Robust Beamforming Design for Secure Near-Field ISAC Systems

2025-07-17

AI Summary

This work addresses robust beamforming design for near-field secure integrated sensing and communication (ISAC) systems operating in multi-user, multi-target, and multi-eavesdropper scenarios under channel uncertainty. The problem is formulated as maximizing the sensing beampattern gain subject to minimum SINR constraints for legitimate users, maximum SINR constraints for eavesdroppers, and a total transmit power budget. To tackle the resulting semi-infinite non-convex optimization, we propose a novel integration of the S-procedure and sequential rank-one constraint relaxation (SROCR), transforming the problem into a tractable linear matrix inequality (LMI) form that ensures both rank-one feasibility and low computational complexity. Compared with conventional semidefinite relaxation (SDR), the proposed method achieves superior security and robustness while maintaining high communication quality and sensing performance.

Technology Category

• Search and Optimization: Non-convex Optimization
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Constraint Satisfaction and Optimization: Mixed Discrete/Continuous Optimization

Application Category

• Security and Privacy: Large-scale security measurements
• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Search and Retrieval-Augmented AI: Web search models and ranking

Abstract

This letter investigates the robust beamforming design for a near-field secure integrated sensing and communication (ISAC) system with multiple communication users (CUs) and targets, as well as multiple eavesdroppers. Taking into account the channel uncertainty constraints, we maximize the minimum sensing beampattern gain for targets, subject to the minimum signal-to-interference-plus-noise ratio (SINR) constraint for each CU and the maximum SINR constraint for each eavesdropper, as well as the ISAC transmit power constraint. The formulated design problem is non-convex. As a low-complexity suboptimal solution, we first apply the S-Procedure to convert semi-infinite channel uncertainty constraints into linear matrix inequalities (LMIs) and then use the state-of-the-art sequential rank-one constraint relaxation (SROCR) method to address the rank-one constraints. The numerical results show that the proposed ISAC beamforming design scheme outperforms the existing semidefinite relaxation (SDR) and other baseline schemes, and it significantly enhances security and robustness for near-field ISAC systems.

Problem

• Design robust beamforming for secure near-field ISAC systems
• Maximize sensing beampattern gain under SINR constraints
• Enhance security and robustness against eavesdroppers

Innovation

• Uses S-Procedure for LMI conversion
• Applies SROCR for rank-one constraints
• Enhances security with robust beamforming