Analysis of message delivery delay in large-scale geographic DTN routing

In this paper, we approximately derive the average message delivery delay in geographic DTN routing under random walk mobility on a large-scale network. A geographic DTN routing aims at realization of message delivery among multiple (generally, geographically-dispersed) geographic locations on a field without necessity of specific communication infrastructure by utilizing mobility of mobile agents. In this paper, we address the following research questions. How well or badly does geographic DTN routing perform in a large-scale network (i.e., a network with many geographic locations)? How is the performance of geographic DTN routing affected by the topology of the network (i.e., connections of many geographic locations)? We try to answer the questions using a hybrid modeling of geographic DTN routing with the help of recent advancement in analytical studies of random walks on a graph. We also show that geographic DTN routing is scalable; i.e., its average message delivery delay is approximately proportional to the network size (i.e., geographic locations) unless heavily loaded. We show that the network topology has limited impact on the performance of geographic DTN routing except heavily loaded conditions; the average message delivery delay is mostly determined by the degree of the destination node.