Random access delay calibration method and system for low-orbit satellite carrying 5g terminal

Abstract

The present disclosure provides a low-orbit satellite-mounted 5G terminal random access time delay calibration method and system, relating to the technical field of satellite communication, and applied to four-step random access, wherein the method comprises: performing time delay pre-compensation according to ephemeris information of a low-orbit satellite and ephemeris information of a high-orbit relay satellite; after performing time delay pre-compensation, detecting a synchronization signal block by using a 5G terminal mounted on the low-orbit satellite, performing downlink frame synchronization through the synchronization signal block, and measuring downlink synchronization error; acquiring a preamble sequence configured by a physical random access channel according to a physical random access channel parameter carried in 5G base station broadcasting, and detecting a time window length by using the preamble sequence; setting an error threshold according to the time window length, judging whether the downlink synchronization error exceeds the error threshold, and the error threshold being half of the time window length; if the downlink synchronization error exceeds the error threshold, performing redundant traversal, and if the downlink synchronization error does not exceed the error threshold, performing normal access.

Description

Technical Field

[0001] This disclosure relates to the field of satellite communication technology, specifically to a random access delay calibration method and system for a 5G terminal mounted on a low-orbit satellite. Background Technology

[0002] In the field of satellite communications, low-Earth orbit (LEO) satellite-borne terminals are characterized by high-speed mobility. For these high-speed mobile LEO satellite-borne terminals, typical random access procedures can increase timing errors, resulting in a lower success rate for LEO satellite-borne terminals to connect to base stations.

[0003] There is currently no effective technical solution to the problem of the low success rate of low-Earth orbit satellite-borne terminals accessing base stations. Summary of the Invention

[0004] The main purpose of this disclosure is to provide a random access latency calibration method and system for 5G terminals mounted on low-Earth orbit satellites, so as to solve the problem of low success rate of low-Earth orbit satellite-mounted terminals accessing base stations in related technologies.

[0005] To achieve the above objectives, the first aspect of this disclosure provides a random access latency calibration method for a 5G terminal mounted on a low-orbit satellite, applicable to a four-step random access process, including:

[0006] Delay pre-compensation is performed based on the ephemeris information of low-orbit satellites and high-orbit relay satellites. After performing delay pre-compensation, the 5G terminal on the low-orbit satellite is used to detect the synchronization signal block, and downlink frame synchronization is performed through the synchronization signal block to measure the downlink synchronization error. By using the physical random access channel parameters carried in the broadcast of 5G base stations, the preamble sequence of the physical random access channel configuration is obtained, and the time window length is detected using the preamble sequence; An error threshold is set based on the time window length to determine whether the downlink synchronization error exceeds the error threshold, where the error threshold is half the time window length; If the downlink synchronization error exceeds the error threshold, a redundancy traversal is performed; if the downlink synchronization error does not exceed the error threshold, normal access is performed.

[0007] Optionally, delay pre-compensation is performed based on the ephemeris information of low-Earth orbit satellites and high-Earth orbit relay satellites, including: The link distance is determined based on the ephemeris information of low-Earth orbit satellites and high-Earth orbit relay satellites. The ephemeris information includes UTC time and orbital six-root number. The link delay is determined based on the link distance and the radio wave transmission speed. Based on link latency, latency pre-compensation is performed on the uplink and downlink signal frame headers of communication between 5G base stations and 5G terminals carried by low-orbit satellites.

[0008] Optionally, the synchronization signal block includes a primary synchronization signal and an auxiliary synchronization signal; Downlink frame synchronization via synchronization signal blocks includes parsing the downlink primary synchronization signal and secondary synchronization signal to perform downlink frame synchronization.

[0009] Optionally, performing redundant traversal includes performing outer loop traversal and inner loop traversal sequentially.

[0010] Furthermore, the steps for performing an outer loop traversal include: Set the first window range and the first sliding window range, and perform outer ring sliding window with the time window length as the sliding window step until the 5G terminal receives Msg2; Set the transmission time for different physical random access channels and adjust the uplink delay to be within the range of N repeating windows resolved by the 5G base station to the physical random access channel, where N is a positive integer.

[0011] Furthermore, the physical random access channel includes a cyclic prefix, a preamble sequence, and a guard interval; The steps for performing an inner loop traversal include: Using the timing advance carried by Msg2, adjust the transmission delay of Msg3 to half the position of the cyclic prefix, and then transmit Msg3 through the 5G terminal; Set the second window range and the second sliding window range, and perform inner loop sliding window with the time window length as the sliding window step until the 5G terminal receives Msg4, fix the current latency configuration, and complete the uplink synchronization of the random access process.

[0012] Optionally, performing normal access includes: The physical random access channel is directly initiated based on the downlink timing, and Msg2 is received by the 5G terminal. After the 5G terminal receives Msg2, it compensates for the transmission delay of Msg3 to half the position of the cyclic prefix according to the timing advance of Msg2, and then sends Msg3 through the 5G terminal. Random access is completed by receiving Msg4 through a 5G terminal.

[0013] The second aspect of this disclosure provides a random access latency calibration system for a 5G terminal mounted on a low-Earth orbit satellite, applied to four-step random access, including: The pre-compensation unit is used to perform delay pre-compensation based on the ephemeris information of low-orbit satellites and high-orbit relay satellites. The detection unit is used to detect the synchronization signal block using the 5G terminal carried by the low-orbit satellite after performing delay pre-compensation, and to perform downlink frame synchronization through the synchronization signal block and measure the downlink synchronization error. The acquisition unit is used to obtain the preamble sequence of the physical random access channel configuration through the physical random access channel parameters carried in the broadcast of the 5G base station, and to detect the time window length using the preamble sequence; The judgment unit is used to determine whether the downlink synchronization error exceeds the error threshold based on the time window length, wherein the error threshold is half of the time window length. The execution unit is used to perform redundant traversal if the downlink synchronization error exceeds the error threshold, and to perform normal access if the downlink synchronization error does not exceed the error threshold.

[0014] A third aspect of this disclosure provides a computer-readable storage medium storing computer instructions for causing a computer to execute the random access delay calibration method for a 5G terminal mounted on a low-Earth orbit satellite provided in any of the first aspects.

[0015] A fourth aspect of this disclosure provides an electronic device comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores a computer program executable by the at least one processor, the computer program being executed by the at least one processor to cause the at least one processor to perform the random access delay calibration method for a 5G terminal mounted on a low-Earth orbit satellite provided in any of the first aspects. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the specific embodiments or related technologies of this disclosure, the accompanying drawings used in the description of the specific embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic diagram of a high-orbit relay satellite communication system that integrates a 5G mobile communication system; Figure 2 A schematic diagram of the random access latency calibration method for a 5G terminal mounted on a low-orbit satellite provided in this embodiment of the disclosure; Figure 3 A block diagram of a random access latency calibration system for a 5G terminal mounted on a low-orbit satellite provided in this embodiment of the disclosure; Figure 4 A block diagram of an electronic device provided in an embodiment of this disclosure. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present disclosure, the technical solutions of the present disclosure will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present disclosure, and not all embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present disclosure.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate for the embodiments of this disclosure described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0020] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other. This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] In recent years, the low-Earth orbit (LEO) satellite industry has flourished both domestically and internationally, continuously releasing enormous commercial value and social benefits in many fields such as communication, remote sensing, and navigation. However, due to the influence of complex and ever-changing geopolitical factors, the global deployment of LEO satellite ground stations faces severe challenges, resulting in a significant reduction in the timeliness of ground stations' telemetry, tracking, and command (TT&C) of LEO satellites. For example, when a satellite enters a ground station's coverage blind spot, the ground station struggles to conduct timely and effective orbit monitoring and transmit attitude adjustment control commands, increasing the risk to satellite operation. Simultaneously, regarding LEO satellite data backhaul, the lack of a sufficient number of reasonably distributed ground stations means that a large amount of observation data cannot be transmitted in a timely manner, severely affecting the real-time nature and integrity of the data. This, in turn, limits the application effectiveness of LEO satellites in fields with high data timeliness requirements, such as disaster early warning and real-time communication.

[0023] High-orbit satellites, with their unique orbits and technical characteristics, provide solutions for real-time telemetry, tracking, and command (TT&C) and data transmission from low-orbit satellites. In terms of TT&C, high-orbit satellites, due to their extremely wide coverage, can effectively fill the coverage blind spots of low-orbit satellite ground stations, enabling real-time monitoring and remote control of low-orbit satellites. In terms of data transmission, high-orbit satellites can overcome the limitations of ground station layout, greatly improving the real-time performance and integrity of transmitted data.

[0024] However, traditional high-orbit satellite communication systems, due to their relatively fixed resource scheduling mechanisms, cannot dynamically adjust resource allocation in real time to serve the random telemetry, tracking, and data transmission needs of a massive number of low-orbit satellite users.

[0025] The fifth-generation mobile communication technology (5G) employs Orthogonal Frequency Division Multiplexing Access (OFDMA) and Time Division Multiple Access (TDMA) technologies. It can dynamically allocate frequency domain subcarriers and time domain time slices to users based on their service needs and link quality, in order to support the transmission of random service data by a large number of users. Specifically, through OFDMA technology, the system divides the spectrum into multiple orthogonal subcarriers and allocates them to different users, while through TDMA technology, the system allocates time slices to different users.

[0026] Combining 5G mobile communication systems with high-orbit relay satellite communication systems can leverage the advantages of high-orbit relay satellites, such as their wide coverage and long coverage time, while also utilizing the advantages of 5G mobile communication systems, such as supporting the transmission of random service data for a large number of users. This allows for the service of telemetry, remote control, and backhaul data for a large number of low-orbit satellite users.

[0027] like Figure 1 As shown, the high-orbit relay satellite communication system integrating the 5G mobile communication system includes: low-orbit satellite users, high-orbit relay satellites, gateway stations, 5G base stations, 5G core networks, and external data networks; Low-Earth orbit (LEO) satellite users, as access nodes of the communication system, can serve as receivers for remote control services, transmitters for telemetry services, and data sources for data transmission services. LEO satellite users must be equipped with 5G terminal chips, enabling them to perform filtering, noise reduction, digital-to-analog signal conversion, modulation and demodulation, encoding and decoding, and other processing on 5G wireless signals. They can also perform physical layer, link layer, and network layer protocol processing.

[0028] High-orbit relay satellites can filter and convert the Ka signal from the user link to the Q / V signal of the feeder link, which is sent by the user link, and then forward it to the 5G base station and 5G core network via the feeder link and gateway station. Conversely, the space-based remote control signal of the 5G base station is filtered and converted to the Ka band by the high-orbit relay satellite via the gateway station and Q / V feeder link, and then forwarded to the low-orbit satellite user via the user link.

[0029] The ground-based gateway station is responsible for filtering the Q / V signal relayed by the high-orbit relay satellite from the feeder link, down-converting it to a 5G intermediate frequency signal, and forwarding it to the 5G base station; or conversely, filtering the intermediate frequency signal of the ground 5G base station, up-converting it to a Q / V signal, and forwarding it to the high-orbit relay satellite via the feeder link. Ground-based 5G base stations receive return wireless signals sent by users, demodulate and decode the signals to recover the original data, and then forward it to an external data network via the 5G core network, ultimately delivering it to a third-party customer center. Simultaneously, 5G base stations encode and modulate remote control commands forwarded from the 5G core network onto 5G intermediate frequency signals, forwarding the signals to gateway stations and then relaying them to users via Q / V feeder links and high-orbit relay satellites. Furthermore, 5G base stations must allocate communication resources such as beams, frequencies, and time slots to user terminals based on user service needs and channel quality to ensure that multiple users can communicate with the network simultaneously and receive good communication services.

[0030] The 5G core network is responsible for authenticating and authorizing the identity of user terminals, and recording the location and status of user terminals by processing the location area registration process of user terminals. The 5G core network also needs to select the optimal data transmission path according to the destination address of the data and network policies, and forward the data to the user terminal or to the external data network. When users are moving at high speed, the 5G core network also needs to ensure the continuity of communication through mobility management.

[0031] The external data network is an external network relative to the 5G network, responsible for routing data transmission services to the final third-party customer center.

[0032] In a typical 5G communication system, the process by which a 5G terminal receives a broadcast, initiates random access, and interacts with the 5G base station is as follows: Step 1: Msg1 (Message 1, random access preamble sequence) User equipment (UE) sends a preamble sequence to a 5G base station on the Physical Random Access Channel (PRACH) to request the establishment of a connection and achieve initial uplink synchronization. The PRACH is a physical layer channel in the 5G network used to establish a communication connection between UE and 5G base station. The PRACH consists of three parts: a cyclic prefix (CP), a preamble sequence, and a guard interval. The preamble sequence is a signal sequence used for identification when a user terminal initiates random access in a wireless communication system. The preamble sequence is generated by the Zadoff-Chu sequence, has good autocorrelation, and is easy for base station detection and synchronization.

[0033] User equipment pre-acquires random access related parameters, including: the set of available preamble sequences, the preamble format (the preamble format is selected according to the coverage area, such as long preambles are suitable for wide coverage and short preambles are suitable for low latency scenarios), and the location of PRACH time and frequency resources, etc. User equipment randomly selects one from a preset preamble sequence and sends it to the 5G base station on PRACH; randomly selecting a preamble sequence is the core source of contention.

[0034] Step 2: Msg2 (Message 2, Random Access Response) After receiving Msg1, the 5G base station sends a response to the user equipment, providing uplink synchronization information, temporary resource allocation, and contention resolution identifier.

[0035] After detecting the PRACH signal, the 5G base station sends the Physical Downlink Control Channel (PDCCH) to the user equipment to specify the time-frequency resources for the Random Access Response (RAR). The PDCCH is scrambled with the Random Access-RadioNetwork Temporary Identifier (RA-RNTI). The RA-RNTI is generated by the 5G base station upon receiving the time-frequency resources of Msg1 to confirm receipt of the time-frequency resources of the user equipment Msg1. The RA-RNTI is dynamically allocated during the random access process.

[0036] 5G base stations calculate the uplink timing advance (TA) of user equipment by using the correlation of the preamble sequence. This TA is then used by user equipment to adjust the uplink transmission time and achieve uplink synchronization.

[0037] The RAR contains the following information: (1) The corresponding preamble index is used to confirm that the preamble sequence sent by the user equipment has been correctly received; (2) Uplink TA, the user equipment adjusts the subsequent uplink transmission time according to the TA; (3) Temporary Cell-Radio Network Temporary Identifier (TC-RNTI), used as a temporary identity for subsequent signaling interactions; (4) Resource allocation information of the Physical Uplink Shared Channel (PUSCH), including time and frequency resources, modulation and coding scheme, etc., for the user equipment to use for subsequent transmission of Msg3.

[0038] Step 3: Msg3 (Message 3, Uplink Message Transmission) User equipment uses the resources allocated in Msg2 to send the specific access reason (such as initial access, service request, etc.) and the user equipment's unique identifier to the 5G base station.

[0039] The user equipment adjusts the uplink transmission timing according to the TA in Msg2 and sends Msg3 on the allocated PUSCH resources. The content includes a Radio Resource Control (RRC) connection request (if it is an initial access) and carries the core network identifier or temporary identifier of the user equipment. Since multiple user equipment may compete for the same preamble sequence, the user equipment identifier in Msg3 is the key to resolving the competition in the future.

[0040] Step 4: Msg4 (Message 4, Race Resolution Message) The 5G base station confirms the winner of the random access competition and completes the final access confirmation.

[0041] After the 5G base station receives and parses Msg3, it uses the TC-RNTI allocated to the user terminal by Msg2 to scramble and schedule the PDCCH of Msg4, ensuring that only the target user equipment can correctly parse it. The PDCCH carries the dynamic video resource information of Msg4.

[0042] The above describes the normal random access process for a 5G terminal. From the perspective of time-frequency synchronization, the relevant steps can be summarized as follows: (1) When the 5G terminal scans the broadcast of the 5G base station that is allowed to access, it parses the primary synchronization signal (PSS) and secondary synchronization signal (SSS) in the synchronization signal block (SSB), and combines the 5G base station system frame number (SFN) carried in the broadcast with the time information of the 5G base station sending the SSB according to the 3GPP protocol. Combined with the time information of the local time of the SSB collected, the timing difference of the downlink is calculated. The timing difference includes the system timing difference of the 5G base station and the 5G terminal, as well as the time consumption of the wireless signal in the hardware processing and spatial transmission of the device.

[0043] (2) The 5G terminal initiates Msg1 (preamble), and the 5G base station also calculates the time difference between the time the preamble is received by the 5G terminal and the time the 5G base station collects it, and calculates the timing difference of the entire uplink. Since the multiple 5G terminals that the 5G base station faces are located in different locations, the link latency difference is different for different 5G terminals. Therefore, the 5G base station sends the timing difference calculated by the test, i.e., TA, to each 5G terminal through Msg2 for its own adjustment.

[0044] (3) After receiving Msg2, the 5G terminal parses the uplink timing difference and adjusts its own uplink timing in reverse to ensure that the subsequent 5G base station can parse the uplink signal at the correct time.

[0045] (4) When the 5G terminal initiates Msg3 again, the initial uplink and downlink synchronization of the 5G base station and the 5G terminal has generally been completed.

[0046] Since terrestrial 5G terminals are stationary or moving at low speeds, the above-mentioned normal access process can basically guarantee the access reliability of terrestrial 5G terminals. However, 5G terminals mounted on low-orbit satellites have the characteristic of high-speed movement, which will lead to increased errors. The orbital environment of low-Earth orbit satellites may have weak GPS signals or be subject to interference, which can lead to larger system timing errors in 5G terminals. In response to the significant real-time changes in the distance between 5G terminals and 5G base stations caused by the high-speed movement of low-orbit satellites, pre-compensation is generally performed by predicting link delays in real time based on low-orbit ephemeris. However, the accuracy of the ephemeris itself and calculation errors can lead to large timing compensation errors. When the above two types of errors exceed the preamble delay characterization window defined by the 3GPP protocol, the 5G base station will be unable to detect the preamble, unable to send Msg2, or the window where the preamble is located will be misaligned, and Msg2 will be sent but the TA it carries will be incorrect. This will cause the time position of the Msg3 subsequently sent by the 5G terminal to be incorrect, which will in turn cause the 5G base station to be unable to parse it correctly.

[0047] The length of the preamble detection time window is also limited by factors such as coverage distance and the configured subcarrier spacing (SCS).

[0048] The above factors combined result in a low success rate for 5G terminals carried by low-orbit satellites to connect to 5G base stations.

[0049] To address the low success rate of 5G terminals mounted on low-Earth orbit satellites accessing 5G base stations, the relevant technologies employ redundancy design from the perspective of the 5G base station. For example, the 5G base station attempts to parse the PRACH or Msg3 of a 5G terminal using a sliding window. However, in practical applications, a single 5G base station needs to serve tens of thousands of 5G terminals, and all 5G terminals share the same receiving and processing link of the 5G base station. Redundancy design at the centralized network element of the 5G base station is clearly not the most efficient approach.

[0050] To address the aforementioned issues, this disclosure provides a random access latency calibration method for a 5G terminal mounted on a low-orbit satellite. By implementing redundancy design in the 5G terminal, compared to related technologies that rely on redundancy design from the 5G base station perspective, this method improves robustness and reduces the processing load on the 5G base station, thereby enhancing overall system performance. This method can be applied to four-step random access or two-step random access, such as... Figure 2 As shown, the method includes the following steps S21 to S25: Step S21: Perform delay pre-compensation based on the ephemeris information of the low-Earth orbit satellite and the ephemeris information of the high-Earth orbit relay satellite; the ephemeris information can also be coordinate information, used to record the satellite's position information and orbital status at UTC time. The 5G terminal on the low-Earth orbit satellite can obtain the ephemeris information of the satellite platform when powered on. In one optional embodiment of this disclosure, step S21 includes: The link distance is determined based on the ephemeris information of low-Earth orbit satellites and high-Earth orbit relay satellites. The ephemeris information includes UTC time and orbital root numbers. The link distance between the low-Earth orbit satellites and high-Earth orbit relay satellites is calculated in real time during the movement. UTC stands for Coordinated Universal Time. Link delay is determined based on link distance and radio wave transmission speed; radio waves travel at the speed of light in a vacuum. Based on link latency, latency pre-compensation is performed on the uplink and downlink signal frame headers of communication between 5G base stations and 5G terminals carried by low-orbit satellites.

[0051] Step S22: After performing delay pre-compensation, the 5G terminal on the low-orbit satellite is used to detect the synchronization signal block, and downlink frame synchronization is performed through the synchronization signal block to measure the downlink synchronization error; the baseband module in the 5G terminal is turned on, the synchronization signal block (SSB) scanning function is started, the SSB is detected, and downlink time and frequency synchronization is completed after the SSB is detected. In one optional embodiment of this disclosure, the synchronization signal block in step S22 includes a primary synchronization signal and a secondary synchronization signal; Step S22, downlink frame synchronization via synchronization signal block, includes parsing the downlink primary synchronization signal and secondary synchronization signal to perform downlink frame synchronization.

[0052] Step S23: Obtain the preamble sequence configured for the Physical Random Access Channel (PRACH) using the PRACH parameters broadcast by the 5G base station, and use the preamble sequence to detect the time window length; obtain the PRACH preamble sequence detection time window length T using the PRACH parameters. prach The PRACH parameter can also be in PRACH format; Step S24: Set an error threshold based on the time window length, and determine whether the downlink synchronization error exceeds the error threshold, where the error threshold is half the time window length; using the time window length T prach Set the error threshold T0, where T0 is 1 / 2. T prach Determine the downlink synchronization error T Δ Whether the error threshold T0 is exceeded is used to determine the magnitude of the downlink synchronization error and ensure basic access time.

[0053] Step S25: If the downlink synchronization error exceeds the error threshold, perform a redundancy traversal; if the downlink synchronization error does not exceed the error threshold, perform normal access. Exceeding the error threshold indicates that the timing error in the current system exceeds the limit for normal access, and the redundancy traversal performed is a redundancy design; normal access is normal random access.

[0054] This disclosure embodiment, without changing the current non-terrestrial network technology, subcarrier spacing, and physical random access channel format, designs redundant random access for 5G terminals mounted on low-Earth orbit satellites. This significantly improves the access success rate of 5G terminals mounted on low-Earth orbit satellites in the network, enhances robustness, solves the problem of low success rate of low-Earth orbit satellite-mounted terminals accessing base stations in related technologies, and is imperceptible to 5G base stations, reducing the processing pressure on 5G base stations.

[0055] In one optional embodiment of this disclosure, the execution of redundant traversal in step S25 includes sequentially executing the outer loop traversal and the inner loop traversal. The outer loop traversal is executed first, followed by the inner loop traversal.

[0056] In one optional embodiment of this disclosure, the step of performing an outer loop traversal includes: Set a first window range and a first sliding window range, and perform outer-loop sliding window operation with the time window length as the sliding window step until the 5G terminal receives Msg2; the first window range can be ±6. T Δ The range of the first sliding window can be ±N1 T prach N1 is a positive integer, ranging from ±6 T Δ Within the first window range, with a time window length T prach We attempted to adjust the sliding window stepping, with the outer ring sliding window used to correctly receive and parse Msg2. By setting different transmission times for the Physical Random Access Channel (PRACH), the uplink latency is adjusted so that the 5G base station can resolve the PRACH within N repeating windows, where N is a positive integer.

[0057] In one optional embodiment of this disclosure, the physical random access channel includes a cyclic prefix (CP), a preamble sequence, and a guard interval; The steps for performing an inner loop traversal include: Using the timing advance carried by Msg2, adjust the transmission delay of Msg3 to half the position of the cyclic prefix, and transmit Msg3 through the 5G terminal; using the timing advance (TA) carried by the currently received Msg2, adjust the transmission delay of Msg3 to half. The CP's location is used to initiate Msg3 via a 5G terminal; Set a second window range and a second sliding window range. Perform inner-loop sliding windowing with the time window length as the sliding window step until the 5G terminal receives Msg4, fix the current latency configuration, and complete the uplink synchronization of the random access process. The second window range can be ±N windows or ±N T Δ The range of the second sliding window can be N2. T prach N2 is a positive integer, with a time window length T. prach The sliding window is used to perform an inner loop sliding window within ±N windows. The inner loop sliding window is used to correctly receive Msg4 and correctly parse Msg4.

[0058] By setting different physical random access channels or the transmission time of Msg3, the uplink latency can be adjusted to fall within the correct window resolved by the 5G base station.

[0059] In one optional embodiment of this disclosure, performing normal access in step S25 includes: The physical random access channel is directly initiated according to the downlink timing, and Msg2 is received by the 5G terminal; if the error threshold T0 is not exceeded, normal access is performed, and PRACH is directly initiated according to the downlink timing. After the 5G terminal receives Msg2, it compensates the transmission delay of Msg3 to half the position of the cyclic prefix according to the timing advance of Msg2, and then transmits Msg3 through the 5G terminal; it also compensates the transmission delay of Msg3 to half the position according to the timing advance of Msg2. The CP's location is used to initiate Msg3 via a 5G terminal; Random access is completed by receiving Msg4 via a 5G terminal. The normal random access process is completed by receiving Msg4 via a 5G terminal.

[0060] In one optional embodiment of this disclosure, the method further includes: if Msg2 is not received after multiple PRACH transmissions during normal access, then a redundant traversal is performed; wherein, multiple times can be three times.

[0061] The random access latency calibration method for 5G terminals mounted on low-Earth orbit satellites provided in this disclosure can enable 5G terminals mounted on low-Earth orbit satellites to resist system timing errors caused by the synchronization uncertainty of the global navigation satellite system and latency errors in space signal transmission caused by the accuracy of orbit coordinates in the actual low-Earth orbit operating environment without the 5G base station's awareness or modification of physical random access channel parameters. This can significantly ensure the success rate of 5G terminal access, and at the same time, the magnitude of downlink synchronization error is judged by the error threshold to ensure basic access time.

[0062] As can be seen from the above description, this disclosure achieves the following technical effects: This disclosure, without changing the current non-terrestrial network technology, subcarrier spacing, and physical random access channel format, designs redundant random access for 5G terminals mounted on low-Earth orbit satellites. This significantly improves the access success rate of 5G terminals mounted on low-Earth orbit satellites in the network, enhances robustness, solves the problem of low success rate of low-Earth orbit satellite-mounted terminals accessing base stations in related technologies, and is imperceptible to 5G base stations, reducing the processing pressure on 5G base stations.

[0063] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0064] This disclosure also provides a random access latency calibration system for a low-orbit satellite-borne 5G terminal used in implementing the above method embodiments, applicable to four-step random access, such as... Figure 3 As shown, the random access delay calibration system 30 includes: The pre-compensation unit 31 is used to perform delay pre-compensation based on the ephemeris information of the low-orbit satellite and the ephemeris information of the high-orbit relay satellite. The detection unit 32 is used to detect the synchronization signal block using the 5G terminal carried by the low-orbit satellite after performing delay pre-compensation, and to perform downlink frame synchronization through the synchronization signal block and measure the downlink synchronization error. The acquisition unit 33 is used to acquire the preamble sequence of the physical random access channel configuration through the physical random access channel parameters carried in the broadcast of the 5G base station, and to detect the time window length using the preamble sequence; The judgment unit 34 is used to set an error threshold according to the time window length and to determine whether the downlink synchronization error exceeds the error threshold, wherein the error threshold is half of the time window length; Execution unit 35 is used to perform redundant traversal if the downlink synchronization error exceeds the error threshold, and to perform normal access if the downlink synchronization error does not exceed the error threshold.

[0065] The specific execution methods of each unit in the above system embodiments have been described in detail in the embodiments related to the method, and will not be elaborated here.

[0066] This disclosure also provides an electronic device, such as... Figure 4 As shown, the electronic device includes one or more processors 41 and a memory 42. Figure 4 Take a processor 41 as an example.

[0067] The controller may also include an input device 43 and an output device 44.

[0068] The processor 41, memory 42, input device 43, and output device 44 can be connected via a bus or other means. Figure 4 Taking the example of a connection between China and Israel via a bus.

[0069] Processor 41 can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or combinations of the above types of chips. The general-purpose processor can be a microprocessor or any conventional processor.

[0070] The memory 42, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs, non-transitory computer-executable programs, and modules, such as the program instructions / modules corresponding to the control method in this embodiment. The processor 41 executes various functional applications and data processing of the server by running the non-transitory software programs, instructions, and modules stored in the memory 42, thereby implementing the random access delay calibration method for a 5G terminal mounted on a low-orbit satellite in the above-described method embodiment.

[0071] The memory 42 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created by the use of the processing device operated by the server. Furthermore, the memory 42 may include high-speed random access memory and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, the memory 42 may optionally include memory remotely located relative to the processor 41, and these remote memories can be connected to a network connection device via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0072] Input device 43 can receive input numerical or character information, and generate key signal inputs related to user settings and function control of the server's processing device. Output device 44 may include display devices such as a display screen.

[0073] One or more modules are stored in memory 42, and when executed by one or more processors 41, they perform actions such as... Figure 2 The method shown.

[0074] Those skilled in the art will understand that all or part of the processes in the above method embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes described in the above method embodiments. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), random access memory (RAM), flash memory (FM), hard disk drive (HDD), or solid-state drive (SSD), etc.; the storage medium can also include combinations of the above types of memory.

[0075] Although embodiments of the present disclosure have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present disclosure, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for random access delay calibration of a 5G terminal mounted on a low-orbit satellite, characterized in that, Applied to four-step random access, including: Delay pre-compensation is performed based on the ephemeris information of low-orbit satellites and high-orbit relay satellites. After performing delay pre-compensation, the 5G terminal on the low-orbit satellite is used to detect the synchronization signal block, and downlink frame synchronization is performed through the synchronization signal block to measure the downlink synchronization error. The preamble sequence of the physical random access channel configuration is obtained by using the physical random access channel parameters carried in the broadcast of the 5G base station, and the length of the time window is detected by using the preamble sequence. An error threshold is set based on the time window length, and it is determined whether the downlink synchronization error exceeds the error threshold, wherein the error threshold is half of the time window length; If the downlink synchronization error exceeds the error threshold, a redundancy traversal is performed; if the downlink synchronization error does not exceed the error threshold, normal access is performed. The execution of redundant traversal includes sequentially executing outer loop traversal and inner loop traversal; The steps for performing an outer loop traversal include: Set a first window range and a first sliding window range, and perform outer ring sliding window with the time window length as the sliding window step until the 5G terminal receives Msg2; Set the transmission time of different physical random access channels and adjust the uplink delay to be within the range of N repeated windows from which the 5G base station resolves the physical random access channel, where N is a positive integer; The physical random access channel includes a cyclic prefix, a preamble sequence, and a guard interval; The steps for performing an inner loop traversal include: Using the timing advance carried by Msg2, the transmission delay of Msg3 is adjusted to half the position of the cyclic prefix, and Msg3 is transmitted through the 5G terminal; Set the second window range and the second sliding window range, and perform inner loop sliding window with the time window length as the sliding window step until the 5G terminal receives Msg4, fix the current latency configuration, and complete the uplink synchronization of the random access process.

2. The random access delay calibration method according to claim 1, characterized in that, The time delay pre-compensation based on the ephemeris information of low-Earth orbit satellites and high-Earth orbit relay satellites includes: The link distance is determined based on the ephemeris information of low-Earth orbit satellites and high-Earth orbit relay satellites, wherein the ephemeris information includes UTC time and orbital six-root number; The link delay is determined based on the link distance and the radio wave transmission speed. Based on the link latency, latency pre-compensation is performed on the uplink and downlink signal frame headers of the communication between the 5G base station and the 5G terminal carried by the low-orbit satellite.

3. The random access delay calibration method according to claim 1, characterized in that, The synchronization signal block includes a main synchronization signal and an auxiliary synchronization signal; The downlink frame synchronization via the synchronization signal block includes: parsing the downlink primary synchronization signal and the secondary synchronization signal to perform downlink frame synchronization.

4. The random access delay calibration method according to claim 1, characterized in that, The execution of normal access includes: The physical random access channel is directly initiated based on the downlink timing, and Msg2 is received by the 5G terminal. After the 5G terminal receives Msg2, it compensates the transmission delay of Msg3 to half the position of the cyclic prefix according to the timing advance of Msg2, and then transmits Msg3 through the 5G terminal. Random access is completed by receiving Msg4 through a 5G terminal.

5. A random access latency calibration system for a 5G terminal mounted on a low-orbit satellite, characterized in that, Applied to four-step random access, including: The pre-compensation unit is used to perform delay pre-compensation based on the ephemeris information of low-orbit satellites and high-orbit relay satellites. The detection unit is used to detect the synchronization signal block using the 5G terminal carried by the low-orbit satellite after performing delay pre-compensation, perform downlink frame synchronization through the synchronization signal block, and measure the downlink synchronization error. The acquisition unit is used to acquire the preamble sequence of the physical random access channel configuration through the physical random access channel parameters carried in the broadcast of the 5G base station, and to detect the time window length using the preamble sequence; The judgment unit is used to determine whether the downlink synchronization error exceeds the error threshold based on the time window length, wherein the error threshold is half of the time window length; An execution unit is configured to perform a redundancy traversal if the downlink synchronization error exceeds the error threshold, and to perform normal access if the downlink synchronization error does not exceed the error threshold. The execution of redundant traversal includes sequentially executing outer loop traversal and inner loop traversal; The outer loop traversal includes: Set a first window range and a first sliding window range, and perform outer ring sliding window with the time window length as the sliding window step until the 5G terminal receives Msg2; Set the transmission time of different physical random access channels and adjust the uplink delay to be within the range of N repeated windows from which the 5G base station resolves the physical random access channel, where N is a positive integer; The physical random access channel includes a cyclic prefix, a preamble sequence, and a guard interval; The inner loop traversal includes: Using the timing advance carried by Msg2, the transmission delay of Msg3 is adjusted to half the position of the cyclic prefix, and Msg3 is transmitted through the 5G terminal; Set the second window range and the second sliding window range, and perform inner loop sliding window with the time window length as the sliding window step until the 5G terminal receives Msg4, fix the current latency configuration, and complete the uplink synchronization of the random access process.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to execute the random access delay calibration method for a 5G terminal mounted on a low-orbit satellite as described in any one of claims 1 to 4.

7. An electronic device, characterized in that, The electronic device includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores a computer program executable by the at least one processor, the computer program being executed by the at least one processor to cause the at least one processor to perform the random access delay calibration method for a 5G terminal mounted on a low-orbit satellite as described in any one of claims 1 to 4.

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