Design of Turbo-MUD Receivers for Overloaded CDMA Systems by Density Evolution Technique

Abstract—This paper deals with a Turbo Multiuser Detector suitable for applications in Overloaded Coded DS-CDMA systems. The Turbo-MUD receiver is based on the use of a linear MMSE detector in the first iteration and a Parallel Interference Cancellation scheme in the successive ones. The inputs of the interference cancellator are both the detector outputs and the soft information from a bank of turbo decoders. The performance of the proposed receiver has been derived by means of computer simulations and applications of the Density Evolution theory: in particular, this technique permits to properly evaluate the number of MMSE iterations, simplifying the overall receiver design.