G.fast Advances DSL Toward 1-Gigabit

Copper-fed digital subscriber lines could soon get a much-needed speed boost, giving telcos around the world a new way to deliver fiber-like speeds without the hassle and expense of deploying fiber all the way to the home.

That technology is embedded in a budding standard called G.fast, which was granted “first-stage approval” last week by the International Telecommunications Union. The ITU expects to finalize G.fast “as early as April 2014.”

Despite being short of finalization, the first-stage stamp on the standard should give chipmakers, modem vendors and network gear suppliers the technical path necessary to develop G.fast products.


The aim is to present telcos with a platform designed to deliver aggregate capacity of 1 Gigabit per second that can be flexibly allocated to a telco’s downstream and upstream pathways.

“The core technology is pretty much set,” Michael Weissman, vice president of marketing for Sckipio, a G.fast silicon startup, said. “Silicon vendors and developers can move forward on product development.”

Based in Israel and founded in 2012, Sckipio last week said it landed $10 million from Gemini Israel Ventures, Genesis Partners, Amiti Capital and Aviv Ventures.

G.fast, which has also gathered interest from Broadcom, will flirt with speeds of 1 Gigabit per second thanks to its use of a wider swath of spectrum. The standard calls for G.fast to handle bandwidth profiles of 106 Megahertz and just north of 200 MHz, comparing to the relatively paltry 17 MHz of bandwidth used for the 17a profile of very-high-bit-rate DSL. Because G.fast can operate in higher frequencies, it will aim to reduce crosstalk interference through vectoring, a technique that is in widespread commercial deployment on DSL networks.

G.fast isn’t a complete slam dunk. Telcos that use it will still be required to pull fiber to within 250 meters of the premises under an architecture referred to as fiberto- the-distribution-point, or FTTdp.

In a recent report about the budding technology, Broadbandtrends LLC analyst Teresa Mastrangelo predicted the “majority” of G.fast loop lengths will be in the range of 30 meters to 50 meters.

With G.fast, “you end up with a very high-speed system for MDU (multiple dwelling unit) environments and single-family dwellings,” Weissman said.

Although G.fast requires that telcos pull fiber closer to the premises, the technology intends to prolong the life of copper-fed DSL plant while being less complicated and less expensive to deploy than FTTH.

If it works as advertised, it could also give telcos another weapon to wield against cable’s DOCSIS platform, which is already capable of hitting 1 Gbps in the downstream with DOCSIS 3.0. The new DOCSIS 3.1 spec is aiming for multi-Gigabit speeds.

“Fiber to the home is a nice response, but it really never pays for itself. They [the telcos] need something that is affordable,” Weissman said. “Cable has the edge because VDSL has struggled to keep up with the performance requirements of DOCSIS 3.0, and the telcos need a response.”

Weissman said Sckipio, with about 25 employees, expects to have some initial G.fast product available in 2014. “We have trials scheduled,” he said.


Weismann doesn’t expect the first batch of G.fast products to deliver 1-Gig speeds right from the chute. “If we could do affordable 200 Mbps at this time next year or 2015 in a deployed scenario … that would be pretty special.”

In the meantime, a select number of operators have already begun to test pre-standard versions of G.fast. Of recent note, BT Group teamed with Huawei Technologies on G.fast tests at BT’s Adastral Park R&D center near Ipswich in the United Kingdom. In July, Alcatel-Lucent and A1, the Austrian subsidiary of Telekom Austria Group, also lab tested prototype G.fast technology.