Starlink's recent Regional Digital Opportunity Fund (RDOF) wins are being scrutinized in the form of a new study (PDF) estimating that the satellite broadband service will fail to meet its RDOF capacity requirements and commitments in the years to come.

According to a Cartesian study commissioned by The Fiber Broadband Association and the NTCA, Starlink would hit a capacity wall within seven years.

Using a "sample analysis" based on current public data from Starlink, the study found that the LEO-powered satellite broadband service would face that bandwidth shortfall by 2028, with more than half of Starlink's RDOF subscribers unable to be fully served during peak hours.

Boiled down further, the study estimates that 56% of SpaceX's RDOF locations in a "low capacity" use case (average data usage of 15.3 Mbit/s per location) and 57% of locations in a "high capacity" use case (average data usage of 20.8 Mbit/s per customer) "will experience service degradation during peak times and not meet the RDOF public interest requirements." The Cartesian study also estimates that 25% to 29% of locations will receive an average of less than 10 Mbit/s of capacity during peak times.

The study's base case assumes SpaceX can meet its goal of deploying about 12,000 Starlink satellites before the mandated RDOF completion data. It also assumes that all subscribers within range of a Starlink satellite can connect to that satellite but doesn't account for terrain and other serviceability considerations that might limit performance. The model is also based on a single satellite's throughput capacity at 20 Gbit/s, per past public statements by SpaceX.

FCC pushed for deeper evaluation of Starlink

The FBA and NTCA believe the study provides a roadmap for the FCC to conduct a deeper evaluation and ultimately verify whether Starlink will, in fact, perform as promised in the RDOF auction. They likewise recommend a long-form assessment that would "stress test the network" under a range of realistic ten-year scenarios for service take-up and usage in peak hours.

The study also calls into question whether the FCC will be able to use terrestrial performance measurement and monitoring for LEO-based systems that are currently used in the Connect America Fund (CAF) program, suggesting that the Commission will need to adjust and increase its oversight of SpaceX's compliance with the RDOF requirements. The FBA and NTCA argue that Starlink, unlike a terrestrial fixed network, can be dynamically configured after deployment and could "deviate at any given point from the design submitted in the long-form application."

"Our goal with our latest FCC filing is to provide tools and technical analysis that will support more indicative assessments of incipient technologies so that the agency can ensure that RDOF winners can deliver the broadband performance promised," Gary Bolton, the FBA's president and CEO, said in a statement.

That study takes aim at long-form applications stemming from Starlink's RDOF award of nearly $900 million to cover 642,925 locations via phase I of the multi-billion-dollar RDOF auction. Per its commitments, Starlink is on the hook to provide speeds of at least 100 Mbit/s down and 20 Mbit/s upstream with low latency to those locations within six years. Starlink, which is supporting more than 10,000 users in its current beta program, is also testing standalone voice services that can be offered on its LEO network.

Last week, SpaceX filed a petition (PDF) with the FCC seeking designation of Starlink as an Eligible Telecommunications Carrier so it can meet a deadline to receive RDOF support.

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— Jeff Baumgartner, Senior Editor, Light Reading