Time-synchronization system, relay apparatus, time-synchronization method, and non-transitory computer readable medium
A time-synchronization system according to the present disclosure includes a relay apparatus ( 10 ) configured to perform time-synchronization with a master apparatus ( 30 ) through a transmission system of which a transmission delay changes depending on a transmission direction, and a relay apparatus ( 20 ) configured to perform time-synchronization with the relay apparatus ( 10 ), in which the relay apparatus ( 20 ) transmits information about a difference between first time information obtained by performing time-synchronization with the relay apparatus ( 10 ) and second time information obtained from a time-synchronization source to the relay apparatus ( 10 ), and the relay apparatus ( 10 ) corrects third time information obtained by performing time-synchronization with the master apparatus ( 30 ) by using the information about the difference, and performs time-synchronization with a slave apparatus ( 50 ) by using the corrected third time information.
1. A time-synchronization system comprising:
a first relay apparatus configured to perform time-synchronization with a master apparatus through a transmission system of which a transmission delay changes depending on a transmission direction; and
a second relay apparatus configured to perform time-synchronization with the first relay apparatus,
wherein the second relay apparatus comprises;
at least one memory storing instructions, and
at least one processor configured to execute the instructions to;
transmit information about a difference between first time information obtained by performing time-synchronization with the first relay apparatus and second time information obtained from a time-synchronization source to the first relay apparatus,
wherein the first relay apparatus comprises;
at least one memory storing instructions, and
at least one processor configured to execute the instructions to;
correct third time information obtained by performing time-synchronization with the master apparatus by using the information about the difference, and perform time-synchronization with a slave apparatus by using the corrected third time information.
2. The time-synchronization system according to claim 1 , wherein the at least one processor of the first relay apparatus is further configured to perform time-synchronization with the second relay apparatus by using the third time information without making a correction thereto by using the difference information.
3. The time-synchronization system according to claim 1 , wherein transmission delays between the first and second relay apparatuses in both directions are equal to each other.
4. The time-synchronization system according to claim 1 , wherein the time-synchronization source is a satellite positioning system.
5. The time-synchronization system according to claim 1 , wherein the first relay apparatus operates as a boundary clock apparatus.
6. A relay apparatus comprising:
at least one memory storing instructions, and
at least one processor configured to execute the instructions to;
perform time-synchronization with a first relay apparatus, the first relay apparatus being configured to perform time-synchronization with a master apparatus through a transmission system of which a transmission delay changes depending on a transmission direction; and
generate information about a difference between first time information obtained by performing time-synchronization with the first relay apparatus and second time information obtained from a time-synchronization source, and
transmit the information about the difference to the first relay apparatus in order to make the first relay apparatus correct third time information obtained by performing time-synchronization with the master apparatus in the first relay apparatus.
7. The relay apparatus according to claim 6 , wherein transmission delays between the first relay apparatus and the relay apparatus in both directions are equal to each other.
8. A time-synchronization method performed in a relay apparatus, comprising:
performing time-synchronization with a first relay apparatus, the first relay apparatus being configured to perform time-synchronization with a master apparatus through a transmission system of which a transmission delay changes depending on a transmission direction;
generating information about a difference between first time information obtained by performing time-synchronization with the first relay apparatus and second time information obtained from a time-synchronization source; and
transmitting the information about the difference to the first relay apparatus in order to make the first relay apparatus correct third time information obtained by performing time-synchronization with the master apparatus in the first relay apparatus.