“The obvious solution is to remove the cross-talk, which is why we add [high-speed] DSL vectoring on top of this,” Vanhastel says. Vectoring eliminates cross-talk in bundled wires by sending a signal down the cable that is exactly the opposite of the cross-talk signal, cancelling the noise out.
Combining the three techniques has the potential to increase transmission speeds far above what’s possible with existing DSL connections. Typical ADSL connections top out at six megabits per second, while advanced, ADSL2+-powered connections to fiber-optic hubs are advertised at speeds of up to 24 megabits per second. Forthcoming VDSL technology could push speeds up to 50 megabits per second, and vectoring could take lines to more than 100 megabits per second. Phantom mode can further increase speeds, depending on the distance, by up to 200%, or simply boost the range of existing high speed connections.
There are a few catches, however. One is that a home or business must have at least two lines already connected (in the United States, many do). In addition, says Vanhastel, manufacturers have yet to introduce a three-channel modem for consumer use.
While Alcatel-Lucent is the first company to publicly announce a technology that combines these three techniques, it is not the first to deploy them in the lab or in field trials, according to Stanford University professor John Cioffi, CEO of DSL management company ASSIA. “I’ve seen it work in the field on customers’ lines, but I can’t say where and how,” Cioffi says. He notes that the cost of bonding and vectoring has deterred telecommunications companies from introducing them until now.
Other approaches are being used to get more speed out of copper connections. Last year Ericsson announced that it had induced a DSL line to transmit data at 500 megabits per second, but that achievement involved bonding six separate lines. Alcatel-Lucent limited its test to two bonded lines, says Vanhastel, because that is the largest number of lines a home or business could realistically be expected to have connected.
Alcatel-Lucent doesn’t believe it will roll out the combination technology until after 2011. Even so, that’s well ahead of the timetable for extending fiber-optic technology to all areas of the U.S.
One-hundred-megabit DSL is “what we can see” in the next five to 10 years, says Cioffi. That will be just in time to realize the Federal Communications Commission’s goal, announced in February, of rolling out 100-megabit-per-second broadband to 100 million U.S. homes by 2020.