Research Of Multiuser Detection Algorithm In WCDMA System In A Fast Fading Channel

Brought forward by Europe ETSI(the third generation of Europe Standardizes organization), WCDMA is also a technology of broadband CDMA(Code Division Multiple Access) which is basically built above CDMA of narrowband. Since CDMA communications systems are interference limitation systems.,its capacities and performances are restricted by multiple access interference, while multi-user detection algorithm can greatly reduce the multiple access interference,which can reduce each user's error performance as a whole. Therefore, adopting the algorithm of multi-user detection in WCDMA system can effectively improve the performance of the system.As existing blind adaptive algorithms need training bits and are unsuited to fast fading channel in WCDMA systems, the NLMS adaptive multiuser algorithm based on differential MMSE (DMMSE) criterion is presented in this paper. According to the typical characteristic of two-layered spreading modulation in the WCDMA systems, the proposed DMMSE criterion solves this problem by tracking the ratio of successive symbols, thus avoiding the task of obtaining OVSF of other users and tracking rapidly varying fading gains, which is based on the assumption that successive symbols are changing small in fast fading. The simulation results illustrate the DMMSE NLMS decreased the bit error rate without increasing the complexity of system.The simulating platform the paper designed can be also applied to the other simulations of WCDMA system by single modifies,such as the downlink WCDMA Simulation,intelligent antenna,code design,power control and so on,which improve system function and have important reference value to latter research.