KR102538217B1 - Method for performing synchronization according to Precision Time Protocol (PTP) in ring topology network, and apparatus therefor - Google Patents

Abstract

An apparatus for performing synchronization according to a precise time synchronization protocol in a ring topology network of the present invention includes a leader node that transmits messages in clockwise and counterclockwise directions on the ring topology, and receives messages transmitted by the leader node and clockwise and a plurality of follower nodes that relay in the direction and counterclockwise direction and synchronize with the clock time of the leader node using the reception time and the transmission time of the message.

Description

Method for performing synchronization according to precision time synchronization protocol in ring topology network and apparatus therefor}

The present invention relates to a synchronization technology based on a precision time synchronization protocol, and more particularly, a method for performing synchronization by transmitting and receiving a Precision Time Protocol (PTP) message according to the IEEE-1588 standard on a ring topology network. and an apparatus therefor.

The Precision Time Protocol (PTP) is a time transfer protocol according to the IEEE 1588 standard that enables accurate synchronization between networks. It guarantees nanosecond accuracy when using hardware-generated timestamps.

Korean Patent Publication No. 2018-0072506 published on June 29, 2018 (Name: Method and apparatus for estimating clock frequency error and clock time error in PTP slave)

An object of the present invention is to provide a method and apparatus for performing synchronization according to a precise time synchronization protocol in a ring topology network.

To achieve the above object, in a method for performing synchronization according to a precise time synchronization protocol in a ring topology network according to a preferred embodiment of the present invention, a leader node transmits a first clockwise message in a clockwise direction on the ring topology. while transmitting the first counterclockwise message in a counterclockwise direction, the leader node transmits a clockwise reference transmission time (Ta_cw1), which is the time at which the leader node transmits the first clockwise message, and the first counterclockwise message A first message transmission step of measuring a counterclockwise reference transmission time (Ta_ccw1), which is the time at which , and a plurality of follower nodes relaying the first clockwise message in the clockwise direction, each of the plurality of follower nodes The clockwise relay reception time (Rx_cw1), which is the time at which the first clockwise message is received, and the clockwise relay transmission time (Tx_cw1), which is the time at which the first clockwise message is transmitted, are measured, and the first counterclockwise message is Counterclockwise relay reception time (Rx_ccw1), which is the time at which each of the plurality of follower nodes received the first counterclockwise message while relaying in the counterclockwise direction, and counterclockwise, which is the time at which the first counterclockwise message was transmitted. A first message relaying step of measuring a directional relay transmission time (Tx_ccw1), and when the leader node receives the first clockwise message and the first counterclockwise message transmitted by the leader node, the first clockwise message is transmitted. A first message receiving step of measuring a clockwise reference reception time (Ra_cw1), which is the received time, and a counterclockwise reference reception time (Ra_ccw1), which is the time at which the first counterclockwise message is received; transmits a second clockwise message including the clockwise reference transmission time (Ta_cw1) and the counterclockwise reference reception time (Ra_ccw1) in the direction, and the counterclockwise reference transmission time (Ta_ccw1) and the counterclockwise direction reference transmission time (Ta_ccw1) A second message transmission step of transmitting a second counterclockwise message including a clockwise reference reception time (Ra_cw1), wherein the plurality of follower nodes transmit the clockwise direction reference transmission time (Ta_cw1) and the counterclockwise reference reception time The second clockwise message including (Ra_ccw1) is relayed in the clockwise direction, and the second counterclockwise message including the counterclockwise reference transmission time (Ta_ccw1) and the clockwise reference reception time (Ra_cw1) A second message relaying step of relaying in the counterclockwise direction, wherein the plurality of follower nodes perform the clockwise reference transmission time (Ta_cw1), the counterclockwise reference reception time (Ra_ccw1), and the clockwise relaying reception time (Rx_cw1). ) and the counterclockwise relay transmission time (Tx_ccw1), or the counterclockwise reference transmission time (Ta_ccw1), the clockwise reference reception time (Ra_cw1), the counterclockwise relay reception time (Rx_ccw1) and the clock and performing synchronization using the directional relay transmission time (Tx_cw1).

The step of performing the synchronization may include a series of equations A = D + O = Rx_cw1 - Ta_cw1 = Rx_ccw1 - Ta_ccw1, B = D - O = Ra_ccw1 - Tx_ccw1 = Ra_cw1 - Tx_cw1, D = (A + Delay and offset are calculated according to B)/2 and O = (A - B)/2, and synchronization is performed according to the calculated delay and offset. Here, D means delay, O means offset, Ta_cw1 is the clockwise reference transmission time, Ra_ccw1 is the counterclockwise reference reception time, and Rx_cw1 is the clockwise relay reception time. wherein Tx_ccw1 is the counterclockwise relay transmission time, Ta_ccw1 is the counterclockwise reference transmission time, Ra_cw1 is the clockwise reference reception time, Rx_ccw1 is the counterclockwise relay reception time, Tx_cw1 is characterized in that the clockwise relay transmission time.

In the second message relaying step, the plurality of follower nodes accumulate and add the delay time of the first clockwise message to the second clockwise message, and add the first counterclockwise message to the second counterclockwise message. It is characterized in that the delay time of is added by accumulating it.

The first message including the first clockwise message and the first counterclockwise message includes a message type field indicating that it is a first message and a message direction field indicating a direction in which the message is transmitted.

A message type field indicating that the second message including the second clockwise message and the second counterclockwise message is a second message, a message direction field indicating the direction in which the corresponding message is transmitted, and the leader node indicating the direction of the message. A transmission time field indicating the time at which the previous message was transmitted, a transmission time field indicating the time at which the leader node received the previous message in a direction opposite to the direction of the message, and a follower node and leader for the first clockwise message. A clockwise correction field indicating the cumulative delay time between nodes and a counterclockwise correction field indicating the cumulative delay time between the follower node and the leader node for the first counterclockwise message.

An apparatus for performing synchronization according to a precision time synchronization protocol in a ring topology network according to a preferred embodiment of the present invention for achieving the above object is a first clockwise message and a first counterclockwise message respectively on the ring topology. Clockwise reference transmission time (Ta_cw1), which is the time at which the first clockwise direction message was transmitted, and counterclockwise reference transmission time (Ta_ccw1, which is the time at which the first counterclockwise direction message was transmitted) while transmitting in the clockwise and counterclockwise directions. ) is measured, and when the first clockwise message and the first counterclockwise message are received, the clockwise reference reception time (Ra_cw1), which is the time at which the first clockwise message is received, and the first counterclockwise message A second clockwise message including the clockwise reference transmission time (Ta_cw1) and the counterclockwise reference reception time (Ra_ccw1) and the counterclockwise reference reception time (Ra_ccw1), which is the time at which A leader node that transmits a second counterclockwise message including a direction reference transmission time (Ta_ccw1) and a clockwise reference reception time (Ra_cw1) in clockwise and counterclockwise directions, respectively; and transmitting the first clockwise message to the clockwise direction. Clockwise relay reception time (Rx_cw1), which is the time at which the first clockwise message is received while relaying in the opposite direction, and clockwise relay transmission time (Tx_cw1), which is the time at which the first clockwise message is transmitted, are measured, and the counterclockwise relay transmission time (Tx_cw1) is measured. Counterclockwise relay reception time (Rx_ccw1), which is the time at which the first counterclockwise direction message is received while relaying the direction message in the counterclockwise direction, and counterclockwise relay transmission time, which is the time at which the first counterclockwise direction message is transmitted. (Tx_ccw1) is measured, and the second clockwise message including the clockwise reference transmission time (Ta_cw1) and the counterclockwise reference reception time (Ra_ccw1) is relayed, and the counterclockwise reference transmission time (Ta_ccw1) and relaying the second counterclockwise message including the clockwise reference reception time (Ra_cw1), the clockwise reference transmission time (Ta_cw1), the counterclockwise reference reception time (Ra_ccw1), and the clockwise relaying and receiving Time (Rx_cw1) and the counterclockwise relay transmission time (Tx_ccw1) are used, or the counterclockwise reference transmission time (Ta_ccw1), the clockwise reference reception time (Ra_cw1), and the counterclockwise relay reception time (Rx_ccw1) and a plurality of follower nodes performing synchronization using the clockwise relay transmission time (Tx_cw1).

According to the present invention, the time of all nodes in a ring network is synchronized with a relatively small number of messages using only broadcast messages. Moreover, the present invention can maintain time synchronization even when a failure occurs in the ring network.

1 is a diagram for explaining a network system having a ring topology according to an embodiment of the present invention.
2 is a flowchart illustrating a method for performing synchronization according to a precise time synchronization protocol in a ring topology network.
3 is a diagram for explaining a method for performing synchronization according to a precise time synchronization protocol in a ring topology network.
4 is a diagram for explaining the configuration of a message for performing synchronization according to a precise time synchronization protocol in a ring topology network.
5 is a diagram for explaining the advantages of a synchronization method for transmitting messages in both directions including clockwise and counterclockwise directions according to an embodiment of the present invention.
6 is a diagram for explaining a failure recovery method when a failure occurs in a connection between nodes according to an embodiment of the present invention and the two linear networks are divided.
FIG. 7 is a diagram for explaining a failure recovery method in the case where one linear network is generated due to a failure of a follower node according to an embodiment of the present invention.

Prior to the detailed description of the present invention, the terms or words used in this specification and claims described below should not be construed as being limited to a common or dictionary meaning, and the inventors should use their own invention in the best way. It should be interpreted as a meaning and concept corresponding to the technical idea of the present invention based on the principle that it can be properly defined as a concept of a term for explanation. Therefore, the embodiments described in this specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention, and do not represent all of the technical ideas of the present invention, so various equivalents that can replace them at the time of the present application. It should be understood that there may be water and variations.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. At this time, it should be noted that the same components in the accompanying drawings are indicated by the same reference numerals as much as possible. In addition, detailed descriptions of well-known functions and configurations that may obscure the gist of the present invention will be omitted. For the same reason, some components in the accompanying drawings are exaggerated, omitted, or schematically illustrated, and the size of each component does not entirely reflect the actual size.

First, a ring topology network according to an embodiment of the present invention will be described. 1 is a diagram for explaining a network system having a ring topology according to an embodiment of the present invention.

Referring to FIG. 1 , a network system according to an embodiment of the present invention includes a plurality of nodes. The plurality of nodes includes one leader node (A) and a plurality of follower nodes (B to I). A plurality of nodes including a leader node (A) and a plurality of follower nodes (B to I) are connected in a ring shape.

According to an embodiment of the present invention, the leader node A may transmit at least one message (CW, CCW) according to the Precision Time Protocol (PTP) clockwise and counterclockwise. When the leader node (A) transmits such a message, the plurality of follower nodes (B to I) relay the message (CW, CCW) transmitted by the leader node (A) clockwise and counterclockwise. In addition, the plurality of follower nodes (B to I) calculate the delay time and offset from the time at which the message is transmitted and received, and synchronize the time of the clock of the leader node (A) using the calculated delay time offset. can fit

Next, a method for performing synchronization according to a precise time synchronization protocol in a ring topology network will be described in detail. 2 is a flowchart illustrating a method for performing synchronization according to a precise time synchronization protocol in a ring topology network. 3 is a diagram for explaining a method for performing synchronization according to a precise time synchronization protocol in a ring topology network. 4 is a diagram for explaining the configuration of a message for performing synchronization according to a precise time synchronization protocol in a ring topology network.

Referring to FIGS. 2, 3 and 4, the leader node A transmits a first clockwise message CW1 in a clockwise direction on the ring topology, as shown in FIG. 3 (a) in step S110, and , transmits a first counterclockwise message (CCW1) in a counterclockwise direction. In particular, in step S110, the leader node A transmits the clockwise standard transmission time Ta_cw1, which is the time at which the first clockwise message (CW1) is transmitted, and the counterclockwise direction, which is the time at which the first counterclockwise message (CCW1) is transmitted. Measure the direction reference transmission time (Ta_ccw1).

As shown in FIG. 4, the first message (MSG1) including the first clockwise message (CW1) and the first counterclockwise message (CCW1) includes a message type field (TYPE) and a message direction field (DIR). include In the message type field (TYPE) of the first message (MSG1), information indicating that it is the first message is recorded. In addition, information indicating whether the message transmission direction is clockwise or counterclockwise is recorded in the message direction field DIR.

Next, as shown in (b) of FIG. 3 in step S120, the plurality of follower nodes B to I relay the first clockwise message CW1 clockwise, and the first counterclockwise message ( CCW1) is relayed counterclockwise. In this step S120, when each of the plurality of follower nodes B to I relays the first clockwise message CW1 clockwise, the clockwise relay reception time (which is the time at which the first clockwise message CW1 is received) ( Rx_cw1) and clockwise relay transmission time (Tx_cw1), which is the time at which the first clockwise message (CW1) is transmitted, are measured. In addition, when each of the plurality of follower nodes B to I relays the counterclockwise message CCW1 in the counterclockwise direction in step S120, the counterclockwise direction is the time at which the first counterclockwise message CCW1 is received. The relay reception time (Rx_ccw1) and the counterclockwise relay transmission time (Tx_ccw1), which is the time at which the first counterclockwise message (CCW1) is transmitted, are measured.

Since the network is configured in a ring topology, the leader node A sends the first clockwise message CW1 and the first clockwise message CW1 transmitted by the leader node A itself, as shown in (c) of FIG. 3 in step S130. A counterclockwise message (CCW1) can be received. In step S130, the leader node A has a clockwise reference reception time (Ra_cw1), which is the time at which the first clockwise message (CW1) is received, and a counterclockwise reference, which is the time at which the first counterclockwise message (CCW1) is received. Measure the reception time (Ra_ccw1).

Then, as shown in (d) of FIG. 3 , in step S140, the leader node A has a second clockwise reference transmission time (Ta_cw1) and a counterclockwise reference reception time (Ra_ccw1) including the clockwise reference transmission time (Ta_cw1). A clockwise message (CW2) is transmitted, and a second counterclockwise message (CCW2) including a counterclockwise reference transmission time (Ta_ccw1) and a clockwise reference reception time (Ra_cw1) is transmitted.

As shown in FIG. 4, the second message MSG2 including the second clockwise message CW2 and the second counterclockwise message CCW2 includes a message type field (TYPE), a message direction field (DIR), It includes a transmission time field (T0), a reception time field (R0), a clockwise correction field (Correction_CW) and a counterclockwise correction field (Correction_CCW). Information indicating that the message type field (TYPE) of the second message (MSG2) is the second message is recorded. In addition, information indicating whether the message transmission direction is clockwise or counterclockwise is recorded in the message direction field DIR. In the transmission time field T0, information indicating the time at which the leader node A transmitted the previous message in the direction of the message, that is, the first clockwise message CW1 or the first counterclockwise message CCW1, is recorded. . In the reception time field R0, information indicating the time at which the leader node A received the previous message in the direction of the message, that is, the first clockwise message CW1 or the first counterclockwise message CCW1, is recorded. . In the clockwise correction field (Correction_CW), the cumulative delay time between the follower nodes (B to I) and the leader node (A) for the first clockwise message (CW1) is recorded. In the counterclockwise correction field (Correction_CCW), the accumulated delay time between the follower nodes (B to I) and the leader node (A) for the first counterclockwise message (CCW1) is recorded.

Next, as shown in (e) of FIG. 3, the plurality of follower nodes B to I include a clockwise reference transmission time (Ta_cw1) and a counterclockwise reference reception time (Ra_ccw1) in step S150. 2 Relays the clockwise message (CW2) in the clockwise direction, and transmits the second counterclockwise message (CCW2) including the counterclockwise reference transmission time (Ta_ccw1) and the clockwise reference reception time (Ra_cw1) in the counterclockwise direction. relay

Then, as shown in (f) of FIG. 3, the plurality of follower nodes B to I have a clockwise reference transmission time (Ta_cw1), a counterclockwise reference reception time (Ra_ccw1), and a clockwise relay in step S160. Reception time (Rx_cw1) and counterclockwise relay transmission time (Tx_ccw1) are used, or counterclockwise reference transmission time (Ta_ccw1), clockwise reference reception time (Ra_cw1), counterclockwise relay reception time (Rx_ccw1) and clockwise direction Synchronization is performed using the relay transmission time (Tx_cw1).

In step S160, the plurality of follower nodes (B to I) calculate the delay and offset of the clock of the leader node (A) according to the following Equations 1, 2, 3 and 4, and calculate the delay and offset according to the calculated delay and offset. Synchronize accordingly. That is, the plurality of follower nodes (B to I) synchronize the time of the watch of the leader node (A) with the time of the watch of the plurality of follower nodes (B to I) by using the calculated delay and offset.

In Equations 1, 2, 3 and 4, Ta_cw1 is the clockwise reference transmission time, Ra_ccw1 is the counterclockwise reference reception time, Rx_cw1 is the clockwise relay reception time, and Tx_ccw1 is the counterclockwise relay transmission time. Further, Ta_ccw1 is a counterclockwise reference transmission time, Ra_cw1 is a clockwise reference reception time, Rx_ccw1 is a counterclockwise relay reception time, and Tx_cw1 is a clockwise relay transmission time. And, D means delay and O means offset.

Meanwhile, according to an additional embodiment of the present invention, if delay times are different from each other in all follower nodes (B to I) of the ring network, node delay times in each follower node (B to I) should be considered. Therefore, when all the follower nodes B to I transmit the second message MSG2 including the second clockwise message CW2 and the second counterclockwise message CCW2, the second message corresponding to the second message MSG2 Delay times of the first message MSG1, that is, the first clockwise message CCW1 and the first counterclockwise message CCW1, should be included in the corresponding second message MSG2 and delivered. To this end, as described above, the second message MSG2 includes a clockwise correction field (Correction_CW) and a counterclockwise correction field (Correction_CCW). In the clockwise correction field (Correction_CW), the cumulative delay time between the follower nodes (B to I) and the leader node (A) for the first clockwise message (CW1) is recorded. In the counterclockwise correction field (Correction_CCW), the accumulated delay time between the follower nodes (B to I) and the leader node (A) for the first counterclockwise message (CCW1) is recorded.

According to a further embodiment of the present invention, each of the plurality of follower nodes (B to I) accumulates and adds the delay time of the first clockwise message (CW1) to the second clockwise message (CW2), and the second counterclockwise message (CW2). The delay time of the first counterclockwise message (CCW2) may be accumulated and added to the direction message (CW2). That is, any one follower node (X) transmits the accumulated clockwise delay time (Lx_cw1) obtained by accumulating the clockwise delay time (Dx_cw1) of the first clockwise message (CW1) in step S150 described above to the second clockwise message. It can be stored in (CW2) and relayed. In addition, any one follower node (X) converts the accumulated counterclockwise delay time (Lx_ccw1) obtained by accumulating the counterclockwise delay time (Dx_ccw1) of the first counterclockwise message (CCW1) to the second counterclockwise message (CCW2). ) can be stored and relayed.

Considering this delay time, Equations 1, 2, 3, and 4 are equivalent to Equations 5, 6, 7, and 8 below. Accordingly, the plurality of follower nodes B to I calculate the delay and offset of the clock of the leader node A according to Equations 5, 6, 7 and 8 below, and use the calculated delay and offset. Thus, the time of the watch of the leader node (A) and the time of the watch of the plurality of follower nodes (B to I) are synchronized.

In Equations 5, 6, 7 and 8, Ta_cw1 is the clockwise reference transmission time, Ra_ccw1 is the counterclockwise reference reception time, Rx_cw1 is the clockwise relay reception time, and Tx_ccw1 is the counterclockwise relay transmission time. Further, Ta_ccw1 is a counterclockwise reference transmission time, Ra_cw1 is a clockwise reference reception time, Rx_ccw1 is a counterclockwise relay reception time, and Tx_cw1 is a clockwise relay transmission time. And, D means delay and O means offset. These parameters are the same as Equations 1, 2, 3 and 4.

Meanwhile, Dx_cw1 added to Equations 5, 6, 7, and 8 is a clockwise delay time, and the clockwise delay time (Dx_cw1) is the delay of the first clockwise message (CW1) in any one follower node (X). indicates the time Dx_ccw1 is a counterclockwise delay time, and the counterclockwise delay time (Dx_ccw1) represents the delay time of the first counterclockwise message (CCW1) in any one follower node (X). In particular, Lx_cw1 is the clockwise cumulative delay time, and the clockwise cumulative delay time (Lx_cw1) represents the sum of the clockwise delay times (Dx_cw1) of the follower nodes existing between the leader node (A) and the follower node (X). In addition, Lx_ccw1 is the counterclockwise cumulative delay time, and the counterclockwise cumulative delay time (Lx_ccw1) is the sum of the counterclockwise delay times (Dx_ccw1) of the follower nodes existing between the leader node (A) and the follower node (X). indicates

Next, advantages of a synchronization method for transmitting messages in both directions including clockwise and counterclockwise directions according to an embodiment of the present invention will be described. 5 is a diagram for explaining the advantages of a synchronization method for transmitting messages in both directions including clockwise and counterclockwise directions according to an embodiment of the present invention.

As shown in (a) of FIG. 5, the plurality of follower nodes B to I relay the first clockwise message CW1 and the first counterclockwise message CCW1 while relaying the first clockwise message ( CW1) and the transmission and reception times of the first counterclockwise message (CCW1), that is, the clockwise relay transmission time (Tx_cw1), the clockwise relay reception time (Rx_cw1), the counterclockwise relay transmission time (Tx_ccw1) and the counterclockwise relay transmission time (Tx_ccw1). Measure clockwise relay reception time (Rx_ccw1).

In addition, as shown in (b), (c) and (d) of FIG. 5, the plurality of follower nodes (B to I) send a second clockwise message (CW2) and a second counterclockwise message (CCW2). Required time information, that is, clockwise reference transmission time (Ta_cw1), clockwise reference reception time (Ra_cw1), counterclockwise reference transmission time (Ta_ccw1), and counterclockwise reference reception time (Ra_ccw1) are received through .

At this time, each of the plurality of follower nodes (B to I) needs to use only one message received first among the second clockwise message (CW2) and the second counterclockwise message (CCW2) regardless of location. Accordingly, even if a message in one direction of the second clockwise message CW2 and the second counterclockwise message CCW2 transmitted in both directions is lost, a message in the other direction can be restored. Moreover, the leader node A may transmit only one of the second clockwise message CW2 and the second counterclockwise message CCW2. However, the first clockwise message (CW1) and the first counterclockwise message (CCW1) must not be lost.

Next, a failure recovery method using both directions including clockwise and counterclockwise directions according to an embodiment of the present invention will be described. 6 is a diagram for explaining a failure recovery method when a failure occurs in a connection between nodes according to an embodiment of the present invention and the two linear networks are divided. Also, FIG. 7 is a diagram for explaining a failure recovery method when one linear network is generated due to a failure of a follower node according to an embodiment of the present invention.

When a failure occurs in the ring network, the network of the ring topology becomes a linear network of two (FIG. 6) or one (FIG. 7), and the follower node that detects the failure sends a first clockwise message (CW1) or a first clockwise message (CW1). The first clockwise message (CW1) or the first counterclockwise message (CCW1) should be generated and transmitted in the opposite direction to when the counterclockwise message (CCW1) is received. Other operations of the leader node (A) and the plurality of follower nodes (B to I) are performed in the same way as before the failure. Accordingly, even when a failure occurs, the failure can be easily restored.

On the other hand, the method according to the embodiment of the present invention described above can be implemented in the form of a program readable through various computer means and recorded on a computer-readable recording medium. Here, the recording medium may include program commands, data files, data structures, etc. alone or in combination. Program instructions recorded on the recording medium may be those specially designed and configured for the present invention, or those known and usable to those skilled in computer software. For example, recording media include magnetic media such as hard disks, floppy disks and magnetic tapes, optical media such as CD-ROMs and DVDs, and magneto-optical media such as floptical disks ( magneto-optical media), and hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of the program command may include a high-level language that can be executed by a computer using an interpreter, as well as a machine language generated by a compiler. These hardware devices may be configured to act as one or more software modules to perform the operations of the present invention, and vice versa.

The present invention has been described above using several preferred examples, but these examples are illustrative and not limiting. As such, those skilled in the art to which the present invention belongs will understand that various changes and modifications can be made according to the doctrine of equivalents without departing from the spirit of the present invention and the scope of rights set forth in the appended claims.

A: Leader node
B to I: follower nodes

Claims (6)

A method for performing synchronization according to a precise time synchronization protocol in a ring topology network,
Clockwise reference transmission, which is the time at which the leader node transmits the first clockwise message while the leader node transmits the first clockwise message in the clockwise direction and the first counterclockwise message in the counterclockwise direction on the ring topology a first message transmission step of measuring time and a counterclockwise reference transmission time, which is the time at which the leader node transmits the first counterclockwise message;
While a plurality of follower nodes relay the first clockwise message in the clockwise direction, each of the plurality of follower nodes transmits the clockwise relay reception time, which is the time at which the first clockwise message is received, and the first clockwise message. A clockwise relay transmission time, which is one hour, is measured, and counterclockwise relay, which is a time when each of the plurality of follower nodes receives the first counterclockwise message while relaying the first counterclockwise message in the counterclockwise direction a first message relaying step of measuring a reception time and a counterclockwise relay transmission time, which is the time at which the first counterclockwise message is transmitted;
When the leader node receives the first clockwise message and the first counterclockwise message transmitted by the leader node, the clockwise reference reception time, which is the time at which the first clockwise message is received, and the first counterclockwise message A first message receiving step of measuring a counterclockwise reference reception time, which is the time at which the received time is received;
The leader node transmits a second clockwise message including the clockwise reference transmission time and the counterclockwise reference reception time in the clockwise direction, and the counterclockwise reference transmission time and the clockwise reference in the counterclockwise direction. a second message transmission step of transmitting a second counterclockwise message including a reception time;
The plurality of follower nodes relay the second clockwise message including the clockwise reference transmission time and the counterclockwise reference reception time in the clockwise direction, and the counterclockwise reference transmission time and the clockwise reference reception time. a second message relaying step of relaying the second counterclockwise message including time in the counterclockwise direction;
The plurality of follower nodes use the clockwise reference transmission time, the counterclockwise reference reception time, the clockwise relay reception time, and the counterclockwise relay transmission time, or the counterclockwise reference transmission time and the clockwise direction Performing synchronization using the reference reception time, the counterclockwise relay reception time, and the clockwise relay transmission time; including,
The second message relaying step
The plurality of follower nodes accumulate and add the delay time of the first clockwise message to the second clockwise message, and accumulate and add the delay time of the first counterclockwise message to the second counterclockwise message. do,
When all follower nodes have different delay times, when all follower nodes transmit a second message including the second clockwise message and the second counterclockwise message, the first clockwise message and the first Characterized in that it is delivered by including the delay time of the counterclockwise message
A method for performing synchronization. According to claim 1,
The step of performing the synchronization is
The plurality of follower nodes
series of equations
A = D + O = Rx_cw1 - Ta_cw1 = Rx_ccw1 - Ta_ccw1;
B = D - O = Ra_ccw1 - Tx_ccw1 = Ra_cw1 - Tx_cw1;
D = (A + B)/2 and
O = (A - B)/2
Calculate the delay and offset according to
Synchronization is performed according to the calculated delay and offset;
D means delay,
The O means an offset,
The Ta_cw1 is the clockwise reference transmission time,
The Ra_ccw1 is the counterclockwise reference reception time,
Rx_cw1 is the clockwise relay reception time;
The Tx_ccw1 is the counterclockwise relay transmission time,
The Ta_ccw1 is the counterclockwise reference transmission time,
The Ra_cw1 is the clockwise reference reception time,
The Rx_ccw1 is the counterclockwise relay reception time;
The Tx_cw1 is the clockwise relay transmission time, characterized in that
A method for performing synchronization. delete According to claim 1,
A first message including the first clockwise message and the first counterclockwise message
A message type field indicating that it is a first message; and
Message direction field indicating the direction in which the message is transmitted.
characterized in that it includes
A method for performing synchronization. According to claim 4,
A second message including the second clockwise message and the second counterclockwise message
a message type field indicating the second message;
A message direction field indicating the direction in which the corresponding message is transmitted;
a send time field indicating the time at which the leader node transmitted a previous message in the direction of the message;
a transmission time field indicating a time at which the leader node received the previous message in a direction opposite to that of the message;
A clockwise correction field indicating an accumulated delay time between a follower node and a leader node for the first clockwise message; and
A counterclockwise correction field representing the cumulative delay time between the follower node and the leader node for the first counterclockwise message.
characterized in that it includes
A method for performing synchronization. delete

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