A scalable and adaptive clock synchronization protocol for IEEE 802.11-based multihop ad hoc networks

This paper studies the fundamental problem of clock synchronization in IEEE 802.11-based multihop ad hoc networks. Clock synchronization is important for power saving, network throughput and many basic operations of 802.11 protocols in a multihop ad hoc network (MANET). The scalability problem of 802.11 timing synchronization has been studied extensively in single hop ad hoc networks and good solutions are available. However these solutions do not perform well in the MANET environment. A few multihop solutions were proposed; but the performance is still not very good. The maximum clock offset is still over 200 mus for these protocols. In this paper, we propose an adaptive protocol through beacon transmission prioritization, frequency adjustment and construction of dominating set. The frequency adjustment is proved to be bounded. Simulation shows that we are able to control the maximum clock offset under 50 mus after protocol stabilization. The improvement is more than 400% over the current solutions with similar complexity. The new protocol also shows great long-term stability