JP2010278546A - Time synchronization network and communication equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide time synchronization for a base station or a communication equipment within a desired accuracy, without increase in the network load accompanied with shortening of a time correction interval, or without increase in the cost by mounting of a highly accurate oscillator. <P>SOLUTION: A packet transmitting device 1 has a difference detection function. The difference detection function detects difference between a clock supplied by a stable and highly precise clock synchronization function actualized at a transmission network side and a clock deriving from GPS. Wherein the former clock is different from the latter clock. The packet transmitting device 1 operates a time synchronization protocol using a GPS emulation clock. The GPS emulation clock operates by a highly accurate clock 5 at the transmission network side, and is corrected suitably by the difference detection function. The packet transmitting device 1 has a derivation means, which derives a time correction interval according to time synchronization needed to satisfy the time synchronization accuracy required between base stations 3 and 4, based on synchronization accuracy request information on a given network synchronization clock etc. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a time synchronization network and a communication apparatus, and in particular, by using a synchronization clock of a high-accuracy clock synchronization network with different original oscillations, time synchronization is performed by different time distribution means although the original oscillations are the same. The present invention relates to a time synchronization network and a communication device that constitute a network for highly accurate time synchronization between communication devices.

In order to synchronize the frequency of carrier waves between base station apparatuses of a cellular phone network and to synchronize between base station apparatuses at the time of handover, for example, time synchronization on the order of 10 ^{−8 is} currently required. ing. Conventionally, in order to realize this, as shown in Non-Patent Document 1 (page 54), each base station prepares a GPS receiving antenna, receives a time signal broadcast from an artificial satellite, and synchronizes time. It is carried out. However, some base stations are installed in places where radio waves from GPS satellites cannot be received directly (for example, underground), and there are cases where time synchronization by GPS is actually difficult. Correspondingly, in recent years, with the progress of packetization of transmission networks that accommodate base station apparatuses, the direction of performing packet-based time synchronization by IEEE 1588 that realizes time synchronization with relatively high accuracy is also sought. ing. However, the time synchronization accuracy according to IEEE 1588 is sub-microsecond, that is, 10 ⁻⁷ order, and the performance is insufficient to realize the synchronization accuracy of 10 ⁻⁸ required between mobile phone base station apparatuses. A case is assumed.
Regarding IEEE 1588, application to a telecom network that requires higher-accuracy clock synchronization has begun to be studied. As shown in Non-Patent Document 2 (Page 15 to Page 17), the time correction interval according to IEEE 1588 is shortened. Standardization in the direction of increasing accuracy is underway. However, in this method, there is a problem that the ratio of time correction packets to the main signal traffic increases due to shortening of the time correction interval, and the network load increases. As a solution to this problem, Non-Patent Document 2 (Page 15 to Page 17) As shown in FIG. 2, standardization is proceeding in the direction of shortening the length of the packet for the time synchronization message. However, in any case, as the synchronization accuracy improves, the network load due to the shortening of the time correction interval tends to increase.

On the other hand, even in the conventional IEEE 1588 protocol, each packet transmission device on the packet transmission network that accommodates the base station device is mounted with a transmitter having a higher accuracy than the required time synchronization accuracy, for example, 10 ^−8. It is possible to achieve the required accuracy by running the watch while it is not being corrected. For example, in a general IEEE 1588 operating environment, the time correction interval is assumed to be 1 second. When the accuracy of the clock mounted on the packet transmission device is 10 ⁻⁹ , one clock cycle of the 10 ⁻⁸ order is the same time as the 10 clock cycles of the 10 ⁻⁹ order. Synchronization plurality of base stations which require found when mounting the respective order of 10 ^-9 accuracy clocks, among the clock of each base station apparatus mounting, the worst 10 ^-9 order of clock 1 clock per second Differences occur. In other words, it can be said that it takes 10 seconds to generate a difference corresponding to one cycle of a clock of 10 ⁻⁸ order between clocks driven by a clock having an accuracy of 10 ⁻⁹ order. Therefore, it is possible to perform time synchronization on the order of 10 ⁻⁸ by correcting the time between the two clocks at a cycle shorter than 10 seconds, for example, at an interval of the order of 1 second, which is 1/10. is there. As described above, in this example, a clock driven with a clock having an accuracy of at least 10 ⁻⁹ order is used, and the IEEE 1588 protocol is operated, so that the accuracy of the order of 10 ⁻⁸ is required between mobile phone base station apparatuses. Time synchronization is possible. However, in reality, a clock that stably generates a high-accuracy clock of the order of 10 ⁻⁹ or higher even when a change in the ambient environment such as temperature occurs occurs at a level that conforms to an atomic clock, and is considered to be expensive.

Here, we turn our attention to the transmission apparatus side that accommodates the mobile phone base station. Conventionally, an SDH / SONET transmission apparatus that accommodates a mobile phone base station is required to perform clock synchronization on the order of, for example, 10 ⁻¹² via an SDH / SONET interface. In order to realize this, transmission devices are arranged in a hierarchy, a clock synchronous network is configured, a clock is supplied from a high-accuracy clock source to a transmission device in the highest layer, and thereafter, transmission devices in lower layers The clock is regenerated and extracted from the data received from the upper layer transmission apparatus by a variable oscillator and synchronized with this clock, thereby realizing clock synchronization with the required accuracy in the entire transmission network. In addition, with the progress of packetization of transmission networks in recent years, in order to realize high-accuracy clock synchronization within the packet network, Synchronous Ethernet (registered trademark) (ITU-T G.8261, G. 8262) has been standardized, and clock synchronization is possible in the packet network with the same accuracy as conventional SDH / SONET.
However, the clock synchronization network configured by the transmission device or the clock synchronization network configured by the packet transmission device performs high-accuracy clock synchronization, but does not perform time management, and the GPS side It is not synchronized with other clocks.

Mechanism of mobile phone (A2A Laboratory, August 2008) 54 (URL-> http://www.a2a.jp/resources/mobile_phone.pdf) IEEE 1588 ™ Telecommunications Applications (URL-> http://ieee1588.nist.gov/tutorial-telcom.pdf)

The problem to be solved by the present invention is that both a base station apparatus that performs time synchronization by GPS and a base station apparatus that performs time synchronization by GPS using a protocol such as IEEE 1588 exist in the same network. If the time synchronization is to be realized within the required accuracy, the load on the network increases as the time correction interval is shortened, or the cost increases due to the mounting of a high-precision oscillator.
In view of the above, the present invention realizes time synchronization of a base station and / or a communication device within the required accuracy without increasing the network load or increasing the cost due to the mounting of a high-precision oscillator. For the purpose.

  The present invention has, for example, a function for detecting a difference between a clock supplied by a stable and highly accurate clock synchronization function realized on the transmission network side and a clock derived from GPS different from this, and the transmission network side The main feature is to operate a time synchronization protocol such as IEEE 1588 using a GPS emulation clock that operates with a high-accuracy network synchronization clock and corrects appropriately with a difference detection function.

According to the first solution of the present invention,
In a time synchronization network for performing time synchronization among a plurality of the communication devices according to time information distributed over the network by a time synchronization protocol, the plurality of communication devices have a hierarchical structure,
The highest level communication device of the time synchronization network is:
A time receiving function for receiving time information from the time source clock;
An external clock reception function that receives an external reference clock signal from an external oscillator that is asynchronous with the time source clock and is more accurate than the time source, and generates a clock signal that is synchronized with the external reference clock signal;
Based on the clock signal cycle count generated by the external clock reception function, to calculate the time derived from the external oscillator, to calculate the time from the time source based on the time received from the time source clock, By comparing the time from the external oscillator and the time from the time source, the offset detection function between the original oscillators detects time difference information between the original oscillator by the time source and the original oscillator by the external oscillator. When,
Driving based on the clock signal generated by the external clock reception function and correcting the time based on the time difference information detected by the offset detection function between original oscillations, it is possible to achieve higher time synchronization than the time synchronization protocol. A master station emulation clock that is synchronized with the time source clock with accuracy;
Based on the time information from the main station emulation clock, a master function to generate a time synchronization message according to the time synchronization protocol;
A function of sending the time synchronization message to a lower-level communication device by a transmission code generated at a timing synchronized with a clock signal supplied from the external clock reception function;

A communication device other than the highest level of the time synchronization network is:
Receiving the time synchronization message from a higher-level communication device;
A main signal clock extraction function that extracts a clock component from the transmission code of the time synchronization message and generates a clock signal that is synchronized with the clock of the highest-level communication device with high accuracy from the time source;
A slave function in the time synchronization protocol for extracting time information from a time synchronization message distributed by the time synchronization protocol;
Based on the count of the clock signal period generated by the main signal clock extraction function, the time derived from the main signal clock is calculated, the time derived from the time synchronization protocol is calculated from the time received by the slave function, and the main signal clock From the comparison between the time derived from the time and the time derived from the time synchronization protocol, an offset detection function between clock sources that detects time difference information between two clock sources,
Driving based on the clock signal generated by the main signal clock extraction function and correcting the time based on the difference information of the time detected by the offset detection function between clock sources, it is more accurate than the time synchronization protocol. A slave emulation clock synchronized with the time of the slave function, the time of the master station emulation clock, and the time of the clock as the time source;
The time synchronization network is provided.

According to the second solution of the present invention,
A plurality of communication devices has a hierarchical structure, and is a top-level communication device in a time synchronization network for performing time synchronization between the plurality of communication devices based on time information distributed via a network by a time synchronization protocol,
A time receiving function for receiving time information from the time source clock;
An external clock reception function that receives an external reference clock signal from an external oscillator that is asynchronous with the time source clock and is more accurate than the time source, and generates a clock signal that is synchronized with the external reference clock signal;
Based on the clock signal cycle count generated by the external clock reception function, to calculate the time derived from the external oscillator, to calculate the time from the time source based on the time received from the time source clock, By comparing the time from the external oscillator and the time from the time source, the offset detection function between the original oscillators detects time difference information between the original oscillator by the time source and the original oscillator by the external oscillator. When,
Driving based on the clock signal generated by the external clock reception function and correcting the time based on the time difference information detected by the offset detection function between original oscillations, it is possible to achieve higher time synchronization than the time synchronization protocol. A master station emulation clock that is synchronized with the time source clock with accuracy;
Based on the time information from the main station emulation clock, a master function to generate a time synchronization message according to the time synchronization protocol;
The communication device is provided with a function of sending the time synchronization message to a lower communication device using a transmission code generated at a timing synchronized with a clock signal supplied from the external clock reception function.

According to the third solution of the present invention,
A communication device other than the highest level in a time synchronization network for performing time synchronization between a plurality of communication devices based on time information distributed via a network by a time synchronization protocol, wherein the plurality of communication devices have a hierarchical structure. ,
Generated according to the time synchronization protocol based on the time information from the emulation clock of the higher-level communication device, and sent out by the transmission code generated at the timing synchronized with the external reference clock signal from the external oscillator with higher accuracy than the time source Received a time synchronization message from a higher-level communication device,
A main signal clock extraction function that extracts a clock component from the transmission code of the time synchronization message and generates a clock signal that is synchronized with the clock of the highest-level communication device with high accuracy from the time source;
A slave function in the time synchronization protocol for extracting time information from a time synchronization message distributed by the time synchronization protocol;
Based on the count of the clock signal period generated by the main signal clock extraction function, the time derived from the main signal clock is calculated, the time derived from the time synchronization protocol is calculated from the time received by the slave function, and the main signal clock From the comparison between the time derived from the time and the time derived from the time synchronization protocol, an offset detection function between clock sources that detects time difference information between two clock sources,
Driving based on the clock signal generated by the main signal clock extraction function and correcting the time based on the difference information of the time detected by the offset detection function between clock sources, it is more accurate than the time synchronization protocol. A slave emulation clock synchronized with the time of the slave function, the time of the master station emulation clock, and the time of the clock as the time source;
The communication apparatus is provided.

According to the present invention, there is a special effect that the time synchronization of the base station and / or the communication device can be realized within the required accuracy without increasing the network load or incurring the cost increase due to the mounting of the high-precision oscillator. is there.
The present invention has a special effect when, for example, a base station apparatus that performs time synchronization using GPS and a base station apparatus that performs time synchronization using GPS via a packet network using a protocol such as IEEE 1588 exist in the same network. Play.

It is a system configuration | structure figure of the time synchronous network of this Embodiment. 1 is a schematic explanatory diagram of a time synchronization protocol shown in IEEE 1588. FIG. It is explanatory drawing which showed the structure of the packet transmission apparatus installed in a main station. It is explanatory drawing which showed the structure of the packet transmission apparatus installed in a slave station. It is a conceptual example figure of the detection of the offset between original oscillations in the packet transmission apparatus installed in the main station. It is explanatory drawing of the list of the various parameters and calculation formulas used in this Embodiment. 5 is a processing flowchart for determining a time correction amount for the main station GPS emulation clock 9 in the GPS time correction function 10. It is a conceptual diagram of the tracking situation to GPS time of GPS emulation time.

FIG. 1 is a system configuration diagram of a time synchronization network according to the present embodiment.
This figure shows an outline of the configuration of a hierarchically structured clock synchronization network and time synchronization network. The time synchronization network is composed of a packet transmission device 1 installed at the master station, which is the highest level of the time synchronization network and the clock synchronization network, and a transmission device 2 installed at the slave station operating in synchronization with the clock and time of the master station in multiple stages. Configure hierarchically. In this example, the base station device 3 having the GPS antenna 13 at the end of the clock and time synchronization network and capable of receiving the time by the GPS signal 73 from the GPS satellite 6 operates as the end device of the clock and time synchronization network. A base station device 4 is connected. In this example, the clock synchronization network uses Synchronous Ethernet as an example, and the time synchronization network uses IEEE 1588 as an example, but other protocols such as NTP may be used for time synchronization, for example.
The packet transmission device 1 installed at the main station has a GPS antenna 13 and has a function of receiving time information from a GPS signal 73 received from the GPS satellite 6. Further, it has a function of receiving a high-accuracy network synchronization clock from the high-accuracy network synchronization source clock 5. In addition, the Synchronous Ethernet has a function of sending an Ethernet signal 71 synchronized with the clock received from the high-accuracy network synchronization source clock 5 and operates as an IEEE 1588 master device. It has a function of transmitting a synchronized Synchronous Ethernet signal and performing time synchronization by an IEEE 1588 message 72.

The packet transmission device 2 installed in the slave station extracts a clock from the synchronous Ethernet signal 71 received from the master station or a higher-order slave station, performs network synchronization, receives time information by an IEEE 1588 message 72, and receives the clock and clock of the master station. It has the function which operates depending on. In addition, the Synchronous Ethernet has a function of sending a Synchronous Ethernet signal 71 synchronized with the clock of the master station or an upper slave station, and operates as an IEEE 1588 master device, and the packet transmission device installed in the slave station is synchronized with the master clock. It has a function of transmitting a signal and performing time synchronization by an IEEE 1588 message 72.
In the present embodiment, the time to be synchronized by IEEE 1588 is synchronized with the time distributed by the GPS satellite 6, and the clock to be synchronized by the Synchronous Ethernet is supplied from the high-accuracy network synchronization source clock 5. Synchronized with the clock. In the packet transmission device 1 installed at the master station and the packet transmission device 2 installed at the slave station, the time distributed by the GPS satellite 6 is not dependent on the internal oscillator, but is synchronized with the high-accuracy high-speed network synchronization source using the Synchronous Ethernet. It has a feature of having a timepiece driven with a clock synchronized with the clock 5 and tracking with high accuracy.
Here, in order to simplify the following explanation, terms are defined. First, the term time will be defined. The time is assumed to be identification information representing a single point in time, such as 12:00:00. Next we define the term time. Time is a quantity that represents the width of time. That is, it can be defined as the difference between two time points, or can be defined as the accumulation of a certain unit time. The time represented as the difference between the time of 12:00:00 and the time of 13:00:00 is 1 hour 00:00. Also, the time represented as 30 times of 1 second is 30 seconds.
At the end of the description of this figure, an outline of accuracy of clock synchronization by GPS and time synchronization by network synchronization and accuracy required for time synchronization by network synchronization will be described. First, the accuracy with which the packet transmission device 1 installed at the main station and the base station device 3 synchronize with time information distributed from a GPS satellite is 10 ⁻⁸ . The accuracy of clock synchronization by network synchronization is ^10-12 . Generally, since the synchronization accuracy with respect to time information distributed by a GPS satellite is 10 ^−8, it is necessary to maintain the accuracy of 10 ^{−8 in} the terminal base station apparatus 4 with respect to the accuracy of time synchronization by network synchronization. . In general, the time synchronization accuracy in IEEE 1588 is said to be on the order of sub-microseconds, that is, about 10 ⁻⁷ , and it is a condition that it is required to improve the accuracy of time synchronization by one digit or more.

FIG. 2 shows an overview of the time synchronization protocol shown in IEEE 1588.
Hereinafter, the outline of the IEEE 1588 time synchronization protocol will be described with reference to this figure, and the time information mounted in the time synchronization message is not simply distributed as it is by the GPS time distribution. It will be explained that time information obtained by a timepiece which is self-propelled between the two and is synchronized with GPS time with high accuracy is required.

  First, an outline of the IEEE 1588 time synchronization protocol will be described. When information is exchanged between two devices connected by a transmission path, a transmission delay corresponding to the transmission distance occurs. For this reason, it is necessary to consider a delay corresponding to a transmission delay when receiving a message carrying time information at a certain time. IEEE 1588 pays attention to this point, and adopts a method of correcting the time by configuring a protocol that detects two parameters, a time lag between two devices and a transmission delay. In IEEE 1588, a device that provides information on which time synchronization is based is called a master, and a device that follows the provided time information is called a slave. In this figure, a sequence diagram is used to explain the protocol, and a state in which messages are exchanged between the master time 113 on the master side and the slave time 114 on the slave side is described in time series. As time series, time passes from the top to the bottom of the figure. On the master device side, the time synchronization protocol is periodically activated in the time synchronization period 121. The time synchronization period 121 is defined as 1 second or longer in this example, but is not limited to this and may be an appropriate value. At the timing of starting the time synchronization protocol on the master device side, first, the time information t1 on the master side at this time is recorded, and the Sync message 115 is sent to the slave device side. When the slave device receives the Sync message 115, it records the time t2 of the slave device at the time of reception. Subsequently, the master device sends 116 a Follow_Up message carrying information of the time t1 at which the Sync message 115 was sent. By this series of protocols, the slave device side obtains information on the master side time t1 at which the master side sent the Sync message 115 and the slave side time t2 at which the own device received the Sync message 115. By calculating the time that is the difference between the two pieces of time information, the slave device side can obtain the sum of the shift between the master side time 113 and the slave side time 114 and the transmission path delay. Subsequently, the slave device sends the Delay_Req message 117 to the master device, and records the time t3 at which the Delay_Req message 117 is sent. The master device that has received the Delay_Req message 117 records the time t4 at that time, writes the time information t4 in the Delay_Resp message 118, and sends it to the slave device. As a result, the slave device obtains information on the slave side time t3 when the slave device sends the Delay_Req message and the master side time t4 when the master device receives the Delay_Req message. By calculating the time which is the difference between the two pieces of time information, the slave side device can obtain the sum of the deviation between the master side time 113 and the slave side time 114 and the transmission path delay. However, the time information obtained here has a relationship in which the message transmission / reception direction is reversed with respect to the time information obtained by the previous Sync message 115 and Follow_Up message 116, and the master side time 113 and the slave side time 114. The deviation is a value added in a state where the sign is inverted. The sum of the time obtained by transmission / reception of the Sync message 115 and the Follow_Up message 116 and the time obtained by transmission / reception of the Delay_Req message 117 and the Delay_Resp message 118 corresponds to twice the transmission line delay. This corresponds to twice the time difference between the side time 113 and the slave side time 114. From the above, the slave side device can know the information of the time difference between the master side time 113 and the slave side time 114, and can follow the slave side time 114 to the master side time 113.

However, here, the time synchronization period 121 based on IEEE 1588 is 1 second or more, and the time distribution period based on GPS is also 1 second. For this reason, a clock that is driven on the master side by a clock in its own device for at least one second, emulates GPS time with a required accuracy, and has a required time resolution is required. The present embodiment is characterized in that, as a high-accuracy clock source for driving a clock that emulates this GPS time, a high-accuracy synchronous clock obtained by clock synchronization is used instead of a high-accuracy internal oscillator. .
At the end of the description of this figure, the operation of the IEEE 1588 protocol is outlined according to actual examples. First, it is assumed that the time difference between the master side device and the slave side device is 10 nsec. Further, assuming that the master side device and the slave side device are connected by a transmission line of 20 km, that is, there is a transmission line delay of 5 nsec / m, it is assumed that there is a transmission line delay of 100 μsec. If the master side device issues a Sync message at the time of 12:00, and the slave side device issues the Delay_Req message at the time of 12:00: 0 + 0.1 sec, the values of t1 to t4 are Considering the time as a reference, it is as follows.
t1 = 12: 00
t2 = 12: 00: 0 + 10 nsec + 100 μsec
t3 = 12: 00: 0 + 0.1 sec + 10 nsec
t4 = 12: 00: +0.1 sec + 100 μsec
The time difference is obtained based on each time information.
t2-t1 = 100,010 nsec = transmission path delay + time difference between master and slave t4-t3 = 99,990 nsec = transmission path delay−time difference between master and slave ) Can be obtained as follows.
Transmission line delay = {(t2−t1) + (t4−t3)} / 2 = 100 μsec
Time difference between master and slave = {(t2-t1)-(t4-t3)} / 2 = 10 nsec

Next, the configuration and operation of each packet transmission apparatus in the clock synchronization and time synchronization network configured according to the present embodiment will be described.
FIG. 3 shows a configuration example of the packet transmission apparatus 1 installed at the main station.
The packet transmission device 1 installed at the main station includes an external clock reception function 21, an original oscillation offset detection function 23, a GPS time reception function 25, a GPS time correction function 10, and a main station GPS emulation clock 9. , An IEEE 1588 master function 11 having a setting information storage function 28, an IEEE 1588 time correction interval calculation function 29, an IEEE 1588 time synchronization message transmission / reception function 30, a GPS antenna 13, and a clock synchronization packet code transmission / reception function 12. The external clock reception function 21 is connected to the high-accuracy network synchronization source clock 5, the GPS antenna 13 receives GPS signals and time information in the GPS signals from the GPS satellite 6, and the setting information storage function 28 is an external monitoring control device 20. The clock synchronous packet code transmission / reception function 12 is connected to the packet transmission apparatus 2 installed in the slave station.

Next, an outline of each function in the apparatus will be described.
First, this apparatus uses a reference clock signal from the high-accuracy network synchronization source clock 5 (generally, the clock is turned ON / OFF once for each cycle. For example, in the case of a 64 kHz clock signal, this ON / OFF cycle is set to 1). The signal is repeated 64,000 times per second (the ON / OFF cycle is always constant) by the external clock reception function 21, and after shaping the waveform after removing the influence of attenuation, waveform deterioration, etc., the external A clock signal synchronized with the high-accuracy network synchronization source clock 5 is stably generated by a PLL mounted inside the clock reception function 21. The external clock reception function 21 supplies the generated clock signal to the original oscillation offset detection function 23, the main station GPS emulation clock 9, and the clock synchronization packet code transmission / reception function 12. The accuracy with which the external clock receiving function 21 synchronizes with the reference clock supplied by the high-accuracy network synchronization source clock 5 is on the order of ^10-12 . On the other hand, the GPS time receiving function 25 receives GPS information from the GPS satellite 6 via the GPS antenna 13, extracts the time information, and periodically supplies the GPS time information to the original vibration offset detection function 23. The original oscillation offset detection function 23 counts the number of ON / OFF cycles of the clock supplied from the external clock reception function 21 and measures the time derived from the external oscillator 5. The original oscillation offset detection function 23 measures the time derived from the GPS satellite 6 based on the time information supplied from the GPS time reception function 25. The original oscillation offset detection function 23 compares the time derived from the external oscillator 5 and the time information derived from the GPS satellite 6 obtained as described above, calculates the time difference between the original oscillations, and outputs the GPS time correction function 10 On the other hand, the difference information of the time between the original oscillations (in this example, it is assumed that the time 1 second from the GPS satellite 6 is shifted by ± how many ps per second from the external oscillator 5) To do. The GPS time correction function 10 is based on the difference information of the time between original vibrations supplied from the offset detection function 23 between original vibrations at a correction cycle determined so as to be able to maintain the required accuracy in the apparatus. The time of the GPS emulation clock 9 is corrected. The main station GPS emulation clock 9 is driven based on the clock signal supplied from the external clock reception function 21 and sends time information (information indicating what hour, minute, and second to the GPS time correction function 10 and the IEEE 1588 master function 11. , The information below the second can be provided as information below the decimal point), and the time correction information from the GPS time correction function 10 is received and the time is corrected.

  The IEEE 1588 master function 11 includes a setting information storage function 28, an IEEE 1588 time correction interval calculation function 29, and an IEEE 1588 time synchronization message transmission / reception function 30. The setting information recording function 28 is set with the required accuracy information for the time synchronization of IEEE 1588 by the external monitoring control device 20 and stores it. The IEEE 1588 time correction interval calculation function 29 reads the required accuracy information stored in the setting information storage function 28, calculates the transmission interval of the IEEE 1588 time synchronization message from the clock synchronization and operation accuracy information in its own device, and the IEEE 1588 time. The transmission interval information of the IEEE 1588 time synchronization message is supplied to the synchronization message transmission / reception function 30. The IEEE 1588 time synchronization message transmission / reception function 30 determines the transmission timing of the time correction message based on the transmission interval information of the IEEE 1588 time synchronization message supplied from the IEEE 1588 time correction interval calculation function 29, and is supplied from the main station GPS emulation clock 9. IEEE 1588 time synchronization message is generated based on the GPS emulation time information, and the IEEE 1588 time synchronization message is transmitted to the packet transmission apparatus 2 (or base station apparatus 4) installed in the slave station via the clock synchronization packet code transmission / reception function 12. Start the IEEE 1588 time synchronization protocol. The IEEE 1588 master function 11 has an operation function as a master side of a protocol defined in IEEE 1588. Finally, the clock synchronization packet code transmission / reception function 12 receives a clock supply from the external clock reception function 21 and sends a transmission path code at a timing synchronized with this. Also, the packet requested to be transmitted from the IEEE 1588 time synchronization message transmission / reception function 30 and the main signal packet transmitted from this apparatus are all supplied from the external clock reception function 21 as the synchronous Ethernet signal by the clock synchronization packet code transmission / reception function 12. It is transmitted with a transmission line code synchronized with the clock.

FIG. 4 shows a configuration example of the packet transmission apparatus 2 installed in the slave station.
The packet transmission device 2 installed in the slave station has a main signal clock extraction function 31, a clock source offset detection function 33, an IEEE 1588 slave function 35, an IEEE 1588 time correction function 17, and a free-running IEEE 1588 clock function 15 having a slave IEEE 1588 emulation clock 16. An IEEE 1588 master function 18 having an information storage function 38, an IEEE 1588 time correction interval calculation function 39, an IEEE 1588 time synchronization message transmission / reception function 40, and a clock synchronization packet code transmission / reception function 19 are provided. The main signal clock extraction function 31 and the IEEE 1588 slave function 35 are connected to the packet transmission apparatus 1 installed in the master station or the packet transmission apparatus 2 installed in the upper slave station, and the setting information storage function 38 is connected to the external control apparatus 20. The synchronous packet code transmission / reception function 19 is connected to the packet transmission device 2 or the base station device 4 installed at a lower slave station.

Next, an outline of each function in the apparatus will be described.
First, the main signal clock extraction function 31 extracts a clock component from the transmission path code of the main signal, which is a Synchronous Ethernet signal received from the packet transmission device 1 installed at the master station or the packet transmission device 2 installed at the upper slave station. The PLL mounted in the signal clock extraction function 31 stably generates a clock signal synchronized with the main signal clock received from the packet transmission device 1 installed at the master station or the packet transmission device 2 installed at the upper slave station. The main signal clock extraction function 31 supplies the generated clock signal to the clock source offset detection function 33, the slave IEEE 1588 emulation clock 16, and the clock synchronization packet code transmission / reception function 19. The accuracy in which the main signal clock extraction function 31 synchronizes with the clock extracted from the main signal received from the packet transmission device 1 installed at the main station or the packet transmission device 2 installed at the upper slave station is on the order of 10 ⁻¹² . On the other hand, the IEEE 1588 slave function 35 has a function of referring to the time information of the slave IEEE 1588 emulation clock 16, and the IEEE 1588 time in the main signal received from the packet transmission device 1 installed at the master station or the packet transmission device 2 installed at the higher slave station. A synchronization message is received, time information in the message is extracted and the time information of the own device at the time of message transmission / reception is recorded in accordance with the IEEE 1588 protocol, and the time information intended by the master station is calculated (a series of operations and calculations). The concept is as described in FIG. 2). Further, the time information provided from the main station side is provided to the IEEE 1588 time correction function 17, and the time information obtained from the IEEE 1588 protocol is supplied to the clock source offset detection function 33. The clock source offset detection function 33 counts the number of ON / OFF cycles of the clock supplied from the main signal clock extraction function 31 and receives it from the packet transmission apparatus 1 installed at the master station or the packet transmission apparatus 2 installed at the upper slave station. The time derived from the main signal clock is measured. The clock source offset detection function 33 measures the time derived from the GPS satellite 6 distributed by the IEEE 1588 based on the time information supplied from the IEEE 1588 slave function 35. The clock source offset detection function 33 compares the time information derived from the main signal clock obtained as described above with the time information derived from IEEE 1588, detects the time difference between the clock sources, and detects the time difference to the IEEE 1588 time correction function 17. Supply difference information. The IEEE 1588 time correction function 17 is based on time difference information between clock sources supplied from the clock source offset detection function 33 and time information on the master device side obtained by the IEEE 1588 protocol supplied from the IEEE 1588 slave function 35. Then, the time correction of the slave IEEE 1588 emulation clock 16 is performed at a correction cycle determined so that necessary accuracy can be maintained in the apparatus. The slave IEEE 1588 emulation clock 16 is driven based on the clock signal supplied from the slave clock generation function 14, and the IEEE 1588 time correction function 17 and the IEEE 1588 master function 18 are compared with the time of the host device on the IEEE 1588 protocol, that is, the originator. In addition to supplying time information emulating the GPS time, periodic time correction information from the IEEE 1588 time correction function 17 is received and time correction is performed.

  The IEEE 1588 master function 18 includes a setting information storage function 38, an IEEE 1588 time correction interval calculation function 39, and an IEEE 1588 time synchronization message transmission / reception function 40. The setting information recording function 38 is set with the required accuracy information for the time synchronization of IEEE 1588 by the external monitoring control device 20 and stores it. The IEEE 1588 time correction interval calculation function 39 reads the required accuracy information stored in the setting information storage function 38, calculates the transmission interval of the IEEE 1588 time synchronization message from the clock synchronization and operation accuracy information in its own device, and generates the IEEE 1588 time. The transmission interval information of the IEEE 1588 time synchronization message is supplied to the synchronization message transmission / reception function 40. The IEEE 1588 time synchronization message transmission / reception function 40 determines the transmission timing of the time correction message based on the transmission interval information of the IEEE 1588 time synchronization message supplied from the IEEE 1588 time correction interval calculation function 39, and is supplied from the slave IEEE 1588 emulation clock 16. An IEEE 1588 time synchronization message is generated based on GPS emulation time information distributed via IEEE 1588, and the IEEE 1588 time is transmitted to the packet transmission apparatus 2 or the base station apparatus 4 installed at a lower slave station via the clock synchronization packet code transmission / reception function 19. Send a synchronization message and activate the IEEE 1588 time synchronization protocol. The IEEE 1588 master function 11 has an operation function as a master side of a protocol defined in IEEE 1588. Finally, the clock synchronous packet code transmission / reception function 19 receives a clock supply from the main signal clock extraction function 31, and sends out a transmission line code as a Synchronous Ethernet signal at a timing synchronized therewith. Also, all the packets requested to be transmitted from the IEEE 1588 time synchronization message transmission / reception function 40 and the main signal packets transmitted from this apparatus are converted to the clock supplied from the main signal clock extraction function 31 by the clock synchronization packet code transmission / reception function 19. It is sent with a synchronized transmission line code. Although the packet transmission device 2 installed at the slave station has both the master function and the slave function of IEEE 1588, it does not relay time information from the slave to the master. Thus, the transmission delay caused by the packet switch of the device itself and the fluctuation of the delay are not affected.

  The slave station-installed packet transmission apparatus 2 shown in the embodiment of FIG. 4 has both an IEEE 1588 master function and a slave function. However, the synchronous network terminal apparatus (the base station apparatus 4 in FIG. Alternatively, in the terminal packet transmission apparatus), the master side function may be omitted, and only the slave side function may be provided.

FIG. 5 is a timing chart showing the concept of detection of the offset between original oscillations in the offset between original oscillations detection function 23 of the packet transmission apparatus 1 installed at the main station.
First, in this figure, the waveform of the external clock reception function supply clock 41 supplied from the external clock reception function 21 is described in the upper stage, and the reception timing of the time 42 received from the GPS satellite 6 is described in the lower stage. Also, in this figure, the time for one cycle of the external clock reception function supply clock 41 is Ts45, and the time difference between one time information received from the GPS satellite 6 and the next time information received is Tg46, and the external clock reception. A difference time between 1 second obtained as an accumulation of the function supply clock 41 and 1 second supplied at time 42 received from the GPS satellite 6 is represented as ΔT47. In this figure, for the sake of simplicity, the external clock reception function supply clock 41 is assumed to be 10 Hz, and the time reception period from the GPS satellite 6 is assumed to be 1 second. Therefore, in the example of this figure, ΔT = 10 × Ts−Tg. The difference between the external clock receiving function supply clock 41 and the time 42 received from the GPS satellite 6 increases by ΔT per second. In the example of this figure, ΔT47 = −Ts, and 1 second generated based on the external clock reception function supply clock 41 is −Ts seconds shorter than 1 second due to the time 42 received from the GPS satellite 6. . This is a time difference that occurs because the atomic clock mounted on the GPS satellite 6 and the atomic clock that constitutes the high-accuracy synchronized original oscillation clock exist independently and are not synchronized with each other. 3 detects the difference between 1 second derived from the external oscillator and 1 second derived from the GPS satellite 6 according to the concept shown in FIG. 5 (FIG. 5). Time difference information is provided to the GPS time correction function 10 in the form of a deviation of ± ps per second.

For the sake of explanation in this figure, the accumulated number information 43 of the external clock receiving function supply clock 41 and the time information from the next GPS satellite 6 are received from the time t0 48 when the time information is received from the GPS satellite 6. The time t0 + 1 49 is shown. For the sake of simplicity, the timing at which time information is received from the GPS satellite 6 and the start point of the external clock reception function supply clock 41 coincide with each other at t0 48, and the timing at which time information is received from the next GPS satellite 6 An example is shown in which the end points of the 11th clock of the external clock reception function supply clock 41 coincide. However, in reality, the accuracy of each clock is 10 ⁻⁸ or more, and the timings of the clocks rarely coincide. Therefore, in the actual inter-offset offset detection function 23, the observation is made for a longer time, and the timing of receiving the time 42 from the GPS satellite 6 corresponding to t0 48 coincides with the start point of the external clock reception function supply clock 41. After detecting the timing, the observation is performed for a longer time until the next timing when the time 42 is received from the GPS satellite 6 and the timing when the end point of the external clock receiving function supply clock 41 coincides (corresponding to t0 + 1 149) A method of obtaining ΔT by dividing the difference time by the cumulative number of hours is conceivable. In addition, a frequency dividing function that further divides each timing into equal parts is mounted inside the offset detection function 23 between the original vibrations, and a method for detecting a coincidence point of each timing earlier by using finely divided timings. You may take.

FIG. 6 is an explanatory diagram of a list of various parameters and a list of calculation formulas used when the present embodiment is applied to a real system.
As a parameter given as an initial value, there is a clock synchronization network synchronization accuracy 50 = 10 ^−h , and a requested GPS time synchronization accuracy 52 = 10 ^−j is a parameter set from the external monitoring controller 20 to the setting information storage function 28. In addition, as a parameter detected by the original vibration offset detection function 23, there is an original vibration offset value (time difference information between original vibrations) 53. For the offset value 53 between the original vibrations, the time difference per second is expressed in picoseconds (10 ⁻¹² seconds), and gfedcba [ps] = a × 10 ⁰ + b × 10 ¹ + c × 10 ² + d × 10 ³ An expression in the form of + e × 10 ⁴ + f × 10 ⁵ + g × 10 ⁶ [ps] is also possible. The above is a parameter required for calculation of the parameter by calculation. In general, the clock synchronization network synchronization accuracy 50 is very high accuracy, but the frequency of the clock generated by the external clock reception function 21 is about the frequency of the main signal, and is coarser than the clock synchronization network synchronization accuracy. For example, the clock network synchronization accuracy of the external clock receiving function 21 by network synchronization is on the order of 10 ⁻¹² , but the frequency of the main signal is realized by a clock of about 10 Gbit / sec, that is, 10 ⁻¹⁰ order.

Calculated are the original fumarate correction timing 56 for 10 ⁰ component of the offset value, the original fumarate correction timing 57 for 10 ¹ component of the offset value, the original fumarate correction timing 58 for 10 ^2-component offset value, the original fumarate correction timing 61 for 10 ⁵ component of the correction timing 60, the original fumarate offset value for 10 ⁴ component of the correction timing 59, the original fumarate offset value for 10 ^three components of the offset value, correction for ¹⁰⁶ components of the original fumarate offset value timing 62, the original fumarate correction amount 63 for 10 ⁰ component of the offset value, the original fumarate correction amount 64 for 10 ¹ component of the offset value, the correction amount 65 for 10 ² components of the original fumarate offset value, the original fumarate offset value correction amount 66 with respect to the 10 ^three components, against the 10 ⁴ components of the original fumarate offset value Correction amount 67, the correction amount 68 for 10 ⁵ components of the original fumarate offset value, there is the correction amount 69 with respect to ¹⁰⁶ components of the original fumarate offset values, each of the formulas has become as follows.

Correction for 10 ⁰ component of the original fumarate offset timing ^{56 = 10 -0 × 10 h-} j-1
Correction timing 57 = ^{10 -1} × for 10 ¹ component of the original fumarate offset ^{10 h-j-1}
Correction timing 58 for 10 ² components of the offset value between original vibrations 58 = 10 ⁻² × 10 ^h−j−1
Correction timing 59 for the 10 ³ components of the offset value between the original vibrations 59 = 10 ⁻³ × 10 ^h−j−1
Correction for 10 ⁴ components of the original fumarate offset timing ^{60 = 10 -4 × 10 h-} j-1
Correction timing 61 for 10 ⁵ components of the original fumarate offset ^{= 10 -5 × 10 h-j} -1
Correction timing 62 = ^{10 -6} × for ¹⁰⁶ components of the original fumarate offset ^{10 h-j-1}
Correction amount for 10 ⁰ component of the original fumarate offset value ^{63 = a × 10 -j-1} [ sec]
Correction amount for 10 ¹ component of the original fumarate offset ^{64 = b × 10 -j-1} [ sec]
Correction amount for 10 ² components of the original fumarate offset value ^{65 = c × 10 -j-1} [ sec]
Correction amount for 10 ³ components of the original fumarate offset value ^{66 = d × 10 -j-1} [ sec]
Correction amount 67 for the ⁴ components of the offset value between original vibrations = e × 10 ^−j−1 [seconds]
Correction amount for ¹⁰⁵ components of the original fumarate offset value ^{68 = f × 10 -j-1} [ sec]
Correction amount for ¹⁰⁶ components of the original fumarate offset value ^{69 = g × 10 -j-1} [ sec]

Hereinafter, the meaning of each calculated parameter will be briefly described.
Further, the correction timings 56 to 62 and the correction amounts 63 to 69 are the timing of the time correction performed by the GPS time correction function 10 in order to operate the main station GPS emulation clock 9 in the synchronization accuracy order of the clock synchronization network, and each timing. Is the correction amount. The GPS satellite 6 provides the main station GPS emulation clock 9 that is self-running by the external clock reception function supply clock 41 by correcting the time lag so that it is within an accuracy one digit higher than the required synchronization accuracy order. It is possible to follow the time with sufficient accuracy. Further, the resolution of the offset value between the original vibrations is higher than the required accuracy. For this reason, the offset of the time component that is one digit smaller than the required accuracy is corrected once per second, for example. Further, the offset of the time component exceeding the required accuracy is corrected by equally dividing it into finer periods according to the number of digits. On the other hand, the offset of the time component that is two digits or more smaller than the required accuracy is corrected in a longer cycle according to the number of digits.

The accuracy of the external clock reception function supply clock 41 that drives the main station GPS emulation clock 9 is higher than the GPS time synchronization accuracy 52. Therefore, even if each emulation clock is driven without time correction by the IEEE 1588 protocol, the synchronization accuracy required by the GPS time synchronization information 52 can be maintained, and the longest time is 10 ^h−j−1 seconds. This is calculated by the IEEE 1588 time correction interval calculation function 29.

Next, an example in which a calculated value is derived assuming actual parameters is shown.
First, the initial value, the set value, and the measured value are assumed as follows.
Clock synchronization network synchronization accuracy 50 = 10 ^−h = 10 ⁻¹²
GPS time synchronization accuracy ⁵² = ¹⁰ -j = 10 ^-8
Original oscillation offset value 53 = gfedcba [ps / sec] = a × 10 ⁰ + b × 10 ¹ + c × 10 ² + d × 10 ³ + e × 10 ⁴ + f × 10 ⁵ + g × 10 ⁶ = 1522 [ps / sec] = 2 × 10 ⁰ + 2 × 10 ¹ + 5 × 10 ² + 1 × 10 ³ + 0 × 10 ⁴ + 0 × 10 ⁵ + 0 × 10 ⁶
The request for time synchronization accuracy when all base stations receive time information from the GPS satellite 6 is on the order of 10 ⁻⁸ , and the request for GPS time synchronization accuracy 52 is also 10 ⁻⁸ .
As described above, the correction timing and correction amount for each source signal offset component are as follows.

10 ⁰ component correction timing ^{56 = 10 -0 × 10 12-} j-1 = 10 12-8-1 = 10 3 second cycle correction amount ^{63 = a × 10 -j-1} = 2 × 10 -8-1 = 2 × 10 ⁻⁹ seconds 10 ¹ component Correction timing 57 = 10 ⁻¹ × 10 ^12−j−1 = 10 ⁻¹ × 10 ^12−8-1 = 10 ² second period Correction amount 64 = b × 10 ^−j−1 = 2 × 10 ^−8-1 = 2 × 10 ⁻⁹ seconds 10 ² components Correction timing 58 = 10 ⁻² × 10 ^12−j−1 = 10 ⁻² × 10 ^12−8-1 = 10 seconds period Correction amount 65 = c × 10 ^−j−1 = 5 × 10 ^−8-1 = 5 × 10 ⁻⁹ seconds 10 ³ components Correction timing 59 = 10 ⁻³ × 10 ^12−j−1 = 10 ⁻³ × 10 ^12−8-1 = 1 second period Correction amount 66 = c × 10 ^−j−1 = 1 × 10 ^−8-1 = 1 × 10 ⁻⁹ seconds In this example, The correction amount for other components is 0, and no correction is necessary.

As described above, the GPS time correction function 10 corrects + 1 × 10 ⁻⁹ seconds in a cycle of 1 second, corrects + 6 × 10 ⁻⁹ (= (1 + 5) × 10 ⁻⁹ ) seconds in a cycle of 10 seconds, Correction of + 8 × 10 ⁻⁹ (= (1 + 5 + 2) × 10 ⁻⁹ ) seconds is performed at a cycle of 100 seconds, and correction of + 10 × 10 ⁻⁹ (= (1 + 5 + 2 + 2) × 10 ⁻⁹ ) seconds is performed at a cycle of 1000 seconds. Further, IEEE1588 master function maximum 1000 seconds (= 10 ³ seconds) by issuing the IEEE1588 time correction messages on a periodic synchronization ^10-8 order of time received from GPS satellites 6 even in the next stage of the packet transmission device It becomes possible to maintain the accuracy. Normally, in IEEE 1588, it is necessary to perform time correction at a cycle of the order of 1 second. However, according to the present embodiment, this interval can be expanded 1000 times, and the load on the network can be greatly reduced.

FIG. 7 is a process flowchart for determining a time correction amount for the main station GPS emulation clock 9 in the GPS time correction function 10. This processing is a processing flow for determining a time correction amount in the GPS time correction function 10 in the packet transmission device 1 installed at the main station. As shown in FIG. 6, the correction timing and the correction amount differ depending on each component of the offset between the original vibrations. Therefore, determination processing 91 to 96 that determines which portion of the components of the offset between the original vibrations corresponds to the periodically generated correction timing, correction amount determination processing 97 to 103 corresponding to each correction cycle, The time correction processing 104 is used. In this embodiment, it is assumed to perform minimum ^{10 -6 × 10 12-j-} 1 cycle correction. Therefore, this process is started with a period of 10 ⁻⁶ × 10 ^{12 -j−1} . When this process is started, first, in a determination process 91, it is determined whether or not the correction timing is for the 10 ⁶ [ps] component of the offset value between the original vibrations. If it is the timing for the 10 ⁶ [ps] component, the correction amount determination process 98 sets the time correction amount to g × 10 ^−j−1 seconds, performs the time correction process 104, and ends the process. If it is not the timing for the 10 ⁶ [ps] component, it is determined in the determination process 92 whether the correction timing corresponds to the 10 ⁵ [ps] component of the offset value between the original oscillations. If it is the timing corresponding to the 10 ⁵ [ps] component, the correction amount determination processing 99 sets the time correction amount to (f + g) × 10 ^−j−1 seconds, performs the time correction processing 104, and ends the processing. If it is not the timing for the 10 ⁵ [ps] component, it is determined in the determination process 93 whether the correction timing corresponds to the 10 ⁴ [ps] component of the offset value between the original oscillations. If it is the timing corresponding to the 10 ⁴ [ps] component, the correction amount determination processing 100 sets the time correction amount to (e + f + g) × 10 ^−j−1 seconds, performs the time correction processing 104, and ends the processing. If it is not the timing for the 10 ⁴ [ps] component, it is determined in the determination process 94 whether the correction timing corresponds to the 10 ³ [ps] component of the offset value between the original oscillations. If it is the timing corresponding to the 10 ³ [ps] component, the correction amount determination processing 101 sets the time correction amount to (d + e + f + g) × 10 ^−j−1 seconds, performs the time correction processing 104, and ends the processing. 10 3 If not the timing for ^[ps] component, the determination processing 95 determines whether the correction timing corresponds to 10 2 ^[ps] components of the original fumarate offset value. If it is the timing corresponding to the 10 ² [ps] component, the correction amount determination processing 102 sets the time correction amount to (c + d + e + f + g) × 10 ^−j−1 seconds, performs the time correction processing 104, and ends the processing. If it is not the timing for the 10 ² [ps] component, a determination process 96 determines whether the correction timing corresponds to the 10 ¹ [ps] component of the offset value between the original oscillations. If it is the timing corresponding to the 10 ¹ [ps] component, the correction amount determination processing 103 sets the time correction amount to (b + c + d + e + f + g) × 10 ^−j−1 seconds, performs the time correction processing 104, and ends the processing. If it is not the timing for the 10 ¹ [ps] component, the correction amount determination processing 97 sets the time correction amount to (a + b + c + d + e + f + g) × 10 ^−j−1 seconds, performs the time correction processing 104, and ends the processing.

FIG. 8 is a conceptual diagram of a situation in which the GPS emulation time follows the GPS time.
In this figure, the horizontal axis represents time and the vertical axis represents time derived from the network synchronization clock. Also, the GPS time 105, the time 106 generated in the network synchronization clock, and the GPS emulation time 107 are graphs. Also, in this figure, the portion of the difference range 108 that is allowed to achieve the required GPS time synchronization accuracy (= 10 ^−j ) with the GPS time 105 as the center is shown as a straight line parallel to the GPS time 105 graph. Show. As can be seen from this figure, the correction is performed so that the GPS emulation time 107 does not exceed the line of the difference range 108 that is allowed to realize the required GPS time synchronization accuracy.
In the example of this figure, the GPS time 105 is on the right side of the graph of the time 106 generated by the network synchronization clock, and the time is advanced earlier. Relative GPS emulation time 107, the period of treatment described in the description of FIG. 7, starts the minimum correction time ^{10 -6} × ^{10 12-8-1} [sec] at 109 cycles, correspond to which components of the original fumarate offset Is determined, a correction amount corresponding to each component is determined, and time correction is performed. In the example of this figure, the correction time corresponding to 10 ⁻⁶ component + g × 10 ^−8-1 [seconds] 110 is corrected six times, and the correction time corresponding to 10 ⁻⁵ component + (f + g) × 10 ^−8-1 [ Second] 111 is executed twice, correction time corresponding to 10 ⁻⁰ component + (a + b + c + d + e + f + g) × 10 ^−8-1 [second] 112 is executed once. As described above, the GPS emulation time 107 is made to follow the GPS time 105 within the difference range 108 that is allowed for realizing the required GPS time synchronization accuracy (= 10 ^−j ).

6, 7, and 8, the calculation rules for various parameters, the time correction amount determination process flow, and the actual operation of the time correction process in the packet transmission apparatus 1 installed at the master station have been described. The transmission apparatus 2 also operates by performing calculations based on the same concept. As a result, in the clock synchronization and time synchronization network in the present embodiment, the GPS time distributed from the main station by IEEE 1588 is set to the time at the terminal base station device 4 and from the base station device 4 and the direct GPS satellite 6. The receiving base station apparatus 3 can also synchronize with an accuracy of the order of 10 ⁻⁸ required for the system.

In general, the correction timing and the correction amount can be expressed as follows.
The difference information = a ₀ × 10 ⁰ + a ₁ × 10 ¹ +... + _An × 10 ⁿ [10 ^−h ],
Clock synchronization network synchronization accuracy = 10 ^−h
Required synchronization accuracy = 10 ^−j
When,
The correction timing for the 10 ⁿ [10 ^−h second] component is 10 ⁻ⁿ × 10 ^h−j−1 ,
Correction ^{_{amount, a n × 10 -j-1}} ,
It is.

  The present invention can be applied to various time synchronization protocols other than IEEE 1588. Further, the present invention can be applied to a system using a time source other than GPS, or a system using another high-accuracy original clock corresponding to the high-accuracy network synchronous original clock 5.

DESCRIPTION OF SYMBOLS 1 Packet transmission apparatus installed in master station 2 Packet transmission apparatus installed in slave station 3, 4 Base station apparatus 5 External clock 6 GPS satellite 8 Self-running GPS clock function 9 Master station GPS emulation clock 10 GPS time correction function 11, 18 IEEE 1588 master function 12, 19 Clock synchronous packet code transmission / reception function 13 GPS antenna 14 Slave station clock generation function 15 Self-propelled IEEE 1588 clock function 16 Slave station IEEE 1588 emulation clock 17 IEEE 1588 time correction function 20 External monitoring control device 21 External clock reception function 23 Source offset detection function 25 GPS time reception function 28, 38 Setting information storage function 29, 39 IEEE 1588 time correction interval calculation function 30, 40 IEEE 1588 time synchronization message transmission / reception function 31 Main signal clock Clock extraction function 33 Clock source offset detection function 35 IEEE 1588 slave function 41 External clock reception function supply clock 42 Time received from GPS satellite 6 43 External clock reception function supply clock count value 45 External clock reception function supply clock cycle Minute time 46 Time reception interval from GPS satellite 6 47 Difference between time derived from external clock receiving function supply clock and time derived from GPS satellite 6 per second 48 Time information from initial external clock receiving function supply clock and GPS satellite 6 Reception timing coincidence time 49 Next time clock receiving function supply clock and time information reception timing coincidence time from GPS satellite 6 50 Clock synchronization network synchronization accuracy 52 Required GPS time synchronization accuracy 53 Original oscillation offset value 56 to 62 Original oscillation interval Correction amount 71 Synchronous Ethernet for each component of the correction timing 63 to 69 original fumarate offset value for each component of the offset value
72 IEEE 1588 time synchronization message 73 GPS signal 91 to 96 determination processing 97 to 103 correction amount determination processing 104 time correction processing 105 GPS time 106 time generated by network synchronization clock 107 GPS emulation time 108 required GPS time synchronization accuracy (= 10 ^−j ) The difference range allowed for realizing 109) Minimum correction time 10 ⁻⁶ × 10 ^12-8-1 [seconds]
110 Correction time + g × 10 ^−j−1 [second]
111 correction time + (f + g) × 10 ^−j−1 [second]
112 Correction time + (a + b + c + d + e + f + g) × 10 ^−j−1 [second]

Claims (11)

In a time synchronization network for performing time synchronization among a plurality of the communication devices according to time information distributed over the network by a time synchronization protocol, the plurality of communication devices have a hierarchical structure,
The highest level communication device of the time synchronization network is:
A time receiving function for receiving time information from the time source clock;
An external clock reception function that receives an external reference clock signal from an external oscillator that is asynchronous with the time source clock and is more accurate than the time source, and generates a clock signal that is synchronized with the external reference clock signal;
Based on the clock signal cycle count generated by the external clock reception function, to calculate the time derived from the external oscillator, to calculate the time from the time source based on the time received from the time source clock, By comparing the time from the external oscillator and the time from the time source, the offset detection function between the original oscillators detects time difference information between the original oscillator by the time source and the original oscillator by the external oscillator. When,
Driving based on the clock signal generated by the external clock reception function and correcting the time based on the time difference information detected by the offset detection function between original oscillations, it is possible to achieve higher time synchronization than the time synchronization protocol. A master station emulation clock that is synchronized with the time source clock with accuracy;
Based on the time information from the main station emulation clock, a master function to generate a time synchronization message according to the time synchronization protocol;
A function of sending the time synchronization message to a lower-level communication device by a transmission code generated at a timing synchronized with a clock signal supplied from the external clock reception function;

A communication device other than the highest level of the time synchronization network is:
Receiving the time synchronization message from a higher-level communication device;
A main signal clock extraction function that extracts a clock component from the transmission code of the time synchronization message and generates a clock signal that is synchronized with the clock of the highest-level communication device with high accuracy from the time source;
A slave function in the time synchronization protocol for extracting time information from a time synchronization message distributed by the time synchronization protocol;
Based on the count of the clock signal period generated by the main signal clock extraction function, the time derived from the main signal clock is calculated, the time derived from the time synchronization protocol is calculated from the time received by the slave function, and the main signal clock From the comparison between the time derived from the time and the time derived from the time synchronization protocol, an offset detection function between clock sources that detects time difference information between two clock sources,
Driving based on the clock signal generated by the main signal clock extraction function and correcting the time based on the difference information of the time detected by the offset detection function between clock sources, it is more accurate than the time synchronization protocol. A slave emulation clock synchronized with the time of the slave function, the time of the master station emulation clock, and the time of the clock as the time source;
The time synchronization network comprising:
A plurality of communication devices has a hierarchical structure, and is a top-level communication device in a time synchronization network for performing time synchronization between the plurality of communication devices based on time information distributed via a network by a time synchronization protocol,
A time receiving function for receiving time information from the time source clock;
An external clock reception function that receives an external reference clock signal from an external oscillator that is asynchronous with the time source clock and is more accurate than the time source, and generates a clock signal that is synchronized with the external reference clock signal;
Based on the clock signal cycle count generated by the external clock reception function, to calculate the time derived from the external oscillator, to calculate the time from the time source based on the time received from the time source clock, By comparing the time from the external oscillator and the time from the time source, the offset detection function between the original oscillators detects time difference information between the original oscillator by the time source and the original oscillator by the external oscillator. When,
Driving based on the clock signal generated by the external clock reception function and correcting the time based on the time difference information detected by the offset detection function between original oscillations, it is possible to achieve higher time synchronization than the time synchronization protocol. A master station emulation clock that is synchronized with the time source clock with accuracy;
Based on the time information from the main station emulation clock, a master function to generate a time synchronization message according to the time synchronization protocol;
The communication apparatus comprising: a function of transmitting the time synchronization message to a lower communication apparatus by a transmission code generated at a timing synchronized with a clock signal supplied from the external clock reception function.
A communication device other than the highest level in a time synchronization network for performing time synchronization between a plurality of communication devices based on time information distributed via a network by a time synchronization protocol, wherein the plurality of communication devices have a hierarchical structure. ,
Generated according to the time synchronization protocol based on the time information from the emulation clock of the higher-level communication device, and sent out by the transmission code generated at the timing synchronized with the external reference clock signal from the external oscillator with higher accuracy than the time source Received a time synchronization message from a higher-level communication device,
A main signal clock extraction function that extracts a clock component from the transmission code of the time synchronization message and generates a clock signal that is synchronized with the clock of the highest-level communication device with high accuracy from the time source;
A slave function in the time synchronization protocol for extracting time information from a time synchronization message distributed by the time synchronization protocol;
Based on the count of the clock signal period generated by the main signal clock extraction function, the time derived from the main signal clock is calculated, the time derived from the time synchronization protocol is calculated from the time received by the slave function, and the main signal clock From the comparison between the time derived from the time and the time derived from the time synchronization protocol, an offset detection function between clock sources that detects time difference information between two clock sources,
Driving based on the clock signal generated by the main signal clock extraction function and correcting the time based on the difference information of the time detected by the offset detection function between clock sources, it is more accurate than the time synchronization protocol. A slave emulation clock synchronized with the time of the slave function, the time of the master station emulation clock, and the time of the clock as the time source;
The communication apparatus comprising:
The communication device other than the top is further,
A master function that terminates the message of the time synchronization protocol from a higher-level communication device and generates a time synchronization message according to the time synchronization protocol based on time information from the slave emulation clock,
A function of sending the time synchronization message to a lower communication device by a transmission code generated at a timing synchronized with a clock signal supplied from the main signal clock extraction unit;
The time synchronization network according to claim 1 or the communication device according to claim 3, wherein:
One or more base stations connected to a lower communication device and receiving the time synchronization message,
2. The time synchronization network according to claim 1, wherein time synchronization is performed between the plurality of communication apparatuses and one or a plurality of base stations based on time information distributed via the network according to the time synchronization protocol.
Satisfy the required time synchronization accuracy from the difference information of the time between the original oscillations detected by the offset detection function between the original oscillations according to the clock synchronization network synchronization accuracy by the external clock from the external oscillator and the required synchronization accuracy A main station time correction function for deriving the correction timing and correction amount according to the time synchronization protocol required to
The time synchronization network according to claim 1, wherein the main station emulation clock corrects the time with the correction timing and correction amount derived by the main station time correction function. The communication device described in 1. According to the clock synchronization network synchronization accuracy by the external clock from the external oscillator and the required synchronization accuracy, the required time synchronization accuracy is obtained from the time difference information between the two clock sources detected by the clock source offset detection function. A slave time correction function for deriving the correction timing and correction amount according to the time synchronization protocol required to satisfy
The time synchronization network according to claim 1, wherein the slave station emulation clock corrects the time with the correction timing and the correction amount derived by the slave time correction function. Communication device.
The difference information = a ₀ × 10 ⁰ + a ₁ × 10 ¹ +... + _An × 10 ⁿ [10 ^−h ],
Clock synchronization network synchronization accuracy = 10 ^−h
When the required synchronization accuracy = 10 ^−j ,
The correction timing for the 10 ⁿ [10 ^−h second] component is 10 ⁻ⁿ × 10 ^h−j−1 ,
Correction amount, characterized in that it is a a _n × 10 ^-j-1, time synchronization network according to claim 1, or, communication apparatus according to claim 2 or 3.
The time synchronization network according to claim 1, wherein the time source is included in a GPS satellite having a time distribution function, and time information is periodically supplied by a GPS signal. Or the communication apparatus described in 3.
The time synchronization protocol has means for transmitting time information from the master side to the slave side and measuring the propagation delay time between the master and slave, and taking into account the correction amount based on the measured propagation delay time. The time synchronization network according to claim 1 or the communication apparatus according to claim 2 or 3, wherein synchronization is performed.
The communication device
Means for deriving a time correction interval according to the time synchronization protocol required to satisfy the time synchronization accuracy required between the base stations, from the given clock network stage number information and / or network synchronization clock synchronization accuracy request information Comprising
By issuing a time synchronization message according to the time synchronization protocol at a time correction interval determined by the time correction interval deriving means, the time correction is performed at a cycle longer than the time correction interval normally defined by the time synchronization protocol. 4. The time synchronization network according to claim 1, or the communication device according to claim 2 or 3.

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