Photo: Ligado.

The plot has thickened yet again in Iridium and Ligado’s dispute over spectrum, with Iridium slamming Ligado’s most recent analysis as “divorced from the legal reality that Ligado exists in today.” Iridium’s March 27 filing to the Federal Communications Commission (FCC) is just the latest addendum to a debate that has seethed since last May, when Iridium brought to light its concerns that Ligado’s proposed terrestrial wireless network would interfere with Iridium’s own transmissions from Low Earth Orbit (LEO).

While Ligado already provides connectivity services in North America via the L-band SkyTerra 1 satellite, the company has plans to modify its block of spectrum to create a more advanced network comprised of both satellite and ground infrastructure. But Iridium isn’t having it, claiming that Ligado’s Out-of-Band Emissions (OOBE) from 1627.5-1637.5 MHz would disrupt Iridium’s adjacent operations at 1617.775-1626.5 MHz.

This isn’t Ligado’s first roadblock — its proposed network has seen some resistance from a flock of organizations nervous about interference, particularly within the Global Positioning Satellite (GPS) sector. But the company has forged ahead nonetheless, entering a cooperation agreement with five major GPS equipment manufacturers back in December. Ligado also highlighted a February report penned by the National Advanced Spectrum and Communications Test Network (NASCTN) as evidence its network would be compatible with such existing systems.

However, Iridium is particularly worried about the “potentially millions of mobile devices” that will operate just 1 MHz away from the spectrum it already uses for uplink and downlink satellite services. In a September 27 presentation, Iridium urged the FCC to “impose conditions on any grant of Ligado’s applications” to ensure those services will remain unaffected, and noted “the burden is on Ligado to resolve Iridium’s interference concerns.”

Although both companies stated as recently as last month that they would work together to find a reasonable solution, the conversation has more or less stalled, reflecting the difficult question of how to properly repurpose licensed spectrum.

One of the major points of contention is whether Ligado’s Ancillary Terrestrial Component (ATC) and 5G/LTE terminals would interfere with Iridium’s terminals due to geographic proximity. Iridium says, yes, absolutely, and in its September 1 filing attempted to distinguish Ligado from companies with similar infrastructure. “Iridium does currently receive interference from Globalstar and Inmarsat MSS systems,” the company pointed out. However, “these interference levels are manageable,” the company said, because Iridium and Globalstar user terminals are rarely co-located and Inmarsat’s terminals have directional antennas focused on the Geosynchronous Earth Orbit (GEO) arc.

Ligado, on the other hand, believes Iridium is both simplifying and overestimating its calculations. In a November 2 filing, Ligado framed Iridium’s assumptions as “an unlikely worst-case scenario,” and argued that Iridium “ignores the losses associated with in-building usage, which alone eliminates most of the interference concerns.”

Iridium has also called into question the viability of Ligado providing terrestrial and satellite services concurrently, stating in one of its filings that Ligado will be forced to “take spectrum away from prospective use by its satellite customers” due to self-interference. Here, Ligado says Iridium is “just plain wrong.”

“Our advanced satellite system built by Boeing is designed for compatibility with terrestrial operations … Further, Ligado has developed and patented advanced mobility management techniques that allow coexistence of satellite and terrestrial subnetworks sharing common spectrum without self-interference,” the company said in a statement.

On this and other points the two companies have grown increasingly antagonistic. In its most recent filing, Iridium went so far as to describe Ligado’s attempts to persuade the FCC as “the Greeks entering Troy in the Trojan Horse.” Meanwhile, a Ligado spokesperson has suggested this debate is becoming more about competitive advantage than spectrum policy.

“Given that Iridium has twice said it ‘does not oppose Ligado’s plans’ and other proceedings have successfully shown that satellite and terrestrial can coexist in close proximity, it’s unfortunate that Iridium is not spending its resources discussing those solutions when they are so clearly present,” a Ligado spokesperson said in an exclusive statement to Via Satellite.

At this point the FCC has yet to come down on one side or another, but there is no doubt the Commission’s decision on this issue will influence how policy is set further down the line. Iridium’s concern about the costs it has sunk into developing its Next constellation is a particularly important factor, as federal agencies are now considering whether to favor licensees who have already made substantial investments into their networks. As the Phoenix Center for Advanced Legal and Economic Public Policy Studies wrote last week in a bulletin, “While federal agencies must repurpose spectrum to create value, they also must avoid destroying value through the unartful management of interference.”