Cellular and Wi-Fi clash in air war: Page 2 of 4

August 11, 2016 // By Rick Merritt
 Cellular and Wi-Fi clash in air war
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.

Qualcomm’s Brenner says the -82 dBm test in the current draft suite is already too rigorous. Wi-Fi itself – along with Bluetooth and Zigbee – only back off at levels of -62 dBm, he notes. A related spec called License Assisted Access (LAA), already ratified by the 3GPP which sets cellular standards, compromised on a -72 dBm level and a listen-before talk approach to co-existence.

All sides agree that LTE-U should be as fair in sharing spectrum as existing Wi-Fi access points. However the two camps are divided over how to measure that sharing in today’s Wi-Fi products, with Qualcomm claiming the WFA test sets an unrealistically high bar.

Qualcomm claims the WFA plans to create future tests for LAA that could put new restrictions on the already finished 3GPP standard. In addition, the draft test already “tries to dictate [LTE-U] device features that have nothing to do with spectrum sharing,” said Brenner.

At last week’s meeting, a representative of CableLabs pressed the WFA to finalize the LTE-U tests based on its draft first released in April. At this point, only WFA technical staff should make any further changes in the tests based on results from the plugfest, wrote Jennifer Andreoli-Fang, a distinguished technologist at CableLabs, the R&D arm of major U.S. cable-TV carriers.

Andreoli-Fang noted that LTE-U backers want to remove several elements of the draft test. They include ones covering multi-channel LTE-U, the presence of more than one LTE-U base station and checks to ensure users can choose a Wi-Fi connection in the presence of LTE-U, she wrote in a presentation. In addition she defended use of the -82 dBm test level as “anchored to real-world network data and the minimum level of fairness of Wi-Fi in the 802 standard.”

Several WFA staff presentations last week made it clear the standards body is pressing forward with the current draft amid the ongoing debate. Contentious issues like the choice of the -82 dBm test level are now fixed, said Kevin Robinson, vice president of marketing for the WFA.

“There’s no doubt everyone has had to compromise in an effort to move the work along and deliver a successful coexistence test plan,” said Robinson. “Stakeholders have strong, passionate views on where the test plan lands,” he said.

The WFA expects its co-existence test plan will serve as basis for equipment vendors to determine whether their gear is fair in sharing 5 GHz spectrum, he said. The FCC is encouraging the industry to address concerns around coexistence and do it in Wi-Fi Alliance, he added.

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