AT&T is developing wireless technology that uses power lines to guide wireless signals to their destination and potentially deliver multi-gigabit Internet speeds. The technology is experimental and not close to commercial deployment, but it could potentially—in a few years—be used to deliver smartphone data or home Internet.
Project AirGig from AT&T Labs, announced yesterday, revives the possibility of using power lines for Internet service—but in a surprising way. Signals would not travel inside the power lines, but near the lines. "Low-cost plastic antennas and devices located along the power line" send wireless signals to each other, using the power lines as a guide, AT&T said.
“We’re experimenting with multiple ways to send a modulated radio signal around or near medium-voltage power lines,” AT&T’s announcement said. “There’s no direct electrical connection to the power line required, and it has the potential of multi-gigabit speeds in urban, rural, and underserved parts of the world.”
The choice of medium-voltage lines has nothing to do with their voltage, but rather their placement on utility poles. “Those lines are generally highest on the pole and provide the clearest line of sight,” AT&T told Ars.
The power lines themselves apparently don’t do anything to help the signals travel. The power lines simply “serve as a guide for the signals, not an antenna," AT&T said. Exactly what “guide” means in this context is unclear, and AT&T did not provide any further details in response to our questions.
AT&T was also somewhat vague in a call with reporters. "This is not a technology that utilizes the actual power line itself, the actual conductive material. It actually rides alongside it," AT&T CTO Andre Fuetsch said, before adding that he "can't go into much detail at this stage."
From antenna to smartphone, or your house
AT&T is using millimeter wave signals—those above 30GHz—to send data from pole to pole. “Initial testing shows that high-frequency millimeter wave signals result in better performance than lower frequency signals when transmitted along power lines,” AT&T told Ars.
But AT&T said its system provides the flexibility of being able to deliver Internet service using any part of the radio spectrum. While millimeter waves travel along the power lines from one antenna to the next, a signal going from an antenna to a mobile device or home Internet connection would use a different frequency. The signals can be converted to use 4G LTE spectrum or any other licensed or unlicensed spectrum that AT&T has in its arsenal, the company said.
The antennas essentially form a mesh network that connects back to AT&T’s core network for Internet access. AT&T said that its cell towers, or the central offices that provide wired home Internet access, could serve as the origin point for an Internet signal that would then be distributed across the antennas. AirGig could also be configured to work with small cells and distributed antenna systems, AT&T said.
Many AT&T customers in rural areas are suffering from slow, unreliable Internet access delivered over aging copper lines, and some people in AT&T territory can’t get wired Internet access at all because the company hasn’t upgraded its network to accommodate enough homes. AirGig could theoretically solve this problem, and it doesn’t require installation of new towers or cables, but it’s at least a few years away from being deployed widely.
Fuetsch said that the company needs “favorable regulation” and must coordinate with utility companies. AT&T aims to start field trials next year, but it's still looking for “the right global location,” whether that’s in the US or elsewhere, company officials said.
AirGig is about a year behind 5G cellular technology, which went into field trials at AT&T this year but doesn’t have a firm deployment date.
AT&T hopes utility companies will jump on board, as AirGig technology could help them deploy smart grid applications and even detect problems, like encroaching tree branches. “Power companies could use it to pinpoint specific locations, down to the line segment, where proactive maintenance could prevent problems,” AT&T said. “It could also support utility companies’ meter, appliance, and usage control systems.”
AT&T has the system up and running at some of its own facilities, delivering data for 4K TV and other applications. Earlier attempts at broadband over power line technology that sent data through the wires hasn’t been cost-effective and wouldn’t deliver speeds fast enough, Fuetsch said. “That's why we believe this is such a game changer and why it's revolutionarily different from the old broadband over power line technologies we're familiar with,” he said.
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