Joint Beamforming and Power Allocation for Green and Secure JSAC Systems

Joint sensing and communications (JSAC) has been proposed as a key technology for future wireless networks, but it faces potential security challenges due to its integrated nature. This paper investigates a multiple-input multiple-output (MIMO) JSAC system with multiple communications users (CUs), where the base station (BS) performs both communications and sensing tasks in the presence of an eavesdropper with imperfect joint channel state information (CSI). Two schemes, time division (TD) and superposition (SP), are proposed. To achieve green and secure operations, two joint optimization problems are formulated to maximize the sum secrecy rate while ensuring sensing performance by conducting beamforming for communications and sensing, and allocating the power for different CUs for TD or SP. To solve the non-convex optimization problems, the semidefinite relaxation (SDR) method and the block coordinate descent (BCD) method are adopted to iteratively obtain the solutions to sub-problems. Simulation results demonstrate the performance gains of the proposed algorithms in the sum secrecy rate over other benchmarks.