GPS relies on faint radio signals from satellites about 12,000 miles away, requiring a quiet spectrum neighborhood to operate. (Photo: NASA)
By Alex Damato
Acting Executive Director
GPS Innovation Alliance
From its humble beginnings in the 1970s to its expanded use in the present day, GPS technology has been vital for nearly every industry from defense and aviation to farming and construction. GPS devices are designed to receive faint GPS signals transmitted from satellites about 12,000 miles away. Acknowledging this reality, regulators have historically maintained for GPS, which relies on such faint radio signals and sensitive equipment, an appropriately quiet spectrum neighborhood—populated by similar users.
With the NASEM report’s confirmation of harmful interference, the deficiencies of the FCC’s April 2020 decision are even more striking
Although these GPS signals and equipment have benefitted from decades of optimization, it is impractical to place highly sensitive GPS receivers designed to capture faint signals from remote transmission facilities immediately next to high-power communications equipment. Unlike those from communications systems, GPS signals are below the thermal noise floor when they are received. As a result, increases in that noise floor often decrease the availability of GPS services, which in turn places at risk high-consequence and safety-of-life services that rely on GPS.
Alex Damato
Why does this matter? In April 2020, the FCC approved a plan to deploy a terrestrial network in spectrum adjacent to the frequency bands used by GPS — operating communications signals that would be around two billion times more powerful than GPS signals at the same location.
This past September, the National Academies of Sciences, Engineering, and Medicine (NASEM) released a report detailing the harmful effects of a terrestrial communications network that would operate in a frequency band close to that of GPS.
Expert concern within 14 federal agencies and departments, a broad coalition in Congress, and the GPS industry resulted in a congressional mandate that NASEM conduct an independent technical review of potential interference to GPS. After a thorough review of the materials, NASEM concluded that the proposed terrestrial network would result in harmful interference to a substantial number of GPS receivers.
In particular, the report noted that high precision GPS devices, which are used in the most economically significant GPS applications, are the most vulnerable receiver class and likely to be affected by interference. The potential for any interference with GPS, especially with devices used by the Department of Defense, poses a threat to national security, the economy, and our daily lives.
With the NASEM report’s confirmation of harmful interference, the deficiencies of the FCC’s April 2020 decision are even more striking: potentially millions of farmers, pilots, construction companies, and first responders may be required to repair or replace GPS equipment at their own cost. Although the FCC assumed that this equipment could be repaired through upgrades or filters, some devices cannot be filtered without significant financial and performance costs, and some devices simply cannot be filtered at all.
GPS is estimated to provide up to $300 billion annually in benefits to the economy. Any disruption in GPS accuracy and usage would have detrimental effects on productivity and economic growth. Moreover, the year before the FCC’s flawed decision, another key report revealed that the loss of GPS service would have an average impact of $1 billion per-day on the nation.
The GPS Innovation Alliance will continue to work with all federal and industry stakeholders to maintain open channels of communication to connect, listen, and learn from all those involved in the discussion. As technological innovation continues, these debates on harmful interference are not going away, and GPSIA is looking forward to engaging further.
