CableLabs' Warnings of LTE-U/Wi-Fi Interference Off Base, Qualcomm Says
Qualcomm has "a mountain of test results" to prove that LTE-U's carrier-sensing adaptive transmission coexistence (CSAT) mechanism ensures no adverse interference with Wi-Fi, said Dean Brenner, senior vice president-government affairs. His statement responded to a CableLabs blog post Tuesday in…
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which it advocated for LTE-U to have a "listen before talk" (LBT) protocol (see 1509230078). While LBT is required in the 5 GHz band in Europe and Japan, elsewhere around the world "different technologies use different coexistence techniques in unlicensed spectrum," Brenner said. The maximum continuous transmission time for an LTE-U small cell, as spelled out in the LTE-U Forum specification, is 50 milliseconds, and the small cell will periodically rescan the spectrum looking for vacant or less-trafficked channels to transit on, he said. Meanwhile, he said, Wi-Fi access points "often do not share spectrum fairly with one another even though they use LBT for coexistence." Ultimately, Brenner said, "the real issue isn’t about LBT or CSAT [but] whether equipment will share the unlicensed spectrum fairly. And, the answer is clear from our testing: we have proven that LTE-U does share spectrum fairly and will not harm Wi-Fi. In addition, LTE-U Forum has defined a comprehensive and stringent Coexistence Spec to ensure all LTE-U equipment will coexist fairly with neighboring Wi-Fi or LTE-U nodes."