Summary
International Symposium on Nonlinear Theory and its Applications
2009
Session Number:B1L-C
Session:
Number:B1L-C3
Independent Two Skew Estimations Improves Accuracy and Robustness of Synchronization in Wireless Sensor Networks
Kazuhiro Yonekura, Hisa-Aki Tanaka, Kenta Shinohara,
pp.-
Publication Date:2009/10/18
Online ISSN:2188-5079
Summary:
Among several timing synchronization protocols proposed so far, flooding time synchronization protocol (FTSP) is now accepted as one of the most energy-efficient and the highest-precision synchronization protocols for wireless sensor networks. FTSP is based on a periodic flooding of time synchronization messages in a tree-like network of sensor nodes. Therefore, when the root node is lost and reelected, a certain amount of degradation in synchronization precision is temporally observed. Also, in our experiments with Mica2Dot platform we found that the synchronization precision can still be improved by using less synchronization points than in the original FTSP. In this study, we analyze the underlying mechanism of the above observations, and as a result, the following two components are turned out to be problematic; (a) a long term frequency modulation of crystal oscillators in each sensor node, and (b) the resulting error in the estimation of the clock drift (i.e. skew) in FTSP. Based on this analysis, we propose an effective improvement of FTSP with two sets of independent estimations for synchronization offsets between sender and receiver nodes, for robust and better synchronization. Systematic experiments with Mica2Dot platform are carried out, where higher synchronization precision is constantly obtained and dynamical robustness in root reelection process is also enhanced by this improvement.