JP6227888B2 - Communication system, synchronization system, and communication method - Google Patents

Description

  The present invention relates to a communication system, a synchronization system, a communication data transfer device, and a communication data transfer method for synchronizing an internal clock between a master and a slave via a wide area network.

  In order to synchronize the slave's internal clock with the master's internal clock using a packet communicated between the master serving as a reference and a slave dependent on the master, there is a method using, for example, a known Precision Time Protocol (PTP). is there.

  In PTP, each master and slave has a counter. The value of each counter of each device is stamped as a time stamp in each device, and a packet including the time stamp (hereinafter referred to as a message) is exchanged between the master and the slave for control.

  7 and 8 show a general sequence diagram of a known PTP for synchronizing the clock frequency and time between the master 70 and the slave 80. FIG. FIG. 7 shows a frequency synchronization, and FIG. 8 shows a sequence for time synchronization (for example, Non-Patent Document 1).

In frequency synchronization, time stamps t ₁ and t ₃ are notified from the master 70 to the slave 80 as shown in FIG. The slave 80 holds the counter values in the slave 80 when receiving t ₁ and t ₃ as t ₂ and t ₄ , respectively. Then, the frequency of the internal clock of the slave 80 is adjusted so that the message transmission interval (t ₃ -t ₁ ) is equal to the message reception interval (t ₄ -t ₂ ).

In time synchronization as shown in FIG. 8, and notifies the timestamp T ₁ from the master 70 to the slave 80. In slave 80 retains the counter value of the slave 80 upon receiving the _{T 1} as _{T 2.} Thereafter, slave 80 sends a time stamp T ₃ to the master 70, when it master 70 has received, to request to send the counter values in the master 70 as T _4.

In the master 70 notifies the slave 80 to the counter value in the master 70 upon receiving the _{T 3} as _{T 4.} The slave 80 determines the delay between T ₁ , T ₂ , T ₃ , T ₄ and the master 70 to the slave 80 as Delay [(T ₂ −T ₁ ) + (T ₄ −T ₃ )] / 2, the initial master 70. The initial time difference between the slave 80 and the slave 80 is calculated as Offset [(T ₂ −T ₁ ) − (T ₄ −T ₃ )] / 2, and the time difference between the master 70 and the slave 80 is corrected.

  In the exchange of PTP time stamps, the delay is adjusted on the assumption that it is always constant. Therefore, if the transmission delay between the master 70 and the slave 80 fluctuates, the accuracy of frequency synchronization and time synchronization may deteriorate. There is.

  In the time synchronization, adjustment is performed on the assumption that the transmission delay from the master 70 to the slave 80 and the transmission delay from the slave 80 to the master 70 are equal. However, the transmission delay from the master 70 to the slave 80 and the transmission delay from the slave 80 to the master 70 are different. That is, when the network delay is asymmetric, the time synchronization accuracy may be degraded.

9 and 10 show sequence diagrams when the transmission delay in the direction from the master 70 to the slave 80 is increased by δ. In the case of frequency synchronization, as shown in FIG. 9, the time at which the counter value of t ₁ is received by the slave 80 becomes t ₂ ′, which is deviated from the original t ₂ by δ. For this reason, the value of t ₄ −t ₂ ′ is smaller than the original Message reception interval by δ, and the frequency of the slave 80 is equal to (t ₃ −t ₁ ) / [(t ₃ −t ₁ ) −δ]. The frequency shifts from the frequency of the master 70, and accurate frequency synchronization cannot be performed.

In the case of time synchronization, as shown in FIG. 10, the time when the slave 80 receives the T ₂ counter value is T ₂ ′, which is shifted from the original T ₂ by δ. For this reason, since the value of [(T ₂ −T ₁ ) − (T ₄ −T ₃ )] / 2 becomes δ / 2 larger than the original offset, the time is shifted by δ / 2, and accurate time synchronization is achieved. I can't.

  As a method for improving the deterioration of the synchronization accuracy, there is a method using a PTP boundary clock or a transparent clock. The boundary clock or transparent clock operates as a communication device connected between the grand master and the slave. Here, the grand master is a master having a clock that is the most basic in a domain that performs clock synchronization.

  The boundary clock terminates messages exchanged between the grand master and the slave, and is slave-synchronized with an upper master and operates as a master with a lower slave. Here, the upper level represents the direction with the smaller number of hops from the grand master 90, and the lower level represents the direction with the larger number of hops from the grand master 90.

  By using all the communication devices between the master and slave as a boundary clock, the message can be terminated in each transmission section, and this causes the message in each communication device to be the main cause of fluctuations in transmission delay. The fluctuation of the residence time can be suppressed. Further, the asymmetry of the message residence time in each communication device, which is the main cause of the transmission delay being asymmetric, can be suppressed.

  The transparent clock writes the dwell time in the communication device itself in each message exchanged between the master and the slave. The master and slave correct the time based on this residence time.

  The residence time in the transparent clock is calculated from the difference between the time stamps entered and exited by the communication device 10 itself. Here, as an example, the case of an end-to-end transparent clock has been described.

  By making all communication devices between the master and slaves transparent clocks, it is possible to correct the residence time in each communication device, which, like the boundary clock, is the main cause of fluctuations in transmission delay, Fluctuations in the message residence time in the communication device can be suppressed.

  It is also possible to suppress the asymmetry of the message residence time in each communication apparatus, which is the main cause of the transmission delay becoming asymmetric. With these introductions, more accurate frequency and time synchronization can be performed using PTP.

IEEE Instrumentation and Measurement Society, “IEEE Standard for a Precise Clock Synchronization Protocol for Networked Measurement and Control E200.

  Here, assuming the operation of a network as shown in FIG. 11 in which a plurality of networks 75 of the operator A including the ground master 90 and the slave 80 are connected by a wide area network, the clock of the slave 80 of the operator A Is synchronized with the clock of the grand master 90 belonging to another network 75 of the operator A through the wide area network.

  However, when the boundary clock is used, each communication device belonging to the wide area network between the grand master 90 and the slave 80 needs to be synchronized with the upper master. Therefore, in the network of FIG. 11 that performs synchronization between the grand master 90 and the slave 80 via the wide area network, it is necessary to synchronize each communication device belonging to the wide area network with the grand master 90 as a boundary clock.

  Each communication device belonging to the current wide area network often does not have a boundary clock function, so that a large amount of devices need to be replaced, resulting in a high cost.

  When using a transparent clock, it is not essential that each communication device belonging to a wide area network is synchronized with the grand master 90. However, in order to improve the accuracy of calculation of the residence time, It is recommended to synchronize. For this reason, there is a problem that the cost becomes high as in the case of the boundary clock when high-precision synchronization is required.

  On the other hand, when assuming the operation of a network as shown in FIG. 12 in which a plurality of carriers share a wide area network and each independently operates a reference clock, the clock of the slave 80 possessed by each carrier is assigned to each carrier. It is required to synchronize with the clock of the grand master 90 of the. Here, the clock domain refers to a group of logical communication devices 10 synchronized with a common clock.

  However, when a boundary clock or a high-accuracy transparent clock is used, it is necessary to synchronize the clock of each communication device 10 belonging to the wide area network with the grand master 90 corresponding to each clock domain. There is also a problem that clock management becomes complicated because it is necessary to always know which grandmaster 90 the ten clocks are synchronized with.

  In order to solve the above problems, the present invention realizes high-accuracy clock transmission at low cost by reducing deterioration in clock synchronization accuracy due to delay fluctuation and asymmetry of transmission delay between master and slave. With the goal.

  The present invention provides a means for obtaining a sending time, a means for calculating a time to stay for a packet transmitted bi-directionally between communication devices connected oppositely via a network, and the packet. By using a communication system characterized by having a staying means, the bidirectional transmission delay between the master and the slave is made equal and constant.

Specifically, the communication system of the present invention includes:
A communication system comprising a plurality of communication data transfer devices connected between communication devices,
The first communication data transfer device connected to the communication device that is the transmission source of the communication data among the plurality of communication data transfer devices,
When receiving communication data from the communication device, a time information insertion unit that inserts the reception time of the communication data into the communication data,
A second communication data transfer device that receives the communication data from the first communication data transfer device of the plurality of communication data transfer devices,
A dwell time calculation unit that calculates a dwell time of the communication data using the reception time of the first communication data transfer device inserted into the communication data by the time information insertion unit;
A communication data retention unit that retains the communication data over the residence time calculated by the residence time calculation unit.

In the communication system of the present invention,
The second communication data transfer device is
When receiving communication data, further comprising a time information reading unit for reading the reception time of the first communication data transfer device inserted in the communication data,
The dwell time calculation unit calculates a first time obtained by subtracting a reception time read by the time information reading unit from a reception time when the second communication data transfer device receives the communication data, and stores the first time in advance. The dwell time of the communication data may be calculated by calculating a second time obtained by subtracting the certain time and the first time.

In the communication system of the present invention,
The first communication data transfer device and the second communication data transfer device are:
A time synchronization unit that performs time synchronization between the time synchronization unit of the communication data transfer device and the time synchronization unit of another communication data transfer device, and further includes a time synchronization unit that supplies the time synchronization time to the time supply unit,
The time information insertion unit of the first communication data transfer device inserts the reception time of the communication data using the time supplied from the time information supply unit synchronized with the time of the time synchronization unit,
The dwell time calculation unit of the second communication data transfer device receives the communication data received by the second communication data transfer device using the time supplied from the time information supply unit synchronized with the time of the time synchronization unit. May be obtained.

The synchronization system of the present invention includes:
A communication device that transmits communication data to the first communication data transfer device; and
A communication apparatus that receives the communication data transferred by the second communication data transfer apparatus and that synchronizes time or frequency with the transmission communication apparatus;

The communication method of the present invention includes:
A communication method using a plurality of communication data transfer devices connected between communication devices,
When the first communication data transfer device connected to the communication device that is the transmission source of the communication data among the plurality of communication data transfer devices receives the communication data from the communication device, the communication data Time information insertion procedure for inserting the reception time into the communication data;
The second communication data transfer device that receives the communication data from the first communication data transfer device among the plurality of communication data transfer devices, wherein the time information insertion unit inserts the first communication into the communication data. A residence time calculation procedure for calculating the residence time of the communication data using the reception time of the data transfer device;
The second communication data transfer apparatus sequentially has a communication data retention procedure for retaining the communication data for the retention time calculated by the retention time calculation procedure.

In the communication method of the present invention,
In the dwell time calculation procedure, when communication data is received, the reception time of the first communication data transfer device inserted in the communication data is read,
The first time obtained by subtracting the read reception time of the first communication data transfer device from the reception time when the second communication data transfer device received the communication data is calculated and stored in advance. By calculating a second time obtained by subtracting the first time from the first time, the dwell time of the communication data may be calculated.

In the communication method of the present invention,
A time synchronization procedure in which the first communication data transfer device and the second communication data transfer device perform time synchronization with a time synchronization unit of another communication data transfer device is performed before the time information insertion procedure. In addition,
In the time information insertion procedure, the first communication data transfer device inserts the reception time of the communication data using the time synchronized in the time synchronization procedure,
In the dwell time calculation procedure, the second communication data transfer device acquires the reception time of the communication data received by the second communication data transfer device using the time synchronized in the time synchronization procedure. Also good.

  The above inventions can be combined as much as possible.

  Since the bidirectional transmission delay between the master and slave communication devices is equalized, the present invention reduces deterioration in clock synchronization accuracy due to delay fluctuation and asymmetry of the transmission delay between the master and slave, and highly accurate clock transmission. Can be realized.

1 is a configuration diagram illustrating an example of a communication system according to a first embodiment. It is a block diagram which shows an example of communication adapter 11A which concerns on this Embodiment 1. FIG. It is a block diagram which shows an example of the communication adapter 11B which concerns on this Embodiment 1. FIG. It is a sequence diagram which shows an example of the communication system corresponding to the communication system which concerns on this Embodiment 1. FIG. It is a block diagram which shows an example of the communication system which concerns on this Embodiment 2. It is a block diagram which shows an example of communication adapter 11C1 which concerns on this Embodiment 2. FIG. It is a sequence diagram which shows an example of the frequency synchronization of the clock which concerns on related technology. It is a sequence diagram which shows an example of the time synchronization of the clock which concerns on related technology. It is a sequence diagram when the transmission delay in the frequency synchronization which concerns on related technology fluctuates. It is a sequence diagram when the transmission delay in the time synchronization which concerns on related technology fluctuates. It is a schematic diagram which shows an example of the network which performs frequency synchronization between a grand master and a slave via the wide area network which concerns on related technology. It is an outline figure showing an example of a network which performs time synchronization between a grand master and a slave via a wide area network shared by a plurality of companies concerning related technology.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

  The communication system and the synchronization system according to the present embodiment include a transmission-side communication device that is a communication device, a communication data transfer device, and a reception-side communication device that is a communication device, and between the transmission-side communication device and the reception-side communication device. A communication system and a synchronization system that transmit and receive communication data to synchronize time or frequency. The communication device receives, for example, the communication data transferred by the master 70 or the communication data transfer device that functions as the transmission-side communication device that transmits the communication data with the transmission time inserted, and synchronizes the time or frequency with the transmission-side communication device This is a slave 80 that functions as a side communication device. The master 70 may be a grand master 90.

  The communication method of the communication apparatus according to the present embodiment is a communication method using a plurality of communication data transfer apparatuses that transfer communication data that is connected between communication apparatuses and into which a transmission time from the communication apparatus is inserted. A time information insertion procedure, a residence time calculation procedure, and a communication data residence procedure are sequentially provided.

  In the time information insertion procedure, when a first communication data transfer device connected to a communication device that is a transmission source of communication data among a plurality of communication data transfer devices receives communication data from the communication device, the communication data The data reception time is inserted into the communication data. In the dwell time calculation procedure, the second communication data transfer device that receives the communication data from the first communication data transfer device among the plurality of communication data transfer devices has the first time information insertion unit inserted into the communication data. The dwell time of communication data is calculated using the reception time of the communication data transfer device. In the communication data retention procedure, communication data is retained for the retention time calculated in the retention time calculation procedure. Communication data may be transmitted and received between communication devices as packets.

(Embodiment 1)
FIG. 1 is an example of a communication system according to the present embodiment. As shown in FIG. 1, the communication system according to the present embodiment is configured to have communication adapters 11A and 11B facing each other between the communication devices 10a and 10b facing each other, and a network 75 therebetween. Here, the network 75 is an example in which the transmission of packets that are communication data between the communication devices 10a in FIG. 1 is limited to the transmission direction from the communication device 10a located on the left side to the communication device 10b located on the right side. Is assumed. The communication device 10a functions as the master 70, and the communication device 10b functions as the slave 80. The communication adapter 11B functions as a communication data transfer device according to the present embodiment.

  The communication adapter 11A has a function of acquiring a transmission time of a packet that is communication data transmitted from the communication device 10a. Further, the communication adapter 11B has a function of calculating a time for which a packet should stay from the transmission time and a predetermined time, and a function for retaining the packet over the calculated time to stay. Specific configuration examples of the communication adapter 11A and the communication adapter 11B are shown in FIGS. 2 and 3, respectively. The fixed time is determined by the transmission delay time between the communication device 10a and the communication device 10b.

  In FIG. 2, the communication adapter 11A includes an interface to the communication device 10a, an interface to the network 75, a time synchronization interface, a receiver (hereinafter Rx20), a transmitter (hereinafter Tx24), a time information supply unit 23, and a time information insertion unit. 21 and a time synchronization unit 22, and packet transmission time acquisition is performed by a transmission time acquisition unit 25 including a time information supply unit 23, a time information insertion unit 21, and a time synchronization unit 22.

  In the communication adapter 11A, a packet (hereinafter referred to as packet A) input through the interface to the communication device 10a is received by Rx20. At this time, the Rx 20 outputs a trigger notifying the time information supply unit 23 that the packet A has been received. Based on this trigger, the time information supply unit 23 supplies the time when the packet A is received to the time information insertion unit 21 as time information.

  The time information insertion unit 21 inserts the time information obtained from the time information supply unit 23 into the packet A. Thereafter, the packet A in which the time information is inserted is transmitted to the network 75 through the interface to Tx 24 and the network 75. Here, the time information may be in the form of a time stamp, for example.

  In FIG. 3, the communication adapter 11B functioning as a communication data transfer device includes an interface to the network 75, an interface to the communication device 10b, a time synchronization interface, a transmitter (hereinafter referred to as Tx37), a receiver (hereinafter referred to as Rx30), a communication. It comprises a packet retention unit 36 that functions as a data retention unit, a time information reading unit 31, a delay amount notification unit 34, a residence time calculation unit 35, a time information supply unit 33, and a time synchronization unit 32. The residence time of a packet as communication data is calculated by a residence time calculation unit 38 including a time information reading unit 31, a delay amount notification unit 34, a residence time calculation unit 35, a time information supply unit 33, and a time synchronization unit 32. .

  In the communication adapter 11B, a packet (hereinafter referred to as packet B) input through the interface to the network 75 is received by Rx30. Thereafter, the time information reading unit 31 reads the time information inserted into the packet B from the other communication adapter 11. The read time information a is sent to the dwell time calculation unit 35, and at the same time, a trigger for notifying that the time information has been read is sent to the time information supply unit 33.

  Based on this trigger, the time information supply unit 33 supplies the time when the time information is read to the residence time calculation unit 35 as time information b. In addition, the delay amount notification unit 34 sends a delay amount c desired between the communication device 10 a and the communication device 10 b to the residence time calculation unit 38. The residence time calculation unit 38 calculates a time d during which the packet should stay in the communication device 10 b from the obtained time information a and b and the delay amount c, and transmits the time d to the packet retention unit 36. The packet retention unit 36 retains the packet B for a time d and then sends it to the Tx 37. Tx37 transmits the packet through the interface to the communication device 10b.

Here, the delay time between the two communication devices 10a and 10b is (b−a) unless the delay is particularly controlled. However, here, the delay time between the communication device 10a and the communication adapter 11A and between the communication device 10b and the communication adapter 11B is assumed to be negligibly small compared to (b-a). Here, let c be a fixed time determined by the delay time between the two communication devices 10a and 10b. In order to make the delay time between the two communication devices 10a and 10b constant, the packet is retained in the communication device 10b for the remaining (c- (ba)) time in the communication device 10b. There is a need. If it writes with a formula, it will become as follows.
(Equation 1)
d = c- (ba)

  Here, it is desirable to set c ≧ (b−a). When c <(b−a), that is, when the delay time is longer than the desired delay amount when the control is not performed, the delay amount due to packet retention cannot be accurately controlled, and the delay time deviates from a predetermined value. Becomes larger.

  The delay amount c can be stored in advance in the memory of the communication adapter 11B and can be operated in a fixed state during operation. Further, it can be determined by mutual exchange with other communication devices through an interface to the network 75, an interface to other communication devices, a time synchronization interface, or the like. For example, c is updated so that the maximum delay time in the exchange becomes c. Alternatively, it is possible to provide an interface to the outside of the independent communication adapter 11 for delay amount control, and to determine the mutual communication with other communication adapters 11.

  Here, the case where the delay time between the communication adapter 11A and the communication device 10a and the delay time between the communication device 10b and the communication adapter 11B are small compared with the delay between the communication adapter 11A and the communication adapter 11B and the packet residence time has been described. However, when the delay between the communication adapter 11A and the communication device 10a, and between the communication device 10b and the communication adapter 11B is large, the delay time is measured in advance, the packet retention time is shortened by the delay time, and the packet Can be output to other communication devices having the transmission destination as the transmission destination.

  In addition, the time synchronization unit 22 and the time synchronization unit 32 generate a clock that is time-synchronized with the communication device 10a and the communication device 10b that are opposed to each other through the time synchronization interface, and send the clock to the time information supply unit 23 and the time information supply unit 33. Output. Time synchronization may be performed by packet communication using a protocol such as PTP with one of the opposing communication devices 10a or 10b as the master 70 and one as the slave 80. Moreover, you may perform by each of the communication apparatus 10a or the communication apparatus 10b which opposes with respect to common clock sources, such as Global Positioning System (GPS).

  The time synchronizer 22 and the time synchronizer 32 send a reference frequency signal (for example, 10 MHz clock) and a reference time signal (for example, 1 Parts Per Second (PPS)) to the time information supply unit 23 and the time information supply unit 33, The accuracy of the time information output from the time information supply unit 23 and the time information supply unit 33 is improved.

  Here, the case of performing time synchronization has been described as an example. Time synchronization is preferably performed in order to improve the accuracy of control of the delay amount.

  Although the case where the communication device 10 and the communication adapter 11 are separate devices has been described here as an example, the communication device 10a may be operated with the function of the communication adapter 11A, or the communication device 10b may be operated. The function of the communication adapter 11B may be provided and operated.

  FIG. 4 is a sequence diagram showing an example of a communication method corresponding to the communication system of FIG. The communication adapter 11A acquires the reception time at the communication adapter 11A of the packet transmitted from the communication device 10a (S100), and sends the obtained time to the adapter B as time information (S110).

  The communication adapter 11B calculates a time d for which the packet should stay from the obtained time information and a predetermined delay time between the communication device 10a and the communication device 10b (S120), and after retaining the packet for this time d The packet is output to another communication device 10b having the transmission destination (S130). The communication device 10b can perform time synchronization of communication data with the communication device 10a by retaining the communication data over the delay time described with reference to FIGS. Note that although time synchronization has been described in this embodiment, frequency synchronization can be performed using a method similar to the method described with reference to FIGS.

  According to the invention according to the present embodiment, even when a network 75 asynchronous with the grand master 90 such as a wide area network is connected between the grand master 90 and at least two communication devices functioning as the slave 80, the grand master The transmission delays of packets exchanged bidirectionally between 90 and the slave 80 are made equal and constant. Also, since the delay times in both directions are equal, it is possible to make the transmission delay symmetrical. Therefore, it is not necessary to change the communication device belonging to the wide area network to a device corresponding to a boundary clock or a transparent clock, and an increase in cost can be prevented.

  In addition, even when multiple operators share a wide area network and each operate their own reference clock, it is necessary to synchronize the clock of each communication device in the wide area network with the clock of the grand master of each company. Therefore, the problem that the clock management of each communication device belonging to the wide area network becomes complicated can be overcome.

(Embodiment 2)
FIG. 5 shows a second embodiment of the communication system. The difference between FIG. 5 and FIG. 1 is whether the direction of transmission is bidirectional or unidirectional. In the case of bi-directional communication, the communication adapters 11C1 and C2 obtain a transmission time of a packet transmitted from the communication device 10a or the communication device 10b, and between the communication device 10a and the communication device 10b determined as the transmission time. Means for calculating the time for which the packet should stay from the transmission delay time, and means for retaining the packet for the calculated time to stay.

  A specific configuration of the communication adapter 11C1 is shown in FIG. Unlike FIGS. 2 and 3, the functions of the communication adapter 11 </ b> A and the communication adapter 11 </ b> B are included in one communication adapter 11.

  In the above-described embodiment, the embodiment in which the communication device 10a or the communication device 10b and the network 75 are connected to each communication adapter 11 has been described. .

  In addition, although the embodiment in which the communication adapter 11 is operated in a pair has been described here, the communication adapter 11 does not have to be a pair. For example, one communication adapter 11 and a plurality of communication adapters 11 may communicate. .

  In these cases, the processing may be performed by determining from which communication device the packet is transmitted. The determination can be made, for example, based on the source and destination IP addresses assigned to the packet.

  In the above-described embodiment, the time synchronization system in which the transmission time from the communication device 10a is included in the communication data has been described. However, the present invention is not limited to this and is applied to a communication system that transmits and receives general communication data. can do.

  The present invention can be applied to the information communication industry.

10, 10a, 10b: Communication devices 11, 11A, 11B, 11C1: Communication adapters 20, 30, 40, 45: Rx
21, 41: Time information insertion units 22, 32, 42: Time synchronization units 23, 33, 43: Time information supply units 24, 37, 44, 50: Tx
25: Sending time acquisition unit 31, 46: Time information reading unit 34, 47: Delay amount notification unit 35, 48: Residence time calculation unit 36, 49: Packet retention unit 38: Residence time calculation unit 70: Master 75: Network 80 : Slave 90: Grand master

Claims (7)

A communication system in which a communication data transfer device that synchronizes time with a communication device is connected by a network that is asynchronous with the communication device,
The first communication data transfer device connected to the communication device that is the transmission source of the communication data among the communication data transfer devices,
When receiving communication data from the communication device, a time information insertion unit that inserts the reception time of the communication data into the communication data,
A second communication data transfer device that receives the communication data from the first communication data transfer device of the communication data transfer devices,
A dwell time calculation unit that calculates a dwell time of the communication data using the reception time of the first communication data transfer device inserted into the communication data by the time information insertion unit;
The allowed to stay communication data over a residence time of the residence time calculation unit has calculated, and the communication data retention unit that to reduce the delay jitter between the communication data transfer device,
The provided under the delay amount with a reduced fluctuation, communication systems that and performing time synchronization between the communication device. The second communication data transfer device is
When receiving communication data, further comprising a time information reading unit for reading the reception time of the first communication data transfer device inserted in the communication data,
The dwell time calculation unit calculates a first time obtained by subtracting a reception time read by the time information reading unit from a reception time when the second communication data transfer device receives the communication data, and stores the first time in advance. 2. The communication system according to claim 1, wherein a dwell time of the communication data is calculated by calculating a second time obtained by subtracting the predetermined time and the first time. The first communication data transfer device and the second communication data transfer device are:
A time synchronization unit that performs time synchronization between the time synchronization unit of the communication data transfer device and the communication device connected to each communication data transfer device, and supplies the time synchronization time to the time supply unit; Prepared,
The time information insertion unit of the first communication data transfer device inserts the reception time of the communication data using the time supplied from the time supply unit synchronized with the time of the time synchronization unit, The dwell time calculation unit of the communication data transfer device acquires the reception time of the communication data received by the second communication data transfer device using the time supplied from the time supply unit synchronized with the time of the time synchronization unit. The communication system according to claim 2. A transmission-side communication device that transmits communication data to the first communication data transfer device according to any one of claims 1 to 3;
A synchronization system comprising: a communication device that receives communication data transferred by the second communication data transfer device according to any one of claims 1 to 3 and that synchronizes time or frequency with the transmission communication device. . A communication method for a communication system in which a communication data transfer device that is time-synchronized with a communication device is connected to a network that is asynchronous with the communication device,
When the first communication data transfer device connected to the communication data transmission source of the communication data transfer device receives the communication data from the communication device, the reception time of the communication data Inserting time information into the communication data,
Of the communication data transfer devices, the second communication data transfer device that receives the communication data from the first communication data transfer device inserts the first communication data transfer into the communication data in the time information insertion procedure. A residence time calculation procedure for calculating the residence time of the communication data using the reception time of the device;
The second communication data transfer device, the allowed to stay the communication data over the residence time calculated by the residence time calculation procedure, and communication data retention instructions on reducing the delay jitter between the communication data transfer device,
A time synchronization procedure for performing time synchronization between the communication devices under a delay amount in which fluctuation is reduced in the communication data retention procedure;
A communication method comprising: In the dwell time calculation procedure, when communication data is received, the reception time of the first communication data transfer device inserted in the communication data is read,
The first time obtained by subtracting the read reception time of the first communication data transfer device from the reception time when the second communication data transfer device received the communication data is calculated and stored in advance. The communication method according to claim 5, wherein a dwell time of the communication data is calculated by calculating a second time obtained by subtracting the first time and the first time. A time synchronization procedure in which the first communication data transfer device and the second communication data transfer device perform time synchronization with the communication devices connected to the respective communication data transfer devices; And even before
In the time information insertion procedure, the first communication data transfer device inserts the reception time of the communication data using the time synchronized in the time synchronization procedure,
In the dwell time calculation procedure, the second communication data transfer device acquires a reception time of the communication data received by the second communication data transfer device using a time synchronized in the time synchronization procedure.
The communication method according to claim 5 or 6, characterized by the above.

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