Air-to-air radio channel measurement at 2.3 GHz for unmanned aircraft services

This paper presents a summary of a measurement campaign regarding radio propagation characteristics between airplanes based on a usage scenario of unmanned aircraft services (UASs) for disaster recovery. In order to reveal the characteristics air-to-air (A2A) links, the measurement campaign has been conducted in Hawaii, by using two small manned airplanes, through a 20-MHz bandwidth OFDM signal designed to this measurement at 2.3 GHz. The OFDM signal is continuously transmitted from one airplane, and at the other airplane signals received is repeatedly recorded. The recorded signals are utilized to calculate channel impulse responses (CIRs) in A2A links. Through analysis on the obtained CIRs, it is revealed that ground reflection gives an impact on the CIR when flying over the sea; on the other hand, it is not clearly observed when flying over urban areas due to tall buildings likely block the reflection.