Satellite, Wi-Fi Clash Over Globalstar Claims of 5.1 GHz Band Interference

Satellite and terrestrial interests are lining up on opposite sides over whether increasing interference Globalstar says it's seeing in the 5.1 GHz band is attributable to sharing that band with outdoor Unlicensed National Information Infrastructure operations. That the FCC will act on Globalstar's call for a notice of inquiry on mobile satellite service sharing with U-NII (see 1805220006) has doubters. Michael Calabrese, director of the Wireless Future Program at New America, told us the FCC isn't likely to reopen the 2014 sharing rules governing the band without more direct evidence of harmful interference.

Globalstar is raising valid issues in its petition, but that it hasn't shown it's yet experiencing harmful interference somewhat offsets its arguments, Dynamic Spectrum Alliance President Kalpak Gude told us. He said it can't be assumed the increase in noise floor the company has seen since 2014 will continue at the same pace, if at all, given changing Wi-Fi technologies. And he said it's not clear yet if that interference growth will plateau.

General Counsel Barbee Ponder emailed that Globalstar "has presented compelling evidence that the noise level within the 5.1 GHz band is increasing to unacceptable levels." He said there's "no substance to the few comments in opposition" and it plans to submit "a comprehensive reply" later this month.

With the FCC increasingly considering letting widely deployed terrestrial devices use satellite uplink spectrum, it should "investigate and remedy" any harmful interference to Globalstar, the Satellite Industry Association recommended in RM-11808 posted Monday. Such an investigation and remedy could have ramifications for other proceedings, SIA said.

Actually assessing spectrum sharing based on real-world outcomes "would be beneficial," the National Public Safety Telecommunications Council filed in support of Globalstar. It said the noise floor increase that company describes is "an opportunity" to assess that sharing provisions governing the 5 GHz band are enough.

The problems Globalstar is having in the U-NII-1 band point to potential problems satellite digital audio radio service could see if unlicensed activities are allowed in the 7025-7075 MHz band, SiriusXM said. It said the Globalstar petition reinforces the idea the FCC needs to evaluate interference predictions from backers of new unlicensed devices "with extreme skepticism" and that agency monitoring and control of unlicensed device proliferation is "simply inadequate."

Critics challenge whether Globalstar has met the burden of showing it's suffering problems or that those are due to unlicensed operations in the band. There's no evidence the rules governing U-NII-1 band have any relationship to the RF issues Globalstar "has allegedly observed," said Wi-Fi Alliance. It said any proceeding based on the Globalstar petition would only hamper further investment in the band and undermine the U.S. position at the ITU backing a sharing of that band between MSS and radio local area networks under the U.S. regulatory framework.

NCTA called Globalstar's petition "premature" since the company isn't currently experiencing harmful interference from unlicensed devices and is unlikely to in the future. It said Globalstar's relatively few duplex service subscribers globally mean claims about future harmful interference are dubious. The association said Globalstar's noise floor measurement methodology and system impact analysis are flawed and make it impossible to say measured noise is due to U.S. Wi-Fi operations or other causes such as operations in adjacent spectrum or transmissions from other countries.

Globalstar's proof is "thin gruel" given its measurements aren't fine enough to say what noise floor rise has been, if any, and if that new level is more than the 1 dB rise expected when the 2014 rules were adopted, Cisco said. It called Globalstar's data "associational at best."

Also critical of Globalstar methodology, the Wireless ISP Association said if the FCC goes ahead with an NOI, it should exclude fixed wireless ISPs due to Globalstar's acknowledgement that's not a source of alleged interference. WISPA said Globalstar's petition leaves unanswered big questions like how it's sure the measured signals originate from the 5.1 GHz band and what accounts for the big variations in signal levels detected by different satellites.

No, the sharp rise in noise level "clearly seems to be caused" by Wi-Fi access points and other outdoor, high power U-NII-1 devices, Space & Satellite Professionals International said. Globalstar service users and resellers also filed with worries about the noise level rise. Geos Response, operator of the International Emergency Response Coordination Center, said it was "gravely concerned" and that since the noise rise is apparently over North America, it's likely that the cause is the 2014 order.