Terminal positioning method, terminal and computer readable medium

Abstract

The present disclosure provides a terminal positioning method, comprising: obtaining first positioning data of a target terminal corresponding to each reference base station from reference signals sent by at least one reference base station, the first positioning data representing a position relationship between the target terminal and the reference base station; the reference signal is sent by a reference base station through a communication satellite operating in a preset height range; and determining position information of the target terminal according to the first positioning data and second positioning data of a preset reference terminal, the preset reference terminal being a predetermined terminal with a fixed position, and the second positioning data representing a position relationship between the preset reference terminal and a reference base station. The invention further provides a terminal and a computer readable medium.

Description

Technical Field

[0001] The present disclosure relates to the field of communication technology, and in particular to a terminal positioning method, a terminal and a computer-readable medium. Background Art

[0002] The current broadband satellite network processes and transmits data through communication satellites. Communication satellites can locate terminals through GPS-like pseudo-code positioning methods or RTL (Return To Launch)-like Doppler frequency shift positioning methods. However, the algorithms used in these methods to locate terminals are too computationally intensive, and none of them can utilize existing 5G or 6G technologies, nor are they compatible with ground-based 5G or 6G, and cannot achieve the integration of a space-ground integrated network. Summary of the invention

[0003] The present disclosure aims to solve at least one of the technical problems existing in the prior art, and proposes a terminal positioning method, a terminal and a computer-readable medium.

[0004] To achieve the above objectives, in a first aspect, an embodiment of the present disclosure provides a terminal positioning method, including:

[0005] Acquire first positioning data corresponding to the target terminal and each reference base station from a reference signal sent by at least one reference base station, wherein the first positioning data represents a positional relationship between the target terminal and the reference base station, and the first positioning data includes: a cell identifier and navigation information, and the reference signal is sent by the reference base station through a communication satellite operating within a preset altitude range;

[0006] The location information of the target terminal is determined based on the first positioning data and the second positioning data of a preset reference terminal, wherein the preset reference terminal is a terminal with a predetermined fixed position, and the second positioning data represents the positional relationship between the preset reference terminal and the reference base station.

[0007] In a second aspect, an embodiment of the present disclosure further provides a terminal, including:

[0008] one or more processors;

[0009] A memory having one or more programs stored thereon, when the one or more programs are executed by the one or more processors, the one or more processors implement the terminal positioning method as described above.

[0010] In a third aspect, an embodiment of the present disclosure further provides a computer-readable medium having a computer program stored thereon, and when the program is executed by a processor, the terminal positioning method as described above is implemented.

[0011] The present disclosure has the following beneficial effects:

[0012] The embodiments of the present disclosure provide a terminal positioning method, a terminal and a computer-readable medium, which can determine the location information of the target terminal through the first positioning data between the target terminal and at least one reference base station and the second positioning data between the preset reference terminal and at least one reference base station, thereby realizing accurate positioning of the location information of the target terminal and realizing the integration of NTN system positioning, navigation and communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram of a process flow of a terminal positioning method provided by an embodiment of the present disclosure;

[0014] Figure 2 This is a flowchart of a specific implementation method of step S1 in the embodiment of the present disclosure;

[0015] Figure 3 Schematic diagram of the time-frequency structure of PSS, SSS and PBCH in an embodiment of the present disclosure;

[0016] Figure 4 This is a flowchart of a specific implementation method of step S11 in the embodiment of the present disclosure;

[0017] Figure 5 This is a flowchart of a specific implementation method of step S113 in the embodiment of the present disclosure;

[0018] Figure 6 A schematic diagram of a process for synchronizing a reference signal in an embodiment of the present disclosure;

[0019] Figure 7 A flowchart of a specific implementation method of step S2 in the embodiment of the present disclosure;

[0020] Figure 8 A schematic diagram of the position relationship among a reference base station, a target terminal and a preset reference terminal under two-dimensional position coordinates in an embodiment of the present disclosure;

[0021] Fig. 9 A schematic diagram of the structure of a terminal provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solution of the present disclosure, the terminal positioning method, terminal and computer-readable medium provided by the present disclosure are described in detail below with reference to the accompanying drawings.

[0023] Example embodiments will be described more fully below with reference to the accompanying drawings, but the example embodiments may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. On the contrary, the purpose of providing these embodiments is to make the present disclosure thorough and complete and to enable those skilled in the art to fully understand the scope of the present disclosure.

[0024] In the absence of conflict, the various embodiments of the present disclosure and the various features therein may be combined with each other.

[0025] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0026] The terms used herein are only used to describe specific embodiments and are not intended to limit the present disclosure. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It will also be understood that when the terms "comprising" and / or "made of" are used in this specification, the presence of the features, wholes, steps, operations, elements and / or components is specified, but the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or groups thereof is not excluded.

[0027] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art. It will also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted as having an idealized or overly formal meaning unless explicitly defined as such herein.

[0028] According to some related technologies, in broadband satellite networks, the most effective way to obtain the location, time, frequency information, etc. of the terminal is to use GNSS (Global Navigation Satellite System) systems such as GPS (Global Positioning System), but since these systems need to rely on the support of other systems, the instability of the system increases. In addition, the signals of satellite positioning technologies such as GPS and Beidou are weak. GPS positioning usually uses pseudo-code positioning technology. GPS satellites have built-in atomic clocks for high-precision time synchronization between satellites. Then, by measuring the pseudo-range between multiple satellites and the receiver antenna, a set of equations is listed to solve the position of the receiver. Since the four parameters X, Y, Z, and Δt need to be solved, at least 4 equations need to be listed, that is, at least 4 satellites are required to participate in positioning. In addition, the antenna is required to be as unobstructed as possible. This also leads to the current broadband satellite network technology requiring use in areas with open sky views. Rain, snow, leaves, and buildings have a great impact on GPS signals, and there are problems in application in forests, bad weather, and high mountain obstructions. In addition, because there is no AGPS (Assisted Global Positioning System) and other network technologies to cooperate, the GPS cold start time is very long, resulting in a long startup time for GPS or Beidou ground terminals (such as GPS, Beidou receivers), generally from several minutes to more than ten minutes.

[0029] The application scenarios of the embodiments of the present disclosure are described below:

[0030] In the embodiment of the present disclosure, the reference base station sends a reference signal to the target terminal through a satellite operating in a preset altitude range, wherein the preset altitude range in which the satellite operates includes: LEO (Low Earth Orbit) satellites with an altitude range of 500 to 2000km, MEO (Medium Earth Orbit) satellites with an altitude range of 8000 to 20000km, and GEO (Geostationary Earth Orbit) satellites with an altitude of about 35786km. Among them, LEO has the advantages of low cost and small signal attenuation, and is a hot spot for satellite broadband Internet of Things and an important research direction of 6G.

[0031] NTN (Non-Terrestrial Network) network (i.e., integrated space-air and ground network) is currently a hot topic in the industry. Among them, 5G NTN is a terminal-satellite direct communication technology based on 5G (Fifth Generation) new air interface technology developed by 3GPP (3rd Generation Partnership Project) in the R17 stage. NTN is a deterministic requirement for 6G networks, and 3GPP will carry out standardization work on the 6G NTN integrated space-air system in R21.

[0032] In some examples, the reference base station sends a reference signal to the target terminal via a LEO satellite. The application environment of NTN is different from that of the terrestrial 5G system. LEO has a relatively fast speed and a large Doppler shift, which should be estimated and compensated in real time. Depending on the orbit, its speed range is 6.9km / s to 7.9km / s, resulting in a large Doppler frequency and fast changes. With a satellite speed of 7.9km / s and a carrier frequency of 2GHz, the maximum Doppler frequency deviation is ±53KHz, the maximum change rate is 530Hz / s, and the maximum spatial delay change rate is 26.3us / s. For OFDM subcarriers of 15KHz, real-time frequency tracking and correction should be performed, otherwise the signal cannot be demodulated. Since three-dimensional searches of frequency, phase, and PCI (Physical Cell Identifier) ​​are required and real-time compensation is performed, and the SSB (Single Side Band) period of 5G is as long as 20ms, the traditional 5G time-frequency synchronization algorithm, such as frame header synchronization methods such as sliding correlation, is too computationally intensive and is not applicable. Based on this, the reference signal of the LEO satellite can be compensated in time and frequency in advance by obtaining prior information such as time, frame header, and frequency.

[0033] Figure 1 is a flow chart of a terminal positioning method according to an embodiment of the present disclosure. Figure 1 The present disclosure provides a terminal positioning method. More specifically, the method is applied to a target terminal and includes:

[0034] S1. Acquire first positioning data corresponding to a target terminal and each reference base station from a reference signal sent by at least one reference base station, wherein the first positioning data represents a positional relationship between the target terminal and the reference base station, and the first positioning data includes: a cell identifier and navigation information, and the reference signal is sent by the reference base station through a communication satellite operating within a preset altitude range;

[0035] S2. Determine the location information of the target terminal according to the first positioning data and the second positioning data of a preset reference terminal, wherein the preset reference terminal is a terminal with a predetermined fixed position, and the second positioning data represents the position relationship between the preset reference terminal and the reference base station.

[0036] In the disclosed embodiment, the location information of the target terminal is determined by first positioning data between the target terminal and at least one reference base station and second positioning data between a preset reference terminal and at least one reference base station, wherein a preset reference terminal with a fixed position is introduced to eliminate the influence of the asynchrony between the reference base stations when determining the location information of the target terminal, thereby achieving accurate positioning of the location information of the target terminal and realizing the integration of positioning, navigation and communication of the NTN system.

[0037] In some embodiments, each reference base station, target terminal, and preset reference terminal should be within the communication coverage of a communication satellite operating within a preset altitude range.

[0038] In the embodiments of the present disclosure, there is no special limitation on the reference base station, which may be a ground station, a gateway station, etc. within the coverage of a communication satellite.

[0039] In some embodiments, first positioning data corresponding to at least three reference base stations are required to achieve two-dimensional positioning of the target terminal; first positioning data corresponding to at least four reference base stations are required to achieve three-dimensional positioning of the target terminal; first positioning data corresponding to at least one reference base station is required to achieve positioning of whether the target terminal is in place. The embodiments of the present disclosure do not specifically limit the number of reference base stations, and the number of reference base stations can be determined according to the positioning requirements of the target terminal.

[0040] In some embodiments, the communication satellite operating within the preset altitude range is a LEO satellite with an altitude range of 500 to 2000 km.

[0041] In some embodiments, the preset reference terminal is a terminal with a predetermined fixed position, and the fixed position here means that the relative position of the preset reference terminal with respect to the reference base station is fixed.

[0042] In the embodiments of the present disclosure, there is no special limitation on the target terminal, which may be a CPE (Customer Premises Equipment), a vehicle-mounted, aircraft-mounted, ship-mounted modem device, or other terminal device that can be used to receive a reference signal.

[0043] Figure 2 FIG. 1 is a flowchart of a specific implementation method of step S1 in the embodiment of the present disclosure. Figure 2In some embodiments, S1 includes:

[0044] S11, extracting the reference signal to obtain a target primary synchronization signal PSS;

[0045] S12. Determine a cell identifier and navigation information corresponding to the target terminal according to the target PSS and the reference signal.

[0046] In an embodiment of the present disclosure, the first positioning data includes: a cell identification (i.e., a cell ID) and navigation information. In some embodiments, the navigation information is relevant information of a reference base station, and the relevant information of the reference base station includes: ephemeris information of a communication satellite, and at least one of the system messages of the reference base station. Among them, the system message may be a MIB (Master Information Block), a SIB (System Information Block), etc. It is worth noting that the navigation information can be used to determine the position, speed, and other information of a communication satellite operating within a preset altitude range.

[0047] The reference base station sends a reference signal to a communication satellite target terminal operating within a preset altitude range, wherein the target terminal receives the reference signal from the communication satellite as a downlink signal and extracts a target primary synchronization signal PSS from the reference signal.

[0048] Next, PSS is described:

[0049] Reference Figure 3 , PCI (Physical Cell Identifier) ​​is composed of the primary synchronization signal PSS and the secondary synchronization signal SSS, with a total of 1008. The 1008 means that there are a total of 1008 different sequence combinations of PSS and SSS. Among them, PSS is located in the middle 127 subcarriers of symbol 0 (frequency is 56-182), and its sequence value is three: 0, 1, 2; SSS is located in the middle 127 subcarriers of symbol 2 (frequency is 56-182), and its sequence value is 336, namely (0-355). Different protection subcarriers {48-55, 183-191} Set 0 are set at both ends of PSS and SSS, where Set 0 represents the protection subcarrier, and {48-55, 183-191} is the frequency of the protection subcarrier. The PBCH (Physical Broadcast Channel) is located at symbols 1, 3, and 2. Symbols 1 and 3 occupy all subcarriers from 0 to 239, and symbol 2 occupies all subcarriers except the subcarriers occupied by the SSS and the protection subcarrier Set 0 used to protect the SSS.

[0050] PSS and SSS are used to determine the cell identity. PSS has 3 sequences, which are used to transmit NID2 in the cell physical layer ID, with values ​​of 0, 1, and 2. SSS has 336 sequences, which are used to transmit NID1 in the cell ID, with a value range of 0-335. The cell identity is determined by the formula: cell ID = 3 × NID1 + NID2. Therefore, there are 1008 cell identities in total, and the cell identity value range is 0-1007.

[0051] According to the above description of PSS, when the target PSS is determined, the corresponding SSS and PBCH can be determined, and then the cell identifier can be determined.

[0052] Accordingly, Figure 4 FIG. 1 is a flowchart of a specific implementation method of step S11 in the embodiment of the present disclosure. Figure 4 In some embodiments, S11 includes:

[0053] S111, converting a preset number of groups of frequency domain PSS to obtain a first time domain signal;

[0054] S112. Determine a coarse synchronization position in the reference signal according to the first time domain signal and the reference signal;

[0055] S113, determining a fine synchronization position within an error range corresponding to the coarse synchronization position, wherein the PSS corresponding to the fine synchronization position has the highest correlation with a second time domain signal corresponding to a preset local signal;

[0056] S114. Obtain a target PSS according to the fine synchronization position; the fine synchronization position indicates a frame header position of the target PSS.

[0057] The embodiments of the present disclosure do not specifically limit the preset number, which can be determined according to actual conditions. In one embodiment, the preset number of frequency domain PSS groups is 3 groups, so as to reduce the computational complexity of correlation processing between the first time domain signal and the reference signal by three times.

[0058] In some embodiments, the frequency domain PSS is converted by performing IFFT (Inverse Fast Fourier Transform) processing on the frequency domain PSS to transform it into a first time domain signal.

[0059] In some embodiments, before determining the rough synchronization position of the reference signal, the process may further include: filtering the reference signal. More specifically, the filtering process may be a low-pass filtering process to remove noise interference and reduce the difficulty of subsequent processing.

[0060] In an embodiment of the present disclosure, the reference signal received by the target terminal comes from at least one reference base station. Due to Doppler frequency shift, there are different frequency differences between the reference signals of different reference base stations. Therefore, the coarse synchronization position in the reference signal is first determined, and then the fine synchronization position is determined to improve the accuracy of the location information of the target terminal. When the fine synchronization position is determined, the fine synchronization position indicates the frame header position of the target PSS, and the fine synchronization position is subjected to frame synchronization processing to determine the frame header position of the target PSS and obtain the target PSS.

[0061] In some embodiments, S112 includes:

[0062] Perform correlation processing on a first sequence corresponding to the first time domain signal and a second sequence corresponding to the reference signal to obtain a first correlation modulus value corresponding to each point in the second sequence;

[0063] The first correlation modulus value is compared with a preset threshold to determine the rough synchronization position.

[0064] In an embodiment of the present disclosure, the first time domain signal is divided into a first number group, and the reference signal is divided into a second number group. In some examples, the first number group is equal to the second number group. The first sequence of the first number group is obtained by dividing the first time domain signal, and the second sequence of the second number group is obtained by dividing the reference signal. In some examples, before dividing the first time domain signal and / or the reference signal, sampling processing may also be performed on the first time domain signal and / or the reference signal.

[0065] In one example, the first time domain signal is obtained by converting three groups of frequency domain PSSs, and the first time domain signal includes two groups of first sequences: three groups of frequency domain PSS signals are generated locally, and mapped to subcarriers 56 to 182 in the SSB (Single Side Band) frequency domain in accordance with the 38 series protocol of 3GPP. The remaining subcarriers do not carry other information and are filled with zeros as protection intervals. The frequency domain PSS after zero filling is transformed to the time domain by 4096-point IFFT and down-sampled by 16 times. The three groups of sequences after down-sampling are superimposed to form a new sequence (i.e., the first time domain signal), and the new sequence is divided into two segments 1P and 2P, which are the first sequence.

[0066] The reference signal 20ms Data is downsampled 16 times, and the downsampled reference signal is divided into two segments Data1 and Data2, which are the second sequence.

[0067] In addition, this embodiment does not specifically limit the correlation processing, and it may be a sliding correlation processing, wherein the sliding correlation is a signal processing technology used to measure the similarity between two signals at different time offsets.

[0068] In one example, the first sequence includes 1P and 2P, and the second sequence includes Data1 and Data2. The sliding starts from the first sampling point of Data1, and the sliding window size is N / 2. Each time a sampling point is slid (the sliding step is 1 sampling point), the fragments of length N / 2 corresponding to 1P and Data1 are calculated, conjugate multiplied, and then complexly added to obtain the first correlation modulus value corresponding to each sampling point in Data1; similarly, starting from the first sampling point of Data2, the sliding band length is the sequence length of Data1 minus the sequence length of 1P, and each time it slides, the first correlation modulus value corresponding to each sampling point in Data2 is obtained.

[0069] In the embodiments of the present disclosure, there is no limitation on the comparison method of the first correlation modulus value with the preset threshold value. The first correlation modulus value may be directly compared with the preset threshold value in sequence, or the first correlation modulus value of each section may be processed into a correlation peak curve, and the preset threshold value is used as a decision threshold to compare with the correlation peak curve. In some embodiments, the first correlation modulus value of each first sequence is added to the first correlation modulus value of the corresponding second sequence to obtain a correlation peak curve, the correlation peak curve is normalized, the normalized curve is compared with the preset threshold value, and the sampling point number (i.e., the coarse synchronization position) whose peak value is greater than the preset threshold value is determined.

[0070] In one example, when the detection peak value of the PSS position starting point of the normalized correlation peak curve is close to 1, the decision threshold (i.e., the preset threshold) is set to 0.9, and the sampling point number n in the correlation peak curve that is greater than the decision threshold is determined. coarse .

[0071] Figure 5 FIG. 1 is a flowchart of a specific implementation method of step S113 in the embodiment of the present disclosure. Figure 5 In some embodiments, S113 includes:

[0072] S1131, acquiring at least one reference position within the error range of the coarse synchronization position;

[0073] S1132: Determine a fine synchronization position within the error range according to the coarse synchronization position and the PSS corresponding to the reference position and the second time domain signal.

[0074] Accordingly, in some embodiments, S1132 includes:

[0075] Correlate the third sequence of the second time domain signal with the fourth sequence of the PSS corresponding to the coarse synchronization position and the reference position respectively to obtain at least two second correlation modulus values;

[0076] Comparing at least two of the second correlation modulus values ​​to obtain a target second correlation modulus value, wherein the target second correlation modulus value is a maximum value of the at least two second correlation modulus values;

[0077] The position corresponding to the target second correlation modulus value is determined as the fine synchronization position.

[0078] In this embodiment, the error range of the coarse synchronization position is related to the sliding window moving step size when the second sequence of the reference signal and the first sequence of the first time domain signal are correlated. In some embodiments, the sliding window moving step size when the second sequence of the reference signal and the first sequence of the first time domain signal are sliding correlated is 16Ts, that is, the second sequence of the reference signal is downsampled by 16 times, and the coarse synchronization position searched at this time may have an error range of -16Ts to 16Ts.

[0079] Since the error range of the coarse synchronization position has a great influence on the search for the SSS (Secondary Synchronization Signal), it is necessary to search for a reference position to reduce the error in the coarse synchronization position determination process. The number of reference positions within the error range of the coarse synchronization position can be determined according to the error range expected for the final fine synchronization position.

[0080] In some embodiments, the coarse synchronization position n coarse The sampling point after each shift (i.e., the reference position) and the fourth sequence of at least two PSSs corresponding to the original rough synchronization position are respectively normalized and slidingly correlated with the third sequence of the second time domain signal to obtain at least two second correlation modulus values; the second correlation modulus values ​​are compared to determine the maximum value among the second correlation modulus values ​​as the target second correlation modulus value, and the position corresponding to the target second correlation modulus value is determined as the fine synchronization position n. exact , so that the error of the final fine synchronization position is reduced to -1Ts~1Ts.

[0081] In some embodiments, before S113, the process further includes:

[0082] Performing a frequency search on the reference signal by using a preset local signal to determine a frequency deviation value;

[0083] Compensating a first PSS corresponding to the coarse synchronization position according to the frequency offset value;

[0084] The coarse synchronization position is updated according to the updated first PSS.

[0085] In this embodiment, since the broadband satellite network uses OFDM (Orthogonal Frequency Division Multiplexing) technology, it is sensitive to frequency offset and requires communication satellite beam tracking (for example, the visible time of a LEO satellite is about 10 minutes, while the target terminal may only stay in a beam for 1 minute), the target terminal needs to first determine the coarse synchronization position and then perform tracking and Doppler shift compensation.

[0086] In addition, before performing a frequency search on the reference signal through a preset local signal to determine the frequency offset value, the method further includes: converting the preset local signal to obtain a second time domain signal.

[0087] In some embodiments, the conversion of the preset local signal can be: after mapping the preset local signal to subcarriers No. 56 to 182 in the SSB frequency domain in accordance with the 38 series protocol specifications of 3GPP, other information is filled with zeros as a protection interval, and the frequency domain PSS after zero filling is transformed into the time domain by a 4096-point IFFT, and then passed through NCO (Numerically Controlled Oscillator) to generate a second time domain signal, which identifies the frequency deviation signal.

[0088] In the embodiments of the present disclosure, there is no special limitation on the frequency search method, which may be a linear search.

[0089] In some embodiments, the reference signal is searched according to a certain search step until the target frequency deviation value is found and / or all elements are searched, where the elements are sampling points corresponding to the coarse synchronization position in the reference signal. In some examples, the search step is 7.5KHz, and the search method is a linear search capture algorithm that gradually searches the frequency bands on both sides in alternating left and right.

[0090] In some embodiments, determining the frequency deviation value specifically includes: matching the frequency point of the frequency deviation signal corresponding to the element with the element, and the matching process may be sliding correlation between the element and the frequency point of the corresponding frequency signal to obtain a target correlation value, and determining the frequency deviation value (i.e., Doppler frequency deviation integer value) according to the correlation value. The target correlation value here may be a correlation value with a maximum value, or may be a correlation result greater than the preset frequency deviation threshold value according to a comparison result of the sliding correlation and a preset frequency deviation threshold value, and the present disclosure is not limited thereto.

[0091] The first PSS corresponding to the coarse synchronization position is compensated according to the frequency deviation value to obtain an updated first PSS. The coarse synchronization position is updated according to the updated first PSS. By compensating the first PSS corresponding to the coarse synchronization position, the accuracy of the coarse synchronization position can be improved, and further, a more accurate fine synchronization position can be obtained.

[0092] In one example, the target terminal receives the reference signal sent by all communication satellites in the air through a receiving link, and the process of coarse synchronization of the reference signal includes: normalized sliding correlation, first correlation modulus merging, coarse synchronization position calculation and cell ID matching. The specific method is to use the local PSS sequence converted to the time domain to slide correlate with the reference data, and use the normalized correlation method to determine the coarse synchronization position, and then the cell ID can be preliminarily identified based on the coarse synchronization position. Further, the coarse synchronization position is updated (frequency offset compensation) by frequency search: the communication satellite is a LEO satellite with an altitude of 1500km. Considering that the communication satellite with an inclination of 15 degrees is visible, the distance to be supported is 1500*3.86=5790km, so the data length to be searched is 20ms (corresponding to a distance of 6000km), that is, the set SSB period is 20ms. According to the characteristics of PSS, 3 preset local signals, that is, preset local PSS, need to search for 20ms+1ms time domain sampling points.

[0093] Among them, when the carrier frequency is estimated at 14 GHz, the maximum Doppler frequency deviation is + / -371 KHz, with a maximum change rate of 3710 Hz / s; when the carrier frequency is estimated at 2 GHz, the maximum Doppler frequency deviation is + / -53 KHz, with a maximum change rate of 530 Hz / s.

[0094] Taking 2G as an example, the frequency to be searched is + / -53KHz, the RE (Resource Element) of 2G is 15KHz, and [-4 -3-2 -1 0 1 2 3 4]*15KHz is required, corresponding to 9 Doppler frequencies; depending on the cell ID, there are three PSS sequences. When searching the frequency of the coarse synchronization position, the three preset local PSS sequences need to be normalized and correlated with the reference signal respectively. By comparing the correlation values, the updated coarse synchronization position is determined, and the cell ID can be determined based on the updated coarse synchronization position.

[0095] Furthermore, a local PSS sequence is generated according to the cell ID. The three local PSS sequences are mapped to the corresponding RE resources respectively, and other RE positions are filled with zeros. Then, they are transformed into the time domain, and a CP (Cyclic Prefix) is added to generate the local main synchronization sequences P0, P1, and P2 of the cell ID corresponding to the coarse synchronization position.

[0096] In some embodiments, S12 includes:

[0097] Determine, according to the target PSS, a target secondary synchronization signal SSS corresponding to the target PSS;

[0098] Calculate the target PSS and the target SSS to obtain a cell identifier corresponding to the target terminal;

[0099] The reference signal is demodulated to obtain the navigation information, wherein the navigation information includes at least one of ephemeris information and system information of the reference base station.

[0100] In this embodiment, NID1 in the cell ID can be determined according to the target PSS. SSS is located in the middle 127 subcarriers (56-182) of symbol 2, and at both ends of the target PSS and the corresponding SSS, there are different protection subcarriers {48-55, 183-191} Set 0, which has a total of 336 values.

[0101] According to the target PSS, the time domain SSS signal is extracted from the reference signal, and the extracted time domain SSS signal is transformed to the frequency domain by FFT (Fast Fourier Transform), and the 127-bit SSS signal in the frequency domain is extracted. The 336 sets of preset local frequency domain SSS sequences are cross-correlated with the frequency domain SSS signal extracted from the received signal to obtain the correlation results. The SSS corresponding to the target correlation result corresponding to the maximum value of the 336 correlation results is the target secondary synchronization signal SSS, and then the NID1 in the cell ID is determined.

[0102] The cell ID is obtained according to the target PSS and the corresponding target SSS, wherein the target PSS provides NID2 in the cell ID and the corresponding SSS provides NID1 in the cell ID.

[0103] Furthermore, the PBCH corresponding to the target PSS is demodulated to obtain navigation information of the reference base station.

[0104] In some embodiments, the time synchronization accuracy of the reference base station can be reduced to below 1.5us, and the positioning accuracy of the fine synchronization position can reach about 300m, which can meet the preliminary positioning requirements.

[0105] In one example, referring to Figure 6 , the process of the target terminal synchronizing the received reference signal includes:

[0106] Performing low-pass filtering on the reference signal to obtain a reference signal with noise or clutter removed;

[0107] Convert a preset number of groups of frequency domain PSS to obtain a first time domain signal;

[0108] Performing sliding correlation processing on a first sequence corresponding to the first time domain signal and a second sequence corresponding to the reference signal to obtain a first correlation modulus value corresponding to each point in the second sequence, thereby determining a coarse synchronization position;

[0109] Based on the coarse synchronization position, a fine synchronization position is determined from an error range corresponding to the coarse synchronization position to reduce an error caused by a sliding step when a first sequence corresponding to the first time domain signal and a second sequence corresponding to the reference signal are subjected to sliding correlation processing;

[0110] The time domain SSS signal is extracted from the reference signal according to the target PSS, and the SSS is frame synchronized to determine the NID1 corresponding to the SSS. At the same time, the target PSS provides the NID2 in the cell ID, and the cell identifier is determined by the formula cell ID = 3 × NID1 + NID2.

[0111] Figure 7 FIG. 1 is a flowchart of a specific implementation method of step S2 in the embodiment of the present disclosure. Figure 7 In some embodiments, S2 includes:

[0112] S21. Determine, according to the first positioning data and the second positioning data, a time difference relationship between the target terminal and the preset reference terminal and each of the reference base stations;

[0113] S22. Determine the location information of the target terminal according to the time difference relationship.

[0114] In this embodiment, the first positioning data and the second positioning data both include a cell identifier and navigation information, wherein the cell identifier can be used to calculate the position of the target terminal, and the navigation information can include ephemeris information and system information, and the position and speed of the communication satellite can be determined according to the ephemeris information. The ephemeris information of the communication satellite includes an orbital parameter table of the communication satellite, and the orbital parameter table describes the scheduled position of a certain star body at regular intervals, or the scheduled position of a certain artificial satellite at regular intervals, through list data.

[0115] In some examples, the process of calculating the position of the target terminal is:

[0116] The estimated position coordinates of the target terminal Ue are (x, y, z), and the known position coordinates of the i-th reference base station i are (x i ,y i ,z i ), then the first distance r between the target terminal Ue and the i-th reference base station i Satisfies formula (1):

[0117] ri 2 =(x i -x) 2 +(y i -y) 2 +(z i -z) 2 =K i -2xx i -2yy i -2zz i +x 2 +y 2 +z 2 (1)

[0118] Where i = 1…m, c is the propagation speed of electromagnetic waves.

[0119] The difference between the first distance between the i-th reference base station and the target terminal Ue and the second distance between the first reference base station and the target terminal Ue is: i,1 =r i -r1;

[0120] The difference r i,1 =r i Substituting -r1 into the above formula (1), we get the relationship (2):

[0121] r i,1 2 +2r i,1 r1+r1 2 =K i -2xx i -2yy i -2zz i +x 2 +y 2 +z 2 (2)

[0122] At the same time, the formula (3) of the second distance between the first reference base station and the target terminal Ue is obtained:

[0123] r1 2 =K1-2xx1-2yy1-2zz1+x 2 +y 2 +z 2 (3)

[0124] According to formula (3), r1 is eliminated from relation (2) 2 and x 2 +y 2 +z 2 , then we get relation (4):

[0125] r i,12 +2r i,1 r1=-2xx i,1 -2yy i,1 -2zz i,1 +K i -K1,i=2…m (4)

[0126] Among them, x i,1 =x i -x1,y i,1 =y i -y1,z i,1 =z i -z1;

[0127] Then the linear equation about the first distance and the second distance is obtained as formula (5):

[0128]

[0129] xyz r1 are 4 unknowns. It can be seen that when the total number of reference base stations is equal to 4, r1 can be measured by the TOA (Time of Arrival) method, and then the linear equations (5) can be directly solved. When the total number of reference base stations is equal to 5 and the base stations are synchronized, the linear equations can be directly solved. When the total number of reference base stations is greater than 5, the equations can be solved by the LS (Least Square) method.

[0130] Furthermore, a high-precision positioning calibration of the target terminal is performed based on the second positioning data of a preset reference terminal, wherein the preset reference terminal is fixed and does not move. The preset reference terminal receives the reference signal sent by the reference base station as an ordinary terminal UE, and then the preset reference terminal is used to eliminate the impact of the asynchrony between the reference base stations.

[0131] In some examples, taking two-dimensional position coordinates as an example, a process of performing high-precision positioning calibration of a target terminal according to second positioning data of a preset reference terminal is described:

[0132] Reference Figure 8 , AP1 is the first reference base station, AP2 is the second reference base station, AP3 is the third reference base station, UE1 is the target terminal, UE2 is the preset reference terminal, the locations of AP1, AP2, AP3 and UE2 are all known, and UE1 accesses AP1.

[0133] Among them, the time it takes for UE1 to receive the signal from AP1 is t1 = δ 1,1 +L 1,1 / v; The time it takes for UE1 to receive the signal from AP2 is t2 = δ 1,2 +L1,2 / v; The time it takes for UE2 to receive the signal from AP1 is T1 = δ 2,1 +L 2,1 / v; The time it takes for UE2 to receive the signal from AP2 is T2 = δ 2,2 +L 2,2 / v; where δ i,j Indicates Ue i With Ap j The synchronization time error between i,j Indicates Ue i With Ap j The real distance between them.

[0134] According to the two-dimensional TDOA (Time Difference Of Arrival), we get equation (6):

[0135]

[0136] In formula (6), x i,1 ,y i,1 , K i is the value of the reference base station Api coordinates, r1 is an unknown quantity, and r i -r1 is used as a variable to estimate r using the reception time i -r1.

[0137] Here, taking r2-r1 as an example, for traditional TDOA, then: r2-r1=v*(t2-t1)+v*(δ 1,2 -δ 1,1 );

[0138] Without ensuring the synchronization of Ap1 and Ap2, the traditional TDOA method cannot estimate the accurate r2-r1 by measuring the receiving time of the reference base stations Ap1 and Ap2.

[0139] Based on this, the preset reference terminal UE2 is used for calculation, and then:

[0140] The signal time difference between the reference signal of AP1 to the target terminal UE1 and the preset reference terminal UE2 is expressed as formula (7):

[0141]

[0142] The signal time difference between AP2's reference signal to the target terminal UE1 and the preset reference terminal UE2 is expressed as formula (8):

[0143]

[0144] Therefore, the time difference relationship between the target terminal and the preset reference terminal to the first reference base station and the second reference base station is obtained as formula (9):

[0145]

[0146] Among them, δ 1,1 -δ 1,2 is the synchronization time error between AP1 and AP2, δ 2,1 -δ 2,2 is the synchronization time error between AP1 and AP2, that is, (δ 1,1 -δ 1,2 )-(δ 2,1 -δ 2,2 )=0, the synchronization error between AP1 and AP2 is eliminated, and L 2,1 With L 2,2 is a known number. Then the difference between the first distance between the second reference base station and the target terminal Ue and the second distance between the first reference base station and the target terminal Ue is: r2-r1=L 1,2 -L 1,1 =v*(Td1-Td2)+L 2,2 -L 2,1 ;

[0147] In this way, by measuring the receiving time t1, t2, T1, T2 of the reference signal of the reference base station Ap, there is no need for strict synchronization between the target terminal Ue and the reference base station Ap, nor is there any need for time synchronization between the reference base stations Ap. Instead, the TDOA formula is applied to improve positioning accuracy.

[0148] In some other examples, taking the three-dimensional position coordinates as an example, the process of performing high-precision positioning calibration of the target terminal according to the second positioning data of the preset reference terminal is:

[0149] There are 5 reference base stations AP, the location coordinates are AP j (X j ,Y j ,Z j ), j∈{1,2,3,4,5}, 1 preset reference terminal UE2, whose location coordinates are UE2(x2,y2,z2), and the location coordinates of the target terminal are UE1(x,y,z);

[0150] According to OTDOA (Observed Time Difference of Arrival), the time difference Td between UE1 receiving the reference signal and UE2 receiving the reference signal is obtained. j Formula (10):

[0151]

[0152] Since T2-T1 and t2-t1 are both the phase difference between AP2 and AP1, which are the same value, the time difference formula (11) is obtained:

[0153]

[0154] Among them, Td j represents the jth reference base station AP j The time difference between the reference signal of the preset reference terminal UE2 and the reference signal of the target terminal UE1 can be obtained by observation; ij Indicates UEi and AP j The distance between them, i∈{1,2}, j∈{1,2,3,4,5}.

[0155] Td j , L 2j can be calculated by known parameters, so the unknown quantity in formula (11) is L 1j , and according to the spatial coordinate geometric relationship, formula (12) is obtained:

[0156]

[0157] Get the time difference formula:

[0158]

[0159] The nonlinear equations are converted into linear equations as formula (13):

[0160] 2[x j,1 y j,1 z j,1 r j,1 ]*[xyz r1] T =K j -K1-r j,1 2 (13) Solving formula (13), we can obtain the unique (x, y, z):

[0161] Among them, r j,1 =-(v(Td j -Td1)+L 21 -L 2j ) is calculated from the observed data.

[0162] By presetting the reference terminal, a higher precision positioning of the target terminal can be achieved. In some embodiments, the precision positioning error can be reduced from 450m error to decimeter level. At the same time, the problem of different frequency differences between reference base stations of different communication satellites caused by Doppler frequency shift and the need for multiple receiving circuits for multiple communication satellites is solved, thereby reducing the cost of the receiving circuit on the target terminal side.

[0163] The embodiments of the present disclosure determine the location information of the target terminal through the first positioning data between the target terminal and at least one reference base station and the second positioning data between the preset reference terminal and at least one reference base station, thereby achieving accurate positioning of the location information of the target terminal and realizing the integration of NTN system positioning, navigation and communication.

[0164] Second, refer to Fig. 9 , an embodiment of the present disclosure provides a terminal, which includes:

[0165] One or more processors 901;

[0166] A memory 902 storing at least one program, wherein when the one or more programs are executed by the one or more processors 901, the one or more processors 901 implement any one of the above terminal positioning methods;

[0167] One or more I / O interfaces 903 are connected between the processor 901 and the memory 902 and are configured to implement information exchange between the processor 901 and the memory 902 .

[0168] Among them, the processor 901 is a device with data processing capabilities, including but not limited to a central processing unit (CPU); the memory 902 is a device with data storage capabilities, including but not limited to random access memory (RAM, more specifically SDRAM, DDR, etc.), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory (FLASH); the I / O interface (read-write interface) 903 is connected between the processor 901 and the memory 902, and can realize information interaction between the processor 901 and the memory 902, including but not limited to a data bus (Bus), etc.

[0169] In a third aspect, an embodiment of the present disclosure provides a computer-readable medium having a computer program stored thereon, and when the program is executed by a processor, any one of the above-mentioned terminal positioning methods is implemented.

[0170] It will be appreciated by those skilled in the art that all or some of the steps, systems, and functional modules / units in the methods disclosed above may be implemented as software, firmware, hardware, and appropriate combinations thereof. In hardware implementations, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed by several physical components in cooperation. Some or all physical components may be implemented as software executed by a processor, such as a central processing unit, a digital signal processor, or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium (or non-transitory medium) and a communication medium (or temporary medium). As known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, it is well known to those skilled in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

[0171] Example embodiments have been disclosed herein, and although specific terms are employed, they are used and should be interpreted only in a general illustrative sense and not for limiting purposes. In some instances, it will be apparent to those skilled in the art that, unless otherwise expressly noted, features, characteristics, and / or elements described in conjunction with a particular embodiment may be used alone or in combination with features, characteristics, and / or elements described in conjunction with other embodiments. Therefore, those skilled in the art will appreciate that various changes in form and detail may be made without departing from the scope of the present disclosure as set forth in the appended claims.

Claims

1. A terminal positioning method, comprising: Acquire first positioning data corresponding to the target terminal and each reference base station from a reference signal sent by at least one reference base station, wherein the first positioning data represents a positional relationship between the target terminal and the reference base station, and the first positioning data includes: a cell identifier and navigation information, and the reference signal is sent by the reference base station through a communication satellite operating within a preset altitude range; The location information of the target terminal is determined based on the first positioning data and the second positioning data of a preset reference terminal, wherein the preset reference terminal is a terminal with a predetermined fixed position, and the second positioning data represents the positional relationship between the preset reference terminal and the reference base station.

2. The terminal positioning method according to claim 1, wherein: Acquiring first positioning data corresponding to a target terminal and each reference base station from a reference signal sent by at least one reference base station includes: Extracting the reference signal to obtain a target primary synchronization signal PSS; The cell identifier and navigation information corresponding to the target terminal are determined according to the target PSS and the reference signal.

3. The terminal positioning method according to claim 2, wherein: Extracting the reference signal to obtain a target primary synchronization signal PSS includes: Convert a preset number of groups of frequency domain PSS to obtain a first time domain signal; Determine a coarse synchronization position in the reference signal according to the first time domain signal and the reference signal; Determine a fine synchronization position within an error range corresponding to the coarse synchronization position, wherein the PSS corresponding to the fine synchronization position has the highest correlation with the second time domain signal corresponding to the preset local signal; According to the fine synchronization position, a target PSS is obtained; the fine synchronization position indicates a frame header position of the target PSS.

4. The terminal positioning method according to claim 3, wherein: Determining a coarse synchronization position in the reference signal according to the first time domain signal and the reference signal includes: Perform correlation processing on a first sequence corresponding to the first time domain signal and a second sequence corresponding to the reference signal to obtain a first correlation modulus value corresponding to each point in the second sequence; The first correlation modulus value is compared with a preset threshold to determine the rough synchronization position.

5. The terminal positioning method according to claim 3, wherein: Determining a fine synchronization position within an error range corresponding to the rough synchronization position includes: Acquire at least one reference position within the error range of the rough synchronization position; A fine synchronization position within the error range is determined according to the PSS and the second time domain signal corresponding to the coarse synchronization position and the reference position.

6. The terminal positioning method according to claim 5, wherein: Determining a fine synchronization position within the error range according to the coarse synchronization position and the PSS corresponding to the reference position and the second time domain signal, comprising: Correlate the third sequence of the second time domain signal with the fourth sequence of the PSS corresponding to the coarse synchronization position and the reference position respectively to obtain at least two second correlation modulus values; Comparing at least two of the second correlation modulus values ​​to obtain a target second correlation modulus value, wherein the target second correlation modulus value is a maximum value of the at least two second correlation modulus values; The position corresponding to the target second correlation modulus value is determined as the fine synchronization position.

7. The terminal positioning method according to claim 3, wherein: Before determining the fine synchronization position within the error range corresponding to the rough synchronization position, the method further includes: Performing a frequency search on the reference signal by using a preset local signal to determine a frequency deviation value; Compensating a first PSS corresponding to the coarse synchronization position according to the frequency offset value; The coarse synchronization position is updated according to the updated first PSS.

8. The terminal positioning method according to claim 2, wherein: Determining, according to the target PSS and the reference signal, a cell identifier and navigation information corresponding to the target terminal, including: Determine, according to the target PSS, a target secondary synchronization signal SSS corresponding to the target PSS; Calculate the target PSS and the target SSS to obtain a cell identifier corresponding to the target terminal; The reference signal is demodulated to obtain the navigation information, wherein the navigation information includes at least one of ephemeris information and system information of the reference base station.

9. The terminal positioning method according to any one of claims 1 to 8, wherein: Determining the location information of the target terminal according to the first positioning data and the second positioning data of a preset reference terminal includes: Determine, according to the first positioning data and the second positioning data, a time difference relationship between the target terminal and the preset reference terminal and each of the reference base stations; The location information of the target terminal is determined according to the time difference relationship.

10. A terminal, comprising: one or more processors; A memory having one or more programs stored thereon, wherein when the one or more programs are executed by the one or more processors, the one or more processors implement the terminal positioning method according to any one of claims 1 to 9.

11. A computer-readable medium having a computer program stored thereon, wherein when the program is executed by a processor, the terminal positioning method according to any one of claims 1 to 9 is implemented.

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