A representative and accurate characterization of inter-contact times in mobile opportunistic networks

Abstract

A representative characterisation of inter-contact times between nodes is essential for the performance evaluation of mobile networks. The most common characterization of inter-contact times is based on the study of the aggregate distribution of contacts between individual pairs of nodes. The problem with this aggregate distribution is that it is not always representative of the individual pair distributions, especially in the short term and when the number of nodes in the network is high. Thus, deriving results from this characterisation, can lead to inaccurate performance evaluations results. In this paper, we propose and evaluate two new methods for characterising the inter-contact times distribution in mobile networks. We prove that these characterizations have a higher representativeness, thereby improving the accuracy of the derived performance results. For evaluating the precision of the different characterizations we use the epidemic routing protocol, which has an analytical performance expression that is based on a contact rate lambda. We derive from each of the characterizations the corresponding lambda values. Then, we compare the results obtained using the analytical expression with simulation results using both synthetic and real contact traces. It is shown that the new characterization methods are very accurate, even for reduced contact traces and high number of nodes.