The pros and cons of vectoring

Vectoring is an extension of DSL technology that employs the coordination of line signals to reduce crosstalk levels to improve performance. It is based on the concept of noise cancellation: the technology analyses noise conditions on copper lines and creates a cancelling anti-noise signal. While data rates of up to 100Mb/s are achievable, as with all DSL-based services this is distance related: the maximum available bit rate is possible at a range of about 300-400 meters. Performance degrades rapidly as the loop attenuation increases, becoming ineffective after 700-800 meters. The technology is seen as an intermediate step to full FttH networks.

Vectoring is also specific to the DSL environment, being more appropriate to DSL LLU but becoming severely limited when applied with VDSL2 sub-loops unless all the lines are managed by the same system. Vectoring requires that all copper pairs of a cable binder are operated by the same DSLAM, and several DSLAMs need to work in combination in order to eliminate crosstalk. A customer’s DSL modem also needs to support vectoring. Though the ITU has devised a Recommendation for vectoring (G.993.5), the technology is still under development and currently there remains a lack of standardisation across these various elements.

The quality of the copper network is also an issue, with better quality (newer) copper providing better results. Poorer quality copper cabling (e.g. having poorer isolation, less copper pair drilling) can also result in higher crosstalk, and thus a higher degree of pair-related interference. Nevertheless, these issues could be addressed within the vectoring process.

Vectoring is also incompatible with some current regulatory measures, though again future amendments could bring a resolution to these difficulties. While Telekom Deutschland has been engaged in vectoring since late 2012, the technology requires regulatory approval since it is based on DSL infrastructure, and some services which TD must provide to competitors is incompatible with vectoring. As such, TD must negotiate with the regulator the removal of those services from its service obligations. A partial solution may be achieved through the proposal that the regulator restricts total unbundling obligations for copper access lines to the frequency space below 2.2MHz.

Operators which have looked to deploy vectoring are being driven by cost considerations. The European Commission’s target in its ‘Digital Agenda 2020’ is for all citizens in the region to have access to speeds of at least 30Mb/s by 2020, with at least half of all premises to receive broadband at over 100Mb/s. This presupposed fibre for most areas, with the possibility of LTE to furnish rural and remote areas. However, some cash-strapped incumbents are considering vectoring to enable them to meet these looming targets more cheaply, while still pursuing fibre (principally FttC, supplemented by FttH in some cities).

Belgium was an early adopter of vectoring: the incumbent Belgacom had been one of the first players to deploy VDSL1, which has since been phased out for the more widely used VDSL2, supplying up to 50Mb/s for its bundled services customers. The company’s investment in vectoring will enable it to upgrade a portion of its urban customers more quickly and cheaply than would otherwise be possible with FttH. Yet it is perceived as a stop-gap measure to buy it time and to forestall customer churn to the cablecos which have already introduced 120Mb/s services across their footprints and are looking to release 200Mb/s services or higher. The inherent limitations of copper, regardless of technological tweaking, will mean that Belgacom will have to follow Scandinavian operators and deploy 1Gb/s FttH services in order to keep pace with consumer demand for bandwidth for the next decade.

Vectoring technology has also been trialled by Telekom Austria as part of its FttC GigaNet initiative, as also by P&T Luxembourg which in early 2013 contracted Alcatel-Lucent (one of the vendors leading vectoring R&D) to develop one of the world’s first trials of combined VDSL2 bonding and vectoring technologies. The Italian altnet Fastweb is also investing in vectoring, in conjunction with a programme to deliver FttC to about 20% of households by the end of 2014. Fastweb’s parent company Swisscom has budgeted €400 million for the project (as part of a wider FttC co-investment with Telecom Italia), costing each connection at about €100 per home. The low figure is partly explained by Fastweb being able to utilise its existing fibre networks. Nevertheless, Fastweb in the long-term is aiming to have an FttH-based network across its footprint, having recently committed an additional €2 billion investment to 2016, contracting Huawei to upgrade its network from 100Mb/s to 1Gb/s.

For more information on these developments see the reports:

We invite your comments: Please click here to comment

Tagged in: , , , , , , , , , ,