Suchetana Chakraborty

A Tree-Based Local Repairing Approach for Increasing Lifetime of Query Driven WSN

Query driven Broadcast through wireless sensor nodes also leads to the domain of event driven converge cast. A query-response based application in Wireless Sensor Networks(WSN) demands the correct delivery of data message at each sensor node. A Breadth-First Search(BFS) tree rooted at the base station offers shortest path traversal for each data message which utilizes the sensor resources efficiently. Resource constrained sensor nodes are highly prone to sudden crash. So the application demands a quick and smart approach to repair the tree when a node dies. In this paper a novel scheme has been proposed to locally repair the tree with constant round of message transmissions. Each node piggybacks a few bytes of extra information along with each query and response messages. Based on these piggybacked values each node calculates its alternate parent. When a parent node fails, its children can contact their respective alternate parents immediately to establish an alternate path to the root. Reduced communication cost in terms of extra message transmissions saves battery power at each node. Efficient query-response message handler ensures the correct delivery of messages. Fast repairing offers good Quality of Service(QoS). Simulation result shows that no message is lost except the one holding by the crashed node.

Fault resilience in sensor networks

Sensor network deployed for the critical infrastructure monitoring requires high degree of reliability in sensory data gathering, in spite of arbitrary node or sink failures. This paper proposes a robust data gathering scheme specially designed to provide guaranteed delivery of the sensory data for applications on the critical infrastructure monitoring. Redundancy in a sensor network, in terms of both the number of deployed sensors and the amount of duplicate data delivery, is explored to design an effective protocol that ensures the reliable data delivery while assuring the timeliness, connectivity and the sensing coverage. A set of active sensors is selected from all the sensors deployed, based on the network connectivity and the sensing coverage criteria that participates in the data forwarding process. Rest of the sensors go to the sleep state, and act as a replacement on the failure of an active sensor. The proposed protocol aims to find out multiple node-disjoint paths to multiple sinks, so that the loss of connectivity in one path due to node failure does not disrupt application services. The effectiveness of the proposed scheme has been analyzed using simulation results, and compared with other protocols proposed in the literature for reliable data delivery.

Beyond conventional routing protocols: Opportunistic path selection for IEEE 802.11s mesh networks

IEEE 802.11s provides Hybrid Wireless Mesh Protocol (HWMP) to find out the forwarding path in a mesh network based on mesh peering and MAC layer scheduling information. However, both proactive and reactive modes of HWMP perform poorly for multi-radio mesh network because of inefficient radio selection, time-varying channel conditions and interference among the radios. This paper proposes an improved opportunistic path selection protocol over HWMP for multi-radio support that goes beyond the traditional routing mechanisms, operates either in proactive, reactive or hybrid mode. The efficiency of the proposed scheme is analyzed using simulation results.

Convergecast tree management from arbitrary node failure in sensor network

Abstract The efficiency and reliability of convergecast in sensor network depends on the correct and efficient accumulation of data to the sink. A tree, rooted at the sink, that utilizes sensor resources properly is an ideal topology for data gathering. Resource constrained sensor nodes are highly prone to sudden crash. So the application demands a quick and efficient repairing of the tree when a node dies. The proposed scheme builds a data gathering tree rooted at the sink. The tree eventually becomes a Breadth First Search (BFS) tree where each node maintains the shortest hop-count to the root to reduce the routing delay. Each node collects some extra neighborhood information during the tree construction. Thus a little pre-processing at each node helps in taking prompt actions to repair the tree through local adjustment if any arbitrary single or multiple nodes fail in future. On failure of a node, each affected node in its vicinity fixes the parent through a pair of control message transmissions. Simulation results show that the repairing delay is significantly less in average and the convergecast messages are delivered with minimum data loss and no redundancy even in presence of node crash.

Formalization of a Fully-Decoupled Reactive Tuple Space Model for Mobile Middleware

This paper suggests an approach for formalizing Tuple Space based Mobile Middleware (TSMM) that contains a fully-decoupled reactive tuple space model as coordination medium. Formalization of TSMM is carried out using Mobile UNITY.

A reliable and total order tree based broadcast in wireless sensor network

A reliable broadcast demands that each data packet forwarded from the source node is received by all other nodes in the network without any loss. A flooding based Broadcast scheme incurs significant overhead due to explosion of packets in the network. So an efficient way of routing packets in order to broadcast saves the energy of resource constrained sensor nodes. The delivery of broadcast packets at each node in correct sequence is also crucial for certain applications. In this paper a tree based broadcast mechanism is proposed that constructs a spanning tree out of all nodes in the network rooted at the source of the broadcast. The broadcast tree eventually becomes a Breadth-First Search(BFS) tree where each node maintains the shortest path to the root. So packets routed through the shortest paths reduce transmission delay and packet loss. BFS tree based broadcast saves the battery power at each node by reducing the number of packet transmissions. The proposed scheme for broadcast is also crash tolerant. Each node computes a maintenance plan during the broadcast tree construction for future requirement. If a node dies, all the nodes in neighborhood repairs the tree locally within constant round of message transmissions. Each broadcast packet is assured to be delivered at each node without redundancy and maintaining the correct order.

Dynamic Tree Switching for Distributed Message-Passing Applications

The changes in environmental parameters may demand switching between underlying topologies for better performance of distributed message passing applications. Arbitrary topology switching using distributed tree construction may lead to loss or redundancy in delivery of application messages. In this work, a set of algorithms has been proposed for dynamic switching between two spanning trees to offer better adaptivity towards the environment for different applications. Here, two extreme cases of spanning trees, a Breadth First Search (BFS) tree and a Depth First Search (DFS) tree, rooted at the core node, have been considered for switching. The core node initiates the switching and all other nodes cooperatively change their parents on the fly maintaining the DFS or BFS properties as required. However, the application remains transparent to the switching that assures the availability of the system at any instance of time. Simulation results show that each application message is delivered correctly to the destination without any loss or redundancy. The proposed scheme is scalable and the control message overhead for switching is linear with respect to the number of edges in the communication graph. Furthermore, there is no control message overhead to assure the delivery of application messages at the time of switching.

Exploring gradient in sensor deployment pattern for data gathering with sleep based energy saving

The lifetime of sensor network depends on the efficient utilization of resource-constrained sensor nodes. Several MAC protocols like DMAC and its variants have been proposed to save critical sensor resources through sleep-wakeup scheduling over data gathering tree. For applications where data aggregation is not possible, the sleep duration decreases gradually from the leaves to the root of the data gathering tree. This results early failure of sensor nodes near the sink, and affects network connectivity and coverage. Deploying redundant sensors can solve this problem where a faulty node is replaced by a redundant node to maintain network connectivity and coverage. However, the amount of redundancy depends on the node failure pattern, and thus more number of redundant nodes required to be deployed near the sink. This paper proposes a gradient based sensor deployment scheme for energy-efficient data gathering exploring the trade-off among connectivity, coverage, fault-tolerance and redundancy. The density of deployment is estimated based on the distance of a node from the sink while dealing with connectivity, coverage and fault-tolerance. The effectiveness of the proposed scheme has been analyzed both theoretically and with the help of simulation.

A novel crash-tolerant data gathering in wireless sensor networks

Event driven data gathering or convergecast through sensor nodes requires efficient and correct delivery of data at the sink. A tree rooted at the sink is an ideal topology for data gathering which utilizes sensor resources properly. Resource constrained sensor nodes are highly prone to sudden crash. A set of algorithms, proposed in this paper, builds a data gathering tree rooted at the sink. The tree eventually becomes a Breadth First Search (BFS) tree where each node maintains the shortest distance in hop-count to the root to reduce the routing delay and power consumption. The data gathering tree is repaired locally within a constant round of message transmissions after any random node fails. Simulation result shows that the repairing delay is very less in average, and the proposed scheme can repair from arbitrary node failure using constant number of message passing.

RelBAS: Reliable data gathering from border area sensors

Sensor networks deployed for the border area monitoring requires a high degree of reliability for the data gathering in spite of any arbitrary node or sink failures. This paper proposes RelBAS, a robust data gathering scheme specially designed for the border area network to provide a guaranteed delivery of sensory data. The proposed protocol aims to find out multiple node-disjoint paths to multiple sinks so that the disconnectivity in one path due to a node failure does not disrupt the delivery of data to the sink. The forwarding path selection at every node in RelBAS is based on the combination of three parameters - the hop-count, the residual energy and the number of children for for parent of the corresponding tree. This helps in adapting the protocol to the application requirement depending on the delay, energy efficiency and data aggregation. Moreover, RelBAS is capable of detecting an affected zone due to multiple node failures. The effectiveness of the proposed scheme has been analyzed using the simulation results.