M MILITARY SYSTEMS & Technology
Impacts of GNSS interference on military systems In the light of the Ukrainian war, reports emerged that the full spectrum of Navigation Warfare is being used within Ukraine on both sides. This especially includes intentional GNSS (Global Navigation Satellite System) interference and has a significant influence on troop and also civilian operations in the area. The most recent reports of system malfunctions due to GNSS signal issues show that there is a clear need for improvement in terms of defence against Navigation Warfare attacks and training within Navigation Warfare environments.
What is interference? Interference to GNSS can be unintentional (e.g., inter-system interference, multipath, etc.) or intentional. Unintentional interference can generally be better controlled and mitigated. Intentional interference is categorized into the two main categories jamming and spoofing, which pose a significant risk to GNSS measurements. Jamming denotes the transmission of highpowered signals with the goal to shadow the GNSS signals so that a receiver cannot acquire and track them. Ty T pical jamming signals are chirp or noise signals with a bandwidth matching or exceeding the bandwidth of the respective GNSS bands they target. In general, jamming detection can be performed pre-correlation or postcorrelation, while the most suitable approach depends on the type and possibilities of the receiver in use. Since different detectors have different advantages and disadvantages, an optimal jamming detector should be based on the combination of several detector values.
Background Due to their nature, GNSSs are susceptible to intentional interference without requiring very high signal power or overly complex equipment. The two main factors for the vulnerability of GNSS signals against interference are the low received signal power (below thermal noise) and the open and publicly known signal structure. Although modernized signals counter the vulnerabilities by employing more sophisticated modulation schemes like higher-order binary offset carrier (BOC) or incorporating authentication features, these countermeasures cannot provide perfect interference mitigation and also many systems still rely on older signals. Governmental authorities, armed forces, system integrators and GNSS equipment manufacturers should be aware of the danger caused by GNSS signal interference. They should get the possibility to test their equipment in a protected and realistic environment to assess vulnerabilities and improve equipment in order to better tackle GNSS interference.
jamming
Spoofing denotes the transmission of fake GNSS signals with the goal to falsify (spoof) the position, velocity and time (PVT) solution of the receiver under attack. For this, spoofing signals have to be modulated in the same way than authentic satellites are modulated and also the navigation messages usually have to be mimicked for
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