Bertrand Ducourthial

On the Sybil attack detection in VANET

Since few years, Vehicular Ad hoc Networks deserve much attention. The development of wireless communication in VANET implies to take into account the need of security. In VANET, many attacks rely on having the attacker generate multiple identities to simulate multiple nodes: this is called the Sybil attack. In this paper, we propose a precise quantification of the effects of various assumptions (type of antenna, transmission signal strength) on the effectiveness of a Sybil attack.

Sybil Nodes Detection Based on Received Signal Strength Variations within VANET

A Vehicular Ad hoc Network is a collection of mobile hosts forming a temporary network without the aid of any established infrastructure. This flexibility in space and time induces new challenges towards the security needed to support secure communications. Indeed, VANET are subject to attacks due to their vulnerabilities; one of the most compromising attacks is the Sybil nodes attack. We present in this context a Sybil detection approach, based on received signal strength variations, allowing a node to verify the authenticity of other communicating nodes, ac- cording to their localizations. In addition, we define an estimated metric of the distinguishability degree between two nodes, allowing to determine Sybil and malicious ones within VANET. The applicability of our contributions is validated through geometrical analysis, simulations and real measurements.

Conditional Transmissions: Performance Study of a New Communication Strategy in VANET

Many solutions have been developed for routing messages in ad hoc networks. However, few of them are efficient when the network is highly dynamic. Indeed, building a routing table, discovering and maintaining a route, or localizing a node is a great challenge when the dynamic is high. This topic is currently attracting attention with vehicular ad hoc networks (VANETs), which are a special case of highly dynamic networks. VANET may allow us to enhance road safety and to develop new driver-or passenger-oriented services. In this paper, we present a novel approach for routing in highly dynamic networks, relying on condition-based communication. Instead of transporting addresses (or positions), a message is sent with some conditions used for retransmission or reception. Owing to the dynamic evaluation of the conditions, we show that this solution can efficiently support the high dynamic of vehicular networks.

IEEE 802.11 performances for inter-vehicle communication networks

The growth of wireless local area networks based on the IEEE 802.11 standard these last years represents a practical network solution offering mobility, flexibility and low cost deployment. This encourages the use of this protocol for new nomadic applications. Among such applications, wireless inter-vehicle networks could improve road security and offer new driving services. In this paper, we are interested by the performances of IEEE 802.11 protocol in networks with strong mobility like vehicle networks. Through simulations of vehicles convoys, we discuss the assessment of such protocol for large-scale vehicle-to-vehicle communications.

Self-stabilization with r -operators

Abstract. This paper describes a parameterized distributed algorithm applicable to any directed graph topology. The function parameter of our algorithm is instantiated to produce distributed algorithms for both fundamental and high level applications, such as shortest path calculus and depth-first-search tree construction. Due to fault resilience properties of our algorithm, the resulting protocols are self-stabilizing at no additional cost. Self-stabilizing protocols can resist transient failures and guarantee system recovery in a finite time. Since the condition on the function parameter (being a strictly idempotent r-operator) permits a broad range of applications to be implemented, the solution presented in our paper can be useful for a large class of distributed systems.

Self-stabilization with path algebra

Self-stabilizing protocols can resist transient failures and guarantee system recovery in a finite time. We highlight the connexion between the formalism of self-stabilizing distributed systems and the formalism of generalized path algebra and asynchronous iterations with delay. We use the later to prove that a local condition on locally executed algorithm (being a strictly idempotent r-operator) ensures self-stabilization of the global system. As a result, a parametrized distributed algorithm applicable to any directed graph topology is proposed, and the function parameter of our algorithm is instantiated to produce distributed algorithms for both fundamental and high-level applications. Due to fault resilience properties of our algorithm, the resulting protocols are self-stabilizing at no additional cost.

Self-Stabilization with r-Operators revisited

We present a generic distributed algorithm for solving silents tasks such as shortest path calculus, depth-first-search tree construction, best reliable transmitters, in directed networks where communication may be only unidirectional. Our solution is written for the asynchronous message passing communication model, and tolerates multiple kinds of failures (transient and intermittent). First, our algorithm is self-stabilizing, so that it recovers correct behavior after finite time starting from an arbitrary global state caused by a transient fault. Second, it tolerates fair message loss, finite message duplication, and arbitrary message reordering, during both the stabilizing phase and the stabilized phase. This second property is most interesting since, in the context of unidirectional networks, there exist no self-stabilizing reliable data-link protocol. The correctness proof subsumes previous proofs for solutions in the simpler reliable shared memory communication model.

Efficient data dissemination in cooperative vehicular networks

Vehicular networks are drawing the attention of both research community and automotive industry because they provide intelligent transportation systems as well as drivers and passengers’ assistant services. However, the industrialization of such networks faces a number of challenges, in particular, the high cost of the infrastructure to deploy. To overcome this problem, an effective solution is to rely on cooperative vehicle-to-vehicle communication to minimize the deployed infrastructure. Because a large number of cooperative vehicle-to-vehicle applications are broadcasting by nature, we proposed an efficient dissemination protocol: Road-Oriented Dissemination (ROD). ROD consists in two modules: (i) Optimized Distance Defer Transfer Module and (ii) Store-and-Forward Module. We compare our protocol with other dissemination protocols and analyze its performance by simulations, on-road tests and analytically. Performance study shows interesting results of ROD compared with the other existing solutions. ROD is able to provide a low end-to-end delay, high delivery ratios, and a minimum bandwidth usage because only a limited number of vehicles are involved in the broadcast scheme. Copyright

A new framework of self-organization of vehicular networks

Vehicular networks are drawing a great attention from the research community and the automotive industry, where they are beneficial in providing ITS (Intelligent Transportation System) services as well as assisting the drivers on the road. In this context, vehicular networks are based on V2I (Vehicle to Infrastructure) and V2V (Vehicle to Vehicle) communications. The special characteristics of these networks such as high mobility, potentially large scale, and network partitioning introduce several challenges, which greatly impact the deployment of these networks. An efficient solution to these problems is to define a robust self-organizing architecture. Thus, the function of these dynamic networks can be quite improved. In this paper, we introduce a new proactive self-organizing protocol called CSP (Cluster-based Self-organizing Protocol) that uses the geographic clustering and the virtual backbone to structure intelligently the vehicular network. We compare CSP to other self-organizing solution by analyzing its performances using Qualnet simulator. Simulation results show good performance of CSP in terms of architecture stability, overhead and delivery ratio.

Parallel asynchronous computations for image analysis

Many works have been done for parallelizing low-level image analysis computations. However the task is harder for higher levels, as the data manipulations are complex, and there is a wide range of algorithms to encompass. To allow concurrently speed and programmability, a high-level programming model that can be efficiently implemented on parallel architectures is required. To achieve this goal, we propose the associative nets model, a parallel computing model for image analysis based on simple data-parallelism paradigms, providing special features, such as graph-based data structures to handle irregular data, virtual data-structures to ease hierarchical image descriptions, and specific primitives (dirassoc) to compute on the interpixels relation graph. For implementation purposes, the dirassoc computing primitive performs asynchronous local computations until it reaches stability. Asynchronism has many advantages for hardware (speed, power consumptions, and chip size) as well as in software (less synchronization barriers). However to insure completion of the asynchronous operation, the dirassoc must use a set of specific operators (r-operators) introduced by Ducourthial. In this paper we emphasize on the interest of the r-operators and of the asynchronous computations for image analysis algorithms. We give applications in distance transforms, contour closing, Voronoi segmentation, watershed segmentation, and mathematical morphology. Hence, we show that asynchronous computations are powerful tools for image analysis on interpixel graphs.