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

Abstract

The invention discloses an HARQ retransmission method suitable for a satellite low-orbit HD-FDD system. The HARQ retransmission method comprises the following steps: receiving terminal duplex capability information, position information and a terminal message; calculating dynamic propagation time delay by combining the terminal position and the satellite ephemeris; respectively generating a gateway station processing time delay component and a terminal processing time delay component in combination with the real-time operation state of the gateway station and the terminal report, and adding to form a total processing time delay; and the dynamic propagation time delay and the dynamic total processing time delay are fused to construct total HARQ time delay, and an efficient HARQ transmission pattern is created for the terminal in the HD-FDD mode according to the total HARQ time delay. According to the method, the accuracy of the HARQ time sequence and the resource utilization rate are improved through precise and bidirectional dynamic sensing of the processing time delay.

Description

Technical Field

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

[0002] In the current wave of communication technologies, satellite Internet is moving from the era of traditional geostationary orbit (GEO) satellite communication towards a new era centered on low-earth orbit (LEO) satellite constellations. Due to the significant reduction in the orbital altitude of LEO satellites, a series of revolutionary advantages such as low signal propagation delay, small link loss, and high signal-to-noise ratio are brought about, making it possible to provide high-speed, low-latency network services with seamless global coverage. This transformation is not only a change in the satellite orbital altitude but also triggers a profound revolution in the entire communication system, especially in terminal and ground station technologies. To cope with the high-speed movement of LEO satellites relative to the ground, communication beams must be tracked and aligned in real time and accurately, which greatly promotes the wide application of phased array antenna technology in the field of satellite communication. Especially in portable terminal devices for individual users, due to strict restrictions on volume, power consumption, and cost, the design scheme of co-aperture and co-planar transceiver antennas has become the mainstream choice. This antenna architecture naturally adapts to the half-duplex frequency division duplex (HD-FDD) system, making it an important operating mode in modern LEO satellite communication systems. At the same time, the high signal-to-noise ratio link conditions make it normal to adopt high-order modulation and coding (High-Order Modulation and Coding) schemes to pursue higher spectral efficiency, but this inevitably brings challenges of increased frame error rate at the air interface. Therefore, introducing an efficient and reliable hybrid automatic repeat request (HARQ) mechanism is of crucial research significance and application value for ensuring the reliability of data transmission, reducing the frame error rate at the air interface, and improving the overall system throughput.

[0003] Currently, the HARQ technology for wireless communication systems has been quite mature, especially widely deployed and verified in terrestrial cellular communications (such as 4G LTE and 5G NR). The HARQ timing design in these systems is centered around a relatively fixed or predictable loopback time (RTT). In the context of non-geostationary orbit (NGSO) satellite communications, especially low-earth orbit (LEO) satellite communications, the prior art has also recognized the drastic changes in propagation delay caused by the high-speed movement of satellites. Some preliminary improvement schemes have started to attempt to incorporate the dynamic propagation delay into the HARQ timing calculation. The common approach of such schemes is to calculate the physical propagation delay of the signal in space in real-time or near real-time through satellite ephemeris and terminal position information. Then, this dynamically changing propagation delay is added to a pre-set and fixed processing delay margin to serve as the total HARQ loopback time, and the relevant parameters of HARQ, such as the number of HARQ processes, are configured accordingly. This fixed processing delay margin is usually calibrated and reserved based on the processing capabilities of network devices (such as gateway stations) and terminal devices in the worst-case scenario, and it is regarded as a static parameter determined during the system design stage and does not adjust with changes in network load or terminal status during actual operation.

[0004] However, through in-depth analysis, it is found that the above prior art solutions have profound and specific technical problems when dealing with highly dynamic LEO satellite communication scenarios. The core crux lies in the static and one-size-fits-all approach to processing delay, which leads to two key defects in practical applications: First, the mismatch problem between HARQ timing and actual processing capabilities. Second, the low resource utilization rate of the HD-FDD transmission pattern. Summary of the Invention

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

[0006] Technical solution: A HARQ retransmission method applicable to a satellite low-orbit HD-FDD system includes:

[0007] Receiving terminal duplex capability information, terminal position information, and terminal messages;

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

[0009] Combining the real-time operating status of the satellite gateway station and the terminal message to generate a dynamic processing delay;

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

[0011] In response to the HD-FDD mode indicated by the terminal duplex capability information, 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, ensuring accurate timing of the HARQ process; improving the spectrum resource utilization rate and system throughput under the HD-FDD system. Description of the Drawings

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

[0014] Figure 2 It is a flowchart of the steps for calculating the dynamic propagation delay provided by an embodiment of the present application.

[0015] Figure 3 It is a flowchart of the steps for generating the dynamic processing delay provided by an embodiment of the present application.

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

[0017] Figure 5 It is the transmission pattern when the HARQ delay is 8 ms in an embodiment of the present application. Detailed Embodiments

[0018] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

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

[0020] In the research, it is found that the existing technology adopts a fixed processing delay margin, completely ignoring the real-time dynamics of the processing capabilities at both ends of the communication link (i.e., the satellite gateway station and the user terminal). On the network side, the processing load of the satellite gateway station fluctuates in real time with the changes in the number of active users, traffic volume, and scheduling complexity within its coverage area. On the terminal side, modern intelligent terminals often need to run multiple applications simultaneously, and the computing resources used for communication protocol stack processing will be preempted by local high-load tasks (such as software updates, high-definition video playback, and even local artificial intelligence computing), resulting in a significant fluctuation in its actual processing ability. In this case, a fixed processing delay margin set to cope with the worst-case scenario is too conservative for the vast majority of terminals and gateway stations in a normal working state, which will introduce unnecessary waiting delays and directly reduce the spectrum utilization rate. On the contrary, if the margin is set too optimistically, when the gateway station or the terminal is truly under high load pressure, it will cause the HARQ process to fail due to processing timeout, triggering unnecessary retransmissions, and ultimately seriously deteriorating the system throughput and user experience. In the HD-FDD system, the transmission pattern composed of the uplink and downlink transmission time slots, feedback time slots, and guard time slots is highly correlated with the accuracy of the total HARQ delay. Since the existing technology cannot accurately perceive and quantify the real, two-way, and dynamic processing delays, there are inherent biases in the calculated total HARQ delay. This bias directly leads to the generated transmission pattern being suboptimal, which may cause frequent interruptions or pauses in the HARQ process pipeline, or leave an overly long guard time during the uplink and downlink handover. In satellite communication where spectrum resources are extremely precious, this causes resource waste and fails to maximize the potential of the system.

[0021] As Figure 1 shown, a HARQ retransmission method applicable to the low-earth-orbit HD-FDD satellite system is proposed, including the following steps:

[0022] Receive the terminal duplex capability information, terminal location information, and terminal message 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 operating status of the satellite gateway station and the terminal message to generate the dynamic processing delay;

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

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

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

[0028] Parsing satellite ephemeris information to obtain the real-time coordinates of the satellite, and combining with the terminal position information to calculate the straight-line distance between the satellite and the terminal;

[0029] Dividing the straight-line distance between the satellite and the terminal by the speed of light to convert the dynamic propagation delay.

[0030] In an embodiment of the present application, the satellite gateway station receives various types of information from the user terminal. These information include terminal duplex capability information for identifying the terminal duplex mode (for example, indicated as the HD-FDD mode), terminal position information for positioning (for example, GPS coordinates), and terminal messages carrying other communication parameters. The gateway station combines the terminal position information with the satellite ephemeris information of a low-earth orbit satellite it serves to calculate the dynamic propagation delay. Specifically, the gateway station parses the real-time three-dimensional coordinates of the satellite from the ephemeris information, and combines with the terminal position information to calculate the real-time straight-line distance between the satellite and the terminal. Dividing this straight-line distance between the satellite and the terminal by the speed of light (about 300,000 km / s in vacuum) to convert the one-way dynamic propagation delay T propagation . For example, if at a certain moment the satellite orbital altitude is 600 km, the terminal altitude is 0, and the satellite is in the zenith direction of the terminal, the straight-line distance between the satellite and the terminal is approximately 600 km, and the calculated T propagation is about 600 km / 300000 km / s = 2 ms. If at another moment the satellite orbital altitude becomes 1200 km, the calculated T propagation is about 4 ms. The gateway station, based on its own real-time operating state, processes the received terminal messages to generate a dynamic total processing delay T proc_total . Obtaining the dynamic propagation delay T propagation and the dynamic processing delay T proc_total and then fusing the two to construct the total HARQ delay T HARQ_total . The calculation formula is: T HARQ_total = T proc_total + T propagation . The gateway station responds to the HD-FDD mode indicated by the terminal duplex capability information and uses the total HARQ delay T HARQ_total to create a dedicated HARQ transmission pattern for this terminal. This HARQ transmission pattern defines the timing arrangement of the uplink and downlink transmissions in subsequent communications, and is used by the satellite gateway station to perform precise communication scheduling with this terminal. Through the above steps, this embodiment can dynamically adjust the HARQ timing according to the relative positions of the satellite and the terminal, and initially solves the retransmission efficiency problem caused by the change of the propagation delay.

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

[0032] Evaluating the real-time operating status of the satellite gateway station to determine the gateway station processing delay component;

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

[0034] Summing the gateway station processing delay component and the terminal processing delay component to obtain the dynamic processing delay.

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

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

[0037] Mapping the comprehensive load factor to a dynamic load delay through a non-linear function;

[0038] Adding the dynamic load delay to the preset inherent processing delay to form the gateway station processing delay component.

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

[0040] Parsing the baseline capability level and operating status indication from the terminal message;

[0041] Determining the reference processing delay based on the baseline capability level and determining the status multiplier factor based on the operating status indication;

[0042] Multiplying the reference processing delay by the status multiplier factor to generate the terminal processing delay component.

[0043] In an embodiment of the present application, the gateway station monitors its own multiple key performance indicators (KPIs) in real time, such as the CPU occupancy rate ρ cpu , the number of active users N active_users and the depth Q of the downlink scheduling queue depth . Performing weighted quantization on these real-time operating status indicators to generate a comprehensive load factor L GW , which is a normalized dimensionless value in the range [0, 1]. Specifically, normalizing each indicator, for example, the normalized CPU occupancy rate ρ* cpu = ρ cpu / ρ max , and then performing weighted summation: L GW = w cpu · ρ* cpu + w N · N* + wQ ·Q*; where w cpu , w N , w Q is a preset weight coefficient, and the sum of the three is 1; for example, it can be set as w cpu = 0.5, w N = 0.3, w Q = 0.2; ρ max is the maximum CPU occupancy rate, N* is the normalized number of active users, and Q* is the normalized downlink scheduling queue depth. Through a non-linear function, the comprehensive load factor L GW is mapped to the dynamic load delay T load，GW . Preferably, an exponential function is used to simulate the sharp deterioration of the delay under high load, and the formula is as follows: T load，GW = α·(L GW )β; where α is the load delay scaling coefficient, such as 2.0 ms; β is the load sensitivity index, such as 2. Adding this dynamic load delay to an inherent processing delay T inherent，GW (such as 1.0 ms) representing the basic performance of the gateway station forms the final gateway station processing delay component T proc，GW , T proc，GW = T inherent，GW + T load，GW , which is used to quantify the processing delay on the network side.

[0044] The gateway station parses two key pieces of information from the received terminal messages: the baseline capability level CUT and the real-time operating status indication SUT. A reference processing delay T base，UT is determined based on the baseline capability level CUT. The gateway station internally maintains a mapping table, for example: CUT = 1 (high-performance terminal) corresponds to T base，UT = 0.5 ms; CUT = 2 (standard terminal) corresponds to T base，UT = 1.0 ms; CUT = 3 (Internet of Things terminal) corresponds to T base，UT = 1.5 ms. A status multiplier factor MUT is determined based on the operating status 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. Multiplying the reference processing delay T base，UT by the status multiplier factor MUT generates the terminal processing delay component T proc，UT , T proc，UT = T base，UT ·MUT(SUT), which is used to quantify the processing delay on the terminal side.

[0045] Adding the gateway station processing delay component T proc，GW to the terminal processing delay component Tproc，UT Perform summation to obtain the final dynamic total processing delay T proc_total , T proc_total = T proc，GW + T proc，UT . In a specific application, assume that a standard terminal (CUT = 2) communicates with a gateway station in a normal state (SUT = Nominal). The inherent processing delay T inherent，GW of the gateway station = 1.0 ms, and L GW calculated from the current load = 0.5. Calculate the terminal delay: T base，UT = 1.0 ms, MUT = 1.0, then T proc，UT = 1.0 * 1.0 = 1.0 ms. Calculate the gateway station delay: T load，GW = 2.0 * (0.5) 2 = 0.5 ms, then T proc，GW = 1.0 + 0.5 = 1.5 ms. Calculate the total processing delay: T proc_total = 1.5 + 1.0 = 2.5 ms. This result of 2.5 ms will be used as the output for the subsequent calculation of the total HARQ delay. Through the above steps, the two-way, multi-dimensional, and dynamic accurate calculation of the HARQ processing delay is realized, improving the accuracy of the delay estimation.

[0046] In another embodiment of the present application, the dynamic total processing delay T proc_total consists of two parts: the processing delay T proc，GW of the satellite gateway station and the processing delay T proc，UT of the user terminal, T proc_total = T proc，GW + T proc，UT . The processing delay of the terminal is jointly determined by its hardware baseline capability and the current operating state. During baseline capability negotiation (Baseline Capability Negotiation) when the terminal accesses the network, it not only reports the HD-FDD capability but also reports a terminal processing capability level (UT Processing Capability Class, CUT). This level represents its hardware performance, CUT ∈ {1, 2, 3,...} (for example: 1 represents a high-performance computing platform, 2 represents a standard portable terminal, 3 represents a low-power Internet of Things terminal). The gateway station side maintains a mapping table that maps the capability level 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. The terminal of the OperatingStateFactor will report a ProcessingStateIndicator (SUT) to the gateway station periodically or when the state changes. SUT ∈ {Idle, Nominal, Stressed}, where Idle means the terminal is in low power consumption or standby mode; Nominal means the terminal is running normally and the processing load is within the expected range; Stressed means the terminal is executing high-load tasks (such as software updates, local AI calculations, etc.) and the CPU / memory resources are tense. The gateway station applies a state multiplication factor MUT according to SUT. MUT(Idle) = 1.2 (extra time is required to wake up from standby); MUT(Nominal) = 1.0 (benchmark state); MUT(Stressed) = 1.5 (communication processing slows down due to resource preemption); Finally, T proc，UT The calculation formula is T proc，UT = T base，UT ·MUT(SUT).

[0047] The processing delay of the gateway station is determined by its inherent processing time and the real-time system load. The inherent processing delay (T inherent，GW ) is a pre-calibrated value, representing the shortest time required for the gateway station to process a HARQ process under zero load, depending on its hardware and software architecture. This value is relatively fixed. For example, T inherent，GW = 1.0ms. The real-time load factor (L GW ) The gateway station monitors multiple key performance indicators (KPIs) of itself in real time and calculates a normalized comprehensive load factor. The monitored indicators include CPU occupancy rate: ρ cpu ; Number of active users: N active_users ; Downlink scheduling queue depth: Q depth . Normalize each indicator to the [0, 1] interval, 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, and Q max_depth is the maximum downlink scheduling queue depth. Calculate the weighted load factor: L GW = w cpu ρ* cpu + w NN* + w Q Q*; where w cpu + w N + w Q = 1, and the weights can be adjusted according to experimental data to reflect the impact degree of different metrics on the delay. The dynamic load delay (T load，GW ) The processing delay usually grows non - linearly with the increase of the load. An exponential function is used to model this relationship to reflect the sharp deterioration of the delay under high load: T load，GW = α·(L GW )β, where α is the load - delay scaling coefficient with the unit of millisecond; β is the load sensitivity index, and usually β > 1 (for example, β = 2), indicating that the delay grows at an accelerating rate with the increase of the load. Finally, the calculation formula of T proc，GW : 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 station integrates all the dynamically calculated values into the original HARQ pattern generation logic. The total HARQ delay calculation formula: T HARQ_total = T proc_total + T propagation ; T HARQ_total =(T proc，GW + T proc，UT ) + f(ephemeris, terminal position).

[0048] This embodiment takes into account both the network - side load and the terminal - side status, making the delay estimation more comprehensive and fair; decomposes the abstract load into quantifiable and multi - dimensional KPIs, and uses a non - linear model, which is closer to the real - world system behavior; introduces the reporting of the terminal capability level and service status, realizing the negotiation of processing capabilities between the network and the terminal, rather than the one - sided assumption of 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 a downlink scheduling authorization period, an uplink data transmission period, and a downlink HARQ feedback period;

[0051] 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, uplink - downlink handover protection periods are respectively set.

[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 the HARQ resource allocation of the satellite gateway station.

[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 based on the total HARQ delay.

[0054] In one embodiment of the present application, the gateway station calculates the total HARQ delay T HARQ_total as a key decision input to determine a number of HARQ processes N HARQ . In an HD-FDD system, the number of HARQ processes is directly related to the maximum round-trip time that can be supported. A simple determination method is (assuming a frame length of 1 ms): N HARQ =┌T HARQ_total / (Frame_Length) ┐ - 1 or other predefined mapping rules, where Frame_Length is the duration of a single frame, and ┌ ┐ represents rounding up. For example, if T HARQ_total is 6 ms, then N HARQ may be determined to be 5. If T HARQ_total increases to 8 ms, N HARQ is correspondingly determined to be 7. This number of HARQ processes is used by the gateway station for subsequent HARQ resource allocation and scheduling. The HARQ transmission pattern specifically includes a set of timing relationships. This timing relationship at least includes: 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, uplink and downlink handover protection periods are respectively 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 station dynamically sets the duration or relative position of each period in the HARQ transmission pattern according to the total HARQ delay T HARQ_total . In particular, the duration of the uplink data transmission period or its position in the pattern is determined according to 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 a frame length of 1 ms, each of the uplink and downlink handover protection periods occupies 1 subframe. The calculated T HARQ_total is 6 ms. The gateway station determines N HARQis 5. The generated transmission pattern can be: 5 downlink subframes (for transmitting scheduling grants) -> 1 protection subframe -> 5 uplink subframes (for data transmission) -> 1 protection subframe -> downlink HARQ feedback. At this time, the time intervals from UL grant to uplink transmission, and from uplink transmission to downlink feedback are both 6 subframes (6 ms). Due to satellite position changes or increased terminal load, the calculated T HARQ_total increases to 8 ms. The gateway determines N HARQ to be 7. The generated transmission pattern is adjusted accordingly to: 7 downlink subframes -> 1 protection subframe -> 7 uplink subframes -> 1 protection subframe -> downlink HARQ feedback. At this time, the time intervals between key events are adjusted to 8 subframes (8 ms). Through the above steps, the dynamically calculated total delay is implemented in the specific transmission pattern, achieving end-to-end full dynamic adaptation of the entire HARQ process and ensuring the retransmission efficiency and throughput in a complex and changing satellite communication environment. Here, -> represents the phase transition in the time sequence, that is, the transmission process between different subframes.

[0056] According to one aspect of the present application, the 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 the satellite gateway in response to the reported information;

[0058] following the HARQ transmission pattern, sending uplink data during one or more uplink data transmission periods defined therein, and listening for downlink HARQ feedback during 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 an embodiment of the present application, the behaviors on the user terminal side are specifically as follows: When the terminal accesses the network (gets online), it reports its own baseline capability level CUT to the satellite gateway station. During the communication process with the gateway station, the terminal will periodically or when its own operating state changes, dynamically report its current operating state indication SUT. These two parts of information, together with the terminal duplex capability information, terminal location information, etc., are included in the terminal message and sent to the gateway station. The terminal receives the HARQ transmission pattern dynamically generated by the satellite gateway station in response to various information reported by it. The terminal strictly follows the timing arrangement of the HARQ transmission pattern. Specifically, it sends uplink data during one or more uplink data transmission periods defined in the pattern, and listens for the downlink HARQ feedback (ACK / NACK information) from the gateway station during one or more downlink HARQ feedback periods defined therein. Through the above steps, the terminal can actively inform the network of its processing capabilities and real-time status, and cooperate with the network side to jointly complete the adjustment of the dynamic HARQ timing, so as to obtain the optimal communication performance under various conditions.

[0061] In a specific embodiment of the present application, the satellite payload can receive a duplex capability message indicating the end station from the satellite end station. The subsequent HARQ process is processed based on this capability. After the satellite end station gets online, it will report its own duplex capability and location information. After the satellite gateway station obtains this information, if it is found that this terminal only supports HD-FDD, a transmission pattern will be generated for this end station. The transmission pattern needs to consider the link transmission delay. The transmission delay is determined according to the ephemeris information and the terminal location. For example, if the satellite orbit altitude is 600 km and the end station altitude is 0, it can be approximately considered that the transmission delay is 600 / 300000 = 2 ms. Assuming that there is a fixed delay (4 ms) between downlink (DL) transmission, uplink (UL) transmission, and DL confirmation, and the frame length is 1 ms, then the fixed HARQ delay of the air interface is 6 ms, and the transmission pattern is as Figure 4 shown. At this time, the number of HARQ processes is 5. Among them, the white downlink subframes 0 to 4 transmit scheduling authorizations, the subsequent green subframe is an uplink-downlink handover protection subframe, and the next 5 yellow subframes are used for uplink data transmission. After a protection subframe, downlink HARQ feedback will be performed. Therefore, UL authorization + 6 (subframes) is the uplink transmission, and uplink transmission + 6 (subframes) is the downlink HARQ feedback. Assuming that the satellite altitude is 1200 km and the terminal altitude is 0, then the transmission delay between the satellite and the terminal is 1200 / 300000 = 4 ms. Assuming that there is a fixed delay (4 ms) between DL transmission, UL transmission, and DL confirmation, and the frame length is 1 ms, then the fixed HARQ delay of the air interface is 8 ms, and the transmission pattern is as Figure 5As shown, the number of HARQ processes is 7 at this time. Among them, the white downlink subframes 0 to 6 transmit scheduling authorizations. The subsequent green subframe is an uplink-downlink handover protection subframe. The next 7 yellow subframes are for uplink data transmission. After a protection subframe, downlink HARQ feedback will be carried out. Therefore, UL authorization + 8 (subframes) is for uplink transmission, and uplink transmission + 8 (subframes) is for downlink HARQ feedback. In this embodiment, the transmission pattern will be dynamically adjusted according to different orbital positions of the satellite. The algorithm is that the number of HARQ processes and the HARQ delay are a fixed processing delay (4 ms) plus the satellite link delay.

[0062] Through a two-way and multi-dimensional dynamic processing delay calculation method, this application solves the problem of HARQ timing mismatch caused by the use of a fixed processing delay margin in the prior art. Instead of relying on a static margin preset for the worst case, this application decomposes the total processing delay into two dynamic components on the network side and the terminal side. On the terminal side, by introducing a negotiation mechanism, that is, the terminal reports the processing capacity level representing its hardware performance when accessing the network, and periodically reports the processing status indication reflecting its current CPU or memory load during the communication process. Based on this, the gateway can calculate a dedicated terminal processing delay component for each terminal, which varies with its real-time status. On the network side, the gateway monitors multiple key performance indicators such as its own CPU occupancy rate, the number of active users, and the depth of the scheduling queue in real time, generates a comprehensive load factor through weighted quantization, and uses a non-linear function to map this load factor to the gateway's own processing delay component. By summing these two dynamically quantized delay components accurately obtained from the terminal and the network side respectively, a total processing delay that can truly reflect the current actual processing capabilities at both ends of the link is obtained, thus fundamentally solving the timing deviation problem caused by static assumptions and ensuring the accurate timing of the HARQ process. By applying the above high-precision total HARQ delay to the dynamic generation and adjustment of the transmission pattern, the problem of low resource utilization rate of the HD-FDD transmission pattern caused by inaccurate timing in the prior art is solved, and the optimization of resource utilization efficiency is achieved. The calculated total HARQ delay that integrates two-way dynamic processing delay and real-time propagation delay is directly used as the core decision basis for configuring the HARQ transmission scheme. Specifically, this 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 caused by insufficient delay estimation or resource idleness caused by excessive delay estimation. In addition, this total HARQ delay is also used to accurately set the duration and relative positions of key time periods such as downlink scheduling, uplink transmission, and downlink feedback in the HD-FDD pattern, as well as the uplink-downlink handover protection interval between them. The entire transmission pattern can adaptively adjust with every subtle change in the total HARQ delay, ensuring that data and acknowledgment information can be sent and received within the correct time window, minimizing invalid waiting and protection overhead, and thus improving the spectrum resource utilization rate and system throughput under the HD-FDD system.

[0063] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of 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 belong to the protection scope of the present invention.

Claims

1. A HARQ retransmission method applicable to a satellite low-earth orbit HD-FDD system, characterized in that It includes: Receiving terminal duplex capability information, terminal location information, and terminal messages; Combining the terminal location information with pre-stored satellite ephemeris information to calculate the dynamic propagation delay; Combining the real-time operating status of the satellite gateway station and the terminal messages to generate the dynamic processing delay; Fusing the dynamic propagation delay and the dynamic processing delay to construct the total HARQ delay; In response to the HD-FDD mode indicated by the terminal duplex capability information, using the total HARQ delay to create a HARQ transmission pattern for the terminal.

2. The method according to claim 1, wherein Calculating the dynamic propagation delay includes: Parsing the satellite ephemeris information to obtain the real-time coordinates of the satellite, and combining the terminal location information to calculate the straight-line distance between the satellite and the terminal; Dividing the straight-line distance between the satellite and the terminal by the speed of light to convert the dynamic propagation delay.

3. The method according to claim 1, wherein Generating the dynamic processing delay includes: Evaluating the real-time operating status of the satellite gateway station to determine the gateway station processing delay component; Parsing the terminal messages to obtain the terminal processing delay component; Summing the gateway station processing delay component and the terminal processing delay component to obtain the dynamic processing delay.

4. The method according to claim 3, characterized in that Determining the gateway station processing delay component includes: Performing weighted quantization on the real-time operating status of the satellite gateway station to generate a comprehensive load factor; where the real-time operating status includes at least one of CPU occupancy rate, number of active users, or depth of the scheduling queue; Mapping the comprehensive load factor to a dynamic load delay through a non-linear function; Adding the dynamic load delay to the preset inherent processing delay to form the gateway station processing delay component.

5. The method according to claim 3, wherein Obtaining the terminal processing delay component includes: Parsing the baseline capability level and the operating status indication from the terminal messages; Determining the reference processing delay based on the baseline capability level and determining the status multiplier factor based on the operating status indication; Multiplying the reference processing delay by the status multiplier factor to generate the terminal processing delay component.

6. The method according to claim 1, wherein The HARQ transmission pattern includes a timing relationship; The timing relationship includes a downlink scheduling authorization period, an uplink data transmission period, and a downlink HARQ feedback period; Setting an uplink-downlink handover protection period 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, respectively.

7. The method according to claim 1, characterized in that, It also includes: Using the total HARQ delay as a decision input to determine the number of HARQ processes; Wherein, the number of HARQ processes is used for the HARQ resource configuration of the satellite gateway station.

8. The method according to claim 6, characterized in that, It also includes: Dynamically setting the duration of the uplink data transmission period in the HARQ transmission pattern according to the total HARQ delay.

9. A HARQ retransmission method applicable to a satellite low-earth orbit HD-FDD system, characterized in that, When applied to a terminal, it includes: Reporting the terminal duplex capability information, terminal location information, and terminal messages including the baseline capability level and the operating status indication to the satellite gateway station; Receiving the HARQ transmission pattern dynamically generated by the satellite gateway station in response to the reported information; Following the HARQ transmission pattern, sending uplink data within one or more uplink data transmission periods defined therein, and listening for downlink HARQ feedback within one or more downlink HARQ feedback periods defined therein.

10. The method according to claim 9, wherein When applied to a terminal, the step of reporting the terminal messages including the baseline capability level and the operating status indication includes: When the terminal accesses the network, report the baseline capability level; during the communication process, dynamically report the operation status indication.

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