Satellite terminal satellite searching method, electronic device, storage medium and program product

Abstract

The application provides a satellite terminal satellite searching method, an electronic device, a storage medium and a program product, and relates to the technical field of satellite communication. The method introduces a position confidence evaluation, and a satellite terminal can adaptively select a satellite searching path according to the positioning quality of the satellite terminal. When the positioning is reliable, the local ephemeris is directly used to quickly capture a low-orbit satellite, and when the positioning is unreliable or the ephemeris is aging, the high-orbit satellite is used to obtain a differential correction quantity and auxiliary position information, so that the ephemeris error and the position error are effectively compensated without relying on real-time accurate positioning, the search pointing deviation of the low-orbit satellite is reduced, the search range is reduced, the long waiting time and power waste caused by blind scanning are avoided, the capture success rate is improved, the terminal can still realize fast network access under poor network conditions, and the timeliness of user service establishment and the survival ability of the terminal under extreme environment are ensured.

Description

Technical Field

[0001] This application relates to the field of satellite communication technology, and more specifically, to a satellite terminal satellite search method, electronic device, storage medium, and program product. Background Technology

[0002] Traditional satellite terminal satellite acquisition methods are primarily designed for geostationary Earth Orbit (GEO) satellite systems. In these methods, the terminal typically relies on known, high-precision satellite position information (obtained through long-term orbit prediction or by receiving beacon signals broadcast by the satellite), combined with its own precise position and attitude information (generally provided by a Global Navigation Satellite System (GNSS) and inertial navigation equipment). After obtaining the antenna pointing angle through geometric calculations, the terminal utilizes the stable beacon signals continuously transmitted by the GEO satellite to perform precise alignment procedures such as single-pulse or step-tracking, ultimately achieving synchronization and link establishment with the satellite.

[0003] However, with the rapid development of Low Earth Orbit (LEO) satellite communication systems, their characteristics—numerous satellites, low orbital altitude, short overhead time (several minutes to over ten minutes), and high-speed motion relative to the ground—are fundamentally different from those of GEO satellite systems. Directly applying the satellite search methods of traditional high-orbit terminals to LEO terminals faces significant technical obstacles.

[0004] First, low-Earth orbit (LEO) satellites typically do not carry dedicated beacon payloads like high-Earth orbit (HEO) satellites. This is mainly due to limitations in satellite power consumption, size, and the need for rapid constellation reconfiguration. Therefore, if the terminal antenna initially points incorrectly, it cannot utilize a stable and easily acquired beacon signal to guide the antenna for precise correction and tracking, as it can when pointing to a HEO satellite.

[0005] Secondly, during a cold start, satellite terminals typically rely solely on locally stored ephemeris data for satellite position extrapolation. Due to the complex perturbations of atmospheric drag and solar radiation pressure, the extrapolated position of low-Earth orbit (LEO) satellites exhibits significant errors compared to the satellite's real-time position. Furthermore, while the terminal primarily relies on GNSS for its own position, in situations of GNSS signal rejection (e.g., indoors, underground, or in complex electromagnetic environments), spoofing, or receiver malfunction, the terminal cannot obtain accurate latitude and longitude information, or may even be completely unable to locate itself. In such cases, combined with inaccurate ephemeris extrapolation results, the calculated antenna pointing angle deviation will be drastically amplified, far exceeding the coverage range of the narrow beam of a LEO satellite (typically only a few degrees wide).

[0006] The aforementioned problems collectively make it difficult for low-Earth orbit satellite terminals to capture and lock onto high-speed moving low-Earth orbit satellite signals in a short period of time after a cold start, affecting the timeliness of user service establishment and even potentially preventing the terminal from joining the network. Summary of the Invention

[0007] The purpose of this application is to provide a satellite terminal satellite search method, electronic device, storage medium, and program product to improve the efficiency and success rate of satellite terminals in capturing low-Earth orbit satellites.

[0008] In a first aspect, embodiments of this application provide a satellite terminal satellite search method, the method comprising: After the satellite terminal is powered on, a positioning calculation is performed to obtain the terminal's positioning result; The location confidence level is determined based on the terminal positioning results; If the location confidence level is the first level, then the low-Earth orbit satellite search is performed using the locally stored low-Earth orbit satellite ephemeris. If the location confidence level is the second level or the low-Earth orbit satellite search fails, the differential ephemeris correction amount is received through the locked high-Earth orbit satellite, and the low-Earth orbit satellite ephemeris is updated using the differential ephemeris correction amount, where the first level is higher than the second level. Based on the updated low-Earth orbit satellite ephemeris and the auxiliary position information obtained from the high-Earth orbit satellites, a new low-Earth orbit satellite search is performed.

[0009] In the above implementation process, by introducing position confidence assessment, the satellite terminal can adaptively select the satellite search path based on its own positioning quality. When positioning is reliable, it directly uses local ephemeris to quickly acquire low-Earth orbit satellites. When positioning is unreliable or ephemeris is outdated, it switches to high-Earth orbit satellites to obtain differential correction and auxiliary position information. This effectively compensates for ephemeris and position errors without relying on real-time accurate positioning, reduces the searching pointing deviation of low-Earth orbit satellites, and narrows the search range. This avoids long waiting times and wasted power due to blind scanning, and improves the acquisition success rate. This allows the terminal to quickly join the network even under harsh network conditions, ensuring the timeliness of user service establishment and the terminal's survivability in extreme environments.

[0010] Optionally, the differential ephemeris correction is broadcast by the high-orbit satellite in beam-segmentation, and updating the low-orbit satellite ephemeris using the differential ephemeris correction includes: Decode the corresponding data fragments based on the beam identifier of the area where the satellite terminal is located; The data fragments are overlaid with the locally stored low-Earth orbit satellite ephemeris to obtain the updated low-Earth orbit satellite ephemeris.

[0011] In the above implementation process, by broadcasting the differential ephemeris correction amount in beam segments, the satellite terminal only needs to decode the corresponding data segments according to its own beam identifier, avoiding the reception and processing of a large amount of redundant data in irrelevant areas, and significantly reducing the terminal's storage overhead, decoding power consumption and ephemeris update time.

[0012] Optionally, the differential ephemeris correction is issued by the high-orbit satellite when it receives a broadcast command sent by the ground network side. The broadcast command is generated by the ground network side when it detects that the low-orbit satellite pointing deviation predicted based on the locally stored low-orbit satellite ephemeris exceeds a preset threshold.

[0013] In the above implementation process, the pointing deviation of low-orbit satellites is monitored in real time by the ground network side. The differential ephemeris correction of high-orbit satellite broadcast is only triggered when the deviation exceeds the preset threshold. This avoids the continuous occupation of downlink channel resources by frequently sending invalid or redundant data under the traditional fixed-period broadcasting method, and reduces the bandwidth consumption of the broadcast channel.

[0014] Optionally, determining the location confidence level based on the terminal positioning result includes: If the terminal positioning result is that valid location information is obtained within a preset time and the horizontal accuracy factor is less than a set threshold, then the location confidence level is determined to be high. If the terminal positioning result is that no valid position information is obtained within a preset time or the horizontal accuracy factor is greater than or equal to a set threshold, then dead reckoning is performed using an inertial measurement unit. If the reckoned displacement is less than the radius threshold, then the position confidence level is determined to be medium level. The first level includes the high level and the medium level, and the high level is higher than the medium level.

[0015] In the above implementation process, by introducing a two-level position confidence classification of high-level and medium-level, the complementary advantages of GNSS and IMU are fully utilized. When the GNSS signal is good, a high-precision position (high-level) is obtained directly. When GNSS fails but the terminal's movement range is limited in a short period of time, a medium-confidence position (medium-level) is maintained by using IMU dead reckoning. This avoids simply classifying the terminal as unlocatable due to a brief GNSS failure or obstruction, thus preserving more usable information for subsequent differentiated satellite search strategies. At the same time, the existence of the medium-level position allows the terminal to continue to attempt low-Earth orbit satellite acquisition based on relatively reliable historical displacement constraints even when it cannot obtain a precise position. This effectively reduces unnecessary auxiliary requests and power consumption, and improves the overall efficiency and adaptability of the satellite search process in complex environments.

[0016] Optionally, if the location confidence level is level one, then a low-Earth orbit (LEO) satellite search is performed using locally stored LEO satellite ephemeris data, including: Calculate the predicted pointing angle of low-Earth orbit satellites using locally stored low-Earth orbit satellite ephemeris data; If the location confidence level is the high level, then a low-orbit satellite search is performed using the first timeout threshold and the first search range corresponding to the predicted pointing angle; If the location confidence level is medium, then a low-orbit satellite search is performed using a second timeout threshold and a second search range, wherein the second timeout threshold is less than the first timeout threshold and the second search range is greater than the first search range.

[0017] In the above implementation process, based on the position uncertainty of high-level and medium-level positions, differentiated search parameters are adaptively configured. At high-level positions, the position is precise, and a narrow search range and a longer timeout threshold are used to achieve rapid focusing and scanning while ensuring a high acquisition probability, reducing power consumption and time waste. At medium-level positions, the position is only roughly constrained by dead reckoning, and a wider search range is used to cover the pointing uncertainty caused by position errors. At the same time, a shorter timeout threshold is used to prevent long-term ineffective searches due to high uncertainty, thereby quickly determining whether to switch to high-orbit assistance and improving search efficiency.

[0018] Optionally, the step of re-performing the low-Earth orbit satellite search based on the updated low-Earth orbit satellite ephemeris and the auxiliary position information obtained from the high-Earth orbit satellite includes: Determine whether the auxiliary position information obtained from the high-orbit satellite is available; If available, a new low-Earth orbit satellite search is performed based on the updated low-Earth orbit satellite ephemeris and the auxiliary position information obtained from the high-Earth orbit satellite. If unavailable, the constraint search window is determined using the displacement calculated by the inertial measurement unit with the historical location as the origin. The historical location includes the previous successful positioning result and / or the precise location sent down after being solved by the ground network. Perform a narrowband constraint blind search within the constraint search window.

[0019] In the above implementation process, by introducing an availability judgment of auxiliary location information, a seamless switch between accurate search when the HEO auxiliary is reliable and degraded blind search when the auxiliary fails is achieved. This mechanism enables the terminal to maintain basic access capabilities even in extreme environments such as GNSS denial and complete failure of HEO auxiliary, relying on its stored historical accurate location and IMU short-time integration, thus avoiding the risk of being unable to access the network due to the interruption of the auxiliary link.

[0020] Optionally, the high-orbit satellite is locked in the following manner: By scanning the beacon frequencies of multiple pre-stored high-orbit satellites, the current elevation angle and received signal strength of each high-orbit satellite can be obtained. The comprehensive score of each high-orbit satellite is calculated based on the current elevation angle and received signal strength. Select the high-orbit satellite with the highest overall score for downlink synchronization and lock it in.

[0021] In the above implementation process, by simultaneously evaluating the current elevation angle and actual received signal strength of the high-orbit satellite, and using a weighted comprehensive score for optimal selection, the selection bias caused by relying solely on theoretical elevation angle or single signal strength is avoided. Satellites with high theoretical elevation angles may have poor signal quality due to local obstruction or atmospheric attenuation, while satellites with high signal strength may have unstable links due to excessively low elevation angles. The comprehensive scoring mechanism can balance geometric visibility and actual link quality, ensuring that the terminal locks onto the high-orbit satellite with the highest probability of synchronization at the current location and the most stable long-term reception.

[0022] Optionally, the method further includes: After establishing operational communication with the target low-Earth orbit satellite, an uplink probe signal is sent. The precise location transmitted from the ground network side is received and stored. The precise location is obtained by the ground network side using the time difference of arrival and frequency difference of arrival measured by the signals received from multiple low-orbit satellites, combined with the beam coverage of the high-orbit satellite and the downlink synchronization delay as prior constraints.

[0023] In the above implementation process, by actively sending uplink probe signals using the established service links and introducing the high-orbit beam coverage and downlink synchronization delay as prior constraints, the ground network side can calculate the precise location of the satellite terminal with less computational overhead and faster convergence speed.

[0024] Optionally, the auxiliary location information includes the actual center position of the beam coverage area corresponding to the high-orbit satellite. The actual center position is obtained by the satellite terminal according to the location mapping table on the ground network side. The location mapping table stores the correspondence between beam identifiers and position correction amounts. The actual center position is the sum of the position correction amount and the theoretical center position of the beam coverage area corresponding to the high-orbit satellite. The position correction amount is obtained by the ground network side by comparing the precise position of each satellite terminal with the theoretical center position of the beam coverage range of the high-orbit satellite corresponding to the satellite terminal to obtain the deviation vector, classifying the deviation vector according to the beam, and clustering the classified deviation vector.

[0025] In the above implementation process, a location mapping table containing the correspondence between beam identifiers and position corrections is constructed and continuously updated on the ground network side. The deviation statistics and cluster analysis of the precise positions fed back by massive terminals in service communication and the theoretical center of the beam are performed to obtain the actual center position of each beam. This allows the terminal to directly obtain the corrected center as auxiliary position information in the subsequent high-orbit auxiliary stage, effectively eliminating the systematic deviation between the theoretical center and the actual coverage center caused by factors such as beam pointing error, antenna deformation or orbital drift.

[0026] Optionally, the step of using locally stored low-Earth orbit satellite ephemeris for low-Earth orbit satellite search includes: Use locally stored low-Earth orbit satellite ephemeris to identify candidate low-Earth orbit satellites that are currently visible and have an elevation angle lower than a set angle; The candidate low-Earth orbit satellites are sorted according to priority; Point the antenna at the predicted pointing angle of the highest priority low-Earth orbit satellite and search within the corresponding range.

[0027] In the above implementation process, visible low-orbit satellites that meet the elevation angle requirements (e.g., higher than the minimum available elevation angle) at the current time are selected through local ephemeris, and the optimal target is determined according to priority. The terminal points the antenna to the predicted direction of the satellite with the highest priority and performs directional search within the specified cone angle range. This avoids long-term invalid scanning caused by blind scanning of the entire sky or random selection of targets, and improves the effectiveness and speed of the first acquisition.

[0028] Secondly, embodiments of this application provide an electronic device, including a processor and a memory, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the processor, the steps of the method provided in the first aspect above are performed.

[0029] Thirdly, embodiments of this application provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the steps of the method provided in the first aspect above.

[0030] Fourthly, embodiments of this application provide a computer program product, including computer program instructions, which, when read and executed by a processor, perform the steps of the method provided in the first aspect above.

[0031] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing embodiments of this application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A schematic diagram of a system architecture for applying the solution of this application is provided as an embodiment of this application; Figure 2 A flowchart illustrating a satellite terminal satellite search method provided in this application embodiment; Figure 3 A structural block diagram of a satellite terminal satellite search device provided in an embodiment of this application; Figure 4 This is a schematic diagram of the structure of an electronic device for performing a satellite terminal satellite search method, provided in an embodiment of this application. Detailed Implementation

[0034] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0035] It should be noted that the terms "system" and "network" in the embodiments of this invention can be used interchangeably. "Multiple" refers to two or more; therefore, in the embodiments of this invention, "multiple" can also be understood as "at least two". "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / ", unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0036] It should also be noted that all actions involving the acquisition of signals, information, or data in this application are carried out in compliance with the relevant data protection laws and policies of the country where the application is located, and with the authorization granted by the owner of the relevant device.

[0037] The technical solution of this application can be applied to non-terrestrial network (NTN) systems such as satellite communication systems and high altitude platform station (HAPS) communication, for example, integrated communication and navigation (ICaN) systems and global navigation satellite systems.

[0038] Satellite communication systems can be integrated with traditional mobile communication systems. For example, the mobile communication system can be a fourth-generation (4G) communication system (e.g., Long Term Evolution (LTE) system), a worldwide interoperability for microwave access (WiMAX) communication system, a fifth-generation (5G) communication system (e.g., a new radio (NR) system), and future mobile communication systems, etc.

[0039] The system architecture or scenario primarily applied in this application is as follows: Figure 1 As shown, it includes high-orbit satellites, low-orbit satellites, ground network side, and satellite terminals.

[0040] The ground network consists of a gateway station, a data processing center, and an ephemeris monitoring system. It is connected to high-orbit and low-orbit satellites via uplink feeder links. It is responsible for maintaining real-time high-precision low-orbit ephemeris, monitoring ephemeris pointing deviations in various regions, generating differential ephemeris corrections, and processing uplink probe signals from satellite terminals to calculate precise positions.

[0041] High-orbit satellites (such as geostationary communication satellites) act as transparent or regenerative relay nodes, receiving differential ephemeris fragments and broadcast commands uploaded from the ground network side, and broadcasting correction values ​​and beam geofence information downwards within their point beam coverage area; at the same time, satellite terminals can achieve downlink synchronization and report auxiliary requests through high-orbit satellite beacons.

[0042] The low-Earth orbit satellite constellation consists of multiple high-speed moving satellites that establish service links with satellite terminals, forward uplink detection signals to the ground network side, and carry user data communication.

[0043] The satellite terminal mentioned in the embodiments of this application includes various handheld devices, vehicle-mounted devices, wearable devices, computing devices or other processing devices connected to a wireless modem with wireless communication functions. Specifically, it can refer to user equipment (UE), access terminal, user unit, user station, mobile station, mobile station, remote station, remote terminal, mobile device, user terminal, terminal, wireless communication equipment, user agent or user device. Terminals can also be satellite phones, cellular phones, smartphones, wireless data cards, wireless modems, machine-type communication devices, cordless phones, session initiation protocol (SIP) phones, wireless local loop (WLL) stations, personal digital assistants (PDAs), handheld devices with wireless communication capabilities, computing devices or other processing devices connected to a wireless modem, in-vehicle devices or wearable devices, virtual reality (VR) terminal devices, augmented reality (AR) terminal devices, wireless terminals in industrial control, wireless terminals in self-driving, wireless terminals in remote medical care, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, wireless terminals in smart homes, terminal devices in 5G networks or future communication networks, etc.

[0044] In the entire system, high-orbit satellites mainly provide wide-area reliable downlink broadcast auxiliary channels, low-orbit satellites provide high-bandwidth, low-latency service connections and distributed positioning measurements, ground network side centrally completes ephemeris differential calculation, event-triggered broadcast decision-making and precise positioning calculation, and satellite terminals realize intelligent fusion and decision-making at the end side, ultimately achieving rapid network access for low-orbit satellites without relying on GNSS for real-time precise positioning.

[0045] This application provides a satellite terminal satellite acquisition method. By introducing a position confidence assessment, the satellite terminal can adaptively select the acquisition path based on its own positioning quality. When positioning is reliable, it directly uses local ephemeris to quickly acquire low-Earth orbit satellites. When positioning is unreliable or ephemeris is aging, it switches to using high-Earth orbit satellites to obtain differential correction and auxiliary position information. This effectively compensates for ephemeris and position errors without relying on real-time accurate positioning, thereby improving the acquisition success rate.

[0046] Please refer to Figure 2 , Figure 2 A flowchart of a satellite terminal satellite search method provided in this application embodiment, the method including the following steps: Step S110: After the satellite terminal is powered on, perform positioning calculation to obtain the terminal positioning result.

[0047] After powering on, the satellite terminal can first perform positioning calculations. If a GNSS positioning system is installed in the satellite terminal, the GNSS receiver can be activated to perform positioning calculations. Of course, if other positioning modules are installed in the satellite terminal, the corresponding positioning module will be activated to perform positioning calculations.

[0048] In some implementations, when performing positioning calculations, the satellite terminal sets a timeout threshold (e.g., 15 seconds) and continuously attempts to acquire valid positioning data during this period. If positioning data containing latitude and longitude, a timestamp, and a Horizontal Dilution of Precision (HDOP) is acquired within the timeout period, and the HDOP is less than a preset threshold (e.g., 2.5), the positioning is considered successful, and the current position coordinates are recorded as a high-precision positioning result. If no valid data is acquired within the timeout period or the HDOP does not meet the threshold, the GNSS positioning is considered a failure. In this case, the satellite terminal can attempt to call the Inertial Measurement Unit (IMU) for dead reckoning: it reads the last known position (coordinates saved during the last successful positioning) and its timestamp stored in the non-volatile memory, combines the acceleration and angular velocity integrals measured by the IMU, calculates the displacement vector from the last stored time to the present, and thus estimates the approximate current position (with an accuracy in the kilometers). If no position information can be obtained (e.g., no historical records and the IMU is not calibrated), the positioning result is marked as invalid.

[0049] Step S120: Determine the location confidence level based on the terminal positioning results.

[0050] Location confidence level is a classification based on the reliability of the terminal positioning results. It can be divided into a first level and a second level. The first level is higher than the second level. The first level indicates that the terminal positioning results are accurate and reliable, while the second level indicates that the terminal positioning results are unreliable or that the precise location cannot be obtained.

[0051] In some implementations, location confidence levels can be categorized according to the following criteria: (1) If the terminal positioning result is that the valid location information is obtained within a preset time (such as the timeout threshold mentioned above) and the horizontal accuracy factor is less than the set threshold, then the location confidence level is determined to be the first level.

[0052] (2) If the terminal positioning result is that no valid location information is obtained within a preset time or the horizontal accuracy factor is greater than or equal to the set threshold, the location confidence level is determined to be the second level.

[0053] Valid location information can refer to the location data obtained by the satellite terminal through the built-in GNSS receiver, which includes latitude and longitude, altitude, timestamp, and location status flag. The location status flag indicates that the location is valid.

[0054] The Horizontal Accuracy Factor (HDOP) is an indicator used to measure the impact of the geometric distribution of GNSS satellites on horizontal positioning accuracy. The smaller the HDOP value, the more favorable the satellite distribution is for horizontal positioning, and the smaller the error; the larger the value, the greater the positioning error. Generally, HDOP < 1 is ideal, 1-2 is excellent, 2-3 is good, and above 3 the error increases significantly.

[0055] The preset time is the maximum waiting time set by the satellite terminal for GNSS positioning calculation, usually referred to as the timeout threshold. If valid location information is not obtained after this time, the positioning is considered to have failed. The preferred range is 10-15 seconds.

[0056] A threshold is set to determine whether the horizontal accuracy of the HDOP is acceptable. Positioning results below this threshold are considered reliable; otherwise, accuracy is considered insufficient. Based on design requirements, 2.5 can be used as the set threshold in this embodiment.

[0057] After the satellite terminal is powered on, the GNSS receiver can be started immediately to begin the positioning calculation process. Simultaneously, a timeout timer is started, with a timeout duration set to a preset time T_gnss, for example, 15 seconds. In each positioning calculation cycle (usually once per second), the satellite terminal reads the positioning data frames output by the GNSS receiver and checks the positioning status flags and HDOP values.

[0058] If, during the period when the timeout timer is not triggered, the satellite terminal reads the positioning status flag as "valid" and simultaneously obtains a horizontal precision factor (HDOP) less than a set threshold (e.g., 2.5), then the positioning is considered successful. The satellite terminal saves this positioning result (latitude and longitude, timestamp, etc.) as valid location information and determines the location confidence level as Level 1 based on this.

[0059] If valid location information is not obtained within the preset time T_gnss (e.g., the positioning status flag remains invalid or no data is output), or if valid location information is obtained but its HDOP value is greater than or equal to a set threshold (e.g., HDOP=3.0), then positioning is determined to have failed or insufficient accuracy. In this case, the satellite terminal no longer waits and directly sets the position confidence level to Level 2. At Level 2, the terminal cannot subsequently rely on the precise position provided by GNSS and can instead use other positioning methods (such as inertial measurement unit dead reckoning, historical position, or high-orbit satellite-aided information).

[0060] It should be noted that the first level indicates that the terminal knows its own precise position (the error is usually in the range of several meters to tens of meters), which is sufficient to support high-precision pointing calculation of low-Earth orbit satellites directly using local ephemeris; the second level indicates that the terminal's position information is unavailable or too inaccurate, and cannot be directly used for low-Earth orbit satellite acquisition, but can be corrected for position and ephemeris errors with the help of auxiliary means.

[0061] Step S130: If the location confidence level is Level 1, then use the locally stored low-Earth orbit satellite ephemeris to perform a low-Earth orbit satellite search.

[0062] Low Earth Orbit (LEO) satellite ephemeris is a data set that describes the orbital parameters of LEO satellites (such as Kepler elements or position-velocity vectors) and is used to predict the satellite's position in the sky (azimuth and elevation) at a specific moment.

[0063] When the position confidence level is first level (high confidence), the satellite terminal believes that its position is accurate, so it will prioritize trying to quickly search for satellites by directly using the locally stored low-orbit satellite ephemeris.

[0064] The satellite terminal reads the local ephemeris database (e.g., TLE format data), calculates candidate low-Earth orbit (LEO) satellites visible at the current time with an elevation angle lower than a set angle based on the current timestamp and the satellite terminal's precise location, and then sorts the candidate LEO satellites according to priority. The satellite terminal points its antenna at the predicted pointing angle (azimuth and elevation) of the highest priority target LEO satellite and attempts to acquire the LEO satellite's beacon or synchronization signal within the range corresponding to that predicted pointing angle (e.g., a conical scan range of ±5°). If successful acquisition is achieved within a set time (e.g., 30 seconds), the satellite search process ends, and the process proceeds to the service establishment phase. If acquisition fails after the timeout, the LEO search is deemed a failure, and the process proceeds to step S140.

[0065] Specifically, after obtaining its precise position, the satellite terminal first reads a pre-stored low-Earth orbit (LEO) satellite ephemeris database from its local non-volatile memory. This database typically contains the latest Time-to-Earth (TLE) data for dozens to hundreds of LEO satellites. The satellite terminal then obtains its current timestamp and, combined with its own precise position coordinates, performs orbit extrapolation calculations for each satellite in the ephemeris database. The extrapolation results provide the antenna pointing angle (azimuth and elevation) and Doppler frequency offset of each LEO satellite relative to the satellite terminal at the current moment. The satellite terminal filters out LEO satellites with elevation angles greater than a set angle (e.g., 10°) as candidate satellites. LEO satellites with elevation angles lower than this set angle are generally not considered due to their long signal paths and severe effects from atmospheric refraction and obstruction. For example, if a LEO satellite has a predicted elevation angle of 8°, it is excluded; another LEO satellite with a predicted elevation angle of 35° is included in the candidate list.

[0066] After obtaining the list of candidate low-Earth orbit (LEO) satellites, the satellite terminal sorts these LEO satellites according to a preset priority ranking rule. For example, let the priority scoring function be:

[0067] Where El is the predicted elevation angle (in degrees), and F pref For frequency band preference coefficients (e.g., 1.2 if the low-Earth orbit satellite operating frequency band is the preferred frequency band for satellite terminals, otherwise 1.0), |Δf Doppler To estimate the absolute value of the Doppler frequency offset, f norm The maximum Doppler frequency offset of the system (typically ±40kHz for LEO satellites) is defined by w1, w2, and w3, which are weight values ​​for each component and can be allocated according to requirements. Then, a priority score is calculated for each satellite, with higher values ​​indicating higher priority. For example, if the priority score calculation reveals that LEO satellite A has a higher priority than LEO satellite B, the satellite terminal will prioritize attempting to acquire LEO satellite A.

[0068] The satellite terminal aligns its antenna beam center with the predicted pointing angle of the low-Earth orbit (LEO) satellite A (e.g., azimuth 120°, elevation 35°) using a mechanical or phased array antenna. Then, the satellite terminal initiates a signal acquisition procedure within a cone-shaped scanning range around the predicted pointing angle. This cone-shaped range is defined as follows: azimuth between 115° and 125° (predicted value ± 5°), and elevation between 30° and 40° (predicted value ± 5°). Within this three-dimensional space, the satellite terminal scans for predefined beacon frequencies or synchronization sequences of the LEO satellite at predetermined steps (e.g., every 0.5°). Once a correlation peak greater than a preset threshold is detected at a certain pointing angle, the LEO satellite is considered successfully acquired, and the synchronization and service establishment phase begins. If no valid signal is detected within the entire cone-shaped range, the LEO search is considered a failure, and the satellite terminal proceeds to subsequent auxiliary correction steps (e.g., obtaining differential ephemeris data from high-Earth orbit (HEO) satellites).

[0069] The above method uses local ephemeris to filter out visible low-orbit satellites that meet the elevation angle requirements (e.g., higher than the minimum available elevation angle) at the current time, and determines the optimal target according to priority. The terminal points the antenna to the predicted direction of the satellite with the highest priority and performs a directional search within the specified cone angle range. This avoids long-term invalid scanning caused by blindly scanning the entire sky or randomly selecting targets, and improves the effectiveness and speed of the first acquisition.

[0070] Step S140: If the position confidence level is level 2 or the low-Earth orbit satellite search fails, the differential ephemeris correction is received through the locked high-Earth orbit satellite, and the low-Earth orbit satellite ephemeris is updated using the differential ephemeris correction.

[0071] The differential ephemeris correction is a correction data generated by the difference between the real-time accurate ephemeris and the reference ephemeris stored locally on the satellite terminal, used to correct pointing errors in the local ephemeris. Auxiliary position information can refer to beam geofences (i.e., the boundaries of the Earth's surface area covered by the high-orbit satellite beam) obtained from high-orbit satellite broadcasts, providing kilometer-level position constraints.

[0072] When the location confidence level is level two (low confidence), or when the search for low-Earth orbit satellites at level one in step S130 fails, the satellite terminal requests assistance from high-Earth orbit satellites. The satellite terminal first locks onto a high-Earth orbit satellite with the best signal and completes downlink synchronization. Specifically, when locking onto a high-Earth orbit satellite, it first scans the beacon frequencies of multiple pre-stored high-Earth orbit satellites to obtain the current elevation angle and received signal strength of each satellite. Then, based on the current elevation angle and received signal strength, it calculates a comprehensive score for each high-Earth orbit satellite, selects the high-Earth orbit satellite with the highest comprehensive score for downlink synchronization, and locks onto it.

[0073] In this context, the beacon frequency of a high-orbit satellite refers to a continuous or periodic signal at a known frequency broadcast by the satellite, typically containing a carrier wave, synchronization sequence, or broadcast information. Satellite terminals can pre-store the beacon frequencies and orbital parameters of multiple GEO satellites in their local non-volatile memory.

[0074] Elevation angle refers to the angle (in degrees) of a high-orbit satellite relative to the horizon when observed from the location of a satellite terminal. Since the position of a high-orbit satellite is relatively fixed, the elevation angle can be calculated using a geometric formula from the current (known or estimated) position of the satellite terminal and the coordinates of the satellite's nadir point. A higher elevation angle results in a shorter path for the signal through the atmosphere, and less impact from obstruction and attenuation.

[0075] Received signal strength refers to the reference signal received power (unit: dBm) of the high-orbit satellite beacon signal actually received by the satellite terminal. This value is affected by transmit power, free space loss, atmospheric attenuation, terminal antenna gain, and local environment (such as obstruction and multipath), and can reflect the current actual link quality.

[0076] The overall score is a single value obtained by linearly weighting the elevation angle and the received signal strength according to certain weights, and is used to evaluate the overall availability of each high-orbit satellite.

[0077] In practice, when a satellite terminal needs to lock onto a high-orbit satellite as an auxiliary data source, it first reads a pre-stored list of high-orbit satellites from its local non-volatile memory. This list contains parameters such as beacon frequencies and orbital positions (nadir longitude) of multiple high-orbit satellites covering different longitudes. To adapt to global or regional coverage, satellite terminals typically pre-store 3-5 commonly used high-orbit satellites.

[0078] The satellite terminal initiates the high-orbit scanning process. For each high-orbit satellite in the list, the satellite terminal performs the following operations: tunes its antenna to the preset beacon frequency of that high-orbit satellite, and attempts to receive the beacon signal. After successfully receiving the beacon, the satellite terminal acquires parameters in the following two ways: The current elevation angle is calculated by the satellite terminal based on its current position (which may be the position obtained in step S110) and the coordinates of the nadir point of the high-orbit satellite.

[0079] The Reference Signal Receiving Power (RSRP) can be read directly from the receiver's automatic gain control or signal power measurement register. Satellite terminals can average multiple consecutive symbols to reduce the impact of transient fading.

[0080] The satellite terminal records the elevation angle and RSRP value of each high-orbit satellite, and then calculates the comprehensive score. The formula for calculating the comprehensive score is as follows:

[0081] in and RSRP i Let be the elevation angle and the received signal strength of the i-th high-orbit satellite, respectively. and This represents the maximum elevation angle and signal strength among all currently scanned high-orbit satellites (used for normalization). This indicates the weight corresponding to the elevation angle. The weights represent the received signal strength. Optionally, the weight corresponding to the elevation angle can be set slightly higher than the weight corresponding to the received signal strength, for example... Prioritize ensuring the quality of the geometric link.

[0082] Then, the satellite terminal selects and locks onto the high-orbit satellite with the highest overall score and an elevation angle greater than 15°. For example, if high-orbit satellite 1 has the highest overall score and an elevation angle greater than 15°, the satellite terminal will point its antenna in the predicted direction of high-orbit satellite 1 (based on the calculated azimuth and elevation angles) and initiate the downlink synchronization process. Downlink synchronization includes: adjusting the local carrier frequency to match the Doppler frequency offset of the beacon signal, detecting the synchronization sequence in the beacon, and reading system information such as the system frame number and beam ID from the broadcast channel. After synchronization is completed, the satellite terminal locks onto the high-orbit satellite and can receive auxiliary data such as differential ephemeris fragments and beam geofencing broadcast by it.

[0083] If the high-orbit satellite with the highest overall score fails to synchronize due to temporary obstruction or brief signal fading, the satellite terminal can try other high-orbit satellites in descending order of their scores. If all pre-stored high-orbit satellites cannot be locked (e.g., all elevation angles are less than 15° or synchronization fails), the satellite terminal determines that high-orbit assistance is unavailable and automatically enters a degraded mode (e.g., blind search based on historical positions and IMU constraints), which will be explained in detail in subsequent embodiments.

[0084] The above method simultaneously evaluates the current elevation angle and actual received signal strength of high-orbit satellites, and uses a weighted comprehensive score for optimal selection, avoiding selection bias caused by relying solely on theoretical elevation angle or a single signal strength. Satellites with high theoretical elevation angles may have poor signal quality due to local obstruction or atmospheric attenuation, while satellites with high signal strength may have unstable links due to excessively low elevation angles. The comprehensive scoring mechanism can balance geometric visibility and actual link quality, ensuring that the terminal locks onto the high-orbit satellite with the highest probability of synchronization at its current location and the most stable long-term reception.

[0085] Using the locked high-orbit satellite, the satellite terminal receives the differential ephemeris correction broadcast by the high-orbit satellite. Then, the satellite terminal performs a superposition operation: E_fresh = E_base + ΔE, thereby obtaining the updated low-orbit satellite ephemeris E_fresh. Simultaneously, the satellite terminal obtains the geofencing information (i.e., the latitude and longitude polygon covered by the beam) of the current beam from the high-orbit satellite's broadcast channel, as auxiliary location information for subsequent searches.

[0086] Step S150: Based on the updated low-Earth orbit satellite ephemeris and the auxiliary position information obtained from high-Earth orbit satellites, perform a new low-Earth orbit satellite search.

[0087] The satellite terminal uses the updated LEO ephemeris and auxiliary position information obtained in the above steps to re-perform the LEO satellite search. Specifically, the auxiliary position information may include the center position of a beam geofence or the entire area corresponding to the beam geofence. When searching for LEO satellites, the center position of the beam geofence or the entire area can be used as the satellite terminal's approximate position (accuracy at the kilometer level). Combined with the updated LEO satellite ephemeris, the precise pointing angle (azimuth and elevation) of the currently visible LEO satellites is recalculated, and then the satellite search method in step S130 above is used to search for LEO satellites. Since the ephemeris error and position error are significantly reduced in this method, the satellite terminal can compress the search cone range from the previous ±5° to within ±2°, directly aligning with the predicted position for correlation peak detection. Within this narrow angle range, the satellite terminal's acquisition success rate and speed are greatly improved.

[0088] If the re-search is successful, the satellite terminal establishes a low-orbit satellite link and completes the satellite search process; if it still fails, step S140 can be repeated (e.g., re-requesting differential ephemeris) or it can fall back to blind search mode (using the historical position as the center and combining the IMU displacement to define the constraint window for a wide-range scan, which will be described in detail in subsequent embodiments) to ensure basic access capabilities in extreme environments.

[0089] In the above implementation process, by introducing position confidence assessment, the satellite terminal can adaptively select the satellite search path based on its own positioning quality. When positioning is reliable, it directly uses local ephemeris to quickly acquire low-Earth orbit satellites. When positioning is unreliable or ephemeris is outdated, it switches to high-Earth orbit satellites to obtain differential correction and auxiliary position information. This effectively compensates for ephemeris and position errors without relying on real-time accurate positioning, reduces the searching pointing deviation of low-Earth orbit satellites, and narrows the search range. This avoids long waiting times and wasted power due to blind scanning, and improves the acquisition success rate. This allows the terminal to quickly join the network even under harsh network conditions, ensuring the timeliness of user service establishment and the terminal's survivability in extreme environments.

[0090] Based on the above embodiments, the differential ephemeris correction amount can be broadcast by high-orbit satellites in beam segments. When updating the ephemeris of low-orbit satellites, the corresponding data segments can be decoded first according to the beam identifier of the area where the satellite terminal is located, and then the data segments can be superimposed with the locally stored low-orbit satellite ephemeris to obtain the updated low-orbit satellite ephemeris.

[0091] Beam slicing refers to the process by which the ground network divides the differential ephemeris correction values ​​of low-Earth orbit (LEO) satellites according to the beam coverage area of ​​high-Earth orbit (HEO) satellites, with each beam corresponding to a data slice. HEO satellites broadcast these slices periodically or on demand in transparent forwarding mode. Satellite terminals only need to receive and decode the corresponding slices based on their own beam ID, without processing data from other areas, thus saving storage and computing resources.

[0092] A beam ID is a unique identifier for each point beam of a high-orbit satellite. After completing downlink synchronization with the high-orbit satellite, the satellite terminal resolves the beam ID of its current beam from the broadcast channel. This identifier corresponds to a specific geographical coverage area (beam geofence), which the satellite terminal uses to determine which segment it should decode.

[0093] Differential ephemeris corrections can be correction vectors calculated by the ground network based on the difference between real-time accurate low-Earth orbit satellite ephemeris and the reference ephemeris stored locally on the terminal. The corrections are typically expressed as differences in Kepler elements (such as Δsemi-major axis, Δeccentricity, etc.) or differences in position and velocity vectors. The corrections are encapsulated in slices, with each slice containing correction information specific to a particular beam region.

[0094] After the satellite terminal locks onto a high-orbit satellite and completes downlink synchronization through the above steps, it first reads the current beam ID from the system information block of the high-orbit satellite's broadcast channel. This ID is typically an integer from 1 to N, such as "Beam ID=5". The satellite terminal then initiates the differential ephemeris reception process: it listens to the high-orbit satellite's broadcast channel, which periodically transmits multiple beam fragments in a time-slice or fixed-frame format. Each fragment header contains the target beam ID and ephemeris version number. The satellite terminal filters out fragments that match its own beam ID and ignores fragments from other beams. If the broadcast is event-triggered (only sent when the pointing deviation exceeds the limit), the satellite terminal needs to continuously listen for a period of time (e.g., 5 seconds) to wait for a matching fragment.

[0095] After decoding the differential correction value for the corresponding beam using the Beam ID, the satellite terminal reads the pre-stored reference ephemeris E_base (i.e., the LEO satellite ephemeris, such as a reference epoch in TLE format) from its local non-volatile memory. The reference ephemeris and the differential correction value must be based on the same reference time (or the same arc segment). The satellite terminal algebraically superimposes the differential correction value with the corresponding parameters of the reference ephemeris to obtain the updated LEO satellite ephemeris. After superposition, the satellite terminal can store the new ephemeris in a temporary working area, replacing the original ephemeris data, for use in subsequent reacquisition steps. If updated differential correction values ​​are received again (e.g., through periodic broadcasts), the satellite terminal can continue superimposing to achieve continuous ephemeris refinement.

[0096] In the above implementation process, by broadcasting the differential ephemeris correction amount in beam segments, the satellite terminal only needs to decode the corresponding data segments according to its own beam identifier, avoiding the reception and processing of a large amount of redundant data in irrelevant areas, and significantly reducing the terminal's storage overhead, decoding power consumption and ephemeris update time.

[0097] Based on the above embodiments, the differential ephemeris correction amount can be issued by the high-orbit satellite when it receives a broadcast command sent by the ground network side. The broadcast command is generated by the ground network side when it detects that the low-orbit satellite pointing deviation predicted based on the locally stored low-orbit satellite ephemeris exceeds a preset threshold.

[0098] Pointing deviation refers to the angular difference between the pointing angle of a low-Earth orbit (LEO) satellite antenna predicted by the LEO satellite ephemeris stored locally on the satellite terminal by the ground network and the correct pointing angle corresponding to the actual position of the LEO satellite. This deviation is caused by both ephemeris aging and terminal position errors, and is a core indicator for determining whether an ephemeris update is necessary. The ground network possesses real-time, high-precision LEO ephemeris data, which can accurately calculate the predicted pointing deviation at any geographic reference point.

[0099] The preset threshold is a threshold for determining whether the pointing deviation is acceptable, such as 1°. When the deviation exceeds this value, it indicates that the local ephemeris is severely outdated. If it is not updated, the satellite terminal will be unable to acquire low-Earth orbit satellites within a narrow beam. In this case, differential ephemeris broadcasting needs to be triggered. If the deviation does not exceed the threshold, the local ephemeris can still meet the acquisition requirements, and broadcasting is not necessary to save channel resources.

[0100] In practice, the ground network continuously monitors the pointing deviation predicted by each region based on locally stored low-Earth orbit (LEO) satellite ephemeris (i.e., the reference ephemeris version commonly used by terminals). To accomplish this monitoring, the ground network maintains a real-time, high-precision LEO satellite ephemeris (obtained through continuous tracking and correction via a global network of tracking and control stations). Simultaneously, the ground network stores the same reference ephemeris version as the terminal. For the geographical area covered by each high-Earth orbit (HEO) satellite beam, the ground network selects several reference points within the area (such as the beam center point or typical city locations), calculates the predicted pointing angle (using the reference ephemeris) and the actual pointing angle (using real-time, high-precision ephemeris) for each visible LEO satellite, then calculates the angle difference between the two, and takes the maximum value (or 95th percentile) of the pointing deviation for all reference points and all LEO satellites within the area as the current pointing deviation δ_point for that area.

[0101] The ground network compares δ_point with a preset threshold θ_thresh (e.g., 1°). If δ_point ≤ 1°, it means that the current reference ephemeris can still meet the terminal's acquisition requirements in this area, and the ground network remains silent and does not trigger any broadcast.

[0102] Once the ground network detects a pointing deviation δ_point exceeding 1° in a certain area (e.g., the area covered by beam ID=5), for example, δ_point=1.5°, it determines that satellite terminals within that area can no longer reliably acquire low-Earth orbit satellites using local ephemeris data. At this point, the ground network immediately generates a broadcast command. The broadcast command includes: the target beam ID (=5), the differential ephemeris correction data packet (containing the difference ΔE between the Kepler elements or the position-velocity vector), the broadcast start time, and the duration (e.g., 30 seconds, repeated every second). This command is transmitted via the network's uplink feeder link to the high-Earth orbit satellite covering that area (i.e., the high-Earth orbit satellite corresponding to beam ID=5).

[0103] After receiving the broadcast command, the high-orbit satellite parses the target beam ID=5 and the correction data packet. According to the command, the high-orbit satellite transmits differential ephemeris correction fragments in the downlink broadcast channel of beam 5, following the set frame format and period. The header of this fragment carries beam ID=5 and a version number for satellite terminal identification. If the satellite terminal is currently locked to the same high-orbit satellite and is within beam 5, it can receive this fragment on the broadcast channel. After receiving the fragment, the satellite terminal decodes it to obtain ΔE and superimposes it with the locally stored reference ephemeris to obtain the fresh ephemeris (the specific superposition process is as described in the previous implementation method).

[0104] If the ground network subsequently detects that the pointing deviation in this area has fallen below the threshold (for example, δ_point drops to 0.8° after continuous ephemeris updates), the ground network will stop sending broadcast commands, and the high-orbit satellites will also stop broadcasting differential ephemeris fragments of this area. The system will then return to a silent state until the deviation exceeds the limit again.

[0105] In some implementations, if the satellite terminal has the capability to transmit signals to high-orbit satellites (e.g., equipped with a GEO uplink power amplifier), the satellite terminal can send an auxiliary request message via the GEO uplink channel. The message includes at least the terminal ID, the current BeamID, and the request type (e.g., "request differential ephemeris"). Upon receiving the request, the ground network unicasts the corresponding differential ephemeris fragments as needed via the GEO satellite.

[0106] In the above implementation process, the pointing deviation of low-orbit satellites is monitored in real time by the ground network side. The differential ephemeris correction of high-orbit satellite broadcast is only triggered when the deviation exceeds the preset threshold. This avoids the continuous occupation of downlink channel resources by frequently sending invalid or redundant data under the traditional fixed-period broadcasting method, and reduces the bandwidth consumption of the broadcast channel.

[0107] Based on the above embodiments, in the above implementation method of determining the position confidence level according to the terminal positioning result, the first level may also include a high level and a medium level, with the high level being higher than the medium level. The specific judgment logic is as follows: if the terminal positioning result is that valid position information is obtained within a preset time and the horizontal accuracy factor is less than a set threshold, then the position confidence level is determined to be a high level; if the terminal positioning result is that valid position information is not obtained within a preset time or the horizontal accuracy factor is greater than or equal to the set threshold, then dead reckoning is performed using an inertial measurement unit. If the reckoned displacement is less than the radius threshold, then the position confidence level is determined to be a medium level.

[0108] The inertial measurement unit (IMU) is a sensor module composed of accelerometers and gyroscopes. It can measure the acceleration and angular velocity of the satellite terminal and calculate displacement and attitude changes by integrating over time.

[0109] Dead reckoning refers to the method of calculating the approximate current position when GNSS fails, using acceleration and angular velocity measured by IMU, combined with the previous known position (i.e., the last known position) and direction.

[0110] The radius threshold is used to determine the acceptable limit of dead reckoning displacement. If the reckoning displacement is less than the threshold, the satellite terminal position is considered to have changed little, and the historical position still has some reference value; if the displacement is too large, the position uncertainty is too high. In this embodiment, the radius threshold can be selected as 50 kilometers.

[0111] The methods for obtaining and determining valid location information and horizontal accuracy factor can be referred to the previous embodiments. Here, we mainly explain the dead reckoning situation. If the terminal positioning result is that no valid location information is obtained within a preset time or the horizontal accuracy factor is greater than or equal to a set threshold, the location confidence level is not directly determined to be level two, but dead reckoning is further performed.

[0112] The dead reckoning process is as follows: The satellite terminal reads the "last known position" (e.g., the coordinates and timestamp saved at the time of the last power-off) from non-volatile memory. The satellite terminal reads the acceleration and angular velocity data recorded by the IMU in the most recent hour and calculates the displacement vector relative to the last known position through integration. For example, the IMU estimates that the satellite terminal has moved approximately 30 kilometers northeast. The satellite terminal adds the displacement vector to the last known position to obtain the current estimated position. Simultaneously, the satellite terminal calculates the absolute value of the displacement (30 kilometers) and compares it with a preset radius threshold R_thresh (e.g., 50 kilometers).

[0113] If the estimated displacement is less than the radius threshold (30km < 50km), it indicates that the satellite terminal has not moved far from the last known area, and the estimated position still has high reference value (the error is usually between a few kilometers and tens of kilometers). In this case, the satellite terminal determines the position confidence level to be medium. Medium level indicates that the terminal does not have a precise absolute position, but has a relatively small (radius < 50km) rough position constraint, which can still be corrected later using auxiliary means (such as high-orbit beam geofencing).

[0114] If the estimated displacement is greater than or equal to the radius threshold (e.g., an estimated displacement of 80km ≥ 50km), it indicates that the satellite terminal has moved too far, the cumulative error of dead reckoning may be very large, and the position is unreliable. In this case, the satellite terminal will set the confidence level to low (i.e., level two), indicating that the position information is completely unusable.

[0115] In the above implementation process, by introducing a two-level position confidence classification of high-level and medium-level, the complementary advantages of GNSS and IMU are fully utilized. When the GNSS signal is good, a high-precision position (high-level) is obtained directly. When GNSS fails but the terminal's movement range is limited in a short period of time, a medium-confidence position (medium-level) is maintained by using IMU dead reckoning. This avoids simply classifying the terminal as unlocatable due to a brief GNSS failure or obstruction, thus preserving more usable information for subsequent differentiated satellite search strategies. At the same time, the existence of the medium-level position allows the terminal to continue to attempt low-Earth orbit satellite acquisition based on relatively reliable historical displacement constraints even when it cannot obtain a precise position. This effectively reduces unnecessary auxiliary requests and power consumption, and improves the overall efficiency and adaptability of the satellite search process in complex environments.

[0116] After dividing the first level into high and medium levels, the satellite search strategy under the first level can also be configured differently. For example, the predicted pointing angle of the low-Earth orbit satellite can be calculated using the locally stored low-Earth orbit satellite ephemeris. If the position confidence level is high, the low-Earth orbit satellite search is performed using the first timeout threshold and the first search range corresponding to the predicted pointing angle. If the position confidence level is medium, the low-Earth orbit satellite search is performed using the second timeout threshold and the second search range. The second timeout threshold is less than the first timeout threshold, and the second search range is greater than the first search range.

[0117] The predicted pointing angle is the antenna pointing direction calculated based on the terminal location and the local low-orbit satellite ephemeris. It includes the azimuth angle (Az) and elevation angle (E1) and is used to guide the antenna to point at the target satellite.

[0118] The first search range refers to the conical scanning angle range around the predicted pointing angle when the position confidence level is high (terminal position is accurate). Since the position and ephemeris errors are very small, a narrower search range can be used to speed up the acquisition process. A typical value is ±5° (a cone formed by ±5° each of the azimuth and elevation angles).

[0119] The second search range is used when the position confidence level is medium (the terminal position only has a rough constraint at the kilometer level), and the uncertainty is relatively large, so it is necessary to expand the search range to cover possible actual satellite directions. The second search range is larger than the first search range, and its value is generally ±8° or ±10°, which can be adjusted according to the terminal position error model.

[0120] The first timeout threshold refers to the maximum allowed duration for performing a low-Earth orbit satellite search at a high level. Due to the precise location and high acquisition probability, a longer time can be set to allow for sufficient attempts, typically 30 seconds.

[0121] The second timeout threshold refers to the maximum permissible duration for performing a low-Earth orbit satellite search at the medium-level. Due to the high uncertainty of location, prolonged periods without results may waste energy and opportunities; therefore, a shorter time (e.g., 15 seconds) is set. If no acquisition is achieved within this time, subsequent auxiliary steps are quickly initiated. The second timeout threshold is less than the first timeout threshold.

[0122] After the satellite terminal completes the position confidence level assessment (obtaining a high or medium level), it attempts to directly acquire low-Earth orbit (LEO) satellites using locally stored LEO satellite ephemeris data. At this point, the satellite terminal can dynamically configure search parameters based on different confidence levels. For example: If the location confidence level is high, the satellite terminal is configured with a first timeout threshold T. high =30 seconds, first search range θ high =±5 (that is, scanning within a cone-shaped area of ​​±5° azimuth and ±5° elevation of the predicted pointing angle).

[0123] If the location confidence level is medium, the satellite terminal is configured with a second timeout threshold T. mid =15 seconds, second search range θ mid =±8 (The scanning cone angle is increased to ±8° to cope with pointing errors caused by position uncertainty).

[0124] First, the satellite terminal reads the locally stored low-orbit satellite ephemeris, combines the current timestamp and the terminal's current location, calculates the candidate low-orbit satellites visible at the current moment, sorts them according to a finite set, and selects the low-orbit satellite with the highest priority as the target low-orbit satellite (the specific implementation process can be referred to the relevant description in the aforementioned embodiments). At this time, the predicted pointing angle is the predicted pointing angle of the target low-orbit satellite.

[0125] The satellite terminal then performs an acquisition scan. It aligns the antenna beam center with the predicted pointing angle of the target low-Earth orbit satellite and then performs a spiral or grid scan within the configured search range, following a set step (e.g., every 0.5°). At each scan point, the satellite terminal attempts to detect the low-Earth orbit satellite's beacon signal or synchronization sequence. Once a valid signal is detected, acquisition is considered successful, the search is terminated, and the process transitions to the subsequent service establishment procedure.

[0126] If no valid signal is detected within the entire search range and the time taken reaches the set timeout threshold (30 seconds or 15 seconds), the low-orbit search is determined to be a failure, the satellite terminal terminates the current search, and proceeds to the high-orbit auxiliary step (i.e., step S140).

[0127] In addition, since the mid-level position is not accurate, if there are still no results after a long search, in order to avoid consuming too much power and time, the timeout threshold is set to a short time (15 seconds). After a quick failure, it can switch to high orbit to obtain differential ephemeris, thereby completing the ephemeris correction more efficiently.

[0128] Conversely, at higher levels, the location is more precise, requiring only a narrow search range (±5°) for rapid acquisition, while allowing for a longer timeout (30 seconds) to tolerate occasional temporary obstruction or signal fading, thus improving the success rate on the first attempt.

[0129] In the above implementation process, based on the position uncertainty of high-level and medium-level positions, differentiated search parameters are adaptively configured. At high-level positions, the position is precise, and a narrow search range and a longer timeout threshold are used to achieve rapid focusing and scanning while ensuring a high acquisition probability, reducing power consumption and time waste. At medium-level positions, the position is only roughly constrained by dead reckoning, and a wider search range is used to cover the pointing uncertainty caused by position errors. At the same time, a shorter timeout threshold is used to prevent long-term ineffective searches due to high uncertainty, thereby quickly determining whether to switch to high-orbit assistance and improving search efficiency.

[0130] In the above method of re-searching for low-Earth orbit (LEO) satellites by combining the updated LEO satellite ephemeris and auxiliary position information obtained from high-Earth orbit (HEO) satellites, to avoid search failures due to the unavailability of auxiliary position information, it is necessary to first determine whether the auxiliary position information obtained from HEO satellites is available. If it is available, the LEO satellite search can be performed again based on the updated LEO satellite ephemeris and the auxiliary position information obtained from HEO satellites. If it is unavailable, a degraded mode is entered, that is, the historical position is used as the origin, and the displacement calculated by the inertial measurement unit is used to determine the constraint search window. The historical position includes the previous successful positioning result and / or the precise position sent down after being solved by the ground network. Then, a narrow-band constraint blind search is performed within the constraint search window.

[0131] After obtaining the updated low-Earth orbit satellite ephemeris and the auxiliary location information (beam geofencing) parsed from the high-Earth orbit satellite broadcast channel, the satellite terminal first determines the availability of the auxiliary location information before performing reacquisition. The specific operation for availability determination is as follows: The satellite terminal checks whether it has successfully locked onto a high-orbit satellite and obtained the Beam ID of the current beam. If the lock is successful, the satellite terminal further verifies the integrity of the beam geofencing data. Simultaneously, the satellite terminal calculates the coverage area or maximum span of the geofencing (e.g., diagonal distance). If this span exceeds a preset threshold (e.g., 500 km), the data is deemed potentially abnormal (because the diameter of a single GEO beam typically does not exceed 500 km) and marked as unavailable. Furthermore, if the satellite terminal has not locked onto any high-orbit satellites (e.g., a degraded mode has been triggered), or if it has locked onto a satellite but the broadcast channel does not carry auxiliary location information, it is also deemed unavailable.

[0132] If auxiliary position information is available, the satellite terminal updates its coarse position to the center point of the geofence for that beam or the entire geofence area (taking the center point as representative), and recalculates the predicted pointing angle of the low-Earth orbit satellite by combining it with the fresh ephemeris obtained in step S140. Since the position constraint accuracy is at the kilometer level and the ephemeris error has been compressed to within 1°, the satellite terminal can compress the search cone angle to ±2° for efficient acquisition, as described above.

[0133] If auxiliary location information is unavailable (e.g., the satellite terminal has locked onto a high-orbit satellite but cannot obtain the fence due to missing or abnormal broadcast data, or the satellite terminal is in a degraded mode that cannot lock onto a GEO satellite), the satellite terminal immediately switches to degraded mode and performs a narrowband constrained blind search.

[0134] The satellite terminal reads the last stored historical location (i.e., the last known location described in the preceding embodiments) from its non-volatile memory. This historical location may originate from the GNSS positioning result before the last normal shutdown, or the precise location calculated and sent by the network side during the last service establishment. The satellite terminal simultaneously reads acceleration and angular velocity data recorded in the most recent time period (e.g., the last hour) and integrates them to calculate the displacement vector relative to the historical location. For example, if the IMU calculates that the terminal has moved 12 kilometers to the northwest, the current possible location area is a circle with a radius of 12 kilometers and the historical location as its origin.

[0135] To cover potential estimation errors, the terminal sets the radius of the constraint search window to "estimated displacement + fixed margin". Assuming a fixed margin of 10 kilometers, the search window radius = 12 + 10 = 22 kilometers. The constraint search window is a circular area with a radius of 22 kilometers centered on the historical location. Within this area, the satellite terminal employs a narrowband blind search strategy: since the overpass times and elevation trajectories of low-Earth orbit satellites over this area are predictable, the satellite terminal can roughly estimate the possible frequency bands and time windows based on locally stored ephemeris data (even if aged), and then scan for typical narrowband beacon frequencies within the area, without relying on precise pointing angles. Within the constraint search window, the satellite terminal receives signals in an omnidirectional or wide-beam manner. If any low-Earth orbit satellite beacon is detected within a preset time (e.g., 60 seconds), it attempts to synchronize and establish a link.

[0136] In the above implementation process, by introducing an availability judgment of auxiliary location information, a seamless switch between accurate search when the HEO auxiliary is reliable and degraded blind search when the auxiliary fails is achieved. This mechanism enables the terminal to maintain basic access capabilities even in extreme environments such as GNSS denial and complete failure of HEO auxiliary, relying on its stored historical accurate location and IMU short-time integration, thus avoiding the risk of being unable to access the network due to the interruption of the auxiliary link.

[0137] Based on the above embodiments, after the satellite terminal successfully searches for the target low-Earth orbit satellite and establishes service communication with the target low-Earth orbit satellite, it can send uplink detection signals. The ground network side performs position calculation based on the uplink detection signals. For example, it can use the time difference of arrival and frequency difference of arrival measured by the signals received by multiple low-Earth orbit satellites, and combine the beam coverage range of the corresponding high-Earth orbit satellite and the downlink synchronization delay as prior constraints to calculate the precise position. The precise position is then sent to the satellite terminal, which receives and stores the precise position sent by the ground network side.

[0138] Among them, the uplink probe signal refers to a known sequence signal (such as pilot, ranging code or reference signal) sent by the satellite terminal on a specific time and frequency resource after establishing a service channel with the target low-Earth orbit satellite, according to the instructions or periodic configuration of the ground network side. This signal is used by the ground network side to measure the time difference and frequency difference of the signal arriving at multiple low-Earth orbit satellites.

[0139] The Time Difference of Arrival (TDOA) refers to the time difference between the arrival of the same uplink probe signal at two different low-Earth orbit (LEO) satellites. Since the positions of the LEO satellites are known, the TDOA corresponds to the distance difference between the satellite terminal and the two satellites, which can form a hyperbolic positioning constraint.

[0140] Frequency Difference of Arrival (FDOA) refers to the Doppler frequency difference between the arrival times of the same uplink probe signal at two different low-Earth orbit (LEO) satellites. The high-speed motion of LEO satellites causes different Doppler frequency shifts in the signals. FDOA provides velocity-related constraints for the satellite terminal and also assists in position calculation.

[0141] Once the satellite terminal successfully acquires a low-Earth orbit (LEO) satellite through the aforementioned steps (S130, S150, or degraded mode) and completes random access and establishes uplink and downlink service channels according to the LEO satellite communication protocol, the satellite terminal enters the service communication state. At this time, in order to obtain a high-precision self-position (for subsequent accelerated cold start, beam mapping calibration, etc.), the satellite terminal initiates an assisted positioning request to the ground network side, or the ground network side actively triggers the fine positioning process.

[0142] The satellite terminal periodically transmits uplink probe signals in the service channel according to the uplink probe signal parameters (including time and frequency resources, sequence index, transmission period, etc.) configured by the ground network side through the downlink control channel. This signal typically uses a Zadoff-Chu sequence or a pseudo-random noise sequence, which has good autocorrelation characteristics, facilitating accurate measurement of delay and frequency at the receiver.

[0143] The ground network connects to multiple low-Earth orbit (LEO) satellites via a gateway station. These LEO satellites simultaneously receive uplink probe signals transmitted by satellite terminals. Assume that M LEO satellites (M≥3) all receive the signal, and each LEO satellite records the time of arrival (TOA) and frequency of arrival (FOA). The ground network collects the measurements from all LEO satellites and selects one as a reference satellite (usually the satellite with the strongest signal or highest elevation angle). It then calculates the time difference of arrival (TDOA) and frequency difference of arrival (FDOA) of the remaining LEO satellites relative to the reference satellite. Let the reference satellite be Sat0 and the other satellite be Sat_i, then: TDOA_i = TOA_i - TOA_0, and the corresponding distance difference = c * TDOA_i (c is the speed of light).

[0144] FDOA_i = FOA_i - FOA_0, which reflects the Doppler frequency difference caused by the relative velocity difference between the satellite terminal and the low-orbit satellite.

[0145] The ground network side simultaneously acquires prior constraint information for assisted positioning: (1) the beam coverage range Ω of the high-orbit satellite locked by the satellite terminal in step S140. beam (The geographical boundary of the beam can be retrieved from the database based on the known Beam ID reported by the terminal on the ground network side.) (2) Downlink synchronization delay measured and reported by the satellite terminal when locking onto the high-orbit satellite. (The satellite terminal measures and stores data during the relevant process, and then transmits it to the network side via the service channel.) The ground network side can then use the precise ephemeris of the high-orbit satellite to... Converted to pseudorange from satellite terminal to the high-orbit satellite The pseudorange-constrained satellite terminal is located with the high-orbit satellite as the center and a radius of d. geo On the surface of the sphere, it intersects with the surface of the Earth to form a circle.

[0146] On the ground network side, the TDOA / FDOA localization solution equations are constructed, and prior constraints are introduced. A common method is to minimize the following cost function:

[0147] Where x is the precise location to be solved. To constrain the weights, This represents the spatial prior penalty function, when x falls within the beam coverage area Ω. beam The value is 0 when x is within the bounds, otherwise it is proportional to the square of the distance to the boundary. This applies when the distance from x to the high-orbit satellite is within d. geo The value is 0 if the error is within the range, otherwise it is proportional to the square of the error. This represents the vector of observations obtained from the k-th measurement (such as a vector composed of strategy data like time difference of arrival and frequency difference of arrival). It is a function of x, which describes the theoretically expected measurement value given x (assuming x is calculated through a mathematical model). This represents the weight matrix, which is used to weight different measurements according to their importance. For example, higher-precision measurements can be assigned a larger weight, while lower-precision measurements can be assigned a smaller weight, so that the positioning solution is more accurate.

[0148] On the ground network side, iterative least squares or particle filtering methods are used to solve the above optimization problem to obtain the precise location P_true of the terminal. Since the prior constraints have restricted the solution space to the beam coverage area (hundreds of kilometers in diameter) and the narrow circle determined by the pseudorange of the high-orbit satellite, the ambiguity of TDOA / FDOA is greatly reduced, improving the convergence speed. Typically, meter-level accuracy can be obtained in a short time.

[0149] The ground network transmits the calculated precise location (longitude, latitude, and altitude) and the calculation timestamp to the satellite terminal via the low-Earth orbit satellite's downlink service channel or dedicated signaling. Upon receiving this precise location, the satellite terminal writes it to the "Last Known Location" field in its non-volatile memory and records the timestamp. Subsequently, even during a cold start, the satellite terminal can directly use this high-precision historical location, significantly improving the efficiency of subsequent satellite searches.

[0150] If the ground network cannot calculate a position that meets the accuracy requirements (e.g., horizontal positioning error > 100 meters) due to insufficient number of low-orbit satellites or poor signal quality, it will not send the position, or will send a rough position with a low-precision flag. The satellite terminal can choose not to cover the original high-precision historical position.

[0151] In the above implementation process, by actively sending uplink probe signals using the established service links and introducing the high-orbit beam coverage and downlink synchronization delay as prior constraints, the ground network side can calculate the precise location of the satellite terminal with less computational overhead and faster convergence speed.

[0152] Building upon the above embodiments, to achieve long-term self-evolution of assisted positioning accuracy, a position mapping table is constructed and continuously updated on the ground network side. The core function of this mapping table is that when the satellite terminal needs to obtain assisted position information, the ground network side no longer directly provides the theoretical beam center, but instead provides a refined center after correction. This makes the approximate position of the satellite terminal closer to the actual geographical location, further improving the accuracy of subsequent low-Earth orbit satellite pointing calculations.

[0153] The aforementioned auxiliary location information may include the actual center position of the beam coverage area corresponding to the high-orbit satellite. The actual center position is obtained by the satellite terminal based on the location mapping table on the ground network side. The location mapping table stores the correspondence between beam identifiers and location correction amounts. The actual center position is the sum of the location correction amount and the theoretical center position of the beam coverage area corresponding to the high-orbit satellite.

[0154] The position correction is obtained by comparing the precise position of each satellite terminal with the theoretical center position of the beam coverage of the corresponding high-orbit satellite on the ground network side to obtain the deviation vector, classifying the deviation vector according to the beam, and then clustering the classified deviation vectors.

[0155] The location mapping table is a database table maintained by the ground network side, storing the location correction amount corresponding to each high-orbit satellite beam (identified by beam ID). This correction amount is used to compensate for the systematic deviation between the theoretical center position of the beam and the actual geographical location of the satellite terminal. The mapping table structure may include: beam ID, nominal center latitude and longitude (theoretical value), location correction amount (Δ longitude, Δ latitude), confidence level, version number, and effective timestamp, etc.

[0156] The theoretical center of beam coverage refers to the geometric center of the theoretically designed coverage area of ​​a point beam of a high-orbit satellite (e.g., the center of a circular beam, or the centroid of a rectangular / polygonal beam). This center position is calculated from the satellite antenna pattern, the nadir position, and beam pointing parameters. It is a theoretical value and may deviate from the optimal center of actual coverage.

[0157] The position correction is an offset vector used to correct the nominal center position of the beam. When acquiring auxiliary position information, the satellite terminal adds the theoretical center position to the position correction to obtain a position that is closer to the actual coverage center, thereby improving the accuracy of coarse positioning.

[0158] When constructing the location mapping table, as described in the previous implementation method, the satellite terminal sends an uplink probe signal after establishing a service channel with the low-Earth orbit satellite. The ground network side uses the TDOA / FDOA measured by multiple low-Earth orbit satellites, combined with the geofencing of the high-Earth orbit beam and the downlink synchronization delay, to calculate the terminal's precise location P_true (with an error on the order of meters). The ground network side also knows the high-Earth orbit beam ID (e.g., Beam ID=5) reported by the satellite terminal during this access process and the theoretical center position P_nominal of that beam (e.g., read from the satellite database). The network side calculates the deviation vector: ΔP=P_true P_nominal; The deviation vector, along with the beam ID, timestamp, and terminal ID (optional), is stored in a temporary sample database on the ground network side.

[0159] The ground network can periodically (e.g., hourly or daily) categorize newly acquired deviation vector samples according to beam ID. Each beam ID accumulates hundreds or thousands of ΔP samples from different satellite terminals. These samples may contain measurement noise, multipath errors, anomalies reported by satellite terminals, and actual systematic deviations in beam coverage.

[0160] For a sample set under a specific beam ID, the ground network employs a clustering algorithm to extract robust and representative corrections. For example, the coverage area of ​​each beam is divided into a 0.1×0.1 grid, and the median ΔP of all satellite terminals within each grid is calculated and used as a fixed correction for that grid. Alternatively, methods such as mean shift or weighted averaging can also be used.

[0161] The cluster centers obtained after clustering can be used as the position correction value. After the clustering calculation is completed, the ground network side obtains the final position correction value ΔP_corr for each beam ID (or each subgrid). The ground network side writes this correction value into the position mapping table, along with a version number and timestamp. The position mapping table can be stored in key-value format: key (beam ID), value (position correction value ΔP_corr).

[0162] The mapping table can be updated periodically (e.g., daily) on the terrestrial network side, and older versions can be retained for a period of time for rollback.

[0163] When the satellite terminal needs to obtain auxiliary position information from a high-orbit satellite during a subsequent cold start, the satellite terminal first locks onto the high-orbit satellite and obtains the current beam ID (e.g., Beam ID=5). The satellite terminal can obtain the mapping table content in the following two ways: Method 1 (Online Query): The satellite terminal sends a query request to the ground network via the low-Earth orbit satellite service channel (or GEO uplink channel), carrying the current beam ID. The ground network retrieves the corresponding position correction ΔP_corr from the position mapping table and sends it to the satellite terminal along with the theoretical beam center position P_nominal.

[0164] Method 2 (Local Caching): The satellite terminal has already downloaded the complete mapping table from the ground network side (or cached it in local non-volatile memory by beam segment) when the link was successfully established. The satellite terminal directly reads the local mapping table to obtain the position correction.

[0165] The satellite terminal then calculates auxiliary position information: P_refined = P_nominal + ΔP_corr, which is the theoretical beam center position plus the position correction. The satellite terminal uses this corrected center position as its own coarse position (in kilometers) for subsequent calculation of the low-Earth orbit satellite pointing angle by combining it with the latest ephemeris.

[0166] After the service ends, the satellite terminal writes the precise location, the latest high-precision ephemeris, and the current timestamp sent by the network side into a non-volatile memory, which will be used as the historical location and reference ephemeris for the next cold start.

[0167] As satellite terminal usage increases and the number of samples grows, the ground network can periodically (e.g., weekly) re-cluster the data and update the position corrections in the position mapping table. If the coverage characteristics of a certain beam change slowly due to satellite attitude adjustments or antenna aging, the clustering results will automatically track these changes, thus achieving long-term self-evolution of assisted positioning accuracy.

[0168] In the above implementation process, a location mapping table containing the correspondence between beam identifiers and position corrections is constructed and continuously updated on the ground network side. The deviation statistics and cluster analysis of the precise positions fed back by massive terminals in service communication and the theoretical center of the beam are performed to obtain the actual center position of each beam. This allows the terminal to directly obtain the corrected center as auxiliary position information in the subsequent high-orbit auxiliary stage, effectively eliminating the systematic deviation between the theoretical center and the actual coverage center caused by factors such as beam pointing error, antenna deformation or orbital drift.

[0169] Please refer to Figure 3 , Figure 3This is a structural block diagram of a satellite terminal satellite search device 200 provided in an embodiment of this application. The satellite terminal satellite search device 200 may be a module, program segment, or code on an electronic device. It should be understood that the satellite terminal satellite search device 200 corresponds to the above method embodiment and is capable of executing the various steps involved in the method embodiment. The specific functions of the satellite terminal satellite search device 200 can be found in the description above. To avoid repetition, detailed descriptions are appropriately omitted here.

[0170] Optionally, the satellite terminal satellite search device 200 includes: The positioning module 210 is used to perform positioning calculations to obtain the positioning result of the satellite terminal after it is powered on. Location assessment module 220 is used to determine the location confidence level based on the terminal positioning result; The first search module 230 is used to perform a low-orbit satellite search using locally stored low-orbit satellite ephemeris if the location confidence level is the first level. The ephemeris update module 240 is used to receive differential ephemeris corrections from locked high-orbit satellites and update the ephemeris of the low-orbit satellites using the differential ephemeris corrections if the position confidence level is the second level or the low-orbit satellite search fails. The first level is higher than the second level. The second search module 250 is used to re-search for low-orbit satellites based on the updated low-orbit satellite ephemeris and the auxiliary position information obtained from the high-orbit satellites.

[0171] Optionally, the differential ephemeris correction is broadcast by the high-orbit satellite in beam segments, and the ephemeris update module 240 is used to decode the corresponding data segments according to the beam identifier of the area where the satellite terminal is located; and to superimpose the data segments with the locally stored low-orbit satellite ephemeris to obtain the updated low-orbit satellite ephemeris.

[0172] Optionally, the differential ephemeris correction is issued by the high-orbit satellite when it receives a broadcast command sent by the ground network side. The broadcast command is generated by the ground network side when it detects that the low-orbit satellite pointing deviation predicted based on the locally stored low-orbit satellite ephemeris exceeds a preset threshold.

[0173] Optionally, the position evaluation module 220 is configured to determine the position confidence level as high if the terminal positioning result is that valid position information is obtained within a preset time and the horizontal accuracy factor is less than a set threshold; if the terminal positioning result is that valid position information is not obtained within a preset time or the horizontal accuracy factor is greater than or equal to the set threshold, then dead reckoning is performed using an inertial measurement unit, and if the reckoned displacement is less than a radius threshold, the position confidence level is determined as medium, wherein the first level includes the high level and the medium level, and the high level is higher than the medium level.

[0174] Optionally, the first search module 230 is used to calculate the predicted pointing angle of a low-Earth orbit satellite using locally stored low-Earth orbit satellite ephemeris; if the position confidence level is the high level, then a low-Earth orbit satellite search is performed using a first timeout threshold and a first search range corresponding to the predicted pointing angle; if the position confidence level is the medium level, then a low-Earth orbit satellite search is performed using a second timeout threshold and a second search range, wherein the second timeout threshold is less than the first timeout threshold, and the second search range is greater than the first search range.

[0175] Optionally, the second search module 250 is used to determine whether the auxiliary position information obtained from the high-orbit satellite is available; if available, the low-orbit satellite search is performed again based on the updated low-orbit satellite ephemeris and the auxiliary position information obtained from the high-orbit satellite; if unavailable, the constraint search window is determined using the historical position as the origin and the displacement calculated by the inertial measurement unit, wherein the historical position includes the previous successful positioning result and / or the precise position sent after calculation by the ground network side; and a narrow-band constraint blind search is performed within the constraint search window.

[0176] Optionally, the high-orbit satellite is locked in the following manner: By scanning the beacon frequencies of multiple pre-stored high-orbit satellites, the current elevation angle and received signal strength of each high-orbit satellite can be obtained. The comprehensive score of each high-orbit satellite is calculated based on the current elevation angle and received signal strength. Select the high-orbit satellite with the highest overall score for downlink synchronization and lock it in.

[0177] Optionally, the satellite terminal satellite search device 200 further includes: The location receiving module is used to send uplink detection signals after establishing service communication with the target low-Earth orbit satellite; receive and store the precise location sent down by the ground network side. The precise location is obtained by the ground network side using the time difference of arrival and frequency difference of arrival measured by the signals received from multiple low-Earth orbit satellites, combined with the beam coverage range of the corresponding high-Earth orbit satellite and the downlink synchronization delay as prior constraints.

[0178] Optionally, the auxiliary location information includes the actual center position of the beam coverage area corresponding to the high-orbit satellite. The actual center position is obtained by the satellite terminal according to the location mapping table on the ground network side. The location mapping table stores the correspondence between beam identifiers and position correction amounts. The actual center position is the sum of the position correction amount and the theoretical center position of the beam coverage area corresponding to the high-orbit satellite. The position correction amount is obtained by the ground network side by comparing the precise position of each satellite terminal with the theoretical center position of the beam coverage range of the high-orbit satellite corresponding to the satellite terminal to obtain the deviation vector, classifying the deviation vector according to the beam, and clustering the classified deviation vector.

[0179] Optionally, the first search module 230 is used to determine candidate low-orbit satellites that are visible at the current time and whose elevation angle is lower than a set angle using locally stored low-orbit satellite ephemeris; sort the candidate low-orbit satellites according to priority; point the antenna to the predicted pointing angle of the low-orbit satellite with the highest priority, and search within the corresponding range.

[0180] It should be noted that those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system and apparatus described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0181] Please refer to Figure 4 , Figure 4 This application provides a schematic diagram of the structure of an electronic device for performing a satellite terminal satellite search method. The electronic device may include: at least one processor 310, such as a CPU; at least one communication interface 320; at least one memory 330; and at least one communication bus 340. The communication bus 340 is used to establish communication between these components. In this embodiment, the communication interface 320 is used for signaling or data communication with other node devices. The memory 330 may be a high-speed RAM or non-volatile memory, such as at least one disk storage device. Optionally, the memory 330 may also be at least one storage device located remotely from the aforementioned processor. The memory 330 stores computer-readable instructions; when these computer-readable instructions are executed by the processor 310, the electronic device performs the aforementioned method process.

[0182] Understandable. Figure 4 The structure shown is for illustrative purposes only; the electronic device may also include components that are more advanced than those shown. Figure 4 The more or fewer components shown, or having the same Figure 4 The different configurations shown. Figure 4 The components shown can be implemented using hardware, software, or a combination thereof.

[0183] This application provides a computer-readable storage medium storing a computer program thereon. When the computer program is executed by a processor, it performs the method process executed by the electronic device in the above method embodiments.

[0184] This embodiment discloses a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions, and when the program instructions are executed by a computer, the computer can perform the methods provided in the above-described method embodiments, such as including: After the satellite terminal is powered on, a positioning calculation is performed to obtain the terminal's positioning result; The location confidence level is determined based on the terminal positioning results; If the location confidence level is the first level, then the low-Earth orbit satellite search is performed using the locally stored low-Earth orbit satellite ephemeris. If the location confidence level is the second level or the low-Earth orbit satellite search fails, the differential ephemeris correction amount is received through the locked high-Earth orbit satellite, and the low-Earth orbit satellite ephemeris is updated using the differential ephemeris correction amount, where the first level is higher than the second level. Based on the updated low-Earth orbit satellite ephemeris and the auxiliary position information obtained from the high-Earth orbit satellites, a new low-Earth orbit satellite search is performed.

[0185] In summary, this application provides a satellite terminal satellite search method, electronic device, storage medium, and program product. This method, by introducing position confidence assessment, enables the satellite terminal to adaptively select a satellite search path based on its own positioning quality. When positioning is reliable, it directly utilizes local ephemeris to quickly acquire low-Earth orbit (LEO) satellites. When positioning is unreliable or ephemeris is outdated, it instead uses high-Earth orbit (HEO) satellites to obtain differential correction and auxiliary position information. This effectively compensates for ephemeris and position errors without relying on real-time precise positioning, reduces the searching pointing deviation of LEO satellites, and narrows the search range. This avoids long waiting times and wasted power due to blind scanning, while also improving the acquisition success rate. This allows the terminal to quickly access the network even under harsh network conditions, ensuring the timeliness of user service establishment and the terminal's survivability in extreme environments.

[0186] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. The apparatus 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. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some communication interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0187] Furthermore, 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.

[0188] Furthermore, the functional modules in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0189] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.

[0190] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A satellite terminal satellite search method, characterized in that, The method includes: After the satellite terminal is powered on, a positioning calculation is performed to obtain the terminal's positioning result; The location confidence level is determined based on the terminal positioning results; If the location confidence level is the first level, then the low-Earth orbit satellite search is performed using the locally stored low-Earth orbit satellite ephemeris. If the location confidence level is the second level or the low-Earth orbit satellite search fails, the differential ephemeris correction amount is received through the locked high-Earth orbit satellite, and the low-Earth orbit satellite ephemeris is updated using the differential ephemeris correction amount, where the first level is higher than the second level. Based on the updated low-Earth orbit satellite ephemeris and the auxiliary position information obtained from the high-Earth orbit satellites, a new low-Earth orbit satellite search is performed.

2. The method according to claim 1, characterized in that, The differential ephemeris correction is broadcast by the high-orbit satellite in beam-segmentation. Updating the low-orbit satellite ephemeris using the differential ephemeris correction includes: Decode the corresponding data fragments based on the beam identifier of the area where the satellite terminal is located; The data fragments are overlaid with the locally stored low-Earth orbit satellite ephemeris to obtain the updated low-Earth orbit satellite ephemeris.

3. The method according to claim 2, characterized in that, The differential ephemeris correction is issued by the high-orbit satellite when it receives a broadcast command from the ground network side. The broadcast command is generated by the ground network side when it detects that the low-orbit satellite pointing deviation predicted based on the locally stored low-orbit satellite ephemeris exceeds a preset threshold.

4. The method according to claim 1, characterized in that, Determining the location confidence level based on the terminal positioning result includes: If the terminal positioning result is that valid location information is obtained within a preset time and the horizontal accuracy factor is less than a set threshold, then the location confidence level is determined to be high. If the terminal positioning result is that no valid position information is obtained within a preset time or the horizontal accuracy factor is greater than or equal to a set threshold, then dead reckoning is performed using an inertial measurement unit. If the reckoned displacement is less than the radius threshold, then the position confidence level is determined to be medium level. The first level includes the high level and the medium level, and the high level is higher than the medium level.

5. The method according to claim 4, characterized in that, If the location confidence level is Level 1, then a low-Earth orbit (LEO) satellite search is performed using locally stored LEO satellite ephemeris data, including: Calculate the predicted pointing angle of low-Earth orbit satellites using locally stored low-Earth orbit satellite ephemeris data; If the location confidence level is the high level, then a low-orbit satellite search is performed using the first timeout threshold and the first search range corresponding to the predicted pointing angle; If the location confidence level is medium, then a low-orbit satellite search is performed using a second timeout threshold and a second search range, wherein the second timeout threshold is less than the first timeout threshold and the second search range is greater than the first search range.

6. The method according to claim 1, characterized in that, The step of re-searching for low-Earth orbit satellites based on the updated low-Earth orbit satellite ephemeris and the auxiliary position information obtained from the high-Earth orbit satellites includes: Determine whether the auxiliary position information obtained from the high-orbit satellite is available; If available, a new low-Earth orbit satellite search is performed based on the updated low-Earth orbit satellite ephemeris and the auxiliary position information obtained from the high-Earth orbit satellite. If unavailable, the constraint search window is determined using the displacement calculated by the inertial measurement unit with the historical location as the origin. The historical location includes the previous successful positioning result and / or the precise location sent down after being solved by the ground network. Perform a narrowband constraint blind search within the constraint search window.

7. The method according to claim 1, characterized in that, The high-orbit satellite is locked in the following manner: By scanning the beacon frequencies of multiple pre-stored high-orbit satellites, the current elevation angle and received signal strength of each high-orbit satellite can be obtained. The comprehensive score of each high-orbit satellite is calculated based on the current elevation angle and received signal strength. Select the high-orbit satellite with the highest overall score for downlink synchronization and lock it in.

8. The method according to any one of claims 1-7, characterized in that, The method further includes: After establishing operational communication with the target low-Earth orbit satellite, an uplink probe signal is sent. The system receives and stores the precise location transmitted from the ground network side. The precise location is obtained by the ground network side using the time difference of arrival and frequency difference of arrival measured by the signals received from multiple low-orbit satellites, combined with the beam coverage area of ​​the high-orbit satellite and the downlink synchronization delay as prior constraints.

9. The method according to claim 8, characterized in that, The auxiliary location information includes the actual center position of the beam coverage area corresponding to the high-orbit satellite. The actual center position is obtained by the satellite terminal according to the location mapping table on the ground network side. The location mapping table stores the correspondence between beam identifiers and position correction amounts. The actual center position is the sum of the position correction amount and the theoretical center position of the beam coverage area corresponding to the high-orbit satellite. The position correction amount is obtained by the ground network side by comparing the precise position of each satellite terminal with the theoretical center position of the beam coverage range of the high-orbit satellite corresponding to the satellite terminal to obtain the deviation vector, classifying the deviation vector according to the beam, and clustering the classified deviation vector.

10. The method according to claim 1, characterized in that, The method of using locally stored low-Earth orbit satellite ephemeris for low-Earth orbit satellite search includes: Use locally stored low-Earth orbit satellite ephemeris to identify candidate low-Earth orbit satellites that are visible at the current time and have an elevation angle greater than a set angle; The candidate low-Earth orbit satellites are sorted according to priority; Point the antenna at the predicted pointing angle of the highest priority low-Earth orbit satellite and search within the corresponding range.

11. An electronic device, characterized in that, It includes a processor and a memory, the memory storing computer-readable instructions that, when executed by the processor, perform the method as described in any one of claims 1-10.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it performs the method as described in any one of claims 1-10.

13. A computer program product, characterized in that, It includes computer program instructions, which, when read and executed by a processor, perform the method as described in any one of claims 1-10.

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