Cell access methods and devices, storage media and electronic equipment

Abstract

This application discloses a cell access method, apparatus, storage medium, and electronic device. The method, applicable to a terminal, includes: determining multiple time epochs based on ephemeris data of low-Earth orbit (LEO) satellites extracted from system information blocks; measuring the Doppler frequency shift value corresponding to each time epoch; determining the satellite position corresponding to each time epoch based on the ephemeris data; determining the terminal's position and frequency deviation based on the Doppler frequency shift value, satellite position, and preset elevation parameters; and sending an access message to the LEO satellite's base station based on the terminal's position and frequency deviation to control the terminal's access to the target cell. This application solves the technical problem of cell access failure due to the terminal's inability to obtain accurate location information, thereby achieving the technical effect of high-precision autonomous positioning and access to LEO satellites by the terminal.

Description

Technical Field

[0001] This application relates to the field of computers, and more specifically, to a cell access method and apparatus, storage medium and electronic device. Background Technology

[0002] In existing technologies, when a terminal accesses a cell, it needs to rely on the Global Navigation Satellite System (GNSS) to obtain accurate location information in order to calculate downlink propagation delay and Doppler frequency shift, and then complete uplink timing advance and frequency pre-compensation. However, due to signal obstruction, attenuation or interference in the environment where the terminal is located, the terminal may be unable to obtain location information or the obtained location information may be unusable, thus failing to accurately pre-compensate for the time and frequency deviation of the communication link, resulting in terminal access failure.

[0003] There is currently no effective solution to the above problems. Summary of the Invention

[0004] This application provides a cell access method and apparatus, storage medium and electronic device to at least solve the technical problem of cell access failure caused by the terminal's inability to obtain its own accurate location information.

[0005] According to one aspect of the embodiments of this application, a cell access method without satellite navigation is provided, applied to a terminal, comprising: determining multiple time epochs based on ephemeris data of low-Earth orbit satellites extracted from a system information block, wherein the system information block corresponds to a target cell served by the low-Earth orbit satellite; measuring the Doppler frequency shift value corresponding to each of the multiple time epochs; determining the satellite position corresponding to each time epoch based on the ephemeris data; determining the terminal position and frequency deviation of the terminal based on the Doppler frequency shift value, the satellite position, and a preset elevation parameter; and sending an access message to the satellite base station of the low-Earth orbit satellite based on the terminal position and the frequency deviation to control the terminal to access the target cell.

[0006] According to one aspect of the embodiments of this application, a cell access method without satellite navigation is also provided, applied to low-Earth orbit satellites, comprising: receiving an access message sent by a terminal, wherein the access message is sent by the terminal based on the terminal position and frequency deviation, the terminal position and the frequency deviation being determined based on Doppler frequency shift values, satellite position and preset elevation parameters, the satellite position corresponding to each time epoch being determined based on the ephemeris data of the low-Earth orbit satellite, the Doppler frequency shift value corresponding to each time epoch being obtained by measurement by the terminal, and multiple time epochs being determined based on the ephemeris data extracted from a system information block, the system information block corresponding to a target cell served by the low-Earth orbit satellite; and sending a response message to the terminal to control the terminal to access the target cell.

[0007] According to another aspect of the embodiments of this application, a cell access device without satellite navigation is also provided, applied to a terminal, comprising: a first determining module, configured to determine multiple time epochs based on ephemeris data of low-orbit satellites extracted from a system information block, wherein the system information block corresponds to a target cell served by the low-orbit satellite; a measuring module, configured to measure the Doppler frequency shift value corresponding to each of the multiple time epochs; a second determining module, configured to determine the satellite position corresponding to each time epoch based on the ephemeris data; a third determining module, configured to determine the terminal position and frequency deviation of the terminal according to the Doppler frequency shift value, the satellite position, and a preset elevation parameter; and a first transmitting module, configured to transmit an access message to the satellite base station of the low-orbit satellite based on the terminal position and the frequency deviation, so as to control the terminal to access the target cell.

[0008] In an exemplary embodiment, the apparatus is configured to send an access message to a satellite base station of the low-Earth orbit satellite based on the terminal location and the frequency deviation in the following manner to control the terminal to access the target cell: determining the transmission time and carrier frequency of the access message based on the terminal location and the system information block; and sending the access message to the satellite base station using the carrier frequency at the transmission time to control the terminal to access the target cell.

[0009] In an exemplary embodiment, the apparatus is configured to determine the transmission time and carrier frequency of the access message based on the terminal location and the system information block by: calculating the one-way propagation delay using location data of the terminal location and the ephemeris data; and determining the transmission time based on the common timing advance and common timing advance drift rate extracted from the system information block, and the one-way propagation delay.

[0010] In an exemplary embodiment, the apparatus is configured to determine the transmission time and carrier frequency of the access message based on the terminal location and the system information block by: calculating the real-time frequency shift corresponding to the transmission time according to the terminal location and the ephemeris data; and determining the carrier frequency according to the real-time frequency shift and the frequency deviation.

[0011] In an exemplary embodiment, the apparatus is configured to control the terminal to access the target cell by sending an access message to a satellite base station of the low-Earth orbit satellite based on the terminal location and the frequency deviation in the following manner: sending the access message to the satellite base station based on the terminal location and the frequency deviation; receiving a response message from the satellite base station in response to the access message; and adjusting the start time and transmission frequency for sending uplink data to the satellite base station according to the response message, so as to control the terminal to access the target cell.

[0012] In an exemplary embodiment, the apparatus is configured to control the terminal to access the target cell by adjusting the start time and transmission frequency of uplink data transmission according to the response message in the following manner: parsing the response message to obtain a timing adjustment amount and a frequency adjustment amount; updating the start time using the timing adjustment amount; and updating the transmission frequency using the frequency adjustment amount.

[0013] In an exemplary embodiment, the device is configured to determine the terminal position and frequency deviation of the terminal based on the Doppler frequency shift value, the satellite position, and a preset elevation parameter in the following manner: constructing an initial state vector of the terminal, wherein the initial state vector includes coordinate parameters and a frequency deviation parameter, the coordinate parameters indicating the position coordinates of the terminal, and the frequency deviation parameter indicating the local oscillator frequency deviation of the terminal; iteratively updating the initial state vector using an extended Kalman filter algorithm to obtain a target state vector, wherein the Doppler frequency shift value, the satellite position, and the preset elevation parameter are used to construct the observation equation used in the extended Kalman filter algorithm; determining the terminal position based on the value of the coordinate parameter in the target state vector; and determining the frequency deviation based on the value of the frequency deviation parameter in the target state vector.

[0014] In an exemplary embodiment, the apparatus is configured to iteratively update the initial state vector using an extended Kalman filter algorithm to obtain a target state vector by: sequentially determining the satellite position data corresponding to each time epoch as the current satellite position data in chronological order, and determining the Doppler frequency shift value corresponding to each time epoch as the current frequency shift value; performing the following operations on the current satellite position data and the current frequency shift value to obtain the target state vector: using an identity matrix state transition matrix to perform state prediction on the initial state vector to obtain a priori state estimation state vector and a priori error covariance matrix; based on the nonlinear Doppler observation model... The comparable matrix, the preset elevation parameter, the current frequency shift value, and the current satellite position data are used to observe and update the prior state estimation state vector and the prior error covariance matrix to obtain the posterior state estimation state vector and the posterior error covariance matrix. If the trace value of the posterior error covariance matrix is ​​less than a preset convergence threshold, the posterior state estimation state vector is determined as the target state vector. If the trace value of the posterior error covariance matrix is ​​greater than or equal to the preset convergence threshold, the current satellite position data is updated to the position data of the satellite position corresponding to the next time epoch, and the current frequency shift value is updated to the Doppler frequency shift value corresponding to the next time epoch.

[0015] In an exemplary embodiment, the apparatus is configured to transmit an access message to a satellite base station of the low-Earth orbit satellite based on the terminal location and the frequency deviation, before controlling the terminal to access the target cell, by: generating a physical random access channel preamble sequence; adding an autonomous positioning auxiliary information control element to a physical layer protocol data unit, wherein the autonomous positioning auxiliary information control element encapsulates the location information of the terminal location, the trace of the location error covariance, and an uncompensated residual Doppler frequency offset estimate, the trace of the location error covariance being the trace of the posterior error covariance matrix corresponding to the target state vector, and the uncompensated residual Doppler frequency offset estimate being the difference between the Doppler frequency shift value measured at the transmission time and the expected frequency shift value, the expected frequency shift value being determined using a nonlinear Doppler observation model; and generating the access message based on the physical random access channel preamble sequence and the physical layer protocol data unit.

[0016] In one exemplary embodiment, the physical random access channel preamble sequence includes at least one of the following: the physical random access channel preamble sequence adopts a preamble format without a cyclic prefix; the physical random access channel preamble sequence is configured with an extended guard interval.

[0017] In an exemplary embodiment, the apparatus is further configured to: when the low-orbit satellite does not have baseband processing capabilities, the frequency deviation also includes a frequency offset drift term and a propagation delay compensation term corresponding to the feed link between the satellite base station and the low-orbit satellite.

[0018] In one exemplary embodiment, the apparatus is further configured to: determine the terminal location using a multi-satellite instantaneous time difference of arrival and frequency difference of arrival joint positioning model when multiple low-orbit satellites are present.

[0019] In an exemplary embodiment, the apparatus is further configured to: receive downlink signaling sent by a network-side location management function server, wherein the location management function server is configured to receive the Doppler frequency shift value sent by the terminal, and perform nonlinear positioning calculation based on the Doppler frequency shift value and the ephemeris data to generate the downlink signaling, the downlink signaling being used to determine the transmission time of the access message and the carrier frequency used to transmit the access message.

[0020] According to another aspect of the embodiments of this application, a cell access device without satellite navigation is also provided, applied to low-Earth orbit satellites, comprising: a receiving module for receiving an access message sent by a terminal, wherein the access message is sent by the terminal based on the terminal position and frequency deviation, the terminal position and the frequency deviation being determined based on Doppler frequency shift values, satellite position and preset elevation parameters, the satellite position corresponding to each time epoch being determined based on the ephemeris data of the low-Earth orbit satellite, the Doppler frequency shift value corresponding to each time epoch being obtained by measurement by the terminal, and multiple time epochs being determined based on the ephemeris data extracted from a system information block, the system information block corresponding to a target cell served by the low-Earth orbit satellite; and a second sending module for sending a response message to the terminal to control the terminal to access the target cell.

[0021] In an exemplary embodiment, the apparatus is configured to send a response message to a terminal in the following manner to control the terminal to access the target cell: encapsulating a timing adjustment amount and a frequency adjustment amount in the response message, wherein the timing adjustment amount is used to update the start time of the terminal sending uplink data to the satellite base station, and the frequency adjustment amount is used to update the transmission frequency of the terminal sending the uplink data to the satellite base station; and sending the response message to the terminal to control the terminal to access the target cell.

[0022] In an exemplary embodiment, the apparatus is configured to, before encapsulating the timing adjustment amount and the frequency adjustment amount in the response message, acquire the uplink angle of arrival and the uplink time difference of arrival corresponding to the access message; parse the access message to obtain an autonomous positioning assistance information control element, wherein the autonomous positioning assistance information control element encapsulates the location information of the terminal location; perform position correction on the location information of the terminal location based on the uplink angle of arrival and the uplink time difference of arrival, and generate the timing adjustment amount and the frequency adjustment amount.

[0023] In an exemplary embodiment, the device is configured to perform position correction on the position information of the terminal location based on the uplink angle of arrival and the uplink time difference of arrival, and generate the timing adjustment amount and the frequency adjustment amount by: determining the measured position of the terminal based on the uplink angle of arrival and the uplink time difference of arrival; performing a cross-comparison operation on the position information of the measured position and the position information of the terminal location to obtain an unbiased position error value; obtaining the trace value of the position error covariance and the estimated value of the uncompensated residual Doppler frequency offset encapsulated in the autonomous positioning assistance information control element; and performing a fusion filtering operation on the position information of the terminal location and the position information of the measured position using the trace value of the position error covariance, the estimated value of the uncompensated residual Doppler frequency offset, and the unbiased position error value to generate the timing adjustment amount and the frequency adjustment amount.

[0024] According to another aspect of the embodiments of this application, a computer-readable storage medium is also provided, wherein a computer program is stored in the computer-readable storage medium, and the computer program is configured to execute the above-described cell access method when it is run.

[0025] According to another aspect of the embodiments of this application, a computer program product or computer program is provided, which includes computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the computer device to perform the cell access method as described above.

[0026] According to another aspect of the embodiments of this application, an electronic device is also provided, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to execute the above-described cell access method through the computer program.

[0027] In this embodiment, the terminal first determines multiple time epochs based on the ephemeris data of the low-Earth orbit satellite extracted from the system information block. This system information block corresponds to the target cell served by the low-Earth orbit satellite. Next, it measures the Doppler frequency shift value corresponding to each of the multiple time epochs. Further, it determines the satellite position corresponding to each time epoch based on the ephemeris data. Based on the Doppler frequency shift value, the satellite position, and preset elevation parameters, it determines the terminal position and frequency deviation. Finally, based on the terminal position and frequency deviation, it sends an access message to the satellite base station of the low-Earth orbit satellite to access the target cell. That is, by using the motion trajectory of the low-Earth orbit satellite at multiple time epochs to determine the satellite position without the assistance of a global navigation satellite system, and combining the elevation constraints of the Doppler observation value and preset elevation parameters, the terminal achieves autonomous positioning and frequency deviation estimation. This achieves the goal of accurate time and frequency pre-compensation without relying on an external navigation system, thereby solving the technical problem of cell access failure caused by the terminal's inability to obtain its own accurate position information. Attached Figure Description

[0028] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0029] Figure 1 This is an optional overall architecture diagram of an integrated communication and navigation system according to an embodiment of this application;

[0030] Figure 2 This is a flowchart illustrating an optional cell access method for a terminal without satellite navigation, according to an embodiment of this application.

[0031] Figure 3 This is an optional internal module structure diagram of a terminal device according to an embodiment of this application;

[0032] Figure 4 This is a flowchart illustrating an optional cell access method for low-Earth orbit satellites without satellite navigation, according to an embodiment of this application.

[0033] Figure 5 This is a service flow diagram of an optional cell access method without satellite navigation according to an embodiment of this application;

[0034] Figure 6 This is a schematic diagram of an optional cell access device for a terminal without satellite navigation, according to an embodiment of this application.

[0035] Figure 7 This is a schematic diagram of the structure of an optional cell access device for low-Earth orbit satellites without satellite navigation, according to an embodiment of this application.

[0036] Figure 8 This is a schematic diagram of the structure of an optional electronic device according to an embodiment of this application. Detailed Implementation

[0037] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0038] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application 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 application 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.

[0039] The present application will be described below with reference to embodiments:

[0040] According to one aspect of the embodiments of this application, a cell access method without satellite navigation is provided.

[0041] Optionally, in this embodiment, the above-mentioned cell access method can be applied to the cross-technology field of mobile communication and satellite navigation, specifically involving wireless communication, core network and access network (RAN), radio resource control (RRC), and satellite communication, navigation, and positioning technologies. It can be further applied to the initial access scenario of a terminal in an environment without global navigation satellite system signal coverage or with limited signal coverage. Specifically, it can be applied to scenarios such as... Figure 1 The above-described cell access method is applied in the application environment shown.

[0042] Considering that in typical low-Earth orbit satellite communication scenarios, satellites operate at altitudes of 500 to 1500 kilometers above the ground, their relative speed to ground user equipment is extremely high (for example, a satellite at an orbital altitude of 600 km can have a relative speed exceeding 7 km / s). This extremely high relative speed and ultra-long communication distance result in extremely severe propagation delays (tens to hundreds of milliseconds) and extreme Doppler shifts (up to tens or even hundreds of kHz) and drastic Doppler rates between the satellite and the terminal. Current technologies often directly use the initial access and time-frequency synchronization mechanism for non-terrestrial network terminals (NTNs) based on the Global Navigation Satellite System, as defined in the 3GPP Rel-17 / 18 standard. Specifically:

[0043] The first step is the system broadcast and coarse synchronization phase. Next-generation Node Bs (gNBs) can be deployed on the ground and connected to satellites via transparent relay payloads, or they can be deployed directly on satellites as regenerative payloads. They continuously transmit the Primary Synchronization Signal (PSS), Secondary Synchronization Signal (SSS), and Physical Broadcast Channel (PBCH) via the downlink. Crucially, the base station broadcasts satellite ephemeris data (including the satellite's instantaneous position and state vectors, velocity and state vectors, or Keplerian orbital elements), Common Timing Advance (CommonTA) parameters, Common Timing Advance Drift Rate (K_offset), and the effective time of the uplink synchronization epoch to the entire network via System Information Block 19 (SIB19).

[0044] The second step is the terminal-forced global navigation satellite system positioning phase. Due to the extreme dynamic latency and frequency offset of non-terrestrial network links, the terminal must force the activation of its built-in global navigation satellite system receiver module (such as GPS, BeiDou, Galileo, etc.) before initiating Random Access Channel (RACH) to obtain its precise three-dimensional geographical coordinates (longitude, latitude, and altitude). This is a mandatory prerequisite under the existing protocol architecture.

[0045] The third step is the autonomous open-loop pre-compensation stage. The terminal uses its own absolute position information obtained from the Global Navigation Satellite System (GNSS) and combines it with satellite ephemeris information decoded from system information block 19 to autonomously calculate the precise line-of-sight (LoS) distance and relative radial velocity between the terminal and the satellite. Based on this, the terminal locally calculates the UE-specific timing advance (TA) and Doppler shift pre-compensation value.

[0046] The fourth step is the traditional random access phase. After completing local time-frequency pre-compensation, the terminal applies the calculated timing advance and Doppler pre-compensation at the transmitting end to initiate either a 4-Step RACH or a 2-Step RACH. The terminal sends a Physical Random Access Channel (PRACH) preamble (Msg1 or Random Access Preamble with Uplink Data, MsgA). Due to the precise pre-compensation, the uplink signal arriving at the satellite receiver is roughly aligned with the base station's uplink receiving window in time and frequency, thus avoiding severe inter-symbol interference (ISI) and inter-carrier interference (ICI). The base station then sends a random access response (Msg2 or Random Access Response (in 2-Step RACH), MsgB) to establish a connection.

[0047] In addition, existing technologies also include cellular network-based positioning methods (such as Downlink Time Difference of Arrival (DL-TDOA), Multi-Round Trip Time (Multi-RTT), and Angle of Arrival (AoA) defined by the 3rd Generation Partnership Project). However, in non-terrestrial network scenarios, existing methods typically rely on the terminal already being connected to the network (RRC_CONNECTED state), and often require the terminal to simultaneously observe multiple satellites (e.g., DL-TDOA requires at least 3 satellites) to complete position calculation.

[0048] Therefore, uplink pre-compensation based on propagation delay and Doppler characteristics can only be performed when the terminal can obtain its own accurate location information. Furthermore, when the global navigation satellite system signal is blocked, suppressed, or spoofed (i.e., GNSS denial environment), the terminal cannot obtain high-precision absolute position, and cannot complete accurate pre-compensation for timing advance and Doppler frequency offset, nor can it meet the geometric constraints of multi-satellite observation in traditional cellular positioning methods. This will directly lead to the uplink random access preamble sequence being unable to be correctly detected by the base station due to severe time and frequency inaccuracies, ultimately causing the technical problem of cell access failure.

[0049] To address the aforementioned technical issues, the cell access method described in this application can be applied. Specifically, by utilizing the extremely high Doppler variation rate caused by the high-speed motion of low-Earth orbit satellites, a single continuously moving low-Earth orbit satellite can be treated as multiple virtual anchor points on its spatial trajectory within a short period of time, further determining the satellite position indicated by each virtual anchor point. The terminal independently calculates its precise terminal position and frequency deviation locally by continuously measuring the Doppler frequency shift of the synchronization signal block and the downlink reference signal at multiple time epochs, combined with the Extended Kalman Filter (EKF) algorithm. After completing time-frequency pre-compensation, a two-step random access is initiated through a specially constructed two-step random access first message MsgA (encapsulating self-positioning coordinates and error covariance in the uplink payload), with the non-terrestrial network base station performing rapid closed-loop verification.

[0050] Furthermore, by using the aforementioned cell access method without satellite navigation, even when conventional global navigation satellite system signals are missing or interfered with, high-precision autonomous positioning and seamless initial access communication and location navigation of the terminal can be achieved by utilizing non-terrestrial network systems and low-Earth orbit communication satellite operating modes.

[0051] Optionally, as an alternative implementation, the above-described cell access method without satellite navigation can be applied to a terminal, which can be a terminal configured with an application, and may include, but is not limited to, at least one of the following: mobile phones (such as Android phones, iOS phones, etc.), laptops, tablets, handheld computers, MIDs (Mobile Internet Devices), PADs, desktop computers, smart TVs, smart voice interaction devices, smart home appliances, vehicle terminals, aircraft, virtual reality (VR) terminals, augmented reality (AR) terminals, mixed reality (MR) terminals, and other computer devices. Figure 2 The following are included:

[0052] S202, based on the ephemeris data of the low-orbit satellite extracted from the system information block, determine multiple time epochs, wherein the system information block corresponds to the target cell served by the low-orbit satellite;

[0053] Optionally, in this embodiment, the aforementioned system information block may be SIB19. The correspondence between the system information block and the target cell served by the low-Earth orbit satellite means that the system information block is broadcast by the low-Earth orbit satellite within the current beam coverage area, and its content is dedicated to initial access and positioning assistance for all terminals within that cell. Specifically:

[0054] In scenarios where low-Earth orbit communication satellites employ multi-beam dynamic coverage, including but not limited to the satellite beam center area, beam edge transition area, cross-beam switching critical area, or inter-satellite link coverage overlap area, each beam corresponds to an independent SIB19 broadcast period and ephemeris update timestamp. The terminal only needs to parse the SIB19 corresponding to its residing beam to obtain ephemeris data.

[0055] Optionally, in the embodiments of this application, the above-mentioned ephemeris data may include, but is not limited to, the satellite's spatial position state vector, velocity state vector, and epoch time at the reference epoch.

[0056] Optionally, in the embodiments of this application, in the scenario where the satellite adopts a transparent forwarding architecture, the above-mentioned system information block may also be the original SIB19 content transmitted by the satellite radio frequency relay after being forwarded by the ground gateway station, including but not limited to ephemeris parameters, common timing advance, common timing advance drift rate, epoch effective time and power supply link delay compensation factor.

[0057] Optionally, in the embodiments of this application, the target cell served by the aforementioned low-orbit satellite can also be a virtual cell defined based on the access area division of the ground gateway station, including but not limited to logical cells identified by geographical latitude and longitude range, elevation angle threshold, beam number or satellite orbit period. The terminal completes cell identification and matching based on the received SIB19 broadcast identifier and beam index.

[0058] It should be noted that the broadcasting method, ephemeris update frequency, cell boundary definition method, and link connection mode between the terminal and the satellite can all be flexibly configured according to the network deployment architecture, satellite orbit type, channel conditions, or terminal mobility characteristics. For example, SIB19 can be periodically distributed through the broadcast channel or unicast on demand when the terminal first accesses the network. Ephemeris data can be encoded based on Kepler orbital elements, state vectors, or predicted orbit models. The target cell can correspond to a single beam of a single satellite or to the joint coverage area of ​​multiple satellites. This application does not impose any limitations on these aspects.

[0059] It should also be noted that the terminal can also extract the common timing advance and the common timing advance drift rate from the system information block.

[0060] Optionally, in the embodiments of this application, the aforementioned time epoch refers to a discrete time point in which the terminal performs Doppler frequency shift sampling on the downlink reference signal in a continuous time dimension. Each time epoch corresponds to an independent signal measurement window, which is used to capture the instantaneous motion characteristics of the low-orbit satellite at that moment in order to determine the satellite position.

[0061] S204, measures the Doppler frequency shift value corresponding to each time epoch in multiple time epochs;

[0062] Optionally, in the embodiments of this application, the aforementioned Doppler frequency shift value can be understood as the carrier frequency offset extracted by the terminal after performing frequency domain analysis on the received downlink reference signal (including synchronization signal block or positioning reference signal) within a specific time epoch. Specifically:

[0063] In scenarios where the high-speed motion of a low-Earth orbit satellite results in a significant relative radial velocity, including but not limited to the terminal being located at the perigee, apogee, beam center region, beam edge region, or mid-latitude region where the orbital inclination changes drastically, the Doppler frequency shift value is manifested as a positive or negative frequency offset of tens to hundreds of kilohertz caused by the radial motion of the satellite relative to the terminal. Its magnitude is closely related to the cosine relationship between the satellite velocity vector, downlink carrier frequency, and the terminal's geographical location.

[0064] Optionally, in another application scenario, such as when the terminal uses multiple antennas for reception, the aforementioned Doppler frequency shift value can also be a weighted average frequency offset value obtained by jointly estimating the phase difference of the signals received by multiple antennas or by spatial filtering algorithms. This includes, but is not limited to, frequency offset estimation algorithms based on minimum mean square error, frequency domain peak detection methods based on maximum likelihood, or dynamic compensation results based on joint tracking of phase-locked loop and fast Fourier transform. The corresponding time epoch can be an integer multiple of the system frame period, including but not limited to fixed intervals of 1 millisecond, 5 milliseconds, 10 milliseconds, or 20 milliseconds, or it can be a non-uniform sampling interval, including but not limited to adaptive sampling period dynamically adjusted according to the signal-to-noise ratio, dense sampling in high dynamic periods or sparse sampling in low dynamic periods based on satellite ephemeris prediction.

[0065] It should be noted that the measurement of Doppler frequency shift values ​​can be based on any reference signal in the downlink of a non-terrestrial network, including: Synchronization Signal Block (SSB), Positioning Reference Signal (PRS), Channel State Information Reference Signal (CSI-RS), or Demodulation Reference Signal (DMRS).

[0066] Furthermore, the measurement method can be implemented using various techniques such as Fast Fourier Transform Peak Detection in Frequency Domain, Time-Domain Correlation Peak Offset Estimation, Pilot Subcarrier Phase Difference Accumulation, or Deep Learning-Assisted Estimation, and this application does not limit the specific methods used.

[0067] S206, determines the satellite position corresponding to each time epoch based on ephemeris data;

[0068] Specifically, a virtual anchor point can be determined for each time epoch based on ephemeris data, and then the satellite position of the low-Earth orbit satellite within the corresponding time epoch can be determined based on the virtual anchor point.

[0069] Optionally, in the embodiments of this application, the aforementioned virtual anchor point can be understood as the instantaneous spatial position point corresponding to its ephemeris data at different times during the continuous movement of a single low-orbit communication satellite. This position point is abstracted as a virtual observation source equivalent to multiple static satellites, in order to construct a multi-point spatial geometric relationship in the time dimension.

[0070] For example, in scenarios where low-Earth orbit satellites operate in near-Earth circular or elliptical orbits, including but not limited to peak satellite transit periods, near perigee, near apogee, or regions where the terminal is at the edge of the satellite beam and the elevation angle changes rapidly, the virtual anchor point corresponding to each time epoch represents the precise three-dimensional coordinates of the satellite in the geocentric geofixed coordinate system (ECEF) at that moment, and its spatial distribution trajectory forms a continuous spatial motion arc, thereby simulating the geometric configuration of multi-satellite observation under single-satellite visibility conditions.

[0071] Optionally, in another application scenario, such as when the satellite adopts a regenerative payload architecture and has on-board real-time orbit prediction capability, the virtual anchor point can also be a predicted position point generated locally in real-time by combining the Kepler orbital elements or state vector broadcast by the terminal using SIB19 with a local time interpolation algorithm, including but not limited to trajectory approximation results based on analytical extrapolation of a two-body motion model.

[0072] It should be noted that the sampling density of virtual anchor points depends on the time interval between adjacent time epochs.

[0073] For example, during periods when satellites are passing overhead at high speed and Doppler shifts are drastic, the time interval between adjacent time epochs can be shortened to the millisecond level to improve trajectory resolution; during periods when satellite motion is relatively stable and Doppler shifts are slow, the time interval can be extended to tens of milliseconds to reduce the computational and power consumption burden on the terminal. This application does not impose any limitations on this.

[0074] S208, determines the terminal position and frequency deviation based on Doppler frequency shift value, virtual anchor point and preset elevation parameters;

[0075] Optionally, the aforementioned terminal position can be represented using three-dimensional coordinates, and the aforementioned frequency deviation refers to the frequency drift of the terminal's local oscillator.

[0076] For example, the terminal position and frequency deviation obtained by joint inversion using a nonlinear state estimation algorithm can be utilized. Specifically, in scenarios such as urban canyons, dense forests, indoor edges, or high latitudes in polar regions, the terminal uses an extended Kalman filter or least squares iterative algorithm to nonlinearly map the Doppler frequency shift measurement value of each time epoch to the satellite position of the corresponding virtual anchor point. Combined with preset elevation parameters, constraints are applied to the solution equation, thereby stably converging the terminal's longitude, latitude, altitude coordinates, and local crystal oscillator deviation under single-satellite visibility conditions, achieving high-precision autonomous positioning and clock calibration.

[0077] Optionally, the preset elevation parameter refers to the prior elevation information introduced by the terminal to constrain the ambiguity of the elevation dimension in the three-dimensional positioning solution when there is no assistance from the global navigation satellite system. Its function is to reduce the terminal position solution from a three-dimensional spatial problem to a two-dimensional planar search problem, thereby improving the convergence speed and accuracy of single-satellite Doppler positioning.

[0078] For example, preset elevation parameters can be determined by Earth surface elevation constraints. For instance, if the terminal is located near the Earth's surface, the altitude can be set as the preset elevation parameter using a coarse Digital Elevation Model (DEM) or the default sea level.

[0079] It should be noted that the calculation of the terminal position and frequency deviation can be achieved using various algorithms, including extended Kalman filtering, unscented Kalman filtering, nonlinear least squares, or convex optimization iteration; the preset elevation parameters can be static constants, dynamically updated regional averages, or terrain-aided information broadcast by satellite, and their sources can be local storage, cloud push, or network signaling; the calculation process can be directly output based on the Earth-Centered, Earth-Fixed (ECEF) coordinate system, or it can be converted to the geographic coordinate system (latitude, longitude, and altitude) before output, and this application does not limit this.

[0080] S210 sends an access message to the satellite base station of the low-Earth orbit satellite based on the terminal's location and frequency deviation in order to control the terminal's access to the target cell.

[0081] Optionally, in the embodiments of this application, the above-mentioned access message can be understood as an uplink initial access request initiated by the terminal to establish a communication connection with the low-orbit satellite base station after completing autonomous positioning and frequency pre-compensation without the assistance of a global navigation satellite system.

[0082] For example, in order to efficiently implement an integrated communication and navigation system, a device architecture that integrates communication and navigation computing capabilities can be as follows: Figure 3 As shown, its hardware and logic structure includes the following modules and their connections:

[0083] Broadband RF front-end and digitization unit: Responsible for receiving S-band, Ka-band, or Ku-band microwave signals transmitted by the Low Earth Orbit Base Station (LEO gNB). After signal amplification by a low-noise amplifier (LNA), the signal is converted to intermediate frequency by a mixer, and finally digitized by a high-speed analog-to-digital converter (ADC). A unique feature of this part is that its local oscillator (LO) is subject to closed-loop feedback control by a "pre-compensation waveform generation matrix," which dynamically applies a frequency offset based on the positioning calculation results to achieve pre-compensation before transmission.

[0084] The integrated signal detection and fast Fourier transform processing unit is responsible for converting time-domain digital signals into frequency-domain signals using digital signal processing algorithms. It identifies and separates the Synchronization Signal Block (SSB) and Positioning Reference Signal (PRS) pilot signals in the 5G New Radio (5G NR) Orthogonal Frequency Division Multiplexing Resource Grid (RG), and then transmits them to the downstream Doppler feature extraction engine.

[0085] Multi-epoch Doppler tracking module: Responsible for caching and calculating the Doppler frequency shift characteristic sequence of the received downlink reference signal on a continuous system frame (SF) time series, and calculating its first derivative—the Doppler rate. This module integrates a multi-level digital phase-locked loop (DPLL) and a frequency offset register for high-precision, low-noise frequency offset tracking and historical data storage.

[0086] No Global Navigation Satellite System (GNSS) positioning calculation coprocessor: Implemented using a dedicated Digital Signal Processor (DSP) or Field-Programmable Gate Array (FPGA). This module hardware-integrated includes the Extended Kalman Filter (EKF) state estimation algorithm, the World Geodetic System 1984 (WGS84) parameter calculation module, and the local clock drift compensation algorithm. Its inputs are the multi-epoch Doppler frequency shift sequence output from the Doppler tracking module and satellite ephemeris information decoded from System Information Block 19 (SIB19). The output is the absolute three-dimensional spatial coordinates of the User Equipment (UE).

[0087] Pre-compensation and waveform generation module: Based on the three-dimensional coordinates output by the GNSS-free positioning coprocessor and the current satellite ephemeris, it calculates the timing advance (TA) and carrier frequency offset (CFO) in real time. Before the baseband I / Q signal input is subjected to an inverse fast fourier transform (IFFT) to generate the uplink OFDM waveform, a frequency correction with equal amplitude and opposite direction to the residual Doppler is applied to the signal through a digital phase rotation matrix. The transmission start time of the uplink data is dynamically adjusted through a first-in-first-out (FIFO) buffer in the time domain to achieve precise pre-compensation for propagation delay and ensure accurate alignment of the uplink signal at the satellite receiver.

[0088] Integrated Media Access Control Layer Encapsulator: This is the control module of the radio protocol stack. Based on instructions issued by the Radio Resource Control (RRC) layer, it encapsulates the geographic coordinate data and the trace (confidence indicator) of the position error covariance matrix output by the GNSS-less positioning coprocessor into a Media Access Control Protocol Data Unit (MAC PDU) using a specific Logical Channel Identifier (LCID). Finally, it maps this data to the Physical Uplink Shared Channel (PUSCH) payload of the Two-Step Random Access Message A (MsgA) at the physical layer and transmits it to the satellite base station.

[0089] Specifically, in scenarios where the terminal is in an environment without global navigation satellite system-assisted denial, the terminal applies precise time-frequency pre-compensation to the physical random access channel preamble sequence based on its calculated position and frequency deviation, and encapsulates an enhanced access payload containing autonomous positioning results in the physical uplink shared channel to initiate a two-step random access process, thereby achieving coordinated transmission of communication and navigation information.

[0090] Optionally, in another application scenario, such as when a satellite base station adopts a regenerative payload architecture and has on-board processing capabilities, the aforementioned access message may also be a customized physical layer control element that the terminal encapsulates at the physical layer, including self-positioning coordinates, position error covariance, residual Doppler estimation, and terminal capability identifier, and embeds it into the physical uplink shared channel payload of the layer.

[0091] Optionally, in the embodiments of this application, the satellite base station of the aforementioned low-orbit satellite refers to a regenerative base station deployed on a low-orbit communication satellite or a ground base station connected via a power supply link, including but not limited to a regenerative payload node with on-board baseband processing capabilities, or a radio frequency relay platform that works in collaboration with a ground gateway station through a transparent forwarding architecture.

[0092] In an exemplary embodiment, the above-described cell access method is applied to a terminal in a low-Earth orbit communication satellite network. This method, in environments where no global navigation satellite system signals are available, achieves high-precision autonomous positioning and integrated communication and navigation access for the terminal under single-satellite visibility conditions by fusing non-terrestrial network downlink communication signals with an autonomous positioning algorithm. Taking 5G as an example, the specific process is as follows:

[0093] S1. After the terminal is powered on, it enters a global navigation satellite system denial environment, such as urban canyons, deep mountains and dense forests or polar high-latitude regions, and cannot obtain external satellite navigation and positioning information.

[0094] S2, the terminal first scans the new radio frequency band of fifth-generation mobile communication, captures the primary synchronization signal and secondary synchronization signal broadcast by the low-orbit satellite base station, and completes the initial frame synchronization and cell search;

[0095] S3, the terminal demodulates the system information block SIB19 in the physical downlink shared channel to obtain the ephemeris data of the currently serving low-Earth orbit satellite, including the satellite's spatial position state vector, velocity state vector, effective time of the epoch, common timing advance and its drift rate at the reference epoch.

[0096] S4, the terminal determines multiple time epochs based on the ephemeris data of the low-orbit satellite extracted from the system information block and combined with the satellite orbit dynamics model. Each time epoch corresponds to a virtual anchor point, which is used to indicate the satellite position of the low-orbit satellite within the corresponding time epoch.

[0097] S5, within each time epoch, the terminal performs high-precision Doppler frequency shift measurement on the downlink positioning reference signal through baseband phase-locked loop and fast Fourier transform to obtain a set of continuous Doppler frequency shift value sequences. The Doppler frequency shift value is used to indicate the signal frequency offset of the terminal received signal within the corresponding time epoch.

[0098] S6, the terminal associates the Doppler frequency shift value corresponding to each time epoch with the location of the corresponding virtual anchor point, and introduces a preset elevation parameter. The preset elevation parameter is the altitude of the corresponding geographical location in the digital elevation model stored locally by the terminal, which serves as a constraint condition for the height dimension in positioning.

[0099] S7, the terminal determines its position and frequency deviation based on the Doppler frequency shift value, virtual anchor point, and preset elevation parameters, specifically including:

[0100] S7-1, Construct the initial state vector of the terminal. The initial state vector includes coordinate parameters and frequency offset parameters. The coordinate parameters are used to indicate the position coordinates of the terminal, and the frequency offset parameters are used to indicate the frequency deviation of the local oscillator of the terminal.

[0101] S7-2, the initial state vector is iteratively updated using the extended Kalman filter algorithm to obtain the target state vector, where the Doppler frequency shift value, virtual anchor point and preset elevation parameters are used to construct the observation equation in the extended Kalman filter algorithm;

[0102] S7-3, sequentially using the virtual anchor point corresponding to each time epoch as the current virtual anchor point according to the time sequence, and using the Doppler frequency shift value of the corresponding time epoch as the current frequency shift value, perform the following operations:

[0103] S7-4: The initial state vector is predicted using the identity matrix state transition matrix to obtain the prior state estimate state vector and the prior error covariance matrix. Based on the Jacobian matrix of the nonlinear Doppler observation model, preset elevation parameters, current frequency shift value, and current satellite position data, the prior state estimate state vector and the prior error covariance matrix are updated by observation to obtain the posterior state estimate state vector and the posterior error covariance matrix. When the trace value of the posterior error covariance matrix is ​​less than the preset convergence threshold, the posterior state estimate state vector is determined as the target state vector. When the trace value of the posterior error covariance matrix is ​​greater than or equal to the preset convergence threshold, the current virtual anchor point is updated to the virtual anchor point corresponding to the next time epoch, and the current frequency shift value is updated to the Doppler frequency shift value corresponding to the next time epoch, and the iteration continues.

[0104] S7-5, the terminal determines its position based on the coordinate parameters in the target state vector, and determines the frequency deviation based on the frequency offset parameters in the target state vector;

[0105] S8, the terminal sends an access message to the satellite base station of the low-orbit satellite based on the terminal's location and frequency deviation, in order to control the terminal to access the target cell;

[0106] S9. After receiving the access message, the satellite base station uses its multi-beam phased array receiving antenna to measure the uplink time difference and angle of arrival of the uplink signal to obtain the physical layer waveform measurement results. The base station cross-compares and fuses the measurement results with the terminal-reported location information encapsulated in the access message. After determining that it is reliable, it generates accurate timing adjustment and frequency adjustment amounts and feeds them back to the terminal through a random access response message.

[0107] S10, the terminal receives the random access response message, parses out the timing adjustment amount and frequency adjustment amount, updates the start time of uplink data transmission using the timing adjustment amount, updates the transmission frequency using the frequency adjustment amount, and completes the access process;

[0108] Furthermore, after completing the access process, the terminal can begin transmitting service data to the satellite base station, and the entire access process is completed within a single round-trip latency period.

[0109] In this embodiment, the terminal first determines multiple time epochs based on the ephemeris data of the low-Earth orbit satellite extracted from the system information block. This system information block corresponds to the target cell served by the low-Earth orbit satellite. Next, it measures the Doppler frequency shift value corresponding to each of the multiple time epochs. Further, it determines a virtual anchor point corresponding to each time epoch based on the ephemeris data. The virtual anchor point indicates the satellite position of the low-Earth orbit satellite within the corresponding time epoch. The terminal's position and frequency deviation are determined based on the Doppler frequency shift value, the virtual anchor point, and preset elevation parameters. Finally, based on the terminal's position and frequency deviation, it sends an access message to the low-Earth orbit satellite's base station to access the target cell. That is, by constructing virtual anchor points using the motion trajectory of the low-Earth orbit satellite at multiple time epochs without the assistance of a global navigation satellite system, and combining Doppler observations with elevation constraints from preset elevation parameters, the terminal achieves autonomous positioning and frequency offset estimation. This achieves the goal of accurate time-frequency pre-compensation without relying on an external navigation system, thereby solving the technical problem of cell access failure due to the terminal's inability to obtain its own accurate position information.

[0110] As an optional approach, the above-mentioned method of sending an access message to the satellite base station of the low-Earth orbit satellite based on the terminal location and the frequency deviation to control the terminal to access the target cell includes: determining the transmission time and carrier frequency of the access message based on the terminal location and the system information block; and sending the access message to the satellite base station using the carrier frequency at the transmission time to control the terminal to access the target cell.

[0111] Optionally, in the embodiments of this application, the aforementioned transmission time refers to the optimal time point at which the uplink signal should arrive at the base station receiving window, calculated by the terminal based on the terminal location and satellite ephemeris. This includes, but is not limited to, a combination of system frame number, subframe index and symbol position, or a discrete time slot index calculated based on common timing advance and one-way propagation delay.

[0112] Optionally, in the embodiments of this application, the aforementioned carrier frequency refers to the uplink transmission frequency set by the terminal to compensate for Doppler frequency shift and local crystal oscillator deviation, including but not limited to the superposition value of the center carrier frequency and the pre-compensation offset, or the dynamic frequency offset value calculated from real-time relative velocity and ephemeris data.

[0113] For example, the one-way propagation delay can be calculated based on the location data and ephemeris data of the terminal location, and combined with the common timing advance and drift rate of the broadcast in the system information block, the transmission time of the uplink signal within the base station receiving window can be deduced.

[0114] For example, the real-time frequency shift at the current moment can be calculated based on the terminal location and ephemeris data, and the frequency rotation offset (pre-compensation) can be obtained by superimposing the local frequency deviation to determine the carrier frequency. The terminal applies an equal but opposite frequency rotation offset to the uplink carrier signal to be transmitted at the radio frequency front end or digital baseband to determine the carrier frequency. That is, the carrier frequency is the transmission frequency offset that is superimposed in the opposite direction after the theoretical frequency shift calculated by the terminal based on the terminal location, satellite instantaneous velocity vector, downlink carrier center frequency and speed of light through the Doppler observation model, and after local crystal oscillator deviation compensation. The physical layer transmission process is started at the specified transmission time so that the access message is synchronously aligned with the base station receiving resources in the time domain and frequency domain.

[0115] Through the embodiments of this application, the access transmission time and carrier frequency are jointly calculated based on the terminal's autonomous positioning results and system information blocks. This achieves the technical effect of completing high-precision uplink time-frequency synchronization and communication access in an environment without a global navigation satellite system, thereby improving the terminal's access success rate and system robustness in a denied environment.

[0116] As an optional approach, determining the transmission time and carrier frequency of the access message based on the terminal location and the system information block includes: calculating the one-way propagation delay using the location data of the terminal location and the ephemeris data; and determining the transmission time based on the common timing advance and common timing advance drift rate extracted from the system information block, as well as the one-way propagation delay.

[0117] Optionally, in the embodiments of this application, the above-mentioned terminal location refers to the three-dimensional spatial coordinates of the terminal in the Earth coordinate system, including but not limited to the X, Y, and Z components in the geocentric geofixed coordinate system, or the geographic coordinates in latitude, longitude, and height format.

[0118] Optionally, in the embodiments of this application, the aforementioned one-way propagation delay refers to the propagation time required for a signal to travel from the terminal to the low-orbit satellite base station, including but not limited to the propagation delay calculated based on the line-of-sight distance between the terminal and the satellite and the speed of light, or the correction value after superimposing ionospheric and tropospheric corrections.

[0119] Optionally, in the embodiments of this application, the aforementioned common timing advance refers to the timing compensation benchmark value uniformly broadcast by the network side to compensate for typical propagation delay.

[0120] Optionally, in the embodiments of this application, the aforementioned common timing advance drift rate refers to the rate at which the reference value changes over time, including but not limited to the dynamic change rate of time delay caused by the high-speed motion of the satellite, or the periodic offset slope caused by orbital perturbation.

[0121] It should be noted that the coordinate system of the terminal location can be a geocentric coordinate system, a geographic coordinate system, or a local tangent plane coordinate system, and its accuracy is determined by the posterior error covariance output by the positioning solution module; the update cycle of the ephemeris data can be at the second level, sub-second level, or frame level, and its source is either direct satellite broadcast or relayed via ground gateway stations. This application does not limit this.

[0122] For example, the Euclidean distance between the terminal and the low-orbit satellite is calculated based on the three-dimensional coordinates of the terminal in the geocentric-fixed coordinate system and the instantaneous position state vector of the low-orbit satellite at the current moment. Then, the time required for signal propagation is calculated back based on the speed of light to obtain the one-way propagation delay value.

[0123] Then, the one-way propagation delay is added to the common timing advance to obtain the initial total compensation delay. Then, based on the drift rate of the common timing advance and the time difference between the current time and the ephemeris reference epoch, the dynamic correction amount is calculated. This correction amount is added to the initial total compensation delay to finally determine the start time of the terminal uplink access message transmission, so as to ensure that the signal is aligned within the base station receiving window.

[0124] Through the embodiments of this application, the access transmission time is jointly calculated based on the terminal's autonomous positioning results and system information blocks, achieving the technical effect of accurate pre-compensation of uplink timing in the absence of a global navigation satellite system, thereby improving the access synchronization accuracy and system reliability of the terminal in a highly dynamic non-terrestrial network.

[0125] As an optional approach, determining the transmission time and carrier frequency of the access message based on the terminal location and the system information block includes: calculating the real-time frequency shift corresponding to the transmission time based on the terminal location and the ephemeris data; and determining the carrier frequency based on the real-time frequency shift and the frequency deviation.

[0126] Optionally, in the embodiments of this application, the aforementioned real-time frequency shift refers to the Doppler frequency shift caused by the relative motion between the terminal and the satellite at the time of transmission, including but not limited to the frequency offset generated by the combined action of the radial velocity component and the carrier center frequency.

[0127] It should be noted that the calculation of real-time frequency shift can be derived using a nonlinear Doppler observation model, and this application does not limit this.

[0128] For example, based on the three-dimensional coordinates of the terminal in the geocentric geofixed coordinate system and the instantaneous position and velocity state vector of the low-orbit satellite at the time of transmission, the relative velocity vector between the two is calculated, and the radial component of the vector in the direction of the line connecting the terminal and the satellite is obtained. Then, based on the Doppler frequency shift formula corresponding to the nonlinear Doppler observation model, the real-time frequency shift value caused by the relative motion is calculated with the carrier center frequency and the speed of light as parameters.

[0129] Specifically, assuming the satellite is in the Earth coordinate system, The actual location at any given moment is The speed is (Obtained by extrapolation from the orbital elements of SIB19). Let the unknown position of the terminal be... Since the UE (such as an IoT node or pedestrian) moves extremely slowly relative to a low-Earth orbit satellite (approximately 7000 m / s), it can be approximated as being stationary. .

[0130] Theoretical Doppler frequency shift under error-free conditions The Doppler frequency shift formula is as follows:

[0131]

[0132] Among them, f c denoted as 5G downlink carrier center frequency, and c as the speed of light.

[0133] Furthermore, the real-time frequency shift value calculated from relative motion is algebraically added to the frequency deviation value of the terminal's local oscillator to obtain the frequency rotation bias required for uplink transmission. The terminal applies an equal but opposite frequency rotation bias to the uplink carrier signal to be transmitted at the RF front-end or digital baseband. That is, the frequency rotation bias is superimposed in reverse to the nominal carrier frequency of the system to form the actual transmission frequency used by the terminal, so as to offset the Doppler effect and local clock error in the propagation path.

[0134] Through the embodiments of this application, the uplink carrier frequency is jointly calculated based on the terminal's autonomous positioning results and ephemeris data, achieving the technical effect of accurate uplink frequency domain compensation in the absence of a global navigation satellite system, thereby improving the signal reception reliability and access success rate of the terminal in highly dynamic non-terrestrial networks.

[0135] As an optional approach, the above-mentioned method of sending an access message to the satellite base station of the low-Earth orbit satellite based on the terminal location and the frequency deviation to control the terminal to access the target cell includes: sending the access message to the satellite base station based on the terminal location and the frequency deviation; receiving a response message from the satellite base station in response to the access message; and adjusting the start time and transmission frequency of sending uplink data to the satellite base station according to the response message to control the terminal to access the target cell.

[0136] Optionally, in the embodiments of this application, the above-mentioned response message refers to the confirmation feedback of the satellite base station to the terminal access request, including but not limited to messages in the two-step random access process, which include scheduling authorization, contention resolution identifier, timing adjustment amount and frequency correction instruction.

[0137] It should be noted that the response message can be carried by the downlink shared channel or the downlink control channel, and its content can include timing advance, frequency correction value, uplink resource allocation and identity confirmation information.

[0138] For example, the terminal calculates the timing advance and carrier frequency compensation value required for uplink transmission based on the self-calculated three-dimensional position and local frequency deviation, and generates an access message containing self-positioning coordinates and error covariance at a specified time, which is then sent to the satellite base station through the physical layer channel.

[0139] Next, if the terminal receives a response message from the satellite base station within the preset listening window, it parses the timing adjustment amount and frequency correction instructions carried in the message to confirm that the access request has been received and the physical layer verification has been completed.

[0140] Furthermore, the terminal adds the precise timing adjustment amount contained in the response message to the local pre-compensation value, updates the uplink data transmission start time, and adds the frequency correction command to the local frequency deviation to correct the uplink carrier frequency, so that the subsequent dedicated channel transmission is fully aligned with the base station receiving window, thus completing the access process.

[0141] Through the embodiments of this application, the technical effect of high-precision access synchronization and connection establishment in the absence of a global navigation satellite system is achieved by adopting terminal autonomous positioning and network closed-loop correction. This achieves the goal of improving the access reliability and system convergence speed of the terminal in a highly dynamic non-terrestrial network.

[0142] As an optional approach, adjusting the start time and transmission frequency of uplink data transmission based on the response message to control the terminal to access the target cell includes: parsing the response message to obtain a timing adjustment amount and a frequency adjustment amount; updating the start time using the timing adjustment amount; and updating the transmission frequency using the frequency adjustment amount.

[0143] Optionally, in the embodiments of this application, the aforementioned timing adjustment amount refers to the precise delay correction value calculated by the network side based on the timing deviation between the arrival time of the terminal's uplink signal and the expected reception window of the base station, including but not limited to absolute or incremental correction amounts in units of symbols, time slots, or nanoseconds; the aforementioned frequency adjustment amount refers to the frequency compensation command calculated by the network side based on the deviation between the terminal's uplink carrier frequency offset and the target center frequency, including but not limited to absolute frequency offset correction values ​​in units of Hertz or fine-tuning amounts relative to the pre-compensation value.

[0144] Optionally, in the embodiments of this application, the aforementioned start time refers to the precise transmission time point at which the terminal transmits data on the dedicated physical uplink shared channel, including but not limited to the combination of system frame number, subframe index and symbol position, and the aforementioned transmission frequency refers to the actual transmission carrier frequency used by the terminal for uplink data transmission, including but not limited to the algebraic sum of the system nominal carrier frequency, the local pre-compensation value and the network-sent correction amount.

[0145] It should be noted that the format of the response message can follow the standard definition or be customized and extended by the network side. Its timing adjustment and frequency adjustment can be encapsulated in the control element of the downlink media access control protocol data unit. The calculation of the timing adjustment can be based on the uplink time difference of arrival, uplink angle of arrival, preamble detection delay, or feedback channel state information. Its update method can be absolute value overlay or incremental superposition. The calculation of the frequency adjustment can be based on the residual Doppler reported by the terminal, the frequency offset estimation of the base station receiver, or beamforming feedback. Its update method can be direct setting or iterative correction.

[0146] It should also be noted that the update of the start time can be performed by the baseband scheduling unit according to the system clock synchronization mechanism, and its time granularity can be at the symbol level or microsecond level; the update of the transmission frequency can be realized by the digital quadrature modulation module or the local oscillator control circuit, and its frequency adjustment accuracy can be at the Hertz level or the subcarrier level. This application does not limit this.

[0147] For example, the terminal decodes the received access response message, extracts the timing adjustment control element and frequency adjustment control element configured by the network side, obtains the precise values ​​used to correct the uplink transmission timing and frequency, algebraically superimposes the timing adjustment amount with the pre-compensated transmission time calculated locally by the terminal to generate the corrected uplink data transmission start time, ensuring that the transmission time of the dedicated physical uplink shared channel is aligned with the base station's receiving window; alternatively, the frequency adjustment amount can be algebraically added with the pre-compensated frequency offset calculated locally by the terminal to generate the final uplink transmission carrier frequency, and precise frequency correction can be achieved through digital phase rotation or radio frequency synthesizer to make the uplink signal center frequency consistent with the base station's desired receiving frequency.

[0148] By utilizing the embodiments of this application to dynamically update the start time and transmission frequency of uplink data on the network side, the purpose of improving channel transmission reliability and overall transmission throughput performance is achieved.

[0149] As an optional approach, determining the terminal position and frequency deviation based on the Doppler frequency shift value, the satellite position, and the preset elevation parameters includes: constructing an initial state vector for the terminal, wherein the initial state vector includes coordinate parameters and a frequency offset parameter, the coordinate parameters indicating the position coordinates of the terminal, and the frequency offset parameter indicating the local oscillator frequency deviation of the terminal; iteratively updating the initial state vector using an extended Kalman filter algorithm to obtain a target state vector, wherein the Doppler frequency shift value, the satellite position, and the preset elevation parameters are used to construct the observation equation used in the extended Kalman filter algorithm; determining the terminal position based on the values ​​of the coordinate parameters in the target state vector; and determining the frequency deviation based on the values ​​of the frequency offset parameter in the target state vector.

[0150] Optionally, in the embodiments of this application, the aforementioned initial state vector refers to the initial state estimation set of the extended Kalman filter algorithm, including but not limited to the joint state variable of three-dimensional position coordinates and local oscillator frequency deviation.

[0151] Optionally, in the embodiments of this application, the coordinate parameters mentioned above refer to the spatial position components of the terminal in the Earth coordinate system, including but not limited to the X, Y, and Z components in the geocentric coordinate system or geographical coordinates in the form of latitude, longitude, and altitude.

[0152] Optionally, in the embodiments of this application, the frequency offset parameter mentioned above refers to the systematic offset of the terminal local oscillator relative to the standard frequency.

[0153] Optionally, in the embodiments of this application, the aforementioned target state vector refers to the optimal state estimation result output by the extended Kalman filter after multi-epoch iteration convergence, including but not limited to the joint optimal value of the terminal position and frequency deviation after smoothing optimization.

[0154] It should be noted that the Doppler frequency shift value can be measured based on the downlink reference signal, and its calculation method can be Fourier transform spectrum peak detection, pilot interpolation, or least squares fitting, etc. The initial value of the initial state vector can be set to zero or a coarse estimate, and its covariance matrix can be set according to the sensor accuracy. The coordinate system of the coordinate parameters can be the geocentric coordinate system, the geographic coordinate system, or the local tangent plane coordinate system. The unit of the frequency offset parameter can be Hertz or normalized frequency offset. The convergence condition of the target state vector can be based on the trace or residual sum of squares of the state covariance matrix; this application does not limit this.

[0155] For example, the initial three-dimensional position of the terminal is set as the origin or a preset default value in the geocentric-geo-fixed coordinate system, and the local frequency deviation is set to zero or a priori estimate based on the nominal drift range of the crystal oscillator, forming an initial state vector containing four state variables, where the first three are position coordinates and the fourth is the frequency deviation.

[0156] Then, based on the nonlinear observation function of Doppler frequency shift, combined with the satellite position at each epoch and the terminal's predicted position, the theoretical Doppler frequency shift is calculated and compared with the measured value as a residual. At the same time, a preset elevation parameter is introduced as a strongly constrained observation term. The nonlinear model is locally linearized through the Jacobian matrix, and the state vector and its covariance matrix are recursively updated to achieve optimal convergence of the state estimation.

[0157] Finally, the state variables representing coordinate parameters in the target state vector are extracted as the final three-dimensional spatial coordinates of the terminal in the geocentric-geo-fixed coordinate system, i.e., the location information of the terminal. The state variables representing frequency offset parameters in the target state vector can also be extracted as the frequency deviation of the terminal's local oscillator after filtering and convergence, which is used for pre-compensation of subsequent uplink signal transmission.

[0158] Through the embodiments of this application, by employing extended Kalman filtering joint estimation based on multi-time epoch Doppler observations and elevation constraints, the technical effect of achieving high-precision terminal positioning and local oscillator frequency deviation synchronization using downlink reference signals from low-orbit communication satellites is realized.

[0159] As an optional approach, the above-mentioned extended Kalman filter algorithm is used to iteratively update the initial state vector to obtain the target state vector. This includes: determining the satellite position data corresponding to each time epoch in chronological order as satellite position data, and determining the Doppler frequency shift value corresponding to each time epoch as the current frequency shift value; performing the following operations on the current satellite position data and the current frequency shift value to obtain the target state vector: using the identity matrix state transition matrix to predict the state of the initial state vector, obtaining the prior state estimation state vector and the prior error covariance matrix; based on the Jacobian matrix of the nonlinear Doppler observation model, The aforementioned preset elevation parameters, the aforementioned current frequency shift value, and the aforementioned current satellite position data are used to update the prior state estimation state vector and the prior error covariance matrix through observation, resulting in the posterior state estimation state vector and the posterior error covariance matrix. If the trace value of the posterior error covariance matrix is ​​less than a preset convergence threshold, the posterior state estimation state vector is determined as the aforementioned target state vector. If the trace value of the posterior error covariance matrix is ​​greater than or equal to the aforementioned preset convergence threshold, the aforementioned current satellite position data is updated to the position data of the aforementioned satellite position corresponding to the next aforementioned time epoch, and the aforementioned current frequency shift value is updated to the aforementioned Doppler frequency shift value corresponding to the next aforementioned time epoch.

[0160] Optionally, in the embodiments of this application, the aforementioned current satellite position data refers to the position data of the satellite position indicated by the corresponding virtual anchor point. The virtual anchor point is the instantaneous position of the satellite used in the current iteration step, including but not limited to the satellite position state vector corresponding to the current time epoch; the aforementioned current frequency shift value refers to the measured Doppler frequency shift value corresponding to the current time epoch, including but not limited to the frequency offset estimation result output by the baseband signal processing unit.

[0161] Optionally, in the embodiments of this application, the aforementioned identity matrix state transition matrix refers to the motion model used in extended Kalman filtering to characterize the near-static state of the terminal within a short period of time, including but not limited to the state transition equation in identity matrix form; the aforementioned prior state estimation state vector refers to the uncorrected state estimate output in the state prediction stage, including but not limited to the terminal position and frequency deviation estimate obtained based on the posterior state deduction of the previous moment; the aforementioned prior error covariance matrix refers to the state uncertainty measure output in the state prediction stage, including but not limited to the covariance matrix calculated by the propagation of system noise and the covariance of the previous moment.

[0162] Optionally, in the embodiments of this application, the aforementioned nonlinear Doppler observation model refers to a nonlinear function that describes the physical relationship between the terminal position, the satellite position, and the Doppler frequency shift, including but not limited to observation equations based on the dot product of the speed of light, carrier frequency, and relative velocity vector.

[0163] Optionally, in the embodiments of this application, the Jacobian matrix mentioned above refers to the partial derivative matrix of the nonlinear observation model with respect to the state vector, which is used for local linearization processing, including but not limited to the gradient matrix obtained by analytical derivation or numerical difference.

[0164] Optionally, in the embodiments of this application, the aforementioned posterior state estimation state vector refers to the optimal state estimate after the observation update, which integrates the observation information and the prior information, including but not limited to the joint estimate of the terminal position and frequency deviation after Kalman gain correction; the aforementioned posterior error covariance matrix refers to the updated state uncertainty measure after the observation update, including but not limited to the covariance matrix reflecting the improved estimation accuracy.

[0165] Optionally, in the embodiments of this application, the aforementioned preset convergence threshold refers to the covariance trace value threshold for determining the convergence of the filter, including but not limited to a fixed value or a dynamic adaptive threshold set by the system positioning accuracy requirements.

[0166] It should be noted that the state transition matrix of the identity matrix is ​​set based on the physical assumption that the terminal moves slowly within the observation window; the initial value of the prior error covariance matrix can be set according to the stability of the terminal hardware crystal oscillator and prior knowledge of positioning; the nonlinear Doppler observation model can introduce an ionospheric delay rate compensation term or an atmospheric refraction correction factor; the filtering iteration termination condition can be the convergence of the covariance trace, the reaching of the maximum number of iterations, or the exhaustion of available observation data; this application does not limit this.

[0167] For example, at each time epoch, the current instantaneous satellite position and the current Doppler observation are used as inputs to the extended Kalman filter to initiate a state prediction and observation update cycle:

[0168] Using the posterior state estimate of the previous time epoch as the starting point for this prediction, the state is kept unchanged by identity matrix multiplication, and the system noise covariance matrix is ​​superimposed to generate the prior state estimate state vector and the corresponding prior error covariance matrix at the current time. The theoretical Doppler value is calculated based on the current satellite position and the predicted terminal position, and the observation residual is constructed in combination with the preset elevation constraint. The nonlinear observation model is linearized using the Jacobian matrix, the Kalman gain is calculated, and the state estimate and covariance matrix are updated to achieve joint correction of the terminal position and frequency deviation.

[0169] If the trace of the posterior error covariance matrix is ​​less than the preset convergence threshold, the posterior state estimate state vector is determined as the target state vector, including: when the sum of the diagonal elements of the covariance matrix is ​​less than the preset convergence threshold, the filter is determined to have converged, the iteration is terminated, and the current posterior state estimate is used as the final three-dimensional position and local frequency deviation of the terminal output; if the filter has not yet converged, the satellite position and Doppler measurement value of the next time epoch are read, and the prediction and update steps are repeated until the convergence condition is met.

[0170] In one exemplary embodiment, the extended Kalman filter joint elevation constraint solution includes, but is not limited to:

[0171] Construct the initial state vector of the terminal To accelerate the convergence of single-satellite Doppler positioning and eliminate Z-axis ambiguity, this application's embodiments introduce an Earth surface elevation constraint (assuming the terminal is located near the Earth's surface, and the altitude can be set as a virtual observation value using a coarse digital elevation model or the default sea level). ).

[0172] In the extended Kalman filter algorithm framework, the state prediction equation is:

[0173]

[0174] Since the terminal is approximately stationary, the state transition matrix F is set as the identity matrix I.

[0175] The observation update equation utilizes the Doppler observation function Jacobian Matrix Perform local linearization:

[0176]

[0177]

[0178] in, For the first The actual Doppler frequency shift measured at the epoch, This is the observation noise covariance matrix dynamically adjusted based on the signal-to-noise ratio (SNR). After multi-epoch recursive iteration, the filter converges, outputting a high-precision absolute position estimate of the UE. Estimation of deviation from local crystal oscillator P k|k-1 It is the prior error covariance matrix at the k-th time epoch, representing the mathematical assessment of the uncertainty of the current terminal position and clock difference prediction results based solely on the state at the previous moment before the latest Doppler measurement value at the k-th epoch is received.

[0179] It should be noted that, The filter is dynamically calculated and applied in real time by the terminal's underlying baseband module at each epoch. It represents the reliability of the Doppler measurement at that instant and is mainly obtained through the following methods:

[0180] 1. Real-time mapping based on carrier-to-noise ratio (CNR) or signal-to-noise ratio (SNR): When the phase-locked loop (PLL) inside the terminal extracts the Doppler frequency, the variance of its measurement (i.e., the severity of error fluctuation) is highly correlated with the quality of the currently received downlink signal. Theoretically and in engineering practice, a direct mathematical mapping relationship can be established between the variance of the Doppler estimate and the CNR. If the signal is strong in the current epoch, A smaller value indicates extremely high confidence in the measurement; if the signal is blocked, causing a sharp drop in the signal-to-noise ratio, the signal-to-noise ratio will be lower. The value will be dynamically amplified.

[0181] 2. Phase-locked loop (PLL) internal state parameters: In addition to external signal quality, the order, loop bandwidth, and coherent integration time of the receiver's baseband tracking loop directly determine the measurement variance of the Doppler frequency at the underlying level. The baseband chip quantifies the uncertainties caused by these hardware states in real time.

[0182] Through the embodiments of this application, extended Kalman filtering iterative convergence based on multi-epoch continuous observation and elevation constraints is adopted to effectively determine the terminal position and frequency deviation, thereby improving the autonomous positioning stability and convergence speed of the terminal.

[0183] As an optional approach, before sending an access message to the satellite base station of the low-Earth orbit satellite based on the terminal location and the frequency deviation to control the terminal's access to the target cell, the method further includes: generating a physical random access channel preamble sequence; adding an autonomous positioning auxiliary information control element to the physical layer protocol data unit, wherein the autonomous positioning auxiliary information control element encapsulates the terminal location information, the trace of the location error covariance, and the estimated value of the uncompensated residual Doppler frequency offset, the trace of the location error covariance is the trace of the posterior error covariance matrix corresponding to the target state vector, the estimated value of the uncompensated residual Doppler frequency offset is the difference between the Doppler frequency shift value measured at the transmission time and the expected frequency shift value, the expected frequency shift value is determined using a nonlinear Doppler observation model; and generating the access message based on the physical random access channel preamble sequence and the physical layer protocol data unit.

[0184] Optionally, in the embodiments of this application, the aforementioned physical random access channel preamble sequence refers to the time-frequency domain identifier sequence used by the terminal to initiate an access request during the two-step random access process, including but not limited to a preamble structure without a cyclic prefix or extended guard interval constructed based on the Zadoff-Chu sequence or its variants.

[0185] Optionally, in the embodiments of this application, the aforementioned physical layer protocol data unit refers to a data block carried on the physical uplink shared channel, including but not limited to a transport block that is encapsulated by the media access control layer protocol data unit and mapped to the physical layer.

[0186] Optionally, in the embodiments of this application, the aforementioned autonomous positioning auxiliary information control element refers to a media access control layer control element added to the physical layer protocol data unit, used to carry auxiliary information for terminal autonomous positioning, including but not limited to customized information elements identified by a specific logical channel identifier.

[0187] Optionally, in the embodiments of this application, the location information of the terminal location mentioned above refers to the three-dimensional spatial coordinates calculated by the terminal through extended Kalman filtering, including but not limited to the X, Y, and Z components in the geocentric coordinate system or geographic coordinates in the form of longitude, latitude, and altitude; the trace value of the location error covariance mentioned above refers to the sum of the diagonal elements of the posterior error covariance matrix after the terminal has converged in positioning, which is used to characterize the overall confidence of the location estimation, including but not limited to scalar values ​​in square meters.

[0188] Optionally, in the embodiments of this application, the aforementioned uncompensated residual Doppler frequency offset estimate refers to the difference between the measured Doppler frequency shift at the time of transmission and the theoretical expected frequency shift calculated based on the predicted position, including but not limited to the residual frequency offset estimate in Hertz.

[0189] Optionally, in the embodiments of this application, the aforementioned expected frequency shift value refers to the theoretical Doppler frequency shift calculated based on the current predicted position of the terminal and the instantaneous position of the satellite using a nonlinear Doppler observation model, including but not limited to the predicted value derived from the dot product of the speed of light, carrier frequency, and relative velocity vector.

[0190] It should be noted that the format of the physical layer protocol data unit can follow the standard definition or the network-side extension specification, and its content can include radio resource control connection request or terminal identifier. The uncompensated residual Doppler frequency offset estimate can be calculated based on the latest observation and prediction value, and its update frequency can be synchronized with the transmission time. This application does not limit this.

[0191] For example, a preamble sequence is generated according to the preamble format and sequence family configured by the system. This sequence has low cross-correlation and strong anti-frequency offset characteristics. The trace value of the posterior error covariance matrix, the three-dimensional position coordinates solved by the terminal, and the residuals of the current measured Doppler frequency shift and the theoretical expected frequency shift are encoded into media access control layer control elements according to a predefined format and inserted into the protocol data unit of the physical uplink shared channel.

[0192] Furthermore, the preamble sequence is placed in the preamble portion of the uplink time-frequency resources, and the physical layer protocol data unit encapsulating autonomous positioning assistance information control elements is placed in the payload portion of the uplink shared channel, thus forming a complete two-step random access message.

[0193] Through the embodiments of this application, by reusing the signaling encapsulation of autonomous positioning information in the access message, the technical effect of synchronously feeding back high-precision positioning accuracy and residual frequency offset status to the network is achieved, thereby improving the accuracy of base station closed-loop verification, reducing access failure rate and shortening connection establishment latency.

[0194] As an optional scheme, the physical random access channel preamble sequence includes at least one of the following: the physical random access channel preamble sequence adopts a preamble format without a cyclic prefix; the physical random access channel preamble sequence is configured with an extended guard interval.

[0195] Optionally, in the embodiments of this application, the aforementioned extended protection interval refers to an additional zero-filling or low-correlation protection period configured before and after the preamble sequence, including but not limited to a time-domain gap with a length more than twice that of the conventional protection interval, used to suppress inter-symbol interference caused by multipath interference and residual frequency offset.

[0196] For example, when generating the preamble sequence, the terminal omits the copying step of the traditional cyclic prefix and directly uses the original Zadoff-Chu sequence as the transmission time-domain waveform of the physical random access channel to reduce the preamble length and increase the frequency domain energy concentration.

[0197] For example, additional zero-value sampling points are added at the beginning and end of the preamble sequence to make the guard interval length exceed the standard-defined cyclic prefix length in order to tolerate greater frequency offset and sign alignment deviation caused by self-localization residual errors.

[0198] Through the embodiments of this application, the preamble waveform design combining a non-cyclic prefix structure and an extended guard interval is adopted to achieve the technical effect of suppressing inter-carrier interference and preamble missed detection under the condition that residual Doppler frequency offset is not completely eliminated, thereby improving the access success rate and resource utilization of the terminal in non-terrestrial networks.

[0199] As an optional approach, the above method further includes: when the low-orbit satellite does not have baseband processing capabilities, the frequency deviation also includes the frequency offset drift term and propagation delay compensation term corresponding to the feeder link between the satellite base station and the low-orbit satellite.

[0200] Considering that when a low-Earth orbit satellite adopts a transparent relay architecture and does not have baseband processing capabilities, the satellite only acts as a radio frequency relay device. The downlink signals it receives need to be forwarded to the ground base station for protocol processing through the feeder link. The feeder link itself will generate additional propagation delay and Doppler frequency shift due to the relative motion between the ground station and the satellite. This delay and frequency shift are not caused by the direct link between the terminal and the satellite. If the terminal ignores this part of the impact when calculating locally, it will lead to virtual anchor point position deviation and propagation delay estimation error, which will affect the positioning accuracy and uplink pre-compensation accuracy.

[0201] In the embodiments of this application, when the low-orbit satellite adopts a transparent forwarding architecture and does not have baseband processing capabilities, the frequency deviation also includes the frequency offset drift term and propagation delay compensation term corresponding to the feeder link between the satellite base station and the low-orbit satellite. When the terminal calculates the virtual anchor point and propagation delay, the above-mentioned feeder link compensation term is included in the model to ensure positioning and pre-compensation accuracy.

[0202] As an optional approach, the above method further includes: in the presence of multiple low-orbit satellites, using a joint positioning model of multi-satellite instantaneous time difference of arrival and frequency difference of arrival to determine the location of the terminal.

[0203] Considering that a single low-Earth orbit satellite still needs a certain amount of time to build a virtual anchor point and complete multi-epoch observation calculations under high dynamic conditions, and that when the terminal is in a densely covered area of ​​a low-Earth orbit satellite constellation, it may simultaneously receive downlink synchronization signals and positioning reference signals from three or more satellites.

[0204] Through the embodiments of this application, when the terminal receives downlink signals from multiple low-orbit satellites simultaneously, the terminal can also use a joint positioning model of instantaneous time difference of arrival and frequency difference of arrival of multiple satellites to determine the terminal position, replacing the extended Kalman filter algorithm, so as to shorten the positioning convergence time.

[0205] As an optional approach, the above method further includes: receiving downlink signaling sent by a network-side location management function server, wherein the location management function server is used to receive the Doppler frequency shift value sent by the terminal, and perform nonlinear positioning calculation based on the Doppler frequency shift value and the ephemeris data to generate the downlink signaling, wherein the downlink signaling is used to determine the transmission time of the access message and the carrier frequency used to transmit the access message.

[0206] For example, when the terminal is a low-computing-power terminal and cannot run the extended Kalman filter algorithm locally, the terminal only reports the original Doppler frequency shift values ​​and corresponding timestamps of multiple time epochs. The network-side location management function server receives the original data, performs nonlinear positioning calculation, and sends control commands for the sending time and carrier frequency to the terminal through downlink signaling. The terminal only performs pre-compensation and access operations.

[0207] The embodiments of this application support two modes: local independent computation and network-side collaborative computation. This balances the rapid response capability of high-performance terminals with the low-cost deployment requirements of low-computing-power terminals, significantly reducing terminal hardware costs and power consumption.

[0208] As an optional implementation method, the above-described cell access method can also be applied to low-Earth orbit satellites, such as... Figure 4 As shown, it includes:

[0209] S402, receiving an access message sent by a terminal, wherein the access message is sent by the terminal based on the terminal location and frequency deviation, the terminal location and frequency deviation are determined based on Doppler frequency shift value, satellite location and preset elevation parameters, the satellite location corresponding to each time epoch is determined based on the ephemeris data of the low-orbit satellite, the virtual anchor point is used to indicate the satellite location of the low-orbit satellite within the corresponding time epoch, the Doppler frequency shift value corresponding to each time epoch is obtained by measurement by the terminal, multiple time epochs are determined based on the ephemeris data extracted from the system information block, the system information block corresponds to the target cell served by the low-orbit satellite;

[0210] S404, send a response message to the terminal to control the terminal to access the target cell.

[0211] In an exemplary embodiment, when the above-described cell access method is implemented on a low-Earth orbit satellite, the low-Earth orbit satellite includes, but is not limited to, performing the following operations:

[0212] The system captures access messages sent by the terminal using a multi-beam phased array receiving antenna, decodes the physical random access channel preamble sequence and the physical uplink shared channel payload, and extracts the terminal position coordinates, position error covariance trace, and uncompensated residual Doppler frequency offset estimate encapsulated in the autonomous positioning auxiliary information control element. Then, combining its own ephemeris and precise clock information from the reception time, it calculates the theoretical arrival time and theoretical Doppler frequency shift of the terminal's uplink signal. Furthermore, it can use the uplink angle of arrival and uplink time difference measurement results to cross-validate the terminal's reported position, generating a fused and corrected true terminal position. Based on the corrected position and residual frequency offset information, it calculates precise timing advance and frequency correction commands, encapsulates them in a random access response message, and feeds them back to the terminal.

[0213] Through the embodiments of this application, a joint verification mechanism based on terminal autonomous positioning information and network-side physical layer measurement is adopted to achieve high-precision closed-loop calibration of terminal position and frequency offset, thereby improving the success rate of random access and the reliability of connection establishment in low-orbit satellite communication systems.

[0214] As an optional approach, sending a response message to the terminal to control the terminal to access the target cell includes: encapsulating a timing adjustment amount and a frequency adjustment amount in the response message, wherein the timing adjustment amount is used to update the start time of the terminal sending uplink data to the satellite base station, and the frequency adjustment amount is used to update the transmission frequency of the terminal sending uplink data to the satellite base station; and sending the response message to the terminal to control the terminal to access the target cell.

[0215] In an exemplary embodiment, a low-orbit satellite can calculate the terminal's true position and residual time-frequency deviation based on the autonomous positioning information reported by the terminal and the joint measurement results of the uplink time difference and uplink angle of arrival from the network side. It can then generate high-precision timing adjustment and frequency adjustment amounts and embed them into the media access control layer control element of the random access response message as a closed-loop correction command for pre-compensation error of the terminal.

[0216] Through the embodiments of this application, a closed-loop feedback mechanism that dynamically encapsulates time-frequency correction instructions in random access response messages is adopted, which achieves the purpose of improving uplink synchronization accuracy, ensuring stable demodulation of subsequent data channels, and reducing access failure rate.

[0217] As an optional approach, before encapsulating the timing adjustment and frequency adjustment amounts in the response message, the method further includes: obtaining the uplink angle of arrival and uplink time difference of arrival corresponding to the access message; parsing the access message to obtain an autonomous positioning auxiliary information control element, wherein the autonomous positioning auxiliary information control element encapsulates the location information of the terminal; performing position correction on the location information of the terminal based on the uplink angle of arrival and the uplink time difference of arrival, and generating the timing adjustment amount and the frequency adjustment amount.

[0218] Optionally, in the embodiments of this application, the uplink angle of arrival refers to the incident direction of the terminal's transmitted signal relative to the low-orbit satellite receiving antenna array, including but not limited to the combination of azimuth and elevation angles estimated by multi-antenna beamforming or MUSIC algorithm; the uplink time difference of arrival refers to the time difference of the terminal signal arriving at different receiving antenna elements of the satellite, including but not limited to the time delay difference obtained based on cross-correlation detection or maximum likelihood estimation.

[0219] It should be noted that the uplink angle of arrival can be estimated using beam scanning or spatial spectrum estimation techniques of phased array antennas, and its accuracy is affected by the signal-to-noise ratio and the number of antenna elements; the uplink time difference of arrival can be measured based on peak detection or correlation peak interpolation of pilot signals, and its resolution is related to the sampling rate.

[0220] In an exemplary embodiment, a low-orbit satellite uses a multi-beam phased array receiving antenna to perform high-resolution measurements of the uplink signal direction of arrival and time difference of arrival (TDOA) of the access message sent by the terminal, thereby obtaining the spatial angle of arrival (AOA) and time difference parameters of the terminal signal. By demodulating the physical uplink shared channel payload, the satellite analyzes the autonomous positioning auxiliary information control elements encapsulated therein and extracts the three-dimensional position coordinates autonomously calculated by the terminal. After calculating the spatial deviation of the position information reported by the terminal using the uplink AOA and uplink TDOA, the satellite combines the position error covariance trace value reported by the terminal with the uncompensated residual Doppler frequency offset estimate to perform a weighted fusion estimation of the terminal position and frequency deviation, outputting accurate timing adjustment and frequency adjustment amounts, which are then encapsulated in a response message and sent to the terminal.

[0221] Through the embodiments of this application, a network-side multi-beam receiving array is used to perform physical layer measurements of the uplink angle of arrival and uplink time difference of arrival for terminal access messages. Spatial consistency verification and error fusion are performed in conjunction with the positioning information autonomously reported by the terminal, thereby achieving the goals of improving the accuracy of random access response, enhancing the reliability of uplink synchronization, and reducing access failure rate.

[0222] As an optional approach, the above-mentioned position correction based on the uplink angle of arrival and the uplink time difference of arrival to generate the timing adjustment and frequency adjustment includes: determining the measured position of the terminal based on the uplink angle of arrival and the uplink time difference of arrival; performing a cross-comparison operation on the measured position information and the terminal position information to obtain an unbiased position error value; obtaining the trace of the position error covariance and the estimated value of the uncompensated residual Doppler frequency offset encapsulated in the autonomous positioning auxiliary information control element; and performing a fusion filtering operation on the terminal position information and the measured position information using the trace of the position error covariance, the estimated value of the uncompensated residual Doppler frequency offset, and the unbiased position error value to generate the timing adjustment and frequency adjustment.

[0223] Optionally, in the embodiments of this application, the measured position refers to the terminal spatial coordinates calculated by combining the uphill arrival angle and the uphill arrival time difference, including but not limited to the three-dimensional estimated value in the geocentric coordinate system based on triangulation or geometric positioning models.

[0224] Optionally, in the embodiments of this application, the above-mentioned cross-comparison operation refers to performing spatial difference analysis on the autonomous positioning location reported by the terminal and the actual measurement location on the network side, including but not limited to calculating the Euclidean distance or vector deviation between the two in the same coordinate system.

[0225] Optionally, in the embodiments of this application, the aforementioned unbiased position error value refers to the residual vector reflecting the deviation of the positioning system after statistical correction, including but not limited to the error component obtained after eliminating systematic offset by weighted averaging or least squares method.

[0226] Optionally, in the embodiments of this application, the trace value of the location error covariance mentioned above refers to the overall confidence index of the terminal's autonomous positioning results, including but not limited to the positioning uncertainty represented by the sum of the diagonal elements of the posterior covariance matrix.

[0227] Optionally, in the embodiments of this application, the aforementioned uncompensated residual Doppler frequency offset estimate refers to the residual deviation between the measured Doppler at the time of terminal transmission and the theoretical expected value, including but not limited to the Hertz-level frequency offset caused by crystal oscillator drift or dynamic error.

[0228] Optionally, in the embodiments of this application, the above-mentioned fusion filtering operation refers to state weighted fusion by combining the confidence level reported by the terminal and the measured accuracy on the network side, including but not limited to joint state optimization based on Kalman filtering or Bayesian estimation.

[0229] For example, using the angle of arrival measurement results of the satellite multi-beam receiving antenna and the time difference information of the multi-antenna reception, a geometric constraint equation for the propagation of the terminal signal is constructed. The actual position coordinates of the terminal in the geocentric coordinate system are calculated by the three-dimensional spatial intersection algorithm. The autonomous positioning coordinates reported by the terminal and the actual coordinates measured by the network side are vector subtracted in the coordinate system to obtain the position deviation vector. The systematic deviation is removed by the historical deviation statistical model to obtain the unbiased position error value after removing the bias.

[0230] Furthermore, the media access control layer control elements can be parsed from the physical uplink shared channel payload of the access message, and the encapsulated covariance trace value and residual frequency offset estimate can be extracted and used as input parameters for fusion filtering. The terminal-reported location is used as the prior estimate, the network-side measured location is used as the observation value, the covariance trace value is used as the prior uncertainty weight, and the residual frequency offset estimate is used as the frequency correction basis. The corrected terminal real location is calculated through a weighted fusion algorithm, and the accurate timing advance and frequency offset correction command is derived based on this location.

[0231] Understandably, cross-comparison and fusion filtering verification fall under the category of network-side base station-assisted positioning verification. This mechanism aligns with the network-verified user equipment location concept proposed in 3GPP Release 18. In this process, the base station (or the location management entity in the core network) does not directly accept the autonomous positioning results reported by the terminal. Instead, it compares and analyzes two high-precision physical layer observations—the Uplink Angle of Arrival (UL-AoA) and Uplink Time Difference of Arrival (UL-TDOA)—obtained through its own phased array antenna system, with the theoretical angle of arrival and theoretical time difference of arrival calculated from the three-dimensional coordinates reported by the terminal.

[0232] Specifically, base stations can, but are not limited to, calculate the deviation (i.e., residuals) between actual observed values ​​and theoretically estimated values, and then use mathematical optimization methods such as weighted least squares or network-side Kalman filtering to comprehensively process these residuals. Weighted least squares assigns different weights based on the reliability of each observation data point, prioritizing measurement results with higher accuracy. By minimizing the weighted sum of the squares of all residuals, it solves for the systematic deviation of the terminal location. Network-side Kalman filtering further introduces dynamic time-series modeling, utilizing historical observation information from multiple access processes to recursively smooth and predictively correct the terminal location error, thereby obtaining a more stable and unbiased location correction.

[0233] Through the embodiments of this application, by combining network-side physical layer measurements and terminal autonomous positioning confidence information, a high-precision collaborative estimation and dynamic compensation effect for terminal position and frequency offset error is achieved.

[0234] In one exemplary embodiment, considering that at least the following technical problems exist in the prior art:

[0235] 1. Access deadlock caused by high dependence on and vulnerability to external GNSS signals: Existing 3G Partner Program (NGLP) non-terrestrial network protocols mandate that terminals possess GNSS positioning capabilities and successfully acquire a location before initiating access. However, numerous GNSS-denied or restricted environments exist globally. For example, in urban canyons, deep forests, and indoor edge scenarios, GNSS signals are easily blocked or severely attenuated. In extreme scenarios such as national defense, public safety, or local conflicts, GNSS signals are highly susceptible to malicious jamming and spoofing. Once a terminal loses GNSS position input, it cannot calculate timing advance and Doppler shift pre-compensation. Without pre-compensation, the physical random access channel preamble sequence sent by the user equipment will not be detected by the base station due to significant propagation delay and frequency shift, directly preventing the user equipment from accessing the network and creating a deadlock state of "no positioning, no communication; no communication, no network-assisted positioning."

[0236] 2. Extremely low detection success rate and resource waste under a wide-area beam blind access mechanism: If completely disconnected from the global navigation satellite system and using the existing "blind trial" access mechanism (i.e., without Doppler shift pre-compensation, or relying solely on beam-specific pre-compensation at the satellite beam center), user equipment at the beam edge still faces residual Doppler shifts as high as tens of kilohertz (approximately 15-20 ppm) due to the extremely wide coverage of low-Earth orbit communication satellite beams (single beam diameters can reach hundreds of kilometers). Existing fifth-generation mobile communication physical random access channel preamble sequences (such as designs based on Zadoff-Chu sequences) are extremely sensitive to frequency offsets and cannot resist such large residual frequency offsets, leading to severe inter-carrier interference and partial periodic cross-correlation interference, resulting in an extremely high false detection rate, severely wasting radio-side air interface resources and causing system access congestion.

[0237] 3. The demanding conditions of multi-satellite positioning and the instability of long-delay closed-loop control: Existing cellular positioning technologies (such as downlink time difference of arrival or multi-satellite multiple round-trip time) require user equipment to simultaneously receive signals from multiple satellites when applied in non-terrestrial networks. However, in actual low-Earth orbit communication satellite constellation deployments, due to limitations in elevation angle, terrain obstruction, and constellation density, user equipment can only observe a single satellite most of the time. Under single-satellite conditions, the traditional time difference of arrival mechanism completely fails. Furthermore, non-terrestrial networks have extremely long round-trip times. If a traditional network-side closed-loop positioning and synchronization mechanism is used (i.e., the base station measures and sends timing advance or frequency offset indications to user equipment in an idle state), multiple signaling interactions are required. Under long round-trip times, this closed-loop control is highly susceptible to instability due to rapid channel aging and rapid satellite movement, and it also consumes a large amount of valuable physical downlink control channel resources.

[0238] 4. The power consumption and hardware cost of IoT and lightweight terminals are incompatible: For large-scale non-terrestrial IoT, narrowband IoT, or lightweight 5G mobile communication terminals, forcing the integration of high-precision independent global navigation satellite system receiver modules into the device and requiring it to frequently wake up for cold start satellite search before each data transmission will significantly increase the hardware cost, circuit board area, and energy consumption of the terminal. This directly violates the technical specifications that require low-power wide area network devices to have a battery life of more than ten years, limiting the commercialization of non-terrestrial networks in massive machine-type communication scenarios.

[0239] To address the aforementioned technical deficiencies, this application provides an integrated method and device for terminal communication, navigation, and positioning based on the fifth-generation mobile communication system. Specifically, in single-satellite visibility scenarios where conventional global navigation satellite system signals are absent, high-precision autonomous Doppler positioning of the terminal can be achieved using only downlink communication signals from non-terrestrial networks of fifth-generation mobile communication (such as synchronization signal blocks / positioning reference signals) and ephemeris information in system information block 19. Furthermore, an enhanced two-step random access communication mechanism that integrates positioning result feedback is designed. This completely solves the problem of low-Earth orbit communication satellite network access disruption in global navigation satellite system denied environments, eliminates the disruption of preamble sequence detection by residual Doppler frequency shift, significantly reduces the power consumption of IoT terminals, and achieves rapid time-frequency synchronization convergence within a single baseband cycle under ultra-long round-trip delays.

[0240] The aforementioned integrated communication and navigation system and equipment based on a fifth-generation mobile communication non-terrestrial network without a global navigation satellite system, including but not limited to: utilizing the extremely high Doppler change rate caused by the high-speed motion of low-Earth orbit communication satellites, a single continuously moving low-Earth orbit communication satellite is regarded as multiple "virtual anchor points" on its spatial trajectory within a short period of time. The terminal continuously measures the Doppler frequency shift of the fifth-generation mobile communication downlink reference signal at multiple time epochs, and independently calculates its precise three-dimensional position and local clock deviation locally using an extended Kalman filter algorithm. After completing timing advance and frequency offset pre-compensation, a two-step random access process is initiated through a specially constructed first-step access message (encapsulating the autonomously calculated position coordinates and estimated error covariance in the uplink payload). The non-terrestrial network base station performs rapid cross-validation and closed-loop correction based on uplink signal characteristics and information reported by the terminal.

[0241] For example, the overall architecture of the above-mentioned integrated communication and navigation system includes at least one low-orbit communication satellite node (New Radio Non-Terrestrial Network Base Station, abbreviated as NTN gNB), several ground user terminals (User Equipment, abbreviated as UE), and a location management function (LMF) entity in the 5th Generation Core Network (5GC).

[0242] Low Earth Orbit (LEO) satellite nodes: These utilize LEO communication satellites with a regenerative payload architecture. The complete protocol stack of the base station (including the Physical Layer (PHY), Medium Access Control Layer (MAC), and Radio Link Control Layer (RLC)) is directly deployed on the satellite, supporting on-board processing and inter-satellite links (ISL Xn interface). The satellite is equipped with multi-beam phased array antennas, transmitting fifth-generation New Radio (NR) Orthogonal Frequency Division Multiplexing (OFDM) waveforms. In the downlink resource grid, the base station time-frequency multiplexes the Synchronization Signal Block (SSB) and Positioning Reference Signal (PRS) to provide high-density pilot patterns, supporting high-precision Doppler shift and Doppler rate of change estimation by the terminal.

[0243] Terminal node: It has standard fifth-generation New Radio (NR) transceiver functionality and deeply integrates the "integrated baseband processing engine for self-positioning and access without a global navigation satellite system" proposed in this application embodiment. This engine includes: an integrated signal Doppler extraction module, a multi-epoch "virtual anchor" positioning solver (with built-in Extended Kalman Filter, EKF), a time-frequency pre-compensation and waveform generation module, and a customized encapsulation of the enhanced media access control layer protocol stack (supporting the first-step access message physical uplink shared channel payload, MsgA PUSCH Payload, MsgA PUSCH payload).

[0244] Specifically, such as Figure 5 As shown, the operational procedures include, but are not limited to, the following:

[0245] Step 1: Lower planetary ephemeris acquisition and multi-epoch integrated signal measurement (blind / semi-blind synchronization):

[0246] When a user equipment is powered on or moves into a GNSS-denied area, the terminal cannot use the existing precise open-loop pre-compensation mechanism because it cannot obtain the GNSS position. At this time, the blind / semi-blind measurement process of the embodiment of this application is initiated:

[0247] S1, Initial Cell Search: The terminal scans the 5th generation New Radio (NR) band, capturing the downlink Primary Synchronization Signal (PSS) and Secondary Synchronization Signal (SSS). Since the terminal does not know its absolute position at this time and cannot calculate the precise Doppler frequency offset, it uses the signal after beam-specific Doppler pre-compensation (Beam-Specific DPC) applied by the satellite at the beam center for blind acquisition. By relaxing the search tolerance for local carrier frequency offset (CFO), the terminal achieves coarse frame synchronization and symbol synchronization.

[0248] S2, SIB19 Ephemeris Decoding: The terminal demodulates the system information block on the Physical Downlink Shared Channel (PDSCH) and reads System Information Block 19 (SIB19). From SIB19, the terminal extracts the ephemeris data of the currently serving satellite (including the satellite's spatial position and state vector at the reference epoch). Velocity state vector The epoch time, common timing advance (ta-CommonDrift), and common timing advance (Common TA) are also included.

[0249] It should be noted that the terminal needs to calculate the Total Transmit Pre-compensation Timing Advance (TA_total) when sending uplink data. The transmission time of the aforementioned access message is determined through closed-loop iterative calculation of the transmission pre-compensation timing advance and time consistency verification.

[0250] Furthermore, since the low-orbit communication satellite (New Radio Non-Terrestrial Network BaseStation, or NTN gNB) is in a high-speed motion state (typically about 7 km / s), the common propagation delay between it and the ground reference point changes continuously and dynamically over time. Therefore, when the terminal calculates the common timing advance (ta-Common) component of the network broadcast, it cannot rely solely on a fixed initial value. The terminal must use the following parameters obtained from System Information Block 19 (SIB19): common timing advance reference value (ta-Common), common timing advance drift rate (ta-CommonDrift), in symbols adjusted per second (symbols / s), epoch time (epochTime), i.e., the reference timestamp corresponding to the ephemeris information in SIB19, and combine them with the time reference corresponding to the system frame number and subcarrier spacing (SCS) at the current moment, and substitute them into the dynamic common TA compensation equation defined in Section 11.1 of the 3GLP Technical Specification TS 38.213 to calculate the pre-compensation timing advance for the terminal to send the access message.

[0251] S3, Multi-epoch Doppler Feature Extraction: Since a single measurement cannot pinpoint the location, the terminal needs to perform multi-epoch Doppler feature extraction over N consecutive time epochs. Within the system, downlink positioning reference signals (PRS) and synchronization signal blocks (SSBs) are continuously received. Using a baseband phase-locked loop (PLL) or a high-precision CFO estimation algorithm based on Fast Fourier Transform (FFT), the sequence of residual Doppler frequency shift measurements received over these N epochs is extracted. .

[0252] It should be noted that multiple time epochs ( The reference epoch can be a series of time points derived from the satellite reference epoch obtained after decoding SIB19. After successfully resolving the initial spatial state of the satellite at the reference epoch (determined by ephemeris data), the terminal needs to actively divide multiple subsequent measurement time windows based on this known trajectory in order to extract the Doppler frequency shift at these specific time points, thereby constructing a "virtual anchor point" for positioning in space.

[0253] It should also be noted that the continuously received synchronization signal block is the core physical layer input for implementing the embodiments of this application, specifically:

[0254] As a high-precision Doppler shift measurement beacon: Although the initial Synchronization Signal Block (SSB) acquired in the first step has completed coarse synchronization and cell identifier identification, in the low-Earth orbit satellite scenario, the satellite is in a state of high-speed relative motion with respect to the terminal. Therefore, in the subsequent N time epochs, the terminal continues to use the SSB and positioning reference signal as physical layer pilot signals to continuously track carrier phase changes, thereby accurately measuring the instantaneous carrier frequency offset (CFO) value caused by the high-speed motion of the satellite at each moment.

[0255] As the direct input to the Extended Kalman Filter (EKF) algorithm in step 2, the sequence of residual Doppler frequency shift measurements extracted by the terminal through continuous reception of synchronization signal blocks over the aforementioned N epochs is the only nonlinear observation input value upon which the Extended Kalman Filter (EKF) algorithm in step 2 (user equipment autonomous positioning calculation based on multi-epoch virtual anchor points) relies. If it is impossible to continuously receive synchronization signal blocks to obtain continuous and high-precision Doppler frequency shift variation characteristics, the subsequent autonomous three-dimensional spatial coordinate calculation process of the equipment will be completely unable to start and converge.

[0256] Step 2: Device autonomous positioning calculation based on multi-epoch "virtual anchor points" (without the core algorithm of the Global Navigation Satellite System): It can replace the core mechanism of the Global Navigation Satellite System. The traditional Global Navigation Satellite System positioning requires simultaneous observation of at least four satellites for spatial rendezvous. The embodiment of this application uses the idea of ​​time for space to complete high-precision three-dimensional positioning calculation in the single-satellite visibility scenario.

[0257] Physical propagation model establishment: Assume the satellite is in the Earth coordinate system... The actual location at any given moment is The speed is (Obtained by extrapolation from the orbital elements of SIB19). Let the unknown position of the terminal be... Since the UE (such as an IoT node or pedestrian) moves extremely slowly relative to a low-Earth orbit satellite (approximately 7000 m / s), it can be approximated as being stationary. .

[0258] Theoretical Doppler frequency shift under error-free conditions The nonlinear observation function is:

[0259]

[0260] in This is the center frequency of the 5G downlink carrier. It is the speed of light.

[0261] Considering the frequency deviation caused by the instability of the local low-cost crystal oscillator in the terminal (Clock Drift), the actual measurement model is:

[0262]

[0263] in To account for the comprehensive observation noise, which includes the rate of change of atmospheric ionospheric delay and thermal noise, the theoretical model of the extended Kalman filter algorithm... It is a statistical model variable representing unknown random error.

[0264] In actual system calculations, the terminal does not need to know the specific values ​​at every point in time. The algorithm uses statistical features, specifically the observation noise covariance matrix mentioned in subsequent steps. The method for obtaining the covariance parameter representing the overall noise level is actually a dynamic evaluation result combining real-time measurement status with historical / empirical models.

[0265] The underlying thermal noise component (derived from dynamic actual observations): This part is mainly caused by receiver thermal noise and phase-locked loop tracking jitter. In actual operation, it is dynamically calculated in real time based on the signal-to-noise ratio or carrier-to-noise ratio of the downlink reference signal received at the current epoch. The worse the signal quality, the greater the variance of the observation value assigned by the system at that epoch (i.e., the less trust is placed in the measurement at that point).

[0266] Atmospheric and ionospheric delay variation rate (history fitting and empirical model): Due to refraction and delay as low-Earth orbit satellite signals pass through the atmosphere, the rate of change of these delays affects the Doppler shift. Terminals typically cannot directly measure atmospheric conditions; therefore, the boundary of this error usually relies on the system's built-in empirical physical model or history fitting data (e.g., typical tropospheric / ionospheric error distribution patterns based on satellite elevation angle). Residual uncertainties that the model cannot fully compensate for are quantified as a statistical variance and added to the observation noise covariance matrix.

[0267] That is, comprehensive observation noise In this algorithm, a statistical variance limit is dynamically calculated based on real-time signal quality and combined with an empirical model of atmospheric errors, thereby conveying the reliability of the current Doppler observations to the filter.

[0268] It should be noted that the formula f in this physical propagation model... D (t i ) is a theoretical mathematical physics model (i.e., a nonlinear observation function). It merely describes the pure spatial geometric and dynamic relationship between the known satellite state (satellite position, satellite velocity) and the unknown terminal position under ideal error-free conditions.

[0269] In this embodiment, the terminal's underlying hardware continuously receives downlink signals and extracts a sequence of residual Doppler frequency shift measurements using a phase-locked loop (PLL) or fast Fourier transform (FFT). These measurements are actual, direct physical observations with inherent errors. These observations are not calculated based on the theoretical model but are real radio frequency signal characteristics, which objectively incorporate actual physical Doppler frequency offset, the terminal's own crystal oscillator clock drift, and various types of thermal noise.

[0270] In the extended Kalman filter solution logic of step 2, the two work together: the actual observation value serves as the only true and reliable external input for the entire system; the filter substitutes the unknown terminal coordinates (the aforementioned coordinate parameters) guessed during the current iteration into this theoretical formula to calculate a theoretically expected frequency shift that should be measured; residual correction: the algorithm subtracts the actual directly measured observation value from the expected theoretical value calculated by the formula. Using the difference between the two (called innovation / residual in the filtering algorithm), the unknown terminal position is continuously corrected and updated until the value output by the theoretical model infinitely approaches the actual measurement value, thereby achieving precise positioning.

[0271] Virtual Anchors Construction: Due to the high-speed motion of low-Earth orbit satellites, after N epochs (e.g., continuous observation for 1 to 2 seconds), the satellite has moved tens of kilometers in its orbit, forming multiple "virtual anchors" with significantly different spatial locations. The terminal converts these time-series-based single-satellite measurements into an equivalent multi-satellite instantaneous measurement model in space.

[0272] Extended Kalman filter combined with elevation constraint solution:

[0273] Construct the initial state vector of the terminal To accelerate the convergence of single-satellite Doppler positioning and eliminate Z-axis ambiguity, this application's embodiments introduce an Earth surface elevation constraint (i.e., the aforementioned preset elevation parameters; assuming the terminal is located near the Earth's surface, the altitude can be set as a virtual observation value using a rough digital elevation model or the default sea level). ).

[0274] In the extended Kalman filter algorithm framework, the state prediction equation is:

[0275]

[0276] Since the terminal is approximately stationary, the state transition matrix... Set as a unit matrix .

[0277] The observation update equation utilizes the Doppler observation function Jacobian Matrix Perform local linearization:

[0278]

[0279]

[0280] in, For the first The actual Doppler frequency shift measured at the epoch, This is the observation noise covariance matrix dynamically adjusted based on the signal-to-noise ratio (SNR). After multi-epoch recursive iteration, the filter converges, outputting a high-precision absolute position estimate of the UE. Estimation of deviation from local crystal oscillator Pk|k-1 is the prior error covariance matrix at the k-th time epoch, representing the mathematical assessment of the uncertainty of the current terminal position and clock difference prediction results based solely on the state at the previous moment before the latest Doppler measurement value at the k-th epoch is received.

[0281] It should be noted that, The filter is dynamically calculated and applied in real time by the terminal's underlying baseband module at each epoch. It represents the reliability of the Doppler measurement at that instant and is mainly obtained through the following methods:

[0282] Real-time mapping based on carrier-to-noise ratio (CNR) or signal-to-noise ratio (SNR): When the phase-locked loop (PLL) inside the terminal extracts the Doppler frequency, the variance of its measurement (i.e., the severity of error fluctuation) is highly correlated with the quality of the currently received downlink signal. Theoretically and in engineering practice, a direct mathematical mapping relationship can be established between the Doppler estimation variance and the CNR. If the signal is strong in the current epoch, A smaller value indicates extremely high confidence in the measurement; if the signal is blocked, causing a sharp drop in the signal-to-noise ratio, the signal-to-noise ratio will be lower. The value will be dynamically amplified.

[0283] Phase-locked loop (PLL) internal state parameters: In addition to external signal quality, the order, loop bandwidth, and coherent integration time of the receiver's baseband tracking loop directly determine the measurement variance of the Doppler frequency at the underlying level. The baseband chip quantifies the uncertainties caused by these hardware states in real time.

[0284] Furthermore, during the execution of the extended Kalman filter algorithm, h DEM As an additional auxiliary constraint derived from external geographic information, it is introduced into the observation update process to enhance positioning accuracy and stability.

[0285] First, h DEMIt is not the actual location of the terminal, but a ground elevation reference value obtained from the Digital Elevation Model (DEM) that corresponds to the approximate geographical location of the terminal. It reflects the topographic features of the Earth's surface, such as the average height of plains, mountains, or oceans, and is expressed in elevation.

[0286] Secondly, without elevation constraints, the observation vector only contains Doppler frequency shift measurements extracted from the downlink synchronization signal block and the positioning reference signal, constituting a one-dimensional observation input. In this case, the filter can only infer the three-dimensional position of the terminal based on the trajectory of a single satellite. However, since the Doppler equation itself has low sensitivity to the vertical direction (Z-axis), it is easy to cause multiple solutions or divergence in the height dimension, i.e., the Z-axis ambiguity problem.

[0287] To address this issue, in the embodiment of this application, during the observation update phase, h... DEM As a virtual observation, it is used in conjunction with measured Doppler data to form the expanded observation vector. In other words, in each iteration, the filter not only relies on the frequency shift information caused by satellite motion, but also simultaneously senses the indirect height reference from the terrain database.

[0288] Step 3: Multi-dimensional autonomous pre-compensation of uplink timing and frequency on the terminal side: After completing autonomous positioning without a global navigation satellite system, the terminal has the prerequisite for initiating high-precision uplink transmission. It is necessary to perform dual pre-compensation on the transmission timing and carrier frequency of the uplink signal to ensure that the signal can accurately reach the receiving window of the low-orbit satellite base station.

[0289] Timing advance compensation: The terminal calculates its own precise three-dimensional spatial position based on step 2. Combined with the satellite's instantaneous ephemeris corresponding to the moment when the uplink signal is about to be transmitted. The formula for calculating the specific timing advance of the one-way electromagnetic wave propagation delay from the terminal to the satellite, which can be independently calculated, is as follows: The total transmit pre-compensation TA equals the common timing advance TA of the network broadcast plus... .

[0290] Based on this, the terminal calculates its own unique timing advance, which reflects the amount of time needed to advance the transmission to compensate for propagation delay. The terminal then adds this unique timing advance to the common timing advance broadcast by the network through system information blocks, obtaining the final total pre-compensated timing advance. This total value is used to adjust the start time of uplink data transmission, ensuring that the signal arrives at the satellite precisely within its preset reception time slot, avoiding time-domain misalignment and inter-symbol interference caused by propagation delay.

[0291] It is understandable that the instantaneous position and velocity information of a low-Earth orbit satellite at the moment the terminal initiates uplink transmission is not directly broadcast by the network, but rather autonomously calculated in real time by the terminal based on its local time reference and the ephemeris parameters sent by the network. In the 3GPP non-terrestrial network protocol, the terminal first uses its own local system time as a reference to calculate the specific time slot when it is about to send uplink data. Then, it performs a difference calculation between this time and the satellite ephemeris reference time (called the reference epoch time) broadcast in System Information Block 19 to obtain the time interval between the two. Based on this time difference, the terminal combines the initial spatial position vector and velocity vector of the satellite at the reference epoch time contained in SIB19, and then calls the orbital motion extrapolation model explicitly defined in the 3GPP TS 38.331 protocol to perform precise dynamic evolution calculations of the satellite's orbital state. This model advances the satellite's state variables at the reference time to the precise moment when the terminal actually sends the signal, thereby obtaining the satellite's three-dimensional spatial coordinates and velocity vector at that instant. This process is completed entirely locally on the terminal, without relying on real-time network updates, ensuring that the terminal can still obtain high-precision ephemeris prediction data in low-Earth orbit satellite communication scenarios with long latency and high dynamism.

[0292] Frequency offset pre-compensation: Based on the calculated spatial relative velocity vector relationship between the transceiver and receiver, the terminal calculates the precise uplink Doppler frequency shift. Simultaneously, the terminal also incorporates the local crystal oscillator drift error estimated in step two. This is taken into consideration. Subsequently, in the RF front-end or digital baseband processing module, the terminal applies a frequency rotation offset (pre-compensation) to the uplink carrier signal to be transmitted, which is equal in magnitude but opposite in direction to the total frequency offset mentioned above. This operation is equivalent to actively canceling the frequency offset caused by relative motion and local clock deviation before transmission, so that the center frequency of the uplink signal is as close as possible to its desired frequency point when it reaches the satellite receiver, thereby greatly reducing inter-carrier interference and improving the signal demodulation success rate.

[0293] It should be noted that the spatial relative velocity vector relationship between the transceiver and receiver is determined based on the relative velocity vector between their own positions calculated in step 2 and the instantaneous positions of the satellite. In other words, although the terminal's own velocity (relative to the Earth's surface) is usually extremely small or zero, the low-Earth orbit satellite is moving at an extremely high speed. The magnitude of the Doppler shift caused by the satellite's motion depends entirely on the projection of the satellite's velocity vector onto the line-of-sight (LoS) direction between the satellite and the terminal. Therefore, by using the calculated terminal position and the calculated instantaneous satellite position to obtain the precise unit vector in the line-of-sight direction, and then taking the dot product with the satellite's velocity vector, the spatial relative velocity vector relationship is obtained.

[0294] Through the aforementioned coordinated pre-compensation of timing and frequency, the terminal achieved precise adaptive alignment with high-speed mobile satellite links without relying on external global navigation satellite systems, laying a reliable time-frequency synchronization foundation for the successful initiation of subsequent enhanced two-step random access.

[0295] To accommodate this expanded observation vector, the observation function within the filter has also been expanded: the function, originally used only to describe the Doppler physical relationship, now includes a new term specifically for determining the coordinates (x, y) of the currently predicted terminal position. u y u , z u This module converts the predicted elevation (x) into theoretical elevation. Based on the Earth ellipsoid model, this module converts the predicted elevation (x) into theoretical elevation. u y u , z u The three-dimensional coordinates are converted into the corresponding theoretical altitude values ​​and used as the second part of the output of the observation model.

[0296] Similarly, the Jacobian matrix used to linearize the observation model also adds a row, which expresses the sensitivity of the theoretical elevation to each coordinate component in the terminal's three-dimensional position; that is, how the calculated elevation value will respond when the terminal's X, Y, or Z coordinates change slightly. This added derivative information allows the filter to reasonably assess the contribution of the "height constraint" to the overall state estimation.

[0297] Ultimately, by using h DEM As virtual observations participating in the calculation of Kalman gain and state residual update, the system is guided in two ways during each iteration of the algorithm: firstly, it must ensure that the estimated position satisfies the Doppler law generated by satellite motion; secondly, it must ensure that the converted altitude of that position is as close as possible to the preset terrain reference value. In other words, by utilizing known geographical common sense, it introduces strong prior information into the originally uncertain single-satellite positioning problem, thereby significantly suppressing vertical uncertainty, accelerating the convergence speed of the filter, and greatly improving the positioning stability and accuracy of the terminal in three-dimensional space. This mechanism achieves highly reliable terminal positioning without relying on any external positioning system, solely through the collaboration of communication signals and publicly available terrain data.

[0298] Step 4: Enhanced two-step random access and navigation information fusion transmission:

[0299] Compared to the traditional four-step random access procedure, which requires multiple signaling interactions including preamble transmission, response reception, connection request reporting, and final confirmation, the two-step random access mechanism (consisting of MsgA and MsgB) introduced in the 3rd Generation Partnership Project standard significantly reduces communication overhead and connection establishment time in non-terrestrial network environments with long round-trip latency. This invention fundamentally innovates this mechanism, transforming MsgA, originally used only for communication access, into a fusion carrier for the coordinated transmission of communication and navigation information, achieving bidirectional empowerment with a single transmission.

[0300] First, in the physical layer preamble sequence design, although the terminal has completed autonomous pre-compensation for Doppler frequency offset in the previous stage, the uplink preamble signal may still face slight carrier frequency offset due to the slight residual error in the estimation of the extended Kalman filter. Therefore, this embodiment can abandon the traditional structure relying on long cyclic prefixes to resist delay spread, and instead adopt a preamble format without cyclic prefixes, or configure a wider guard interval based on the Zadoff-Chu sequence. This waveform design reduces the risk of false detection or missed detection caused by periodic cross-correlation of the preamble sequence under the influence of frequency offset, significantly improving the base station's success rate in detecting the preamble, and maintaining an extremely low access failure rate even in the presence of residual frequency offset.

[0301] Secondly, in the uplink data channel portion, in standard two-step access, the physical uplink shared channel portion of MsgA only carries a small amount of control information, such as radio resource control connection requests or terminal identification. This invention adds a dedicated data field called "Autonomous Positioning Assist Information Control Element" to the protocol data unit of the media access control layer. This field is not used for traditional communication control, but is specifically used to carry navigation information autonomously calculated by the terminal in the absence of a global navigation satellite system, enabling the multiplexing and transmission of navigation data through the communication link. Specifically, it includes:

[0302] First, the three-dimensional spatial position information of the terminal obtained in step 2 through multi-epoch Doppler observation and extended Kalman filter solution can be X, Y, and Z coordinates in the geocentric geofixed coordinate system, or it can be converted into latitude, longitude, and height format for direct use by the network side.

[0303] Second, the terminal reports the trace of the location estimation error covariance matrix calculated during the solution process as a quantitative indicator of location confidence. The smaller the value, the more confident the terminal is in its location estimation; the larger the value, the higher the location uncertainty. The network side can use this to determine whether further correction is needed or whether the terminal's location report can be trusted.

[0304] It's important to note that the trace of the position estimation error covariance matrix refers to the sum of the diagonal elements of the posterior error covariance matrix output by the extended Kalman filter algorithm after convergence. The diagonal elements represent the estimated variances of the terminal along the X, Y, and Z coordinate axes after filter convergence. The trace is essentially the sum of these three variances, mathematically equivalent to the mean squared error of the 3D spatial positioning, serving as a confidence metric for how confident the terminal is in its calculated position.

[0305] Third, the terminal also reports its own uncompensated residual Doppler frequency offset estimate. The uncompensated residual Doppler frequency offset estimate provides a direct physical layer reference for the network side, which helps the base station to more accurately assess the dynamic characteristics of the channel, especially in the low-Earth orbit environment where Doppler changes are drastic, and provides auxiliary basis for subsequent beamforming, frequency tracking and uplink scheduling.

[0306] It should be noted that the uncompensated residual Doppler frequency offset estimate originates from the terminal baseband layer, and can be extracted through, but is not limited to, the following two methods:

[0307] The filter residual generated in the last step of the algorithm processing in step 2 is the difference between the Doppler frequency shift actually measured by the terminal and the expected frequency shift calculated by substituting the finally determined estimated position into the theoretical formula.

[0308] In terms of hardware implementation, the error can also be directly read from the residual frequency error register of the digital phase-locked loop during frequency pre-compensation. This represents the portion of frequency offset that the terminal clearly knows it has not perfectly eliminated, limited by the accuracy of the baseband hardware and the convergence limit of the algorithm.

[0309] Through the above design, MsgA is no longer just an "access request signal," but becomes a "smart beacon carrying location and status." While initiating a connection, it transmits the terminal's autonomous positioning results to the network in real time, enabling the base station to obtain the terminal's spatial coordinates, positioning reliability, and channel status information upon first receiving the uplink signal. This creates crucial conditions for subsequent accurate closed-loop calibration.

[0310] Step 5: Network-verified Closed-loop verification and random access response message:

[0311] After receiving the Two-Step Random Access Message A (MsgA), which includes a preamble sequence and uplink data, the base station first decodes the signal. Utilizing the multiple receiving beams of its phased array antenna system, the base station performs uplink angle of arrival (UL-AoA) and uplink time difference of arrival (UL-TDOA) measurements on the physical layer radio signal of MsgA. This allows it to obtain the multi-beam spatial pointing and time difference characteristics of the terminal signal arriving at the base station, forming a high-precision physical layer spatial positioning vector.

[0312] Subsequently, the base station cross-checks the UL-AoA and UL-TDOA ray vector information obtained directly from the physical layer waveform measurement with the three-dimensional spatial location information autonomously reported by the user equipment decoded from the Physical Uplink Shared Channel (PUSCH) of MsgA. A fusion filtering algorithm is then used for joint verification to obtain the network-confirmed, unbiased position error. This process achieves bidirectional verification between the terminal's self-localization results and the network's measured results, effectively eliminating outliers or estimates with large errors, and improving the reliability and accuracy of the location information.

[0313] Based on the unbiased position error, the base station further calculates the precise timing advance command (TAC) and fine frequency adjustment (i.e., the timing and frequency adjustments mentioned above). The base station then issues a random access response MsgB (SuccessRAR). The downlink media access control element (MAC CE) of the MsgB not only includes the conventional communication scheduling allocation (Uplink Grant) and contention resolution flags, but also encapsulates the aforementioned precise timing advance command and frequency offset correction instructions.

[0314] It should be noted that the above cross-comparison operation falls under the category of network-side base station-assisted verification (aligning with the Network-verified UE Location concept introduced in 3GPPRel-18). If existing technologies are used, the algorithm typically employs Weighted Least Squares (WLS) or Network-side Kalman Filtering. The base station compares the actual AoA / TDOA values ​​measured by the physical antenna with the theoretical Uplink Angle of Arrival (UL-AoA) and Uplink Time Difference of Arrival (UL-TDOA) calculated using the coordinates reported by the terminal. The unbiased position error is obtained by minimizing the sum of squared residuals.

[0315] After receiving MsgB, the user equipment not only completes the Radio Resource Control Connection Establishment (RRC Connection Establishment) within a single round-trip time, but also simultaneously obtains high-precision positioning closed-loop correction parameters from the network. This achieves a secondary improvement in terminal positioning accuracy, effectively ensuring the high-order modulation and demodulation performance of the subsequent Physical Downlink Shared Channel (PDSCH) and Physical Uplink Shared Channel (PUSCH), laying a solid foundation for the stable transmission of high-speed, low-latency services.

[0316] Understandably, cross-comparison and fusion filtering verification fall under the category of network-side base station-assisted positioning verification. This mechanism aligns with the network-verified user equipment location concept proposed in 3GPP Release 18. In this process, the base station (or the location management entity in the core network) does not directly accept the autonomous positioning results reported by the terminal. Instead, it compares and analyzes two high-precision physical layer observations—the Uplink Angle of Arrival (UL-AoA) and Uplink Time Difference of Arrival (UL-TDOA)—obtained through its own phased array antenna system, with the theoretical angle of arrival and theoretical time difference of arrival calculated from the three-dimensional coordinates reported by the terminal.

[0317] Specifically, base stations can, but are not limited to, calculate the deviation (i.e., residuals) between actual observed values ​​and theoretically estimated values, and then use mathematical optimization methods such as weighted least squares or network-side Kalman filtering to comprehensively process these residuals. Weighted least squares assigns different weights based on the reliability of each observation data point, prioritizing measurement results with higher accuracy. By minimizing the weighted sum of the squares of all residuals, it solves for the systematic deviation of the terminal location. Network-side Kalman filtering further introduces dynamic time-series modeling, utilizing historical observation information from multiple access processes to recursively smooth and predictively correct the terminal location error, thereby obtaining a more stable and unbiased location correction.

[0318] It should be noted that the base station can use the existing standard closed-loop time and frequency synchronization offset estimation algorithm to calculate the timing adjustment and frequency offset adjustment values. That is, the base station physical layer measures the actual time offset and phase / frequency rotation of the physical random access channel preamble sequence in MsgA arriving at the base station's receiving window, and directly maps it to the standard timing adjustment and frequency offset adjustment values.

[0319] It should also be noted that the trace value of the position error covariance reported by the terminal can be used to determine the weight that the base station needs to assign to the coordinates reported by the terminal in the weighted least squares method. If the trace value is large, it means that the terminal's reported position is ambiguous, and the base station's fusion algorithm will reduce the weight of the terminal's data, placing more trust in the measured position determined by the base station antenna through the measured uplink angle of arrival and uplink time difference of arrival. Conversely, if the trace value is small, the base station will use it as strong prior information, thereby accelerating and optimizing the solution of unbiased position error. Considering that when the base station's physical antenna receives the signal, it can only measure a total comprehensive frequency offset. This total frequency offset is mixed with Doppler caused by inaccurate spatial distance calculation and clock error caused by the terminal's local inexpensive crystal oscillator. Since the terminal reports the estimated value of the uncompensated residual Doppler frequency offset in MsgA, the base station can decouple and separate the clock drift and spatial physical frequency offset, thereby issuing extremely accurate frequency adjustment commands that are free from clock error interference. In addition, after obtaining the residual frequency offset, the base station can also perform reverse compensation on the physical layer receiving side to ensure successful demodulation of the physical random access channel data load of MsgA itself.

[0320] In one exemplary embodiment, a terminal communication and navigation integrated access method for non-terrestrial networks can be implemented, comprising the following steps performed sequentially:

[0321] In the downlink, the terminal receives the system information block (SIB19) broadcast by a single communication satellite base station to obtain ephemeris information and receives the downlink communication reference signal;

[0322] Doppler frequency shift measurements are performed on the reference signal over multiple consecutive time epochs to construct a set of "virtual anchor points" based on a single satellite trajectory;

[0323] Using the extended Kalman filter algorithm and combined with the Earth's surface elevation constraint, the three-dimensional spatial absolute position and local clock drift of the terminal are autonomously and iteratively calculated under the condition of no global navigation satellite system signal input.

[0324] Based on the calculated terminal location and ephemeris information, the timing advance and Doppler frequency offset pre-compensation values ​​are calculated and applied to the radio frequency transmission link.

[0325] A two-step random access process is initiated using the pre-compensated link. In the first step, the physical uplink shared channel payload contains a specially customized Media Access Control (MAC) element, which encapsulates the spatial location coordinates and estimation error covariance indications autonomously calculated by the terminal.

[0326] Specifically, the satellite base station receiving the MsgA uses its multi-beam phased array receiving antenna to measure the uplink time difference of arrival and angle of arrival; the base station cross-compares and fuses the physical layer waveform measurement results with the terminal-reported location information encapsulated in the MsgA to generate an accurate absolute time-frequency correction command; and feeds it back to the terminal through the second-step random access response message (MsgB) to complete a coarse-to-fine communication and navigation closed-loop calibration.

[0327] Furthermore, when the terminal transmits MsgA, the physical random access channel preamble sequence it includes adopts a sequence structure without a cyclic prefix or with a configured extended guard interval to suppress inter-carrier interference caused by self-location residual error.

[0328] The terminal's hardware architecture can be independent of the global navigation satellite system: including a multi-epoch Doppler tracking engine for extracting continuous epoch frequency offsets, a global navigation satellite system-free positioning solution coprocessor with built-in extended Kalman filtering and Earth ellipsoid model, and an integrated network layer encapsulator in the physical random access channel payload that can map positioning coordinate data across layers to MsgA.

[0329] This application completely eliminates the rigid dependence of 5G / 6G Non-Terrestrial Network (NTN) specifications on external independent global navigation satellite systems for position input and assisted synchronization. For the first time within the 5G communication system, it mines the physical layer Doppler kinematic characteristics inherent in the downlink communication waveforms—synchronization signal blocks and positioning reference signals—and combines this with deep customization and structured integration of the two-step random access channel (2-Step RACH) signaling process at the media access control layer. This constructs an endogenous, closed-loop linkage mechanism that "achieves navigation ranging using communication waveforms and ensures communication access using navigation results." This mechanism does not rely on any external positioning system, enabling the terminal to independently complete high-precision 3D positioning and low-latency initial access even in environments where global navigation satellite systems deny access. It achieves deep integration and autonomous collaboration of communication and navigation functions at the physical layer, protocol layer, and system architecture levels, providing a new technological paradigm with high robustness, low power consumption, and scalable deployment for future 6G integrated air-space-ground networks.

[0330] Firstly, it enables seamless replacement of the global navigation satellite system, greatly enhancing network survivability and robustness in signal-denied environments:

[0331] When existing non-terrestrial network terminals face interference or obstruction of global navigation satellite system signals, they will directly fall into a paralyzed state, unable to complete time and frequency synchronization and unable to initiate access.

[0332] This application employs an autonomous calculation technique (i.e., virtual anchor point construction) based on the multi-epoch Doppler rate of change evolution law inherent in the 5G New Radio downlink communication waveform (synchronization signal block and positioning reference signal). This enables user equipment to independently complete high-precision autonomous calculation of its own three-dimensional position using only the transit signal of a single low-Earth orbit communication satellite, even under extreme conditions such as complete suppression, spoofing, or terrain obstruction of the Global Navigation Satellite System (GNSS) signal. This solution completely eliminates the rigid dependence of non-terrestrial networks on independent GNSS-assisted positioning, significantly enhancing the communication availability and system resilience of critical information infrastructure in complex electromagnetic environments and satellite-free scenarios.

[0333] Secondly, it significantly reduces the overall power consumption and hardware cost of IoT and lightweight terminals:

[0334] This application completely eliminates the need for a separate high-power global navigation satellite system (GNSS) radio frequency front-end and dedicated positioning baseband chip, which are required in non-terrestrial network IoT terminals or 5G lightweight terminals (RedCap terminals), in terms of hardware architecture. The terminal only needs to reuse the existing 5G New Radio (NR) communication receiving link to achieve autonomous positioning while receiving and processing downlink synchronization signal blocks and positioning reference signals. Compared to traditional access methods relying on GNSS assistance, this eliminates the continuous energy consumption burden caused by the GNSS cold start satellite search process (which typically takes tens of seconds and consumes extremely high power), reducing the overall power consumption of the terminal during the initial access phase by 15% to 40%. This advantage significantly extends the device's battery life and greatly improves the economy and feasibility of large-scale commercial deployment of machine-type communications (MMOs) in non-terrestrial networks.

[0335] Third, it overcomes the positioning challenges in single-satellite visibility scenarios, significantly improving the convergence speed and accuracy of idle-state positioning:

[0336] In the early stages of low-Earth orbit communication satellite constellation deployment, or when terminals are located in areas with limited elevation angles, such as urban canyons, mountainous areas, or indoor edges, user equipment can usually only observe a single communication satellite. Traditional multi-satellite positioning methods based on downlink time difference of arrival of multiple satellites become completely ineffective due to underdetermined observation equations.

[0337] This application utilizes the significant spatial trajectory changes caused by the high-speed motion of low-Earth orbit communication satellites to represent the continuous motion of a single satellite across multiple time epochs as multiple "virtual spatial anchor points." Combined with the iterative smoothing capability of the extended Kalman filter algorithm in multi-epoch time series and the introduction of digital elevation model constraints, this effectively alleviates the technical bottleneck of severely degraded geometric accuracy factors in traditional single-satellite positioning. This method not only achieves stable and high-precision single-satellite 3D positioning but also boasts fast state convergence, enabling terminals to complete positioning and initiate precise uplink synchronization access within an extremely short power-on wake-up time (e.g., within hundreds of milliseconds), meeting the requirements for low latency and high energy efficiency access.

[0338] Fourth, it achieves ultimate optimization of communication and navigation signaling interaction, significantly shortening synchronization time in long-latency environments:

[0339] Traditional blind access mechanisms, lacking pre-compensation, result in residual Doppler frequency offsets of up to several kilohertz, severely reducing the success rate of random access preamble detection. Traditional network-side positioning mechanisms based on connection states (such as multiple measurements and timing advances via the network) require signaling interactions with multiple round-trip delays, which are limited by the long latency of hundreds of milliseconds in non-terrestrial networks, resulting in slow response and low efficiency.

[0340] The enhanced two-step random access closed-loop mechanism in this embodiment utilizes the payload space of the physical uplink shared channel in the first message (the aforementioned access message, MsgA) to directly embed the terminal's autonomously calculated three-dimensional position coordinates and positioning confidence information into the communication signaling and upload them concurrently with the data. Upon receiving MsgA, the base station immediately performs cross-validation and filtering calibration on the terminal's reported position by combining its own physical layer-measured uplink angle of arrival and uplink time difference of arrival. In the second-step random access response (the aforementioned response message, MsgB), it instantly feeds back precise timing adjustment and frequency correction commands. This mechanism compresses the traditional three serial steps of access—positioning—calibration into parallel execution within a single baseband round-trip delay period, reducing the number of air interface signaling interactions by more than 50%, significantly improving access success rate, and completely solving the industry problem of communication and navigation coordination failure in long-latency, high-dynamic environments.

[0341] In summary, compared with the prior art, the embodiments of this application have advantages including, but not limited to, those shown in Table 1:

[0342] Table 1

[0343]

[0344] Furthermore, the network-side payload architecture can be adaptively modified, for example, to accommodate transparent forwarding: Although this application describes a preferred embodiment as a regenerative payload (i.e., the base station is directly deployed on the satellite and has independent computing capabilities) with fully built-in base station functions, it can also be perfectly compatible with the more widely deployed transparent forwarding (Transparent Payload / Bent-pipe) architecture in terms of mathematical derivation and signaling flow. In transparent forwarding networking, the satellite does not have baseband processing capabilities and only acts as a radio frequency analog repeater. The Location Management Function Server (LMF Server) and the base station baseband processing unit are deployed after the ground gateway. At this time, the modification of the autonomous pre-compensation algorithm for Doppler and timing adjustment on the terminal side is that it is necessary to... D (t i In this context, additional fixed or semi-dynamic frequency offset drift terms and propagation delay compensation terms are superimposed due to the relative motion of the feeder link between the base station and the satellite broadcast by SIB19. Apart from this, the extended Kalman filter logic and the MsgA payload multiplexing logic remain completely consistent.

[0345] Furthermore, the algorithm degrades and accelerates its deformation when expanding from single-satellite visibility scenarios to multi-satellite visibility scenarios: In some high-latitude regions, or when the terminal is in a densely covered area of ​​a large low-Earth orbit communication satellite constellation (such as the Starlink second-generation constellation), the user equipment may simultaneously receive downlink synchronization signal blocks and positioning reference signals from three or more low-Earth orbit communication satellites.

[0346] At this point, the virtual anchor point multi-epoch tracking and positioning algorithm used in step 2 of this application can undergo reasonable model dimensionality reduction and functional degradation: the system no longer forcibly relies on long-term (multiple system frame periods) continuous observation accumulation, but automatically switches to the classic multi-satellite instantaneous spatial time difference of arrival and frequency difference of arrival solution model (i.e., TDOA / FDOA joint positioning model, the principle of which is similar to the fusion of multiple round-trip time and downlink time difference of arrival algorithms in cellular networks). In this modified embodiment, the iterative convergence time of the extended Kalman filter algorithm can be further reduced from the second level to the millisecond level, achieving near-instantaneous high-precision positioning; at the same time, the Earth elevation constraint (digital elevation model) originally used to eliminate elevation ambiguity can be downgraded from a strong constraint condition to an auxiliary verification term, used only to further improve the solution accuracy and robustness, without affecting the solvability of the positioning equation. This modified mechanism can achieve intelligent adaptive switching of positioning performance in a multi-satellite visible environment, taking into account both high accuracy and low latency, and significantly improving the system's adaptability and generalization ability under different constellation densities and geographical scenarios.

[0347] The aforementioned cell access method also adapts to cloud computing / edge computing offloading variations for limited hardware terminals: If certain extremely low-cost IoT terminal nodes, such as the lowest-level 5G Reduced Capability Terminal, passive environmental sensing IoT, or passive / ubiquitous IoT nodes, have limited computing power in their internal digital signal processors, they cannot independently calculate the complex Jacobian matrix inversion operation of extended Kalman filtering within microseconds. In this case, reasonable variations for low-computing-power hardware are included in the embodiments, including but not limited to:

[0348] The terminal does not need to derive the final 3D coordinates locally. (i.e., the aforementioned terminal location), but instead, the raw measurement sequence extracted from the physical layer is directly reported in the MsgA's physical uplink shared channel payload. This consists of a list of precise residual Doppler frequency values ​​recorded at multiple time epochs and their corresponding timestamps. The network-side location management server with ample computing power performs the complete nonlinear positioning solution matrix operation, and then the network side directly sends a precise synchronization adjustment command to the IoT node via downlink dedicated signaling. This variation is essentially a transfer of computational load between the network layer and the device layer in the algorithm of this invention.

[0349] It is understood that in the specific embodiments of this application, data such as user information are involved. When the above embodiments of this application are applied to specific products or technologies, user permission or consent is required, and the collection, use and processing of related data must comply with the relevant laws, regulations and standards of the relevant countries and regions.

[0350] 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 this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. 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 this application.

[0351] 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.

[0352] Based on this understanding, the technical solution of this application, 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 read-only memory (ROM) / random access memory (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 this application.

[0353] According to another aspect of the embodiments of this application, a cell access apparatus for implementing the above-described cell access method is also provided. This cell access apparatus can be used to implement the cell access method provided in the above embodiments, and details already described will not be repeated. As used below, the term "module" can refer to a combination of software and / or hardware that implements a predetermined function. Although the apparatus described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0354] Figure 6 This is a structural block diagram of an optional cell access device without satellite navigation according to an embodiment of this application, such as... Figure 6 As shown, the cell access device is applied to a terminal and includes:

[0355] The first determining module 602 is used to determine multiple time epochs based on the ephemeris data of the low-orbit satellite extracted from the system information block, wherein the system information block corresponds to the target cell served by the low-orbit satellite.

[0356] Measurement module 604 is used to measure the Doppler frequency shift value corresponding to each time epoch in multiple time epochs;

[0357] The second determining module 606 is used to determine the satellite position corresponding to each time epoch based on ephemeris data;

[0358] The third determining module 608 is used to determine the terminal position and frequency deviation of the terminal based on the Doppler frequency shift value, satellite position and preset elevation parameters;

[0359] The first transmitting module 610 is used to send access messages to the satellite base station of the low-orbit satellite based on the terminal's location and frequency deviation, so as to control the terminal to access the target cell.

[0360] In an exemplary embodiment, the apparatus is configured to send an access message to a satellite base station of a low-Earth orbit satellite based on the terminal location and frequency deviation in the following manner to control the terminal to access the target cell: determining the transmission time and carrier frequency of the access message based on the terminal location and system information block; and sending the access message to the satellite base station using the carrier frequency at the transmission time to control the terminal to access the target cell.

[0361] In an exemplary embodiment, the apparatus is configured to determine the transmission time and carrier frequency of the access message based on the terminal location and the system information block by: calculating the one-way propagation delay using location data and ephemeris data of the terminal location; and determining the transmission time based on the common timing advance and common timing advance drift rate extracted from the system information block, as well as the one-way propagation delay.

[0362] In an exemplary embodiment, the apparatus is configured to determine the transmission time and carrier frequency of the access message based on the terminal location and system information block by: calculating the real-time frequency shift corresponding to the transmission time based on the terminal location and ephemeris data; and determining the carrier frequency based on the real-time frequency shift and frequency deviation.

[0363] In an exemplary embodiment, the apparatus is configured to control the terminal to access a target cell by sending an access message to a satellite base station of a low-Earth orbit satellite based on the terminal's location and frequency deviation in the following manner: sending the access message to the satellite base station based on the terminal's location and frequency deviation; receiving a response message from the satellite base station in response to the access message; and adjusting the start time and transmission frequency for sending uplink data to the satellite base station according to the response message, so as to control the terminal to access the target cell.

[0364] In an exemplary embodiment, the apparatus is configured to adjust the start time and transmission frequency of uplink data transmission according to a response message in the following manner to control the terminal to access the target cell: parsing the response message to obtain a timing adjustment amount and a frequency adjustment amount; updating the start time using the timing adjustment amount; and updating the transmission frequency using the frequency adjustment amount.

[0365] In an exemplary embodiment, the device is configured to determine the terminal position and frequency deviation of a terminal based on Doppler frequency shift values, virtual anchor points, and preset elevation parameters in the following manner: constructing an initial state vector of the terminal, wherein the initial state vector includes coordinate parameters and frequency deviation parameters, the coordinate parameters indicating the position coordinates of the terminal, and the frequency deviation parameters indicating the local oscillator frequency deviation of the terminal; iteratively updating the initial state vector using an extended Kalman filter algorithm to obtain a target state vector, wherein the Doppler frequency shift values, virtual anchor points, and preset elevation parameters are used to construct the observation equation used in the extended Kalman filter algorithm; determining the terminal position based on the values ​​of the coordinate parameters in the target state vector; and determining the frequency deviation based on the values ​​of the frequency deviation parameters in the target state vector.

[0366] In an exemplary embodiment, the apparatus is configured to iteratively update the initial state vector using an extended Kalman filter algorithm to obtain a target state vector by: sequentially determining the virtual anchor point corresponding to each time epoch as the current virtual anchor point in chronological order, and determining the Doppler frequency shift value corresponding to each time epoch as the current frequency shift value; performing the following operations on the current satellite position data and current frequency shift value corresponding to the current virtual anchor point to obtain the target state vector: using the identity matrix state transition matrix to perform state prediction on the initial state vector to obtain a priori state estimation state vector and a priori error covariance matrix; based on nonlinear Doppler observations... The Jacobian matrix of the measurement model, preset elevation parameters, current frequency shift value, and current satellite position data are used to update the prior state estimation state vector and prior error covariance matrix to obtain the posterior state estimation state vector and posterior error covariance matrix. If the trace value of the posterior error covariance matrix is ​​less than the preset convergence threshold, the posterior state estimation state vector is determined as the target state vector. If the trace value of the posterior error covariance matrix is ​​greater than or equal to the preset convergence threshold, the current virtual anchor point is updated to the virtual anchor point corresponding to the next time epoch, and the current frequency shift value is updated to the Doppler frequency shift value corresponding to the next time epoch.

[0367] In an exemplary embodiment, the apparatus is configured to transmit an access message to a satellite base station of a low-Earth orbit satellite based on the terminal's location and frequency deviation, before controlling the terminal's access to a target cell, by: generating a physical random access channel preamble sequence; adding an autonomous positioning auxiliary information control element to the physical layer protocol data unit, wherein the autonomous positioning auxiliary information control element encapsulates the terminal's location information, the trace of the location error covariance, and an uncompensated residual Doppler frequency offset estimate, the trace of the location error covariance being the trace of the posterior error covariance matrix corresponding to the target state vector, and the uncompensated residual Doppler frequency offset estimate being the difference between the Doppler frequency shift value measured at the transmission time and the expected frequency shift value, the expected frequency shift value being determined using a nonlinear Doppler observation model; and generating an access message based on the physical random access channel preamble sequence and the physical layer protocol data unit.

[0368] In one exemplary embodiment, the physical random access channel preamble sequence includes at least one of the following: the physical random access channel preamble sequence adopts a preamble format without a cyclic prefix; the physical random access channel preamble sequence is configured with an extended guard interval.

[0369] In an exemplary embodiment, the apparatus is further configured to: when the low-orbit satellite does not have baseband processing capabilities, the frequency deviation also includes frequency offset drift terms and propagation delay compensation terms corresponding to the feed link between the satellite base station and the low-orbit satellite.

[0370] In one exemplary embodiment, the apparatus is further configured to: determine the terminal location using a joint positioning model of multi-satellite instantaneous time difference of arrival and frequency difference of arrival when multiple low-orbit satellites are present.

[0371] In an exemplary embodiment, the apparatus is further configured to: receive downlink signaling sent by a network-side location management function server, wherein the location management function server is configured to receive Doppler frequency shift values ​​sent by the terminal, and perform nonlinear positioning calculations based on the Doppler frequency shift values ​​and ephemeris data to generate downlink signaling, the downlink signaling being used to determine the transmission time of the access message and the carrier frequency used to transmit the access message.

[0372] Figure 7 This is a structural block diagram of another optional cell access device without satellite navigation according to an embodiment of this application, such as... Figure 7 As shown, this cell access device is used for low-Earth orbit satellites and includes:

[0373] The receiving module 702 is used to receive access messages sent by the terminal. The access messages are sent by the terminal based on the terminal position and frequency deviation. The terminal position and frequency deviation are determined based on the Doppler frequency shift value, virtual anchor point and preset elevation parameters. The virtual anchor point corresponding to each time epoch is determined based on the ephemeris data of the low-orbit satellite. The virtual anchor point is used to indicate the satellite position of the low-orbit satellite within the corresponding time epoch. The Doppler frequency shift value corresponding to each time epoch is obtained by the terminal measurement. Multiple time epochs are determined based on the ephemeris data extracted from the system information block. The system information block corresponds to the target cell served by the low-orbit satellite.

[0374] The second sending module 704 is used to send a response message to the terminal to control the terminal to access the target cell.

[0375] In an exemplary embodiment, the apparatus is configured to send a response message to a terminal in the following manner to control the terminal to access the target cell: encapsulating a timing adjustment amount and a frequency adjustment amount in the response message, wherein the timing adjustment amount is used to update the start time of the terminal sending uplink data to the satellite base station, and the frequency adjustment amount is used to update the transmission frequency of the terminal sending uplink data to the satellite base station; and sending the response message to the terminal to control the terminal to access the target cell.

[0376] In an exemplary embodiment, the apparatus is configured to, before encapsulating timing adjustment and frequency adjustment amounts in a response message, acquire the uplink angle of arrival and uplink time difference of arrival corresponding to the access message; parse the access message to obtain an autonomous positioning auxiliary information control element, wherein the autonomous positioning auxiliary information control element encapsulates the location information of the terminal location; perform position correction on the location information of the terminal location based on the uplink angle of arrival and uplink time difference of arrival, and generate timing adjustment and frequency adjustment amounts.

[0377] In an exemplary embodiment, the apparatus is configured to perform position correction on the position information of the terminal position based on the uplink angle of arrival and the uplink time difference of arrival, and generate timing adjustment and frequency adjustment amounts by: determining the measured position of the terminal based on the uplink angle of arrival and the uplink time difference of arrival; performing a cross-comparison operation on the position information of the measured position and the position information of the terminal position to obtain an unbiased position error value; obtaining the trace value of the position error covariance and the estimated value of the uncompensated residual Doppler frequency offset encapsulated in the autonomous positioning assistance information control element; and performing a fusion filtering operation on the position information of the terminal position and the position information of the measured position using the trace value of the position error covariance, the estimated value of the uncompensated residual Doppler frequency offset, and the unbiased position error value to generate timing adjustment and frequency adjustment amounts.

[0378] Regarding the apparatus in the above embodiments, the terms "module" or "unit" refer to a computer program or part of a computer program with a predetermined function, which works together with other related parts to achieve a predetermined goal, and can be implemented wholly or partially using software, hardware (such as processing circuitry or memory), or a combination thereof. Similarly, a processor (or multiple processors or memory) can be used to implement one or more modules or units. Furthermore, each module or unit can be part of an overall module or unit that includes the functionality of that module or unit. The specific manner in which each module performs its operations has been described in detail in the embodiments relating to the method, and will not be elaborated upon here.

[0379] According to another aspect of the embodiments of this application, an electronic device is provided.

[0380] The electronic device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. The processor is configured to perform the steps in any of the above method embodiments via the computer program. In an exemplary embodiment, the electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the processor, and the input / output device is connected to the processor. Specific examples in this embodiment can be found in the examples described in the above embodiments and exemplary implementations, and will not be repeated here.

[0381] Figure 8 A schematic block diagram of a computer system architecture for implementing embodiments of the present application is shown. Figure 8As shown, the computer system includes a Central Processing Unit (CPU) 801, which performs various appropriate actions and processes based on programs stored in ROM 802 or loaded into RAM 803 from storage section 808. Random Access Memory 803 also stores various programs and data required for system operation. The CPU 801, ROM 802, and RAM 803 are interconnected via bus 804. Input / Output (I / O) interface 805 is also connected to bus 804.

[0382] The following components are connected to I / O interface 805: an input section 806 including a keyboard, mouse, etc.; an output section 807 including a cathode ray tube (CRT), liquid crystal display (LCD), and speakers, etc.; a storage section 808 including a hard disk, etc.; and a communication section 809 including a network interface card, such as a local area network card or modem, etc. The communication section 809 performs communication processing via a network such as the Internet. A drive 810 is also connected to I / O interface 805 as needed. Removable media 811, such as a disk, optical disk, magneto-optical disk, semiconductor memory, etc., are installed on drive 810 as needed so that computer programs read from them can be installed into storage section 808 as needed.

[0383] According to one aspect of this application, a computer program product is also provided, which includes a computer program.

[0384] The computer program product includes a computer program / instructions containing program code for performing the methods shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from a network via communication section 809, and / or installed from a removable medium. When the computer program is executed by central processing unit 801, it performs various functions provided in the embodiments of this application. The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0385] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0386] Specifically, according to embodiments of this application, the processes described in the various method flowcharts can be implemented as computer programs / instructions. For example, embodiments of this application include a computer program / instruction comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via a communication component, and / or installed from a removable medium. When the computer program is executed by a central processing unit, it performs various functions defined in the system of this application. In such embodiments, the computer program / instruction can be downloaded and installed from a network via a communication component, and / or installed from a removable medium. When the computer program / instruction is executed by a central processing unit, the aforementioned cell access method is performed.

[0387] According to one aspect of this application, a computer-readable storage medium is also provided.

[0388] The processor of the aforementioned electronic device can read the computer instructions from a computer-readable storage medium, and execute the computer instructions to cause the electronic device to perform the cell access method provided in the various alternative implementations of the aforementioned cell access aspect.

[0389] Optionally, in this embodiment, the computer-readable storage medium described above may be configured to store methods for performing the embodiments of this application.

[0390] Optionally, in this embodiment, those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be implemented by a program instructing the hardware related to the terminal device. The program can be stored in a computer-readable storage medium, which may include: flash drive, read-only memory (ROM), random access memory (RAM), disk or optical disk, etc.

[0391] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0392] If the integrated units in the above embodiments are implemented as software functional units and sold or used as independent products, they can be stored in the aforementioned computer-readable storage medium. Based on this understanding, the technical solution of this application, 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 one or more electronic devices to execute all or part of the steps of the methods described in the various embodiments of this application.

[0393] In the several embodiments provided in this application, it should be understood that the disclosed application 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 couplings, direct couplings, or communication connections may be through some interfaces; indirect couplings or communication connections between units or modules may be electrical or other forms.

[0394] 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.

[0395] Furthermore, the functional units in the various embodiments of this application 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.

[0396] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A cell access method, characterized in that, Applied to terminals, including: Based on the ephemeris data of the low-orbit satellite extracted from the system information block, multiple time epochs are determined, wherein the system information block corresponds to the target cell served by the low-orbit satellite; Measure the Doppler frequency shift value corresponding to each of the multiple time epochs; The satellite position corresponding to each time epoch is determined based on the ephemeris data; The terminal position and frequency deviation are determined based on the Doppler frequency shift value, the satellite position, and the preset elevation parameters. Based on the terminal's location and the frequency deviation, an access message is sent to the satellite base station of the low-orbit satellite to control the terminal to access the target cell.

2. The method according to claim 1, characterized in that, The step of sending an access message to the satellite base station of the low-Earth orbit satellite based on the terminal location and the frequency deviation to control the terminal to access the target cell includes: The sending time and carrier frequency of the access message are determined based on the terminal location and the system information block; The access message is sent to the satellite base station using the carrier frequency at the specified transmission time to control the terminal to access the target cell.

3. The method according to claim 2, characterized in that, Determining the transmission time and carrier frequency of the access message based on the terminal location and the system information block includes: The one-way propagation delay is calculated using the location data of the terminal location and the ephemeris data. The transmission time is determined based on the common timing advance and common timing advance drift rate extracted from the system information block, and the one-way propagation delay.

4. The method according to claim 2, characterized in that, Determining the transmission time and carrier frequency of the access message based on the terminal location and the system information block includes: Calculate the real-time frequency shift corresponding to the transmission time based on the terminal location and the ephemeris data; The carrier frequency is determined based on the real-time frequency shift and the frequency deviation.

5. The method according to claim 1, characterized in that, The step of sending an access message to the satellite base station of the low-Earth orbit satellite based on the terminal location and the frequency deviation to control the terminal to access the target cell includes: The access message is sent to the satellite base station based on the terminal location and the frequency deviation. Receive the response message sent by the satellite base station in response to the access message; The system adjusts the start time and transmission frequency for sending uplink data to the satellite base station based on the response message, thereby controlling the terminal to access the target cell.

6. The method according to claim 5, characterized in that, The step of adjusting the start time and transmission frequency of uplink data transmission according to the response message to control the terminal to access the target cell includes: Parse the response message to obtain the timing adjustment amount and the frequency adjustment amount; Update the start time using the time adjustment amount; The transmission frequency is updated using the frequency adjustment amount.

7. The method according to claim 1, characterized in that, The step of determining the terminal position and frequency deviation based on the Doppler frequency shift value, the satellite position, and preset elevation parameters includes: Construct an initial state vector for the terminal, wherein the initial state vector includes coordinate parameters and frequency offset parameters, the coordinate parameters being used to indicate the position coordinates of the terminal, and the frequency offset parameters being used to indicate the local oscillator frequency offset of the terminal; The initial state vector is iteratively updated using the extended Kalman filter algorithm to obtain the target state vector, wherein the Doppler frequency shift value, the satellite position, and the preset elevation parameter are used to construct the observation equation used in the extended Kalman filter algorithm; The terminal position is determined based on the values ​​of the coordinate parameters in the target state vector; The frequency deviation is determined based on the value of the frequency offset parameter in the target state vector.

8. The method according to claim 7, characterized in that, The step of iteratively updating the initial state vector using the extended Kalman filter algorithm to obtain the target state vector includes: The satellite position data corresponding to each time epoch is sequentially determined as the current satellite position data according to the time sequence, and the Doppler frequency shift value corresponding to each time epoch is determined as the current frequency shift value. The following operations are performed on the current satellite position data and the current frequency shift value to obtain the target state vector: The initial state vector is used to predict the state using the identity matrix state transition matrix to obtain the prior state estimate state vector and the prior error covariance matrix. Based on the Jacobian matrix of the nonlinear Doppler observation model, the preset elevation parameters, the current frequency shift value, and the current satellite position data, the prior state estimation state vector and the prior error covariance matrix are updated by observation to obtain the posterior state estimation state vector and the posterior error covariance matrix. If the trace of the posterior error covariance matrix is ​​less than a preset convergence threshold, the posterior state estimation state vector is determined as the target state vector. If the trace of the posterior error covariance matrix is ​​greater than or equal to the preset convergence threshold, the current satellite position data is updated to the position data of the satellite position corresponding to the next time epoch, and the current frequency shift value is updated to the Doppler frequency shift value corresponding to the next time epoch.

9. The method according to claim 7, characterized in that, Before sending an access message to the satellite base station of the low-Earth orbit satellite based on the terminal location and the frequency deviation to control the terminal to access the target cell, the method further includes: Generate the physical random access channel preamble sequence; An autonomous positioning auxiliary information control element is added to the physical layer protocol data unit. The autonomous positioning auxiliary information control element encapsulates the location information of the terminal, the trace of the location error covariance, and the estimated value of the uncompensated residual Doppler frequency offset. The trace of the location error covariance is the trace of the posterior error covariance matrix corresponding to the target state vector. The estimated value of the uncompensated residual Doppler frequency offset is the difference between the Doppler frequency shift value measured at the time of sending the access message and the expected frequency shift value. The expected frequency shift value is determined by using a nonlinear Doppler observation model. The access message is generated based on the physical random access channel preamble sequence and the physical layer protocol data unit.

10. The method according to claim 9, characterized in that, The physical random access channel preamble sequence includes at least one of the following: The physical random access channel preamble sequence adopts a preamble format without a cyclic prefix; The physical random access channel preamble sequence is configured with an extended guard interval.

11. The method according to claim 1, characterized in that, The method further includes: In the case that the low-orbit satellite does not have baseband processing capabilities, the frequency deviation also includes the frequency offset drift term and propagation delay compensation term corresponding to the power supply link between the satellite base station and the low-orbit satellite.

12. The method according to claim 1, characterized in that, The method further includes: In the presence of multiple low-orbit satellites, the terminal location is determined using a joint positioning model based on the instantaneous time difference of arrival and the frequency difference of arrival of multiple satellites.

13. The method according to claim 1, characterized in that, The method further includes: The system receives downlink signaling sent by a network-side location management function server. The location management function server receives the Doppler frequency shift value sent by the terminal and performs nonlinear positioning calculation based on the Doppler frequency shift value and the ephemeris data to generate the downlink signaling. The downlink signaling is used to determine the transmission time of the access message and the carrier frequency used to transmit the access message.

14. A cell access device without satellite navigation, characterized in that, Applied to terminals, including: The first determining module is used to determine multiple time epochs based on the ephemeris data of the low-orbit satellite extracted from the system information block, wherein the system information block corresponds to the target cell served by the low-orbit satellite. The measurement module is used to measure the Doppler frequency shift value corresponding to each of the multiple time epochs; The second determining module is used to determine the satellite position corresponding to each time epoch based on the ephemeris data; The third determining module is used to determine the terminal position and frequency deviation of the terminal based on the Doppler frequency shift value, the satellite position, and the preset elevation parameters; The first transmitting module is used to send an access message to the satellite base station of the low-orbit satellite based on the terminal location and the frequency deviation, so as to control the terminal to access the target cell.

15. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method according to any one of claims 1 to 13.

16. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, wherein the computer program, when executed by a processor, implements the steps of the method according to any one of claims 1 to 13.

17. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 13.

18. A chip comprising a circuit system configured to implement the steps of the method of any one of claims 1 to 13.

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