The Study Of ICA-Based Multi-user Detection In CDMA Communication System

Independent Component Analysis (ICA) is an approach to blind signal separation, which has been developed during the past twenty years. It is a statistical method, which aims to recover independent original signals from observed signals given by sensors which are linear mixtures of the independent original signals, and attempts to make the separated signals as independent as possible. It need not privor knowledge except that the latent variables are statistically independent. There have many motivating reasons to use the means of ICA in signal separation. It is widely useful in signal processing such as speech recognition system, telecommunications, and medical signal processing. At present, ICA is an issue in blind signal processing, artificial neural network etc.Multi—user Detection (MUD) is a pivotal technology of code division multiple access(CDMA)communication system to suppress the present interference. In the actual CDMA system, there is some correlatedness between the users' symbol. This is why the multiple-access interence (MAI) exists. The use of independent component analysis (ICA) in CDMA communication system's multi—user detection can make good use of the independence of the users' information and then we can suppress MAI better and alleviate the problem of near-far. In this paper, we propose a scheme of multi—user detection based on FastICA algorithm and the role of ICA is to provide a jammer-mitigated signal to the conventional detection. If the jammer signal is weak, preprocessing by ICA is not advisable. Therefore we also consider two possible switching schemes, called pre-swiching and post-switching, which activate the ICA-based jammer canceller only when it is expected to improve conventional detection. we compare two possible switching strategies at both ends of the receiver chain, pre and post switching schemes, and evaluate their impacts to the overall performance improvement of the array receiver.This paper briefly shows the development, applications and state of ICA, particularly treats basic principle and implementation of ICA, roundly introduces current several main ICA algorithms and the relation of them. Chapter 4 describes the basic principle of CDMA communication system, expatiates upon the multiple access interfere and near-far effect's influence on CDMA communication system, analyzes the feasibility of use of FastICA in multiple users detective, and designs a simulated experiment. Chapter 5 we compare two possible switching strategies at both ends of the receiver chain, pre and post switching schemes, and evaluate their impacts to the overall performance improvement of the array receiver.