Achieving stable network performance for wireless sensor networks

Extensive empirical results reveal that interference can cause link qualities to change quickly and dramatically. For such highly dynamic links, the short term link quality estimations widely used in existing protocols require frequent measurements and may not be accurate. As a result, when these links are selected, end-to-end communication quality varies significantly. Also, route changes occur frequently, introducing traffic oscillation and excessive overhead in network protocols. To achieve good and stable network performance, it is not enough to use short term link estimation. It is essential to characterize a link's capacity to perform well at a desired level in the presence of interference and environmental changes. Therefore, we propose a performance metric called competence. We have incorporated the competence metric into routing algorithm designs. We have also designed and implemented a maintenance framework that stabilizes performance at both link and network layers. This framework allocates the desired performance level among multiple links along an active route by using an end-to-end feedback loop, and enforces the performance level of each link through adaptive transmission power control and retransmission control. In real system evaluations with 48 TMotes, our solution outperforms previous protocols significantly and achieves end-to-end stable performance for more than 99% of the time over 24 hours.