HTML5 Webook

68/182

or telemetering. Some models of drones have been using that band. As for the 920 MHz band, because it is also used for ground sensor networks or RF tags, for the purpose of ensuring frequency sharing, the output power of a station is limited by a regulation to 20 mW—note, a registered ground station is permitted to transmit with a power of up to 250 mW—, and at the same time, the channel bandwidth is limited to 200 KHz—up to 5-channel-bundling is permit-ted—and the transmission rate (duty rate) is limited. So, the band is not suitable for high-precision video transmis-sion, but not yet congested compared to 2.4 GHz although the device prices are low. In addition, because, in this band, the bandwidth and number of channels of a certain level is securable and the range is longer than that of 2.4 GHz, the band can be suitable mainly for business-use drone control or telemetry. Actually, the adjacent frequency bands are used for sensors or robots in many countries in the world, so such devices using the frequency band can have an opportunity to enter the international market. As will be mentioned later, we have already started the develop-ment of technologies using the frequency band.On the one hand, the Information and Communications Council of the MIC made a recommendation on the technical conditions for advanced radio wave utilization in March 2016, stating that frequency bandwidth of over 130 MHz in total (including the 169 MHz band, a part of the 2.4 GHz band and the 5.7 GHz band) should be made available under a license for image transmission by un-manned vehicles like robots. e license system has been eective since August 2016 [9][10].e opened frequency bands are for business opera-tions; a radio operator license is required to operate in those frequency bands (the 3rd or upper land special radio engineer license); antenna power over 1W (unless other-wise permitted, limited to 10 mW for 169 MHz band when used above the ground) is permitted, so the use of the bands is suitable for operations where over-5-km com-munication range is required. Note that the frequency bands are supposed to be shared with other operations.Although the main usage of those frequency bands is supposed to be ying object image transmission, they are usable for sending control signals. However, they are shar-able bands and there is a risk of interference with other wireless systems. CSMA methods as used in wireless LAN systems might be applicable, but high eciency is not expected in frequency utilization; particularly in some situations where a nearby station is transmitting with high power, the carrier sense mechanism is activated to halt transmission. So, in principle the use of these bands does not assume the CSMA method and the operators who are to share the frequency bands have to make operational arrangements.Under the circumstances as described above, for the purpose of the realization of safe and ecient utilization of the three licensed frequency bands, under the recom-mendation of the Radio Engineering & Electronics Association, discussions were made on the introduction of a proper operation arrangement scheme and the realization of services for centrally controlling the following manage-ment items: robot operation management, including the management of robot ID and robot ight/operation area, location, and others; and radio wave management, includ-ing the management of frequency channels, bandwidths, antenna powers and others. en, on July 11, 2016, the group “Japan Unmanned System Trac and Radio Management Consortium” (JUTM) was established [11]. e group is chaired by Prof. Shinji Suzuki, Tokyo University, and participated in by communication business operators, universities, national institutes, private corpora-tions, and others. Figure 9 shows a schematic diagram of the group’s target system [12]. e group, at rst, will limit their services to the provision of UAS pre-ight scheduling services on a public platform, and then they will enhance their system to provide real-time locations of unmanned and manned aircras in ight, weather reports, and wave propagation simulation 3D outputs. Furthermore, they have a plan for the future to introduce a system that enables alteration, in ight and real-time, of UAS’s radio resources (transmission slot or frequency, antenna power, and others). Such a system will contribute to the safe navigation of robots, in particular business operation-use drones, and the ecient utilization of radio waves, which FiF9Schematic diagram of operation and radio wave management systemPublic networksRadio management server(Sharing of licensed frequency band and output power, wireless resource allocation, and aids for mutual adjustment)Link of image, control and telemetryTraffic management server(providing aircraft ID, flight route/range, location, and aids for mutual adjustments)CollaborationRegistration of radio useWeb sharing, mutual adjustment, wireless resource allocationRegistration of ID, flight route, and locationSafety info, weather info, and mutual adjustmentManned aircraftLocation/flight informationRadio propagation simulatorIn visual line of sight/radio line of sightBeyond visual line of sightBeyond/in radio line of sightShort distance operation drone/robot(Using no license required frequency bands, not controlled by radio management service, but subject to use traffic management service)Long distance operation drone/robot(Using license required frequency bands and subject to use both the radio and traffic management services2 Terrestrial Communication Technology Research and Development64　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 2 (2017)