CCQR: Constant Cost Quality-based Routing Protocol in Delay Tolerant Networks

Quality-based routing protocols are proposed to restrict message flooding within only high quality nodes in delay tolerant networks (DTNs). However, different quality threshold mechanisms have diverse impact on the network and we investigate this issue in the paper. Through theoretical analysis we show that heterogeneous threshold mechanism suffers a severe nodal cost imbalance problem. Furthermore, for both homogeneous and heterogeneous mechanisms, routing cost depends on the total number of nodes, and becomes significant in large-scale networks. To address these issues, we propose Constant Cost Quality-based Routing (CCQR) protocol, which not only retains the favorable features of quality-based routing protocols, but also achieves a constant routing cost. More importantly, thanks to the wise message distribution rules, CCQR protocol is capable of alleviating nodal cost imbalance problem effectively. We also conduct extensive simulations to verify our conclusions and the efficacy of the new protocol.