Sensing-Assisted Secure Communication in MA-Aided ISAC: CRB Analysis and Robust Design

2026-04-26

AI Summary

This work addresses the challenge of acquiring eavesdropper channel state information in physical-layer security by proposing a sensing-assisted secure communication scheme that, for the first time, integrates reconfigurable mobile antenna (MA) placement optimization with integrated sensing and communication (ISAC) systems. The approach operates in two stages: first, the MA positions at both transmitter and receiver are optimized to enhance the accuracy of estimating the eavesdropper’s angle-of-departure (AoD), for which a closed-form Cramér–Rao bound (CRB) is derived; second, leveraging the AoD uncertainty region, a worst-case robust beamforming design is formulated and jointly optimized with MA placement to maximize the secrecy rate. The resulting problem is solved via alternating optimization, convex hull construction, and backward induction. Simulation results demonstrate that the proposed scheme significantly outperforms existing benchmark methods.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Mixed Discrete/Continuous Search
• Intelligent Robots: State Estimation

Application Category

• Security and Privacy: Large-scale security measurements
• Systems and Infrastructure for Web, Mobile and WoT: Location- and context-aware Web and WoT applications and services
• User Modeling, Personalization and Recommendation: Attacks and countermeasures in recommendation systems

Abstract

A core challenge in physical-layer security is the difficulty of obtaining the channel state information (CSI) of potential eavesdroppers. The inherent sensing functionality of integrated sensing and communication (ISAC) systems offers a promising solution by enabling the estimation of key parameters, such as the eavesdropper's angles of departure (AoDs). Capitalizing on this capability, we propose a sensing-assisted secure communication scheme for a movable antenna (MA)-aided ISAC system. The scheme comprises two stages: eavesdropper AoD sensing and secure communication. In the first stage, the base station (BS) optimizes the positions of its transmit and receive MAs to enhance sensing accuracy. We derive the closed-form Cramer-Rao bound (CRB) for the estimated AoDs to fundamentally characterize how MA positions influence the estimation uncertainty. In the second stage, the BS ensures secure communication by designing a robust beamforming vector that accounts for the AoD uncertainty region and by further optimizing the transmit MAs' positions to maximize the secrecy rate. To manage the end-to-end design, we formulate a joint optimization problem. This intractable non-convex problem is decomposed into two subproblems. For the first subproblem, we develop an alternating optimization (AO) algorithm to solve the CRB minimization problem. For the second subproblem, we solve the worst-case secrecy rate maximization problem using a method based on backward induction, convex hull construction, and AO. Finally, simulation results are provided to demonstrate the significant advantages of the proposed scheme compared to various benchmarks.

Problem

• physical-layer security
• channel state information
• eavesdropper
• integrated sensing and communication
• secrecy rate

Innovation

• Integrated Sensing and Communication (ISAC)
• Movable Antenna (MA)
• Cramer-Rao Bound (CRB)
• Physical-Layer Security
• Robust Beamforming