Real-world instances of Global Navigation Satellite System jamming and spoofing have been steadily increasing in recent years. Those incidents include hundreds of commercial ships being spoofed in the Black Sea and repeated GNSS jamming affecting commercial aviation in Norway.
Air traffic manager Eurocontrol recently disclosed more than 3,500 instances of GPS jamming were reported by pilots during 2019 alone.
Elsewhere, the U.S. Federal Communications Commission has conditionally approved an application by satellite communications provider Ligado Networks to deploy a low-power terrestrial nationwide network in the L-Band to support 5G and Internet of Things services. The decision means that GNSS systems and devices must be capable of resisting adjacent-band radio frequency interference at extremely high-power levels while still providing extremely accurate and precise data to users.
Over-dependence on GPS and other navigation aids along with growing vulnerabilities including jamming, spoofing and other forms of interference highlight the need for terrestrial backups to current GNSS systems. We take a hard look at the scope of the problem and possible remedies in our upcoming GPS Special Project.
Most if not all the major GNSS providers are meanwhile experiencing space, control and user segment issues, where the transmitted data from satellites contains errors or is corrupted to the point where it becomes practically unusable.
There is little doubt that users of GNSS positioning and timing data will be dealing with a growing spectrum of threats to their services. While the weak power of GNSS signals remains a fundamental issue for users on the ground, overdependence is another.
GNSS has become an “invisible utility,” its use deeply embedded in our society, often used to obtain precise timing or positioning data for the operation of key elements of our critical national infrastructures. In many cases, dependencies and reliance on GNSS-derived data are not fully understood, and in some cases are not even identified. All of which leaves vital services extremely vulnerable to any disruption or denial of GNSS signals.
European and U.S. policy makers have recognized the dependence of critical national infrastructure on GNSS signals, along with the vulnerability of such systems to GNSS disruption or denial.
In the U.S., “Father of GPS” Bradford Parkinson has proposed a “Protect, Toughen, Augment” framework for GNSS. This triad encourages a systems-level, multi-strand approach to improving the situation when using position, navigation and timing (PNT) data.
Elsewhere, the U.K. government commissioned a review of GNSS dependencies on satellite-derived time and position. The review recommended several measures to improve the resilience of U.K. systems.
A key aim of the U.K. report was to ensure PNT resilience at the point of use, not to prescribe technology solutions. Again, a systems-of-systems approach to boosting PNT resilience was strongly advocated.
Both approaches make clear there is no silver-bullet solution to our GNSS dilemma. Rather, there needs to be a well-coordinated approach to the problem that provides users with the education, policies, standards and guidance needed to boost PNT resilience.
System and devices testing to gauge their ability to withstand interference has become important, helping to understand whether, and how well, they can perform as expected when there is disruption or denial of GNSS services. Testing also uncovers consequences when performance is compromised.
Testing is an essential part of any risk assessment.
Cost-effective mitigation should adopt a system-of-systems approach encouraged by both U.K. and U.S. policymakers. This means looking beyond GNSS device resilience to ensure operational procedures are in place to cover situations when GNSS is disrupted or denied. Where necessary, mitigation also includes augmenting or complementing the precise positioning and timing data from GNSS with information from other sensors.
Hardening existing GNSS systems could include improving antenna technology and investing in multi-constellation, multi-frequency GNSS receivers. Alternative or complementary PNT sources must also be considered, including the use of improved holdover technologies for timing, use of additional terrestrial or space-based positioning and timing services as they become available.
Examples include Time over Fiber, Enhanced Long-Range Navigation, or eLORAN and broader use of LEO satellite providers along with the use of inertial or dead reckoning technology for dynamic platforms. All of these solutions offer improved resilience or robustness when implemented properly.
Improving the resilience of our GNSS-dependent infrastructure is no longer optional, but rather an imperative. The rising incidence of real-world threats makes it essential. It is not an unsolvable problem, we just need to act.
Improving GNSS resilience and solving dependencies based on quantifiable evidence will help ensure a safer world driven by precise and reliable use of PNT services.
— Guy Buesnel is a PNT security technologist at Spirent Communications.