The US Defense Department said a study released Friday shows Ligado Networks' planned nationwide mobile broadband network will interfere with military global positioning system receivers (GPS) receivers.
The Federal Communications Commission in April 2020 voted to permit Ligado to deploy a low-power network. In January 2021, the FCC rejected a bid by US government agencies to put its decision on hold.
The National Academy of Sciences, Engineering, and Medicine report released Friday warned some Iridium Communications mobile satellite services "used by the US Department of Defense and others will experience harmful interference under certain conditions and warned some high-precision devices sold before about 2012 "can be vulnerable to significant harmful interference."
The Defense Department said the study is consistent with its view that "Ligado’s system will interfere with critical GPS receivers and that it is impractical to mitigate the impact of that interference" and noted the study found FCC's proposed mitigation and replacement measures "are impractical, cost prohibitive, and possibly ineffective."
Ligado argued the report found "a small percentage of very old and poorly designed GPS devices may require upgrading."
It noted that with the FCC it established a 2020 program "to upgrade or replace federal equipment, and we remain ready to help any agency that comes forward with outdated devices. So far, none have."
Ligado said it hopes U.S. agencies "will stop blocking Ligado’s license authority and focus instead on working with Ligado to resolve potential impacts relating to all DOD systems."
Iridium said the study shows "that Ligado’s proposed operations will cause harmful interference.... Iridium urges the FCC to take swift action to reverse the order before Ligado starts its technical demonstrations this fall."
The FCC did not immediately comment.
The study also found Ligado's network "will not cause most commercially produced general navigation, timing, cellular, or certified aviation GPS receivers to experience harmful interference."
In May 2020, the U.S. Commerce Department filed a request with the FCC on behalf of executive branch agencies, including the Defense and Transportation departments, arguing it would cause "irreparable harms to federal government users" of GPS. The report called on FCC and Commerce to conduct joint testing and "a more collaborative approach to resolving spectrum issues."
