Joint Beamforming and Phase Shift Design for IRS-Assisted MISO SWIPT System with Finite-Alphabet Inputs

Abstract

In this paper, we investigate the transmission design in an intelligent reflecting surface (IRS)-assisted multiple-input single-output (MISO) simultaneous wireless information and power transfer (SWIPT) system, where a multi-antenna access point (AP) transmits energy and information signals to an energy harvesting receiver (ER) and an information receiver (IR). A specially deployed IRS adjusts its reflect phase shifts to facilitate information transfer and energy harvesting. Different from previous works, we assume the inputs to be finite-alphabet signals, such as phase shift keying (PSK), instead of Gaussian signals, which coincides with the practical scenario. Our goal is to maximize the mutual information from the AP to the IR by jointly optimizing the transmit beamforming at the AP and the phase shifts at the IRS under the constraints of transmit power and required harvested energy. Although the formulated problem is an intractable non-convex problem, we propose an efficient algorithm to alternately optimize the beamforming and the phase shifts, and finally obtain a high-quality solution. Simulation results show the superiority of our proposed algorithm over other benchmark schemes.