How Contact Probing Affects the Transmission Capacity and Energy Consumption in DTNs

Link duration is a main factor in determining the transmission capacity between two encounter nodes in Delay Tolerant Networks (DTNs). Existing research on DTN transmission capacity usually assumes that a node is able to immediately discover the nodes which move into its transmission range. Under this assumption, the link duration in DTNs is determined by the moving speed and transmission distance of encounter nodes. However, this assumption could be invalid in realistic DTNs where the nodes use a contact probing protocol to detect their neighbors. In this paper, we investigate the impact of contact probing mechanisms on link duration, and thus the transmission capacity of DTNs. We first derive the probability distribution of link duration, and analyze the impact of contact probing mechanisms on the total link durations. Based on that, we derive the theoretical node throughput and energy consumption, and explore their tradeoff. In addition, we provide an approach to compute the optimal contact probing frequency under energy limitation and adjust the probing frequency according to the node encountering rate. Simulation experiments based on simulator The ONE validates the correctness and the accuracy of our analytical model.