Satellite terminal, crystal oscillator error estimation method, device and application

Abstract

The invention discloses a satellite terminal, a crystal oscillator error estimation method, a crystal oscillator error estimation device and application, relates to the field of wireless communication, and is used for quickly estimating a crystal oscillator error between a satellite and the terminal and ensuring that an uplink signal can be smoothly accessed to a satellite network after being subjected to frequency offset pre-compensation. According to the method, carrier frequency offset estimation is carried out on monitored downlink signals, the frequency offset change rate is calculated, Doppler frequency offset is matched according to the frequency offset change rate, and then the crystal oscillator error is calculated according to the carrier frequency offset and the Doppler frequency offset. And the estimation precision of the crystal oscillator error can be improved by repeating multiple rounds. The method does not need to depend on ephemeris information in real time to calculate Doppler frequency offset, and avoids the problem of large estimation error caused by low ephemeris timeliness; by independently considering the compensation for the crystal oscillator error, the terminal can be smoothly synchronized to the satellite network.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication, and in particular to a crystal oscillator error estimation method and apparatus, an uplink synchronization method and apparatus, and a satellite terminal. Background Art

[0002] In a satellite communication system including a satellite terminal and a satellite, for the uplink transmission link on the terminal side, during initial uplink frequency synchronization, each terminal usually needs to perform frequency offset pre-compensation on the signals it transmits (i.e., uplink signals). Otherwise, uplink signal frequency domain aliasing will occur on the base station side, causing performance degradation.

[0003] Most of the current frequency offset pre-compensation methods can only be applied to scenarios where the crystal oscillator error in the satellite communication system is small. When the performance of the crystal oscillator itself is poor, or due to long-term non-use or other environmental reasons such as temperature and humidity, the performance of the crystal oscillator deteriorates significantly, resulting in a large crystal oscillator error between the satellite and the terminal. The above frequency offset pre-compensation method will cause a large frequency offset error in the uplink signal. When it is large enough to exceed the frequency offset adjustment range that the network side can tolerate, the terminal will be difficult to complete normal satellite communication. Therefore, it is necessary to estimate the crystal oscillator error between the satellite and the terminal and separately consider it in the frequency offset pre-compensation of the uplink signal. Summary of the Invention

[0004] The object of the present invention is to provide a crystal oscillator error estimation method for quickly estimating the crystal oscillator error between a satellite and a terminal, so as to facilitate separately considering the crystal oscillator error when performing frequency offset pre-compensation and the like, aiming at all or part of the above problems.

[0005] The technical solution adopted by the present invention is as follows: A crystal oscillator error estimation method, which includes: Listening to a downlink signal; Estimating the carrier frequency offset of the downlink signal and calculating the first frequency offset change rate of the downlink signal; Obtaining a first Doppler frequency offset corresponding to the first frequency offset change rate; Calculating the crystal oscillator error based on the estimated carrier frequency offset of the downlink signal and the first Doppler frequency offset.

[0006] On the other hand, the present invention also provides a crystal oscillator error estimation apparatus, which includes: A first processing module configured to listen to a downlink signal; A second processing module configured to estimate the carrier frequency offset of the downlink signal and calculate the first frequency offset change rate of the downlink signal; A third processing module configured to obtain a first Doppler frequency offset corresponding to the first frequency offset change rate; A fourth processing module, configured to: calculate an oscillator error based on the carrier frequency offset estimated from the downlink signal and the first Doppler frequency offset.

[0007] On the other hand, the present invention also provides another oscillator error estimation device, including a first processor and a first storage medium. The first storage medium stores a computer program, and the first processor executes the computer program to run the above-mentioned oscillator error estimation method.

[0008] On the other hand, the present invention also provides a satellite terminal configured with the above-mentioned oscillator error estimation device.

[0009] On the other hand, the present invention also provides an uplink synchronization method, which includes: The terminal listens to the downlink signal; The terminal estimates the oscillator error using the above-mentioned oscillator error estimation method; The terminal performs frequency offset pre-compensation on the uplink signal based on the estimated oscillator error.

[0010] On the other hand, the present invention also provides an uplink synchronization device, including a second processor and a second storage medium. The second storage medium stores a computer program, and the second processor executes the computer program to run the above-mentioned uplink synchronization method.

[0011] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are: Based on the carrier frequency offset and the frequency offset change rate calculated from the listened downlink signal, this application estimates the Doppler frequency offset of the downlink signal from the mapping relationship between the Doppler frequency offset caused by the relative motion of the satellite and the terminal and the frequency offset change rate of the downlink signal, without relying on real-time ephemeris information, and completes the estimation of the oscillator errors of the satellite and the terminal. When performing frequency offset pre-compensation, the compensation for the oscillator error is considered separately to ensure that even in scenarios with large oscillator errors, the frequency deviation of the uplink signal can be compensated to a state not exceeding the tolerance range on the satellite side, ensuring that the terminal can be successfully synchronized to the satellite network. In addition, this application can control the granularity of the pre-constructed mapping relationship according to the tolerance range of the frequency offset on the satellite side in a specific application scenario, so as to achieve the effect of balancing the computing power and storage resource costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention will be described by way of examples with reference to the accompanying drawings, where: Figure 1 is a signal flow diagram of the synchronization process between a satellite and a terminal in a satellite communication system.

[0013] Figure 2 is a flowchart of the oscillator error estimation method provided by an embodiment of the present application.

[0014] Figure 3 It is a three-dimensional schematic diagram of the space of the satellite communication system in the embodiment of the present application.

[0015] Figure 4 Is Figure 3 A schematic diagram of the geometric relationship within the STO plane in

[0016] Figure 5 Is Figure 3 A schematic diagram of the geometric relationship within the MNO plane in

[0017] Figure 6 It is a flowchart of the uplink synchronization method provided by the embodiment of the present application.

[0018] Figure 7 It is a signal flow diagram of the theory of the uplink synchronization method provided by the embodiment of the present application.

[0019] Figure 8 It is an actual signal flow diagram of the uplink synchronization method provided by the embodiment of the present application.

[0020] Figure 9 It is a structural diagram of the crystal oscillator error estimation device provided by the embodiment of the present application.

[0021] Figure 10 It is a structural diagram of the satellite terminal provided by the embodiment of the present application.

[0022] Figure 11 It is a structural diagram of the electronic device provided by the embodiment of the present application. Detailed implementation manners

[0023] All the features disclosed in this specification, or all the steps in the disclosed methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

[0024] Any feature disclosed in this specification (including any additional claims, abstract) can be replaced by other equivalent or features with similar purposes, unless specifically stated otherwise. That is, unless specifically stated, each feature is only an example of a series of equivalent or similar features.

[0025] The ordinal words such as "first", "second", etc. mentioned in this specification, unless specifically stated, are only used to more clearly refer to the described object and do not have a special limiting effect on the corresponding object. The azimuth prepositions such as "upper", "lower", "left", "right", etc. mentioned in this specification are for the perspective of the specific embodiment of the present application. After the perspective changes, unless specifically stated, the corresponding azimuth should change synchronously.

[0026] Due to the relatively high-speed movement between the satellite and the terminal, a large Doppler frequency offset will be introduced in the downlink signal received by the terminal. In addition, there will be a certain deviation between the output frequency of the crystal oscillator and the nominal frequency. Therefore, the crystal oscillator error between the terminal side and the satellite side always exists. Assume that the Doppler frequency offset introduced by the relative movement between the satellite and the terminal in the downlink signal is ; the crystal oscillator error caused by the crystal oscillator on the terminal side relative to the satellite side is , where , is the actual carrier frequency generated by the crystal oscillator on the satellite side, is the actual carrier frequency generated by the crystal oscillator on the terminal side.

[0027] Currently, the frequency offset pre-compensation performed on the terminal side generally includes two methods: Method 1: The terminal uses its own position, movement speed, ephemeris information, etc. to estimate the Doppler frequency offset value of the downlink signal, and performs frequency pre-compensation on the uplink signal according to .

[0028] Method 2: The terminal uses the downlink signal to complete the downlink frequency offset estimation, and records the frequency offset estimation value as . The terminal uses to perform frequency offset pre-compensation on the uplink signal according to . Among them, the estimated downlink frequency offset value is the superimposed value of the Doppler frequency offset and the frequency offset caused by the crystal oscillator error , that is .

[0029] The above Method 1 requires accurate estimation of the Doppler frequency offset , which requires relatively accurate real-time satellite position, and thus requires relatively quasi-real-time satellite ephemeris information. However, in actual applications, the satellite ephemeris can only guarantee the information timeliness at the minute level, which will introduce a large deviation to the real-time relative position between the satellite and the terminal, and further introduce a large error to the estimation of the Doppler frequency offset . Eventually, it may cause the terminal to be unable to successfully access the network due to the inability to complete the uplink frequency synchronization. On the other hand, the actually compensated frequency offset value will leave a crystal oscillator error residual in the uplink frequency offset. Only when is small, the satellite communication system will assist the terminal to complete the uplink frequency synchronization adjustment through the closed-loop frequency synchronization mechanism.

[0030] The above Method 2 directly uses to perform frequency offset pre-compensation on the uplink signal, which will introduce a new frequency offset , therefore, this method is also only applicable to the crystal oscillator errors of satellites and terminals in application scenarios where the crystal oscillator errors are basically constant or the error fluctuations are within a small range. For the newly introduced frequency offset , when it is small, the satellite communication system can also assist the terminal to complete the uplink synchronization adjustment through the closed-loop frequency synchronization mechanism, so that the synchronization accuracy meets the service channel synchronization requirements.

[0031] Such as Figure 1 shown in the signal flow diagram of the satellite and terminal synchronization process. The satellite sends down (such as broadcasts) the downlink signal. After the terminal detects the downlink signal, it sends an uplink signal in order to access the satellite communication network. Before sending the uplink signal, it is necessary to perform frequency offset pre-compensation on its uplink signal. The two existing methods can only be used in scenarios with small crystal oscillator errors. Once the crystal oscillator error exceeds the tolerance limit of the satellite side for the frequency offset, the terminal cannot synchronize to the satellite network smoothly. Therefore, in the frequency offset pre-compensation of this application, the compensation for the crystal oscillator error is considered separately.

[0032] For the need to separately compensate for the crystal oscillator error of the satellite communication system, it is necessary to first estimate this crystal oscillator error. The embodiment of this application provides a method for estimating the crystal oscillator error. Such as Figure 2 shown, this method includes: S1: Detect the downlink signal.

[0033] The so-called downlink signal is the signal sent by the satellite to the terminal, which can be in the form of directional transmission or broadcast transmission, etc. This application does not limit this.

[0034] The downlink signal of the satellite carries the ephemeris information of the current serving beam. This ephemeris information includes information representing the real-time position of the satellite and information representing the satellite orbit. In the previous method 1 when performing real-time Doppler frequency offset estimation, the real-time position information of the satellite was used. Therefore, in the case of poor timeliness of the ephemeris information, it will cause a deviation in the estimation of the satellite position, resulting in a large deviation in the estimated Doppler frequency offset. The satellite orbit information usually includes the semi-major axis, eccentricity, orbital inclination, longitude of the ascending node, argument of perigee, etc. The satellite orbit information basically does not change within the minute-level timeliness. Through the satellite orbit information, using existing orbit fitting methods of aerospace orbital kinematics, etc., the satellite orbit (or satellite trajectory) within the orbit parameter timeliness can be simulated.

[0035] S2: Estimate the carrier frequency offset of the downlink signal and calculate the first frequency offset change rate of the downlink signal.

[0036] Calculate the carrier frequency offset of the detected downlink signal, which can be achieved by using existing frequency estimation algorithms. It is the same as the downlink frequency offset estimation performed in method 2 mentioned above. Among the estimated carrier frequency offsets, it includes the Doppler frequency offset generated by the relative motion of the satellite and the terminal , and the crystal oscillator error between the satellite and the terminal . Since the aging of the crystal oscillator is a relatively slow process, in the short term, this crystal oscillator error usually remains stable. Therefore, the difference between the carrier frequency offsets estimated within a short period of time is actually the difference between the Doppler frequency offsets estimated between two moments .

[0037] In step S2, it is also necessary to calculate the first frequency offset change rate of the downlink signal. The so-called frequency offset change rate is a parameter characterizing the speed of frequency offset change. Therefore, when calculating the frequency offset change rate, at least one reference frequency offset value, one reference frequency offset value, and the time interval for generating these two frequency offset values are required.

[0038] As an optional implementation manner, the method for calculating the first frequency offset change rate of the downlink signal includes:[[]] Calculating the first frequency offset change rate of the downlink signal according to the carrier frequency offsets estimated for at least two continuously monitored downlink signals.

[0039] Taking the continuous monitoring of two downlink signals as an example, assuming that the carrier frequency offsets estimated for the two continuously monitored downlink signals are successively and . As mentioned above, the carrier frequency offset estimated for the downlink signal includes the Doppler frequency offset corresponding to the satellite communication system state and the crystal oscillator error . Here, it is assumed that the Doppler frequency offset included in is , the Doppler frequency offset included in is . Since the two downlink signals are continuously monitored, therefore and the crystal oscillator errors included in can be regarded as equal. Then there is:[[]] (1), (2).

[0040] Assume that the time interval between monitoring the above two downlink signals is . Then, according to the following formula (3), the frequency offset change rate between these two downlink signals can be calculated :[[]] (3).

[0041] For the scenario of continuously monitoring multiple downlink signals, it can be that after calculating the frequency offset change rate between every two consecutive downlink signals through the above method, the average value is calculated as the first frequency offset change rate. Alternatively, it can also be that the frequency offset change rate between any two of the multiple downlink signals is calculated as the first frequency offset change rate.

[0042] S3: Obtain a first Doppler frequency offset corresponding to the first frequency offset change rate.

[0043] As an alternative implementation, in step S3, based on the pre-constructed mapping relationship between the Doppler frequency offset and the frequency offset change rate, the corresponding first Doppler frequency offset is matched by the first frequency offset change rate.

[0044] The so-called pre-construction means that the construction is completed before matching the first frequency offset change rate, and its time node can be before step S1, or after step S1 and before step S3.

[0045] In this application, by using the mapping relationship between the Doppler frequency offset and the frequency offset change rate, the required Doppler frequency offset can be quickly matched. Compared with the method of calculating the Doppler frequency offset in real time through ephemeris information mentioned in the first method above, on the one hand, it is not necessary to interact with the satellite frequently, and the Doppler frequency offset can be quickly matched from the mapping relationship according to the frequency offset change rate of the downlink signal, which improves the Doppler frequency offset estimation speed; on the other hand, the matching method based on the mapping relationship also reduces the dependence on the timeliness of the ephemeris information, so it is less affected by the timeliness of the ephemeris information.

[0046] In some feasible implementation manners, the mapping relationship between the Doppler frequency offset and the frequency offset change rate can be constructed in the form of a mapping table. In the mapping table, there is a one-to-one correspondence between the Doppler frequency offset and the frequency offset change rate. In addition, for the convenience of explaining the technical solution, hereinafter, the mapping relationship between the Doppler frequency offset and the frequency offset change rate will be referred to by taking the mapping table as an example.

[0047] As an alternative implementation, the mapping table is constructed from the Doppler frequency offsets estimated at multiple moments within the visible range of the satellite and the corresponding calculated frequency offset change rates.

[0048] Doppler frequency offset Is calculated through the following formula (4): (4), In the formula, Is the carrier frequency of the satellite downlink signal. c is the speed of light, usually taking the value of 3×10 8 m / s. v represents the relative motion speed between the satellite and the terminal, which is obtained through vector operation of the satellite motion speed vector and the terminal motion speed vector. Indicates the angle between the direction of v and the line connecting the satellite to the terminal. As Figure 3 shown, use to represent the satellite motion velocity vector, use to represent the terminal motion velocity vector, use to represent the satellite motion velocity vector and the angle between the line connecting the satellite to the terminal, use to represent the terminal motion velocity vector and the angle between the line connecting the satellite to the terminal, then represents the component of v in the direction of the line connecting the satellite to the terminal, which is equivalent to and for the vector addition performed.

[0049] The magnitude of the satellite motion velocity can be calculated by the following formula (5): (5), where g represents the acceleration due to gravity, usually taking a value of 9.8 m / s 2 ; R represents the radius of the Earth; h represents the height of the satellite from the Earth's surface, i.e., the satellite orbit height, which can be obtained by analyzing the satellite orbit information in the ephemeris.

[0050] Since the motion of the terminal relative to the satellite can be considered to be stationary on the Earth's surface, therefore, the trajectory of the terminal can be considered to be the latitude line of its location, and the direction of the terminal motion velocity vector is the tangent direction of the latitude line. The magnitude of the terminal motion velocity is the rotation speed of the location where the terminal is located, and the magnitude can be calculated by the following formula (6): (6), where represents the geographical latitude where the terminal is located, which can be obtained through the positioning information of the terminal; T represents the rotation period, taking a value of 86400 s. The magnitude range of the terminal motion velocity vector is between 0 and 465 m / s (465 m / s is the speed at the equator), and the direction is along the tangent direction of the circle in the latitude plane parallel to the Earth's equatorial plane.

[0051] In particular, when the satellite orbit is a near-polar orbit, i.e., the satellite orbit inclination is 90°, then when the terminal is at the sub-satellite point position, the terminal motion velocity vector is perpendicular to the satellite orbit plane, i.e., is always perpendicular to the satellite motion velocity vector , there is , at this time , then the method of calculating the Doppler frequency shift by formula (4) at this time can be equivalent to: (7).

[0052] The method for calculating the Doppler frequency offset of the downlink signal was introduced above. When the satellite is within the visible range, at a determined moment, the position of the satellite and the position of the terminal at that moment can be determined, so as to determine v and , and then the Doppler frequency offset at that moment can be calculated through Equation (4) (or an equivalent method). The so-called visible range refers to the satellite trajectory segment where the satellite is visible relative to the terminal. In this satellite trajectory segment, the elevation angle of the satellite's orbital plane ε ranges from .

[0053] By determining multiple moments within the visible range of the satellite (assuming a total of n moments are set), the Doppler frequency offsets of the satellite at these multiple moments during the overflight period (i.e., the period of flight within the visible range) can be correspondingly calculated. Assume that the Doppler frequency offsets at these multiple moments are sequentially recorded as , represents the moment i and the obtained Doppler frequency offset.

[0054] Correspondingly, when multiple moments are determined, the time intervals between the moments can be known. By calculating the difference between the estimated Doppler frequency offsets at every two moments and then dividing it by the time interval between these two moments, the frequency offset change rate at the corresponding moment (usually the previous moment of these two moments) can be obtained. The calculation method is: (8), In the formula, is the time interval between the moment j and the moment i , . In some feasible implementation manners, in the constructed mapping table, j the moment is the next moment of the moment i , that is, the frequency offset change rate between the estimated Doppler frequency offsets at every two adjacent moments is used as the frequency offset change rate of the previous moment i . Of course, this is only one of the feasible ways. In specific implementation, it is not limited to this. It can also be the frequency offset change rate between the estimated Doppler frequency offsets at moments with an interval, that is, in Equation (8), j the moment and i the moment are not adjacent and the calculated frequency offset change rate.

[0055] As an alternative implementation manner, the state of the satellite at multiple moments within the visible range can be simulated to estimate the Doppler frequency offsets of the satellite at multiple moments and calculate the corresponding frequency offset change rates.

[0056] The so-called states of the simulated satellite at multiple moments within the visible range, namely the positions, flight speeds, flight directions, etc. of the simulated satellite at multiple moments within the visible range, so as to estimate the Doppler frequency offset at each moment according to the method introduced above, and then calculate the frequency offset change rate corresponding to each moment.

[0057] In some alternative embodiments, the satellite trajectory can be simulated, such as the complete flight trajectory of the satellite or the flight trajectory within the visible range, and then based on the set step size, multiple moments can be determined. Since the satellite trajectory has been simulated, the states of the satellite at each determined moment can be obtained respectively. According to the state of the satellite at each moment, the Doppler frequency offset at that moment can be calculated; according to the Doppler frequency offsets calculated at multiple moments, the frequency offset change rate at each moment can be calculated respectively, and the Doppler frequency offset and the frequency offset change rate at each moment are associated one by one, thereby constructing a mapping table.

[0058] As a feasible implementation, the step size set for sampling the simulated satellite trajectory can be the step size set in the time dimension, such as the time step size, that is, how often a sampling moment is determined; it can also be the step size set in the distance dimension, such as the arc length step size of the satellite movement, that is, how far the satellite flies to determine a sampling moment; it can also be the step size set in the angle dimension, such as the step size of the elevation angle within the satellite orbital plane, that is, how many degrees the elevation angle within the satellite orbital plane is spaced apart to determine a sampling moment. Regardless of the set step size, preferably, equal-step sampling is performed on the entire visible range of the satellite. As a simple and effective method, the step size of the elevation angle within the satellite orbital plane can be considered to determine each moment. For example, in interval, at every interval of step size to determine all moments. In this way, the angle difference between adjacent moments is determined, which is more beneficial for calculating the Doppler frequency offset at each moment when constructing the mapping table.

[0059] For the consideration of the later Doppler frequency offset matching accuracy, if the granularity of the constructed mapping table is finer (i.e., the step size is lower), the sampled satellite positions will be denser, and the frequency offset change rate and the corresponding Doppler frequency shift in the mapping table will be more consistent with the actual situation. Therefore, in some alternative embodiments, the duration corresponding to the set step size does not exceed the duration between two consecutive downlink signals listened by the (terminal). That is, in the constructed mapping table, the time difference between two adjacent moments should be shorter than the shortest time interval for the terminal to listen to the downlink signal. For example, assuming that the time interval between two consecutive downlink signals listened by the terminal is 200 ms, when constructing the mapping table, the set time interval between adjacent moments should be less than 200 ms, such as 50 ms - 100 ms. In this way, when the terminal listens to the downlink signal at any two moments, in the mapping table, there is data with finer time granularity available for matching, thus ensuring the degree of agreement between the matched Doppler frequency offset and the actual state.

[0060] The simulated satellite trajectory can be completed according to the ephemeris information. In some alternative implementation manners, the method for simulating the satellite trajectory includes: Receiving the downlink signal; Parsing the ephemeris information of the satellite from the received downlink signal; Based on the satellite orbit information in the ephemeris information, simulating the satellite trajectory.

[0061] Different from the aforementioned Method 1 and Method 2, in the embodiments of the present application, the satellite orbit information is obtained from the ephemeris information, rather than the satellite position information. Since the satellite orbit information in the ephemeris information still has relatively high accuracy within the minute-level time limit, only the satellite orbit information needs to be parsed and obtained within the effective time to simulate the satellite trajectory, and there is no need to synchronize the ephemeris information for a long time or frequently. Therefore, the method of constructing the mapping table by simulating the satellite trajectory is hardly affected by the timeliness of the ephemeris information.

[0062] In addition, the inclination angle of the satellite orbit plane has a certain influence on the Doppler frequency offset of the downlink signal received by the terminal, and the terminal does not always access the satellite at the sub-satellite point. Therefore, using the same mapping table constructed under the same conditions in different situations may introduce relatively large deviations. Considering this, in some alternative implementation manners, the mapping table constructed in the present application includes the mapping relationship between the Doppler frequency offset and the frequency offset change rate at different over-the-top elevation angles of the satellite. The so-called over-the-top elevation angle is the elevation angle of the terminal position relative to the satellite at the over-the-top moment, denoted by representation.

[0063] Such as Figure 3 shown, in three-dimensional space, assuming that the terminal position is located at the T point on the earth's surface, the projection of the satellite on the earth's surface is called the sub-satellite point, and calculate the terminal position TThe straight-line distance between the point and all sub-satellite points, and find the sub-satellite point closest to the terminal and denote it as P the point, and this P point is the sub-satellite point position at the satellite overpass moment. Denote P the satellite position corresponding to the point as S , and denote the shortest straight-line distance, i.e., the side length TP = l . Through the terminal position T point, draw a perpendicular line to the satellite orbital plane, and the intersection point is the projection position of the terminal in the satellite orbital plane, denoted as C point. Then ∠ STC is T the overpass elevation angle of the point. When the terminal is located at the sub-satellite point, its overpass elevation angle is 90°, and at this time T point, C point and P point coincide. Figure 3 In, perpendicular to SC through C point intercept the earth, then the angle between the connection line of the satellite ( M point or S point) and C point and this cross-section is the in-plane elevation angle of the satellite orbital plane mentioned above, simply referred to as the satellite elevation angle, denoted by ε . In some alternative embodiments of the present application, for different overpass elevation angles, the Doppler frequency shift is estimated at multiple moments within the visible range of the satellite, the corresponding frequency shift change rate is calculated, and the mapping relationship between the Doppler frequency shift and the frequency shift change rate of the satellite at different overpass elevation angles is constructed. Assuming that a mapping table is constructed for each different overpass elevation angle, then when matching the first Doppler frequency shift in step S3, it is to match the corresponding Doppler frequency shift from the calculated frequency shift change rate in the mapping table corresponding to the overpass elevation angle.

[0064] Such as Figure 4 shown is the cross-sectional view of the earth through T point, P point and S point. Taking O point to represent the position of the earth's center of the sphere, then the side length TC is the distance from the terminal to the satellite orbital plane, and the side length OC is the distance between the earth's center of the sphere and the projection position of the terminal in the satellite orbital plane. Here, in combination with Figure 3 , Figure 4 and Figure 5 , a feasible implementation manner for solving the angle β is described.

[0065] In ΔOTP , it is known that OT = OP = R ( R is the earth's radius), and the side length is knownTP = l , assume the central angle of the earth's core ∠ TOS = δ . According to the cosine theorem, we have: . Therefore, the central angle of the earth's core δ is: (9).

[0066] In the right triangle Δ OCT, from the central angle of the earth's core δ and the side length OT = R, it can be known that the distance from the terminal to the satellite orbit plane, that is, the side length , and the distance between the position of the earth's core O point and the projection position of the terminal in the satellite orbit plane, that is, the side length .

[0067] As Figure 5 shown, extend the line connecting the position of the earth's core O point and the projection position of the terminal in the satellite orbit plane C point until it intersects with the velocity direction of the satellite M point, and mark the intersection position as N point. Based on the satellite elevation angle ε and the distance between the position of the earth's core O point and the projection position of the terminal in the satellite orbit plane C point, calculate the distance between the satellite position M point and the projection position of the terminal in the satellite orbit plane, that is, the side length MC , the distance between the intersection position N point and the projection position of the terminal in the satellite orbit plane C point, that is, the side length NC , and the distance between the satellite position M point and the intersection position N point, that is, the side length MN .

[0068] As Figure 5 shown, in ΔMOC , given the side length OC , OM = R + h , ∠OCM = ε + 90°, according to the cosine theorem, we have: . Let , . Solving the quadratic equation can obtain the side length MC as: (10).

[0069] Assume ∠MOC = η . According to the cosine theorem , we can obtain η . Then, using the formula and The side length can be obtained MN and ON , and finally it is obtained that: the side length NC = ON - OC .

[0070] Based on the distance from the terminal to the satellite orbital plane, i.e., the side length TC , the distance between the satellite position and the projection position of the terminal in the satellite orbital plane C points, i.e., the side length MC , the intersection position N point to the projection position of the terminal in the satellite orbital plane C points, i.e., the side length NC , and the distance from the satellite position to the intersection position N point, i.e., the side length MN , calculate the satellite motion velocity vector corresponding to the satellite elevation angle and the included angle MT between the satellite and the connection line of the terminal β : Since the connection line between the terminal position T point and the projection position of the terminal in the satellite orbital plane C point is perpendicular to the satellite orbital plane, therefore, in right triangles ΔMCT and ΔNCT respectively, using the Pythagorean theorem, the side lengths MT and NT are obtained: (11), (12).

[0071] In ΔMNT , ∠NMT is the included angle between the satellite motion velocity vector MT and the connection line between the satellite and the terminal β , using the cosine theorem to obtain: (13).

[0072] When the remaining angles need to be calculated, they can be completed using trigonometric functions, and the embodiments of the present application will not be described in detail one by one.

[0073] In addition, in the same mapping table, there may be more than two Doppler frequency offsets corresponding to the same frequency offset change rate. For example, in the mapping table constructed based on the symmetric sampling satellite elevation angles at an overhead elevation angle of 90°, the frequency offset change rates calculated at the two satellite elevation angles with a complementary relationship may be the same, and the corresponding Doppler frequency offsets may also be the same or similar. Then, when performing the first frequency offset change rate matching in step S3, more than two Doppler frequency offsets may be matched. In this regard, in some alternative embodiments, when more than one Doppler frequency offset is matched from the mapping table by the first frequency offset change rate, the one closest to the carrier frequency offset among all the matched Doppler frequency offsets is used as the first Doppler frequency offset.

[0074] Here, take the one closest to the carrier frequency offset of the first downlink signal being monitored among all the matched Doppler frequency offsets as an example of the first Doppler frequency offset. As introduced above, the carrier frequency offsets of the two downlink signals being monitored are and , and the calculated frequency offset change rate is . From this frequency offset change rate , a match is made in the pre-constructed mapping table. The matching principle is to first find the frequency offset change rate in the corresponding mapping table that is closest to . This closest frequency offset change rate is represented by . Assume that in the mapping table, there are two Doppler frequency offsets associated with , which are respectively denoted as and . Then, the one closest to is selected as the first Doppler frequency offset, denoted as . Then, there is: (14).

[0075] Among them, abs represents taking the absolute value. If taking the one closest to the carrier frequency offset of the second downlink signal being monitored among all the matched Doppler frequency offsets as an example of the first Doppler frequency offset, then in formula (14) needs to be modified to .

[0076] Through the above steps, the current Doppler frequency offset can be quickly estimated without relying on real-time ephemeris information.

[0077] For example, assume that the satellite orbital altitude is h = 1800 km, the satellite orbital inclination is 0°, that is, a near-polar orbit, the synchronous channel operating frequency point = 17 GHz, the terminal is in a stationary state, and after the terminal side completes parsing the broadcast message to obtain ephemeris information and performs satellite trajectory simulation and estimation, the overhead elevation angle of the terminal relative to the satellite orbital plane is 90°, that is, the terminal is located at the sub-satellite point of the satellite trajectory.

[0078] Construct a mapping table for the satellite elevation angle ε in the range of [0:180]° with a step size of 0.05° to obtain the over-the-top elevation angle When it is 90°, the Doppler frequency offset and the frequency offset change rate between them are shown in Table 1 as follows.

[0079] Similarly, under the same conditions, when the constructed mapping table is shown in Table 2.

[0080] When estimating the crystal oscillator error, it is necessary to first look up the mapping table corresponding to the over-the-top elevation angle based on the over-the-top elevation angle at the location of the terminal, and then match the Doppler frequency offset from the frequency offset change rate in the mapping table.

[0081] Table 1 Mapping table between Doppler frequency offset and frequency offset change rate ( )

[0082] Table 2 Mapping table between Doppler frequency offset and frequency offset change rate ( )

[0083] In addition, the embodiment of the present application also considers the influence of the estimation error of the crystal oscillator error on the feasibility of the scheme, and uses to represent this estimation error.

[0084] In the initial uplink frequency synchronization scenario, the satellite payload can assist the terminal to complete the uplink synchronization adjustment through a closed-loop frequency synchronization mechanism, that is, it has a certain tolerance range for the frequency offset of the uplink signal. Therefore, when the frequency offset of the uplink signal sent by the terminal side estimated by the satellite side is within the frequency adjustment range that the satellite side can tolerate, the terminal can continue the subsequent synchronization adjustment or the initial access process. Therefore, as long as the introduced estimation error is within the frequency adjustment range that the satellite side can tolerate, the scheme provided by the embodiment of the present application is feasible.

[0085] For example, for a low Earth orbit (LEO) satellite communication system, during its initial uplink synchronization phase, the tolerance threshold of the satellite side for the frequency deviation of the uplink signal is generally on the order of ten KHz. For example, taking the middle value of 5 KHz, therefore, as long as the introduced estimation error Below this tolerance threshold, the terminal can successfully complete uplink synchronization, that is, the solution of this application has a certain tolerance range and is feasible. Of course, all the designs of this application can also be applied to other satellite communication systems, such as Medium Earth Orbit (MEO) satellite communication systems and High Earth Orbit (HEO) satellite communication systems, and the tolerance principle is the same. In addition, the design concept of this application can also be applied to Non Terrestrial Network (NTN) communication systems.

[0086] Estimation error There are three influencing factors: Influencing factor 1: The error between the satellite orbit parameters carried in the broadcast message and the actual satellite orbit parameters.

[0087] Influencing factor 2: The influence brought by the change of orbit parameters within a minute-level time limit.

[0088] Influencing factor 3: The positioning error of the terminal itself.

[0089] For influencing factor 1, the satellite orbit parameters in the ephemeris information are configured by the satellite side and carried by the broadcast channel. The configured parameter error is determined by the satellite side, and the satellite orbit parameters obtained by the terminal side within the time limit will not introduce errors. Therefore, influencing factor 1 can be ignored. And within the minute-level time limit, the changes of various satellite orbit parameters are very small. Therefore, influencing factor 2 can also be ignored. The positioning error of influencing factor 3 is determined by the positioning mechanism and positioning algorithm adopted by the terminal side and cannot be ignored. Therefore, in the embodiments of this application, the verification of the feasibility of the solution mainly focuses on considering the influence of the estimation error introduced by the terminal positioning error on the feasibility of the solution.

[0090] The problem directly caused by the terminal positioning error is the influence on the estimated overhead elevation angle In the embodiments of this application, what is directly affected is that when matching the Doppler frequency offset based on the frequency offset change rate calculated from the downlink signal, it may lead to finding the wrong mapping table.

[0091] Assume that the satellite orbit altitude is h = 1800 km, the satellite orbit inclination is 0°, the working frequency point of the synchronization channel = 17 GHz, and the terminal is in a stationary state. Now assume two scenarios: Scenario 1: The overhead elevation angle of the terminal relative to the satellite orbit plane . The downlink carrier frequency offsets of two adjacent intervals of 200 ms measured by the terminal through downlink signal synchronization are respectively: = 193954.392 Hz and = 193812.597 Hz, and the calculated frequency deviation change rate is as follows: .

[0092] Through matching in the mapping table of Table 1, the closest frequency deviation change rate is -708.981 Hz / s, and there are two corresponding Doppler frequency deviations, which are F1 = 186.394 kHz and F2 = -186.394 kHz respectively. Select the one closest to the Doppler frequency deviation F1 = 186.394 kHz as the final first Doppler frequency deviation. Based on this, the crystal oscillator error of the satellite communication system is calculated as follows: .

[0093] Scenario 2: The over-the-top elevation angle of the terminal relative to the satellite orbital plane . The frequency deviation change rate between two adjacent downlink carrier frequency deviations measured by the terminal through downlink signal synchronization with an interval of 200 ms is still -708.969 Hz / s.

[0094] Through matching in the mapping table of Table 2, the closest frequency deviation change rate is -709.2382 Hz / s, and its corresponding Doppler frequency deviations are F1 = 185.458 kHz and F2 = -185.458 kHz respectively. Select the Doppler frequency deviation F1 = 185.458 kHz closest to the frequency deviation estimated value of the downlink signal = 193954.392 Hz as the final first Doppler frequency deviation. Based on this, the crystal oscillator error of the satellite communication system is calculated as follows: . Assume that Scenario 1 (i.e., ) is the real scenario, and Scenario 2 (i.e., ) is the scenario actually measured due to the terminal positioning error. Therefore, the estimation error introduced to the crystal oscillator error due to the terminal positioning error is as follows: .

[0095] According to the above experiments, when the change in the over-the-top elevation angle of the terminal position due to the terminal positioning error is within 5°, the difference between the estimated crystal oscillator errors (i.e., the estimation error ) is within 1 kHz. Even considering the time delay (usually on the order of dozens of Hz) in the carrier frequency deviation estimation of the downlink signal, it is far lower than the tolerance threshold of the satellite side for the frequency deviation of the uplink signal. Therefore, the solution of this application is at least effective within the range of a 5° estimation deviation of the over-the-top elevation angle.

[0096] On the other hand, based on the above phenomena, in some preferred embodiments, for each over-the-top elevation angle corresponding in the pre-constructed mapping table, the maximum angular difference between adjacent over-the-top elevation angles should be adapted to the frequency offset range tolerable on the satellite side and should not exceed this tolerance range. For example, for a low-earth orbit satellite communication system with a frequency offset tolerance range on the order of ten KHz, the angular difference between adjacent over-the-top elevation angles in the pre-constructed mapping table is set at about 5°.

[0097] S4: Calculate the oscillator error based on the carrier frequency offset estimated from the downlink signal and the first Doppler frequency offset.

[0098] Since in the previous embodiments, the first Doppler frequency offset is taken as the one closest to the carrier frequency offset of the first downlink signal monitored among all the matched Doppler frequency offsets as an example, in this step, subtract the first Doppler frequency offset estimated in step S3 from the carrier frequency offset of the first downlink signal monitored to obtain the oscillator error of the satellite communication system : : (15).

[0099] As an alternative embodiment, the oscillator error estimation method provided in this application further includes: S5: Monitor the downlink signal in multiple rounds and calculate the oscillator error for each round, that is, repeat the above steps S1 - S4 multiple times. Each time it is repeated, an oscillator error will be calculated respectively. Take the mean of the oscillator errors calculated in multiple rounds as the finally estimated oscillator error. This can further improve the accuracy of the oscillator error estimation for the satellite communication system.

[0100] Assume that the oscillator errors calculated in each round of the loop are respectively , m represents the total number of loops, represents the oscillator error calculated in the k-th round of the loop. Then the finally evaluated oscillator error is: (16).

[0101] The above embodiments introduce the oscillator error estimation method provided in this application. On this basis, this application also provides an uplink synchronization method.

[0102] As Figure 6 shown, the uplink synchronization method provided in this application includes the following steps: Step1: Monitor the downlink signal. This step is the same as step S1 in the previous embodiments. Here, it is for the sake of describing the integrity of the above synchronization method.

[0103] Step 2: Estimate the crystal oscillator error using the crystal oscillator error estimation method of the above embodiment .

[0104] Step 3: Based on the estimated crystal oscillator error Perform frequency offset pre - compensation on the uplink signal.

[0105] As can be seen from the prior art introduced above, Method 1 only considers the compensation for Doppler frequency offset, while Method 2, although considering the crystal oscillator error during frequency offset pre - compensation, directly pre - compensates the uplink signal according to the frequency offset estimation value at in this way, which will introduce a new frequency offset .

[0106] In some alternative embodiments of the present application, a pre - compensation method that takes into account both the crystal oscillator error and does not introduce a new frequency offset during frequency offset pre - compensation is provided. That is, the above - mentioned Step 3 includes: Step 31: Based on the estimated crystal oscillator error and the carrier frequency offset estimated for the downlink signal, calculate the estimated value of the Doppler frequency offset of the downlink signal.

[0107] As mentioned above, the carrier frequency offset estimated for the downlink signal includes two parts: Doppler frequency offset and crystal oscillator error. Therefore, by subtracting the estimated crystal oscillator error from the carrier frequency offset, the estimated value of the Doppler frequency offset is obtained. Taking the calculation of the crystal oscillator error in the above - mentioned embodiment as an example (the calculation is the same for ), this process is expressed as: ), (17).

[0108] For the embodiment that only estimates the crystal oscillator error once (such as Equation (15)), this estimated value of the Doppler frequency offset is the first Doppler frequency offset matched from the mapping table. For the embodiment that estimates the crystal oscillator error multiple times and then takes the average as the final estimated crystal oscillator error (such as Equation (16)), the estimated value of the Doppler frequency offset needs to be calculated by subtracting the estimated crystal oscillator error from the carrier frequency offset.

[0109] Step 32: Perform frequency offset pre - compensation on the uplink signal in the way of subtracting the estimated value of the Doppler frequency offset and adding the estimated crystal oscillator error.

[0110] The compensation value for the frequency offset pre - compensation of the uplink signal in this step is , as Figure 7 shown. In this way, theoretically, no other frequency offset will be introduced after the frequency offset pre - compensation, and the estimated value of the frequency offset of the uplink signal received by the satellite side after the frequency offset pre - compensation It is expected to be 0. In fact, the compensated uplink signal only carries the frequency offset caused by the errors introduced during terminal positioning, carrier frequency offset estimation, and mapping table construction. The errors introduced by terminal positioning and carrier frequency offset estimation have been proven to be much lower than the deviation range tolerated by the satellite-side closed-loop frequency synchronization mechanism in the previous text. The error introduced during mapping table construction can be minimized by increasing the granularity of the mapping table (such as reducing the step size) to reduce the error caused by matching as much as possible. This factor is highly controllable and can be effectively reduced or even avoided under a certain table construction granularity, and this factor does not affect the effectiveness of the solution of this application. As Figure 8 shown, taking the estimation error caused by the terminal positioning error, which has the relatively most serious impact among the above three factors as an example, the compensation value of the frequency offset pre-compensation of the uplink signal on the terminal side is at this time, and the frequency offset estimation value of the uplink signal estimated by the satellite side after frequency offset pre-compensation only has this estimation error .

[0111] Based on the concept of this application, an oscillator error estimation device is also provided in an embodiment of this application. As Figure 9 shown, this device includes: A first processing module, configured to: monitor the downlink signal.

[0112] A second processing module, configured to: estimate the carrier frequency offset of the downlink signal and calculate the first frequency offset change rate of the downlink signal.

[0113] A third processing module, configured to: obtain the first Doppler frequency offset corresponding to the first frequency offset change rate.

[0114] A fourth processing module, configured to: calculate the oscillator error based on the estimated carrier frequency offset and the first Doppler frequency offset of the downlink signal.

[0115] In addition, a fifth processing module can also be configured in the oscillator error estimation device proposed in this application to improve the accuracy of oscillator error estimation.

[0116] The fifth processing module is configured to: control the first to fourth processing modules to work in multiple rounds. In each round of loop, the fourth processing module will obtain an oscillator error. In addition, the mean value of the oscillator errors output by the fourth processing module in multiple rounds is also calculated as the finally estimated oscillator error.

[0117] In a specific embodiment, the data specifically configured by the above first processing module - fifth processing module can respectively refer to steps S1 - S5 in the foregoing embodiment of the crystal oscillator error estimation method. For example, the third processing module is configured or connected to a storage medium storing a mapping table (i.e., a pre - constructed mapping relationship between Doppler frequency offset and frequency offset change rate).

[0118] As another feasible way, in the present application, another crystal oscillator error estimation device is provided. The device includes a first processor and a first storage medium. The first storage medium stores a computer program, and the first processor executes the computer program to run the crystal oscillator error estimation method of the above - mentioned embodiment.

[0119] The present application also configures the crystal oscillator error estimation device of the above - mentioned embodiment into a satellite terminal, obtaining a satellite terminal that can evaluate the crystal oscillator error of a satellite communication system, as Figure 10 shown.

[0120] In addition, the satellite terminal designed by the present application also performs frequency offset pre - compensation on the uplink signal based on the estimated crystal oscillator error. In some optional implementation manners, the satellite terminal further includes: A sixth processing module, configured to: perform frequency offset pre - compensation on the uplink signal based on the estimated crystal oscillator error.

[0121] The frequency offset pre - compensation performed by the sixth processing module is the same as the principle of the frequency offset pre - compensation in the foregoing embodiment of the uplink synchronization method. Specifically, in some feasible implementation manners, the sixth processing module performs frequency offset pre - compensation on the uplink signal through the following configuration: Calculate an estimated value of the Doppler frequency offset of the downlink signal based on the estimated crystal oscillator error and the estimated carrier frequency offset of the downlink signal; and perform frequency offset pre - compensation on the uplink signal in a manner of subtracting the estimated value of the Doppler frequency offset and adding the estimated crystal oscillator error.

[0122] In some other feasible implementation manners, the present application also provides another uplink synchronization device. The device includes a second processor and a second storage medium. The second storage medium stores a computer program, and the second processor executes the computer program to run the uplink synchronization method of the above - mentioned embodiment.

[0123] As an optional implementation manner, in the present application, the structural relationship between the processor and the storage medium is as Figure 11 shown. The processor is communicatively connected to a communication port. By executing the computer program in the storage medium, the corresponding device can execute the corresponding method through the communication interface. Figure 11 The structure is described in a way that the processor, the storage medium, and the communication interface are connected through a bus. The bus is shown in Figure 11The medium is represented by a thick line. The connection manners between other components are only for illustrative purposes and are not limiting. The bus can be divided into an address bus, a data bus, a control bus, etc. For the convenience of representation, Figure 11 it is only represented by a thick line in the medium, but it does not mean that there is only one bus or one type of bus. It should be understood that the processor mentioned in the embodiments of the present application can be implemented by hardware or by software. When implemented by hardware, the processor can be a logic circuit, an integrated circuit, etc. When implemented by software, the processor can be a general-purpose processor that implements by reading software code stored in a storage medium.

[0124] In addition, the processor and the storage medium can be coupled through an interface circuit or integrated together.

[0125] Exemplarily, the processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor, etc.

[0126] It should be understood that the storage medium mentioned in the embodiments of the present application may be a volatile storage medium or a non-volatile storage medium, or may include both volatile and non-volatile storage media. Among them, the non-volatile storage medium may be a read-only memory (ROM), a programmable ROM (PROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), or a flash memory. The volatile storage medium may be a random access memory (RAM), which is used as an external cache. By way of example but not limitation, many forms of RAM are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchlink DRAM (SLDRAM), and direct rambus RAM (DR RAM).

[0127] It should be noted that when the processor is a general-purpose processor, DSP, ASIC, FPGA, or other programmable logic device, discrete gate or transistor logic device, or discrete hardware component, the storage medium (storage module) may be integrated in the processor.

[0128] It should be noted that the storage media described herein are intended to include, but are not limited to, these and any other suitable types of storage media.

[0129] As another possible product form, the embodiments of the present application also provide a computer-readable storage medium storing computer program instructions, which, when executed by a processor or the like, cause the computer to execute any one of the method steps in the above method examples.

[0130] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0131] The present invention is not limited to the foregoing specific embodiments. The present invention extends to any new feature or any new combination disclosed in this specification, as well as any new combination of steps of any new method or process disclosed.

Claims

1. A crystal oscillator error estimation method, characterized in that: include: Monitor downlink signals; estimating a carrier frequency deviation of the downlink signal, and calculating a first frequency deviation change rate of the downlink signal; Acquire a first Doppler frequency deviation corresponding to the first frequency deviation change rate; A crystal oscillator error is calculated based on the carrier frequency offset estimated for the downlink signal and the first Doppler frequency offset.

2. The crystal oscillator error estimation method according to claim 1, characterized in that: Calculating a first frequency deviation change rate of the downlink signal includes: A first frequency offset change rate of the downlink signal is calculated based on carrier frequency offsets estimated from at least two downlink signals monitored continuously.

3. The crystal oscillator error estimation method according to claim 1, characterized in that: Acquiring a first Doppler frequency offset corresponding to the first frequency offset change rate includes: Based on the pre-constructed mapping relationship between the Doppler frequency offset and the frequency offset change rate, the corresponding first Doppler frequency offset is matched from the first frequency offset change rate.

4. The crystal oscillator error estimation method as claimed in claim 3, characterized in that: The mapping relationship includes a mapping relationship between Doppler frequency deviation and frequency deviation change rate at different satellite overpass elevation angles, and the overpass elevation angle is an elevation angle relative to the satellite at the overpass moment.

5. The crystal oscillator error estimation method as claimed in claim 3, characterized in that: The mapping relationship is constructed by estimating the Doppler frequency deviation of the satellite at multiple moments in the visible range and the corresponding calculated frequency deviation change rate.

6. The crystal oscillator error estimation method according to claim 5, characterized in that: By simulating the states of the satellite at multiple times within the visible interval, the Doppler frequency deviation of the satellite at the multiple times is estimated, and the corresponding frequency deviation change rate is calculated.

7. The crystal oscillator error estimation method according to claim 6, characterized in that: By simulating the satellite trajectory, based on the set step size, the status of the satellite at multiple moments within the visible range is simulated.

8. The crystal oscillator error estimation method according to claim 7, characterized in that: The duration corresponding to the set step length shall not exceed the duration between continuous monitoring of two downlink signals.

9. The crystal oscillator error estimation method according to claim 7, characterized in that: The set step size is the step size of the elevation angle in the satellite orbit plane, or the time step size, or the arc length step size of the satellite motion.

10. The crystal oscillator error estimation method according to any one of claims 3 to 9, characterized in that: The matching of the first frequency deviation change rate to obtain the corresponding first Doppler frequency deviation based on the pre-constructed mapping relationship between the Doppler frequency deviation and the frequency deviation change rate includes: When more than one Doppler frequency offset is matched from the mapping relationship by the first frequency offset change rate, one of all matched Doppler frequency offsets that is closest to the carrier frequency offset is used as the first Doppler frequency offset.

11. The crystal oscillator error estimation method according to claim 1, characterized in that: The method monitors downlink signals in multiple rounds and calculates the crystal oscillator error in each round, and uses the average of the crystal oscillator errors calculated in multiple rounds as the final estimated crystal oscillator error.

12. A crystal oscillator error estimation device, characterized in that: include: The first processing module is configured to: monitor a downlink signal; The second processing module is configured to: estimate the carrier frequency deviation of the downlink signal and calculate a first frequency deviation change rate of the downlink signal; A third processing module is configured to: obtain a first Doppler frequency offset corresponding to the first frequency offset change rate; The fourth processing module is configured to calculate a crystal oscillator error based on the carrier frequency offset estimated for the downlink signal and the first Doppler frequency offset.

13. A crystal oscillator error estimation device, comprising a first processor and a first storage medium, wherein the first storage medium stores a computer program, characterized in that: The first processor executes the computer program to run the crystal oscillator error estimation method as described in any one of claims 1-11.

14. A satellite terminal, characterized in that: The satellite terminal is equipped with the crystal oscillator error estimation device as claimed in claim 12 or 13.

15. The satellite terminal according to claim 14, characterized in that Also includes: The sixth processing module is configured to: perform frequency offset pre-compensation on the uplink signal based on the estimated crystal oscillator error.

16. The satellite terminal according to claim 15, characterized in that The sixth processing module performs frequency offset pre-compensation on the uplink signal through the following configuration: Calculating a Doppler frequency deviation estimate of the downlink signal based on an estimated crystal oscillator error and an estimated carrier frequency deviation of the downlink signal; as well as The frequency offset pre-compensation is performed on the uplink signal in a manner of subtracting the Doppler frequency offset estimation value and adding the estimated crystal oscillator error.

17. An uplink synchronization method, characterized in that: include: Monitor downlink signals; Estimating a crystal oscillator error using the crystal oscillator error estimation method as described in any one of claims 1 to 11; The frequency offset of the uplink signal is pre-compensated based on the estimated crystal oscillator error.

18. The uplink synchronization method according to claim 17, characterized in that: The pre-compensating the uplink signal for frequency offset based on the estimated crystal oscillator error includes: Calculating a Doppler frequency deviation estimate of the downlink signal based on an estimated crystal oscillator error and an estimated carrier frequency deviation of the downlink signal; The frequency offset pre-compensation is performed on the uplink signal in a manner of subtracting the Doppler frequency offset estimation value and adding the estimated crystal oscillator error.

19. An uplink synchronization device, comprising a second processor and a second storage medium, wherein the second storage medium stores a computer program, characterized in that: The second processor executes the computer program to run the uplink synchronization method according to claim 17 or 18.

Images