Abstract: A mobile ad hoc network (MANET) is a self-organized collection of mobile nodes which communicate with each other without the help of any fixed infrastructure or central coordinator. A node intending to communicate with another node that is not within its communication range, takes help of intermediate nodes to relay its message. The topology of the network dynamically changes over time as nodes move about, some new nodes join the network or few other nodes disengage themselves from the network. Intrusion Detection Systems (IDS) are used in MANETs to monitor activities so as to detect any intrusion in the otherwise vulnerable network. Communication has become very important for exchanging information between people from, to any time via mobiles. MANET is a group of mobile nodes that form a network independently of any centralized administrator for communication. Since those mobile devices are battery operated and extending the battery lifetime has become an important aim. Most of the researchers have recently started to consider Power –aware development of efficient protocols for MANETs. Also the nodes in the network are moving if a node moves out of the radio range of the other node, the link between them is broken. so we presented an original solution called IMAPC – MAC Protocol(Improved Autonomous Power Control) In this paper, an efficient scheme for analyzing and optimizing the time duration for which the intrusion detection systems need to remain active in a mobile ad hoc network is presented. A probabilistic model is proposed that makes use of cooperation between IDSs among neighborhood nodes to reduce their individual active time. Usually, an IDS has to run all the time on every node to oversee the network behavior. This can turn out to be a costly overhead for a battery-powered mobile device in terms of power and computational resources. Hence, this work is to reduce the duration of active time of the IDSs without compromising on their effectiveness.

Keywords: Adhoc Networks, Intrusion Detection, Energy efficiency, MANET, IMAPC-MAC protocol.