Date Added: Mar 2012
Many advances have been made in sensor technologies which are as varied as the applications; and many more are in progress. It has been reasonable to design and develop small size sensor nodes of low cost and low power. In this paper, the authors have explored some energy-efficient routing protocols (LEACH, Directed Diffusion, Gossiping and EESR) and their expansions (enhancements), and furthermore, their tactics specific to wireless sensor network, such as data aggregation and in-network processing, clustering, different node role assignment, and data-centric methods. After that they have compared these explored routing protocols based on different metrics that affect the specific application requirements and WSN in general.