  Enhancement of network lifetime is a key design criterion for most of the
energy constrained networks as nodes are battery operated. In multi-hop
wireless network, proper utilization of battery power is very much necessary to
maintain network connectivity. If the battery power of a node drains quickly
then its connectivity in its neighborhood will be lost. So the study of network
lifetime is very much crucial as compared to other network parameters.
Considering this importance we made an attempt to study the behaviour of three
most common routing protocols in ad hoc network. Extensive simulations are done
on AODV, DSR and ZRP to determine the network lifetime at different node
mobility and at different network load. Simulation results suggest that AODV is
the most energy efficient protocol as compared to other
