An Optimal RIS Design Strategy for Jointly Improving Key Rate and Communication Performance in Quasi-Static Environments

This letter explores a joint improvement scheme for physical-layer secret key generation rate and communication performance with the aid of a reconfigurable intelligent surface (RIS) in quasi-static environments. Some RIS elements are exploited to construct random beams for key generation, and others are designed for energy-enhanced directional beamforming to improve the legitimate users’ signal-to-noise ratio (SNR). A joint design protocol is proposed, and the optimal RIS design strategy is analyzed to minimize the transmit power. Simulation results show that our scheme can resist the instantaneous SNR loss caused by the fast-fading effect in random channels and achieve joint improvement of key rate and communication performance.