JP5905811B2 - Frequency synchronization accuracy monitoring method, frequency synchronization accuracy monitoring device, communication method, and communication system - Google Patents

Description

  The present invention relates to a frequency synchronization accuracy monitoring method, a frequency synchronization accuracy monitoring device, a communication method, and a communication system for monitoring the frequency synchronization accuracy of a slave clock with respect to a master clock.

  In the case where only the data signal is transmitted between the master and the slave and the clock signal is not transmitted, in order to obtain a clock synchronized with the internal clock of the master in the slave, a transmission signal is used using, for example, Phase Locked Loop (PLL). It is necessary to extract the clock from

  FIG. 1 is a block diagram of the PLL. The phase comparator 11 performs phase comparison between the data string and the divided internal clock, detects a phase error from the internal clock, and outputs an error signal having a pulse width proportional to the error. The filter 12 flattens an error signal having a pulse width proportional to the error and outputs it as a control signal having an amplitude proportional to the magnitude of the phase error.

  A voltage controlled oscillator (VCO: Voltage Controlled Oscillator) 13 adjusts the frequency and phase of an internal clock to be output according to an input control signal. The frequency divider 14 changes the frequency by, for example, multiplying the output internal clock to a frequency suitable for phase comparison.

  The clock output from the frequency divider 14 is input again to the phase comparator 11 for phase comparison. These series of loops synchronize the frequency and phase of the internal clock of the receiver with the frequency and phase of the input data signal. In this way, the internal clock of the receiver can be synchronized with the internal clock of the transmitter by frequency synchronization using the PLL.

  Here, for example, the device performance may be deteriorated due to deterioration of the performance of the transistor included in the VCO 13 or deterioration of the performance of the transistor included in the phase comparator 11. Due to this device performance degradation, the frequency of the internal clock generated by the PLL of the ONU as the slave may be shifted from the frequency of the internal clock of the OLT as the master.

  In the first place, the output frequency of the VCO is uniquely determined by a certain characteristic as shown in FIG. 2, for example, with respect to the control voltage of the VCO. The control voltage of the VCO is mainly determined by a phase comparator and a filter, and can be changed only within a certain range.

  In the normal case where there is no aging deterioration of the device, the control voltage of the VCO corresponding to the output frequency of the desired VCO is included in the control voltage range of the VCO. By appropriately adjusting (for example, operating in the condition of point A in the case of FIG. 2), a desired frequency is output from the PLL.

  However, for example, when the performance of the transistor in the VCO deteriorates, the characteristics of the output frequency of the VCO with respect to the control voltage of the VCO may change. At this time, if the control voltage of the VCO corresponding to the desired output frequency of the VCO is within the adjustable range of the control voltage of the VCO (for example, in the case of an abnormality (a) in FIG. 2), it is Since feedback is applied, an output frequency of a desired VCO is output (for example, feedback is applied so as to operate under the condition of point B in FIG. 2).

  However, when the VCO control voltage corresponding to the desired VCO output frequency is not within the adjustable range of the VCO control voltage due to significant device performance degradation or the like (for example, in the case of abnormality (b) in FIG. 2) In addition, even if negative feedback is applied by the feedback loop of the PLL, the control voltage cannot be adjusted beyond the control voltage adjustment range, so that the desired VCO output frequency is not output and a frequency shift occurs. There is a concern that the synchronization accuracy of the output frequency of the VCO deteriorates.

  Thus, for frequency synchronization that may be degraded due to device performance degradation or the like, it is necessary to constantly monitor the synchronization accuracy in order to determine whether or not the frequency synchronization has been degraded. As one method for monitoring the frequency synchronization accuracy between two clocks, there is a method of measuring the frequency synchronization accuracy between each of the master and slave internal clocks and a common stable clock.

As a method of calculating the frequency synchronization accuracy between two clocks, for example, there is a method of measuring the Maximum Time Interval Error (MTIE) of two clocks and calculating the frequency synchronization accuracy from the value. Time Interval Error (TIE) represents the phase difference between the rising edges of two clocks, and represents the maximum variation in TIE as MTIE at a certain measurement time. When the MTIE is A at the measurement time T, the frequency synchronization accuracy at the measurement time can be evaluated as A / T (for example, when the measurement time is 100 seconds and the MTIE is 1 ns, the frequency synchronization accuracy is The accuracy can be calculated as 1 * 10 ⁻¹¹ ).

  Here, for example, a clock synchronized with the Coordinated Universal Time (UTC) provided by the Global Positioning System (GPS) is input as a reference to the master and slave, and this clock, the master internal clock, and the slave internal clock are input. Is a method for measuring the frequency difference between the slave's internal clock and the master's internal clock by transmitting the MTIE information obtained at the slave to the master. (For example, refer to Patent Document 1).

  In the case of Patent Document 1, it is necessary to install a GPS signal receiver in each of the master and the slave and receive the GPS signal.

JP 2010-288085 A

  However, there is a possibility that the reception status of the GPS signal receiver may be deteriorated by the influence of weather changes such as lightning strikes, and it is difficult to monitor the frequency synchronization accuracy stably and stably.

  In addition, if it is difficult to install the receiver in an environment where GPS receivers can receive GPS signals because it is necessary to install the receiver in the basement etc., it is not possible to obtain a clock synchronized with UTC, and it is possible to monitor frequency synchronization accuracy. There is also a problem that is difficult.

  Therefore, in order to solve the above problems, the present invention provides a frequency synchronization accuracy monitoring method, a frequency synchronization accuracy monitoring device, a communication method, and a communication system that can stably monitor the frequency synchronization system regardless of the environment. With the goal.

  In order to achieve the above goal, the present invention monitors the clock frequency difference between the master and the slave by the master based on the time stamp sent from the slave.

Specifically, the frequency synchronization accuracy monitoring method according to the present invention uses the time information signal transmitted and received between the master and the slave to receive and transmit the time information signal measured by the slave clock. The time is received by the master,
For the specific time set based on the time information signal, the measured value in the master clock and the measured value in the slave clock are compared in the master,
When the difference between the measurement value at the master clock and the measurement value at the slave clock is equal to or greater than a predetermined threshold, the master determines that the frequency synchronization accuracy of the slave clock with respect to the master clock has deteriorated. To do.

The frequency synchronization accuracy monitoring device according to the present invention is arranged on the master side,
Time information reception function for receiving the reception time and transmission time of the time information signal measured by the clock of the slave using the time information signal transmitted and received between the master and the slave,
For a specific time set based on the time information signal, a comparison function that compares the measured value at the master clock and the measured value at the slave clock at the master;
When the difference between the measurement value at the master clock and the measurement value at the slave clock is equal to or greater than a predetermined threshold, the master determines that the frequency synchronization accuracy of the slave clock with respect to the master clock has deteriorated. A decision function to
Is provided.

  In the present invention, the reception time and transmission time of the time information signal measured by the slave are notified to the master, and a specific time is set based on these times. The frequency difference between the clocks of the master and the slave can be detected by comparing the value measured with the master clock with the value measured with the slave clock. Thus, the present invention can detect the frequency difference between the clocks of the master and the slave without using a GPS signal. Therefore, the present invention can provide a frequency synchronization accuracy monitoring method and a frequency synchronization accuracy monitoring device that can stably monitor the frequency synchronization system regardless of the environment.

  The specific time may be a time obtained by excluding a round trip delay time of the time information signal from a time for the time information signal to make one round trip between the master and the slave or a time for making a round trip multiple times.

  The specific time may be a time for the time information signal to make one round trip between the master and the slave or a time for making a round trip multiple times.

  The specific time is from the time when the time information signal reciprocates a plurality of times between the master and the slave until the transmission / reception of the time information signal is started again after the transmission / reception of the time information signal is completed. The time can be excluded.

  The specific time is from the time when the time information signal reciprocates a plurality of times between the master and the slave until the transmission / reception of the time information signal is started again after the transmission / reception of the time information signal is completed. The time and the time information signal round trip delay time can be excluded.

  In the frequency synchronization accuracy monitoring method according to the present invention, the difference can be output from the master as a frequency error between the master clock and the slave clock. The present invention can constantly monitor the frequency synchronization system.

  Further, the present invention performs the frequency synchronization accuracy monitoring method at a predetermined time, and monitors the frequency synchronization accuracy between the slave's internal clock and the master's internal clock in the master, while the master and the slave A communication method and a communication system for transmitting and receiving data signals between them. When the master performs the frequency synchronization accuracy monitoring method at a predetermined time, the frequency synchronization accuracy of the slave's internal clock can be monitored by the master. If the frequency synchronization accuracy is within a specified value, data transmission / reception is continued. If the synchronization accuracy is outside the specified value, data transmission / reception can be stopped.

  The present invention can provide a frequency synchronization accuracy monitoring method, a frequency synchronization accuracy monitoring device, a communication method, and a communication system that do not require a GPS receiver and can stably monitor the frequency synchronization system regardless of the environment.

It is a figure explaining an example of the block diagram of PLL. It is a figure explaining the relationship between the output frequency of VCO, and a control voltage. 3 is a flowchart illustrating a frequency synchronization accuracy monitoring method according to the present invention. 3 is a flowchart illustrating a frequency synchronization accuracy monitoring method according to the present invention. 3 is a flowchart illustrating a frequency synchronization accuracy monitoring method according to the present invention. 3 is a flowchart illustrating a frequency synchronization accuracy monitoring method according to the present invention. 3 is a flowchart illustrating a frequency synchronization accuracy monitoring method according to the present invention. 3 is a flowchart illustrating a frequency synchronization accuracy monitoring method according to the present invention. It is a figure explaining the time in the master of a time information signal and a slave in the frequency-synchronization accuracy monitoring method which concerns on this invention. 1 is a block diagram illustrating a frequency synchronization accuracy monitoring apparatus according to the present invention.

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

(Embodiment 1)
In the present embodiment, an internal clock of a slave and an internal clock of the master are transmitted and received between a master having an internal clock and transmitting / receiving a time stamp and a slave having an internal clock synchronized with the frequency of the internal clock of the master In this method, the master monitors whether the frequency synchronization accuracy between internal clocks has deteriorated.

In this embodiment, using the time information signal transmitted and received between the master and the slave, the reception time and transmission time of the time information signal measured by the clock of the slave are received by the master,
For the specific time set based on the time information signal, the measured value in the master clock and the measured value in the slave clock are compared in the master,
When the difference between the measurement value at the master clock and the measurement value at the slave clock is equal to or greater than a predetermined threshold, the master determines that the frequency synchronization accuracy of the slave clock with respect to the master clock has deteriorated. This is a frequency synchronization accuracy monitoring method.

  Here, the time stamp is the time of transmission or reception of the time information signal. Also, transmitting or receiving a time stamp means transmitting or receiving a transmission time or reception time as a time information signal.

To describe this embodiment in more detail, to emboss the time T _k to the transmission of packets in a random or regular intervals from the transmission of the master time stamp, and sends the time stamp embossing to the slave reads the time t _k which has received the time stamp sent from the master by the receiver of the slave, the time stamp the time t _{k 'for} transmitting a time stamp toward the receiving portion of the master from the transmission section of the slave in the slave was embossed on, the t _k and t _{k 'or} (t _k' a -t _k) transmitted from the slave transmission unit to the master receiver, the time T _{k 'time} received from the slave transmission unit at the master receiver A stamp is stamped, and a round-trip delay time (hereinafter referred to as RTT) between the master and the slave is calculated from a set of one or a plurality of (T _k , T _k ′, t _k , t _k ′). ( _k, T _k calculated from _{', t k, t k'} ) set the delay time of the one round trip, a particular time, the master, the value counted by each counter operating in the slave respective internal clocks The frequency difference between the master and slave is calculated based on those values, and the frequency synchronization accuracy between the master, clock, and slave clock is degraded when there is a difference greater than the preset threshold. Is determined. Further, the frequency difference between the clocks of the transmitter and the receiver may be output to the outside of the receiver.

  In this embodiment, if there is a transmission line delay, the transmission time delay is constant because the transmission time interval and the reception time interval are different even if the frequency synchronization accuracy is not degraded. Is desirable. However, when the connection between the master and the slave is not via a switch or router, the delay of the transmission path is considered to be almost constant.

  3 to 5 are flowcharts for explaining the frequency synchronization accuracy monitoring method of the present embodiment.

  The operations of the master transmission unit and the monitoring unit will be described with reference to FIG. First, the master transmitting unit and the monitoring unit substitute 1 for the variable K (step S32), wait for a certain time (step S33), send the time stamp, and store the time stamp value ( Step S34), and K + 1 is substituted for K (Step S35). Here, the waiting time is a parameter corresponding to the time stamp transmission interval. This waiting time may be a fixed time or a random time. Here, K corresponds to the total number of time stamps sent from the start until the time stamp is sent.

  The operation of the slave will be described with reference to FIG. The slave first assigns 1 to the variable K (step S42), and then waits until a time stamp is received from the master (step S43). Here, K corresponds to the total number of time stamps received from the start until the time stamp is received. When the transmitter and the receiver are started at the same time and all the transmitted time stamps are received without any loss, the value matches the value of K managed on the master side. Here, for the sake of convenience, a flow for monitoring the frequency synchronization accuracy between the transmitter and the receiver based on the value of K will be described, but K is not necessarily required in the present embodiment. This is because, in frequency monitoring, it is sufficient that a combination of time stamps exchanged between the master and the slave is linked in the master.

Then it receives a time stamp T _k from the master at the slave, whereby the embossing timestamps t _k at the slave in the slave (step S44). Next, the time stamp t _k and the transmission time t _k ′ are sent as a time stamp from the slave to the master (step S45). Here, it is described that t _k and t _k ′ are sent separately. However, since a necessary value is a difference between these (t _k ′ −t _k ) as will be described later, t _k and t _k ′. (T _k ′ −t _k ) may be sent instead of sending them individually. Thereafter, K + 1 is substituted for K (step S46), and the process waits until a time stamp is received from the master.

The operation of the master receiving unit and the monitoring unit will be described with reference to FIG. When receiving the time stamp t _k and the transmission time t _k ′ from the slave transmission unit, the master reception unit and the monitoring unit stamp the time stamp T _k ′ on the master (step S502). Here, it is determined whether K is 1 (step S503).

If K is 1, a round trip time (RTT: Round Trip Time) between the master and the slave is calculated as ((T _k ′ −T _k ) − (t _k −t _k ′)) (step S504). ). Here, a method for obtaining RTT based on a set of (T _k , T _k ′, t _k , t _k ′) when K is 1 has been described. (T _k , T _k ′, t _k , t _k ′) may be obtained, and RTT may be obtained from the average value thereof.

  If K is not 1 (2 or more), a frequency difference between the slave clock and the master clock is calculated (step S505), and the calculated frequency error is notified outside the master (step S506).

Here, step S505 will be further described.
When calculating the frequency difference between the master clock and the slave clock, the time stamp T ₁ is _first transmitted from the master until the time stamp value T _N ′ is received by the slave. Suppose the frequency difference is constant and the propagation delay between the master and slave is constant. The frequency of the clock at the transmitter is denoted by f1, and the frequency of the clock at the receiver is denoted by f2.

  When a frequency error is generated between the master and the slave, the counter value is shifted because the time count speed is different in each device. The frequency error is calculated from the deviation of the counter value.

At this time, the relationship between the time of the master and the slave is assumed as shown in FIG. Each time T _k and T _k in the master 'respectively, the time t _k and t _k at the _slave', the frequency f1 of the master clock, are inscribed by the frequency f2 of the slave clock.

The frequency difference ratio (f2-f1) / f1 is calculated as follows, for example. Here, the specific time used when calculating the frequency difference is a time obtained by excluding the round trip delay time of the time information signal from the time of the round trip of the time information signal between the master and the slave. .

Moreover, the ratio (f2-f1) / f1 of the wave number difference can also be calculated as follows. Here, the specific time used when calculating the frequency difference is a time for the time information signal to make one round trip between the master and the slave.

In the above description, the frequency difference ratio is described as an example. However, the frequency error itself may be calculated instead of the frequency difference ratio. Here, f1 represents a desired frequency to be received by the slave, and if it is known by the slave, the frequency difference is calculated by multiplying the frequency difference ratio by f1. Equations for calculating the frequency error corresponding to Equations 1 and 2 are Equations 3 and 4, respectively.

The frequency difference ratio or the frequency difference obtained in this way is small compared to a predetermined frequency difference ratio threshold (for example, 5 × 10 ⁻⁸ ) or a frequency difference (for example, 5 Hz). It is determined whether or not (step S507).

  If the difference is smaller than the threshold value (Yes in step S507), it is determined that the frequency synchronization accuracy has not deteriorated, and the process waits again until the next time stamp is received (step S501). On the other hand, if the difference is larger than the threshold value (No in step S507), it is determined that the frequency synchronization accuracy has deteriorated (step S508) and notifies the receiver that the frequency error has deteriorated (step S509).

In the above method, the example of determining whether or not the frequency synchronization accuracy has deteriorated based on the frequency difference ratio or the frequency difference has been given as an example, but in the actual operation, the frequency difference ratio, Alternatively, it is possible to determine whether or not the frequency synchronization accuracy has deteriorated from the phase difference without obtaining the frequency difference. For example, it is also possible to determine whether or not the frequency synchronization accuracy has deteriorated by comparing the absolute value of (T _K '-T _K )-(t _K -t _K ') with RTT.

  In the above method, the ratio of the frequency difference is calculated based on the time stamp values of k and k + 1 for each of the master and the slave. However, any time such as k and k + 2 or k and k + 3 is used. A frequency difference ratio or the like may be calculated based on the stamp value.

For example, an equation for calculating a frequency difference ratio based on a combination of time stamps from k = m to k = n (n> m) is as follows. Here, the specific time used when calculating the frequency difference is the time after the time information signal is transmitted / received a plurality of times between the master and the slave, and after the transmission / reception of the time information signal is completed. This is the time until the transmission / reception of the time information signal is restarted and the round-trip delay time of the time information signal.

The specific time used when calculating the frequency difference is the time information signal from the time when the time information signal reciprocates a plurality of times between the master and the slave and after the transmission / reception of the time information signal is completed. It is good also as the time which excluded the time until it starts again transmitting / receiving.

The specific time used when calculating the frequency difference may be a time for the time information signal to reciprocate a plurality of times between the master and the slave.

The specific time used when calculating the frequency difference may be a time obtained by excluding a round-trip delay time of the time information signal from a time when the time information signal reciprocates a plurality of times between the master and the slave.

  According to the above method, frequency synchronization accuracy can be monitored only by the master-slave signal without using the signal from the GPS. Therefore, the frequency synchronization can be performed stably and stably without depending on the weather change. It is possible to monitor the accuracy. Further, even when a master and a slave are installed in the basement where it is difficult to receive GPS signals, it is possible to monitor the frequency synchronization accuracy.

(Embodiment 2)
6 to 8 are flowcharts for explaining the frequency synchronization accuracy monitoring method of the present embodiment. The difference from the frequency synchronization accuracy monitoring method of the first embodiment is that when the frequency synchronization accuracy is deteriorated, the receiver is informed that the synchronization accuracy has deteriorated, and thereafter the control flow is not terminated and monitoring is continuously performed. In the point. Thus, even if the frequency synchronization accuracy once deteriorates, the subsequent frequency synchronization accuracy can be continuously monitored.

(Embodiment 3)
The frequency synchronization accuracy monitoring apparatus according to the present embodiment is an apparatus provided in a master that realizes the frequency synchronization accuracy monitoring method described in the first and second embodiments. The frequency synchronization accuracy monitoring device of the present embodiment is arranged on the master side,
Time information reception function for receiving the reception time and transmission time of the time information signal measured by the clock of the slave using the time information signal transmitted and received between the master and the slave,
For a specific time set based on the time information signal, a comparison function that compares the measured value at the master clock and the measured value at the slave clock at the master;
When the difference between the measurement value at the master clock and the measurement value at the slave clock is equal to or greater than a predetermined threshold, the master determines that the frequency synchronization accuracy of the slave clock with respect to the master clock has deteriorated. A decision function to
Is provided.

  FIG. 10 is a diagram for explaining the configuration of the frequency synchronization accuracy monitoring apparatus of this embodiment.

The embodiment will be described in more detail. The master 100 has an internal clock 21 and transmits / receives a data signal and a time stamp, and has a clock synchronized with the frequency of the internal clock 21 of the master 100. a frequency synchronization accuracy monitoring device in the master 100 that operates between the slave 200 to transmit and receive, to emboss the time T _k to the transmission of packets in a random or regular intervals from the transmission section 22 of the master 100 to the time stamp The function (time stamp generating unit 23), the function of transmitting the stamped time stamp to the slave (time stamp transmitting unit 24), and the time stamp sent from the master 100 are received by the receiving unit of the slave 200. a function of reading the time _{t k,} the master 1 from the transmission section of the slave 200 Toward 0 of the reception unit 25 transmits the time t _k to transmit a time stamp _'and a function of embossed the timestamp in the slave 200, the t _k and t _k' from the slave transmission unit to the master receiver 25 A function, a function of time stamping the time T _k ′ received by the master receiver 25 from the slave transmitter (time stamp generator 23), and one or more (T _k , T _k ′, t _k , t _k ′) and a function of calculating a one-way delay time between the master 100 and the slave 200, a plurality of (T _k , T _k ′, t _k , t _k ′) A function that calculates the value obtained by counting each specific time interval with each counter operating with the internal clock of the master and slave from one round-trip delay time, and between the master and slave based on those values Frequency difference And a function (frequency difference detection unit 26) that determines that the frequency synchronization accuracy between the master, the clock, and the slave clock has deteriorated when there is a difference equal to or greater than a preset threshold. The frequency difference detection unit 26 has a comparison function and a determination function.

  The transmission unit 22 includes a time stamp transmission unit 24 and a data transmission unit 31. Data input from the outside is input to the data transmission unit 31, converted into a format in which data can be transmitted and received between the master and slave, and transmitted to the slave 200. A control signal is sent to the time stamp generating unit 23 at a transmission timing so as to generate a time stamp.

  As a result, the time stamp generation unit 23 generates a time stamp and sends the time stamp to the time stamp transmission unit 24. Based on the obtained time stamp, the time stamp transmission unit 24 converts the data into a format in which data can be transmitted and received between the master and the slave, and is transmitted to the slave 200.

  The receiving unit 25 includes a time stamp reading unit 32 and a data reading unit 33. The time stamp reading unit 33 reads the value of the time stamp obtained from the slave 200. When the time stamp is received, the time stamp reading unit 33 sends a control signal to the time stamp generating unit 23 so as to generate a time stamp. The read time stamp value is sent to the time stamp holding unit 34 and held in the time stamp holding unit 34. The data reading unit 33 reads the data sent from the slave 200 and outputs it to the outside of the master.

  The monitoring unit 35 includes a counter 36, a time stamp generation unit 23, a time stamp holding unit 34, and a frequency difference detection unit 26. The counter 36 operates the counter based on the clock supplied from the internal clock 21 (for example, a crystal resonator) of the master 100. This counter value is always sent to the time stamp generation unit 23 and is used when the time stamp generation unit 23 generates a time stamp.

  The time stamp generation unit 23 generates a time stamp based on the counter value obtained from the counter when the control signals generated by the time stamp transmission unit 24 and the time stamp reading unit 32 are sent. When the control signal generated by the time stamp transmission unit 24 is sent, the generated time stamp is sent to the time stamp transmission unit 24 and also sent to the time stamp holding unit 34. When the control signal generated by the time stamp reading unit 32 is sent, the time stamp generating unit 23 sends the generated time stamp to the time stamp holding unit 34.

  The time stamp holding unit 34 holds the time stamp sent from the time stamp generating unit 23 and sends the time stamp held to the frequency difference detecting unit 26 as necessary. Based on the time stamp sent from the time stamp holding unit 34, the frequency difference detecting unit 26 uses the equations 1 to 8 to reduce the frequency synchronization accuracy such as the frequency difference ratio, frequency difference, or phase difference. A value necessary for determining whether or not the determination has been made is calculated. The frequency difference detecting unit 26 compares the calculated value with a predetermined threshold value to determine whether or not the synchronization accuracy has deteriorated, and determines whether or not the frequency error and the synchronization accuracy have deteriorated. Output to. The frequency difference detection unit 26 outputs a frequency error (for example, a frequency difference ratio or a frequency difference) to the outside of the master.

  Here, as the internal clock 21, it is conceivable to use, for example, a crystal oscillator with an oven (Oven Controlled Xtal Oscillator, OCXO). When the frequency of the internal clock 21 and the frequency of the clock to be input to the counter 36 are different, the frequency may be input by using a clock extraction unit such as a multiplier or a frequency divider.

  The monitoring flow as shown in FIGS. 3 to 8 is preferably started after the frequency of the clock output from the clock extraction unit is stabilized. For example, in the case of OCXO, the output clock is stabilized when the temperature chamber is sufficiently warmed. Therefore, the master internal clock 21 can be stabilized by waiting for a time sufficiently longer than the time required to warm the oven.

  In this embodiment, the frequency difference detection unit 26 in the master determines whether the frequency synchronization accuracy has deteriorated in the master based on the time stamp value, and calculates a frequency error or the like. As mentioned above, a configuration is also conceivable in which the value of the time stamp is notified to the outside of the master and it is determined whether or not the frequency synchronization accuracy has deteriorated outside the master, or a frequency error is calculated.

  According to such a master, since the frequency synchronization accuracy can be monitored only by the signal between the master and the slave without using the signal from the GPS, it does not depend on the change of the weather and is stably stable. Thus, it is possible to monitor the frequency synchronization accuracy. Further, even when a master and a slave are installed in the basement where it is difficult to receive GPS signals, it is possible to monitor the frequency synchronization accuracy.

(Embodiment 4)
In the present embodiment, the frequency synchronization accuracy monitoring method described in the first or second embodiment is performed at a predetermined time, and the master 100 monitors the frequency synchronization accuracy between the internal clock of the slave 200 and the internal clock of the master 100 while monitoring the master. 100 is a communication method and communication system for transmitting and receiving data signals between 100 and a slave 200. When the master 100 performs the frequency synchronization accuracy monitoring method at a predetermined time, the frequency synchronization accuracy of the internal clock of the slave 200 can be monitored by the master 100. The master 100 and the slave 200 continue to transmit / receive data if the frequency synchronization accuracy is within the specified value, and stop transmitting / receiving data if the frequency synchronization accuracy is outside the specified value. At that time, the master 100 can raise an alarm indicating that the synchronization accuracy of the internal clock of the slave 200 has deteriorated.

  The following describes the frequency synchronization accuracy monitoring method and the frequency synchronization accuracy monitoring device of the present embodiment.

  (1): A method of monitoring frequency synchronization accuracy in a master operating between opposing transmitters and receivers that exchange time information, wherein a time stamp is transmitted from the master at random or regular intervals, and the time stamp The transmission time of the master is held at the master, the time stamp sent from the master to the slave is received at the slave, and the time stamp is received at the slave, and the time stamp is transmitted from the slave to the master. When the time is sent from the slave as a time stamp to the master, the master reads the time stamp value sent from the slave, holds it in the master, and holds the time when the time stamp was received from the slave in the master. From multiple time stamp values -Calculate the delay time for one round trip between slaves, and use a counter that operates with the clock of each master and slave for a specific time interval from multiple timestamp values and one round trip delay time between master and slave. Calculates the counted value, calculates the frequency difference between the master and slave from the count difference, and the frequency synchronization accuracy between the master clock and the slave clock deteriorates when there is a difference greater than the preset threshold This is a frequency synchronization accuracy monitoring method that determines that the signal has deteriorated.

  (2): In the above (1), a time obtained by subtracting a transmission delay of a time stamp from a time required for exchanging one round trip or a plurality of round trip time stamps is used as the specific time interval. The frequency synchronization accuracy monitoring method described.

  (3): The frequency synchronization accuracy monitoring method according to (1), wherein a time required for exchanging one or more round-trip time stamps is used as the specific time interval.

  (4): As the above-mentioned specific time interval, after finishing the round-trip exchange of time stamps, the time taken to start the next round-trip exchange is subtracted from the time taken to exchange multiple round-trip time stamps. The frequency synchronization accuracy monitoring method as described in (1) above, wherein the time is used.

  (5): As the above-mentioned specific time interval, the time taken from the end of one round-trip exchange of the time stamp to the next round-trip exchange again, and the time minus the propagation delay of the time stamp The frequency synchronization accuracy monitoring method according to (1) above, wherein a time subtracted from a time required for exchanging a plurality of time stamps is used.

  (6): The frequency synchronization accuracy monitoring method according to any one of (1) to (5) above, wherein a frequency difference between the master and slave clocks is output to the outside of the receiver.

  (7): Monitoring device for frequency synchronization accuracy in a master that operates between two opposing transmitters / receivers to exchange time information, a function for transmitting a time stamp from the master at random or regular intervals, and The function of holding the transmission time at the master, the reception time of the time stamp at the slave when the time stamp sent from the master to the slave is received at the slave, and the time at which the time stamp is transmitted from the slave to the master When a slave sends a time stamp as a time stamp, the master reads the time stamp value sent from the slave, the master holds the time stamp, and the master holds the time when the time stamp is received from the slave. Multiple stored timestamp values Based on the function to calculate the delay time for one round trip between master and slave, and the one round trip delay time between multiple time stamp values and master-slave, it operates with a specific time interval with each clock of master and slave. The function that calculates the value counted by the counter, the function that calculates the frequency difference between the master and slave from the count difference, and the difference between the master clock and slave clock when there is a difference that exceeds a preset threshold. A frequency synchronization accuracy monitoring device having a function of determining that the frequency synchronization accuracy of the device has deteriorated and a function of notifying that the frequency synchronization accuracy has deteriorated to the outside.

  As a result, the frequency synchronization accuracy can be monitored only by the master-slave signal without using the signal from the GPS, so that the frequency synchronization accuracy can be monitored stably and stably without depending on the weather change. Can be done. Further, even when a master and a slave are installed in the basement where it is difficult to receive GPS signals, it is possible to monitor the frequency synchronization accuracy.

11: Phase comparator 12: Filter 13: Voltage controlled oscillator 14: Frequency divider 21: Internal clock 22: Transmitter 23: Time stamp generator 24: Time stamp transmitter 25: Receiver 26: Frequency difference detector 31: Data transmission unit 32: Time stamp reading unit 33: Data reading unit 34: Time stamp holding unit 35: Monitoring unit 100: Master 200: Slave

Claims (9)

Using the time information signal transmitted and received between the master and the slave, the reception time and the transmission time of the time information signal measured by the clock of the slave are received by the master,
For the specific time set based on the time information signal, the measured value in the master clock and the measured value in the slave clock are compared in the master,
When the difference between the measurement value at the master clock and the measurement value at the slave clock is equal to or greater than a predetermined threshold, the master determines that the frequency synchronization accuracy of the slave clock with respect to the master clock has deteriorated. Frequency synchronization accuracy monitoring method.   The specific time is a time obtained by excluding a round-trip delay time of the time information signal from a time for the time information signal to make one round trip between the master and the slave or a time for making a round trip multiple times. The frequency synchronization accuracy monitoring method according to claim 1.   The frequency synchronization accuracy monitoring method according to claim 1, wherein the specific time is a time for the time information signal to reciprocate once or a plurality of times between the master and the slave.   The specific time is from the time when the time information signal reciprocates a plurality of times between the master and the slave until the transmission / reception of the time information signal is started again after the transmission / reception of the time information signal is completed. The frequency synchronization accuracy monitoring method according to claim 1, wherein the time is excluded from the time.   The specific time is from the time when the time information signal reciprocates a plurality of times between the master and the slave until the transmission / reception of the time information signal is started again after the transmission / reception of the time information signal is completed. 2. The frequency synchronization accuracy monitoring method according to claim 1, wherein the time is a time excluding a round-trip delay time of the time information signal.   6. The frequency synchronization accuracy monitoring method according to claim 1, wherein the difference is output from the master as a frequency error between the master clock and the slave clock. Placed on the master side,
Time information reception function for receiving the reception time and transmission time of the time information signal measured by the clock of the slave using the time information signal transmitted and received between the master and the slave,
For a specific time set based on the time information signal, a comparison function that compares the measured value at the master clock and the measured value at the slave clock at the master;
When the difference between the measurement value at the master clock and the measurement value at the slave clock is equal to or greater than a predetermined threshold, the master determines that the frequency synchronization accuracy of the slave clock with respect to the master clock has deteriorated. A decision function to
A frequency synchronization accuracy monitoring device comprising:   The frequency synchronization accuracy monitoring method according to any one of claims 1 to 6 is performed at a predetermined time, while monitoring the frequency synchronization accuracy between the internal clock of the slave and the internal clock of the master at the master, A communication method for transmitting / receiving a data signal to / from the slave. A communication system for transmitting and receiving data signals between a master and a slave,
8. The communication system according to claim 7, wherein the master has the frequency synchronization accuracy monitoring device according to claim 7, and monitors the frequency synchronization accuracy between the slave internal clock and the master internal clock at a predetermined time.

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