Qualcomm, CableLabs reach opposing conclusions after LTE-U tests

Qualcomm Technologies (NASDAQ:QCOM) said new tests in collaboration with CableLabs confirm LTE-U and Wi-Fi can coexist fairly, but CableLabs' engineers said their own tests show otherwise.

It's the latest collision in the debate over whether LTE-U can share unlicensed spectrum fairly with existing users like Wi-Fi. The Wi-Fi Alliance held a workshop in Palo Alto, Calif., last week which brought together more than 100 attendees from 54 companies, including AT&T (NYSE: T), Dell, Google (NASDAQ: GOOG), LG, Microsoft (NASDAQ: MSFT), Sony, Toyota, Verizon (NYSE: VZ) and ZTE to talk about concerns related to Wi-Fi and LTE-U coexistence. But the most recent clash indicates that the LTE-U proponents and Wi-Fi communities remain far apart.

In a blog post this week, CableLabs Vice President of Technology Rob Alderfer said CableLabs recently concluded a brief technical engagement at Qualcomm's campus in San Diego. "Unfortunately, our main conclusion from the three weeks we spent on site at Qualcomm is that there is no basis for definitive technical statements about LTE-U coexistence," he said. "The reason for this is surprisingly simple: LTE-U is in a prototype phase of development and does not possess the features that its proponents have noted are important to coexistence."

For its part, Qualcomm said it followed the guidance CableLabs provided in terms of what scenarios to test, the density of nodes, the types and location of test devices, and what Wi-Fi equipment vendors to include. Since Wi-Fi equipment performance varies across brands and models -- as each is designed for different types of customers and environment -- the principles of coexistence tests focused on the impact of the LTE-U equipment. "The results show excellent coexistence performance for the studied test cases. The performance of Wi-Fi in the presence of LTE-U was comparable to if not better than the examined Wi-Fi to Wi-Fi baseline scenario, demonstrating the effectiveness of LTE-U coexistence protocols," wrote Dean Brenner, SVP, government affairs at Qualcomm, and John Kuzin, senior director of regulatory at Qualcomm, in a blog post.

As members of both the Wi-Fi and LTE communities, Qualcomm said it is constantly collaborating and working very closely with all key stakeholders to ensure that LTE-U and Wi-Fi will coexist very well. "Along with other members of the LTE-U Forum, we are working together to address technical concerns and answer technical questions in great detail," the Qualcomm executives wrote. "We are cooperating openly with Wi-Fi industry and will support the test development effort jointly with Wi-Fi Alliance, who agrees with us on focusing on LTE-U behavior as much as possible rather than Wi-Fi performance."

The cable industry has been particularly skeptical of the so-called advantages that LTE-U can bring in unlicensed spectrum, and it has repeatedly pointed out the closed nature of how it was developed in the LTE-U Forum. CableLabs said the tests at Qualcomm's facilities raised more questions than answers and it continues to press for an open standards process like that being pursued wtih LAA. 

The Wi-Fi Alliance is also looking for further collaboration. "One of the major industry concerns has been the degree of ambiguity in defining how LTE-U devices will operate, and more specifically, how this could impact fair unlicensed spectrum sharing with Wi-Fi," Edgar Figueroa, president and CEO of the Wi-Fi Alliance, said in a statement. "A number of updates to the LTE-U specification were presented at the workshop, which we believe to be a good step toward addressing some of these concerns. We reached consensus on a number of points, including agreement that more specificity would improve the LTE-U specification and a broader set of test scenarios will be necessary to ensure fairness. There is also broad interest in collaborating on the work to establish the testing that will be required."

For more:
- see this Network World article
- see this Qualcomm blog
- see this CableLabs post and this post

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Wi-Fi Alliance pushes ahead on coexistence guidelines for LTE-U
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