Clock Synchronization in IEEE 802.11 Ad Hoc Networks

In an Independent Basic Service set (IBSS), of IEEE 802.11 standards, it is important that all stations are synchronized to a common clock. When the number of stations in an IBSS is very small, there is a negligible probability that stations may go out of synchronization. More the stations, higher is the probability of getting out of synchronization. Thus, the current IEEE 802.11's synchronization mechanism does not scale; it cannot support a large-scale ad hoc network. To alleviate the synchronization problem, “Adaptive Time Synchronization Procedure” (ATSP) is proposed [1]. ATSP is scalable up to 300 nodes. As the number of nodes increases beyond 300 again synchronization become problem. In this paper, we modify ATSP to further increase the scalability of IEEE 802.11 ad hoc networks. The modified algorithm divides nodes in priority levels depending on their clock speed. This algorithm allows nodes only with highest priority to contend for beacon transmission. Reduction in beacon contention increases scalability of IBSS.