ABE YumaResearcher, Space Communications Laboratory, Wireless Networks Research CenterAfter completing his master course, he joined NICT in 2017 and completed his doctoral course in 2020. He is currently engaged in the Engineering Test Satel-lite 9 project and research on resource and network management for large-scale satellite communications systems. Ph.D. (Engineering).Optimization of Global Communication Networks to Connect High-throughput and Numerous SatellitesTowards demonstration of Engineering Test Satellite-9 and network control technologyatellite communication systems are expanding in scale due to the rapid increase in satellite numbers, and addition-ally, communication satellites are becoming more sophisticated. At NICT, we are aiming to realize satellite communication systems that can be operated eciently, advance research on control models and optimiza-tion algorithms for resource allocation and network construction, and are planning to demonstrate a portion of the technologies by using Engineering Test Satellite-9 (ETS-9), scheduled to be launched in FY2022.■Background of satellite communicationsSatellite communication between space communication satellites and the ground is mainly used in places where it is not possible to connect to terrestrial communication net-works. A familiar example of satellite com-munication is in-ight internet, where aircraft and ground stations communicate via satel-lites. Additionally, satellite communication can provide communication links even when many terrestrial networks are unavailable, such as after a disaster. Furthermore, the de-mand for the Internet of Things (IoT) commu-nications has rapidly increased in recent years, and there is demand for increasing the capaci-ty of satellite communication systems.■Overall plan for ETS-9In order to make effective use of limited radio resources, at NICT, we are promoting research and development on technologies that increase satellite communication capacity and exibility, and we are aiming for demon-stration with ETS-9, scheduled to launch in FY2022 [1].Figure 1 shows an overview of the ETS-9 communication missions. ETS-9 is equipped with xed-beam, variable-beam, and optical feeder link communication missions, with Japan Aerospace Exploration Agency (JAXA) developing the satellite bus system and NICT developing the communication missions. The technologies to be demonstrated on ETS-9 roughly fall into two categories shown below:Frequency / Area Flexibility TechnologyWith conventional communication satel-lites, the communication resources allocated to each region are xed, so if communication demand suddenly increases at a certain time, such as during a disaster, then many users may not be able to communicate.Satellite communication exibility tech-nologies solve this problem. Frequency ex-ibility technologies are functions that can exibly change frequency bands, and area exibility technologies are functions that can exibly change available communication ar-eas.By using these technologies and con-trolling satellite communication missions in response to user requests, it is possible to al-locate the required amount of communication resources to the required location, and ETS-9 is equipped with a communication mission to achieve this. It uses frequencies in the 20 to 30 GHz band (Ka band), and the goal is to achieve transmission speeds of 100 Mbps per user.Figure 2 shows simulation results using the frequency exibility control algorithm proposed by NICT. This simulation assumes satellite communication services to an air-craft, and it can be seen that communication resource allocations change as the communi-cation requests change over time [2]. By using communication satellites with functionality like this, we believe that the number of people who can communicate will increase more than ever, even after a disaster.Optical Feeder Link TechnologyOptical communication, when compared with communication using radio waves, has Reference[1] Amane Miura, Toshihiro Kubooka, and Eiichi Sakai, "Activity to Establish Communications Technology on Next Gen-eration High Throughput Satellite by the Engineering Test Satellite 9," IEICE, vol.102, no.12, pp.1080-1084, 2019. (in Jap-anese)[2] Yuma Abe, Hiroyuki Tsuji, Amane Miura, and Shuichi Adachi, “Frequency Resource Management Based on Model Pre-dictive Control for Satellite Communications System,” IEICE Transactions on Fundamentals of Electronics, Communica-tions and Computer Sciences, vol.E101-A, no.12, pp.2434-2445, 2018. DOI: https://doi.org/10.1587/transfun.E101.A.2434[3] Yuma Abe, Masaki Ogura, Hiroyuki Tsuji, Amane Miura, and Shuichi Adachi, “Resource and Network Man-agement Framework for a Large-Scale Satellite Commu-nications System,” IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, vol.E103-A, no.2, pp.492-501, 2020. DOI: https://doi.org/10.1587/transfun.2019EAP1088SSpecial Issue for Space ICTNICT NEWS 2021 No.18
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