In the modern era of the autonomous world, UAVs, UUVs, and UGVs have proven themselves to be indispensable systems for a wide range of military, commercial, and civilian applications. Such systems are dependent upon Global Navigation Satellite Systems (GNSS) for Position, Navigation, and Timing (PNT) data. However, this dependence creates a critical vulnerability.
There are jamming and spoofing risks to the GNSS receiver and its association with the number of autonomous vehicles. The signal overwhelms the receiver with noise and makes it deaf to the navigation system; this form of interference is called jamming. The more sophisticated threat known as spoofing happens when counterfeit false signals make the receiver compute erroneous position or timing information instead. For self-driving cars in delicate environments or in mission-critical operations, these attacks are likely to be catastrophic.
Due to the proliferation of jamming and spoofing capability that is relatively cheap to obtain while being costly to defend against, the requirement for effective countermeasures has only become more pressing. This is where Inertial Navigation Systems (INS) play a crucial role, providing an independent means of navigation that can operate effectively even when GNSS signals are compromised.
Aeron’s PLX is a family of highly compact MEMS-based inertial navigation systems. Pollux 2 and 3 inertial navigators designed for uncrewed systems (UAVs, UUVs, and UGVs) offer gps jamming, spoofing detection, and mitigation capabilities as described below.
How does GNSS get jammed and spoofed?
Electronic Warfare—Jammers and spoofers are not just theoretical "ideas"; they're being proven in today's electronic warfare tactics. In war scenarios, intensive GPS jamming endangers navigation in restricted areas.
Jamming
Intentional interference signals disrupt GNSS antennas and receivers at elevated frequencies, resulting in interference levels surpassing a specified threshold (see Figure 1). Consequently, this can cause GNSS to lose satellite signals and send inaccurate position data.
Figure 1: Jamming Interference
Spoofing
To spoof a receiver, an adversary must accurately mimic signals from several satellites and then send that spoofed signal to deceive a local GPS receiver. (See Figure 2.) If the targeted GPS receiver cannot differentiate between genuine satellite signals and the spoofed ones, it will be misled into reporting a false location.
INS Anti-Spoofing and Anti-Jamming Methods
Multi-Constellation and Multi-Frequency GNSS: Use multi-constellation or multi-frequency GNSS and frequency bands to tolerate the jamming/spoofing, which may cause loss of positioning.
Multi-Sensor Fusion: If GNSS information is corrupted or jammed, the system changes its input sources to other navigation data including internal IMU, continues to provide position and attitude estimates, and maintains navigation.
How does Pollux detect gps jamming & spoofing?
Pollux 2 and Pollux 3 are modern MEMS (Micro-Electro-Mechanical Systems) based on an Inertial Navigation System that employs multiple source method techniques to provide accurate position and orientation. Pollux engages a multi-layered approach to detect, mitigate, and overcome gps jamming and spoofing:
Detection: Pollux detects jamming and spoofing by continuously monitoring the signal strength of the received GNSS signal. Significant deviations from the expected C/N₀ levels, especially if the change is sudden, can be used to detect jamming and spoofing. Sudden inconsistencies or implausible shifts in GNSS data trigger alerts, signaling the control systems to initiate the mitigation process.
Mitigation: To mitigate issues, Pollux utilises both multi-frequency and multi-constellation techniques. Since it operates with multiple frequency GNSS, if a specific band fails, Pollux automatically transitions reception to a working band. Secondly, Pollux has advanced filtering techniques to filter out suspected GNSS data and rely on other external aiding data (speed-aided sources, aerial-aiding data) for continued navigation. Mitigation strategies combine advanced signal processing, robust algorithms, and multi-sensor fusion to maintain resilience. Pollux immunises against the traditional radio frequency jamming and spoofing attacks that plague GNSS systems.
Circumvention: If the threat persists, Pollux switches to pure inertial or aided navigation (dead reckoning), maintaining position and attitude estimates without GNSS inputs. The duration and accuracy of this mode depend on the quality of data inputs and availability of additional aiding sources.
Reintegration: Once the GNSS input stabilises, the system safely re-shifts the measurement priority to prior data sources by correcting any accumulated INS drifts.
The flowchart illustrates how Pollux detects jamming and spoofing interference:
Figure 3: Jamming Detection & Mitigation
Figure 4: Spoofing Detection & Mitigation
Once Pollux detects jamming or spoofing, its proprietary Extended Kalman Filter fuses the output of the IMU and an external aiding source to correct the position data. If aiding is not available, Pollux switches to the pure inertial mode. Figure 5 demonstrates the performance of Pollux under jamming and spoofing.
Figure 5: Pollux Performance under Jamming & Spoofing
Author : Rohini Shinde
