CDMA通信系统多用户检测研究
摘 要
在现代移动通信的快速发展过程中，码分多址（CDMA）技术因拥有出众的优点而被确定为第三代移动通信系统的主要接入方式，它是以扩频信号为基础，利用不同的码型实现多用户的信息传输，被传输的信号在空域跟时域上是叠加的，所以它可以支持高速率和高容量高速率数据业务。第三代移动通信系统能够改善和克服第二代通信系统（GSM）速率过慢，容量不足与目前IP技术多媒体业务要求距离甚远，不能完全实现全球的无缝连接等缺点和不足。
多用户检测技术不同于传统的检测方法，而是考虑到其他用户之间的相关特性等信息，充分利用CDMA通信系统用户特征码的内在结构等信息来改进接收系统的性能。应用多用户检测技术可以提升系统容量，并能克服远近效应带来的影响。它是引用信息论并经过了严格的理论分析后提出的一种先进的多址干扰抑制技术。目前理论上已趋于成熟，是第三代移动通信系统关键技术之一。
本文首先介绍了CDMA（Code Division Multiple Access）通信系统的基本原理及优缺点，由此提出多用户检测的基本原理和系统模型，并研究了多种多用户检测算法，重点研究讨论了其中的解相关线性（DEC）多用户检测法和最小均方误差（MMSE）检测法，这两种算法各有优势，是多用户检测算法中比较具有代表性的。最后通过matlab仿真环境进行了仿真，绘制误码率随着信噪比变化的曲线，将这两种算法与传统单用户检测算法进行比较，验证了理论的正确性。
关键词: 码分多址；多址干扰 ；多用户检测 ；解相关线性多用户检测；最小均方误差检测
Abstract
With the rapid development of the mobile telecommunication, Code Division Multiple Access (CDMA) technology is identified as main access method of the third generation mobile telecommunication system (3G) because of its outstanding advantages. CDMA, based on the spread-spectrum signal, uses different patterns to realize multi-user information transmission, the signals transmitted of which are overlaid in the time domain and the airspace domain, so it can support high capacity and high speed data services. The third generation mobile telecommunication system can overcome and improve the shortage of the second generation telecommunication system (GSM), such as low capacity and low speed which is far away from the required demand of multimedia services of the recent IP technologies and can’t realize global seamless connection
Multi-user detection, in consideration of other users’ information,, fully uses the inner structural information of feature codes of CDMA users to improve the performance of reception system. Multi-user detection can improve system capacity and overcome the effects of near-far problem. At present, it has been already mature theoretically, but due to the complexity of realizing it, it is still needed to be put into engineering use. But it has become one of the key technologies of the third generation mobile telecommunication.
First, this paper introduces the basic principles and advantages and disadvantages of CDMA (Code Division Multiple Access) communication system, whereby the proposed basic principles and system model of multi-user detection among which it puts emphasis on the research of a linear multi-user detection algorithm--- Minimum Mean Squared Error (MMSE) and Decorrelation linear (DEC) multiuser detection method.The design intent of multi-user detection is to make the mean square error between the transmission signal of the. K users and its estimate value smallest. Both algorithms have their own advantages, it is a multi-user detection algorithm representative. Finally matlab simulation environment simulation, drawing BER change with SNR curve, these two algorithms with the traditional single-user detection algorithms were compared to verify the correctness of the theory. Key words: Multi-access Interference , Multi-user Detection, MMSEUMD, CDMA
目录
第1章 绪论 ................................................................................................................................................................. 1 第2章 CDMA通信系统介绍 ................................................................................................................................ 2
2.1 CDMA通信系统的产生及发展 .............................................................................................................. 2 2.2 CDMA通信系统的关键技术 ................................................................................................................... 5 第3章 多用户检测技术的理论基础 .................................................................................................................... 7
3.1多用户检测技术的发展和分类方案 ....................................................................................................... 7 3.2 多用户检测技术的应用 ......................................................................................................................... 10 3.3多用户检测器的主要优势 ...................................................................................................................... 10 3.4 多用户检测器的主要缺陷 ..................................................................................................................... 10 第4章 各种多用户检测技术方案的研究 .........................................................................................................11
4.1系统模型 ......................................................................................................................................................11 4.2传统信号检测器(CMUD) ....................................................................................................................... 14 4.3最佳多用户检测器(Optimal Detector) .................................................................................................. 16 4.4线性多用户检测器 ................................................................................................................................... 17
4.4.1解相关多用户检测器(DECMUD) ......................................................................................... 17 4.4.2 最小均方误差检测器(MMSEMUD) .................................................................................... 19 4.5非线性多用户检测器(Non-linear MUD) ............................................................................................. 22
4.5.1基于判决反馈的多址干扰抵消检测(DFMUD) .................................................................. 22
第5章 计算机仿真验证及分析 .......................................................................................................................... 26
5.1 MATLAB软件介绍 ................................................................................................................................. 26 5.2建立MATLAB仿真模型 ....................................................................................................................... 26 5.3典型多用户检测方法仿真及分析 ........................................................................................................ 27 结论 .............................................................................................................................................................................. 32 参考文献 ..................................................................................................................................................................... 33 致 谢 ............................................................................................................................................................................ 34
CDMA通信系统多用户检测研究【毕业作品】
