Handover method and communication apparatus

Abstract

The present application provides a handover method and a communication apparatus. Handover of a user plane bearer of a terminal device may be initiated according to a notification message used for indicating a target cell to which the terminal device is to be handed over. In other words, the handover of the user plane bearer of the terminal device may be triggered by the notification message. Compared with initiating handover of the user plane bearer of the terminal device after receiving an indication that the terminal device successfully accesses the target cell, the handover of the user plane bearer of the terminal device may be executed earlier. Moreover, after executing the handover of the user plane bearer of the terminal device, service data of the terminal device can be directly sent to a target access network device without forwarding by a source access network device. Therefore, data in a data forwarding process from the source access network device to the target access network device can be reduced, so as to reduce invalid data, thereby improving the service experience.

Description

Switching method and communication device

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on June 15, 2023, with application number 202310718509.9 and application name “A Switching Method and Communication Device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of communication technology, and more specifically, to a switching method and a communication device. Background Art

[0003] In a mobile communication system, the movement of a terminal device may cause a change in the communication link between the terminal device and a network device. The network device will instruct the terminal device to perform a cell handover based on the movement of the terminal device.

[0004] During the handover process, downlink data is forwarded from the source access network device to the target access network device, which then sends the data to the terminal device. This data forwarding process introduces latency, which can cause the data to be invalid by the time it reaches the terminal device, impacting the service experience.

[0005] Summary of the Invention

[0006] The present application provides a switching method and a communication device, which can reduce the data that undergoes data forwarding, thereby reducing invalid data and improving the service experience.

[0007] In a first aspect, a switching method is provided. The method can be executed by a source centralized unit (CU) or by a module or unit (such as a chip or circuit) in the source CU. The source CU is used for description below.

[0008] The method includes: a source CU receives a first notification message from a source distributed unit (DU), wherein the first notification message is used to indicate a target cell to which the terminal device will switch, and the target cell is a cell of a target DU under the target CU; the source CU sends a first request message to a core network device based on the first notification message, and the first request message is used to request that the user plane bearer of the terminal device be switched to the target CU.

[0009] Based on the above method, the source CU can initiate the switching of the user plane bearer of the terminal device according to the first notification message for indicating the target cell to which the terminal device will switch. In other words, the switching of the user plane bearer of the terminal device can be triggered by the first notification message. Compared with initiating the switching of the user plane bearer of the terminal device after receiving the indication that the terminal device has successfully accessed the target cell, the above method can execute the switching of the user plane bearer of the terminal device earlier. After executing the switching of the user plane bearer of the terminal device, the service data of the terminal device can be sent directly to the target CU without going through the data forwarding process from the source CU to the target CU. Therefore, the above method can reduce the data forwarded from the source CU to the target CU, thereby reducing invalid data and improving the service experience.

[0010] In combination with the first aspect, in a possible implementation method, the first notification message includes the first identifier of the target cell; the source CU sends a first request message to the core network device based on the first notification message, including: the source CU sends the first request message to the core network device based on the first identifier and the first association relationship, the first association relationship is used to indicate the association relationship between the first identifier and the first information, the first information is used to indicate the channel information carried by the user plane of the target CU, and the first request message includes the first information.

[0011] Based on the above method, the source CU can obtain the channel information of the user plane bearer of the target CU based on the first identifier of the target cell and the first association relationship between the channel information of the user plane bearer indicating the target CU, thereby providing the channel information of the user plane bearer of the target CU to the core network device, thereby realizing the switching of the user plane bearer of the terminal device initiated by the source CU.

[0012] In combination with the first aspect or any implementation thereof, in another possible implementation, before the source CU receives the first notification message, the method further includes: the source CU sends a second request message to the target CU, the second request message being used to request the first information; the source CU receives a second response message from the target CU, the second response message including a second identifier of the target cell and the first information; the source CU determines the first association relationship based on the second identifier and the first information.

[0013] Based on the above method, it is possible to pre-configure the first association relationship for the source CU before the source CU sends the first request message to the core network device, which can reduce the delay in switching the user plane bearer of the initiating terminal device.

[0014] In combination with the first aspect or any implementation manner thereof, in another possible implementation manner, the first notification message includes the first identifier of the target cell; the source CU sends a first request message to the core network device based on the first notification message, including: the source CU determines the identifier of the target CU to which the target cell belongs based on the first identifier; the source CU sends the first request message to the core network device based on the identifier of the target CU and a second association relationship, the second association relationship is used to indicate the association relationship between the identifier of the target CU and the first information, the first information is used to indicate the channel information carried by the user plane of the target CU, and the first request message includes the first information.

[0015] Based on the above method, the source CU can obtain the channel information of the user plane bearer of the target CU according to the first identifier of the target cell, the target CU and the second association relationship between the channel information of the user plane bearer indicating the target CU, thereby providing the channel information of the user plane bearer of the target CU to the core network device, thereby realizing the switching of the user plane bearer of the terminal device initiated by the source CU.

[0016] In combination with the first aspect or any implementation thereof, in another possible implementation, before the source CU sends a first request message to the core network device based on the first notification message, the method also includes: the source CU sends a second request message to the target CU, and the second request message is used to request the first information; the source CU receives a second response message from the target CU, and the second response message includes the identifier of the target CU and the first information; the source CU determines the second association relationship based on the identifier of the target CU and the first information.

[0017] Based on the above method, it is possible to pre-configure the second association relationship for the source CU before the source CU sends the first request message to the core network device, which can reduce the delay in switching the user plane bearer of the initiating terminal device.

[0018] In combination with the first aspect or any implementation thereof, in another possible implementation, the second request message also includes second information, and the second information is used to request that the source CU initiate the path switch; the second response message also includes third information, and the third information is used to indicate that the source CU is allowed to initiate the path switch.

[0019] Based on the above method, the source CU and the target CU can negotiate to determine that the source CU initiates the switching of the user plane bearer of the terminal device, which helps to initiate the switching of the user plane bearer of the terminal device by a more suitable CU.

[0020] In combination with the first aspect or any implementation manner thereof, in another possible implementation manner, the second request message further includes fourth information, where the fourth information is used to indicate that the path switch is initiated by the source CU.

[0021] In other words, the source CU only needs to notify the target CU when it determines to initiate the switching of the user plane bearer of the terminal device, without the need for confirmation or permission from the target CU.

[0022] In combination with the first aspect or any implementation thereof, in another possible implementation, the method further includes: the source CU sends at least one association relationship to the candidate CU, the candidate CU includes the target CU, and the at least one association relationship includes the first association relationship.

[0023] Based on this, when the target CU serves as the source CU for subsequent switching, it is not necessary to re-obtain the association relationship between the candidate cell and the channel information carried by the user plane of the corresponding candidate CU, thereby reducing the signaling overhead and allowing the subsequent switching process and the corresponding path switching process to be executed faster.

[0024] In combination with the first aspect or any implementation manner thereof, in another possible implementation manner, the first information includes at least one of the following information: an Internet Protocol (IP) address of a downlink endpoint of a user plane bearer of the target CU, or a GPRS tunneling protocol-tunnel endpoint identifier (GTP-TEID) of a downlink endpoint of a user plane bearer of the target CU. GPRS is a general packet radio system.

[0025] In combination with the first aspect or any implementation manner thereof, in another possible implementation manner, the method further includes: the source CU forwarding the service data of the terminal device to the target CU according to the first notification message.

[0026] In combination with the first aspect or any implementation thereof, in another possible implementation, the method further includes: the source CU sends a second notification message to the target CU, and the second notification message is used to indicate the target cell to which the terminal device will switch.

[0027] In combination with the first aspect or any implementation thereof, in another possible implementation, the second notification message includes at least one of the following information: a first identifier of the target cell, beam information, or access information, wherein the beam information is used to indicate the beam direction used by the target cell to communicate with the terminal device, and the access information is used to indicate the access method used by the terminal device to access the target cell.

[0028] In combination with the first aspect or any implementation thereof, in another possible implementation, the method further includes: the source CU sends the correspondence between the first identifier of the target cell and the second identifier of the target cell to the target CU, the first identifier being the identifier of the target cell on the air interface, and the second identifier being the identifier of the target cell on the network side.

[0029] Based on the above method, different cell identifiers can be used on the air interface and network side, which helps to avoid exposing the real identity information of the cell on the air interface, making the communication system more secure. In addition, considering that the first identifier of the target cell is determined by the source CU and the target CU is not aware of it, the above method can enable the target CU to know the correspondence between the first identifier of the target cell and the second identifier of the target cell. In this way, both the source CU and the target CU can use the same first identifier of the candidate cell when communicating with the terminal, which can avoid repeated configuration of the terminal device.

[0030] In combination with the first aspect or any implementation thereof, in another possible implementation, the length of the first identifier is smaller than the length of the second identifier, thereby reducing air interface signaling overhead.

[0031] In combination with the first aspect or any implementation manner thereof, in another possible implementation manner, the method further includes: the source CU receiving a first response message from the core network device, where the first response message is used to indicate that the path switching is successful.

[0032] In combination with the first aspect or any implementation thereof, in another possible implementation, the method further includes: the source CU receives a fifth notification message from the target CU, and the fifth notification message is used to indicate that the terminal device has successfully accessed the target cell.

[0033] In a second aspect, a switching method is provided. The method can be executed by a target CU or by a module or unit (such as a chip or circuit) in the target CU. The target CU is used for description below.

[0034] The terms or features in the second aspect or its implementation that are the same as those in the first aspect or its implementation can refer to the first aspect or its implementation, and its technical effects can refer to the technical effects in the first aspect or its implementation.

[0035] The method includes: the target CU receives a second request message from the source CU, the second request message is used to request first information, and the first information is used to indicate the channel information carried by the user plane of the target CU; the target CU sends a second response message to the source CU, the second response message includes a second identifier of a target cell and the first information, and the target cell is a cell of a target distributed unit DU under the target CU.

[0036] In combination with the second aspect, in a possible implementation, the second request message also includes second information, and the second information is used to request that the source CU initiate a path switch; the second response message also includes third information, and the third information is used to indicate that the source CU is allowed to initiate a path switch.

[0037] In combination with the second aspect or any implementation manner thereof, in another possible implementation manner, the second request message further includes fourth information, where the fourth information is used to indicate that the path switching is initiated by the source CU.

[0038] In combination with the second aspect or any implementation thereof, in another possible implementation, the method further includes: the target CU receives at least one association relationship from the source CU, the at least one association relationship includes a first association relationship, and the first association relationship is used to indicate the association relationship between the first identifier of the target cell and the first information.

[0039] In combination with the second aspect or any implementation thereof, in another possible implementation, the method further includes: the target CU receives the service data of the terminal device from the source CU; the target CU sends the service data to the target DU; after sending the service data to the target DU, the target CU receives a fourth notification message from the target DU, and the fourth notification message is used to indicate that the terminal device has successfully accessed the target cell.

[0040] Based on the above method, after the terminal device successfully accesses the target cell of the target DU of the target CU, the target DU can immediately send data to the terminal device, which is conducive to sending the data to the terminal device as soon as possible and avoiding data failure.

[0041] In combination with the second aspect or any implementation thereof, in another possible implementation, the method further includes: the target CU sends a fifth notification message to the source CU, and the fifth notification message is used to indicate that the terminal device has successfully accessed the target cell.

[0042] In combination with the second aspect or any implementation thereof, in another possible implementation, the method further includes: the target CU receives a second notification message from the source CU, and the second notification message is used to indicate the target cell to which the terminal device will switch.

[0043] In combination with the second aspect or any implementation thereof, in another possible implementation, the second notification message includes at least one of the following information: a first identifier of the target cell, beam information, or access information, wherein the beam information is used to indicate the beam direction used by the target cell to communicate with the terminal device, and the access information is used to indicate the access method used by the terminal device to access the target cell.

[0044] In combination with the second aspect or any implementation thereof, in another possible implementation, the method further includes: the target CU sends a sixth notification message to the target DU based on the second notification message, and the sixth notification message includes at least one of the following information: the first identifier of the target cell, the beam information, or the access information.

[0045] In combination with the second aspect or any implementation thereof, in another possible implementation, the second notification message includes seventh information, and the seventh information is used to indicate that the source CU has initiated path switching; the method also includes: the target CU does not perform path switching according to the seventh information.

[0046] In combination with the second aspect or any implementation thereof, in another possible implementation, the method further includes: the target CU receives the correspondence between the first identifier of the target cell and the second identifier of the target cell from the source CU, the first identifier being the identifier of the target cell on the air interface, and the second identifier being the identifier of the target cell on the network side.

[0047] In a third aspect, a switching method is provided. The method can be executed by a target CU or by a module or unit (such as a chip or circuit) in the target CU. The target CU will be used for description below.

[0048] The method includes: the target CU receives a first notification message from the source CU, where the first notification message is used to indicate the target cell to which the terminal device will switch, and the target cell is the cell of the target DU under the target CU; the target CU sends a first request message to the core network device based on the first notification message, where the first request message is used to request that the user plane bearer of the terminal device be switched to the target CU.

[0049] Based on the above method, the target CU can initiate the switching of the user plane bearer of the terminal device according to the first notification message for indicating the target cell to which the terminal device will switch. In other words, the switching of the user plane bearer of the terminal device can be triggered by the first notification message. Compared with initiating the switching of the user plane bearer of the terminal device after receiving the indication that the terminal device has successfully accessed the target cell, the above method can execute the switching of the user plane bearer of the terminal device earlier. After executing the switching of the user plane bearer of the terminal device, the service data of the terminal device can be sent directly to the target CU without going through the data forwarding process from the source CU to the target CU. Therefore, the above method can reduce the data forwarded from the source CU to the target CU, thereby reducing invalid data and improving the service experience.

[0050] In combination with the third aspect, in a possible implementation manner, the first notification message includes fifth information, and the fifth information is used to indicate that the source CU does not initiate a path switch.

[0051] In combination with the third aspect or any implementation thereof, in another possible implementation, before receiving the first notification message from the source CU, the method further includes: the target CU receives a second request message from the source CU, the second request message is used to request first information, the first information is used to indicate the channel information carried by the user plane of the target CU, the second request message also includes second information, the second information is used to request the source CU to initiate a path switch; the target CU sends a second response message to the source CU, the second response message includes sixth information, and the sixth information is used to indicate that the source CU is not allowed to initiate a path switch.

[0052] Based on the above method, the source CU and the target CU can negotiate to determine that the source CU initiates the switching of the user plane bearer of the terminal device, which helps to initiate the switching of the user plane bearer of the terminal device by a more suitable CU.

[0053] In combination with the third aspect or any implementation thereof, in another possible implementation, the first information includes at least one of the following information: the IP address of the downlink termination point carried by the user plane corresponding to the target CU, or the GTP-TEID of the downlink termination point carried by the user plane corresponding to the target CU.

[0054] In combination with the third aspect or any implementation thereof, in another possible implementation, the first notification message includes at least one of the following information: a first identifier of the target cell, beam information, or access information, wherein the beam information is used to indicate the beam direction used by the target cell to communicate with the terminal device, and the access information is used to indicate the access method used by the terminal device to access the target cell.

[0055] In combination with the third aspect or any implementation thereof, in another possible implementation, the method further includes: the target CU sends a third notification message to the target DU based on the first notification message, and the third notification message includes at least one of the following information: the first identifier, the beam information, or the access information.

[0056] In combination with the third aspect or any implementation thereof, in another possible implementation, the method further includes: the target CU receives at least one association relationship from the source CU, and the association relationship is used to indicate the association relationship between the identifier of the candidate cell and the channel information carried by the user plane of the candidate CU corresponding to the candidate cell.

[0057] Based on this, when the target CU serves as the source CU for subsequent switching, it is not necessary to re-obtain the association relationship between the candidate cell and the channel information carried by the user plane of the corresponding candidate CU, thereby reducing the signaling overhead and allowing the subsequent switching process and the corresponding path switching process to be executed faster.

[0058] In combination with the third aspect or any implementation thereof, in another possible implementation, the method further includes: the target CU receives the service data of the terminal device from the source CU; the target CU sends the service data to the target DU; after sending the service data to the target DU, the target CU receives a fourth notification message from the target DU, and the fourth notification message is used to indicate that the terminal device has successfully accessed the target cell.

[0059] Based on the above method, after the terminal device successfully accesses the target cell of the target DU of the target CU, the target DU can immediately send data to the terminal device, which is conducive to sending the data to the terminal device as soon as possible and avoiding data failure.

[0060] In combination with the third aspect or any implementation thereof, in another possible implementation, the method further includes: the target CU receives the correspondence between the first identifier of the target cell and the second identifier of the target cell from the source CU, the first identifier being the identifier of the target cell on the air interface, and the second identifier being the identifier of the target cell on the network side.

[0061] Based on the above method, different cell identifiers can be used on the air interface and network side, which helps to avoid exposing the real identity information of the cell on the air interface, making the communication system more secure. In addition, considering that the first identifier of the target cell is determined by the source CU and the target CU is not aware of it, the above method can enable the target CU to know the correspondence between the first identifier of the target cell and the second identifier of the target cell. In this way, both the source CU and the target CU can use the same first identifier of the candidate cell when communicating with the terminal, which can avoid repeated configuration of the terminal device.

[0062] In conjunction with the third aspect or any implementation thereof, in another possible implementation, the length of the first identifier is smaller than the length of the second identifier, thereby reducing air interface signaling overhead.

[0063] In combination with the third aspect or any implementation thereof, in another possible implementation, the method further includes: the target CU receiving a first response message from the core network device, where the first response message is used to indicate that the path switching is successful.

[0064] In a fourth aspect, a switching method is provided. The method can be executed by a source CU or by a module or unit (such as a chip or circuit) in the source CU. The source CU will be used for description below.

[0065] The terms or features in the fourth aspect or its implementation methods that are the same as those in the third aspect or its implementation methods can refer to the third aspect or its implementation methods, and its technical effects can refer to the technical effects in the third aspect or its implementation methods.

[0066] The method includes: the source CU receives an eighth notification message from the source DU, where the eighth notification message is used to indicate the target cell to which the terminal device will switch, and the target cell is the cell of the target DU under the target CU; the source CU sends a first notification message to the target CU based on the eighth notification message, where the first notification message is used to indicate the target cell to which the terminal device will switch.

[0067] In combination with the fourth aspect, in a possible implementation manner, the first notification message includes fifth information, and the fifth information is used to indicate that the source CU does not initiate a path switch.

[0068] In combination with the fourth aspect or any implementation manner thereof, in another possible implementation manner, before the source CU sends a first notification message to the target CU according to the eighth notification message, the method further includes: the source CU sends a second request message to the target CU, the second request message is used to request first information, the first information is used to indicate the channel information carried by the user plane of the target CU, the second request message also includes second information, the second information is used to request the source CU to initiate a path switch; the source CU receives a second response message from the target CU, the second response message includes sixth information, and the sixth information is used to indicate that the source CU is not allowed to initiate a path switch.

[0069] In combination with the fourth aspect or any implementation thereof, in another possible implementation, the first notification message also includes at least one of the following information: a first identifier of the target cell, beam information, or access information, wherein the beam information is used to indicate the beam direction used by the target cell to communicate with the terminal, and the access information is used to indicate the access method used by the terminal device to access the target cell.

[0070] In combination with the fourth aspect or any implementation thereof, in another possible implementation, the method further includes: the source CU sends at least one association relationship to the candidate CU, the candidate CU includes the target CU, and the association relationship is used to indicate the association relationship between the identifier of the candidate cell and the channel information carried by the user plane of the candidate CU corresponding to the candidate cell.

[0071] In combination with the fourth aspect or any implementation manner thereof, in another possible implementation manner, the method further includes: the source CU forwarding the service data of the terminal device to the target CU according to the eighth notification message.

[0072] In combination with the fourth aspect or any implementation thereof, in another possible implementation, the method further includes: the source CU sends the correspondence between the first identifier of the target cell and the second identifier of the target cell to the target CU, the first identifier being the identifier of the target cell on the air interface, and the second identifier being the identifier of the target cell on the network side.

[0073] In the fifth aspect, a switching method is provided, which can be executed by the target access network device or by a module or unit (such as a chip or circuit) in the target access network device. The target access network device will be used for description below.

[0074] The method includes: the target access network device determines the configuration information of the target cell, the configuration information of the target cell includes the configuration information of the first carrier, and the first carrier is a normal uplink (NUL) carrier or a supplementary uplink (SUL) carrier; the target access network device sends the configuration information of the target cell to the terminal device.

[0075] In one possible implementation, the target access network device sends the configuration information of the target cell to the terminal device through the source access network device.

[0076] Based on the above method, when the target cell has two carriers, NUL and SUL, the target access network device can determine whether to use NUL or SUL to complete the switching process of the target cell, and provide the terminal device with the configuration information of the corresponding carrier, so that the terminal device can use the configuration information of the carrier to switch to the target cell, which helps to ensure the successful cell switching.

[0077] In the sixth aspect, a switching method is provided, which can be executed by a terminal device or by a module or unit (such as a chip or circuit) in the terminal device. The terminal device will be used for description below.

[0078] The method includes: the terminal device receives configuration information of a target cell from a target access network device, the configuration information of the target cell includes configuration information of a first carrier, and the first carrier is a NUL carrier or a SUL carrier; the terminal device receives a switching command from a source access network device, and the switching command is used to indicate switching to the target cell; the terminal device uses the first carrier to perform a switching process to the target cell according to the configuration information of the target cell.

[0079] Based on the above method, when the target cell has two carriers, NUL and SUL, the target access network device can determine whether to use NUL or SUL to complete the switching process of the target cell, and provide the terminal device with the configuration information of the corresponding carrier. The terminal device can use the configuration information of the carrier to switch to the target cell, which helps to ensure the successful cell switching.

[0080] In the seventh aspect, a switching method is provided, which can be executed by a target access network device or by a module or unit (such as a chip or circuit) in the target access network device. The target access network device will be used for description below.

[0081] The method includes: a target access network device determines configuration information of a target cell, the configuration information of the target cell includes configuration information of a NUL carrier, configuration information of a SUL carrier, and carrier information, the carrier information is used to indicate the use of the NUL carrier to complete a switching process of the target cell, or the carrier information is used to indicate the use of the SUL carrier to complete a switching process of the target cell; the target access network device sends the configuration information of the target cell to a terminal device.

[0082] Based on the above method, when the target cell has two carriers, NUL and SUL, the target access network device can determine whether to use NUL or SUL to complete the switching process for the target cell and indicate it to the terminal device, which helps to ensure the successful cell switching.

[0083] In the eighth aspect, a switching method is provided, which can be executed by a terminal device or by a module or unit (such as a chip or circuit) in the terminal device. The terminal device will be used for description below.

[0084] The method includes: a terminal device receives configuration information of a target cell from a target access network device, the configuration information of the target cell includes configuration information of a NUL carrier, configuration information of a SUL carrier, and carrier information, the carrier information is used to indicate the use of a first carrier to complete a switching process of the target cell, the first carrier being the NUL carrier or the SUL carrier; the terminal device receives a switching command from a source access network device, the switching command being used to indicate switching to the target cell; the terminal device uses the first carrier to perform a switching process to the target cell according to the carrier information.

[0085] Based on the above method, when the target cell has two carriers, NUL and SUL, the target access network device can determine whether to use NUL or SUL to complete the switching process for the target cell and indicate it to the terminal device, which helps to ensure the successful cell switching.

[0086] In the ninth aspect, a switching method is provided, which can be executed by the target access network device or by a module or unit (such as a chip or circuit) in the target access network device. The target access network device will be used for description below.

[0087] The method includes: the target access network device sends configuration information of the target cell to the terminal device, the configuration information of the target cell includes configuration information of the NUL carrier and configuration information of the SUL carrier; the target access network device sends a first message to the source access network device, and the first message is used to notify the terminal device that the configuration information of the NUL carrier and the configuration information of the SUL carrier are provided.

[0088] Based on the above method, when the target cell has two carriers, NUL and SUL, the target access network device can provide the terminal device with the configuration information of the NUL carrier and the configuration information of the SUL carrier of the target cell, and inform the source access network device of the configuration information of the NUL carrier and the configuration information of the SUL carrier of the target cell provided to the terminal device, so that the source access network device can determine whether to use NUL or SUL to complete the switching process of the target cell, which helps to ensure the successful cell switching.

[0089] In the tenth aspect, a switching method is provided, which can be executed by a source access network device or by a module or unit (such as a chip or circuit) in the source access network device. The source access network device will be used for description below.

[0090] The method includes: a source access network device receives a first message from a target access network device, where the first message is used to notify a terminal device that configuration information of a NUL carrier and configuration information of a SUL carrier of a target cell are provided; the source access network device determines to use a first carrier to complete a switching process of the target cell; the source access network device sends a switching command to the terminal device, where the switching command is used to instruct switching to the target cell, the switching command includes carrier information, and the carrier information is used to instruct to use the first carrier to complete the switching process of the target cell, where the first carrier is the NUL carrier or the SUL carrier.

[0091] Based on the above method, when the target cell has two carriers, NUL and SUL, the source access network device can determine whether to use NUL or SUL to complete the switching process for the target cell, and indicate it to the terminal device through a switching command, which helps to ensure the successful cell switching.

[0092] In the eleventh aspect, a switching method is provided, which can be executed by a target access network device or by a module or unit (such as a chip or circuit) in the target access network device. The target access network device will be used for description below.

[0093] The method includes: a target access network device sends configuration information of a target cell to a terminal device, wherein the configuration information of the target cell includes configuration information of a NUL carrier and configuration information of a SUL carrier; and the target access network device sends carrier information to a source access network device, wherein the carrier information is used to indicate that a first carrier is used to complete a switching process of the target cell, wherein the first carrier is the NUL carrier or the SUL carrier.

[0094] Based on the above method, when the target cell has two carriers, NUL and SUL, the target access network device can provide the terminal device with the configuration information of the NUL carrier and the configuration information of the SUL carrier of the target cell, and inform the source access network device to use the NUL carrier or the SUL carrier to complete the switching process of the target cell, which helps to ensure the successful cell switching.

[0095] In the twelfth aspect, a switching method is provided, which can be executed by a source access network device or by a module or unit (such as a chip or circuit) in the source access network device. The source access network device will be used for description below.

[0096] The method includes: a source access network device receives carrier information from a target access network device, where the carrier information is used to indicate the use of a first carrier to complete a switching process of a target cell, where the first carrier is a NUL carrier of the target cell or a SUL carrier of the target cell; and the source access network device sends a switching command to the terminal device, where the switching command is used to indicate switching to the target cell, and the switching command includes the carrier information.

[0097] Based on the above method, when the target cell has two carriers, NUL and SUL, the target access network device can provide the terminal device with the configuration information of the NUL carrier and the configuration information of the SUL carrier of the target cell, and inform the source access network device to use the NUL carrier or the SUL carrier to complete the switching process of the target cell. The source access network device can instruct the terminal device through a switching command whether to use the NUL carrier or the SUL carrier to complete the switching process of the target cell, which helps to ensure the successful cell switching.

[0098] In the thirteenth aspect, a switching method is provided, which can be executed by a terminal device or by a module or unit (such as a chip or circuit) in the terminal device. The terminal device will be used for description below.

[0099] The method includes: a terminal device receives configuration information of a target cell from a target access network device, the configuration information of the target cell includes configuration information of a NUL carrier and configuration information of a SUL carrier; the terminal device receives a switching command from a source access network device, the switching command is used to indicate switching to the target cell, the switching command includes carrier information, the carrier information is used to indicate using a first carrier to complete a switching process of the target cell, the first carrier being the NUL carrier or the SUL carrier; the terminal device uses the first carrier to perform a switching process to the target cell according to the carrier information.

[0100] Based on the above method, when the target cell has two carriers, NUL and SUL, the source access network device can indicate whether to use NUL or SUL to complete the switching process for the target cell through a handover command, which helps to ensure the successful cell switching.

[0101] In the fourteenth aspect, a switching method is provided, which can be executed by a terminal device or by a module or unit (such as a chip or circuit) in the terminal device. The terminal device will be used for description below.

[0102] The method includes: a terminal device receives configuration information of a target cell from a target access network device, the configuration information of the target cell including configuration information of a NUL carrier and configuration information of a SUL carrier; the terminal device receives a switching command from a source access network device, the switching command being used to instruct switching to the target cell; the terminal device determines, based on the channel quality of the target cell, to use a first carrier to complete a switching process of the target cell, the first carrier being the NUL carrier or the SUL carrier; and the terminal device uses the first carrier to perform a switching process to the target cell.

[0103] Based on the above method, when the target cell has two carriers, NUL and SUL, the terminal device can determine whether to use NUL or SUL to complete the switching process for the target cell, which helps to ensure the successful cell switching.

[0104] In combination with the fourteenth aspect, in a possible implementation method, the terminal device determines to use the first carrier to complete the switching process of the target cell based on the channel quality of the target cell, including: the terminal device determines to use the first carrier to complete the switching process of the target cell based on the channel quality of the target cell and a preset threshold value.

[0105] One possible implementation method is that when the channel quality of the target cell is less than a preset threshold value, the terminal device determines to use the SUL carrier of the target cell to perform the switching process to the target cell, otherwise the terminal device determines to use the NUL carrier of the target cell to perform the switching process to the target cell.

[0106] For example, when the reference signal reception power of the downlink reference signal of the target cell is less than the preset power threshold value, the terminal device determines to use the SUL carrier of the target cell to perform the switching process to the target cell; otherwise, the terminal device determines to use the NUL carrier of the target cell to perform the switching process to the target cell.

[0107] In a fifteenth aspect, a communication device is provided, the device being configured to execute the method provided by any one of the above aspects or its implementations. Specifically, the device may include units and / or modules, such as a processing unit and / or a communication unit, for executing the method provided by any one of the above aspects or its implementations.

[0108] In one implementation, the apparatus is a source CU, a target CU, a source access network device, a target access network device, or a terminal device. When the apparatus is a source CU, a target CU, a source access network device, a target access network device, or a terminal device, the communication unit may be a transceiver, an input / output interface, or a communication interface; and the processing unit may be at least one processor. Optionally, the transceiver is a transceiver circuit. Optionally, the input / output interface is an input / output circuit.

[0109] In another implementation, the apparatus is a chip, chip system, or circuit used in a source CU, a target CU, a source access network device, a target access network device, or a terminal device. When the apparatus is a chip, chip system, or circuit used in a source CU, a target CU, a source access network device, a target access network device, or a terminal device, the communication unit may be an input / output interface, an interface circuit, an output circuit, an input circuit, a pin, or related circuits on the chip, chip system, or circuit; and the processing unit may be at least one processor, a processing circuit, or a logic circuit.

[0110] In the sixteenth aspect, a communication device is provided, which includes: a memory for storing programs; and at least one processor for executing computer programs or instructions stored in the memory to execute the method provided by any one of the above aspects or its implementation.

[0111] In one implementation, the apparatus is a source CU, a target CU, a source access network device, a target access network device, or a terminal device.

[0112] In another implementation, the device is a chip, a chip system or a circuit used in a source CU, a target CU, a source access network device, a target access network device or a terminal device.

[0113] In a seventeenth aspect, a communication device is provided, comprising: at least one processor and a communication interface, wherein the at least one processor is configured to retrieve a computer program or instruction stored in a memory through the communication interface to execute the method provided by any one of the above aspects or implementations thereof. The communication interface may be implemented in hardware or software.

[0114] In one implementation, the device further includes the memory.

[0115] In the eighteenth aspect, a processor is provided for executing the methods provided in the above aspects.

[0116] For the operations such as sending and acquiring / receiving involved in the processor, unless otherwise specified, or if they do not conflict with their actual functions or internal logic in the relevant descriptions, they can be understood as operations such as processor output, reception, and input, or as sending and receiving operations performed by the radio frequency circuit and antenna. This application does not limit this.

[0117] In the nineteenth aspect, a computer-readable storage medium is provided, which stores program code for execution by a device, and the program code includes a method for executing any of the above aspects or its implementation method.

[0118] In the twentieth aspect, a computer program product comprising instructions is provided, which, when run on a computer, enables the computer to execute the method provided by any one of the above aspects or its implementation.

[0119] In a twenty-first aspect, a chip is provided, comprising a processor and a communication interface, wherein the processor reads instructions stored in a memory through the communication interface and executes the method provided in any one of the above aspects or implementations thereof. The communication interface may be implemented in hardware or software.

[0120] Optionally, as an implementation method, the chip also includes a memory, in which a computer program or instruction is stored, and the processor is used to execute the computer program or instruction stored in the memory. When the computer program or instruction is executed, the processor is used to execute the method provided by any of the above aspects or its implementation methods.

[0121] When the method provided in this application is executed by a chip, this application does not limit the number of chips that implement the method. For example, the method can be executed by one chip or by two or more chips. Furthermore, when the number of chips implementing the method of this application is two or more, the chip manufacturers are not limited and can be the same manufacturer or different manufacturers.

[0122] In aspect 22, a communication system is provided, comprising at least one of the source CU, target CU, source access network device, target access network device or terminal device mentioned above.

[0123] In the twenty-third aspect, a computer program is provided, which, when run on a computer, enables the method provided by any one of the above aspects or its implementation to be executed. BRIEF DESCRIPTION OF THE DRAWINGS

[0124] FIG1 is a diagram of a network architecture applicable to an embodiment of the present application.

[0125] FIG2 is a schematic diagram of the CU-DU architecture.

[0126] FIG3 is a schematic flowchart of L1 / L2 Triggered Mobility (LTM) switching between different DUs under the same CU.

[0127] FIG4 is a schematic flowchart of cell handover between base stations.

[0128] FIG5 is a schematic flowchart of a switching method 500 provided in this application.

[0129] FIG6 is a schematic flowchart of a switching method 600 provided in this application.

[0130] FIG7 is a schematic flowchart of a switching method 700 provided in this application.

[0131] FIG8 is a schematic flowchart of a switching method 800 provided in this application.

[0132] FIG9 is a schematic flowchart of a switching method 900 provided in this application.

[0133] FIG10 is a schematic flowchart of a switching method 1000 provided in this application.

[0134] FIG11 is a schematic structural diagram of a communication device provided in this application.

[0135] FIG12 is another structural diagram of the communication device provided in this application. DETAILED DESCRIPTION

[0136] To facilitate understanding of the embodiments of the present application, the following explanations are made before introducing the embodiments of the present application.

[0137] "For indicating" or "indicating" can include direct indication and indirect indication, or "for indicating" or "indicating" can be explicitly and / or implicitly indicated. The various digital numbers such as first, second, etc. are only used for the convenience of description and are not used to limit the scope of the embodiments of the present application, such as distinguishing different messages, different information, etc. "Pre-definition" can be implemented by pre-saving corresponding codes, tables or other methods that can be used to indicate relevant information in the device. The present application does not limit its specific implementation method. The "protocol" involved may refer to a standard protocol in the field of communications, for example, it may include the long term evolution (LTE) protocol, the new radio (NR) protocol and related protocols used in future communication systems. The present application does not limit this. Words such as "example", "for example", "exemplarily", "as (another) example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as an "example" in this application should not be interpreted as being more preferred or more advantageous than other embodiments or design schemes. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized. "At least one" means one or more, and "more" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b and c can mean: a, or b, or c, or a and b, or a and c, or b and c, or a, b and c. Where a, b and c can be single or multiple, respectively. Descriptions of network element A sending a message, information, or data to network element B, or network element B receiving a message, information, or data from network element A, are intended to clarify the network element to which the message, information, or data is sent, and do not limit whether the messages, information, or data are sent directly or indirectly through other network elements. Phrases such as "when," "under the circumstances," "if," and "if" all imply that the device will take appropriate action under certain objective circumstances. They do not specify a time limit, do not require the device to perform a judgment action, and do not imply any other limitations.

[0138] In addition, the network architecture and business scenarios described in the embodiments of the present application are intended to more clearly illustrate the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided in the embodiments of the present application. Ordinary technicians in this field can know that with the evolution of network architecture and the emergence of new business scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

[0139] A communication system to which the embodiments of the present application can be applied is described below.

[0140] The embodiments of the present application can be applied to various communication systems, such as LTE systems, frequency division duplex (FDD) systems, time division duplex (TDD) systems, universal mobile telecommunication systems (UMTS), worldwide interoperability for microwave access (WiMAX) communication systems, fifth generation (5G) systems or NR systems, sixth generation (6G) systems or future communication systems. The 5G mobile communication system described in this application includes a non-standalone (NSA) 5G mobile communication system or a standalone (SA) 5G mobile communication system. The communication system may also be a public land mobile network (PLMN) network, a device-to-device (D2D) communication system, a machine-to-machine (M2M) communication system, an Internet of Things (IoT) communication system, a vehicle to everything (V2X) communication system, an uncrewed aerial vehicle (UAV) communication system, or other communication systems.

[0141] For example, Figure 1 illustrates a network architecture diagram applicable to embodiments of the present application. As shown in Figure 1 , the network architecture may specifically include three parts: a terminal device part, a data network (DN), and an operator network part. The following briefly describes the functions of the network elements in each part.

[0142] The terminal equipment section may include terminal equipment. Terminal equipment may also be referred to as user equipment (UE), access terminal, terminal, user unit, user station, mobile station, mobile station, remote station, remote terminal, mobile device, user terminal, user agent, or user device. It is a device with wireless transceiver capabilities that can communicate with one or more core network (CN) devices via access network equipment (or also referred to as access equipment) in a radio access network (RAN). Terminal equipment can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; it can also be deployed on the water (such as a ship); it can also be deployed in the air (such as an airplane, balloon, and satellite). Terminal equipment can be a cellular phone, a cordless phone, a session initiation protocol (SIP) phone, a smart phone, a mobile phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), etc. Alternatively, the terminal device may also be a handheld device with wireless communication capabilities, a computing device or other device connected to a wireless modem, an in-vehicle device, a wearable device, an unmanned aerial vehicle device or a terminal in the Internet of Things, the Internet of Vehicles, a terminal in any form in a 5G network and future networks, a relay user device or a terminal in a future evolved 6G network, etc. The terminal device may also be a virtual reality (VR) terminal, an augmented reality (AR) terminal, a wireless terminal in industrial control, a wireless terminal in self-driving, a wireless terminal in remote medical care, a wireless terminal in a smart grid, a wireless terminal in transportation safety, a wireless terminal in a smart city, a wireless terminal in a smart home, etc. The embodiments of the present application do not limit the specific technology and specific device form adopted by the terminal device.

[0143] A data network, also known as a packet data network (PDN), is typically a network located outside of an operator's network, such as a third-party network. Of course, in some implementations, the DN can also be deployed by the operator, meaning the DN is part of the PLMN. An operator's network can access multiple data network DNs, which can deploy a variety of services and provide data and / or voice services to terminal devices. Terminal devices can also access data network DNs through the operator's network and use operator services deployed on the data network DNs, and / or services provided by third parties.

[0144] The operator network part includes but is not limited to the (radio) access network (R)AN) part and the core network (CN) part.

[0145] (R)AN can be considered a subnetwork of the operator network and is the implementation system between the service nodes and terminal devices in the operator network. To access the operator network, the terminal device first passes through the (R)AN, and then connects to the service nodes of the operator network through the (R)AN. The access network device (RAN device) in the embodiments of this application is a device that provides wireless communication functions for the terminal device. The embodiments of this application do not limit the specific technology and specific device form used by the access network device.

[0146] In one possible scenario, the access network device may be a base station, an evolved NodeB (eNodeB), an access point (AP), a transmission reception point (TRP), a next-generation NodeB (gNB), a next-generation base station in a sixth-generation (6G) mobile communication system, an access node in a wireless fidelity (WiFi) system, or an access node in a base station in a future mobile communication system. The access network device may be a macro base station, a micro base station, or an indoor station, a relay node or a donor node, or a wireless controller in a CRAN scenario. Optionally, the access network device may also be a server, a wearable device, a vehicle, or an on-board device. For example, the access network device in vehicle to everything (V2X) technology may be a road side unit (RSU).

[0147] In another possible scenario, multiple access network devices collaborate to assist terminal devices in achieving wireless access, and different access network devices respectively implement part of the functions of the base station. For example, the access network device can be a CU, DU, CU-control plane (CP), CU-user plane (UP), or radio unit (RU). The CU and DU can be set separately, or they can be included in the same network element, such as a baseband unit (BBU). The RU can be included in a radio frequency device or radio frequency unit, such as a remote radio unit (RRU), an active antenna unit (AAU), or a remote radio head (RRH).

[0148] In different systems, CU (or CU-CP and CU-UP), DU or RU may also have different names, but those skilled in the art can understand their meanings. For example, in the ORAN system, CU may also be called O-CU (Open CU), DU may also be called O-DU, CU-CP may also be called O-CU-CP, CU-UP may also be called O-CU-UP, and RU may also be called O-RU. For the convenience of description, this application uses CU, CU-CP, CU-UP, DU and RU as examples for description. Any unit of CU (or CU-CP, CU-UP), DU and RU in this application can be implemented by a software module, a hardware module, or a combination of a software module and a hardware module.

[0149] The CN part includes but is not limited to the following network functions (NF): user plane function (UPF), network exposure function (NEF), network function repository function (NRF), policy control function (PCF), UDM, UDR, access and mobility management function (AMF), session management function (SMF) and application function (AF).

[0150] The following is a brief description of the NF functions included in CN.

[0151] 1. UPF is the gateway for communication between the operator network and the data network DN. It mainly provides user plane functions such as forwarding and processing of user messages, connection with DN, session anchor point, and quality of service (QoS) policy execution.

[0152] 2. NEF is a control plane function that is primarily used to securely expose services and capabilities provided by 3GPP network functions to external parties (such as AF). NEF also allows authenticated and authorized application functions to securely provide information in the 3GPP network.

[0153] 3. NRF is a control plane function that can be used to maintain real-time information of network functions and services in the network.

[0154] 4. PCF is the control plane function, which supports a unified policy framework to govern network behavior, provide policy rules to other control functions, and contract information related to policy decisions.

[0155] 5. UDM is a control plane function, which is mainly responsible for storing the contract data of contracted users in the operator network.

[0156] 6. UDR is a control plane function, mainly responsible for data storage and retrieval, such as providing the UDM with the function of storing and retrieving contract data, providing the PCF with the function of storing and retrieving policy data, and storing and retrieving the user's NF group ID information.

[0157] 7. AMF is a control plane function, which is mainly responsible for access control and mobility management of terminal devices accessing the operator's network, such as mobile state management, allocation of user temporary identity, authentication and authorization of users, etc.

[0158] 8. SMF is the control plane function, which is mainly responsible for session management (such as session establishment, modification and release), selection and control of UPF network functions, service and session continuity (SSC) mode selection, roaming and other session-related functions.

[0159] 9. AF is a control plane function used to provide application layer information.

[0160] In Figure 1, Nnef, Nnrf, Npcf, Nudm, Nudr, Namf, Nsmf, N1, N2, N3, N4, N6, and N9 are interface serial numbers. For example, the meaning of the above interface serial numbers can be found in the meaning defined in the 3GPP standard protocol, and this application does not limit the meaning of the above interface serial numbers. It should be noted that the interface name between the various network functions in Figure 1 is only an example. In a specific implementation, the interface name of the system architecture may also be other names, which is not limited in this application. The interface between each network element can be a point-to-point interface or a service-oriented interface, which is not limited in this application.

[0161] It should be understood that the network architecture shown above is only an exemplary illustration, and the network architecture applicable to the embodiments of the present application is not limited to this. Any network architecture that can realize the functions of the above-mentioned network elements is applicable to the embodiments of the present application.

[0162] It should also be understood that the functions or network elements such as AMF, SMF, UPF, PCF, UDM, UDR, NEF, NRF, AF shown in Figure 1 can be understood as network elements for implementing different functions, for example, they can be combined into network slices as needed. These network elements can be independent devices, or they can be integrated into the same device to implement different functions, or they can be network elements in hardware devices, or they can be software functions running on dedicated hardware, or they can be virtualized functions instantiated on a platform (for example, a cloud platform). This application does not limit the specific form of the above network elements.

[0163] It should also be understood that the above naming is defined only to facilitate the distinction between different functions and should not constitute any limitation to this application. This application does not exclude the possibility of adopting other naming in 6G networks and other future networks. For example, in a 6G network, some or all of the above network elements may continue to use the terminology used in 5G, or may adopt other names.

[0164] To facilitate understanding of the embodiments of the present application, some terms or technologies involved in the embodiments of the present application are briefly described below.

[0165] 1. CU-DU separation architecture

[0166] FIG2 is a schematic diagram of the CU-DU architecture.

[0167] As shown in Figure 2, the base station can be logically divided into a CU and one or more DUs. Each DU is connected to the CU through the F1 logical interface. Operations related to the Radio Link Control (RLC) layer, the Media Access Control (MAC) layer, and the Physical Layer (PHY) are handled by the DU, while operations related to the Service Data Adaptation Protocol (SDAP) layer, the Radio Resource Control (RRC) layer, and the Packet Data Convergence Protocol (PDCP) layer are handled by the CU.

[0168] 2. Long-Term Transaction (LTM)

[0169] L1 in LTM refers to the PHY layer, and L2 refers to the MAC layer, RLC layer, PDCP layer, and SDAP layer.

[0170] LTM refers to handover-related operations primarily performed at L1 and / or L2. For example, a terminal device sends L1 measurement results to a base station via physical layer control signaling, which can be carried on a physical uplink control channel (PUCCH). The base station's physical layer reads the L1 measurement results, makes a handover decision based on them, and then sends the handover decision to the terminal device via L1 / L2 signaling, which can be a message carried on a physical downlink control channel (PDCCH) or a MAC control element (MAC CE).

[0171] It should be noted that L1 / L2 represents L1 and / or L2. When the relationship is "and", the switching process-related operations are mainly completed by L1 and L2; when the relationship is "or", the switching-related operations are mainly completed by L1 or L2.

[0172] 3. LTM switching between different DUs under the same CU

[0173] Figure 3 is a schematic flowchart of LTM handover between different DUs within the same CU. The S-DU refers to the source DU, and the T-DU refers to the target DU. Both the source DU and the target DU belong to the same CU. The target DU is one of the candidate DUs. Before handover, there may be multiple candidate DUs. During handover, one of the candidate DUs becomes the target DU. Figure 3 only illustrates the signaling interaction between the CU and the target DU.

[0174] Step 301: The CU obtains candidate cell configuration information from the candidate DU.

[0175] There can be one or more candidate cells. There can also be one or more candidate DUs. When there are multiple candidate DUs, the CU obtains the configuration information of the candidate cells under each candidate DU.

[0176] A complete candidate cell configuration information may include a portion generated by the CU and a portion generated by the DU. The portion generated by the CU can be described as "CU-side configuration information," and the portion generated by the DU can be described as "DU-side configuration information." The candidate cell configuration information here refers to "DU-side configuration information."

[0177] Step 302: The CU sends the candidate cell configuration information to the terminal device via the source DU.

[0178] The candidate cell configuration information here may refer to complete candidate cell configuration information, namely, “CU side configuration information” and “DU side configuration information”.

[0179] Step 303: The terminal device performs cell measurement and reports the measurement result to the source DU.

[0180] In LTM handover, the terminal device reports the L1 measurement results. The terminal device sends the L1 measurement results of different cells to the source DU via the communication resources of the source cell. The L1 measurement results include at least one of the following: the L1 measurement result of the source cell or the L1 measurement result of at least one candidate cell.

[0181] The L1 measurement results of the above-mentioned source cell and / or candidate cell may be cell-level measurement results or beam-level measurement results.

[0182] Step 304: The source DU determines to switch the terminal device to the target cell based on the L1 measurement result reported by the terminal device, and sends a switching command to the terminal device.

[0183] The target cell is one of the candidate cells. The handover command includes identification information of the target cell. The handover command can be sent to the terminal device via L1 / L2 signaling, which is still sent via the communication resources of the source cell and can be a MAC CE.

[0184] The source DU may also send the cell switching triggered situation to the CU.

[0185] Step 305: The terminal device performs LTM switching and switches to the target cell.

[0186] Specifically, the terminal device uses the configuration information of the target cell received in step 302 to access the target cell.

[0187] After the terminal device successfully accesses the target cell, the terminal device transmits uplink and downlink data with the target cell.

[0188] Step 306: After the terminal device successfully accesses the target cell, the target DU sends a handover success notification to the CU to notify the terminal device of successful handover to the target cell.

[0189] As shown in FIG3 , in LTM handover, before handover, the base station pre-configures the configuration information of the candidate cells to the terminal device.

[0190] 4. Data forwarding and path switching during cell handover across base stations

[0191] 1) Data forwarding

[0192] The downlink data sent to the terminal device is sent by the UPF of the core network to the base station, and then sent to the terminal device by the base station.

[0193] In a mobile communication system, the movement of a terminal device may cause a change in the communication link between the terminal device and a base station. The base station will instruct the terminal device to perform a cell handover based on the movement of the terminal device.

[0194] Before the handover, a user plane transmission bearer is established between the UPF and the source base station. Downlink data can be sent to the source base station through the user plane transmission bearer between the UPF and the source base station, and further sent to the terminal device by the source base station. As the terminal device moves, when cell handover is required, the source base station will send a handover command to the terminal device. After that, the source base station can no longer send downlink data from the UPF to the terminal device. In this case, the source base station can send the downlink data cached in the source base station to the target base station so that after the handover is completed, the target base station can send it to the terminal device, thereby ensuring data losslessness. The process of forwarding data from the source base station to the target base station is called data forwarding.

[0195] The above-mentioned user plane transmission bearer can also be described as a user plane channel, a user plane tunnel, a user plane data channel or a user plane data tunnel, etc.

[0196] 2) Path switching

[0197] After the terminal device successfully switches to the target base station, the target base station can send the data forwarded by the source base station to the terminal device. However, since the UPF has not yet established a user plane transmission bearer with the target base station at this time, the target base station needs to send a path switch request message to the AMF of the core network to request the establishment of a user plane transmission bearer between the UPF and the target base station. After receiving the path switch request message from the target base station, the AMF can control the UPF to establish a user plane transmission bearer with the target base station. Thereafter, the UPF can send downlink data directly to the target base station without the need for data forwarding through the source base station.

[0198] The following describes data forwarding and path switching in inter-base station cell switching with reference to FIG. 4 .

[0199] Figure 4 is a schematic flow chart of cell handover across base stations, which is illustrated by taking downlink data transmission as an example.

[0200] Step 401: When the source base station determines that the terminal device needs to be switched, the source base station sends a switching request message to the target base station.

[0201] Step 402: When the target base station allows the terminal device to access, the target base station sends a handover request response message to the source base station.

[0202] The handover request response message may include configuration information of the target cell.

[0203] Step 403: After receiving the handover request response message, the source base station sends a handover command to the terminal device.

[0204] The handover command includes the configuration information of the target cell.

[0205] Step 404: After the source base station sends a switching command to the terminal device, the source base station forwards the downlink data from the UPF to the target base station.

[0206] After the source base station sends a switching command to the terminal device, the source base station can no longer send downlink data to the terminal device. The source base station sends the downlink data cached in the source base station to the target base station so that the target base station can send it to the terminal device after the terminal device accesses the target cell.

[0207] Step 405: The terminal device accesses the target cell using the configuration information of the target cell according to the received handover command.

[0208] Step 406: After the terminal device successfully accesses the target cell, the target base station sends a path switching request message to the AMF.

[0209] Step 407: AMF controls UPF to perform path switching and establishes a user plane transmission bearer between UPF and the target base station.

[0210] Step 408: After step 407, the UPF can send the downlink data sent to the terminal device to the target base station without data forwarding through the source base station.

[0211] Step 409: The AMF sends a path switch request response message to the target base station.

[0212] Step 410: The target base station sends data to the terminal device.

[0213] The downlink data includes downlink data forwarded by the source base station and downlink data directly from the UPF. It should be noted that the target base station can send the downlink data forwarded by the source base station to the terminal device after step 405.

[0214] For a more detailed description of inter-base station cell handover, please refer to the prior art and will not be described in detail here. The above step 404 shows data forwarding during inter-base station cell handover, and the above steps 406 to 409 show path switching during inter-base station cell handover.

[0215] Currently, downlink data needs to be sent from the UPF to the terminal device within a specific time, for example, within 20ms. As shown above, during the handover process, some data needs to pass through the data forwarding process from the source base station to the target base station. This additional delay may cause this data (especially data for delay-sensitive services) to reach the terminal device after the specific time has expired. Data that exceeds this specific time will become invalid and unavailable to the terminal device, which will result in a reduced service experience.

[0216] To address the above issues, the present application provides a switching method that can reduce the amount of data forwarded from the source CU to the target CU by advancing the path switching process, thereby reducing invalid data and improving the service experience.

[0217] The following describes the method embodiments provided in this application.

[0218] The embodiments of the present application can be applied to LTM switching between different DUs under different CUs, and can also be applied to other similar switching scenarios and switching technologies, without limitation. It should be noted that the order of the step numbers in the following method embodiments does not imply the order of execution. The order of the steps can be determined by internal logic, and the order of the steps described below is only an example and is not limited to this.

[0219] FIG5 is a schematic flow chart of a handover method 500 provided in the present application. The method 500 includes at least part of the following contents.

[0220] Step 501: Receive a first notification message.

[0221] The first notification message is used to indicate the target cell to which the terminal device will switch. The target cell is the cell of the target DU under the target CU.

[0222] Step 502: Send a first request message to the core network device according to the first notification message.

[0223] The first request message is used to request that the user plane bearer of the terminal device be switched to the target CU. The user plane bearer can also be described as a user plane transmission bearer, a user plane channel, or a user plane tunnel. The user plane bearer of the terminal device can be understood as a bearer, channel, or tunnel used to transmit user plane data of the terminal device.

[0224] Compared to initiating the switching of the user plane bearer of the terminal device after receiving the indication that the terminal device has successfully accessed the target cell, method 500 can initiate the switching of the user plane bearer of the terminal device based on the first notification message used to indicate the target cell to which the terminal device will switch. In other words, the switching of the user plane bearer of the terminal device can be triggered by the first notification message, so that the switching of the user plane bearer of the terminal device can be performed earlier. After executing the switching of the user plane bearer of the terminal device, the service data of the terminal device can be sent directly to the target CU without going through the data forwarding process from the source CU to the target CU. Therefore, based on method 500, the data forwarded from the source CU to the target CU can be reduced, thereby reducing invalid data and improving the service experience.

[0225] Method 500 may be executed by a source CU or a module or unit in the source CU, or may be executed by a target CU or a module or unit in the target CU. The following description will uniformly use the source CU or the target CU.

[0226] The scheme executed by the source CU or the modules or units in the source CU will be described in detail below with reference to FIG. 6 .

[0227] FIG6 is a schematic flow chart of a handover method 600 provided in the present application. The method 600 may include at least part of the following contents.

[0228] Step 601: The source DU sends a notification message #1 to the source CU, or in other words, the source CU receives the notification message #1 from the source DU.

[0229] Notification message #1 may correspond to the first notification message in method 500, and is used to indicate the target cell to which the terminal device will switch. Notification message #1 is used to indicate the target cell to which the terminal device will switch, and may also be described as: notification message #1 is used to indicate that the terminal device will switch to the target cell, or the first notification message is used to notify the source CU of the initiation of the LTM command for the terminal device and the identification of the target cell.

[0230] In one possible implementation, the source DU may determine to switch the terminal device to the target cell based on the L1 measurement result reported by the terminal device, and after determining to switch the terminal device to the target cell, send a notification message #1 to the source CU.

[0231] Step 602: The source CU sends a request message #1 to the core network device according to the notification message #1.

[0232] Among them, request message #1 can correspond to the first request message in method 500, which is used to request to switch the user plane bearer of the terminal device to the target CU.

[0233] Exemplarily, the request message #1 may be a path switching request message.

[0234] Request message #1 is used to request that the user plane bearer of the terminal device be switched to the target CU, and can also be replaced by: Request message #1 is used to request that the downlink termination point of the user plane transmission bearer of the terminal device be switched to the downlink termination point of the user plane transmission bearer corresponding to the target cell, wherein the downlink termination point of the user plane transmission bearer corresponding to the target cell can be the target CU to which the target cell belongs.

[0235] For example, the core network device may be an AMF. After receiving the request message #1, the AMF may control the UPF to switch the user plane bearer of the terminal device to the target CU.

[0236] In this way, in method 600, the source CU can initiate the switching of the user plane bearer of the terminal device based on the notification message #1 used to indicate the target cell to which the terminal device will switch, and can execute the switching process of the user plane bearer of the terminal device earlier, thereby reducing the data forwarded from the source CU to the target CU, thereby reducing invalid data and improving the service experience.

[0237] The embodiments of the present application do not limit the specific implementation of step 602.

[0238] In the first possible implementation method, the notification message #1 includes the first identifier of the target cell. Step 602 may specifically include: the source CU sends a request message #1 to the core network device according to the first identifier of the target cell in the notification message #1 and the first association relationship, wherein the first association relationship is used to indicate the association relationship between the first identifier of the target cell and the first information, the first information is used to indicate the channel information carried by the user plane of the target CU, and the request message #1 may include the first information.

[0239] Exemplarily, the first information may include at least one of the following information: an IP address of a downlink termination point of a user plane bearer of the target CU, or a GTP-TEID of a downlink termination point of a user plane bearer of the target CU.

[0240] The first information is used to indicate the channel information carried by the user plane of the target CU, and can also be replaced by: the first information is used to indicate the channel information carried by the user plane corresponding to the target cell. It should be noted that in the embodiment of the present application, each cell managed by a CU can correspond to a channel information carried by a user plane, or a cell managed by a candidate CU can also correspond to the same channel information carried by the user plane, without limitation.

[0241] The embodiments of the present application do not limit the method for obtaining the first association relationship.

[0242] In a possible implementation, the first association relationship is preconfigured. Exemplarily, before step 602, method 600 may further include steps 603-605, which are specifically as follows.

[0243] Step 603: The source CU sends a request message #2 to the target CU, or the target CU receives the request message #2 from the source CU.

[0244] Among them, the request message #2 is used to request the channel information carried by the user plane of the target CU, that is, the above-mentioned first information.

[0245] In one possible implementation, request message #2 may be a multiplexing or enhancement of the message for requesting candidate cell configuration information. In other words, the source CU may request the channel information carried by the user plane of the target CU at the same time as requesting the candidate cell configuration information from the target CU. The request for the channel information carried by the user plane of the target CU may be explicit or implicit, without restriction. For example, the source CU may add additional information to the message for requesting candidate cell configuration information, such as the identifier of the target CU, to indicate the channel information carried by the user plane of the target CU. For another example, the source CU may send a message for requesting candidate cell configuration information, and the message itself may indicate the channel information carried by the user plane of the target CU.

[0246] Step 604: After receiving the request message #2, the target CU sends a response message to the request message #2 to the source CU, namely the response message #2 in Figure 6. Accordingly, the source CU receives the response message #2 from the target CU.

[0247] Among them, the response message #2 includes the first information.

[0248] Step 605: The source CU determines a first association relationship based on the first information.

[0249] In one possible implementation, the source CU determines the first association relationship based on the target cell, the cell managed by the target CU, and the first information. For example, when the source CU knows the cell managed by the target CU, the source CU can generate an association relationship between the cell managed by the target CU and the first information after receiving the first information. Since the cell managed by the target CU includes the target cell, the generated association relationship includes the first association relationship.

[0250] Another possible implementation method is that the response message #2 also includes the second identifier of the target cell. In this case, the source CU can generate a first association relationship based on the second identifier of the target cell and the first information in the response message #2. In an embodiment of the present application, the first identifier of the target cell can be the identifier of the target cell on the air interface, and the second identifier of the target cell can be the identifier of the target cell on the network side. The first identifier of the target cell and the second identifier of the target cell can be the same or different. When the first identifier of the target cell and the second identifier of the target cell are different, the true identity information of the candidate cell can be avoided from being exposed on the air interface, making the communication system more secure.

[0251] Optionally, the length of the first identifier of the target cell is smaller than the length of the second identifier of the target cell. In this way, the signaling overhead of the air interface can be reduced.

[0252] For the case where the first identifier of the target cell and the second identifier of the target cell are different, the source CU generates a first association relationship based on the second identifier of the target cell and the first information in the response message #2. Specifically, it may include: the source CU may convert the second identifier of the target cell included in the response message #2 into the first identifier, and then generate an association relationship between the first identifier and the first information, that is, the first association relationship.

[0253] It should be noted that Figure 6 only shows the signaling interaction between the target DU and target CU belonging to the target cell, and the determination of the first association relationship. In fact, steps 603-605 may involve signaling interaction between the source CU and at least one candidate CU including the target CU, as well as determining the association relationship between the channel information carried by the user plane of at least one candidate cell including the target cell and the corresponding candidate CU.

[0254] In other embodiments, method 600 may further include step 606: the source CU sends at least one association relationship to the target CU, or the target CU receives at least one association relationship from the source CU. The at least one association relationship is an association relationship between the channel information carried by the user plane of at least one candidate cell and the corresponding candidate CU generated by steps 603-605, and the at least one association relationship includes the above-mentioned first association relationship. Based on this, when the target CU serves as the source CU for subsequent switching, it is not necessary to re-execute steps 603-604 to obtain the association relationship between the channel information carried by the user plane of the candidate cell and the corresponding candidate CU, thereby reducing the signaling overhead and enabling the subsequent switching process and the corresponding path switching process to be executed faster.

[0255] FIG6 only takes the example of the source CU sending at least one association relationship to the target CU. In practice, the source CU may send the at least one association relationship to all candidate CUs.

[0256] This application does not limit the timing of executing step 606. For example, as shown in Figure 6, the source CU may send at least one association relationship to the candidate cell after determining at least one association relationship. For another example, the source CU may send at least one association relationship to the target CU and / or candidate CU after learning that the terminal device has successfully accessed the target cell.

[0257] The second possible implementation method is that the notification message #1 includes the first identifier of the target cell. Step 602 may specifically include: the source CU sends a request message #1 to the core network device based on the first identifier of the target cell in the notification message #1 and the second association relationship, wherein the second association relationship is used to indicate the association relationship between the target CU and the first information, the first information is used to indicate the channel information carried by the user plane of the target CU, and the request message #1 may include the first information.

[0258] Exemplarily, the source CU determines the identifier of the target CU to which the target cell belongs based on the first identifier of the target cell in notification message #1 and the cell managed by the target CU, and then sends a request message #1 to the core network device based on the identifier of the target CU and the second association relationship.

[0259] The embodiments of the present application do not limit the method for obtaining the second association relationship.

[0260] In one possible implementation, the second association is preconfigured. Similar to the acquisition of the first association, refer to steps 603-605. The difference is that response message #2 may include the target CU identifier and the first information, so that the source CU can generate a correspondence between the target CU identifier and the first information.

[0261] Similar to step 606, method 600 may further include: the source CU sends at least one association relationship to the target CU, or the target CU receives at least one association relationship from the source CU. The association relationship is the association relationship between the candidate CU and the channel information carried by its user plane, and at least one association relationship includes the above-mentioned second association relationship. Based on this, when the target CU serves as the source CU for subsequent switching, it may not need to re-obtain the association relationship between the candidate CU and the channel information carried by the user plane, thereby reducing signaling overhead and enabling subsequent switching processes and corresponding path switching processes to be executed faster. For a more detailed description, please refer to step 606.

[0262] In addition, considering that the first identifier of the target cell is determined by the source CU and the target CU does not know it, method 600 can also include step 607: the source CU sends the correspondence between the first identifier of the target cell and the second identifier of the target cell to the target CU, so that the target CU knows the correspondence between the first identifier of the target cell and the second identifier of the target cell.

[0263] Similarly, Figure 6 only takes the correspondence between the first identifier of the target cell and the second identifier of the target cell sent by the source CU to the target CU as an example. In fact, the source CU can send the correspondence between the first identifier and the second identifier of all candidate cells to each CU in all candidate CUs.

[0264] In this way, multiple CUs including the source CU and the target CU can use the same first identifier of the candidate cell when communicating with the terminal, thereby avoiding repeated configuration of the terminal device.

[0265] This application does not limit the implementation method of sending the correspondence between the first identifier of the target cell and the second identifier of the target cell. In one possible implementation method, the correspondence between the first identifier of the target cell and the second identifier of the target cell can be sent to the candidate CU together with at least one association relationship. In another possible implementation method, if the source CU knows the cell managed by the candidate CU, the source CU can convert the candidate cell identity in advance and carry the correspondence between the first identifier of the target cell and the second identifier of the target cell in the request message #2 of step 603.

[0266] In the embodiment of the present application, the switching of the user plane bearer of the terminal device initiated by the source CU may be specified in the protocol or determined by negotiation between the source CU and the target CU. The following describes the negotiation between the source CU and the target CU.

[0267] This application does not limit the specific implementation method of the negotiation between the source CU and the target CU.

[0268] In one possible implementation, the source CU may include second information in the request message #2 of step 603, requesting that the source CU initiate a user plane bearer handover (i.e., path handover) of the terminal device. Accordingly, the target CU may include third information in the response message #2 of step 604, indicating that the source CU is permitted to initiate a user plane bearer handover of the terminal device. In this case, the source CU may determine that it is responsible for initiating the user plane bearer handover of the terminal device.

[0269] In another possible implementation, the source CU may include fourth information in request message #2 of step 603. The fourth information is used to indicate that the source CU initiates the switching of the user plane bearer of the terminal device. In other words, the source CU only needs to notify the target CU after determining that it will initiate the switching of the user plane bearer of the terminal device, without the target CU's permission.

[0270] In some other embodiments, method 600 may further include steps 608 and 609, as detailed below.

[0271] Step 608: After receiving notification message #1, the source CU sends notification message #2 to the target CU, or in other words, the target CU receives notification message #2 from the source CU.

[0272] Among them, notification message #2 is used to indicate the target cell to which the terminal device will switch, or to indicate that the terminal device will switch to the target cell.

[0273] Illustratively, notification message #2 may include at least one of the following information: a first identifier of the target cell, beam information, or access information. The beam information indicates the beam direction used by the target cell for communication with the terminal device. The access information indicates the access method used by the terminal device to access the target cell, such as a random access-based access method or a random access-free access method.

[0274] Step 609: After receiving notification message #2, the target CU sends notification message #3 to the target DU, or in other words, the target DU receives notification message #3 from the target CU.

[0275] Among them, notification message #3 is used to indicate the target cell to which the terminal device will switch, or to indicate that the terminal device will switch to the target cell.

[0276] Exemplarily, the notification message #3 may include at least one of the following information: a first identifier of the target cell, beam information, or access information, so that the target DU uses this information to perform an access process with the terminal device.

[0277] In one possible implementation, notification message #2 in step 608 may further include seventh information, where the seventh information is used to indicate that the source CU has initiated a handover of the user plane bearer of the terminal device. For example, if the source CU and the target CU have not negotiated who will initiate a handover of the user plane bearer of the terminal device, and the source CU has already sent request message #1, notification message #2 may carry the seventh information so that the target CU does not initiate a handover of the user plane bearer of the terminal device based on the seventh information.

[0278] In some other embodiments, method 600 may further include steps 610 and 611 , as follows.

[0279] In step 610 , the source CU forwards the service data # 1 of the terminal device cached in the source CU to the target CU according to the notification message # 1 , so that the service data # 1 is sent to the terminal device by the target base station after the terminal device accesses the target cell.

[0280] Step 611: After receiving service data #1, the target CU sends service data #1 to the target DU.

[0281] In one possible implementation, the target CU may send service data #1 to the target DU after determining that the terminal device has successfully accessed the target cell. For example, the target CU may send service data #1 to the target DU after receiving notification message #4 as shown in step 612, where notification message #4 is used to indicate that the terminal device has successfully accessed the target cell. This avoids ineffective transmission of service data #1 to the target DU.

[0282] In another possible implementation, the target CU can send service data #1 to the target DU after receiving notification message #2. In this way, after the terminal device successfully accesses the target cell of the target DU of the target CU, the target DU can immediately send data to the terminal device, thereby facilitating the early transmission of data to the terminal device and avoiding data failure.

[0283] In other embodiments, method 600 may further include step 613: the source CU receives a response message #1 from the core network device, and the response message #1 is used to indicate that the switching of the user plane bearer of the terminal device is successful or to indicate that the switching of the user plane bearer of the terminal device fails.

[0284] In some other embodiments, the method 600 may further include step 614: the target CU receives a notification message #5 from the core network device, where the notification message #5 is used to indicate one of the following information:

[0285] 1) The protocol data unit (PDU) session identifier (ID) of the successfully completed user plane bearer handover, and the channel information of the uplink user plane bearer corresponding to the PDU session ID;

[0286] 2) The PDU session ID of the unsuccessful user plane bearer handover and the reason for the failure.

[0287] In other embodiments, method 600 may further include step 615: after receiving notification message #4, the target CU sends notification message #6 to the source CU, or the source CU receives notification message #6 from the target CU, and notification message #6 is used to indicate that the terminal device has successfully accessed the target cell, so that the source CU processes the configuration information and context information of the terminal device in the source cell.

[0288] It should be noted that the names and numbers of the above-mentioned messages, information, and data are merely exemplary, and this application does not limit the names and numbers of the messages and information. For example, request message #1, request message #2, response message #1, response message #2, notification message #1, notification message #2, notification message #3, notification message #4, notification message #5, and notification message #6 may also be numbered as the first request message, the second request message, the first response message, the second response message, the first notification message, the second notification message, the sixth notification message, the fourth notification message, the seventh notification message, and the fifth notification message, respectively.

[0289] The solution executed by the target CU or the modules or units in the target CU is described in detail below with reference to FIG. 7 .

[0290] FIG7 is a schematic flow chart of a handover method 700 provided in the present application. The method 700 may include at least part of the following contents.

[0291] In step 701, the source DU sends a notification message #7 to the source CU, or in other words, the source CU receives the notification message #7 from the source DU. Step 701 can refer to step 601 and will not be described in detail.

[0292] Step 702: After receiving notification message #7, the source CU sends notification message #8 to the target CU, or in other words, the target CU receives notification message #8 from the source CU.

[0293] Notification message #8 may correspond to the first notification message in method 500, and is used to indicate the target cell to which the terminal device will switch. Notification message #8 is used to indicate the target cell to which the terminal device will switch, and may also be described as follows: Notification message #1 is used to indicate that the terminal device will switch to the target cell, or the first notification message is used to notify the source CU of the initiation of the LTM command for the terminal device and the identification of the target cell.

[0294] Step 703: The target CU sends a request message #3 to the core network device according to the notification message #8.

[0295] Request message #3 may correspond to the first request message in method 500, and is used to request handover of the user plane bearer of the terminal device to the target CU. Request message #3 may be described with reference to request message #1 and will not be described in detail here.

[0296] The implementation method of the target CU sending the request message #3 to the core network device can refer to the path switching process in the existing standard and will not be described in detail.

[0297] Exemplarily, the core network device may be an AMF. After receiving request message #3, the AMF may control the UPF to switch the user plane bearer of the terminal device to the target CU.

[0298] In this way, in method 700, the target CU can initiate the switching of the user plane bearer of the terminal device based on the notification message #8 used to indicate the target cell to which the terminal device will switch, and can execute the switching process of the user plane bearer of the terminal device earlier, thereby reducing the data forwarded from the source CU to the target CU, thereby reducing invalid data and improving the service experience.

[0299] In an embodiment of the present application, the switching of the user plane bearer of the terminal device initiated by the target CU may be specified by the protocol or determined by negotiation between the source CU and the target CU.

[0300] This application does not limit the specific implementation method of the negotiation between the source CU and the target CU.

[0301] In a possible implementation, method 700 may include steps 704 and 705, as follows.

[0302] Step 704: The source CU sends a request message #4 to the target CU, or the target CU receives the request message #4 from the source CU.

[0303] Request message #4 is used to request first information, which indicates the channel information of the user plane bearer of the target CU. For a description of request message #4, refer to request message #2. For a description of the first information, refer to the description in step 602.

[0304] The source CU may carry second information in the request message #4 of step 704, where the second information is used to request the source CU to initiate switching of the user plane bearer of the terminal device, ie, path switching.

[0305] Step 705: After receiving the request message #4, the target CU sends a response message to the request message #4 to the source CU, that is, the response message #4 in FIG7 .

[0306] Response message #4 includes the sixth information. The sixth information is used to indicate that the source CU is not allowed to initiate the switching of the user plane bearer of the terminal device. In this case, the target CU subsequently initiates the switching of the user plane bearer of the terminal device.

[0307] It should be noted that Figure 7 only shows the signaling interaction related to the target DU and target CU belonging to the target cell. In fact, steps 704-705 may involve signaling interaction between the source CU and at least one candidate CU including the target CU. If there are other candidate CUs that allow the source CU to initiate user plane bearer switching of the terminal device and provide the source CU with the channel information of its user plane bearer, the source CU can determine the association relationship between the candidate cell of the candidate CU and the channel information of the user plane bearer of the candidate cell, or determine the association relationship between the candidate CU and the channel information of the user plane bearer of the candidate cell. The specific implementation method can refer to steps 603-605.

[0308] In other embodiments, if the source CU determines the association relationship between the channel information carried by the user plane of the candidate cell of other candidate CUs and the candidate cell, or determines the association relationship between the channel information carried by the user plane of other candidate CUs and the candidate cell, the source CU may send the determined association relationship to at least one candidate CU including the target CU. Based on this, when the target CU serves as the source CU for subsequent switching, it is not necessary to re-execute steps 704-705, thereby reducing signaling overhead and enabling the subsequent switching process and the corresponding path switching process to be executed faster.

[0309] In other embodiments, similar to method 600, if the source CU converts the identifier of at least one candidate cell including the target cell, such as from a first identifier to a second identifier, method 700 may further include step 706: the source CU sends the target CU a correspondence between the first identifier of the at least one candidate cell and the second identifier of the at least one candidate cell. For specific implementation, reference may be made to step 607. In this way, multiple CUs including the source CU and the target CU may use the same first identifier of the candidate cell when communicating with the terminal, thereby avoiding repeated configuration of the terminal device.

[0310] In other embodiments, the notification message #8 in step 702 may further include at least one of the following information: a first identifier of the target cell, beam information, or access information. The beam information is used to indicate the beam direction used by the target cell to communicate with the terminal device. The access information is used to indicate the access method used by the terminal device to access the target cell, such as an access method based on random access or an access method based on random access-free access. In this case, method 700 may further include step 707: after receiving notification message #8, the target CU sends notification message #9 to the target DU, or the target DU receives notification message #9 from the target CU.

[0311] Among them, notification message #9 is used to indicate the target cell to which the terminal device will switch, or to indicate that the terminal device will switch to the target cell.

[0312] Exemplarily, the notification message #9 may include at least one of the following information: a first identifier of the target cell, beam information, or access information, so that the target DU uses this information to perform an access process with the terminal device.

[0313] In other embodiments, notification message #8 in step 702 may further include fifth information, where the fifth information is used to indicate that the source CU did not initiate the handover of the user plane bearer of the terminal device. For example, if the source CU and the target CU have not negotiated who will initiate the handover of the user plane bearer of the terminal device, and the source CU did not initiate the handover of the user plane bearer of the terminal device, notification message #8 may carry the fifth information so that the target CU initiates the handover of the user plane bearer of the terminal device.

[0314] In some other embodiments, method 700 may further include steps 708 and 709, as follows.

[0315] In step 708 , the source CU forwards the service data # 2 of the terminal device cached in the source CU to the target CU according to the notification message # 7 , so that the target base station sends the service data # 2 to the terminal device after the terminal device accesses the target cell.

[0316] Step 709: After receiving service data #2, the target CU sends service data #2 to the target DU.

[0317] In one possible implementation, the target CU may send service data #2 to the target DU after determining that the terminal device has successfully accessed the target cell. For example, the target CU may send service data #2 to the target DU after receiving notification message #10 as shown in step 710, where notification message #10 indicates that the terminal device has successfully accessed the target cell. This avoids ineffective transmission of service data #2 to the target DU.

[0318] In another possible implementation, the target CU can send service data #2 to the target DU after receiving notification message #8. In this way, after the terminal device successfully accesses the target cell of the target DU of the target CU, the target DU can immediately send data to the terminal device, thereby facilitating the early transmission of data to the terminal device and preventing data failure.

[0319] In other embodiments, method 700 may further include step 711: the target CU receives a response message #3 from the core network device, and the response message #3 is used to indicate that the switching of the user plane bearer of the terminal device is successful or to indicate that the switching of the user plane bearer of the terminal device fails.

[0320] In other embodiments, method 700 may further include step 712: after receiving notification message #10, the target CU notifies the source CU of message #11, or the source CU receives notification message #11 from the target CU, and notification message #11 is used to indicate that the terminal device has successfully accessed the target cell, so that the source CU processes the configuration information and context information of the terminal device in the source cell.

[0321] It should be noted that the names and numbers of the above-mentioned messages, information, and data are merely exemplary, and this application does not limit the names and numbers of the messages and information. For example, request message #3, request message #4, response message #3, response message #4, notification message #7, notification message #8, notification message #9, notification message #10, and notification message #11 may also be numbered as the first request message, the second request message, the first response message, the second response message, the eighth notification message, the first notification message, the third notification message, the fourth notification message, and the fifth notification message, respectively.

[0322] The switching method of the present application is described below with reference to specific embodiments.

[0323] FIG8 is a schematic flowchart of a switching method 800 provided in this application.

[0324] In method 800, the source CU and the target CU may negotiate to determine whether the source CU or the target CU initiates the path switch. Request message #A in method 800 may correspond to request message #2 or request message #4 described above, response message #A may correspond to response message #2 or response message #4 described above, notification message #A may correspond to notification message #1 or notification message #7 described above, notification message #B may correspond to notification message #5 described above, notification message #C may correspond to notification message #2 or notification message #8 described above, notification message #D may correspond to notification message #3 or notification message #9 described above, and indication information #1, indication information #2, indication information #3, indication information #4, indication information #5, and indication information #6 may correspond to the second information, fourth information, third information, sixth information, seventh information, and fifth information described above, respectively.

[0325] Method 800 includes at least part of the following.

[0326] Step 801: The source CU sends a request message #A to the candidate CU, or in other words, the candidate CU receives the request message #A from the source CU.

[0327] The request message #A is used to request candidate cell configuration information.

[0328] In one possible implementation, the request message #A may include indication information #1, which is used to request the source CU to initiate a path switch. The indication information #1 here can be used to negotiate with the candidate CU whether the source CU can initiate a path switch.

[0329] In another possible implementation, the request message #A may include indication information #2, where the indication information #2 is used to indicate that the source CU initiates the path switching.

[0330] The candidate CUs here can be one or more, and are CUs that the terminal device can switch to. In one possible implementation, the candidate CU can be determined by the source CU based on measurement information from the terminal device. It should be noted that the target CU shown in Figure 8 is one of the candidate CUs. Before switching, these CUs that the terminal device can switch to are called candidate CUs. During switching, one of the candidate CUs becomes the target CU.

[0331] In step 802, each candidate CU sends a request message #B to the candidate DU under the candidate CU, or in other words, the candidate DU under the candidate CU receives the request message #B from the candidate CU.

[0332] Request message #B is used to request the "DU-side configuration information" of the candidate cell. A complete candidate cell configuration information may include a CU-generated part and a DU-generated part. "CU-side configuration information" may refer to the CU-generated part, and "DU-side configuration information" may refer to the DU-generated part.

[0333] It should be noted that the target DU shown in FIG8 is one of the candidate DUs, and during switching, one of the candidate DUs becomes the target DU.

[0334] In step 803, the candidate DU under the candidate CU sends a response message #B to the candidate CU, or in other words, the candidate CU receives a response message #B from the candidate DU under the candidate CU.

[0335] Among them, the response message #B includes the "DU side configuration information" of the candidate cell.

[0336] Step 804: The candidate CU sends a response message #A to the source CU, or the source CU receives a response message #A from the candidate CU.

[0337] The response message #A includes candidate cell configuration information, which includes the "CU side configuration information" and "DU side configuration information" mentioned above.

[0338] If the request message #A carries indication information #1 and the candidate CU allows path switching to be initiated by the source CU, in addition to the candidate cell configuration information, the response message #A may also include at least one of the following: the candidate cell's identity, indication information #3, or channel information for the user plane bearer of the candidate CU. This information can be used by the source CU when initiating a path switch. Indication information #3 indicates that the candidate CU allows path switching to be initiated by the source CU.

[0339] If the request message #A carries indication information #1 and the candidate CU does not allow path switching initiated by the source CU, in addition to the candidate cell configuration information, the response message #A may also include at least one of the following information: the candidate cell's identity or indication information #4. Indication information #4 indicates that the candidate CU does not allow path switching initiated by the source CU.

[0340] When the request message #A carries the indication information #2, in addition to the candidate cell configuration information, the response message #A may also include at least one of the following information: the identity of the candidate cell, or the channel information of the user plane bearer of the candidate CU.

[0341] If the request message #A carries indication #2, the source CU can subsequently initiate a path switch. If the response message #A includes indication #3, indicating that the candidate CU permits the source CU to initiate a path switch, the source CU can subsequently initiate a path switch. If the response message #A includes indication #4, indicating that the candidate CU does not permit the source CU to initiate a path switch, the candidate CU can subsequently initiate a path switch.

[0342] The candidate cell identity is information that can uniquely identify the candidate cell. For example, the candidate cell identity information may include at least one of a global cell identifier (CGI) or a physical cell ID (PCI) of the candidate cell.

[0343] The channel information carried by the user plane of the candidate CU may also be referred to as the tunnel information carried by the user plane of the candidate CU, which is used to indicate the termination point of the data sent by the UPF to the candidate CU. Exemplarily, the channel information carried by the user plane may be NG-U user plane transport network layer information (NG-U UP TNL Information), where NG-U is the interface name between the UPF and the CU, which is the interface name defined in the protocol, and NG-U refers to the next generation user plane. For example, the channel information carried by the user plane may include at least one of the following information: the IP address of the termination point, or the GTP-TEID of the termination point.

[0344] It should be noted that the user plane bearer of the candidate CU may refer to the PDU session of the candidate CU. In one possible implementation, each PDU session in the PDU session of the same candidate CU may correspond to the channel information of a user plane bearer. For example, different service types correspond to different PDU sessions, and each PDU session has its own user plane bearer channel information. In another possible implementation, the PDU session of the same candidate CU may also correspond to the same user plane bearer channel information.

[0345] It should also be noted that Figure 8 only shows the signaling interaction between the target DU and target CU selected as the target cell in the candidate cell. In fact, steps 801 to 804 may involve signaling interaction between one or more candidate CUs and one or more candidate DUs.

[0346] Step 805: Based on the response message #A of each candidate CU, the source CU may determine the association relationship between the candidate cell and the channel information of the user plane bearer of the candidate CU corresponding to the candidate cell.

[0347] Exemplarily, the source CU may determine the association between the candidate cell and the channel information carried by the user plane of the candidate CU corresponding to the candidate cell based on the identity information of the candidate cell in the response message #A, indication information #3, and the channel information carried by the user plane of the candidate CU.

[0348] For example, the source CU can determine that the path switching is initiated by the source CU based on the indication information #3 in the response message #A, and then determine the association relationship between the candidate cell and the channel information carried by the user plane of the candidate CU corresponding to the candidate cell based on the identity information of the candidate cell in the response message #A and the channel information carried by the user plane of the candidate CU.

[0349] In a possible implementation, the source CU may generate an association relationship between the identity of the candidate cell included in the response message #A and the channel information of the user plane bearer of the corresponding candidate CU.

[0350] In another possible implementation, the source CU may convert the identity of the candidate cell included in the response message #A into a new identity, and then generate an association relationship between the new identity and the channel information carried by the user plane of the candidate CU.

[0351] For example, when the identity identifier of the candidate cell included in the response message #A is CGI or PCI, the source CU can convert the CGI or PCI of the candidate cell into a shorter candidate cell ID, such as an ID with a value range of 0-7; and then generate an association relationship between the candidate cell ID and the channel information carried by the user plane of the candidate CU. In this case, the source CU can use the candidate cell ID to communicate with the terminal device and / or other network elements during subsequent communications. In this way, the signaling overhead can be reduced, and the true identity information of the candidate cell can be avoided from being exposed on the air interface, making the communication system more secure.

[0352] It should be noted that for the candidate CU that sends the response message #A including the indication information #4, since the candidate CU does not allow the source CU to initiate path switching, the candidate CU does not provide the source CU with the channel information carried by its user plane. Therefore, the source CU will not determine the association relationship between the candidate cell managed by the candidate CU and the channel information carried by the user plane of the candidate CU. In other words, after step 805, there is no association relationship between the candidate cell managed by the candidate CU and the channel information carried by the user plane of the candidate CU in the source CU.

[0353] In step 806 , the source CU sends the received candidate cell configuration information to the terminal device, or in other words, the terminal device receives the candidate cell configuration information from the source CU.

[0354] Step 807: The source DU determines to switch the terminal device to the target cell.

[0355] Between step 806 and step 807, the terminal device may perform a step of reporting measurement results of candidate cells and serving cells, which is not shown in Figure 8. The source DU may determine a target cell from the candidate cells based on the measurement results reported by the terminal device.

[0356] Step 808: The source DU sends a handover command to the terminal device, or the terminal device receives a handover command from the source DU.

[0357] The handover command includes the identity of the target cell, such as the candidate cell ID generated by the source CU in step 805. At this time, the candidate cell ID becomes the target cell ID.

[0358] Step 809: The source DU sends a notification message #A to the source CU, or the source CU receives the notification message #A from the source DU.

[0359] The notification message #A is used to indicate that the terminal device will switch to the target cell. The notification message #A includes the identity of the target cell, such as the candidate cell ID generated by the source CU in step 805. At this time, the candidate cell ID becomes the target cell ID.

[0360] Depending on the response message #A sent by the target CU, the subsequent execution steps are also different, which are described below in different situations.

[0361] Case 1: The response message #A sent by the target CU includes indication information #3, ie, the candidate CU permits the source CU to initiate path switching. In this case, steps 810 - 817 may be executed.

[0362] In step 810, the source CU sends a path switch request message to the AMF according to the notification message #A, or in other words, the AMF receives the path switch message from the source CU.

[0363] The path switch request message is used to request that the user plane bearer of the terminal device be switched to the target CU. The path switch request message may include channel information of the user plane bearer corresponding to the target cell and the identity of the terminal device. The identity of the terminal device may be a RAN UE next generation application protocol ID (RAN UE NGAP ID).

[0364] In one possible implementation method, the source CU can obtain the identity of the target cell according to the notification message #A, and further obtain the channel information carried by the user plane of the target CU based on the association relationship between the identity of the target cell and the channel information carried by the user plane of the target CU, such as the association relationship generated in step 805. Then, the channel information carried by the user plane of the target CU and the identity of the terminal device are sent to the AMF through the path switching request message.

[0365] It should be noted that this application does not limit the timing of the source CU sending the path switching request message.

[0366] One possible implementation method, as shown in Figure 8, is that the source CU can send a path switching request message immediately after receiving the notification message #A, or the path switching initiated by the source CU can be triggered by the notification message #A, or the source CU sends a path switching request message in response to the notification message #A.

[0367] In another possible implementation, the source CU may initiate a path switch after the terminal device successfully accesses the target DU, or after the terminal device successfully switches to the target cell of the target DU.

[0368] Step 811: After receiving the path switching request message, AMF and UPF perform path switching.

[0369] The implementation method of path switching between AMF and UPF can refer to the existing protocol and will not be described in detail here.

[0370] Optionally, the method 800 may further include step 812, where the AMF sends a path switch request response message to the source CU in response to the path switch request message in step 810. The path switch request response message is used to indicate whether the path switch is successfully completed.

[0371] Optionally, the method 800 may further include step 813, where the AMF sends a notification message #B to the target CU, or the target CU receives the notification message #B from the AMF. The notification message #B may include one of the following information:

[0372] 1) The PDU session ID for which path switching has been successfully completed, and the channel information of the uplink user plane bearer corresponding to the PDU session ID;

[0373] 2) The PDU session ID of the unsuccessful path switching and the reason for the failure.

[0374] Step 814: After the path is switched, the UPF can send the downlink data of the terminal device to the target CU instead of the source CU.

[0375] In step 815, the source CU may also send a notification message #C to the target CU based on the notification message #A, or in other words, the target CU receives the notification message #C from the source CU.

[0376] Notification message #C includes at least one of the following information: the target cell's identity, beam information, or access information. The beam information indicates the beam direction used by the target cell for communication with the terminal device. The access information indicates the access method used by the terminal device to access the target cell. The access method used by the terminal device to access the target cell is either random access or random access-free.

[0377] Optionally, if the source CU and the target CU have not negotiated in steps 801 and 804 who initiates the path switch, and the source CU has sent a path switch request message, the notification message #C also includes indication information #5, where the indication information #5 is used to indicate that the source CU has initiated the path switch, the source CU has executed the path switch, or the source CU has executed the step of sending the path switch request message, so that the target CU determines that it is not necessary to initiate the path switch.

[0378] Step 816: After receiving the notification message #C, the target CU sends a notification message #D to the target DU, or the target DU receives the notification message #D from the target CU.

[0379] Notification message #D includes at least one of the following information: the target cell's identity, beam information, or access information. For a description of beam information and access information, refer to step 815. The target DU can then complete the random access process with the terminal device based on the information in notification message #D.

[0380] In a possible implementation, the target CU determines not to perform path switching based on the negotiation results of steps 801 and 804 .

[0381] In another possible implementation, if the notification message #C includes indication information #5, the target CU may not perform path switching according to the indication information #5 in the notification message #C.

[0382] Step 817: After receiving the notification message #A, the source CU may also send the data of the terminal device to the target CU, or in other words, the target CU may receive the data from the source CU. That is, the source CU may forward the data to the target CU.

[0383] For example, for downlink data for a terminal device, the source CU may send downlink data that has not yet been sent to the terminal device and / or data that has not yet been successfully sent to the terminal device to the target CU. The data that has not yet been successfully sent to the terminal device may include data that has been sent to the terminal device but for which feedback of successful reception by the terminal device has not yet been received.

[0384] Exemplarily, for uplink data for a terminal device, the source CU forwards the uplink data from the terminal device to the target CU.

[0385] Case 2: The response message #A sent by the target CU includes indication information #4, ie, the candidate does not allow the source CU to initiate path switching. In this case, steps 818-824 may be executed.

[0386] In step 818, after receiving the notification message #A, the source CU may send the data of the terminal device to the target CU, or in other words, the target CU receives the data from the source CU. For detailed description, please refer to step 817.

[0387] In step 819, the source CU may also send a notification message #C to the target CU based on the notification message #A, or in other words, the target CU receives the notification message #C from the source CU.

[0388] Notification message #C includes at least one of the following information: the target cell's identity, beam information, or access information. The beam information indicates the beam direction used by the target cell for communication with the terminal device. The access information indicates the access method used by the terminal device to access the target cell. The access method used by the terminal device to access the target cell is either random access or random access-free.

[0389] Optionally, if the source CU and the target CU do not negotiate who initiates the path switch in steps 801 and 804, and the source CU does not initiate the path switch, the notification message #C also includes indication information #6, where the indication information #6 is used to indicate that the source CU does not initiate the path switch, the source CU does not perform the path switch, the source CU does not perform the step of sending the path switch request message, or the path switch is initiated by the target CU.

[0390] Step 820: After receiving the notification message #C, the target CU sends a path switching request message to the AMF according to the identity of the target cell in the notification message #C, or in other words, the AMF receives the path switching message from the target CU.

[0391] For a description of the path switch request message, reference may be made to step 810 .

[0392] In one possible implementation, the target CU determines to perform the path switching by itself based on the negotiation results of steps 801 and 804, and then sends a path switching request message to the AMF after receiving the notification message #C.

[0393] Another possible implementation method is that if the notification message #C includes indication information #6, the target CU can determine to perform path switching based on the indication information #6, thereby sending a path switching request message to the AMF.

[0394] It should be noted that this application does not limit the timing of the target CU sending the path switching request message.

[0395] One possible implementation method, as shown in Figure 8, is that the target CU can send a path switching request message immediately after receiving the notification message #C, or in other words, the path switching initiated by the target CU can be triggered by the notification message #C, or in response to the notification message #C, the target CU sends a path switching request message.

[0396] In another possible implementation, the target CU may initiate a path switch after the terminal device successfully accesses the target DU, or after the terminal device successfully switches to the target cell of the target DU.

[0397] Step 821: After receiving the path switching request message, AMF and UPF perform path switching.

[0398] The implementation method of path switching between AMF and UPF can refer to the existing protocol and will not be described in detail here.

[0399] Optionally, the method 800 may further include step 822, where the AMF sends a path switch request response message to the target CU in response to the path switch request message in step 820. The path switch request response message is used to indicate whether the path switch is successfully completed.

[0400] Step 823: After the path is switched, the UPF can send the downlink data of the terminal device to the target CU instead of the source CU.

[0401] Step 824: After receiving the notification message #C, the target CU may also send a notification message #D to the target DU, or the target DU may receive the notification message #D from the target CU.

[0402] Notification message #D includes at least one of the following information: the target cell's identity, beam information, or access information. For a description of beam information and access information, refer to step 815. The target DU can then complete the random access process with the terminal device based on the information in notification message #D.

[0403] It should be noted that if the request message #A in step 801 carries indication information #2, then after step 809, steps 810-817 can be continued to be executed.

[0404] Optionally, the method 800 may include step 825 , ie, the target CU sends data to the target DU in advance.

[0405] The "in advance" here means that the terminal device may not have accessed the target cell of the target DU of the target CU at this time, but the target CU sends the data of the terminal device from the source CU or UPF to the target DU in advance. For example, after receiving the second notification message #C, the target CU can perform early data transmission.

[0406] In this way, after the terminal device successfully accesses the target cell of the target DU of the target CU, the target DU can immediately send data to the terminal device, which is conducive to sending the data to the terminal device as soon as possible and avoiding data failure.

[0407] It should be noted that in any of the above cases 1, 2, or the case where the request message #A carries indication information #2, method 800 may include step 825 without limitation.

[0408] Step 826: The terminal device and the target DU perform the target cell access process.

[0409] In a possible implementation, the specific implementation of step 826 may refer to existing standards and will not be described in detail.

[0410] In another possible implementation, the terminal device switches to the target cell using an access method based on random access-free. The target cell may be configured with multiple carriers, for example, two carriers, NUL and SUL. As to which carrier of the NUL and SUL of the target cell the terminal device switches to using the random access-free method, the terminal device and the target access network device (target CU and / or target DU) need to have a consistent understanding to ensure that the cell switching can be successful. Several possible solutions are provided below:

[0411] Solution 1: In the candidate cell configuration information provided in steps 804 and 806, a candidate cell only provides a SUL configuration or only provides a NUL configuration. When the terminal device receives the handover command in step 808, it determines whether to use the SUL or NUL configuration for access / handover to the target cell based on the SUL or NUL configuration provided by the target cell.

[0412] Solution 2: In the candidate cell configuration information provided in steps 804 and 806, one candidate cell provides both SUL and NUL configurations, and includes an additional field indicating whether SUL or NUL should be used. Upon receiving the handover command in step 808, the terminal device determines whether to use SUL or NUL for access / handover to the target cell based on the field indicating whether SUL or NUL should be used in the target cell.

[0413] Solution 3: In the configuration information of the candidate cells provided in steps 804 and 806, a candidate cell provides SUL configuration and NUL configuration, and notifies the source access network device (e.g., source CU and / or source DU) of the provision of SUL and NUL configurations. The source access network device determines the uplink carrier that the target cell should use during a certain handover. Exemplarily, the source access network device determines to select a certain uplink carrier based on the channel measurement result fed back by the terminal device, and notifies the terminal device of the determination result through the handover command of step 808. The terminal device selects SUL or NUL to access / handover to the target cell based on the carrier information indicated in the handover command (e.g., MAC CE). Further optionally, the source access network device may notify the target access network device (e.g., target CU and / or target DU) of the selected carrier information through steps 809, 815, and 824.

[0414] Solution 4: In the candidate cell configuration information provided in steps 804 and 806, a candidate cell provides SUL and NUL configurations. Before sending the handover command in step 808, the source access network device (e.g., source CU and / or source DU) interacts with the target access network device (e.g., target CU and / or target DU). This interaction process is not shown in the figure. For example, a request message is sent and a response message is received. In the response message, the target access network device informs the source access network device which uplink carrier of the target cell should be selected. The source access network device notifies the terminal device of the handover command in step 808. The terminal device selects SUL or NUL based on the carrier information indicated in the handover command (e.g., MAC CE) to access / handover to the target cell.

[0415] Solution 5: In the configuration information of the candidate cells provided in steps 804 and 806, a candidate cell provides a SUL configuration and a NUL configuration. After receiving the handover command in step 808, the terminal device selects the uplink carrier of the target cell based on the channel quality of the target cell. For example, when the reference signal received power (RSRP) of the downlink reference signal of the target cell is less than a configured threshold value, the terminal device selects the SUL access of the target cell; otherwise, it selects the NUL access of the target cell. It should be understood that in this solution, the target access network device (e.g., the target CU and / or target DU) will attempt to receive the uplink signal sent by the terminal device on both the SUL and NUL (e.g., the target access network device receives uplink messages on the pre-configured uplink granted resources of the SUL and NUL), or attempt to send downlink signals to the terminal device on both the SUL and NUL (e.g., the target access network device sends scheduling information to the terminal device on both the SUL and NUL).

[0416] It should be noted that the random access scheme in step 826 can be implemented in combination with the switching method of the embodiment of the present application, or can be implemented independently as a separate embodiment.

[0417] Step 827: After the terminal device successfully accesses the target cell of the target DU of the target CU, the target DU sends a handover success indication to the target CU to notify the target CU that the terminal device has successfully switched to the target cell.

[0418] Step 828: After receiving the switching success indication, the target CU sends the data from the terminal device of the source CU or UPF to the target DU.

[0419] Steps 825 and 828 are two different implementations of the target CU sending data from the source CU or UPF to the target DU. The two differ in the timing of data transmission. Step 825 is executed after receiving the notification message #C, while step 828 is executed after receiving the handover success indication. Either one can be executed.

[0420] Step 829: The target DU sends the received data to the terminal device.

[0421] Optionally, method 800 may include step 830, that is, the target CU sends a notification message #E to the source CU, which is used to notify the source CU that the terminal device has successfully accessed the target cell, so that the source CU processes the configuration information and context information of the terminal device in the source cell.

[0422] In one possible implementation, the source CU may retain the configuration information and context information of the terminal device in the source cell so that the terminal device can continue to use the information after switching back.

[0423] Another possible implementation method is that after receiving the notification message #E, the source CU releases the configuration information and context information of the terminal device in the source cell.

[0424] Optionally, method 800 may include step 831, that is, the source CU sends a notification message #F to the candidate CU, or the candidate CU receives a notification message #F from the source CU, wherein the notification message #F includes the association relationship between the candidate cell determined in step 805 and the channel information carried by the user plane of the candidate CU corresponding to the candidate cell. Once the target CU learns of the association relationship, it can send a path switching request message to the AMF based on the association relationship when it subsequently acts as the source CU to instruct the terminal device to switch the cell. Based on this, the target CU that is switched for the first time does not need to re-execute steps 801 to 804 to obtain the association relationship between the candidate cell identity and the channel information carried by the user plane of the corresponding candidate CU when it acts as the source CU for subsequent switching, thereby reducing the signaling overhead and enabling the subsequent switching process and the corresponding path switching process to be executed faster.

[0425] This application does not limit the timing of executing step 831.

[0426] In one possible implementation, as shown in FIG8 , the source CU may execute after step 830 , that is, the source CU sends a notification message #F to the candidate CU after learning that the terminal device has successfully accessed the target cell.

[0427] In another possible implementation, the source CU may execute after step 805 without waiting until the terminal device successfully accesses the target cell. For example, CU#1 is the source CU, CU#2 and CU#3 are candidate CUs, and after executing steps 801 to 805, CU#1 has obtained the association relationship between the candidate cell identities of CU#2 and CU#3 and the channel information carried by the user plane of CU#2, as well as the association relationship between the candidate cell identity of CU#3 and the channel information carried by the user plane of CU#3. After step 805, CU#1 may send the obtained association relationship to CU#2 and CU#3, so that after the terminal device switches to CU#2 or CU#3, CU#2 or CU#3 can continue to initiate a path switching request to the AMF.

[0428] It should be noted that if the association relationship in step 805 is an association relationship between the new identifier obtained by converting the identity identifier of the candidate cell carried in the response message #A and the channel information carried by the user plane of the candidate CU, then method 800 also includes the source CU sending the correspondence between the new identifier and the identity identifier of the candidate cell before the conversion to the candidate CU.

[0429] This application does not limit the implementation method of sending the correspondence between the new identifier and the identity identifier of the candidate cell before the conversion.

[0430] One possible implementation method is that the correspondence between the new identifier and the identity identifier of the candidate cell before the conversion is carried in the notification message #E, that is, the correspondence between the new identifier and the identity identifier of the candidate cell before the conversion can be sent to the candidate CU together with the association relationship between the new identifier and the channel information carried by the user plane of the candidate CU.

[0431] Another possible implementation method is that if the source CU knows the cells managed by the candidate CU, the source CU can convert the candidate cell identity in advance and carry the correspondence between the new identity and the identity of the candidate cell before the conversion in the request message #A of step 801.

[0432] It should be noted that the embodiments of the present application do not limit the order of steps 808 and 809, nor do they limit the order of steps 810, 815, and 817, nor do they limit the order of steps 818 and 819.

[0433] FIG9 is a schematic flowchart of a switching method 900 provided in this application.

[0434] Unlike method 800, the path switching is initiated by the source CU and does not require a negotiation process between the source CU and the target CU. Specifically, steps 901-904 can refer to steps 801-804, except that the request message #A does not need to carry indication information #1 or indication information #2, and the response message #A does not need to carry indication information #3 or indication information #4. Steps 905-917 can refer to steps 805-818, except that the notification message #C does not need to carry indication information #5 or indication information #6. Steps 918-924 are the same as steps 825-831 and can refer to steps 825-831.

[0435] FIG10 is a schematic flowchart of a switching method 1000 provided in this application.

[0436] Unlike method 800, the path switching is initiated by the target CU and does not require a negotiation process between the source CU and the target CU. Specifically, steps 1001-1004 can refer to steps 801-804, except that the request message #A does not need to carry indication information #1 or indication information #2, the response message #A does not need to carry indication information #3 or indication information #4, and the response message #A does not need to carry the channel information carried by the user plane of the candidate CU. Steps 1005-1008 are the same as steps 806-809 and can refer to steps 806-809. Steps 1009-1021 can refer to steps 818-830, except that the notification message #C does not need to carry indication information #5 or indication information #6.

[0437] The above describes in detail the method embodiment provided by the present application in conjunction with Figures 5 to 10 , and the following will describe the device embodiment of the present application in conjunction with Figures 11 to 12 .

[0438] It is understood that, in order to implement the functions in the above embodiments, the apparatus in FIG. 11 or FIG. 12 includes hardware structures and / or software modules corresponding to the functions. Those skilled in the art should readily appreciate that, in conjunction with the various exemplary units and method steps described in the embodiments disclosed herein, the present application can be implemented in the form of hardware or a combination of hardware and computer software.

[0439] Figures 11 and 12 are schematic diagrams of possible apparatuses provided in embodiments of the present application. These apparatuses can be used to implement the functions of the source CU, target CU, source access network device, target access network device, or terminal device in the above method embodiments, thereby also achieving the beneficial effects of the above method embodiments.

[0440] As shown in FIG11 , the apparatus 10 includes a transceiver unit 11 and a processing unit 12 . The transceiver unit 11 is used to execute the transceiver steps of the apparatus 10 . The transceiver unit 12 is used to execute the processing steps of the apparatus 10 .

[0441] Exemplarily, when the apparatus 10 is used to implement the function of the source CU in FIG6 , the transceiver unit 11 is used to perform the transceiver steps of the source CU, such as steps 601-604, 606-608, 610, 613, and 615, and the processing unit 12 is used to perform the processing steps of the source CU, such as step 605. When the apparatus 10 is used to implement the function of the target CU in FIG6 , the transceiver unit 11 is used to perform the transceiver steps of the target CU, such as steps 603, 604, 606-612, and 614-615.

[0442] Exemplarily, when the apparatus 10 is used to implement the function of the source CU in FIG7 , the transceiver unit 11 is used to perform the transceiver steps of the source CU, such as steps 701-702, 704-706, 708, and 712. When the apparatus 10 is used to implement the function of the target CU in FIG7 , the transceiver unit 11 is used to perform the transceiver steps of the target CU, such as steps 702-712.

[0443] Exemplarily, when the device 10 is used to implement the function of the source access network device, target access network device or terminal device in step 826 in Figure 8, the transceiver unit 11 is used to execute the transceiver steps of the source access network device, target access network device or terminal device, and the processing unit 12 is used to execute the processing steps of the source access network device, target access network device or terminal device.

[0444] For a more detailed description of the transceiver unit 11 and the processing unit 12 , please refer to the relevant description in the above method embodiment, which will not be described again here.

[0445] As shown in FIG12 , the apparatus 20 includes a processor 21. The processor 21 is coupled to a memory 23, which is used to store instructions. When the apparatus 20 is used to implement the method described above, the processor 21 is used to execute the instructions in the memory 23 to implement the functions of the processing unit 12 described above.

[0446] Optionally, the device 20 further includes a memory 23 .

[0447] Optionally, the apparatus 20 further includes an interface circuit 22. The processor 21 and the interface circuit 22 are coupled to each other. It will be appreciated that the interface circuit 22 may be a transceiver or an input / output interface. When the apparatus 20 is used to implement the method described above, the processor 21 is configured to execute instructions to implement the functions of the processing unit 12, and the interface circuit 22 is configured to implement the functions of the transceiver unit 11.

[0448] Exemplarily, when the device 20 is a chip applied to a source CU, a target CU, a source access network device, a target access network device, or a terminal device, the chip implements the functions of the source CU, the target CU, the source access network device, the target access network device, or the terminal device in the above-mentioned method embodiment. The chip receives information from other modules (such as a radio frequency module or antenna) in the source CU, the target CU, the source access network device, the target access network device, or the terminal device, and the information is sent by other devices to the source CU, the target CU, the source access network device, the target access network device, or the terminal device; or, the chip sends information to other modules (such as a radio frequency module or antenna) in the source CU, the target CU, the source access network device, the target access network device, or the terminal device, and the information is sent by the source CU, the target CU, the source access network device, the target access network device, or the terminal device to other devices.

[0449] The present application also provides a communication device, comprising a processor coupled to a memory, the memory being configured to store computer programs or instructions and / or data, the processor being configured to execute the computer programs or instructions stored in the memory, or to read data stored in the memory, to perform the methods described in the above method embodiments. Optionally, there are one or more processors. Optionally, the communication device includes a memory. Optionally, there are one or more memories. Optionally, the memory is integrated with the processor or provided separately.

[0450] The present application also provides a chip, including a processor, which is coupled to a memory, the memory is used to store computer programs or instructions, and the processor is used to execute the computer programs or instructions stored in the memory to implement the methods performed by the source CU, target CU, source access network device, target access network device or terminal device in the above-mentioned method embodiments.

[0451] The present application also provides a computer-readable storage medium storing computer instructions for implementing the methods executed by the source CU, target CU, source access network device, target access network device or terminal device in the above-mentioned method embodiments.

[0452] The present application also provides a computer program product comprising instructions, which, when executed by a computer, implement the methods performed by the source CU, target CU, source access network device, target access network device or terminal device in the above-mentioned method embodiments.

[0453] The present application also provides a communication system, which includes at least one of the source CU, target CU, source access network device, target access network device or terminal device in the above embodiments.

[0454] The explanation of the relevant contents and beneficial effects of any of the above-mentioned devices can be referred to the corresponding method embodiments provided above, which will not be repeated here.

[0455] It is understood that the processor in the embodiments of the present application may be a central processing unit (CPU), or may be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0456] The method steps in the embodiments of the present application can be implemented by hardware or by a processor executing software instructions. The software instructions can be composed of corresponding software modules, and the software modules 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, mobile hard disks, compact disc read-only memory (CD-ROM) or any other form of storage medium well known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be an integral part of the processor. The processor and the storage medium can be located in an ASIC. In addition, the ASIC can be located in a source CU, a target CU, a source access network device, a target access network device or a terminal device. Of course, the processor and the storage medium can also exist as discrete components in the source CU, the target CU, the source access network device, the target access network device or the terminal device.

[0457] In the above embodiments, all or part of the embodiments may be implemented using software, hardware, firmware, or any combination thereof. When implemented using software, all or part of the embodiments may be implemented in the form of a computer program product. The computer program product includes one or more computer programs or instructions. When the computer program or instructions are loaded and executed on a computer, the processes or functions described in the embodiments of the present application are performed in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, a network device, a user device, or other programmable device. The computer program or instructions may 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 may 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 may be any available medium that can be accessed by a computer or a data storage device such as a server or data center that integrates one or more available media. The available medium may be a magnetic medium, such as a floppy disk, hard disk, or magnetic tape; an optical medium, such as a digital video disk; or a semiconductor medium, such as a solid-state drive.

[0458] In the various embodiments of the present application, unless otherwise specified or there is a logical conflict, the terms and / or descriptions between different embodiments are consistent and can be referenced by each other. The technical features in different embodiments can be combined to form new embodiments according to their inherent logical relationships.

[0459] Unless otherwise indicated, all technical and scientific terms used in the embodiments of the present application have the same meaning as those generally understood by those skilled in the art of the technical field of the application. The terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit the scope of this application. It should be understood that the above are for illustration, and the examples above are only for helping those skilled in the art to understand the embodiments of the present application, rather than limiting the application embodiments to the specific numerical values ​​or specific scenarios illustrated. Those skilled in the art can obviously carry out various equivalent modifications or changes based on the examples given above, and such modifications and changes also fall within the scope of the embodiments of the present application.

[0460] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A switching method, It is characterized in that The method comprises: Receive a first notification message, where the first notification message is used to indicate a target cell to which the terminal device will switch, where the target cell is a cell of a target distributed unit DU under a target centralized unit CU; According to the first notification message, a first request message is sent to the core network device, where the first request message is used to request that the user plane bearer of the terminal device be switched to the target CU.

2. The method according to claim 1, It is characterized in that The receiving the first notification message includes: receiving the first notification message from a source DU.

3. The method according to claim 2, It is characterized in that The first notification message includes a first identifier of the target cell; According to the first notification message, a first request message is sent to the core network device, including: according to the first identifier and a first association relationship, the first request message is sent to the core network device, the first association relationship is used to indicate the association relationship between the first identifier and the first information, the first information is used to indicate the channel information carried by the user plane of the target CU, and the first request message includes the first information.

4. The method according to claim 3, It is characterized in that Before receiving the first notification message from the source DU, the method further includes: Sending a second request message to the target CU, where the second request message is used to request the first information; receiving a second response message from the target CU, where the second response message includes a second identifier of the target cell and the first information; The first association relationship is determined according to the second identifier and the first information.

5. The method according to claim 4, It is characterized in that The second request message further includes second information, where the second information is used to request the source CU to initiate a path switch; The second response message also includes third information, where the third information is used to indicate that the source CU is allowed to initiate a path switch.

6. The method according to claim 4, It is characterized in that The second request message also includes fourth information, where the fourth information is used to indicate that the path switching is initiated by the source CU.

7. The method according to any one of claims 3 to 6, It is characterized in that The method further comprises: At least one association relationship is sent to a candidate CU, where the candidate CU includes the target CU, and the at least one association relationship includes the first association relationship.

8. The method according to any one of claims 3 to 7, It is characterized in that The first information includes at least one of the following information: an Internet Protocol IP address of a downlink termination point of the user plane bearer of the target CU, or a General Packet Radio System Tunneling Protocol-Tunnel Endpoint Identifier GTP-TEID of a downlink termination point of the user plane bearer of the target CU.

9. The method according to any one of claims 2 to 8, It is characterized in that The method further comprises: According to the first notification message, the service data of the terminal device is forwarded to the target CU.

10. The method according to any one of claims 2 to 9, It is characterized in that The method further comprises: A second notification message is sent to the target CU, where the second notification message is used to indicate the target cell to which the terminal device will switch.

11. The method according to claim 10, It is characterized in that The second notification message includes at least one of the following information: a first identifier of the target cell, beam information, or access information, wherein the beam information is used to indicate the beam direction used by the target cell to communicate with the terminal device, and the access information is used to indicate the access method used by the terminal device to access the target cell.

12. The method according to any one of claims 1 to 11, It is characterized in that The method further comprises: A correspondence between a first identifier of the target cell and a second identifier of the target cell is sent to the target CU, where the first identifier is an identifier of the target cell on an air interface, and the second identifier is an identifier of the target cell on a network side.

13. The method according to any one of claims 1 to 12, It is characterized in that The method is applied to a source CU or a module or a unit in a source CU.

14. The method according to claim 1, It is characterized in that The receiving the first notification message includes: receiving the first notification message from a source CU.

15. The method according to claim 14, It is characterized in that The first notification message includes fifth information, where the fifth information is used to indicate that the source CU does not initiate a path switch.

16. The method according to claim 14, It is characterized in that Before receiving the first notification message from the source CU, the method further includes: receiving a second request message from the source CU, where the second request message is used to request first information, where the first information is used to indicate channel information carried by a user plane of the target CU, and the second request message further includes second information, where the second information is used to request that the source CU initiate a path switch; A second response message is sent to the source CU, where the second response message includes sixth information, and the sixth information is used to indicate that the path switching initiated by the source CU is not allowed.

17. The method according to claim 16, It is characterized in that The first information includes at least one of the following information: an Internet Protocol IP address of a downlink termination point of the user plane bearer corresponding to the target CU, or a General Packet Radio System Tunneling Protocol-Tunnel Endpoint Identifier GTP-TEID of a downlink termination point of the user plane bearer corresponding to the target CU.

18. The method according to any one of claims 14 to 17, It is characterized in that The first notification message includes at least one of the following information: a first identifier of the target cell, beam information, or access information, wherein the beam information is used to indicate the beam direction used by the target cell to communicate with the terminal device, and the access information is used to indicate the access method used by the terminal device to access the target cell.

19. The method according to claim 18, It is characterized in that The method further comprises: According to the first notification message, a third notification message is sent to the target DU, and the third notification message includes at least one of the following information: the first identifier, the beam information, or the access information.

20. The method according to any one of claims 15 to 19, It is characterized in that The method further comprises: Receive at least one association relationship from the source CU, where the association relationship is used to indicate an association relationship between an identifier of a candidate cell and channel information carried by a user plane of a candidate CU corresponding to the candidate cell.

21. The method according to any one of claims 14 to 20, It is characterized in that The method further comprises: Receiving service data of the terminal device from the source CU; Sending the service data to the target DU; After sending the service data to the target DU, a fourth notification message is received from the target DU, where the fourth notification message is used to indicate that the terminal device has successfully accessed the target cell.

22. The method according to any one of claims 14 to 21, It is characterized in that The method further comprises: Receive a correspondence between a first identifier of the target cell and a second identifier of the target cell from the source CU, where the first identifier is an identifier of the target cell on an air interface, and the second identifier is an identifier of the target cell on a network side.

23. The method according to any one of claims 14 to 22, It is characterized in that The method is applied to a target CU or a module or a unit in the target CU.

24. A communication device, It is characterized in that The method comprises a module or a unit for executing the method as claimed in any one of claims 1 to 23.

25. A communication device, It is characterized in that It includes a processor and an interface circuit, wherein the interface circuit is used to receive signals from other communication devices outside the communication device and transmit them to the processor or send signals from the processor to other communication devices outside the communication device, and the processor is used to implement the method as described in any one of claims 1 to 23 through a logic circuit or executing code instructions.

26. A chip, It is characterized in that The invention comprises a processor, wherein the processor is coupled to a memory, the memory is used to store a computer program, and the processor is used to execute the computer program stored in the memory to implement the method according to any one of claims 1 to 23.

27. A computer-readable storage medium, It is characterized in that The storage medium stores a computer program or an instruction, and when the computer program or the instruction is executed by the communication device, the method according to any one of claims 1 to 23 is implemented.

28. A computer program product, It is characterized in that The invention comprises a computer program which, when being executed, implements the method according to any one of claims 1 to 23.

29. A communication system, It is characterized in that include: A source CU for executing the method according to any one of claims 1 to 13, and a source DU interacting with the source CU; or, A target CU for executing the method according to any one of claims 1, 14 to 23, and a source DU interacting with the target CU.

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