How to test Jamming - Assessment of GNSS positioning systems to detect and mitigate the effects of jammers

WHAT IS A GNSS JAMMING?

GNSS jammers pose a significant threat to critical transportation and agricultural applications.

These radiofrequency devices (jamming and unintentional interferences) can interfere with GNSS signals used for air, rail, road, waterway and maritime navigation. These waves interfere with GNSS signals and can lead to service interruptions and even accidents.

For example, in the agricultural sector, GNSS signals are widely used for crop management. These disruptions can lead to significant decreases in productivity and even crop losses.

So, it is essential to implement countermeasures to detect the presence of jammers and mitigate their effects on the accuracy of geolocation measurements.

RESILIENCE AGAINST GNSS SIGNAL JAMMING

Thus, tests are needed to evaluate the detection capabilities and resilience of positioning systems against GNSS signal interferers.

The aim is to assess the detection sensitivity of jamming signals (CW, NB, PCW, WB, PWB, MS, etc.) and to determine their impacts on the accuracy of position, speed and angular orientation measurements.

To be usable, these tests must be performed under real or similar conditions, with representative interferences of the jammers likely to be used. Indeed, the interfering signals impact differently a GNSS receiver in a rural or urban environment.

The results of these tests provide essential analyses for estimating the robustness of positioning systems. They shall also give crucial indications on the level of vulnerability of applications integrating these GNSS technologies.

TEST CERTIFICATeS OF ANTI-SPOOFING DEVICES

Depending on the profile of the positioning systems to be assessed and their usage profiles, several test methods can be implemented.

Strictly speaking, the sensitivity of a GNSS receiver to given interference signals can be graded in simulation. The power of these interferences is then progressively increased up to the alert and saturation thresholds.

However, in the real world, these interferences are aggravated by those caused by the local environment such as bridges, buildings, vegetation or landforms. In the maritime domain, the pitching of ships and the diffraction phenomena of GNSS signals on swell are elements to be considered when establishing declarations of conformities under accreditation.

Based on the European standard EN16803-3, the replay technique is perfectly suited to perform representative, repeatable and reproducible tests.

In the case of highly hybridized positioning systems, some tests must be carried out on board the typical carrier vehicle (car, train, ship…). Our test laboratory is equipped to conduct these tests safely and without disturbing other GNSS terminals.

The conclusions of these tests shall contribute to the selection of the most suitable solution and the implementation of more reliable positioning functions.