Secure Transmission for Fluid Antenna-Aided ISAC Systems

2026-02-26

AI Summary

This work addresses the security threat posed by sensing targets acting as eavesdroppers in integrated sensing and communication (ISAC) systems. To enhance physical-layer security, the paper introduces fluid antennas into ISAC for the first time, leveraging their spatial agility to jointly optimize antenna positions and beamforming for maximizing the sum secrecy rate across multiple users. The proposed approach is developed within a block successive upper-bound minimization (BSUM) framework, incorporating a proximal distance algorithm (PDA) to enable closed-form beamforming updates and an extrapolated projected gradient (EPG) method for efficient antenna position optimization. Numerical results demonstrate that the proposed scheme achieves over a 20% improvement in sum secrecy rate compared to conventional fixed-antenna systems, significantly strengthening secure transmission in ISAC.

Technology Category

• Search and Optimization: Mixed Discrete/Continuous Search
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Multiagent Systems: Agent Communication

Application Category

• Security and Privacy: Large-scale security measurements
• Search and Retrieval-Augmented AI: Agentic search
• Systems and Infrastructure for Web, Mobile and WoT: Location- and context-aware Web and WoT applications and services

Abstract

Fluid antenna (FA) has become a highly promising technology and has recently been used to enhance the integrated sensing and communication (ISAC) system. However, the scenario where sensing targets act as eavesdroppers in ISAC and how to maximize the sum secrecy rate has not been addressed. This letter investigates secure transmission in FA-aided ISAC systems, where the spatial agility of FAs enables enhanced physical layer security. We jointly optimize antenna position vector (APV) and beamforming to maximize the multiuser sum secrecy rate, which complicates the solution process. To solve the resulting non-convex problem, we use a block successive upper-bound minimization (BSUM) algorithm, which incorporates the proximal distance algorithm (PDA) for closed-form beamformer updates and extrapolated projected gradient (EPG) for APV optimization. Simulation results show that the proposed FA-ISAC scheme achieves over 20$\%$ sum secrecy rate gain compared to fixed-position antenna (FPA) systems.

Problem

• Fluid Antenna
• ISAC
• Physical Layer Security
• Secrecy Rate
• Eavesdropping

Innovation

• Fluid Antenna
• Integrated Sensing and Communication (ISAC)
• Physical Layer Security
• Sum Secrecy Rate
• BSUM Algorithm