Optimal activation and transmission control in delay tolerant networks

Abstract—Much research has been devoted to maximize the life time of mobile ad-hoc networks. Life time has often been defined as the time elapsed until the first node is out of battery power. In the context of static networks, this could lead to disconnectivity. In contrast, Delay Tolerant Networks (DTNs) leverage the mobility of relay nodes to compensate for lack of permanent connectivity, and thus enable communication even after some nodes deplete their stored energy. One can thus consider the lifetimes of nodes as some additional parameters that can be controlled to optimize the performance of a DTN. In this paper, we consider two ways in which the energy state of a mobile can be controlled. Both listening and transmission require energy, besides each of these has a different type of effect on the network performance. Therefore we study two coupled problems: i) the activation problem which determines when a mobile will turn on in order to receive packets, and ii) the transmission control problem, which regulates the beaconing. The optimal solutions are shown to be of the threshold type. This paper introduces new methods to derive the threshold structure of optimal policies, as previously used methods, are not useful in this context due to the multidimensional nature of the problem. The findings are validated through extensive simulations. Index Terms—Optimal control, fluid models, delay tolerant networks, threshold policies I