Qiongqiong Jia

Adaptive Interference Mitigation in GNSS

Principles of Satellite Navigation System -- Jamming Suppression -- High-Dynamic Jamming Suppression -- Spoofing Suppression -- Multipath Interference Suppression -- Pulsed Interference Suppression.

Multipath interference mitigation in GNSS via WRELAX

In order to suppress the multipath interference in global navigation satellite system, two algorithms based on NLS (nonlinear least square) parameter estimation are proposed. Instead of the classic delay lock loop, the first proposed algorithm estimates the parameters of the line of sight signal and the multipath interference in the correlation domain. The NLS cost function is solved by WRELAX (weighted Fourier transform and RELAXation), which decouples the multidimensional optimization problem into a sequence of one-dimensional optimization problems in a conceptually and computationally simple way. In order to further reduce the complexity, the second NLS algorithm utilizing the characteristic of the C/A code is proposed, which estimate the parameters in the data domain. Finally, the two proposed algorithms are compared with the existing multipath interference methods and show excellent performance and less computational burden.

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.

FFT-Based Efficient Algorithms for Time Delay Estimation

Suppose that we have a single sensor receiving a superimposition of attenuated and delayed replicas of a known signal plus noise. From the received data we want to estimate the arrival times of the various replicas and their (complex or real) attenuation coefficients (gains). This is the well-known time delay estimation problem which occurs in many fields including radar, active sonar, wireless communications, Global Navigation Satellite System (GNSS), nondestructive testing, geophysical/seismic exploration, and medical imaging. In this chapter, we will focus on time delay estimation based on one sensor with known probing signal shapes.

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.

Adaptive blind anti-jamming algorithm using acquisition information to reduce the carrier phase bias

Jamming destroys the integrity and functionality of the Global Satellite Navigation System (GNSS) in various applications. Hence, anti-jamming techniques are critical. The most significant problem with the existing array-based anti-jamming technique in GNSS is the errors introduced in the carrier phase, which affects the GNSS solution, especially for high-precision measurement applications. We present an adaptive array-based blind anti-jamming algorithm for GNSS high-precision applications. The main advantages of the proposed algorithm include (1) the received data containing multiple satellite signals are processed in parallel channels simultaneously thanks to the acquisition information. (2) The adaptive weight is constructed in each individual channel, directly from an eigenvector of the despread data covariance matrix, resulting in low implementation complexity. (3) The carrier phase of the weighted data at the initial moment is used to normalize the subsequent ones, so as to completely remove the introduced carrier phase bias by adaptive weighting. (4) Since the array manifold is not used, the proposed algorithm is robust to array errors. Theoretical and numerical simulations verify the superiority of the proposed algorithm.