Reduced-complexity iterative multi-user detection for turbo coded DS/CDMA systems

A low-complexity iterative multi-user receiver is derived for turbo coded synchronous DS/CDMA systems. The receiver performs two successive soft output decisions, achieved by a soft-input soft-output (SISO) multi-user detector based on probabilistic data association (PDA) and a bank of single-user SISO turbo 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. The simulations show that the proposed iterative receiver structure offers significant performance gain over the traditional noniterative receiver structure. Moreover, at high signal-to-noise ratio, the detrimental effects of MAI and ISI in the channel can almost be completely overcome by iterative processing, and single-user performance can be approached.