One feedback-based time synchronization method for wireless sensor networks

Time synchronization is a fundamental technology in wireless sensor networks (WSNs), and its energy efficiency is a major factor that should be concerned. In this paper, one feedback-based time synchronization (FBTS) method is proposed to real-time regulate the re-synchronization period according to the disagreement between synchronization accuracy requirement and synchronization error. The re-synchronization period is valued as large as possible in the case of that the accuracy requirement is met with. The network is divided into several parent-child groups, and for each group one or more pairwise synchronization (PS) nodes are selected. All the nodes´ clock skews and offsets with respect to their parents are estimated through the use of joint maximum likelihood estimation (JMLE) method. All the parent nodes evaluate the group synchronization error and regulates the group re-synchronization period periodically. The methods of receive-only synchronization (ROS) and sender-receiver synchronization (SRS) are combined here to reduce the number of packets transmitted among the network. Some numerical simulation results verify the effectiveness of this FBTS method.