Satellite communication time synchronization method, device, equipment, medium and program product

Abstract

The present application relates to the field of satellite communication technology, and in particular to a time synchronization method, device, equipment, medium and program product for satellite communication. The terminal receives a synchronization signal block broadcast by a satellite base station for preliminary synchronization, and decodes a master information block broadcast by a satellite base station to obtain a cell-level common timing advance parameter and time-frequency resources; selects a preamble code and time-frequency resources in combination with the cell-level common timing advance parameter, initiates a random access request, and sends a first message to the satellite base station; receives a second message from the satellite base station, the second message containing a timing advance instruction fed back based on the detection result of the preamble code; adjusts the uplink timing synchronization according to the timing advance instruction, and sends a third message to the satellite base station through a physical uplink shared channel. Through the present application, a terminal without GNSS capability can also achieve initial random access and maintain uplink time synchronization without changing the existing preamble format and timing advance indication range.

Description

Technical Field

[0001] The present application relates to the field of satellite communication technology, and in particular to a time synchronization method, device, equipment, medium and program product for satellite communication. Background Art

[0002] In satellite communication systems, due to the large distance between the satellite and the ground, the propagation delay increases significantly compared to the ground communication system. The preamble format and timing advance indication range of existing terminals are difficult to cope with such a large propagation delay, making it impossible to complete initial random access. In addition, the high-speed movement of the satellite causes the propagation delay to change continuously, which also poses a challenge to maintaining uplink time synchronization after access. Especially in the staring beam scenario, the existing technology has failed to effectively solve the problem that terminals without global navigation satellite system (GNSS) capabilities have difficulty in achieving initial access and uplink time synchronization tracking. Most of them use methods such as changing the preamble format and expanding the timing advance range, requiring the terminal to have positioning capabilities. However, this method has high requirements for the terminal and requires modification of the terminal side protocol, which is not conducive to promotion. Frequent positioning will increase the power consumption of the terminal. Summary of the invention

[0003] In order to solve the above-mentioned technical problem of difficult uplink time synchronization in satellite communication, the present application provides a time synchronization method, device, equipment, medium and program product for satellite communication, which realizes a technical solution for providing initial random access and uplink time synchronization tracking for terminals without GNSS capability without changing the existing preamble format and timing advance indication range. The present application implements delay compensation on the base station side and delayed reception on the terminal side to complete the initial random access, adopts a user grouping strategy to improve the calculation method of the timing advance adjustment amount, and monitors and tracks the timing advance changes of the terminal according to the calculated reference point information. While reducing the requirements for the terminal, it also reduces the burden of the base station to maintain the uplink time synchronization of each user, which is conducive to the lightweighting of the satellite base station. In addition, the present application improves the accuracy and stability of uplink time synchronization by correcting the timing drift rate and timing drift acceleration based on the reference point, thereby effectively reducing the uplink desynchronization rate in the face of a large delay and rapidly changing satellite communication environment.

[0004] A first aspect of the present application provides a time synchronization method for satellite communication, which is applied to a terminal, and the method includes:

[0005] receiving a synchronization signal block broadcasted by a satellite base station for preliminary synchronization, and decoding a master information block broadcasted by the satellite base station to obtain a cell-level common timing advance parameter and time-frequency resources;

[0006] selecting a preamble code and time-frequency resources in combination with the cell-level common timing advance parameter, initiating a random access request, and sending a first message to the satellite base station;

[0007] delaying reception of a second message from the satellite base station, wherein the second message includes a timing advance instruction fed back according to a detection result of the preamble code;

[0008] The uplink timing synchronization is adjusted according to the timing advance instruction, and a third message is sent to the satellite base station through a physical uplink shared channel to complete subsequent access steps and realize initial random access.

[0009] In some embodiments of the present application, after the initial random access is implemented, the method further includes: periodically reporting the total timing advance to the satellite base station, or reporting the total timing advance when instructed by the satellite base station.

[0010] In some embodiments of the present application, decoding the master information block broadcasted by the satellite base station to obtain the cell-level common timing advance parameter includes:

[0011] Blindly decoding downlink control information according to the master information block and configuring a physical downlink shared channel decoder;

[0012] Decoding the downlink shared channel based on the decoder and obtaining a preset system information block;

[0013] The cell-level common timing advance parameter and time-frequency resources are extracted from the preset system information block.

[0014] In some embodiments of the present application, the selecting a preamble code and a time-frequency resource in combination with the cell-level common timing advance parameter, initiating a random access request, and sending a first message to the satellite base station includes:

[0015] Determine the advance time for sending the first message according to the cell-level common timing advance parameter;

[0016] A preamble code is randomly selected from a preset preamble code sequence, and a first message is sent to the satellite base station on the time-frequency resource with the advance time length.

[0017] In some embodiments of the present application, the delaying receiving the second message from the satellite base station includes:

[0018] Determine the opening time of the RAR receiving window based on the minimum RTT in the cell;

[0019] Determine the duration of the RAR receiving window according to the RTT range within the cell;

[0020] A second message sent by a satellite base station is received in the RAR receiving window, wherein the message includes a timing advance instruction and uplink authorization information.

[0021] In some embodiments of the present application, after the initial random access is implemented, the method further includes: adjusting the timing advance amount according to a timing advance adjustment instruction sent by the satellite base station.

[0022] A second aspect of the present application provides a time synchronization method for satellite communication, which is applied to a satellite base station, and the method comprises:

[0023] Broadcasting a synchronization signal block and a master information block so that a terminal initiates a random access request according to the synchronization signal block and the master information block;

[0024] receiving a preamble in a random access request sent by the terminal, and detecting the preamble in parallel in a plurality of windows for each possible delay time slot to estimate an open-loop timing advance;

[0025] Determine a timing advance value in a second message according to the open-loop timing advance, and send the second message after determining the timing advance value to the terminal;

[0026] Monitor the uplink signal of the terminal, calculate the timing advance adjustment amount and send a timing advance adjustment command to the terminal.

[0027] In some embodiments of the present application, for each possible delay time slot, detecting the preamble code in parallel in multiple windows to estimate the open-loop timing advance includes:

[0028] For each possible delay time slot, multiple preamble detection windows are opened, a cyclic prefix is ​​removed from the signal corresponding to the preamble code, and a fast Fourier transform is performed after the prefix is ​​removed to obtain a frequency domain representation;

[0029] Perform frequency domain cross-correlation calculation on the frequency domain representation and the locally stored preamble template to obtain a frequency domain cross-correlation result;

[0030] The frequency domain cross-correlation result is converted back to the time domain by inverse fast Fourier transform to generate a power delay spectrum;

[0031] determining a delay peak index in the power delay spectrum, and obtaining an estimated open-loop timing advance based on the peak index;

[0032] The estimated open-loop timing advance is converted to an initial timing advance value.

[0033] In some embodiments of the present application, performing frequency domain cross-correlation calculation on the frequency domain representation and the locally stored preamble template to obtain a frequency domain cross-correlation result includes:

[0034] For each possible delayed time slot, extract the frequency domain representation within the corresponding time slot detection window;

[0035] A cross-correlation operation is performed on the frequency domain representation of the corresponding time slot and the frequency domain representations of a preset number of ZC sequences with different root sequence numbers stored locally to obtain a frequency domain cross-correlation result.

[0036] In some embodiments of the present application, the method further includes:

[0037] After the terminal enters the connection mode, receiving the total timing advance reported by each terminal;

[0038] The users are grouped according to the total timing advance of each terminal, and the timing advance adjustment amount is corrected according to the timing drift rate and timing drift acceleration of the preset reference point of each user group;

[0039] A timing advance adjustment command is determined based on the timing advance adjustment amount, and the timing advance adjustment command is sent to the terminal.

[0040] In some embodiments of the present application, the grouping of users according to the total timing advance of each terminal includes:

[0041] According to the total timing advance reported by each terminal and the pre-calculated and stored reference point location information and real-time RTT, a clustering algorithm is used to divide the terminals into different user groups, where each user group corresponds to a reference point, so that the difference between the total timing advance of the terminals in the group and the real-time RTT of the reference point is minimized.

[0042] In some embodiments of the present application, the method for calculating the timing drift rate and the timing drift acceleration of the preset reference point of each user group includes:

[0043] Obtaining location information of a preset reference point for each user group;

[0044] Calculating the round trip delay of the preset reference point at each moment in a specific time period;

[0045] Calculating the timing drift rate and timing drift acceleration of the preset reference point within a specific time period according to the round-trip delay to form a time series;

[0046] The timing drift rate and the timing drift acceleration of the terminals in each user group at a specific moment are determined according to the time series.

[0047] A third aspect of the present application provides a time synchronization device for satellite communication, the device comprising:

[0048] A parsing module, configured to receive a synchronization signal block broadcasted by a satellite base station for preliminary synchronization, and decode a master information block broadcasted by the satellite base station to obtain a cell-level common timing advance parameter and time-frequency resources;

[0049] An access module, configured to select a preamble and time-frequency resources in combination with the cell-level common timing advance parameter, initiate a random access request, and send a first message to the satellite base station;

[0050] A receiving module, configured to delay receiving a second message from the satellite base station, wherein the second message includes a timing advance instruction fed back according to a detection result of the preamble code;

[0051] The adjustment module is used to adjust the uplink timing synchronization according to the timing advance instruction, and send a third message to the satellite base station through a physical uplink shared channel to complete subsequent access steps and realize initial random access.

[0052] A fourth aspect of the present application provides a time synchronization device for satellite communication, the device comprising:

[0053] A broadcast module, used for broadcasting a synchronization signal block and a master information block, so that the terminal initiates a random access request according to the synchronization signal block and the master information block;

[0054] A detection module, configured to receive a preamble in a random access request sent by the terminal, and detect the preamble in parallel in multiple windows for each possible delay time slot to estimate an open-loop timing advance;

[0055] A sending module, configured to determine a timing advance value in a second message according to the open-loop timing advance value, and send the second message after determining the timing advance value to the terminal;

[0056] The adjustment module is used to monitor the uplink signal of the terminal, calculate the timing advance adjustment amount and send a timing advance adjustment command to the terminal.

[0057] The fifth aspect of the present application provides an electronic device, including a memory and a processor, characterized in that computer-readable instructions are stored in the memory, and when the computer-readable instructions are executed by the processor, the processor executes the method described in the embodiments of the present application.

[0058] In a sixth aspect, the present application provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the method described in the embodiments of the present application is implemented.

[0059] A seventh aspect of the present application provides a computer program product, including a computer program, characterized in that the computer program implements the method described in the embodiments of the present application when executed by a processor.

[0060] The technical solution provided in the embodiments of the present application has at least the following technical effects or advantages:

[0061] The satellite communication time synchronization method provided in each embodiment of the present application is applied to a terminal, and the method includes: receiving a synchronization signal block broadcast by a satellite base station for preliminary synchronization, and decoding a master information block broadcast by the satellite base station to obtain a cell-level common timing advance parameter and time-frequency resources; selecting a preamble and time-frequency resources in combination with the cell-level common timing advance parameter, initiating a random access request, and sending a first message to the satellite base station; receiving a second message from the satellite base station, the second message including a timing advance instruction fed back according to the detection result of the preamble; adjusting uplink timing synchronization according to the timing advance instruction, and sending a third message to the satellite base station through a physical uplink shared channel; reporting the total timing advance amount periodically or according to the instruction of the satellite base station; receiving a timing advance adjustment instruction from the satellite base station, the timing advance adjustment instruction including a timing advance adjustment amount calculated according to a preset reference point of the user group; adjusting uplink timing synchronization according to the timing advance adjustment amount. In this way, without changing the existing preamble format and timing advance range, a terminal without GNSS capability can also achieve initial random access and maintain uplink time synchronization, and only needs to modify the protocol on the base station side.

[0062] The satellite communication time synchronization method described in each embodiment of the present application is applied to a satellite base station, and the method includes: broadcasting a synchronization signal block and a master information block so that a terminal initiates a random access request according to the synchronization signal block and the master information block; receiving a preamble code in the random access request sent by the terminal, and performing preamble code detection for each possible delay time slot to estimate an open-loop timing advance; determining a timing advance value in a second message according to the open-loop timing advance, and sending the second information after determining the timing advance value to the terminal; grouping users according to a total timing advance; monitoring the uplink signal of the terminal, correcting the user's timing advance adjustment amount according to the timing drift rate and timing drift acceleration of a preset reference point of the user group, and sending a timing advance adjustment command to the terminal. For each satellite, the reference point within its service cell only needs to be calculated once. This information does not need to be sent to the terminal, avoiding additional signaling overhead. After grouping the users, the base station uses these reference points to track the user's timing advance TA changes. By correcting the user's TA adjustment value, the TA error caused by the service link delay change is reduced, and the accuracy of TA estimation is improved. Ultimately, in satellite communication scenarios with large delays and fast delay changes, the initial establishment and maintenance of uplink time synchronization is achieved based on the existing terminal protocol, reducing the uplink desynchronization rate.

[0063] In short, the terminal and the satellite base station can achieve highly accurate uplink time synchronization, ensuring stable communication in the complex communication environment between the satellite and the ground, dynamically adapting to the delay changes caused by satellite movement, and timely adjusting the timing advance to maintain uplink time synchronization.

[0064] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0066] Figure 1 It is a schematic diagram of the steps of a time synchronization method for satellite communication in an exemplary embodiment of the present application;

[0067] Figure 2 is a schematic diagram of a RAR window starting position and duration in an exemplary embodiment of the present application;

[0068] Figure 3 It is a schematic diagram of the steps of another method for time synchronization of satellite communication in an exemplary embodiment of the present application;

[0069] Figure 4 It is a schematic diagram of reference point distribution and terminal grouping in a low-altitude area of ​​a ground fixed cell in an exemplary embodiment of the present application;

[0070] Figure 5 is a schematic diagram of a TA error in an exemplary embodiment of the present application;

[0071] Figure 6 It is a schematic diagram of the interaction between a terminal and a satellite base station using the uplink time synchronization method in a satellite communication scenario;

[0072] Figure 7 It is a structural schematic diagram of an uplink time synchronization device for satellite communication in an exemplary embodiment of the present application;

[0073] Figure 8 It is a structural schematic diagram of another uplink time synchronization device for satellite communication in an exemplary embodiment of the present application;

[0074] Fig. 9 It is a schematic diagram of the structure of an electronic device provided by an exemplary embodiment of the present application.

[0075] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. DETAILED DESCRIPTION

[0076] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is understood that the embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It should also be noted that, for ease of description, only the parts related to the relevant invention are shown in the accompanying drawings.

[0077] In the staring beam scenario of the satellite communication system, due to the large distance between the satellite and the ground, its propagation delay far exceeds the propagation delay of the ground communication system. The preamble code format and timing advance indication range of the existing terminal are difficult to cope with the large propagation delay, and thus the initial random access cannot be completed.

[0078] In addition, the high-speed movement of satellites causes the propagation delay to change continuously, which also brings challenges to maintaining uplink time synchronization.

[0079] To this end, the present application provides a satellite communication time synchronization method in some embodiments, which is applied to a terminal, such as Figure 1 As shown, the method includes S11 to S14.

[0080] S11. Receive a synchronization signal block broadcast by a satellite base station to perform preliminary synchronization, and decode a master information block broadcast by the satellite base station to obtain a cell-level common timing advance parameter and time-frequency resources.

[0081] Receiving the synchronization signal block broadcast by the satellite base station for preliminary synchronization is specifically as follows: the satellite base station broadcasts a synchronization signal block SSB set that has been pre-compensated for frequency offset, the terminal receives the SSB set, and synchronizes and demodulates the received waveform to determine the system frame number, cell identifier and SSB. It should be noted that the satellite uses a staring beam to serve ground fixed cells, and the terminal does not have GNSS (Global Navigation Satellite System) capabilities. For each satellite and its service cell, a reference point set is calculated through a series of algorithms, and the set includes the location information of several reference points. In the initial random access phase, the terminal decodes the SIB (System Information Block) information and then applies the cell-level timing advance to initiate random access. In a specific implementation method, the decoding of the master information block MIB broadcast by the satellite base station obtains the cell-level common timing advance parameters. , including: blindly decoding downlink control PDCCH information according to the master information block, and configuring a physical downlink shared channel PDSCH decoder; decoding the downlink shared channel based on the decoder and obtaining a preset system information block SIB1; extracting a cell-level common timing advance parameter in SIB1 and time-frequency resources RO.

[0082] It can be understood that there are at least two deployment modes for base stations: one is that the satellite base station is deployed at the satellite gateway, and the other is that the satellite base station is deployed on the satellite. If the satellite base station is deployed at the satellite gateway, all subsequent steps use the satellite as the synchronization reference point, and only the service link delay is considered when calculating the timing advance. The feeder link delay is calculated by the network end through For the convenience of description, the subsequent steps assume that the satellite base station is deployed on the satellite.

[0083] The random access time-frequency resource RO in the above step S11 includes the system frame number and subframe number that the base station allows the user to initiate random access and the frequency range that carries the preamble sequence.

[0084] The calculation formula of the cell-level common timing advance parameter is: ,

[0085] in The minimum RTT between the ground terminal and the satellite during the period when the satellite is in the service cell, in milliseconds (ms). are different subcarrier configuration parameters, , which is the smallest time unit in 5G.

[0086] S12: Select a preamble code and time-frequency resources in combination with the cell-level common timing advance parameter, initiate a random access request, and send a first message to the satellite base station.

[0087] In a possible implementation, the method of selecting a preamble code and time-frequency resources in combination with the cell-level common timing advance parameter, initiating a random access request, and sending a first message msg1 to the satellite base station includes: determining an advance duration for sending msg1 according to the cell-level common timing advance parameter (i.e., sending the first message a period of time in advance); randomly selecting a preamble code from a preset preamble code sequence, and sending msg1 to the satellite base station on the RO with the advance duration.

[0088] The user initiates random access, randomly selects one from a preset preamble sequence, such as 64 preambles, as its own preamble, records its RAPID (Random Access Preamble IDentifier, random access preamble identifier, value 0~63), and then selects any RO obtained from step S11 as the time-frequency resource for sending msg1, in advance relative to the time domain position indicated in the RO Send preamble, , the unit is milliseconds (ms).

[0089] The base station delays opening the msg1 receiving window in different time slots after RO, detects the leading signal in parallel in multiple windows, calculates the initial TA of the terminal, and compensates for most of the delay from the terminal to the satellite based on the number of delayed time slots in the subsequent access process. After that, the terminal delays and expands the RAR (Random Access Response) receiving window to obtain msg2, completes the subsequent access steps, and achieves initial uplink time synchronization. In the connected (RRC CONNECTED) mode, the base station groups users according to their total timing advance. Each group of users shares a reference point. The TA adjustment value of each user is corrected with the help of the timing drift rate and timing drift acceleration of the reference point. After receiving the TAC, the user updates its TA value according to the closed-loop TA mechanism.

[0090] S13. Delay receiving a second message from the satellite base station, where the second message includes a timing advance instruction fed back based on a detection result of the preamble code.

[0091] In a specific implementation, when the second message from the satellite base station is received with delay, the opening time of the RAR receiving window is first determined according to the minimum RTT in the cell, and then the duration of the RAR receiving window is determined according to the RTT range in the cell, and the second message sent by the satellite base station is received in the RAR receiving window, wherein the message includes a timing advance instruction and uplink authorization information. Once the random access is successful, the terminal will receive feedback from the satellite base station, i.e., the second message msg2. This message is generated after the base station successfully decodes the preamble in the first message msg1, and includes a series of control instructions tailored for the terminal. A crucial part of msg2 is the timing advance instruction, which instructs the terminal how to adjust its transmission timing to more accurately match the satellite's receiving window. This adjustment is based on the time error obtained from the analysis of the preamble reception, ensuring that subsequent data exchange can be carried out in the best synchronization state.

[0092] S14. Adjust uplink timing synchronization according to the timing advance instruction, and send a third message to the satellite base station through a physical uplink shared channel to complete subsequent access steps and implement initial random access.

[0093] The terminal adjusts its uplink timing synchronization settings according to the instruction of the satellite base station, i.e., the timing advance instruction, which may involve fine-tuning the transmission delay or adjusting the parameters such as the transmission power to meet the requirements of the base station and the current channel conditions. After the adjustment is completed, the terminal sends a third message msg3 through the physical uplink shared channel PUSCH. msg3 usually contains user data or higher-level access information (such as identity authentication data, etc.), further confirming the communication link with the satellite base station and completing the access process.

[0094] It can be seen that the above S11~S14 belong to the initial random access stage. The terminal uses the cell-level public timing advance parameters broadcast by the satellite base station to send the first message, and receives the second message fed back by the satellite base station in the delayed and extended RAR window. The second message includes uplink authorization, TA, RAPID and time-frequency resources for the third message msg 3. The satellite base station uses open-loop TA to send the third message to complete the random access. After the random access is successful, it enters the uplink time synchronization maintenance stage. At this time, the satellite base station uses closed-loop TA to send messages, that is, the terminal adjusts the timing advance according to the timing advance adjustment command (TAC). It can be understood that without changing the existing preamble format and timing advance range, terminals without GNSS capabilities can also achieve initial random access and maintain uplink time synchronization, and only need to modify the protocol on the base station side.

[0095] The terminal sends the first message msg1 after a preset time such as the first The RAR receiving window is opened for subframes, and the second message sent by the satellite base station is received in the RAR receiving window, wherein the message includes a timing advance instruction, i.e., a TA instruction, and uplink authorization information, wherein the uplink authorization information includes an uplink authorization, RAPID, and time-frequency resources for msg 3. PDCCH is monitored in the receiving window, and the window lasts for Ra-ResponseWindowSize subframes. Among them, the starting subframe , Ra-ResponseWindowSize= . Figure 2 It is a schematic diagram of the starting position and duration of a RAR window, such as Figure 2 As shown in FIG. 1 , if the preamble code spans multiple subframes in the time domain, the last subframe is used for calculation. The starting subframe of the RAR receiving window The parameter Ra-ResponseWindowSize is included in SIB1. The user obtains the value from SIB1 in step S11. The parameter Ra-ResponseWindowSize is included in the RACH-ConfigCommon field in SIB 2. The terminal decodes the RAR received in the RAR receiving window. If the RAPID in the RAR is consistent with the RAPID of the preamble used in step S12, the allocated time-frequency resource RO is used to advance the time point of the authorization to send PUSCH. Send msg3 and complete the subsequent access steps. Otherwise, the random access fails and the process goes to step S12. After a short backoff time, the terminal initiates random access again.

[0096] If the user does not receive msg4 within the contention resolution timer CR during the subsequent access process, the random access fails and the process goes to step S12. After a short backoff time, the terminal initiates random access again. The CR value range is {8, 16, 24, 32, 40, 48, 56, 64} , whose length is determined by ra-ContentionResolutionTimer in SIB2. , indicating the subframe duration.

[0097] In another specific implementation, after the third message is sent to the satellite base station through the physical uplink shared channel PUSCH, it also includes: periodically reporting the total timing advance to the satellite base station, or reporting the total timing advance when instructed by the satellite base station. In other words, after the terminal sends the third message to the satellite base station, it has completed the initial random access phase of the first phase and entered the uplink time synchronization maintenance phase after successful access. The terminal needs to perform TAR (Timing Advance Report) to report to the base station its current total timing advance, including the base station delay compensation value, the cell-level public timing advance and the user's timing advance, so that the satellite base station can replace other reference points for the terminal in time.

[0098] It can be understood that the terminal adjusts its transmission timing according to the timing advance parameters received from the satellite base station, so as to accurately align the interaction time window with the satellite. This precise adjustment of time synchronization is very critical, especially in satellite communications, because even a small synchronization deviation may lead to a significant decrease in communication effect. After receiving the second message from the satellite base station, further optimizing the time synchronization according to the timing advance adjustment instruction can effectively deal with the time offset caused by the high-speed movement of the satellite and maintain continuous uplink stability.

[0099] In some other embodiments of the present application, a satellite communication time synchronization method is provided, which is applied to a satellite base station, such as Figure 3 As shown, the method includes S21 to S24.

[0100] S21. Broadcast a synchronization signal block and a master information block, so that the terminal initiates a random access request according to the synchronization signal block and the master information block.

[0101] S22: Receive a preamble in a random access request sent by the terminal, and detect the preamble in parallel in multiple windows for each possible delay time slot to estimate an open-loop timing advance.

[0102] In one possible implementation, for each possible delayed time slot, the preamble code is detected in parallel in multiple windows to estimate the open-loop timing advance, including: for each possible delayed time slot, the cyclic prefix CP is removed from the signal corresponding to the preamble code, and a fast Fourier transform FFT is performed after the prefix is ​​removed to obtain a frequency domain representation; for each possible delayed time slot, the frequency domain representation of the corresponding time slot detection window is extracted; the frequency domain representation of the corresponding time slot is cross-correlated with the frequency domain representation of a preset number of ZC sequences with different root sequence numbers stored locally to obtain a frequency domain cross-correlation result; the frequency domain cross-correlation result is converted back to the time domain through an inverse fast Fourier transform IFFT to generate a power delay spectrum PDP; the delay peak index is determined in the power delay spectrum PDP, and an estimated open-loop timing advance is obtained based on the peak index; and the estimated open-loop timing advance is converted into an actual open-loop timing advance.

[0103] Specifically, for each RO, the base station delays the original time domain position in sequence. Try to receive the preamble code in time slots and estimate the user's open-loop TA value through the preamble detection algorithm , determine the delay compensation for the user And send the second message msg2 to the user, i.e. the terminal.

[0104] in, , , This is the maximum RTT between the ground terminal in the service cell and the satellite. is the time slot duration in milliseconds (ms). There are many options for the preamble detection algorithm, such as time domain cross-correlation and frequency domain cross-correlation. Taking frequency domain cross-correlation as an example, we briefly introduce how to calculate , the specific calculation process is as follows:

[0105] The base station removes the CP from the obtained time domain pilot signal, performs FFT and de-resource mapping, and finally obtains a length of Frequency domain ZC sequence , is the length of the leading sequence;

[0106] calculate Correlation sequence with all local non-cyclic shift ZC sequences :

[0107]

[0108] in, is the root sequence number, is a ZC sequence without local cyclic shift, and * indicates conjugation.

[0109] For relevant results Execute IFFT to obtain the time domain correlation results and calculate the power delay spectrum PDP;

[0110] Set the detection threshold and divide the entire detection window into several sections with lengths of interval, find the PDP peak index that exceeds the threshold in each interval , is the number of cyclic shifts of the ZC sequence;

[0111] Calculate the user's open-loop TA value:

[0112]

[0113]

[0114] in, is the open-loop timing advance TA, i.e. the actual TA value, is the number of FFT points.

[0115] Delay compensation for users ,in, The delay time slot is the same as the user preamble code. It includes msg1 processing delay, msg2 propagation delay, msg3 sending delay and msg3 propagation delay, and the unit is milliseconds (ms). In other words, if the delay The base station delays the uplink signal of the user by time slot reception.

[0116] The second message msg2 fed back by the base station includes uplink authorization, , RAPID (random access preamble identifier) ​​and time-frequency resources for the third message msg3.

[0117] S23: Determine a timing advance value in a second message according to the open-loop timing advance, and send the second message after the timing advance value is determined to the terminal.

[0118] Specifically, a timing advance adjustment instruction is determined according to the open-loop timing advance of the terminal; the timing advance adjustment instruction is included in a second message msg2, and the msg2 is fed back to the terminal.

[0119] S24: monitor the uplink signal of the terminal, calculate the timing advance adjustment amount and send a timing advance adjustment command to the terminal.

[0120] It can be understood that steps S21 to S23 mainly involve the initial random access phase, in which the satellite base station first broadcasts the synchronization signal block and the main information block so that the terminal can initiate a random access request based on this information. After receiving the random access request from the terminal, the satellite base station performs preamble code detection and estimates the open-loop timing advance based on the detection result. At this time, the second message msg2 sent by the satellite base station contains a timing advance instruction based on the open-loop timing advance. This is the first time synchronization adjustment for the terminal, which is intended to help the terminal adjust the transmission time of its uplink signal to ensure that the signal can accurately reach the satellite base station. Step S24 indicates that the stage after the random access is successful has been entered, that is, the uplink time synchronization maintenance stage has been entered. At this time, the role of the satellite base station is changed to monitoring and maintaining the time synchronization state of the terminal. The satellite base station continuously monitors the uplink signal received from the terminal and calculates its timing advance adjustment amount. At this stage, the base station sends a timing advance adjustment command, which is based on the closed-loop TA mechanism, and the purpose is to further optimize and maintain the time synchronization accuracy of the terminal. During this process, the satellite base station divides the terminals into different user groups, calculates the timing advance adjustment amount according to the timing drift rate and timing drift acceleration of the preset reference point of each user group, and guides each group of terminals to adjust their timing advance amount based on these calculation results.

[0121] After the terminal enters the connection mode, the total timing advance reported by each terminal is received; the satellite base station uses a clustering algorithm to divide the terminal into different user groups according to the total timing advance reported by each terminal and the pre-calculated and stored reference point location information and real-time RTT, wherein each user group corresponds to a reference point, so that the difference between the total timing advance of the terminal in the group and the real-time RTT of the reference point is minimized. The timing advance adjustment is calculated according to the timing drift rate and timing drift acceleration of the preset reference point of each user group; based on the calculation result, each group of terminals is guided to adjust the timing advance. It can be understood that each user group has a reference point, and the timing advance adjustment is corrected according to the timing drift rate and timing drift acceleration at the reference point. Therefore, by implementing delay compensation on the base station side and delaying reception on the terminal side to complete the initial random access, the user grouping strategy is used to improve the calculation method of the timing advance adjustment, and the timing advance change of the terminal is monitored and tracked according to the calculated reference point information, which reduces the requirements for the terminal and also reduces the burden of the base station to maintain the uplink time synchronization of each user, which is conducive to the lightweight satellite base station. By correcting the timing advance adjustment amount according to the timing drift rate and timing drift acceleration at the reference point, the accuracy and stability of uplink time synchronization are improved, thereby effectively reducing the uplink desynchronization rate when facing a large delay and rapidly changing satellite communication environment.

[0122] In one of the embodiments, the method for calculating the timing drift rate and timing drift acceleration of each user group to a preset reference point includes: obtaining the location information of the preset reference point of each user group; calculating the round-trip delay of the preset reference point at each moment in a specific time period; calculating the timing drift rate and timing drift acceleration of the preset reference point in the specific time period based on the round-trip delay to form a time series; and determining the timing drift rate and timing drift acceleration of the terminal in each user group at a specific moment based on the time series.

[0123] In a specific implementation, after the terminal completes the initial random access, it enters the connected mode (RRCCONNECTED), and the satellite base station calculates the total timing advance of each terminal. Group them so that each user group uses the same reference point, e.g. Figure 4 As shown, the reference point is used for the subsequent closed-loop TA update to facilitate the satellite base station to track the TA changes of users in the group.

[0124] The base station knows the initial :

[0125]

[0126] in, represents the total timing advance, Indicates the base station delay compensation value, Indicates the cell-level public timing advance, Represents the timing advance of the user, where the timing advance of the user is the sum of the open-loop TA and the closed-loop TA.

[0127] The process of grouping users can be achieved using clustering algorithms. The specific steps are as follows:

[0128] The base station calculates the RTT of all reference points in the serving cell at this time, using express;

[0129]

[0130] in, and The reference points are and satellites in The location at the moment, is the L2 norm, , is the speed of light.

[0131] At each reference point As the cluster center, calculate each user’s The distance from all cluster centers, i.e., the differential delay, is calculated and assigned to the cluster closest to it, completing the grouping of all users who have successfully accessed random access.

[0132] The calculation of the reference point is completed during the network deployment phase, and the steps are as follows:

[0133] Uniformly select on a low-altitude plane at a certain distance from the ground fixed cell Reference points, such as Figure 5 As shown, the position of each reference point is expressed in Earth-centered Earth-fixed coordinates as ;

[0134] Select evenly within the cell The points represent the terminals, and the location of each terminal is also expressed in Earth-centered Earth-fixed coordinates, and ;

[0135] According to the known orbit information, the real movement of the satellite is simulated, and the RTT from each terminal and each reference point to the satellite at all times during the satellite service of the ground fixed cell is calculated. Furthermore, their timing drift rate is calculated. curve, , , Indicates A reference point from time arrive The delay change rate, in milliseconds per second (ms / s), Indicates from time arrive The delay variation of

[0136] Allocate the reference point with the highest fitting degree to all terminals according to the fitting degree between the terminal timing drift rate curve and the reference point timing drift rate curve;

[0137] If there is no reference point that can be fitted with the terminal timing drift rate curve, increase the number of reference points and go to step A to recalculate until the timing drift rate curve of any terminal in the cell can match a reference point;

[0138] Then the obtained reference point set Stored in the base station, , .

[0139] Specifically, the base station applies different delays to the uplink signal of each terminal, monitors the uplink signal of each terminal, calculates its TA error, and obtains the TA adjustment value. , and correct it according to the reference point of the user group, and then use TAC signaling to adjust the corrected TA value Send to the terminal.

[0140] It can be understood that for each satellite, the reference point within its service cell only needs to be calculated once. This information does not need to be sent to the terminal, avoiding additional signaling overhead. After the satellite base station groups the users, it uses these reference points to track the changes in the user's timing advance TA. By correcting the user's TA adjustment value, the TA error caused by the change in the service link delay is reduced, and the accuracy of TA estimation is improved. Ultimately, in satellite communication scenarios with large delays and rapidly changing delays, the initial establishment and maintenance of uplink time synchronization is achieved based on the existing terminal protocol, thereby reducing the uplink desynchronization rate.

[0141] Figure 5 A schematic diagram of TA error is shown, such as Figure 5 As shown in the figure, TA error is defined as the difference between the actual arrival time of the uplink signal at the base station and the ideal arrival time, expressed as Indicates that the unit is microseconds (us).

[0142] .

[0143] According to the user group's reference point The specific steps for correction are as follows:

[0144] Base station The uplink signal of the user is received at all times. Group of users whose reference points The position coordinates are , the base station estimates that after a period of time time The timing drift rate and timing drift acceleration :

[0145]

[0146]

[0147] in, It is the time it takes for the base station to process the user uplink signal, that is, the time from when the base station receives the user uplink signal to when it sends the TAC.

[0148] Correction based on the timing drift rate and timing drift acceleration of the reference point get :

[0149]

[0150]

[0151] After receiving the TAC, the terminal accumulates the TA adjustment value to update its TA value, and executes TAR in the subsequent communication process to report its current total timing advance to the base station. .

[0152]

[0153] If the terminal's updated TA reaches the maximum value, the base station reports the Adjust the delay compensation value for this user , , and the new Sent to the terminal, the terminal re-accumulates and updates the TA value based on the new open-loop TA:

[0154]

[0155]

[0156] The terminal can perform TAR and report its current total timing advance to the base station at a fixed period. , and also supports irregular reporting to the base station under other necessary circumstances, such as when the terminal is moving, or when the MAC layer receives an indication from the RRC layer to perform TAR.

[0157] If the terminal is moving during the communication process, the base station needs to Re-divide it into The grouping process is similar to the above implementation:

[0158]

[0159] The base station uses the reference point of the new group Follow the above steps to correct the user .

[0160] It can be seen that by performing preamble detection on each possible delayed time slot, the satellite base station can more accurately determine which time slot contains a valid preamble, thereby calculating a more accurate open-loop timing advance. In addition, by continuously monitoring the uplink signal of the terminal and dynamically adjusting the timing advance command based on the timing advance adjustment amount based on the reference point correction, the satellite base station not only improves the accuracy of time synchronization, but also ensures that the challenges brought by the ever-changing propagation delay in satellite communications are effectively managed. This method based on real-time monitoring and adjustment greatly improves the dynamic adaptability and accuracy of timing synchronization, and reduces the risk of data transmission errors and uplink interruptions.

[0161] In a satellite communication scenario, the satellite communication time synchronization method described in the above embodiment is applied, such as Figure 6 As shown, the steps include S31-S39.

[0162] S31. The satellite base station broadcasts the synchronization signal block and the master information block so that the terminal can initiate a random access request based on the synchronization signal block and the master information block. The satellite base station sends system information, such as the cell ID and the information of the synchronization signal block SSB, through a specific broadcast channel so that the terminal can obtain accurate time synchronization and frequency synchronization information. At the same time, the master information block MIB contains parameters such as the frequency band information of the cell, system bandwidth, PHICH configuration and reference signal power, which will help the terminal to correctly parse the data for preliminary synchronization, especially to obtain the cell-level public timing advance parameters for subsequent access.

[0163] S32, the terminal receives the synchronization signal block broadcast by the satellite base station for preliminary synchronization, and decodes the master information block broadcast by the satellite base station to obtain the cell-level common timing advance parameters and time-frequency resources. After obtaining and decoding the synchronization signal block, the terminal adjusts the synchronization of its local oscillator with the satellite, and understands the basic configuration of the base station by decoding the MIB. In addition, by further decoding the system information block SIB1, the terminal obtains the cell-level common timing advance parameters and random access time-frequency resources RO, which are crucial for subsequent random access.

[0164] S33, select the preamble code and time-frequency resources in combination with the cell-level common timing advance parameter, initiate a random access request, and send a first message to the satellite base station. The terminal selects the appropriate preamble code and time-frequency resources according to the cell-level common timing advance parameter obtained from SIB1, and sends the first message msg1 after adjusting the time advance. This ensures the correct alignment of the transmission time and the receiving window, thereby increasing the possibility of successful access.

[0165] S34. The satellite base station receives the preamble in the random access request sent by the terminal, and detects the preamble in parallel in multiple windows for each possible delayed time slot to estimate the open-loop timing advance. The satellite base station receives the random access request (msg1) from the terminal, which includes a preamble selected from 64 available preambles. The base station receives the preamble in the original time slot, opens multiple preamble detection windows, and detects the preamble in parallel in multiple windows to cover the impact caused by large delays and delay variations. The base station uses the preamble detection algorithm to estimate the open-loop timing advance of each terminal.

[0166] S35, calculate the delay compensation according to the open-loop timing advance and send the second information to the terminal. The base station determines the TA instruction according to the open-loop timing advance estimated in step S33, calculates the appropriate delay compensation based on the delayed time slot, and sends the second message msg2 to the terminal, including the uplink authorization information and the TA instruction, to prepare for the next msg3.

[0167] S36, delay receiving the second message from the satellite base station, the second message includes the timing advance instruction fed back according to the detection result of the preamble code. Specifically, the terminal determines the opening time of the RAR receiving window according to the minimum RTT in the cell, determines the duration of the RAR receiving window according to the RTT range in the cell, and receives the second message sent by the satellite base station in the RAR receiving window, wherein the message includes the timing advance instruction and uplink authorization information. The second message includes the timing advance adjustment instruction, i.e., the TA instruction, and the uplink authorization information, and the uplink authorization information includes the uplink authorization, RAPID, and the time-frequency resources for msg 3. After receiving msg2 containing the time command, the terminal updates the local timing advance according to the command to ensure that its uplink signal can be accurately aligned with the receiving window of the base station.

[0168] S37, adjust the uplink timing synchronization according to the timing advance instruction, and send a third message to the satellite base station through the physical uplink shared channel to complete the subsequent access steps and achieve initial random access. After receiving the TA instruction from the base station, the terminal adjusts the time synchronization of its uplink transmission according to the new TA value, and sends a third message (msg3) through the physical uplink shared channel (PUSCH), including its identity information and any necessary uplink data.

[0169] S38. Periodically report the total timing advance to the satellite base station, or report the total timing advance when instructed by the satellite base station. The terminal reports its total timing advance through the uplink channel periodically or as required by the base station. This value reflects the current time adjustment state, which includes the base station delay compensation value, the cell-level common timing advance and the user's timing advance, where the user's timing advance is the sum of the open-loop TA and the closed-loop TA. Such reports help the base station optimize the time adjustment strategy for all users in the entire cell to ensure efficient and stable communication.

[0170] S39. The satellite base station monitors the uplink signal of the terminal, calculates the timing advance adjustment amount and sends a timing advance adjustment command to the terminal.

[0171] S310. The terminal adjusts the timing advance amount according to the timing advance adjustment instruction sent by the satellite base station.

[0172] Specifically, after the terminal enters the connection mode, the satellite base station receives the total timing advance reported by each terminal; based on the total timing advance reported by each terminal and the pre-calculated and stored reference point location information and real-time RTT, a clustering algorithm is used to divide the terminal into different user groups, wherein each user group corresponds to a reference point, so that the difference between the total timing advance of the terminal in the group and the real-time RTT of the reference point is minimized. The timing advance adjustment amount is corrected for the timing drift rate and timing drift acceleration of the preset reference point of each user group; based on the calculation result, each group of terminals is guided to adjust the timing advance amount, and when calculating the error, the error between the actual arrival time and the expected arrival time is calculated according to the uplink signal of the terminal monitored by the base station, and the TA adjustment value is calculated based on the error, and the timing advance value of the terminal is updated again through the corresponding signaling. After the terminal receives the timing advance adjustment instruction sent by the satellite base station based on the timing advance adjustment value, it will adjust the timing advance amount according to the instruction to maintain the accuracy of time synchronization.

[0173] In one embodiment of the present application, a satellite communication uplink time synchronization device is also provided. Figure 7 As shown, the device comprises:

[0174] The analysis module 701 is used to receive the synchronization signal block broadcast by the satellite base station for preliminary synchronization, and decode the main information block broadcast by the satellite base station to obtain the cell-level public timing advance parameters and time-frequency resources; the analysis module 701 is responsible for preliminary signal synchronization and extracting key information from the signal broadcast by the satellite base station, including timing advance parameters and time-frequency resources, to provide the terminal device with necessary synchronization baseline and access resource information.

[0175] The access module 702 is used to select the preamble code and time-frequency resources in combination with the cell-level common timing advance parameters, initiate a random access request, and send a first message to the satellite base station; the access module 702 uses the information obtained by the analysis module 701 to select a suitable preamble code and time-frequency resource RO, thereby effectively initiating a random access request, and sending the first message to the satellite base station to start the uplink communication process.

[0176] The receiving module 703 is used to delay the reception of a second message from the satellite base station, wherein the second message includes a timing advance adjustment instruction fed back based on the detection result of the preamble code; and receive a second message fed back by the satellite base station during a random access process, wherein the message includes a timing advance instruction based on the preamble code detection in the first message, thereby providing a basis for adjusting the timing.

[0177] The adjustment module 704 is used to adjust the uplink timing synchronization according to the timing advance instruction, and send a third message to the satellite base station through the physical uplink shared channel; the adjustment module 704 finely adjusts the uplink timing synchronization according to the received adjustment instruction to ensure that the communication synchronization between the terminal and the satellite is accurately aligned, and then sends the third message through the physical uplink shared channel to complete the access process.

[0178] In general, Figure 7 The device shown solves the delay variation problem caused by the high-speed movement of the satellite by accurately adjusting the sending timing, thereby ensuring the real-time and accuracy of communication; through reasonable time-frequency resource allocation and preamble code selection, it effectively manages and optimizes the network load and spectrum resource usage, thereby improving the network service quality and user experience; by dynamically adjusting the synchronization parameters, the system can adjust operations according to the actual communication environment, thereby improving the system's adaptability and stability.

[0179] In another embodiment of the present application, a satellite communication uplink time synchronization device is also provided. Figure 8 As shown, the device comprises:

[0180] The broadcast module 801 is used to broadcast the synchronization signal block and the main information block so that the terminal can initiate a random access request based on the synchronization signal block and the main information block; the broadcast module 801 is responsible for broadcasting the synchronization signal block and the main information block to the terminal, and these information blocks contain all necessary data so that the terminal can correctly initiate a random access request based on these data.

[0181] The detection module 802 is used to receive the preamble code in the random access request sent by the terminal, and for each possible delay time slot, detect the preamble code in parallel in multiple windows to estimate the open-loop timing advance; the detection module 802 receives the preamble code in the random access request from the terminal, opens multiple preamble detection windows, and performs precise parallel detection of the preamble code to estimate the open-loop timing advance to ensure the accuracy of time synchronization.

[0182] The sending module 803 is used to determine the timing advance value in the second message according to the open-loop timing advance, and send the second information after the timing advance value is determined to the terminal; the sending module 803 determines the timing advance value according to the detection result of the preamble code and the estimated open-loop timing advance, and then sends the second message containing the timing advance instruction back to the terminal.

[0183] The adjustment module 804 is used to monitor the uplink signal of the terminal, calculate the timing advance adjustment amount and send a timing advance adjustment command to the terminal; the monitoring module 804 monitors the uplink signal of the terminal, calculates the timing advance adjustment amount, and sends a timing advance command based on these errors to further correct and optimize the uplink timing.

[0184] Understandably, Figure 8 The device shown ensures that the uplink synchronization is always in the optimal state through real-time monitoring and dynamic estimation, and responds to the rapid changes in signal propagation delay in a timely manner; accurate preamble code processing and delay compensation calculation enable the system to process random access requests more quickly and efficiently, reducing errors and retry rates; through continuous monitoring and adjustment, the communication link is maintained in the optimal state, greatly improving the reliability of the link and the continuity of communication.

[0185] Please refer to the following Fig. 9 , which shows a schematic diagram of an electronic device provided by some embodiments of the present application. Fig. 9 As shown, the electronic device 2 includes: a processor 200, a memory 201, a bus 202 and a communication interface 203, wherein the processor 200, the communication interface 203 and the memory 201 are connected via the bus 202; the memory 201 stores a computer program that can be run on the processor 200, and when the processor 200 runs the computer program, the time synchronization method for satellite communication provided in any of the aforementioned embodiments of the present application is executed.

[0186] The memory 201 may include a high-speed random access memory (RAM), and may also include a non-volatile memory, such as at least one disk memory. The communication connection between the system network element and at least one other network element is realized through at least one communication interface 203 (which may be wired or wireless), and the Internet, wide area network, local area network, metropolitan area network, etc. may be used.

[0187] The bus 202 may be an ISA bus, a PCI bus, or an EISA bus, etc. The bus may be divided into an address bus, a data bus, a control bus, etc. The memory 201 is used to store programs, and the processor 200 executes the programs after receiving execution instructions. The control method disclosed in any implementation of the above-mentioned embodiment of the present application may be applied to the processor 200, or implemented by the processor 200.

[0188] The processor 200 may be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method can be completed by the hardware integrated logic circuit or software instructions in the processor 200. The above processor 200 can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. The methods, steps and logic block diagrams disclosed in the embodiments of the present application can be implemented or executed. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor. The steps of the method disclosed in the embodiments of the present application can be directly embodied as a hardware decoding processor to be executed, or the hardware and software modules in the decoding processor can be executed. The software module can be located in a mature storage medium in the field such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The storage medium is located in the memory 201, and the processor 200 reads the information in the memory 201 and completes the steps of the satellite communication time synchronization method in combination with its hardware.

[0189] An embodiment of the present application also provides a computer-readable storage medium corresponding to the satellite communication time synchronization method provided in the aforementioned embodiment, on which a computer program is stored. When the computer program is executed by a processor, it will execute the satellite communication time synchronization method provided in any of the aforementioned embodiments.

[0190] In addition, examples of the computer-readable storage medium may also include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other optical or magnetic storage media, which are not listed here one by one.

[0191] In addition, an embodiment of the present application further provides a computer program product, including a computer program, which, when executed by a processor, implements the satellite communication time synchronization method provided by any of the aforementioned embodiments.

[0192] Those skilled in the art will appreciate that the various component embodiments of the present application may be implemented in hardware, or in software modules running on one or more processors, or in a combination thereof. Those skilled in the art will appreciate that a microprocessor or digital signal processor (DSP) may be used in practice to implement some or all functions of some or all components of the virtual machine creation device according to the embodiments of the present application.

[0193] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A time synchronization method for satellite communication, characterized in that: Applied to a terminal, the method comprises: receiving a synchronization signal block broadcasted by a satellite base station for preliminary synchronization, and decoding a master information block broadcasted by the satellite base station to obtain a cell-level common timing advance parameter and time-frequency resources; selecting a preamble code and time-frequency resources in combination with the cell-level common timing advance parameter, initiating a random access request, and sending a first message to the satellite base station; delaying reception of a second message from the satellite base station, wherein the second message includes a timing advance instruction fed back according to a detection result of the preamble code; adjusting uplink timing synchronization according to the timing advance instruction, and sending a third message to the satellite base station through a physical uplink shared channel to complete subsequent access steps and implement initial random access; After the initial random access is achieved, the method further includes: periodically reporting the total timing advance to the satellite base station, or reporting the total timing advance when instructed by the satellite base station, so as to support the satellite base station in grouping users and correcting the timing advance adjustment amount for the timing drift rate and timing drift acceleration of the preset reference point of each user group; Receive a timing advance adjustment command determined by the satellite base station based on the timing advance adjustment amount; including receiving a new open-loop timing advance sent by the satellite base station, wherein the new open-loop timing advance is calculated after the satellite base station adjusts the delay compensation value of the satellite base station for the user according to the total timing advance of each terminal when the updated timing advance of each terminal reaches a maximum value.

2. The satellite communication time synchronization method according to claim 1, characterized in that: The delaying receiving a second message from the satellite base station comprises: Determine the opening time of the RAR receiving window based on the minimum RTT in the cell; Determine the duration of the RAR receiving window according to the RTT range within the cell; A second message sent by a satellite base station is received in the RAR receiving window, wherein the message includes a timing advance instruction and uplink authorization information.

3. A time synchronization method for satellite communication, characterized in that: Applied to a satellite base station, the method comprises: Broadcasting a synchronization signal block and a master information block so that a terminal initiates a random access request according to the synchronization signal block and the master information block; receiving a preamble in a random access request sent by the terminal, and detecting the preamble in parallel in a plurality of windows for each possible delay time slot to estimate an open-loop timing advance; Determine a timing advance value in a second message according to the open-loop timing advance, and send the second message after determining the timing advance value to the terminal; Monitoring an uplink signal of the terminal, calculating a timing advance adjustment amount and sending a timing advance adjustment command to the terminal; The calculating the timing advance adjustment amount and sending the timing advance adjustment command to the terminal includes: After the terminal enters the connection mode, receiving the total timing advance reported by each terminal; The users are grouped according to the total timing advance of each terminal, and the timing advance adjustment amount is corrected according to the timing drift rate and timing drift acceleration of the preset reference point of each user group; Determine a timing advance adjustment command based on the timing advance adjustment amount, and send the timing advance adjustment command to the terminal; This includes adjusting the satellite base station's delay compensation value for the user according to the total timing advance of each terminal when the updated timing advance of each terminal reaches a maximum value, calculating a new open-loop timing advance, and sending the new open-loop timing advance to the corresponding terminal.

4. The satellite communication time synchronization method according to claim 3, characterized in that: The user grouping according to the total timing advance of each terminal includes: According to the total timing advance reported by each terminal and the pre-calculated and stored reference point location information and real-time RTT, the terminals are divided into different user groups, where each user group corresponds to a reference point, so that the difference between the total timing advance of the terminals in the group and the real-time RTT of the reference point is minimized.

5. The satellite communication time synchronization method according to claim 3, characterized in that: The method for calculating the timing drift rate and timing drift acceleration of the preset reference point of each user group includes: Obtaining location information of a preset reference point for each user group; Calculating the round trip delay of the preset reference point at each moment in a specific time period; Calculating the timing drift rate and timing drift acceleration of the preset reference point within a specific time period according to the round-trip delay to form a time series; The timing drift rate and the timing drift acceleration of the terminals in each user group at a specific moment are determined according to the time series.

6. A time synchronization device for satellite communication, characterized in that: The device comprises: A parsing module, configured to receive a synchronization signal block broadcasted by a satellite base station for preliminary synchronization, and decode a master information block broadcasted by the satellite base station to obtain a cell-level common timing advance parameter and time-frequency resources; An access module, configured to select a preamble and time-frequency resources in combination with the cell-level common timing advance parameter, initiate a random access request, and send a first message to the satellite base station; A receiving module, configured to delay receiving a second message from the satellite base station, wherein the second message includes a timing advance instruction fed back according to a detection result of the preamble code; An adjustment module, configured to adjust uplink timing synchronization according to the timing advance instruction, and send a third message to the satellite base station through a physical uplink shared channel to complete subsequent access steps and implement initial random access; A reporting module, configured to periodically report the total timing advance to the satellite base station after the initial random access is implemented, or report the total timing advance when instructed by the satellite base station, so as to support the satellite base station in grouping users and correct the timing advance adjustment amount for the timing drift rate and timing drift acceleration of a preset reference point of each user group; The receiving module is also used to receive a timing advance adjustment command determined by the satellite base station based on the timing advance adjustment amount; this includes receiving a new open-loop timing advance amount sent by the satellite base station, and the new open-loop timing advance amount is calculated after the satellite base station adjusts the delay compensation value of the satellite base station for the user according to the total timing advance amount of the time synchronization device of each satellite communication when the timing advance amount updated by the time synchronization device of each satellite communication reaches a maximum value.

7. A time synchronization device for satellite communication, characterized in that: The device comprises: A broadcast module, used for broadcasting a synchronization signal block and a master information block, so that the terminal initiates a random access request according to the synchronization signal block and the master information block; A detection module, configured to receive a preamble in a random access request sent by the terminal, and detect the preamble in parallel in multiple windows for each possible delay time slot to estimate an open-loop timing advance; A sending module, configured to determine a timing advance value in a second message according to the open-loop timing advance value, and send the second message after determining the timing advance value to the terminal; An adjustment module, configured to monitor an uplink signal of the terminal, calculate a timing advance adjustment amount and send a timing advance adjustment command to the terminal; The calculating the timing advance adjustment amount and sending the timing advance adjustment command to the terminal includes: After the terminal enters the connection mode, receiving the total timing advance reported by each terminal; The users are grouped according to the total timing advance of each terminal, and the timing advance adjustment amount is corrected according to the timing drift rate and timing drift acceleration of the preset reference point of each user group; Determine a timing advance adjustment command based on the timing advance adjustment amount, and send the timing advance adjustment command to the terminal; This includes adjusting the delay compensation value of the satellite communication time synchronization device for the user according to the total timing advance of each terminal when the updated timing advance of each terminal reaches the maximum value, calculating the new open-loop timing advance, and sending the new open-loop timing advance to the corresponding terminal.

8. An electronic device, comprising a memory and a processor, characterized in that: The memory stores computer-readable instructions, which, when executed by the processor, enable the processor to execute the method described in any one of claims 1-2 or 3-5.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 2 or 3 to 5 is implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the method of any one of claims 1 to 2 or 3 to 5 is implemented.

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