Supernode routing: a grid-based message passing scheme for sparse opportunistic networks

In opportunistic networks (Oppnets), messages are transferred from one node to another when the opportunity arrives and until then, these messages are stored in their buffers. Challenges in such scenarios can arise due to multiple reasons such as buffer space, energy limitations, density of nodes and sparse networks. This paper takes into consideration these factors and proposes a novel routing protocol. Supernode routing is proposed for networks in which nodes are organised in clusters, also known as cells, and takes advantage of this property to limit flooding. Special nodes called supernodes are utilised to transmit a message from one cell to another. Nodes within cells forward their messages to the optimal supernodes based on the direction of the destination cell. The messages are propagated by flooding in intermediate cells until the message is passed over to the next cell in the path using supernodes. When the message is transferred to another cell, it is dropped from all nodes in the current cell. In this manner, messages are streamlined to an expected path to an extent, based on the sender and receiver. This is in contrast to random paths of messages found in most other protocols. The proposed model has been simulated in spatially separated scenarios using ONE simulator. It has high delivery probabilities with drastically low overhead ratios in comparison to the other existing routing protocols.