Just when you think the telcos have squeezed all the bandwidth they can out of existing copper, along comes the next big thing in DSL to push the capacity of twisted pair to the next level. Such is the case with a relatively new technology known as VDSL2 vectoring.
One of the biggest impediments to good VDSL performance is noise from other VDSL lines, according to ADTRAN (News - Alert) product manager, Ryan McCowan. Vectoring addresses that by coordinating all VDSL pairs in the cable in an effort to cancel noise.
As a result, data rates can be improved by up to 50 percent. And that, of course, enables operators to get more value out of the copper they already have installed and depreciated.
That may seem unimportant in light of all the focus on fiber access these days, but copper remains an important and prominent part of our communications infrastructure – and DSL enables broadband access for 42 percent of the nation’s broadband lines. (Cable modems account for 50 percent of broadband lines in the U.S.; fiber 8 percent.)
VDSL2 vectoring promises to deliver 100mbps and more downstream, and 40mbps upstream. (Without vectoring, VDSL2 can deliver 100mbps speeds, but not at any practical distance, says McCowan.)
In a recent blog headlined “VDSL2 Vectoring Delivers on Its Promise,” Dr. Stefaan Vanhastel, marketing director for wireline fixed access at Alcatel-Lucent (News - Alert), and Jan Verlinden, senior DSL expert for the fixed access domain competence center at Alcatel-Lucent, reveal the results of VDSL2 vectoring in communication service provider trials.
“Seventeen very high speed digital subscriber line 2 vectoring trials, conducted by Alcatel-Lucent with various CSPs around the world, have demonstrated that 100mbps is achievable over copper at 400m – and even up to 500m,” Vanhastel and Verlinden wrote. “These trials focused mostly on 300m to 600m loop lengths, reflecting the typical fiber-to-the-node topologies that CSPs are considering for vectoring.”
They add that while early trials, beginning in July 2010, were capped at 100mbps, trials conducted in April 2012 achieved rates of as high as 130mbps.
And, by adding copper bonding into the mix, service providers can realize even higher data rates. For example, one CSP (News - Alert) (using normal UPBO settings) worked with Alcatel-Lucent to get “an astonishing 200mbps downstream and 50mbps upstream at 400m.”
Heidi Adams, director of product marketing at Alcatel-Lucent’s networks business unit, tells INTERNET TELEPHONY that DSL to date has not been widely used for wireless backhaul given it’s been seen as too slow to do the job. But, she adds, new advances like pair bonding and vectoring that now enable 100-250mbps rates over legacy connections are making copper a good candidate for small cell backhaul.
So why is VDSL2 vectoring garnering attention now, and when can we expect more widespread use of this promising technology?
The techniques involved in vectoring are very computationally involved and only recently have chip vendors figured out a way to implement them in a way that’s practical and affordable, says McCowan.
ADTRAN in mid October announced the addition of system-level vectoring to its broadband portfolio. Alcatel-Lucent also offers products featuring VDSL2 vectoring. Calix (News - Alert) had its E7-2 and E3-48 products, both of which are vectoring-capable, in trials as of late October. Zhone Technologies expects to come out with its first onboard vectoring gear in the first quarter of 2013, Brian Caskey (News - Alert), chief marketing offer at broadband access gear supplier, told INTERNET TELEPHONY.
And ZyXEL has two VDSL2 gateways with vectoring features that are currently shipping – the VSG1435 and VSG1432.
Expect service provider trials of VDSL2 vectoring to continue this year and into next year. By 2013, McCowan indicates, we should see small deployments of this technology, with wider deployments expected in 2014.
Edited by Braden Becker