Measurement-based command and control radio channel characterisation for UAVs

In recent years, the amount of unmanned aerial vehicle (UAV) based applications has strongly increased. In order to fly the UAVs safely, their command and control link needs a reliable and robust communication channel. A line of sight (LOS) between the UAV operator and UAV is, at the moment, an essential requirement to guarantee an error-free communication. However, even in LOS conditions, the reception of a constant signal level is not assured. In this paper, we present the results of a measurement campaign with a UAV and a drone moving on the ground that were electronically tracked with simultaneous dedicated beams at 3.2 GHz coming from a 10 element antenna array. Small software-defined-radio modules were integrated in the drones to record the strength of the received signal when moving. The instantaneous GPS coordinates of the UAV were transmitted via a 4G link to a ground station that translated them into spherical coordinates used at the antenna array side. We show that the UAV itself and its flying inclination produce around 10 dB fluctuations in the received power, even in LOS conditions, and therefore shadowing cannot be ignored.