Question

Smart sensor nodes can process data collected from sensors, make decisions, and recognize relevant events based on the sensed information before sharing it with other nodes. In wireless sensor networks, the smart sensor nodes are usually grouped in clusters for effective cooperation. One sensor node in each cluster must act as a cluster head. The cluster head depletes its energy resources faster than the other nodes. Thus, the cluster-head role must be periodically reassigned (rotated) to different sensor nodes to achieve a long lifetime of wireless sensor network. Discuss in detail what are the major attributes required for choosing the optimal cluster head and explain how the choosing of optimal cluster head helps in
extending the lifetime of the wireless sensor networks, rotating the cluster-head role among sensor nodes with suppression of unnecessary data transmissions. ()

Answer 1

Clustering means grouping of sensor nodes into clusters and selecting one cluster heads for all the clusters. Cluster head is used to collect the data from respective cluster’s nodes, aggregates data and forwards to base station.

-It is one of the important methods to achieve long lifetime for the network in wireless sensor network.

example image:-

Figure gives idea about sensor nodes, cluster and cluster head. In this sensor nodes works on batteries due to which the lifetime of each one sensor node is limited and energy source is limited.

-But in WSNs energy requirement is high, and to overcome this issue clustering algorithm is used.

-Clustering is used in network management for connectivity, coverage and lifetime optimization.

-Optimal cluster head selection:-

-Cluster head selection algorithm is considered as a major modification of Centralized Energy Efficient Distance (CEED) algorithm known as Modified CEED (MOD-CEED). It balances the energy consumption between all sensor nodes by distributing the workload among them.

-While selecting Optimal number of cluster heads in the network attributes considered are the energy dissipation, residual energy of sensor node, and distance between sensor node and base station.All these selection algorithms contributes in efficiently extending the lifetime of network.

-Clustering helps in optimizing energy consumption, reducing transmission interference and enhancing nodes lifetime.

Cluster head selection and assignment works as follows :-

-When the cluster head leaves the cluster, new cluster head must be assigned. If the cluster is fragmented then new cluster head must be assigned to each fragment.

-Suppose that the cluster head has access to the latest information about the position of the target, and keeps an updated list of the best eligible candidates for cluster head post.

-When the present cluster head decides to leave the cluster, it sends the list of best eligible cluster head candidates to its neighbors.

- Each cluster member removes candidtates which are not in neighbourhood from candidtate list. Then election takes place and new cluster head is selected.

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