Max–Min Rate Optimization for Multigroup Multicast MISO Communication Systems via Transmissive RIS Transceiver

Abstract

This article investigates a transmissive reconfigurable intelligent surface (TRIS) transceiver architecture-enabled multigroup multicast downlink communication system. Under this setup, an optimization problem is formulated to maximize the sum of the minimum user rates of all groups, subject to the per-unit transmit power constraints of the TRIS transceiver. Due to the nondifferentiable nature of the objective function, the sum-minimum-group-rate maximization problem is challenging to solve. To tackle this difficult problem, we develop an iterative solution by leveraging the successive convex approximation (SCA) and the penalty function method. However, the above approach has high computational complexity. To overcome this drawback, we design an efficient second-order cone programming (SOCP)-based method using the weighted minimum mean squared error (WMMSE) framework to reduce computational complexity. To further reduce the computational complexity, we also propose a low-complexity and solver-free algorithm that analytically updates all variables by combining the smooth approximation theory and the majorization-minimization (MM) method. Numerical results are provided to verify the convergence and effectiveness of the proposed algorithms. It is also demonstrated that the low-complexity design achieves lower complexity with only slightly degraded performance.