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Wi-Fi Alliance publishes LTE/WiFi coexistence test plan

Would-be LTE-U carriers told to take these tests, or just leave off

By Richard Chirgwin, 22 Sep 2016

The Wi-Fi Alliance's long-awaited – and controversial – LTE-U Coexistence Test plan has landed.

The reg-walled test plan is supposed to help work out if LTE-U – the mobile carriers' plan to use unlicensed spectrum if nobody else is talking – can coexist with Wi-Fi.

Carriers, already under a spectrum squeeze, are hoping they can pitch their tents on Wi-Fi's campground, promising that LTE-U won't disrupt Wi-Fi. will play nice if there are Wi-Fi users around.

Negotiations between the groups and America's Federal Communications Commission have been tense, and at one point, Qualcomm complained its input to the test plan had been ignored.

In particular, Qualcomm had complained that the proposal to use -82 dBm as the threshold LTE-U would treat as “vacant” was too loose, and would leave a lot of Wi-Fi users out in the cold. That, however, is the lowest test threshold in the test plan.

Qualcomm is already conducting LTE-U field trials with T-Mobile, and early this week it asked the FCC for a 12-month extension to the authorisation it first received in May of this year.

Reading between the lines of the Wi-Fi Alliance's love-in-media-release, The Register gets the impression the arguments remained unresolved. The document says "Early agreement on foundational principles, such as a commitment to maintaining the typical connectivity experience for Wi-Fi users and a clear definition of fairness, allowed completion of the work on an aggressive timeline and guided development of test plan specifics."

"These same, shared principles augmented by robust technical data were instrumental in finalizing aspects of the test plan where consensus was unachievable. Coming to an industry-agreed solution required compromises from all sides. Therefore, the test plan is designed to be used as an unedited whole. Alternate test approaches, such as selectively omitting or modifying portions of the test plan would not have been acceptable in this cross-industry effort since those tactics will not provide assurances of fair coexistence."

Which sounds a lot like "take it or leave it", a sentiment re-enforced with the further pronouncement that "“the test plan is designed to be used as an unedited whole” and an accompanying warning against carriers cherry-picking the document in their tests.

The test plan itself is a 51-page thicket of densely technical procedures. If you can find something of interest in it, let us know. ®

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