Energy Efficiency Optimization of Joint Active and Passive Beamforming in IRS-Assisted MISO-SWIPT System

This paper investigates a multi-input single-output (MISO) wireless information and power transfer (SWIPT) communication system based on intelligent reflecting surfaces (IRS) for multiple users. The system includes a base station with a multi-antenna array that simultaneously transmits energy and data to single-antenna users, where users communicate through power splitting (PS) technology. This approach simultaneously processes data reception and energy collection, introducing new energy efficiency metrics aiming to achieve equilibrium between transmission rate and power harvesting capacity. Through the joint optimization of the base station’s active beamforming, IRS passive beamforming, and PS proportion of users. Considering the problem’s nonlinear complexity, our approach initially constructs the minimum upper bound to derive a fractional function, which leads to a fractional function that can be effectively tackled utilizing the Dinkelbach algorithm. Thereafter, a cyclic resolution approach is used to solve two subproblems separately. For the first subproblem, upper bound minimization and semi-definite relaxation are employed; for the second subproblem, a block coordinate descent search method is used to improve system efficiency. Numerical trials confirm our methodology’s superior performance compared to benchmark algorithms, with energy efficiency improved by 13% when compared to systems without IRS.