Building a mobile network that is out of this world

If you say ‘the space race’, people often think of the rivalry between the Soviet Union and the United States to conquer space exploration. However, these days there’s a new competition going on, the one for space-based mobile communications.

These networks aim to use low-Earth orbit satellites to provide mobile signals in remote areas with no terrestrial base stations, creating a direct-to-phone service from space.

Our partner, AST SpaceMobile, is the only company building a global mobile broadband network in space that’s designed to work with standard, unmodified mobile devices. They’re also the first company to prove space-based cellular broadband works, thanks in part to Vodafone’s assistance.

This means everyday smartphones don’t need specialised equipment and can switch between space and ground-based networks automatically, effectively eliminating coverage gaps and keeping customers connected on the move.

How it works
AST SpaceMobile plans to launch large-area satellites called BlueBirds, which have solar cells on one side and thousands of antenna elements on the other.

The solar cells generate electricity for the antennas, which then work together to enable beam forming ­­– a technique that focuses cellular signals toward mobile devices back on Earth. You can think of it like a torch light but channelling radio waves instead of light. This makes the signal strong enough to be picked up by mobile phones on the ground.

With an area of more than 64 square metres, a BlueBird is also sensitive enough to pick up relatively weak mobile signals from hundreds of kilometres away.

On current terrestrial networks, the signal gets weaker and can be blocked by obstacles when you move away from a base station. Space-based mobile networks provide a solution.

Landing in the right place
Catching up with Rowan Chesmer, Vodafone’s Future Technologies Researcher, he tells us how it was “right place, right time” when he landed his dream job at Vodafone.

Always fascinated by space, he graduated from Durham University with a Master’s degree in Engineering, specialising in electronics before joining Vodafone’s graduate scheme.

Six years on, he is part of the Research & Development team and is responsible for trialling and developing cutting-edge satellite technologies that will improve global connectivity.

One of his first projects was an environmental proof of concept, monitoring water levels in the Yorkshire Dales to understand whether beavers were impacting flooding in that area. Terrestrial networks weren’t getting reliable results, so it was up to Rowan to see if satellites could help.

“Unfortunately, it didn’t quite go as planned because the beavers ate the sensor,” Rowan laughs.

It wasn’t long before fate stepped in and Rowan was asked to turn his attention to a new topic, space-based mobile technology.

Getting things off the ground
The first step was to establish if a space-based mobile network with AST SpaceMobile was viable.

A daunting task? Not for Rowan.

“It’s all maths,” says Rowan brightly. “Spherical geometry.”

He then explains the various calculations involved. From working out the angle of the signal and how the atmosphere might affect a set of wireless frequencies, to knowing how much signal power is coming from the satellite.

You also have to take into account environmental losses such as noise, compensate for signal delay, and adjust for Doppler effect, which is the shift in radio waves as something moves closer or further away – like when a siren passes you in the street. Then, if the final figure is within the realms of what amount of signal a mobile phone can detect, a connection is technically possible.

Before creating a viable product, you then have to consider wider implications such as regulatory compliance, technical network planning and commercial operations.

After lots of meetings and simulations with Vodafone, September 2022 saw lift off as AST SpaceMobile’s BlueWalker 3 test satellite was launched.

With an array of antennas that span more than 64 square metres in size (roughly ¼ of a tennis court), BlueWalker 3 is now the largest ever commercial communications array ever deployed in low-Earth orbit.

Celebrating milestones
In February, Rowan went out to help test the network in AST SpaceMobile’s headquarters in Midland, Texas.

Located within the Midland International Air and Space Port, the company used the ample room to build out more than 17,100 square metres of satellite manufacturing space and R&D facilities.

During his time there, Rowan was part of some crucial initial moments, including pinging the satellite.

“Everyone was very excited,” Rowan recalls, explaining that “a ping is basically where you send a packet of data to an address on the internet, and then it responds saying, ‘yes, I’m here’. We did that over the satellite to confirm it was working.”

The first call directly to an ordinary smartphone1, without any extra hardware or software, happened in April. Over the summer, the company demonstrated 4G downloads to ordinary phones at speeds of more than 14 Mbps. Then on September 8, AST SpaceMobile engineers located in what’s normally a dead zone in Maui, Hawaii, used the first-ever 5G connectivity from space directly to an everyday smartphone to call Rowan’s colleague Jose Guevara, an Open RAN engineering specialist for Vodafone Spain in Madrid.

“As the satellite is flying at 17,000mph, you only have a short window of a few minutes in which to connect, and do your tests, before the satellite disappears over the horizon again. This will all change when more satellites are launched, but currently we’re only testing with a single satellite,” Rowan says.

“It depends on where the orbit is, but you tend to get two passes a day roughly 11 hours apart, and then that shifts each day.” Which is why the team often works around the clock.

For Rowan, his job is to monitor signal frequencies and to test regulatory compliance with terrestrial networks. Checking things like link budget – which determines whether or not the signal power is enough for a device to connect – and interference management for cross-border coordination.

The other key part of his role is building the system’s architecture, creating performance simulations and working out how it can integrate into Vodafone’s existing networks.

And that’s without mentioning the work he is doing outside of the AST SpaceMobile partnership, across all non-terrestrial networks, high altitude platform systems such as balloons and drones in the stratosphere, 6G and Amazon Kuiper.

Reaching new heights
It’s not only at work that Rowan sets his sights high. An avid mountaineer, Rowan has completed expeditions across the Alps and the Caucasus mountains, as well as trekking to the Atacama Desert situated between two mountain chains, the Andes and the Chilean Coast Range.

Sometimes going without connectivity for days or even weeks at a time, the projects he’s working on have a close interest to his hobbies as well.

CT Bureau