Numerical and experimental evaluation of Radiohelmet-to-UAV LoRa Links

Body-worn radios exploiting the recently introduced LoRa protocol are very promising for Search and Rescue (SaR) operations in harsh environments. If the GPS signal is unavailable and there is not visual Line-of-Sight (LoS), the body-worn transmitting beacon could be localized based on the Received Signal Strength (RSS) measured by the rescuers. Moreover, an Unmanned Aerial Vehicle (UAV) equipped with a LoRa receiver could scout a vast area in little time and swiftly collect multiple RSS measurements. In this paper, the RSS seen by the UAV when a transmitting LoRa beacon is embedded in a safety helmet is evaluated through a two-ray model. The numerical values are corroborated using a flying UAV with good agreement.