High-precision time synchronization method for high-dynamic missile-borne networking data link

Abstract

A high-precision time synchronization method for a high-dynamic missile-borne networking data link mainly comprises the following steps: calculating a time deviation epsilon between a master node and a slave node through inquiry and response of an RTT message based on a round-trip timing synchronization technology; further analyzing and estimating the time synchronization error Delta under the high dynamic condition; and the slave node compensates the local time according to epsilon '= epsilon + Delta to realize time synchronization. The method is suitable for a high-precision time synchronization system of a high-dynamic missile-borne collaborative networking data link, external position information assistance is not needed, the algorithm complexity is low, and the time synchronization precision is high.

Description

Technical Field

[0001] The present invention relates to the technical field of data link communication, and particularly relates to a high-precision time synchronization method for a high-dynamic missile-borne networking data link. Background Art

[0002] With the rapid development of information technology, collaborative combat is an inevitable trend in the development of future wars. To achieve collaborative combat, it is necessary to highly unify the spatio-temporal reference of the combat space. The collaborative combat of information-based weaponry highly depends on spatio-temporal unity, and the data link, as the communication bridge of weapon platforms, the high-precision autonomous time synchronization function realized based on the data link is an important basis and prerequisite for implementing integrated joint operations.

[0003] For a data link system adopting the Time Division Multiple Access (TDMA) system, high-precision time synchronization among members is a basic condition for system networking.

[0004] The prior art one, "Tactical Data Link Autonomous Time Synchronization Algorithm Based on Adaptive Kalman Filter", analyzed the autonomous time synchronization mechanism of the tactical data link and the characteristics of various error sources, and gave a design approach to reduce the influence of time synchronization error sources. Aiming at the problem that it is difficult to accurately establish the clock drift model in a complex physical environment. This technology analyzed the error sources, but did not elaborate on the calculation of error elimination, and could not effectively eliminate the influence of error sources on the synchronization accuracy.

[0005] The prior art two, "Design of Inter-Machine Data Link Network Time Synchronization Based on FPGA", pointed out that aiming at the time synchronization problem in the inter-machine data link network, a network time synchronization scheme based on field programmable gate array was designed and implemented. Using position messages and arrival detection time, the time deviation between the master and slave nodes was calculated to achieve time synchronization with a single interaction. This technology calculated the distance and propagation delay according to the terminal position information, analyzed a single error source, had a large calculation amount, and needed to be further optimized in engineering practice. Summary of the Invention

[0006] The present disclosure provides a high-precision time synchronization method for a high-dynamic missile-borne networking data link system, which is implemented by using the Round-Trip Time (RTT) synchronization method. It fully considers the error sources of time synchronization accuracy, analyzes the influence of errors on time synchronization performance, and through calculation and analysis, gives an algorithm to reduce the influence of errors. This algorithm improves the system synchronization performance, has the characteristics of low complexity, high precision, and low jitter, and can ensure the time unity among users in a high-dynamic multi-user usage scenario.

[0007] The high-precision time synchronization method for a high-dynamic missile-borne networking data link provided by the present disclosure mainly includes the following steps:

[0008] S1. Assume that the on-board networking data link adopts the TMDA networking method, and each terminal node shares the channel according to the time slot allocation.

[0009] Based on the round-trip time synchronization technology, through the inquiry and response of RTT messages, calculate the time deviation ε between the master node and the slave node.

[0010] S2. Since the time synchronization error includes the error caused by the high-speed movement of the carrier, and this error cannot be ignored, further analyze and estimate the time synchronization error Delta in the high-dynamic situation.

[0011] S3. The slave node compensates its local time according to ε′ = ε + Delta to achieve time synchronization.

[0012] Furthermore, the step S1 specifically includes:

[0013] S11. The slave node sends an RTT inquiry message to the master node at the start of its own time slot, and the inquiry message is included in the link maintenance message sent by the slave node.

[0014] S12. The master node receives and parses the link maintenance message, determines the arrival time of the RTT inquiry message, that is, the time relative to the start of its current time slot, denoted as TOA I , and then sends TOA I to the slave node through an RTT response message at the start of its next time slot.

[0015] S13. The slave node measures the arrival time of the RTT response message, that is, the time relative to the start of the time slot when it sends the RTT inquiry message, denoted as TOA R , and demodulates the RTT response message to obtain TOA I .

[0016] S14. The slave node calculates its time deviation ε from the master node according to the TOA R , TOA I and the time slot length T slot .

[0017] Furthermore, the time deviation in the step S14 is calculated according to the following formula:

[0018] ε = (TOA I - TOA R + T slot ) / 2.

[0019] Furthermore, the time synchronization error in the step S2 specifically includes: the error caused by the asymmetry of the transmission path due to the relative speed and the calibration period calculation; the error caused by the calibration period and the clock stability; and the arrival time estimation error.

[0020] Furthermore, the method for estimating the error includes:

[0021] Calculating the error caused by the transmission path asymmetry according to the relative speed and the time calibration period, that is, Delta1 = T slot ×Δv / (c - Δv);

[0022] According to the time calibration period T slot and the clock stability, calculating the error caused by the time calibration period and the clock stability, that is, Delta2 = T slot ×10 -7 ;

[0023] According to the signal processing sampling rate of f s , calculating the arrival time estimation error, that is, Delta3 = (±1 / f s ) ns; then the maximum synchronization error is:

[0024] Delta = Delta1 + Delta2 + Delta3;

[0025] Since Delta1 is much larger than Delta2 and Delta3, so Delta ≈ Delta1.

[0026] Compared with the prior art, the beneficial effects of the present disclosure are: ① Applying cooperative networking, frequency hopping communication, and time synchronization to the high-dynamic networking data link system, and by adopting the method combining round-trip time synchronization and error source analysis and calculation, the synchronization performance of the system is improved, featuring low complexity, high precision, and low jitter; ② A time synchronization method for low-overhead multi-nodes without external position information assistance; ③ Applied to the high-maneuver missile-borne cooperative networking data link, with a simple algorithm and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] By describing the exemplary embodiments of the present disclosure in more detail in conjunction with the accompanying drawings, the above and other objects, features, and advantages of the present disclosure will become more apparent. Among them, in the exemplary embodiment mode of the present disclosure, the same reference numerals generally represent the same components.

[0028] Figure 1 Is a flowchart of an exemplary embodiment according to the present disclosure;

[0029] Figure 2 Is an exemplary round-trip time synchronization process diagram. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] Preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure will be more thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0031] The present disclosure proposes a high-precision time synchronization method for a high-dynamic missile-borne networking data link, which can ensure time unity among users in a high-dynamic multi-user usage scenario.

[0032] To achieve the above object, the technical solution of the present disclosure is as follows:

[0033] 1. Compared with the communication system of the missile-borne data link with a relatively low relative motion speed on the traditional platform, the present disclosure is applicable to a high-mobility frequency-hopping cooperative networking data link, adopts the TMDA networking method, and each terminal node shares the channel according to the time slot allocation. For data exchange between weapon platforms, tactical information cooperation, interference cooperation, flight trajectory cooperation, etc. are realized.

[0034] 2. The present disclosure uses the round-trip timing synchronization method in the missile-borne data link system to achieve time synchronization between nodes of the data link; according to the application scenario, the error sources, characteristics of the errors and their impacts on time synchronization are analyzed, and a calculation method for reducing the impacts of these error sources is proposed.

[0035] The present disclosure applies cooperative networking, frequency-hopping communication and time synchronization to a high-dynamic networking data link system, and by adopting the method of combining round-trip timing synchronization and error source analysis and calculation, improves the synchronization performance of the system, and has the characteristics of low complexity and high precision.

[0036] Among them, the round-trip timing synchronization (RTT) technology is used for time synchronization between communication terminals. The round-trip timing synchronization (RTT) is a two-way comparison method based on time-of-arrival measurement, which does not rely on external timekeeping. By using the two-way transmission of the time-of-arrival (TOA) of both parties participating in time synchronization, the time of the wireless signal in the path transmission is offset, and the accurate time difference between the two parties is calculated.

[0037] The technical principle is further described as follows:

[0038] An example of the round-trip timing synchronization process is shown in the attached Figure 2 As shown, among them, the slave node (the inquiry party in the figure) sends an inquiry message (contained in the link maintenance message) to the master node (the response party in the figure) at the start of its time slot;

[0039] The master node measures the arrival time of the message and sends it to the slave node through the response message in the determined response time slot, which contains the arrival time of the inquiry message and the sending time of the response message;

[0040] The arrival time of the signal of the response message is measured at the slave node, and its time deviation from the master node is calculated; then the time deviation is compensated to the local time count value to achieve time synchronization.

[0041] TOA I : The arrival time of the RTT query message determined by the master node;

[0042] TOA R : The arrival time of the RTT response message determined by the slave node;

[0043] T slot : The time slot period;

[0044] T P : The propagation time of the RTT message. It is considered that the propagation times of the RTT query and the RTT response are the same;

[0045] ε: The clock error between two terminals, that is, the error that the synchronization terminal should correct.

[0046] From ε + T P = TOA I , (1)

[0047] T slot + T P = TOA R + ε, (2)

[0048] It can be obtained that: ε = (TOA I - TOA R + T slot ) / 2 (3)

[0049] The slave node sends a query message when its own synchronization request signaling time slot arrives, and the master node is ready to receive the query message at the synchronization response signaling time slot. After sending the query message, the slave node immediately switches to receiving the response message, and also calculates TOA R by capturing the information of the master node, and demodulates the response message to obtain TOA I . After the slave node obtains TOA I and TOA R , the time error is calculated by Equation 3, and fine synchronization is completed.

[0050] For a high-dynamic networking data link system, due to factors such as relative motion between nodes and time calibration period, there are errors in the calculated time deviation. Therefore, in this disclosure, the time synchronization error in the dynamic case is further analyzed, and the final compensation value is: time deviation + time synchronization error value.

[0051] In this disclosure, the error sources of time synchronization mainly include:

[0052] a. Errors caused by asymmetric transmission paths

[0053] In the RTT time synchronization principle and time error calculation, it is assumed that the transmission delays of the RTT request message and the RTT response message are the same, which is one of the sources of time synchronization errors. When the transmission delays are different and the time difference is ΔT, the corresponding transmission speed is (c - Δv), where c is the propagation speed of the wireless signal and Δv is the relative speed between the end machines. The transmission distance difference corresponding to the time difference is:

[0054] d = ΔT × (c - Δv) (4)

[0055] At the same time, this distance difference can be expressed by the relative speed and the synchronization time slot length, that is

[0056] d = Δv × T slot (5)

[0057] From equations (4) and (5), we can get:

[0058] ΔT = T slot × Δv / (c - Δv)

[0059] That is: Delta1 = T slot × Δv / (c - Δv) (6)

[0060] This error can be compensated according to the relative speed value during the implementation of time synchronization to eliminate the error. The relative speed can be obtained by calculating the Doppler frequency offset or by calculating the path transmission delay difference of adjacent time calibration cycles.

[0061] b. Errors caused by the time calibration cycle and clock stability

[0062] The second source of time synchronization error is the time calibration cycle T slot and clock stability. For a clock stability of ±0.1 ppm, that is 10 -7 .

[0063] Delta2 = T slot × 10 -7 (7)

[0064] c. Arrival time estimation error

[0065] As Figure 2 shown, TOA I and TOA R are the arrival times estimated by the slave node and the master node respectively. This time is the estimated time. TOA I and TOA RInevitably, there are estimation errors. Moreover, the representation accuracy of time is limited. Therefore, there must be a certain error in time synchronization. The signal processing sampling rate is f s , considering the influence of noise and quantization effect, the arrival time estimated by the signal acquisition module based on matched filtering is within 1 sampling point from the true arrival time. Therefore, the maximum value of the time synchronization error caused thereby is:

[0066] Delta3 = (±1 / f s ) ns (8)

[0067] According to the above analysis, the maximum synchronization error can be obtained as approximately Delta = Delta1 + Delta2 + Delta3;

[0068] The slave node compensates ε' = ε + Delta (ε' is the time error relative to the clock reference node, i.e., the master node) to the local time count value to achieve time synchronization.

[0069] The process of an exemplary embodiment based on the above principle is as shown in the appendix Figure 1 and includes the following steps:

[0070] Step 1, using a fixed frequency hopping sequence, the slave node sends a link maintenance message in a fixed time slot (known T slot ). The link maintenance message carries the time information of the slave node and the synchronization node number;

[0071] Step 2, the master node receives the link maintenance message through signal detection, determines whether the local node is consistent with the synchronization node number. If consistent, it parses the link maintenance message and records the TOA I , and then sends it to the slave node through a response message in the determined response time slot, which includes the arrival time of the inquiry message and the sending time of the response message; the slave node measures the signal arrival time of the response message and calculates its time deviation from the master node;

[0072] Step 3, the slave node measures the signal arrival time of the response message, records the TOA R , calculates its time deviation ε from the master node, that is, ε = (TOA I - TOA R + T slot ) / 2;

[0073] Step 4, calculates the error caused by the transmission path asymmetry according to the relative speed and the time calibration period, that is, Delta1 = T slot × Δv / (c - Δv);

[0074] Step 5, calculates the error caused by the time calibration period T slot and the clock stability according to the time calibration period, that is, Delta2 = Tslot ×10 -7 ;

[0075] Step 6: Calculate the arrival time estimation error according to the signal processing sampling rate of f s , that is, Delta3 = (±1 / f s ) ns;

[0076] Step 7: According to the above analysis, the maximum synchronization error is approximately Delta = Delta1 + Delta2 + Delta3;

[0077] Since Delta1 is much larger than Delta2 and Delta3, Delta ≈ Delta1.

[0078] Step 8: The slave node compensates ε′ = ε + Delta to the local time to achieve time synchronization.

[0079] In this embodiment, the sources of time synchronization error are systematically analyzed, an error estimation and compensation algorithm is adopted, and the error sources are corrected to reduce the time synchronization error and improve the synchronization accuracy.

[0080] This scheme is applicable to the high-precision time synchronization system of the high-dynamic missile-borne cooperative networking data link, without the assistance of external position information, with low algorithm complexity and high time synchronization accuracy.

[0081] The above technical solution is only an exemplary embodiment of the present invention. For those skilled in the art, based on the disclosed application methods and principles of the present invention, various types of improvements or deformations can be easily made, not limited to the methods described in the above specific embodiments of the present invention. Therefore, the above-described manner is only preferred and does not have a restrictive meaning.

Claims

1. A high-precision time synchronization method for a high-dynamic missile-borne networking data link, comprising the following steps: S1, assuming that the missile-borne networking data link adopts the TMDA networking mode, and each terminal node is allocated a shared channel according to the time slot; Based on the round-trip timing synchronization technology, the time deviation ε between the master and slave nodes is calculated through the inquiry and response of the RTT message; S2, since the time synchronization error includes the error caused by the high-speed movement of the carrier, and this error cannot be ignored, the time synchronization error Delta under high dynamic conditions is further analyzed and estimated; S3, the slave node compensates the local time according to ε′=ε+Delta to achieve time synchronization.

2. The method according to claim 1, characterized in that The step S1 specifically includes: S11, the slave node sends an RTT inquiry message to the master node at the start of its own time slot, where the inquiry message is included in the link maintenance message sent by the slave node; S12, the master node receives and parses the link maintenance message, determines the arrival time of the RTT query message, that is, the time relative to the start of its current time slot, recorded as TOA I , and then at the beginning of the next time slot, the TOA is sent via an RTT response message. I Send to slave nodes; S13, the slave node measures the arrival time of the RTT reply message, that is, the time relative to the start of the time slot when it sends the RTT query message, recorded as TOA R , and demodulate the RTT response message to obtain TOA I ; S14, the slave node uses the TOA R 、TOA I And the time slot length T slot Calculate its time deviation ε from the master node.

3. The method according to claim 1, characterized in that The time deviation in step S14 is calculated as follows: ε=(TOA) I -TOA R +T slot ) / 2.

4. The method according to claim 1 or 2, characterized in that: The time synchronization error in step S2 specifically includes: an error caused by asymmetric transmission paths due to relative speed and timing cycle calculation; an error caused by timing cycle and clock stability; and an arrival time estimation error.

5. The method according to claim 4, characterized in that The error estimation method includes: The error caused by the asymmetry of the transmission path is calculated based on the relative speed and the timing cycle, that is, Delta1 = T slot ×Δv / (c-Δv); According to the time calibration period T slot and clock stability, calculate the error caused by the time calibration period and clock stability, that is, Delta2 = T slot ×10 -7 ; According to the signal processing sampling rate of fs, the arrival time estimation error is calculated, that is, Delta3 = (±1 / f s )ns; The maximum synchronization error is: Delta=Delta1+Delta2+Delta3; Since Delta1 is much larger than Delta2 and Delta3, Delta≈Delta1.

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