WO2024189860A1

WO2024189860A1 - Transfer device, transfer method, and program

Info

Publication number: WO2024189860A1
Application number: PCT/JP2023/010181
Authority: WO
Inventors: 佳祐山形; 慎一吉原; 尊広久保; 隆中西
Original assignee: 日本電信電話株式会社
Priority date: 2023-03-15
Filing date: 2023-03-15
Publication date: 2024-09-19

Abstract

A transfer device (100) according to the present disclosure transmits a Pdelay_Req message to a higher-order device; receives a Pdelay_Resp message from the higher-order device; receives a Pdelay_Resp_Follow_Up message from the higher-order device; calculates an offset on the basis of a transmission time t1, a reception time t2, a transmission time t3, and a reception time t4; receives a Sync message from the higher-order device and transmits the Sync message to the lower-order device; calculates a time T1' of synchronization with the higher-order device as the time of transmission of the Sync message by the higher-order device, on the basis of a transmission time dt2; includes the time T1' in a Follow_Up message from the higher-order device and transmits the Follow_Up message to the lower-order device; receives a Delay_Req message from the lower-order device; calculates a time T4' of synchronization with the higher-order device as a reception time of the Delay_Req message, on the basis of a reception time dt3 and the offset; and transmits a Delay_Resp message including the time T4' to the lower-order device.

Description

Transfer device, transfer method, and program

This disclosure relates to a transfer device, a transfer method, and a program.

The Precision Time Protocol (PTP) defined in the IEEE-1588 standard is a protocol that synchronizes the time (internal device time) of computers on a Local Area Network (LAN) with high precision (see Non-Patent Document 1). Figures 4A and 4B show an example configuration of a time synchronization system 10A that uses PTP to synchronize the time of devices on a network.

As shown in Figures 4A and 4B, the time synchronization system 10A includes a Grand Master Clock 1 and a Client device 2.

The Grand Master Clock 1 is equipped with a GNSS antenna 1a that receives signals (GNSS signals) from satellites of the Global Navigation Satellite System (GNSS), such as the Global Positioning System (GPS). The Grand Master Clock 1 receives the GNSS signals via the GNSS antenna 1a and acquires Universal Time Coordinated (UTC) from the received GNSS signals. The Grand Master Clock 1 has a master function that distributes the acquired UTC as the reference time via the network.

The client device 2 has a slave function that synchronizes the internal time of the device with the time distributed from a device with a master function. The client device 2 is a device used by a user, such as a base station device in a mobile phone network.

When synchronizing the Grand Master Clock 1, which serves as the time source, with the Client device 2 used by the user, a relay device that relays signals may be installed between the Grand Master Clock 1 and the Client device 2 depending on the distance between the Grand Master Clock 1 and the Client device 2 and the number of Client devices 2 that are synchronized with the Grand Master Clock 1. Relay devices that can be used with PTP include the Boundary Clock 3 shown in Figure 4A and the Transparent Clock 4 shown in Figure 4B.

The Boundary Clock 3 shown in FIG. 4A functions as a device with a slave function for synchronizing its own internal time with the time distributed from a higher-level device with a master function, and functions as a device with a master function for a lower-level device with a slave function. In the time synchronization system 10A shown in FIG. 4A, the Boundary Clock 3 functions as a device with a slave function for the Grand Master Clock 1, and functions as a device with a master function for the Client device 2. Specifically, the Boundary Clock 3 measures the offset, which is the difference between the internal time of the higher-level device, Grand Master Clock 1, and the internal time of its own device (the difference between the internal time of the device with the master function and the internal time of the device with the slave function), by sending and receiving PTP packets with the Grand Master Clock 1, and synchronizes the internal time of its own device with the time distributed from the Grand Master Clock 1 (reference time) based on the measured offset. In addition, the Boundary Clock 3 synchronizes the internal time of the Client device 2 with the internal time of its own device by sending and receiving PTP packets with the Client device 2.

The Transparent Clock 4 shown in Figure 4B transfers PTP packets received from the higher-level device, Grand Master Clock 1, to the lower-level device, Client device 3, and transfers PTP packets received from the lower-level device, Client device 3, to the higher-level device, Grand Master Clock 1. Here, Transparent Clock 4 measures the time it takes for a PTP packet to pass through its own device, and writes the result into the PTP packet while transferring it. In this way, the internal time of Client device 2 can be synchronized with the internal time of Grand Master Clock 1.

In PTP, different formats, called profiles, are specified for each field of use, which contain different required parameters and time information formats, and time synchronization is not possible between different profiles. One of the reasons time synchronization is not possible between different profiles is the difference in the delay measurement method.

There are two methods for measuring delay for Transparent Clock 4 shown in Figure 4B: the End to End method and the Peer to Peer method. Because these methods use different messages, time synchronization cannot be achieved between a device using the End to End method and a device using the Peer to Peer method by simply forwarding a message from one device to the other. If time synchronization is not possible between devices with different profiles, it would be necessary to build a separate time distribution network for each profile, resulting in high costs.

The purpose of this disclosure, made in consideration of the above problems, is to provide a transfer device, a transfer method, and a program that can enable time synchronization between devices using different profiles, in particular between a higher-level device that performs time synchronization by sending and receiving messages using a Peer-to-Peer method, and a lower-level device that performs time synchronization by sending and receiving messages using an End-to-End method.

In order to solve the above problem, a transfer device according to the present disclosure is a transfer device that transfers messages between a higher-level device that performs time synchronization by transmitting and receiving messages in a Peer to Peer manner and a lower-level device that performs time synchronization by transmitting and receiving messages in an End to End manner,
a first message processor that transmits a Pdelay_Req message to the higher-level device and acquires a transmission time t1 of the Pdelay_Req message; a second message processor that receives a Pdelay_Resp message transmitted from the higher-level device and acquires a reception time t2 of the Pdelay_Req message by the higher-level device contained in the Pdelay_Resp message and acquires a reception time t4 of the Pdelay_Resp message; a third message processor that receives a Pdelay_Resp_Follow_Up message transmitted from the higher-level device and acquires a transmission time t3 of the Pdelay_Resp message by the higher-level device contained in the Pdelay_Resp_Follow_Up message; an offset calculator that calculates an offset that is a difference between the device internal time of the higher-level device and the device internal time of the transfer device based on the transmission time t1, the reception time t2, the transmission time t3, and the reception time t4; the Sync message is transmitted to the lower device and the transmission time dt3 of the Delay_Req message is obtained; a fourth message processing unit that transmits the Sync message to a lower device and obtains the transmission time dt2 of the Sync message by the transfer device; a first synchronization time calculation unit that calculates a time T1' synchronized with the upper device as the transmission time of the Sync message by the upper device based on the transmission time dt2; a fifth message processing unit that receives a Follow_Up message transmitted from the upper device, changes the transmission time T1 of the Sync message by the upper device contained in the Follow_Up message to the time T1', and transmits the message to the lower device; a sixth message processing unit that receives a Delay_Req message transmitted from the lower device and obtains the reception time dt3 of the Delay_Req message; a second synchronization time calculation unit that calculates a time T4' synchronized with the upper device as the reception time of the Delay_Req message based on the offset and the reception time dt3; and a seventh message processing unit that transmits a Delay_Resp message including the time T4' to the lower device.

In addition, in order to solve the above problem, the transfer method disclosed herein is a transfer method by a transfer device that transfers messages between a higher-level device that performs time synchronization by transmitting and receiving messages in a Peer to Peer manner and a lower-level device that performs time synchronization by transmitting and receiving messages in an End to End manner, and includes the steps of: transmitting a Pdelay_Req message to the higher-level device and acquiring a transmission time t1 of the Pdelay_Req message; receiving a Pdelay_Resp message transmitted from the higher-level device and acquiring a reception time t2 of the Pdelay_Req message by the higher-level device, which is included in the Pdelay_Resp message, and acquiring a reception time t4 of the Pdelay_Resp message; receiving a Pdelay_Resp_Follow_Up message transmitted from the higher-level device and acquiring a transmission time t3 of the Pdelay_Resp message by the higher-level device, which is included in the Pdelay_Resp_Follow_Up message; The method includes the steps of: calculating an offset, which is the difference between the internal time of the upper device and the internal time of the transfer device; receiving a Sync message transmitted from the upper device and transmitting it to the lower device, and acquiring a transmission time dt2 of the Sync message by the transfer device; calculating a time T1' synchronized with the upper device as the transmission time of the Sync message by the upper device based on the transmission time dt2; receiving a Follow_Up message transmitted from the upper device, changing the transmission time T1 of the Sync message by the upper device contained in the Follow_Up message to the time T1', and transmitting it to the lower device; receiving a Delay_Req message transmitted from the lower device, and acquiring a reception time dt3 of the Delay_Req message; calculating a time T4' synchronized with the upper device as the reception time of the Delay_Req message based on the offset and the reception time dt3; and transmitting a Delay_Resp message including the time T4' to the lower device.

In addition, to solve the above problem, the program disclosed herein causes a computer to operate as the above-mentioned transfer device.

The transfer device, transfer method, and program disclosed herein enable time synchronization between devices using different profiles, in particular between a higher-level device that performs time synchronization by sending and receiving messages using a Peer-to-Peer method, and a lower-level device that performs time synchronization by sending and receiving messages using an End-to-End method.

FIG. 2 is a diagram illustrating a configuration example of a transfer device according to an embodiment of the present disclosure. 2 is a sequence diagram illustrating an example of an operation of the transfer device illustrated in FIG. 1 . 2 is a sequence diagram illustrating an example of a hardware configuration of the transfer device illustrated in FIG. 1 . FIG. 1 illustrates an example of a time synchronization system. FIG. 11 illustrates another example of a time synchronization system. This is a sequence diagram showing an example of the operation of a Transparent Clock when the End to End method is used. This is a sequence diagram showing an example of the operation of a Transparent Clock when the Peer to Peer method is used.

The following describes an embodiment of the present disclosure with reference to the drawings.

First, for comparison, we will explain the operation of Transparent Clock 4 shown in Figure 4B.

Figure 5 is a sequence diagram showing an example of the operation of Transparent Clock 4 when a Master device and a Client device perform time synchronization by sending and receiving messages using the End to End method. The Master device is a device with a Master function, such as Grand Master Clock 1 shown in Figure 4B, and the Client device is Client device 2 such as a wireless base station shown in Figure 4B. There are two methods for distributing time in PTP: the two-step method and the one-step method. Figure 5 explains the case where the two-step method is used.

At time T1, the Master device sends a Sync message to Transparent Clock 4 (step S101). Messages sent and received between devices in PTP include a field called correctionField (CF), which contains a correction value used for time correction (for example, a value obtained by adding the time it takes for a frame to pass through the device). The Master device sets the CF of the Sync message to 0.

When Transparent Clock 4 receives the Sync message at time dt1, it transmits the received Sync message to the Client device at time dt2 (step S102). Transparent Clock 4 leaves the CF of the Sync message at 0. Transparent Clock 4 also stores the reception time dt1 of the Sync message from the Master device and the transmission time dt2 of the Sync message to the Client device.

The client device receives the Sync message sent from Transparent Clock 4 at time T2. The client device stores the time T2 when the Sync message was received.

After sending the Sync message, the Master device sends a Follow_Up message to Transparent Clock 4 (step S103). The Master device includes the sending time T1 of the Sync message in the Follow_Up message. The Master device also sets CF of the Follow_Up message to 0.

When Transparent Clock 4 receives the Follow_Up message, it transmits the received Follow_Up message to the Client device (step S104). Transparent Clock 4 sets the CF of the Follow_Up message to the processing time of the Sync message at Transparent Clock 4 (= dt2 - dt1).

When the client device receives the Sync message and the Follow_Up message, it transmits a Delay_Req message to Transparent Clock 4 at time T3 (step S105). The client device includes the transmission time T3 of the Delay_Req message in the Delay_Req message. The client device also sets CF of the Delay_Req message to 0.

When Transparent Clock 4 receives the Delay_Req message at time dt3, it transmits the received Delay_Req message to the Master device at time dt4 (step S106). Transparent Clock 4 leaves the CF of the Delay_Req message at 0. Transparent Clock 4 also stores the reception time dt3 of the Delay_Req message from the Client device and the transmission time dt4 of the Delay_Req message to the Master device.

At time T4, the Master device receives the Delay_Req message sent from Transparent Clock 4. The Master device stores the time T4 at which the Delay_Req message was received.

When the master device receives the Delay_Req message, it sends a Delay_Resp message to Transparent Clock 4 (step S107). The master device includes the reception time T4 of the Delay_Req message in the Delay_Resp message. In addition, the client device sets CF of the Delay_Resp message to 0.

When Transparent Clock 4 receives the Delay_Resp message, it transfers the received Delay_Resp message to the Client device (step S108). Transparent Clock 4 sets the processing time of the Delay_Req message at Transparent Clock 4 (= dt4 - dt3) to the CF of the Delay_Resp message.

The client device calculates an offset, which is the difference between the device time of the Master device and the device time of the Client device, using the following formula (1) based on the time T1 when the Sync message was sent by the Master device, the time T2 when the Sync message was received by the Client device, the time T3 when the Delay_Req message was sent by the Client device, the time T4 when the Delay_Req message was received by the Master device, which is included in the Delay_Resp message, the processing time of the Sync message in Transparent Clock 4 set in the CF of the Follow_Up message (= dt2 - dt1), and the processing time of the Delay_Req message in Transparent Clock 4 set in the CF of the Delay_Resp message (= dt4 - dt3).
Offset = ((T2-T1-(dt2-dt1))-(T4-T3-(dt4-dt3)))/2 Formula (1)

The client device can synchronize its internal time with the internal time of the master device by correcting the internal time based on the calculated offset.

In Figure 5, the case where the two-step method is used is explained, but in the case of the one-step method, the Follow_Up message is not used. In this case, the transmission time T1 of the Sync message and the processing time of the Sync message at Transparent Clock 4 (= dt2 - dt1) contained in the Follow_Up message can be included in the Sync message.

Figure 6 is a sequence diagram showing an example of the operation of Transparent Clock 4 when a Master device and a Client device perform time synchronization by sending and receiving messages using the Peer to Peer method. Figure 6 explains the case where the two-step method is used.

Transparent Clock 4 transmits a Pdelay_Req message to the Master device at time t1 (step S201). Transparent Clock 4 sets CF of the Pdelay_Req message to 0. Transparent Clock 4 also stores the transmission time t1 of the Pdelay_Req message to the Master device.

The master device receives the Pdelay_Req message at time t2. The master device stores the time t2 when it received the Pdelay_Req message from Transparent Clock 4.

When the master device receives the Pdelay_Req message, it transmits a Pdelay_Resp message to Transparent Clock 4 at time t3 (step S202). The master device includes the reception time t2 of the Pdelay_Req message in the Pdelay_Resp message. The master device also sets the CF of the Pdelay_Resp message to 0. The master device also stores the transmission time t3 of the Pdelay_Resp message to Transparent Clock 4.

After sending the Pdelay_Resp message, the master device sends a Pdelay_Resp_Follow_Up message to Transparent Clock 4 (step S203). The master device includes the sending time t3 of the Pdelay_Resp message to Transparent Clock 4 in the Pdelay_Resp_Follow_Up message. The master device also sets CF of the Pdelay_Resp_Follow_Up message to 0.

The Transparent Clock 4 receives the Pdelay_Resp message at time t4. The Transparent Clock 4 stores the reception time t4 of the Pdelay_Resp message from the Master device. The Transparent Clock 4 also receives the Pdelay_Resp_Follow_Up message. The Transparent Clock 4 calculates the transmission delay time pt1 between the Master device and the Transparent Clock 4 using the following formula (2) based on the transmission time t1 of the Pdelay_Req message by the Transparent Clock 4, the reception time t2 of the Pdelay_Req message by the Master device, which is included in the Pdelay_Resp message, the transmission time t3 of the Pdelay_Resp message by the Master device, which is included in the Pdelay_Resp_Follow_Up message, and the reception time t4 of the Pdelay_Resp message by the Transparent Clock 4.
pt1 = ((t2-t1) + (t4-t3))/2 Equation (2)

At time t5, the client device transmits a Pdelay_Req message to Transparent Clock 4 (step S204). The client device sets CF of the Pdelay_Req message to 0. The client device also stores the transmission time t5 of the Pdelay_Req message to Transparent Clock 4.

Transparent Clock 4 receives the Pdelay_Req message at time t6. Transparent Clock 4 stores the time t6 when the Pdelay_Req message was received from the Client device.

When Transparent Clock 4 receives the Pdelay_Req message, it transmits a Pdelay_Resp message to the Client device at time t7 (step S205). Transparent Clock 4 includes the reception time t6 of the Pdelay_Req message from the Client device in the Pdelay_Resp message. Transparent Clock 4 also sets CF of the Pdelay_Resp message to 0. Transparent Clock 4 also stores the transmission time t7 of the Pdelay_Resp message to the Client device.

After transmitting the Pdelay_Resp message, Transparent Clock 4 transmits a Pdelay_Resp_Follow_Up message to the Client device (step S206). Transparent Clock 4 includes in the Pdelay_Resp_Follow_Up message the transmission time t7 of the Pdelay_Resp message to the Client device. Transparent Clock 4 also sets CF of the Pdelay_Resp_Follow_Up message to 0.

The client device receives the Pdelay_Resp message at time t8. The client device stores the reception time t8 of the Pdelay_Resp message from Transparent Clock 4. The client device also receives the Pdelay_Resp_Follow_Up message. The client device calculates the transmission delay time pt2 between Transparent Clock 4 and the client device using the following formula (3) based on the transmission time t5 of the Pdelay_Req message by the client device, the reception time t6 of the Pdelay_Req message by Transparent Clock 4 which is included in the Pdelay_Resp message, the transmission time t7 of the Pdelay_Resp message by Transparent Clock 4 which is included in the Pdelay_Resp_Follow_Up message, and the reception time t8 of the Pdelay_Resp message by the client device.
pt2=((t6-t5)+(t8-t7))/2 Formula (3)

After the transmission delay times pt1 and pt2 are calculated, the Master device sends a Sync message to Transparent Clock 4 at time T1 (step S207). The Master device sets CF of the Sync message to 0.

When Transparent Clock 4 receives the Sync message at time dt1, it transmits the received Sync message to the Client device at time dt2 (step S208). Transparent Clock 4 leaves the CF of the Sync message at 0. Transparent Clock 4 also stores the reception time dt1 of the Sync message from the Master device and the transmission time dt2 of the Sync message to the Client device.

At time T2, the client device receives the Sync message sent from Transparent Clock 4.

After sending the Sync message, the Master device sends a Follow_Up message to Transparent Clock 4 (step S209). The Master device includes in the Follow_Up message the sending time T1 of the Sync message to Transparent Clock 4. The Master device also sets CF of the Follow_Up message to 0.

When Transparent Clock 4 receives the Follow_Up message, it transmits the received Follow_Up message to the Client device (step S210). Transparent Clock 4 sets the CF of the Follow_Up message to a value obtained by adding the transmission delay time pt1 between the Master device and Transparent Clock 4 and the processing time of the Sync message in Transparent Clock 4 (=pt1 + (dt2 - dt1)).

The client device calculates the reception time T2 of the Sync message at the client device using the following equation (4) based on the transmission time T1 of the Sync message by the Master device, which is included in the Follow_Up message, the transmission delay time pt2 between the Transparent Clock 4 and the client device, and the transmission delay time pt1 between the Master device and the Transparent Clock 4, which is set in the CF of the Follow_Up message, plus the processing time of the Sync message at the Transparent Clock 4 (=pt1 + (dt2 - dt1)).
T2=T1+pt1+(dt2-dt1)+pt2 Formula (4)

The client device synchronizes its internal time with the calculated reception time T2 of the Sync message. This allows the client device's internal time to be synchronized with the master device's internal time.

Note that while Figure 6 illustrates the case where the two-step method is used, the Follow_Up message and the Pdelay_Resp_Follow_Up message are not used in the case of the one-step method. In this case, the transmission time T1 of the Sync message by the Master device, which was included in the Follow_Up message, can be included in the Sync message. The CF of the Sync message can be set to the sum (pt1+(dt2-dt1)) of the transmission delay time pt1 between the Master device and Transparent Clock 4 and the processing time of the Sync message in Transparent Clock 4 (dt2-dt1). The transmission time t3 of the Pdelay_Resp message by the Master device and the transmission time t7 of the Pdelay_Resp message by Transparent Clock 4, which were included in the Pdelay_Resp_Follow_Up message, can be set in the CF of the Pdelay_Resp message.

Next, the transfer device 100 according to this embodiment will be described. As shown in FIG. 1, the transfer device 100 according to this embodiment transfers messages between a Grand Master Clock 1 (higher-level device) which is a master device, and a Client device 2 (lower-level device) in a time synchronization system 10 in which the two perform time synchronization. In this embodiment, the Grand Master Clock 1 performs time synchronization by sending and receiving messages using the Peer to Peer method, and the Client device 2 performs time synchronization by sending and receiving messages using the End to End method. Thus, the transfer device 100 transfers messages between a higher-level device which performs time synchronization by sending and receiving messages using the Peer to Peer method, and a lower-level device which performs time synchronization by sending and receiving messages using the End to End method.

First, the operation of the transfer device 100 according to this embodiment will be described.

FIG. 2 is a sequence diagram showing an example of the operation of the transfer device 100 according to this embodiment, and is a diagram for explaining the transfer method by the transfer device 100.

As described above, the transfer device 100 according to this embodiment transfers messages between a Master device (Grand Master Clock 1) that performs time synchronization by sending and receiving messages using the Peer to Peer method, and a Client device (Client device 2) that performs time synchronization by sending and receiving messages using the End to End method. As described above, there are two methods for distributing time in PTP: the two-step method and the one-step method. Figure 2 describes the case where the two-step method is used.

At time t1, the transfer device 100 transmits a Pdelay_Req message to the master device (step S301). The transfer device 100 sets the CF of the Pdelay_Req message to 0. In addition, the Transparent Clock 4 stores the transmission time t1 of the Pdelay_Req message to the master device.

The master device receives the Pdelay_Req message at time t2. The master device stores the time t2 at which the Pdelay_Req message was received from the transfer device 100.

When the master device receives the Pdelay_Req message, it transmits a Pdelay_Resp message to the transfer device 100 at time t3 (step S302). The master device includes the reception time t2 of the Pdelay_Req message from the transfer device 100 in the Pdelay_Resp message. The master device also sets the CF of the Pdelay_Resp message to 0. The master device also stores the transmission time t3 of the Pdelay_Resp message to the transfer device 100.

After sending the Pdelay_Resp message, the master device sends a Pdelay_Resp_Follow_Up message to the transfer device 100 (step S303). The master device includes in the Pdelay_Resp_Follow_Up message the sending time t3 of the Pdelay_Resp message to the transfer device 100. The master device also sets the CF of the Pdelay_Resp_Follow_Up message to 0.

The transfer device 100 receives a Pdelay_Resp message at time t4. The Transparent Clock 4 stores the reception time t4 of the Pdelay_Resp message from the master device. The transfer device 100 also receives a Pdelay_Resp_Follow_Up message. The transfer device 100 calculates an offset X, which is the difference between the device time of the master device and the device time of the transfer device 100, using the following formula (5) based on the transmission time t1 of the Pdelay_Req message by the transfer device 100, the reception time t2 of the Pdelay_Req message by the master device, which is included in the Pdelay_Resp message, the transmission time t3 of the Pdelay_Resp message by the master device, which is included in the Pdelay_Resp_Follow_Up message, and the reception time t4 of the Pdelay_Resp message by the transfer device 100.
Offset X = ((t2-t1)-(t4-t3))/2 Equation (5)

At time T1, the master device transmits a Sync message to the transfer device 100 (step S304). The master device sets the CF of the Sync message to 0.

When the transfer device 100 receives the Sync message at time dt1, it transmits the received Sync message to the Client device at time dt2 (step S305).

After sending the Sync message, the master device sends a Follow_Up message to the transfer device 100 (step S306). The master device includes in the Follow_Up message the sending time T1 of the Sync message to the transfer device 100. The master device also sets CF of the Follow_Up message to 0.

When the transfer device 100 receives the Follow_Up message, it transmits the received Follow_Up message to the client device (step S307). The transfer device 100 calculates time T1' synchronized with the master device as the transmission time of the Sync message by the master device. Specifically, the transfer device 100 calculates time T1' by the following formula (6) or formula (7).
T1'=T1+pt1+(dt2-dt1) Formula (6)
T1'=dt2+offsetX Equation (7)

The transfer device 100 sets the calculated time T1' to the CF of the Follow_Up message. In FIG. 6, Transparent Clock 4 sets the CF of the Follow_Up message to a value obtained by adding the transmission delay time pt1 between the Master device and Transparent Clock 4 and the processing time of the Sync message at Transparent Clock 4 (=pt1 + (dt2 - dt1)). On the other hand, in this embodiment, the transfer device 100 sets the CF of the Follow_Up message to 0.

The client device receives the Sync message at time T2. The client device stores the time T2 at which the Sync message was received from the transfer device 100. The client device also receives a Follow_Up message.

When the client device receives the Sync message and the Follow_Up message, it transmits a Delay_Req message to the transfer device 100 at time T3 (step S308). The client device includes in the Delay_Req message the transmission time T3 of the Delay_Req message to the transfer device 100. The client device also sets CF of the Delay_Req message to 0.

The transfer device 100 receives the Delay_Req message at time dt3. In FIG. 6, Transparent Clock 4 forwards the received Delay_Req message to the Master device. On the other hand, in this embodiment, the transfer device 100 terminates the Delay_Req message without forwarding it.

The transfer device 100 calculates the time T4' synchronized with the master device as the reception time of the Delay_Req message. Specifically, the transfer device 100 calculates the time T4' by the following formula (8).
T4' = dt3 + offset X Equation (8)

The transfer device 100 transmits a Delay_Resp message to the Client device (step S309). The transfer device 100 includes the calculated time T4' in the Delay_Resp message. The transfer device 100 also sets CF of the Delay_Resp message to 0.

Based on the time T1' included in the Follow_Up message, the time T4' included in the Delay_Resp message, the time T2 at which the client device receives the Sync message, and the time T3 at which the client device sends the Delay_Req message, the client device calculates an offset Y, which is the difference between the client device's internal time and the transfer device 100's internal time, using the following equation (9):
Offset Y = ((T2-T1')-(T4'-T3))/2 Equation (9)

The client device synchronizes its own internal time with the internal time of the transfer device 100 (i.e., the internal time of the master device) based on the calculated offset Y.

In Figure 2, the case where the two-step method is used is explained, but in the case of the one-step method, the Pdelay_Resp_Follow_Up message and the Follow_Up message are not used. In this case, the transmission time t3 of the Pdelay_Resp message by the Master device, which was included in the Pdelay_Resp_Follow_Up message, can be included in the Pdelay_Resp message. Also, the time T1' included in the Follow_Up message can be included in the Sync message.

By performing the above-described processing, the transfer method using the transfer device 100 according to this embodiment virtually transmits and receives messages between the transfer device 100 and a client device using the End to End method, thereby enabling time synchronization between devices using different profiles, in particular between a higher-level device using Peer to Peer and a lower-level device using End to End.

Next, the configuration of the transfer device 100 according to this embodiment will be described with reference to FIG. 1. Note that FIG. 1 shows an example in which the higher-level device is Grand Master Clock 1 and the lower-level device is Client device 2, but the present disclosure is not limited to this. The higher-level device may be a device with a master function, and the lower-level device may be a device with a slave function. Thus, for example, the higher-level device and the lower-level device may be Boundary Clock 3.

As shown in FIG. 1, the transfer device 100 according to this embodiment includes packet transmission/

reception units

101, 102, a Pdelay_Req message processing unit 103, a Pdelay_Resp message processing unit 104, a Pdelay_Resp_Follow_Up message processing unit 105, an offset calculation unit 106, a Sync message processing unit 107, synchronization

time calculation units

108, 111, a Follow_Up message processing unit 109, a Delay_Req message processing unit 110, a Delay_Resp message processing unit 112, and a CF processing unit 113.

The packet transmission/reception unit 101 transmits and receives PTP packets (messages) with the Grand Master Clock 1, which is a higher-level device. The packet transmission/reception unit 102 transmits and receives PTP packets (messages) with the Client device 2, which is a lower-level device.

The Pdelay_Req message processing unit 103, which serves as the first message processing unit, transmits the Pdelay_Req message to the Grand Master Clock 1 via the packet transmitting/receiving unit 101. The Pdelay_Req message processing unit 103 also obtains the transmission time t1 of the Pdelay_Req message by the transfer device 100, and outputs this to the offset calculation unit 106.

The Pdelay_Resp message processing unit 104, acting as the second message processing unit, receives the Pdelay_Resp message transmitted from Grand Master Clock 1 via the packet transmitting/receiving unit 101, and acquires the reception time t2 of the Pdelay_Req message by Grand Master Clock 1, which is included in the Pdelay_Resp message. The Pdelay_Resp message processing unit 104 also acquires the reception time t4 of the Pdelay_Resp message by the transfer device 100. The Pdelay_Resp message processing unit 104 outputs the acquired reception time t2 of the Pdelay_Req message by Grand Master Clock 1 and the reception time t4 of the Pdelay_Resp message by the transfer device 100 to the offset calculation unit 106.

The Pdelay_Resp_Follow_Up message processing unit 105, which serves as the third message processing unit, receives the Pdelay_Resp_Follow_Up message transmitted from Grand Master Clock 1 via the packet transmitting/receiving unit 101, and acquires the transmission time t3 of the Pdelay_Resp message by Grand Master Clock 1, which is included in the Pdelay_Resp_Follow_Up message. The Pdelay_Resp_Follow_Up message processing unit 105 outputs the acquired transmission time t3 of the Pdelay_Resp message by Grand Master Clock 1 to the offset calculation unit 106.

The offset calculation unit 106 calculates the offset X, which is the difference between the device time of Grand Master Clock 1 and the device time of transfer device 100, using the above-mentioned formula (5) based on the transmission time t1 of the Pdelay_Req message by transfer device 100, the reception time t2 of the Pdelay_Req message by Grand Master Clock 1, the transmission time t3 of the Pdelay_Resp message by Grand Master Clock 1, and the reception time t4 of the Pdelay_Resp message by transfer device 100. The offset calculation unit 106 outputs the calculation result of offset X to the synchronization time calculation unit 111. Furthermore, when offset X is used in the calculation of time T1' described later, the offset calculation unit 106 outputs the calculation result of offset X to the synchronization time calculation unit 108.

The Sync message processing unit 107, which serves as the fourth message processing unit, receives the Sync message transmitted from the Grand Master Clock 1 via the packet transmission/reception unit 101. The Sync message processing unit 107 outputs the received Sync message to the CF processing unit 113. As described below, the Sync message output to the CF processing unit 113 has CF set to 0 and is transmitted to the Client device 2 via the packet transmission/reception unit 102. Therefore, the Sync message processing unit 107 receives the Sync message transmitted from the Grand Master Clock 1 and transmits it to the Client device 2, which is a lower-level device, via the CF processing unit 113 and the packet transmission/reception unit 102. The Sync message processing unit 107 also obtains the transmission time dt2 of the Sync message by the transfer device 100, and outputs it to the synchronization time calculation unit 108.

The synchronization time calculation unit 108, which serves as the first synchronization time calculation unit, calculates the time T1' synchronized with Grand Master Clock 1 as the transmission time of the Sync message by Grand Master Clock 1 based on the transmission time dt2 of the Sync message by the transfer device 100 output from the Sync message processing unit 107.

The synchronization time calculation unit 108 may calculate the time T1', for example, using the above-mentioned formula (6). That is, the synchronization time calculation unit 108 may calculate the time T1' by adding the transmission time dt2 of the Sync message by the transfer device 100, the transmission delay time pt1 between the Grand Master Clock 1 and the transfer device 100, and the processing time of the Sync message in the transfer device 100 (i.e., the difference between the transmission time dt2 of the Sync message by the transfer device 100 and the reception time dt1 of the Sync message by the transfer device 100). In this case, the synchronization time calculation unit 108 can calculate the transmission delay time pt1 using the above-mentioned formula (2) based on the time t1 when the Pdelay_Req message is sent by the transfer device 100, the time t2 when the Pdelay_Req message is received by Grand Master Clock 1, the time t3 when the Pdelay_Resp message is sent by Grand Master Clock 1, and the time t4 when the Pdelay_Resp message is received by the transfer device 100.

The synchronization time calculation unit 108 may also calculate the time T1' using, for example, the above-mentioned formula (7). That is, the synchronization time calculation unit 108 may calculate the time T1' by adding the transmission time dt2 of the Sync message by the transfer device 100 and the offset X.

The synchronization time calculation unit 108 outputs the calculated time T1' to the Follow_Up message processing unit 109.

The Follow_Up message processing unit 109, which serves as the fifth message processing unit, receives the Follow_Up message transmitted from Grand Master Clock 1 via the packet transmission/reception unit 101. The Follow_Up message processing unit 109 changes the transmission time T1 of the Sync message by Grand Master Clock 1, which is included in the received Follow_Up message, to time T1', and outputs the message to the CF processing unit 113. The Sync message output to the CF processing unit 113 has CF set to 0 by the CF processing unit 113, and is transmitted to the Client device 2 via the packet transmission/reception unit 102. Therefore, the Follow_Up message processing unit 109 receives the Follow_Up message transmitted from Grand Master Clock 1, changes the transmission time T1 of the Sync message by Grand Master Clock 1, which is included in the Follow_Up message, to time T1', and transmits the message to the Client device 2.

The Delay_Req message processing unit 110, which serves as the sixth message processing unit, receives the Delay_Req message sent from the Client device 2 via the packet transmitting/receiving unit 102. The Delay_Req message processing unit 110 acquires the reception time dt3 of the Delay_Req message and outputs it to the synchronization time calculation unit 111.

The synchronization time calculation unit 111, which serves as the second synchronization time calculation unit, calculates time T4' synchronized with Grand Master Clock 1 as the reception time of the Delay_Req message using the above-mentioned formula (8) based on the offset X calculated by the offset calculation unit 106 and the reception time dt3 of the Delay_Req message by the transfer device 100 output from the Delay_Req message processing unit 110. The synchronization time calculation unit 111 outputs the calculation result of time T4' to the Delay_Resp message processing unit 112.

The Delay_Resp message processing unit 112, which serves as the seventh message processing unit, outputs a Delay_Resp message including the time T4' calculated by the synchronization time calculation unit 111 to the CF processing unit 113. The Delay_Resp message output to the CF processing unit 113 has CF set to 0 by the CF processing unit 113, and is transmitted to the Client device 2 via the packet transmission/reception unit 102. Therefore, the Delay_Resp message processing unit 112 transmits a Delay_Resp message including the time T4' to the Client device 2, which is a lower-level device.

As described above, each message sent and received for time synchronization includes a CF in which a value used for time correction is set. The CF processing unit 113 sets the CF included in each message to 0. In this embodiment, the CF processing unit 113 sets the CF of the Sync message, Follow_Up message, and Delay_Resp message to 0.

As explained with reference to Figure 5, the CF of the Delay_Resp message sent from Transparent Clock 4 to the Client device is set to the processing time of the Delay_Req message at Transparent Clock 4 (= dt4 - dt3). Also, as explained with reference to Figure 6, the CF of the Sync message sent from Transparent Clock 4 to the Client device is set to 0, and the CF of the Follow_Up message sent from Transparent Clock 4 to the Client device is set to the sum of the transmission delay time pt1 between the Master device and Transparent Clock 4 and the processing time of the Sync message at Transparent Clock 4 (= pt1 + (dt2 - dt1)).

On the other hand, in this embodiment, the information set in the CF of the above-mentioned message is unnecessary due to the processing described with reference to FIG. 2. The CF processing unit 113 sets the CF of the message to 0, thereby preventing the transmission of information unnecessary for processing in the client device 2.

With the above-described configuration, the transfer device 100 according to this embodiment can virtually send and receive messages between the transfer device 100 and a client device using the End to End method, thereby enabling time synchronization between devices using different profiles, in particular between a higher-level device using Peer to Peer and a lower-level device using End to End.

Next, we will explain the hardware configuration of the transfer device 100 according to this embodiment.

FIG. 3 is a diagram showing an example of the hardware configuration of the transfer device 100 according to this embodiment. FIG. 3 shows an example of the hardware configuration of the transfer device 100 when the transfer device 100 is configured by a computer capable of executing program instructions. Here, the computer may be a general-purpose computer, a dedicated computer, a workstation, a PC (Personal computer), an electronic notepad, etc. The program instructions may be program code, code segments, etc. for performing the required tasks.

As shown in FIG. 3, the transfer device 100 has a processor 201, a ROM (Read Only Memory) 202, a RAM (Random Access Memory) 203, storage 204, an input unit 205, a display unit 206, and a communication interface (I/F) 207. Each component is connected to each other via a bus 209 so that they can communicate with each other. The processor 201 is specifically a CPU (Central Processing Unit), MPU (Micro Processing Unit), GPU (Graphics Processing Unit), DSP (Digital Signal Processor), SoC (System on a Chip), etc., and may be composed of multiple processors of the same or different types.

Processor 201 is a control unit that controls each component and executes various types of arithmetic processing. That is, processor 201 reads a program from ROM 202 or storage 204, and executes the program using RAM 203 as a working area. Processor 201 controls each of the above components and executes various types of arithmetic processing according to the program stored in ROM 202 or storage 204. In this embodiment, ROM 202 or storage 204 stores a program for operating a computer as transfer device 100 according to the present disclosure. When the program is read and executed by the processor 201, each component of the transfer device 100, such as the Pdelay_Req message processing unit 103, the Pdelay_Resp message processing unit 104, the Pdelay_Resp_Follow_Up message processing unit 105, the offset calculation unit 106, the Sync message processing unit 107, the synchronization

time calculation units

108 and 111, the Follow_Up message processing unit 109, the Delay_Req message processing unit 110, the Delay_Resp message processing unit 112, and the CF processing unit 113, are realized.

The program may be provided in a form stored on a non-transitory storage medium such as a CD-ROM (Compact Disk Read Only Memory), a DVD-ROM (Digital Versatile Disk Read Only Memory), or a USB (Universal Serial Bus) memory. The program may also be provided via a network.

ROM 202 stores various programs and data. RAM 203 temporarily stores programs or data as a working area. Storage 204 is composed of a HDD (Hard Disk Drive) or SSD (Solid State Drive), and stores various programs and data including the operating system.

The input unit 205 includes a pointing device such as a mouse and a keyboard, and is used to perform various input operations.

The display unit 206 is, for example, a liquid crystal display, and displays various information. The display unit 206 may also function as the input unit 205 by adopting a touch panel system.

The communication interface 207 is an interface for communicating with other devices (e.g., the Grand Master Clock 1 and the Client device 2), and is, for example, an interface for a LAN. The packet transmission/

reception units

101 and 102 are, for example, configured with the communication interface 207.

A computer can be suitably used to function as each part of the transfer device 100 described above. Such a computer can be realized by storing a program describing the processing contents for realizing the functions of each part of the transfer device 100 in the memory of the computer, and having the processor of the computer read and execute this program. In other words, the program can cause the computer to function as the transfer device 100 described above. The program can also be stored in a non-transitory storage medium. The program can also be provided via a network.

The following notes are further provided with respect to the above embodiment.

[Additional Note 1]
A transfer device that transfers messages between a higher-level device that performs time synchronization by transmitting and receiving messages in a Peer-to-Peer manner and a lower-level device that performs time synchronization by transmitting and receiving messages in an End-to-End manner,
A control unit is provided,
The control unit is
Transmitting a Pdelay_Req message to the higher-level device and acquiring a transmission time t1 of the Pdelay_Req message;
receiving a Pdelay_Resp message transmitted from the higher-level device, acquiring a time t2 of the Pdelay_Req message received by the higher-level device, the time t2 being included in the Pdelay_Resp message, and acquiring a time t4 of the Pdelay_Resp message;
receiving a Pdelay_Resp_Follow_Up message transmitted from the higher-level device, and acquiring a transmission time t3 of the Pdelay_Resp message by the higher-level device, the transmission time being included in the Pdelay_Resp_Follow_Up message;
calculating an offset, which is a difference between the device time of the higher-level device and the device time of the transfer device, based on the sending time t1, the receiving time t2, the sending time t3, and the receiving time t4;
Receive a Sync message transmitted from the upper device and transmit it to the lower device, and obtain a transmission time dt2 of the Sync message by the transfer device;
Calculate a time T1' synchronized with the higher-level device as a transmission time of the Sync message by the higher-level device based on the transmission time dt2;
receiving a Follow_Up message transmitted from the higher-level device, changing the transmission time T1 of the Sync message by the higher-level device contained in the Follow_Up message to the time T1', and transmitting the changed message to the lower-level device;
Receive a Delay_Req message transmitted from the lower device, and obtain a reception time dt3 of the Delay_Req message;
Calculating a time T4' synchronized with the higher-level device as the reception time of the Delay_Req message based on the offset and the reception time dt3;
The transfer device transmits a Delay_Resp message including the time T4' to the lower device.

[Additional Note 2]
In the transfer device according to claim 1,
The control unit calculates a transmission delay time pt1 between the higher-level device and the transfer device based on the sending time t1, the receiving time t2, the sending time t3, and the receiving time t4, and calculates the time T1' by adding the sending time T1, the transmission delay time pt1, and the difference between the sending time dt2 and the sending time dt1 of the Sync message by the transfer device.

[Additional Note 3]
In the transfer device according to claim 1,
The control unit calculates the time T1' by adding the transmission time dt2 and the offset.

[Additional Item 4]
In the transfer device according to any one of claims 1 to 3,
Each of the messages includes a correctionField (CF) in which a value used for time correction is set,
The control unit sets the CF included in each message to 0.

[Additional Note 5]
A method for transferring messages between a higher-level device that performs time synchronization by transmitting and receiving messages in a Peer-to-Peer manner and a lower-level device that performs time synchronization by transmitting and receiving messages in an End-to-End manner, comprising:
Transmitting a Pdelay_Req message to the higher-level device and acquiring a transmission time t1 of the Pdelay_Req message;
receiving a Pdelay_Resp message transmitted from the higher-level device, acquiring a time t2 of the Pdelay_Req message received by the higher-level device, the time t2 being included in the Pdelay_Resp message, and acquiring a time t4 of the Pdelay_Resp message;
receiving a Pdelay_Resp_Follow_Up message transmitted from the higher-level device, and acquiring a transmission time t3 of the Pdelay_Resp message by the higher-level device, the transmission time being included in the Pdelay_Resp_Follow_Up message;
calculating an offset, which is a difference between the device time of the higher-level device and the device time of the transfer device, based on the sending time t1, the receiving time t2, the sending time t3, and the receiving time t4;
Receive a Sync message transmitted from the upper device and transmit it to the lower device, and obtain a transmission time dt2 of the Sync message by the transfer device;
Calculate a time T1' synchronized with the higher-level device as a transmission time of the Sync message by the higher-level device based on the transmission time dt2;
receiving a Follow_Up message transmitted from the higher-level device, changing the transmission time T1 of the Sync message by the higher-level device contained in the Follow_Up message to the time T1', and transmitting the changed message to the lower-level device;
Receive a Delay_Req message transmitted from the lower device, and obtain a reception time dt3 of the Delay_Req message;
Calculating a time T4' synchronized with the higher-level device as the reception time of the Delay_Req message based on the offset and the reception time dt3;
A transfer method comprising: transmitting a Delay_Resp message including the time T4' to the lower device.

[Additional Note 6]
A non-transitory storage medium storing a program executable by a computer, the non-transitory storage medium storing the program causing the computer to operate as a transfer device according to any one of claims 1 to 4.

The above-mentioned embodiments have been described as representative examples, but it will be apparent to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present disclosure. Therefore, the present invention should not be interpreted as being limited by the above-mentioned embodiments, and various modifications or changes are possible without departing from the scope of the claims. For example, it is possible to combine multiple configuration blocks shown in the configuration diagram of the embodiment into one, or to divide one configuration block.

1. Grand Master Clock (higher-level device)
2 Client device (lower device)
3. Boundary Clock
4. Transparent Clock
10, 10A Time synchronization system 100

Transfer device

101, 102 Packet transmission/reception unit 103 Pdelay_Req message processing unit (first message processing unit)
104 Pdelay_Resp message processing unit (second message processing unit)
105 Pdelay_Resp_Follow_Up message processing unit (third message processing unit)
106 Offset calculation unit 107 Sync message processing unit (fourth message processing unit)
108 Synchronization time calculation unit (first synchronization time calculation unit)
109 Follow_Up message processing unit (fifth message processing unit)
110 Delay_Req message processing unit (sixth message processing unit)
111 Synchronization time calculation unit (second synchronization time calculation unit)
112 Delay_Resp message processing unit (seventh message processing unit)
113 CF processing unit 201 Processor 202 ROM
203 RAM
204 Storage 205 Input unit 206 Display unit 207 Communication I/F
209 Pass

Claims

A transfer device that transfers messages between a higher-level device that performs time synchronization by transmitting and receiving messages in a Peer-to-Peer manner and a lower-level device that performs time synchronization by transmitting and receiving messages in an End-to-End manner,
a first message processor that transmits a Pdelay_Req message to the higher-level device and acquires a transmission time t1 of the Pdelay_Req message;
a second message processor that receives a Pdelay_Resp message transmitted from the higher-level device, acquires a time t2 of the Pdelay_Req message received by the higher-level device, and acquires a time t4 of the Pdelay_Resp message, the time being included in the Pdelay_Resp message;
a third message processor that receives a Pdelay_Resp_Follow_Up message transmitted from the higher-level device and acquires a transmission time t3 of the Pdelay_Resp message by the higher-level device, the transmission time being included in the Pdelay_Resp_Follow_Up message;
an offset calculation unit that calculates an offset, which is a difference between the device time of the higher-level device and the device time of the transfer device, based on the sending time t1, the receiving time t2, the sending time t3, and the receiving time t4;
a fourth message processing unit that receives a Sync message transmitted from the higher-level device, transmits the Sync message to the lower-level device, and acquires a transmission time dt2 of the Sync message by the transfer device;
a first synchronization time calculation unit that calculates a time T1' synchronized with the higher-level device as a transmission time of the Sync message by the higher-level device based on the transmission time dt2;
a fifth message processor that receives a Follow_Up message transmitted from the higher-level device, changes a transmission time T1 of the Sync message by the higher-level device included in the Follow_Up message to the time T1', and transmits the changed message to the lower-level device;
a sixth message processor that receives a Delay_Req message transmitted from the lower device and acquires a reception time dt3 of the Delay_Req message;
a second synchronization time calculation unit that calculates a time T4′ synchronized with the higher-level device as a reception time of the Delay_Req message based on the offset and the reception time dt3;
a seventh message processing unit that transmits a Delay_Resp message including the time T4' to the lower device.
2. The transfer device according to claim 1,
The first synchronization time calculation unit calculates a transmission delay time pt1 between the higher-level device and the transfer device based on the sending time t1, the receiving time t2, the sending time t3, and the receiving time t4, and calculates the time T1' by adding the sending time T1, the transmission delay time pt1, and the difference between the sending time dt2 and the sending time dt1 of the Sync message by the transfer device.
2. The transfer device according to claim 1,
The first synchronization time calculation unit calculates the time T1' by adding the transmission time dt2 and the offset.
2. The transfer device according to claim 1,
Each of the messages includes a correctionField (CF) in which a value used for time correction is set,
The transfer device further comprises a CF processing unit that sets the CF included in each of the messages to 0.
A method for transferring messages between a higher-level device that performs time synchronization by transmitting and receiving messages in a Peer-to-Peer manner and a lower-level device that performs time synchronization by transmitting and receiving messages in an End-to-End manner, comprising:
transmitting a Pdelay_Req message to the higher-level device and acquiring a transmission time t1 of the Pdelay_Req message;
receiving a Pdelay_Resp message transmitted from the higher-level device, acquiring a time t2 of the Pdelay_Req message received by the higher-level device, the time t2 being included in the Pdelay_Resp message, and acquiring a time t4 of the Pdelay_Resp message received by the higher-level device;
receiving a Pdelay_Resp_Follow_Up message transmitted from the higher-level device, and acquiring a transmission time t3 of the Pdelay_Resp message by the higher-level device, the transmission time being included in the Pdelay_Resp_Follow_Up message;
calculating an offset, which is a difference between the device time of the higher-level device and the device time of the transfer device, based on the sending time t1, the receiving time t2, the sending time t3, and the receiving time t4;
receiving a Sync message transmitted from the upper device and transmitting it to the lower device, and acquiring a transmission time dt2 of the Sync message by the transfer device;
calculating a time T1' synchronized with the higher-level device as a transmission time of the Sync message by the higher-level device based on the transmission time dt2;
receiving a Follow_Up message transmitted from the higher-level device, changing the transmission time T1 of the Sync message by the higher-level device included in the Follow_Up message to the time T1', and transmitting the same to the lower-level device;
receiving a Delay_Req message transmitted from the lower device and acquiring a reception time dt3 of the Delay_Req message;
calculating a time T4' synchronized with the higher-level device as a reception time of the Delay_Req message based on the offset and the reception time dt3;
and transmitting a Delay_Resp message including the time T4' to the lower device.
A program that causes a computer to operate as the transfer device described in claim 1.