CN115361086B - Time synchronization method, device and medium for inter-satellite link - Google Patents
Time synchronization method, device and medium for inter-satellite link Download PDFInfo
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Abstract
The invention discloses a time synchronization method, a time synchronization device and a time synchronization medium of an inter-satellite link, which are suitable for the field of satellite communication. The method comprises the steps that a current reference point and adjacent satellite nodes are obtained in an inter-satellite link, wherein the current reference point is a synchronous satellite node, at least one satellite node exists, and the time synchronization of the adjacent satellite nodes corresponding to the current reference point is completed through a time synchronization method determined by first time difference, second time difference, path transmission delay time and processing delay time, so that the time synchronization of the adjacent satellite nodes corresponding to the next time reference point is performed. The method can avoid the serious dependence on time service of other systems, realize the time synchronization under the condition that the Beidou/GPS time service system cannot be used for time service in a special period, and improve the independence and the reliability of the time synchronization of the inter-satellite link.
Description
Technical Field
The present invention relates to the field of satellite communications, and in particular, to a method, an apparatus, and a medium for time synchronization of inter-satellite links.
Background
The conventional ground network time synchronization and satellite network time synchronization mainly use navigation systems such as the Beidou or Global Positioning System (GPS) to carry out time service synchronization, the accuracy of the network time synchronization is determined by a Beidou/GPS receiver, and the time synchronization performance of the visible low-earth satellite network is seriously dependent on the navigation systems.
The low-orbit satellite network is limited by international situation or has the condition that the Beidou/GPS can not be used, meanwhile, the ground time service synchronization can not ensure the global satellite constellation full-network synchronization, and the reliability of the low-orbit satellite network communication is reduced under the condition that the time service can not be positioned based on the two conditions.
Therefore, it is necessary to solve the problem in the art to find a time synchronization method for inter-satellite links.
Disclosure of Invention
The invention aims to provide a time synchronization method, a device and a medium of an inter-satellite link, which can avoid the serious dependence on time service of other systems, realize the time synchronization under the condition that the time service cannot be carried out through a Beidou/GPS time service system in a special period, and improve the independence and the reliability of the time synchronization of the inter-satellite link.
In order to solve the above technical problem, the present invention provides a time synchronization method for an inter-satellite link, comprising:
acquiring a current reference point and adjacent satellite nodes in an inter-satellite link, wherein the current reference point is a synchronous satellite node, and at least one satellite node exists;
controlling the satellite node to send the time measurement frame to the current reference point so that the current reference point determines a first time difference according to the time measurement frame, and generating a corresponding time measurement feedback frame according to the first time difference and the time measurement frame to send to the satellite node;
the control satellite node determines a second time difference according to the time measurement feedback frame, and determines path transmission delay time according to the corresponding relation between the first time difference and the second time difference;
determining the time difference of the satellite node according to the corresponding relation among the path transmission delay time, the first time difference, the second time difference and the processing delay time of the satellite node;
and calibrating the satellite nodes according to the time difference so as to complete the time synchronization of the satellite nodes.
Preferably, determining the first time difference from the time measurement frame comprises:
generating a time difference by the frame header starting time of the time measurement frame and the rising edge time of the local pulse per second signal of the current reference point to determine the time difference as a first time difference, wherein the starting position of the frame header of the time measurement frame is aligned with the rising edge position of the local pulse per second signal of the satellite node;
correspondingly, the first time difference comprises a first delay time of the satellite node for sending the time measurement frame to the current reference point and a first processing time delay of the current reference point for receiving the time measurement frame.
Preferably, determining the second time difference from the time measurement feedback frame comprises:
determining a time difference generated by the frame header starting time of the time measurement feedback frame and the rising edge time of the local pulse per second signal of the satellite node as a second time difference;
correspondingly, the second time difference includes a second delay time for the current reference point to send the time measurement feedback frame to the satellite node and a second processing delay time for the satellite node to receive the time measurement feedback frame.
Preferably, when the satellite node and the current reference point are located on the same-track link, determining the path transmission delay time according to the correspondence between the first time difference and the second time difference includes:
the path propagation delay time is determined by a time error value of a first delay time of the first time difference and a second delay time of the second time difference.
Preferably, when the satellite node and the current reference point are located on the different-rail link, determining the path transmission delay time according to the correspondence between the first time difference and the second time difference includes:
determining an initial path transmission delay time by a time error value of a first delay time of the first time difference and a second delay time of the second time difference;
acquiring ephemeris information of a time measurement feedback frame of a current reference point;
determining distance information and relative transmission speed between the current reference point and the satellite node according to the ephemeris information;
and correcting the initial path transmission delay time through the distance information and the relative transmission speed to obtain the path transmission delay time.
Preferably, the frame format of the time measurement feedback frame of the co-orbit link includes a synchronization header, a frame header, a link type, a number of a satellite node to be synchronized, a number of a time reference node, and a time difference.
Preferably, the frame format of the time measurement feedback frame of the off-orbit link comprises a synchronization header, a frame header, a link type, a number of a satellite node to be synchronized, a number of a time reference node, a time difference and ephemeris information.
Preferably, the processing delay time of the satellite node comprises a delay difference between the first processing delay and the second processing delay.
Preferably, the determining the time difference of the satellite node according to the corresponding relationship among the path transmission delay time, the first time difference, the second time difference, and the processing delay time of the satellite node includes:
subtracting the second time difference from the first time difference to obtain a time difference value;
subtracting the path transmission delay time from the time difference value to obtain an error value;
and subtracting the delay time from the error value to obtain a time difference.
In order to solve the above technical problem, the present invention further provides a time synchronization device for an inter-satellite link, including:
the acquisition module is used for acquiring a current reference point and adjacent satellite nodes in an inter-satellite link, wherein the current reference point is a synchronous satellite node, and at least one satellite node exists;
a transmitting module, configured to control the satellite node to transmit the time measurement frame to the current reference point so that the current reference point determines a first time difference according to the time measurement frame, and generate a corresponding time measurement feedback frame according to the first time difference and the time measurement frame to transmit the time measurement feedback frame to the satellite node;
the first determining module is used for controlling the satellite node to determine a second time difference according to the time measurement feedback frame and determining the path transmission delay time according to the corresponding relation between the first time difference and the second time difference;
the second determining module is used for determining the time difference of the satellite node according to the corresponding relation among the path transmission delay time, the first time difference, the second time difference and the processing delay time of the satellite node;
and the calibration module is used for calibrating the satellite nodes according to the time difference so as to complete the time synchronization of the satellite nodes.
In order to solve the above technical problem, the present invention further provides a time synchronization device for an inter-satellite link, including:
a memory for storing a computer program;
and the processor is used for realizing the steps of the time synchronization device of the inter-satellite link when executing the computer program.
In order to solve the above technical problem, the present invention further provides a computer-readable storage medium, on which a computer program is stored, and the computer program, when executed by a processor, implements the steps of the time synchronization apparatus for an inter-satellite link as described above.
The invention provides a time synchronization method of an inter-satellite link, which comprises the following steps: acquiring a current reference point and adjacent satellite nodes in an inter-satellite link, wherein the current reference point is a synchronous satellite node, and at least one satellite node exists; controlling the satellite node to send the time measurement frame to the current reference point so that the current reference point determines a first time difference according to the time measurement frame, and generating a corresponding time measurement feedback frame according to the first time difference and the time measurement frame to send to the satellite node; the control satellite node determines a second time difference according to the time measurement feedback frame, and determines path transmission delay time according to the corresponding relation between the first time difference and the second time difference; determining the time difference of the satellite node according to the corresponding relation among the path transmission delay time, the first time difference, the second time difference and the processing delay time of the satellite node; and calibrating the satellite nodes according to the time difference so as to complete the time synchronization of the satellite nodes. According to the method, a synchronous satellite node is used as a time reference point, and the time synchronization of the adjacent satellite node corresponding to the current reference point is completed through a time synchronization method determined by a first time difference, a second time difference, path transmission delay time and processing delay time, so that the time synchronization of the adjacent satellite node corresponding to the next time reference point is performed. The method can avoid the serious dependence on time service of other systems, realize the time synchronization under the condition that the Beidou/GPS time service system cannot be used for time service in a special period, and improve the independence and the reliability of the time synchronization of the inter-satellite link.
In addition, the invention also provides a time synchronization device and medium of the inter-satellite link, which have the same beneficial effects as the time synchronization method of the inter-satellite link.
Drawings
In order to illustrate the embodiments of the present invention more clearly, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings can be obtained by those skilled in the art without inventive effort.
Fig. 1 is a flowchart of a method for time synchronization of an inter-satellite link according to an embodiment of the present invention;
fig. 2 is an architecture diagram of an inter-satellite link system according to an embodiment of the present invention;
fig. 3 is a timing chart of the time difference measurement process according to the embodiment of the present invention;
fig. 4 is a frame structure diagram of a time measurement frame according to an embodiment of the present invention;
fig. 5 is a frame structure diagram of a time measurement feedback frame of an on-track link according to an embodiment of the present invention;
fig. 6 is a frame structure diagram of a time measurement feedback frame of an inter-track link according to an embodiment of the present invention;
fig. 7 is a structural diagram of a time synchronization apparatus for an inter-satellite link according to an embodiment of the present invention;
fig. 8 is a structural diagram of another time synchronization apparatus for an inter-satellite link according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative work belong to the protection scope of the present invention.
The core of the invention is to provide a time synchronization method, a device and a medium of an inter-satellite link, which can avoid the serious dependence on time service of other systems, realize the time synchronization under the condition that the time service cannot be carried out through a Beidou/GPS time service system in a special period, and improve the independence and the reliability of the time synchronization of the inter-satellite link.
In order that those skilled in the art will better understand the disclosure, the invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
It should be noted that satellites are roughly classified into three types, namely, high orbit satellites, medium orbit satellites, and low orbit satellites, according to different operation altitudes. The low-orbit satellite system generally refers to a large-scale satellite system which is composed of a plurality of low-orbit satellites and can process real-time information, wherein the distribution of the low-orbit satellites is called as a low-orbit satellite constellation. Because the distance between the satellite and the ground is close, the low-orbit satellite communication system has the advantages of small time delay, small path loss, small transmitting power and the like, and is widely applied to various fields. The low-orbit satellite constellation can provide global coverage, and rapidly improve the capabilities of satellite communication, satellite remote sensing and the like; the potential is huge in the aspect of communication broadband, and the service quality can be improved by lower signal propagation delay; the low-orbit constellation is applied to the signal enhancement of the current global navigation satellite system, and the rapid and accurate positioning can be realized. The time synchronization method based on the inter-satellite link is suitable for low-orbit satellite constellations. Because the earth stations of the constellation system of the low-orbit satellite limited by the international situation are mainly arranged in China, the cost control and the realization complexity are also core restriction factors, and the ground station time service synchronization can not ensure the global satellite constellation whole-network synchronization.
Fig. 1 is a flowchart of a method for time synchronization of an inter-satellite link according to an embodiment of the present invention, as shown in fig. 1, the method includes:
s11: acquiring a current reference point and adjacent satellite nodes in an inter-satellite link, wherein the current reference point is a synchronous satellite node, and at least one satellite node exists;
FIG. 2 is a schematic diagram of an inter-satellite chain according to an embodiment of the present inventionAs shown in fig. 2, the relative distance variation trend of adjacent satellites in the same orbit on the same orbital plane is stable, and the relative distance of adjacent satellites in different orbits on different orbital planes is highly dynamically varied. The inter-satellite link system is composed of N satellites and earth stations distributed on M orbital planes. Each satellite is provided with 2 same-orbit inter-satellite links which are respectively in two-way communication with the same-orbit front and rear satellites, and each orbit surface selects 2 satellites (which are backup each other and are 0) ° <Phase difference<90 ° Or 90 ° <Phase difference<180 ° ) Each is provided with 2 different-orbit inter-satellite links which respectively carry out two-way communication with the same-phase satellites of two adjacent orbits. The same-orbit inter-satellite link and the different-orbit inter-satellite link are fixedly connected with adjacent satellites, and the different-orbit inter-satellite link can be periodically disconnected and reconnected near the equator and the two stages.
And acquiring a current reference point and adjacent satellite nodes in the inter-satellite link, wherein the current reference point is positioned at the synchronized satellite nodes in the inter-satellite link. For synchronized satellite nodes, when a first satellite node in an inter-satellite link is synchronized, time service calibration can be performed on the first satellite node according to an earth station system of a satellite-ground link. The satellite nodes adjacent to the current reference point can be satellites of different-orbit inter-satellite links or satellites of same-orbit inter-satellite links. In order to ensure the synchronization of the satellite nodes of the inter-satellite link, at least one adjacent satellite node is provided, and if the current reference point is the first synchronous satellite node, at most 3 satellite nodes to be synchronized exist on the same-orbit or different-orbit link at the corner position of the inter-satellite link. In the present invention, adjacent directions of the upper and lower satellite nodes of the in-orbit link and the left and right satellite nodes of the out-of-orbit link of the adjacent satellite nodes are determined based on the current reference point. In the subsequent time synchronization process of the satellite nodes on the same-orbit link and the satellite nodes on the different-orbit link, the time synchronization sequence is not distinguished, and the time synchronization can be carried out simultaneously, or the satellite nodes on the same-orbit link or the satellite nodes on the different-orbit link and the like can be carried out firstly.
And after the time synchronization is finished by the satellite nodes adjacent to the current reference point, searching the satellite nodes adjacent to the current reference point as a next new current reference point, and continuing the time synchronization calibration until all the satellite nodes of the inter-satellite link are used as the current reference point for calibration completion.
S12: controlling the satellite node to send the time measurement frame to the current reference point so that the current reference point determines a first time difference according to the time measurement frame, and generating a corresponding time measurement feedback frame according to the first time difference and the time measurement frame to send to the satellite node;
specifically, the satellite nodes are controlled to send the time measurement frames to the current reference point, and the satellite nodes on the same-orbit or different-orbit links can simultaneously send the corresponding time measurement frames to the current reference point by combining the content of the upper segment. The current reference point determines a first time difference according to data of the time measurement frame, a frame structure of the time measurement frame can stipulate an effective content starting position of the current frame and a signal sending time of the satellite node, a time difference corresponding to the current reference point can be known through the starting position, a corresponding time feedback frame is generated according to the first time difference and the time measurement frame, and the corresponding time feedback frame is sent to the satellite node.
It should be noted that, the time feedback frame is set differently according to the link relationship between the satellite node and the current reference point, and if the satellite node and the current reference point are the same-orbit link, the change of the relative distance between the satellite node and the current reference point is small, and other data does not need to be added and sent to the satellite node. If the satellite node and the current reference point are the different-orbit links, the different-orbit links are in a high dynamic distance and have large changes, the position information of the current reference point needs to be known at any time, and the track information of the current reference point can be obtained in real time to be additionally added to be sent to the satellite node.
S13: the control satellite node determines a second time difference according to the time measurement feedback frame, and determines path transmission delay time according to the corresponding relation between the first time difference and the second time difference;
and determining a corresponding second time difference according to the time measurement feedback frames received by the satellite nodes of different inter-satellite links, and determining the path transmission delay time of the satellite nodes and the current reference point according to the corresponding relationship between the first time difference and the second time difference by following the information of the first time difference in the data of the time measurement feedback frames.
It should be noted that, in combination with the distance change between the satellite node of the inter-satellite link of the upper section in the same orbit and different orbit and the current reference point, the path transmission delay time is different. When the link is the same track link, the path transmission delay time determined by the first time difference and the second time difference does not need to be corrected. When the link is an off-rail link, on the basis of the first time difference and the second time difference, due to the change of the high dynamic distance, the corresponding path transmission delay time needs to be obtained by correcting the high dynamic distance.
S14: determining the time difference of the satellite node according to the corresponding relation among the path transmission delay time, the first time difference, the second time difference and the processing delay time of the satellite node;
specifically, the processing delay time of the satellite node is based on a difference value between the processing delay time of the frame data corresponding to transmission and reception between the satellite node and the current reference point, and the processing delay time of each satellite can be obtained in advance through ground test and stored in the corresponding satellite for table lookup. And determining the time difference of the satellite nodes according to the obtained four time parameters. The correspondence relationship between the four time parameters specifically includes:
subtracting the second time difference from the first time difference to obtain a time difference value;
subtracting the path transmission delay time from the time difference value to obtain an error value;
and subtracting the delay time from the error value to obtain a time difference.
S15: and calibrating the satellite nodes according to the time difference so as to complete the time synchronization of the satellite nodes.
And correcting the local time reference of the satellite node through the obtained time difference so as to complete the time synchronization of the satellite node.
The time synchronization method for the inter-satellite link provided by the embodiment of the invention comprises the following steps: acquiring a current reference point and adjacent satellite nodes in an inter-satellite link, wherein the current reference point is a synchronous satellite node, and at least one satellite node exists; controlling the satellite node to send the time measurement frame to the current reference point so that the current reference point determines a first time difference according to the time measurement frame, and generating a corresponding time measurement feedback frame according to the first time difference and the time measurement frame to send to the satellite node; the control satellite node determines a second time difference according to the time measurement feedback frame, and determines path transmission delay time according to the corresponding relation between the first time difference and the second time difference; determining the time difference of the satellite node according to the corresponding relation among the path transmission delay time, the first time difference, the second time difference and the processing delay time of the satellite node; and calibrating the satellite nodes according to the time difference so as to complete the time synchronization of the satellite nodes. According to the method, a synchronous satellite node is used as a time reference point, and the time synchronization of the adjacent satellite node corresponding to the current reference point is completed through a time synchronization method determined by a first time difference, a second time difference, path transmission delay time and processing delay time, so that the time synchronization of the adjacent satellite node corresponding to the next time reference point is performed. The method can avoid the serious dependence on time service of other systems, realize the time synchronization under the condition that the Beidou/GPS time service system cannot be used for time service in a special period, and improve the independence and the reliability of the time synchronization of the inter-satellite link.
On the basis of the above embodiment, the determining the first time difference according to the time measurement frame in step S12 includes:
generating a time difference by the frame header starting time of the time measurement frame and the rising edge time of the local pulse per second signal of the current reference point to determine the time difference as a first time difference, wherein the starting position of the frame header of the time measurement frame is aligned with the rising edge position of the local pulse per second signal of the satellite node;
correspondingly, the first time difference comprises a first delay time of the satellite node for sending the time measurement frame to the current reference point and a first processing time delay of the current reference point for receiving the time measurement frame.
Fig. 3 is a timing diagram of a time difference measurement process according to an embodiment of the present invention, as shown in fig. 3, a satellite node sends a time measurement frame to a current reference point, where a time difference between a start time of a frame header of the time measurement frame and a rising edge time of a local pulse-per-second signal of the current reference point is determined as a first time difference, provided that a start bit of the frame header of the time measurement frame is aligned with a rising edge bit of the pulse-per-second signal of the satellite node.
Correspondingly, the first time difference
The time difference between the starting time of the frame head of the time measurement frame sent by the satellite node and the local 1PPS time reference of the current reference point comprises the first delay time from the time measurement frame sent by the satellite node to the current reference point
First processing delay of receiving time measurement frame with current reference point
The specific formula is as follows:
accordingly, the determining the second time difference from the time measurement feedback frame in step S13 includes:
determining a time difference generated by the frame header starting time of the time measurement feedback frame and the rising edge time of the local pulse per second signal of the satellite node as a second time difference;
correspondingly, the second time difference comprises a second delay time of sending the time measurement feedback frame to the satellite node by the current reference point and a second processing time delay of receiving the time measurement feedback frame by the satellite node.
As shown in fig. 3, the current reference point sends a time measurement feedback frame, and a time difference between a frame header start time of the time measurement feedback frame and a rising edge time of the local pulse per second signal of the current reference point is determined as a second time difference, provided that a frame header start bit of the time measurement frame is aligned with a rising edge bit of the pulse per second signal of the satellite node.
Correspondingly, the second time difference
Measuring the time difference between the start time of the frame header of the feedback frame and the local 1PPS time reference of the current reference point for the time received by the satellite nodeSending a time measurement feedback frame to the satellite node including the current reference point for a second delay time
Second processing delay with satellite node receiving time measurement feedback frame
The specific formula is as follows:
wherein the content of the first and second substances,
the time difference to be solved. By passing
Can obtain
I.e. by
。
In this embodiment, the first time difference is determined according to the time measurement frame, and the second time difference is determined according to the time measurement feedback frame, so that the time difference can be obtained subsequently.
After the first time difference and the second time difference are obtained, because the corresponding relations between the satellite nodes and the inter-satellite links of the current reference point are different, the two situations are divided into two situations, wherein one situation is that the satellite nodes and the current reference point are located on the same-orbit link, the other situation is that the satellite nodes and the current reference point are located on the different-orbit link, and the determined path transmission delay time is different under the two situations.
When the satellite node and the current reference point are positioned on the same-track link, determining the path transmission delay time according to the corresponding relation between the first time difference and the second time difference, wherein the method comprises the following steps:
the path propagation delay time is determined by a time error value of a first delay time of the first time difference and a second delay time of the second time difference.
Specifically, the first delay time
Sending time measurement frames for the satellite nodes to the delay time received by the current reference point, and the second delay time
Sending a time measurement feedback frame to the current reference point to measure the delay time received by the satellite node, the path transmission delay time
Is a first delay time
And a second delay time
The specific formula of the time difference value of (2) is as follows:
when the satellite node and the current reference point are positioned on the different-track link, determining the path transmission delay time according to the corresponding relation between the first time difference and the second time difference, wherein the method comprises the following steps:
determining an initial path transmission delay time by a time error value of a first delay time of the first time difference and a second delay time of the second time difference;
acquiring ephemeris information of a time measurement feedback frame of a current reference point;
determining distance information and relative transmission speed between the current reference point and the satellite node according to the ephemeris information;
and correcting the initial path transmission delay time through the distance information and the relative transmission speed to obtain the path transmission delay time.
Specifically, when the link is an off-rail link, on the basis of the first time difference and the second time difference, due to the change of the high dynamic distance, the corresponding path transmission delay time needs to be obtained by correcting the high dynamic distance.
The initial path propagation delay time and the path propagation delay time when the satellite node and the current reference point are located on the same orbit link
The acquisition mode is the same, and the ephemeris information of the time measurement feedback frame is acquired on the basis of the initial path transmission delay time. The ephemeris is an accurate position or a track table of the celestial body movement changing along with time in the GPS measurement and is a function of time, and the satellite ephemeris is an expression for describing the position and the speed of a space flight body and can accurately calculate, predict, depict and track the time, the position, the speed and other running states of the satellite and the flight body.
The distance between satellites is changed dynamically from hundreds kilometers to thousands of kilometers; taking the distance between the satellites as 5000km as an example, the unidirectional transmission delay is 16.67ms; taking the distance between the satellites as 100km as an example, the one-way transmission time delay is 333us; according to the ephemeris information of the satellites, the relative operation speed between the satellites is calculated, the total transmission delay is small, the distance information between the current reference point and the satellite node and the relative transmission speed are determined through the ephemeris information, the initial path transmission delay time is corrected to obtain the corrected path transmission delay time, and the magnitude of ns can be achieved.
According to the method, the subsequent time difference can be conveniently obtained through the determined path transmission delay time on the same-rail link and the different-rail link, and meanwhile, the final path transmission delay time is obtained through ephemeris information aiming at the different-rail link, so that the precision of the error value is improved, the error is reduced, and the precision of time synchronization is improved.
On the basis of the above embodiment, the frame format of the time measurement feedback frame of the co-orbit link includes a synchronization header, a frame header, a link type, a number of a satellite node to be synchronized, a number of a time reference node, and a time difference.
Before the frame format of the time measurement feedback frame is obtained, as shown in fig. 4, fig. 4 is a schematic frame structure diagram of the time measurement frame provided in the embodiment of the present invention, and as shown in fig. 4, the time measurement frame includes a synchronization header, a frame header, a link type, a serial number of a satellite node to be synchronized, and a sending time, and the meaning of each parameter in the time measurement frame is as follows:
a) A synchronous head: for assisting satellite receiver reception;
b) Frame head: for characterizing the start position of the effective content of the frame; the start bit of the frame header is aligned with the local 1PPS time reference of the satellite transmitting the measurement frame;
c) The link type is as follows: the method is used for representing link types, inter-satellite links and the like;
d) Numbering the nodes of the satellites to be synchronized: transmitting a satellite number of the time measurement frame;
e) And (3) sending time: the time of sending the signal is X months, X days, X minutes and X seconds.
Correspondingly, the frame format of the time measurement feedback frame of the co-orbit link includes a synchronization header, a frame header, a link type, a number of a satellite node to be synchronized, a number of a time reference node, and a time difference, fig. 5 is a frame structure diagram of the time measurement feedback frame of the co-orbit link according to the embodiment of the present invention, and as shown in fig. 5, the meaning of each parameter in the co-orbit time measurement feedback frame is as follows:
a) A synchronous head: for assisting satellite receiver reception;
b) Frame header: for characterizing the frame valid content start position; the frame header start bit is aligned with the local 1PPS time reference of the satellite transmitting the feedback frame;
c) The link type is as follows: the method is used for representing link types, inter-satellite links and the like;
d) Numbering the nodes of the satellites to be synchronized: transmitting a satellite number of the time measurement frame;
e) Time reference node number: receiving a time measurement frame and sending a satellite number of a measurement feedback frame;
f) Time difference: and receiving the time difference between the frame header time of the time measurement frame and the local 1PPS time reference of the target satellite.
Correspondingly, the frame format of the time measurement feedback frame of the different-orbit link comprises a synchronization head, a frame head, a link type, the number of the satellite node to be synchronized, the number of a time reference point, time difference and ephemeris information. Fig. 6 is a frame structure diagram of a time measurement feedback frame of an inter-track link according to an embodiment of the present invention, and as shown in fig. 6, the meaning of each parameter in the inter-track time measurement feedback frame is as follows:
a) A synchronous head: for assisting satellite receiver reception;
b) Frame head: for characterizing the start position of the effective content of the frame; the frame header start bit is aligned with the local 1PPS time reference of the satellite transmitting the feedback frame;
c) The link type is as follows: the method is used for representing link types, inter-satellite links and the like;
d) Numbering the nodes of the satellite to be synchronized: transmitting a satellite number of the time measurement frame;
e) Time reference point number: receiving a time measurement frame and sending a satellite number of a measurement feedback frame;
f) Time difference: receiving a time difference between a frame header time of a time measurement frame and a local 1PPS time reference of a target satellite;
g) Ephemeris information: ephemeris information for the current time reference point.
The embodiment of the invention introduces the frame format structures of the time measurement feedback frames of the same-track link and the different-track link, is convenient to carry different types of information, and ensures the data transmission so as to obtain the subsequent time difference. And the ephemeris information of the different-orbit link is added through a time measurement feedback frame, so that the calculation precision of the path transmission delay time is improved.
On the basis of the foregoing embodiment, the processing delay time of the satellite node includes a delay difference between the first processing delay and the second processing delay.
Specifically, it is obtained by the following formula:
The process for determining the processing delay time of the satellite node provided by the embodiment facilitates determination of the time difference. So as to calibrate the satellite nodes according to the time difference to complete the time synchronization of the satellite nodes.
On the basis of the above detailed description of each embodiment corresponding to the inter-satellite link time synchronization method, the present invention further discloses an inter-satellite link time synchronization device corresponding to the above method, and fig. 7 is a structural diagram of an inter-satellite link time synchronization device provided in an embodiment of the present invention. As shown in fig. 7, the time synchronization apparatus for inter-satellite link includes:
the acquisition module 11 is configured to acquire a current reference point and adjacent satellite nodes in an inter-satellite link, where the current reference point is a geostationary satellite node and at least one of the satellite nodes exists;
a sending module 12, configured to control the satellite node to send the time measurement frame to the current reference point so that the current reference point determines a first time difference according to the time measurement frame, and generate a corresponding time measurement feedback frame according to the first time difference and the time measurement frame to send to the satellite node;
a first determining module 13, configured to control the satellite node to determine a second time difference according to the time measurement feedback frame, and determine a path transmission delay time according to a correspondence between the first time difference and the second time difference;
a second determining module 14, configured to determine a time difference of the satellite node according to a corresponding relationship between the path transmission delay time, the first time difference, the second time difference, and the processing delay time of the satellite node;
and the calibration module 15 is configured to calibrate the satellite node according to the time difference to complete time synchronization of the satellite node.
Since the embodiment of the apparatus portion corresponds to the above-mentioned embodiment, the embodiment of the apparatus portion is described with reference to the embodiment of the method portion, and is not described again here.
For the introduction of the inter-satellite link time synchronization apparatus provided by the present invention, please refer to the above method embodiment, which is not described herein again, and has the same beneficial effects as the inter-satellite link time synchronization method.
Fig. 8 is a structural diagram of another time synchronization apparatus for an inter-satellite link according to an embodiment of the present invention, as shown in fig. 8, the apparatus includes:
a memory 21 for storing a computer program;
and the processor 22 is used for realizing the steps of the time synchronization method of the inter-satellite link when executing the computer program.
The time synchronization device for the inter-satellite link provided in this embodiment may include, but is not limited to, a tablet computer, a notebook computer, or a desktop computer.
The processor 22 may include one or more processing cores, such as a 4-core processor, an 8-core processor, and so on. The Processor 22 may be implemented in hardware using at least one of a Digital Signal Processor (DSP), a Field-Programmable Gate Array (FPGA), and a Programmable Logic Array (PLA). The processor 22 may also include a main processor and a coprocessor, the main processor is a processor for Processing data in an awake state, and is also called a Central Processing Unit (CPU); a coprocessor is a low power processor for processing data in a standby state. In some embodiments, the processor 22 may be integrated with a Graphics Processing Unit (GPU) that is responsible for rendering and drawing the content that the display screen needs to display. In some embodiments, processor 22 may also include an Artificial Intelligence (AI) processor for processing computational operations related to machine learning.
Memory 21 may include one or more computer-readable storage media, which may be non-transitory. Memory 21 may also include high speed random access memory, as well as non-volatile memory, such as one or more magnetic disk storage devices, flash memory storage devices. In this embodiment, the memory 21 is at least used for storing the following computer program 211, wherein after being loaded and executed by the processor 22, the computer program can implement the relevant steps of the time synchronization method for inter-satellite links disclosed in any of the foregoing embodiments. In addition, the resources stored in the memory 21 may also include an operating system 212, data 213, and the like, and the storage manner may be a transient storage or a permanent storage. Operating system 212 may include Windows, unix, linux, etc., among others. Data 213 may include, but is not limited to, data involved in the time synchronization method of the inter-satellite link, and the like.
In some embodiments, the time synchronization device for inter-satellite link may further include a display 23, an input/output interface 24, a communication interface 25, a power supply 26, and a communication bus 27.
Those skilled in the art will appreciate that the architecture shown in fig. 8 does not constitute a limitation of the time synchronization means of the inter-satellite links and may include more or fewer components than those shown.
The processor 22 implements the time synchronization method of the inter-satellite link provided by any of the above embodiments by calling instructions stored in the memory 21.
For the introduction of the inter-satellite link time synchronization apparatus provided by the present invention, please refer to the above method embodiment, which is not described herein again, and has the same beneficial effects as the above inter-satellite link time synchronization method.
Further, the present invention also provides a computer readable storage medium, on which a computer program is stored, and the computer program when executed by the processor 22 realizes the steps of the time synchronization method for inter-satellite links as described above.
It is understood that, if the method in the above embodiments is implemented in the form of software functional units and sold or used as a stand-alone product, it can be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention, which is substantially or partially contributed by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and performs all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.
For the introduction of a computer-readable storage medium provided by the present invention, please refer to the above method embodiment, which is not described herein again, and has the same beneficial effects as the above time synchronization method for inter-satellite links.
The time synchronization method of the inter-satellite link, the time synchronization device of the inter-satellite link and the medium provided by the invention are described in detail above. The embodiments are described in a progressive manner in the specification, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed in the embodiment corresponds to the method disclosed in the embodiment, so that the description is simple, and the relevant points can be referred to the description of the method part. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
It is further noted that, in the present specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
Claims (10)
1. A method for time synchronization of inter-satellite links, comprising:
acquiring a current reference point and adjacent satellite nodes in an inter-satellite link, wherein the current reference point is a synchronous satellite node, and at least one adjacent satellite node exists;
controlling the satellite node to send a time measurement frame to the current reference point so that the current reference point determines a first time difference according to the time measurement frame, and generating a corresponding time measurement feedback frame according to the first time difference and the time measurement frame to send the time measurement feedback frame to the satellite node;
controlling the satellite node to determine a second time difference according to the time measurement feedback frame, and determining path transmission delay time according to the corresponding relation between the first time difference and the second time difference;
determining the time difference of the satellite node according to the corresponding relation among the path transmission delay time, the first time difference, the second time difference and the processing delay time of the satellite node;
calibrating the satellite nodes according to the time difference to complete time synchronization of the satellite nodes;
correspondingly, controlling the current reference point to determine a first time difference according to the time measurement frame includes:
controlling the current reference point to generate a time difference through a frame header starting time of the time measurement frame and a rising edge time of a local pulse per second signal of the current reference point, and determining the time difference as the first time difference, wherein a starting bit of a frame header of the time measurement frame is aligned with a rising edge bit of the local pulse per second signal of the satellite node;
correspondingly, the first time difference comprises a first delay time of the satellite node for sending the time measurement frame to the current reference point and a first processing time delay of the current reference point for receiving the time measurement frame;
correspondingly, the determining the second time difference according to the time measurement feedback frame includes:
determining the time difference generated by the frame header starting time of the time measurement feedback frame and the rising edge time of the local pulse per second signal of the satellite node as the second time difference;
correspondingly, the second time difference includes a second delay time for the current reference point to send the time measurement feedback frame to the satellite node and a second processing delay time for the satellite node to receive the time measurement feedback frame.
2. The method for time synchronization of inter-satellite links according to claim 1, wherein determining the path transmission delay time according to the correspondence between the first time difference and the second time difference when the satellite node and the current reference point are on the co-rail link comprises:
determining the path propagation delay time by a time error value of the first delay time of the first time difference and the second delay time of the second time difference.
3. The method for time synchronization of inter-satellite links according to claim 1, wherein said determining a path transmission delay time according to a correspondence between the first time difference and the second time difference when the satellite node and the current reference point are located on an off-orbit link comprises:
determining an initial path transmission delay time by a time error value of the first delay time of the first time difference and the second delay time of the second time difference;
acquiring ephemeris information of the time measurement feedback frame of the current reference point;
determining distance information and relative transmission speed between the current reference point and the satellite node according to the ephemeris information;
and correcting the initial path transmission delay time through the distance information and the relative transmission speed to obtain the path transmission delay time.
4. The method for time synchronization of an inter-satellite link according to claim 2, wherein the frame format of the time measurement feedback frame of the co-orbital link includes a synchronization header, a frame header, a link type, a satellite node number to be synchronized, a time reference node number, and a time difference.
5. The method according to claim 3, wherein the frame format of the time measurement feedback frame of the inter-satellite link comprises a synchronization header, a frame header, a link type, a number of a satellite node to be synchronized, a number of a time reference node, a time difference, and the ephemeris information.
6. The method of time synchronization of inter-satellite links according to claim 1, wherein the processing delay time of the satellite node comprises a delay difference of the first processing delay and the second processing delay.
7. The method according to any one of claims 1 to 6, wherein the determining the time difference of the satellite node according to the correspondence between the path transmission delay time, the first time difference, the second time difference, and the processing delay time of the satellite node comprises:
subtracting the second time difference from the first time difference to obtain a time difference value;
subtracting the path transmission delay time from the time difference value to obtain an error value;
and subtracting the processing delay time from the error value to obtain the time difference.
8. A time synchronization apparatus for an inter-satellite link, comprising:
the system comprises an acquisition module, a judging module and a judging module, wherein the acquisition module is used for acquiring a current reference point and adjacent satellite nodes in an inter-satellite link, the current reference point is a synchronous satellite node, and at least one adjacent satellite node exists;
the transmitting module is used for controlling the satellite node to transmit a time measurement frame to the current reference point so that the current reference point can determine a first time difference according to the time measurement frame, and generating a corresponding time measurement feedback frame according to the first time difference and the time measurement frame to transmit the time measurement feedback frame to the satellite node;
a first determining module, configured to control the satellite node to determine a second time difference according to the time measurement feedback frame, and determine a path transmission delay time according to a correspondence between the first time difference and the second time difference;
a second determining module, configured to determine a time difference of the satellite node according to a correspondence between the path transmission delay time, the first time difference, the second time difference, and a processing delay time of the satellite node;
the calibration module is used for calibrating the satellite nodes according to the time difference so as to complete the time synchronization of the satellite nodes;
correspondingly, controlling the current reference point to determine a first time difference according to the time measurement frame includes:
controlling the current reference point to generate a time difference through the starting time of the frame header of the time measurement frame and the rising edge time of the local pulse per second signal of the current reference point, and determining the time difference as the first time difference, wherein the starting position of the frame header of the time measurement frame is aligned with the rising edge position of the local pulse per second signal of the satellite node;
correspondingly, the first time difference comprises a first delay time of the satellite node for sending the time measurement frame to the current reference point and a first processing time delay of the current reference point for receiving the time measurement frame;
correspondingly, the determining the second time difference according to the time measurement feedback frame includes:
determining the time difference generated by the frame header starting time of the time measurement feedback frame and the rising edge time of the local pulse per second signal of the satellite node as the second time difference;
correspondingly, the second time difference includes a second delay time for the current reference point to send the time measurement feedback frame to the satellite node and a second processing delay for the satellite node to receive the time measurement feedback frame.
9. A time synchronization apparatus for an inter-satellite link, comprising:
a memory for storing a computer program;
a processor for implementing the steps of the method of time synchronization of inter-satellite links according to any one of claims 1 to 7 when executing said computer program.
10. A computer-readable storage medium, characterized in that a computer program is stored on the computer-readable storage medium, which computer program, when being executed by a processor, carries out the steps of the method for time synchronization of inter-satellite links according to any one of claims 1 to 7.
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