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frequencies in the Ku/Ka band to connect drones to satel-lites. However, because the 5 GHz band is already con-gested, we have to prepare interference avoidance measures or frequency sharing rules—ground wireless access systems use frequencies in the same band, and airport wireless access systems use frequencies in adjacent bands. Moreover, with regard to satellite links, we have to avoid interference with other satellite links. So, for the purpose of preparing such interference avoidance measures, the following have become the urgent matters: creating a quantitative wave propagation model; knowing the interference situations; developing interference reduction technologies; and in addition, highly reliable and ecient wave resources wire-less communication technologies have been largely re-quired.In the abovementioned situations, the Ministry of Internal Aairs and Communications requested contract research proposals of “Research and Development of the Technologies for the Collaboration and Sharing of Wireless Link Systems using Unmanned Aerial Vehicle and Terrestrial Networks.”NICT, in response to the RFP, took a leading role in the establishment of a research consortium consisting of the ve organizations—NICT, Tohoku University, Electronic Navigation Research Institute, KDDI Research, Inc., and NEC Corporation, acquiring contracts and conducting research and development in the three years from FY2013 to 2015. Figure 7 shows a schematic diagram of how an unmanned aerial vehicle works for keeping communica-tions sustainable in a disaster situation—the diagram had been referred to during the research and development as the concept scenario. e research and development in-cluded a variety of items as shown below.5 GHz band CNPC link sharing:(1)Developing radio propagation models for evaluat-ing frequency sharing (NICT),(2)Technologies for frequency sharing with other ground wireless operations (Electronic Navigation Research Institute).Sharing of via satellite CNPC link:(3)Technologies for sharing frequencies in the Ku / Ka band between an UAV and satellite links for other uses (NICT).Technologies of eective frequency utilization for com-munications by using drones in disaster situations, etc.:(4)Technologies of advanced store-and-forward links by a drone-mounted small-sized server (KDDI Research Inc.),(5)Research and development on delay-tolerant net-work congurations (Tohoku University),(6)Link technologies for space-time coded signals in a massive MIMO system consisting of ground sta-tions and drones (Tohoku University),(7)Advanced frequency control technologies adaptable to the drone-use environment (NICT and Electronic Navigation Research Institute),(8)Drone-assisted terrestrial network trouble diagnosis algorithm (NICT).Eective frequency utilization in drone CNPC link:(9)Technologies of ground-drone multi-link MIMO coding (NICT),(10)Implementation and evaluation of ground stations-to-drone hand-over control algorithm (NEC Corporation).Every above mentioned item, except for item (3), is related to wireless link in the 5 GHz band for drones to ground stations, or drones simultaneously in the air.In the latter half of FY2015, we conducted actual ight tests jointly with the member organizations in the test elds in Fukushima and Kagawa to evaluate the performance of the test model we developed in a real ight environment, mounting the model on a xed-wing type drone and multi-rotor type drone (Fig. 8). We will leave the details of the research and development results to another paper [7].We used a part of those results in our international standardization activities; in FY2014, we participated in the 17th AWG meeting held in September (AWG 17), submit-ting a paper on “Technologies of Drone Control Ground Station-to-Station Handover,” persuading other participat-ing countries to nalize the APT Report; in addition, at the 18th AWG meeting (AWG 18) held in Japan in March 2015, we made a proposal from another report on the public use of drones, and at the meeting site, we had a FiF7Drone application scenario for keeping communications in a large disaster situationIsolated areaIsolated areaStably operating a UAS using a highly reliable control link established through terrestrial network and MIMO coding-assisted relay communication technology“Life messenger,” sequentially and circularly flying over a shelter to deliver messages via delay-tolerant relay linkSecondary control stationMIMO coded linkDelay-tolerant relay linkDetection of isolated areas and acquisition of damage situations by onboard camera videoInstalling a virtual radio tower using a drone circling above an isolated area to promptly recover communicationsUsers are allowed to connect their mobile terminals via Wi-Fi (email, IP phone or web access available)Some areas have cut-off communication in a large-scale disaster⇒Launching small UAVsNote: UAS：UnmannedAircraftSystemUAV：Unmanned Aerial VehiclePrimary ground control station (in a municipal office or fire station)2 Terrestrial Communication Technology Research and Development62　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 2 (2017)