SoftBank Validates Stratospheric Mobile Connectivity Ahead of 2027 HAPS Launch
SoftBank says it has completed a series of High Altitude Platform Station (HAPS) connectivity trials in Japan, demonstrating mobile communications, drone connectivity and edge computing from a stratospheric platform as it targets commercial services from 2027.
The tests were conducted in August 2026 using a lighter-than-air HAPS developed by US company Sceye. The platform travelled from New Mexico to Japan over 13 days before conducting communications trials near Kochi Prefecture at an altitude of approximately 17km. It subsequently returned to the US, completing a 30,000km round trip over 30 days.
The demonstration is a significant step in SoftBank’s HAPS programme’s journey, which dates back as far as 2017. Unlike satellite-based NTN systems, HAPS operates within the stratosphere, providing an aerial communications layer that can supplement terrestrial mobile networks without requiring infrastructure to be deployed in orbit.
SoftBank equipped the platform with a base station supporting 4G LTE-equivalent communications, connected to its mobile core network through a ground gateway. The system successfully supported voice calls, SMS, web browsing, LINE messaging, Zoom video calls and YouTube streaming on smartphones.
Peak speeds reached 36Mbps downlink and 4.8Mbps uplink using experimental equipment. SoftBank also reported successful connections across 100 consecutive call attempts, alongside testing of geographic coverage and potential interference with existing terrestrial mobile networks.
Network resilience has been a key focus of the trials, with SoftBank successfully testing emergency alert delivery, including earthquake and tsunami warnings, and conducted maritime emergency call tests in cooperation with the Japan Coast Guard. The company sees HAPS as a way to rapidly restore mobile coverage when terrestrial infrastructure is damaged or unavailable following natural disasters.
The programme also demonstrated autonomous drone operations over HAPS connectivity, including remote flight control, positioning data and video transmission. This could support disaster assessment, emergency logistics and other aerial mobility applications in areas lacking conventional mobile coverage.
Also of note was the validation of onboard edge computing, with smartphone data being processed directly on a server carried by the HAPS platform, SoftBank says that this reduced latency by more than 40% compared with conventional cloud-based processing. The company also demonstrated laser-based ranging and tracking of the airborne platform as part of its work on future optical communications.
SoftBank is now moving toward commercial HAPS deployment in Japan from 2027, initially focusing on disaster-response connectivity. Its longer-term plans include keeping platforms airborne for several months and developing domestic launch, recovery and operational facilities within the next two years.