A growing number of special interest groups from across the country are banding together to oppose a controversial move by the Federal Communication Commission earlier this year that some say threatens GPS reliability. Agriculture groups including the Agricultural Retailers Association (ARA), American Soybean Association (ASA), Equipment Dealers Association (EDA), Iowa-Nebraska Equipment Dealers Association, National Corn Growers Association (NCGA), National Cotton Council of America (National Cotton Council) and USA Rice Federation (USA Rice) recently announced their support for the “Keep GPS Working Coalition.” Below is a breakdown of the issue and more information on what exactly could be at stake:
What is the L band: L-band is described as the range of frequencies between 1 to 2 GHz. GPS, and other international navigation systems, rely on L-band because it can easily penetrate clouds, fog, rain and vegetation. Midband spectrum is considered important for 5G deployments because it offers an attractive mix of both geographic coverage and high speeds, making it a critical component of the US’ strategy to win the 5G race.
FCC Decision: The FCC on April 20 of this year granted a spectrum license to Ligado Networks (formerly known as LightSquared) to build a terrestrial wireless 5G network on the 1 to 2 Gigahertz frequency range, aka the L band.
GPS Interference: Opponents argue that opening the L band threatens segments of that range that are already used by Global Positioning System (GPS) signals and other systems, including military.
Ligado History: Officials from Ligado, and its predecessor LightSquared, have sought the FCC approval for roughly 10 years. Ligado plans to meld satellite communications with an on-the-ground 5G network to build a smart device network geared for industries like manufacturing, agriculture, commercial transportation and utilities. Over the years, Ligado officials have argued their system would use less spectrum, have lower power levels, and reduce out-of-channel emissions. In the face of complaints from major commercial GPS companies such as Garmin and John Deere, Ligado has also offered to reduce the amount of spectrum it had initially planned. The company has also said it will work with government agencies to repair and replace equipment if necessary.
FCC and Other Proponents Response: The FCC says its technical experts had concluded that interference with GPS signals was unlikely. And if it did occur, it would be very minor. “Fortunately, it has been proven time and time again that Federal users can reduce their spectrum holdings without putting at risk their vital missions. Nonetheless, these same entities, especially the Department of Defense (DoD), which is the largest holder of the most ideal mid-band spectrum, are exceptionally reluctant to part with one single megahertz,” FCC Commissioner Mike O’Rielly said in an April 8 letter to President Donald Trump. Other experts, who see Ligado as a way to help boost the economy and to help compete with China, claim that the Defense Department’s analysis does not show that interference is a certainty.
DoD and Other Opponents Response: The Department of Defense (DoD) is mounting one of the biggest pushbacks, with Senior Pentagon leaders warning the move will lead to “unacceptable” harm to the GPS system by creating new interference that could disrupt satellites critical to national security. Some satellite operators, including Iridium, whose services are used by the DoD, are also worried about potential interference from Ligado. Other federal government opposition includes leaders from NASA, the Federal Aviation Administration, the Department of Transportation, and the National Oceanic and Atmospheric Administration. In a letter announcing their support for Keep GPS Working, the previously mentioned ag groups say the FCC’s “highly unusual order puts dozens of industries reliant on GPS at risk while granting a single company and its Wall Street investors a financial windfall at the expense of farmers, businesses, and consumers.” Other supporters of Keep GPS Working include the Association of Equipment Manufacturers, American Farm Bureau Federation, American Road & Transportation Builders Association, Aircraft Owners & Pilots Association, and Boat Owners Association of The United States.
GPS vs Communication: In trying to determine how FCC engineers came to different conclusions about GPS interference than so many others, some think the problem lies in the fundamentally different ways communications and navigation systems use the airwaves. And that the communications engineers at the Federal Communications Commission unconsciously used inappropriate criteria in their analysis. Brad Parkinson of Stanford University, the original chief architect of GPS, explains that GPS and communications systems are very different. “Communications is about strong signals with an unknown message pushing through the background noise so the receiver can read the ones and zeros. GPS receivers look for a known, but very weak messages down within the background noise. They precisely measure the time between the ones and zeros. Typically, GPS receivers resolve time of arrival to 1 billionth of a second or better.” The important difference is that some interference is tolerable in communications. A bit of static, or even a momentary break, often does not prevent the message from getting through. Not so in navigation. Long experience has shown that one of the first effects of interference with many navigation receivers is hazardously misleading information that can lead to things like a plane crash or even the misfiring of a military drone. (Sources: c4isrnet, Cnet, SpaceNews, ArsTechnica)
