Telecom equipment maker Ericsson says the unthinkable is now the possible: 500Mbps transmission speeds over ordinary copper wiring. Looking at the details, though, it's not clear that the news will give Verizon any reason to rethink its hugely expensive fiber-to-the-home strategy... or that such speeds will be coming to a DSL line near you anytime soon.

DSL, which relies on twisted-pair copper wiring in common usage around the world, suffers from a host of problems as distance increases between the home and the central office with the DSLAM. Crosstalk, the interference that one wire causes on the other wire, increases along with distance, for one thing. Using crosstalk cancellation technology and a short line length of 500m, Ericsson was able to see sustained data transfer rates of just over 0.5Gbps. It's the latest telecom maker to report the potential for huge speed increases on copper wiring.

But not on a single line. To get these numbers, the company had to "bond" six different lines together (channel bonding is a technology also seen in cable's DOCSIS 3.0 rollouts, but there it refers to bonding multiple 6Mhz radio frequency channels rather than physical wires), and it used an updated VDSL2 technology that Ericsson refers to as "vectorized" VDSL2.

As a lab result, Ericsson's demo is impressive. Anything that can pump those sort of bitrates over existing copper wire could be a huge asset for incumbent DSL providers who look enviously at cable and its (relatively) inexpensive DOCSIS speed boosts. For DSL, achieving speeds of more than 25Mbps on a single line have been difficult, and operators like AT&T and Verizon have responded by either running fiber further into the neighborhood (AT&T's U-Verse) or running it all the way to the home (Verizon's FiOS). Ericsson's announcement today might put a smile on AT&T's corporate face, since it suggests that copper can continue to be used as a legitimate last-mile solution.

But in the real world, these results aren't likely to be seen at home. For one thing, few existing homes have six lines, so companies like AT&T will still need to pay something in order to run additional wire. The test distance was also quite short—and many DSL users live well over a mile from their local exchange. The system only appears to work at these speeds if fiber is run quite a ways into the neighborhood, and it then needs to employ copper wire channel bonding from there to the home.

Ericsson suggests that take-up could be quite swift in the market for mobile backhaul, however. When site operators put up a tower, they need some way of bringing all that tower's data back to the main network. For years, this sort of backhaul has mostly come from incumbent telcos offering expensive, symmetrical dedicated lines to the tower site. Recently, wireless backhaul has become more popular due to its lower cost. Ericsson suggests that its technology can make plain copper wiring viable again from a cost perspective as operators in the US and elsewhere roll out 4G networks.