Asymmetric Dual-Mode Constellation and Protograph LDPC Code Design for Generalized Spatial MPPM Systems

TL;DR

This paper introduces a novel PLDPC-coded GSMPPM system with asymmetric dual-mode constellations and an improved I-PLDPC code, achieving enhanced performance in free-space optical communications over weak turbulence channels.

Contribution

It proposes asymmetric dual-mode constellations integrated with MPPM and GSSK, and develops an improved PLDPC code using PEXIT, advancing FSO communication reliability.

Findings

Notable performance gains over existing codes and constellations.

Effective handling of weak turbulence channels in FSO systems.

Enhanced reliability for free-space optical applications.

Abstract

To achieve reliable and efficient transmissions in free-space optical (FSO) communication, this paper designs a new protograph low-density parity-check (PLDPC) coded generalized spatial multipulse position modulation (GSMPPM) system over weak turbulence channels. Specifically, we investigate the PLDPC code, generalized space shift keying (GSSK) modulation, and MPPM constellation. First, we propose a type of novel GSMPPM constellations that intelligently integrates the GSSK into MPPM, referred to as asymmetric dual-mode (ADM) constellations, so as to improve the performance of the PLDPC-coded GSMPPM system. Furthermore, exploiting a protograph extrinsic information transfer (PEXIT) algorithm, we construct a type of improved PLDPC code, referred to as I-PLDPC code, which outperforms the existing PLDPC codes over weak turbulence channels. Analytical and simulation results show that the proposed ADM constellations and the proposed I-PLDPC code can obtain noticeable performance gains over their counterparts. Therefore, the proposed PLDPC-coded GSMPPM system with ADM constellations is competent to satisfy the high-reliability requirement for FSO applications.