G.fast standard ratified by ITU

The ITU announced December 5 that its members successfully met industry's "by the end of the year" expectations for ratifying the G.fast standard. The organization added that its ITU-T Study Group 15 is already hard at work on extensions.

Recommendation ITU-T G.9701, "Fast Access to Subscriber Terminals (FAST) - Physical layer specification," will offer carriers who aren't ready to invest in fiber to the home (FTTH) a way to provide broadband access services at data rates greater than VDSL2 with vectoring can provide. The goal of the standards makers and vendors who expect to offer the technology is 1 Gbps – although just how such services levels will work and when they might be available remain something of a mystery.

While the specifications start at a maximum distance of 400 m, technology vendors say that G.fast doesn't offer material improvements over VDSL2 with vectoring at distances greater thatn 250 m. The specification calls out aggregate (upstream and downstream combined) data rate targets starting at this shorter distance. These include:

• 150 Mbps at 250 m
• 200 Mbps at 200 m
• 500 Mbps at 100 m
  

The expectation is that vendors will leverage the specifications to support as much as 1 Gbps as well, likely at distances less than 100 m to start.

The ITU-T has cooperated with the Broadband Forum on a fiber to the distribution point (FTTdp) architecture for G.fast, which will see fiber connect the central office to distribution point nodes; the nodes will convert the light signal to electrical for the final connection to as many as 20 customers via the installed base of copper. At the customer premises, the standard has been engineered to enable customers to "self-install" G.fast CPE. The standard also will support reverse powering of the distribution point nodes.

The Broadband Forum has selected the University of New Hampshire's Interoperability Lab (UNH-IOL) as its test and plugfest partner. The two groups plan to hold the first plugfest in January at UNH-IOL. The forum also has begun to develop a test suite and certification program for G.fast systems. The test suite will cover interoperability, functional, and performance testing. The Broadband Forum expects to conduct a beta-trial of the certification program in the middle of next year, with certified G.fast implementations expected on the market before the end of 2015.

Uncertified implementations have already been announced. Startup Sckipio Technologies as well as semiconductor stalwart Broadcom Corp. have announced chip sets (see "G.fast chipsets from Sckipio Technologies debut" and "Broadcom debuts end-to-end G.fast offering"). Others are expected to follow. Meanwhile, Alcatel-Lucent has announced it plans to have a distribution point node available early next year (see "G.fast ONT available early next year says Alcatel-Lucent"). Other companies, particularly ADTRAN and Huawei, have been vocal in their support of G.fast's prospects (see "BT to field trial G.fast fiber to the distribution point technology from Huawei" and watch the video "ADTRAN makes case for VDSL2, G.fast alongside FTTH").

Finally, Study Group 15 expects to finish its work on extensions in time for vendors to incorporate them in their G.fast implementations by this summer. The extensions target performance enhancements that include a wider variety of low-power states.

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