Blind Spoofer Detection and Mitigation using an Array of Spatially Distributed Subarrays

Marius Brachvogel, Michael Niestroj, Can Özmaden, Tobias Bamberg, Michael Meurer

Abstract: Spatial signal processing techniques using antenna arrays have proven as the most effective countermeasure against radio interference (RFI) and spoofers. Conventionally uniform rectangular arrays (URA) are used, which spread in two spatial dimensions. However, due to their large size, a hidden installation of those arrays in passenger cars is not possible, as a mounting below the metallic car body would block the signal reception and an apparent mounting on top of the car infringes the aesthetic design. The authors of this paper presented a new array design approach consisting of a set of at least two linear subarrays (ULAs) to counteract that problem: Through their reduced size, those ULAs can be mounted inside the synthetic parts of a car, such as the front and rear bumpers or the side mirrors. The authors have proved the robustness against jamming using a prototype of this new array concept by experiment. The next step of development is a performance analysis to identify and suppress more sophisticated error sources such as spoofers. Most state-of-the-art algorithms using array antennas for spoofing detection and mitigation are deterministic approaches. However, as they require exact knowledge about the pattern, frontend calibration and attitude estimation, blind algorithms are anticipated for spoofer detection and mitigation in combination with the array of subarrays. An active spoofer can be detected by comparing the spatial characteristics, i.e. the relative phase differences between the channels for each satellite during signal processing: The receiver estimates the covariance matrices of the correlator outputs and extracts the spatial characteristics of the received GNSS signals. In the nominal case the spatial characteristics will show nearly no correlation since all satellite signals are incident from different DOAs. In case of a spoofer, which transmits all spoofed satellite signals with one transmission antenna, and a receiver which locks onto its signals, the aforementioned phase differences will be highly correlated. A possible mitigation filter can be found and applied in the same way: Since the relative phase differences between the antenna channels are determined for the spoofer DOA, those can be used to form spatial filter weights to combine the spoofed signals destructively and mitigate the DOA of the spoofer. This paper introduces a new blind spoofing detection and mitigation method for arrays with distributed antenna elements. Both methods are described in detail and its performance are analyzed on a simulative basis and through a real-world spoofing measurement campaign. A spoofing attack using a satellite signal generator is set up and real data captured by software defined radios are processed with a GNSS software receiver. It is shown, that even under real-world conditions an incident spoofer can be successfully detected and mitigated by the new antenna array concept of distributed subarrays.
Published in: Proceedings of the 36th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2023)
September 11 - 15, 2023
Hyatt Regency Denver
Denver, Colorado
Pages: 3802 - 3814
Cite this article: Brachvogel, Marius, Niestroj, Michael, Özmaden, Can, Bamberg, Tobias, Meurer, Michael, "Blind Spoofer Detection and Mitigation using an Array of Spatially Distributed Subarrays," Proceedings of the 36th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2023), Denver, Colorado, September 2023, pp. 3802-3814. https://doi.org/10.33012/2023.19365
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