Distributed maintenance of minimum-cost path information in wireless sensor networks

The quality of the communication links in a Wireless Sensor Network often shows significant asymmetry and variation over time, due to, for example, heterogeneous settings of the transmission power, moving nodes or changing external interference. This makes it difficult for nodes to accurately maintain system-level properties, such as the minimum-energy path from the node to a given reference node, as required by many protocols. In this paper, we introduce a distributed service that allows nodes to maintain accurate information related to the minimum-cost path, such as its cost or parent on that path. Using controlled n-hop forwarding, to deal with asymmetric links, every node disseminates minimum-cost path and connectivity information allowing every connected node in the network to iteratively derive minimum-cost path information. This controlled n-hop forwarding is repeated to avoid stale information due to dynamic changes in link qualities. The parameters of the service allow a trade-off between the accuracy and overhead. We study the characteristics of a deployment that impact this trade-off and how the service should be parameterized accordingly. Extensive simulations and experiments for an actual deployment show a significant increase in the accuracy of the maintained minimum-cost path information, compared to the typically used local broadcasting approach.