Performance Modeling of Epidemic Routing with Heterogeneous Node Types

The delay performance of delay tolerant networks (DTN) can be improved by adding or replacing mobile nodes with higher mobility or transmit power. In this paper, we examine the design trade-offs in heterogeneous DTNs with two types of mobile relay nodes: normal and super. First we present the range of parameters in the Random Direction (RD) mobility model in which we have validated the Markovian assumption on the node inter-encounter intervals. Next, we describe the two-dimensional continuous time Markov chain (CTMC) model with absorption state, used for evaluating the performance of the heterogeneous DTNs. We demonstrate that the performance improvement of adding super nodes is not linear. For example, replacing 10% of the normal nodes with super nodes ones can achieve 40% of the delay reduction versus replacing all of them. Finally, Fluid Flow Approximation (FFA) and Moment Closure Methods for solving the CTMC with various error rates (about 10%) were developed to allow faster analysis of networks with large number of nodes.