Method and apparatus for data transmission

Abstract

The application provides a method and device for data transmission. The method can include: configuring a terminal device with a condition-based candidate primary secondary cell (PSCell) addition or change; and performing early data transmission by a master network device to a network device to which the candidate PSCell belongs, such as sending a data packet to the network device to which the candidate PSCell belongs before the terminal device accesses the candidate PSCell, the data packet being in the form of a protocol data unit of a packet data convergence protocol; and the data packet including a master node (MN)-terminated secondary cell group bearer and / or an MN-terminated split bearer. In this way, after the terminal device accesses the candidate network device, the candidate network device can send the terminal device the transferred data, thereby reducing the latency of data transmission. Furthermore, the application can support early data transfer of the MN-terminated secondary cell group bearer and / or the MN-terminated split bearer, thereby reducing the transmission latency of data in these bearers.

Description

Technical Field

[0001] This application relates to the field of communication technology, and more specifically, to a method and apparatus for data transmission. Background Technology

[0002] In conditional primary secondary cell group cell (PSCell) addition / change (CPAC), a terminal device can directly access a candidate PSCell that meets the corresponding conditions when one or more candidate PSCells meet the conditions, thereby reducing the latency required to add or change a PSCell.

[0003] However, after the terminal device connects to the candidate PSCell, it needs to wait for the device before the handover to send data packets to the candidate PSCell before it can send data to the terminal device, which increases the transmission latency of these data packets. Summary of the Invention

[0004] This application provides a method and apparatus for data transmission, which aims to reduce data transmission latency.

[0005] Firstly, a method for data transmission is provided. This method can be executed by a network device, or by a chip or circuit used in a network device. This application does not limit the method in this regard. For ease of description, the following description will take execution by a network device as an example.

[0006] The method may include: configuring condition-based candidate primary and secondary cells (PSCells) for the terminal device to add or change; performing early data transmission to the network device to which the candidate PSCell belongs, wherein early data transmission refers to sending one or more data packets to the network device to which the candidate PSCell belongs before the terminal device accesses the candidate PSCell, the data packets being in the form of Protocol Data Units (PDUs) of the Packet Data Convergence Layer Protocol; the one or more data packets include: data packets on the secondary cell group bearer terminated by the primary base station (MN) configured for the terminal device, and / or data packets on the split bearer terminated by the MN configured for the terminal device.

[0007] The above method can be executed by the main network device (such as the master node (MN) (or main base station)), or by the chip or circuit used in the main network device.

[0008] Regarding the secondary cell group bearer (SCG bearer) or the split bearer that terminates MN, early data transmission can also be referred to as early data transfer, or other names, and its naming does not limit the scope of protection of the embodiments of this application.

[0009] Based on the above technical solution, early data transfer can be performed between the primary network device and the candidate network device (such as the candidate secondary node (SN)). In this way, after the terminal device accesses the candidate network device, the candidate network device can send the transferred data to the terminal device, thereby reducing the latency of data transmission.

[0010] Furthermore, for secondary cell group bearers terminated by the MN and / or split bearers terminated by the MN, the MN can also perform early data transmission to candidate network devices, such as through early data transfer in the form of protocol data units (PDUs) of the Packet Data Convergence Protocol (PDCP). Therefore, the embodiments of this application can support early data transfer of data packets for secondary cell group bearers terminated by the MN and / or split bearers terminated by the MN, which can reduce the transmission latency of data in these bearers.

[0011] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes: sending a first indication message to the network device to which the candidate PSCell belongs, the first indication message being used to indicate early data transmission of the secondary cell group bearer for MN termination and / or the split bearer for MN termination.

[0012] One possible approach is that the first indication information can be sent via the control plane interface between the primary network device and the candidate network device (such as MN and candidate SN), or via the user plane interface between the primary network device and the candidate network device.

[0013] In conjunction with the first aspect, in some implementations of the first aspect, the method further includes: sending a second indication message to the network device to which the candidate PSCell belongs, the second indication message being used to indicate that some or all of the data packets in one or more data packets should be discarded or ignored.

[0014] Based on the above technical solution, the master network device can send a second indication message to the candidate network device, instructing it to discard or ignore some or all data packets from earlier data transmissions. This avoids retaining or repeatedly sending data packets that the candidate network device has already successfully received to the terminal device, thus reducing resource waste.

[0015] In conjunction with the first aspect, in some implementations of the first aspect, the second indication information includes information on one or more sequence numbers, which are used to indicate the discarding or ignoring of some or all of the data packets in one or more data packets.

[0016] One possible approach is that the second indication information can be a sequence number, denoted as sequence number #A. For example, sequence number #A can be used to instruct candidate network devices to discard or ignore packets in previously transferred packets (such as PDCPPDUs) whose corresponding sequence numbers are lower than #A. In other words, if the master network device wants to instruct the discarding or ignoring of packets with sequence numbers lower than #A, then the master network device can indicate sequence number #A to the candidate network device.

[0017] Another possible approach is that the second indication information can be multiple sequence numbers, such as a sequence number list. For example, this sequence number list can instruct candidate network devices to discard or ignore those packets corresponding to sequence numbers in the sequence number list of previously transferred packets (such as PDCP PDUs). In other words, the master network device can indicate the sequence numbers corresponding to the packets to be discarded or ignored.

[0018] In conjunction with the first aspect, in some implementations of the first aspect, the sequence number is either the packet data aggregation protocol sequence number or the new air interface user plane sequence number.

[0019] In conjunction with the first aspect, in some implementations of the first aspect, sending a second instruction message to the network device to which the candidate PSCell belongs includes: sending a second instruction message to the network device to which the candidate PSCell belongs when preset conditions are met.

[0020] The preset conditions can be time-related limitations (such as periodic sending), data volume limitations (such as comparison of data volume with threshold value or threshold range), or other limitations.

[0021] Secondly, a method for data transmission is provided. This method can be executed by a network device, or by a chip or circuit used in a network device. This application does not limit the method in this regard. For ease of description, the following description will take execution by a network device as an example.

[0022] The method may include: before the terminal device accesses the network, receiving one or more data packets from the primary base station MN, the data packets being in the form of Protocol Data Units (PDUs) of the Packet Data Convergence Layer Protocol, the one or more data packets including: data packets on a secondary cell group bearer terminated by the MN configured for the terminal device, and / or data packets on a split bearer terminated by the MN configured for the terminal device; after the terminal device accesses the network, sending some or all of the data packets from the one or more data packets to the terminal device; wherein the terminal device is configured to add or change candidate primary and secondary cells (PSCells) based on conditions.

[0023] The above method can be performed by a candidate network device (such as a candidate SN), or by a chip or circuit used in a candidate network device.

[0024] Based on the above technical solution, early data transfer can be performed between the main network device and the candidate network device. After the terminal device connects to the candidate network device, the candidate network device can send the transferred data to the terminal device, thereby reducing the latency of data transmission.

[0025] Furthermore, for secondary cell group bearers terminated by the MN and / or split bearers terminated by the MN, the MN can also perform early data transmission to candidate network devices, such as early data transfer via PDCP PDUs. Therefore, the embodiments of this application can support early data transfer of data packets for secondary cell group bearers terminated by the MN and / or split bearers terminated by the MN, thereby reducing the transmission latency of data in these bearers.

[0026] In conjunction with the second aspect, in some implementations of the second aspect, receiving second indication information, the second indication information being used to indicate discarding or ignoring part or all of the data packets in one or more data packets; sending part or all of the data packets in one or more data packets to a terminal device includes: sending data to the terminal device according to one or more data packets and the second indication information.

[0027] Based on the above technical solution, candidate network devices can avoid repeatedly sending data packets that have already been successfully received by the terminal device to the terminal device, thereby reducing resource waste.

[0028] In conjunction with the second aspect, in some implementations of the second aspect, the second indication information includes information on one or more sequence numbers, which are used to indicate the discarding or ignoring of some or all of the data packets in one or more data packets.

[0029] In conjunction with the second aspect, in some implementations of the second aspect, the sequence number is either the packet data aggregation protocol sequence number or the new air interface user plane sequence number.

[0030] In conjunction with the second aspect, in some implementations of the second aspect, receiving the second instruction information includes: periodically receiving the second instruction information.

[0031] For example, a candidate network device can send data to a terminal device based on data from earlier data transfers and the most recently received second instruction information.

[0032] Thirdly, a method for data transmission is provided, which can be executed by a network device, or by a chip or circuit used in a network device. This application does not limit this, but for ease of description, the following description takes execution by a network device as an example.

[0033] The method may include: the target network device determining N first network devices to configure for the terminal device, wherein the N first network devices include second network devices, and N is an integer greater than or equal to 1; wherein, before the terminal device switches from the source network device to the target network device, the second network device belongs to the candidate network devices in the scenario of adding or changing the conditional candidate primary / secondary cell PSCell configured for the terminal device; after the terminal device switches from the source network device to the target network device, the second network device belongs to the candidate network devices in the scenario of adding or changing the conditional candidate PSCell configured for the terminal device; or, the second network device belongs to the candidate network devices provided for the terminal device. The network device provides services; or, after the terminal device switches from the source network device to the target network device, if the second network device is a candidate network device in the scenario of adding or changing the conditional candidate primary and secondary cell PSCell configured for the terminal device, before the terminal device switches from the source network device to the target network device, if the second network device is a candidate network device in the scenario of adding or changing the conditional candidate PSCell configured for the terminal device, or if the second network device is a network device that provides services to the terminal device; the target network device sends third indication information, which is used to indicate the use of information related to the terminal device in the second network device.

[0034] The above method can be performed by the target network device (such as the target MN or the target SN), or by a chip or circuit used in the target network device (such as the target MN or the target SN).

[0035] For example, before a terminal device switches from a source network device to a target network device, it can be understood as before the network device providing services to the terminal device changes from a source network device to a target network device, or before the candidate network device configured for the terminal device changes from a source network device to a target network device, or before the network device providing services to the terminal device or the candidate network device configured for the terminal device changes.

[0036] For example, after a terminal device switches from a source network device to a target network device, it can be understood that the network device providing services to the terminal device changes from the source network device to the target network device, or the candidate network device configured for the terminal device changes from the source network device to the target network device, or the network device providing services to the terminal device or the candidate network device configured for the terminal device changes.

[0037] Based on the above technical solution, for scenarios where condition-based candidate primary and secondary cell PSCells are added or changed before the handover, and / or condition-based candidate primary and secondary cell PSCells are added or changed after the handover, if the network device configured for the terminal device after the handover includes the network device configured for the terminal device before the handover, the previously transferred data can be utilized, thereby avoiding the need to transfer these data packets again and reducing the transmission latency of these data packets.

[0038] In conjunction with the third aspect, in some implementations of the third aspect, the target network device sends third indication information, including: the target network device sending third indication information to the second network device; or, the target network device sending third indication information to the source network device.

[0039] As an example, the target network device may send a third instruction to the second network device, instructing the use or retention of information related to the terminal device in the second network device, such as including but not limited to: the context of the terminal device in the second network device, and previous data transfers performed by the second network device.

[0040] In another example, the target network device may send a third indication to the source network device. This third indication may be carried in a handover request response message.

[0041] In conjunction with the third aspect, in some implementations of the third aspect, the method further includes: the target network device receiving early data transmission information from a second network device that is a source network device.

[0042] Therefore, by learning about the early data transmission of the second network device, the target network device can make reasonable decisions, such as not needing to transfer previously transferred data packets again.

[0043] For example, the early data transmission information of the second network device may include one or more of the following: which data packets the source network device has already transmitted to the candidate second network device in the early stages, and which data packets the candidate second network device may discard or ignore in the early stages.

[0044] For example, the target network device can notify the second network device which packets from earlier data transfers can be dropped or ignored.

[0045] In conjunction with the third aspect, in some implementations of the third aspect, the method further includes: the target network device performing early data transmission with the second network device based on the early data transmission information of the second network device.

[0046] In conjunction with the third aspect, in some implementations of the third aspect, the method further includes: the target network device sending the identification information of the second network device to the source network device.

[0047] Therefore, by carrying identification information, it is possible to determine which network devices(s) need to retain previously transferred data before the handover, making the solution feasible and simple. Furthermore, when multiple candidate network devices need to retain previously transferred data, indicating the identifiers of these candidate network devices can save signaling and resources.

[0048] In conjunction with the third aspect, in some implementations of the third aspect, the method further includes: the target network device receiving information from one or more network devices from the source network device, wherein the one or more network devices include a second network device, and the one or more network devices are: candidate network devices configured for the terminal device in the scenario of adding or changing the condition-based candidate PSCell before the terminal device switches from the source network device to the target network device, or network devices that provide services to the terminal device, and the information of the one or more network devices includes one or more of the following: identification information of the one or more network devices, and identification information of the terminal device in the one or more network devices.

[0049] Therefore, taking CPAC occurring both before and after the handover as an example, the target network device can determine whether the candidate network devices before and after the handover are the same based on the information of the candidate network devices before the handover. This avoids the need to transfer these data packets again during the early data transfer when the candidate network devices before and after the handover are the same, thus reducing the transmission latency of these data packets.

[0050] In conjunction with the third aspect, in some implementations of the third aspect, the information of one or more network devices includes the identification information of one or more network devices, and based on the identification information of one or more network devices, N first network devices are determined to include second network devices.

[0051] Therefore, after the target network device receives the identification information of the network device or candidate network device (i.e., one or more of the above-mentioned network devices) that provided services to the terminal device before the handover from the source network device, the target network device can decide which network devices to select to provide services to the terminal device based on this information, or the target network device can also decide which candidate network devices to select based on this information. This can also reuse the previously transmitted data as much as possible, reduce transmission latency, and improve user experience.

[0052] In conjunction with the third aspect, in some implementations of the third aspect, the target network device receives information from one or more network devices from the source network device, including: the target network device receiving a handover request message, the handover request message including information from one or more network devices.

[0053] Therefore, when the source network device sends a handover request message to the target network device, it can notify the target network device of the information of the network device before the handover (such as a candidate network device). Thus, by receiving the handover request message carrying information about the network device before the handover (such as a candidate network device), the target network device can determine whether the network device before and after the handover is the same.

[0054] In conjunction with the third aspect, in some implementations of the third aspect, the target network device sends the identification information of the terminal device in the second network device to the second network device.

[0055] For example, the target network device sends a SN addition request message to the second network device, which includes the identification information of the terminal device in the second network device.

[0056] In conjunction with the third aspect, in some implementations of the third aspect, the method further includes: the target network device sending information about the N first network devices to the source network device.

[0057] For example, the target network device sends the identification information of the N first network devices to the source network device.

[0058] Fourthly, a method for data transmission is provided. This method can be executed by a network device, or by a chip or circuit used in a network device. This application does not limit the method in this regard. For ease of description, the following description will use the example of execution by a network device.

[0059] The method may include: the source network device determining that the network device configured for the terminal device after handover includes a second network device, wherein, before the terminal device hands over from the source network device to the target network device, if the second network device is a candidate network device in a scenario where the conditional candidate primary / secondary cell PSCell is added or changed for the terminal device, after the terminal device hands over from the source network device to the target network device, the second network device is a candidate network device in a scenario where the conditional candidate PSCell is added or changed for the terminal device, or the second network device is a network device providing services to the terminal device; or, after the terminal device hands over from the source network device to the target network device, if the second network device is a candidate network device in a scenario where the conditional candidate primary / secondary cell PSCell is added or changed for the terminal device, before the terminal device hands over from the source network device to the target network device, the second network device is a candidate network device in a scenario where the conditional candidate PSCell is added or changed for the terminal device, or the second network device is a network device providing services to the terminal device; the source network device sends third indication information to the second network device, the third indication information being used to indicate the use of information related to the terminal device in the second network device.

[0060] The above method can be performed by a source network device (such as a source MN or source SN), or by a chip or circuit used in a source network device (such as a source MN or source SN).

[0061] For example, the source network device receives a handover request response message and determines, based on the handover request response message, that the network device configured for the terminal device after the handover includes the second network device.

[0062] For example, third indication information can be carried in a release request message (such as an SN release request message).

[0063] In conjunction with the fourth aspect, in some implementations of the fourth aspect, the source network device determines that the network device configured for the terminal device after the handover includes the second network device, including: the source network device receiving identification information of the second network device from the target network device; and based on the identification information of the second network device, the source network device determines that the network device configured for the terminal device after the handover includes the second network device.

[0064] In conjunction with the fourth aspect, in some implementations of the fourth aspect, the method further includes: the source network device receiving information from N first network devices from the target network device, wherein the N first network devices are network devices configured by the target network device for the terminal device.

[0065] For example, the source network device receives identification information of N first network devices from the target network device.

[0066] For example, the source network device can determine whether the network device configured for the terminal device after the handover includes the network device configured for the terminal device before the handover, based on information from N first network devices (such as the identification information of N first network devices). Similarly, the source network device can determine whether the network device configured for the terminal device after the handover includes the second network device, based on information from N first network devices (such as the identification information of N first network devices).

[0067] In conjunction with the fourth aspect, in some implementations of the fourth aspect, the method further includes: the source network device sending early data transmission information of the second network device to the target network device.

[0068] In conjunction with the fourth aspect, in some implementations of the fourth aspect, the method further includes: the source network device sending information about one or more network devices to the target network device, wherein the one or more network devices include a second network device, and the one or more network devices are: candidate network devices added or changed in the scenario of condition-based candidate PSCells configured for the terminal device before the terminal device switches from the source network device to the target network device, or network devices that provide services to the terminal device, and the information about the one or more network devices includes one or more of the following: identification information of the one or more network devices, and identification information of the terminal device in the one or more network devices.

[0069] In conjunction with the fourth aspect, in some implementations of the fourth aspect, the source network device sends information about one or more network devices to the target network device, including: the source network device sending a handover request message to the target network device, the handover request message including information about one or more network devices.

[0070] In conjunction with the fourth aspect, in some implementations of the fourth aspect, the method further includes: the source network device sending a data packet to be sent to the terminal device to the target network device or the second network device.

[0071] Fifthly, a method for data transmission is provided. This method can be executed by a network device, or by a chip or circuit used in a network device. This application does not limit the method in this regard. For ease of description, the following description will use the example of execution by a network device.

[0072] The method may include: a second network device receiving third indication information from a source network device or a target network device, the third indication information being used to indicate the use of information related to the terminal device in the second network device. Specifically, if the second network device is a candidate network device in a conditional candidate primary / secondary cell PSCell addition or change scenario configured for the terminal device before the terminal device switches from the source network device to the target network device, and after the terminal device switches from the source network device to the target network device, the second network device remains a candidate network device in the conditional candidate PSCell addition or change scenario configured for the terminal device, or the second network device is a network device providing services to the terminal device; or, if the second network device is a candidate network device in a conditional candidate primary / secondary cell PSCell addition or change scenario configured for the terminal device after the terminal device switches from the source network device to the target network device, and before the terminal device switches from the source network device to the target network device, the second network device remains a candidate network device in the conditional candidate PSCell addition or change scenario configured for the terminal device, or the second network device is a network device providing services to the terminal device.

[0073] The above method can be performed by a second network device, or by a chip or circuit used in the second network device.

[0074] As an example, if a second network device receives third indication information from a source network device, the third indication information may be carried in a release request message (such as an SN release request message).

[0075] In another example, when the second network device receives third indication information from the target network device, the third indication information may be carried in an add request message (such as an SN add request message).

[0076] In conjunction with the fifth aspect, in some implementations of the fifth aspect, the second network device receives identification information of the terminal device in the second network device from the target network device.

[0077] For example, the second network device receives a SN addition request message from the target network device, which includes the identification information of the terminal device in the second network device.

[0078] In conjunction with aspects three through five, in some implementations, the information related to the terminal device includes one or more of the following: context information of the terminal device, data packets of the terminal device that have been transmitted to the second network device, and information about data packets of the terminal device that the second network device can discard or ignore.

[0079] In conjunction with aspects three through five, in some implementations, the target network device is a network device in a scenario where candidate PSCells are added or changed based on conditions, and the source network device is a network device in a scenario where candidate PSCells are added or changed based on conditions; or, the target network device is a network device in a scenario where candidate PSCells are added or changed based on conditions, and the source network device is a network device in a scenario where carrier aggregation is used; or, the target network device is a network device in a scenario where carrier aggregation is used, and the source network device is a network device in a scenario where candidate PSCells are added or changed based on conditions.

[0080] Sixthly, a method for data transmission is provided, which can be executed by a network device or by a chip or circuit used in a network device. This application does not limit the method, but for ease of description, the following description takes execution by a network device as an example.

[0081] The method may include: receiving information about candidate network devices configured for the terminal device before the terminal device switches from a source network device to a target network device; determining that the network devices configured for the terminal device after the terminal device switches from the source network device to the target network device include candidate network devices configured for the terminal device before the switch; and receiving information about early data transmission of the candidate network devices configured for the terminal device before the terminal device switches from the source network device to the target network device.

[0082] Taking the candidate network device configured for the terminal device before the terminal device switches from the source network device to the target network device as the second network device as an example, the method may include: receiving information of the second network device; determining that the network device configured for the terminal device after the switch includes the second network device; and receiving early data transmission information of the second network device.

[0083] The above method can be performed by the target network device (such as the target MN or the target SN), or by a chip or circuit used in the target network device (such as the target MN or the target SN).

[0084] In conjunction with the sixth aspect, in some implementations of the sixth aspect, the early data transmission information of the candidate network device may include, for example, one or more of the following: which data packets have been transferred to the candidate network device in the early data transfer (e.g., indicated by the packet data convergence protocol sequence number (PDCP SN) or the new radio user plane sequence number (NR-USN)), and which early data transfer data packets the candidate network device may discard or ignore.

[0085] In conjunction with the sixth aspect, in some implementations of the sixth aspect, the method further includes: receiving third indication information, the third indication information being used to indicate information related to the terminal device from candidate network devices configured for the terminal device before the handover.

[0086] In conjunction with the sixth aspect, in some implementations of the sixth aspect, the information related to the terminal device includes one or more of the following: the context information of the terminal device, the data packets of the terminal device transmitted to the candidate network devices configured for the terminal device before the handover from the source network device to the target network device, and the information of the data packets of the terminal device that can be discarded or ignored by the candidate network devices configured for the terminal device before the handover from the source network device to the target network device.

[0087] In conjunction with the sixth aspect, in some implementations of the sixth aspect, the method further includes: receiving second indication information, the second indication information being used to indicate that some or all of the data packets transmitted in the earlier period should be discarded or ignored.

[0088] In conjunction with the sixth aspect, in some implementations of the sixth aspect, the second indication information includes information on one or more sequence numbers used to indicate the discarding or ignoring of some or all data packets transmitted earlier.

[0089] In conjunction with the sixth aspect, in some implementations of the sixth aspect, the sequence number is either the packet data aggregation protocol sequence number or the new air interface user plane sequence number.

[0090] In conjunction with the sixth aspect, in some implementations of the sixth aspect, early data transmission is performed to the network device configured for the terminal device after the handover, based on the early data transmission between the candidate network device configured for the terminal device before the handover and the candidate network device before the handover.

[0091] In a seventh aspect, a method for data transmission is provided. This method can be executed by a network device, or by a chip or circuit used in a network device. This application does not limit the method in this regard. For ease of description, the following description will take execution by a network device as an example.

[0092] The method may include: sending information about candidate network devices configured for the terminal device before the terminal device switches from the source network device to the target network device; determining the network devices configured for the terminal device after the terminal device switches from the source network device to the target network device, including candidate network devices configured for the terminal device before the switch; and sending early data transmission information of the candidate network devices configured for the terminal device before the terminal device switches from the source network device to the target network device.

[0093] Taking the candidate network device configured for the terminal device before the terminal device switches from the source network device to the target network device as the second network device as an example, the method may include: sending information about the second network device; determining that the network device configured for the terminal device after the terminal device switches from the source network device to the target network device includes the second network device; and sending early data transmission information of the second network device.

[0094] The above method can be performed by a source network device (such as a source MN or source SN), or by a chip or circuit used in a source network device (such as a source MN or source SN).

[0095] In conjunction with the seventh aspect, in some implementations of the seventh aspect, the early data transmission information of the candidate network device may include, for example, one or more of the following: which data packets have been transferred to the candidate network device in the early data transfer (e.g., indicated by PDCP SN or NR-U sequence number), and which data packets the candidate network device may discard or ignore in the early data transfer.

[0096] In conjunction with the seventh aspect, in some implementations of the seventh aspect, the method further includes: sending third indication information, the third indication information being used to indicate information related to the terminal device among candidate network devices configured for the terminal device before the terminal device switches from the source network device to the target network device.

[0097] In conjunction with the seventh aspect, in some implementations of the seventh aspect, the information related to the terminal device includes one or more of the following: the context information of the terminal device, the data packets of the terminal device that have been transmitted to the candidate network devices configured for the terminal device before the terminal device switches from the source network device to the target network device, and the information of the data packets of the terminal device that can be discarded or ignored by the candidate network devices configured for the terminal device before the terminal device switches from the source network device to the target network device.

[0098] In conjunction with the seventh aspect, in some implementations of the seventh aspect, the method further includes: sending a second indication message, the second indication message being used to indicate that some or all of the data packets transmitted in the earlier period should be discarded or ignored.

[0099] In conjunction with the seventh aspect, in some implementations of the seventh aspect, the second indication information includes information on one or more sequence numbers used to indicate the discarding or ignoring of some or all data packets from earlier data transmissions.

[0100] In conjunction with aspect seven, in some implementations of aspect seven, the sequence number is either the packet data aggregation protocol sequence number or the new air interface user plane sequence number.

[0101] In conjunction with the seventh aspect, in some implementations of the seventh aspect, early data transmission is performed to the target network device based on the early data transmission between the candidate network devices configured for the terminal device before the terminal device switches from the source network device to the target network device.

[0102] Eighthly, a method for data transmission is provided. This method can be executed by a network device, or by a chip or circuit used in a network device. This application does not limit the method in this regard. For ease of description, the following description will use the example of execution by a network device.

[0103] The method may include: receiving information about network devices configured for the terminal device before the terminal device switches from a source network device to a target network device; determining candidate network devices configured for the terminal device after the terminal device switches from the source network device to the target network device, including network devices configured for the terminal device before the switch; and receiving early data transmission information of network devices configured for the terminal device before the terminal device switches from the source network device to the target network device.

[0104] Taking the network device configured for the terminal device before it switches from the source network device to the target network device as the second network device as an example, the method may include: receiving information about the second network device; determining that the candidate network devices configured for the terminal device after it switches from the source network device to the target network device include the second network device; and receiving early data transmission information from the second network device.

[0105] The above method can be performed by the target network device (such as the target MN or the target SN), or by a chip or circuit used in the target network device (such as the target MN or the target SN).

[0106] In a ninth aspect, a method for data transmission is provided. This method can be executed by a network device, or by a chip or circuit used in a network device. This application does not limit the method in this regard. For ease of description, the following description will take execution by a network device as an example.

[0107] The method may include: sending information about the network devices configured for the terminal device before the terminal device switches from the source network device to the target network device; determining candidate network devices configured for the terminal device after the terminal device switches from the source network device to the target network device, including the network devices configured for the terminal device before the switch; and sending early data transmission information of the network devices configured for the terminal device before the terminal device switches from the source network device to the target network device.

[0108] Taking the network device configured for the terminal device before it switches from the source network device to the target network device as the second network device as an example, the method may include: sending information about the second network device; determining that the candidate network devices configured for the terminal device after it switches from the source network device to the target network device include the second network device; and sending early data transmission information of the second network device.

[0109] The above method can be performed by a source network device (such as a source MN or source SN), or by a chip or circuit used in a source network device (such as a source MN or source SN).

[0110] A tenth aspect provides a communication apparatus for performing the methods provided in the first to ninth aspects. Specifically, the apparatus may include units and / or modules for performing the methods provided in the first to ninth aspects, such as processing units and / or communication units.

[0111] In one implementation, the device is a network device. When the device is a network device, the communication unit may be a transceiver or an input / output interface; the processing unit may be a processor.

[0112] In another implementation, the device is a chip, chip system, or circuit used in a network device. When the device is a chip, chip system, or circuit used in a communication device, the communication unit may be an input / output interface, interface circuit, output circuit, input circuit, pin, or related circuit on the chip, chip system, or circuit; the processing unit may be a processor, processing circuit, or logic circuit.

[0113] Optionally, the transceiver described above can be a transceiver circuit. Optionally, the input / output interface described above can be an input / output circuit.

[0114] Eleventhly, a communication device is provided, the device comprising: a memory for storing a program; and a processor for executing the program stored in the memory, wherein when the program stored in the memory is executed, the processor is configured to execute the methods provided in the first to ninth aspects.

[0115] In one implementation, the device is a terminal device or a network device.

[0116] In another implementation, the device is a chip, chip system, or circuit used in terminal equipment or network equipment.

[0117] In a twelfth aspect, this application provides a processor for executing the methods provided in the foregoing aspects. During the execution of these methods, the processes related to sending and receiving the aforementioned information can be understood as the processor outputting the aforementioned information and the processor receiving the input information. When outputting the aforementioned information, the processor outputs the information to a transceiver for transmission. After being output by the processor, the information may require further processing before reaching the transceiver. Similarly, when the processor receives the input information, the transceiver acquires / receives the information and inputs it into the processor. Furthermore, after the transceiver receives the information, the information may require further processing before being input into the processor.

[0118] Based on the above principles, for example, the acquisition of information about the second network device before the handover mentioned in the aforementioned method can be understood as the processor receiving input information.

[0119] Unless otherwise specified, or unless their actual function or internal logic in the relevant description is contradicted, the operations of the processor, such as transmitting, sending, and receiving, can be more generally understood as processor output and receiving, input, etc., rather than transmission, sending, and receiving operations performed directly by radio frequency circuits and antennas.

[0120] In implementation, the processor can be a dedicated processor for executing these methods, or it can be a processor that executes computer instructions stored in memory to execute these methods, such as a general-purpose processor. The memory can be a non-transitory memory, such as read-only memory (ROM), which can be integrated with the processor on the same chip or disposed on different chips. This application does not limit the type of memory or the arrangement of the memory and the processor.

[0121] In a thirteenth aspect, a computer-readable storage medium is provided that stores program code for execution by a device, the program code including methods provided in the first to ninth aspects described above.

[0122] In a fourteenth aspect, a computer program product containing instructions is provided, which, when run on a computer, causes the computer to perform the methods provided in the first to ninth aspects.

[0123] In a fifteenth aspect, a chip is provided, the chip including a processor and a communication interface, wherein the processor reads instructions stored in a memory through the communication interface and executes the methods provided in the first to ninth aspects.

[0124] Optionally, as one implementation, the chip may further include a memory storing instructions, and the processor is configured to execute the instructions stored in the memory. When the instructions are executed, the processor is configured to perform the methods provided in the first to ninth aspects described above.

[0125] In a sixteenth aspect, a communication system is provided, including the main network device and the candidate network device described above.

[0126] In a seventeenth aspect, a communication system is provided, comprising the source network device and the target network device as described above; or, the source network device and the second network device; or, the target network device and the second network device; or, the source network device, the target network device, and the second network device. Attached Figure Description

[0127] Figure 1 A schematic diagram of the architecture of CU and DU is shown.

[0128] Figure 2 A schematic diagram of a wireless communication system 200 applicable to embodiments of this application is shown.

[0129] Figure 3 A schematic diagram of a wireless communication system 300 applicable to embodiments of this application is shown.

[0130] Figure 4 A schematic diagram of a DC control plane architecture applicable to embodiments of this application is shown.

[0131] Figure 5 The diagram shows the protocol stack for MCG bearer, SCG bearer, and split bearer on the network side of EN-DC.

[0132] Figure 6 This diagram illustrates the protocol stack for MCG bearer, SCG bearer, and split bearer on the network side of NGEN-DC / NE-DC / NR-DC.

[0133] Figure 7 This is a schematic diagram of a data transmission method provided in an embodiment of this application.

[0134] Figure 8 This is a schematic diagram of a data transmission method provided in another embodiment of this application.

[0135] Figure 9 This is a schematic diagram of a CPA process applicable to an embodiment of this application.

[0136] Figure 10 This is a schematic diagram of a CPC process triggered by an MN according to an embodiment of this application.

[0137] Figure 11 This is a schematic diagram of a CPC process triggered by an SN, applicable to an embodiment of this application.

[0138] Figure 12 This is a schematic flowchart illustrating a scenario applicable to another embodiment of this application where CPAC is configured before the switch and then an MN switch occurs.

[0139] Figure 13 This is a schematic flowchart illustrating a scenario applicable to another embodiment of this application where CPC is configured before the switch and then SN switch occurs.

[0140] Figure 14 This is a schematic flowchart illustrating a scenario applicable to another embodiment of this application where no CPAC was configured before the switch, and then an MN switch occurred.

[0141] Figure 15 This is a schematic block diagram of a data transmission apparatus provided according to an embodiment of this application.

[0142] Figure 16 This is another schematic block diagram of a data transmission apparatus provided according to an embodiment of this application.

[0143] Figure 17 This is a schematic diagram of the structure of a network device provided in an embodiment of this application. Detailed Implementation

[0144] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0145] The technical solutions of this application can be applied to various communication systems, such as 5th generation (5G) systems, new radio (NR) systems, long term evolution (LTE) systems, LTE frequency division duplex (FDD) systems, LTE time division duplex (TDD) systems, etc. The technical solutions provided in this application can also be applied to future communication systems, such as 6th generation mobile communication systems. The technical solutions of this application can also be applied to device-to-device (D2D) communication, vehicle-to-everything (V2X) communication, machine-to-machine (M2M) communication, machine-type communication (MTC), and Internet of Things (IoT) communication systems or other communication systems.

[0146] The terminal device in this application embodiment can also be referred to as user equipment (UE), access terminal, user unit, user station, mobile station, mobile station (MS), mobile terminal (MT), remote station, remote terminal, mobile device, user terminal, terminal, wireless communication device, user agent, or user device. The terminal device in this application embodiment can be a device that provides voice and / or data connectivity to a user, and can be used to connect people, objects, and machines, such as a handheld device with wireless connectivity, vehicle-mounted device, etc. The terminal devices in the embodiments of this application can be mobile phones, tablets, laptops, PDAs, mobile internet devices (MIDs), wearable devices, virtual reality (VR) devices, augmented reality (AR) devices, wireless terminals in industrial control, self-driving, remote medical surgery, smart grids, transportation safety, smart cities, and smart homes, etc. Optionally, the UE can act as a base station. For example, the UE can act as a scheduling entity, providing sidelink signals between UEs in V2X or D2D, etc. For example, cellular phones and cars communicate with each other using sidelink signals. Cellular phones and smart home devices communicate without relaying communication signals through a base station.

[0147] The network device in this application embodiment can be a device used to communicate with terminal devices. This network device can also be called an access network device or a wireless access network device, such as a base station. The network device in this application embodiment can refer to a radio access network (RAN) node (or device) that connects a terminal device to a wireless network. The term "base station" can broadly encompass various names below, or be replaced by the following names, such as: NodeB, evolved NodeB (eNB), next-generation NodeB (gNB), relay station, access point, transmitting and receiving point (TRP), transmitting point (TP), master station MeNB, auxiliary station SeNB, multi-mode radio (MSR) node, home base station, network controller, access node, wireless node, access point (AP), transmission node, transceiver node, baseband unit (BBU), remote radio unit (RRU), active antenna unit (AAU), radio head (RRH), central unit (CU), distributed unit (DU), positioning node, etc. A base station can be a macro base station, micro base station, relay node, donor node, or a combination thereof. A base station can also refer to a communication module, modem, or chip installed within the aforementioned equipment or apparatus. A base station can also be a mobile switching center, equipment performing base station functions in device-to-device (D2D), vehicle-to-everything (V2X), and machine-to-machine (M2M) communications, network-side equipment in 6G networks, and equipment performing base station functions in future communication systems. Base stations can support networks using the same or different access technologies. The embodiments of this application do not limit the specific technologies or equipment forms used in the network equipment.

[0148] Base stations can be fixed or mobile. For example, a helicopter or drone can be configured to act as a mobile base station, and one or more cells can move depending on the location of the mobile base station. In other examples, a helicopter or drone can be configured as a device to communicate with another base station.

[0149] In some deployments, the network device in this application embodiment may refer to a CU or a DU, or the network device may include both a CU and a DU. The gNB may also include an active antenna unit (AAU). See also, as an example, [link to example description]. Figure 1 , Figure 1 A schematic diagram of the CU and DU architecture is shown. The CU implements some of the functions of the gNB, and the DU implements some of the functions of the gNB. For example, the CU is responsible for handling non-real-time protocols and services, implementing the functions of the radio resource control (RRC) layer and the packet data convergence protocol (PDCP) layer. The DU is responsible for handling physical layer protocols and real-time services, implementing the functions of the radio link control (RLC) layer, the medium access control (MAC) layer, and the physical (PHY) layer. The AAU implements some physical layer processing functions, radio frequency processing, and related functions of the active antenna. Since the information of the RRC layer will eventually become the information of the PHY layer, or be transformed from the information of the PHY layer, in this architecture, higher-layer signaling, such as RRC layer signaling, can also be considered to be sent by the DU, or by the DU+AAU. It can be understood that network devices can be devices including one or more of the following: CU nodes, DU nodes, and AAU nodes. In addition, the CU can be classified as a network device in the radio access network (RAN) or as a network device in the core network (CN), and this application does not limit this.

[0150] Furthermore, the CU can be divided into the central unit-control plane (CU-CP) and the central unit-user plane (CU-UP). CU-CP and CU-UP can be deployed on different physical devices. CU-CP is responsible for control plane functions, mainly comprising the RRC layer and the PDCP-C layer. The PDCP-C layer is primarily responsible for control plane data encryption / decryption, integrity protection, and data transmission. CU-UP is responsible for user plane functions, mainly comprising the Service Data Adaptation Protocol (SDAP) layer and the PDCP-U layer. The SDAP layer is primarily responsible for processing core network data and mapping flows to bearers. The PDCP-U layer is primarily responsible for at least one function of data plane encryption / decryption, integrity protection, header compression, sequence number maintenance, and data transmission. Specifically, CU-CP and CU-UP are connected via a communication interface (e.g., an E1 interface). CU-CP represents the network device connecting to the core network device via a communication interface (e.g., an Ng interface) and to the DU via a communication interface (e.g., an F1-C (control plane) interface). The CU-UP connects to the DU via a communication interface (e.g., the F1-U (user plane) interface).

[0151] Another possible implementation is that the PDCP-C layer is also included in CU-UP.

[0152] It is understood that the above protocol layer division of CU and DU, as well as CU-CP and CU-UP, is only an example, and there may be other division methods. This application does not limit the specific division methods.

[0153] The network devices mentioned in the embodiments of this application may be devices including CU, or DU, or devices including CU and DU, or devices including control plane CU nodes (CU-CP nodes), user plane CU nodes (CU-UP nodes), and DU nodes.

[0154] Network devices and terminal devices can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; they can also be deployed on water; and they can also be deployed in the air on airplanes, balloons, and satellites. This application does not limit the scenario in which the network devices and terminal devices are located.

[0155] Some embodiments in this application also relate to core network equipment. Specifically, core network equipment refers to equipment in the core network (CN) that provides service support for terminal equipment. Examples of core network equipment include: access and mobility management function (AMF) entities, session management function (SMF) entities, user plane function (UPF) entities, etc., which will not be listed here. The AMF entity can be responsible for access management and mobility management of terminal equipment. The SMF entity can be responsible for session management, such as session establishment for terminal equipment. The UPF entity can be a user plane function entity, mainly responsible for connecting to external networks. It should be noted that in this application, entities can also be called network elements or functional entities. For example, an AMF entity can also be called an AMF network element or an AMF functional entity; similarly, an SMF entity can also be called an SMF network element or an SMF functional entity, etc.

[0156] It should be understood that the above naming is defined solely for the purpose of distinguishing different functions and should not constitute any limitation on this application. This application does not preclude the possibility of using other naming conventions in 5G networks and other future networks. For example, in 6G networks, some or all of the above-mentioned network elements may use the terminology from 5G, or they may use other names, etc.

[0157] To facilitate understanding of the embodiments of this application, firstly, in conjunction with Figure 2 and Figure 3 The communication system applicable to the embodiments of this application is described in detail.

[0158] As an example, see Figure 2 , Figure 2 A schematic diagram of a wireless communication system 200 applicable to embodiments of this application is shown. Figure 2 As shown, the wireless communication system 200 may include at least one network device, such as Figure 2 The network device 210 shown, the wireless communication system 200 may also include at least one terminal device, such as Figure 2 The terminal device 220 shown. Both the network device and the terminal device can be configured with multiple antennas, and the network device and the terminal device can communicate using multi-antenna technology.

[0159] When the network device and the terminal device communicate, the network device can manage one or more cells, and a cell can contain an integer number of terminal devices. Optionally, the network device 210 and the terminal device 220 form a single-cell communication system. Without loss of generality, the cell is referred to as cell #1. The network device 210 can be a network device in cell #1, or in other words, the network device 210 can serve the terminal devices (such as terminal device 220) in cell #1.

[0160] It should be noted that a residential area can be understood as the area within the wireless signal coverage of network devices.

[0161] It should be understood that Figure 2 This is a simplified illustration for ease of understanding only. The wireless communication system 200 may also include other network devices or other terminal devices. Figure 2 It was not drawn in the middle.

[0162] The method provided in this application can also be applied to dual connectivity (DC) scenarios. For ease of understanding, let's take the terminal device as the UE and the network device as the base station as an example, and combine... Figure 3 This section introduces the DC (Data Center) scenario.

[0163] In a wireless network, a UE may communicate with multiple base stations, a phenomenon known as dual connectivity (DC), also called multi-radio dual connectivity (MR-DC). For consistency, this will be referred to as DC below. These multiple base stations may belong to the same radio access technology (RAT) (e.g., all 4G base stations, or all 5G base stations), or they may belong to different RATs (e.g., one is a fourth-generation 4G base station, and the other is a fifth-generation 5G base station).

[0164] As an example, see Figure 3 , Figure 3 Another schematic diagram of a wireless communication system 300 applicable to embodiments of this application is shown. See also Figure 3 UE 320 can communicate with base stations 311 and 312 via DC technology. Base stations 311 and 312 jointly access the core network 330. The core network 330 may be a 4G core network or a 5G core network.

[0165] The network side can utilize the resources of multiple base stations to provide communication services to the UE, thereby providing high-speed transmission for the UE. In a DC scenario, for a given UE, the base station that interacts with the core network through control plane signaling is called the master node (MN), and other base stations are called secondary nodes (SN). MN may sometimes be referred to as the master base station, and SN may sometimes be referred to as the secondary base station. Each base station has different RLC and MAC entities. In a DC scenario, the data radio bearer (DRB) can be divided into the following three types: master cell group bearer (MCGbearer), secondary cell group bearer (SCG bearer), and split bearer. Among them, MCG bearer means that the RLC and MAC entities of the DRB are on the master base station; SCG bearer means that the RLC and MAC entities of the DRB are on the secondary base station; and split bearer means that the RLC and MAC entities of the DRB are on both the master and secondary base stations. Similarly, for bearers whose PDCP terminates on the MN, they can be called MN-terminated bearers. Downlink (DL) data travels directly from the core network to the MN, is processed by the MN's PDCP / SDAP, and then sent to the UE via the MN's or SN's RLC / MAC. Uplink (UL) data is processed by the MN's PDCP / SDAP and then sent to the core network. For bearers whose PDCP terminates on the SN, they can be called SN-terminated bearers. DL data travels directly from the core network to the SN, is processed by the SN's PDCP / SDAP, and then sent to the UE via the MN or SN's RLC / MAC. UL data is processed by the SN's PDCP / SDAP and then sent to the core network. It is understandable that in some cases, such as when the terminal device is connected to the 5G core network, protocol layer SDAP exists.

[0166] Furthermore, in dual connectivity, both the primary and secondary base stations have RRC entities and can generate RRC messages (i.e., control messages, such as measurement messages). See also [link to example illustration]. Figure 4 , Figure 4A schematic diagram of a DC control plane architecture applicable to embodiments of this application is shown. The primary base station and the core network communicate via a communication interface (e.g., NG-C interface), the primary base station and the secondary base station communicate via a communication interface (e.g., Xn-C interface), the primary base station and the UE communicate via a communication interface (e.g., Uu interface), and the secondary base station and the UE communicate via a communication interface (e.g., Uu interface).

[0167] The secondary base station can directly send the RRC messages it generates to the UE. In this case, the RRC messages sent by the UE to the secondary base station are also sent directly to the secondary base station. The RRC messages exchanged directly between the secondary base station and the UE are called Signalling Radio Bearer 3 (SRB3). Alternatively, the secondary base station can notify the primary base station of the generated RRC messages, and the primary base station then sends them to the UE. In this case, the UE forwards the RRC messages intended for the secondary base station to the secondary base station through the primary base station. For a UE in a DC scenario, the user plane of the secondary base station may be connected to the core network connected to the primary base station, meaning the core network can directly send data to the UE through the secondary base station.

[0168] It should be understood that the interfaces between devices involved in this application (such as communication between the main base station and the auxiliary base station via the Xn-C interface) are merely illustrative examples and do not limit the scope of protection of the embodiments of this application.

[0169] The scenarios to which this application applies may include the following DC types: Evolved Universal Terrestrial Radio Access and New Radio Dual Connectivity (E-UTRA-NR dual connectivity, EN-DC), Next Generation Radio Access Network Evolved Universal Terrestrial Radio Access and New Radio Dual Connectivity (NG-RAN E-UTRA-NR dual connectivity, NGEN-DC), New Radio and Evolved Universal Terrestrial Radio Access Dual Connectivity (NR-E-UTRA dual connectivity, NE-DC), and New Radio and New Radio Dual Connectivity (NR-NR dual connectivity, NR-DC).

[0170] In EN-DC, the primary base station is an LTE base station (e.g., eNB) connected to the 4G core network, and the secondary base station is an NR base station (e.g., gNB).

[0171] In NGEN-DC, the main base station is an LTE base station connected to the 5G core network, and the secondary base station is an NR base station.

[0172] In NE-DC, the primary base station is an NR base station connected to the 5G core network, and the secondary base station is an LTE base station. EN-DC is sometimes also called NSA because in the initial stages of 5G, UEs cannot camp on NR cells in the EN-DC network. NR base stations that can camp on UEs are sometimes called SA NR base stations.

[0173] In NR-DC, the main base station is an NR base station connected to the 5G core network, and the auxiliary base station is an NR base station.

[0174] As an example, see Figure 5 , Figure 5 This diagram illustrates the protocol stack for MCG bearer, SCG bearer, and split bearer on the network side of EN-DC. See also [link to example diagram]. Figure 6 , Figure 6 This diagram illustrates the protocol stack for MCG bearer, SCG bearer, and split bearer on the network side of NGEN-DC / NE-DC / NR-DC. From... Figure 5 and Figure 6 It can be seen that the transmission of each bearer needs to go through RLC / MAC and PDCP / SDAP.

[0175] A UE can simultaneously receive services from multiple cells under one base station. The serving cell group provided by the MN for the UE can be called the master cell group (MCG), which includes one or more cells. The serving cell group provided by the SN for the UE can be called the secondary cell group (SCG), which includes one or more cells. When there is only one cell in the MCG, that cell is the UE's primary cell (PCell). When there is only one cell in the SCG, that cell is the UE's primary secondary cell (PSCell). In NR, to standardize various terms, PCell and PSCell are collectively referred to as special cells (SpCell). When there are multiple cells in the MCG or SCG, the cells other than the SpCell can be called secondary cells (SCell). SCells and SpCells in the MCG or SCG can perform carrier aggregation to jointly provide transmission resources for the UE.

[0176] It should be understood that the application scenarios of this application are not limited to the above-mentioned DC scenarios. This application is also applicable to DC scenarios of other systems, such as DC scenarios composed of 5G base stations and WIFI, or DC scenarios composed of base stations deployed in licensed spectrum and base stations deployed in unlicensed spectrum.

[0177] To facilitate understanding of the embodiments of this application, several basic concepts involved in the embodiments of this application are briefly explained. It should be understood that the basic concepts introduced below are based on the basic concepts specified in the current protocol for simple explanation, but do not limit the embodiments of this application to be applied only to existing communication systems. Therefore, the standard names that appear when describing existing communication systems are functional descriptions, and the specific names are not limited.

[0178] 1. Carrier aggregation (CA): A technology that configures multiple carriers (cells) for a single terminal device to transmit data together.

[0179] 2. Primary Cell (PCell): A cell deployed on the primary frequency (or, a cell operating on the primary carrier). A PCell is the cell corresponding to the initial connection establishment or connection reconstruction process initiated by the terminal device. That is, if a terminal device initiates an initial connection establishment or connection reconstruction process in a certain cell, that cell is called a PCell. During handover, a cell can be designated as a PCell.

[0180] 3. Primary and Secondary Cells (PSCell): These are cells in which terminal devices perform random access or initial physical uplink shared channel (PUSCH) transmissions in an SCG (e.g., when an SCG change is performed and no random access procedure is required, the UE initiates an initial PUSCH transmission), or cells in an SCG cell where terminal devices perform random access during synchronization reconfiguration.

[0181] 4. Secondary Cell (SCell): This is a cell that operates on a secondary carrier. Once an RRC connection is established, an SCell may be configured to provide additional radio resources. In a dual-connectivity system, all cells in both the MCG and SCG except for PCell and PSCell can be referred to as SCells.

[0182] It should be understood that in some places PSCell is also referred to as SCell, meaning that SCell also includes PSCell.

[0183] 5. Serving cell: A terminal device in RRC connected state has only one serving cell, PCell, if carrier aggregation or dual connectivity is not configured. If carrier aggregation or dual connectivity is configured, the serving cell of the terminal device can be considered to consist of PCell, PSCell and all SCells.

[0184] It should be understood that the PCell, PSCell and all SCell mentioned above are merely examples, and in future agreements, the meanings used to indicate the same function shall apply to the embodiments of this application.

[0185] It should also be understood that each component carrier (CC) corresponds to an independent cell. In one possible design, a terminal device configured with carrier aggregation or dual connectivity can connect to one PCell and up to 31 SCells. The PCell, PSCell, and all SCells of the terminal device constitute the serving cell set of that terminal device. The serving cell of the terminal device can refer to the PCell, the PSCell, or the SCell.

[0186] In dual connectivity, generally, due to the mobility of terminal devices, the network side triggers a change in the PSCell (i.e., the network side notifies the terminal device to switch from one PSCell to another, and notifies it of the configuration information corresponding to the changed PSCell). For example, the network side may determine from the terminal device's measurement results that the signal quality of one PSCell has deteriorated, while the signal quality of another PSCell has improved, and thus notify the terminal device to change the PSCell. It should be understood that a PSCell change may be a switch from one SN cell to another SN cell, or it may be a switch from one SN cell to another cell within the same SN. Furthermore, this PSCell change may be triggered by the MN (Meaning Node), i.e., the MN determines (or initiates) the switch from one PSCell to another, or it may be triggered by the SN, i.e., the SN determines (or initiates) the switch from one PSCell to another.

[0187] A conditional PSCell addition / change (CPAC) method involves the network side pre-configuring multiple candidate PSCells and informing the terminal device of the configuration of these candidate PSCells and the conditions corresponding to each candidate PSCell. Subsequently, when the terminal device determines that a candidate PSCell meets its corresponding conditions, the terminal device can directly access that candidate PSCell. This eliminates the need for the network side to wait for the terminal device to report a measurement report before sending a new PSCell configuration, thus reducing the latency required for adding or changing PSCells. Furthermore, for scenarios where the SN triggers a PSCell change, it avoids the inability to report measurement reports and send reconfiguration messages via SRB3 when the PSCell signal quality changes rapidly, thereby improving the robustness of PSCell changes.

[0188] It is understood that CPAC as used in this application is a general term. In this application, CPAC may refer to the configuration of PSCell based on the addition and / or change of conditions.

[0189] In CPAC, although a terminal device can directly connect to a candidate PSCell that meets its corresponding conditions, thereby reducing the latency required to add or change a PSCell, the candidate PSCell cannot immediately send data to the terminal device after the terminal device connects. It must wait for the device before the terminal device connects to the candidate PSCell to send data packets before it can send data to the terminal device. This increases the transmission latency of these data packets.

[0190] This application provides a solution that can shorten the latency of data transmission.

[0191] It should be noted that, in the embodiments of this application, the switching process mainly includes processes related to CPAC, such as adding or changing PSCell.

[0192] The various embodiments provided in this application will now be described in detail with reference to the accompanying drawings.

[0193] Figure 7 This is a schematic diagram of a data transmission method 700 provided in an embodiment of this application. Method 700 may include the following steps.

[0194] 710, The primary network device performs a condition-based process for adding or changing candidate PSCells between candidate network devices.

[0195] The primary network device can be, for example, MN, and the candidate network device and the secondary network device can be, for example, SN.

[0196] In step 710, the primary access network device or the secondary access network can trigger the addition or modification of condition-based candidate PSCells for the terminal device. That is, the primary access network device or the secondary access network triggers the candidate network device to pre-configure multiple candidate PSCells. Then, the primary access network device can notify the terminal device of the configuration of these multiple candidate PSCells and the triggering conditions corresponding to each candidate PSCell. Subsequently, when the terminal device determines that a candidate PSCell meets its corresponding triggering conditions, the terminal device can directly access that candidate PSCell. When multiple candidate PSCells meet their corresponding triggering conditions, the specific candidate PSCell that the terminal device accesses can be designed according to the needs of its system. For example, the terminal device can decide for itself to choose arbitrarily, or it can choose one it has previously accessed; this is not limited here.

[0197] It should be understood that Figure 7 For ease of understanding, this example uses a primary network device and a candidate network device. The number of candidate network devices is not limited in this embodiment. For instance, in practice, a greater number of candidate network devices may be included.

[0198] 720. The master network device sends one or more data packets to the candidate network device, the one or more data packets including: data packets on the SCG bearer terminated by the MN configured for the terminal device, and / or, data packets on the split bearer terminated by the MN configured for the terminal device.

[0199] In other words, in step 720, the master network device can send one or more data packets, i.e., one or more downlink data packets, to the network device to which the candidate PSCell belongs. The network device to which the candidate PSCell belongs, i.e., the candidate network device, can be, for example, a candidate SN.

[0200] One possible approach is that, in step 720, the master network device performs early data transmission to the network device to which the candidate PSCell belongs. Early data transmission refers to sending one or more data packets to the network device to which the candidate PSCell belongs before the terminal device accesses the candidate PSCell.

[0201] The one or more data packets sent by the master network device to the candidate network device can be in the form of a protocol data unit (PDU) of the packet data aggregation layer protocol (PDCP PDU).

[0202] In this embodiment of the application, the master network device can transmit data packets on the SCGbearer that terminates MN to the candidate network device in the early data transmission stage, and the master network device can also transmit data packets on the splitbearer that terminates MN to the candidate network device in the early data transmission stage.

[0203] In this context, a data packet on an SCG bearer terminated by MN indicates that the corresponding DRB's RLC and MAC entities are on SN, while the PDCP entity is on MN. Similarly, a data packet on a split bearer terminated by MN indicates that the corresponding DRB's RLC and MAC entities exist on both SN and MN, while the PDCP entity is on MN. In other words, in early data transmission, data packets on an SCG bearer or a split bearer terminated by MN were processed by the MN's PDCP / SDAP.

[0204] It should be understood that the embodiments of this application do not limit whether the candidate network device (such as the candidate SN) deploys a PDCP layer or supports the functions of the PDCP layer.

[0205] In this application, the term "early data transfer" may also refer to the SCG bearer or split bearer that terminates with MN, or it may be referred to by other names. Such naming does not limit the scope of protection of the embodiments in this application. For consistency, the data transfer between the primary network device or secondary network device and the candidate network device in the CPAC will be referred to as "early data transfer."

[0206] Optionally, method 700 may also include step 730.

[0207] 730. After the terminal device accesses the candidate network device, the candidate network device sends some or all of the data packets in the one or more data packets to the terminal device.

[0208] In other words, after a terminal device connects to a candidate network device, the candidate network device can send the transferred data to the terminal device, thereby reducing data transmission latency.

[0209] Through the embodiments of this application, early data transfer can be performed between the primary network device and candidate network devices (such as MN and candidate SN). This allows the candidate network device to send the transferred data to the terminal device after the terminal device connects, thereby reducing data transmission latency. Furthermore, for MN-terminated SCG bearers and / or MN-terminated split bearers, the primary network device can also perform early data transfer to candidate network devices, such as through PDCP PDUs. Therefore, the embodiments of this application can support early data transfer of data packets from MN-terminated SCG bearers and / or MN-terminated split bearers, reducing the transmission latency of data in these bearers.

[0210] Optionally, the primary network device can also send indication information #1 to the candidate network device (i.e., the network device to which the candidate PSCell belongs), instructing it to discard or ignore some or all of the data packets in the one or more data packets. For example, the MN can send indication information #1 to the candidate SN, instructing it to discard or ignore some or all of the data packets from the earlier data transfer. In this way, the candidate network device can send data to the terminal device based on the data from the earlier data transfer and the indication information #1. In this case, the candidate network device may send some of the data packets from the one or more data packets to the terminal device. By way of example and not limitation, the candidate network device may discard the data packets indicated to be discarded, or it may simply ignore these data packets. For example, after the primary network device sends the CPAC configuration to the terminal device, the primary or secondary network device will continue to send data to the terminal device. Thus, between sending the CPAC configuration to the terminal device and the terminal device accessing the candidate PSCell, the primary or secondary network device may have already successfully sent some data packets to the terminal device. In order to prevent the candidate network device from resending these successfully sent data packets to the terminal device after the terminal device accesses the candidate PSCell, the primary or secondary network device will notify the candidate network device to discard or ignore some data packets that have already been successfully sent to the terminal device.

[0211] This method avoids reserving or repeatedly sending data packets that the terminal device has already successfully received to the terminal device in the candidate network device, thus reducing resource waste.

[0212] In this embodiment of the application, for distinction, indication information #1 is used to indicate information used to indicate the discarding or ignoring of some or all data packets from the early data transfer.

[0213] The timing of sending indication information #1 is not limited. For example, indication information #1 can be sent if preset conditions are met. Preset conditions can be time-related limitations (such as periodic sending), data volume limitations (such as comparison of data volume with a threshold value or threshold range), or other limitations.

[0214] Furthermore, the form of the instruction information #1 is not limited. One possible form is that the instruction information #1 can be one or more sequence numbers (SNs). Sequence numbers are mentioned multiple times in this application, and their specific form is not limited. For example, the sequence number can be a packet data convergence protocol sequence number (PDCP SN), a new radio user plane sequence number (NR-U SN), or other sequence numbers; there is no limitation on this. This will not be further elaborated below.

[0215] There are no restrictions on how the instruction message #1 is sent. For example, the instruction message #1 can be sent through the user plane between the primary network device and the candidate network device, or through the control plane between the primary network device and the candidate network device (such as the primary network device sending a message to the candidate network device, for example, the primary network device carrying the instruction message #1 in an early status transfer message).

[0216] Taking indication information #1 sent via the user plane between the primary network device and the candidate network device as an example. For instance, the primary network device sends data to the candidate network device via the user plane carrying the sequence number corresponding to the data packet to be discarded or ignored, such as a PDCP SN, indicating that all data packets before that sequence number should be discarded or ignored, including the data packet corresponding to that sequence number. Alternatively, it may carry indication information indicating the data packets corresponding to multiple blocks. For example, the indication information may include the number of blocks, the PDCP SN corresponding to the first data packet to be discarded or ignored in each block, and the number of data packets corresponding to that block. Each block corresponds to a series of consecutive PDCP SNs and their associated data packets.

[0217] Regarding the specific content of instruction message #1, the following text is in conjunction with... Figure 9 The method shown in 900 is described in detail.

[0218] Optionally, the master network device can also send indication information #2 to the candidate network device (i.e., the network device where the PSCell resides). Indication information #2 is used to indicate early data transmission of the SCG bearer and / or the split bearer of the MN termination. For example, the MN can send indication information #2 to the candidate SN, indicating early data transmission of the SCG bearer and / or the split bearer of the MN termination. After the master network device sends indication information #2 to the candidate network device, early data transmission of the SCG bearer and / or the split bearer of the MN termination can occur with the candidate network device.

[0219] In this embodiment of the application, for distinction, indication information #2 is used to indicate the early data transmission of the SCGbearer and / or the split bearer for MN termination.

[0220] The instruction information #2 can be sent through the control plane interface between the primary network device and the candidate network device, or through the user plane interface between the primary network device and the candidate network device, without limitation.

[0221] Furthermore, regarding the form of the instruction, it can be indicated through the specific content of instruction information #2, or it can be indicated by the action of sending instruction information #2; there is no limitation in this regard. Taking the action of sending instruction information #2 as an example, and not a limitation, a certain field can be pre-agreed or pre-configured. When this field is sent, it indicates the early data transmission of the SCG bearer and / or the split bearer that is MN-terminated.

[0222] Regarding the specific procedures applicable to Method 700, the following text combines... Figure 9-11 The illustrated examples are as follows.

[0223] Figure 8 This is a schematic diagram of a data transmission method 800 provided in an embodiment of this application. Method 800 may include the following steps.

[0224] 810, The target network device is determined to be the terminal device configured with N first network devices, and the N first network devices include second network devices.

[0225] Where N is an integer greater than or equal to 1.

[0226] In this embodiment of the application, for distinction, the target network device represents the network device after the handover, and the source network device represents the network device before the handover. The network device can be, for example, MN, SN, etc. For example, switching from the source MN to the target MN; or switching from the source SN to the target SN; or switching from the source MN to the target MN and from the source SN to the target SN.

[0227] The target network device determines N first network devices to be configured for the terminal device. These N first network devices may include: network devices that provide services to the terminal device, and / or, candidate network devices. After handover, if the N first network devices include a second network device, the second network device may be either a network device that provides services to the terminal device or a candidate network device.

[0228] In this application, "before the handover" refers to the period before the terminal device switches from the source network device to the target network device. In other words, it refers to the period before the network device providing services to the terminal device changes from the source network device to the target network device, or before the candidate network device configured for the terminal device changes from the source network device to the target network device, or before the network device providing services to the terminal device or the candidate network device configured for the terminal device changes. "After the handover" refers to the period after the terminal device switches from the source network device to the target network device. In other words, it refers to the period after the network device providing services to the terminal device changes from the source network device to the target network device, or after the candidate network device configured for the terminal device changes from the source network device to the target network device, or after the network device providing services to the terminal device or the candidate network device configured for the terminal device changes. For brevity, the following description uses "before the handover" and "after the handover."

[0229] The second network device before and after the handover can fall into the following categories.

[0230] In one possible scenario, the second network device after the handover belongs to the candidate network device in the scenario of adding or changing the condition-based candidate primary and secondary cell PSCell configured for the terminal device.

[0231] For example, in scenarios involving conditional PSCell addition (CPA) or conditional PSCell change (CPC) after handover, the target network device may configure candidate network devices that are partially or entirely the same as the network devices configured before the handover (e.g., network devices that provided services to the terminal devices before the handover, or candidate network devices configured for the terminal devices before the handover). In other words, the candidate network devices configured by the target network device include the network devices configured for the terminal devices before the handover, i.e., the second network devices.

[0232] The second network device may be a network device that provides services to the terminal device before the handover, such as a network device in a DC scenario, like a secondary network device; or the second network device may be a candidate network device configured for the terminal device before the handover, such as a network device in a CPA / CPC scenario.

[0233] Another possible scenario is that the second network device before the handover belongs to the candidate network device in the scenario of adding or changing the condition-based candidate primary and secondary cell PSCell configured for the terminal device.

[0234] For example, in a scenario where CPA / CPC was in place before the handover, the second network device was a candidate network device configured for the terminal device. After the handover, the second network device may remain a candidate network device or it may become a network device providing services to the terminal device.

[0235] In one example, in a CPA / CPC scenario after the handover, the target network device decides to configure candidate network devices that are partially or entirely the same as the candidate network devices configured for the terminal device before the handover. In other words, the target network device decides to configure candidate network devices that include the candidate network devices configured for the terminal device before the handover, i.e., the second network device.

[0236] In another example, in a scenario where the data center (DC) becomes the new location after the handover, the target network device (e.g., the primary network device) decides to configure network devices (e.g., secondary network devices) that are partially or entirely the same as the candidate network devices configured for the terminal devices before the handover. In other words, the target network device decides to configure network devices that include the candidate network devices configured for the terminal devices before the handover, i.e., the second network devices.

[0237] Another possible scenario is that, both before and after the handover, the second network device is a candidate network device in the scenario of adding or changing the condition-based candidate primary and secondary cell PSCell configured for the terminal device.

[0238] For example, in a scenario where CPA / CPC was configured before the handover, the second network device was a candidate network device configured for the terminal device. In a scenario where CPA / CPC was configured after the handover, the target network device determined that the candidate network devices configured were partially or entirely the same as the candidate network devices configured for the terminal device before the handover.

[0239] It should be understood that the above three possible scenarios are merely illustrative examples, and variations of any of the above scenarios are applicable to the embodiments of this application. For example, N first network devices include multiple second network devices, that is, the target network device can decide to maintain the multiple second network devices configured for the terminal device before the handover.

[0240] After the handover, if the target network device is determined to be one of the N first network devices configured for the terminal device, including the network device configured for the terminal device before the handover, then data transferred in the earlier data transfer can be utilized, or some unnecessary data transfers can be reduced. For example, the target network device can send an indication message, such as indication message #3, to indicate the use or retention of information related to the terminal device in the second network device.

[0241] The information related to the terminal device in the second network device may include, for example, one or more of the following: the context of the terminal device in the second network device, data packets of the terminal device that have been transmitted to the second network device, and information on data packets that the second network device can discard or ignore. The data packets that the second network device can discard refer to data packets that can be discarded in previous data transfers within the second network device. As an example, and not a limitation, instruction information #3 may be used to indicate the maintenance of the context of the terminal device in the second network device. Alternatively, instruction information #3 may be used to indicate the use or maintenance of information on previous data transfers of the second network device. Information on previous data transfers of the second network device includes: data packets from previous data transfers of the second network device (i.e., data packets of the terminal device that have been transmitted to the second network device), and / or information on data packets that the second network device can discard or ignore.

[0242] In this embodiment of the application, for distinction, indication information #3 is used to indicate information related to the terminal device in certain network devices configured for the terminal device before the handover. Regarding the specific method of indication, it can be indicated through the specific content of indication information #3, or it can be indicated through the action of sending indication information #3; this embodiment of the application does not limit this approach.

[0243] For example, the specific content in instruction information #3 can indicate whether to use or retain information related to the terminal device from certain network devices configured for the terminal device before the handover.

[0244] For example, suppose the protocol predefined indication information #3 functions to use or retain information related to the terminal device from certain network devices configured for the terminal device before the handover. This can be indicated using a 1-bit field. Here, 0 corresponds to using or retaining the information related to the terminal device from certain network devices configured for the terminal device before the handover, and 1 corresponds to not using or not needing to retain the information related to the terminal device from certain network devices configured for the terminal device before the handover, or releasing the information related to the terminal device from certain network devices configured for the terminal device before the handover.

[0245] For example, a 1-bit field can be used to indicate whether indication information #3 is used to indicate whether to maintain the context of the terminal device in the second network device or to indicate whether to use or maintain information about an earlier data transfer of the second network device. Specifically, 0 corresponds to indication information #3 indicating whether to maintain the context of the terminal device in the second network device, and 1 corresponds to indication information #3 indicating whether to use or maintain information about an earlier data transfer of the second network device.

[0246] Another example is that the action of sending instruction message #3 can instruct the use or retention of certain network device-related information configured for the terminal device before the handover. For example, a dedicated function can be designed to instruct the use or retention of certain network device-related information configured for the terminal device before the handover. When this message is received, it is determined that the information configured for the terminal device before the handover needs to be used or retained; when this message is not received, it is determined that the information configured for the terminal device before the handover does not need to be used or retained, or that the information configured for the terminal device before the handover needs to be released.

[0247] Method 800 may include step 8201 or step 8202.

[0248] 8201, The target network device sends instruction information #3 to the second network device.

[0249] In step 8201, the target network device sends indication information #3 to the second network device. Upon receiving indication information #3, the second network device can determine, based on this information, that it does not need to release data packets transferred in the earlier data transfer. The second network device can use information related to the terminal device to indicate that it will retain or preserve the data packets transferred in the earlier data transfer. Alternatively, if the second network device receives indication information #1 before receiving indication information #3, such as receiving indication information #1 from the source network device (indicating the discarding or ignoring of some or all data packets), then the second network device can determine, based on the data packets transferred in the earlier data transfer and indication information #1, which data packets to retain or preserve, or which data packets to send to the terminal device.

[0250] 8202, The target network device sends instruction information #3 to the source network device.

[0251] In step 8202, the target network device sends indication information #3 to the source network device. Upon receiving indication information #3, the source network device can determine that the second network device does not need to release the data packets transferred in the earlier data transfer. For example, the source network device can continue to transfer data packets to the second network device, and subsequently, the second network device can send the transferred data packets to the terminal device. The source network device can also send indication information #1 to the second network device, indicating that some or all data packets should be discarded or ignored.

[0252] Furthermore, the source network device can also forward the indication information #3 to the second network device. Based on this indication information #3, the second network device can determine that it does not need to release the data packets transferred in the earlier data transfer. The indication information #3 sent by the source network device to the second network device may be the same as or different from the indication information #3 received by the source network device from the target network device; this is not limited. For example, the indication information #3 sent by the source network device to the second network device may be different from the indication information #3 received by the source network device from the target network device. For instance, the indication information #3 received by the source network device from the target network device may indicate the use or retention of information related to the earlier data transfer of the second network device, while the indication information #3 sent by the source network device to the second network device may indicate the retention of the context of the terminal device in the second network device. In yet another example, the indication information #3 sent by the source network device to the second network device may be the same as the indication information #3 received by the source network device from the target network device. For example, the indication information #3 received by the source network device from the target network device is used to indicate the use or maintenance of early data transfer of the second network device, and the indication information #3 sent by the source network device to the second network device is also used to indicate the use or maintenance of early data transfer of the second network device.

[0253] The above is just a brief explanation. The specific procedures applicable to Method 800 will be detailed below. Figure 12-14 The illustrated examples are as follows.

[0254] In the embodiments of this application, if the network device configured for the terminal device after the switch is the same as the network device configured for the terminal device before the switch, the data transferred in the previous early data transfer can be used, thereby avoiding the need to transfer these data packets again in the early data transfer and reducing the transmission latency of these data packets.

[0255] Optionally, method 800 may also include step 830.

[0256] 830, After the source network device is determined to be switched, the network device configured for the terminal device includes the second network device.

[0257] One possible approach is for the target network device to send the identification information of the second network device to the source network device. Based on this identification information, the source network device determines whether the network device configured for the terminal device after the handover includes the second network device, or in other words, determines the network device from which data packets transferred earlier need to be retained. Using identification is simple and accurate. Furthermore, when multiple second network devices are involved—that is, when the N first network devices after the handover include multiple candidate network devices from before the handover (i.e., multiple second network devices)—using identification methods uses fewer resources.

[0258] For example, the source network device sends a handover request message to the target network device, and the target network device sends a handover request response message to the source network device, with the handover request response message carrying the identification information of the second network device. Alternatively, the identification information and indication information #3 of the second network device can be carried in the same signaling message.

[0259] The following example illustrates a scheme in which the identification information and indication information #3 of the second network device are carried in the same signaling.

[0260] For example, when the network device configured for the terminal device after the handover includes a second network device, the source network device receives a signaling message from the target network device. This signaling message includes indication information #3 and the identifier of the second network device. The indication information #3 is used to indicate the use of information related to the terminal device in the second network device. Based on this signaling message, the source network device determines that the network device configured for the terminal device after the handover includes the second network device. Furthermore, the signaling message may also include indication information indicating whether the second network device configured by the target network device for the terminal device is a candidate network device or a secondary network device.

[0261] For example, when the network devices configured for the terminal device after the handover include multiple second network devices, the source network device receives a signaling message from the target network device. This signaling message includes indication information #3 and identifiers of the multiple second network devices. The indication information #3 is used to indicate the use of information related to the terminal device from among the multiple second network devices. Based on the identifiers of the multiple second network devices included in the signaling message, the source network device determines that the network devices configured for the terminal device after the handover include these multiple second network devices. Furthermore, the signaling message may also include indication information indicating whether the second network device configured by the target network device for the terminal device is a candidate network device or a secondary network device.

[0262] For example, when the network devices configured for the terminal device after the handover include multiple second network devices, the source network device receives multiple signaling messages sent by the target network device. Each signaling message includes an indication message #3 and an identifier of a second network device. The indication message #3 indicates the use of information related to the terminal device from the second network device. Based on the identifiers of the multiple second network devices included in the signaling messages, the source network device determines that the network devices configured for the terminal device after the handover include these multiple second network devices. Furthermore, each signaling message may also include indication information indicating whether the second network device configured by the target network device for the terminal device is a candidate network device or a secondary network device.

[0263] It should be understood that the above is merely an illustrative example and is not intended to limit the scope of the application. Any scheme that enables the source network device to determine whether the network devices configured for the terminal device after the handover include the network devices before the handover is applicable to the embodiments of this application. For example, the target network device may send N identification information of first network devices to the source network device, and the source network device may determine whether the network devices configured for the terminal device after the handover include the network devices before the handover based on the identification information of the N first network devices.

[0264] Optionally, the target network device may receive information related to the terminal device from the second network device. For example, such as... Figure 8 As shown, method 800 may further include step 840.

[0265] 840. The target network device can receive information about the early data transfer from the source network device.

[0266] Therefore, the target network device can determine which data packets to be sent to the terminal device will be subsequently transferred to the second network device based on the information of the early data transfer, such as the data packets transferred in the early data transfer previously performed in the second network device, and / or the information of the data packets that the second network device can discard or ignore.

[0267] In addition, the target network device can also notify the second network device which early data transfer packets can be discarded, such as by sending indication information #1 to the second network device.

[0268] Optionally, the target network device can also obtain information about the network devices configured for the terminal device before the handover. Taking the second network device as an example, the information about the second network device configured for the terminal device before the handover may include, for example, the identification information of the second network device, and / or, the identification information of the terminal device in the second network device. This information about the network devices configured for the terminal device before the handover may be carried in a handover request message, i.e., when the source network device sends a handover request message to the target network device, the handover request message may include the information about the network devices configured for the terminal device before the handover.

[0269] Furthermore, the target network device can also determine whether the N configured first network devices include the network devices configured for the terminal device before the handover, based on the identification information of the network devices configured for the terminal device before the handover. For example, the target network device can determine whether the network devices before and after the handover are the same based on the network device identification.

[0270] In addition, after the target network device learns the information of the network devices configured for the terminal device before the switchover, it can decide which network devices to select to provide services to the terminal device based on this information. Alternatively, the target network device can also decide which candidate network devices to select based on this information. This can also make the most of the previously transmitted data, reduce transmission latency, and improve user experience.

[0271] Optionally, the target network device may also send the terminal device's identification information on the second network device to the second network device.

[0272] The above text combined Figure 7 and Figure 8 Methods for data transmission according to embodiments of this application are described respectively. It should be understood that methods 700 and 800 can be used alone or in combination, and there is no limitation thereto. For example, taking the combination of methods 700 and 800 as an example, the scheme shown in method 700 can be used for early data transfer before switching, and the scheme shown in method 800 can be used when it is determined that the network device needs to be switched.

[0273] To facilitate understanding, examples of different processes are provided for illustration.

[0274] First, combined Figures 9 to 11 A possible process applicable to the embodiment shown in method 700 is described.

[0275] Figure 9 This is a schematic diagram of a conditional PSCelladdition (CPA) process applicable to embodiments of this application. Figure 9 As shown, method 900 is illustrated primarily by taking the interaction between the terminal device, MN, candidate SN1, and candidate SN2 as examples. Figure 9 The method 900 shown may include the following steps.

[0276] 910, a conditional PSCell increment process is performed between MN and candidate SN.

[0277] like Figure 9 As shown, MN performs a conditional PSCell increment process (i.e., CPA process) with candidate SN1 and candidate SN2.

[0278] For example, MN sends SN addition request messages to each candidate SN. For instance, this SN addition request message may carry indication information to indicate that this SN addition request message is for conditional SN addition. Alternatively, for instance, regardless of whether it's a conditional SN addition or a conditional SN change, this SN addition request message is used to indicate that this SN addition request message is for conditional SN addition.

[0279] A candidate SN can send a response message to the MN in response to a SN addition request message, or it can send a confirmation message to the MN confirming the SN addition request message. For example, this confirmation message may carry indication information indicating that the confirmation message is a response to a conditional SN addition. For example, this confirmation message may also carry the radio configuration information of the corresponding candidate PSCell configured by the candidate SN for the terminal device.

[0280] The above is merely an illustrative example, and the embodiments of this application do not limit step 910. For example, step 910 may refer to existing technology or future methods.

[0281] It should be understood that, in the embodiments of this application, a single conditional SN increment process can correspond to one candidate PSCell, that is, a single SN increment request message and SN increment request confirmation message are for one candidate PSCell. Alternatively, a single conditional SN increment process can also correspond to multiple candidate PSCells, that is, a single SN increment request message and SN increment request confirmation message are for multiple candidate PSCells.

[0282] 920, MN sends CPA configuration information to the terminal device.

[0283] For example, MN sends an RRC reconfiguration message to the terminal device, which includes CPA configuration information.

[0284] CPA configuration information may include, for example, one or more of the following: trigger conditions configured by MN for each candidate PSCell, radio configuration information configured by candidate SN for the corresponding candidate PSCell for the terminal device, and radio configuration information of the MCG for each candidate PSCell configured by MN for the terminal device when the terminal device accesses each candidate PSCell. Trigger conditions indicate that the terminal device can access the candidate PSCell cell when the candidate PSCell cell meets certain conditions. Trigger conditions may, for example, be that the signal quality of the candidate PSCell meets certain conditions, such as the signal quality of the candidate PSCell being better than a certain threshold, or the signal quality of the candidate PSCell being better than the signal quality of the PCell by a certain threshold, or the signal quality of the PCell being lower than a certain threshold and the signal quality of the candidate PSCell being better than a certain threshold, etc.

[0285] Furthermore, when a terminal device selects a candidate PSCell that meets certain conditions as the final PSCell, the terminal device can use the radio configuration information corresponding to that candidate PSCell. If the CPA configuration includes the radio configuration information of the MCG corresponding to each candidate PSCell configured by MN for the terminal device, then the terminal device also uses the radio configuration information of the MCG corresponding to that candidate PSCell.

[0286] The above is merely an illustrative example, and the embodiments of this application do not limit step 920. For example, step 920 may refer to existing technology or future methods.

[0287] 930, the terminal device determines whether the candidate PSCell meets the triggering condition corresponding to the candidate PSCell in CPA.

[0288] For example, when a terminal device receives CPA configuration information from an MN, it determines whether the triggering conditions of the corresponding PSCell are met based on the candidate PSCells and their corresponding triggering conditions.

[0289] The above is merely an illustrative example, and the embodiments of this application do not limit step 930. For example, step 930 may refer to existing technology or future methods.

[0290] 940, MN sends indication message #1 to candidate SN, indicating to discard or ignore some or all of the data packets from the earlier data transfer.

[0291] like Figure 9 As shown, MN sends indication message #1 to candidate SN1, indicating that some or all of the data packets from the earlier data transfer should be discarded or ignored.

[0292] That is, in step 940, the MN sends indication information #1 to the candidate SN. This indication information #1 is used to indicate which early data transfer packets in the MN-terminated SCG bearer and / or MN-terminated split bearer are discarded or ignored.

[0293] In this embodiment of the application, for distinction, indication information #1 is used to indicate information used to indicate the discarding or ignoring of some or all data packets from the early data transfer.

[0294] For example, prior to step 940, the MN may perform early data forwarding of the SCG bearer terminated by the MN to a candidate SN (such as candidate SN1). In step 940, the MN sends indication information #1 to the candidate SN (such as candidate SN1) indicating which early data forwarding packets in the SCG bearer terminated by the MN should be discarded or ignored.

[0295] In another example, prior to step 940, the MN may perform an early data transfer of the split bearer terminated by the MN to a candidate SN (such as candidate SN1). In step 940, the MN sends indication information #1 to the candidate SN (such as candidate SN1) indicating which early data transfer packets in the split bearer terminated by the MN should be discarded or ignored.

[0296] As mentioned above, regarding the MN-terminated SCG bearer or the MN-terminated split bearer, early data transfer can also be called early data transfer, or other names, and its naming does not limit the scope of protection of the embodiments of this application. This application mainly uses early data transfer as an example for illustration.

[0297] The MN performs an early data transfer to the candidate SN for the MN-terminated SCG bearer or the MN-terminated split bearer. For these bearers (i.e., the MN-terminated SCG bearer or the MN-terminated split bearer), one possible implementation is that the early data transfer performed by the MN can be to send data packets to the SN in the form of PDCP PDUs.

[0298] One possible implementation is that the MN sends these PDCPPDUs to the candidate SN through the user plane interface between the MN and the candidate SN. For example, the MN sends these packets to the candidate SN via the General Packet Radio Service (GPRS) Tunneling Protocol User Plane (GTP-U) protocol.

[0299] In addition, during early data transfers, the sequence number (SN) corresponding to the data packet can also be carried. For example, the new radio user plane (NR-U) sequence number corresponding to the data packet can be carried in the extended header of the GTP-U. Generally, the MN assigns consecutive NR-U sequence numbers to each transferred data packet. By carrying the NR-U sequence number corresponding to the data packet, it can be determined which data packets have undergone early data transfer.

[0300] After an early data transfer has been performed, the MN can send indication information #1 to the candidate SN based on the current data being sent to the terminal device, indicating which early data transfer packets for the SCG bearer and / or the splitbearer terminated by the MN should be discarded or ignored.

[0301] The timing of sending indication information #1 is not limited. For example, indication information #1 can be sent if preset conditions are met. Preset conditions can be time-related limitations (such as periodic sending), data volume limitations (such as comparison of data volume with a threshold value or threshold range), or other limitations.

[0302] For example, in one possible scenario, the MN can periodically send indication information #1. In another possible scenario, when the amount of downlink data sent by the MN to the terminal device reaches a certain threshold, the MN sends indication information #1 to the candidate SN. In yet another possible scenario, after the downlink data sent by the MN to the terminal device is correctly received by the terminal device, the MN sends indication information #1 to the candidate SN.

[0303] Furthermore, there are no limitations on the form of the instruction message #1. One possible form is that the instruction message #1 can be in the form of one or more serial numbers.

[0304] One possible approach is that the instruction information #1 can be a sequence number, such as sequence number #A. For example, sequence number #A can be used to instruct the candidate SN to discard those previously transferred data packets (such as PDCP PDUs) whose corresponding sequence numbers are lower than sequence number #A (it can even discard the data packet corresponding to sequence number #A). That is, if the MN wants to instruct the candidate SN to discard or ignore data packets corresponding to sequence numbers lower than #A (or even indicate that the data packet corresponding to sequence number #A can be discarded), then the MN can instruct the candidate SN to send sequence number #A. If the candidate SN has not yet sent the data packets corresponding to sequence numbers lower than #A (or even the data packets corresponding to sequence number #A) to the terminal device, then the candidate SN will not send these data packets (i.e., data packets corresponding to sequence numbers lower than #A, or even the data packets corresponding to sequence number #A) to the terminal device. By way of example and not limitation, the candidate SN can discard these data packets (i.e., data packets corresponding to sequence numbers lower than #A, or even the data packets corresponding to sequence number #A), or it can simply ignore these data packets.

[0305] Another possible approach is that the indication information #1 can be multiple sequence numbers, such as a sequence number list. For example, this sequence number list could instruct the candidate SN to discard those packets corresponding to sequence numbers in the sequence number list of previously transferred packets (such as PDCP PDUs). In other words, the MN can indicate the sequence numbers corresponding to packets to be discarded or ignored. If the candidate SN has not yet sent the packets corresponding to the sequence numbers in the sequence number list to the terminal device, then the candidate SN will not send these packets (i.e., the packets corresponding to the sequence numbers in the sequence number list) to the terminal device. As an example and not a limitation, the candidate SN can either discard these packets (i.e., the packets corresponding to the sequence numbers in the sequence number list) or simply ignore them.

[0306] Another possible approach is that the indication information #1 can be multiple packets corresponding to blocks, along with the starting sequence number of each packet corresponding to the block and the number of packets in that block. Each block corresponds to packets with a sequence number of consecutive sequence numbers starting from that starting sequence number. For example, it could carry the number of downlink discarded blocks (DL discard number of blocks), the starting sequence number (SN) of each packet (e.g., NR PDCP PDU), and the size of each block (discarded block size). This information instructs the candidate SN to discard packets whose sequence numbers in previously transferred packets (e.g., PDCP PDUs) correspond to the sequence numbers in these blocks. In other words, MN can indicate the sequence numbers corresponding to the packets to be discarded or ignored. If the candidate SN has not yet sent the packets corresponding to these sequence numbers to the terminal device, then the candidate SN will not send these packets (i.e., the packets corresponding to these sequence numbers) to the terminal device. As an example and not a limitation, the candidate SN can discard these packets (i.e., the packets corresponding to these sequence numbers), or it can simply ignore them.

[0307] It should be understood that the above two methods are merely illustrative and are not intended to be limiting. For example, the MN can also indicate the sequence numbers corresponding to the reserved data packets to the candidate SN, and the candidate SN can discard or ignore data packets other than those data packets (i.e., the sequence numbers corresponding to the reserved data packets indicated by the MN).

[0308] It should also be understood that in future agreements, the naming used to indicate the same function as indication information #1 is applicable to the embodiments of this application. For example, indication information #1 may also belong to information from an earlier data transfer.

[0309] Optionally, the MN may also indicate the DRB corresponding to indication information #1 to the candidate SN. For example, the information provided by the MN to the candidate SN may carry a list of DRBs for the SCG bearer and / or the split bearer terminated by the MN. This list may include the DRB ID of each DRB, and may also include information indicating the downlink transfer packets that the candidate SN can discard, as indicated by indication information #1.

[0310] It should be understood that the above information (such as indication information #1, and / or the DRB corresponding to indication information #1, etc.) can be sent through the user plane between the MN and the candidate SN (such as being carried in the GTP-U protocol), or through the control plane between the MN and the candidate SN (such as the MN sending a message to the candidate SN, for example, the MN carrying the above information in an early status transfer message).

[0311] Alternatively, if the transmission is via the user plane between the MN and the candidate SN, since the GTP-U protocol tunnel established in the user plane is per bearer, the DRB ID does not need to be carried in any indication information #1.

[0312] Optionally, the MN may also send indication information #2 to the candidate SN, indicating that the MN can or supports early data transfer of the SCG beare or split bearer that the MN is terminating. For example, before the MN performs an early data transfer to the candidate SN, the MN sends indication information to the candidate SN, indicating that the MN can or supports early data transfer of one or more of the SCG beare or split bearer that the MN is terminating. For example, this indication information #2 can be sent through the control plane interface between the MN and the candidate SN, or through the user plane interface between the MN and the candidate SN, without limitation.

[0313] It should be understood that, Figure 9 In the example shown, the MN-terminated SCG bearer refers to the MN-terminated SCG bearer in the CPA configured by the network side for the terminal device. Figure 9 In the example shown, the MN-terminated split bearer refers to the MN-terminated split bearer in the CPA configured by the network side for the terminal device.

[0314] It should also be understood that the MN can send indication information #1 multiple times to the candidate SN. For example, the MN can periodically send indication information #1 to the candidate SN. In this way, the candidate SN can determine whether to discard or ignore the data packets indicated by each indication information #1 based on the multiple received indication information #1s. Alternatively, the candidate SN can also determine which data packets to discard or ignore based on the most recently received indication information #1. If the indication information #1 is a sequence number, such as the sequence number #A mentioned above, the candidate SN can determine whether to discard or ignore the data packets corresponding to sequence numbers lower than sequence number #A based on the most recently received indication information #1.

[0315] It should also be understood that, Figure 9 The example shown primarily illustrates the interaction between MN and candidate SN1, but is not intended to be limiting. For instance, early data transfer can also occur between MN and candidate SN2, and MN can send indication information #1 to candidate SN2 once or multiple times. Furthermore, after MN determines that the terminal device will access a candidate SN that meets the conditions, MN can perform early data transfer with that candidate SN and can also send indication information #1 to that candidate SN.

[0316] 950, terminal equipment accesses a candidate SN that meets the conditions.

[0317] When the terminal device determines that the triggering conditions of a candidate PSCell are met, the terminal device connects to the candidate PSCell. For example, the terminal device may perform a random connection process with a candidate PSCell. Figure 9 As shown, assuming the triggering condition of the candidate PSCell in candidate SN1 is met, the terminal device can access candidate SN1.

[0318] The above is merely an illustrative example, and the embodiments of this application do not limit step 950. For example, step 950 may refer to existing technology or future methods.

[0319] 960, the candidate SN sends downlink data to the terminal device.

[0320] Once the terminal device connects to the candidate SN, the candidate SN can send downlink data to the terminal device. For example, the candidate SN can send downlink data to the terminal device based on the early data transfer information. Alternatively, the candidate SN can send downlink data to the terminal device based on the early data transfer information and indication information #1.

[0321] The following examples, using MN-terminated SCG bearers or MN-terminated split bearers as examples, illustrate several possible scenarios.

[0322] One possible scenario is that after the terminal device connects to the candidate SN, for the SCG bearer or split bearer that terminates with the MN, the candidate SN can send downlink data to the terminal device based on the data transferred in the early stages of the MN data transfer.

[0323] Alternatively, in another possible scenario, after the terminal device connects to the candidate SN, for SCG bearers or split bearers that terminate with the MN, the candidate SN can also send downlink data to the terminal device based on the data from the early data transfer of the MN and indication information #1 (such as the most recently received indication information #1). For example, the candidate SN will not send data packets (such as PDCP PDUs) that are indicated to be discarded in indication information #1 (such as the most recently received indication information #1) to the terminal device; the candidate SN can discard these data packets or simply ignore them.

[0324] Alternatively, in another possible scenario, after the MN learns that the terminal device has connected to the candidate SN (e.g., the MN receives an indication from the terminal device that the terminal device has met the triggering conditions of the candidate PSCell; or after successfully connecting to the candidate SN, the candidate SN sends an indication of the terminal device's connection to the MN), the MN sends indication information #1 to the candidate SN. The candidate SN then sends downlink data to the terminal device based on the data transferred by the MN in the earlier data transfer and this indication information #1. For example, after the MN learns that the terminal device has connected to the candidate SN, for the SCG bearer and / or the split bearer terminated by the MN, the MN can send an indication information #1 to the candidate SN, indicating which early data transfer packets in the SCG bearer and / or the split bearer terminated by the MN should be discarded or ignored (same as in step 940).

[0325] The above text combined Figure 9 Steps 910-960 illustrated above provide a CPA process. It should be understood that these steps are merely illustrative and not intended to be strictly limited. Furthermore, the sequence numbers of the processes do not imply an order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0326] Figure 10 This is a schematic diagram of a conditional PSCell change (CPC) process triggered by an MN, applicable to embodiments of this application.

[0327] like Figure 10As shown, method 1000 is mainly illustrated by taking the interaction between the terminal device, MN, candidate SN1, candidate SN2, and source SN as an example. For distinction, the source SN is used to represent the SN currently configured by the terminal device. It should be understood that the source SN is a name given for distinction; for example, the source SN can also be written as the current SN, and its specific naming method does not limit the protection scope of the embodiments of this application. Figure 10 The method 1000 shown may include the following steps.

[0328] 1010, a CPC process is performed between MN and candidate SN.

[0329] In other words, a conditional PSCell change process is performed between MN and candidate SN. For example... Figure 10 As shown, MN undergoes a conditional PSCell change process (i.e., a CPC process) with candidate SN1 and candidate SN2.

[0330] For example, MN sends SN addition request messages to each candidate SN. For instance, this SN addition request message may carry indication information to indicate that the SN addition request message is for a conditional SN change. Alternatively, for instance, regardless of whether it's a conditional SN addition or a conditional SN change, the SN addition request message is used to indicate that the SN addition request message is for a conditional SN change.

[0331] A candidate SN can send a response message to the MN for a SN addition request message, such as a SN addition request confirmation message. For example, this SN addition request confirmation message may carry indication information to indicate that the confirmation message is a response to a change in the condition SN. For example, the SN addition request confirmation message may also carry the radio configuration information of the corresponding candidate PSCell configured by the candidate SN for the terminal device. For example, the radio configuration information of the corresponding candidate PSCell configured by the candidate SN for the terminal device is carried in the SN addition request confirmation message in the form of an RRC reconfiguration message configured by the candidate SN for the terminal device.

[0332] The above is merely an illustrative example, and the embodiments of this application do not limit step 1010. For example, step 1010 may refer to existing technology or future methods.

[0333] For example, method 1000 may also include step 1001.

[0334] 1001, MN can instruct the source SN, and the source SN can perform an early data transfer on the bearer terminated by the SN.

[0335] In other words, after step 1010, the MN can send an indication message to the source SN, instructing the source SN to perform early data transfer on the bearers that are terminated by the SN (here, the bearers that are terminated by the SN are the bearers before the CPC, that is, before the CPC, these bearers are the bearers that are terminated by the SN), thereby transferring the data packets in the source SN that are to be sent to the terminal device. Alternatively, the MN can send an indication message to the source SN, instructing the MN to trigger the CPC, so that the source SN can determine whether to perform early data transfer on the bearers that are terminated by the SN, that is, the source SN decides whether to perform early data transfer on the bearers that are terminated by the SN.

[0336] It should be understood that step 1001 is merely an example and is not intended to be limiting. For example, the source SN can send an indication message to the MN indicating that an early data transfer can be performed on the bearer of the terminated SN.

[0337] Before step 1001, method 1000 may also include step 1020.

[0338] 1020, MN sends CPC configuration information to the terminal device.

[0339] For example, MN sends an RRC reconfiguration message to the terminal device, which includes CPC configuration information.

[0340] CPC configuration information may include, for example, one or more of the following: trigger conditions configured by MN for each candidate PSCell, radio configuration information configured by candidate SN for the corresponding candidate PSCell for the terminal device, and radio configuration information of the MCG for each candidate PSCell configured by MN for the terminal device when the terminal device accesses each candidate PSCell. For the trigger conditions, please refer to the description in step 920 above; it will not be repeated here.

[0341] When a terminal device selects a candidate PSCell that meets the conditions as the final PSCell, the terminal device can use the radio configuration information corresponding to that candidate PSCell. If the CPC configuration includes radio configuration information for the MCG corresponding to each candidate PSCell configured for the terminal device, then the terminal device also uses the radio configuration information for the MCG corresponding to that candidate PSCell.

[0342] The above is merely an illustrative example, and the embodiments of this application do not limit step 1020. For example, step 1020 may refer to existing technology or future methods.

[0343] 1030, the terminal device determines whether the candidate cell meets the conditions.

[0344] In other words, the terminal device determines whether the candidate PSCell meets the conditions, and the PSCell changes the corresponding triggering condition.

[0345] For example, when a terminal device receives CPC configuration information from an MN, it determines whether the triggering conditions of the corresponding PSCell are met based on the candidate PSCells and their corresponding triggering conditions.

[0346] The above is merely an illustrative example, and the embodiments of this application do not limit step 1030. For example, step 1030 may refer to existing technology or future methods.

[0347] 1040, MN sends indication message #1 to candidate SN, indicating to discard or ignore some or all of the data packets from the earlier data transfer.

[0348] like Figure 10 As shown, MN sends indication message #1 to candidate SN1, indicating that some or all of the data packets from the earlier data transfer should be discarded or ignored.

[0349] That is, in step 1040, the MN sends indication information #1 to the candidate SN. This indication information #1 is used to indicate which early data transfer packets in the MN-terminated SCG bearer and / or MN-terminated split bearer are discarded or ignored.

[0350] For example, prior to step 1040, the MN may perform an early data transfer of the SCG bearer terminated by the MN to a candidate SN (such as candidate SN1). In step 1040, the MN sends indication information #1 to the candidate SN (such as candidate SN1) indicating which early data transfer packets in the SCG bearer terminated by the MN should be discarded or ignored.

[0351] In another example, prior to step 1040, the MN may perform an early data transfer of the split bearer terminated by the MN to a candidate SN (such as candidate SN1). In step 1040, the MN sends indication information #1 to the candidate SN (such as candidate SN1) indicating which early data transfer packets in the split bearer terminated by the MN should be discarded or ignored.

[0352] Optionally, for bearers that were previously terminated by the SN during the CPC process, these bearers become either split bearers terminated by the MN or SCG bearers terminated by the MN. The source SN can perform early data transfer to the MN according to step 1001. The MN can then perform early data transfer and indicate which early data transfer packets in the MN-terminated split bearers to discard or ignore, as described in step 1040. In this case, the MN can discard or ignore which early data transfer packets in the SN-terminated bearers based on the indication sent by the source SN. For example, the source SN might send some indication information to the MN, indicating which early data transfer packets in the SN-terminated bearers to discard or ignore. This indication information is similar to indication information #1, and the form of the early data transfer packets between the source SN and the MN can be a PDCP SDU. The MN can generate indication information #1 for the candidate SN based on the indication from the source SN.

[0353] Optionally, for bearers that were MN-terminated before CPC, if during CPC the bearers become MN-terminated split bearers or MN-terminated SCG bearers, then MN can generate instruction information #1 on its own.

[0354] Step 1040 is the same as step 940 in the previous CPA process, and will not be repeated here.

[0355] It should be understood that, Figure 10 In the example shown, the MN-terminated SCG bearer refers to the MN-terminated SCG bearer in the CPC configured for the terminal device on the network side. Figure 10 In the example shown, the MN-terminated split bearer refers to the MN-terminated split bearer in the CPC configured by the network side for the terminal device. These bearers may be SN-terminated MCG / SCG / Split bearers or MN-terminated MCG / SCG / Split bearers before the CPC triggered by the MN.

[0356] 1050, The terminal device accesses a candidate SN that meets the conditions.

[0357] When the terminal device determines that the triggering conditions of a candidate PSCell are met, the terminal device connects to the candidate PSCell. For example, the terminal device may perform a random connection process with a candidate PSCell. Figure 10 As shown, assuming the triggering condition of the candidate PSCell in candidate SN1 is met, the terminal device can access candidate SN1.

[0358] Step 1050 is the same as step 950 in the previous CPA process, and will not be repeated here.

[0359] 1060, the candidate SN sends downlink data to the terminal device.

[0360] Once the terminal device connects to the candidate SN, the candidate SN can send downlink data to the terminal device. For example, the candidate SN can send downlink data to the terminal device based on the early data transfer information. Alternatively, the candidate SN can send downlink data to the terminal device based on the early data transfer information and indication information #1.

[0361] Step 1060 is the same as step 960 in the previous CPA process, and will not be repeated here.

[0362] The above text combined Figure 10 Steps 1010-1060 illustrated above provide a case study of the CPC process triggered by MN. It should be understood that the above steps are merely illustrative and are not intended to be strictly limited. Furthermore, the sequence numbers of the above processes do not imply an order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0363] Figure 11 This is a schematic diagram of the SN-triggered CPC process applicable to embodiments of this application.

[0364] like Figure 11 As shown, method 1100 is mainly illustrated by taking the interaction between the terminal device, MN, candidate SN1, candidate SN2, and source SN as an example. For distinction, the source SN is used to represent the SN currently configured by the terminal device. It should be understood that the source SN is a name given for distinction; for example, the source SN can also be written as the current SN, and its specific naming method does not limit the protection scope of the embodiments of this application. Figure 11 The method 1100 shown may include the following steps.

[0365] 1110, A CPC process is performed between the source SN and the candidate SN.

[0366] In other words, a conditional PSCell modification process is performed between the source SN and the candidate SN. For example... Figure 11 As shown, MN performs a conditional PSCell change process (i.e., CPC process) with candidate SN1, candidate SN2 and source SN.

[0367] For example, the source SN sends an SN change request message to the MN. This SN change request message may, for instance, carry indication information indicating that the SN change request is for a conditional SN change. The SN change request message may also carry an identifier for a candidate SN.

[0368] The MN sends an SN addition request message to the candidate SN. For example, this SN addition request message may carry indication information to indicate that the SN addition request message is for a conditional SN change. Alternatively, for example, regardless of whether it's a conditional SN addition or a conditional SN change, the SN addition request message is used to indicate that the SN addition request message is for a conditional SN change.

[0369] A candidate SN can send a response message to the MN for a SN addition request message, such as a SN addition request confirmation message. For example, this SN addition request confirmation message may carry indication information to indicate that the confirmation message is a response to a change in the condition SN. For example, the SN addition request confirmation message may also carry the radio configuration information of the corresponding candidate PSCell configured by the candidate SN for the terminal device. For example, the radio configuration information of the corresponding candidate PSCell configured by the candidate SN for the terminal device may be carried in the SN addition request confirmation message in the form of an RRC reconfiguration message configured by the candidate SN for the terminal device.

[0370] The above is merely an illustrative example, and the embodiments of this application do not limit step 1110. For example, step 1110 may refer to existing technology or future methods.

[0371] For example, method 1100 may also include step 1101.

[0372] 1101, MN can instruct the source SN, and the source SN can perform an early data transfer on the bearer terminated by the SN.

[0373] In other words, after step 1010, the MN can send an indication message to the source SN, instructing the source SN to perform early data transfer on the bearers that are terminated by the SN (here, the bearers that are terminated by the SN are the bearers before the CPC, that is, before the CPC, these bearers are the bearers that are terminated by the SN), thereby transferring the data packets in the source SN that are to be sent to the terminal device. Alternatively, the MN can send an indication message to the source SN, instructing the MN to trigger the CPC, so that the source SN can determine whether to perform early data transfer on the bearers that are terminated by the SN, that is, the source SN decides whether to perform early data transfer on the bearers that are terminated by the SN.

[0374] It should be understood that step 1101 is merely an example and is not intended to be limiting. For example, the source SN can send an indication message to the MN indicating that an early data transfer can be performed on the bearer of the terminated SN.

[0375] Before step 1101, method 1100 may also include step 1120.

[0376] At 1120, MN sends CPC configuration information to the terminal device.

[0377] Step 1120 is the same as step 1020 in the CPC triggered by MN above, and will not be repeated here.

[0378] 1130, the terminal device determines whether the candidate cell meets the conditions.

[0379] In other words, the terminal device determines whether the candidate PSCell meets the conditions, and the PSCell changes the corresponding triggering condition.

[0380] Step 1130 is the same as step 1030 in the CPC triggered by MN above, and will not be repeated here.

[0381] 1140, MN sends indication message #1 to candidate SN, indicating to discard or ignore some or all of the data packets from the earlier data transfer.

[0382] That is, in step 1140, the MN sends indication information #1 to the candidate SN. This indication information #1 is used to indicate which early data transfer packets in the MN-terminated SCG bearer and / or MN-terminated split bearer are discarded or ignored.

[0383] For example, prior to step 1140, the MN may perform an early data transfer of the SCG bearer terminated by the MN to a candidate SN (such as candidate SN1). In step 1140, the MN sends indication information #1 to the candidate SN (such as candidate SN1) indicating which early data transfer packets in the SCG bearer terminated by the MN should be discarded or ignored.

[0384] In another example, prior to step 1140, the MN may perform an early data transfer of the split bearer terminated by the MN to a candidate SN (such as candidate SN1). In step 1140, the MN sends indication information #1 to the candidate SN (such as candidate SN1) indicating which early data transfer packets in the split bearer terminated by the MN should be discarded or ignored.

[0385] Optionally, for bearers that were previously terminated by the SN during the CPC process, these bearers become either split bearers terminated by the MN or SCG bearers terminated by the MN. The source SN will perform early data transfer to the MN according to step 1101. The MN can then perform early data transfer and indicate which early data transfer packets in the MN-terminated split bearers to discard or ignore, as described in step 1140. In this case, the MN can discard or ignore which early data transfer packets in the SN-terminated bearers based on the indication sent by the source SN. For example, the source SN might send some indication information to the MN, indicating which early data transfer packets in the SN-terminated bearers to discard or ignore. This indication information is similar to indication information #1, and the form of the early data transfer packets between the source SN and the MN could be a PDCP SDU. The MN can generate indication information #1 for the candidate SN based on the indication from the source SN.

[0386] Optionally, for bearers that were MN-terminated before CPC, if during CPC the bearers become MN-terminated split bearers or MN-terminated SCG bearers, then MN can generate instruction information #1 on its own.

[0387] Step 1140 is the same as step 1040 in the CPC triggered by MN above, and will not be repeated here.

[0388] 1150, The terminal device accesses a candidate SN that meets the conditions.

[0389] When the terminal device determines that the triggering conditions of a candidate PSCell are met, the terminal device connects to the candidate PSCell. For example, the terminal device may perform a random connection process with a candidate PSCell. Figure 11 As shown, assuming the triggering condition of the candidate PSCell in candidate SN1 is met, the terminal device can access candidate SN1.

[0390] Step 1150 is the same as step 1050 in the CPC triggered by MN above, and will not be repeated here.

[0391] 1160, the candidate SN sends downlink data to the terminal device.

[0392] Step 1160 is the same as step 1060 in the CPC triggered by MN above, and will not be repeated here.

[0393] The above text combined Figure 11Steps 1110-1160 illustrated above provide an example of the CPC process triggered by the SN. It should be understood that the above steps are merely illustrative and are not intended to be strictly limited. Furthermore, the sequence numbers of the above processes do not imply an order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0394] The above text combined Figures 9 to 11 The following describes a possible process applicable to the embodiment shown in method 700. Based on the above scheme, for the SCG bearer terminated by the MN and / or the split bearer terminated by the MN, the MN can perform early data transfer to the SN. Furthermore, the MN can also send indication information #1 to the SN, indicating which early data transfer packets to discard or ignore. Thus, when the terminal device accesses the candidate PSCell, the candidate PSCell can send the downlink data of these bearers to the terminal device, thereby reducing the transmission latency of the downlink data in these bearers.

[0395] Below, in conjunction with Figures 12 to 14 A possible process applicable to the embodiment shown in method 800 is described.

[0396] Figure 12 This is a schematic flowchart illustrating a scenario applicable to embodiments of this application where CPAC is configured before the switch and then an MN switch occurs.

[0397] like Figure 12 As shown, method 1200 is illustrated primarily using the interaction between the terminal device, the source MN, candidate SN1, candidate SN2, and the target MN as examples. For distinction, the source MN represents the MN before the switch, and the target MN represents the MN after the switch. It should be understood that the source MN and target MN are names used for distinction, and their specific naming conventions do not limit the scope of protection of the embodiments of this application. Figure 12 The method 1200 shown may include the following steps.

[0398] 1210, Configure CPAC for terminal devices on the network side.

[0399] The embodiments of this application do not limit step 1210. For example, reference can be made to the descriptions of steps 910 and 920 above, as well as the descriptions of steps 1010 and 1020, and steps 1110 and 1120. Step 1210 can refer to existing technology or future embodiments, which will not be described here.

[0400] 1220, the source MN sends a handover request message to the target MN.

[0401] The source MN decides to switch the terminal device to the target MN and sends a handover request message to the target MN. The handover request message may include one or more of the following: the identifier of the candidate SN, and the identifier of the terminal device on the candidate SN. The identifier of the terminal device on the candidate SN may, for example, be an identifier assigned to the terminal device by the candidate SN in the control plane interface established between the MN and the candidate SN, such as an XnAP ID or X2AP ID. Optionally, the above information (i.e., the identifier of the candidate SN and the identifier of the terminal device on the candidate SN) can be referred to as the context reference information of the terminal device on the candidate SN. It should be noted that this information is specific to each candidate SN; that is, the handover request message carries the above information of the terminal device on each candidate SN.

[0402] It should be understood that the above example, which uses the context reference information of the terminal device in the candidate SN carried in the handover request message, is provided as an example and is not intended to be limiting. For example, the context reference information of the terminal device in the candidate SN can also be sent separately to the target MN.

[0403] At 1230, the target MN sends an SN addition request message to the SN.

[0404] like Figure 12 As shown, the target MN can send SN increase request messages to candidate SN1 and candidate SN2.

[0405] The following explanation will be provided using several scenarios.

[0406] Scenario 1: A scenario where the system is CPA before and after the switch.

[0407] The target MN decides to configure CPA for the terminal device.

[0408] If the target MN decides to configure the same candidate SN as the candidate SN before the handover, that is, the target MN decides to keep one or more candidate SNs, the target MN sends an SN establishment request message to the candidate SN, which carries the identifier of the terminal device in the candidate SN before the handover.

[0409] For example, the target MN can determine whether the candidate SN before and after the handover is the same based on the identifier of the candidate SN sent by the source MN (such as the identifier of the candidate SN carried in the handover request message sent by the source MN).

[0410] It should be understood that, in the case of multiple candidate SNs, the target MN can be judged separately.

[0411] Scenario 2: The scenario where the character is CPA before the switch and DC after the switch.

[0412] The target MN decides to configure a DC for the terminal device, that is, to configure an SN for the terminal device (at this time, it is not called a candidate SN, but can be called an SN or a target SN).

[0413] If the target MN decides to configure the same SN as the candidate SN before the handover, that is, the target MN decides to use a certain candidate SN as the configured SN, the target MN sends an SN establishment request message to that SN, which carries the identifier of the terminal device in the candidate SN before the handover.

[0414] For example, the target MN can determine whether the SN before and after the handover is the same based on the identifier of the candidate SN sent by the source MN (such as the identifier of the candidate SN carried in the handover request message sent by the source MN).

[0415] It should be understood that when multiple SNs are configured, the target MN can be judged separately.

[0416] Scenario 3: The scenario is CPC before the switch and CPC after the switch.

[0417] (1) For a scenario where CPC is triggered by MN before the switch and CPC is triggered by MN after the switch.

[0418] The target MN determines the CPC triggered by the MN for the terminal device.

[0419] If the target MN decides to configure the same candidate SN as the candidate SN before the handover, that is, the target MN decides to keep one or more candidate SNs, the target MN sends an SN establishment request message to the candidate SN, which carries the identifier of the terminal device in the candidate SN before the handover.

[0420] For example, the target MN can determine whether the candidate SN before and after the handover is the same based on the identifier of the candidate SN sent by the source MN (such as the identifier of the candidate SN carried in the handover request message sent by the source MN).

[0421] It should be understood that, in the case of multiple candidate SNs, the target MN can be judged separately.

[0422] (2) For scenarios where CPC is triggered by SN before the switch and is triggered by SN after the switch.

[0423] The target MN sends an SN establishment request message to the target SN after the handover (i.e., the SN that triggered CPC after the handover). This SN establishment request message may carry the identifier of the candidate SN before the handover. In addition, the SN establishment request message may also carry the identifier of the terminal device in each candidate SN (one or more candidate SNs). The SN triggers CPC. If the candidate SN determined by the target SN is the same as the candidate SN before the handover, then the following two situations may occur.

[0424] In one possible scenario, if the target SN obtains the identifier of the terminal device in each candidate SN (one or more candidate SNs) from the target MN, taking one of the candidate SNs as an example, the target SN sends the identifier of the terminal device in that candidate SN to the candidate SN. For example, the target SN directly sends the identifier of the terminal device in that candidate SN to the candidate SN; or the target MN may send the identifier of the terminal device in that candidate SN to the candidate SN (e.g., the target SN sends it to the target MN first, and then the target MN sends it to the candidate SN).

[0425] Another possible scenario is that if the target SN does not obtain the identifier of the terminal device in each candidate SN (one or more candidate SNs) from the target MN, taking one of the candidate SNs as an example, the target SN sends the identifier of the candidate SN to the target MN. The target MN obtains the identifier of the terminal device in the candidate SN before the handover based on the identifier of the candidate SN, and then sends the identifier of the terminal device in the candidate SN to the candidate SN.

[0426] It should be understood that, in the case of multiple candidate SNs, the target MN can be judged separately.

[0427] (3) For a scenario where the CPC was triggered by SN before the switch and was triggered by MN after the switch.

[0428] The target MN determines the CPC triggered by the MN for the terminal device.

[0429] If the target MN decides to configure the same candidate SN as the candidate SN before the handover, that is, the target MN decides to keep one or more candidate SNs, the target MN sends an SN establishment request message to the candidate SN, which carries the identifier of the terminal device in the candidate SN before the handover.

[0430] For example, the target MN can determine whether the candidate SN before and after the handover is the same based on the identifier of the candidate SN sent by the source MN (such as the identifier of the candidate SN carried in the handover request message sent by the source MN).

[0431] It should be understood that, in the case of multiple candidate SNs, the target MN can be judged separately.

[0432] (4) For a scenario where the CPC was triggered by MN before the switch and was triggered by SN after the switch.

[0433] The target MN sends an SN establishment request message to the target SN after the handover (i.e., the SN that triggered CPC after the handover). This SN establishment request message may carry the identifier of the candidate SN before the handover. In addition, the SN establishment request message may also carry the identifier of the terminal device in each candidate SN (one or more candidate SNs). The SN triggers CPC. If the candidate SN determined by the target SN is the same as the candidate SN before the handover, then the following two situations may occur.

[0434] In one possible scenario, if the target SN obtains the identifier of the terminal device in each candidate SN (one or more candidate SNs) from the target MN, taking one of the candidate SNs as an example, the target SN sends the identifier of the terminal device in that candidate SN to the candidate SN. For example, the target SN directly sends the identifier of the terminal device in that candidate SN to the candidate SN; or the target MN may send the identifier of the terminal device in that candidate SN to the candidate SN (e.g., the target SN sends it to the target MN first, and then the target MN sends it to the candidate SN).

[0435] Another possible scenario is that if the target SN does not obtain the identifier of the terminal device in each candidate SN (one or more candidate SNs) from the target MN, taking one of the candidate SNs as an example, the target SN sends the identifier of the candidate SN to the target MN. The target MN obtains the identifier of the terminal device in the candidate SN before the handover based on the identifier of the candidate SN, and then sends the identifier of the terminal device in the candidate SN to the candidate SN.

[0436] It should be understood that the above example uses one candidate SN as an illustration. In the case of multiple candidate SNs, the target MN can be judged separately.

[0437] Scenario 4: The scenario where CPC was used before the switch and CPA was used after the switch.

[0438] The target MN decides to configure CPA for the terminal device.

[0439] If the target MN decides to configure the same candidate SN as the candidate SN before the handover, that is, the target MN decides to keep one or more candidate SNs, the target MN sends an SN establishment request message to the candidate SN, which carries the identifier of the terminal device in the candidate SN before the handover.

[0440] For example, the target MN can determine whether the candidate SN before and after the handover is the same based on the identifier of the candidate SN sent by the source MN (such as the identifier of the candidate SN carried in the handover request message sent by the source MN).

[0441] It should be understood that, in the case of multiple candidate SNs, the target MN can be judged separately.

[0442] The above solution can be applied, for example, to a scenario where CPC is triggered by MN before the switch and becomes CPA after the switch, or it can be applied to a scenario where CPC is triggered by SN before the switch and becomes CPA after the switch.

[0443] Scenario 5: The scene before the switch is CPC, and after the switch is DC.

[0444] The target MN decides to configure a DC for the terminal device, that is, to configure an SN for the terminal device (at this time, it is not called a candidate SN, but can be called an SN or a target SN).

[0445] If the target MN decides to configure the same SN as the candidate SN before the handover, that is, the target MN decides to use a certain candidate SN as the configured SN, the target MN sends an SN establishment request message to that SN, which carries the identifier of the terminal device in the candidate SN before the handover.

[0446] For example, the target MN can determine whether the SN before and after the handover is the same based on the identifier of the candidate SN sent by the source MN (such as the identifier of the candidate SN carried in the handover request message sent by the source MN).

[0447] It should be understood that when multiple SNs are configured, the target MN can be judged separately.

[0448] The above scheme can be applied, for example, to a scenario where CPC is triggered by MN before the switch and becomes DC after the switch, or it can also be applied to a scenario where CPC is triggered by SN before the switch and becomes DC after the switch.

[0449] The above five scenarios illustrate how the target MN sends an SN addition request message to the SN. It should be understood that adjustments can be made adaptively according to the specific circumstances of each scenario.

[0450] 1240, the target MN sends a switch request response message to the source MN.

[0451] In addition, the target MN can also send instruction information #3 to the source MN to indicate whether to use or retain information related to the terminal device in the candidate SN.

[0452] The information related to the terminal device in the candidate SN may include one or more of the following: the context of the terminal device in the candidate SN, and information about previous data transfers performed by the candidate SN.

[0453] Optionally, the target MN can also send an indication to the source MN of which candidate SNs' contexts to retain or which candidate SNs' earlier data transfers to retain, such as by carrying the identifiers of the candidate SNs. For example, the indication information #3 or the handover request response message carries the identifiers of one or more candidate SNs, thereby indicating whether to retain the contexts of the terminal devices in those one or more candidate SNs or to indicate whether to retain the earlier data transfers to retain those one or more candidate SNs.

[0454] Instruction message #3 can be included in the handover request response message or sent separately; there is no limitation on this.

[0455] 1250, the source MN sends an SN release request message to the candidate SN.

[0456] like Figure 12 As shown, the target MN can send SN release request messages to candidate SN1 and candidate SN2.

[0457] In addition, the source MN can also send indication information #3 to the candidate SN to indicate whether to use or retain information related to the terminal device in the candidate SN.

[0458] Instruction message #3 can be included in the SN release request message or sent separately; there is no limitation on this.

[0459] 1260, information indicating the early data transfer of candidate SNs from source MN to target MN.

[0460] Optionally, the source MN sends information about the early data transfer of each candidate SN to the target MN.

[0461] Information regarding early data transfers of the candidate SN may include, for example, one or more of the following: which packets the source MN has already transferred to the candidate SN (e.g., indicated by a PDCP SN or NR-U sequence number), and which early data transfer packets the candidate SN may discard. Optionally, the target MN may subsequently notify the candidate SN which early data transfer packets may be discarded. It should be understood that this may include early data transfers of the bearer to which the SN is terminated.

[0462] The following explanation will be provided using several scenarios.

[0463] Scenario 1: A scenario where the system is CPA before and after the switch.

[0464] In this scenario, the source MN can send information about the early data transfer of the candidate SN to the target MN.

[0465] In this scenario, the source MN can transfer data in its bearer to the target MN. For example, it can transfer downlink data packets that have not yet been correctly received by the terminal device to the target MN, or it can transfer uplink data packets received out of order from the terminal device to the target MN.

[0466] Scenario 2: The scenario where the character is CPA before the switch and DC after the switch.

[0467] In this scenario, at least the following two implementation schemes can be included.

[0468] Option 1: The source MN continues to transfer early data to the candidate SN.

[0469] Under this scheme, the source MN does not need to send early data transfer information of the candidate SN to the target MN. After the source MN has transferred all the data packets corresponding to the bearer before the end marker received from the core network to the candidate SN, the source MN can send an indication message #4 to the candidate SN, indicating that all the data packets of the corresponding bearer have been transferred to the candidate SN. For example, this indication message #4 can be a user plane indication, such as an end marker. Alternatively, this indication message #4 can also be a control plane indication, that is, the control plane sends this indication message #4 to the candidate SN. Under this scheme, the candidate SN before the handover is the SN after the handover.

[0470] In this embodiment of the application, for distinction, indication information #4 is used to indicate that the corresponding data packets have been transferred to the candidate SN. The form of the indication is not limited; it can be indicated by the specific content in indication information #4 or by the action of sending indication information #4.

[0471] Furthermore, the source MN can send indication information #4 directly to the candidate SN, or it can send indication information #4 through the target MN. Once the candidate SN (which is also the SN after the handover in this scenario) receives indication information #4, it can begin sending the new data packets corresponding to the bearer, which it received directly from the core network, to the terminal device. In this scheme, the candidate SN can use the early data transfer packets previously received from the source MN as the data to be sent to the terminal device after the handover, thus avoiding the latency caused by the source MN transferring data packets to the target MN and then the target MN sending them to the SN.

[0472] Option 2: The source MN stops transferring data to the candidate SN.

[0473] Under this scheme, the source MN can send information about the early data transfer of the candidate SN to the target MN.

[0474] In this scheme, the source MN can transfer the data packets corresponding to the bearer received from the core network to the target MN. For example, for a bearer that terminates after the handover and is terminated by the SN, the source MN can transfer the data packets corresponding to the bearer received from the core network to the target MN, which then forwards them to the SN. Similarly, for an SCG bearer or a splitbearer that terminates after the handover and is terminated by the MN, the source MN can transfer the data packets corresponding to the bearer received from the core network to the target MN, which then processes them (e.g., changes from a PDCP SDU to a PDCP PDU) and sends them to the SN. In this scheme, the SN before the handover is the SN after the handover.

[0475] It should be understood that the above two schemes are merely illustrative and are not intended to be limiting. For example, the source MN can continue to transfer some data packets to the candidate SN and send the remaining data packets to the SN through the target MN.

[0476] Scenario 3: The scenario is CPC before the switch and CPC after the switch.

[0477] Scenario 3 is similar to Scenario 1 (i.e., the scenario where CPA is used before and after the handover). For example, in Scenario 3, the source MN can transfer data in its bearer to the target MN. For instance, it can transfer downlink data packets that have not yet been correctly received by the terminal device to the target MN, or transfer uplink data packets received out of order from the terminal device to the target MN.

[0478] Furthermore, in Scenario 3, there are no restrictions on the device that triggers the CPC. For example, Scenario 3 could be a scenario where the CPC was triggered by MN before the handover and is triggered by MN after the handover. Or, Scenario 3 could be a scenario where the CPC was triggered by SN before the handover and is triggered by SN after the handover. Or, Scenario 3 could be a scenario where the CPC was triggered by MN before the handover and is triggered by SN after the handover. Or, Scenario 3 could be a scenario where the CPC was triggered by SN before the handover and is triggered by MN after the handover.

[0479] Scenario 4: The scenario where CPC was used before the switch and CPA was used after the switch.

[0480] In this scenario, the source MN can send information about the early data transfer of the candidate SN to the target MN.

[0481] In this scenario, the source MN can transfer data in its bearer to the target MN. For example, it can transfer downlink data packets that have not yet been correctly received by the terminal device to the target MN, or it can transfer uplink data packets received out of order from the terminal device to the target MN.

[0482] In Scenario 4, there are no restrictions on the device that triggers the CPC. For example, Scenario 4 could be a CPC triggered by MN before the handover and a CPC triggered by CPA after the handover. Or, Scenario 4 could be a CPC triggered by SN before the handover and a CPC triggered by CPA after the handover.

[0483] Scenario 5: The scene before the switch is CPC, and after the switch is DC.

[0484] (1) For early data transfer between the source MN and the candidate SN before the handover, such as the early data transfer between the bearer of the source MN that terminates in the source MN and the bearer of the candidate SN that terminates in the CPC (i.e. before the handover, the data packets on the bearer of the MN that terminates in the CPC are transferred to the data packets of the bearer of the SN that terminates in the CPC).

[0485] One possible solution is to adopt solution 1 in scenario 2 above; another possible solution is to adopt solution 2 in scenario 2 above.

[0486] (2) For early data transfer between the source SN and the candidate SN before the handover, such as the early data transfer between the source SN and the candidate SN, which is the early data transfer between the bearer of the SN termination in the source SN and the bearer of the SN termination in the candidate SN in the CPC (i.e. before the handover, the data packets on the bearer of the SN termination in the source SN before the CPC are transferred to the data packets on the bearer of the SN termination in the candidate SN in the CPC).

[0487] One possible approach is for the source SN to continue data transfer to the candidate SN. In this approach, the source MN does not need to send early data transfer information about the candidate SN to the target MN. After the source SN has transferred all the data packets corresponding to the bearer up to the end marker received from the core network to the candidate SN, the source SN can send an indication message #4 to the candidate SN, indicating that all the data packets corresponding to the bearer have been transferred to the candidate SN. For example, this indication message #4 could be a user plane indication, such as an end marker. Alternatively, this indication message #4 could also be a control plane indication, i.e., sent to the candidate SN via the control plane. Furthermore, the source SN can send this indication message #4 directly to the candidate SN, or it can be sent to the candidate SN through the target MN. After receiving this indication message #4, the candidate SN can then send the new data packets corresponding to the bearer received from the core network to the terminal device.

[0488] Another possible solution is for the source SN to stop transferring data to the candidate SN. In this solution, the source MN can send early data transfer information about the candidate SN to the target MN. Alternatively, the source SN can transfer the data packets received from the core network corresponding to the data carrier to the target MN, which then forwards them to the SN.

[0489] It should be understood that in Scenario 5, there are no restrictions on the device that triggers the CPC. For example, Scenario 5 could be a scenario where the CPC was triggered by MN before the handover and by DC after the handover. Or, Scenario 5 could be a scenario where the CPC was triggered by SN before the handover and by DC after the handover.

[0490] Based on the above scheme, the target MN can obtain relevant information about the candidate SNs configured on the network side before the handover (such as the identifier of the candidate SN and the identifier of the terminal device on the candidate SN). The target MN can send the identifier of the terminal device on the candidate SN to the candidate SN. Therefore, early data transfer in CPAC is performed before the handover, and after the handover, the network side can continue to utilize the data transferred in the previous early data transfer. If CPAC is still configured after the handover, early data transfer is not required for this data. If DC is configured after the handover, normal data transfer (i.e., the traditional data transfer between the bearer terminated by the MN and the bearer terminated by the SN) is not required for this data.

[0491] The above text combined Figure 12 Steps 1210-1260 illustrate a scenario where CPAC is configured before the switchover and then an MN switchover occurs. It should be understood that the above steps are merely illustrative and are not strictly limited. Furthermore, the sequence numbers of the above processes do not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0492] Figure 13 This is a schematic flowchart illustrating a scenario applicable to embodiments of this application where CPC is configured before the switch and then SN switch occurs.

[0493] like Figure 13 As shown, method 1300 is mainly illustrated by taking the interaction between the terminal device, MN, source SN, candidate SN1, candidate SN2, and target SN as an example. For distinction, the source SN represents the SN before the handover, and the target SN represents the SN after the handover. It should be understood that the source SN and target SN are names used for distinction, and their specific naming method does not limit the protection scope of the embodiments of this application. Figure 13 The method 1300 shown may include the following steps.

[0494] 1310, The network side configures CPC for the terminal device.

[0495] The embodiments of this application do not limit step 1310. For example, reference can be made to the descriptions of steps 910 and 920 above, as well as the descriptions of steps 1010 and 1020, or steps 1110 and 1120. Step 1310 can refer to existing technology or future embodiments, which will not be described here.

[0496] 1320, The source SN or MN sends relevant information about the candidate SN configured on the network side before the handover to the target SN.

[0497] Information related to the candidate SN may include one or more of the following: the identifier of the candidate SN configured on the network side before the handover, and the identifier of the terminal device on the candidate SN.

[0498] It should be understood that any method that enables the target SN to learn about the relevant information of the candidate SN configured on the network side before the handover falls within the protection scope of the embodiments of this application. For example, it could be as follows: Figure 13 The information shown is sent from the source SN, or it could be sent in other ways (such as forwarding through the source MN), and there are no restrictions on this.

[0499] The following explanation will be provided using several scenarios.

[0500] Scenario A: Before the switch, CPC is triggered by MN; after the switch, CPC is triggered by SN.

[0501] When the source SN triggers an SN switch, for example, when the source SN sends an SN change request message to the MN, the SN change request message may carry the identifier of the target SN.

[0502] After receiving an SN change request message from the source SN, the MN can send relevant information about the candidate SN to the target SN (such as the identifier of the candidate SN before the handover and the identifier of the terminal device on the candidate SN). For example, after receiving an SN change request message from the source SN, the MN can send an SN addition request message to the target SN, which can carry relevant information about the candidate SN.

[0503] MN triggers SN switching, for example, MN sends an SN addition request message to the target SN, and the SN addition request message can carry relevant information about the candidate SN.

[0504] Scenario B is a scenario where CPC is triggered by SN before the switch and CPC is triggered by SN after the switch.

[0505] When a source SN triggers a handover, for example, by sending an SN change request message to the MN, this message may carry information that the source SN is sending to the target SN (such as information about candidate SNs). After receiving the SN change request message from the source SN, the MN can send information about candidate SNs to the target SN (such as the identifier of the candidate SN before the handover and the identifier of the terminal device on the candidate SN). For instance, after receiving the SN change request message from the source SN, the MN can send an SN addition request message to the target SN, which may carry information about candidate SNs.

[0506] In other words, in scenario B, the source SN can first send relevant information about the candidate SN to the MN (such as the identifier of the candidate SN before the handover and the identifier of the terminal device in the candidate SN), and then the MN sends the relevant information about the candidate SN to the target SN (for example, carried in the SN addition request message).

[0507] MN triggers SN switching, for example, MN sends an SN addition request message to the target SN, and the SN addition request message can carry relevant information about the candidate SN.

[0508] Scene C is a scene where MN triggers CPC before the switch and DC after the switch.

[0509] When a source MN triggers a handover to the target SN, for example, the source MN sends relevant information about the candidate SN (such as the identifier of the candidate SN before the handover and the identifier of the terminal device on the candidate SN). For instance, the MN sends a SN addition request message to the target SN, which may carry relevant information about the candidate SN.

[0510] Scenario D is a scenario where the CPC is triggered by SN before the switch and becomes DC after the switch.

[0511] When a source SN triggers a SN switch, for example, when the source SN sends a SN change request message to the MN, the SN change request message can carry the identifier of the target SN and relevant information about the candidate SN.

[0512] After receiving a SN change request message from the source SN, the MN can send a SN addition request message to the target SN. This SN addition request message can carry relevant information about the candidate SN.

[0513] When the source MN triggers the SN switch, the solution is similar to that in scenario C, and will not be elaborated here.

[0514] The above describes how the target SN obtains relevant information about the candidate SNs configured on the network side before the handover, based on four scenarios. It should be understood that adjustments can be made adaptively according to the specific circumstances of each scenario. Any scheme that enables the target SN to ultimately obtain relevant information about the candidate SNs configured on the network side before the handover is applicable to the embodiments of this application.

[0515] 1330, the target SN sends the terminal device's identification information on the candidate SN to the candidate SN.

[0516] like Figure 13 As shown, the target SN can send the terminal device's identification information in the candidate SN to candidate SN1 and candidate SN2.

[0517] The following explanation will be provided using several scenarios.

[0518] Scenario A: Before the switch, CPC is triggered by MN; after the switch, CPC is triggered by SN.

[0519] The target SN receives relevant information about the candidate SN sent by the MN. When the target SN decides to trigger CPC, and the candidate SN is the same as the candidate SN before the handover (e.g., based on the relevant information about the candidate SN sent by the MN, it is determined that the candidate SN is the same as the candidate SN before the handover), the target SN can send information to the candidate SN, which may carry the identifier of the terminal device on the candidate SN.

[0520] Optionally, the target SN may also send indication information #3 to the MN. This indication information #3 is used to indicate the use or retention of information related to the terminal device in the candidate SN (e.g., it may include one or more of the following: the context of the terminal device in the candidate SN, and previous data transfers performed by the candidate SN). The indication information #3 may be carried in the same message as the identifier of the terminal device in the candidate SN, or it may be sent separately, without limitation.

[0521] After receiving instruction message #3, MN can send instruction message #3 to candidate SN, such as sending an SN release request message to candidate SN, which carries instruction message #3.

[0522] Scenario B is a scenario where CPC is triggered by SN before the switch and CPC is triggered by SN after the switch.

[0523] The target SN receives relevant information about the candidate SN from the source SN. When the target SN decides to trigger CPC, and the candidate SN is the same as the candidate SN before the handover (e.g., based on the relevant information about the candidate SN sent by the MN, it is determined that the candidate SN is the same as the candidate SN before the handover), the target SN can send information to the candidate SN, which may carry the identifier of the terminal device on the candidate SN.

[0524] Optionally, the target SN may also send indication information #3 to the MN. This indication information #3 is used to indicate the use or retention of information related to the terminal device in the candidate SN (e.g., it may include one or more of the following: the context of the terminal device in the candidate SN, and previous data transfers performed by the candidate SN). The indication information #3 may be carried in the same message as the identifier of the terminal device in the candidate SN, or it may be sent separately, without limitation.

[0525] After receiving instruction message #3, MN can send instruction message #3 to candidate SN, such as sending an SN release request message to candidate SN, which carries instruction message #3.

[0526] Optionally, after step 1330, the MN may send configuration information to the terminal device. The configuration information may be the configuration information of the DC or the configuration information of the CPC.

[0527] 1340, the target SN receives information about the early data transfer from the candidate SN.

[0528] The MN or source SN can send early data transfer information of the candidate SN to the target SN. For example, the MN can directly send the early data transfer information of the candidate SN to the target SN. Alternatively, the MN can first send the early data transfer information of the candidate SN to the source SN, and then the source SN can send the early data transfer information of the candidate SN to the target SN. Figure 13 The diagram only shows the case where the source SN sends information about the early data transfer of the candidate SN to the target SN. It should be understood that... Figure 13 This is merely an illustrative example and does not limit the scope of this application.

[0529] Information about early data transfers to a candidate SN may include one or more of the following: which data packets the source MN has already transferred to the candidate SN (e.g., indicated by the PDCP SN or NR-U sequence number), and which early data transfer packets the candidate SN may discard.

[0530] The following explanation will be provided using several scenarios.

[0531] Scenario A: Before the switch, CPC is triggered by MN; after the switch, CPC is triggered by SN.

[0532] In this scenario, the MN can send information about the early data transfer of the candidate SN to the target SN.

[0533] After receiving the early data transfer information from the candidate SN, the target SN can notify the candidate SN which early data transfer packets can be discarded, that is, the target SN can send indication information #1 to the candidate SN.

[0534] In addition, the target SN can determine which packets need to be transferred to the candidate SN based on which packets the MN has already transferred to the candidate SN in the early data transfer.

[0535] In addition, after step 1340, the target SN can send multiple indication messages #1 to the candidate SN based on the downlink data packets it sends to the terminal device, in order to indicate which early data transfer data packets the candidate SN can discard.

[0536] Regarding the content of instruction message #1, please refer to the description in method 900 above, and it will not be repeated here.

[0537] Scenario B is a scenario where CPC is triggered by SN before the switch and CPC is triggered by SN after the switch.

[0538] In this scenario, the MN or the source SN can send information about the early data transfer of the candidate SN to the target SN. After receiving the information about the early data transfer of the candidate SN, the target SN can notify the candidate SN which early data transfer packets can be dropped, that is, the target SN can send indication information #1 to the candidate SN.

[0539] Furthermore, the target SN can determine which packets to transfer to the candidate SN based on which packets the MN has already transferred to the candidate SN, and which packets the source SN has already transferred to the candidate SN. Therefore, transferring duplicate packets can be avoided as much as possible.

[0540] In addition, after step 1340, the target SN can send multiple indication messages #1 to the candidate SN based on the downlink data packets it sends to the terminal device, in order to indicate which early data transfer data packets the candidate SN can discard.

[0541] Scene C is a scene where MN triggers CPC before the switch and DC after the switch.

[0542] In this scenario, the MN can send information about the early data transfer of the candidate SN to the target SN.

[0543] Scene D is a scene where SN triggers CPC before the switch and DC after the switch.

[0544] In this scenario, the MN or the source SN can send information about the early data transfer of the candidate SN to the target SN.

[0545] The above describes the information on early data transfers by the target SN to the candidate SN, based on four scenarios. It should be understood that adjustments can be made adaptively according to the specific circumstances of each scenario. Any scheme that enables the target SN to obtain information on early data transfers by the candidate SN is applicable to the embodiments of this application.

[0546] 1350, the target SN sends downlink data to the terminal device.

[0547] The following explanation will be provided using several scenarios.

[0548] Scenario A: Before the switch, CPC is triggered by MN; after the switch, CPC is triggered by SN.

[0549] Once the terminal device determines that the triggering conditions of the candidate PSCell are met and accesses the candidate PSCell, the candidate SN can send downlink data to the terminal device based on the most recent early data transfer information and the early transferred data. For example, the candidate SN can send downlink data to the terminal device based on the most recent indication information #1 and the early transferred data, such as discarding the data packets indicated in indication information #1 and sending the remaining data packets from the early transferred data packets to the terminal device.

[0550] Scenario B is a scenario where CPC is triggered by SN before the switch and CPC is triggered by SN after the switch.

[0551] The solution is similar to that in scenario A, so it will not be described in detail here.

[0552] Scene C is a scene where MN triggers CPC before the switch and DC after the switch.

[0553] Once the terminal device determines that the triggering conditions of the candidate PSCell are met and accesses the candidate PSCell, the SN can send the data from the previous early data transfer to the terminal device.

[0554] Scene D is a scene where SN triggers CPC before the switch and MR-DC after the switch.

[0555] The solution is similar to that in scenario C, so it will not be described in detail here.

[0556] Based on the above scheme, the target SN learns relevant information about the candidate SNs configured on the network side before the handover (such as the identifier of the candidate SN and the identifier of the terminal device on the candidate SN). The target SN can send the identifier of the terminal device on the candidate SN before the handover to the candidate SN. Furthermore, the target SN can receive information about early data transfers from the candidate SNs before the handover, so that after the handover, the network side can continue to utilize the data transferred in the earlier data transfers. Additionally, if a CPC is configured after the handover, no further early data transfer is needed for this data. If a DC is configured after the handover, no normal data transfer (i.e., traditional data transfer between bearers terminated by the MN and bearers terminated by the SN) is needed for this data.

[0557] The above text combined Figure 13 Steps 1310-1350 illustrate a scenario where CPC is configured before the handover and then SN handover occurs. It should be understood that the above steps are merely illustrative and are not strictly limited. Furthermore, the sequence numbers of the above processes do not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0558] Figure 14 This is a schematic flowchart applicable to the scenario in this application embodiment where no CPAC was configured before the switch, and then an MN switch occurred.

[0559] like Figure 14 As shown, method 1400 is mainly illustrated by taking the interaction between the terminal device, the source MN, the source SN, the candidate SN1, the target SN, and the target MN as an example. For distinction, the source SN represents the SN before the handover, and the target SN represents the SN after the handover; the source MN represents the MN before the handover, and the target MN represents the MN after the handover. It should be understood that the source SN and target SN, as well as the source MN and target MN, are names used for distinction, and their specific naming methods do not limit the protection scope of the embodiments of this application. Figure 14 The method 1400 shown may include the following steps.

[0560] 1410, The network side configures a DC for the terminal device.

[0561] For example, the MN sends an SN Add Request message to the SN, and the SN responds to the MN with an SN Add Request response. The MN can also notify the terminal device to configure the DC, for example, by sending an RRC Reconfiguration message to the terminal device, which instructs the terminal device to configure the DC.

[0562] The above is merely an illustrative example, and the embodiments of this application do not limit step 1410. For example, step 1410 may refer to existing technology or future methods.

[0563] At 1420, the source MN sends a handover request message to the target MN.

[0564] Optionally, the source MN can also send the identifier of the SN before the handover and the identifier of the terminal device on the SN to the target MN. For example, the handover request message carries the identifier of the SN before the handover and the identifier of the terminal device on the SN.

[0565] At 1430, the target MN sends an SN addition request message to the target SN or the candidate SN.

[0566] Optionally, the target MN can also send the identifier of the terminal device on the SN before the handover to the target SN or candidate SN. For example, the SN adds the identifier of the terminal device on the SN before the handover to the request message.

[0567] It should be understood that the target SN may or may not be the SN before the handover, and no limitation is made in this regard.

[0568] The following explanation considers three scenarios.

[0569] One possible scenario is that the switch will result in CPA.

[0570] In this case, in step 1430, the target MN sends an SN addition request message to the candidate SN.

[0571] In this scenario, the source SN can transfer data to the target MN. For example, the source SN can directly transfer data to the target MN; alternatively, the source SN can first transfer data packets to the source MN, and then the source MN can send these transferred data packets to the target MN.

[0572] The target MN can determine which data packets the candidate SN has already received based on the data packets transferred by the source SN. This eliminates the need to transfer these data packets during early data transfers between the target MN and the candidate SN. One possible approach is for the target MN to know which data packets the candidate SN has already received based on the downlink sequence number it needs to be allocated, carried in the SN status transfer sent by the source MN, and the data packets it received from the source MN.

[0573] Another possible scenario is that the CPC is triggered by MN after the switch.

[0574] In this case, in step 1430, the target MN sends an SN addition request message to the candidate SN.

[0575] In this scenario, the source SN can transfer data to the target SN. For example, the source SN can directly transfer data to the target SN; or the source SN can first transfer the data packet to the source MN, then the source MN can transfer it to the target MN, and finally the target MN can send these transferred data packets to the target SN.

[0576] The target SN can determine which data packets the candidate SN has already received based on the data packets transferred by the source SN. For details, please refer to the method described in the first scenario above.

[0577] Another possible scenario is that the CPC is triggered by SN after the switch.

[0578] In this case, in step 1430, the target MN sends an SN addition request message to the target SN. Afterwards, the target S can send the identifier of the terminal device on the SN before the handover to the candidate SN.

[0579] Furthermore, the source SN can transfer data to the target SN. The target SN can then determine which data packets the candidate SN has already received based on the transferred data packets from the source SN. For details, refer to the second scenario described above; further explanation is unnecessary here.

[0580] The above examples illustrate three scenarios and are not intended to be strictly limited.

[0581] Optionally, after step 1430, the target MN may also send configuration information to the terminal device, including CPAC configuration information.

[0582] 1440, Candidate SN receiving instruction information #3, indicating whether to use or retain information related to the terminal device in the candidate SN.

[0583] The information related to the terminal device in the candidate SN may include one or more of the following: the context of the terminal device in the candidate SN, and the early data transfers previously performed by the candidate SN.

[0584] For example, such as Figure 14 As shown, in step 1440, candidate SN1 receives indication information #3, indicating that the data packets received before the handover should continue to be used as data packets for early data transfer.

[0585] Furthermore, for CPCs triggered by CPA or MN after the handover, in step 1440, the target MN sends indication information #3 to the candidate SN. For CPCs triggered by SN after the handover, in step 1440, the target SN sends indication information #3 to the candidate SN; or the target SN first sends it to the MN, and then the MN sends it to the candidate SN.

[0586] The description of instruction #3 is as above and will not be repeated here.

[0587] At 1450, the candidate SN sends downlink data to the terminal device.

[0588] Optionally, prior to this step, the candidate SN may receive indication information #1, which notifies the candidate SN which packets from earlier data transfers can be discarded. The candidate SN may receive indication information #1 from the MN or from the target SN.

[0589] When the terminal device determines that the triggering conditions of the candidate PSCell are met, the terminal device accesses the candidate PSCell. For example, the terminal device performs a random access process with the candidate PSCell.

[0590] When a terminal device connects to a candidate SN, the candidate SN can send data packets from the early data transfer (including data packets received before the handover) to the terminal device according to the instruction information #1 and the information from the early data transfer. Alternatively, if the candidate SN knows that the SN before the handover and the candidate SN after the handover are the same SN, the candidate SN can send data packets from the early data transfer (including data packets received before the handover) to the terminal device according to the most recent instruction information #1 it received.

[0591] Based on the above scheme, for scenarios where no CPAC was configured before the handover and a MN handover subsequently occurred, the target MN is configured with CPAC for early data transfer of the terminal device. For bearers in the CPAC configured after the MN handover that are terminated by the SN, data packets already received by the candidate SN before the handover can be used as data packets for early data transfer, thereby avoiding the need to transfer these data packets again during the early data transfer and reducing the transmission latency of these data packets.

[0592] The above text combined Figure 14 Steps 1410-1450 illustrate a scenario where CPAC was not configured before the switchover and an MN switchover subsequently occurred. It should be understood that the above steps are merely illustrative and are not intended to be strictly limited. Furthermore, the sequence numbers of the above processes do not imply an order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0593] It should be understood that in some of the above embodiments, some message names are involved, such as early data transfer (or early data transmission), SN add request message, indication information #1, indication information #2, etc. It should be understood that their naming does not limit the protection scope of the embodiments of this application.

[0594] It should also be understood that in some of the above embodiments, the examples are mainly based on base stations (such as MN and SN). It should be understood that other forms of network devices are also applicable to the embodiments of this application.

[0595] It should also be understood that in some of the above embodiments, the SN addition request message is mentioned many times, which can also be referred to as the SN addition request message. The naming does not limit the scope of protection of the embodiments of this application.

[0596] It should also be understood that in some of the above embodiments, when adding a PSCell, an SN increase request message is sent for conditional SN increase; when changing a PSCell, an SN increase request message is sent for conditional SN change. The above is merely illustrative, and the specific content indicated by the SN increase request message is not strictly limited. For example, regardless of whether a PSCell is added or changed, the SN increase request message is sent for conditional SN increase. That is, the SN increase request message can be defined as being for conditional SN increase, without specifically distinguishing between SN change and SN increase.

[0597] It should also be understood that in some of the above embodiments, the repeated mention of transferring data packets primarily refers to transferring untransmitted data packets and / or data packets whose transmission failed. Here, the data packet can be either an uplink data packet or a downlink data packet, without limitation. For example, a source network device can transfer a downlink data packet to be sent to a terminal device to a target network device. Similarly, a source network device can transfer an uplink data packet received out of order from the terminal device to the target network device.

[0598] It should also be understood that Figures 12 to 14 Early data transfer between MN and SN includes early data transfer of SCG / MCG / split bearers terminated by SN in candidate SN of CPAC, and may also include early data transfer of SCG / split bearers terminated by MN in MN between MN and SN. Unless otherwise specified, this application does not limit the form of the data packets for early data transfer.

[0599] The various embodiments described herein can be independent solutions or combinations thereof based on their inherent logic, and all such solutions fall within the protection scope of this application.

[0600] It is understood that, in the above-described method embodiments, the methods and operations implemented by the terminal device can also be implemented by components (e.g., chips or circuits) that can be used in the terminal device, and the methods and operations implemented by the network device (e.g., MN, SN) can also be implemented by components (e.g., chips or circuits) that can be used in the network device.

[0601] The above, combined with Figures 7 to 14 The methods provided in the embodiments of this application are described in detail below. Figures 15 to 17 This application provides a detailed description of the data transmission apparatus provided in the embodiments. It should be understood that the descriptions of the apparatus embodiments correspond to the descriptions of the method embodiments; therefore, any content not described in detail can be found in the above method embodiments, and for the sake of brevity, will not be repeated here.

[0602] Figure 15 This is a schematic block diagram of a data transmission apparatus provided in an embodiment of this application. The apparatus 1500 includes a transceiver unit 1510 and a processing unit 1520. The transceiver unit 1510 can implement corresponding communication functions, and the processing unit 1520 is used for data processing. The transceiver unit 1510 can also be referred to as a communication interface or a communication unit.

[0603] Optionally, the device 1500 may further include a storage unit for storing instructions and / or data, and the processing unit 1520 may read the instructions and / or data from the storage unit to enable the device to implement the aforementioned method embodiments.

[0604] The device 1500 can be used to perform the actions performed by the network device in the above method embodiment. In this case, the device 1500 can be a network device or a component that can be configured on the network device. The transceiver unit 1510 is used to perform the transceiver-related operations on the network device side in the above method embodiment, and the processing unit 1520 is used to perform the processing-related operations on the network device side in the above method embodiment.

[0605] As a design, the device 1500 is used to perform the actions performed by the main network device (such as MN) in the above method embodiments.

[0606] One possible implementation includes a processing unit 1520 configured to add or change condition-based candidate PSCells for the terminal device; and a transceiver unit 1510 configured to perform early data transmission to the network device to which the candidate PSCell belongs. Early data transmission refers to sending one or more data packets to the network device to which the candidate PSCell belongs before the terminal device accesses the candidate PSCell. The data packets are in the form of Protocol Data Units (PDUs) of the Packet Data Convergence Layer Protocol. The one or more data packets include: data packets on the secondary cell group bearer terminated by the MN configured for the terminal device, and / or data packets on the split bearer terminated by the MN configured for the terminal device.

[0607] As an example, transceiver unit 1510 is further configured to send first indication information to the network device to which the candidate PSCell belongs, the first indication information being used to indicate early data transmission of secondary cell group bearers and / or split bearers for MN termination.

[0608] In another example, transceiver unit 1510 is also used to send a second indication message to the network device to which the candidate PSCell belongs, the second indication message being used to indicate that some or all of the data packets in one or more data packets should be discarded or ignored.

[0609] In another example, the second indication information includes information on one or more sequence numbers, which are used to indicate whether to discard or ignore some or all of the data packets in one or more data packets.

[0610] Another example is a packet data aggregation protocol sequence number or a new air interface user plane sequence number.

[0611] In another example, transceiver unit 1510 is specifically used to send a second indication message to the network device to which the candidate PSCell belongs when preset conditions are met.

[0612] The device 1500 can implement steps or processes corresponding to those executed by the main network device (such as MN) in the method embodiments according to the present application. The device 1500 may include methods for performing... Figure 7 , Figures 9 to 11 The unit is a method executed by the main network device (such as MN) in the device. Furthermore, each unit in the device 1500 and the other operations and / or functions described above are respectively for implementing... Figure 7 , Figures 9 to 11 The corresponding flow of the method embodiment in the main network device (such as MN).

[0613] Among them, when the device 1500 is used to perform Figure 7 When method 700 is used, the transceiver unit 1510 can be used to execute step 720 in method 700; the processing unit 1520 can be used to execute the processing steps in method 700, such as step 710.

[0614] When the device 1500 is used to perform Figure 9 When performing method 900, the transceiver unit 1510 can be used to execute steps 920 and 940 in method 900; the processing unit 1520 can be used to execute processing steps in method 900, such as step 910.

[0615] When the device 1500 is used to perform Figure 10When performing method 1000, the transceiver unit 1510 can be used to execute steps 1020 and 1040 in method 1000; the processing unit 1520 can be used to execute processing steps in method 1000, such as step 1010.

[0616] When the device 1500 is used to perform Figure 11 When using method 1100, the transceiver unit 1510 can be used to execute steps 1120 and 1140 in method 1100; the processing unit 1520 can be used to execute processing steps in method 1100, such as step 1110.

[0617] It should be understood that the specific process of each unit performing the above-mentioned corresponding steps has been described in detail in the above method embodiments, and will not be repeated here for the sake of brevity.

[0618] As an alternative design, the device 1500 is used to perform the actions performed by the candidate network device (such as the candidate SN) in the above method embodiments.

[0619] One possible implementation is that the transceiver unit 1510 is used to receive one or more data packets from the MN, the data packets being in the form of Protocol Data Units (PDUs) of the Packet Data Convergence Layer Protocol. The one or more data packets include: data packets on the secondary cell group bearer terminated by the MN configured for the terminal device, and / or data packets on the split bearer terminated by the MN configured for the terminal device; the processing unit 1520 is used to access the terminal device; the transceiver unit 1510 is also used to send part or all of the data packets in the one or more data packets to the terminal device; wherein the terminal device is configured to add or change candidate primary and secondary cells (PSCells) based on conditions.

[0620] As an example, the transceiver unit 1510 is also configured to receive second indication information, which indicates that some or all of the data packets in one or more data packets should be discarded or ignored; specifically, the transceiver unit 1510 is configured to send data to the terminal device according to one or more data packets and the second indication information.

[0621] In another example, the second indication information includes information on one or more sequence numbers, which are used to indicate whether to discard or ignore some or all of the data packets in one or more data packets.

[0622] Another example is a packet data aggregation protocol sequence number or a new air interface user plane sequence number.

[0623] Another example is transceiver unit 1510, which is specifically used to periodically receive second instruction information.

[0624] The device 1500 can implement steps or processes corresponding to those performed by a candidate network device (such as a candidate SN) in a method embodiment according to the present application. The device 1500 may include methods for performing... Figure 7 , Figures 9 to 11 The unit is a candidate network device (such as a candidate SN) that executes the method. Furthermore, each unit in the apparatus 1500 and the other operations and / or functions described above are respectively for implementing... Figure 7 , Figures 9 to 11 The corresponding flow of the method embodiment in the candidate network device (such as the candidate SN) in the SN.

[0625] Among them, when the device 1500 is used to perform Figure 7 When the method is 700, the transceiver unit 1510 can be used to execute steps 720 and 730 in the method 700; the processing unit 1520 can be used to execute the processing steps in the method 700, such as step 710.

[0626] When the device 1500 is used to perform Figure 9 When performing method 900, the transceiver unit 1510 can be used to execute steps 940, 950, and 960 in method 900; the processing unit 1520 can be used to execute processing steps in method 900, such as step 910.

[0627] When the device 1500 is used to perform Figure 10 When performing method 1000, the transceiver unit 1510 can be used to execute steps 1040, 1050, and 1060 in method 1000; the processing unit 1520 can be used to execute processing steps in method 1000, such as step 1010.

[0628] When the device 1500 is used to perform Figure 11 When performing method 1100, the transceiver unit 1510 can be used to execute steps 1140, 1150, and 1160 in method 1100; the processing unit 1520 can be used to execute processing steps in method 1100, such as step 1110.

[0629] It should be understood that the specific process of each unit performing the above-mentioned corresponding steps has been described in detail in the above method embodiments, and will not be repeated here for the sake of brevity.

[0630] As an alternative design, the device 1500 is used to perform the actions performed by the source network device (such as the source MN or source SN) in the above method embodiments.

[0631] One possible implementation is that the processing unit 1520 is used to determine that the network device configured for the terminal device after handover includes a second network device. Specifically, if the second network device is a candidate network device in a conditional candidate primary / secondary cell (PSCell) addition or change scenario configured for the terminal device before the terminal device hands over from device 1500 to the target network device, and after the handover, the second network device is a candidate network device in a conditional candidate PSCell addition or change scenario configured for the terminal device, or the second network device is a network device providing services to the terminal device; or, in the case of handover from device 1500 to the target network device, the second network device is either a candidate network device in a conditional candidate PSCell addition or change scenario configured for the terminal device, or the second network device is a network device providing services to the terminal device. After the terminal device switches from device 1500 to the target network device, if the second network device is a candidate network device in the scenario of adding or changing the condition-based candidate primary and secondary cell PSCell configured for the terminal device, before switching from device 1500 to the target network device, the second network device is a candidate network device in the scenario of adding or changing the condition-based candidate PSCell configured for the terminal device, or the second network device is a network device that provides services to the terminal device; the transceiver unit 1510 is used to send third indication information to the second network device, the third indication information being used to indicate the use of information related to the terminal device in the second network device.

[0632] As an example, information related to the terminal device includes one or more of the following: context information of the terminal device, data packets of the terminal device that have been transmitted to the second network device, and information about data packets of the terminal device that the second network device can discard.

[0633] In another example, the transceiver unit 1510 is also configured to receive identification information of a second network device sent from the target network device; the processing unit 1520 is specifically configured to determine, based on the identification information of the second network device, that the network device configured for the terminal device after the handover includes the second network device.

[0634] In another example, transceiver unit 1510 is also used to send early data transmission information of a second network device to a target network device.

[0635] In another example, transceiver unit 1510 is also used to send information about one or more network devices to a target network device, wherein the one or more network devices include a second network device, and the one or more network devices are: candidate network devices in the scenario of adding or changing the condition-based candidate PSCell configured for the terminal device before the terminal device switches from the source network device to the target network device, or network devices that provide services to the terminal device, and the information about the one or more network devices includes one or more of the following: identification information of the one or more network devices, and identification information of the terminal device in the one or more network devices.

[0636] In another example, transceiver unit 1510 is specifically used to send a handover request message to a target network device, the handover request message including information about one or more network devices.

[0637] In another example, transceiver unit 1510 is also used to send data packets to be sent to a terminal device to a target network device or a second network device.

[0638] In another example, the target network device is a network device in a scenario where candidate PSCells are added or changed based on conditions, and the device 1500 is a network device in a scenario where candidate PSCells are added or changed based on conditions; or, the target network device is a network device in a scenario where candidate PSCells are added or changed based on conditions, and the device 1500 is a network device in a scenario where carrier aggregation is used; or, the target network device is a network device in a scenario where carrier aggregation is used, and the device 1500 is a network device in a scenario where candidate PSCells are added or changed based on conditions.

[0639] The device 1500 can implement steps or processes corresponding to those performed by a source network device (such as a source MN or source SN) in a method embodiment according to the present application. The device 1500 may include methods for performing... Figure 8 , Figures 12 to 14 The unit is a source network device (such as a source MN or source SN) that performs the method. Furthermore, each unit in the device 1500 and the other operations and / or functions described above are respectively for implementing... Figure 8 , Figures 12 to 14 The corresponding flow of the method implementation in the example.

[0640] Among them, when the device 1500 is used to perform Figure 8 When method 800 is executed, the transceiver unit 1510 can be used to execute steps 8202 and 840 in method 800; the processing unit 1520 can be used to execute processing steps in method 800, such as step 830.

[0641] When the device 1500 is used to perform Figure 12 When performing method 1200, the transceiver unit 1510 can be used to execute steps 1220, 1240, 1250, and 1260 in method 1200; the processing unit 1520 can be used to execute processing steps in method 1200, such as step 1210.

[0642] When the device 1500 is used to perform Figure 13 When using method 1300, the transceiver unit 1510 can be used to execute steps 1320 and 1340 in method 1300; the processing unit 1520 can be used to execute processing steps in method 1300, such as step 1310.

[0643] When the device 1500 is used to perform Figure 14 When method 1400 is used, the transceiver unit 1510 can be used to execute step 1420 in method 1400; the processing unit 1520 can be used to execute the processing steps in method 1400, such as step 1410.

[0644] It should be understood that the specific process of each unit performing the above-mentioned corresponding steps has been described in detail in the above method embodiments, and will not be repeated here for the sake of brevity.

[0645] As an alternative design, the device 1500 is used to perform the actions performed by the target network device (such as the target MN or the target SN) in the above method embodiments.

[0646] One possible implementation is that the processing unit 1520 is configured to configure N first network devices for the terminal device, the N first network devices including second network devices, where N is an integer greater than or equal to 1. Specifically, before the terminal device switches from the source network device to the device 1500, if the second network device is a candidate network device in a conditional candidate primary / secondary cell (PSCell) addition or change scenario configured for the terminal device, after the terminal device switches from the source network device to the device 1500, if the second network device is a candidate network device in a conditional candidate PSCell addition or change scenario configured for the terminal device, or if the second network device is a candidate network device configured for the terminal device... The second network device provides services; or, after the terminal device switches from the source network device to the device 1500, if the second network device is a candidate network device in the scenario of adding or changing the conditional candidate primary and secondary cell PSCell configured for the terminal device, or before the terminal device switches from the source network device to the device 1500, if the second network device is a candidate network device in the scenario of adding or changing the conditional candidate PSCell configured for the terminal device, or if the second network device is a network device providing services to the terminal device; the transceiver unit 1510 is used to send third indication information, which is used to indicate the use of information related to the terminal device in the second network device.

[0647] As an example, information related to the terminal device includes one or more of the following: context information of the terminal device, data packets of the terminal device that have been transmitted to the second network device, and information about data packets of the terminal device that the second network device can discard.

[0648] In another example, transceiver unit 1510 is specifically used to send third indication information to a second network device; or to send third indication information to a source network device.

[0649] In another example, transceiver unit 1510 is also used to receive early data transmission information of a second network device sent by the source network device.

[0650] In another example, transceiver unit 1510 is also configured to perform early data transmission with the second network device based on early data transmission information of the second network device.

[0651] In another example, transceiver unit 1510 is also used to send identification information of a second network device to the source network device.

[0652] In another example, transceiver unit 1510 is further configured to receive information from one or more network devices from a source network device, wherein the one or more network devices include a second network device, and the one or more network devices are: candidate network devices configured for the terminal device in the scenario of adding or changing the condition-based candidate PSCell before the terminal device switches from the source network device to the target network device, or network devices that provide services to the terminal device, and the information of the one or more network devices includes one or more of the following: identification information of the one or more network devices, and identification information of the terminal device in the one or more network devices.

[0653] In another example, the information of one or more network devices includes the identification information of one or more network devices. The processing unit 1520 is also used to determine, based on the identification information of one or more network devices, that N first network devices include second network devices.

[0654] In another example, transceiver unit 1510 is specifically used to receive handover request messages, which include information about one or more network devices.

[0655] In another example, device 1500 is a network device in a scenario where candidate PSCells are added or changed based on conditions, and the source network device is a network device in a scenario where candidate PSCells are added or changed based on conditions; or, device 1500 is a network device in a scenario where candidate PSCells are added or changed based on conditions, and the source network device is a network device in a scenario where carrier aggregation is used; or, device 1500 is a network device in a scenario where carrier aggregation is used, and the source network device is a network device in a scenario where candidate PSCells are added or changed based on conditions.

[0656] The device 1500 can implement steps or processes corresponding to those performed by a target network device (such as a target MN or a target SN) in the method embodiments according to the present application. The device 1500 may include methods for performing... Figure 8 , Figures 12 to 14 The device 1500 is a unit that executes a method for a target network device (such as a target MN or a target SN). Furthermore, each unit in the device 1500 and the other operations and / or functions described above are respectively for implementing... Figure 8 , Figures 12 to 14 The corresponding flow of the method implementation in the example.

[0657] Among them, when the device 1500 is used to perform Figure 8 When the method is 800, the transceiver unit 1510 can be used to execute steps 8201, 8202, and 840 in the method 800; the processing unit 1520 can be used to execute the processing steps in the method 800, such as step 810.

[0658] When the device 1500 is used to perform Figure 12 When method 1200 is used, the transceiver unit 1510 can be used to execute steps 1220, 1230, 1240, and 1260 in method 1200; the processing unit 1520 can be used to execute the processing steps in method 1200.

[0659] When the device 1500 is used to perform Figure 13 When method 1300 is used, the transceiver unit 1510 can be used to execute steps 1320, 1330, and 1340 in method 1300; the processing unit 1520 can be used to execute the processing steps in method 1300.

[0660] When the device 1500 is used to perform Figure 14 When method 1400 is used, the transceiver unit 1510 can be used to execute steps 1420, 1430, and 1440 in method 1400; the processing unit 1520 can be used to execute the processing steps in method 1400.

[0661] It should be understood that the specific process of each unit performing the above-mentioned corresponding steps has been described in detail in the above method embodiments, and will not be repeated here for the sake of brevity.

[0662] The processing unit 1520 in the above embodiments can be implemented by at least one processor or processor-related circuitry. The transceiver unit 1510 can be implemented by a transceiver or transceiver-related circuitry. The storage unit can be implemented by at least one memory.

[0663] like Figure 16 As shown, this application embodiment also provides a data transmission apparatus 1600. The apparatus 1600 includes a processor 1610, which is coupled to a memory 1620. The memory 1620 is used to store computer programs or instructions and / or data. The processor 1610 is used to execute the computer programs or instructions and / or data stored in the memory 1620, so that the methods in the above method embodiments are executed.

[0664] Optionally, the device 1600 may include one or more processors 1610.

[0665] Optionally, such as Figure 16 As shown, the device 1600 may also include a memory 1620.

[0666] Optionally, the device 1600 may include one or more memories 1620.

[0667] Alternatively, the memory 1620 may be integrated with the processor 1610 or set separately.

[0668] Optionally, such as Figure 16 As shown, the device 1600 may further include a transceiver 1630 for receiving and / or transmitting signals. For example, a processor 1610 is used to control the transceiver 1630 to receive and / or transmit signals.

[0669] As one option, the device 1600 is used to implement the operations performed by the network device in the above method embodiments.

[0670] For example, processor 1610 is used to implement processing-related operations performed by the main network device (such as MN) in the above method embodiments, and transceiver 1630 is used to implement transmission-reception-related operations performed by the main network device in the above method embodiments.

[0671] For example, processor 1610 is used to implement the processing-related operations performed by the candidate network device (such as candidate SN) in the above method embodiments, and transceiver 1630 is used to implement the transmission-reception-related operations performed by the candidate network device in the above method embodiments.

[0672] For example, processor 1610 is used to implement processing-related operations performed by the source network device (such as source MN or source SN) in the above method embodiments, and transceiver 1630 is used to implement transmission-reception-related operations performed by the source network device in the above method embodiments.

[0673] For example, processor 1610 is used to implement processing-related operations performed by the target network device (such as target MN or target SN) in the above method embodiments, and transceiver 1630 is used to implement transmission-reception-related operations performed by the target network device in the above method embodiments.

[0674] This application also provides a communication device 1700, which can be a network device or a chip. The communication device 1700 can be used to perform the operations performed by the network device in the above method embodiments.

[0675] When the communication device 1700 is a network device, such as a base station. Figure 17A simplified schematic diagram of a base station structure is shown. The base station includes section 1710 and section 1720. Section 1710 is mainly used for transmitting and receiving radio frequency signals and converting radio frequency signals to baseband signals; section 1720 is mainly used for baseband processing and base station control. Section 1710 is commonly referred to as a transceiver unit, transceiver, transceiver circuit, or transceiver. Section 1720 is typically the control center of the base station, often referred to as a processing unit, used to control the base station to perform the processing operations on the receiving end device side in the above method embodiments.

[0676] The transceiver unit of section 1710, also known as a transceiver or transceiver unit, includes an antenna and radio frequency (RF) circuitry, where the RF circuitry is primarily used for RF processing. Optionally, the devices in section 1710 that implement the receiving function can be considered as receiving units, and the devices that implement the transmitting function can be considered as transmitting units; that is, section 1710 includes both receiving and transmitting units. The receiving unit can also be called a receiver, receiver circuit, or receiving unit, while the transmitting unit can be called a transmitter, transmitter, or transmitting circuit.

[0677] Section 1720 may include one or more single boards, each single board may include one or more processors and one or more memories. The processor is used to read and execute programs in the memory to implement baseband processing functions and control the base station. If multiple single boards exist, they can be interconnected to enhance processing capabilities. As an alternative implementation, multiple single boards may share one or more processors, multiple single boards may share one or more memories, or multiple single boards may simultaneously share one or more processors.

[0678] It should be understood that Figure 17 This is merely an example and not a limitation; the network devices described above, including transceiver units and processing units, may not rely on... Figure 17 The structure shown.

[0679] When the device 1700 is a chip, the chip includes a transceiver unit and a processing unit. The transceiver unit can be an input / output circuit or a communication interface; the processing unit is a processor, microprocessor, or integrated circuit integrated on the chip. Alternatively, the device 1700 can be a chip system or a processing system, enabling devices equipped with the device 1700 to implement the methods and functions of the embodiments of this application. For example, the processing unit 1720 can be a processing circuit within the chip system or processing system, controlling devices equipped with the chip system or processing system. It can also be coupled to a storage unit to call instructions stored in the storage unit, enabling the device to implement the methods and functions of the embodiments of this application. The transceiver unit 1710 can be an input / output circuit within the chip system or processing system, outputting information processed by the chip system or inputting data or signaling information to be processed into the chip system for processing.

[0680] This application also provides a computer-readable storage medium storing computer instructions for implementing the methods executed by a network device in the above-described method embodiments.

[0681] For example, when the computer program is executed by a computer, it enables the computer to implement the method executed by the network device in the above method embodiments.

[0682] This application also provides a computer program product containing instructions that, when executed by a computer, cause the computer to implement the method executed by the network device in the above method embodiments.

[0683] This application also provides a communication system, which includes network devices in the above embodiments, such as a main network device and a candidate network device, or a source network device and a target network device, or a source network device, a target network device and a candidate network device.

[0684] The explanations and beneficial effects of the relevant contents in any of the devices provided above can be found in the corresponding method embodiments provided above, and will not be repeated here.

[0685] It should be understood that the processor mentioned in the embodiments of this application can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor.

[0686] It should also be understood that the memory mentioned in the embodiments of this application can be volatile memory and / or non-volatile memory. Non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. Volatile memory can be random access memory (RAM). For example, RAM can be used as an external cache. By way of example and not limitation, RAM can include a variety of forms, such as: static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous linked dynamic random access memory (SLDRAM), and direct rambus RAM (DR RAM).

[0687] It should be noted that when the processor is a general-purpose processor, DSP, ASIC, FPGA, or other programmable logic device, discrete gate or transistor logic device, or discrete hardware component, the memory (storage module) can be integrated into the processor.

[0688] It should also be noted that the memory described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0689] Those skilled in the art will recognize that the units and steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of protection of this application.

[0690] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces, and the indirect coupling or communication connection of apparatus or units may be electrical, mechanical, or other forms.

[0691] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to implement the solution provided in this application, depending on actual needs.

[0692] In addition, the functional units in the various embodiments of this application can be integrated into one unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0693] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. For example, the computer can be a personal computer, a server, or a network device, etc. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available media can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., DVDs), or semiconductor media (e.g., solid-state disks, SSDs). For example, the aforementioned available media may include, but are not limited to, USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks, and other media capable of storing program code.

[0694] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for data transmission, characterized in that, include: Configure condition-based candidate primary and secondary cells (PSCells) for terminal devices by adding or changing them; Early data transmission is performed to the network device to which the candidate PSCell belongs. The early data transmission refers to sending one or more data packets to the network device to which the candidate PSCell belongs before the terminal device accesses the candidate PSCell. The data packets are in the form of Protocol Data Units of Packet Data Convergence Layer Protocol. The one or more data packets include: data packets on the secondary cell group bearer terminated by the primary base station MN configured for the terminal device, and / or data packets on the split bearer terminated by the MN configured for the terminal device.

2. The method according to claim 1, characterized in that, The method further includes: Send a first indication message to the network device to which the candidate PSCell belongs. The first indication message is used to indicate early data transmission of the secondary cell group bearer and / or the split bearer of the MN termination.

3. The method according to claim 1 or 2, characterized in that, The method further includes: Send a second indication message to the network device to which the candidate PSCell belongs, the second indication message being used to indicate that some or all of the data packets in the one or more data packets should be discarded or ignored.

4. The method according to claim 3, characterized in that, The second indication information includes information on one or more serial numbers, which are used to indicate whether to discard or ignore some or all of the data packets in the one or more data packets.

5. The method according to claim 4, characterized in that, The sequence number is either a packet data aggregation protocol sequence number or a new air interface user plane sequence number.

6. The method according to claim 3, characterized in that, Sending the second indication information to the network device to which the candidate PSCell belongs includes: If the preset conditions are met, the second indication information is sent to the network device to which the candidate PSCell belongs.

7. A method for data transmission, characterized in that, include: Before the terminal device accesses the network, one or more data packets are received from the main base station MN. The data packets are in the form of protocol data units of the packet data aggregation layer protocol. The one or more data packets include: data packets on the secondary cell group bearer terminated by the MN configured for the terminal device, and / or data packets on the split bearer terminated by the MN configured for the terminal device. After the terminal device is connected, send some or all of the data packets from the one or more data packets to the terminal device; The terminal device is configured to add or change candidate primary and secondary cells (PSCells) based on conditions.

8. The method according to claim 7, characterized in that, The method further includes: Receive a second indication message, the second indication message being used to indicate that some or all of the data packets in the one or more data packets should be discarded or ignored; Sending some or all of the data packets from the one or more data packets to the terminal device includes: Data is sent to the terminal device based on the one or more data packets and the second indication information.

9. The method according to claim 8, characterized in that, The second indication information includes information on one or more serial numbers, which are used to indicate whether to discard or ignore some or all of the data packets in the one or more data packets.

10. The method according to claim 9, characterized in that, The sequence number is either a packet data aggregation protocol sequence number or a new air interface user plane sequence number.

11. The method according to any one of claims 8 to 10, characterized in that, Receiving the second indication information includes: periodically receiving the second indication information.

12. A communication device, characterized in that, Includes units and / or modules for performing the method according to any one of claims 1 to 6.

13. A communication device, characterized in that, It includes units and / or modules for performing the method according to any one of claims 7 to 11.

14. A computer-readable storage medium, characterized in that, include: The computer-readable storage medium stores a computer program; when executed by one or more processors, the computer program causes a device including the processors to perform the method as described in any one of claims 1-11.

15. A computer program product, characterized in that, The computer program product includes computer program code, which, when run on a computer, implements the method of any one of claims 1-11.

16. A communication system, characterized in that, include: The communication device according to claim 12 and the communication device according to claim 13.

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