Research On Incentive Mechanism In Opportunistic Networks

Opportunistic networks is a kind of wireless ad hoc network, in which the complete path between the source node and destination node is not required and communication is done by using encounter chance during process of nodes mobility. Due to the characteristics of intermittent connectivity and network partitions of Opportunistic networks, the routing mechanism works by the mode called ―store-carry-forward‖. In the mode, the messages were stored in intermediate nodes firstly. Then the nodes would not forward these messages until they contact another node. Finally, messages arrive at the destination node. Because of forwarding messages would consume constrained resources, such as buffer, energy, etc., some nodes would behavior selfishly because of the limitation of resources, i.e., these selfish nodes do not forward messages, which would degrade the performance of network sharply. Therefore, stimulating selfish nodes to cooperate is becoming an important research topic recently.Aiming at the problems of lacking encouraging nodes with the high reputation value in Reputation and the uniform transaction price in Credit, which lead to the low incentive effect, a novel Reputation and Credit based incentive mechanism(RCM) is proposed. We define the altruism degree, correlative node and link degree, and set them as the factors of price, then calculate the reasonable price of forwarding service and pay a certain amount of virtual money in order to stimulate selfish nodes to participate in the forwarding process. Finally, this message forwarding task is completed.In view of the problems in existing auction mechanisms, e.g., untruthful bid of relay nodes and arbitrary payment of source, a staged auction mechanism(SAM) is proposed. SAM divides the deadline and budget of the source node into several stages, then adjusts budget constraint and payment in each stage dynamically by defining a parameter called benefit density threshold, which make the payment for relay nodes more reasonable and effective, and stimulate them more collaboratively.To verify the effectiveness of the incentive mechanisms which are proposed above, simulation experiment is performed on the simulator ONE(Opportunistic Networks Environment) by integrating RCM and SAM with PROPHET routing algorithms and Spray and Wait routing algorithms respectively. Simulation results show that the two mechanisms are more advantageous in the aspects of improving message delivery rate and reducing delay.