Faced with the choice between investing huge sums in new fiber-to-the-home infrastructure, and trying to squeeze even more capability out of their old copper lines, a growing number of European operators are turning to a technology called vectoring to prolong the life of their existing access networks.

While Telekom Austria and Belgacom stand out as the early pioneers in this space, Germany's Deutsche Telekom has fairly recently put vectoring at the heart of its broadband strategy, Ireland's Eircom has committed to the technology, and UK incumbent BT is also examining the technology as a means of invigorating its copper connections. (See Fiber Revival at Deutsche Telekom and Eircom Rolls Out VDSL2 Vectoring With Huawei.)

Swisscom is another European incumbent that sees value in vectoring. In July, the Swiss operator claimed to have upgraded the fixed broadband connections to more than 200,000 homes and businesses with the technology. (See Swisscom Boasts FTTX Milestone.)

But how exactly does vectoring work, and what does it promise? (See The Value of Vectoring.)

A so-called 'noise reduction' system, vectoring essentially cuts out much of the interference, or 'crosstalk,' that occurs between copper lines in a telephony cable, and that's very useful in production networks.

In laboratory conditions, VDSL -- a high-speed broadband technology used over copper wires -- is capable of supporting 100 Mbit/s connections, making it competitive with some hybrid-fiber-coax (HFC) and fiber-to-the-home (FTTH) deployments. Yet it loses this speed advantage in a commercial setting due to crosstalk: Get rid of the interference, and VDSL can flourish.

That, at least, is the spin. The reality seems to be that vectoring is highly effective over shorter distances, but not so good at boosting VDSL speeds over loop lengths of more than 1 kilometer. Although it still does its job of cutting out noise at these distances, it cannot overcome the problem of attenuation, a reduction in the intensity of the signal as it travels along the copper line.

Indeed, few of the operators deploying vectoring say it will allow them to provide 100 Mbit/s services across their VDSL footprint. Belgacom reckons it can boost downlink connection speeds from 30 Mbit/s to 70 Mbit/s through the use of vectoring, while Telekom Austria noted that 100 Mbit/s would be impractical on loop lengths of more than 300 meters when announcing its launch of vectoring in January 2012.

Hopeful that vectoring will help it to challenge Germany's cable operators, Deutsche Telekom has made bolder claims in a presentation to investors, but acknowledges (in small print) that actual performance depends largely on copper cable length. BT, meanwhile, is reported to have described vectoring in underwhelming terms as a speed enabler rather than a speed booster.

Point Topic has also cautioned against expecting too much from vectoring. In a white paper published last year, the market-research company said that vectoring-enabled VDSL was unlikely to support 100 Mbit/s services for more than a small minority of users.

As far as Point Topic is concerned, if vectoring really is to prolong the life of copper, it will have to prove it can support downlink speeds of at least 30 Mbit/s for the majority of customers, and connections of 100 Mbit/s for a large proportion.

Want to know more about broadband networking developments? Check out this invitation to the Ultra-Broadband Forum 2014, to be held in London on Sept. 24-25, where vectoring will be one of the hot topics being discussed.

Another challenge for vectoring lies on the regulatory front. If the technology is be truly effective, the operator deploying it must have control over all of the lines in a cable. That prohibits the use of sub-loop unbundling – whereby alternative operators take control of lines between street cabinets and customer premises – in VDSL deployments. In markets such as Germany, where VDSL unbundlers have already made significant progress, regulators are likely to have a tough time keeping all broadband stakeholders happy.

Even so, Point Topic expects commercial services based on vectoring to become widespread in Europe between 2014 and 2017, with financial austerity forcing broadband providers to find lower-cost alternatives to fiber-to-the-home deployment. Deutsche Telekom estimates that rolling out vectoring-enabled VDSL in Germany costs 70% less "per connected home" than installing FTTH. And it says the technology alone will satisfy all of its customers' bandwidth demands until 2020.

After that, the need to invest in fiber access looks set to become acute.

— Iain Morris, Site Editor, Ultra-Broadband