Covert Communication in RIS-Based Integrated Sensing and Communication System

The integrated sensing and communication system based on the reconfigurable intelligent surface (RIS) technology have found many crucial applications, while the covert communication serves as an attractive approach to implement secure transmission in an RIS-based integrated sensing and communication system. By exploring the RIS functionality, sensing-assisted signal hiding, and two-hop transmission mechanism, this paper proposes a novel covert communication strategy for the considered system. Specifically, we first develop theoretical models to depict covertness, sensing, and transmission performances in terms of detection error probability (DEP), Signal-to-Noise-plus-Interference Ratio (SINR) of echo signals, and transmission outage probability (TOP), respectively. We then formulate an optimization problem to determine the optimal settings of target rate and transmit powers of probing/covert signals for covert throughput maximization, subject to the constraints of DEP, SINR, TOP, and upper bound on transmit powers. By applying the alternating optimization technique to solve this optimization problem, we further derive the analytical formula for the maximum covert throughput. Finally, extensive numerical results illustrate the overall system performance of an RIS-based integrated sensing and communication system as well as demonstrate the effectiveness of the proposed covert communication strategy.