A Summer Guide to the LTE-U Dustup

Few tech stories are as loaded with hyperbole, angst and vitriol as the matter of mobile LTE-U and its possible crushing effect on WiFi.

Headlines crackle with pre-emptive fury. For instance, “LTE-U: How the Wireless Industry Plans to Conquer Your (and the Cable Industry’s) Home Wi-Fi Hotspot” and “LTE’s Backers Vow to KILL OFF WI-FI and BlueTooth” are two of many recent doozies.

For that reason, we offer you this summertime reading guide to the LTE-U dustup — important because WiFi carries more broadband traffic than any other medium, and especially video. If WiFi were to get squashed to obliteration, as many believe it will (and many believe it won’t), so goes our ability to stay connected to our digital lives.

So pour yourself an icy beverage and snuggle in to one of the spicier tech stories of recent times.

Refresher: The “U” in “LTE-U” stands for Unlicensed. Mobile carriers traditionally move their traffic over the licensed spectrum they spent billions of dollars to own and operate. Their foray, via LTEU, into the unlicensed bands — where WiFi lives — is on the drawing boards of at least two carriers, T-Mobile and Verizon Wireless. Both plan to test it in unspecified markets this year and launch it in 2016.

Their motivation: Network congestion, especially as more of us use more WiFi-connected screens to stream video. No matter the connection medium — wired or wireless — video remains a whale when it comes to seizing available capacity.

LTE-U’s more vocal proponents, beyond the mobile carriers and their trade associations, are Qualcomm, Ericsson and Google. Qualcomm’s fi ling to the Federal Communications Commission cheerfully characterizes LTE-U as “a friendly neighbor to Wi-Fi.” Confident subheadings abound, such as “Claims That LTE-U Will Harm Wi-Fi Are Plain Wrong.” For the adventurous, the 50-plus-page fi ling also includes a 30-page, Google-authored appendix titled “Technical Response to Parties Opposed to LTE Unlicensed.”

Detractors to LTE-U proliferation include Cable vision Systems, Microsoft, the National Cable & Telecommunications Association, Ruckus Wireless, ViaSat, and pretty much everyone with a business model that requires a healthy and growing WiFi network.


Also worth reading is the latest in CableLabs’ ongoing work to characterize the impact of LTE-U on WiFi. In a recent blog post, CableLabs lead architect Joey Padden explained how he dropped some LTE-U traffic onto a WiFi area covering 20 cubicles, 25 connected devices, and a break area for a week, without telling anyone, so as “to ensure the user/traffic load and sample noise was as normal as possible.”

The tests involved placing an LTE signal source about three meters from the WiFi access point, then applying two “duty cycles” — tech talk for the knob mobile carriers will turn when they want to offload their traffic onto WiFi. One was set at 50% of 80 milliseconds, and the other at 50% of 200 milliseconds; two power levels were also tested.

Guess what happened? If you guessed badness, you’re correct! Padden’s experiments show that two key test parameters — throughput and latency — buckled when hit with duty-cycled LTE-U traffic.

(Tech-talk detangler: Throughput measures how well, or not well, data moves over a transmission medium. With throughput, higher is better. Latency measures how long it takes for a bit or packet to move from source to destination, based on things that get in the way. With latency, lower is better.)

And yes, Padden’s co-workers did ultimately figure it out, “followed by various defamatory comments about me and my methods,” he quipped in the blog.


At this moment, here on the edge of autumn, some 40 people and companies sent detailed reply comments to the Federal Communications Commission. Most argue for or against the FCC’s further involvement in the matter — meaning for or against regulations.

The NCTA’s position, titled “Unless the FCC Acts, A New Technology Could Disrupt WiFi,” asks for “appropriate sharing protocols, so that the norms of sharing in the 5-GHz band will be honored, and that consumers can secure the benefits of all technologies fairly by using the band, be they LTE-U or WiFi.”

Will thing go amok when the mobile guys turn up their LTE-U spigots? Ample evidence exists on the side of “yes” and “no.” So keep an eye on Verizon and T-Mobile, and those undisclosed market trials. This is a horse that won’t be easy to get back in the barn if things go bad.

Time for a refill on that icy beverage!