Time, clocks, and the ordering of events in a distributed system
Communications of the ACM
Time synchronization in ad hoc networks
MobiHoc '01 Proceedings of the 2nd ACM international symposium on Mobile ad hoc networking & computing
Synchronization of Digital Telecommunications Networks
Synchronization of Digital Telecommunications Networks
A Clock Synchronization Algorithm for Multi-Hop Wireless Ad Hoc Networks
ICDCS '04 Proceedings of the 24th International Conference on Distributed Computing Systems (ICDCS'04)
Adaptive clock synchronization in sensor networks
Proceedings of the 3rd international symposium on Information processing in sensor networks
Fine-grained network time synchronization using reference broadcasts
OSDI '02 Proceedings of the 5th symposium on Operating systems design and implementationCopyright restrictions prevent ACM from being able to make the PDFs for this conference available for downloading
Behavior of clock-sampling mutual network synchronization in wireless sensor networks
Proceedings of the 2009 International Conference on Wireless Communications and Mobile Computing: Connecting the World Wirelessly
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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.