Could 5G networks in the future be fixed in the sky, aboard fleets of hydrogen-powered aircraft, instead of being fixed to masts and buildings with expensive rents? This is a vision for network operator Deutsche Telekom, which has backed UK-based startup Stratospheric Platforms Limited (SPL) and Capgemini-owned Cambridge Consultants to develop and test an airborne 5G network, slated for commercial release in 2024.
SPL said it has developed a high-altitude platform (HAP), in the shape of an unmanned zero-emissions aircraft, to carry a new kind of wireless antenna designed by Cambridge Consultants – and described as 
“unlike anything seen before”. The duo reckon they can provide 5G coverage to the whole of the UK, from 20,000 metres up, from an airborne antenna array mounted on just 60 aircraft. They could cover Germany with 67, they say.
By comparison, they suggested on a press call yesterday (November 2) the U.K. will require another 400,000 masts to provide national 5G coverage. “This single mega cell tower in the stratosphere will provide coverage that is equal to the combined efforts of hundreds of terrestrial cellular masts, rewriting the economics of mobile broadband,” said Richard Deakin, chief executive at SPL.
A prototype has already been tested with Deutsche Telekom in southern Germany, according to SPL. Deutsche Telekom has not yet responded to a request from Enterprise IoT Insights for comment. The project raises a number of questions, not least about its viability, as well as about the interplay with existing terrestrial networks and deployment schedules, and whether the new system might be utilised as a shared neutral-host infrastructure.
There is also a question about its likely usage, whether for consumer 5G connectivity or, more likely, for consumer in-fill coverage, plus as a vehicle for massive machine-type communications (mMTC), and redundancy, in general. But the innovation looks considerable, with its authors calling the whole thing, even in proof-mode, a “remarkable technical achievement”.
The antenna is designed to be powerful and low-energy, at the same time, as well as both huge (three meters square) and lightweight (120kg). It will be the “world’s largest commercial airborne communications antenna”, when it finally launches in 2024, said UK-based Cambridge Consultants, acquired by Capgemini in April. The firm called the prototype, even at one eighth of the intended size of the commercial model, one of its “crowning achievements”.
The firm said: “Advanced calibration across the four tiles of the prototype deliver beams with astonishing accuracy, maintaining laser-like performance during flight motion and paving the way for the huge 32-tile commercial array to now be developed. Each antenna produces 480 individual, steerable beams, creating patterns that can be ‘painted’ onto the ground to cover specific areas such as roads, railway lines or shipping lanes.
“The ability to produce hundreds of beams enables the antenna to reuse spectrum ensuring fast and even coverage across the entire covered area. A unique, wholly digital beamforming capability gives massive flexibility in how services are deployed, allowing in-flight reconfiguration to deliver services beyond the reach of conventional fixed terrestrial networks. This includes following mobile users, including trains and autonomous vehicles, and providing coverage exactly where required, for example ending at national borders.”
The hydrogen-powered aircraft, as the other piece of the innovation, is designed to fly at an altitude of 20,000 metres for around eight days, before coming down for refueling. It offers a low environmental impact, said SPL, with low noise, zero CO2 and zero NOx emissions.
A single HAP will provide coverage over an area of up to 140 kilometres in diameter – “equivalent to hundreds of today’s terrestrial masts,” said SPL and Cambridge Consultants in a statement. A fleet of around 60 HAPs over the UK would provide blanket 5G connectivity with peak 5G speeds in excess of 100 Gbps “in aggregate”, the pair said. This proposed flying-5G network will be a “fraction of the cost of building and maintaining terrestrial infrastructure”, they claimed.
They said: “With radically cheaper costs, this new platform has the potential to connect the unconnected in the developing world, to fill gaps in coverage across the developed world and to ensure rural areas aren’t left behind anywhere across the globe.”
Richard Deakin, chief executive at Cambridge Consultants, said: “This unique antenna is at the heart of SPL’s stratospheric communications system. It was essential that we overcame significant technical challenges in the design of the antenna to enable us to deliver massive data rates in a unique environment where power was limited, where weight was critical and where cooling in the thin, stratospheric air was difficult.
“The development and testing of the antenna has met or exceeded the design criteria and working with such a talented team at Cambridge Consultants has been one of the highlights of the program to date. We look forward to continuing the journey as we progress to the production-standard antenna.”
Tim Fowler, chief sales officer at Cambridge Consultants, added: “Four years ago SPL approached Cambridge Consultants with an ambitious vision to revolutionize the telecoms experience by beaming connectivity from the sky. Our role, to design and build this ‘mega cell tower in the stratosphere’, has seen us make breakthrough after breakthrough and we’re excited to build on these innovations with SPL, on the path to commercial deployment.”
