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T-Mobile came up short compared to Verizon and AT&T in the last 4G spectrum auction, but it looks like it’s found another source of airwaves, and these won’t cost it anything. At Mobile World Congress on Monday, T-Mo revealed that in 2016 it plans to deploy LTE in the unlicensed 5 GHz bands, the traditional home of Wi-Fi, and it’s likely the Wi-Fi industry isn’t going to be very happy about it.

[company]T-Mobile US[/company] has never made a secret of its interest in operating in the unlicensed bands, but until now we’ve never had a firm deployment date, and that date is actually pretty darn close.

The country’s fourth largest carrier will use [company]Alcatel-Lucent[/company] small cells – which are like big tower-mounted cells, just tinier – embedded with [company]Qualcomm[/company]’s radio processing chips and LTE-Unlicensed technology (T-Mobile has tested similar systems from [company]Nokia[/company] and [company]Ericsson[/company] as well). The carrier plans to start a trial of LTE-Unlicensed this year and then adopt LTE-U’s more technically sophisticated brother LTE-License Assisted Access (LTE-LAA) when it takes that network commercial next year.

I just spouted off a lot of acronyms there, but the key thing you need to know about LTE in the unlicensed bands is it will share the 5 GHz airwaves with Wi-Fi, moving from channel to channel to find a clear path for its 4G transmissions, just as Wi-Fi networks coexist with another in the same spectrum today. The problem is, according to the Wi-Fi industry, LTE won’t necessarily play nicely with the other Wi-Fi networks in the band, potentially forcing Wi-Fi users off of their own spectrum.

This issue is going to come to a head over the next year – it’s already becoming a major topic at MWC this year – as more carriers announce their unlicensed intentions. Basically the mobile and Wi-Fi industry are engaging in an old-fashioned turf war. It’s easy to see why carriers are interested in the unlicensed bands. They have hundreds of megahertz of airwaves they could potentially tap for their 4G networks, which could translate into faster speeds and more capacity for their customers.

But it’s also clear why the Wi-Fi industry isn’t exactly welcoming the carriers with open arms. The unlicensed band is meant to be open and shared, but carriers traditionally aren’t the open and sharing types. They’re accustomed to owning their airwaves and doing with them whatever they please.