Blind Online Optimal Forwarding in Heterogeneous Delay Tolerant Networks

In this paper we consider a heterogeneous DTN formed by different classes of nodes. A core problem in DTNs literature is to optimize forwarding control such in a way to deliver messages from source to destination under a given energy budget. In this context, we model the presence of different classes and describe the structure of the optimal solution. The closed form of an optimal policy is found in the family of the multi-dimensional dynamic strategies. These policies assign a specific threshold to each class of mobiles. We also show that in the multi-class case there exists an order of the classes that depends on the system parameters in a very simple form. In particular, we exploit the ordering induced by the optimal control with the goal of designing a new class of multidimensional stochastic approximation algorithms that apply to the heterogeneous DTNs. These algorithms are blind because they drive online the source node to the optimal operating point without requiring explicit estimation of network parameters (intermeeting intensities and the number of nodes for each class).