Sharing is caring: a cooperation scheme for RPL network resilience and efficiency

International audienceThe IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) builds a Direction Oriented Directed Acyclic Graph (DODAG) rooted at one node.This node may act as a border router to provide Internet connectivity to the members of the DODAG but such a situation creates a single point of failure.Upon border router failure, all nodes connected to the DODAG are affected as all ongoing communications are instantly broken and no new communications can be initiated.Moreover, nodes close to the border router should forward traffic from farther nodes in addition to their own, which may cause congestion and energy depletion inequality.In this article we specify a full solution to enable border router redundancy in RPL networks.To achieve this, we propose a mechanism leveraging cooperation between colocated RPL networks.It enables failover to maintain Internet connectivity and load balancing to improve the overall energy consumption and bandwidth.Our contribution has been implemented in Contiki OS and was evaluated through experiments performed on the FIT IoT-LAB testbed

Guard time optimisation and adaptation for energy efficient multi-hop TSCH networks

International audienceIn the IEEE 802.15.4-2015 standard, Time Slotted Channel Hopping (TSCH) aims to guarantee high-level network reliability by keeping nodes time-synchronised. In order to ensure successful communication between a sender and a receiver, the latter starts listening shortly before the expected time of a MAC layer frame's arrival. The offset between the time a node starts listening and the estimated time of frame arrival is called guard time and it aims to reduce the probability of missed frames due to clock drift. In this paper, we investigate the impact of the guard time on network performance. We identify that, when using the 6tisch minimal schedule, the most significant cause of energy consumption is idle listening during guard time. Therefore, we first perform mathematical modelling on a TSCH link to identify the guard time that maximises the energy-efficiency of the TSCH network in single hop topology. We then continue in multi-hop network, where we empirically adapt the guard time locally at each node depending its distance, in terms of hops, from the sink. Our performance evaluation results, conducted using the Contiki OS, demonstrate that the proposed decentralised guard time adaptation can reduce the energy consumption by up to 40%, without compromising network reliability

Lossless Multicast Handovers in Proxy Fast Mobile IPv6 Networks

There is a demand in the Public Protection and Disaster Relief (PPDR) community for high bandwidth services on mobile devices. Group communication is an important aspect of PPDR networks. In IP based networks multicast is the preferred method to efficiently transmit data to more than one receiver simultaneously. It is important PPDR users can switch seamlessly between wireless networks. This paper describes improvements to multicast in Fast handovers for Proxy Mobile IPv6 (PFMIPv6) to provide seamless mobility to its users. We also identify and explore the specific problems stemming from difference in end-to-end delay between the old and new path during handovers for multicast traffic. A novel mechanism to determine the delay difference between two paths in a PFMIPv6 system is described and an implementation of this system is evaluated. It is shown the proposed approach can prevent multicast packet loss during a handover

Poster: 4th Industrial Revolution: Toward Deterministic Wireless Industrial Networks

International audienceCritical applications such as industrial process control, smart grid and vehicle automation require networks which offer on-time data delivery and wire-like end-to-end reliability. This paper proposes to exploit path diversity to compensate for the lossy nature of the wireless medium. We introduce " Leapfrog Collaboration " , a communication mechanism in which multiple copies of the same packet traverse the network on disjoint paths. Emulation results on Cooja show that, compared to single-path transmission, this technique reduces end-to-end delay by up to 28%, and jitter by up to 58%

Stratégies d'ancêtre commun pour les réseaux RPL multi-chemins

National audienceThe IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) networks is designed for Internet of Things (IoT) networks to generate routes between devices with minimal processing. This protocol creates a DODAG (Destination Oriented Directed Acyclic Graph) network topology through the use of DODAG Information Object (DIO) control packets. The DODAG routes the data packets upstream to the destination device. In order to obtain a reliable network, we implement Packet Replication and Elimination (PRE) to perform multi-path data transmission via multiple parent devices. However, there is no standard way to select an alternative path. This document presents three types of Alternative Parent (AP) selection following a braided model. We focus on analyzing its performance in terms of delay and compromise between network traffic and reliability.Le protocole de routage IPv6 pour les réseaux à faible puissance et fort taux de pertes (RPL) est conçu pour les réseaux Internet des objets (IoT) afin de générer des itinéraires entre les appareils avec un traitement minimal. Ce protocole crée une topologie de réseau DODAG (Destination Oriented Directed Acyclic Graph) grâce à l'utilisation de paquets de contrôle DODAG Information Object (DIO). Le DODAG achemine les paquets de données en amont vers le périphérique de destination. Afin d'obtenir un réseau fiable, nous implémentons la réplication et l'élimination des paquets (PRE) pour effectuer une transmission de données à chemins multiples via plusieurs périphériques parents. Cependant, il n'existe aucun moyen standard de sélectionner un chemin alternatif. Ce document présente trois types de sélection de parent alternatif (AP) suivant un modèle triangulaire. Nous nous concentrons sur l'analyse de ses performances en termes de retard et de compromis entre trafic réseau et fiabilité

The revenge of asynchronous protocols: Wake-up Radio-based Multi-hop Multi-channel MAC protocol for WSN

International audienceSynchronized MAC protocols are now considered as the ultimate solution to access the medium in wireless sensor networks. They guarantee both high throughout and constant latency and achieve reasonable energy consumption performance. However, synchronization is achieved at the cost of a complex framework with low flexibility on its parameters that is not suitable for some network topologies or application requirements. By contrast, asynchronous MAC protocols are versatile by nature but suffer from the tradeoff between energy consumption and latency. However, the addition of Wake-up Radio (WuR) can reduce the energy consumption of such protocols while maintaining very low latency thanks to its always-on feature and ultra-low power consumption. In this article, we present WuR- based Multi-hop Multi-channel (W2M), an asynchronous MAC protocol for wireless sensor networks. We also provide a fair comparison with Time Synchronized Channel Hopping (TSCH) through an extensive simulation campaign based on Contiki-NG and Cooja. Our results show that in low traffic scenarios, W2M outperforms TSCH in reducing both the energy consumption and the latency (at least 68% of energy is saved), but at the cost of slightly lower reliability

Exploring efficient seamless handover in VANET systems using network dwell time

Vehicular ad hoc networks are a long-term solution contributing significantly towards intelligent transport systems (ITS) in providing access to critical life-safety applications and services. Although vehicular ad hoc networks are attracting greater commercial interest, current research has not adequately captured the real-world constraints in vehicular ad hoc network handover techniques. Therefore, in order to have the best practice for vehicular ad hoc network services, it is necessary to have seamless connectivity for optimal coverage and ideal channel utilisation. Due to the high velocity of vehicles and smaller coverage distances, there are serious challenges in providing seamless handover from one roadside unit (RSU) to another. Though other research efforts have looked at many issues in vehicular ad hoc networks (VANETs), very few research work have looked at handover issues. Most literature assume that handover does not take a significant time and does not affect the overall VANET operation. In our previous work, we started to investigate these issues. This journal provides a more comprehensive analysis involving the beacon frequency, the size of beacon and the velocity of the vehicle. We used some of the concepts of Y-Comm architecture such as network dwell time (NDT), time before handover (TBH) and exit time (ET) to provide a framework to investigate handover issues. Further simulation studies were used to investigate the relation between beaconing, velocity and the network dwell time. Our results show that there is a need to understand the cumulative effect of beaconing in addition to the probability of successful reception as well as how these probability distributions are affected by the velocity of the vehicle. This provides more insight into how to support life critical applications using proactive handover techniques

Trends in pediatric epilepsy surgery in Europe between 2008 and 2015: Country‐, center‐, and age‐specific variation

OBJECTIVE: To profile European trends in pediatric epilepsy surgery (<16 years of age) between 2008 and 2015. METHODS: We collected information on volumes and types of surgery, pathology, and seizure outcome from 20 recognized epilepsy surgery reference centers in 10 European countries. RESULTS: We analyzed retrospective aggregate data on 1859 operations. The proportion of surgeries significantly increased over time (P < .0001). Engel class I outcome was achieved in 69.3% of children, with no significant improvement between 2008 and 2015. The proportion of histopathological findings consistent with glial scars significantly increased between the ages of 7 and 16 years (P for trend = .0033), whereas that of the remaining pathologies did not vary across ages. A significant increase in unilobar extratemporal surgeries (P for trend = .0047) and a significant decrease in unilobar temporal surgeries (P for trend = .0030) were observed between 2008 and 2015. Conversely, the proportion of multilobar surgeries and unrevealing magnetic resonance imaging cases remained unchanged. Invasive investigations significantly increased, especially stereo‐electroencephalography. We found different trends comparing centers starting their activity in the 1990s to those whose programs were developed in the past decade. Multivariate analysis revealed a significant variability of the proportion of the different pathologies and surgical approaches across countries, centers, and age groups between 2008 and 2015. SIGNIFICANCE: Between 2008 and 2015, we observed a significant increase in the volume of pediatric epilepsy surgeries, stability in the proportion of Engel class I outcomes, and a modest increment in complexity of the procedures

Phenomenological psychology Husserl’s static and genetic methods

A new framework for phenomenological psychology is proposed based on Husserl’s static and genetic methods. Static phenomenology holds a eidetic psychology centred on the processes of noetic-noematic constitution and elaborates typologies and general notions about human beings in connection with the world. Genetic analysis is research into facticity, it focus on the personal history of a subject, which is constantly in the process of becoming. When the temporal dimension of consciousness is considered, the phenomenological method becomes ‘static’, as it excludes the factitious dimension of self, its personal and individual history, sedimented in layers of meaning, which are in part pre-reflective, non-thematic and anonymous to the self, but which nevertheless continue to influence the experience of itself with the other and with the world. This paper aims to present some of the fundamental principals of genetic phenomenology and it’s application to existential-phenomenological psychotherapy. There are three main aspects underlying geneticphenomenological analysis as it is being proposed: inner time-consciousness theory, the experiential self and the theory of passive geneses