Low earth orbit satellite feeder link cross-gateway station handover control system and method

Abstract

The application discloses a low-orbit satellite feeder link cross-gateway station switching control system and method, wherein, in view of the drastic change of a low-orbit satellite link topology, the system monitors signal-to-noise ratio, bit error rate and elevation angle data in real time, predicts future link quality through an elevation angle change rate extrapolation, triggers switching in advance when the link quality is lower than a threshold, and realizes the upgrade from time-driven to prediction-driven. In order to eliminate synchronization mismatch, a target gateway station pre-compensates transmission delay and Doppler frequency offset based on ephemeris. A satellite synchronously constructs a second feeder backup link, and smoothly migrates data flow after route configuration is completed. In addition, the system has an abnormal rollback mechanism built-in to guarantee fault tolerance. The scheme realizes zero-interruption switching without terminal awareness, and significantly improves communication continuity and robustness.

Description

Technical Field

[0001] This invention relates to the field of low-Earth orbit satellite communication systems, and in particular to a control system and method for switching between gateway stations in a low-Earth orbit satellite feeder link. Background Technology

[0002] In low-Earth orbit satellite communication systems, the visible communication duration between a single satellite and a fixed ground gateway station is relatively short due to the limitations of satellite orbital motion characteristics. To ensure continuous connectivity of the satellite-to-ground feeder link, the satellite needs to sequentially establish, switch, and disconnect links with multiple ground gateway stations within a single orbital cycle, achieving uninterrupted data exchange through relay transmission from multiple gateway stations.

[0003] The existing traditional satellite-to-ground power supply link switching generally adopts a hard switching mechanism of "disconnect first and then reconnect". This switching mode has obvious technical defects. During the switching process, there will be a link interruption problem of several seconds to tens of seconds, which will directly lead to the interruption of satellite data transmission and the failure of service transmission continuity. This will significantly reduce the user service experience of the space-ground integrated communication system and cannot meet the needs of high-speed and stable communication services such as high-definition transmission and real-time communication.

[0004] To overcome the shortcomings of hard handover link interruption, existing technologies have proposed soft handover schemes for satellite feed links. Chinese patent document CN115882928A discloses a satellite soft handover scheme based on dual independent feed link payloads. This scheme achieves uninterrupted soft handover by configuring dual auxiliary feed antennas, dual radio frequency channels, dual baseband signal processing units, and dual onboard routing and switching units at the low-Earth orbit satellite end. Its core handover process is as follows: the satellite maintains normal communication between the first feed link and the source gateway station, pre-controlling the second feed link to align with the target gateway station and establishing the link; after the communication status of the second feed link stabilizes, the space-based network controller performs routing calculations and dynamically configures the forwarding table, achieving zero-latency handover at the routing layer; finally, the feed link connection of the original source gateway station is released, effectively solving the problems of link interruption and data loss in traditional hard handover and ensuring continuous operation of communication services.

[0005] Meanwhile, Chinese patent document CN114567366B also discloses a satellite feed link switching method, which can realize the automatic switching control of the satellite-to-ground feed link. However, this scheme only completes the basic link switching logic and does not involve core optimization mechanisms such as real-time perception and prediction of link quality and time-frequency synchronization compensation at the ground station. Its technical limitations are quite obvious.

[0006] Practical experience has shown that the existing soft handover technology solutions still have several technical shortcomings that urgently need to be addressed, as follows: First, the handover triggering mechanism is passive and rigid, with poor adaptability. Current mainstream soft handover solutions all trigger the handover process based on preset orbital time nodes, only achieving passive handover with a fixed timing, lacking the ability to perceive, monitor, and dynamically predict the real-time quality of the satellite-to-ground link. In actual low-Earth orbit satellite communication scenarios, the quality of the satellite-to-ground link is easily affected by multiple dynamic factors: dynamic changes in the atmospheric and ionospheric meteorological environment exacerbate wireless signal attenuation; inherent errors in satellite on-orbit attitude control can easily cause the feed antenna to deviate from the optimal communication orientation; and fluctuations in the operating status of ground gateway station equipment can cause a decrease in signal reception sensitivity. These dynamic interferences can lead to deviations between the actual link quality and the preset handover conditions. If the link quality deteriorates before the preset handover time, existing solutions cannot respond and adapt in advance, resulting in a significant drop in communication quality and even sudden communication interruptions. Furthermore, if the target gateway station fails to establish a link due to excessive service load or equipment malfunctions, existing technologies cannot perceive the fault status in real time and dynamically adjust the handover strategy, exhibiting poor fault tolerance.

[0007] Second, the lack of a synchronization and coordination mechanism at the ground gateway station results in incomplete optimization of handover latency. Existing soft handover solutions focus on the switching control logic of dual antennas and dual links at the satellite end, without adapting to the timing and frequency synchronization mechanisms of the ground gateway station. The high-speed on-orbit motion of low-Earth orbit satellites causes the communication transmission latency and Doppler frequency offset between the satellite and the ground gateway station to fluctuate dramatically. When the satellite elevation angle increases from 5° to 90°, the satellite-to-ground transmission latency can fluctuate by tens of milliseconds, and the radial velocity change causes rapid Doppler frequency offset synchronization drift. Current technologies lack real-time timing compensation and frequency pre-synchronization compensation mechanisms at the ground station, requiring user terminals to re-execute the time-frequency synchronization process after link handover. This synchronization process can take hundreds of milliseconds or even seconds, contradicting the core design goal of uninterrupted and low-latency soft handover, and thus failing to achieve seamless communication handover.

[0008] Third, the lack of a failover mechanism in handover results in insufficient system robustness and reliability. Existing soft handover solutions employ a unidirectional execution mechanism. If the target gateway station experiences link establishment failure or link anomalies, the handover is immediately deemed a failure, leading to an interruption of user communication links. This technical solution lacks automatic fallback capabilities after a handover failure, cannot quickly restore the communication link of the original gateway station, and also lacks a mechanism for searching and adapting to alternative gateway stations. Consequently, it suffers from insufficient fault tolerance in complex and dynamic on-orbit communication scenarios, resulting in poor overall system stability.

[0009] In summary, current low-Earth orbit (LEO) satellite feeder link switching technologies generally suffer from problems such as unintelligent switching triggering, poor adaptability to satellite-to-ground synchronization, and weak fault tolerance. These issues make it difficult to adapt to complex and dynamic LEO satellite communication scenarios. The industry urgently needs an adaptive soft handover technology solution that can proactively sense and predict link quality, support time and frequency pre-synchronization compensation at ground stations, and has the ability to intelligently back off in case of handover failure. Summary of the Invention

[0010] This invention provides a control system and method for cross-gateway handover of low-orbit satellite feed links, aiming to solve the problems of passive handover triggering mechanism, lack of link quality prediction capability, imperfect synchronization compensation at ground station end, and lack of failure back-off mechanism in existing soft handover schemes, and to achieve zero interruption, zero perception and no data loss during the feed link handover process.

[0011] This invention provides a low-Earth orbit satellite feed link inter-gateway handover control system, comprising: The first power supply link load is used to establish and maintain the initial data channel; The second power supply link load is used to build a backup data channel in parallel during the switching phase; The link quality real-time monitoring module is located between the satellite platform and the first feed link payload and the second feed link payload. It is used to collect the signal-to-noise ratio, bit error rate and satellite elevation angle data of the current link in real time and output them to the link quality prediction module. The link quality prediction module is electrically connected to the link quality real-time monitoring module. It is used to calculate the link quality parameters for future moments based on the trend of elevation angle change and generate a prediction report. The switching decision module is communicatively coupled to the link quality prediction module, the first satellite routing switching unit, and the second satellite routing switching unit, respectively. It is used to compare the prediction report with the preset threshold and output the switching trigger command to start the pre-synchronization compensation process. The space-based network controller is deployed between the satellite platform and the ground gateway station. It is used to receive handover trigger commands and perform routing calculations and forwarding table configurations to achieve uninterrupted data flow switching.

[0012] In one embodiment of the present invention, the first feed link payload includes a first feed antenna, a first radio frequency channel, a first baseband signal processing unit, and a first satellite routing and switching unit.

[0013] In one embodiment of the present invention, the second feed link payload includes a second feed antenna, a second radio frequency channel, a second baseband signal processing unit, and a second satellite routing and switching unit.

[0014] In one embodiment of the present invention, a satellite platform is also included for carrying two or more independently controllable feeder link payloads, wherein the feeder link payloads support simultaneous independent pointing and tracking of multiple ground gateway stations. Ground gateway stations are used to receive satellite downlink signals and perform pre-compensation alignment for transmission delay and Doppler frequency offset.

[0015] In one embodiment of the present invention, the ground gateway station includes: The source gateway station is configured as the gateway station currently providing services; The target gateway station is configured to be the gateway station that will take over.

[0016] In one embodiment of the present invention, it further includes: The operations control center is configured to be responsible for task planning and issuing switching instructions; The GPS / BeiDou receiver module is configured to ensure clock synchronization among all nodes.

[0017] This invention also provides a method for controlling cross-gateway handover of low-Earth orbit satellite feeder links, comprising: The signal-to-noise ratio, bit error rate, and satellite elevation angle data of the current feeder link are collected through the link quality real-time monitoring module. The link quality prediction module calculates the link quality parameters for future moments based on the changing trend of the satellite elevation angle data. The switching decision module compares the calculated link quality parameters with preset thresholds. When the prediction result is lower than the preset threshold, a switching trigger command is output. According to the switching trigger command, the second power supply link load is controlled to establish a communication connection with the target gateway station, while maintaining the communication connection between the first power supply link load and the source gateway station. The space-based network controller performs route calculations and forwarding table configurations to switch the data stream from the source gateway to the destination gateway. After confirming that the new link is operating stably, the load of the first feeder link is disconnected from the source signal station.

[0018] In one embodiment of the present invention, the step of using the link quality prediction module to estimate the link quality parameters for future times based on the changing trend of the satellite elevation angle data includes: Obtain the current satellite elevation angle and historical elevation angle change rate; Input the elevation angle change rate into a Kalman filter algorithm or a neural network prediction model; Output the predicted signal-to-noise ratio and bit error rate at a future preset time point.

[0019] In one embodiment of the present invention, it further includes: During the pre-link establishment process, the target gateway station performs frequency and phase pre-compensation based on the Doppler frequency offset prediction value and transmission delay prediction value issued by the space-based network controller. If the target gateway station fails to complete the link establishment attempt after the preset timeout period, the link establishment process is interrupted while maintaining the communication link with the source gateway station, and a switchover cancellation instruction is reported to the operation control center.

[0020] In one embodiment of the present invention, when the target gateway station fails to complete the link establishment attempt after a preset timeout period, the link establishment process is interrupted while maintaining the communication link with the source gateway station, and a handover cancellation instruction is reported to the operation control center, including: The system accumulates the number of failed chain establishment attempts and determines whether the maximum failure threshold has been reached. When the maximum failure threshold is reached, the system enters degrade mode and selects the gateway station with the strongest signal within the current visible range. Initiate an emergency chain establishment process and report multiple switchover failure alarms to the operations control center to await manual intervention and decision-making; After receiving the handover cancellation command, the operations control center reassesses the visibility range of the candidate gateway stations. Update the switching plan and point it to the new target gateway; The pre-built chain and route switching will be performed again in the new handover interval.

[0021] The present invention has the following beneficial effects: (1) This invention introduces a predictive triggering mechanism based on real-time link quality monitoring and trend prediction. Given the limited visibility window of low-Earth orbit satellites and the dynamic decay of link quality with elevation angle, this mechanism collects the current signal-to-noise ratio and bit error rate in real time, and inputs the elevation angle change rate into a linear extrapolation algorithm or Kalman filter model to calculate the link quality parameters at a preset time in the future. When the predicted signal-to-noise ratio falls below a preset threshold, the system will generate a predictive handover trigger signal in advance, upgrading the traditional fixed-time driven handover logic to an event-driven and prediction-driven collaborative mode. Thanks to this pre-triggered strategy, the system can detect the link deterioration trend more than ten seconds in advance and start the handover process, thereby effectively avoiding communication blockage caused by a sudden drop in link quality, compressing the interruption time caused by hard handover from hundreds of milliseconds to several seconds to zero, and substantially improving the handover success rate.

[0022] (2) Ground station-based timing and frequency pre-synchronization technology based on ephemeris: Due to the high-speed motion of the satellite causing continuous fluctuations in transmission delay and Doppler frequency offset, in order to achieve seamless time-frequency alignment between the onboard baseband and the target gateway station at the moment of handover, the target station pre-calls real-time ephemeris data during the handover preparation phase and calculates the spatial distance transmission delay and radial velocity Doppler frequency offset accordingly. By advancing the transmission time and delaying the reception time to correct the transmission and reception sequence, and simultaneously performing pre-compensation on the receiving local oscillator frequency based on the predicted frequency offset value, the system achieves pre-locking between the target node and the satellite signal. Thanks to this pre-synchronization operation, the user terminal does not need to re-execute the time-frequency synchronization process after the handover is completed, thereby ensuring zero interruption and zero loss of user data during the handover process, achieving a completely seamless handover for the terminal.

[0023] (3) Multi-level anomaly fallback and degradation handling mechanism: Once the target gateway station's link establishment attempt exceeds the preset timeout threshold, the system immediately interrupts the current link establishment process and maintains the existing communication link with the source gateway station, while simultaneously reporting a handover cancellation instruction to the operation control center. If the source link quality can still be maintained, the service continues until the next handover window; otherwise, if the source link can no longer be maintained or the cumulative number of link establishment failures reaches the maximum threshold, the system will switch to degradation mode, select the backup gateway station with the strongest signal in the current visible range to initiate emergency link establishment and request manual intervention. Through this hierarchical fault tolerance strategy, the system can avoid cascading link loss under abnormal conditions such as link establishment failure, route update timeout, or weather interference, ensuring the communication continuity and service robustness of the power supply link in complex environments.

[0024] (4) Scalable system architecture and adaptive compensation parameter configuration: To adapt to the transmission characteristics of different frequency bands and complex multi-station relay scenarios, this scheme not only supports the expansion of pre-synchronization compensation parameters from basic transmission delay and Doppler frequency offset to polarization angle compensation and atmospheric attenuation pre-correction, but also allows the dual-link architecture to be expanded into three or more sets of feeder links according to the satellite platform payload capacity. When the system operates in high-frequency bands such as Ka and Q / V or performs multi-gate relay tasks, this architecture can not only perform accurate pre-correction for frequency band-specific interferences such as rain attenuation and multipath effects, but also improve the flexibility of space resource scheduling by relying on multi-link redundancy, thereby greatly enhancing the universality and engineering implementation value of the technical solution in different orbital configurations and frequency band environments. Attached Figure Description

[0025] Figure 1 This diagram illustrates the overall architecture of a low-orbit satellite feed link cross-gateway switching control system according to an embodiment of the present invention. Figure 2 A flowchart of the predictive switching triggering judgment process in one embodiment of the present invention is shown; Figure 3 A schematic diagram illustrating the timing and frequency pre-synchronization principle at the ground station end in one embodiment of the present invention is shown; Figure 4 A timing diagram of dual-channel soft handover in one embodiment of the present invention is shown; Figure 5 A flowchart of a failure rollback mechanism in one embodiment of the present invention is shown. Detailed Implementation

[0026] In the following description, the invention is described with reference to various embodiments. However, those skilled in the art will recognize that the embodiments may be practiced without one or more specific details or with other alternatives and / or additional methods, materials, or components. In other instances, well-known structures, materials, or operations are not shown or described in detail so as not to obscure the inventive points of the invention. Similarly, for illustrative purposes, specific quantities, materials, and configurations are set forth to provide a comprehensive understanding of embodiments of the invention. However, the invention is not limited to these specific details.

[0027] In this invention, the various embodiments are merely intended to illustrate the solutions of the invention and should not be construed as limiting.

[0028] In this specification, references to "an embodiment" or "this embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. The phrase "in one embodiment" appearing throughout this specification does not necessarily refer to the same embodiment in all instances.

[0029] Furthermore, the numbering of the steps in the methods of the present invention does not limit the execution order of the method steps. Unless otherwise specified, the method steps may be executed in different orders.

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] Figure 1 The diagram shows the overall architecture of a low-orbit satellite feed link inter-gateway switching control system according to an embodiment of the present invention.

[0032] like Figure 1 As shown, in one embodiment of the present invention, the low-orbit satellite feeder link inter-gateway switching control system provided by the present invention is deployed on satellite platform 1 and ground system, and includes the following components: Upper part: The first feed link payload includes a first feed antenna 11, a first radio frequency channel 12, a first baseband signal processing unit 13, and a first spaceborne routing and switching unit 14. The second feed link payload includes a second feed antenna 21, a second radio frequency channel 22, a second baseband signal processing unit 23, and a second spaceborne routing and switching unit 24. Link quality real-time monitoring module 31: used to monitor the signal-to-noise ratio (SNR), bit error rate, and satellite elevation angle of the current link in real time; Link quality prediction module 32: Predicts link quality at future moments based on elevation angle change trends; Switching Decision Module 33: Based on the link quality prediction results and ground instructions, decides when to trigger the switchover.

[0033] The two power supply links are independently controllable, supporting simultaneous independent pointing and tracking of two gateway stations.

[0034] Ground section: Space-based Network Controller 51: Responsible for route calculation and overall network topology management; Source Gateway A41: The gateway currently providing services; Target Customs Station B42: The customs station that will take over soon; Operations Control Center 52: Responsible for task planning and issuing switching instructions.

[0035] GPS / BeiDou receiver module 34: to ensure high-precision clock synchronization among all nodes.

[0036] Satellite platform 1 serves as the core carrier, with a first feed link payload and a second feed link payload arranged in parallel on it. These two payloads are physically adjacent to each other to enable independent pointing and tracking of multiple ground gateway stations. The first feed link payload is cascaded from top to bottom with a first feed antenna 11, a first radio frequency channel 12, a first baseband signal processing unit 13, and a first onboard routing and switching unit 14. Similarly, the second feed link payload is configured with a second feed antenna 21, a second radio frequency channel 22, a second baseband signal processing unit 23, and a second onboard routing and switching unit 24. To achieve precise control of the link status, a real-time link quality monitoring module 31 is located between satellite platform 1 and the two sets of feed link payloads. It collects the current link's signal-to-noise ratio, bit error rate, and satellite elevation angle data in real time via a data bus and outputs the data to the link quality prediction module 32. The link quality prediction module 32 is electrically connected to the real-time link quality monitoring module 31 and is used to predict future link quality parameters based on the elevation angle change trend. The handover decision module 33 is communicatively coupled with the link quality prediction module 32 and the first and second onboard routing switching units. It compares the prediction report with preset thresholds and outputs a handover trigger command. Furthermore, the GPS / BeiDou receiver module 34 is deployed within the satellite platform 1, providing a unified clock reference for all nodes. On the ground side, the space-based network controller 51 is deployed between the satellite platform 1 and the ground gateway station, responsible for receiving the handover trigger command and performing routing calculations and forwarding table configurations; the operations control center 52 is responsible for macro-level mission planning and command issuance. The ground gateway station is specifically divided into the currently providing service source gateway station A41 and the target gateway station B42, which will take over the service. The entire system achieves uninterrupted data flow switching through the coordination of onboard dual-link parallelism and ground pre-compensation.

[0037] In another embodiment of the present invention, the low-orbit satellite feed link inter-gateway handover control method includes: S1, Real-time link quality awareness.

[0038] During communication between the satellite and source gateway A, the on-board link quality real-time monitoring module continuously monitors the following parameters: Real-time signal-to-noise ratio of the current link ( The sampling period is 50ms, and the trend of its changes is observed. Real-time bit error rate of the current link ( ); Real-time elevation angle of the satellite relative to source gateway A ( ) and its rate of change ( ).

[0039] Simultaneously, the expected link quality parameters of the target gateway station B are calculated using ephemeris, including: the elevation angle of the target gateway station B (…). ), expected signal-to-noise ratio ( ).

[0040] S2, Predictive switching trigger judgment.

[0041] like Figure 2 As shown, the switching decision module makes predictive judgments based on the real-time data obtained in step 1, according to the following rules: Current link quality trend prediction: Based on real-time elevation angle change rate and current elevation angle Extrapolation calculation Angle of elevation after seconds And thus predict Signal-to-noise ratio after seconds .

[0042] The above Using a pre-calibrated SNR-elevation mapping table Obtained by looking up a table or using an empirical formula. Calculation. Among them... is the SNR at the maximum communication angle, and k is the link loss coefficient (unit dB / °, obtained from the link budget calibration). The largest possible angle of faith. Substitute into the calculation to obtain .

[0043] like Below the preset link quality threshold If so, it is determined that a switch needs to be triggered in advance.

[0044] Current link bit error rate monitoring: If the current bit error rate Continuously exceeding the preset threshold Time exceeded (The default value is 1 second), then it is determined that the switch needs to be triggered in advance.

[0045] Target link availability assessment: If the target gateway station B has entered the satellite's line of sight (elevation angle) If the minimum elevation angle threshold (usually 5°) is exceeded and the current link quality is lower than expected, then a handover needs to be triggered.

[0046] When any of the above conditions are met, the system generates a predictive handover trigger signal, and the handover trigger time is specified. Determined according to the following rules: ; That is, take the earlier of the preset plan switching time and the predicted trigger time, where =Current time + (default =10 seconds, to ensure sufficient preparation time for the switchover.

[0047] S3, Ground station timing and frequency pre-synchronization.

[0048] like Figure 3 As shown, during the handover preparation phase (i.e. (From the time the switch is initiated until the actual switchover is executed), target gateway station B performs the following pre-synchronization operations based on ephemeris data: Transmission delay calculation and transmit / receive timing adjustment: Target gateway B calculates the transmission delay with the satellite based on real-time ephemeris data. : ; Where d is the spatial distance between the satellite and the target gateway B (calculated based on ephemeris), and c is the speed of light.

[0049] Target gateway B adjusts its send / receive start times accordingly: Send start time: ; Start time of reception: ; in A unified time reference is provided for all nodes (achieved through GPS / BeiDou time synchronization).

[0050] Doppler frequency offset calculation and frequency compensation: Target gateway station B calculates the Doppler frequency offset relative to the on-board reference point. : ; in The center frequency of the carrier. Let be the radial velocity of the satellite relative to the target gateway station B (calculated based on ephemeris, positive for direction and negative for distance), and c be the speed of light.

[0051] Based on this, target gateway B adjusts its transmit and receive frequencies to ensure that the transmit and receive frequencies of the on-board user links remain consistent during the handover, so that user terminals do not need to resynchronize frequencies after the handover.

[0052] Cooperative operation of source gateway station A: After receiving the handover preparation instruction, source gateway station A starts the data stream replication mode and synchronously mirrors the current user data stream to the cache queue of the space-based network controller to ensure data continuity during the routing handover; at the same time, it reduces the uplink transmission power to 80% of the rated value to reduce adjacent channel interference to the target gateway station B for link establishment.

[0053] S4, on-board dual-channel link establishment and routing switching.

[0054] like Figure 4 As shown, the uninterrupted soft handover is performed in the following order: The second feed link is pre-tracked and pointed towards the target gateway station B: The satellite controls the second feed antenna to point in the direction of the target gateway station B, completes antenna alignment and signal tracking, and enters staring tracking state.

[0055] The second power supply link establishes a link with the target gateway station B: the second baseband signal processing unit completes signal synchronization and link establishment with the target gateway station B.

[0056] Route handover preparation: Target gateway B reports the satellite-to-ground topology change information to the space-based network controller, and the space-based network controller completes route calculation and forwarding table configuration.

[0057] Route handover execution: The space-based network controller performs full network route propagation, switching all data paths from source gateway station A to target gateway station B. During this process, since the second link has been established in advance and pre-synchronization has been completed on the ground, the routing layer handover latency is less than 1ms (no user-perceived interruption).

[0058] Link release: After the second link is running stably and the route switching is confirmed (usually 20 seconds after the second link is established), the first feeder link is disconnected from the source station A.

[0059] The above steps are characterized by the following: during normal switching processes, no data caching is relied upon, and all data is forwarded in real time; only in abnormal rollback scenarios is the origin server data mirror enabled as a safety net to ensure uninterrupted user communication and no data loss.

[0060] S5, Failure rollback mechanism.

[0061] like Figure 5 As shown, if the following abnormal situations occur during the switching process, the rollback process will be initiated: Abnormal situation A: Target gateway B connection establishment timed out (from the start of connection establishment to the preset timeout threshold, default 10 seconds); Abnormal Situation B: The link quality of the target gateway station B does not meet the requirements (SNR is lower than the preset threshold, which is the default minimum requirement for communication). Abnormal situation C: The space-based network controller route update failed or timed out (the default timeout threshold is 5 seconds).

[0062] The rollback process is as follows: Interrupt the link establishment attempt with target gateway station B and release the second power supply link resources; Report the switchover failure event and the reason for the failure to the Operations Control Center; Maintain communication between the first feeder link and the source gateway station A. If the quality of the first link is still maintainable, continue to provide service until the next handover opportunity (i.e., when the satellite enters the line of sight of the next gateway station). Based on the current satellite location and gateway station status, the operations control center reassessed the candidate gateway stations and updated the switchover plan.

[0063] If the quality of the first link cannot be maintained (e.g., the satellite is about to leave the line of sight of the source gateway station A), the system triggers emergency mode: the link is directly disconnected and the breakpoint information is recorded, and communication is restored after the satellite enters the line of sight of the next gateway station.

[0064] Furthermore, if the link establishment fails again at the next candidate gateway after a rollback, the system will accumulate the number of failures. ;when (default When =3), the system enters degrade mode: it selects the gateway station with the strongest signal in the current visible range to initiate emergency link establishment, and reports a 'multiple handover failures' alarm to the operation control center, allowing for manual intervention and decision-making.

[0065] The basic solution of the present invention is as described above. Based on this, those skilled in the art can make the following improvements and modifications, all of which should fall within the protection scope of the present invention: (1) The link quality prediction algorithm is not limited to the linear extrapolation method based on the elevation angle change rate. More accurate prediction methods such as Kalman filtering and neural network prediction can also be used to improve the prediction accuracy.

[0066] (2) The parameters of pre-synchronization compensation are not limited to transmission delay and Doppler frequency offset, but may also include polarization angle compensation, atmospheric attenuation pre-correction, etc., to adapt to the transmission characteristics of different frequency bands (such as Ka band, Q / V band).

[0067] (3) In the failure fallback mechanism, when the quality of the first link cannot be maintained, it can further search for whether there are other available gateway stations nearby (such as gateway station C). If there are, it can directly transfer to gateway station C to avoid communication interruption.

[0068] (4) The system architecture of the present invention is not limited to two sets of power supply links, but can be expanded to three or more sets according to the satellite platform capabilities to support more complex multi-station relay scenarios.

[0069] In one specific embodiment of the present invention, it is assumed that a low-Earth orbit satellite passes through the line of sight of source gateway station A41 and target gateway station B42 in a certain orbit. The preset scheduled switching time is 12:00:00 (UTC time). The satellite is currently transmitting data through source gateway station A and is performing a 5-minute onboard baseband restart mission (Level I mission, interruption not allowed).

[0070] Step 1: Real-time link quality awareness.

[0071] Approximately 30 seconds before 12:00:00 (i.e., 11:59:30), the on-board link quality real-time monitoring module 31 continuously collected data: Current parameters: Source station A elevation angle =12°, rate of change =-0.5° / s (the satellite is moving away); Current signal-to-noise ratio =12dB; Current bit error rate =10⁻ 7 ; Target gateway station B parameters (based on ephemeris calculation): Target signal station B elevation angle =3° (about to enter the visible range); Link quality prediction module 32 extrapolates the elevation angle after 10 seconds: (10s)=12°-0.5° / s×10s=7°; Corresponding prediction signal-to-noise ratio (10s) = 8dB.

[0072] Preset link quality threshold =10dB.

[0073] Judgment result: (10s) = 8dB < 10dB, which satisfies the predictive triggering condition.

[0074] Step 2: Predictive triggering.

[0075] The switching decision module 33 generates a predictive trigger signal. =Current time + 10 seconds = 11:59:40.

[0076] =12:00:00.

[0077] =min(12:00:00,11:59:40)=11:59:40.

[0078] The system triggers the handover process 20 seconds before the scheduled handover time.

[0079] Step 3: Ground station pre-synchronization.

[0080] Between 11:59:40 and 12:00:00, target gateway B performs pre-synchronization: Based on ephemeris calculations, the current distance between the satellite and the host is d=1200km, and the transmission delay is... =1200km / 3×10 8 m / s ≈ 4ms. Target gateway B will advance its transmission time by 4ms and postpone its reception time by 4ms.

[0081] Radial velocity calculated based on ephemeris =2.5km / s (satellite is approaching), Doppler frequency offset =20GHz×(2.5km / s / 3×10 8 The frequency (m / s) is approximately 166.7 kHz. Target gateway B will compensate for the received frequency offset of 166.7 kHz.

[0082] Step 4: Dual-channel switching.

[0083] At 11:59:45, the satellite control second feed antenna 21 turned towards the target gateway station B and entered staring tracking.

[0084] At 11:59:55, the second power supply link was successfully established with the target gateway station B, and the target gateway station B reported that it was ready.

[0085] At 11:59:58, the space-based network controller 51 completed the route calculation and forwarding table configuration.

[0086] At 12:00:00, the space-based network controller performs a full-network route switch, changing the data flow from source gateway station A to target gateway station B, with a switchover latency of less than 1ms.

[0087] At 12:00:20, it was confirmed that the new link was operating stably, and the first power supply link was disconnected from the source signal station A.

[0088] Throughout the entire handover process, the spaceborne baseband reboot mission continued to execute, and user data was not interrupted or lost in any way. The handover process was completely imperceptible to ground users.

[0089] Step 5: Rollback in abnormal scenarios.

[0090] Assuming that in step 4, the link establishment at target gateway B times out (remains incomplete after more than 10 seconds): System interruption and attempt to establish a link with target gateway B; Report to Operations Control Center 52: "Target station link establishment timed out, switchover canceled"; The communication link with source gateway A is maintained. Since the elevation angle of source gateway A has dropped to 7°, it is expected that communication can still be maintained for about 25 seconds. The operations control center reassessed the situation and found that gateway station C would enter the line of sight in 20 seconds. The switchover plan was updated to "source gateway station A → gateway station C". The system executes the handover process again in the new handover zone.

[0091] In another specific embodiment of the present invention, it is assumed that when the elevation angle of source station A drops to 8°, the SNR suddenly decreases due to the multipath effect. The voltage dropped from 12dB to 7dB within 2 seconds. Upon reaching 10⁻³, the triggering condition is met, and the system initiates a switchover 18 seconds in advance. The link quality prediction module, based on the SNR-elevation angle mapping table, predicts that the SNR will drop to 6dB after 10 seconds, below... =10dB, confirming the necessity of handover. The target gateway station B has now reached an elevation angle of 15°, the link quality is good, and the handover is completed smoothly.

[0092] In another specific embodiment of the present invention, assuming that rainfall causes an additional 8dB loss in the link between the source and gateway stations A, the link quality prediction module corrects this loss by incorporating meteorological data. The system predicts that the SNR will drop to 5 dB after 5 seconds. The system triggers a handover to the target gateway station C, which is unaffected by rainfall, 12 seconds in advance. During the handover, the target gateway station C performs frequency pre-compensation based on the predicted Doppler frequency offset of 166.7 kHz to ensure frequency alignment at the moment of handover.

[0093] Although various embodiments of the invention have been described above, it should be understood that they are presented by way of example only and not as limitations. It will be apparent to those skilled in the art that various combinations, modifications, and alterations can be made without departing from the spirit and scope of the invention. Therefore, the breadth and scope of the invention disclosed herein should not be limited by the exemplary embodiments disclosed above, but should be defined solely by the appended claims and their equivalents.

Claims

1. A low-orbit satellite feeder link cross-gateway switching control system, characterized in that, include: The first power supply link load is used to establish and maintain the initial data channel; The second power supply link load is used to build a backup data channel in parallel during the switching phase; The link quality real-time monitoring module is located between the satellite platform and the first feed link payload and the second feed link payload. It is used to collect the signal-to-noise ratio, bit error rate and satellite elevation angle data of the current link in real time and output them to the link quality prediction module. The link quality prediction module is electrically connected to the link quality real-time monitoring module. It is used to calculate the link quality parameters for future moments based on the trend of elevation angle change and generate a prediction report. The switching decision module is communicatively coupled to the link quality prediction module, the first satellite routing switching unit, and the second satellite routing switching unit, respectively. It is used to compare the prediction report with the preset threshold and output the switching trigger command to start the pre-synchronization compensation process. The space-based network controller is deployed between the satellite platform and the ground gateway station. It is used to receive handover trigger commands and perform routing calculations and forwarding table configurations to achieve uninterrupted data flow switching.

2. The low-orbit satellite feeder link inter-gateway switching control system according to claim 1, characterized in that, The first feed link payload includes a first feed antenna, a first radio frequency channel, a first baseband signal processing unit, and a first satellite routing and switching unit.

3. The low-orbit satellite feed link inter-gateway switching control system according to claim 1, characterized in that, The second feed link payload includes a second feed antenna, a second radio frequency channel, a second baseband signal processing unit, and a second onboard routing and switching unit.

4. The low-orbit satellite feeder link inter-gateway switching control system according to claim 1, characterized in that, Also includes: A satellite platform for carrying two or more independently controllable feeder link payloads, wherein the feeder link payloads support simultaneous independent pointing and tracking of multiple ground gateway stations; Ground gateway stations are used to receive satellite downlink signals and perform pre-compensation alignment for transmission delay and Doppler frequency offset.

5. The low-orbit satellite feeder link inter-gateway switching control system according to claim 1, characterized in that, The ground gateway station includes: The source gateway station is configured as the gateway station currently providing services; The target gateway station is configured to be the gateway station that will take over.

6. The low-orbit satellite feeder link inter-gateway switching control system according to claim 1, characterized in that, Also includes: The operations control center is configured to be responsible for task planning and issuing switching instructions; The GPS / BeiDou receiver module is configured to ensure clock synchronization among all nodes.

7. A method for controlling cross-gateway handover of a low-orbit satellite feeder link, characterized in that, include: The signal-to-noise ratio, bit error rate, and satellite elevation angle data of the current feeder link are collected through the link quality real-time monitoring module. The link quality prediction module calculates the link quality parameters for future moments based on the changing trend of the satellite elevation angle data. The switching decision module compares the calculated link quality parameters with preset thresholds. When the prediction result is lower than the preset threshold, a switching trigger command is output. According to the switching trigger command, the second power supply link load is controlled to establish a communication connection with the target gateway station, while maintaining the communication connection between the first power supply link load and the source gateway station. The space-based network controller performs route calculations and forwarding table configurations to switch the data stream from the source gateway to the destination gateway. After confirming that the new link is operating stably, the load of the first feeder link is disconnected from the source signal station.

8. The low-orbit satellite feeder link cross-gateway handover control method according to claim 7, characterized in that, The link quality parameters for future moments, calculated by the link quality prediction module based on the changing trend of the satellite elevation angle data, include: Obtain the current satellite elevation angle and historical elevation angle change rate; Input the elevation angle change rate into a Kalman filter algorithm or a neural network prediction model; Output the predicted signal-to-noise ratio and bit error rate at a future preset time point.

9. The low-orbit satellite feeder link inter-gateway switching control method according to claim 7, characterized in that, Also includes: During the pre-link establishment process, the target gateway station performs frequency and phase pre-compensation based on the Doppler frequency offset prediction value and transmission delay prediction value issued by the space-based network controller. If the target gateway station fails to complete the link establishment attempt after the preset timeout period, the link establishment process is interrupted while maintaining the communication link with the source gateway station, and a switchover cancellation instruction is reported to the operation control center.

10. The low-orbit satellite feeder link cross-gateway handover control method according to claim 9, characterized in that, When the target gateway station fails to complete the link establishment attempt after a preset timeout period, the link establishment process is interrupted while maintaining the communication link with the source gateway station. Simultaneously, a handover cancellation command is reported to the operations control center, including: The system accumulates the number of failed chain establishment attempts and determines whether the maximum failure threshold has been reached. When the maximum failure threshold is reached, the system enters degrade mode and selects the gateway station with the strongest signal within the current visible range. Initiate an emergency chain establishment process and report multiple switchover failure alarms to the operations control center to await manual intervention and decision-making; After receiving the handover cancellation command, the operations control center reassesses the visibility range of the candidate gateway stations. Update the switching plan and point it to the new target gateway; The pre-built chain and route switching will be performed again in the new handover interval.

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