QoE Maximization for RIS-Assisted Scattering Suppression in Offshore Communication Systems

The scattering environment in offshore regions leads to serious attenuation in wireless transmission, reconfigurable intelligent surfaces (RISs) have emerged as a promising technology for future offshore communication systems. In this paper, we consider an RIS-assisted three-dimensional (3D) offshore communication system. Unlike quality of service (QoS), which does not accurately represent user-centric offshore communication systems, the mean opinion score (MOS) is adopted as a quality of experience (QoE) metric to evaluate device-to-device (D2D) vessel user (DVU) satisfaction. We aim to maximize the sum MOS of DVUs by jointly optimizing power allocation, spectrum reuse, and RIS reflection coefficients, subject to the minimum signal-to-interference-plus-noise ratio (SINR) requirements for unmanned surface vessels (USVs) and the maximum MOS constraints for DVUs. To tackle this non-convex optimization problem, we adopt the block coordinate descent (BCD) method to decompose the original problem into three sub-problems. Specifically, power allocation, spectrum reuse, and RIS reflection coefficients are iteratively optimized using the fractional programming (FP) method, the successive convex approximation (SCA) technique, and the semi-definite relaxation (SDR) algorithm, respectively. Simulation results demonstrate that the proposed RIS-SDR algorithm achieves sum MOS gains of 4%, 17%, 22%, and 46% compared to the baseline schemes, respectively.