You might remember press releases from AT&T in 2018 that promised a revolution in rural broadband from a technology called AirGig. The technology was described as using millimeter-wave spectrum to shoot focused radio beams along power lines, with the electric field of the powerlines somehow acting to keep the transmissions focused to follow the wires.
AT&T said at the time that the technology could deliver hundreds of megabits of data to rural homes using a network built from inexpensive plastic components mounted on power lines. The last I heard of the technology was this AT&T video released in 2019.
There had been a field trial of the technology conducted with Georgia Power, and the CEO of the electric company was enthusiastic at the time about the technology. AT&T talked about starting the process of manufacturing hardware. And then . . . crickets. There hasn’t been a word on the web about the technology since then.
I saw articles published by IEEE in 2019 that talked about a different broadband-over-powerline (BPS) technology developed by Panasonic. IEEE amended the standard for BPL to recognize Panasonic’s HD-PLC technology. Panasonic claims to have reached 60 Mbps transmissions using the technology but thought they could goose this to several hundred Mbps.
I always wondered how much of the AT&T announcement on AirGig was hype. Timing-wise, the AT&T AirGig announcement came in the middle of the 5G craze where the cellular carriers were trying to gain major concessions from the government to promote 5G. AT&T and the other carriers wanted a lot more spectrum – and they’ve largely gotten it. Perhaps they were using the AirGig to justify more spectrum. But the video shows that AT&T has gotten a pile of patents for the technology, so it seems to be the real deal.
Today’s blog asked what happened, and I hope somebody who knows will say. Did field trials reveal a fatal flaw in the technology? That’s always possible with any wireless technology. Did the technology just underperform and not deliver the promised broadband speeds? Or will AT&T spring a finished technology on the world one of these days?
Facebook has been exploring two technologies in its labs that they hope will make broadband more accessible for the many communities around the world that have poor or zero broadband. The technology I’m discussing today is Terragraph which uses an outdoor 60 GHz network to deliver broadband. The other is Project ARIES which is an attempt to beef up the throughput on low-bandwidth cellular networks.
The Terragraph technology was originally intended as a way to bring street-level WiFi to high-density urban downtowns. Facebook looked around the globe and saw many large cities that lack basic broadband infrastructure – it’s nearly impossible to fund fiber in third world urban centers. The Terragraph technology uses 60 GHz bandwidth and the 802.11ay standard – this technology combination was originally called AirGig.
Using 60GHz and 801.11ay together is an interesting choice for an outdoor application. On a broadcast basis (hotspot) this frequency only carries between 35 and 100 feet depending upon humidity and other factors. The original intended use of the AirGig was as an indoor gigabit wireless network for offices. The 60 GHz spectrum won’t pass through anything, so it was intended to be a wireless gigabit link within a single room. 60 GHz faces problems as an outdoor technology since the frequency is absorbed by both oxygen and water vapor. But numerous countries have released 60Ghz as unlicensed spectrum, making it available without costly spectrum licenses, and the channels are large enough to still be able to deliver bandwidth even with the physical limitations.
It turns out that a focused beam of 60 GHz spectrum will carry up to about 250 meters when used as backhaul. The urban Terragraph network planned to mount 60 GHz units on downtowns poles and buildings. These units would act as both hotspots and to create a backhaul mesh network between units. This is similar to the WiFi networks we saw being tried in a few US cities almost twenty years ago. The biggest downside to the urban idea is the lack of cheap handsets that can use this frequency.
Facebook took a right turn on the urban idea and completed a trial of the technology deployed in a different network design. Last May Facebook worked with Deutsche Telekom to deploy a fixed Terragraph network in Mikebuda, Hungary. This is a small town of about 150 homes covering 0.4 square kilometers – about 100 acres. This is drastically different than a dense urban deployment with a far lower housing density than US suburbs – this is similar to many small rural towns in the US with large lots, and empty spaces between homes. The only current broadband in the town was about 100 DSL customers.
In a fixed mesh network every unit deployed is part of the mesh network each unit can deliver bandwidth into that home as well as bounce signal to the next home. In Mikebuda the two companies decided that the ideal network would be to serve 50 homes (not sure why they couldn’t serve all 100 of the DSL customers). The network is delivering about 650 Mbps to each home, although each home is limited to about 350 Mbps due to the limitations of the 802.11ac WiFi routers inside the home. This is a big improvement over the 50 Mbps DSL that is being replaced.
The wireless mesh network is quick to install and the network was up and running to homes within two weeks. The mesh network configures itself and can instantly reroute and heal to replace a bad mesh unit. The biggest local drawback is the need for pure line-of-sight since 60 GHz can’t tolerate any foliage or other impediments, and tree trimming was needed to make this work.
Facebook envisions this fixed deployment as a way to bring bandwidth to the many smaller towns that surround most cities. However, they admit in the third world that the limitation will be for backhaul bandwidth since the third world doesn’t typically have much middle mile fiber outside of cities – so figuring out how to get the bandwidth to the small towns is a bigger challenge than serving the homes within a town. Even in the US, the cost of bandwidth to reach a small town is often the limiting factor on affordably building a broadband solution. In the US this will be a direct competitor to 5G for serving small towns. The Terragraph technology has the advantage of using unlicensed spectrum, but ISPs are going to worry about the squirrelly nature of 60 GHz spectrum.
Assuming that Facebook can find a way to standardize the equipment and get it into mass production, then this is another interesting wireless technology to consider. Current point-to-multipoint wireless network don’t work as well in small towns as they do in rural areas, and this might provide a different way for a WISP to serve a small town. In the third world, however, the limiting factor for many of the candidate markets will be getting backhaul bandwidth to the towns.
John Donovan, the chief strategy officer for AT&T, spoke at the Mobile World Congress recently and said that the company was trying five different technologies for the last mile. This includes WLL (wireless local loop), G.Fast, 5G, AirGig and fiber-to-the-premise. He said the company would be examining the economics of all of different technologies. Let me look at each one, in relation to AT&T.
Wireless Local Loop (WLL). The technology uses the companies LTE bandwidth but utilizes a point-to-multipoint network configuration. By using a small dish on the house to receive the signal the company is getting better bandwidth than can be received from normal broadcast cellular. The company has been doing trials on various different versions of the technology for many years. But there are a few recent trials of the newest technology that AT&T will be using for much of its deployment in rural America as part of the CAF II plan. That plan requires the ISP to deliver at least 10/1 Mbps. AT&T says that the technology is delivering speeds of 15 to 25 Mbps. The company says that even at the edge of a cellular network that a customer can get 10 Mbps about 90% of the time.
G.Fast. This is a technology that uses high frequencies to put more bandwidth on telephone copper wire. Speeds are reported to be as high as 500 Mbps, but only for very short distances under 200 feet. AT&T recently announced a G.Fast trial in an apartment building in Minneapolis. The technology is also being tested by CenturyLink and Windstream. All of these trials are using existing telephone copper inside of existing apartment buildings to deliver broadband. So this is not really a last mile technology. AT&T brings fiber to the apartment complex and then uses G.Fast as an inside wire technology. If they find it to be reliable this would be a great alternative to rewiring apartments with fiber.
5G. AT&T recently announced a few trials of early 5G technologies in Austin. They are looking at several technology ideas such carrier aggregation (combining many frequencies). But these are just trials, and AT&T is one of the companies helping to test pre-5G ideas as part of the worldwide effort to define the 5G specifications. These are not tests of market-ready technologies, but are instead field trials for various concepts needed to make 5G work. There is no doubt that AT&T will eventually replace LTE wireless with 5G wireless, but that transition is still many years in the future. The company is claiming to be testing 5G for the press release benefits – but these are not tests of a viable last mile technology – just tests that are moving lab concepts to early field trials.
AirGig. This one remains a mystery. AT&T says it will begin trialing the technology later this year with two power companies. There has been a little bit of clarification of the technology since the initial press release. This is not a broadband over powerline technology – it’s completely wireless and is using the open lines-of-sight on top of power poles to create a clear path for millimeter wave radios. The company has also said that they don’t know yet which wireless technology will be used to go from the poles into the home – they said the whole range of licensed spectrum is under consideration including the LTE frequencies. And if that’s the case then the AirGig is a fiber-replacement, but the delivery to homes would be about the same as WLL.
FTTP. Donovan referred to fiber-to-the-home as a trial, but by now the company understands the economics of fiber. The company keeps stretching the truth a bit about their fiber deployments. The company keeps saying that they have deployed fiber to 4 million homes, with 8 million more coming in the next three years. But the fact is they have actually only passed the 4 million homes that they can market to as is disclosed on their own web site. The twelve million home target was something that was dictated by the FCC as part of the settlement allowing the company to buy DirecTV.
We don’t know how many fiber customers AT&T has. They are mostly marketing this to apartment buildings, although there are residential customers around the country saying they have it. But they have not sold big piles of fiber connections like Verizon FiOS. This can be seen by looking at the steady drop in total AT&T data customers – 16.03 million in 2014, 15.78 million in 2015 and 15.62 million at the end of the third quarter of 2016. AT&T’s fiber is not really priced to be super-competitive, except in markets where they compete with Google Fiber. Their normal prices elsewhere on fiber are $70 for 100 Mbps, $80 for 300 Mbps and $99 for a gigabit.