Sustainable IRS-Aided Integrated Sensing and Communication System with SWIPT

The intelligent reflecting surface (IRS)-assisted integrated sensing and communication (ISAC) system is currently under extensive research, which can share spectrum and reduce hardware costs. Nevertheless, due to the limitation of the power supply strategy of IRS, the IRS-assisted ISAC system faces the dilemma of being unable to continuously operate. To meet this demand, simultaneous wireless information and power transfer (SWIPT) is considered a promising technology that can prolong the lifespan of energy-constrained communication systems. In this paper, an IRS-aided ISAC system with SWIPT is described, where the IRS performs target detection and device communication, and the base station (BS) powers the IRS. Our goal is to form the reflective sensing beamforming gain (RSBG) from IRS toward the desired targets, while satisfying the quality-of-service requirement of the communication device and the energy collection demand at the IRS. To maximize the minimum RSBG, a non-convex optimization problem is constructed, which involves the beamforming of the BS, the phase-shift and reflection coefficient of the IRS elements. Specially, in order to solve this problem, we proposed an algorithm that employ the alternating optimization (AO), singular value decomposition (SVD) and minorize-maximization (MM). The simulation results demonstrate that our proposed algorithm achieves a significant improvement in the minimum RSBG compared to the benchmark, while ensuring that the IRS can obtain sufficient energy through SWIPT technology. This will contribute to achieving a more environmentally friendly and sustainable communication network for energy-constrained ISAC systems.