Skip to main content

LTE-U Steamrolls Into WiFi

Here we are, ever closer to market trials from Verizon Wireless and T-Mobile of the “LTE-U” technique that many believe could hamstring everyday WiFi connectivity, which is increasingly being used to deliver high-quality video.

Refresher: LTE stands for Long Term Evolution, and is the mobile industry’s consumer- facing brand meaning “next-generation.”

The “U” stands for “unlicensed.” All WiFi traffic runs in unlicensed bands, at 2.4 Gigahertz and 5 GHz.

Up until LTE-U, mobile traffic rode in its own, private lanes — lanes which cost the wireless carriers multiple billions of dollars to buy.

LTE-U also goes by “LAA,” for “Licensed Assisted Access.” At first glance, it’s a bit of a communications oxymoron: “We have a license to assist us in accessing” the unlicensed WiFi bands, as one interpretation. What’s missing: “And you don’t.”

Just about a year ago, we (in fun) compared WiFi’s communication methods to Canadians: Polite, in a “listen-before-you-speak” way. By contrast, we likened LTE-U to a seemingly endless group of large people, shouting instructions to each other.

That wasn’t quite right. Turns out they’ll keep the instruction bits in their owned, private mobile spectrum and just dump their burdensome traffic into the WiFi spectral territories. Like toxic waste, but digital.

This is bad on two fronts: One, because the LTE-U “control plane,” as it’s called, resides solely in the spectral footprint of the mobile carriers; only they can control its behavior.

Two, WiFi devices contain no way to see LTE-U traffic coming. All they can do is back off once it hits, because they’re built to be polite that way.

Just how screwed are the purveyors and users of WiFi broadband connectivity — and services? Lab tests conducted by CableLabs consistently show the potential for LTE-U traffi c to stomp WiFi connectivity all the way to zero.

At the recent WiFi Global Congress, headlines busted out like “Hostilities Break Out Over LTE-U,” with the LTE-U camp (Qualcomm, in this and every case) continuing its stance of “Relax, it’s gonna be OK,” and the WiFi side (CableLabs, Sky) pushing back — hard.

Here’s an exemplary zinger from Cable- Labs director of wireless and network technologies Vikas Sarawat: “Doing LTE-U in a proprietary manner is not in the favor of people who have multimillion [dollar] businesses running in unlicensed bands.”

Tech translation of the LTE-U side’s arguments: Techniques like “duty cycling” and “Listen Before Talk” (LBT) will suffice to protect WiFi traffic in the 5-Gigahertz zone from being trampled.

“Duty cycle-based approaches” sequence LTE traffic in an on/off pattern. How long LTE is “on” or “off” is decided (by the mobile carrier) as some percentage of the take. Maybe they dump into WiFi for 5% of the time; maybe 50%. Either way, WiFi capacity goes down by as much.

Not to worry, though! The Federal Communications Commission in early May jumped into the fray, seeking comments on LTE-U and LAA’s impact on WiFi. The deadline is this Thursday (June 11.) We’ll be watching.