Modeling and simulation comparison of two time synchronization protocols

ABSTRACT

To infer correctly application semantics, sensor network applications often need accurate times on observations that are reported from distributed sensor nodes. Since the nodes' local clocks can go out-of-sync due to clock drifts, a networked time synchronization protocol is needed to synchronize their clocks to a reference clock. This paper provides performance modeling and comparison between two time synchronization protocols: TPSN clock synchronization (clock-sync) and TSS event synchronization (event-sync). Their main difference is that the TPSN clock-sync synchronizes all nodes' local clocks to a global reference clock, whereas TSS event-sync synchronizes events' generation times from different local nodes to their sink nodes' clocks. Although these two time synchronization protocols have their respective limitations in application scenarios, they are comparable in that they also share a large domain with none of these limitations. This paper evaluates these two protocols by considering different ad-hoc network sizes, node mobility levels, and traffic volumes. In order to fully understand the tradeoffs between these two time synchronization protocols, we have derived analytical models on their performances and conducted simulations to measure the impact of these variables. Both the simulation results and analytical models show that (1) event-sync provides much better accuracy than clock-sync, (2) under very high node mobility level, clock-sync may achieve better accuracy than event-sync, and (3) under increasing traffic volume clock-sync scales better.

REFERENCES

• 1: Alberto Cerpa , Jeremy Elson , Deborah Estrin , Lewis Girod , Michael Hamilton , Jerry Zhao, Habitat monitoring: application driver for wireless communications technology, ACM SIGCOMM Computer Communication Review, v.31 n.2 supplement, April 2001 [doi>10.1145/844193.844196]
• 2: Z. Zhang, "Investigation of Wireless Sensor Networks for Precision Agriculture," Paper number 041154,2004 ASAE Annual Meeting. H. Poor, An Introduction to Signal Detection and Estimation. New York: Springer-Verlag, 1985, ch. 4.
• 3: Lakshman Krishnamurthy , Robert Adler , Phil Buonadonna , Jasmeet Chhabra , Mick Flanigan , Nandakishore Kushalnagar , Lama Nachman , Mark Yarvis, Design and deployment of industrial sensor networks: experiences from a semiconductor plant and the north sea, Proceedings of the 3rd international conference on Embedded networked sensor systems, November 02-04, 2005, San Diego, California, USA [doi>10.1145/1098918.1098926]
• 4: Jeremy Elson , Kay Römer, Wireless sensor networks: a new regime for time synchronization, ACM SIGCOMM Computer Communication Review, v.33 n.1, p.149-154, January 2003 [doi>10.1145/774763.774787]
• 5: Jeremy Elson , Lewis Girod , Deborah Estrin, Fine-grained network time synchronization using reference broadcasts, Proceedings of the 5th symposium on Operating systems design and implementation

  Due to copyright restrictions we are not able to make the PDFs for this conference available for downloading

  , December 09-11, 2002, Boston, Massachusetts [doi>10.1145/1060289.1060304]
• 6: D. L. Mills, "Internet Time Synchronization: the Network Time Protocol," IEEE Trans. Communications, Vol 39, no 10, pp. 1482--1493, Oct. 1991.
• 7: Leslie Lamport, Time, clocks, and the ordering of events in a distributed system, Communications of the ACM, v.21 n.7, p.558-565, July 1978 [doi>10.1145/359545.359563]
• 8: Saurabh Ganeriwal , Ram Kumar , Mani B. Srivastava, Timing-sync protocol for sensor networks, Proceedings of the 1st international conference on Embedded networked sensor systems, November 05-07, 2003, Los Angeles, California, USA [doi>10.1145/958491.958508]
• 9: Kay Römer, Time synchronization in ad hoc networks, Proceedings of the 2nd ACM international symposium on Mobile ad hoc networking & computing, October 04-05, 2001, Long Beach, CA, USA [doi>10.1145/501436.501440]
• 10: Chalermek Intanagonwiwat , Ramesh Govindan , Deborah Estrin, Directed diffusion: a scalable and robust communication paradigm for sensor networks, Proceedings of the 6th annual international conference on Mobile computing and networking, p.56-67, August 06-11, 2000, Boston, Massachusetts, United States [doi>10.1145/345910.345920]

INDEX TERMS

Primary Classification:
  C. Computer Systems Organization
  C.2 COMPUTER-COMMUNICATION NETWORKS
      C.2.4 Distributed Systems

General Terms:
Performance

Keywords:
performance evaluation, sensor networks, time synchronization