We propose a probabilistic store-carry-forward message delivery scheme based on node density estimation. In our scheme, when a node with a message copy encounters another node, the former forwards its copy to the latter with a certain probability. The forwarding probability is determined depending on a node density at the contact location where two nodes encounter. More specifically, when the node density is high, the forwarding probability is set to be low. This policy is designed to avoid excess message copy transmissions in a high node-density area. In general, nodes frequently encounter each other in high node-density areas and message copies rapidly spread over the nodes. In order to determine whether the node density is high or not, each node estimates the node density distribution over the whole network based on the contact location information. The information is collected by each node and exchanged among nodes. With simulation experiments, we evaluate the performance of our scheme in terms of the mean delivery delay and the number of forwarded message copies.
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