One of the key problems for Wireless Sensor Network (WSN) is the design of Medium Access Control (MAC) protocol.MAC protocol controls the activity of wireless communication module of sensor nodes

which is the major consumer of sensor energy.The energy efficiency of MAC protocol makes a strong impact on the network performance.TDMA-based MAC protocol is inherently collision free

and can rule out idle listening since nodes know when to transmit.In this paper

we present ED-TDMA

an event driven TDMA protocol for wireless sensor network.ED-TDMA improves channel utility by changing the length of TDMA frame according to the number of source nodes

while saving energy with bitmap-assisted TDMA schedule.In addition

ED-TDMA employs intra-cluster coverage to prolong network lifetime and to improve system scalability.Simulation results show that ED-TDMA performs better for wireless sensor network with high-density deployment and low traffic.