CN116865890A - High-precision network time service system and service and evaluation method thereof - Google Patents

Abstract

The invention discloses a high-precision network time service system and a service and evaluation method thereof, wherein the system comprises system hardware, server software and client software, the system hardware, the server software and the client software are connected through a network, the system hardware comprises an external time source, a time code generator, a network time server and a network switch, the external time source is a time source for generating a reference time signal as the network time server, the system hardware adopts an atomic clock group, the atomic clock group comprises a clock and a hydrogen clock, and a mode of driving the hydrogen clock by adopting a clock is adopted, so that a stable and high-precision time standard is obtained through an ALGOS atomic time algorithm. The present invention provides a synchronous time mechanism by employing NTP, which can adjust time allocation with light speed in large, complex and diverse internet, and provides precise measurement of offset and delay, and provides a clear maximum error range, so that the user interface can determine not only time, but also accuracy of time.

Description

High-precision network time service system and service and evaluation method thereof

Technical Field

The invention belongs to the field of network time service, and particularly relates to a high-precision network time service system; meanwhile, the invention also relates to a service method of the high-precision network time service system and an evaluation method of the high-precision network time service system.

Background

The inter-frequency plays an important role in national economy, national defense construction and basic science research as an important basic physical quantity. The method is the most accurate basic physical quantity at present, has good transmissibility and is closely related to the daily life of the masses. With the rapid development of electronic information technology and the Internet, high-precision time constraint services such as electronic commerce and electronic government service have increasingly strict time synchronization requirements on the whole society, and in public service systems such as financial industry, telecommunications industry, mobile communication industry, power grid digital transformer stations, electronic parking timing and charging systems, transportation scheduling centers, oil and gas pipeline control centers, aviation air traffic control centers and the like, safe, reliable and high-precision time synchronization needs to be realized, and in the activities, a computer plays a vital role in information processing and transmission. The clock precision of the computer is very low, and the clock drifts for a few seconds or even a few minutes in one day, so that the requirement of high-precision time constraint service cannot be met, and therefore, how to realize high-precision time synchronization in a network system is a quite important problem.

Disclosure of Invention

The invention aims to solve the defects in the prior art, and provides a high-precision network time service system and a service and evaluation method thereof.

In order to achieve the above purpose, the present invention provides the following technical solutions:

the high-precision network time service system comprises system hardware, server software and client software, wherein the system hardware, the server software and the client software are connected through a network;

the system hardware comprises an external time source, a time code generator, a network time server and a network switch, wherein the external time source is used for generating a time signal serving as a reference of the network time server, the system hardware adopts an atomic clock group, the atomic clock group comprises a cesium clock and a hydrogen clock, and a stable and high-precision time standard is obtained through an ALGOS atomic time algorithm in a mode that the cesium clock is used for driving the hydrogen clock; the time code generator is used for converting the time signal output by the atomic clock group into a B code signal which can be received by the network time server; the network time server is used for obtaining a time source and a server supporting time transmission; the network switch is used for connecting user equipment;

the server software comprises a serial port data processing module, a local clock updating module, a time data processing module and a request receiving and response transmitting module, wherein the serial port data processing module is used for communicating with an external time source through a serial port and a network time server and is used for obtaining standard time information of the external time source, the local clock updating module is used for carrying out time updating on a local clock of the network time server according to standard time data of the external time source, the time data processing module is used for processing the time data based on a network time protocol, the request receiving module is used for receiving a time correction request of user equipment, and the response transmitting module is used for transmitting the standard time information to the user equipment;

and a serial data receiving and processing module is arranged in the server software and is used for communicating with the clock source part through a serial port, so that relatively accurate UTC time information generated by the clock source part is obtained.

Preferably, when the server software receives and detects a time service instruction from a clock source through the serial port, the server software immediately acquires time information therein and transmits the time information to the local clock updating module to update the local clock of the server.

Preferably, the time information is also immediately transmitted to a time data processing module, and the data processing module selects and calculates data required by packaging of the NTP data packet according to the NTP protocol, and completes a data packaging flow; the server software sends the packed NTP data packet to the client software in the form of a client response through a sending process; and the client software immediately sends the NTP data packet to an NTP data message processing module after receiving the response from the server, and updates the local clock of the client by using the extracted corresponding time information.

Preferably, the main responsibility of the client software sends an NTP message to the server software, requests time service, calculates the returned NTP message, obtains local clock deviation and network delay, and adjusts the local clock; each returned message contains four time stamps, and the time deviation and the network time delay are calculated according to the four time stamps; and each synchronization process needs to carry out 8 times of NTP message exchange, each time a group of network delay and clock deviation can be obtained, and the client selects a group of most accurate network delay and clock deviation from the 8 groups of network delay and clock deviation to synchronize the local clock by using a filtering algorithm.

A service method of a high-precision network time service system comprises the following steps:

s1, an atomic clock group formed by a hydrogen clock and a cesium clock stably operates for half a year;

s2, calculating standard time by adopting an ALGOS atomic time algorithm based on data of half year of operation of an atomic clock group;

s3, adopting a cesium clock driving hydrogen clock mode to convert standard time signals output by an atomic clock group into B code time signals which can be received by a network time server through a time code generator;

s4, the network time server is connected with the time code generator, the network time server and the time code generator are in serial communication, and the serial data processing part is utilized to acquire standard time signals of the atomic clock group;

s5, analyzing a standard time signal of the atomic clock group, and updating the local clock of the network time service by the analyzed time information to synchronize the time of the network time service with the time of the atomic clock group;

s6, the user equipment sends a timing request to a network time server through a network switch, and records the sending time t1;

s7, a server-side time transmission module monitors a time correction request sent by user equipment, records time t2 for acquiring the time correction request, and builds a time data packet based on a network time protocol;

s8, the server-side time transmission module transmits the constructed time data packet to the user equipment through the network switch, and records the transmission time t3;

s9, the user equipment receives the time data packet sent by the server side and records the receiving time t4;

s10, a user equipment transmission module analyzes a time data packet based on a network time protocol, calculates to obtain time deviation by subtracting half of the difference between t2 and t1 from the difference between t4 and t3, and calculates to obtain network delay by adding half of the difference between t2 and t1 to the difference between t4 and t3;

s11, repeating the steps S6-S10, wherein according to the statistical center limit theorem, when the overall distribution is unknown and the number of samples is large enough, the average value of the samples tends to be normally distributed; let the mean value of the network delay be d, d-N (Σdelay) _i /n,∑(delay _i -∑delay _i N)/n) n is the number of times steps S6-S10 are repeated;

s12, when the delay deviation mean value of the network is larger, the network is considered to be congested or the network is considered to have a problem, the measured time deviation data are meaningless, and the time deviation data are filtered and proposed;

and S13, the user equipment transmission module uses the average value as a final time deviation result according to the reserved time deviation data, and updates the local clock by using the time deviation so as to synchronize the time of the user equipment with the time of the network time server.

The evaluation method of the high-precision network time service system specifically evaluates the uncertainty of the system and comprises the following steps:

s1, measuring a model, and measuring time service precision T _i Time difference measurement T between local UTC pulse and detected pulse _UTC And the standard time deviation delta is as follows:

T _i ＝T _UTC +δ

δ：T _i and T is _UTC A deviation value between the two;

s2, uncertainty sources, (a) measuring a standard uncertainty component u1 (rated as a standard uncertainty class A) caused by repeatability;

(b) A standard uncertainty component u2 (rated as standard uncertainty class B) caused by uncertainty of the time analyzer;

s3, evaluating a standard uncertainty component u1, namely evaluating the uncertainty of repeatability by adopting a class A method, wherein a measurement column can be obtained through continuous measurement; carrying out repeated measurement on a standard time signal output by a network time service system, and continuously measuring for 10 times;

and S4, calculating and evaluating the standard uncertainty component u2, the synthesized standard uncertainty and the expanded uncertainty according to the standard time signal output by the network time service system.

Preferably, the environmental conditions of the measurement model described in step S1 are: temperature: 15-35 ℃; relative humidity: (20-80)%.

The invention has the technical effects and advantages that:

the present invention provides a synchronous time mechanism by employing NTP, which can adjust time allocation with light speed in large, complex and diverse internet, and provides precise measurement of offset and delay, and provides a clear maximum error range, so that the user interface can determine not only time, but also accuracy of time.

Drawings

FIG. 1 is a block diagram of a high-precision network timing system of the present invention;

fig. 2 is a diagram of an NTP system architecture of the present invention;

FIG. 3 is a schematic diagram of a communication mode in the network timing system of the present invention;

FIG. 4 is a schematic diagram of communication interaction between a user equipment and a network time server according to the present invention;

FIG. 5 is a schematic diagram of the calculation of network delay and time offset according to the present invention;

FIG. 6 is a flow chart of server software communications in accordance with the present invention;

FIG. 7 is a flowchart of the server software program operation of the present invention;

FIG. 8 is a flow chart of client software communication in accordance with the present invention;

FIG. 9 is a flowchart of the client software program operation of the present invention.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The invention provides a high-precision network time service system as shown in fig. 1-2, which comprises system hardware, server software and client software, wherein the system hardware, the server software and the client software are connected through a network;

the system hardware comprises an external time source, a time code generator, a network time server and a network switch, wherein the external time source is a time source for generating a reference time signal serving as the network time server, the system hardware adopts an atomic clock group, the atomic clock group comprises a clock and a hydrogen clock, and a stable and high-precision time standard is obtained through an ALGOS atomic time algorithm in a mode of controlling the hydrogen clock by adopting the clock; the time code generator is used for converting the time signal output by the atomic clock group into a B code signal which can be received by the network time server; the network time server is used for obtaining a time source and a server supporting time transmission; the network switch is used for connecting the user equipment;

the server software comprises a serial port data processing module, a local clock updating module, a time data processing module and a request receiving and response transmitting module, wherein the serial port data processing module is used for communicating with an external time source through a serial port and a network time server and is used for obtaining standard time information of the external time source, the local clock updating module is used for carrying out time updating on a local clock of the network time server according to standard time data of the external time source, the time data processing module is used for processing the time data based on a network time protocol, the request receiving module is used for receiving a time correction request of user equipment, and the response transmitting module is used for transmitting the standard time information to the user equipment;

the server software is internally provided with a serial data receiving and processing module which is used for communicating with the clock source part through a serial port so as to acquire relatively accurate UTC time information generated by the clock source part;

as shown in fig. 4, 6 and 7, when the server software receives and detects a time service instruction from a clock source through a serial port, the server software immediately acquires time information therein and transmits the time information to a local clock updating module to update a local clock of the server, the time information is immediately transmitted to a time data processing module, and the data processing module selects and calculates data required by packaging of an NTP data packet according to an NTP protocol and completes a data packaging flow; the server software sends the packed NTP data packet to the client software in the form of client response through a sending process; the client software immediately sends the NTP data packet to an NTP data message processing module after receiving the response from the server, and updates the local clock of the client by using the extracted corresponding time information;

as shown in fig. 8 and 9, the main responsibility of the client software is to send NTP message to the server software, request time service, calculate the returned NTP message, obtain local clock deviation and network delay, and adjust the local clock; each returned message contains four time stamps, and the time deviation and the network time delay are calculated according to the four time stamps; and each synchronization process needs to carry out 8 times of NTP message exchange, each time a group of network delay and clock deviation can be obtained, and the client selects a group of most accurate network delay and clock deviation from the 8 groups of network delay and clock deviation to synchronize the local clock by using a filtering algorithm.

Further, as shown in fig. 5, the software in the present invention implements a main algorithm, specifically:

(1) Network delay and time offset calculation

The device nodes in the network synchronize their own clocks with the standard clock by sending and receiving time-stamped data packets.

The time synchronization process of the NTP protocol is divided into an offset measurement phase and a delay measurement phase. The NTP protocol is based on UDP, defining four clock messages: synchronous message Sync, delay_Req, follow_Up and delay_Resp;

the offset measurement stage is used to correct the time difference between the server and the client. In the offset measurement phase:

1) The server sends a synchronous message Sync to the client, wherein the message comprises a time stamp which indicates the predicted time when the message is sent out;

2) After the synchronous message Sync is sent, the server sends a Follow message Follow_Up to the client, wherein the message contains a time stamp which indicates the real sending time T1 of the synchronous message;

3) After receiving the synchronization message Sync, the client records the receiving time T2;

the offset measurement phase separates the message transmission and the time measurement, and has no influence on each other.

Let the network Delay of the server and the client be Delay1, the exact time Offset of the server and the client be Offset (slave clock minus master clock), then the client can derive formula (1) from T1 and the receiving time T2 in the following message follow_up:

T2–T1＝Offset+Delay1...............................(1)

the delay measurement stage is used to measure the time delay caused by the network transmission. In the delay measurement phase:

1) After receiving the synchronization message Sync, the client sends a Delay request message Delay_req to the server at the moment T3;

2) After receiving the Delay request message delay_req, the server sends a Delay request response message delay_resp to the client, and the message records the accurate receiving time T4 of the master clock;

the network Delay of the server and the client is denoted as Delay2, the accurate time Offset of the server and the client is denoted as Offset (the client minus the server), and the client can obtain the formula (2) according to the sending time T3 of the Delay request message delay_req and the time T4 recorded in the Delay request response message delay_resp:

T3–Offset+Delay2＝T4...........................(2)

namely, the formula (3) is obtained:

T4–T3＝Delay2–Offset........................(3)

assuming that the network Delay1 of the offset measurement phase is equal to Delay2 of the Delay measurement phase, equation (4) is obtained:

Delay1＝Delay2＝Delay..................................(4)

the network Delay and the time Offset can be derived as in equations (5) and (6):

Delay＝[(T2–T1)+(T4–T3)]/2..........(5)

Offset＝[(T2–T1)–(T4–T3)]/2............(6)

(2) Data filtering algorithm

The data filtering algorithm is mainly responsible for filtering the calculated network delay and time deviation, and then selecting the best group of data from the plurality of groups of data according to the mathematical statistics method to carry out clock correction on the client. In the network time protocol, the algorithm selects a group of data with optimal quality from 8 data messages provided by a server according to corresponding rules. This selection rule is the minimum delay criterion. The minimum time delay criterion is to select the offset data with the minimum network transmission time delay from all the data.

The function of the algorithm is to confirm the validity of the data packet and to select the best sample from among the time samples of a given time reference source. It can be divided into two parts, the sanity check sum filter. Soundness mainly refers to whether data has uniqueness, whether related communication parameters are reasonable, and the like. The filtering mainly comprises the steps of calculating current network delay and time deviation according to current four time stamps, and updating a register array.

(3) Clock correction algorithm

The algorithm is mainly responsible for correcting the system clock, influences the accuracy of local clock adjustment to a great extent, and adjusts the clock by adopting two modes of linear phase adjustment and nonlinear phase adjustment. The linear adjustment means to progressively adjust the clock to achieve the effect of fine tuning, so that the system clock increases monotonically.

The linear adjustment means to progressively adjust the clock to achieve the effect of 'fine tuning', so that the system clock is monotonically increased, the linear adjustment adjusts the system clock by dividing the local clock offset into a plurality of tiny offsets, the effect is better than that of the one-time adjustment when the clock offset is smaller, the process of correcting the local clock offset is also described that the correction of the local clock offset is a long time-needed process, and the nonlinear adjustment directly compensates the time offset calculated by various algorithms to the system clock, so that the method is more suitable for the situation that the clock offset is larger.

Clock correction is an important link for realizing network time synchronization, and factors affecting time synchronization accuracy, as well as jitter generated by network response capability change and drift generated by oscillator frequency stability. Phase-locked loops and frequency-locked loops may be used to compensate for the natural frequency error. Phase locked loops can eliminate jitter but do not adjust offset well, and frequency locked loops are the opposite.

When the client is started, larger time deviation is usually generated, and the method is suitable for directly selecting an immediate synchronization function in a client software main interface to synchronize in place once, namely, a nonlinear adjustment mode is adopted to adjust a clock.

When the system is gradually operated stably, the system clock is adjusted by adopting a linear adjustment mode, and the system clock is usually composed of two loops: external circulation and internal circulation. The external circulation modifies the system clock every correction period m time, and the internal circulation fine-tunes the clock every trace adjustment interval n.

If the predicted value of the moment deviation is far greater than the expected precision, the value of m is too large, the stability of the oscillator cannot maintain the requirement of the precision, the adjustment times are not increased, and the predicted value of the deviation between the precision is met by only reducing the value of m to reach the required precision level; if the predicted value is far smaller than the measured value, the correction period value is obviously smaller, the stability of the crystal oscillator can maintain the accuracy, and the value of m is increased to reduce the system overhead.

(4) Big data based network delay threshold analysis

And (3) carrying out statistical analysis on round trip network delay of at least 10000 times of timing requests, and setting a network delay threshold in a program under the condition of larger network delay caused by accidents, namely discarding the time information packet when the network delay exceeds the threshold, and resending the timing request so as to play a role in ensuring the timing precision.

Specifically, as shown in fig. 3, the basic architecture of the network time protocol is divided into the following parts:

(1) A time server; (2) a server interface module; (3) a system processing module; (4) a clock correction module;

in network time protocol, it is indispensable that a time server is used as a reference source, after the time server receives an NTP message sent by a server interface module of a client, the time server fills in local time in the NTP message and returns the NTP message to the server interface module of the client, and in general, the client uses the network time protocol to synchronize and needs multiple time servers, so that the reliability of the network time protocol is ensured, the server interface module is responsible for interacting with the time server and processing the received NTP message to obtain information about the quality of the time server, and provides the information to a system processing module, corresponding to multiple time servers, the module comprises multiple filters, namely, each filter corresponds to one time server, and each filter is responsible for processing a group of information provided by the corresponding server and selecting information which can represent the state of the server most.

The system processing module selects the best one or a group of time servers as the actually adopted synchronous information source according to the information provided by the server interface module, obtains the most accurate time information according to the information provided by the servers, and then transmits the information to the Clock correction module; and the time integrating part is responsible for calculating the current accurate time according to the information provided by the server.

The clock correction module corrects the clock according to the time offset calculated by the system processing module.

A service method of a high-precision network time service system comprises the following steps:

s1, an atomic clock group formed by a hydrogen clock and a cesium clock stably operates for half a year;

s2, calculating standard time by adopting an ALGOS atomic time algorithm based on data of half year of operation of an atomic clock group;

s3, adopting a cesium clock driving hydrogen clock mode to convert standard time signals output by an atomic clock group into B code time signals which can be received by a network time server through a time code generator;

s4, the network time server is connected with the time code generator, the network time server and the time code generator are in serial communication, and the serial data processing part is utilized to acquire standard time signals of the atomic clock group;

s5, analyzing a standard time signal of the atomic clock group, and updating the local clock of the network time service by the analyzed time information to synchronize the time of the network time service with the time of the atomic clock group;

s6, the user equipment sends a timing request to a network time server through a network switch, and records the sending time t1;

s7, a server-side time transmission module monitors a time correction request sent by user equipment, records time t2 for acquiring the time correction request, and builds a time data packet based on a network time protocol;

s8, the server-side time transmission module transmits the constructed time data packet to the user equipment through the network switch, and records the transmission time t3;

s9, the user equipment receives the time data packet sent by the server side and records the receiving time t4;

s10, a user equipment transmission module analyzes a time data packet based on a network time protocol, calculates to obtain time deviation by subtracting half of the difference between t2 and t1 from the difference between t4 and t3, and calculates to obtain network delay by adding half of the difference between t2 and t1 to the difference between t4 and t3;

s11, repeating the steps S6-S10, and according to the statistical center limit theorem, when the overall distribution is unknown and the sample number is large enoughSample means tend to be normally distributed; let the mean value of the network delay be d, d-N (Σdelay) _i /n,∑(delay _i -∑delay _i N)/n) n is the number of times steps S6-S10 are repeated;

s12, when the delay deviation mean value of the network is larger, the network is considered to be congested or the network is considered to have a problem, the measured time deviation data are meaningless, and the time deviation data are filtered and proposed;

and S13, the user equipment transmission module uses the average value as a final time deviation result according to the reserved time deviation data, and updates the local clock by using the time deviation so as to synchronize the time of the user equipment with the time of the network time server.

The evaluation method of the high-precision network time service system specifically evaluates the uncertainty of the system and comprises the following steps:

s1, measuring a model, and measuring time service precision T _i Time difference measurement T between local UTC pulse and detected pulse _UTC And the standard time deviation delta is as follows:

T _i ＝T _UTC +δ

δ：T _i and T is _UTC A deviation value between the two;

the environmental conditions of the measurement model in step S1 are as follows: temperature: 15-35 ℃; relative humidity: (20-80)%;

s2, uncertainty sources, (a) measuring a standard uncertainty component u1 (rated as a standard uncertainty class A) caused by repeatability;

(b) A standard uncertainty component u2 (rated as standard uncertainty class B) caused by uncertainty of the time analyzer;

s3, evaluating a standard uncertainty component u1, namely evaluating the uncertainty of repeatability by adopting a class A method, wherein a measurement column can be obtained through continuous measurement; carrying out repeated measurement on a standard time signal output by a network time service system, and continuously measuring for 10 times;

and S4, calculating and evaluating the standard uncertainty component u2, the synthesized standard uncertainty and the expanded uncertainty according to the standard time signal output by the network time service system.

Finally, it should be noted that: the foregoing description is only illustrative of the preferred embodiments of the present invention, and although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described, or equivalents may be substituted for elements thereof, and any modifications, equivalents, improvements or changes may be made without departing from the spirit and principles of the present invention.

Claims (7)

1. A high-precision network time service system is characterized in that: the system comprises system hardware, server software and client software, wherein the system hardware, the server software and the client software are connected through a network;

the system hardware comprises an external time source, a time code generator, a network time server and a network switch, wherein the external time source is used for generating a time signal serving as a reference of the network time server, the system hardware adopts an atomic clock group, the atomic clock group comprises a cesium clock and a hydrogen clock, and a stable and high-precision time standard is obtained through an ALGOS atomic time algorithm in a mode that the cesium clock is used for driving the hydrogen clock; the time code generator is used for converting the time signal output by the atomic clock group into a B code signal which can be received by the network time server; the network time server is used for obtaining a time source and a server supporting time transmission; the network switch is used for connecting user equipment;

the server software comprises a serial port data processing module, a local clock updating module, a time data processing module and a request receiving and response transmitting module, wherein the serial port data processing module is used for communicating with an external time source through a serial port and a network time server and is used for obtaining standard time information of the external time source, the local clock updating module is used for carrying out time updating on a local clock of the network time server according to standard time data of the external time source, the time data processing module is used for processing the time data based on a network time protocol, the request receiving module is used for receiving a time correction request of user equipment, and the response transmitting module is used for transmitting the standard time information to the user equipment;

and a serial data receiving and processing module is arranged in the server software and is used for communicating with the clock source part through a serial port, so that relatively accurate UTC time information generated by the clock source part is obtained.

2. The high-precision network time service system according to claim 1, wherein: when the server software receives and detects a time service instruction from a clock source through the serial port, the server software immediately acquires time information in the time service instruction and transmits the time information to a local clock updating module to update a local clock of the server.

3. The high-precision network time service system according to claim 2, wherein: the time information is immediately transmitted to a time data processing module, and the data processing module selects and calculates data required by packaging of the NTP data packet according to the NTP protocol and completes a data packaging flow; the server software sends the packed NTP data packet to the client software in the form of a client response through a sending process; and the client software immediately sends the NTP data packet to an NTP data message processing module after receiving the response from the server, and updates the local clock of the client by using the extracted corresponding time information.

4. A high precision network time service system according to claim 3, wherein: the main responsibility of the client software sends an NTP message to the server software to request time service, calculates the returned NTP message, obtains local clock deviation and network time delay, and adjusts the local clock; each returned message contains four time stamps, and the time deviation and the network time delay are calculated according to the four time stamps; and each synchronization process needs to carry out 8 times of NTP message exchange, each time a group of network delay and clock deviation can be obtained, and the client selects a group of most accurate network delay and clock deviation from the 8 groups of network delay and clock deviation to synchronize the local clock by using a filtering algorithm.

5. A service method of a high-precision network time service system according to any one of claims 1 to 4, characterized in that: the method comprises the following steps:

s1, an atomic clock group formed by a hydrogen clock and a cesium clock stably operates for half a year;

s2, calculating standard time by adopting an ALGOS atomic time algorithm based on data of half year of operation of an atomic clock group;

s3, adopting a cesium clock driving hydrogen clock mode to convert standard time signals output by an atomic clock group into B code time signals which can be received by a network time server through a time code generator;

s4, the network time server is connected with the time code generator, the network time server and the time code generator are in serial communication, and the serial data processing part is utilized to acquire standard time signals of the atomic clock group;

s5, analyzing a standard time signal of the atomic clock group, and updating the local clock of the network time service by the analyzed time information to synchronize the time of the network time service with the time of the atomic clock group;

s6, the user equipment sends a timing request to a network time server through a network switch, and records the sending time t1;

s7, a server-side time transmission module monitors a time correction request sent by user equipment, records time t2 for acquiring the time correction request, and builds a time data packet based on a network time protocol;

s8, the server-side time transmission module transmits the constructed time data packet to the user equipment through the network switch, and records the transmission time t3;

s9, the user equipment receives the time data packet sent by the server side and records the receiving time t4;

s10, a user equipment transmission module analyzes a time data packet based on a network time protocol, calculates to obtain time deviation by subtracting half of the difference between t2 and t1 from the difference between t4 and t3, and calculates to obtain network delay by adding half of the difference between t2 and t1 to the difference between t4 and t3;

s11, repeating the steps S6-S10, wherein according to the statistical center limit theorem, when the overall distribution is unknown and the number of samples is large enough, the average value of the samples tends to be normally distributed; let the mean value of the network delay be d, d-N (Σdelay) _i /n,∑(delay _i -∑delay _i N)/n) n is the number of times steps S6-S10 are repeated;

s12, when the delay deviation mean value of the network is larger, the network is considered to be congested or the network is considered to have a problem, the measured time deviation data are meaningless, and the time deviation data are filtered and proposed;

and S13, the user equipment transmission module uses the average value as a final time deviation result according to the reserved time deviation data, and updates the local clock by using the time deviation so as to synchronize the time of the user equipment with the time of the network time server.

6. An evaluation method of a high-precision network time service system according to any one of claims 1 to 4, characterized in that the evaluation method of the high-precision network time service system specifically evaluates the uncertainty of the system, comprising the following steps:

s1, measuring a model, and measuring time service precision T _i Time difference measurement T between local UTC pulse and detected pulse _UTC And the standard time deviation delta is as follows:

T _i ＝T _UTC +δ

δ：T _i and T is _UTC A deviation value between the two;

s2, uncertainty sources, (a) measuring a standard uncertainty component u1 (rated as a standard uncertainty class A) caused by repeatability;

(b) A standard uncertainty component u2 (rated as standard uncertainty class B) caused by uncertainty of the time analyzer;

s3, evaluating a standard uncertainty component u1, namely evaluating the uncertainty of repeatability by adopting a class A method, wherein a measurement column can be obtained through continuous measurement; carrying out repeated measurement on a standard time signal output by a network time service system, and continuously measuring for 10 times;

and S4, calculating and evaluating the standard uncertainty component u2, the synthesized standard uncertainty and the expanded uncertainty according to the standard time signal output by the network time service system.

7. The method for evaluating a high-precision network time service system according to claim 6, wherein: the environmental conditions of the measurement model described in step S1 are: temperature: 15-35 ℃; relative humidity: (20-80)%.