Performance of Hybrid RF/FSO Cooperative Systems Based on Quasicyclic LDPC Codes and Space-Coupled LDPC Codes

Abstract

Free space optical (FSO) communication systems provide wireless line of sight connectivity in the unlicensed spectrum, and wireless optical communication achieves higher data rates compared to their radio frequency (RF) counterparts. FSO systems are particularly attractive for last mile access problem by bridging fiber optic backbone connectivity to RF access networks. To cope with this practical deployment scenario, there has been increasing attention to the so-called dual-hop (RF/FSO) systems where RF transmission is used at a hop followed by FSO transmission to another. In this article, we study the performance of cooperative transmission systems using a mixed RF-FSO DF (decode and forward) relay using error-correcting codes including QC-LDPC codes at the relay level. The FSO link is modeled by the gamma-gamma distribution, and the RF link is modeled by the Additive White Gaussian Noise (AWGN) model. Another innovation in this article is the use of cooperative systems using a mixed FSO/RF DF relay using quasicyclic low-density parity check (QC-LDPC) codes at the relay level. We also use the space-coupled low-density parity check (SC-LDPC) codes on the same scheme to show its importance in cooperative optical transmission but also in hybrid RF/FSO transmission. The latter will be compared with QC-LDPC codes. The use of mixed RF/FSO cooperative transmission systems can improve the reliability and transmission of information in networks. The results demonstrate an improvement in the performance of the cooperative RF/FSO DF system based on QC-LDPC and SC-LDPC codes compared to RF/FSO systems without the use of codes, but also to the DF systems proposed in the existing literature.

A Free Space Optic/Optical Wireless Communication: A Survey

“…A gamma distribution was used to describe the FSO connection, and the White Gaussian noise (AWGN) model was used to simulate the frequency correlation. The results showed that the performance of the cooperating RF/FSO DF system based on QC-LDPC and SC-LDPC codes was better than that of RF/FSO systems without codes [49].…”

Free Space Optical Communication: An Enabling Backhaul Technology for 6G Non-Terrestrial Networks

“…Li et al [124] analyzed the outage probability, average BER, and average transmission rate of a dual-hop link between deep space and terrestrial in a weather-dependent satellite-terrestrial network with a rate adaptation hybrid RF/FSO link. Gueye et al, in [125], investigated the performance of cooperative transmission systems in FSO communication. Their study focused on dual-hop systems, combining RF and FSO transmission.…”