Turbo multiuser detection

An iterative receiver structure is proposed for decoding multiuser information data in a convolutionally coded DS-CDMA system. The receiver performs two successive soft-output decisions, achieved by a soft-input soft-output (SISO) multiuser detector and a bank of single-user SISO channel decoders, through an iterative process. At each iteration, extrinsic information is extracted from detection and decoding stages and is then used as a priori information in the next iteration, just as in Turbo decoding. A low-complexity SISO multiuser detector is developed based on a novel nonlinear interference suppression technique, which makes use of both soft-interference cancellation and instantaneous linear MMSE filtering. Simulation results demonstrate that the proposed receiver offers significant performance gain over the traditional non-iterative receiver structure. Moreover, at high signal-to-noise ratio (SNR), single-user performance can be approached by iterative processing.