Maximize Sensing Energy Efficiency of RIS-Assisted ISCPT Systems With Imperfect Channels and Charging

To supply energy for IoT devices, the reconfigurable intelligent surface (RIS) assisted integrated sensing and communication system with energy harvesting nodes becomes a common scenario in 6G. Considering a practical system with imperfect channel state information and nonlinear charging characteristics, this letter studies the sensing energy efficiency (SEE) maximization problem under the charging, communication, and sensing requirements. Since the charging rate, data transmission rate, and sensing quality interact and are related to the beamforming and RIS phase shifts, the formulated SEE maximization problem is highly coupled. To address this coupled problem, incorporating some optimization methods, an alternating optimization-based algorithm is then developed to jointly optimize the beamforming matrix and RIS phase shifts. Simulation results demonstrate that the proposed algorithm achieves robust SEE improvement and a balance among communication, sensing, and charging.