SoftBank HAPS trial in Japan tests edge computing ahead of 2027 launch

SoftBank and US aerospace company Sceye have completed a High Altitude Platform Station (HAPS) communications trial in Japan as the operator prepares to commercialise the technology from 2027.

The companies tested mobile connectivity between a stratospheric platform and smartphones on the ground, along with communications involving drones. SoftBank also tested edge computing directly aboard the HAPS.

Sceye’s lighter-than-air platform departed New Mexico on August 9 and travelled more than 15,000km across the Pacific in around 13 days. It entered Japanese airspace on August 23 before operating around Muroto City in Kochi Prefecture, off Cape Muroto.

Sceye said the platform operated at an altitude of around 16.5km during the communications tests. It remained in Japanese managed airspace for more than seven days and maintained its position within a radius as small as 5km during part of the operation.

From stratosphere to mobile core

The communications test used a 4G LTE-equivalent base station installed on the HAPS. A ground gateway connected the airborne base station to SoftBank’s mobile core network.

SoftBank and Sceye tested voice calls, text messaging, internet applications, video calls, and video streaming between the HAPS and smartphones on the ground. They also tested earthquake and tsunami warning messages and completed a call to Japan’s 118 maritime emergency number in cooperation with the Japan Coast Guard.

The International Telecommunication Union’s World Radiocommunication Conference in 2023 identified spectrum in the 2GHz and 2.6GHz bands for HAPS operating as IMT base stations, known as HIBS. The ITU said HIBS can provide mobile broadband using the same frequencies and devices as terrestrial IMT networks.

SoftBank said the Japan trial achieved communications performance comparable with its terrestrial networks while reducing radio interference with ground-based base stations. The tests also provided information on equipment and network configurations required for commercial HAPS operations.

In 2025, SoftBank tested a 5G HAPS radio architecture using a light aircraft flying at about 3,000 metres. The test used a six-cell payload with a 1.7GHz service link to mobile devices and a 26GHz feeder link connecting the aerial system to a ground gateway.

Digital beamforming kept six coverage cells fixed on the ground while the aircraft moved above the test area. SoftBank reported an average downlink speed of about 33Mbps at a location designed to reproduce the elevation angle expected near the edge of a HAPS coverage area.

The latest trial also extended connectivity to a drone operating in the test area. SoftBank used the HAPS connection for remote flight control, location-data transmission, and video transmission from the aircraft.

SoftBank has separately tested ways for aerial and terrestrial base stations to share mobile spectrum. In a December 2025 field trial, announced in April 2026, the operator used dynamic nullforming to reduce radio emissions from an airborne base station towards a terrestrial base station operating in the same 1.7GHz band.

SoftBank said the technique improved average throughput for the device connected to the terrestrial base station by about 80% compared with operation without dynamic nullforming. The company has not said the technology was used in the latest Sceye trial.

Edge computing moves onboard

SoftBank also moved mobile-network processing onto the HAPS. It installed mobile core functions and a web server aboard the platform, allowing smartphone requests to be processed in the stratosphere rather than routed through a terrestrial network to an internet-based cloud service.

SoftBank reported an average round-trip response time of 68 milliseconds during the onboard processing test. That was more than 40% lower than the latency measured when traffic was processed using the internet-based cloud service selected for the company’s comparison.

SoftBank described the test as the first to install both a mobile core network and web server on a HAPS and process smartphone communications entirely aboard the platform. The company said the claim was based on publicly available information as of August 23, 2026.

SoftBank did not disclose the location of the comparison cloud service, the wider network path, or equivalent measurements from a terrestrial edge-computing deployment.

Linking HAPS with satellites

SoftBank has been working on HAPS technology since 2017. Its development has covered aircraft platforms as well as telecommunications payloads, antennas, batteries, motors, and related network technologies.

The operator expanded that work in June 2025 when it invested in Sceye and secured exclusive rights to provide services in Japan using the US company’s lighter-than-air platform. Sceye’s aircraft uses buoyancy to remain airborne rather than the aerodynamic lift used by fixed-wing HAPS platforms.

When it announced the investment in June 2025, SoftBank said it planned to begin pre-commercial HAPS services in Japan in 2026. The operator identified communications recovery during large-scale disasters and connectivity for mountainous regions and remote islands among its planned applications.

SoftBank is developing HAPS alongside terrestrial and satellite networks.

“SoftBank aims to build next-generation communications infrastructure that seamlessly connects the ground, the sky and space,” SoftBank President and CEO Junichi Miyakawa said.

Its wider programme includes work with Japan’s National Institute of Information and Communications Technology, ArkEdge Space, and Kiyohara Optics on optical links between HAPS and low-Earth orbit satellites.

The organisations plan to attempt bidirectional optical communications between a HAPS and a LEO satellite in 2027. The optical communications equipment is being designed for bidirectional transmission at 10Gbps.

NICT said the planned HAPS-to-LEO test could cover a distance of up to approximately 2,000km.

SoftBank and Sceye will use data collected from the Japan trial to develop operating procedures and further work on communications performance ahead of commercial services planned from 2027 onward.

(Photo by Softbank)

See also: Ericsson Japan begins AI network research with Tokyo partners

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