Communication method and related apparatus

Abstract

The present application provides a communication method and a related apparatus, which aid terminals in flexibly performing random access so as to improve the efficiency of random access. The method comprises: a satellite determines uplink out-of-synchronization of a terminal; the satellite transmits a PDCCH command to the terminal, the PDCCH command indicating a plurality of SSBs or indicating a first SSB among the plurality of SSBs, and the plurality of SSBs satisfying: the transmit power being the same and the directions of transmitting beams being the same, or the receive power being the same and the directions of receiving beams being the same; and, on the basis of a random access resource corresponding to a second SSB, the terminal initiates random access to the satellite, the second SSB being one of the plurality of SSBs.

Description

Communication methods and related devices

[0001] This application claims priority to Chinese Patent Application No. 202410497408.8, filed on April 23, 2024, entitled "Communication Method and Related Apparatus", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of communications, and more particularly to a communication method and related apparatus. Background Technology

[0003] In satellite communication, when a satellite detects that a terminal cannot maintain uplink synchronization, the satellite can send a physical downlink control channel (PDCCH) order to the terminal. The PDCCH order is used by the terminal to resynchronize uplink.

[0004] Typically, a PDCCH command can indicate a synchronization signal block (SSB), and the terminal can re-initiate random access to the satellite based on the random access resources corresponding to the SSB indicated by the PDCCH command.

[0005] However, this random access method is not flexible enough, resulting in low efficiency. Summary of the Invention

[0006] This application provides a communication method and related apparatus, which facilitates flexible random access by terminals and improves the efficiency of random access.

[0007] Firstly, a communication method is provided, which can be executed by a first communication device. This first communication device can be a terminal, a component configured in the terminal (e.g., a processor, chip, or chip system), or a logic module or software capable of implementing all or part of the terminal's functions; this application does not limit the specific implementation. The communication method of this application is described below using the first communication device as an example of a terminal.

[0008] The method includes: receiving a PDCCH command, which indicates a plurality of SSBs, or indicates a first SSB among the plurality of SSBs, wherein the plurality of SSBs satisfy the following conditions: having the same transmit power and the same transmit beam direction, or having the same receive power and the same receive beam direction; and initiating random access to the satellite based on the random access resources corresponding to a second SSB, wherein the second SSB is one of the plurality of SSBs.

[0009] In wireless communication, a terminal and a satellite may lose synchronization for various reasons, meaning the terminal may be unable to maintain synchronization with the satellite, which will affect data transmission between the terminal and the satellite. When the terminal loses uplink synchronization, it can receive a PDCCH command from the satellite. This PDCCH command is used by the terminal to re-initiate random access and thus re-establish uplink synchronization with the satellite.

[0010] In this application, the multiple SSBs are associated, specifically in the following ways: the multiple SSBs have the same transmit power and transmit beam direction, or the multiple SSBs have the same receive power and receive beam direction. Alternatively, the multiple SSBs have a quasi-co-location relationship.

[0011] The first SSB can be any one of the plurality of SSBs, and the second SSB may be the same as the first SSB or may be different SSBs.

[0012] In one possible implementation, since the multiple SSBs have this association, the satellite can instruct the multiple SSBs via the PDCCH command. Each SSB has its corresponding random access resource, meaning the terminal can select one SSB (the second SSB) from the multiple SSBs and initiate random access based on the random access resource corresponding to the second SSB. Compared to the method where the terminal must initiate random access based on the random access resource corresponding to an SSB indicated by the PDCCH command, the technical solution of this application allows the terminal more opportunities to initiate random access to the satellite. This random access method is more flexible and has higher efficiency.

[0013] In another possible implementation, before receiving the PDCCH command, the terminal is aware of the association relationship among the multiple SSBs. Thus, after receiving the PDCCH command, although the command only indicates the first SSB, considering the association relationship among the multiple SSBs, the terminal can select one SSB (the second SSB) and initiate random access to the satellite based on the random access resources corresponding to the second SSB. Compared to the method where the terminal must initiate random access based on the random access resources corresponding to only one SSB indicated by the PDCCH command, the technical solution of this application provides the terminal with more opportunities to initiate random access to the satellite, making this random access method more flexible and efficient.

[0014] In conjunction with the first aspect, in some implementations of the first aspect, the second SSB satisfies one of the following conditions: after receiving the PDCCH command, the second SSB is the first SSB received by the terminal among the plurality of SSBs; or, the second SSB is the highest priority SSB among the plurality of SSBs that have not been received by the terminal.

[0015] In conjunction with the first aspect, in some implementations of the first aspect, before initiating random access to the satellite based on the random access resources corresponding to the second SSB, the method further includes: receiving first indication information, which is used to indicate the conditions satisfied by the second SSB.

[0016] In conjunction with the first aspect, in some implementations of the first aspect, before initiating random access to the satellite based on the random access resource corresponding to the second SSB, the method further includes: receiving second indication information, which is used to indicate the priority of the plurality of SSBs.

[0017] In conjunction with the first aspect, in some implementations of the first aspect, the PDCCH command indicates a first SSB; before receiving the PDCCH command, the method further includes: receiving third indication information, the third indication information being used to indicate that the plurality of SBBs satisfy: the same transmission power and the same direction of the transmission beam; or, the same reception power and the same direction of the reception beam.

[0018] Secondly, a communication method is provided, which can be executed by a second communication device. This second communication device can be a satellite, a component configured within the satellite (e.g., a processor, chip, or chip system), or a logic module or software capable of implementing all or part of the satellite's functions; this application does not limit the specific device. The communication method of this application is described below using a satellite as an example of the second communication device.

[0019] The method includes: determining that the terminal has lost uplink synchronization; and sending a PDCCH command, the PDCCH command indicating a plurality of SSBs, or indicating a first SSB among the plurality of SSBs, the plurality of SSBs satisfying that: they have the same transmit power and the same transmit beam direction, or they have the same receive power and the same receive beam direction.

[0020] In conjunction with the second aspect, in some implementations of the second aspect, the method further includes: sending first indication information, the first indication information being used to indicate the conditions satisfied by the second SSB, the second SSB being the SSB among the plurality of SSBs used by the terminal to initiate random access to the satellite.

[0021] In conjunction with the second aspect, in some implementations of the second aspect, the second SSB satisfies one of the following conditions: after receiving the PDCCH command, the second SSB is the first SSB received by the terminal among the plurality of SSBs; or, the second SSB is the highest priority SSB among the plurality of SSBs that have not been received by the terminal.

[0022] In conjunction with the second aspect, in some implementations of the second aspect, before sending the PDCCH command, the method further includes: receiving second indication information, the second indication information being used to indicate the priority of the plurality of SSBs.

[0023] In conjunction with the second aspect, in some implementations of the second aspect, the PDCCH command instructs the first SSB; before sending the PDCCH command, the method further includes: sending third indication information, the third indication information being used to instruct the plurality of SBBs to satisfy: having the same transmission power and the same direction of the transmission beam; or having the same reception power and the same direction of the reception beam.

[0024] It should be understood that the second aspect of this application corresponds to the technical solution of the first aspect of this application, and the beneficial effects achieved by each aspect and the corresponding feasible implementation are similar, and will not be repeated here.

[0025] Thirdly, a communication apparatus is provided, comprising: a method for performing any possible implementation of any of the above aspects. Specifically, the apparatus includes a module for performing the method in any possible implementation of any of the above aspects.

[0026] In one design, the device may include modules that perform the methods / operations / steps / actions described in the first aspect above. These modules may be hardware circuits, software, or a combination of hardware circuits and software.

[0027] In another design, the device is a communication chip, which may include input circuitry or interface for transmitting information or data, and output circuitry or interface for receiving information or data.

[0028] In another design, the device is a terminal or a satellite, which may include a transmitter for sending information or data and a receiver for receiving information or data.

[0029] In another design, the device is used to perform any possible implementation of the methods described above, and the device can be configured in a terminal or a satellite.

[0030] Fourthly, a communication device is provided, comprising at least one processor, the at least one processor being configured to call and run a computer program from a memory, such that the device performs the method in any possible implementation of any of the preceding aspects.

[0031] Optionally, the device further includes a memory for storing instructions and data. The memory is coupled to the processor, which, when executing the instructions stored in the memory, can implement the methods described in the foregoing aspects.

[0032] Optionally, the device may also include a transmitter and a receiver, which may be separate or integrated together and referred to as a transceiver.

[0033] Fifthly, a computer program product is provided, the computer program product comprising: a computer program (also referred to as code or instructions), which, when run, causes a computer to perform a method in any possible implementation of any of the above aspects.

[0034] In a sixth aspect, a computer-readable storage medium is provided that stores a computer program (also referred to as code or instructions) that, when executed on a computer, causes the computer to perform the methods in any possible implementation of any of the above aspects.

[0035] In a seventh aspect, this application provides a chip system including at least one processing unit for supporting the implementation of the functions involved in any possible implementation of any of the above aspects, such as receiving or processing data involved in the above methods.

[0036] In one possible design, the chip system also includes a memory for storing program instructions and data, which may be located within or outside the processor.

[0037] Optionally, the chip system may consist of chips or may include chips and other discrete components. Attached Figure Description

[0038] Figure 1 is a flowchart illustrating a competition-based random access method;

[0039] Figure 2 is a schematic flowchart of a non-contention-based random access method;

[0040] Figure 3 is a schematic diagram of the mapping relationship between SSB and RO;

[0041] Figure 4 is a schematic diagram of a PRACH configuration;

[0042] Figure 5 is a schematic diagram of a terminal implementing uplink synchronization based on PDCCH commands;

[0043] Figures 6, 7A, and 7B are schematic diagrams of satellites instructing SSBs via PDCCH commands;

[0044] Figure 8 is a schematic diagram of the architecture of a communication system applicable to an embodiment of this application;

[0045] Figure 9 is a schematic diagram of an NTN architecture applicable to an embodiment of this application;

[0046] Figures 10 to 12 are schematic flowcharts of the communication method provided in the embodiments of this application;

[0047] Figures 13 and 14 are schematic block diagrams of a communication device provided in an embodiment of this application. Detailed Implementation

[0048] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0049] Before introducing the communication method and related apparatus provided in the embodiments of this application, the following points should be made first.

[0050] First, in the embodiments shown below, the terms and English abbreviations, such as PDCCH, SSB, transmit beam, receive beam, etc., are merely exemplary examples given for ease of description and should not constitute any limitation on this application. This application does not preclude the possibility of defining other terms that can achieve the same or similar functions in existing or future protocols.

[0051] Second, in the embodiments shown below, the first, second, and various numerical designations are merely distinctions for ease of description and are not intended to limit the scope of the embodiments of this application.

[0052] Third, "at least one" means one or more, while "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, and c can mean: a, or b, or c, or a and b, or a and c, or b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0053] Fourth, in this application, "send" and "receive" indicate the direction of signal transmission. For example, "send a PDCCH command to the terminal" can be understood as the destination of the PDCCH command being the terminal, which can include direct transmission via the air interface or indirect transmission via the air interface from other units or modules. "Receive a PDCCH command from a satellite" can be understood as the source of the PDCCH command being the satellite, which can include direct reception from the satellite via the air interface or indirect reception from the satellite via the air interface from other units or modules. "Send" can also be understood as the "output" of the chip interface, and "receive" can also be understood as the "input" of the chip interface.

[0054] In other words, sending and receiving can occur between devices, such as between a terminal and a satellite; or they can occur within a device, such as between components, modules, chips, software modules, or hardware modules within the device via buses, wiring, or interfaces.

[0055] The relevant technologies and concepts involved in this application are introduced below.

[0056] 1. Random access (RA)

[0057] The random access process refers to the process from when a terminal sends a random access preamble to attempt to access the network until a basic signaling connection is established with the network. The purpose of random access is to enable uplink synchronization between the terminal and the access network equipment, allowing the access network equipment to allocate uplink resources to the terminal. During random access, the terminal needs to initiate access on a specific physical random access channel (PRACH) time-frequency resource. The signal used by the terminal to initiate access is the random access preamble, which indicates to the access network equipment that there is a random access request, allowing the access network equipment to estimate the transmission delay between itself and the terminal.

[0058] Currently, there are two different mechanisms for random access: contention-based random access and non-contention-based random access.

[0059] For contention-based random access, the terminal randomly selects a random access preamble within the range broadcast in System Information Block 1 (SIB1). This can lead to multiple terminals selecting the same random access preamble, resulting in a random access preamble collision. Since the access network device cannot distinguish between random access preambles sent by different terminals, each terminal needs to send a message related to itself to the access network device so that the access network device can differentiate between the random access preambles sent by different terminals.

[0060] The two different random access procedures described above are described below.

[0061] Figure 1 is a flowchart illustrating a contention-based random access method 100. As shown in Figure 1, method 100 includes steps S101 to S104, with the specific steps as follows:

[0062] S101, the terminal sends a random access preamble to the access network device. Correspondingly, the access network device receives the random access preamble.

[0063] This step can also be referred to as the transmission of message 1. Initial random access is initiated by the terminal's media access control (MAC) sublayer. Before S101, the access network device can notify all terminals which PRACH resources are allowed to transmit the random access preamble.

[0064] After receiving the random access preamble, the access network device detects the random access preamble to obtain its identifier and downlink transmission beam, and estimates the transmission delay between the terminal and the access network device.

[0065] S102, the access network device sends a random access response (RAR) to the terminal. The terminal then receives the RAR.

[0066] This step can also be referred to as the transmission of message 2. After receiving the random access preamble, the access network device schedules resources for the temporary cell-radio network temporary identity (TC-RNTI), uplink, and downlink.

[0067] Access network devices send random access responses via the physical downlink shared channel (PDSCH). The random access response includes the random access preamble identifier, timing advance (TA), initial uplink scheduling, and cell-radio network temporary identity (C-RNTI). A single PDSCH can carry the random access response and send it to multiple terminals.

[0068] After sending the random access preamble, the terminal monitors the PDCCH and waits for the random access response in the random access response window. Specifically, if the identifier of the random access preamble received by the terminal in the random access response window is the same as the identifier of the random access preamble sent by the terminal in message 1, the response is successful, and the terminal can then send uplink scheduling information to the access network equipment. If the terminal does not receive a response to message 1 in the random access response window or fails to verify the response to message 1, the response fails. In this case, if the number of random access attempts is less than the upper limit, the terminal continues to send the random access preamble to re-initiate random access; if the number of random access attempts reaches the upper limit, the random access fails.

[0069] S103, the terminal sends uplink scheduling information to the access network device. Correspondingly, the access network device receives the uplink scheduling information.

[0070] This step can also be referred to as the transmission of message 3. The terminal sends uplink scheduling information through the physical uplink shared channel (PUSCH). The uplink scheduling information may include the TC-RNTI and a contention resolution identifier. After the terminal sends the uplink scheduling information, the contention resolution timer (e.g., 4ms) begins counting.

[0071] The messages sent by the terminal differ in different RA scenarios, as shown in the following example:

[0072] Initial Radio Resource Control (RRC) connection setup scenario: The terminal transmits an RRC setup request message through the common control channel (CCCH) in the transparent mode (TM) of the Radio Link Control (RLC) layer.

[0073] RRC connection reestablishment scenario: The terminal transmits the RRC reestablishment request message through the CCCH in the TM of the RLC layer.

[0074] Handover (HO) scenario: When a terminal accesses the target cell and there is no dedicated random access preamble during the handover process, a contention-based access control (RA) is triggered. The terminal transmits an RRC handover confirmation message and a C-RNTI via a dedicated control channel. Optionally, the terminal also sends a buffer status report (BSR).

[0075] Other scenarios: at least send the terminal's C-RNTI.

[0076] S104, the access network device sends contention resolution information to the terminal. Accordingly, the terminal receives the contention resolution information.

[0077] This step can also be referred to as the transmission of message 4. The access network device uses the C-RNTI on the PDCCH or the contention resolution identifier on the PDCSH to help the terminal resolve contention.

[0078] The terminal continues to monitor the PDCCH until the contention resolution timer expires. When any of the following conditions are met, the contention is considered successfully resolved and the timer stops:

[0079] 1. The terminal receives C-RNTI via PDCCH.

[0080] 2. The terminal receives the TC-RNTI via PDCCH, and the MAC-PDU is successfully decoded. Specifically, the contention resolution identifier received by the terminal via PSCDH is the same as the contention resolution identifier carried in message 3 sent by the terminal.

[0081] If any of the above conditions are not met before the contention resolution timer expires, the terminal considers the contention resolution to have failed. In this case, if the number of random access attempts has not reached the limit, the terminal will initiate random access again; if the number of random access attempts has reached the limit, the random access will fail.

[0082] The following section, with reference to Figure 2, introduces non-contention-based random access.

[0083] For non-contention-based random access, the access network device assigns a dedicated random access preamble to each terminal. In this case, collisions of random access preambles will not occur between terminals. However, when there are insufficient dedicated random access preambles, the access network device will instruct the terminal to initiate contention-based random access.

[0084] Figure 2 is a schematic flowchart of a non-contention-based random access method 200. As shown in Figure 2, method 200 includes steps S201 to S204, and the specific steps are as follows:

[0085] S201, the access network device sends random access preamble allocation information to the terminal. This random access preamble allocation information is used to indicate a random access preamble specific to the terminal. Accordingly, the terminal receives the random access preamble allocation information.

[0086] Access network devices assign unique random access preambles to different terminals. These preamble allocations are carried by the access network devices via RRC messages or downlink control information (DCI). Below are some examples of scenarios for sending this random access preamble allocation information:

[0087] Switching scenario: The source base station carries the random access preamble allocation information through mobility control information.

[0088] Downlink data arrival scenario: When downlink data arrives at the access network device, the access network device instructs the terminal to start RA through DCI on the PDCCH. The PDCCH carries the random access preamble allocation information.

[0089] In a non-standalone (NSA) network scenario, when a new radio (NR) cell is added to an NSA, the access network device commands the terminal to initiate an access preamble (RA) via the PDCCH. The PDCCH carries the dedicated random access preamble assigned to the terminal.

[0090] S202, the terminal sends a random access preamble to the access network device. Correspondingly, the access network device receives the random access preamble.

[0091] This step can also be referred to as the transmission of message 1.

[0092] S203, the access network device sends a random access response to the terminal. Correspondingly, the terminal receives the random access response.

[0093] This step can also be referred to as the transmission of message 2.

[0094] For the handover scenario described above, the random access response includes a time lead and initial uplink scheduling.

[0095] For the downlink data arrival scenario described above, when downlink data arrives at the access network device, the random access response includes timing alignment information and a random access preamble identifier (RAPID).

[0096] For the NSA networking scenario described above, when adding an NR cell to the NSA, the random access response includes timing alignment information and RAPID.

[0097] S204, the terminal sends uplink scheduling information to the access network device. Correspondingly, the access network device receives the uplink scheduling information.

[0098] This step can also be referred to as the transmission of message 3. The terminal sends uplink scheduling information to the access network equipment at a predetermined transmission time, based on the timing advance or timing alignment information.

[0099] Common RA triggering scenarios include, but are not limited to: initial RRC connection establishment, RRC connection reconstruction, handover, downlink data arrival, uplink data transmission, RRC inactive state (RRC_inactive) to RRC connected state (RRC_connected), requesting other system information (OSI) based on message 1 or requesting OSI based on message 3.

[0100] According to the 3rd generation partnership project (3GPP) protocol, there is a corresponding relationship between the SSB and the random access channel (RACH) occasion, called the RACH occasion (RO). The terminal can determine the corresponding RO based on the SSB and initiate random access on the RO. The time and frequency resource location of the RO is configured by the access network equipment.

[0101] SSB can also be called the synchronization signal and physical broadcast channel block (SS / PBCH). An SSB includes primary synchronization signals (PSS), secondary synchronization signals (SSS), and PBCH. An SSB can also be described as an SS / PBCH block.

[0102] Figure 3 is a schematic diagram of the mapping relationship between SSB and RO. As shown in Figure 3, the mapping relationship between RO and SSB in the frequency domain can be one-to-one, as shown in Figure 3, where SSB_0 and RO_0 have a mapping relationship; it can also be many-to-one, as shown in Figure 3, where RO_0, RO_1, RO_2, and RO_3 all have a mapping relationship with SSB_0; or it can be one-to-many, as shown in Figure 3, where RO_0 has a mapping relationship with SSB_0, SSB_1, SSB_2, and SSB_3 respectively.

[0103] In addition to sending the mapping relationship between RO and SSB to the terminal, the access network device can also send RO resource configuration information to the terminal. Table 1 shows one type of RO resource configuration information with random access configuration index 251.

[0104] Table 1

[0105] In Table 1, the PRACH configuration period is in units of radio frames, determined by the period x and the offset value y, i.e., within frame number (N... SFN PRACH resources are configured at mod(x) = y. The random access preamble format (also known as the preamble format) is C2. The subframe numbers with ROs are 2 and 7. The start symbol l0 = 0 indicates that the starting position of the first RO in the time domain is symbol 0. This indicates the number of 30 kHz PRACH slots corresponding to one subframe. This indicates the number of ROs that can be configured for each PRACH slot. This represents the number of symbols used for random access time-domain resources. Based on Table 1, the PRACH configuration diagram shown in Figure 4 can be obtained.

[0106] As shown in Figure 4, there are 10 subframes in a 10-millisecond (ms) system frame. The subframe numbers with ROs are 2 and 7. Each subframe corresponds to two 30kHz PRACH time slots. Each PRACH time slot can be configured with two time-domain ROs. Therefore, eight time-domain ROs can be configured within 10ms.

[0107] 2. NTN communication

[0108] Compared to terrestrial networks (TN), NTN communication features wider coverage and more flexible networking, enabling seamless global network coverage. The NTN network serves both as a supplement to current terrestrial networks and as an independent communication system providing users with high-speed global network access. Currently, research institutes, communication organizations, and communication companies worldwide are involved in researching NTN communication technologies and developing standards, striving to build a unified communication network encompassing air, space, and terrestrial communication.

[0109] NTN communication involves networking using equipment such as drones, high-altitude platforms, and satellites to provide data transmission and voice communication services to terminals. High-altitude platform equipment is typically located at an altitude of 8–50 km above the ground. Based on the satellite's orbital altitude, satellite communication systems can be categorized into three types: geostationary earth orbit (GEO) satellite communication systems (also known as synchronous orbit satellite systems), medium earth orbit (MEO) satellite communication systems, and low earth orbit (LEO) satellite communication systems.

[0110] GEO satellites orbit at an altitude of 35,786 km. Their main advantages are that they can remain relatively stationary relative to the ground and provide a large coverage area. However, GEO satellite communication also has significant disadvantages: 1) The long distance between GEO satellites and Earth results in high free-space propagation loss, leading to tight communication link budgets. To increase transmit / receive gain, larger aperture antennas are required for the satellites; 2) Communication transmission latency is high, reaching approximately 500 ms round-trip time, which cannot meet the needs of low-latency services; 3) GEO orbital resources are relatively scarce, launch costs are high, and coverage cannot be provided to the polar regions of Earth.

[0111] MEO satellites orbit at altitudes between 2000 and 35786 km. Their advantage is that they can achieve global coverage with a relatively small number of satellites. However, their orbital altitude is higher than LEO, resulting in significantly longer communication transmission delays. Considering both the advantages and disadvantages of MEO satellite communication, MEO satellites are primarily used for positioning and navigation.

[0112] LEO satellites orbit at altitudes ranging from 300 to 2000 km. Compared to MEO and GEO orbits, LEO satellites operate at lower altitudes, offering advantages such as shorter data propagation delays, lower transmission losses, and lower launch costs. Therefore, LEO satellite communication has gained increasing attention in recent years.

[0113] In recent years, several companies have planned to build mega-LEO constellations, including thousands or even tens of thousands of LEO satellites. As the size of satellite constellations increases, more than one satellite will be present within the line of sight of a terminal. Single-satellite transmission offers limited improvement to system capacity. To effectively increase the capacity of overlapping satellite coverage areas, satellite systems are gradually evolving from single-satellite transmission to multi-satellite collaborative transmission. Utilizing multi-satellite collaborative transmission can reduce the requirements for single-satellite transmission capabilities, thereby reducing the manufacturing cost of a single satellite. Multi-satellite collaborative transmission is a key technology for future satellite communication systems.

[0114] Because satellites are not easily affected by natural disasters or external damage, research is currently underway to use them as access network equipment (e.g., base stations) for mobile communication systems to provide communication services to areas such as oceans and forests.

[0115] To support broader service coverage, given the link budget and system resources, satellites improve overall coverage by increasing the coverage area of ​​a single beam through beam design. However, since the coverage range of a single beam is limited, a single satellite still requires a large number of beams to achieve wider coverage.

[0116] In this context, a beam is the main lobe of a signal's directional pattern. The coverage area of ​​a beam refers to the area projected onto the ground. Access network equipment can adjust the antenna weights to direct the beam in different directions, resulting in different coverage areas. The beam coverage area discussed in this application refers to the beam's coverage area on the ground. As satellite base stations move and weights are adjusted, the beam coverage area will also change.

[0117] During the random access phase, the satellite, acting as an access network device (e.g., a base station), sequentially scans all beams to configure random access resources for the terminal. Currently, satellites can broadcast different Service Blocks (SSBs) for different communication areas and distinguish them by their index numbers. Typically, different SSB index numbers indicate downlink synchronization signals in different beam directions, covering and serving different areas. After receiving an SSB, the terminal completes timing synchronization and confirms the time-frequency position of System Information Block (SIB) 1 based on the information in the SSB. It then parses SIB 1 to obtain random access resources, such as the transmit power and RO of the random access preamble. Based on the search space of SIB 19 configured in SIB 1, it detects SIB 19 and completes data parsing to obtain the satellite's ephemeris information. After obtaining cell information and / or ephemeris information, the terminal sends the random access preamble on the corresponding uplink resources according to the configuration information and the SSB index. For the access network device, the received random access preamble and the corresponding uplink resources can be used to determine the area where the terminal is located and establish a connection with the terminal.

[0118] Figure 5 is a schematic diagram illustrating the process of a terminal achieving uplink synchronization based on a PDCCH command. Referring to Figure 5, when the terminal is in an RRC connection state, and the base station (e.g., a satellite base station) detects that the terminal cannot maintain uplink synchronization, or is out of synchronous, the base station can send a PDCCH command to the terminal. This PDCCH command triggers the terminal to initiate random access. The PDCCH command indicates an SSB, such as SSB 0. After receiving SSB 0, the terminal initiates random access to the satellite based on the transmit power of the random access preamble corresponding to SSB 0 and the RO (Redirect Access Point). After this, the terminal can maintain uplink synchronization. The random access process is described above and will not be repeated here.

[0119] In NR, DCI format 1_0 is used as a PDCCH command to trigger random access on the SSB beam where the terminal is camped. The fields included in DCI format 1_0 are shown in Table 2. This refers to the number of resource blocks (RBs) contained in the downlink active bandwidth part (BWP).

[0120] Table 2

[0121] In a satellite communication scenario, as shown in Figure 6, the satellite sends a PDCCH command to the terminal, which indicates an SSB. For example, the index field of SS / PBCH in Table 1 is 0, indicating SSB 0. After receiving SSB 0, the terminal can initiate random access to the satellite based on the random access resource corresponding to SSB 0.

[0122] However, in satellite communication scenarios, the communication rate requirements of different geographical areas within the satellite coverage area can vary greatly. Some geographical areas have high communication rate requirements, while others have low requirements. To fully utilize satellite resources, one possible implementation is for the satellite to allocate more resources to geographical areas with high communication rate requirements. For example, during a beam scan, the satellite can allocate more Service Blocks (SSBs) to geographical areas with higher rate requirements. Each of the allocated SSBs has its corresponding random access resources. These multiple SSBs have the same transmission power and the same transmission beam direction.

[0123] Referring to Figure 7A, the satellite periodically transmits SSB burst sets (also known as SSB bursts) within its network coverage area. For example, an SSB burst set includes 8 SSBs, denoted as: SSB 0, SSB 1, SSB 2, SSB 3, SSB 4, SSB 5, SSB 6, and SSB 7. Assume that the satellite transmits SSB 0 in a geographical area within its network coverage area at time T1. At some later time, the satellite sends a PDCCH command to a terminal in that geographical area. The PDCCH command indicates SSB 0, meaning that the terminal needs to initiate random access to the satellite based on the random access resources corresponding to SSB 0. However, since the PDCCH command is sent after SSB 0, the terminal has missed this access opportunity. The terminal needs to wait until the next beam scan receives SSB 0 again before it can initiate random access to the satellite based on the random access resources corresponding to SSB 0.

[0124] Referring to Figure 7B, after the satellite sends the PDCCH command, assuming the satellite transmits SSB 3 in the same geographical area at time T2, SSB 3 has its corresponding random access resources. SSB 0 and SSB 3 have the same transmit power and the same transmit beam direction, which also means that SSB 0 and SSB 3 have the same receive power and the same receive beam direction. The terminal could initiate random access to the satellite based on the random access resources corresponding to SSB 3. However, since the PDCCH command indicates SSB 0, the terminal will abandon the random access resources corresponding to SSB 3 and wait until the next beam scan receives SSB 0 again before initiating random access to the satellite based on the random access resources corresponding to SSB 0. This wastes the random access resources corresponding to SSB 3, making the random access method less flexible and reducing the efficiency of random access.

[0125] In view of this, embodiments of this application provide a communication method in which a satellite can indicate multiple SSBs or one of the multiple SSBs (denoted as the first SSB) to a terminal via a PDCCH command. The multiple SSBs are associated in the following ways: they have the same transmit power and the same transmit beam direction; or they have the same receive power and the same receive beam direction. This association ensures that the terminal receives the multiple SSBs with the same receive configuration (e.g., the same receive power and receive beam direction). In other words, if the terminal can receive one of the multiple SSBs, it is highly likely that it can receive the other SSBs with the same receive configuration. After receiving the PDCCH command, the terminal initiates random access based on the random access resource corresponding to one of the multiple SSBs (denoted as the second SSB), which is the SSB received by the terminal after receiving the PDCCH command. In this way, the satellite is no longer limited to instructing only one SSB through the PDCCH command, and the terminal is no longer limited to initiating random access based solely on the SSB indicated by the PDCCH command. This random access method is more flexible and has higher efficiency.

[0126] Figure 8 is a schematic diagram of the architecture of a communication system 100 applicable to an embodiment of this application. As shown in Figure 8, the communication system 100 may include at least one node in a radio access network (RAN), referred to as RAN nodes (110a, 110b, and 110c in Figure 8), and may also include at least one terminal (120a-120g in Figure 8). RAN nodes can be interconnected via wired or wireless means. Figure 8 is only a schematic diagram; the communication system may also include other network devices, such as wireless relay devices and wireless backhaul devices.

[0127] In some scenarios, the roles of RAN nodes and terminals are relative. For example, in Figure 8, network element 120c can be a helicopter or a drone, which can be configured as a mobile base station. For terminals 120d that access the RAN through network element 120c, network element 120c is a base station; but for base station 110a, network element 120c is a terminal. RAN nodes and terminals are sometimes referred to as communication devices. For example, in Figure 5, network elements 110a, 110b, and 110c can be understood as communication devices with base station functions, and network elements 120a-120g can be understood as communication devices with terminal functions.

[0128] In one possible scenario, a RAN node can be a base station, an evolved NodeB (eNodeB), an access point (AP), a transmission reception point (TRP), a next-generation NodeB (gNB), or a base station in 5G, 6G, or a future mobile communication system. A RAN node can be a macro base station (as shown in Figure 1, 110a), a micro base station or indoor station (as shown in Figure 1, 110b), a relay node or donor node, or a radio controller in a cloud-radio access network (CRAN) scenario. Optionally, a RAN node can also be a server, wearable device, vehicle, or in-vehicle equipment. For example, the access network equipment in vehicle-to-everything (V2X) technology can be a roadside unit (RSU).

[0129] In another possible scenario, multiple RAN nodes collaborate to assist the terminal in achieving wireless access, with each RAN node performing a portion of the base station's functions. For example, RAN nodes can be central units (CUs), distributed units (DUs), CU-control plane (CPs), CU-user plane (UPs), or radio units (RUs). CUs and DUs can be separate entities or included in the same network element, such as a baseband unit (BBU). RUs can be included in radio frequency equipment or radio frequency units, such as remote radio units (RRUs), active antenna units (AAUs), or remote radio heads (RRHs).

[0130] In different systems, CU (or CU-CP and CU-UP), DU, or RU may have different names, but those skilled in the art will understand their meaning. For example, in an open-RAN (ORAN or O-RAN) system, CU can also be called O-CU (open CU), DU can also be called O-DU, CU-CP can also be called O-CU-CP, CU-UP can also be called O-CU-UP, and RU can also be called O-RU. Any of the units among CU (or CU-CP, CU-UP), DU, and RU in this application can be implemented through software modules, hardware modules, or a combination of software modules and hardware modules.

[0131] Figure 9 is a schematic diagram of an NTN architecture applicable to an embodiment of this application. As shown in Figure 9, the satellite has some or all of the functions of an access network device and can be called a satellite base station. The satellite base station can provide wireless access services and schedule wireless resources for terminals accessing the network through the satellite base station. The satellite base station and the terminal communicate through the User-Universal Terrestrial Radio Access Network (Uu) interface. The satellite base station and the core network (CN) can communicate through the Next Generation (NG) interface. The satellite base station and the core network can exchange non-access stratum (NAS) signaling of the core network and user service data through the NG interface. The satellite radio interface (SRI) is the feeder link between the NTN gateway and the satellite. In Figure 9, the SRI can be used as part of the NG interface to realize communication interaction between the satellite base station and the core network.

[0132] Satellite equipment can be categorized into transparent mode and regenerative mode based on its operating mode. When operating in transparent mode, the satellite functions as a relay station. Gateway stations / signaling stations possess base station functions or some base station functions; in this case, the gateway station / signaling station can be considered a base station.

[0133] When the satellite operates in regeneration mode, it possesses data processing capabilities and functions as a base station, or partially as one. In this case, the satellite can be considered a base station. It should be noted that the technical solutions of this application are applicable to communication systems that integrate terrestrial and satellite communications, which can also be called NTN communication systems. The terrestrial communication system can be, for example, a Long Term Evolution (LTE) system, a Universal Mobile Telecommunications System (UMTS), a 5G communication system, an NR system, or a next-generation communication system, etc., and is not limited here.

[0134] Figure 10 is a schematic flowchart of a communication method 1000 provided in an embodiment of this application. The steps of method 1000 can be executed interactively by a terminal and a satellite, such as 110a shown in Figure 8 above, or a satellite base station as shown in Figure 9 above, that is, the satellite has the functions of a base station or part of the functions of a base station.

[0135] Method 1000 includes steps S1001 to S1006, and the specific steps are as follows:

[0136] S1001, the satellite has determined that the terminal has lost uplink synchronization.

[0137] The satellite can use a timing advance mechanism to achieve uplink synchronization of the terminal. For example, the satellite can configure a timer for the terminal via radio resource control (RRC) messages. In the media access control layer, this timer is called a time alignment timer, or an inactive timer. Simultaneously, the satellite can also maintain a time alignment timer. If the satellite does not receive an acknowledgment (ACK) from the terminal for the timing advance command before the time alignment timer expires, the satellite can determine that the terminal has lost uplink synchronization.

[0138] S1002, the satellite sends a PDCCH command to the terminal. This PDCCH command indicates multiple SSBs, or indicates the first SSB among the multiple SSBs, wherein the multiple SSBs satisfy the following conditions: they have the same transmit power and the same transmit beam direction, or they have the same receive power and the same receive beam direction. Accordingly, the terminal receives the PDCCH command.

[0139] In one possible implementation, the PDCCH command instructs the plurality of SSBs to have an association relationship, indicating that the plurality of SSBs have the same transmit power and the same transmit beam direction, or that the plurality of SSBs have the same receive power and the same receive beam direction. Wherein, the plurality of SSBs having the same transmit power and the same transmit beam direction means that the plurality of SSBs have the same receive power and the same receive beam direction. The plurality of SSBs having the same receive beam direction can be understood as the plurality of SSBs having the same receive beam; in other words, the terminal can use the same receive beam to receive the plurality of SSBs.

[0140] In one example, the fact that the multiple SSBs have the same received power means that the multiple SSBs have the same reference signal receiving power (RSRP).

[0141] In another possible implementation, the PDCCH command indicates a first SSB, which is any one of the plurality of SSBs. This does not change the signaling design of the existing PDCCH command and is simple to implement.

[0142] For ease of description, the implementation method of the PDCCH command instructing the multiple SSBs will be referred to as Method 1, and the implementation method of the PDCCH command instructing the first SSB among the multiple SSBs will be referred to as Method 2.

[0143] S1003, the terminal initiates random access to the satellite based on the random access resources corresponding to the second SSB.

[0144] In conjunction with the above method one, after receiving the PDCCH command, the terminal can determine the second SSB from the plurality of SSBs and initiate random access to the satellite based on the random access resources corresponding to the second SSB.

[0145] In conjunction with Method 2 above, after receiving the PDCCH command, the terminal can determine the second SSB by combining the known association relationships among the multiple SSBs, and initiate random access to the satellite based on the random access resources corresponding to the second SSB. The association relationships among the multiple SSBs indicate that the multiple SSBs have the same transmit power and the same transmit beam direction, or that the multiple SSBs have the same receive power and the same receive beam direction. Alternatively, the association relationships among the multiple SSBs indicate one or more SSBs that are associated with the first SSB, where the association relationship is: the one or more SSBs have the same transmit power and the same transmit beam direction as the first SSB, or the one or more SSBs have the same receive power and the same receive beam direction as the first SSB. The multiple SSBs include the first SSB and the one or more SSBs mentioned above.

[0146] For example, the first SSB is SSB i, and the association relationship of the multiple SSBs indicates that SSB i, SSB j, and SSB k have the same transmission power and the same transmission beam direction, or the association relationship of the multiple SSBs indicates that SSB i, SSB j, and SSB k have the same reception power and the same reception beam direction.

[0147] The terminal initiates random access to the satellite based on the random access resources corresponding to the second SSB, including: the terminal sending a random access preamble to the satellite based on the random access resources corresponding to the second SSB. The random access preamble is used by the satellite to identify the terminal during random access and can also be used by the satellite to estimate the transmission delay between the terminal and the satellite to determine the timing advance (TA). The terminal can maintain uplink synchronization with the satellite based on the TA.

[0148] Random access resources include, for example, the transmission power of the random access preamble and the RO (Route of Access).

[0149] In this embodiment, when the satellite detects uplink synchronization failure of the terminal, the satellite can indicate multiple SSBs, or the first SSB among the multiple SSBs, to the terminal via PDCCH commands, instead of being limited to indicating only one SSB for initiating random access via PDCCH commands. For the terminal, it can select one SSB from multiple related SSBs to initiate random access, increasing the terminal's opportunities to initiate random access, rather than being limited to initiating random access based solely on the random access resources corresponding to an SSB indicated by the PDCCH command. This random access method is more flexible and helps improve the efficiency of random access.

[0150] In other embodiments, method 1000 may also include further steps, such as S1004 to S1006 described below.

[0151] Optionally, prior to S1003, method 1000 further includes S1004: the satellite sends first indication information to the terminal, the first indication information indicating the conditions satisfied by the second SSB. Accordingly, the terminal receives the first indication information. This allows the terminal to select the SSB for initiating random access with greater confidence, facilitating the synchronization of random access resources used by the satellite and the terminal for initiating random access.

[0152] Optionally, the second SSB satisfies one of the following conditions: Condition 1: After receiving the PDCCH command, the second SSB is the first SSB received by the terminal among the plurality of SSBs; or, Condition 2: The second SSB is the highest priority SSB among the plurality of SSBs that have not been received by the terminal.

[0153] Regarding condition two above, the terminal needs to determine the second SSB that satisfies condition two based on the known priorities of multiple SSBs. The priorities of the multiple SSBs can be configured for the terminal by the satellite. For example, before S1003, method 1000 further includes S1005: the satellite sends second indication information to the terminal, which indicates the priorities of the multiple SSBs. Accordingly, the terminal receives the second indication information.

[0154] The following example illustrates the second SSB that satisfies condition one above, taking as an example the multiple SSBs including SSB i, SSB j, and SSB k, which are transmitted sequentially by the satellite.

[0155] For example, the satellite first sends a PDCCH command to the terminal, and then sequentially sends SSB i, SSB j, and SSB k. Correspondingly, the terminal first receives the PDCCH command, and then the satellite sequentially receives SSB i, SSB j, and SSB k. SSB i is the first SSB received by the terminal among SSB i, SSB j, and SSB k. Therefore, SSB i is the second SSB, and the terminal can initiate random access to the satellite based on the random access resource corresponding to SSB i.

[0156] For example, the satellite first transmits SSB i. After transmitting SSB i, the satellite sends a PDCCH command to the terminal. After sending the PDCCH command, the satellite transmits SSB j. Accordingly, the terminal first receives SSB i, then receives the PDCCH command, and then receives SSB j. SSB j is the first SSB among SSB i, SSB j, and SSB k received by the terminal after receiving the PDCCH command. Therefore, SSB j is the second SSB, and the terminal can initiate random access to the satellite based on the random access resource corresponding to SSB j.

[0157] The following example illustrates the second SSB that satisfies condition two above, taking as an example the multiple SSBs including SSB i, SSB j, and SSB k, which are transmitted sequentially by the satellite.

[0158] Assuming SSB i has the highest priority, SSB j has the next highest priority, and SSB k has the lowest priority, the following example illustrates the second SSB:

[0159] For example, the satellite first sends a PDCCH command to the terminal, and the terminal receives the PDCCH command accordingly. After the terminal receives the PDCCH command, the SSBs that were not received by the terminal among the plurality of SSBs include SSB i, SSB j, and SSB k, where SSB i is the highest priority SSB. Therefore, SSB i is the second SSB, and after receiving SSB i, the terminal can initiate random access to the satellite based on the random access resources corresponding to SSB i.

[0160] For example, the satellite first transmits SSB i, and then sends a PDCCH command to the terminal. Accordingly, the terminal first receives SSB i, and then receives the PDCCH command. After the terminal receives the PDCCH command, the SSBs that were not received by the terminal among the plurality of SSBs include SSB j and SSB k, where SSB j is the highest priority SSB. Therefore, SSB j is the second SSB, and after receiving SSB j, the terminal can initiate random access to the satellite based on the random access resources corresponding to SSB j.

[0161] For example, the satellite first transmits SSB i and SSB j sequentially, and then sends a PDCCH command to the terminal. Correspondingly, the terminal first receives SSB i and SSB j sequentially, and then receives the PDCCH command. After receiving the PDCCH command, the SSBs that were not received by the terminal among the plurality of SSBs include SSB k. Therefore, SSB k is the second SSB. After receiving SSB k, the terminal can initiate random access to the satellite based on the random access resources corresponding to SSB k.

[0162] Assuming SSB j has the highest priority, SSB i has the next highest priority, and SSB k has the lowest priority, the following example illustrates the second SSB.

[0163] For example, the satellite first sends a PDCCH command to the terminal, and the terminal receives the PDCCH command accordingly. After the terminal receives the PDCCH command, the SSBs that have not been received by the terminal among the plurality of SSBs include SSB i, SSB j, and SSB k. SSB j is the highest priority SSB among them, so SSB j is the second SSB. When the terminal receives SSB i first in sequence, the terminal does not initiate random access temporarily, but waits until it receives SSB j, and then initiates random access to the satellite based on the random access resources corresponding to SSB j.

[0164] For example, the satellite first transmits SSB i, and then sends a PDCCH command to the terminal. Correspondingly, the terminal first receives SSB i, and then receives the PDCCH command. After receiving the PDCCH command, the SSBs that were not received by the terminal among the plurality of SSBs include SSB j and SSB k, where SSB j is the highest priority SSB. Therefore, the second SSB is SSB j. After receiving SSB j, the terminal initiates random access to the satellite based on the random access resources corresponding to SSB j.

[0165] For example, the satellite sequentially transmits SSB i and SSB j, and then sends a PDCCH command to the terminal. Correspondingly, the terminal sequentially receives SSB i and SSB j, and then receives the PDCCH command. After receiving the PDCCH command, the SSBs not received by the terminal among the plurality of SSBs include SSB k. Therefore, SSB k is the second SSB. After receiving SSB k, the terminal can initiate random access to the satellite based on the random access resources corresponding to SSB k.

[0166] The satellite can determine the priority of each of the multiple SSBs according to preset rules.

[0167] In one possible implementation, the satellite determines the priority of each SSB based on the idle level of the RO corresponding to each SSB. The idle level of the RO corresponding to each SSB is related to the number of terminals initiating random access on that RO. The fewer the number of terminals initiating random access on the RO corresponding to a certain SSB, the higher the priority of that SSB, and vice versa.

[0168] In another possible implementation, the satellite determines the priority of each of the plurality of SSBs according to the transmission order of each SSB. For example, if the plurality of SSBs includes SSB i, SSB j, and SSB k, and the satellite transmits SSB i, SSB j, and SSB k in sequence, then among the plurality of SSBs, SSB i has the highest priority, SSB j has the second highest priority, and SSB k has the lowest priority.

[0169] For cases where the PDCCH command indicates the first SSB among the plurality of SSBs, optionally, before S1002, the method further includes S1006: the satellite sends third indication information to the terminal, the third indication information indicating that the plurality of SSBs satisfy: the same transmission power and the same transmission beam direction; or, the same reception power and the same reception beam direction. Alternatively, the third indication information indicates that the plurality of SSBs are associated. Or, the third indication information indicates one or more SSBs associated with the first SSB, the plurality of SSBs including the first SSB and the one or more SSBs. This association is: the same transmission power and the same transmission beam direction; or, the same reception power and the same reception beam direction.

[0170] After receiving the third instruction, the terminal determines that the multiple SSBs are associated. Therefore, after receiving the PDCCH command, the terminal knows that it can select one SSB from the multiple SSBs to initiate random access, without being limited to the SSB indicated by the PDCCH command.

[0171] In this embodiment, the association relationship of the multiple SSBs is configured by the satellite. After receiving the third indication information, the terminal can record the association relationship of the multiple SSBs. In a scenario where the satellite subsequently triggers the terminal to re-initiate random access via a PDCCH command, the satellite does not need to configure the association relationship of the multiple SSBs for the terminal again. That is, the association relationship of the multiple SSBs can be configured once and used multiple times.

[0172] It should be noted that the "same" or "equal" described in the embodiments of this application are not limited to absolute sameness or absolute equality, but can also be understood as approximately the same or approximately equal. For example, the fact that the multiple SSBs have the same transmission power means that the multiple SSBs have approximately the same transmission power; the fact that the multiple SSBs have the same reception power means that the multiple SSBs have approximately the same reception power.

[0173] To more clearly describe the communication method of the embodiments of this application, the communication method when the PDCCH command instructs multiple SSBs is first introduced below.

[0174] Figure 11 is a schematic flowchart of another communication method 1100 provided in an embodiment of this application. Method 1100 includes steps S1101 to S1108, and the specific steps are as follows:

[0175] S1101, the satellite confirmed that the terminal's uplink synchronization had failed.

[0176] For an explanation of this step, please refer to the description of S1001 above; it will not be repeated here.

[0177] S1102, the satellite sends a PDCCH command to the terminal, which indicates multiple SSBs. The terminal then receives the PDCCH command.

[0178] The plurality of SSBs satisfy the following conditions: they have the same transmission power and the same transmission beam direction; or, they have the same reception power and the same reception beam direction.

[0179] S1103, the satellite sends a first indication message to the terminal, which indicates the conditions satisfied by the SSB among the plurality of SSBs used by the terminal to initiate random access. Accordingly, the terminal receives the first indication message.

[0180] The SSB used by the terminal to initiate random access among the plurality of SSBs is designated as the second SSB. That is, the first indication information is used to indicate the conditions that the second SSB must meet, or in other words, the first indication information is used to indicate the rules for selecting the second SSB.

[0181] The conditions that the second SSB must meet are: after receiving the PDCCH command, the second SSB is the first SSB that the terminal receives among the plurality of SSBs; or, the second SSB is the highest priority SSB among the plurality of SSBs that have not been received by the terminal.

[0182] For more details on the conditions that the second SSB must satisfy, please refer to the description above, which will not be repeated here.

[0183] S1104, the satellite sends a second indication message to the terminal, which indicates the priority of the plurality of SSBs. Accordingly, the terminal receives the second indication message.

[0184] When determining which of the multiple SSBs satisfies condition two above, the terminal needs to make a judgment based on the priorities of the multiple SSBs. Therefore, the satellite indicates the priorities of the multiple SSBs to the terminal.

[0185] Optionally, when the satellite indicates to the terminal via the first indication information the conditions that the SSBs among the plurality of SSBs used by the terminal to initiate random access meet, it may simultaneously indicate the priority of the plurality of SSBs via the first indication information.

[0186] Optionally, the first instruction information and the second instruction information can be carried in the same message or in two separate messages; this application embodiment does not limit this.

[0187] S1105, the terminal determines a second SSB from the plurality of SSBs, the second SSB being the SSB used by the terminal to initiate random access.

[0188] For more information on determining the second SSB, please refer to the description above, which will not be repeated here.

[0189] S1106, the terminal sends a random access preamble to the satellite based on the random access resources corresponding to the second SSB. The satellite receives the random access preamble accordingly.

[0190] Among them, random access resources include, for example, the transmission power of RO and the random access preamble.

[0191] S1107, the satellite sends a random access response to the terminal. The terminal then receives the random access response.

[0192] The random access response includes TA information, which is used by the terminal for uplink synchronization.

[0193] S1108, the terminal maintains uplink synchronization with the satellite based on TA information.

[0194] In this embodiment, if the terminal loses uplink synchronization, the satellite can trigger the terminal to re-initiate random access via a PDCCH command. This PDCCH command indicates multiple SSBs, and the terminal can initiate random access to the satellite based on the second SSB among these multiple SSBs. By indicating multiple SSBs, the satellite can provide the terminal with more opportunities to initiate random access, making this random access method more flexible and efficient.

[0195] Figure 12 is a schematic flowchart of another communication method 1200 provided in an embodiment of this application. Method 1200 includes steps S1201 to S1209, and the specific steps are as follows:

[0196] S1201, the satellite sends a third indication message to the terminal, which indicates that multiple SSBs meet the following conditions: they have the same transmission power and the same transmission beam direction; or, they have the same reception power and the same reception beam direction. Accordingly, the terminal receives the third indication message.

[0197] For example, the third indication information indicates that SSB i, SSB j, and SSB k have the same transmission power and the same transmission beam direction; or, SSB i, SSB j, and SSB k have the same reception power and the same reception beam direction.

[0198] S1202, the satellite confirmed that the terminal's uplink synchronization had failed.

[0199] For an explanation of this step, please refer to the description of S1001 above; it will not be repeated here.

[0200] S1203, the satellite sends a PDCCH command to the terminal, which indicates the first SSB among the plurality of SSBs. Accordingly, the terminal receives the PDCCH command.

[0201] In this embodiment, the PDCCH command indicates one of the plurality of SSBs, which does not change the original signaling format of the PDCCH command and simplifies the implementation.

[0202] For example, the plurality of SSBs includes SSB i, SSB j, and SSB k, and the first SSB indicated by the PDCCH command is SSB i.

[0203] After receiving the PDCCH command, the terminal can determine one or more SSBs with the same transmit power and transmit beam direction as the first SSB, or one or more SSBs with the same receive power and receive beam direction as the first SSB, based on the aforementioned third indication information.

[0204] For example, the plurality of SSBs includes SSB i, SSB j, and SSB k, and the first SSB indicated by the PDCCH command is SSB i. Based on the third indication information, the terminal can determine that the SSBs with the same transmit power and the same transmit beam direction as SSB i include SSB j and SSB k, or that the SSBs with the same receive power and the same receive beam direction as SSB i include SSB j and SSB k. The second SSB is the SSB among SSB i, SSB j, and SSB k that meets the conditions.

[0205] By combining the third indication information and the PDCCH command, the terminal is not limited to using the random access resources corresponding to the first SSB to initiate random access. Instead, it can select a second SSB that meets the conditions from the plurality of SSBs and initiate random access based on the random access resources corresponding to the second SSB.

[0206] S1204, the satellite sends a first indication message to the terminal, which indicates the conditions satisfied by the SSB among the plurality of SSBs used by the terminal to initiate random access to the satellite. Accordingly, the terminal receives the first indication message.

[0207] The SSB used by the terminal to initiate random access to the satellite among the plurality of SSBs is designated as the second SSB. That is, the first indication information is used to indicate the conditions that the second SSB must meet, or in other words, the first indication information is used to indicate the rules for selecting the second SSB.

[0208] The conditions that the second SSB must meet are: after receiving the PDCCH command, the second SSB is the first SSB that the terminal receives among the plurality of SSBs; or, the second SSB is the highest priority SSB among the plurality of SSBs that have not been received by the terminal.

[0209] For more details on the conditions that the second SSB must satisfy, please refer to the description above, which will not be repeated here.

[0210] S1205, the satellite sends a second indication message to the terminal, which indicates the priority of the plurality of SSBs. Accordingly, the terminal receives the second indication message.

[0211] When determining which of the multiple SSBs satisfies condition two above, the terminal needs to make a judgment based on the priorities of the multiple SSBs. Therefore, the satellite indicates the priorities of the multiple SSBs to the terminal.

[0212] Optionally, when the satellite indicates to the terminal via the first indication information the conditions that the SSBs among the plurality of SSBs used by the terminal to initiate random access meet, it may simultaneously indicate the priority of the plurality of SSBs via the first indication information.

[0213] Optionally, the first instruction information and the second instruction information can be carried in the same message or in two separate messages; this application embodiment does not limit this.

[0214] S1206, the terminal determines a second SSB from the plurality of SSBs. The second SSB is the SSB used by the terminal to initiate random access to the satellite.

[0215] For more information on determining the second SSB, please refer to the description above, which will not be repeated here.

[0216] S1207, the terminal sends a random access preamble to the satellite based on the random access resources corresponding to the second SSB. The satellite receives the random access preamble accordingly.

[0217] Among them, random access resources include, for example, the transmission power of RO and the random access preamble.

[0218] S1208, the satellite sends a random access response to the terminal. The terminal then receives the random access response.

[0219] The random access response includes TA information, which is used by the terminal for uplink synchronization.

[0220] S1209, the terminal maintains uplink synchronization with the satellite based on TA information.

[0221] In this embodiment, if the terminal loses uplink synchronization, the satellite can trigger the terminal to re-initiate random access via a PDCCH command. The PDCCH command specifies the first SSB among the plurality of SSBs, but the terminal can also initiate random access to the satellite based on the second SSB among the plurality of SSBs, not just the random access resources corresponding to the first SSB. This increases the chances of the terminal initiating random access, making the random access method more flexible and efficient.

[0222] It is understood that the various numerical designations used in the embodiments of this application are merely for descriptive convenience and are not intended to limit the scope of the embodiments of this application. The order of the process numbers does not imply the order of execution; the execution order of each process should be determined by its function and internal logic.

[0223] It is understood that, in order to achieve the functions in the above embodiments, the satellite and terminal include hardware structures and / or software modules corresponding to perform each function. Those skilled in the art should readily recognize that, based on the units and method steps of the various examples described in conjunction with the embodiments disclosed in this application, this application can be implemented in hardware or a combination of hardware and computer software. Whether a function is executed in hardware or by computer software driving hardware depends on the specific application scenario and design constraints of the technical solution.

[0224] The communication method according to the embodiments of this application has been described in detail above with reference to Figures 10 to 12. The communication device according to the embodiments of this application will be described in detail below with reference to Figures 13 and 14.

[0225] Figures 13 and 14 are schematic block diagrams of communication devices provided in embodiments of this application. These communication devices can be used to implement the functions of terminals or satellites in the above method embodiments, and thus can also achieve the beneficial effects of the above method embodiments.

[0226] As shown in Figure 13, the communication device 1300 includes a transceiver module 1310 and a processing module 1320. The transceiver module 1310 can also be referred to as a communication interface or a communication module.

[0227] Device 1300 can be used to perform the actions performed by the terminal or satellite in the above method embodiments. Alternatively, device 1300 can be a component (e.g., a chip) configured in the terminal or satellite. Processing module 1320 is used to perform processing-related operations of the terminal or satellite in the above method embodiments. Transceiver module 1310 is used to perform receiving and transmitting-related operations of the terminal or satellite in the above method embodiments.

[0228] Optionally, the transceiver module 1310 may include a sending module and a receiving module. The sending module is used to perform the sending operation in the above method embodiments. The receiving module is used to perform the receiving operation in the above method embodiments.

[0229] It should be noted that device 1300 may include a transmitting module but not a receiving module. Alternatively, device 1300 may include a receiving module but not a transmitting module. Specifically, it depends on whether the above-described scheme executed by device 1300 includes both transmitting and receiving actions.

[0230] Optionally, the device 1300 is used to perform the actions performed by the terminal or satellite in the embodiments shown in Figures 10 to 12. For details, please refer to the relevant descriptions in the embodiments shown in Figures 10 to 12, which will not be repeated here.

[0231] Optionally, the device 1300 may further include a storage module, which can be used to store data and / or to store computer programs or instructions. The processing module 1320 can read the computer programs / instructions and / or data in the storage module so that the device 1300 can implement the above-described method embodiments.

[0232] When device 1300 is used to implement the terminal functions in the method embodiments shown in Figures 10 to 12: transceiver module 1310 is used to: receive a PDCCH command, which indicates a plurality of SSBs, or indicates a first SSB among the plurality of SSBs, wherein the plurality of SSBs satisfy: the same transmit power and the same transmit beam direction, or the same receive power and the same receive beam direction. Processing module 1320 is used to: initiate random access to the satellite based on the random access resources corresponding to a second SSB, wherein the second SSB is one of the plurality of SSBs.

[0233] Optionally, the transceiver module 1310 is further configured to: receive first indication information, which is used to indicate the conditions satisfied by the second SSB.

[0234] Optionally, the transceiver module 1310 is further configured to: receive second indication information, which is used to indicate the priority of the plurality of SSBs.

[0235] Optionally, the PDCCH command indicates the first SSB; the transceiver module 1310 is configured to: receive third indication information, which indicates that the plurality of SBBs satisfy: the same transmission power and the same direction of the transmission beam; or, the same reception power and the same direction of the reception beam.

[0236] A more detailed description of the transceiver module 1310 can be found in the relevant descriptions of the method embodiments shown in Figures 10 to 12, and will not be repeated here. The processing module 1320 can be implemented by a processor, and the transceiver module 1310 can be implemented by a transceiver.

[0237] For a more detailed description of the first instruction information, the second instruction information, and the third instruction information, please refer to the relevant descriptions in the method embodiments above, which will not be repeated here.

[0238] Figure 14 is a schematic block diagram of another communication device 1400 provided in an embodiment of this application. As shown in Figure 14, the device 1400 includes one or more processors 1410 and an interface circuit 1420. The one or more processors 1410 and the interface circuit 1420 are coupled to each other. It is understood that the interface circuit 1420 can be a transceiver or an input / output interface. Optionally, the device 1400 may also include a memory 1430 for storing instructions executed by the processor 1410, or for storing input data required by the processor 1410 to execute instructions, or for storing data generated after the processor 1410 executes instructions. Sometimes, the interface circuit 1420 can also be understood as part of the one or more processors 1410, in which case the device 1400 includes the one or more processors 1410.

[0239] The one or more processors 1410 and memory 1430 can be configured separately or integrated, and this application does not limit this.

[0240] When the device 1400 is used to implement the method shown in Figures 10 to 12, the one or more processors 1410 are used to implement the functions of the processing module 1320, and the interface circuit 1420 is used to implement the functions of the transceiver module 1310.

[0241] When the aforementioned device 1400 is a chip applied to a terminal, the terminal chip implements the functions of the terminal in the above method embodiments. The terminal chip receiving information from a satellite can be understood as the information being first received by other modules (such as an RF module or antenna) within the terminal, and then sent to the terminal chip by these modules. The terminal chip sending information to a satellite can be understood as the information being first sent to other modules (such as an RF module or antenna) within the terminal, and then sent to the satellite by these modules.

[0242] When the aforementioned device 1400 is a chip applied to a satellite, the satellite chip implements the functions of the satellite in the above method embodiments. The satellite chip receives information from the terminal, which can be understood as the information being first received by other modules in the satellite (such as radio frequency modules or antennas), and then sent to the satellite chip by these modules. The satellite chip sends information to the terminal, which can be understood as the information being first sent to other modules in the satellite (such as radio frequency modules or antennas), and then sent to the terminal by these modules.

[0243] This application also provides a computer-readable storage medium for storing a computer program that, when run on a computer, causes the computer to execute the aforementioned communication method. Alternatively, the computer program includes instructions for implementing the aforementioned communication method.

[0244] This application also provides a computer program product, including: a computer program or instructions, which, when run on a computer, cause the computer to execute the above-described communication method.

[0245] This application also provides a chip, which includes at least one processor for supporting the implementation of the above-described communication method, such as receiving or processing data involved in the above-described communication method.

[0246] It should be understood that, in the embodiments of this application, the processor may be a central processing unit (CPU), or it may 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, etc. The general-purpose processor may be a microprocessor or any conventional processor.

[0247] In implementation, each step of the above method can be completed by integrated logic circuits in the processor's hardware or by instructions in software. The steps of the method disclosed in the embodiments of this application can be directly manifested as execution by a hardware processor, or as a combination of hardware and software modules within the processor. The software modules can reside in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. This storage medium is located in memory, and the processor executes the instructions in the memory, combining them with its hardware to complete the steps of the above method. To avoid repetition, detailed descriptions are omitted here.

[0248] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0249] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and modules described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0250] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or modules may be electrical, mechanical, or other forms.

[0251] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules; that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0252] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0253] If the aforementioned functions are implemented as software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0254] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A communication method, characterized in that, include: Receive a Physical Downlink Control Channel (PDCCH) command, wherein the PDCCH command indicates a plurality of Synchronization Signal Blocks (SSBs), or indicates a first SSB among the plurality of SSBs, wherein the plurality of SSBs satisfy the following conditions: the transmit power is the same and the transmit beam direction is the same, or the receive power is the same and the receive beam direction is the same. Random access is initiated to the satellite based on the random access resources corresponding to the second SSB, where the second SSB is one of the plurality of SSBs.

2. The method according to claim 1, characterized in that, The second SSB satisfies one of the following conditions: After receiving the PDCCH command, the second SSB is the first SSB that the terminal receives among the plurality of SSBs; or, The second SSB is the highest priority SSB among the SSBs that were not received by the terminal.

3. The method according to claim 2, characterized in that, Before initiating random access to the satellite based on the random access resources corresponding to the second SSB, the method further includes: Receive first indication information, which is used to indicate the conditions that the second SSB must satisfy.

4. The method according to claim 2 or 3, characterized in that, Before initiating random access to the satellite based on the random access resources corresponding to the second SSB, the method further includes: Receive second indication information, which is used to indicate the priority of the plurality of SSBs.

5. The method according to any one of claims 1 to 4, characterized in that, The PDCCH command instructs the first SSB; Prior to receiving the PDCCH command, the method further includes: Receive third indication information, the third indication information being used to indicate that the plurality of SBBs satisfy: The transmission power is the same and the direction of the transmission beam is the same; or, The received power is the same and the direction of the received beam is the same.

6. A communication method, characterized in that, include: Confirm that the terminal has lost uplink synchronization; Send a Physical Downlink Control Channel (PDCCH) command, which indicates a plurality of Synchronization Signal Blocks (SSBs), or indicates a first SSB among the plurality of SSBs, wherein the plurality of SSBs satisfy the following conditions: the transmit power is the same and the transmit beam direction is the same, or the receive power is the same and the receive beam direction is the same.

7. The method according to claim 6, characterized in that, The method further includes: Send a first indication message, which is used to indicate the conditions satisfied by the second SSB, wherein the second SSB is the SSB among the plurality of SSBs used by the terminal to initiate random access to the satellite.

8. The method according to claim 7, characterized in that, The second SSB satisfies one of the following conditions: After receiving the PDCCH command, the second SSB is the first SSB received by the terminal among the plurality of SSBs; or, The second SSB is the highest priority SSB among the SSBs that were not received by the terminal.

9. The method according to claim 7 or 8, characterized in that, Before sending the PDCCH command, the method further includes: Send a second indication message, which is used to indicate the priority of the plurality of SSBs.

10. The method according to any one of claims 6 to 9, characterized in that, The PDCCH command instructs the first SSB; Before sending the PDCCH command, the method further includes: Send a third indication message, the third indication message being used to indicate that the plurality of SBBs satisfy: The transmission power is the same and the transmission beam direction is the same; or, The received power is the same and the direction of the received beam is the same.

11. A communication device, characterized in that, It includes modules for implementing the method as described in any one of claims 1 to 5, or modules for implementing the method as described in any one of claims 6 to 10.

12. A communication device, characterized in that, The method includes at least one processor coupled to a memory for storing a program or instructions that, when executed by the at least one processor, cause the method as claimed in any one of claims 1 to 5 to be executed, or cause the method as claimed in any one of claims 6 to 10 to be executed.

13. A computer-readable storage medium, characterized in that, Used to store a computer program that, when run on a computer, causes the method as described in any one of claims 1 to 5 to be performed, or causes the method as described in any one of claims 6 to 10 to be performed.

14. A computer program product, characterized in that, include: A computer program or instruction that, when executed, causes the method as claimed in any one of claims 1 to 5 to be performed, or causes the method as claimed in any one of claims 6 to 10 to be performed.

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