STOCKHOLM – Alcatel-Lucent has found a way to move data at 300 Mbps (megabits per second) over two copper lines. 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 300 Mbps 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 100 Mbps over a distance of 1,000 meters, he said.
On its own VDSL2 tops out at about 100 Mbps over a distance of 400 meters, so to get to three times that capacity Alcatel-Lucent combines a number of different technologies. The first 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 300M bps you only get about 200 Mbps. To solve this Alcatel-Lucent uses vectoring, a technology that works like noise-cancelling headphones, according to Vanhastel. It continuously analyzes 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 optic 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 around the world. About 65 per cent of subscribers have a broadband connection that’s based on DSL (Digital Subscriber Line), compared to 20 per cent for cable and 12 per cent for fibre, according to market research company Point Topic. Today, the average advertised DSL speeds for residential users vary between 9.2 Mbps in Western Europe and Asia Pacific and 1.9 Mbps in South and East Asia, Point Topic said.
The use of vectoring on VDSL2 is currently being standardized 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 LM 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 300M bps 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 1 Gbps or 2 Gbps, but on purpose we chose not to do that because it is not a realistic scenario,” said Vanhastel.
