Coverage Optimization for Reliable UAV-Assisted 5G/6G Communication Systems

Unmanned aerial vehicles (UAVs) play a pivotal role in 5G/6G wireless communication systems due to their deployment flexibility. This article explores optimal UAV positioning to maximize coverage in hybrid aerial–ground communication links. Exploiting a probabilistic line-of-sight (LOS) model, we examine coverage radius behavior in mixed urban and suburban environments to meet specific quality-of-service (QoS) targets. The analysis reveals that the coverage radius expands as the probability of LOS increases, which in turn increases with the UAV height. However, beyond a certain height, path loss becomes dominant, and further increases in altitude negatively impact the coverage radius. By studying the maximum coverage radius for minimum signal strength and spectral efficiency requirements, we numerically determine a configuration space of UAV altitudes and the corresponding maximum radius that satisfies the target QoS. The results illustrate a dual-regime behavior, where coverage increases with altitude up to a certain value, beyond which it declines, indicating the existence of an optimal altitude for reliability. In addition, the analysis of ground surface effects shows that flying over concrete surfaces significantly enhances coverage, offering a radius up to five times larger compared to rough, vegetated surfaces.