Rate maximization for STAR-RIS-assisted SWIPT communication systems

This paper investigates optimal design of simultaneously transmitting and reflecting reconfigurable intelligent surfaces (STAR-RIS)-assisted simultaneous wireless information and power transfer (SWIPT) systems with perfect channel state information. The system consists of an Access Point (AP), a STAR-RIS, users, and energy receiving devices. The AP simultaneously transmits information and energy signals through direct links and cascaded links with the STAR-RIS. Through the joint optimization of the AP's active beamforming scheme and the phase shift angles as well as amplitude coefficients of STAR-RIS components, the system achieves maximization of its information transmission rate. Initially, the original problem is divided into two subproblems for solution. Then, optimization methods such as semidefinite relaxation, successive convex approximation, and penalty function methods are applied to convexify the subproblems. Finally, these subproblems are iteratively solved using a continuous alternating iteration method until convergence criteria are met, yielding the optimal solution. Experimental analysis demonstrates that STAR-RIS can markedly elevate the communication performance of SWIPT systems.