Abstract
The IEEE 802.11 standards support the peer-to-peer mode Independent Basic Service Set (IBSS), which is an ad hoc network with all its stations within each other’s transmission range. In an IBSS, it is important that all stations are synchronized to a common clock. Synchronization is essential for the MAC layer power management. Also, if frequency hopping spread spectrum is used in the physical layer, synchronization is needed to ensure that all stations “hop” at the same time. This paper evaluates the synchronization mechanism as specified in the IEEE 802.11 standards. Through rigorous analysis, it is shown that when the number of stations in an IBSS is not very small, there is a non-negligible probability that stations may get out of synchronization. The more stations, the higher probability of asynchronism. In this sense, the current IEEE 802.11 synchronization algorithm does not scale; it cannot support a large-scale IBSS. To alleviate the asynchronism problem, this paper proposes a simple remedy to the 802.11 algorithm. The resulting algorithm enjoys many nice properties—it is compatible, scalable, effective, mobility-friendly and simple. We are able to exceed the industry expectation of time accuracy (maximum clock offset under 12 μs) without any change of beacon format.
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References
S. Bregni, Synchronization of Digital Telecommunications Networks, (John Wiley & Sons, 2002).
J.H. Chen and W.C. Lindsey, Network Frequency Synchronization with Application-Part-I: General Theory, Milcom (1998).
J. Elson, L. Girod, and D. Estrin, Fine-grained network time synchronization using reference broadcasts, in: Proceedings of the Fifth Symposium on Operating systems Design and Implementation, (2002) pp. 147–163.
IEEE Std 802.11. Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specification, 1999 edition.
IEEE Std 802.11a. Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specification, 1999 edition.
IEEE Std 802.11b. Higher-Speed Physical Layer Extension in the 2.4 GHz Band, 1999 edition.
IEEE Std 802.11g. Amendment 4: Further Higher Data Rate Extension in the 2.4 GHz Band, 2003 edition.
L. Lamport, Time, clocks and the ordering of events in distributed systems, Communications of the ACM 21(7) (1978) 558–565.
Q. Li and D. Rus, Global clock synchronization in sensor networks, in: Proceedings of the 23rd Conference of the IEEE Communications Society (2004) pp. 564–574.
W. C. Lindsey, Network synchronization, IEEE 73(10) (1985) 1445–1467.
D. L. Mills, Internet time synchronization: The network time protocol, IEEE Transaction on Communications (1991) 1482–1493.
S. PalChaudhuri, A.K. Saha and D.B. Johnson, Adaptive clock synchronization in sensor networks, in: Proceedings of 3rd International Symposium on Information Processing in Sensor Networks (2004) pp. 340–348.
Private communications with vendors.
C.H. Rentel and T. Kunz, A non-hierarchical convergent timing synchronization function for real-time QoS support in Wireless LANs: Towards an autonomous network synchronization algorithm for wireless Ad Hoc networks, Wireless World Research Forum, (2004).
C.H. Rentel and T. Kunz, A clock-sampling mutual network time-synchronization algorithm for wireless Ad Hoc networks, in: Proceedings of IEEE Wireless Communications and Networking Conference (2005) pp. 638–644.
K. Römer and E. Zurich, Time synchronization in ad hoc networks, in: Proceedings of 2nd ACM international symposium on Mobile Ad Hoc Networking and Computing (2001) pp. 173–182.
J.P. Sheu, C.M. Chao and C.W. Sun, A clock synchronization algorithm for multi-hop wireless Ad Hoc Networks, in: Proceedings of the 24th international conference on Distributed Computing Systems (2004) pp. 574–581.
D. Zhou and T.H. Lai, Analysis and implementation of scalable clock synchronization protocols in IEEE 802.11 Ad Hoc Networks, in: Proceedings of the first IEEE international conference on Mobile and Sensor Systems (2004) pp. 255–263.
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Dong Zhou is a Member of Technical Staff with Lucent Technologies. He has 11-year experience in networking and telecommunication industry. He got his Ph.D. degree in Computer Science from Ohio State University. He got his B.S. and M.S. degrees in Computer Science from Beijing University. He is an IEEE senior member and has served as a technical committee member in several IEEE conferences. His research interests include 3G/4G wireless network, wireless Ad Hoc networks, fixed and mobile network convergence.
Lifei Huang received the B.E. degree from Tsinghua University, Beijing, China, in 2000, and the M.S. degree from Ohio State University, Columbus, Ohio, in 2002. Currently he is a software engineer at Microsoft. His research interests are in the areas of computer networking and wireless networks.
Ten H. Lai is a Professor of Computer Science and Engineering at the Ohio State University. A pioneer of Zen Networking, he is interested in the art of applying Zen to teaching and research of protocol design. He served as program chair of ICPP’98, general chair of ICPP’00, program co-chair of ICDCS’04, and, recently, general chair of ICDCS’05. He is/was an editor of IEEE Transactions on Parallel and Distributed Systems, ACM/Springer Wireless Networks, Academia Sinica’s Journal of Information Science and Engineering, International Journal of Sensor Networks, and International Journal of Ad Hoc and Ubiquitous Computing.
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Zhou, D., Huang, L. & Lai, T.H. On the scalability of IEEE 802.11 ad-hoc-mode timing synchronization function. Wireless Netw 14, 479–499 (2008). https://doi.org/10.1007/s11276-006-0732-8
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DOI: https://doi.org/10.1007/s11276-006-0732-8