Characterizing the Small-Scale Fading for Low Altitude UAV Channels

In this contribution, a recently conducted measurement
campaign in a suburban scenario for the Unmanned Aerial
Vehicle (UAV) Air-to-Ground (A2G) radio channel is introduced.
The downlink signals in an in-service Long Term Evolution
(LTE) network were collected and utilized to extract the Channel
Impulse Responses (CIRs). A high-resolution parameter
estimation algorithm derived based on the Space-Alternating
Generalized Expectation-maximization (SAGE) principle is applied
to estimate the delays, Doppler frequencies and complex
amplitudes of MultiPath Components (MPCs) from the CIRs.
Based on the MPC estimation results, fast fading characteristics
of the A2G channels are investigated. It is found that the
Rician distribution models the fast fading the best compared
to Nakagami, Lognormal and Rayleigh distributions. Rician Kfactors
are also calculated for the A2G channels.