Dan Lu

Spoofing Jamming Suppression Techniques for GPS Based on DOA Estimating

This paper studies GPS receiver anti-spoofing jamming problems. Unlike blanket jamming, spoofing jamming is hidden because its power level below noise floor. Besides, spoofing jamming has the same format with satellite signals. A designed spoofing jamming can guide GPS receiver positioning errors occurred and change its navigation line. The existing jamming suppression methods of satellite navigation systems are more suitable for blanket jamming suppression, while for spoofing jamming suppression, these methods are almost invalid. The current published literature make the spoofing jamming detection technology as the major research direction, and rarely involve how to suppress spoofing jamming. This paper analyzes the characteristics of repeater spoofing jamming. For one and multiple of repeater spoofing jamming scenarios, beam forming and RELAX algorithm are proposed to estimate the DOA (Direction of Arrival) of spoofing jamming respectively. After detecting the DOA of spoofing jamming, GPS receiver can steer nulling to the direction of spoofing jamming and suppress spoofing jamming by constructing the projection matrix of spoofing jamming. Simulation experiments prove the correctness and the effectiveness of the two methods.

A High-Dynamic Null-Widen GPS Anti-jamming Algorithm Based on Statistical Model of the Changing Interference DOA

The directions of arrival (DOA) of interference changes rapidly with time in high-dynamic satellite navigation system, which leads to the mismatch between weights training data and weights applying data during the adaptive processing. In this case, the conventional adaptive anti-jamming algorithms are invalid since jammers may easily move out of the array pattern nulls and could not be suppressed. In this letter, a novel method of null-widen is deduced based on the Laplace distribution model of the changing interference DOA in high-dynamic environment. By taking the moving interferences as discrete interference sources obey the Laplace distribution, the extension matrix can be obtained and the average covariance matrix can be calculated from matrix product to broaden the width of nulls. The new method does not alter the noise contribution to the covariance matrix and does not require information about interference DOA. The width of nulls is easy to control. In addition, by combining with the power minimization approach, the new null-widen method does not need the DOA of desired satellite signal. The proposed method can provide correctly acquisition.

A High-Dynamic Null-Widen GNSS Anti-jamming Algorithm Based on Reduced-Dimension Space-Time Adaptive Processing

Space-Time Adaptive Processing (STAP) is an effective method to suppress interference in Global Navigation Satellite System (GNSS). But in high-dynamic environment, conventional adaptive anti-jamming algorithms are invalid since jammers may easily move out of the array pattern nulls. To solve this problem, a new null-widen method based on the Laplace distribution model is deduced in this paper, the method can get wider null at direction of jammers. However this method is computationally intensive by using STAP, thus a new null-widen method based on reduced-dimension multistage wiener filters (MWF) is deduced here. It has proved in simulation section that the new method can get better performance in few snapshots.

Principles of Satellite Navigation System

Satellite navigation is the technology that uses navigation satellites to transmit positioning signals, in order to provide real-time positioning for users in the air, on the ground, at sea, and in space. Since it can provide high-precision information such as three-dimensional position, velocity and time (PVT) for any location and on any people and objects, it has unparalleled advantages over other navigational technologies. Thus, it can be widely applied in civil fields such as transportation, surveying, mapping, telecommunications, water conservancy, fishery, forest fire prevention, disaster reduction, and disaster relief. It can also be used in military fields such as aerospace and weapon guidance. Consequently, the satellite navigation system has become a keystone for a country’s space information infrastructure, and an important indicator to reflect its status as a modern country, a great power, and the country’s comprehensive national strength. Major countries and organizations all around the world have been vigorously developing satellite navigation systems with various characteristics.

Multipath Interference Suppression

Interferences on GNSS can be categorized into two types: intentional interference and unintentional interference. Jamming and spoofing, mainly discussed in Chaps. 2 and 4 in this book, belong to the category of intentional interference. Multipath interference studied in this chapter, and pulse interference that will be studied in Chap. 6 both belong to unintentional interference.

Pulse Interference Suppression Techniques

Intentional interferences mainly include multipath interference and pulse interference. We studied multipath interference in the last chapter. In this chapter we study the suppression of the other type of intentional interference—the pulse interference.

Spoofing Countermeasure Techniques

As described in Chap. 1, common types of intentional interference mainly include jamming and spoofing. Chapters 2 and 3 mainly discuss jamming. In this chapter we discuss techniques to suppress the interference emitted by spoofers. Different from jamming, the power level, signal format and frequency spectrum structure of interference emitted by spoofers are similar to the authentic satellite signals. The intent of spoofing is to trick a receiver locking onto interference without awareness, so a navigational positioning result, which seems to be reliable but actually misleading, can be produced. In the worst case, a receiver may be controlled by spoofers. Under the impacts of spoofing, receivers usually are not aware of the spoofers, so consequently spoofing is more harmful than jamming.

High-Dynamic GNSS Jamming Suppression Techniques

All the jamming mitigation techniques introduced in Chap. 2 assume that receivers are in a stationary state or in a state of low to medium dynamic motion, which means that relative to GNSS receivers, the direction of jamming does not change or changes slowly, as a result there is enough snapshots to perform jamming covariance matrix estimation, so adaptive jamming suppression can be achieved.

Spoofing Interference Suppression for GNSS Based on Estimating Steering Vectors

The paper proposes a spoofing interference suppression algorithm for multiple spoofing interferences existing simultaneously. First, the signals which received from the reference antenna array are captured. The information about visible satellite signals’ Doppler frequency and code delay are acquired. Using these information, we can reconstruct the visible satellite signals. Then, the visible satellite signals’ steering vectors are estimated by calculating cross-correlation between the estimated visible satellite signals and the antenna array received signals. Utilizing the normalized cross-correlation coefficients of the visible satellite signals’ steering vectors to detect spoofing interference and its steering vectors. Final, the proposed algorithm constructs an orthogonal projection matrix based on spoofing interference’ steering vectors. Spoofing interference are suppressed by utilizing the constructed orthogonal projection matrix. The proposed novel spoofing interference suppression algorithm can simultaneously suppress multiple spoofing interference, which does not need to know the array manifold in advance and the DOAs (Direction of Arrival) of satellite signals and spoofing interference.

Satellite Navigation Anti-jamming Algorithm Based on Extended Array

In the complex electromagnetic environment, the Global Navigation Satellite System (GNSS) was seriously influenced by the interference. The anti-jamming algorithm based on the uniform array have been widely used in GNSS interference suppression technology, but the number of the interference is limited by the number of the antenna sensor. This paper proposed an interference suppression algorithm based on the extended array, the algorithm could suppress more interference than the number of antenna sensor. Firstly, the covariance matrix of the non-uniform array is vectorized. After that, the spatial smoothing is used to build up the rank of the covariance matrix. With the smoothed covariance matrix, power inversion algorithm is used to estimate the directions of the interference. Then, forming an overdetermined equation based on the interference subspace and an arbitrary signal’s steering vector, whose direction is different form the interference. Finally, solving its least-squares solution to get the optimal weight, which can form nulls in the direction of interference without affecting the useful signal. The simulation results verify the effectiveness of the proposed algorithm.