The University of British Columbia

In wireless sensor networks (WSNs), when a stimulus or event is detected within a particular region, data reports from the neighboring sensor nodes (sources) are sent to the sink or destination. Data from these sources are usually aggregated along their way to the sink. The data aggregation via in-network processing reduces communication cost and improves energy efficiency. In this paper, we propose an overlay structure in which the sources within the event region form a tree to facilitate data aggregation. We call this tree a lifetime-preserving tree (LPT). LPT aims to prolong the lifetime of the sources which are transmitting data reports periodically. In LPT, nodes which have higher residual energy are chosen as the aggregating parents. LPT also includes a self-healing feature by which the tree will be re-constructed again whenever a node is no longer functional or a broken link is detected. By choosing the directed diffusion as the underlying routing platform, simulation results show that in a WSN with 250 sensor nodes, the lifetime of sources can be extended significantly when data are aggregated using the LPT algorithm