The Division of Protection has weighed in towards a proposal earlier than the Federal Communications Fee to open the 1 to 2 Gigahertz frequency vary—the L band—to be used in 5G mobile networks. The explanation: segments of that vary of radio spectrum are already utilized by International Positioning System indicators and different army techniques.
In a letter to FCC Chairman Ajit Pai, Secretary of Protection Mark Esper pressed for the rejection of the proposal by Ligado Networks (previously often known as Lightspeed), saying, “There are too many unknowns and the dangers are far too nice to federal operations to permit Ligado’s proposed system to proceed… This might have a major detrimental impression on army operations, each in peacetime and battle.”
The FCC has already largely brushed apart comparable opposition from NASA, the US Navy, and the Nationwide Oceanographic and Atmospheric Administration, amongst others, over one other spectrum block within the 24GHz vary—which is utilized by climate satellites for distant monitoring of water vapor. However feedback are nonetheless being collected on the Ligado plan for sharing the 1675 to 1680 MHz block of the L Band. Pai has been supportive of the plan as a result of that vary is adjoining to the prevailing 1670 to 1675 MHz block already in use for wi-fi providers.
GPS indicators use a number of blocks of the L band, together with a main channel centered on 1575.42 MHz. GPS makes use of L band indicators due to their skill to penetrate cloud cowl, rain, and vegetation. The L band can also be utilized by the DOD for a variety of different functions, together with tactical air navigation, touchdown help telemetry, Determine Good friend or Foe (IFF) indicators, and missile vary and plane telemetry—although the DOD has already needed to transfer a few of these functions additional up the spectrum vary to make room for earlier “business reallocation.”
Ligado’s request for bandwidth sharing is tied to the corporate’s deliberate collaboration with satellite tv for pc communications firm Inmarsat, which would offer satellite tv for pc protection for Legato’s 5G community. Inmarsat presently makes use of L band for cellular satellite tv for pc communications providers, together with tactical satellite tv for pc communications marketed to the army across the 1.5GHz vary.
In an e-mail to Bloomberg, Ligado spokesperson Ashley Durmer criticized the DOD’s objections, citing the low energy of the proposed 5G indicators. “Can it actually be true that our army operations are weak to a 10-watt lightbulb?” she wrote. “We don’t assume so. However that’s what this letter suggests.”
However because of the inverse-square regulation, indicators might be prone to even low-power sign interference, significantly these from GPS. For this reason the unique Lightspeed proposal for a blended satellite tv for pc and 4G community within the 1.525 to 1.555 GHz vary was opposed by DOD and others—GPS indicators arriving from area might be overpowered by ground-based transmissions, as proven in exams carried out in 2011. The exams “demonstrated there are important detrimental impacts to all GPS functions assessed,” a report from the Nationwide House-Based mostly Positioning, Navigation, and Timing Methods Engineering Discussion board famous.