Kalman Filtering For Precision Time Synchronization In Wireless Sensor Networks

As emerging distributed networks, Wireless Sensor Networks (WSNs) have advantages in self-organizing, deployment flexibility and low cost. However, its reliability and stability are relatively low. Due to the inherent uncertainties of wireless channels and the shared medium, the packet loss, collisions and retransmissions require more energy consumption and result in low network throughput and short life-time. The literatures of WSNs show that, time synchronization is one of the key technologies to enhance the reliability and stability of WSNs. Furthermore, a mass of applications and network protocols in WSNs require precision time synchronization, especially in time-sensitive industrial applications. In such time-sensitive systems, the requirements on real-time performance and reliability in communication networks are much higher than that in home and office networks. Therefore, how to obtain accurate time synchronization and high synchronization performance has been a key issue in the field of WSNs.In this thesis, we have analyzed the generation mechanism of synchronization error of the IEEE1588Precision Time Synchronization (PTP), which is developed for wired Ethernet on the basis of time package exchanges. We then develop a state space model describing the behavior of time package exchange in PTP and treat the time synchronization as a state estimation of dynamic systems. As a result, time synchronization is transformed into a set of state estimation in distributed sampling system to improve the performance of PTP in WSNs. The key contributions of thesis are:1) The IEEE1588PTP is firstly adopted in WSNs and a state space model is developed to describe the behavior of the IEEE1588PTP.2) A state space model of WSN node’s clock is developed and a Kalman Filter is proposed to improve the performance of the PTP in WSN.3) A MATLAB/SIMULINK simulation platform is developed to simulate the the IEEE1588PTP and our proposed Kalman Filter for time synchronization in WSNs The simulation results show that the proposed Kalman filter is able to improve the performance of PTP in the scenario of WSNs.