Robust Fast 3D Beam Alignment for UAV-Assisted mmWave and Terahertz Communications

Area of Science:

• Wireless Communication
• Next-Generation Networks (5G/6G)
• Signal Processing

Background:

• Unmanned Aerial Vehicle (UAV)-assisted millimeter-wave (mmWave) and terahertz (THz) communications are key for ultra-reliable, low-latency next-generation wireless networks.
• Initial access and beam alignment in 3D environments with highly directional beams present significant challenges for UAV-assisted mmWave/THz systems.

Purpose of the Study:

• To develop a risk-aware beam alignment framework for UAV-assisted mmWave/THz systems.
• To minimize expected cell-search latency and its variance while meeting detection-failure and link-quality constraints.
• To enable fast and dependable initial access in 5G mmWave and 6G THz networks.

Main Methods:

• Investigated a risk-aware beam alignment framework where user equipment scans a 3D spherical region for UAV base stations.
• Employed the Lévy Self-Renewable Flow Direction Algorithm (LSRFDA) to solve the non-convex optimization problem, combining Lévy-flight exploration with self-renewal.
• Utilized a unified propagation model incorporating free-space spreading loss and frequency-dependent molecular absorption for mmWave and THz regimes.

Main Results:

• LSRFDA demonstrated lower latency and latency variation compared to Particle Swarm Optimization, Random Search, Reinforcement Learning, and PPO-Lagrangian methods.
• The proposed approach achieved more reliable detection and lower energy consumption across various UAV densities and coverage radii.
• Validated the effectiveness of risk-aware geometric optimization for initial access in UAV-assisted mmWave/THz networks.

Conclusions:

• The LSRFDA-based risk-aware beam alignment framework significantly enhances initial access performance in UAV-assisted mmWave/THz systems.
• The method provides a robust solution for minimizing latency and its variance while ensuring reliable communication.
• This research contributes to the advancement of fast and dependable initial access for future 5G and 6G wireless networks.