An iterative multiuser detector for turbo-coded CDMA in multipath fading channels
Conference Paper
Overview
Identity
Additional Document Info
Other
View All
Overview
abstract
Multiuser detection and turbo coding are two of the most powerful techniques for enhancing the performance of next-generation wideband CDMA systems. In this paper, we develop an iterative multiuser receiver structure for turbo-coded CDMA systems with aperiodic spreading sequences in a multipath fading environment, which exploits the power of both techniques. The key innovation in the proposed receiver is a low-complexity soft multiuser detector which uses the same decision statistic as the conventional RAKE receiver and performs soft-interference cancellation and instantaneous MMSE filtering. During iterations, extrinsic information is computed and exchanged by the soft multiuser detector and a bank of modified turbo decoders, to achieve successively refined estimate of the users' signal. The soft multiuser detector has a complexity of O(K2) per bit per user, where K is the number of users. A single-user receiver which employs a soft RAKE detector followed by a turbo decoder is also considered. Simulation results demonstrate that under various channel impairment, such as multiple-access interference, multipath dispersion and time-variant fading, the proposed multiuser receiver offers significant performance gain over the single-user RAKE receiver. Moreover, it is seen that the turbo multiuser receiver in a multiuser environment even outperforms the single-user RAKE receiver in a single-user environment, because the RAKE receiver neglects intersymbol interference.