Abstract: To improve the overall system transmission rate while ensuring fairness among users in intelligent reflecting surface ( IRS) assisted wireless powered communication network, an optimization algorithm is proposed that jointly optimizes hybrid access point beamforming, uplink-downlink time allocation, user transmission power, and IRS phase shift matrix, with the objective of maximizing the minimum user transmission rate. The original non-convex optimization problem with coupled variables is transformed using relaxation variables and semi-definite relaxation. Methods such as golden section search, successive convex approximation, and alternating iterative optimization are then applied to solve it. Simulation results indicate that, compared with the algorithm aiming to maximize the sum rate, the proposed algorithm significantly improves the minimum user rate and enhances fairness among users. Additionally, compared to the algorithm without IRS, the proposed algorithm achieves higher minimum user rates and system sum rates, with performance improving as the number of IRS elements increases, indicating that IRS effectively enhances both energy and information transmission efficiency.

Key words: intelligent reflecting surface , wireless powered communication network , beam forming