NGSO Spectrum-Splitting Mechanism Getting Support, Criticism

TechFreedom questioned the FNPRM being an NPRM, saying it "has all the hallmarks" of a notice of inquiry, "not an FNPRM." The FNPRM asks dozens of questions but proposes no draft rules, TechFreedom said. It said the FCC's "gym membership model" for satellite spectrum sharing -- with sharing rules that invite as many users as possible, then the agency hoping most of the proposed NGSO systems never get deployed -- "can't work over the long term" due to the increased ease of putting up satellites. Before focusing on issues like degraded throughput analysis, the agency should focus on gating issues such as how many NGSOs a given frequency band can support and if sharing rules encourage efficient spectrum use, it said.

Backing use of a degraded throughput metric, Intelsat said the record needs more development on two issues for that methodology -- what spectral efficiency degradation value to use and what absolute value to use for short-term unavailability increases. Any throughput degradation baselines should include existing sources of interference, including from geostationary orbit satellites, it said. Intelsat said an aggregate interference cap is unnecessary, and the FCC shouldn't extend protections to early round systems beyond the sunset period.

Any spectrum sharing framework should measure short-term interference between NGSO operators using an absolute change in link availability, said SpaceX, calling a relative change yardstick "potentially misleading." It said assessment of harmful interference risk should be based on an earlier-round system's next deployment milestone and actual operational parameters. Saying sunset of interference protections could chill investment in satellite networks, it said the agency should look at options for ensuring post-sunset transitions lead to "seamless and efficient co-frequency operation between NGSO systems in different processing rounds." Those options include ensuring systems with milestones after the sunset date don't delay their operations until after the sunset to avoid coordination, it said.

Spectrum sharing rules the FCC adopts should define the maximum level of interference that “victim” systems should tolerate from all other NGSO systems, Viasat said. Standards should ensure operators that choose to design their NGSO systems in ways that make them more susceptible to interference can't limit other operators' access to spectrum, it said. The agency's default band-splitting rewards inefficient system designs, and the sunsetting of interference protections exacerbates that problem of inequitable access, it said, pushing for the agency to look instead to other mechanisms instead.

The FCC needs to put a more emphasis on coordination, with rules on inter-processing round spectrum sharing needing to make clear the need to coordinate first and that such coordination includes information sharing, said OneWeb. There should be a definition of aggregate interference criteria before establishing any degraded throughput methodology, it said.

Consider a performance degradation analysis only to justify a later-round system’s compatibility with existing operations if coordination efforts haven't worked, O3b said. Instead of an across-the-board limit on increased interference, the agency should let operators specify protection criteria needed to maintain link usability and avoid synchronization loss, it said. Once a later-round system successfully shows compatibility with an earlier-round system, the interference mitigations used for that showing should be part of the FCC's authorization until coordination between the constellations is done, it said. An aggregate interference cap on new systems "would thwart innovation and competition now to address a problem that would materialize -- if ever -- years in the future," said Amazon's Kuiper. Backing the default spectrum-splitting process, it said any alternatives offered up will just be efforts to "extend the advantages of earlier-licensed systems and undermine the Commission’s goal of placing systems on equal footing."

Telesat backed a throughput methodology using average degradation throughput as the long-term criteria and increase in unavailability as the short-term one. Telesat said the agency should wait until it has more firsthand expertise with operation of multiple systems in common frequency bands before tackling such issues as what to do after sunset, managing aggregate interference and whether there should be a maximum number of authorized systems operating in any frequency band.