Uplink and downlink signal synchronization method and device, equipment and storage medium

Abstract

Provided are an uplink and downlink signal synchronization method, apparatus and device, and a storage medium, the method comprising: sending a random access request to a satellite base station, the random access request being a message compensated by using a first time-frequency compensation value, the first time-frequency compensation value initially using an initial time-frequency compensation value; receiving an RAR sent by the satellite base station, and determining a second time-frequency offset compensation value by using the first time-frequency compensation value and an uplink time-frequency offset value carried in the RAR; sending an RRC connection request to the satellite base station, wherein the RRC connection request is a message compensated by using the second time-frequency offset compensation value; if the connection request fails, determining an additional time offset adjustment amount; updating the first time frequency compensation value according to the initial time frequency offset compensation value and the additional time offset adjustment amount, and re-triggering random access according to the updated first time frequency compensation value; the dependence on the prefabricated ephemeris is reduced, and the receiving performance and the access success rate of the terminal under the dynamic satellite channel are remarkably improved.

Description

Technical Field

[0001] This application relates to the field of wireless communication technology, and in particular to an uplink and downlink signal synchronization method, apparatus, device, and storage medium. Background Technology

[0002] Many existing studies on satellite-to-ground synchronization focus on how to pre-calculate path delay and Doppler shift using the relative position and velocity between the ground receiving station and the satellite. However, if the synchronization between the satellite base station and the terminal is achieved solely by inferring the satellite-to-ground signal delay and uplink / downlink Doppler shift using pre-obtained ephemeris information, problems such as unstable synchronization, large residual time and frequency offset, and high accuracy requirements for pre-made ephemeris and the algorithms for calculating time and frequency offset from pre-made ephemeris will arise. Summary of the Invention

[0003] This application provides an uplink and downlink signal synchronization method, apparatus, device, and storage medium, which achieves highly robust satellite-to-ground synchronization, effectively reduces dependence on pre-prepared ephemeris, significantly reduces residual time-frequency offset, and thus significantly improves the terminal's reception performance and access success rate under dynamic satellite channels.

[0004] In a first aspect, this application provides an uplink / downlink signal synchronization method, applied to a terminal UE, comprising: Send a random access request to the satellite base station. The random access request is a message compensated by a first time-frequency compensation value. The first time-frequency compensation value is initially determined based on ephemeris information. Receive the Random Access Response (RAR) sent by the satellite base station, and determine the second time-frequency offset compensation value using the first time-frequency compensation value and the uplink time-frequency offset value carried in the RAR; Send an RRC connection request to the satellite base station, wherein the RRC connection request is a message compensated using a second time-frequency offset compensation value; If the connection request fails, determine the additional time offset adjustment; The first time-frequency compensation value is updated based on the initial time-frequency offset compensation value and the additional time-frequency adjustment amount, and random access is retried based on the updated first time-frequency compensation value.

[0005] In one or more possible embodiments, determining an additional time offset adjustment if the connection request fails includes: If the connection request fails, the additional time offset adjustment is determined based on the number of times random access is triggered and the preset time offset step size.

[0006] In one or more possible embodiments, the initial time-frequency offset compensation value is determined in the following manner: Determine the upper planetary ephemeris frequency offset based on the pre-stored ephemeris information; The path delay is determined based on the distance between the satellite base station and the terminal; The initial delay compensation value is determined based on twice the path delay and the preset delay compensation value; The initial time-frequency compensation value is determined based on the initial time delay compensation value and the upper planetary ephemeris frequency offset.

[0007] In one or more possible embodiments, it also includes: If the connection request is confirmed to be successful, the second time-frequency offset compensation value is used as the uplink time-frequency adjustment amount, and the uplink signal is compensated according to the uplink time-frequency adjustment amount.

[0008] In one or more possible embodiments, compensating the uplink signal according to the uplink time-frequency adjustment includes: Receive the closed-loop time-frequency offset command sent by the satellite base station, wherein the closed-loop time-frequency offset command carries the closed-loop time-frequency offset; The uplink signal is compensated based on the closed-loop time-frequency offset and the uplink time-frequency adjustment.

[0009] Secondly, this application provides a downlink signal synchronization method, applied to a terminal UE, comprising: Receive downlink signals broadcast by satellite base stations and determine the first SSB estimated frequency offset based on the first synchronization signal block (SSB) in the downlink signals; Based on the frequency offset estimated by the first SSB, the downlink signal is initially compensated for to obtain the compensated downlink signal; The main information block (MIB) in the compensated downlink signal is parsed, and the second SSB and the corresponding estimated frequency offset of the second SSB are obtained from the compensated downlink signal. When it is confirmed that the MIB parsing is successful, there is a consecutive preset number of second SSBs, and the estimated frequency offset of the second SSBs meets the preset frequency offset compensation conditions, the frequency offset compensation value is determined based on the estimated frequency offset of the second SSBs. Frequency offset compensation is performed on the compensated downlink signal based on the frequency offset compensation value.

[0010] In one or more possible embodiments, the preset frequency offset compensation condition is that the frequency offset difference between every two estimated frequency offsets of the second SSB is less than a preset threshold.

[0011] In one or more possible embodiments, after determining the frequency offset compensation value based on the second SSB estimated frequency offset, the method further includes: The SIB estimated frequency offset is determined based on the System Information Block (SIB) in the downlink signal; The frequency offset compensation value is optimized based on the frequency offset estimated by the SIB to determine the optimized frequency offset compensation value.

[0012] In one or more possible embodiments, it also includes: If the second SSB cannot be detected, the transmission frequency offset change is determined based on the ephemeris information; The downlink signal is compensated based on the transmission frequency offset change.

[0013] In one or more possible embodiments, it also includes: The beam type covering the UE beam is determined to be an unrestricted beam; During the period when the second SSB cannot be detected, the change in transmission delay is determined based on ephemeris information; The downlink signal is compensated based on the change in transmission delay.

[0014] In one or more possible embodiments, prior to parsing the Master Information Block (MIB) in the compensated downlink signal, the method further includes: Obtain the primary synchronization signal (PSS) from the compensated downlink signal; The PSS correlation peaks in multiple time slots are continuously detected. When it is determined that the detected PSS correlation peaks meet the preset time domain interval conditions, the main information block (MIB) in the SSB is parsed. The time-domain interval conditions include: the first symbol number of PSS-related peak intervals within the same time slot, and the second symbol number of PSS-related peak intervals between adjacent time slots.

[0015] Thirdly, this application provides an uplink signal synchronization device, applied to a terminal UE, comprising: The random access sending module sends a random access request to the satellite base station. The random access request is a message compensated by a first time-frequency compensation value. The first time-frequency compensation value is initially determined based on ephemeris information. The second time-frequency offset compensation value determination module is used to receive the random access response (RAR) sent by the satellite base station and determine the second time-frequency offset compensation value using the initial time-frequency compensation value and the uplink time-frequency offset value carried in the RAR. The RRC connection request sending module is used to send an RRC connection request to the satellite base station. The RRC connection request is a message compensated using a second time-frequency offset compensation value. The additional time offset adjustment determination module is used to determine the additional time offset adjustment if the connection request fails. The first time-frequency compensation value determination module is used to update the first time-frequency compensation value according to the initial time-frequency offset compensation value and the additional time offset adjustment amount, and to re-trigger random access according to the updated first time-frequency compensation value.

[0016] Fourthly, this application provides a downlink signal synchronization device applied to a terminal UE, comprising: The first SSB estimated frequency offset determination module is used to receive the downlink signal broadcast by the satellite base station and determine the first SSB estimated frequency offset based on the first synchronization signal block SSB in the downlink signal; The initial compensation module is used to perform initial frequency offset compensation on the downlink signal based on the frequency offset estimated by the first SSB, so as to obtain the compensated downlink signal. The MIB parsing module is used to parse the main information block (MIB) in the compensated downlink signal and obtain the second SSB and the corresponding estimated frequency offset of the second SSB from the compensated downlink signal. The frequency offset compensation value determination module is used to determine the frequency offset compensation value based on the estimated frequency offset of the second SSB when the MIB parsing is successful, there is a consecutive preset number of second SSBs, and the estimated frequency offset of the second SSBs meets the preset frequency offset compensation conditions. The downlink signal compensation module is used to perform frequency offset compensation on the compensated downlink signal according to the frequency offset compensation value.

[0017] Fifthly, this application provides an electronic device, the electronic device comprising: At least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform a method as described in the first aspect or the second aspect.

[0018] Sixthly, this application provides a computer storage medium storing a computer program for causing a computer to perform any of the methods described in the first or second aspect.

[0019] According to the uplink and downlink signal synchronization method, apparatus, device and storage medium provided in this application, highly robust satellite-to-ground synchronization is achieved, effectively reducing the dependence on pre-made ephemeris and significantly reducing residual time and frequency offset, thereby significantly improving the terminal's reception performance and access success rate under dynamic satellite channels. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application, and do not constitute an undue limitation of this application.

[0021] Figure 1 This is a schematic diagram of an application environment provided according to an embodiment; Figure 2 This is a flowchart of an uplink signal synchronization method according to an embodiment; Figure 3This is a flowchart of a downlink signal synchronization method according to an embodiment; Figure 4 This is a schematic diagram of uplink and downlink time-domain synchronization according to an embodiment; Figure 5 This is a schematic diagram of an uplink signal synchronization device according to an embodiment; Figure 6 This is a schematic diagram of a downlink signal synchronization device according to an embodiment; Figure 7 This is a schematic diagram of an electronic device according to an embodiment; Figure 8 This is a schematic diagram of a computer-readable storage medium provided according to an embodiment. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0023] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented in orders other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0024] Furthermore, in the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of this application, "multiple" means two or more.

[0025] In low-Earth orbit (LEO) satellite communication systems, terminals need to operate for extended periods in environments with significant interference and attenuation. Furthermore, the high-speed relative motion between the terminal and the satellite generates substantial Doppler frequency shift and path transmission delay at the receiver. Transmission delay disrupts subcarrier orthogonality, causing inter-symbol and inter-subcarrier interference at the receiver, necessitating complex timing synchronization algorithms. Frequency offset leads to severe inter-subcarrier interference and phase rotation. In real-world scenarios, time and frequency offsets coexist, and their combined effect causes a rapid increase in the system's bit error rate. Therefore, in OFDM satellite internet systems, accurate and stable satellite-to-ground time and frequency offset synchronization at the terminal is crucial.

[0026] Current research on satellite-to-ground synchronization primarily focuses on how to pre-calculate path delay and Doppler shift using the relative position and velocity between the ground receiving station and the satellite. However, if synchronization between the satellite base station and the terminal is achieved solely by inferring satellite-to-ground signal delay and uplink / downlink Doppler shift using pre-obtained ephemeris information, problems arise such as unstable synchronization, large residual time and frequency offsets, and high accuracy requirements on pre-prepared ephemeris and the algorithms for calculating time and frequency offsets from pre-prepared ephemeris. Therefore, a stable satellite-to-ground synchronization method is needed that can ensure uninterrupted uplink and downlink signal synchronization across the entire arc, reduce reliance on pre-prepared ephemeris, and minimize residual time and frequency offsets, thereby improving reception performance.

[0027] Based on the above problems, this application proposes an uplink and downlink signal synchronization method, apparatus, device and storage medium. It uses SSB (Synchronization Signal Block) and SIB (System Information Block) to estimate the frequency offset and the lower planetary ephemeris frequency offset for downlink signal synchronization, presets the uplink frequency offset to achieve uplink frequency offset pre-compensation, and performs uplink time offset initial synchronization by pre-compensating twice the path delay on the uplink after the downlink signal synchronization is completed.

[0028] The terminal devices involved in the embodiments of this application can be devices that provide voice and / or data connectivity to users, handheld devices with wireless connectivity, or other processing devices connected to a wireless modem. The names of the terminal devices may differ in different systems; for example, in a 5G system, a terminal device can be called User Equipment (UE). Wireless terminal devices can communicate with one or more core networks (CNs) via a Radio Access Network (RAN). Wireless terminal devices can be mobile terminal devices, such as mobile phones (or "cellular" phones) and computers with mobile terminal devices, for example, portable, pocket-sized, handheld, computer-embedded, or vehicle-mounted mobile devices that exchange voice and / or data with the RAN. Examples include Personal Communication Service (PCS) phones, cordless phones, Session Initiated Protocol (SIP) phones, Wireless Local Loop (WLL) stations, and Personal Digital Assistants (PDAs). Wireless terminal equipment can also be referred to as a system, subscriber unit, subscriber station, mobile station, mobile station, remote station, access point, remote terminal, access terminal, user terminal, user agent, or user device, but this application does not limit the terminology.

[0029] like Figure 1 The diagram shown is a schematic of an application environment according to an embodiment of this application. The application environment includes multiple satellites located on the orbital plane in a satellite communication system and terminals communicating with the satellites. For example, it includes satellites 102_1, 102_2, ..., 102_N in the figure, where N is a positive integer. In practice, the size of N is determined according to specific needs and scenarios. Terminal 101 can communicate with other destination terminals 103 through satellites.

[0030] This application provides an uplink signal synchronization method, applied to a terminal UE, specifically as follows: Figure 2 As shown, it includes: Step 201: Send a random access request to the satellite base station. The random access request is a message compensated by a first time-frequency compensation value. The first time-frequency compensation value is initially the initial time-frequency compensation value. In one or more possible embodiments, the random access request is determined based on the System Information Block (SIB) in the downlink signal broadcast by the satellite base station; the initial time-frequency offset compensation value is determined as follows: the uplink ephemeris frequency offset is determined based on the pre-stored ephemeris; the path delay is determined based on the distance between the satellite base station and the terminal; the initial delay compensation value is determined based on twice the path delay and a preset delay compensation value; the initial time-frequency compensation value is determined based on the initial delay compensation value and the uplink ephemeris frequency offset; specifically, if the path delay is not compensated during downlink synchronization when the terminal sends the random access request after compensation by the first time-frequency compensation value, twice the path delay needs to be compensated during uplink to ensure uplink time domain synchronization; at the same time, to prevent uplink time offset over-compensation, premature transmission of PRACH (Physical Random Access Channel), and time offset of MSG3 (i.e., RRC connection request) across the preamble (channel preamble used for access), a preset delay compensation value needs to be set to forcibly delay the transmission of the preamble. The preset delay compensation value is generally set to 3µs.

[0031] Step 202: Receive the Random Access Response (RAR) sent by the satellite base station, and determine the second time-frequency offset compensation value using the first time-frequency compensation value and the uplink time-frequency offset value carried in the RAR. Step 203: Send an RRC connection request to the satellite base station. The RRC connection request is a message compensated using the second time-frequency offset compensation value. In one or more possible embodiments, the satellite base station receives the random access signal sent by the terminal and returns a random access response (RAR), which carries an uplink frequency offset value and an uplink time offset value. The terminal determines a second time-frequency offset compensation value based on the uplink frequency offset value, the uplink time offset value and the determined first time-frequency compensation value carried in the RAR, and then compensates the RRC connection request according to the second time-frequency offset compensation value, and sends the compensated RRC connection request to the satellite base station.

[0032] Step 204: If the connection request fails, determine the additional time offset adjustment. In one or more possible embodiments, after sending the initial RRC connection request (MSG3), the terminal will start a response timer of a preset duration and wait to receive the RRC connection request success message (MSG4) sent by the satellite base station. If the MSG4 is not received correctly before the timer expires, the uplink synchronization and access process is determined to have failed. At this time, although the terminal has applied the time-frequency offset carried in the random access response (RAR) for compensation, the base station has failed to demodulate MSG3 successfully, which means that the uplink synchronization has not yet been completed. In this case, the terminal will terminate the current process, clear the uplink time-frequency offset value fed back in the existing RAR, and re-initiate the complete random access process starting from the transmission of the physical random access channel (PRACH) preamble (random access request) until the MSG4 is successfully received, confirming that the uplink synchronization and connection establishment are complete.

[0033] In one or more possible embodiments, since the satellite base station determines the uplink timing offset of PRACH by detecting the correlation peak, but a PRACH signal is composed of repeated preambles, the timing offset sent by the satellite base station to the terminal is always a positive value within a preamble length range. After receiving the uplink timing offset value contained in the RAR, the terminal can only mechanically interpret it as a "positive delay instruction". Therefore, if the terminal itself is late in timing (affected by ephemeris accuracy, satellite motion, crystal oscillator jitter, etc.), compensating for the uplink timing offset value contained in the RAR will cause MSG3 to be late in the time domain by one or even multiple preamble lengths, thereby preventing the satellite base station from correctly demodulating MSG3 within the expected reception window, ultimately leading to uplink synchronization failure.

[0034] In one or more possible embodiments, to avoid the problem of uplink timing offset crossing the preamble, this application determines an additional time offset adjustment amount by using the number of times random access is triggered and a preset time offset step size to compensate for the random access request. Specifically, when the terminal sends an initial RRC connection request and fails to receive a message from the satellite base station in a timely manner, the initial connection request is determined to have failed, i.e., the uplink synchronization fails. At this time, the terminal does not immediately repeat the process using the same second time-frequency offset compensation value, but adjusts the first time-frequency compensation value and the second time-frequency offset compensation value. Specifically, based on the number of times random access is triggered (n) and a preset time offset step size (ΔTa), an additional time offset adjustment amount is calculated. The specific calculation formula for the additional time offset adjustment amount is as follows: This formula ensures that the timing adjustment direction of each retransmission attempt changes alternately (positive and negative) and the adjustment magnitude gradually increases, thereby systematically searching for the correct uplink transmission opportunity on the time axis.

[0035] Step 205: Update the first time-frequency compensation value according to the initial time-frequency offset compensation value and the additional time-frequency adjustment amount, and re-trigger random access according to the updated first time-frequency compensation value; In one or more possible embodiments, after the initial connection request fails, the terminal clears the uplink time-frequency offset value previously received and applied in the random access response (RAR) (because the uplink time-frequency offset value has been proven to have failed to achieve effective synchronization). Subsequently, the terminal adds the additional time offset adjustment amount calculated above to the initial time-frequency compensation value to form the time-frequency compensation value for the next random access (i.e., the first time-frequency compensation value) until it receives the confirmation response of the RRC connection request, and finally determines that the satellite base station and the terminal have successfully established a connection. Specifically, the preset time offset step size is ΔTa. In the second attempt after the first connection failure: the retransmission number n = 1, and the terminal calculates an additional time offset adjustment of -ΔTa. This means the terminal will send a second random access request ΔTa earlier than the initial time-frequency compensation value. If the second attempt also fails, a random access request is sent. In this case, the retransmission number n = 2, and the new additional time offset adjustment is 2ΔTa. This time, the terminal will delay sending the random access request by 2ΔTa compared to the initial time-frequency compensation value, and the adjustment magnitude is ΔTa larger than the first adjustment. This process will continue to loop until the terminal successfully receives a successful response to the connection request, signifying successful uplink synchronization and completion of random access. This method, by introducing active probing with alternating directions and increasing magnitude, effectively breaks out of the vicious cycle caused by the terminal lingering in the error range due to the limited uplink time-frequency offset value fed back by the satellite base station. This greatly improves the success rate of random access and the robustness of uplink synchronization in scenarios with large initial timing errors or high-speed dynamics.

[0036] In one or more possible embodiments, if the connection request is confirmed to be successful, the second time-frequency offset compensation value is used as the uplink time-frequency adjustment amount, and the uplink signal is compensated according to the uplink time-frequency adjustment amount. Specifically, at this time, the uplink frequency offset adjustment amount is the sum of the uplink ephemeris frequency offset and the frequency offset carried by the RAR, and the uplink time offset adjustment amount is the sum of twice the path delay, the fixed post-adjustment preset delay compensation value, the additional time offset adjustment amount, and the time offset carried by the RAR. The terminal locks this calculated value as the reference parameter of the uplink transmitter, and compensates the subsequent uplink signals (such as RRC connection establishment completion messages and service data) accordingly, thereby stably maintaining uplink synchronization in the connected state.

[0037] In one or more possible embodiments, the compensation of the uplink signal based on the uplink time-frequency adjustment includes: receiving a closed-loop time-frequency offset instruction sent by the satellite base station, the closed-loop time-frequency offset instruction carrying a closed-loop time-frequency offset; and compensating the uplink signal based on the closed-loop time-frequency offset and the uplink time-frequency adjustment. Specifically, after the terminal receives the closed-loop time-frequency offset, the terminal needs to perform calibration based on the closed-loop time-frequency offset fed back by the base station. However, for multi-user terminals, multiple users can receive adjustment information, and the satellite base station can schedule uplink PUSCH or SRS (Sounding Reference Signal) sent by different users within a very short time. If all closed-loop time-frequency offset data from different users are adjusted, there will be a problem of duplicate calibration, causing the terminal to lose uplink synchronization. Therefore, for multi-user terminals, when processing the closed-loop time-frequency offset, only the closed-loop time-frequency offset received by one user is selected for adjustment. At this time, the final uplink time-frequency adjustment of the terminal is: uplink time-frequency adjustment + closed-loop time-frequency offset.

[0038] This application provides a downlink signal synchronization method, such as... Figure 3 As shown, it is applied to the terminal UE and includes: Step 301: Receive the downlink signal broadcast by the satellite base station, and determine the first SSB estimated frequency offset based on the first synchronization signal block (SSB) in the downlink signal; Step 302: Based on the frequency offset estimated by the first SSB, perform initial frequency offset compensation on the downlink signal to obtain the compensated downlink signal; In one or more possible embodiments, before the initial parsing of the MIB (Master Information Block) and downlink synchronization, the first synchronization signal block (SSB) found by the terminal cannot be confirmed as correct. To avoid downlink synchronization loss caused by superimposing compensation to the incorrect SSB estimated frequency offset, no frequency offset accumulation operation is performed before synchronization is completed. Instead, the estimated ephemeris frequency offset of the current time node is added to the latest detected first SSB estimated frequency offset for AD frequency domain calibration, reducing the impact of falsely detected erroneous signals on synchronization, and finally obtaining the downlink signal after initial frequency offset compensation.

[0039] Step 303: parse the main information block (MIB) in the compensated downlink signal, and obtain the second SSB and the corresponding estimated frequency offset of the second SSB from the compensated downlink signal; In one or more possible embodiments, before parsing the Master Information Block (MIB) in the compensated downlink signal, the method further includes: obtaining the Master Synchronization Signal (PSS) from the compensated downlink signal; continuously detecting PSS-related peaks in multiple time slots; and parsing the MIB in the SSB when the detected PSS-related peaks meet a preset time-domain interval condition. The time-domain interval condition includes: a first symbol interval between PSS-related peaks in the same time slot, and a second symbol interval between PSS-related peaks in adjacent time slots. Specifically, the terminal first extracts the Master Synchronization Signal (PSS) from the downlink signal that has undergone frequency offset compensation, and detects and records the position of the PSS-related peaks in each time slot within multiple consecutive time slots (e.g., four time slots). Subsequently, the terminal performs a rigorous time-domain regularity check on the detected related peak position sequence. The preset time-domain interval condition includes two judgments: first, the PSS-related peaks detected in the same time slot (e.g., double peaks caused by the repetitive structure of the PSS sequence) should be spaced between a first symbol interval (e.g., four OFDM symbol lengths); second... Second, the PSS correlation peaks detected between adjacent time slots (such as time slot n and time slot n+1) should be spaced apart by the second symbol number (e.g., approximately 12 OFDM symbol lengths). Assuming the terminal detects PSS correlation peaks in time slots n, n+1, n+2, and n+3, the terminal first checks whether the "double peak interval of 4 symbols" rule is satisfied within each time slot. Then, the terminal compares the main peak position of time slot n with the main peak position of time slot n+1, calculating whether the symbol interval is within the expected tolerance range of "approximately 12 symbols." The same checks are performed between time slots n+1 and n+3. 2. The interval between n+2 and n+3 is such that only when the detection data of four consecutive time slots can simultaneously meet the above two time-domain interval conditions, the terminal can confidently determine that the captured signal is a real and valid SSB sequence, rather than an accidental false peak caused by noise or interference. Only under this premise will the terminal attempt to parse the Master Information Block (MIB). The above method can efficiently filter out a large number of false detection signals before starting the computationally complex MIB parsing process, thereby improving the reliability of downlink timing synchronization and significantly reducing the overhead of invalid operations.

[0040] After the first MIB is correctly resolved and downlink timing adjustment has been performed, the terminal has completed the initial satellite-to-ground downlink frequency domain synchronization. At this point, the correct SSB has been found. As the position and relative speed between the satellite and the terminal in the arc (usually referring to the continuously changing band-shaped area covered by the satellite antenna beam on the Earth's surface) continue to change, the frequency offset of the subsequent arc will deviate from the frequency offset of the current AD calibration. Therefore, it is necessary to continuously correct the frequency domain based on the frequency offset of the initial synchronization compensation in order to maintain downlink frequency domain synchronization for the entire arc.

[0041] Step 304: If it is confirmed that the MIB parsing is successful, there is a consecutive preset number of second SSBs, and the estimated frequency offset of the second SSBs meets the preset frequency offset compensation conditions, then determine the frequency offset compensation value based on the estimated frequency offset of the second SSBs. In one or more possible embodiments, the preset frequency offset compensation condition is that the frequency offset difference between any two second SSB estimated frequency offsets is less than a preset threshold. Specifically, the terminal needs to continuously and successfully receive and measure the second SSB estimated frequency offset of the second SSB signal within multiple time slots (e.g., four time slots). For these continuously measured multiple second SSB estimated frequency offsets, the absolute difference between any two second SSB estimated frequency offsets is required to be less than a preset threshold, such as 100 Hz. Only when the continuously measured multiple SSB estimated frequency offsets meet the above preset frequency offset compensation condition is the measurement result determined to be stable and reliable, and subsequent compensation operations can be triggered. To optimize processing efficiency, after determining that the preset frequency offset compensation condition is met... Instead of fusing all estimated second SSB frequency offsets, the terminal selects the estimated second SSB frequency offset corresponding to one time slot as the first-level frequency offset compensation value. For example, if the terminal continuously measures the estimated second SSB frequency offsets of four time slots from time slot 1 to time slot 4, with values ​​of +1012 Hz, +1005 Hz, +1018 Hz, and +1009 Hz respectively, and since the difference between any two of the four values ​​does not exceed the preset threshold of 100 Hz, the terminal selects the measurement value of time slot 1, +1012 Hz, as the first-level frequency offset compensation value to compensate for the downlink signal frequency offset. This method avoids complex calculations and reduces the resource overhead of real-time signal processing while ensuring the effectiveness of the compensation.

[0042] Step 305: Perform frequency offset compensation on the compensated downlink signal according to the frequency offset compensation value.

[0043] In one or more possible embodiments, after determining the frequency offset compensation value based on the second SSB estimated frequency offset, the method further includes: determining the SIB estimated frequency offset based on the System Information Block (SIB) in the downlink signal; optimizing the frequency offset compensation value based on the SIB estimated frequency offset to determine the optimized frequency offset compensation value; specifically: after the terminal compensates the downlink signal based on the second SSB estimated frequency offset, the carrier frequency of the downlink signal has been basically calibrated to the range where the System Information Block (SIB) can be correctly demodulated. Since the SIB is always sent after the SSB, when the terminal demodulates the SIB, the signal has already been compensated by the second SSB estimated frequency offset. Therefore, the SIB estimated frequency offset measured from the SIB signal reflects a more subtle residual frequency offset that still exists after the second SSB estimated frequency offset compensation, and its value is usually much smaller than the second SSB estimated frequency offset. For example, after the terminal corrects the frequency by +1012 Hz using the second SSB estimated frequency offset, it successfully demodulates the SIB and measures a +15 Hz SIB estimated frequency offset from the SIB signal, which is the second-level residual frequency offset. The terminal adds the SIB estimated frequency offset to the previously determined first-level frequency offset compensation value to calculate an optimized and more accurate total frequency offset compensation value (e.g., +1012 Hz + 15 Hz = +1027 Hz). Since the SIB transmission period is relatively long and does not occur frequently, the terminal can perform this fine optimization once every time the SIB is successfully demodulated, without limiting the number of SIB compensations. Through this two-level sequential calibration mechanism, high-precision compensation for downlink signal frequency offset is ultimately achieved.

[0044] In one or more possible embodiments, the method further includes: when the second SSB is not detected, determining the transmission frequency offset change based on ephemeris information; compensating the downlink signal based on the transmission frequency offset change; specifically: when the terminal is under the coverage of the random beam and the SSB signal is not detected for a period of time, in order to maintain downlink frequency domain synchronization, the terminal will enable a predictive compensation mode based on ephemeris information. The terminal calculates the frequency offset change caused by the relative motion between the satellite and the terminal in real time based on the pre-stored satellite orbit ephemeris information and the precise local time. The terminal calculates the cumulative frequency offset change since the last compensation time at a fixed time period, for example, every 10 milliseconds, and uses the cumulative frequency offset change as the transmission frequency offset change to compensate the downlink receiving link; for example, assuming the terminal calculates the current frequency offset change based on the ephemeris information... The downlink frequency offset changes at a rate of 0.1 kHz every 10 milliseconds. After the most recent disappearance of the SSB signal, the terminal initiates periodic compensation. When the first 10-millisecond period arrives, the terminal calculates the frequency offset change as +0.1 kHz. After another 10 milliseconds, the terminal calculates again, and the accumulated change reaches +0.2 kHz (transmission frequency offset change). This continues until the terminal successfully captures the SSB signal again and determines the final transmission frequency offset change. Finally, based on the previously determined frequency offset compensation value and the final transmission frequency offset change, the current frequency offset compensation value is determined. This periodic predictive compensation effectively combats long-term signal interruptions caused by periodic scanning of the beam pointing, preventing excessive accumulation of downlink frequency offset during interruptions, thereby ensuring the continuity of downlink frequency domain synchronization throughout the entire communication arc.

[0045] In one or more possible embodiments, the method further includes: determining that the beam type covering the UE beam is a random beam; determining the transmission delay change based on ephemeris information during the period when the second SSB is not detected; and compensating the downlink signal based on the transmission delay change. Specifically, when the terminal is under the coverage of the random beam and the second SSB signal is not detected for a period of time, in order to maintain downlink time domain synchronization, the terminal will initiate a transmission delay change prediction and compensation mechanism based on ephemeris information. The terminal calculates the rate of change of satellite-to-ground distance caused by satellite motion in real time based on the pre-stored satellite orbit ephemeris and the current time, and then derives the change in one-way path transmission delay. The terminal calculates the change in one-way path transmission delay at a fixed period, for example, every 10 milliseconds. The change in transmission delay is calculated and applied to adjust the timing window for downlink reception. For example, assuming the terminal calculates from ephemeris data that the satellite is moving away and the path delay is changing at a rate of 0.3 microseconds per 10 milliseconds, the terminal performs a compensation operation every 10 milliseconds during the period when the SSB is not detected: when the first 10-millisecond cycle arrives, the terminal compensates the downlink reception timing by +0.3 microseconds; by the second 10-millisecond cycle, the cumulative change reaches +0.6 microseconds, and the terminal performs the corresponding compensation again. This process continues, dynamically offsetting the timing drift caused by satellite motion, thereby effectively maintaining the accuracy of downlink symbol timing during long intervals when real-time measurement via the SSB is not possible.

[0046] In one or more possible embodiments, if the beam type covering the UE beam is a service beam, downlink continuous synchronization can be completed directly based on SSB blind detection without needing to compensate for changes in transmission delay based on ephemeris information.

[0047] In one or more possible embodiments, a schematic diagram of uplink and downlink time domain synchronization on the terminal side is given, specifically as follows: Figure 4 As shown, the satellite base station gNB sends downlink frame n at time T on its own timeline. After a spatial propagation delay (Delay), the downlink signal is received at time T + Delay on the terminal UE's timeline. To ensure that the uplink frame n sent by the terminal arrives at the time expected by the satellite base station, the terminal must send it in advance. Therefore, the terminal needs to calculate a time advance (TA) and send uplink frame n at time (T + Delay) - TA on its own timeline. This uplink signal, after a propagation delay (Delay), finally arrives at time T + 2 on the base station's timeline. Delay - TA is received at this time. In other words, by precisely setting TA, the uplink frame can be time-aligned with the downlink frame on the base station side.

[0048] The uplink and downlink signal synchronization method provided in this application has the following advantages: For downlink synchronization, a stepped frequency offset calibration technique is proposed. This technique comprehensively utilizes multi-source information, including downlink ephemeris frequency offset changes, synchronization signal block (SSB) estimated frequency offset, and system information block (SIB) estimated frequency offset, to perform hierarchical compensation. This effectively reduces the residual frequency offset of the received signal and significantly improves the terminal demodulation performance. Simultaneously, the method designs differentiated time-domain synchronization strategies for the different coverage characteristics of unrestricted beams and service beams: for unrestricted beams with long SSB transmission intervals, the delay and frequency offset changes based on ephemeris predictions are periodically compensated during periods without signal to maintain synchronization continuity; for service beams with short SSB periods, the processing is simplified, and ephemeris changes are not compensated, thus optimizing computational complexity while ensuring performance.

[0049] In terms of uplink synchronization, an innovative physical random access channel (PRACH) time offset variation value ΔTa is introduced. When uplink synchronization fails and an access request needs to be retransmitted, the terminal dynamically adjusts the transmission time of the next PRACH based on the previous transmission timing and the number of attempts. This alternating direction and increasing amplitude probing mechanism can effectively avoid the uplink timing "cross-preamble" problem caused by environmental changes or excessive initial timing errors. It fundamentally solves the technical problem of access failure caused by the base station's inability to correctly demodulate MSG3, thereby significantly improving the success rate of random access and the robustness of uplink synchronization.

[0050] In one or more possible embodiments, this application also provides an uplink signal synchronization device, specifically as follows: Figure 5 As shown, it includes:

[0051] The random access sending module 501 sends a random access request to the satellite base station. The random access request is a message compensated by a first time-frequency compensation value. The first time-frequency compensation value is initially determined based on ephemeris information. The second time-frequency offset compensation value determination module 502 is used to receive the random access response (RAR) sent by the satellite base station and determine the second time-frequency offset compensation value using the initial time-frequency compensation value and the uplink time-frequency offset value carried in the RAR. RRC connection request sending module 503 is used to send an RRC connection request to the satellite base station. The RRC connection request is a message compensated by the second time-frequency offset compensation value. The additional time offset adjustment determination module 504 is used to determine the additional time offset adjustment if the connection request fails. The first time-frequency compensation value determination module 505 is used to update the first time-frequency compensation value according to the initial time-frequency offset compensation value and the additional time offset adjustment amount, and to re-trigger random access according to the updated first time-frequency compensation value.

[0052] In one or more possible embodiments, this application also provides a downlink signal synchronization device, specifically as follows: Figure 6 As shown, it includes:

[0053] The first SSB estimated frequency offset determination module 601 is used to receive the downlink signal broadcast by the satellite base station and determine the first SSB estimated frequency offset based on the first synchronization signal block SSB in the downlink signal. The initial compensation module 602 is used to perform initial frequency offset compensation on the downlink signal based on the frequency offset estimated by the first SSB, so as to obtain the compensated downlink signal. MIB parsing module 603 is used to parse the main information block (MIB) in the compensated downlink signal and obtain the second SSB and the corresponding estimated frequency offset of the second SSB from the compensated downlink signal. The frequency offset compensation value determination module 604 is used to determine the frequency offset compensation value based on the estimated frequency offset of the second SSB when the MIB parsing is successful, there is a consecutive preset number of second SSBs, and the estimated frequency offset of the second SSBs meets the preset frequency offset compensation conditions. The downlink signal compensation module 605 is used to perform frequency offset compensation on the compensated downlink signal according to the frequency offset compensation value.

[0054] This application also provides an electronic device, including at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the above-described uplink and downlink signal synchronization method.

[0055] like Figure 7 As shown, the device includes a processor 701, a memory 702, a communication interface 703, and a bus 704. The processor 701, memory 702, and communication interface 703 are interconnected via the bus 704.

[0056] Processor 701 is configured to read instructions from memory 702 and execute them, so that at least one processor can perform the uplink and downlink signal synchronization method provided in the above embodiments.

[0057] The memory 702 is used to store various instructions and programs for the uplink and downlink signal synchronization method provided in the above embodiments.

[0058] The 704 bus can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of representation, Figure 7 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.

[0059] Processor 701 can be a central processing unit (CPU), a network processor (NP), a graphics processing unit (GPU), or any combination of CPU, NP, and GPU. It can also be a hardware chip. The aforementioned hardware chip can be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The aforementioned PLD can be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a generic array logic (GAL), or any combination thereof.

[0060] In addition, this application also provides a computer-readable storage medium, such as Figure 8 As shown, the computer storage medium stores a computer program that is used to cause the computer to perform any of the methods described in the above embodiments.

[0061] The memory may include readable media in the form of volatile memory, such as random access memory (RAM) 801 and / or cache memory 802, and may further include read-only memory (ROM) 803.

[0062] The memory may also include a program / utility 805 having a set (at least one) of program modules 804, including but not limited to: an operating system, one or more application programs, other program modules, and program data, each or some combination of these examples may include an implementation of a network environment.

[0063] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0064] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to this application. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0065] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0066] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0067] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. An uplink signal synchronization method, characterized in that, Applied to terminal UE, including: Send a random access request to the satellite base station. The random access request is a message compensated with a first time-frequency compensation value. The first time-frequency compensation value is initially the initial time-frequency compensation value. Receive the Random Access Response (RAR) sent by the satellite base station, and determine the second time-frequency offset compensation value using the first time-frequency compensation value and the uplink time-frequency offset value carried in the RAR; Send an RRC connection request to the satellite base station, wherein the RRC connection request is a message compensated using a second time-frequency offset compensation value; If the connection request fails, determine the additional time offset adjustment; The first time-frequency compensation value is updated based on the initial time-frequency offset compensation value and the additional time-frequency adjustment amount, and random access is retried based on the updated first time-frequency compensation value.

2. The method according to claim 1, characterized in that, If the connection request fails, the determination of the additional time offset adjustment includes: If the connection request fails, the additional time offset adjustment is determined based on the number of times random access is triggered and the preset time offset step size.

3. The method according to claim 1, characterized in that, The initial time-frequency offset compensation value is determined in the following manner: Determine the upper planetary ephemeris frequency offset based on the pre-stored ephemeris information; The path delay is determined based on the distance between the satellite base station and the terminal; The initial delay compensation value is determined based on twice the path delay and the preset delay compensation value; The initial time-frequency compensation value is determined based on the initial time delay compensation value and the upper planetary ephemeris frequency offset.

4. The method according to claim 1, characterized in that, Also includes: If the connection request is confirmed to be successful, the second time-frequency offset compensation value is used as the uplink time-frequency adjustment amount, and the uplink signal is compensated according to the uplink time-frequency adjustment amount.

5. The method according to claim 4, characterized in that, The compensation of the uplink signal based on the uplink time-frequency adjustment includes: Receive the closed-loop time-frequency offset command sent by the satellite base station, wherein the closed-loop time-frequency offset command carries the closed-loop time-frequency offset; The uplink signal is compensated based on the closed-loop time-frequency offset and the uplink time-frequency adjustment.

6. A downlink signal synchronization method, characterized in that, Applied to terminal UE, including: Receive downlink signals broadcast by satellite base stations and determine the first SSB estimated frequency offset based on the first synchronization signal block (SSB) in the downlink signals; Based on the frequency offset estimated by the first SSB, the downlink signal is initially compensated for to obtain the compensated downlink signal; The main information block (MIB) in the compensated downlink signal is parsed, and the second SSB and the corresponding estimated frequency offset of the second SSB are obtained from the compensated downlink signal. When it is confirmed that the MIB parsing is successful, there is a consecutive preset number of second SSBs, and the estimated frequency offset of the second SSBs meets the preset frequency offset compensation conditions, the frequency offset compensation value is determined based on the estimated frequency offset of the second SSBs. Frequency offset compensation is performed on the compensated downlink signal based on the frequency offset compensation value.

7. The method according to claim 6, characterized in that, The preset frequency offset compensation condition is that the frequency offset difference between every two estimated frequency offsets of the second SSB is less than a preset threshold.

8. The method according to claim 6, characterized in that, After determining the frequency offset compensation value based on the second SSB estimated frequency offset, the method further includes: The SIB estimated frequency offset is determined based on the System Information Block (SIB) in the downlink signal; The frequency offset compensation value is optimized based on the frequency offset estimated by the SIB to determine the optimized frequency offset compensation value.

9. The method according to claim 6, characterized in that, Also includes: If the second SSB cannot be detected, the transmission frequency offset change is determined based on the ephemeris information; The downlink signal is compensated based on the transmission frequency offset change.

10. The method according to claim 6, characterized in that, Also includes: The beam type covering the UE beam is determined to be an unrestricted beam; During the period when the second SSB cannot be detected, the change in transmission delay is determined based on ephemeris information; The downlink signal is compensated based on the change in transmission delay.

11. The method according to claim 6, characterized in that, Before parsing the main information block (MIB) in the compensated downlink signal, the method further includes: Obtain the primary synchronization signal (PSS) from the compensated downlink signal; The PSS correlation peaks in multiple time slots are continuously detected. When it is determined that the detected PSS correlation peaks meet the preset time domain interval conditions, the main information block (MIB) in the SSB is parsed. The time-domain interval conditions include: the first symbol number of PSS-related peak intervals within the same time slot, and the second symbol number of PSS-related peak intervals between adjacent time slots.

12. An uplink signal synchronization device, characterized in that, Applied to terminal UE, including: The random access sending module sends a random access request to the satellite base station. The random access request is a message compensated by a first time-frequency compensation value, which is initially adopted as the initial time-frequency compensation value. The second time-frequency offset compensation value determination module is used to receive the random access response (RAR) sent by the satellite base station and determine the second time-frequency offset compensation value using the initial time-frequency compensation value and the uplink time-frequency offset value carried in the RAR. The RRC connection request sending module is used to send an RRC connection request to the satellite base station. The RRC connection request is a message compensated using a second time-frequency offset compensation value. The additional time offset adjustment determination module is used to determine the additional time offset adjustment if the connection request fails. The first time-frequency compensation value determination module is used to update the first time-frequency compensation value according to the initial time-frequency offset compensation value and the additional time offset adjustment amount, and to re-trigger random access according to the updated first time-frequency compensation value.

13. A downlink signal synchronization device, characterized in that, Applied to terminal UE, including: The first SSB estimated frequency offset determination module is used to receive the downlink signal broadcast by the satellite base station and determine the first SSB estimated frequency offset based on the first synchronization signal block SSB in the downlink signal; The initial compensation module is used to perform initial frequency offset compensation on the downlink signal based on the frequency offset estimated by the first SSB, so as to obtain the compensated downlink signal. The MIB parsing module is used to parse the main information block (MIB) in the compensated downlink signal and obtain the second SSB and the corresponding estimated frequency offset of the second SSB from the compensated downlink signal. The frequency offset compensation value determination module is used to determine the frequency offset compensation value based on the estimated frequency offset of the second SSB when the MIB parsing is successful, there is a consecutive preset number of second SSBs, and the estimated frequency offset of the second SSBs meets the preset frequency offset compensation conditions. The downlink signal compensation module is used to perform frequency offset compensation on the compensated downlink signal according to the frequency offset compensation value.

14. An electronic device, characterized in that, The electronic device includes: At least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method as claimed in any one of claims 1-5 or 6-11.

15. A computer storage medium, characterized in that, The computer storage medium stores a computer program that causes the computer to perform the method as claimed in any one of claims 1-5 or 6-11.

Images