Final Report of BeJamDetect Project 
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Yolr 
Even more dangerous situations may occur when the radio-frequency interference (RFI) results in 
an integrity risk due to unrecognised wrongful operation of the navigation receiver. This risk is 
typically associated with a special type of RFI named GNSS spoofing [3]. Spoofing denotes 
transmission of GNSS-like signals which may be acquired and tracked in the navigation receiver or 
instead of the authentic signals from the corresponding GNSS satellite constellations. If not 
‚ecognised, the usage of spoofing signals may lead to the generation of misleading PNT (Position, 
Navigation, Timing) information. Therefore, GNSS spoofing is commonly accepted as a serious 
threat for civil GNSS applications which rely on the use of open-service (i.e. not encrypted) GNSS 
signals. The structure of such signals is described in sufficient level of detail in publicly available 
documents [4]. Due to the technological progress in the field of digital signal processing, suitable 
low-budget software-defined radio platforms for generating the GNSS-like signals are easily 
accessable. 
The radio frequency interference to GNSS receivers can also be of unintentional nature. Some 
natural phenomena like solar bursts or ionospheric scintillations may create such interference [5]. 
Also, man-made emissions in form of harmonics of radio signals from other frequencies, energy 
spillover from adjacent bands, accidental interference from malfunctioning equipment can act as 
ınterference sources [1]. 
Because of continuously increasing dependency of radio equipment on ships on the navigation and 
timing services of GNSS, the disruption of GNSS because of radio-frequency interference is a serious 
threat for the operation of governmental agencies in the maritime domain. In the past, there have 
been a number of reports about individual jamming and spoofing incidents in the costal sea areas. 
Nowadays, a good picture of the severity of the RFI threat can be obtained by using the 
corresponding information from the aviation domain where the PNT status of the onboard 
navigation system of an airplane is known from the radio messages of ADS-B [6] system used for 
aircraft collision avoidance. In this way the disruption of GNSS can be detected. By collecting the 
information from multiple airplanes passing through the same geographic area a reliable 
assessment of the strength of the RFI effect and the size of the affected areas can be obtained. An 
axample of such assessment results is presented in Figure 2-2. It can be observed, that large areas 
in the eastern Mediterranean, in the Black Sea and in the eastern part of the Baltic Sea are 
potentially affected by GNSS jamming. The size and position of the affected areas allows to assume 
that GNSS jJamming is used not by private persons but by state actors at the zone of international 
zonflicts. This highlights the necessity of monitoring the interference situation and developing 
adequate countermeasures for the GNSS receivers, including the receivers used by the German 
governmental agencies. 
One of the most promising technologies for detecting and mitigating radio-frequency interference 
is to make use of adaptive antenna arrays which allow to utilise the spatial domain of signal 
processing. The DLR Institute of Communications and Navigation (DLR-KN) has been working for 
more than 10 years on the development of array signal processing techniques for GNSS and the 
practical demonstration of the advantages of such systems. In this context, a demonstrator GALANT 
of an RFl-resilient satellite navigation receiver was developed that can reliably detect and 
subsequently suppress RFI signals. Two different receiver platforms had been used by DLR-KN at 
the start of the project. The first platform, the GALANT receiver, is characterized by the ability to 
‚eceive open-service signals on GNSS frequencies E1 and E5a from up to seven antenna elements, 
Which results in a high degree of flexibility in the choice of signal processing algorithms. This 
platform had been already tested in two maritime measurement campaigns. As part of the DLR- 
internal EMSec project, the platform was used for jJamming and spoofing tests in the Baltic Sea. As 
part of the national SiNaFa project, the platform was used for long-time interference monitoring 
campaign on board of a Hapag Lloyd container ship. Though being very good for enabling 
Title: Final Report 
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