  The use of the LoRa communication protocol in a new generation of
transceivers is attractive for search and rescue(SaR) procedures because they
can operate in harsh environmentscovering vast areas while maintaining a low
power consumption.The possibility of wearing helmets equipped with
LoRa-radiosand installing LoRa transceivers in unmanned aerial vehicles (UAVs)
will accelerate the localization of the targets, probably unconscious. In this
paper, the achievable communication ranges of such links are theoretically and
experimentally evaluated by considering the possible positions of the helmet
wearer (standing or lying) on a flat field, representing a simple SaR
scenario.Simulations and experimental tests demonstrated that, for the standing
position, the ground-bounce multi-path produces strong fluctuations of the
received power versus the Tx-Rx distances. Such fluctuations can be kept
confined within 100 m from the target by lowering the UAV altitude. Instead,
for a more critical lying position, the received power profile is monotonic and
nearly insensitive to the posture. For all the considered cases, the signal
emitted by the body-worn transceiver can be exploited to localize the helmet
wearer based on its strength, and it is theoretically detectable by the UAV
radio up to 5 km on flat terrain.
