Satellite-ground communication data transmission method and system

Abstract

The invention provides a satellite-ground communication data transmission method and system, and the method comprises the steps: enabling a transmitting end to divide to-be-transmitted data into a plurality of data segments, packaging the data segments into a plurality of physical frames with unique and continuously increasing serial numbers, and continuously transmitting the plurality of physical frames in a transmitting window; the receiving end verifies the received physical frame and updates the receiving state bitmap based on a verification result; when a feedback condition is met, the receiving end generates an uplink feedback frame comprising a starting sequence number and a receiving state bitmap; a sending end receives an uplink feedback frame, identifies a physical frame needing to be retransmitted according to an initial sequence number and a receiving state bitmap, adds the physical frame needing to be retransmitted into a retransmission scheduling queue and performs selective retransmission, counts link quality indexes according to the uplink feedback frame, and dynamically adjusts the size of a sending window based on the link quality indexes. Therefore, continuous transmission and efficient feedback of multiple frames in a satellite-ground communication link can be realized, the channel utilization rate and the system throughput are improved, and the adaptability to a dynamic change link environment is enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser communication technology, and in particular to a method and system for data transmission in satellite-to-ground communication. BACKGROUND

[0002] As a key technology for space information transmission, satellite-to-ground laser communication has significant advantages in dealing with the explosive growth of space data due to its high bandwidth and strong anti-interference characteristics. However, when laser signals pass through the atmosphere, they are inevitably disturbed by factors such as atmospheric turbulence, cloud attenuation, and aerosol scattering, resulting in a dramatic fluctuation in link quality. During wide-area satellite-to-ground data transmission, when the satellite passes through different meteorological regions, extreme changes in local atmospheric seeing can cause link interruptions of several milliseconds to several seconds, resulting in the risk of real-time data loss and seriously affecting the data integrity of key services such as remote sensing observation and scientific exploration.

[0003] To ensure transmission reliability, existing systems generally use a "stop-and-wait" retransmission mechanism based on physical frames: the ground station checks each frame after receiving the downlink data and feeds back an acknowledgment signal through the uplink, and the satellite decides on retransmission based on the feedback. This mechanism has a fundamental flaw in the context of satellite-to-ground laser communication. The significant propagation delay caused by the long transmission distance results in a round-trip delay of 10-20 milliseconds for low-orbit satellites, and in the "stop-and-wait" mode, the sending end must wait for the acknowledgment signal after transmitting a single frame, causing the channel to be idle for a long time and seriously wasting the limited satellite overpass communication time. At the same time, the single-frame acknowledgment mechanism cannot adapt to the dynamic characteristics of the link, and when the atmospheric conditions deteriorate temporarily, the system falls into an inefficient "transmission-failure-retransmission" cycle and cannot take advantage of the subsequent window of good link quality for bulk recovery.

[0004] Therefore, how to improve channel utilization and system throughput, enhance the adaptability to dynamically changing link environments, and ensure the integrity and reliability of key data transmission is a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0005] The present application provides a method and system for data transmission in satellite-to-ground communication to improve channel utilization and system throughput, enhance the adaptability to dynamically changing link environments, and ensure the integrity and reliability of key data transmission.

[0006] In one aspect, the present application provides a method for data transmission in satellite-to-ground communication, comprising: The sending end divides the data to be transmitted into multiple data segments and encapsulates them into multiple physical frames with unique and continuously increasing sequence numbers, and continuously transmits the multiple physical frames within a sending window. The receiving end checks the received physical frame, and updates a receiving state bitmap based on a checking result; the receiving state bitmap contains the receiving state of the physical frame with multiple continuous serial numbers; The receiving end generates an uplink feedback frame including a starting serial number and the receiving state bitmap when a feedback condition is reached; The sending end receives the uplink feedback frame, identifies the physical frame to be retransmitted according to the starting serial number and the receiving state bitmap, adds the physical frame to be retransmitted into a retransmission scheduling queue and performs selective retransmission, and dynamically adjusts the size of the sending window based on a link quality index according to the uplink feedback frame.

[0007] In another aspect, the application also provides a satellite-ground communication data transmission system including a sending end and a receiving end; The sending end divides the data to be transmitted into multiple data segments and encapsulates the data segments into multiple physical frames with unique and continuously increasing serial numbers, and continuously sends the multiple physical frames within a sending window; The receiving end checks the received physical frame, and updates a receiving state bitmap based on a checking result; the receiving state bitmap contains the receiving state of the physical frame with multiple continuous serial numbers; The receiving end generates an uplink feedback frame including a starting serial number and the receiving state bitmap when a feedback condition is reached; The sending end receives the uplink feedback frame, identifies the physical frame to be retransmitted according to the starting serial number and the receiving state bitmap, adds the physical frame to be retransmitted into a retransmission scheduling queue and performs selective retransmission, and dynamically adjusts the size of the sending window based on a link quality index according to the uplink feedback frame.

[0008] The satellite-ground communication data transmission method and system provided by the application change the mode of single-frame transmission of the traditional "stop-and-wait" protocol by dividing and encapsulating the data to be transmitted into physical frames with unique and continuously increasing serial numbers through the sending end, and continuously sending the multiple physical frames within a sending window. Meanwhile, the receiving end updates a receiving state bitmap based on the checking result of the physical frame, and feeds back the starting serial number and the receiving state bitmap to the sending end in an uplink feedback frame when a feedback condition is reached, so that the sending end can accurately identify the physical frame to be retransmitted and perform selective retransmission, and can also dynamically adjust the size of the sending window according to the link quality index counted according to the uplink feedback frame. In this way, the continuous transmission and efficient feedback of multiple frames in the satellite-ground communication link are realized, the channel utilization and system throughput are effectively improved, the adaptability to the dynamically changing link environment is enhanced, and the integrity and reliability of the transmission of critical data are guaranteed. BRIEF DESCRIPTION OF DRAWINGS

[0009] In order to more clearly illustrate the technical solutions of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort based on these drawings.

[0010] Figure 1 is a flowchart of a satellite-ground communication data transmission method provided by an embodiment of the present application; Figure 2 is a structural diagram of a satellite-ground communication data transmission system provided by an embodiment of the present application. DETAILED DESCRIPTION

[0011] In order to make the objectives, technical solutions and advantages of the present application clearer, the following will combine the drawings in the present application to clearly and completely describe the technical solutions in the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort fall within the scope of protection of the present application.

[0012] It should be noted that similar reference numerals and letters indicate similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. Meanwhile, in the description of the present application, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0013] Figure 1 is a flowchart of a satellite-ground communication data transmission method provided by an embodiment of the present application.

[0014] As shown in Figure 1 , the satellite-ground communication data transmission method provided by the embodiment of the present application mainly includes the following steps: 101、The sending end divides the to-be-transmitted data into multiple data segments and encapsulates the multiple data segments into multiple physical frames with unique and continuously increasing sequence numbers, and continuously sends the multiple physical frames in a sending window; In one specific implementation, the operation of splitting the data to be transmitted into multiple data segments can be implemented in various ways. For example, a fixed length splitting method can be used to uniformly split the data stream according to a preset byte number; or a dynamic length splitting method can be used to dynamically adjust the length of each data segment according to the characteristics of the data content or real-time transmission requirements. Further, the process of encapsulating into multiple physical frames with unique and continuously increasing sequence numbers can be an operation of attaching identification information to the split data segments, where the generation of the sequence number can be implemented by a counter increment method, or by a timestamp or other unique identifier generation algorithm, so as to provide a basis for subsequent frame order tracking and loss detection.

[0015] In one specific implementation, each physical frame can include a packet header, a signaling segment, and multiple data segments. The management field contained in the frame header is an N-bit sequence number for the signaling area, which is globally unique and continuously increasing within a communication session period. For example, using a 32-bit sequence number can ensure that there is no wraparound problem under high-speed transmission.

[0016] 102. The receiving end checks the received physical frame, and updates the receiving status bitmap based on the checking result; In one specific implementation, the operation of the receiving end checking the received physical frame can be implemented by various technical means. For example, a cyclic redundancy check (CRC) algorithm can be used to verify the integrity of the physical frame; or a hash check algorithm can be used to determine whether the frame has been tampered with or damaged by calculating the hash value of the frame content and comparing it with the expected value. Further, the process of updating the receiving status bitmap based on the checking result can be a state mapping operation, where the receiving status bitmap contains the receiving status of multiple physical frames with consecutive sequence numbers, i.e. each bit of the receiving status bitmap corresponds to a physical frame with a specific sequence number, and its state value can be directly updated by logical operation, where 1 indicates that the physical frame has been successfully received, and 0 indicates that the physical frame has not been received or the check has failed. The main purpose of this design is to efficiently record the receiving status of multiple physical frames for subsequent centralized feedback.

[0017] 103. The receiving end generates an uplink feedback frame including a starting sequence number and the receiving status bitmap when the feedback condition is reached; In one specific implementation, the process of the receiving end generating an uplink feedback frame including a starting sequence number and a receiving status bitmap can be implemented in various ways. For example, the selection of the starting sequence number can be based on the smallest unacknowledged sequence number of the current receiving window; the encoding of the receiving status bitmap can optimize the storage space by using compression algorithms, such as run-length encoding or differential encoding techniques.

[0018] 104. The transmitting end receives the uplink feedback frame, identifies the physical frames that need to be retransmitted based on the starting sequence number and the receiving status bitmap, adds the physical frames that need to be retransmitted to the retransmission scheduling queue and performs selective retransmission, and calculates the link quality index based on the uplink feedback frame, and dynamically adjusts the size of the sending window based on the link quality index.

[0019] In one specific implementation, after receiving the uplink feedback frame, the transmitting end can perform parsing and matching operations based on the starting sequence number and the receive status bitmap to identify the physical frames that need to be retransmitted. The physical frames that need to be retransmitted can be quickly located using bits with a value of zero in the bitmap. In this way, the physical frames that need to be retransmitted can be added to the retransmission scheduling queue for selective retransmission.

[0020] Furthermore, the transmitting end can also statistically analyze link quality indicators based on uplink feedback frames and dynamically adjust the size of the transmitting window based on these indicators. This allows for intelligent adaptation to dynamic interference such as atmospheric turbulence, enabling the window to quickly shrink to maintain stability when the link deteriorates and gradually expand to increase throughput when the link improves. The dynamic adjustment of the transmitting window size is implemented according to the following principles: when link quality is good (low data loss rate, stable round-trip time), the current transmitting window size is dynamically adjusted, gradually increasing W to allow more data to be "in transit," thereby increasing throughput. When link quality is poor (high data loss rate, large fluctuations in round-trip time), W is rapidly decreased to reduce congestion of "in-transit data" in the network and improve system stability and robustness.

[0021] The satellite-to-ground communication data transmission method and system of this embodiment divides and encapsulates the data to be transmitted into physical frames with unique, continuously increasing sequence numbers at the transmitting end, and continuously transmits multiple physical frames within the transmission window, changing the traditional "stop-and-wait" protocol single-frame transmission mode. At the same time, the receiving end updates the receiving status bitmap based on the physical frame verification result, and when the feedback condition is met, it includes the starting sequence number and the receiving status bitmap in the uplink feedback frame and feeds it back to the transmitting end. This allows the transmitting end to accurately identify physical frames that need to be retransmitted and perform selective retransmission. It can also dynamically adjust the size of the transmission window based on the link quality indicators statistically analyzed by the uplink feedback frame. In this way, continuous transmission and efficient feedback of multiple frames in the satellite-to-ground communication link are realized, effectively improving channel utilization and system throughput, enhancing adaptability to dynamically changing link environments, and ensuring the integrity and reliability of critical data transmission.

[0022] In some embodiments, the link quality metrics include frame loss rate and round-trip time. The process of dynamically adjusting the size of the transmission window based on the link quality metrics may include: Based on the frame loss rate and the round-trip delay, a window adjustment factor is determined; wherein the adjustment factor is negatively correlated with the frame loss rate and positively correlated with the round-trip delay stability; the current size of the sending window is multiplied by the adjustment factor to obtain the target size of the sending window; a smooth transition algorithm is used to gradually approach the target size of the sending window over multiple feedback cycles.

[0023] In a specific implementation, link quality metrics refer to a set of parameters used to quantify the state of the communication link, which can be implemented using frame loss rate and round-trip time (RTD). Frame loss rate is a key indicator reflecting the reliability of data transmission. It is calculated by statistically analyzing the proportion of physical frames that fail to be received per unit time to the total number of transmitted frames. Its purpose is to capture the impact of environmental factors such as atmospheric turbulence and cloud attenuation on data integrity. Round-trip time (RTD) is a core parameter characterizing the delay and fluctuation characteristics of ultra-long-distance transmission between satellite and ground. It is obtained by measuring the time interval from sending a physical frame to receiving the corresponding uplink feedback frame. Its purpose is to evaluate the stability of link delay.

[0024] The window adjustment factor is a coefficient used to dynamically scale the transmission window size. It can be implemented using a mathematical model based on frame loss rate and round-trip delay stability. Its purpose is to intelligently respond to changes in link state through a bidirectional correlation of negative and positive relationships. The smooth transition algorithm can be implemented using methods such as weighted averaging or exponential smoothing. Its purpose is to eliminate the risk of sudden changes in window size and ensure smooth convergence of the transmission process.

[0025] Specifically, when determining the window adjustment factor based on frame loss rate and round-trip delay, the design where the adjustment factor is negatively correlated with frame loss rate ensures that the factor value automatically decreases when link quality deteriorates, thereby suppressing excessive window size expansion and avoiding congestion caused by sending too much data in a high packet loss environment. Simultaneously, the mechanism where the adjustment factor is positively correlated with round-trip delay stability allows the system to increase the factor value when delay fluctuations are small, allowing the window size to expand reasonably to fully utilize link bandwidth. This not only achieves intelligent response to link status but also effectively solves the instability problem in dynamic window size adjustment. The operation of multiplying the current size of the sending window by the adjustment factor to obtain the target size, and then directly mapping the real-time link quality to the target window size value through linear scaling, can fix the rigidity of step size adjustment while ensuring continuous matching between the target size and the current link status. Furthermore, the design of gradually approaching the target size over multiple feedback cycles using a smooth transition algorithm eliminates the risk of sudden changes in window size through incremental adjustment, preventing size oscillations caused by short-term link fluctuations.

[0026] In some embodiments, the process of determining the window adjustment factor based on the frame loss rate and the round-trip time may include the following: The window adjustment factor is obtained by dividing the product of the baseline scaling factor and the loss rate factor by the delay stability factor. The loss rate factor is obtained by subtracting the frame loss rate from 1 and then performing a first exponential operation on the difference. The exponent of the first exponential operation is the loss rate sensitivity coefficient. The time delay stability factor is obtained by adding 1 to the round-trip time delay variance and then performing a second exponential operation on the sum. The exponent of the second exponential operation is the time delay stability sensitivity coefficient. The loss rate sensitivity coefficient is greater than the delay stability sensitivity coefficient, and both are greater than 1.

[0027] In a specific implementation, the frame loss rate factor is a parameter reflecting the impact of frame loss rate on window adjustment, and it can be implemented in various ways. For example, different mathematical functions can be used to express the non-linear relationship between frame loss rate and the frame loss rate factor, such as logarithmic functions and power functions. The purpose of introducing the frame loss rate factor is to amplify small changes in low packet loss scenarios, enabling the window to shrink quickly when link quality deteriorates, thereby improving the system's response speed.

[0028] The time delay stability factor is an adjustment parameter used to suppress the excessive influence of time delay fluctuations on the window size. Its implementation can be achieved, but is not limited to, using different statistical indicators to characterize time delay stability, such as standard deviation and range. The purpose of introducing this factor is to avoid severe window oscillations caused by instantaneous jitter, ensuring that the system maintains window stability during time delay fluctuations.

[0029] Specifically, the frame loss rate factor is obtained by subtracting the frame loss rate from 1 and then performing a first exponential operation on the difference, amplifying changes in low packet loss scenarios. The exponent of the first exponential operation is the frame loss rate sensitivity coefficient. The latency stability factor is obtained by adding 1 to the round-trip latency variance and then performing a second exponential operation on the sum, to suppress the excessive impact of latency fluctuations. The exponent of the second exponential operation is the latency stability sensitivity coefficient. The frame loss rate sensitivity coefficient is greater than the latency stability sensitivity coefficient, and both are greater than 1.

[0030] In some embodiments, the process of using a smooth transition algorithm to gradually approach the target size of the sending window over multiple feedback cycles includes the following: The actual size of the sending window is obtained by weighting the current size and the target size of the sending window using a smoothing coefficient. The weighting calculation includes: multiplying the current size of the sending window by the smoothing coefficient to obtain a first weighted value, multiplying the target size of the sending window by the difference between 1 and the smoothing coefficient to obtain a second weighted value, and then adding the first weighted value and the second weighted value.

[0031] In a specific implementation process, the smoothing coefficient refers to a value between 0 and 1. It can be implemented by setting a fixed value or by a dynamic adjustment strategy. The purpose is to balance the relationship between historical state and target orientation, and to avoid drastic changes in window size caused by instantaneous fluctuations in the link.

[0032] In practical applications, the first weighting value is obtained by multiplying the current size of the sending window by the smoothing coefficient. This utilizes the stability information of the existing window size to prevent the system from becoming overly sensitive to short-term link quality deterioration and prematurely shrinking the window. The second weighting value is obtained by multiplying the target size of the sending window by the difference between 1 and the smoothing coefficient. This weighted calculation method balances historical state and target orientation in the window adjustment process, responding to long-term link quality trends while filtering out transient noise interference.

[0033] Furthermore, the process of setting the smoothing coefficient includes the following methods: Obtain the round-trip delay sequence and frame loss rate sequence measured over multiple feedback cycles; Calculate the variance of the round-trip delay sequence as a delay stability index score; Calculate the standard deviation of the frame loss rate sequence and use it as a packet loss stability index score; The comprehensive score of the link quality index is obtained by weighting the latency stability index score and the packet loss stability index score. Based on the preset correlation between scores and smoothing coefficients, the smoothing coefficient corresponding to the comprehensive score of the link quality index is determined.

[0034] In a specific implementation, the latency stability score quantifies the fluctuation of link latency by calculating the variance of the round-trip latency sequence. This can be achieved using variance calculation methods in statistics, aiming to reflect the stability of link latency. The packet loss stability score quantifies the variation of packet loss rate by calculating the standard deviation of the frame loss rate sequence. This can be achieved using the standard deviation calculation formula, aiming to capture the fluctuation characteristics of packet loss rate during data transmission. The comprehensive score is the weighted sum of the latency stability score and the packet loss stability score. Different weight values ​​can be set to adapt to the needs of specific application scenarios, aiming to comprehensively evaluate the stability of link quality. The preset relationship between the score and the smoothing coefficient refers to a mapping mechanism used to transform the comprehensive score into the optimal smoothing coefficient value. This can be implemented using a lookup table method or function mapping, aiming to dynamically adjust the smoothing coefficient to match changes in link conditions.

[0035] In detail, a latency stability score is calculated by analyzing the variance of the round-trip latency sequence. A smaller variance indicates more stable link latency, resulting in a higher score to support a larger smoothing coefficient; conversely, a larger variance lowers the score to trigger a smaller smoothing coefficient, thus achieving a dynamic balance between speed and stability. Simultaneously, a packet loss stability score is calculated by analyzing the standard deviation of the frame loss rate sequence. A smaller standard deviation indicates higher transmission reliability, resulting in a higher score to maintain smooth adjustment; conversely, a higher standard deviation lowers the score to accelerate window response and effectively capture the reliability variation characteristics of data transmission. Furthermore, a comprehensive link quality score is obtained by weighting the latency stability and packet loss stability scores. Weight settings allow for emphasizing key indicators based on the actual scenario, forming a comprehensive quantitative representation of link quality. Finally, based on the preset correlation between the score and the smoothing coefficient, the comprehensive score is mapped to the optimal smoothing coefficient value. When the link is stable, a high smoothing coefficient is used to achieve a slow transition to avoid oscillation. When the link is unstable, a low smoothing coefficient is used to speed up the adjustment. This ensures that changes in window size can adapt to dynamic interferences such as atmospheric turbulence in a timely manner, while avoiding system instability caused by over-adjustment. This improves the robustness and resource utilization efficiency of satellite-to-ground communication in complex environments.

[0036] In some embodiments, the above-described satellite-to-ground communication data transmission method may further include: when the transmitting end sends the nth physical frame, the nth physical frame is cached as a copy, and a retransmission timer corresponding to the nth physical frame is started. After the timer reaches a preset duration, if the receiving end does not receive a reception status bitmap including the nth physical frame, the nth physical frame is retransmitted.

[0037] Specifically, replica caching refers to the process of completely copying and storing the data content of the nth physical frame in a local buffer when the sender transmits it. Its purpose is to provide a data foundation for subsequent retransmission operations, avoiding the additional overhead caused by data loss or regeneration. In practical applications, replica caching can be implemented through memory mapping technology, queued caching structures, or distributed storage mechanisms to adapt to resource constraints and performance requirements in different scenarios.

[0038] The retransmission timer establishes an independent feedback waiting time reference for each physical frame. Specifically, the retransmission timer is precisely bound to a specific physical frame, starting its count from the moment of transmission. When the countdown reaches a preset value, a timeout is triggered. In practical applications, the retransmission timer can be implemented using a hardware timer, a software timing thread, or an event-driven time management module, with the aim of ensuring the accuracy and real-time performance of the timeout judgment. The preset duration can be determined dynamically through link round-trip delay statistics, historical transmission data modeling and analysis, or adaptive algorithms to adapt to transmission requirements under different link conditions.

[0039] In detail, when the sending end transmits the nth physical frame, it first caches a copy of its data content. This operation, triggered instantly by the transmission event, avoids the extra overhead of regenerating data during subsequent retransmissions. This significantly reduces the processing burden, especially considering the limited resources of onboard equipment in satellite-to-ground communication. Simultaneously, a retransmission timer corresponding to the nth physical frame is started. By precisely binding the timer to a specific physical frame and starting the count from the transmission moment, an independent feedback waiting time base is established for each frame, ensuring that timeout judgments closely match the actual transmission status of that frame. Thus, if the receiver does not receive a reception status bitmap including that frame after the preset timeout period, a retransmission operation is proactively triggered. This avoids the system getting stuck in invalid waiting, maintains the continuity of the data flow, and improves overall transmission efficiency.

[0040] In some embodiments, the above-described satellite-to-ground communication data transmission method may further include: if the transmitting end receives a reception status bitmap including the nth physical frame from the receiving end before the timing duration reaches a preset duration, and the nth physical frame is in a received state, the transmitting end releases the copy of the nth physical frame and stops the retransmission timing for the nth physical frame.

[0041] In detail, when the receiver's reception status bitmap clearly indicates that the nth physical frame has been successfully received, the sender immediately performs a resource release operation, including clearing the copy buffer of that frame and terminating the corresponding retransmission timer. This avoids wasting memory resources and potential risks of false retransmissions caused by the continuous running of the timer. Furthermore, triggering this operation before a preset time ensures that it only applies to valid feedback scenarios, preventing premature processing of unacknowledged frames.

[0042] In some embodiments, the above-described satellite-to-ground communication data transmission method may further include: the transmitting end predicting the predicted frame loss rate and predicted round-trip delay for the next k feedback cycles based on the link quality index time series and a preset link quality prediction model, and obtaining the link quality index development trend; if the link quality index development trend shows that the link quality is improving, the size of the transmission window is increased in advance; if the link quality index development trend shows that the link quality continues to deteriorate, the size of the transmission window is decreased in advance.

[0043] In a specific implementation, the preset link quality prediction model can be a prediction model based on a Long Short-Term Memory (LSTM) network. The input of the LSTM model includes historical frame loss rate sequences, historical round-trip delay sequences, the current satellite elevation angle, and the cloud cover index from the ground weather forecast. The output of the LSTM model is the predicted frame loss rate and predicted round-trip delay for the next k feedback cycles. The LSTM model adopts an online learning mechanism, updating the model parameters with the latest link quality indicators each time a new uplink feedback frame is received. The development trend of the link quality indicators is obtained by calculating the linear regression slopes of the predicted frame loss rate and predicted round-trip delay for the next k feedback cycles. If the slope of the predicted frame loss rate is less than a first threshold and the slope of the predicted round-trip delay is less than a second threshold, the link quality is improved. If the slope of the predicted frame loss rate is greater than a third threshold or the slope of the predicted round-trip delay is greater than a fourth threshold, the link quality continues to deteriorate. The first and second thresholds are negative values, while the third and fourth thresholds are positive values.

[0044] Specifically, the development trend of link quality indicators refers to the rate and direction of change obtained by performing linear regression analysis on the predicted frame loss rate and predicted round-trip time. This can be quantitatively characterized by calculating the linear regression slopes of the predicted frame loss rate and predicted round-trip time over the next k feedback cycles. Furthermore, the first increment step and the first decrement step refer to the specific step values ​​for dynamically adjusting the transmission window size based on the prediction results. This allows the window size change to dynamically match the evolution of link quality.

[0045] Specifically, this embodiment integrates historical frame loss rate sequences, historical round-trip delay sequences, the satellite's current elevation angle, and cloud cover index from ground weather forecasts as inputs to an LSTM model, constructing a multi-dimensional link quality prediction mechanism. This mechanism comprehensively reflects the impact of atmospheric turbulence, satellite trajectory, and meteorological conditions on link quality, and identifies potential link quality deterioration or improvement trends in advance. Based on this, by calculating the linear regression slopes of the predicted frame loss rate and predicted round-trip delay, the system can accurately quantify the rate and direction of link quality change, using this as an objective basis for window adjustment. When the slope of the predicted frame loss rate is less than a first threshold and the slope of the predicted round-trip delay is less than a second threshold, the system determines that the link quality has improved and gradually increases the transmission window size with a first increment step. When the slope of the predicted frame loss rate is greater than a third threshold or the slope of the predicted round-trip delay is greater than a fourth threshold, the system determines that the link quality continues to deteriorate and gradually decreases the transmission window size with a first decrement step.

[0046] In some embodiments, the present invention further proposes a process for determining k including: Get the current elevation angle and elevation angle change rate of the transmitting end; Obtain the weather condition index for a future period of time from the surface weather forecast; the weather condition index is calculated based on cloud cover and atmospheric turbulence intensity. The absolute value of the elevation angle change rate is divided by the preset reference change rate, and then multiplied by the preset negative coefficient to obtain the negative adjustment amount related to the speed of the transmitting end. Multiply the weather condition index by a preset positive coefficient to obtain a positive adjustment amount related to the severity of weather conditions; Add the base value, the negative adjustment amount, and the positive adjustment amount together, and round the final result up to get the value of k.

[0047] Specifically, the elevation angle change rate refers to the rate of change of the satellite's (transmitter's) velocity relative to the ground station (receiver) in the vertical direction, which can be obtained by combining satellite orbit parameters with real-time telemetry and control data. In practical applications, the elevation angle change rate can be obtained by calculating the elevation angle at consecutive moments using a differential method, the purpose of which is to accurately reflect the satellite's motion state.

[0048] Weather condition indices can be obtained by weighted calculation of cloud cover and atmospheric turbulence intensity. In practical applications, meteorological radar data or the results of numerical weather prediction models can be used as input parameters to provide reliable environmental data for link prediction.

[0049] The negative adjustment is a correction parameter used to dynamically compress the k-value. It is obtained by multiplying the absolute value of the elevation angle change rate by the reference change rate and then by a negative coefficient. In practical applications, the specific values ​​of the reference change rate and the negative coefficient can be set based on historical statistical data. The purpose is to enable the prediction period to respond quickly to changes in the satellite's motion state.

[0050] The positive adjustment is a correction parameter used to optimize the k value, obtained by multiplying the weather condition index by a positive coefficient. In practical applications, the specific value of the positive coefficient can be set according to the meteorological characteristics of different regions, with the aim of adapting the forecast period to changes in meteorological conditions.

[0051] In detail, when the satellite moves rapidly, the increased rate of change of elevation angle leads to a significant reduction in the negative adjustment value (k), thereby shortening the prediction period to capture rapid fluctuations in the link status. Simultaneously, by acquiring weather condition indices from ground-based meteorological forecasts, the intensity of atmospheric interference with the laser signal can be objectively quantified. When weather conditions worsen, the positive adjustment increases. Combined with the base value and the negative adjustment, the k value is optimized to a reasonable range suitable for current weather conditions. This linear combination method efficiently integrates the dual influences of motion speed and weather conditions. Rounding up ensures that the k value is an integer to match the discrete characteristics of the feedback period, ultimately achieving precise coordination between the prediction period and the real-time dynamic characteristics of the satellite-to-ground communication link.

[0052] Based on the above, the beneficial effects of the present invention compared to the prior art are as follows: The most noticeable improvement is the significant increase in throughput. By eliminating inter-frame latency, the downlink can maintain near-saturation operation. Theoretical analysis and simulations show that, in typical LEO satellite-to-ground scenarios, the system throughput can be increased by 3-5 times compared to the traditional "stop-and-wait" protocol, greatly alleviating the conflict between high-speed services and limited transit time.

[0053] The enhanced anti-interference capability stems from the redundant design of the feedback mechanism. The loss of a single uplink frame no longer leads to system stalemate, because subsequent uplink frames can still carry the state information of previously unacknowledged frames. This "state memory" characteristic significantly reduces the stringent requirements for uplink reliability, making the system more robust in turbulent atmospheric environments.

[0054] Resource utilization efficiency optimization is reflected in multiple dimensions: on-board processing resources avoid frequent context switching; channel spatiotemporal resources are made more fully; and power resources are saved by reducing unnecessary retransmissions. These improvements collectively contribute to a greener and more efficient space-to-ground communication system.

[0055] The retransmission mechanism design is not only applicable to space-to-ground laser communication, but also has reference value for future high-end applications such as deep space optical communication and integrated space-air-ground networks. As space laser communication technology develops towards higher speeds and wider coverage, intelligent and efficient retransmission mechanisms will become a key technological support for unleashing its potential and lay a solid foundation for building a global high-speed space information network.

[0056] Based on the same general inventive concept, this invention also protects a satellite-to-ground communication data transmission system. The satellite-to-ground communication data transmission system provided by this invention will be described below. The satellite-to-ground communication data transmission system described below can be referred to in correspondence with the satellite-to-ground communication data transmission method described above.

[0057] Figure 2 This is a schematic diagram of the structure of the satellite-to-ground communication data transmission system provided in an embodiment of the present invention, as shown below. Figure 2 As shown, the satellite-to-ground communication data transmission system of this embodiment includes a transmitter 21 and a receiver 22.

[0058] The transmitting end 21 divides the data to be transmitted into multiple data segments and encapsulates them into multiple physical frames with unique and continuously increasing sequence numbers, and continuously sends multiple physical frames within the transmission window. The receiving end 22 verifies the received physical frames and updates the receiving status bitmap based on the verification result; the receiving status bitmap contains the receiving status of physical frames with multiple consecutive sequence numbers. When the feedback condition is met, the receiver 22 generates an uplink feedback frame including the start sequence number and the received state bitmap; The transmitting end 21 receives the uplink feedback frame, identifies the physical frames that need to be retransmitted based on the starting sequence number and the receiving status bitmap, adds the physical frames that need to be retransmitted to the retransmission scheduling queue and performs selective retransmission, and calculates the link quality index based on the uplink feedback frame, and dynamically adjusts the size of the sending window based on the link quality index.

[0059] It should be noted that all relevant information that may be involved in the various embodiments of the present invention is processed in strict accordance with the requirements of laws and regulations, following the principles of legality, legitimacy, and necessity, based on the reasonable purpose of the business scenario, and is information that users actively provide or generate during the use of the product / service, as well as information obtained with user authorization.

[0060] The information processed by this invention may vary depending on the specific product / service scenario and should be based on the specific scenario in which the user uses the product / service. This may involve user account information, device information, or other related information. This invention will treat the relevant information and its processing with the utmost diligence.

[0061] This invention places great emphasis on the security of relevant information and has adopted reasonable and feasible security protection measures that comply with industry standards to protect user information and prevent unauthorized access, public disclosure, use, modification, damage or loss of relevant information.

[0062] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0063] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A satellite-to-ground communication data transmission method, characterized in that, include: The sending end divides the data to be transmitted into multiple data segments and encapsulates them into multiple physical frames with unique and continuously increasing sequence numbers, and continuously sends multiple physical frames within the sending window; The receiving end verifies the received physical frames and updates the receiving status bitmap based on the verification results. The receive status bitmap contains the receive status of physical frames with multiple consecutive sequence numbers; When the feedback condition is met, the receiving end generates an uplink feedback frame including the start sequence number and the receiving state bitmap. The transmitting end receives the uplink feedback frame, identifies the physical frames that need to be retransmitted based on the starting sequence number and the receiving status bitmap, adds the physical frames that need to be retransmitted to the retransmission scheduling queue and performs selective retransmission, and calculates the link quality index based on the uplink feedback frame, and dynamically adjusts the size of the sending window based on the link quality index.

2. The satellite-to-ground communication data transmission method according to claim 1, characterized in that, The link quality metrics include frame loss rate and round-trip latency; Dynamically adjusting the size of the sending window based on the aforementioned link quality metrics includes: A window adjustment factor is determined based on the frame loss rate and the round-trip delay; wherein the adjustment factor is negatively correlated with the frame loss rate and positively correlated with the round-trip delay stability. The target size of the sending window is obtained by multiplying the current size of the sending window by the adjustment factor; A smooth transition algorithm is used to gradually approach the target size of the sending window over multiple feedback cycles.

3. The satellite-to-ground communication data transmission method according to claim 2, characterized in that, Based on the frame loss rate and the round-trip time, the window adjustment factor is determined, including: The window adjustment factor is obtained by dividing the product of the baseline scaling factor and the loss rate factor by the delay stability factor. The loss rate factor is obtained by subtracting the frame loss rate from 1 and then performing a first exponential operation on the difference. The exponent of the first exponential operation is the loss rate sensitivity coefficient. The time delay stability factor is obtained by adding 1 to the variance of the round-trip time delay and then performing a second exponential operation on the sum. The exponent of the second exponential operation is the time delay stability sensitivity coefficient. The loss rate sensitivity coefficient is greater than the delay stability sensitivity coefficient, and both are greater than 1.

4. The satellite-to-ground communication data transmission method according to claim 2, characterized in that, A smooth transition algorithm is used to gradually approach the target size of the transmission window over multiple feedback cycles, including: The actual size of the sending window is obtained by weighting the current size and the target size of the sending window using a smoothing coefficient. The weighted calculation includes: multiplying the current size of the sending window by the smoothing coefficient to obtain a first weighted value; multiplying the target size of the sending window by the difference between 1 and the smoothing coefficient to obtain a second weighted value; and then adding the first weighted value and the second weighted value.

5. The satellite-to-ground communication data transmission method according to claim 4, characterized in that, The process of setting the smoothing coefficient includes: Obtain the round-trip delay sequence and frame loss rate sequence measured over multiple feedback cycles; Calculate the variance of the round-trip delay sequence as a delay stability index score; Calculate the standard deviation of the frame loss rate sequence and use it as a packet loss stability index score; The comprehensive score of the link quality index is obtained by weighting the latency stability index score and the packet loss stability index score. Based on the preset correlation between scores and smoothing coefficients, the smoothing coefficient corresponding to the comprehensive score of the link quality index is determined.

6. The satellite-to-ground communication data transmission method according to claim 1, characterized in that, Also includes: When the sending end sends the nth physical frame, it buffers the nth physical frame as a copy and starts the retransmission timer corresponding to the nth physical frame. If the receiving end does not receive the receiving status bitmap including the nth physical frame after the timer has reached the preset duration, the nth physical frame is retransmitted.

7. The satellite-to-ground communication data transmission method according to claim 6, characterized in that, Also includes: If the sending end receives a reception status bitmap including the nth physical frame from the receiving end before the preset timeout period, and the nth physical frame is in a received state, it releases the copy of the nth physical frame and stops the retransmission timeout for the nth physical frame.

8. The satellite-to-ground communication data transmission method according to claim 6, characterized in that, Also includes: Based on the link quality index time series and the preset link quality prediction model, the sending end predicts the predicted frame loss rate and predicted round-trip delay for the next k feedback cycles, and obtains the development trend of the link quality index. If the trend of the link quality indicators shows that the link quality is improving, start increasing the size of the sending window; if the trend of the link quality indicators shows that the link quality continues to deteriorate, start decreasing the size of the sending window.

9. The satellite-to-ground communication data transmission method according to claim 8, characterized in that, The process of determining k includes: Get the current elevation angle and elevation angle change rate of the transmitting end; Obtain a weather condition index for a future period of time from the surface meteorological forecast; the weather condition index is calculated based on cloud cover and atmospheric turbulence intensity. The absolute value of the elevation angle change rate is divided by the preset reference change rate, and then multiplied by the preset negative coefficient to obtain the negative adjustment amount related to the speed of the transmitting end. Multiply the weather condition index by a preset positive coefficient to obtain a positive adjustment amount related to the severity of weather conditions; Add the base value, the negative adjustment amount, and the positive adjustment amount together, and round the final result up to get the value of k.

10. A satellite-to-ground communication data transmission system, characterized in that, Includes the sending end and the receiving end; The sending end divides the data to be transmitted into multiple data segments and encapsulates them into multiple physical frames with unique and continuously increasing sequence numbers, and continuously sends multiple physical frames within the sending window; The receiving end verifies the received physical frames and updates the receiving status bitmap based on the verification results. The receive status bitmap contains the receive status of physical frames with multiple consecutive sequence numbers; When the feedback condition is met, the receiving end generates an uplink feedback frame including the start sequence number and the receiving state bitmap. The transmitting end receives the uplink feedback frame, identifies the physical frames that need to be retransmitted based on the starting sequence number and the receiving status bitmap, adds the physical frames that need to be retransmitted to the retransmission scheduling queue and performs selective retransmission, and calculates the link quality index based on the uplink feedback frame, and dynamically adjusts the size of the sending window based on the link quality index.

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