Non-ground 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

[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 entireties 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, provide more data transmission resources and support more connections.

[0004] When a satellite provides services to a cell, each satellite covers one or more cells on the ground. Since the satellite is a moving body, the satellite may have different coverage areas on the ground at different times as the satellite moves. However, generally, the cell accessed by the terminal remains unchanged for a certain period. Only after the old satellite can no longer provide services to a physical area (e.g., a cell) due to the movement of the old satellite does the new satellite provide services. Generally, the services are provided by other satellites in the same orbit. To increase the distance between satellites, the distance between two satellites becomes longer. Since 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 the cell on the ground served by the new satellite may also be different from the coverage area of the cell on the ground served by the old satellite. Therefore, when alternating between the new satellite and the old satellite, it is an urgent technical problem to be solved how the terminal can sense whether it is located within the coverage area of the cell on the ground served by the new satellite so as to be more beneficial to the NTN communication system.

SUMMARY OF THE INVENTION

[0005] Embodiments of this application provide a communication method, apparatus, and system for triggering a terminal to sense whether the terminal is located within the coverage area of a cell on the ground 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 subsequent terminal when alternating between the new satellite and the old satellite.

[0006] According to a first aspect, embodiments of this application provide a communication method including: A terminal receives a first message from a first network device. The first message indicates that a satellite providing services to a first cell is 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 the first satellite, the first message includes first information, and the first information is used to determine a coverage area of a second cell on the ground served by the second satellite. In response to the first message, the terminal determines whether the terminal is located within the coverage area or outside the coverage area based on the position of the terminal and the coverage area of the second cell on the ground. The first cell and the second cell have the same cell identifier.

[0007] This embodiment of this application provides a communication method. In this method, when it is determined that the satellite providing services to the first cell is updated from the first satellite to the second satellite, that is, when there is an alternation between the new satellite and the old satellite, the first network device transmits a first message to the terminal. Since the first message indicates to the terminal that the satellite providing services to the first cell is updated from the first satellite to the second satellite, the terminal can sense that the satellite covering the first cell has changed. The second satellite provides services to the second cell, and the first cell and the second cell have the same cell identifier. Although the first cell and the second cell have the same cell identifier, the coverage areas of the first cell and the second cell on the ground may be different. The terminal may be located outside the coverage area of the second cell on the ground or may be located within the coverage area of the second cell on the ground. Therefore, in order to avoid communication interruption caused by the case where the terminal cannot normally access the second cell when the terminal is located outside the coverage area of the second cell, in this application, the first network device transmits information about the coverage area of the second cell on the ground served by the second satellite to the terminal, so that the terminal can further determine whether the terminal is located within the coverage area of the second cell on the ground or outside the coverage area with reference to the position of the terminal, and take appropriate processing measures.

[0008] In a possible implementation of this application, based on the position of the terminal and the coverage area of the second cell on the ground, after the terminal determines whether it is located within the coverage area or outside the coverage area, the method provided in this embodiment of this application may further include the following. The terminal sends a second message to the 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. After the second message is sent, 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 then performs subsequent processing.

[0009] In a possible implementation of this application, the second message includes second indication information, and the second indication information indicates that the terminal is located within the coverage area of the second cell on the ground served by the second satellite. Alternatively, the second indication information indicates that the terminal is located outside the coverage area of the second cell on the ground served by the second satellite. For example, the second indication information may be a first indicator, and the first indicator indicates that the terminal is located within the coverage area of the second cell on the ground served by the second satellite. The second indication information may be a second indicator, and the second indicator indicates that the terminal is located outside the coverage area of the second cell on the ground served by the second satellite. The second indication information is carried in the second message, whereby the second indication information can be shown to the first network device in an explicit manner.

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

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

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

[0013] In a possible implementation of this application, 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, the terminal synchronizes with the second network device corresponding to the second cell.

[0014] In a possible implementation of this application, when the terminal synchronizes with the second network device, the method provided in this embodiment of this application may further include the following. The terminal starts a random access process to the second network device. In this way, the terminal executes subsequent communication through the established connection with the second network device, for example, receives a downlink transmission delivered by the second network device, or transmits an uplink transmission to the second network device.

[0015] In a possible implementation of this application, when the following first condition is satisfied, the terminal starts a random access process to the second network device. The first condition includes any one or more of the following, namely, being before the coverage end time of the first satellite on the ground, being after the coverage start time of the second satellite on the ground, requiring data transmission, or the uplink time alignment timer of the terminal not expiring.

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

[0017] In a possible implementation of this application, in this embodiment of this application, the method provided further includes the following. The terminal receives a first command (for example, an uplink timing alignment command) from a second network device in a random access process. The terminal restarts the uplink timing alignment timer of the terminal based on the uplink timing 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, in this embodiment of this application, the method provided further includes the following. The terminal skips evaluating other CHO conditions, or the terminal skips measuring candidate target cells corresponding to the CHO configuration, or the terminal releases other CHO configurations.

[0019] In a possible implementation of this application, when the terminal is located within the coverage area of a second cell on the ground, in this embodiment of this application, the method provided further includes the following. The terminal sends a fifth message to the first network device, and the fifth message indicates to 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 information that indicates to 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 the terminal is located outside the coverage area of the second cell on the ground, the method provided in this embodiment of this application further includes the following. The terminal receives a third message from the first network device. The third message indicates to the terminal to switch to the target cell, and the target cell and the first cell have different cell identifiers, and the terminal is located within the coverage area of the target cell. The terminal changes the serving cell of the terminal 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 indicating to 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, and the first configuration information is used by the terminal to determine information about the target cell. Correspondingly, the terminal changing the serving cell of the terminal from the first cell to the target cell based on the third message includes the following. The terminal determines information about the target cell based on the first configuration information, and the terminal changes the serving cell of the terminal 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, and the second configuration information includes cell handover conditions configured for the terminal. The terminal changing the serving cell of the terminal from the first cell to the target cell based on the third message includes the following. When the cell handover conditions included in the second configuration information are satisfied, the terminal changes the serving cell of the terminal 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 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. The method provided in this embodiment of this application further includes the following. Based on the first time parameter and / or the second time parameter, the terminal synchronizes with a second network device corresponding to the second satellite after the coverage start time of the second satellite on the ground, or sends a 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 includes the following information, that is, time information for the terminal to perform downlink synchronization in the second cell, NTN parameter information of the second satellite, where the NTN parameter information includes parameter information required for the terminal to access the NTN corresponding to the second satellite, NTN parameter information, third indication information, where the third indication information indicates the position information of the NTN parameter information, third indication information, or information about the measurement timing configuration for indicating to the terminal to search for the downlink synchronization signal of the second cell in the second satellite based on the measurement timing configuration, and further includes one or more of the above information.

[0026] According to a second aspect, an embodiment of this application provides a communication method including the following. A first network device corresponding to a first satellite sends a first message, and the first message indicates that the satellite providing services to a first cell is updated from the first satellite to a second satellite. The first message includes first information, and the first information is used to determine the coverage area of a second cell on the ground served by the second satellite. The first cell and the second cell 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, namely, 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 required 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 a 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, where 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, where 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, where 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 location information of the first terminal and / or the measurement report information of the first terminal, and the measurement report information includes information indicating the signal quality of the adjacent cells of the first terminal.

[0033] 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, where 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 the location information of the first terminal, and the first network device determines, based on the second message, whether the first terminal is located outside the coverage area of the second cell on the ground or whether the first terminal is located within the coverage area of the second cell on the ground, which includes the following. 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, whether the first terminal is located outside the coverage area of the second cell on the ground or whether the first terminal is located within the coverage area of the second cell on the ground.

[0035] According to a third aspect, an embodiment of this application provides a communication device. The communication device can implement the method in any one of the first aspect or the possible implementations of the first aspect, and thus can also achieve the advantageous effects in any one of the first aspect or the possible implementations of the first aspect. The communication device may be a terminal, or a device that supports a terminal when implementing the method in any one of the first aspect or the possible implementations of the first aspect, for example, a chip used in the terminal. The communication device can implement the above method by using software or hardware, or by executing corresponding software by hardware.

[0036] In one example, an embodiment of this application provides a communication device. The communication device is a terminal or a chip used within the 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, where the first message indicates that a satellite providing services to a first cell is 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 the first satellite, the first message includes first information, the first information is used to determine the coverage area of a second cell on the ground served by the second satellite, and the first cell and the second cell have the same cell identifier. The processing unit is configured to determine whether the terminal is located within the coverage area or outside the coverage area based on the first message, the position of the terminal, and the coverage area of the 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 the first network device, where the second message indicates that the terminal is located within the coverage area of the second cell on the ground, or the second message indicates that the terminal is located outside the coverage area of the second cell on the ground.

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

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

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

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

[0042] In a possible implementation of this application, when the terminal is located outside the coverage area of a second cell on the ground that is served by a second satellite, the communication unit is to receive a third message from the first network device, where the third message indicates to the terminal to switch to a target cell, the target cell and the first cell have different cell identifiers, and the terminal is further configured to be 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, the third message includes first configuration information, and the first configuration information is used by the terminal to determine information about the target cell. The processing unit is specifically configured to determine information about the target cell based on the first configuration information. The processing unit is configured to change the serving cell of the terminal 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, and 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 serving cell of the terminal 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 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. The processing unit is further configured to synchronize with a second network device corresponding to the second satellite after the coverage start time of the second satellite on the ground or transmit a second message to a 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 includes one or more of the following information, namely, time information for the terminal to perform downlink synchronization in the second cell; NTN parameter information of the second satellite, where 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 position information of the NTN parameter information; or information about the measurement timing configuration for indicating to the terminal to search for the downlink synchronization signal of the second cell in the second satellite based on the measurement timing configuration.

[0047] According to a fourth aspect, an embodiment of this application provides a communication device. The communication device can implement the method in any one of the second aspect or the possible implementations of the second aspect, and thus can also achieve the advantageous effects in any one of the second aspect or 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 any one of the second aspect or the possible implementations of the second aspect, for example, a chip used within the first network device. The communication device can implement the above method by using software or hardware, or by executing the corresponding software by hardware.

[0048] In one example, an embodiment of this application provides a communication device. The communication device is a first network device or a chip used within the 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, where the first message indicates that a satellite providing services to a first cell is updated from a first satellite to a second satellite, the first message includes first information, and the first information is used to determine the coverage area of a second cell on the ground served by the second satellite, and the first cell and the second cell have 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 is used to determine the coverage start time of the second satellite corresponding to the 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.

[0050] 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 via the second satellite; NTN parameter information of the second satellite, where the NTN parameter information includes parameter information required 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 the measurement timing configuration for indicating to the terminal to search for the downlink synchronization signal of the second cell in the second satellite based on the measurement timing configuration.

[0051] In a possible implementation of this application, the first message includes information about the measurement timing configuration, and 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, and 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.

[0052] In a possible implementation of this application, the communication unit is further configured to send a third message to the first terminal to be accessed, and the third message indicates to 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 send the first configuration information and / or the 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.

[0054] 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 location information of the first terminal and / or the measurement report information of the first terminal, and the measurement report information includes information indicating the signal quality of the adjacent cells of the first terminal.

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

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

[0058] According to a sixth aspect, an embodiment of this application provides a computer-readable storage medium. The computer-readable storage medium stores a computer program or instructions. When the computer program or instructions are executed on a computer, the computer is capable of executing the communication method described in any one of the second aspect or the possible implementations of the second aspect.

[0059] According to a seventh aspect, an embodiment of this application provides a computer program product including instructions. When the instructions are executed on a computer, the computer is capable of executing the communication method described in any one of the first aspect or the possible implementations of the first aspect.

[0060] According to an eighth aspect, an embodiment of this application provides a computer program product including instructions. When the instructions are executed on a computer, the computer can execute the communication method described in any one of the second aspect or possible implementations of the second aspect.

[0061] According to a ninth aspect, an embodiment of this application provides a communication device configured to implement various methods in any possible design of the first aspect and the second aspect. The communication device may be the above terminal, or a device including the above terminal, or a component (for example, a chip) used in the terminal. Alternatively, the communication device may be the above first network device, or a device including the above first network device, or the communication device may be a component (for example, a chip) used in the first network device. The communication device includes corresponding modules or units for implementing the above methods. The modules or units can be realized by using hardware or software, or by executing corresponding software by hardware. The hardware or software includes one or more modules or units corresponding to the above functions.

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

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

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

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

[0067] According to the 13th aspect, an embodiment of this application provides a communication device. The communication device includes one or more modules configured to implement the method in either the 1st aspect or the 2nd aspect, and the one or more modules may correspond to the steps in the method in either the 1st aspect or the 2nd aspect.

[0068] According to the 14th aspect, an embodiment of this application provides a chip. The chip includes 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 the communication method described in either the 1st aspect or any one of the possible implementations of the 1st aspect. The communication interface is configured to communicate with modules other than the chip.

[0069] According to the 15th aspect, an embodiment of this application provides a chip. The chip includes 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 the communication method described in either the 2nd aspect or any one of the possible implementations of the 2nd aspect. The communication interface is configured to communicate with modules other than the chip.

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

[0071] According to the 16th aspect, an embodiment of this application provides a communication system. The communication system includes a terminal and a first network device. The first network device is configured to execute the communication method in either the 2nd aspect or any one of the possible implementations of the 2nd aspect. The terminal is configured to execute the communication method in either the 1st aspect or any one of the possible implementations of the 1st aspect.

[0072] Any apparatus, computer storage medium, computer program product, chip, or communication system provided above is configured to execute the corresponding method provided above. Therefore, for the advantageous effects that can be achieved by the apparatus, computer storage medium, computer program product, chip, or communication system, reference may be made to the advantageous effects of the corresponding solutions in the corresponding method provided above. For details, they will not be described again here.

Brief Description of the Drawings

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Figure 13

Embodiments for Carrying Out the Invention

[0074] In this application, "at least one" means one or more, and "a plurality of" means two or more. The term "and / or" describes the association relationship between related objects and indicates that three relationships can exist. For example, A and / or B can represent the following cases, namely, only A exists, both A and B exist, and only B exists, and A and B can be singular or plural. The symbol " / " generally indicates the "or" relationship between related objects. "At least one of the following items (components)" or a similar expression indicates any combination of these items, including a single item (component) or any combination of multiple items (components). For example, at least one item (component) of a, b, or c can represent a, b, c, a and b, a and c, b and c, or a, b, and c, and a, b, and c can be singular or plural.

[0075] The technical solution in this application can be applied to various communication systems, such as long time evolution (LTE) systems, LTE frequency division duplex (FDD) systems, LTE time division duplex (TDD) systems, universal mobile telecommunications system (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 architecture and service scenarios described in the embodiments of this application are intended to more clearly illustrate the technical solution in the embodiments of this application and do not constitute a limitation on the technical solution provided in the embodiments of this application. Those skilled in the art can know that with the evolution of the network architecture and the emergence of new service scenarios, the technical solution provided in the embodiments of this application can also be applicable to similar technical problems.

[0077] In terrestrial communication, one 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 are maintained without change for a very long time. However, in satellite communication, since the satellite moves at high speed, the physical area (e.g., a cell) on the ground covered by the satellite changes. Of course, the following placement solutions are used for the satellite's cell identifier and broadcast area identifier. Solution (1): As shown in Fig. 1(a), an association relationship between a cell identifier and a physical area is established. Specifically, for the physical area, the cell identifier and the broadcast area identifier corresponding to the physical area are maintained without change. After the satellite (abbreviated as satellite 1) moves, another satellite (abbreviated as satellite 2) provides services to the physical area. The cell identifier and the 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 for the physical area, the position of the UE (user equipment, also referred to as user device or terminal) is maintained without change. Since the terminal senses that the cell remains unchanged, the network device does not need to trigger the cell handover process for the terminal, the number of handovers in the network is reduced, and the signaling overhead of the radio interface is reduced. In this solution, generally, the satellite always provides services to the physical area within a certain period (i.e., the satellite always covers the physical area). Due to the movement of the satellite, when the satellite cannot provide services to the physical area, another satellite provides services to the physical area. As shown in Fig. 1(a), when satellite 1 is at geographical position 2 at time T+T1, the cell identifier of the cell included in the terrestrial coverage area is cell 2, and when satellite 1 is at geographical position 1 at time T, the cell identifier of the cell included in the terrestrial coverage area is cell 1.

[0078] Solution (2): As shown in FIG. 1(b), the cell identifier is associated with a satellite. When the coverage area of the satellite changes due to the movement of the satellite, the cell identifier of the satellite is maintained without being changed. In this solution, it can be understood that as the satellite moves, the cell identifier is scanned in the physical coverage area. In this solution, even if the position of the terminal is maintained without change, when the coverage area of the satellite on the ground cannot cover the terminal due to the movement of the satellite, the network side needs to notify the terminal to perform a handover to switch to another cell. As shown in FIG. 1(b), since the cell identifier is associated with the satellite, when satellite 1 is at geographical position 2 at time T+T1, the cell identifier of the cell included in the coverage area on the ground is cell 1, and when satellite 1 is at geographical position 1 at time T, the cell identifier of the cell included in the coverage area on the ground is cell 1. In FIG. 1(b), although the cells served by satellite 1 at different geographical positions have the same cell identifier, the coverage areas of the cells at different geographical positions may be different.

[0079] In a new radio (NR) system, non-terrestrial networks (NTN) are introduced. In NTN, a base station or some functions of a base station are deployed on a high-altitude platform or a satellite to provide seamless coverage for terminals. Since the satellite moves around the earth and the terminal also moves relative to the earth, the satellite corresponding to the cell accessed by the terminal currently using the network service changes from one satellite to another. To ensure communication continuity and service quality, the terminal needs to sense the alternation between the new satellite and the old satellite and determine whether the terminal is located within the range of the coverage area of the cell on the ground served by the new satellite.

[0080] As shown in FIG. 2 or FIG. 3, an embodiment of this application provides a communication system. The communication system includes one or more terminals (for example, terminals 1 to n), a network device 100, and a satellite 200. The terminal accesses a cell 300, and the cell 300 is one of the one or more cells covered by the network device 100. The cell 300 may be served by the satellite 200, or the cell 300 may be a terrestrial cell covered by the satellite 200.

[0081] The terminal is located on the surface of the earth, and the satellite 200 and the following satellite 400 are located in the earth's orbit. The satellite 200 or the satellite 400 can provide a communication service to a physical area (for example, cell 300 or cell 500) covered by a signal, and can communicate with a terminal located within the range of the physical area covered by the signal.

[0082] In one example, a satellite generally generates one or more beams on the ground (also referred to as beam footprints), and the one or more beams form a cell on the ground.

[0083] In satellite communication, since the satellite moves at high speed, the physical area on the ground covered by the satellite changes. Therefore, the coverage area of the same satellite on the ground may be different at different times. Assume that the satellite 200 serves the cell 300 during a first period. The start time of the first period is the coverage start time of the satellite 200 on the ground, and the end time of the first period is the coverage end time of the satellite 200 on the ground. The network device 100 corresponds to the satellite 200 during the first period.

[0084] As shown in (a) of FIG. 2 or (a) of FIG. 3, at time point 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 point T1 includes the coverage area of cell 300 on the ground. Due to the movement of satellite 200, at time point 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 (b) of FIG. 2, satellite 400 may cover the coverage area of cell 300 on the ground, or it may be considered that the coverage area of cell 500 on the ground covered by satellite 400 is 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 (c) of FIG. 2, at time point T3, the coverage area of cell 300 is covered by satellite 400, or at time point T3, cell 500 on the ground covered by satellite 400 may be considered as cell 300.

[0085] It can be understood that when satellite 200 provides services to cell 300, cell 300 can be one of the one or more cells covered by network device 100. In this case, any one of terminals 1 to n can communicate with satellite 200 via network device 100. When satellite 400 provides services to cell 500, cell 500 can be one of the one or more cells covered by network device 600. In this case, any one of terminals 1 to n can communicate with satellite 200 via network device 600. Of course, network device 100 and network device 600 can be the same network device. Specifically, although the satellite providing services to the cell changes, the network device accessed by the terminal is maintained without change.

[0086] In one example, network device 600 and network device 100 may be the same network device. Specifically, although the satellite providing services to cell 300 changes from satellite 200 to satellite 400, the network device to which cell 300 belongs is maintained without change. In other examples, network device 600 and network device 100 are different network devices. Specifically, the satellite providing services to cell 300 changes from satellite 200 to satellite 400, and the network device to which cell 300 belongs also changes.

[0087] When the cells served by satellite 400 and satellite 200 have the same cell identifier, it should be noted that the coverage area of cell 500 on the ground served by satellite 400 can be the same as the coverage area of cell 300 on the ground served by satellite 200, as shown in Fig. 2(b). However, the scenario shown in Fig. 3(b) may exist. The coverage area of cell 500 on the ground served by satellite 400 is different from the coverage area of cell 300 on the ground served by satellite 200. For example, there is an intersection of the coverage areas. Of course, there may also be no intersection between the coverage area of cell 500 on the ground served by satellite 400 and the coverage area of cell 300 on the ground served by satellite 200. As a result, the difference between Fig. 2 and Fig. 3 is as follows. In Fig. 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 Fig. 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, and terminals 2 to n are located within the coverage area of cell 500 on the ground.

[0088] Figs. 2(c) and 3(c) are diagrams showing that satellite 2 covers cell 500 after satellite 1 has left.

[0089] In a possible embodiment of this application, the communication system shown in FIG. 2 or FIG. 3 may further include a core network device (not shown). The core network device is a device in a core network (CN) that provides service support to terminals. Currently, examples of some core network devices include an access and mobility management function (AMF) entity, a session management function (SMF) entity, and a user plane function (UPF) entity, which are not enumerated one by one here. The AMF entity may be responsible for access management and mobility management of terminals. The SMF entity is responsible for session management, for example, establishing user sessions. The UPF entity may be a functional entity on the user plane and is mainly responsible for connecting to external networks. It should be noted that the entities in this application may also be referred to as network elements or functional entities. For example, the AMF entity may also be referred to as an AMF network element or an AMF functional entity. As another example, the SMF entity may also be referred to as an SMF network element or an SMF functional entity.

[0090] Specifically, the satellite in the embodiment of this application can be regarded as a spacecraft carrying a transparent payload (which can also be a bent pipe payload) or a regenerative payload signal transmitter. The satellite typically travels within a low earth orbit (LEO) at an altitude of 300 kilometers (km) to 1500 km, within a medium earth orbit (MEO) at an altitude of 7000 km to 25000 km, within a geostationary earth orbit (GEO) at an altitude of 35786 km, or within a high elliptical orbit (HEO) at an altitude of 400 km to 50000 km. In other words, the satellite can be classified into LEO satellites, MEO satellites, GEO satellites, HEO satellites, etc. based on different orbital altitudes.

[0091] The terminal in the embodiments of this application may also be referred to as a user equipment (UE), a mobile station (MS), or a mobile terminal (MT), etc., and is a device that provides a voice and / or data connection to a user, for example, a handheld device or an in-vehicle device with a wireless connection function. Currently, some examples of terminals include mobile phones, tablet computers, notebook computers, palmtop computers, mobile internet devices (MIDs), 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 grid, wireless terminals in transportation safety, wireless terminals in smart city, and wireless terminals in smart home.

[0092] The network device in the embodiment of this 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) system or a 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 radio communication system. Alternatively, the network device may be an access point (AP) in a Wireless Local Area Network (WLAN), a relay station, a network device in a future evolved Public Land Mobile Network (PLMN), or a network device in an NTN communication system, etc.

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

[0094] In addition, in the network structure, as shown in FIG. 4, the network device may include a central unit (CU) node, a distributed unit (DU) node, or a radio access network (RAN) device including the CU node and the DU node. The RAN device including the CU node and the DU node divides the protocol layers of the gNB in the NR system. The functions of some protocol layers are centrally controlled by the CU. The functions of some or all of the remaining protocol layers are distributed within the DU, and the CU centrally controls the DU. Optionally, as shown in FIG. 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 the control plane functions and mainly includes the RRC layer and the packet data convergence protocol (PDCP) layer corresponding to the control plane, i.e., 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 the user plane functions and mainly includes the service data adaptation protocol (SDAP) layer and the PDCP layer corresponding to the user plane (i.e., PDCP-U). The SDAP layer is mainly responsible for processing the data of the core network and mapping the flow to the bearer. PDCP-U is responsible for encryption and decryption, integrity protection, header compression, sequence number maintenance, and data transmission on the data plane. The CU-CP and the 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 may alternatively be within the CU-UP.

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

[0096] Architecture 1 shown in Figure 5 is a RAN architecture with transparent satellite according to the embodiments of this application. Architecture 1 includes a terminal, an access network node (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 terminal, the non-terrestrial network gateway, and the gNB are located on the surface of the earth, and the satellite is located in the earth's orbit. In addition, the satellite, the non-terrestrial network gateway, and the gNB may be used as a 5G radio access network (NG-RAN), and the NG-RAN is connected to the 5G core network via a second interface (e.g., the 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 the transparent scenario, the functions of the satellite are radio frequency filtering and frequency conversion and amplification. That is, the satellite is mainly used as an L1 relay to regenerate physical layer signals and does not have other upper protocol layers.

[0101] Architecture 2 shown in Figure 6: The difference between Architecture 2 and Architecture 1 is that in Architecture 2, the NG-RAN includes a 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 and has the processing function of a base station (a regenerative satellite without an ISL, payload processed by the gNB), where the inter-satellite link is an inter-satellite link (ISL). In this architecture, the satellite is used as a gNB.

[0103] Architecture 3 shown in Figure 7: The common point between Architecture 3 and Architecture 2 is that the satellite is used as a gNB. However, the difference between Architecture 3 and Architecture 2 is that there is an ISL in the scenario shown in Architecture 3.

[0104] Architecture 4 shown in Figure 8: The difference between Architecture 4 and Architecture 1 is that the access network node (NG-RAN) in Architecture 4 includes a satellite and a network device. The satellite is used as a gNB-DU, the network device is used as a gNB-CU, the gNB-DU communicates with the gNB-CU via an F1 interface, and the terminal communicates with the gNB-DU via a first interface.

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

[0106] Architecture 5: There is a base station with the IAB function (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 communication, in some scenarios (for example, when some parameters configured for the terminal by the network side need to be changed, or when the network side needs to change the key assigned to the terminal), the network side triggers the terminal to perform an intra-cell handover. Specifically, although the cell accessed by the terminal is maintained without change, the network side requires the terminal to re-access the cell. Generally, the network side sends a handover command (for example, referred to as reconfiguration by a synchronization message) to the terminal, and the terminal performs a random access within the cell again based on the handover command (note that the current protocol requires the terminal to perform a random access, and in the subsequent protocol evolution, it may not be necessary for the terminal to perform a random access). According to the current protocol, in a handover scenario, a formula for calculating the interruption time caused by the handover is used. The formula includes the time Tsearch for searching the target cell. When the target cell is known, Tsearch = 0; otherwise, the value of Tsearch is specified by the protocol.

[0108] In satellite communication, in some other scenarios, the network side also notifies the terminal to perform an in-cell handover (here, for example, because the position of the terminal changes, the terminal enters from one country to another, different countries use different core networks, and the network side needs to select a new core network for the terminal, so the network side triggers an in-cell handover).

[0109] In the placement solution 1 shown in Fig. 1 (a), since the old satellite (hereinafter referred to as the first satellite) moves, the new satellite (hereinafter referred to as the second satellite) provides services only after the old satellite can no longer provide services to the physical area on the ground (here, the coverage area of the satellite is the physical area of the satellite on the ground surface). Generally, the services are provided by other satellites in the same orbit. To increase the distance between satellites, the distance between the two satellites becomes longer. Since 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 of the terminal reach the two satellites at different times (here, the asynchrony of the downlink signal here means that the time when the terminal detects the downlink pilot signal changes, or the frame number, subframe number, slot number, or the start or end point of the symbol detected by the terminal changes. Note this). However, when the new satellite provides coverage, if the terminal is not located within the coverage area of the cell on the ground served 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, subsequently, the terminal cannot correctly receive the downlink signal transmitted within the current cell of that satellite, and the terminal cannot successfully transmit the uplink signal to the cell served by the new satellite. As shown in Fig. 3 or Fig. 2, when the ground cell 500 covered by the new satellite (for example, satellite 400) and the ground cell 300 covered by the old satellite (for example, satellite 200) have the same cell identifier, the coverage area of the ground cell 500 covered by satellite 400 and the coverage area of cell 300 may be the same (as shown in Fig. 2) or different (as shown in Fig. 3). Therefore, how to determine whether the terminal is located within the coverage area of the ground cell 500 covered by satellite 400 so that any one of terminals 1 to n within the accessed cell 300 can be determined is a technical problem that needs to be urgently solved in this application.

[0110] In the embodiments of this application, the specific structure of the execution entity of the communication method is not particularly limited in the embodiments of this application as long as the execution entity can execute a program that records the code of the communication method in the embodiments of this application and perform communication according to the communication method in the embodiments of this application. For example, the execution subject of the communication method provided in the embodiments of this application may be a functional module that is within the first network device and can call and execute a program, or may be a communication device used within the first network device, such as a chip. The execution subject of the communication method provided in the embodiments of this application may be a functional module that is within the terminal and can call and execute a program, or may be a communication device used within the terminal, such as a chip. This is not limited in this application. An example where the execution entity of the communication method is the first network device and the terminal is used to describe the following embodiments.

[0111] FIG. 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: The first network device corresponding to the first satellite transmits a first message. Correspondingly, the terminal receives the first message from the first network device. The first network device is a network device to which the first cell belongs, and the first cell is a cell accessed by the terminal.

[0113] The first message indicates that the satellite providing services to the first cell is updated from the first satellite to the second satellite. Alternatively, the first message indicates to the terminal that the satellite providing services to the first cell is changed, that is, it indicates the alternation between the new satellite and the old satellite.

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

[0115] In a possible implementation of this application, a first message may carry first information to assist a terminal in determining whether it is located within the coverage area of a second cell on the ground served by a second satellite. The first information indicates the coverage area of the second cell on the ground served by the second satellite. The second cell and the first cell have the same cell identifier. Alternatively, it can 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 cell on the ground served by the second satellite. The information about the physical area is used to determine the coverage area of the second cell on the ground served by the second satellite. Optionally, the first information may be the coverage area parameter information of the second cell. For example, the information about the physical area covered by a second cell on the ground served by the second satellite may be represented using a reference point and a radius (or a distance threshold), or may be represented using a series of coordinate points.

[0117] It can be understood that the coverage area of the first cell is mostly included in the coverage area of the second satellite on the ground. For example, the second satellite may serve one or more cells, i.e., 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 this application may be a terminal in a radio resource control (RRC)_connected state, or may be a terminal in an RRC_idle (IDLE) / RRC_inactive (INACTIVE) state.

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

[0120] In a possible implementation of this application, step 901 may be implemented in the following manner. The first network device broadcasts a first message to the terminal, that is, the first message is a broadcast message transmitted by the first network device. In this way, a plurality of terminals accessing the first cell, or a plurality of terminals located within the first cell, may receive the first message, and thereby, the terminal may determine that the satellite serving the first cell has changed. For example, the terminals accessing the first cell include terminal A and terminal B, and the first message is transmitted in a broadcast manner. In this way, the first network device may transmit the broadcast message once, and thereby, terminal A and terminal B sense that the satellite providing services to the first cell is updated from the first satellite to the second satellite, and sense 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 can be implemented in the following manner. The first message sent by the first network device to the terminal is a dedicated message. That is, the first network device uses the dedicated message to send the first message to a specific terminal within the first cell. For example, the first message may be an RRC message or a media 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 send the first message to terminal A or send the first message to terminal B.

[0122] Step 902: The terminal determines whether the terminal is located within the coverage area of the second terrestrial cell served by the second satellite based on the first message, the position of the terminal, and the coverage area of the second terrestrial cell served by the second satellite.

[0123] In one example, with reference to FIG. 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 can determine, in real time or periodically, whether the position of the terminal is within the coverage area of the second terrestrial cell.

[0125] Optionally, when the first message does not carry the first information and the terminal determines that the satellite serving the first cell changes using the first message, the terminal can alternatively request the first network device to provide the coverage area of the second terrestrial cell served by the second satellite for the terminal.

[0126] This embodiment of this application provides a communication method. In the method, when it is determined that the satellite providing services to the first cell is updated from the first satellite to the second satellite, that is, when there is an alternation between the new satellite and the old satellite, the first network device transmits a first message to the terminal. Since the first message indicates to the terminal that the satellite providing services to the first cell is updated from the first satellite to the second satellite, the terminal can sense that the satellite covering the first cell has changed. The second satellite serves the second cell, and the first cell and the second cell have the same cell identifier. Although the first cell and the second cell have the same cell identifier, the coverage areas of the first cell and the second cell on the ground may be different. The terminal may be located outside the coverage area of the second cell on the ground or may be located within the coverage area of the second cell on the ground. Therefore, in order to avoid communication interruption caused by the case where the terminal cannot normally access the second cell when the terminal is located outside the coverage area of the second cell, in this application, the first network device transmits information about the coverage area of the second cell on the ground served by the second satellite to the terminal, so that the terminal can further determine whether the terminal is located within the coverage area of the second cell on the ground or outside the coverage area with reference to the position of the terminal, and can take appropriate processing measures.

[0127] In a possible embodiment of this application, before step 901, the method provided in this embodiment of this application may further include the following. The first network device determines that the satellite providing services to the first cell is updated from the first satellite to the second satellite.

[0128] In a possible implementation, the determination by the first network device that the satellite providing services to the first cell is updated from the first satellite to the second satellite may be implemented in the following manner. The operator sends information about the second satellite to the first network device. Alternatively, the satellite control function of the second satellite sends the ephemeris information of the second satellite to the first network device (base station), or the satellite control function of the second satellite sends the ephemeris information of the second satellite to the core network, and then the core network transfers the ephemeris information of the second satellite to the first network device (base station).

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

[0130] In a possible implementation of this application, the first message may further carry seventh indication information. The seventh indication information indicates to the terminal whether the position of the terminal is within the coverage area of a second cell on the ground served by the second satellite. In this way, after receiving the seventh indication information, the terminal may perform an action to determine whether the terminal 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 in 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 perform an action to determine whether the terminal is located within the coverage area of the second cell on the ground based on the first information.

[0131] In a possible implementation of this application, the first network device does not need to execute an indication on the terminal. After receiving the first information, the terminal actively 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, alternatively, the first network device indicates to the terminal 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 sends a message other than the first message to the terminal and notifies the terminal to report the determination result. For example, the indication information x indicates to the terminal to report the determination 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 the determination 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, when receiving the determination result from the terminal, the first network device may determine that the terminal is located outside the coverage area of the second cell on the ground. Alternatively, the indication information x indicates to the terminal to report the determination result when the terminal is located within the coverage area of the second cell on the ground. Alternatively, the indication information x indicates that the terminal needs to report the determination result regardless of whether the position of the terminal is within or outside the coverage area of the second satellite. The first network device sends to the terminal a message for notifying the terminal of the indication information x or whether to report the result of determining whether the terminal is located within the coverage area of the second cell, so that the terminal executes corresponding actions based on the indication from the first network device. Alternatively, the indication information x indicates to the terminal to execute the report when the determination result is the first determination result and not to execute the report when the determination result is the second determination result. For example, the first determination result is different from the second determination result.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 a possible implementation, after receiving the first piece of information, the terminal may actively report the position information of the terminal to the first network device. In other possible implementations, the terminal reports the position information of the terminal to the first network device when triggered by the first network device. For example, the first network device may further use the indication information y to indicate to the terminal to report the position information of the terminal. The indication information y is carried by the first message or a message other than the first message. This is not limited in the embodiments of this application.

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

[0134] In a possible implementation of this application, when the 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 the second cell on the ground covered by the second satellite.

[0135] In a possible implementation of this application, the time when the first network device sends the first message to the terminal is earlier than the coverage start time of the second satellite serving the second cell on the ground. The coverage start time indicates the time when the second satellite corresponding to the second cell starts to cover the physical area (including the first cell) of the first cell on the ground corresponding to the first satellite.

[0136] Examples are used for illustration. When the first network device determines the coverage start time of the second satellite corresponding to the second cell, assume that the terminal is still accessing the first cell before the coverage start time of the second satellite corresponding to the second cell, and assume that downlink data / signaling transmission is required between the first network device and the terminal. Then, in the process of transmitting downlink data / signaling to the terminal, the first network device may send the first message to the terminal. Assume 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. Then, the first network device may choose to send the first message to the terminal at any time or when the terminal is in the RRC connected state.

[0137] In a possible implementation of this application, the first message may be a pre-defined message specifically used to notify the terminal that the satellite serving the cell is updated. In this way, after receiving the first message, the terminal may know that satellite handover occurs. Of course, the first message may alternatively be an existing message between the terminal and the first network device. This is not limited in the embodiments of this application.

[0138] In other possible implementations of this application, the first message includes first indication information, and the first indication information indicates that the satellite providing services to the first cell is updated from the first satellite to the second satellite, or the satellite serving the first cell changes. In this way, for the terminal, based on the first indication information, the terminal may determine that the satellite of the first cell accessed by the terminal is updated from the first satellite to the second satellite. This method can be regarded as what the first network device indicates to the terminal in an explicit manner. 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 in the embodiments of this application. Optionally, the first indication information may be information about the terrestrial physical area covered by the second cell served by the second satellite.

[0139] Of course, in addition to indicating to the terminal in an explicit manner that satellite handover occurs, the first network device may further indicate to the terminal in an implicit indication manner that satellite handover occurs.

[0140] In an example of implicit indication, the first message in this embodiment of this application may further include one or more of the following parameters, namely, the first time parameter, the second time parameter, time information for the terminal to perform downlink synchronization in the second cell via the second satellite, NTN parameter information of the second satellite, the 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 that serves the second cell on the ground. The second time parameter is used to determine the coverage end time of the second satellite that serves 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 time and the coverage end time of the second satellite on the ground. Then, the terminal may synchronize with the second network device corresponding to the second satellite after the coverage start time of the second satellite on the ground, or may transmit the second message or the fourth message to the first network device before the coverage start time of the second satellite on the ground.

[0142] Of course, when the terminal knows the coverage end time of the second satellite on the ground, assuming that the terminal subsequently performs communication via the second satellite, the terminal may further obtain information about the updated satellite of the second cell and / or the coverage area of the updated cell covered by the satellite from the second network device corresponding to the second satellite before the coverage end 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 + a preset duration. The second time parameter is 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 and the duration for which the second satellite serves the second cell.

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

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

[0146] In one example, information about the measurement timing configuration is used to determine the measurement timing configuration. The measurement timing configuration indicates to the terminal to search for the downlink synchronization signal of the second cell in the second satellite based on the measurement timing configuration. 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 configured based on the downlink timing relationship of the first cell of the first satellite. Optionally, the measurement timing configuration is configured based on the downlink timing relationship of the second cell in the second satellite. The terminal calculates the first subframe number and the first system frame number (i.e., the first measurement window starts from the time 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 then performed within the measurement window based on the periodicity) used to search for the downlink synchronization signal of the second cell according to the following mathematical formula.

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

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

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

[0151] FLOOR is a mathematical operator that truncates a number to the nearest integer (truncation).

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

[0153] In the above solution, the process by which a terminal senses a change in the satellite of the first cell is described. After the first network device notifies the terminal that a satellite handover has occurred in the first cell, although the second cell and the first cell have the same cell identifier, the second cell and the first cell may have different coverage areas on the ground. Therefore, the terminal may be located within the coverage area of the second cell on the ground served by the second satellite, or the terminal 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 this application describes different scenarios in relation to each other.

[0154] Scenario (1): The terminal is located outside the coverage area of the second cell on the ground served by the second satellite.

[0155] In Scenario (1), FIG. 10 shows the specific process of another communication method according to an embodiment of this application. Steps 1001 and 1002 in FIG. 10 are the same as steps 901 and 902. Details are not described again here. Optionally, after step 1002, the method provided in this embodiment of this application may further include the following steps. Step 1003a: The terminal transmits a second message to the first network device. Correspondingly, 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 served 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 transmitting the second message to the first network device.

[0157] When the terminal determines that it is located outside the coverage area of the second cell on the ground, the terminal transmits the second message to the first network device, whereby the first network device immediately learns that the terminal is located outside the coverage area of the second cell on the ground, and immediately triggers the terminal to perform a cell handover to ensure subsequent normal communication of the terminal. In particular, when the first network device transmits the first message in a broadcast manner, there may be multiple terminals accessing the first cell, some of the multiple terminals may be located outside the coverage area of the second cell on the ground, and some of the multiple terminals may be located within the coverage area of the second cell on the ground. Therefore, when the 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 feed back that the terminal is within the coverage area of the second cell on the ground, there is no need to trigger a cell handover. Optionally, the second message may further include an identifier of the terminal, whereby the first network device determines the terminal located outside the coverage area of the second cell on the ground.

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

[0159] When the second message includes the second indication information, it can be understood that the first network device determines, 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 analyzes the second message to obtain the second indication information.

[0160] Optionally, the second message may be a pre-defined message specifically used to exchange, between the terminal and the first network device, a message 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 analyze the second message. Optionally, the second message may alternatively be an existing message for communication between the terminal and the first network device.

[0161] It should be noted that when the first network device does not indicate to the terminal to report the determination result, the act of the terminal sending the second message is a spontaneous act of the terminal. Of course, when the first network device indicates to the terminal to report the determination result, the terminal can send the second message to the first network device based on the indication of the first network device.

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

[0163] In a possible embodiment of this application, when the terminal acquires the first time parameter of the second satellite, the terminal may send a second message to the first network device before the coverage start time of the second satellite. The transmission time of the second message may be determined by the terminal or indicated to the terminal by the first network device. This is not limited in the embodiments of this application. For example, in the process where the first network device notifies the terminal that satellite handover occurs, the first network device notifies the terminal to report the determination result before the coverage start time of the second satellite, or notifies the terminal to report the determination result 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 the second cell on the ground, optionally, as shown in FIG. 10, the method provided in this embodiment of this application may further include the following steps. Step 1004a: The terminal sends the position information of the terminal and / or the measurement report information of the terminal to the first network device. Correspondingly, the first network device receives the position information of the terminal and / or the measurement report information from the terminal.

[0165] The measurement report information can be understood as the network measurement result obtained by the terminal by performing measurements based on the measurement configuration constituted by the first network device. The network measurement result includes parameter information such as the signal strength and signal quality of adjacent cells or the frequency of the terminal. The terminal provides the measurement report information to the first network device, whereby the first network device constitutes the 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 the following. A first network device determines first configuration information and / or second configuration information of the terminal by using the measurement report 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 conditions for performing cell handover.

[0167] The terminal provides the position information of the terminal to the first network device, whereby the first network device determines, based on the position information of the terminal and the coverage area of the second terrestrial cell served by the second satellite, whether the terminal is located within or outside the coverage area of the second terrestrial cell.

[0168] In addition, the first network device may determine the first configuration information and / or the second configuration information of the terminal by using the position information of the terminal. In this way, the first configuration information and / or the second configuration information configured for the terminal will contribute to the subsequent communication of the terminal, ensuring that the subsequent communication of the terminal is not interrupted.

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

[0170] In another possible implementation of this application, when the terminal is located outside the coverage area of the second cell on the ground served by a second satellite, the terminal may actively send the location information of the terminal and / or the measurement report information of the terminal to the first network device. Alternatively, when the terminal detects that it is located outside the coverage area of a cell on the ground served by a satellite, the protocol stipulates that the terminal needs to send the location information of the terminal and / or the measurement report information of the terminal to the first network device.

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

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

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

[0174] In another possible implementation of this application, the first network device determines, based on the position information of the terminal and the coverage area of the second cell on the ground served by the second satellite, that the terminal is located outside the coverage area of the second cell on the ground 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 position information of the terminal 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 subsequent normal communication of the terminal, when the first network device determines that the terminal is located outside the coverage area of the second cell on the ground 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 step 1003a and step 1004a is not limited in the embodiments of this application. The terminal may first execute step 1004a and then execute step 1003a, or may execute step 1003a and step 1004a simultaneously. In other words, the second message includes the location information of the terminal and / or the measurement report information of the terminal.

[0178] In a possible embodiment of this application, as shown in FIG. 10, when the first network device determines that the terminal is located outside the coverage area of the second satellite on the ground, 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. Correspondingly, 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 an example, the third message includes fourth indication information, and the fourth indication information 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 of course, may be different information. This is not limited in the embodiments of this application.

[0181] In other examples, the third message includes information about the target cell. The target cell is a cell to which the terminal will switch and which 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 location information of the terminal and / or the measurement report information of the terminal. For example, the signal quality or signal strength of the target cell is 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 alternatively belong to different network devices. For example, the first cell belongs to one of the one or more cells covered by the first network device, and the target cell is one of the one or more cells covered by the third network device.

[0183] In a possible implementation of this application, the target cell may alternatively be served by the second satellite, but the target cell is different 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. Although the terminal may be located outside the coverage area of the second cell on the ground, the terminal may be located within the coverage area of the target cell on the ground. Therefore, the terminal can switch to the target cell, and thereby the terminal can continue to perform communication via the second satellite and avoid communication interruption. Of course, the target cell may alternatively be a cell covered by a third satellite on the ground. This is not limited in 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 served by a second satellite, as shown in FIG. 10, the method provided in this embodiment of this application further includes the following steps.

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

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

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

[0188] In a possible embodiment of this application, after transmitting the third message to the terminal, the first network device may actively provide the first configuration information and / or the second configuration information to the terminal. Alternatively, when receiving a request from the terminal, the first network device may transmit the first configuration information and / or the 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 may be any one or more of a time-based CHO trigger condition, a location-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 any one or more of the following events, namely, event (event A3), event A4, or event A5. The CHO execution conditions include a location-based trigger condition and any one or more of the following events, namely, event (event A3), event A4, or event A5.

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

[0191] Step 1007a: The terminal changes the serving cell of the terminal from the first cell to the target cell based on the third message.

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

[0193] In a possible implementation of this application, after receiving the third message, the terminal may evaluate the handover condition, and when the cell handover condition indicated by the second configuration information is satisfied, the terminal changes the serving cell from the first cell to the target cell. In this way, the handover failure caused by the blind handover of the terminal is avoided.

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

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

[0196] It should be noted that when the terminal is located outside the coverage area of the second terrestrial cell, if the terminal has configuration information regarding the second satellite, the terminal may execute 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 regarding the second satellite has been deleted.

[0198] In this embodiment of this application, when the terminal is located outside the coverage area of the second terrestrial cell, the terminal deletes the configuration information regarding the second satellite to reduce the occupancy of the terminal's memory.

[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 indicate to the terminal to delete the configuration information regarding the second satellite. For example, when triggering the terminal to perform a cell handover, the first network device may send the sixth indication information to the terminal to indicate to the terminal to delete the configuration information regarding the second satellite. Of course, alternatively, the terminal may actively delete the configuration information regarding the second satellite when the terminal is located outside the coverage area of the second terrestrial cell.

[0200] Optionally, when the target cell is a ground cell covered by the second satellite, the terminal may execute a step of acquiring ephemeris information of the second satellite instead of executing step 1008a.

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

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

[0203] Scenario (2): The terminal is located within the coverage area of the second ground cell served by the second satellite.

[0204] In scenario (2), as shown in FIG. 10, optionally, after step 1002, the method provided in this embodiment of this application may further include one or more of a notification phase, a synchronization phase, and a random access phase. The notification phase includes step 1003b and step 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 ground cell, that is, the terminal can perform subsequent communication via the second satellite.

[0205] Step 1003b: The terminal transmits a fourth message to the first network device. Correspondingly, 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 ground cell.

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

[0207] Optionally, the fourth message may be a predefined message specifically used to exchange, between the terminal and the network device, a message indicating that the terminal is located within the coverage area of a second terrestrial cell served 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 the second terrestrial cell served by the second satellite.

[0208] When the terminal is located within the coverage area of the second terrestrial cell, the terminal may also send the terminal's location information and / or the terminal's measurement report information to the first network device. For specific processes and implementations, refer to the process in which the terminal sends the terminal's location information and / or the terminal's measurement report information to the first network device when the terminal is located outside the coverage area of the second terrestrial cell.

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

[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 the second terrestrial cell, the terminal may not need to feedback the 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 implemented in the following manner. The first network device determines, based on the fourth message, that the terminal is located within the coverage area of the second terrestrial cell served by the second satellite.

[0212] Optionally, when the fourth message includes the fourth indication information, step 1004b may be implemented in the following manner. The first network device determines, based on the fourth indication information, that the terminal is located within the coverage area of the second terrestrial cell served by the second satellite.

[0213] In a possible implementation of this application, when the first network device obtains the location information of the terminal, step 1004b may be implemented 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 terrestrial cell, that the terminal is located within the coverage area of the second terrestrial cell.

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

[0215] Optionally, when the first network device determines that the terminal is located within the coverage area of the second terrestrial cell, the first network device may further transmit the NTN parameter information of the second satellite to the terminal. The NTN parameter information includes the parameter information required for the terminal to access the NTN (or the second cell) corresponding to the second satellite. When the terminal accesses the NTN via the second satellite, the NTN parameter information is parameter information such as satellite ephemeris, the valid time of the ephemeris, and the common timing advance parameter.

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

[0217] It should be noted that when the terminal is located within the coverage area of the second cell on the ground, the first network device sends the NTN parameter information of the second satellite and / or the indication information of the NTN parameter information of the second satellite to the terminal. In this way, it can be guaranteed that the transmitted information is available information at 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 alternatively be provided to the terminal by the first network device in a process of notifying the terminal that satellite handover occurs, for example, carried in the first message.

[0219] The purpose of the synchronization phase is to enable the terminal to synchronize with the second network device corresponding to the second satellite and 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 one example, the second network device and the first network device can be the same network device. Alternatively, the second network device and the first network device are different network devices. This is not limited in the embodiments of this application.

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

[0223] In one example, step 1005b can be implemented 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, searches for the synchronization signal of the second cell and obtains the downlink timing, that is, obtains the system frame, subframe, slot, and symbol boundaries of the second cell in the second satellite). Alternatively, the terminal updates the downlink synchronization of the terminal in the second cell based on the position of the second satellite, the position of the first satellite, and the current position information of the terminal, that is, updates the downlink synchronization of the second cell currently achieved by the first terminal.

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

[0225] Examples are used for illustration. When the terminal synchronizes with the second network device, the terminal can immediately start a random access process to the second network device. Of course, the terminal can alternatively start the random access process when the first condition is met. The terminal starts the random access process, whereby the terminal transmits an uplink transmission to the second network device.

[0226] In one example, the first condition includes any one of the following: being before the coverage end time of the first satellite, being after the coverage start time of the second satellite, requiring data transmission (e.g., downlink data is received from the second network device and / or uplink data is transmitted to the second network device), or the uplink time alignment timer of the terminal not expiring.

[0227] If the uplink time alignment timer of the terminal 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 the transmission of the uplink data has not been completed.

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

[0229] Optionally, when the uplink time alignment timer of the terminal has expired and the terminal does not start a random access process to the second network device, when uplink data transmission is subsequently required, the terminal can also start a random access process.

[0230] For the specific implementation of the terminal starting a random access process to the second network device, refer to the description in the prior art. This is not limited in the embodiments of this application.

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

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

[0233] In a possible implementation of this application, when the terminal is located within the coverage area of a second satellite on the ground, the method provided in this embodiment of this application may further include the following. The terminal re-acquires 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 acquire the NTN parameter information of the second satellite via the first satellite.

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

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

[0238] The above mainly describes the solutions in the embodiments of this application from the perspective of the interaction between network elements. To implement the above functions, it can be understood that each network element, for example, the first network device or the terminal, includes a corresponding structure and / or a software module for executing each function. Those skilled in the art should easily notice that this application can be realized by hardware or a combination of hardware and computer software in combination with the example units and algorithm steps described in the embodiments disclosed herein. Whether the function is executed by hardware or by hardware driven by computer software depends on the design constraints of the specific application and technical solution. Those skilled in the art can implement the described functions using different methods for each specific application, but the implementation should not be considered to exceed the scope of this application.

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

[0240] Above, with reference to FIGS. 9 and 10, the method in the embodiments of this application has been described. Below, the communication device provided in the embodiments of this application and performing the above method will be described. Those skilled in the art can understand that the method and the device can be combined and referenced with each other. The communication device provided in the embodiments of this application can execute the steps executed by the terminal and the first network device in the above communication method.

[0241] When the integrated unit is used, FIG. 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 program code and data of the communication device.

[0243] In an 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 (for example, the first network device). For example, the communication module 113 is configured to execute the signal reception and transmission operations executed by the terminal in the above method embodiments. The processing module 112 is configured to execute the signal processing operations executed by the terminal in the above method embodiments.

[0244] Examples are used for illustration. The communication module 113 is configured to execute a receiving action executed by the terminal in step 901 of FIG. 9 or step 1001 of FIG. 10 in the above embodiment. The processing module 112 is configured to support the communication device when executing an action executed by the terminal in step 902 of FIG. 9 or step 1002 of FIG. 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 execute a transmitting action executed by the terminal in step 1003a of FIG. 10 in the above embodiment. Optionally, the communication module 113 is further configured to execute a transmitting action executed by the terminal in step 1004a of FIG. 10 in the above embodiment. Optionally, the communication module 113 is further configured to execute a receiving action executed by the terminal in step 1005a and / or step 1006a of FIG. 10 in the above embodiment. Optionally, the processing module 112 is further configured to execute step 1007a of FIG. 10 in the above embodiment. Optionally, the processing module 112 is further configured to execute step 1008a and / or step 1009a of FIG. 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 execute the transmission action performed by the terminal in step 1003b and / or step 1004b of FIG. 10 in the above embodiment. Optionally, the processing module 112 is further configured to execute steps 1005b and 1006b. Optionally, the communication module 113 is further configured to execute the reception action performed by the terminal in step 1007b of FIG. 10 in the above embodiment. The processing module 112 is further configured to execute step 1008b.

[0247] In other examples, the communication device is the 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 execute the signal reception and transmission operations performed by the first network device in the above method embodiment. The processing module 112 is configured to execute the signal processing operations performed by the first network device in the above method embodiment.

[0248] Examples are used for illustration. The communication module 113 is configured to execute the transmission action performed by the first network device in step 901 of FIG. 9 or step 1001 of FIG. 10 in the above embodiment.

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

[0250] Optionally, the communication module 113 is configured to perform a receiving action executed by the first network device in step 1004a or step 1004b of FIG. 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 a transmitting action executed by the first network device in step 1005a of FIG. 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 a transmitting action executed by the first network device in step 1006a of FIG. 10 in the above embodiment.

[0253] In FIG. 11, it should be noted that the communication module 113 may alternatively be replaced by a communication unit, the processing module 112 may alternatively be replaced by a processing unit, and the storage module 111 may alternatively 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 execute information / data processing steps executed by the communication device. The communication unit is configured to support the communication device when performing information / data transmission or reception steps.

[0254] In a possible implementation, the 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 a 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 logical blocks, modules, and circuits described in connection with the content disclosed 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 a memory.

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

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

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

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

[0260] Communication interface 1203 is configured to exchange information with other devices using any type of device, such as a transceiver, and is configured 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 a memory 1202.

[0262] The memory 1202 may be a read-only memory (ROM), other types of static storage devices capable of storing static information and instructions, a random access memory (RAM), or other types of dynamic storage devices capable of storing information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a 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 disk 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 a computer, but not limited thereto. The memory may exist independently and be connected to the processor via the communication line 1204. Alternatively, the memory may be integrated into the processor.

[0263] The memory 1202 is configured to store computer-executable instructions for executing the solutions in this application, and the processor 1201 controls the execution of the computer-executable instructions. The processor 1201 is configured to execute the computer-executable instructions stored in the memory 1202 to implement 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 in the embodiments of this application.

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

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

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

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

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

[0270] In this embodiment of this application, the corresponding operation is executed by calling the operation instructions stored in the memory 1340 (where the operation instructions may be stored in the operating system).

[0271] In a possible implementation, the chip structures used by the terminal and the first network device are 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 may also be referred to as a central processing unit (CPU).

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

[0274] The method disclosed in the embodiments of this application can be applied to, or implemented by, processor 1310. Processor 1310 may be an integrated circuit chip and has signal processing capabilities. In the implementation process, each step of the above method can be completed by using the integrated logic circuit of the hardware in processor 1310 or instructions in the form of software. 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 devices, discrete gates, or transistor logic devices, or discrete hardware components. The processor can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor may be a microprocessor, or the processor may be any conventional processor, etc. The steps in the method disclosed in connection with the embodiments of this application may be directly executed and completed by a hardware decoding processor, or may be executed and completed by using a combination of hardware and software modules in the decoding processor. The software module may be disposed in a well-developed storage medium in the art, such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, an electrically erasable programmable memory, or a register. The storage medium is disposed in memory 1340. Processor 1310 reads the information in memory 1340 and combines it with the hardware of processor 1310 to complete the steps of the above method.

[0275] In a possible implementation, 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 FIGS. 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 FIGS. 6-10.

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

[0277] According to one aspect, a computer-readable storage medium is provided. The computer-readable storage medium stores instructions that, when executed, implement the functions performed by the terminal in FIG. 9 or FIG. 10.

[0278] According to one aspect, a computer-readable storage medium is provided. The computer-readable storage medium stores instructions that, when executed, implement the functions performed by the first network device in FIG. 9 or FIG. 10.

[0279] According to one aspect, a computer program product including instructions is provided. The computer program product includes instructions that, when executed, implement the functions performed by the terminal in FIG. 6.

[0280] According to another aspect, a computer program product including instructions is provided. The computer program product includes instructions that, when executed, implement the functions performed by the first network device in FIG. 9 or FIG. 10.

[0281] According to one aspect, a chip is provided. The chip is used within a terminal and includes at least one processor and a communication interface. The communication interface is coupled to the at least one processor. The processor is configured to execute instructions to implement the functions executed by the terminal in FIG. 9 or FIG. 10.

[0282] According to other aspects, embodiments of this application provide a chip. The chip is used within an access management network element. The chip includes at least one processor and a communication interface. The communication interface is coupled to the at least one processor. The processor is configured to execute instructions to implement the functions executed by the first network device in FIG. 9 or FIG. 10.

[0283] Embodiments of this application provide a communication system. The communication system includes a first network device and a terminal. The first network device is configured to execute the functions executed by the first network device in FIG. 9 or FIG. 10, and the terminal is configured to execute the functions executed by the terminal in FIG. 9 or FIG. 10.

[0284] All or part of the above embodiments can be realized using software, hardware, firmware, or any combination thereof. When software is used to realize an embodiment, all or part of the embodiment can be implemented in the form of a computer program product. The computer program product includes one or more computer programs or instructions. When the computer program or instructions are loaded and executed on a computer, the procedures or functions in the embodiments of this application are executed in whole or in part. The computer may be a general-purpose computer, a dedicated computer, a computer network, a network device, a user device, or other programmable devices. The computer program or instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer program or instructions may be transmitted in a wired or wireless manner from a 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 integrating one or more available media, such as a server or a data center. The available medium may be a magnetic medium, such as a floppy disk, a hard disk, or a magnetic tape, or an optical medium, such as a digital video disc (DVD), or a semiconductor medium, such as a solid state drive (SSD).

[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 a plurality of 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, as long as they fall within the scope of the claims of this application and the scope of their equivalent technologies, this application is intended to cover these modifications and variations of this application.

Claims

Claim 1 A step of receiving, by a terminal, a first message from a first network device, wherein the first message indicates that a satellite providing service to a first cell is 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 the first satellite, the first message includes first information, and the first information is used to determine a coverage area of a second cell on the ground served by the second satellite, and the first cell and the second cell have the same cell identifier; A step of determining, by the terminal, based on the first message, the position of the terminal, and the coverage area of the second cell on the ground, whether the terminal is located within the range of the coverage area or outside the coverage area; A communication method comprising the above steps. Claim 2 After the step of determining, by the terminal, 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 range of the coverage area or outside the coverage area, the method further comprises: A step of transmitting, by the terminal, a second message to the first network device, wherein the second message indicates that the terminal is located within the range of the coverage area of the second cell on the ground, or the second message indicates that the terminal is located outside the coverage area of the second cell on the ground. The method according to Claim 1. Claim 3 After the step of determining, by the terminal, 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 range of the coverage area or outside the coverage area, the method further comprises: A step of transmitting, by the terminal, the position information of the terminal and / or the measurement report information of the terminal to the first network device, wherein the measurement report information includes information indicating the signal quality of adjacent cells of the terminal. The method according to Claim 1 or 2. Claim 4 When the terminal is located within the coverage area of the second cell on the ground served by the second satellite, the method comprises: executing, by the terminal, 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, the step further comprising: The method according to any one of claims 1 to 3.

5. When a first condition is satisfied, the method comprises: starting, by the terminal, a random access process to the second network device, the first condition being any one or more of the following, namely: before the coverage end time of the first satellite on the ground; after the coverage start time of the second satellite on the ground; data transmission is required, or the uplink time alignment timer of the terminal has not expired the step further comprising: The method according to claim 4.

6. When a second condition is satisfied, the terminal does not need to start a random access process to the second network device, the second condition including at least that the uplink time alignment timer of the terminal has expired or the uplink time alignment timer of the terminal has not been started. The method according to claim 4.

7. When the terminal is located outside the coverage area of the second cell on the ground served by the second satellite, the method comprises: receiving, by the terminal, a third message from the first network device, the third message indicating to 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 changing, by the terminal, the serving cell of the terminal from the first cell to the target cell based on the third message the method further comprising: The method according to any one of claims 1 to 3.

8. The third message includes first configuration information, and the first configuration information is used by the terminal to determine information about the target cell. The step of the terminal changing the serving cell of the terminal from the first cell to the target cell based on the third message includes: The step of the terminal determining the information about the target cell based on the first configuration information; and The step of the terminal changing the serving cell of the terminal from the first cell to the target cell based on the information about the target cell. The method according to claim 7.

9. The third message includes second configuration information, and the second configuration information includes cell handover conditions configured for the terminal. The step of the terminal changing the serving cell of the terminal from the first cell to the target cell based on the third message includes: When the cell handover conditions included in the second configuration information are satisfied, the step of the terminal changing the serving cell of the terminal from the first cell to the target cell. The method according to claim 7 or 8.

10. 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, 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. The method further includes: Based on the first time parameter and / or the second time parameter, the step of the terminal synchronizing with the second network device corresponding to the second satellite after the coverage start time of the second satellite on the ground, or the step of the terminal transmitting the second message to the first network device before the coverage start time of the second satellite on the ground. The method according to any one of claims 1 to 9.

11. The first message includes the following information, that is, Time information for the terminal to perform downlink synchronization in the second cell. ​ NTN parameter information of the second satellite, where the NTN parameter information includes parameter information necessary for the terminal to access the NTN corresponding to the second satellite. Third indication information, where the third indication information indicates the position information of the NTN parameter information. Information about the measurement timing configuration, which indicates to the terminal to search for the downlink synchronization signal of the second cell in the second satellite based on the measurement timing configuration. Further includes one or more of the above. The method according to any one of claims 1 to 10.

12. A step of transmitting a first message by a first network device corresponding to a first satellite, where the first message indicates that a satellite providing service to a first cell is updated from the first satellite to a second satellite, the first message includes first information, and the first information is used to determine the coverage area of a second cell on the ground served by the second satellite, and the first cell and the second cell have the same cell identifier. A communication method including the above.

13. 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 method according to claim 12.

14. The first message includes the following information, that is, Time information for the terminal to perform downlink synchronization in the second cell via the 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 position information of the NTN parameter information. Information about a measurement timing configuration, which indicates to a terminal to search for a downlink synchronization signal of the second cell in the second satellite based on the measurement timing configuration, the information about the measurement timing configuration further including one or more of The method according to claim 12 or 13.

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

16. When the first network device determines that a first terminal accessing the first cell is located outside the coverage area of the second cell on the ground, the method includes a step of transmitting, by the first network device, a third message to the first terminal accessing, 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 a coverage area of the target cell The method according to any one of claims 12 to 15.

17. The method includes a step of transmitting, by the first network device, first configuration information and / or second configuration information to the first terminal, 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 method according to claim 16.

18. One or both of the first configuration information and the second configuration information are determined based on position information of the first terminal and / or measurement report information of the first terminal, and the measurement report information includes information indicating signal quality of adjacent cells of the first terminal The method according to claim 17.

19. The method includes: receiving, by the first network device, a second message from the first terminal, where the first terminal is a terminal accessing the first cell; determining, by the first network device, based on the second message, whether the first terminal is located outside the coverage area of the second cell on the ground or whether the first terminal is located within the coverage area of the second cell on the ground; and further includes: The method according to any one of claims 12 to 18. **Claim 20** The second message includes the location information of the first terminal, and the step of determining, by the first network device, based on the second message, whether the first terminal is located outside the coverage area of the second cell on the ground or whether the first terminal is located within the coverage area of the second cell on the ground includes: determining, by the first network device, 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 whether the first terminal is located within the coverage area of the second cell on the ground; The method according to claim 19. **Claim 21** A computer-readable storage medium storing instructions that, when executed, implement the method according to any one of claims 1 to 11 or the method according to any one of claims 12 to 20. **Claim 22** A chip including a processor coupled to a communication interface, the processor configured to execute a computer program or instructions to implement the method according to any one of claims 1 to 11 or the method according to any one of claims 12 to 20, and the communication interface configured to communicate with modules other than the chip. **Claim 23** A terminal including 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 a memory to execute the method according to any one of claims 1 to 11.

24. A network device including 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 a memory to execute the method according to any one of claims 12 to 20.

25. A communication system including a terminal and a first network device corresponding to a first satellite, wherein the first network device is configured to execute the method according to any one of claims 12 to 20, and the terminal is configured to implement the method according to any one of claims 1 to 11.

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