Avionics-based GNSS integrity augmentation performance in a jamming environment

Intentional and unintentional radiofrequency interference (i.e., jamming) can result in degraded navigation accuracy or complete loss of the GNSS signal tracking. Jammers can be classified into three broad categories: Narrowband Jammers (NBJ), Spread Spectrum Jammers(SSJ) and Wideband Gaussian Jammers (WGJ). In recent years, a number of effective jamming detection and anti-jamming (filtering and suppression) techniques have been developed for military GNSS applications and some of them are envisaged to be used for civil purposes (e.g., terrorist attacks). The synergies between these jamming detection techniques and our newly developed Avionics-Based Integrity Augmentation (ABIA) system are investigated in this paper. In particular, GNSS vulnerability to NBJ, SSJ and WGJ types of jamming is analytically described in terms of Jamming to Signal (J/S) tracking thresholds and the models for calculating the minimum acceptable aircraft-to-jammer ranges are presented. Simulation results demonstrate that the proposed ABIA architecture is capable of performing jamming detection and avoidance when GNSS is considered as the primary source of navigation data

Reason-Resilience and security of geospatial data for critical infrastructures

Peer reviewe

Cooperative Interference Detection, Localization, and Mitigation in GNSS

Due to the low cost of GNSS receivers and their consequent diffusion, a wide range of location-aware applications are arising. Some of these applications are critical and have strict requirements in terms of availability, integrity and reliability. Examples of critical applications are precision landing and en-route navigation in air transportations; automated highways and mileage-based toll in road transportations; search and rescue in safety of life applications. A failure in fulfilling one or more requirements of a critical application may have dramatic consequences and cause serious damage. One of the most challenging threats for critical GNSS application, is represented by interference. In particular, jamming devices, operating inside GNSS bands, are easily and cheaply purchasable on the Internet. These devices transmit disturbing signals with the aim of preventing the correct operations of GNSS receivers. In order to satisfy the requirements of critical applications, it is necessary to promptly detect, localize and remove such interfering sources. Moreover, it is important to characterize the interfering signals in order to develop interference avoidance and mitigation techniques that ensure robustness of GNSS receivers to interference. This thesis studies the problem of interference in GNSS, from a cooperative perspective

Radio Frequency Interference Impact Assessment on Global Navigation Satellite Systems

The Institute for the Protection and Security of the Citizen of the EC Joint Research Centre (IPSC-JRC) has been mandated to perform a study on the Radio Frequency (RF) threat against telecommunications and ICT control systems. This study is divided into two parts. The rst part concerns the assessment of high energy radio frequency (HERF) threats, where the focus is on the generation of electromagnetic pulses (EMP), the development of corresponding devices and the possible impact on ICT and power distribution systems. The second part of the study concerns radio frequency interference (RFI) with regard to global navigation satellite systems (GNSS). This document contributes to the second part and contains a detailed literature study disclosing the weaknesses of GNSS systems. Whereas the HERF analysis only concerns intentional interference issues, this study on GNSS also takes into account unintentional interference, enlarging the spectrum of plausible interference scenarios.JRC.DG.G.6-Security technology assessmen

다중 기준국 기반의 위성항법시스템 기만신호 검출 및 위치추정 기법

학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부, 2015. 2. 박찬국.위성항법시스템은 인공위성을 이용하는 전파항법시스템으로 사용자의 위치 및 시각을 정밀하게 측정할 수 있어 국방뿐 아니라 다양한 민수분야에서 광범위하게 활용되고 있다. 그러나 약 2만킬로미터 상공으로부터 수신기에 도달하는 위성항법신호의 세기는 잡음 레벨 이하이므로 전파교란신호에 취약하다는 단점이 있다. 전파교란신호는 크게 자연적인 전파교란신호와 인위적인 전파교란신호로 구분할 수 있는데, 그 중에서 인위적인 전파교란신호는 특정 목적에 의해서 시스템에 악영향을 주므로 이에 대응하는 연구가 필요하다. 인위적인 전파교란신호는 재밍, 미코닝, 기만신호로 나눌 수 있고 이중에서 기만신호는 실제 위성항법신호를 그대로 모사하여 수신기를 기만시킨 후에 잘못된 항법해를 유발시키기 때문에 심각한 결과를 초래할 수 있다. 따라서 본 논문에서는 기만신호에 대한 대응기법으로 다중 기준국 기반에서 항법해 품질을 감시하기 위해 기만신호를 검출하고 위치를 추정하는 방법에 대한 연구를 진행하였다. 기만신호를 검출하는 방법은 검출 파라미터 및 기만 시나리오에 따라 다양한 방법들이 있으며 최근 몇 년 동안 연구가 활발히 진행되고 있다. 본 논문에서는 다양한 기만 시나리오를 포괄적으로 검출하기 위한 방법으로 이미 알고 있는 고정된 위치의 기준국 기반에서 적응 페이딩 칼만 필터의 페이딩 팩터를 검출 파라미터로 사용한 검출방법에 대해서 소개하였다. 이때 기만신호는 스마트 기만 시나리오를 모사하여 그 영향을 램프 바이어스 형태의 의사거리 오차로 모델링 하였다. 또한 이에 따른 페이딩 팩터 변화값을 정량적으로 분석하였고 분석결과를 바탕으로 기만신호 검출을 위한 임계치를 설정하였다. 이 방법은 최종적으로 페이딩 팩터로 칼만 게인을 조절함으로써 기만신호의 영향을 완화시키는 효과도 나타났다. 앞에서 설명한 기만신호 검출 방법을 이용하여 기만신호가 있다고 판단하면 다중 기준국에서의 측정치를 통해 기만신호원의 위치를 추정하게 된다. 전파간섭원의 위치를 추정하는 방법은 사용하는 측정치에 따라 다양하게 분류되는데 본 논문에서는 주기준국을 기준으로 하여 각 기준국에서 수신된 신호세기차이를 이용하여 위치를 추정하였으며, 이때 신호세기 측정치로 C/No를 사용하였고 시뮬레이션을 위해 전파손실모델은 COST231-Walfisch-Ikegami 모델을 사용하여 신호감쇄를 계산하였다. 본 논문에서 제안한 검출 및 위치추정 기법은 각각 간단한 시뮬레이션을 통해 성능을 분석하였다. 이러한 방법은 채널별 의사거리 이상을 검출할 수 있으므로 사용자의 위치가 고정된 경우 무결성 감시 알고리즘으로 사용이 가능할 것으로 기대된다. 또한 추가적인 하드웨어나 복잡한 알고리즘 구현이 필요하지 않아 실용적인 측면에서 유용할 것으로 기대된다.The Global Navigation Satellite System (GNSS) is a radio navigation system using satellites and has been widely used by both military and civilian systems since it can provide an accurate position and timing information to users. However, the strength of the GNSS signal on the users receiver is weak since GNSS satellites are approximately 20,000 Km away and transmit several watts of signal power such that at the ground level. Therefore, GNSS signal is quite vulnerable to different types of interference. Interference signals can be categorized as unintentional and intentional. Intentional interference, such as jamming, meaconing, and spoofing, are specifically designed with malicious intention to deny or mislead GNSS receivers, thus they are serious threat to GNSS applications. Among them, spoofing is much more dangerous since it is designed to mislead their target receiver that is not aware of the attack and this can lead to disastrous consequences in scores of applications. Therefore, in this thesis, a detection and localization method for GNSS spoofing signal based on multiple base stations has been researched for monitoring the quality of navigation solutions. There are various spoofing detection methods according to detection parameters and spoofing scenarios. The related researches have been actively performed for recent years. In this thesis, GNSS spoofing detection method based on adaptive fading Kalman filter is proposed to detect spoofing signal and the fading factor of the filter is used as a detection parameter. In order to detect spoofing signal regardless of spoofing scenarios, the proposed method is based on multiple base stations whose locations are fixed and already known. The effect of the spoofing is modeled by the ramp type bias error of the pseudorange to emulate smart spoofer. In addition, the change of the fading factor according to ramp type bias error is quantitatively analyzed and the detection threshold is established to detect spoofing signal by analyzing the change of the error covariance. The proposed method also has an effect on spoofing mitigation by adjusting the Kalman gain of the filter. If spoofing signal is detected by using the proposed method, spoofing localization method based on multiple base stations is performed to estimate spoofing location. There are various localization methods according to measurements. However, in this thesis, spoofing location is estimated by differential received signal strength (DRSS) method because of simplicity and efficiency. The carrier to noise ratio (C/No) measurement characterizes the received signal strength (RSS), therefore, the difference of the C/No between main station (MS) and each base station (BS) is used as measurement for DRSS method. In addition, the Cost231-Walfisch-Ikegami model is applied as path-loss model for calculating signal attenuation. To verify the performance analysis of the proposed spoofing detection and localization method, simple simulations are implemented, respectively. This method can be applied for integrity monitoring algorithm in case of fixed user because it can detect abnormal pseudorange of each channel. In addition, this method is expected to be easily applied to practical system because they do not need to additional hardware and realization of complex algorithm.Abstract i Contents iv List of Figures vi List of Tables vii Chapter 1.Introduction 1 1.1 Motivation and Background 1 1.2 Objectives and Contributions 2 1.3 Organization 2 Chapter 2. GNSS Intentional Interference 4 2.1 Introduction 4 2.2 Jamming 5 2.3 Meaconing 8 2.4 Spoofing 11 Chapter 3. Spoofing Detection Method 13 3.1 Introduction 13 3.2 Adaptive Fading Kalman Filter 15 3.2.1 Backgroud 15 3.2.2 Adaptive Fading Factor 17 3.2.3 Parameter Analysis 21 3.3 Simulation 25 Chapter 4. Spoofing Localization Method 34 4.1 Introduction 34 4.2 DRSS Method 35 4.3 Simulation 38 Chapter 5. Conclusions 43 Bibliography 45 국문초록 51Maste

Interference Mitigation and Localization Based on Time-Frequency Analysis for Navigation Satellite Systems

Interference Mitigation and Localization Based on Time-Frequency Analysis for Navigation Satellite SystemsNowadays, the operation of global navigation satellite systems (GNSS) is imperative across a multitude of applications worldwide. The increasing reliance on accurate positioning and timing information has made more serious than ever the consequences of possible service outages in the satellite navigation systems. Among others, interference is regarded as the primary threat to their operation. Due the recent proliferation of portable interferers, notably jammers, it has now become common for GNSS receivers to endure simultaneous attacks from multiple sources of interference, which are likely spatially distributed and transmit different modulations. To the best knowledge of the author, the present dissertation is the first publication to investigate the use of the S-transform (ST) to devise countermeasures to interference. The original contributions in this context are mainly: • the formulation of a complexity-scalable ST implementable in real time as a bank of filters; • a method for characterizing and localizing multiple in-car jammers through interference snapshots that are collected by separate receivers and analysed with a clever use of the ST; • a preliminary assessment of novel methods for mitigating generic interference at the receiver end by means the ST and more computationally efficient variants of the transform. Besides GNSSs, the countermeasures to interference proposed are equivalently applicable to protect any direct-sequence spread spectrum (DS-SS) communication

Signal processing techniques for GNSS anti-spoofing algorithms

The Global Navigation Satellite Systems (GNSS) usage is growing at a very high rate, and more applications are relying on GNSS for correct functioning. With the introduction of new GNSSs, like the European Galileo and the Chinese Beidou, in addition to the existing ones, the United States Global Positioning System (GPS) and the Russian GLONASS, the applications, accuracy of the position and usage of the signals are increasing by the day. Given that GNSS signals are received with very low power, they are prone to interference events that may reduce the usage or decrease the accuracy. From these interference, the spoofing attack is the one that has drawn major concerns in the GNSS community. A spoofing attack consist on the transmission of GNSS-like signals, with the goal of taking control of the receiver and make it compute an erroneous position and time solution. In the thesis, we focus on the design and validation of different signal processing techniques, that aim at detection and mitigation of the spoofing attack effects. These are standalone techniques, working at the receiver’s level and providing discrimination of spoofing events without the need of external hardware or communication links. Four different techniques are explored, each of them with its unique sets of advantages and disadvantages, and a unique approach to spoofing detection. For these techniques, a spoofing detection algorithm is designed and implemented, and its capabilities are validated by means of a set of datasets containing spoofing signals. The thesis focuses on two different aspects of the techniques, divided as per detection and mitigation capabilities. Both detection techniques are complementary, their joint use is explored and experimental results are shown that demonstrate the advantages. In addition, each mitigation technique is analyzed separately as they require specialized receiver architecture in order to achieve spoofing detection and mitigation. These techniques are able to decrease the effects of the spoofing attacks, to the point of removing the spoofing signal from the receiver and compute navigation solutions that are not controlled by the spoofer and lead in more accurate end results. The main contributions of this thesis are: the description of a multidimensional ratio metric test for distinction between spoofing and multipath effects; the introduction of a cross-check between automatic gain control measurements and the carrier to noise density ratio, for distinction between spoofing attacks and other interference events; the description of a novel signal processing method for detection and mitigation of spoofing effects, based on the use of linear regression algorithms; and the description of a spoofing detection algorithm based on a feedback tracking architecture

On the Use of an Ultra-Tight Integration for Robust Navigation in Jammed Scenarios

Peer reviewe

Modes dégradés résultant de l'utilisation multi constellation du GNSS

Actuellement, on constate dans le domaine de la navigation, un besoin croissant de localisation par satellites. Apres une course a l'amelioration de la precision (maintenant proche de quelques centimetres grace a des techniques de lever d'ambiguite sur des mesures de phase), la releve du nouveau defi de l'amelioration de l'integrite du GNSS (GPS, Galileo) est a present engagee. L'integrite represente le degre de confiance que l'on peut placer dans l'exactitude des informations fournies par le systeme, ainsi que la capacite a avertir l'utilisateur d'un dysfonctionnement du GNSS dans un delai raisonnable. Le concept d'integrite du GNSS multi-constellation necessite une coordination au niveau de l'architecture des futurs recepteurs combines (GPS-Galileo). Le fonctionnement d'un tel recepteur dans le cas de passage du systeme multi-constellation en mode degrade est un probleme tres important pour l'integrite de navigation. Cette these se focalise sur les problemes lies a la navigation aeronautique multiconstellation et multi-systeme GNSS. En particulier, les conditions de fourniture de solution de navigation integre sont evaluees durant la phase d'approche APV I (avec guidage vertical). En disposant du GPS existant, du systeme Galileo et d'un systeme complementaire geostationnaire (SBAS), dont les satellites emettent sur des frequences aeronautiques en bande ARNS, la question fondamentale est comment tirer tous les benefices d'un tel systeme multi-constellation pour un recepteur embarque a bord d'un avion civil. En particulier, la question du maintien du niveau de performance durant cette phase de vol APV, en termes de precision, continuite, integrite et disponibilite, lorsque l'une des composantes du systeme est degradee ou perdu, doit etre resolue. L'objectif de ce travail de these est donc d'etudier la capacite d'un recepteur combine avionique d'effectuer la tache de reconfiguration de l'algorithme de traitement apres l'apparition de pannes ou d'interferences dans une partie du systeme GNSS multiconstellation et d'emettre un signal d'alarme dans le cas ou les performances de la partie du systeme non contaminee ne sont pas suffisantes pour continuer l'operation en cours en respectant les exigences de l'aviation civile. Egalement, l'objectif de ce travail est d'etudier les methodes associees a l'execution de cette reconfiguration pour garantir l'utilisation de la partie du systeme GNSS multi-constellation non contaminee dans les meilleures conditions. Cette etude a donc un interet pour les constructeurs des futurs recepteurs avioniques multiconstellation. ABSTRACT : The International Civil Aviation Organization (ICAO) has defined the concept of Global Navigation Satellite System (GNSS), which corresponds to the set of systems allowing to perform satellite-based navigation while fulfilling ICAO requirements. The US Global Positioning Sysem (GPS) is a satellite-based navigation system which constitutes one of the components of the GNSS. Currently, this system broadcasts a civil signal, called L1 C/A, within an Aeronautical Radio Navigation Services (ARNS) band. The GPS is being modernized and will broadcast two new civil signals: L2C (not in an ARNS band) and L5 in another ARNS band. Galileo is the European counterpart of GPS. It will broadcast three signals in an ARNS band: Galileo E1 OS (Open Service) will be transmitted in the GPS L1 frequency band and Galileo E5a and E5b will be broadcasted in the same 960-1215 MHz ARNS band than that of GPS L5. GPS L5 and Galileo E1, E5a, E5b components are expected to provide operational benefits for civil aviation use. However, civil aviation requirements are very stringent and up to now, the bare systems alone cannot be used as a means of navigation. For instance, the GPS standalone does not implement sufficient integrity monitoring. Therefore, in order to ensure the levels of performance required by civil aviation in terms of accuracy, integrity, continuity of service and availability, ICAO standards define different systems/algorithms to augment the basic constellations. GPS, Galileo and the augmentation systems could be combined to comply with the ICAO requirements and complete the lack of GPS or Galileo standalone performance. In order to take benefits of new GNSS signals, and to provide the service level required by the ICAO, the architecture of future combined GNSS receivers must be standardized. The European Organization for Civil Aviation Equipment (EUROCAE) Working Group 62, which is in charge of Galileo standardization for civil aviation in Europe, proposes new combined receivers architectures, in coordination with the Radio Technical Commission for Aeronautics (RTCA). The main objective of this thesis is to contribute to the efforts made by the WG 62 by providing inputs necessary to build future receivers architecture to take benefits of GPS, Galileo and augmentation systems. In this report, we propose some key elements of the combined receivers' architecture to comply with approach phases of flight requirements. In case of perturbation preventing one of the needed GNSS components to meet a phase of flight required performance, it is necessary to be able to switch to another available component in order to try to maintain if possible the level of performance in terms of continuity, integrity, availability and accuracy. That is why future combined receivers must be capable of detecting the impact of perturbations that may lead to the loss of one GNSS component, in order to be able to initiate a switch. These perturbations are mainly atmospheric disturbances, interferences and multipath. In this thesis we focus on the particular cases of interferences and ionosphere perturbations. The interferences are among the most feared events in civil aviation use of GNSS. Detection, estimation and removal of the effect of interference on GNSS signals remain open issues and may affect pseudorange measurements accuracy, as well as integrity, continuity and availability of these measurements. In literature, many different interference detection algorithms have been proposed, at the receiver antenna level, at the front-end level. Detection within tracking loops is not widely studied to our knowledge. That is why, in this thesis, we address the problem of interference detection at the correlators outputs. The particular case of CW interferences detection on the GPS L1 C/A and Galileo E1 OS signals processing is proposed. Nominal dual frequency measurements provide a good estimation of ionospheric delay. In addition, the combination of GPS or GALILEO navigation signals processing at the receiver level is expected to provide important improvements for civil aviation. It could, potentially with augmentations, provide better accuracy and availability of ionospheric correction measurements. Indeed, GPS users will be able to combine GPS L1 and L5 frequencies, and future GALILEO E1 and E5 signals will bring their contribution. However, if affected by a Radio Frequency Interference, a receiver can lose one or more frequencies leading to the use of only one frequency to estimate the ionospheric code delay. Therefore, it is felt by the authors as an important task to investigate techniques aimed at sustaining multi-frequency performance when a multi constellation receiver installed in an aircraft is suddenly affected by radiofrequency interference, during critical phases of flight. This problem is identified for instance in [NATS, 2003]. Consequently, in this thesis, we investigate techniques to maintain dual frequency performances when a frequency is lost (L1 C/A or E1 OS for instance) after an interference occurrence