If the network breathes, leave

Originally published in the Revolution.Aero Newsletter, as reported by Yves Le Marquand, 10/4/23

We are all familiar with signal troubles. On one road you have 5G, a few streets over you can barely load a WhatsApp message. Phone companies don’t really care, if you can’t get signal for any reason that’s on you. That is because cellular networks 'breathe' – meaning that if one tower reaches capacity the coverage areas shift so other towers can help out.

Network systems in aviation cannot act this way. Regulations don’t allow it and you’d be mad to fly if they did. Today’s air traffic communication systems are the result of billions of dollars of investment and a century-plus of development. But while building them out for the use of advanced – and then somewhere along the line autonomous aircraft might seem like a relatively simple step change, the task of making a network through which real-time data transfer is guaranteed constantly to make it safe enough to fly commercially is hard.

That said, companies right across AAM are making strides in this respect. For example, Volocopter is developing its VoloIQ as an operating system for all passenger and drone operations. Also, Eve has a deal with ecosystem developer SkyWay Technologies. And in the US, there is AURA Network Systems, a company building aviation-spectrum communications networks for crewed, uncrewed and autonomous aircraft. 

“You can’t have networks that operate like typical networks do today, which say: ‘We’re going to get you that data one way or another and if you have to wait 10, 20 seconds that is on you, not us’. You see that in cellular networks all the time, because they breathe. That doesn’t work in a safety of life-type situation,"  AURA's CEO, Bill Tolpegin told us.

“We have built a spectrum management system and that enables our links to be what we call deterministic, meaning we can guarantee coverage at a specific point in space and time,” he tells Revolution.Aero.

The fact that cellular networks ‘breathe’ means that whilst AURA can partner with firms in those industries, it has had to pioneer much of the technology in order to achieve FAA standards. The spectrum management system runs over a private network using AURA’s proprietary radios which are capable of supporting heavier mission requirements. AURA also uses digital twin technologies.

In order to guarantee connection, the first step, says Tolpegin, is to build a waveform and pick the right modulation scheme (modulation is the process by which data is converted into electrical signals to be transferred over a medium). AURA also operates on very low band spectrum at 450MHz so its radio propagation is strong. This is important because the way radio waves travel when they are transmitted from one point to another are affected by the medium in which they travel, such as atmospheric changes.

“You have to build your network to provide coverage to meet these requirements. That is both where you put your sites and how you build your sites so that if something breaks in the site, you can still keep going and provide service. So, you also have to have a lot of redundancy in your sites and in your ground networks. You’ve got to have multiple aggregation points. All these extra things have to be doubled up for the sole purpose of maintaining high operational standards,” says Tolpegin. What is challenging is that no one has really built these kinds of networks before, because no one has really had these kinds of safety of life requirements engrained in the network, he adds.

The network, once built, will sit within Ohio’s wider FlyOhio initiative launched to encourage the rollout of AAM in the state. Part of idea is to make Ohio’s airspace one of the first in the US in which BVLOS operations are permitted at higher altitude. The FAA is making ground on BVLOS regulations having just handed out its first approvals to four firms including Zipline to conduct operations at or below 400ft. “Data collected from these operations will inform the FAA’s ongoing policy and rulemaking activities,” a spokesperson told us. “The FAA’s long-term goal is to safely integrate drones into the National Airspace System rather than set aside separate airspace exclusively for drones.” 

AURA’s network, which has a typical radius of 50-200+ miles out from the site, will act as testbed for a variety of OEMs and operators (announcements to come). That 200-mile range seems pretty big. Size of network is dependent on where a tower is mounted and what the concept of operations (CONOPS) is, says Tolpegin. With a guaranteed level of coverage from one mast, AURA can then build out more sites along any given route creating corridors for autonomous aircraft to operate. Masts, if placed at altitude, can provide coverage for hundreds of miles, but these need to be brought closer to the ground in order to guarantee connection in takeoff and landing zones.

“We have a test network up right now across the country. It is made of up of a little over 50 sites in the US. As well as the mainland, from a test point of view we also cover Alaska, Hawaii, Puerto Rico, Guam and American Samoa,” explains Tolpegin. “But those are with the original radios we were using and not the commercial-grade radios we have since developed. Since we control the band, we can put the sites where they are needed.” Think of it like a mobile carrier’s ability to add sites to its spectrum. Again, not unlike a mobile phone network (except without the breathing), AURA is able to install its hardware on an existing mast if required. At Springfield airport the firm has it positioned on top of the five-storey former air traffic control tower. To ensure best service when flying AURA installs masts on the top of infrastructure like broadcast towers that are anywhere from 500ft-1,000ft tall.

So what about cost? Tolpegin explains that “measured capital deployment” means redundancy can be ensured at virtually no extra cost versus a network without the same safety-of-life requirements. This means AURA doesn’t have to build its network and hope that customers come. “We support their CONOPS and deploy our network where they want us to be. In other words, we can meet the market where it is,” says Tolpegin. “We don’t have to deploy well in advance and hope customers will start flying with us. We’ll do it when they’re ready to fly. That actually provides our partners with a great deal of efficiency and allows them to use our communications network when and where they need it.”

Advanced aircraft makers wishing to test their aircraft are welcome to reach out to AURA, says Tolpegin. Ohio, through its FlyOhio initiative founded back in 2018, has been providing a testbed to a host of UAS concepts. For example, NASA decided on Springfield-Beckley Municipal Airport in 2021 as a launch site for its first AAM ecosystem with the help of the US Air Force’s Agility Prime programme. “You’ve got a BETA [Technologies] vertiport a few hundred feet away from our site, for example,” adds Tolpegin. “I think it is going to be the larger cargo aircraft and linear inspection folks we will be doing work with initially. Once you get this nexus of utility, then people start to gather round it and utilise it. Ohio was attractive to us for this reason. They are so open to commerce, they are trying to build a full stack to show that this works.”

In the middle of the fourth aviation revolution it might not seem right to look further. But the advent of widespread operations of autonomous people-carrying aircraft is probably going to be the fifth. Although, don’t hold your breath on a certification date.

Regardless, Tolpegin says his firm is here now to help OEMs and operators reach that day faster. Leaving plenty of time to get on the phone to the service provider about that coverage.