Interleaver Design for Small-Coupling-Length Spatially Coupled Protograph LDPC-Coded BICM Systems Over Wireless Fading Channels

Yunlong Zhao,Yi Fang,Zhaojie Yang

doi:10.1109/access.2020.2974002

Abstract

As a class of convolutional error-correction codes (ECCs), spatially coupled protograph low-density parity-check (SC-PLDPC) codes with a sufficiently large coupling length can approach the channel capacity under belief propagation (BP) decoding. However, such codes suffer from poor performance in the case of small coupling lengths. To address the above weakness, we investigate the optimization and analysis of SC-PLDPC-coded bit-interleaved coded modulation (BICM) systems over Rayleigh fading channels. Specially, inspired by the unequal-error-protection (UEP) mechanism of M-ary phase-shift keying/ quadrature amplitude modulation (M-PSK/QAM), we put forward a novel interleaver design scheme, referred to as spatial position match mapping (SPMM) scheme. Based on the mutual information (MI) analysis, the proposed interleaver can be used to significantly boost the performance of the SC-PLDPC codes in BICM systems. Furthermore, we propose a block-scheduling protograph-based extrinsic information transfer (BS-PEXIT) algorithm to estimate the convergence performance (i.e, decoding threshold) of the SPMM-aided SC-PLDPC codes in BICM scenarios. Simulation results are well consistent with the theoretical analyses, and show that the proposed SPMM-aided SC-PLDPC-coded BICM systems are superior to the state-of-the-art counterparts.

Highlights

Bit-interleaved coded modulation (BICM) is of particular effectiveness to achieve both capacity-approaching performance and high transmission rate in various communication scenarios, e.g., wireless communications [1]–[4], vehicular communications [5], and aeronautical communications [6]–[8]
We assume that the transmitted codeword length of all the above mentioned SC-publication was Jiankang Zhang .low-density parity-check (PLDPC) codes is set as n = 4800
BER PERFORMANCE FOR THE 16-QAM bit-interleaved coded modulation (BICM) SYSTEMS For the Gray-mapped 16-QAM BICM systems, we study the simulated bit error rate (BER) of the regular SC-PLDPC code, i.e., (3, 6) SC-PLDPC code, with different coupling lengths

Summary

INTRODUCTION

Bit-interleaved coded modulation (BICM) is of particular effectiveness to achieve both capacity-approaching performance and high transmission rate in various communication scenarios, e.g., wireless communications [1]–[4], vehicular communications [5], and aeronautical communications [6]–[8]. Y. Zhao et al.: Interleaver Design for Small-Coupling-Length SC-PLDPC-Coded BICM Systems Over Wireless Fading Channels. Motivated by the superiorities of PLDPC codes, a class of convolutional-like PLDPC codes, called spatially coupled PLDPC (SC-PLDPC) codes, has been widely investigated Such codes benefit from relatively low complexity, and approach the maximum-a-posteriori (MAP) thresholds under believe propagation (BP) decoding [15]–[17]. In the case of a sufficiently large coupling length, the SC-PLDPC codes can achieve MAP-approaching performance due to the decoding-wave (i.e., threshold saturation) phenomenon [19] Such codes have a large codeword length, which cannot satisfy the low-latency requirement of modern wireless communication systems. To the best of our knowledge, few works have been reported to investigate the interleaver design for SC-PLDPC-coded BICM systems under fading environments from the perspective of mutual information (MI) analysis. The demapper and decoder are implemented via the max-sum approximation of the logdomain maximum a-posteriori probability (Max-log-Map) algorithm and the belief propagation (BP) algorithm [20], respectively

SC-PLDPC CODES

SIMULATION RESULTS

CONCLUSION