Power Management In Delay Tolerant Networks: A Framework And Knowledge-Based Mechanisms

Delay tolerant networks (DTNs) are mobile wireless networks that are characterized by frequent partitions and potentially long message delivery delays. Such networks have the potential for use in important application environments where energy sources are limited. Therefore, efficient power management mechanisms are necessary to allow these networks to operate over a long period of time. In this paper, we leverage the observation that many DTNs are characterized by sparse connectivity, providing the opportunity to save energy by aggressively disabling node radios (sleeping). The major challenge is to balance sleeping periods with wake-up periods so that valuable and infrequent communication opportunities between nodes are not missed. We develop a power management framework that allows a node to save energy while missing few communication opportunities. The framework is tailored to the available knowledge about network connectivity over time. Further, the framework supports an explicit tradeoff between energy savings and connectivity, so that network operators can choose, for example, to conserve energy at the cost of reduced message delivery performance. We evaluate our mechanisms using ns-2 simulations. Our results show that our power management mechanisms consume from 10% to 50% of the energy expended when the network operates without power management. These energy savings come at the cost of some performance degradation when available knowledge is incomplete, though our tuning parameter allows a rich set of tradeoffs between energy consumption and performance.