权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

A Study on Synchronous Acquisition Methods with Code-Orthogonalizing Filters in Asynchronous Direct Sequence/Code Division Multiple Access (DS/CDMA) Communication Systems

异步直接序列/码分多址(DS/CDMA)通信系统中码正交滤波器同步采集方法的研究

基本信息

批准号：
11650375
负责人：
TACHIKAWA Shin'ichi
金额：
$ 2.3万
依托单位：
Nagaoka University of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

Recently, an synchronous direct sequence / code division multiple access (DS/CDMA) communication system has been studied as a digital communication system because of its high capacity, robustness against interference, and so on. However, in large multiple access interference (MAI) environment, it is difficult to achieve the sequence acquisition by the sliding correlator, because large peaks of cross-correlation functions appear periodically. In order to overcome this problem, a novel acquisition method (direct detection method) with code-orthogonalizing filter (COF), which can reduce MAI without the knowledge of other user's PN sequence and signal delay, have been proposed previously, however, the average acquisition time becomes very long.This paper proposes a modified acquisition method with COF (pre-estimation method), which uses the orthogonalization of partial correlations and pre-estimation by sliding the own sequence. First, a model and principle of the two acquisition methods using COF (direct detection method and pre-estimation method) are described and the reduction effect of the acquisition time is shown. Second, a complex style LMS algorithm over multipath fading channels is presented. Next, in the direct detection method, the step size parameter of LMS algorithm is examined to shorten training time. Finally, an acquisition method with COF by multiple-dwell detection considering false alarm penalty is proposed. As a result, for example, over multipath fading channels, when code length is 127, Eb/No=24.0[dB], the number of users is 24, and signal to interference ratio (SIR) is -6.0[dB], the average acquisition time 1.32×10^6T (T is data duration) is necessary for the direct detection method, however, it can be improved to 7.94 × 10^4T for the combination of direct detection method and pre-estimation method using the modified step size parameter, further, 5.96 × 10^4T for the method using multiple-dwell delection (i.e., about 1/20 of the previous method).

近年来，同步直接序列/码分多址（DS/CDMA）通信系统以其高容量、抗干扰鲁棒性等优点被作为数字通信系统进行研究，但在大的多址干扰（MAI）环境下，由于互相关函数的大峰值周期性出现，滑动相关器难以实现序列捕获。为了克服这个问题，一种新的采集方法，针对码正交化滤波器（COF）直接检测法（Direct Detection Method）在不知道其他用户的PN序列和信号时延的情况下可以降低多址干扰（MAI）的缺点，提出了一种改进的COF捕获方法（预估计方法），其使用偏相关的正交化和通过滑动自身序列的预估计。首先，描述了使用COF的两种捕获方法（直接检测方法和预估计方法）的模型和原理，并且示出了捕获时间的减少效果。其次，提出了一种多径衰落信道下的复合型LMS算法。其次，在直接检测方法中，对LMS算法的步长参数进行了检验，以缩短训练时间。最后，提出了一种考虑虚警惩罚的多驻留检测COF捕获方法。结果表明，在多径衰落信道中，当码长为127，Eb/No=24.0[dB]，用户数为24，信干比（SIR）为-6.0[dB]时，平均捕获时间为1.32×10^6T（T是数据持续时间）对于直接检测方法是必需的，然而，直接检测法和使用修正步长参数的预估计法相结合，可以将其提高到7.94 × 10^4T，5.96 × 10^4T（使用多次驻留偏差的方法）（即，约为前一方法的1/20）。