Cooperative transmission method, device and equipment of low-orbit satellite network and storage medium

Abstract

The application discloses a low-orbit satellite network cooperative transmission method and device, equipment and storage medium, relates to the multi-satellite cooperative transmission technical field, and discloses a low-orbit satellite network cooperative transmission method, comprising the following steps: when receiving the multi-satellite cooperative transmission request sent by a mobile terminal, determining a cooperative auxiliary satellite according to the positioning information of the mobile terminal and the ephemeris information of the low-orbit satellite network; starting a cooperative session with the cooperative auxiliary satellite according to the mobile terminal information of the mobile terminal; switching the current waveform modulation mode from orthogonal frequency division multiplexing to a target modulation mode, and converting the service data packet into a target service waveform according to the target modulation mode; compensating the target service waveform to obtain a time-frequency compensation signal and a plurality of waveform signals; sending the plurality of waveform signals to the mobile terminal, and sending the time-frequency compensation signal to the cooperative auxiliary satellite according to the cooperative session to obtain service data, and completing the cooperative transmission of the low-orbit satellite network. The stability and effectiveness of the multi-satellite cooperative transmission can be ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of multi-satellite cooperative transmission, in particular to a cooperative transmission method and device for a low-orbit satellite network, equipment and a storage medium. BACKGROUND

[0002] In the current development trend of mobile communication, low-orbit satellites gradually become an important means to expand global network coverage and enhance remote communication capabilities. Especially in the application scenario of satellite direct connection with mobile phones, low-orbit satellites can provide continuous and wide-area communication services for remote areas, oceans and disaster areas. In the communication scenario of satellite direct connection with mobile phones, due to the limited antenna capability of mobile terminals, it is difficult to achieve high-speed and large-bandwidth transmission of the downlink user link.

[0003] The existing traditional method mainly compensates for the deficiency of mobile terminals by improving the resource configuration of the satellite end, such as increasing the gain of the satellite antenna or increasing the number of on-orbit satellites, so as to improve the throughput performance of the overall link. Although improving the resource configuration of the satellite end can enhance the transmission capability of the downlink to some extent, it will significantly increase the construction and operation cost of the satellite network, and therefore is difficult to be applied to large-scale scenarios.

[0004] The above content is only used to assist in understanding the technical solutions of the present application and does not represent the acknowledgement of the above content as prior art. SUMMARY

[0005] The main purpose of the present application is to provide a cooperative transmission method, device, equipment and storage medium for a low-orbit satellite network, aiming to solve the technical problem that in the scenario of satellite direct connection with mobile phones, the downlink cannot stably realize high-speed and large-bandwidth transmission.

[0006] To achieve the above purpose, the present application provides a cooperative transmission method for a low-orbit satellite network, which comprises:

[0007] When receiving a multi-satellite cooperative transmission request sent by a mobile terminal, a cooperative satellite is determined according to the positioning information of the mobile terminal and the ephemeris information of the low-orbit satellite network;

[0008] A cooperative session with the cooperative satellite is started according to the mobile terminal information of the mobile terminal;

[0009] When receiving a service data packet, the current waveform modulation mode is switched from orthogonal frequency division multiplexing to a target modulation mode, and the service data packet is converted into a target service waveform according to the target modulation mode, wherein the target modulation mode includes orthogonal time frequency space modulation or affine frequency division multiplexing;

[0010] The target service waveform is compensated to obtain a time-frequency compensation signal and a plurality of waveform signals;

[0011] transmit the multi-path waveform signal to the mobile terminal and transmit the time-frequency compensation signal to the cooperative satellite according to the cooperative session, so that the mobile terminal obtains service data according to the multi-path waveform signal and the time-frequency compensation signal, and completes cooperative transmission of the low-orbit satellite network, wherein the service data is obtained by the mobile terminal by analyzing the multi-path waveform signal and the time-frequency compensation signal, and the time-frequency compensation signal is forwarded to the mobile terminal by the cooperative satellite according to the cooperative session.

[0012] In addition, to achieve the above object, the application further provides a cooperative transmission device of a low-orbit satellite network, which comprises a storage, a processor and a computer program stored in the storage and capable of running on the processor, and the computer program is configured to implement the steps of the cooperative transmission method of the low-orbit satellite network.

[0013] a session opening module configured to open a cooperative session with the cooperative satellite according to mobile terminal information of the mobile terminal;

[0014] a waveform conversion module configured to switch a current waveform modulation mode from orthogonal frequency division multiplexing to orthogonal time-frequency space modulation or affine frequency division multiplexing to obtain a target modulation mode, and convert the service data packet into a target service waveform according to the target modulation mode;

[0015] a signal compensation module configured to perform compensation processing on the target service waveform to obtain a time-frequency compensation signal and a multi-path waveform signal;

[0016] a service transmission module configured to transmit the multi-path waveform signal to the mobile terminal and transmit the time-frequency compensation signal to the cooperative satellite according to the cooperative session, so that the mobile terminal obtains service data according to the multi-path waveform signal and the time-frequency compensation signal, and completes cooperative transmission of the low-orbit satellite network, wherein the service data is obtained by the mobile terminal by analyzing the multi-path waveform signal and the time-frequency compensation signal, and the time-frequency compensation signal is forwarded to the mobile terminal by the cooperative satellite according to the cooperative session.

[0017] In addition, to achieve the above object, the application further provides a cooperative transmission device of a low-orbit satellite network, which comprises a storage, a processor and a computer program stored in the storage and capable of running on the processor, and the computer program is configured to implement the steps of the cooperative transmission method of the low-orbit satellite network.

[0018] In addition, to achieve the above object, the application further provides a storage medium, which is a computer readable storage medium, and a computer program is stored on the storage medium, and the computer program is executed by a processor to implement the steps of the cooperative transmission method of the low-orbit satellite network.

[0019] In addition, to achieve the above object, the application further provides a computer program product, which comprises a computer program, and the computer program is executed by a processor to implement the steps of the cooperative transmission method of the low-orbit satellite network.

[0020] The one or more technical solutions provided by the application have at least the following technical effects:

[0021] Due to the adoption of the technical means of determining the cooperative auxiliary satellite according to the mobile terminal positioning information and the low-orbit satellite network ephemeris information, starting the cooperative session with the cooperative auxiliary satellite based on the mobile terminal information, switching the waveform modulation mode from orthogonal frequency division multiplexing to orthogonal time-frequency-space modulation or affine frequency division multiplexing and converting the target service waveform, compensating the target service waveform to obtain the time-frequency compensation signal and the multi-path waveform signal, sending the multi-path waveform signal to the mobile terminal and sending the time-frequency compensation signal to the cooperative auxiliary satellite according to the cooperative session so as to be forwarded to the mobile terminal, and finally analyzing the two types of signals by the mobile terminal to obtain the service data, the problems of insufficient downlink user link transmission performance caused by the limited antenna capability of the mobile terminal in the mobile phone direct satellite scene in the prior art, and the sharp increase of the deployment cost of the low-orbit satellite system by increasing the satellite antenna gain and the number of satellites are solved; compared with the prior art, the average signal-to-noise ratio of the received signal of the mobile terminal is improved by multi-satellite cooperative transmission, the time-varying fast fading caused by the dynamic change of the phase difference of the multi-path data stream is counteracted by the orthogonal time-frequency-space modulation or the affine frequency division multiplexing waveform, the time delay difference of each signal reaching the mobile terminal is ensured to meet the transmission requirements by compensation processing, the transmission performance of the mobile terminal downlink in the low-orbit satellite network is effectively enhanced without significantly increasing the system deployment cost, and efficient cooperative transmission of the low-orbit satellite network is realized. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the application and, together with the specification, serve to explain the principles of the application.

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the accompanying drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows, and obviously, other drawings can also be obtained by those skilled in the art without creative labor.

[0024] Figure 1A flowchart provided by the embodiment one of the coordinated transmission method of the low-orbit satellite network of the present application is shown in the figure;

[0025] Figure 2 A distributed multi-satellite coordination architecture provided by the embodiment one of the coordinated transmission method of the low-orbit satellite network of the present application is shown in the figure;

[0026] Figure 3 A multi-satellite coordination control plane connection architecture provided by the embodiment one of the coordinated transmission method of the low-orbit satellite network of the present application is shown in the figure;

[0027] Figure 4 A multi-satellite coordination user plane protocol stack architecture provided by the embodiment one of the coordinated transmission method of the low-orbit satellite network of the present application is shown in the figure;

[0028] Figure 5 A multi-satellite coordination transmission beam control provided by the embodiment one of the coordinated transmission method of the low-orbit satellite network of the present application is shown in the figure;

[0029] Figure 6 A field of the downlink control information waveform modulation mode provided by the embodiment one of the coordinated transmission method of the low-orbit satellite network of the present application is shown in the figure;

[0030] Figure 7 A time-frequency arrangement of the physical downlink control channel and the physical downlink shared channel in the multi-satellite coordination transmission mode provided by the embodiment one of the coordinated transmission method of the low-orbit satellite network of the present application is shown in the figure;

[0031] Figure 8 A flowchart provided by the embodiment two of the coordinated transmission method of the low-orbit satellite network of the present application is shown in the figure;

[0032] Figure 9 A module structure of the coordinated transmission device of the low-orbit satellite network of the embodiment of the present application is shown in the figure;

[0033] Figure 10 A device structure of the hardware running environment involved in the coordinated transmission method of the low-orbit satellite network in the embodiment of the present application is shown in the figure.

[0034] The purpose of the present application, the functional characteristics and the advantages will be further explained in combination with the embodiments and with reference to the drawings. DETAILED DESCRIPTION

[0035] It should be understood that the specific embodiments described herein are only used to explain the technical solutions of the present application, and are not used to limit the present application.

[0036] In order to better understand the technical solutions of the present application, the specific embodiments will be described in detail below with reference to the drawings and the specific embodiments.

[0037] The main solution of this application embodiment is as follows: upon receiving a multi-satellite cooperative transmission request sent by a mobile terminal, a cooperative auxiliary satellite is determined based on the mobile terminal's positioning information and the ephemeris information of the low-Earth orbit satellite network; a cooperative session with the cooperative auxiliary satellite is initiated based on the mobile terminal information of the mobile terminal; upon receiving a service data packet, the current waveform modulation mode is switched from orthogonal frequency division multiplexing to the target modulation mode, and the service data packet is converted into a target service waveform based on the target modulation mode; the target service waveform is compensated to obtain a time-frequency compensation signal and multiple waveform signals; the multiple waveform signals are sent to the mobile terminal, and the time-frequency compensation signal is sent to the cooperative auxiliary satellite based on the cooperative session, so that the mobile terminal obtains service data based on the multiple waveform signals and the time-frequency compensation signal, thus completing the cooperative transmission of the low-Earth orbit satellite network.

[0038] In this embodiment, for ease of description, the following description will focus on the collaborative transmission equipment that identifies low-Earth orbit satellite networks.

[0039] Because existing technologies cannot stably achieve high-speed and high-bandwidth transmission in scenarios where mobile phones directly connect to low-Earth orbit satellites, this application provides a solution. This solution involves determining a cooperative auxiliary satellite based on the mobile terminal's location information and the low-Earth orbit satellite network ephemeris information. A cooperative session with the auxiliary satellite is initiated based on the mobile terminal's information. The waveform modulation method is switched from orthogonal frequency division multiplexing (OFDM) to orthogonal time-frequency modulation (TFM) or simulated radio frequency division multiplexing (RFDM), and the target service waveform is converted. The target service waveform is then compensated to obtain a time-frequency compensation signal and multiple waveform signals. These multiple waveform signals are sent to the mobile terminal, and the time-frequency compensation signal is sent to the cooperative auxiliary satellite according to the cooperative session. This technology forwards signals to the mobile terminal, which then parses the two types of signals to obtain service data. This solves the problems of insufficient downlink transmission performance in direct satellite connection scenarios where mobile phones are limited by the antenna capabilities of the mobile terminal, and the problem that increasing satellite antenna gain and the number of satellites would drastically increase the deployment cost of the low-Earth orbit satellite system. Compared with existing technologies, this technology ensures that the time delay difference of each signal arriving at the mobile terminal meets the transmission requirements through compensation processing. Without significantly increasing the system deployment cost, it effectively enhances the downlink transmission performance of the mobile terminal in the low-Earth orbit satellite network and achieves efficient collaborative transmission in the low-Earth orbit satellite network.

[0040] It should be noted that the executing entity in this embodiment can be a computing service device with data processing, network communication, and program execution functions, such as a tablet computer, personal computer, or mobile phone, or an electronic device capable of performing the above functions, a collaborative transmission device for a low-Earth orbit satellite network, or a host satellite. The following description uses a host satellite as an example to illustrate this embodiment and the subsequent embodiments.

[0041] Based on this, embodiments of this application provide a cooperative transmission method for low-Earth orbit satellite networks, referring to... Figure 1 ,Figure 1 Figure 1 is a flowchart of a first embodiment of a cooperative transmission method for a low-orbit satellite network.

[0042] In this embodiment, the cooperative transmission method for a low-orbit satellite network includes steps S10-S50:

[0043] Step S10, upon receiving a multi-satellite cooperative transmission request sent by a mobile terminal, determine a cooperative secondary satellite according to the positioning information of the mobile terminal and the ephemeris information of the low-orbit satellite network.

[0044] It should be noted that the multi-satellite cooperative transmission request is a request signal sent by the mobile terminal when it needs high-reliability and large-bandwidth service transmission to the low-orbit satellite, and the purpose is to request multiple low-orbit satellites to provide transmission services to improve the downlink transmission performance. In this embodiment, when the mobile terminal has such service requirements, it will automatically generate and send the request to trigger the subsequent cooperative secondary satellite determination process.

[0045] Further, the mobile terminal refers to a terminal device that needs to realize high-reliability and large-bandwidth service transmission through a low-orbit satellite network, such as a smartphone supporting Non-Terrestrial Network (NTN) communication function, a portable data terminal, etc.

[0046] In addition, the positioning information of the mobile terminal is data used to determine the specific position of the mobile terminal in space, usually including the latitude and longitude coordinates and altitude of the mobile terminal, etc. These information can be obtained through the Global Navigation Satellite System (GNSS) module of the mobile terminal.

[0047] In addition, the ephemeris information of the low-orbit satellite network is data describing the orbit parameters of the low-orbit satellite in space, including the real-time orbit position, running speed, communication payload state and inter-satellite link bandwidth of each low-orbit satellite. Through the ephemeris information, it can be judged whether the satellite is in a usable state and whether it can meet the resource requirements of cooperative transmission.

[0048] Further, the cooperative secondary satellite is a low-orbit satellite selected from the low-orbit satellite network to provide cooperative transmission services with the primary satellite for the mobile terminal. The cooperative secondary satellite needs to meet the conditions of being in the visible range of the mobile terminal, the satellite-ground link budget meeting the communication requirements, and there being idle communication resources, etc. Its main role is to assist the primary satellite to send service data streams, improve the average signal-to-noise ratio of the mobile terminal receiving signals, and enhance the transmission performance.

[0049] It can be understood that the mobile terminal sends a multi-satellite cooperative transmission request, which indicates that the mobile terminal has high reliability and large bandwidth service transmission requirements; the distances and communication angles between each low earth orbit satellite and the mobile terminal are calculated, and a candidate satellite list is screened; the low earth orbit satellite is excluded from the candidate satellite list, and at least one low earth orbit satellite is selected as a cooperative satellite according to the inter-satellite link bandwidth in the ephemeris information.

[0050] Referring to Figure 2 , Figure 2 The figure is a distributed multi-satellite cooperative architecture of the first embodiment of the low earth orbit satellite network cooperative transmission method of the application.

[0051] As Figure 2 shown, the figure includes a cooperative satellite cluster and a non-cooperative satellite, wherein the cooperative satellite cluster is composed of low earth orbit satellite 1 (primary satellite) and low earth orbit satellite 2 (secondary satellite), and low earth orbit satellite P (secondary satellite), and these secondary satellites are directly connected to the primary satellite through inter-satellite microwave links (inter-satellite links use 5G Xn interface protocol). The primary satellite serves as a data packet replication and separation node, responsible for copying and sending the received data packets to the secondary satellites in the cooperative satellite cluster; the signaling interaction of the terminal is only completed through the primary satellite, while the secondary satellites are used to assist the primary satellite in sending the business data stream. The figure also shows a new radio (NR) Uu interface, which is a communication interface between the handheld terminal and the satellite. The NGu interface is connected to the data network through a satellite radio interface (SRI), realizing the transmission of user plane data. On the ground part, the core network 5GC is connected to the gateway through the N6 interface, and the gateway is connected to the data network through the user plane interface. The whole system realizes the organic integration of 5G NTN technology and multi-satellite cooperative transmission technology through this architecture, significantly enhances the transmission performance of the handheld terminal downlink, and at the same time reduces the deployment cost of the multi-satellite cooperative system, facilitating the commercialization of the multi-satellite cooperative transmission technology. The cellular structure in the figure may represent the coverage of the ground network, and the handheld terminal represents the user equipment, which communicates with the satellite through the NR Uu interface to realize broadband access. Among them, NTN represents the handheld terminal; NR Uu interface represents the new radio interface; NGu interface represents the new radio (NR) user plane (User Plane) interface; core network 5GC represents the 5G core network; Gateway represents the gateway; Xn interface represents the inter-satellite link interface; SRI represents the satellite radio interface; N6 interface represents the interface in the 5G core network, used to connect the user plane function.

[0052] In a possible implementation, step S10 can include steps S11-S14:

[0053] Step S11, upon receiving the multi-satellite cooperative transmission request sent by the mobile terminal, obtaining ephemeris information of the low-orbit satellite, a preset distance threshold and a preset elevation angle threshold, wherein the ephemeris information includes real-time orbital position, communication payload state and inter-satellite link bandwidth of each low-orbit satellite;

[0054] The preset distance threshold is set in advance and is used to determine whether the distance between the low-orbit satellite and the mobile terminal meets the distance standard of communication requirement. The threshold is determined according to the communication coverage capability of the low-orbit satellite, signal transmission attenuation characteristics and other factors. If the distance between the satellite and the mobile terminal is less than the threshold, it means that the signal attenuation in the transmission process is small, otherwise, the communication may be unstable due to too large attenuation.

[0055] The preset elevation angle threshold is set in advance and is used to determine whether the low-orbit satellite is within the visual range of the mobile terminal. The threshold is determined based on the receiving characteristics of the mobile terminal antenna. The communication elevation angle is the angle of elevation of the satellite relative to the horizontal line of the mobile terminal. If the angle is greater than the preset elevation angle threshold, it means that the satellite is within the visual range of the mobile terminal, otherwise, the satellite may be blocked or beyond the receiving range of the antenna, and normal communication cannot be realized.

[0056] Step S12, calculating the satellite-ground link distance and the communication elevation angle between the low-orbit satellite and the mobile terminal according to the positioning information of the mobile terminal and the real-time orbital position;

[0057] It should be noted that the real-time orbital position refers to the three-dimensional coordinates of the low-orbit satellite in space at a specific time. The spatial position of the satellite can be accurately determined through the real-time orbital position, and the relative distance and angle between the satellite and the mobile terminal can be calculated by combining the positioning information of the mobile terminal. The communication elevation angle is the angle between the horizontal direction of the mobile terminal and the line connecting the low-orbit satellite. The angle is calculated based on the real-time orbital position of the satellite and the positioning information of the mobile terminal.

[0058] It can be understood that the main satellite extracts the positioning information of the mobile terminal from the multi-satellite cooperative transmission request received previously, and extracts the real-time orbital position of each low-orbit satellite from the obtained ephemeris information. Based on the spatial geometric calculation method, the positioning information of the mobile terminal and the real-time orbital position of the satellite are taken as two spatial points, and the straight-line distance between the two points is calculated. The distance is the satellite-ground link distance between the low-orbit satellite and the mobile terminal, which is used to determine whether the signal transmission attenuation is within an acceptable range. Similarly, based on the spatial geometric relationship, a horizontal coordinate system is established with the position of the mobile terminal as the origin, and the angle of elevation of the real-time orbital position of the satellite relative to the horizontal direction of the coordinate system is calculated. The angle is the communication elevation angle.

[0059] Step S13, screening the low-orbit satellite whose satellite-ground link distance is less than the preset distance threshold, whose communication elevation angle is greater than the preset elevation angle threshold and whose communication payload has idle resources, to form a candidate satellite list;

[0060] It should be noted that the candidate satellite list is formed by screening satellites that meet the three conditions of satellite-ground link distance, communication elevation angle and communication payload resource from all low-orbit satellites. The satellites in the list are candidate satellites that have the basic conditions to participate in cooperative transmission.

[0061] The idle resource of the communication payload means that the communication equipment of the low-orbit satellite is not fully occupied, and there are still resources available for carrying cooperative transmission services. In this embodiment, it mainly refers to the existence of at least one idle service beam of the satellite, because the service beam is the key equipment for sending service data flow to the mobile terminal. Only if there is an idle service beam, the satellite can assist the primary satellite to complete the cooperative transmission task.

[0062] It can be understood that each low-orbit satellite is judged one by one. First, it is judged whether the satellite-ground link distance is less than the preset distance threshold. If it is greater than or equal to, the satellite is excluded. If it is less than, the second judgment is entered. Second, it is judged whether the communication elevation angle is greater than the preset elevation angle threshold. If it is less than or equal to, the satellite is excluded. If it is greater than, the third judgment is entered. Third, it is judged whether there is an idle resource of the communication payload, that is, whether there is at least one idle service beam. If there is not, the satellite is excluded. If there is, the satellite is included in the candidate range. All low-orbit satellites that pass the three judgments are sorted into a list.

[0063] Step S14, determining a cooperative secondary satellite from the candidate satellite list according to the inter-satellite link bandwidth.

[0064] It should be noted that the inter-satellite link bandwidth is the channel capacity of the inter-satellite link between low-orbit satellites for transmitting data, that is, the amount of data that the inter-satellite link can transmit per unit time. In cooperative transmission, the primary satellite needs to send time-frequency compensation signals and other data to the cooperative secondary satellite through the inter-satellite link. The inter-satellite link bandwidth determines the data transmission rate and stability. The greater the bandwidth, the faster the data transmission rate, which can better meet the real-time data interaction requirements in cooperative transmission and avoid data transmission delay or loss due to insufficient bandwidth.

[0065] The primary satellite extracts the inter-satellite link bandwidth data of each satellite in the candidate satellite list from the ephemeris information, analyzes the bandwidth in combination with the required data amount in cooperative transmission, determines a bandwidth threshold that meets the requirements, and screens the candidate satellites whose bandwidth is greater than or equal to the threshold. If there are multiple satellites that meet the conditions, they can be sorted according to the bandwidth size and the larger bandwidth is selected first. The larger bandwidth can speed up data transmission and reduce interaction delay. At least one satellite that meets the bandwidth requirement is selected as a cooperative secondary satellite according to the actual cooperative transmission requirements, the identification information of the satellite is recorded, and the determination of the cooperative secondary satellite is completed.

[0066] In this embodiment, in the scenario of mobile phone direct connection with low earth orbit satellite (LEO), there is a problem that high-speed and large-bandwidth transmission cannot be stably realized in the downlink. When the handheld terminal has a high-reliability and large-bandwidth service transmission demand, the initial connection is established with the satellite with the best link quality in the visual range, and the cell search, random access, radio resource control connection establishment and non-access layer registration are sequentially completed to access the low earth orbit satellite internet; then the terminal sends a multi-satellite coordinated transmission request (DMCT Request) to the satellite (main satellite). After receiving the request, the main satellite combines the terminal positioning information and the LEO satellite network ephemeris information to find and calculate the target auxiliary satellite resources that can participate in coordinated transmission (which need to meet the following conditions: the orbital position is in the visual range of the terminal, that is, the communication elevation angle is 30°-150°, the satellite-ground link budget meets the communication conditions, the communication payload has idle resources, that is, at least one idle service beam, and there is a communicable inter-satellite microwave link with the main satellite). If the main satellite does not find the schedulable auxiliary satellite resources, it will feed back a DMCTReject message to the terminal, and the terminal only enjoys the NTN single-satellite service transmission service; if P-1 schedulable coordinated auxiliary satellite resources are found, the main satellite reports the auxiliary satellite information to the core network, and forms a master-slave type coordinated satellite cluster with these auxiliary satellites.

[0067] Referring to Figure 3 , Figure 3 Figure 1 is a schematic diagram of the multi-satellite coordinated control plane connection architecture of the first embodiment of the low earth orbit satellite network coordinated transmission method of the present application.

[0068] As shown in Figure 3 , the figure includes a 5G core network, which communicates with the main satellite (Sat.1) through the next-generation core interface of the 5G core network. The main satellite is responsible for radio resource control and is connected with the auxiliary satellite (Sat.2) through the inter-satellite control plane interface to realize inter-satellite communication and control. The auxiliary satellite is also responsible for radio resource control and communicates with the user equipment through the user plane radio interface. The user equipment includes a radio resource control module for connecting with the main satellite. In the entire system, the 5G core network exchanges data with the main satellite through the inter-satellite control plane interface, and the main satellite communicates with the user equipment through the user plane radio interface to realize control and management of radio resources. This architecture allows the 5G core network to expand its coverage through the satellite network and provide more extensive wireless communication services for users. The dashed line in the figure represents the user plane radio interface, and the solid line represents the control plane interface. The entire system realizes data transmission and control of radio resources through these interfaces.

[0069] Referring to Figure 4 , Figure 4 Figure 2 is a schematic diagram of the multi-satellite coordinated user plane protocol stack architecture of the first embodiment of the low earth orbit satellite network coordinated transmission method of the present application.

[0070] As shown in Figure 4As shown, the main star part starts from the service data adaptation protocol (SDAP), passes through the packet data convergence protocol (PDCP), the radio link control (RLC), the media access control (MAC), reaches the physical layer (PHY), and then sends signals through the radio frequency (RF) and the antenna (Antenna). The signal processing flow includes channel coding, rate matching, scrambling, constellation mapping, layer mapping, antenna precoding, resource mapping, followed by waveform modulation, which can select orthogonal frequency division multiplexing (OFDM), orthogonal time frequency space modulation (OTFS) or affine frequency division multiplexing (AFDM), then add a cyclic prefix (CP), and compensate Sat.1 and Sat.2 through a time-frequency pre-compensation module, and finally send through a new radio user equipment interface (NR Uu). The secondary star is in an idle state (Idle state), and its protocol stack is similar to that of the main star, including SDAP, PDCP, RLC, MAC, PHY, RF and Antenna, but there is no active signal processing flow at present. The separation node is also marked in the figure, which is the demarcation point of the main star and the secondary star signal processing. The design of the whole system aims to improve the coverage range and communication quality of the signal through the cooperative work of the main star and the secondary star, and to ensure that the user equipment can stably receive and send data through the wireless interface.

[0071] Step S20, according to the mobile terminal information of the mobile terminal, open the cooperative session with the cooperative secondary star;

[0072] It should be noted that the cooperative session is a communication session established between the main star and the cooperative secondary star for realizing the cooperative transmission of the mobile terminal. The session is used for transmitting control signaling and service related information between the main star and the cooperative secondary star, ensuring that the main star and the cooperative secondary star act in coordination during the cooperative transmission process, and ensuring that the service data can be transmitted in order and accurately to the mobile terminal.

[0073] It can be understood that the main star sends a session opening instruction to the cooperative secondary star when receiving the session receiving message, and opens the cooperative session with the cooperative secondary star.

[0074] In a possible implementation, step S20 can include steps S21-S25:

[0075] Step S21, determining the identification information and the positioning information according to the mobile terminal information of the mobile terminal;

[0076] It should be noted that the identification information is information used to uniquely identify the corresponding mobile terminal during the cooperative transmission of the low-orbit satellite. The positioning information is data used to determine the specific position of the mobile terminal in space, and in this embodiment, mainly refers to the global navigation satellite system position information of the mobile terminal.

[0077] Step S22, sending the identification information and the positioning information to the cooperative satellite to make the cooperative satellite center the service beam on the mobile terminal according to the identification information and the positioning information, and feed back a virtual radio resource control connection established with the mobile terminal;

[0078] It should be noted that the service beam is a signal beam on the low-orbit satellite for transmitting service data to the mobile terminal. In the cooperative transmission scenario, the service beam is accurately centered on the mobile terminal to ensure that the mobile terminal can efficiently receive the service data and improve the transmission quality. The pointing of the service beam can be dynamically adjusted according to the positioning information of the mobile terminal to adapt to possible position changes of the mobile terminal.

[0079] The virtual radio resource control connection, i.e., the virtual RRC connection, is a non-fully-physicalized radio resource control connection established between the cooperative satellite and the mobile terminal. Unlike the real radio resource control connection established between the primary satellite and the mobile terminal, the virtual radio resource control connection does not need to go through a complex signaling interaction process, is used for the cooperative satellite to confirm that it is ready to provide service data transmission services for the mobile terminal, embodies the service association state between the cooperative satellite and the mobile terminal, and does not involve complete resource allocation and signaling management processes.

[0080] The primary satellite transmits the determined identification information and positioning information to the cooperative satellite that has been screened through an inter-satellite microwave link using a 5G Xn interface protocol to ensure the compatibility and stability of information transmission; the cooperative satellite receives the information, confirms the identity of the mobile terminal to be served according to the identification information to avoid confusion, analyzes the spatial position of the mobile terminal according to the positioning information, starts a beam control module to adjust the pointing of the service beam, and makes the beam center the mobile terminal to ensure effective signal coverage; after the cooperative satellite completes the beam alignment, it confirms that it has the basic conditions for cooperative transmission services, generates feedback information for establishing a virtual radio resource control connection with the mobile terminal, and then transmits the feedback information to the primary satellite through the inter-satellite link to inform the primary satellite that the preparation work has been completed.

[0081] Step S23, when receiving the virtual radio resource control connection, sending a multi-satellite cooperative transmission permission message to the mobile terminal to make the mobile terminal feed back a session establishment request message according to the multi-satellite cooperative transmission permission message;

[0082] It should be noted that the multi-satellite cooperative transmission permission message is a notification message sent by the primary satellite to the mobile terminal after confirming that the cooperative satellite has completed the service beam alignment and established the virtual radio resource control connection. The message is used to inform the mobile terminal that it currently has the conditions for starting multi-satellite cooperative transmission, including that the cooperative satellite is ready, the transmission link is prepared, and other information, and is a trigger signal for the mobile terminal to initiate a subsequent session establishment request, which ensures that the mobile terminal starts the subsequent process at the right time and avoids resource waste or process confusion.

[0083] The session establishment request message is a message sent by the mobile terminal to the primary satellite for requesting to establish a dedicated session for cooperative transmission after receiving the multi-satellite cooperative transmission permission message. In the embodiment, the message is specifically a cooperative transmission dedicated PDU session establishment request message, which contains information such as the service requirement of the mobile terminal and the required resource type, and provides session support for subsequent cooperative transmission of service data.

[0084] It can be understood that the primary satellite continuously monitors whether the virtual radio resource control connection feedback information sent by the cooperative secondary satellite is received. When the feedback information is received, it indicates that the cooperative secondary satellite has completed the service beam alignment and is ready for cooperative transmission, and the current overall system has the basic conditions for starting multi-satellite cooperative transmission. The primary satellite generates a multi-satellite cooperative transmission permission message, which specifically contains the core information that the cooperative transmission condition is met, and sends the message to the mobile terminal through the signaling beam of the primary satellite to ensure that the mobile terminal can timely obtain the notification. After receiving the multi-satellite cooperative transmission permission message, the mobile terminal parses the message content to confirm that the cooperative transmission can be started at present, and then starts the non-access layer module of the mobile terminal to generate a session establishment request message, which contains the service parameters required by the mobile terminal for this cooperative transmission and other key contents. The mobile terminal sends the generated session establishment request message to the primary satellite.

[0085] In step S24, the session establishment request message is sent to the core network, so that the core network establishes and feeds back a session reception message according to the session establishment request message;

[0086] It should be noted that the core network is the core control and management part of the low-orbit satellite communication network, which is responsible for processing signaling interaction, resource allocation, session management and other key functions in the network. According to the session establishment request message of the mobile terminal, it can be judged whether the resources and conditions for establishing a cooperative transmission session are met, and it is also responsible for allocating necessary network resources for the established session to ensure that the session can operate normally.

[0087] The session reception message is a confirmation message fed back by the core network to the primary satellite after processing the session establishment request message of the mobile terminal. In the embodiment, the message is specifically a cooperative transmission dedicated PDU session establishment reception message (DMCT-specific PDU Session Establishment Accept), which contains resource information and session parameters allocated by the core network for the cooperative transmission session, and is used to inform the primary satellite that the core network has agreed to establish the cooperative transmission session and complete the related resource configuration.

[0088] The primary satellite sends a session establishment request message to the core network through a dedicated communication link between the primary satellite and the core network in compliance with a low-orbit satellite network and core network communication protocol, thereby ensuring safe and reliable message transmission. After receiving the message, the core network starts a session management module, analyzes mobile terminal service requirements, required resource types, and checks its own resource status, and determines whether to support collaborative transmission session establishment. If the resources are sufficient and meet the service requirements, the core network allocates network resources for the session, determines operating parameters, and generates a session reception message, and then feeds back the message to the primary satellite through the dedicated communication link, thereby informing that the session establishment request has been approved and configured.

[0089] Step S25, when receiving the session reception message, a collaborative session with the collaborative secondary satellite is started.

[0090] It can be understood that after the primary satellite receives the session reception message fed back by the core network, the message is parsed to extract session parameters, resource configuration information, and other key contents, and it is confirmed that the core network has completed resource allocation and parameter configuration for the collaborative transmission session. Then, according to the parsed session parameters, communication parameters such as data transmission rate and signaling interaction format of the inter-satellite link between the primary satellite and the collaborative secondary satellite are configured to ensure that the collaborative session requirements are met. Subsequently, a collaborative session start instruction containing a session identifier and session parameters is sent to the collaborative secondary satellite through the inter-satellite microwave link, thereby informing the specific configuration and start requirements. After the collaborative secondary satellite receives the instruction, it configures its communication module and data processing module according to the parameters, completes the configuration, and feeds back confirmation information to the primary satellite. After that, the collaborative session between the primary satellite and the collaborative secondary satellite is officially started, and both of them have the condition to collaboratively transmit service data, and can enter the subsequent service data processing and transmission phase.

[0091] Referring to Figure 5 , Figure 5 FIG. 1 is a multi-satellite collaborative transmission beam control schematic diagram of a first embodiment of the low-orbit satellite network collaborative transmission method of the present application.

[0092] As Figure 5As shown, the figure includes a coordinated satellite cluster and a non-coordinated satellite, the coordinated satellite cluster is composed of low-orbit satellite 1 (primary satellite) and low-orbit satellite 2 (secondary satellite), which communicate with each other through Xn over ISL (inter-satellite link) to realize coordinated transmission of data. The primary satellite is responsible for the replication and separation of business data, and distributes the data to the secondary satellite. The figure also shows the business beam and the signaling beam, where the business beam is used to transmit user data, and the signaling beam is used to transmit control signals. In the ground part, the core network 5GC is connected to the gateway station Gateway through the N6 interface, and the gateway station is connected to the data network through the NGu interface. The handheld terminal communicates with the satellite through the NR Uu interface to realize wideband access. The figure also shows the connection mode of NGu over SRI (satellite wireless interface), which is the user plane data transmission interface between the ground network and the satellite network. The whole system realizes the organic integration of 5G NTN technology and multi-satellite coordinated transmission technology through this architecture, significantly enhances the transmission performance of the handheld terminal downlink, and at the same time reduces the deployment cost of the multi-satellite coordinated system, facilitating the commercialization of multi-satellite coordinated transmission technology. The cellular structure in the figure may represent the coverage of the ground network, and the handheld terminal represents the user equipment, which communicates with the satellite through the NR Uu interface to realize wideband access. Among them, NTN represents the handheld terminal; NR Uu interface represents the new radio interface; NGu interface represents the new radio (NR) user plane (User Plane) interface; Core network 5GC represents the 5G core network; Gateway represents the gateway; Xn interface represents the inter-satellite link interface; SRI represents the satellite wireless interface; N6 interface represents the interface in the 5G core network, used to connect the user plane function.

[0093] Step S30, when receiving the service data packet, switching the current waveform modulation mode from orthogonal frequency division multiplexing to the target modulation mode, and converting the service data packet into a target service waveform according to the target modulation mode, wherein the target modulation mode includes orthogonal time frequency space modulation or affine frequency division multiplexing;

[0094] It should be noted that the service data packet is a data packet containing the service data required by the mobile terminal, and these data can be video data, audio data, file data, and various types of user service data. In this embodiment, the service data packet is issued by the core network to the primary satellite, which needs to be processed and sent to the mobile terminal through coordinated transmission to meet the service requirements of the mobile terminal.

[0095] Orthogonal Frequency Division Multiplexing (OFDM) is a waveform modulation mode, which divides the channel into multiple orthogonal sub-channels, transmits independent signals on each sub-channel, effectively counteracts frequency selective fading, and improves spectrum utilization. In this embodiment, OFDM is the initial waveform modulation mode, which is used in non-cooperative transmission scenarios or specific cases.

[0096] The target modulation mode is a waveform modulation mode selected from Orthogonal Time Frequency Space modulation and Affine Frequency Division Multiplexing in a cooperative transmission scenario to improve the performance of service data transmission. This modulation mode can better counteract the time-varying fast fading caused by the dynamic change of the phase difference of multiple data streams.

[0097] Orthogonal Time Frequency Space (OTFS) is a waveform modulation mode with time-frequency two-dimensional interleaving characteristics, which can process signals in the time-frequency domain, effectively counteract time-varying fast fading and Doppler frequency offset and other channel interference. Affine Frequency Division Multiplexing (AFDM) is also a waveform modulation mode suitable for multi-satellite cooperative transmission scenarios, which also has the characteristics of counteracting time-varying fast fading.

[0098] The target service waveform is a signal waveform formed by modulating the initial service waveform by the target modulation mode, which is suitable for transmission in the channel. This waveform combines the advantages of the target modulation mode, can effectively adapt to the characteristics of the cooperative transmission channel, and reduce the influence of channel interference on data transmission.

[0099] It can be understood that the initial service waveform is converted into the target service waveform by modulating and converting the initial service waveform according to the selected target modulation mode.

[0100] In the embodiment, the primary satellite distributes a cell radio network temporary identifier C-RNTI and global navigation satellite system positioning information GNSS positioning information to the terminal of the secondary satellite, controls the secondary satellite to aim the idle traffic beam center at the terminal, and at this time, the terminal and the secondary satellite complete virtual radio resource control connection virtual RRC connection establishment; a multi-satellite coordinated transmission permission message DMCT Granted is sent to the terminal, and the terminal is informed that the multi-satellite coordinated transmission condition has been met; a non-access layer NAS layer of the terminal generates a coordinated transmission special packet data unit session establishment request message DMCT-specific PDUSession Establishment Request and sends the message to the core network through the primary satellite; after processing the request message, the core network sends a coordinated transmission special packet data unit session establishment acceptance message DMCT-specific PDU Session Establishment Accept to the terminal through the signaling beam of the primary satellite, the primary satellite informs the secondary satellite through the inter-satellite link that the special packet data unit session has been started, and each secondary satellite adjusts the protocol layer above the radio frequency layer of the user plane protocol stack to the idle state, that is, the secondary satellite degenerates from the regeneration mode to the transparent forwarding mode.

[0101] In a feasible implementation, the step S30 can include steps S31-S34.

[0102] In step S31, when the service data packet is received, the service data packet is sequentially subjected to packet data convergence, packet data compression, radio link control and media access processing to obtain a service bit stream.

[0103] It should be noted that the packet data convergence is the first processing operation on the service data packet, which is performed by the service data convergence protocol (SDAP) layer of the primary satellite. This operation mainly classifies, marks and maps the service data packets of different QoS (quality of service) flows, so that the service data packets can adapt to the subsequent transmission protocol and channel, and ensure that different priority and different type of services can be transmitted according to the preset quality of service requirements.

[0104] The packet data compression is a processing operation performed by the packet data convergence protocol (PDCP) layer of the primary satellite. This operation compresses the header information of the service data packet processed by the packet data convergence through a specific compression algorithm, reduces the overall volume of the data packet, thereby reducing the bandwidth occupation in the data transmission process and improving the transmission efficiency; at the same time, this operation also encrypts and protects the integrity of the data packet, so as to protect the security of the service data in the transmission process and prevent the data from being stolen or tampered.

[0105] Radio Link Control is a processing operation performed by the Radio Link Control (RLC) layer of the primary satellite, mainly for processing service data after packet data compression. This operation includes segmentation, concatenation and retransmission control of data. When the length of service data exceeds the maximum length that can be carried by the physical layer channel, the RLC layer will segment the data into appropriate lengths. If the data length is too short, multiple short data will be concatenated into a data unit that meets the requirements. At the same time, if subsequent data transmission fails, the RLC layer will start a retransmission mechanism to ensure that the service data can be reliably transmitted to the next layer.

[0106] Medium Access Processing is a processing operation performed by the Medium Access Control (MAC) layer of the primary satellite, which is the processing of service data packets before entering the physical layer in the user plane protocol stack. It is mainly responsible for scheduling, priority management and logical channel multiplexing of data units from the RLC layer.

[0107] Service Bit Stream is a binary data stream obtained after service data packets are sequentially processed by packet data aggregation, packet data compression, radio link control and medium access processing. The bit stream has completed a series of processes such as format adaptation, compression, encryption, segmentation and multiplexing, and meets the transmission requirements of the physical layer.

[0108] It can be understood that the primary satellite receives service data packets transmitted by the core network, confirms the integrity of the service data packets, and transmits them to the SDAP layer. The SDAP layer performs packet data aggregation processing on the service data packets, classifies, labels and QoS flow maps the data packets according to the QoS requirements, and transmits the data packets to the PDCP layer after completing the processing. The PDCP layer performs packet data compression processing on the received data packets, reduces the volume of the data packets through header compression algorithms, and performs encryption and integrity protection. After the processing is completed, the data packets are transmitted to the RLC layer. The RLC layer performs radio link control processing on the data packets, segments or concatenates the data according to the physical layer channel carrying capacity, and records the retransmission if necessary. After processing, the data unit is transmitted to the MAC layer. The MAC layer performs medium access processing on the data unit, performs resource scheduling, priority management and logical channel multiplexing, and multiplexes the data of multiple logical channels into a data unit of a physical channel, and outputs a service bit stream.

[0109] Step S32, inputting the service bit stream into the physical downlink shared channel of the physical layer to obtain an initial service waveform;

[0110] It should be noted that the physical downlink shared channel (Physical Downlink Shared Channel, PDSCH) is a channel in the physical layer for transmitting service data to the terminal, and is a key carrier for transmitting service data from the primary satellite to the terminal. This channel has a sharing feature and can transmit service data to multiple terminals at the same time. The primary satellite realizes efficient transmission of service data through resource allocation and scheduling of the channel; in the cooperative transmission scenario, the primary satellite and the secondary satellite both transmit service-related signals to the terminal through their respective physical downlink shared channels, which are the main transmission paths for service data to reach the terminal. The initial service waveform is the signal waveform formed after the service bit stream is input into the physical downlink shared channel of the physical layer and is preliminarily processed by the physical layer.

[0111] It can be understood that the service bit stream is transmitted from the MAC layer to the physical layer, and after the physical layer receives the service bit stream, it is processed by channel coding and interleaving. Channel coding increases the redundancy of data to improve the ability of data to resist interference and fading during transmission, and interleaving processing disperses continuous errors to facilitate subsequent error correction; the physical layer maps the service bit stream processed by channel coding and interleaving to the time-frequency resource block of the physical downlink shared channel to determine the transmission position of the service data in the physical downlink shared channel; the physical layer uses orthogonal frequency division multiplexing modulation to modulate the mapped service bit stream, converting the digital service bit stream into an analog signal waveform; only a cyclic prefix (Cyclic Prefix, CP) is added in front of the modulated signal waveform to eliminate inter-symbol interference and inter-carrier interference, forming an initial service waveform and completing the conversion of the service bit stream to the initial service waveform.

[0112] Step S33, switching the current waveform modulation mode from orthogonal frequency division multiplexing to the target modulation mode;

[0113] In this embodiment, when the cooperative transmission is started, the physical downlink shared channel (Physical Downlink Shared Channel, PDSCH) carrying the service data switches the waveform modulation mode from orthogonal frequency division multiplexing OFDM to orthogonal time frequency space modulation OTFS or affine frequency division multiplexing AFDM to overcome the double selection characteristics of the distributed satellite channel.

[0114] It can be understood that the physical layer of the primary satellite monitors the current transmission scenario in real time. When it is confirmed that the multi-satellite cooperative transmission scenario has been entered and the initially adopted orthogonal frequency division multiplexing modulation mode cannot meet the requirement of resisting time-varying rapid fading, the waveform modulation mode switching process is triggered. The physical layer of the primary satellite selects a suitable one from the two modulation modes of orthogonal time-frequency-space modulation and affine frequency division multiplexing as the target modulation mode according to the current channel condition, the type of service data and the transmission requirement. If the time-varying rapid fading in the channel is relatively serious and the service has a very high requirement on transmission stability, the orthogonal time-frequency-space modulation can be selected preferentially. If the channel condition is relatively mild and the requirement on transmission efficiency is relatively high, the affine frequency division multiplexing can be selected. The physical layer of the primary satellite configures the modulation parameters corresponding to the target modulation mode, including the time-frequency resource grid structure, the subcarrier spacing, the symbol length and the like, to ensure that the modulation parameters match the target modulation mode. The physical layer of the primary satellite completes the switching of the modulation module and formally switches the current waveform modulation mode from the orthogonal frequency division multiplexing to the selected target modulation mode, thereby preparing for the subsequent conversion of the initial service waveform into the target service waveform.

[0115] In step S34, the initial service waveform is converted into a target service waveform according to the target modulation mode.

[0116] It can be understood that if the target modulation mode is the orthogonal time-frequency-space modulation, the orthogonal time-frequency-space modulation module of the physical layer will convert the initial service waveform from the time-frequency domain to the time-frequency domain, perform resource mapping and pulse shaping processing on the signal in the time-frequency domain, utilize the time-frequency two-dimensional interleaving characteristics of the orthogonal time-frequency-space modulation to enhance the ability of the signal to resist time-varying rapid fading, and form the target service waveform corresponding to the orthogonal time-frequency-space modulation. If the target modulation mode is the affine frequency division multiplexing, the affine frequency division multiplexing module of the physical layer will divide and adjust the frequency of the initial service waveform by using affine transformation, improve the spectrum utilization rate by a specific frequency multiplexing mode, and meanwhile enhance the anti-interference and anti-fading ability of the signal, to form the target service waveform corresponding to the affine frequency division multiplexing.

[0117] In step S40, compensation processing is performed on the target service waveform to obtain a time-frequency compensated signal and a plurality of waveform signals.

[0118] It should be noted that the compensation processing is an adjustment processing for the time delay difference and the frequency offset problem that may occur in the transmission process of the target service waveform, including downlink timing advance adjustment and Doppler frequency offset pre-compensation operations. It can ensure that the time delay difference of the signals sent by the plurality of satellites to the mobile terminal is controlled within the cyclic prefix, and the frequency offset of the signals is within the allowable range. The time-frequency compensated signal is a signal obtained after the target service waveform is subjected to time-frequency pre-compensation processing, which can effectively eliminate the influence of the time delay and the frequency offset that may occur in the transmission process of the signal.

[0119] The multi-path waveform signal is obtained by copying the target service waveform according to the number of satellites in the cooperative satellite cluster, and compensating each copied signal. Each signal corresponds to a satellite, including the main satellite and the cooperative auxiliary satellite. By transmitting the multi-path waveform signal through multiple satellites, the average signal-to-noise ratio of the mobile terminal receiving signal can be improved, and the transmission performance can be enhanced.

[0120] It can be understood that after completing the compensation processing, the time-frequency compensation signal and the multi-path waveform signal are obtained, which prepares for subsequent signal transmission to the mobile terminal and the cooperative auxiliary satellite.

[0121] In a feasible implementation, step S40 can include steps S41-S44:

[0122] Step S41, performing time-frequency pre-compensation processing on the target service waveform to obtain a time-frequency compensation signal;

[0123] It should be noted that the time-frequency pre-compensation processing is an adjustment operation performed by the time-frequency pre-compensation module (TFPC) of the main satellite physical layer on the target service waveform. The core is to eliminate the time delay deviation and frequency deviation that may occur in the process of signal transmission from the satellite to the ground in advance. This processing needs to combine the ephemeris information of the cooperative satellite and the positioning information of the terminal, and determine the compensation parameters through calculation to ensure that the signal meets the time delay and frequency requirements of multi-satellite cooperative transmission when it reaches the terminal.

[0124] The time-frequency compensation signal is a signal obtained after the target service waveform is subjected to time-frequency pre-compensation processing. The signal has completed downlink timing advance adjustment and Doppler frequency pre-compensation, and can effectively offset the time delay caused by the distance and the frequency deviation caused by relative motion in the process of signal transmission from the main satellite to the terminal.

[0125] It can be understood that the real-time orbital position of each satellite is calculated according to the ephemeris information, and the air interface propagation time delay from the main satellite to the terminal and the Doppler frequency deviation caused by the relative motion between the main satellite and the terminal are calculated in combination with the terminal positioning information; the time-frequency pre-compensation module determines the downlink timing advance amount according to the calculated air interface propagation time delay, and adjusts the target service waveform in time to ensure that the signal meets the preset time requirement when it is transmitted to the terminal; at the same time, the frequency deviation compensation amount is determined according to the Doppler frequency deviation value, and the target service waveform is adjusted in frequency to offset the frequency deviation caused by the relative motion; after the time and frequency adjustment are completed, the time-frequency compensation signal is obtained, which has the condition for stable transmission in the satellite-ground link.

[0126] Step S42, determining a cooperative satellite cluster according to the cooperative auxiliary satellite, and determining the number of satellites according to the cooperative satellite cluster;

[0127] It should be noted that the cooperative satellite cluster is a satellite group composed of a master satellite and all screened cooperative satellites, adopting a master-slave configuration. The master satellite assumes the role of overall coordination in the cluster, responsible for processing business data, generating compensation signals, and interacting with the core network and terminals; the cooperative satellites assume the role of assisting transmission in the cluster, only responsible for receiving and forwarding signals sent by the master satellite, and the two work together to realize multi-satellite transmission service for the terminal, which is the core execution unit of multi-satellite cooperative transmission. The number of satellites refers to the total number of auxiliary satellites in the cooperative satellite cluster.

[0128] It can be understood that the master satellite, on the basis of having determined the cooperative satellites, classifies itself and all the screened cooperative satellites into a whole, forming a master-slave cooperative satellite cluster, and clearly defining the overall coordination responsibilities of the master satellite and the assisting transmission responsibilities of the cooperative satellites; the master satellite counts the satellites in the cluster one by one to confirm that the cluster contains one master satellite and a number of cooperative satellites; and the number of auxiliary satellites is counted.

[0129] Step S43, copying the target service waveform into a plurality of signals corresponding to the number of satellites;

[0130] It can be understood that the waveform signal is copied P times (each time corresponds to a cooperative satellite), and each cooperative satellite waveform signal is adjusted for downlink timing advance (DTA) and Doppler frequency offset pre-compensation, thereby ensuring that the time delay difference of each cooperative satellite signal reaching the terminal is controlled within CP, and the residual frequency offset of each cooperative satellite waveform signal is controlled within a fractional carrier spacing.

[0131] Step S44, adjusting the plurality of signals for downlink timing advance and Doppler frequency offset pre-compensation to obtain a plurality of waveform signals, wherein the time delay difference of the plurality of waveform signals is controlled within a cyclic prefix.

[0132] It should be noted that the downlink timing advance adjustment is an operation of adjusting the signal transmission time of the corresponding satellite in the plurality of signals according to the air interface propagation delay between the satellite and the terminal. Due to the difference in distance between different satellites and the terminal, the signal transmission time delay is different, and through this adjustment, each signal can reach the terminal at the same time after being sent from the corresponding satellite, avoiding signal superposition confusion caused by time delay difference, and is one of the key operations to ensure multi-satellite signal synchronization.

[0133] The Doppler frequency offset pre-compensation is an operation of adjusting the signal frequency of the corresponding satellite in the plurality of signals according to the relative motion speed between the satellite and the terminal, to offset the Doppler frequency offset generated in the signal transmission process. The relative motion between the satellite and the terminal will cause the signal frequency to shift, and if not compensated, the signal frequency received by the terminal will deviate from the preset value, affecting the demodulation accuracy.

[0134] In addition, the cyclic prefix (CP) is a protection interval added in front of each symbol during signal modulation. Its main role is to eliminate inter-symbol interference and inter-carrier interference. In multi-satellite cooperative transmission, the time delay difference of multi-path signals is controlled within the cyclic prefix, which can ensure that the signals do not produce inter-symbol interference due to time delay difference when they arrive at the terminal, and the signals can be accurately received and superimposed.

[0135] It can be understood that the time-frequency pre-compensation module of the main satellite calculates the air interface propagation delay and Doppler frequency offset value between each satellite in the cooperative satellite cluster and the terminal according to the ephemeris information of each satellite and the positioning information of the terminal. Then, for each satellite corresponding signal in the multi-path signal, the downlink timing advance is determined according to the air interface propagation delay to adjust the transmission time, so as to ensure that the signal arrives at the terminal on time, and the frequency offset compensation is determined according to the Doppler frequency offset value to adjust the signal frequency, so as to offset the frequency offset caused by relative motion. After the adjustment of all multi-path signals is completed, the time-frequency pre-compensation module performs time delay detection on each signal, calculates the time delay difference of any two signals arriving at the terminal, and if the time delay difference exceeds the cyclic prefix range, the downlink timing advance is adjusted again until the time delay difference is controlled within the cyclic prefix. Finally, each corresponding satellite is obtained, and the multi-path signal transmitted by the corresponding satellite to the terminal is obtained.

[0136] Step S50, the multi-path waveform signal is sent to the mobile terminal, and the time-frequency compensation signal is sent to the cooperative secondary satellite according to the cooperative session, so that the mobile terminal obtains service data according to the multi-path waveform signal and the time-frequency compensation signal, and completes the cooperative transmission of the low-orbit satellite network. The service data is obtained by the mobile terminal by analyzing the multi-path waveform signal and the time-frequency compensation signal, which is forwarded by the cooperative secondary satellite to the mobile terminal according to the cooperative session.

[0137] The service data is the effective data that the mobile terminal finally needs to obtain, which is obtained after the cooperative transmission of the main satellite and the cooperative secondary satellite and the analysis and processing of the mobile terminal.

[0138] The main satellite sends the multi-path waveform signals to the mobile terminal through a physical downlink shared channel, and sends time-frequency compensation signals to the cooperative satellite through an inter-satellite link according to the established cooperative session; the cooperative satellite forwards the time-frequency compensation signals to the mobile terminal through its own physical downlink shared channel according to the cooperative session agreement. In the process, the main satellite also sends downlink control information containing the time-frequency resource position of the physical downlink shared channel and the waveform modulation mode indication to the mobile terminal through the physical downlink control channel. After receiving the above signals and information, the mobile terminal first parses the downlink control information to determine the time-frequency resource position of the physical downlink shared channel and the waveform demodulation mode, then finds the corresponding signals and demodulates them according to the above information, and finally extracts the service data through protocol layer parsing to complete the cooperative transmission of the low-orbit satellite network and meet the service needs of the mobile terminal.

[0139] In a feasible implementation, the step of "sending the multi-path waveform signals to the mobile terminal" in step S50 can include steps S51-S54:

[0140] In step S51, a preset field format, a preset aggregation level, and a current downlink control information format of the current physical downlink control channel are obtained.

[0141] It should be noted that the preset field format is defined in advance, which is a structure specification for adding a specific function field in the downlink control information format. In this embodiment, the format specifies the specific position, bit occupation, and coding rule of the "waveform modulation mode" field to be added in the downlink control information format. The "waveform modulation mode" field occupies 2 bits and is fixed at the end of the downlink control information format 1_1, which is used to indicate the waveform demodulation mode (such as orthogonal time-frequency-space modulation or affine frequency division multiplexing) of the physical downlink shared channel to the mobile terminal. This format is the basic standard to ensure that the added field can be correctly added by the main satellite and accurately parsed by the mobile terminal.

[0142] The preset aggregation level, i.e., the preset aggregation level (AL), is a preset resource aggregation degree standard of the physical downlink control channel when carrying the downlink control information. In this embodiment, the preset aggregation level is configured as 16, which means that the physical downlink control channel aggregates 16 resource element groups (REGs) into one resource unit to transmit the downlink control information.

[0143] The initial downlink control information format of the current physical downlink control channel does not contain a waveform modulation mode field, and the set level can not adapt to the multi-satellite cooperative transmission demand. The channel is a key carrier for transmitting control signaling between the main satellite and the mobile terminal, mainly used for transmitting resource allocation, modulation and coding mode and other control information of the physical downlink shared channel to the mobile terminal, and its performance directly affects the reception and demodulation efficiency of the mobile terminal to the service signal. The current downlink control information format is adopted by the current physical downlink control channel, which is a structural form for organizing and carrying downlink control information.

[0144] In step S52, the current downlink control information format is updated according to the preset field format to obtain a target downlink control information format.

[0145] It should be noted that the target downlink control information format is obtained by updating the current downlink control information format according to the preset field format, and is a downlink control information structural form adapted to the multi-satellite cooperative transmission demand. In this embodiment, the target downlink control information format is formed by adding a waveform modulation mode field of 2 bits at the end of the original downlink control information format 1_1, can transmit waveform demodulation mode information of the physical downlink shared channel to the mobile terminal, solves the problem that the original format cannot support waveform switching indication in multi-satellite cooperative transmission, and is the core structure of the main satellite transmitting key control information to the mobile terminal.

[0146] It can be understood that according to the requirement of the preset field format, the waveform modulation mode field is added at the last position of the current downlink control information format 1_1, the field occupies 2 bits, and the coding rule is agreed in advance, such as 01 representing orthogonal time-frequency-space modulation and 10 representing affine frequency division multiplexing; the control information processing module detects the integrity and compatibility of the updated downlink control information format, confirms that the added field does not destroy the structure and function of the original field, and the overall format meets the transmission requirements of the physical downlink control channel; after the detection is completed, the target downlink control information format is obtained.

[0147] In step S53, the current physical downlink control channel is updated according to the preset set level and the target downlink control information format to obtain a target physical downlink control channel.

[0148] It should be noted that the target physical downlink control channel is obtained by updating the current physical downlink control channel according to the preset set level and the target downlink control information format, and is a control signaling transmission channel adapted to the multi-satellite cooperative transmission demand. The channel transmits the target downlink control information format by using the preset set level 16, and is only sent by the main satellite, can stably transmit downlink control information containing the waveform modulation mode field to the mobile terminal, solves the problems of insufficient reliability and incomplete control information of the current physical downlink control channel, and is the core carrier of the main satellite transmitting key control instructions to the mobile terminal in multi-satellite cooperative transmission.

[0149] It can be understood that, according to the requirements of the preset set level 16, the resource aggregation mode of the current physical downlink control channel is adjusted, the resource element groups of the channel are aggregated in groups of 16, new resource transmission units are formed, the anti-interference ability and reception reliability of the channel signal are improved, the target downlink control information format is set as the default control information format of the current physical downlink control channel, and it is ensured that the subsequent transmission of the downlink control information of the channel contains the waveform modulation mode field; the channel configuration module also adjusts the time-frequency resource position of the physical downlink control channel, ensures that it does not overlap with the time-frequency resource of the physical downlink shared channel, and avoids signal interference.

[0150] Step S54, transmitting the multi-path waveform signal to the mobile terminal through the target physical downlink control channel.

[0151] After the main star signal sending module obtains the multi-path waveform signal and the target physical downlink control channel, the signal corresponding to the main star in the multi-path waveform signal is integrated with the target downlink control information carried by the target physical downlink control channel in time-frequency resources, so as to ensure that they are transmitted in the same time slot and the resources do not overlap; the main star transmitting unit converts the integrated signal into a radio frequency signal and sends it to the service beam of the mobile terminal, and monitors the transmission state of the target physical downlink control channel in real time to prevent signal interruption or serious interference. After the mobile terminal receiving unit receives the main star signal, it obtains the target downlink control information through the target physical downlink control channel, receives the main star signal in the multi-path waveform signal, and waits for the other signals forwarded by the cooperative satellite to complete subsequent analysis.

[0152] After the mobile terminal receives the signal issued by the cooperative satellite cluster, it first blindly detects PDCCH to analyze DCI Format 1_1, and obtains the waveform debugging mode (OTFS) of the current PDSCH. The mobile terminal demodulates OTFS according to the PDSCH time-frequency resource block indicated by the DCI, and parses the service data layer by layer. Referring to Figure 6 , Figure 6 is a field diagram of the waveform modulation mode of the downlink control information of the first embodiment of the cooperative transmission method of the low-orbit satellite network of the present application. As shown in Figure 6As shown, the structure of downlink control information format 1_1 (DCI Format 1_1) consists of two parts: downlink control information original bits (DCI original bits) and a new field of waveform modulation mode. DCI original bits are the original control information bits, and the new field is a 2-bit field used to indicate the waveform modulation mode. The three possible values of the new field are: 00 represents orthogonal frequency division multiplexing modulation (OFDM), 01 represents orthogonal time frequency space modulation (OTFS), and 10 represents affine frequency division multiplexing modulation (AFDM). These waveform modulation modes are used to guide the user equipment (UE) on how to demodulate the received signal. The appropriate modulation mode can be selected according to different communication conditions and requirements to improve communication efficiency and signal quality.

[0153] Referring to Figure 7 , Figure 7 is a schematic diagram of the time-frequency arrangement of the physical downlink control channel and the physical downlink shared channel in the multi-satellite cooperative transmission mode of the first embodiment of the cooperative transmission method of the low-orbit satellite network of the present application.

[0154] As Figure 7 shown, the horizontal axis in the figure represents time, and the vertical axis represents frequency. One OFDM symbol occupies a certain time and frequency resource. Different fill shapes are used in the figure to represent different channels and resource elements: the diagonal fill area represents PDCCH (OFDM waveform), which is a channel used to transmit control information, and schedules PDSCH in the same time slot unit. The horizontal fill area represents PDSCH (OTFS waveform), which is a channel used to transmit user data, and uses orthogonal time frequency space modulation (OTFS) technology to improve performance in high-speed mobile environments. The blank area represents the zero resource element (RE), which is not used for data transmission, but is used for flexible scheduling, which can be allocated to PDCCH or PDSCH as needed. The time slot unit is also marked in the figure, which is the basic time unit used for scheduling resources in the 5G system. The scheduling of PDCCH and PDSCH in the same time slot unit means that the control information and user data are closely related in time, which helps to improve the efficiency and accuracy of scheduling. In this way, the system can flexibly allocate and adjust the resources of PDCCH and PDSCH according to the actual communication needs and environmental conditions to optimize the overall communication performance.

[0155] The embodiment provides a cooperative transmission method of a low-orbit satellite network, and solves the technical problem that in the scene of mobile phone direct connection with a low-orbit satellite, a downlink cannot stably realize high-rate and large-bandwidth transmission through the technical means of realizing multi-satellite cooperative transmission in the low-orbit satellite network. Through cooperative work of a main satellite and a cooperative auxiliary satellite, not only is the transmission performance of a downlink of a handheld terminal enhanced, but also the deployment cost of the multi-satellite cooperative system is significantly reduced, commercial popularization of the multi-satellite cooperative transmission technology is facilitated, and beneficial effects of improving communication efficiency, enhancing a signal coverage range, improving signal quality and reliability are achieved.

[0156] Based on the first embodiment of the application, in the second embodiment of the application, the same or similar contents as the above embodiment one can refer to the above introduction, and subsequent details will not be repeated. On this basis, please refer to Figure 8 The cooperative transmission method of the low-orbit satellite network in step S50 further includes steps S60-S80.

[0157] In step S60, when the service data reception completion signal sent by the mobile terminal is received, a session release instruction is sent to the cooperative auxiliary satellite through the cooperative session, so that the cooperative auxiliary satellite stops forwarding the time-frequency compensation signal according to the session release instruction, releases the service beam resource allocated for cooperative transmission, and feeds back a release completion signal.

[0158] It should be noted that the service data reception completion signal is an acknowledgement message sent by the mobile terminal to the main satellite after successfully parsing all the multi-path waveform signals and the time-frequency compensation signals and obtaining complete service data. The signal contains the mobile terminal identifier, the session number of this cooperative transmission and other information, and is used to inform the main satellite that the current service transmission has been completed and there is no need to continue sending or forwarding service-related signals. It is a key trigger signal for triggering the cooperative transmission release process, and ensures that the resource release operation is only executed after the service is completed.

[0159] The session release instruction is a control instruction sent by the main satellite to the cooperative auxiliary satellite through the cooperative session after receiving the service data reception completion signal. The instruction contains the session identifier, the release time requirement and other information, and explicitly requires the cooperative auxiliary satellite to stop the current signal forwarding operation and release the allocated resources. It is a direct basis for the cooperative auxiliary satellite to execute the resource release action, and ensures that all cooperative auxiliary satellites can start the release process synchronously.

[0160] The service beam resource is a dedicated beam resource allocated by the cooperative auxiliary satellite for sending service signals to the mobile terminal in the cooperative transmission process, including time-frequency resources, power resources and the like of the service beam. The resource is a key hardware support for the cooperative auxiliary satellite to realize signal forwarding, and is released in time after completing transmission, so as to avoid waste caused by long-term occupation of the resource and ensure that other mobile terminals or services can normally schedule the resource.

[0161] The release completion signal is a status confirmation message fed back by the cooperative secondary satellite to the primary satellite after the cooperative secondary satellite performs the operation of stopping forwarding the time-frequency compensation signal and releasing the service beam resource. The message contains the cooperative secondary satellite identifier, the released resource type and the like, and is used to inform the primary satellite that the resource release has been completed, to provide a status basis for the primary satellite to subsequently initiate a resource recovery request to the core network, and to ensure that the release process is promoted layer by layer.

[0162] It can be understood that the primary satellite continuously monitors whether the service data reception completion signal of the mobile terminal is received, parses the session number and the mobile terminal identifier in the signal after the signal is received, confirms that the corresponding cooperative transmission service has been completed, and then locates the cooperative session according to the session number, sends a session release instruction containing the resource type to be released and the time limit requirement to all cooperative secondary satellites participating in the cooperative transmission through the session, stops forwarding the time-frequency compensation signal immediately after the cooperative secondary satellite receives the instruction, and then starts the service beam resource release process, releases the specially allocated time-frequency, power and the like service beam resources and updates the resource state to idle, generates a release completion signal, feeds back the signal to the primary satellite through the cooperative session to inform that the resource release has been completed, and waits for the subsequent instruction of the primary satellite.

[0163] In step S70, a session resource recovery request is sent to the core network when the release completion signal is received, so that the core network releases the network resources allocated for the cooperative transmission according to the session resource recovery request, and feeds back a resource recovery confirmation message.

[0164] It should be noted that the session resource recovery request is a resource management request sent by the primary satellite to the core network after confirming that all cooperative secondary satellites complete the resource release. The request contains the PDU session identifier of the cooperative transmission and the allocated network resource type, and is used to inform the core network that the current cooperative transmission service has ended and the network resources allocated for the service need to be recovered.

[0165] The network resources are resources allocated by the core network to support service data transmission when the cooperative transmission is started, including dedicated bearer resources, QoS (quality of service) guarantee resources, session management resources and the like. These resources are the key support for the transmission of service data between the core network and the primary satellite, and timely release can avoid waste of network resources and ensure that other terminals or services can normally apply and use network resources.

[0166] The resource recovery confirmation message is a status message fed back by the core network to the primary satellite after all network resources are released. The message contains the session identifier, the recovered resource list and the like, and is used to inform the primary satellite that the resources on the core network side have been completely released, to provide a final basis for the primary satellite to send a cooperative transmission termination message to the mobile terminal, and to ensure that the entire resource release process is closed on the network level.

[0167] It can be understood that the primary star receives all the release completion signals of the cooperative satellites, and the verification signals are summarized to confirm that each satellite completes resource release, avoiding omission; a session resource recovery request is generated, which clearly marks the PDU session identification of this cooperative transmission, the core network allocated bearer number and QoS resource type, to ensure that the core network accurately locates the resources to be recovered; the request is safely and reliably sent to the core network through a dedicated signaling link between the low-orbit satellite network and the core network in accordance with the low-orbit satellite network and core network communication protocol. After receiving the request, the core network looks up and releases the dedicated bearer resources, QoS guarantee resources, etc. one by one according to the session identification, updates the resource scheduling list and marks the released resources as allocable, generates a resource recovery confirmation message, and feeds back to the primary star through the dedicated signaling link, informing the network that all resources have been recovered.

[0168] Step S80, when receiving the resource recovery confirmation message, a cooperative transmission termination message is sent to the mobile terminal to stop parsing the multi-path waveform signal and the time-frequency compensation signal according to the cooperative transmission termination message, so as to complete the resource release of cooperative transmission.

[0169] The cooperative transmission termination message is a termination notification sent by the primary star to the mobile terminal after receiving the resource recovery confirmation message. The message contains session termination identification, switching guidance for subsequent single-satellite transmission and other information, which is used to explicitly inform the mobile terminal that the current cooperative transmission has completely ended, and the mobile terminal needs to stop parsing the multi-path waveform signal and the time-frequency compensation signal, and at the same time guide the mobile terminal to switch back to the single-satellite transmission mode.

[0170] It can be understood that after the primary star receives the resource recovery confirmation message from the core network, it parses the resource recovery list and combines the release completion signals of the cooperative satellites to confirm that the full-link resource release is ready; then a cooperative transmission termination message containing the session number of this cooperative transmission, the termination time and the switching single-satellite transmission configuration parameters of the mobile terminal is generated and sent to the mobile terminal through the target physical downlink control channel which still maintains normal signaling transmission function. The mobile terminal receives and parses the message, confirms that the cooperative transmission is over, and immediately stops demodulating and protocol layer parsing of the multi-path waveform signal and the time-frequency compensation signal to release its own signal processing resources, and then automatically switches back to the single-satellite transmission mode according to the switching guidance in the message to wait for connection with a single satellite, thus completing the full-link resource release of cooperative transmission.

[0171] The embodiment provides a cooperative transmission method of a low-orbit satellite network, which realizes the technical means of multi-satellite cooperative transmission resource release after receiving service data in a low-orbit satellite network, solves the technical problem of how to release the on-satellite and ground network resources allocated for cooperative transmission after the end of multi-satellite cooperative transmission, ensures timely recovery and effective utilization of resources, improves the resource utilization rate and communication efficiency of the low-orbit satellite network, and achieves the beneficial effect of improving the overall performance of the system.

[0172] It should be noted that the above examples are only used for understanding the present application and do not constitute a limitation on the low-orbit satellite network cooperative transmission method of the present application, and more forms of simple transformation based on this technical concept are within the protection scope of the present application.

[0173] The present application also provides a low-orbit satellite network cooperative transmission device, which refers to Figure 9 The low-orbit satellite network cooperative transmission device comprises:

[0174] The auxiliary satellite determination module 10 is configured to determine a cooperative auxiliary satellite according to the positioning information of the mobile terminal and the ephemeris information of the low-orbit satellite network when receiving the multi-satellite cooperative transmission request sent by the mobile terminal.

[0175] The session opening module 20 is configured to open a cooperative session with the cooperative auxiliary satellite according to the mobile terminal information of the mobile terminal.

[0176] The waveform conversion module 30 is configured to switch the current waveform modulation mode from orthogonal frequency division multiplexing to orthogonal time frequency space modulation or affine frequency division multiplexing to obtain a target modulation mode when receiving a service data packet, and convert the service data packet into a target service waveform according to the target modulation mode.

[0177] The signal compensation module 40 is configured to perform compensation processing on the target service waveform to obtain a time-frequency compensation signal and a plurality of waveform signals.

[0178] The service transmission module 50 is configured to send the plurality of waveform signals to the mobile terminal and send the time-frequency compensation signal to the cooperative auxiliary satellite according to the cooperative session, so that the mobile terminal obtains service data according to the plurality of waveform signals and the time-frequency compensation signal, and completes the cooperative transmission of the low-orbit satellite network, wherein the service data is obtained by the mobile terminal by analyzing the plurality of waveform signals and the time-frequency compensation signal, and the cooperative auxiliary satellite forwards the time-frequency compensation signal to the mobile terminal according to the cooperative session.

[0179] The low-orbit satellite network cooperative transmission device provided by the present application adopts the low-orbit satellite network cooperative transmission method in the above embodiment, which can solve the technical problem that the downlink cannot stably realize high-speed and large-bandwidth transmission in the scene of mobile phone direct connection with low-orbit satellites. Compared with the prior art, the low-orbit satellite network cooperative transmission device provided by the present application has the same beneficial effects as the low-orbit satellite network cooperative transmission method provided by the above embodiment, and other technical features in the low-orbit satellite network cooperative transmission device are the same as the features disclosed in the above embodiment method, which will not be repeated here.

[0180] The application provides a low-orbit satellite network cooperative transmission device. The low-orbit satellite network cooperative transmission device comprises at least one processor and a memory connected with the at least one processor. The memory stores instructions executable by the at least one processor. The instructions are executed by the at least one processor to enable the at least one processor to perform the low-orbit satellite network cooperative transmission method in the above embodiment one.

[0181] Reference will be made to the following description Figure 10 which shows a structural diagram of the low-orbit satellite network cooperative transmission device suitable for implementing the embodiments of the application. The low-orbit satellite network cooperative transmission device in the embodiments of the application can include, but is not limited to, mobile terminals such as mobile phones, notebook computers, digital broadcast receivers, PDAs (Personal Digital Assistant), PADs (Portable Application Description), PMPs (Portable Media Player), vehicle-mounted terminals (for example, vehicle-mounted navigation terminals), and the like, and fixed terminals such as digital TVs, desktop computers, and the like. Figure 10 The low-orbit satellite network cooperative transmission device shown is only an example and should not bring any limitation to the functions and use range of the embodiments of the application.

[0182] As Figure 10As shown, the cooperative transmission device of the low-orbit satellite network can include a processing apparatus 1001 (e.g., a central processor, a graphics processor, etc.) that can perform various appropriate actions and processes according to programs stored in a ROM (Read Only Memory) 1002 or programs loaded from a storage apparatus 1003 into a RAM (Random Access Memory) 1004. In the RAM 1004, various programs and data required for the operation of the cooperative transmission device of the low-orbit satellite network are also stored. The processing apparatus 1001, the ROM 1002, and the RAM 1004 are connected to each other through a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Generally, the following systems can be connected to the I / O interface 1006: an input apparatus 1007 including, for example, a touch screen, a touch pad, a keyboard, a mouse, an image sensor, a microphone, an accelerometer, a gyroscope, etc.; an output apparatus 1008 including, for example, a liquid crystal display (LCD), a speaker, a vibrator, etc.; the storage apparatus 1003 including, for example, a magnetic tape, a hard disk, etc.; and a communication apparatus 1009. The communication apparatus 1009 can allow the cooperative transmission device of the low-orbit satellite network to communicate with other devices wirelessly or by wire to exchange data. Although the cooperative transmission device of the low-orbit satellite network with various systems is shown in the figure, it should be understood that all the systems shown are not required to be implemented or possessed. More or fewer systems can be alternatively implemented or possessed.

[0183] In particular, according to the embodiments disclosed in the present application, the processes described above with reference to the flowcharts can be implemented as a computer software program. The embodiments disclosed in the present application include a computer program product comprising a computer program carried on a computer readable medium, containing program codes for executing the methods shown in the flowcharts. The computer program can be downloaded and installed from a network through the communication apparatus, or installed from the storage apparatus 1003, or installed from the ROM 1002. When the computer program is executed by the processing apparatus 1001, the above-mentioned functions defined in the methods of the embodiments disclosed in the present application are executed.

[0184] The cooperative transmission device of the low-orbit satellite network provided in the present application adopts the low-orbit satellite network cooperative transmission method in the above-mentioned embodiments, and can solve the technical problem that in the scenario of direct connection of a mobile phone to a low-orbit satellite, the downlink cannot stably realize high-rate and large-bandwidth transmission. Compared with the prior art, the low-orbit satellite network cooperative transmission device provided in the present application has the same beneficial effects as the low-orbit satellite network cooperative transmission method provided in the above-mentioned embodiments, and other technical features in the low-orbit satellite network cooperative transmission device are the same as the features disclosed in the previous embodiment method, which will not be described here.

[0185] It should be understood that each part of the present application can be realized by hardware, software, firmware or a combination thereof. In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner. The above is only a specific implementation of the present application, and the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. The protection scope of the present application should be subject to the protection scope of the claims.

[0186] The present application provides a computer readable storage medium having stored thereon computer readable program instructions (i.e. computer programs) for performing the low-orbit satellite network cooperative transmission method in the above embodiments.

[0187] The computer readable storage medium provided by the present application may, for example, be a U disk, but is not limited to an electric, magnetic, optical, electromagnetic, infrared, or semiconductor system, system or device, or any combination of the above. In the present embodiment, the computer readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, system or device. The program code contained on the computer readable storage medium can be transmitted by any appropriate medium.

[0188] The above computer readable storage medium can be contained in the low-orbit satellite network cooperative transmission device; or can exist separately and not be assembled into the low-orbit satellite network cooperative transmission device.

[0189] The above computer readable storage medium carries one or more programs, which, when executed by the low-orbit satellite network cooperative transmission device, cause the low-orbit satellite network cooperative transmission device to: when receiving a multi-satellite cooperative transmission request sent by a mobile terminal, determine a cooperative auxiliary satellite according to the positioning information of the mobile terminal and the ephemeris information of the low-orbit satellite network; start a cooperative session with the cooperative auxiliary satellite according to the mobile terminal information of the mobile terminal; switch the current waveform modulation mode from orthogonal frequency division multiplexing to a target modulation mode, and convert the service data packet into a target service waveform according to the target modulation mode; perform compensation processing on the target service waveform to obtain a time-frequency compensation signal and a plurality of waveform signals; send the plurality of waveform signals to the mobile terminal, and send the time-frequency compensation signal to the cooperative auxiliary satellite according to the cooperative session, so that the mobile terminal obtains the service data according to the plurality of waveform signals and the time-frequency compensation signal, and completes the low-orbit satellite network cooperative transmission.

[0190] Computer program code for carrying out operations of the present application can be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like, and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code can execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0191] The computer program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0192] The modules involved in the embodiments of the present application can be implemented in a software manner, or can be implemented in a hardware manner. The name of the module does not constitute a limitation on the unit itself in some cases.

[0193] The computer readable storage medium provided by the present application is a computer readable storage medium, which stores computer readable program instructions (i.e. computer programs) for executing the above-mentioned low-orbit satellite network cooperative transmission method, and can solve the technical problem that in the scene of mobile phone direct connection to low-orbit satellites, the downlink cannot stably realize high-speed and large-bandwidth transmission. Compared with the prior art, the computer readable storage medium provided by the present application has the same beneficial effects as the low-orbit satellite network cooperative transmission method provided by the above-mentioned embodiments, and will not be described here.

[0194] The application further provides a computer program product comprising a computer program which, when executed by a processor, implements the steps of the cooperative transmission method of the low-orbit satellite network as described above.

[0195] The computer program product provided by the application can solve the technical problem that the downlink cannot stably realize high-rate and large-bandwidth transmission in the scenario of mobile phone direct connection to a low-orbit satellite. Compared with the prior art, the beneficial effects of the computer program product provided by the application are the same as those of the cooperative transmission method of the low-orbit satellite network provided by the above-described embodiments, and are not described herein.

[0196] The above only describes some embodiments of the application, and does not limit the patent scope of the application. Any equivalent structural transformation made by using the content of the specification and drawings, or direct / indirect application in other related technical fields under the technical concept of the application is included in the patent protection scope of the application.

Claims

1. A method for cooperative transmission of a low earth orbit satellite network, characterized in that, The method comprises: Upon receiving a multi-satellite cooperative transmission request sent by a mobile terminal, determining a cooperative auxiliary satellite according to positioning information of the mobile terminal and ephemeris information of a low-orbit satellite network; Starting a cooperative session with the cooperative auxiliary satellite according to mobile terminal information of the mobile terminal; Upon receiving a service data packet, switching a current waveform modulation mode from orthogonal frequency division multiplexing to a target modulation mode, and converting the service data packet into a target service waveform according to the target modulation mode, wherein the target modulation mode comprises orthogonal time-frequency-space modulation or affine frequency division multiplexing; Performing compensation processing on the target service waveform to obtain a time-frequency compensation signal and a plurality of waveform signals; Sending the plurality of waveform signals to the mobile terminal, and sending the time-frequency compensation signal to the cooperative auxiliary satellite according to the cooperative session, so that the mobile terminal obtains service data from the plurality of waveform signals and the time-frequency compensation signal, and completes cooperative transmission of the low-orbit satellite network, wherein the service data is obtained by the mobile terminal by analyzing the plurality of waveform signals and the time-frequency compensation signal, and the cooperative auxiliary satellite forwards the time-frequency compensation signal to the mobile terminal according to the cooperative session; The step of, upon receiving a service data packet, switching a current waveform modulation mode from orthogonal frequency division multiplexing to a target modulation mode, and converting the service data packet into a target service waveform according to the target modulation mode, comprises: Upon receiving a service data packet, sequentially performing packet data aggregation, packet data compression, radio link control, and media access processing on the service data packet to obtain a service bit stream; Inputting the service bit stream into a physical downlink shared channel of a physical layer to obtain an initial service waveform; Switching a current waveform modulation mode from orthogonal frequency division multiplexing to a target modulation mode; Converting the initial service waveform into a target service waveform according to the target modulation mode; The step of performing compensation processing on the target service waveform to obtain a time-frequency compensation signal and a plurality of waveform signals, comprises: Performing time-frequency pre-compensation processing on the target service waveform to obtain a time-frequency compensation signal; Determining a cooperative satellite cluster according to the cooperative auxiliary satellite, and determining a number of satellites according to the cooperative satellite cluster; Copying the target service waveform into a plurality of signals of the number of satellites; Performing downlink timing advance adjustment and Doppler frequency offset pre-compensation on the plurality of signals to obtain a plurality of waveform signals, wherein a time delay difference of the plurality of waveform signals is controlled within a cyclic prefix; The step of sending the plurality of waveform signals to the mobile terminal, comprises: Obtaining a preset field format, a preset set level, and a current downlink control information format of a current physical downlink control channel; Updating the current downlink control information format according to the preset field format to obtain a target downlink control information format; Updating the current physical downlink control channel according to the preset set level and the target downlink control information format to obtain a target physical downlink control channel; Sending the plurality of waveform signals to the mobile terminal through the target physical downlink control channel.

2. The method of claim 1, wherein, The step of initiating a collaborative session with the auxiliary satellite based on the mobile terminal information includes: The identification information and location information are determined based on the mobile terminal information. The identification information and the positioning information are sent to the cooperative auxiliary satellite so that the cooperative auxiliary satellite aligns the service beam center with the mobile terminal according to the identification information and the positioning information, and feeds back the virtual radio resource control connection established with the mobile terminal. Upon receiving the virtual radio resource control connection, a multi-satellite cooperative transmission permission message is sent to the mobile terminal, so that the mobile terminal responds with a session establishment request message based on the multi-satellite cooperative transmission permission message; The session establishment request message is sent to the core network so that the core network establishes and sends back a session reception message based on the session establishment request message. Upon receiving the session reception message, a collaborative session with the cooperative auxiliary satellite is initiated.

3. The method of claim 1, wherein, The step of determining the cooperating auxiliary satellites based on the mobile terminal's positioning information and the ephemeris information of the low-Earth orbit satellite network upon receiving a multi-satellite cooperative transmission request from the mobile terminal includes: When a multi-satellite collaborative transmission request is received from a mobile terminal, the ephemeris information, preset distance threshold, and preset elevation angle threshold of the low-orbit satellites are obtained. The ephemeris information includes the real-time orbital position, communication payload status, and inter-satellite link bandwidth of each low-orbit satellite. Based on the location information of the mobile terminal and the real-time orbit position, calculate the satellite-to-ground link distance and communication angle between the low-orbit satellite and the mobile terminal; A candidate satellite list is formed by filtering low-Earth orbit satellites whose satellite-to-ground link distance is less than the preset distance threshold, whose communication angle is greater than the preset elevation angle threshold, and whose communication payload has idle resources. Cooperative auxiliary satellites are determined from the candidate satellite list based on the inter-satellite link bandwidth.

4. The method of claim 1, wherein, After the steps of sending the multi-channel waveform signals to the mobile terminal and sending the time-frequency compensation signal to the cooperative auxiliary satellite according to the cooperative session, so that the mobile terminal can obtain service data based on the multi-channel waveform signals and the time-frequency compensation signal to complete the cooperative transmission of the low-Earth orbit satellite network, the method further includes: Upon receiving the service data reception completion signal sent by the mobile terminal, a session release command is sent to the cooperative auxiliary star through the cooperative session, so that the cooperative auxiliary star stops forwarding the time-frequency compensation signal according to the session release command, releases the service beam resources allocated for cooperative transmission, and sends back a release completion signal. Upon receiving the release completion signal, a session resource reclamation request is sent to the core network, so that the core network releases the network resources allocated for cooperative transmission according to the session resource reclamation request and sends back a resource reclamation confirmation message. Upon receiving the resource reclamation confirmation message, a collaborative transmission termination message is sent to the mobile terminal, so that the mobile terminal stops parsing the multi-channel waveform signal and the time-frequency compensation signal according to the collaborative transmission termination message, thereby completing the resource release of collaborative transmission. 5.A low earth orbit satellite network cooperative transmission apparatus, the low earth orbit satellite network cooperative transmission apparatus performing the low earth orbit satellite network cooperative transmission method according to any one of claims 1 to 4, characterized in that, The device includes: The auxiliary satellite determination module is configured to determine a cooperative auxiliary satellite according to the positioning information of the mobile terminal and ephemeris information of the low-orbit satellite network when receiving a multi-satellite cooperative transmission request sent by the mobile terminal. The session opening module is configured to open a cooperative session with the cooperative auxiliary satellite according to the mobile terminal information of the mobile terminal. The waveform conversion module is configured to switch a current waveform modulation mode from orthogonal frequency division multiplexing to orthogonal time frequency space modulation or affine frequency division multiplexing to obtain a target modulation mode when receiving a service data packet, and convert the service data packet into a target service waveform according to the target modulation mode. The signal compensation module is configured to perform compensation processing on the target service waveform to obtain a time-frequency compensation signal and a plurality of waveform signals. The service transmission module is configured to send the plurality of waveform signals to the mobile terminal and send the time-frequency compensation signal to the cooperative auxiliary satellite according to the cooperative session, so that the mobile terminal obtains service data according to the plurality of waveform signals and the time-frequency compensation signal, and completes cooperative transmission of the low-orbit satellite network, wherein the service data is obtained by the mobile terminal by analyzing the plurality of waveform signals and the time-frequency compensation signal, and the cooperative auxiliary satellite forwards the time-frequency compensation signal to the mobile terminal according to the cooperative session. 6.A cooperative transmission device of a low earth orbit satellite network, characterized by, The device comprises a memory, a processor, and a computer program stored on the memory and executable on the processor, and the computer program is configured to implement the steps of the cooperative transmission method of the low-orbit satellite network according to any one of claims 1 to 4.

7. A storage medium, characterized by The storage medium is a computer readable storage medium, and the storage medium stores a computer program, and the computer program is executed by the processor to implement the steps of the cooperative transmission method of the low-orbit satellite network according to any one of claims 1 to 4.

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