Global Navigation Satellite Systems (GNSS)—including GPS, Galileo, GLONASS, and BeiDou—provide the critical positioning and timing foundation for aerospace, maritime, telecommunications, transportation, and countless consumer applications. However, the extremely weak nature of GNSS signals (typically around –130 dBm at the Earth’s surface) makes them highly vulnerable to radio-frequency interference.
With the increasing availability of low-cost jammers, ultra-wideband devices, and intentional spoofing tools, interference has become a major threat to navigation reliability. This article summarizes the sources, effects, and mitigation strategies for GNSS interference, based on recent research and real-world monitoring data.
1. Sources of GNSS Interference
GNSS interference can be classified into unintentional and intentional disruptions.
1.1 Unintentional Interference
These arise from systems emitting RF energy near GNSS bands, such as:
- Aviation beacons (DME/TACAN)
- Radar systems
- Broadcast transmitters
- Ultra-wideband (UWB) devices
Unintentional interference can be narrowband (CW tones, spurious emissions) or wideband (UWB noise). Narrowband threats are often manageable with classical filtering, but wideband interference requires more advanced techniques.
1.2 Intentional Interference
Intentional attacks include:
- Jamming: raises the noise floor using CW, noise, or chirp signals
- Spoofing: transmits false GNSS-like signals to mislead receivers
- Meaconing: replays genuine GNSS signals with a delay
Commercially available jammers—often marketed as “privacy devices”—have made intentional interference increasingly common.
2. Impact on Key Application Domains
GNSS interference affects civilian, aerial, and maritime systems in different but serious ways.
2.1 Civilian Infrastructure
From smartphones to power grids, GNSS timing is a core dependency. Studies show:
- Airports have experienced GNSS disruptions linked to nearby jammers
- Telecom networks suffer timing instability from GNSS outages
- Emergency services and ports risk operational delays when GPS is unavailable
Even local interference can trigger cascading failures across multiple sectors.
2.2 Uncrewed Aerial Vehicles (UAVs)
UAVs rely heavily on satellite navigation for autonomous flight.
- Loss of GNSS causes instability or uncontrolled drift
- Spoofing can redirect or hijack drones
- Even with INS aiding, prolonged GNSS outages lead to rapid error accumulation
Modern anti-jam strategies, including CRPA-equipped receivers, are becoming essential for UAV safety.
2.3 Maritime and Naval Platforms
Maritime interference is increasingly documented.
- Ships in the Black Sea have experienced large-scale spoofing
- Baltic Sea monitoring logged 84+ hours of jamming within six months
- Prolonged outages disrupt navigation, docking, and vessel tracking
- Naval missions may lose situational awareness or synchronization
GNSS denial at sea poses both commercial and security risks.
3. Interference Mitigation Techniques
Mitigation is often split into pre-correlation (RF/IF domain) and post-correlation (measurement domain) defenses. A layered approach is most effective.
3.1 Pre-Correlation Techniques
Adaptive Notch Filtering
Used to suppress tones, chirps, or narrowband jammers.
Modern Multi-Parameter ANF (MPANF) can adapt notch width and depth dynamically, improving performance.
Pulse Blanking
Suppresses high-power pulses such as DME/TACAN bursts.
Highly effective in radar-rich environments when duty cycle is low.
Kalman-Based Tracking & GNSS/INS Fusion
Kalman filters predict jammer frequency or support vector tracking.
GNSS/INS integration allows a receiver to “coast” during outages with minimal drift.
3.2 Post-Correlation Techniques
Measurement Quality Monitoring
Interference often reveals itself through:
- C/N₀ drops
- AGC level increases
- Code residual jumps
Studies across Europe, Canada, and the U.S. confirm these metrics as reliable indicators.
RAIM (Receiver Autonomous Integrity Monitoring)
RAIM compares multiple satellite combinations to detect corrupted measurements.
Essential for spoofing detection and position-domain integrity.
4. CRPA: The Most Effective Anti-Jam Solution
Controlled Reception Pattern Antennas (CRPAs) use multiple antenna elements to form spatial nulls against interference sources.
Key Advantages of CRPA
- Simultaneous multi-source suppression (up to M–1 nulls for an M-element array)
- Preserved GNSS bandwidth, since interference is suppressed directionally
- Effective against all modulation types, including CW, chirp, pulsed, or spoofing signals
- Compatible with STAP (Space-Time Adaptive Processing) for advanced resilience
CRPAs act as the first line of defense, significantly reducing the load on filtering, RAIM, and multi-constellation tracking.
5. Conclusion
GNSS interference is a rapidly escalating global challenge that impacts aviation, maritime operations, telecommunications, and autonomous systems. While software-based filtering and measurement screening play vital roles, CRPA technology stands out as the most powerful and scalable solution for modern anti-jam protection.
With interference events growing in frequency and complexity, industries are increasingly adopting CRPA-enabled systems to ensure resilient and secure Positioning, Navigation, and Timing (PNT).
