Turbo soft interference cancellation for coded asynchronous ds/cdma

Abstract

In this paper we propose a Multiuser receiver architecture which removes the Multiple Access Interference (Mai) by means of a Soft Input Soft Output (siso) multiuser detector followed by a bank of channel decoders. The extrinsic information at the output of the channel decoders are used to estimate the values of the interfering bits and the SISO multiuser detector subtracts the vector of the interfering bits from the incoming signal. The resulting vector is then filtered by an adaptive mmse filter to help remove the residual mai. The paper examines the use of such a receiver in the context of a synchronous awgn channel and then we generalize to the case of asynchronous multipath fading channels.