Design and Optimization of Sounding Sequence for Multi-antenna Air-to-ground Channel Measurements

Unmanned aerial vehicle (UAV) has been widely used in different areas, where air-to-ground (A2G) channel characteristics are the fundamental to design reliable UAV to ground communication systems. For the channel measurement system with multiple transmitting antennas, this paper designs two sounding sequences based on the root index and nonlinear phase modulation, respectively. Due to the non-stationarity of A2G channels, the traditional time-division multiplex mode is not appropriate for the multi-antenna A2G channel measurement system anymore. The proposed sounding sequence can enable the measurement system to transmit the sounding sequence simultaneously but do not increase the complexity of data processing in the receiver. Meanwhile, the pros and cons of two sequences are analyzed. Finally, the effectiveness of two proposed methods is verified by the channel measurement in real A2G scenario.