Samira Chouikhi

A survey on fault tolerance in small and large scale wireless sensor networks

Fault tolerance is one of the most important wireless sensor networks requirements. It ensures that the network continues to function correctly even when some components fail. In fact, fault tolerance is a need in this type of networks due to sensor node characteristics, radio communications and hostile environments in which these networks are deployed. In this survey, we give an overview of WSN mechanisms that provide or improve the fault tolerance property of wireless sensor networks. However, the different solutions presented in this survey are not only intended to mechanisms dedicated to fault tolerance, but they also include all the mechanisms allowing the prevention of fault occurrence such as energy aware routing and data aggregation and compression. Besides the classification of fault tolerance mechanisms according to the tasks they target (data management, flow management), we also propose a new classification based on the network size, since the performance of the majority mechanisms depends on the size in terms of geographical area and number of nodes. Thus, a well performing protocol conceived for small networks may be inadequate for large networks and vice versa.

Fault tolerant multi-channel allocation scheme for wireless sensor networks

One of the most common needs in wireless sensor networks (WSNs) is the continuity of network function even in the presence of some node failures. This is called fault tolerance. In general, fault tolerant solutions can be preventive or reactive: the preventive techniques aim to prevent the failure by minimizing and balancing the energy consumption in each node, while the reactive techniques intervene after a failure was detected. In this paper, we propose a new preventive/reactive fault tolerant scheme dedicated to manage the energy consumption and reconnect the WSN in case of articulation node failure. The specificity of this scheme is the use of multichannel communications, allowing simultaneous data transmission, which decreases the interferences between nodes and then decreases data retransmissions. The second task of this scheme targets the reorganization of the network after a network portioning episode. Such episode means that the WSN is partitioned in many segments after an articulation node failure. More precisely, we present here two heuristics for channel allocation/reallocation and WSN reorganization after a network failure. The performances of the proposed scheme is evaluated and proved through simulation.

Routing-based multi-channel allocation with fault recovery for Wireless Sensor Networks

One of the common challenges in Wireless Sensor Networks (WSNs) is the degradation of the performance due to several factors. In one hand, the interference between concurrent transmissions can affect the efficiency of the network and considerably degrades its performance. The exploitation of the multiple channels available in sensor technology and the development of protocols for WSNs can be a solution to mitigate this interference. In this case, the way the channels are assigned has a significant impact on the performance of multi-channel communication. In the other hand, the faults occurred in WSNs are another factor that degrades the WSN performance. In this paper, we propose a distributed energy-efficient solution for multi-channel allocation based on the routing. This solution implements a fault recovery mechanism to reconnect the network after an articulation node failure. A main task of the proposed approach is to minimize the number of interferences when allocating the limited number of available channels. As a second task, the approach minimizes the energy consumption by defining a sleeping/activity strategy. The fault recovery mechanism aims to restore the network connectivity and reallocate channels without affecting the whole WSN. The performance of the proposed solution is evaluated by simulation.

Articulation Node Failure Recovery for Multi-Channel Wireless Sensor Networks

Wireless sensor networks (WSNs) are widely used nowadays and in a various domains. However, the specificity of the nodes deployed in this type of networks makes them prone to failures. To overcome this problem and guarantee the continuity of the network functioning even in the presence of node failure, fault tolerance mechanisms need to be designed and integrated to the operation of those networks. These fault tolerance mechanisms will more precisely deal with recovering from a failures and resuming the correct functioning of a WSN. With that aim, we propose in this paper a new centralized curative approach, called Rotating Nodes based Failure Recovery (RNFR), dedicated to restore connectivity in multi-channel WSNs. The proposed solution targets the failure of particular nodes designated as articulation nodes, which leads to the partitioning of the WSN into many segments isolated from each other and leading to connectivity loss. Therefore, the main tasks of RNFR are the restoration of the connectivity after an articulation node failure using reorganization and reallocation of channels. Moreover, the solution uses a node rotation technique to communicate the recovery information to all the disjoint parts of the network. The proposed approach proved to be interesting by giving motivating results while evaluated through simulation.

Recovery from simultaneous failures in a large scale wireless sensor network

Abstract The Wireless sensor networks (WSNs) become more and more recognized these recent years and their applications spread in several domains. In general, these applications require that the network presents a minimum degree of reliability, effectiveness and robustness. However, the specificity of the nodes used in this type of networks makes them prone to failures. Indeed, the multichannel communications are generally privileged in the interference context which is very frequent in several WSNs’ applications due to the density of sensors and the harsh environment in which they are deployed. Moreover, in real applications, the occurrence of some faults (for example fire) may alter an entire zone of the network especially in the case of large scale deployment. Therefore, in this paper, we propose a network fault recovery approach from simultaneous failures in a large scale multichannel WSN. To make our solution as realistic as possible, we consider the case of the precision agriculture application and propose a detailed deployment of the WSN for that application. The choice of precision agriculture application is motivated by the fact that this application require large scale WSN (thousands and thousands of sensors) to supervise such a large area. Based on such precision agriculture scenario, we propose our fault recovery approach, called Simultaneous Failure Recovery based on Relay Node Relocation (SFR-RNR), that aims to restore the connectivity and partially the coverage in the network. The performance of the proposed approach is evaluated by simulation.

Distributed connectivity restoration in multichannel wireless sensor networks

Abstract Wireless sensor networks (WSNs) are widely used in various domains. However, the specificity of the nodes deployed in these networks makes them prone to failures. To overcome this problem and guarantee the continuity of the network functioning in the presence of node failures, fault tolerance mechanisms need to be designed and integrated to ensure the correct WSN operation. In addition to node failure, the interferences present a serious problem in WSNs. Such a problem is commonly solved by using multichannel communications. Thus, in this paper, we propose a distributed solution, called Connectivity Restoration for Multi-Channel WSNs (CR-MC), to recover from a connectivity loss for multichannel WSNs. The main task of this approach targets the restoration of the connectivity and the reassignment of the channels in a multichannel network after the failure of an articulation node whose failure leads to the network partitioning. CR-MC uses only the neighborhood information to execute the recovery and the channel reassignment tasks. On the other hand, if we consider multi-hop WSNs, a routing tree is generally constructed to disseminate the information to the sink node. Hence, the radio channels should be assigned with a great care to respect these network particularities. In this context, we propose a second solution, called Connectivity Restoration for Routing based Multi-Channel WSNs (CR-RMC) that exploits the routing tree as well as the vicinity information while allocating the channels. We compare the performance of the two proposed approaches CR-MC and CR-RMC by evaluating them through simulations.

A novel simultaneous failure recovery technique for large scale wireless sensor networks

Wireless sensor networks (WSNs) are widely used nowadays in various domains. In general, the applications in which the WSN is deployed need that this network presents a minimal degree of reliability, effectiveness and robustness. However, the specificity of the nodes deployed in this type of networks makes them prone to failures. In this paper, we discuss the recovery from simultaneous failures for a large scale WSN in a multichannel context. Indeed, we propose a deployment scenario which uses thousands of sensor nodes and relay nodes. Then, we propose Simultaneous Failure Recovery based on Relay Node Relocation (SFR-RNR) approach which aims to recover from simultaneous failures. These failures lead to the damage of a whole segment of the WSN, and hence, the loss of the monitored field coverage and/or connectivity. SFR-RNR rearranges a minimal set of relay nodes to restore, partially, the coverage and improve or restore the connectivity; then it reallocates the channels to minimize the interferences. The performance of the proposed approach is evaluated by simulation.

Connectivity Restoration in Multi-Channel Wireless Sensor Networks

Fault tolerance is one of the most important requirements in the Wireless Sensors Networks (WSNs). In fact, the performance and the reliability of a RCSF degrade because of several factors. On one hand, the interferences between simultaneous transmissions generate infinite phenomena of collision / retransmission. On the other hand, the failure of some components of the network may introduce the failure of the whole network. In this fact, the integration of the mechanisms which prevent or reduce the impacts of these two problems (interferences and failures) becomes an obligation. In this work, we propose the Connectivity Restoration for wireless sensor networks in Routing based Multi-Channel Context approach (CR-RMC) to improve the WSN reliability. This solution uses multi-channel communications to reduce the interference ratio, as well as network reorganization to recover from a critical node and restore the connectivity. We evaluate the obtained results regarding the fixed objectives.