CN114650117A - GNSS-based cluster time synchronization system - Google Patents
GNSS-based cluster time synchronization system Download PDFInfo
- Publication number
- CN114650117A CN114650117A CN202111632464.0A CN202111632464A CN114650117A CN 114650117 A CN114650117 A CN 114650117A CN 202111632464 A CN202111632464 A CN 202111632464A CN 114650117 A CN114650117 A CN 114650117A
- Authority
- CN
- China
- Prior art keywords
- time
- clock
- signal
- information
- user terminal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
- H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
- H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation
- H04J3/0658—Clock or time synchronisation among packet nodes
- H04J3/0661—Clock or time synchronisation among packet nodes using timestamps
- H04J3/0667—Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Electric Clocks (AREA)
- Synchronisation In Digital Transmission Systems (AREA)
Abstract
The invention discloses a GNSS-based cluster time synchronization system, which can solve the problem of time synchronization of a cluster system. The system comprises a signal layer, a service layer, a network layer and a terminal layer; the signal layer receives Beidou or GPS satellite information and provides a time signal; the service layer processes the time signal sent by the signal layer to obtain standard time information and provide time service for the user terminal; the service layer comprises a time synchronization server, a secondary time server, a switch and a monitoring device; the network layer is used for realizing information transmission and information isolation between the user terminal and the time synchronization server, and comprises a network isolation switch; the terminal layer comprises user terminals in the cluster, the user terminals are users of time service, and each user terminal receives time information of the time synchronization server and feeds back local clock information of the user terminal to the monitoring device.
Description
Technical Field
The invention relates to the field of clusters, in particular to a cluster time synchronization system based on GNSS.
Background
With the time-frequency application of the Beidou navigation satellite, a cluster system formed by computers has higher and higher requirements on the time of equipment systems in the system. At present, the internal clock unification of the system mostly depends on the time of a computer in the system, and the long-time local self-time keeping precision is poor; in a system using the standard time information of the GPS satellite, the local time keeping precision is difficult to guarantee under the condition that the satellite time information is unavailable. Meanwhile, the current time synchronization system lacks the functions of managing the health state of equipment in the system and carrying out closed-loop regulation on time service results.
Disclosure of Invention
In view of the above, the present invention provides a GNSS-based cluster time synchronization system, which can solve the problem of time synchronization of a cluster system, and can ensure that the internal time of the cluster system is unified with the standard time of a satellite (including beidou and GPS).
In order to solve the above-mentioned technical problems, the present invention has been accomplished as described above.
A cluster time synchronization system based on GNSS comprises a signal layer, a service layer, a network layer and a terminal layer;
the signal layer receives Beidou or GPS satellite information and provides a time signal based on the acquired reference frequency and satellite ephemeris information, wherein the time signal is a Beidou time signal or a GPS time signal; the signal layer comprises an antenna and a time service receiver, wherein the antenna is used for receiving Beidou or GPS satellite information, and the time service receiver is used for processing the Beidou or GPS satellite information and providing a time signal and a second pulse to a time service module of the service layer;
the service layer processes the time signal sent by the signal layer to obtain standard time information and provide time service for the user terminal; the service layer comprises a time synchronization server, a secondary time server, a switch and a monitoring device;
the network layer is used for realizing information transmission and information isolation between the user terminal and the time synchronization server, and comprises a network isolation switch;
the terminal layer comprises user terminals in the cluster, the user terminals are users of time service, and each user terminal receives time information of the time synchronization server and feeds back local clock information of the user terminal to the monitoring device.
Preferably, the time service receiver is configured to receive a time signal transmitted by a signal layer, and generate a standard navigation satellite time, a 1PPS and a 10M frequency signal based on the time signal, where the 1PPS is configured to provide a time reference signal, and the 10MHz signal is configured to clock a clock frequency.
Preferably, the time synchronization server receives the time signal transmitted by the signal layer, decodes the time information, generates time information, and has an NTP network time service function; when the time synchronization server cannot acquire the time signal transmitted by the signal layer, a rubidium atomic clock of the time synchronization server generates a clock signal, and time information is generated based on the clock signal generated by the rubidium atomic clock;
the time synchronization server comprises a rubidium atomic clock and a time service module; the rubidium atomic clock is used for generating a local standard 10MHz signal when a time signal transmitted by a signal layer cannot be acquired, and the local standard 10MHz signal is used as an internal clock signal and is matched with external clock information to provide time service; the time service module is used for receiving a signal layer time signal, decoding the time signal and providing continuous time service; the external clock is composed of standard navigation satellite time, 1PPS and 10M frequency signals generated after the time service receiver demodulates the satellite time information;
the secondary time server is a private network server and is used for receiving the time service transmitted by the time synchronization server and forwarded by the switch and providing time service for the user terminal in the private network range;
the monitoring device is connected with the time synchronization server and each user terminal in the cluster and used for monitoring the equipment information of the time synchronization server and the user terminals, generating a timing strategy when the time information of the user terminals is deviated, and timing the user terminals.
Preferably, the time service module internally comprises a high-precision time synchronization and management module and a time sending module; the high-precision time synchronization and management module is used for resolving time signals and correcting the time of a local rubidium atomic clock by matching with 1 PPS; the high-precision time synchronization and management module carries out cycle counting on an external clock signal to generate time information; the time sending module is used for timing clock frequency distribution and performing pulse per second time alignment control by judging pulse per second time errors.
Preferably, the high-precision time synchronization and management module comprises a serial port time receiving submodule, a clock management submodule, a B code receiving submodule and a time synchronization punctuality processing submodule;
the serial port time receiving submodule maintains the local time of the time synchronization server according to a serial port protocol and the 1PPS signal, supports the input of a plurality of paths of PPS signals, and automatically selects the next path of PPS signal according to priority setting when the PPS signal fails;
the clock management submodule supports multi-path clock signal input;
the clock management submodule takes a clock signal of the local constant-temperature crystal oscillator as a backup of an external rubidium atomic clock or other clock signals; when no external clock signal is detected for 10us continuously, automatically switching to a clock signal of a local constant temperature crystal oscillator under the state that the clock allows automatic switching, and sending clock switching information to a main control computer through a serial port or a network port;
the B code receiving submodule supports B code time information input by a remote optical fiber or cable to synchronize the local time of the time synchronization server;
the time synchronization timekeeping processing submodule counts a sub-second counter of a time code through an externally input clock, the counting adopts an adding counting mode, and when the counting value of the counter reaches the counting value of 1s time, a second pulse signal is output; and when the satellite signals are normal and the time service receiver outputs the second pulse to be normal, the satellite time is aligned by taking the second pulse signals as a reference, and when the satellite signals are abnormal, the rubidium atomic clock automatically maintains the whole second time signals.
Preferably, the monitoring device is configured to perform clock control on the time synchronization server and determine a time service policy of the user terminal; the clock control of the time synchronization server comprises the following steps: the locking state of the time service receiver is interpreted, if the time service receiver is unlocked, the external clock is determined to be invalid, the monitoring device automatically generates a clock switching instruction, and a clock signal is switched to an internal clock, so that the clock is ensured to be continuous and stable; after the external clock is recovered, the monitoring device automatically generates a clock switching instruction, switches a clock signal to the external clock, and synchronizes an internal clock signal through the external clock; and if the time service receiver is in a normal locking state, determining that the external clock is effective and keeping continuously outputting the external clock.
Preferably, the time service policy of the user terminal is determined based on a directional time synchronization method, where the directional time synchronization method includes:
step S1: after the time synchronization server receives the time service request of the monitoring device, the monitoring device calls the time service of the time synchronization server according to the time service frequency;
step S2: the time synchronization server outputs available clock information according to the states of the internal clock and the external clock, wherein the available clock information is a unique and continuous uniform time reference in the system and is provided by the internal clock or the external clock;
step S3: for each of the user terminals, the monitoring device calculates the clock deviation of the user terminal by defining the clock deviation theta and the round trip delay theta between the time synchronization server and the user terminal
Wherein, T1 is the time of the user terminal at the time when the user terminal sends a message, T2 is the time of the time synchronization server at the time when the time synchronization server receives a request message, T3 is the time of the time synchronization server at the time when the local time information of the time synchronization server is sent out, T4 is the time of the user terminal updated after the user terminal receives the time of the time synchronization server, d1 is the time delay from the client to the time synchronization server, and d2 is the time delay from the time synchronization server to the client;
step S4: determining a backoff time for each of the user terminals, comprising: for each of the user terminals, determining the clock resolution as the inverse of the local clock frequency of the user terminal and calculating the clock frequency offset rate
The frequency deviation estimation is carried out by utilizing a maximum likelihood estimation method,
determining time service accurate timet＝(1-Δy)(ti-1- θ); determining the compensation time of the user terminal based on the accurate time service and the local time of the user terminal; performing time compensation of the user terminal according to the compensation time; wherein y (t) is the clock frequency of the user terminal, i is the ith time service, n is the result of counting n time services, Δ θ is the variation of clock deviation between the time synchronization server and the user terminal, Δ t is the difference between two time services, ti-1The time is the previous time.
Has the advantages that:
(1) the invention provides a GNSS-based cluster time synchronization system, which can provide high-precision time reference signals for a system requiring standard time scale by adopting NTP protocol in a high-stability manner, and meets the requirements of various automatic devices on time signals. The time reference is referenced to GNSS time, and the frequency reference is referenced to rubidium atomic clock output signals. The time signal completes the time synchronization of the whole network computer and the application equipment by NTP timing mode, and can also be expanded to adopt IRIG-B code to perform time synchronization to the specific computer or the application equipment. Meanwhile, the health state of the equipment in the device is managed in a centralized manner, the time of the terminal equipment is monitored in real time, and automatic time synchronization is realized by a directional time synchronization method; the device provides abundant signal interface resources, meets the time setting interface requirements of different equipment, provides conditions for future expansion, and has excellent compatibility.
(2) The invention receives the stable receiving of Beidou and GPS standard time information by the antenna, ensures the stability of the time information by the rubidium atomic clock, has flexible integral architecture, modular design and unified time monitoring, ensures that the time service is suitable for being applied to various scenes, has strong expandability and stable time service, and simultaneously adopts a closed-loop directional control method to ensure that the long-term time stability deviation between equipment in the system is better than 50 ms.
(3) The GNSS-based cluster time synchronization system is used for transmitting time signals including information of year, month, day, time, minute, second, millisecond and the like, so that time deviation between equipment on a network and coordinated universal time is in a smaller range, and a unified time reference is provided for various computers and application equipment of users.
(4) The GNSS-based cluster time synchronization system uses the NTP protocol with the highest application degree at present to design a time frequency reference system based on a satellite and an atomic clock, can provide a high-precision time reference for a system needing a standard time scale, and meets the requirements of various automatic equipment on time signals. The time reference takes Beidou time or GPS time as reference. The time signal completes the time synchronization of the whole network computer and the application equipment by NTP timing mode, and also can adopt IRIG-B code to perform the time synchronization of the specific computer or the application equipment. Meanwhile, the health state of the equipment in the device is managed in a centralized manner, the time of the terminal equipment is monitored in real time, and automatic time synchronization is realized.
(5) The GNSS-based cluster time synchronization system adopts a reasonable modular structure in design and can be flexibly configured according to user requirements; the excellent processor is used for control, so that the processing capacity of the system is ensured; meanwhile, abundant signal interface resources are provided, the time setting interface requirements of different devices are met, conditions are provided for future expansion, and the method has excellent compatibility.
(6) The invention provides a GNSS-based cluster time synchronization method, which is successfully applied to a plurality of complex systems and stably provides time service.
Drawings
FIG. 1 is a schematic diagram of a GNSS-based cluster time synchronization system;
FIG. 2 is a schematic diagram of a north half signal receiving and processing module;
FIG. 3(A) is a schematic diagram of the input and output of the time service module;
FIG. 3(B) is a schematic diagram of the time service module;
FIG. 4 is a diagram illustrating a communication structure of a time synchronization apparatus;
fig. 5 is a basic flow diagram of directional timing time synchronization.
Detailed Description
The invention is described in detail below with reference to the figures and examples.
As shown in fig. 1, the present invention relates to a GNSS-based cluster time synchronization system, which includes: a signal layer, a service layer, a network layer, and a terminal layer.
The signal layer receives Beidou or GPS satellite information and provides a time signal based on the acquired reference frequency and satellite ephemeris information, wherein the time signal is a Beidou time signal or a GPS time signal; the signal layer comprises an antenna and a time service receiver, wherein the antenna is used for receiving Beidou or GPS satellite information, and the time service receiver is used for processing the Beidou or GPS satellite information and providing time signals and second pulses for a time service module of the service layer.
As shown in fig. 2, the time service receiver is configured to receive a time signal transmitted by a signal layer, and generate a standard navigation satellite time, a 1PPS and a 10M frequency signal based on the time signal, where the 1PPS is configured to provide a time reference signal to ensure uniform trigger time, and the 10MHz signal is used for a timing clock frequency.
The service layer processes the time signal sent by the signal layer to obtain standard time information and provide time service for the user terminal; the service layer comprises a time synchronization server, a secondary time server, a switch and a monitoring device.
The time synchronization server receives the time signal transmitted by the signal layer, decodes the time information to generate time information, and has the NTP network time service function; when the time synchronization server cannot acquire the time signal transmitted by the signal layer, the time synchronization server generates a clock signal by the rubidium atomic clock of the time synchronization server and generates time information based on the clock signal generated by the rubidium atomic clock.
The time synchronization server comprises a rubidium atomic clock and a time service module. The rubidium atomic clock is used for generating a local standard 10MHz signal when the time signal transmitted by the signal layer cannot be acquired, and the local standard 10MHz signal is used as an internal clock signal and is matched with external clock information to provide time service. The time service module is used for receiving the signal layer time signal, decoding the time signal and providing continuous time service. The external clock is composed of standard navigation satellite time, 1PPS and 10M frequency signals generated after the time service receiver demodulates the satellite time information.
The secondary time server is a private network server and is used for receiving the time service transmitted by the time synchronization server and forwarded by the switch and providing time service for the user terminal in the private network range;
the monitoring device is connected with the time synchronization server and each user terminal in the cluster and is used for monitoring the equipment information of the time synchronization server and the user terminals, generating a timing strategy when the time information of the user terminals is deviated, and timing the user terminals;
the network layer is used for realizing information transmission and information isolation between the user terminal and the time synchronization server, and comprises a network isolation switch;
the terminal layer comprises user terminals in the cluster, the user terminals are users of time service, and each user terminal receives time information of the time synchronization server and feeds back local clock information of the user terminal to the monitoring device.
In this embodiment, the signal receiving antenna adopts a lightning protection design and electromagnetic shielding, and can receive standard time information. The time service receiver processes the received signals and can be compatible with Beidou and GPS standard time information at the same time.
As shown in fig. 3(a), the time service module is configured to receive a pulse-per-second signal generated by the time service receiver, a 10MHz clock frequency, or a 10MHz clock frequency generated by the rubidium atomic clock module; and generating time information based on the NTP protocol, and providing NTP service for time service terminal equipment, namely each user terminal.
As shown in fig. 3(B), the time service module internally includes a high-precision time synchronization and management module and a time transmission module. The high-precision time synchronization and management module is used for resolving time signals and correcting the time of a local rubidium atomic clock by matching with 1 PPS; the high-precision time synchronization and management module carries out periodic counting on external clock signals to generate time information; the time sending module is used for timing clock frequency distribution, and second pulse time alignment control is carried out by judging second pulse time errors, so that the external clock and the internal clock can work normally. In FIG. 3(A), the IRIG-B code is a parallel time code, and the system has the capability of receiving and outputting the IRIG-B code.
The high-precision time synchronization and management module comprises a serial port time receiving submodule, a clock management submodule, a B code receiving submodule and a time synchronization punctuality processing submodule. The serial port time receiving submodule maintains the local time of the time synchronization server according to a serial port protocol and the 1PPS signals, supports multi-path PPS signal input, and can automatically select the next path of PPS signals according to priority setting when the PPS signals fail. The clock management submodule supports multiple clock signal inputs. In order to improve the reliability of the timekeeping function of the time service module, the clock management submodule takes the clock signal of the local constant temperature crystal oscillator as the backup of an external rubidium atomic clock or other clock signals. When no external clock signal is detected for 10us continuously, the clock signal can be automatically switched to the clock signal of the local constant temperature crystal oscillator under the state of 'clock allowing automatic switching', and the clock switching information is sent to the master control computer through a serial port or a network port to inform operation and maintenance personnel. The B code receiving submodule supports remote optical fiber or cable input B code time information to synchronize the local time of the time synchronization server. The B code receiving interface can decode B code time data transmitted remotely, synchronize local time according to decoded time information and output 1PPS pulse signals. The time synchronization timekeeping processing submodule counts a sub-second counter of a time code through a high-stability clock input from the outside, the counting adopts an adding counting mode, and when the counting value of the counter reaches the counting value of 1s time, a second pulse signal is output; and when the satellite signals are normal and the time service receiver outputs the second pulse to be normal, the satellite time is aligned by taking the second pulse signals as a reference, and when the satellite signals are abnormal, the rubidium atomic clock automatically maintains the whole second time signals.
The secondary time server provides time service through forwarding processing time synchronization server, and special requirements of partial secret-related network confidentiality are guaranteed.
The monitoring device is used for carrying out clock control on the time synchronization server and determining a time service strategy of the user terminal. The clock control of the time synchronization server comprises the following steps: the locking state of the time service receiver is interpreted, if the time service receiver is unlocked, the external clock is determined to be invalid, the monitoring device automatically generates a clock switching instruction, and a clock signal is switched to an internal clock, so that the clock is ensured to be continuous and stable; and when the external clock is recovered, the monitoring device automatically generates a clock switching instruction, switches the clock signal to the external clock, and synchronizes the internal clock signal through the external clock. And if the time service receiver is in a normal locking state, determining that the external clock is effective and keeping continuously outputting the external clock.
The timing strategy for determining the user terminal is as follows: the monitoring device collects the time of the time synchronization server and the time of the user terminal, adopts a directional time synchronization method, compares the time difference between the user terminal and the time synchronization server, adjusts the time difference through alarm monitoring, time service frequency and other modes, generates a corresponding time synchronization strategy by utilizing a three-level alarm threshold, and automatically sets the time synchronization of the ultralimit user terminal.
The directional time synchronization method dynamically monitors and adjusts online user terminals in the system in real time, adopts a closed-loop feedback strategy, collects time information between the user terminals in the system in real time, compares the time information with the time of a standard time synchronization server to calculate the time deviation of the user terminals in the system, directionally performs time synchronization on the over-limit user terminals according to the calculation result, and ensures that the time between the user terminals in the system is uniform. And the ultralimit user terminal determines a time service strategy through a three-level threshold of time deviation, if the time deviation exceeds 500ms and is 3-level, automatic alarm prompting is carried out, time service distribution is preferentially carried out, and the time service frequency is increased to 5 s.
The directional time synchronization method comprises the following steps:
step S1: after the time synchronization server receives the time service request of the monitoring device, the monitoring device calls the time service of the time synchronization server according to the time service frequency;
step S2: the time synchronization server outputs available clock information according to the states of the internal clock and the external clock, wherein the available clock information is a unique and continuous uniform time reference in the system and is provided by the internal clock or the external clock;
step S3: for each of the user terminals, the monitoring device calculates the clock deviation of the user terminal by defining the clock deviation theta and the round trip delay theta between the time synchronization server and the user terminal
Wherein, T1 is the user terminal time at the time when the user terminal sends the message, T2 is the time of the time synchronization server at the time when the time synchronization server receives the request message, T3 is the time of the time synchronization server at the time when the local time information of the time synchronization server is sent out, T4 is the user terminal time updated after the user terminal receives the time of the time synchronization server, d1 is the time delay from the client to the time synchronization server, and d2 is the time delay from the time synchronization server to the client.
In this embodiment, the clock offset value θ may be calculated by using a plurality of sets of data statistics.
Step S4: determining a backoff time for each of said user terminals, comprising: for each of the user terminals, determining the clock resolution as the inverse of the local clock frequency of the user terminal and calculating the clock frequency offset rate
The frequency deviation estimation is carried out by utilizing a maximum likelihood estimation method,
determining time accurate time t ═ (1-delta gamma) (t)i-1- θ); determining the compensation time of the user terminal based on the accurate time service and the local time of the user terminal; performing time compensation of the user terminal according to the compensation time; wherein y (t) is the clock frequency of the user terminal, i is the ith time service, n is the result of counting n time services, Δ θ is the variation of clock deviation between the time synchronization server and the user terminal, Δ t is the difference between two time services, ti-1The time is the previous time.
The equipment time in the cluster system is generally kept by the clock of the equipment, but the long-term operation causes larger time deviation between the equipment, thereby influencing the stability of the system operation. The system of the embodiment is used for transmitting time signals, and the deviation between equipment on a network and standard time is enabled to be a relative value within a smaller range through a directional time synchronization method, so that a uniform time reference is provided for various computers and application equipment of users in a cluster system.
In normal use, satellite standard time information is received and NTP service is provided by the time synchronization server, and the terminal operating system time is synchronized at the "next synchronization time" when the terminal system time drifts to generate a time difference. On a monitoring software interface, the current time of each terminal can be monitored at any time through an equipment connection diagram and a list; and monitoring the clock error of the terminal and the server through the clock error data and the curve. And time service strategies can be set for different time service terminals according to user requirements. The timing strategy makes three grades according to the requirements of different terminals. When the alarm mode is overtime, because the equipment is newly accessed, the time drifts, or the system time is changed by other software, and other events occur, the monitoring software alarms and records the events, and automatically adjusts the time service frequency to service the time for the equipment.
When the signal receiving antenna does not receive the satellite signal, the time synchronization device automatically switches to the time keeping mode, the time service precision is not reduced, and stable time information is provided.
The above embodiments only describe the design principle of the present invention, and the shapes and names of the components in the description may be different without limitation. Therefore, a person skilled in the art of the present invention can modify or substitute the technical solutions described in the foregoing embodiments; such modifications and substitutions do not depart from the spirit and scope of the present invention.
Claims (7)
1. A cluster time synchronization system based on GNSS is characterized in that the system comprises a signal layer, a service layer, a network layer and a terminal layer;
the signal layer receives Beidou or GPS satellite information and provides a time signal based on the acquired reference frequency and satellite ephemeris information, wherein the time signal is a Beidou time signal or a GPS time signal; the signal layer comprises an antenna and a time service receiver, wherein the antenna is used for receiving Beidou or GPS satellite information, and the time service receiver is used for processing the Beidou or GPS satellite information and providing a time signal and a second pulse for a time service module of the service layer;
the service layer processes the time signal sent by the signal layer to obtain standard time information and provide time service for the user terminal; the service layer comprises a time synchronization server, a secondary time server, a switch and a monitoring device;
the network layer is used for realizing information transmission and information isolation between the user terminal and the time synchronization server, and comprises a network isolation switch;
the terminal layer comprises user terminals in the cluster, the user terminals are users of time service, and each user terminal receives time information of the time synchronization server and feeds back local clock information of the user terminal to the monitoring device.
2. The system of claim 1, wherein the time service receiver is configured to receive a time signal from a signal layer, and to generate a standard navigation satellite time, 1PPS, and a 10M frequency signal based on the time signal, the 1PPS providing a time reference signal, and the 10MHz signal being used for a clock timing frequency.
3. The system of claim 2, wherein:
the time synchronization server receives the time signal transmitted by the signal layer, decodes the time information to generate time information, and has the NTP network time service function; when the time synchronization server cannot acquire the time signal transmitted by the signal layer, a rubidium atomic clock of the time synchronization server generates a clock signal, and the time synchronization server generates time information based on the rubidium atomic clock;
the time synchronization server comprises a rubidium atomic clock and a time service module; the rubidium atomic clock is used for generating a local standard 10MHz signal when a time signal transmitted by a signal layer cannot be acquired, and the local standard 10MHz signal is used as an internal clock signal and is matched with external clock information to provide time service; the time service module is used for receiving a signal layer time signal, decoding the time signal and providing continuous time service; the external clock is composed of standard navigation satellite time, 1PPS and 10M frequency signals generated after the time service receiver demodulates satellite time information;
the secondary time server is a private network server and is used for receiving the time service transmitted by the time synchronization server and forwarded by the switch and providing time service for the user terminal in the private network range;
the monitoring device is connected with the time synchronization server and each user terminal in the cluster and used for monitoring the equipment information of the time synchronization server and the user terminals, generating a timing strategy when the time information of the user terminals is deviated, and timing the user terminals.
4. The system of claim 3, wherein the time service module internally includes a high precision time synchronization and management module, and a time transmission module; the high-precision time synchronization and management module is used for resolving time signals and correcting the time of the local rubidium atomic clock by matching with 1 PPS; the high-precision time synchronization and management module carries out cycle counting on an external clock signal to generate time information; the time sending module is used for timing clock frequency distribution and performing pulse per second time alignment control by judging pulse per second time errors.
5. The system of claim 4, wherein the high-precision time synchronization and management module comprises a serial port time receiving submodule, a clock management submodule, a B code receiving submodule and a time synchronization time keeping processing submodule;
the serial port time receiving submodule maintains local time of the time synchronization server according to a serial port protocol and the 1PPS signal, supports multi-path PPS signal input, and automatically selects the next path of PPS signal according to priority setting when the PPS signal fails;
the clock management submodule supports multi-path clock signal input;
the clock management submodule takes a clock signal of the local constant-temperature crystal oscillator as a backup of an external rubidium atomic clock or other clock signals; when no external clock signal is detected for 10us continuously, automatically switching to a clock signal of a local constant temperature crystal oscillator under the state that the clock allows automatic switching, and sending clock switching information to a main control computer through a serial port or a network port;
the B code receiving submodule supports B code time information input by a remote optical fiber or cable to synchronize local time of a time synchronization server;
the time synchronization timekeeping processing submodule counts a sub-second counter of a time code through an externally input clock, the counting adopts an adding counting mode, and when the counting value of the counter reaches the counting value of 1s time, a second pulse signal is output; and when the satellite signals are normal and the time service receiver outputs the second pulse to be normal, the satellite time is aligned by taking the second pulse signals as a reference, and when the satellite signals are abnormal, the rubidium atomic clock automatically maintains the whole second time signals.
6. The system according to claim 5, wherein the monitoring device is configured to perform clock control on the time synchronization server and determine a time service policy of the user terminal; the clock control of the time synchronization server comprises the following steps: interpreting the locking state of the time service receiver, if the time service receiver is unlocked, determining that the external clock is invalid, automatically generating a clock switching instruction by the monitoring device, and switching a clock signal to an internal clock so as to ensure the clock to be continuous and stable; after the external clock is recovered, the monitoring device automatically generates a clock switching instruction, switches a clock signal to the external clock, and synchronizes an internal clock signal through the external clock; and if the time service receiver is in a normal locking state, determining that the external clock is effective and keeping continuously outputting the external clock.
7. The system of claim 6, wherein the timing policy of the user terminal is determined based on a directional time synchronization method, the directional time synchronization method comprising:
step S1: after the time synchronization server receives the time service request of the monitoring device, the monitoring device calls the time service of the time synchronization server according to the time service frequency;
step S2: the time synchronization server outputs available clock information according to the states of the internal clock and the external clock, wherein the available clock information is a unique and continuous unified time reference in the system and is provided by the internal clock or the external clock;
step S3: for each user terminal, the monitoring device calculates the clock deviation of the user terminal by defining the clock deviation theta and round trip delay between the time synchronization server and the user terminal
Wherein, T1 is the user terminal time at the time when the user terminal sends the message, T2 is the time of the time synchronization server at the time when the time synchronization server receives the request message, T3 is the time of the time synchronization server at the time when the local time information of the time synchronization server is sent out, T4 is the user terminal time updated after the user terminal receives the time of the time synchronization server, d1 is the time delay from the client to the time synchronization server, and d2 is the time delay from the time synchronization server to the client;
step S4: determining a backoff time for each of the user terminals, comprising: for each of the user terminals, determining a clock resolution as an inverse of a local clock frequency of the user terminal, and calculating a clock frequency offset rate
The frequency deviation estimation is carried out by utilizing a maximum likelihood estimation method,
determining time accurate time t ═ (1-delta gamma) (t)i-1- θ); determining the compensation time of the user terminal based on the accurate time service and the local time of the user terminal; performing time compensation of the user terminal according to the compensation time; wherein y (t) is the clock frequency of the user terminal, i is the ith time service, n is the result of counting n time services, Δ θ is the variation of clock deviation between the time synchronization server and the user terminal, Δ t is the difference between two time services, ti-1The time is the previous time.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111632464.0A CN114650117A (en) | 2021-12-29 | 2021-12-29 | GNSS-based cluster time synchronization system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111632464.0A CN114650117A (en) | 2021-12-29 | 2021-12-29 | GNSS-based cluster time synchronization system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN114650117A true CN114650117A (en) | 2022-06-21 |
Family
ID=81994155
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111632464.0A Pending CN114650117A (en) | 2021-12-29 | 2021-12-29 | GNSS-based cluster time synchronization system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114650117A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20220174629A1 (en) * | 2020-11-30 | 2022-06-02 | Viettel Group | Method and apparatus for data frame synchronization of 5g base station |
-
2021
- 2021-12-29 CN CN202111632464.0A patent/CN114650117A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20220174629A1 (en) * | 2020-11-30 | 2022-06-02 | Viettel Group | Method and apparatus for data frame synchronization of 5g base station |
| US11683771B2 (en) * | 2020-11-30 | 2023-06-20 | Viettel Group | Method and apparatus for data frame synchronization of 5G base station |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US8873589B2 (en) | Methods and devices for clock synchronization | |
| US7146516B2 (en) | Time synchronization schemes wherein at least one data message associates a hardware pulse with a future time | |
| CN100583730C (en) | System and method for calibrating a TOD clock | |
| US9106352B2 (en) | Frequency distribution using precision time protocol | |
| CN105656590B (en) | Realize the methods, devices and systems of time synchronization | |
| WO2014037684A1 (en) | Methods and devices for clock synchronization | |
| CN114650117A (en) | GNSS-based cluster time synchronization system | |
| CN113014345A (en) | Clock synchronization early warning method, device and system | |
| Sterzbach | GPS-based clock synchronization in a mobile, distributed real-time system | |
| CN109283829A (en) | A kind of control method of regional clock system | |
| CN100586055C (en) | Clock transmission apparatus for performing network synchronization of systems | |
| EP1179763A2 (en) | Real time stamp distribution system | |
| CN113141227B (en) | Time determination method, system and medium based on hierarchical control | |
| US8867681B2 (en) | Transmission system, transmission device, and clock synchronization method | |
| US5973640A (en) | Method and device for managing status/alarm message of GPS receiver and broadcasting system time | |
| CN208999781U (en) | A kind of regional clock system | |
| JP3538374B2 (en) | Time supply system and time supply device | |
| RU226534U1 (en) | SECONDARY MASTER OSCILLATOR FOR CLOCK NETWORK SYNCHRONIZATION AND TIME-FREQUENCY PROVISION OF COMMUNICATION NETWORKS | |
| JPH01231450A (en) | Synchronizing clock supply system for communication system | |
| Loschmidt | On enhanced clock synchronization performance through dedicated ethernet hardware support | |
| US20230023487A1 (en) | Multiple redundant disciplined oscillator systems in a spoofing resistant reference time source system and methods thereof | |
| KR200379901Y1 (en) | UTC device of NTP server by using Sync signal of mobile communication system | |
| Ryzhkov et al. | Maintaining the Timeline Reliability in the Master Network Clock in Conditions of Deliberate Interference | |
| CN113114450B (en) | Whole network clock feedback method and system | |
| EP4199384A1 (en) | Method and apparatus for determining a clock frequency offset |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |