Space Compass, NTT DOCOMO, INC., Nippon Telegraph and Telephone Corporation (NTT) and SKY Perfect JSAT Corporation (SKY Perfect JSAT) jointly announced that they have been selected by the National Institute of Information and Communications Technology (NICT) to develop direct-to-device (D2D) mobile services, which will be deployed via a space-based non-terrestrial network (NTN) using high-altitude platform stations (HAPS).

The project is part of the NICT's Innovative ICT Fund Projects for Beyond 5G/6G, known as Beyond 5G, which envisions a society where connectivity is assured over the air, sea, and space regardless of user location.

The project comprises two phases:

Early commercialization (Phase 1)
The four participating companies aim to solve various technical issues and demonstrate a communication service using HAPS positioned in the stratosphere over Japan, with the goal of accelerating the commercialization of HAPS D2D communication services.

System evolution (Phase 2)
Research and development (R&D) will be conducted on high-speed, high-capacity technology and time-division duplex (TDD) communication (downlink and uplink use same frequency band but in different time slots), aiming to expand the business scope and applicability of HAPS services in the coming 6G era. Phase 2 will also focus on upgrading the feeder link, including increasing its capacity, and installing a satellite backhaul system for flexible operation in areas where it is not possible to install terrestrial gateway stations connecting HAPS and terrestrial networks.

Space Compass, which plans to launch HAPS services in Japanese fiscal year 2025, will lead the project, define network service requirements and evaluate demonstrations conducted under the project. DOCOMO, which plans to develop a HAPS-based mobile communications business spanning air, sea and space for 5G evolution and 6G, will mainly develop ground base stations and HAPS-equipped base stations for mobile communications, focusing on maximizing service-link efficiency and capacity. NTT will mainly develop the control technology of the HAPS feeder link, such as site diversity and control of the transmit power, for robust service quality. SKY Perfect JSAT, which plans to offer the NTN business by connecting satellites and HAPS networks to multi-terrestrial networks, will mainly focus on developing alternative feeder link methods, such as satellite-backhaul and improvement of connection rates through the multi-connection of ground gateway stations.

Through this R&D project and beyond, the four participating companies are committed to improving the quality, efficiency and flexibility of HAPS services, extending mobile coverage to extreme levels, and ensuring seamless connectivity.

Previously, the four companies began jointly researching and developing a space-based radio access network (RAN) as an NTN, with HAPS serving as key components to support ultra-wide mobile communication services in air, sea and space. In the coming future, HAPS-based networks are expected to facilitate the broad expansion of communication services, such as support for disaster communications, ship and drone connectivity, and communications in mountainous and remote areas such as islands.