HARQ retransmission method for low-orbit HD-FDD satellite system

Abstract

This invention discloses a HARQ retransmission method suitable for satellite low-orbit HD-FDD systems. The method includes: receiving terminal duplex capability information, location information, and terminal messages; calculating dynamic propagation delay by combining terminal location with satellite ephemeris; generating gateway processing delay components and terminal processing delay components based on the real-time operating status of the gateway itself and terminal reports, and adding them together to form a total processing delay; fusing the dynamic propagation delay with the dynamic total processing delay to construct a total HARQ delay, and based on this, creating an efficient HARQ transmission pattern for terminals in HD-FDD mode. By accurately and dynamically sensing processing delay, the method improves HARQ timing accuracy and resource utilization.

Description

Technical Field

[0001] The present invention belongs to the field of satellite communications, and in particular to a HARQ retransmission method suitable for a satellite low-orbit HD-FDD system. Background Art

[0002] In today's wave of communications technology, satellite internet is transitioning from the traditional era of high-Earth Earth Orbit (GEO) satellite communications to a new era centered around low-Earth Earth Orbit (LEO) satellite constellations. Due to their significantly lower orbital altitude, LEO satellites offer revolutionary advantages, including low signal propagation latency, minimal link loss, and high signal-to-noise ratio (SNR). This makes it possible to provide seamless, high-speed, low-latency network services worldwide. This shift involves more than just a change in satellite orbital altitude; it also triggers profound changes in the entire communications system, particularly in terminal and ground station technology. To cope with the high-speed motion of LEO satellites relative to the ground, communication beams must be tracked and aligned in real time, significantly driving the widespread adoption of phased array antenna technology in satellite communications. In particular, in portable devices for personal use, due to strict constraints on size, power consumption, and cost, co-aperture and co-planar transmit and receive antennas have become the mainstream choice. This antenna architecture naturally adapts to the half-duplex frequency division duplex (HD-FDD) system, making it a key operating mode in modern LEO satellite communication systems. At the same time, high signal-to-noise ratio (SNR) link conditions have made the use of high-order modulation and coding (HOMC) schemes to achieve higher spectral efficiency a common practice. However, this inevitably brings the challenge of increased air interface frame error rates (FERs). Therefore, the introduction of an efficient and reliable Hybrid Automatic Repeat Request (HARQ) mechanism is of vital research significance and application value for ensuring data transmission reliability, reducing FERs, and improving overall system throughput.

[0003] Currently, HARQ technology for wireless communication systems is quite mature, particularly in terrestrial cellular communications (such as 4G LTE and 5G NR), where it has been widely deployed and proven. The core of HARQ timing design in these systems is built around a relatively fixed or predictably varying round-trip time (RTT). In the context of non-geostationary satellite orbit (NGSO), particularly low-Earth Orbit (LEO), existing technologies also recognize the dramatic variations in propagation delay caused by high satellite mobility. Some preliminary improvements have begun to incorporate dynamic propagation delay into HARQ timing calculations. These solutions typically calculate the signal's physical propagation delay in space in real time or near real time using satellite ephemeris and terminal location information. This dynamically varying propagation delay is then added to a pre-defined, fixed processing delay margin to form the total HARQ round-trip time, which is then used to configure HARQ parameters, such as the number of HARQ processes. This fixed processing delay margin is typically calibrated and reserved based on the worst-case processing capabilities of network equipment (such as gateways) and terminal devices. It is considered a static parameter determined during the system design phase and does not adjust in actual operation with changes in network load or terminal status.

[0004] However, in-depth analysis revealed that these existing solutions present profound and specific technical challenges when addressing the highly dynamic low-orbit satellite communication scenarios. The core issue lies in their static, one-size-fits-all approach to processing latency, which leads to two key drawbacks in practical applications: first, a mismatch between HARQ timing and actual processing capabilities; and second, low resource utilization of HD-FDD transmission patterns. Summary of the Invention

[0005] The purpose of the invention is to provide a HARQ retransmission method suitable for a satellite low-orbit HD-FDD system, in order to solve at least one technical problem existing in the prior art.

[0006] The technical solution is applicable to the HARQ retransmission method of the satellite low-orbit HD-FDD system, including:

[0007] Receive terminal duplex capability information, terminal location information, and terminal messages;

[0008] Combine the terminal location information with the pre-stored satellite ephemeris information to calculate the dynamic propagation delay;

[0009] Combine the real-time operation status of the satellite gateway and the terminal message to generate dynamic processing delay;

[0010] Integrate dynamic propagation delay and dynamic processing delay to construct total HARQ delay;

[0011] In response to the HD-FDD mode indicated by the duplex capability information of the terminal, a HARQ transmission pattern is created for the terminal using the total HARQ delay.

[0012] Beneficial effects: The present invention solves the timing deviation problem caused by static assumptions, ensures the accurate timing of the HARQ process, and improves the spectrum resource utilization and system throughput under the HD-FDD system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A flowchart of the steps of a HARQ retransmission method applicable to a satellite low-orbit HD-FDD system provided in an embodiment of the present application.

[0014] Figure 2 A flowchart of the steps for calculating dynamic propagation delay provided in an embodiment of the present application.

[0015] Figure 3 A flowchart of the steps for generating dynamic processing delay provided in an embodiment of the present application.

[0016] Figure 4 This is the transmission pattern when the HARQ delay is 6ms in the embodiment of the present application.

[0017] Figure 5 This is the transmission pattern when the HARQ delay is 8ms in the embodiment of the present application. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or are inherent to these processes, methods, products or apparatus.

[0020] Research has found that existing technologies use a fixed processing delay margin, completely ignoring the real-time dynamics of processing capacity at both ends of the communication link (i.e., satellite gateways and user terminals). On the network side, the processing load of satellite gateways fluctuates in real time with the number of active users, traffic volume, and scheduling complexity within their coverage area. On the terminal side, modern smart terminals often need to run multiple applications simultaneously. Their computing resources for communication protocol stack processing are preempted by local high-load tasks (such as software updates, HD video playback, and even local artificial intelligence computing), causing significant fluctuations in their actual processing capacity. In this case, a fixed, worst-case processing delay margin is overly conservative for most terminals and gateways operating normally, introducing unnecessary latency and directly reducing spectrum utilization. Conversely, an overly optimistic margin can lead to HARQ process failures due to processing timeouts when the gateway or terminal is under real load, triggering unnecessary retransmissions and ultimately severely degrading system throughput and user experience. In HD-FDD systems, the structure and efficiency of the transmission pattern—composed of uplink and downlink transmission slots, feedback slots, and guard slots—are highly correlated with the accuracy of the total HARQ delay. Because existing technologies cannot accurately perceive and quantify true, bidirectional, and dynamic processing delays, the calculated total HARQ delay exhibits inherent bias. This bias directly results in a suboptimal transmission pattern, potentially causing frequent interruptions or pauses in the HARQ process pipeline or excessively long guard times between uplink and downlink handoffs. This wastes resources in satellite communications, where spectrum resources are extremely precious, and prevents maximizing the system's potential.

[0021] like Figure 1 As shown, a HARQ retransmission method suitable for a satellite low-orbit HD-FDD system is proposed, comprising the following steps:

[0022] receiving terminal duplex capability information, terminal location information, and terminal messages from the terminal;

[0023] Combine the terminal location information with the pre-stored satellite ephemeris information to calculate the dynamic propagation delay;

[0024] Combine the real-time operation status of the satellite gateway and the terminal message to generate dynamic processing delay;

[0025] Integrate dynamic propagation delay and dynamic processing delay to construct total HARQ delay;

[0026] In response to the HD-FDD mode indicated by the terminal duplex capability information, a total HARQ delay is used to create a HARQ transmission pattern for the terminal, for use by the satellite gateway to perform subsequent communication scheduling with the terminal.

[0027] like Figure 2 As shown, according to one aspect of the present application, calculating the dynamic propagation delay includes:

[0028] Analyze satellite ephemeris information to obtain the real-time coordinates of the satellite, and combine it with the terminal location information to calculate the straight-line distance between the satellite and the terminal;

[0029] Divide the straight-line distance between the satellite and the earth by the speed of light to calculate the dynamic propagation delay.

[0030] In one embodiment of the present application, a satellite gateway receives various types of information from user terminals. This information includes terminal duplex capability information for identifying the terminal duplex mode (for example, indicating HD-FDD mode), terminal location information for positioning (for example, GPS coordinates), and terminal messages carrying other communication parameters. The gateway combines the terminal location information with the satellite ephemeris information of a low-orbit satellite being served to calculate the dynamic propagation delay. Specifically, the gateway parses the real-time three-dimensional coordinates of the satellite from the ephemeris information, and calculates the real-time straight-line distance between the satellite and the terminal in combination with the terminal location information. The straight-line distance between the satellite and the ground is divided by the speed of light (approximately 300,000 kilometers per second in a vacuum) to convert it into a one-way dynamic propagation delay T. propagation For example, if the satellite orbit height is 600km at a certain moment, the terminal altitude is 0, and the satellite is located at the zenith of the terminal, then the straight-line distance between the satellite and the ground is approximately 600km, and the calculated T propagation It is about 600km / 300000km / s=2ms. If the satellite orbit height changes to 1200km at another moment, the calculated T propagation The gateway generates a dynamic total processing delay T based on its own real-time operating status and processing the received terminal messages. proc_total . Get the dynamic propagation delay T propagation and dynamic processing delay T proc_total Then, the two are combined to construct the total HARQ delay T HARQ_total The calculation formula is: T HARQ_total =T proc_total +T propagation The gateway responds to the HD-FDD mode indicated by the terminal duplex capability information and adopts the total HARQ delay T HARQ_total , creating a dedicated HARQ transmission pattern for the terminal. This HARQ transmission pattern defines the timing of uplink and downlink transmissions in subsequent communications, enabling the satellite gateway to accurately schedule communications with the terminal. Through the above steps, this embodiment dynamically adjusts HARQ timing based on the relative position of the satellite and the terminal, preliminarily resolving retransmission efficiency issues caused by varying propagation delays.

[0031] like Figure 3 As shown, according to one aspect of the present application, generating a dynamic processing delay includes:

[0032] Evaluate the real-time operational status of satellite gateways and determine the processing delay components of gateways;

[0033] Parse the terminal message to obtain the terminal processing delay component;

[0034] The dynamic processing delay is obtained by summing the gateway processing delay component and the terminal processing delay component.

[0035] According to one aspect of the present application, determining a gateway processing delay component includes:

[0036] Performing weighted quantification on the real-time operating status of the satellite gateway to generate a comprehensive load factor; wherein the real-time operating status includes at least one of CPU occupancy, number of active users, or scheduling queue depth;

[0037] The comprehensive load factor is mapped to dynamic load delay through a nonlinear function;

[0038] The dynamic load delay is added to the preset inherent processing delay to form the gateway processing delay component.

[0039] According to one aspect of the present application, obtaining a terminal processing delay component includes:

[0040] Parse baseline capability levels and operational status indications from terminal messages;

[0041] Determine the baseline processing delay based on the baseline capability level and determine the status multiplier factor based on the operating status indication;

[0042] Multiply the baseline processing delay by the state multiplier factor to generate the terminal processing delay component.

[0043] In one embodiment of the present application, the gateway monitors multiple key performance indicators (KPIs) of itself in real time, such as CPU occupancy rate ρ cpu , Number of active users N active_users And the downstream scheduling queue depth Q depth These real-time operating status indicators are weighted and quantified to generate a comprehensive load factor L GW , which is a normalized dimensionless value in the range [0, 1]. Specifically, each indicator is normalized, for example, the normalized CPU occupancy ρ* cpu =ρ cpu / ρ max , and then perform weighted summation: L GW =w cpu ·ρ* cpu +w N ·N*+wQ Q*; where w cpu , w N , w Q is the preset weight coefficient, and the sum of the three is 1; for example, it can be set to w cpu =0.5, w N =0.3, w Q =0.2;ρ max is the maximum CPU occupancy, N* is the normalized number of active users, and Q* is the normalized downlink scheduling queue depth. Through a nonlinear function, the comprehensive load factor L GW Mapped to dynamic load delay T load，GW Preferably, an exponential function is used to simulate the sharp deterioration of latency under high load, and the formula is as follows: load，GW =α·(L GW )β; where α is the load delay scaling factor, for example, 2.0ms; β is the load sensitivity index, for example, 2. The dynamic load delay is compared with a preset intrinsic processing delay T representing the basic performance of the gateway station. inherent，GW (e.g. 1.0ms) are added to form the final gateway processing delay component T proc，GW , T proc，GW =T inherent，GW +T load，GW , used to quantify the processing delay on the network side.

[0044] The gateway parses two key pieces of information from the received terminal message: the baseline capability level CUT and the real-time operation status indicator SUT. Based on the baseline capability level CUT, a benchmark processing delay T is determined. base，UT The gateway maintains a mapping table, for example: CUT = 1 (high performance terminal) corresponds to T base，UT =0.5ms; CUT=2 (standard terminal) corresponds to T base，UT =1.0ms; CUT=3 (IoT terminal) corresponds to T base，UT =1.5ms. A state multiplier MUT is determined based on the operating state indication SUT. For example: SUT=Idle corresponds to MUT=1.2; SUT=Nominal corresponds to MUT=1.0; SUT=Stressed corresponds to MUT=1.5. base，UT Multiplied by the state multiplier factor MUT, the terminal processing delay component T is generated. proc，UT , T proc，UT =T base，UT MUT(SUT), used to quantify the processing delay on the terminal side.

[0045] The gateway processing delay component T proc，GW and the terminal processing delay component Tproc，UT Sum up and get the final dynamic total processing delay T proc_total , T proc_total =T proc，GW +T proc，UT In a specific application, it is assumed that a standard terminal (CUT=2) communicates with a gateway in a normal state (SUT=Nominal). The inherent processing delay of the gateway is T inherent，GW =1.0ms, and the current load calculated L GW =0.5, calculate the terminal delay: T base，UT =1.0ms, MUT=1.0, then T proc，UT =1.0*1.0=1.0ms. Calculate the gateway delay: T load，GW =2.0*(0.5) 2 =0.5ms, then T proc，GW =1.0+0.5=1.5ms. Calculate the total processing delay: T proc_total =1.5+1.0=2.5ms. This 2.5ms result is used as the output for the subsequent calculation of the total HARQ delay. Through the above steps, bidirectional, multi-dimensional, and dynamic precise calculation of HARQ processing delay is achieved, improving the accuracy of delay estimation.

[0046] In another embodiment of the present application, the dynamic total processing delay T proc_total It consists of two parts: the processing delay T of the satellite gateway proc，GW and the processing delay T of the user terminal proc，UT , T proc_total =T proc，GW +T proc，UT . The processing delay of the terminal is determined by its hardware baseline capability and current operating status. Baseline Capability Negotiation When the terminal joins the network, it not only reports the HD-FDD capability, but also reports a terminal processing capability class (UT Processing Capability Class, CUT). This class represents its hardware performance, CUT∈{1, 2, 3, ...} (for example: 1 represents a high-performance computing platform, 2 represents a standard portable terminal, and 3 represents a low-power IoT terminal). The gateway maintains a mapping table to map the capability class CUT to a baseline processing delay T base，UT , T base，UT=LookupTable(CUT); For example: LookupTable(1)=0.5ms, LookupTable(2)=1.0ms, LookupTable(3)=1.5ms. Operating State Factor (OperatingStateFactor) The terminal will report a processing state indicator (ProcessingStateIndicator, SUT) to the gateway periodically or when the state changes, SUT∈{Idle, Nominal, Stressed}, where Idle means the terminal is in low power or standby mode; Nominal means the terminal is operating normally and the processing load is within the expected range; Stressed means the terminal is performing high-load tasks (such as software updates, local AI calculations, etc.) and CPU / memory resources are tight. The gateway applies a state multiplier factor MUT based on the SUT, MUT(Idle)=1.2 (additional time is required to wake up from standby); MUT(Nominal)=1.0 (baseline state); MUT(Stressed)=1.5 (resource preemption causes communication processing to slow down); and finally T proc，UT The calculation formula is T proc，UT =T base，UT ·MUT(SUT).

[0047] The processing delay of the gateway is determined by its inherent processing time and the real-time system load. inherent，GW ) is a pre-calibrated value that represents the minimum time required for the gateway to process a HARQ process under zero load, which depends on its hardware and software architecture. This value is relatively fixed, for example, T inherent，GW =1.0ms. Real-time load factor (L GW The gateway monitors its own key performance indicators (KPIs) in real time and calculates a normalized comprehensive load factor. The monitoring indicators include CPU usage: ρ cpu ; Number of active users: N active_users ; Downstream scheduling queue depth: Q depth Normalize each indicator to the interval [0, 1], ρ* cpu =ρ cpu / ρ max ; N*=N active_users / N max_users ; Q*=Q depth / Q max_depth ; where N max_users is the maximum number of active users, Q max_depth The maximum downlink scheduling queue depth. Weighted calculation load factor: L GW =w cpu ρ* cpu +w NN*+w Q Q*; where w cpu +w N +w Q =1, the weight can be adjusted according to the experimental data to reflect the impact of different indicators on the delay. Dynamic load delay (T load，GW ) Processing latency typically increases nonlinearly with increasing load. An exponential function is used to model this relationship to reflect the sharp deterioration of latency under high load: T load，GW =α·(L GW )β, where α is the load delay scaling factor in milliseconds; β is the load sensitivity index, usually β>1 (for example, β=2), indicating that the delay increases faster as the load increases. proc，GW Calculation formula: T proc，GW =T inherent，GW +T load，GW =T inherent，GW +α(w cpu ρ* cpu +w N N*+w Q Q*)β. The gateway integrates all dynamically calculated values ​​into the original HARQ pattern generation logic. The total HARQ delay calculation formula is: T HARQ_total =T proc_total +T propagation ;T HARQ_total =(T proc，GW +T proc，UT )+f(ephemeris, terminal position).

[0048] This embodiment considers both the network-side load and the terminal-side status, making latency estimation more comprehensive and fairer. It decomposes the abstract load into quantifiable, multi-dimensional KPIs and uses a nonlinear model to more closely align with real-world system behavior. It introduces reporting of terminal capability levels and service status, enabling negotiation between the network and the terminal regarding processing capabilities, rather than unilateral assumptions on the network side.

[0049] According to one aspect of the present application, the HARQ transmission pattern includes a timing relationship;

[0050] The timing relationship includes the downlink scheduling grant period, the uplink data transmission period, and the downlink HARQ feedback period;

[0051] An uplink and downlink switching protection period is set between the downlink scheduling grant period and the uplink data transmission period, and between the uplink data transmission period and the downlink HARQ feedback period.

[0052] According to one aspect of the present application, the total HARQ delay is used as a decision input to determine the number of HARQ processes; wherein the number of HARQ processes is used for HARQ resource configuration of a satellite gateway.

[0053] According to one aspect of the present application, the duration of the uplink data transmission period in the HARQ transmission pattern is dynamically set according to the total HARQ delay.

[0054] In one embodiment of the present application, the gateway calculates the total HARQ delay T HARQ_total As a key decision input to determine the number of HARQ processes N HARQ In HD-FDD systems, the number of HARQ processes is directly related to the maximum supported round trip time (RoundTripTime). A simple way to determine it is (assuming the frame length is 1ms): N HARQ =┌T HARQ_total / (Frame_Length) ┐-1 or other predefined mapping rules, where Frame_Length is the length of a single frame and ┌ ┐ means rounding up. For example, if T HARQ_total is 6ms, then N HARQ It may be determined to be 5. If T HARQ_total Increased to 8ms, N HARQ It is correspondingly determined to be 7. The number of HARQ processes is used by the gateway to perform subsequent HARQ resource configuration and scheduling. The HARQ transmission pattern specifically includes a set of timing relationships. The timing relationship includes at least: a downlink scheduling authorization period for sending uplink resource allocation information, an uplink data transmission period for the terminal to send data, and a downlink HARQ feedback period for sending ACK / NACK feedback. Preferably, in order to avoid uplink and downlink signal interference, an uplink and downlink switching protection period is set between the downlink scheduling authorization period and the uplink data transmission period, and between the uplink data transmission period and the downlink HARQ feedback period. The gateway determines the HARQ delay based on the total HARQ delay T HARQ_total , dynamically set the duration or relative position of each period in the HARQ transmission pattern. In particular, the duration of the uplink data transmission period or its position in the pattern is based on T HARQ_total To ensure that after the transmission delay changes, the HARQ feedback can still accurately correspond to the corresponding data transmission.

[0055] In a specific application, assuming the frame length is 1ms, the uplink and downlink switching protection periods each occupy 1 subframe. HARQ_total The gateway determines N HARQ=5. The generated transmission pattern can be: 5 downlink subframes (for transmission scheduling grant) -> 1 protection subframe -> 5 uplink subframes (for data transmission) -> 1 protection subframe -> downlink HARQ feedback. In this case, the time interval from UL grant to uplink transmission and from uplink transmission to downlink feedback is 6 subframes (6ms). Due to changes in satellite position or increased terminal load, the calculated T HARQ_total Increased to 8ms. The gateway determines N HARQ =7. The generated transmission pattern is adjusted accordingly: 7 downlink subframes -> 1 protection subframe -> 7 uplink subframes -> 1 protection subframe -> downlink HARQ feedback. At this point, the interval between each key event is adjusted to 8 subframes (8ms). Through the above steps, the dynamically calculated total delay is implemented in the specific transmission pattern, achieving end-to-end dynamic adaptation of the entire HARQ process, ensuring retransmission efficiency and throughput in complex and changing satellite communication environments. The -> represents the temporal phase transition, that is, the transmission process between different subframes.

[0056] According to one aspect of the present application, a HARQ retransmission method applicable to a satellite low-orbit HD-FDD system, when applied to a terminal, includes: reporting terminal duplex capability information, terminal location information, and a terminal message including a baseline capability level and an operating status indication to a satellite gateway;

[0057] receiving a HARQ transmission pattern dynamically generated by a satellite gateway in response to reported information;

[0058] Following the HARQ transmission pattern, sending uplink data in one or more uplink data transmission periods defined therein, and monitoring downlink HARQ feedback in one or more downlink HARQ feedback periods defined therein;

[0059] According to one aspect of the present application, the step of reporting a terminal message including a baseline capability level and an operating status indication includes: reporting the baseline capability level when the terminal accesses the network; and dynamically reporting the operating status indication during the communication process.

[0060] In one embodiment of the present application, the user terminal's behavior is as follows: upon network access, the terminal reports its baseline capability level (CUT) to the satellite gateway. During communication with the gateway, the terminal dynamically reports its current operational status indicator (SUT) periodically or when its operational status changes. These two pieces of information, along with terminal duplex capability information and location information, are included in a terminal message and sent to the gateway. The terminal receives a HARQ transmission pattern dynamically generated by the satellite gateway in response to various information reported by the terminal. The terminal strictly adheres to the timing of the HARQ transmission pattern. Specifically, the terminal transmits uplink data during one or more uplink data transmission periods defined in the pattern and monitors downlink HARQ feedback (ACK / NACK information) from the gateway during one or more downlink HARQ feedback periods defined therein. Through these steps, the terminal can proactively inform the network of its processing capabilities and real-time status, and collaborate with the network to dynamically adjust HARQ timing, thereby achieving optimal communication performance under various conditions.

[0061] In a specific embodiment of the present application, the satellite payload can receive a duplex capability message from the satellite terminal station indicating the duplex capability of the terminal station. This capability is used to process the subsequent HARQ process. After the satellite terminal station joins the network, it will report its own duplex capability and location information. After the satellite gateway obtains this information, if it finds that this terminal only supports HD-FDD, it will generate a transmission pattern for this terminal station. The transmission pattern needs to take into account the link transmission delay. The transmission delay is determined according to the ephemeris information and the terminal position. For example, if the satellite orbit altitude is 600km and the terminal altitude is 0, it can be approximately considered that the transmission delay is 600 / 300000=2ms. Assuming that there is a fixed delay (4ms) between downlink (DL) transmission, uplink (UL) transmission, and DL confirmation, and the frame length is 1ms, then the fixed HARQ delay of the air interface is 6ms, and the transmission pattern is as follows. Figure 4 As shown, the number of HARQ processes is 5 at this time. The white downlink subframes 0 to 4 transmit scheduling authorization, the subsequent green subframe is the uplink and downlink switching protection subframe, and the next 5 yellow subframes are for uplink data transmission. After a protection subframe, downlink HARQ feedback will be performed. Therefore, UL authorization + 6 (subframes) is uplink transmission, and uplink transmission + 6 (subframes) is downlink HARQ feedback. Assuming that the satellite altitude is 1200km and the terminal altitude is 0, the transmission delay between the satellite and the terminal is 1200 / 300000=4ms. Assuming that there is a fixed delay (4ms) between DL transmission, UL transmission, and DL confirmation, and the frame length is 1ms, then the fixed HARQ delay of the air interface is 8ms, and the transmission pattern is as follows Figure 5As shown, the number of HARQ processes is 7. The white downlink subframes 0 to 6 transmit scheduling grants. The following green subframe is the uplink / downlink switching protection subframe. The next seven yellow subframes transmit uplink data. After a protection subframe, downlink HARQ feedback is provided. Therefore, UL grants + 8 (subframes) are uplink transmissions, and uplink transmissions + 8 (subframes) are downlink HARQ feedback. This embodiment dynamically adjusts the transmission pattern based on the satellite's orbital position. The algorithm uses the number of HARQ processes and HARQ delay as the fixed processing delay (4ms) plus the satellite link delay.

[0062] The present application solves the HARQ timing mismatch problem caused by the use of a fixed processing delay margin in the prior art through a two-way, multi-dimensional dynamic processing delay calculation method. The present application no longer relies on a static margin preset for the worst case, but decomposes the total processing delay into two dynamic components on the network side and the terminal side. On the terminal side, a negotiation mechanism is introduced, whereby the terminal reports the processing capability level representing its hardware performance when accessing the network, and periodically reports a processing status indication reflecting its current CPU or memory load during the communication process. Based on this, the gateway station can calculate an exclusive terminal processing delay component for each terminal that changes with its real-time status. On the network side, the gateway station monitors multiple key performance indicators such as its own CPU occupancy rate, number of active users, and scheduling queue depth in real time, generates a comprehensive load factor through weighted quantization, and uses a nonlinear function to map the load factor to the processing delay component of the gateway station itself. By summing these two dynamic delay components that are precisely quantified from the terminal and network sides respectively, a total processing delay that can truly reflect the current actual processing capabilities of both ends of the link is obtained, thereby fundamentally solving the timing deviation problem caused by static assumptions and ensuring the accurate timing of the HARQ process. By applying the above-mentioned high-precision total HARQ delay to the dynamic generation and adjustment of the transmission pattern, the problem of low resource utilization of HD-FDD transmission patterns caused by inaccurate timing in the existing technology is solved, and resource utilization efficiency is optimized. The above-mentioned calculated total HARQ delay, which integrates the two-way dynamic processing delay and the real-time propagation delay, is directly used as the core decision basis for configuring the HARQ transmission scheme. Specifically, the total HARQ delay is used to dynamically determine the optimal number of HARQ processes required to support the current round-trip time, avoiding process blocking due to insufficient delay estimation or resource idleness due to excessive delay estimation. Furthermore, this total HARQ delay is used to precisely define the duration and relative positions of key periods within the HD-FDD pattern, including downlink scheduling, uplink transmission, and downlink feedback, as well as the uplink and downlink handover protection intervals between them. The entire transmission pattern adaptively adjusts to every subtle change in the total HARQ delay, ensuring that data and acknowledgments are sent and received in the correct time windows. This minimizes idle waiting and protection overhead, thereby improving spectrum resource utilization and system throughput in HD-FDD systems.

[0063] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the scope of protection of the present invention.

Claims

1. A HARQ retransmission method applicable to a satellite low-orbit HD-FDD system, characterized in that: include: Receive terminal duplex capability information, terminal location information, and terminal messages; Combine the terminal location information with the pre-stored satellite ephemeris information to calculate the dynamic propagation delay; Combine the real-time operation status of the satellite gateway and the terminal message to generate dynamic processing delay; Integrate dynamic propagation delay and dynamic processing delay to construct total HARQ delay; In response to the HD-FDD mode indicated by the duplex capability information of the terminal, using the total HARQ delay, create a HARQ transmission pattern for the terminal; Generate dynamic processing delays, including: Evaluate the real-time operational status of satellite gateways and determine the processing delay components of gateways; Parse the terminal message to obtain the terminal processing delay component; The dynamic processing delay is obtained by summing the gateway processing delay component and the terminal processing delay component. Determine the components of gateway processing delay, including: Performing weighted quantification on the real-time operating status of the satellite gateway to generate a comprehensive load factor; wherein the real-time operating status includes at least one of CPU occupancy, number of active users, or scheduling queue depth; The comprehensive load factor is mapped to dynamic load delay through a nonlinear function; Add the dynamic load delay to the preset inherent processing delay to form the gateway processing delay component; Obtain terminal processing delay components, including: Parse baseline capability levels and operational status indications from terminal messages; Determine the baseline processing delay based on the baseline capability level and determine the status multiplier factor based on the operating status indication; Multiply the baseline processing delay by the state multiplier factor to generate the terminal processing delay component.

2. The method according to claim 1, characterized in that Calculate dynamic propagation delay, including: Analyze satellite ephemeris information to obtain the real-time coordinates of the satellite, and combine it with the terminal location information to calculate the straight-line distance between the satellite and the terminal; Divide the straight-line distance between the satellite and the earth by the speed of light to calculate the dynamic propagation delay.

3. The method according to claim 1, characterized in that The HARQ transmission pattern includes timing relationships; The timing relationship includes the downlink scheduling grant period, the uplink data transmission period, and the downlink HARQ feedback period; An uplink and downlink switching protection period is set between the downlink scheduling grant period and the uplink data transmission period, and between the uplink data transmission period and the downlink HARQ feedback period.

4. The method according to claim 1, wherein Also includes: The total HARQ delay is used as a decision input to determine the number of HARQ processes; The number of HARQ processes is used for HARQ resource configuration of the satellite gateway.

5. The method according to claim 3, characterized in that Also includes: The duration of the uplink data transmission period in the HARQ transmission pattern is dynamically set according to the total HARQ delay.

6. A HARQ retransmission method applicable to a satellite low-orbit HD-FDD system, characterized in that: When applied to a terminal, it includes: Report terminal duplex capability information, terminal location information, and terminal messages containing baseline capability levels and operational status indications to the satellite gateway; receiving a HARQ transmission pattern dynamically generated by a satellite gateway in response to reported information; Following the HARQ transmission pattern, sending uplink data in one or more uplink data transmission periods defined therein, and monitoring downlink HARQ feedback in one or more downlink HARQ feedback periods defined therein; The process of generating the HARQ transmission pattern includes: Combine the terminal location information with the pre-stored satellite ephemeris information to calculate the dynamic propagation delay; Perform weighted quantification on the real-time operating status of satellite gateways to generate a comprehensive load factor; The comprehensive load factor is mapped to dynamic load delay through a nonlinear function; Add the dynamic load delay to the preset inherent processing delay to form the gateway processing delay component; Parse baseline capability levels and operational status indications from terminal messages; Determine the baseline processing delay based on the baseline capability level and determine the status multiplier factor based on the operating status indication; Multiplying the baseline processing delay by the state multiplier factor to generate a terminal processing delay component; The dynamic processing delay is obtained by summing the gateway processing delay component and the terminal processing delay component. Integrate dynamic propagation delay and dynamic processing delay to construct total HARQ delay; In response to the HD-FDD mode indicated by the duplex capability information of the terminal, a HARQ transmission pattern is created for the terminal using the total HARQ delay.

7. The method according to claim 6, characterized in that When applied to a terminal, the steps for reporting a terminal message including a baseline capability level and an operational status indication include: When the terminal accesses the network, the baseline capability level is reported; during the communication process, the operation status indication is dynamically reported.

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