Satellite Spectrum Sharing Changes Have Supporters and Detractors
SpaceX’s push for loosening up the spectrum-sharing rules between geostationary and non-geostationary orbit (GSO and NGSO) satellites in some bands is facing both opposition and support from satellite and terrestrial corners. Comments were due Monday in docket 25-157. Commissioners unanimously adopted the spectrum-sharing NPRM at their April meeting (see 2504280038). It resulted from a 2024 SpaceX petition urging changes to the GSO/NGSO sharing methodology for NGSO fixed satellite service (FSS) downlinks (see 2408120018). The company championed similar changes at the 2023 World Radiocommunication Conference.
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Changes to the GSO/NGSO sharing rules' equivalent power flux density (EPFD) limits would immediately deliver two to four times more system capacity for existing NGSO systems, SpaceX said, which would grow to six to eight times more capacity as satellites designed to leverage the changes are deployed in coming years. None of that would significantly affect GSO systems, the company added, noting that the greater capacity means such systems can support more customers.
Amazon’s Kuiper submitted a study showing that new GSO/NGSO interference limits in the Ka band would let an operator boost by 27% the number of satellites that could serve a location, while the amount of capacity available to an area would increase by 700%. A GSO operator under those interference limits would see less than a 3% reduction in throughput and essentially no increase in unavailability, it added.
“Some updates may be workable” if existing GSO systems are protected, EchoStar said. The company could potentially back forgoing a specific EPFD limit -- which it called a “considerable sacrifice on the part of GSOs” -- in the name of greater spectrum efficiency, as long as that comes with greater regulatory parity among all services sharing the Ku and Ka bands, including GSO, NGSO and terrestrial services.
The existing EPFD limits “are ripe for revisiting,” said Telesat. It urged the FCC to adopt a methodology that could be embraced by other countries and thus harmonized internationally.
The Information Technology and Innovation Foundation said the EPFD limits are restrictive to the point of producing "absurd results." Replacing those limits with the degraded throughput methodology used for NGSO/NGSO spectrum sharing and for NGSO/GSO sharing in the V band would make the shared spectrum more productive than it is under today's EPFD regime, the group said.
Also arguing that the GSO/NGSO sharing framework is outdated were Public Knowledge and New America’s Open Technology Institute, the Software & Information Industry Association, TechNet and Commercial Space Federation.
Criticism
Defending the current EPFD regime, Viasat said advocates for axing the limits have wrongly argued that they're a huge regulatory constraint. Actually, NGSO operators “have been and are able to provide meaningful service within the existing EPFD framework.” Dropping or weakening the EPFD regime would let some big NGSO operators shift costs onto GSO and smaller NGSO operators, Viasat said.
Coexistence with incumbent services requires the use of power limits on NGSO FSS systems as a way of protecting GSO systems and terrestrial services, AT&T said.
Eutelsat, OneWeb, Hispasat and Ovzon said claims that NGSO operators are overly constrained by EPFD limits are overblown. Such claims also trivialize the interference risks that GSO networks face if EPFD limits change, they added.
Given the international nature of satellite operations, any FCC changes “should follow -- not precede -- the related ITU studies,” SES said. The EPFD alternatives proposed in the NPRM “do not deliver a clear, predictable interference environment.” But the FCC could explore adjusting Ka-band EPFD limits “without appreciable impact to existing and future GSO operations,” the company said.
Astranis Space Technologies warned that a GSO avoidance angle alone isn’t adequate protection for GSO systems. The FCC should allow co-primary GSO access to NGSO primary bands as a means of fully modernizing NGSO/GSO sharing, it added.
While DirecTV also championed the existing spectrum-sharing rules, including the EPFD status quo, as a way of protecting GSOs from interference, it said changes to the GSO/NGSO sharing framework would need to address aggregate interference from NGSO systems. There would also need to be a transition period for any framework changes, it said.
As the FCC considers GSO/NGSO spectrum sharing in the 10.7-12.7 GHz, 17.3-18.6 GHz and 19.7-20.2 GHz bands, it should make clear it’s not looking at changes to protection limits in the 3.7-4.2 GHz band, CTIA said. That would protect ongoing terrestrial wireless network deployments in the band, it noted.
Pointing to the numerous fixed links in service in the 11 and 18 GHz bands today, Comsearch said studies of alternatives to the current EPFD limits must show there would be no system reliability degradation to those terrestrial systems.
Any change in the EPFD framework will mean more NGSO satellites in the sky, resulting in additional RF interference for ground-based radio astronomy, according to the National Academy of Sciences' Committee on Radio Frequencies. It said the FCC should look at requiring enhanced coordination between NGSO operators and affected radio observatories. Power limits in the radio astronomy bands should refer to aggregate emissions, as those are what affect radio astronomy observations, the committee added.