Joint Beam Scheduling and Passive Beamforming for IRS-Assisted Hybrid-Field SWIPT

This paper investigates an intelligent reflecting surface (IRS)-assisted simultaneous wireless information and power transfer (SWIPT) system under the hybrid-field model, where the IRS operates in the near-field region of the base station, while one information user (IU) and multiple energy users (EUs) are located in the far-field of the IRS. Specifically, we establish a hybrid-field model and derive a closed-form expression for the element-wise combined channel gain. Based on this, we jointly optimize beam scheduling, power allocation, and IRS phase shift with the quality-of-service (QoS) constraint, enabling dynamic beam steering to maximize the total harvested energy of EUs while maintaining a balanced trade-off between information transfer and energy harvesting. An alternating optimization algorithm is developed to solve the non-convex problem by applying the Lagrange duality method, semidefinite relaxation (SDR), and successive convex approximation (SCA). Our results reveal that the beam is always directed toward the IU to guarantee its QoS and is further adaptively steered toward the EU with the highest energy-harvesting priority in hybrid-field SWIPT. Numerical results validate the effectiveness of the proposed scheme.