TWI773524B - A time synchronization method used in a precision time protocol system - Google Patents

Abstract

A time synchronization method used in a precision time protocol system is provided. The precision time protocol system includes: receiving global navigation satellite system signal as a first time signal; receiving precision time protocol signal as a second time signal; generating calibration information according to the first time signal and the second time signal in response to the first time signal being received successfully, and determining to generate a calibrated time signal according to the second time signal and the calibration information in response to the first time signal not being received successfully; and outputting one of the first time signal and the calibrated time signal.

Description

A time synchronization method and a precise time agreement system using the same

The present invention relates to a system and a time synchronization method for achieving time synchronization through precise time protocol transmission.

At present, the mainstream method for a large number of wireless network devices to achieve high-precision time synchronization is to obtain UTC by receiving global navigation satellite system (GNSS) signals. However, indoors or shaded by nearby buildings can cause wireless network devices to fail to successfully receive GNSS signals to synchronize with UTC. Even within the coverage of GPS satellites, wireless network devices may still be affected by external interference and cannot receive GNSS signals. For example, factors such as ionospheric electromagnetism, shadowing, multipath reflections, jamming, scramble, and spoofing can negatively affect wireless network devices synchronizing with UTC. Therefore, how to propose an off-site backup method for obtaining the UTC signal is one of the goals of those in the art.

The present invention provides a system and a time synchronization method for achieving time synchronization through precise time protocol transmission. When GNSS signals cannot be successfully received, the GNSS time received at different places can be transferred to the precise time protocol as a backup time source. Synchronized with UTC.

A precise time agreement system of the present invention includes a processor, a storage medium and a transceiver. The storage medium stores multiple modules. The processor is coupled to the storage medium and the transceiver, and accesses and executes a plurality of modules, including a GNSS signal synchronization module, a slave clock module, a time synchronization measurement module and a master clock module. The GNSS signal synchronization module receives the first time signal through the transceiver. The second time signal is received from the clock module through the transceiver. The time synchronization measurement module determines whether the first time signal is successfully received, and generates calibration information according to the first time signal and the second time signal in response to determining that the first time signal is successfully received. The master clock module outputs the first time signal through the transceiver in response to determining that the first time signal is successfully received, and generates a corrected time signal according to the second time signal and the correction information in response to determining that the first time signal is not successfully received time signal and output the corrected time signal through the transceiver.

In an embodiment of the present invention, the above-mentioned first time signal is a global satellite navigation system signal.

In an embodiment of the present invention, the above-mentioned first time signal is the current time, wherein the first time signal includes at least one of a pulse output signal per second and a nanosecond unit time.

In an embodiment of the present invention, the second time signal is the current time, wherein the second time signal includes at least one of a pulse output signal per second, a nanosecond unit time, and an offset from the master clock.

In an embodiment of the present invention, the above-mentioned time synchronization measurement module generates calibration information through calculation of satellite common view and time-sharing statistics based on the requirements of ITU-T G 8273.2 of the Institute of Electrical and Electronics Engineers.

A time synchronization method of the present invention includes: receiving a first time signal; receiving a second time signal; judging whether the first time signal is successfully received; and the second time signal to generate calibration information, and output the first time signal. In response to determining that the first time signal is not successfully received, a corrected time signal is generated according to the second time signal and the correction information, and the corrected time signal is output.

Based on the above, the present invention can provide an edge computing system based on a precise time protocol, which can use the UTC obtained from the GNSS signal received in different places as a backup time source when the GNSS time signal corresponding to the UTC is lost. The invention uses the time synchronization measurement result to determine whether the GNSS time signal is successfully received, and corrects the time signal of the backup time source to improve the synchronization accuracy with the world standard time.

In order to make the content of the present invention more comprehensible, the following specific embodiments are given as examples according to which the present invention can indeed be implemented. Additionally, where possible, elements/components/steps using the same reference numerals in the drawings and embodiments represent the same or similar parts.

FIG. 1 is a schematic diagram of a precise time agreement system 100 according to an embodiment of the present invention. The PTC system 100 can provide time signals for synchronization to external electronic devices. The PTA system 100 may include a processor 110 , a storage medium 120 and a transceiver 130 .

The processor 110 is, for example, a central processing unit (CPU), or other programmable general-purpose or special-purpose micro control unit (micro control unit, MCU), microprocessor (microprocessor), digital signal processing digital signal processor (DSP), programmable controller, application specific integrated circuit (ASIC), graphics processor (graphics processing unit, GPU), image signal processor (image signal processor, ISP) ), image processing unit (IPU), arithmetic logic unit (ALU), complex programmable logic device (CPLD), field programmable gate array (field programmable gate array) , FPGA) or other similar elements or a combination of the above. The processor 110 may be coupled to the storage medium 120 and the transceiver 130 , and access and execute a plurality of modules and various application programs stored in the storage medium 120 .

The storage medium 120 is, for example, any type of fixed or removable random access memory (random access memory, RAM), read-only memory (ROM), and flash memory (flash memory). , a hard disk drive (HDD), a solid state drive (SSD), or similar components or a combination of the above components for storing a plurality of modules or various application programs executable by the processor 110 . In this embodiment, the storage medium 120 can store a plurality of modules including a master clock module 121, a slave clock module 122, a time synchronization measurement module 123, and a GNSS signal synchronization module 124, the functions of which will be described later . It is worth noting that the functions of the above-mentioned modules can also be implemented by hardware. For example, the functions of the master clock module 121 and the slave clock module 122 may be implemented by independent electronic devices. The function of the time synchronization measurement module 123 may be implemented by a software-defined network (SDN) controller.

The transceiver 130 transmits and receives signals in a wireless or wired manner. Transceiver 130 may also perform operations such as impedance matching, filtering, and the like.

FIG. 2 is a schematic diagram illustrating a plurality of modules according to an embodiment of the present invention. The GNSS signal synchronization module 124 can receive the time signal S1 through the transceiver 130 . The time signal S1 is, for example, a GNSS signal locally received by a satellite. The time signal S1 is the time of day (ToD). The time signal S1 includes information such as one-pulse-per-second (PPS) or nanosecond unit time. After the GNSS signal synchronization module 124 is successfully received and synchronized with the time signal S1 , it transmits the received time signal S1 to the time synchronization measurement module 123 and the master clock module 121 . The time signal S1 may correspond to the GNSS universal time signal.

The integration of the slave clock module 122 into the master clock module 121 may be implemented by a boundary clock, that is, the boundary clock may include the slave clock module 122 receiving data from an external time source (eg, an offsite GNSS receiver) The precise time agreement time signal. The boundary clock may also include a master clock module 121 to output a time signal to an external electronic device. In this embodiment, the slave clock module 122 can receive the time signal S2 from an external time source through the transceiver 130 . The source of the time signal S2 is, for example, a GNSS signal received in a different place. For example, if the transceiver 130 for receiving the time signal S1 is located at the location A, the time signal S2 may be generated according to the GNSS signal received by the GNSS receiver located at the location B, where the location B is different from location A. The time signal S2 can be the current time. The time signal S2 includes information such as the pulse output signal per second, the nanosecond unit time or the offset from the master clock. The slave clock module 122 can transmit the received time signal S2 to the time synchronization measurement module 123 or the master clock module 121 . The time signal S2 may correspond to a precise time agreement signal.

The master clock module 121 can output a time signal through the transceiver 130, wherein the time signal can be one of the time signal S1 or the corrected time signal S2'. In general, the GNSS signal synchronization module 124 can locally receive the time signal S1 transmitted by the satellite through the transceiver 130 . The master clock module 121 can transmit the time signal S1 to the downstream external electronic device through the transceiver 130 . The downstream external electronic device can synchronize with the universal time according to the time signal S1. However, the signal between the transceiver 130 and the satellite may be affected by factors such as ionospheric electromagnetics, shading, multi-path reflection, unintentional interference, malicious damage, and deliberate deception, etc., so that the GNSS signal synchronization module 124 cannot successfully receive the time signal. S1. Accordingly, the master clock module 121 can instead transmit the corrected time signal S2 to the downstream external electronic device. The downstream external electronic device can synchronize with the UTC according to the corrected time signal S2.

FIG. 3 is a flowchart of a time synchronization method according to an embodiment of the present invention, wherein the time synchronization method can be implemented by the precise time agreement system 100 shown in FIG. 1 . In step S301 , the GNSS signal synchronization module 124 can receive the time signal S1 through the transceiver 130 .

In step S302 , the slave clock module 122 can receive the time signal S2 through the transceiver 130 .

In step S303, the time synchronization measurement module 123 can determine whether the transceiver 130 is currently successfully receiving the time signal S1. If the transceiver 130 is currently successfully receiving the time signal S1, the process proceeds to step S304. If the transceiver 130 has not successfully received the time signal S1 at present, the process proceeds to step S306.

In step S304, the time synchronization measurement module 123 can generate calibration information according to the time signal S1 and the time signal S2. Calibration information may include absolute time errors. Specifically, the time synchronization measurement module 123 uses the time signal S1 as a reference to calculate the time difference between the time signal S1 and the time signal S2. The time synchronization measurement module 123 can generate the above-mentioned time difference through calculation of satellite common view and time-sharing statistics based on the requirements of ITU-T G 8273.2 of the Institute of Electrical and Electronics Engineers (IEEE), for example.

In step S305 , the master clock module 121 can output the time signal S1 through the transceiver 130 . For example, the master clock module 121 can output the time signal S1 to the downstream external electronic device through the transceiver 130 . The downstream external electronic device can achieve synchronization with the universal time according to the time signal S1.

In step S306, the master clock module 121 may correct the time signal S2 according to the correction information to generate a corrected time signal S2'. Since the current transceiver 130 executed in step S306 cannot successfully receive the time signal S1, the calibration information used in step S306 is the signal received at the previous time point, which is passed through the time synchronization measurement module 123 The long-term analysis results of the same satellite and the time-sharing statistical time difference are viewed together.

In step S307, the master clock module 121 can output the corrected time signal S2' through the transceiver 130. For example, the master clock module 121 can output the corrected time signal S2' to the downstream external electronic device through the transceiver 130. The downstream external electronic device can achieve synchronization with UTC according to the corrected time signal S2'.

FIG. 4 is a schematic diagram illustrating the time signal provided by the PTA system 100 to the downstream external electronic device 200 according to an embodiment of the present invention. The PTC system 100 obtains time signals from two time sources. The GNSS signal synchronization module 124 can locally receive the time signal S1 transmitted by the satellite through the transceiver 130 , and the slave clock module 122 can receive the time signal S2 from an upstream external time source through the transceiver 130 . In this embodiment, the upstream external time source may be a time synchronization system including a master clock module 221, a slave clock module 222, a time synchronization measurement module 223 and a GNSS signal synchronization module 224, wherein the master clock module 221. The functions of the slave clock module 222, the time synchronization measurement module 223 and the GNSS signal synchronization module 224 correspond to the functions of the master clock module 121, the slave clock module 122, the time synchronization measurement module 123 and the GNSS signal synchronization respectively. Module 124 is the same. If the GNSS signal synchronization module 124 successfully receives the time signal S1 , the master clock module 121 can output the time signal S1 to the downstream external electronic device 200 . If the GNSS signal synchronization module 124 fails to receive the time signal S1 successfully, the master clock module 121 can output the corrected time signal S2' corresponding to the time signal S2 to the downstream external electronic device 200.

The time signal S2 can be one of the time signal S3 or the corrected time signal S4'. Specifically, if the transceiver 130 of the PTA system 100 is set at the location A, the GNSS signal synchronization module 224 can receive the time signal S3 transmitted by the satellite through the transceiver set at the location B, wherein the location B and the location A different. The slave clock module 222 simultaneously receives the time signal S4 from the more upstream grandmaster clock 321 . If the GNSS signal synchronization module 224 successfully receives the time signal S3, the master clock module 221 can output the time signal S3. If the GNSS signal synchronization module 224 fails to receive the time signal S3 successfully, the master clock module 221 can output the corrected time signal S4 ′ corresponding to the time signal S4 to the slave clock module 122 . For example, the master clock 321 receives the time signal S4 transmitted by the satellite through a transceiver located at a location C, where the location C is different from the location A or the location B.

FIG. 5 is a flowchart illustrating a time synchronization method according to another embodiment of the present invention, wherein the method can be implemented by the precise time agreement system 100 as shown in FIG. 1 . In step S501, a first time signal is received. In step S502, a second time signal is received. In step S503, in response to determining that the first time signal has been successfully received, calibration information is generated according to the first time signal and the second time signal, and the output time adjustment amount is set according to the calibration information, and in response to determining that the first time signal is not is successfully received without changing the output time adjustment, that is, the last adjustment information is used. In step S504, the corrected time signal calculated according to the second time signal and the output time adjustment amount is output forever.

To sum up, the present invention not only allows a large number of time synchronization systems to obtain the time source closest to the GNSS universal time, but also does not cause a significant deterioration in the accuracy of synchronization with the universal time due to the local failure to successfully receive the GNSS time signal. . The master clock module first selects the GNSS signal locally received by the GNSS signal synchronization module as the local time source, so as to generate the time signal closest to the universal standard time to the user of the time synchronization system. The master clock can also obtain the alternate off-site time source, and calculate the time difference between the local time source and the off-site time source to generate correction information. When it is determined that the GNSS signal cannot be successfully received according to the satellite common view and time-sharing statistics, the time synchronization system uses the correction information to correct the remote time source, so as to provide the user with a world standard time source similar to the time when the GNSS signal was successfully received. In this way, the time synchronization system will not fail to synchronize due to corrupted or spoofed GNSS signal reception.

100: Precise Time Agreement System 110: Processor 120: Storage Media 121, 221: master clock module 122, 222: slave clock module 123, 223: Time synchronization measurement module 124, 224, 324: GNSS signal synchronization module 130: Transceiver 200: External Electronics 321: Supreme Master Clock S1, S2, S3, S4: time signal S2', S4': Corrected time signal S301, S302, S303, S304, S305, S306, S307, S501, S502, S503, S504: Steps

FIG. 1 is a schematic diagram of a time synchronization system according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a plurality of modules according to an embodiment of the present invention. FIG. 3 is a flowchart illustrating a time synchronization method according to an embodiment of the present invention. FIG. 4 is a schematic diagram illustrating the time signal provided by the time synchronization system to the downstream external electronic device according to an embodiment of the present invention. FIG. 5 is a flowchart illustrating a time synchronization method according to another embodiment of the present invention.

S501, S502, S503, S504: Steps

Claims (6)

A PTA system, comprising: a transceiver; a storage medium storing a plurality of modules; and a processor coupled to the storage medium and the transceiver, and accessing and executing the plurality of modules, wherein the The plurality of modules include: a GNSS signal synchronization module, receiving a first time signal through the transceiver; a slave clock module, receiving a second time signal through the transceiver; a time synchronization measurement module, judging the whether the first time signal is successfully received, and in response to determining that the first time signal is successfully received, generating calibration information according to the first time signal and the second time signal, wherein the calibration information includes absolute a time error, wherein the absolute time error is based on the first time signal, and a time difference between the first time signal and the second time signal is calculated; and a master clock module, in response to determining the The first time signal is successfully received and the first time signal is output by the transceiver, and in response to determining that the first time signal was not successfully received, the second time signal and the correction information are based on the A corrected time signal is generated and output through the transceiver. The PTA system of claim 1, wherein the first time signal is a global satellite navigation system signal. The PTC system of claim 1, wherein the first time signal is a current time, wherein the first time signal includes at least one of a pulse output signal per second and a nanosecond unit time. The PTC system of claim 1, wherein the second time signal is a current time, wherein the second time signal comprises a pulse-per-second output signal, a nanosecond unit time, and at least an offset from a master clock one of them. The precise time agreement system of claim 1, wherein the time synchronization measurement module generates the correction information through calculation of satellite common view and time division statistics based on the requirements of IEEE ITU-T G 8273.2. A time synchronization method, comprising: receiving a first time signal; receiving a second time signal; judging whether the first time signal is successfully received; A time signal and the second time signal generate calibration information, and output the first time signal, wherein the calibration information includes an absolute time error, wherein the absolute time error is based on the first time signal, calculating a time difference between the first time signal and the second time signal; and generating a correction based on the second time signal and the correction information in response to determining that the first time signal was not successfully received time signal, and output the corrected time signal.

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