Multiuser detection in flat Rayleigh fading channel using an approximate MMSE algorithm

We study multiuser detection for a synchronous DS-CDMA system in a flat Rayleigh fading channel. An approximate MMSE detector which is independent of the magnitude of the received signal is proposed. This detector is not only easier to implement but also easier to analyze than the exact MMSE detector. This is especially true for the case employing ML sequences. We have developed a closed form expression for its performance. Numerical simulations for CDMA systems employing ML and random sequences are provided. These results demonstrate that the performance difference between the exact and approximate MMSE algorithms is very small which makes the latter a very good approximation