Antenna array using a channel estimation technique in a DS/CDMA system with M-ary orthogonal modulation

Adaptive antenna array techniques are known to be good for cancelling multipath and multiuser interference. However, some of them need training signals to estimate the desired signal or have heavy complexity to compute the algorithmic processing. In this paper, we propose an antenna array receiver in a direct sequence/code division multiple access (DS/CDMA) system with M-ary orthogonal modulation. At every antenna a channel estimation technique is used, which refers to the maximum correlator output of a RAKE receiver. The estimated channel coefficients enable coherent detection with no need of training signals. Moreover, the antenna weights, which are determined by the estimated channel coefficients, make it possible to focus the receiver on the desired signal and to suppress the interference signal. Consequently, the proposed receiver has a 2D (dimensions) RAKE structure which can exploit both spatial diversity and temporal diversity. Simulation results show that the performance of the proposed scheme improves 1.5 dB in E_b/N_o at a BER=10^-3 over the receiver of noncoherent detection. The results also show that at a BER=10^-2 the proposed receiver improves about 2.3 times and 3 times the system capacity with 3 and 5 antennas, respectively