The future of mobile data pits cellphone carriers against cable giants

Cellular data is one of the great innovations of the 21st century. Now it's about to take its next big leap, one its supporters say will improve service on carriers such as Verizon and T-Mobile. Its critics, however, say it could undermine WiFi, a free, time-tested technology that handles roughly half of the Internet's mobile traffic today.

It's called LTE-U, and it's being developed by Verizon, the chipmaker Qualcomm and a number of other telecom companies. The innovation represents the next evolution in mobile data — and a looming flashpoint for two gigantic industries. If you use any of the four major national cell carriers, you're probably familiar with 4G LTE, the current cutting edge of mobile data technology. Under ideal conditions, it provides download speeds that rival what you can get on a wired connection — fast enough to download a song in less than a minute. LTE-U is virtually identical to LTE, but with one key difference: It runs on the same frequencies that WiFi does. Unlike regular LTE, which piggybacks on airwaves owned exclusively by your carrier, LTE-U travels on public airwaves that are free to anyone. Under LTE-U, your device will likely report being on "LTE" just as it always has. But its introduction reflects an unprecedented move by wireless carriers onto open airwaves — known in the industry as unlicensed spectrum — and that's going to have important repercussions.