JP6681355B2 - Time synchronization system and time synchronization method - Google Patents

Description

  The present invention relates to a time synchronization system and a time synchronization method for synchronizing time between devices connected via a network.

Conventionally, as a technique for synchronizing a clock in a device to standard time (UTC: world standard time), a method of receiving time information from a GPS (Global Positioning System) satellite is known (for example, Non-Patent Document 1 below). reference).
In addition, in order to achieve time synchronization between terminals connected to a LAN or the like, a master clock is connected to a slave device (terminal), and a standard time is transmitted from the master clock to a slave device under the control using PTP (Precision Time Protocol). The technology of delivering is being put to practical use.
In such a time synchronization system using a master clock, there is a demand for higher accuracy and higher reliability of time synchronization accuracy. In particular, a network configuration in which a plurality of master clocks are distributed and arranged is considered in response to the high reliability. Has been done. By arranging a plurality of master clocks in a distributed manner, time synchronization in a wider range becomes possible.

Takeyasu Sakai, “Basic knowledge of GPS / GNSS”, [online], [Search on February 13, 2017], Internet, <URL: http://www.enri.go.jp/~sakai/pub/symp07a .pdf # search =% 27gps +% E5% 9F% BA% E7% A4% 8E% 27>

However, due to factors such as GPS antenna installation conditions (interference and multipath) at each master clock, supplemented GPS satellite status, environmental disturbance (weather, ionospheric effects), etc., the standard time received at each master clock is true. There may be a difference from the standard time.
If the difference between the true standard time and the standard time distributed by each master clock becomes large, this will affect applications and time services that synchronize with the standard time. Therefore, reduction of the absolute time difference between the true standard time and the standard time distributed by each master clock becomes a problem.

  The present invention has been made in view of the above circumstances, and an object thereof is to reduce the deviation between the standard time distributed by each master clock and the true standard time in a configuration in which a plurality of master clocks are distributed. To do.

  In order to achieve the above-mentioned object, the invention according to claim 1 is connected to a plurality of master clocks for distributing a standard time received from a GPS (Global Positioning System) satellite to a slave device, and the plurality of master clocks. A time synchronization system comprising a controller, wherein the controller uses a controller-side receiving unit that receives the standard time held by each master clock, and a plurality of standard times received from each master clock. A standard time processing unit that calculates a corrected standard time estimated to be true standard time, and a controller-side transmission unit that transmits the corrected standard time calculated by the standard time processing unit to each of the master clocks. The master clock is the standard time from the GPS satellite. A GPS receiving unit for receiving the standard time, a time holding unit for holding the standard time received by the GPS receiving unit as a standard time for delivery to the slave device, and a standard time held by the time holding unit for transmission to the controller. And a master clock side receiving unit that receives the corrected standard time transmitted from the controller, wherein the time holding unit receives the corrected standard time from the controller, The time synchronization system is characterized in that the corrected standard time is held as the standard time to be distributed to the slave device.

  According to a fifth aspect of the present invention, time synchronization in a plurality of master clocks for delivering standard time received from a GPS (Global Positioning System) satellite to a slave device and a controller connected to the plurality of master clocks. A GPS receiving step of receiving the standard time from the GPS satellite at each of the master clocks, and a standard time of delivering the standard time received from the GPS satellite at each of the master clocks to the slave device. And a first time transmission step of transmitting the standard time received from the GPS satellite from each of the master clocks to the controller, and in the controller each of the master clocks. A first receiving step of receiving a plurality of standard times transmitted from the controller, and a correction standard time estimated to be a true standard time using the plurality of standard times received from the master clocks in the controller. A standard time processing step of calculating, a second transmitting step of transmitting the corrected standard time from the controller to each of the master clocks, and a reception of the corrected standard time transmitted from the controller at each of the master clocks A time synchronization method comprising: a second reception step; and a second time holding step of holding the corrected standard time as a standard time to be distributed to the slave device at each of the master clocks. .

  By doing this, it is possible to synchronize a plurality of master clocks that receive the standard time independently of each other with the corrected standard time that is estimated as the true standard time, and to improve the accuracy of the delivery time in the master clock. Can be improved. Further, the standard time held by all master clocks distributed in each area of the entire network can be unified, and the time synchronization can be made highly accurate.

  Further, in the invention according to claim 2, the standard time processing unit is configured such that the reception state and environment information of the GPS reception unit at the master clock, the variation amount of the standard time received from another master clock, and another master. The time synchronization system is characterized in that the corrected standard time is calculated by weighting each of the plurality of standard times using at least one of a time and a frequency synchronization state with a clock.

  Further, in the invention according to claim 6, in the standard time processing step, a reception state and environment information of the standard time from the GPS satellite at the master clock, a variation amount of the standard time received from another master clock. And a synchronization state of time and frequency with another master clock, weighting each of the plurality of standard times to calculate the corrected standard time. did.

  By doing so, the corrected standard time reflecting the reliability of each standard time can be calculated, and the error between the corrected standard time and the true standard time can be further reduced.

  Further, in the invention according to claim 3, the standard time processing unit receives the standard clock received from a master clock other than the master clock that cannot communicate when there is a master clock that cannot communicate among the plurality of master clocks. The correction standard time is calculated using time, the controller-side transmission unit transmits the correction standard time to a master clock other than the master clock that cannot communicate, and the master clock is different from the adjacent master clock. A time synchronization characterized by further comprising a master clock communication unit to be connected, and when the master clock communication unit cannot communicate with the controller, receives the corrected standard time from the other master clock. The system.

  Further, in the invention according to claim 7, in the standard time processing step, if there is a master clock that cannot be communicated among the plurality of master clocks, the standard clock received from a master clock other than the master clock that cannot communicate. The corrected standard time is calculated using time, and in the second transmitting step, the corrected standard time is transmitted to a master clock other than the master clock that cannot communicate, and the second master clock does not communicate with the second master clock that cannot communicate. In place of the reception step of, the inter-clock communication step of receiving the corrected standard time from another adjacent master clock is executed, and a time synchronization method is provided.

  By doing so, the corrected standard time can be calculated even when there is a communication-stop master clock that cannot communicate with the controller. Further, the corrected standard time can be transmitted from the adjacent master clock to the communication-stopped master clock side, and the reliability of the delivery time can be maintained even if a failure occurs in a part of the network.

  Further, in the invention according to claim 4, the master clock distributes the standard time to the slave device by using PTP (Precision Time Protocol), and the master clock side transmission unit and the master clock side reception unit , A transmitter and a receiver connected to the controller, and a master clock side PTP processing section that transmits and receives time information using the PTP, and the controller side receiving section and the controller side transmitting section, A plurality of transmitters and receivers provided corresponding to the respective master clocks, and a plurality of controller-side PTP processing units provided corresponding to the respective master clocks for transmitting and receiving time information using the PTPs And the controller is the master The lock-side PTP processing unit and the controller-side PTP processing unit are further provided with a switching unit that transmits and receives the standard time and the corrected standard time by switching between the master state and the slave state. It was a synchronous system.

  In the invention according to claim 8, the master clock distributes the standard time to the slave device by using PTP (Precision Time Protocol), and the first transmitting step and the second receiving step include: The transmitter and receiver provided in each of the master clocks and connected to the controller, and the master clock side PTP processing unit that transmits and receives time information using the PTP, are executed by the first reception step and The second transmitting step includes a plurality of transmitters and receivers provided in the controller and connected to the respective master clocks, and time information using the PTPs provided corresponding to the respective master clocks. Is executed by a plurality of controller-side PTP processing units that transmit and receive In the controller, the master clock-side PTP processing unit and the controller-side PTP processing unit are switched between a master state and a slave state to transmit and receive the standard time and the corrected standard time. The time synchronization method was used.

  By doing so, since the time information is exchanged using PTP, which has higher time synchronization accuracy than other time synchronization protocols, it is advantageous in improving the accuracy of the standard time distributed from the master clock. .

  According to the present invention, in a configuration in which a plurality of master clocks are arranged in a distributed manner, it is advantageous in reducing the deviation between the standard time distributed by each master clock and the true standard time.

It is an explanatory view showing the composition of the time synchronization system concerning an embodiment. It is a block diagram which shows the structure of a master clock. It is a block diagram which shows the structure of a controller. It is a flow chart which shows processing of a master clock. It is a flow chart which shows processing of a controller. It is explanatory drawing which shows the time synchronization process by a PTP process part.

(Embodiment)
Hereinafter, a time synchronization system and a time synchronization method according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an explanatory diagram showing a configuration of a time synchronization system 10 according to the embodiment.
The time synchronization system 10 includes a plurality of master clocks 20 (20A to 20F) that distribute the standard time received from the GPS satellites 40 to the slave devices 50 (50A and 50B), and a controller 30 connected to each master clock 20A to 20F. And
The time synchronization system 10 reduces the time error by using PTP synchronization between the plurality of master clocks 20 and the controller 30, and determines the absolute time error of the standard time distributed by each master clock 20 from the true standard time. Minimize.

The GPS satellite 40 is equipped with an atomic clock 42 and transmits a signal including standard time (UTC: Coordinated Universal Time).
The master clock 20 extracts the standard time from the signal received from the GPS satellite 40 and distributes the standard time to the slave device 50 under the standard time. It is assumed that the master clocks 20 are connected to each other (master clock network N), and frequency synchronization with the same frequency is established between the master clocks 20.

Examples of the slave device 50 include a boundary clock (BC) 50A and a service node 50B. Although details will be described later, the standard time is distributed between the master clock 20 and the slave device 50 using PTP.
The controller 30 is connected to all the master clocks 20A to 20F in the time synchronization system 10. The controller 30 is, for example, an EMS (Element Management System) / NMS (Network Management System) controller or an SDN (Software Defined Networking) controller.

FIG. 2 is a block diagram showing the configuration of the master clock 20.
The master clock 20 includes a GPS antenna (GPS receiving unit) 202, a time holding unit 206, a time distribution unit 207, a synchronization processing unit 220 (220A, 220B), a port state switching unit 230, and a time switching unit 232.

The GPS antenna 202 receives standard time from the GPS satellite 40. Reception of the standard time by the GPS antenna 202 is performed in a predetermined cycle.
The time holding unit 206 holds the standard time to be delivered to the slave device 50. The time holding unit 206 holds the standard time by synchronizing the built-in clock with the standard time. The time held by the time holding unit 206 is switched by the time switching unit 232. That is, when the GPS antenna 202 receives the standard time, the clock in the time holding unit 206 is synchronized with the standard time received from the GPS satellite 40. As will be described later, when the corrected standard time is received from the controller 30, the clock in the time storage unit 206 is synchronized with the received corrected standard time.

The time distribution unit 207 includes a time distribution PTP processing unit (PTP processing unit) 208, a time distribution transmitter (transmitter) 210, a time distribution receiver (receiver) 212, and a time distribution port (PTP port) 214. It is configured to include.
The time delivery PTP processing unit 208 is held in the time holding unit 206 by exchanging the time stamp with the slave device 50 via the time delivery transmitter 210, the time delivery receiver 212, and the time delivery port 214. The standard time of day is distributed to the slave device 50. More specifically, by exchanging the time stamps, the slave device 50 calculates the offset between the clock on the device side and the clock on the master clock 20 side, and the standard time at which the master clock 20 holds the clock of the slave device 50. Sync to.

FIG. 6 is an explanatory diagram showing the time synchronization processing by the PTP processing unit.
In the process shown in FIG. 6, the delay time in the route from the master clock 20 (hereinafter referred to as “master side”) to the slave device 50 (hereinafter referred to as “slave side”) and the delay time in the route from the slave side to the master side. The time is used to calculate the offset of the slave side time with respect to the master side time.

First, the delay time in the route from the master side to the slave side is calculated.
First, the master side transmits a Sync message to the slave side (S1). The Sync message includes the predicted value of the transmission time T1 of the Sync message. Next, the master side transmits a Sync follow up message including the actual transmission time T1 of the Sync message to the slave side (S2).
The slave side records the time T2 when it receives the Sync message from the master side (S3).
From time T1 and time T2, the delay time on the route from the master side to the slave side can be calculated. That is, the delay time on the route from the master side to the slave side = T2-T1.

Next, the delay time in the route from the slave side to the master side is calculated.
First, the slave side transmits a Delay Request message to the master side (S4), and the slave side records the transmission time T3 of the Delay Request message (S5). Next, the master side transmits a delay response message including the time T4 when the master side receives the delay request message to the slave side (S6).
The delay time in the route from the slave side to the master side can be calculated from time T3 and time T4. That is, the delay time on the path from the slave side to the master side = T4−T3.

The one-way delay time between the master and the slave is calculated using the delay time (first delay time) on the path from the master side to the slave side and the delay time (second delay time) on the path from the slave side to the master side. Can be calculated using the following formula (1).
One-way delay time = (first delay time + second delay time) / 2 = ((T2-T1) + (T4-T3)) / 2 (1)
Then, the offset (time shift) of the slave side time with respect to the master side time is calculated using the following equation (2).
Slave side offset = first delay time-one-way delay time = ((T2-T1)-(T4-T3)) / 2 (2)

Returning to the description of FIG. 2, the synchronization processing unit 220 (220A, 220B) exchanges time information (time stamp) with the controller 30 and another master clock 20, and the correction standard estimated to be the true standard time. Get the time.
A plurality of synchronization processing units 220 are provided. Among them, the synchronization processing unit 220A is connected to the controller 30, and the other synchronization processing unit 220B is connected to another adjacent master clock 20. That is, the synchronization processing unit 220B corresponds to the inter-master-clock communication unit that is connected to another adjacent master clock. When there are a plurality of other master clocks 20 adjacent to each other, the synchronization processing units 220 for the other master clocks are provided by that number.

The synchronization processing unit 220 (220A, 220B) includes a synchronization PTP processing unit (PTP processing unit) 222 (222A, 222B), a synchronization transmitter (transmitter) 224 (224A, 224B), and a synchronization receiver (reception). Device) 226 (226A, 226B) and synchronization port (PTP port) 228 (228A, 228B).
The synchronization PTP processing unit 222 exchanges a time stamp with the controller 30 or another master clock 20 via the synchronization transmitter 224, the synchronization receiver 226, and the synchronization port 228 to estimate the true standard time. Gets the corrected standard time.
Although details will be described later, the acquisition of the corrected standard time is normally performed by the synchronization processing unit 220A connected to the controller 30, but when the connection between the controller 30 and the master clock 20 is disconnected, another This is performed by the synchronization processing unit 220B connected to the master clock 20.

The processing of the synchronization PTP processing unit 222 is similar to that of the time distribution PTP processing unit 208 described with reference to FIG. 6, but the time distribution PTP processing unit 208 performs only the operation on the master side. The synchronization PTP processing unit 222 can switch the operation between the master side and the slave side under the control of the port state switching unit 230. The port state switching unit 230 is connected to the controller 30 and switches the operation of the synchronization PTP processing unit 222 between the master side and the slave side according to a control signal from the controller 30.
Hereinafter, the operation of the synchronization PTP processing unit 222 being on the master side is called a "master state", and the operation being on the slave side is called a "slave state".
Also, when the operation state of the synchronization PTP processing unit 222 is switched, the port state of the synchronization port 228 is switched. That is, when the synchronization PTP processing unit 222 is in the master state, the corresponding synchronization port 228 becomes the master side port, and when the synchronization PTP processing unit 222 is in the slave state, the corresponding synchronization port 228 is It becomes a port on the slave side.

When the synchronization PTP processing unit 222 is switched to the master state, a message including a time stamp based on the standard time held by the time holding unit 206 is transmitted to the slave side (controller 30 or another master clock 20). That is, when the synchronization PTP processing unit 222 is switched to the master state, the synchronization processing unit 220 functions as a master clock side transmission unit that transmits the standard time held by the time holding unit 206 to the controller 30 or the like.
On the other hand, when the synchronization PTP processing unit 222 is switched to the slave state, the time stamp transmitted from the master side (the controller 30 or another master clock 20) and the standard time stored in the time storage unit 206 are used. The offset on the device side with respect to the master time is calculated. That is, when the synchronization PTP processing unit 222 is switched to the slave state, the synchronization processing unit 220 functions as a master clock side receiving unit that receives the corrected standard time transmitted from the controller 30 or the like.

  The time switching unit 232 switches the time stored in the time storage unit 206 between the standard time received by the GPS antenna 202 and the corrected standard time acquired by the synchronization processing unit 220. When the GPS antenna 202 receives the standard time, the time switching unit 232 causes the time holding unit 206 to hold the received standard time. When any of the synchronization processing units 220 acquires the corrected standard time, the time holding unit 206 holds the acquired corrected standard time.

FIG. 3 is a block diagram showing the configuration of the controller 30.
The controller 30 includes a synchronization processing unit 310, a standard time processing unit 320, a weighting information management unit 322, a time holding unit 324, a port state switching unit 326, and a master clock control unit 328.
The synchronization processing unit 310 (310A to 310n) includes a synchronization PTP processing unit (PTP processing unit) 312 (312A to 312n), a synchronization transmitter (transmitter) 314 (314A to 314n), and a synchronization receiver (receiver). ) 316 (316A to 316n) and a plurality of synchronization ports 318 (318A to 318n), respectively.
The synchronization ports 318 (318A to 318n) are connected to different master clocks 20, respectively. In the example of FIG. 3, it is assumed that the controllers 30 are connected to n different master clocks 20, respectively.

The synchronization PTP processing unit 312 exchanges a time stamp with each master clock 20 via the synchronization transmitter 314, the synchronization receiver 316, and the synchronization port 318.
The processing of the synchronization PTP processing unit 312 is similar to that of the time distribution PTP processing unit 208 described with reference to FIG. 6, but the synchronization PTP processing unit 312 is similar to the synchronization PTP processing unit 222 of the master clock 20. The master state and the slave state can be switched and executed under the control of the port state switching unit 326.
Note that the port state switching unit 326 interlocks with the operation switching of the synchronization PTP processing unit 312 of the controller 30, and controls the master clock control signal for switching the operation of the synchronization PTP processing unit 222 of the master clock 20. It is transmitted via the unit 328. The control signal transmitted from the master clock control unit 328 is input to the port state switching unit 230 of the master clock 20 (FIG. 2), and the port state switching unit 230 changes the operating state of the synchronization PTP processing unit 222 of the master clock 20. Can be switched.

Specifically, the port state switching unit 326 sets the synchronization PTP processing unit 222 of the master clock 20 (FIG. 2) to the master state and sets the controller 30 to the synchronization state when the synchronization PTP processing unit 312 of the controller 30 is set to the slave state. When the synchronization PTP processing unit 312 is set to the master state, the synchronization PTP processing unit 222 of the master clock 20 is switched to the slave state.
When the synchronization PTP processing unit 312 is switched to the slave state, the synchronization processing unit 310 functions as a controller-side receiving unit that receives the standard time held by each master clock 20.
Further, when the operation of the synchronization PTP processing unit 312 is switched to the master state, synchronization is performed as a controller-side transmission unit that transmits the corrected standard time calculated by the standard time processing unit 320 described below to each master clock 20. The processing unit 310 functions.

The standard time processing unit 320 calculates the corrected standard time estimated as the true standard time from the plurality of standard times received from each master clock 20.
The standard time processing unit 320 compares a plurality of standard times with each other, for example, and weights each standard time based on various parameters. Then, the corrected standard time is calculated by averaging the weighted standard times (weighted average) or by selecting the standard time with the smallest offset.
It should be noted that an apparent defective value of the standard time or a standard time at which the reliability of the master clock 20 of the transmission source is extremely low is excluded from the calculation target sample of the corrected standard time. For example, when the GPS antenna 202 fails at a certain master clock 20 and the standard time cannot be received, the controller 30 detects the abnormality and excludes the master clock 20 in the abnormal state from the corrected standard time calculation algorithm. This makes it possible to improve the accuracy of the corrected standard time.
In addition, as a method for calculating the corrected standard time based on such a plurality of standard times, various conventionally known methods can be applied.

The following are examples of weighting parameters.
The following information is received together with the time information when the synchronization PTP processing unit 222 of the master clock 20 is switched to the master state and the synchronization PTP processing unit 312 of the controller 30 is switched to the slave state, and the weighted information management is performed. It is recorded in the section 322.
1. Reception state and environment information of GPS antenna 202 at each master clock 20 1-1. Information on GPS satellites, number of GPS satellites captured, year of manufacture of GPS satellites captured, on-board oscillator (Cs or Rb) of GPS satellites captured
・ Information on navigation messages from GPS satellites (satellite orbit (ephemeris), errors in GPS satellite internal clock, etc.)
-Position information of GPS satellites relative to the GPS antenna 202 (zenith, elevation, etc.)
-Error due to GPS Doppler shift and relativistic effect 1-2. Environmental condition / weather monitor value (environmental weather condition)
・ Delay amount due to troposphere and ionosphere 1-3. Status of receiver (GPS antenna 202), GPS radio wave reception status, noise value (SNR (Signal-to-Noise Ratio), etc.)
・ Installation conditions for the GPS antenna 202 (such as the effect of multipath due to reflection)
-Cable delay correction information between the GPS antenna 202 and the receiver 2. 2. Offset of standard time by PTP received from other master clock 20 and its variation amount Time and frequency synchronization state between each master clock 20 in the master clock network N ・ States such as normal / holdover / Free run etc. ・ Quantitative numerical values such as frequency deviation and drift amount of the oscillator in the master clock 20

The time holding unit 324 holds the corrected standard time calculated by the standard time processing unit 320. That is, when the corrected standard time is calculated by the standard time processing unit 320, the clock in the time storage unit 324 is synchronized with the corrected standard time.
The corrected standard time stored in the time storage unit 324 is changed to the master clock 20 (FIG. 2) by switching the synchronization PTP processing unit 222 to the slave state and the synchronization PTP processing unit 312 of the controller 30 to the master state. Sent to 20.

If there is a master clock in the time synchronization system 10 that cannot communicate with the controller 30 (synchronization port 318) (hereinafter referred to as “communication interrupted master clock”), the standard time processing unit 320 will The corrected standard time is calculated using the standard time received from the master clock 20 other than the communication interruption master clock.
Then, the controller-side transmitter (the synchronization processor 310 in the master state) transmits the calculated corrected standard time to the master clock 20 other than the communication interruption master clock. Note that the transmission to the master clock 20 other than the communication interruption master clock does not deny the transmission of the correction standard time from the synchronization port 318 connected to the communication interruption master clock, and as a result, it is not the communication interruption master clock. This means that the corrected standard time arrives only at the master clock 20 of.
When the master clock 20 (FIG. 2) cannot communicate with the controller 30, the master processor 20 receives the corrected standard time from another master clock 20 by the synchronization processing unit 220B that functions as a master clock communication unit. Specifically, the controller 30 transmits the corrected standard time to the master clock 20 other than the communication break master clock, and then sets the communication break master clock synchronization PTP processing unit 222B in the slave state to be adjacent to the communication break master clock. By switching the synchronization PTP processing unit 222B of the master clock 20 to the master state, it becomes possible to receive the corrected standard time from another adjacent master clock 20.

FIG. 4 is a flowchart showing the process of the master clock 20.
In the flowcharts of FIGS. 4 and 5, it is assumed that the master clock 20 and the controller 30 are in a communicable state.
The master clock 20 receives the standard time from the GPS satellite 40 by the GPS antenna 202 every predetermined period (step S400: Yes). The time switching unit 232 causes the time holding unit 206 to hold the received standard time (step S402). That is, the clock in the time storage unit 206 is synchronized with the standard time received in step S400.
The time distribution unit 207 distributes the standard time stored in the time storage unit 206 to the slave device 50 (step S404).
When the operation of the synchronization PTP processing unit 222A corresponding to the controller 30 is switched to the master state by the port state switching unit 230 (control of the controller 30) (step S406: Yes), the synchronization PTP processing unit 222A causes the time holding unit to operate. The standard time stored in 206 is transmitted to the synchronization PTP processing unit 312A of the controller 30 on the slave side (step S408).

Here, if the operation of the synchronization PTP processing unit 222A is not switched to the slave state (step S410: No), the process returns to step S400 to continue the process. On the other hand, when the operation of the synchronization PTP processing unit 222A is switched to the slave state (step S410: Yes), the synchronization PTP processing unit 222A sets the correction standard time from the synchronization PTP processing unit 312A of the master side controller 30. It is received (step S412). The time switching unit 232 causes the time storage unit 206 to store the received corrected standard time (step S414). That is, the clock in the time storage unit 206 is synchronized with the corrected standard time received in step S412. As a result, the standard time held by all the master clocks 20 in the time synchronization system 10 is synchronized with the corrected standard time.
Then, the time distribution unit 207 distributes the corrected standard time stored in the time storage unit 206 to the slave device 50 as the standard time (step S416). After that, the process of the flowchart of FIG. 4 is repeated.

FIG. 5 is a flowchart showing the processing of the controller 30.
The controller 30 first switches the synchronization processing unit 310 on the controller 30 side to the slave state and the synchronization processing unit 220 on the master clock 20 side to the master state by the port state switching unit 326 (step S500, step S406 in FIG. 4: Corresponding to Yes).
The synchronization processing unit 310 of the controller 30 receives the standard time from each master clock 20 (step S502), and the standard time processing unit 320 weights each received standard time to correct the estimated standard time. The standard time is calculated (step S504). The calculated corrected standard time is held in the time holding unit 324 (step S506).
After that, the port state switching unit 326 switches the synchronization processing unit 310 on the controller 30 side to the master state and the synchronization processing unit 220 on the master clock 20 side to the slave state (step S508, step S410 in FIG. 4: Yes). Correspondence). Then, the synchronization processing unit 310 transmits the corrected standard time (step S510). After that, the process of the flowchart of FIG. 5 is repeated at a predetermined cycle.

As described above, the time synchronization system 10 according to the embodiment collects the standard time from the plurality of master clocks 20 in the controller 30 and calculates the corrected standard time estimated to be the true standard time by the controller 30. Then, the corrected standard time is returned to each master clock 20.
By doing so, it is possible to synchronize a plurality of master clocks 20 that are independently receiving the standard time with the corrected standard time, and improve the accuracy of the delivery time in the master clock 20. Further, the standard time held by all the master clocks 20 distributed in each area of the entire network can be unified, and the time synchronization can be made highly accurate.
Further, in the time synchronization system 10, the controller 30 calculates the corrected standard time by reflecting the reliability of the standard time received from each master clock 20, so that the error between the corrected standard time and the true standard time is further reduced. can do.

Further, when there is a communication interruption master clock that cannot communicate with the controller 30, the time synchronization system 10 calculates the corrected standard time using the standard time received from the master clock 20 other than the communication interruption master clock, and communicates with the controller 30. For the disconnected master clock, the corrected standard time is transmitted from another adjacent master clock 20.
By doing so, the corrected standard time can be calculated even when there is a communication-stop master clock that cannot communicate with the controller. Further, the corrected standard time can be transmitted from the adjacent master clock to the communication-stopped master clock side, and the reliability of the delivery time can be maintained even if a failure occurs in a part of the network.
Further, since the time synchronization system 10 exchanges time information using PTP, which has higher time synchronization accuracy than other time synchronization protocols, it is advantageous in improving the accuracy of the standard time distributed from the master clock 20. Becomes

10 time synchronization system 20 (20A-20F) master clock 202 GPS antenna 206 time holding unit 207 time distribution unit 208 time distribution PTP processing unit 210 time distribution transmitter 212 time distribution receiver 214 time distribution port 220 (220A) , 220B) synchronization processing unit 222 (222A, 222B) synchronization PTP processing unit 224 (224A, 224B) synchronization transmitter 226 (226A, 226B) synchronization receiver 228 (228A, 228B) synchronization port 230 port state switching 232 Time switching unit 30 Controller 310 Synchronization processing unit 312 (312A to 312n) Synchronization PTP processing unit 314 (314A to 314n) Synchronization transmitter 316 (316A to 316n) Synchronization receiver 318 (318A to 318n) Synchronization Po DOO 318A synchronization port 320 standard time processing unit 322 weighting information managing unit 324 time holding unit 326 port state switching unit 328 master clock control unit 40 GPS satellites 50 (50A, 50B) slave device N master clock network

Claims (8)

A time synchronization system comprising: a plurality of master clocks for delivering a standard time received from a GPS (Global Positioning System) satellite to a slave device; and a controller connected to the plurality of master clocks.
The controller is
A controller-side receiving unit that receives the standard time held by each of the master clocks,
A standard time processing unit that calculates a corrected standard time estimated to be a true standard time using a plurality of standard times received from each of the master clocks,
A controller-side transmitter that transmits the corrected standard time calculated by the standard time processor to each of the master clocks,
The master clock is
A GPS receiving unit for receiving the standard time from the GPS satellite,
A time holding unit that holds the standard time received by the GPS receiving unit as standard time to be distributed to the slave device;
A master clock side transmitter that transmits the standard time held by the time holder to the controller;
A master clock side receiving unit that receives the corrected standard time transmitted from the controller,
The time holding unit, when receiving the corrected standard time from the controller, holds the corrected standard time as a standard time to be distributed to the slave device,
A time synchronization system characterized in that The standard time processing unit includes a reception state and environment information of the GPS reception unit at the master clock, a variation amount of the standard time received from another master clock, a time and frequency synchronization state with another master clock. , At least one of the plurality of standard times is weighted to calculate the corrected standard time.
The time synchronization system according to claim 1, wherein: If there is a master clock that cannot be communicated among the plurality of master clocks, the standard time processing unit calculates the corrected standard time using the standard time received from a master clock other than the master clock that cannot communicate. ,
The controller-side transmitter transmits the corrected standard time to a master clock other than the master clock that cannot communicate,
The master clock further includes an inter-master-clock communication unit that is connected to another adjacent master clock, and when the master clock cannot communicate with the controller, the master-clock inter-communication unit causes the other master clock to adjust the correction standard. Receive time,
The time synchronization system according to claim 1 or 2, characterized in that. The master clock distributes the standard time to the slave device using PTP (Precision Time Protocol).
The master clock side transmission unit and the master clock side reception unit include a transmitter and a receiver connected to the controller, and a master clock side PTP processing unit that transmits and receives time information using the PTP. ,
The controller-side receiving section and the controller-side transmitting section use a plurality of transmitters and receivers provided corresponding to the respective master clocks, and the PTP provided corresponding to the respective master clocks. It is configured by a plurality of controller-side PTP processing units that transmit and receive time information,
The controller further includes a switching unit for transmitting and receiving the standard time and the corrected standard time by switching the master clock side PTP processing unit and the controller side PTP processing unit between a master state and a slave state.
The time synchronization system according to any one of claims 1 to 3, characterized in that. A time synchronization method in a plurality of master clocks for distributing standard time received from a GPS (Global Positioning System) satellite to a slave device, and a controller connected to the plurality of master clocks,
A GPS receiving step of receiving the standard time from the GPS satellite at each of the master clocks;
A first time holding step of holding the standard time received from the GPS satellite at each of the master clocks as the standard time to be distributed to the slave device;
A first transmitting step of transmitting the standard time received from the GPS satellites to the controller from each of the master clocks;
In the controller, a first receiving step of receiving a plurality of standard times transmitted from the respective master clocks,
In the controller, a standard time processing step of calculating a corrected standard time estimated as a true standard time using the plurality of standard times received from the respective master clocks,
A second transmitting step of transmitting the corrected standard time from the controller to each of the master clocks;
A second receiving step of receiving the corrected standard time transmitted from the controller at each of the master clocks;
A second time holding step of holding the corrected standard time as a standard time to be distributed to the slave device in each of the master clocks;
A time synchronization method characterized by including. In the standard time processing step, a reception state and environment information of the standard time from the GPS satellite at the master clock, a variation amount of the standard time received from another master clock, a time with another master clock, and Calculating the corrected standard time by weighting each of the plurality of standard times using at least one of a frequency synchronization state,
The time synchronization method according to claim 5, wherein. In the standard time processing step, if there is a master clock that cannot be communicated among the plurality of master clocks, the corrected standard time is calculated using the standard time received from a master clock other than the master clock that cannot communicate. ,
In the second transmitting step, the corrected standard time is transmitted to a master clock other than the master clock that cannot communicate,
In the master clock that cannot communicate, in place of the second receiving step, an inter-clock communication step of receiving the corrected standard time from another adjacent master clock is executed.
The time synchronization method according to claim 5 or 6, characterized in that. The master clock distributes the standard time to the slave device using PTP (Precision Time Protocol).
The first transmission step and the second reception step include a master clock side PTP that transmits and receives time information using the PTP, with a transmitter and a receiver provided in each of the master clocks and connected to the controller. Executed by the processing unit,
The first receiving step and the second transmitting step are provided corresponding to the plurality of transmitters and receivers provided in the controller and connected to the respective master clocks, and the respective master clocks. Executed by a plurality of controller-side PTP processing units that transmit and receive time information using the PTP,
In the controller, the master clock side PTP processing section and the controller side PTP processing section are switched between a master state and a slave state to transmit and receive the standard time and the corrected standard time.
The time synchronization method according to any one of claims 5 to 7, wherein:

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