AT&T turned heads in 2016 when it announced preliminary details about its powerline-mounted AirGig project. As of last September, the company announced that the gigabit technology was “still very much in the experimentation phase.” Now, the company has announced that it will move forward with its AirGig plans, having revealed that it is “in advanced discussions” with power companies to start trials of its new broadband technology in at least two locations by this fall.
AirGig is designed to help solve the so-called “last mile” connectivity challenge that service providers face, not just for fixed broadband to the home, but for mobile too. While fiber is already prevalent in large cities, as well as in certain junction points in suburban and rural areas, getting the internet connection from the fiber point to a user’s fixed location up to a few miles away can be cost prohibitive.
To confront this problem of distance and resources, AT&T has chosen a technology that it hopes will provide a low-cost solution by transmitting high bandwidth millimeter RF signals alongside existing power-lines (not inside).
AT&T plans on starting field trials in the U.S. this fall, though it indicated in September that it was also investigating “the right global location” — meaning that it would be considering locations outside of the U.S. The deployment and success of this technology depends strongly on regulation, not just related to spectrum but also from utility-pole owners and regulations related to the poles that would support such a system. Future field trials will demonstrate how Project AirGig can also support power companies’ smart grid technologies, such as meter, appliance, and usage-control systems, as well as early detection of powerline integrity issues.
AT&T has disclosed that AirGig, developed by AT&T labs, includes “more than 200 patents and patent applications.” AT&T labs has developed a Radio Distributed Antenna System (RDAS), which uses mmWave surface wave launchers (antennas) made of low-cost plastic, along with inductive power devices, which receive power without direct electrical connections (for simplified installation). The RDAS will reconstruct signals that travel along or near the medium-voltage wire, not through it, using the wire to guide the wave propagation (with a visible line of light).
This approach will solve some of the major problems that previous broadband over powerline (BPL) systems encountered. Of course, the major benefit of this approach is to re-use existing pole infrastructure that mostly has line-of-sight paths between poles, while not relying on the integrity of power lines and connectors that are not designed for digital communications.
The initial usage will be for fixed wireless access using millimeter wave transmissions that allow very large bandwidths — and thus, Gbps connectivity. The technology can be used in a mesh topology to hop along utility poles from a fiber location (POP), presumably until it reaches a utility pole closest to an end user’s home or building. The RDAS may be able to transmit the signal from the terminating pole directing to an in building CPE (customer premise equipment) — preferable within sight of the terminating pole. A secondary benefit of having these AirGig radios mounted at the top of the utility poles is to provide intelligence to the utility grid, supporting meter and control systems. For example if a pole goes down, or something approaches or impedes a power or utility line (say a branch or tree during a storm), this will cause a disruption in the AirGig radio signal, which can serve to identify the exact location of the problem area.
Millimeter waves, which are radio waves from 24-300 GHz, are already in use globally for wireless backhaul. The benefit of transmitting in these high frequency bands is access to high bandwidth, between 100-800 MHz, which is 20-100x over today’s common cellular systems in the microwave and lower frequency bands. In the past they generally were expensive due to costly hardware required along with the requirement of clear line-of-sight link conditions and accurate physical beam alignment, due to high propagation loss in air.
Due to recent research and technology advances, along with FCC regulation, it is now possible to deploy low-cost, high-bandwidth radios in the millimeter wave bands, yielding Gbps data rates. The new technology includes primarily the use of massive MIMO antenna arrays that can not only form high-gain beams to compensate for the propagation losses in millimeter wave bands, but also be dynamically steered for optimal alignment. The later allows for ease of deployment in fixed wireless cases, and the possibility for mobile wireless connectivity (to smartphones, etc.).
Recently, Facebook also announced a low-cost mesh, fixed-wireless 60 GHz backhaul architecture called Terragraph. The target is to use the unlicensed 60 GHz band, to facilitate connectivity in metropolitan areas of developing countries. Terragraph has an open-sourced platform using a cloud based controller. While AT&T’s initial target for AirGig seems to be more rural than metropolitan deployments, by targeting international partners the metropolitan use case may also be explored.
While AirGig is still being tested, many details are still unclear, including if this research initiative can address any use-cases (metropolitan or rural) cost effectively. What we do know about this project, however, is that it demonstrates, along with AT&T’s recent acquisition of mmWave backhaul company FiberTower, that AT&T has an active interest in the 5G mmWave arena.