Globalstar Warns of Growing MSS Interference in 5.1 GHz Band
Globalstar, which unsuccessfully fought against allowing outdoor Unlicensed National Information Infrastructure (U-NII) devices to operate in the 5.1 GHz band, said it has evidence of growing degradation to its mobile satellite service (MSS) offerings. But spectrum and satellite experts said it isn't clear whether the FCC will take up the company's petition regarding whether the band can continue to allow sharing between MSS and outdoor U-NII operations.
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The FCC opened up the 5.1 GHz band for Wi-Fi and other unlicensed use in 2014 (see 1404010035), and two-plus years of U-NII access point deployments have led to a 2 dB increase in the 5.1 GHz noise floor since the FCC decision, Globalstar said in its petition Tuesday, saying it will continue to face "severe harmful interference" if the U-NII-1 band sharing regime isn't addressed. It said a notice of inquiry would allow for comment on interference and coexistence issues, but it has the right to petition for immediate regulatory relief if the noise rise leads to a "severe" detrimental effect. The agency didn't comment.
"It's a core tenet that FCC-licensed spectrum users, like Globalstar, are protected from unlicensed users, so the FCC is likely to carefully consider technical evidence and investigate Globalstar’s allegations diligently," emailed Andrew D'Uva, president of satellite consultancy Providence Access. Rising noise floor by itself isn't an issue, but a claim of harmful interference now or that the floor will continue to rise and Globalstar will see harmful interference is more serious, emailed Kalpak Gude, Dynamic Spectrum Alliance president.
Satellite Industry Association President Tom Stroup said that spectrum sharing increasingly becoming the norm increases the likelihood for interference and complaints about interference. That the 2014 order also included a route for Globalstar asking for a re-examination should give the company some optimism the agency will act on the petition, Stroup said.
A satellite lawyer questioned whether the FCC would take up the petition, noting the resources an NOI would take up for little perceived value since Globalstar isn't asking for anything. A spectrum expert said asking for an NOI seems to indicate Globalstar doesn't have a strong enough position or case to ask for immediate action and the company could be more worried about a future problem than a current one. The expert said the FCC, if it decides Globalstar is seeing serious interference, has options, such as imposing power levels and antenna directionality, though how realistic any of the fixes might be isn't clear and fixes become more problematic as time goes on. A satellite executive said it's possible other 5.1 GHz users, like cable, will oppose the petition, though it's harder to oppose an NOI than a regulatory fix.
Four years since the FCC order isn't a lot of time, meaning agency action reversing its opening up the 5.1 GHz band isn't inconceivable, a satellite industry consultant said. A longer span, like 10 years, might be having crossed the Rubicon of infrastructure deployment and commercial rollout, the consultant said. The consultant also said such interference issues could become more commonplace as an unintended consequence of trends toward more connectivity such as 5G, where there aren't good predictions of the effects of numerous small cellsites.
Globalstar said it measures the noise level in its feeder uplinks monthly by briefly turning off communications traffic through its North American gateway earth stations. It said between May 2014 and November 2017, it saw no increase in noise level, but that by April, six of the eight Globalstar satellites used for the measuring were seeing a 2 dB noise rise, with the other two measuring a 1 dB noise rise. It said measurements taken over Europe, Australia and the oceans haven't shown a noise rise in the 5096-5250 MHz band. It included a Roberson & Associates report citing deployment of outdoor U-NII-1 access points through the U.S. as the reason for the aggregate emissions increase.
The noise rise is degrading the received signals for Globalstar handsets, diminishing subscriber capacity, draining satellite power and making gaps in MSS signal coverage, the company said. It said Roberson projections are that the U.S. noise floor by 2022 will be up between 4.7 dB and 8.2 dB, and that CDMA downlink capacity could be reduced up to 35 percent. The company said Roberson estimates are that the satellite firm by 2022 could lose area totaling 365,000 square kilometers where it no longer could provide MSS service.
Globalstar brought similar concerns to the attention of the ITU last fall. In a submission to the radiocommunication study groups on agenda item 1.16 for 2019's World Radiocommunication Conference, Globalstar said its satellites have seen a 1 dB noise rise in the 5096-52550 MHz band that it believes was due to aggregated interference of outdoor radio local area network access points deployed in the 5170-5250 MHz band. That increase "is significantly greater" than what's allowed under ITU-R recommendations and it seems likely the number of RLAN deployments around the U.S. are a lot more than the 250,000 outdoor access points the cable industry projected in 2014, Globalstar said.