On improved multiuser detection with iterated soft decision interference cancellation

We present an iterated soft decision interference cancellation scheme (ISDIC) for multiuser detection applying a bank of adapted MMSE filters instead of matched filters. It is shown that in this way the performance of ISDIC for synchronous CDMA can be significantly improved. This includes a lower SER for a given transmit energy per bit and a considerable reduction in the number of required iterations. Next, considering transmission over an AWGN channel as well as a Rayleigh fading channel we show that the corresponding single user bounds can be achieved even in a fully loaded multiuser system with randomly chosen spreading sequences and without any user sorting according to fading amplitudes.