Joint Transmitter Design for Robust Secure Radar-Communication Coexistence Systems

This letter investigates the spectrum sharing between a multiple-input single-output (MISO) secure communication system and a multiple-input multiple-output (MIMO) radar system in the presence of one suspicious eavesdropper. We harness the detrimental radar interference, which traditionally impairs communication systems, as a strategic mechanism to jam the eavesdropper, thereby substantially enhancing the performance of secure communication. In particular, by considering the imperfect channel state information (CSI) for the user and eavesdropper, we present a robust joint design for the radar waveform and communication beamforming vector at the two systems, with the objective of maximizing the worst-case secrecy rate at the user, while ensuring the detection performance of the radar system. To tackle this challenging problem, we propose a two-layer robust cooperative algorithm based on the Charnes-Cooper transformation and the Cauchy-Schwarz inequality. Simulation results reveal the trade-off between secrecy rate and detection probability and highlight the pivotal role of such robust designs in facilitating secure coexistence systems.