Weighted Sum Rate Optimization for STAR-RIS-Assisted MIMO System

In this work, we study a simultaneous transmitting and reflecting reconfigurable intelligent surface (RIS)-assisted multiple-input multiple-output network. For the system under consideration, maximize weighted sum rate, mainly based on energy splitting (ES) scheme. To tackle optimization problem, sub-optimal block coordinate descent (BCD) algorithm is proposed to design precoding matrices coefficients (TRCs) in an alternate manner. Specifically, are solved using Lagrange dual method, while TRCs obtained constrained concave-convex procedure (CCCP). The simulation results reveal that: 1) Simultaneous RIS (STAR-RIS) can achieve better performance than conventional reflecting/transmiting-only RIS; 2) unicast communication, time switching (TS) scheme outperforms ES mode selection (MS) schemes, broadcast TS MS schemes.