Both the pro-LTE-U side of the debate, backed largely by Qualcomm, and the anti-LTE-U side, made up of a host of different tech companies under the aegis of the Wi-Fi Alliance, say that testing has vindicated their respective positions.
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Qualcomm says that its testing was performed according to guidelines from CableLabs, an industry research group that has published several studies suggesting that LTE-U (threatens existing Wi-Fi networks. Broadly, the company’s findings were that LTE-U plays nicer with Wi-Fi than Wi-Fi does with itself – throughput and latency over a Wi-Fi connection were better when an LTE-U unit was nearby than they were with a second Wi-Fi router.
CableLabs’ own tests, however, found that precisely the opposite was true. An LTE-U station, even when ceding 50% of its transmission time to Wi-Fi, decreased throughput by more than half, thanks to LTE-U’s habit of interrupting Wi-Fi transmissions in progress. Where Wi-Fi uses a listen-before-talk protocol to ensure that the channel is clear before broadcasting, LTE-U simply schedules pauses during operation, a practice called duty cycling.
The cause of the discrepancy is unclear – both Qualcomm and CableLabs performed their tests independently, and tech companies carefully structuring such testing to produce favorable results isn’t exactly unheard of. Qualcomm says that it adhered to test case guidelines provided by CableLabs, while that company insists that its testing was done in accordance with the latest available LTE-U Forum specification for coexistence. Yet the results are largely the same as earlier studies performed by both sides.
Wireless analyst and Network World contributor Craig Mathias said that, without much more complete details of the testing process – including specific device makes and models, the physical geometry of the test setup, and so on – it’s “impossible to tell” whether either side’s numbers are valid.
Even so, he added that there’s a developing consensus that LTE-U does, indeed, pose a threat to Wi-Fi networks.
“The IEEE, I think, is so far the arbiter here, and they believe that LTE-U will decimate Wi-Fi, both technologies as they are today,” Mathias told Network World. “Coexistence standards and best practices are a start, no matter how they are developed … but without the carefully-documented testing of specific products (which may or may not adhere to a recommended practice), it's impossible to tell what's real and what's not.”
Despite a summit meeting held last week to hash out testing criteria, the fact that both sides managed to come up with the same old results could be a warning sign that a solution to the coexistence issue is still some distance away. Given that some U.S. carriers are moving to deploy LTE-U in mere months, the problem could well wind up in the hands of government regulators if tech companies can’t solve it themselves. FCC chairman Tom Wheeler, speaking at a wireless industry convention this summer, indicated that his agency could step in to protect Wi-Fi users if a solution isn’t found.