WSN Scheduling for Energy-Efficient Correction of Environmental Modelling

International audienceWireless sensor networks (WSN) are widely used in environmental applications where the aim is to sense a physical parameter such as temperature, humidity, air pollution, etc. Most existing WSN-based environmental monitoring systems use data interpolation based on sensor measurements in order to construct the spatiotemporal field of physical parameters. However, these fields can be also approximated using physical models which simulate the dynamics of physical phenomena. In this paper, we focus on the use of wireless sensor networks for the aim of correcting the physical model errors rather than interpolating sensor measurements. We tackle the activity scheduling problem and design an optimization model and a heuristic algorithm in order to select the sensor nodes that should be turned off to extend the lifetime of the network. Our approach is based on data assimilation which allows us to use both measurements and the physical model outputs in the estimation of the spatiotemporal field. We evaluate our approach in the context of air pollution monitoring while using a dataset from the Lyon city, France and considering the characteristics of a monitoring system developed in our lab. We analyze the impact of the nodes' characteristics on the network lifetime and derive guidelines on the optimal scheduling of air pollution sensors

A Novel Adaptive and Efficient Routing Update Scheme for Low-Power Lossy Networks in IoT

In this paper, we introduce Drizzle, a new algorithm for maintaining routing information in the Low-power and Lossy Networks (LLNs). The aim is to address the limitations of the currently standardized routing maintenance (i.e. Trickle algorithm) in such networks. Unlike Trickle, Drizzle has an adaptive suppression mechanism that assigns the nodes different transmission probabilities based on their transmission history so to boost the fairness in the network. In addition, Drizzle removes the listen-only period presented in Trickle intervals leading to faster convergence time. Furthermore, a new scheme for setting the redundancy counter has been introduced with the goal to mitigate the negative side effect of the short-listen problem presented when removing the listen-only period and boost further the fairness in the network. The performance of the proposed algorithm is validated through extensive simulation experiments under different scenarios and operation conditions. In particular, Drizzle is compared to four routing maintenance algorithms in terms of control-plane overhead, power consumption, convergence time and packet delivery ratio (PDR) under uniform and random distributions and with lossless and lossy links. The results indicated that Drizzle reduces the control-plane overhead, power consumption and the convergence time by up to 76%, 20% and 34% respectively while maintaining approximately the same PDR rates

A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations

Driven by the special requirements of the Low-power and Lossy Networks (LLNs), the IPv6 Routing Protocol for LLNs (RPL) was standardized by the IETF some six years ago to tackle the routing issue in such networks. Since its introduction, however, numerous studies have pointed out that, in its current form, RPL suffers from issues that limit its efficiency and domain of applicability. Thus, several solutions have been proposed in the literature in an attempt to overcome these identified limitations. In this survey, we aim mainly to provide a comprehensive review of these research proposals assessing whether such proposals have succeeded in overcoming the standard reported limitations related to its core operations. Although some of RPL’s weaknesses have been addressed successfully, the study found that the proposed solutions remain deficient in overcoming several others. Hence, the study investigates where such proposals still fall short, the challenges and pitfalls to avoid, thus would help researchers formulate a clear foundation for the development of further successful extensions in future allowing the protocol to be applied more widely

Impact of Surface Treatment of Flax Fibers on Tensile Mechanical Properties Accompanied by a Statistical Study

In this work, a surface treatment with sodium bicarbonate (NaHCO3) at different concentrations of 4 and 8% is applied to the surface of the flax fiber for a period of 80 hours at room temperature. The purpose of this study is to observe the effect of different treatment processes on the flax fiber, i.e. on its mechanical properties such as: stress and strain at break and Young's modulus. A major test campaign of more than 240 tests is carried out. Due to the variability of the plant fibers, more than 80 samples were tested for each group at a gauge length (GL = 10 mm). The results of the quasi-static tensile tests have a large dispersion which makes it possible to measure the degree of variability in the stress and strain deformation and the Young's modulus of the fiber. This degree of variability has been studied by means and statistical tools such as the Weibull distribution at two

Cancer du rein (étude rétrospective sur cinq années à l'hôpital d'Avignon)

AIX-MARSEILLE2-BU Méd/Odontol. (130552103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Ensuring the Reliability of an Autonomous Vehicle: a Formal Approach based on Component Interaction Protocols

International audienceIn automotive applications, several components, offering different services, can be composed in order to handle one specific task (autonomous driving for example). Nevertheless, component composition is not straightforward and is subject to the occurrence ofbugs resulting from components or services incompatibilities for instance. Hence, bugs detection in component-based systems at thedesign level is very important, particularly, when the developed system concerns automotive applications supporting critical services.In this paper, we propose a formal approach for modeling and verifying the reliability of an autonomous vehicle system, communicatingcontinuously with off-road infrastructure. We focus on components offering critical services with hard time constraint defining thedelay of their availability. We propose to verify whether a set of components, when composed according to the system architecturespecified with SysML models, achieve their tasks by respecting their interaction protocols and their time constraints

Efficient and Robust Serial Query Processing Techniques for Large-Scale Wireless Sensor Networks

The goal of query processing in WSN is to get reliable information of interest from sensor nodes whilst preserving, as much as possible, the network resources, mainly energy. Among the various approaches proposed in the literature to tackle this issue, serial approaches, in which the query is carried out serially from node to node, have shown noticeable improvements in terms of query processing responsiveness and communication overhead reduction when compared to centralized and distributed ones. Nevertheless, they suffer two main drawbacks: (a) they are intrinsically very vulnerable and (b) they require the construction of a Hamiltonian path through the network, which is known to be a NP-Complete problem. In this paper, we investigate the issue of efficient and robust query processing by proposing a novel approach, which we refer to as GBT (Greedy & Boundary Traversal). GBT is of a serialized and localized nature (i.e., each node does not maintain any knowledge about the topology of the network). Furthermore, in GBT the selection of the next hop is totally independent from the previous hops (i.e., no path is defined in advance). This feature enforces the robustness of GBT as attested by the simulation results we obtained (a mean improvement of almost 50% reduction in terms of communication, energy and query responsiveness in large-scale network topologies). We also provide a complexity analysis (time, space and communication) of our query processing algorithm as well as formal proof of its correctness (i.e., termination and completeness)

Towards a Formal Analysis of MQtt Protocol in the Context of Communicating Vehicles

International audienceThe paper presents a formal approach to model, analyze, and verify a variant of Message Queue Telemetry Transport protocol (MQtt), dedicated to communicating vehicles (MQtt-CV) that send collected data to automotive infrastructures(subscribers). Our formal approach is based on Promela language and its system verification tool, the model checker SPIN. We propose a slight modification of MQtt protocol to reduce the big volume of data collected and sent by vehicles to infrastructures. Indeed, in the original version of MQtt protocol, when a broker receives data from publishers, it sends them directly to its subscribers without any filtration. As consequence, subscribers may be flooded with unimportant data, which increase the problem in the context where infrastructures should manage a huge volume of data sent by thousands of vehicles. So we propose to model and to analyze formally MQtt-CV protocol, to ensure that the components (broker, publisher, subscriber) that implement this protocol interact correctly and fulfill MQtt requirements

Routing Through Holes in Wireless Sensor Networks

International audienceBesides of its high efficiency, in particular its scalability, geographic greedy routing is of a memoryless nature (i.e., nodes do not maintain any routing tables) which makes it well suitable for large-scale sensor networks with limited resources. Nevertheless, the occurrence of local minimum phenomenon, especially in networks with many holes, limits considerably the applicability of such routing protocol. The local minimum situations occur when the packet could not be delivered by the current node based only on distance to the destination. This problem has been tackled in previous research works to guarantee packets delivery by routing around the boundaries of the hole but at an excessive consumption of control overheads. In this paper, we propose and study a novel approach that is of memoryless nature and performs better that the state-of-art approaches in terms of guarantying packet delivery and deriving efficient routing paths. We provide in this paper proofs of its correctness (guarantying packet delivery) whereas showing, through simulations, its performance effectiveness in terms of reducing routing paths