Publié le 27 août 2013
V for Vectoring
For the last 10 years or so, FTTH has experienced tremendous growth and generated a lot of hype. From inception, it has been all the rage and is still going strong with FTTH shows, forums, panels, etc. Little known fact however - only a very small ratio of all residential lines deployed worldwide have been “fiberized.” The vast majority being still on twisted copper pair (and some coax cable).
Regardless of what you're getting at home, chances are you want high speed... without paying a fortune. For this reason, telcos have been striving to get more bandwidth from twisted pair.
A few blogs ago, we discussed fiber-to-the-distribution-point (FTTdp) and G.fast, which are still a few years down the road. Vectoring is a solution that is available right now today. While not yet vastly deployed, vectoring has been standardized by the ITU-T, and is currently being deployed at a handful of telcos, and under evaluation at various other telcos worldwide.
Sooner or later most tier-1 telcos will have migrated, considering that vectoring is a prerequisite for the ultimate Holy Grail that G.fast promises to be. While more activity is currently being seen in Europe, it is slowly spreading with the growing number of successful trials. But what exactly is vectoring? In a nutshell, much in the way that noise-cancelling headphones increase musical experience, vectoring cancels out some of the noise travelling on the pair. And next to signal loss, noise due to crosstalk is the major cause of bandwidth limitation and data-rate reduction. By monitoring this far-end crosstalk (FEXT), compensation algorithms compensate for it at the emitting end, thus enabling more bandwidth to be used over greater distances.
So, will vectoring provide FTTH-like bandwidth and distances? Not even close, but what it does provide is the breathing room of “enough” bandwidth to either push back FTTH expenses, or allow G.fast to be approved by the Study Group and made commercially available.
A word of wisdom and caution, however. Although vectoring will mitigate FEXT, other noise sources can appear, in which case there is a chance that the vectoring system may not be able to provide an adequate solution algorithm in a timely manner. Other sources of noise can include, but are not limited to: impulse noise and other crosstalk disturbers. Of course, all of these factors should be analyzed before, during and after vectoring deployment. If not, the outcome will be “V” as in “Vulnerable.”