A Job Market Signaling Scheme for Incentive and Trust Management in Vehicular Ad Hoc Networks

International audienceIn collaborative wireless networks with a low infrastructure, the presence of misbehaving nodes can have a negative impact on network performance. In particular, we are interested in dealing with this nasty presence in road safety applications, based on vehicular ad hoc networks (VANETs). In this work, we consider as harmful the presence of malicious nodes, which spread false and forged data; and selfish nodes, which cooperate only for their own benefit. To deal with this, we propose a Distributed Trust Model (DTM2), adapted from the job market signaling model. DTM2 is based on allocating credits to nodes and securely managing these credits. To motivate selfish nodes to cooperate more, our solution establishes the cost of reception to access data, forcing them to earn credits. Moreover, to detect and exclude malicious nodes, DTM2 requires the cost of sending, using signaling values inspired form economics and based on the node's behavior, so that the more a node is malicious, the higher its sending cost, thus limiting their participation in the network. Similarly, rewards are given to nodes whose sent messages are considered as truthful, and that paid a sending cost considered as correct. The latter is a guarantee for the receivers about the truthfulness of the message since, in case of message refusal, the source node is not rewarded despite its payment. We validated DTM2 via a theoretical study using Markov chains; and with a set of simulations, in both urban and highway scenarios. Both theoretical and simulation results show that DTM2 excludes from the network 100% of malicious nodes, without causing any false positive detection. Moreover, our solution guarantees a good ratio of reception even in the presence of selfish nodes

Modeling and Performance Evaluation of Advanced Diffusion with Classified Data in Vehicular Sensor Networks

International audienceIn this paper, we propose a newly distributed protocol called ADCD to manage information harvesting and distribution in Vehicular Sensor Networks (VSN). ADCD aims at reducing the generated overhead avoiding network congestions as well as long latency to deliver the harvested information. The concept of ADCD is based on the characterization of sensed information (i.e. based on its importance, location and time of collection) and the diffusion of this information accordingly. Furthermore, ADCD uses an adaptive broadcasting strategy to avoid overwhelming users with messages in which they have no interest. Also, we propose in this paper a new probabilistic model for ADCD based on Markov chain. This one aims at optimally tune the parameters of ADCD, such as the optimal number of broadcaster nodes. The analytical and simulation results based on different metrics, like the overhead, the delivery ratio, the probability of a complete transmission and the minimal number of hops, are presented. These results illustrate that ADCD allows to mitigate the information redundancy and its delivery with an adequate latency while making the reception of interesting data for the drivers (related to their location) more adapted. Moreover, the ADCD protocol reduces the overhead by 90% compared to the classical broadcast and an adapted version of MobEyes. The ADCD overhead is kept stable whatever the vehicular density

La crise identitaire des élites d'origine maghrébine pendant la guerre du Golfe

Rachedi Nadia. La crise identitaire des élites d'origine maghrébine pendant la guerre du Golfe. In: Horizons Maghrébins - Le droit à la mémoire, N°20-21, 1993. Élites maghrébines de France. Politiques, associatives, religieuses, scientifiques, artistiques. pp. 22-30

DTM²: Adapting job market signaling for distributed trust management in vehicular ad hoc networks

International audienceIn this paper, we address the issue of the presence of malicious and selfish nodes in Vehicular Ad Hoc Networks (VANETs). Malicious nodes spread false and forged messages, while selfish nodes only cooperate for their own interest. To deal with this, we propose DTM², a Distributed Trust Model inspired by Spence's Job Market model from Economics. In our model, a sender node transmits a signal with its message. This signal represents a guarantee of the truthfulness of the message for the potential receivers. In order to use the signal, the sender node has to pay a cost, which depends on the value of the signal and its own behavior. Therefore, the worse the behavior of the sender node, the more expensive the signal cost. This model deters the sender nodes from acting as malicious nodes. Similarly, cooperation of the sender nodes is rewarded proportionally to the signal's value. We validated DTM² via extensive simulation in an urban scenario. We show that our approach is able to detect and evict gradually all malicious nodes in a network composed of 25%, and 50% of them. Moreover, our solution greatly decreases the ratio of corrupted and false data sent through a network to levels as low as 0%, and it increases the participation ratio of selfish nodes by 20%

Advanced diffusion of classified data in vehicular sensor networks

International audienceIn this paper, we propose a newly distributed protocol called ADCD to manage information harvesting, and distribution in Vehicular Sensor Networks (VSN). The concept of ADCD is based on the characterization of sensed information (i.e. its importance, location and time of collection) and the diffusion of this information accordingly. Furthermore, ADCD uses an adaptive broadcasting strategy to avoid overwhelming users with messages for which they have no interests. Thanks to this adaptive broadcasting strategy, ADCD limits the generated overhead avoiding network congestions as well as long latency to deliver the harvested information, which are the main limitations of other existing protocols. Moreover, it is designed to be flexible regarding the use of roadside units or not, which is not the case in other schemes in the literature. To reach its objectives, ADCD operations are divided into three steps: (i) classification of data and the identification of their target area of diffusion, (ii) data-centric election of the set of broadcasters to avoid broadcasting redundancy, and (iii) iterative process for data dispatching in a targeted area. Performance evaluation shows that the ADCD protocol allows for mitigating the information redundancy and its delivery with an adequate latency while making the reception of interesting data for the drivers (related to their location) more adapted. Moreover, the ADCD protocol reduces the overhead by 90% compared to the classical broadcast and an adapted version of MobEyes. The ADCD overhead is kept stable whatever the vehicular density

To Send or To Defer? Improving the IEEE 802.11p/1609.4 Transmission Scheme

International audienceThe IEEE 1609.4 protocol has been proposed to improve message delivery in Vehicular Ad Hoc Networks (VANETs) through its multi-channel usage. To ensure good performance for safety applications, during the first half of a synchronization interval, each vehicle tunes a dedicated Control CHannel (CCH) to exchange safety messages, and during the second half, either it stays on the CCH or switches to one of the six available Service CHannels (SCH). As demonstrated in the literature, such behavior leads safety messages to suffer from synchronous collisions at the start of the CCH interval, as well as from high end-to-end delays caused by the queue-up during the SCH intervals. To address these issues, we propose DMS, a Distributed MAC Scheduler that relies on the Optimal Stopping Theory to evenly balance the channel load by introducing tolerated deferring delays before sending a message. This ensures a higher reception probability and lower collision risks, while complying with Enhanced Distributed Channel Access (EDCA) access categories (ACs). Simulation study shows the ability of our approach to increase the reception rate of safety messages up to 25%, to decrease loses up to 47%, and to improve the load balancing during the CCH interval

Trust and exclusion in vehicular ad hoc networks: an economic incentive model based approach

International audienceIn this body of work, we are interested in road safety applications such as advanced driver assistance systems, based on Vehicular Ad Hoc Networks (VANETs). One of the particular characteristics of this kind of networks is the continuous sharing of safety information by its nodes. Since this kind of information is time sensitive, a node cannot spend much time to verify its validity with an authority. However, the presence of malicious and selfish nodes in VANETs corrupts exchanged data, and lowers the overall data reception ratio in the network. To tackle this, we propose a new incentive model with exclusion for malicious nodes called VIME. VIME is inspired from the signaling theory from economics. It is based on managing a credit count that each node receives at the initialization of the application. Straightforwardly, VIME is based on two pillars. On the one hand, a node pays an appropriate cost for each sent message, which is seen by the receivers as a guarantee from the source about the truthfulness of the information. On the other hand, nodes get rewarded for cooperating in the network. The proposed economic model allows computing the amounts to be paid and those to be awarded in order to fight selfish and malicious nodes. We validate our approach via simulations. We show that VIME is able to detect and evict gradually all malicious nodes in the network, and decreases the ratio of corrupted and false sent data until reaching zero. Moreover, it has a positive impact on the participation of selfish nodes, as our approach increases the average ratio of sent data as to equal the ideal case's percentage, when no selfish node is present

L'instant propice à l'envoi d'un message sur la couche IEEE 802.11p/1609.4

International audienceLe protocole IEEE 1609.4 a été proposé afin d'améliorer la délivrance des messages dans les réseaux Ad Hoc véhiculaires en rajoutant la notion du multi-canal au standard IEEE 802.11p. Pour assurer de bonnes performances aux applications de sécurité routière, la première moitié de l'intervalle de synchronisation leur est dédiée, chaque véhicule écoute alors sur le canal de contrôle (CCH). La deuxième moitié est dédiée aux applications de conforts, un véhicule peut rester sur le canal de contrôle ou changer pour un des six canaux de service (SCH). Néanmoins , ce mécanisme cause des collisions synchronisées au début de l'intervalle dédié au CCH, ainsi qu'un important déséquilibre de charge, tout deux causés par la mise en attente des messages de sécurité routière durant la deuxième moitié de l'intervalle. Nous proposons DMS, un ordonnanceur distribué au niveau de la couche MAC, pour décider de l'instant optimal pour l'envoi d'un message de sécurité routière, afin de lui assurer un haut taux de réception, quitte à allonger d'un peu son délai de transmission. DMS se base sur la théorie de l'arrêt optimal et prend en considération le délai maximum supporté par le message à envoyer. Nos simulations montrent que lors de l'utilisation de DMS, la charge du canal durant l'intervalle CCH est équilibrée, ce qui augmente fortement le taux de réception des messages et décroit le taux de perte