A satellite communication method and satellite terminal

Abstract

This application provides a satellite communication method and a satellite terminal. The method includes: obtaining the current elevation angle of the terminal relative to the satellite in real time based on the satellite's ephemeris data and the terminal's position when the satellite passes overhead; obtaining the current uplink protocol parameters of the terminal from its uplink protocol parameter table based on the current elevation angle; the uplink protocol parameter table includes uplink protocol parameters for communication between the terminal and the satellite at different elevation angles; and configuring the communication protocol of the uplink channel according to the current uplink protocol parameters to transmit data to the satellite using the configured communication protocol. This application abandons the traditional method of adjusting the current uplink channel of the satellite terminal based on signal-to-noise ratio feedback. Instead, it configures the communication protocol parameters of the current uplink channel of the satellite terminal in real time based on the satellite terminal's elevation angle, thereby automatically adjusting the uplink protocol parameters in real time through an adaptive method at different elevation angles, improving communication reliability.

Description

Technical Field

[0001] This application relates to the field of satellite communication technology, and in particular to a satellite communication method and a satellite terminal. Background Technology

[0002] Low Earth Orbit (LEO) satellite Internet of Things (IoT) achieves global coverage using satellite constellations deployed at altitudes of hundreds to thousands of kilometers. To reduce terminal costs and power consumption, linear frequency modulation spread spectrum (CSS) is widely adopted due to its excellent anti-interference capabilities and high receiver sensitivity. However, existing CSS protocols (such as LoRaWAN) are primarily designed for stationary or low-speed mobile scenarios. Their core control logic—including frequency offset tracking at the physical layer, adaptive data rate (ADR) at the link layer, and flow control at the application layer—is based on a closed-loop feedback principle: terminal measures channel quality → reports to the network server → server issues adjustment commands → terminal executes the adjustments. This feedback loop works well in ground-based scenarios because channel changes are relatively slow, and feedback delays are negligible.

[0003] However, when this closed-loop feedback protocol is directly deployed in low-Earth orbit satellite scenarios, a fundamental flaw is exposed: Defect 1: The closed-loop feedback mechanism is incompatible with the rapidly changing characteristics of the channel. For low-Earth orbit satellites at an altitude of 900km, the overpass time is only 10-15 minutes, and the Doppler change rate is as high as hundreds of Hz / s. The signal-to-noise ratio fluctuates exponentially with the elevation angle. Traditional closed-loop feedback mechanisms have a delay of several seconds or even longer from measurement to execution. By the time the adjustment command reaches the terminal, the satellite's elevation angle has already changed significantly, causing the configuration parameters to always lag behind the channel state, resulting in the predicament of "never being able to adjust accurately".

[0004] Defect 2: Feedback loops relying on the downlink are unreliable in asymmetric channels. In satellite IoT, there is a significant difference between the uplink (terminal → satellite) and downlink (satellite → terminal) budgets. Terminal transmit power is limited, and the uplink is often the communication bottleneck. When the uplink quality is poor, the terminal may not be able to receive the adjustment instructions from the network server at all, leading to a broken feedback loop and a protocol deadlock.

[0005] Defect 3: Independent decision-making at each protocol layer, lacking coordination. In existing technologies, frequency offset compensation at the physical layer (such as Automatic Frequency Control, AFC) and adaptive rate adjustment at the link layer (such as Adaptive Rate Adjustment, ADR) are typically performed by two independent modules or processes, lacking a unified "clock" and "coordinate system." This loosely coupled architecture may work in slowly changing terrestrial channels, but in rapidly changing satellite channels, parameter updates at the physical and link layers often occur at different times, leading to configuration mismatches. For example, the physical layer might be using a high spreading factor to combat noise, while the application layer sends a long message, causing the message transmission time to exceed the satellite's visibility window, resulting in transmission interruption.

[0006] Fourth drawback: Traditional solutions have high computational complexity and power consumption. To cope with the rapidly changing characteristics of satellite channels, those skilled in the art might consider using complex adaptive equalization algorithms, high-gain antenna arrays, or continuous pilot signal transmission for channel tracking. However, these solutions are unacceptable for battery-powered IoT terminals with limited computing resources, significantly shortening terminal lifespan or increasing costs.

[0007] In summary, those skilled in the art are accustomed to using feedback protocol architectures to achieve adaptive adjustment of satellite channels. However, this closed-loop feedback control logic is incompatible with the rapidly changing characteristics of satellite channels, and the algorithm is complex and computationally intensive. Summary of the Invention

[0008] In view of this, the present application provides a satellite communication method and a satellite terminal. The technical solution of the present application abandons the traditional method of adjusting the communication protocol parameters of the current uplink channel of the satellite terminal by relying on the adaptive mechanism of signal-to-noise ratio feedback. It avoids the mismatch between the closed-loop feedback control logic and the rapidly changing characteristics of the satellite channel. The communication protocol parameters of the current uplink channel of the satellite terminal are configured in real time according to the elevation angle of the satellite terminal, so as to automatically adjust the uplink protocol parameters in real time through the adaptive method at different elevation angles. Moreover, the algorithm has a small amount of computation, which is very suitable for low-cost satellite Internet of Things terminals.

[0009] In a first aspect, embodiments of this application provide a satellite communication method, operating on a satellite terminal side, comprising: when a satellite passes overhead, obtaining in real time the current elevation angle of the terminal relative to the satellite based on the satellite's ephemeris data and the position of the satellite terminal; obtaining the current uplink protocol parameters of the terminal from the uplink protocol parameter table of the terminal based on the current elevation angle; the uplink protocol parameter table of the terminal includes uplink protocol parameters for the terminal to communicate with the satellite at different elevation angles; and configuring the communication protocol of the uplink channel according to the current uplink protocol parameters, so as to transmit data to the satellite using the configured communication protocol.

[0010] Based on the above, the communication protocol parameters of the current uplink channel of the satellite terminal are configured in real time according to the elevation angle of the satellite terminal. Thus, the uplink protocol parameters are automatically adjusted in real time through an adaptive method at different elevation angles. This method abandons the traditional method of adjusting the communication protocol parameters of the current uplink channel of the satellite terminal by relying on the adaptive mechanism of signal-to-noise ratio feedback. It avoids the mismatch between the closed-loop feedback control logic and the rapidly changing characteristics of the satellite channel. Moreover, the algorithm has a small computational load and is very suitable for low-cost satellite IoT terminals.

[0011] In one possible implementation of the first aspect, the uplink protocol parameter table includes the Doppler frequency shift estimate of the terminal at different elevation angles; the terminal configures the communication protocol of the uplink channel according to the current uplink protocol parameters, including: configuring the Doppler frequency shift estimate corresponding to the current elevation angle in the link layer frame header of the uplink channel; and correcting the carrier frequency of the terminal in the current channel at the physical layer of the uplink channel according to the Doppler frequency shift estimate corresponding to the current elevation angle.

[0012] As described above, by performing Doppler frequency shift compensation in advance through the satellite terminal, the satellite, as the receiver, can quickly track the uplink carrier without needing to track the uplink carrier frequency through complex calculations based on the feedback mechanism. Furthermore, by obtaining the estimated Doppler frequency shift from the link layer as the initial value in the phase-locked loop for frequency offset, residual frequency shift (mainly the influence of crystal oscillator, transmitter, and receiver) can be eliminated quickly and accurately. Symbol frequency offset also exists.

[0013] In one possible implementation of the first aspect, the uplink protocol parameter table includes the Doppler frequency shift rate of the terminal to the satellite at different elevation angles when the satellite passes over, and the Doppler frequency shift estimate corresponding to the current time point is configured in the link layer frame header of the uplink channel, including: when the Doppler frequency shift rate corresponding to the current elevation angle is greater than a set change threshold, the Doppler frequency shift estimate corresponding to the current time point is configured in the link layer frame header of the uplink channel.

[0014] As described above, by performing Doppler frequency shift compensation when the Doppler frequency shift rate is greater than a set threshold, the frequency offset compensation method is simplified when the Doppler frequency shift rate is small, and frequency offset compensation can be performed quickly at the satellite receiver.

[0015] In one possible implementation of the first aspect, the uplink protocol parameter table further includes the channel spreading factor of the terminal at different elevation angles; the terminal configures the communication protocol of the uplink channel according to the current uplink protocol parameters, including: configuring the channel spreading factor corresponding to the current elevation angle in the link layer frame header of the uplink channel to determine the data packet length carried by each data frame in the physical layer.

[0016] As described above, by selecting the channel spreading factor corresponding to the current elevation angle, the channel model corresponding to the current elevation angle can be quickly matched without the need for a feedback mechanism. Moreover, by configuring the channel spreading factor corresponding to the current elevation angle in the link layer frame header of the uplink channel, the uplink rate can be adaptively adjusted in an open loop according to the channel conditions.

[0017] In one possible implementation of the first aspect, the uplink protocol parameter table further includes the channel preamble of the terminal at different elevation angles; the terminal configures the communication protocol of the uplink channel according to the current uplink protocol parameters, including: configuring the channel preamble corresponding to the current elevation angle in the link layer frame header of the uplink channel, so as to enable the satellite and the terminal to perform uplink frame synchronization.

[0018] As described above, by selecting the channel preamble corresponding to the current elevation angle, the satellite can quickly synchronize with the uplink frame of the satellite terminal without needing to perform synchronization through search and matching.

[0019] In one possible implementation of the first aspect, the uplink protocol parameter table further includes the remaining visible time window of the satellite at different elevation angles for the terminal; the terminal configures the communication protocol of the uplink channel according to the current uplink protocol parameters, including: obtaining the amount of data the terminal is currently transmitting within the remaining visible time window based on the remaining visible time window corresponding to the current elevation angle, the channel spreading factor corresponding to each elevation angle in the remaining visible time window, and the length of the channel preamble; and configuring the data packet length of the application layer of the uplink channel according to the amount of data transmitted.

[0020] Based on the above, the application layer fragmentation is automatically adjusted according to the remaining visible time window of the satellite corresponding to the current elevation angle, and the current application layer fragmentation data is transmitted within one satellite transit cycle, avoiding retransmission of already transmitted data across satellite transit cycles or the next satellite.

[0021] In one possible implementation of the first aspect, the method further includes: setting an orbital state machine in the terminal; when the satellite passes overhead, if the elevation angle of the terminal relative to the satellite is not within the synchronization angle range, the terminal and the satellite do not meet the communication requirements, and the terminal is in a search state in the orbital state machine; if the elevation angle of the terminal relative to the satellite is within the synchronization angle range, the terminal and the satellite do not meet the communication requirements, and the terminal is in a synchronized state in the orbital state machine; when the terminal has not connected to the satellite and the current elevation angle of the terminal relative to the satellite is within the synchronization angle range, the terminal begins to connect to the satellite, the terminal is in an access state in the orbital state machine, and after successful connection, the terminal switches to a transmission state in the orbital state machine, both the access state and the transmission state being part of the synchronized state.

[0022] As described above, by using the orbital state machine to manage the satellite terminal's status based on the current elevation angle, the satellite terminal's status can be quickly switched and managed based on an open-loop mechanism, without waiting for a feedback mechanism.

[0023] In one possible implementation of the first aspect, it further includes: dividing the elevation angle region of the terminal located in the synchronization angle range into several transmission states, and when the terminal changes from one transmission state to another, triggering the uplink protocol configuration of the terminal by interruption.

[0024] Therefore, by interrupting the communication protocol parameter switching of the uplink channel of the satellite terminal at different elevation angles, the channel conditions corresponding to different elevation angles can be quickly met.

[0025] In one possible implementation of the first aspect, the method further includes: obtaining the uplink protocol parameter table of the terminal in advance based on the satellite's ephemeris data and the location of the satellite terminal before the satellite passes overhead.

[0026] As described above, by obtaining the uplink protocol parameter table of the satellite terminal for the satellite in advance based on the satellite's ephemeris data and the satellite terminal's location, the configuration and switching of the satellite terminal's uplink communication protocol parameters can be achieved directly by looking up the table, eliminating complex wireless calculations and reducing implementation costs.

[0027] Secondly, embodiments of this application provide a satellite terminal, including: an elevation angle acquisition module, used to obtain the current elevation angle of the terminal relative to the satellite in real time based on the satellite's ephemeris data and the position of the satellite terminal when the satellite passes overhead; a parameter acquisition module, used to obtain the current uplink protocol parameters of the terminal from the uplink protocol parameter table of the terminal based on the current elevation angle; the uplink protocol parameter table of the terminal includes uplink protocol parameters for the terminal to communicate with the satellite at different elevation angles; and a parameter configuration module, used for the terminal to configure the communication protocol of the uplink channel according to the current uplink protocol parameters, so as to transmit data to the satellite using the configured communication protocol.

[0028] Based on the above, the communication protocol parameters of the current uplink channel of the satellite terminal are configured in real time according to the elevation angle of the satellite terminal. Thus, the uplink protocol parameters are automatically adjusted in real time through an adaptive method at different elevation angles. This method abandons the traditional method of adjusting the communication protocol parameters of the current uplink channel of the satellite terminal by relying on the adaptive mechanism of signal-to-noise ratio feedback. It avoids the mismatch between the closed-loop feedback control logic and the rapidly changing characteristics of the satellite channel. Moreover, the algorithm has a small computational load and is very suitable for low-cost satellite IoT terminals.

[0029] In one possible implementation of the second aspect, the uplink protocol parameter table includes the Doppler frequency shift estimate of the terminal at different elevation angles; the parameter configuration module is specifically used to configure the Doppler frequency shift estimate corresponding to the current elevation angle in the link layer frame header of the uplink channel; and in the physical layer of the uplink channel, to correct the carrier frequency of the terminal in the current channel according to the Doppler frequency shift estimate corresponding to the current elevation angle.

[0030] As described above, by performing Doppler frequency shift compensation in advance through the satellite terminal, the satellite, as the receiver, can quickly track the uplink carrier without needing to track the uplink carrier frequency through complex calculations based on the feedback mechanism. Furthermore, by obtaining the estimated Doppler frequency shift from the link layer as the initial value in the phase-locked loop for frequency offset, residual frequency shift (mainly the influence of crystal oscillator, transmitter, and receiver) can be eliminated quickly and accurately. Symbol frequency offset also exists.

[0031] In one possible implementation of the second aspect, the uplink protocol parameter table includes the Doppler frequency shift rate of the terminal to the satellite at different elevation angles when the satellite passes over. Specifically, the parameter configuration module is used to configure the estimated Doppler frequency shift value corresponding to the current time point in the link layer frame header of the uplink channel when the Doppler frequency shift rate corresponding to the current elevation angle is greater than a set change threshold.

[0032] As described above, by performing Doppler frequency shift compensation when the Doppler frequency shift rate is greater than a set threshold, the frequency offset compensation method is simplified when the Doppler frequency shift rate is small, and frequency offset compensation can be performed quickly at the satellite receiver.

[0033] In one possible implementation of the second aspect, the uplink protocol parameter table further includes the channel spreading factor of the terminal at different elevation angles; the parameter configuration module is specifically used to configure the channel spreading factor corresponding to the current elevation angle in the link layer frame header of the uplink channel to determine the data packet length carried by each data frame in the physical layer.

[0034] As described above, by selecting the channel spreading factor corresponding to the current elevation angle, the channel model corresponding to the current elevation angle can be quickly matched without the need for a feedback mechanism. Moreover, by configuring the channel spreading factor corresponding to the current elevation angle in the link layer frame header of the uplink channel, the uplink rate can be adaptively adjusted in an open loop according to the channel conditions.

[0035] In one possible implementation of the second aspect, the uplink protocol parameter table further includes the channel preamble of the terminal at different elevation angles; the parameter configuration module is specifically used to configure the channel preamble corresponding to the current elevation angle in the link layer frame header of the uplink channel so as to enable the satellite and the terminal to synchronize uplink frames.

[0036] As described above, by selecting the channel preamble corresponding to the current elevation angle, the satellite can quickly synchronize with the uplink frame of the satellite terminal without needing to perform synchronization through search and matching.

[0037] In one possible implementation of the second aspect, the uplink protocol parameter table further includes the remaining visible time window of the satellite at different elevation angles for the terminal; the parameter configuration module is specifically used to obtain the amount of data transmitted by the terminal in the remaining visible time window based on the remaining visible time window corresponding to the current elevation angle, the channel spreading factor corresponding to each elevation angle in the remaining visible time window, and the length of the channel preamble; and to configure the data packet length of the application layer of the uplink channel based on the amount of data transmitted.

[0038] Based on the above, the application layer fragmentation is automatically adjusted according to the remaining visible time window of the satellite corresponding to the current elevation angle, and the current application layer fragmentation data is transmitted within one satellite transit cycle, avoiding retransmission of already transmitted data across satellite transit cycles or the next satellite.

[0039] In one possible implementation of the second aspect, the method further includes: setting an orbital state machine in the terminal; when the satellite passes overhead, if the elevation angle of the terminal relative to the satellite is not within the synchronization angle range, the terminal and the satellite do not meet the communication requirements, and the terminal is in a search state in the orbital state machine; if the elevation angle of the terminal relative to the satellite is within the synchronization angle range, the terminal and the satellite do not meet the communication requirements, and the terminal is in a synchronized state in the orbital state machine; when the terminal has not connected to the satellite and the current elevation angle of the terminal relative to the satellite is within the synchronization angle range, the terminal begins to connect to the satellite, the terminal is in an access state in the orbital state machine, and after successful connection, the terminal switches to a transmission state in the orbital state machine, both the access state and the transmission state being part of the synchronized state.

[0040] As described above, by using the orbital state machine to manage the satellite terminal's status based on the current elevation angle, the satellite terminal's status can be quickly switched and managed based on an open-loop mechanism, without waiting for a feedback mechanism.

[0041] In one possible implementation of the second aspect, the elevation angle region of the terminal within the synchronization angle range is divided into several transmission states. When the terminal changes from one transmission state to another, the uplink protocol configuration of the terminal is triggered by an interrupt.

[0042] Therefore, by interrupting the communication protocol parameter switching of the uplink channel of the satellite terminal at different elevation angles, the channel conditions corresponding to different elevation angles can be quickly met.

[0043] In one possible implementation of the second aspect, a parameter table acquisition module is further included to obtain the uplink protocol parameter table of the terminal in advance based on the satellite ephemeris data and the location of the satellite terminal.

[0044] As described above, by obtaining the uplink protocol parameter table of the satellite terminal for the satellite in advance based on the satellite's ephemeris data and the satellite terminal's location, the configuration and switching of the satellite terminal's uplink communication protocol parameters can be achieved directly by looking up the table, eliminating complex wireless calculations and reducing implementation costs. Attached Figure Description

[0045] Figure 1 This is a flowchart illustrating a first embodiment of a satellite communication method according to this application; Figure 2 This is a flowchart illustrating a second embodiment of a satellite communication method according to this application; Figure 3 This is a schematic diagram of a satellite communication method embodiment 2 of this application, in which state management is performed using an orbital state machine as the core. Figure 4 This is a schematic diagram comparing the Doppler frequency shift of the satellite terminal uplink carrier frequency with and without compensation in a second embodiment of a satellite method according to this application; Figure 5 This is a schematic diagram of the state changes of a satellite terminal in an orbital state machine in a second embodiment of a satellite communication method according to this application; Figure 6 This is a schematic diagram of the structure of a satellite terminal according to one embodiment of this application; Figure 7 This is a schematic diagram of the structure of a second embodiment of a satellite terminal according to this application. Detailed Implementation

[0046] In the following description, references are made to “some embodiments,” which describe a subset of all possible embodiments. However, it is understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0047] In the following description, the terms “first, second, third, etc.” or module A, module B, module C, etc. are used not only to distinguish similar objects or different embodiments, but also do not represent a specific ordering of objects. It is understood that a specific order or sequence may be interchanged where permitted so that the embodiments of this application described herein can be implemented in an order other than that illustrated or described herein.

[0048] In the following description, the labels of the steps, such as S110, S120, etc., do not necessarily mean that the steps will be executed in this way. The order of the steps can be interchanged or executed simultaneously if permitted.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0050] This application provides a satellite communication method and a satellite terminal. The method is used on the satellite terminal side and includes: when a satellite passes overhead, obtaining the current elevation angle of the terminal relative to the satellite in real time based on the satellite's ephemeris data and the satellite terminal's position; obtaining the current uplink protocol parameters of the terminal from the uplink protocol parameter table of the terminal based on the current elevation angle; the uplink protocol parameter table of the terminal includes uplink protocol parameters for the terminal to communicate with the satellite at different elevation angles; and configuring the communication protocol of the uplink channel according to the current uplink protocol parameters to transmit data to the satellite using the configured communication protocol.

[0051] The technical solution of this application abandons the traditional method of adjusting the communication protocol parameters of the current uplink channel of the satellite terminal by relying on the adaptive mechanism of signal-to-noise ratio feedback. It avoids the mismatch between the closed-loop feedback control logic and the rapidly changing characteristics of the satellite channel. It configures the communication protocol parameters of the current uplink channel of the satellite terminal in real time according to the elevation angle of the satellite terminal, so as to automatically adjust the uplink protocol parameters in real time through an adaptive method at different elevation angles. Moreover, the algorithm has a small computational load and is very suitable for low-cost satellite IoT terminals.

[0052] The embodiments of this application are described below with reference to the accompanying drawings. Figure 1 This paper introduces an embodiment of a satellite communication method according to the present application.

[0053] Figure 1 The flowchart of a satellite communication method embodiment one is shown, including steps S110 to S130.

[0054] Step S110: When the satellite passes overhead, obtain the current elevation angle of the satellite terminal relative to the satellite in real time based on the satellite's ephemeris data and the satellite terminal's position; Step S120: Based on the current elevation angle, obtain the current uplink protocol parameters of the satellite terminal from the uplink protocol parameter table of the satellite terminal; wherein, the uplink protocol parameter table of the satellite terminal includes the uplink protocol parameters of the terminal communicating with the satellite at different elevation angles; Step S130: The terminal configures the communication protocol of the uplink channel according to the current uplink protocol parameters, so as to transmit data to the satellite using the configured communication protocol.

[0055] In step S110, the transit time of each satellite to a fixed-location satellite terminal is fixed, and the elevation angle of the satellite terminal to the transiting satellite at each time point within the transit cycle is also determined.

[0056] In step S120, an uplink protocol parameter table must be established in advance between each satellite terminal and each satellite. Before a satellite passes overhead, each satellite terminal calculates and determines the uplink protocol parameter table between itself and the satellite based on the satellite's ephemeris data and its own position. Each elevation angle in the uplink protocol parameter table corresponds to uplink protocol parameters used to configure the application layer, link layer, and physical layer communication protocol parameters of the uplink channel between the satellite terminal and the satellite.

[0057] In some embodiments of step S130, each satellite terminal's uplink protocol parameter table for a satellite includes the Doppler shift estimate for the terminal at different elevation angles; the satellite terminal configures the Doppler shift estimate corresponding to the current elevation angle in the link layer frame header of the uplink channel; at the physical layer of the uplink channel, the satellite terminal corrects the carrier frequency of the satellite terminal in the current channel according to the Doppler shift estimate corresponding to the current elevation angle to eliminate the impact of Doppler shift on the carrier frequency; moreover, at this time, the satellite, as the receiver, also obtains the current Doppler shift estimate from the link layer of the uplink channel.

[0058] At this point, the carrier frequency received by the satellite has largely eliminated the Doppler shift, and the satellite has quickly tracked the uplink carrier without needing complex calculations based on a feedback mechanism to track the uplink carrier frequency. However, residual frequency shift still exists in the carrier (mainly due to the influence of the crystal oscillator, transmitter, and receiver), and symbol frequency offset still exists. In the phase-locked loop that eliminates these frequency offsets, the satellite uses the estimated Doppler frequency shift value obtained from the analysis as the initial value in advance, thereby quickly eliminating these frequency offsets.

[0059] In some embodiments of step S130, the uplink protocol parameter table for each satellite terminal includes the Doppler frequency shift rate of the satellite terminal at different elevation angles when the satellite passes overhead. When the Doppler frequency shift rate corresponding to the current elevation angle is greater than a set threshold, the estimated Doppler frequency shift value corresponding to the current elevation angle is configured in the link layer frame header of the satellite's uplink channel. This set threshold changes positively with the uplink communication bandwidth. That is, if the Doppler frequency shift rate corresponding to the current elevation angle is within the tolerable range of the satellite terminal's uplink communication bandwidth, no Doppler frequency shift correction is required.

[0060] In some embodiments of step S130, the uplink protocol parameter table for each satellite terminal includes the channel spreading factor of the terminal at different elevation angles. The spreading factor changes inversely with the absolute value of the difference between the elevation angle of the satellite terminal and 90 degrees. The channel spreading factor corresponding to the current elevation angle is configured in the link layer frame header of the uplink channel of the satellite terminal to determine the data packet length carried by each data frame of the physical layer. The data in each data frame of the physical layer is spread using the channel spreading factor of the corresponding link layer frame header.

[0061] In some embodiments of step S130, the uplink protocol parameter table for each satellite terminal to a satellite also includes the channel preamble of the satellite terminal at different elevation angles. The channel preamble changes in the opposite direction to the absolute value of the difference between the elevation angle of the terminal and 90 degrees. The channel preamble corresponding to the current elevation angle is configured in the link layer frame header of the uplink channel of the satellite terminal so as to facilitate uplink frame synchronization between the satellite and the satellite terminal.

[0062] In some embodiments of step S130, an orbital state machine is set in the satellite terminal; when the satellite passes overhead, if the elevation angle of the satellite terminal relative to the satellite is not within the synchronization angle range, the communication requirements between the two are not met, and the satellite terminal is in the search state in the orbital state machine; when the elevation angle of the satellite terminal relative to the satellite is within the synchronization angle range, the communication requirements between the two are met, and the satellite terminal is in the synchronization state in the orbital state machine; when the satellite terminal has not connected to the satellite and the current elevation angle of the satellite terminal relative to the satellite is within the synchronization angle range, the satellite terminal begins to connect to the satellite, and the satellite terminal is in the access state in the orbital state machine. After successful connection, the satellite terminal switches to the transmission state in the orbital state machine. Both the access state and the transmission state belong to the synchronization state.

[0063] In some embodiments of step S130, when the satellite terminal changes state in the orbital state machine, the satellite terminal transitions state by triggering an interrupt.

[0064] In some implementations of this embodiment, during the satellite transit cycle, the satellite transit cycle is divided into several intervals according to the elevation angle of the satellite terminal. Each interval uses the same channel spreading factor and preamble, corresponding to a transmission state. When the satellite terminal changes from one transmission state to another, the uplink protocol configuration of the satellite terminal is triggered by an interrupt.

[0065] In summary, the satellite communication method embodiment 1 of this application abandons the traditional method of adjusting the communication protocol parameters of the current uplink channel of the satellite terminal by relying on the adaptive mechanism of signal-to-noise ratio feedback. It avoids the mismatch between the closed-loop feedback control logic and the rapidly changing characteristics of the satellite channel. It configures the communication protocol parameters of the current uplink channel of the satellite terminal in real time according to the elevation angle of the satellite terminal, so as to automatically adjust the uplink protocol parameters in real time through the adaptive method at different elevation angles. Moreover, the algorithm has a small computational load and is very suitable for low-cost satellite IoT terminals.

[0066] The following is combined with Figures 2 to 5 This application presents a second embodiment of a satellite communication method.

[0067] A second embodiment of a satellite communication method is a detailed implementation of a first embodiment of a satellite communication method, and has all its advantages.

[0068] Figure 2 The flowchart of a second embodiment of a satellite communication method is shown, including steps S210 to S270.

[0069] For ease of description, this embodiment will be introduced using the uplink communication between satellite terminal A and satellite B as an example.

[0070] Step S210: Satellite terminal B obtains the uplink protocol parameter table and synchronization angle range between satellite terminal B and satellite A in advance based on the ephemeris data of satellite A and the position of satellite terminal B.

[0071] This step includes the following sub-steps: (1) Based on the ephemeris data (TLE data) of satellite A and the position of satellite terminal B, obtain the transit period of satellite A, and calculate the elevation angle of satellite terminal B to satellite A at each time point in the transit period.

[0072] (2) Calculate the elevation angle of satellite terminal B relative to satellite A at each time point in the transit cycle. Calculate the Doppler frequency shift, transmission delay and channel fading at each time point to form the channel model parameters for each elevation angle.

[0073] (3) Based on the channel model parameters for each elevation angle, calculate the synchronization angle range during the transit period. When the elevation angle of satellite terminal B relative to satellite A is within the synchronization angle range, the uplink channel parameters of satellite terminal B and satellite A do not meet the communication conditions; when it is not within the synchronization angle range, the uplink channel parameters of satellite terminal B and satellite A meet the communication conditions. (4) Divide the elevation angle of the transit cycle into several intervals. The elevation angles on both sides outside the synchronization angle range are respectively a region, which is the search area. The elevation angle region within the synchronization angle range is divided into the synchronization area. The synchronization area is divided into the edge area and the center area according to the elevation angle.

[0074] (5) For each synchronization interval, obtain a typical elevation angle, obtain the Doppler frequency shift estimate and the Doppler frequency shift change rate corresponding to the typical elevation angle of each interval, and calculate the channel spreading factor and channel preamble of the uplink channel of the satellite terminal B to satellite A in the interval based on the uplink channel model parameters corresponding to the elevation angle; and determine the frame structure of the link layer corresponding to the elevation angle interval. The frame header of the link layer includes the spreading factor, channel preamble and Doppler frequency shift indicator; when the Doppler frequency shift change rate in the interval is greater than the set change threshold, the Doppler frequency shift indicator is the Doppler frequency shift estimate corresponding to the typical elevation angle of the interval, otherwise it is 0.

[0075] (6) Based on the transit period of satellite A and the time point of each interval in the synchronization zone, calculate the remaining visible time window of the satellite at the start time point of each interval.

[0076] (7) Configure an orbital state machine in satellite terminal B. When the elevation angle of satellite terminal B is in the search area, the orbital state machine of satellite terminal B is configured as search state; when the elevation angle of satellite terminal B is in the synchronization area, the orbital state machine of satellite terminal B is configured as synchronization state; when satellite terminal B connects in the synchronization area, the orbital state machine of satellite terminal B is configured as access state; when satellite terminal B successfully connects in the synchronization area, the orbital state machine of satellite terminal B is configured as transmission state, and data can be transmitted.

[0077] Among them, the uplink protocol parameter table of satellite terminal B to satellite A includes the elevation angle corresponding to different times of the transit cycle, as well as the Doppler frequency shift estimate, Doppler frequency shift change rate, channel spreading factor, channel preamble, and the initial satellite remaining visible time window corresponding to different elevation angle intervals.

[0078] Step S220: When satellite A passes overhead and satellite terminal B transmits data, obtain the current elevation angle of satellite terminal B relative to satellite A in real time based on the ephemeris data of satellite A and the position of satellite terminal B.

[0079] When satellite terminal B has no data to be transmitted, it is in search mode. It only obtains the elevation angle with the overpassing satellite A when there is data to be transmitted.

[0080] Step S230: Obtain the current uplink protocol parameters of the satellite terminal from the uplink protocol parameter table of the satellite terminal B according to the current elevation angle.

[0081] The obtained current uplink protocol parameters include: the interval's Doppler frequency shift estimate and the interval's Doppler frequency shift rate of change, the channel spreading factor, the link layer preamble, and the interval's starting satellite remaining visible time window.

[0082] Step S240: Determine the next state of the satellite terminal based on the state of satellite terminal B and whether the current elevation angle is within the synchronization angle range. Specifically, when satellite terminal B is in search mode and its current elevation angle is outside the synchronization angle range, satellite terminal B waits for a set interval and returns to step S220. When satellite terminal B's current elevation angle is within the synchronization angle range and it is in search mode, satellite terminal B executes step S250 to connect to satellite A. When satellite terminal B's current elevation angle is within the synchronization angle range and it is in transmission mode, step S260 is executed.

[0083] Step S250: Satellite terminal B enters the access state through a state interrupt, begins accessing satellite A, and after successful access, sets itself to the transmission state in the orbit state machine through a synchronization state interrupt.

[0084] In the event of a collision, satellite terminal B avoids the collision using the backoff window corresponding to the current elevation angle.

[0085] When satellite terminal B loses synchronization with satellite A due to a large Doppler change rate, satellite terminal B also performs this step through a status interruption.

[0086] Step S260: Satellite terminal B configures the communication protocol of the uplink channel according to the current uplink protocol parameters, and configures the protocol of the uplink channel between satellite terminal B and satellite A.

[0087] This step involves the following sub-steps: (1) Calculate the remaining visible time window of the satellite in the current interval based on the satellite remaining visible time window at the beginning of the current interval, the current time point, and the start and end time points of the interval. Then, combine the time of other intervals to obtain the final remaining visible time window of the satellite. (2) Based on the channel spreading factor and link layer preamble of the current interval, obtain the transmission rate of the satellite terminal B application layer in the application layer, and combine it with the final remaining visible time window of the satellite to obtain the current fragmentation length of the satellite terminal B in the application layer. (3) Obtain the Doppler frequency shift indication (DIF) corresponding to the current elevation angle based on the rate of change of the Doppler frequency shift in the current interval.

[0088] (4) Configure the Doppler frequency shift indicator, channel spreading factor and link layer preamble of the current interval according to the current link layer frame header.

[0089] Specifically, when the change in the current elevation angle causes satellite terminal B to transition from one transmission state to another, this step is triggered by a state interruption.

[0090] Step S270: Satellite terminal B transmits data to satellite A according to the configured uplink channel protocol.

[0091] Specifically, at the physical layer, the carrier frequency is compensated in advance based on the Doppler frequency shift indication in the link layer frame header, and the data transmitted from the link is spread based on the channel spreading factor in the link layer frame header.

[0092] The uplink protocol stack between satellite terminal B and satellite A in this application logically includes a physical sensing layer, an adaptive link layer, and an application fragmentation layer, with its core being an embedded orbital state machine. Figure 3 This embodiment illustrates state management using a track state machine core. The physical sensing layer in the figure executes steps S220 and S230 of this embodiment; the track state machine executes steps S240, S250, and S260 of this embodiment.

[0093] The following example illustrates this embodiment using a scenario with a satellite orbital altitude of 900km, a carrier frequency of 400MHz, and a current CSS bandwidth (application layer bandwidth) of 10.4kHz.

[0094] The synchronization angle range obtained from simulation is: to This elevation angle range is the synchronization zone; in the orbital state machine, satellite terminal B is in a synchronized state. to The search area is defined as the outward elevation angle region, and satellite terminal B is in search mode in the orbital state machine; At this point, the estimated Doppler frequency shift is +9.5kHz, the rate of change of the Doppler frequency shift is approximately +120Hz / s, and the threshold for change is 5%. In this case, Doppler frequency shift compensation must be performed on the carrier frequency.

[0095] Figure 4 The diagram shows a comparison of the Doppler frequency shift of the satellite terminal's uplink carrier frequency with and without compensation in this embodiment. It can be seen from the diagram that the frequency shift is almost zero after Doppler frequency shift.

[0096] The elevation angle region in the synchronous state is divided into two or three intervals. The channel spreading factor (SF) and preamble of each interval are shown in Table 1 (obtained through simulation optimization for 900km orbit and UHF band).

[0097] Table 1

[0098] It should be noted that the above division is only a preferred embodiment of this application. For satellites at different orbital altitudes (such as 600km or 1200km), the elevation threshold angle and uplink protocol parameters can be re-optimized through simulation.

[0099] For example, within the edge region, based on the same time base and the same set of uplink protocol parameters, the orbital state machine synchronously outputs the following three strategies: Physical layer spectrum strategy: The transmit carrier frequency is set to 400MHz - 9.5kHz = 399.9905MHz to compensate for the uplink Doppler shift; Link layer access strategy: SF=11 (high processing gain), preamble length=16 (long synchronization sequence).

[0100] Application layer traffic strategy: Based on the fact that the current elevation angle is in the rising phase and there are enough remaining visible windows (about 7 minutes), sharding will not be triggered for the time being.

[0101] These strategies are then synchronously distributed to each layer for execution based on the same time reference. Satellite terminal B transmits uplink data frames in the edge region at a frequency of 399.9905MHz, using SF11 and preamble 16. The link layer header of this data frame also includes a Doppler frequency shift indicator (DIF) field, which stores +9.5kHz information in quantization. After receiving this frame, satellite receiver A performs rapid synchronization using the pre-compensated open-loop signal (the actual frequency offset upon arrival at the satellite is close to zero). Simultaneously, it reads the DIF field as the initial value for the phase-locked loop, further eliminating residual frequency offsets caused by ephemeris errors or crystal oscillator drift, thus achieving high-sensitivity demodulation.

[0102] It should be noted that satellite A utilizes the DIF field of this application to construct a "semi-open-loop" mechanism: satellite A also performs secondary fine-tuning of the residual frequency offset (closed-loop assistance). This architecture retains the core advantage of open-loop control with no feedback delay, while eliminating residual deviations that may be caused by ephemeris errors or crystal oscillator drift through the DIF field, thus achieving the best balance between prediction accuracy and system robustness in engineering.

[0103] Furthermore, this application exhibits extremely low computational overhead. Uplink protocol parameters require only a single table lookup operation. The entire decision-making process eliminates the need for any complex adaptive filtering, matrix inversion, or iterative optimization algorithms, and can be completed in microseconds even on MCUs with clock speeds of only tens of MHz. In contrast, traditional solutions require equalizers or pilot-aided estimations to track rapidly changing channels, resulting in computational complexity that is more than an order of magnitude higher. Therefore, this application achieves highly reliable communication while perfectly meeting the core demands of IoT terminals for low power consumption and low cost.

[0104] For example, the moment the elevation angle exceeds the 20° threshold, the orbital state machine detects that the state of the regional satellite terminal B is about to flip. At this moment, the state machine immediately triggers a hardware interrupt, forcing the protocol stack to perform a hard switch of uplink protocol parameters: at the physical layer, based on the Doppler rate of change corresponding to the new elevation angle (at which point the rate of change is at its maximum, approximately +250Hz / s), the dynamic adjustment coefficient of the pre-compensation slope is recalculated and updated; at the link layer, the SF is switched from 11 to 7, and the preamble is shortened from 16 to 8. This switch is completed instantaneously, without waiting for any downlink acknowledgment instructions; at the application layer, due to the reduction in SF, the transmission time per bit is shortened, the state machine recalculates the number of bytes that can be transmitted within the remaining visible window, and notifies the application layer that it can start sending larger data blocks.

[0105] The aforementioned open-loop predictive hard handover mechanism contrasts sharply with the slow closed-loop adjustment in existing LoRaWAN ADR mechanisms that rely on commands issued by the network server. Within the short few minutes of a satellite passing overhead, this application can achieve parameter configuration synchronized with channel changes, while traditional solutions are always stuck in a lagging loop of "measurement-reporting-waiting-adjustment".

[0106] For example, when the satellite is in the late overhead phase and the elevation angle drops to 20°, the orbital state machine predicts the remaining visible time window of the satellite based on the orbital motion vector. Only 10 seconds remain. At this point, the state machine, based on the current link layer configuration of SF=11, calculates the unit bit transmission time (assuming 1ms / byte), and concludes that a maximum of 10,000 bytes can be transmitted within the remaining window. If the application layer attempts to send a long message of 15,000 bytes at this time, the state machine will refuse to send it directly and notify the application layer that the current remaining window is insufficient to complete the transmission of the message. It is recommended to split the message into two fragments (e.g., 10,000 bytes and 5,000 bytes), send the first fragment first, and wait for the next satellite overhead window for the second fragment. This strategy ensures that channel resources are not wasted on a transmission that is destined to fail. It is a manifestation of the negative feedback constraint of the orbital state machine on the application layer and a concrete implementation of "spatiotemporal resource mapping" at the application layer.

[0107] Figure 5 This embodiment illustrates the state changes in the orbital state machine, from an elevation angle less than... Change to greater than At that time, it transitions from the search state to the synchronization state; after access, it changes from an elevation angle of less than... Change to greater than At that time, the transmission state changes from the edge region to the central region.

[0108] In summary, the second embodiment of the satellite communication method has the following beneficial effects: Breaking down technological biases: When used in satellite IoT, it is the first time that the control logic of the satellite IoT protocol has been shifted from "closed-loop feedback" to "open-loop prediction", fundamentally solving the contradiction between feedback delay and rapid channel changes; Cross-layer collaborative optimization: Through a unified orbital state machine, based on the same driving source and the same time base, synchronous decision-making and spatiotemporal consistency of parameters of the physical layer, link layer, and application layer are achieved, avoiding conflicts and mismatches caused by independent optimization of each layer; Improved link reliability: Open-loop pre-compensation combined with DIF field-assisted demodulation enables narrowband CSS signals to remain reliably synchronized even with a large frequency offset of ±10kHz, solving the problem that traditional AFC loops cannot track high-speed changes; Improve spectrum efficiency: By using an elevation angle-resource mapping table (which can be extended to parameters such as Doppler change rate), the central area automatically switches to a high-speed configuration while ensuring edge coverage, resulting in a significant increase in the total system throughput.

[0109] Low complexity and low power consumption: This embodiment mainly relies on table lookup and simple arithmetic operations, without the need for complex adaptive algorithms or high-gain antennas, resulting in extremely low computational overhead, making it particularly suitable for battery-powered and cost-sensitive IoT terminals.

[0110] The following is combined with Figure 6 This application introduces one embodiment of a satellite terminal.

[0111] The satellite terminal embodiment of this application executes the method described in the satellite communication method embodiment of this application, and has all its advantages.

[0112] Figure 6 The structure of a satellite terminal embodiment 1 is shown, including an elevation angle acquisition module 610, a parameter acquisition module 620, and a parameter configuration module 630.

[0113] The elevation angle acquisition module 610 is used to obtain the current elevation angle of the satellite terminal relative to the satellite at the current time point based on the satellite's ephemeris data and the satellite terminal's position when the satellite passes overhead. For its working principle and advantages, please refer to step S110 of an embodiment of a satellite communication method of this application.

[0114] The parameter acquisition module 620 is used to obtain the current uplink protocol parameters of the satellite terminal from the uplink protocol parameter table of the satellite terminal according to the current elevation angle. For its working principle and advantages, please refer to step S120 of an embodiment of a satellite communication method of this application.

[0115] The parameter configuration module 630 is used by the terminal to configure the communication protocol of the uplink channel according to the current uplink protocol parameters, so as to transmit data to the satellite using the configured communication protocol. For its working principle and advantages, please refer to step S130 of an embodiment of a communication method of this application.

[0116] The following is combined with Figure 7 This application introduces a second embodiment of a satellite terminal.

[0117] The satellite terminal embodiment of this application implements the method described in the satellite communication method embodiment of this application, and has all its advantages.

[0118] Figure 7 The structure of a second embodiment of a satellite terminal is shown, including: a parameter table acquisition module 710, an elevation angle acquisition module 720, a parameter acquisition module 730, a satellite access module 740, a parameter configuration module 750, and a data transmission module 760.

[0119] For ease of description, this embodiment will be introduced using the uplink communication between satellite terminal A and satellite B as an example.

[0120] The parameter table acquisition module 710 is used by satellite terminal B to obtain the uplink protocol parameter table and synchronization angle range between satellite terminal B and satellite A in advance based on the ephemeris data of satellite A and the position of satellite terminal B. For its working principle and advantages, please refer to step S210 of embodiment two of the communication method of this application.

[0121] The elevation angle acquisition module 720 is used to obtain the current elevation angle of satellite terminal B relative to satellite A in real time, based on the ephemeris data of satellite A and the position of satellite terminal B, when satellite A passes overhead and satellite terminal B is transmitting data. For its working principle and advantages, please refer to step S230 of a second embodiment of a communication method in this application.

[0122] The parameter acquisition module 730 is used to obtain the current uplink protocol parameters of the satellite terminal from the uplink protocol parameter table of the satellite terminal B according to the current elevation angle. For its working principle and advantages, please refer to step S230 of a second embodiment of a communication method in this application.

[0123] The satellite access module 740 is used to determine the next state of the satellite terminal based on the state of the satellite terminal B and whether the current elevation angle is within the synchronization angle range; it is also used for the satellite terminal B to enter the access state through a state interrupt, begin accessing satellite A, and, after successful access, to set itself to the transmission state in the orbital state machine through a synchronization state interrupt. For its working principle and advantages, please refer to steps S240 and S250 of a second embodiment of a communication method in this application.

[0124] The parameter configuration module 750 is used by satellite terminal B to configure the communication protocol of the uplink channel according to the current uplink protocol parameters, and to configure the uplink channel protocol of satellite terminal B to satellite A. For its working principle and advantages, please refer to step S260 of a second embodiment of a communication method in this application.

[0125] The data transmission module 760 is used by satellite terminal B to transmit data to satellite A according to the configured uplink channel protocol. For its working principle and advantages, please refer to step S270 of embodiment two of the communication method in this application.

[0126] Note that the above are merely preferred embodiments and the technical principles employed in this application. Those skilled in the art will understand that this application is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of this application. Therefore, although this application has been described in detail through the above embodiments, this application is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of this application, all of which fall within the scope of protection of this application.

Claims

1. A satellite communication method, characterized in that, Operating on the satellite terminal side, including: When a satellite passes overhead, the current elevation angle of the terminal relative to the satellite is obtained in real time based on the satellite's ephemeris data and the satellite terminal's position. Based on the current elevation angle, the current uplink protocol parameters of the terminal are obtained from the uplink protocol parameter table of the terminal; the uplink protocol parameter table of the terminal includes the uplink protocol parameters of the terminal communicating with the satellite at different elevation angles; The terminal configures the communication protocol of the uplink channel according to the current uplink protocol parameters, so as to transmit data to the satellite using the configured communication protocol.

2. The method according to claim 1, characterized in that, The uplink protocol parameter table includes the Doppler frequency shift estimate of the terminal at different elevation angles; The terminal configures the communication protocol of the uplink channel according to the current uplink protocol parameters, including: Configure the Doppler frequency shift estimate corresponding to the current elevation angle in the link layer frame header of the uplink channel; At the physical layer of the uplink channel, the carrier frequency of the terminal in the current channel is corrected based on the estimated Doppler frequency shift corresponding to the current elevation angle.

3. The method according to claim 2, characterized in that, The uplink protocol parameter table includes the Doppler frequency shift rate of the terminal at different elevation angles when the satellite passes overhead, and the Doppler frequency shift estimate corresponding to the current time point is configured in the link layer frame header of the uplink channel, including: When the rate of change of the Doppler frequency shift corresponding to the current elevation angle is greater than the set change threshold, the estimated value of the Doppler frequency shift corresponding to the current time point is configured in the link layer frame header of the uplink channel.

4. The method according to claim 1, characterized in that, The uplink protocol parameter table also includes the channel spreading factor of the terminal at different elevation angles; The terminal configures the communication protocol of the uplink channel according to the current uplink protocol parameters, including: Configure the channel spreading factor corresponding to the current elevation angle in the link layer frame header of the uplink channel to determine the data packet length carried by each data frame in the physical layer.

5. The method according to claim 4, characterized in that, The uplink protocol parameter table also includes the channel preamble of the terminal at different elevation angles; The terminal configures the communication protocol of the uplink channel according to the current uplink protocol parameters, including: Configure the channel preamble corresponding to the current elevation angle in the link layer frame header of the uplink channel so that the satellite and the terminal can synchronize uplink frames.

6. The method according to claim 5, characterized in that, The uplink protocol parameter table also includes the remaining visible time window of the satellite at different elevation angles for the terminal; the terminal configures the communication protocol of the uplink channel according to the current uplink protocol parameters, including: Based on the remaining visible time window corresponding to the current elevation angle, the channel spreading factor corresponding to each elevation angle in the remaining visible time window, and the length of the channel preamble, the amount of data transmitted by the terminal in the remaining visible time window is obtained. The data packet length of the application layer in the uplink channel is configured according to the amount of data transmitted.

7. The method according to claim 1, characterized in that, Also includes: An orbital state machine is installed in the terminal; When the satellite passes overhead, if the elevation angle of the terminal relative to the satellite is not within the synchronization angle range, the communication requirements between the terminal and the satellite are not met, and the terminal is in the search state in the orbital state machine; if the elevation angle of the terminal relative to the satellite is within the synchronization angle range, the communication requirements between the terminal and the satellite are not met, and the terminal is in the synchronization state in the orbital state machine. When the terminal is not connected to the satellite and the current elevation angle of the terminal relative to the satellite is within the synchronization angle range, the terminal begins to connect to the satellite. The terminal is in the access state in the orbital state machine, and after successful connection, the terminal switches to the transmission state in the orbital state machine. Both the access state and the transmission state belong to the synchronization state.

8. The method according to claim 7, characterized in that, Also includes: The elevation angle region of the terminal within the synchronization angle range is divided into several transmission states. When the terminal changes from one transmission state to another, the uplink protocol configuration of the terminal is triggered by an interrupt.

9. The method according to claim 1, characterized in that, Also includes: Before the satellite passes overhead, the uplink protocol parameter table of the terminal is obtained in advance based on the satellite's ephemeris data and the terminal's location.

10. A satellite terminal, characterized in that, include: An elevation angle acquisition module is used to obtain the current elevation angle of the terminal relative to the satellite in real time, based on the satellite's ephemeris data and the position of the satellite terminal, when the satellite passes overhead. The parameter acquisition module is used to obtain the current uplink protocol parameters of the terminal from the uplink protocol parameter table of the terminal based on the current elevation angle; The uplink protocol parameter table of the terminal includes the uplink protocol parameters for the terminal to communicate with the satellite at different elevation angles; The parameter configuration module is used by the terminal to configure the communication protocol of the uplink channel according to the current uplink protocol parameters, so as to transmit data to the satellite using the configured communication protocol.

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