Low-orbit non-ground network terminal autonomous positioning method and device without network access

Abstract

This invention discloses an autonomous positioning method and apparatus for a low-Earth orbit non-terrestrial network terminal without network access. The method includes the following steps: S1: The terminal receives the NTN downlink signal transmitted by the satellite and performs time-frequency acquisition to obtain the physical cell identifier and the local SSB signal reception time; S2: Based on the time-frequency acquisition results and the physical cell identifier, the downlink signal is synchronized, ephemeris information in SIB19 is extracted, and the satellite position is calculated; S3: Based on the local SSB signal reception time and the fixed SSB transmission period, TDOA observations are assembled; S4: The TDOA observations and satellite position information are used as least squares inputs for positioning calculation.

Description

Technical Field

[0001] This invention relates to the field of low-Earth orbit satellite positioning technology, and in particular to a method and apparatus for autonomous positioning of a low-Earth orbit non-terrestrial network terminal without network access. Background Technology

[0002] In existing non-terrestrial networks (NTNs), ground terminals rely on their own location and satellite positions for Doppler compensation, timing advance, and uplink / downlink synchronization during random access and communication. Common positioning methods depend on GNSS systems. However, GNSS signals have low ground power and fixed frequency bands, making them highly susceptible to interference or spoofing. Recent frequent GNSS interference incidents indicate that positioning systems relying solely on GNSS signals pose potential reliability risks.

[0003] This invention aims to provide a ground terminal autonomous positioning method based on NR-NTN low-orbit satellite downlink signals, enabling the terminal to obtain its own location under conditions of no GNSS assistance and no network access, providing necessary location information for NTN terminal access and communication. This invention can enhance the availability and reliability of the terminal in GNSS interference scenarios. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method and device for autonomous positioning of low-Earth orbit non-terrestrial network terminals without network access.

[0005] The objective of this invention is achieved through the following technical solution: Firstly, this invention provides a method for autonomous positioning of a low-Earth orbit non-terrestrial network terminal without network access, the method comprising the following steps: S1: The terminal receives the NTN downlink signal transmitted by the satellite and performs time and frequency acquisition to obtain the physical cell identifier and the local reception synchronization signal block (SSB) signal time; S2: Synchronize downlink signals based on time-frequency acquisition results and physical cell identifiers, extract ephemeris information from System Information Block (SIB) 19 and calculate satellite positions; S3: Assemble the Time Difference of Arrival (TDOA) observation based on the local SSB signal reception time and the fixed SSB transmission period; S4: TDOA observations and satellite position information are used as least squares inputs for positioning calculation.

[0006] Furthermore, the terminal receives downlink signals via a directional antenna or an omnidirectional antenna; when a directional antenna is used, the terminal performs antenna beam scanning to search for satellite downlink signals; after detecting a satellite signal, the antenna is finely adjusted along the direction of the largest signal metric to maintain the pointing towards the satellite signal.

[0007] Furthermore, in the first epoch, the terminal performs initial time-frequency acquisition of the baseband signal to obtain the physical cell identifier, carrier frequency offset, and sampling time offset. Specifically, the terminal correlates a local copy of the primary synchronization signal (PSS) with the received baseband signal to obtain cell identifier 2 and sampling time offset. Then, it correlates a local copy of the secondary synchronization signal (SSS) with the received baseband signal to obtain cell identifier 1 and physical cell identifier. Based on the PSS / SSS phase difference, the terminal estimates the first fine carrier frequency offset. The acquired sampling time offset is multiplied by the sampling period to convert it into the local received SSB signal time of the first epoch.

[0008] Furthermore, based on the first k The results of the precise carrier frequency offset and sampling time offset captured in the -1 epoch are used to perform SSB signal time-frequency acquisition to obtain the first epoch. k The sampling time offset of each epoch; then, based on the PSS / SSS phase difference, the sampling time offset of the first epoch is calculated. k The estimation of the precise carrier frequency offset for each epoch is obtained by multiplying the captured sampling time offset by the sampling period to convert it into the first epoch. k The local reception time of the SSB signal in each epoch.

[0009] Furthermore, based on the captured time-frequency information and physical cell identifier, the downlink signal is synchronized to extract SIB19 messages, including five parameters for determining the orbit: semi-major axis, eccentricity, right ascension of the ascending node, orbital inclination, and perigee distance, as well as two parameters for determining the precise position within the satellite orbit: ephemeris reference time and mean perigee angle of the reference time; the terminal calculates the satellite position using the ephemeris reference time and orbit information.

[0010] Furthermore, after continuously capturing the SSBs in the downlink signal, the terminal obtains multiple local SSB signal times. Using the first epoch as a reference, it obtains a set of local reception time differences. The SSB transmission interval set is determined by the satellite's SSB transmission period. Combining the local reception time difference set and the SSB transmission interval set, the TDOA measurement set is obtained.

[0011] Furthermore, regarding satellites s First, the Jacobian matrix of TDOA measurement relative to the estimated terminal position is calculated by estimating the terminal position and the known satellite positions. Then, considering the Earth's rotation, a residual vector is constructed based on TDOA measurements, the terminal position, and known satellite positions. The final Jacobian matrix is ​​constructed by combining the Jacobian matrices and residual vectors of different satellites. and b The estimated terminal position is then updated using the least squares method until it converges to the required accuracy.

[0012] Secondly, the present invention also provides an autonomous positioning device for a low-Earth orbit non-terrestrial network terminal without network access, comprising a memory and one or more processors, wherein the memory stores executable code, and when the processor executes the executable code, it implements the aforementioned autonomous positioning method for a low-Earth orbit non-terrestrial network terminal without network access.

[0013] Thirdly, the present invention also provides a computer-readable storage medium having a program stored thereon, which, when executed by a processor, implements the aforementioned method for autonomous positioning of a low-orbit non-terrestrial network terminal without network access.

[0014] Fourthly, the present invention also provides a computer program product, including a computer program, which, when executed by a processor, implements the aforementioned method for autonomous positioning of a low-Earth orbit non-terrestrial network terminal without network access. The beneficial effects of this invention are: 1. The terminal achieves autonomous positioning without GNSS assistance, breaking through the dependence of existing NTN terminals on GNSS; 2. Positioning calculation is completed using NR-NTN low-orbit satellite downlink signals, without the need to introduce additional dedicated positioning reference signals. This is suitable for scenarios where terminals randomly access the network, and provides necessary support for subsequent Doppler compensation, timing advance, and link synchronization of NTN terminals. 3. Low implementation complexity, no need to use additional sensor equipment, autonomous positioning can be completed by relying only on the equipment required for communication of ordinary NTN terminals. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is an overall flowchart of a method for autonomous positioning of low-orbit non-terrestrial network terminals without network access.

[0017] Figure 2 This is a detailed flowchart of step S1.

[0018] Figure 3 This is a detailed flowchart of step S3.

[0019] Figure 4 This is a detailed flowchart of step S4.

[0020] Figure 5 This is a structural diagram of a low-orbit non-terrestrial network terminal autonomous positioning device that does not require network access, provided by the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are merely illustrative and not intended to limit the invention.

[0022] The overall process of the low-Earth orbit non-terrestrial network terminal autonomous positioning method of the present invention without network access is as follows: Figure 1 As shown, the specific steps include: S1: The terminal receives the NTN downlink signal transmitted by the satellite and performs time and frequency acquisition to obtain the physical cell identifier and the time of local SSB signal reception.

[0023] The detailed process of S1 is as follows: Figure 2 As shown, the details are as follows: S1.1: The terminal receives downlink signals through a directional antenna or an omnidirectional antenna; when a directional antenna is used, the terminal can perform antenna beam scanning based on the received signal power metric or a metric constructed from the statistical characteristics of the received signal to search for satellite downlink signals; after detecting a satellite signal, the antenna can be finely adjusted along the direction of the maximum signal metric to maintain the pointing towards the satellite signal.

[0024] S1.2: The terminal performs down-conversion, filtering, and analog-to-digital conversion on the received radio frequency signal to obtain the baseband signal.

[0025] S1.3: In the first epoch, the terminal performs initial SSB time-frequency acquisition on the baseband signal to obtain the physical cell identifier, carrier frequency offset, and sampling time offset. Specifically, the terminal correlates the local copy of the PSS signal with the received baseband signal, as shown below: in The first local copy signal generated based on the PSS sequence corresponding to the cell identifier to be determined 2 (NID2) is... n The complex conjugate of each sample, with superscript This represents the operation of finding the complex conjugate. For the received baseband signal,N The number of samples used for correlation operations is equal to the length of the generated PSS local copy signal. The sampling period is This represents the maximum Doppler shift that a low-Earth orbit satellite can produce. For the coarse carrier frequency offset estimation to be determined, the search range is: Search Steps It is a quarter of a subcarrier spacing. It is a sampling time-partial estimate to be determined. It is the number of sampling points corresponding to the SSB transmission cycle. To account for the maximum potential time delay caused by satellite movement, the operating speed of low-Earth orbit satellites generally does not exceed 7.8 km / s, combined with the speed of light. c Will Set as .

[0026] Then, the SSS local copy signal is correlated with the received baseband signal to obtain cell identifier 1 (NID1): in The first local replica signal generated based on the SSS sequence corresponding to the undetermined NID1 n The complex conjugate of each sample, The sampling point interval corresponds to the known SSS and PSS signal transmission intervals.

[0027] Then, based on the PSS / SSS phase difference, a fine carrier frequency offset estimate is performed, expressed as: in Indicates the phase angle as a complex number, superscript This represents the complex conjugate operation; The final physical cell identifier is 3×NID1+NID2. The captured sampling time offset... Multiply by the sampling period To convert to the local received SSB signal time of the first epoch ,in s This indicates the sequence number of the satellite currently captured.

[0028] S1.4: Based on the time-frequency acquisition results of the previous epoch, SSB time-frequency acquisition is performed to obtain carrier frequency offset and sampling time offset estimates. After acquiring the SSB in the previous epoch, NID2 has determined that no further search is needed, and the time-domain search range for this acquisition is significantly reduced. k Individual calendar (k The capture formula for >1) is expressed as: exist k When =2, and These are the sampling time offset and fine carrier frequency offset captured by S1.3 corresponding to the first epoch. k >2 o'clock is the previous epoch. k -1 corresponds to the sampling time offset and fine carrier frequency offset captured by S1.4.

[0029] Then, a fine carrier frequency offset estimation is performed, expressed as: in: use Normalized correlation power peak after modulus calculation If the value exceeds the threshold, the acquisition is considered successful, and the signal for the next epoch is sent to S1.4 for time-frequency acquisition. k Increment by one; if the value is less than the threshold, acquisition is considered a failure. In this case, it is necessary to switch to S1.1 to perform beam scanning and signal time-frequency acquisition for the next satellite, and the satellite sequence number... s Add one, k Reset to 1. The threshold can be 7.8 times the noise power, and the noise power can be the average of 64 non-peak normalized correlation powers.

[0030] The sampling time bias obtained from successful capture Multiply by the sampling period To transform into the first k Local SSB signal received at epoch 1 .

[0031] S2: Synchronize downlink signals based on time-frequency acquisition results and physical cell identifiers, extract ephemeris information from SIB19 and calculate satellite positions.

[0032] The detailed process of S2 is as follows: Downlink signal synchronization is performed based on the time-frequency acquisition results and physical cell identifier. SIB19 is obtained from the Physical Downlink Shared Channel (PDSCH) carrying SIB19. For specific operations, please refer to "Detailed Explanation of 5G Mobile Communication System Design and Standards - Wang Yingmin". Five parameters used to determine the orbit are extracted from SIB19: semi-major axis, eccentricity, right ascension of the ascending node, orbital inclination, and perigee distance; and two parameters used to determine the precise position within the satellite orbit: ephemeris reference time and the mean perigee angle of the reference time. Then, the first... kIndividual Era Satellite s Three-dimensional position vector in geocentric-ground-fixed coordinate system at the time of SSB transmission For methods of calculating satellite positions, please refer to "GPS Principles and Receiver Design - Xie Gang".

[0033] S3: Assemble TDOA observations based on the local SSB signal reception time and fixed SSB transmission period.

[0034] The detailed process of S3 is as follows: Figure 3 As shown, the details are as follows: S3.1: After continuously capturing the SSB in the downlink signal via S1, the terminal obtains... The time when a local SSB signal is received is denoted as . Without losing generality, As a reference time, the local reception time difference set is represented as .

[0035] S3.2: By satellite s SSB transmission cycle The set of transmission intervals is represented as follows: .

[0036] S3.3: Combining the local reception time difference set and the SSB transmission interval set, the TDOA measurement set is represented as: .

[0037] S4: TDOA observations and satellite position information are used as least squares inputs for positioning calculation.

[0038] The detailed process of S4 is as follows: Figure 4 As shown, the details are as follows: S4.1: The terminal position vector to be estimated in the geocentric coordinate system is Record the connection from the terminal to the satellite. s exist The geometric distance of an epoch is: Get Compared to Partial derivative: So the satellites observed by the terminal s All TDOA measurements Compared to The Jacobian matrix can be expressed as: in represent right exist The observation vector at this location, here This represents the current iteration number in the Newton iteration.

[0039] S4.2: Residual Vector Represented as: in This indicates the effect of Earth's rotation. This is the Earth's rotational angular velocity.

[0040] To reduce the amount of computation, we can... and Perform downsampling processing.

[0041] S4.3: Most of the time, only one satellite is visible to the terminal, but different satellites are observed at different times. The terminal processes the data transmitted by different satellites separately. The terminal received a total of m The downlink signals of each satellite, and the Jacobian matrix corresponding to all satellites at this time. G and residual vector b Represented as: S4.4: Obtain the correction amount of the terminal position using the least squares method. , is represented as: Update the terminal location: If the length of the displacement vector If the value is less than the threshold, it is considered to have converged to the required accuracy. As the current epoch positioning result of the terminal, otherwise it will be output as the current epoch positioning result. k Increment the value by 1, and return to S4.1 to perform Newton's iteration calculation.

[0042] Corresponding to the aforementioned embodiment of an autonomous positioning method for a low-Earth orbit non-terrestrial network terminal without network access, the present invention also provides an embodiment of an autonomous positioning device for a low-Earth orbit non-terrestrial network terminal without network access.

[0043] See Figure 5 The present invention provides an autonomous positioning device for a low-Earth orbit non-terrestrial network terminal without network access, comprising a memory and one or more processors. The memory stores executable code, and when the processor executes the executable code, it is used to implement an autonomous positioning method for a low-Earth orbit non-terrestrial network terminal without network access as described in the above embodiment.

[0044] The embodiment of the low-Earth orbit non-terrestrial network terminal autonomous positioning device provided by this invention can be applied to any device with data processing capabilities, such as a computer. The device embodiment can be implemented through software, hardware, or a combination of both. Taking software implementation as an example, as a logical device, it is formed by the processor of any data processing device loading the corresponding computer program instructions from non-volatile memory into memory for execution. From a hardware perspective, such as... Figure 5 The diagram shown is a hardware structure diagram of any device with data processing capabilities, which is a low-orbit non-terrestrial network terminal autonomous positioning device that does not require network access, provided by the present invention. Except for... Figure 5 In addition to the processor, memory, network interface, and non-volatile memory shown, any data processing device in the embodiment may also include other hardware depending on the actual function of the data processing device, which will not be described in detail here.

[0045] The specific implementation process of the functions and roles of each unit in the above device can be found in the implementation process of the corresponding steps in the above method, and will not be repeated here.

[0046] For the device embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to in the description of the method embodiments. The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and 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 modules can be selected to achieve the purpose of the present invention according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0047] This invention also provides a computer-readable storage medium storing a program that, when executed by a processor, implements a method for autonomous positioning of a low-Earth orbit non-terrestrial network terminal without network access as described in the above embodiments.

[0048] The computer-readable storage medium can be an internal storage unit of any data processing device described in any of the foregoing embodiments, such as a hard disk or memory. The computer-readable storage medium can also be an external storage device of any data processing device, such as a plug-in hard disk, smart media card (SMC), SD card, flash card, etc., equipped on the device. Furthermore, the computer-readable storage medium can include both internal storage units and external storage devices of any data processing device. The computer-readable storage medium is used to store the computer program and other programs and data required by the data processing device, and can also be used to temporarily store data that has been output or will be output.

[0049] The present invention also provides a computer program product, including a computer program, which, when executed by a processor, implements the aforementioned method for autonomous positioning of a low-orbit non-terrestrial network terminal without network access.

[0050] The above embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for autonomous positioning of a low-Earth orbit non-terrestrial network terminal without network access, characterized in that, The method includes the following steps: S1: The terminal receives the NTN downlink signal transmitted by the satellite and performs time and frequency acquisition to obtain the physical cell identifier and the time of local SSB signal reception; S2: Synchronize downlink signals based on time-frequency acquisition results and physical cell identifiers, extract ephemeris information from SIB19 and calculate satellite positions; S3: Assemble TDOA observations based on the local SSB signal reception time and fixed SSB transmission period; S4: TDOA observations and satellite position information are used as least squares inputs for positioning calculation.

2. The method for autonomous positioning of a low-orbit non-terrestrial network terminal without network access as described in claim 1, characterized in that, The terminal receives downlink signals via a directional antenna or an omnidirectional antenna. When a directional antenna is used, the terminal performs antenna beam scanning to search for satellite downlink signals. After detecting a satellite signal, the antenna is finely adjusted along the direction of the largest signal metric to maintain the pointing towards the satellite signal.

3. The method for autonomous positioning of a low-orbit non-terrestrial network terminal without network access as described in claim 1, characterized in that, In the first epoch, the terminal performs initial SSB time-frequency acquisition of the baseband signal to obtain the physical cell identifier, carrier frequency offset, and sampling time offset. Specifically, the terminal correlates the local copy of the PSS with the received baseband signal to obtain cell identifier 2 and sampling time offset, then correlates the local copy of the SSS with the received baseband signal to obtain cell identifier 1, performs fine carrier frequency offset estimation for the first epoch based on the PSS / SSS phase difference, and obtains the physical cell identifier. The acquired sampling time offset is multiplied by the sampling period to convert it into the local received SSB signal time for the first epoch.

4. The method for autonomous positioning of a low-orbit non-terrestrial network terminal without network access according to claim 1, characterized in that, Based on the k The results of the precise carrier frequency offset and sampling time offset captured in the -1 epoch are used to perform SSB signal time-frequency acquisition to obtain the first epoch. k The precise carrier frequency offset and sampling time offset estimates for each epoch are obtained by multiplying the captured sampling time offset by the sampling period to convert it into the first epoch. k The local reception time of the SSB signal in each epoch.

5. The method for autonomous positioning of a low-orbit non-terrestrial network terminal without network access according to claim 1, characterized in that, Based on the captured time and frequency information and physical cell identifier, the downlink signal is synchronized to extract SIB19 messages, including five parameters for determining the orbit: semi-major axis, eccentricity, right ascension of the ascending node, orbital inclination, and perigee distance, as well as two parameters for determining the precise position within the satellite orbit: ephemeris reference time and mean perigee angle of the reference time; the terminal calculates the satellite position using the ephemeris reference time and orbit information.

6. The method for autonomous positioning of a low-orbit non-terrestrial network terminal without network access according to claim 1, characterized in that, After continuously capturing SSBs in the downlink signal, the terminal obtains multiple local SSB signal times. Using the first epoch as a reference, it obtains a set of local reception time differences. The SSB transmission interval set is determined by the satellite's SSB transmission period. Combining the local reception time difference set and the SSB transmission interval set, the TDOA measurement set is obtained.

7. The method for autonomous positioning of a low-orbit non-terrestrial network terminal without network access according to claim 1, characterized in that, For satellites s First, the Jacobian matrix of TDOA measurement relative to the estimated terminal position is calculated by estimating the terminal position and the known satellite positions. Then, considering the Earth's rotation, a residual vector is constructed based on TDOA measurements, the terminal position, and known satellite positions. The final Jacobian matrix is ​​constructed by combining the Jacobian matrices and residual vectors of different satellites. and b The estimated terminal position is then updated using the least squares method until it converges to the required accuracy.

8. A low-Earth orbit non-terrestrial network terminal autonomous positioning device without network access, comprising a memory and one or more processors, wherein the memory stores executable code, characterized in that, When the processor executes the executable code, it implements a method for autonomous positioning of a low-orbit non-terrestrial network terminal without network access, as described in any one of claims 1-7.

9. A computer-readable storage medium having a program stored thereon, characterized in that, When the program is executed by the processor, it implements a method for autonomous positioning of a low-orbit non-terrestrial network terminal without network access, as described in any one of claims 1-7.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements a method for autonomous positioning of a low-orbit non-terrestrial network terminal without network access as described in any one of claims 1-7.

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