A method, apparatus, and storage medium for positioning a low-Earth orbit satellite communication terminal.

Abstract

This application discloses a method, apparatus, and storage medium for locating low-Earth orbit (LEO) satellite communication terminals, relating to the field of satellite communication technology. The method includes: acquiring independent signal frames transmitted from ground terminals to LEO satellites within the coverage area of ​​a positioning station; extracting radio frequency (RF) fingerprint features of the independent signal frames, and clustering the independent signal frames using an unsupervised clustering algorithm based on the RF fingerprint features to determine the signal frame sets corresponding to each ground terminal; constructing a set of nonlinear overdetermined equations corresponding to the respective ground terminals based on the signal frame sets, wherein the nonlinear overdetermined equations represent the Doppler frequency shift between the corresponding ground terminal and the LEO satellite; and determining the location of the ground terminals based on the nonlinear overdetermined equations. Therefore, this application can autonomously complete the signal frame separation and location calculation for multiple ground terminals, possessing advantages such as no need for ground terminal cooperation, strong anti-interference capability, automatic multi-terminal sorting and identification, and no need for large-scale dedicated hardware deployment.

Description

Technical Field

[0001] This application relates to the field of satellite communication technology, and in particular to a low-orbit satellite communication terminal positioning method, device, and storage medium. Background Technology

[0002] Currently, low-Earth orbit (LEO) satellite communication terminal positioning technology has been widely used in many fields such as satellite Internet of Things (IoT), emergency communication, and aviation surveillance. However, existing LEO satellite communication terminal positioning technologies are mainly divided into two categories, both of which have obvious limitations and are difficult to meet the actual needs of positioning without network control, passive operation, and multiple terminals.

[0003] For example, the invention with publication number CN112242865A, entitled "A Satellite Communication Positioning System," includes multiple satellite communication positioning devices, a communication satellite, a satellite communication receiving gateway, a satellite integrated internet platform, and a terminal application platform. The satellite communication positioning devices receive or send field operation information to the communication satellite. The communication satellite receives the information and sends it to the satellite communication gateway device. The satellite communication gateway device uploads the received field operation information to the satellite internet platform via wired or wireless means. The satellite internet platform parses and encapsulates the received information and pushes it to the terminal application platform. The terminal application platform receives the information and calls the satellite internet platform interface for point-to-point or point-to-multipoint data interaction. The gateway device can be a dedicated gateway or a general-purpose device with software installed to connect to the server for transparent data transmission.

[0004] For example, the invention with publication number CN113242081A, entitled "An Intelligent Terminal Based on Tiantong Satellite Communication," includes: an application processing module, a Tiantong module, and a positioning and navigation module. The Tiantong module has a built-in radio frequency (RF) front-end module for connecting to a satellite antenna. The RF front-end module is used to transmit RF signals received or transmitted by the satellite antenna to the Tiantong module. The Tiantong module is connected to the application processing module. The Tiantong module includes a baseband processing unit, an RF processing unit, and power management and interface units. The baseband processing unit is connected to the RF processing unit. The baseband processing unit is used for RF signal processing and running the Tiantong standard protocol and physical layer software to achieve access to the Tiantong network. The RF processing unit is used for transmitting and receiving RF signals. The RF processing unit includes an RF transceiver chip controlled by the baseband processing unit. The RF transceiver chip is connected to the RF front-end module.

[0005] Specifically, the first category is positioning technology based on network control assistance. This technology relies on the demodulation of satellite downlink network control signals and requires the acquisition of key information such as the nominal operating frequency assigned to the terminal, the terminal ID, and time slot planning. Positioning is achieved through multi-satellite collaboration or direction finding. However, once the network control signal is encrypted, interfered with, or blocked, the positioning function will directly fail, exhibiting weak anti-interference capabilities and being completely unsuitable for scenarios without network control assistance.

[0006] The second category is passive positioning technology without network control. Most existing technologies of this type rely on collaborative observation from multiple satellites or direction-finding information from terminals, requiring the deployment of multiple sets of receiving equipment, resulting in high hardware costs. More importantly, this type of technology has not yet solved the problem of multi-terminal signal sorting—when multiple terminals simultaneously transmit in the airspace, it is impossible to distinguish the terminal affiliation of each signal frame, thus failing to complete the positioning calculation. Furthermore, existing passive positioning technologies often require preset frequency ranges or rely on additional equipment for frequency measurement, further limiting their applicable scenarios.

[0007] There are currently no effective solutions to the technical problems of the existing technologies, such as strong reliance on network control, weak anti-interference ability, difficulty in selecting multiple terminals, and high hardware deployment costs. Summary of the Invention

[0008] The embodiments of this disclosure provide a low-orbit satellite communication terminal positioning method, apparatus, and storage medium to at least solve the technical problems of strong network control dependence, weak anti-interference ability, difficulty in multi-terminal selection, and high hardware deployment cost in the prior art.

[0009] According to one aspect of the present disclosure, a method for locating a low-Earth orbit (LEO) satellite communication terminal is provided, comprising: acquiring independent signal frames transmitted from ground terminals to LEO satellites within the coverage area of ​​a positioning station; extracting radio frequency fingerprint features of the independent signal frames, and clustering the independent signal frames using an unsupervised clustering algorithm based on the radio frequency fingerprint features to determine signal frame sets corresponding to each ground terminal; constructing a set of nonlinear overdetermined equations corresponding to the corresponding ground terminal based on the set of signal frames, wherein the set of nonlinear overdetermined equations is used to represent the Doppler frequency shift between the corresponding ground terminal and the LEO satellite; and determining the location of the ground terminal based on the set of nonlinear overdetermined equations.

[0010] According to another aspect of the present disclosure, a storage medium is also provided, the storage medium including a stored program, wherein, when the program is executed, a processor performs any of the methods described above.

[0011] According to another aspect of the present disclosure, a low-Earth orbit satellite communication terminal positioning device is also provided, comprising: an independent signal frame acquisition module, configured to acquire independent signal frames transmitted from ground terminals to low-Earth orbit satellites within the coverage area of ​​a positioning station; a signal frame set determination module, configured to extract radio frequency fingerprint features of the independent signal frames, and cluster the independent signal frames using an unsupervised clustering algorithm based on the radio frequency fingerprint features to determine signal frame sets corresponding to each ground terminal; an equation system construction module, configured to construct a nonlinear overdetermined equation system corresponding to the corresponding ground terminal based on the signal frame set, wherein the nonlinear overdetermined equation system is used to represent the Doppler frequency shift between the corresponding ground terminal and the low-Earth orbit satellite; and a ground terminal position determination module, configured to determine the position of the ground terminal based on the nonlinear overdetermined equation system.

[0012] According to another aspect of the present disclosure, a low-Earth orbit satellite communication terminal positioning device is also provided, comprising: a processor; and a memory connected to the processor, configured to provide the processor with instructions for processing the following steps: acquiring independent signal frames transmitted by ground terminals to low-Earth orbit satellites within the coverage area of ​​a positioning station; extracting radio frequency fingerprint features of the independent signal frames, and clustering the independent signal frames using an unsupervised clustering algorithm based on the radio frequency fingerprint features to determine signal frame sets corresponding to each ground terminal; constructing a set of nonlinear overdetermined equations corresponding to the corresponding ground terminal based on the set of signal frames, wherein the set of nonlinear overdetermined equations is used to represent the Doppler frequency shift between the corresponding ground terminal and the low-Earth orbit satellite; and determining the location of the ground terminal based on the set of nonlinear overdetermined equations.

[0013] This application first receives uplink radio frequency signals transmitted from ground terminals within the coverage area of ​​the positioning station to low-Earth orbit satellites via broadband reconnaissance. After time-domain energy detection, the effective signal range and signal silence interval of the uplink radio frequency signals are identified. Thus, by segmenting the effective signal range, independent signal frames transmitted from each ground terminal to the low-Earth orbit satellite are obtained. Then, the radio frequency fingerprint features of each independent signal frame are extracted. Subsequently, based on these radio frequency fingerprint features, an unsupervised clustering algorithm is used to classify and group all the mixed independent signal frames, creating a set of signal frames corresponding one-to-one with each ground terminal. Next, for each set of signal frames, a multi-time observation equation is established. Based on the multi-time observation equation, a nonlinear overdetermined system of equations is constructed with the three-dimensional spatial coordinates of the ground terminal and the nominal operating frequency as unknowns. Finally, the nonlinear overdetermined system of equations is optimized and solved using a least-squares iterative algorithm to ultimately determine the three-dimensional spatial coordinates of each ground terminal.

[0014] Therefore, this application can independently complete the signal frame separation and location calculation of multiple ground terminals, possessing the advantages of no terminal cooperation, strong anti-interference capability, automatic multi-terminal sorting and identification, and no need for large-scale dedicated hardware deployment. This solves the technical problems of strong network control dependence, weak anti-interference capability, difficulty in multi-terminal sorting, and high hardware deployment costs in existing technologies. Attached Figure Description

[0015] The accompanying drawings, which are included to provide a further understanding of this disclosure and form part of this application, illustrate exemplary embodiments of this disclosure and are used to explain this disclosure, but do not constitute an undue limitation of this disclosure. In the drawings: Figure 1 This is a schematic diagram of a low-orbit satellite communication terminal positioning system according to Embodiment 1 of this disclosure; Figure 2 This is a hardware structure block diagram of the positioning station of the low-orbit satellite communication terminal positioning method according to Embodiment 1 of this disclosure; Figure 3 This is a flowchart illustrating the low-orbit satellite communication terminal positioning method according to Embodiment 1 of this disclosure; Figure 4 This is a schematic diagram of the clustering results of independent signal frames according to the method described in Embodiment 1 of this disclosure; Figure 5 This is a schematic diagram of a low-orbit satellite communication terminal positioning device according to Embodiment 2 of this disclosure; Figure 6 This is a schematic diagram of a low-orbit satellite communication terminal positioning device according to Embodiment 3 of this disclosure. Detailed Implementation

[0016] To enable those skilled in the art to better understand the technical solutions of this disclosure, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0017] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0018] Example 1

[0019] According to this embodiment, a method for positioning a low-orbit satellite communication terminal is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0020] Figure 1 A schematic diagram of a low-Earth orbit satellite communication terminal system according to this embodiment is shown. (Refer to...) Figure 1 As shown, the system includes a low-Earth orbit satellite 10, a ground terminal 20, and a positioning station 30. The low-Earth orbit satellite 10 orbits the Earth at high speed along a predetermined orbit, and its position and velocity at any given time are known ephemeris information. The ground terminal 20 calculates the Doppler frequency shift based on the real-time position and velocity of the low-Earth orbit satellite 10 before transmitting uplink radio frequency signals, and performs Doppler frequency pre-compensation on the uplink radio frequency signals to ensure that the uplink radio frequency signals can be correctly received by the low-Earth orbit satellite 10. The positioning station 30 is a single-station passive broadband receiving device used to detect uplink radio frequency signals transmitted by all ground terminals 20 within its coverage area. The positioning station 30 cannot demodulate downlink network control signals transmitted by the low-Earth orbit satellite 10, nor can it obtain the nominal operating frequency, terminal identification, or time slot planning information of the ground terminals 20.

[0021] Figure 2 Further shown Figure 1 A schematic diagram of the hardware architecture of the positioning station 30. (Reference) Figure 2As shown, the positioning station 30 may include one or more processors (processors may include, but are not limited to, microprocessors such as MCUs or programmable logic devices such as FPGAs), a memory for storing data, a transmission device for communication functions, and an input / output interface. The memory, transmission device, and input / output interface are connected to the processor via a bus. In addition, it may also include a display, keyboard, and cursor control device connected to the input / output interface. Those skilled in the art will understand that... Figure 2 The structure shown is for illustrative purposes only and does not limit the structure of the aforementioned electronic device. For example, the positioning station 30 may also include... Figure 2 The more or fewer components shown, or having the same Figure 2 The different configurations shown.

[0022] It should be noted that, Figure 2 One or more processors and / or other data processing circuits shown herein may generally be referred to as "data processing circuitry". This data processing circuitry may be embodied, in whole or in part, in software, hardware, firmware, or any other combination thereof. Furthermore, the data processing circuitry may be a single, independent processing module, or may be integrated, in whole or in part, into any other element in a computing device. As involved in embodiments of this disclosure, the data processing circuitry serves as processor control (e.g., selection of a variable resistor termination path connected to an interface).

[0023] Figure 2 The memory shown can be used to store software programs and modules of application software, such as the program instruction / data storage device corresponding to the low-Earth orbit satellite communication terminal positioning method in this embodiment of the present disclosure. The processor executes various functional applications and data processing by running the software programs and modules stored in the memory, thereby realizing the low-Earth orbit satellite communication terminal positioning method of the above-mentioned application. The memory may include high-speed random access memory, and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory.

[0024] It should be noted here that, in some optional embodiments, the above... Figure 2 The device shown may include hardware elements (including circuitry), software elements (including computer code stored on a computer-readable medium), or a combination of both hardware and software elements. It should be noted that... Figure 2 This is only one instance of a specific particular instance, and is intended to illustrate the types of components that may exist in the aforementioned devices.

[0025] Under the aforementioned operating environment, according to the first aspect of this embodiment, a low-Earth orbit satellite communication terminal positioning method is provided, which consists of... Figure 2 The positioning station 30 shown is implemented. Figure 3 A flowchart illustrating the method is shown below. (Refer to...) Figure 3 As shown, the method includes: S302: Acquire independent signal frames sent from ground terminals to low-orbit satellites within the coverage area of ​​the positioning station; S304: Extract the radio frequency fingerprint features of independent signal frames, and based on the radio frequency fingerprint features, use an unsupervised clustering algorithm to cluster the independent signal frames to determine the set of signal frames corresponding to each ground terminal. S306: Construct a set of nonlinear overdetermined equations corresponding to the ground terminal based on the set of signal frames, wherein the set of nonlinear overdetermined equations is used to represent the Doppler frequency shift between the corresponding ground terminal and the low-orbit satellite; S308: Determine the location of the ground terminal based on the nonlinear overdetermined equations.

[0026] Specifically, the positioning station 30 first receives the uplink radio frequency signal transmitted from the ground terminal 20 to the low-Earth orbit satellite 10 within its coverage area via broadband detection. Then, the positioning station 30 performs time-domain energy detection on the uplink radio frequency signal to identify the effective signal range and signal silence interval of the uplink radio frequency signal, thereby dividing the signal into independent signal frames transmitted from each ground terminal 20 to the low-Earth orbit satellite 10 according to the effective signal range (corresponding to step S302).

[0027] Specifically, the positioning station 30 continuously collects uplink radio frequency signals transmitted directionally from the ground terminal 20 to the low-Earth orbit satellite 10, and performs time-domain energy detection on the continuously collected uplink radio frequency signals. Then, the positioning station 30 compares the instantaneous energy of the uplink radio frequency signal with a preset noise threshold to distinguish between background noise and valid communication signals. When the instantaneous energy of the uplink radio frequency signal exceeds the preset noise threshold, the positioning station 30 determines the uplink radio frequency signal as a valid signal range. When the instantaneous energy of the uplink radio frequency signal is lower than the preset noise threshold, the positioning station 30 determines the uplink radio frequency signal as a signal silence gap.

[0028] Furthermore, the positioning station identifies the rising edge of the uplink radio frequency signal (the moment when the instantaneous energy jumps from below a preset noise threshold to above a preset noise threshold) as the start time of an independent signal frame for each of the 30 detected effective signal intervals. Simultaneously, the positioning station identifies the falling edge of the uplink radio frequency signal (the moment when the instantaneous energy decreases from above a preset noise threshold to below a preset noise threshold) as the end time of an independent signal frame for each pair of detected effective signal intervals. .

[0029] Next, the positioning station 30 determines the start and end times of the identified uplink radio frequency signal. The continuous uplink radio frequency signals are divided into time domains to obtain independent signal frames transmitted separately by each ground terminal, which do not interfere with each other and have complete frame structures. ~ Where n is the total number of independent signal frames.

[0030] Furthermore, after acquiring the independent signal frames sent from the ground terminals 20 to the low-Earth orbit satellite 10, the positioning station 30 processes each independent signal frame... (j=1, 2, ..., n) Perform comprehensive analysis in both the time and frequency domains to extract the unique radio frequency fingerprint feature that can characterize the ground terminal 20 to which the independent signal frame belongs (corresponding to the first half of step S304). Then, the positioning station 30 integrates the extracted radio frequency fingerprint features to construct a multi-dimensional radio frequency fingerprint feature vector. This serves as the identifier for each independent signal frame. The radio frequency fingerprint feature is used to characterize the inherent hardware differences and subtle waveform features of the uplink radio frequency signals transmitted by different ground terminals 20.

[0031] Subsequently, positioning station 30 uses unsupervised clustering algorithms (such as DBSCAN or K-Means) to perform clustering on all independent signal frames. ~ Corresponding multidimensional radio frequency fingerprint feature vector ~ Cluster analysis is performed. Then, based on the cluster analysis results, the positioning station 30 divides independent signal frames transmitted by the same ground terminal 20 into the same cluster category. Each cluster category corresponds to one ground terminal 20, ultimately forming a set of signal frames that corresponds one-to-one with each ground terminal 20 (there are multiple ground terminals 20, for example, ground terminal 201 to ground terminal 20m). ~ (Corresponding to the second half of step S304). Where m is the total number of ground terminals 20 and m < n, and each signal frame set... (q=1, 2, ..., m) each includes multiple independent signal frames.

[0032] For example, refer to Figure 4 As shown, the signal frame set corresponding to ground terminal 201 ; Ground terminal 202 corresponding signal frame set ; And so on, Ground terminal 20m corresponding signal frame set .

[0033] It should be noted that, ~ All belong to the range 1 to n. The method for clustering the multidimensional radio frequency fingerprint feature vectors corresponding to all independent signal frames will be explained later.

[0034] Next, for a set of signal frames belonging to the same ground terminal 20, the positioning station 30 extracts the measured frequencies corresponding to each independent signal frame within the set and establishes multi-time observation equations. Then, based on the multi-time observation equations, the positioning station 30 constructs a set of nonlinear overdetermined equations with the three-dimensional spatial coordinates of the ground terminal 20 and the nominal operating frequency as unknowns. This set of nonlinear overdetermined equations quantitatively characterizes the Doppler frequency shift correlation caused by the relative motion between the ground terminal 20 and the low-Earth orbit satellite 10 at different observation times (corresponding to step S306).

[0035] Finally, the positioning station 30 uses the least squares iterative solution algorithm to numerically solve the constructed nonlinear overdetermined equations to determine the three-dimensional spatial coordinates of the ground terminal 20 (corresponding to step S308). The solution process for the nonlinear overdetermined equations will be explained later.

[0036] As described in the background section, existing low-Earth orbit satellite communication terminal positioning technologies mainly fall into two categories, both of which have significant limitations and struggle to meet the practical needs of positioning without network control, passive positioning, and multi-terminal positioning. Specifically, the first category is network control-assisted positioning technology. This technology relies on demodulation of satellite downlink network control signals and requires obtaining key information such as the terminal's assigned nominal operating frequency, terminal ID, and time slot planning. Positioning is achieved through multi-satellite collaboration or direction finding. However, once the network control signal is encrypted, interfered with, or blocked, the positioning function will directly fail, exhibiting weak anti-interference capabilities and being completely unsuitable for scenarios without network control. The second category is network-free passive positioning technology. Existing technologies of this type mostly rely on multi-satellite collaborative observation or terminal direction finding information, requiring the deployment of multiple sets of receiving equipment, resulting in high hardware costs. More importantly, this type of technology has not yet solved the problem of multi-terminal signal sorting—when multiple terminals simultaneously transmit in the airspace, it is impossible to distinguish the terminal affiliation of each signal frame, thus failing to complete the positioning calculation. Furthermore, existing network-free positioning technologies often require preset frequency ranges or rely on additional equipment for frequency measurement, further limiting their applicable scenarios.

[0037] In view of this, this application first receives uplink radio frequency signals transmitted from ground terminals within the coverage area of ​​the positioning station to low-Earth orbit satellites via broadband reconnaissance. After time-domain energy detection, the effective signal range and signal silence interval of the uplink radio frequency signal are identified. Thus, by segmenting the effective signal range, independent signal frames transmitted from each ground terminal to the low-Earth orbit satellite are obtained. Then, the radio frequency fingerprint features of each independent signal frame are extracted. Subsequently, based on these radio frequency fingerprint features, an unsupervised clustering algorithm is used to classify and group all the mixed independent signal frames, dividing them into signal frame sets corresponding one-to-one with each ground terminal. Then, for each signal frame set, a multi-time observation equation is established, and based on the multi-time observation equation, a nonlinear overdetermined system of equations is constructed with the three-dimensional spatial coordinates of the ground terminal and the nominal operating frequency as unknowns. Finally, the nonlinear overdetermined system of equations is optimized and solved using a least-squares iterative algorithm to ultimately determine the three-dimensional spatial coordinates of each ground terminal.

[0038] Therefore, this application can independently complete the signal frame separation and position calculation of multiple ground terminals, and has the advantages of not requiring terminal cooperation, strong anti-interference ability, automatic sorting and identification of multiple terminals, and no need for large-scale dedicated hardware deployment. Thus, it solves the technical problems of strong network control dependence, weak anti-interference ability, difficulty in sorting multiple terminals, and high hardware deployment cost in the prior art.

[0039] Optionally, the operation of extracting the radio frequency fingerprint features of the independent signal frame includes: performing time-domain analysis and frequency-domain analysis on the independent signal frame to extract the radio frequency fingerprint features of the independent signal frame, wherein the radio frequency fingerprint features include one or more of the following: signal frame duration, signal peak amplitude, peak frequency of the spectrum, 3dB bandwidth of the spectrum, standard deviation of the time-domain amplitude, signal start-up time, signal fall time, I / Q branch amplitude ratio, peak phase noise, and peak spurious signal.

[0040] Specifically, the positioning station pairs each independent signal frame 30 Time-domain and frequency-domain analyses are performed separately. That is, positioning station 30 extracts each independent signal frame from the time domain. Duration of signal frames in Signal peak amplitude Time-domain amplitude standard deviation Signal start-up time Signal descent time Furthermore, positioning station 30 extracts each independent signal frame from the frequency domain. Peak frequency in the spectrum 3dB bandwidth of spectrum I / Q branch amplitude ratio Phase noise peak spurious signal peak Then, the positioning station 30 combines any one or more of the time-domain and frequency-domain feature parameters mentioned above and uses them as a unified radio frequency fingerprint feature of an independent signal frame to characterize the inherent hardware differences in the uplink radio frequency signals transmitted by different ground terminals 20.

[0041] Among them, the duration of the signal frame Independent signal frames From the start time of the uplink radio frequency signal Until the end time The complete duration. This is determined by the transmission protocol and hardware driving characteristics of the ground terminal 20; different ground terminals 20 have slight differences, which the positioning station 30 can directly extract. That is: (1) signal peak amplitude Independent signal frames The maximum signal amplitude that the time-domain waveform can reach is determined by the power amplifier hardware characteristics of the ground terminal 20. Different ground terminals 20 have inherent differences in the peak output of their power amplifiers. Without any calculation, the positioning station 30 can directly read the independent signal frames. Time-domain amplitude sequence The maximum value. That is: (2) Peak frequency of the spectrum This refers to the center peak frequency corresponding to the location where the signal spectrum energy is concentrated. In other words, the positioning station has 30 pairs of independent signal frames. Perform a Fast Fourier Transform to obtain the spectral amplitude sequence. The spectral amplitude sequence The frequency corresponding to the maximum amplitude of the spectrum is the peak frequency of the spectrum. Therefore, positioning station 30 can directly read from the spectrum diagram.

[0042] 3dB bandwidth of spectrum It is a positioning station with 30 pairs of independent signal frames. The spectrum is analyzed by directly measuring the frequency range corresponding to a 3dB drop in the amplitude of the spectral peak, which is obtained through spectrum measurement. That is, (3) in, The upper cutoff frequency is the frequency at which the amplitude of the peak value drops by 3dB. This is the lower cutoff frequency where the amplitude of the peak value in the spectrum drops by 3dB.

[0043] Time-domain amplitude standard deviation Independent signal frames The degree of dispersion of the overall fluctuation of the time-domain amplitude. It can be calculated by positioning station 30 according to the following formula: (4) Where N is the number of sampling points in the signal frame. The average amplitude in the time domain. The first value in the time-domain amplitude sequence The t-th observation time of a sampled signal frame.

[0044] Signal start-up time This refers to the time required for the signal to rise from a quiet noise level to a stable operating level, i.e., the time it takes for the uplink RF signal to reach 90% of its peak amplitude from the start. It can be obtained directly from an independent signal frame by the positioning station 30. Measured in the time-domain waveform and read directly from the time-domain waveform.

[0045] signal fall time This is the time required for the signal to drop from a stable operating level to a quiet noise level, i.e., the time it takes for the uplink RF signal to decrease from 90% of its peak amplitude to 10%. It is related to the signal start-up time. Correspondingly, all values ​​can be directly measured from the time-domain waveform by the positioning station 30 and read directly.

[0046] I / Q branch amplitude ratio This represents the amplitude ratio between the in-phase branch and the quadrature branch of the signal. Specifically, this is the amplitude ratio of the I / Q branch. The ratio of the amplitude of the I-branch to the amplitude of the Q-branch can be directly calculated by demodulating the j-th independent signal frame using 1 / Q at positioning station 30. That is: (5) Phase noise peak It is a positioning station with 30 pairs of independent signal frames. After performing spectrum analysis, the maximum phase noise value at a frequency offset of 1 kHz is directly read.

[0047] Spurious signal peak This is the maximum peak value of spurious radiation outside the signal's operating frequency band. That is, the peak value of this spurious signal. It can be generated by 30 independent signal frames from the positioning station. Analyze the spectrum and eliminate useful signal frequency bands (based on peak frequency). Centered on the spectrum, 3dB bandwidth (Within), the maximum amplitude of spurious signals in the remaining frequency band can be directly read without the need for additional definition standards; direct measurement is sufficient.

[0048] Thus, the above methods provide quantifiable feature basis for subsequent sorting and classification of independent signal frames by ground terminals 20 using unsupervised clustering algorithms, and for dividing the signal frame sets corresponding to each ground terminal 20.

[0049] Optionally, based on the radio frequency fingerprint features, an unsupervised clustering algorithm is used to cluster independent signal frames to determine the signal frame sets corresponding to each ground terminal. This operation includes: constructing a multi-dimensional radio frequency fingerprint feature vector based on the radio frequency fingerprint features; and dividing independent signal frames whose similarity to the multi-dimensional radio frequency fingerprint feature vectors meets preset conditions into the same cluster category based on the unsupervised clustering algorithm, thereby determining the signal frame sets corresponding to each ground terminal.

[0050] Specifically, the positioning station 30 first normalizes the extracted 10 radio frequency fingerprint features in sequence (eliminating the influence of dimensions and avoiding excessive influence of a single radio frequency fingerprint feature on the clustering results). Then, the positioning station 30 constructs each independent signal frame. Multidimensional radio frequency fingerprint feature vector The specific form is as follows: .

[0051] Subsequently, the positioning station 30 calculates the spatial similarity distance between each multidimensional radio frequency fingerprint feature vector using an unsupervised clustering algorithm, and sets a preset threshold condition for similarity judgment. Then, the positioning station 30 classifies the independent signal frames corresponding to multidimensional radio frequency fingerprint feature vectors whose spatial similarity meets the preset threshold requirement and whose feature distribution patterns tend to be consistent into the same cluster category. Among them, different cluster categories correspond to the inherent hardware attribute differences of different ground terminals 20, so the positioning station 30 can automatically distinguish independent signal frames that do not belong to the same ground terminal 20, and finally divide and determine the signal frame set that corresponds one-to-one with each ground terminal 20.

[0052] Thus, through the above methods, passive sorting and attribution of mixed independent signal frames from multiple ground terminals 20 can be achieved, and autonomous classification can be completed without pre-entering the identity information of the ground terminals 20.

[0053] Optionally, the method further includes: sorting the measured frequencies corresponding to independent signal frames in the same signal frame set according to the transmission time, and determining the timing observation frequency sequence of the corresponding ground terminal.

[0054] Specifically, after dividing the signal frame sets corresponding to each ground terminal 20, the positioning station 30 extracts the measured frequencies corresponding to each independent signal frame within the same signal frame set. Then, the positioning station 30 sorts the signals in ascending order according to the transmission time of each independent signal frame, and organizes them into a time-continuous and time-aligned measured frequency sequence, thereby determining the time-series observation frequency sequence that uniquely corresponds to the ground terminal 20.

[0055] Thus, the above methods provide a standardized time-series observation data source for subsequently combining low-orbit satellite ephemeris information to construct a set of nonlinear overdetermined equations characterizing the Doppler frequency shift relationship.

[0056] Optionally, the operation of constructing a set of nonlinear overdetermined equations corresponding to the ground terminal based on the signal frame set includes: constructing multi-time observation equations based on the measured frequency of each independent signal frame in the signal frame set, the position and velocity information of the low-orbit satellite at the corresponding observation time, and the Doppler pre-compensation relationship of the uplink radio frequency signal of the ground terminal; and constructing a set of nonlinear overdetermined equations with the three-dimensional spatial coordinates and nominal operating frequency of the ground terminal as unknowns based on the Earth's spherical constraint conditions, wherein the Earth's spherical constraint conditions are that a coordinate system is established with the Earth's center as the origin, and the magnitude of the position vector of the ground terminal is equal to the average radius of the Earth.

[0057] Specifically, for a set of signal frames belonging to the same ground terminal 20, the positioning station 30 sequentially extracts the measured frequency corresponding to each independent signal frame within the set. Then, the positioning station 30 matches the ephemeris data of the low-orbit satellite 10 corresponding to each observation time, thereby obtaining the three-dimensional spatial coordinate information and three-dimensional orbital velocity information of the low-orbit satellite 10 at the corresponding observation time.

[0058] Furthermore, to compensate for the Doppler frequency shift between the low-Earth orbit satellite 10 and itself, and to ensure that its transmitted uplink radio frequency signal can be correctly received by the low-Earth orbit satellite 10, the ground terminal 20 will perform Doppler pre-compensation before transmitting the uplink radio frequency signal. That is: (6) In the formula, For the i-th observation time, the measured frequency received by positioning station 30; This is the nominal operating frequency of the ground terminal 20. The actual Doppler shift between ground terminal 20 and low-orbit satellite 10 at the i-th observation time.

[0059] It should be noted that the actual Doppler frequency shift between the ground terminal 20 and the low-orbit satellite 10 is determined by their radial relative velocity, and its theoretical formula is as follows: (7) Where c is the speed of light in a vacuum. = The three-dimensional spatial coordinates of the ground terminal. These are the coordinate components of the three-dimensional spatial coordinates of the ground terminal 20; For the i-th observation time, the velocity vector of low-orbit satellite 10; For the i-th observation time, the position vector of low-orbit satellite 10; Let be the dot product of the velocity vector of the low-Earth orbit satellite 10 and the satellite-terminal line-of-sight vector, that is, represent the magnitude of the projection component of the velocity vector of the low-Earth orbit satellite 10 in the line-of-sight direction multiplied by the line-of-sight distance. The distance between the ground terminal 20 and the low-Earth orbit satellite 10 is the distance between them. The ratio of the two is the radial relative velocity of the low-Earth orbit satellite 10 relative to the ground terminal 20.

[0060] Therefore, the positioning station 30 will combine the Doppler pre-compensation relationship when the ground terminal 20 transmits uplink radio frequency signals to the low-orbit satellite 10 to establish independent multi-time observation equations for each observation moment, forming a set of simultaneous multi-time observation equations (nonlinear overdetermined equations). The specific construction formula of the multi-time observation equations will be explained later.

[0061] Simultaneously, positioning station 30 establishes a geocentric rectangular coordinate system with the Earth's center as the origin, sets the Earth's average radius R as a fixed constant, and introduces the Earth's spherical constraint condition. This Earth's spherical constraint condition is: the magnitude of the spatial position vector of ground terminal 20 is always equal to the Earth's average radius, thus limiting ground terminal 20 to be located on the Earth's surface. That is: (8) Then, the positioning station 30 combines the multi-time observation equations with the equations constrained by the Earth's sphere to form a unified nonlinear overdetermined set of equations with the three-dimensional spatial coordinates of the ground terminal 20 and the nominal operating frequency as the unknowns to be solved.

[0062] Thus, the above methods can provide a complete mathematical model and constraints for subsequent iterative calculations of the location of the ground terminal 20.

[0063] Optionally, this includes: constructing a multi-time observation equation based on the following formula:

[0064] in, For the i-th observation time, the measured frequency received by the positioning station; is the nominal operating frequency of the ground terminal; c is the speed of light in a vacuum; The three-dimensional spatial coordinates of the ground terminal; The velocity vector of the low-orbit satellite at the i-th observation time; For the i-th observation time, the position vector of the low-orbit satellite.

[0065] Specifically, the positioning station 30 can obtain the following multi-time observation equations according to formulas (6) and (7): (9) in, For the i-th observation time, the measured frequency received by positioning station 30; is the nominal operating frequency of ground terminal 20; c is the speed of light in a vacuum; The three-dimensional spatial coordinates of the ground terminal 20; For the i-th observation time, the velocity vector of low-orbit satellite 10; For the i-th observation time, the position vector of low-orbit satellite 10.

[0066] Thus, this equation establishes the measured frequency. With unknown quantities ( The direct relationship between them is the basis for location solution.

[0067] Furthermore, positioning station 30 takes k consecutive observation times (k≥3), and each observation time can yield a multi-time observation equation as shown in formula (9), forming a set of multi-time observation equations: (10) Therefore, the location of the ground terminal 20 can be determined by solving the multi-time observation equation set by least squares optimization according to formula (8) and formula (10).

[0068] Optionally, the operation of determining the location of the ground terminal based on the nonlinear overdetermined equations includes: constructing a residual sum of squares objective function, wherein the residual sum of squares objective function is used to indicate the sum of squares of the differences between the measured frequency and the predicted frequency calculated based on the Doppler frequency shift model at each observation time; and determining the location of the ground terminal based on the residual sum of squares objective function.

[0069] Specifically, since the nonlinear overdetermined system of equations cannot be solved analytically directly, the positioning station 30 needs to use the least squares criterion to construct the objective function and solve the unknowns through a numerical iterative algorithm to ensure the optimality of the solution.

[0070] Specifically, positioning station 30 constructs an objective function to measure the deviation between the measured frequency and the nominal operating frequency: (11) in, These are represented as coordinate components in the three-dimensional spatial coordinate system of the ground terminal 20; is the nominal operating frequency of ground terminal 20; k is the total number of observation times; c is the speed of light in a vacuum; The three-dimensional spatial coordinates of the ground terminal 20; For the i-th observation time, the velocity vector of low-orbit satellite 10; For the i-th observation time, the position vector of low-orbit satellite 10.

[0071] Then, positioning station 30 uses a Gauss-Newton or LM iterative algorithm to minimize the residual objective function, while blindly estimating the position and nominal operating frequency of ground terminal 20. First, positioning station 30 initializes the initial values ​​of unknowns: setting the initial three-dimensional spatial coordinates of ground terminal 20. = Compared with the initial nominal operating frequency .in, These are the initial coordinate components of the initial three-dimensional spatial coordinates of the ground terminal 20. Simultaneously, the initial three-dimensional spatial coordinates must satisfy the Earth's spherical constraint condition: (12) And the initial value vector of the unknowns is denoted as It is initialized to t=1.

[0072] Furthermore, the positioning station 30 will initialize the vector of the current unknowns. Substitute the equation (9) into the multi-time observation equation to calculate the model prediction frequency at each observation time. The calculation formula is as follows: (13) in, These are the current three-dimensional spatial coordinates of ground terminal 20. The current coordinate components. Current nominal operating frequency .

[0073] Simultaneously, positioning station 30 calculates the current value of the objective function. The formula is: (14) Next, positioning station 30 constructs the residual vector and Jacobian matrix according to formula (14). Wherein, the residual vector... Defined as the difference between the measured frequency and the predicted frequency, i.e. Jacobian matrix for An n-order matrix whose elements are the first-order partial derivatives of the objective function J with respect to each unknown.

[0074] Then, positioning station 30 uses the LM iterative algorithm to solve for the correction amount. : (15) in The damping factor at the t-th observation time ( ≥0 is used to adjust the stability of iteration and avoid matrix singularities. Jacobian matrix The transpose of , where F is the 4th order identity matrix.

[0075] Next, positioning station 30 updates the estimated value of the unknowns for the next observation time according to the following formula. : (16) It should be noted that the updated estimates of unknown quantities After the update, the Earth's spherical surface constraint condition must be satisfied again. The constraint correction formula is as follows: (17) Subsequently, positioning station 30 performs iterative convergence judgment and calculates the updated objective function value. The convergence criterion is as follows: (18) In the formula, This is the convergence threshold.

[0076] If the current iteration meets the convergence condition, positioning station 30 stops iterating; if the current iteration does not meet the convergence condition, positioning station 30 proceeds to the next iteration, adjusting the damping factor at the (t+1)th observation time. (like The number of positioning stations will decrease if the number of stations is 30. Conversely, it increases. Until the maximum number of iterations is reached. .Right now: (19) After iterative convergence, positioning station 30 outputs the optimal estimate of the unknowns. .in, The final coordinate components of the final three-dimensional spatial coordinates of the ground terminal 20. This is the final nominal operating frequency of the ground terminal 20. Additionally, the final formula for converting three-dimensional spatial coordinates to latitude is: (20) The formula for converting three-dimensional spatial coordinates to longitude is: (twenty one) The error verification formula includes positioning error. and frequency estimation error Positioning error for: (twenty two) Frequency estimation error for: (twenty three) in, This refers to the actual nominal operating frequency of the ground terminal 20. The actual coordinate components are the actual three-dimensional spatial coordinates of the ground terminal 20.

[0077] In addition, refer to Figure 1 As shown, according to a second aspect of this embodiment, a storage medium is provided. The storage medium includes a stored program, wherein, when the program is executed, a processor performs any of the methods described above.

[0078] Therefore, according to this embodiment, this application can autonomously complete the signal frame separation and location calculation of multiple ground terminals, possessing the advantages of no terminal cooperation required, strong anti-interference capability, automatic multi-terminal sorting and identification, and no need for large-scale dedicated hardware deployment. This solves the technical problems of strong network control dependence, weak anti-interference capability, difficulty in multi-terminal sorting, and high hardware deployment costs in the prior art.

[0079] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0080] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods according to the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0081] Example 2

[0082] Figure 5 A low-Earth orbit satellite communication terminal positioning device according to this embodiment is shown, which corresponds to the method described according to Embodiment 1. (Reference) Figure 5As shown, the device includes: an independent signal frame acquisition module 510, used to acquire independent signal frames transmitted from ground terminals to low-Earth orbit satellites within the coverage area of ​​the positioning station; a signal frame set determination module 520, used to extract the radio frequency fingerprint features of the independent signal frames, and based on the radio frequency fingerprint features, use an unsupervised clustering algorithm to cluster the independent signal frames to determine the signal frame sets corresponding to each ground terminal; an equation system construction module 530, used to construct a nonlinear overdetermined equation system corresponding to the corresponding ground terminal based on the signal frame set, wherein the nonlinear overdetermined equation system is used to represent the Doppler frequency shift between the corresponding ground terminal and the low-Earth orbit satellite; and a ground terminal location determination module 540, used to determine the location of the ground terminal based on the nonlinear overdetermined equation system.

[0083] Optionally, the operation of extracting the radio frequency fingerprint features of independent signal frames includes: performing time-domain analysis and frequency-domain analysis on independent signal frames to extract radio frequency fingerprint features of independent signal frames, wherein the radio frequency fingerprint features include one or more of the following: signal frame duration, signal peak amplitude, peak frequency of the spectrum, 3dB bandwidth of the spectrum, standard deviation of time-domain amplitude, signal start-up time, signal fall time, I / Q branch amplitude ratio, peak phase noise, and peak spurious signal.

[0084] Optionally, based on the radio frequency fingerprint features, an unsupervised clustering algorithm is used to cluster independent signal frames to determine the signal frame sets corresponding to each ground terminal. This operation includes: constructing a multi-dimensional radio frequency fingerprint feature vector based on the radio frequency fingerprint features; and dividing independent signal frames whose similarity to the multi-dimensional radio frequency fingerprint feature vectors meets preset conditions into the same cluster category based on the unsupervised clustering algorithm, thereby determining the signal frame sets corresponding to each ground terminal.

[0085] Optionally, the device further includes: sorting the measured frequencies corresponding to independent signal frames in the same signal frame set according to the transmission time, and determining the timing observation frequency sequence of the corresponding ground terminal.

[0086] Optionally, the operation of constructing a set of nonlinear overdetermined equations corresponding to the ground terminal based on the signal frame set includes: constructing multi-time observation equations based on the measured frequency of each independent signal frame in the signal frame set, the position and velocity information of the low-orbit satellite at the corresponding observation time, and the Doppler pre-compensation relationship of the uplink radio frequency signal of the ground terminal; and constructing a set of nonlinear overdetermined equations with the three-dimensional spatial coordinates and nominal operating frequency of the ground terminal as unknowns based on the Earth's spherical constraint conditions, wherein the Earth's spherical constraint conditions are that a coordinate system is established with the Earth's center as the origin, and the magnitude of the position vector of the ground terminal is equal to the average radius of the Earth.

[0087] Optionally, the equation system construction module 530 includes: constructing multi-time observation equations according to the following formula:

[0088] in, For the i-th observation time, the measured frequency received by the positioning station; is the nominal operating frequency of the ground terminal; c is the speed of light in a vacuum; The three-dimensional spatial coordinates of the ground terminal; The velocity vector of the low-orbit satellite at the i-th observation time; For the i-th observation time, the position vector of the low-orbit satellite.

[0089] Optionally, the operation of determining the location of the ground terminal based on the nonlinear overdetermined equations includes: constructing a residual sum of squares objective function, wherein the residual sum of squares objective function is used to indicate the sum of squares of the differences between the measured frequency and the predicted frequency calculated based on the Doppler frequency shift model at each observation time; and determining the location of the ground terminal based on the residual sum of squares objective function.

[0090] Therefore, according to this embodiment, this application can autonomously complete the signal frame separation and location calculation of multiple ground terminals, possessing the advantages of no terminal cooperation required, strong anti-interference capability, automatic multi-terminal sorting and identification, and no need for large-scale dedicated hardware deployment. This solves the technical problems of strong network control dependence, weak anti-interference capability, difficulty in multi-terminal sorting, and high hardware deployment costs in the prior art.

[0091] Example 3

[0092] Figure 6 A low-Earth orbit satellite communication terminal positioning device according to this embodiment is shown, which corresponds to the method described according to Embodiment 1. (Reference) Figure 6 As shown, the device includes: a processor 610; and a memory 620 connected to the processor 610, used to provide the processor 610 with instructions to process the following steps: acquiring independent signal frames transmitted by ground terminals within the coverage area of ​​the positioning station to low-Earth orbit satellites; extracting the radio frequency fingerprint features of the independent signal frames, and clustering the independent signal frames using an unsupervised clustering algorithm based on the radio frequency fingerprint features to determine the signal frame sets corresponding to each ground terminal; constructing a set of nonlinear overdetermined equations corresponding to the corresponding ground terminal based on the signal frame sets, wherein the set of nonlinear overdetermined equations is used to represent the Doppler frequency shift between the corresponding ground terminal and the low-Earth orbit satellite; and determining the location of the ground terminal based on the set of nonlinear overdetermined equations.

[0093] Optionally, the operation of extracting the radio frequency fingerprint features of independent signal frames includes: performing time-domain analysis and frequency-domain analysis on independent signal frames to extract radio frequency fingerprint features of independent signal frames, wherein the radio frequency fingerprint features include one or more of the following: signal frame duration, signal peak amplitude, peak frequency of the spectrum, 3dB bandwidth of the spectrum, standard deviation of time-domain amplitude, signal start-up time, signal fall time, I / Q branch amplitude ratio, peak phase noise, and peak spurious signal.

[0094] Optionally, based on the radio frequency fingerprint features, an unsupervised clustering algorithm is used to cluster independent signal frames to determine the signal frame sets corresponding to each ground terminal. This operation includes: constructing a multi-dimensional radio frequency fingerprint feature vector based on the radio frequency fingerprint features; and dividing independent signal frames whose similarity to the multi-dimensional radio frequency fingerprint feature vectors meets preset conditions into the same cluster category based on the unsupervised clustering algorithm, thereby determining the signal frame sets corresponding to each ground terminal.

[0095] Optionally, the memory 620 is also used to provide the processor 610 with instructions to process the following processing steps: sorting the measured frequencies corresponding to independent signal frames in the same set of signal frames according to the transmission time, and determining the timing observation frequency sequence of the corresponding ground terminal.

[0096] Optionally, the operation of constructing a set of nonlinear overdetermined equations corresponding to the ground terminal based on the signal frame set includes: constructing multi-time observation equations based on the measured frequency of each independent signal frame in the signal frame set, the position and velocity information of the low-orbit satellite at the corresponding observation time, and the Doppler pre-compensation relationship of the uplink radio frequency signal of the ground terminal; and constructing a set of nonlinear overdetermined equations with the three-dimensional spatial coordinates and nominal operating frequency of the ground terminal as unknowns based on the Earth's spherical constraint conditions, wherein the Earth's spherical constraint conditions are that a coordinate system is established with the Earth's center as the origin, and the magnitude of the position vector of the ground terminal is equal to the average radius of the Earth.

[0097]

[0098] in, For the i-th observation time, the measured frequency received by the positioning station; is the nominal operating frequency of the ground terminal; c is the speed of light in a vacuum; The three-dimensional spatial coordinates of the ground terminal; The velocity vector of the low-orbit satellite at the i-th observation time; For the i-th observation time, the position vector of the low-orbit satellite.

[0099] Optionally, the operation of determining the location of the ground terminal based on the nonlinear overdetermined equations includes: constructing a residual sum of squares objective function, wherein the residual sum of squares objective function is used to indicate the sum of squares of the differences between the measured frequency and the predicted frequency calculated based on the Doppler frequency shift model at each observation time; and determining the location of the ground terminal based on the residual sum of squares objective function.

[0100] Therefore, according to this embodiment, this application can autonomously complete the signal frame separation and location calculation of multiple ground terminals, possessing the advantages of no terminal cooperation required, strong anti-interference capability, automatic multi-terminal sorting and identification, and no need for large-scale dedicated hardware deployment. This solves the technical problems of strong network control dependence, weak anti-interference capability, difficulty in multi-terminal sorting, and high hardware deployment costs in the prior art.

[0101] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0102] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0103] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.

[0104] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0105] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0106] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0107] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A positioning method for a low-Earth orbit satellite communication terminal, characterized in that, include: Acquire independent signal frames transmitted from ground terminals to low-orbit satellites within the coverage area of ​​the positioning station; Extract the radio frequency fingerprint features of the independent signal frames, and based on the radio frequency fingerprint features, use an unsupervised clustering algorithm to cluster the independent signal frames to determine the signal frame sets corresponding to each ground terminal. Based on the set of signal frames, a set of nonlinear overdetermined equations corresponding to the corresponding ground terminal is constructed, wherein the set of nonlinear overdetermined equations is used to represent the Doppler frequency shift between the corresponding ground terminal and the low-orbit satellite. The location of the ground terminal is determined based on the nonlinear overdetermined equations.

2. The method according to claim 1, characterized in that, The operation of extracting the radio frequency fingerprint features of the independent signal frames includes: The independent signal frames are subjected to time-domain and frequency-domain analysis to extract radio frequency fingerprint features. The radio frequency fingerprint features include one or more of the following: signal frame duration, signal peak amplitude, peak frequency of the spectrum, 3dB bandwidth of the spectrum, standard deviation of time-domain amplitude, signal start-up time, signal fall time, I / Q branch amplitude ratio, peak phase noise, and peak spurious signal.

3. The method according to claim 2, characterized in that, Based on the radio frequency fingerprint features, an unsupervised clustering algorithm is used to cluster the independent signal frames to determine the set of signal frames corresponding to each ground terminal. This operation includes: Based on the radio frequency fingerprint features, a multidimensional radio frequency fingerprint feature vector is constructed; Based on the unsupervised clustering algorithm, independent signal frames whose similarity of multidimensional radio frequency fingerprint feature vectors meets the preset conditions are divided into the same cluster category, and the signal frame set corresponding to each ground terminal is determined.

4. The method according to claim 3, characterized in that, Also includes: The measured frequencies corresponding to independent signal frames in the same signal frame set are sorted by transmission time to determine the time-series observation frequency sequence of the corresponding ground terminal.

5. The method according to claim 4, characterized in that, The operation of constructing a set of nonlinear overdetermined equations corresponding to the ground terminal based on the set of signal frames includes: Based on the measured frequencies corresponding to each independent signal frame in the signal frame set, the position and velocity information of the low-orbit satellite at the corresponding observation time, and combined with the Doppler pre-compensation relationship of the uplink radio frequency signal of the ground terminal, a multi-time observation equation is constructed; and Based on the Earth's spherical constraints, a set of nonlinear overdetermined equations is constructed with the three-dimensional spatial coordinates of the ground terminal and the nominal operating frequency as unknowns. The Earth's spherical constraints are that a coordinate system is established with the Earth's center as the origin, and the magnitude of the position vector of the ground terminal is equal to the average radius of the Earth.

6. The method according to claim 5, characterized in that, include: Construct a multi-time observation equation based on the following formula: ， in, For the i-th observation time, the measured frequency received by the positioning station; is the nominal operating frequency of the ground terminal; c is the speed of light in a vacuum; The three-dimensional spatial coordinates of the ground terminal; The velocity vector of the low-orbit satellite at the i-th observation time; For the i-th observation time, the position vector of the low-orbit satellite.

7. The method according to claim 6, characterized in that, The operation of determining the location of the ground terminal based on the aforementioned nonlinear overdetermined equations includes: Construct a residual sum of squares objective function, wherein the residual sum of squares objective function is used to indicate the sum of squares of the difference between the measured frequency and the predicted frequency calculated based on the Doppler frequency shift model at each observation time; The location of the ground terminal is determined based on the objective function of the residual sum of squares.

8. A storage medium, characterized in that, The storage medium includes a stored program, wherein, when the program is executed, the method described in any one of claims 1 to 7 is performed by a processor.

9. A low-orbit satellite communication terminal positioning device, characterized in that, include: Independent signal frame acquisition module, used to acquire independent signal frames sent from ground terminals to low-orbit satellites within the coverage area of ​​the positioning station; The signal frame set determination module is used to extract the radio frequency fingerprint features of the independent signal frames, and based on the radio frequency fingerprint features, use an unsupervised clustering algorithm to cluster the independent signal frames to determine the signal frame sets corresponding to each ground terminal. The equation construction module is used to construct a nonlinear overdetermined equation set corresponding to the corresponding ground terminal based on the signal frame set, wherein the nonlinear overdetermined equation set is used to represent the Doppler frequency shift between the corresponding ground terminal and the low-orbit satellite. The ground terminal location determination module is used to determine the location of the ground terminal based on the nonlinear overdetermined equations.

10. A low-orbit satellite communication terminal positioning device, characterized in that, include: processor; as well as A memory, connected to the processor, for providing the processor with instructions to perform the following processing steps: Acquire independent signal frames transmitted from ground terminals to low-orbit satellites within the coverage area of ​​the positioning station; Extract the radio frequency fingerprint features of the independent signal frames, and based on the radio frequency fingerprint features, use an unsupervised clustering algorithm to cluster the independent signal frames to determine the signal frame sets corresponding to each ground terminal. Based on the set of signal frames, a set of nonlinear overdetermined equations corresponding to the corresponding ground terminal is constructed, wherein the set of nonlinear overdetermined equations is used to represent the Doppler frequency shift between the corresponding ground terminal and the low-orbit satellite. The location of the ground terminal is determined based on the nonlinear overdetermined equations.

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