, the prevention of information eavesdropping，enabling many users to use one frequency band and so on. At our country, the market prospects of CDMA are very bright just because of the beginning of its prevailing .As result, this technology is an issue deserved to research. By grasping the basic theory of it through simulating CDMA via Matlab, I can lay the foundation for studying it deeper later. This paper includes the following contents: spread spec