基于CDMA信号的DOA估计方法研究

发布时间：2018-03-14 19:41

本文选题：空间谱估计　切入点：CDMA　出处：《电子科技大学》2014年硕士论文　论文类型：学位论文

【摘要】：无线通信技术在当今通信领域发展迅猛,应用广泛,成为最为活跃且富有挑战性的研究课题。码分多址(Code Division Multiple Access,简称CDMA)通信方式由于以扩频理论为基础,使其具有抗干扰,能在低功率谱密度下工作等优势,所以成为了第三代移动通信系统的核心技术,为提高系统性能质量,阵列天线技术在移动通信系统中必不可少,而其中的空间谱估计也成为了近十几年来的研究热点。波达方向(DOA)估计在阵列信号处理中是一个重要的研究领域,在众多现有的方法中,基于子空间的算法由于它的高分辨和低复杂度特点,受到了最多关注与研究。CDMA无线通信系统复杂,诸如MUSIC的子空间算法难以直接利用。在CDMA系统中每个传输的用户信号都被分配了独特的扩频码,这些扩频码大都具有尖锐的自相关特性和较好的互相关特性。全文围绕如何利用这一特点对基于CDMA信号的波达方向估计做出了研究。主要分为以下三个部分:第一部分首先考虑单径情况下的DOA估计,由于MUSIC算法在阵列信号处理中是一种代表性的高分辨率DOA估计技术。它要求阵元数至少比入射信号数多1。然而在CDMA系统中由于用户数量众多,上述约束往往是不适用的,所以在已知用户扩频码的情况下,采用码匹配滤波对接收信号进行预处理,再利用MUSIC算法对各个用户进行角度估计,最后考虑了多径情况,将多用户检测中的解相关检测结合到码匹配滤波之后,可以在一定程度上抑制多径及多址干扰。第二部分将伪码估计与DOA估计结合起来,针对非协作通信环境下,接收端不知道期望用户扩频码的情形对CDMA信号进行DOA估计。首先采用基于特征分解的方法对伪码进行估计,在获得扩频码序列后通过前面介绍的基于码匹配滤波的并行MUSIC算法得到各个用户的角度估计值。第三部分将介绍联合角度时延的估计算法,由于多径的影响,接收端在处理CDMA信号时,时延也是一个重要的影响参数。先给出了联合角度时延估计中两个重要概念,阵列流形和时间流形。最后介绍基于TST-MUSIC的CDMA信号联合角度时延估计算法,该算法通过结合时域滤波以及空域波束形成技术最后得到相匹配的各个路径时延角度估计值。
[Abstract]:Wireless communication technology is developing rapidly and widely used in the field of communication nowadays. It has become the most active and challenging research topic. CDMA (Code Division multiple access Code Division Multiple access) communication mode has anti-interference because of its base on spread spectrum theory. Therefore, it has become the core technology of the third generation mobile communication system. In order to improve the performance of the system, array antenna technology is essential in the mobile communication system. The spatial spectrum estimation has become a hot topic in the past decade. The DOA estimation is an important research field in array signal processing, and has been used in many existing methods. Because of its high resolution and low complexity, subspace-based algorithm has attracted the most attention and research on the complex wireless communication system of .CDMA. Subspace algorithms such as MUSIC are difficult to use directly. In CDMA systems, each transmitted user signal is assigned a unique spread spectrum code. Most of these spread spectrum codes have sharp autocorrelation characteristics and good cross-correlation characteristics. This paper focuses on how to use this characteristic to study the DOA estimation based on CDMA signal. In part, we first consider the DOA estimation in the case of single path. Because MUSIC algorithm is a representative high resolution DOA estimation technique in array signal processing, it requires at least 1 more array elements than the number of incident signals. However, because of the large number of users in CDMA system, the above constraints are often not applicable. So in the case of known user spread spectrum code, the code matching filter is used to preprocess the received signal, and then the MUSIC algorithm is used to estimate the angle of each user. Finally, the multipath case is considered. After combining de-correlation detection in multi-user detection with code matched filtering, multi-path and multi-access interference can be suppressed to a certain extent. In the second part, pseudo-code estimation and DOA estimation are combined to solve the problem in non-cooperative communication environment. The receiver does not know the desired spread spectrum code for DOA estimation of the CDMA signal. Firstly, the pseudo-code is estimated based on the eigen-decomposition method. After obtaining the spread spectrum code sequence, the angle estimation of each user is obtained by using the parallel MUSIC algorithm based on the code matching filter previously introduced. The third part will introduce the joint angle delay estimation algorithm, because of the influence of multipath. Delay is also an important parameter when the receiver processes CDMA signals. Firstly, two important concepts of joint angle delay estimation, array manifold and time manifold, are given. Finally, a joint angle delay estimation algorithm for CDMA signals based on TST-MUSIC is introduced. The time domain filtering and spatial beamforming techniques are combined to estimate the time delay angles of each path.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.533

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