Communication method, communication station and program

Abstract

The communication method executed by the communication station (100) is a communication method executed by the communication station (100) of a network system including a plurality of communication stations (100) that perform communication connections, and includes a calculation step of calculating the sum of a value obtained by multiplying the value of the transmission period of an Announce frame including information indicating the priority of the communication station (100) in the network system by a value obtained by subtracting 1 from the number of communication stations (100) included in the network system, and the value of the transmission period of a Sync frame including time information indicating the time held by the communication station (100), as a synchronization completion time required for the communication station (100) to synchronize with the time indicated by time information distributed from a grandmaster station selected from the plurality of communication stations (100) from the start of the communication station (100).

Description

[Technical Field]

[0001] The present disclosure relates to a communication method, a communication station, and a program. [Background technology]

[0002] The IEEE802.1AS standard for time synchronization protocols specifies the selection of a grandmaster station with highly accurate time information and the distribution of that information from the grandmaster station. A communication station that establishes a communication connection compliant with the IEEE802.1AS standard can start the execution of an application that uses time information after it has been selected as the grandmaster station or after it has synchronized with the time indicated by the time information distributed by the grandmaster station.

[0003] In a communication connection conforming to the IEEE802.1AS standard, a technique is known that shortens the time required to synchronize with the time indicated by the time information distributed from a grandmaster station in order to start the execution of an application that uses time information as early as possible. For example, Patent Document 1 discloses a technique in a network system whose configuration does not change, in which information indicating the connection relationships between nodes and information on delay times between the nodes are stored in advance, and the nodes are started based on the information indicating the connection relationships and the information on delay times, thereby shortening the time from startup to completion of time synchronization. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-005214 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is no means for determining whether the Sync frame transmitted for time synchronization of the network system contains the time information distributed from the grandmaster station, which means that each communication station in the network system cannot determine whether it has synchronized with the time indicated by the time information distributed from the grandmaster station.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a communication method, a communication station, and a program that are capable of determining whether synchronization has been achieved with the time indicated by time information distributed from a grandmaster station. [Means for solving the problem]

[0007] In order to achieve the above object, the communication method according to the present disclosure includes: Compliant with IEEE802.1AS standard A communication method executed by a communication station in a network system including a plurality of communication stations that perform communication connections, the communication method according to the present disclosure includes a calculation step of calculating, as a synchronization completion time required for the communication station to synchronize with a time indicated by time information distributed from a grandmaster station selected from among the plurality of communication stations, the sum of a value obtained by multiplying a value of a transmission period of an Announce frame including information indicating the priority of the communication station in the network system by a value obtained by subtracting 1 from the number of the communication stations included in the network system, and a value of a transmission period of a Sync frame including time information indicating a time held by the communication station. When a communication station receives an Announce frame including information indicating a higher priority than the priority of the communication station from another communication station, the communication station suspends transmission of the Announce frame including the information indicating the priority of the communication station, and transmits the received Announce frame including the information indicating the higher priority in a transmission cycle. [Effects of the Invention]

[0008] According to the present disclosure, the synchronization completion time required from the startup of a communication station until it synchronizes with the time indicated by the time information distributed from a grandmaster station selected from among multiple communication stations is calculated, so that it is possible to determine whether it has synchronized with the time indicated by the time information distributed from the grandmaster station. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a state of communication in a network system according to a first embodiment. [Figure 2] FIG. 1 is a block diagram showing a hardware configuration of a communication station according to a first embodiment. [Figure 3] FIG. 1 is a diagram showing the functional configuration of a communication station according to a first embodiment. [Figure 4] FIG. 10 is a diagram showing the functional configuration of a communication station according to a second embodiment. [Figure 5] FIG. 10 is a diagram showing a state of communication in a network system according to a second embodiment. [Figure 6] 10 is a flowchart showing a communication process according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Embodiment 1) The network system according to the first embodiment is a system including a plurality of communication stations that establish communication connections in accordance with the IEEE802.1AS time synchronization protocol standard.

[0011] As an example, the network system 1 of the first embodiment includes three communication stations 100-1, 100-2, and 100-3 as shown in Fig. 1. Hereinafter, except when a specific communication station is described, the communication stations 100-1, 100-2, and 100-3 will be collectively referred to as communication station 100. The communication station 100 is a communication device having functions conforming to the IEEE 802.1AS standard.

[0012] FIG. 1 shows the selection of a grandmaster station and the distribution of time information that occurs when communication stations 100-1, 100-2, and 100-3 are powered on simultaneously.

[0013] When the communication station 100 is powered on, it transmits, at predetermined transmission intervals, an Announce frame containing information indicating the priority of the communication station in the network system 1 and a Sync frame containing time information indicating the time held by the communication station and information identifying the communication station (hereinafter referred to as the "time source") that holds the time information. The transmission intervals of the Announce frames and the Sync frames are arbitrarily determined by the administrator of the network system 1. Since the transmission priority of Announce frames decreases when a grandmaster station is selected, the transmission interval of Announce frames is generally set to be longer than the transmission interval of Sync frames. In the following, it is assumed that the transmission interval ta of Announce frames is set to be longer than the transmission interval ts of Sync frames.

[0014] For example, as shown in FIG. 1, the communication station 100-1 transmits an Announce frame at a transmission cycle ta (≧ts) and transmits a Sync frame at a transmission cycle ts.

[0015] First, the selection of the grandmaster station will be described.

[0016] When a communication station 100 receives an Announce frame including information indicating a higher priority than the priority of its own communication station 100 from another communication station, the communication station 100 suspends transmission of the Announce frame including the information indicating the priority of its own communication station 100, and transmits the received Announce frame including the information indicating the higher priority at a predetermined transmission period.

[0017] 1, when communication station 100-2 receives an Announce frame including information of priority level "254" from communication station 100-3, the communication station 100-2 transmits Announce frames including information of priority level "253" to communication stations 100-1 and 100-3 because the communication station 100-2's priority level "253" is higher than the communication station 100-3's priority level "254." After that, when communication station 100-2 receives an Announce frame including information of priority level "252" from communication station 100-1, the communication station 100-2 suspends transmission of the Announce frame including information of priority level "253" to communication station 100-1 and transmits an Announce frame including information of communication station 100-1's priority level "252" to communication station 100-3 because the communication station 100-1's priority level "252" is higher than the communication station 100-2's priority level "253."

[0018] In a network system, a communication station that does not receive an Announce frame containing information indicating a priority higher than its own priority until the Announce frame reaches the terminal communication station (hereinafter referred to as the "terminal station") is selected as the grandmaster station.

[0019] For example, until an Announce frame containing information indicating a priority level of "252" transmitted from communication station 100-2 reaches communication station 100-3, which is an end station from the perspective of communication station 100-1, communication station 100-1 does not receive any Announce frame containing information indicating a priority level higher than its own, and is therefore selected as the grandmaster station.

[0020] Next, the distribution of time will be described.

[0021] When a communication station 100 receives a Sync frame from another communication station 100, it synchronizes with the time indicated by the time information included in the received Sync frame and transmits a Sync frame including time information indicating the synchronized time at a predetermined transmission period.

[0022] 1, for example, the communication station 100-1 transmits a Sync frame containing time information held by the communication station 100-1 and information on the time source "100-1" to the communication station 100-2 at a predetermined transmission cycle. Also, the communication station 100-2 transmits a Sync frame containing time information held by the communication station 100-2 and information on the time source "100-2" to the communication station 100-3 at a predetermined transmission cycle. After receiving an Announce frame containing information on the priority level "252" of the communication station 100-1 from the communication station 100-1, the communication station 100-2 receives a Sync frame containing the time information held by the communication station 100-1 and information on the time source "100-1", and then synchronizes with the time indicated by the time information held by the communication station 100-1. Then, the communication station 100-2 transmits a Sync frame containing the time information held by the communication station 100-1 and information on the time source "100-1" to the communication station 100-3 at a predetermined transmission cycle.

[0023] In network system 1, when a Sync frame reaches an end station, the Sync frame containing time information is distributed along the transmission path of the Announce frame, starting from the grandmaster station, and all communication stations in the network system are synchronized to the time indicated by the time information distributed from the grandmaster station.

[0024] For example, when a Sync frame containing the time information held by communication station 100-1 and information on the time source “100-1” reaches communication station 100-3, communication stations 100-1, 100-2, and 100-3 of network system 1 synchronize with the time indicated by the time information distributed from communication station 100-1, which is the grandmaster station.

[0025] FIG. 2 shows an example of the hardware configuration of the communication station 100. As shown in FIG.

[0026] The communication station 100 has a processor 11 that executes various processes, a main memory unit 12 that is used as a work area for the processor 11, an auxiliary memory unit 13 that stores various data used in the processes of the processor 11, and a communication unit 14 for communicating with external devices. The main memory unit 12, the auxiliary memory unit 13, and the communication unit 14 are all connected to the processor 11 via a bus 15.

[0027] The processor 11 is a CPU (Central Processing Unit) having multiple cores. The processor 11 executes programs stored in the auxiliary storage unit 13 to realize various functions of the communication station 100.

[0028] The main memory unit 12 includes a RAM (Random Access Memory). Programs are loaded into the main memory unit 12 from the auxiliary memory unit 13. The main memory unit 12 is used as a working area for the processor 11.

[0029] Auxiliary storage unit 13 includes a non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read-Only Memory). In addition to programs, auxiliary storage unit 13 stores various data used in the processing of processor 11. In accordance with instructions from processor 11, auxiliary storage unit 13 supplies processor 11 with data used by processor 11 and stores data supplied from processor 11.

[0030] The communication unit 14 includes a network interface circuit for communicating with an external device. The communication unit 14 receives a signal from the external device and outputs data indicated by the signal to the processor 11. The communication unit 14 also transmits a signal indicating the data output from the processor 11 to the external device.

[0031] FIG. 3 shows the functional configuration of the communication station 100 of this embodiment.

[0032] Functionally, communication station 100 comprises a memory unit 101 that stores information on the transmission period of frames transmitted from communication station 100, time information, etc., an Announce frame transmission / reception unit 102 that transmits and receives Announce frames, a Sync frame transmission / reception unit 103 that transmits and receives Sync frames, and a calculation unit 104 that calculates the time synchronization completion time in the network system.

[0033] Transmission cycle information 101-1, priority information 101-2, time information 101-3, and communication station number information 101-4 are stored in the storage unit 101. For example, the storage unit 101 is realized by the auxiliary storage unit 13.

[0034] The transmission period information 101-1 is information indicating the transmission period of frames transmitted from the communication station 100, and includes information indicating the transmission period of Announce frames and information indicating the transmission period of Sync frames. For example, the storage unit 101 of the communication station 100 stores the transmission period information 101-1 including information indicating the transmission period "ta" of Announce frames and information indicating the transmission period "ts" of Sync frames.

[0035] The priority information 101-2 is information indicating the priority of the communication station 100 in the network system. For example, the priority information 101-2 includes information indicating the priority set for the communication station itself and information indicating the highest priority that is higher than the communication station itself and is included in the received Announce frame. For example, when the communication stations 100 are started up, the memory unit 101 of the communication station 100-1 stores the priority information 101-2 indicating its own priority "252", the memory unit 101 of the communication station 100-2 stores the priority information 101-2 indicating its own priority "253", and the memory unit 101 of the communication station 100-3 stores the priority information 101-2 indicating its own priority "254".

[0036] The time information 101-3 is information indicating the time at which the communication station 100 is synchronized. For example, the time information 101-3 includes time information indicating the time held by the communication station 100 and information specifying the time source. For example, when the communication station 100 is started up, the storage unit 101 of the communication station 100-1 stores time information 101-3 indicating time "t100-1" and time source "100-1," the storage unit 101 of the communication station 100-2 stores time information 101-3 indicating time "t100-2" and time source "100-2," and the storage unit 101 of the communication station 100-3 stores time information 101-3 indicating time "t100-3" and time source "100-3."

[0037] The communication station number information 101-4 is information indicating the number of communication stations 100 in the network system 1. For example, the storage unit 101 of the communication station 100 in the network system 1 stores communication station number information 101-4 indicating the number of communication stations "3".

[0038] The Announce frame transmitting / receiving unit 102 transmits Announce frames to other communication stations 100 and receives Announce frames from other communication stations 100. The Announce frame transmitting / receiving unit 102 is realized by the processor 11 and the communication unit 14.

[0039] For example, the Announce frame transmitting / receiving unit 102 refers to the transmission cycle information 101-1 and the priority information 101-2 stored in the storage unit 101, and transmits an Announce frame including information indicating the highest priority among the information included in the priority information 101-2 to another communication station 100 at the transmission cycle ta. The Announce frame transmitting / receiving unit 102 also receives an Announce frame from another communication station 100. Here, the Announce frame transmitting / receiving unit 102 replaces the priority information included in the Announce frame transmitted from a communication station 100 with a higher priority than the highest priority included in the priority information 101-2 with the information indicating the highest priority included in the priority information 101-2 in the storage unit 101, and stores the replaced information.

[0040] The Sync frame transmitting / receiving unit 103 receives Sync frames from other communication stations 100 and transmits Sync frames to other communication stations 100. The Sync frame transmitting / receiving unit 103 is realized by the processor 11 and the communication unit .

[0041] For example, the Sync frame transmitting / receiving unit 103 refers to the transmission cycle information 101-1 and time information 101-3 stored in the memory unit 101, and transmits a Sync frame including the time information and time source information included in the time information 101-3 to another communication station 100 at the transmission cycle ts. The Sync frame transmitting / receiving unit 103 also receives a Sync frame from another communication station 100. Here, the Sync frame transmitting / receiving unit 103 stores the time information and time source information included in a Sync frame transmitted from a communication station 100 with a higher priority than the highest priority included in the priority information 101-2 as time information 101-3 in the memory unit 101.

[0042] The calculation unit 104 calculates the sum of a value obtained by multiplying the value of the transmission period of an Announce frame including information indicating the priority of the communication station 100 in the network system 1 by a value obtained by subtracting 1 from the number of communication stations 100 included in the network system 1, and the value of the transmission period of a Sync frame including information indicating the time held by the communication station 100 and information specifying the communication station 100 that holds the information indicating the time. The calculation unit 104 calculates this sum as a synchronization completion time required for the communication station 100 to synchronize with the time indicated by time information distributed from a grandmaster station selected from the multiple communication stations 100, from the start of the communication station 100. The calculation unit 104 is realized by the processor 11. The calculation unit 104 is an example of a calculation means, and executes the calculation step.

[0043] From the time the communication station 100 starts up until it completes synchronization with the time indicated by the time information distributed from the grandmaster station, it is necessary for the communication station 100 to select a grandmaster station and receive time information from the grandmaster station. Therefore, the synchronization completion time is calculated as the sum of the time required to select a grandmaster station and the time required for the grandmaster station to distribute the time.

[0044] The selection of a grandmaster station requires time for an Announce frame containing information on the priority of the communication station 100 that will become the grandmaster station to reach an end station from the communication station 100 that will become the grandmaster station. This time can take up to the transmission period of the Announce frame multiplied by (the number of communication stations in the network system - 1). Therefore, the time required to select a grandmaster station in a network system can be estimated using the following formula (1).

[0045] Time required to select a grandmaster station ≦ Announce frame transmission period × (number of communicating stations in the network system − 1) (1)

[0046] For example, in the network system 1 of FIG. 1, the time 1001 required to select the grandmaster station (communication station 100-1) can be estimated to be equal to or less than the transmission period ta×2 of the Announce frame.

[0047] Because the transmission period of Sync frames is set to be shorter than the transmission period of Announce frames, it takes time for the grandmaster station to receive the first Sync frame after receiving the Announce frame containing the priority information of the communication station 100 that will become the grandmaster station. This time can take up to the transmission period of the Sync frame. Therefore, in a network system, the time required for the grandmaster station to distribute the time can be estimated using the following equation (2):

[0048] The time required for the grandmaster station to distribute the time is less than or equal to the sync frame transmission period (2).

[0049] For example, in the network system 1 of FIG. 1, the time 1002 required for the grandmaster station (communication station 100-1) to distribute the time can be estimated to be equal to or less than the transmission cycle ts of the Sync frame.

[0050] That is, the calculation unit 104 calculates the synchronization completion time by the following equation (3).

[0051] Synchronization completion time = Announce frame transmission period × (number of communication stations in the network system - 1) + Sync frame transmission period (3)

[0052] For example, the calculation unit 104 calculates the synchronization completion time as (ta × 2) + (ts) for the Announce frame transmission period for the network system 1 in Fig. 1. When the synchronization completion time has elapsed, the communication station 100 can be considered to have synchronized with the time indicated by the time information distributed from the grandmaster station. Therefore, the communication station 100 can start executing an application that uses time information, for example, an application that uses TSN (Time Sensitive Networking) communication technology, during a period 1004 from a point 1003, which is the sum of time 1001 and time 1002 in Fig. 1.

[0053] According to this embodiment, in a network system including multiple communication stations that establish communication connections in accordance with the IEEE 802.1AS standard, it is possible to calculate the time required for determining whether a communication station has synchronized with the time indicated by the time information distributed from the grandmaster station, thereby determining the timing at which an application can be started.

[0054] (Embodiment 2) The network system according to the second embodiment is a system including a plurality of communication stations that establish communication connections in accordance with the IEEE802.1AS standard for time synchronization protocols, and the communication stations have the function of adjusting the transmission period of Announce frames and the transmission period of Sync frames.

[0055] FIG. 4 shows the functional configuration of the communication station 100 of this embodiment.

[0056] The communication station 100 functionally comprises a storage unit 101 storing information on the transmission cycle of frames transmitted from the communication station 100, time information, etc., an Announce frame transmitting / receiving unit 102 that transmits and receives Announce frames, a Sync frame transmitting / receiving unit 103 that transmits and receives Sync frames, a calculation unit 104 that calculates a synchronization completion time in the network system, and an adjustment unit 105 that adjusts the transmission cycle. Below, functions that differ from the communication station 100 of embodiment 1 will be described.

[0057] The adjustment unit 105 shortens the transmission period of the Announce frames until the synchronization completion time has elapsed to be shorter than a predetermined first transmission period, and shortens the transmission period of the Sync frames until the synchronization completion time has elapsed to be shorter than a predetermined second transmission period. The adjustment unit 105 is realized by the processor 11. The adjustment unit 105 executes the shortening step and the extension step.

[0058] The time until the synchronization completion time elapses refers to the time until synchronization is completed by the communication station 100 at the time indicated by the time information distributed by the grandmaster station. For example, in Fig. 5, the time until the synchronization completion time elapses refers to the time from the start of the communication station 100 to a time 2003 which is the sum of the time 2001 required to select the grandmaster station (communication station 100-1) and the time 2002 required for the grandmaster station (communication station 100-1) to distribute the time.

[0059] The first transmission period is the transmission period of the Announce frame set after the elapse of the synchronization completion time, which is predetermined by the administrator of the network system 1. Also, the second transmission period is the transmission period of the Sync frame set after the elapse of the synchronization completion time, which is predetermined by the administrator of the network system 1. Hereinafter, it is assumed that the administrator of the network system 1 has determined the first transmission period ta and the second transmission period ts (≤ ta). The adjustment unit 105 shortens the transmission period of the Announce frame transmitted until time point 2003 to be shorter than the first transmission period ta, and shortens the transmission period of the Sync frame to be shorter than the second transmission period ts.

[0060] The shortening time width of the transmission period of the Sync frame is required to be a length that enables the communication station 100 to perform time synchronization according to the transmission period of the shortened Sync frame. Also, the shortening time width of the transmission period of the Announce frame is required to be a length that results in a transmission period longer than or equal to the transmission period of the shortened Sync frame. For example, it is assumed that the administrator of the network system 1 has determined that the transmission period of the Announce frame until the elapse of the synchronization completion time is a transmission period ta' shorter than the first transmission period ta (< ta), and the transmission period of the Sync frame until the elapse of the synchronization completion time is a transmission period ts' shorter than the second transmission period ts (< ts), and the transmission period ta' is determined to be longer than or equal to the transmission period ts'.

[0061] The transmission period information 101-1 stored in the storage unit 101 includes information indicating the transmission period (first transmission period) ta of the Announce frame after the elapse of the synchronization completion time and information indicating the transmission period (second transmission period) ts of the Sync frame, as well as information indicating the transmission period ta' of the Announce frame until the elapse of the synchronization completion time and information indicating the transmission period ts' of the Sync frame.

[0062] Here, the adjustment unit 105 executes the shortening of the transmission period at the time of startup of the communication station 一百. That is, the adjustment unit 105 shortens the transmission period of the Announce frame and the transmission period of the Sync frame at the time of startup of the communication station 一百.

[0063] For example, when the communication station 100 is started up, the adjustment unit 105 refers to the transmission period information 101-1 stored in the memory unit 101, and sets the transmission period of the Announce frame to a transmission period ta' that is shorter than the first transmission period ta, and sets the transmission period of the Sync frame to a transmission period ts' that is shorter than the second transmission period ts.

[0064] Next, the calculation unit 104 calculates the synchronization completion time.

[0065] For example, the calculation unit 104 calculates the synchronization completion time as the Announce frame transmission period ta'×2+Sync frame transmission period ts' for the network system 1 in Fig. 5. That is, the calculation unit 104 obtains the time up to time point 2003, which is the sum of time 2001 and time 2002 in Fig. 5.

[0066] Then, after the synchronization completion time has elapsed, adjustment section 105 extends the transmission period of Announce frames beyond the shortened transmission period of Announce frames, and extends the transmission period of Sync frames beyond the shortened transmission period of Sync frames.

[0067] For example, when time 2003, which is the sum of time 2001 and time 2002 in Figure 5, has passed, adjustment unit 105 refers to transmission period information 101-1 stored in memory unit 101 and sets the transmission period of the Announce frame to transmission period ta, which is longer than transmission period ta', and sets the transmission period of the Sync frame to transmission period ts, which is longer than transmission period ts'.

[0068] In a period 2004 after the time point 2003, the communication station 100 becomes able to use applications that use time information.

[0069] Next, a communication process executed by the communication station 100 according to this embodiment will be described with reference to the flowchart of Fig. 6. The communication process of Fig. 6 is executed when the communication station 100 is powered on, for example.

[0070] The adjustment unit 105 shortens the transmission period of the Announce frame until the synchronization completion time has elapsed and the transmission period of the Sync frame until the synchronization completion time has elapsed (step S101).

[0071] For example, when the communication station 100 is started up, the adjustment unit 105 refers to the transmission period information 101-1 stored in the memory unit 101, and sets the transmission period of the Announce frame to the shortened transmission period ta', and sets the transmission period of the Sync frame to the shortened transmission period ts'.

[0072] The Announce frame transmitting / receiving unit 102 starts transmitting Announce frames at a set transmission cycle, and the Sync frame transmitting / receiving unit 103 starts transmitting Sync frames at a set transmission cycle (step S102).

[0073] For example, the Announce frame transmitting / receiving unit 102 starts transmitting Announce frames at a transmission cycle ta', and the Sync frame transmitting / receiving unit 103 starts transmitting Sync frames at a transmission cycle ts'.

[0074] The calculation unit 104 calculates the synchronization completion time (=transmission period of Announce frames×(number of communication stations−1)+transmission period of Sync frames) (step S103).

[0075] The calculation unit 104 calculates the synchronization completion time as the transmission period ta' of the Announce frames × 2 + the transmission period ts' of the Sync frames.

[0076] The adjustment unit 105 determines whether the synchronization completion time has elapsed (step S104). If the adjustment unit 105 determines that the synchronization completion time has elapsed (step S104; YES), the adjustment unit 105 extends the shortened transmission period of the Announce frame and the shortened transmission period of the Sync frame (step S105). On the other hand, if the adjustment unit 105 determines that the synchronization completion time has not elapsed (step S104; NO), it continues to wait.

[0077] For example, when adjustment unit 105 determines that time point 2003 in Fig. 5 has passed, it references transmission period information 101-1 stored in storage unit 101, and sets the transmission period of Announce frames to transmission period ta, which is longer than transmission period ta', and sets the transmission period of Sync frames to transmission period ts, which is longer than transmission period ts'. Thereafter, Announce frame transceiver unit 102 transmits Announce frames at transmission period ta, and Sync frame transceiver unit 103 transmits Sync frames at transmission period ts. On the other hand, when adjustment unit 105 determines that time point 2003 in Fig. 5 has not passed, it remains on standby.

[0078] According to this embodiment, the transmission period of Announce frames until the synchronization completion time has elapsed and the transmission period of Sync frames until the synchronization completion time has elapsed are shortened when the communication station is started up, thereby shortening the time from the startup of the communication station until synchronization is completed at the time indicated by the time information distributed by the grandmaster station, and enabling applications that use time information to start earlier.

[0079] Furthermore, if the transmission cycle of the Announce frame and the transmission cycle of the Sync frame are left shortened, there is a risk that resources will be insufficient for other applications that do not use time information and are executed in parallel. However, according to this embodiment, when synchronization is completed at the time indicated by the time information distributed from the grandmaster station, the shortened transmission cycle is extended. This makes it possible to accelerate the start of applications that use time information without affecting the execution of other applications that do not use time information.

[0080] (Variation) Although the embodiments of the present disclosure have been described above, various modifications and applications are possible in implementing the present disclosure.

[0081] In the above embodiment, the storage unit 101 stores information indicating the transmission period (first transmission period) ta of the Announce frame after the synchronization completion time has elapsed, and information indicating the transmission period ta' of the Announce frame until the synchronization completion time has elapsed. The adjustment unit 105 shortens the transmission period of the Announce frame by setting the transmission period of the Announce frame until the synchronization completion time has elapsed to a transmission period ta' shorter than the transmission period ta, and after the synchronization completion time has elapsed, extends the transmission period of the Announce frame by setting it to a transmission period ta longer than the transmission period ta'. However, the present invention is not limited to this. For example, the storage unit 101 stores only information indicating one transmission period ta for the transmission period of the Announce frame. The communication station 100 may shorten the transmission period ta to a value vta2 (<vta1) shorter than the value vta1 of the transmission period ta indicated by the stored information at startup, and extend the transmission period ta to a value vta3 (>vta2) longer than the shortened value vta2 after the synchronization completion time has elapsed.

[0082] Similarly, the storage unit 101 stores information indicating the transmission period (second transmission period) ts of the Sync frame after the synchronization completion time has elapsed, and information indicating the transmission period ts' of the Sync frame until the synchronization completion time has elapsed. The adjustment unit 105 shortens the transmission period of the Sync frame by setting the transmission period of the Sync frame until the synchronization completion time has elapsed to a transmission period ts' shorter than the transmission period ts, and after the synchronization completion time has elapsed, extends the transmission period of the Sync frame by setting it to a transmission period ts longer than the transmission period ts'. However, the present invention is not limited to this. For example, the storage unit 101 stores only information indicating one transmission period ts for the transmission period of the Sync frame. The communication station 100 may shorten the transmission period ts to a value vts2 (<vts1) shorter than the value vts1 of the transmission period ts indicated by the stored information at startup, and extend the transmission period ts to a value vts3 (>vts2) longer than the shortened value vts2 after the synchronization completion time has elapsed.

[0083] In the above embodiment, the flowchart of the communication process executed by the communication station 100 is shown in Fig. 6, but the order of the processes of the steps is not limited to this. For example, the order of step S102 and step S103 in Fig. 6 may be reversed.

[0084] In addition, by applying an operating program that defines the operation of the communication station 100 according to the above embodiment to an existing personal computer or information terminal device, it is also possible to make the personal computer or information terminal device function as the communication station 100 according to the embodiment.

[0085] Furthermore, the method of distribution of such a program is arbitrary; for example, it may be stored on a computer-readable recording medium such as a CD-ROM (Compact Disk Read-Only Memory), a DVD (Digital Versatile Disk), or a memory card and distributed, or it may be distributed via a communication network such as the Internet.

[0086] The present disclosure allows various embodiments and modifications without departing from the broad spirit and scope of the present disclosure. Furthermore, the above-described embodiments are intended to explain the present disclosure and do not limit the scope of the present disclosure. That is, the scope of the present disclosure is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and the meaning of equivalent disclosures are considered to be within the scope of the present disclosure. [Industrial Applicability]

[0087] According to the present disclosure, it is possible to provide a communication method, a communication station, and a program that are capable of determining whether or not synchronization has been achieved with the time indicated by the time information distributed from the grandmaster station. [Explanation of symbols]

[0088] 1 Network system, 11 Processor, 12 Main memory unit, 13 Auxiliary memory unit, 14 Communication unit, 15 Bus, 100, 100-1, 100-2, 100-3 Communication station, 101 Memory unit, 101-1 Transmission period information, 101-2 Priority information, 101-3 Time information, 101-4 Number of communication stations information, 102 Announce frame transmission / reception unit, 103 Sync frame transmission / reception unit, 104 Calculation unit, 105 Adjustment unit, 1001, 1002, 2001, 2002 Time, 1003, 2003 Point in time, 1004, 2004 Period.

Claims

1. A communication method executed by a communication station in a network system including a plurality of communication stations that perform communication connections compliant with the IEEE 802.1AS standard, comprising: a calculation step of calculating, as a synchronization completion time required for the communication station to synchronize with a time indicated by time information distributed from a grandmaster station selected from the plurality of communication stations, the sum of a value obtained by multiplying a value of a transmission period of an Announce frame including information indicating a priority of the communication station in the network system by a value obtained by subtracting 1 from the number of the communication stations included in the network system, and a value of a transmission period of a Sync frame including time information indicating a time held by the communication station, When the communication station receives an Announcement frame including information indicating a priority higher than the priority of the other communication station from the other communication station, the communication station suspends transmission of the Announcement frame including the information indicating the priority of the other communication station, and transmits the received Announcement frame including the information indicating the higher priority in the transmission period. Communication method.

2. a shortening step of shortening a transmission period of the Announce frame until the synchronization completion time has elapsed to be shorter than a predetermined first transmission period, and shortening a transmission period of the Sync frame until the synchronization completion time has elapsed to be shorter than a predetermined second transmission period; The communication method according to claim 1 .

3. the method further comprises an extension step of extending the transmission period of the Announce frames beyond the shortened transmission period of the Announce frames and extending the transmission period of the Sync frames beyond the shortened transmission period of the Sync frames after the synchronization completion time has elapsed. The communication method according to claim 2 .

4. The shortening step is performed at the start-up of the communication station. The communication method according to claim 2 or 3.

5. The Sync frame further includes information for identifying a communication station that holds the time information. The communication method according to any one of claims 1 to 3.

6. A calculation means is provided for calculating the sum of a value obtained by multiplying the value of the transmission period of an Announce frame containing information indicating the priority of a communication station in a network system including a plurality of communication stations making communication connections compliant with the IEEE802.1AS standard by a value obtained by subtracting 1 from the number of communication stations included in the network system, and a value of the transmission period of a Sync frame containing time information indicating the time held by the communication station, as a synchronization completion time required for the communication station to synchronize with the time indicated by time information distributed from a grandmaster station selected from among the plurality of communication stations from the start of the communication station, When the communication station receives an Announcement frame including information indicating a priority higher than the priority of the other communication station from the other communication station, the communication station suspends transmission of the Announcement frame including the information indicating the priority of the other communication station, and transmits the received Announcement frame including the information indicating the higher priority in the transmission period. Communications Bureau.

7. Computer, the calculation means functions as a calculation means for calculating the sum of a value obtained by multiplying the value of a transmission period of an Announcement frame containing information indicating the priority of a communication station in a network system including a plurality of communication stations making a communication connection in accordance with the IEEE 802.1AS standard by a value obtained by subtracting 1 from the number of communication stations included in the network system, and a value of a transmission period of a Sync frame containing time information indicating the time held by the communication station, as a synchronization completion time required for the communication station to synchronize with the time indicated by time information distributed from a grandmaster station selected from the plurality of communication stations after starting up the communication station, When the communication station receives an Announcement frame including information indicating a priority higher than the priority of the other communication station from the other communication station, the communication station suspends transmission of the Announcement frame including the information indicating the priority of the other communication station, and transmits the received Announcement frame including the information indicating the higher priority in the transmission period. program.

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