NTP timing method based on satellite timing

Abstract

The present application discloses an NTP time synchronization method based on satellite timing, comprising: a terminal device located on the ground generates a first timestamp; the terminal device writes the first timestamp into an NTP query instruction, and sends the NTP query instruction to a transponder device located on the ground; the transponder device forwards the NTP query instruction to a first satellite; the first satellite receives the NTP query instruction and generates a second timestamp; the first satellite generates NTP response information corresponding to the NTP query instruction, and generates a third timestamp; the first satellite writes the first timestamp, the second timestamp and the third timestamp into the NTP response information, and sends the NTP response information to the transponder device; the transponder device forwards the NTP response information to the terminal device; the terminal device receives the NTP response information and generates a fourth timestamp; and the terminal device calibrates the clock of the terminal device according to the first timestamp, the second timestamp, the third timestamp and the fourth timestamp.

Description

Technical Field

[0001] The present application relates to the field of satellite timing technology, and in particular to a NTP timing method based on satellite timing. Background Art

[0002] NTP (Network Time Protocol) is a protocol used to synchronize the time of terminal devices. It can synchronize terminal devices with respect to a server or clock source, thereby providing high-precision time correction for terminal devices.

[0003] The existing NTP system achieves time synchronization through multiple levels. The highest level is the authoritative clock source (such as atomic clock, GPS, etc.). Then the clock synchronization is carried out layer by layer through multiple levels, thereby providing clock synchronization and time calibration for the NTP servers at the lower levels. The terminal device can interact with the NTP servers at the lower levels, so as to perform time calibration through the NTP servers at the lower levels.

[0004] Since the existing NTP system requires setting up multiple levels of NTP servers on the ground to synchronize the time of terminal devices, a large number of NTP server devices are needed to build NTP servers at each level, which not only increases the complexity of the system, but also increases the cost of the system.

[0005] Currently, no effective solution has been proposed to address the technical problem that the existing NTP system requires multiple levels of NTP servers to build, which makes the system complex and costly. Summary of the invention

[0006] The present disclosure provides an NTP time synchronization method based on satellite timing, so as to at least solve the technical problem that the existing NTP system requires multiple levels of NTP servers to be constructed, resulting in a complex system and high cost.

[0007] According to one aspect of the present application, a NTP time synchronization method based on satellite timing is provided, including: a terminal device located on the ground generates a first timestamp corresponding to a first sending time of sending an NTP query instruction; the terminal device writes the first timestamp into the NTP query instruction, and sends the NTP query instruction to a transponder device located on the ground; the transponder device forwards the NTP query instruction to a first satellite, wherein the first satellite can perform time synchronization based on time information sent by a second satellite; the first satellite receives the NTP query instruction and generates a second timestamp corresponding to the first receiving time of receiving the NTP query instruction; the first satellite generates NTP response information corresponding to the NTP query instruction, and generates a third timestamp corresponding to the second sending time of sending the NTP response information; the first satellite writes the first timestamp, the second timestamp and the third timestamp into the NTP response information, and sends the NTP response information to the transponder device; the transponder device forwards the NTP response information to the terminal device; the terminal device receives the NTP response information, and generates a fourth timestamp corresponding to the second receiving time of receiving the NTP response information; and the terminal device calibrates the clock of the terminal device according to the first timestamp, the second timestamp, the third timestamp and the fourth timestamp.

[0008] In summary, according to the technical solution disclosed in the present invention, an NTP server that performs the time calibration function is no longer set on the ground, but only a transponder for forwarding messages between the terminal device and the first satellite is set, so that low-orbit or ultra-low-orbit satellites (such as the first satellite) can be used to provide time calibration services for terminal devices in a larger geographical range. Therefore, the technical solution disclosed in the present invention no longer needs to build a complex multi-level NTP server on the ground to provide NTP services, but instead loads the service on the first satellite, and the first satellite provides time calibration services to the terminal device through the transponder. In this way, this solution greatly simplifies the architecture of the NTP service, thereby reducing the complexity and cost of the system.

[0009] Based on the detailed description of the specific embodiments of the present application in combination with the accompanying drawings below, those skilled in the art will become more aware of the above and other objects, advantages and features of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Hereinafter, some specific embodiments of the present application will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0011] Figure 1 is a schematic diagram of an NTP timing system based on satellite timing according to an embodiment of the present application;

[0012] Figure 2It is a flowchart of the NTP timing method based on satellite timing according to the embodiment of the present application;

[0013] Figure 3 and Figure 4 A schematic diagram showing, by way of example, the interaction between a terminal device and a first satellite according to an embodiment of the present application;

[0014] Figure 5 is a schematic diagram of a time management system of a first satellite according to an embodiment of the present application;

[0015] Figure 6 is a schematic diagram of transmitting calibration time information to a first satellite via a second satellite according to an embodiment of the present application; and

[0016] Figure 7 It is a schematic diagram of the PPS second pulse signal, the GPIO interrupt signal, the reference time corresponding to the PPS second pulse signal, the first crystal oscillator time and the second crystal oscillator time according to the embodiment of the present application. DETAILED DESCRIPTION

[0017] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present disclosure may be combined with each other. The present disclosure will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0018] In order to enable those skilled in the art to better understand the scheme of the present disclosure, the technical scheme in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present disclosure.

[0019] It should be noted that the terms "first", "second", etc. in the specification and claims of the present disclosure and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so as to describe the embodiments of the present disclosure described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0020] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0021] Figure 1 Schematic diagram of a satellite-based NTP timing system according to an embodiment of the present application. Figure 1 As shown, the NTP time synchronization system includes: a terminal device 10, a transponder 20, a first satellite 30 and a second satellite 40.

[0022] The second satellite 40 may be, for example, a satellite with high time accuracy, such as a GNSS system satellite, and is used to provide time information for time synchronization to the first satellite 30. The first satellite 30 may be, for example, a low-orbit or ultra-low-orbit satellite, and is used to provide time synchronization services to ground terminal devices. In addition, the terminal device 10 and the transponder 20 are ground devices, wherein the transponder 20 is used to provide a message forwarding function between the terminal device 10 and the first satellite 30. Based on the above system, the present disclosure provides a NTP time synchronization method based on satellite timing. Figure 2 The flowchart of the time calibration method is shown in FIG. Figure 2 As shown, the method includes:

[0023] S202: The terminal device located on the ground generates a first timestamp corresponding to the first sending time of sending the NTP query instruction;

[0024] S204: The terminal device writes the first timestamp into the NTP query instruction, and sends the NTP query instruction to the transponder device located on the ground;

[0025] S206: The transponder device forwards the NTP query instruction to the first satellite, wherein the first satellite can perform time synchronization based on the time information sent by the second satellite;

[0026] S208: The first satellite receives the NTP query instruction and generates a second timestamp corresponding to the first receiving time of receiving the NTP query instruction;

[0027] S210: The first satellite generates NTP response information corresponding to the NTP query instruction, and generates a third timestamp corresponding to the second sending time of sending the NTP response information;

[0028] S212: The first satellite writes the first timestamp, the second timestamp, and the third timestamp into NTP response information, and sends the NTP response information to the transponder device;

[0029] S214: The answering machine device forwards the NTP response information to the terminal device;

[0030] S216: The terminal device receives the NTP response information, and generates a fourth timestamp corresponding to the second receiving time of receiving the NTP response information; and

[0031] S218: The terminal device calibrates the clock of the terminal device according to the first timestamp, the second timestamp, the third timestamp and the fourth timestamp.

[0032] Specifically, refer to Figure 3 As shown, the terminal device 10 and the transponder 20 are both arranged on the ground. The terminal device 10 can communicate with the transponder 20. In addition, the transponder 20 can interact with the first satellite 30 through a remote control channel and a telemetry channel.

[0033] Therefore, when the terminal device 10 needs to calibrate the time, it can send an NTP query instruction to the transponder 20. When sending the NTP query instruction, the terminal device 10 first generates a timestamp corresponding to the sending time of sending the NTP query instruction (ie, the first sending time), namely, the first timestamp (S202).

[0034] The terminal device 10 then writes the first timestamp into the NTP query instruction, and sends the NTP query instruction to the transponder 20 (S204).

[0035] After receiving the NTP query instruction, the transponder 20 forwards the NTP query instruction to the first satellite 30 (S206). Figure 1 As shown, the first satellite 30 is used to provide time synchronization service to the terminal device 10, but the first satellite 30 is not the device with the highest time accuracy, and it needs the second satellite 40 for time synchronization. Preferably, the first satellite 30 can be a low-orbit satellite or an ultra-low-orbit satellite, for example.

[0036] After receiving the NTP query instruction, the first satellite 30 first generates a timestamp corresponding to the time of receiving the NTP query instruction (ie, the first receiving time), ie, a second timestamp (S208).

[0037] Then, the first satellite 30 generates NTP response information corresponding to the NTP query command, and generates a timestamp corresponding to the time of sending the NTP response information (ie, the second sending time), ie, a third timestamp, when sending the NTP response information (S210).

[0038] Then, the first satellite 30 writes the first time stamp, the second time stamp, and the third time stamp into the NTP response information, and sends the NTP response information to the transponder 20 (S212).

[0039] Then, after receiving the NTP response information, the answering machine 20 forwards the NTP response information to the terminal device 10 (S214).

[0040] After receiving the NTP response information, the terminal device 10 generates a timestamp corresponding to the time of receiving the NTP response information (ie, the second receiving time), ie, a fourth timestamp (S216).

[0041] Finally, the terminal device 10 calibrates the time on the terminal device 10 according to the first time stamp to the fourth time stamp ( S218 ).

[0042] As described in the background technology, the existing NTP system requires multiple levels to achieve time synchronization. The highest level is the authoritative clock source (such as atomic clock, GPS, etc.). Then, multiple levels of NTP servers are set up on the ground to synchronize clocks layer by layer, thereby providing clock synchronization and time calibration for the NTP servers at the lower levels. The terminal device can interact with the NTP servers at the lower level, so as to perform time calibration through the NTP servers at the lower level.

[0043] Since the existing NTP system requires setting up multiple levels of NTP servers on the ground to synchronize the time of terminal devices, a large number of NTP server devices are needed to build NTP servers at various levels on the ground, which not only increases the complexity of the system, but also increases the cost of the system.

[0044] In view of this, according to the technical solution of the present disclosure, an NTP server that performs the time calibration function is no longer set on the ground, but only a transponder 20 for forwarding messages between the terminal device 10 and the first satellite 30 is set, so that low-orbit or ultra-low-orbit satellites (such as the first satellite 30) can be used to provide time calibration services for terminal devices in a larger geographical range. Therefore, the technical solution of the present disclosure no longer needs to build a complex multi-level NTP server on the ground to provide NTP services, but loads the service on the first satellite 30, and the first satellite 30 provides the time calibration service to the terminal device 10 through the transponder 20. In this way, the present solution greatly simplifies the architecture of the NTP service, thereby reducing the complexity and cost of the system.

[0045] Optionally, the operation of calibrating the clock of the terminal device according to the first timestamp, the second timestamp, the third timestamp and the fourth timestamp includes: the terminal device determines the time difference of the terminal device relative to the first satellite according to the first timestamp, the second timestamp, the third timestamp and the fourth timestamp; and the terminal device calibrates the clock of the terminal device according to the time difference.

[0046] Specifically, according to the technical solution of the present disclosure, the terminal device 10 can determine the time difference between the time of the terminal device 10 and the time of the first satellite 30 according to the first timestamp to the fourth timestamp described above. Then the terminal device 10 calibrates the clock of the terminal device 10 according to the time difference, so that the clock time of the terminal device 10 is consistent with the clock time of the first satellite 30.

[0047] Optionally, the operation of the terminal device determining the time difference of the terminal device relative to the first satellite based on the first timestamp, the second timestamp, the third timestamp and the fourth timestamp includes: the terminal device determining the round-trip delay between the terminal device and the first satellite based on the first timestamp, the second timestamp, the third timestamp and the fourth timestamp; and the terminal device determining the time difference based on the first timestamp, the second timestamp and the round-trip delay.

[0048] refer to Figure 3 and Figure 4 As shown, the time from the terminal device 30 sending out the NTP query command to the terminal device 30 receiving the NTP response information consists of three parts: the time when the NTP query command is transmitted from the terminal device 30 to the first satellite 30; the time when the first satellite 30 receives the NTP query command and generates and sends the NTP response information; and the time when the NTP response information is transmitted from the first satellite 30 to the terminal device 10.

[0049] In theory, the time when the NTP query instruction is transmitted from the terminal device 30 to the first satellite 30 is the same as the time when the NTP response information is transmitted from the first satellite 30 to the terminal device 10. That is, the difference between the second timestamp and the first timestamp is the same as the difference between the fourth timestamp and the third timestamp. However, due to the time deviation between the terminal device 10 and the first satellite 30, the difference between the second timestamp and the first timestamp is different from the difference between the fourth timestamp and the third timestamp.

[0050] Therefore, in the technical solution of the present disclosure, the terminal device 10 can obtain the round-trip delay between the terminal device 10 and the first satellite 30 by subtracting the difference between the third timestamp and the second timestamp from the difference between the fourth timestamp and the first timestamp:

[0051] t_delay=(stamp_4-stamp_1)-(stamp_3-stamp_2)(1)

[0052] Wherein t_delay is the round trip delay between the terminal device 10 and the first satellite 30, stamp_1 is the first timestamp, stamp_2 is the second timestamp, stamp_3 is the third timestamp, and stamp_4 is the fourth timestamp.

[0053] Then, the terminal device 10 determines the time deviation from the first satellite 30 according to the following formula:

[0054]

[0055] Here, t_offset is the time deviation between the terminal device 10 and the first satellite 30.

[0056] Thus, through the above method, the terminal device 10 can determine the time deviation between the terminal device 10 and the first satellite 30, and calibrate the clock time of the terminal device 10 according to the time deviation.

[0057] Optionally, the operation of the terminal device determining the time difference of the terminal device relative to the first satellite based on the first timestamp, the second timestamp, the third timestamp and the fourth timestamp includes: the terminal device determining the round-trip delay between the terminal device and the first satellite based on the first timestamp, the second timestamp, the third timestamp and the fourth timestamp; and the terminal device determining the time difference based on the third timestamp, the fourth timestamp and the round-trip delay.

[0058] Specifically, the terminal device 10 may calculate the round-trip delay t_delay between the terminal device 10 and the first satellite 30 according to the above formula (1).

[0059] Then, the terminal device 10 can determine the time offset t_offset between the terminal device 10 and the first satellite 30 according to the following formula:

[0060]

[0061] Optionally, the operation of the transponder device forwarding the NTP query instruction to the first satellite includes: the transponder device writing the NTP query instruction into a corresponding remote control transmission frame; and the transponder device transmitting the remote control transmission frame to the first satellite through the remote control channel.

[0062] Specifically, refer to Figure 2 As shown, the transponder 20 uploads data to the first satellite 30 through a remote control channel (e.g., a multi-packet remote control channel). Thus, after receiving the NTP query instruction, the transponder 20 writes the NTP query instruction into a corresponding remote control transmission frame according to the relevant protocol standard. Then, the transponder 20 transmits the remote control transmission frame to the first satellite 30 through the remote control channel.

[0063] Optionally, the operation of the first satellite sending NTP response information to the transponder device includes: the first satellite writing the NTP response information into a corresponding telemetry frame; and the first satellite transmitting the telemetry frame to the transponder device through a telemetry channel.

[0064] Specifically, refer to Figure 2As shown, the first satellite 30 transmits data information to the transponder 20 through the telemetry channel. Thus, after generating the NTP response information, the first satellite 30 writes the NTP response information into the corresponding telemetry frame, and then the first satellite transmits the telemetry frame to the transponder 20 through the telemetry channel.

[0065] Therefore, through the above method, the transponder 20 and the first satellite 30 can exchange data information using the existing remote control standard protocol and telemetry standard protocol.

[0066] Optionally, the operation of the first satellite generating a second timestamp corresponding to the first reception time of receiving the NTP query instruction includes: the first satellite determines the first crystal oscillator clock time corresponding to the first reception time according to the first crystal oscillator clock; the first satellite determines the second crystal oscillator clock time corresponding to the first reception time according to the second crystal oscillator clock; and the first satellite determines the second timestamp according to the first crystal oscillator clock time and the second crystal oscillator clock time.

[0067] Specifically, Figure 5 FIG. 2 shows a schematic diagram of a time management system of the first satellite 30. Figure 5 As shown, the time management system of the first satellite 30 includes an SMU processor module 100. The SMU processor module 100 includes a real-time clock module 120 and a processor module 110. The real-time clock module 120 includes a first crystal oscillator 130a and a second crystal oscillator 130b, and a first crystal oscillator clock unit 122a connected to the first crystal oscillator 130a and a second crystal oscillator clock unit 122b connected to the second crystal oscillator 130b.

[0068] The first crystal oscillator clock unit 122a generates a first crystal oscillator clock time based on an oscillation signal of the first crystal oscillator 130a, and the second crystal oscillator clock unit 122b generates a second crystal oscillator clock time based on an oscillation signal of the second crystal oscillator 130b.

[0069] Thus, at the first receiving time of receiving the NTP query instruction, the processor module 110 obtains the first crystal oscillator clock time corresponding to the first receiving time from the first crystal oscillator clock unit 122a, and obtains the second crystal oscillator clock time corresponding to the first receiving time from the second crystal oscillator clock unit 122b. Then, the processor module 110 determines the second timestamp corresponding to the first receiving time according to the first crystal oscillator clock time and the second crystal oscillator clock time corresponding to the first receiving time.

[0070] According to the inventor's research, the accuracy and stability of the crystal oscillator clock are mainly affected by two factors. The first factor is the influence of the aging degree of the crystal oscillator; the second factor is the influence of the change in the ambient temperature of the crystal oscillator. Since the prior art usually sets the crystal oscillator in a constant temperature environment (such as a constant temperature bath), the influence of temperature changes on the accuracy of the crystal oscillator clock presents characteristics that conform to the (0, σ) normal distribution. Therefore, the technical solution of the present disclosure combines the first crystal oscillator clock time of the first crystal oscillator clock unit 122a with the second crystal oscillator clock time of the second crystal oscillator clock unit 122b, so as to more accurately determine the time of the second timestamp.

[0071] Optionally, the operation of the first satellite determining the second timestamp based on the first crystal oscillator clock time and the second crystal oscillator clock time includes: after calibrating the first crystal oscillator clock and the second crystal oscillator clock based on the second satellite, the first satellite determining the second timestamp based on the first crystal oscillator clock time, the deviation variance of the first crystal oscillator clock, the second crystal oscillator clock time and the deviation variance of the second crystal oscillator clock.

[0072] Specifically, as described above, the accuracy and stability of the crystal oscillator clock are mainly affected by two factors. The first factor is the influence of the aging degree of the crystal oscillator; the second factor is the influence of the change in the ambient temperature of the crystal oscillator. The frequency characteristics of the crystal oscillator will drift over time due to the aging degree of the crystal oscillator, so that after the crystal oscillator clock is powered on, the time error will gradually increase over time. In addition, the stability of the crystal oscillator is also affected by the ambient temperature. Since the prior art usually sets the crystal oscillator in a constant temperature environment (such as a constant temperature bath), the influence of temperature changes on the accuracy of the crystal oscillator clock presents a characteristic that conforms to the (0, σ) normal distribution.

[0073] Therefore, in the technical solution of the present disclosure, the processor module 110 can use the second satellite 40 to determine the deviation mean and deviation variance of the first crystal oscillator clock and the second crystal oscillator clock. Figure 5 As shown, the second satellite 40 may be a GNSS satellite, for example, so as to send a PPS second pulse signal and a GPS data packet corresponding to the PPS second pulse signal to the first satellite 30. And the GPS data packet includes a time value corresponding to the PPS second pulse.

[0074] Then refer to Figure 6 As shown, the navigation satellite system module 200 of the first satellite 30 receives the PPS pulse second signal and the GPS data packet transmitted by the second satellite 40 , and transmits the PPS pulse second signal to the real-time clock acquisition unit 121 of the real-time clock module 120 .

[0075] The real-time clock acquisition unit 121 extracts the leading edge of the PPS second pulse signal, and triggers the first crystal oscillator clock unit 122a to lock the first crystal oscillator clock time corresponding to the leading edge and triggers the second crystal oscillator clock unit 122b to lock the second crystal oscillator clock time corresponding to the leading edge.

[0076] In addition, the real-time clock acquisition unit 121 generates a GPIO interrupt signal corresponding to the PPS second pulse signal. Thus, the processor module 110 obtains the first crystal oscillator clock time corresponding to the corresponding PPS second pulse signal from the first crystal oscillator clock unit 122a and obtains the second crystal oscillator clock time corresponding to the corresponding PPS second pulse signal from the second crystal oscillator clock unit 122b in response to the GPIO interrupt signal. In addition, the processor module 110 can obtain the GPS data packet corresponding to the PPS second pulse from the navigation satellite system module 200 through the CAN bus, and determine the reference time corresponding to the PPS second pulse according to the time information contained in the GPS data packet.

[0077] in, Figure 7 The PPS pulse-per-second signal received by the navigation satellite system module 200, the GPIO interrupt signal generated by the real-time clock acquisition unit 121, the reference time corresponding to the PPS pulse-per-second signal, the first crystal oscillator clock time and the second crystal oscillator clock time are exemplarily shown.

[0078] Therefore, according to the technical solution of the present disclosure, the first satellite 30 can periodically turn on the navigation satellite system module 200 to determine the error information of the first crystal oscillator clock unit 122a and the second crystal oscillator clock unit 122b.

[0079] According to the technical solution disclosed in the present invention, the first satellite 30 can periodically (for example, once a day, or once every two days) turn on the GNSS time synchronization function, and determine the error information of the first crystal oscillator clock unit 122a and the second crystal oscillator clock unit 122b through the PPS second pulse and GPS data packet provided by the second satellite 40.

[0080] Specifically, in the process of determining the error information between the first crystal oscillator clock unit 122a and the second crystal oscillator clock unit 122b, the processor module 110 can obtain the first crystal oscillator clock time t output by the first crystal oscillator clock unit 122a at multiple measurement times 0 to m according to the GPIO interrupt signal corresponding to the PPS pulse and the preset time interval length ΔT (i.e., the preset number of GPIO interrupt signals). 1,0 ~t 1,m and the second crystal oscillator clock time t output by the second crystal oscillator clock unit 122b 2,0 ~t 2,mIn addition, the processor module 110 also obtains GPS data packets from the navigation satellite system module 200 at multiple measurement times 0 to m, and determines the reference time t0 to t1 corresponding to each measurement time 0 to m based on the time information in the GPS data packets. m The details are shown in the following table:

[0081] Table 1

[0082] Measurement time 0 1 2 3 4 .... m Base time <![CDATA[t0]]> <![CDATA[t1]]> <![CDATA[t2]]> <![CDATA[t3]]> <![CDATA[t4]]> .... <![CDATA[t m ]]> First crystal clock time <![CDATA[t 1,0 ]]> <![CDATA[t 1,1 ]]> <![CDATA[t 1,2 ]]> <![CDATA[t 1,3 ]]> <![CDATA[t 1,4 ]]> .... <![CDATA[t 1,m ]]> Second crystal oscillator clock time <![CDATA[t 2,0 ]]> <![CDATA[t 2,1 ]]> <![CDATA[t 2,2 ]]> <![CDATA[t 2,3 ]]> <![CDATA[t 2,4 ]]> .... <![CDATA[t 2,m ]]>

[0083] Among them, the reference time t0~t m For example, the method described above may be used to determine the satellite timing time obtained from the GPS data packet.

[0084] In addition, the crystal oscillator clock time output by the first crystal oscillator clock unit 122a at the time 0 determined according to the GPIO interrupt signal is t 1,0 ; The crystal oscillator clock time output at the moment determined by the GPIO interrupt signal is t 1,1 ; The crystal oscillator clock time output at the moment 2 determined by the GPIO interrupt signal is t 1,2 ;......;The crystal oscillator clock time output at time m determined by the GPIO interrupt signal is t 1,m .

[0085] The crystal oscillator clock time output by the second crystal oscillator clock unit 122a at time 0 determined according to the GPIO interrupt signal is t 2,0 ; The crystal oscillator clock time output at the moment determined by the GPIO interrupt signal is t 2,1 ; The crystal oscillator clock time output at the moment 2 determined by the GPIO interrupt signal is t 2,2 ;......;The crystal oscillator clock time output at time m determined by the GPIO interrupt signal is t 2,m .

[0086] Then, the processor module 110 calculates the first crystal oscillator clock time t output by the first crystal oscillator clock unit 122a according to the following formula (4): 1,0 ~t 1,m And the corresponding reference time t0~t m , determine the first crystal oscillator clock time t output by the first crystal oscillator clock unit 122a 1,0 ~t 1,m At time 0 to m relative to reference time t0 to t m Time deviation Δt 1,0 ~Δt 1,m :

[0087] Δt 1,i =t 1,i -ti (4)

[0088] Among them, i=0~m.

[0089] The details are shown in Table 2 below:

[0090] Table 2

[0091]

[0092] At the same time, the processor module 110 calculates the crystal clock time t output by the second crystal clock unit 122b according to the following formula (5): 2,0 ~t 2,m And the corresponding reference time t0~t m , determine the crystal oscillator clock time t output by the second crystal oscillator clock unit 122b 2,0 ~t 2,m At time 0 to m relative to reference time t0 to t m Time deviation Δt 2,0 ~Δt 2,m :

[0093] Δt 2,i =t 2,i -t i (5)

[0094] Among them, i=0~m.

[0095] The details are shown in Table 3 below:

[0096] Table 3

[0097]

[0098] Then, the processor module 110 calculates the time deviation Δt of the first crystal oscillator clock unit 122a according to the following formula: 1,0 ~Δt 1,m , calculate the corresponding deviation mean μ1 and deviation variance σ1.

[0099]

[0100]

[0101] And, the processor module 110 calculates the time deviation Δt of the second crystal oscillator clock unit 122b according to the following formula: 2,0 ~Δt 2,m , calculate the corresponding deviation mean μ2 and deviation variance σ2.

[0102]

[0103]

[0104] Thus, the deviation mean and deviation variance of the first crystal oscillator clock unit 122a and the second crystal oscillator clock unit 122b can be determined in the above manner. The deviation mean can reflect the error caused by aging of the first crystal oscillator clock unit 122a and the second crystal oscillator clock unit 122b at the current moment. The deviation variance can reflect the random error caused by the ambient temperature of the first crystal oscillator clock unit 122a and the second crystal oscillator clock unit 122b.

[0105] Then, the processor module 110 calibrates the crystal oscillator clock of the first crystal oscillator clock unit 122a using the deviation mean μ1 corresponding to the first crystal oscillator clock unit 122a, and calibrates the crystal oscillator clock of the second crystal oscillator clock unit 122b using the deviation mean μ2 corresponding to the second crystal oscillator clock unit 122b. Specifically, the processor module 110 corrects the first crystal oscillator clock time tcur1 obtained from the first crystal oscillator clock unit 122a and the second crystal oscillator clock time tcur2 obtained from the second crystal oscillator clock unit 122b according to the following formula to obtain a first correction time tcrt1 corresponding to the first crystal oscillator clock time tcur1 and a second correction time tcrt2 corresponding to the second crystal oscillator clock time:

[0106] tcrt1=tcur1-μ1 (10)

[0107] tcrt2=tcur2-μ2 (11)

[0108] Then the processor module 110 uses the first correction time tcrt2 to correct the crystal oscillator clock of the first crystal oscillator clock unit 122a and uses the second correction time tcrt2 to correct the crystal oscillator clock of the second crystal oscillator clock unit 122b, thereby completing the GNSS time calibration function. In this way, the measurement error caused by the frequency drift caused by the aging of the crystal oscillator can be corrected by regularly performing GNSS time calibration. And the deviation variance of the crystal oscillator clock unit can be continuously updated, thereby obtaining a more accurate deviation variance.

[0109] Then, at the first receiving time after GNSS time calibration, the processor module 110 first obtains the first crystal oscillator clock time Trec_1 corresponding to the first receiving time from the first crystal oscillator clock unit 122a, and obtains the second crystal oscillator clock time Trec_2 corresponding to the first receiving time from the second crystal oscillator clock unit 122b.

[0110] Then, the processor module 110 determines the time information Trec corresponding to the first receiving time according to the following formula:

[0111] Trec=Trec_1+k*(Trec_2-Trec_1) (12)

[0112]

[0113] The processor module 110 then determines a second timestamp corresponding to the first receiving time according to the time information Trec.

[0114] Thus, through the above method, the technical solution of the present disclosure corrects the crystal oscillator clocks of the first crystal oscillator clock unit 122a and the second crystal oscillator clock unit 122b according to formulas (10) and (11), thereby reducing the measurement error of the first crystal oscillator clock unit 122a and the second crystal oscillator clock unit 122b caused by the aging of the crystal oscillator. In addition, the technical solution of the present disclosure fuses the corrected first crystal oscillator clock time of the first crystal oscillator clock unit 122a and the corrected second crystal oscillator clock time of the second crystal oscillator clock unit 122b according to formulas (12) and (13), thereby obtaining more accurate time information and overcoming the measurement error caused by the ambient temperature of the crystal oscillator. Thus, through the above operation, the time information of the second timestamp is made more accurate.

[0115] Therefore, the technical solution of the present disclosure can effectively reduce the measurement error caused by the frequency drift of the crystal oscillator clock unit due to the aging of the crystal oscillator by periodically performing GNSS calibration on the crystal oscillator clock unit. And the deviation value and deviation variance of the crystal oscillator clock unit can be continuously updated through GNSS calibration, so that the calculated deviation variance of the crystal oscillator clock unit can be continuously updated with the GNSS calibration, so as to be more accurate. In addition, the present disclosure uses multiple crystal oscillator clock units to fuse the time measurement results based on the deviation variance, which can effectively reduce the random error of the crystal oscillator clock caused by the change of ambient temperature.

[0116] Optionally, the operation of the first satellite generating a third timestamp corresponding to the second sending time of sending the NTP response information includes: the first satellite determines a third crystal oscillator clock time corresponding to the second sending time according to the first crystal oscillator clock; the first satellite determines a fourth crystal oscillator clock time corresponding to the second sending time according to the second crystal oscillator clock; and the first satellite determines the third timestamp according to the third crystal oscillator clock time and the fourth crystal oscillator clock time.

[0117] Specifically, when the first satellite 30 generates a third timestamp corresponding to the second sending time of the NTP response information, the processor module 110 obtains the third crystal oscillator clock time corresponding to the second sending time from the first crystal oscillator clock unit 122a, and obtains the fourth crystal oscillator clock time corresponding to the second sending time from the second crystal oscillator clock unit 122b. Thus, the processor module 110 can overcome the measurement error caused by the change in ambient temperature and obtain a more accurate third timestamp by fusing the crystal oscillator clock times of the first crystal oscillator clock unit 122a and the second crystal oscillator clock unit 122b.

[0118] Optionally, the operation of the first satellite determining the third timestamp according to the third crystal oscillator clock time and the fourth crystal oscillator clock time includes: after calibrating the first crystal oscillator clock and the second crystal oscillator clock based on the second satellite, the first satellite determines the third timestamp according to the third crystal oscillator clock time, the mean deviation of the first crystal oscillator clock, the deviation variance of the first crystal oscillator clock, the fourth crystal oscillator clock time, the mean deviation of the second crystal oscillator clock, and the deviation variance of the second crystal oscillator clock.

[0119] Specifically, at the second sending time after GNSS time calibration, the processor module 110 first obtains the third crystal oscillator clock time Tsen_1 corresponding to the second sending time from the first crystal oscillator clock unit 122a, and obtains the fourth crystal oscillator clock time Tsen_2 corresponding to the second sending time from the second crystal oscillator clock unit 122b.

[0120] Then, the processor module 110 determines the time information Tsen corresponding to the second sending time according to the following formula:

[0121] Tsen=Tsen_1+k*(Tsen_2-Tsen_1) (14)

[0122] The parameter k is determined according to the formula (13) described above. Then the processor module 110 determines a third timestamp according to the time information Tsen.

[0123] Thus, through the above method, the technical solution of the present disclosure fuses the corrected third crystal oscillator clock time of the first crystal oscillator clock unit 122a and the corrected fourth crystal oscillator clock time of the second crystal oscillator clock unit 122b according to formula (14), thereby obtaining more accurate time information and overcoming the measurement error caused by the ambient temperature of the crystal oscillator. Thus, the time information of the third timestamp is more accurate.

[0124] Therefore, the technical solution of the present disclosure can effectively reduce the measurement error caused by the frequency drift of the crystal oscillator clock unit due to the aging of the crystal oscillator by periodically performing GNSS calibration on the crystal oscillator clock unit. And the deviation value and deviation variance of the crystal oscillator clock unit can be continuously updated through GNSS calibration, so that the calculated deviation variance of the crystal oscillator clock unit can be continuously updated with the GNSS calibration, so as to be more accurate. In addition, the present disclosure uses multiple crystal oscillator clock units to fuse the time measurement results based on the deviation variance, which can effectively reduce the random error of the crystal oscillator clock caused by the change of ambient temperature.

[0125] In summary, according to the technical solution disclosed in the present invention, an NTP server that performs the time calibration function is no longer set on the ground, but only a transponder for forwarding messages between the terminal device and the first satellite is set, so that low-orbit or ultra-low-orbit satellites (such as the first satellite) can be used to provide time calibration services for terminal devices in a larger geographical range. Therefore, the technical solution disclosed in the present invention no longer needs to build a complex multi-level NTP server on the ground to provide NTP services, but instead loads the service on the first satellite, and the first satellite provides time calibration services to the terminal device through the transponder. In this way, this solution greatly simplifies the architecture of the NTP service, thereby reducing the complexity and cost of the system.

[0126] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present disclosure. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0127] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0128] In the description of the present disclosure, it is necessary to understand that the orientation or positional relationship indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present disclosure and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present disclosure; the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0129] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A NTP timing method based on satellite timing, characterized in that: include: The terminal device located on the ground generates a first timestamp corresponding to the first sending time of sending the NTP query instruction; The terminal device writes the first timestamp into an NTP query instruction, and sends the NTP query instruction to a transponder device located on the ground; The transponder device forwards the NTP query instruction to the first satellite, wherein the first satellite can perform time synchronization based on the time information sent by the second satellite; The first satellite receives the NTP query instruction and generates a second timestamp corresponding to a first receiving time of receiving the NTP query instruction; The first satellite generates NTP response information corresponding to the NTP query instruction, and generates a third timestamp corresponding to a second sending time of sending the NTP response information; The first satellite writes the first timestamp, the second timestamp, and the third timestamp into the NTP response information, and sends the NTP response information to the transponder device; The transponder device forwards the NTP response information to the terminal device; The terminal device receives the NTP response information, and generates a fourth timestamp corresponding to the second receiving time of receiving the NTP response information; as well as The terminal device calibrates a clock of the terminal device according to the first timestamp, the second timestamp, the third timestamp, and the fourth timestamp.

2. The method according to claim 1, characterized in that The operation of calibrating, by the terminal device, a clock of the terminal device according to the first timestamp, the second timestamp, the third timestamp, and the fourth timestamp includes: The terminal device determines, according to the first timestamp, the second timestamp, the third timestamp, and the fourth timestamp, a time difference of the terminal device relative to the first satellite; and The terminal device calibrates a clock of the terminal device according to the time difference.

3. The method according to claim 2, characterized in that The operation of the terminal device determining the time difference of the terminal device relative to the first satellite according to the first timestamp, the second timestamp, the third timestamp, and the fourth timestamp includes: Determining, by the terminal device, a round trip delay between the terminal device and the first satellite according to the first timestamp, the second timestamp, the third timestamp, and the fourth timestamp; and The terminal device determines the time difference based on the first timestamp, the second timestamp and the round-trip delay.

4. The method according to claim 2, characterized in that: The operation of the terminal device determining the time difference of the terminal device relative to the first satellite according to the first timestamp, the second timestamp, the third timestamp, and the fourth timestamp includes: Determining, by the terminal device, a round trip delay between the terminal device and the first satellite according to the first timestamp, the second timestamp, the third timestamp, and the fourth timestamp; and The terminal device determines the time difference based on the third timestamp, the fourth timestamp and the round-trip delay.

5. The method according to claim 1, characterized in that The operation of the transponder device forwarding the NTP query instruction to the first satellite includes: The transponder device writes the NTP query instruction into a corresponding remote control transmission frame; and The transponder device transmits the remote control transmission frame to the first satellite through a remote control channel.

6. The method according to claim 1, characterized in that The operation of the first satellite sending the NTP response information to the transponder device includes: The first satellite writes the NTP response information into a corresponding telemetry frame; and The first satellite transmits the telemetry frame to the transponder device via a telemetry channel.

7. The method according to claim 1, characterized in that The operation of the first satellite generating a second timestamp corresponding to the first receiving time of receiving the NTP query instruction includes: The first satellite determines, according to a first crystal oscillator clock, a first crystal oscillator clock time corresponding to the first receiving time; The first satellite determines, according to a second crystal oscillator clock, a second crystal oscillator clock time corresponding to the first receiving time; and The first satellite determines the second timestamp according to the first crystal oscillator clock time and the second crystal oscillator clock time.

8. The method according to claim 7, characterized in that The operation of determining, by the first satellite, the second timestamp according to the first crystal oscillator clock time and the second crystal oscillator clock time includes: After calibrating the first crystal oscillator clock and the second crystal oscillator clock based on the second satellite, the first satellite determines the second timestamp according to the first crystal oscillator clock time, the deviation variance of the first crystal oscillator clock, the second crystal oscillator clock time, and the deviation variance of the second crystal oscillator clock.

9. The method according to claim 1, characterized in that: The operation of the first satellite generating a third timestamp corresponding to the second sending time of sending the NTP response information includes: The first satellite determines, according to the first crystal oscillator clock, a third crystal oscillator clock time corresponding to the second sending time; The first satellite determines, according to the second crystal oscillator clock, a fourth crystal oscillator clock time corresponding to the second sending time; and The first satellite determines the third timestamp according to the third crystal oscillator clock time and the fourth crystal oscillator clock time.

10. The method according to claim 9, characterized in that The operation of determining, by the first satellite, the third timestamp according to the third crystal oscillator clock time and the fourth crystal oscillator clock time comprises: After calibrating the first crystal oscillator clock and the second crystal oscillator clock based on the second satellite, the first satellite determines the third timestamp according to the third crystal oscillator clock time, the deviation variance of the first crystal oscillator clock, the fourth crystal oscillator clock time, and the deviation variance of the second crystal oscillator clock.

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