Author

François Chan

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Open access 2026

Loss-Aware Wave-Domain Beamforming With Stacked Intelligent Metasurfaces for URLLC Systems

This paper investigates a stacked intelligent metasurface (SIM)-assisted multiuser multiple-input single-output (MISO) downlink ultra-reliable and low-latency communication (URLLC) system under the finite blocklength (FBL) regime. By leveraging multiple programmable metasurface layers, SIM enables direct wave-domain beamforming with enhanced electromagnetic wave control, which makes it particularly attractive for reliable and delay-sensitive communications. We propose a joint optimization framework for transmit power allocation, user blocklength, and phase shifts across the stacked metasurface layers, with the objective of maximizing the sum rate under the transmit power constraint while accounting for SIM insertion loss. The resulting problem is non-convex due to the coupled optimization variables and the FBL rate expression. To tackle this problem, an alternating optimization (AO) algorithm is developed, where successive convex approximation is adopted for transmit power and blocklength optimization, while projected gradient ascent is employed for SIM phase shift design. Numerical results show that the proposed design achieves up to an 140% higher sum FBL rate than conventional transmission without SIM. In addition, the optimized blocklength allocation provides approximately an 8% gain over equal blocklength allocation, while the impact of practical insertion loss becomes more pronounced in deeper SIMs, with the degradation reaching about 17% for the six-layer configuration. Moreover, the proposed algorithm exhibits fast convergence, making it suitable for low-latency wireless applications and highlighting the potential of SIM-enabled wave-domain beamforming for next-generation mission-critical wireless networks.

Zahra Rostamikafaki, François Chan, C. D’amours · IEEE Open Journal of the Com... · 0 citations

Preprint Sep 2026

Enhancing UAV Trajectory and Communications Through Vision-Inertial Tracking

In this paper, we propose an energy-efficient and reliable communication system for non-terrestrial networks deployed in dynamic GPS-denied wireless environments, enabled by a Vision--Inertial Tracking-Assisted UAV Communication (VIT-UAVCom) system. To the best of our knowledge, this is the first work to exploit onboard UAV cameras and IMU sensors for UAV-assisted communications. We consider a complete VIT-UAVCom system that incorporates the key design parameters while explicitly accounting for system noise and residual tracking inaccuracies. Building on this framework, we formulate an optimization problem for jointly designing the UAV trajectory and communication performance to improve propulsion energy efficiency, reduce outage probability, and enhance physical-layer security. We then develop a dedicated solution framework to efficiently compute near-optimal trajectory and communication control actions in dynamic scenarios. Furthermore, to enable real-time implementation, we propose and evaluate three optimizers, namely linear search (LS), binary search (BS), and genetic search. Our numerical results demonstrate that our proposed VIT-UAVCom framework significantly outperforms the K-means benchmark in terms of energy consumption while maintaining robust secrecy performance and reliable user coverage. Specifically, our proposed framework improves the energy efficiency by 144% compared to the benchmark. Interestingly, our results also show that, compared with the LS, the BS reduces the computational time by approximately 50%.

Abdallah S. Ghazy, Hussein A. Ammar, James H. Bayes et al. · 0 citations