Alcatel-Lucent Bell Labs has demonstrated downstream rates of 300 megabits per second over ordinary copper telephone lines. This was achieved in lab tests using two telephone lines over a distance of 400 meters. Rates of 100Mbps could be possible over line lengths of up to a kilometre. That could buy time for existing copper infrastructure in the face of competition from cable and fibre connections.
The result is achieved by bonding pairs of wires, reducing crosstalk between them, and creating a third virtual or “phantom” channel from the combination of the two pairs of wires.
Gee Rittenhouse, head of research for Bell Labs, said the so-called phantom mode technology showed how innovation could inject new value into existing networks. “What makes DSL Phantom Mode such an important breakthrough is that it combines cutting edge technology with an attractive business model that will open up entirely new commercial opportunities for service providers, enabling them in particular to offer the latest broadband IP-based services using existing network infrastructure.”
Further research is being conducted to determine how the approach could be deployed. In many cases there may not be a spare pair of wires to connect to the home.
“Reusing copper wire will always be cheaper than laying fibre but the biggest benefit is time,” said Stefaan Vanhastel, director of product marketing for wireline networks at Alcatel-Lucent.
AT&T is already experimenting with bonding lines to extend the speed and reach of its U-Verse service.
Cable operators are meanwhile offering speeds of 50Mbps with 100Mbps or more to come by bonding multiple channels within their coaxial cables. Such speeds will soon become the norm as the demand for bandwidth increases.
With around 60% of broadband connections worldwide still delivered over DSL copper wires, there is clearly a need to breathe new life into existing infrastructure, although the future ultimately lies in fibre, which can offer speeds of up to 1Gbps or more.