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tions, measurements were taken. We have conrmed that, although the outreach distance was shorter than about 8 km, ights are as stable as those of 2 GHz.Although almost all of the civil-use drones on the market these days are multi-rotor types, those multi-rotor type drones are operable for only 15 to 20 minutes. However, communication-link drones are required to stay in the air for longer hours. So, we believe that xed-wing type drones, which can stay in the air for long hours, are more suitable to communication use.2.2Proof of concept experimentsWe demonstrated the ight and operation of the sys-tems we developed for the rst time on March 25 and 26, 2013, as an open experiment held at the “Disaster Resilient ICT Research Symposium.” We proved in the experiment that the exchange of safe conrmation information or mail to and from isolated areas at a long distance is secured even in a situation with no internet connection available, by our system using drones in the air—our system was connected to the testbed, independently installed at a campus of Tohoku University, of “Disaster Resilient Wireless mesh network.” In the years since the rst ight to March 2017, in many places in Japan, we have conducted more than 200 ight tests—for longer than 100 hours in total. rough those tests, we veried the performance, conducted mea-surements on wave propagation characteristics, carried out demonstrations to municipalities and participated in disas-ter prevention exercises. In addition, we have conducted measurements on high above the ground radio wave envi-ronments and radio propagation characteristics (Fig. 4). We are introducing below the experiments in Sendai and Kochi, out of the large number of our trials.(a) Experiments on long-range communication (Sendai, Miyagi)We set the experiment conguration as follows: we put a Puma AE circling at sea level of 750 m above the re-claimed land where Tohoku University’s New Aobayama Campus is to build; we placed a number of ground stations in an area in the direction to the Pacic Coast across Sendai at the elementary/middle schools and hospitals—they are to be designated as shelters in a disaster situation. We conducted measurements of the propagation characteristics and throughput characteristics in the 2 GHz band at the various distances up to 14 km (Fig. 5). In the experiments, we observed diraction eects caused by urban-area build-ings leading to a degradation in communication quality compared to that of a simple free space propagation—we found up to a 30 percent drop in throughput at around a point 10 km away. However, we conrmed, in another experiment of long-distance communication conducted in Hokkaido—the ground was covered with woods or grass elds—that we suered less diraction eect and com-munication was good between the two points up to 20 km away.(b) Experiments on mobile phone relay by the femto cell / satellite communication combination (Shimanto-cho, Kochi)We conducted experiments on the temporary relief of mobile phone communications using a femto cell/satellite communication link—a femto-cell is a micro mobile phone hub station with a communication area of a 100 m radius or less—, on the assumption that ground mobile phone networks are shut down, where we used a femto cell, a drone communication link, and satellite links (Wideband Internetworking Engineering Test and Demonstration Satellite WINDS)[4] (Fig. 6).FiF5Urban area long distance communication experiment (Sendai, Miyagi, July 2013)Measuring throughput at each of designated shelters10km83.7kbpa14km12km32.6kbps6km8km49.2kbps4km93.7kbpsDrone circling center（AobayamaCampus, Tohoku University）Pacific OceanArahamaElementary SchoolKoriyama Middle School（capacity: 11400）ShichigoMiddle School（capacity: 8800）KatahiraCampus, Tohoku University（capacity: 5300）Vicinity of Kosei NenkinHospital（capacity: 14700）Altitude above sea level: 750mCommunication speed: average of the measurements of effective UDP transmission speed at the transmission rate of 100kbps）FiF4　Major experiments (conducted so far)Memuro-cho, Hokkaido（Agriculture ICT application experiment）June 2014Taiki-cho, Hokkaido（Long distance communication experiment）June, November 2013Aobayamacampus, Tohoku University（Disaster-link experiment, open campus collaboration) March, July 2013, July2014OotoneAirfield（TV program shooting, TV Tokyo WBS）December 2013ShonanKokusai Mura（Flight training）March 2013Shirahama-cho, Wakayama（Disaster-link experiment) March 2014(On the air, NHK News Watch 9）Sakaide, Kagawa（Disaster relief exercise at SanukiMedical Rally, etc.）May 2014, May 2015, March 2016Conducted flights more than 200 times and longer than 100 hours in totalTomioka-cho, Fukushima（Wild boar signal capture experiment in restricted habitation area) October 2014Shimanto-cho, Kochi（Femtocell relay experiment in mountain area) February 2015 (On the air, News Watch 9, NHK）Oushu, Kanegasaki-cho, Iwate(Comprehensive disaster exercise）July 2015Fukushima Sky Park（Wireless communication experiment）December 2015Sanagouchi-mura, Tokushima（Wild monkey signal capture experiment）June 2016Hitoyoshi, Kumamoto（Forestry ICT basic experiment）November 2016* For each experiment, submitted request for permission or reported flight planas specified in the Civil Aviation Actor2 Terrestrial Communication Technology Research and Development60　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 2 (2017)