HARQ-LDPC method and device for remote power grid satellite-ground link

Abstract

The invention relates to the technical field of wireless communication, and discloses a remote power grid satellite-ground link oriented HARQ-LDPC method and device, the rotation process of a wind power facility is divided into a sheltering period and a non-sheltering period, a satellite receiving end detects the signal to noise ratio of a received signal to distinguish whether the signal is in the sheltering period, and once the signal is detected to be in the sheltering period, the satellite receiving end sends the sheltering period to the remote power grid satellite-ground link. A satellite receiving end can send feedback control signals at a certain time interval in combination with satellite-ground round-trip delay, effective avoidance of a receiving end and a transmitting end to a shielding period is achieved, a dynamic updating mechanism based on node reliability is creatively established by cooperatively utilizing a static topological structure and dynamic node information of LDPC codes, and the dynamic updating mechanism is applied to the field of satellite communication. In the iteration process, low-reliability nodes with rich information are preferentially processed, and meanwhile, the redundant influence of updated nodes on subsequent iteration is effectively inhibited.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication, in particular to a HARQ-LDPC method and device for remote power grid satellite-ground link. BACKGROUND

[0002] The stability and reliability of power grid data transmission in remote areas are of great significance to ensure power supply safety and improve operation and maintenance efficiency. Due to complex geographical environment and relatively weak ground infrastructure, traditional ground communication networks often fail to meet the stability and real-time requirements of power grid data transmission in remote areas. In this context, the introduction of low-orbit satellite communication technology provides an efficient and reliable solution for power grid data transmission.

[0003] Low-orbit satellites have the advantages of low transmission delay, wide coverage, and flexible deployment, which can effectively make up for the shortcomings of ground communication networks and realize all-weather and all-region monitoring and data backhaul of power grid operation status in remote areas. However, in actual application, power grid facilities themselves will have a certain impact on signal transmission, especially wind power facilities, whose rotating blades will cause periodic blockage of satellite-ground uplink signals during operation, resulting in severe signal attenuation and time-varying characteristics. During the blocking period, the free space loss increases significantly, the signal-to-noise ratio (SNR) drops sharply, and the blocking duration is usually much longer than the signal frame length (up to tens to hundreds of milliseconds), thus causing large-scale burst errors and seriously affecting the reliability of data transmission. Therefore, it is urgent to design a high-performance decoding communication mechanism suitable for this scenario. SUMMARY

[0004] Therefore, the present application provides a HARQ-LDPC method and device for remote power grid satellite-ground link to solve the problem of low reliability of decoding retransmission strategy for periodic blockage in satellite-ground communication of remote power grid facilities in the prior art, which leads to satellite-ground communication failure.

[0005] In a first aspect, the present application provides a HARQ-LDPC method for remote power grid satellite-ground link, applied to a ground transmitting end, which comprises:

[0006] receiving power grid data original information, and obtaining a modulated signal based on the original information;

[0007] The modulated signal is sent to a pre-constructed star-ground uplink channel considering the periodic shading of the fan blades of the wind power facility, so that the star-ground uplink channel is shaded or unshaded based on the transmission time of the modulated signal.

[0008] When the satellite receiving end receives the channel noise added signal to form a received signal, the received signal is LDPC decoder iterative decoding, and whether the transmission modulated signal is in the shading period is judged based on the signal-to-noise ratio of the received signal, and after sending the feedback control signal based on the CRC check decoding result, the transmission strategy of the modulated signal is adjusted based on the feedback control signal.

[0009] The HARQ-LDPC method for remote power grid star-ground link provided by the application is constructed for the periodic shading problem of the fan blades of the remote power grid facility. A time-varying star-ground uplink channel (strong noise in shading period, weak noise in unshading period) is constructed. The satellite receiving end adjusts the transmission strategy of the feedback control signal based on the signal-to-noise ratio of the received signal and the CRC check result, realizes the avoidance of the shading period at both ends of the receiver and transmitter, reduces the influence of signal attenuation and noise enhancement caused by shading on transmission, significantly reduces the decoding failure probability caused by shading, and guarantees the reliable transmission of power grid facility monitoring data. By dynamically adapting the shading channel, optimizing the retransmission strategy and enhancing the decoding performance, the periodic shading problem in the star-ground communication of the remote power grid facility is effectively solved, the high-reliability and high-efficiency star-ground uplink transmission is realized, and key technical support is provided for remote monitoring and operation of the power grid.

[0010] In an optional implementation, the modulated signal is obtained based on the original information, including:

[0011] The original information is CRC check encoded to obtain a CRC encoded code word;

[0012] The CRC encoded code word is encoded by using a preset LDPC code check matrix to obtain an LDPC encoded code word;

[0013] The LDPC encoded code word is binary phase shift keying modulated to obtain a binary phase shift keying modulated signal.

[0014] This invention provides a HARQ-LDPC method for remote power grid satellite-to-ground links. The modulated signal is obtained through CRC checksum coding, LDPC coding, and BPSK (Binary Phase Shift Keying) modulation. CRC checksum coding enables the signal to have self-error detection capabilities, facilitating the receiver's judgment of data reception correctness. LDPC coding, through redundant design, endows the signal with strong error correction capabilities, providing robust support against channel multipath fading and additive noise. BPSK modulation efficiently converts the encoded digital signal into an analog signal suitable for satellite-to-ground channel transmission, reducing performance loss in the modulation stage. The synergistic effect of these three methods ensures that the original information possesses error correction and detection capabilities before entering the complex satellite-to-ground uplink, laying a solid foundation for decoding and recovery at the satellite receiver, ultimately improving the overall reliability and efficiency of satellite-to-ground communication for power grid facilities.

[0015] In one alternative implementation, the satellite-to-ground uplink channel, taking into account the periodic blocking by wind power facilities, is implemented in the following manner:

[0016] A traditional satellite-to-ground uplink channel is constructed based on preset tap delay line channel model parameters;

[0017] Based on the obstruction of the transmitted modulated signal, the rotation process of the wind turbine blades is divided into obstruction period and unobstructed period, and adjacent obstruction period and unobstructed period are combined into a complete obstruction-unobstructed cycle.

[0018] The signal-to-noise ratio (SNR) of the satellite receiver is set separately for the obstructed period and the unobstructed period. The complete obstructed-unobstructed cycle and the SNR of the satellite receiver during the obstructed period and the unobstructed period are added to the traditional satellite-to-ground uplink channel to construct a satellite-to-ground uplink channel that takes into account the periodic obstruction of wind power facility blades.

[0019] This invention provides a HARQ-LDPC method for satellite-to-ground links in remote power grids. Traditional satellite-to-ground uplink channel models already consider inherent characteristics of satellite channels such as multipath fading. Building upon this foundation, the method accurately incorporates the real-world scenario characteristics of periodic wind turbine obstruction. By dividing the rotation process of wind turbines into obstruction periods and unobstructed periods, and defining a complete obstruction-unobstructed cycle, the channel model can realistically reproduce the periodic changes in channel state caused by wind turbine obstruction during communication between ground equipment and satellite. This solves the problem of traditional models neglecting the impact of specific environmental obstructions, significantly improving the adaptability of the channel model to real-world application scenarios.

[0020] In one alternative implementation, the method further includes:

[0021] The maximum waiting time for retransmitting the modulated signal at the ground transmitter is set to be greater than the duration of the obstruction period, and the retransmission signal transmission time is calculated based on the feedback control signal reception.

[0022] This invention provides a HARQ-LDPC method for satellite-to-ground links in remote power grids, ensuring that the satellite receiver has sufficient time to wait for the obstruction period to end before sending a feedback control signal. This avoids forced retransmission during the worst obstruction phase of the channel, fundamentally reducing retransmission failures caused by poor channel quality and significantly improving the success rate of a single retransmission.

[0023] In one optional implementation, adjusting the modulation signal transmission strategy based on the feedback control signal includes:

[0024] When transmitting a modulated signal for the first time, the modulation signal transmission time is generated directly, and the modulation signal transmission operation is performed.

[0025] When an acknowledgment (ACK) control signal is received within the maximum waiting time, it is determined that the LDPC decoder at the satellite receiver has successfully decoded the signal and there is no need to retransmit the modulated signal.

[0026] When a Negative Acknowledgement (NACK) control signal is received within the maximum waiting time, the retransmission signal transmission time is obtained based on the satellite-to-ground round-trip time.

[0027] If no feedback control signal is received within the maximum waiting time, the retransmission signal transmission time is obtained based on the maximum waiting time.

[0028] Based on the retransmission time of the retransmitted signal, the modulated signal is retransmitted.

[0029] This invention provides a HARQ-LDPC method for satellite-to-ground links in remote power grids. The entire strategy achieves real-time response to channel status (coverage period / uncoverage period) and reception effect (success / failure) through a closed-loop process of control signal sensing, state judgment, time planning, and transmission execution. Whether it is the rapid start-up of the initial transmission, the resource release upon successful reception, or the precise retransmission planning in case of failure or no feedback, all are dynamically adjusted around the core objective of adapting to periodic coverage and improving transmission reliability. This enables the system to flexibly cope with the complex changes in the satellite-to-ground uplink and significantly enhances communication robustness in scenarios where power grid facilities are obstructed.

[0030] Secondly, this invention provides a HARQ-LDPC method for remote power grid satellite-to-ground links, applied at a satellite receiver, the method comprising:

[0031] When the ground transmitter receives the original grid data information, it obtains a modulated signal based on the original information; the modulated signal is sent to a pre-constructed satellite-ground uplink channel that takes into account the periodic obstruction of wind power facilities, so that the satellite-ground uplink channel adds noise during the obstruction period or adds noise during the unobstructed period based on the transmission time of the modulated signal, and then receives the signal passing through the satellite-ground uplink channel to form a received signal.

[0032] The received signal is iteratively decoded by an LDPC decoder, and the signal-to-noise ratio of the received signal is used to determine whether the transmitted modulation signal is in a period of obstruction. At the same time, a feedback control signal is sent to the ground transmitter based on the CRC check decoding result.

[0033] This invention provides a HARQ-LDPC method for satellite-to-ground links in remote power grids. Addressing the issue of periodic obstruction by wind turbine blades in remote power grid facilities, it constructs a time-varying dynamic channel for the satellite-to-ground uplink under periodic obstruction (strong noise during obstruction periods and weak noise during unobstructed periods). The satellite receiver adjusts the transmission strategy of the feedback control signal based on the received signal-to-noise ratio and CRC check results, achieving obstruction avoidance at both ends. This reduces the impact of signal attenuation and noise enhancement caused by obstruction on transmission, significantly lowering the probability of decoding failure due to obstruction, and ensuring reliable transmission of power grid facility monitoring data. By dynamically adapting to obstructed channels, optimizing retransmission strategies, and enhancing decoding performance, it effectively solves the periodic obstruction problem in satellite-to-ground communication for remote power grid facilities, achieving highly reliable and efficient satellite-to-ground uplink transmission, and providing key technical support for remote monitoring and maintenance of power grids.

[0034] In one optional implementation, the received signal is iteratively decoded using an LDPC decoder, including:

[0035] The log-likelihood ratio of the received signal is calculated based on the received signal and the noise variance, and the log-likelihood ratio of the received signal is combined with the historical log-likelihood ratio and then sent to the LDPC decoder.

[0036] Initialize all messages passed from the variable node to the check node and all messages passed from the check node to the variable node based on the merged log-likelihood ratio.

[0037] The verification nodes are grouped by degree and sorted in ascending order among the groups to obtain the update order of the verification nodes.

[0038] Based on the update order of the verification nodes, a hierarchical belief propagation decoding algorithm is used to update the verification node messages;

[0039] Perform a hard decision on the update result of the variable node message to obtain the decoding result under the current iteration;

[0040] If the decoding result does not meet the termination condition, calculate the residual values ​​of all messages passed from the check nodes to the variable nodes before and after the update in this iteration, obtain the maximum residual of each check node message, keep the inter-group order unchanged when sorting by degree, sort the check nodes in each group in descending order according to the maximum residual, obtain the new check node update order, and return to the step of grouping the check nodes by degree and sorting them in ascending order between groups to obtain the check node update order; if the decoding result meets the termination condition, use the decoded codeword of this iteration as the final output decoding result.

[0041] This invention provides a HARQ-LDPC method for remote power grid satellite-to-ground links. Based on LDPC codes, it utilizes the inherent degree distribution characteristics of LDPC codes to construct a static decoding scheduling benchmark. Check nodes with the same degree are divided into groups, and the resulting groups are arranged in ascending order of degree. At the same time, a dynamic residual analysis mechanism is introduced to track the reliability changes of nodes in real time during the iteration process. Based on the dynamic residual value of the nodes in the previous iteration, the check nodes in each group are sorted in descending order, thereby effectively improving decoding efficiency.

[0042] In one optional implementation, the method determines whether the transmitted modulated signal is in a period of obstruction based on the received signal-to-noise ratio, and simultaneously sends a feedback control signal to the ground transmitter based on the CRC check decoding result, including:

[0043] Perform CRC check on the decoding result of the LDPC decoder;

[0044] After performing CRC check, the signal-to-noise ratio of the received signal is used to determine whether the transmitted modulated signal is in a period of obstruction.

[0045] When the received signal is blocked, the duration of the blocking period is determined based on the wind speed at the geographical location of the ground transmitter and the size of the fan blades in the power grid used. Feedback control signals are sent to the ground transmitter at time intervals based on the time difference between the duration of the blocking period and the round-trip delay between the satellite and the ground, so that the ground transmitter can adjust the modulation signal transmission strategy based on the feedback control signals.

[0046] When the received signal is in an unobstructed period, a feedback control signal is sent directly to the ground transmitter, so that the ground transmitter can adjust the modulation signal transmission strategy based on the feedback control signal.

[0047] This invention provides a HARQ-LDPC method for satellite-to-ground links in remote power grids. It constructs a complete closed-loop mechanism, from verifying decoding results to determining channel status and then to differentiating feedback control signals. The satellite receiver accurately identifies obstruction periods and dynamically adjusts the timing and content of the feedback control signal transmission; the ground transmitter adjusts its modulation signal transmission strategy based on the received control signals. This satellite-to-ground collaborative mechanism enables the communication system to proactively adapt to the characteristics of periodically obstructed channels, reduce invalid transmissions during obstruction periods, fully utilize high-quality channels during unobstructed periods, and ultimately significantly improve the communication reliability and resource utilization of low-Earth orbit satellite uplinks in scenarios where power grid facilities obstruct communication.

[0048] Thirdly, the present invention provides a HARQ-LDPC device for remote power grid satellite-to-ground links, applied at a ground transmitter, the device comprising:

[0049] The raw information processing module is used to receive raw power grid data and obtain modulated signals based on the raw information;

[0050] The channel construction and signal transmission module is used to send the modulated signal to the pre-constructed satellite-to-ground uplink channel that takes into account the periodic shading of the wind power facility's fan blades, so that the satellite-to-ground uplink channel adds noise during the shading period or adds noise during the unshading period based on the transmission time of the modulated signal.

[0051] The modulation signal transmission strategy adjustment module is used to form a received signal after the satellite receiver receives the signal through the satellite-to-ground uplink channel, perform iterative decoding on the received signal using an LDPC decoder, determine whether the transmitted modulation signal is in a period of obstruction based on the signal-to-noise ratio of the received signal, and adjust the modulation signal transmission strategy based on the control signal after sending a feedback control signal based on the CRC check decoding result.

[0052] Fourthly, the present invention provides a HARQ-LDPC device for remote power grid satellite-to-ground links, applied at a satellite receiver, the device comprising:

[0053] The receiving signal forming module is used to receive the original information of the power grid data at the ground transmitter and obtain the modulated signal based on the original information; the modulated signal is sent to the pre-constructed satellite-ground uplink channel that takes into account the periodic shading of the wind power facility blades, so that the satellite-ground uplink channel adds noise during the shading period or adds noise during the unshading period based on the transmission time of the modulated signal, and then receives the signal passing through the satellite-ground uplink channel to form the received signal.

[0054] The decoding and control signal feedback module is used to perform iterative decoding of the received signal using an LDPC decoder, determine whether the transmitted modulation signal is in a period of obstruction based on the signal-to-noise ratio of the received signal, and send a feedback control signal to the ground transmitter based on the CRC check decoding result.

[0055] Fifthly, the present invention provides a computer device comprising: a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the computer instructions to perform the HARQ-LDPC method for remote power grid satellite-to-ground links described in the first aspect or any corresponding embodiment thereof, and the second aspect or any corresponding embodiment thereof.

[0056] In a sixth aspect, the present invention provides a computer-readable storage medium storing computer instructions for causing a computer to execute the HARQ-LDPC method for remote power grid satellite-to-ground links according to the first aspect or any corresponding embodiment thereof and the second aspect or any corresponding embodiment thereof.

[0057] In a seventh aspect, the present invention provides a computer program product, including computer instructions for causing a computer to execute the HARQ-LDPC method for remote power grid satellite-to-ground links as described in the first aspect or any corresponding implementation thereof and the second aspect or any corresponding implementation thereof. Attached Figure Description

[0058] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0059] Figure 1 This is a flowchart illustrating the HARQ-LDPC method for remote power grid satellite-to-ground links according to an embodiment of the present invention.

[0060] Figure 2 This is a flowchart illustrating another HARQ-LDPC method for remote power grid satellite-to-ground links according to an embodiment of the present invention;

[0061] Figure 3 This is a flowchart illustrating another HARQ-LDPC method for remote power grid satellite-to-ground links according to an embodiment of the present invention.

[0062] Figure 4 This is a flowchart illustrating another HARQ-LDPC method for remote power grid satellite-to-ground links according to an embodiment of the present invention.

[0063] Figure 5 This is a flowchart illustrating the LDPC dynamic scheduling strategy algorithm according to an embodiment of the present invention;

[0064] Figure 6 This is a flowchart illustrating another HARQ-LDPC method for remote power grid satellite-to-ground links according to an embodiment of the present invention.

[0065] Figure 7 This is a simulation comparison of the BER (Bit Error Rate) performance of the method of the present invention and the traditional LDPC decoding algorithm (without considering the periodic shading of the wind turbine blades) under different signal-to-noise ratio conditions according to embodiments of the present invention.

[0066] Figure 8 This is a simulation comparison of BER performance under different signal-to-noise ratio conditions after one retransmission for RDB (Residual and Degree-Based)-LBP (Layered Belief Propagation) with and without HARQ mechanism, with traditional HARQ mechanism, and with HARQ mechanism proposed in this invention (considering periodic shading of wind turbine blades).

[0067] Figure 9 This is a structural block diagram of a HARQ-LDPC device for remote power grid satellite-to-ground links according to an embodiment of the present invention;

[0068] Figure 10 This is a structural block diagram of another HARQ-LDPC device for remote power grid satellite-to-ground links according to an embodiment of the present invention;

[0069] Figure 11 This is a schematic diagram of the hardware structure of a computer device according to an embodiment of the present invention. Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] Forward error correction (FEC) technology is crucial for ensuring reliable data transmission because it can correct a finite number of codeword errors. Low-density parity-check (LDPC) codes, as a high-performance FEC code, possess error correction capabilities approaching the Shannon limit and are widely used in satellite communications. However, relying solely on FEC technology is insufficient to effectively address the large-scale burst errors caused by the periodic obstruction of wind power facilities.

[0072] Hybrid Automatic Repeat Request (HARQ) technology combines the advantages of FEC and Automatic Repeat Request (ARQ). It determines whether data retransmission is necessary by receiving ACK (Acknowledge) or NACK (Negative Acknowledgment) signals. It also soft-combines failed decoding signals with retransmission signals to improve decoding performance. However, traditional HARQ strategies often employ immediate ACK / NACK signal transmission. When considering the periodic obstruction of wind turbine blades, the obstruction duration is much longer than the round-trip time (a few milliseconds) between low-Earth orbit satellites. If the transmitted modulation signal falls within the obstruction period, the retransmission message still has a high probability of falling within the obstruction period, making it difficult to effectively improve decoding performance.

[0073] This invention provides a HARQ-LDPC method for remote power grid satellite-to-ground links. This method divides the rotation process of wind turbine blades into obstruction periods and unobstructed periods. The satellite receiver distinguishes whether the signal is in an obstruction period by detecting the signal-to-noise ratio (SNR) of the received signal. Once an obstruction period is detected, the satellite receiver sends ACK / NACK signals at certain time intervals, taking into account the satellite-to-ground round-trip delay, effectively avoiding the obstruction period for both the transmitting and receiving ends. Furthermore, this method uses 5G standard LDPC codes as its basic architecture, utilizing the inherent degree distribution characteristics of LDPC codes to construct a static decoding scheduling benchmark. Check nodes with the same degree are grouped into a group, and the resulting groups are arranged in ascending order of degree. Simultaneously, a dynamic residual analysis mechanism is introduced to track the reliability changes of nodes in real time during the iteration process. Based on the dynamic residual value of the nodes in the previous iteration, the check nodes in each group are sorted in descending order, thereby effectively improving decoding efficiency.

[0074] According to an embodiment of the present invention, a HARQ-LDPC method embodiment for remote power grid satellite-to-ground links is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0075] This embodiment provides a HARQ-LDPC method for remote power grid satellite-to-ground links, which can be used at the ground transmitter. Figure 1 This is a flowchart of the HARQ-LDPC method for remote power grid satellite-to-ground links according to an embodiment of the present invention, as follows: Figure 1 As shown, the process includes the following steps:

[0076] Step S101: Receive the original power grid data information and obtain the modulated signal based on the original information.

[0077] Specifically, taking a wind power facility in a remote area as an example, this wind power facility is a three-bladed wind power facility.

[0078] The raw data of the power grid includes operational monitoring data of wind power facilities (such as wind speed, blade speed, power generation, equipment temperature, fault status, etc.), status reporting information, control command feedback, and other valid data that need to be transmitted to the satellite receiver (satellite or ground control center) via satellite link. It is the core content that needs to be reliably transmitted during the communication process.

[0079] The raw information is usually a discrete digital signal (such as a binary data sequence) or an analog signal, whose spectrum is concentrated in the low-frequency band (baseband signal). However, actual communication channels (such as satellite links) have inherent transmission characteristics that limit their transmission. Therefore, the acquired raw information to be transmitted needs to be converted into a modulated signal that adapts to the channel's transmission characteristics.

[0080] Step S102: The modulated signal is sent to a pre-constructed satellite-to-ground uplink channel that takes into account the periodic shading of the wind turbine blades, so that the satellite-to-ground uplink channel adds noise during the shading period or adds noise during the unshading period based on the transmission time of the modulated signal.

[0081] Specifically, the pre-constructed satellite-to-ground uplink channel that considers the periodic obstruction of wind power facilities is a dynamic channel model that simulates the impact of wind power generation facilities (such as fan blade rotation) on satellite uplink signal transmission. This model uses mathematical modeling and simulation tools to transform the real-world periodic obstruction effect into reproducible channel parameters, which are used to study and optimize the performance of satellite communication systems in complex environments. This channel is a virtual channel.

[0082] The rotation process of wind turbine blades is divided into shading period and unshading period. Adjacent shading and unshading periods are combined into a complete shading-unshading cycle. Since wind turbine blades generally have three blades, there are three complete shading-unshading cycles in one rotation of the blades.

[0083] The processed modulated signal (such as a BPSK modulated signal) is sent to a pre-built satellite-to-ground uplink channel that is periodically blocked by power grid facilities. This virtual channel specifically simulates the real situation where the blades of wind power facilities periodically block satellite signals. If the transmission time of the modulated signal happens to be during the blocking period (such as when the blades turn to block the signal), strong noise is superimposed on the signal (simulating the signal quality degradation caused by the blocking); if the transmission time is during the unblocked period (when the blades turn open and the signal is unblocked), only weak background noise is superimposed on the signal (simulating normal communication).

[0084] Step S103: After the satellite receiver receives the signal after the channel is noisy, it forms a received signal. The received signal is iteratively decoded by an LDPC decoder. Based on the signal-to-noise ratio of the received signal, it is determined whether the transmitted modulation signal is in a period of obstruction. At the same time, after sending a feedback control signal based on the CRC check decoding result, the modulation signal transmission strategy is adjusted based on the feedback control signal.

[0085] Specifically, this transmitted modulated signal refers to the modulated signal transmitted by the ground transmitter. First, the satellite receiver captures the noisy signal transmitted through the satellite-to-ground uplink channel, taking into account the periodic obstruction of wind turbine blades (strong noise is superimposed during obstruction periods, and weak noise is superimposed during unobstructed periods), forming the received signal to be processed. The satellite receiver processes the received signal (e.g., calculating the log-likelihood ratio (LLR) and merging it with the historical LLR), and inputs it into the LDPC decoder for iterative decoding. That is, through message passing between variable nodes and check nodes, the bit reliability judgment is gradually corrected, and the strong error correction capability of LDPC codewords is used to recover the original signal.

[0086] Next, the channel status is analyzed based on the decoding results. If the signal-to-noise ratio (SNR) of the received signal is significantly low, it is determined that the current period is an obstruction period; if the SNR is high, it is determined that the current period is an unobstructed period.

[0087] Then, feedback control signals are sent: the satellite receiver sends feedback control signals to the ground transmitter based on the judgment result, including: successful decoding: ACK (acknowledgment signal) is sent to inform the ground that retransmission is not required; during the obstruction period and decoding failure: NACK (no acknowledgment signal) is sent at the time interval of the difference between the obstruction period and the round-trip delay between the satellite and the ground; during the no obstruction period and decoding failure: NACK (no acknowledgment signal) is sent immediately.

[0088] Finally, the ground signal transmission strategy is as follows: Upon receiving an ACK, the current signal retransmission process is terminated, and a new modulated signal is transmitted; upon receiving a NACK, retransmission is performed immediately.

[0089] This invention provides a HARQ-LDPC method for satellite-to-ground links in remote power grids. Addressing the issue of periodic obstruction of the fan blades in remote power grid facilities, it constructs a time-varying satellite-to-ground uplink channel with periodic obstruction (strong noise during obstruction periods and weak noise during unobstructed periods). The satellite receiver adjusts the transmission strategy of the feedback control signal based on the received signal-to-noise ratio and CRC check results, enabling both the transmitting and receiving ends to avoid obstruction periods. This reduces the impact of signal attenuation and noise enhancement caused by obstruction on transmission, significantly lowering the probability of decoding failure due to obstruction, and ensuring reliable transmission of power grid facility monitoring data. By dynamically adapting to obstructed channels, optimizing retransmission strategies, and enhancing decoding performance, it effectively solves the periodic obstruction problem in satellite-to-ground communication for remote power grid facilities, achieving highly reliable and efficient satellite-to-ground uplink transmission, and providing key technical support for remote monitoring and maintenance of power grids.

[0090] This embodiment provides a HARQ-LDPC method for remote power grid satellite-to-ground links, which can be used at the ground transmitter. Figure 2 This is a flowchart of the HARQ-LDPC method for remote power grid satellite-to-ground links according to an embodiment of the present invention, as follows: Figure 2 As shown, the process includes the following steps:

[0091] Step S201: Receive the original power grid data information and obtain the modulation signal based on the original information.

[0092] Specifically, step S201 includes:

[0093] Step S2011: Perform CRC check encoding on the original information to obtain CRC encoded codewords.

[0094] Specifically, the original information bits are encoded using Cyclic Redundancy Check (CRC) to obtain CRC encoded codewords.

[0095] The structure of the CRC encoded codeword is: [Original Information Bits] + [CRC Check Bits]. Assuming the original data is a binary information bit of length k (e.g., 1011001), a check bit (redundant bit, usually determined by the generator polynomial, such as 8 bits, 16 bits, or 32 bits) of length r is generated through CRC encoding. The final total length of the CRC encoded codeword is k + r bits. The specific process of CRC verification can be found in relevant technical documents and will not be elaborated here.

[0096] For example, CRC-32 encoding of the original information bits m of length 496 yields a CRC encoded codeword m of length 528. CRC .

[0097] Step S2012: Encode the CRC codeword using a preset LDPC code check matrix to obtain the LDPC codeword.

[0098] Specifically, LDPC code stands for Low-Density Parity-Check code. LDPC code is a powerful error-correcting code, and its encoding rules are defined by a predefined parity-check matrix (usually denoted as H). The parity-check matrix is ​​a matrix composed of 0s and 1s, where the number of rows represents the number of parity-check equations, and the number of columns equals the total length of the encoded codeword.

[0099] The process of LDPC encoding CRC-encoded codewords is essentially as follows: taking the CRC-encoded codewords as input information (containing original information and CRC check bits), and calculating and adding additional LDPC redundancy bits (redundant information for error correction) based on the constraints of the check matrix H. The final generated LDPC-encoded codeword has the structure: original information bits + CRC check bits + LDPC redundancy bits.

[0100] For example, using a 528×1128 5G NR LDPC code generation matrix G, a CRC codeword m of length 528 is generated. CRC LPDC encoding is performed to obtain a codeword c of length 1128. This includes the generator matrix G and the CRC encoded codeword m. CRC And the encoded codeword c satisfies the following relationship:

[0101] c = m CRC G(1).

[0102] Step S2013: Perform binary phase shift keying modulation on the LDPC encoded codeword to obtain a binary phase shift keying modulation signal.

[0103] Specifically, as mentioned above, LDPC-encoded codewords are binary sequences (composed of 0s and 1s) after CRC error detection encoding and LDPC error correction encoding, such as 1001101011... It contains the original information, CRC check bits, and LDPC redundancy bits, with the aim of improving the signal's anti-interference capability in noisy / obstructed channels, but at this point it is still a digital baseband signal (not loaded onto the carrier and cannot be directly transmitted over long distances).

[0104] LDPC coded codewords are low-frequency digital signals (baseband signals), while wireless channels such as satellite-to-ground uplinks require high-frequency electromagnetic waves (carrier waves) to transmit signals (high-frequency signals are easier to radiate through antennas and are suitable for long-distance propagation). The essence of modulation is to load low-frequency digital information onto a high-frequency carrier wave, enabling the signal to be transmitted effectively in the channel.

[0105] The resulting binary phase shift keying modulation signal is a high-frequency carrier signal formed by phase modulation of LDPC encoded codewords. Its function is to convert digital information into an electromagnetic wave form suitable for transmission via satellite-to-ground links.

[0106] Step S202: The modulated signal is sent to a pre-constructed satellite-to-ground uplink channel that takes into account the periodic shading of the wind turbine blades, so that the satellite-to-ground uplink channel adds noise during the shading period or adds noise during the unshading period based on the transmission time of the modulated signal.

[0107] Specifically, the satellite-to-ground uplink channel pre-constructed in step S202 above, which considers the periodic blocking of wind turbine blades, is implemented in the following manner:

[0108] Step S2021: Construct a traditional satellite-to-ground uplink channel based on preset tap delay line channel model parameters.

[0109] Specifically, according to the TDL-D channel model (Tap Delay Line) parameters given by the 3GPP TR38.811 standard, as shown in Table 1 below, a traditional satellite-to-ground uplink channel model is constructed.

[0110] Table 1 TDL-D Channel Model Parameters

[0111]

[0112] Based on pre-defined key parameters describing multipath effects, the temporal dispersion fading effect caused by multipath propagation in the traditional satellite-to-ground uplink (communication link from the ground terminal to the satellite) is reproduced using mathematical modeling or simulation tools, thereby constructing a channel model that can be used for system simulation and performance evaluation. Its core is to use a parameterized mathematical model to simulate the real propagation characteristics of the satellite-to-ground uplink, providing a reliable testing environment for communication system design.

[0113] Step S2022: Based on the rotation of the wind power facility, the rotation process of the wind power facility blades is divided into a shading period and an unshading period, and adjacent shading periods and unshading periods are combined into a complete shading-unshading cycle.

[0114] Specifically, the rotation process of wind turbine blades is divided into shading period and unshading period, and adjacent shading and unshading periods are combined into a complete shading-unshading cycle. Since wind turbine blades generally have three blades, there will be three complete shading-unshading cycles when the blades of a wind turbine rotate once.

[0115] For example, the signal-to-noise ratio (SNR) of the satellite receiver during the obstruction period is set to be 15 dB lower than that during the unobstructed period. Since this embodiment uses a wind power generation facility with a blade rotation speed of wms / revolution, the duration of one cycle is... If T1 is set as the duration of the occlusion period in a cycle, then the duration of the unocclusion period in a cycle is T2 = T - T1.

[0116] Step S2023: Set the signal-to-noise ratio of the satellite receiver during the obstruction period and the unobstructed period respectively, and add the complete obstruction-unobstruction cycle and the signal-to-noise ratio of the satellite receiver during the obstruction period and the unobstructed period to the traditional satellite-to-ground uplink channel to construct a satellite-to-ground uplink channel that considers the periodic obstruction of wind power facility blades.

[0117] Specifically, traditional satellite-to-ground uplink channels have simulated the inherent characteristics of satellite-to-ground communication (such as signal attenuation over long distances, atmospheric interference, and multipath scattering) through preset parameters (such as fading distribution and multipath delay), but have not considered the periodic obstruction effects of ground power grid facilities (such as rotating wind turbine blades).

[0118] Signal-to-noise ratio (SNR, the ratio of signal power to noise power) is a core indicator for measuring the signal quality at the receiver, including:

[0119] The signal-to-noise ratio of the satellite receiver during the obstruction period and the unobstructed period are set separately as follows:

[0120] Blocked period: Wind power facilities (such as fan blades) block the signal transmission path, resulting in increased signal attenuation and relatively prominent noise. Therefore, a low signal-to-noise ratio (SNR) is set to simulate the scenario of deteriorated signal quality. Unblocked period: The signal transmission path is unblocked, with small attenuation and weak noise. Therefore, a high signal-to-noise ratio (SNR) is set to simulate the scenario of normal communication.

[0121] The above-mentioned obstruction-free period and the SNR parameters of the two periods are superimposed on the traditional satellite-to-ground uplink channel to form a satellite-to-ground uplink channel for periodic obstruction of power grid facilities.

[0122] Step S203: After the satellite receiver receives the signal passing through the channel, it forms a received signal. The received signal is iteratively decoded using an LDPC decoder. Based on the signal-to-noise ratio of the received signal, it determines whether the transmitted modulated signal is in a period of obstruction. Simultaneously, based on the CRC checksum decoding result, a feedback control signal is sent, and the modulation signal transmission strategy is adjusted based on the feedback control signal. For details, please refer to [link to details]. Figure 1 Step S103 of the illustrated embodiment will not be described again here.

[0123] The HARQ-LDPC method for remote power grid satellite-to-ground links provided in this embodiment obtains a modulated signal through CRC checksum coding, LDPC coding, and BPSK (Binary Phase Shift Keying) modulation. CRC checksum coding enables the signal to have self-error detection capability, facilitating the receiver's judgment of the correctness of data reception. LDPC coding, through redundant design, endows the signal with strong error correction capability, providing robust support against channel multipath fading and additive noise. BPSK modulation efficiently converts the encoded digital signal into an analog signal suitable for satellite-to-ground channel transmission, reducing performance loss in the modulation stage. The synergistic effect of these three methods enables the original information to have error correction and detection capabilities before entering the complex satellite-to-ground uplink, laying a solid foundation for decoding and recovery at the satellite receiver, and ultimately improving the overall reliability and efficiency of satellite-to-ground communication for power grid facilities.

[0124] This embodiment provides a HARQ-LDPC method for remote power grid satellite-to-ground links, which can be used at the ground transmitter. Figure 3 This is a flowchart of the HARQ-LDPC method for remote power grid satellite-to-ground links according to an embodiment of the present invention, as follows: Figure 3 As shown, the process includes the following steps:

[0125] Step S301: Receive raw power grid data and obtain a modulated signal based on the raw data. For details, please refer to [link to relevant documentation]. Figure 2 Step S201 of the illustrated embodiment will not be described again here.

[0126] Step S302: The modulated signal is transmitted to a pre-constructed satellite-to-ground uplink channel that considers the periodic shading of wind turbine blades, such that the satellite-to-ground uplink channel adds noise during the shading period or during the unshading period based on the transmission time of the modulated signal. For details, please refer to... Figure 2 Step S202 of the illustrated embodiment will not be described again here.

[0127] Step S303: Set the maximum waiting time for retransmitting the modulated signal at the ground transmitter to be greater than the duration of the obstruction period, and calculate the retransmission signal transmission time based on the feedback control signal reception status.

[0128] Specifically, the maximum waiting time T for the ground transmitter to retransmit the signal is set. wait Slightly longer than the duration of the blocking period T1, the ground transmitter may encounter the following situations:

[0129] 1. Initial transmission of modulated signal: Initial transmission time t of generated signal start Proceed to step S304.

[0130] 2. If the ground transmitter receives the ACK signal within the maximum waiting time, it indicates that the satellite receiver has successfully decoded the signal, will not retransmit the signal, and will end the entire transmission process.

[0131] 3. The ground transmitter receives the NACK signal within the maximum waiting time: Calculate the retransmission signal transmission time based on the satellite-to-ground round-trip delay, and proceed to step S304. The satellite-to-ground round-trip delay τ is calculated using the following formula:

[0132]

[0133] Where c is the speed of light, D is the distance between the satellite and the Earth, and the retransmission time is... It is calculated by the following formula:

[0134]

[0135] 4. If the ground transmitter does not receive an ACK / NACK signal within the maximum waiting time: Calculate the retransmission signal transmission time based on the maximum waiting time, and proceed to step S304, retransmission signal transmission time. It is calculated by the following formula:

[0136]

[0137] Among them, t start T is the initial signal transmission time. wait This represents the maximum waiting time.

[0138] Step S304: After the satellite receiver receives the signal after the channel is noisy, it forms a received signal. The received signal is iteratively decoded by an LDPC decoder. Based on the signal-to-noise ratio of the received signal, it is determined whether the transmitted modulation signal is in a period of obstruction. At the same time, after sending a feedback control signal based on the CRC check decoding result, the modulation signal transmission strategy is adjusted based on the feedback control signal.

[0139] Specifically, step S304 includes:

[0140] Step S3041: When it is the first time to transmit the modulated signal, the modulation signal transmission time is directly generated and the modulation signal transmission operation is performed.

[0141] Specifically, as described in step S303, when the modulation signal is transmitted for the first time, the initial transmission time of the signal is directly generated, and there is no need to retransmit the modulation signal at this time.

[0142] Step S3042: When an acknowledgment control signal is received within the maximum waiting time, it is determined that the LDPC decoder at the satellite receiver has successfully decoded the signal and there is no need to retransmit the modulated signal.

[0143] Specifically, after the ground transmitter sends the modulated signal, it does not immediately retransmit it. Instead, it enters a maximum waiting period (this period is preset to be longer than the obstruction period to ensure sufficient time to receive satellite feedback control signals). During this period, it listens for feedback control signals sent by the satellite receiver, which are used to inform the ground end whether the data has been received correctly.

[0144] After receiving the signal through the channel, the satellite receiver performs iterative decoding using an LDPC decoder (recovering the original data by utilizing the strong error correction capability of LDPC codes). If the decoding result passes the CRC check (confirming that the data is error-free), the decoding is considered successful, and an ACK (acknowledgment and response control signal) is then sent to the ground transmitter to indicate that the data has been correctly received.

[0145] When the ground transmitter receives the ACK signal within the maximum waiting time, it will immediately determine that the satellite receiver has successfully decoded the data and the original data does not need to be transmitted again. Therefore, there is no need to start the retransmission mechanism, and the transmission process of the next set of data can be started directly.

[0146] Step S3043: When a denial response control signal is received within the maximum waiting time, the retransmission signal transmission time is obtained based on the satellite-to-ground round-trip time delay.

[0147] Specifically, after the ground transmitter sends the modulated signal, it will initiate a maximum waiting period (this period is preset to be greater than the obstruction period to ensure sufficient time to receive satellite feedback). If a NACK signal (i.e., denial acknowledgment control signal) is received from the satellite during this period, the decoding is determined to have failed, triggering the retransmission mechanism. At this time, the ground transmitter needs to immediately retransmit the data (the retransmission signal transmission time is calculated based on formula (3)).

[0148] The preset satellite-to-ground round-trip time refers to the theoretical time for one round trip of the signal between the ground transmitter and the satellite receiver. This parameter is predetermined based on factors such as satellite ephemeris data and the geographical coordinates of the ground transmitter.

[0149] Step S3044: When no control signal is received within the maximum waiting time, calculate the retransmission signal transmission time based on the maximum waiting time.

[0150] Specifically, after the ground transmitter sends the modulated signal, it starts a maximum waiting timer to wait for feedback from the satellite receiver (which may be an acknowledgment signal ACK or a denial signal NACK). If no feedback control signal is received within this time (which may be due to signal attenuation during the obstruction period), the current transmission is deemed unsuccessful, and a retransmission mechanism needs to be initiated. At this time, the ground transmitter needs to immediately retransmit the data (the retransmission signal transmission time is calculated based on formula (4)).

[0151] Step S3045: Retransmit the modulated signal based on the retransmission signal transmission time.

[0152] Specifically, based on the feedback control signal received by the corresponding ground transmitter, the modulated signal is retransmitted to the satellite-ground uplink channel at the corresponding retransmission signal transmission time, so that the satellite receiver can receive the signal after passing through the channel, form a received signal, and re-decode it to achieve smooth transmission between the satellite and the ground.

[0153] The HARQ-LDPC method for remote power grid satellite-to-ground links provided in this embodiment achieves real-time response to channel status (coverage period / uncoverage period) and reception effect (success / failure) through a closed-loop process of control signal sensing, state judgment, time planning, and transmission execution. Whether it is the rapid start-up of the initial transmission, the resource release upon successful reception, or the precise retransmission planning in case of failure or no feedback, all are dynamically adjusted around the core objective of adapting to periodic coverage and improving transmission reliability. This enables the system to flexibly cope with the complex changes in the satellite-to-ground uplink and significantly enhances communication robustness in scenarios where power grid facilities are obstructed.

[0154] This embodiment provides a HARQ-LDPC method for satellite-to-ground links in remote power grids, which can be used at the satellite receiver. Figure 4 This is a flowchart of the HARQ-LDPC method for remote power grid satellite-to-ground links according to an embodiment of the present invention, as follows: Figure 4 As shown, the process includes the following steps:

[0155] Step S401: When the ground transmitter receives the original information of the power grid data, it obtains a modulated signal based on the original information; the modulated signal is sent to the pre-constructed satellite-ground uplink channel that takes into account the periodic shading of the wind power facility blades, so that the satellite-ground uplink channel adds noise during the shading period or adds noise during the unshading period based on the transmission time of the modulated signal, and then receives the signal passing through the satellite-ground uplink channel to form a received signal.

[0156] For a detailed description of the process, please refer to steps S301 to S304, which will not be repeated here.

[0157] Step S402: The received signal is iteratively decoded by an LDPC decoder, and the signal-to-noise ratio of the received signal is used to determine whether the transmitted modulation signal is in a period of obstruction. At the same time, a feedback control signal is sent to the ground transmitter based on the CRC check decoding result.

[0158] In an optional implementation, step S402 includes:

[0159] Step S4021: Perform iterative decoding on the received signal using an LDPC decoder, such as... Figure 5 As shown, it includes:

[0160] Step a1: Calculate the log-likelihood ratio of the received signal based on the received signal and the noise variance, and then combine the log-likelihood ratio of the received signal with the historical log-likelihood ratio before sending it to the LDPC decoder.

[0161] Specifically, based on the received signal y and the noise variance σ 2 The log-likelihood ratio (LLR) is calculated and combined with the historical LLR of the signal. The combined LLR is then fed into an LDPC decoder for iterative decoding using the LDPC decoder's decoding algorithm. Under BPSK modulation, the LLR is calculated using the following formula:

[0162]

[0163] Where LLR represents the log-likelihood ratio.

[0164] Step a2: Initialize the messages passed from all variable nodes to the check nodes and the messages passed from all check nodes to the variable nodes based on the merged log-likelihood ratio.

[0165] Specifically, during the algorithm initialization phase, the maximum number of iterations I is set. max The posterior probability log-likelihood ratio L of all variable nodes v Initialize the received signal to the LLR value, and pass the message m from all check nodes to the variable node. c→v Initialize to 0.

[0166] Step a3: Group the verification nodes by degree and sort them in ascending order between groups to obtain the verification node update order.

[0167] Specifically, the degree of all check nodes is calculated based on the check matrix (the degree of a check node is defined as the number of variable nodes connected to it). Check nodes with the same degree are grouped into a group, and the groups containing several check nodes are sorted in ascending order of degree to obtain the initial check node update order Q after recombination. c .

[0168] Step a4: Based on the update order of the verification nodes, the hierarchical belief propagation decoding algorithm is used to update the verification node messages.

[0169] Specifically, according to the update order of the verification nodes Q c The Layered Belief Propagation (LBP) decoding algorithm is used to update the messages of each check node and variable node.

[0170] The update steps specifically include:

[0171] Step a41: Update the message passed from variable node j to check node i using the following formula.

[0172]

[0173] in, This represents the message that variable node j passes to verification node i. This represents the log-likelihood ratio of the verification node i.

[0174] Step a42: Update the message passed from check node i to variable node j using the following formula.

[0175]

[0176] Wherein, N(c i Let ) be the set of variable nodes connected to the verification node i, and v a Represents variable node a, This represents the message that variable node a passes to check node i.

[0177] Step a43: Update the posterior probability log-likelihood ratio of variable node j using the following formula.

[0178]

[0179] in, This is the log-likelihood ratio of the posterior probability of the updated variable node.

[0180] Step a5: Perform a hard decision on the update result of the variable node message to obtain the decoding result under the current iteration.

[0181] Specifically, the log-likelihood ratio of the posterior probability of the variable node. Perform a hard decision to obtain the decoding result for the current iteration:

[0182]

[0183] in, This indicates the decoding result.

[0184] Step a6: If the decoding result does not meet the termination condition, calculate the residual values ​​of all messages passed from the check nodes to the variable nodes before and after the update in this iteration, obtain the maximum residual of each check node message, keep the inter-group order unchanged when sorting by degree, sort the check nodes in each group in descending order according to the maximum residual, obtain the new check node update order, and return to the step of grouping the check nodes by degree and sorting them in ascending order between groups to obtain the check node update order; if the decoding result meets the termination condition, use the decoded codeword of this iteration as the final output decoding result.

[0185] Specifically, the termination condition is set as follows: when the judgment condition is met. Or reach the maximum number of iterations I max The decoding process is now complete, where H is the 5G NR LDPC code verification matrix.

[0186] At this point, depending on whether the decoding result meets the termination condition, there are two possibilities:

[0187] 1. If the decoding result does not meet the termination condition: then utilize the pre-update messages passed from all verification nodes to the variable nodes in this iteration. and the updated message m c→v The residual value for each edge is calculated as follows:

[0188]

[0189] Where, r c→v This represents the residual value for each edge.

[0190] Calculate the maximum residual in the edges connected to each verification node:

[0191]

[0192] in, R is used as the criterion for prioritizing the verification nodes within each group. Maintaining the inter-group order from step a3, the verification nodes within each group are sorted in descending order based on the maximum residual, resulting in a new verification node update order Q. c Then return to step a4.

[0193] 2. If the decoding result meets the termination condition: then the decoding result of this iteration is... As the final decoding result, the iteration stops.

[0194] like Figure 7As shown, the decoding algorithm RDB-LBP proposed in this invention, compared with the traditional residual-based LDPC dynamic scheduling decoding algorithm RB-LBP (Residual-Based Layered Belief Propagation), achieves better performance at a specific bit error rate (BER of 10). -4 It has a coding gain of approximately 0.2 dB at that time. This means that:

[0195] Lower transmit power: In satellite communications, a gain of 0.2 dB can reduce transmit power by about 5% (10^(0.2 / 10)≈1.047), thereby saving energy or extending equipment life.

[0196] Enhanced anti-interference capability: In complex channels (such as multipath fading and noise interference), RDB-LBP can maintain a lower bit error rate at the same power, improving communication reliability.

[0197] Step S4022: Determine whether the transmitted modulation signal is in a period of obstruction based on the signal-to-noise ratio of the received signal, and send a feedback control signal to the ground transmitter based on the CRC check decoding result.

[0198] In an optional implementation, step S4022 includes:

[0199] Step b1: Perform CRC check on the decoding result of the LDPC decoder.

[0200] Specifically, the satellite receiver decodes the LDPC decoder result. Perform CRC-32 checksum encoding. The specific CRC checksum encoding process can be found in relevant technical documents and will not be elaborated upon here.

[0201] Step b2: After CRC verification, determine whether the transmitted signal is in a period of obstruction based on the signal-to-noise ratio of the received signal.

[0202] Specifically, the satellite receiver determines whether the transmitted modulated signal is in a period of obstruction based on the signal-to-noise ratio (SNR) of the received signal y. Without considering the signal processing time and transmission time at both ends, the following situations exist, as described in steps b3 and b4.

[0203] Step b3: When the received signal is blocked, the duration of the blocking period is determined based on the wind speed at the geographical location of the ground transmitter and the size of the fan blades in the power grid. Feedback control signals are sent to the ground transmitter at time intervals with the time difference between the duration of the blocking period and the round-trip delay between the satellite and the ground, so that the ground transmitter can adjust the modulation signal transmission strategy based on the feedback control signals.

[0204] Specifically, when the signal is blocked, the satellite receiver calculates the duration T1 of the blocking period based on the wind speed at the geographical location of the ground transmitter and the size of the wind turbine blades used. It then sends ACK / NACK signals to the ground transmitter at time intervals T1-τ, taking into account the satellite-to-ground round-trip delay τ, to ensure that the ACK / NACK signals avoid the blocking period. Finally, it returns to the ground transmitter to adjust the modulation signal transmission strategy based on the control signal.

[0205] Step b4: When the received signal is in an unobstructed period, a feedback control signal is sent directly to the ground transmitter, so that the ground transmitter adjusts the modulation signal transmission strategy based on the feedback control signal.

[0206] Specifically, when the signal is unobstructed, the satellite receiver immediately sends an ACK / NACK signal to the ground transmitter and returns to the ground transmitter to adjust the modulation signal transmission strategy based on the control signal.

[0207] As one or more specific application embodiments of the present invention, combined with Figures 5 to 8 The HARQ-LDPC method for remote power grid satellite-to-ground links provided by this invention will be described in further detail, such as... Figure 6 As shown, the specific process is as follows:

[0208] Step 1: Obtain the raw information of the wind power generation facility. This raw information is 496 bits in length. Perform CRC-32 encoding on the 496 bits of the raw information to obtain a CRC encoded codeword m of length 528. CRC .

[0209] Step 2: Using a 528×1128 5G NR LDPC code generation matrix G, the CRC codeword m of length 528 is encoded. CRC LPDC encoding is performed to obtain a codeword c of length 1128. This includes the generator matrix G and the CRC encoded codeword m. CRC And the encoded codeword c satisfies the following relationship:

[0210] c = m CRC G(1).

[0211] Step 3: Perform binary phase shift keying (BPSK) modulation on the LDPC encoded codeword c to obtain the modulated signal;

[0212] Step 4: Construct a satellite-to-ground uplink channel model that takes into account the periodic blocking of wind power generation facility blades.

[0213] Step 4.1: Construct a traditional satellite-to-ground uplink channel model according to the TDL-D channel model parameters given in the 3GPP TR38.811 standard, as shown in Table 1 above. The specific process includes:

[0214] Step 4.2: Divide the rotation process of the wind turbine blades into a shading period and an unshading period, and combine adjacent shading periods and unshading periods into a complete shading-unshading cycle.

[0215] Step 4.3: Set the signal-to-noise ratio (SNR) of the satellite receiver during the obstruction period to be 15 dB lower than that during the unobstructed period. Since this embodiment uses a wind power generation facility with a blade rotation speed of wms / revolution, the duration of one cycle is... If T1 is set as the duration of the occlusion period in a cycle, then the duration of the unocclusion period in a cycle is T2 = T - T1.

[0216] Step 5: Set the maximum waiting time T for the ground transmitter to retransmit the signal. wait Slightly longer than the duration of the blocking period T1, the ground transmitter may encounter the following situations:

[0217] 1. Initial transmission of modulated signal: Initial transmission time t of generated signal start Proceed to step 6.

[0218] 2. If the ground transmitter receives the ACK signal within the maximum waiting time, it indicates that the satellite receiver has successfully decoded the signal, will not retransmit the signal, and will end the entire transmission process.

[0219] 3. The ground transmitter receives the NACK signal within the maximum waiting time: Calculate the retransmission signal transmission time based on the satellite-to-ground round-trip delay, and proceed to step 6. The satellite-to-ground round-trip delay τ is calculated using the following formula:

[0220]

[0221] Where c is the speed of light, D is the distance between the satellite and the Earth, and the retransmission time is... It is calculated by the following formula:

[0222]

[0223] 4. If the ground transmitter does not receive an ACK / NACK signal within the maximum waiting time: Calculate the retransmission signal transmission time based on the maximum waiting time, and proceed to step 6, retransmission signal transmission time. It is calculated by the following formula:

[0224]

[0225] Among them, t start T is the initial signal transmission time. wait This represents the maximum waiting time.

[0226] Step 6: Send the BPSK modulated signal into the satellite-to-ground uplink channel constructed in Step 4, and add noise during the obstruction period or the unobstructed period according to the signal transmission time to finally form the received signal y.

[0227] Step 7: Based on the received signal y and the noise variance σ 2 The log-likelihood ratio (LLR) is calculated and combined with the historical LLR of the signal. The combined LLR is then fed into an LDPC decoder for iterative decoding according to the decoding algorithm. Under BPSK modulation, the LLR is calculated as follows:

[0228]

[0229] Where LLR represents the log-likelihood ratio.

[0230] The flowchart of the LDPC dynamic scheduling strategy is shown below. Figure 5 As shown, the specific process is as follows:

[0231] Step 7.1: In the algorithm initialization phase, set the maximum number of iterations I. max The posterior probability log-likelihood ratio L of all variable nodes v Initialize the received signal to the LLR value, and pass the message m from all check nodes to the variable node. c→v Initialize to 0.

[0232] Step 7.2: Calculate the degree of all check nodes based on the check matrix (the degree of a check node is defined as the number of variable nodes connected to it). Divide check nodes with the same degree into groups, and sort the groups containing several check nodes in ascending order of degree to obtain the initial check node update order Q after recombination. c .

[0233] Step 7.3: Update Q according to the verification node update order c The hierarchical belief propagation (LBP) decoding algorithm is used to update the messages of each check node and variable node.

[0234] Step 7.3.1: Update the message passed from variable node j to check node i using the following formula.

[0235]

[0236] in, This represents the message that variable node j passes to verification node i. This represents the log-likelihood ratio of the verification node i.

[0237] Step 7.3.2: Update the message passed from check node i to variable node j using the following formula.

[0238]

[0239] Wherein, N(c i Let ) be the set of variable nodes connected to the verification node i, and v a Represents variable node a, This represents the message that variable node a passes to check node i.

[0240] Step 7.3.3: Update the posterior probability log-likelihood ratio of variable node j using the following formula.

[0241]

[0242] in, This is the log-likelihood ratio of the posterior probability of the updated variable node.

[0243] Step 7.4: Perform a hard decision on the posterior probability log-likelihood ratio of the variable nodes to obtain the decoding result for the current iteration:

[0244]

[0245] in, This indicates the decoding result.

[0246] The termination condition is set as follows: when the judgment condition is met. Or reach the maximum number of iterations I max The decoding process is now complete, where H is the 5G NR LDPC code verification matrix.

[0247] At this point, depending on whether the decoding result meets the termination condition, there are two possibilities:

[0248] 1. If the decoding result does not meet the termination condition: then utilize the pre-update messages passed from all verification nodes to the variable nodes in this iteration. and the updated message m c→v The residual value for each edge is calculated as follows:

[0249]

[0250] Where, r c→v This represents the residual value for each edge.

[0251] Calculate the maximum residual in the edges connected to each verification node:

[0252]

[0253] in, R is then used as the criterion for prioritizing the verification nodes within each group. Maintaining the inter-group order from step 7.2, the verification nodes within each group are sorted in descending order based on the maximum residual, resulting in a new verification node update order Q. c Then return to step 7.3.

[0254] 2. If the decoding result meets the termination condition: then the decoding result of this iteration is... As the final decoding result, the iteration stops.

[0255] like Figure 7 As shown, simulation diagrams of the proposed decoding algorithm RDB (Residual-and Degree-Based)-LBP (Layered Belief Propagation) compared to the traditional residual-based LDPC dynamic scheduling decoding algorithm RB-LBP under different signal-to-noise ratios and specific bit error rates are presented. The 5G NR LDPC code (1128, 528) is used, and the satellite-to-ground uplink channel model parameters refer to the TDL-D model of the 3GPP TR38.811 standard (as shown in Table 1). RDB-LBP is the method proposed in this invention; BP stands for Belief Propagation; LBP stands for Layered Belief Propagation; and RB-LBP stands for Residual-Based Layered Belief Propagation.

[0256] The proposed algorithm RDB-LBP, compared to the traditional residual-based LDPC dynamic scheduling decoding algorithm RB-LBP, achieves better performance at a specific bit error rate (BER of 10). -4 It has a coding gain of approximately 0.2 dB at that time. This means that:

[0257] Lower transmit power: In satellite communications, a gain of 0.2 dB can reduce transmit power by about 5% (10^(0.2 / 10)≈1.047), thereby saving energy or extending equipment life.

[0258] Enhanced anti-interference capability: In complex channels (such as multipath fading and noise interference), RDB-LBP can maintain a lower bit error rate at the same power, improving communication reliability.

[0259] Step 8: The satellite receiver performs CRC-32 verification on the decoding result of the LDPC decoder.

[0260] Step 9: The satellite receiver determines whether the transmitted modulated signal is in a period of obstruction based on the signal-to-noise ratio (SNR) of the received signal y. Without considering the signal processing time at both ends and the signal transmission time, the following situations exist:

[0261] 1. Signal is blocked: The satellite receiver determines the duration of the blocking period based on the wind speed at the geographical location of the ground transmitter and the size of the wind turbine blades used. It then sends ACK / NACK signals to the ground transmitter at time intervals, taking into account the satellite-to-ground round-trip time delay, to ensure that the ACK / NACK signals avoid the blocking period. Then, return to step 5.

[0262] 2. Signal is unobstructed: The satellite receiver immediately sends an ACK / NACK signal to the ground transmitter and returns to step 5.

[0263] like Figure 8 The figure shows a simulation comparison of BER performance under different signal-to-noise ratio (SNR) conditions after one retransmission for RDB-LBP (considering periodic shading of wind turbine blades) without HARQ, with traditional HARQ, and with the HARQ mechanism proposed in this invention. Proposed-HARQ (the proposed hybrid automatic repeat request mechanism) + RDB-LBP is the method proposed in this invention, while conventional-HARQ + RDB-LBP is the method of combining the traditional hybrid automatic repeat request mechanism (HARQ) with RDB-LBP.

[0264] from Figure 8 It can be seen that the Hybrid Automatic Repeat Request (HARQ) mechanism proposed in this invention, by combining the periodic shading characteristics of wind power plant blades and rationally designing the retransmission strategy, achieves effective avoidance of shading periods and solves the problem that the traditional HARQ mechanism is difficult to reduce the bit error rate under the condition of periodic shading of wind power plant blades.

[0265] The HARQ-LDPC method for remote power grid satellite-to-ground links provided in this invention has the following advantages:

[0266] 1) The rotation process of wind turbine blades is divided into obstruction period and unobstructed period. The satellite receiver distinguishes whether the signal is in obstruction period by detecting the signal-to-noise ratio (SNR) of the received signal. Once the signal is detected to be in obstruction period, the satellite receiver will send ACK / NACK signals at certain time intervals in combination with the satellite-to-ground round-trip delay. This enables both the transmitting and receiving ends to effectively avoid obstruction period and improves the reliability of satellite-to-ground uplink communication for power grid facilities in remote areas.

[0267] 2) This invention innovatively establishes a dynamic update mechanism based on node reliability by synergistically utilizing the static topology and dynamic node information of LDPC codes. During the iteration process, it prioritizes the processing of low-reliability nodes with abundant information, while effectively suppressing the redundant impact of updated nodes on subsequent iterations. Compared to traditional decoding methods, this invention achieves superior bit error rate performance under complex channel conditions in satellite-to-ground links.

[0268] This embodiment also provides a HARQ-LDPC device for remote power grid satellite-to-ground links, which is used to implement the above embodiments and preferred embodiments; details already described will not be repeated. As used below, the term "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0269] This embodiment provides a HARQ-LDPC device for remote power grid satellite-to-ground links, applied at the ground transmitter, such as... Figure 9 As shown, it includes:

[0270] The raw information processing module 901 is used to receive raw power grid data and obtain a modulated signal based on the raw information.

[0271] The channel construction and signal transmission module 902 is used to send the modulated signal to the pre-constructed satellite-to-ground uplink channel that takes into account the periodic shading of the wind power facility's fan blades, so that the satellite-to-ground uplink channel adds noise during the shading period or adds noise during the unshading period based on the transmission time of the modulated signal.

[0272] The modulation signal transmission strategy adjustment module 903 is used to form a received signal after the satellite receiver receives the signal with added noise from the channel, perform iterative decoding on the received signal using an LDPC decoder, determine whether the transmitted modulation signal is in a period of obstruction based on the signal-to-noise ratio of the received signal, and adjust the modulation signal transmission strategy based on the feedback control signal after sending a feedback control signal based on the CRC check decoding result.

[0273] In some alternative implementations, the raw information processing module 901 includes:

[0274] The CRC check unit is used to perform CRC check encoding on the original information to obtain the CRC encoded codeword.

[0275] The LDPC encoding unit is used to encode the CRC codeword using a preset LDPC code check matrix to obtain the LDPC codeword.

[0276] The modulation unit is used to perform binary phase shift keying modulation on the LDPC encoded codeword to obtain a binary phase shift keying modulated signal.

[0277] In one alternative implementation, the satellite-to-ground uplink channel, taking into account the periodic blocking of wind turbine blades, is implemented in the following manner:

[0278] A traditional satellite-to-ground uplink channel is constructed based on preset tap delay line channel model parameters. The wind turbine blade rotation process is divided into occlusion periods and unocclusion periods according to the obstruction of the transmitted modulated signal. Adjacent occlusion periods and unocclusion periods are merged into a complete occlusion-unocclusion cycle. The signal-to-noise ratio (SNR) of the satellite receiver is set for both the occlusion and unocclusion periods. The complete occlusion-unocclusion cycle and the SNR of the satellite receiver for both periods are added to the traditional satellite-to-ground uplink channel, thus constructing a satellite-to-ground uplink channel that considers the periodic obstruction of wind turbine blades.

[0279] In one alternative implementation, the HARQ-LDPC device for remote power grid satellite-to-ground links further includes:

[0280] The maximum waiting time setting module is used to set the maximum waiting time for retransmitting modulated signals at the ground transmitter to be greater than the duration of the obstruction period, and to calculate the retransmission signal transmission time based on the feedback control signal reception status.

[0281] In one optional implementation, the modulation signal transmission strategy adjustment module 903 includes:

[0282] The initial transmission unit is used to directly generate the modulation signal transmission time and perform the modulation signal transmission operation when it is the first time to transmit the modulation signal.

[0283] The first retransmission signal transmission time calculation unit is used to determine that the LDPC decoder at the satellite receiver has successfully decoded the signal when an acknowledgment (ACK) control signal is received within the maximum waiting time, and therefore no retransmission of the modulated signal is required.

[0284] The second retransmission signal transmission time calculation unit is used to obtain the retransmission signal transmission time based on the satellite-to-ground round-trip time when a negative acknowledgment (NACK) control signal is received within the maximum waiting time.

[0285] The third retransmission signal transmission time calculation unit is used to obtain the retransmission signal transmission time based on the maximum waiting time when no feedback control signal is received within the maximum waiting time.

[0286] The retransmission unit is used to retransmit the modulated signal based on the transmission time of the retransmission signal.

[0287] This embodiment also provides a HARQ-LDPC device for remote power grid satellite-to-ground links, applied at the satellite receiver, such as... Figure 10As shown, it includes:

[0288] The receiving signal forming module 1001 is used to receive the original information of the power grid data at the ground transmitter and obtain a modulated signal based on the original information; send the modulated signal to a pre-constructed satellite-ground uplink channel that takes into account the periodic shading of the wind power facility blades, so that the satellite-ground uplink channel adds noise during the shading period or adds noise during the unshading period based on the transmission time of the modulated signal, and then receives the signal passing through the satellite-ground uplink channel to form a received signal.

[0289] The decoding and control signal feedback module 1002 is used to perform iterative decoding of the received signal using an LDPC decoder, determine whether the transmitted modulation signal is in a period of obstruction based on the signal-to-noise ratio of the received signal, and send a feedback control signal to the ground transmitter based on the CRC check decoding result.

[0290] In one optional implementation, the decoding and control signal feedback module 1002 includes:

[0291] The decoding unit is used to perform iterative decoding of the received signal using an LDPC decoder.

[0292] The obstruction period judgment and feedback unit is used to determine whether the transmitted modulation signal is in an obstruction period based on the signal-to-noise ratio of the received signal, and at the same time send a feedback control signal to the ground transmitter based on the CRC check decoding result.

[0293] In one alternative implementation, the decoding unit includes:

[0294] The log-likelihood ratio calculation and merging subunit is used to calculate the log-likelihood ratio of the received signal based on the received signal and the noise variance, and then merge the log-likelihood ratio of the received signal with the historical log-likelihood ratio before sending it to the LDPC decoder.

[0295] The initialization sub-unit is used to initialize the messages passed from all variable nodes to the check nodes and the messages passed from all check nodes to the variable nodes based on the merged log-likelihood ratio.

[0296] The verification node grouping and sorting subunit is used to group the verification nodes by degree and sort them in ascending order between groups to obtain the verification node update order.

[0297] The node update subunit is used to update the check node messages based on the check node update order and using a hierarchical belief propagation decoding algorithm.

[0298] The decoding result calculation subunit is used to perform hard decision on the update result of the variable node message to obtain the decoding result under the current iteration.

[0299] The termination condition judgment subunit is used to calculate the residual values ​​of all messages passed to the variable nodes before and after the update in this iteration if the decoding result does not meet the termination condition. It obtains the maximum residual of each verification node message, keeps the inter-group order unchanged when sorting by degree, sorts the verification nodes in each group in descending order according to the maximum residual, obtains the new verification node update order, and returns the step of grouping the verification nodes by degree and sorting them in ascending order between groups to obtain the verification node update order. If the decoding result meets the termination condition, the decoded codeword of this iteration is used as the final output decoding result.

[0300] In one optional implementation, the occlusion period determination and feedback unit includes:

[0301] The verification subunit is used to perform CRC verification on the decoding result of the LDPC decoder.

[0302] The obstruction period determination subunit is used to determine whether the transmitted modulated signal is in an obstruction period based on the signal-to-noise ratio of the received signal after CRC verification.

[0303] The first feedback subunit is used to determine the duration of the obstruction period based on the wind speed at the geographical location of the ground transmitter and the size of the fan blades in the power grid used when the received signal is obstructed. It then sends a feedback control signal to the ground transmitter at a time interval between the duration of the obstruction period and the round-trip delay between the satellite and the ground, so that the ground transmitter can adjust the modulation signal transmission strategy based on the feedback control signal.

[0304] The second feedback subunit is used to directly send a feedback control signal to the ground transmitter when the received signal is in an unobstructed period, so that the ground transmitter can adjust the modulation signal transmission strategy based on the feedback control signal.

[0305] Further functional descriptions of the above modules and units are the same as those in the corresponding embodiments described above, and will not be repeated here.

[0306] In this embodiment, the HARQ-LDPC device for remote power grid satellite-to-ground links is presented in the form of functional units. Here, a unit refers to an ASIC (Application Specific Integrated Circuit) circuit, a processor and memory that execute one or more software or fixed programs, and / or other devices that can provide the above functions.

[0307] This invention also provides a computer device having the above-described features. Figure 9 and Figure 10 The HARQ-LDPC device shown is designed for remote power grid satellite-to-ground links.

[0308] Please see Figure 11 ,Figure 11 This is a schematic diagram of the structure of a computer device provided in an optional embodiment of the present invention, such as... Figure 11 As shown, the computer device includes one or more processors 10, memory 20, and interfaces for connecting the components, including high-speed interfaces and low-speed interfaces. The components communicate with each other via different buses and can be mounted on a common motherboard or otherwise installed as needed. The processors can process instructions executed within the computer device, including instructions stored in or on memory to display graphical information of a GUI on external input / output devices (such as display devices coupled to the interfaces). In some alternative implementations, multiple processors and / or multiple buses can be used with multiple memories and multiple memory modules, if desired. Similarly, multiple computer devices can be connected, each providing some of the necessary operations (e.g., as a server array, a group of blade servers, or a multiprocessor system). Figure 11 Take a processor 10 as an example.

[0309] Processor 10 may be a central processing unit, a network processor, or a combination thereof. Processor 10 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The programmable logic device may be a complex programmable logic device (CAMP), a field-programmable gate array (FPGA), a general-purpose array logic (GDA), or any combination thereof.

[0310] The memory 20 stores instructions executable by at least one processor 10 to cause the at least one processor 10 to perform the method shown in the above embodiments.

[0311] The memory 20 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created based on the use of the computer device. Furthermore, the memory 20 may include high-speed random access memory and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some alternative embodiments, the memory 20 may optionally include memory remotely located relative to the processor 10, and these remote memories may be connected to the computer device via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0312] The memory 20 may include volatile memory, such as random access memory; the memory may also include non-volatile memory, such as flash memory, hard disk or solid-state drive; the memory 20 may also include a combination of the above types of memory.

[0313] The computer device also includes an input device 30 and an output device 40. The processor 10, memory 20, input device 30, and output device 40 can be connected via a bus or other means. Figure 11 Taking the example of a connection between China and Israel via a bus.

[0314] Input device 30 can receive input numerical or character information, and generate key signal inputs related to user settings and function control of the computer device, such as a touchscreen, keypad, mouse, trackpad, touchpad, joystick, one or more mouse buttons, trackball, joystick, etc. Output device 40 may include display devices, auxiliary lighting devices (e.g., LEDs), and haptic feedback devices (e.g., vibration motors). The aforementioned display devices include, but are not limited to, liquid crystal displays, light-emitting diodes, displays, and plasma displays. In some alternative embodiments, the display device may be a touchscreen.

[0315] This invention also provides a computer-readable storage medium. The methods described above according to embodiments of the invention can be implemented in hardware or firmware, or implemented as computer code that can be recorded on a storage medium, or implemented as computer code downloaded over a network and originally stored on a remote storage medium or a non-transitory machine-readable storage medium and then stored on a local storage medium. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; further, the storage medium can also include combinations of the above types of memory. It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components capable of storing or receiving software or computer code, which, when accessed and executed by the computer, processor, or hardware, implements the methods shown in the above embodiments.

[0316] A portion of this invention can be applied as a computer program product, such as computer program instructions, which, when executed by a computer, can invoke or provide the methods and / or technical solutions according to the invention through the operation of the computer. Those skilled in the art will understand that the forms in which computer program instructions exist in a computer-readable medium include, but are not limited to, source files, executable files, installation package files, etc. Correspondingly, the ways in which computer program instructions are executed by a computer include, but are not limited to: the computer directly executing the instructions, or the computer compiling the instructions and then executing the corresponding compiled program, or the computer reading and executing the instructions, or the computer reading and installing the instructions and then executing the corresponding installed program. Here, the computer-readable medium can be any available computer-readable storage medium or communication medium accessible to a computer.

[0317] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A HARQ-LDPC method for remote power grid satellite-to-ground links, characterized in that, Applied to a ground-based transmitter, the method includes: Receive raw power grid data information and obtain a modulated signal based on the raw information; The modulated signal is sent to a pre-constructed satellite-to-ground uplink channel that takes into account the periodic shading of wind turbine blades, so that the satellite-to-ground uplink channel adds noise during the shading period or adds noise during the unshading period based on the transmission time of the modulated signal. After the satellite receiver receives the signal passing through the satellite-to-ground uplink channel, it forms a received signal. The received signal is iteratively decoded by an LDPC decoder. Based on the signal-to-noise ratio of the received signal, it determines whether the transmitted modulation signal is in a period of obstruction. At the same time, based on the CRC check decoding result, it sends a feedback control signal and adjusts the modulation signal transmission strategy based on the feedback control signal.

2. The method according to claim 1, characterized in that, Based on the original information, a modulated signal is obtained, including: The original information is subjected to CRC check encoding to obtain CRC encoded codewords; The CRC-encoded codeword is encoded using a preset LDPC code check matrix to obtain the LDPC-encoded codeword; The LDPC encoded codeword is subjected to binary phase shift keying modulation to obtain a binary phase shift keying modulated signal.

3. The method according to claim 1, characterized in that, The satellite-to-ground uplink channel, which takes into account the periodic blocking of wind turbine blades, is implemented in the following manner: Construct a traditional satellite-to-ground uplink channel based on preset tapped delay line channel model parameters; Based on the obstruction of the transmitted modulated signal, the rotation process of the wind turbine blades is divided into obstruction period and unobstructed period. Adjacent obstruction periods and unobstructed periods are combined into a complete obstruction-unobstructed cycle. The signal-to-noise ratio (SNR) of the satellite receiver is set separately for the obstructed period and the unobstructed period. The complete obstructed-unobstructed cycle and the SNR of the satellite receiver during the obstructed period and the unobstructed period are added to the traditional satellite-to-ground uplink channel to construct a satellite-to-ground uplink channel that takes into account the periodic obstruction of wind power facility blades.

4. The method according to claim 1, characterized in that, The method further includes: The maximum waiting time for retransmitting the modulated signal at the ground transmitter is set to be greater than the duration of the obstruction period, and the retransmission signal transmission time is calculated based on the feedback control signal reception status.

5. The method according to claim 4, characterized in that, The adjustment of the modulation signal transmission strategy based on the feedback control signal includes: When transmitting a modulated signal for the first time, the modulation signal transmission time is generated directly, and the modulation signal transmission operation is performed. When an acknowledgment control signal is received within the maximum waiting time, it is determined that the LDPC decoder at the satellite receiver has successfully decoded the signal and there is no need to retransmit the modulated signal. When a denial response control signal is received within the maximum waiting time, the retransmission signal transmission time is obtained based on the satellite-to-ground round-trip time. When no feedback control signal is received within the maximum waiting time, the retransmission signal transmission time is obtained based on the maximum waiting time. The modulated signal is retransmitted based on the transmission time of the retransmitted signal.

6. A HARQ-LDPC method for remote power grid satellite-to-ground links, characterized in that, Applied to a satellite receiver, the method includes: When the ground transmitter receives the original information of the power grid facilities and obtains the modulated signal based on the original information, the modulated signal is sent to the pre-constructed satellite-ground uplink channel that takes into account the periodic shading of the wind power facility blades. The satellite-ground uplink channel adds noise during the shading period or adds noise during the unshading period based on the transmission time of the modulated signal. After receiving the signal passing through the satellite-ground uplink channel, a received signal is formed. The received signal is iteratively decoded by an LDPC decoder, and the signal-to-noise ratio of the received signal is used to determine whether the transmitted modulation signal is in a period of obstruction. At the same time, a feedback control signal is sent to the ground transmitter based on the CRC check decoding result.

7. The method according to claim 6, characterized in that, The received signal is then iteratively decoded using an LDPC decoder: The log-likelihood ratio of the received signal is calculated based on the received signal and the noise variance, and the log-likelihood ratio of the received signal is combined with the historical log-likelihood ratio and then sent to the LDPC decoder. Initialize all messages passed from the variable node to the check node and all messages passed from the check node to the variable node based on the merged log-likelihood ratio. The verification nodes are grouped by degree and sorted in ascending order among the groups to obtain the update order of the verification nodes. Based on the update order of the verification nodes, a hierarchical belief propagation decoding algorithm is used to update the verification node messages; Hard-determine the update results of the variable node messages to obtain the decoding result under the current iteration; If the decoding result does not meet the termination condition, calculate the residual value of the messages passed to the variable node by all check nodes before and after the update in this iteration, obtain the maximum residual of each check node message, keep the inter-group order unchanged when sorting by degree, sort the check nodes in each group in descending order according to the maximum residual, obtain the new check node update order, and return the step of grouping the check nodes by degree and sorting them in ascending order between groups to obtain the check node update order. If the decoding result meets the termination condition, the decoded codeword of this iteration will be used as the final output decoding result.

8. The method according to claim 6, characterized in that, The step of determining whether the received signal is in a period of obstruction based on the received signal-to-noise ratio, and simultaneously sending a feedback control signal to the ground transmitter based on the CRC check result, includes: Perform CRC check on the decoding result of the LDPC decoder; After performing CRC check, the signal-to-noise ratio of the received signal is used to determine whether the transmitted modulated signal is in a period of obstruction. When the transmitted modulation signal is in a period of obstruction, the duration of the obstruction period is obtained based on the wind speed at the geographical location of the ground transmitter and the size of the wind turbine blades used. The time difference between the duration of the obstruction period and the round-trip delay between the satellite and the ground is used as the time interval to send a feedback control signal to the ground transmitter, so that the ground transmitter can adjust the modulation signal transmission strategy based on the feedback control signal. When the transmitted modulation signal is in an unobstructed period, a feedback control signal is sent directly to the ground transmitter, so that the ground transmitter adjusts the modulation signal transmission strategy based on the feedback control signal.

9. A HARQ-LDPC device for remote power grid satellite-to-ground links, characterized in that, The device, used in a ground-based transmitter, includes: The raw information processing module is used to receive raw power grid data and obtain a modulated signal based on the raw information; The channel construction and signal transmission module is used to send the modulated signal to a pre-constructed satellite-to-ground uplink channel that takes into account the periodic shading of the wind turbine blades, so that the satellite-to-ground uplink channel adds noise during the shading period or adds noise during the unshading period based on the transmission time of the modulated signal. The modulation signal transmission strategy adjustment module is used to form a received signal after the satellite receiver receives the signal passing through the satellite-to-ground uplink channel, perform iterative decoding on the received signal using an LDPC decoder, determine whether the transmitted modulation signal is in a period of obstruction based on the signal-to-noise ratio of the received signal, and adjust the modulation signal transmission strategy based on the feedback control signal after sending a feedback control signal based on the CRC check decoding result.

10. A HARQ-LDPC device for remote power grid satellite-to-ground links, characterized in that, The device, applied to a satellite receiver, includes: The receiving signal forming module is used to receive the original information of the power grid data at the ground transmitter and obtain a modulated signal based on the original information; send the modulated signal to a pre-constructed satellite-ground uplink channel that takes into account the periodic shading of the wind power facility blades, so that the satellite-ground uplink channel adds noise during the shading period or adds noise during the unshading period based on the transmission time of the modulated signal, and then receives the signal passing through the satellite-ground uplink channel to form a received signal. The decoding and control signal feedback module is used to perform iterative decoding of the received signal using an LDPC decoder, determine whether the transmitted modulation signal is in a period of obstruction based on the signal-to-noise ratio of the received signal, and send a feedback control signal to the ground transmitter based on the CRC check decoding result.

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