MIMO Channel Measurements in a Tree Covered Urban Environment for Low-Altitude UAVs.

This paper presents the preliminary results of multiple-input-multiple-output (MIMO) air-to-ground channel measurements analysis for low-altitude unmanned aerial vehicles (UAVs). The measurement campaign is carried out in an urban area where trees exist between the transmitter and receiver. The ergodic channel capacity is found 4.7 and 4.3 b/s/Hz for line-of-sight (LOS) and non-line-of-sight (NLOS) conditions, respectively. It is also observed that the capacity of the MIMO channel varies significantly with the elevation angle. Finally, the attenuation induced by the tree shadowing is found between 4.9 and 12 dB, depending directly on the selected polarization combination.