Cellular and Wi-Fi clash in air war

August 11, 2016 //By Rick Merritt
The tug-of-war between cellular and Wi-Fi over unlicensed spectrum is close to a breaking point at the Wi-Fi Alliance (WFA). Qualcomm claims the LTE-U co-existence tests the group is about to ratify are unfair and could restrict or even prevent from coming to market products using the 4G protocol for 5 GHz spectrum.

The battle pits Wi-Fi vendors such as Broadcom and cable-TV carriers against Qualcomm, cellular carriers and their equipment suppliers. It foreshadows bigger battles ahead as engineers hammer out standards for 5G cellular, expected to span licensed and unlicensed frequency bands from below 900 MHz to above 60 GHz.

The stakes are high. Last year, the Wi-Fi Alliance submitted a request to the Federal Communications Commission (FCC), suggesting it withhold certification of any LTE-U equipment until the Alliance had coexistence tests in place. Ericsson, T-Mobile, Verizon, Qualcomm and others sent a rebuttal letter warning of “far-reaching, negative consequences” should the FCC delay LTE-U network deployments.

The WFA currently plans to issue on September 21 a version 1.0 of its LTE-U test plan, a suite it has been working on for more than a year. The group is ironing out final details in meetings this week with plans to issue a beta version of the test August 11 and conduct a plugfest starting August 22. A final workshop on the issue is tentatively slated for September 7.

“If they stick with the plan they have now that is so biased and lacking technical merit they are risking their credibility,” said Dean Brenner, senior vice president of government affairs at Qualcomm who has attended the meetings.


The WFA retained testing agencies Cetecom and AT4 who will run LTE-U plugfests in labs like this one. Image courtesy of Cetecom).

In presentations released online by the WFA, his opponents are equally vociferous. “LTE-U technology (CSAT) can ever effectively coexist with Wi-Fi in real deployments,” wrote Thomas Derham of Broadcom in a presentation last week made public on the WFA site.

Derham argues in part that LTE-U acts as a master of 5 GHz channel access, treating Wi-Fi contenders as slaves, unlike Wi-Fi links that negotiate for spectrum as peers. The draft WFA tests are not stringent enough, he wrote, suggesting they should include tests for more scenarios at signal sensitivity as low as -89 dBm.

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