Space-time cancellation detector for up-link CDMA QPSK receivers with adaptive antenna arrays

This paper deals with a multiuser cancellation detector for DS-CDMA wireless communication systems. The proposed detector´s main feature lies in the joint utilization of the space and time processing techniques since optimum beamforming for adaptive antenna arrays and interference cancellation are supposed to be used together: in particular, different multiuser multisensor receiver architectures are considered and compared but only one is chosen according to the best performance/complexity trade-off. The proposed receiver is supposed to be used for an asynchronous DS/CDMA communication system in which QPSK modulation scheme is used in transmission. It is shown here that the proposed receiver shows light performance degradation in comparison with the adaptive array decorrelating detector (Del Re et al. 1998), reasonable near-far resistance, and, thanks to inherent low complexity of canceling techniques, allows real-time operation. Performance is expressed in terms of bit error rate (BER), which has been derived by simulations under the assumption of a slowly frequency-selective Rayleigh fading channel