Global Positioning System Interference Research Articles

Impact of GPS Interference on Time Synchronization of DVB-T Transmitters

Nowadays, the Global Positioning System (GPS) is widely used in all aspects of our lives. GPS signals are not used only in positioning and navigation applications and services in transport and military, but, thanks to quite precise information about time, also for synchronization of world trade and synchronization of wireless transmitters. However, with the recent spread of location-based services, a large number of GPS jammers had appeared. Use of these jammers is prohibited by law; however, their use is gaining popularity especially in the transport segment since jammers can be used to trick vehicle onboard units and help avoid paying toll fees on highways or avoid tracking of company cars when used privately. In this paper, we will investigate the impact of GPS interference caused by jamming and spoofing on the synchronization of Single Frequency Network (SFN) Digital Video Broadcasting–Terrestrial (DVB-T) transmitters. Since GPS signals are used in the DVB-T SFN to provide synchronization which is crucial for the correct network operation, the interference of GPS signals can cause problems with signal distribution. Thus, signals received from a DVB-T SFN network might be out of synchronization and disrupt the service for users.

GPS Interference Signal Recognition Based on Machine Learning

The Global Positioning System (GPS) is not only widely used in navigation, measurement and other services, but also an indispensable key equipment for the military. With the increasing complexity of the communication environment and the increasing number of interference factors, the recognition of GPS interference signal types is a prerequisite for the development of efficient anti-interference means. This paper focuses on three typical GPS interference signals, by extracting four different entropy features including power spectral entropy, establishing a hybrid entropy dataset and then using support vector machine (SVM) and random forest (RF) methods so as to classify and identify the dataset. The results show that the RF has a high recognition rate for the interference signal, and the average accuracy is above 90%, which greatly exceeds the SVM. Also, in the three kinds of interference signals, the noise FM interference is the least concealed and the most easily recognized.

Design of a four‐element array for accurate direction of arrival estimation in phase interferometry systems

AbstractThis article proposes the design of a four‐element array antenna for the accurate direction of arrival (DOA) estimation of Global Positioning System (GPS) interference signals. The proposed array antenna has four individual antenna elements, and each element consists of a radiating patch on the upper layer and a feeding loop on the lower layer. The patch and loop are intentionally designed in a circular shape to obtain the symmetric current distributions on the radiators. The feeding loop is directly connected by two output ports of an external hybrid chip coupler, and the radiating patch is then electromagnetically coupled by near‐fields of the feeding loop. This feeding mechanism in the proposed structure allows for a more uniform current and H‐field distribution for phase characteristics of the radiation that are close to the ideal isotropic radiators in the azimuth angle. In addition, the high‐dielectric ceramic substrate is adopted to minimize the physical height of the antenna for the phase characteristics of the radiation close to the ideal isotropic radiators in elevation angles. To validate that the phase characteristics are similar to those of an ideal radiator, the DOA estimation performances are observed using a dual‐axis interferometry. The results demonstrate that the proposed four‐element array antenna with phase difference characteristics similar to those of an ideal radiator is suitable for the accurate DOA estimation of GPS interference signals.

Novel Anti-spoofing Methods Based on Discrete Wavelet Transform in the Acquisition and Tracking Stages of Civil GPS Receiver

The growing dependence of critical civil infrastructure on Global Positioning System (GPS) makes GPS interference not only a safety threat, but also a matter of national security. Spoofing could pose a major threat for GPS navigation systems, so the GPS users have to gain an in-depth understanding of GPS spoofing. Therefore, spoofing countermeasure is a significant subject of research these days. In this paper, we utilize wavelets transform (WT) as a tool that effectively hinders the adverse activities of these groups, and then introduce two novel methods to mitigate spoofing in the acquisition and tracking processes. In the first suggested algorithm, using WT in the acquisition process, we control satellite constellation to mitigate spoofing errors. After generating the in-phase and quadrature correlator output signals, called I and Q respectively, we apply the wavelet db3 to the Q samples to remove their noise components. In the second method, WT is used in a tracking loop. In this way, we apply sym4 to the Q arm, which results in spoofing reduction. We apply our new algorithms to both simulated and measurement data sets, to shed light on its performance. Results show that both methods successfully mitigate the spoofing effect on the tested data sets.

Dual-polarized GPS antenna array algorithm to adaptively mitigate a large number of interference signals

Intentional or unintentional interference experienced by the Global Positioning System (GPS) is a significant concern for GPS-based critical infrastructures and services including aviation. An effective way to mitigate GPS interference is to utilize a GPS antenna array capable of electronically changing its gain pattern. Although a conventional GPS antenna array consists of single-polarized antenna elements, a dual-polarized antenna array has the potential to mitigate approximately twice the number of interference signals in the spatial domain as a single-polarized array because of the additional degrees of freedom provided. This paper proposes an adaptive beamforming algorithm using a dual-polarized GPS antenna array for mitigation of interference signals with various polarizations. In this paper, a dual-polarized antenna element specifically refers to two co-located crossed linearly polarized dipole antennas. The proposed minimum-variance-distortionless-response (MVDR)-based space–time adaptive processing (STAP) method utilizes a novel constraint vector that is specially designed for a dual-polarized GPS array. As the proposed constraint vector considers realistic radiation patterns of the antenna, the performance of the proposed method in terms of the signal-to-interference-plus-noise power ratio (SINR) is noticeably superior to that of previous methods under a representative interference scenario. The performance of the proposed method is compared with three previous methods utilizing dual-polarized antenna arrays.

A Novel Ratio-Phase Metric of Signal Quality Monitoring for Real-Time Detection of GPS Interference

Through the growing usage of Global Positioning System (GPS) for civilian applications, healthcare of the system has special importance. However, according to the characteristics of the GPS signals, there is a possibility of interferences on GPS signals. Among all distorting factors, spoofing is more deceitful, because the civil receiver is not able to distinguish the counterfeit signal from the genuine signal. In recent years, many efforts have been made to deal with spoofing. We studied recognition of the clear certainty of a spoofed condition in this work, which focuses on Signal Quality Monitoring (SQM) method. In an effort to troubleshoot the previous metrics and methods, we have introduced a new metric for interference detection that investigate both of in-phase and quadrature components of correlation outputs also use parameters associated with the main peak in proper form. As a consequence of simultaneous evaluation of phase and amplitude of GPS signal, the proposed metric is more reliable and average of detection accuracy has increased from 1.3 (related to previous metrics) to 4.8.

De-noising and spoofing extraction from position solution using wavelet transform on stationary single-frequency GPS receiver in immediate detection condition

Abstract The growing dependence of critical civil infrastructure on global positioning system (GPS) makes GPS interference not only a safety threat, but also a matter of national security. The research done in this paper is initiated by the need to diminish this trouble on GPS based positioning. The suggested compensation technique assumes that the presence of a spoofing signal is immediately determined. The position residuals of the last authentic and new fake signals are passed to the wavelet transform (WT). We utilized WT for de-noising. Afterwards, position deviations due to an attack can be extracted and then the estimated position of the received signal will be corrected. As a primary step, the proposed algorithm has been implemented in a stationary software GPS receiver to prove the concept of the idea. The performance of the technique is validated using several laboratory and measurement data sets. Interference mitigation having tolerance of 3% and average of 99.5% is yielded on laboratory data set and complete compensation is achieved on measurement data set. The test results show that the proposed technique supremely gain strength the reliability of civil stationary GPS receiver against interference.

Robust Set-Membership Filtering Techniques on GPS Sensor Jamming Mitigation

The global positioning system (GPS) is a satellite-based navigation sensor that supplies the consumer/military users with the proper equipment access to accurate positioning and timing information anywhere in the world. Interference has a significant influence on the acquisition and tracking of satellite signals from a GPS sensor. An adaptive BEACON filter based on optimal bounding ellipsoid (OBE) criterion is proposed for GPS interference mitigation applications. The OBE algorithm that provides the low computational efficiency and highly selective update mechanism is adopted to adjust the weights and thereby track swiftly the stationary and non-stationary frequency modulation (FM) waveforms. According to the GPS signal specification, a time-varying error bound mechanism is derived and incorporated into the BEACON method. The remarkable properties of the proposed BEACON canceller are their rapider convergence rate and favorable lower complexity burden. Simulation results demonstrate that its SNR improvement factor exceeds the factors of conventional NLMS, SM-NLMS, and SM-APA filters under the single-tone CWI, multi-tone CWI, pulse CWI, and FM jamming environments, respectively.

Jamming mitigation in global positioning system receivers using wavelet packet coefficients thresholding

In this paper, the authors describe a new pre-correlation mitigation technique for global positioning system (GPS) receivers. Proposed mitigation technique is based on wavelet packet coefficients thresholding. This technique employs adaptive thresholding to mitigate GPS jammers. The authors compare proposed technique against discrete wavelet coefficient thresholding method. In this paper, the interferers are generated by an RF signal generator. The received GPS signal and interference are combined in a combiner. Then, the combined signal is processed by a software GPS receiver which includes the proposed mitigation technique. Simulation results show benefits of the proposed method in terms of signal-to-noise power ratio improvement and mean square error (MSE) in contrary to previous methods. Comparison of presented method and the discrete wavelet method illustrates that the average improvement is 50% and 80% in terms of SNR improvement and MSE, respectively.

Enhanced GPS interference detection and localisation

Low power levels of global positioning system (GPS) signals make them susceptible to radio frequency interference (RFI) from intentional or unintentional sources. Reliance of safety critical and modern applications on GPS has made GPS critical infrastructure which must be protected. Time-difference-of-arrival (TDOA) is a common approach for locating emitters. The TDOAs are estimated by correlating signals received at different sensor nodes. However, RFI detection can be hampered by the in-band GPS signals which create undesired correlation peaks that can be mistaken for weak RFI. A sub-space projection-based approach for removing the GPS signals and leaving the RFI is proposed, and its performance is evaluated using signals from two synchronised Spirent GPS signal generators captured using a NordNav multi-front-end receiver. The results show that the proposed approach can remove the GPS signals, resulting in better RFI detection and localisation performance under various scenarios.

Power minimization with derivative constraints for high dynamic GPS interference suppression

In this paper, a novel adaptive interference suppression algorithm is proposed for high dynamic GPS (global positioning system) receiver. The new method incorporates derivative constraints on the interference DOA (direction of arrival) into power minimization approach, which could broaden the width of nulls in the interferences directions and adapt to the rapid change of the interference directions. Compared with the traditional wide nulling algorithm based on the derivative constraints, the new method does not have to know or estimate the DOAs of the desired signal and the interference. The new method is firstly discussed in the context of spatial processing, and then extended to space-time adaptive processing to mitigate wideband diffusive multipath interference. Effectiveness of the new method is verified via simulation examples.

Multicomponent receiver architectures for GPS interference suppression

The global positioning system (GPS) is a one-way satellite-based navigation system employing spread-spectrum techniques that is widely used for commercial and military applications. Although the very low signal-to-noise ratio (SNR) is handled by the large spreading gain, GPS is susceptible to high-power interference signals and various types of jammers. We propose multicomponent receiver architectures for GPS interference suppression. A conventional antenna system is first considered which utilizes a minimum-variance distortionless-response (MVDR) beam former and assumes that the GPS signal angle of arrival (AOA) and the antenna model are known at the receiver. However, this receiver is sensitive to AOA estimation errors and can have a high computational complexity. This sensitivity problem is eliminated by a multicomponent system based on a multistage matched filter (MF). Since this MF receiver also has a high computational complexity because the jammer AOAs must be estimated, we introduce a blind interference canceler based on the constant modulus (CM) array that is insensitive to AOA estimation errors and has a low computational complexity. Computer simulations are provided to illustrate the performance of the various systems for interference suppression in example signal scenarios.

Test Results of the Joint FAA/DoD Investigation of GPS Interference

This paper describes the test results of the joint Federal Aviation Administration (FAA) and Department of Defense (DoD) effort to identify the source of interference to civil Global Positioning System (GPS) receivers, also known as the “wormhole,” observed in October 1994 just north of St. Louis, Missouri. The investigation focused on television transmissions as the possible cause of the interference. Flight tests were conducted in areas where theoretical analysis of TV transmissions indicated sufficient signal strength to affect GPS operation. These tests answered several technical questions regarding the potential for GPS interference and solved the “wormhole” mystery. This paper also describes the effects of electromagnetic polarization on GPS operations.