Abstract: Wireless Sensor Network is a highly distributed network of small and lightweight sensing nodes which are deployed in a large number at multiple locations. These networks are helpful in monitoring the system or environment. These sensor nodes performs sensing, processing and then communicating. Now a day’s these networks are applied in various fields like military, defence, forest fire, medical, crisis management etc. In this paper it has been discussed about sensor network architecture and major factors affecting the wireless sensor networks. Routing is a major challenge faced by wireless sensor networks due to the dynamic nature of WSNs. Since energy efficient routing protocols are of major concern in the field of wireless sensor network. Therefore in further sections of this paper it has presented a brief review of different energy efficient routing protocols proposed for wireless sensor networks.

Keywords: Clustering, Energy efficient routing, LEACH, Sensor Nodes, Wireless Sensor Networks, WSNs.