Time synchronization slave apparatus capable of adjusting time synchronization period, and method of determining time synchronization period

A method of determining a time synchronization period by a time synchronization slave apparatus, the method comprising:

• performing a time synchronization operation in conjunction with a time synchronization master apparatus that provides global time;
• determining an offset and a rate used to correct local time based on a calculated time error;
• correcting the local time based on the determined offset and rate during each of a plurality of time synchronization operations;
• generating an estimated time error curve of a present time synchronization period based on a time error curve of a previous synchronization period ending at a time at which the present time synchronization begins, the time error curve of the previous synchronization period including a change of an error, calculated as a result of a previous time synchronization operation, over time during the previous synchronization period;
• generating excess error information regarding an excess point at which the estimated time error curve exceeds a threshold;
• determining a subsequent time synchronization period, starting at an end of the present time synchronization period, based on a determination of whether the excess point of the excess error information is positioned before or after the end of the present time synchronization period;
• transmitting synchronization period information regarding the determined subsequent time synchronization period to the time synchronization master apparatus;
• determining the subsequent time synchronization period to be shorter than a duration of the present time synchronization period in response to the excess point of the excess error information being determined to be positioned before the end of the present time synchronization period;
• and
• determining the subsequent time synchronization period to be longer than the duration of the present time synchronization period in response to the excess point of the excess error information being determined to be positioned after the end of the present time synchronization period.

A time synchronization apparatus, comprising:

• a master device;
• and
• a slave device comprising one or more processors configured to:
• perform a time synchronization operation in conjunction with the master device;
• determine an offset and a rate used to correct local time based on a calculated time error;
• generate an estimated time error curve of a present time synchronization period based on a time error curve of a previous synchronization period ending at a time at which the present time synchronization begins;
• correct the local time based on the determined offset and rate during each of a plurality of time synchronization operations;
• estimate the time error in the local time during the present time synchronization period and generate excess error information regarding an excess point at which the estimated time error curve exceeds a threshold, the time error curve of the previous synchronization period including a change of an error, calculated as a result of a previous time synchronization operation, over time during the previous synchronization period;
• determine a subsequent time synchronization period in which the subsequent time synchronization operation is scheduled at an end of the present time synchronization period, based on a determination of whether the excess point of the excess error information is positioned before or after the end of the present time synchronization period,
• transmit synchronization period information regarding the subsequent time synchronization period to the master device;
• determine the duration of the subsequent time synchronization period to be shorter than a duration of the present time synchronization period in response to the excess point of the excess error information being determined to be positioned before the end of the present time synchronization period;
• and
• determine the duration of the subsequent time synchronization period to be longer than the duration of the present time synchronization period in response to the excess point of the excess error information being determined to be positioned after the end of the present time synchronization period.