S-band radio propagation characteristics in urban environment for unmanned aircraft systems

This paper describes the radio propagation characteristics in urban environment for a fixed-wing unmanned aircraft (UA) system. In the Great East-Japan Earthquake in 2011, the even the latest mobile phones became almost unavailable due to the breakdown of base stations, electricity outage, and traffic congestion. In addition, many areas in mountains or islands were isolated due to the damage of roads, harbors, and communication infrastructures. In such a situation, a UA system has a potential to provide temporal communication links to the isolated areas while monitoring the situation in the disaster area. Therefore, we have conducted a measurement campaign in order to characterize ground-to-air radio channels for small UA at several locations, including urban and non-urban environments. Some measurement results of ground-to-air link in urban environment are reported in this paper. It is demonstrated that there is a suitable flight altitude for long-range ground-to-air channel in terms of radio propagation.