FCC asks how LTE can share the airwaves with Wi-Fi

On Tuesday, the agency asked for public comments on LTE-U (LTE-Unlicensed), which Verizon Wireless, T-Mobile USA, SK Telecom and other operators are exploring as a way to get more spectrum for better service. The FCC wants to know how LTE-U might affect Wi-Fi and other services. Comments are due June 11.

Wi-Fi, Bluetooth and other technologies run over unlicensed frequencies that are open to any device approved by the FCC, while mobile operators' LTE networks use frequency bands licensed exclusively for the carrier's use. But licensed spectrum is expensive -- bids in the latest U.S. mobile auction topped US$40 billion -- and may not always be enough to serve a lot of subscribers in one area. So some operators want to send part of their LTE traffic over the unlicensed frequencies.

If the prospect of cell subscribers streaming data, video and music over frequencies that Wi-Fi users depend on sounds like a recipe for a traffic jam, well, that's what the FCC is concerned about, too. The two technologies use different methods to deal with other users nearby.

The FCC says it has been approached by a number of organizations about LTE-U. Among other things, the agency wants to know how things are going between the main standards groups that regulate cellular and Wi-Fi and are supposed to be working out ways to make sure LTE-U doesn't unfairly hog all the frequencies. It also wants to know how the technology will work and how soon it's likely to be here, including deployments that may come out before a standard is finished.

With the extra bandwidth, carriers could head off slowdowns in busy places or just give subscribers a faster connection than they can get on LTE. But the idea has proved controversial.

For now, LTE-U development is focused mainly on using a carrier's regular licensed spectrum as an "anchor" and just using unlicensed frequencies for downloads, which typically need a fatter pipe than upstream traffic. LTE-U might use the unlicensed 5GHz band, where Wi-Fi has most of its channels, and the 3.5GHz band, where the FCC is working on frequency sharing with the military and other users.

Carriers are expected to start rolling out LTE-U first in the U.S., and possibly South Korea, because regulations are more lax in those countries. T-Mobile USA has said it expects to use the technology in the 5GHz band starting next year.

Stephen Lawson covers mobile, storage and networking technologies for The IDG News Service. Follow Stephen on Twitter at @sdlawsonmedia. Stephen's e-mail address is stephen_lawson@idg.com