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Jamming and Spoofing: Two Threats for Your UAS GNC System

As technology advances and geopolitical challenges arise, the demand for reliable and secure navigation for Unmanned Aerial Systems (UAS) intensifies. Ensuring operational integrity in both civil and defense sectors is paramount. With Global Navigation Satellite Systems (GNSS) signals increasingly under threat from both unintentional and intentional interference, the shortcomings of traditional navigation systems are evident.

Various sources can disrupt GNSS signals, including natural events, technical issues, and, more worryingly, deliberate interference or jamming by adversaries, which poses a threat to the reliability of GNSS signals. This article will concentrate on the latter, which can be divided into two types of attacks: Jamming, where GNSS signals are intentionally blocked, and spoofing, which is even more hazardous as adversaries create false GNSS signals to mislead aircraft, potentially causing crashes or directing them to unintended destinations.

When confronted with such disruptions, the consequences can be severe for operations reliant solely on these signals for navigation. In time-sensitive scenarios like military operations or emergency responses, even minor deviations from planned routes or brief interruptions in navigation can lead to disastrous outcomes. The increasing frequency of GNSS signal disruptions underscores this vulnerability, highlighting the urgent need for a more robust navigation solution.

 

What is Jamming?

Jamming refers to the intentional disruption or interference of GNSS signals, overwhelming genuine frequencies with noise or interruptions, making it difficult to receive the original signal and often resulting in lost connections or inaccurate data. 

During these attacks, the signal power experiences an increase with respect to its normal values. As we can see in the attached example, the signal increases its values at frequencies close to L1 (1575.42 MHz) due to the “jammer.”

Figure 1. Effect of a jamming attack on a signal with nominal values close to 120 dBm. Source: ResearchGate
 

The risks associated with jamming are significant. Systems that are heavily dependent on GNSS may lose navigation capabilities, potentially deviating from their intended course, jeopardizing missions, or exposing assets to threats.

 

What is Spoofing?

Conversely, spoofing involves generating and transmitting fake GNSS signals. Instead of merely disrupting signals like jamming, spoofing tricks a GNSS receiver into believing it's receiving a genuine signal, producing false positioning data that leads to inaccurate navigation.

The process of identifying a spoofing attack is more difficult than a jamming attack since the effects on the signal are more complex. When a signal is disrupted by a spoofing attack, it affects the modulation pattern of the signal. This modulation pattern includes changes in both the amplitude and phase of the signal, represented by the in-phase (I) and quadrature (Q) components. Even if the spoofing attack tries to mimic certain characteristics of the original signal, such as the Doppler effect caused by motion, it may not perfectly replicate these features. As a result, discrepancies emerge in the modulation pattern, leading to detectable changes in the quadrature of the signal. These changes can be analyzed to identify and counteract the effects of the spoofing attack, helping to maintain the integrity and security of the system.

Figure 2. I/Q Modulation of a signal under a spoofing attack. Left: Original signal; Center: End of the spoofing attack; Right: Effect when the spoofing attack tries to copy the Doppler effect. Source. Wasy Research

 

The dangers of spoofing are profound. Advanced spoofing attacks can allow adversaries to potentially redirect aircraft trajectory by sending wrong Position, Velocity and Time (PVT) measurements, which could cause a crash.

 

A Threat to the Flight Control System

Most Unmanned Aerial Systems (UAS) autopilots heavily rely on Global Navigation Satellite Systems (GNSS) along with Microelectromechanical Systems (MEMS) inertial sensors to maintain precise position and velocity, as well as to navigate between waypoints. However, in the event of a GNSS jamming or spoofing attack, the exclusive dependence on MEMS inertial sensors to estimate the aircraft's position and velocity can render the navigation solution vulnerable. Without the corrective input from the GNSS, the inertial solution begins to propagate over time, leading to progressively increasing deviations and heightened uncertainty in navigation variables.

UAV Navigation-Grupo Oesía's design philosophy is that the UAV cannot depend upon the availability of a GNSS signal; the system must be able to continue the mission even in a GNSS-denied environment.

When a flight control system is jammed or operates in a GNSS-denied navigation area, the UAS no longer has access to a GNSS PVT solution. With inferior systems, the only alternative is for the remote pilot to take manual control, making it likely that the mission will fail and, depending on the distance between the Ground Control Station (GCS), the UAV may be lost. As mentioned above, some systems may be unable to maintain UAV stability and the aircraft will fall out of the sky.

This is a major weakness of many commercially available drone systems, and it is what has made jammers and other counter-UAV measures so popular in the industry.

 

UAV Navigation-Grupo Oesía’s Flight Control System Proven Against External Attacks

UAV Navigation-Grupo Oesía's systems show robust resistance to external attacks on the GNSS signal. The flight control system incorporates advanced internal algorithms capable of detecting jamming and spoofing attempts, thereby reducing the reliance on GNSS signals. Once detected, the system automatically prioritizes other navigational sources to guarantee flight safety. In this sense, the UAS GNC system fuses inertial and visual navigation data from our Visual Navigation System, with VNS01 serving as its primary navigation source, ensuring seamless operation even in GNSS-denied environments.

The combination of different navigational sources integrated with multiple cross-supervisory logic and control algorithms further fortifies the flight control system’s resilience against disruptions.

The fusion of inertial and visual navigation, enabling accurate dead reckoning with minimal drift, constitutes the cornerstone of our GNSS-Denied Navigation Kit's capabilities.

Moreover, unlike open-source or other autopilots on the market, our system utilizes the UAV Navigation-Grupo Oesía property ICD (Interface Control Document). This empowers our system to effectively prevent, analyze, and detect any potential interference or system failure, thereby enhancing overall operational integrity.

 

User Case: Alpha Unmanned Systems

As mentioned in one of our previous articles, Alpha Unmanned Systems, a customer of the UAV Navigation-Grupo Oesía flight control system, has carried out robustness tests on its ALPHA 800 rotary-wing platform. Despite the severity of these tests, carried out by a specialized company equipped with anti-drone jamming guns, the UAV Navigation-Grupo Oesía flight control computer was able to continue the mission without any sign of attack or degradation in its performance, demonstrating its reliability and robustness against anti-drone systems.

 

 

In conclusion, UAV Navigation-Grupo Oesía has a deep commitment to designing highly robust systems, encompassing both hardware and software components. Through the integration of advanced algorithms capable of detecting external attacks and managing different navigational sources, our solution ensures safe and reliable operation, even in GNSS-denied environments. This clear commitment to innovation and resilience underscores our dedication to providing unparalleled navigation solutions tailored to meet the evolving challenges of modern aviation.

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About

UAV Navigation is a privately-owned company that has specialized in the design of flight control solutions for Unmanned Aerial Vehicles (UAVs) since 2004. It is used by a variety of Tier 1 aerospace manufacturers in a wide range of UAV - also known as Remotely Piloted Aircraft Systems (RPAS) or 'drones'. These include high-performance tactical unmanned planes, aerial targets, mini-UAVs and helicopters.