The LTE test was carried out between the HAPS flying at altitudes around 20km and a 4G device on the ground.

The LTE base station was connected to the ground gateway station, and non-regenerative relay technology was used to reflect the radio waves through the communication device mounted on the HAPS and connected to the 4G device on the ground.

Space Compass says throughput of more than 4.66 Mbps was observed during reception of the radio wave transmitted from the ground gateway station to the 4G device via HAPS.

"Successful delivery of the reflected radio waves to the 4G equipment was confirmed at the test site in Kenya," Space Compass says.

"This is the world’s first successful establishment of wireless communication between a fixed-wing HAPS flying in the stratosphere at altitudes above 18 km and a smartphone on the ground."

The fixed-wing HAPS aircraft Zephyr, made by AALTO HAPS, a subsidiary of Airbus Defence and Space, was used for the testing.

Zephyr claimed a record for the longest flight of HAPS in 2022, with a continuous duration of 64 days.

Space Compass and NTT Docomo have targeted entry-into service in 2026 of a space-based RAN, with HAPS serving as key components to support ultra-wide mobile communication services in air, sea and space.

"We are dedicated to working towards the commercialisation of our HAPS service in 2026, and the success of this trial marks a significant step forward in achieving this goal," said Shigehiro Hori, Co-Chief Executive Officer of Space Compass Corporation.

"With this important milestone, we will continue to conduct testing and accelerate the development of our HAPS service.

"We are confident that the future of HAPS holds great potential, and we invite everyone to look forward to what’s to come."

Takaaki Sato, Senior Executive Vice President and Representative Member of the Board of Directors of NTT DOCOMO, said the successful test marks a significant step forward in shaping the future of mobile communications.

"By combining long-duration stratospheric flights with DOCOMO's wireless technology, we aim to not only enhance disaster response and expand coverage areas but also to accelerate the delivery of innovative HAPS services that offer unprecedented value," Sato said.