Abstract

Jamming and spoofing are the two main types of intentional interference for global navigation satellite system (GNSS) receivers. Due to the entirely different signal characteristics they have, a few techniques can deal with them simultaneously. This paper proposes a two-stage interference suppression scheme based on antenna arrays, which can detect and mitigate jamming and spoofing before the despreading of GNSS receivers. First, a subspace projection was adopted to eliminate the high-power jamming signals. The output signal is still a multi-dimensional vector so that the spatial processing technique can be used in the next stage. Then, the cyclostationarity of GNSS signals were fully excavated to reduce or even remove the noise component in the spatial correlation matrix. Thus, the signal subspace, including information of the power and the directions-of-arrival (DOAs) of the GNSS signals, can be obtained. Next, a novel cyclic correlation eigenvalue test (CCET) algorithm was proposed to detect the presence of a spoofing attack, and the cyclic music signal classification (Cyclic MUSIC) algorithm was employed to estimate the DOAs of all the navigation signals. Finally, this study employed a subspace projection again to eliminate the spoofing signals and provide a higher gain for authentic satellite signals through beamforming. All the operations were performed on the raw digital baseband signal so that they did not introduce additional computational complexity to the GNSS receiver. The simulation results show that the proposed scheme not only suppresses jamming and spoofing effectively but also maximizes the power of the authentic signals. Nonetheless, the estimated DOA of spoofing signals may be helpful for the interference source positioning in some applications.

Highlights

  • With the extensive application of global navigation satellite systems (GNSS) in both military and civilian fields, the research of navigation countermeasure technology has gained more and more attention

  • A uniform linear array was used, in which ten omnidirectional antennas were arranged in a straight line and the spacing between adjacent elements was half of a GPS L1 were arranged in a straight line and the spacing between adjacent elements was half of a GPS L1 wavelength

  • Five authentic satellite signals PRN2, PRN5, PRN8, PRN19 and PRN26 were transmitted from the direction at the azimuth of −50°, −30°, 0°, 20° and 70° with the power assumed to be −157 dBW

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Summary

Introduction

With the extensive application of global navigation satellite systems (GNSS) in both military and civilian fields, the research of navigation countermeasure technology has gained more and more attention. Due to the inherent weakness of the satellite navigation systems, GNSS receivers are susceptible to both intentional and unintentional interference [1,2]. A jammer transmits high-power signals to the target receiver, which is very easy to implement because the power of the satellite signal reaching the ground is weak (about 20–30 dB below the thermal noise). Spatial processing based on an antenna array is considered as the most effective one. It can shape the reception beam pattern of the antenna array to form nulls toward jamming sources, the interferences are suppressed [8,9]

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