Preserving Area Coverage in Wireless Sensor Networks by using Surface Coverage Relay Dominating Sets

International audienceSensor networks consist of autonomous nodes with limited battery and of base stations with theoritical infinite energy. Nodes can be sleep to extend the lifespan of the network without compromising neither area coverage nor network connectivity. This paper addresses the area coverage problem with equal sensing and communicating radii. The goal is to minimize the number of active sensors involved in coverage task, while computing a connected set able to report to monitoring stations. Our solution is fully localized, and each sensor is able to make decision on whether to sleep or to be active based on two messages sent by each sensor. The first message is a “hello” message to gather position of all neighboring nodes. Then each node computes its own relay area dominating set, by taking the futhest neighbor as the first node, and then adding neighbors farthest to the isobarycenter of already selected neighbors, until the area covered by neighbors is fully covered. The second message broadcasts this relay set to neighbors. Each node decides to be active if it has highest priority among its neighbors or is a relay node for its neighbor with the highest priority

Etude et extension des relais de couverture de surface dans les réseaux de capteurs

National audienceL'objectif des protocoles de couverture de surface est de mettre en veille des capteurs redondants tout en assurant une couverture totale de la zone par les noeuds restant allumés. La connexité de l'ensemble des noeuds actifs doit également être préservée dans la mesure où il est impératif d'assurer l'acheminement des rapports de surveillance vers les stations puits. La plupart des solutions existantes ne considèrent pas ces deux problèmes comme un seul et sont rarement évaluées sous des conditions réalistes. Dans cet article, nous proposons une analyse approfondie et des améliorations d'un protocole localisé maintenant la couverture de zone par des ensembles connectés en se basant sur des relais de couverture de surface (SCR). Dans un premier temps, nous avons amélioré l'une des phases critiques de l'algorithme ; la sélection des relais. Ceci nous a permis de diminuer le nombre de noeuds actifs sans altérer la couverture fournie. Nous avons ensuite soulevé le problème de sa résistance à des conditions de communication plus réalistes. Nous verrons alors comment de nouvelles modifications durant la phase de sélection des relais nous ont permis d'obtenir un protocole robuste et facilement configurable

Optimal Transmission Radius for Energy Efficient Broadcasting Protocols in Ad Hoc and Sensor Networks

International audienceWe investigate the problem of minimum energy broadcasting in ad hoc networks where nodes have capability to adjust their transmission range. The minimal transmission energy needed for correct reception by neighbor at distance r is proportional to r^alpha + c_e, alpha and c_e being two environment-dependent constants. We demonstrate the existence of an optimal transmission radius, computed with a hexagonal tiling of the network area, that minimizes the total power consumption for a broadcasting task. This theoretically computed value is experimentally confirmed. The existing localized protocols are inferior to existing centralized protocols for dense networks. We present two localized broadcasting protocols, based on derived 'target' radius, that remain competitive for all network densities. The first one, TR-LBOP, computes the minimal radius needed for connectivity and increases it up to the target one after having applied a neighbor elimination scheme on a reduced subset of direct neighbors. In the second one, TR-DS, each node first considers only neighbors whose distance is no greater than the target radius (which depends on the power consumption model used), and neighbors in a localized connected topological structure such as RNG or LMST. Then, a connected dominating set is constructed using this subgraph. Nodes not selected for the set may be sent to sleep mode. Nodes in selected dominating set apply TR-LBOP. This protocol is the first one to consider both activity scheduling and minimum energy consumption as one combined problem. Finally, some experimental results for both protocols are given, as well as comparisons with other existing protocols. Our analysis and protocols remain valid if energy needed for packet receptions is charged

A Survey of Coverage Problems in Wireless Sensor Networks

Coverage problem is an important issue in wireless sensor networks, which has a great impact on the performance of wireless sensor networks. Given a sensor network, the coverage problem is to determine how well the sensing field is monitored or tracked by sensors. In this paper, we classify the coverage problem into three categories: area coverage, target coverage, and barrier coverage, give detailed description of different algorithms belong to these three categories. Moreover, we specify the advantages and disadvantages of the existing classic algorithms, which can give a useful direction in this area

From MANET to people-centric networking: Milestones and open research challenges

In this paper, we discuss the state of the art of (mobile) multi-hop ad hoc networking with the aim to present the current status of the research activities and identify the consolidated research areas, with limited research opportunities, and the hot and emerging research areas for which further research is required. We start by briefly discussing the MANET paradigm, and why the research on MANET protocols is now a cold research topic. Then we analyze the active research areas. Specifically, after discussing the wireless-network technologies, we analyze four successful ad hoc networking paradigms, mesh networks, opportunistic networks, vehicular networks, and sensor networks that emerged from the MANET world. We also present an emerging research direction in the multi-hop ad hoc networking field: people centric networking, triggered by the increasing penetration of the smartphones in everyday life, which is generating a people-centric revolution in computing and communications

Lifetime maximization for connected target coverage in wireless sensor networks

Ph.DDOCTOR OF PHILOSOPH

Performance studies of wireless multihop networks

Wireless multihop networks represent a fundamental step in the evolution of wireless communications, a step that has proven challenging. Such networks give rise to a wide range of novel performance and design problems, most of which are of a geometric nature. This dissertation addresses a selection of such problems. The first part of this thesis presents studies in which the network nodes are assumed to receive signals sufficiently clearly only from within some fixed range of operation. Using this simple model, the first two problems addressed are to predict the probabilities that a network with randomly placed nodes is connected or completely covers a given target domain, respectively. These problems are equivalent to determining the probability distribution of the minimal range providing connectivity or coverage. Algorithms for determining these threshold ranges for a given set of network nodes are developed. Because of the complex nature of these problems in finite settings, they are both approached by empirically modeling the convergence of these distributions to their known asymptotic limits. Next, a novel optimization problem is presented, in which the task is to make a given disconnected network into a connected one by adding a minimal number of additional nodes to the network, and heuristic algorithms are proposed for this problem. In the second part, these networks are studied in the context of a more realistic model in which the condition for successful communication between network nodes is expressed as an explicit minimum value for the received signal-to-noise-and-interference ratio. The notion of the threshold range for connectivity is first generalized to this network model. Because connectivity is now affected by medium access control (MAC), two alternative MAC schemes are considered. Finally, an infinite random network employing slotted Aloha is studied under this model. Since the probability of successful reception in a random time slot is a function of the locations of other nodes, this temporal probability is a random variable with its own probability distribution over different node configurations. Numerical approximations for evaluating both the mean and the tail probability of this distribution are developed. The accuracy of these approximations can be improved indefinitely, at the cost of numerical computations.reviewe