A Kalman Filter Approach To Clock Synchronization Of Cascaded Network Elements*

The Precision Time Protocol specified by IEEE 1588 standard has been proved to be an appropriate network synchronization protocol. The PTP protocol is based on exchanging appropriate timing information, generated by time stamping according to the local clocks, between adjacent clocks. Using the time-stamps, a slave element learns the relation between its own clock and the master clock so that it can synchronize its time to the reference time provided by the master. Uncertainties, e.g., random stamping and quantization errors, greatly affect the synchronization precision. This paper presents a probabilistic state-space model which quantifies the uncertainties and represents the relation between the system variables. Then clock synchronization is posed as a state estimation problem and solved by using Kalman filter. The performance of this approach is verified by numerical results.