Wireless Sensor Network

What is wireless sensor network?

A wireless sensor network is composed of a large number of sensor nodes and one or more sink nodes (base stations). The sensor nodes are deployed inside the area of interest to collect useful information from the surrounding environment and report it to a base station located generally at the extremity of the area of interest in different Monitoring applications of WSN include indoor/outdoor environmental monitoring, health monitoring, power monitoring, location monitoring, factory and process automation.

• Tracking applications include tracking objects, animals, humans and vehicles.
• WSN also used underground like coal mine or underwater.
• WSN used in military for enemy detection or chemical bomb detection.
• WSN used for pollution monitoring.

More recent work has begun to consider collaborating nearby sensor nodes to generate a more concrete report of the object being traced. Such issue has been recognized by which further provides a dynamic convoy tree-based collaboration (DCTC) framework for tracking a mobile target.

The root can dynamically collect and refine the readings gathered from various tree nodes. The challenge of their work lies on finding a sequence of minimum cost trees, so called minimum-cost convoy tree sequence, whose coverage on the moving object is above a certain threshold.

The tree they have considered is the one that has the root being closest to the target. Furthermore, all other nodes are arranged in a way that the cost of sending a packet via some nodes to this root is minimized

] E-Span, is an energy aware spanning tree algorithm. E-Span is a distributed

protocol and facilitates the sources within an event region to perform data aggregation. In E-span, the source node which has the highest residual energy is chosen as the root. Each other node chooses its parent node among its neighbors based on the information of the residual energy and distance to the root. Authors compare their result with Direct Diffusion approach for data aggregation. E-Span also maintains a low average packet transfer delay and a high packet delivery ratio.

In the field of wireless sensor network Data aggregation is an important issue of research.New algorithm has been developed for data aggregation process in cluster, tree, chain and grid based wireless sensor network. for example in Cluster based data aggregation LEACH, E-LEACH, TL-LEACH,M-LEACH, V-LEACH protocol has been developed for making the data aggregation process energy efficient. In Tree based network different algorithm has been developed by researchers such as Energy efficient spanning tree for data aggregation.

Since energy is an important constraint in WSN so to make data aggregation process more energy efficient and to provide more accurate data to the user some new algorithm are also required to maximize the lifetime of the network. So in data aggregation there is a lot scope of research work in both flat as well as hierarchical network.

In tree based WSN the nodes are structured in a tree format at different level of tree and during the distribution phase root node send the query message to other nodes at successive lower levels and during the collection phase nodes at lower levels send their data to root node. So there is a need of selecting the path which is shortest and in which energy consumption is minimized to send the query message from root node to nodes at lower levels and same for lower level nodes to root of the tree. Hence the objective of the problem identification is to increase the lifetime of the network in term of shortest distance traversed and energy consumption.

Since in wireless sensor network energy is the main critical factor.Node in wireless sensor network has limited amount of energy. So Data aggregation is an approach by which we can reduce the number of packet transmission to the base station by aggregating the data sensed by the different source node and can provide the high quality of data to the user. In tree based wireless sensor network the important task is the construction of such type of tree in which energy consumption can be minimized and distance traversed in for data transmission should also be shortest. So in this chapter we have presented some IEEE papers or paper some other journal in work is focused on constructing the data aggregation tree for increasing the network lifetime.