Double-RIS aided Full-Duplex communication system: uplink, downlink and rate maximization

To explore the full potential and application of intelligent reflective surfaces (RISs) in complex and highly specialized communication environments, this paper investigates a system architecture composed of cascaded double-RISs. The system is further enhanced by the integration of advanced full-duplex (FD) communication and multiple-input-multiple-output (MIMO) technologies, forming a highly robust and adaptive framework. The key objective of this study is to maximize the sum achievable rate of the system (SARS) by jointly optimizing the proposed system constraints and the phase-shift control of the cascaded double-RISs. Considering the inherent complexity and high-dimensional nature of the optimization problem, we propose an iterative optimization algorithm. This algorithm is grounded in advanced mathematical techniques, specifically leveraging fractional programming (FP) to iteratively refine the objective, and Maximize-Minimize (MM) methods to ensure a balanced and globally optimized solution. Through rigorous simulation results, we demonstrate that the proposed algorithm significantly enhances the system’s overall performance. When compared to conventional techniques, the new approach exhibits marked improvements in system efficiency, data throughput, and overall robustness, thus indicating its superior efficacy in real-world applications over existing methodologies. These results highlight the practical advantages of applying double-RIS and FD-MIMO technology in modern wireless networks, making this a promising solution for next-generation communication systems.