Four companies partner to develop a direct communication system — Connecting HAPS and mobile terminals in the stratosphere

In pursuit of achieving early practical use of a direct communication system for mobile terminals using a high-altitude platform station (HAPS: flying in the stratosphere), Space Compass, NTT DOCOMO, INC., Nippon Telegraph and Telephone Corporation (NTT) and SKY Perfect JSAT Corporation are collaboratively researching and developing a high-speed, high-capacity technology. This research and development is directed toward accelerating the development of the direct communication system and expanding the application scope of this system after its practical use. This initiative was adopted by the Innovative Information and Communication Technology (Beyond 5G (6G)) Fund Project, which was publicly solicited by the National Institute of Information and Communications Technology (NICT). This initiative will be exhibited and introduced at Docomo Open House '24, which will be held by DOCOMO from January 17, 2024.

The four companies have been investigating "super coverage expansion" to provide communication services to any location in the sky, sea, and space and realize Beyond 5G. They have been conducting research and development on building a space radio access network (RAN), which is a non-terrestrial network (NTN), and HAPS. Among these, HAPS allows the construction of unconventional networks that can provide communication services from the stratosphere (approximately 20 km above the ground) to air, the oceans, and the ground.

HAPS, an unmanned aerial vehicle that can fly non-stop in the stratosphere for long periods (from several days to several months), will be equipped with a transponder and other equipment to cover an area of 100 to 200 km in diameter, depending on the design of the aircraft. Delivering communication services in the sky and ocean, as well as in depopulated and mountainous areas, has been challenging and capital-intensive. However, with the implementation of this new technology, providing communication services in the sky and ocean and to the aforementioned areas will become a reality.

The project is expected to achieve a dramatic improvement in the convenience of communication services in various ways - not only in its application in disaster countermeasures, but also in the widening of service areas to remote islands, mountainous areas, and the sea and the resulting expansion of applications for drones and vessels.

This technological development is aimed at achieving early practical application and advancement of a system that provides communication services directly to mobile terminals, such as smartphones and tablets, via unmanned HAPS flights in the stratosphere. In addition, communication experiments for mobile terminals in the stratospheric environment will be conducted using a HAPS aircraft in Japan.

To promote the spread of HAPS and expand its application scope in the Beyond 5G era, they will promote the development for advancement of the system. The purposes of this development include achievement of high-speed, high-capacity communications between mobile terminals and HAPS (service link), realization of uninterrupted communications between HAPS and ground gateway stations (feeder link), and utilization of time division duplex (TDD) frequency bands.

Space Compass, a joint venture by NTT and SKY Perfect JSAT, is the principal investigator of this development. The company aims to launch HAPS communication services by the end of FY2025, and in anticipation of its commercialization, the company will resolve all the associated technical issues for social implementation as well as conduct demonstration experiments.