Joint beamforming design and resource allocation for double-IRS-assisted RSMA SWIPT systems

Abstract

Being able to achieve high passive beamforming gains cost-effectively, intelligent reflecting surface (IRS) is envisioned as a promising technique in assisting simultaneous wireless information and power transfer (SWIPT). Different from existing works that consider deploying a single IRS or applying conventional multiple access schemes like space division multiple access (SDMA) and non-orthogonal multiple access (NOMA), we consider a double-IRS-assisted multi-user SWIPT system applying the rate-splitting multiple access (RSMA) scheme in this paper. To maximize the minimum achievable rate of all users and guarantee their minimum energy harvesting amount, we jointly optimize the transmit beamforming for both the common and private messages at the access point of the system, the reflecting beamforming of the two IRSs, as well as the power splitting coefficients and the individual common rates of all users. Although the considered optimization problem is difficult to solve due to its coupling variables and non-convex structure, we propose an efficient alternative optimization-based algorithm to obtain a high-quality solution to it. Simulation results validate the effectiveness of the proposed algorithm and demonstrate the superior performance of deploying two IRSs and applying RSMA, as compared to the baseline schemes that deploy a single IRS or use SDMA/NOMA.