Low-Altitude Ground-UAV LoRa Path Loss over Mountainous Hills with and without Snow

The low-power wide-area network (LPWAN) LoRa protocol has been recently proposed for enabling a new generation of search-and-rescue (SaR) systems. The use of unmanned aerial vehicles (UAVs) and systems (UASs) can further improve the effectiveness of such SaR devices. However, the path loss (PL) of ground-air (GA) LoRa links is still underexplored, even in the simplest case of line-of-sight (LoS) links. In this work, the LoRa GA PL, when the receiver is mounted on a UAV in the presence and absence of snow, is characterized in the particular case of mountainous hills. In both cases, the PL is higher than predicted by the free space (FS) single-ray model, and the snowy environment did not show a higher PL than the dry one. The new PL fits can be used to extend existing GA frameworks to describe the mountainous hills scenario.