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Facebook Says Terragraph and Aries Are the Keys to Better Urban and Rural Wireless Internet

Facebook turns to WiGig technology for connecting mobile users in cities, “Massive MIMO” for bringing higher capacity cellular networks to rural areas without building more towers

2 min read
Facebook vice president of engineering Jay Parikh.
Facebook vice president of engineering Jay Parikh.
Photo: Tekla Perry

Facebook’s overriding goal is to have everybody in the world sharing everything all the time. And that takes technology for fast, seamless, constant connectivity—technology that, it seems, wireless carriers aren’t developing nearly quickly enough.

So today, at Facebook’s F8 developer’s conference, vice president of engineering Jay Parikh announced two projects coming out of what the company calls its Connectivity Lab: Terragraph and Aries. Terragraph will use 60-gigahertz WiGig technology for fast internet in dense urban areas; Aries is intended to give rural cell towers better reach and more capacity using a version of a technology called Massive MIMO. Facebook plans to make both innovations open to the wireless research community.

Here’s a little more detail, as provided by Facebook under embargo before today’s announcement.

Terragraph: Terragraph’s WiGig approach uses WiGig, or IEEE 802.11ad, which operates in the 60 GHz frequency range (Wi-Fi operates in the 2.4 GHz and 5 GHz range), with data transmission rates using current technology of 7 Gb per second, some 10 times faster than today’s Wi-Fi. However, WiGig sacrifices range and doesn’t pass through walls and other solid objects making it, to date, of limited use for communications outside of a single room. The Terragraph plan is to get around that limitation by using steerable arrays of antennas to avoid buildings and dodge general network interference from crowded frequencies. It will require transmitters placed every 200 to 250 meters throughout a city.

Says Parikh:

“60 GHz has always been frowned upon because it gets easily absorbed by water and oxygen—we take advantage of the fact that it doesn’t have a good range to minimimize interference and keep capacity high.”

The technology, the company said, combined with Wi-Fi access points for longer-range transmissions, is a low-cost way of rolling out street-level gigabit communications. Facebook is testing Terragraph on its Menlo Park campus, where it has been hitting multi-gigabit-per-second, transmission rates and is planning a trial in San Jose later this year. “It’s really exciting that we will be able to see this thing in the wild,” says Parikh, “and from there will expand to more cities around the world.”

Aries: Aries (Antenna Radio Integration for Efficiency in Spectrum) is Facebook’s attempt to cheaply and easily extend cellular communications networks from city centers to more rural areas as far as 40 kilometers away. The project uses Massive MIMO, a large antenna array designed to increase network capacity and to allow signals to travel further at lower power. To date, Facebook has built a proof-of-concept test platform with 96 antennas that can handle 24 mobile devices simultaneously using the same spectrum.

“We  have set what we believe is a record of 71 bits per second per hertz, in a couple of weeks we believe we will hit 100 bits per second,” Parikh said. “We think this is at least an order of magnitude better than what is available today.”

Updated 13 April 11 a.m. PDT.

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Metamaterials Could Solve One of 6G’s Big Problems

There’s plenty of bandwidth available if we use reconfigurable intelligent surfaces

12 min read
An illustration depicting cellphone users at street level in a city, with wireless signals reaching them via reflecting surfaces.

Ground level in a typical urban canyon, shielded by tall buildings, will be inaccessible to some 6G frequencies. Deft placement of reconfigurable intelligent surfaces [yellow] will enable the signals to pervade these areas.

Chris Philpot

For all the tumultuous revolution in wireless technology over the past several decades, there have been a couple of constants. One is the overcrowding of radio bands, and the other is the move to escape that congestion by exploiting higher and higher frequencies. And today, as engineers roll out 5G and plan for 6G wireless, they find themselves at a crossroads: After years of designing superefficient transmitters and receivers, and of compensating for the signal losses at the end points of a radio channel, they’re beginning to realize that they are approaching the practical limits of transmitter and receiver efficiency. From now on, to get high performance as we go to higher frequencies, we will need to engineer the wireless channel itself. But how can we possibly engineer and control a wireless environment, which is determined by a host of factors, many of them random and therefore unpredictable?

Perhaps the most promising solution, right now, is to use reconfigurable intelligent surfaces. These are planar structures typically ranging in size from about 100 square centimeters to about 5 square meters or more, depending on the frequency and other factors. These surfaces use advanced substances called metamaterials to reflect and refract electromagnetic waves. Thin two-dimensional metamaterials, known as metasurfaces, can be designed to sense the local electromagnetic environment and tune the wave’s key properties, such as its amplitude, phase, and polarization, as the wave is reflected or refracted by the surface. So as the waves fall on such a surface, it can alter the incident waves’ direction so as to strengthen the channel. In fact, these metasurfaces can be programmed to make these changes dynamically, reconfiguring the signal in real time in response to changes in the wireless channel. Think of reconfigurable intelligent surfaces as the next evolution of the repeater concept.

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