DOD Concerns About the FCC-Approved
Ligado Network
Updated February 5, 2021
On April 20, 2020, the Federal Communications Commission (FCC) unanimously approved an
application by Ligado Networks LLC (Ligado) to “deploy a low-power [9.8 decibel watts (dBW)]
terrestrial nationwide network in the 1526-1536 MHz, 1627.5-1637.5 MHz, and 1646.5-1656.5 MHz
bands [of the electromagnetic spectrum] that will primarily support Internet of Things (IoT) services.”
These frequency bands are traditionally used for satellite operations. The Department of Defense (DOD)
opposed this decision—along with the Department of Homeland Security, Department of Transportation
(DOT), Department of Interior, Department of Justice, the Federal Aviation Administration (FAA), and
others. That opposition related to concerns that Ligado’s proposed network could interfere with signals
from satellites to Global Positioning System (GPS) receivers. Congress may consider federal agency
concerns, including DOD concerns related to mission-critical systems and the FCC’s response, as it
conducts oversight of the FCC’s ruling. Congress may also consider broader issues related to fifth
generation (5G) mobile technologies, such as the allocation of spectrum among competing users and the
impact of spectrum decisions on national security.
DOD Concerns and Related Studies on GPS Interference
In both its formal response to the FCC’s ruling and its May 6, 2020, testimony before the Senate Armed
Services Committee (SASC), DOD cited two primary studies that shaped its belief that the Ligado
network “would cause unacceptable operational impacts and adversely affect the military potential of
GPS”: a 2018 DOT study and a 2016 classified study conducted by the U.S. Air Force (USAF). The 2018
DOT study assessed the extent to which cellular base stations with power levels ranging from -6 dBW to
31 dBW and cellular handsets of -7 dBW would interfere with GPS. (At the time of the study, Ligado
proposed a base station power level of 32 dBW and a handset power level of -7 dBW.) The study
concluded that base stations at the proposed Ligado frequency would have to be limited to 9.8 dBW to
ensure the protection of certified avionics in most scenarios. In conversation with CRS, DOT officials
asserted that the protection of other categories of GPS equipment—including noncertified aviation,
general location/navigation, high precision, timing, and space-based—could not be assured at this power
level. DOD additionally recommended “that proposals for use of bands adjacent to GPS should not be
approved unless they meet the transmission power levels described in the [DOT test].” Based on the DOT
study findings for certified aviation, Ligado submitted an amended application to the FCC, reducing its
