An iterative multiuser detector for DS-CDMA systems in multipath fading channels

We propose an iterative multiuser detector for turbo coded direct sequence CDMA (DS-CDMA) systems in the uplink channel. The receiver is derived from the maximum a-posteriori (MAP) estimation of the single user´s transmitted data, conditioned on the information about the estimate of the multiple access interference (MAl) and the received signal from the channel. The complexity of the proposed receiver increases linearly with the number of users. Error rate performances of the receiver is found to be better than those of the receiver in which a direct subtraction of the estimated multiple access interference is performed. The performance of the developed iterative multiuser receiver is investigated in the multipath fading environment with and without the knowledge of the side information. It was observed that the performance of the proposed receiver improves in a multipath fading channel when the channel side information is considered in the development of the receiver.