BT In Tests To Beam Down 5G Coverage From The Stratosphere

BT is helping to test out antenna technology for a company planning to deliver 4G and 5G coverage from high-flying aircraft. The system is intended to provide connectivity in remote areas that are not well served by terrestrial networks.

The project, which has received funding from Innovate UK – Britain's "innovation agency" – will see Stratospheric Platforms Ltd (SPL) use the telecoms giant to pilot the antenna, however, this early stage phase is a world away from the ultimate ambition to mount the technology on an uncrewed High-Altitude Platform Station (HAPS) aircraft to give a cellular service from the stratosphere.

SPL's antenna uses phased array tech featuring 500 individually steerable beams, and is able to provide data speeds of up to 150Mbps across an area as wide as 15,000 square kilometers, the company told us.

SPL's proposed HAPS aircraft

The beam from one phased array antenna is equivalent to a cell created by traditional terrestrial masts, SPL said. The aim is that the technology will support standard smartphones without any hardware or software changes being required by consumers.

Trials will be conducted at BT's global R&D headquarters at Adastral Park near Ipswich, where a phased array antenna will be affixed to "a high building" to simulate a high-altitude platform and its interaction with BT's 5G network tested via a connection to its Open RAN testbed.

The tests will include supporting multiple user groups and different potential use cases, concurrently on the same network, BT's press people said.

But SPL's HAPS aircraft does not yet exist. It is planned to be powered by a hydrogen fuel system that will provide it with endurance of "over a week on station" due to its lightweight structure and "huge power source."

The company's website describes an aircraft with a wingspan of 60 meters (196 feet) that it claims is designed to be "strong enough to fly through the turbulent lower altitudes to reach the more benign environment of the stratosphere" where it will "hold station."

But what happens to the service when the plane needs to come down and refuel?

"The aircraft comes down and is refueled just like an airliner – it's a straightforward process," CEO Richard Deakin told us.

"A new aircraft flies to the same spot as the one it’s replacing and there is a seamless hand-over which won’t interrupt the signal."

Deakin told us SPL has modeled the airport and air traffic procedures extensively to confirm the ease of operation and the certification and design requirements for the aircraft and its infrastructure.

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SPL is currently in Series B fund-raising for the aircraft. The prototype will be built in the US by Scaled Composites – of SpaceShipOne fame – but production will be undertaken in the UK, Deakin said.

"First flight is planned for Q4 24 and we've made very significant breakthrough progress with our Hydrogen technology," he told us. A certified commercial HAP service was slated for late 2026, the CEO added.

"We've had significant interest from international telcos in this service which as you can imagine is a game changer for 4G/5G coverage with one aircraft doing the same job as 450 terrestrial telecom towers," he claimed.

The company was interviewed about its technology by the BBC in 2020, when Deakin said a prototype plane was expected to fly in 2022.

Deakin said: "Clearly the work is being undertaken with significant commercial applications in mind. It’s not just a test of the technology - its to validate some very exciting applications for mobile and fixed wireless access coverage."

In a statement announcing the tests, Tim Whitley, BT managing director for Research and Network Strategy, trilled that HAPS aircraft has "huge potential" to "further" strengthen" 45 and 5G connectivity.

This is not the only technology being considered for delivering a wireless service to remote or hard-to-reach areas. In December, the UK government announced it was testing the Starlink satellite service as an option to connect homes and businesses in poorly served areas of the country, while Starlink and T-Mobile US previously confirmed plans to use satellites in low-Earth orbit to provide cellphone coverage for remote locations across the US and possibly beyond.

Deakin insisted that such satellite services would not be able to compete. "Their technology and costs are quite an impediment to them providing a competing service. 5G satellites have a very wide beam and low data speeds compared to our solution," he claimed.

BT told us it is "exploring a range of technologies such as Low Earth Orbit technology as well as HAPS technology as viable options for providing connectivity to hard-to-reach areas. Both remain formative in their application to real world consumers." ®