NTT Docomo partnered with Airbus to conduct trials using a solar-powered, high-altitude platform station (HAPS) to deliver wireless broadband connectivity using a variety of bandwidths to simulate direct-to-device communications service.

The trial, conducted in the US over 18 days using Airbus’ Zephyr S aircraft, demonstrated the “viability and versatility” of 2GHz spectrum for HAPS-based services and the use of the 450MHz band to provide connectivity in a range of up to 140km, Docomo said in a statement.

Test data was captured at different altitudes at different times to measure how connectivity is affected in the stratosphere by factors such as weather conditions, different elevation angles and aircraft flight patterns.

Takehiro Nakamura, GM of Docomo’s 6G-IOWN Promotion Department, said the company believes HAPS will be a promising option for coverage expansion of 5G and 6G.

He explained: “We were able to demonstrate the effectiveness of HAPS, especially for direct communication to smartphones, through long-term propagation measurements using actual HAPS equipment.”

Nakamura noted it wants to study the practical application of HAPS in the evolution of 5G and 6G with Airbus, adding the data will be used to guide future 4G LTE direct-to-device services expected via the Zephyr HAPS.

In late September, rival SoftBank acquired 200 patents from Alphabet’s deflated balloon business Loon, with the aim to accelerate the launch of commercial services by subsidiary HAPSMobile.