Verizon, T-Mobile expect to use Wi-Fi Alliance coexistence test before deploying LTE-U gear

Representatives from Verizon and T-Mobile said they will use the coexistence test plan hammered out through the Wi-Fi Alliance before they deploy any LTE-U equipment. They made their comments during an event moderated by the Washington, D.C.-based Open Technology Institute at New America that featured speakers from several sides of the LTE-U/Wi-Fi debate.

Verizon is still reviewing the Wi-Fi Alliance test plan, which saw significant changes up until it was publicly released last week, according to Patrick Welsh, assistant VP of Federal Regulatory Affairs at Verizon. “But we anticipate that all LTE-U equipment would undergo that testing and pass before it’s deployed. The same would go for LAA, we anticipate that all LAA devices would fully comply with Release 13 of 3GPP and hopefully get on to the next generation technology.”

Verizon hopes to deploy LTE-U later this year and LAA sometime next year, he said.

Steve Sharkey, VP of Engineering and Technology Policy at T-Mobile, said that to the extent that coexistence has been a question, “we want to make sure that devices do coexist and live up to what we expect them to do. So the test plan is an important part of that and we expect devices will demonstrate that they coexist fairly … whether they’re LTE-U or LAA, which would comply with the Release 13. And we do require manufacturers [to ensure] we are not deploying equipment that doesn’t comply with standards.”

The event on Wednesday included Kevin Robinson, VP of marketing for the Wi-Fi Alliance; Chris Szymanski, director, product marketing and government affairs at Broadcom; David Don, VP for regulatory policy at Comcast; and Harold Feld, senior VP at Public Knowledge. Josh Breitbart, senior advisor for broadband in New York City Mayor Bill de Blasio’s office, was there to discuss that city’s extensive Wi-Fi buildout and Link NYC. Michael Calabrese, director of the Wireless Future Project at Open Technology Institute at New America, moderated.

Breitbart explained New York City's interest in the LTE-U/Wi-Fi debate in which Wi-Fi players are suspicious of LTE's ability to play fair with Wi-Fi. He said Wi-Fi plays a critical role in the city’s efforts to connect everybody in New York City and to assist as much as 35 percent of low income people who don’t have connections at home. Wi-Fi is an essential ingredient to everything the city is doing, he said. The city’s team manages about 70,000 access points across all kinds of buildings, and the school system is covered by Wi-Fi as well.

Robinson reiterated that the Wi-Fi Alliance is not seeking a regulatory solution, and it's not seeking to get involved in LAA, which is being developed through the 3GPP standards process. The industry set out more than a year ago to develop a fair coexistence test plan, and after many hours in meetings, workshops and labs, the Wi-Fi and LTE industries came up with a plan they could all live with.

Even within 24 hours of the test plan's release, members of the Wi-Fi and LTE communities were looking for creative ways to incorporate one more contribution that might get more parties on board. “It was that engagement and that commitment to the very end that really allowed us to accomplish this goal,” he said.

The final test plan isn’t perfect, but it will provide assurances that Wi-Fi’s critical role around the world will be maintained. It covers a diverse set of scenarios, including indoor and mixed indoor networks overlapping with outdoor, Robinson said.

Despite the Wi-Fi and LTE industries' ability to come together, however, there's still divisiveness that lives on between the two, which was clear during the panel's discussion.

When trying to define what is fair coexistence, “we looked to Wi-Fi first, and there is no coexistence test for Wi-Fi,” Welsh said. Right now, under the Wi-Fi Alliance test plan, LTE-U will protect Wi-Fi 100 times more sensitively than Wi-Fi will protect LTE-U or any other technology. “I think it’s important going forward to make sure that those standards are improved, that we have a race to the top, rather than a race to the bottom.”

Szymanski said there’s already a widespread Wi-Fi ecosystem in 5 GHz, and there hasn’t been a need to look at coexistence with other devices until now. Wi-Fi ensures fair coexistence in two ways: Energy detection, which is just raw energy, and understanding the waveform of other Wi-Fi devices.

“This isn’t a secret,” said Szymanski, it’s embedded in billions of devices around the world. LTE designers understood this: It’s pretty cheap to implement, but they chose not to incorporate a method of mutual detection at lower levels, he added.

“I think this is a little bit of a race to the bottom, because you’re going to have interference now below minus 72 [dBm],” whereas you wouldn’t have had interference if they had injected or put in a Wi-Fi preamble or other form of mutual recognition technology at minus 82, Szymanski said. "So we’re going to now have collisions and no way to traffic manage” at these lower level signals when you could do it in the past.

Feld said it’s not fair to say there hasn’t been work on the coexistence problem – on both sides. “The fact is you’re each doing things that are so different” from each other. The next stage of coexistence is going to necessitate that each industry develops a better understanding of the nature of the unwritten rules, which each of the industries has developed internally for trying to resolve some of these problems and figuring out where they overlap and intersect.

For more:
- see the webcast

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