Enhanced ADR for LoRaWAN networks with mobility

International audienceLoRa is becoming an attractive low cost and low power WAN solution for many real-world IoT applications. LoRa has been designed for static end-devices to individually use the optimal configuration through an adaptive data rate mechanism (ADR), thanks to the possibility to choose a set of LoRa physical layer transmission parameters. However a large class of IoT applications (e.g. connected farm) also includes mobile nodes with specific mobility patterns. For those applications, the current ADR control algorithm may not be efficient when the radio channel attenuation rapidly changes because of the node mobility. This paper contributes to enhance the ADR mechanism by taking into account the position of the mobile devices and their trajectories in order to have a dynamic allocation. The Enhanced-ADR (E-ADR) minimizes the transmission time and energy consumption as well as packet loss for mobile devices. The testbed-based experiments show that E-ADR improves the quality of service (QoS) of the overall networks

Enhanced Dynamic Duty Cycle in LoRaWAN Network

International audienceLoRa’s long-range and low-power features have made it an attractive candidate for IoT devices in various fields. In this work, we present an enhanced LoRaWAN protocol. LoRaWAN MAC protocol is characterized by the restrictive use of the channel, limited by the regulatory authorities to a 1% duty cycle per cycle (i.e., 36 s per hour) per node. This regulation penalizes the nodes which require a channel access time greater than the limited duty cycle to occasionally transmit a large amount of data such as video surveillance or access control information in applications like smart school surveillance. However, some other nodes like environment sensors sharing a same LoRaWAN server may send very small amounts of information (e.g. temperature, humidity, ...) and under-use the authorized activity time of 1% duty cycle. Hence the idea of implementing an activity time sharing mechanism among nodes that allows devices to borrow additional activity time from a device or set of devices that have completed the transmission of their packets and do not need the remaining time of the corresponding duty cycle. Our work extends and improves the activity time sharing mechanism initially proposed in [1]. Instead of FIFO sharing-time allocation based on a global activity time, which may lead to the starvation of the nodes that are others than that in the head of FIFO line, we propose a new time allocation algorithm based on the classification of the different requests according to their needs in terms of their QoS requirements. It allows to satisfy a larger number of nodes requiring extra time, with less control overheads while ensuring fairness. Our time-sharing algorithm has been implemented and tested on the wasp-mote chip of libelium, showing the performance improvement and its practical usability

Small packets aggregation in an IP domain

International audience

Router queue management for multimedia traffic in the Internet

International audience

Caractérisation structurale et suivi du vieillissement par diffusion X aux petits angles d'un polymère époxyde (Contribution à l'étude des propriétés électriques)

Ce travail constitue une approche innovante mettant en complémentarité diverses techniques de caractérisation physicochimique, électrique et structurale. Menées sur un polymère époxyde, ces études ont pour principal objectif la compréhension des phénomènes et propriétés diélectriques associés aux charges d espace, ainsi que le suivi de leur évolution dans le temps ou suite à l application de contraintes extérieures. Les mesures de spectroscopie d impédance et de courant de dépolarisation thermo-stimulé (CDTS), ont mis en évidence des processus de relaxations dipolaires et interfaciales. L origine de ces phénomènes a pu être expliquée à partir des analyses physico-chimiques et structurales. Tout d abord à l aide des mesures de fluorescence X qui ont révélé la présence de deux types d impuretés, pouvant créer des états énergétiques plus ou moins profonds dans la bande interdite. Ensuite, par des mesures en réflectométrie X qui ont mis en évidence plusieurs structures ordonnées au sein d une matrice amorphe. Cette hétérogénéité structurale explique les mécanismes de piégeage et d accumulation des charges d espaces aux interfaces. De même, l ordre local favorisant la mobilité des charges, ces résultats donnent une première réponse quant à la valeur relativement élevée de la conductivité électrique du polymère, telle qu elle a pu être déterminée à partir des mesures des caractéristiques courant-tension. Des études de vieillissement accéléré ont également été menées. Les différents recuits appliqués ont contribué à la création de charges qui sont piégées dans des niveaux énergétiques de plus en plus profonds. Cela s est traduit par une diminution de la quantité de charges qui relaxent par activation thermique ainsi que par une diminution de la conductivité électrique des échantillons. Ces changements de propriétés électriques ont été corrélés aux changements structuraux qui se sont produits au sein du polymère, et dont la principale manifestation est la disparition progressive des structures ordonnées. Cette disparition de l ordre local a aussi été observée en l absence de contraintes thermiques (vieillissement naturel), où il a été montré que le comportement superficiel et en volume des échantillons n était pas identique.This work constitutes an innovative approach in epoxy based polymer characterization, where complementary physico-chemical, electric and structural techniques are used. The main objective of these studies is to understand both dielectric phenomena and properties associated to the space charges, as well as to follow-up their evolution in time or after the application of external constraints.Impedance spectroscopy and thermo-stimulated depolarization current (TSDC), measurements have highlighted dipolar and interfacial relaxations processes. Origin of these phenomena has been explained from physico-chemical and structural analyses. First, X-ray fluorescence measurements revealed the presence of two types of impurities, which are able to create deep energetic levels in the forbidden energy band. Then, X ray reflectometry measurements highlighted several periodic structures within an amorphous matrix. This structural heterogeneity explains the mechanisms of trapping and accumulation of space charges at the interfaces and gives a first reply as for the relatively high value of the polymer electric conductivity, calculated from current-voltage measurements.Accelerated ageing studies have been also carried out. They have shown that annealing creates charges which are trapped in increasingly deep energetic levels. Consequently, both the quantity of released charges and annealed samples conductivities have decreased.These electric properties changes have been correlated with the structural changes occurring within the polymer, and whose principal manifestation is the progressive disappearance of the ordered structures. This disappearance of the local periodicity has also been observed in the absence of thermal constraints (natural ageing), where it was shown that samples surface s behavior is different from the bulk.PARIS-CNAM (751032301) / SudocSudocFranceF

FENS: Fog-Enabled Network Slicing in SDN/NFV-Based IoV

International audienceModern vehicular networks support various services with variable QoS (Quality of Service) constraints. Two major classes of vehicular applications are identified, namely, safety and non safety services. The former are delay-sensitive while the latter depends mainly on throughput. However, many regions are suffering from a shortage of network resources while an increasing number of vehicle users need to be satisfied. Thus, the design of efficient allocation schemes of available resources is necessary. In this regard, one of the promising technologies is network slicing, a next-generation 5G perspective, that creates multiple logical networks on a common physical infrastructure. This paradigm enables efficient exploitation of shared physical infrastructure resources to meet the diverse needs of different use cases.In this paper we design a framework for a road-state-based and adaptive network slicing scheme for vehicular networks.The goal is to temporarily prioritize emergency traffic in incident situations while maintaining acceptable QoS for non-safety related sevices in a resource constrained environment. Our proposal adds to native slicing the ability to take into account road conditions besides of customer’s specifications in terms of QoS. Moreover, our adaptive scheme makes it possible to judiciously exploit the available resources even if they are limited according to the rigor of the application. SDN (Software Defined Networking), NFV (Network Function Virtualization) and Fog computing paradigms are the key enablers of our proposed solution. We implemented the proposed architecture based on the Mininet-Wifi emulator to create a vehicular network, the ONOS SDN controller, and the network slicing tool OpenVirteX. Experimental results prove that our suggested adaptive resource allocation scheme enhances the performance of the emergency services in terms of end-to-end delay while keeping acceptable throughput for non-safety traffic in stressed situations

Software Defined Internet of Vehicles: a survey from QoS and scalability perspectives

International audienceThe idea of leveraging Software Defined Networking (SDN) in vehicular networks has drawn a lot of attention in the last years. SDN flexibility and programmability brought promising solutions for VANET challenges, namely Quality of Services (QoS) and scalability which are the main characteristics of Internet of Vehicles (IoV). Such networks are characterized by fast topological changes due to their variable dynamicity and density. In fact, SDN decouples control plane and data plane, providing programmability to configure the network. However, based on a single controller, SDN is criticized for not supporting scalability and for decreasing the overall network Quality of service. Using multiple controllers becomes the tendency of recent works to meet the need of large networks. Throughout this paper, we survey the proposed SDN-based architectures for vehicular networks. Considering the control plane impact, centralized or distributed, the QoS improvements brought by theses architectures are studied and criticized in order to derive the suitability of each proposal to resolve the IoV challenges and meet its requirements for the various applications

Delay Study in Multi-controller Software Defined Vehicular Network Using OpenDaylight for Emergency Applications

International audienceSDN is a promising solution for vehicular networks challenges. Distributing the SDN control plane achieved more scalability and performance. However, synchronization between different controllers of network state generates extra-delay that is not suitable with delay-sensitive applications in vehicular networks like emergency services. In this paper, we investigate the e2e (end-to-end) delay in variable density vehicular scenarios with variable number of controllers. Our experiments prove the benefits of using multi-controllers in terms of delay but also the need of the deployment of the effective number according to the vehicular network density

Efficient SDN Controller for Safety Applications in SDN-Based Vehicular Networks: POX, Floodlight, ONOS or OpenDaylight?

International audienceThanks to its open programmability and logically centralized control, the software-defined networking (SDN) paradigm presents new potentials for communication and networking management in vehicular networks and promises improved performances. The variety of applications delivered on the road like safety, traffic efficiency and infotainment, in addition to the diversity of developed SDN controllers, triggered the challenge to determine which controller can act better in which service. In this paper we conduct a performance comparison of four open source controllers (POX, Floodlight, ONOS and OpenDaylight) in terms of e2e delay in the context of safety applications in variable vehicular density environment. Experimental study done with advanced tools such as Iperf and Mininet-wifi indicates that ODL is the best in this context