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Adtran Offers G.Fast Crosstalk Cure

Carol Wilson

Adtran today is unveiling a patent-pending approach to enabling the newest form of advanced copper technology -- G.fast -- to more easily co-exist with the VDSL2 technology already being deployed, and thus be brought to market faster and at lower cost by telcos eager to get to near-gigabit speeds over their existing infrastructure. (See Adtran Speeds Up Copper Links With Frequency Division Vectoring.)

Frequency Division Vectoring essentially allows G.fast, which delivers higher speeds over shorter loop lengths, to be added as an over-the-top channel on VDSL, eliminating the crosstalk issues that make the two incompatible over a single copper pair. By enabling that compatibility, Adtran Inc. (Nasdaq: ADTN)'s FDV can allow a telco to get started deploying G.fast where it has loop lengths of 250 meters or less, to deliver close to 1 Gbit/s, without ripping out existing VDSL2 deployments or having to invest heavily in deploying G.fast over an entire service area.

"Vectored VDSL can provide 100 Mbit/s downstream and 40 Mbit/s upstream, so it provides as much capacity for sustained loads as GPON [gigabit passive optical networks]," says Adtran CTO Kevin Schneider. "Now a carrier can also use G.fast with dynamic crosstalk avoidance at speeds up to 500 Mbit/s over short lines."

G.fast, which is still an evolving standard at the ITU, increases speed over copper lines by using wider frequency profiles than those used by VDSL2, operating on 106MHz and at some point promising to operate at 212MHz. VDSL2 uses 17MHz or 30MHz bands.

For more coverage of broadband innovation, visit Light Reading's dedicated DSL content channel.

Adtran's FDV technology will be presented to the ITU for inclusion in the standards process later this month, Schneider says. Adtran realizes that for the technology to take hold, it has to be offered by more than one vendor, he adds. But Adtran also hopes to leverage its invention in competing with its prime rivals in access, Alcatel-Lucent (NYSE: ALU) and Huawei Technologies Co. Ltd.

Telcos have to be able to compete with cable companies in the speed wars and have been disadvantaged by the DOCSIS 3.0 technology that let cable deliver speeds up to 100 Mbit/s, the Adtran CTO notes. What the industry is looking for is the ability to bump up speeds as close to one gig as possible, but do so cost-effectively.

What Adtran is proposing allows telcos to take advantage of their existing distribution plant, including aggregation points and deployments of fiber-to-the-building for office towers and multi-dwelling units, he notes. By eliminating the crosstalk issue, Adtran is making the full range of bandwidth available for use by G.fast deployment without disrupting the services already deployed.

— Carol Wilson, Editor-at-Large, Light Reading

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User Rank: Light Sabre
8/18/2014 | 8:27:14 AM
Re: Niche
If it works and is cost effective it surely will be the way for telcos to keep up with the cable guys. The ads are awash with speed as the selling point, and the telco company can now equalize that advantage if the costs are reasonable to do so.
User Rank: Light Sabre
8/15/2014 | 12:29:55 PM
Re: Niche

You won't get improved results by doing G.fast at the distance that VDSL2 deployed.  The copper network is the limiting factor and that doesn't change as the vectored versions of DSL run pretty close to the Shannon Limits.  

So, the way to get a faster rate is to shorten the loops by moving the Fiber to Copper transition closer to the home.  Which means that you are running Fiber to say 500' from the home instead of 2500' today (which was the original U-Verse Model).  At 500', G.fast has a lot better result.

Now, think through this deployment.  You have to run fiber out to the 500' mark from where it is today and then overlay put the products out at that point.  There will be a crossconnect at the drop point which is where you will want to insert G.fast.  So, to have interference with VDSL2 that means you want to KEEP the older method and then ADD the newer one on top of it.

This seems like not the way the large carriers will work in bulk.  One would be better off converting a neighborhood.  The only way I see this having value is a box that does both G.fast and VDSL2 at the 500' mark.  That would allow the carrier to deploy G.fast and then sell upgrades after the network was upgraded.  That seems like a minority case to me.



User Rank: Lightning
8/15/2014 | 7:39:56 AM
Re: Niche
Doesn't seem odd to me. Increasing speeds from thousands of deployed fibre connected VDSL2 street cabinets over the existing copper is a no brainer. Much cheaper and quicker to deploy than FTTH to all premises. 
User Rank: Light Sabre
8/14/2014 | 11:46:19 PM
Carol, This seems like a very niche solution. You would have to want to overlay a very short reach g.fast solution OVER an existing a vdsl2 solution. That means you run fiber into a distribution box and then keep the copper in place beyond it. Seems like a very odd solution. seven
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