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Critical Links Detection in Spatial-Temporal Airway Networks Using Complex Network Theories
No full textInternational audienceIn an airway network, some critical links exist that are vital for the structural integrity and performance of the network. The detection of such links may assist with improving the imbalance between the limited airspace capacity and the ever-increasing traffic demand, which elicit flight delays, significant economic losses, etc. However, it is challenging to identify such links as they evolve (both in space and time) with changing traffic flow dynamics. This paper proposes a complex network approach for spatial-temporal critical links detection in a given airway network. First, flight track data is employed to characterize the airway network as weighted spatial-temporal networks. Then edge centrality and network percolation metrics are adopted to detect the critical links in each snapshot of the spatial-temporal networks. Afterward, the critical links detected by the two metrics are spatially overlapped to determine the final critical links over time. To examine the operational validity of the proposed method, we carry out a case study on the Southeast Asia airway network derived from one-month flight track data. Results demonstrate that the spatial distribution of the critical links varies over different traffic scenarios, and most of the identified critical links are found in the transition sectors with complex traffic situations. Four links, which are parts and at crosses of major trunk airways connecting to major navigation aids (VOR/DME) in the studied network, appear highly in all examined traffic scenarios. The unavailability of such links may lead to traffic flow disruptions. Observations by subject matter experts from air-traffic data visualizations demonstrate that the complex network-based methods can dynamically identify airway links that are operationally critical under time-evolving air-traffic scenarios. With good traffic flow prediction tools in the future, this method can be adopted to predict critical links in airway networks to better assist controllers in real-time air traffic management
A Multifractal Analysis and Machine Learning Based Intrusion Detection System with an Application in a UAS/RADAR System
No full textInternational audienceThe rapid development of Internet of Things (IoT) technology, together with mobile network technology, has created a never-before-seen world of interconnection, evoking research on how to make it vaster, faster, and safer. To support the ongoing fight against the malicious misuse of networks, in this paper we propose a novel algorithm called AMDES (unmanned aerial system multifractal analysis intrusion detection system) for spoofing attack detection. This novel algorithm is based on both wavelet leader multifractal analysis (WLM) and machine learning (ML) principles. In earlier research on unmanned aerial systems (UAS), intrusion detection systems (IDS) based on multifractal (MF) spectral analysis have been used to provide accurate MF spectrum estimations of network traffic. Such an estimation is then used to detect and characterize flooding anomalies that can be observed in an unmanned aerial vehicle (UAV) network. However, the previous contributions have lacked the consideration of other types of network intrusions commonly observed in UAS networks, such as the man in the middle attack (MITM). In this work, this promising methodology has been accommodated to detect a spoofing attack within a UAS. This methodology highlights a robust approach in terms of false positive performance in detecting intrusions in a UAS location reporting system
L'utilisation des blockchains pour renforcer la sécurité etaméliorer la confiance dans les réseaux distribués
No full textAs of 2016, the number of deaths induced by road injuries reached 1.35 million andis often due to human error. The technological expansion of the Internet and interconnected devices facilitate the exchange of information, sometimes vital. That is why a lot of work has been done towards the automatization of vehicles. Improving roadsafety is one of the motivational factors for research in this area and the widespreadadoption of Intelligent Transportation Systems (ITSs) and Vehicular Ad-hoc NETworks(VANETs).A VANET is defined as a particular ad-hoc network formed by vehicles with processingand wireless communication abilities, evolving in an urban environment (streets orhighways). Vehicles can communicate either directly or through an intermediary node.The main focus of security in VANETs and vehicular communications is on providingintegrity of the exchanged messages and availability of the services that support them,rather than the confidentiality of what they contain. Providing accountability, i.e. away to identify the communicating entities and hold them accountable for the messagesthey broadcast, in vehicular communications is essential. It ensures that any faulty ormisbehaving node is identified, revoked, eventually punished for its actions and subsequent consequences. However, such an identifying mechanism poses aprivacy risk to the users, even when they are behaving honestly.This thesis focuses on the delicate trade-off between anonymity and traceability indistributed systems such as ITSs. We study the use of blockchains in the constructionof privacy-preserving yet accountable threshold cryptographic primitives and theirapplication to the case of VANETs.Our first contribution is a blockchain-based group signature scheme with distributedopening functionality called DOGS. We will show that the system improves on atraditional group signature scheme and leverages a distributed key generation protocolto distribute the opener's role over a set of nodes called the sub-openers.Our second contribution is an anonymous-yet-traceable distributed key generation(DKG) protocol, called BAT-Key that utilizes a blockchain to provide trust amongthe participating distrusting entities. We will present how we augmented traditionalDKG propositions with the anonymity property that protects the identities of theparticipants.Our third contribution is a blockchain-based threshold encryption scheme with ananonymous-yet-accountable decryption service called TOAD. We will show that thescheme builds on threshold encryption and proposes a collaborative decryption processthat protects the identity of the decryption servers.Throughout the chapters, we will explain how the use of blockchain guaranteesthe traceability of the actions performed within the system by anonymous nodes andtherefore ensuring their accountability while preserving privacy.These schemes are of utmost importance in the era of digitization, even outside thefield of ITS. Yet, we chose to exemplify their significance in the context of VANETsthrough our last contribution: the description of our construction of a blockchain-basedprivacy-preserving yet accountable Traffic Reporting system.En 2016, le nombre de décès dus aux accidents de la route atteignait 1,35 million, et ces accidents sont souvent imputable à l’erreur humaine. L'expansion technologique d'Internet et des réseaux interconnectés facilitent l'échange d'informations, parfois vitales. C'est pourquoi beaucoup de travaux ont été produit sur l'automatisation des véhicules. L’amélioration de la sécurité routière est l'un des facteurs qui motive la recherche dans ce domaine et pousse vers l’adoption de systèmes de transport intelligents (ITS) et de réseaux véhiculaires ad hoc (VANET).Un VANET est défini comme un réseau ad-hoc particulier, formé de véhicules capables de communiquer et de traiter l’information reçue, et évoluent en milieu urbain (rues ou autoroutes). Les véhicules peuvent communiquer directement, de pair à pair, ou via un nœud intermédiaire.L'objectif principal de la sécurité des VANETs et des communications véhiculaires est de fournir l'intégrité des messages échangés et la disponibilité des services qui supportent ces échanges. La protection de la confidentialité de ce qu'ils contiennent est un objectif secondaire car non vital. Assurer la responsabilité, c'est-à-dire proposer un moyen d'identifier les entités communicantes et de les tenir responsables pour les messages qu’ils diffusent, est essentiel voire légalement obligatoire. Ce mécanisme doit garantir que tout nœud qui subit une faute, panne ou agit de façon malveillante, soit identifié, révoqué, finalement puni pour ses actions et leurs conséquences. Cependant, un tel mécanisme d'identification pose un problème et risque de compromettre la vie privée des utilisateurs, même lorsqu'ils sont honnêtes.Cette thèse porte sur le délicat compromis entre anonymat et traçabilité dans systèmes distribués tels que les ITSs. Nous étudions l'utilisation des blockchains (chaînes de blocs) dans la construction de primitives cryptographiques à seuil. Ces primitives sont utilisées afin de préserver la vie privée mais aussi la responsabilité des acteurs et étudiées dans leur application au cas des VANETs.Notre première contribution, appelée DOGS, est un schéma de signature de groupe basé sur la blockchain qui propose la fonctionnalité d'ouverture distribuée. Nous montrons, dans cette thèse, que le système améliore un schéma de signature de groupe existant et exploite un protocole de génération de clé distribuée pour répartir le rôle de l'ouvreur (Opener) sur un ensemble de nœuds appelés les sous-ouvreurs (sub-openers).Notre deuxième contribution est une génération de clé distribuée anonyme mais traçable, appelé BAT-Key, qui utilise une blockchain pour assurer la confiance entre les différentes entités qui composent le système. Dans la suite de la thèse, nous expliquons comment nous avons amélioré les protocoles traditionnels avec la propriété d'anonymat qui protège l'identité des participants.Notre troisième contribution, appelée TOAD, est un schéma de chiffrement à seuil basé sur la blockchain avec un service de déchiffrement anonyme mais traçable. Nous montrons que le schéma s'appuie sur un schéma de chiffrement à seuil connu et l’améliore par un processus de déchiffrement collaboratif qui protège l'identité des serveurs de déchiffrement.Tout au long des chapitres, nous expliquons comment l'utilisation de la blockchain garantit la traçabilité des actions effectuées au sein du système par des nœuds anonymes et assure ainsi leur responsabilité tout en préservant la vie privée.Ces schémas sont de la plus haute importance dans l'ère du numérique, même en dehors du domaine des ITSs. Pourtant, nous avons choisi d'illustrer leur importance dans le contexte des VANETs à travers notre dernière contribution : la description de notre construction d'un système de rapport de trafic routier basé sur la blockchain qui préserve l’anonymat des nœuds qui rapportent les informations, mais les tient pour responsables de leurs messages en cas de litige
A Study of Robustness Between Two Strategic 4D Trajectory Plannings
No full textInternational audienceStrategic 4D trajectory planning is a promising technology for next-generation air traffic management and systems. Some approaches attempt to satisfy the capacity constraint to reduce traffic congestion, while others aim to reduce potential conflicts between trajectories. This paper investigates two approaches to organizing the real traffic in the French airspace at the strategic level. The first approach minimizes interaction between trajectories, while the second reduces traffic congestion so that the controller maintains the traffic without much effort. The associated optimization problems are formulated and resolved by an approximative approach based on simulated annealing. The departure time perturbation was introduced to study the robustness of the two proposed methods. The evaluation of the robustness is performed by Monte Carlo simulation. According to the results, the strategic deconfliction method completely solved all interactions between trajectories, and the strategic decongestion method reduced traffic congestion by 99.94%. Furthermore, the comparative study shows that the method reducing congestion is more robust against the departure time perturbation than the method minimizing interaction between trajectories. These findings encourage the appropriate use of proposed methods in the strategic 4D trajectory planning framework
Cross Fertilization between ATM and UTM
No full textInternational audienceThis short paper analyzes the ATM concepts which could be succefully transfered to the UTM world. It then identifies the limits of this UTM fertilization from the ATM. On the other way, UTM can also be a good test-bed to try new air transportation concepts which could be transfered to the ATM world
Introduction to Optimal Control
No full textMasterThe application of optimal control theory to the practical design of multivariablecontrol systems started in the 1960s1: in 1957 R. Bellman applied dynamicprogramming to the optimal control of discrete-time systems. His procedureresulted in nonlinear feedback schemes. By 1958, L.S. Pontryagin has developedthe maximum principle relying on the calculus of variations developed by L.Euler (1707-1783). He solved the minimum-time problem, deriving in 1962 anon/o relay control law as an optimal control. In 1960 three major paperswere published by R. Kalman and coworkers, working in the U.S. One of thesepublicized the vital work of Lyapunov (1857-1918) in the time-domain control ofnonlinear systems. The next discussed the optimal control of systems, providingthe design equations for the Linear Quadratic Regulator (LQR). The third paperhas provided the design equations for the discrete Kalman lter. The continuousKalman lter was developed by Kalman and Bucy in 1961
Target Netgrams: An Annulus-Constrained Stress Model for Radial Graph Visualization
No full textInternational audienceWe present Target Netgrams as a visualization technique for radial layouts of graphs. Inspired by manually created target sociograms, we propose an annulus-constrained stress model that aims to position nodes onto the annuli between adjacent circles for indicating their radial hierarchy, while maintaining the network structure (clusters and neighborhoods) and improving readability as much as possible. This is achieved by having more space on the annuli than traditional layout techniques. By adapting stress majorization to this model, the layout is computed as a constrained least square optimization problem. Additional constraints (e.g., parent-child preservation, attribute-based clusters and structure-aware radii) are provided for exploring nodes, edges, and levels of interest. We demonstrate the effectiveness of our method through a comprehensive evaluation, a user study, and a case study
Dual-Horizon Reciprocal Collision Avoidance for Aircraft and Unmanned Aerial Systems
No full textInternational audienceThe aircraft conflict detection and resolution problem has been addressed with a wide range of centralised methods in the past few decades, e.g. constraint programming, mathematical programming or metaheuristics. In the context of autonomous, decentralized collision avoidance without explicit coordination, geometric methods provide an elegant, cost-effective approach to avoid collisions between mobile agents, provided they all share a same logic and a same view of the traffic. The Optimal Reciprocal Collision Avoidance (ORCA) algorithm is a state-of-the art geometric method for robot collision avoidance, which can be used as a Detect & Avoid logic on-board aircraft or Unmanned Aerial Vehicles. However, ORCA does not handle well some degenerate situations where agents operate at constant or near-constant speeds, which is a widespread feature of commercial aircraft or fixed-winged Unmanned Airborne Systems. In such degenerate situations, pairs of aircraft could end up flying parallel tracks without ever crossing paths to reach their respective destination. The Constant Speed ORCA (CS-ORCA) was proposed in 2018 to better handle these situations. In this paper, we discuss the limitations of both ORCA and CS-ORCA, and introduce the Dual-Horizon ORCA (DH-ORCA) algorithm, where two time horizons are used respectively for short-term collision avoidance and medium-term path-crossing. We show that this new approach mitigates the main issues of ORCA and CS-ORCA and yields better performances with dense traffic scenarios
Gaze direction as a facial cue of memory retrieval state
No full textInternational audienceGaze direction is a powerful social cue that indicates the direction of attention and can be used to decode others’ mental states. When an individual looks at an external object, inferring where their attention is focused from their gaze direction is easy. But when people are immersed in memories, their attention is oriented towards their inner world. Is there any specific gaze direction in this situation, and if so, which one? While trying to remember, a common behavior is gaze aversion, which has mostly been reported as an upward-directed gaze. Our primary aim was to evaluate whether gaze direction plays a role in the inference of the orientation of attention—i.e., external vs. internal—in particular, whether an upward direction is considered as an indicator of attention towards the internal world. Our secondary objective was to explore whether different gaze directions are consistently attributed to different types of internal mental states and, more specifically, memory states (autobiographical or semantic memory retrieval, or working memory). Gaze aversion is assumed to play a role in perceptual decoupling, which is supposed to support internal attention. We therefore also tested whether internal attention was associated with high gaze eccentricity because the mismatch between head and eye direction alters visual acuity. We conducted two large-sample (160–163 participants) online experiments. Participants were asked to choose which mental state—among different internal and external attentional states—they would attribute to faces with gazes oriented in different directions. Participants significantly associated internal attention with an upward-averted gaze across experiments, while external attention was mostly associated with a gaze remaining on the horizontal axis. This shows that gaze direction is robustly used by observers to infer others’ mental states. Unexpectedly, internal attentional states were not more associated with gaze eccentricity at high (30°) than low (10°) eccentricity and we found that autobiographical memory retrieval, but not the other memory states, was highly associated with 10° downward gaze. This reveals the possible existence of different types of gaze aversion for different types of memories and opens new perspectives
Development of A Mission-Tailored Tail-Sitter MAV
No full textInternational audienceVertical takeoff and landing (VTOL) vehicles are among the most versatile UAVs, appropriate for various missions. Given that there are still open challenges regarding the VTOL design, this paper presents the full development and test cycle of a tail-sitter. IMAV 2022 competition rules are used to define the mission objective and constraints. A multidisciplinary design and optimization strategy is defined with the goal of maximizing competition score considering design, manufacturing, and competition constraints. While still being a work in progress, the resulting vehicle is designed to fly at 18 m/s, for around 14 minutes while carrying 200g of payload and weighting approximately 750g