Iterative cochannel interference cancellation in synchronous CDMA on a frequency selective channel

In a synchronous CDMA system the orthogonality of the codes insures no interference between the users. However, when strong multipath distortion is present, the orthogonality is destroyed. In this paper we propose a signal processing technique for multiuser detection which iteratively seeks for the maximum likelihood solution. This nonlinear technique is shown to perform much better than the optimal linear solution. The algorithm lends itself to an efficient DSP or VLSI implementation. At the transmitter a set of approximately orthogonal Gold codes is used. In addition to evaluating the performance of a coded or uncoded system by simulations, we are able to develop a simple and easy to use metric of channel quality which can approximately predict the system performance