Design of a Capacity-Approaching Chaos-Based Multiaccess Transmission System

As an enhanced version of Walsh-code-based multiaccess differential chaos shift keying (DCSK-WC), the differentially DCSK-WC (DDCSK-WC) benefits from better error performance and stronger robustness against inter-symbol interference in multipath fading channels. In this paper, the Bahl-Cocke-Jelinek-Raviv (BCJR) decoding algorithm is applied in the detection of DDCSK-WC to form DDCSK-WC-BCJR. Theoretical analyses and simulation results demonstrate that the BCJR detector achieves a significant performance gain with respect to the conventional generalized-maximum-likelihood detector, while retaining the hardware complexity almost unchanged. To further improve the performance, protograph-based low-density-parity-check channel codes are incorporated into the DDCSK-WC-BCJR system so as to construct a serial concatenated coding scheme. However, the capacity-approaching protograph code in additive white Gaussian noise (AWGN) channels performs poorly in the DDCSK-WC-BCJR system over multipath fading channels. To tackle this problem, a new protograph code is designed with the help of a modified extrinsic information transfer analysis. The proposed code has decoding thresholds gap within 1.0 dB way from to the system capacity limits. Besides, the performance superiority of the protograph-coded DDCSK-WC-BCJR architecture is illustrated over a practical UWB channel. More importantly, the proposed scheme does not require channel state information as in uncoded-DCSK schemes, which makes it extremely promising for low-cost and low-complexity wireless communication applications.