Communication system and method based on low earth orbit satellite

Abstract

A low earth orbit satellite (LEO)-based communication system and method. The system comprises a low-orbit satellite constellation, a ground station, a user terminal and a network management and control center. The network management and control center comprises a track and link prediction module, a link quality prediction and evaluation module, a predictive resource pre-allocation and dynamic adjustment module and a space-ground cooperative control module. According to the communication system, active resource optimization and dynamic adjustment before actual switching are realized through track and link prediction, link quality prediction, predictive resource pre-allocation and dynamic adjustment and air-ground cooperative control. According to the method, the switching time delay can be greatly reduced, the packet loss rate is remarkably reduced, and the system throughput and the access success rate are also remarkably improved. Through predictive management, the performance, reliability and user experience of LEO communication are comprehensively improved.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a communication system and method based on a low Earth Orbit (LEO) satellite. Background Art

[0002] Low-Earth Orbit (LEO) satellite communications networks are increasingly becoming a critical component of global communications infrastructure due to their unique advantages. Compared to traditional geosynchronous earth orbit (GEO) satellites, LEO satellites are closer to the Earth, significantly reducing signal propagation latency and providing higher bandwidth and regional capacity. This low latency gives LEO satellite communications great potential in delivering an experience close to that of terrestrial fiber networks. This is particularly true in the 5G and 6G eras, where satellite communications are seen as a crucial component in achieving seamless global coverage and the interconnectedness of everything.

[0003] Low-Earth Orbit (LEO) satellite communication networks, with their inherent advantages of low latency and high bandwidth, are playing an increasingly important role in building integrated space-ground information networks. Compared to traditional geosynchronous earth orbit (GEO) satellites, LEO satellites, due to their lower orbital altitude, significantly reduce communication latency. This performance improvement enables LEO satellite networks to support latency-sensitive real-time applications such as online gaming, high-definition video streaming, and VoIP calls.

[0004] However, despite the broad application prospects of LEO satellite communications, their inherent high dynamics also bring significant technical challenges. The high-speed movement of satellites causes frequent changes in the link relationship between the satellite and the ground terminal (User Terminal, UT) or ground station (Gateway Station, GS), which in turn triggers frequent handover events. This dynamic environment poses a severe test to the network's resource management, service quality assurance, and the adaptability of transmission protocols. Currently, the general challenge facing the industry is how to ensure communication continuity, reduce data transmission interruptions and packet loss, and effectively utilize limited spectrum and power resources in such a highly dynamic environment. Solving these fundamental problems is the key to fully realizing the potential of LEO satellite communications and is also a strategic requirement for promoting global connectivity and the development of the digital economy.

[0005] The high-speed motion of low-Earth orbit satellites (several thousand meters per second) presents inherent challenges. This causes satellite beams to rapidly pass over the ground, leading to dynamic changes in network connectivity and frequent handoffs. This high dynamics is a major issue for existing LEO networks, resulting in a series of performance bottlenecks. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides a low-orbit satellite-based communication system, the system comprising: a low-orbit satellite constellation, a ground station, a user terminal, and a network management and control center; wherein the control system of the network management and control center comprises: an orbit and link prediction module, a link quality prediction and evaluation module, a predictive resource pre-allocation and dynamic adjustment module, and a ground-ground coordinated control module; The orbit and link prediction module calculates the precise position and velocity of the satellite constellation over a period of time in the future; calculates the geometric relationship between the satellite constellation and the ground station or terminal, and predicts it as a potential switching point; The link quality prediction and evaluation module is used to predict the quality of the link and predict the link status change; The predictive resource pre-allocation and dynamic adjustment module proactively performs optimized pre-allocation and dynamic adjustment of communication resources before actual handover occurs based on the precise position and speed of the satellite constellation in the future, the potential handover point, the quality of the link, and the change in the state of the link; The space-ground collaborative control module is used to ensure that predictive resource allocation decisions can be synchronized and executed among the satellite constellation, the ground station and the terminal.

[0007] Preferably, the orbit and link prediction module uses the International Celestial Reference System, combined with the satellite's Kepler orbit parameters and high-precision timestamp, to accurately calculate the satellite's precise position and velocity in the future through the SGP4 / SDP4 model; based on the predicted position of the satellite constellation and the specific position of the ground station or the terminal, the geometric relationship between the two is calculated, and when the elevation angle is lower than a preset threshold or the satellite is about to leave the service area, it is predicted as a potential switching point.

[0008] Preferably, before the actual switching occurs, the communication resources are proactively optimized, pre-allocated, and dynamically adjusted as follows: when it is predicted that a switching is about to occur, necessary communication resources are reserved and configured in advance for the target satellite or target link; in combination with the multi-beam dynamic characteristics of the satellite constellation, the beam direction and power are dynamically adjusted according to the terminal's position and the predicted link quality to optimize signal coverage and anti-interference capability; when it is predicted that the current path may be interrupted or the performance may degrade, an alternative path is calculated and established in advance; in combination with the potential switching point, the quality of the link, and the state change of the link, the transport layer protocol is notified of the impending switching event.

[0009] Preferably, the quality of the link is the link delay, packet loss rate and bandwidth.

[0010] Preferably, the ground-space collaborative control module is used to ensure that the predictive resource allocation decision can be synchronized and executed among the satellite constellation, the ground station and the terminal. Specifically, the network management and control center is responsible for collecting the ephemeris of the satellite constellation of global satellites, the location information of the ground station, the location information of the terminal, network load and performance data, and distributes the prediction information and resource allocation instructions to relevant satellites, relevant ground stations and relevant terminals through satellite-to-ground links or inter-satellite links. The relevant satellites, the relevant ground stations and the relevant terminals adjust their communication parameters and behaviors according to the received instructions.

[0011] The present invention also provides a communication method based on a low-orbit satellite communication system, the method comprising the following steps: Step S1: Calculate the precise position and velocity of the satellite constellation over a period of time in the future; calculate the geometric relationship between the satellite constellation and the ground station or the terminal, and predict a potential switching point; Step S2: predicting the quality of the link and the state change of the link; Step S3: proactively performing optimized pre-allocation and dynamic adjustment of communication resources before actual handover occurs based on the precise position and velocity of the satellite constellation in the future, the potential handover point, the quality of the link, and the change in the link state; Step S4: The network management and control center sends resource allocation instructions and switching warning information to relevant satellites, relevant ground stations and relevant user terminals through the control channel; the relevant satellites, the relevant ground stations and the relevant terminals adjust their communication parameters and behaviors according to the received instructions, and perform predictive resource allocation and switching.

[0012] Preferably, in step S1, the International Celestial Reference System is used, combined with the satellite's Kepler orbit parameters and high-precision timestamp, to accurately calculate the precise position and velocity of the satellite in the future through the SGP4 / SDP4 model; based on the predicted position of the satellite constellation and the specific position of the ground station or the terminal, the geometric relationship between the two is calculated, and when the elevation angle is lower than a preset threshold or the satellite is about to leave the service area, it is predicted as a potential switching point.

[0013] Preferably, in step S2, the quality of the link is the link delay, packet loss rate and bandwidth.

[0014] Preferably, in step S3, when it is predicted that a switch is about to occur, necessary communication resources are reserved and configured in advance for the target satellite or target link; in combination with the multi-beam dynamic characteristics of the satellite constellation, the beam direction and power are dynamically adjusted according to the terminal position and the predicted link quality to optimize signal coverage and anti-interference capability; when it is predicted that the current path may be interrupted or the performance degraded, an alternative path is calculated and established in advance; in combination with the potential switching point, the quality of the link and the state change of the link, the transport layer protocol is notified of the impending switching event.

[0015] Preferably, in step S4, the network management and control center is responsible for collecting the ephemeris of the satellite constellation of global satellites, the location information of the ground station, the location information of the terminal, network load and performance data, and distributing the prediction information and resource allocation instructions to relevant satellites, relevant ground stations and relevant terminals through satellite-to-ground links or inter-satellite links. The relevant satellites, the relevant ground stations and the relevant terminals adjust their communication parameters and behaviors according to the received instructions.

[0016] Compared with the existing technical solutions, the present invention has at least the following beneficial effects: 1) This invention transforms the reactive handoffs common in existing technologies into predictive, seamless handoffs by predicting and pre-allocating resources. This means that new links and resources are ready before link quality degrades or is interrupted, significantly reducing data interruptions and link reconfiguration time during the handoff process, and significantly reducing end-to-end communication latency. For example, this invention can reduce handoff latency from 250 milliseconds in existing solutions to under 20 milliseconds, enabling users in low-orbit satellite networks to enjoy a real-time communication experience closer to that of terrestrial fiber-optic networks. 2) By predictively establishing backup links, optimizing transmission paths, and combining "handoff awareness" optimization of the transport layer protocol, the present invention effectively avoids packet loss caused by link interruptions or transport layer protocol misjudgment of handoff events. In traditional systems, packet loss caused by handoffs is often misjudged by the transport protocol as congestion, resulting in unnecessary retransmissions and reduced throughput. Through early warning and adjustment, the present invention can reduce the packet loss rate during handoffs from the existing 5-15% to below 1%, significantly improving the reliability and efficiency of data transmission. 3) By dynamically and on-demand pre-allocation and adjustment of communication resources such as frequency, time slots, power, and beams, this invention enables more precise and timely matching of dynamically changing service demands. This avoids idle resources or localized congestion, significantly improving overall network throughput and user access success rates. For example, simulation results show that this invention can increase system throughput by 20-50% and achieve access success rates exceeding 98%, which is crucial for the cost-effective operation of large-scale LEO constellations. 4) Comprehensively reduce latency and packet loss, enabling users to enjoy more stable, smooth, and high-quality communication services in low-orbit satellite networks. This is particularly critical for applications with high real-time requirements (such as online gaming, HD video calls, and telemedicine), significantly improving user satisfaction. By shifting network management from reactive to proactive, this invention fundamentally addresses the performance challenges posed by the highly dynamic nature of LEO networks, providing users with seamless, imperceptible connectivity. 5) Predictive response to link changes and potential failures empowers the network with greater adaptability and self-healing capabilities, improving overall system resilience. Even in complex dynamic environments, the network ensures normal communication through pre-planned resource allocation and routing adjustments, thereby enhancing the overall resilience and robustness of the network. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 1 is a schematic diagram of the system architecture of a predictive resource allocation method based on low-orbit satellite communications provided by the present invention; Figure 2 is a flow chart of the predictive resource allocation method of the present invention.

[0018] The present invention is further described in detail below. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0020] Example 1 like Figure 1 As shown, the low-orbit satellite communication system provided by the present invention includes: a network management and control center 1, a ground station 2, a low-orbit satellite constellation 3, and a user terminal 4.

[0021] Low Earth Orbit Satellite Constellation 3: This includes multiple low-orbit communications satellites, such as those in a Walker or polar orbit configuration. Each satellite is capable of inter-satellite links (ISLs) and satellite-to-ground links (including user and feeder links) and integrates the prediction module and resource allocation module of the present invention. The number of satellites can range from hundreds to thousands.

[0022] Gateway Stations (GS): These connect the satellites to the terrestrial internet backbone and are capable of exchanging data and controlling signaling with the satellites. The deployment of GSs must be optimized based on the constellation configuration and service distribution to maximize system capacity and throughput.

[0023] User Terminal 4 (UT): This terminal has the ability to communicate with low-orbit satellites and can be a fixed terminal, mobile terminal, or IoT device. The terminal should be able to receive and process prediction information and adjust its own communication behavior in response to instructions from the network management center.

[0024] Network Management and Control Center (NMCC): This can be deployed centrally or distributed and is the core control entity of this invention. The NMCC is responsible for collecting information such as global satellite ephemeris, ground terminal locations, network load, and link quality. It runs core prediction and resource allocation decision-making algorithms and distributes decision instructions to satellites and ground stations. This center can be implemented based on a software-defined networking (SDN) architecture to provide more flexible network management and control capabilities. The synergy between this intelligent network and lightweight terminals is key to achieving seamless wide-area access and adaptive transmission.

[0025] like Figure 2 As shown, the present invention provides a low-orbit satellite communication method that can significantly reduce switching delay and packet loss rate, improve system resource utilization and overall communication performance, and the method includes the following steps: Step S1: prediction of tracks and links; Step S11: Satellite constellation orbit prediction uses the International Celestial Reference System (ITRS) or similar coordinate systems, combined with the satellite's Keplerian orbit parameters (semi-major axis, eccentricity, orbit inclination, ascending node right ascension, argument of perigee, true anomaly) and high-precision timestamps, to accurately calculate the satellite's precise position and velocity over a period of time in the future (e.g., minutes to hours). This prediction utilizes the inherent predictability of satellite motion and provides basic data for subsequent link prediction.

[0026] Step S12: Link visibility and handover point prediction. Based on the predicted positions of the satellite and ground station / terminal, the geometric relationship between them is calculated, including distance and elevation angle. When the elevation angle falls below a preset threshold (e.g., 10 degrees) or when the satellite is about to leave the service area, it is predicted as a potential handover point. This allows the system to perform preprocessing and resource preparation before the actual handover occurs, avoiding the performance degradation associated with traditional reactive handovers.

[0027] Step S13: Link quality prediction, (1) Delay prediction, combining the predicted propagation distance (the propagation delay at the speed of light is about 1.8-3.6 milliseconds per trip, and the round trip is usually less than 10 milliseconds) and the network load prediction to estimate the end-to-end delay. In addition to the physical propagation delay, non-physical factors such as scheduling delay and processing delay must also be considered. (2) Packet loss rate prediction, considering the impact of link congestion, bit errors, and switching events on packet loss, combining historical data and real-time channel quality, using statistical models or machine learning algorithms to predict future packet loss rates. For example, spectrum efficiency and bit error rate are predicted based on the signal-to-noise ratio (SNR), and a more refined prediction is made based on the relationship between the fade margin and the elevation angle. (3) Bandwidth prediction, combining the link budget, channel conditions, and resource allocation strategy to predict the effective bandwidth that the link can provide.

[0028] Step S2: Predictive resource pre-allocation and dynamic adjustment; Step S21: The handover triggering method sets a prediction window (e.g., 500 milliseconds to 2 seconds before a handover occurs). When the track and link prediction module predicts that a handover event will occur within this window, the NMCC immediately initiates the pre-allocation process. This window should be long enough to complete resource allocation and notification, but not too long to waste resources or cause unnecessary reservations.

[0029] Step S22: Resource reservation and configuration method, (1) Frequency / time slot pre-allocation, before the predicted switching time arrives, the required frequency and time slot resources are allocated to the target satellite and target link in advance, reducing the resource negotiation time during the switching. This helps to ensure the smoothness of the switching and avoid resource conflicts and interruptions. (2) Power control and beamforming, based on the predicted link quality and terminal location, dynamically adjust the satellite transmission power and beam direction to ensure the continuity of signal strength and coverage during the switching process. For example, a directional antenna is used to achieve good spatial filtering and interference elimination. (3) Route pre-calculation and backup path establishment, when it is predicted that the current path is about to be disconnected, the backup routing path to the target satellite or ground station is calculated and established in advance, and can be pre-loaded into the routing table of the satellite or ground station. This enables the network to have dynamic networking and reconstruction capabilities to ensure normal network operation.

[0030] Step S23: Transport layer protocol optimization: The network management and control center notifies affected user terminals or ground stations of predicted handover event information (e.g., handover time, target satellite ID) via a control channel. Upon receiving the handover warning, the user terminal's or ground station's transport layer protocol (e.g., QUIC or TCP) can temporarily adjust its congestion control behavior (e.g., avoiding aggressive congestion window reductions within the handover window, or briefly pausing data transmission to avoid sudden packet loss) to avoid misinterpreting handover-induced packet loss as congestion. This "handover-aware" congestion control algorithm has been shown to significantly improve performance, for example, improving QUIC completion time by 35%.

[0031] Step S3: Space-ground coordinated control Step S31: Data collection and update: NMCC continuously collects data such as satellite ephemeris, ground terminal location, network load, link quality, etc., and updates them in real time.

[0032] Step S32: Track and link prediction: The track and link prediction module runs in the NMCC, predicts all potential switching events and link states in the future, and outputs the prediction results.

[0033] Step S33: Link quality assessment: The link quality prediction and assessment module assesses and predicts future link quality based on the track and link prediction results and real-time monitoring data, and generates a detailed link quality report.

[0034] Step S34: Resource allocation decision, the predictive resource pre-allocation and dynamic adjustment module generates a resource pre-allocation and dynamic adjustment plan based on the prediction results and link quality report, combined with preset optimization goals (such as minimizing latency, minimizing packet loss rate, and maximizing throughput).

[0035] Step S35: Instruction issuance: The NMCC issues resource allocation instructions and handover warning information to relevant low-orbit satellites, ground stations and / or user terminals via a control channel (such as in-band or out-of-band signaling).

[0036] Step S36: Execution and Feedback: LEO satellites, ground stations, and user terminals adjust their communication parameters and behaviors based on the received commands, executing predictive resource allocation and handover. The system continuously monitors actual performance and feeds this data back to the NMCC, which optimizes the prediction model and resource allocation strategy, forming a closed-loop control loop and achieving continuous performance improvement.

[0037] The present invention can achieve the following significant beneficial technical effects through the above technical solution: 1. Significantly Reduced Handover Latency: This invention transforms the reactive handover common in existing technologies into predictive, seamless handover by predicting and pre-allocating resources in advance. This means that new links and resources are ready before link quality degrades or is interrupted, significantly reducing data interruption and link reconstruction time during the handover process and significantly reducing end-to-end communication latency. For example, this invention can reduce handover latency from 250 milliseconds in existing solutions to less than 20 milliseconds, allowing users in low-orbit satellite networks to enjoy a real-time communication experience closer to that of terrestrial fiber optic networks.

[0038] 2. Significantly reduce packet loss rate: By predictively establishing backup links, optimizing transmission paths, and combining the "handoff perception" optimization of the transport layer protocol, the present invention effectively avoids packet loss caused by link interruption or misjudgment of handoff events by the transport layer protocol. In traditional systems, packet loss caused by handoffs is often misjudged by the transport protocol as congestion, resulting in unnecessary retransmissions and reduced throughput. Through early warning and adjustment, the present invention can reduce the packet loss rate during handoffs from 5-15% in the prior art to below 1%, thereby significantly improving the reliability and efficiency of data transmission.

[0039] 3. Improved system resource utilization: This invention dynamically and on-demand pre-allocates and adjusts communication resources such as frequency, time slots, power, and beams, enabling more precise and timely matching of dynamically changing service demands. This avoids idle resources or localized congestion, significantly improving overall network throughput and user access success rates. Simulation results show that this invention can increase system throughput by 20-50% and achieve access success rates exceeding 98%, which is crucial for the cost-effective operation of large-scale LEO constellations.

[0040] 4. Improved User Experience: Comprehensively reducing latency and packet loss, users experience more stable, smooth, and high-quality communication services within low-orbit satellite networks. This is particularly critical for applications requiring high real-time performance, such as online gaming, HD video calls, and telemedicine, significantly improving user satisfaction. By shifting network management from reactive to proactive, this invention fundamentally addresses the performance challenges posed by the highly dynamic nature of LEO networks, providing users with seamless, imperceptible connectivity.

[0041] 5. Enhanced network resilience and robustness: Predictive responses to link changes and potential failures empower the network with greater adaptability and self-healing capabilities, improving overall system resilience. Even in complex dynamic environments, the network ensures normal communication through pre-planned resource allocation and routing adjustments, enhancing overall network resilience and robustness.

[0042] In order to verify the effectiveness of the predictive resource allocation method proposed in this invention, a detailed simulation experiment was carried out.

[0043] Simulation environment and parameters: Simulation Tools: MATLAB, STK (Satellite Tools Kit), and a professional satellite network simulation platform were used to build the simulation environment. These tools can simulate large-scale network nodes and real-world traffic processing tasks. Their efficient multi-threaded task scheduling mechanism improves CPU utilization, significantly reducing simulation time.

[0044] Constellation configuration: A typical low-orbit satellite Walker constellation or polar orbit constellation is used, with the number of satellites set to 1,000, the orbit altitude to 550 km, and the orbit inclination to 90°.

[0045] Ground station deployment: 20 ground stations are set up around the world, and their geographical distribution is optimized to maximize system throughput.

[0046] Service model: This model simulates mixed service traffic, including web browsing (sensitive to latency), HD video streaming (sensitive to bandwidth and packet loss), VoIP (sensitive to both latency and packet loss), and online gaming (extremely sensitive to latency). The traffic load is set to medium to high to fully demonstrate the challenges of resource allocation.

[0047] Channel model: It takes into account factors such as atmospheric attenuation, rain attenuation, Doppler frequency shift and multipath fading, and introduces a model in which the fading margin is related to the elevation angle.

[0048] Comparison benchmarks: Typical reactive switching mechanisms and non-predictive resource allocation methods in existing technologies are selected as comparison benchmarks, such as routing metrics based on minimum hop count, random beam hopping (random-BH), or traditional genetic algorithms.

[0049] Simulation performance indicators: (1) Switching delay: the time from the disconnection of the old link to the establishment of the new link and the resumption of data transmission, in milliseconds (ms); (2) Packet loss rate: the percentage of data packets lost during data transmission to the total number of data packets sent (%); (3) System throughput: the amount of effective data passing through the network per unit time, in Gbps; (4) Access success rate: the rate at which user terminals successfully access the network (%).

[0050] Simulation results and analysis: Table 1 Comparison between the prior art and the present invention As shown in Table 1, the present invention significantly reduces handover latency to below 20 milliseconds through predictive pre-allocation and space-ground coordinated control. This significantly improves performance compared to existing optimization solutions (e.g., the average of 20.87 milliseconds proposed in [1]. This significant latency reduction is crucial for applications with extremely high real-time requirements, such as online gaming and video conferencing. It brings the user experience closer to that of terrestrial fiber networks and significantly enhances the service quality of LEO satellite communications. Through proactive prediction and resource preparation, the present invention avoids the additional latency incurred by link reconfiguration in traditional reactive handovers, achieving smooth and imperceptible handovers.

[0051] Simulation results show that the packet loss rate of the present invention during switching is significantly lower than that of the prior art. In existing LEO networks, a high packet loss rate is caused by link interruptions caused by frequent switching and the misjudgment of "false congestion" signals by the transport layer protocol. The present invention effectively avoids these problems by predictively establishing backup links, optimizing transmission paths, and combining the "switching awareness" optimization of the transport layer protocol. For example, by informing the transport protocol of an impending switching event, it can prevent it from unnecessarily reducing the congestion window or triggering a slow start. This improvement is crucial for applications that rely on transport protocols such as TCP / QUIC. It can significantly improve throughput and data transmission reliability, reduce data retransmission, and thus improve the overall network efficiency and the integrity of user data transmission.

[0052] The predictive resource allocation mechanism of the present invention enables communication resources such as frequency, time slots, power and beams to match dynamically changing business needs in a more refined and timely manner. In the prior art, due to the rapid changes in network topology and the reactive nature of resource allocation, resources are often idle or locally congested, thereby reducing overall resource utilization. The present invention avoids these inefficiencies by actively reserving and dynamically adjusting resources, thereby significantly improving the overall system throughput and user access success rate. For example, the system throughput can be increased by 20-50%, and the access success rate can reach more than 98%. This is consistent with the idea of ​​improving throughput and average delay through multi-dimensional resource allocation proposed in the prior art, verifying the effectiveness of the present invention in improving network capacity and efficiency, and is of great significance to the commercial operation and sustainable development of large-scale LEO constellations.

[0053] These simulation results fully demonstrate the significant advantages of the predictive resource allocation method proposed in this paper in addressing the highly dynamic nature of low-orbit satellite communication networks. By transforming the predictability of orbital motion into a preemptive advantage in network management, this method fundamentally improves the performance of LEO networks, enabling them to better meet the high-speed, low-latency, and high-reliability requirements of future global communications.

[0054] Example 2 The low-orbit satellite communication system provided in this embodiment includes: a low-orbit satellite constellation, a ground station, a user terminal, and a network management and control center; the control system of the network management and control center includes: an orbit and link prediction module, a link quality prediction and evaluation module, a predictive resource pre-allocation and dynamic adjustment module, and a ground-space collaborative control module.

[0055] The Orbit and Link Prediction module accurately predicts the relative motion between satellites, ground terminals (UTs), and ground stations (GSs), including satellite visibility, elevation angle changes, link establishment / disconnection times, and potential handover events (UT-satellite handovers, inter-satellite link (ISL) handovers). This module builds and runs a highly dynamic motion model based on satellite ephemeris data, orbital parameters, and high-precision clock synchronization. This module predicts all potential communication link state changes over a period of time (e.g., multiple handover windows within the next 15 seconds), including link availability, handover timing, and handover targets. By predicting the availability of inter-satellite links, the useful life of the current transmission path can be determined, providing a basis for triggering route reconfiguration in advance. This exploitation of satellite motion predictability is fundamental to the transition from reactive to proactive predictive management.

[0056] Specifically, the Orbit and Link Prediction Module (O&LPM) is responsible for continuously and accurately predicting the motion trajectory of low-orbit satellites during the operation of the communication system, and based on this, calculates the key geometric relationship between the satellite and the ground station or user terminal, and then identifies potential switching points.

[0057] 1. Accurate calculation of satellite constellation position and velocity: The O&LPM receives and processes the latest orbital elements from the satellite constellation (such as two-line elements (TLEs), Kepler orbital parameters, or other more accurate orbital data). Combined with high-precision orbital propagation models (e.g., the SGP4 / SDP4 models for short-term predictions of LEO satellites, or more complex numerical integration models for high-precision long-term predictions), it calculates the precise three-dimensional position (longitude, latitude, altitude) and velocity vector of each LEO satellite in real time for the next period (e.g., 5 minutes to several hours). This data forms the basis for all subsequent geometric calculations. To ensure accuracy, the O&LPM periodically updates the orbital elements from the satellite control center or external orbit data sources.

[0058] 2. Calculation of the geometric relationship between the satellite and the ground station / user terminal: Based on the acquired precise satellite position and velocity, and the geographical coordinates (longitude, latitude, altitude) of the ground station or user terminal, O&LPM calculates several geometric relationship parameters between the two: Elevation Angle calculation and threshold judgment: O&LPM continuously calculates the elevation angle of the satellite from the perspective of a ground station or user terminal. Elevation angle is a key metric for satellite visibility and link quality. When the satellite elevation angle falls below a preset elevation threshold, link quality typically degrades significantly, becoming susceptible to ground obstruction and atmospheric loss.

[0059] Elevation Angle Threshold Setting: In this embodiment, the elevation angle threshold can be set dynamically or statically based on the specific application scenario and system design requirements. For example, for services requiring high reliability, the elevation angle threshold can be set to 10°; for services that tolerate a certain level of link quality degradation, it can be set to 5°. When the calculated elevation angle falls below this threshold, O&LPM predicts this point in time as a potential handover point.

[0060] Calculation method: The elevation angle is usually calculated by calculating the angle between the vector pointing from the ground station / terminal to the satellite and the local horizontal plane.

[0061] Distance (Range) calculation and threshold judgment: O&LPM calculates the straight-line distance between the satellite and the ground station or user terminal. Distance directly affects the signal's free-space propagation loss. When the distance is too large, signal strength attenuates, resulting in reduced link quality.

[0062] Distance Threshold Setting: A distance threshold can be set based on the satellite's orbital altitude and the power budget for the communication link. For example, for a specific LEO constellation, link degradation may begin when the distance between the satellite and the ground station / terminal exceeds 2000 kilometers. When the calculated distance exceeds this threshold, O&LPM also predicts this point as a potential handover point.

[0063] Calculation method: The distance is calculated using the Euclidean distance formula between the three-dimensional coordinates of the satellite and the ground station / terminal.

[0064] Calculation of relative velocity and Doppler shift prediction: O&LPM calculates the relative velocity vector of the satellite relative to the ground station or user terminal. The high-speed motion of low-orbit satellites causes significant Doppler shift, affecting the frequency accuracy of the signal and requiring compensation.

[0065] Calculation method: The relative velocity is calculated from the vector difference between the satellite velocity vector and the ground station / terminal velocity vector (caused by the Earth's rotation).

[0066] Doppler shift prediction: Based on relative velocity and carrier frequency, the O&LPM predicts the Doppler shift value and its changing trend (i.e., the Doppler rate) over a period of time. For example, if the absolute value of the relative velocity continues to increase in a certain direction, the Doppler shift is predicted to continue to increase. This prediction provides key input for Doppler compensation in the subsequent link quality prediction module.

[0067] 3. Comprehensive prediction of potential switching points: O&LPM considers geometric parameters such as elevation angles falling below a threshold, distances exceeding a threshold, and significant Doppler shift changes (indicating an impending entry into an unavailable area or departure from the current optimal service area) to identify and mark potential future link handover windows or specific moments. These predicted potential handover points are then passed to the subsequent Link Quality Prediction and Assessment Module and the Predictive Resource Pre-allocation and Dynamic Adjustment Module as triggers for initiating the predictive resource management process.

[0068] The Link Quality Prediction and Assessment module, while predicting link status changes, is designed to assess and predict the quality of links to be established or currently in use. This module includes key performance indicators (KPIs) such as latency, packet loss rate, bandwidth, signal-to-noise ratio (SNR), fade margin, and elevation angle. This module combines real-time monitoring data (such as historical performance data and channel measurement information) with relative motion parameters output by the orbit and link prediction modules, using machine learning or statistical models to predict future link quality. This module considers the impact of Doppler shift on signal acquisition and transmission and predicts its changing trends to compensate for it. It also assesses link reliability, for example, by determining link conditions based on elevation angle, and predicts potential link degradation. By continuously monitoring and analyzing these indicators, the system can predict potential link degradation and trigger a timely switch to a more reliable link. This predictive capability provides a basis for subsequent resource pre-allocation decisions, ensuring effective resource allocation and link reliability.

[0069] The Predictive Resource Pre-allocation and Dynamic Adjustment Module (PRADA-M) is the core of this invention. It aims to proactively optimize and pre-allocate communication resources and dynamically adjust them before actual handover, based on trajectory and link prediction results and link quality predictions, to ensure seamless handover and efficient transmission. Its implementation includes: (1) Pre-allocation before switching: When a switching is predicted to occur (for example, a threshold time of several hundred milliseconds to several seconds is set before the switching occurs), the necessary communication resources (such as frequency, time slot, power, beam) are reserved and configured for the target satellite or target link in advance. This helps to reduce the resource negotiation time during the switching and achieve "smooth" switching, thereby avoiding the service interruption and performance degradation common in traditional reactive switching. (2) Dynamic beamforming and power control: Combining the dynamic characteristics of satellite multi-beams, the beam direction and power are dynamically adjusted according to the predicted terminal position and link quality to optimize signal coverage and anti-interference capabilities. For example, a directional antenna with high sidelobe suppression can achieve good spatial filtering effects and eliminate potential interference to other systems. (3) Multipath routing optimization: When it is predicted that the current path may be interrupted or the performance may degrade, an alternative path is calculated and established in advance and can be pre-loaded into the routing table of the satellite or ground station. This enables the network to have dynamic networking and reconstruction capabilities to ensure the normal operation of the network.

[0070] PRADA-M receives detailed output from the Orbit and Link Prediction Module (O&LPM), including the precise position and velocity of the satellite constellation over the coming period, potential switching points (for example, the time when the elevation angle is about to fall below a threshold or the distance is about to exceed a threshold), and link quality prediction results (such as delay, packet loss rate, bandwidth, SNR, fade margin, etc.) and link status change trends from the Link Quality Prediction and Evaluation Module (LQPE-M).

[0071] Unlike traditional "ad hoc access" or "reactive handover" mechanisms (which only initiate new link searches and resource allocation when link quality deteriorates or is interrupted), PRADA-M's core principle lies in its proactive and proactive nature. Leveraging predictive information, it proactively initiates resource pre-allocation within a preset threshold before the actual handover occurs (for example, within a window of 200 milliseconds to 2 seconds before a predicted link outage or handover, with the specific timeframe dynamically adjusted based on service sensitivity and link change rate).

[0072] Additionally, when PRADA-M predicts a potential handoff is about to occur, it performs the following optimized pre-allocation steps: Target Link Identification and Evaluation: Based on the best next visible satellite or optimal link path predicted by O&LPM, PRADA-M evaluates the predicted quality of the target link. If multiple potential links are available, the system selects the best link based on pre-defined optimization objectives (e.g., maximizing throughput, minimizing latency, ensuring a specific QoS).

[0073] Communication resource reservation and configuration: PRADA-M will issue instructions to other relevant functional modules of the network management and control center (such as spectrum management and scheduling modules) in advance to reserve and configure the required communication resources for the target link to be switched to. These resource types include but are not limited to: Frequency resources: Pre-allocation of specific carrier frequencies or frequency bands.

[0074] Time slot resource: A specific time slot is reserved in a TDMA (Time Division Multiple Access) system.

[0075] Power resources: Preconfigure transmit power levels to adapt to new link conditions.

[0076] Beam resources: Adjust the beam pointing and beam width of the satellite or ground station to ensure effective coverage and gain of the target link.

[0077] Code channel resources: Pre-assigned spreading codes in CDMA (Code Division Multiple Access) systems.

[0078] Network bandwidth: Reserve end-to-end bandwidth to support business continuity.

[0079] Pre-connection establishment: In some cases, PRADA-M can even attempt to establish a "soft" connection or auxiliary connection between the target link and the user terminal before the main link is disconnected, preparing for subsequent seamless handover.

[0080] After resource pre-allocation is complete, PRADA-M continuously monitors the match between the predicted information and the actual link status. If the actual link changes deviate from the prediction, PRADA-M will make real-time dynamic adjustments. This may include: Reallocation: Fine-tune or reallocate pre-allocated resources based on the latest link quality assessment or unexpected events (such as unexpected obstruction).

[0081] Priority adjustment: Rescheduling resources according to business priorities to ensure the continuity of critical business.

[0082] Feedback and correction: The adjustment results of PRADA-M will be fed back to O&LPM and LQPE-M to optimize future prediction models and algorithms, forming a closed-loop optimization.

[0083] Transport protocol optimization: This approach incorporates prediction information to notify transport layer protocols (such as TCP / QUIC) of impending handover events, preventing handover-induced packet loss from being misinterpreted as congestion, thereby avoiding unnecessary congestion window reductions and slow start. For example, by adopting the principles of StarTCP, transmission can be proactively paused during handovers to avoid sudden packet loss and false congestion signals. Simulation results show that such reconfiguration-aware modifications can significantly improve throughput or reduce latency.

[0084] The space-ground collaborative control module ensures that predictive resource allocation decisions are efficiently synchronized and executed across satellites, ground stations, and user terminals. This module is implemented by: The ground Network Management Center (NMCC) collects global satellite ephemeris, ground terminal location information, network load, and performance data. Predictive information and resource allocation instructions are distributed to relevant satellites and ground stations via satellite-to-ground or inter-satellite links. Satellites and terminals adjust their communication parameters and behavior based on the instructions received. Software-defined networking (SDN) architectures or similar centralized control planes are used for network management and resource scheduling, enabling more flexible control. This collaboration between intelligent networks and lightweight terminals is key to achieving seamless wide-area access and adaptive transmission for users. This collaborative control ensures the effective implementation of predictive decisions and forms a closed-loop system for continuous optimization.

[0085] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0086] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0087] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A communication system based on a low-orbit satellite, characterized in that: The system includes: a low-orbit satellite constellation, a ground station, a user terminal, and a network management and control center; wherein the control system of the network management and control center includes: an orbit and link prediction module, a link quality prediction and evaluation module, a predictive resource pre-allocation and dynamic adjustment module, and a ground-ground collaborative control module; The orbit and link prediction module calculates the precise position and velocity of the satellite constellation over a period of time in the future; calculates the geometric relationship between the satellite constellation and the ground station or the user terminal, and predicts a potential switching point; The link quality prediction and evaluation module is used to predict the quality of the link and predict the link status change; The predictive resource pre-allocation and dynamic adjustment module is used to proactively optimize pre-allocated communication resources based on predictions of link quality and state changes before actual handover occurs, so as to achieve seamless handover and continuity of communication services. The predictive resource pre-allocation and dynamic adjustment module proactively optimizes pre-allocation and dynamically adjusts communication resources before actual handover occurs based on the precise position and speed of the satellite constellation over a period of time in the future, the potential handover points, the quality of the links, and the state changes of the links. The space-ground collaborative control module is used to ensure that predictive resource allocation decisions can be synchronized and executed among the satellite constellation, the ground station and the terminal.

2. The system according to claim 1, wherein: The orbit and link prediction module uses the International Celestial Reference System, combined with the satellite's Kepler orbit parameters and high-precision timestamp, to accurately calculate the satellite's precise position and velocity over a period of time in the future through the SGP4 / SDP4 model; based on the predicted position of the satellite constellation and the specific position of the ground station or the terminal, the geometric relationship between the two is calculated. When the elevation angle is lower than a preset threshold or the satellite is about to leave the service area, it is predicted as a potential switching point.

3. The system according to claim 1, wherein: Before the actual switching occurs, the communication resources are proactively optimized, pre-allocated, and dynamically adjusted as follows: when a switching is predicted to occur, necessary communication resources are reserved and configured in advance for the target satellite or target link; in combination with the multi-beam dynamic characteristics of the satellite constellation, the beam direction and power are dynamically adjusted according to the terminal's location and predicted link quality to optimize signal coverage and anti-interference capabilities; when it is predicted that the current path may be interrupted or the performance may degrade, an alternative path is calculated and established in advance; and in combination with the potential switching point, the quality of the link, and the change in the state of the link, the transport layer protocol is notified of the impending switching event.

4. The system according to claim 1, wherein: The quality of the link is the link delay, packet loss rate and bandwidth.

5. The system according to claim 1, wherein: The space-ground collaborative control module is used to ensure that predictive resource allocation decisions can be synchronized and executed among the satellite constellation, the ground station and the terminal. Specifically, the network management and control center is responsible for collecting the ephemeris of the satellite constellation of global satellites, the location information of the ground station, the location information of the terminal, network load and performance data, and distributes the prediction information and resource allocation instructions to relevant satellites, relevant ground stations and relevant terminals through satellite-to-ground links or inter-satellite links. The relevant satellites, the relevant ground stations and the relevant terminals adjust their communication parameters and behaviors according to the received instructions.

6. A communication method based on a low-orbit satellite communication system, characterized in that: The system includes: a low-orbit satellite constellation, a ground station, a user terminal, and a network management and control center; and the method includes the following steps: Step S1: Calculate the precise position and velocity of the satellite constellation over a period of time in the future; calculate the geometric relationship between the satellite constellation and the ground station or the terminal, and predict a potential switching point; Step S2: predicting the quality of the link and the state change of the link; Step S3: proactively optimizing pre-allocation and dynamically adjusting communication resources before actual handover occurs based on the precise position and velocity of the satellite constellation over a period of time in the future, the potential handover point, the quality of the link, and the change in the link state, so as to achieve seamless handover and continuity of communication services. Step S4: The network management and control center sends resource allocation instructions and switching warning information to relevant satellites, relevant ground stations and relevant user terminals through the control channel; the relevant satellites, relevant ground stations and relevant terminals adjust their communication parameters and behaviors according to the received instructions and perform predictive resource allocation and switching.

7. The method according to claim 6, characterized in that: In step S1, the International Celestial Reference System is used, combined with the satellite's Kepler orbit parameters and high-precision timestamp, to accurately calculate the precise position and velocity of the satellite in the future through the SGP4 / SDP4 model; based on the predicted position of the satellite constellation and the specific position of the ground station or the terminal, the geometric relationship between the two is calculated, and when the elevation angle is lower than a preset threshold or the satellite is about to leave the service area, it is predicted as a potential switching point.

8. The method according to claim 6, wherein: In step S3, when it is predicted that a handover is about to occur, necessary communication resources are reserved and configured in advance for the target satellite or target link; in combination with the multi-beam dynamic characteristics of the satellite constellation, the beam direction and power are dynamically adjusted according to the terminal's position and the predicted link quality to optimize signal coverage and anti-interference capability; when it is predicted that the current path may be interrupted or the performance may degrade, an alternative path is calculated and established in advance; and in combination with the potential handover point, the quality of the link, and the state change of the link, the transport layer protocol is notified of the impending handover event.

9. The method according to claim 6, wherein: In step S2, the quality of the link is the link delay, packet loss rate and bandwidth.

10. The method according to claim 6, wherein: In step S4, the network management and control center is responsible for collecting the ephemeris of the satellite constellation of global satellites, the location information of the ground station, the location information of the terminal, network load and performance data, and distributing the prediction information and resource allocation instructions to relevant satellites, relevant ground stations and relevant terminals through satellite-to-ground links or inter-satellite links. The relevant satellites, the relevant ground stations and the relevant terminals adjust their communication parameters and behaviors according to the received instructions.

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