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The connectivity brain behind Loon’s network
January 31, 2019

The connectivity brain behind Loon’s network

How software that orchestrates balloon-powered internet can do the same for satellites

Written by Salvatore Candido, CTO, Loon

Editor’s note: This blog was originally published by the Loon team on January 31, 2019. In 2021, Loon's journey came to an end. The Loon team have shared their flight data and technical, operational and scientific insights in The Loon Collection to support the next generation of stratospheric innovation. Thank you to everyone who supported the Loon team along the way.

Last fall I discussed Loon’s ability to extend the reach of the internet long distances by highlighting a test in which we established a connection that spanned 1,000 km across 7 balloons operating 20 km above the Earth. Taking the internet from where it is now and bringing it closer to people who need it is key to the commercial deployment of Loon, which will begin this year.

While I discussed the challenge of creating the links that allow the internet to reach further, I didn’t mention the orchestration challenge presented by this approach.

To understand this challenge, it helps to think about how things work today. When you’re accessing the internet from your phone, your data moves through a set of network nodes, e.g., a cellular tower, a fiber cable, or a network router, whose positions are fixed at their location in the world. The only piece of the puzzle moving is you, so the amount of “mobility” to manage is at the very edge of the network.

This is not the case for Loon. Since our balloons move with the winds, their physical coordinates are constantly changing in relation to the ground, each other, and you. Not only do we have to manage your mobility, we have to manage ours as well.

Suppose your phone is connected to Loon and you hit send on a text message. That message will jump up 20km to a balloon in the stratosphere. It may then hop across two, three, or more balloons to reach one connected to a ground station. Once there, your message will be routed through conventional fiber connections to your mobile carrier.

A few hours later you may send another message to the same person. However, because the balloons have moved in the meantime, it may jump up to a different balloon, hop across different balloons to a different ground station on the other side of the country, and be routed through different fiber connections to your carrier. This may be the case even if you are in the exact same spot and you’ve been online the entire time.

Because balloons move, the network of links between them must change constantly in order to deliver sustained connectivity below.

To manage a network like this we need to continually decide which balloons should make connections with which neighboring balloons (a topology) and how data packets should transit the various links to move across the network (routing). The topology needs to be planned not only for where the balloons are now, but also where they will be in the future in order to ensure that when one path becomes obsolete a new path is already in place. The routing needs to happen logically given the topology at any given time and place. The ultimate goal is to ensure that data is constantly flowing across the network in an efficient way, without disruption, even as things are in constant motion.

Managing this level of complexity means we can’t plan our network just once. We have to do it continuously. And in order to scale we must do it automatically.

To do this we created a network brain. This custom-built software defined network (SDN) orchestrates Loon’s connectivity efforts. SDN is not a new concept, but what we’ve built is something unique. It consumes forecasts of the future state of everything in our network — the balloons, the ground stations, even the weather — and then structures connections and routes data to optimize connection speeds, minimize latency, and avoid network disruptions. We call this a Temporospatial SDN. The Loon SDN functions autonomously on a massive scale to ensure people below our balloons have a connection to the internet.

This software is not only integral to our connectivity efforts, but is also proving to be useful for the efforts of others. As we announced today, Loon has been selected by Telesat, a leading global satellite operator, to adapt the Loon SDN to support the development of their next generation low Earth orbit (LEO) global communications satellites.

Similar to Loon's balloons, NGSO satellites are constantly moving relative to one another and the Earth below.

The synergy between balloons and non-geostationary orbit (NGSO) satellites comes from a shared characteristic — both are in constant motion relative to the Earth and one another. Because of that motion, the network challenges present in Loon’s internet balloon system will also be present for future NGSO communications satellites. The Loon SDN offers a promising solution to power these systems and create hybrid connectivity efforts to bring the reach of the internet even further.

We’re excited to leverage our expertise to assist in the development of this next generation of global communications satellite constellations. We see it as yet another opportunity for Loon to pursue our mission of connecting people everywhere by inventing and integrating audacious technology, in parallel to the commercial rollout of balloon-powered internet.

With about half of the world’s population still lacking internet access, there’s a need and room for multiple approaches to solving the problem. We’re excited to expand the number of ways that Loon can help.

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