Patent ID: 8301181
Filing Date: 2012-10-30
Classification: H04J

Abstract:
1. A method of determining an accuracy of an oscillator used to generate a local clock signal, the method comprising: sending bursts of requests to a time server over a computer network; receiving a plurality of bursts each of a plurality of timestamped response messages from the time server over the computer network, each of said response messages being subject to a network propagation delay, said network propagation delay being a sum of a minimum network propagation delay and a jitter component; for each received response message, determining an apparent network propagation delay as a function of a difference between a first timestamp applied by the time server and a second timestamp based on a clock derived from said oscillator; preselecting one response message from each burst of response messages having a minimum apparent network propagation delay; defining a time interval, over which the accuracy of the oscillator is to be determined; dividing said time interval into time windows; within each time window, selecting one of the preselected response messages as the minimum network propagation delay response message, based on the determined network propagation delay of each preselected response message and each preselected response message's corresponding time position within said time window; and determining the accuracy of the oscillator based on changes over time in the apparent network propagation delays of the selected received response messages.