Pushpendu Kar

D3: distributed approach for the detection of dumb nodes in wireless sensor networks

SUMMARY In this work, we propose D3—a distributed approach for the detection of ‘dumb’ nodes in a wireless sensor network (WSN). A dumb node can sense its surroundings, but is unable to transmit these sensed data to any other node, due to the sudden onset of adverse environmental effects. However, such a node resumes its normal operations with the resumption of favorable environmental conditions. Due to the presence of dumb nodes, the network is unable to provide the expected services. Therefore, it is prudent to re-establish connectivity between dumb and other nodes, so that sensed data can be reliably transmitted to the sink. Before the re-establishment of connectivity, a node needs to confirm its actual state of being dumb. Dumb behavior is dynamic in nature, and is, thus, distinct from the traditional node isolation problem considered in stationary WSNs. Therefore, the existing schemes for the detection of other misbehaviors are not applicable for detecting a dumb node in a WSN. Considering this temporal behavior of a dumb node, we propose an approach, D3, for the detection of dumb nodes. In the propose scheme, we uses cumulative sum test, which helps in detecting the dumb behavior. The simulation results show that there is 56% degradation in detection percentage with the increment in the detection threshold, whereas energy consumption and the message overhead increase by 40% with the increment in detection threshold.

Detouring dynamic routing holes in stationary wireless sensor networks in the presence of temporarily misbehaving nodes

Summary In this work, we propose a scheme, named BRIDGE, to bypass dynamic routing holes arising in stationary wireless sensor networks in the presence of temporarily misbehaving nodes such as dumb [1, 2] or transfaulty nodes. The affected nodes behave normally after the resumption of favorable environmental conditions. Therefore, both dumb and transfaulty behaviors of sensor nodes are dynamic in nature. The nodes in these networks get temporarily isolated from the network, when they behave as dumb or transfaulty. Because of the presence of nodes with such behavior, dynamic communication holes may occur in the network, which are formed or removed and thus increase or decrease in size with time. Connectivity re-establishment procedures can mitigate holes by re-connecting isolated nodes with the network after activating the intermediate sleep nodes, adjusting the communication range of intermediate nodes, or by using an alternative communication mode. However, such procedures cannot always re-establish connectivity because of the lack of neighbor nodes in reduced or adjusted communication range. Therefore, routing schemes using greedy forwarding approaches need to bypass holes to avoid the data packets from getting stuck at the boundary nodes and efficiently delivering them to the sink. However, the existing hole avoidance schemes consider holes as static. The proposed scheme, BRIDGE, detects hole boundary and bypasses routing traffics in the dynamic hole scenario. In the proposed scheme, a boundary node selects the next hop based on the minimum distance from all the neighbor nodes to the destination node, although this minimum distance is more than the distance to the destination from the node itself. Simulation results show that the performance of the proposed scheme degrades with the increase in hole area. Copyright

Reliable and Efficient Data Acquisition in Wireless Sensor Networks in the Presence of Transfaulty Nodes

A collection of spatially distributed sensor nodes in a wireless sensor network (WSN) work collaboratively to sense the physical phenomena around them and then send the sensed information to the sink node through single-hop or multihop paths. In this work, we propose a scheme, named ReDAST, for reliable and efficient data acquisition in a stationary WSN in the presence of transfaulty nodes. Due to the transfaulty behavior, a sensor node gets temporarily isolated from the network. Temporary node isolation leads to the formation of dynamic communication holes in the network, which form and disappear dynamically. Furthermore, they may increase or decrease in size dynamically as well. These effects result in loss of information in the radiation-affected area. To prevent information loss in WSN due to transfaulty behavior of sensor nodes, in the proposed scheme, we construct the network using sensor nodes having dual mode of communication-RF and acoustic. To get redundant coverage within a radiation affected area, all the sensor nodes in the area become activated and switch to the acoustic communication mode after detecting themselves to be affected by radiations. In-network data fusion is performed to get actual information from the redundant information received from the radiation-affected area. Simulation results exhibit that the proposed scheme, ReDAST, achieves better energy efficiency and reduced average end-to-end delay than sensor nodes having only acoustic mode of communication.

Connectivity Reestablishment in Self-Organizing Sensor Networks with Dumb Nodes

In this work, we propose a scheme, named CoRAD, for the reestablishment of lost connectivity using sensor nodes with adjustable communication range in stationary wireless sensor networks (WSNs), when “dumb” behavior occurs some of the nodes. Due to the occurrence of such behavior, there may be temporary loss of connectivity between among the nodes. Such a phenomenon is different from the commonly known node isolation problem in stationary WSNs. The mere activation of intermediate sleep nodes cannot guarantee reestablishment of connectivity, because there may not exist neighbor nodes of the isolated nodes. On the contrary, the increase in communication range of a single sensor node may make it die quickly. Including this, a sensor node has maximum limit of increase in communication range that may not be sufficient to reestablish connectivity. Therefore, considering all these factors for self-organization of the network and isolated node re-connection, we propose a price-based scheme, which addresses the issue by activating intermediate sleep nodes or by adjusting the communication range of some of the other nodes in the network. The scheme also deactivates the additional activated nodes and reduces the increased communication range when the dumb nodes resume their normal behavior, upon the return of favorable environmental conditions. To implement the proposed scheme, CoRAD it is required to construct the network using GPS-enabled adjustable communication range sensor nodes. Through simulation we compare our proposed scheme with the existing topology management schemes -- LETC and A1 -- in the same scenario by considering the number of activated nodes, message overhead, and energy consumption. We find that the proposed scheme shows improved performance compared to the existing topology management schemes.

Detection of dumb nodes in a stationary wireless sensor network

A sensor node is termed as “dumb” [1], if at a certain time instant it can sense its surroundings, but is unable to communicate with any of its neighbors due to the shrinkage in communication range. Such isolation occurs because of the presence of adverse environmental effects. However, the node starts its normal operation with the resumption of favorable environmental conditions. Thus, the detection of dumb nodes is essential in order to re-establish network connectivity. However, the temporal behavior of a dumb node in a network makes the detection of such a node challenging. In the present work, we address a plausible solution to this problem by taking into account the evidences from neighboring nodes.

Energy-efficient connectivity re-establishment in WSN in the presence of dumb nodes

In this work, we propose a scheme, named LECRAD, for the re-construction of temporarily lost connectivity in the presence of dumb nodes in stationary wireless sensor networks. A sensor node is termed as “dumb”, when it continues its physical sensing, but fails to communicate due to shrinkage in communication range, typically attributed to adverse environmental effects such as rainfall, fog and high temperature. On the resumption of favorable environmental conditions, the node starts to behave normally. So, dumb behavior is dynamic in nature. Such behavior of a node leads to network partitioning and node isolation, which results in disruption of connected topology. Therefore, the proposed scheme in this paper reconstructs the lost connectivities between nodes by activating intermediate sleep nodes or by adjusting the communication range of the sensor nodes, while there is no neighbor node within the reduced communication range. In the proposed scheme, a learning automata-based approach is used for activation of intermediate sleep nodes or adjustment of communication range of isolated or intermediate nodes to decrease the message overhead and energy consumption of the network. Simulation results show that the proposed scheme, LECRAD, exhibits better energy efficiency and message overhead than that of the recently proposed topology management protocols, LETC and A1, if they are applied in such scenario.

Topology Control for Self-Adaptation in Wireless Sensor Networks with Temporary Connection Impairment

In this work, the problem of topology control for self-adaptation in stationary Wireless Sensor Networks (WSNs) is revisited, specifically for the case of networks with a subset of nodes having temporary connection impairment between them. This study focuses on misbehaviors arising due to the presence of\enskip “dumb” nodes [Misra et al. 2014; Roy et al. 2014a, 2014b, 2014c; Kar and Misra 2015], which can sense its surroundings but cannot communicate with its neighbors due to shrinkage in its communication range by the environmental effects attributed to change in temperature, rainfall, and fog. However, a dumb node is expected to behave normally on the onset of favorable environmental conditions. Therefore, the presence of such dumb nodes in the network gives rise to impaired connectivity between a subset of nodes and, consequently, results in change in topology. Such phenomena are dynamic in nature and are thus distinct from the phenomena attributed to traditional isolation problems considered in stationary WSNs. Activation of all the sensor nodes simultaneously is not necessarily energy efficient and cost-effective. In order to maintain self-adaptivity of the network, two algorithms, named Connectivity Re-establishment in the presence of Dumb nodes (CoRD) and Connectivity Re-establishment in the presence of Dumb nodes Without Applying Constraints (CoRDWAC), are designed. The performance of these algorithms is evaluated through simulation-based experiments. Further, it is also observed that the performance of CoRD is better than the existing topology control protocols—LETC and A1—with respect to the number of nodes activated, overhead, and energy consumption.

On the Effects of Communication Range Shrinkage of Sensor Nodes in Mobile Wireless Sensor Networks Due to Adverse Environmental Conditions

A wireless sensor network (WSN) is a collection of spatially distributed sensor nodes working collaboratively to monitor a physical environment. A mobile wireless sensor network (MWSN) is a specific type of WSN, in which the sensor nodes move within a designated area. In this paper, we consider the effects of adverse environmental conditions on MWSN. Conditions such as high temperature, rainfall, and fog cause attenuation and fading effects on the communication of sensor nodes. Consequently, the communication ranges of such nodes shrink, and the sensor nodes cannot communicate with any of their peers. The shrinkage in communication range creates impairment in the normal communication ability of sensor nodes, which results in link disruption, packet loss, performance degradation, and reduced lifetime of the network. As the adverse environmental conditions are temporal in nature, the sensor nodes function normally with the resumption of favorable environmental conditions. The existing literature did not consider this type of temporary problem on MWSNs. In this paper, we evaluated the performance of MWSN due to the presence of adverse environmental conditions. Simulation results confirm the hypotheses that the performance of MWSN degrades in the presence of adverse environmental conditions. From the results it can be inferred that throughput and delivery ratio nearly decreases by 66% and 42%, respectively, whereas delay increases by 75% due to the shrinkage in communication range.

RILoD: Reduction of Information Loss in a WSN System in the Presence of Dumb Nodes

A sensor node behaves as “dumb,” when it continues to sense its vicinity, but fail to communicate with its neighbors due to the shrinkage in the communication range attributed to adverse environmental conditions such as rainfall, fog, and high temperature. However, the node behaves normally with the resumption of favorable environmental conditions. The nodes get isolated from the network only temporarily because of the temporal nature of adverse environmental conditions. Therefore, the dumb behavior of sensor nodes is temporary in nature. During the period of isolation, a sensor node continues its sensing, but it cannot send the sensed information to the sink, which increases the possibility of information loss in the network. Connectivity reestablishment of an isolated node with the network by activating the intermediate sleep nodes or adjusting the communication range gives the opportunity to send data to the sink. However, all the isolated nodes cannot reestablish connectivity due to the unavailability of intermediate nodes in the reduced or adjusted communication range. In this context, we propose a scheme, named RILoD, for a self-adaptive wireless sensor network, in which we use mobile mules to collect data from these isolated nodes and deliver them to the parent node, which can, in turn, forward the data to the sink. Using this technique, every isolated node can send their sensed information to the sink. Simulation results show that the proposed scheme reduces information loss by up to 32%. Furthermore, the proposed scheme has improved success probability of data delivery over the existing state of the art.