Communication method, communication station, and program

Abstract

A communication method performed by a communication station (100) is a communication method executed by the communication station (100) in a network system including a plurality of the communication stations (100) that make communication connections, the method including a calculation step in which the communication station (100) calculates a synchronization completion time required from startup of the communication station (100) until synchronization with a time indicated by time information distributed from a grandmaster station selected from among the plurality of communication stations (100), the synchronization completion time being calculated as the sum of a value obtained by multiplying a transmission period value, of an Announce frame including information indicating the priority level of the communication stations (100) in the network system, by a value obtained by subtracting 1 from the number of the communication stations (100) included in the network system, and the transmission period value of a Sync frame containing time information indicating the time kept by the communication station (100).

Description

Communication Method, Communication Station, and Program

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

[0002] In the time synchronization protocol IEEE 802.1AS standard, it is stipulated to select a grandmaster station having high-precision time information and distribute time information from the grandmaster station. A communication station performing a communication connection compliant with the IEEE 802.1AS standard can start executing an application using time information after it is selected as the grandmaster station or after synchronizing with the time indicated by the time information distributed from the grandmaster station.

[0003] In a communication connection compliant with the IEEE 802.1AS standard, in order to start executing an application using time information as early as possible, a technique for shortening the time until synchronization with the time indicated by the time information distributed from the grandmaster station is known. For example, in Patent Document 1, in a network system whose configuration does not change, information indicating the connection relationship between nodes and information on the delay time between nodes are stored in advance, and based on the information indicating the connection relationship and the information on the delay time, by starting the nodes, a technique for shortening the time from startup until time synchronization is completed is disclosed.

[0004] Japanese Patent Application Laid-Open No. 2016-005214

[0005] On the other hand, there is no means for determining whether time information distributed from the grandmaster station is stored in a Sync frame transmitted for time synchronization of a network system. For this reason, there has been a problem that each communication station included 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 view of the above circumstances, and an object thereof is to provide a communication method, a communication station, and a program capable of determining whether synchronization has been achieved with the time indicated by the time information distributed from the grandmaster station.

[0007] To achieve the above objective, the communication method relating to this disclosure is 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 relating to this disclosure includes a calculation step in which the communication station calculates the synchronization completion time required from the startup of the communication station until it synchronizes with the time indicated by time information distributed from a grandmaster station selected from among the plurality of communication stations, by multiplying the transmission period value of an Announce frame containing information indicating the priority of the communication station in the network system by a value obtained by subtracting 1 from the number of communication stations included in the network system, and the transmission period value of a Sync frame containing time information indicating the time held by the communication station.

[0008] According to this disclosure, the synchronization completion time required from the startup of the communication station until it synchronizes with the time indicated by the time information distributed from the grandmaster station selected from among multiple communication stations is calculated, so it is possible to determine whether or not it has synchronized with the time indicated by the time information distributed from the grandmaster station.

[0009] A figure showing the communication process in the network system according to Embodiment 1. A block diagram showing the hardware configuration of the communication station according to Embodiment 1. A figure showing the functional configuration of the communication station according to Embodiment 1. A figure showing the functional configuration of the communication station according to Embodiment 2. A figure showing the communication process in the network system according to Embodiment 2. A flowchart showing the communication process according to Embodiment 2.

[0010] (Embodiment 1) The network system according to Embodiment 1 is a system that includes multiple communication stations that perform communication connections in accordance with the IEEE 802.1AS time synchronization protocol standard.

[0011] As an example, the network system 1 of Embodiment 1 includes three communication stations 100-1, 100-2, and 100-3, as shown in Figure 1. Hereinafter, unless a specific communication station is described, communication stations 100-1, 100-2, and 100-3 will be collectively referred to as communication station 100. Communication station 100 is a communication device having functions compliant with the IEEE 802.1AS standard.

[0012] Figure 1 shows the process of selecting a grandmaster station and distributing time information when communication stations 100-1, 100-2, and 100-3 are powered on simultaneously.

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

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

[0015] First, let me explain the selection process for the Grandmaster station.

[0016] When communication station 100 receives an Announce frame from another communication station that contains information indicating a higher priority than its own, it interrupts the transmission of the Announce frame containing information indicating its own priority and transmits the received Announce frame containing information indicating the higher priority at a predetermined transmission interval.

[0017] For example, as shown in Figure 1, when communication station 100-2 receives an Announce frame from communication station 100-3 containing information about priority "254", communication station 100-2 has a higher priority of "253" than communication station 100-3 has a higher priority of "254", so it transmits an Announce frame containing information about priority "253" to communication stations 100-1 and 100-3. Subsequently, when communication station 100-2 receives an Announce frame from communication station 100-1 containing information indicating priority "252", it determines that communication station 100-1's priority "252" is higher than communication station 100-2's priority "253". Therefore, it interrupts the transmission of an Announce frame containing information indicating priority "253" to communication station 100-1 and transmits an Announce frame containing information indicating priority "252" from communication station 100-1 to communication station 100-3.

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

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

[0020] Next, I will explain how to distribute time information.

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

[0022] For example, as shown in Figure 1, communication station 100-1 transmits a Sync frame containing time information and information about the time source "100-1" held by communication station 100-1 to communication station 100-2 at a predetermined transmission interval. Communication station 100-2 also transmits a Sync frame containing time information and information about the time source "100-2" held by communication station 100-2 to communication station 100-3 at a predetermined transmission interval. After communication station 100-2 receives an Announce frame from communication station 100-1 containing information about the priority of communication station 100-1 "252", and then receives a Sync frame containing time information and information about the time source "100-1" held by communication station 100-1, it synchronizes with the time indicated by the time information held by communication station 100-1. Then, communication station 100-2 transmits to communication station 100-3 a Sync frame containing time information held by communication station 100-1 and information of the time source "100-1" at a predetermined transmission interval.

[0023] In network system 1, when a Sync frame reaches a terminal station, the Grandmaster station initiates the distribution of Sync frames containing time information along the transmission path of the Announce frame, and all communication stations in the network system synchronize to the time indicated by the time information distributed from the Grandmaster station.

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

[0025] Figure 2 shows an example of the hardware configuration of the communications station 100.

[0026] The communication station 100 includes a processor 11 that performs various processes, a main memory unit 12 used as a workspace for the processor 11, an auxiliary memory unit 13 that stores various data used in the processing 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) with multiple cores. The processor 11 realizes various functions of the communication station 100 by executing programs stored in the auxiliary storage unit 13.

[0028] The main memory unit 12 includes 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 then used as a workspace for the processor 11.

[0029] The auxiliary storage unit 13 includes non-volatile memory, such as EEPROM (Electrically Erasable Programmable Read-Only Memory). In addition to programs, the auxiliary storage unit 13 stores various data used in the processing of the processor 11. The auxiliary storage unit 13 supplies data to be used by the processor 11 according to the instructions of the processor 11, and stores the data supplied by the 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 the data indicated by this 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] Figure 3 shows the functional configuration of the communication station 100 in this embodiment.

[0032] Functionally, the communication station 100 includes a storage unit 101 that stores information such as the transmission cycle and time information of frames transmitted from the communication station 100, 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] The memory unit 101 stores transmission cycle information 101-1, priority information 101-2, time information 101-3, and communication station number information 101-4. For example, the memory unit 101 is implemented by the auxiliary memory 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 the Announce frame and information indicating the transmission period of the Sync frame. For example, the memory unit 101 of the communication station 100 stores the transmission period information 101-1 which includes information indicating the transmission period "ta" of the Announce frame and information indicating the transmission period "ts" of the Sync frame.

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

[0036] Time information 101-3 is information indicating the time to which the communication station 100 is synchronized. For example, time information 101-3 includes time information indicating the time held by the communication station 100 and information identifying the time source. For example, when the communication station 100 is started up, time information 101-3 indicating the time "t100-1" and time source "100-1" is stored in the storage unit 101 of the communication station 100-1, time information 101-3 indicating the time "t100-2" and time source "100-2" is stored in the storage unit 101 of the communication station 100-2, and time information 101-3 indicating the time "t100-3" and time source "100-3" is stored in the storage unit 101 of the communication station 100-3.

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

[0038] The Announce frame transmission / reception unit 102 transmits an Announce frame to another communication station 100 and receives an Announce frame from the other communication station 100. The Announce frame transmission / reception unit 102 is implemented by the processor 11 and the communication unit 14.

[0039] For example, the Announce frame transmission / reception unit 102 refers to the transmission cycle information 101-1 and priority information 101-2 stored in the storage unit 101 and transmits an Announce frame to another communication station 100 at a transmission cycle ta, containing information indicating the highest priority among the information included in the priority information 101-2. The Announce frame transmission / reception unit 102 also receives an Announce frame from another communication station 100. Here, the Announce frame transmission / reception 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, and stores it in the storage unit 101.

[0040] The Sync frame transmission / reception unit 103 receives Sync frames from other communication stations 100 and transmits Sync frames to other communication stations 100. The Sync frame transmission / reception unit 103 is implemented by the processor 11 and the communication unit 14.

[0041] For example, the Sync frame transmission / reception 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 containing the time information and time source information included in the time information 101-3 to another communication station 100 at a transmission cycle ts. The Sync frame transmission / reception unit 103 also receives Sync frames from other communication stations 100. Here, the Sync frame transmission / reception unit 103 stores the time information and time source information included in the 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 transmission period value of an Announce frame containing information indicating the priority of communication stations 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 transmission period value of a Sync frame containing information indicating the time held by the communication station 100 and information identifying the communication station 100 that holds the time information. The calculation unit 104 calculates this sum as the synchronization completion time required for the communication station 100 from the startup of the communication station 100 until it synchronizes with the time indicated by the time information distributed from the grandmaster station selected from among the multiple communication stations 100. The calculation unit 104 is implemented by the processor 11. Note that the calculation unit 104 is an example of a calculation means and executes the calculation steps.

[0043] For communication station 100 to synchronize with the time indicated by the time information distributed from the grandmaster station from startup, the selection of the grandmaster station and the distribution of time information from the grandmaster station are required. Therefore, the synchronization completion time is calculated by the sum of the time required for the selection of the grandmaster station and the time required for the distribution of time from the grandmaster station.

[0044] For the selection of the grand master station, it takes time until an Announce frame containing the priority information of the communication station 100 that will become the grand master station reaches the terminal station from the communication station 100 that will become the grand master station. This time takes up to the time of the transmission cycle of the Announce frame × (the number of communication stations in the network system - 1). Therefore, in the network system, the time required for the selection of the grand master station can be estimated as shown in the following formula (1).

[0045] Time required for the selection of the grand master station ≦ Transmission cycle of the Announce frame × (Number of communication stations in the network system - 1) ··· (1)

[0046] For example, in the network system 1 of FIG. 1, the time 1001 required for the selection of the grand master station (communication station 100 - 1) can be estimated as the time within 2 times the transmission cycle ta of the Announce frame.

[0047] For the time distribution from the grand master station, since the transmission cycle of the Sync frame is set to be less than or equal to the transmission cycle of the Announce frame, it takes time until the first Sync frame is received after receiving the Announce frame containing the priority information of the communication station 100 that will become the grand master station. This time takes up to the time of the transmission cycle of the Sync frame. Therefore, in the network system, the time required for the time distribution from the grand master station can be estimated as shown in the following formula (2).

[0048] Time required for the time distribution from the grand master station ≦ Transmission cycle of the Sync frame ··· (2)

[0049] For example, in the network system 1 of FIG. 1, the time 1002 required for the time distribution from the grand master station (communication station 100 - 1) can be estimated as the time within the transmission cycle ts of the Sync frame.

[0050] That is, the calculation unit 104 calculates the synchronization completion time according to the following formula (3).

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

[0052] For example, the calculation unit 104 calculates the synchronization completion time for the network system 1 in Figure 1 as the transmission period ta × 2 of the Announce frame + the transmission period ts of the Sync frame. Once 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, such as an application that uses TSN (Time Sensitive Networking) communication technology, during the period 1004 from the time 1003 which is the sum of time 1001 and time 1002 in Figure 1.

[0053] According to this embodiment, in a network system including multiple communication stations that perform communication connections compliant with the IEEE 802.1AS standard, the communication stations can calculate the time required to determine whether or not they have synchronized with the time information distributed from the grandmaster station. This makes it possible to identify the timing at which an application can begin execution.

[0054] (Embodiment 2) The network system according to Embodiment 2 is a system that includes multiple communication stations that perform communication connections in accordance with the IEEE 802.1AS time synchronization protocol standard, and the communication stations have a function to adjust the transmission period of the Announce frame and the transmission period of the Sync frame.

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

[0056] Functionally, the communication station 100 includes a storage unit 101 that stores information such as the transmission cycle and time information of frames transmitted from the communication station 100, an Announce frame transmission / reception unit 102 that sends and receives Announce frames, a Sync frame transmission / reception unit 103 that sends and receives Sync frames, a calculation unit 104 that calculates the synchronization completion time in the network system, and an adjustment unit 105 that adjusts the transmission cycle. The following describes functions that differ from the communication station 100 of Embodiment 1.

[0057] The adjustment unit 105 shortens the transmission cycle of the Announce frame until the synchronization completion time has elapsed from a predetermined first transmission cycle, and shortens the transmission cycle of the Sync frame until the synchronization completion time has elapsed from a predetermined second transmission cycle. The adjustment unit 105 is implemented by the processor 11. The adjustment unit 105 performs shortening and extension steps.

[0058] The "time until synchronization completion time elapses" refers to the time until the communication station 100 completes synchronization according to the time information distributed by the grandmaster station. For example, in Figure 5, "time until synchronization completion time elapses" refers to the time from the startup of the communication station 100 to the time 2003 which is the sum of the time 2001 required for the selection of the grandmaster station (communication station 100-1) and the time 2002 required for the distribution of the time from the grandmaster station (communication station 100-1).

[0059] The first transmission cycle is the transmission cycle of the Announce frame, which is set after the synchronization completion time has elapsed, as predetermined by the administrator of the network system 1. The second transmission cycle is the transmission cycle of the Sync frame, which is set after the synchronization completion time has elapsed, as predetermined by the administrator of the network system 1. Hereinafter, the first transmission cycle is assumed to be ta and the second transmission cycle is assumed to be ts (≤ ta), as predetermined by the administrator of the network system 1. The adjustment unit 105 shortens the transmission cycle of the Announce frame to be transmitted by time 2003 from the first transmission cycle ta, and shortens the transmission cycle of the Sync frame from the second transmission cycle ts.

[0060] The shortening time interval for the transmission period of the Sync frame must be such that the shortened transmission period of the Sync frame allows the communication station 100 to perform time synchronization. Furthermore, the shortening time interval for the transmission period of the Announce frame must be such that the transmission period is equal to or greater than the shortened transmission period of the Sync frame. For example, the administrator of the network system 1 may set the transmission period of the Announce frame until the synchronization completion time has elapsed to a transmission period ta' shorter than the first transmission period ta (< ta), and the transmission period of the Sync frame until the synchronization completion time has elapsed to a transmission period ts' shorter than the second transmission period ts (< ts), with the transmission period ta' being set to be equal to or greater than the transmission period ts'.

[0061] The transmission period information 101-1 stored in the memory unit 101 includes 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 (second transmission period) ts of the Sync frame, and information indicating the transmission period ta' of the Announce frame and the transmission period ts' of the Sync frame until the synchronization completion time has elapsed.

[0062] Here, the adjustment unit 105 shortens the transmission cycle when the communication station 100 is started up. That is, when the communication station 100 is started up, the adjustment unit 105 shortens the transmission cycle of the Announce frame and the transmission cycle of the Sync frame.

[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' which is shorter than the first transmission period ta, and sets the transmission period of the Sync frame to a transmission period ts' which 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 for the network system 1 in Figure 5 as the transmission period ta' × 2 of the Announce frame + the transmission period ts' of the Sync frame. That is, the calculation unit 104 finds the time up to point 2003, which is the sum of time 2001 and time 2002 in Figure 5.

[0066] Then, once the synchronization completion time has elapsed, the adjustment unit 105 extends the transmission period of the Announce frame to be longer than the shortened transmission period of the Announce frame, and extends the transmission period of the Sync frame to be longer than the shortened transmission period of the Sync frame.

[0067] For example, when the adjustment unit 105 has elapsed time 2003, which is the sum of time 2001 and time 2002 in Figure 5, it refers to the transmission period information 101-1 stored in the storage unit 101 and sets the transmission period of the Announce frame to a transmission period ta that is extended beyond the transmission period ta', and sets the transmission period of the Sync frame to a transmission period ts that is extended beyond the transmission period ts'.

[0068] The communications station 100 will be able to use applications that utilize time information during the period 2004, after time 2003 has elapsed.

[0069] Next, the communication processing performed by the communication station 100 according to this embodiment will be explained using the flowchart in Figure 6. The communication processing in Figure 6 is executed, for example, when power is turned on to the communication station 100.

[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 a shortened transmission period ta' and the transmission period of the Sync frame to a shortened transmission period ts'.

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

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

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

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

[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 transmission period of the shortened Announce frame and the transmission period of the shortened 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 remains in standby mode.

[0077] For example, when the adjustment unit 105 determines that time point 2003 in Figure 5 has elapsed, it refers to the transmission cycle information 101-1 stored in the memory unit 101 and sets the transmission cycle of the Announce frame to a transmission cycle ta that is longer than the transmission cycle ta', and sets the transmission cycle of the Sync frame to a transmission cycle ts that is longer than the transmission cycle ts'. Subsequently, the Announce frame transmitting / receiving unit 102 transmits the Announce frame at transmission cycle ta, and the Sync frame transmitting / receiving unit 103 transmits the Sync frame at transmission cycle ts. On the other hand, when the adjustment unit 105 determines that time point 2003 in Figure 5 has not elapsed, it remains in standby mode.

[0078] According to this embodiment, the transmission cycle of the Announce frame and the transmission cycle of the Sync frame until the synchronization completion time has elapsed are shortened when the communication station is started up. This shortens the time from the start up of the communication station until synchronization is completed to the time indicated by the time information distributed from the grandmaster station, and allows for the start of applications that use time information to be accelerated.

[0079] Furthermore, if the transmission cycles of the Announce frame and the Sync frame are kept shortened, there is a risk that other applications running in parallel that do not use time information may run out of resources. However, according to this embodiment, once synchronization with the time indicated by the time information distributed from the grandmaster station is complete, the shortened transmission cycle is extended. This makes it possible to start applications that use time information earlier without affecting the execution of other applications that do not use time information.

[0080] (Variations) Although embodiments of the present disclosure have been described above, various forms of modification and application are possible when 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' that is shorter than the transmission period ta, and after the synchronization completion time has elapsed, it extends the transmission period of the Announce frame to a transmission period ta that is longer than the transmission period ta', but it is not limited to this. For example, the memory unit 101 stores only information indicating one transmission period ta for the transmission period of the Announce frame. The communication station 100 may, at startup, shorten the transmission period ta to value vta2 (<vta1) by shortening it from the value vta1 of the transmission period ta indicated by the stored information, and after the synchronization completion time has elapsed, extend the transmission period ta to value vta3 (>vta2) by extending it from the shortened value vta2.

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

[0083] Furthermore, although Figure 6 shows a flowchart of the communication processing performed by the communication station 100 in the above embodiment, the order of processing in each step is not limited to this. For example, the order of steps S102 and S103 in Figure 6 may be reversed.

[0084] Furthermore, 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 programs is optional. For example, they may be distributed by storing them on computer-readable recording media such as CD-ROMs (Compact Disk Read-Only Memory), DVDs (Digital Versatile Disks), or memory cards, or they may be distributed via communication networks such as the Internet.

[0086] This disclosure allows for various embodiments and modifications without departing from the broad spirit and scope of this disclosure. Furthermore, the embodiments described above are for illustrative purposes only and do not limit the scope of this disclosure. In other words, the scope of this disclosure is indicated by the claims, not by the embodiments. Various modifications made within the scope of the claims and the equivalent significance of the disclosure are considered to be within the scope of this disclosure.

[0087] According to this disclosure, it is possible to provide a communication method, a communication station, and a program that can determine whether or not the time is synchronized with the time information distributed from the grandmaster station.

[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 cycle 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 performed by a communication station in a network system including a plurality of communication stations that make communication connections, comprising a calculation step of calculating the synchronization completion time required for the communication station from the startup of the communication station until it synchronizes with the time indicated by time information distributed from a grandmaster station selected from among the plurality of communication stations, by multiplying the transmission period value of an Announce frame containing information indicating the priority of the communication station in the network system by a value obtained by subtracting 1 from the number of communication stations included in the network system, and the transmission period value of a Sync frame containing time information indicating the time held by the communication station.

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

3. The communication method according to claim 2, further comprising an extension step in which, after the synchronization completion time has elapsed, the transmission period of the Announce frame is extended to be longer than the shortened transmission period of the Announce frame, and the transmission period of the Sync frame is extended to be longer than the shortened transmission period of the Sync frame.

4. The communication method according to claim 2 or 3, wherein the shortened step is performed when the communication station is started up.

5. The communication method according to any one of claims 1 to 4, wherein the Sync frame further includes information identifying the communication station that holds the time information.

6. A communication station comprising a calculation means for calculating the 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 multiple communication stations, from the startup of the communication station until the communication station synchronizes with the time indicated by time information distributed from a grandmaster station selected from among the multiple communication stations, by multiplying the transmission period value of an Announce frame containing information indicating the priority of the communication stations in a network system including multiple communication stations that perform communication connections by a value obtained by subtracting 1 from the number of communication stations included in the network system, and the transmission period value of a Sync frame containing time information indicating the time held by the communication station.

7. A program that causes a computer to function as a calculation means for calculating the synchronization completion time required for a communication station to synchronize with the time indicated by time information distributed from a grandmaster station selected from among the multiple communication stations, from the startup of the communication station until the communication station synchronizes with the time indicated by time information distributed from a grandmaster station selected from among the multiple communication stations, by multiplying the transmission period value of an Announce frame containing information indicating the priority of a communication station in a network system including multiple communication stations that make communication connections by a value obtained by subtracting 1 from the number of communication stations included in the network system, and the transmission period value of a Sync frame containing time information indicating the time held by the communication station.

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