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A Flexible Cooperation Scheme for Mitigating the Effect of Selfish Nodes over MANETs
Wan-Jung Chang, Hong-Yuan Li and Jing-Jou Tang

In a MobileAd hoc NETwork (MANET), node cooperation in routing and packet forwarding is essential for the network to operate properly. However, in order to save resources (e.g., energy, memory, CPU cycles and so forth), some selfish nodes might not intend to forward packets, which significantly degrade the network performance. To cope with such misbehavior phenomena in MANET, this study proposes a cooperation-agent reputation system, designated as Co-Agent, which consists of three schemes designed specifically to detect and avoid selfish nodes for mitigating the effect of routing misbehavior, to designate agents for finding an alternative route in the present of selfish nodes, and to allow misjudged nodes which have been isolated from the network to redeem their reputation as well as to rejoin the network.Unlike the previously proposed schemes in the literature which only support the DSR routing, Co-Agent can be applied in both DSR and AODV routing scenarios, and hence provides a flexible solution for MANETs with collaborative systems. Moreover, since Co-Agent ensures that selfish nodes can come back to the network, rather than punish them over a long period of time, and guarantees that packets are permitted to reroute via the designated agents, a robustness capability of packet forwarding is provided to maintain an excellent packet throughput of MANETs. Simulation results performed using the Qualnet simulator confirm the effectiveness and efficiency of the proposed Co-Agent system.

Keywords: MANET; Reputation Mechanism; Cooperation; Selfish Nodes; Protocol; Routing.

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