Non-terrestrial network communication method, apparatus, and system

Abstract

Embodiments of this application relate to non-terrestrial network communication technologies. When the identifiers of the cells served by a new satellite and an old satellite are the same during the replacement of the new satellite for the old satellite, the terminal is triggered to detect whether it is located within the coverage area of the cell on the ground served by the new satellite, thereby providing a non-terrestrial network communication method, apparatus, and system for ensuring subsequent normal communication of the terminal. The method includes the following. The terminal receives, from a first network device, a message indicating that the satellite providing service to a first cell is updated to a second satellite, and the first message includes information used to determine the coverage area of a second cell on the ground served by the second satellite. The terminal determines, based on the position of the terminal and the coverage area of the second cell on the ground, whether the terminal is located within the coverage area or outside the coverage area. In the solution, the terminal detects the replacement of the new satellite for the old satellite, and the terminal determines whether it is located within the coverage area of the second cell on the ground, whereby the terminal can execute different processes based on different determination results.

Description

Technical Field

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[0003]

[0001] This application claims priority to Chinese Patent Application No. 202210798859.6, filed with the China National Intellectual Property Administration on July 6, 2022, under the title "COMMUNICATION METHOD AND APPARATUS", and Chinese Patent Application No. 202210957934.9, filed with the China National Intellectual Property Administration on August 10, 2022, under the title "NON-TERRESTRIAL NETWORK COMMUNICATION METHOD, APPARATUS, AND SYSTEM", the entire contents of both of which are incorporated herein by reference.

[0002] Embodiments of this application relate to the field of non-terrestrial network communication technologies, and in particular, to communication methods, apparatuses, and systems.

Background Art

[0003] A non-terrestrial network (NTN) is a radio-frequency-based network or network segment mounted on a satellite (uncrewed aircraft system (UAS) platform). Satellite communication has advantages such as a wide coverage area, long communication distance, high reliability, high flexibility, and high throughput, is not affected by geographical environment, weather conditions, or natural disasters, and has been widely used in fields such as aviation communication, maritime communication, and military communication. The introduction of satellites into future fifth-generation (5G) mobile networks makes it possible to provide communication services for areas such as the sea and forests that are difficult to cover by terrestrial networks, improve the reliability of 5G communication, for example, provide a more stable communication service with better quality for users on trains, airplanes, and such means of transportation, and further make it possible to provide more data transmission resources and support more connections.

[0004] When satellites provide service to cells, each satellite covers one or more cells on the ground. Because satellites are mobile, they may have different coverage areas on the ground at different times as they move. However, generally, the cells accessed by terminals remain unchanged over a period of time. A new satellite provides service only after the old satellite can no longer provide service to a physical area (e.g., a cell) due to the movement of the old satellite. Generally, service is provided by other satellites in the same orbit. To maintain spacing between satellites, the distance between two satellites increases. Because the distance from the new satellite to the terminal is different from the distance from the old satellite to the terminal, the coverage area of ​​ground cells served by the new satellite may also differ from the coverage area of ​​ground cells served by the old satellite. Therefore, a technical challenge that urgently needs to be solved is how terminals can sense whether they are located within the coverage area of ​​ground cells served by the new satellite, in order to be more beneficial to the NTN communication system during the transition between new and old satellites. [Overview of the project]

[0005] Embodiments of this application provide a communication method, apparatus, and system for triggering a terminal to sense whether it is located within the coverage area of ​​a ground cell served by a new satellite, when the identifiers of the cells served by the new satellite and the old satellite are the same, in order to ensure normal communication of the terminal thereafter when a new satellite is replaced by an old satellite.

[0006] According to a first aspect, an embodiment of the present application provides a communication method comprising: a terminal receiving a first message from a first network device; the first message indicating that the satellite providing service to a first cell is being updated from a first satellite to a second satellite; the first cell is a cell accessed by the terminal, the first network device corresponds to a first satellite, the first message includes first information which is used to determine the coverage area of ​​a second cell on the ground, which is serviced by the second satellite; in response to the first message, the terminal determines, based on its location and the coverage area of ​​the second cell on the ground, whether it is located within or outside the coverage area; the first cell and the second cell have the same cell identifier.

[0007] This embodiment of the application provides a communication method in which, when it is decided that the satellite serving a first cell is to be replaced from a first satellite to a second satellite, that is, when the old satellite is replaced by a new satellite, a first network device sends a first message to a terminal. The first message indicates to the terminal that the satellite serving the first cell is to be replaced from a first satellite to a second satellite, so that the terminal can sense that the satellite covering the first cell is changing. The second satellite serves a second cell, and the first and second cells have the same cell identifier. Although the first and second cells have the same cell identifier, the ground coverage areas of the first and second cells may be different. The terminal may be located outside the ground coverage area of ​​the second cell, or it may be located within the ground coverage area of ​​the second cell. Therefore, in order to avoid communication interruptions caused by cases in which the terminal is unable to access the second cell when the terminal is located outside the coverage area of ​​the second cell, this application provides that the first network device transmits information to the terminal about the coverage area of ​​the second cell on the ground, which is serviced by the second satellite, so that the terminal can, by referring to its location, further determine whether the terminal is located within or outside the coverage area of ​​the second cell on the ground and take appropriate processing measures.

[0008] In a possible implementation of this application, after the terminal determines whether it is located within or outside a coverage area based on the terminal's location and the coverage area of ​​the second cell on the ground, the method provided in this embodiment of this application may further include: the terminal sends a second message to a first network device; the second message indicates that the terminal is located within the coverage area of ​​the second satellite on the ground, or the second message indicates that the terminal is located outside the coverage area of ​​the second satellite on the ground. The second message has been sent, and thereafter the first network device determines whether the terminal is located within the coverage area of ​​the second satellite on the ground, and the first network device performs subsequent processing.

[0009] In a possible implementation of this application, the second message includes second indication information, which indicates that the terminal is located within the coverage area of ​​a second cell on the ground, serviced by a second satellite. Alternatively, the second indication information indicates that the terminal is located outside the coverage area of ​​a second cell on the ground, serviced by a second satellite. For example, the second indication information may be a first indicator, which indicates that the terminal is located within the coverage area of ​​a second cell on the ground, serviced by a second satellite. The second indication information may be a second indicator, which indicates that the terminal is located outside the coverage area of ​​a second cell on the ground, serviced by a second satellite. The second indication information may be carried in a second message, thereby explicitly indicating the second indication information to the first network device.

[0010] In a possible implementation of this application, after the terminal determines whether it is located within or outside the coverage area based on the terminal's location and the coverage area of ​​the second cell on the ground, the method provided in this embodiment of this application may further include: the terminal transmits terminal location information and / or terminal measurement report information to a first network device. In this way, the first network device determines, based on the terminal's location information, whether the terminal is located within the coverage area of ​​the second cell on the ground, which is serviced by the second satellite. The measurement report information helps the first network device to select a third cell for the terminal or to configure a cell handover condition for the terminal when the terminal is located outside the coverage area of ​​the second cell on the ground, which is serviced by the second satellite.

[0011] In a possible implementation of this application, terminal location information and / or terminal measurement report information may be carried in a second message. In this way, signaling overhead can be reduced.

[0012] In a possible implementation of this application, when a terminal is located within the coverage area of ​​a second cell on the ground, which is serviced by a second satellite, the method provided in this embodiment of the application further includes: the terminal performs downlink synchronization in the second cell to synchronize with the second network device to which the second cell belongs. When the terminal is located within the coverage area of ​​the second cell on the ground, which is serviced by a second satellite, the terminal performs downlink synchronization again in the current serving cell (i.e., the first cell). In this way, after the terminal has synchronized with the second network device to which the second cell belongs, the terminal can receive downlink broadcast messages from the second network device to ensure subsequent normal communication.

[0013] In a possible implementation of this application, the terminal synchronizes with a second network device corresponding to the second cell before the coverage end time of the first satellite on the ground and / or after the coverage start time of the second cell served by the second satellite.

[0014] In a possible implementation of this application, when a terminal synchronizes with a second network device, the method provided in this embodiment of this application may further include: the terminal initiates a random access process to the second network device; the terminal then performs subsequent communications via the connection established with the second network device, for example, receiving downlink transmissions delivered by the second network device or transmitting uplink transmissions to the second network device.

[0015] In a possible implementation of this application, a terminal initiates a random access process to a second network device when the following first condition is met: the first condition includes one or more of the following: it is before the end of coverage of the first satellite on the ground; it is after the start of coverage of the second satellite on the ground; data transmission is required; or the terminal's uplink time alignment timer has not expired.

[0016] In a possible implementation of this application, when the second condition is met, the terminal does not need to initiate a random access process to the second network device. The second condition includes, at a minimum, that the terminal's uplink time alignment timer has expired or that the terminal's uplink time alignment timer has not been started.

[0017] A possible implementation of this application includes, in this embodiment of the application, a method provided: a terminal receives a first command (e.g., an uplink time alignment command) from a second network device in a random access process; and the terminal restarts its uplink time alignment timer based on the uplink time alignment command.

[0018] In a possible implementation of this application, when the terminal is located within the coverage area of ​​a second cell on the ground, the method provided in this embodiment of this application further includes: the terminal skipping to evaluate other CHO conditions, or the terminal skipping to measure candidate target cells corresponding to the CHO configuration, or the terminal releasing other CHO configurations.

[0019] In a possible implementation of this application, when a terminal is located within the coverage area of ​​a second cell on the ground, the method provided in this embodiment of the application further includes: the terminal sending a fifth message to a first network device, the fifth message indicating the terminal to skip evaluating the CHO configuration, or to skip measuring the CHO configuration, or to release the CHO configuration. For example, the fifth message includes one indication piece of information indicating the terminal to skip evaluating the CHO configuration, or to skip measuring the CHO configuration, or to release the CHO configuration.

[0020] In a possible implementation of this application, when a terminal is located outside the coverage area of ​​a second cell on the ground, the method provided in this embodiment of the application further includes: the terminal receives a third message from a first network device; the third message instructs the terminal to switch to a target cell, the target cell and the first cell having different cell identifiers, and the terminal is located within the coverage area of ​​the target cell; the terminal changes its serving cell from the first cell to the target cell based on the third message.

[0021] In a possible implementation of this application, the third message includes indication information that instructs the terminal to switch to the target cell. Optionally, the third message may be a cell handover message.

[0022] In a possible implementation of this application, the third message includes first configuration information, which is used by the terminal to determine information about the target cell. Accordingly, the terminal changing its serving cell from the first cell to the target cell based on the third message includes: the terminal determining information about the target cell based on the first configuration information, and the terminal changing its serving cell from the first cell to the target cell based on the information about the target cell.

[0023] In a possible implementation of this application, the third message includes second configuration information, the second configuration information includes cell handover conditions configured for the terminal. The terminal changing its serving cell from the first cell to the target cell based on the third message includes: When the cell handover conditions contained in the second configuration information are met, the terminal changes its serving cell from the first cell to the target cell.

[0024] In a possible implementation of this application, the first message includes a first time parameter and / or a second time parameter, the first time parameter being used to determine the coverage start time of the second satellite corresponding to the second cell on the ground, and the second time parameter being used to determine the coverage end time of the second satellite corresponding to the second cell on the ground. The method provided in this embodiment of this application further includes: Based on the first time parameter and / or the second time parameter, the terminal synchronizes with the second network device corresponding to the second satellite after the coverage start time of the second satellite on the ground, or sends the second message to the first network device before the coverage start time of the second satellite on the ground.

[0025] In a possible implementation of this application, the first message further includes one or more of the following information: time information for a terminal to perform downlink synchronization in a second cell; NTN parameter information for a second satellite, wherein the NTN parameter information includes parameter information necessary for the terminal to access the NTN corresponding to the second satellite; third indication information, wherein the third indication information indicates location information of the NTN parameter information; or information about a measurement timing configuration that indicates the terminal to search for a downlink synchronization signal for a second cell in the second satellite based on the measurement timing configuration.

[0026] According to a second aspect, embodiments of the present application provide a communication method comprising: a first network device corresponding to a first satellite transmits a first message indicating that the satellite providing service to a first cell is being updated from the first satellite to a second satellite; the first message includes first information, which is used to determine the coverage area of ​​a second cell on the ground, which is serviced by the second satellite; and the first and second cells have the same cell identifier.

[0027] In a possible implementation of this application, the first message includes a first time parameter and / or a second time parameter. The first time parameter is used to determine the coverage start time of a second satellite corresponding to a second cell on the ground, and the second time parameter is used to determine the coverage end time of the second satellite corresponding to the second cell on the ground.

[0028] In a possible implementation of this application, the first message further includes one or more of the following information: time information for the terminal to perform downlink synchronization in a second cell via a second satellite; NTN parameter information of the second satellite, where the NTN parameter information includes parameter information necessary for the terminal to access the second cell; third indication information, where the third indication information indicates the location information of the NTN parameter information; or information about a measurement timing configuration for indicating to the terminal to search for a downlink synchronization signal of the second cell in the second satellite based on the measurement timing configuration.

[0029] In a possible implementation of this application, the first message includes information about a measurement timing configuration, and the measurement timing configuration is configured based on the downlink timing relationship of a first cell in a first satellite or the measurement timing configuration is configured based on the downlink timing relationship of a second cell in a second satellite. The downlink timing relationship is used to determine the first subframe number and the first system frame number of the downlink synchronization signal of the second cell.

[0030] In a possible implementation of this application, when a first network device determines that a first terminal accessing a first cell is located outside the coverage area of a second cell on the ground, the method provided in this embodiment of this application further includes the following. The first network device transmits a third message to the first terminal being accessed, and the third message indicates to the first terminal to switch to a target cell. The target cell and the first cell have different cell identifiers, and the first terminal is located within the coverage area of the target cell.

[0031] In a possible implementation of this application, the method provided in this embodiment of this application further includes the following. The first network device transmits first configuration information and / or second configuration information to the first terminal. The first configuration information is used by the first terminal to determine information about the target cell, and the second configuration information is used by the first terminal to determine cell handover conditions.

[0032] In a possible implementation of this application, one or both of the first configuration information and the second configuration information are determined based on the position information of the first terminal and / or the measurement report information of the first terminal. The measurement report information includes information indicating the signal quality of adjacent cells of the first terminal.

[0033] [[ID= twelfth]]In a possible implementation of this application, the method provided in this embodiment of this application further includes the following. The first network device receives a second message from the first terminal, and the first terminal is a terminal accessing the first cell. The first network device determines, based on the second message, that the first terminal is located outside the coverage area of the second cell on the ground or that the first terminal is located within the coverage area of the second cell on the ground.

[0034] In a possible implementation of this application, the second message includes location information of the first terminal, and the first network device determines, based on the second message, that the first terminal is located outside the coverage area of ​​the second cell on the ground or within the coverage area of ​​the second cell on the ground, which includes: The first network device determines, based on the location information of the first terminal and the coverage area of ​​the second cell on the ground, that the first terminal is located outside the coverage area of ​​the second cell on the ground or within the coverage area of ​​the second cell on the ground.

[0035] According to a third aspect, embodiments of this application provide a communication device. The communication device can implement the method in either the first aspect or a possible implementation of the first aspect, and thus can achieve the advantageous effects of either the first aspect or a possible implementation of the first aspect. The communication device may be a terminal, or a device that supports the terminal when implementing the method in either the first aspect or a possible implementation of the first aspect, such as a chip used within the terminal. The communication device may implement the above method by utilizing software or hardware, or by running corresponding software in hardware.

[0036] In one example, embodiments of this application provide a communication device, which is a terminal or a chip used within a terminal. The communication device includes a communication unit and a processing unit. The processing unit is configured to process information. The communication unit is configured to receive or transmit information. For example, the communication unit is configured to receive a first message from a first network device, the first message indicating that the satellite providing service to a first cell is being updated from a first satellite to a second satellite, the first cell being a cell accessed by a terminal, the first network device corresponding to a first satellite, the first message including first information used to determine the coverage area of ​​a second cell on the ground, which is serviced by a second satellite, and the first and second cells having the same cell identifier. The processing unit is configured to determine whether a terminal is located within or outside a coverage area based on a first message, the terminal's location, and the coverage area of ​​a second cell on the ground.

[0037] In a possible implementation of this application, the communication unit is further configured to transmit a second message to a first network device, the second message indicating that the terminal is located within the coverage area of ​​a second cell on the ground, or the second message indicating that the terminal is located outside the coverage area of ​​a second cell on the ground.

[0038] In a possible implementation of this application, the communication unit is further configured to transmit terminal location information and / or terminal measurement report information to a first network device. The measurement report information includes information indicating the signal quality of the terminal's adjacent cells.

[0039] In a possible implementation of this application, if the terminal is located within the coverage area of ​​a second cell on the ground, which is serviced by a second satellite, the processing unit is further configured to perform downlink synchronization in the second cell to synchronize with a second network device corresponding to the second cell, the second network device corresponding to the second satellite.

[0040] In a possible implementation of this application, the communication unit in this embodiment of the application is further configured to initiate a random access process to a second network device when the following first condition is met. The first condition includes one or more of the following: it is before the end of coverage time for the first satellite on the ground; it is after the start of coverage time for the second satellite on the ground; data transmission is required; or the uplink time alignment timer of the terminal has not expired.

[0041] In a possible implementation of this application, when the second condition is met, the communication unit does not need to initiate a random access process to the second network device. The second condition includes, at a minimum, that the uplink time alignment timer of the terminal has expired or that the uplink time alignment timer of the terminal has not been started.

[0042] In a possible implementation of this application, if a terminal is located outside the coverage area of ​​a second cell on the ground, which is serviced by a second satellite, the communication unit is further configured to receive a third message from a first network device, the third message instructing the terminal to switch to a target cell, the target cell and the first cell having different cell identifiers, and the terminal being located within the coverage area of ​​the target cell, and the processing unit is further configured to change the serving cell of the terminal from the first cell to the target cell based on the third message.

[0043] In a possible implementation of this application, a third message includes first configuration information, which is used by the terminal to determine information about a target cell. A processing unit is specifically configured to determine information about a target cell based on the first configuration information. The processing unit is configured to change the terminal's serving cell from the first cell to the target cell based on the information about the target cell.

[0044] In a possible implementation of this application, the third message includes second configuration information, the second configuration information includes cell handover conditions configured for the terminal. When the cell handover conditions included in the second configuration information are met, the processing unit is configured to change the terminal's serving cell from the first cell to the target cell.

[0045] In a possible implementation of this application, the first message includes a first time parameter and / or a second time parameter, the first time parameter being used to determine the coverage start time of the second satellite corresponding to the second cell on the ground, and the second time parameter being used to determine the coverage end time of the second satellite corresponding to the second cell on the ground. The processing unit is further configured to synchronize with the second network device corresponding to the second satellite after the coverage start time of the second satellite on the ground, or to send the second message to the first network device before the coverage start time of the second satellite on the ground, based on the first time parameter and / or the second time parameter.

[0046] In a possible implementation of this application, the first message further includes one or more of the following information: time information for the terminal to perform downlink synchronization in the second cell; NTN parameter information for the second satellite, wherein the NTN parameter information includes parameter information necessary for the terminal to access the NTN corresponding to the second satellite; third indication information indicating the location of the NTN parameter information; or information about a measurement timing configuration that indicates to the terminal to search for a downlink synchronization signal for the second cell in the second satellite based on the measurement timing configuration.

[0047] According to a fourth aspect, embodiments of this application provide a communication device. The communication device can implement the method in the second aspect or one of the possible implementations of the second aspect, and thus can achieve the advantageous effects of the second aspect or one of the possible implementations of the second aspect. The communication device may be a first network device, or a device that supports the first network device when implementing the method in the second aspect or one of the possible implementations of the second aspect, for example, a chip used within the first network device. The communication device may implement the above method by utilizing software or hardware, or by executing the corresponding software by hardware.

[0048] In one example, embodiments of this application provide a communication device, which is a first network device or a chip used within a first network device. The communication device includes a communication unit and a processing unit. The processing unit is configured to process information. The communication unit is configured to receive or transmit information. For example, the communication unit is configured to transmit a first message, which indicates that the satellite providing service to a first cell is being updated from the first satellite to a second satellite, which includes first information, which is used to determine the coverage area of ​​a second cell on the ground, which is serviced by the second satellite, and which has the same cell identifier.

[0049] In a possible implementation of this application, the first message includes a first time parameter and / or a second time parameter, the first time parameter being used to determine the start time of coverage of the second satellite corresponding to the second cell on the ground, and the second time parameter being used to determine the end time of coverage of the second satellite corresponding to the second cell on the ground.

[0050] In a possible implementation of this application, the first message further includes one or more of the following information: time information for a terminal to perform downlink synchronization in a second cell via a second satellite; NTN parameter information for the second satellite, wherein the NTN parameter information includes parameter information necessary for the terminal to access the second cell; third indication information, wherein the third indication information indicates location information of the NTN parameter information; or information about a measurement timing configuration that indicates the terminal to search for a downlink synchronization signal for the second cell on the second satellite based on the measurement timing configuration.

[0051] In a possible implementation of this application, the first message includes information about a measurement timing configuration, which is configured based on the downlink timing relationship of a first cell in a first satellite, or the measurement timing configuration is configured based on the downlink timing relationship of a second cell in a second satellite, which is used to determine the first subframe number and the first system frame number of the downlink synchronization signal of the second cell.

[0052] In a possible implementation of this application, the communication unit is further configured to send a third message to a first terminal to be accessed, the third message instructing the first terminal to switch to a target cell whose cell identifier is different from that of the first cell. The first terminal is located within the coverage area of ​​the target cell.

[0053] In a possible implementation of this application, the communication unit is further configured to transmit first configuration information and / or second configuration information to a first terminal. The first configuration information is used by the first terminal to determine information about a target cell, and the second configuration information is used by the first terminal to determine cell handover conditions.

[0054] In a possible implementation of this application, one or both of the first and second configuration information are determined based on the location information of the first terminal and / or the measurement report information of the first terminal, the measurement report information includes information indicating the signal quality of adjacent cells of the first terminal.

[0055] In a possible implementation of this application, a communication unit is further configured to receive a second message from a first terminal, the first terminal being a terminal accessing a first cell. A processing unit is further configured to determine, based on the second message, that the first terminal is located outside the coverage area of ​​the second cell on the ground, or that the first terminal is located within the coverage area of ​​the second cell on the ground.

[0056] In a possible implementation of this application, the second message includes location information of the first terminal, and the processing unit is particularly configured to determine, based on the location information of the first terminal and the coverage area of ​​the second cell on the ground, whether the first terminal is located outside the coverage area of ​​the second cell on the ground or within the coverage area of ​​the second cell on the ground.

[0057] According to a fifth aspect, an embodiment of the present application provides a computer-readable storage medium that stores a computer program or instruction. When the computer program or instruction is executed on a computer, the computer becomes capable of executing a communication method described in the first aspect or one of the possible implementations of the first aspect.

[0058] According to a sixth aspect, an embodiment of the present application provides a computer-readable storage medium that stores a computer program or instruction. When the computer program or instruction is executed on a computer, the computer becomes capable of executing a communication method described in either the second aspect or a possible implementation of the second aspect.

[0059] According to a seventh aspect, an embodiment of the present application provides a computer program product including instructions. When the instructions are executed on a computer, the computer becomes capable of executing a communication method described in either the first aspect or a possible implementation of the first aspect.

[0060] According to the eighth aspect, an embodiment of the present application provides a computer program product including instructions. When the instructions are executed on a computer, the computer becomes capable of executing a communication method described in either the second aspect or a possible implementation of the second aspect.

[0061] According to the ninth aspect, embodiments of the present application provide a communication device configured to implement various methods in any possible design of the first and second aspects. The communication device may be the terminal described above, a device including the terminal described above, or a component (e.g., a chip) used within the terminal. Alternatively, the communication device may be the first network device described above, a device including the first network device described above, or a component (e.g., a chip) used within the first network device. The communication device includes a corresponding module or unit for implementing the above method. The module or unit may be implemented by utilizing hardware or software, or by running the corresponding software through hardware. The hardware or software includes one or more modules or units corresponding to the above function.

[0062] According to a tenth aspect, an embodiment of the present application provides a communication device. The communication device includes at least one processor and a communication interface. When the communication device is operating, the processor executes computer executable instructions or programs stored in the communication device, enabling the communication device to perform a method in any one of the possible implementations of the first and second aspects. For example, the communication device may be a terminal or a component used within a terminal. For example, the communication device may be a first network device or a component used within a first network device.

[0063] The communication device described in the tenth embodiment should be understood to further include a bus and memory. The memory is configured to store code and data. Optionally, at least one processor, a communication interface, and the memory are coupled to each other.

[0064] According to an eleventh aspect, an embodiment of the present application provides a communication device. The communication device includes at least one processor. The at least one processor is coupled to memory. When the communication device is operating, the processor executes computer executable instructions or programs stored in memory, enabling the communication device to perform a method in any one of the possible implementations of the first and second aspects. For example, the communication device may be a terminal or a chip used within a terminal.

[0065] According to a twelfth aspect, an embodiment of the present application provides a communication device. The communication device includes at least one processor. The at least one processor is coupled to memory. When the communication device is operating, the processor executes computer executable instructions or programs stored in memory, enabling the communication device to perform a method in any one of the possible designs of the first and second aspects. For example, the communication device may be a first network device or a chip used within a first network device.

[0066] It should be understood that the memory described in any one of the tenth to twelfth embodiments may be replaced by a storage medium, and this is not limited to the embodiments of this application. In possible implementations, the memory described in any one of the tenth to twelfth embodiments may be memory inside the communication device. Of course, the memory may be located outside the communication device, but at least one processor can still execute computer executable instructions or programs stored in the memory.

[0067] According to a thirteenth aspect, an embodiment of the present application provides a communication device, comprising one or more modules configured to carry out the method in either the first or second aspect, the one or more modules being able to correspond to a step in the method in either the first or second aspect.

[0068] According to a fourteenth aspect, an embodiment of the present application provides a chip comprising a processor and a communication interface. The communication interface is coupled to the processor, and the processor is configured to execute a computer program or instructions to implement a communication method described in the first aspect or one of the possible implementations of the first aspect. The communication interface is configured to communicate with a module other than the chip.

[0069] According to the 15th aspect, an embodiment of the present application provides a chip, the chip including a processor and a communication interface, the communication interface being coupled to the processor, the processor being configured to execute a computer program or instructions to implement a communication method described in the second aspect or any one of the possible implementations of the second aspect, the communication interface being configured to communicate with a module other than the chip.

[0070] Specifically, the chip provided in this embodiment of this application further includes memory configured to store computer programs or instructions.

[0071] According to the sixteenth aspect, an embodiment of the present application provides a communication system. The communication system includes a terminal and a first network device. The first network device is configured to perform a communication method in either the second aspect or a possible implementation of the second aspect. The terminal is configured to perform a communication method in either the first aspect or a possible implementation of the first aspect.

[0072] Any device, computer storage medium, computer program product, chip, or communication system provided above is configured to perform the corresponding method provided above. Therefore, for the advantageous effects that can be achieved by the device, computer storage medium, computer program product, chip, or communication system, please refer to the advantageous effects of the corresponding solution in the corresponding method provided above. Further details are not provided here. [Brief explanation of the drawing]

[0073] [Figure 1] Two arrangement solutions for cell identifiers in a satellite, according to embodiments of this application, are shown. [Figure 2] This is a diagram of the architecture of a communication system according to an embodiment of this application. [Figure 3] This is a diagram of the architecture of another communication system according to an embodiment of this application. [Figure 4] This is a distribution map of base stations according to an embodiment of this application. [Figure 5] This is a diagram of the architecture of a transparent satellite communications system according to an embodiment of this application. [Figure 6] This is a diagram of the architecture of another satellite communication system according to an embodiment of this application. [Figure 7] This is a diagram of yet another satellite communication system architecture according to an embodiment of this application. [Figure 8] This is a diagram of yet another satellite communication system architecture according to an embodiment of this application. [Figure 9] This is a schematic flowchart of a communication method according to an embodiment of this application. [Figure 10] This is a schematic flowchart of another communication method according to an embodiment of this application. [Figure 11] This is a diagram showing the structure of a communication device according to an embodiment of this application. [Figure 12]This is a diagram showing the structure of another communication device according to an embodiment of this application. [Figure 13] This is a diagram of the chip structure according to an embodiment of this application. [Modes for carrying out the invention]

[0074] In this application, “at least one” means one or more, and “multiple” means two or more. The term “and / or” describes an association relationship between related objects and indicates that three relationships may exist. For example, A and / or B may represent the following cases: only A exists, both A and B exist, and only B exists, and A and B may be singular or plural. The symbol “ / ” generally indicates an “or” relationship between related objects. “At least one of the following items (parts)” or a similar expression refers to any combination of these items, including a single item (part) or any combination of multiple items (parts). For example, at least one item (part) among a, b, or c may represent a, b, c, a and b, a and c, b and c, or a and b and c, and a, b, and c may be singular or plural.

[0075] The technical solutions in this application can be applied to various communication systems, such as long-term evolution (LTE) systems, LTE frequency division duplex (FDD) systems, LTE time division duplex (TDD) systems, universal mobile telecommunications systems (UMTS), worldwide interoperability for microwave access (WiMAX) communication systems, public land mobile network (PLMN) systems, device-to-device (D2D) network systems, machine-to-machine (M2M) network systems, and future 5G communication systems.

[0076] The network architectures and service scenarios described in embodiments of this application are intended to provide a clearer illustration of the technical solutions in embodiments of this application and do not constitute a limitation on the technical solutions provided in embodiments of this application. Those skilled in the art will know that, with the evolution of network architectures and the emergence of new service scenarios, the technical solutions provided in embodiments of this application may also be applicable to similar technical challenges.

[0077] In terrestrial communications, a single network device (e.g., a base station) can cover one or more cells. Generally, the cell identifiers (physical cell identifiers, PCIs) and broadcast area identifiers (e.g., tracking area codes, TACs) or tracking area identifiers, TAIs) of these cells remain unchanged for very long periods. However, in satellite communications, because satellites move at high speeds, the physical area on the ground (e.g., cells) covered by the satellite changes. Of course, the following deployment solutions are used for satellite cell identifiers and broadcast area identifiers. Solution (1): As shown in Figure 1(a), an association relationship is established between the cell identifier and the physical area. Specifically, for a physical area, the cell identifier and broadcast area identifier corresponding to the physical area remain unchanged. After a satellite (abbreviated as Satellite 1) moves, another satellite (abbreviated as Satellite 2) provides service to the physical area. The cell identifier and broadcast area identifier of Satellite 2 are the same as those of Satellite 1. The main advantage of this solution is that it is assumed that the location of the UE (user equipment, also called terminal) remains unchanged for the physical area. Because the terminal senses that the cell remains unchanged, network devices do not need to trigger a cell handover process for the terminal, reducing the number of handovers in the network and reducing the signaling overhead of the wireless interface. In this solution, generally, a satellite always serves a physical area within a given period (i.e., the satellite always covers the physical area). When a satellite is unable to provide service to a physical area due to satellite movement, another satellite provides service to the physical area. As shown in Figure 1(a), when satellite 1 is at geographical location 2 at time T+T1, the cell identifier of the cell included in the ground coverage area is cell 2, and when satellite 1 is at geographical location 1 at time T, the cell identifier of the cell included in the ground coverage area is cell 1.

[0078] Solution (2): As shown in Figure 1(b), cell identifiers are associated with satellites. When the satellite's coverage area changes due to satellite movement, the satellite's cell identifier remains unchanged. In this solution, it can be understood that as the satellite moves, cell identifiers are scanned within the physical coverage area. In this solution, even if the terminal's location remains unchanged, if the satellite's ground-based coverage area can no longer cover the terminal due to satellite movement, the network must notify the terminal to perform a handover to switch to another cell. As shown in Figure 1(b), since cell identifiers are associated with satellites, when satellite 1 is at geographical location 2 at time T+T1, the cell identifier of cells included in the ground-based coverage area is cell 1, and when satellite 1 is at geographical location 1 at time T, the cell identifier of cells included in the ground-based coverage area is cell 1. In Figure 1(b), cells served by satellite 1 at different geographical locations have the same cell identifier, but the coverage areas of cells at different geographical locations may be different.

[0079] NTN will be introduced in the new radio (NR) system. In NTN, base stations or some functions of base stations will be located on high-altitude platforms or satellites to provide seamless coverage to terminals. As satellites move around the Earth and terminals also move relative to the Earth, the satellite corresponding to the cells accessed by terminals currently using network services will change from one satellite to another. To guarantee communication continuity and quality of service, terminals need to sense the change between the old and new satellites and determine whether the terminal is located within the coverage area of ​​the ground cells served by the new satellite.

[0080] As shown in Figure 2 or Figure 3, an embodiment of this application provides a communication system. The communication system includes one or more terminals (e.g., terminals 1 to n), a network device 100, and a satellite 200. The terminals access a cell 300, which is one of one or more cells covered by the network device 100. The cell 300 may be serviced by the satellite 200, or the cell 300 may be a ground cell covered by the satellite 200.

[0081] The terminals are located on the Earth's surface, while satellites 200 and 400 are located in Earth orbit. Satellites 200 or 400 may provide communication services to a physical area covered by the signal (e.g., cell 300 or cell 500) and may communicate with terminals located within the range of the physical area covered by the signal.

[0082] In one example, a satellite typically generates one or more beams (also called beam footprints) on the ground, and these beams form a cell on the ground.

[0083] In satellite communications, the physical area of ​​the ground covered by a satellite changes because the satellite moves at high speed. Therefore, the coverage area of ​​the same satellite on the ground can differ over different periods. Assume that satellite 200 serves cell 300 during a first period. The start time of the first period is the start time of satellite 200's coverage on the ground, and the end time of the first period is the end time of satellite 200's coverage on the ground. Network device 100 corresponds to satellite 200 during the first period.

[0084] As shown in Figure 2(a) or Figure 3(a), at time T1 (belonging to the first period), cell 300 is covered by satellite 200. Specifically, the coverage area of ​​satellite 200 on the ground at time T1 includes the coverage area of ​​cell 300 on the ground. Due to the movement of satellite 200, at time T2, satellite 400 moves to a position where it can cover cell 300, and satellite 200 gradually moves to a position away from cell 300. As shown in Figure 2(b), satellite 400 may cover the coverage area of ​​cell 300 on the ground, or the coverage area of ​​cell 500 on the ground, which is covered by satellite 400, may be considered the same as the coverage area of ​​cell 300. Finally, as satellite 200 moves, the coverage area of ​​satellite 200 on the ground no longer includes the coverage area of ​​cell 300. As shown in Figure 2(c), at time T3, the coverage area of ​​cell 300 is covered by satellite 400, or at time T3, cell 500 on the ground that is covered by satellite 400 can be considered to be cell 300.

[0085] When satellite 200 provides service to cell 300, it can be understood that cell 300 may be one of one or more cells covered by network device 100. In this case, one of terminals 1 to n may communicate with satellite 200 via network device 100. When satellite 400 provides service to cell 500, cell 500 may be one of one or more cells covered by network device 600. In this case, one of terminals 1 to n may communicate with satellite 200 via network device 600. Of course, network device 100 and network device 600 may be the same network device. Specifically, although the satellite providing service to the cell changes, the network device accessed by the terminal remains unchanged.

[0086] In one example, network device 600 and network device 100 may be the same network device. Specifically, the satellite providing service to cell 300 changes from satellite 200 to satellite 400, but the network device to which cell 300 belongs remains unchanged. In another example, network device 600 and network device 100 are different network devices. Specifically, the satellite providing service to cell 300 changes from satellite 200 to satellite 400, and the network device to which cell 300 belongs also changes.

[0087] It should be noted that when cells served by satellites 400 and 200 have the same cell identifier, the coverage area of ​​ground cell 500 served by satellite 400 may be the same as the coverage area of ​​ground cell 300 served by satellite 200, as shown in Figure 2(b). However, the scenario shown in Figure 3(b) may exist in which the coverage area of ​​ground cell 500 served by satellite 400 is different from the coverage area of ​​ground cell 300 served by satellite 200. For example, there may be an intersection of coverage areas. Of course, there may also be no intersection between the coverage area of ​​ground cell 500 served by satellite 400 and the coverage area of ​​ground cell 300 served by satellite 200. As a result, the differences between Figure 2 and Figure 3 are as follows. In Figure 2, the satellite of cell 300 changes from satellite 200 to satellite 400, but the coverage area of ​​cell 500 on the ground, covered by satellite 400, is the same as the coverage area of ​​cell 300 on the ground, served by satellite 200. It can be understood that cell 500 and cell 300 are the same cell and have the same cell identifier. In the system shown in Figure 3, the satellite of cell 300 changes from satellite 200 to satellite 400. However, the coverage area of ​​cell 500 on the ground, covered by satellite 400, is different from the coverage area of ​​cell 300 on the ground, served by satellite 200. For example, terminal 1 is located outside the coverage area of ​​cell 500 on the ground, while terminals 2 to n are located within the coverage area of ​​cell 500 on the ground.

[0088] Figures 2(c) and 3(c) show satellite 2 covering cell 500 after satellite 1 has departed.

[0089] In possible embodiments of this application, the communication system shown in Figure 2 or Figure 3 may further include core network devices (not shown). Core network devices are devices within a core network (CN) that provide service support to terminals. Currently, some examples of core network devices include access and mobility management function (AMF) entities, session management function (SMF) entities, and user plane function (UPF) entities, which are not listed here one by one. AMF entities may be responsible for terminal access management and mobility management. SMF entities are responsible for session management, e.g., establishing user sessions. UPF entities may be function entities on the user plane, primarily responsible for connecting to external networks. It should be noted that entities in this application may also be referred to as network elements or function entities. For example, an AMF entity may also be referred to as an AMF network element or an AMF function entity. Another example is an SMF entity, which may also be referred to as an SMF network element or an SMF function entity.

[0090] Specifically, the satellite in the embodiments of this application can be considered a spacecraft carrying a transparent payload (which may also be a bent pipe payload) or a regenerative payload signal transmitter. Satellites typically orbit in low Earth orbits (LEO) at altitudes of 300 km to 1500 km, medium Earth orbits (MEO) at altitudes of 7000 km to 25000 km, geostationary Earth orbits (GEO) at altitudes of 35786 km, or high elliptical orbits (HEO) at altitudes of 400 km to 50000 km. In other words, satellites can be classified as LEO satellites, MEO satellites, GEO satellites, and HEO satellites, etc., based on their different orbital altitudes.

[0091] The terminals in the embodiments of this application may also be referred to as user equipment (UE), mobile station (MS), or mobile terminal (MT), and are devices that provide voice and / or data connectivity to a user, such as handheld devices or in-vehicle devices with wireless connectivity. Currently, some examples of terminals include mobile phones, tablet computers, notebook computers, palmtop computers, mobile internet devices (MID), wearable devices, virtual reality (VR) devices, augmented reality (AR) devices, wireless terminals in industrial control, wireless terminals in self-driving, wireless terminals in remote medical surgery, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, and wireless terminals in smart homes.

[0092] The network device in this embodiment of the application is a radio access network (RAN) node (or device) that connects a terminal to a wireless network, and may also be referred to as a base station. The network device may be a base transceiver station (BTS) in a global system for mobile communications (GSM) or code division multiple access (CDMA) communication system, a node B (NB) in a wideband code division multiple access (WCDMA) communication system, an evolved node B (eNB or eNodeB) in a long-term evolution (LTE) communication system, or a base station (next-generation node B, gNB) in a new wireless communication system. The network device may alternatively be an access point (AP) or relay station in a Wireless Local Area Network (WLAN), a network device in a future advanced Public Land Mobile Network (PLMN), or a network device in the NTN communication system.

[0093] Currently, some examples of RAN nodes include progressive node B (gNB), transmission reception point (TRP), evolved node B (eNB), radio network controller (RNC), node B (NB), base station controller (BSC), base transceiver station (BTS), home base station (e.g., home evolved node B, or home node B, HNB), baseband unit (BBU), and wireless fidelity (Wi-Fi) access point (AP).

[0094] In addition, in the network structure, as shown in Figure 4, network devices may include central unit (CU) nodes, distributed unit (DU) nodes, or RAN devices that include both CU and DU nodes. RAN devices that include both CU and DU nodes divide the protocol layers of the gNB in ​​the NR system. Some protocol layer functions are centrally controlled by the CU. Some or all of the remaining protocol layer functions are distributed within the DU, and the CU centrally controls the DU. Optionally, as shown in Figure 4, the CU may be further divided into a control plane (CU-CP) and a user plane (CU-UP). The CU-CP is responsible for control plane functions and mainly includes the RRC layer and the control plane, i.e., the packet data convergence protocol (PDCP) layer corresponding to PDCP-C. PDCP-C is mainly responsible for data encryption and decryption, integrity protection, and data transmission on the control plane. The CU-UP is responsible for user plane functions and primarily includes a Service Data Adaptation Protocol (SDAP) layer and a PDCP layer corresponding to the user plane (i.e., PDCP-U). The SDAP layer is primarily responsible for processing data on the core network and mapping flows to bearers. The PDCP-U is responsible for encryption and decryption on the data plane, integrity protection, header compression, sequence number maintenance, and data transmission. The CU-CP and CU-UP are connected via the E1 interface. Instead of the gNB, the CU-CP is connected to the core network via the NG interface and to the DU via the F1 interface-control plane, i.e., F1-C. The CU-UP is connected to the DU via the F1 interface-user plane, i.e., F1-U. Of course, in other possible implementations, PDCP-C is alternatively located within the CU-UP.

[0095] Currently, TR38.821 specifies five NTN-based RAN architectures (NTN-based NG-RAN architectures). The methods provided in embodiments of this application are applicable to any one of the following architectures.

[0096] Architecture 1 shown in Figure 5 is an architecture of a communication system with a transparent satellite (RAN architecture with transparent satellite) according to an embodiment of this application. Architecture 1 includes terminals, access network nodes (NG-RAN), a 5G core network (5GC), and a data network (DN).

[0097] NG-RAN includes a remote radio unit (RRU) and a gNB. The RRU includes a satellite and an NTN gateway.

[0098] The terminals, non-terrestrial network gateways, and gNBs are located on the Earth's surface, while the satellites are in Earth orbit. In addition, the satellites, non-terrestrial network gateways, and gNBs may be used as a 5G radio access network (NG-RAN), which is connected to the 5G core network via a second interface (e.g., an NG interface).

[0099] In Architecture 1, the terminal communicates with the gNB via a first interface (e.g., NR Uu). The 5G core network communicates with the data network via the N6 interface.

[0100] In a transparent scenario, the satellite's functions are radio frequency filtering and frequency conversion and amplification. In other words, the satellite is primarily used as an L1 relay to regenerate physical layer signals and does not have other higher-level protocol layers.

[0101] The difference between Architecture 2 and Architecture 1, as shown in Figure 6, is that in Architecture 2, the NG-RAN includes the gNB, the gNB is a satellite, the satellite communicates with the terminal via a first interface, and there is a second interface between the satellite and the 5G core network.

[0102] In Architecture 2, there is a regenerative satellite that does not have an inter-satellite link but has base station processing capabilities (a regenerative satellite without an ISL, with a payload processed by a gNB), where the inter-satellite link is an inter-satellite link (ISL). In this architecture, the satellite is used as a gNB.

[0103] The commonality between Architecture 3 and Architecture 2, as shown in Figure 7, is that the satellite is used as a gNB (Global Nozzle). However, the difference between Architecture 3 and Architecture 2 is that the ISL (Infrastructure Storage Level) is present in the scenario shown for Architecture 3.

[0104] The architecture shown in Figure 8 is Architecture 4. The difference between Architecture 4 and Architecture 1 is that in Architecture 4, the Access Network Node (NG-RAN) includes both a satellite and network devices. The satellite is used as a gNB-DU, the network devices are used as gNB-CUs, the gNB-DU communicates with the gNB-CU via the F1 interface, and the terminal communicates with the gNB-DU via the first interface.

[0105] Architecture 4: There is a regenerative satellite with base station DU processing capabilities (NG-RAN with a regenerative satellite based on gNB-DU). In this scenario, the satellite is used as a DU.

[0106] Architecture 5: There is a base station with IAB functionality (payload processed by gNB based on a relay-like architecture). In this scenario, the satellite is used as a relay node (integrated access and backhaul, IAB).

[0107] In terrestrial communications, in several scenarios (for example, because certain parameters configured for the terminal by the network need to be changed, or because the network needs to change the key assigned to the terminal), the network triggers the terminal to perform an intra-cell handover. Specifically, the cell accessed by the terminal remains unchanged, but the network requires the terminal to re-access the cell. Generally, the network sends a handover command (e.g., referred to as reconfiguration by a synchronous message) to the terminal, and the terminal performs random access within the cell again based on the handover command (note that the current protocol requires the terminal to perform random access, and that in subsequent protocol evolution, this may no longer be necessary). According to the current protocol, in a handover scenario, a formula is used to calculate the interruption time caused by the handover. The formula includes the time Tsearch for searching for the target cell. If the target cell is known, Tsearch = 0; otherwise, the value of Tsearch is specified by the protocol.

[0108] In satellite communications, in several other scenarios, the network also notifies the terminal to perform an intra-cell handover (for example, because the terminal's location changes, it enters one country from another, and the different countries utilize different core networks, so the network needs to select a new core network for the terminal, and therefore the network triggers an intra-cell handover).

[0109] In the configuration solution 1 shown in Figure 1(a), the old satellite (hereinafter referred to as the first satellite) moves, so the new satellite (hereinafter referred to as the second satellite) provides service only after the old satellite can no longer provide service to the physical area on the ground (where the satellite's coverage area is the physical area of ​​the satellite on the ground surface). Generally, the service is provided by other satellites in the same orbit. To create a gap between the satellites, the distance between the two satellites becomes longer. Because the distance from the new satellite to the terminal is different from the distance from the old satellite to the terminal, the downlink signals received by the terminal from the same cell are asynchronous, and the uplink signals from the terminal reach the two satellites at different times (note that here, asynchronous downlink signals mean that the time at which the terminal detects the downlink pilot signal changes, or that the start or end point of the frame number, subframe number, slot number, or symbol detected by the terminal changes). However, when a new satellite provides coverage, if a terminal is not located within the coverage area of ​​a ground cell serviced by the new satellite, the terminal may fail to perform downlink synchronization with the new satellite when the new satellite provides coverage. In this case, the terminal will subsequently be unable to correctly receive downlink signals transmitted within the current cell on that satellite, and will be unable to successfully transmit uplink signals to the cell serviced by the new satellite. As shown in Figure 3 or Figure 2, when a ground cell 500 covered by a new satellite (e.g., satellite 400) and a ground cell 300 covered by an older satellite (e.g., satellite 200) have the same cell identifier, the coverage area of ​​ground cell 500 covered by satellite 400 and the coverage area of ​​cell 300 may be the same (as shown in Figure 2) or different (as shown in Figure 3). Therefore, a technical problem that urgently needs to be solved in this application is how to enable one of terminals 1 to n within the cell 300 being accessed to determine whether the terminal is located within the coverage area of ​​the ground cell 500 covered by satellite 400.

[0110] In embodiments of this application, the specific structure of the execution entity of the communication method is not particularly limited in this application, as long as the execution entity can execute a program that records the code of the communication method in embodiments of this application and execute communication according to the communication method in embodiments of this application. For example, the execution entity of the communication method provided in embodiments of this application may be a functional module located in a first network device and capable of calling and executing a program, or it may be a communication device used in the first network device, such as a chip. The execution entity of the communication method provided in embodiments of this application may be a functional module located in a terminal and capable of calling and executing a program, or it may be a communication device used in the terminal, such as a chip. This is not limited in this application. The following embodiments will be described using examples in which the execution entity of the communication method is a first network device and a terminal.

[0111] Figure 9 is a schematic interaction flowchart of a non-terrestrial network communication method according to an embodiment of this application. The method includes the following steps:

[0112] Step 901: A first network device corresponding to the first satellite transmits a first message. In response, the terminal receives the first message from the first network device. The first network device is the network device to which the first cell belongs, and the first cell is the cell accessed by the terminal.

[0113] The first message indicates that the satellite providing service to the first cell is being replaced from the first satellite to the second satellite. Alternatively, the first message indicates that the satellite providing service to the first cell is changing, i.e., that the old satellite is being replaced by a new one.

[0114] Optionally, the first network device corresponds to the first satellite. As shown in Figure 5 or Figure 6, the first satellite is the first network device, for example, a base station. For example, as shown in Figure 8, the first network device is gNB-CU and the first satellite is gNB-DU.

[0115] In a possible implementation of this application, a first message may carry first information to help determine whether a terminal is located within the coverage area of ​​a second cell on the ground serviced by a second satellite. The first information indicates the coverage area of ​​a second cell on the ground serviced by a second satellite. The second cell and the first cell have the same cell identifier. Alternatively, it may be understood that the first cell and the second cell are the same cell, i.e., the first cell and the second cell are identical.

[0116] In one example, the first information may be information about the physical area covered by a second ground cell serviced by a second satellite. The information about the physical area is used to determine the coverage area of ​​the second ground cell serviced by the second satellite. Optionally, the first information may be coverage area parameter information for the second cell. For example, the information about the physical area covered by a second ground cell serviced by a second satellite may be represented using a reference point and radius (or distance threshold), or using a series of coordinate points.

[0117] It can be understood that the coverage area of ​​the first cell largely falls within the coverage area of ​​the second satellite on the ground. For example, the second satellite may serve one or more cells; that is, the coverage area of ​​the second satellite on the ground includes one or more cells. The fact that one or more cells include the second cell can be understood as the cell identifier of the second satellite being the same as the cell identifier of the first cell.

[0118] In one example, the terminal in this embodiment of the application may be a terminal in the radio resource control (RRC)_connected state, or a terminal in the RRC_idle (IDLE) / RRC_inactive (INACTIVE) state.

[0119] The terminal may be any terminal that accesses the first cell.

[0120] In a possible implementation of this application, step 901 may be carried out in the following manner: A first network device broadcasts a first message to terminals, i.e., the first message is a broadcast message transmitted by the first network device. In this way, multiple terminals accessing the first cell, or multiple terminals located within the first cell, can receive the first message, thereby enabling the terminals to determine that the satellite serving the first cell has changed. For example, terminals accessing the first cell include terminals A and B, and the first message is transmitted in a broadcast manner. In this way, the first network device may transmit the broadcast message once, thereby enabling terminals A and B to perceive that the satellite serving the first cell has been updated from the first satellite to the second satellite, and to perceive the coverage area of ​​the second cell on the ground served by the second satellite.

[0121] In other possible implementations of this application, step 901 may be carried out in the following manner: The first message transmitted to a terminal by the first network device is a dedicated message. That is, the first network device uses dedicated messages to transmit the first message to a specific terminal in the first cell. For example, the first message may be an RRC message or a medium access control (MAC) message. In this scenario, if the terminals accessing the first cell include terminal A and terminal B, the first network device may transmit the first message to terminal A or to terminal B.

[0122] Step 902: The terminal determines, based on the first message, the terminal's location, and the coverage area of ​​the second ground cell served by the second satellite, whether the terminal is located within or outside the coverage area of ​​the second ground cell.

[0123] In one example, relating to Figure 2, the first network device may be network device 100. The first satellite may be satellite 200. The first cell may be cell 300. The second satellite may be satellite 400. The second cell may be cell 500.

[0124] After receiving the first message, it can be understood that the terminal may determine, in real time or periodically, whether its location is within the coverage area of ​​a second cell on the ground.

[0125] Optionally, if the first message does not carry the first information, and the terminal decides, using the first message, that the satellite serving the first cell will change, the terminal may request the first network device to alternatively provide for the terminal the coverage area of ​​the second cell on the ground, which is served by the second satellite.

[0126] This embodiment of the application provides a communication method. In the method, when it is decided that the satellite providing service to a first cell will be replaced from the first satellite to the second satellite, that is, when the old satellite is replaced by a new satellite, the first network device sends a first message to a terminal. The first message indicates to the terminal that the satellite providing service to the first cell will be replaced from the first satellite to the second satellite, so that the terminal can sense that the satellite covering the first cell is changing. The second satellite provides service to the second cell, and the first and second cells have the same cell identifier. Although the first and second cells have the same cell identifier, their ground coverage areas may be different. The terminal may be located outside the ground coverage area of ​​the second cell, or it may be located within the ground coverage area of ​​the second cell. Therefore, in order to avoid communication interruptions caused by cases in which the terminal is unable to access the second cell when the terminal is located outside the coverage area of ​​the second cell, this application provides that the first network device transmits information to the terminal about the coverage area of ​​the second cell on the ground, which is serviced by the second satellite, so that the terminal can, by referring to its location, further determine whether the terminal is located within or outside the coverage area of ​​the second cell on the ground and take appropriate processing measures.

[0127] In possible embodiments of this application, prior to step 901, the method provided in this embodiment of this application may further include: A first network device determines that the satellite providing service to the first cell is being upgraded from the first satellite to the second satellite.

[0128] In possible implementations, the first network device may decide that the satellite providing service to the first cell is being updated from the first satellite to the second satellite in the following manner: The operator transmits information about the second satellite to the first network device. Alternatively, the satellite control function of the second satellite transmits ephemeris information for the second satellite to the first network device (base station), or the satellite control function of the second satellite transmits ephemeris information for the second satellite to the core network, which then forwards the ephemeris information for the second satellite to the first network device (base station).

[0129] In other possible implementations, a second network device corresponding to the second satellite (e.g., a second base station) transmits information about the second satellite to a first network device corresponding to the first satellite (e.g., a first base station).

[0130] In a possible implementation of this application, the first message may further carry a seventh indication information. The seventh indication information indicates to the terminal whether its location is within the coverage area of ​​a second cell on the ground serviced by the second satellite. Thus, after receiving the seventh indication information, the terminal may take action to determine whether it is located within the coverage area of ​​the second cell on the ground. Of course, the seventh indication information may be carried in a message other than the first message. This is not limited to the embodiments of this application. In other embodiments of this application, the first message does not need to carry the seventh indication information. After receiving the first message, the terminal may take action based on the first information to determine whether it is located within the coverage area of ​​the second cell on the ground.

[0131] In a possible implementation of this application, the first network device does not need to perform an indication on the terminal; after receiving the first information, the terminal proactively reports to the first network device the result of determining whether the terminal is located within the coverage area of ​​the second cell on the ground. In other possible implementations, the first network device alternatively indicates to the terminal that it is located within the coverage area of ​​the second cell on the ground to report the result of determining whether the terminal is located within the coverage area of ​​the second cell on the ground. For example, the first message may carry indication information x, or the first network device may send a message other than the first message to the terminal to notify the terminal to report the decision result. For example, indication information x indicates to the terminal to report the decision result when the terminal is located outside the coverage area of ​​the second cell on the ground. In this way, if the first network device does not receive a decision result reported by the terminal, the first network device may determine that the terminal is located within the coverage area of ​​the second cell on the ground. Of course, upon receiving a decision from the terminal, the first network device may determine that the terminal is located outside the coverage area of ​​the second cell on Earth. Alternatively, indication information x may indicate that the terminal should report the decision when it is located within the coverage area of ​​the second cell on Earth. Alternatively, indication information x may indicate that the terminal should report the decision regardless of whether its location is within or outside the coverage area of ​​the second satellite. The first network device sends indication information x, or a message to the terminal to inform it whether it should report the result of determining whether it is located within the coverage area of ​​the second cell, thereby causing the terminal to take the corresponding action based on the indication from the first network device. Alternatively, indication information x may indicate that the terminal should perform a report when the decision is the first decision, and not perform a report when the decision is the second decision. For example, the first decision is different from the second decision.For example, the first determination result is that the terminal is located within the coverage area of ​​the second satellite on the ground. The second determination result is that the terminal is located outside the coverage area of ​​the second satellite on the ground.

[0132] In possible implementations, after receiving the first information, the terminal may proactively report its location to the first network device. In other possible implementations, the terminal reports its location to the first network device when triggered by the first network device. For example, the first network device may further indicate to the terminal to report its location using indication information y. The indication information y is carried in the first message or a message other than the first message. This is not limited to the embodiments of this application.

[0133] It can be understood that the first network device may transmit both indication information a and indication information y to the terminal.

[0134] In a possible implementation of this application, when a terminal obtains the coverage end time of the first satellite on the ground, the terminal may further send a request message to the first network device before the coverage end time of the first satellite on the ground to request information about a second cell on the ground covered by the second satellite.

[0135] In a possible implementation of this application, the time by which the first network device transmits the first message to the terminal is earlier than the coverage commencement time of the second satellite serving the second cell on the ground. The coverage commencement time is the time when the second satellite corresponding to the second cell begins to cover the physical area of ​​the first cell on the ground (including the first cell) corresponding to the first satellite.

[0136] An example is used for illustrative purposes. When a first network device determines the coverage start time of the second satellite corresponding to the second cell, assuming that the terminal is still accessing the first cell before the coverage start time of the second satellite corresponding to the second cell, and assuming that downlink data / signaling transmission is required between the first network device and the terminal, the first network device may send the first message to the terminal in the process of sending downlink data / signaling to the terminal. If it is assumed that downlink data / signaling transmission is not required between the first network device and the terminal before the coverage start time of the second satellite corresponding to the second cell, the first network device may choose to send the first message to the terminal at any time, or when the terminal is in an RRC connection state.

[0137] In a possible implementation of this application, the first message may be a predefined message specifically used to notify a terminal that a satellite servicing a cell is being replaced. Thus, after receiving the first message, the terminal can be aware that a satellite change is occurring. Of course, the first message may alternatively be an existing message between the terminal and a first network device. This is not limited to the embodiments of this application.

[0138] In other possible implementations of this application, the first message includes first indication information, which indicates that the satellite serving the first cell is being updated from the first satellite to the second satellite, or that the satellite serving the first cell is changing. Thus, for a terminal, the terminal can determine, based on the first indication information, that the satellite of the first cell accessed by the terminal is being updated from the first satellite to the second satellite. This scheme can be considered as an explicit indication by the first network device to the terminal. Of course, the first message may be the first indication information, or the first indication information may be a field within the first message. This is not limited to the embodiments of this application. Optionally, the first indication information may be information about a physical area on the ground covered by the second cell served by the second satellite.

[0139] Of course, in addition to explicitly indicating to the terminal that a satellite changeover is occurring, the first network device may also implicitly indicate to the terminal that a satellite changeover is occurring.

[0140] In an example of implicit indication, the first message in this embodiment of the application may further include one or more of the following parameters: a first time parameter, a second time parameter, time information for the terminal to perform downlink synchronization in the second cell via the second satellite, NTN parameter information for the second satellite, a third indication information, or information about the measurement timing configuration.

[0141] The first time parameter is used to determine the coverage start time of the second satellite serving the second cell on the ground. The second time parameter is used to determine the coverage end time of the second satellite serving the second cell on the ground. In this way, after receiving the first time parameter and / or the second time parameter, the terminal can determine the coverage start and end times of the second satellite on the ground. The terminal may then synchronize with the second network device corresponding to the second satellite after the coverage start time of the second satellite on the ground, or it may send the second or fourth message to the first network device before the coverage start time of the second satellite on the ground.

[0142] Of course, assuming that the terminal then communicates via the second satellite, knowing the end-of-coverage time of the second satellite on the ground, the terminal may also obtain information from the second network device corresponding to the second satellite about the updated coverage area of ​​the second cell and / or the updated cell covered by the satellite, before the end-of-coverage time of the second satellite on the ground.

[0143] In one example, the first time parameter is the coverage start time of the second satellite on the ground. Alternatively, the first time parameter is the first time information plus a preset duration. The second time parameter is either the coverage end time of the second satellite corresponding to the second cell on the ground, or the second time parameter includes the first time parameter plus the duration for which the second satellite serves the second cell.

[0144] Of course, when the first message contains the first indication information, the first message may also contain one or more of the parameters mentioned above. For example, the first message may contain the first indication information and the first time parameter.

[0145] The third indication information indicates the location information of the NTN parameter information, for example, information about the system information block in which the NTN parameter information is located.

[0146] In one example, information about the measurement timing configuration is used to determine the measurement timing configuration. The measurement timing configuration is then indicated to the terminal to search for the downlink synchronization signal of the second cell on the second satellite. The measurement timing configuration includes a measurement window for receiving the downlink synchronization signal, and the period and offset of the measurement window.

[0147] Optionally, the measurement timing configuration is based on the downlink timing relationship of the first cell of the first satellite. Optionally, the measurement timing configuration is based on the downlink timing relationship of the second cell of the second satellite. The terminal calculates the first subframe number and the first system frame number used to search for the downlink synchronization signal of the second cell according to the following formula (i.e., the first measurement window begins at the point corresponding to the first subframe number and the first system frame number, the duration is the length of the measurement window, and signal reception is subsequently performed within the measurement window based on the periodicity).

[0148] SFN mod T = (FLOOR(Offset / 10)).

[0149] If the periodicity is greater than 5 subframes, then subframe = Offset mod 10; otherwise, subframe = Offset or (Offset + 5), where T = CEIL(Periodicity / 10).

[0150] MOD is a mathematical operator that indicates the modulo (also called modulus) operation.

[0151] FLOOR is a mathematical operator that rounds a number down to the nearest integer (truncating).

[0152] CEIL is a mathematical operator that rounds a number up to the nearest integer (rounding up).

[0153] The above solution describes a process by which a terminal senses a satellite change in a first cell. After the first network device notifies the terminal that a satellite change is occurring in the first cell, the second cell and the first cell may have the same cell identifier, but may have different ground coverage areas. Thus, the terminal may be located within the coverage area of ​​the second cell on the ground served by the second satellite, or it may be located outside the coverage area of ​​the second cell on the ground served by the second satellite. In different scenarios, the subsequent actions performed by the terminal are generally different. Therefore, this embodiment of the application describes different scenarios in relation to this.

[0154] Scenario (1): The terminal is located outside the coverage area of ​​the second cell on Earth, which is serviced by the second satellite.

[0155] In scenario (1), Figure 10 shows a specific process of another communication method according to an embodiment of this application. Steps 1001 and 1002 in Figure 10 are the same as steps 901 and 902. Further details are not described here. Optionally, after step 1002, the method provided in this embodiment of this application may further include the following steps. Step 1003a: The terminal sends a second message to the first network device. In response, the first network device receives the second message from the terminal. The second message indicates that the terminal is located outside the coverage area of ​​the second cell on the ground, which is serviced by the second satellite.

[0156] It should be noted that step 1003a is an optional step. Specifically, when the terminal determines that it is located outside the coverage area of ​​the second cell on the ground, the terminal may omit the process of sending the second message to the first network device.

[0157] When a terminal determines that it is located outside the coverage area of ​​the second cell on the ground, the terminal sends a second message to the first network device, so that the first network device immediately knows that the terminal is located outside the coverage area of ​​the second cell on the ground and triggers the terminal to perform a cell handover immediately, thereby ensuring the terminal's continued normal communication. In particular, when the first network device sends the first message via broadcast, there may be multiple terminals accessing the first cell, some of which may be located outside the coverage area of ​​the second cell on the ground, and some of which may be located within the coverage area of ​​the second cell on the ground. Therefore, if a terminal feeds back the second message to the first network device, the first network device triggers the terminal to perform a cell handover. However, for terminals that do not feed back the second message, or terminals that feed back that they are within the coverage area of ​​the second cell on the ground, a cell handover does not need to be triggered. Optionally, the second message may further include a terminal identifier, thereby allowing the first network device to determine that a terminal is located outside the coverage area of ​​the second cell on the ground.

[0158] Optionally, the second message may include second indication information, which indicates that the terminal is located outside the coverage area of ​​a second cell on the ground. Alternatively, the second message may be second indication information. This is not limited to the embodiments of this application.

[0159] When the second message contains second indication information, it can be understood that the first network device will determine, based on the second indication information, that the terminal is located outside the coverage area of ​​the second satellite on the ground. For example, the first network device parses the second message to obtain the second indication information.

[0160] Optionally, the second message may be a predefined message specifically used to exchange a message between the terminal and the first network device indicating that the terminal is located outside the coverage area of ​​the second satellite on the ground. In this way, after receiving the second message, the first network device can know that the terminal is located outside the coverage area of ​​the second satellite on the ground. For example, the first network device does not need to parse the second message. Optionally, the second message may be an existing message for communication between the terminal and the first network device.

[0161] It should be noted that if the first network device does not indicate to the terminal that it should report the decision result, the terminal sending the second message is a voluntary action by the terminal. Of course, if the first network device does indicate to the terminal that it should report the decision result, the terminal may send the second message to the first network device based on the indication from the first network device.

[0162] Of course, whether a terminal reports a second message to a first network device, or whether the terminal reports a second message within the coverage area of ​​a second cell on the ground, or a second message outside the coverage area of ​​a second cell on the ground, can be predefined in the protocol. This is not limited to the embodiments of this application.

[0163] In possible embodiments of this application, when a terminal obtains a first time parameter of a second satellite, the terminal may send a second message to a first network device before the coverage start time of the second satellite. The time of sending the second message may be determined by the terminal or indicated to the terminal by the first network device. This is not limited to embodiments of this application. For example, in the process by which the first network device notifies a terminal that a satellite change is occurring, the first network device may notify the terminal to report the determination result before the coverage start time of the second satellite, or before the coverage end time of the first satellite on the ground.

[0164] In a possible implementation of this application, when the terminal is located outside the coverage area of ​​a second cell on the ground, the method provided in this embodiment of this application may optionally further include the following steps, as shown in Figure 10. Step 1004a: The terminal transmits its location information and / or measurement report information to the first network device. In response, the first network device receives the terminal's location information and / or measurement report information from the terminal.

[0165] Measurement report information can be understood as network measurement results obtained by a terminal by performing measurements based on a measurement configuration configured by a first network device. Network measurement results include parameter information such as signal strength and signal quality of neighboring cells, or the terminal's frequency. The terminal provides the measurement report information to the first network device, thereby the first network device configures second configuration information for the terminal based on the measurement report information, where the second configuration information includes cell handover conditions. Optionally, the first network device may further configure a target cell for the terminal based on the measurement report information.

[0166] In a possible implementation of this application, after step 1004a, the method provided in this embodiment of this application may further include: A first network device uses measurement report information from a terminal to determine first and / or second configuration information of the terminal. The first configuration information is used by the terminal to determine a target cell. The second configuration information is used by the terminal to determine the conditions for performing a cell handover.

[0167] The terminal provides its location information to the first network device, which then determines, based on the terminal's location information and the coverage area of ​​the second ground cell serviced by the second satellite, whether the terminal is located within or outside the coverage area of ​​the second ground cell.

[0168] In addition, the first network device may use the terminal's location information to determine the terminal's first and / or second configuration information. In this way, the first and / or second configuration information configured for the terminal will contribute to the terminal's subsequent communication, and it is guaranteed that the terminal's subsequent communication will not be interrupted.

[0169] In a possible implementation of this application, a terminal may transmit terminal location information and / or terminal measurement report information to the first network device when triggered by the first network device. For example, after a terminal has transmitted a second message to the first network device, the first network device may transmit a request command to the terminal to request the terminal to provide terminal location information and / or terminal measurement report information in order to further determine that the terminal is located outside the coverage area of ​​a second cell on the ground, or to configure a target cell that the terminal can switch to or to configure cell handover conditions (for which the terminal decides to switch from the first cell to the target cell when specific conditions are met). Alternatively, the first network device may obtain terminal location information from another device (e.g., an AMF network element). This is not limited to the embodiments of this application.

[0170] In other possible implementations of this application, when the terminal is located outside the coverage area of ​​a second ground cell serviced by the second satellite, the terminal may proactively transmit its location information and / or measurement report information to the first network device. Alternatively, the protocol stipulates that when the terminal detects that it is located outside the coverage area of ​​a ground cell serviced by the satellite, the terminal is required to transmit its location information and / or measurement report information to the first network device.

[0171] In one example, terminal location information and / or measurement report information is carried in a second message, and signaling overhead can be reduced by using the second message to carry the terminal location information and / or measurement report information. Of course, terminal location information and / or measurement report information may be carried in a message different from the second message. This is not limited to the embodiments of this application.

[0172] In a possible implementation of this application, when it is determined that the terminal is located outside the coverage area of ​​a second cell on the ground served by the second satellite, the terminal may decide to report the determination to the first network device, even if the first network device does not indicate to the terminal that it should report the determination.

[0173] In a possible implementation of this application, the determination by a first network device that a terminal is located outside the coverage area of ​​a second cell on the ground served by a second satellite may be carried out in the following manner: The first network device determines, based on a second message, that a terminal is located outside the coverage area of ​​a second cell on the ground served by a second satellite.

[0174] In other possible implementations of this application, the first network device determines, based on the terminal's location information and the coverage area of ​​a second ground cell served by the second satellite, that the terminal is located outside the coverage area of ​​a second ground cell served by the second satellite.

[0175] Alternatively, when the first network device receives the second message, the first network device may further refer to the terminal's location information to determine whether the terminal is located outside the coverage area of ​​the second cell on the ground corresponding to the second satellite.

[0176] To ensure the terminal's subsequent normal communication, when the first network device determines that the terminal is located outside the coverage area of ​​the second cell on Earth served by the second satellite, the first network device may further instruct the terminal to change its serving cell.

[0177] It should be noted that the order of steps 1003a and 1004a is not limited to the embodiments of this application. The terminal may first perform step 1004a and then step 1003a, or it may perform steps 1003a and 1004a simultaneously. In other words, the second message includes the terminal's location information and / or the terminal's measurement report information.

[0178] In a possible embodiment of this application, when the first network device determines that the terminal is located outside the coverage area of ​​the second satellite on the ground, as shown in Figure 10, after step 1002, the method provided in this embodiment of this application may include the following steps:

[0179] Step 1005a: The first network device sends a third message to the terminal. In response, the terminal receives the third message from the first network device. The third message instructs the terminal to change its serving cell from the first cell to the target cell. That is, the third message instructs the terminal to perform a cell handover. The target cell and the first cell have different cell identifiers.

[0180] In one example, the third message includes fourth indication information, which instructs the terminal to change its serving cell from the first cell to the target cell. The fourth indication information and the first configuration information may be the same information, or they may be different information. This is not limited to the embodiments of this application.

[0181] In other examples, the third message contains information about the target cell. The target cell is the cell to which the terminal switches and is selected for the terminal by the first network device, and the terminal is located within the range of the target cell. Optionally, the first network device may select a cell for the terminal as the target cell based on the terminal's location information and / or the terminal's measurement report information. For example, the signal quality or signal strength of the target cell may be higher than a preset value.

[0182] The target cell and the first cell may belong to the same network device, for example, the first network device. Of course, the target cell and the first cell may also belong to different network devices. For example, the first cell may belong to one or more cells covered by the first network device, and the target cell may be one or more cells covered by the third network device.

[0183] In possible implementations of this application, the target cell may alternatively be serviced by a second satellite, but the target cell is distinct from the second cell. For example, the coverage area of ​​the second satellite on the ground includes the coverage area of ​​the target cell on the ground and the coverage area of ​​the second cell on the ground. A terminal may be located outside the coverage area of ​​the second cell on the ground, but may be located within the coverage area of ​​the target cell on the ground. Thus, the terminal can switch to the target cell, thereby continuing to communicate via the second satellite and avoiding communication interruptions. Of course, the target cell may alternatively be a cell covered by a third satellite on the ground. This is not limited to the embodiments of this application.

[0184] In a possible embodiment of this application, when the first network device determines that the terminal is located within the coverage area of ​​a second cell on the ground that is serviced by the second satellite, the method provided in this embodiment of this application further includes the following steps, as shown in Figure 10.

[0185] Step 1006a: The first network device transmits the first configuration information and / or the second configuration information to the terminal. In response, the terminal receives the first configuration information and / or the second configuration information from the first network device.

[0186] Optionally, step 1006a may be omitted if the third message includes the first configuration information and / or the second configuration information.

[0187] Of course, the first configuration information and / or the second configuration information may alternatively be sent to the terminal using a fourth message, which is different from the third message.

[0188] In possible embodiments of this application, after sending a third message to the terminal, the first network device may proactively provide the terminal with first and / or second configuration information. Alternatively, upon receiving a request from the terminal, the first network device may send first and / or second configuration information to the terminal.

[0189] In one example, the second configuration information includes the configuration of the CHO candidate cell and the CHO execution conditions. The CHO execution conditions can be one or more of the following: a time-based CHO trigger condition, a position-based trigger condition, an event (event A3), an event A4, or an event A5. For example, the CHO execution conditions include a time-based CHO trigger condition and one or more of the following events: event (event A3), event A4, or event A5. The CHO execution conditions include a position-based trigger condition and one or more of the following events: event (event A3), event A4, or event A5.

[0190] It should be noted that the order of steps 1005a and 1006a is not limited to the embodiments of this application. The first network device may first perform step 1005a and then step 1006a, or it may first perform step 1006a and then step 1005a. Of course, alternatively, steps 1005a and 1006a may be performed simultaneously. In addition, when the first network device determines from a terminal that the terminal is located outside the coverage area of ​​the second cell on the ground, step 1005a or step 1006a is performed after step 1003a or step 1004a.

[0191] Step 1007a: Based on the third message, the terminal changes its serving cell from the first cell to the target cell.

[0192] In a possible implementation of this application, when the terminal acquires first configuration information and / or second configuration information, step 1007a may be performed in the following manner: The terminal determines information about the target cell based on the first configuration information. Based on the information about the target cell, the terminal switches from the first cell to the target cell.

[0193] In a possible implementation of this application, after receiving a third message, the terminal may evaluate the handover conditions, and if the cell handover conditions indicated by the second configuration information are met, the terminal changes the serving cell from the first cell to the target cell. In this way, handover failures caused by blind handovers by the terminal are avoided.

[0194] In possible embodiments of this application, optionally, as shown in Figure 10, after step 1002, the method provided in this embodiment of this application may include either or both of steps 1008a and 1009a.

[0195] Step 1008a: The terminal deletes configuration information relating to the second satellite, such as NTN parameter information for the second satellite, or coverage start time or coverage end time for the second satellite, such as ephemeris information for the second satellite, timing advance (TA) parameter information for the second satellite, measurement configuration information relating to the second cell, and handover and / or conditional handover configuration information relating to the second cell.

[0196] It should be noted that when the terminal is located outside the coverage area of ​​the second cell on the ground, if the terminal has configuration information regarding the second satellite, the terminal may perform step 1008a, or if the terminal does not have configuration information regarding the second satellite, step 1008a may be omitted.

[0197] Optionally, after step 1008a, the terminal may send a feedback response to the first network device to indicate that the configuration information relating to the second satellite has been deleted.

[0198] In this embodiment of the application, when the terminal is located outside the coverage area of ​​the second cell on the ground, the terminal reduces the memory usage of the terminal by deleting configuration information relating to the second satellite.

[0199] Of course, when the first network device determines that the terminal is located outside the coverage area of ​​the second satellite on the ground, the first network device may instruct the terminal to delete the configuration information about the second satellite. For example, when triggering the terminal to perform a cell handover, the first network device may send a sixth indication to the terminal to indicate that it should delete the configuration information about the second satellite. Of course, alternatively, the terminal may proactively delete the configuration information about the second satellite when the terminal is located outside the coverage area of ​​the second cell on the ground.

[0200] Optionally, if the target cell is a ground cell covered by a second satellite, the terminal may perform the step of obtaining ephemeris information of the second satellite instead of performing step 1008a.

[0201] Step 1009a: The terminal skips the step of obtaining ephemeris information from the second satellite.

[0202] It should be noted that the order in which a terminal performs steps 1008a and 1009a is not limited in this application. For example, a terminal may first perform step 1009a and then step 1008a.

[0203] Scenario (2): The terminal is located within the coverage area of ​​a second cell on the ground, which is serviced by the second satellite.

[0204] In scenario (2), as shown in Figure 10, optionally, after step 1002, the method provided in this embodiment of the application may further include one or more of a notification phase, a synchronization phase, and a random access phase. The notification phase includes steps 1003b and 1004b. The purpose of the notification phase is to enable the first network device to determine that the terminal is located within the coverage area of ​​the second cell on the ground, i.e., that the terminal can perform subsequent communications via the second satellite.

[0205] Step 1003b: The terminal sends a fourth message to the first network device. In response, the first network device receives the fourth message from the terminal. The fourth message indicates that the terminal is located within the coverage area of ​​the second cell on the ground.

[0206] Optionally, the fourth message may include fourth indication information, which indicates that the terminal is located within the coverage area of ​​a second cell on the ground.

[0207] Optionally, the fourth message may be a predefined message specifically used to exchange a message between the terminal and the network device indicating that the terminal is located within the coverage area of ​​a second ground cell serviced by the second satellite. In this way, after receiving the fourth message, the first network device may determine that the terminal is located within the coverage area of ​​a second ground cell serviced by the second satellite.

[0208] When the terminal is located within the coverage area of ​​the second cell on the ground, the terminal may also transmit its location information and / or measurement report information to the first network device. For specific processes and implementations, see the process by which the terminal transmits its location information and / or measurement report information to the first network device when it is located outside the coverage area of ​​the second cell on the ground.

[0209] Step 1004b: The first network device determines that the terminal is located within the coverage area of ​​the second cell on the ground.

[0210] In a possible implementation of this application, step 1003b may be omitted. Specifically, when the terminal determines that it is located within the coverage area of ​​a second cell on the ground, the terminal may not need to feed back a fourth message to the first network device.

[0211] In a possible implementation of this application, when the first network device receives the fourth message, step 1004b may be carried out in the following manner: Based on the fourth message, the first network device determines that the terminal is located within the coverage area of ​​a second cell on the ground that is serviced by the second satellite.

[0212] Optionally, if the fourth message includes fourth indication information, step 1004b may be carried out in the following manner: Based on the fourth indication information, the first network device determines that the terminal is located within the coverage area of ​​a second cell on the ground that is serviced by the second satellite.

[0213] In a possible implementation of this application, when the first network device acquires the location information of a terminal, step 1004b may be carried out in the following manner: The first network device may determine, based on the location information of the terminal and the coverage area of ​​the second cell on the ground, that the terminal is located within the coverage area of ​​the second cell on the ground.

[0214] Optionally, when a terminal notifies the first network device using a fourth message that it is located within the coverage area of ​​a second cell on the ground, the first network device may further determine, based on the terminal's location information and the coverage area of ​​the second cell on the ground, whether the terminal is actually located within the coverage area of ​​the second cell on the ground.

[0215] Optionally, when the first network device determines that the terminal is located within the coverage area of ​​a second cell on Earth, the first network device may further transmit NTN parameter information for the second satellite to the terminal. The NTN parameter information includes the parameter information necessary for the terminal to access the NTN (or second cell) corresponding to the second satellite. If the terminal accesses the NTN via the second satellite, the NTN parameter information includes parameter information such as the satellite ephemeris, the ephemeris validity period, and common timing advance parameters.

[0216] Optionally, when the first network device determines that the terminal is located within the coverage area of ​​a second cell on the ground, the first network device may further transmit indication information for the NTN parameter information of the second satellite to the terminal. The indication information indicates location information for the NTN parameters, for example, information about the system information block in which the NTN parameter information of the second satellite is located.

[0217] When the terminal is located within the coverage area of ​​the second cell on the ground, the first network device should be noted to transmit NTN parameter information for the second satellite and / or indication information for the NTN parameter information for the second satellite to the terminal. In this way, it can be ensured that the transmitted information is available to the terminal.

[0218] Optionally, the NTN parameter information of the second satellite and / or the indication information of the NTN parameter information of the second satellite may be provided to the terminal by the first network device in the process of notifying the terminal that a satellite change is occurring, for example, by being carried in the first message.

[0219] The purpose of the synchronization phase is to synchronize the terminal with a second network device corresponding to the second satellite, enabling it to receive downlink transmissions, such as broadcast messages, from the second network device. In one example, the synchronization phase includes step 1005b.

[0220] Step 1005b: The terminal performs downlink synchronization in the second cell to synchronize with the second network device corresponding to the second satellite.

[0221] In some cases, the second network device and the first network device may be the same network device. Alternatively, the second network device and the first network device may be different network devices. This is not limited to the embodiments of this application.

[0222] In a possible implementation of this application, the terminal synchronizes with a second network device before the end of coverage time for the first satellite on the ground and / or after the start of coverage time for the second satellite on the ground.

[0223] In one example, step 1005b may be performed in the following manner: The terminal searches for the downlink synchronization signal of the second cell in the first cell and performs downlink synchronization (for example, searching for the synchronization signal of the second cell and obtaining the downlink timing, i.e., obtaining the system frame, subframe, slot, and symbol boundaries of the second cell in the second satellite). Alternatively, the terminal updates its downlink synchronization in the second cell based on the position of the second satellite, the position of the first satellite, and the terminal's current position information, i.e., updating the downlink synchronization of the second cell currently achieved by the first terminal.

[0224] In possible embodiments of this application, when a terminal synchronizes with a second network device, as shown in Figure 10, the method provided in this embodiment of this application may further include the following steps: Step 1006b: The terminal initiates a random access process to the second network device.

[0225] An example is used for illustrative purposes. When a terminal synchronizes with a second network device, the terminal may immediately initiate a random access process to the second network device. Of course, the terminal may alternatively initiate the random access process when the first condition is met. The terminal initiates the random access process, thereby sending an uplink transmission to the second network device.

[0226] In one example, the first condition includes any one of the following: it is before the end of coverage for the first satellite, after the start of coverage for the second satellite, data transmission is required (e.g., downlink data is received from the second network device and / or uplink data is sent to the second network device), or the terminal's uplink time alignment timer has not expired.

[0227] If the terminal's uplink time alignment timer has not expired, it can be understood that there is uplink data to be transmitted between the terminal and the first network device corresponding to the first satellite, and that the transmission of the uplink data has not yet been completed.

[0228] In a possible implementation of this application, when the second condition is met, after the terminal has synchronized with the second network device, the terminal does not need to initiate a random access process to the second network device. In some examples, the second condition includes at least that the terminal's uplink time alignment timer has expired, or that the terminal does not require uplink data transmission, or that the terminal's uplink time alignment timer has not been started.

[0229] Optionally, if the terminal does not initiate a random access process to a second network device when the terminal's uplink time alignment timer has expired, the terminal may also initiate a random access process if uplink data transmission is subsequently required.

[0230] For specific implementations of how a terminal initiates a random access process to a second network device, please refer to the prior art descriptions, which are not limited to the embodiments of this application.

[0231] In an optional embodiment of this application, when a terminal accesses a second network device via a random access process, the method provided in this embodiment of this application may further include the following steps, as shown in Figure 10. Step 1007b: The second network device sends a first command (e.g., an uplink time alignment command) to the terminal. In response, the terminal receives a first command (e.g., an uplink time alignment command) from the second network device.

[0232] Step 1008b: The terminal restarts its uplink time alignment timer based on the first command.

[0233] In a possible implementation of this application, when the terminal is located within the coverage area of ​​the second satellite on the ground, the method provided in this embodiment of this application may further include: the terminal reacquiring the NTN parameter information of the second satellite before the NTN parameter information corresponding to the second satellite becomes invalid.

[0234] Optionally, the terminal should acquire the NTN parameter information of the second satellite before the first satellite departs (i.e., before the coverage end time of the first satellite). In other words, the terminal should ensure that the NTN parameter information of the second satellite is valid when the first satellite departs.

[0235] Optionally, the terminal may obtain NTN parameter information of the second satellite via the first satellite.

[0236] Optionally, the terminal may obtain NTN parameter information of the second satellite via the second satellite.

[0237] Optionally, when the terminal is located within the coverage area of ​​a second cell on the ground, the terminal may skip evaluating other CHO conditions. Optionally, the terminal may skip measuring candidate target cells corresponding to a CHO. Optionally, the terminal may release other CHO configurations. Optionally, the terminal may further transmit indication information to the first network device to indicate to the terminal to skip evaluation, skip measurement, or release a CHO configuration. Optionally, indication information for skipping evaluation, skipping measurement, or releasing a CHO configuration may be carried in a fourth message. In one example, a CHO configuration may be released using CHO identification information. For example, the terminal reports an identifier corresponding to a CHO configuration that needs to be released.

[0238] The above describes the solutions in embodiments of this application primarily from the perspective of interaction between network elements. To implement the above functions, it can be understood that each network element, for example, a first network device or terminal, includes a corresponding structure and / or a software module for performing each function. Those skilled in the art will readily realize, in combination with the example units and algorithmic steps described in the embodiments disclosed herein, that this application can be implemented by hardware, or by a combination of hardware and computer software. Whether the functions are performed by hardware or by hardware driven by computer software depends on the specific application and the design constraints of the technical solution. Those skilled in the art may implement the described functions using different methods for each specific application, but such implementations should not be considered to exceed the scope of this application.

[0239] In embodiments of this application, the first network device and terminal may be divided into functional units based on the above-described method example. For example, each functional unit may be obtained through division based on each corresponding function, or two or more functions may be integrated into a single processing unit. The integrated unit may be implemented in hardware form or in the form of a software functional unit. It should be noted that in embodiments of this application, the division into units is merely an example and is simply a logical functional division. Other division methods may be used in actual implementations.

[0240] The method in the embodiments of this application has been described above with reference to Figures 9 and 10. Below, a communication device provided in the embodiments of this application and capable of performing the above method will be described. Those skilled in the art will understand that the method and the device may be coupled and referenced to one another. The communication device provided in the embodiments of this application can perform the steps performed by the terminal and the first network device in the above communication method.

[0241] When an integrated unit is used, Figure 11 shows the communication device in the above embodiment. The communication device may include a communication module 113 and a processing module 112.

[0242] In an optional implementation, the communication device may further include a storage module 111 configured to store the communication device's program code and data.

[0243] In one example, the communication device is a terminal or a chip used within the terminal. In this case, the communication module 113 is configured to support the communication device when communicating with an external network element (e.g., a first network device). For example, the communication module 113 is configured to perform signal reception and transmission operations performed by the terminal in the above method embodiment. The processing module 112 is configured to perform signal processing operations performed by the terminal in the above method embodiment.

[0244] An example is used for illustrative purposes. The communication module 113 is configured to perform a receiving action performed by the terminal in step 901 of Figure 9 or step 1001 of Figure 10 in the above embodiment. The processing module 112 is configured to support the communication device when performing an action performed by the terminal in step 902 of Figure 9 or step 1002 of Figure 10.

[0245] When the terminal is located outside the coverage area of ​​the second cell on the ground, optionally, the communication module 113 is further configured to perform a transmit action performed by the terminal in step 1003a of Figure 10 in the above embodiment. Optionally, the communication module 113 is further configured to perform a transmit action performed by the terminal in step 1004a of Figure 10 in the above embodiment. Optionally, the communication module 113 is further configured to perform a receive action performed by the terminal in steps 1005a and / or step 1006a of Figure 10 in the above embodiment. Optionally, the processing module 112 is further configured to perform step 1007a of Figure 10 in the above embodiment. Optionally, the processing module 112 is further configured to perform steps 1008a and / or step 1009a of Figure 10 in the above embodiment.

[0246] When the terminal is located within the coverage area of ​​the second cell on the ground, optionally, the communication module 113 is further configured to perform a transmit action performed by the terminal in steps 1003b and / or 1004b of Figure 10 in the above embodiment. Optionally, the processing module 112 is further configured to perform steps 1005b and 1006b. Optionally, the communication module 113 is further configured to perform a receive action performed by the terminal in step 1007b of Figure 10 in the above embodiment. The processing module 112 is further configured to perform step 1008b.

[0247] In other examples, the communication device is a first network device or a chip used within the first network device. In this case, the communication module 113 is configured to support the communication device when communicating with an external network element (e.g., a terminal). For example, the communication module 113 is configured to perform signal reception and transmission operations performed by the first network device in the above method embodiment. The processing module 112 is configured to perform signal processing operations performed by the first network device in the above method embodiment.

[0248] An example is used for illustrative purposes. The communication module 113 is configured to perform a transmission action that is performed by the first network device in step 901 in Figure 9 or step 1001 in Figure 10 in the above embodiment.

[0249] Optionally, the communication module 113 is configured to perform a receive action that is performed by the first network device in step 1003a or step 1003b of Figure 10 in the above embodiment.

[0250] Optionally, the communication module 113 is configured to perform a receive action performed by the first network device in step 1004a or step 1004b of Figure 10 in the above embodiment.

[0251] Optionally, when the terminal is located outside the coverage area of ​​the second cell on the ground, the communication module 113 is configured to perform the transmission action performed by the first network device in step 1005a of Figure 10 in the above embodiment.

[0252] Optionally, when the terminal is located outside the coverage area of ​​the second cell on the ground, the communication module 113 is configured to perform the transmission action performed by the first network device in step 1006a of Figure 10 in the above embodiment.

[0253] It should be noted that in Figure 11, the communication module 113 may be replaced by a communication unit, the processing module 112 may be replaced by a processing unit, and the storage module 111 may be replaced by a storage unit. The processing unit is configured to control and manage the actions of the communication device. For example, the processing unit is configured to perform information / data processing steps performed by the communication device. The communication unit is configured to support the communication device when performing information / data transmission or reception steps.

[0254] In possible implementations, a communication unit may include a receiving unit and a transmitting unit. The receiving unit is configured to receive signals, and the transmitting unit is configured to transmit signals.

[0255] The processing module 112 may be a processor or controller, for example, a central processing unit, a general-purpose processor, a digital signal processor, an application-specific integrated circuit, a field-programmable gate array or other programmable logic device, a transistor logic device, a hardware component, or any combination thereof. The processor may implement or execute various exemplary logic blocks, modules, and circuits described in relation to the disclosures in this application. Alternatively, the processor may be a combination of processors that implement computing functions, for example, a combination of one or more microprocessors, or a combination of a digital signal processor and a microprocessor. The communication module may be a transceiver, a transceiver circuit, or a communication interface, etc. The storage module may be memory.

[0256] When the processing module 112 is a processor 1201 or a processor 1205, the communication module 113 is a communication interface 1203, the storage module 111 is a memory 1202, and the communication device in this application may be the communication device shown in Figure 12.

[0257] Figure 12 is a diagram of the hardware structure of a communication device according to an embodiment of this application. For the structure of the terminal and the first network device in an embodiment of this application, please refer to the diagram of the communication device structure shown in Figure 12. The communication device includes a processor 1201, a communication line 1204, and at least one communication interface (wherein communication interface 1203 is used as an example for illustrative purposes in Figure 12).

[0258] The processor 1201 may be a central processing unit (CPU), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits for controlling the program execution of the solution in this application.

[0259] The communication line 1204 may include a path for transmitting information between the above components.

[0260] The communication interface 1203 is configured to exchange information with other devices using any type of device, such as a transceiver, and to communicate with other devices or communication networks, such as Ethernet, a radio access network (RAN), or a wireless local area network (WLAN).

[0261] Optionally, the communication device may further include memory 1202.

[0262] The memory 1202 may be, but is not limited to, read-only memory (ROM), other types of static storage devices capable of storing static information and instructions, random access memory (RAM), or other types of dynamic storage devices capable of storing information and instructions, or it may be electrically erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM), other compact disc storage, optical disc storage (including compact discs, laser discs, optical discs, digital versatile discs, and Blu-ray discs), magnetic disc storage media, other magnetic storage devices, or any other medium capable of carrying or storing program code expected in the form of instructions or data structures and accessible by the computer. The memory may exist independently and be connected to the processor via communication line 1204. Alternatively, the memory may be integrated into the processor.

[0263] Memory 1202 is configured to store computer-executable instructions for performing the solution in this application, and processor 1201 controls the execution of computer-executable instructions. Processor 1201 is configured to execute computer-executable instructions stored in memory 1202 to perform the communication method provided in the above embodiments of this application.

[0264] Optionally, the computer executable instructions in this embodiment of this application may also be referred to as application program code. This is not particularly limited to the embodiments of this application.

[0265] In a specific implementation, the processor 1201 may include one or more CPUs, such as CPU0 and CPU1 in Figure 12.

[0266] In a specific implementation, the communication device may include a plurality of processors, for example, processors 1201 and 1205 in Figure 12. Each of the processors may be a single-core (single-CPU) processor or a multi-core (multi-CPU) processor. The processor may, in this context, be one or more devices, circuits, and / or processing cores configured to process data (e.g., computer program instructions).

[0267] Figure 13 is a diagram showing the structure of a chip 130 according to an embodiment of this application. The chip 130 includes one or more (including two) processors 1310 and a communication interface 1330.

[0268] Optionally, the chip 130 further includes memory 1340. Memory 1340 may include read-only memory and random access memory, and may provide operational instructions and data for the processor 1310. A portion of memory 1340 may further include non-volatile random access memory (NVRAM).

[0269] In some implementations, memory 1340 stores the following elements: executable modules or data structures, subsets thereof, or extensions thereof.

[0270] In this embodiment of the application, the corresponding operation is performed by calling an operation instruction stored in memory 1340 (wherein the operation instruction may be stored in the operating system).

[0271] In possible implementations, the structure of the chips used by the terminal and the first network device is similar, and different devices may use different chips to implement individual functions.

[0272] The processor 1310 controls the processing operations of either the terminal or the first network device. The processor 1310 is sometimes also referred to as the central processing unit (CPU).

[0273] Memory 1340 may include read-only memory and random-access memory, providing instructions and data for processor 1310. A portion of memory 1340 may further include NVRAM. For example, in application, memory 1340 and communication interface 1330 are coupled together using bus system 1320. In addition to the data bus, bus system 1320 may include power buses, control buses, and status signal buses, etc. However, for the sake of brevity, various types of buses are marked as bus system 1320 in Figure 13.

[0274] The methods disclosed in embodiments of this application may be applied to or implemented by a processor 1310. The processor 1310 may be an integrated circuit chip having signal processing capabilities. In the implementation process, each step of the above method may be completed using hardware integrated logic circuits or instructions in software form in the processor 1310. The processor 1310 may be a general-purpose processor, a digital signal processor (DSP), an ASIC, a field programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component. The processor may implement or execute the methods, steps, and logic block diagrams disclosed in embodiments of this application. The general-purpose processor may be a microprocessor, and the processor may be any conventional processor, etc. The steps in the methods disclosed in relation to embodiments of this application may be performed and completed directly by a hardware decoding processor, or they may be performed and completed using a combination of hardware and software modules in the decoding processor. The software module may be located in a storage medium that is mature in this field, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, or registers. The storage medium is located in memory 1340. The processor 1310 reads the information in memory 1340 and completes the steps of the method described above in combination with the hardware of the processor 1310.

[0275] In possible implementations, the communication interface 1330 is configured to perform the receiving and transmitting steps of the terminal and the first network device in the embodiments shown in Figures 9 and 10. The processor 1310 is configured to perform the processing steps of the terminal and the first network device in the embodiments shown in Figures 6 to 10.

[0276] A communication module may be a communication interface for a device and is configured to receive signals from other devices. For example, when a device is implemented as a chip, the communication module is a communication interface used by the chip to receive signals from or transmit signals to other chips or devices.

[0277] In one embodiment, a computer-readable storage medium is provided. The computer-readable storage medium stores instructions, and when an instruction is executed, a function is realized that is performed by a terminal in Figure 9 or Figure 10.

[0278] In one embodiment, a computer-readable storage medium is provided. The computer-readable storage medium stores instructions, and when an instruction is executed, a function is realized that is performed by the first network device in Figure 9 or Figure 10.

[0279] In one embodiment, a computer program product containing instructions is provided. The computer program product contains instructions, and when the instructions are executed, a function is realized that is performed by the terminal in Figure 6.

[0280] In another embodiment, a computer program product including instructions is provided. The computer program product includes instructions. When the instructions are executed, a function is realized that is performed by the first network device in Figure 9 or Figure 10.

[0281] In one embodiment, a chip is provided. The chip is used in a terminal and includes at least one processor and a communication interface. The communication interface is coupled to at least one processor. The processor is configured to execute instructions to realize a function performed by the terminal in Figure 9 or Figure 10.

[0282] In another embodiment, embodiments of this application provide a chip used within an access management network element. The chip includes at least one processor and a communication interface. The communication interface is coupled to at least one processor. The processor is configured to execute instructions to realize a function performed by the first network device in Figure 9 or Figure 10.

[0283] Embodiments of this application provide a communication system, the communication system including a first network device and a terminal. The first network device is configured to perform functions performed by the first network device in Figure 9 or Figure 10, and the terminal is configured to perform functions performed by the terminal in Figure 9 or Figure 10.

[0284] All or part of the embodiments described above may be implemented using software, hardware, firmware, or any combination thereof. When software is used to implement an embodiment, all or part of the embodiment may be implemented in the form of a computer program product. A computer program product includes one or more computer programs or instructions. When a computer program or instruction is loaded onto a computer and executed, the procedure or function in the embodiments of this application is executed in whole or in part. The computer may be a general-purpose computer, a dedicated computer, a computer network, a network device, user equipment, or other programmable device. The computer program or instruction may be stored on a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, a computer program or instruction may be transmitted by wire or wirelessly from one website, computer, server, or data center to another website, computer, server, or data center. The computer-readable storage medium may be any available medium accessible by a computer, or a data storage device that integrates one or more available media, such as a server or data center. The available media may be magnetic media, such as floppy disks, hard disks, or magnetic tapes; optical media, such as digital video discs (DVDs); or semiconductor media, such as solid-state drives (SSDs).

[0285] Although this application has been described in connection with embodiments, in the process of implementing this application for which protection is claimed, those skilled in the art can understand and implement other variations of the disclosed embodiments by looking at the accompanying drawings, the disclosed content, and the appended claims. In the claims, "comprising" does not exclude other components or other steps, and "a" or "one" does not exclude multiple cases. A single processor or other unit can implement the various functions listed in the claims. Although some means are recorded in different dependent claims, this does not mean that these means cannot be combined to produce better effects.

[0286] Although this application has been described in connection with specific features and their embodiments, it is clear that various modifications and combinations can be made to this application without departing from the spirit and scope of this application. Correspondingly, the specification and the accompanying drawings are merely illustrative descriptions of this application defined by the appended claims, and are also considered to cover any or all modifications, variations, combinations, or equivalents within the scope of this application. It is clear that those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Thus, this application is intended to cover these modifications and variations of this application as long as they fall within the scope of the claims of this application and their equivalent technologies.

Claims

1. A communication method performed by a communication device, Steps include: receiving a first message from a first network device, the first message indicating that the satellite providing service to a first cell is being updated from a first satellite to a second satellite, the first cell being a cell accessed by the communication device, the first network device corresponding to the first satellite, the first message including first information, the first information being used to determine the coverage area of ​​a second cell on the ground serviced by the second satellite, and the first cell and the second cell having the same cell identifier; A step of determining whether the communication device is located within or outside the coverage area based on the first message, the location of the communication device, and the coverage area of ​​the second cell on the ground. Includes, If the communication device is located outside the coverage area of ​​the second cell on the ground, which is serviced by the second satellite, the communication method is: The steps include receiving a third message from the first network device, wherein the third message indicates to the communication device to switch to a target cell, the target cell and the first cell have different cell identifiers, and the communication device is located within the coverage area of ​​the target cell; Based on the third message, the steps include changing the serving cell of the communication device from the first cell to the target cell, and A communication method that further includes this.

2. After the step of determining whether the communication device is located within or outside the coverage area based on the location of the communication device and the coverage area of ​​the second cell on the ground, the communication method: A step of transmitting a second message to the first network device, the second message indicating that the communication device is located within the coverage area of ​​the second cell on the ground, or the second message indicating that the communication device is located outside the coverage area of ​​the second cell on the ground. The communication method according to claim 1.

3. After the step of determining whether the communication device is located within or outside the coverage area based on the location of the communication device and the coverage area of ​​the second cell on the ground, the communication method: A step of transmitting location information of the communication device and / or measurement report information of the communication device to the first network device, the measurement report information further comprising the step of including information indicating the signal quality of adjacent cells of the communication device. The communication method according to claim 1.

4. If the communication device is located within the coverage area of ​​the second cell on the ground, which is serviced by the second satellite, the communication method is: The steps include performing downlink synchronization in the second cell to synchronize with a second network device corresponding to the second cell, wherein the second network device corresponds to the second satellite, The communication method according to claim 1.

5. When the first condition is met, the communication method is The step of initiating a random access process to the second network device, wherein the first condition is as follows: It is before the end of coverage time for the first satellite on the ground. This is after the start time of coverage of the second satellite on the ground. The need for data transmission, or The uplink time alignment timer of the aforementioned communication device has not expired. The step further includes one or more of the following: The communication method according to claim 4.

6. When the second condition is met, the communication device does not need to initiate a random access process to the second network device, and the second condition includes at least the uplink time alignment timer of the communication device having expired or the uplink time alignment timer of the communication device not having started. The communication method according to claim 4.

7. The third message includes first configuration information, which is used by the communication device to determine information about the target cell. The step of changing the serving cell of the communication device from the first cell to the target cell based on the third message is: A step of determining the information about the target cell based on the first configuration information, A step of changing the serving cell of the communication device from the first cell to the target cell based on the information about the target cell. including, The communication method according to claim 1.

8. The third message includes second configuration information, the second configuration information includes cell handover conditions configured for the communication device, The step of changing the serving cell of the communication device from the first cell to the target cell based on the third message is: The process includes the step of changing the serving cell of the communication device from the first cell to the target cell when the cell handover condition included in the second configuration information is met, The communication method according to claim 1.

9. The first message includes a first time parameter and / or a second time parameter, the first time parameter being used to determine the coverage start time of the second satellite corresponding to the second cell on the ground, and the second time parameter being used to determine the coverage end time of the second satellite corresponding to the second cell on the ground. The aforementioned communication method is, The further steps include synchronizing with a second network device corresponding to the second satellite after the coverage start time of the second satellite on the ground, based on the first time parameter and / or the second time parameter, or transmitting a second message to the first network device before the coverage start time of the second satellite on the ground. The communication method according to claim 1.

10. The first message above contains the following information, namely, Time information for performing downlink synchronization in the second cell, NTN parameter information of the second satellite, wherein the NTN parameter information includes parameter information necessary for the communication device to access the NTN corresponding to the second satellite. A third indication information, wherein the third indication information indicates the position information of the NTN parameter information, or Information relating to a measurement timing configuration, which, based on the measurement timing configuration, indicates to the communication device to search for the downlink synchronization signal of the second cell in the second satellite. Including one or more of the following: The communication method according to claim 1.

11. A communication method performed by a communication device corresponding to a first satellite, Steps include: transmitting a first message, the first message indicating that the satellite providing service to a first cell is being updated from the first satellite to a second satellite; the first message includes first information, the first information being used to determine the coverage area of ​​the second cell on the ground, which is serviced by the second satellite; and the first cell and the second cell having the same cell identifier. Includes, When the communication device determines that the first terminal accessing the first cell is located outside the coverage area of ​​the second cell on the ground, the communication method A communication method further comprising the step of sending a third message to a first terminal to access, the third message indicating to the first terminal to switch to a target cell, the target cell and the first cell having different cell identifiers, and the first terminal being located within the coverage area of ​​the target cell.

12. The first message includes a first time parameter and / or a second time parameter, The first time parameter is used to determine the coverage start time of the second satellite corresponding to the second cell on the ground. The second time parameter is used to determine the coverage end time of the second satellite corresponding to the second cell on the ground. The communication method according to claim 11.

13. The first message above contains the following information, namely, The terminal transmits time information to perform downlink synchronization in the second cell via the second satellite. The NTN parameter information of the second satellite, wherein the NTN parameter information includes parameter information necessary for a terminal to access the second satellite. A third indication information, wherein the third indication information indicates the position information of the NTN parameter information, or Information relating to a measurement timing configuration, which, based on the measurement timing configuration, is shown to the terminal to search for the downlink synchronization signal of the second cell on the second satellite. Including one or more of the following: The communication method according to claim 11.

14. The first message includes the information regarding the measurement timing configuration, wherein the measurement timing configuration is configured based on the downlink timing relationship of the first cell in the first satellite, or the measurement timing configuration is configured based on the downlink timing relationship of the second cell in the second satellite, wherein the downlink timing relationship is used to determine the first subframe number and the first system frame number of the downlink synchronization signal of the second cell. The communication method according to claim 13.

15. The aforementioned communication method is, A step of transmitting first configuration information and / or second configuration information to the first terminal, further comprising the steps of: the first configuration information being used by the first terminal to determine information about the target cell; and the second configuration information being used by the first terminal to determine cell handover conditions. The communication method according to claim 11.

16. The first configuration information and the second configuration information, or both, are determined based on the location information and / or measurement report information of the first terminal, wherein the measurement report information includes information indicating the signal quality of adjacent cells of the first terminal. The communication method according to claim 15.

17. The aforementioned communication method is, A step of receiving a second message from a first terminal, wherein the first terminal is a terminal that accesses the first cell, The steps of determining, based on the second message, that the first terminal is located outside the coverage area of ​​the second cell on the ground, or that the first terminal is located within the coverage area of ​​the second cell on the ground. Further including, The communication method according to claim 11.

18. The second message includes location information of the first terminal, and the step of determining, based on the second message, that the first terminal is located outside the coverage area of ​​the second cell on the ground, or that the first terminal is located within the coverage area of ​​the second cell on the ground, The process includes determining, based on the location information of the first terminal and the coverage area of ​​the second cell on the ground, whether the first terminal is located outside the coverage area of ​​the second cell on the ground or within the coverage area of ​​the second cell on the ground. The communication method according to claim 17.

19. A computer-readable storage medium, wherein the computer-readable storage medium stores instructions, and when an instruction is executed, the communication method described in any one of claims 1 to 10 or the communication method described in any one of claims 11 to 17 is performed.

20. A communication device comprising at least one processor, wherein the at least one processor is connected to a communication interface, the communication interface is configured to receive or transmit information, and the at least one processor is configured to execute instructions stored in memory to perform the communication method according to any one of claims 1 to 10.

21. A communication device comprising at least one processor, wherein the at least one processor is connected to a communication interface, the communication interface is configured to receive or transmit information, and the at least one processor is configured to execute instructions stored in memory to perform the communication method according to any one of claims 11 to 17.

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