Time Segmentation Approach Allowing QoS and Energy Saving for Wireless Sensor Networks

Wireless sensor networks are conceived to monitor a certain application or physical phenomena and are supposed to function for several years without any human intervention for maintenance. Thus, the main issue in sensor networks is often to extend the lifetime of the network by reducing energy consumption. On the other hand, some applications have high priority traffic that needs to be transferred within a bounded end-to-end delay while maintaining an energy efficient behavior. We propose MaCARI, a time segmentation protocol that saves energy, improves the overall performance of the network and enables quality of service in terms of guaranteed access to the medium and end-to-end delays. This time segmentation is achieved by synchronizing the activity of nodes using a tree-based beacon propagation and allocating activity periods for each cluster of nodes. The tree-based topology is inspired from the cluster-tree proposed by the ZigBee standard. The efficiency of our protocol is proven analytically, by simulation and through real testbed measurements

An IEEE 802.15.4 based adaptive communication protocol in wireless sensor network : application to monitoring the elderly at home

International audienceMonitoring behaviour of the elderly and the disabled living alone has become a major public health problem in our modern societies. Among the various scientific aspects involved in the home monitoring field, we are interested in the study and the proposal of a solution allowing distributed sensor nodes to communicate with each other in an optimal way adapted to the specific application constraints. More precisely, we want to build a wireless network that consists of several short range sensor nodes exchanging data between them according to a communication protocol at MAC (Medium Access Control) level. This protocol must be able to optimize energy consumption, transmission time and loss of information. To achieve this objective, we have analyzed the advantages and the limitations of WSN (Wireless Sensor Network) technologies and communication protocols currently used in relation to the requirements of our application. Then we proposed a deterministic, adaptive and energy saving medium access method based on the IEEE 802.15.4 physical layer and a mesh topology. It ensures the message delivery time with strongly limited collision risk due to the spatial reuse of medium in the two-hop neighbourhood. This proposal was characterized by modelling and simulation using OPNET network simulator. Finally we implemented the proposed mechanisms on hardware devices and deployed a sensors network in real situation to verify the accuracy of the model and evaluate the proposal according to different test configurations

Deployment Experience with Low Power Lossy Wireless Sensor Networks

Protocols that are to be employed in the context of the Internet of Things (IoT) have to meet a wide variety of application-specific requirements. In this report, we reflect on recent experiences, gained from several real-world deployments in which we have participated, which use low power, embedded networking devices. We discuss the lessons learned from these deployments, with an emphasis on questions affecting the IP layer and, in particular, on the routing protocols for these networks. We point out open issues and possible directions of future work for such routing protocols

Ordonnancement de l'activité des noeuds dans les réseaux ad hoc et les réseaux de capteurs sans fil

National audienceL'efficacité énergétique est une exigence majeure pour les réseaux sans fil où certains noeuds opèrent sur batterie. L'ordonnancement de l'activité des noeuds permet de distinguer périodes actives où la communication radio est possible et périodes inactives où la radio est arrêtée. Cet ordonnancement contribue largement à améliorer l'efficacité énergétique : d'une part en évitant les collisions entre transmissions conflictuelles et donc les retransmissions associées et d'autre part en permettant aux noeuds non concernés par la transmission de dormir pour économiser leur énergie. Parmi les solutions possibles, nous étudierons plus particulièrement le coloriage des noeuds. Après avoir défini le problème et ses différentes déclinaisons, nous donnerons sa complexité et proposerons SERENA, un algorithme de coloriage distribué qui s'adapte à la collecte de données. Nous présenterons OSERENA, l'optimisation de SERENA pour les réseaux denses et son utilisation dans le réseau de capteurs sans fil OCARI. Lorsque les noeuds ont des charges de trafic fortement hétérogènes, il devient plus intéressant d'effectuer une assignation de slots. Disposer d'un accès au médium multicanal et d'un puits multi-interfaces permet de gagner en nombre de slots nécessaires à la collecte de données, de réduire les interférences et d'améliorer la résistance aux perturbations. Nous présenterons une formalisation en ILP (Integer Linear Programming) du problème d'assignation de slots visant à minimiser le nombre de slots en profitant d'un environnement mono ou multicanal et d'un puits mono ou multi-interfaces. Nous donnerons des bornes théoriques sur le nombre optimal de slots dans diverses configurations et divers environnements (mono ou multicanal, puits mono ou multi-interfaces). Nous présenterons MODESA un algorithme centralisé d'allocatoion conjointe de canaux et slots temporels. Nous terminerons par quelques questions ouvertes

A critical analysis of research potential, challenges and future directives in industrial wireless sensor networks

In recent years, Industrial Wireless Sensor Networks (IWSNs) have emerged as an important research theme with applications spanning a wide range of industries including automation, monitoring, process control, feedback systems and automotive. Wide scope of IWSNs applications ranging from small production units, large oil and gas industries to nuclear fission control, enables a fast-paced research in this field. Though IWSNs offer advantages of low cost, flexibility, scalability, self-healing, easy deployment and reformation, yet they pose certain limitations on available potential and introduce challenges on multiple fronts due to their susceptibility to highly complex and uncertain industrial environments. In this paper a detailed discussion on design objectives, challenges and solutions, for IWSNs, are presented. A careful evaluation of industrial systems, deadlines and possible hazards in industrial atmosphere are discussed. The paper also presents a thorough review of the existing standards and industrial protocols and gives a critical evaluation of potential of these standards and protocols along with a detailed discussion on available hardware platforms, specific industrial energy harvesting techniques and their capabilities. The paper lists main service providers for IWSNs solutions and gives insight of future trends and research gaps in the field of IWSNs

The Internet of Things and The Web of Things

International audienceThe Internet of Things is creating a new world, a quantifiable and measureable world, where people and businesses can manage their assets in better informed ways, and can make more timely and better informed decisions about what they want or need to do. This new con-nected world brings with it fundamental changes to society and to consumers. This special issue of ERCIM News thus focuses on various relevant aspects of the Internet of Things and the Web of Things

Optimal Number of Message Transmissions for Probabilistic Guarantee in the IoT

International audienceThe Internet of Things (IoT) is now experiencing its first phase of industrialization. Industrial companies are completing proofs of concept and many of them plan to invest in automation, flexibility and quality of production in their plants. Their use of a wireless network is conditioned upon its ability to meet three Key Performance Indicators (KPIs), namely a maximum acceptable end-to-end latency L, a targeted end-to-end reliability R and a minimum network lifetime T. The IoT network has to guarantee that at least R% of messages generated by sensor nodes are delivered to the sink with a latency ≤ L, whereas the network lifetime is at least equal to T. In this paper, we show how to provide the targeted end-to-end reliability R by means of retransmissions to cope with the unreliability of wireless links. We present two methods to compute the maximum number of transmissions per message required to achieve R. M F air is very easy to compute, whereas M Opt minimizes the total number of transmissions necessary for a message to reach the sink. M F air and M Opt are then integrated into a TSCH network with a load-based scheduler to evaluate the three KPIs on a generic data-gathering application. We first consider a toy example with eight nodes where the maximum number of transmissions M axT rans is tuned per link and per flow. Finally, a network of 50 nodes, representative of real network deployments, is evaluated assuming M axT rans is fixed. For both TSCH networks, we show that M Opt provides a better reliability and a longer lifetime than M F air, which provides a shorter average end-to-end latency. M Opt provides more predictable end-to-end performances than Kausa, a KPI-aware, state-of-the-art scheduler

CONGESTION CONTROL FOR A ULTRA-WIDEBAND DYNAMIC SENSOR NETWORK USING AUTONOMIC BASED LEARNING

The physical conditions of the area of interest is being collected at the central location using a set of dedicated sensors that forms a network is referred to as Wireless Sensor Network. A dynamic environment is required for a secure multi-hop communication between nodes of the heterogeneous Wireless Sensor Network. One such solution is to employ autonomic based learning in a MAC Layer of the UWB TxRx. Over a time period the autonomic based network learns from the previous experience and adapts to the environment significantly. Exploring the Autonomicity would help us in evading the congestion of about 30% in a typical UWB-WSNs. Simulation results showed an improvement of 5% using Local Automate Collision Avoidance Scheme (LACAS-UWB) compared to LACAS

Wave : un Algorithme d'Ordonnancement Distribué pour la Collecte de Données dans les R\'eseaux IEEE 802.15.4e (Version Etendue)

Wireless NetworksWireless sensor networks (WSNs) play a major role in industrial environments for data gathering (convergecast). Among the industrial requirements, we can name a few like 1) determinism and bounded convergecast latencies, 2) throughput and 3) robustness against interferences.The classical IEEE 802.15.4 that has been designed for low power lossy networks (LLNs) partially meets these requirements. That is why the IEEE~802.15.4e MAC amendmenthas been proposed recently. This amendment combines a slotted medium access with a channel hopping (i.e. Time Slotted Channel Hopping TSCH). The MAC layer orchestrates the medium accesses of nodes according to a given schedule. Nevertheless, this amendment does not specify how this schedule is computed. The purpose of this paper is to propose a distributed joint time slot and channel assignment, called Wave for data gathering in LLNs. This schedule targets minimized data convergecast delays by reducing the number of slots assigned to nodes. Moreover, Wave ensures the absence of conflicting transmissions in the schedule provided. In such a schedule, a node is awake only during its slots and the slots of its children in the convergecast routing graph. Thus, energy efficiency is ensured. In this paper, we describe in details the functioning of Wave, highlighting its features (e.g. support of heterogeneous traffic, support of a sink equipped with multiple interfaces) and properties in terms of worst case delays and buffer size. We discuss its features with regard to a centralized scheduling algorithm like TMCP and a distributed one like DeTAS. Simulation results show the good performance of Wave compared to TMCP. Since in an industrial environment, several routing graphs can coexist, we study how Wave supports this coexistence.Les réseaux de capteurs sans fil jouent un rôle majeur pour la collecte de données dans les environnements industriels.Parmi les exigences industrielles visées, nous pouvons citer 1) le déterminisme et les latences de collecte bornées supérieurement, 2) le débit et 3) la robustesse vis-à-vis des interférences.La norme IEEE 802.15.4 classique, qui a été conçue pour les réseaux avec pertes et contraintes énergétiques (ou Low power Lossy Networks, LLNs), ne répond que partiellement à ces exigences. C'est pourquoi l'amendement IEEE~802.15.4e a été proposé récemment.Cet amendement propose un mode d'utilisation TSCH (Time Slotted Channel Hopping) combinant l'accès au médium par slots temporels et le saut de fréquence.La couche MAC orchestre les accès au médium des noeuds du réseau selon un ordonnancement donné. Néanmoins, l'amendement ne spécifie pas comment cet ordonnancement est calculé.Le propos de ce papier est d'offrir un algorithme distribué d'assignation conjointe de fr\équences et de slots temporels pour la collecte dans les LLNs, dénommé Wave.Cet ordonnancement vise à minimiser le temps de collecte en r\éduisant le nombre de slots temporels assignés à l'ensemble des noeuds du réseau.De plus, Wave assure l'absence de transmissions conflictelles dans l'ordonnancement fourni.Dans un tel ordonnancement, un noeud est réveillé uniquement pendant ses slots de transmissions et ceux de ses enfants dans le graphe de routage de la collecte.Ainsi, l'efficacité énergétique est assurée.Dans ce papier, nous décrivons en détails le fonctionnement de Wave, mettant en exergue ses caractéristiques (support du trafic hétérogène, support d'un puits de données avec de multiples interfaces de communication) et ses propriétés en termee de d\élais et de la taille des buffers.Nous discutons ses caract\éristiques en regard d'un algorithme d'ordonnancement centralisé tel que TMCP et d'un algorithme distribué tel que DeTAS.Les résultats de simulations démontrent une meilleure performance de Wave par rapport à TMCP.Enfin, puisque dans un environnement industriel plusieurs graphes de routage peuvent cohabiter, nous étudions comment Wave assure cette coexistence

Optimal Number of Message Transmissions for Probabilistic Guarantee in the IoT

International audienceThe Internet of Things (IoT) is now experiencing its first phase of industrialization. Industrial companies are completing proofs of concept and many of them plan to invest in automation, flexibility and quality of production in their plants. Their use of a wireless network is conditioned upon its ability to meet three Key Performance Indicators (KPIs), namely a maximum acceptable end-to-end latency L, a targeted end-to-end reliability R and a minimum network lifetime T. The IoT network has to guarantee that at least R% of messages generated by sensor nodes are delivered to the sink with a latency ≤ L, whereas the network lifetime is at least equal to T. In this paper, we show how to provide the targeted end-to-end reliability R by means of retransmissions to cope with the unreliability of wireless links. We present two methods to compute the maximum number of transmissions per message required to achieve R. M F air is very easy to compute, whereas M Opt minimizes the total number of transmissions necessary for a message to reach the sink. M F air and M Opt are then integrated into a TSCH network with a load-based scheduler to evaluate the three KPIs on a generic data-gathering application. We first consider a toy example with eight nodes where the maximum number of transmissions M axT rans is tuned per link and per flow. Finally, a network of 50 nodes, representative of real network deployments, is evaluated assuming M axT rans is fixed. For both TSCH networks, we show that M Opt provides a better reliability and a longer lifetime than M F air, which provides a shorter average end-to-end latency. M Opt provides more predictable end-to-end performances than Kausa, a KPI-aware, state-of-the-art scheduler