DRL-Based Phase Optimization for O-RIS in Dual-Hop Hard-Switching FSO/RIS-aided RF and UWOC Systems

TL;DR

This paper introduces a dual-hop hybrid FSO/RIS and UWOC system optimized with DRL algorithms, significantly enhancing reliability and capacity for 6G underwater optical communications.

Contribution

It develops DRL-based phase optimization for O-RIS in a novel dual-hop FSO/RIS and UWOC framework, improving system performance under realistic underwater turbulence.

Findings

DRL algorithms effectively optimize O-RIS phases.

System improves outage probability and channel capacity.

TD3 algorithm shows superior robustness.

Abstract

This paper presents a dual-hop hybrid framework that integrates a free-space optical (FSO)/RIS-aided radio frequency (RF) link operating under a hard-switching protocol as the first hop, and an optical reconfigurable intelligent surface (O-RIS)-assisted underwater wireless optical communication (UWOC) link as the second hop. To capture realistic underwater dynamics, the Oceanic Turbulence Optical Power Spectrum (OTOPS) is employed for accurate turbulence modeling. For efficient O-RIS phase control, deep reinforcement learning (DRL) algorithms, specifically the Deep Deterministic Policy Gradient (DDPG) and Twin Delayed DDPG (TD3), have been developed to optimize the phase shifts of O-RIS elements. Simulation results demonstrate that the proposed system substantially improves outage probability and channel capacity, with TD3 achieving superior robustness and adaptability. These findings highlight the DRL-enabled O-RIS as a promising approach for achieving reliable and high-capacity 6G cross-domain UWOC networks.