Terminal access method, base station, terminal, and non-terrestrial communication system

Abstract

The application provides a terminal access method, a base station, a terminal and a non-ground communication system. The terminal access method applied to the base station comprises the following steps: generating a cell synchronization auxiliary signal; wherein the cell synchronization auxiliary signal comprises a space-time synchronization signal and a frequency offset measurement signal; the space-time synchronization signal carries base station direction information and timing time information of the base station; the frequency offset measurement signal carries a pilot sequence; and the cell synchronization auxiliary signal is sent to a terminal, so that the terminal demodulates the cell synchronization auxiliary signal and performs terminal access based on the demodulated base station direction information, timing time information and pilot sequence. The above scheme integrates the base station direction information and the timing time information in the space-time synchronization signal, so that the terminal can complete direction alignment and symbol timing without pre-acquiring the dynamic parameters of the base station, and the initial access success rate of the terminal is improved.

Description

Technical Field

[0001] This application relates to the field of wireless communication technology, and more specifically, to a terminal access method, a base station, a terminal, and a non-terrestrial communication system. Background Technology

[0002] In 5G-based non-terrestrial wireless communication systems, initial access for terminals depends on the detection of cell synchronization signals. Base stations (such as low-Earth orbit satellites) periodically transmit synchronization signals according to pre-defined time-frequency resources and beam directions. Terminals must continuously receive signals at known or estimated receiving directions and frequencies, and compensate for Doppler frequency offsets caused by the high-speed movement of the base station, before completing synchronization detection and entering the subsequent access process. Therefore, terminals typically rely on external information such as ephemeris data and GPS / BeiDou to pre-calculate the satellite's position, motion state, and signal arrival direction, thereby capturing synchronization signals at the correct time, frequency, and spatial beam.

[0003] However, the aforementioned terminal access methods heavily rely on the real-time nature and accuracy of base station dynamic information (including base station movement direction and status information). When a terminal is offline for an extended period or in an area without terrestrial network coverage, ephemeris failure prevents accurate calculation of the receiving beam direction, forcing the terminal to resort to compromises such as beam scanning or wide-beam reception. However, beam scanning carries the risk of search failure, while wide-beam reception weakens signal strength due to reduced array gain. Both methods sacrifice a certain level of access success rate to achieve access capability in scenarios lacking base station node dynamic information. Therefore, the access success rate of the aforementioned terminal access methods is relatively low. Summary of the Invention

[0004] The purpose of this application is to provide a terminal access method, a base station, a terminal, and a non-terrestrial communication system to solve the above-mentioned problems.

[0005] Firstly, embodiments of this application provide a terminal access method applied to a base station. The method includes: generating a cell synchronization auxiliary signal; wherein the cell synchronization auxiliary signal includes a spatiotemporal synchronization signal and a frequency offset measurement signal; the spatiotemporal synchronization signal carries base station direction information and timing information of the base station; the frequency offset measurement signal carries a pilot sequence; sending the cell synchronization auxiliary signal to a terminal, so that the terminal demodulates the cell synchronization auxiliary signal and performs terminal access based on the demodulated base station direction information, the timing information, and the pilot sequence. In the implementation of the above scheme, by integrating the base station direction information and timing information into the spatiotemporal synchronization signal, the terminal can complete the direction alignment and symbol timing without prior acquisition of the base station dynamic parameters, which is beneficial to improving the initial access success rate of the terminal; on the other hand, the frequency offset measurement signal is sent in the form of a fixed pilot sequence, and after obtaining the direction and timing information, the terminal can directly use the sequence to estimate and compensate for the residual frequency offset, avoiding secondary signaling interaction and reducing air interface load; furthermore, the base station direction information, timing information, and pilot sequence are all transmitted in a signal embedding manner, and the terminal can complete the terminal access process without external assistance, improving the reliability of terminal access.

[0006] In one implementation of the first aspect, the spatiotemporal synchronization signal includes a primary spatiotemporal synchronization signal and an auxiliary spatiotemporal synchronization signal; the determination of the spatiotemporal synchronization signal includes: acquiring a primary spatiotemporal synchronization signal sequence and an auxiliary spatiotemporal synchronization signal sequence; in the baseband frequency domain, mapping the primary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of a preset beam and performing modulation processing to acquire the primary spatiotemporal synchronization signal; in the baseband frequency domain, mapping the auxiliary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of the preset beam and performing modulation processing to acquire the auxiliary spatiotemporal synchronization signal. In the implementation of the above scheme, by mapping the main spatiotemporal synchronization signal sequence and the auxiliary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of the preset beam, unified resource allocation under the same center frequency is achieved, simplifying the RF front-end filtering and carrier configuration and reducing hardware complexity. On the other hand, center subcarrier mapping can reduce the filter roll-off and adjacent channel interference that may be introduced by the edge frequency band, so that the main spatiotemporal synchronization signal sequence and the auxiliary spatiotemporal synchronization signal sequence obtain symmetrical and consistent channel response in the frequency domain, thereby improving the detection reliability of cell synchronization auxiliary signal. Furthermore, the design of the main spatiotemporal synchronization signal sequence and the auxiliary spatiotemporal synchronization signal sequence being sequentially cascaded in the time domain and co-centered in the frequency domain enables the terminal to continuously acquire the auxiliary spatiotemporal synchronization signal without retuning the local oscillator after completing coarse timing, which is beneficial to shortening the terminal access time.

[0007] In one implementation of the first aspect, the base station direction information of the base station includes spatial wavelets; after acquiring the primary spatiotemporal synchronization signal sequence and the secondary spatiotemporal synchronization signal sequence, the method further includes: acquiring a first index of the primary spatiotemporal synchronization signal sequence and a second index of the secondary spatiotemporal synchronization signal sequence; based on the first index and the second index, acquiring an index group of synchronization signal sequence groups composed of the primary spatiotemporal synchronization signal sequence and the secondary spatiotemporal synchronization signal sequence; assigning a unique spatial wavelet to each index group; wherein the spatial wavelet is used to indicate the spatial orientation of the base station relative to the terminal. In the implementation of the above scheme, by mapping a unique index group consisting of the first index of the primary synchronization signal sequence and the second index of the secondary synchronization signal sequence to a unique spatial spectral position, the terminal can directly obtain the spatial orientation of the base station relative to the terminal after completing synchronization detection, without the need for additional direction-finding hardware or signaling interaction, thus reducing implementation complexity. On the other hand, the spatial spectral position discretizes the entire hemispherical coverage area in the form of solid angle units, and the index group corresponds one-to-one with the spatial spectral position, which helps to improve the accuracy of direction indication and the uniqueness of mapping, and avoids beam alignment errors caused by ambiguity of multiple spectral positions. Furthermore, the mapping relationship can be solidified before system deployment, and the terminal only needs to look up the table to resolve the direction information, which helps to reduce air interface overhead and shorten the initial access latency. Moreover, the mapping mechanism between the index group and the spatial spectral position reuses existing synchronization sequence resources, without the need to add a new direction signaling field, improving spectrum efficiency and maintaining compatibility with the current frame structure specifications.

[0008] In one implementation of the first aspect, the method further includes: determining a first subcarrier interval of the main spatiotemporal synchronization signal based on the system downlink subcarrier interval; wherein the system downlink subcarrier interval is determined by the system frame structure; the first subcarrier interval is smaller than the system downlink subcarrier interval, and the first subcarrier interval is larger than the intra-beam frequency offset protection interval; the intra-beam frequency offset protection interval is used to characterize the minimum frequency domain protection interval required by the terminal within the same beam coverage area, and the intra-beam frequency offset protection interval is determined based on the maximum difference in Doppler frequency offset between the downlink beam center and the downlink beam edge position. In the implementation of the above scheme, setting the first subcarrier spacing of the primary spatiotemporal synchronization signal to a value smaller than the system downlink subcarrier spacing and larger than the intra-beam frequency offset protection spacing helps to extend the symbol duration and improve the signal energy concentration, thereby improving the detection probability of the primary spatiotemporal synchronization signal under wide-beam reception conditions and enhancing the robustness of initial access. On the other hand, the intra-beam frequency offset protection spacing is determined based on the maximum difference in Doppler frequency offset between the downlink beam center and the beam edge, ensuring that the first subcarrier spacing can cover the maximum residual frequency offset at any terminal position, which helps to achieve complete and distortion-free primary spatiotemporal synchronization signal in the frequency domain and reduces the risk of synchronization failure due to frequency offset. Furthermore, the narrowband design of the first subcarrier spacing reduces the occupation of spectrum resources while maintaining frequency offset tolerance, reserving more idle bandwidth for the frequency offset measurement signal in the cell synchronization auxiliary signal and optimizing the resource allocation efficiency of the entire cell synchronization auxiliary signal.

[0009] In one implementation of the first aspect, the method further includes: determining a second subcarrier interval of the auxiliary spatiotemporal synchronization signal based on the system downlink subcarrier interval; wherein the system downlink subcarrier interval is determined by the system frame structure; and the second subcarrier interval is equal to the system downlink subcarrier interval. In the implementation of the above scheme, by setting the second subcarrier interval of the auxiliary spatiotemporal synchronization signal to be equal to the system downlink subcarrier interval, the auxiliary spatiotemporal synchronization signal maintains consistency with the subsequent broadcast channel in terms of frequency domain position, symbol duration, and cyclic prefix length. This allows the terminal to directly parse the auxiliary spatiotemporal synchronization signal without reconfiguring baseband parameters after acquiring the main spatiotemporal synchronization signal, reducing state switching delay. Furthermore, the auxiliary spatiotemporal synchronization signal is synchronized with the system resource grid, reducing frequency domain resampling or interpolation operations caused by differences in factor carrier intervals, thus reducing the computational load and power consumption of the digital front-end. Moreover, the unified subcarrier interval ensures that all terminals within the beam use the same frequency offset compensation coefficient at any position, eliminating the need for the network side to issue additional calibration information for different terminal positions, thus simplifying the system signaling process.

[0010] In one implementation of the first aspect, the method further includes: determining the first bandwidth of the spatiotemporal synchronization signal; wherein the first bandwidth is not less than the minimum frequency domain protection bandwidth; the minimum frequency domain protection bandwidth is determined based on the occupied bandwidth of the spatiotemporal synchronization signal and the full-link frequency offset protection bandwidth; the full-link frequency offset protection bandwidth is determined based on the maximum downlink Doppler frequency offset of the system. In the implementation of the above scheme, setting the lower bound of the first bandwidth to be not less than the minimum frequency domain protection bandwidth ensures that the spatiotemporal synchronization signal always has sufficient frequency domain resources within the entire beam coverage area, avoiding spectrum truncation and improving the terminal detection success rate. Furthermore, the minimum frequency domain protection bandwidth is jointly determined by the occupied bandwidth and the full-link frequency offset protection bandwidth, ensuring precise matching of resource allocation with link Doppler conditions, reducing redundant frequency bands, and improving spectrum utilization. Moreover, the full-link frequency offset protection bandwidth is calculated based on the maximum downlink Doppler frequency offset of the system, which helps simplify the network-side parameter configuration process.

[0011] In one implementation of the first aspect, before sending the cell synchronization auxiliary signal to the terminal, the method further includes: determining the Doppler frequency offset of the spatiotemporal synchronization signal based on the expected center frequency of the spatiotemporal synchronization signal, the base station location, the base station motion state, and the downlink beam direction; and performing frequency offset pre-compensation on the auxiliary spatiotemporal synchronization signal based on the Doppler frequency offset. In the implementation of the above scheme, frequency offset pre-compensation is performed on the auxiliary spatiotemporal synchronization signal before transmission based on the real-time location, motion state, and beam direction of the base station, ensuring that the residual frequency offset of the downlink signal reaching the terminal is within a correctable range. This allows the terminal to directly complete synchronization sequence detection, shortening the initial acquisition time. Furthermore, the frequency offset pre-compensation only applies to the auxiliary synchronization signal, preserving the original frequency offset tolerance of the primary synchronization signal, forming a primary-auxiliary hierarchical processing architecture that balances acquisition stability and direction resolution accuracy.

[0012] In one implementation of the first aspect, the determination of the frequency offset measurement signal includes: determining the sequence length of the pilot sequence based on the third subcarrier spacing and the second bandwidth of the frequency offset measurement signal; generating the pilot sequence based on the sequence length; performing sparse sampling on the pilot sequence to obtain a frequency-domain sparse pilot sequence; and mapping the pilot sequence to the center subcarrier position of the second bandwidth of a preset beam in the baseband frequency domain and performing modulation processing to obtain the frequency offset measurement signal. In the implementation of the above scheme, by calculating the pilot sequence length with the third subcarrier spacing and the second bandwidth as constraints, it is ensured that the sequence length strictly matches the fixed bandwidth, avoiding spectrum waste and simplifying resource planning. Furthermore, after sparse sampling of the pilot sequence in the baseband frequency domain, it is mapped to the center subcarrier to form the pilot sequence, enabling the terminal to accurately extract phase information within a wide frequency offset range, thus improving the frequency offset estimation accuracy. Moreover, sparse sampling reduces pilot density while maintaining estimation performance, lowering pilot overhead and improving spectrum utilization.

[0013] In one implementation of the first aspect, the method further includes: determining the third subcarrier spacing of the frequency domain measurement signal; wherein the third subcarrier spacing is greater than the full-link frequency offset protection bandwidth; wherein the full-link frequency offset protection bandwidth is determined based on the system's downlink maximum Doppler frequency offset. In the implementation of the above scheme, by setting the third subcarrier spacing to be greater than the full-link frequency offset protection bandwidth, the frequency offset measurement signal remains resolvable within the full-link frequency offset range, allowing the terminal to directly extract the frequency offset estimation result; on the other hand, a larger spacing can reduce pilot density, lower resource overhead, and improve spectrum utilization.

[0014] In one implementation of the first aspect, the preset beam is an access beam; wherein the access beam is a downlink beam in the base station used for initial access; the step of sending a cell synchronization assistance signal to the terminal includes: using the idle bandwidth resources in the access beam to send a cell synchronization assistance signal to the terminal; wherein the sum of the first bandwidth of the spatiotemporal synchronization signal and the second bandwidth of the frequency offset measurement signal is not greater than the idle bandwidth resources. In the implementation of the above scheme, the cell synchronization auxiliary signal is transmitted using the idle bandwidth of the access beam, eliminating the need to allocate frequency domain resources separately for the cell synchronization auxiliary signal. This helps improve spectrum utilization and reduce the complexity of system bandwidth planning. On the other hand, the sum of the first and second bandwidths is limited by the idle bandwidth, avoiding interference with other channels. Furthermore, the transmission parameters of the access beam have been optimized for the initial acquisition scenario, ensuring reliable reception by the terminal even without prior information. The cell synchronization auxiliary signal reuses these parameters, sharing the same gain, coverage, and power control link with existing service signals, eliminating the need for an independent beam management module and simplifying the design of the onboard radio frequency link. Moreover, the fixed mapping mechanism of the access beam's idle bandwidth allows the base station to send cell access signals and cell synchronization auxiliary signals to the terminal via the access beam with only one configuration, avoiding the signaling overhead caused by dynamic resource scheduling and simplifying the onboard processing flow.

[0015] In one implementation of the first aspect, sending the cell synchronization assistance signal to the terminal includes: continuously sending a spatiotemporal synchronization signal to the terminal; and continuously or periodically sending a frequency offset measurement signal to the terminal. In the implementation of the above scheme, continuously transmitting the spatiotemporal synchronization signal allows the terminal to capture the synchronization signal throughout the entire access window, avoiding missed detections due to intermittent transmission, increasing the probability of first-time acquisition, and shortening the search time. On the other hand, the frequency offset measurement signal is transmitted in the same beam as the spatiotemporal synchronization signal in a continuous or periodic manner, allowing the terminal to perform frequency offset estimation after obtaining coarse synchronization without waiting for additional triggering, thus reducing access latency.

[0016] Secondly, embodiments of this application provide a terminal access method applied to a terminal. The method includes: receiving a spatiotemporal synchronization signal from a cell auxiliary synchronization signal sent by a base station; determining base station direction information and timing information of the base station based on the spatiotemporal synchronization signal; after obtaining the base station direction information and the timing information, receiving a frequency offset measurement signal from the cell auxiliary synchronization signal sent by the base station; wherein the frequency offset measurement signal carries a pilot sequence; performing residual frequency offset compensation on subsequently received downlink signals based on the pilot sequence; and completing terminal access based on the cell access signal after detecting a cell access signal.

[0017] Thirdly, embodiments of this application provide a terminal access method, the method comprising: a base station performing the following steps: generating a cell synchronization assistance signal; wherein the cell synchronization assistance signal includes a spatiotemporal synchronization signal and a frequency offset measurement signal; the spatiotemporal synchronization signal carries base station direction information and timing information of the base station; the frequency offset measurement signal carries a pilot sequence; sending the cell synchronization assistance signal to a terminal, so that the terminal demodulates the cell synchronization assistance signal and performs terminal access based on the demodulated base station direction information, the timing information and the pilot sequence; the terminal performing the following steps: receiving the spatiotemporal synchronization signal in the cell assistance synchronization signal sent by the base station; determining the base station direction information and the timing information of the base station based on the spatiotemporal synchronization signal; after obtaining the base station direction information and the timing information, receiving the frequency offset measurement signal in the cell assistance synchronization signal sent by the base station; wherein the frequency offset measurement signal carries the pilot sequence; performing residual frequency offset compensation on subsequently received downlink signals based on the pilot sequence; and completing terminal access based on the cell access signal after detecting a cell access signal.

[0018] Fourthly, embodiments of this application provide a base station, including: a cell synchronization auxiliary signal generation module, used to generate a cell synchronization auxiliary signal; wherein, the cell synchronization auxiliary signal includes a spatiotemporal synchronization signal and a frequency offset measurement signal; the spatiotemporal synchronization signal carries base station direction information and timing information of the base station; the frequency offset measurement signal carries a pilot sequence; and a cell synchronization auxiliary signal transmission module, used to transmit the cell synchronization auxiliary signal to a terminal, so that the terminal demodulates the cell synchronization auxiliary signal and performs terminal access based on the demodulated base station direction information, the timing information, and the pilot sequence.

[0019] Fifthly, embodiments of this application provide a terminal, comprising: a spatiotemporal synchronization signal receiving module, configured to receive a spatiotemporal synchronization signal from a cell auxiliary synchronization signal transmitted by a base station; a spatiotemporal synchronization signal demodulation module, configured to determine base station direction information and timing information of the base station based on the spatiotemporal synchronization signal; a frequency offset measurement signal receiving module, configured to receive a frequency offset measurement signal from the cell auxiliary synchronization signal transmitted by the base station after obtaining the base station direction information and the timing information; wherein the frequency offset measurement signal carries a pilot sequence; a residual frequency offset compensation module, configured to perform residual frequency offset compensation on subsequently received downlink signals based on the pilot sequence; and a terminal access module, configured to complete terminal access based on a cell access signal after detecting a cell access signal.

[0020] Sixthly, embodiments of this application provide a non-terrestrial communication system, including a base station as provided in the fourth aspect or any possible implementation of the fourth aspect, and a terminal as provided in the fifth aspect or any possible implementation of the fifth aspect, wherein the terminal is communicatively connected to the base station.

[0021] In a seventh aspect, embodiments of this application provide an electronic device, including: a processor, a memory, and a communication bus, wherein the processor and the memory communicate with each other through the communication bus; the memory stores computer program instructions executable by the processor, and the computer program instructions are read and executed by the processor to perform the method provided in the first aspect or any possible implementation of the first aspect.

[0022] Eighthly, embodiments of this application provide a computer-readable storage medium storing computer program instructions, which, when read and executed by a processor, perform the method provided by the first aspect or any possible implementation thereof, or the second aspect or any possible implementation thereof.

[0023] Ninthly, embodiments of this application provide a computer program product, the computer program product including a computer program, which, when executed by a processor, implements the method provided by the first aspect or any possible implementation of the first aspect or the second aspect or any possible implementation of the second aspect.

[0024] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing embodiments of this application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 A schematic diagram of a multi-beam mobile satellite communication system provided in an embodiment of this application; Figure 2 A schematic flowchart illustrating a terminal access method applied to a base station, provided in an embodiment of this application; Figure 3A flowchart illustrating a terminal access method applied to a terminal, as provided in an embodiment of this application; Figure 4 A flowchart illustrating the terminal access method provided in this application embodiment; Figure 5 This is a schematic diagram of the base station structure provided in an embodiment of this application; Figure 6 This is a schematic diagram of the terminal structure provided in the embodiments of this application; Figure 7 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will now be described with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of this application, and are therefore merely examples and should not be used to limit the scope of protection of this application.

[0028] Initial terminal access refers to the process by which a terminal attempts to establish a wireless connection with a base station for the first time. This process is a prerequisite for the terminal to enter the network and obtain communication services. The initial terminal access process mainly includes: (1) Obtaining ephemeris information: The terminal obtains the ephemeris information of the satellite (including the satellite's position, velocity, orbital parameters, etc.) through its built-in storage or external network (such as ground station, cellular network). This information has a certain timeliness and needs to be updated regularly. (2) Calculating satellite dynamic information: The terminal combines its own real-time position (real-time position can be obtained through GPS, Beidou and other positioning systems) and uses ephemeris information to calculate the satellite's real-time position, direction of motion, velocity and other dynamic information at the current moment. (3) Calculating the receiving beam direction: Based on the relative geometric relationship between the terminal's own position and the satellite's real-time position, the azimuth and elevation angles of the satellite relative to the terminal are calculated, thereby determining the receiving beam direction required for the terminal to receive satellite signals. (4) Calculating Doppler frequency offset: Based on the radial velocity of the satellite relative to the terminal, the downlink Doppler frequency offset (frequency offset) caused by high-speed motion is calculated. (5) Configure receiving parameters: Based on the calculation results, the terminal adjusts its receiving beam to point towards the satellite and continuously receives the cell synchronization signal transmitted by the satellite on the fixed frequency resources specified in the communication protocol. (6) Doppler frequency offset compensation: The terminal performs Doppler frequency offset compensation on the received signal to eliminate signal distortion caused by frequency offset. (7) Detect cell access signal: After completing the above steps, the terminal can accurately detect and demodulate the cell access signal transmitted by the satellite, and successfully complete the initial access process.

[0029] Before initiating an access process, a terminal needs to obtain the base station's direction and motion status information (which can be collectively referred to as the base station's dynamic information) to calculate the appropriate signal receiving beam direction. For example, in satellite communication systems, terminals typically use ephemeris data to obtain this information. Ephemeris data is either input from the terrestrial network or obtained from the base station information after the terminal's last access to the satellite network. Furthermore, ephemeris information has a certain time sensitivity; if it is not updated for a long time, it can lead to significant errors or even become unusable. Therefore, in some application scenarios, such as areas without other communication network coverage and where the terminal has not accessed a satellite network for a considerable period, the terminal cannot pre-calculate the appropriate signal receiving beam direction, making it difficult for the terminal to complete the initial access process.

[0030] Currently, there are roughly three types of solutions for dealing with the above scenarios, including: The first type: beam scanning scheme; when the terminal cannot obtain prior information about the current location or beam direction of the base station, it can continuously switch the receiving beam direction according to a predetermined pattern (such as random or fixed order) to search for cell synchronization signals in all possible spatial angles. However, the cell synchronization signal of the base station is not always omnidirectionally transmitted, but periodically and intermittently transmitted along its own high-speed trajectory in a direction that changes over time. Therefore, the terminal's scanning beam and the base station's transmitted beam need to coincide in time and space to detect the signal. Once they are misaligned, even if the terminal scans in all directions, it may never capture the synchronization signal, leading to access failure or extremely long access times. The second type: wide beam receiving scheme; the terminal uses a receiving beam with a large beamwidth to cover the potential airspace to capture the cell synchronization signal transmitted by the satellite base station. This scheme simplifies the spatial search dimension by expanding the beam coverage, thereby avoiding dependence on real-time satellite location information. However, beamwidth is inversely proportional to antenna array gain. According to antenna theory, beam widening leads to a decrease in effective array gain, and consequently, a reduction in received signal power. Under limited satellite link budgets, the carrier-to-noise ratio also deteriorates, resulting in a lower probability of synchronization sequence detection. When the signal strength falls below the receiver sensitivity threshold, the terminal will be unable to complete downlink synchronization, ultimately leading to access failure. The third approach combines beam scanning and wide-beam reception. In summary, existing technologies sacrifice a certain probability of successful access to achieve access capabilities in scenarios lacking dynamic information from base station nodes, potentially leading to excessively long access times or inability to access the network at all.

[0031] In view of this, embodiments of this application provide a terminal access method. This method integrates base station direction information and timing information into a spatiotemporal synchronization signal. The terminal can complete direction alignment and symbol timing without having to obtain base station dynamic parameters in advance, which is beneficial to improving the initial access success rate of the terminal. On the other hand, the frequency offset measurement signal is sent in the form of a fixed pilot sequence. After obtaining the direction and timing information, the terminal can directly use this sequence to estimate and compensate for the residual frequency offset, avoiding secondary signaling interaction and reducing air interface load. Furthermore, the base station direction information, timing information, and pilot sequence are all transmitted in a signal embedded manner, and the terminal can complete the terminal access process without external assistance, improving the reliability of terminal access.

[0032] Before introducing the aforementioned terminal access method, its application scenarios are first described: The technical solution of this application can be applied to non-terrestrial network (NTN) systems such as satellite communication systems and High Altitude Platform Station (HAPS) communication, for example, integrated communication and navigation (ICaN) systems, Global Navigation Satellite System (GNSS), etc. Satellite communication systems can be integrated with traditional mobile communication systems. For example, the mobile communication system can be a 4th generation (4G) communication system (e.g., Long Term Evolution (LTE) system), a Worldwide Interoperability for Microwave Access (WiMAX) communication system, a 5th generation (5G) communication system (e.g., New Radio (NR) system), and future mobile communication systems, etc. Please see [link to relevant documentation]. Figure 1 , Figure 1 This is a schematic diagram of a multi-beam mobile satellite communication system applicable to embodiments of this application. For example... Figure 1As shown, the satellite provides communication services to terminal devices through multiple beams. In this scenario, the satellite is a non-geostationary earth orbit (NGEO) satellite connected to core network equipment. The satellite uses multiple beams to cover the service area, and different beams can communicate through one or more of time division, frequency division, and space division. The satellite provides communication and navigation services to terminal devices by broadcasting communication and navigation signals. The satellite mentioned in this embodiment can also be a satellite base station or a network-side device mounted on a satellite. Exemplarily, satellite communication systems can be classified into three types based on their orbital altitude: Geostationary Earth Orbit (GEO) satellite communication systems (also known as synchronous orbit satellite communication systems); Medium Earth Orbit (MEO) satellite communication systems; and Low Earth Orbit (LEO) satellite communication systems. GEO satellites, with an orbital altitude of 35,786 km, have the main advantage of remaining relatively stationary relative to the ground and providing a large coverage area. However, GEO satellite communication also has significant drawbacks: GEO satellites orbit at great distances from Earth, resulting in high free-space propagation loss and strained communication link budgets. Furthermore, to increase transmission or reception gain, large-aperture antennas are required. GEO communication suffers from high transmission latency, reaching approximately 500ms round-trip time, which fails to meet the demands of low-latency services. GEO orbital resources are also relatively scarce, leading to high launch costs and an inability to provide coverage to the polar regions. MEO satellites orbit at altitudes between 2000 and 35786 km. Their advantage lies in achieving global coverage with a relatively small number of satellites, but their orbital altitude is higher than LEO, resulting in still relatively high transmission latency. LEO satellites, on the other hand, orbit at altitudes between 300 and 2000 km. Lower than MEO and GEO orbits, LEO satellites offer advantages such as lower data propagation latency, lower transmission loss, and lower launch costs. Of course, in specific application scenarios, LEO satellites can be replaced by GEO or MEO satellites, or even combinations of multiple satellite types.

[0033] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings. Please refer to... Figure 2 This application provides a terminal access method, which includes: Step S110: Generate cell synchronization auxiliary signal; wherein, the cell synchronization auxiliary signal includes spatiotemporal synchronization signal and frequency offset measurement signal; the spatiotemporal synchronization signal carries base station direction information and timing information of the base station; the frequency offset measurement signal carries pilot sequence.

[0034] The spatiotemporal synchronization signal in the aforementioned cell synchronization auxiliary signal is used to transmit the spatial pointing and symbol timing reference of the satellite base station to the terminal in the downlink, enabling the terminal to complete beam alignment and symbol boundary alignment even without knowing the dynamic information of the base station. The frequency offset measurement signal is used to provide the terminal with a known pilot sequence in the downlink, allowing the terminal to estimate and compensate for residual Doppler frequency offset through phase or frequency domain processing, ensuring the correctness of subsequent data demodulation. The aforementioned base station direction information refers to the azimuth-elevation vector with the ground terminal as the reference origin, used to indicate the spatial pointing of the satellite base station relative to the terminal, allowing the terminal to adjust the receiving beam direction. The timing information refers to the downlink symbol start time and radio frame boundary, used by the terminal to align the OFDM (Orthogonal Frequency Division Multiplexing) demodulation window and avoid inter-symbol interference. The pilot sequence is a predefined, known complex numerical sequence embedded in the frequency offset measurement signal; its phase rotation is used by the terminal to calculate and correct the downlink Doppler frequency offset. It is understandable that the above description of the initial terminal access process mentions cell access signals. The following explains the difference between cell access signals and the cell synchronization auxiliary signals provided in the embodiments of this application: Cell access signals refer to the set of downlink physical layer signals specifically transmitted by the satellite base station for the initial network access of the terminal. These may include the primary synchronization sequence (PSS), secondary synchronization sequence (SSS), physical broadcast channel (PBCH), and the main information block (MIB) it carries. Cell access signals generally employ service-level subcarrier spacing and dynamically scheduled resources. Their transmission period, bandwidth, and beam pointing all change with service requirements, failing to meet the terminal's need for continuous, fixed, and narrowband synchronization resources in scenarios without prior information. The aforementioned newly added cell synchronization auxiliary signals can carry direction information, timing references, and pilot sequences, thereby achieving an independent link for the terminal's initial acquisition, frequency offset estimation, and direction alignment without interfering with existing services, ensuring initial access success rate and latency performance. Furthermore, the process by which the terminal uses the aforementioned cell synchronization auxiliary signal to complete direction acquisition, timing synchronization, and frequency offset estimation can be referred to as the blind access process. After this process is completed, the terminal still needs to receive and parse the cell access signal to obtain the random access configuration, and then execute the random access procedure to complete the final terminal access.

[0035] The following describes the composition and generation scheme of the aforementioned cell synchronization auxiliary signal: Optionally, the aforementioned spatiotemporal synchronization signal includes a primary spatiotemporal synchronization signal and a secondary spatiotemporal synchronization signal. The determination method of the spatiotemporal synchronization signal in the aforementioned cell synchronization auxiliary signal includes: acquiring the primary spatiotemporal synchronization signal sequence and the secondary spatiotemporal synchronization signal sequence; in the baseband frequency domain, mapping the primary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of a preset beam and performing modulation processing to obtain the primary spatiotemporal synchronization signal; in the baseband frequency domain, mapping the secondary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of a preset beam and performing modulation processing to obtain the secondary spatiotemporal synchronization signal. Both the primary spatiotemporal synchronization signal sequence and the secondary spatiotemporal synchronization signal sequence are discrete complex-valued sequences generated by the base station, and can respectively adopt the root sequence form of PSS (Primary Synchronization Signal) and SSS (Secondary Synchronization Signal) as defined in the 5G NR specification, each with a length of 127 symbols. The primary spatiotemporal synchronization signal sequence is mainly used by the terminal to extract symbol timing references and extend frequency offset tolerance, while the secondary spatiotemporal synchronization signal sequence is used by the terminal to obtain the direction index of the satellite base station and confirm the frame boundary. The two can be mapped to the same bandwidth center subcarrier in the baseband frequency domain and then modulated to obtain the corresponding time domain synchronization signal.

[0036] The above scheme maps the primary and secondary spatiotemporal synchronization signal sequences to the same bandwidth location of a preset beam, forming a single carrier reference in the frequency domain. This allows the base station to simultaneously carry two synchronization sequences with only one RF configuration, avoiding the additional local oscillator and filtering resources required for separate center frequencies. Sharing a center subcarrier also ensures that the two sequences experience the same channel response, eliminating gain mismatch caused by frequency domain position differences. After acquiring the primary spatiotemporal synchronization signal sequence, the terminal can seamlessly receive the secondary spatiotemporal synchronization signal sequence at the same frequency point without retuning, shortening synchronization time and reducing hardware complexity. Furthermore, after inverse Fourier transform, the primary and secondary spatiotemporal synchronization signal sequences are concatenated end-to-end in the time domain in the order of primary to secondary, forming a continuous symbol stream. This allows the primary and secondary spatiotemporal synchronization signal sequences to be sequentially concatenated in the time domain and co-centered in the frequency domain.

[0037] For example, the above-mentioned scheme for modulating the synchronization signal sequence to obtain the synchronization signal can be as follows: after completing the sequence mapping in the baseband frequency domain, perform an inverse discrete Fourier transform on the mapping result to generate a time-domain OFDM symbol, and insert a cyclic prefix at the front end of the symbol to form a synchronization signal.

[0038] The above scheme achieves unified resource allocation at the same center frequency by mapping the primary and secondary spatiotemporal synchronization signal sequences to the center subcarrier position of the first bandwidth of the preset beam. This simplifies RF front-end filtering and carrier configuration and reduces hardware complexity. On the other hand, center subcarrier mapping can reduce the filter roll-off and adjacent channel interference that may be introduced by the edge frequency band, so that the primary and secondary spatiotemporal synchronization signal sequences obtain symmetrical and consistent channel responses in the frequency domain, thereby improving the detection reliability of cell synchronization auxiliary signals. Furthermore, the design of the primary and secondary spatiotemporal synchronization signal sequences being sequentially cascaded in the time domain and co-centered in the frequency domain allows the ground terminal to continuously acquire the secondary spatiotemporal synchronization signal without retuning the local oscillator after completing coarse timing, which helps to shorten the terminal access time.

[0039] The following describes the method by which the aforementioned spatiotemporal synchronization signal carries base station direction information: Optionally, the base station direction information includes spatial wavelets. After obtaining the primary spatiotemporal synchronization signal sequence and the secondary spatiotemporal synchronization signal sequence, the aforementioned terminal access method further includes: obtaining a first index of the primary spatiotemporal synchronization signal sequence and a second index of the secondary spatiotemporal synchronization signal sequence; based on the first and second indices, obtaining an index group of synchronization signal sequence groups composed of the primary spatiotemporal synchronization signal sequence and the secondary spatiotemporal synchronization signal sequence; assigning a unique spatial wavelet to each index group; wherein, the spatial wavelet is used to indicate the spatial orientation of the base station relative to the terminal. The principle that the aforementioned spatiotemporal synchronization signal can carry base station direction information is as follows: assuming the primary spatiotemporal synchronization signal sequence adopts PSS format and the secondary spatiotemporal synchronization signal sequence adopts SSS format. Then, the value range of the primary spatiotemporal synchronization signal sequence is 0, 1, and 2, a total of 3 values. The value range of the secondary spatiotemporal synchronization signal sequence is 0 to 335, a total of 336 values. By combining the values ​​of the primary and secondary spatiotemporal synchronization signal sequences one by one, 3 × 336 = 1008 unique index groups can be formed. Before assigning unique corresponding spatial positions to the index groups, the spatial positions can be divided. For example, with the ground terminal as the origin, the upper hemisphere airspace can be discretized to form 1008 non-overlapping solid angle units, each unit being a spatial position. Each spatial position is then assigned a unique number from 0 to 1007 in sequence. Finally, a one-to-one mapping table can be established between the 1008 index pairs and the 1008 spatial position numbers. When the terminal detects a certain index group, it can directly obtain the corresponding spatial position number by looking up the table, thereby determining the spatial orientation of the base station relative to the terminal.

[0040] The aforementioned method for dividing the airspace prepositions is as follows: Using the ground terminal as the origin, the entire upper hemisphere airspace is discretized into a finite number of non-overlapping solid angle units. First, the airspace boundary is determined based on the satellite orbital altitude and ground visibility, ensuring coverage of all possible service elevation angles. Then, using a latitude-longitude grid or regular polyhedral subdivision method, the airspace is progressively subdivided into several sub-regions of equal area or equal solid angle. Each sub-region corresponds to one airspace preposition and is assigned a unique index. During the division process, the angular interval between adjacent prepositions is kept uniform to avoid beam pointing blind spots or overlaps. The final preposition set does not exceed a specified number, and the center direction of each preposition is known and fixed, serving as a reference for terminal beam alignment and direction information mapping.

[0041] The above scheme maps a unique index group, consisting of a first index of the primary synchronization signal sequence and a second index of the secondary synchronization signal sequence, to a unique spatial spectral position. This allows the terminal to directly obtain the spatial orientation of the base station relative to the terminal after completing synchronization detection, without the need for additional direction-finding hardware or signaling interaction, thus reducing implementation complexity. On the other hand, the spatial spectral position discretizes the entire hemispherical coverage area in the form of solid angle units, with a one-to-one correspondence between the index group and the spatial spectral position, which helps improve the accuracy of direction indication and the uniqueness of the mapping, avoiding beam alignment errors caused by ambiguity of multiple spectral positions. Furthermore, the mapping relationship can be fixed before system deployment, and the terminal only needs to look up a table to resolve the direction information, which helps reduce air interface overhead and shorten the initial access latency. Moreover, the mapping mechanism between the index group and the spatial spectral position reuses existing synchronization sequence resources, without the need to add a new direction signaling field, improving spectral efficiency and maintaining compatibility with the current frame structure specifications.

[0042] The following describes a frequency offset pre-compensation scheme for spatiotemporal synchronization signals: Optionally, before sending the cell synchronization auxiliary signal to the terminal, the terminal access method further includes: determining the Doppler frequency offset of the spatiotemporal synchronization signal based on the expected center frequency of the spatiotemporal synchronization signal, the base station location, the base station motion state, and the downlink beam direction; and performing frequency offset pre-compensation on the auxiliary spatiotemporal synchronization signal based on the Doppler frequency offset. For example, in this implementation: the base station transmits the spatiotemporal synchronization signal... The expected center frequency, the base station's own location, and the base station's motion state determine the downlink beam direction and calculate the Doppler frequency offset of the spatiotemporal synchronization signal. Then use the frequency offset compensation value. Auxiliary spatiotemporal synchronization signal Frequency offset pre-compensation is performed. The above scheme involves transmitting a spatiotemporal synchronization signal. The expected center frequency, the base station's own location, and the base station's motion state determine the downlink beam direction and calculate the Doppler frequency offset of the spatiotemporal synchronization signal. The methods described above, including the method of frequency offset pre-compensation for the secondary spatiotemporal synchronization signal using Doppler frequency offset, are both relatively mature existing technologies in the field. For specific implementation details, please refer to related technologies; these will not be elaborated upon in the embodiments of this application. It is understood that the above scheme can only perform frequency offset pre-compensation on the secondary spatiotemporal synchronization signal within the spatiotemporal synchronization signal. This is because the primary spatiotemporal synchronization signal uses a narrow subcarrier spacing, which already provides sufficient frequency offset tolerance; additional compensation may introduce errors. The secondary spatiotemporal synchronization signal carries directional information, and frequency offset pre-compensation can further compress the residual frequency offset, ensuring accurate directional indication.

[0043] The above scheme performs frequency offset pre-compensation on the auxiliary spatiotemporal synchronization signal based on the real-time location, motion state and beam direction of the base station before transmission, so that the residual frequency offset of the downlink signal when it arrives at the terminal is within the correctable range, and the terminal can directly complete the synchronization sequence detection, shortening the initial acquisition time. On the other hand, the frequency offset pre-compensation can be applied only to the auxiliary synchronization signal, retaining the original frequency offset tolerance of the main synchronization signal, taking into account both acquisition stability and direction resolution accuracy.

[0044] The subcarrier spacing design schemes for the primary and secondary spatiotemporal synchronization signals are described below: Optionally, the terminal access method further includes: determining the first subcarrier spacing of the primary spatiotemporal synchronization signal based on the system downlink subcarrier spacing; wherein, the system downlink subcarrier spacing is determined by the system frame structure; the first subcarrier spacing is smaller than the system downlink subcarrier spacing and larger than the intra-beam frequency offset protection spacing; the intra-beam frequency offset protection spacing is used to characterize the minimum frequency domain protection spacing required by the terminal within the same beam coverage area, and the intra-beam frequency offset protection spacing is determined based on the maximum difference in Doppler frequency offset between the downlink beam center and the downlink beam edge. For example, this implementation method involves using the primary spatiotemporal synchronization signal... The first subcarrier spacing is set to And the first subcarrier spacing satisfies: .in, The system downlink subcarrier spacing; It is a positive integer; This is the beam-internal frequency offset protection interval; This represents the maximum difference in Doppler frequency offset between the downlink beam center and the downlink beam edge, expressed in Hertz (Hz). The downlink subcarrier spacing of the above system... Downlink subcarrier spacing refers to the fixed frequency spacing between adjacent subcarriers in the downlink OFDM waveform. This parameter is uniformly set by the system frame structure specification and directly affects the symbol duration, cyclic prefix length, and maximum supported Doppler tolerance. It is the fundamental granularity for physical layer processes such as waveform generation, resource mapping, and frequency offset estimation. The values ​​can be selected from discrete levels such as 15kHz, 30kHz, 60kHz, 120kHz, and 240kHz, and the corresponding relationship is indicated by the numberology in the higher-layer signaling. In 5G NR, numberology refers to the parameter combination of subcarrier spacing and symbol duration. The method for determining numberology is described in the prior art and will not be repeated in the embodiments of this application.

[0045] Furthermore, since the 5G NR physical layer specification stipulates that all subcarrier spacing can only be an integer power of 2 multiplied by 15kHz, the aforementioned scaling factor can be... Setting it to a positive integer ensures the first subcarrier spacing. It remains within the aforementioned discrete set, thus maintaining an integer multiple relationship with the existing sampling clock, FFT length, and cyclic prefix length, reducing implementation complexity and ensuring terminal compatibility.

[0046] The maximum difference in Doppler frequency offset between the downlink beam center and the downlink beam edge positions mentioned above It can be defined as: the maximum absolute value of the difference between the downlink Doppler frequency offset of the beam edge point and the beam center point due to satellite motion within the same beam coverage area. The determination method can be as follows: the base station obtains the satellite velocity vector based on the real-time ephemeris, and calculates the maximum radial velocity difference between the beam edge and the satellite velocity direction by combining the beam center pointing and the beam angle; after mapping this velocity difference to the downlink carrier frequency, it can be obtained.

[0047] It is understandable that the aforementioned intra-beam frequency offset protection interval can be directly taken as the maximum difference in Doppler frequency offset between the downlink beam center and the downlink beam edge. twice as much, that is The intra-beam frequency offset protection interval is mainly used to reserve extra bandwidth for the frequency-dominant spatiotemporal synchronization signal, ensuring that the maximum bidirectional residual frequency offset that may occur at the beam edge terminal does not cause signal energy to fall into adjacent subcarriers. When the first subcarrier interval is less than At this time, the residual frequency offset of the beam-edge terminals may exceed the fault tolerance range of a single OFDM subcarrier, causing inter-symbol interference. Setting the first subcarrier spacing to be greater than the intra-beam frequency offset protection spacing can ensure that the residual frequency offset of all terminal locations falls within the bandwidth of the main synchronization signal subcarrier. In addition, a larger subcarrier spacing corresponds to a longer symbol duration and a higher energy concentration, allowing the terminal to obtain sufficient correlation peaks even under low-gain wide-beam conditions, thus improving the first acquisition probability.

[0048] The above scheme, by setting the first subcarrier spacing of the primary spatiotemporal synchronization signal to a value smaller than the system downlink subcarrier spacing but larger than the intra-beam frequency offset protection spacing, helps to extend the symbol duration and improve the signal energy concentration. This improves the detection probability of the primary spatiotemporal synchronization signal under wide-beam reception conditions and enhances the robustness of initial access. On the other hand, the intra-beam frequency offset protection spacing is determined based on the maximum difference in Doppler frequency offset between the downlink beam center and the beam edge, ensuring that the first subcarrier spacing can cover the maximum residual frequency offset at any terminal location. This helps to achieve a complete and distortion-free primary spatiotemporal synchronization signal in the frequency domain and reduces the risk of synchronization failure due to frequency offset. Furthermore, the narrowband design of the first subcarrier spacing, while maintaining frequency offset tolerance, reduces the occupation of spectrum resources, reserving more idle bandwidth for the frequency offset measurement signal in the cell synchronization auxiliary signal and optimizing the resource allocation efficiency of the entire cell synchronization auxiliary signal.

[0049] Optionally, the above terminal access method further includes: determining a second subcarrier interval for the auxiliary spatiotemporal synchronization signal based on the system downlink subcarrier interval; wherein the system downlink subcarrier interval is determined by the system frame structure; and the second subcarrier interval is equal to the system downlink subcarrier interval. For example, this implementation method uses the auxiliary spatiotemporal synchronization signal... The second subcarrier spacing is set to the same as the system downlink subcarrier spacing. Equal values. This is understandable, given the system downlink subcarrier spacing. This is a fixed granularity defined by the system frame structure. Downlink physical channels (such as broadcast channels, control channels, and data channels) all use this as a reference for resource mapping and parameter calculation. The second subcarrier interval of the auxiliary spatiotemporal synchronization signal is directly set to the same as the system downlink subcarrier interval. Equal values ​​ensure that the secondary spatiotemporal synchronization signal remains consistent with the existing downlink in terms of frequency domain position, symbol duration, cyclic prefix length, and resource unit partitioning, without the need to introduce new sampling rates or transformation lengths. This maintains a unified time-frequency grid and ensures that the terminal can continuously complete synchronization, system information reception, and subsequent service processing under the same numberology.

[0050] The above scheme sets the second subcarrier spacing of the auxiliary spatiotemporal synchronization signal to be equal to the downlink subcarrier spacing of the system. This ensures that the auxiliary spatiotemporal synchronization signal maintains consistency with the subsequent broadcast channel in terms of frequency domain position, symbol duration, and cyclic prefix length. This allows the terminal to directly parse the auxiliary spatiotemporal synchronization signal without reconfiguring baseband parameters after acquiring the main spatiotemporal synchronization signal, reducing state switching delay. On the other hand, the auxiliary spatiotemporal synchronization signal is synchronized with the system resource grid, reducing frequency domain resampling or interpolation operations caused by differences in factor carrier spacing, thus reducing the computational load and power consumption of the digital front end. Furthermore, the unified subcarrier spacing ensures that all terminals within the beam use the same frequency offset compensation coefficient at any position, eliminating the need for the network side to issue additional calibration information for different terminal positions, thus simplifying the system signaling process.

[0051] The following describes a method for determining the bandwidth occupied by the spatiotemporal synchronization signal in a preset beam: Optionally, the above terminal access method further includes: determining a first bandwidth of the spatiotemporal synchronization signal; wherein, the first bandwidth is not less than the minimum frequency domain protection bandwidth; the minimum frequency domain protection bandwidth is determined based on the occupied bandwidth of the spatiotemporal synchronization signal and the full-link frequency offset protection bandwidth; the full-link frequency offset protection bandwidth is determined based on the maximum downlink Doppler frequency offset of the system. For example, this implementation requires the first bandwidth of the spatiotemporal synchronization signal to meet the following constraints: .in, The system downlink subcarrier spacing; Auxiliary spatiotemporal synchronization signal sequence The sequence length; This represents the second bandwidth of the auxiliary spatiotemporal synchronization signal; This represents the maximum downlink Doppler frequency offset of the system. This is the bandwidth for full-link frequency offset protection.

[0052] It is understandable that the above content describes a design where the primary and secondary spatiotemporal synchronization signal sequences are time-domain cascaded and frequency-domain co-centered, sharing the same center carrier but with different subcarrier spacings. The primary spatiotemporal synchronization signal sequence uses a narrower subcarrier spacing, and its first bandwidth is always less than or equal to the second bandwidth of the secondary synchronization sequence. Therefore, the second bandwidth of the secondary spatiotemporal synchronization signal sequence can be used... This represents the bandwidth occupied by the spatiotemporal synchronization signal.

[0053] The above system downlink maximum Doppler frequency offset This refers to the maximum frequency offset that may occur in the downlink of a non-terrestrial wireless communication system due to the high-speed movement of the satellite-borne base station. The calculation can be performed based on the downlink carrier frequency and the maximum speed of the base station. The calculation method can be found in relevant technologies, and will not be repeated in the embodiments of this application. End-link frequency offset protection bandwidth. This is to address the maximum downlink Doppler frequency offset of the system. The frequency drift that may be introduced in both positive and negative directions, and the symmetrical guard band width reserved for the synchronization signal in the frequency domain, are equal in value to Twice the bandwidth is used to ensure that the residual frequency offset at any terminal location does not exceed this bandwidth range. It is understood that the constraints mentioned above... This indicates the constraint on the bandwidth requirements of the spatiotemporal synchronization signal. This represents the constraint of the spatiotemporal synchronization signal on the maximum bidirectional participation frequency offset of the downlink coverage. Together, these two constitute the requirement constraint of the spatiotemporal synchronization signal on the minimum frequency domain bandwidth. If the first bandwidth of the spatiotemporal synchronization signal does not meet the above constraint, the residual frequency offset of the beam edge terminal will exceed the spectrum boundary, causing sequence energy leakage to neighboring subcarriers, resulting in the terminal being unable to correctly decode the direction index.

[0054] The above scheme sets the lower bound of the first bandwidth to be no less than the minimum frequency domain protection bandwidth, which ensures that the spatiotemporal synchronization signal always has sufficient frequency domain resources within the entire beam coverage area, avoids spectrum truncation, and improves the terminal detection success rate. On the other hand, the minimum frequency domain protection bandwidth is jointly determined by the occupied bandwidth and the full-link frequency offset protection bandwidth, so that the resource allocation is precisely matched with the link Doppler conditions, reducing redundant frequency bands and improving spectrum utilization. Furthermore, the full-link frequency offset protection bandwidth is calculated based on the maximum downlink Doppler frequency offset of the system, which helps to simplify the network-side parameter configuration process.

[0055] It is understandable that the difference between the primary spatiotemporal synchronization signal in this embodiment and the PSS in the protocol lies in the redesign of the subcarrier spacing and the expansion of the frequency offset tolerance. The difference between the secondary spatiotemporal synchronization signal and the SSS in the protocol lies in the additional spatial bit information carried through the index group mapping mechanism. Specifically, the protocol PSS in the protocol is only used for symbol timing and preliminary detection of the cell group ID, while the primary spatiotemporal synchronization signal is designed with an extended frequency offset tolerance. Therefore, its transmit subcarrier spacing is explicitly set to a value smaller than the system downlink subcarrier spacing and larger than the intra-beam frequency offset protection interval, resulting in a longer symbol duration and increased energy concentration, thus enabling reliable detection even when the terminal uses wide-beam reception and there is a large frequency offset. The subcarrier spacing of the protocol PSS is fixed equal to the system downlink subcarrier spacing and is not further optimized for wide-beam scenarios. The SSS in the protocol is only used to carry the cell group ID and the intra-cell ID. The secondary spatiotemporal synchronization signal, while retaining the aforementioned identification function, also maps to one of 1008 spatial positions through a unique index group composed of the first index of the primary spatiotemporal synchronization signal sequence and the second index of the secondary spatiotemporal synchronization signal sequence. This embeds the spatial pointing information of the satellite base station relative to the terminal into the sequence combination. After demodulating the secondary spatiotemporal synchronization signal, the terminal can directly obtain the base station direction without additional direction-finding hardware or signaling interaction. The SSS protocol itself does not contain any spatial pointing information.

[0056] The following describes the generation scheme for the frequency offset measurement signal: Optionally, the determination method for the frequency offset measurement signal in the cell synchronization auxiliary signal includes: determining the sequence length of the pilot sequence based on the third subcarrier spacing and the second bandwidth of the frequency offset measurement signal; generating the pilot sequence based on the sequence length; sparsely sampling the pilot sequence to obtain a frequency-domain sparse pilot sequence; and mapping the pilot sequence to the center subcarrier position of the second bandwidth of a preset beam in the baseband frequency domain, and performing modulation processing to obtain the frequency offset measurement signal. For example, in this implementation: first, the sequence length of the pilot sequence is calculated. ,in, The third subcarrier spacing of the frequency offset measurement signal; It is a positive integer; The second bandwidth of the frequency offset measurement signal is given; then, a pilot sequence of length [length missing] can be generated using existing protocols. pilot sequence and in Fill after each element A zero, to get Then Placed in the second bandwidth The center position; finally, the frequency offset measurement signal located in the baseband time domain is generated using the method of generating baseband time domain signals according to the protocol. The above. A positive integer, which can be used to adjust the sparsity of the pilot sequence. Fill after each element After the zero, the effective subcarrier spacing of the pilot sequence is expanded to the original value. This results in a sparse frequency domain structure. This sparse structure helps the terminal to perform accurate frequency offset estimation over a large frequency offset range, while reducing the spectral resource occupation of the pilot sequence. Furthermore, the second bandwidth of the aforementioned frequency offset measurement signal can be determined by the bandwidth resources available from the preset beam and the first bandwidth of the spatiotemporal synchronization signal. The bandwidth occupied by the spatiotemporal synchronization signal and the frequency offset measurement signal should be less than the bandwidth resources available from the preset beam; that is, the sum of the first and second bandwidths should be less than the bandwidth resources available from the preset beam.

[0057] The above scheme calculates the pilot sequence length by using the third subcarrier spacing and the second bandwidth as constraints, ensuring that the sequence length strictly matches the fixed bandwidth, avoiding spectrum waste and simplifying resource planning. On the other hand, after sparsely sampling the pilot sequence in the baseband frequency domain, it is mapped to the center subcarrier to form a pilot sequence, enabling the terminal to accurately extract phase information within a wide frequency offset range, thus improving the frequency offset estimation accuracy. Furthermore, sparse sampling reduces pilot density while maintaining estimation performance, thereby reducing pilot overhead and improving spectrum utilization.

[0058] The subcarrier spacing design scheme for the frequency offset measurement signal is described below: Optionally, the terminal access method further includes: determining the third subcarrier spacing of the frequency domain measurement signal; wherein the third subcarrier spacing is greater than the full-link frequency offset protection bandwidth; wherein the full-link frequency offset protection bandwidth is determined based on the system's downlink maximum Doppler frequency offset. For example, this implementation sets the third subcarrier spacing of the frequency offset measurement signal to... And satisfy: ,in, For end-to-end frequency offset protection bandwidth, It is a positive integer. The aforementioned third subcarrier spacing must satisfy... This is to ensure that the frequency offset measurement signal can cover the maximum frequency offset range of the entire link, thereby providing accurate frequency offset estimation. This not only avoids spectrum leakage to adjacent subcarriers due to excessive frequency offset, improving the accuracy of frequency offset estimation, but also enhances the robustness of the aforementioned terminal access method under harsh conditions such as high-speed movement, improving the reliability and stability of communication.

[0059] The above scheme sets the third subcarrier spacing to be greater than the full-link frequency offset protection bandwidth, so that the frequency offset measurement signal remains resolvable within the full-link frequency offset range, and the terminal can directly extract the frequency offset estimation result; on the other hand, the larger spacing can reduce pilot density, reduce resource overhead, and improve spectrum utilization.

[0060] Step S120: Send a cell synchronization assist signal to the terminal so that the terminal can demodulate the cell synchronization assist signal and access the terminal based on the demodulated base station direction information, timing information and pilot sequence.

[0061] Optionally, the aforementioned preset beam is an access beam; wherein, the access beam is a downlink beam in the base station used for initial access. Step S120 may include: using the idle bandwidth resources in the access beam to send a cell synchronization assist signal to the terminal; wherein, the sum of the first bandwidth of the spatiotemporal synchronization signal and the second bandwidth of the frequency offset measurement signal is not greater than the idle bandwidth resources.

[0062] The aforementioned idle bandwidth resources refer to the bandwidth resources that will not be occupied at any time during the access beam's operation. This means that throughout the entire operation of the access beam, regardless of the dynamic scheduling of service data or control signaling, this portion of bandwidth can always be reserved for the cell synchronization auxiliary signal. The idle bandwidth resources can be dedicated to carrying spatiotemporal synchronization signals and frequency offset measurement signals, ensuring that these signals can be transmitted stably at any time without interference from other services or control signals. The aforementioned cell synchronization auxiliary signal can be compatible with the existing cell access signal in the following three aspects: (1) Frequency domain compatibility: The cell synchronization auxiliary signal is mapped to the idle bandwidth of the access beam, and the sum of its first bandwidth and second bandwidth does not exceed the idle bandwidth resources, ensuring no frequency domain overlap with the existing cell access signal and avoiding interference. (2) Time domain compatibility: The cell synchronization auxiliary signal is continuously transmitted, while the existing cell access signal is dynamically scheduled as needed. The two are independent in the time domain, sharing the same beam but not interfering with each other. (3) Functional compatibility: The cell synchronization auxiliary signal provides the terminal with the direction, timing and pilot sequence required for initial access, while the existing cell access signal carries system information and access configuration. The two complement each other in function and jointly complete the terminal's network access process.

[0063] The above scheme uses the idle bandwidth of the access beam to transmit cell synchronization auxiliary signals, eliminating the need to allocate separate frequency domain resources for cell synchronization auxiliary signals. This helps improve spectrum utilization and reduce the complexity of system bandwidth planning. Furthermore, the sum of the first and second bandwidths is limited by the idle bandwidth, avoiding interference with other channels. Additionally, the transmission parameters of the access beam have been optimized for the initial acquisition scenario, ensuring reliable reception by the terminal even without prior information. The cell synchronization auxiliary signal reuses these parameters, sharing the same gain, coverage, and power control link with existing service signals, eliminating the need for a separate beam management module and simplifying the onboard RF link design. Moreover, the fixed mapping mechanism of the access beam's idle bandwidth allows the base station to send cell access signals and cell synchronization auxiliary signals to the terminal via the access beam with only one configuration, avoiding the signaling overhead caused by dynamic resource scheduling and simplifying the onboard processing flow.

[0064] Optionally, step S120 may include: continuously sending a spatiotemporal synchronization signal to the terminal; and continuously or periodically sending a frequency offset measurement signal to the terminal. It is understood that since the spatiotemporal synchronization signal is responsible for providing the terminal with the symbol timing and base station direction information required for initial access, and it is necessary to ensure that the terminal can complete synchronization acquisition at any time, the spatiotemporal synchronization signal can be continuously transmitted to the terminal. The frequency offset measurement signal is used for subsequent frequency offset estimation and compensation; therefore, the transmission mechanism of the frequency offset measurement signal can be flexibly switched between continuous transmission and periodic transmission.

[0065] The above scheme enables the terminal to capture the synchronization signal throughout the entire access window by continuously transmitting the spatiotemporal synchronization signal, avoiding missed detections caused by intermittent transmission, improving the probability of first capture and shortening the search time. On the other hand, the frequency offset measurement signal is transmitted in the same beam as the spatiotemporal synchronization signal in a continuous or periodic manner. After obtaining coarse synchronization, the terminal can perform frequency offset estimation without waiting for additional triggering, thus reducing access latency.

[0066] Please see Figure 3 Based on the same inventive concept, embodiments of this application also provide a terminal access method applied to a terminal, the method comprising: Step S210: Receive the spatiotemporal synchronization signal from the cell auxiliary synchronization signal sent by the base station.

[0067] Within a preset first bandwidth, the terminal uses a wide beam to listen to the spatiotemporal synchronization signal from the base station. The spatiotemporal synchronization signal contains the base station's direction information and timing information. By detecting the primary and secondary spatiotemporal synchronization signals in the spatiotemporal synchronization signal, the terminal achieves initial synchronization with the base station and obtains the base station's direction and timing information, laying the foundation for subsequent communication steps.

[0068] Step S220: Based on the spatiotemporal synchronization signal, determine the base station direction information and timing information of the base station.

[0069] The terminal detected the main spatiotemporal synchronization signal in the spatiotemporal synchronization signal. Later, due to The first subcarrier spacing is designed as And the system parameters satisfy The terminal can successfully capture data using existing PSS detection algorithms without frequency offset pre-compensation. This allows the terminal to obtain the timing position, i.e., the timing time information. Upon successful acquisition, the terminal obtains the timing position of the primary spatiotemporal synchronization signal, which is the timing time information used to complete symbol timing synchronization. Subsequently, based on the timing position of the primary spatiotemporal synchronization signal, the terminal calculates the secondary spatiotemporal synchronization signal. The start time is determined, and the received signal segment within the corresponding time period is extracted. The terminal processes this signal segment using the existing SSS detection algorithm to complete the detection of the secondary spatiotemporal synchronization signal. Since the base station has already performed frequency offset pre-compensation for the secondary spatiotemporal synchronization signal, and the system design has ensured that the first bandwidth of the spatiotemporal synchronization signal meets the following requirements: The terminal can accurately demodulate the secondary spatiotemporal synchronization signal under controllable residual frequency offset. The terminal uses a unique index group formed by combining the first index of the primary spatiotemporal synchronization signal and the second index of the secondary spatiotemporal synchronization signal to look up and map to one of the multiple pre-configured spatial positions in the system. Each spatial position uniquely corresponds to a spatial pointing angle. Through this mapping relationship, the terminal can directly obtain the base station direction information of the satellite base station relative to the terminal, which is used for subsequent beam alignment.

[0070] Step S230: After obtaining the base station direction information and timing information, receive the frequency offset measurement signal in the cell auxiliary synchronization signal sent by the base station; wherein, the frequency offset measurement signal carries a pilot sequence.

[0071] After successfully acquiring the base station direction information and timing information in step S220, the terminal precisely aligns the receiving beam with the direction of the satellite-borne base station based on the acquired base station direction information (i.e., the azimuth-elevation vector corresponding to the spatial wave position), and based on the timing information (i.e., the main spatiotemporal synchronization signal). Timing position and auxiliary time-space synchronization signal A precise symbol timing reference is established at the start time. At this point, the terminal has completed initial synchronization and direction alignment, and is capable of stably receiving subsequent signals. Subsequently, the terminal, according to the system's pre-configured frequency offset measurement signal period (if the frequency offset measurement signal is periodically transmitted) or continuous reception mechanism, receives signals within the second bandwidth of the preset beam. Internal receive frequency offset measurement signal The signal carries a frequency-sparse pilot sequence. Its third subcarrier spacing is And satisfy This ensures coverage of the maximum Doppler frequency offset range across the entire link. The terminal utilizes established timing synchronization to extract the frequency offset measurement signal within the correct time window, and estimates the residual Doppler frequency offset through phase or frequency domain processing, providing a basis for frequency offset compensation for subsequent signal demodulation.

[0072] Step S240: Perform residual frequency offset compensation on the subsequently received downlink signal based on the pilot sequence.

[0073] The terminal extracts the sparse pilot sequence. Subsequently, existing frequency offset estimation algorithms (such as those based on pilot phase rotation or frequency domain correlation) can be used to estimate the residual Doppler frequency offset. After determining the estimated residual frequency offset, the terminal can use it as a frequency offset compensation amount to compensate for the residual frequency offset of all subsequently received downlink signals through complex conjugate multiplication or frequency domain rotation. For specific compensation methods, please refer to relevant technologies; this application's embodiments will not elaborate further. After compensation, the residual frequency offset is eliminated, and the carrier frequency of the downlink signal is aligned with the terminal's local oscillator frequency, meeting the frequency offset tolerance requirements for subsequent demodulation, channel estimation, and data detection. The entire compensation process requires no additional signaling from the base station and is entirely completed autonomously by the terminal based on the received pilot sequence.

[0074] Step S250: After detecting the cell access signal, complete the terminal access based on the cell access signal.

[0075] After completing residual frequency offset compensation, the terminal continuously aligns its receiving beam with the direction of the base station and listens for cell access signals on the system's preset fixed frequency resources. These cell access signals are transmitted by the base station through the access beam at service-level subcarrier intervals and dynamically scheduled resources. The terminal uses the frequency offset compensation result obtained in step S240 to correct the frequency offset of the received signal, ensuring complete carrier frequency alignment.

[0076] It should be noted that the technology of using existing cell access signals for terminal access is a relatively mature existing technology in this field. For specific implementation methods, please refer to the relevant technologies. The embodiments in this application will not be repeated.

[0077] Please see Figure 4 Based on the same inventive concept, this application also provides a terminal access method, which includes the following steps performed by a base station: Step S110: generating a cell synchronization assistance signal; wherein, the cell synchronization assistance signal includes a spatiotemporal synchronization signal and a frequency offset measurement signal; the spatiotemporal synchronization signal carries base station direction information and timing information of the base station; the frequency offset measurement signal carries a pilot sequence; Step S120: sending the cell synchronization assistance signal to the terminal so that the terminal demodulates the cell synchronization assistance signal and performs terminal access based on the demodulated base station direction information, timing information and pilot sequence. The terminal performs the following steps: Step S210: Receive the spatiotemporal synchronization signal from the cell auxiliary synchronization signal sent by the base station; Step S220: Determine the base station direction information and timing information based on the spatiotemporal synchronization signal; Step S230: After obtaining the base station direction information and timing information, receive the frequency offset measurement signal from the cell auxiliary synchronization signal sent by the base station; wherein, the frequency offset measurement signal carries a pilot sequence; Step S240: Perform residual frequency offset compensation on the subsequently received downlink signal based on the pilot sequence; Step S250: After detecting the cell access signal, complete the terminal access based on the cell access signal.

[0078] For ease of understanding, this application provides specific implementation steps of the above-described terminal access method in a certain application scenario for the base station and the terminal, mainly including: Step 1: Configure the static parameters of the communication system on the base station side; The static parameters that need to be configured include: (1) the maximum downlink Doppler frequency offset of the system. (1) Calculated using existing methods based on downlink carrier frequency and maximum base station speed, in Hertz; (2) Downlink system subcarrier spacing (3) The maximum difference in Doppler frequency offset between the downlink beam center and the edge position. , ...

[0079] Step 2: Design the cell synchronization auxiliary signal; 1. Spatiotemporal Synchronization Signal: The spatiotemporal synchronization signal is used by the terminal to measure the timing of the downlink signal from the base station and the direction of the satellite base station relative to the terminal. The design of the spatiotemporal synchronization signal includes the spatiotemporal synchronization sequence. Design and transmission subcarrier spacing design, including: spatiotemporal synchronization sequence Including the main spatiotemporal synchronization signal With auxiliary spatiotemporal synchronization signal Both use the existing 5G protocol's synchronization sequences PSS and SSS respectively. and There are 3 and 336 possible values ​​respectively, resulting in 1008 possible combinations. Each combination can represent one spatial wavelet, and all of these can be configured before the communication system begins operation. Main spatiotemporal synchronization signal. The first subcarrier spacing is set to ,in are positive integers and satisfy Auxiliary time-space synchronization signal The second subcarrier spacing can be directly set to .

[0080] 2. Frequency Offset Measurement Signal: The frequency offset measurement signal is used to measure the Doppler frequency offset of the downlink signal. Its design includes: frequency offset measurement pilot sequence design and transmit subcarrier spacing design, wherein: pilot sequence Any pilot sequence with frequency offset measurement capability in existing technologies (such as DMRS, SRS, CSIRS) can be used, but the sequence values ​​are pre-configured and known to the terminal. Frequency offset measurement pilot sequence The third transmit subcarrier spacing is ,in are positive integers and satisfy .

[0081] Step 3: Configure the frequency domain resources for the cell synchronization auxiliary signal; Assuming the total bandwidth of the access beam is The bandwidth already occupied by existing signals is Occupied bandwidth refers to the bandwidth resources that may be occupied by existing technology at any time when accessing the beam. Therefore, idle bandwidth resources can be represented as... Idle bandwidth resources refer to the bandwidth resources that will not be occupied by existing technologies at any time when the access beam belongs. Frequency resources for transmitting spatiotemporal synchronization signals and frequency offset measurement signals are separately planned within the idle bandwidth resources. These two frequency resources are required to have fixed frequencies and bandwidths of [missing information]. and ,Require: , . Represents the secondary spatiotemporal synchronization signal sequence The sequence length; and All Integer multiples of.

[0082] Step 4: The base station generates a cell synchronization auxiliary signal; The main steps in generating a spatiotemporal synchronization signal include: generating the main spatiotemporal synchronization signal sequence in the baseband frequency domain. Placed in the first bandwidth The center position is then used to generate the main spatiotemporal synchronization signal in the baseband time domain using the existing method for generating baseband time domain signals. Similarly, in the baseband frequency domain, the auxiliary spatiotemporal synchronization signal sequence Placed in the first bandwidth The center position is then used to generate the auxiliary spatiotemporal synchronization signal in the baseband time domain using the existing method for generating baseband time domain signals. Finally, the time-domain signal of the spatiotemporal synchronization baseband is constructed. ,in, and All are one-dimensional row vectors. Furthermore, it should be noted that, due to... subcarrier spacing ratio Small times, so The absolute length of time will be greater than long times.

[0083] The main steps in generating the frequency offset measurement signal include: First, calculating the sequence length. Then, using the existing method for generating pilot sequences, a sequence of length is generated. Pilot measurement pilot sequence and in Fill after each element A zero, to get Then Placed in the second bandwidth The center location; finally, using existing protocols to generate baseband time-domain signals, a frequency offset measurement signal located in the baseband time domain is generated. .

[0084] Step 5: The base station transmits a cell synchronization assistance signal to the terminal; The base station first determines the transmission The Doppler frequency offset of the spatiotemporal synchronization signal is calculated based on the expected center frequency (which can consider the carrier frequency and is calculated using methods from existing protocols), its own position, motion state (including direction and speed of motion), and downlink beam direction. Then use the frequency offset compensation value. right Frequency offset pre-compensation is performed. Transmission is performed after pre-compensation, because... Therefore, after frequency offset pre-compensation The transmission frequency will not exceed the first bandwidth. The range. Additionally. It is possible to transmit directly without frequency offset compensation, but The start time needs to be consistent with The start time of a certain cycle is aligned. In addition, it should be noted that the access beam will continuously transmit cell synchronization auxiliary signals as long as it is in working state. Among them, the spatiotemporal synchronization signal is continuously transmitted in a cycle (there is no time interval between different cycles), and the frequency offset measurement signal can be transmitted continuously or periodically. If it is transmitted periodically, the transmission period information is also preset by the communication system and is known to the terminal.

[0085] Step 6: The terminal detects the spatiotemporal synchronization signal; The terminal continuously receives downlink signals using existing technologies (such as random beam scanning or fixed-sequence beam scanning); then, it detects the signal using existing PSS signal detection methods. After successful testing, you can obtain The timing position and inference Timing position ( The start time is (End time); secondly, extract Receive the signal and complete the detection using existing SSS signal detection methods. The detection is performed; finally, the directional information of the satellite base station is obtained based on the detection results of both.

[0086] During the aforementioned terminal detection process, since the base station has already performed frequency offset pre-compensation for the Doppler frequency offset of the spatiotemporal synchronization signal, although the pre-compensation is based on the downlink beam center position (i.e., the downlink beam direction), this may result in residual frequency offset after the terminal receives the spatiotemporal synchronization signal (the terminal may be located at a random position within the beam coverage area). However, this is ensured during the system parameter design. In other words, the residual frequency offset is generally no greater than 100%. Subcarrier spacing, and existing PSS sequence detection techniques can correct for the maximum half-subcarrier frequency offset, so the terminal can use existing techniques to complete... Demodulation.

[0087] Step 7: Terminal frequency offset measurement; After detecting the spatiotemporal synchronization signal, the terminal obtains the direction and timing information of the satellite-borne base station. Next, the terminal can align its receiving beam with the direction of the satellite-borne base station and configure the reception of the frequency offset measurement signal based on the timing and the period of the frequency offset measurement signal. After receiving the frequency offset measurement signal, the terminal can use existing technology to perform Doppler frequency offset measurement. This is because the frequency offset measurement pilot sequence is used during configuration. The third transmit subcarrier spacing satisfies In other words, the maximum Doppler frequency offset will not be greater than half of the pilot subcarrier spacing for frequency offset measurement. Existing frequency offset measurement techniques can estimate the frequency offset of the maximum half subcarrier, so the terminal can use existing frequency offset measurement techniques to complete Doppler frequency offset compensation.

[0088] Step 8: Terminal completes connection; The terminal aligns its receiving beam with the satellite base station to continuously receive signals and uses the frequency offset measurement results to pre-compensate the frequency offset of the received signals. Then, it uses existing technology to detect the cell access signal broadcast by the satellite base station and complete the subsequent access process.

[0089] Please see Figure 5Based on the same inventive concept, this application also provides a base station 300, including: a cell synchronization auxiliary signal generation module 310, used to generate a cell synchronization auxiliary signal; wherein, the cell synchronization auxiliary signal includes a spatiotemporal synchronization signal and a frequency offset measurement signal; the spatiotemporal synchronization signal carries base station direction information and timing information of the base station; the frequency offset measurement signal carries a pilot sequence; and a cell synchronization auxiliary signal transmission module 320, used to transmit the cell synchronization auxiliary signal to a terminal, so that the terminal demodulates the cell synchronization auxiliary signal and performs terminal access based on the demodulated base station direction information, the timing information, and the pilot sequence.

[0090] Optionally, the spatiotemporal synchronization signal includes a primary spatiotemporal synchronization signal and an auxiliary spatiotemporal synchronization signal; the aforementioned cell synchronization auxiliary signal generation module 310 is specifically used for: acquiring a primary spatiotemporal synchronization signal sequence and an auxiliary spatiotemporal synchronization signal sequence; in the baseband frequency domain, mapping the primary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of a preset beam and performing modulation processing to acquire the primary spatiotemporal synchronization signal; in the baseband frequency domain, mapping the auxiliary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of the preset beam and performing modulation processing to acquire the auxiliary spatiotemporal synchronization signal.

[0091] Optionally, the base station direction information of the base station includes spatial wave positions; the cell synchronization auxiliary signal generation module 310 is specifically used for: after acquiring the primary spatiotemporal synchronization signal sequence and the secondary spatiotemporal synchronization signal sequence, acquiring a first index of the primary spatiotemporal synchronization signal sequence and a second index of the secondary spatiotemporal synchronization signal sequence; based on the first index and the second index, acquiring an index group of synchronization signal sequence groups composed of the primary spatiotemporal synchronization signal sequence and the secondary spatiotemporal synchronization signal sequence; assigning a unique spatial wave position to each index group; wherein, the spatial wave position is used to indicate the spatial orientation of the base station relative to the terminal.

[0092] Optionally, the base station 300 further includes: a first subcarrier spacing determination module, used to determine the first subcarrier spacing of the main spatiotemporal synchronization signal based on the system downlink subcarrier spacing; wherein the system downlink subcarrier spacing is determined by the system frame structure; the first subcarrier spacing is less than the system downlink subcarrier spacing, and the first subcarrier spacing is greater than the intra-beam frequency offset protection spacing; the intra-beam frequency offset protection spacing is used to characterize the minimum frequency domain protection spacing required by the terminal within the same beam coverage area, and the intra-beam frequency offset protection spacing is determined based on the maximum difference in Doppler frequency offset between the downlink beam center and the downlink beam edge position.

[0093] Optionally, the base station 300 further includes: a second subcarrier spacing determination module, used to determine the second subcarrier spacing of the auxiliary spatiotemporal synchronization signal based on the system downlink subcarrier spacing; wherein the system downlink subcarrier spacing is determined by the system frame structure; and the second subcarrier spacing is equal to the system downlink subcarrier spacing.

[0094] Optionally, the base station 300 further includes: a first bandwidth determination module, used to determine the first bandwidth of the spatiotemporal synchronization signal; wherein the first bandwidth is not less than the minimum frequency domain protection bandwidth; the minimum frequency domain protection bandwidth is determined based on the occupied bandwidth of the spatiotemporal synchronization signal and the full-link frequency offset protection bandwidth; the full-link frequency offset protection bandwidth is determined based on the maximum downlink Doppler frequency offset of the system.

[0095] Optionally, the base station 300 further includes: a frequency offset pre-compensation module, used to determine the Doppler frequency offset of the spatiotemporal synchronization signal based on the expected center frequency of the spatiotemporal synchronization signal, the base station location, the base station motion state, and the downlink beam direction; and to perform frequency offset pre-compensation on the auxiliary spatiotemporal synchronization signal based on the Doppler frequency offset.

[0096] Optionally, the cell synchronization auxiliary signal generation module 310 is specifically used for: determining the sequence length of the pilot sequence based on the third subcarrier spacing and the second bandwidth of the frequency offset measurement signal; generating the pilot sequence based on the sequence length; sparsely sampling the pilot sequence to obtain the frequency-domain sparse pilot sequence; and mapping the pilot sequence to the center subcarrier position of the second bandwidth of a preset beam in the baseband frequency domain and performing modulation processing to obtain the frequency offset measurement signal.

[0097] Optionally, the base station 300 further includes: a third subcarrier spacing determination module, used to determine the third subcarrier spacing of the frequency domain measurement signal; wherein the third subcarrier spacing is greater than the full-link frequency offset protection bandwidth; wherein the full-link frequency offset protection bandwidth is determined based on the system downlink maximum Doppler frequency offset.

[0098] Optionally, the preset beam is an access beam; wherein, the access beam is the downlink beam in the base station used for initial access; the cell synchronization auxiliary signal transmission module 320 is specifically used to: use the idle bandwidth resources in the access beam to send a cell synchronization auxiliary signal to the terminal; wherein, the sum of the first bandwidth of the spatiotemporal synchronization signal and the second bandwidth of the frequency offset measurement signal is not greater than the idle bandwidth resources.

[0099] Optionally, the aforementioned cell synchronization auxiliary signal sending module 320 is specifically used for: continuously sending a spatiotemporal synchronization signal to the terminal; and continuously or periodically sending a frequency offset measurement signal to the terminal.

[0100] Please see Figure 6 Based on the same inventive concept, this application also provides a terminal 400, including: a spatiotemporal synchronization signal receiving module 410, used to receive the spatiotemporal synchronization signal in the cell auxiliary synchronization signal sent by a base station; a spatiotemporal synchronization signal demodulation module 420, used to determine the base station direction information and timing information of the base station based on the spatiotemporal synchronization signal; a frequency offset measurement signal receiving module 430, used to receive the frequency offset measurement signal in the cell auxiliary synchronization signal sent by the base station after obtaining the base station direction information and the timing information; wherein, the frequency offset measurement signal carries a pilot sequence; a residual frequency offset compensation module 440, used to perform residual frequency offset compensation on subsequently received downlink signals based on the pilot sequence; and a terminal access module 450, used to complete terminal access based on the cell access signal after detecting a cell access signal.

[0101] Based on the same inventive concept, this application also provides a non-terrestrial communication system, including a base station 300 and a terminal 400 provided in this application, wherein the base station 300 and the terminal 400 are communicatively connected.

[0102] Please refer to Figure 7 , Figure 7 This application provides a structural block diagram of an electronic device 500, comprising at least one processor 510, at least one memory 520, at least one communication interface 530, and at least one communication bus 540. The communication bus 540 enables direct communication between these components, the communication interface 530 facilitates signaling or data communication with other node devices, and the memory 520 stores machine-readable instructions executable by the processor 510. When the electronic device 500 is running, the processor 510 communicates with the memory 520 via the communication bus 540. When the machine-readable instructions are invoked by the processor 510, the aforementioned terminal access method applied to a base station or a terminal access method applied to a terminal is executed.

[0103] In one implementation, when the machine-readable instructions in the electronic device 500 are invoked by the processor 510 to execute the terminal access method applied to the base station, the electronic device 500 can be a base station, and the terminal can connect to the base station wirelessly. The base station can also connect to or transmit and receive information with Evolved Universal Terrestrial Radio Access (E-UTRA), New Radio (NR), and future radio access systems or WiFi systems as defined in the 3rd Generation Partnership Project (3GPP). The base station can also connect to devices from two or more of the aforementioned different radio access systems. The base station can also connect to an Open Radio Access Network (O-RAN). The base station may be configured with modules for implementing base station functions. The module for implementing base station functions can perform the functions of the following devices: base station, evolved NodeB (eNodeB or eNB), transmission reception point (TRP), next-generation NodeB (gNB) in 5th generation (5G) mobile communication systems, next-generation base station in 6th generation (6G) mobile communication systems, base station in future mobile communication systems, or access node in a WiFi system. The aforementioned base station may also include an antenna and a transceiver. In the uplink, uplink signals from the terminal are received via the antenna, mediated by the transceiver, and further processed by the processor 510 to recover the signaling information sent by the terminal; in the downlink, signaling messages are processed by the processor 510, mediated by the transceiver to generate downlink signals, and transmitted to the terminal via the antenna. The processor 510 is also used to execute the terminal access method applied to the base station as described in the above embodiments. The base station may include a macro base station, a micro base station, or an indoor station, and may also be a relay node or a donor node. It is understood that the above only describes a simplified design of the base station. In practical applications, the base station may include any number of transmitters, receivers, processors, controllers, memory, communication units, etc., and all base stations that can implement this application are within the protection scope of this application.

[0104] As one implementation, when the machine-readable instructions in the electronic device 500 are invoked by the processor 510 to execute the terminal access method applied to the terminal, the electronic device 500 can be a terminal, and different terminals can be interconnected via wired or wireless means. Terminals can be widely used in various scenarios, such as Near Field Communication (NFC) device-to-device (D2D), vehicle-to-everything (V2X) communication, machine-type communication (MTC), Internet of Things (IoT), virtual reality, augmented reality, industrial control, autonomous driving, telemedicine, smart grids, smart furniture, smart offices, smart wearables, smart transportation, and smart cities. The terminal can also be referred to as a mobile station (MS), terminal, or terminal equipment, and may include a subscriber unit, cellular phone, smartphone, wireless data card, personal digital assistant (PDA) computer, tablet computer, wireless modem, handheld device, laptop computer, cordless phone, wireless local loop (WLL) station, machine type communication (MTC) terminal, etc. For ease of description, the device terminal mentioned above is used in all embodiments of this application. The aforementioned terminal may also include an antenna and a transceiver. The transceiver modulates (e.g., analog-to-analog conversion, filtering, amplification, and up-conversion) the output sample and generates an uplink signal, which is transmitted to the network device via an antenna. On the downlink, the antenna receives the downlink signal transmitted by the network device, and the transceiver modulates (e.g., filtering, amplification, down-conversion, and digitization) the signal received from the antenna and provides input sampling. The processor 510 is used to execute the terminal access method applied to a terminal as described in the above embodiments. The embodiments of this application do not limit the specific technology or device form used in the terminal.

[0105] The processor 510 may include one or more, and may be an integrated circuit chip with signal processing capabilities. The processor 510 may be a general-purpose processor, including a Central Processing Unit (CPU), a Microcontroller Unit (MCU), a Network Processor (NP), or other conventional processors; it may also be a special-purpose processor, including a Neural-network Processing Unit (NPU), a Graphics Processing Unit (GPU), a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. Furthermore, when there are multiple processors 510, some may be general-purpose processors, and others may be special-purpose processors. The memory 520 includes one or more, which may be, but is not limited to, random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), etc.

[0106] This application also provides a computer-readable storage medium that stores computer program instructions. When the computer program instructions are executed by a computer, the computer performs various functions or steps in the above-described terminal access method embodiments.

[0107] This application also provides a computer program product that, when run on a computer, causes the computer to perform various functions or steps in the above-described terminal access method embodiments.

[0108] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A terminal access method, characterized in that, Applied to a base station, the method includes: Generate a cell synchronization auxiliary signal; wherein, the cell synchronization auxiliary signal includes a spatiotemporal synchronization signal and a frequency offset measurement signal; the spatiotemporal synchronization signal carries the base station direction information and timing information of the base station; the frequency offset measurement signal carries a pilot sequence; A cell synchronization assist signal is sent to the terminal so that the terminal can demodulate the cell synchronization assist signal and access the terminal based on the demodulated base station direction information, timing information and pilot sequence; The spatiotemporal synchronization signal includes a primary spatiotemporal synchronization signal and an auxiliary spatiotemporal synchronization signal; The method for determining the spatiotemporal synchronization signal includes: acquiring a primary spatiotemporal synchronization signal sequence and a secondary spatiotemporal synchronization signal sequence; in the baseband frequency domain, mapping the primary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of a preset beam and performing modulation processing to acquire the primary spatiotemporal synchronization signal; in the baseband frequency domain, mapping the secondary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of the preset beam and performing modulation processing to acquire the secondary spatiotemporal synchronization signal; the preset beam is an access beam; wherein, the access beam is the downlink beam used for initial access in the base station; The base station's direction information includes spatial wave positions; after acquiring the primary spatiotemporal synchronization signal sequence and the secondary spatiotemporal synchronization signal sequence, the method further includes: acquiring a first index of the primary spatiotemporal synchronization signal sequence and a second index of the secondary spatiotemporal synchronization signal sequence; based on the first index and the second index, acquiring an index group of synchronization signal sequence groups composed of the primary spatiotemporal synchronization signal sequence and the secondary spatiotemporal synchronization signal sequence; assigning a unique spatial wave position to each index group; wherein, the spatial wave position is used to indicate the spatial orientation of the base station relative to the terminal; The method for determining the frequency offset measurement signal includes: determining the sequence length of the pilot sequence based on the third subcarrier spacing and the second bandwidth of the frequency offset measurement signal; generating the pilot sequence based on the sequence length; performing sparse sampling on the pilot sequence to obtain the frequency-domain sparse pilot sequence; and mapping the pilot sequence to the center subcarrier position of the second bandwidth of a preset beam in the baseband frequency domain and performing modulation processing to obtain the frequency offset measurement signal.

2. The terminal access method according to claim 1, characterized in that, The method further includes: Based on the system downlink subcarrier spacing, the first subcarrier spacing of the main spatiotemporal synchronization signal is determined; wherein, the system downlink subcarrier spacing is determined by the system frame structure; the first subcarrier spacing is less than the system downlink subcarrier spacing, and the first subcarrier spacing is greater than the intra-beam frequency offset protection spacing; the intra-beam frequency offset protection spacing is used to characterize the minimum frequency domain protection spacing required by the terminal within the same beam coverage area, and the intra-beam frequency offset protection spacing is determined based on the maximum difference in Doppler frequency offset between the downlink beam center and the downlink beam edge position.

3. The terminal access method according to claim 1, characterized in that, The method further includes: The second subcarrier interval of the auxiliary spatiotemporal synchronization signal is determined based on the system downlink subcarrier interval; wherein the system downlink subcarrier interval is determined by the system frame structure; the second subcarrier interval is equal to the system downlink subcarrier interval.

4. The terminal access method according to claim 1, characterized in that, The method further includes: The first bandwidth of the spatiotemporal synchronization signal is determined; wherein the first bandwidth is not less than the minimum frequency domain protection bandwidth; the minimum frequency domain protection bandwidth is determined based on the occupied bandwidth of the spatiotemporal synchronization signal and the full-link frequency offset protection bandwidth; the full-link frequency offset protection bandwidth is determined based on the maximum downlink Doppler frequency offset of the system.

5. The terminal access method according to claim 1, characterized in that, Before sending the cell synchronization assistance signal to the terminal, the method further includes: Based on the expected center frequency of the spatiotemporal synchronization signal, the base station location, the base station motion state, and the downlink beam direction, the Doppler frequency offset of the spatiotemporal synchronization signal is determined. Based on the Doppler frequency offset, frequency offset pre-compensation is performed on the auxiliary spatiotemporal synchronization signal.

6. The terminal access method according to claim 1, characterized in that, The method further includes: The third subcarrier spacing of the frequency offset measurement signal is determined; wherein the third subcarrier spacing is greater than the full-link frequency offset protection bandwidth; wherein the full-link frequency offset protection bandwidth is determined based on the system downlink maximum Doppler frequency offset.

7. The terminal access method according to any one of claims 1 to 6, characterized in that, Sending the cell synchronization assistance signal to the terminal includes: Using the idle bandwidth resources in the access beam, a cell synchronization assistance signal is sent to the terminal; wherein the sum of the first bandwidth of the spatiotemporal synchronization signal and the second bandwidth of the frequency offset measurement signal is not greater than the idle bandwidth resources.

8. The terminal access method according to any one of claims 1 to 6, characterized in that, Sending the cell synchronization assistance signal to the terminal includes: Continuously send spatiotemporal synchronization signals to the terminal; The frequency offset measurement signal is continuously or periodically sent to the terminal.

9. A terminal access method, characterized in that, Applied to a terminal, the method includes: The system receives a spatiotemporal synchronization signal from a cell auxiliary synchronization signal sent by a base station. The spatiotemporal synchronization signal includes a primary spatiotemporal synchronization signal and an auxiliary spatiotemporal synchronization signal. The determination of the spatiotemporal synchronization signal includes: acquiring a primary spatiotemporal synchronization signal sequence and an auxiliary spatiotemporal synchronization signal sequence; in the baseband frequency domain, mapping the primary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of a preset beam and performing modulation processing to acquire the primary spatiotemporal synchronization signal; in the baseband frequency domain, mapping the auxiliary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of the preset beam and performing modulation processing to acquire the auxiliary spatiotemporal synchronization signal; the preset beam is an access beam; wherein the access beam is the downlink beam in the base station used for initial access. Based on the spatiotemporal synchronization signal, the base station direction information and timing information of the base station are determined; the base station direction information of the base station includes spatial wave positions; after acquiring the main spatiotemporal synchronization signal sequence and the auxiliary spatiotemporal synchronization signal sequence, the method further includes: acquiring a first index of the main spatiotemporal synchronization signal sequence and a second index of the auxiliary spatiotemporal synchronization signal sequence; based on the first index and the second index, acquiring an index group of synchronization signal sequence groups composed of the main spatiotemporal synchronization signal sequence and the auxiliary spatiotemporal synchronization signal sequence; assigning a unique spatial wave position to each index group; wherein, the spatial wave position is used to indicate the spatial orientation of the base station relative to the terminal; After obtaining the base station direction information and the timing information, the frequency offset measurement signal in the cell auxiliary synchronization signal sent by the base station is received; wherein, the frequency offset measurement signal carries a pilot sequence; Residual frequency offset compensation is performed on the subsequently received downlink signals based on the pilot sequence; After detecting the cell access signal, the terminal access is completed based on the cell access signal; The method for determining the frequency offset measurement signal includes: determining the sequence length of the pilot sequence based on the third subcarrier spacing and the second bandwidth of the frequency offset measurement signal; generating the pilot sequence based on the sequence length; performing sparse sampling on the pilot sequence to obtain the frequency-domain sparse pilot sequence; and mapping the pilot sequence to the center subcarrier position of the second bandwidth of a preset beam in the baseband frequency domain and performing modulation processing to obtain the frequency offset measurement signal.

10. A terminal access method, characterized in that, The method includes: The base station performs the following steps: Generate a cell synchronization auxiliary signal; wherein, the cell synchronization auxiliary signal includes a spatiotemporal synchronization signal and a frequency offset measurement signal; the spatiotemporal synchronization signal carries the base station direction information and timing information of the base station; the frequency offset measurement signal carries a pilot sequence; A cell synchronization assist signal is sent to the terminal so that the terminal can demodulate the cell synchronization assist signal and access the terminal based on the demodulated base station direction information, timing information and pilot sequence; The spatiotemporal synchronization signal includes a primary spatiotemporal synchronization signal and an auxiliary spatiotemporal synchronization signal; The method for determining the spatiotemporal synchronization signal includes: acquiring a primary spatiotemporal synchronization signal sequence and a secondary spatiotemporal synchronization signal sequence; in the baseband frequency domain, mapping the primary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of a preset beam and performing modulation processing to acquire the primary spatiotemporal synchronization signal; in the baseband frequency domain, mapping the secondary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of the preset beam and performing modulation processing to acquire the secondary spatiotemporal synchronization signal; the preset beam is an access beam; wherein, the access beam is the downlink beam used for initial access in the base station; The base station's direction information includes spatial wave positions; after acquiring the primary spatiotemporal synchronization signal sequence and the secondary spatiotemporal synchronization signal sequence, a first index of the primary spatiotemporal synchronization signal sequence and a second index of the secondary spatiotemporal synchronization signal sequence are acquired; based on the first index and the second index, an index group of synchronization signal sequence groups composed of the primary spatiotemporal synchronization signal sequence and the secondary spatiotemporal synchronization signal sequence is acquired; a unique spatial wave position is assigned to each index group; wherein, the spatial wave position is used to indicate the spatial orientation of the base station relative to the terminal; The method for determining the frequency offset measurement signal includes: determining the sequence length of the pilot sequence based on the third subcarrier spacing and the second bandwidth of the frequency offset measurement signal; generating the pilot sequence based on the sequence length; performing sparse sampling on the pilot sequence to obtain the frequency-domain sparse pilot sequence; and mapping the pilot sequence to the center subcarrier position of the second bandwidth of a preset beam in the baseband frequency domain and performing modulation processing to obtain the frequency offset measurement signal. The terminal performs the following steps: Receive the spatiotemporal synchronization signal from the cell auxiliary synchronization signal sent by the base station; Based on the spatiotemporal synchronization signal, the base station direction information and the timing information of the base station are determined; After obtaining the base station direction information and the timing information, the frequency offset measurement signal in the cell auxiliary synchronization signal sent by the base station is received; wherein, the frequency offset measurement signal carries the pilot sequence; Residual frequency offset compensation is performed on the subsequently received downlink signals based on the pilot sequence; After detecting a cell access signal, the terminal access is completed based on the cell access signal.

11. A base station, characterized in that, include: A cell synchronization auxiliary signal generation module is used to generate a cell synchronization auxiliary signal. The cell synchronization auxiliary signal includes a spatiotemporal synchronization signal and a frequency offset measurement signal. The spatiotemporal synchronization signal carries base station direction information and timing information of the base station. The frequency offset measurement signal carries a pilot sequence. The spatiotemporal synchronization signal includes a primary spatiotemporal synchronization signal and a secondary spatiotemporal synchronization signal. The determination method of the spatiotemporal synchronization signal includes: acquiring the primary spatiotemporal synchronization signal sequence and the secondary spatiotemporal synchronization signal sequence; in the baseband frequency domain, mapping the primary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of a preset beam and performing modulation processing to acquire the primary spatiotemporal synchronization signal; in the baseband frequency domain, mapping the secondary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of the preset beam and performing modulation processing to acquire the secondary spatiotemporal synchronization signal; the preset beam is an access beam; wherein, the access beam is the downlink beam in the base station used for initial access. A cell synchronization auxiliary signal transmission module is used to send a cell synchronization auxiliary signal to a terminal, so that the terminal demodulates the cell synchronization auxiliary signal and performs terminal access based on the demodulated base station direction information, timing information, and pilot sequence; the base station direction information includes spatial wavelets; after acquiring the primary spatiotemporal synchronization signal sequence and the secondary spatiotemporal synchronization signal sequence, a first index of the primary spatiotemporal synchronization signal sequence and a second index of the secondary spatiotemporal synchronization signal sequence are acquired; based on the first index and the second index, an index group of synchronization signal sequence groups composed of the primary spatiotemporal synchronization signal sequence and the secondary spatiotemporal synchronization signal sequence is acquired; a unique spatial wavelet is assigned to each index group; wherein, the spatial wavelet is used to indicate the spatial orientation of the base station relative to the terminal; The method for determining the frequency offset measurement signal includes: determining the sequence length of the pilot sequence based on the third subcarrier spacing and the second bandwidth of the frequency offset measurement signal; generating the pilot sequence based on the sequence length; performing sparse sampling on the pilot sequence to obtain the frequency-domain sparse pilot sequence; and mapping the pilot sequence to the center subcarrier position of the second bandwidth of a preset beam in the baseband frequency domain and performing modulation processing to obtain the frequency offset measurement signal.

12. A terminal, characterized in that, include: The spatiotemporal synchronization signal receiving module is used to receive the spatiotemporal synchronization signal in the cell auxiliary synchronization signal sent by the base station; The spatiotemporal synchronization signal includes a primary spatiotemporal synchronization signal and an auxiliary spatiotemporal synchronization signal; The method for determining the spatiotemporal synchronization signal includes: acquiring a primary spatiotemporal synchronization signal sequence and a secondary spatiotemporal synchronization signal sequence; in the baseband frequency domain, mapping the primary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of a preset beam and performing modulation processing to acquire the primary spatiotemporal synchronization signal; in the baseband frequency domain, mapping the secondary spatiotemporal synchronization signal sequence to the center subcarrier position of the first bandwidth of the preset beam and performing modulation processing to acquire the secondary spatiotemporal synchronization signal; the preset beam is an access beam; wherein, the access beam is the downlink beam used for initial access in the base station; A spatiotemporal synchronization signal demodulation module is used to determine the base station direction information and timing information of the base station based on the spatiotemporal synchronization signal; the base station direction information of the base station includes spatial wavelets; after acquiring the main spatiotemporal synchronization signal sequence and the auxiliary spatiotemporal synchronization signal sequence, it acquires a first index of the main spatiotemporal synchronization signal sequence and a second index of the auxiliary spatiotemporal synchronization signal sequence; based on the first index and the second index, it acquires an index group of synchronization signal sequence groups composed of the main spatiotemporal synchronization signal sequence and the auxiliary spatiotemporal synchronization signal sequence; it assigns a unique spatial wavelet to each index group; wherein, the spatial wavelet is used to indicate the spatial orientation of the base station relative to the terminal; A frequency offset measurement signal receiving module is used to receive a frequency offset measurement signal from the cell auxiliary synchronization signal sent by the base station after obtaining the base station direction information and the timing information; wherein the frequency offset measurement signal carries a pilot sequence; the determination method of the frequency offset measurement signal includes: determining the sequence length of the pilot sequence based on the third subcarrier spacing and the second bandwidth of the frequency offset measurement signal; generating the pilot sequence based on the sequence length; sparsely sampling the pilot sequence to obtain the frequency-domain sparse pilot sequence; mapping the pilot sequence to the center subcarrier position of the second bandwidth of a preset beam in the baseband frequency domain, and performing modulation processing to obtain the frequency offset measurement signal; The residual frequency offset compensation module is used to perform residual frequency offset compensation on the subsequently received downlink signals based on the pilot sequence. The terminal access module is used to complete terminal access based on the cell access signal after detecting the cell access signal.

13. A non-terrestrial communication system, characterized in that, include: The base station as described in claim 11 and the terminal as described in claim 12, wherein the terminal is communicatively connected to the base station; the base station and the terminal are used to implement non-terrestrial communication.

14. An electronic device, characterized in that, include: A processor, a memory, and a communication bus, wherein the processor and the memory communicate with each other via the communication bus; The memory stores program instructions that can be executed by the processor, and the processor can execute the method as described in any one of claims 1 to 10 by calling the program instructions.

15. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that, when executed by a computer, cause the computer to perform the method as described in any one of claims 1 to 10.

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