A Consensus-Based Time Synchronization Scheme With Low Overhead for Clustered Wireless Sensor Networks

For clustered wireless sensor networks, this letter presents a time synchronization scheme with low overhead that is based on the maximum consensus approach. The synchronization process is initiated by the cluster head and includes three steps: 1) threshold-based intracluster time synchronization (TITS); 2) forwarding-based intercluster time synchronization (FITS); and 3) one-way intracluster time synchronization (OITS). Specifically, first, TITS achieves the logical clock of cluster head to be synchronized to the largest logical clock of intracluster nodes with three times point-to-point message exchange in two cycles. Especially, by comparing the logical skew of each intracluster node with the logical skew of cluster head, member nodes with smaller logical skew will not reply to cluster head to reduce the number of message exchanges. Then, in FITS, the cluster heads synchronize with each other and the message exchanges of cluster heads are realized through the message forwarding of the gateway nodes. At last, OITS utilizes the one-way communication to synchronize all the intracluster nodes with cluster head via two times broadcasting of cluster head. Theoretical analysis and simulation results demonstrate that the proposed scheme can reduce the communication traffic greatly and improve the convergence rate.