An Adaptive Localized Algorithm for Multiple Sensor Area Coverage

International audienceWireless sensor networks are made up of hundreds of devices deployed over a distant or sensitive field to be monitored. Energy consumption is balanced by taking advantage of the redundancy induced by the random deployment of nodes. Some nodes are active while others are in sleep mode, thus using less energy. Such a dynamic topology should not impact the monitoring activity. Area coverage protocols aim at turning off redundant sensor nodes while ensuring full coverage of the area by the remaining active nodes. Providing k-area coverage therefore means that every physical point of the monitored field is sensed by at least k sensor devices. Connectivity of the active nodes subset must also be provided so that monitoring reports can reach the sink stations. Existing solutions hardly address these two issues as a unified one. In this paper, we propose a localized algorithm for multiple sensor area coverage able to build connected active nodes sets. We also show that a simple feature of the protocol, called the coverage evaluation scheme, can be enhanced to handle various k-area coverage problem definitions. Experimental results show that our coverage scheme is resistant to collisions of messages as k-area-coverage of the deployment area and connectivity of the active nodes set can still be ensured

Etude et extension des relais de couverture de surface dans les réseaux de capteurs

National audienceL'objectif des protocoles de couverture de surface est de mettre en veille des capteurs redondants tout en assurant une couverture totale de la zone par les noeuds restant allumés. La connexité de l'ensemble des noeuds actifs doit également être préservée dans la mesure où il est impératif d'assurer l'acheminement des rapports de surveillance vers les stations puits. La plupart des solutions existantes ne considèrent pas ces deux problèmes comme un seul et sont rarement évaluées sous des conditions réalistes. Dans cet article, nous proposons une analyse approfondie et des améliorations d'un protocole localisé maintenant la couverture de zone par des ensembles connectés en se basant sur des relais de couverture de surface (SCR). Dans un premier temps, nous avons amélioré l'une des phases critiques de l'algorithme ; la sélection des relais. Ceci nous a permis de diminuer le nombre de noeuds actifs sans altérer la couverture fournie. Nous avons ensuite soulevé le problème de sa résistance à des conditions de communication plus réalistes. Nous verrons alors comment de nouvelles modifications durant la phase de sélection des relais nous ont permis d'obtenir un protocole robuste et facilement configurable

Preserving Area Coverage in Wireless Sensor Networks by using Surface Coverage Relay Dominating Sets

International audienceSensor networks consist of autonomous nodes with limited battery and of base stations with theoritical infinite energy. Nodes can be sleep to extend the lifespan of the network without compromising neither area coverage nor network connectivity. This paper addresses the area coverage problem with equal sensing and communicating radii. The goal is to minimize the number of active sensors involved in coverage task, while computing a connected set able to report to monitoring stations. Our solution is fully localized, and each sensor is able to make decision on whether to sleep or to be active based on two messages sent by each sensor. The first message is a “hello” message to gather position of all neighboring nodes. Then each node computes its own relay area dominating set, by taking the futhest neighbor as the first node, and then adding neighbors farthest to the isobarycenter of already selected neighbors, until the area covered by neighbors is fully covered. The second message broadcasts this relay set to neighbors. Each node decides to be active if it has highest priority among its neighbors or is a relay node for its neighbor with the highest priority

Is Link-Layer Anycast Scheduling Relevant for IEEE802.15.4-TSCH Networks?

International audienceWith the wide adoption of low-power wireless transmissions , industrial networks have started to incorporate wireless devices in their communication infrastructure. Specifically, IEEE802.15.4-TSCH enables slow channel hopping to increase the robustness, and relies on a strict schedule of the transmissions to increase the energy efficiency. Anycast is a link-layer technique to improve the reliability when using lossy links. Several receivers are associated to a single transmission. That way, a transmission is considered erroneous when none of the receivers was able to decode and acknowledge it. Appropriately exploited by the routing layer, we can also increase the fault-tolerance. However, most of the anycast schemes have been evaluated by simulations, for a sake of simplicity. Besides, most evaluation models assume that packet drops are independent events, which may not be the case for packet drops due to e.g. external interference. Here, we use a large dataset obtained through an indoor testbed to assess the gain of using anycast in real conditions. We also propose a strategy to select the set of forwarding nodes: they must increase the reliability by providing the most independent packet losses. We demonstrate using our experimental dataset that anycast improves really the performance, but only when respecting a set of rules to select the next hops in the routing layer

La k-couverture de surface dans les réseaux de capteurs

National audienceLes protocoles d'ordonnancement d'activité dans les réseaux de capteurs visent à constituer un sous-ensemble de noeuds devant être actifs pour une période donnée, permettant aux autres de passer dans un mode passif moins consommateur d'énergie. La décision d'activité peut se faire selon divers critères. Celui que nous considérons ici est la couverture de surface multiple, ou k-couverture; Tout point physique de la zone de déploiement doit être couvert par au moins k noeuds actifs. Nous décrivons dans ce papier différentes méthodes pour l'adaptation d'algorithmes localisés de couverture simple à la k-couverture de surface

Towards Secure and Leak-Free Workflows Using Microservice Isolation

Data leaks and breaches are on the rise. They result in huge losses of money for businesses like the movie industry, as well as a loss of user privacy for businesses dealing with user data like the pharmaceutical industry. Preventing data exposures is challenging, because the causes for such events are various, ranging from hacking to misconfigured databases. Alongside the surge in data exposures, the recent rise of microservices as a paradigm brings the need to not only secure traffic at the border of the network, but also internally, pressing the adoption of new security models such as zero-trust to secure business processes. Business processes can be modeled as workflows, where the owner of the data at risk interacts with contractors to realize a sequence of tasks on this data. In this paper, we show how those workflows can be enforced while preventing data exposure. Following the principles of zero-trust, we develop an infrastructure using the isolation provided by a microservice architecture, to enforce owner policy. We show that our infrastructure is resilient to the set of attacks considered in our security model. We implement a simple, yet realistic, workflow with our infrastructure in a publicly available proof of concept. We then verify that the specified policy is correctly enforced by testing the deployment for policy violations, and estimate the overhead cost of authorization

Ensuring K-Coverage in Wireless Sensor Networks under Realistic Physical Layer Assumptions

International audienceWireless sensor networks are composed of hundreds of small and low power devices deployed over a field to monitor. Energy consumption is balanced by taking advantage of the redundancy induced by the random deployment of nodes. Some nodes are active while others are in sleep mode. Area coverage protocols aim at turning off redundant sensor nodes while preserving satisfactory monitoring by the set of active nodes. The problem addressed here consists in building k distinct subsets of active nodes (layers), in a fully decentralized manner, so that each layer covers the area. In our protocol, each node selects a waiting timeout, listening to messages from neighbors. Activity messages include the layer at which a node has decided to be active. Depending on the physical layer used for sensing modeling, any node can evaluate if the provided coverage is sufficient for each layer. If so, node can sleep, otherwise it selects a layer to be active. Here, we describe a localized area coverage protocol able to maintain an area k-covered under realistic physical layer assumptions for both sensing and communicating modules

Maintien de la couverture de surface dans les réseaux de capteurs avec une couche physique non idéale

Nous considérons le problème de la couverture de surface dans les réseaux de capteurs lorsqu'une couche physique non idéale est utilisée, la plupart des travaux récents dans ce domaine ayant été effectués dans un environnement idéal. Dans cette étude, nous montrons qu'un protocole prévu pour un tel environnement ne peut que difficilement fonctionner en l'état dans un milieu plus réaliste. Dans ce but, nous analysons avec le modèle du masquage lognormal un protocole localisé répandu dans la littérature, de Tian et Georganas. Cette analyse démontre clairement que la couverture de surface n'est plus suffisamment assurée, et que des modifications sont nécessaires pour obtenir à nouveau de bonnes performances. Nous proposons dans cette optique une version améliorée de ce protocole et montrons par expérimentations qu'elle est très efficace quel que soit l'environnement considéré

Preserving Area Coverage in Sensor Networks with a Realistic Physical Layer

International audienceWe consider the problem of activity scheduling and area coverage in sensor networks, and especially focus on problems that arise when using a more realistic physical layer. Indeed, most of the previous work in this area has been studied within an ideal environment, where messages are always correctly received. In this paper, we argue that protocols developed with such an assumption can hardly provide satisfying results in a more realistic world. To show this, we replace the classic unit disk graph model by the lognormal shadowing one. The results show that either the resulting area coverage is not sufficient or the percentage of active nodes is very high. We thus present an original method, where a node decides to turn off when there exists in its vicinity a sufficiently reliable covering set of neighbors. We show that our solution is very efficient as it preserves area coverage while minimizing the quantity of active nodes

Maintien de la couverture de surface dans les réseaux de capteurs avec une couche physique réaliste

We consider the problem of area coverage in sensor networks with a realistic physical layer. Most of the previous work in this area has been done with an ideal environment. In this paper, we show that protocols developped in such an environment cannot provide satisfying results in a more realistic world. To do this, we analyze a well-spread localized protocol, from Tian and Georganas, considering the lognormal shadowing model. This study clearly demonstrates that the resulting area coverage is not sufficient, and that some modifications are needed to get back some good results. We thus propose an enhanced version of this protocol and experimentally show that it is very efficient, regardless of the considered environment