A Geometry-Based Modelling Approach for the Line-of-Sight Probability in UAV Communications

This paper presents a geometry-based three-dimensional Probability of Line of Sight
$(P_{\mathrm {LoS}})$
model for generic urban environments. The existing
$P_{\mathrm {LoS}}$
models are mostly empirical, based on measurements or ray-tracing simulations at specific environments. To enable Unmanned Aerial Vehicle (UAV) communication in various environments, it is urgently necessary to develop an analytical model with high parameter scalability. Through introducing the ITU model that describes a built-up environment with three parameters, we derive a closed-form
$P_{\mathrm {LoS}}$
model with the inputs of city built-up parameters, UAV altitude, elevation
$\theta $
and azimuth
$\varphi $
angles between UAV and User Equipment (UE). Furthermore, we develop a geometry-based simulator to validate the proposed analytical model. The results show good agreements between the simulated results, analytical results, and 3GPP
$P_{\mathrm {LoS}}$
measurements. We demonstrate that the existing models provide less accurate results, which calls for re-evaluating the use cases and performance of UAV-mounted communication equipment in urban environments.