A sum-rate maximization for IRS-aided broadcast SWIPT with time-switching structure and nonlinear energy harvester

This study evaluates the sum-rate gain of the intelligent reflecting surface (IRS) in a broadcast simultaneous wireless information and power transfer network. Users are equipped with a time-switching (TS) structure for an alternating information decoder and a nonlinear energy harvester. The sum-rate maximization (SRM) problem is formulated subject to the constraints of the energy-harvesting threshold required by users and limited transmission power at the base station (BS). To address the SRM problem, we jointly designed a broadcast beamforming precoding vector at the BS, reflective phase shifters at the IRS, and TS factors at the users. Subsequently, after certain manipulations, we propose efficient iterative algorithms that combine alternating optimization, successive convex approximation, semidefinite relaxation, and rank-one penalty function methods to obtain a suboptimal solution. Finally, the numerical results show the promising sum-rate gain of the proposed scheme compared with the conventional schemes.