GNSS Airport Interference Monitoring System
The GNSS airport interference monitoring system (GAIMS) project plans to develop a demonstrator which reliably detects interfering signals and classifies them if possible.
Applications of Global Navigation Satellite Systems (GNSS) like GPS/Galileo, and Satellite Based Augmentation Systems (SBAS) like EGNOS, are increasingly threatened by interferences like spoofing and jamming. Particularly in the field of safety critical applications, GNSS has gained an important position in recent years. One safety critical application, requiring highest standards of the system, is aviation. By using GNSS as well as satellite-based or ground-based augmentation systems (SBAS, GBAS), the positioning accuracy is increased to a level which allows for landing approaches with GNSS. GNSS landing systems (GLS) are in the implementation phase. SBAS approaches and GNSS based SMGCS (Surface Movement Guidance and Control System) are already widely used by airports.
In the past years, reports have repeatedly been published in which interference of SBAS/SMGCS was detected. At Newark airport, for example, the SMGCS is disturbed by jammers which are installed on trucks and cars passing by on near highways, which surround the airport. Although the use of jammers and spoofers is illegal in most countries, many truck and car drivers utilize such devices to put the built-in GNSS-based tracking systems out of action. The problem is that they unknowingly affect the SBAS/SMGCS of the nearby airport significantly, thus bringing people in danger.
This example shows the absolute necessity to monitor the affected radio-frequency spectrum to detect interferers and thus increase reliability and availability of GNSS and SBAS/SMGCS at airfields.
The GNSS airport interference monitoring system (GAIMS) project plans to develop a demonstrator which reliably detects interfering signals, whether it is a spoofer or a jammer. To accomplish this goal, state of the art detection algorithms will be analysed, improved if necessary and implemented. Moreover, the GAIMS project will try to classify the different interfering signals not only into spoofer and jammer, but make further separations of the parameters of these signals, like power, bandwidth and repetition rate. Since the trend in the receiver development community throughout the last decade is going toward software defined radio (SDR), the GAIMS project consortium will develop the detection and classification algorithms in an SDR framework. This leads to increased flexibility and adaptation of the solutions and reduced hardware costs. In parallel to the technological development, a market and business analysis will be performed to explore opportunities and possibilities for an interference monitoring system. Flughafen Graz, which is in a similar situation with respect to being surrounded by highways as Newark is very interested in the project topic and has thus agreed to be a technical consultant during the project.
GNSS Jammer detected in Graz
Researchers of TeleConsult Austria have been able to detect a GNSS jammer during an intensive measurement campaign in the vicinity of the airport Graz Thalerhof. These measurements have been performed within the GAIMS project.
Jammers can influence GNSS receivers within a distance of 1000 m significantly. This influence can lead to an inferior position accuracy, a wrong position or in the worst case to a total loss of the position, velocity and time solution.
Such a jammer has been detected on the 19th of August 2014 at 11:24 in the vicinity of the airport Graz Thalerhof. Different algorithms, developed during the GAIMS project, detected the jammer at the same time.
In the following plot, which depicts the power spectral density, the jammer influencing the E1/L1 band is clearly visible. Since the jammer transmitted for approximately 7 seconds, a so called “personal privacy device” installed on a truck/car passing by can be assumed. These “personal privacy devices” can be powered with the cigarette lighter in a car. The profile of the power furthermore supports the assumption of a passing by jammer.
Moreover can the effect of the jammer also be seen at the signal-to-noise-density ratios (SN0R) of the satellites. In the following plot, the theoretical SN0R values are shown with a dashed line, while the measured values are depicted with a solid line. While the jammer is passing by, the received signal strength of the satellites clearly dips.
Currently, the measurements are analyzed in more depths during the GNSS airport interference monitoring system (GAIMS) project and the GAIMS-II project.
- TeleConsult Austria GmbH (Lead)
- Brimatech Services GmbH
- Institute for Navigation, Graz University of Technology
- Austrian Research Promotion Agency (FFG)
- Successfully completed in 2014