Distributed competition to compute localized scheduling

Duty-cycled medium access protocols allow for long lasting au- tonomous networks by periodically putting nodes to sleep. However, this life expectancy improvement comes at the cost of a lesser network capacity and a poor adaptability to bursty traffic loads. Indeed, existing contention algorithms do not provide efficient algorithms to dynamically elect multiple senders per wake-up periods. In this paper, the medium is divided in several logical chan- nels (eg. obtained by a time/frequency division of the communication medium) and we propose to allocate them dynamically among senders. For this purpose, we propose a joint contention/scheduling algorithm, named Extended Slot Se- lection (ESS), that schedules multiple sender/receiver pairs to available logical channels

Mécanisme de compétition pour allocation localisée de ressources multiples

Session Réseaux de capteursInternational audienceL'endormissement cyclique permet l'élaboration de protocoles d'accès au canal peu consommants en énergie pour des réseaux de noeuds limités en ressources et devant opérer durant plusieurs années.Cependant le gain en durée de vie que confèrent ces protocoles est obtenu au détriment de la capacité du réseau et de son adaptabilité aux bouffées de trafic. Les mécanismes existants de gestion de la compétition ne permettent en effet pas d'élire et ordonnancer plusieurs transmissions de façon dynamique et localisée. Dans ce travail, nous considérons un médium sub-divisé en plusieurs canaux logiques (obtenus par exemple par un partage en temps/fréquence du medium de communication) et nous proposons d'allouer dynamiquement ces différentes ressources aux noeuds désirant émettre. Dans cette optique, nous proposons un mécanisme localisé de compéti- tion/ordonnancement, appelé Extended Slot Selection (ESS), qui permet l'allocation dynamique d'une pluralité de canaux logiques aux différentes paires émetteurs/récepteurs

RTXP : A Localized Real-Time Mac-Routing Protocol for Wireless Sensor Networks

Protocols developed during the last years for Wireless Sensor Networks (WSNs) are mainly focused on energy efficiency and autonomous mechanisms (e.g. self-organization, self-configuration, etc). Nevertheless, with new WSN applications, appear new QoS requirements such as time constraints. Real-time applications require the packets to be delivered before a known time bound which depends on the application requirements. We particularly focus on applications which consist in alarms sent to the sink node. We propose Real-Time X-layer Protocol (RTXP), a real-time communication protocol. To the best of our knowledge, RTXP is the first MAC and routing real-time communication protocol that is not centralized, but instead relies only on local information. The solution is cross-layer (X-layer) because it allows to control the delays due to MAC and Routing layers interactions. RTXP uses a suited hop-count-based Virtual Coordinate System which allows deterministic medium access and forwarder selection. In this paper we describe the protocol mechanisms. We give theoretical bound on the end-to-end delay and the capacity of the protocol. Intensive simulation results confirm the theoretical predictions and allow to compare with a real-time centralized solution. RTXP is also simulated under harsh radio channel, in this case the radio link introduces probabilistic behavior. Nevertheless, we show that RTXP it performs better than a non-deterministic solution. It thus advocates for the usefulness of designing real-time (deterministic) protocols even for highly unreliable networks such as WSNs

Reconfigurable medium access control solutions for resource constrained wireless networks

Wireless Sensor Networks (WSNs) consist of several autonomous resource constrained sensor nodes distributed over a geographical area. The sensor nodes can measure, for instance humidity, temperature or vibration. Therefore, these networks can be deployed in many different types of dynamic environments. Traditionally, Medium Access Control (MAC) protocols used in WSNs are implemented in a monolithic fashion with tight coupling to the underlying hardware. Although this approach of design and implementation can usually make full use of the capability of the underlying hardware, theMACsolution is static and provides satisfying performance only under the pre-defined conditions. However, as application requirements and network conditions may change, adaptability and reconfigurability of MAC protocols are desired. In this thesis, we have designed and implemented a toolchain which enables runtimeMACprotocol reconfiguration for WSNs. The toolchain has been implemented in TinyOS using component-based design and hardware independence, allowing users to develop MAC solutions for WSNs, execute and reconfigure them in many platforms. Finally, a user is able to interact with the sensor node through a user interface developed in Java. Furthermore, this toolchain has been enhanced by the features introduced in [1] to enable also simplifying the design of MAC protocols, allowing non-specific sensors users to implement and finally execute and reconfigure them in sensor nodes. The toolchain has been compared to monolithic implementations in terms of execution time and reconfiguration costs. The results show that the toolchain enables fast runtime reconfiguration of MAC protocols with an quantify execution time overhead. Our toolchain saves from 26% up to 98% the time needed to reconfigure a MAC protocol compared to the monolithic approach

A tool for rapid MAC protocols prototyping and designing for wireless sensor networks

Wireless Sensor Networks (WSNs)consists of several resource constrained sensor nodes distributed over an specific geographical area. WSNs are typically energy constraint due to the fact the sensor nodes are battery powered. Medium Access Control (MAC) protocols used in WSNs are usually designed to be power aware, i.e., they are more energy efficient than MAC protocols used for other ad-hoc wireless networks such as IEEE 802.11 [2]; to increase the lifetime of the nodes. Traditional MAC protocol implementations are done for specific hardware platforms using a monolithic approach. Therefore, it is very difficult to port from one platform to another without modifying the whole implementation protocol. This reduces code reusage and increases the implementation efforts. We have designed and implemented a toolchain which allows to design and prototype MAC protocols for WSNs in a simple manner. In addition, it allows non-specific sensors users to implement and execute them in sensor nodes without worrying about technical specifications of the platforms. The toolchain has been implemented in TinyOS using a component-based design. Special care has been taken to ensure hardware independence of the protocol implementations described in this thesis has been integrated with [1] to allow runtime reconfiguration of MAC protocols. We have evaluated our toolchain against monolithic implementations in terms of memory consumption and execution time. The results show that the toolchain introduces an acceptable memory and execution time overhead, less than 5 %, compared to the monolithic approach and substantially eases the implementation efforts

Protocoles de routage sans connaissance de voisinage pour réseaux radio multi-sauts

L'efficacité énergétique constitue l'objectif clef pour la conception des protocoles de communication pour des réseaux de capteurs radio multi-sauts. Beaucoup d'efforts ont été réalisés à différents niveaux de la pile protocolaire à travers des algorithmes d'agrégation spatiale et temporelle des données, des protocoles de routage efficaces en énergie, et des couches d'accès au médium avec des mécanismes d'ordonnancement permettant de mettre la radio en état d'endormissement afin d'économiser l'énergie. Pour autant, ces protocoles utilisent de façon importante des paquets de contrôle et de découverte du voisinage qui sont coûteux en énergie. En outre, cela se fait très souvent sans aucune interaction entre les différentes couches de la pile. Ces travaux de thèse s'intéressent donc particulièrement à la problématique de l'énergie des réseaux de capteurs à travers des protocoles de routage et d'accès au médium. Les contributions de cette thèse se résument de la manière suivante : Nous nous sommes tout d'abord intéressés à la problématique de l'énergie au niveau routage. Dans cette partie, les contributions se subdivisent en deux parties. Dans un premier temps, nous avons proposé une analyse théorique de la consommation d'énergie des protocoles de routage des réseaux radio multi-sauts d'appréhender au mieux les avantages et les inconvénients des uns et des autres en présence des modèles de trafic variables, un diamètre du réseau variable également et un modèle radio qui permet de modéliser les erreurs de réception des paquets. À l'issue de cette première étude, nous sommes parvenus à la conclusion que pour être économe en énergie, un protocole de routage doit avoir des approches similaires à celle des protocoles de routage géographique sans message hello. Puis, dans un second temps, nous introduisons une étude de l'influence des stratégies de relayage dans un voisinage à 1 saut sur les métriques de performance comme le taux de livraison, le nombre de messages dupliqués et la consommation d'énergie. Cette étude est suivie par une première proposition de protocole de routage géographique sans message hello (Pizza-Forwarding (PF)) exploitant des zones de relayage optimisées et sans aucune hypothèse sur les propriétés du canal radio. Dans le but de réduire considérablement la consommation de PF, nous proposons de le combiner avec une adaptation d'un protocole MAC asynchrone efficace en énergie à travers une approche transversale. La combinaison de ces deux approches montre un gain significatif en terme d'économie d'énergie avec des très bon taux de livraison et cela quels que soient les scénarios et la nature de la topologique.Energy-efficient communication protocol is a primary design goal for Wireless Sensor Networks (WSNs). Many efforts have been done to save energy anywhere in the protocol stack through temporal and spatial data aggregation schemes, energy-aware routing protocols, activity scheduling and energy-efficient MAC protocols with duty cycle. However both control packets and beacons remain which induces a huge waste energy. Moreover, their design follows the classical layered approach with the principle of modularity in system development, which can lead to a poor performance in WSNs. This thesis focuses on the issues of energy in WSNs through energy-efficient routing and medium access control protocols. The constributions of this thesis can be summarized as follows: First, we are interested on the energy issues at the routing layer for multihop wireless sensor networks (WSNs). We propose a mathematical framework to model and analyze the energy consumption of routing protocols in multihop WSNs by taking into account the protocol parameters, the traffic pattern and the network characteristics defined by the medium channel properties, the dynamic topology behavior, the network diameter and the node density. In this study, we show that Beacon-less routing protocol should be a best candidate to save energy in WSNs. We investigate the performance of some existing relay selection schemes which are used by Beacon-less routing protocols. Extensive simulations are proposed to evaluate their performance locally in terms of packet delivery ratio, duplicated packet and delay. Then, we extend the work in multihop wiriless networks and develop an optimal solution, Enhanced Nearest Forwarding within Radius, which tries to minimize the per-hop expected number of retranmissions in order to save energy. We present a new beaconless routing protocol called Pizza-Forwarding (PF) without any assumption on the radio environment: neither the radio range nor symmetric radio links nor radio properties (shadowing, etc.) are assumed or restricted. A classical greedy mode is proposed. To overcome the hole problem, packets are forwarded to an optimal node in the two hop neighbor following a reactive and optimized neighborhood discovery. In order to save energy due to idle listening and overhearing, we propose to combine PF's main concepts with an energy-efficient MAC protocol to provide a joint MAC/routing protocol suitable for a real radio environment. Performance results lead to conclude to the powerful behavior of PFMAC.VILLEURBANNE-DOC'INSA-Bib. elec. (692669901) / SudocSudocFranceF