Characterization of near-ground radiohelmet-UAV LoRa links with transmitter buried under the snow

The LoRa protocol has proven instrumental in advancing search and rescue (SaR) operations within harsh environments wherein current localization technologies underperform or are unusable. Measurement campaigns are hence investigating the radiowave propagation of LoRa to draw limits and opportunities posed by the technology, also when combined with wearable antennas and unmanned aerial vehicles (UAV): This contribution reports a measurement campaign of a LoRa link between a radiohelmet buried under 1 m of snow and a UAV, and then proposes an angular model for the excessive aerial path loss (PL) of this peculiar scenario which has not ever been considered. Indeed, the radiowave propagation in these links when the transmitter is buried under the snow has not been investigated to the best of author's knowledge. The presence of the human body is simulated by using a homogeneous meat phantom and the resulting model is in line with a similar one in mountain canyons, highlighting a significant reduction of the path loss (down to -50 dB) for low depression angles, and a more significant benefit of the use of UAVs than in suburban scenarios.