A statistical method for time synchronization of computer clocks with precisely frequency-synchronized oscillators

Abstract

With the growing of computer networks, continuous media communication and processing are expected in distributed systems. Continuous media communication and processing require both time and frequency synchronization between computer clocks. The authors propose a statistical time synchronization method for computer clocks that have precisely frequency-synchronized oscillators. This method not only improves time synchronization accuracy but also prevents degradation of the frequency stability of the precise oscillators when errors in the measured time offset between computer clocks caused by network traffic possess a Gaussian distribution. The improvement of time synchronization accuracy is achieved by estimating the confidence interval of the measured time offsets between the computer clocks. The prevention of frequency stability degradation is achieved by testing the difference between the latest mean and the mean at the last time adjustment for deciding the need for time correction. Evaluation by simulation of changes in the time offset in an ISDN clock synchronization system showed that this method achieves accurate time and stable frequency synchronization.