Alcatel-Lucent boosts broadband over copper to 300Mbit/s

Copper will be able to deliver high-speed broadband while subscribers wait for fibre, the vendor said

Alcatel-Lucent has found a way to move data at 300Mbit/s over two copper lines, the company said on Wednesday. However, so far it is only in a lab environment — real products and services won't show up until next year.

Researchers at the company's Bell Labs demonstrated the 300Mbit/s technology over a distance of 400 meters using VDSL2 (Very high bitrate Digital Subscriber Line), according to Stefaan Vanhastel, director of product marketing at Alcatel-Lucent Wireline Networks. The test showed that it can also do 100Mbit/s over a distance of 1,000 meters, he said.

On its own VDSL2 tops out at about 100Mbit/s over a distance of 400 meters, so to get to three times that capacity Alcatel-Lucent combines a number of different technologies. Alcatel-Lucent's first trick is to use two copper pairs at the same time, a technology called bonding. Next Alcatel-Lucent uses a feature it has developed called Phantom Mode to create a third virtual copper pair that sends data over a combination of the two physical ones.

The problem is that when you use bonding and Phantom Mode you also get a lot of crosstalk, a form of noise that degrades the signal quality and decreases the bandwidth. So instead of 300Mbit/s you only get about 200Mbit/s. To solve this Alcatel-Lucent uses vectoring, a technology that works like noise-cancelling headphones, according to Vanhastel. It continuously analyses the noise conditions on the copper cables, and then creates a new signal to cancel it out, he said.

"It is a really complex technology that requires ... you to process gigabytes of signal data just to calculate the noise patterns," Vanhastel said.

Fibre to the home is the ideal long-term solution for fast broadband, and in 15 to 20 years all homes will have it, according to Vanhastel. But in the meantime operators should be able to use existing copper networks to offer faster speeds to households that don't have a fibre connection, he said.

Currently, copper is the most common broadband medium. About 65 percent of subscribers have a broadband connection that's based on DSL (Digital Subscriber Line), compared to 20 percent for cable and 12 percent for fibre, according to market research company Point Topic. Today, the average advertised DSL speeds for residential users vary between 9.2Mit/s in Western Europe and Asia Pacific and 1.9Mbit/s in South and East Asia, Point Topic said.

The use of vectoring on VDSL2 is currently being standardised by the International Telecommunication Union (ITU). The final review of the standard ends today, and if there are no further comments it will be approved by the end of April, according to Alcatel-Lucent. At the latest, it will arrive by July, according to Ericsson, which is also working on products that will support vectoring.

Alcatel-Lucent and Ericsson expect field trials using vectoring to start during 2010, and the technology will become commercially available in 2011, according to the two vendors.

Even higher speeds than 300Mbit/s can be achieved by using more copper pairs. However, Alcatel-Lucent settled on two copper pairs because it is a more realistic scenario for when the technology is rolled out to residential users in the future, according to Vanhastel. You might find six pairs in the field, but just for businesses and maybe mobile backhaul applications, he said.

"We could have made an announcement talking about 1Gbit/s or 2Gbit/s, but on purpose we chose not to do that because it is not a realistic scenario," said Vanhastel.

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