Communication method and communication device

Abstract

Embodiments of the present application relate to the technical field of communications, and disclose a communication method and a communication device, capable of supporting the handover of a terminal from a non-terrestrial cell to a terrestrial cell, and capable of reducing the handover duration and energy consumption of the terminal. In the method, information about a first network element of a terrestrial PLMN which a terminal is allowed to access can be indicated; the first network element can provide terrestrial cell information covering area information or location information of the terminal, wherein the terrestrial cell information is used for enabling the terminal, upon entering a coverage area of any terrestrial cell, to hand over or reselect from a non-terrestrial cell to the terrestrial cell. In this way, when neighboring cell information cannot be configured between a non-terrestrial network and a terrestrial network, fast handover of a terminal from a non-terrestrial cell to a terrestrial cell is supported, and the need for the terminal to frequently perform frequency search is eliminated, thereby reducing energy consumption of the terminal.

Description

A communication method and a communication device

[0001] This application claims priority to Chinese Patent Application No. 202411188313.4, filed with the State Intellectual Property Office of China on August 27, 2024, entitled "A Communication Method and Communication Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of communication technology, and in particular to a communication method and a communication device. Background Technology

[0003] Considering the coverage gaps in terrestrial networks (TN), 5G introduces non-terrestrial networks (NTN). For example, when the NTN is a satellite network, the terminal can access the network via satellite cells. Thus, the terminal may move between TN and NTN. Typically, satellite cells have a wider coverage area than terrestrial cells, and when a terminal moves within the coverage area of ​​a non-terrestrial cell, it may enter the coverage area of ​​a terrestrial cell.

[0004] When a terminal moves between terrestrial and satellite cells, it may need to perform cell handover, i.e., switch from a satellite cell to a terrestrial cell. In idle mode, although the satellite network can broadcast frequency information of terrestrial cells within a certain geographical area, the terminal still needs to switch frequencies to search for cells. For the terminal, handover from a satellite cell to a terrestrial cell is time-consuming and power-intensive. In connected mode, the satellite cell needs to configure neighboring cell information for adjacent terrestrial cells to support handover from a satellite cell to a terrestrial cell. However, due to the high speed of satellite movement and the rapid changes in terrestrial neighboring cells, configuring neighboring terrestrial cells is complex, and satellite and terrestrial cells usually belong to different operators, with cross-operator support for configuring neighboring cell information typically not supported. Therefore, handover from a satellite cell to a terrestrial cell cannot be supported. Summary of the Invention

[0005] This application provides a communication method and a communication device that can support the handover of a terminal from a non-terrestrial cell to a terrestrial cell, and can reduce the handover time and energy consumption of the terminal.

[0006] This application provides a communication method and a communication device that can reduce the time and energy consumption of a terminal switching from a satellite cell to a terrestrial cell.

[0007] Firstly, a communication method is provided. The executing entity of this method can be a terminal, a component or device applied to the terminal (e.g., a processor, chip, or chip system), or a logic module or software capable of implementing all or part of the terminal's functions. The method includes: receiving first indication information, which indicates information about a first network element of a public land mobile network (PLMN); sending second indication information, which is used by the terminal to request information about a terrestrial cell from the first network element, wherein the first network element is determined based on information from the first network element, and the second indication information includes area information, which indicates the area covered by the requested terrestrial cell, and the terrestrial cell belongs to the PLMN; receiving third indication information, which indicates information about at least one terrestrial cell, wherein the coverage area of ​​any one of the at least one terrestrial cells intersects with the area indicated by the area information, and the information about the at least one terrestrial cell is used by the terminal to switch or reselect from a non-terrestrial cell to a terrestrial cell when entering the coverage area of ​​any one of the at least one terrestrial cells; or, the third indication information indicates the area indicated by the area information without terrestrial cell coverage.

[0008] The first network element can be understood as the topology service network element or topology server deployed in the terrestrial core network of this application.

[0009] Therefore, this application introduces a first network element of the terrestrial PLMN, namely, topology services in the terrestrial network. This first network element can provide the terminal with information about at least one terrestrial cell based on the terminal's area information. The coverage area of ​​the terrestrial cell indicated by this information overlaps with the area indicated by the terminal's area information. Thus, even when terrestrial and non-terrestrial cells are operated by different carriers, when the terminal moves within the area indicated by the area information, or enters the coverage area of ​​any terrestrial cell that overlaps with the area indicated by the area information, the terminal can determine the target terrestrial cell based on the information of at least one terrestrial cell, thereby switching from a non-terrestrial cell to a terrestrial cell. In this way, this application supports rapid switching from non-terrestrial cells to terrestrial cells even when neighbor cell information cannot be configured between non-terrestrial and terrestrial networks. The terminal also does not need to frequently perform frequency searches, saving power consumption.

[0010] In one possible design, before receiving the first indication information, the method further includes: sending capability information indicating that the terminal has at least one of the following capabilities: supporting reselection from a non-terrestrial cell to a terrestrial cell for access; supporting handover from non-terrestrial cell access to a terrestrial cell for access; and supporting redirection from non-terrestrial cell access to a terrestrial cell for access. Thus, if the terminal supports access from a non-terrestrial cell to a terrestrial cell, the terminal can access the terrestrial cell when it enters the coverage area of ​​a terrestrial cell, allowing the terrestrial cell to provide network services to the terminal.

[0011] In one possible design, the information of the first network element includes its Internet Protocol (IP) address or fully qualified domain name (FQDN). In this way, the terminal can request information about the terrestrial cell that allows the terminal to access from the first network element based on its IP address or FQDN.

[0012] In one possible design, the information of each ground cell in at least one ground cell includes at least one of the following: global cell identifier, physical cell identifier, frequency information, cell coverage information, measurement configuration information, priority information, or the PLMN identifier to which the ground cell belongs. This information of the ground cells can be used by the terminal to determine candidate ground cells during cell handover or cell reselection, so as to measure the candidate ground cells to determine the target ground cell.

[0013] In one possible design, the method further includes: determining, based on the terminal's location information and the coverage information of at least one terrestrial cell, the coverage area of ​​at least one candidate terrestrial cell that the terminal has entered or is about to enter; and performing cell measurement on the at least one candidate terrestrial cell. This is because accessing a terrestrial cell is more energy-efficient than accessing a non-terrestrial cell; therefore, when the terminal determines that it has entered the coverage area of ​​a candidate terrestrial cell, the terrestrial cell can be measured to determine the target terrestrial cell that can be switched over.

[0014] In one possible design, cell measurement is performed on at least one candidate ground cell, including: cell measurement based on at least one of the following information of the candidate ground cell: frequency information, physical cell identifier, or measurement configuration information. This allows the terminal to perform cell measurement based on the frequency information, physical cell identifier, or measurement configuration information received from the ground cell information received from the first network element, enabling the terminal to switch from non-ground cells to ground cells and solving the existing problem of difficulty in configuring neighboring cells for ground cells.

[0015] In one possible design, the method further includes sending a fourth indication message to the serving network device of the non-terrestrial network. This fourth indication message instructs the terminal to switch from the serving network device's cell to a target terrestrial cell, which is determined by the terminal based on cell measurement results from at least one candidate terrestrial cell. The serving network device of the non-terrestrial network can be understood as the source satellite base station before the terminal's handover. Thus, when the source satellite base station receives the fourth indication message, it can initiate a process to switch the terminal from the non-terrestrial cell to the target terrestrial cell, enabling the target terrestrial cell to provide the terminal with more energy-efficient network services.

[0016] In one possible design, the terminal determines the target ground cell based on cell measurement results of at least one candidate ground cell, including: the terminal further determines the target ground cell based on at least one of the following: priority information of at least one candidate ground cell, PLMN information to which at least one candidate ground cell belongs, or cell coverage information of at least one candidate ground cell. For example, the terminal may select the ground cell with the highest priority among the candidate ground cells whose signal quality is greater than a quality threshold as the target ground cell. For example, the priority information is based on the PLMN level; for example, the terminal may preferentially select ground cells under its own PLMN.

[0017] In one possible design, the method further includes: sending fifth indication information to the serving network equipment of the non-terrestrial network. The fifth indication information indicates the cell measurement results of at least one candidate terrestrial cell. This fifth indication information is used by the serving network equipment to determine the target terrestrial cell from the at least one candidate terrestrial cell. Alternatively, the target terrestrial cell can be determined by the source satellite base station accessed by the terminal based on the cell measurement results; the determination method is described in the section on how a terminal determines its target terrestrial cell.

[0018] In one possible design, when the information of at least one ground cell does not include measurement configuration information, the method further includes: sending a sixth indication message, the sixth indication message being used to request measurement configuration information of at least one candidate ground cell from the first network element; and receiving a seventh indication message, the seventh indication message being used to indicate the measurement configuration information of at least one candidate ground cell. That is, the first network element can also provide the measurement configuration information of the ground cell to help the terminal measure the candidate ground cells based on the measurement configuration information and determine the target ground cell.

[0019] In one possible design, the method further includes receiving an eighth indication message sent by a first network element, the eighth indication message indicating updated information about at least one ground cell. This update of ground cell information may be due to changes in the ground cells covering the terminal caused by terminal movement, or it may be due to changes in network-side deployment. For the terminal, receiving the updated ground cell information in a timely manner allows for a more accurate determination of the target ground cell.

[0020] In one possible design, before receiving the sixth indication information, the method further includes: sending a ninth indication information, which is used to request the first network element to update the information of at least one ground cell. The ninth indication information includes updated area information, and is sent when the terminal determines that it is moving out of or about to move out of the coverage area and / or area information of at least one ground cell before the update. This design is equivalent to the terminal, based on its own location information, determining that it is moving out of or about to move out of the area indicated by the area information or the area of ​​at least one ground cell, promptly requesting the first network element to update the ground cell information, so as to determine candidate ground cells and then the target ground cell based on the latest ground cell information, thereby completing the handover to the target ground cell.

[0021] Secondly, a communication method is provided. The executing entity of this method can be a core network device of a non-terrestrial network, a component or device (e.g., a processor, chip, or chip system) applied to the core network device, or a logic module or software capable of implementing all or part of the functions of the core network device. The method includes: sending first information, which is used to instruct the serving network device of the non-terrestrial network to which the terminal is accessed to allow the terminal to switch to a terrestrial network; and sending first indication information, which indicates information about a first network element of a terrestrial public land mobile network (PLMN) to which the terminal is allowed to access. The first network element is used to provide the terminal or the serving network device of the non-terrestrial network with information about the terrestrial cells of the PLMN. The information about the terrestrial cells is used by the terminal to perform a handover or reselection from a non-terrestrial cell to a terrestrial cell.

[0022] For example, the entity executing this method may be an access and mobility management function (AMF) network element or other network elements in the core network.

[0023] In this way, for non-terrestrial core networks accessed by terminals, when instructing the serving network equipment of the non-terrestrial network to allow the terminal to access the terrestrial network, and instructing the terminal or the serving network equipment of the non-terrestrial network to provide information on the first network element of the terrestrial PLMN that the terminal is allowed to access, the terminal or the serving network equipment of the non-terrestrial network can obtain information about terrestrial cells from the first network element. This allows the terminal to switch or reselect from a non-terrestrial cell to a terrestrial cell based on the information of the terrestrial cell, or allows the serving network equipment of the non-terrestrial network to configure the terminal to measure candidate terrestrial cells based on the information of the terrestrial cells obtained from the first network element, and determine the target terrestrial cell based on the measurement results, so as to switch or redirect the terminal from a non-terrestrial cell to a terrestrial cell. This not only solves the problem that non-terrestrial networks and terrestrial networks cannot configure neighboring cells across operators and supports the terminal switching from a non-terrestrial network to a terrestrial network, but also allows the terminal to perform cell handover or reselection to a terrestrial cell based on the obtained terrestrial cell information, and avoids the time-consuming and power-consuming problem caused by the terminal frequently searching for cells according to the frequency information broadcast by the non-terrestrial network.

[0024] In one possible design, before sending the first information, the method further includes: receiving capability information, which indicates that the terminal has at least one of the following capabilities: supporting reselection from a non-terrestrial cell to a terrestrial cell; supporting handover from non-terrestrial cell access to a terrestrial cell; and supporting redirection from non-terrestrial cell access to a terrestrial cell. Thus, if the source satellite network equipment determines that the terminal supports access to the terrestrial network, a handover or reselection process from a non-terrestrial cell to a terrestrial cell can be performed.

[0025] In one possible design, the first network element of the PLMN that the terminal is allowed to access is determined based on at least one of the terminal's subscription information, location information, or roaming agreements between non-terrestrial network operators and terrestrial network operators. This allows the terminal to avoid requesting terrestrial cell information from network elements that do not support cross-operator access.

[0026] In one possible design, the first information includes the identifier of the terrestrial PLMN that the terminal is allowed to access. This is equivalent to the satellite core network equipment indicating the identifier of the terrestrial PLMN that the terminal is allowed to access to the source satellite base station. This helps the source satellite base station determine the target terrestrial cell from the terrestrial PLMNs for the terminal when switching to a terrestrial cell.

[0027] In one possible design, the information of the first network element includes the Internet Protocol address or fully qualified domain name of the first network element.

[0028] Thirdly, a communication method is provided. The executing entity of this method can be an access network device or a core network device of a terrestrial network, or a component or device (e.g., a processor, chip, or chip system) applied to the access network device or core network device, or a logic module or software capable of implementing all or part of the functions of the access network device or core network device. For example, the access network device or core network device can be a topology service network element or a topology server, which can be understood as the first network element in this application. The method includes: receiving second indication information, the second indication information being used by a terminal to request information about a terrestrial cell, the second indication information including area information, the area information being used to indicate the area covered by the terrestrial cell requested by the terminal; sending third indication information, the third indication information being used to indicate information about at least one terrestrial cell, wherein the coverage area of ​​any of the at least one terrestrial cell intersects with the area indicated by the area information, the information of the at least one terrestrial cell being used by the terminal to switch or reselect from a non-terrestrial cell to a terrestrial cell when entering the coverage area of ​​any of the at least one terrestrial cell; or, the third indication information being used to indicate the area indicated by the area information without terrestrial cell coverage.

[0029] In this way, when the first network element or topology service of the terrestrial network provides the terminal with information on at least one terrestrial cell, the terminal can determine the target terrestrial cell based on the information of at least one terrestrial cell when entering the coverage area of ​​any of the at least one terrestrial cells, thereby switching or reselecting from a non-terrestrial cell to a terrestrial cell. This not only supports rapid switching from a non-terrestrial network to a terrestrial network when terrestrial and non-terrestrial cells are linked across operators, but also avoids the time-consuming and power-consuming problem caused by the terminal performing cell searches based on broadcast frequency information when accessing a non-terrestrial network.

[0030] In one possible design, the information for each ground cell in at least one ground cell includes at least one of the following: global cell identifier, physical cell identifier, frequency information, cell coverage information, measurement configuration information, priority information, or the Public Land Mobile Network (PLMN) identifier to which the ground cell belongs. When the first network element provides the terminal with ground cell information, the terminal can configure neighboring cell information when accessing a non-ground cell, enabling the terminal to perform cell handover or reselection based on the neighboring cell information.

[0031] In one possible design, when the information of at least one ground cell does not include measurement configuration information, the method further includes: receiving sixth indication information, the sixth indication information being used by the terminal to request measurement configuration information of at least one candidate ground cell; and sending seventh indication information, the seventh indication information being used to indicate the measurement configuration information of at least one candidate ground cell. That is, the first network element can also provide the terminal with the measurement configuration information of the ground cell, helping the terminal to perform cell measurements on the candidate opposite cells and determine the target ground cell.

[0032] In one possible design, the method further includes sending an eighth indication message, which is used to indicate to the terminal the updated information of at least one ground cell. This could occur when the terminal determines the range or area information indicated by the stored ground cell information that it is moving out of or about to move out of, and requests an update to the ground cell information from the first network element. Alternatively, it could occur when the first network element determines that an instruction to update ground cell information has been sent to the terminal due to energy saving or network deployment changes. Both scenarios allow the terminal to perform handover or reselection of access to a ground cell based on the latest ground cell information.

[0033] In one possible design, before sending the sixth indication information, the method further includes: receiving a ninth indication information, the ninth indication information being used by the terminal to request an update of information for at least one ground cell, the ninth indication information including updated area information of the terminal, the ninth indication information being sent when the terminal determines that it has moved out of or is about to move out of the coverage area and / or area information of at least one ground cell before the update; or, receiving an information change for at least one ground cell, the information change for at least one ground cell being used to determine the updated information of at least one ground cell.

[0034] Fourthly, a communication method is provided. The executing entity of this method can be an access network device of a non-terrestrial network, a component or device (e.g., a processor, chip, or chip system) applied to the access network device, or a logic module or software capable of implementing all or part of the functions of the access network device. The access network device can be understood, for example, as a service network device for terminal services or a source satellite base station. The method includes: receiving first information, the first information indicating permission for a terminal to switch from a non-terrestrial network to a terrestrial network; acquiring information about at least one terrestrial cell, the information about the at least one terrestrial cell being used by the terminal to perform cell handover or cell redirection when entering the coverage area of ​​any one of the at least one terrestrial cells; and determining the target terrestrial cell of the terminal based on the information about the at least one terrestrial cell, the target terrestrial cell being the target cell for the terminal handover or redirection.

[0035] Therefore, in this application, the serving network equipment via a non-terrestrial network, upon determining that the terminal supports switching from a non-terrestrial network to a terrestrial network, can obtain information on at least one terrestrial cell that allows the terminal to access, and use this information to determine the target terrestrial cell for handover or redirection. In this way, even if the terrestrial and non-terrestrial cells are from different operators, this application not only supports the terminal's rapid switching from a non-terrestrial network to a terrestrial network, but also avoids the time-consuming and power-consuming problem caused by the terminal performing cell searches based on broadcast frequency information when accessing a non-terrestrial network.

[0036] In one possible design, obtaining information about at least one ground cell includes: first information including information about at least one ground cell; or the first information including information about a first network element of a public terrestrial mobile network (PLMN) that the terminal is allowed to access, and obtaining information about at least one ground cell from the first network element based on the information of the first network element; or the first information including an identifier of at least one terrestrial PLMN, the identifier of which is used to determine the information of the first network element, and obtaining information about at least one ground cell from the first network element based on the information of the first network element. That is, the source satellite base station can directly obtain information about at least one ground cell when receiving the first information from the satellite core network, or the source satellite base station can request information about at least one ground cell from the first network element based on the information of the first network element of the terrestrial PLMN that the terminal is allowed to access, or the source satellite base station can first determine the first network element based on the terrestrial PLMN that the terminal is allowed to access, and then request information about at least one ground cell from the first network element.

[0037] In one possible design, obtaining information about at least one ground cell from a first network element includes: sending second information, which requests information about at least one ground cell from the first network element; the second information includes area information, which indicates the area covered by the requested ground cell and the ground cell belongs to a terrestrial PLMN; and receiving third information, which includes information about at least one ground cell. That is, the source satellite base station can send the terminal's area information to the first network element, so that the first network element can determine the information about at least one ground cell based on the area information and send it to the source satellite base station. Based on the information about at least one ground cell, the source satellite base station can determine when the terminal needs to hand over to a ground cell and initiate a handover process.

[0038] In one possible design, the information of the first network element includes the Internet Protocol address or fully qualified domain name of the first network element.

[0039] In one possible design, the information of each ground cell in at least one ground cell includes at least one of the following: global cell identifier, physical cell identifier, frequency point information, cell coverage information, measurement configuration information, priority information, or the PLMN identifier to which the ground cell belongs.

[0040] In one possible design, determining the target ground cell for the terminal based on information from at least one ground cell includes: determining, based on the terminal's location information and the information of the at least one ground cell, the coverage area of ​​at least one candidate ground cell that the terminal has entered or is about to enter; sending a measurement request to the terminal, the measurement request instructing the terminal to measure the at least one candidate ground cell; receiving a measurement report, the measurement report including the measurement results of the at least one candidate ground cell; and determining the target ground cell based on the measurement results. That is, the source satellite base station can determine the target ground cell based on the terminal's measurement results of the at least one candidate ground cell to initiate the process of the terminal handing over to the target ground cell.

[0041] In one possible design, the measurement request includes at least one of the following information for at least one candidate ground cell: the frequency of the Synchronization Signal Block (SSB), the frequency of the Channel State Information Reference Signal (CSI-RS), the switching timing of the CSI-RS, the switching cycle of the CSI-RS, or the Physical Cell Identifier (PCI).

[0042] In one possible design, when the information of at least one ground cell does not include measurement configuration information, the method further includes: sending fourth information, the fourth information being used to request measurement configuration information of at least one candidate ground cell from the first network element; and receiving fifth information, the fifth information being used to indicate the measurement configuration information of at least one candidate ground cell. That is, the first network element or topology service in the ground core network can also provide the measurement configuration information of the ground cell to the source satellite base station, so that the terminal can perform measurements of the ground cell based on the measurement configuration information.

[0043] In one possible design, the method further includes: determining the coverage area of ​​at least one ground cell from which the terminal has moved out or is about to move out; and receiving sixth information, which includes updated information about at least one ground cell, the updated information of which is determined by a first network element based on the updated area information of the terminal. This allows the source satellite base station to determine the target ground cell based on the latest information of the ground cell, enabling flexible switching to the ground cell when the terminal's area information changes.

[0044] Fifthly, a communication device is provided, which may be, for example, a terminal. The communication device includes: a receiving unit for receiving first indication information, the first indication information indicating information about a first network element of a terrestrial public land mobile network (PLMN); a sending unit for sending second indication information, the second indication information indicating that the terminal requests information about a terrestrial cell from the first network element, the first network element being determined based on information about the first network element, the second indication information including area information indicating the area covered by the requested terrestrial cell, the terrestrial cell belonging to the PLMN; and the receiving unit further for receiving third indication information, the third indication information indicating information about at least one terrestrial cell, wherein the coverage area of ​​any one of the at least one terrestrial cell intersects with the area indicated by the area information, the information about the at least one terrestrial cell being used by the terminal to switch or reselect from a non-terrestrial cell to a terrestrial cell when entering the coverage area of ​​any one of the at least one terrestrial cells; or, the third indication information indicating an area indicated by the area information without terrestrial cell coverage.

[0045] For the beneficial effects of the fifth aspect, please refer to the explanation of the first aspect.

[0046] In one possible design, before receiving the first indication information, the sending unit is also used to send capability information, which indicates that the terminal has at least one of the following capabilities: supporting reselection from a non-terrestrial cell to a terrestrial cell access; supporting handover from a non-terrestrial cell access to a terrestrial cell access; and supporting redirection from a non-terrestrial cell access to a terrestrial cell access.

[0047] In one possible design, the information of the first network element includes the Internet Protocol address or fully qualified domain name of the first network element.

[0048] In one possible design, the information of each ground cell in at least one ground cell includes at least one of the following: global cell identifier, physical cell identifier, frequency point information, cell coverage information, measurement configuration information, priority information, or the PLMN identifier to which the ground cell belongs.

[0049] In one possible design, a processing unit is also included, which determines, based on the terminal's location information and the coverage information of at least one ground cell, the coverage area of ​​at least one candidate ground cell into which the terminal has entered or is about to enter; and performs cell measurement on the at least one candidate ground cell.

[0050] In one possible design, the processing unit is used to perform cell measurements based on at least one of the following information of the candidate ground cells: frequency information, physical cell identifier, or measurement configuration information.

[0051] In one possible design, the transmitting unit is further configured to send a fourth indication message to the serving network device of the non-terrestrial network. The fourth indication message is used to instruct the terminal to switch from the cell of the serving network device to a target terrestrial cell, which is determined by the terminal based on cell measurement results of at least one candidate terrestrial cell.

[0052] In one possible design, the processing unit is used to determine the target ground cell based on at least one of the following information: priority information of at least one candidate ground cell, PLMN information to which at least one candidate ground cell belongs, or cell coverage information of at least one candidate ground cell.

[0053] In one possible design, the transmitting unit is further configured to transmit fifth indication information to the serving network equipment of the non-terrestrial network. The fifth indication information is used to indicate the cell measurement results of at least one candidate terrestrial cell. The fifth indication information is used by the serving network equipment to determine the target terrestrial cell from the at least one candidate terrestrial cell to be handed over by the terminal.

[0054] In one possible design, if the information of at least one ground cell does not include measurement configuration information, the transmitting unit is further configured to transmit sixth indication information, which is used to request measurement configuration information of at least one candidate ground cell from the first network element; the receiving unit is further configured to receive seventh indication information, which is used to indicate the measurement configuration information of at least one candidate ground cell.

[0055] In one possible design, the method further includes: receiving an eighth indication message sent by a first network element, the eighth indication message being used to indicate information of at least one ground cell after updates.

[0056] In one possible design, before receiving the sixth indication information, the sending unit is also configured to send a ninth indication information, which is used to request the first network element to update the information of at least one ground cell. The ninth indication information includes updated area information and is sent when the terminal determines that it has moved out of or is about to move out of the coverage area and / or area information of at least one ground cell before the update.

[0057] Sixthly, a communication device is provided, which may be, for example, a core network device of a satellite network. The communication device includes: a transmitting unit configured to transmit first information, the first information being used to instruct a serving network device of a non-terrestrial network to which a terminal is accessed to allow the terminal to switch to a terrestrial network; the transmitting unit is further configured to transmit first indication information, the first indication information indicating information about a first network element of a terrestrial public land mobile network (PLMN) to which the terminal is allowed to access, the first network element being used to provide information about the terrestrial cells of the PLMN to the terminal or the serving network device of the non-terrestrial network, the information about the terrestrial cells being used by the terminal to perform a handover or reselection from a non-terrestrial cell to a terrestrial cell.

[0058] For the beneficial effects of the sixth aspect, please refer to the explanation of the second aspect.

[0059] In one possible design, before sending the first information, a receiving unit is also included for receiving capability information, which indicates that the terminal has at least one of the following capabilities: supporting reselection from a non-terrestrial cell to a terrestrial cell access; supporting handover from a non-terrestrial cell access to a terrestrial cell access; and supporting redirection from a non-terrestrial cell access to a terrestrial cell access.

[0060] In one possible design, the first network element of the PLMN that allows the terminal to access is determined based on at least one of the terminal's subscription information, location information, or roaming agreement between a non-terrestrial network operator and a terrestrial network operator.

[0061] In one possible design, the first information includes the identifier of the ground PLMN that allows terminal access.

[0062] In one possible design, the information of the first network element includes the Internet Protocol address or fully qualified domain name of the first network element.

[0063] A seventh aspect provides a communication apparatus, which may be, for example, an access network device or a core network device of a terrestrial network, such as a topology server or a topology service network element. It includes: a receiving unit for receiving second indication information, the second indication information being used by a terminal to request information about a terrestrial cell, the second indication information including area information used to indicate the area covered by the terrestrial cell requested by the terminal; and a sending unit for sending third indication information, the third indication information being used to indicate information about at least one terrestrial cell, wherein the coverage area of ​​any one of the at least one terrestrial cell intersects with the area indicated by the area information, and the information about at least one terrestrial cell is used by the terminal to switch or reselect from a non-terrestrial cell to a terrestrial cell when entering the coverage area of ​​any one of the at least one terrestrial cell; or, the third indication information is used to indicate an area not covered by the area information indicated by the terrestrial cell coverage area.

[0064] For the beneficial effects of the seventh aspect, please refer to the explanation of the third aspect.

[0065] In one possible design, the information of each ground cell in at least one ground cell includes at least one of the following: global cell identifier, physical cell identifier, frequency point information, cell coverage information, measurement configuration information, priority information, or the Public Land Mobile Network (PLMN) identifier to which the ground cell belongs.

[0066] In one possible design, if the information of at least one ground cell does not include measurement configuration information, the receiving unit is further configured to receive sixth indication information, which is used by the terminal to request measurement configuration information of at least one candidate ground cell; the sending unit is further configured to send seventh indication information, which is used to indicate the measurement configuration information of at least one candidate ground cell.

[0067] In one possible design, the transmitting unit is also used to transmit an eighth indication message, which is used to indicate to the terminal the updated information of at least one ground cell.

[0068] In one possible design, before sending the sixth indication information, the receiving unit is also configured to receive a ninth indication information, which is used by the terminal to request an update of information of at least one ground cell. The ninth indication information includes the updated area information of the terminal. The ninth indication information is sent when the terminal determines that it has moved out of or is about to move out of the coverage area and / or area information of at least one ground cell before the update; or, receiving an information change of at least one ground cell, which is used to determine the updated information of at least one ground cell.

[0069] Eighthly, a communication apparatus is provided, such as a source satellite base station accessed by a terminal. The communication apparatus includes: a receiving unit for receiving first information, the first information indicating permission for the terminal to switch from a non-terrestrial network to a terrestrial network; a processing unit for acquiring information about at least one terrestrial cell, the information about the at least one terrestrial cell being used by the terminal to perform cell handover or cell redirection when entering the coverage area of ​​any one of the at least one terrestrial cell; the processing unit is further configured to determine a target terrestrial cell for the terminal based on the information about the at least one terrestrial cell, the target terrestrial cell being the target cell for the terminal handover or redirection.

[0070] For the beneficial effects of the eighth aspect, please refer to the explanation of the fourth aspect.

[0071] In one possible design, the processing unit is configured to: provide first information including information of at least one terrestrial cell; or provide first information including information of a first network element of a terrestrial public land mobile network (PLMN) that the terminal is allowed to access, and obtain information of at least one terrestrial cell from the first network element based on the information of the first network element; or provide first information including an identifier of at least one terrestrial PLMN, the identifier of which is used to determine information of the first network element, and obtain information of at least one terrestrial cell from the first network element based on the information of the first network element.

[0072] In one possible design, a sending unit is used to send second information, which is used to request information of at least one ground cell from a first network element. The second information includes area information, which is used to indicate the area covered by the ground cell requested by the terminal, and the ground cell belongs to a ground PLMN. A receiving unit is used to receive third information, which includes information of at least one ground cell.

[0073] In one possible design, the information of the first network element includes the Internet Protocol address or fully qualified domain name of the first network element.

[0074] In one possible design, the information of each ground cell in at least one ground cell includes at least one of the following: global cell identifier, physical cell identifier, frequency point information, cell coverage information, measurement configuration information, priority information, or the PLMN identifier to which the ground cell belongs.

[0075] In one possible design, the processing unit, configured to determine a target ground cell for the terminal based on information from at least one ground cell, includes: determining, based on the terminal's location information and the information from the at least one ground cell, the coverage area of ​​at least one candidate ground cell that the terminal has entered or is about to enter; the sending unit, configured to send a measurement request to the terminal, the measurement request instructing the terminal to perform measurements on at least one candidate ground cell; receiving a measurement report, the measurement report including the measurement results of at least one candidate ground cell; and determining the target ground cell based on the measurement results.

[0076] In one possible design, the measurement request includes at least one of the following information for at least one candidate ground cell: the frequency of the Synchronization Signal Block (SSB), the frequency of the Channel State Information Reference Signal (CSI-RS), the switching timing of the CSI-RS, the switching cycle of the CSI-RS, or the Physical Cell Identifier (PCI).

[0077] In one possible design, if the information of at least one ground cell does not include measurement configuration information, the transmitting unit is further configured to transmit fourth information, which is used to request measurement configuration information of at least one candidate ground cell from the first network element; the receiving unit is configured to receive fifth information, which is used to indicate the measurement configuration information of at least one candidate ground cell.

[0078] In one possible design, a processing unit is used to determine the coverage area of ​​at least one ground cell from which the terminal has moved out or is about to move out; a receiving unit is used to receive sixth information, which includes updated information of at least one ground cell, the updated information of the at least one ground cell being determined by the first network element based on the updated area information of the terminal.

[0079] A ninth aspect provides a communication device, including at least one processor connected to a memory, the at least one processor being configured to read and execute a program stored in the memory, such that the device performs the method as described in the first aspect or any of the first aspects above, or performs the method as described in the second aspect or any of the second aspects above, or performs the method as described in the third aspect or any of the third aspects above, or performs the method as described in the fourth aspect or any of the fourth aspects above.

[0080] A tenth aspect provides a computer-readable storage medium storing computer instructions that, when executed on a communication device, cause the communication device to perform the method described in the first aspect or any one thereof, or to perform the method described in the second aspect or any one thereof, or to perform the method described in the third aspect or any one thereof, or to perform the method described in the fourth aspect or any one thereof.

[0081] Eleventhly, a computer program product is provided, which, when run on a computer or processor, causes the computer or processor to execute the antenna gain adjustment method in any of the above aspects and any possible implementations.

[0082] In a twelfth aspect, a communication system is provided, which may include a terminal, a first network element, a network device for a non-terrestrial network, and a core network device for a terrestrial network, as described in any possible implementation of any of the above aspects. The communication system can execute the communication methods described in any of the above aspects and any possible implementations.

[0083] It is understood that any of the terminals, first network elements, non-terrestrial network network devices, and terrestrial network core network devices, computer-readable storage media, or computer program products provided above can be applied to the corresponding methods provided above. Therefore, the beneficial effects they can achieve can be referred to the beneficial effects in the corresponding methods, and will not be repeated here.

[0084] These or other aspects of this application will become more readily apparent in the following description. Attached Figure Description

[0085] Figure 1 is a schematic diagram of a network architecture that integrates terrestrial and non-terrestrial networks to provide services to terminals, according to an embodiment of this application.

[0086] Figure 2 is a coverage diagram of a satellite cell and a ground cell provided in an embodiment of this application;

[0087] Figure 3 is a flowchart illustrating a communication method provided in an embodiment of this application;

[0088] Figure 4 is a flowchart illustrating a communication method provided in an embodiment of this application;

[0089] Figure 5 is a flowchart illustrating a communication method provided in an embodiment of this application;

[0090] Figure 6 is a flowchart illustrating a communication method provided in an embodiment of this application;

[0091] Figure 7 is a flowchart illustrating a communication method provided in an embodiment of this application;

[0092] Figure 8 is a schematic diagram of the area information indication of a terminal provided in an embodiment of this application;

[0093] Figure 9 is a flowchart illustrating a communication method provided in an embodiment of this application;

[0094] Figure 10 is a schematic diagram of the structure of a communication device provided in an embodiment of this application;

[0095] Figure 11 is a schematic diagram of the structure of a communication device provided in an embodiment of this application. Detailed Implementation

[0096] This application can be applied to a network architecture that integrates terrestrial networks (TN) and non-terrestrial networks (NTN). Non-terrestrial networks are an important supplement to terrestrial cellular communication technology and represent one of the technological directions for direct satellite connection to terminals. By integrating satellite communication networks with terrestrial networks, ubiquitous coverage can be provided regardless of terrain, connecting multiple dimensions of space, air, land, and sea to form an integrated ubiquitous access network, enabling on-demand access across all scenarios.

[0097] There are two common architectures for non-terrestrial network technologies: transparent mode, also known as transparent forwarding or transparent payload; and regenerative mode, also known as regenerative payload or base station onboarding. Transparent forwarding essentially treats the satellite merely as a signal relay link. The 5G base station, as part of the terrestrial network, is deployed behind the gateway station in the NTN. The satellite does not process the signals transmitted by the base station; it simply acts as a bridge between the terminal and the gateway station. Base station onboarding, on the other hand, deploys the functionality of the 5G base station on the satellite. The inter-satellite links are similar to the Xn interface between terrestrial base stations, and the feeder link between the satellite and the gateway station can be understood as part of the backhaul network between the base station and the core network. Simply put, the satellite possesses the functions of a base station, capable of processing data before transmitting it to the terminal.

[0098] Terrestrial networks can be wireless communication systems such as 5G and future possible communication technologies, including but not limited to narrowband internet of things (NB-IoT), global system for mobile communications (GSM), enhanced data rate for GSM evolution (EDGE), wideband code division multiple access (WCDMA), code division multiple access 2000 (CDMA2000), time division-synchronization code division multiple access (TD-SCDMA), long term evolution (LTE), and the three major application scenarios of 5G mobile communication systems: enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and enhanced machine-type communication (eMTC), as well as future possible mobile communication systems.

[0099] Figure 1 illustrates a network architecture 100 that integrates terrestrial and non-terrestrial networks to provide services to terminals. In this network architecture 100, the terrestrial network may include a terrestrial radio access network (RAN) 1001, a terrestrial core network 1002, and an operation administration and maintenance (OAM) network element 1003. The non-terrestrial network may include a satellite radio access network 1004 and a satellite core network 1005. The network architecture 100 also includes a terminal 1006.

[0100] The terrestrial radio access network 1001 may include at least one RAN node, and may also include other RAN nodes, such as wireless relay equipment and / or wireless backhaul equipment. Terminals connect to RAN nodes wirelessly. Terminals and RAN nodes can be interconnected via wired or wireless means. RAN nodes connect to the terrestrial core network via wireless or wired means. The core network equipment in the terrestrial core network and the RAN nodes in the RAN may be independent physical devices, or they may be the same physical device integrating the logical functions of the core network equipment and the logical functions of the RAN node.

[0101] A RAN node, also known as a radio access network device, RAN entity, or access node, is used to help terminals access a communication system wirelessly. In one application scenario, an RAN node can be a base station, an evolved NodeB (eNodeB), a transmission reception point (TRP), a next-generation NodeB (gNB) in a 5G mobile communication system, or a base station in a future mobile communication system. An RAN node can be a macro base station, a micro base station, an indoor station, a relay node, or a donor node. In this application, a terrestrial radio access network using a terrestrial base station as an example is used for illustration.

[0102] The terrestrial core network 1002 is connected to terrestrial base stations. The terrestrial core network may include capability-opening network elements, which can communicate with capability-opening network elements in the satellite core network. The terrestrial core network 1002 may also include access and mobility management function (AMF) network elements, session management function (SMF) network elements, unified data management (UDM) network elements, network exposure function (NEF) network elements, and authentication server function (AUSF) network elements, etc. In future networks, the functions of the terrestrial core network may be recombined; this application applies to the core network of future networks after the recombination of terrestrial core network functions.

[0103] In this network architecture 100, the satellite core network 1005 and the terrestrial core network 1002 can also be co-located, meaning that a single core network device can simultaneously support both terrestrial and satellite access. The satellite core network 1005 and the terrestrial core network 1002 can also be partially co-located and partially separated; this application does not impose any limitations on this.

[0104] In this application, the satellite core network 1005 can receive the capabilities of the terminal 1006 and determine whether the terminal 1006 can access the network via a non-terrestrial network and whether it supports handover to a terrestrial network based on the terminal 1006's capabilities, subscription information, and roaming agreement. If it is determined that handover to a terrestrial network is supported, the satellite core network 1005 can send an indication to the source satellite base station that the terminal 1006 supports handover to a terrestrial network. The satellite core network 1005 can also select a terrestrial network for the terminal 1006 to access, select the corresponding topology service of the satellite core network 1005, and send the address information of the topology service to the terminal 1006 or obtain auxiliary information from the topology service and send it to the terminal 1006. The auxiliary information is used by the terminal 1006 to handover from a non-terrestrial network to a terrestrial network. For example, the auxiliary information can be understood as the information of the terrestrial cell in this application. When the source satellite base station triggers cell handover, the satellite core network 1005 can also obtain the auxiliary information and send it to the source satellite base station. For example, the functions of the satellite core network 1005 of this application can be performed by AMF network elements or by other network elements of the satellite core network 1005, and this application does not limit them.

[0105] The OAM1003 primarily performs daily network and service analysis, prediction, planning, and configuration. Maintenance mainly involves routine operations such as testing and fault management of the network and its services. In this application, for example, the topology service can obtain terrestrial cell information from the OAM1003, or it can directly obtain terrestrial cell information from the terrestrial radio access network 1001; this application does not impose any limitations.

[0106] The satellite wireless access network 1004 includes satellite base stations. In this application, the satellite base stations can be connected to the satellite core network 1005. The satellite base stations can be deployed on a satellite. This application does not limit the deployment location of the satellite base stations. That is, the satellite base stations can be deployed on the ground, i.e., in a transparent mode, with only the radio frequency module of the base station deployed on the satellite. The satellite base stations can also adopt a regenerative mode, possessing some of the functions of a base station. The satellite base stations can communicate with the satellite core network 1005 through the gateway station 1007.

[0107] In this application, when terminal 1006 accesses a satellite base station, the satellite base station can trigger a handover to the terrestrial network when it determines that terminal 1006 has no available non-terrestrial cells, and send a handover notification to terminal 1006 or satellite core network 1005. The satellite base station can also receive a target terrestrial cell selected by terminal 1006 or a measurement report (selecting a target terrestrial cell based on the measurement report). The satellite base station can also trigger a cell handover process via the core network.

[0108] Terminal 1006 is a device with wireless transceiver capabilities, capable of sending signals to or receiving signals from a base station. The base station can be a terrestrial base station or a non-terrestrial base station in transparent or regenerative mode, such as a satellite base station. The terminal can also be referred to as a terminal device, user equipment (UE), mobile station, mobile terminal, etc. Terminals can be widely used in various scenarios, such as device-to-device (D2D), vehicle-to-everything (V2X) communication, machine-type communication (MTC), Internet of Things (IoT), virtual reality, augmented reality, industrial control, autonomous driving, telemedicine, smart grids, smart furniture, smart offices, smart wearables, smart transportation, smart cities, etc. Terminals can be mobile phones, tablets, computers with wireless transceiver capabilities, wearable devices, vehicles, airplanes, ships, robots, robotic arms, smart home devices, etc. The embodiments of this application do not limit the specific technology or device form used in the terminal.

[0109] In this application, terminal 1006 can send capability information to satellite core network 1005 and receive auxiliary information from the network or directly obtain auxiliary information from topology services. Terminal 1006 can search for and select target ground cells based on auxiliary information, or perform measurements on candidate ground cells. In idle state, terminal 1006 can access the network through the selected target ground cell; in connected state, terminal 1006 can send the target ground cell or measurement report to the satellite base station.

[0110] As shown in Figure 1, this application can add a topology service to the network architecture 100. The topology service stores information about ground cells, including at least one of the following: the identifier of the ground cell (such as a physical cell identifier), the frequency information of the ground cell, the coverage information of the ground cell, measurement configuration information, priority information, or the identifier of the public land mobile network (PLMN) to which the ground cell belongs. The ground cell belongs to a ground base station. The topology service can return information about ground cells covering a region or location upon request. For example, the topology service sends ground cell information to terminal 1006 upon request. For terminal 1006 in a connected state, the ground cell information may also include information for measuring candidate ground cells. In this application, the topology service can be a server or other network element, and this application does not limit it. This application does not limit the deployment location of the topology service; for example, the topology service can be deployed in the ground core network 1002 or in the ground radio access network 1001.

[0111] In the embodiments of this application, the functions of the base station can be executed by modules (such as chips) within the base station, or by a control subsystem that includes base station functions. This control subsystem, including base station functions, can be a control center in the aforementioned application scenarios such as smart grids, industrial control, intelligent transportation, and smart cities. The functions of the terminal can also be executed by modules (such as chips or modems) within the terminal, or by a device that includes terminal functions. The functions of the core network equipment can also be executed by modules (such as chips) within the core network equipment, or by a device that includes core network equipment functions. The functions of the topology service can also be executed by modules (such as chips) within the topology service, or by a device that includes topology service functions.

[0112] Considering the coverage gaps in terrestrial networks, 5G introduces non-terrestrial networks, such as satellite network access, allowing terminals to access the network via satellite. The introduction of satellite networks enables operators to provide network access to areas previously lacking terrestrial network coverage, filling these gaps. This allows terminals to move between terrestrial and non-terrestrial networks. Typically, the coverage area of ​​a non-terrestrial cell in a non-terrestrial network is wider than that of a terrestrial cell in a terrestrial network. In other words, the coverage area of ​​a satellite cell is wider than that of a terrestrial cell. When a terminal moves within the coverage area of ​​a non-terrestrial cell, it may enter the coverage area of ​​a terrestrial cell. Figure 2 illustrates a coverage diagram of satellite and terrestrial cells. In V2X communication, vehicle 204, during its movement, may pass through non-terrestrial cell 201 and enter terrestrial cells 202 or 203. When vehicle 204 moves between terrestrial and non-terrestrial cells, it may need to perform cell handover. This is because terrestrial cells are closer to the terminal, have higher bandwidth and capacity, and transmitting signals from the terminal to a terrestrial cell is more energy-efficient than transmitting signals from the terminal to a satellite. Therefore, vehicle 204 can switch the network it is connected to from a non-terrestrial cell to a terrestrial cell.

[0113] Understandably, when a terminal is in an idle state and inter-cell movement occurs, it performs cell reselection to access the network through a new cell. When searching for a target cell, if the terminal is unsure of the target cell's frequency information, it needs to attempt searches on various supported frequencies. Therefore, cell search is a time-consuming and power-intensive process. In terrestrial networks, ground base stations broadcast information about neighboring cells to help the terminal quickly search for neighboring cells. For example, ground base stations broadcast information such as the identifier and center frequency of neighboring cells. The terminal can then use this information to search for specific frequencies, thereby reducing cell search time and saving power.

[0114] In 5G non-terrestrial network technologies, satellite cells broadcast spectrum information used by base stations covering a ground area to optimize the performance of terminal cell selection during the migration process from a non-terrestrial network to a terrestrial network, reducing the time spent searching for a ground cell. However, this method offers limited optimization potential, primarily because satellite cells typically have a large coverage area, which is often also covered by numerous terrestrial cells. In such cases, relying solely on satellite cell information is often insufficient to determine the target terrestrial cell the terminal needs to search for.

[0115] In terrestrial networks, when a terminal switches cells across base stations, the source base station needs to sense the configuration information of neighboring cells and instruct the terminal to measure the target cell based on the target cell's configuration information. The source base station then selects the target cell based on the measurement results. However, due to the high dynamism of satellites and the barriers between operators—that is, satellites and terrestrial base stations belong to different operators—it is difficult for satellite cells and terrestrial cells to configure neighboring cell information with each other. This makes cell handover during connected states quite challenging for the terminal.

[0116] Specifically, taking a satellite cell as an example (not a terrestrial cell), when the terminal is in connected mode, the satellite cell needs to configure neighboring cell information of adjacent terrestrial cells to support handover from the satellite cell to the terrestrial cell. However, due to the rapid movement of satellites, neighboring cells change quickly, making neighbor configuration very complex. Furthermore, since satellite cells and terrestrial cells usually belong to different operators, cross-operator configuration of neighboring cell information is generally not supported. Therefore, handover from satellite cells to terrestrial cells cannot be supported. When the terminal is in idle mode, although the satellite base station broadcasts frequency information of neighboring cells within a certain ground area, the terminal still needs to switch frequencies to search for cells, which consumes time and power for the terminal.

[0117] Therefore, this application provides a communication method to address the issues of how a terminal can quickly select a terrestrial cell when moving from the coverage area of ​​a non-terrestrial cell to the coverage area of ​​a terrestrial cell, and how to support the terminal to quickly switch from a non-terrestrial cell to a terrestrial cell while minimizing the terminal's energy consumption. In this application, a topology service is introduced into the terrestrial core network. This topology service can provide information on terrestrial cells within a region. This information can be used by base stations or terminals in non-terrestrial cells to determine candidate target terrestrial cells and assist the terminal in switching from a non-terrestrial cell to a terrestrial cell.

[0118] Based on this, Figure 3 shows a flowchart of a communication method provided in an embodiment of this application. In this method, when the core network of the non-terrestrial network determines that the terminal supports switching from the non-terrestrial network to the terrestrial network, it can select a topology service that allows the terminal to access the terrestrial network and indicate the identifier of the topology service to the terminal. In this way, the terminal can request information about terrestrial cells from the topology service, and determine candidate terrestrial cells based on the terrestrial cell information and the terminal's location information. Then, it can measure the candidate terrestrial cells, determine the target terrestrial cell, and perform cell handover or reselection. This method includes the following steps.

[0119] 301. The terminal receives the first indication information, which is used to indicate the information of the first network element of the ground PLMN.

[0120] In some embodiments, receiving the first indication information by the terminal includes: the terminal receiving the first indication information sent by a non-terrestrial core network. Accordingly, the non-terrestrial core network sends the first indication information to the terminal.

[0121] For example, the non-terrestrial core network includes a satellite core network, such as the first indication information sent by the AMF network element in the satellite core network to the terminal.

[0122] In some embodiments, the first indication information used to indicate the information of the first network element of the terrestrial PLMN includes: the first indication information used to indicate the information of the first network element of the terrestrial PLMN that the terminal is allowed to access. The first network element can be understood as a topology service in the terrestrial network. For example, the first network element can be a server or topology server in the terrestrial core network or terrestrial access network. That is, the information of the first network element can be used to characterize the topology service information of the terrestrial PLMN. The terrestrial PLMN that the terminal is allowed to access is a terrestrial PLMN that has an interface with the current non-terrestrial network, and this terrestrial PLMN is the terminal's home PLMN, or there is a roaming relationship between the terminal and the terminal's home PLMN.

[0123] There can be one or more ground PLMNs that terminals are allowed to access. There can also be one or more first network elements. In other words, when the satellite core network determines that there are multiple ground PLMNs that terminals are allowed to access, the satellite core network sends information about the first network element corresponding to each ground PLMN to the terminal.

[0124] In some embodiments, the information of the first network element includes the Internet Protocol (IP) address or fully qualified domain name (FQDN) of the first network element.

[0125] 302. The terminal sends a second instruction message. The second instruction message is used by the terminal to request information about the ground cell from the first network element. The first network element is determined based on the information of the first network element. The second instruction message includes area information, which is used to indicate the area covered by the ground cell requested by the terminal. The ground cell belongs to the ground PLMN.

[0126] In some embodiments, the terminal sending the second indication information includes: the terminal sending the second indication information to the first network element. Accordingly, the first network element receives the second indication information sent by the terminal.

[0127] If, in step 301, the information of the first network element obtained by the terminal indicates the IP addresses or FQDNs of multiple first network elements, the terminal can send second indication information to each of the multiple first network elements to request information about the ground cell. Each ground cell is a ground cell under a ground PLMN that the terminal is allowed to access, that is, the ground cell belongs to the ground PLMN indicated in step 301.

[0128] In some embodiments, the area information can be understood as an area that includes the location information of the terminal, for example, an area centered on the current location of the terminal.

[0129] In some embodiments, the second indication information may not include area information, but may include location information, such as the location information of the terminal. The first network element determines the area information after obtaining the location information; for example, the area information may indicate an area centered on the location indicated by the location information.

[0130] 303. The terminal receives third indication information, which is used to indicate information of at least one ground cell, wherein the coverage area of ​​any one of the at least one ground cell intersects with the area indicated by the area information, and the information of at least one ground cell is used by the terminal to switch or reselect from a non-ground cell to a ground cell when entering the coverage area of ​​any one of the at least one ground cell; or, the third indication information is used to indicate the area indicated by the area information without ground cell coverage.

[0131] In some embodiments, the terminal receiving the third indication information includes: the terminal receiving the third indication information sent by the first network element. Accordingly, the first network element sends the third indication information to the terminal.

[0132] In some embodiments, the information of each ground cell in at least one ground cell includes at least one of the following:

[0133] Global cell ID (GCID), physical cell identity (PCI), frequency information, cell coverage information, measurement configuration information, priority information, or PLMN identifier of the ground cell.

[0134] The priority information can be at the PLMN level, at the cell level within the PLMN, or both.

[0135] The coverage area of ​​any cell in at least one ground cell intersects with the area indicated by the area information. This can be understood as follows: when the first network element sends information about at least one ground cell, the coverage area of ​​each of the at least one ground cell must intersect with the coverage area indicated by the area information. In this way, when the terminal moves within the area indicated by the area information, the terminal can switch or reselect from a non-ground cell to the target ground cell according to the determined target ground cell when it enters the coverage area of ​​any of the at least one ground cell.

[0136] Alternatively, in some embodiments, when the first network element determines, based on the area information sent by the terminal, that no terrestrial cell covers the area indicated by the area information, the third indication information is used to indicate the area indicated by the area information without terrestrial cell coverage. In this way, the terminal will not switch or reselect to a terrestrial cell.

[0137] Therefore, this application introduces a first network element of the terrestrial PLMN, namely, topology service in the terrestrial network. This first network element can provide the terminal with information about at least one terrestrial cell based on the terminal's area information. The coverage area of ​​the terrestrial cell indicated by this information overlaps with the area indicated by the terminal's area information. Thus, when the terminal moves within the area indicated by the area information, it can determine the target terrestrial cell based on the information of at least one terrestrial cell, thereby switching from a non-terrestrial cell to a terrestrial cell. In this way, this application can support rapid switching from a non-terrestrial cell to a terrestrial cell even when neighbor cell information cannot be configured between non-terrestrial and terrestrial networks. The terminal also does not need to frequently perform frequency point searches, saving terminal energy consumption.

[0138] Accordingly, for the non-terrestrial core network, a first indication message can be sent to the terminal or the serving network device of the non-terrestrial network to which the terminal belongs, indicating the information of the first network element of the terrestrial PLMN that the terminal is allowed to access. This allows the terminal or the serving network device of the non-terrestrial network to request information about the terrestrial cell of the terrestrial PLMN from the first network element, enabling the terminal to switch or reselect from the non-terrestrial cell to a terrestrial cell. Figure 4 shows a flowchart of a communication method provided in an embodiment of this application. The method includes the following steps.

[0139] 401. The non-terrestrial core network sends first information, which is used to instruct the serving network equipment of the non-terrestrial network to which the terminal is connected to to allow the terminal to switch to the terrestrial network.

[0140] In some embodiments, the non-terrestrial core network sending the first information includes: the satellite core network sending the first information to the serving network device of the non-terrestrial network to which the terminal belongs. Correspondingly, the serving network device receives the first information sent by the satellite core network.

[0141] For example, the satellite core network sends first information to the base station of the satellite network accessed by the terminal, or in other words, the satellite core network sends first information to the source satellite base station. Thus, if the source satellite base station determines that the terminal is permitted to switch to a terrestrial network, the source satellite base station can execute a handover procedure from a non-terrestrial cell to a terrestrial cell, or the source satellite base station can obtain information about the terrestrial cells that the terminal is permitted to access from the first network element and send it to the terminal.

[0142] In some embodiments, before sending the first information, the method further includes: the non-terrestrial core network receiving capability information, the capability information being used to indicate that the terminal has at least one of the following capabilities: supporting reselection from a non-terrestrial cell to a terrestrial cell access; supporting handover from a non-terrestrial cell access to a terrestrial cell access; supporting redirection from a non-terrestrial cell access to a terrestrial cell access.

[0143] For example, the satellite core network receives capability information sent by the terminal. Correspondingly, the terminal sends capability information to the satellite core network. For instance, the terminal might include this capability information in its registration request when sending the registration request to the satellite core network. Thus, when the satellite core network determines that the terminal supports terrestrial network access or supports switching to terrestrial network access, it can select a terrestrial PLMN and its corresponding topology service that the terminal is allowed to access, so that the topology service can provide the terminal with information about the terrestrial cell.

[0144] In some embodiments, the first information includes an identifier of a terrestrial PLMN that the terminal is allowed to access. Thus, when the source satellite base station receives the first information, it can determine, based on the first information, which terrestrial cell the terminal can switch to or reselect, or determine that the target terrestrial cell selected by the terminal is a terrestrial PLMN that the terminal is allowed to access, and initiate a handover or reselection process to that terrestrial cell.

[0145] 402. The non-terrestrial core network sends a first indication message, which indicates the information of the first network element of the terrestrial PLMN that the terminal is allowed to access. The first network element is used to provide the terminal or the service network equipment of the non-terrestrial network with the information of the PLMN's terrestrial cell. The information of the terrestrial cell is used by the terminal to switch from the non-terrestrial cell or reselect to the terrestrial cell.

[0146] In some embodiments, the non-terrestrial core network sending the first indication information includes: the non-terrestrial core network sending the first indication information to the terminal. Accordingly, the terminal receives the first indication information sent by the non-terrestrial core network.

[0147] In some embodiments, the first network element of the PLMN that the terminal is allowed to access is determined by the non-terrestrial core network based on at least one of the terminal's subscription information, location information, or roaming agreement between the non-terrestrial network operator and the terrestrial network operator.

[0148] For example, the non-terrestrial core network needs to determine, based on the terminal's subscription information, whether the terminal has subscribed to the interconnection between the non-terrestrial network and the terrestrial PLMN, and based on the roaming agreement, whether there is a terrestrial PLMN operator cooperating with the non-terrestrial operator at the current location. Based on the above information, the non-terrestrial core network selects a terrestrial PLMN that the terminal is allowed to access, and selects the first network element corresponding to that terrestrial PLMN.

[0149] In some embodiments, the information of the first network element includes the IP address or FQDN of the first network element.

[0150] In this way, for non-terrestrial core networks accessed by terminals, by instructing the serving network equipment of the non-terrestrial network to allow the terminal to access the terrestrial network, and by instructing the terminal or the serving network equipment of the non-terrestrial network to provide information on the first network element of the terrestrial PLMN that the terminal is allowed to access, the terminal or the serving network equipment of the non-terrestrial network can obtain information on the terrestrial cell from the first network element. This allows the terminal to switch or reselect from the non-terrestrial cell to the terrestrial cell based on the information on the terrestrial cell, or allows the serving network equipment of the non-terrestrial network to configure the terminal to measure candidate terrestrial cells based on the information on the terrestrial cells obtained from the first network element, and determine the target terrestrial cell based on the measurement results, so as to switch or redirect the terminal from the non-terrestrial cell to the terrestrial cell. This not only solves the problem that non-terrestrial networks and terrestrial networks cannot configure neighboring cells across operators and supports the terminal switching from the non-terrestrial network to the terrestrial network, but also allows the terminal to perform cell handover or reselection to the terrestrial cell based on the obtained terrestrial cell information, and avoids the time-consuming and power-consuming problem caused by the terminal frequently searching for cells according to the frequency information broadcast by the non-terrestrial network.

[0151] For the first network element of the terrestrial network, when the first network element receives a request from a terminal for information about a terrestrial cell, it can determine, based on the area information, the information of at least one terrestrial cell that the terminal is allowed to access, so that when the terminal enters any of the at least one terrestrial cells, it can switch or reselect from a non-terrestrial cell to a terrestrial cell. Figure 5 shows a flowchart of a communication method provided in an embodiment of this application, which includes the following steps.

[0152] 501. The first network element receives the second indication information, which is used to request information about the ground cell. The second indication information includes area information or location information. The area information is used to indicate the area covered by the requested ground cell, and the location information is used to indicate the location covered by the requested ground cell.

[0153] In some embodiments, the first network element receiving the second indication information includes: the first network element receiving the second indication information sent by the terminal. Accordingly, the terminal sends the second indication information to the first network element.

[0154] In other embodiments, the first network element receives second indication information sent by a non-terrestrial core network or a non-terrestrial service network device. Correspondingly, the non-terrestrial core network or the non-terrestrial service network device sends the second indication information to the first network element.

[0155] In some embodiments, the second indication information includes location information, and the first network element determines area information based on the location information. For example, the first network element may determine an area centered on the location indicated by the location information.

[0156] That is, the first network element can determine the information of the ground cells that the terminal is allowed to access based on the regional information, so that the terminal can switch from a non-ground cell or reselect to a ground cell.

[0157] 502. The first network element sends third indication information, which is used to indicate information of at least one ground cell. The coverage area of ​​any one of the at least one ground cell intersects with the area indicated by the area information. The information of at least one ground cell is used by the terminal to switch or reselect from a non-ground cell to a ground cell when entering the coverage area of ​​any one of the at least one ground cell; or, the third indication information is used to indicate the area indicated by the area information without ground cell coverage.

[0158] In some embodiments, the first network element sending the third indication information includes: the first network element sending the third indication information to the terminal. Accordingly, the terminal receives the third indication information sent by the first network element.

[0159] In other embodiments, the first network element sending the third indication information includes: the first network element sending the third indication information to the non-terrestrial core network. After receiving the third indication information, the non-terrestrial core network may further send information about at least one terrestrial cell indicated by the third indication information to the terminal.

[0160] In this way, when the first network element or topology service of the terrestrial core network provides the terminal with information on at least one terrestrial cell, the terminal can determine the target terrestrial cell based on the information of at least one terrestrial cell when entering the coverage area of ​​any of the at least one terrestrial cells, thereby switching or reselecting from a non-terrestrial cell to a terrestrial cell. This not only supports the terminal's rapid switch from a non-terrestrial network to a terrestrial network, but also avoids the time-consuming and power-consuming problem caused by the terminal searching for cells based on broadcast frequency information when accessing a non-terrestrial network.

[0161] For service network equipment of non-terrestrial networks accessed by the terminal, such as the source satellite base station accessed by the terminal, the source satellite base station may, upon determining that the terminal is allowed to switch from a non-terrestrial network to a terrestrial network, obtain information on at least one terrestrial cell that the terminal is allowed to access from the first network element, and determine the target terrestrial cell based on the terminal's measurement results of the terrestrial cells, so that the terminal can switch or redirect to the target terrestrial cell. Figure 6 shows a flowchart of a communication method provided in an embodiment of this application, which includes the following steps.

[0162] 601. The serving network device of the non-terrestrial network receives first information, which is used to indicate that the terminal is allowed to switch from the non-terrestrial network to the terrestrial network.

[0163] In some embodiments, the receiving of first information by the serving network device of the non-terrestrial network includes: the serving network device of the non-terrestrial network receiving first information sent by the core network of the non-terrestrial network. Accordingly, the core network of the non-terrestrial network sends the first information to the serving network device of the non-terrestrial network.

[0164] For example, the source satellite base station receives first information sent by the satellite core network, and correspondingly, the satellite core network sends first information back to the source satellite base station. Thus, in some embodiments, when the source satellite base station determines that a terminal is permitted to switch from a non-terrestrial network to a terrestrial network, it can switch or redirect the terminal to a terrestrial cell based on the target terrestrial cell information sent by the terminal; or, in other embodiments, when the source satellite base station determines that a terminal is permitted to switch from a non-terrestrial network to a terrestrial network, the source satellite base station can obtain information about the terrestrial cells that the terminal is permitted to access from a first network element, allowing the terminal to switch or redirect to a terrestrial cell.

[0165] 602. The service network equipment of the non-terrestrial network obtains information about at least one terrestrial cell. The information about at least one terrestrial cell is used by the terminal to perform cell handover or cell redirection when entering the coverage area of ​​any of the at least one terrestrial cells.

[0166] There are several ways for a non-terrestrial network serving network device to obtain information about at least one terrestrial cell. For example, in some embodiments, the first information in step 601 includes information about at least one terrestrial cell. Alternatively, the first information includes information about a first network element of a terrestrial PLMN that the terminal is allowed to access, and the non-terrestrial network serving network device obtains information about at least one terrestrial cell from the first network element based on the information of the first network element. Alternatively, the first information includes an identifier of at least one terrestrial PLMN, which is used to determine the information of the first network element, and the non-terrestrial network serving network device obtains information about at least one terrestrial cell from the first network element based on the information of the first network element.

[0167] In some embodiments, obtaining information about at least one terrestrial cell from the first network element includes: a serving network device of a non-terrestrial network sending second information, the second information being used to request information about at least one terrestrial cell from the first network element, the second information including area information or location information, the area information being used to indicate the area covered by the terrestrial cell requested by the terminal, the location information being used to indicate the location of the terminal, and the terrestrial cell belonging to a terrestrial PLMN; the serving network device of the non-terrestrial network receiving third information sent by the first network element, the third information including information about at least one terrestrial cell.

[0168] 603. The service network equipment of the non-terrestrial network determines the target terrestrial cell of the terminal based on the information of at least one terrestrial cell. The target terrestrial cell is the target cell for terminal handover or redirection.

[0169] For example, when a non-terrestrial network service device determines candidate terrestrial cells for a terminal based on information from at least one terrestrial cell, it can send a measurement request to the terminal and determine the target terrestrial cell from the candidate terrestrial cells based on the measurement report sent by the terminal, so that the terminal can switch or redirect to the target terrestrial cell.

[0170] Therefore, in this application, when the serving network equipment of a non-terrestrial network determines that the terminal supports switching from a non-terrestrial network to a terrestrial network, it can obtain information on at least one terrestrial cell that allows the terminal to access, and use this information to determine the target terrestrial cell for handover or redirection. This not only supports rapid switching from a non-terrestrial network to a terrestrial network, but also avoids the time-consuming and power-intensive problem caused by the terminal searching for cells based on broadcast frequency information when accessing a non-terrestrial network.

[0171] Based on the above introduction of various network elements, namely the terminal, the non-terrestrial core network, the first network element of the terrestrial network, and the service network equipment of the non-terrestrial network, the signaling interaction process of the communication method of this application will be described below in conjunction with the implementation of the above network elements.

[0172] Figure 7 shows a flowchart of a communication method provided in an embodiment of this application. In this method, the terminal obtains information about a ground cell from a first network element based on the identifier of that first network element, and performs cell measurement when determining candidate ground cells to obtain measurement results. Then, the terminal or a serving network device from a non-terrestrial network determines the target ground cell based on the measurement results, and the serving network device from the non-terrestrial network initiates a handover or reselection to the target ground cell. The following explanation uses the serving network device from the non-terrestrial network as the source satellite base station, the core network of the non-terrestrial network as the satellite core network, and the target ground cell as the target ground base station as an example. The method includes the following steps.

[0173] 701. The terminal registers with the satellite core network and sends its capability information to the satellite core network.

[0174] For example, when a terminal initiates a registration process with the satellite core network through the source satellite base station, the registration request message sent by the terminal to the satellite core network includes the terminal's capability information.

[0175] Alternatively, the terminal's capability information can be carried in messages such as attach request messages or service request messages sent by the terminal to the satellite core network through the source satellite base station.

[0176] Alternatively, in future communication networks, the registration request message may be other messages, and this application does not impose any restrictions.

[0177] Alternatively, the capability information can be carried in a dedicated request message for the sending terminal's capabilities.

[0178] 702. The satellite core network determines which terminals are allowed to access the network via the terrestrial network, and determines the terrestrial PLMNs that terminals are allowed to access and the first network element corresponding to the terrestrial PLMNs.

[0179] For example, in this application, the satellite core network can be an AMF network element in the satellite core network.

[0180] For example, the satellite core network can determine whether to allow the terminal to access the network through a terrestrial base station or a terrestrial network by using the terminal's subscription information, terminal capability information, terminal current location information, and roaming agreements between the satellite operator and the terrestrial operator, and determine the identifier of the terrestrial network that the terminal is allowed to access, i.e., the PLMN ID.

[0181] For example, the terminal's current location information can be reported by the terminal to the satellite core network, or it can be determined by a non-terrestrial network based on the current beam information and the satellite's position. For instance, the satellite base station can determine the terminal's location using the method described above and send the terminal's location to the satellite core network. For example, the terminal's location can be the geographical area where the terminal is currently located, or even the terminal's two-dimensional geographic coordinates. This application does not limit the precision of the terminal's geographic coordinates.

[0182] When the location of the terminal is covered by the terrestrial network of its home operator, the satellite core network determines the terrestrial networks that the terminal is allowed to access, including the terminal's home operator, based on the roaming support between the satellite network operator and the home operator. For example, the terminal's home operator is a terrestrial operator.

[0183] When the terminal's subscription information supports roaming across terrestrial operators, the terminal can also access the network through a terrestrial operator's base station that has roaming agreements with both its home operator and the satellite operator it is currently accessing, and that has terrestrial coverage at its current location. In this case, the satellite core network can identify that terrestrial operator as a terrestrial PLMN that the terminal is allowed to access.

[0184] If the terminal's home operator is a satellite operator, the terminal's subscription information may include an indication of whether the terminal is allowed to access the network via a terrestrial network. In this case, the satellite core network can determine whether to allow the terminal to access the network via a terrestrial network based on the terminal's subscription information. It will then select a terrestrial operator with a roaming agreement with the satellite operator and terrestrial coverage at the current location as the terrestrial PLMN that the terminal is allowed to access.

[0185] In this way, the satellite core network can identify one or more ground PLMNs that terminals are allowed to access. When a terminal's current location has a home PLMN (HPLMN), the HPLMN is included in the ground PLMNs that terminals are allowed to access. If other PLMNs exist at the terminal's current location, and the terminal supports roaming, the satellite core network can also identify these other PLMNs as ground PLMNs that terminals are allowed to access.

[0186] The satellite core network can prioritize the ground PLMNs that are allowed for terminal access. For example, HPLMNs can be set as the highest priority, so that the ground base station of the HPLMN of the terminal can be preferred for access.

[0187] After identifying the terrestrial PLMNs that are allowed for terminal access, the satellite core network determines the first network element corresponding to the terrestrial PLMN, or in other words, the topology service corresponding to the terrestrial PLMN. When there are multiple terrestrial PLMNs that are allowed for terminal access, the satellite core network can also determine the first network element corresponding to each terrestrial PLMN that is allowed for terminal access.

[0188] For example, different ground PLMNs can correspond to different first network elements, or they can share the same first network element.

[0189] 703. The satellite core network sends first information to the source satellite base station currently accessed by the terminal. The first information is used to instruct the source satellite base station to allow the terminal to switch to the terrestrial network.

[0190] Accordingly, the source satellite base station receives the first information sent by the satellite core network.

[0191] In some embodiments, the first information is used not only to indicate to the source satellite base station that the terminal is allowed to switch from a non-terrestrial network to a terrestrial network, but also may include the PLMN identifier (ID) of the terrestrial network that the terminal is allowed to access, i.e., the terrestrial PLMN ID. If the satellite core network determines that the terminal is allowed to access one or more terrestrial PLMNs, the first information here may include the PLMN IDs of one or more terrestrial PLMNs.

[0192] In this way, the source satellite base station can determine the ground base station that allows the terminal to switch to the target PLMN based on the first information.

[0193] 704. The satellite core network sends a first indication message to the terminal. The first indication message is used to indicate the information of the first network element of the ground PLMN that the terminal is allowed to access.

[0194] Accordingly, the terminal receives the first instruction information sent by the satellite core network.

[0195] For example, when the satellite core network determines that the terminal is allowed to access one or more ground PLMNs, the first indication information may include information about the first network element corresponding to these one or more PLMNs. For example, the information of the first network element may include the IP address or FQDN of the first network element, which is used by the terminal to obtain information about the ground cell from the first network element.

[0196] If the first indication information includes information about the first network elements of multiple PLMNs, and also indicates the priority information of the multiple PLMNs (e.g., HPLMN has the highest priority), then the terminal can preferentially obtain the information of the ground cell from the first network element corresponding to the PLMN with the highest priority.

[0197] The first instruction information may also include the identifier of the PLMN that the terminal is allowed to access; that is, the first information includes the identifier of the PLMN and the identifier of the first network element corresponding to the PLMN.

[0198] 705. The terminal sends a second instruction message to the first network element. The second instruction message is used by the terminal to request information about the ground cell from the first network element. The second instruction message includes the terminal's area information or location information.

[0199] Accordingly, the first network element receives the second instruction information sent by the terminal.

[0200] If the first instruction information includes information about multiple first network elements, the terminal can send the second instruction information to each of the multiple first network elements to obtain information about the ground cell fed back by the multiple first network elements.

[0201] For example, the terminal's area information is used to indicate the area covered by the requested terrestrial cell, or in other words, the area where the terminal is located. For instance, Figure 8 shows a schematic diagram of the area indicated by the terminal's area information. Figure 8(a) shows a circular area centered on the terminal's location (e.g., latitude and longitude), that is, area information indicated by adding radius a to the terminal's location as the center point A. Figure 8(b) shows a square area starting from the terminal's location (e.g., latitude and longitude), for example, area information indicated by adding side length b to the center point B of one side of the square area where the terminal's location is located. Of course, the area indicated by the terminal's area information can also be of other shapes, such as an equilateral polygon. This application does not limit this, nor does it limit the relationship between the terminal and the area, that is, it does not limit the terminal to being located at the center or edge of the area.

[0202] For example, the first indication information does not include area information, but includes location information. The location information may be the location information of the terminal. In the example, the first network element determines the area information based on the location information. The shape of the area, the relationship between the terminal location and the area, can be referred to the description above.

[0203] 706. The first network element sends a third indication message to the terminal. The third indication message is used to indicate information about at least one ground cell.

[0204] Accordingly, the terminal receives the third indication information sent by the first network element. If there are multiple first network elements, each first network element sends its own third indication information to the terminal.

[0205] For example, the first network element can determine information about at least one terrestrial cell based on the area information requested by the terminal. When the first network element sends information about at least one terrestrial cell, the coverage area of ​​any one of the at least one terrestrial cell intersects with the area indicated by the area information requested by the terminal. Thus, when the terminal moves within this area, it can use the information about at least one terrestrial cell to determine the target terrestrial cell and thereby access the target terrestrial cell.

[0206] For example, the information of each ground cell in at least one ground cell includes at least one of the following: Global Cell Identifier (GCID), Physical Cell Identifier, Frequency Point Information, Cell Coverage Information, Measurement Configuration Information, Priority Information, or the PLMN Identifier to which the ground cell belongs.

[0207] For example, the information for each ground cell may also exclude measurement configuration information.

[0208] Cell coverage information can be, for example, the area covered by a terrestrial cell, indicated by the coordinates of the cell's center and its radius. Priority information can indicate the priority of a terrestrial cell within its PLMN, which is used by the terminal to select the preferred terrestrial cell, i.e., prioritizing higher-priority terrestrial cells. Measurement configuration information can be, for example, the frequency or physical cell identifier of the terrestrial cell, synchronization signal / PBCH block (SSB) information, or channel state information-reference signal (CSI-RS) information, etc.

[0209] Of course, if the first network element determines, based on the terminal's location information, that there is no terrestrial cell coverage of a PLMN that allows the terminal to access the area requested by the terminal, the third indication information is used to indicate the area indicated by the area information requested by the terminal without terrestrial cell coverage. In this case, the terminal will not be able to switch or reselect to a terrestrial network.

[0210] For example, when the second indication information does not include area information but includes location information, the third indication information may also include area information determined by the first network element based on the location information.

[0211] 707. If the terminal leaves the coverage area of ​​the acquired ground cell and / or the area indicated by the area information, the terminal sends a ninth indication message. The ninth indication message is used to request the first network element to update the information of at least one ground cell. The ninth indication message includes the updated area information or the updated location information.

[0212] In some embodiments, the ninth indication information is sent when the terminal determines the range indicated by the coverage and / or area information of at least one ground cell prior to the removal or imminent removal update. For example, it is sent when the coverage and / or area information of at least one ground cell is obtained in the removal or imminent removal step 706.

[0213] For example, the terminal may first determine whether it has moved out of the range indicated by the area information previously determined by the terminal. If it is determined that it has moved out of the range indicated by the area information, the terminal may then determine whether it has moved out of the coverage range of at least one ground cell previously received. If the terminal has moved out of the coverage range of some ground cells, the terminal sends the ninth indication information to the first network element.

[0214] Alternatively, if the terminal has not yet received information from at least one ground cell, the terminal can determine that it has moved out of the range indicated by the area information based on the range indicated by the area information, and then send the ninth indication information to the first network element.

[0215] This is because, as the terminal moves, some of the ground cells indicated by the information of at least one ground cell acquired previously may no longer cover the area where the terminal's latest updated location is located, or, in other words, some newly added ground cells may cover the area where the terminal's latest updated location is located. Therefore, the terminal may request the first network element to update the information of at least one ground cell acquired previously, and carry the updated area information of the terminal in the ninth indication information.

[0216] Alternatively, in some embodiments, when the first network element determines that the information of the ground cells within the area indicated by the area information previously requested by the terminal has changed, it proactively updates the information of the ground cells to the terminal. That is, in this embodiment, the terminal does not send the ninth indication information. The area information previously requested by the terminal can be sent by the terminal to the first network element, or it can be determined by the first network element based on the location information. Therefore, step 708 can also be executed. For example, the change in the information of the ground cells may be due to the opening or closing of the cells for energy saving, or it may be due to the deployment of the ground operator, such as the ground operator adding ground cells or adjusting the configuration of ground cells.

[0217] For example, the first network element receives information changes from at least one ground cell. For instance, the first network element receives information changes from at least one ground cell from a ground base station or from OAM. The information changes from at least one ground cell are used to determine the updated information of at least one ground cell.

[0218] 708. The first network element sends the eighth indication information to the terminal. The eighth indication information is used to indicate the updated information of at least one ground cell.

[0219] For example, in step 705, the second indication information sent by the terminal includes the address information of the terminal receiving the update message. Thus, when the first network element determines that the information of at least one ground cell within the area indicated by the area information previously requested by the terminal has changed, it can send the eighth indication information to the terminal based on this address information.

[0220] 709. Based on the terminal's location information and the coverage information of at least one ground cell, the terminal determines the coverage area of ​​at least one candidate ground cell that the terminal has entered or is about to enter.

[0221] For example, the terminal can periodically acquire its location information. For instance, the terminal can acquire its location information through satellite positioning. The satellites used for satellite positioning can be dedicated navigation satellites, such as the Global Positioning System (GPS) or BeiDou, or communication satellites, i.e., the constellation of communication satellites currently connected to by the terminal.

[0222] At least one candidate ground cell is denoted as a subset of at least one ground cell. The terminal can determine, based on its own location information and the coverage area of ​​at least one ground cell, that the ground cell the terminal is entering or about to enter is at least one candidate ground cell.

[0223] The terminal can then measure at least one candidate ground cell.

[0224] If the information of each ground cell in at least one ground cell includes the measurement configuration information required for cell measurement, the terminal can perform cell measurement on at least one candidate ground cell based on the measurement configuration information.

[0225] For example, if a terminal enters the coverage area of ​​a candidate ground cell, it can measure the signal of that candidate ground cell. Taking the 5G New Radio (NR) standard as an example, the terminal can measure the ground cell based on the SSB or based on the Channel State Information-Reference Signal (CSI-RS). The SSB is a normally open synchronization signal, therefore no measurement configuration information needs to be configured for the terminal. When measuring based on the CSI-RS signal, the terminal needs to obtain measurement configuration information, such as the timing of CSI-RS activation, deactivation, and period.

[0226] If the information of at least one ground cell mentioned above does not include measurement configuration information, the terminal must first request measurement configuration information of at least one candidate ground cell from the first network element. This also includes steps 710-712.

[0227] 710. The terminal sends a sixth instruction message, which is used to request measurement configuration information of at least one candidate ground cell from the first network element.

[0228] For example, the sixth indication information includes at least one candidate ground cell identification information, such as the GCID of at least one candidate ground cell. If there is overlapping coverage between the candidate ground cells, the sixth indication information includes the identification information of multiple candidate ground cells.

[0229] For example, the first network element is the first network element of the PLMN to which the candidate ground cell belongs.

[0230] If the first network element does not save the measurement configuration information of at least one candidate ground cell, the first network element must first obtain the measurement configuration information of at least one candidate ground cell, that is, execute step 711.

[0231] 711. The first network element acquires the measurement configuration information of at least one candidate ground cell.

[0232] For example, for any one of the at least one candidate ground cells, the first network element requests the measurement configuration information of the ground cell from the ground base station corresponding to the candidate ground cell. If the measurement signal of the ground base station is in a turned-off state, the ground base station can turn on the measurement signal and then feed back the measurement configuration information of the ground cell to the first network element.

[0233] Alternatively, the first network element requests the OAM network element to obtain the measurement configuration information of the candidate ground cells. If the measurement signal of the OAM network element is in a closed state, the OAM network element can first configure the candidate ground cells to turn on the measurement signal and then feed back the measurement configuration information of the candidate ground cells to the first network element.

[0234] 712. The first network element sends a seventh indication message to the terminal. The seventh indication message is used to indicate the measurement configuration information of at least one candidate ground cell.

[0235] 713. The terminal performs cell measurement on at least one candidate ground cell.

[0236] In some embodiments, cell measurement of at least one candidate ground cell includes: performing cell measurement based on at least one of the following information of the candidate ground cell: frequency point information (e.g., SSB), physical cell identifier (PCI) or measurement configuration information or CSI-RS information.

[0237] 714. The terminal sends a fifth indication information to the source satellite base station. The fifth indication information is used to indicate the cell measurement results of at least one candidate ground cell. The fifth indication information is used by the source satellite base station to determine the target ground cell from the at least one candidate ground cell to be handed over by the terminal.

[0238] Alternatively, step 714 can be replaced by: the terminal sending a fourth indication message to the source satellite base station, the fourth indication message being used to indicate that the terminal should be switched from the cell of the serving network equipment to the target ground cell, the target ground cell being determined by the terminal based on cell measurement results of at least one candidate ground cell.

[0239] In other words, in one implementation, when the terminal obtains the measurement results of at least one candidate ground cell, the terminal sends the measurement results to the source satellite base station through the fifth indication information. The source satellite base station then selects the target ground cell based on the measurement results. For example, when the terminal enters the coverage area of ​​the target ground cell, the target ground cell selected by the source satellite base station is the ground cell with the best signal quality among at least one candidate ground cell.

[0240] In another implementation, the terminal can first determine the target ground cell based on the measurement results of at least one candidate ground cell, and then indicate the target ground cell to the source satellite base station via a fourth indication information. For example, when the terminal enters the coverage area of ​​the target ground cell, the target ground cell selected by the terminal is the ground cell with the best signal quality among at least one candidate ground cell. The fourth indication information includes the identifier of the target ground cell.

[0241] In some embodiments, the terminal or source satellite base station determines the target ground cell based on the cell measurement results of at least one candidate ground cell, including: the terminal or source satellite base station further determines the target ground cell based on at least one of the following information: priority information of at least one candidate ground cell, priority of the PLMN to which at least one candidate ground cell belongs, measurement results of at least one candidate ground cell, or cell coverage information of at least one candidate ground cell.

[0242] For example, when a terminal or source satellite base station obtains measurement results for at least one candidate ground cell, it can further determine the target ground cell by combining the priority information, PLMN information, or cell coverage information of the at least one candidate ground cell. For instance, the terminal or source satellite base station may select the ground cell with the highest priority among ground cells with signal quality greater than a quality threshold as the target ground cell. Alternatively, the terminal or source satellite base station may select a ground cell belonging to an HPLMN among ground cells with signal quality greater than a quality threshold as the target ground cell. Or, the terminal or source satellite base station may select the ground cell with the largest coverage area indicated by the cell coverage information among ground cells with signal quality greater than a quality threshold as the target ground cell.

[0243] 715. The source satellite base station initiates the cell handover process.

[0244] If the source satellite base station determines, based on the first information in step 703, that the terminal is allowed to switch to the terrestrial network and that the target terrestrial cell belongs to the PLMN that the terminal is allowed to access, the source satellite base station may initiate a cell handover procedure. For example, this handover procedure involves both the satellite core network and the terrestrial core network. This procedure can be referenced to the N2 handover procedure in 5G, whereby the source satellite base station interacts with the source AMF network element in the satellite core network, the target AMF network element in the terrestrial core network, and the terrestrial base station of the target terrestrial cell to complete the cell handover procedure.

[0245] It should be noted that steps 709-715 above can be understood as the process of cell handover performed by the terminal in connected mode. The information of at least one ground cell obtained by the terminal can also be used for cell reselection when the terminal enters idle mode, so that the terminal can select a ground cell for access. In idle mode, after executing steps 701-708 above, steps 709-715 can be replaced with the process of cell reselection performed by the terminal. The terminal itself selects a target ground cell to initiate registration or location update based on the information of at least one ground cell obtained, that is, accesses the ground network through the target ground cell.

[0246] Therefore, in this application, when a first network element or topology service is introduced into the terrestrial core network, the first network element can provide the terminal with information on terrestrial cells within the coverage area, indicating the area information. This information can be used by the terminal to determine candidate terrestrial cells, assisting the terminal in switching or reselecting from non-terrestrial cells to terrestrial cells. This application can solve the problem of non-terrestrial operators and terrestrial operators being unable to configure neighboring cells, supporting the terminal to quickly switch from non-terrestrial cells to terrestrial cells. It can also avoid the time-consuming and power-consuming problem caused by searching by frequency point when the terminal searches for terrestrial cells.

[0247] Figure 9 shows a flowchart of a communication method provided in an embodiment of this application. In this method, the serving network device of the non-terrestrial network to which the terminal belongs obtains information about a terrestrial cell from the first network element based on the identifier of the first network element. When determining candidate terrestrial cells, the device instructs the terminal to perform cell measurement and obtain the measurement results. Then, the serving network device determines the target terrestrial cell based on the measurement results and initiates a handover or redirection to the target terrestrial cell. The following description uses the serving network device of the non-terrestrial network as the source satellite base station, the core network of the non-terrestrial network as the satellite core network, and the target terrestrial cell as the target terrestrial base station as an example. The method includes the following steps.

[0248] 901. The terminal registers with the satellite core network and includes the terminal's capability information in the registration request.

[0249] For details on how to implement step 901, please refer to the description of step 701.

[0250] 902. The satellite core network determines which terminals are allowed to access the network via the terrestrial network, and determines the terrestrial PLMNs that terminals are allowed to access and the first network element corresponding to the terrestrial PLMNs.

[0251] The implementation method of step 901 can be found in the description of step 702.

[0252] Optionally, 903, the satellite core network requests information from the first network element for at least one ground cell.

[0253] In some embodiments, information from at least one ground cell is used by the terminal to perform cell handover or cell redirection when entering the coverage area of ​​any of the at least one ground cell.

[0254] In step 903, the process by which the satellite core network requests information about at least one ground cell from the first network element is similar to the process described in steps 705-706 above, where the terminal obtains information about a ground cell from the first network element. That is, the satellite core network can send a request message to the first network element. This request message includes the terminal's area information, which is determined based on the terminal's location information, and the request message is used to request information about at least one ground cell from the first network element. Specifically, when the terminal registers with the satellite core network, the satellite core network can obtain the terminal's location information.

[0255] 904. The satellite core network sends first information to the source satellite base station. The first information is used to indicate that the terminal is allowed to switch from the non-terrestrial network to the terrestrial network.

[0256] In some embodiments, if the satellite core network obtains information about at least one ground cell in step 903, the first information here may include information about at least one ground cell.

[0257] Alternatively, if step 903 is not executed, meaning the satellite core network has not obtained information about at least one ground cell, when step 904 is executed after step 902, the first information includes information about the first network element of the ground PLMN that the terminal is allowed to access. The source satellite base station obtains information about at least one ground cell from the first network element based on the information of the first network element. That is, step 905 is executed.

[0258] Alternatively, the first information includes the identifier of at least one terrestrial PLMN, which is used to determine the information of the first network element. For example, the first information may also indicate the priority of each PLMN in the at least one terrestrial PLMN, which can be used to select a terrestrial cell of a higher-priority PLMN as the target terrestrial cell for the terminal. After the source satellite base station determines the information of the first network element based on the first information, the source satellite base station obtains the information of at least one terrestrial cell from the first network element based on the information of the first network element. That is, step 905 is executed.

[0259] The content of the first information here can refer to the implementation method of the first information in step 703 above, or it can include the information included in the implementation method of the first instruction information in step 704 above.

[0260] Optionally, the 905 source satellite base station requests information about at least one ground cell from the first network element.

[0261] The process by which the source satellite base station requests information about at least one ground cell from the first network element is similar to the process described in steps 705-706 above, whereby the terminal obtains information about a ground cell from the first network element. That is, after the source satellite base station determines the terminal's region information based on the terminal's location information or sends the terminal's location information to the first network element, the request message sent by the source satellite base station to the first network element includes the terminal's region information. This request message is used to request information about at least one ground cell from the first network element.

[0262] 906. The source satellite base station determines that the terminal has moved out of or is about to move out of the coverage area of ​​at least one ground cell. The source satellite base station receives the sixth information, which includes the updated information of at least one ground cell. The updated information of at least one ground cell is determined by the first network element based on the updated area information of the terminal.

[0263] The implementation method of receiving the sixth information by the source satellite base station in step 906 is similar to the reason for needing to update the information of at least one ground cell as shown in step 707 above. For details, please refer to the description in step 707.

[0264] For example, if the source satellite base station determines, based on the terminal's latest location information, that the terminal has moved out of or is about to move out of the coverage area of ​​at least one ground cell, it can send an update request to the first network element. The update request carries the area information determined by the source satellite base station based on the terminal's latest location information, and is used to request the first network element to update the information of at least one ground cell. The first network element can then send a sixth message to the source satellite base station, carrying the updated information of at least one ground cell.

[0265] Alternatively, the source satellite base station may notify the satellite core network that a terminal has moved out of or is about to move out of the coverage area of ​​at least one ground cell. The satellite core network then determines the updated area information based on the terminal's latest location information and sends the update request to the first network element. Upon receiving the updated information about at least one ground cell from the first network element, the satellite core network transmits this updated information to the source satellite base station via a sixth piece of information.

[0266] Alternatively, when the first network element determines that the information of at least one ground cell has changed due to network deployment or energy saving reasons, the first network element may indicate the updated information of at least one ground cell to the source satellite base station through the sixth information.

[0267] 907. The source satellite base station determines the coverage area of ​​at least one candidate ground cell that the terminal has entered or is about to enter, based on the terminal's location information and the information of at least one ground cell.

[0268] For example, the source satellite base station can periodically acquire the terminal's location information, such as the terminal periodically reporting its location information to the source satellite base station. If the source satellite base station determines, based on the terminal's location information, that the terminal has entered the coverage area of ​​at least one candidate ground cell, the source satellite base station can consider that the terminal is ready to perform cell handover or redirect to a ground cell at this time.

[0269] 908. The source satellite base station acquires measurement configuration information for at least one candidate ground cell.

[0270] In some embodiments, when the information of at least one ground cell does not include measurement configuration information, the source satellite base station obtains the measurement configuration information of at least one candidate ground cell by: the source satellite base station sending fourth information, the fourth information being used to request the measurement configuration information of at least one candidate ground cell from the first network element; and receiving fifth information, the fifth information being used to indicate the measurement configuration information of at least one candidate ground cell.

[0271] For example, the first network element can obtain the measurement configuration information of the candidate ground cell from the ground base station or OAM network element of the candidate ground cell, as detailed in steps 710 to 712 above.

[0272] 909. The source satellite base station sends a measurement request to the terminal, which instructs the terminal to measure at least one candidate ground cell.

[0273] In some embodiments, the source satellite base station may send a measurement request to the terminal based on measurement configuration information.

[0274] The measurement request includes at least one of the following information for at least one candidate ground cell: the frequency of the SSB, the frequency of the CSI-RS, the switching timing of the CSI-RS, the switching cycle of the CSI-RS, or the PCI.

[0275] 910. The terminal sends a measurement report to the source satellite base station. The measurement report includes the measurement results of at least one candidate ground cell.

[0276] That is, the terminal can measure at least one candidate ground cell based on the measurement request, obtain a measurement report, and send the measurement report to the source satellite base station.

[0277] 911. The source satellite base station initiates the cell handover process.

[0278] In some embodiments, the source satellite base station may determine the target ground cell based on a measurement report, i.e., determine the target ground cell from at least one candidate ground cell.

[0279] For example, the source satellite base station may select the ground cell with the best signal quality from at least one candidate ground cell as the target ground cell. The cell handover procedure initiated by the source satellite base station can be found in the description of step 715.

[0280] In this application, the source satellite base station can also obtain information about at least one ground cell in step 905. When the terminal is in a connected state, the source satellite base station sends information about at least one ground cell to the terminal. The information about at least one ground cell is used for cell handover or cell redirection. If it is used for cell redirection, step 911 can be replaced by: the source satellite base station initiating a cell redirection process.

[0281] Alternatively, when the terminal enters the idle state, the source satellite base station can send information about at least one ground cell to the terminal. The information about at least one ground cell is used by the terminal to perform cell reselection in the idle state so as to reselect to a ground cell.

[0282] Therefore, in this application, when a first network element or topology service is introduced into the terrestrial core network, the first network element can provide the terminal's source satellite base station with information on terrestrial cells within the coverage area indicated by regional information. This information can be used by the source satellite base station to determine candidate terrestrial cells and assist the terminal in switching or reselecting from non-terrestrial cells to terrestrial cells. This application can solve the problem of non-terrestrial operators and terrestrial operators being unable to configure neighboring cells, supporting the terminal to quickly switch from non-terrestrial cells to terrestrial cells. It can also avoid the time-consuming and power-consuming problem caused by searching by frequency point when the terminal searches for terrestrial cells.

[0283] It is understood that, in order to achieve the functions in the above embodiments, the network devices and terminals include hardware structures and / or software modules corresponding to perform each function. Those skilled in the art should readily recognize that, based on the units and method steps described in conjunction with the embodiments disclosed in this application, this application can be implemented in hardware or a combination of hardware and computer software. Whether a function is executed by hardware or by computer software driving hardware depends on the specific application scenario and design constraints of the technical solution.

[0284] Figures 10 and 11 are schematic diagrams of possible communication devices provided in embodiments of this application. These communication devices can be used to implement the functions of the terminal, the first network element, the core network equipment of the non-terrestrial network, or the service network equipment of the non-terrestrial network in the above method embodiments, and thus can also achieve the beneficial effects of the above method embodiments. In the embodiments of this application, the communication device can be the terminal 1006 shown in Figure 1, the topology service shown in Figure 1, the core network equipment in the satellite core network 1005 shown in Figure 1, the satellite base station shown in Figure 1, or a module (such as a chip) applied to the core network equipment or satellite base station of the terminal, topology service, or satellite core network.

[0285] As shown in Figure 10, the communication device 1000 includes a processing unit 1010 and a transceiver unit 1020. The communication device 1000 is used to implement the functions of the terminal or network device in the method embodiments shown in Figures 3 to 7 and Figure 9.

[0286] When the communication device 1000 is used to implement the functions of the terminal in the method embodiment shown in FIG3 or FIG7: the transceiver unit 1020 is used to receive the first indication information, indicating the information of the first network element of the ground PLMN; send the second indication information, for requesting the information of the ground cell from the first network element; receive the third indication information, indicating the information of at least one ground cell; the processing unit 1010 is used to determine the target ground cell from at least one ground cell, and switch or reselect from a non-ground cell to a ground cell.

[0287] When the communication device 1000 is used to implement the functions of the terminal in the method embodiment shown in FIG7 or FIG9: the transceiver unit 1020 is also used to send the terminal's capability information to the satellite core network; receive a measurement request and instruct the terminal to measure at least one candidate ground cell; and send the cell measurement results of at least one candidate ground cell.

[0288] When the communication device 1000 is used to implement the functions of the terminal in the method embodiment shown in FIG7: the transceiver unit 1020 is further used to send a ninth indication information, which is used to request the first network element to update the information of at least one ground cell; send a sixth indication information, which is used to request the first network element to obtain the measurement configuration information of at least one candidate ground cell; send a fifth indication information, which is used to indicate the cell measurement results of at least one candidate ground cell; the processing unit 1010 is further used to determine, based on the location information of the terminal and the coverage information of at least one ground cell, the coverage area of ​​at least one candidate ground cell that the terminal has entered or is about to enter; and perform cell measurement on at least one candidate ground cell.

[0289] When the communication device 1000 is used to implement the functions of the network equipment of the non-terrestrial core network in the method embodiment shown in FIG4 or FIG9: the transceiver unit 1020 is used to send first information to instruct the service network equipment of the non-terrestrial network to allow the terminal to switch to the terrestrial network; send first indication information to indicate the information of the first network element of the terrestrial PLMN that the terminal is allowed to access; the processing unit 1010 is used to configure the terminal to perform candidate terrestrial cell measurement according to the terrestrial cell information obtained from the first network element, and determine the target terrestrial cell according to the measurement results, so as to switch or redirect the terminal from the non-terrestrial cell to the terrestrial cell.

[0290] When the communication device 1000 is used to implement the function of the network device of the non-terrestrial core network in the method embodiment shown in FIG7 or FIG9: the processing unit 1010 is used to determine that the terminal is allowed to access the terrestrial network, and to determine the terrestrial PLMN that the terminal is allowed to access and the first network element corresponding to the terrestrial PLMN; the transceiver unit 1020 is used to send first information to the source satellite base station currently accessed by the terminal, the first information being used to instruct the source satellite base station to allow the terminal to switch to the terrestrial network.

[0291] When the communication device 1000 is used to implement the function of the network device of the non-terrestrial core network in the method embodiment shown in FIG7: the transceiver unit 1020 is used to send a first indication information to the terminal, the first indication information being used to indicate the information of the first network element of the terrestrial PLMN that the terminal is allowed to access.

[0292] When the communication device 1000 is used to implement the function of the first network element of the terrestrial network in the method embodiment shown in FIG5 or FIG7: the transceiver unit 1020 is used to receive second indication information, requesting information of the terrestrial cell; and send third indication information, indicating information of at least one terrestrial cell. The processing unit 1010 is used to determine the information of the terrestrial cell that the terminal is allowed to access based on the area information or location information, so that the terminal can switch or reselect from a non-terrestrial cell to a terrestrial cell.

[0293] When the communication device 1000 is used to implement the function of the first network element of the terrestrial network in the method embodiment shown in FIG7: the transceiver unit 1020 is further used to send an eighth indication information to the terminal, the eighth indication information being used to indicate the updated information of at least one terrestrial cell; send a seventh indication information to the terminal, the seventh indication information being used to indicate the measurement configuration information of at least one candidate terrestrial cell; the processing unit 1010 is further used to obtain the measurement configuration information of at least one candidate terrestrial cell.

[0294] When the communication device 1000 is used to implement the function of the service network device of the non-terrestrial network in the method embodiment shown in FIG6 or FIG9: the transceiver unit 1020 is used to receive first information indicating that the terminal is allowed to switch from the non-terrestrial network to the terrestrial network; the processing unit 1010 is used to obtain information of at least one terrestrial cell; and determine the target terrestrial cell of the terminal based on the information of at least one terrestrial cell, wherein the target terrestrial cell is the target cell for the terminal to switch or redirect.

[0295] When the communication device 1000 is used to implement the function of the service network device (source satellite base station) of the non-terrestrial network in the method embodiment shown in FIG7: the transceiver unit 1020 is also used to receive the cell measurement results of at least one candidate ground cell indicated by the fifth indication information; the processing unit 1010 is also used to initiate the cell handover process.

[0296] When the communication device 1000 is used to implement the function of the service network device (source satellite base station) of the non-terrestrial network in the method embodiment shown in FIG9: the transceiver unit 1020 is used to receive six pieces of information, the sixth pieces of information including updated information of at least one ground cell; send a measurement request to the terminal, the measurement request being used to instruct the terminal to measure at least one candidate ground cell; receive a measurement report, including the measurement results of at least one candidate ground cell; the processing unit 1010 is used to determine, based on the location information of the terminal and the information of at least one ground cell, the coverage area of ​​at least one candidate ground cell that the terminal has entered or is about to enter; obtain the measurement configuration information of at least one candidate ground cell; and initiate a cell handover process.

[0297] For a more detailed description of the above-mentioned processing unit 1010 and transceiver unit 1020, please refer to the relevant descriptions in the method embodiments shown in Figures 3 to 7 and Figure 9.

[0298] As shown in Figure 11, the communication device 1100 includes a processor 1110 and an interface circuit 1120. The processor 1110 and the interface circuit 1120 are coupled to each other. It is understood that the interface circuit 1120 can be a transceiver or an input / output interface. Optionally, the communication device 1100 may also include a memory 1130 for storing instructions executed by the processor 1110, or storing input data required by the processor 1110 to execute instructions, or storing data generated after the processor 1110 executes instructions.

[0299] When the communication device 1100 is used to implement the methods shown in Figures 3 to 7 and Figure 9, the processor 1110 is used to implement the functions of the processing unit 1010, and the interface circuit 1120 is used to implement the functions of the transceiver unit 1020.

[0300] When the aforementioned communication device is a chip applied to a terminal, the terminal chip implements the functions of the terminal in the above method embodiments. The terminal chip receives information from the base station, which can be understood as the information being first received by other modules in the terminal (such as an RF module or antenna), and then sent to the terminal chip by these modules. The terminal chip sends information to the base station, which can be understood as the information being first sent to other modules in the terminal (such as an RF module or antenna), and then sent to the base station by these modules.

[0301] When the aforementioned communication device is a chip applied to network equipment (core network equipment or access network equipment), the network equipment chip implements the functions of the network equipment in the above method embodiments. The network equipment chip receiving information from the terminal can be understood as the information being first received by other modules (such as radio frequency modules or antennas) in the network equipment, and then sent to the network equipment chip by these modules. The network equipment chip sending information to the terminal can be understood as the information being forwarded to other modules (such as radio frequency modules or antennas) in the network equipment, and then sent to the terminal by these modules.

[0302] In this application, entity A sends information to entity B, either directly or indirectly through other entities. Similarly, entity B receives information from entity A, either directly or indirectly through other entities. Entities A and B can be RAN nodes or terminals, or modules within RAN nodes or terminals. Information transmission and reception can be between RAN nodes and terminals, such as between a base station and a terminal; between two RAN nodes, such as between a CU and a DU; or between different modules within a single device, such as between a terminal chip and other modules of the terminal, or between a base station chip and other modules of the base station.

[0303] It is understood that the processor in the embodiments of this application can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. A general-purpose processor can be a microprocessor or any conventional processor.

[0304] The method steps in the embodiments of this application can be implemented in hardware or in software instructions executable by a processor. The software instructions can consist of corresponding software modules, which can be stored in random access memory, flash memory, read-only memory, programmable read-only memory, erasable programmable read-only memory, electrically erasable programmable read-only memory, registers, hard disks, portable hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to a processor, enabling the processor to read information from and write information to the storage medium. The storage medium can also be a component of the processor. The processor and storage medium can reside in an ASIC. Alternatively, the ASIC can reside in a base station or terminal. The processor and storage medium can also exist as discrete components in a base station or terminal.

[0305] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially 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 processes or functions described in the embodiments of this application are performed entirely or partially. The computer can be a general-purpose computer, a special-purpose computer, a computer network, a network device, a user equipment, or other programmable device. The computer program or instructions can be stored in a computer-readable storage medium or transferred from one computer-readable storage medium to another. For example, the computer program or instructions can be transferred from one website, computer, server, or data center to another website, computer, server, or data center via wired or wireless means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium, such as a floppy disk, hard disk, or magnetic tape; it can also be an optical medium, such as a digital video optical disc; or it can be a semiconductor medium, such as a solid-state drive. The computer-readable storage medium may be a volatile or non-volatile storage medium, or may include both types of storage media.

[0306] In the various embodiments of this application, unless otherwise specified or in case of logical conflict, the terminology and / or descriptions of different embodiments are consistent and can be referenced by each other. The technical features of different embodiments can be combined to form new embodiments according to their inherent logical relationship.

[0307] In this application, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, or B exists alone, where A and B can be singular or plural. In the textual description of this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship. "Including at least one of A, B, and C" can mean: including A; including B; including C; including A and B; including A and C; including B and C; including A, B, and C.

[0308] It is understood that the various numerical designations used in the embodiments of this application are merely for descriptive convenience and are not intended to limit the scope of the embodiments of this application. The order of the process numbers described above does not imply the order of execution; the execution order of each process should be determined by its function and internal logic.

Claims

1. A communication method, characterized in that, include: Receive first indication information, the first indication information being used to indicate information about a first network element of a public land mobile network (PLMN); Send a second indication message, which is used by the terminal to request information about the ground cell from the first network element. The first network element is determined based on the information of the first network element. The second indication message includes area information, which is used to indicate the area covered by the ground cell requested by the terminal. The ground cell belongs to the PLMN. The terminal receives third indication information, which is used to indicate information about at least one ground cell. The coverage area of ​​any one of the at least one ground cell intersects with the area indicated by the area information. The information about the at least one ground cell is used by the terminal to switch or reselect from a non-ground cell to the ground cell when entering the coverage area of ​​any one of the at least one ground cell. Alternatively, the third indication information is used to indicate an area indicated by the area information that is not covered by any ground cell.

2. The method according to claim 1, characterized in that, Before receiving the first indication information, the method further includes: Send capability information, the capability information indicating that the terminal has at least one of the following capabilities: It supports reselection from the non-terrestrial cell to the terrestrial cell for access; it supports handover from the non-terrestrial cell to the terrestrial cell for access; it supports redirection from the non-terrestrial cell to the terrestrial cell for access.

3. The method according to claim 1 or 2, characterized in that, The information for each of the at least one ground cell includes at least one of the following: Global cell identifier, physical cell identifier, frequency information, cell coverage information, measurement configuration information, priority information, or the PLMN identifier to which the ground cell belongs.

4. The method according to any one of claims 1-3, characterized in that, The method further includes: Based on the location information of the terminal and the coverage information of the at least one ground cell, determine the coverage area of ​​the at least one candidate ground cell that the terminal has entered or is about to enter; Cell measurements are performed on the at least one candidate ground cell.

5. The method according to claim 4, characterized in that, Performing cell measurements on the at least one candidate ground cell includes: performing cell measurements based on at least one of the following information of the candidate ground cell: frequency point information, physical cell identifier, or measurement configuration information.

6. The method according to claim 4 or 5, characterized in that, The method further includes: A fourth indication message is sent to the serving network device of the non-terrestrial network, the fourth indication message being used to instruct the terminal to switch from the cell of the serving network device to a target terrestrial cell, the target terrestrial cell being determined by the terminal based on cell measurement results of the at least one candidate terrestrial cell.

7. The method according to claim 6, characterized in that, The terminal determines the target ground cell based on the cell measurement results of the at least one candidate ground cell, including: The terminal further determines the target ground cell based on at least one of the following: priority information of the at least one candidate ground cell, PLMN information to which the at least one candidate ground cell belongs, or cell coverage information of the at least one candidate ground cell.

8. The method according to claim 4 or 5, characterized in that, The method further includes: A fifth indication message is sent to the serving network device of the non-terrestrial network. The fifth indication message is used to indicate the cell measurement results of the at least one candidate terrestrial cell. The fifth indication message is used by the serving network device to determine the target terrestrial cell from the at least one candidate terrestrial cell to be handed over to by the terminal.

9. The method according to claim 4 or 5, characterized in that, If the information of the at least one ground cell does not include measurement configuration information, the method further includes: Send a sixth indication message, the sixth indication message being used to request the measurement configuration information of the at least one candidate ground cell from the first network element; Receive a seventh indication message, which is used to indicate the measurement configuration information of the at least one candidate ground cell.

10. The method according to any one of claims 1-9, characterized in that, The method further includes: The system receives an eighth indication message sent by the first network element, the eighth indication message being used to indicate the updated information of at least one ground cell.

11. The method according to claim 10, characterized in that, Before receiving the sixth indication information, the method further includes: A ninth indication message is sent, which is used to request the first network element to update the information of the at least one ground cell. The ninth indication message includes the updated area information. The ninth indication message is sent when the terminal determines that it has moved out of or is about to move out of the coverage area of ​​the at least one ground cell before the update and / or the area information.

12. A communication method, characterized in that, include: Send a first message, the first message being used to instruct the serving network device of the non-terrestrial network to which the terminal is connected to allow the terminal to switch to the terrestrial network; Send a first indication message, which indicates information about a first network element of a public terrestrial mobile network (PLMN) that the terminal is allowed to access. The first network element is used to provide the terminal or the serving network equipment of the non-terrestrial network with information about the terrestrial cells of the PLMN. The information about the terrestrial cells is used by the terminal to perform handover or reselection from a non-terrestrial cell to the terrestrial cell.

13. The method according to claim 12, characterized in that, Before sending the first information, the method further includes: Receive capability information, the capability information being used to indicate that the terminal has at least one of the following capabilities: It supports reselection from the non-terrestrial cell to the terrestrial cell for access; it supports handover from the non-terrestrial cell to the terrestrial cell for access; it supports redirection from the non-terrestrial cell to the terrestrial cell for access.

14. The method according to claim 12 or 13, characterized in that, The first network element of the PLMN that the terminal is allowed to access is determined based on at least one of the terminal's subscription information, location information, or roaming agreement between the non-terrestrial network operator and the terrestrial network operator.

15. The method according to any one of claims 12-14, characterized in that, The first information includes the identifier of the ground PLMN that the terminal is allowed to access.

16. A communication method, characterized in that, include: Receive second indication information, the second indication information being used to request information about a ground cell, the second indication information including area information or location information, the area information being used to indicate the area covered by the requested ground cell, the location information being used to indicate the location covered by the requested ground cell; Send a third indication message, which is used to indicate information about at least one ground cell, wherein the coverage area of ​​any one of the at least one ground cell intersects with the area indicated by the area information, and the information about the at least one ground cell is used by the terminal to switch or reselect from a non-ground cell to the ground cell when entering the coverage area of ​​any one of the at least one ground cell; or, the third indication message is used to indicate an area indicated by the area information that is not covered by any ground cell.

17. The method according to claim 16, characterized in that, The information for each of the at least one ground cell includes at least one of the following: Global cell identifier, physical cell identifier, frequency point information, cell coverage information, measurement configuration information, priority information, or the Public Land Mobile Network (PLMN) identifier to which the ground cell belongs.

18. The method according to claim 17, characterized in that, If the information of the at least one ground cell does not include measurement configuration information, the method further includes: The terminal receives a sixth indication message, which is used to request the measurement configuration information of the at least one candidate ground cell. Send a seventh indication message, which is used to indicate the measurement configuration information of the at least one candidate ground cell.

19. The method according to any one of claims 16-18, characterized in that, The method further includes: Send an eighth indication message, which is used to indicate to the terminal the updated information of at least one ground cell.

20. The method according to claim 19, characterized in that, Before sending the sixth instruction message, the method further includes: The terminal receives a ninth indication message, which is used to request an update of the information of the at least one ground cell. The ninth indication message includes the updated area information of the terminal. The ninth indication message is sent when the terminal determines that it has moved out of or is about to move out of the coverage area of ​​the at least one ground cell before the update and / or the area information. Alternatively, receive information changes from the at least one ground cell, the information changes from the at least one ground cell being used to determine the updated information of the at least one ground cell.

21. A communication method, characterized in that, include: Receive first information, the first information being used to instruct the terminal to switch from a non-terrestrial network to a terrestrial network; Information on at least one ground cell is obtained, and the information on the at least one ground cell is used by the terminal to perform cell handover or cell redirection when entering the coverage area of ​​any of the at least one ground cell; The target ground cell of the terminal is determined based on the information of the at least one ground cell, and the target ground cell is the target cell for the terminal to be switched or redirected.

22. The method according to claim 21, characterized in that, The acquisition of information from at least one ground cell includes: The first information includes information about the at least one ground cell; or The first information includes information about a first network element of a public terrestrial mobile network (PLMN) that the terminal is allowed to access; and information about the at least one terrestrial cell is obtained from the first network element based on the information of the first network element; or The first information includes the identifier of at least one terrestrial PLMN, which is used to determine the information of the first network element, and the information of the at least one terrestrial cell is obtained from the first network element based on the information of the first network element.

23. The method according to claim 22, characterized in that, The step of obtaining information about at least one ground cell from the first network element includes: Send a second message, the second message being used to request the first network element to obtain information about the at least one ground cell, the second message including area information, the area information being used to indicate the area covered by the ground cell requested by the terminal, the ground cell belonging to the ground PLMN; Receive third information, which includes information about the at least one ground cell.

24. The method according to any one of claims 21-23, characterized in that, The information for each of the at least one ground cell includes at least one of the following: Global cell identifier, physical cell identifier, frequency information, cell coverage information, measurement configuration information, priority information, or the PLMN identifier to which the ground cell belongs.

25. The method according to any one of claims 22-24, characterized in that, Determining the target ground cell for the terminal based on the information of the at least one ground cell includes: Based on the location information of the terminal and the information of at least one ground cell, determine the coverage area of ​​at least one candidate ground cell that the terminal has entered or is about to enter. A measurement request is sent to the terminal, the measurement request being used to instruct the terminal to measure the at least one candidate ground cell; Receive a measurement report, the measurement report including the measurement results of the at least one candidate ground cell; The target ground cell is determined based on the measurement results.

26. The method according to claim 25, characterized in that, The measurement request includes at least one of the following information for the at least one candidate ground cell: The frequency of the Synchronization Signal Block (SSB), the frequency of the Channel State Information Reference Signal (CSI-RS), the switching timing of the CSI-RS, the switching cycle of the CSI-RS, or the Physical Cell Identifier (PCI).

27. The method according to any one of claims 24-26, characterized in that, When the information of the at least one ground cell does not include measurement configuration information, the method further includes: Send a fourth message, the fourth message being used to request the measurement configuration information of the at least one candidate ground cell from the first network element; Receive fifth information, which is used to indicate the measurement configuration information of the at least one candidate ground cell.

28. The method according to any one of claims 22-27, characterized in that, The method further includes: Determine whether the terminal has moved out of or is about to move out of the coverage area of ​​at least one ground cell; The sixth information is received, which includes updated information about at least one ground cell. The updated information about at least one ground cell is determined by the first network element based on the updated area information of the terminal.

29. A communication device, characterized in that, The communication device includes a module for performing the method as described in any one of claims 1-11, or a module for performing the method as described in any one of claims 12-15, or a module for performing the method as described in any one of claims 16-20, or a module for performing the method as described in any one of claims 21-27.

30. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that, when executed on a communication device, cause the communication device to perform the method as described in any one of claims 1-11, or the method as described in any one of claims 12-15, or the method as described in any one of claims 16-20, or the method as described in any one of claims 21-27.

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