Study Of Multiuser Detection In DS-CDMA System

Mutiluser detection is one of the key techniques in the 3G mobilecommunication systems. The main idea behind it is to make joint detection on thereceived signals by making full use of the information of all the users' signals, whicheliminates the multiple access interference (MAI) and relaxes the 'near-far' effect, andconsequently increases the capacity of the system. The multiuser detection is studiedin this paper, and several novel multiuser detectors with excellent performance aregiven as follows. A new adaptive detector for uplink in the CDMA system is given, with neitherthe training sequences nor the computation of the invert of complex big correlationmatrix needed, and the performance of it is equal to that of the decorrelating detector.Moreover, it can be used to estimate the amplitudes of the signals. A novel near-far resistant semi-blind adaptive multiuser detector is presented andthe detection performance of it is improved comparing with the blind and non-blinddetectors. Meanwhile, a group decision feedback semi-blind adaptive multiuserdetector is given which reduces the detection delays. Moreover, a novel method to eliminate the phase illegibility with differentialcoded decision direction is provided, and a new blind adaptive detector overfrequency–selective fading channels is given. The detector can work without trainingsequences, and its computational complexity is reduced and the precision is improvedcomparing with the blind adaptive decorrelating RAKE receiver based on the Kalmanfilter. This paper is supported by The National Natural Science Foundation of China(No. 60073053, 60133010).