Reduced complexity iterative multiuser detection/decoding for turbo coded CDMA systems

Recently, a novel scheme for iterative multiuser detection and turbo decoding was proposed by the authors (2000). It has been shown that the proposed detector approaches the multiuser capacity limit within 1 dB in the low signal-to-noise ratio region. However, the main drawback of the scheme is its exponential complexity in the number of users, which is due to the complexity of the MAP multiuser detector. In this paper, we show that the complexity of the algorithm can be significantly reduced by employing a greedy multiuser detector. The results for both the additive white Gaussian noise and the single-path fading channels show that the substantial reduction in complexity introduces a slight degradation in performance, 0.5 dB compared to MAP detector