【作者】 杨洁；

【导师】 曾孝平；

【作者基本信息】 重庆大学 ， 通信与信息系统， 2002， 硕士

【摘要】 第三代移动通信系统是建立在ITU-2000建议基础上的工作在2GHz频段、最高速率可达2Mbit/s的宽带移动通信系统。第三代移动通信的主流采用了码分多址（CDMA）的通信方式。CDMA系统中的初始同步技术作为第三代移动系统的关键技术，是其他关键技术得以实现的必要基础。CDMA通信系统接收机的初始同步包括PN码同步、符号同步、帧同步、和扰码同步等。由于DS-SS技术在CDMA系统中应用最为广泛，因此基于DS-SS方面的PN码捕获方法研究很多。伪随机码的同步一般分两步进行。第一步是搜索和捕获伪随机码的初始相位，使与发送端的码相位误差小于1bit，即序列捕获；第2步是在初始同步的基础上，使码相位误差进一步减小，使所建立的同步保持下去，通常称这一步为跟踪。如何判断PN码是否捕获是码同步问题中的重要内容。传统的PN码捕获的判定是通过能量检测的办法进行的。小波分析是目前在科学与工程应用界讨论和研究的一个热门课题。它是在Fourier分析的基础上发展起来的一门数学方法。它与Fourier分析类似，是一种时-频分析的技术。由于小波分析具有多尺度的特点，使得小波分析在进行信号去噪、信号压缩、机械故障诊断及数据处理等方面得以大量运用。本文把小波变换运用到CDMA通信系统码同步问题的研究中，结合PN码捕获时和未捕获时接收信号的特点，在系统的AWGN信道下，利用小波分析进行码捕获判定。这种把新的信号处理工具应用到现代通信系统进行码捕获判定的方法，是一种尝试。论文从理论出发，研究了捕获信号，即被高斯白噪声污染的BPSK或QPSK信号及未捕获信号（高斯白噪声）的特征，分析了DS-CDMA系统的AWGN信道特性，详尽介绍了小波多分辨分解的相关知识，给出了应用于PN码捕获的小波检测的方法。最后，通过Matlab软件进行仿真实验，实验表明通过小波变换可以在AWGN信道下顺利进行PN码捕获的检测。并给出了不同SNR下，捕获时间、虚警概率与小波变换的关系更多还原

【Abstract】 The third mobile communication system is built on the basis of ITU IMT-2000 suggestion, and it can work on 2GHz. Meanwhile, the wideband system’s rate can get 2Mbit/s and this system use communication pattern of CDMA. As a key technique of the third mobile system, initial synchronism technology is the necessary base of other key technologies. Initial synchronisms of CDMA communication system receiver include PN code sync, symbol sync, frame sync, sync of scramble code, and so on. Because that DS-SS technology is used most widely in the system of CDMA, a great deal of research on method for acquisition of PN code is based on DS-SS. The sync of PN code is divided into two steps generally: The first step is the searching and acquiring of PN code phase (namely, acquisition of sequences) so that the phase error between sending code and receiving code is within 1 bit. The second step is tracking which is on the base of the initial acquisition, so the error of phase is decreased more and sync is keeping. The judgement of PN code acquisition is an important problem of the code sync and the traditional method of it is power detection.At present, wavelet analyzing is a hot task in the field of science and engineering application. It is a mathematic method and developed from Fourier analyzing. Similar to Fourier analyzing, it is a kind of technique in time-frequency. Because of the characteristic of its multire-solution analysis, wavelet is applied in signal de-noising, signal data compressing, diagnosing of machine breakdown and data processing. In this paper the wavelet transform is used in the PN code acquisition of CDMA communication system. Considering the signal characteristic of PN code acquisition, the judgment of code acquisition by wavelet transform is made under AWGN channel of system. It is a try to apply the new tool of signal processing to communication system.This thesis studies the characteristic of acquired signal (namely BPSK signal or QPSK signal) and non-acquired signal (namely white Gaussian noise), The AWGN channel of CDMA system is analyzed. At the same time, The pertinent knowledge of wavelet multire-solution decomposition and a method of wavelet detection which apply on the PN code acquisition is given. In the end, The Matlab simulation results show that this method can be used in AWGN channel, And the relations among , under different SNR is given更多还原