Originally featured on
Oct 15

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10/15/2012 2:28 AM  RssIcon

Anyone attending a meeting of the FTTH (Fiber To The Home) Council Europe or its counterparts elsewhere in the world could be forgiven for thinking that the age of copper telephone wires had disappeared almost with the last millennium, and that we are all now served with gleaming new fiber at the very least to the end of our streets. This is, unfortunately, far from the reality. Even in the heartlands of affluent cities, there are many dark spots unreached by fiber, and where copper loop lengths are still so long that broadband speeds struggle to exceed 2Mb/s.

Another reality is that measured as a percentage of the distance reached by copper telephone wires, the penetration of fiber is only increasing by at most 2 percent a year in the developed nations of Europe, and North America, even if it is doing much better than that in some Asian countries such as South Korea. It is true that the rate of penetration is greater than that in terms of the number of households reached, because most people live in or near towns and cities, but there will be a substantial number relying on copper even by 2020.

This has important implications for direction of R&D for broadband services, and for my money, only one company has got the balance right, Alcatel-Lucent. That company has, ever since its creation in 2006 from the merger of Alcatel and Lucent, struggled to maintain momentum against some of its competitors, but remains the leader in wired broadband, particularly on the copper side with its VDSL technology.

Alcatel-Lucent is also active in fiber research, with an announcement likely to make FTTH more reliable and affordable expected this week, and it is in fact one of five founding members of the FTTH Council Europe. But it is advocating a balance between fiber and copper investment, with FTTH for everybody being the distant endgame. In fact, fiber deployment and copper network enhancement should go hand in hand. Pushing fiber deeper shortens the copper loop lengths to increase the bandwidth per person, while advanced VDSL technologies boost end-to-end bit rates further. In other words, a virtuous circle of improving bandwidth is generated by ever more efficient transmission technologies over ever shorter copper loop lengths. We should not forget that fiber will be speeding up as well, as it has to, in order to provide all the extra backhaul and core network capacity to carry all that extra broadband traffic.

Against this background, Alcatel-Lucent has just extended its VDSL technology portfolio with the launch of zero-touch vectoring. This complements its phantom-mode vectoring technology that added about 50 percent to the bit rate achievable over two twisted pair copper circuits of a given length, compared with the industry-standard vectoring technology already available. Two points to note here. One is that the rate at which data can be transmitted along a copper wire is constrained by a number of factors including signal attenuation, but the most significant one that can be countered is electromagnetic crosstalk interference between neighboring wires. Vectoring all but eliminates that interference, enabling VDSL2 to attain speeds up to 100Mb/s per copper pair over loop lengths of 400m, which is an order magnitude greater than earlier versions of DSL. Secondly, carriers in many cases have at least two copper pairs available for each customer for historical reasons, even though only one is needed for conventional voice and data services. With bonding technology, the two pairs can be combined to double the capacity, enabling up to 200Mb/s over 400m.

Alcatel-Lucent then went 50 percent further to reach 300Mb/s over two twisted pairs with its phantom-mode technology, which created a third channel over two pairs together, essentially using one pair as the equivalent of a single wire in one direction, and one pair for the other. Mathematically the principle is quite simple, but requires accurate engineering and is highly effective. But there was one snag, which was that in order to work properly, the firmware on all customer-installed modems had to be upgraded even if just one of them wanted to upgrade to the higher speed vectoring. This meant making a significant upfront investment, which some telcos such as Belgacom have done, but which would be prohibitively expensive for many smaller operators.

This is where zero-touch vectoring comes in with new signal processing technology that is installed as part of the overall vectoring package, with or without phantom mode. It prevents modems that have been upgraded for vectoring from interfering with those that have not. This means that operators can upgrade their networks for vectoring one customer at a time in response to demand, knowing that the investment will be paid back by the presumed increased subscription it can charge as a result.

As to what all this has to do with broadcasting and TV, the answer is everything. It is only because of growing demand for HD delivery over broadband resulting from OTT and IPTV deployments that there was any need for VDSL vectoring in the first place. Otherwise, we would all still be quite content with 4Mb/s over vanilla DSL.

Of course vectoring is only a temporary fix while we wait for fiber to reach our homes. Then the final hop to the TV or home gateway from the fiber termination point will still be over copper, but there will no longer be the same issue of crosstalk interference between nearby wires to worry about. It is a good bet though that vectoring will have a major role to play for delivering video in the multiscreen era for well over a decade to come. There will be plenty of mileage for zero touch.

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