Fast Layered-Synchronization Algorithm for Ad-hoc Networks

In Ad-hoc networks, the MAC protocol based on time division multiple access (TDMA) has a wide application prospect in military and disaster relief emergency communications since it completely avoids access conflicts. However, the high-dynamic topologies of Ad-hoc networks force every node to conduct time synchronization frequently, which would inevitably cause substantial overhead. In this regard, this paper designs the fast layered-synchronization (FLS) algorithm, which is well-suited to high-dynamic network topologies owing to its low overhead. In the network access synchronization phase, FLS initially partitioned the nodes into different layers based on their locations. Then in every periodic synchronization phase, according to the theory of neighbor density, a series of synchronization reference nodes are selected from the network. The layer of each reference node is improved to the highest among all its neighbor nodes, and then provide time reference for them. The newly-accessed nodes also only need to exchange information with their nearest reference nodes to achieve synchronization, so that the overhead of synchronization can be reduced. Finally, in order to evaluate the performance of FLS, the wireless network card with TDMA mechanism is developed and the FLS algorithm is transplanted. The experimental results show that FLS can maintain microsecond-level synchronization accuracy with low overhead.