FEATURE | ALCATEL-LUCENT Michael Peeters, CTO, Wireline, Alcatel-Lucent
The Deployment Vector How to get VDSL2 Vectoring into the field
VDSL2 Vectoring solution raised high hopes. VDSL2 Vectoring promises to help service providers meet aggressive national broadband targets using their existing copper infrastructures today, while pre- paring for their fiber build-out tomorrow. Two key questions followed fast on
T
the heels of the news. One, will Vector- ing perform in the field? And two, how quickly can it be rolled out? More than twenty trials have shown that the answer to the first question is a decisive “yes.” And to the second: “right away.”
A MUCH-NEEDED STEPPING STONE TO HIGH(ER) SPEED Service providers around the world spent the past several years trying to work out practical and affordable strategies for achieving high-speed Internet access tar- gets. The Connecting America plan wants to see at least 100 million U.S. homes with 100Mbps download speeds. The European Union is looking for download rates of 30Mbps for all citizens, with at least 50 percent of households above 100Mbps by 2020. While everyone agrees fiber optics
is ultimately the way to go—fiber has the greatest capacity to scale as society’s appetite for bandwidth continues to grow—it’s not a practical short-term option in many regions. Fiber deploy- ments are complex and take a long time to complete. That’s why VDSL2 Vectoring has
captured the imagination of the telecoms industry. It cancels the crosstalk (i.e., inter- ference) generated among VDSL2 lines as they’re packed into binders en route to the cabinet. That crosstalk degrades the perfor- mance of VDSL2 lines by up to 70 percent.
CUTTING OUT THE CROSSTALK Vectoring has been likened to noise-cance- ling headphones: it strips out crosstalk and boosts the capacity of every line in a binder. Importantly, the lines most affected by crosstalk realize the greatest improvement. In other words, the technol- ogy not only optimizes but also equalizes the performance of lines in a binder.
10 THURSDAY 18TH OCTOBER 2012
he announcement at last year’s Broadband World Forum that Alcatel-Lucent was ready to offer the industry’s first commercial
Field trials over the past year have
shown that, in real-world deployments, VDSL2 Vectoring reliably delivers down- load speeds of 100Mbps (and in many cases even higher bit rates) over distances of up to 400 meters. Upstream performance is also im-
proved. This is important for services such as cloud applications and online storage. Trials showed typical perfor- mance in the range of 40Mbps over loop lengths of 200 to 500 meters. VDSL2 Vectoring actually helps up-
stream performance in two ways. Cancel- ling crosstalk allows for optimum speeds, as with downstream flows; and Vectoring also allows service providers to ease their upstream power back off (UPBO) set- tings, further nudging speeds upward.
GETTING IT OUT THERE VDSL2 Vectoring can be deployed for roughly one third of the cost of a fiber- to-the-home (FTTH) rollout. It requires the installation of additional cabinets in the field—a far less disruptive proposi- tion than ripping up every street and front yard to bring new fiber cables to every household. However, while Vector- ing is easier to deploy than FTTH, it still requires upgrades to customer premises equipment (CPE) to avoid that existing VDSL2 modems negatively impact the new Vectoring lines. The ideal approach would be to be able
to convert customers as they adopt high- er-bandwidth service—and to sell that service at a premium to those hungriest for faster speeds. The only hitch with this plan is that for Vectoring to work, every line in a binder has to be crosstalk- canceled. A single uncanceled line will have a negative impact on its neighbors. The key, then, is to make sure all the
lines feeding into the binder support— or at least, don’t compromise—the benefits of Vectoring. There are a few ways this can be done.
MAKING THE ACCESS NETWORK ‘VECTORING-FRIENDLY’ Ideally, it would be possible to convert all legacy CPEs into Vectoring CPEs. Many recent-model CPEs can be converted to VDSL2 Vectoring by firmware upgrade— many, but not all. Some of those that aren’t convertible can be made ‘Vectoring-friendly’
Figure 1: Impact of crosstalk on a single line
with a small extension to the VDSL2 stand- ard, although again this approach can’t be applied universally across the full range of potential CPEs in the field. This might seem like a fairly major obsta-
cle to the uptake of VDSL2 Vectoring. If the only alternative is to first upgrade all the CPEs in the field—hundreds of thousands of them—before Vectoring can be activated, the time to market suddenly becomes long- er. Carrying out all those upgrades would be operationally challenging and expensive. A certain number of firmware updates and other technical issues will arise and need resolution before the service can go live.
A ZERO-TOUCH ALTERNATIVE Alcatel-Lucent has developed a Zero- Touch Vectoring approach that removes the barrier to Vectoring deployment and accelerates the time-to-market for Vectoring-enabled high-speed services. Through clever signal processing in
the access node, the zero-touch method automatically ensures that even legacy CPEs have no impact on Vectoring gains. As a result, service providers can stick with the original plan of upgrading selected customers—those willing to pay for higher bitrates—using Zero-Touch Vectoring for all other legacy lines. This enables full downstream Vectoring gains on all Vectored lines. Upgrading legacy VDSL2 CPEs more
broadly to Vectoring or Vectoring- friendly modes can then be done in a parallel phase of deployment, unlocking upstream Vectoring gains for Vectored lines as well.
The zero-touch approach also provides
a failsafe for situations in which neither Vectoring nor Vectoring-friendly support is available for certain CPE models.
SHRINKING THE TIMESCALES As mentioned, covering a country with fiber is, realistically, a 20-year proposi- tion. With many regions looking to see significant growth in broadband coverage over the next seven years, on a mass scale fiber simply can’t get to fast fast enough. With VDSL2 Vectoring, particularly
with the advantage of the zero-touch approach for initial deployment, exist- ing copper networks can be brought to 100Mbps download speeds in a well- paced way, delivering more bandwidth to more subscribers sooner. When Vectoring is combined with VDSL2 Bonding—combining pairs of VDSL2 lines to further boost their capac- ity—it can give service providers further options with respect either to increasing speed or distance (and therefore, the num- ber of subscribers) reached. One provider participating in a field trial doubled loop length to 800 meters and, with Bonding, achieved speeds of 75Mbps downstream and 17Mbps upstream. At the shorter 400 meter distance, Bonding produced some high-powered results indeed: 200Mbps downstream and 50Mbps upstream. With or without the Bonding option,
Vectoring has demonstrated its real- world potential to accelerate broadband deployment and leverage to the hilt service providers’ investments in their existing copper infrastructures.
BROADBAND WORLD FORUM DAILY 2012 I
http://www.broadbandworldforum.com/
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20