Mobile ad hoc (MANET) network is collection of nodes, which establish communication among moving nodes in a decentralized way without the use of any fixed infrastructure. Due to unpredictable network topological changes, routing in MANET is a challenging task as it requires a specialized approach to handle these changes due to the random movement of nodes. The routing protocol designed for MANETs should be able to detect and maintain route(s) between the source and the destination nodes in an efficient manner to handle the above defined issues. In this direction, ant colony algorithm is an important category of meta-heuristics techniques, which can provide an efficient solution to many engineering problems. But most of the existing ant colony algorithms explore the search space without initial directions, which lead to the risk of having local optima. To address this issue, in the present paper, we have been motivated and inspired by our previous work (Kumar et al. in Simul Model Pract Theory 19(9):1933---1945, 2011) in which the orientation factor was not considered, and the ant algorithm was applied for service selection in wireless mesh networks (WMNs). But in the current proposal, we have considered the orientation factor and applied the same in MANETs. Hence keeping this point in view, we propose an orientation based ant algorithm (OANTALG) for Routing in MANETs in which the selection of destination nodes and the exchange of ants (agents) between the source and the destination is based upon the orientation factor. During the movement of ants, the pheromone tables and the data structures are created that record the ants trip time between the nodes through which ants make a move. An efficient algorithm for orientation based routing has also been designed in the proposed scheme. The results obtained show that the proposed algorithm performs better than the other state of art algorithms, which are traditional and other ant based algorithms such as AODV, DSR, and HOPNET with respect to various performance metrics such as number of data packets send, throughput, jitter and path length. Simulation results show that OANTALG can send 1.02, 1.44, 1.61 times more number of data packets than AODV, DSR, and HOPNET, respectively. The throughput in OANTALG is 1.79, 30.69, and 48 % more than AODV, DSR and HOPNET, respectively. Packet drop ratio has also been reduced in the proposed OANTALG algorithm as compared to AODV and DSR. Average Jitter is also reduced by 42, 256 and 26.3 % from AODV, DSR and HOPNET, respectively. Average path length of OANTALG is 1.021 and 1.62 times less than AODV and DSR, respectively.
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