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1IntroductionIn a situation of a wide-area disaster caused by an earthquake, tsunami or ood, not only does trac get shut-down due to damages to roads, but also, due to com-munication facility breakdowns or power outages, commu-nication-networks, which we suppose are always available, fall into trouble. As a consequence, a large number of areas lose communication means and become so-called informa-tion-communication-isolated areas. In such information-communication cut-o situations, we have diculties in conrming the safety of local residents or knowing what is going on in the disaster area. Consequently, we cannot start relief operations in a timely manner, or grasp what goods are in shortage.For the purpose of preparing for such situation in di-sasters and promptly establishing emergency communica-tion-links to isolated disaster-areas, we imported a drone system in 2012—in those days, terms or technologies like drone or unmanned aerial vehicle (UAV) were quite new in Japan. e aerial system we introduced was the world’s most advanced type of battery-power xed-wing small unmanned aircra having the following features: no runway required to take o; easy to handle and portable; prompt-ly deployable at any time: long ight-time of two hours; and capable of ying in a beyond-line-of-sight environment if the wireless-connection is kept. By mounting a wireless relay equipment on the aircra, we developed a wireless-link system working as a “ying radio-tower,” a wireless link system, conducting, in collaboration with local govern-ments or other municipalities nation-widely, proof-of-concept experiments in simulated disaster situations from the point of disaster-prevention; and at the same time, we have collected and analyzed a variety of data relating to radio-propagation or communication quality in various environments.Small unmanned aircras, in these days generally called drones—in particular multi-rotor-types—have become widely used—and at a rapid pace of growth—for hobby-use and business-use, particularly for aerial shooting, infra-structure management jobs, or disaster control opera-tions—to the extent that the use of drones is called the “Industrial Revolution in the Air.,”—and reportedly the drone market size is expected to be 200 billion yen domes-tically and on the order of 10 trillion yen worldwide in 2022 (in ve years from now).2-9 Wireless Communication Technology for Small Unmanned Aircraft Systems ~Towards the deployment of IoT in the Sky~Ryu MIURA, Fumie ONO, Toshinori KAGAWA, Lin SHAN, Hiroyuki TSUJI, Huan-Bang LI, Takashi MATSUDA, Kenichi TAKIZAWA, and Fumihide KOJIMAThe “aerial industrial revolution” is widely expected, in which the small unmanned aircrafts, or “drones”, are becoming popular in aerial photography and videography, survey, logistics, and disaster management. However, the safety of the drones is still not sufficient and it is said to be essential for future development of the industrial market. For safety control and telemetry, the reliable radio communication is indispensable. However, the most of the current drones use the radio technology used in radio control toys. We introduced small fixed-wing unmanned aircrafts four years ago aiming to develop “an aerial radio tower” for large-scale disaster situations, and have carried out field trials and radio propagation measurements and analysis. Moreover, based on those experience and its know-hows, we have also promoted R&D on wireless technologies for reliable operation of drones, including multi-rotors, which is necessary for their future growth of industrial applications. We will further extend and develop those technologies for contribution to aerial IoT and aerial industrial revolution.572 Terrestrial Communication Technology Research and Development