Electric power 5G-Advanced clock synchronization method giving consideration to multi-terminal fairness

Abstract

The invention provides an electric power 5G-Advanced clock synchronization method giving consideration to multi-terminal fairness, and belongs to the technical field of electric power 5G-A networks. Comprising the following steps: a time synchronization gateway sends a synchronization authorization instruction to each terminal in turn according to a terminal list; after receiving the synchronization authorization instruction, the terminal exchanges data with the base station, obtains a bidirectional time delay measurement timestamp, generates a time message according to the bidirectional time delay measurement timestamp, and sends the time message to the time synchronization gateway; the time synchronization gateway generates a time adjustment instruction and sends the time adjustment instruction to the terminal according to the received time message and statistical analysis on the time delay; and the terminal performs local clock adjustment according to the received time adjustment instruction. According to the method, 5G-A network slice deterministic transmission and air interface hard time delay guarantee capability are fused, synchronous message microsecond-level deterministic time delay is guaranteed through special slice isolation, sub-microsecond-level error suppression in a complex environment is realized in combination with physical layer hardware stamping and dynamic Kalman filtering, and high-reliability time synchronization service is provided for a novel power system.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power 5G-A network, and particularly relates to a clock synchronization method for power 5G-Advanced considering fairness of multiple terminals. BACKGROUND

[0002] With the development of 5G-Advanced (5G-A) technology, especially the integration of sensing and communication (ISAC) and passive Internet of Things (Passive IoT) capabilities. The integration of sensing and communication technology uses communication signals to achieve high-precision environmental perception, which can provide a new paradigm for three-dimensional security and equipment state monitoring for substations with all-weather, wide coverage and low cost. Passive Internet of Things technology achieves "battery-free and maintenance-free" connection of terminals by obtaining energy from the environment. Therefore, the application of 5G-A technology in smart substations is an urgent need to improve the intelligent level of power grids and ensure the safe operation of power grids.

[0003] However, due to random noise in the environment, timestamp data packets in the 5G-A network may be reordered, delayed or even lost during transmission, resulting in an increase in clock state estimation error, which is difficult to meet the demand for clock synchronization accuracy of power grid business. SUMMARY

[0004] The application provides a clock synchronization method for power 5G-Advanced considering fairness of multiple terminals to solve one or part or all of the above technical problems.

[0005] To solve one or part or all of the above technical problems, the technical solution adopted by the application is: A clock synchronization method for power 5G-Advanced considering fairness of multiple terminals, comprising: A time synchronization gateway sends synchronization authorization instructions to each terminal in turn according to a terminal list; After receiving the synchronization authorization instructions, the terminal exchanges data with the base station and obtains a bidirectional time delay measurement timestamp, generates a time message according to the bidirectional time delay measurement timestamp, and sends the time message to the time synchronization gateway; The time synchronization gateway generates a time adjustment instruction according to the received time message and statistical analysis of the time delay, and sends the time adjustment instruction to the terminal; The terminal adjusts the local clock according to the received time adjustment instruction.

[0006] Further, the bidirectional time delay measurement timestamp includes a sending time of the terminal , a receiving time of the base station , a sending time of the base station , and a receiving time of the terminal .

[0007] Further, the method for generating time adjustment instructions by the time synchronization gateway comprises: obtaining a coarse estimation of the one-way fixed delay and a round-trip jitter , , ; constructing a Kalman filter; a state space model of the Kalman filter , is a fixed propagation delay of the network, is a real one-way delay, is a current network queuing jitter; a state transition equation , A is a state transition matrix, process noise , is a process noise covariance; an observation model of the Kalman filter , , is a pre-measured reference fixed delay, H is an observation matrix, measurement noise , is a measurement noise covariance; recursively performing the Kalman filter to obtain a one-way delay estimation and a jitter estimation ; generating time adjustment instructions according to the recursive results.

[0008] Further, the method for generating time adjustment instructions according to the recursive results comprises: determining a confidence interval according to a terminal type; and generating the time adjustment instructions according to the recursive results if the one-way delay estimation obtained by the recursion falls within the confidence interval.

[0009] Further, the time adjustment instructions issued comprise phase correction data and frequency correction data, the phase correction data , is a theoretical ideal one-way delay, the frequency correction data , is an interval between a last time packet of the terminal processed by the time synchronization gateway and a current time packet of the terminal processed by the time synchronization gateway.

[0010] Further, the state transition matrix , ; the process noise covariance , is a minimum fluctuation of the fixed delay, is drift noise, is jitter noise.

[0011] Further, the observation matrix ; the measurement noise covariance , is each received The original variance, It is a constant.

[0012] Furthermore, the method for the terminal to adjust the local clock according to the received time adjustment instruction includes: aligning the local clock with the base station clock according to phase correction data, and adjusting the frequency of the PLL according to frequency correction data.

[0013] Furthermore, time synchronization-related data between the terminal, base station, and time synchronization gateway is transmitted using dedicated network slices.

[0014] Furthermore, the time synchronization gateway is also connected to a high-precision absolute time source.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention establishes a highly reliable clock synchronization path for 5G-A networks. Time synchronization traffic is transmitted independently in a dedicated network slice, exclusively occupying spectrum resources and configured with the highest priority. This effectively isolates the impact of service traffic, ensures a clean latency measurement environment, and significantly improves the accuracy of latency measurements. The base station clock and the time synchronization gateway are directly bound using a physical timing link, avoiding random latency in the wireless link and ensuring that the base station clock error is within the sub-microsecond range.

[0016] This invention employs a dynamic delay estimation algorithm based on Kalman filtering to intelligently distinguish between hardware errors and network jitter, achieving stable synchronization in noisy environments. It designs state and observation models, capturing slow changes in network topology / slice scheduling abrupt changes through process noise covariance Q, filtering hardware temperature drift jitter by measuring noise covariance R, and updating the Kalman gain in real time. This suppresses fluctuations during periods of stable delay and enables rapid tracking during abrupt changes, reducing the variance of unidirectional delay estimation errors by more than 50%. Based on historical delay distribution, this invention dynamically calculates quantile confidence intervals, automatically discarding data exceeding limits and triggering terminal resynchronization, avoiding sudden delays such as slice resource contention from contaminating synchronization results.

[0017] This invention integrates the deterministic transmission of 5G-A network slicing with the air interface hard latency guarantee capability. It ensures microsecond-level deterministic latency of synchronization messages through dedicated slice isolation, and achieves sub-microsecond-level error suppression in complex environments by combining physical layer hardware stamping and dynamic Kalman filtering. It provides highly reliable time synchronization services for new power systems, and can support core businesses such as wide-area phasor measurement, 5G differential protection, and source-grid-load-storage coordinated control. It can improve the intelligence level of the power grid and ensure the safe operation of the power grid. Detailed Implementation

[0018] For better understanding of the present application, the following further clearly sets forth the content of the present application in conjunction with examples, but the protection scope of the present application is not limited to the following examples. In the following description, a large number of specific details are given in order to provide a more thorough understanding of the present application. However, it is obvious to those skilled in the art that the present application can be implemented without one or more of these details.

[0019] Embodiment 1: The purpose of this embodiment is to provide a clock synchronization method for power 5G-Advanced that takes into account the fairness of multiple terminals.

[0020] The clock synchronization method is applicable to a power 5G-Advanced (5G-A) network, in which power terminals such as PMUs, RTUs, sensors are connected to the base station through the 5G-A network, and a time synchronization gateway is also provided in the 5G-A network. In order to ensure the accuracy of time synchronization, time synchronization related data (such as clock messages) in the 5G-A network are transmitted using a dedicated network slice, which uses exclusive frequency band resources and has the highest priority. The clock synchronization traffic is guaranteed not to be disturbed by service flow through the slice, ensuring the accuracy of latency prediction.

[0021] The time synchronization gateway is also connected to a high-precision absolute time source (such as a GNSS receiver, or connected to a national time center or PRTC through a ground high-precision time transfer network), so that the time synchronization gateway serves as the master clock of the power 5G-A network. The base station is located near the time synchronization gateway, and a dedicated physical time transmission link (such as optical fiber) is provided between the two to transmit time signals, so that the base station clock is consistent with the time synchronization gateway clock.

[0022] The clock synchronization method comprises: S1, the time synchronization gateway sends synchronization authorization instructions to each terminal in turn according to the terminal list.

[0023] In order to ensure the fairness of time synchronization between terminals and avoid queuing competition in the dedicated network slice when multiple terminals send time synchronization requests at the same time, the present application maintains the time synchronization order of the terminals by the time synchronization gateway, and uses a polling scheduler to issue synchronization authorization instructions to the terminals. The terminal only performs subsequent steps of time synchronization after receiving the authorization, which can ensure that each terminal has the same opportunity.

[0024] S2, after receiving the synchronization authorization instruction, the terminal sends an uplink data frame embedding the terminal's local first time to the base station.

[0025] After receiving the synchronization authorization instruction sent by the time synchronization gateway, the terminal first sends a time synchronization request to the base station. Specifically, the terminal reads the first time according to the local clock, and sends the first time (T1) and the terminal ID (ID) to the base station through the uplink data frame. After embedding the uplink data frame, the uplink MAC frame is sent to the base station through a dedicated network slice.

[0026] S3, the base station receives the uplink data frame sent by the terminal, records the second time of arrival, and returns the downlink data frame embedded with the local third time of the base station to the terminal.

[0027] After the base station receives the uplink data frame sent by the terminal at the MAC layer, it records the second time of arrival . Then the base station generates a downlink data frame, embeds the current third time of the base station in the downlink data frame, and sends the downlink data frame to the terminal through a dedicated network slice.

[0028] S4, the terminal generates a time message according to the received downlink data frame, and sends the time message to the time synchronization gateway.

[0029] The terminal receives the downlink data frame sent by the base station, records the fourth time of local reception completion , and parses the downlink data frame to obtain the third time . In the direct interaction process of time synchronization between the terminal and the base station, four timestamp information (bidirectional delay measurement timestamp) are obtained, all of which are obtained through physical layer hardware dotting. Among them, the first time and the fourth time are the local clock information of the terminal, and the second time and the third time are the local clock information of the base station.

[0030] The terminal encapsulates the time message and sends it to the time synchronization gateway through a dedicated network slice. Among them is the MAC address of the terminal.

[0031] After the terminal sends the time message, it enters a fine-tuning waiting state and listens to the downlink fine-tuning control instruction of the time synchronization gateway.

[0032] S5, the time synchronization gateway generates a time adjustment instruction according to the received time message and statistical analysis of the delay, and sends it to the terminal.

[0033] The time synchronization gateway parses the first time , the second time , the third time and the fourth time from the time message, obtains a rough estimate of the one-way fixed delay and the round-trip jitter , , . The rough estimate is the one-way fixed delay (including path fixed delay + slow drift) obtained this time, and the round-trip jitter For the round-trip delay of this measurement, the observation noise will be filtered as the subsequent.

[0034] Set the state space model of Kalman filter , For the fixed propagation delay of the network, it does not change over time. For the real one-way delay, it is a slowly changing variable delay over time. For the current network queuing jitter, the change is often fast and has certain autocorrelation, and a first-order autoregressive model is used. State transition equation State transition matrix , ; The fixed delay is constant in the ideal case and is not affected by other states, so the coefficient of the first row in matrix A is 1; The variable delay is also approximately constant in the slow drift case, so the coefficient of the second row in matrix A is also 1; The jitter often behaves as a first-order Gauss Markov process, the jitter of the last period will continue to exist after forgetting a part with a coefficient φ, the closer φ is to 1, the stronger the memory of the jitter is, and the closer it is to 0, the faster the jitter decays, φ in this application is 0.7~0.9, and experience shows that the autocorrelation time of jitter is about a few hundred milliseconds to a few seconds under 5G-A network, and the corresponding φ can well capture this characteristic in this interval.

[0035] Process noise Process noise will inject random disturbances into each component (especially and ), so although matrix A itself is constant in the second row, the actual will still fluctuate over time, but the drift rate is determined by the process noise, not directly amplified by the system matrix. Process noise covariance , The fixed delay has a very small fluctuation, which can be set to 1e 11s 2 ; Drift noise, reflecting network scheduling slow change, generally take 0.5 ; Jitter noise, take 1 as the initial value, and then dynamically updated by the innovation-based adaptive Kalman filter (IAE, Innovation-based Adaptive Estimation) based on the innovation covariance estimation.

[0036] Observation model , where , The reference fixed delay measured in advance is used as a pseudo-observation to help quickly converge to the correct . Observation matrix , for mapping the state vector to the observation space; , for the measurement noise covariance, , for the original variance of each received , the sample variance estimation of the sliding window can be used; fixed and very small (e.g. 5 ns), which can be regarded as a constant.

[0037] Using the Kalman filter for recursion, the prediction equation is , , the Kalman gain , the update equation is , , , the adaptive process noise equation for the jitter part is , , The one-way delay estimation obtained after recursion is , and the jitter estimation is .

[0038] The time synchronization gateway maintains the empirical distribution of the last N (≥ 50) one-way delay estimations of the terminal, and according to the terminal type, uses quantile (e.g. 95% for PMU and 99% for RTU) to set the confidence interval. Only when the current one-way delay estimation falls within the confidence interval, the time adjustment instruction is issued; otherwise, the "delay abnormal" instruction is returned, requiring the terminal to re-initiate the time synchronization request to the base station. The time adjustment instruction issued includes phase correction data and frequency correction data; where "phase" refers to the instantaneous time offset, i.e. the absolute error of the local clock relative to the reference clock at a certain time, and "frequency" refers to the deviation of the clock rate, i.e. the cumulative time error over a period of time, reflecting temperature drift, aging, oscillator noise, etc. long-term changes. The phase correction data , is the theoretical ideal one-way delay, usually 0 µs; the frequency correction data , represents the cumulative delay slope, is the calculation interval between the last time the time synchronization gateway processed the time packet of the terminal and the current time the time synchronization gateway processed the time packet of the terminal.

[0039] In the 5G-A network, the time delay will have several microseconds of jitter over time, and if only a single measurement is relied on for time synchronization, there will be errors, so this step introduces Kalman filtering, recursive minimum mean square error (MMSE) estimation, which fuses historical measurement information and smooths noise. The 5G-A network may cause sudden time delay mutations when performing special network slice scheduling, so the process noise covariance Q is used to capture "slow changes" and "mutations", and when mutations occur, the Kalman gain K will instantaneously increase, thereby quickly tracking. Since there are errors and temperature drifts in hardware timing, the measurement noise R is used to treat this part of the error as random noise. Through the above processing, the error variance of the optimal one-way time delay estimation obtained by this step is greatly reduced, and the current instantaneous jitter estimation is used to assist in calculating the measurement noise of the Kalman filter and the subsequent filter gain.

[0040] S6, the terminal adjusts the local clock according to the received time adjustment instruction.

[0041] After the terminal receives the time adjustment instruction, the phase correction data and the frequency correction data are obtained by parsing, and the time is immediately adjusted according to the phase correction data to align the local clock with the base station clock; if the terminal has a hardware phase register, the output phase is instantaneously moved forward or backward by the corresponding jump number in the next clock cycle by writing in the phase register to realize time adjustment; if the terminal does not have a hardware phase register, the current counter value is read from the system time register, and the counter is written back after the accurate time is obtained according to the phase correction data. If the terminal has a hardware PLL, the frequency is adjusted by ppb according to the frequency correction data.

[0042] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit it, and other modifications or equivalent replacements of the technical solutions of the present application made by those skilled in the art should be covered within the scope of the claims of the present application, as long as they do not deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A clock synchronization method for power 5G-Advanced that takes into account fairness among multiple terminals, characterized in that, include: The time synchronization gateway sends synchronization authorization instructions to each terminal in turn according to the terminal list; After receiving the synchronization authorization command, the terminal exchanges data with the base station and obtains the bidirectional delay measurement timestamp. Based on the bidirectional delay measurement timestamp, it generates a time message and sends it to the time synchronization gateway. The time synchronization gateway generates a time adjustment command based on the received time message and statistical analysis of the delay, and sends it to the terminal. The terminal adjusts its local clock based on the received time adjustment command.

2. The clock synchronization method for power 5G-Advanced that takes into account the fairness of multiple terminals according to claim 1, characterized in that, The bidirectional delay measurement timestamp includes the terminal's transmission time. The base station's reception time The base station's transmission time and the terminal's receiving time .

3. The clock synchronization method for power 5G-Advanced that takes into account the fairness of multiple terminals according to claim 2, characterized in that, The methods for a time synchronization gateway to generate time adjustment instructions include: obtaining a rough estimate of the one-way fixed delay. and back-and-forth shaking , , ; Constructing a Kalman filter; the state-space model of the Kalman filter. , For the fixed propagation delay of the network, For true one-way delay, For the current network queuing jitter; state transition equation A is the state transition matrix, and process noise is... , For process noise covariance; observation model of Kalman filter. , , The reference time delay is fixed as measured in advance, H is the observation matrix, and the measurement noise is... , To measure the noise covariance; By recursively applying the Kalman filter, a one-way time delay estimate can be obtained. and jitter estimation ; Generate time adjustment instructions based on the recursive results.

4. The clock synchronization method for power 5G-Advanced that takes into account the fairness of multiple terminals according to claim 3, characterized in that, The method for generating time adjustment instructions based on the recursive result includes: determining a confidence interval based on the terminal type; if the one-way delay estimate obtained by recursion falls within the confidence interval, then generating a time adjustment instruction based on the recursive result.

5. The clock synchronization method for power 5G-Advanced that takes into account the fairness of multiple terminals according to claim 3, characterized in that, The issued time adjustment command includes phase correction data and frequency correction data. (Phase correction data...) , For the theoretically ideal one-way time delay, frequency correction data , The interval between the last time the time synchronization gateway processed the terminal's time message and the current time message processed by the terminal.

6. The clock synchronization method for power 5G-Advanced that takes into account multi-terminal fairness according to claim 3, characterized in that, State transition matrix , Process noise covariance , For a very small fluctuation with a fixed delay, For drift noise, This is jitter noise.

7. The clock synchronization method for power 5G-Advanced that takes into account the fairness of multiple terminals according to claim 3, characterized in that, Observation matrix ; Measurement noise covariance , For each received The original variance, It is a constant.

8. The clock synchronization method for power 5G-Advanced that takes into account the fairness of multiple terminals according to claim 5, characterized in that, The method for the terminal to adjust the local clock according to the received time adjustment command includes: aligning the local clock with the base station clock according to phase correction data, and adjusting the frequency of the PLL according to frequency correction data.

9. The clock synchronization method for power 5G-Advanced that takes into account the fairness of multiple terminals according to claim 1, characterized in that, Time synchronization-related data between terminals, base stations, and time synchronization gateways is transmitted using dedicated network slices.

10. The clock synchronization method for power 5G-Advanced that takes into account the fairness of multiple terminals according to claim 1, characterized in that, The time synchronization gateway also connects to a high-precision absolute time source.

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