A study of Adaptive Replication Technique in routing time-constrained messages (VoIP) in MANET

Imposing the constraint of timely delivery on usual messages is referred as time-constrained messages. The utility of such messages depends upon the time at which they arrive at their destination. Due to contention among randomly arriving messages at each node/link and multi-hops between the source and destination that a message must travel, it is difficult to guarantee the timely delivery of such messages. In case of faulty links or node, it is likely impossible for messages to reach at required destination in time. To handle such type of faults, the idea of sending multiple copies or replicated copies is used. The probability of successful message delivery within time will be increased through sending multiple copies through disjoint routes, as at least one copy will be reached within time. But this will degrade the network performance due to congestion and other problems. Therefore, it is require sending only optimum number of copies through disjoint routes. Such copies are estimated on the basis of network load and message deadline. In this paper, we present the method to estimate the optimum number of copies. The system is designed for developing replication strategy named as Adaptive Fault Tolerance Replication Technique (AFTRT) for VoIP applications used for Mobile Ad hoc Network. The parameters such as end-to-end latency, node delivery index and message delivery probability are determine by the destination and send as feedback to the source. Based on this information, source replicates the message. The performance study is conducted through simulation using NS2 simulator.