A survey on unequal clustering protocols in Wireless Sensor Networks

WSN became a key technology for ubiquitous living and remains an active research due to wide range of applications. Energy awareness is a critical design issue in WSN. Clustering is the most popular energy efficient technique and provides various advantages like energy efficiency, lifetime, scalability and less delay; but it leads to hot spot problem. To overcome this, unequal clustering is proposed. In unequal clustering, the cluster size varies proportionally to the distance to Base Station (BS). Absence of recent and detailed survey papers in unequal clustering approaches stimulated us to perform this study. In this paper, a comprehensive survey of various unequal clustering approaches with their objectives, characteristics etc., is presented. Also, the classifications of unequal clustering approaches are made and compared based on various cluster properties, Cluster Head (CH) properties and clustering process.