Study On Multi-user Detection Of DS-CDMA System

Code Division Multiple Access (CDMA) systems have been widely applied in the third generation mobile communication (3G) systems due to its huge capacity, soft switch, high frequency utilization and strong ability of interference resistance. In CDMA systems, multiple access interference (MAI) is the main factor that influences the system performance and the system capability. How to reduce this kind of interference has draw much attention recently years. Multi-user detection (MUD) can effectively reduce multiple access interference and improve system capabilities which make it to be a key technology of 3G systems. Its main purpose is to detect the interest user or all users from a mutually interference sequence.This paper takes DS-CDMA system as research object. The research significance and current research status were analysis. Firstly, the signal model of DS-CDMA system is researched, traditional methods of multi-user detection and their performances is given. The concept of independent component analysis, several classic measurements of Non-Gaussian and common independent component analysis algorithms is introduced. Takes Non-Gaussian measurement as research tool, applied independent component analysis algorithm in multi-user detection, use the interest user's spread code as the prior information to add it into the algorithm, after gradient-based optimization, a kind of multi-user detection based on independent component analysis algorithm is proposed which can effectively detect the interest user's information. Compared to normal multi-user detection, do not have to separation first then detection, simplified the detection method. The algorithm is simple. Then compare it with the traditional multi-user detection, the results show that the performance can be greatly improved.