Application Study Of Blind Multi-user Detection In Diversity System

Code division multiple access (CDMA) has been treated as one of the promising technologies in the third generation of mobile communication system. It is well accepted that blind multi-user detection to suppress Multi-access interference (MAI) and other key technologies are hot research areas. Generally, various key technologies are studied separately that cannot reach best system performance in theory. Therefore, the combination of different key technologies has aroused great attention in recent years. This thesis combines diversity technology, which includes transmit diversity, receive diversity and RAKE technology, and blind multi-user detection technology to suppress MAI and multi-path interference.At the beginning part of this thesis, blind multi-userdetection transmit diversity and space-time code are introduced, then the combination of blind multi-user detection and diversity technology in up-link and down-link, which follow the international research closely, is researched emphatically. It is also the core of this paper.As the different emphases on up-link and down-link receiver technology, the design of the receiver is altered. The contributions of this thesis are as followings:(1) Considering the characteristic of the up-link, the combination of blind multi-user detection and RAKE that is used to suppress the channel fading and MAI in frequency selective fading multi-path channel is researched. As to the problem of line constrained quadratic programming, RLS algorithm is adopted. Computer simulation shows that this receiver is superior to that is based on Rosen in the aspect of stable performance and convergence speed.Then it is spread to the situation of spatial that is of multi-antenna, which combines the array antenna, blindmulti-user detection and RAKE receiver. As to the problem of spatial line constrained quadratic programming, Kalman algorithm is adopted. Finally the stable performance and convergence performance of space-time Kalman and space-time RLS algorithm is proved by computer simulation.(2) Considering the characteristic of the downlink, the blind multi-user detection and STBC is combined and is spread to selective frequency fading multi-path channel from the single path, which is the innovation of this paper. Simulation shows that the proposed method can reduce the bit error rate and increase signal interference rate effectively, and proves that the combination of blind multi-user detection and space-time code in downlink is valid.