GPS' Considerable Jamming and Spoofing Woes Getting Worse

GPS' big vulnerability is that its signals are relatively weak, with more radiant noise coming from starlight, so any noise in the same frequency can deny GPS receivers a signal, said Dana Goward, president-Resilient Navigation and Timing Foundation. That the specifications for GPS signals were deliberately made public to facilitate GPS worldwide also means the signal is easy to imitate, Goward said.

Device manufacturers wanting to operate in foreign markets often must support GPS alternatives, such as China's BeiDou, Russia's GLONASS or Europe's Galileo, Simington said. Those competing systems also sometimes offer higher precision and performance than GPS. The danger is adversary nations could cause widespread disruption by shutting down access in the U.S. to those signals, or sending spoof signals with incorrect data to American receivers, he said.

The FCC needs a better understanding of handsets connecting to foreign satellites for unregulated data services, Simington said. Noting the FCC Enforcement Bureau's probe of U.S. mobile devices processing signals from foreign global navigation satellite systems (GNSS) (see 2403140071), Simington said the results hopefully will give the agency additional insight into how GNSS signals are used domestically. The agency, he said, should know whether smartphone apps connect to foreign navigation satellite constellations as part of their operations. The FCC also should look at "a full regulatory framework" for services that regularly connect to foreign GNSS, Simington added. The agency doesn't know -- but should know -- whether handset makers like Apple and Samsung disable foreign GNSS receivers in devices before shipping them to terrestrial providers in the U.S. Given the agency's statutory mission of protecting the airwaves, its blind spot on GPS "seems like a sort of conspicuous failure." Industry should converge around standards for backing up GPS' positioning, navigation and timing (PNT) functions, he added.

Russia has been at the forefront of intentional GPS disruption, Goward said, pointing to a steep ramp-up of GPS interference in the Baltic region in December after activation of the U.S.' Aegis anti-missile defense system in Poland. Spoofing and jamming also occur regularly in such areas as Kashmir and Myanmar, he said. Jamming and spoofing are generally hard to counter and there are no disincentives, so all signs point to it being a worsening problem, Goward added.

Speakers during the event criticized Congress, the Defense Department, the Space Force and Raytheon. For example, Mark Montgomery, senior director-the Foundation for Defense of Democracies' Center on Cyber and Technology Innovation, pointed to four next-generation GPS III satellites that are ready for launch, joining 17 in orbit and forming a somewhat-upgraded GPS signal that's harder to jam. But he said Space Force must prioritize launching those satellites and hasn't. Moreover, DOD isn't overseeing Raytheon sufficiently to stand up the years-delayed OCX operating system for the GPS III satellites.

Hudson Institute Senior Fellow Robert McDowell said GPS' vulnerabilities haven't received sufficient congressional attention. The former FCC commissioner said an "all of the above" approach is needed, with terrestrial backups to GPS added alongside a more robust GPS III constellation. A big hurdle, McDowell said, are DOD voices who believe GPS satellites will likely be taken out during a full-scale conflict with China. So, why bother finishing the constellation?

GNSS resilience is getting cheaper as prices drop for technologies like software-defined radios and phased array receivers, said Todd Humphreys, Priddy Centennial Professor in Engineering at University of Texas at Austin. He urged deploying 5010-5030 MHz and higher frequencies to promote phased array use on GNSS receivers. Humphreys said his research team is working with Amazon's Kuiper on building a secondary PNT service into the company's forthcoming mega constellation. That would help address some concerns about the lack of GPS redundancy; however, it won't be available for years, he noted.

LTE signals, Wi-Fi and digital TV signals could back up GPS, as could spectrum that LEO operators use now, said Zak Kassas, director-Ohio State University's Autonomous Systems Perception, Intelligence and Navigation Laboratory. LTE signals, even when too faint for communications, can still be used for navigation, he said.

Using a receiver on the International Space Station and the Spire Global RF observation satellite system can allow sources of GNSS interference to be geolocated, Humphreys said, noting research that has identified sources outside of Tehran and an Israeli airbase. He said more geolocation of GNSS interference using low earth orbit satellite systems is needed.

The ITU's Resolution 676, adopted at the 2023 World Radiocommunication Conference, came out against radio navigation satellite service disruptions, but included language that allows nations to do so for security or defense reasons, Humphreys said. That caveat makes interfering with GPS "no longer clearly illegal."