Method for time synchronization in a communications network

A node for use as a second node in a method for time synchronization in a communications network having a plurality of nodes, each of the plurality of nodes comprising a first node and the node, a synchronization message being sent from the first node to the node within a synchronization cycle, the first node providing a first cycle counter state in accordance with a reference clock frequency and the node providing a second cycle counter state in accordance with an internal clock frequency;

• wherein the node is configured to implement time synchronization such that:
• (a) the synchronization message is received at the node;
• (b) an estimated first cycle counter state and an estimated compensation factor are estimated for a measured second cycle counter state of the node based on information contained in the received synchronization message by a stochastic state estimator, the estimated first cycle counter state estimating the first cycle counter state of the first node for a point in time at which the synchronization message is received by the node, and the estimated compensation factor estimating a duty cycle ratio of the reference clock frequency to a respective internal clock frequency for the synchronization cycle;
• (c) a linear-quadratic regulator is utilized to determine from both the estimated first cycle counter state and the estimated compensator factor a controlled first cycle counter state and a controlled compensation factor based on a controlled system which contains a correction term for the controlled compensation factor as a control variable, the controlled compensation factor estimating a duty cycle ratio of the reference clock frequency to the respective internal clock frequency, and the controlled first cycle counter state indicating a synchronized timing;
• and
• (d) a two-dimensional model is utilized for the stochastic state estimator and the linear-quadratic regulator, the two-dimensional model comprising the estimated first cycle counter and the estimated compensation factor as states.

A communications network having a plurality of nodes, each of the plurality of nodes comprising a first node and at least one second node, a synchronization message being sent from the first node to the second node within a synchronization cycle, the first node providing a first cycle counter state in accordance with a reference clock frequency and the second node providing a second cycle counter state in accordance with an internal clock frequency, and a respective node of the at least one second node being configured to implement time synchronization that:

• (a) the synchronization message is received at the respective second node;
• (b) an estimated first cycle counter state and an estimated compensation factor are estimated for a measured second cycle counter state of the respective second node based on information contained in the received synchronization message by a stochastic state estimator, the estimated first cycle counter state estimating the first cycle counter state of the first node for a point in time at which the synchronization message is received by the respective second node, and the estimated compensation factor estimating a duty cycle ratio of the reference clock frequency to a respective internal clock frequency for the synchronization cycle;
• (c) a linear-quadratic regulator is utilized to determine from both the estimated first cycle counter state and the estimated compensator factor a controlled first cycle counter state and a controlled compensation factor based on a controlled system which contains a correction term for the controlled compensation factor as a control variable, the controlled compensation factor estimating a duty cycle ratio of the reference clock frequency to the respective internal clock frequency, and the controlled first cycle counter state indicating a synchronized timing;
• and
• (d) a two-dimensional model is utilized for the stochastic state estimator and the linear-quadratic regulator, the two-dimensional model comprising the estimated first cycle counter and the estimated compensation factor as states.