A Joint PIC/Decoding Algorithm for Convolutionally Coded CDMA Systems

This paper mainly explores parallel interference cancellation and decoding (PIC/decoding) algorithm for convolutionally coded DS-CDMA systems. A new joint PIC/decoding scheme is proposed and analylized, respectively. The proposed scheme is numerically simulated, and compared with other PIC/decoding algorithm over Rayleigh fading channel. From the simulations, the main conclusion can be drawn as : (1) like conventional PIC and decoding algorithms, the proposed algorithms exhibit better performance with the increase in the number of the interference cancellation (IC) stages, but up to three IC stages, the performance improvement is getting less obvious; (2) the proposed joint PIC/decoding acquires the performance close to the ideal joint PIC/decoding if the tentative decisions of coded symbols are linearly estimated by the sum of initial a priori log-likelihood rate (LLR) and updated a priori LLR, while a significant performance degradation will evitably occur if the tentative decisions of coded symbols are linearly computed by the updated a priori LLR only. We also compare the proposed PIC/decoding with matched-filter (MF) receiver and conventional PIC/decoding algorithms, respectively. It is shown that the proposed joint PIC/decoding dominantly outperforms the MF receiver and conventional PIC/decodings in performance. Keywords-DS-CDMA; interference cancellation; decoding; loglikelihood rate(LLR); simulation