Terahertz Coverage Analysis with Fixed-Wing UAVs: Analytical Framework and Closed-Form Outage Modeling

This paper investigates terahertz (THz) coverage using fixed-wing unmanned aerial vehicles (UAVs), where severe free-space path loss, atmospheric absorption, and beam misalignment effects create significant coverage holes. To overcome the high computational cost of Monte Carlo based coverage evaluation, a coverage analysis framework is developed that incorporates circular trajectory parameterization and a composite THz channel including line-of-sight probability, absorption loss, beam misalignment, and small-scale fading. A new closed-form outage probability expression is derived for each grid cell, enabling fast and accurate coverage computation. Using this analytical model, a trajectory-parameter analysis framework is developed to evaluate altitude–radius configurations to minimize coverage holes over the target area. Simulation results validate the exact match between the proposed closed-form and Monte Carlo evaluations and reveal several interesting behaviors for fixed-wing UAVs, including optimal altitude–radius pairs and nontrivial coverage patterns. The proposed framework enables efficient trajectory design and reliable THz coverage with fixed-wing UAV platforms.