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Industry lashes out at Ericsson over LTE-U coexistence claims

Ericsson is getting it in the neck following the publishing of its recent FCC document that paints a rosy picture of the interoperability of LTE-U and WiFi. A group of 7 challengers is accusing Ericsson of misleading the FCC and then industry, and undermining a fundamental test process.

LTE-U is proving to be quite the point of contention between stakeholders in the LTE and WiFi camps. Essentially, the technology would allow LTE to use the same unlicensed spectrum as WiFi, boosting the network capacity of MNOs while coexisting harmoniously with WiFi – according to the likes of Ericsson.

However, for those in the WiFi camp, LTE-U poses an immense risk to WiFi – already semi-infamous for its shakiness in dense deployments. WiFi’s proponents claim that LTE-U is going to be severely disruptive for WiFi – and that Ericsson is misleading the market.

Earlier this month, Ericsson released the results of its WiFi and LTE-U coexistence tests via the FCC, declaring that all was well with the world. However, Broadcom, Boingo, Cypress, HPE (Ruckus), Microsoft, and the NCTA have disputed Ericsson’s findings – calling them anything but scientific, and saying that Ericsson’s tests do not adhere to the WiFi Alliance’s (WFA) methodology as closely as Ericsson says they do.

“While one can certainly detect echoes of ideas from WFA in the Ericsson submission, there is little that is recognizable and much that is completely novel. There are several test cases included that do not appear anywhere in the WFA test plan, and cannot serve as substitutes for the important procedures that Ericsson omitted.”

The joint retort goes on to add that “it is clear that this proprietary internal test changed or failed to include several of the most important features of the WFA test plan, rendering its testing unreliable as a decision-making tool for the FCC. The Ericsson test is therefore very different from the tests prescribed by the WFA test plan.”

That’s a pretty damning challenge, and shows that the six challengers do not want the FCC to blindly adhere to Ericsson’s findings when passing regulations regarding the use of LTE-U. The group asks the FCC to only consider test reports from parties that fully conform with the WFA plans, and that:

“The FCC should reject efforts of a company to alter or omit material elements of the test to suit its own purposes, short-circuiting the WFA process. But that is exactly what Ericsson is attempting to do.”

The document goes on to say that Ericsson omitted test results that the WFA process requires to be submitted, and in doing so makes it impossible for people to evaluate its claims. The group allege, based on what Ericsson did publish, it is clear that this proprietary internal test changed or failed to include several of the most important features of the WFA test plan, “rendering its testing unreliable as a decision-making tool for the FCC. The Ericsson test is therefore very different from the tests prescribed by the WFA test plan.”

A core part of the WFA test plan is the use of a -82dBm WiFi signal, which the WFA says is a typical strength for a WiFi signal. The group say that Ericsson didn’t disclose what signal strengths it tested at, and that it could have completely ignored the typical -82dBm level.

In addition, Ericsson is alleged to have not tested the impact of LTE-U on latency-sensitive applications, such as OTT streaming, and did not include any results that measure the impact on delay, jitter and packet loss caused by LTE-U. Given that so much of total WiFi traffic is streamed media, if LTE-U causes dropped frames and buffering, it can hardly be said to be coexisting – and Ericsson appears to have omitted proof of this.

In conclusion, the letter states that “if Ericsson intends for its report to serve as a replacement for thorough testing under the complete WFA test plan, then it represents an unfortunate effort to bypass the WFA process, even as LTE-U and WiFi stakeholders continue their hard work to finalize the WFA test plan. This would mark a disappointing return to the unilateral, unverifiable, and fundamentally unreliable testing that the WFA test process was designed to avoid. The fact that Ericsson itself has been an active participant in the WFA test development process only makes this more concerning. Ericsson is now threatening to undermine a year of work.”

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