| Code Division Multiple Access (CDMA) technology is one kind of the Spread Spectrum Communication technology which is the key technology of the third generation of communication system. But there are still many problems that need to be solved, of which the most important thing is to suppress Multi Access Interference (MAI). This paper introduces cause of formation of MAI in CDMA systems, and points out that Multi-user Detection (MUD) technology can improve capability and performance of CDMA through suppressing MAI. The MUD technology is made up of two kinds, one is linear multi-user detection and another is non-linear multi-user detection. This paper introduces and analyzes the performance of various detections, especially analyzes the framework and algorithm of DS-CDMA multi-user detector, CORRELATION multi-user detector, MMSE multi-user detector is .From the simulations experiment, we can know the MMSE multi-user detector is better than the CORRELATION multi-user detector which is better than the DS-CDMA multi-user detector.Moreover, this paper uses the blind adaptive detector to solve the problems that the usual multi-user detector have the complex arithmetic and can't eliminate the interference between the different regions. In the emulational experiment, the algorithm of blind adaptive multi-user detection are analyzed and compared. The result from simulation indicates that this algorithm has good suppression effect on dynamic strong MAI and "near-far" effect.Hardware is also very important in the development of the MUD technology. Smart antenna is one of the key hardware technologies which have been adopted in 3G system. Smart Antenna and the MUD technology are combined together first time in TD-SCDMA system. This paper studies the principle and the method of Smart Antenna and joint detection technology in TD-CDMA system. Simulation results show that, Smart antenna and joint detection technology have very good performance and can meet the requirement for real-time processing. |
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