Robust beamforming design for energy harvesting efficiency maximization in RIS-aided SWIPT system

This paper investigates Energy Harvesting Efficiency(EHE) maximization problems for Reconfigurable Intelligent Surface(RIS) aided Simultaneous Wireless Information and Power Transfer(SWIPT). This system focuses on the imperfect RIS-related channel and explores the robust beamforming design to maximize the EHE of all energy receivers while respecting the maximum transmit power of the Access Point(AP), RIS phase shift constraints, and maintaining a minimum signal-to-interference plus noise ratio for all information receivers under both linear and non-linear EH models. To solve these non-convex problem, the channel uncertainty related infinite constraints are approximated by using the S-procedure. With the introduction of slack variables, the transformed subproblems can be iteratively solved using alternating algorithm. Simulation results demonstrate that RIS is able to increase the system EHE.