Beamforming Optimization for Secure THz ISAC Systems

Abstract

This paper introduces a joint beamforming optimization framework for secure Integrated Sensing and Communication (ISAC) systems operating in the terahertz (THz) frequency band. The suggested method minimizes total transmit power while meeting stringent Quality-of-Service (QoS) constraints on secrecy capacity, sensing performance, and energy efficiency. The system model integrates pointing errors (PE) and α-μ fading to accurately represent the realistic behavior of THz propagation, reflecting the characteristics of practical free-space optical and mmWave channels. A semidefinite relaxation (SDR) method is used to address the nonconvexity of the beamforming problem, facilitating an efficient convex formulation that ensures tractability. The framework jointly designs beamforming vectors for information signals and artificial noise, enhancing the security of the physical layer and environmental awareness. Additionally, the algorithm is adapted to THz-specific impairments, such as range-dependent bandwidth and near-field effects. The simulation results demonstrate that the proposed algorithm can effectively balance power consumption, communication security, and sensing accuracy. The performance of the algorithm under various antenna configurations and channel parameters confirms its robustness and suitability for next-generation 6G networks. This work provides a practical reference for developing secure, and energy-efficient THz ISAC systems and highlights the potential of integrating data-driven approaches in future extensions.