Reconfigurable Intelligent Surface-Aided Secure Integrated Radar and Communication Systems

TL;DR

This paper proposes RIS-aided transmission schemes for secure integrated radar and communication systems, optimizing beamforming to enhance secrecy rates and addressing eavesdropper CSI uncertainties, with algorithms tailored for RCCE and DFRC systems.

Contribution

It introduces novel RIS-assisted secure transmission schemes with optimized algorithms for both RCCE and DFRC systems, considering imperfect eavesdropper CSI.

Findings

RIS-aided schemes significantly improve secrecy rate.

RCCE system outperforms DFRC in secrecy rate.

Algorithms effectively handle imperfect CSI.

Abstract

Despite the enhanced spectral efficiency brought by the integrated radar and communication technique, it poses significant risks to communication security when confronted with malicious radar targets. To address this issue, a reconfigurable intelligent surface (RIS)-aided transmission scheme is proposed to improve secure communication in two systems, i.e., the radar and communication co-existing (RCCE) system, where a single transmitter is utilized for both radar sensing and communication, and the dual-functional radar and communication (DFRC) system. At the design stage, optimization problems are formulated to maximize the secrecy rate while satisfying the radar detection constraint via joint active beamforming at the base station and passive beamforming of RIS in both systems. Particularly, a zero-forcing-based block coordinate descent (BCD) algorithm is developed for the RCCE system. Besides, the Dinkelbach method combined with semidefinite relaxation is employed for the DFRC system, and to further reduce the computational complexity, a Riemannian conjugate gradient-based alternating optimization algorithm is proposed. Moreover, the RIS-aided robust secure communication in the DFRC system is investigated by considering the eavesdropper's imperfect channel state information (CSI), where a bounded uncertainty model is adopted to capture the angle error and fading channel error of the eavesdropper, and a tractable bound for their joint uncertainty is derived. Simulation results confirm the effectiveness of the developed RIS-aided transmission scheme to improve the secrecy rate even with the eavesdropper's imperfect CSI, and comparisons between both systems reveal that the RCCE system can provide a higher secrecy rate than the DFRC system.