Efficient routing is a crucial issue in Mobile Adhoc Networks. This paper proposes an improved algorithm for routing in mobile adhoc networks based on the Ant Colony Optimization (ACO) technique. The proposed improved ACO (I-ACO) performs routing by making use of transition probability among nodes along with available pheromone update information in ACO principle. This approach reduces the cost of ant agents. I-ACO has two phases viz route discovery and route maintenance and also utilizes the concept of backtracking when the packets reaches destination node.
Simulation results show that I-ACO achieves better packet delivery ratio and reduces the average end-to-end-delay as compare to its counterpart AODV. This scheme can be incorporated in any version of the on demand routing protocol. In this paper it has been implanted in the basic AODV protocol.