AT&T Whips the Gfast Horse, Demanding Faster

BERLIN -- Broadband World Forum 2017 -- Early deployments of Gfast technology in multi-dwelling units have whet AT&T's appetite for even faster broadband services over existing in-building coax cables, and the operator is now pressing the vendor community for even faster Gfast tech, a senior AT&T executive told UBB2020 here today.

Tom Starr, lead member of technical staff at AT&T, gave an update on the operator’s use of Gfast technology across the US during a Broadband Forum workshop here this week. He noted how it uses the technology -- which can boost downstream and upstream speeds on existing twisted pair copper and coax cables over short distances -- to provide high-speed broadband services both within its existing services markets and beyond.

So far the operator has deployed 16-port Gfast units based on the first iteration of the Gfast standard from the ITU-T, which uses the 106 MHz channel, and has been able to achieve service speeds of up to 750 Mbit/s. But the standard has been evolving, and the broadband chipset and system vendor community has been developing new products based on the Gfast Amendment 3 standard that specifies use of the 212 MHz channel. AT&T plans to start lab trials of 212 MHz technology this year, with a particular focus on backwards compatibility to first-generation Gfast technology.

But already AT&T is pushing the vendor community for more. While the ITU-T currently plans to work on a standard known as G.mgfast (Multi-Gigabit Fast), which would use 424 MHz and 828 MHz profiles and could potentially be ratified some time in 2019, Starr believes it could take up to five years before commercially deployable G.mgfast technology will be ready for use in a production network, "and we don’t want to wait that long," he said on the sidelines of the workshop.

What AT&T wants from the vendor community is a quick and simple version of 424 MHz profile Gfast for coax -- the physical medium over which most of AT&T's Gfast plans are focused -- that simply enables enhanced bandwidth and would not need to come with a full and lengthy list of specification enhancements.

"This is the next big thing that we are looking for in Gfast, this is what we want from the industry -- it would be a game-changer. We want to be able to offer 2 gigabit broadband services over coax -- that’s a big thing for the AT&T marketing team," stated Starr, who believes the 424 MHz profile would be able to deliver that soon.

For multi-dwelling units (MDUs), 424 MHz would only really be of use in buildings with coax cable and not really applicable to twisted pair copper networks as the crosstalk interference between the multiple lines would be too great: "212 MHz is about as far as it goes for twisted pair," noted Starr.

But there is a very specific application of the 424 MHz profile for copper plant outside of MDUs, he said. The speedy development of 424 MHz Gfast, ahead of the G.mgfast standard, would also enable an operator to take a fiber very close to a home or business and offer Gigabit-plus broadband services over a single twisted pair copper line in a deployment model known as "single line DPU" (distribution point unit). In that instance there would be no crosstalk issues because only one twisted pair line would be used, though it’s unclear what the business case would be for such a deployment.

If the vendor community believes there might be enough scale and demand for a "quick and dirty" version of 424 MHz Gfast, then there’s little reason to doubt it could deliver. The sector was quick to react to BT’s demands a few years ago for Gfast technology that could deliver broadband speeds of hundreds of megabits per second over hundreds of meters, a far greater distance than originally envisaged, so it’s likely to be well within the capabilities of chipset specialists such as Broadcom and Sckipio to meet AT&T's requirements.

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—Ray Le Maistre, International Group Editor, Light Reading