Research Of CDMA Multi-user Detection Based On Prior-ICA

CDMA has become the mainstream technology of the third generation mobi-le telecommunication. CDMA system distributes orthogonal(or as orthogonal as possible)code to different users and makes multiple users access system at the same time and frequency. However, due to the users random accessing and the correlation of the different users spreading code, users can not reach the ideal condition, i.e. complete orthogonal. Consequently, it will cause the multiple ace-ss interference(MAI)when lots of people are communicating. In order to get rid of the multiple access interference, multiuser detection plays an important role.First, this dissertation introduced the principle of multi-user detection and some sub-optimal multi-user detectors, summarize the most multi-user detector's advantage and shortcoming and practical application. Because it does not need any prior knowledge of the channel and the training sequence, the blind multiuser detection has attracted much interest in the mobile communication field.Second, this dissertation studies ICA (Independent Component Analysis) algorithm, the purpose of which is to separate the independent components from the observed signal that consists of linear mixed independent signals received from multiple channel measuring. Being a new blind signal separation(BSS) technology which has been developing rapidly in recent years, ICA does not need precise knowledge of the system's parameters, since the estimation is based purely on the high order statistical properties of the signal.At last, this dissertation emphasized the application of ICA in multiuser detection. The conventional ICA-based multi-user detector does not utilize the information of the spread sequences of users. However the expected user's spread sequence is known at the received end and it is helpful in signal detection. Therefore the conventional method wastes the known resource. In this disserta- tion, we present a QR decomposition based method towards solving the indeter-minacy problem arising in ICA algorithms, and avoids the need for complex sub-space computations. Simulation results indicate that the proposed algorithm is able to achieve better BER performance than the conventional matched filtering and conventional ICA approach in the same environment.