An Algorithm for Synchronizing a Clock When the Data Are Received Over a Network With an Unstable Delay

A method is presented for synchronizing the time of a clock to a remote time standard when the channel connecting the two has significant delay variation that can be described only statistically. The method compares the Allan deviation of the channel fluctuations to the free-running stability of the local clock, and computes the optimum interval between requests based on one of the three selectable requirements: 1) choosing the highest possible accuracy; 2) choosing the best tradeoff of cost versus accuracy; or 3) minimizing the number of requests to realize a specific accuracy. Once the interval between requests is chosen, the final step is to steer the local clock based on the received data. A typical adjustment algorithm, which supports both the statistical considerations based on the Allan deviation comparison and the timely detection of errors, is included as an example.