ABSTRACT
Having access to an accurate time is a vital building block in all networks; in wireless sensor networks even more so, because wireless media access or data fusion may depend on it. Starting out with a novel analysis, we show that orthodox clock synchronization algorithms make fundamental mistakes. The state-of-the-art clock synchronization algorithm FTSP exhibits an error that grows exponentially with the size of the network, for instance. Since the involved parameters are small, the error only becomes visible in midsize networks of about 10--20 nodes. In contrast, we present PulseSync, a new clock synchronization algorithm that is asymptotically optimal. We evaluate PulseSync on a Mica2 testbed, and by simulation on larger networks. On a 20 node network, the prototype implementation of PulseSync outperforms FTSP by a factor of 5. Theory and simulation show that for larger networks, PulseSync offers an accuracy which is several orders of magnitude better than FTSP. To round off the presentation, we investigate several optimization issues, e.g. media access and local skew.
- TinyOS. http://www.tinyos.net/.Google Scholar
- M. Allen, L. Girod, R. Newton, S. Madden, D. T. Blumstein, and D. Estrin. VoxNet: An Interactive, Rapidly-Deployable Acoustic Monitoring Platform. In Proc. 7th International Conference on Information Processing in Sensor Networks (IPSN), 2008. Google ScholarDigital Library
- R. Bar-Yehuda, O. Goldreich, and A. Itai. On the Time-Complexity of Broadcast in Multi-hop Radio Networks: An Exponential Gap Between Determinism and Randomization. J. Comput. Syst. Sci., 45(1):104--126, 1992. Google ScholarDigital Library
- S. Biaz and J. L. Welch. Closed Form Bounds for Clock Synchronization Under Simple Uncertainty Assumptions. Inf. Process. Lett., 80(3):151--157, 2001. Google ScholarDigital Library
- I. Chlamtac and S. Kutten. On Broadcasting in Radio Networks - Problem Analysis and Protocol Design. IEEE Transactions on Communications, 33:1240--1246, 1985.Google ScholarCross Ref
- I. Chlamtac and O. Weinstein. The Wave Expansion Approach to Broadcasting in Multihop Radio Networks. In Proc. 6th annual IEEE Conference on Computer Communications (INFOCOM), 1987.Google Scholar
- A. Czumaj and W. Rytter. Broadcasting Algorithms in Radio Networks with Unknown Topology. In Proc. 44th Annual IEEE Symposium on Foundations of Computer Science (FOCS), 2003. Google ScholarDigital Library
- J. Elson, L. Girod, and D. Estrin. Fine-Grained Network Time Synchronization using Reference Broadcasts. In Proc. 5th Symposium on Operating Systems Design and Implementation (OSDI), 2002. Google ScholarDigital Library
- R. Fan and N. Lynch. Gradient Clock Synchronization. In Proc. 23rd annual ACM Symposium on Principles of Distributed Computing (PODC), 2004. Google ScholarDigital Library
- S. Ganeriwal, R. Kumar, and M. B. Srivastava. Timing-Sync Protocol for Sensor Networks. In Proc. 1st International Conference on Embedded Networked Sensor Systems (SenSys), 2003. Google ScholarDigital Library
- J. Hill and D. Culler. Mica: a Wireless Platform for Deeply Embedded Networks. Micro, IEEE, 22(6):12--24, 2002. Google ScholarDigital Library
- W. Hoeffding. Probability Inequalities for Sums of Bounded Random Variables. Journal of the American Statistical Association, 58(301):13--30, 1963.Google ScholarCross Ref
- S. Kim, S. Pakzad, D. Culler, J. Demmel, G. Fenves, S. Glaser, and M. Turon. Health Monitoring of Civil Infrastructures using Wireless Sensor Networks. In Proc. 6th International Conference on Information Processing in Sensor Networks (IPSN), 2007. Google ScholarDigital Library
- H. Kopetz and W. Ochsenreiter. Clock Synchronization in Distributed Real-Time Systems. IEEE Trans. Comput., 36(8), 1987. Google ScholarDigital Library
- F. Kuhn and R. Oshman. Gradient Clock Synchronization using Reference Broadcasts. CoRR, abs/0905.3454, 2009.Google Scholar
- B. Kusy. Spatiotemporal Coordination in Wireless Sensor Networks. PhD thesis, Vanderbilt University, 2007. Google ScholarDigital Library
- C. Lenzen, T. Locher, and R. Wattenhofer. Tight Bounds for Clock Synchronization. In Proc. 28rd Annual ACM Symposium on Principles of Distributed Computing (PODC), 2009. Google ScholarDigital Library
- J. Lundelius and N. A. Lynch. An Upper and Lower Bound for Clock Synchronization. Information and Control, 62(2/3):190--204, 1984.Google ScholarCross Ref
- M. Maróti, B. Kusy, G. Simon, and Á. Lédeczi. The Flooding Time Synchronization Protocol. In Proc. 2nd International Conference on Embedded Networked Sensor Systems (SenSys), 2004. Google ScholarDigital Library
- L. Meier and L. Thiele. Brief announcement: Gradient Clock Synchronization in Sensor Networks. In Proc. 24th annual ACM Symposium on Principles of Distributed Computing (PODC), 2005. Google ScholarDigital Library
- D. Mills. Internet Time Synchronization: the Network Time Protocol. IEEE Transactions on Communications, 39(10):1482--1493, Oct 1991.Google ScholarCross Ref
- T. Moscibroda, P. von Rickenbach, and R. Wattenhofer. Analyzing the Energy-Latency Trade-Off During the Deployment of Sensor Networks. In Proc. 25th Conference on Computer Communications (INFOCOM), 2006.Google ScholarCross Ref
- R. Ostrovsky and B. Patt-Shamir. Optimal and Efficient Clock Synchronization Under drifting Clocks. In Proc. 18th annual ACM Symposium on Principles of Distributed Computing (PODC), 1999. Google ScholarDigital Library
- K. Römer. Time Synchronization in Ad Hoc Networks. In Proc. 2nd ACM International Symposium on Mobile ad hoc Networking&Computing (MobiHoc), 2001. Google ScholarDigital Library
- J. Sallai, B. Kusy, A. Ledeczi, and P. Dutta. On the Scalability of Routing Integrated Time Synchronization. 3rd European Workshop on Wireless Sensor Networks (EWSN), 2006. Google ScholarDigital Library
- J. Schneider and R. Wattenhofer. A log-star Distributed Maximal Independent Set Algorithm for Growth-Bounded Graphs. In Proc. 27th ACM Symposium on Principles of Distributed Computing (PODC), 2008. Google ScholarDigital Library
- G. Simon, M. Maróti, A. Lédeczi, G. Balogh, B. Kusy, A. Nádas, G. Pap, J. Sallai, and K. Frampton. Sensor Network-based Countersniper System. In Proc. 2nd International Conference on Embedded Networked Sensor Systems (SenSys), 2004. Google ScholarDigital Library
- R. Solis, V. Borkar, and P. R. Kumar. A New Distributed Time Synchronization Protocol for Multihop Wireless Networks. In Proc. 45th IEEE Conference on Decision and Control (CDC), 2006.Google ScholarCross Ref
- P. Sommer and R. Wattenhofer. Gradient Clock Synchronization in Wireless Sensor Networks. In Proc. 8th ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN), 2009. Google ScholarDigital Library
- T. K. Srikanth and S. Toueg. Optimal Clock Synchronization. J. ACM, 34(3), 1987. Google ScholarDigital Library
- A. A. Syed and J. Heidemann. Time synchronization for high latency acoustic networks. In Proc. 25th Conference on Computer Communications (InfoCom), 2006.Google ScholarCross Ref
- G. Werner-Allen, K. Lorincz, J. Johnson, J. Lees, and M. Welsh. Fidelity and Yield in a Volcano Monitoring Sensor Network. In Proc. 7th Symposium on Operating Systems Design and Implementation (OSDI), 2006. Google ScholarDigital Library
- G. Werner-Allen, G. Tewari, A. Patel, M. Welsh, and R. Nagpal. Firefly-Inspired Sensor Network Synchronicity with Realistic Radio Effects. In Proc. 3rd International Conference on Embedded Networked Sensor Systems (SenSys), 2005. Google ScholarDigital Library
Index Terms
- Optimal clock synchronization in networks
Recommendations
The flooding time synchronization protocol
SenSys '04: Proceedings of the 2nd international conference on Embedded networked sensor systemsWireless sensor network applications, similarly to other distributed systems, often require a scalable time synchronization service enabling data consistency and coordination. This paper describes the Flooding Time Synchronization Protocol (FTSP), ...
Timing-sync protocol for sensor networks
SenSys '03: Proceedings of the 1st international conference on Embedded networked sensor systemsWireless ad-hoc sensor networks have emerged as an interesting and important research area in the last few years. The applications envisioned for such networks require collaborative execution of a distributed task amongst a large set of sensor nodes. ...
Rate-adaptive time synchronization for long-lived sensor networks
SIGMETRICS '05: Proceedings of the 2005 ACM SIGMETRICS international conference on Measurement and modeling of computer systemsTime synchronization is critical to sensor networks at many layers of its design and enables better duty-cycling of the radio, accurate localization, beamforming and other collaborative signal processing. While there has been significant work in sensor ...
Comments