Abstract: Wireless sensor networks (WSNs) are presently equipped to handle more complex functions. The main challenges in wireless sensor network include enhancement of stability, conservation of energy, the lifetime of the node and the throughput of the network and its node. To improve the stability of the network as well as to reduce the energy consumption clustering is used. In a cluster, efficient routing protocol plays a vital role in maintaining the stability and also helps in saving energy. In this paper we have surveyed some variants of Stable Election Protocol (SEP): SEP-E, TSEP and ETSSEP, they all are heterogeneous aware protocols i.e. sensor nodes are equipped with different amount of energy levels. These variants of SEP have three levels of heterogeneity in terms of normal, intermediate and advanced nodes.
Keywords: Wireless sensor networks, clustering, heterogeneous environment, stable election protocol.