Communication apparatus, communication system, communication method, and computer readable medium

A communication system comprising a plurality of communication apparatuses that selects, from the plurality of communication apparatuses, a grandmaster that is to be a standard of time of the plurality of communication apparatuses, wherein

• the communication apparatus includes a counter circuit configured as a time counter that counts the time of the communication apparatus, and processing circuitry,
• the processing circuitry being configured to
• when receiving a synchronization message that includes time of the grandmaster from the grandmaster, calculate a time difference between the time of the grandmaster and time of the communication apparatus, and
• without changing a frequency of the clock signal inputted into the counter circuit, change a count speed of the time counter in a way that the time of the communication apparatus as counted by the time counter synchronizes with the time of the grandmaster at a time when a time correction period that is specified beforehand elapses, based on the time difference, wherein processing circuitry
• calculates, as a count correction speed ratio, a ratio between a count number of the time counter that is the count number of the time counter in the time correction period for the time of the communication apparatus to synchronize with the time of the grandmaster, and a count number of a time counter of the grandmaster in the time correction period, and changes the count speed based on the count correction speed ratio.

A communication method of a communication apparatus that includes a counter circuit configured as a time counter that counts the time of the communication apparatus, the communication apparatus being included in a communication system that selects from a plurality of communication apparatuses, a grandmaster that is to be a standard of time of the plurality of communication apparatuses, the communication system including the plurality of communication apparatuses, the communication method comprising:

• when receiving a synchronization message that includes time of the grandmaster from the grandmaster, calculating a time difference between the time of the grandmaster and time of the communication apparatus;
• and
• without changing a frequency of the clock signal inputted into the counter circuit, changing count speed of the time counter in a way that the time of the communication apparatus as counted by the time counter synchronizes with the time of the grandmaster at a time when a time correction period that is specified beforehand elapses, based on the time difference, wherein
• the changing the count speed calculates, as a count correction speed ratio, a ratio between a count number of the time counter that is the count number of the time counter in the time correction period for the time of the communication apparatus to synchronize with the time of the grandmaster, and a count number of a time counter of the grandmaster in the time correction period, and changes the count speed based on the count correction speed ratio.

A non-transitory computer readable medium storing a communication program of a communication apparatus that includes a counter circuit configured as a time counter that counts the time of the communication apparatus, the communication apparatus being included in a communication system that selects from a plurality of communication apparatuses, a grandmaster that is to be a standard of time of the plurality of communication apparatuses, the communication system including the plurality of communication apparatuses, the communication program causing a computer to execute:

• a difference calculation process, when receiving a synchronization message that includes time of the grandmaster from the grandmaster, to calculate a time difference between the time of the grandmaster and time of the communication apparatus;
• and
• a correction process to, without changing a frequency of the clock signal inputted into the counter circuit change a count speed of the time counter in a way that the time of the communication apparatus as counted by the time counter synchronizes with the time of the grandmaster at a time when a time correction period that is specified beforehand elapses, based on the time difference, wherein
• the correction process calculates, as a count correction speed ratio, a ratio between a count number of the time counter that is the count number of the time counter in the time correction period for the time of the communication apparatus to synchronize with the time of the grandmaster, and a count number of a time counter of the grandmaster in the time correction period, and changes the count speed based on the count correction speed ratio.