Facebook has big plans for its drones

by Ben Fisher

Posted on July 27, 2014

Last August, Facebook partnered with leading technology companies to launch Internet.org — a global effort to make affordable basic internet services available to everyone in the world.

Building the knowledge economy is the key to solving many of our big social and economic challenges, and creates new growth and opportunities for people in every country. A recent study by Deloitte found that the internet is already an important driver of economic growth in many developing countries. Expanding internet access could create another 140 million new jobs, lift 160 million people out of poverty, and reduce child mortality by hundreds of thousands of lives. Connectivity isn’t an end in itself, but it’s a powerful tool for change.

However, there are significant obstacles to building the knowledge economy, and the internet is growing very slowly. Today, only around 2.7 billion people have access to the internet — just a little more than a third of the world’s population. That number is only growing by about 9% every year.

Internet.org has a plan to deliver basic internet services to everyone by working to decrease the costs of connectivity, building more efficient services that use less data, and by partnering with mobile operators on new models for access that can help the industry grow while also bringing more people onto the internet.

Different communities require different technology

Facebook’s approach to developing new platforms is based on the principle that different communities need different technical solutions.

Their research has shown that approximately 80-90% of the world’s population lives today in areas already covered by 2G or 3G networks. These environments are mostly urban or semi-urban, and the basic cell and fiber infrastructure has already been constructed here by mobile operators. For most people, the obstacles to getting online are primarily economic.

Coverage Heat Map

Facebook Coverage Heat Map

or the remaining 10-20%, the economic challenges also apply, but in this case they also explain why the basic network infrastructure has yet to be built out. The parts of the world without access to 2G or 3G signals are often some of the most remote places on Earth, where physical access to communities is difficult. Deploying the same infrastructure here that is already found in urban environments is uneconomical as well as impractical.

Their strategy is to develop different types of platform to serve different population densities.

Platforms at different altitudes

Facebook Platform Altitude

Higher altitudes generally means beams are more spread out on Earth, but giving more trunking opportunities far away from the sites of interest.

Dense urban areas: in urban environments, wireless mesh networks can provide simple to deploy and cost effective solutions.

Medium density areas: for limited geographical regions, unmanned aerial vehicles can provide a novel and efficient method of access. High altitude solar-powered aircraft can be quickly deployed and have long endurance.

Low density areas: across the largest areas of territory with the lowest population densities, satellites can beam internet access to the ground. Communications satellites today are expensive to deploy, but space-based methods of connectivity are becoming smaller and cheaper to launch.

The physics of aerial connectivity

Before discussing the relative costs, benefits and capabilities of these platforms, it’s important to understand the fundamental constraints we need to consider while working on aerial connectivity. These are not only issues of cost, efficiency and deployment, but also the basic laws of physics.

The most important constraint to consider is that as you increase altitude, assuming all else is equal, the signals emitted by aerial platforms cover a wider area and therefore become weaker. More specifically, the power of a radio signal weakens as a square of distance.

If you consider cell towers, they can provide really strong signals across relatively small areas. And stronger signals creates the ability to deliver higher capacity. A plane at an altitude of 20 kilometers will allow you to reach people more than 100 kilometers away, but the signal loss will be significantly higher than would occur for terrestrial networks. And if you send up a satellite that can beam internet across an entire continent, it might have wide reach across a large territory, but its signal will be a lot weaker than almost any other option for connecting.

Boosting the signal in order to achieve a high bandwidth capacity is also very impractical. Radio signals get weak very quickly, so they require a large amount of power to strengthen. Since satellites generally rely on solar power as their energy source, generating a lot of power (would need to square to make up the difference) would mean constructing either huge, unstable structures, which are impractical, or nuclear powered satellites, which are very expensive.

Physics of electromagnetic propagation

Facebook Propagation

As radio waves or light propagate, everything else being equal, at a distance 4x from the source, a signal is 16 times weaker than at a distance 1x.

So physics creates a number of challenges for deploying aerial platforms for connectivity, and creates different costs and benefits for each platform. For lower population densities, where people are spread out across a large area, the higher up you go, the more cost effective it becomes to place trunk stations and to deliver the internet. But signal loss will also be higher, so satellite access is only really a way of providing a basic internet experience for remote communities. Likewise, for high population densities, only lower altitude platforms will be truly effective, and connection speeds will be faster and the experience better for a lot of people.

Drones and High Altitude Long Endurance systems

High altitude drones are one major area they’re focused on developing. To understand the reasons for this, it is helpful to consider some of their technical constraints.

They want to:

Fly as close to the ground as possible in order to maximize signal strength.

Fly at a high enough altitude where the wind is not very strong in order to maximize endurance.

Fly outside of regulated airspace for safety and quick deployment.

Be able to precisely control the location of these aircraft, unlike balloons.

Build the smallest structure possible so it requires minimal energy to stay aloft.

Build a large enough structure that can effectively harvest all the energy it needs from the sun.

Build the cheapest structure so we can cost effectively produce enough to span many areas.

Build a re-usable structure to make it more cost effective as well.

Based on these constraints, drones operating at 65,000 feet are ideal. At this altitude, a drone can broadcast a powerful signal that covers a city-sized area of territory with a medium pop- ulation density. This is also close to the lowest altitude for unregulated airspace, and a layer in the atmosphere that has very stable weather conditions and low wind speeds. This means an aircraft can easily cruise and conserve power, while generating power through its solar panels during the day to store in its batteries for overnight use.

With the efficiency and endurance of high altitude drones, it’s even possible that aircraft could remain aloft for months or years. This means drones have more endurance than balloons, while also being able to have their location precisely controlled. And unlike satellites, drones won’t burn up in the atmosphere when their mission is complete. Instead, they can be easily returned to Earth for maintenance and redeployment.

They expect to have an initial version of this system working in the near future.

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