WiFly: experimenting with Wireless Sensor Networks and Virtual coordinates

Experimentation is important when designing communication protocols for Wireless Sensor Networks. Lower-layers have a major impact on upper-layer performance, and the complexity of the phenomena can not be entirely captured by analysis or simulation. In this report, we go through the complete process, from designing an energy-efficient self-organizing communication architecture (MAC, routing and application layers) to real-life experimentation roll-outs. The presented communication architecture includes a MAC protocol which avoids building and maintaining neighborhood tables, and a geographically-inspired routing protocol over virtual coordinates. The application consists of a mobile sink interrogating a wireless sensor network based on the requests issued by a disconnected base station. After the design process of this architecture, we verify it functions correctly by simulation, and we perform a temporal verification. This study is needed to calculate the maximum speed the mobile sink can take. We detail the implementation, and the results of the off-site experimentation (energy consumption at PHY layer, collision probability at MAC layer, and routing). Finally, we report on the real-world deployment where we have mounted the mobile sink node on a radio-controlled airplane

Exploiting Asymmetric Links in a Convergecast Routing Protocol for WSNs

Most of the existing routing protocol designed for WSNs assume that links are symmetric which is in contradiction to the reality of these networks. Indeed, asymmetric links cannot be ignored in WSNs as they can be predominant. The apparition of asymmetric links can dramatically decrease routing protocols that are not designed to support them by decreasing the delivery ratio and increasing the duplicated packet received at the destination. Obviously, most of the existing routing protocols prune the asymmetric links and only maintain the symmetric ones. From our point of view, the asymmetric links have to be considered as they can be effective in the network connectivity insurance. Moreover, they open new opportunities to improve the performance of routing protocols. From this perspective and in order to take benefit from asymmetric links, we propose a routing protocol for data collection in WSNs called AsymRP (Asymmetric Routing Protocol). AsymRP is a convergecast routing protocol which is based on a 2-hop neighbor knowledge combined with implicit and explicit source routing acknowledgment. Our proposal takes advantage of asymmetric links, enables the network to achieve higher delivery ratio while reducing significantly the number of duplicated packets and hop counts. Our simulation results show that our proposal AsymRP can significantly outperform traditional routing protocols in the presence of asymmetric links in the network

Self-organization in Sensor and Actuators Networks: Strategies and their optimizations

In Wireless Sensors and Actuators Networks (WSANs), actuator nodes are nodes richer in resources (processing capacity, power transmission and energy storage) and better suited than sensor nodes to process the data, make decisions based on sensed values and perform appropriate actions. In addition, in order to provide timely action, coordination between sensors and actuators is necessary. Thus, in addition to the classical energy constraints of Wireless Sensor Networks (WSNs), WSANs also impose new challenges such as how to support and benefit from the nodes heterogeneity while preserving energy in the self-powered sensor nodes. New communication protocols, specific to WSANs, are needed. In this report, we propose a hybrid self-organizing data-collection protocol in order to provide energy efficiency, low end-to-end delay and high delivery ratio while taking advantage of the resource available on the actuators nodes in the network. This new self-organization protocol constructs its structure from the actuators and other resource-plentiful nodes. The nature of the structure is different inside and outside of transmission range of these resourceful nodes. Two variant of our proposal are detailed also in this report.Dans un réseau sans fil de capteurs et actionneurs (Wireless Sensors and Actuators Networks WSAN), les nœuds actionneurs sont des nœuds riches en ressources (capacité de traitement, de puissance de transmission et de stockage en mémoire et en énergie) et sont mieux adaptés que les nœuds capteurs à traiter les données, prendre des décisions fondées sur les observations remontées par les capteurs et effectuer les actions appropriées. En outre, afin d'offrir une action dans les délais, la coordination entre les capteurs et les actionneurs est nécessaire. Ainsi, outre les contraintes de l'énergie comme dans les réseaux de capteurs classiques (Wireless Sensor Networks WSN), les WSANs imposent également des contraintes de temps sous la forme de délai de bout-en-bout. Ainsi des nouvelles propositions de communication spécifiques aux WSAN sont nécessaires, qui fournissent un délai de bout-en-bout contrôlé tout en préservant l'énergie au niveau des nœuds capteurs. Dans ce contexte, nous décrivons dans ce rapport une proposition d'auto-organisation dans les WSANs. Notre proposition crée une structure autour de chaque actionneur. Une phase d'initialisation et de construction de gradient s'appuyant sur des anneaux concentriques autour des actionneurs, ensuite une phase de découverte de voisinage, de construction de structure logique et enfin une phase de remontée des observations des capteurs vers les nœuds actionneurs. Deux variantes de notre proposition sont présentées par la suite pour répondre à quelques points faibles de la proposition de base

Secure Lossless Aggregation Over Fading and Shadowing Channels for Smart Grid M2M Networks

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Initial Design of a Generalization of the 6TiSCH Standard to Support Multiple PHY Layers

This report introduces early results from an experiment to integrate multiple radios in the same 6TiSCH network. It is provides an initial step towards the publication of an article tentatively titled “Generalized 6TiSCH for an Agile Multi-PHY Wireless Networking”. The work discussed the architecture of the proposed solution, and presents its performance compared to single-PHY networks.Ce rapport contient des résultats préliminaires d’une étude pour utiliser plusieurs couches physiques dans un même réseau 6TiSCH. Il s’agit d’une première étape dans le but de publier nos travaux complets, sous le titre (en anglais) “Generalized 6TiSCH for an Agile Multi-PHY Wireless Networking”. Ce rapport détaille l’architecture évaluée, et présente les performance de l’approche, en comparaison avec un réseau qui n’utilise qu’une seule couche physique

SLA Specification for IoT Operation - The WSN-SLA Framework

In this specification, we provide a guideline to write Service Level Agreements (SLAs) For the Internet Of Things (IoT) Operation. Current growth in the field of connected devices open the door to Wireless Sensor Network (WSN) Operators that share their operated transmission infrastructure among several clients. Each client company has specific application needs for the transmission of messages between their devices and their Information System. Some require bounded delays, others want minimal loss rate. The WSN Operator must fulfill these Quality of Service (QoS) requirements, as specified in a contract, the SLA. In the Web Services domain, SLAs have been studied for long, and a specification was given, in XML format, in the WSLA framework. We extend the specification with specific items that integrate the WSN constraints into the SLA framework. We give the possibility to address specific sets of sensors with a given QoS. We facilitate the construction of complex metrics that express the performance of the WSN. Our solution gives useful information for direct implementation in the field.Dans cette spécification, nous proposons un modèle de rédaction de contrats Service Level Agreements (SLA) pour opérer l'Internet des Objets (IoT). L'importance croissante du domaine des objets connectés permet à des opérateurs de réseaux de capteurs (WSN Operators) de mu- tualiser leur infrastructure radio pour plusieurs clients. Chaque entreprise cliente a des besoins applicatifs spécifiques liés à la transmission de messages entre leurs capteurs et leurs systèmes d'information. L'opérateur de réseaux de capteurs doit respecter ces exigences de Qualité de Service (QoS), comme cela est spécifié dans un contrat, le SLA. Dans le domaine des Web Services, les contrats SLA ont été étudiés depuis longtemps, et il en a été donné une spécification en XML : c'est le modèle WSLA. Nous étendons cette spécification en y intégrant des éléments qui répondent aux contraintes des réseaux de capteurs. Nous donnons la possibilité de respecter la QoS pour des ensembles particuliers de capteurs (par exemple sur une zone donnée). Nous permettons la construction de métriques complexes qui rendent compte de la performances des réseaux de capteurs. Notre solution donne des informations utiles pour un déploiement sur le terrain

Bringing life out of diversity: Boosting network lifetime using multi‐PHY routing in RPL

International audienceIn this article, we propose a routing mechanism based on the RPL protocol in a wireless network that is equipped with a mix of short-range and long-range radios. We introduce Life-OF, an objective function for RPL which uses a combination of metrics and the diverse physical layers to boost the network's lifetime. We evaluate the performance of Life-OF compared to the classical MRHOF objective function in simulations. Two key performance indicators (KPIs) are reported: network lifetime and network latency. Results demonstrate that MRHOF tends to converge to a pure long-range network, leading to short network lifetime. However, Life-OF improves network lifetime by continuously adapting the routing topology to favor routing over nodes with longest remaining lifetime. Life-OF combines diverse radios and balances power consumption in the network. This way, nodes switch between using their short-range radio to improve their own battery lifetime and using their long-range radio to avoid routers that are close to depletion. Results show that using Life-OF improves the lifetime of the network by up to 470% that of MRHOF, while maintaining similar latency

No Free Lunch - Characterizing the Performance of 6TiSCH When Using Different Physical Layers

International audienceLow-power wireless applications require different trade off points between latency, reliability ,data rate and power consumption. Given such a set of constraints, which physical layer should I beusing? We study this question in the context of 6TiSCH,a state-of-the-art recently standardized protocol stack developed for harsh industrial applications. Specifically,we augment OpenWSN, the reference 6TiSCHopen-source implementation,to support one of three physical layers from the IEEE802.15.4g standard FSK 868 MHz which offers long range, OFDM 868 MHz which offers high data rate,and O-QPSK 2.4GHz which offers more balanced performance. We run the resulting firmware on the42-mote Open Testbed deployed in an office environment, once for each physical layer. Performance results show that, indeed, no physical layer outperforms the other for all metrics. This article argues for combining the physical layers, rather than choosing one,in a generalized 6TiSCH architecture in which technology-agile radio chips (of which there are now many) are driven by a protocol stack which c hooses the most appropriate physical layer on a frame-by-frame basis

g6TiSCH: Generalized 6TiSCH for Agile Multi-PHY Wireless Networking

International audienceWireless networks traditionally use a single physical layer for communication: some use high bit-rate short-range radios, others low bit-rate long-range radios. This article introduces g6TiSCH, a generalization of the standards-based IETF 6TiSCH protocol stack. g6TiSCH allows nodes equipped with multiple radios to dynamically switch between them on a link-by-link basis, as a function of link-quality. This approach results in a dynamic trade-off between latency and power consumption. We evaluate the performance of the approach experimentally on an indoor office testbed of 36 OpenMote B boards. Each OpenMote B can communicate using FSK 868 MHz, O-QPSK 2.4 GHz or OFDM 868 MHz, a combination of long-range and short-range physical layers. We measure network formation time, end-to-end reliability, end-to-end latency, and battery lifetime. We compare the performance of g6TiSCH against that of a traditional 6TiSCH stack running on each of the three physical layers. Results show that g6TiSCH yields lower latency and network formation time than any of the individual PHYs, while maintaining a similar battery lifetime

WiFly: experimenting with Wireless Sensor Networks and Virtual coordinates

Experimentation is important when designing communication protocols for Wireless Sensor Networks. Lower-layers have a major impact on upper-layer performance, and the complexity of the phenomena can not be entirely captured by analysis or simulation. In this report, we go through the complete process, from designing an energy-efficient self-organizing communication architecture (MAC, routing and application layers) to real-life experimentation roll-outs. The presented communication architecture includes a MAC protocol which avoids building and maintaining neighborhood tables, and a geographically-inspired routing protocol over virtual coordinates. The application consists of a mobile sink interrogating a wireless sensor network based on the requests issued by a disconnected base station. After the design process of this architecture, we verify it functions correctly by simulation, and we perform a temporal verification. This study is needed to calculate the maximum speed the mobile sink can take. We detail the implementation, and the results of the off-site experimentation (energy consumption at PHY layer, collision probability at MAC layer, and routing). Finally, we report on the real-world deployment where we have mounted the mobile sink node on a radio-controlled airplane