Secure-sensing balance beamforming with artificial-noise-aided for integrated sensing and backscatter communication system

The Integrated Sensing and Backscatter Communication (ISABC) system integrates communication and sensing by using passive tags to reflect signals, enabling simultaneous environmental data acquisition and data transmission at the base station. Balancing security with sensing performance is essential to ensure reliable communication and precise environmental sensing in critical applications. This paper investigates an ISABC system where a full-duplex base station (FD BS) communicates with a legitimate user and performs tag sensing under eavesdropping threats. We propose a weighted optimization problem to balance the minimization of the Cramér-Rao Bound (CRB) for base station sensing with the maximization of the secrecy rate (SR), while maintaining a specified signal-to-interference-plus-noise ratio (SINR). Additionally, to enhance security without degrading sensing performance, we introduce an orthogonalized noise signal to disrupt the eavesdropper. To overcome the inherent non-convexity of the optimization problem, we reformulate it as a convex problem using successive convex approximation (SCA) techniques, including Taylor series expansions and semidefinite relaxation. Numerical simulations validate the effectiveness of the proposed approach in achieving the balance between security and sensing performance. Trade-off analysis indicates the improvement of the secrecy rate is achieved at the cost of degraded sensing accuracy.