Time synchronization system, master station, and time synchronization method
A time synchronization system includes a master station ( 100 ) and slave stations ( 200 ) communicably connected to the master station ( 100 ). The master station ( 100 ) includes a contention determiner ( 114 ) and a time synchronization frame processing unit ( 113 ). The contention determiner ( 114 ) determines, based on receipt timings of a plurality of first time synchronization frames transmitted from the respective slave stations ( 200 ), whether the plurality of first time synchronization frames have a possibility of contention over relay processing. The time synchronization frame processing unit ( 113 ) discards, when the contention determiner ( 114 ) determines that the plurality of first time synchronization frames have the possibility of the contention, out of first time synchronization frames that have a possibility of mutual contention, a first time synchronization frame received later.
1. A time synchronization system comprising:
a master station; and
slave stations communicably connected to the master station,
the master station including
first processing circuitry to
determine, based on receipt timings of a plurality of first time synchronization frames transmitted from the respective slave stations, whether the plurality of first time synchronization frames have a possibility of contention over relay processing, and
discard, when determining that the plurality of first time synchronization frames have the possibility of the contention, out of first time synchronization frames that have a possibility of mutual contention, a first time synchronization frame received later.
2. The time synchronization system according to claim 1 , wherein the first processing circuitry determines that the plurality of first time synchronization frames have the possibility of the contention over the relay processing when a time interval between a time of receipt of one first time synchronization frame among the plurality of first time synchronization frames and a time of receipt of another first time synchronization frame among the plurality of first time synchronization frames is shorter than a predetermined fixed interval.
3. The time synchronization system according to claim 2 , wherein
each of the slave stations includes
second processing circuitry to
measure a receipt waiting time that is a time period from transmission of the first time synchronization frame until receipt of a second time synchronization frame transmitted from the master station as a response to the first time synchronization frame, and
retransmit the first time synchronization frame to the master station when the second time synchronization frame is not received until the receipt waiting time exceeds a predetermined threshold.
4. The time synchronization system according to claim 1 , wherein
each of the slave stations includes
second processing circuitry to
measure a receipt waiting time that is a time period from transmission of the first time synchronization frame until receipt of a second time synchronization frame transmitted from the master station as a response to the first time synchronization frame, and
retransmit the first time synchronization frame to the master station when the second time synchronization frame is not received until the receipt waiting time exceeds a predetermined threshold.
5. A master station communicably connected to slave stations, the master station comprising:
first processing circuitry to
determine, based on receipt timings of a plurality of first time synchronization frames transmitted from the respective slave stations, whether the plurality of first time synchronization frames have a possibility of contention over relay processing, and
discard, when determining that the plurality of first time synchronization frames have the possibility of the contention, out of first time synchronization frames that have a possibility of mutual contention, a first time synchronization frame received later.
6. A time synchronization method executed by a master station communicably connected to slave stations, the time synchronization method comprising:
determining, based on receipt timings of a plurality of first time synchronization frames transmitted from the respective slave stations, whether the plurality of first time synchronization frames have a possibility of contention over relay processing; and
discarding, when a determination is made that the plurality of first time synchronization frames have the possibility of the contention, out of first time synchronization frames that have a possibility of mutual contention, a first time synchronization frame received later.