How Much More Can be Wrung from DSL?

Ericsson engineers have demonstrated in the lab a way to bond together six unshielded copper wire pairs to push 500 Mbps about 500 meters. The technique is promising for the same reason all such technology developments are: they suggest it is possible to wring yet more performance out of a widely-deployed infrastructure that has some real-world performance limitations.

That doesn't mean the lab performance easily can be ported to a real-world environment. For starters, lab tests are not encumbered by all the messy real-world complications. Real-world access plant faces hazards such as squirrels, moisture ingress, corrosion and electromagnetic interference from other services that might be running inside the same cable bundle.

The other practical limitation is that most consumer locations might not have six available spare pairs to use. On the other hand, as fewer people use landlines, there theoretically are more unused pairs to tap. It's a messy process, though, and likely would require installing new drop cables and resplicing the drops to the distribution wiring. That sort of heavy craft work isn't so interesting for any service provider that might contemplate trying to introduce such a service.

On the other hand, in some urban markets in countries with dense housing, copper drops might be short enough that something could be practical, perhaps not delivering 500 Mbps, but still providing enough bandwidth to be quite interesting.

As often is the case, spot deployment seems more promising. Mobile tower backhaul, for example, could benefit, as the upside from deploying a relatively short length of new cable, when a suitable fiber node is available, could be quite helpful. Some enterprise locations also could benefit, much as these locations now do for "Ethernet-over-copper" technologies.

In the consumer market, at least in the United States, where loop lengths generally are longer than in Europe, bonding two pairs is much more practical. As always is the case when trying to market a service to the consumer market, varigated real-world physical constraints are important. Two pairs is typical. In some cases four pairs might be fairly standard. But four pairs might not generally be available everywhere in a region or city.

No question, any developments that increase DSL bandwidth are helpful. How helpful really "depends" on a variety of messy details.