Facebook’s 60-GHz Terragraph Technology Moves From Trials to Commercial Gear

The software suite allows base stations to connect to one another in small groups

4 min read
Photo: Facebook
Wireless world: Technicians in Mikebuda, Hungary, install Terragraph-enabled small-cell base stations for a trial that began in May 2018.
Photo: Facebook

For years, Facebook has been developing a technology to improve the way data is organized and routed in wireless networks. Now, that technology is being integrated into commercially available 60-gigahertz small-cell base stations. And if service providers sign on, it could soon help deliver over-the-air Internet to homes and businesses around the world.

The Facebook technology, called Terragraph, provides a way for a cluster of base stations broadcasting at 60 GHz to autonomously manage and distribute traffic among themselves. If one base station goes down, another can take over in an instant—and they can work together to find the most efficient path for information en route.

Half a dozen equipment vendors, including Cambium Networks, Common Networks, Nokia, and Qualcomm, have now pledged to roll out commercial gear that integrates Terragraph. The latest announcements came in February at the MWC Barcelonatrade show. If it works as promised, Terragraph should make Internet access faster and more affordable in places where it’s deployed.

Increasingly, broadband that was once distributed through expensive fiber-optic cables buried deep underground is being beamed to homes and businesses through the air. To do that, telcos are eyeing high-frequency bands, which have more bandwidth available than crowded lower frequencies that have long been used for consumer electronics.

Of interest to Facebook is the V-band, commonly referred to as simply 60 GHz, though it technically spans from 40 to 75 GHz. This band is unlicensed in many countries, which means it’s free for anyone to use.

While indoor equipment supporting 60 GHz as a Wi-Fi alternativehas been available for years, outdoor gear is just now beginning to appear. Many Internet service providers are considering using 60 GHz to bridge the gap between existing infrastructure and new locations they’d like to reach, or to add capacity to places they already serve.

“It’s definitely interesting,” says Swetank Kumar Saha, a research assistant and Ph.D. candidate in computer science at the University at Buffalo, in New York, who has studied the performance of 60-GHz consumer gear for indoors. “A lot of people have struggled to commercialize 60 GHz. There’s been a lot of talk.”

One problem is that signals at millimeter-wave frequencies (roughly 30 to 300 GHz) do not travel as far as those at lower frequencies, are readily absorbed by rain and foliage, and cannot pass through windows or walls.

To get around these issues, providers typically use fixed wireless networks, in which a base station transmits to a stationary receiver installed on a building’s exterior. From there, Ethernet cables distribute service indoors.

Last year, Facebook teamed up with a subsidiary of Deutsche Telekom to test Terragraph in two villages in Hungary. In the first of those trials, technicians connected about 100 households. With Terragraph, residents enjoyed average Internet speeds of 500 megabits per second, as opposed to the 5 to 10 Mb/s they had been getting through DSL. Facebook is now completing trials with operators in Brazil, Greece, Hungary, Indonesia, Malaysia, and the United States.

The technology itself consists of a suite of software based on the IEEE 802.11ay standard and includes features such as time-division multiple access, which dices up a channel into time slots on which multiple base stations can transmit in rapid succession. In the seven-layer Open Systems Interconnection Model, Terragraph works at Layer 3, the slice that has to do with routing information between IP addresses.

With Terragraph, Facebook took its expertise in routing data around its fiber backbone and applied that expertise to wireless networks, says Chetan Hebbalae, a senior director at Cambium. In 2017, the project came full circle when Facebook made the underlying routing software open source. Called Open/R, it was initially designed for Terragraph but is now also used by Facebook to shuttle information around its own data centers.

There are still limits to the technology, however. Each Terragraph-enabled base station can transmit only up to distances of about 250 meters, and all routes must be line-of-sight with no foliage, walls, or other obstacles in the way. Anuj Madan, product manager for Facebook, says the company has tested Terragraph in rain and snow, and that weather “has not presented an issue so far” for performance. But, just in case, Hebbalae says, many 60-GHz base stations are designed to temporarily switch back to standard Wi-Fi frequencies of 5 GHz or 2.4 GHz if there’s too much loss.

A spokesperson for Sprint said the company plans to test Terragraph equipment and is exploring the 60-GHz band for its network. A representative of AT&T said it has performed lab tests involving 60 GHz but currently has no plans to incorporate the band into its network.

Saha, of the University at Buffalo, is optimistic about Terragraph’s chances of breaking out into the world. “These companies will look at the cost at the end of the day, and if the cost is better than going for fiber, then they will definitely go for it,” he says.

Cambium’s Hebbalae says his company’s first Terragraph-enabled base station is currently in the “design and development phase” and will likely be available later this year. The company’s goal is to offer Terragraph as a software feature that can be easily switched on or reconfigured from afar. “Hopefully, if we talk six months from now, I’ll be able to talk about pilots and trial deployments with customers,” he says.

This article appears in the April 2019 print issue as “Facebook Pushes Networking Tech.”

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