Researchers at Cambridge University say the broadband bandwidth of copper phone lines could be significantly higher than is currently achieved. It could be a workaround for one of the big challenges in expanding high-speed internet provision.

Ergin Dinc’s team were looking for solutions to the “last-mile problem” under which it’s financially efficient to build fiber optic cable networks to connect local hubs, but can be expensive and disruptive to replace copper cabling between those hubs and individual homes.

They looked at the frequency of connections over copper cables: in other words, the number of times the current changes every second. At the moment it’s below 1 gigahertz.

Dinc believes the twisted pairs of copper cable could operate at a higher frequency using a correctly configured device called a balun. In theory the frequency could be as high as 5 gigahertz before the cable effectively turns into an antenna and the signal is lost as radio waves.

In principle, the higher the frequency of current changes, the faster the rate of data transmission. Dinc says the next step is to explore the practical effects, particularly the inevitable increased error rate.

At the moment he estimates that tripling the transmission speed is plausible. That wouldn’t bring the copper cabling anywhere close to the capacity of fiber, but would certainly make the wait for an upgrade a bit more tolerable.