Method and apparatus for uplink and downlink synchronization in mobile satellite communication system

Abstract

The embodiment of the present application relates to the mobile communication technical field, and discloses a kind of mobile satellite communication system uplink and downlink synchronization method and device, the method comprises: obtaining the sampling point deviation value of UE and mobile satellite in preset time unit;First UE air interface data frame received is pre-compensated based on sampling point deviation value downlink synchronization, and first UE air interface data frame after downlink synchronization pre-compensation is used to carry out downlink coarse synchronization;Based on downlink coarse synchronization parameter, uplink coarse synchronization is carried out, and after completing uplink coarse synchronization, the second UE air interface data frame to be transmitted is pre-compensated based on sampling point deviation value uplink synchronization.The scheme carries out uplink and downlink synchronization pre-compensation according to sampling point deviation value, so that baseband processing does not have cumulative timing deviation, frame number and time slot number error do not appear, reduce the number of radio link failure, simultaneously make the physical frame length of mobile satellite base station uplink reception multi-user fixed, reduce the interference between uplink reception multi-user.

Description

Technical Field

[0001] This application relates to the field of mobile communication technology, and more specifically, to a method and apparatus for uplink and downlink synchronization in a mobile satellite communication system. Background Technology

[0002] In the upcoming era of 6G (6th Generation Mobile Networks), mobile satellite communication technology will be a key technology for 6G communication. As the main payload of the satellite, the communication payload of the mobile satellite communication system moves at high speed with the satellite. Therefore, the high-speed relative motion between the user terminal equipment and the satellite base station will generate a significant Doppler shift. This significant Doppler shift will cause changes in the frame duration of the communication system, thus creating a series of problems for terminal demodulation.

[0003] As satellite communication payload equipment in a mobile satellite communication system, like terrestrial cellular networks, it requires air interface physical frame synchronization for downlink transmission and uplink reception at the base station. However, the terminal equipment in a mobile satellite communication system differs from that in a terrestrial cellular network. The former needs to cope with the two major characteristics of mobile satellite communication systems: high-speed relative motion and large path delay. This makes the existing uplink and downlink synchronization schemes for terrestrial cellular networks unsuitable for mobile satellite communication. Summary of the Invention

[0004] The purpose of this application is to at least solve one of the aforementioned technical defects. The technical solution provided by the embodiments of this application is as follows:

[0005] In a first aspect, embodiments of this application provide an uplink and downlink synchronization method for a mobile satellite communication system, including:

[0006] Based on the ephemeris parameters of the mobile satellite and the coordinates of the user equipment (UE), the sampling point deviation value between the UE and the mobile satellite within a preset time unit is obtained.

[0007] Based on the sampling point deviation value, downlink synchronization pre-compensation is performed on the received first UE air interface data frame in each corresponding preset time unit, and downlink coarse synchronization is performed based on the first UE air interface data frame after downlink synchronization pre-compensation.

[0008] Uplink coarse synchronization is performed based on downlink coarse synchronization parameters and the real-time distance between the UE and the mobile satellite. After the uplink coarse synchronization is completed, uplink synchronization pre-compensation is performed on the second UE air interface data frame to be transmitted in each preset time unit based on the sampling point deviation value. Uplink synchronization is then performed based on the second UE air interface data frame after uplink synchronization pre-compensation.

[0009] In one optional embodiment of this application, downlink synchronization pre-compensation is performed on the received first air interface data frame at each corresponding preset time unit based on the sampling point deviation value, and downlink coarse synchronization is performed based on the first UE air interface data frame after downlink synchronization pre-compensation, including:

[0010] Based on the sampling point deviation value and the number of preset sampling points corresponding to each preset time unit of the base station air interface data frame transmitted by the mobile satellite, the synchronization header corresponding to each preset time unit of the first UE air interface data frame is determined, and the first UE air interface data frame after downlink synchronization pre-compensation is obtained.

[0011] For each preset time unit, according to the corresponding synchronization header position, the sampling point corresponding to the preset time unit is taken and processed by baseband to obtain the synchronization signal block SSB signal;

[0012] Downlink coarse synchronization is performed based on the downlink synchronization parameters in the SSB signal.

[0013] In one optional embodiment of this application, the synchronization header of the first UE air interface data frame in each preset time unit is determined based on the sampling point deviation value and the preset number of sampling points corresponding to the base station air interface data frame transmitted by the mobile satellite in each preset time unit, including:

[0014] As the distance between the UE and the mobile satellite decreases, the number of sampling points corresponding to the sampling point deviation value of the cyclic prefix CP of the first orthogonal frequency division multiplexing (OFDM) symbol starting from the synchronization header position in each preset time unit is reduced by the number of sampling points corresponding to the sampling point deviation value, while the number of sampling points corresponding to other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0015] As the distance between the UE and the mobile satellite increases, the number of sampling points corresponding to the sampling point deviation value is increased in the last OFDM symbol starting from the synchronization header position in each preset time unit, while the number of sampling points for other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0016] In one optional embodiment of this application, the downlink synchronization parameters include the local frame number, local timeslot number, downlink air interface frame number, downlink air interface timeslot number, and sampling point index value corresponding to the downlink air interface timeslot at the synchronization frame header position;

[0017] Downlink coarse synchronization based on downlink synchronization parameters in the SSB signal includes:

[0018] The downlink air interface frame number is used as the local frame number, the downlink air interface timeslot number is used as the local timeslot number, and the next timeslot synchronization is performed based on the sampling point index value corresponding to the downlink air interface timeslot.

[0019] In one optional embodiment of this application, uplink coarse synchronization is performed based on downlink coarse synchronization parameters and the real-time distance between the UE and the mobile satellite, including:

[0020] Based on the real-time distance between the mobile satellite and the UE, the first delay corresponding to the distance is obtained, and the second and third delays corresponding to the downlink coarse synchronization are obtained based on the downlink coarse synchronization parameters;

[0021] Based on the first delay, the second delay, and the third delay, obtain the uplink air interface frame number, the uplink air interface timeslot frame number, and the sampling point index value corresponding to the uplink air interface timeslot at the synchronization frame header position.

[0022] The uplink air interface frame number is used as the local frame number at the synchronization frame header position, the uplink air interface timeslot number is used as the local timeslot number at the synchronization frame header position, and the next timeslot synchronization is performed based on the sampling point index value corresponding to the uplink air interface timeslot.

[0023] In one optional embodiment of this application, uplink synchronization pre-compensation is performed on the second UE air interface data frame to be transmitted based on the sampling point deviation value in each corresponding preset time unit, and uplink synchronization is performed based on the second UE air interface data frame after uplink synchronization pre-compensation, including:

[0024] Based on the sampling point deviation value and the number of preset sampling points corresponding to the base station air interface data frames received by the mobile satellite in each preset time unit, the synchronization header corresponding to each preset time unit of the second UE air interface data frame is determined, and the second UE air interface data frame after uplink synchronization pre-compensation is obtained.

[0025] Based on the uplink frame number, uplink timeslot number, and synchronization header corresponding to each preset time unit maintained after uplink coarse synchronization, the uplink synchronization signal is sent to the mobile satellite, and the uplink residual timing deviation control word fed back by the mobile satellite is received. Uplink synchronization is then completed based on the uplink residual timing deviation control word.

[0026] In one optional embodiment of this application, the synchronization header corresponding to each preset time unit of the second UE air interface data frame is determined based on the sampling point deviation value and the preset number of sampling points corresponding to each preset time unit of the base station air interface data frame received by the mobile satellite, including:

[0027] As the distance between the UE and the mobile satellite decreases, the last OFDM symbol starting from the synchronization header position in each preset time unit is increased by the number of sampling points corresponding to the sampling point deviation value, and the increased sampling points are set to zero. The number of sampling points for other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0028] As the distance between the UE and the mobile satellite increases, the number of sampling points corresponding to the sampling point deviation value of the last OFDM symbol starting from the synchronization header position in each preset time unit is reduced, while the number of sampling points corresponding to other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0029] In one optional embodiment of this application, the method further includes:

[0030] Phase compensation is performed on each OFDM symbol in each preset time unit of the first UE air interface data frame after downlink synchronization pre-compensation.

[0031] Phase compensation is performed on each OFDM symbol in each preset time unit of the second UE air interface data frame after uplink synchronization pre-compensation.

[0032] In one optional embodiment of this application, phase compensation is performed on each OFDM symbol in each preset time unit, including:

[0033] Based on the uplink synchronization pre-compensation value or downlink synchronization pre-compensation value within each preset time unit, obtain the average delay value corresponding to each OFDM symbol within each preset time unit.

[0034] Based on the average time delay value, the phase value that each OFDM symbol needs to compensate for in each subcarrier in the frequency domain is obtained, and phase compensation is performed on the OFDM symbol in the frequency domain based on the phase value.

[0035] In one optional embodiment of this application, the method further includes:

[0036] Doppler pre-compensation is performed on each preset time unit of the first UE air interface data frame after downlink synchronization pre-compensation;

[0037] Doppler pre-compensation is performed on each preset time unit of the second UE air interface data frame after uplink synchronization pre-compensation.

[0038] Secondly, embodiments of this application provide an uplink / downlink synchronization device for a mobile satellite communication system, comprising:

[0039] The sampling point deviation value acquisition module is used to acquire the sampling point deviation value between the UE and the mobile satellite within a preset time unit based on the ephemeris parameters of the mobile satellite and the coordinates of the user equipment (UE).

[0040] The downlink coarse synchronization module is used to perform downlink synchronization pre-compensation on the received first UE air interface data frame in each corresponding preset time unit based on the sampling point deviation value, and to perform downlink synchronization based on the first UE air interface data frame after downlink synchronization pre-compensation.

[0041] The uplink synchronization module is used to perform uplink coarse synchronization based on downlink coarse synchronization parameters and the real-time distance between the UE and the mobile satellite. After completing the uplink coarse synchronization, it performs uplink synchronization pre-compensation on the second UE air interface data frame to be transmitted in each corresponding preset time unit based on the sampling point deviation value, and performs uplink synchronization based on the second UE air interface data frame after uplink synchronization pre-compensation.

[0042] In one optional embodiment of this application, the downlink coarse synchronization module is specifically used for:

[0043] Based on the sampling point deviation value and the number of preset sampling points corresponding to each preset time unit of the base station air interface data frame transmitted by the mobile satellite, the synchronization header corresponding to each preset time unit of the first UE air interface data frame is determined, and the first UE air interface data frame after downlink synchronization pre-compensation is obtained.

[0044] For each preset time unit, according to the corresponding synchronization header position, the sampling point corresponding to the preset time unit is taken and processed by baseband to obtain the synchronization signal block SSB signal;

[0045] Downlink coarse synchronization is performed based on the downlink synchronization parameters in the SSB signal.

[0046] In an optional embodiment of this application, the downlink coarse synchronization module is further configured to:

[0047] As the distance between the UE and the mobile satellite decreases, the number of sampling points corresponding to the sampling point deviation value of the cyclic prefix CP of the first orthogonal frequency division multiplexing (OFDM) symbol starting from the synchronization header position in each preset time unit is reduced by the number of sampling points corresponding to the sampling point deviation value, while the number of sampling points corresponding to other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0048] As the distance between the UE and the mobile satellite increases, the number of sampling points corresponding to the sampling point deviation value is increased in the last OFDM symbol starting from the synchronization header position in each preset time unit, while the number of sampling points for other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0049] In one optional embodiment of this application, the downlink synchronization parameters include the local frame number, local timeslot number, downlink air interface frame number, downlink air interface timeslot number, and sampling point index value corresponding to the downlink air interface timeslot at the synchronization frame header position;

[0050] The downlink coarse synchronization module is further used for:

[0051] The downlink air interface frame number is used as the local frame number, the downlink air interface timeslot number is used as the local timeslot number, and the next timeslot synchronization is performed based on the sampling point index value corresponding to the downlink air interface timeslot.

[0052] In one optional embodiment of this application, the uplink synchronization module is specifically used for:

[0053] Based on the real-time distance between the mobile satellite and the UE, the first delay corresponding to the distance is obtained, and the second and third delays corresponding to the downlink coarse synchronization are obtained based on the downlink coarse synchronization parameters;

[0054] Based on the first delay, the second delay, and the third delay, obtain the uplink air interface frame number, the uplink air interface timeslot frame number, and the sampling point index value corresponding to the uplink air interface timeslot at the synchronization frame header position.

[0055] The uplink air interface frame number is used as the local frame number at the synchronization frame header position, the uplink air interface timeslot number is used as the local timeslot number at the synchronization frame header position, and the next timeslot synchronization is performed based on the sampling point index value corresponding to the uplink air interface timeslot.

[0056] In one optional embodiment of this application, the uplink synchronization module is specifically used for:

[0057] Based on the sampling point deviation value and the number of preset sampling points corresponding to the base station air interface data frames received by the mobile satellite in each preset time unit, the synchronization header corresponding to each preset time unit of the second UE air interface data frame is determined, and the second UE air interface data frame after uplink synchronization pre-compensation is obtained.

[0058] Based on the uplink frame number, uplink timeslot number, and synchronization header corresponding to each preset time unit maintained after uplink coarse synchronization, the uplink synchronization signal is sent to the mobile satellite, and the uplink residual timing deviation control word fed back by the mobile satellite is received. Uplink synchronization is then completed based on the uplink residual timing deviation control word.

[0059] In one optional embodiment of this application, the uplink synchronization module is further configured to:

[0060] As the distance between the UE and the mobile satellite decreases, the last OFDM symbol starting from the synchronization header position in each preset time unit is increased by the number of sampling points corresponding to the sampling point deviation value, and the increased sampling points are set to zero. The number of sampling points for other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0061] As the distance between the UE and the mobile satellite increases, the number of sampling points corresponding to the sampling point deviation value of the last OFDM symbol starting from the synchronization header position in each preset time unit is reduced, while the number of sampling points corresponding to other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0062] In one optional embodiment of this application, the device further includes a phase compensation module, used for:

[0063] Phase compensation is performed on each OFDM symbol in each preset time unit of the first UE air interface data frame after downlink synchronization pre-compensation.

[0064] Phase compensation is performed on each OFDM symbol in each preset time unit of the first UE air interface data frame after downlink synchronization pre-compensation.

[0065] In one optional embodiment of this application, the phase compensation module is specifically used for:

[0066] Based on the uplink synchronization pre-compensation value or downlink synchronization pre-compensation value within each preset time unit, obtain the average delay value corresponding to each OFDM symbol within each preset time unit.

[0067] Based on the average time delay value, the phase value that each OFDM symbol needs to compensate for in each subcarrier in the frequency domain is obtained, and phase compensation is performed on the OFDM symbol in the frequency domain based on the phase value.

[0068] In one optional embodiment of this application, the device further includes a Doppler pre-compensation module, used for:

[0069] Doppler pre-compensation is performed on each preset time unit of the first UE air interface data frame after downlink synchronization pre-compensation;

[0070] Doppler pre-compensation is performed on each preset time unit of the second UE air interface data frame after uplink synchronization pre-compensation.

[0071] Thirdly, embodiments of this application provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the uplink and downlink synchronization method of the mobile satellite communication system shown in the first aspect of this application.

[0072] Fourthly, embodiments of this application provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements one or more methods as described in embodiments of this application.

[0073] The beneficial effects of the technical solution provided in this application are:

[0074] Before downlink coarse synchronization and after uplink coarse synchronization, downlink synchronization pre-compensation and uplink synchronization pre-compensation are performed according to the sampling point deviation value corresponding to the preset time unit, respectively. This ensures that the satellite terminal will not have accumulated timing deviation in baseband processing when the local baseband sampling rate remains unchanged, and will not have errors in frame number and time slot number, reducing the number of wireless link failures. At the same time, it ensures that the uplink reception duration of physical frames from multiple users by the mobile satellite base station remains constant, reducing interference between uplink reception from multiple users. This scheme is well applicable to uplink and downlink synchronization in mobile satellite communication systems. Attached Figure Description

[0075] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments of this application will be briefly introduced below.

[0076] Figure 1 A flowchart illustrating an uplink and downlink synchronization method for a mobile satellite communication system provided in this application embodiment;

[0077] Figure 2 This is a schematic diagram illustrating the compression of downlink frame duration in an example of an embodiment of this application;

[0078] Figure 3 This is a schematic diagram illustrating the extension of the downlink frame duration in an example of an embodiment of this application;

[0079] Figure 4 An exemplary flowchart illustrating the uplink and downlink synchronization scheme of a mobile satellite communication system provided in this application embodiment;

[0080] Figure 5 This is a schematic diagram illustrating downlink synchronization pre-compensation for each preset time unit of the first UE air interface data frame in an example of an embodiment of this application, where the mobile satellite and the UE are getting closer and closer.

[0081] Figure 6 This is a schematic diagram illustrating downlink synchronization pre-compensation for each preset time unit of the first UE air interface data frame in an example of an embodiment of this application, where the mobile satellite and the UE are getting farther and farther apart.

[0082] Figure 7 This is a schematic diagram of an example of a coarse downlink synchronization process according to an embodiment of this application;

[0083] Figure 8 This is a schematic diagram of an example of the uplink coarse synchronization process in an embodiment of this application;

[0084] Figure 9 This is a schematic diagram illustrating the principle of uplink synchronization pre-compensation for the air interface data frame of the second UE when the mobile satellite and the UE are getting closer and closer, as an example of an embodiment of this application.

[0085] Figure 10 This is a schematic diagram illustrating the principle of uplink synchronization pre-compensation for the air interface data frame of the second UE when the mobile satellite and the UE are getting farther and farther apart, as an example of an embodiment of this application.

[0086] Figure 11 This is a schematic diagram illustrating uplink synchronization pre-compensation for each preset time unit of the second UE air interface data frame in an example of an embodiment of this application, where the mobile satellite and the UE are getting closer and closer.

[0087] Figure 12 This is a schematic diagram illustrating uplink synchronization pre-compensation for each preset time unit of the second UE air interface data frame in an example of an embodiment of this application, where the mobile satellite and the UE are getting farther and farther apart.

[0088] Figure 13 A structural block diagram of an uplink / downlink synchronization device for a mobile satellite communication system provided in this application embodiment;

[0089] Figure 14 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0090] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0091] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the word “comprising” as used in the specification of this application means the presence of features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, the term “connected” or “coupled” as used herein can include wireless connections or wireless coupling.

[0092] In the various embodiments of this application, it should be understood that the sequence numbers of the following processes do not imply a specific order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application. The terms "first," "second," etc., used in the specification and claims are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, including all or any unit and all combinations of one or more associated listed items, and the character " / " generally indicates that the preceding and following related objects are in an "or" relationship.

[0093] In the embodiments provided in this application, it should be understood that "B corresponding to A" means that B is associated with A, and B can be determined based on A. However, it should also be understood that determining B based on A does not mean determining B solely based on A; B can also be determined based on A and / or other information.

[0094] Furthermore, those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0095] The solutions provided in this application can be executed by any electronic device, such as a terminal device or a server. The server can be an independent physical server, a server cluster or distributed system composed of multiple physical servers, or a cloud server providing cloud computing services. The terminal can be a smartphone, tablet, laptop, desktop computer, smart speaker, smartwatch, etc., but is not limited to these. The terminal and server can be directly or indirectly connected via wired or wireless communication, which is not limited herein. The uplink and downlink synchronization method and apparatus for mobile satellite communication systems provided in this application aim to solve at least one of the technical problems existing in the prior art.

[0096] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0097] Figure 1 This application provides a flowchart illustrating an uplink and downlink synchronization method for a mobile satellite communication system. The executing entity of this method can be the corresponding user equipment (UE) in the mobile satellite communication system, such as... Figure 1 As shown, it includes:

[0098] Step S101: Based on the ephemeris parameters of the mobile satellite and the coordinates of the user equipment (UE), obtain the sampling point deviation value between the UE and the mobile satellite within a preset time unit.

[0099] The preset time unit is the duration corresponding to one or more time slots.

[0100] Specifically, due to the high-speed relative motion between the mobile satellite (which can be understood as the base station in a mobile satellite communication system) and the UE, the path delay between the mobile satellite and the UE changes rapidly over time. If the UE's baseband sampling rate remains constant, the physical frame duration of the baseband signal received by the UE will differ from the duration received by the base station (i.e., the mobile satellite). As the distance between the mobile satellite and the UE decreases, the duration of each physical frame of the first UE air interface data frame received by the UE is less than the frame duration (10ms) on the base station side. Figure 2 As shown, when the distance between the mobile satellite and the UE increases, the duration of each physical frame of the first UE air interface data frame received by the UE is longer than the frame duration (10ms) on the base station side, as... Figure 3 As shown. Because the UE baseband sampling rate remains constant, while the frame duration of the air interface may be compressed or extended, the UE baseband processing must pre-compensate for the changes in the air interface frame duration. Otherwise, downlink synchronization will be repeatedly lost over time, affecting the UE's performance indicators.

[0101] Similarly, during uplink synchronization, it is also necessary to pre-compensate for changes in the air interface frame duration to offset the compression or expansion of the uplink air interface signal caused by changes in the relative distance between the mobile satellite and the UE, so that the frame duration of the air interface signal reaching the mobile satellite base station receiver remains unchanged.

[0102] Therefore, before performing pre-compensation, it is necessary to obtain the sampling point deviation value between the UE and the mobile satellite within a preset time unit based on the ephemeris parameters of the mobile satellite and the coordinates of the user equipment (UE).

[0103] Step S102: Based on the sampling point deviation value, downlink synchronization pre-compensation is performed on the received first UE air interface data frame in each corresponding preset time unit, and downlink coarse synchronization is performed based on the first UE air interface data frame after downlink synchronization pre-compensation.

[0104] Specifically, before performing downlink coarse synchronization, the UE needs to perform downlink synchronization pre-compensation on the received first UE air interface data frame. This pre-compensation, based on the sampling point deviation value, is applied to the received first UE air interface data frame at each corresponding preset time unit. This can be understood as re-determining the synchronization header and sampling point division for each preset time unit based on the sampling point deviation value. After obtaining the first UE air interface data frame with downlink synchronization pre-compensation, downlink coarse synchronization is performed based on this pre-compensated first UE air interface data frame.

[0105] Step S103: Perform uplink coarse synchronization based on downlink coarse synchronization parameters and the real-time distance between the UE and the mobile satellite. After completing uplink coarse synchronization, perform uplink synchronization pre-compensation on the second UE air interface data frame to be transmitted in each corresponding preset time unit based on the sampling point deviation value, and perform uplink synchronization based on the second UE air interface data frame after uplink synchronization pre-compensation.

[0106] Specifically, the uplink coarse synchronization process for the UE differs from that of a terrestrial cellular network system. In this embodiment, uplink coarse synchronization requires calculating the real-time distance between the mobile satellite and the UE based on ephemeris parameters, further calculating the path delay, and then compensating for twice the path delay to obtain the uplink frame number and timeslot number. After the UE completes uplink coarse synchronization, uplink synchronization pre-compensation is required for the second UE air interface data frame to be transmitted. Based on the sampling point deviation value, uplink synchronization pre-compensation is performed on the second UE air interface data frame to be transmitted in each corresponding preset time unit. This can be understood as redetermining the synchronization header and sampling point division of each preset time unit based on the sampling point deviation value.

[0107] The solution provided in this application performs downlink synchronization pre-compensation and uplink synchronization pre-compensation based on the sampling point deviation value corresponding to the preset time unit before downlink coarse synchronization and after uplink coarse synchronization. This ensures that the satellite terminal will not have accumulated timing deviation in baseband processing when the local baseband sampling rate remains unchanged, and will not have errors in frame number and time slot number, thereby reducing the number of wireless link failures. At the same time, it ensures that the uplink reception duration of physical frames from multiple users by the mobile satellite base station remains constant, reducing interference between uplink reception from multiple users. This solution is well applicable to uplink and downlink synchronization in mobile satellite communication systems.

[0108] Figure 4 This is an exemplary flowchart illustrating the uplink and downlink synchronization scheme of a mobile satellite communication system provided in this application embodiment, as shown below. Figure 4As shown, the physical layer processing flow of a UE under the OFDM (Orthogonal Frequency Division Multiplexing) system is presented. Compared with the physical layer processing flow of a UE in a terrestrial cellular network, this example includes uplink and downlink synchronization tracking pre-compensation (i.e., uplink synchronization pre-compensation and downlink synchronization pre-compensation), uplink and downlink Doppler pre-compensation, phase compensation 2, and an ephemeris calculation module. Channel parameters obtained from the CPU (Central Processing Unit) and related parameters from the ephemeris calculation module are configured to the FPGA (Field Programmable Gate Array) via an interface. The FPGA completes the frame number and time slot number synchronization in the uplink and downlink coarse synchronization, and completes the frame number and time slot number synchronization in the uplink and downlink synchronization tracking pre-compensation, as well as phase compensation 2 and uplink and downlink Doppler pre-compensation. Phase compensation 1, like phase compensation in a terrestrial cellular network, needs to compensate for the phase difference caused by the inconsistency between the base station and the UE's transmit and receive frequencies. Phase compensation 2 is a newly added processing module for the UE in a mobile satellite communication system. The following will provide a detailed explanation of each process in the above uplink and downlink synchronization process.

[0109] In one optional embodiment of this application, downlink synchronization pre-compensation is performed on the received first air interface data frame at each corresponding preset time unit based on the sampling point deviation value, and downlink coarse synchronization is performed based on the first UE air interface data frame after downlink synchronization pre-compensation, including:

[0110] Based on the sampling point deviation value and the number of preset sampling points corresponding to each preset time unit of the base station air interface data frame transmitted by the mobile satellite, the synchronization header corresponding to each preset time unit of the first UE air interface data frame is determined, and the first UE air interface data frame after downlink synchronization pre-compensation is obtained.

[0111] For each preset time unit, according to the corresponding synchronization header position, the sampling point corresponding to the preset time unit is taken and baseband processed to obtain the block SSB (Synchronization Signal Block) signal;

[0112] Downlink coarse synchronization is performed based on the downlink synchronization parameters in the SSB signal.

[0113] Specifically, before performing downlink coarse synchronization, the UE first performs downlink synchronization pre-compensation on the received first UE air interface data frame. Downlink synchronization pre-compensation essentially redetermines the synchronization header and the number of sampling points within each preset time unit (denoted as ΔT). This redetermination is based on the preset number of sampling points corresponding to each preset time unit in the base station air interface data frame transmitted by the mobile satellite, and the sampling point deviation value corresponding to each preset time unit. After obtaining the first UE air interface data frame after downlink synchronization pre-compensation, baseband processing is performed on the redetermined synchronization header and corresponding sampling points to obtain the SSB signal, and then downlink coarse synchronization is performed based on the SSB signal.

[0114] Specifically, downlink synchronization pre-compensation may include the following steps:

[0115] Step 1: Based on the ephemeris parameters and the coordinates of the UE, calculate the sampling point deviation caused by the relative motion change within a ΔT in real time, thus obtaining the sampling point deviation value within ΔT.

[0116] Step 2: The UE's downlink synchronization tracking pre-compensation module re-determines the synchronization header corresponding to each ΔT based on the sampling point deviation value within ΔT. Each time, according to the given synchronization header position, the sampling point corresponding to ΔT is taken for baseband processing.

[0117] Step 3: The UE's downlink synchronization tracking pre-compensation module maintains the downlink frame number and time slot number in real time based on the synchronization header of each ΔT to ensure the accuracy of the frame number and time slot number of the baseband processing data.

[0118] Further, in an optional embodiment of this application, the synchronization header of the first UE air interface data frame in each preset time unit is determined based on the sampling point deviation value and the preset number of sampling points corresponding to each preset time unit of the base station air interface data frame transmitted by the mobile satellite, including:

[0119] As the distance between the UE and the mobile satellite decreases, the number of sampling points corresponding to the sampling point deviation value of the CP (Cyclic Prefix) of the first OFDM symbol starting from the synchronization header position in each preset time unit is reduced by the number of sampling points corresponding to the sampling point deviation value, while the number of sampling points of other OFDM symbols and the CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0120] As the distance between the UE and the mobile satellite increases, the number of sampling points corresponding to the sampling point deviation value is increased in the last OFDM symbol starting from the synchronization header position in each preset time unit, while the number of sampling points for other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0121] Specifically, when performing downlink synchronization pre-compensation, it can be divided into the following two scenarios:

[0122] Firstly, the UE's baseband processing module takes the sampling points corresponding to ΔT according to the synchronization header position for baseband processing. In scenarios where the mobile satellite and the UE are getting closer (i.e., the distance between the UE and the mobile satellite decreases), the number of time-domain data sampling points taken after ephemeris information synchronization is less than the theoretical number of time-domain data sampling points. At this time, according to the frame structure characteristics of the OFDM mobile satellite communication system, each OFDM symbol is processed in the baseband, and the time-domain data of each OFDM symbol is obtained through CP removal processing. As follows... Figure 5 As shown, the CP of the first symbol within ΔT is missing k points, while the CPs of the other OFDM symbols are of normal length.

[0123] Secondly, the UE's baseband processing module takes the sampling points corresponding to ΔT according to the synchronization header position for baseband processing. In scenarios where the mobile satellite and the UE are getting farther and farther apart (i.e., the distance between the UE and the mobile satellite increases), the number of time-domain data sampling points taken after ephemeris information synchronization is more than the theoretical number of time-domain data sampling points. At this time, according to the frame structure characteristics of the OFDM mobile satellite communication system, each OFDM symbol is processed in the baseband. The time-domain data of each OFDM symbol is obtained by removing the CP. The CP and data length of each OFDM symbol are fixed, and the extra k sampling points are discarded. As follows. Figure 6 As shown, the k sampling points following the last OFDM symbol within ΔT will be discarded.

[0124] After completing the downlink synchronization pre-compensation, the first UE air interface data frame after downlink synchronization pre-compensation is obtained, and the corresponding SSB signal is obtained based on this first UE air interface data frame after downlink synchronization pre-compensation. Downlink coarse synchronization of the UE in the mobile satellite communication system utilizes the SSB signal for downlink frame number synchronization. After the baseband completes SSB acquisition, it needs to report downlink synchronization parameters to the front-end FPGA. After receiving the synchronization parameters, the FPGA synchronizes the downlink frame number.

[0125] Before downlink coarse synchronization, the UE of the mobile satellite communication system does not know the start of the frame. The UE's frame synchronization module first randomly assumes a frame header position for frame synchronization. After frame synchronization, the downlink synchronization tracking value calculated according to the ephemeris position is used to adjust the synchronization in real time to complete frame synchronization and time slot synchronization. The UE performs Doppler pre-compensation and finally performs front-end filtering and downsampling processing on the SSB signal. The SSB low sampling rate time domain data is output to the SSB acquisition module, and the local frame number of the corresponding time domain data is output.

[0126] In one optional embodiment of this application, the downlink synchronization parameters include the local frame number, local timeslot number, downlink air interface frame number, downlink air interface timeslot number, and sampling point index value corresponding to the downlink air interface timeslot at the synchronization frame header position;

[0127] Downlink coarse synchronization based on downlink synchronization parameters in the SSB signal includes:

[0128] The downlink air interface frame number is used as the local frame number, the downlink air interface timeslot number is used as the local timeslot number, and the next timeslot synchronization is performed based on the sampling point index value corresponding to the downlink air interface timeslot.

[0129] Specifically, such as Figure 7 As shown, the UE's SSB capture module receives the downsampled SSB time domain data at time T0. After completing the blind detection of the SSB at time T1, it calculates the synchronization parameters at time T2 based on the SSB capture results at time T1 and reports the synchronization parameters to the FPGA. At time T2, which is the first sampling point of frame N+6, the FPGA updates the frame number and time slot number and re-maintains the downlink frame number synchronization.

[0130] Specifically, the synchronization parameters at time T2 include the local frame number (local_sfn), local timeslot number (local_slot), downlink air interface frame number (dl_air_sfn), downlink air interface timeslot number (dl_air_slot), and the sampling point index value (dl_sym_offset) corresponding to the downlink air interface timeslot at time T2. At time T2, the FPGA needs to re-synchronize the frame number, timeslot number, and timeslot header. The FPGA replaces the local frame number (local_sfn) with the downlink air interface frame number (dl_air_sfn), replaces local timeslot number (local_slot) 0 with the air interface timeslot number (dl_air_slot), and performs new timeslot synchronization based on the sampling point index value (dl_sym_offset).

[0131] In one optional embodiment of this application, uplink coarse synchronization is performed based on downlink coarse synchronization parameters and the real-time distance between the UE and the mobile satellite, including:

[0132] Based on the real-time distance between the mobile satellite and the UE, the first delay corresponding to the distance is obtained, and the second and third delays corresponding to the downlink coarse synchronization are obtained based on the downlink coarse synchronization parameters;

[0133] Based on the first delay, the second delay, and the third delay, obtain the uplink air interface frame number, the uplink air interface timeslot frame number, and the sampling point index value corresponding to the uplink air interface timeslot at the synchronization frame header position.

[0134] The uplink air interface frame number is used as the local frame number at the synchronization frame header position, the uplink air interface timeslot number is used as the local timeslot number at the synchronization frame header position, and the next timeslot synchronization is performed based on the sampling point index value corresponding to the uplink air interface timeslot.

[0135] Specifically, before performing uplink pre-compensation, the UE needs to perform uplink coarse synchronization. Furthermore, the uplink coarse synchronization of the UE in a mobile satellite communication system differs from that in a terrestrial cellular network system. In a mobile satellite communication system, the uplink coarse synchronization requires calculating the distance between the mobile satellite and the UE in real time based on ephemeris parameters, further calculating the path delay (DT0, the first delay), and then compensating for twice the path delay to obtain the uplink frame number and timeslot number.

[0136] Specifically, the uplink coarse synchronization process is based on Figure 8 Taking the following scenario as an example, time T2 is the time when the FPGA performs its initial local maintenance of the downlink frame header, which is also the time when the downlink coarse synchronization takes effect, and it is also the time when the uplink coarse synchronization takes effect. The UE calculates DT1 (i.e., the second delay) and DT2 (the third delay) based on twice the path delay 2*DT0, and based on the downlink air interface frame number (dl_air_sfn), the downlink air interface slot number (dl_air_slot), and the sampling point index value (dl_sym_offset) of the downlink air interface slot at time T2. Finally, based on 2*DT0+DT1+DT2, the uplink air interface frame number (ul_air_sfn), the uplink air interface slot number (ul_air_slot), and the sampling point index value (ul_sym_offset) of the uplink air interface slot at time T2 are calculated.

[0137] At time T2, the FPGA simultaneously applies the coarse synchronization parameters for both downlink and uplink. For uplink at time T2, the uplink air interface frame number (ul_air_sfn) replaces the initially maintained uplink frame number (i.e., the local frame number), and the uplink air interface slot number (ul_air_slot) replaces the initially maintained uplink slot number (i.e., the local slot number) 0. Based on the sampling point index value (ul_sym_offset) corresponding to the uplink air interface slot number (ul_air_slot), the slot header of the next slot is synchronized.

[0138] After uplink coarse synchronization, the uplink synchronization signal is transmitted according to the maintained uplink frame number and timeslot number (uplink synchronization pre-compensation needs to be performed before transmission, which will be explained in detail later). The base station feeds back the residual timing deviation control word of the uplink synchronization signal transmission, and then performs more precise uplink synchronization according to the uplink timing control word.

[0139] In one optional embodiment of this application, uplink synchronization pre-compensation is performed on the second UE air interface data frame to be transmitted based on the sampling point deviation value in each corresponding preset time unit, and uplink synchronization is performed based on the second UE air interface data frame after uplink synchronization pre-compensation, including:

[0140] Based on the sampling point deviation value and the number of preset sampling points corresponding to the base station air interface data frames received by the mobile satellite in each preset time unit, the synchronization header corresponding to each preset time unit of the second UE air interface data frame is determined, and the second UE air interface data frame after uplink synchronization pre-compensation is obtained.

[0141] Based on the uplink frame number, uplink timeslot number, and synchronization header corresponding to each preset time unit maintained after uplink coarse synchronization, the uplink synchronization signal is sent to the mobile satellite, and the uplink residual timing deviation control word fed back by the mobile satellite is received. Uplink synchronization is then completed based on the uplink residual timing deviation control word.

[0142] Specifically, after completing uplink coarse synchronization, more precise uplink synchronization can be achieved by transmitting synchronization signals. The uplink of the UE in the mobile satellite communication system also needs to calculate the uplink synchronization adjustment value in real time based on the ephemeris, according to changes in the distance between the satellite and the UE, and perform uplink synchronization tracking pre-compensation. Through uplink synchronization tracking pre-compensation, the compression or expansion of the uplink frame duration introduced by changes in the relative distance between the satellite and the UE is offset, ensuring that the frame duration of the uplink signal reaching the satellite base station receiver remains unchanged.

[0143] In principle, uplink synchronization tracking pre-compensation is the opposite of downlink synchronization tracking pre-compensation. For example... Figure 9 As shown, when the distance between the mobile satellite and the UE is getting closer, the uplink synchronization tracking pre-compensation needs to extend the transmitted air interface frame number to offset the air interface frame number compression introduced during the uplink air interface transmission process; when the distance between the mobile satellite and the UE is getting farther, such as Figure 10 As shown, uplink synchronization tracking pre-compensation requires compressing the transmitted air interface frame number to offset the air interface frame number expansion introduced during the uplink air interface transmission process.

[0144] Specifically, uplink synchronization pre-compensation can include the following steps:

[0145] Step 1: Based on the ephemeris parameters and the UE's coordinates, calculate the sampling point deviation caused by relative motion changes within a certain ΔT in real time, thus obtaining the sampling point deviation value within ΔT. Here, ΔT is the same as the downlink ΔT value.

[0146] Step 2: The UE's uplink synchronization tracking pre-compensation module re-determines the synchronization header corresponding to each ΔT based on the sampling point deviation value within ΔT, and the baseband processing transmits according to the given synchronization header position each time.

[0147] Step 3: The UE's uplink synchronization tracking pre-compensation module maintains the downlink frame number and time slot number in real time based on the synchronization header of each ΔT to ensure the accuracy of the frame number and time slot number of the baseband processing data.

[0148] Further, in an optional embodiment of this application, the synchronization header corresponding to each preset time unit of the second UE air interface data frame is determined based on the sampling point deviation value and the preset sampling point number corresponding to each preset time unit of the base station air interface data frame received by the mobile satellite, including:

[0149] As the distance between the UE and the mobile satellite decreases, the last OFDM symbol starting from the synchronization header position in each preset time unit is increased by the number of sampling points corresponding to the sampling point deviation value, and the increased sampling points are set to zero. The number of sampling points for other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0150] As the distance between the UE and the mobile satellite increases, the number of sampling points corresponding to the sampling point deviation value of the last OFDM symbol starting from the synchronization header position in each preset time unit is reduced, while the number of sampling points corresponding to other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0151] Specifically, when performing uplink synchronization pre-compensation, similar to downlink synchronization pre-compensation, it can also be divided into the following two scenarios:

[0152] Firstly, the UE's baseband processing module transmits according to the synchronization header position. In scenarios where the mobile satellite and the UE are getting closer (i.e., the distance between the UE and the mobile satellite is decreasing), after uplink synchronization tracking pre-compensation, the number of baseband transmission time-domain data sampling points is more than the theoretical number of time-domain data sampling points. Therefore, according to the frame structure characteristics of OFDM mobile satellite communication systems, zeros are added to the end of the last transmitted OFDM symbol. For example... Figure 11 As shown, the last OFDM symbol in ΔT is padded with 0.

[0153] Secondly, the UE's baseband processing module transmits according to the synchronization header position. In scenarios where the mobile satellite and the UE are moving further apart (i.e., the distance between the UE and the mobile satellite increases), after uplink synchronization tracking pre-compensation, the number of baseband transmission time-domain data sampling points is less than the theoretical number. Therefore, based on the frame structure characteristics of OFDM mobile satellite communication systems, a few fewer sampling points are transmitted in the last OFDM symbol transmission. (See below.) Figure 12 As shown, the last symbol within ΔT has k fewer sampling points.

[0154] In one optional embodiment of this application, the method may further include:

[0155] Phase compensation is performed on each OFDM symbol in each preset time unit of the first UE air interface data frame after downlink synchronization pre-compensation.

[0156] Phase compensation is performed on each OFDM symbol in each preset time unit of the second UE air interface data frame after uplink synchronization pre-compensation.

[0157] Specifically, since both uplink and downlink UEs in a mobile satellite communication system require synchronous tracking pre-compensation, the aforementioned uplink and downlink synchronous tracking pre-compensation schemes involve concentrated data loss or zero-filling operations within a preset time unit ΔT. Because the timing deviation of each symbol differs within ΔT, and the deviation of ΔT is the result of the gradual accumulation of each symbol, concentrated data loss or zero-filling within a unit of time ΔT will introduce different phase differences in each RE (Resource Element) of the frequency domain for each symbol. The later the symbol within ΔT, the larger the introduced frequency domain phase difference. Therefore, phase compensation (i.e., the corresponding phase compensation 2) is required for each symbol within ΔT, that is, phase compensation is performed on each RE of the frequency domain data of each symbol to avoid degradation of the channel's demodulation performance.

[0158] Specifically, in one optional embodiment of this application, the synchronization header corresponding to each preset time unit of the second UE air interface data frame is determined based on the sampling point deviation value and the preset number of sampling points corresponding to each preset time unit of the base station air interface data frame received by the mobile satellite, including:

[0159] For cases where the distance between the UE and the mobile satellite decreases, the last OFDM symbol from the synchronization header position in each preset time unit is increased by the number of sampling points corresponding to the sampling point deviation value, and the increased sampling points are set to zero. The number of sampling points for other OFDM symbols and the CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0160] For cases where the distance between the UE and the mobile satellite increases, the number of sampling points corresponding to the sampling point deviation value of the last OFDM symbol from the synchronization header position in each preset time unit is reduced, while the number of sampling points corresponding to other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0161] Assume there are M symbols within ΔT, each symbol undergoes an FFT of length L, and the timing deviation of ΔT is P sampling points (positive or negative). Then, the formula for the compensation coefficients for the frequency domain data of the Kth symbol (ranging from 1 to M) within ΔT after performing an L-point FFT is:

[0162] exp(-j*pi*K*[0:L-1] / (M*L))

[0163] Where j represents a complex number and pi represents the periodic law of elements, the physical meaning of this formula is that the timing deviation of averaging the P points of the accumulated deviation of ΔT onto the M symbols in a unit time of ΔT is K*P / M. The timing deviation of this symbol K*P / M corresponds to the carrier phase value in the frequency domain, which is in the range of [0:L-1].

[0164] In one optional embodiment of this application, the method may further include:

[0165] Doppler pre-compensation is performed on each preset time unit of the first UE air interface data frame after downlink synchronization pre-compensation;

[0166] Doppler pre-compensation is performed on each preset time unit of the second UE air interface data frame after uplink synchronization pre-compensation.

[0167] Figure 13 This application provides a structural block diagram of an uplink and downlink synchronization device for a mobile satellite communication system, as shown in the embodiments below. Figure 13 As shown, the device 1300 may include: a sampling point deviation value acquisition module 1301, a downlink coarse synchronization module 1302, and an uplink synchronization module 1303. Wherein:

[0168] The sampling point deviation value acquisition module 1301 is used to acquire the sampling point deviation value between the UE and the mobile satellite within a preset time unit based on the ephemeris parameters of the mobile satellite and the coordinates of the user equipment UE.

[0169] The downlink coarse synchronization module 1302 is used to perform downlink synchronization pre-compensation on the received first UE air interface data frame in each corresponding preset time unit based on the sampling point deviation value, and to perform downlink synchronization based on the first UE air interface data frame after downlink synchronization pre-compensation.

[0170] The uplink synchronization module 1303 is used to perform uplink coarse synchronization based on downlink coarse synchronization parameters and the real-time distance between the UE and the mobile satellite. After completing the uplink coarse synchronization, it performs uplink synchronization pre-compensation on the second UE air interface data frame to be transmitted in each corresponding preset time unit based on the sampling point deviation value, and performs uplink synchronization based on the second UE air interface data frame after uplink synchronization pre-compensation.

[0171] In one optional embodiment of this application, the downlink coarse synchronization module is specifically used for:

[0172] Based on the sampling point deviation value and the number of preset sampling points corresponding to each preset time unit of the base station air interface data frame transmitted by the mobile satellite, the synchronization header corresponding to each preset time unit of the first UE air interface data frame is determined, and the first UE air interface data frame after downlink synchronization pre-compensation is obtained.

[0173] For each preset time unit, according to the corresponding synchronization header position, the sampling point corresponding to the preset time unit is taken and processed by baseband to obtain the synchronization signal block SSB signal;

[0174] Downlink coarse synchronization is performed based on the downlink synchronization parameters in the SSB signal.

[0175] In an optional embodiment of this application, the downlink coarse synchronization module is further configured to:

[0176] As the distance between the UE and the mobile satellite decreases, the number of sampling points corresponding to the sampling point deviation value of the cyclic prefix CP of the first orthogonal frequency division multiplexing (OFDM) symbol starting from the synchronization header position in each preset time unit is reduced by the number of sampling points corresponding to the sampling point deviation value, while the number of sampling points corresponding to other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0177] As the distance between the UE and the mobile satellite increases, the number of sampling points corresponding to the sampling point deviation value is increased in the last OFDM symbol starting from the synchronization header position in each preset time unit, while the number of sampling points for other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0178] In one optional embodiment of this application, the downlink synchronization parameters include the local frame number, local timeslot number, downlink air interface frame number, downlink air interface timeslot number, and sampling point index value corresponding to the downlink air interface timeslot at the synchronization frame header position;

[0179] The downlink coarse synchronization module is further used for:

[0180] The downlink air interface frame number is used as the local frame number, the downlink air interface timeslot number is used as the local timeslot number, and the next timeslot synchronization is performed based on the sampling point index value corresponding to the downlink air interface timeslot.

[0181] In one optional embodiment of this application, the uplink synchronization module is specifically used for:

[0182] Based on the real-time distance between the mobile satellite and the UE, the first delay corresponding to the distance is obtained, and the second and third delays corresponding to the downlink coarse synchronization are obtained based on the downlink coarse synchronization parameters;

[0183] Based on the first delay, the second delay, and the third delay, obtain the uplink air interface frame number, the uplink air interface timeslot frame number, and the sampling point index value corresponding to the uplink air interface timeslot at the synchronization frame header position.

[0184] The uplink air interface frame number is used as the local frame number at the synchronization frame header position, the uplink air interface timeslot number is used as the local timeslot number at the synchronization frame header position, and the next timeslot synchronization is performed based on the sampling point index value corresponding to the uplink air interface timeslot.

[0185] In one optional embodiment of this application, the uplink synchronization module is specifically used for:

[0186] Based on the sampling point deviation value and the number of preset sampling points corresponding to the base station air interface data frames received by the mobile satellite in each preset time unit, the synchronization header corresponding to each preset time unit of the second UE air interface data frame is determined, and the second UE air interface data frame after uplink synchronization pre-compensation is obtained.

[0187] Based on the uplink frame number, uplink timeslot number, and synchronization header corresponding to each preset time unit maintained after uplink coarse synchronization, the uplink synchronization signal is sent to the mobile satellite, and the uplink residual timing deviation control word fed back by the mobile satellite is received. Uplink synchronization is then completed based on the uplink residual timing deviation control word.

[0188] In one optional embodiment of this application, the uplink synchronization module is further configured to:

[0189] As the distance between the UE and the mobile satellite decreases, the last OFDM symbol starting from the synchronization header position in each preset time unit is increased by the number of sampling points corresponding to the sampling point deviation value, and the increased sampling points are set to zero. The number of sampling points for other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0190] As the distance between the UE and the mobile satellite increases, the number of sampling points corresponding to the sampling point deviation value of the last OFDM symbol starting from the synchronization header position in each preset time unit is reduced, while the number of sampling points corresponding to other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit.

[0191] In one optional embodiment of this application, the device further includes a phase compensation module, used for:

[0192] Phase compensation is performed on each OFDM symbol in each preset time unit of the first UE air interface data frame after downlink synchronization pre-compensation.

[0193] Phase compensation is performed on each OFDM symbol in each preset time unit of the first UE air interface data frame after downlink synchronization pre-compensation.

[0194] In one optional embodiment of this application, the phase compensation module specifically uses:

[0195] Based on the uplink synchronization pre-compensation value or downlink synchronization pre-compensation value within each preset time unit, obtain the average delay value corresponding to each OFDM symbol within each preset time unit.

[0196] Based on the average time delay value, the phase value that each OFDM symbol needs to compensate for in each subcarrier in the frequency domain is obtained, and phase compensation is performed on the OFDM symbol in the frequency domain based on the phase value.

[0197] In one optional embodiment of this application, the device further includes a Doppler pre-compensation module, used for:

[0198] Doppler pre-compensation is performed on each preset time unit of the first UE air interface data frame after downlink synchronization pre-compensation;

[0199] Doppler pre-compensation is performed on each preset time unit of the second UE air interface data frame after uplink synchronization pre-compensation.

[0200] The uplink / downlink synchronization device for a mobile satellite communication system provided in this application embodiment can achieve... Figures 1 to 12 The various processes implemented in the method embodiments are not described in detail here to avoid repetition.

[0201] The solution provided in this application performs downlink synchronization pre-compensation and uplink synchronization pre-compensation based on the sampling point deviation value corresponding to the preset time unit before downlink coarse synchronization and after uplink coarse synchronization. This ensures that the satellite terminal will not have accumulated timing deviation in baseband processing when the local baseband sampling rate remains unchanged, and will not have errors in frame number and time slot number, thereby reducing the number of wireless link failures. At the same time, it ensures that the uplink reception duration of physical frames from multiple users by the mobile satellite base station remains constant, reducing interference between uplink reception from multiple users. This solution is well applicable to uplink and downlink synchronization in mobile satellite communication systems.

[0202] The uplink / downlink synchronization device of the mobile satellite communication system in this application embodiment can execute the uplink / downlink synchronization method of the mobile satellite communication system provided in this application embodiment. The implementation principle is similar. The actions performed by each module and unit in the uplink / downlink synchronization device of the mobile satellite communication system in each embodiment of this application correspond to the steps in the uplink / downlink synchronization method of the mobile satellite communication system in each embodiment of this application. For detailed functional descriptions of each module of the uplink / downlink synchronization device of the mobile satellite communication system, please refer to the descriptions in the corresponding uplink / downlink synchronization methods of the mobile satellite communication system shown above. They will not be repeated here.

[0203] Based on the same principles as the methods shown in the embodiments of this application, this application also provides an electronic device, which may include, but is not limited to, a processor and a memory; the memory is used to store computer programs; the processor is used to execute the uplink / downlink synchronization method of the mobile satellite communication system shown in any optional embodiment of this application by calling the computer program. Compared with the prior art, the uplink / downlink synchronization method of the mobile satellite communication system provided in this application performs downlink synchronization pre-compensation and uplink synchronization pre-compensation according to the sampling point deviation value corresponding to the preset time unit before performing downlink coarse synchronization and after completing uplink coarse synchronization, respectively. This ensures that the satellite terminal will not have accumulated timing deviation in baseband processing when the local baseband sampling rate remains unchanged, and will not have errors in frame number and time slot number, reducing the number of wireless link failures. At the same time, it ensures that the uplink reception duration of physical frames from multiple users by the mobile satellite base station remains fixed, reducing interference between uplink reception from multiple users. This scheme is well applicable to the uplink / downlink synchronization of mobile satellite communication systems.

[0204] In an alternative embodiment, an electronic device, such as Figure 14 As shown, Figure 14 The illustrated electronic device 1400 can be a server, including a processor 1401 and a memory 1403. The processor 1401 and the memory 1403 are connected, for example, via a bus 1402. Optionally, the electronic device 1400 may also include a transceiver 1404. It should be noted that in practical applications, the transceiver 1404 is not limited to one, and the structure of this electronic device 1400 does not constitute a limitation on the embodiments of this application.

[0205] Processor 1401 may be a CPU (Central Processing Unit), a general-purpose processor, a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute the various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. Processor 1401 may also be a combination that implements computational functions, such as including one or more microprocessor combinations, a combination of a DSP and a microprocessor, etc.

[0206] Bus 1402 may include a pathway for transmitting information between the aforementioned components. Bus 1402 may be a PCI (Peripheral Component Interconnect) bus or an EISA (Extended Industry Standard Architecture) bus, etc. Bus 1402 can be divided into address bus, data bus, control bus, etc. For ease of representation, Figure 14 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0207] The memory 1403 may be a ROM (Read Only Memory) or other type of static storage device capable of storing static information and instructions, RAM (Random Access Memory) or other type of dynamic storage device capable of storing information and instructions, or an EEPROM (Electrically Erasable Programmable Read Only Memory), CD-ROM (Compact Disc Read Only Memory) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but not limited thereto.

[0208] The memory 1403 is used to store application code that executes the scheme of this application, and its execution is controlled by the processor 1401. The processor 1401 is used to execute the application code stored in the memory 1403 to implement the content shown in the foregoing method embodiments.

[0209] Among them, electronic devices include, but are not limited to: mobile terminals such as mobile phones, laptops, digital radio receivers, PDAs (personal digital assistants), PADs (tablet computers), PMPs (portable multimedia players), and in-vehicle terminals (such as in-vehicle navigation terminals), as well as fixed terminals such as digital TVs and desktop computers. Figure 14 The electronic device shown is merely an example and should not impose any limitation on the functionality and scope of use of the embodiments of this application.

[0210] The server provided in this application can be a standalone physical server, a server cluster or distributed system composed of multiple physical servers, or a cloud server providing basic cloud computing services such as cloud services, cloud mobile communication, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, CDN, and big data and artificial intelligence platforms. The terminal can be a smartphone, tablet, laptop, desktop computer, smart speaker, smartwatch, etc., but is not limited to these. The terminal and server can be directly or indirectly connected via wired or wireless communication, which is not limited herein.

[0211] This application provides a computer-readable storage medium storing a computer program that, when run on a computer, enables the computer to execute the corresponding content in the aforementioned method embodiments.

[0212] It should be understood that although the steps in the flowcharts of the accompanying figures are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the accompanying figures may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

[0213] It should be noted that the computer-readable medium described above in this application can be a computer-readable signal medium, a computer-readable storage medium, or any combination thereof. A computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this application, a 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, apparatus, or device. In this application, a computer-readable signal medium can include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium can be any computer-readable medium other than a computer-readable storage medium, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wires, optical fibers, RF (radio frequency), etc., or any suitable combination thereof.

[0214] The aforementioned computer-readable medium may be included in the aforementioned electronic device; or it may exist independently and not assembled into the electronic device.

[0215] The aforementioned computer-readable medium carries one or more programs, which, when executed by the electronic device, cause the electronic device to perform the methods shown in the above embodiments.

[0216] According to one aspect of this application, a computer program product or computer program is provided, comprising computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the computer device to perform the uplink / downlink synchronization method for a mobile satellite communication system provided in the various alternative implementations described above.

[0217] Computer program code for performing the operations of this application can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0218] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0219] The modules described in the embodiments of this application can be implemented in software or hardware. The name of a module does not necessarily limit the module itself; for example, a sampling point deviation value acquisition module can also be described as a "module for acquiring sampling point deviation values".

[0220] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of disclosure in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A method for uplink and downlink synchronization in a mobile satellite communication system, characterized in that, include: Based on the ephemeris parameters of the mobile satellite and the coordinates of the user equipment (UE), the sampling point deviation value between the UE and the mobile satellite within a preset time unit is obtained; Based on the sampling point deviation value, downlink synchronization pre-compensation is performed on the received first UE air interface data frame in each corresponding preset time unit, and downlink coarse synchronization is performed based on the first UE air interface data frame after downlink synchronization pre-compensation. Uplink coarse synchronization is performed based on downlink coarse synchronization parameters and the real-time distance between the UE and the mobile satellite. After the uplink coarse synchronization is completed, uplink synchronization pre-compensation is performed on the second UE air interface data frame to be transmitted in each corresponding preset time unit based on the sampling point deviation value. Uplink synchronization is then performed based on the second UE air interface data frame after uplink synchronization pre-compensation.

2. The method according to claim 1, characterized in that, The step of performing downlink synchronization pre-compensation on the received first air interface data frame in each corresponding preset time unit based on the sampling point deviation value, and performing downlink coarse synchronization based on the first UE air interface data frame after downlink synchronization pre-compensation, includes: Based on the sampling point deviation value and the number of preset sampling points corresponding to each preset time unit of the base station air interface data frame sent by the mobile satellite, the synchronization header corresponding to each preset time unit of the first UE air interface data frame is determined, and the first UE air interface data frame after downlink synchronization pre-compensation is obtained. For each preset time unit, according to the corresponding synchronization header position, the sampling point corresponding to the preset time unit is taken and processed by baseband to obtain the synchronization signal block SSB signal; Downlink coarse synchronization is performed based on the downlink synchronization parameters in the SSB signal.

3. The method according to claim 2, characterized in that, The step of determining the synchronization header of the first UE air interface data frame in each preset time unit based on the sampling point deviation value and the preset number of sampling points corresponding to the base station air interface data frame transmitted by the mobile satellite in each preset time unit includes: When the distance between the UE and the mobile satellite decreases, the cyclic prefix CP of the first orthogonal frequency division multiplexing (OFDM) symbol starting from the synchronization header position in each preset time unit is reduced by the number of sampling points corresponding to the sampling point deviation value, while the number of sampling points corresponding to other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit. As the distance between the UE and the mobile satellite increases, the number of sampling points corresponding to the sampling point deviation value is added to the last OFDM symbol starting from the synchronization header position in each preset time unit, while keeping the number of sampling points corresponding to other OFDM symbols and CP unchanged, to obtain the synchronization header corresponding to each preset time unit.

4. The method according to claim 2, characterized in that, The downlink synchronization parameters include the local frame number, local timeslot number, downlink air interface frame number, downlink air interface timeslot number, and the sampling point index value corresponding to the downlink air interface timeslot at the synchronization frame header position; The downlink coarse synchronization based on the downlink synchronization parameters in the SSB signal includes: The downlink air interface frame number is used as the local frame number, the downlink air interface timeslot number is used as the local timeslot number, and the next timeslot synchronization is performed based on the sampling point index value corresponding to the downlink air interface timeslot.

5. The method according to claim 1, characterized in that, The uplink coarse synchronization based on downlink coarse synchronization parameters and the real-time distance between the UE and the mobile satellite includes: Based on the real-time distance between the mobile satellite and the UE, the first delay corresponding to the distance is obtained, and the second and third delays corresponding to the downlink coarse synchronization are obtained based on the downlink coarse synchronization parameters; Based on the first delay, the second delay, and the third delay, obtain the uplink air interface frame number, the uplink air interface time slot frame number, and the sampling point index value corresponding to the uplink air interface time slot at the synchronization frame header position; The uplink air interface frame number is used as the local frame number of the synchronization frame header position, the uplink air interface timeslot number is used as the local timeslot number of the synchronization frame header position, and the next timeslot synchronization is performed based on the sampling point index value corresponding to the uplink air interface timeslot.

6. The method according to claim 1, characterized in that, The step of performing uplink synchronization pre-compensation on the second UE air interface data frame to be transmitted based on the sampling point deviation value in each corresponding preset time unit, and performing uplink synchronization based on the second UE air interface data frame after uplink synchronization pre-compensation, includes: Based on the sampling point deviation value and the number of preset sampling points corresponding to the base station air interface data frames received by the mobile satellite in each preset time unit, the synchronization header corresponding to each preset time unit of the second UE air interface data frame is determined, and the second UE air interface data frame after uplink synchronization pre-compensation is obtained. Based on the uplink frame number, uplink timeslot number, and synchronization header corresponding to each preset time unit maintained after uplink coarse synchronization, the uplink synchronization signal is sent to the mobile satellite, and the uplink residual timing deviation control word fed back by the mobile satellite is received, and uplink synchronization is completed based on the uplink residual timing deviation control word.

7. The method according to claim 6, characterized in that, The step of determining the synchronization header corresponding to each preset time unit of the second UE air interface data frame based on the sampling point deviation value and the preset number of sampling points corresponding to each preset time unit of the base station air interface data frame received by the mobile satellite includes: When the distance between the UE and the mobile satellite decreases, the last OFDM symbol starting from the synchronization header position in each preset time unit is increased by the number of sampling points corresponding to the sampling point deviation value, and the increased sampling points are set to zero. The number of sampling points for other OFDM symbols and CP remains unchanged, thus obtaining the synchronization header corresponding to each preset time unit. As the distance between the UE and the mobile satellite increases, the number of sampling points corresponding to the sampling point deviation value is reduced from the last OFDM symbol starting from the synchronization header position in each preset time unit, while the number of sampling points corresponding to other OFDM symbols and CP remains unchanged, to obtain the synchronization header corresponding to each preset time unit.

8. The method according to claim 1, characterized in that, The method further includes: Phase compensation is performed on each OFDM symbol in each preset time unit of the first UE air interface data frame after downlink synchronization pre-compensation; Phase compensation is performed on each OFDM symbol in each preset time unit of the second UE air interface data frame after uplink synchronization pre-compensation.

9. The method according to claim 8, characterized in that, The phase compensation for each OFDM symbol in each preset time unit includes: Based on the uplink synchronization pre-compensation value or downlink synchronization pre-compensation value within each preset time unit, obtain the average delay value corresponding to each OFDM symbol within each preset time unit. Based on the average delay value, the phase value that each OFDM symbol needs to compensate for in each subcarrier in the frequency domain is obtained, and phase compensation is performed on the OFDM symbol in the frequency domain based on the phase value.

10. The method according to any one of claims 1-9, characterized in that, The method further includes: Doppler pre-compensation is performed on each preset time unit of the first UE air interface data frame after downlink synchronization pre-compensation; Doppler pre-compensation is performed on each preset time unit of the second UE air interface data frame after uplink synchronization pre-compensation.

11. A mobile satellite communication system uplink and downlink synchronization device, characterized in that, include: The sampling point deviation value acquisition module is used to acquire the sampling point deviation value between the UE and the mobile satellite within a preset time unit based on the ephemeris parameters of the mobile satellite and the coordinates of the user equipment (UE). The downlink coarse synchronization module is used to perform downlink synchronization pre-compensation on the received first UE air interface data frame in each corresponding preset time unit based on the sampling point deviation value, and to perform downlink synchronization based on the first UE air interface data frame after downlink synchronization pre-compensation. The uplink synchronization module is used to perform uplink coarse synchronization based on downlink coarse synchronization parameters and the real-time distance between the UE and the mobile satellite. After completing the uplink coarse synchronization, it performs uplink synchronization pre-compensation on the second UE air interface data frame to be transmitted in each corresponding preset time unit based on the sampling point deviation value, and performs uplink synchronization based on the second UE air interface data frame after uplink synchronization pre-compensation.

12. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method of any one of claims 1 to 10.

13. A computer-readable storage medium storing a computer program thereon, characterized in that, When the computer program is executed by a processor, it implements the method of any one of claims 1 to 10.

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