U.S. Department of Defense Objects to 5G Spectrum Proposal

Secretary of Defense Mark Esper sent the Federal Communications Commissions (FCC) a letter urging FCC Chairman Ajit Pai to reject a proposal by Ligado Networks to open the radio frequencies between 1 and 2 Gigahertz, also known as the L band, for use by 5G mobile networks.

In his letter to the FCC, Esper posited that opening the frequency range to commercial use would hinder the United States-operated Global Positioning System (GPS) satellite-based radio-navigation system. “I believe there are too many unknowns and the risks are far too great to federal operations to allow Ligado’s proposed system to proceed. All independent and scientifically valid testing and technical data shows the potential for widespread disruption and degradation of GPS services from the proposed Ligado system… This could have a significant negative impact on military operations, both in peacetime and war” he said in the letter dated November 18.

Artist’s conception of GPS Block II-F satellite in Earth orbit (navcen.uscg.gov)

The Department of Defense (DoD) is the most recent government body to raise an issue with the FCC over commercial use of radio spectrums for 5G technology. The FCC shrugged off previous objections from NASA, the US Navy, the National Oceanographic and Atmospheric Administration, and others, over a different spectrum block in the 24 Gigahertz used by weather satellites to monitor water vapor activity.

A decision is yet to be made on the Ligado plan to open up the 1675 to 1680 Megahertz block, but Pai seems to be supportive. GPS uses a primary block of the L band centered around 1575.42. GPS relies on several blocks of the L band due to their ability to penetrate clouds, rain, and vegetation. In addition, the DoD uses the L band for tactical air navigation, landing assistance telemetry, missile and aircraft telemetry, and Identifying Friend or Foe (IFF) signals. 

Ligado hopes to gain approval for use of the L band for a planned project in collaboration with Inmarsat, a satellite communications company that uses the L band to provide the military with satellite communications. It hopes to provide satellite coverage for its 5G network.