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will push forward the social acceptance of drones and the growth of their market.5Beyond line-of-sight drone control and between flying objects location information sharingBefore closing this article, we will introduce the follow-ing two technologies into which we, jointly with the National Institute of Advanced Industrial Science and Technology (AIST), have been putting eorts: 1. Latency-guaranteed multi-hop relay control communication tech-nologies; and 2. Between-ying-objects location information-sharing technologies. Both of them were de-veloped in the Tough Robotics Challenge [13](program managed by Prof. Satoshi Tadokoro, Tohoku University) of the ImPACT (Impulsing Paradigm Change through Disruptive Technologies) Program led by the Council for Science, Technology and Innovation, Cabinet Oce.1. Latency-guaranteed multi-hop relay control communication technologiese technologies enable keeping control communica-tion available in a situation where barriers such as a mountain or a building block direct radio waves—so called “beyond radio line-of-sight.” Flights using such communi-cation means are still strictly regulated by laws and acts. e “Roadmap for Small Unmanned Aircra Utilization and Technology Development” [14] under study by the Government has set the general classication on drone ight into the following four levels: Level 1, manual ight within line-of-sight areas; Level 2, autonomous ight within line-of-sight areas; Level 3, beyond line-of-sight ight over unmanned areas; Level 4, beyond line-of-sight ight over manned areas. e roadmap recommends that beyond line-of-sight ight should be used for Level 3 ight in around 2018 and for Level 4 ight in the 2020s or later. ere are two types of beyond line-of-sight ights: (a) the drone in ight is not in sight (beyond visual line-of-sight) but radio-wave connected; (b) the drone is not in sight and not radio-wave contacted (beyond radio line-of-sight). A drone in the case of (a), because it is radio connected, is able to y safely, although not in sight—for instance, such a drone can be used for ights for drone mounted sensor or video camera operations; this type of ight operations has been realized by applying currently available technolo-gies. e ights in the case of (b), although having much severer diculties than in the case of (a), will become indispensable in the future for long-range goods delivery ight or low-altitude monitoring ight over an urban area or a mountainous area, where radio waves are oen blocked. At present in most cases, we have no other means for accomplishing such ights than a 100-percent autono-mous means depending on GPS and using preprogrammed route information, not depending on wireless communica-tions. However, because the operator has no means to know the drone location or status, this type of ight can be very dangerous—note that generally used drones have a failsafe mechanism, returning automatically to the operator’s posi-tion if it goes out of radio range.Generally, three types of communication path establish-ment methods can be applicable to accomplish safe drone ights in such a “beyond radio line-of-sight” area, as fol-lows: (Fig. 10): (1) connection through ground infrastruc-tures—for example, mobile phone networks; (2) connection through satellites; and (3) connection through a relay sta-tion consisting of other drones or robots in collaboration.Method (1) is the most easily applicable method for the realization of beyond line-of-sight ights, while the use of mobile phone frequencies by a drone has been prohibited so far by regulations. However, the MIC decided last year to give “practical test station licenses” to communication business operators and permit them to use mobile phone frequencies limited for tests [15]. Mobile phone companies have started tests by using the licenses. However, they have problems to solve such as interference with ground mobile phone networks or above-ground service area distributions. So, applications to practical situations are yet to be realized. In addition, their service might be limited to some extent by ight areas, and it is not clear whether their services would be available in a situation where ground facilities are FiF10Method for keeping wireless link connected in a situation of beyond radio line of sight(1)Relayed through ground infrastructure includingpublic or mobile phone networks(handed over by ground stations or hub stations)(3)Relayed through satellites(2)Relayed through otherdrones or a robotsLow-altitude flight operation for observation, shooting or rescueVLOS/RLOSflight operation652-9 Wireless Communication Technology for Small Unmanned Aircraft Systems ~Towards the deployment of IoT in the Sky~