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Wi-Fi Alliance works on LTE-U testing regime

Some consensus is developing around Wi-Fi coexistence with LTE over unlicensed spectrum and a test regime for ensuring the two technologies interact fairly is in the works, according to Wi-Fi Alliance. The group has taken the lead as the primary forum for industry to hash out skepticism and concerns over how well the LTE-U Forum’s LTE-U specifications will work when deployed with Wi-Fi nearby.

Kevin Robinson, VP of marketing for Wi-Fi Alliance, said an initial, recent LTE-U workshop brought together around 100 participants from 54 different companies and delivered consensus in several areas: that more detail was needed in the LTE-U specification; coexistence testing needed to look at a broader set of scenarios than has been studied to date; and a “consensus and commitment,” Robinson said, to develop a test regime within the Wi-Fi Alliance.

“It’s a difficult problem, don’t get me wrong,” Robinson said. “There’s still a lot of work to be done, particularly technical work around coexistence.”

Robinson said the LTE-U testing regime would seek to provide a basis on which to judge whether LTE-U devices share spectrum fairly with Wi-Fi. “Fairly” has been a bit of a hot-button word in the debate over LTE-U/Wi-Fi coexistence.

“By ‘fairly’, what we mean is that if you have a Wi-Fi network that is in operation and you introduce an LTE-U device, that the impact of that device on the Wi-Fi network and Wi-Fi devices is no worse than the impact of bringing a Wi-Fi network into that same environment,” Robinson said.

That concept has been at the root of industry sparring over LTE-U, with proponents such as Qualcomm pointing to testing that shows LTE-U can actually slightly improve Wi-Fi performance – while other testing has indicated significant degradation of Wi-Fi performance in the presence of LTE-U. LTE-U relies on Qualcomm’s carrier adaptive sensing technology, as well as duty cycling, in order to avoid interference with Wi-Fi. This is in contrast to the LAA version of LTE-U, which implements a listen-before-talk mechanism. Robinson said that Wi-Fi Alliance’s work will not determine what mechanisms might need to be added to LTE-U to ensure fair sharing – the testing will simply focus on whether the technology does share fairly.

“That’s up to the developers of LTE-U,” Robinson added.

The complexity of testing scenarios thus far has certainly been an issue. Robinson described the testing of LTE-U to date as “studies” in very controlled environments, done by very skilled testing experts, with limited numbers of scenarios or devices being examined.

“It doesn’t paint a full picture, and they’re limited to very basic scenarios – not at all what real-world deployments look like,” Robinson said. He added that the LTE-U test regime is expected to have three sections: one that covers basic scenarios; one that looks at issues at very low energy detect thresholds when LTE-U may not recognize that Wi-Fi is active, particularly if a device is at a distance; and complex scenarios that could encompass testing of multiple Wi-Fi and LTE-U networks to judge whether fair sharing is maintained.

The next workshop on LTE-U is scheduled for Feb. 10.

Wi-Fi Alliance recently commissioned a survey through Harris Group that confirmed the importance of Wi-Fi to consumers – but also noted most of them have little awareness of the impending technology addition of LTE over unlicensed.

Almost 75% of Americans said that always having Wi-Fi access is important in their daily lives, and they reported having, on average, four devices Wi-Fi enabled. But less than one-quarter of Americas surveyed has heard of LTE-U and even fewer were familiar with the term LAA or license-assisted access, the version of LTE-U which is being standardized for LTE Release 13. However, according to Wi-Fi Alliance, “three-quarters of Americans would be concerned about a technology that could jeopardize their access to free Wi-Fi availability. Moving forward, more than half of Americans say they are interested in the issue as it unfolds.”

ABOUT AUTHOR

Kelly Hill
Kelly Hill
Kelly reports on network test and measurement, as well as the use of big data and analytics. She first covered the wireless industry for RCR Wireless News in 2005, focusing on carriers and mobile virtual network operators, then took a few years’ hiatus and returned to RCR Wireless News to write about heterogeneous networks and network infrastructure. Kelly is an Ohio native with a masters degree in journalism from the University of California, Berkeley, where she focused on science writing and multimedia. She has written for the San Francisco Chronicle, The Oregonian and The Canton Repository. Follow her on Twitter: @khillrcr