Clustering in Wireless Sensor Network: A Study on Three Well-Known Clustering Protocols

Clustering in Wireless Sensor Network: A Study on Three Well-Known Clustering Protocols

Basma M. Mohammad El-Basioni (Electronics Research Institute, Egypt), Sherine M. Abd El-Kader (Electronics Research Institute, Egypt), Hussein S. Eissa (Electronics Research Institute, Egypt) and Mohammed M. Zahra (Al-Azhar University, Egypt)
DOI: 10.4018/978-1-4666-5170-8.ch013
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The purpose of this chapter is the study of the clustering process in Wireless Sensor Networks (WSN), starting with clarifying why there are different clustering protocols for WSN by stating and briefly describing some of the variate features in their design; these features can represent questions the clustering protocol designer asks before the design, and their brief description can be considered probabilities for these questions’ answers to represent design options for the designer. The designer can choose the best answer to each design question or, in better words, the best design options that will make its protocol different from the others and make the resultant clustered network satisfies some requirements for improving the overall performance of the network. The chapter also mentions some of these requirements. The chapter then gives illustrative examples for these design variations and requirements by studying them on three well-known clustering protocols: Low-Energy Adaptive Clustering Hierarchy (LEACH), Energy-Efficient Clustering Scheme (EECS), and Hybrid, Energy-Efficient, Distributed clustering approach for ad-hoc sensor networks (HEED).
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Variation In The Design Of Clustering Protocols

Clustering protocols can differ from each other in many features such as:

  • 1.

    The criteria of selecting the nodes that will take the head role: The head selection criterion may be:

    • a.

      Completely random, for example, node ID or a probability not based on any property of the node itself such as node’s residual energy.

    • b.

      Random selection upon a probability based on nodes properties such as residual energy, i.e., as each node compares its CH selection probability against random number, the probability condition randomly may satisfied or not but with a larger chance for the node has the required property to be a CH.

    • c.

      Non-probabilistic CH selection, rather the CH is selected upon its weight which defines its significance or its suitability to become a CH, this weight may depend on a certain metric such as node degree (number of its neighbors which are the nodes in a certain range around it) and residual energy, may depend on more than one metric, or may be a weighted function in more than one metric like:Weight = w1× metric1 + w2 × metric2 + w3 × metric3(1)

The values of the weighting factors of the used metrics may be chosen according to application requirements.

Key Terms in this Chapter

Inter-Cluster Communication: The transmission of cluster data outside it by its head. This transmission may be through single-hop to the base station or through multi-hops among clusters' heads towards the base station.

Wireless Sensor Network: A distributed system consists of a large number of small electronic devices called sensor nodes, each node performs a particular job depends on the used application, which is based mainly on its work on the collection of information from the surrounding environment. Usually, sensor nodes are deployed randomly and communicate wirelessly.

Hierarchical Routing: The data routing method in which the network is hierarchical, in other words, the nodes constitute multiple levels because they are assigned different roles. In each level of the hierarchicy reside the nodes which perform the same jobs. Hierarchical routing assigns the role which consumes more energy to a small percent of nodes and to achieve load-balance this group of nodes is changed periodically.

Synchronization: To provide a common time frame to different nodes. It is mandatory for some important operations of wireless sensor network which aid in improving nodes’ operations and saving their energy such as sleep scheduling and time-based channel sharing, but in the same time, clock synchronization itself contributes in energy consumption due to the highly energy consuming radio transmissions for delivering timing information.

Deceived Nodes: Nodes that may exist in a clustered wireless sensor network. They can be described by the adjective “deceived” because they are deceived by a message sent to them by another node to inform them that it will be its head while in subsequent clustering setup procedures it becomes a member node for another head without informing its deceived members. The result is that, these nodes remain deceived and unused.

Clustering: An organizational unit of the wireless sensor network, and it is a mean to achieve hierarchical routing in wireless sensor network. It comprises grouping nodes into clusters each cluster has a head for coordinating its cluster members' work and receiving their data, aggregating it, and sending it outside the cluster.

Intra-Cluster Communication: The communication among one cluster members; usually the communication is from members to their head through single-hop or multi-hops.

Energy-Efficiency: To expend less energy in performing a certain task. While saving energy is an advisable design goal for most systems, it represents a necessity for wireless sensor network because sensor nodes are usually battery-powered and operate unattended.

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