A non-cooperative file caching for delay tolerant networks: A reward-based incentive mechanism

This paper introduces a reward-based incentive mechanism for file caching in Delay Tolerant Networks (DTNs). In DTNs, nodes use relay's store-carry and forward paradigm to transmit data till final destinations under intermittent connectivity. However, the relays are not always available to assist data transmission due to limited energy or low storage capacity. Our proposal is based on a reward mechanism to sustain cooperation among relays. We model this distributed network problem as a non-cooperative game. On one hand, the source offers to the relays a positive reward if they accept to cache and to forward a given file successfully to a target destination. On the other hand, the relays can either accept or reject the source offer, depending on the reward value and the expected energy consumption of the caching-forwarding operation. Next, a full characterization of the equilibria of this game is provided. Then, we propose two fully distributed algorithms to discover the game Nash equilibria, both for pure/mixed equilibria and discrete/continuous strategy sets. We validate our proposal using extensive numerical examples and numerous learning simulations, and draw some conclusions and insightful remarks.