The integration of sensing and communication is one of the key feature for 6G networks, but its deployment raises serious concerns over privacy, security, and robust target detection under hostile conditions. In downlink massive multiple-input multiple-output systems, this letter examines the design of a secure multi-target integrated sensing and communication (ISAC) framework under both the availability and absence of eavesdroppers’ (Eves’) channel state information (CSI), as well as under imperfect CSI, for which a robust secure design is proposed under bounded CSI error model. We aim to minimize the direction-of-arrival (DoA) estimation error in terms of root mean square error (RMSE) while satisfying signal-to-interference-plus-noise ratio (SINR) constraints at legitimate users and secrecy constraints at the Eves. We address the dual challenge of robust sensing and secure communication in the presence of Eves. To ensure physical layer security, we incorporate the concept of artificial noise (AN) into the precoding design and analyze the performance in terms of sensing accuracy and secrecy. Simulation results indicate that AN significantly improves the sensing performance, reducing the RMSE of DoA in comparison with the non-AN baseline. Additionally, in the absence of Eve’s CSI, the Eve’s SINR is suppressed up-to significant levels under tight secrecy constraints. The simulation results highlight the dual role of AN in maintaining both sensing fidelity and communication secrecy across a wide range of power budgets and security requirements.
N. Zaman, A. A. Nasir· IEEE Communications Letters· 0 citations
Wideband terahertz (THz) communication systems assisted by active reconfigurable intelligent surfaces (RIS) are susceptible to frequency dependent beam squint, which degrades the array gain at band edge subcarriers and reduces the achievable rate. In active RIS architectures, mitigating this effect requires the insertion of true time delay (TTD) units, along with the joint optimization of their delays and the amplification and phase of all active RIS elements, while accounting for practical hardware constraints including amplifier noise, output power limitations, and finite resolution delay elements. In this work, we propose a hardware aware wideband active RIS design that jointly optimizes the per element amplitude, phase, and TTD responses to mitigate beam squint under realistic hardware impairments. The resulting non convex optimization problem captures the coupling among amplification, hardware induced noise, and frequency dependent beamforming, and is efficiently solved using a projected gradient ascent algorithm with element wise feasibility projections. Numerical results demonstrate that the proposed design significantly improves the signal to interference plus noise ratio (SINR) uniformity across subcarriers and consistently achieves the highest achievable rate among the considered benchmark schemes, including a frequency flat max min array gain active RIS design that optimizes the worst case array gain without employing TTD elements. Furthermore, the proposed scheme consistently outperforms phase only passive RIS, active RIS without TTD elements, and quantized delay active RIS baselines across different transmit power levels and active RIS noise conditions, demonstrating its effectiveness and robustness for practical wideband THz communications.
Faran Awais Butt, A. A. Nasir, A. Muqaibel· IEEE Open Journal of the Com...· 0 citations
This survey provides a systematic review across six interconnected domains—channel estimation (CE) and beam tracking, throughput maximization, weighted sum rate (WSR) and sensing co-optimization, delay and age of information (AoI) minimization, energy efficiency (EE), and PLS—each supported by a structured comparative table covering over 80 methodologies.
Manzoor Ahmed, Syed Tariq Shah, A. A. Nasir et al.· IEEE Open Journal of the Com...· 1 citation