Data transmission method and device

Abstract

The present application provides a data transmission method and apparatus. The method may include the steps of configuring a conditional candidate primary secondary cell group cell PSCell addition or modification for a terminal device; performing early data transmission directed to a network device to which the candidate PSCell belongs by a master network device, for example, sending a data packet to the network device to which the candidate PSCell belongs before the terminal device accesses the candidate PSCell, where the format of the data packet is a protocol data unit of a packet data convergence protocol, and the data packet includes a data packet on a MN terminated secondary cell group bearer and / or a data packet on a MN terminated split bearer. In this way, after the terminal device accesses the candidate network device, the candidate network device may send the forwarded data to the terminal device, reducing data transmission delay. In addition, the present application may support early data forwarding of data packets on a MN terminated secondary cell group bearer and / or data packets on a MN terminated split bearer, thereby reducing transmission delay of data on these bearers.

Description

[Technical field]

[0001] The present application relates to the field of communication technologies, and more particularly to a data transmission method and apparatus. [Background technology]

[0002] In a conditional primary secondary cell group cell (PSCell) addition / change (CPAC), when a candidate PSCell among one or more candidate PSCells satisfies a condition corresponding to the candidate PSCell, a terminal device may directly access the candidate PSCell that satisfies the condition, thereby reducing the delay of the PSCell addition or change.

[0003] However, after the terminal device accesses the candidate PSCell, data can only be transmitted to the terminal device after the pre-handover device has transmitted data packets to the candidate PSCell, which increases the transmission delay of these data packets. Summary of the Invention

[0004] The present application provides a data transmission method and apparatus for reducing data transmission delay.

[0005] According to a first aspect, a data transmission method is provided. The method can be performed by a network device, or can be performed by a chip or circuit used in a network device. This is not limited in the present application. For ease of explanation, an example in which the method is performed by a network device is used below for explanation.

[0006] The method may comprise the steps of configuring a conditional candidate primary secondary cell group cell PSCell addition or modification for a terminal device; and performing an early data transmission directed to a network device to which the candidate PSCell belongs, where the early data transmission includes transmitting one or more data packets to the network device to which the candidate PSCell belongs before the terminal device accesses the candidate PSCell, the format of the data packets being protocol data units of a Packet Data Convergence Protocol, where the one or more data packets include data packets on a master base station MN terminated secondary cell group bearer configured for the terminal device and / or data packets on a MN terminated split bearer configured for the terminal device.

[0007] The method may be performed by a master network device (e.g., a master node (e.g., a master node MN) (or referred to as a master base station)), or may be performed by a chip or circuit used in the master network device.

[0008] For an MN terminated secondary cell group bearer (SCG bearer) or an MN terminated split bearer, the early data transmission may also be referred to as early data forwarding, or may have another name. The name of the early data transmission does not limit the scope of protection of the embodiments of the present application.

[0009] According to the above technical solution, early data transfer can be performed between a master network device and a candidate network device (e.g., a candidate secondary node (SN)). In this way, after the terminal device accesses the candidate network device, the candidate network device can send data transferred to the candidate network device to the terminal device, thereby reducing data transmission delay.

[0010] In addition, for MN terminated secondary cell group bearers and / or MN terminated split bearers, the MN may also perform early data transmissions directed to the candidate network devices, e.g., early data forwarding in the form of packet data convergence protocol (PDCP) protocol data units (PDUs) (PDCP PDUs). Thus, this embodiment of the present application may support early data forwarding of data packets on MN terminated secondary cell group bearers and / or data packets on MN terminated split bearers, thereby reducing the transmission delay of data on these bearers.

[0011] Referring to the first aspect, in some implementations of the first aspect, the method further includes a step of sending first indication information to a network device to which the candidate PSCell belongs, where the first indication information instructs performing early data transmission on the MN terminated secondary cell group bearer and / or the MN terminated split bearer.

[0012] In a possible manner, the first indication information may be transmitted between the master network device and the candidate network device (e.g., the MN and the candidate SN) via a control plane interface, or may be transmitted between the master network device and the candidate network device via a user plane interface.

[0013] Referring to the first aspect, in some implementations of the first aspect, the method further includes a step of sending second instruction information to a network device to which the candidate PSCell belongs, where the second instruction information instructs the network device to discard or ignore some or all of the one or more data packets.

[0014] According to the above technical solution, the master network device can send second instruction information to the candidate network device to instruct it to discard or ignore some or all of the data packets in the early data transmission, which can avoid the case where the candidate network device holds back some data packets that have been successfully received by the terminal device or repeatedly transmits them to the terminal device, thereby reducing resource waste.

[0015] Referring to the first aspect, in some implementations of the first aspect, the second instruction information includes information about one or more sequence numbers, and the information about the one or more sequence numbers instructs discarding or ignoring some or all of the one or more data packets.

[0016] In a possible manner, the second instruction information may be a sequence number. It is assumed that the sequence number is described as sequence number #A. For example, the sequence number #A may indicate that the candidate network device needs to discard or ignore a data packet in a previously forwarded data packet (e.g., a PDCP PDU) whose corresponding sequence number is lower than the sequence number #A. In other words, when the master network device needs to instruct the candidate network device to discard or ignore a data packet whose corresponding sequence number is lower than the sequence number #A, the master network device may indicate the sequence number #A to the candidate network device.

[0017] In another possible manner, the second indication information may be a plurality of sequence numbers, for example in the form of a sequence number list. For example, the sequence number list may indicate that the candidate network device should discard or ignore a data packet in a previously forwarded data packet (e.g., a PDCP PDU) that corresponds to a sequence number in the sequence number list. In other words, the master network device may indicate that a sequence number corresponding to a data packet is to be discarded or ignored.

[0018] Referring to the first aspect, in some implementations of the first aspect, the sequence number is a Packet Data Convergence Protocol sequence number or a new wireless user plane sequence number.

[0019] Referring to the first aspect, in some implementations of the first aspect, sending second indication information to a network device to which the candidate PSCell belongs includes sending the second indication information to the network device to which the candidate PSCell belongs when a preset condition is met.

[0020] The preset condition may be a time restriction (eg, periodic transmission), a data amount restriction (eg, a comparison between the data amount and a threshold or threshold range), or another aspect of the restriction.

[0021] According to a second aspect, a data transmission method is provided. The method can be performed by a network device, or can be performed by a chip or circuit used in a network device. This is not limited in the present application. For ease of explanation, an example in which the method is performed by a network device is used below for explanation.

[0022] The method may comprise a step of receiving one or more data packets from a master base station MN before access of the terminal device, where the format of the data packets is a protocol data unit of a Packet Data Convergence Protocol, and the one or more data packets include data packets on an MN terminated secondary cell group bearer configured for the terminal device and / or data packets on an MN terminated split bearer configured for the terminal device; and a step of transmitting some or all of the one or more data packets to the terminal device after access of the terminal device, where a conditional candidate primary secondary cell group cell PSCell addition or modification is configured for the terminal device.

[0023] The method may be performed by a candidate network device (eg, a candidate SN) or may be performed by a chip or circuit used in a candidate network device.

[0024] According to the above technical solution, early data transfer can be performed between the master network device and the candidate network device. In this way, after the terminal device accesses the candidate network device, the candidate network device can send the data transferred to the candidate network device to the terminal device, thereby reducing the data transmission delay.

[0025] In addition, for MN terminated secondary cell group bearers and / or MN terminated split bearers, the MN may also perform early data transmissions directed to the candidate network devices, for example, early data forwarding in the form of PDCP PDUs. Thus, this embodiment of the present application may support early data forwarding of data packets on MN terminated secondary cell group bearers and / or data packets on MN terminated split bearers, thereby reducing the transmission delay of data on these bearers.

[0026] Referring to the second aspect, in some implementations of the second aspect, the method further includes a step of receiving second instruction information, where the second instruction information instructs to discard or ignore some or all of the one or more data packets, and the step of transmitting some or all of the one or more data packets to the terminal device includes a step of transmitting data to the terminal device based on the one or more data packets and the second instruction information.

[0027] The above technical solution may avoid the case where a candidate network device repeatedly transmits some data packets to a terminal device that have been successfully received by the terminal device, and reduce resource waste.

[0028] Referring to the second aspect, in some implementations of the second aspect, the second instruction information includes information about one or more sequence numbers, and the information about the one or more sequence numbers instructs discarding or ignoring some or all of the one or more data packets.

[0029] Referring to the second aspect, in some implementations of the second aspect, the sequence number is a Packet Data Convergence Protocol sequence number or a new wireless user plane sequence number.

[0030] Referring to the second aspect, in some implementations of the second aspect, receiving the second indication information includes periodically receiving the second indication information.

[0031] For example, the candidate network device may transmit data to the terminal device based on the data in the early data transfer and the last received second indication information.

[0032] According to a third aspect, a data transmission method is provided. The method can be performed by a network device, or can be performed by a chip or circuit used in a network device. This is not limited in the present application. For ease of explanation, an example in which the method is performed by a network device is used below for explanation.

[0033] The method includes a step of determining that a target network device configures N first network devices for a terminal device, where the N first network devices include a second network device, N being an integer equal to or greater than 1, where before the terminal device is handed over from the source network device to the target network device, the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device, and after the terminal device is handed over from the source network device to the target network device, the second network device is a candidate network device in a conditional candidate PSCell addition or modification scenario configured for the terminal device. or the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device before the terminal device is handed over from the source network device to the target network device when the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device after the terminal device is handed over from the source network device to the target network device, or the second network device is a network device serving the terminal device. The target network device may send third indication information, where the third indication information instructs to use information about the terminal device in the second network device.

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

[0035] For example, "before the terminal device is handed over from a source network device to a target network device" may be understood as before the network device serving the terminal device changes from the source network device to the target network device, before a candidate network device configured for the terminal device changes from the source network device to the target network device, or before the network device serving the terminal device or the candidate network device configured for the terminal device changes.

[0036] For example, "after the terminal device is handed over from a source network device to a target network device" may be understood as after the network device serving the terminal device changes from the source network device to the target network device, 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 serving the terminal device or the candidate network device configured for the terminal device changes.

[0037] According to the above technical solution, in a scenario where a conditional candidate primary secondary cell group cell PSCell addition or modification is configured before and / or after a handover, when it is determined after the handover that the network devices configured for the terminal device include the network devices configured for the terminal device before the handover, previously forwarded data can be used to avoid forwarding these data packets again, thereby reducing the transmission delay of these data packets.

[0038] Referring to the third aspect, in some implementations of the third aspect, the target network device sending the third instruction information includes the target network device sending the third instruction information to the second network device; or the target network device sending the third instruction information to the source network device.

[0039] In the example, the target network device may send third instruction information to the second network device to instruct the second network device to use or maintain information about the terminal device in the second network device. For example, the information about the terminal device may include, but is not limited to, a context of the terminal device in the second network device and information about an early data transfer previously performed by the second network device.

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

[0041] Referring to the third aspect, in some implementations of the third aspect, the method further includes the target network device receiving early data transmission information of the second network device from the source network device.

[0042] Thus, by knowing the status of the second network device's earlier data transmission, the target network device may perform appropriate processing, for example, not forward the previously forwarded data packet.

[0043] For example, the early data transmission information of the second network device may include one or more of data packets for which early data transmission was performed from the source network device to the candidate second network device, and data packets in the early data transmission that can be discarded or ignored by the candidate second network device.

[0044] For example, the target network device may inform the second network device that a data packet in an earlier data transmission can be discarded or ignored.

[0045] Referring to the third aspect, in some implementations of the third aspect, the method further includes a step of the target network device performing early data transmission between the second network device based on the early data transmission information of the second network device.

[0046] Referring to the third aspect, in some implementations of the third aspect, the method further includes the target network device transmitting identification information of the second network device to the source network device.

[0047] Therefore, identification information is maintained to recognize one or more network devices that need to maintain the previously forwarded data before the handover. The solution is feasible and simple. In addition, when multiple candidate network devices need to maintain the previously forwarded data, the identifiers of these candidate network devices are indicated, so that signaling can be reduced and resources can be saved.

[0048] Referring to the third aspect, in some implementations of the third aspect, the method further includes a step in which the target network device receives information about one or more network devices from the source network device, where the one or more network devices include a second network device, and the one or more network devices are candidate network devices in a conditional candidate PSCell addition or modification scenario configured for the terminal device before the terminal device is handed over from the source network device to the target network device, or are network devices that provide service to the terminal device; the information about the one or more network devices includes one or more of 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, using the example where CPAC occurs before and after handover, the target network device may know whether the candidate network device before the handover is the same as the candidate network device after the handover based on the information about the candidate network device before the handover. In this way, when the candidate network device before the handover is the same as the candidate network device after the handover, these data packets are not forwarded again in the early data forwarding, and the transmission delay of these data packets may be reduced.

[0050] Referring to the third aspect, in some implementations of the third aspect, the information about the one or more network devices includes identification information of the one or more network devices, and based on the identification information of the one or more network devices, it may be determined that the N first network devices include the second network device.

[0051] Therefore, after the target network device receives the identification information of the network device or candidate network devices (i.e., one or more network devices) serving the terminal device before handover sent by the source network device, the target network device may determine which network device is selected to serve the terminal device based on the information, or may determine which candidate network device is selected based on the information. In this way, previous early transmission data may be reused as much as possible, reducing transmission delay and improving user experience.

[0052] Referring to the third aspect, in some implementations of the third aspect, the target network device receiving information about the one or more network devices from the source network device includes the target network device receiving a handover request message, where the handover request message includes information about the one or more network devices.

[0053] Thus, when sending a handover request message to the target network device, the source network device may inform the target network device of information about the network devices (e.g., candidate network devices) before the handover. Thus, the target network device may determine whether the same network device is included both before and after the handover by receiving the handover request message that carries information about the network devices (e.g., candidate network devices) before the handover.

[0054] Referring to the third aspect, in some implementations of the third aspect, the target network device transmits identification information of the terminal device at 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, where the SN addition request message includes identification information of the terminal device at the second network device.

[0056] Referring to the third aspect, in some implementations of the third aspect, the method further includes the target network device transmitting information about the N first network devices to the source network device.

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

[0058] According to a fourth aspect, a data transmission method is provided. The method can be performed by a network device, or can be performed by a chip or circuit used in a network device. This is not limited in the present application. For ease of explanation, an example in which the method is performed by a network device is used below for explanation.

[0059] The method includes a step of the source network device determining that the network devices configured for the terminal device after the handover include a second network device, where, before the terminal device is handed over from the source network device to the target network device, the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device, and, after the terminal device is handed over from the source network device to the target network device, the second network device is a candidate network device in a conditional candidate PSCell addition or modification scenario configured for the terminal device, or or when the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device after the terminal device is handed over from the source network device to the target network device, the second network device may be a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device before the terminal device is handed over from the source network device to the target network device, or the second network device may be a network device serving the terminal device. The source network device sends third instruction information to the second network device, where the third instruction information instructs using information about the terminal device in the second network device.

[0060] The method may be performed by a source network device (eg, a source MN or source SN) or may be performed by a chip or circuit used in the source network device (eg, 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 devices configured for the terminal device after the handover include the second network device.

[0062] For example, the third indication information may be carried in a release request message (eg, an SN release request message).

[0063] Referring to the fourth aspect, in some implementations of the fourth aspect, the source network device determining that the network devices configured for the terminal device after the handover include the second network device includes the source network device receiving, from the target network device, identification information of the second network device, and the source network device determines, based on the identification information of the second network device, that the network devices configured for the terminal device after the handover include the second network device.

[0064] Referring to the fourth aspect, in some implementations of the fourth aspect, the method further includes a step in which the source network device receives information about the N first network devices from the target network device, where 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 the N first network devices from the target network device.

[0066] For example, the source network device may determine, based on information about the N first network devices (e.g., identification information of the N first network devices), whether the network devices configured for the terminal device after the handover include the network devices configured for the terminal device before the handover. For example, the source network device may determine, based on information about the N first network devices (e.g., identification information of the N first network devices), that the network devices configured for the terminal device after the handover include the second network device.

[0067] Referring to the fourth aspect, in some implementations of the fourth aspect, the method further includes the source network device transmitting early data transmission information of the second network device to the target network device.

[0068] Referring to the fourth aspect, in some implementations of the fourth aspect, the method further includes a step of the source network device sending information about the one or more network devices to the target network device, where the one or more network devices include a second network device, and the one or more network devices are candidate network devices in a conditional candidate PSCell addition or modification scenario configured for the terminal device before the terminal device is handed over from the source network device to the target network device, or are network devices that serve the terminal device; the information about the one or more network devices includes one or more of identification information of the one or more network devices and identification information of the terminal device in the one or more network devices.

[0069] Referring to the fourth aspect, in some implementations of the fourth aspect, the source network device sending information about the one or more network devices to the target network device includes the source network device sending a handover request message to the target network device, where the handover request message includes the information about the one or more network devices.

[0070] Referring to the fourth aspect, in some implementations of the fourth aspect, the method further includes a step in which the source network device transmits a data packet to be transmitted to the terminal device to the target network device or the second network device.

[0071] According to a fifth aspect, a data transmission method is provided. The method can be performed by a network device, or can be performed by a chip or circuit used in a network device. This is not limited in the present application. For ease of explanation, an example in which the method is performed by a network device is used below for explanation.

[0072] The method may comprise the second network device receiving third instruction information from the source network device or the target network device, where the third instruction information instructs using information regarding the terminal device in the second network device. When the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device before the terminal device is handed over from the source network device to the target network device, after the terminal device is handed over from the source network device to the target network device, the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device, or the second network device is a network device serving the terminal device; or, when the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device after the terminal device is handed over from the source network device to the target network device, before the terminal device is handed over from the source network device to the target network device, the second network device is a candidate network device in a conditional candidate PSCell addition or modification scenario configured for the terminal device, or the second network device is a network device serving the terminal device.

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

[0074] For example, when the second network device receives the third indication information from the source network device, the third indication information may be carried in a release request message (e.g., a SN release request message).

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

[0076] Referring to the fifth aspect, in some implementations of the fifth aspect, the second network device receives identification information of a terminal device at 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, where the SN addition request message includes identification information of the terminal device at the second network device.

[0078] With reference to the third to fifth aspects, in some implementations, the information about the terminal device includes one or more of context information of the terminal device, data packets of the terminal device transmitted to the second network device, and information about data packets of the terminal device that can be discarded or ignored by the second network device.

[0079] Referring to the third to fifth aspects, in some implementations, the target network device is a network device in a conditional candidate PSCell addition or modification scenario, and the source network device is a network device in a conditional candidate PSCell addition or modification scenario. Alternatively, the target network device is a network device in a conditional candidate PSCell addition or modification scenario, and the source network device is a network device in a carrier aggregation scenario. Alternatively, the target network device is a network device in a carrier aggregation scenario, and the source network device is a network device in a conditional candidate PSCell addition or modification scenario.

[0080] According to a sixth aspect, a data transmission method is provided. The method can be performed by a network device, or can be performed by a chip or circuit used in a network device. This is not limited in the present application. For ease of explanation, an example in which the method is performed by a network device is used below for explanation.

[0081] The method may include steps of receiving information about candidate network devices configured for the terminal device before the terminal device is handed over from the source network device to the target network device; determining that network devices configured for the terminal device after the terminal device is handed over from the source network device to the target network device include candidate network devices configured for the terminal device before the handover; and receiving early data transmission information of candidate network devices configured for the terminal device before the terminal device is handed over from the source network device to the target network device.

[0082] For example, a candidate network device configured for the terminal device before the terminal device is handed over from a source network device to a target network device is described as a second network device. The method may include receiving information about the second network device; determining that the network devices configured for the terminal device after the handover include the second network device; and receiving early data transmission information of the second network device.

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

[0084] With reference to 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 a data packet for which an early data forwarding directed to the candidate network device was performed (e.g., indicated by a packet data convergence protocol sequence number (PDCP SN) or a new radio user plane sequence number (NR-U SN)), and a data packet in the early data forwarding that may be discarded or ignored by the candidate network device.

[0085] Referring to the sixth aspect, in some implementations of the sixth aspect, the method further includes a step of receiving third instruction information, where the third instruction information instructs using information regarding the terminal device in candidate network devices configured for the terminal device before the handover.

[0086] Referring to the sixth aspect, in some implementations of the sixth aspect, the information about the terminal device includes one or more of context information of the terminal device, data packets of the terminal device transmitted to candidate network devices configured for the terminal device before the terminal device is handed over from the source network device to the target network device, and information about 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 is handed over from the source network device to the target network device.

[0087] Referring to the sixth aspect, in some implementations of the sixth aspect, the method further includes a step of receiving second instruction information, where the second instruction information instructs discarding or ignoring some or all of the data packets in the early data transmission.

[0088] Referring to the sixth aspect, in some implementations of the sixth aspect, the second instruction information includes information about one or more sequence numbers, and the information about the one or more sequence numbers instructs discarding or ignoring some or all of the data packets in the early data transmission.

[0089] Referring to the sixth aspect, in some implementations of the sixth aspect, the sequence number is a Packet Data Convergence Protocol sequence number or a new wireless user plane sequence number.

[0090] Referring to the sixth aspect, in some implementations of the sixth aspect, early data transmission directed to a network device configured for the terminal device after a handover is performed based on a status of early data transmission between candidate network devices configured for the terminal device before the handover.

[0091] According to a seventh aspect, a data transmission method is provided. The method can be performed by a network device, or can be performed by a chip or circuit used in a network device. This is not limited in the present application. For ease of explanation, an example in which the method is performed by a network device is used below for explanation.

[0092] The method may include the steps of: transmitting information about candidate network devices configured for the terminal device before the terminal device is handed over from the source network device to the target network device; determining that network devices configured for the terminal device after the terminal device is handed over from the source network device to the target network device include candidate network devices configured for the terminal device before the handover; and transmitting early data transmission information of the candidate network devices configured for the terminal device before the terminal device is handed over from the source network device to the target network device.

[0093] For example, a candidate network device configured for the terminal device before the terminal device is handed over from the source network device to the target network device is described as a second network device. The method may include: transmitting information about the second network device; determining that the network devices configured for the terminal device after the terminal device is handed over from the source network device to the target network device include the second network device; and transmitting early data transmission information of the second network device.

[0094] The method may be performed by a source network device (eg, a source MN or source SN) or may be performed by a chip or circuit used in the source network device (eg, a source MN or source SN).

[0095] Referring to 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 data packets for which an early data forwarding directed to the candidate network device was performed (e.g., as indicated by a PDCP SN or NR-U sequence number) and data packets in the early data forwarding that can be discarded or ignored by the candidate network device.

[0096] Referring to the seventh aspect, in some implementations of the seventh aspect, the method further includes a step of transmitting third instruction information, where the third instruction information instructs to use information about the terminal device in candidate network devices configured for the terminal device before the terminal device is handed over from the source network device to the target network device.

[0097] Referring to the seventh aspect, in some implementations of the seventh aspect, the information about the terminal device includes one or more of context information about the terminal device, data packets of the terminal device transmitted to candidate network devices configured for the terminal device before the terminal device is handed over from the source network device to the target network device, and information about 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 is handed over from the source network device to the target network device.

[0098] Referring to the seventh aspect, in some implementations of the seventh aspect, the method further includes a step of transmitting second instruction information, where the second instruction information instructs discarding or ignoring some or all of the data packets in the early data transmission.

[0099] Referring to the seventh aspect, in some implementations of the seventh aspect, the second instruction information includes information about one or more sequence numbers, and the information about the one or more sequence numbers instructs discarding or ignoring some or all of the data packets in the early data transmission.

[0100] Referring to the seventh aspect, in some implementations of the seventh aspect, the sequence number is a Packet Data Convergence Protocol sequence number or a new wireless user plane sequence number.

[0101] Referring to the seventh aspect, in some implementations of the seventh aspect, the early data transmission directed to the target network device is performed based on a status of early data transmission between candidate network devices configured for the terminal device before the terminal device is handed over from the source network device to the target network device.

[0102] According to an eighth aspect, a data transmission method is provided. The method can be performed by a network device, or can be performed by a chip or circuit used in a network device. This is not limited in the present application. For ease of explanation, an example in which the method is performed by a network device is used below for explanation.

[0103] The method may include receiving information about network devices configured for the terminal device before the terminal device is handed over from the source network device to the target network device; determining that candidate network devices configured for the terminal device after the terminal device is handed over from the source network device to the target network device include network devices configured for the terminal device before the handover; and receiving early data transmission information of network devices configured for the terminal device before the terminal device is handed over from the source network device to the target network device.

[0104] For example, a network device configured for the terminal device before the terminal device is handed over from the source network device to the target network device is described as a second network device. The method may include receiving information about the second network device; determining that candidate network devices configured for the terminal device after the terminal device is handed over from the source network device to the target network device include the second network device; and receiving early data transmission information of the second network device.

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

[0106] According to a ninth aspect, a data transmission method is provided. The method can be performed by a network device, or can be performed by a chip or circuit used in a network device. This is not limited in the present application. For ease of explanation, an example in which the method is performed by a network device is used below for explanation.

[0107] The method may include the steps of: transmitting information about network devices configured for the terminal device before the terminal device is handed over from the source network device to the target network device; determining that candidate network devices configured for the terminal device after the terminal device is handed over from the source network device to the target network device include network devices configured for the terminal device before the handover; and transmitting early data transmission information of the network devices configured for the terminal device before the terminal device is handed over from the source network device to the target network device.

[0108] For example, a network device configured for the terminal device before the terminal device is handed over from the source network device to the target network device is described as a second network device. The method may include: transmitting information about the second network device; determining that candidate network devices configured for the terminal device after the terminal device is handed over from the source network device to the target network device include the second network device; and transmitting early data transmission information of the second network device.

[0109] The method may be performed by a source network device (eg, a source MN or source SN) or may be performed by a chip or circuit used in the source network device (eg, a source MN or source SN).

[0110] According to a tenth aspect, there is provided a communication device, the device being configured to perform the methods according to the first to ninth aspects. In particular, the device may include units and / or modules, such as a processing unit and / or a communication unit, configured to perform the methods according to the first to ninth aspects.

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

[0112] In another implementation, the apparatus is a chip, chip system, or circuit used in a network device. When the apparatus 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, associated circuit, or the like on the chip, chip system, or circuit, and the processing unit may be a processor, processing circuit, logic circuit, or the like.

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

[0114] According to an eleventh aspect, there is provided a communications apparatus, the apparatus comprising: a memory configured to store a program; and a processor configured to execute the program stored in the memory, the processor being configured to perform a method according to the first to ninth aspects when the program stored in the memory is executed.

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

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

[0117] According to a twelfth aspect, the present application provides a processor configured to perform the methods provided in the above aspects. In the processes of performing these methods, the processes of transmitting the information and acquiring / receiving the information in the above methods may be understood as a process of outputting the information by the processor and a process of receiving the input information by the processor. When outputting the information, the processor outputs the information to the transceiver, and the transceiver then transmits the information. After the information is output by the processor, other processing may need to be performed on the information before it reaches the transceiver. Similarly, when the processor receives input information, the transceiver acquires / receives the information and inputs the information to the processor. Furthermore, after the transceiver receives the information, other processing may need to be performed on the information before it is input to the processor.

[0118] According to the above principle, for example, obtaining information about the second network device before handover in the above method may be understood as receiving input information by the processor.

[0119] Unless otherwise specified or inconsistent with the actual functionality or internal logic in the relevant description, operations such as transmit, send, and acquire / receive performed by a processor may be understood more generally as operations such as output, receive, and input performed by a processor, rather than operations such as transmit, send, and receive performed directly by radio frequency circuits and antennas.

[0120] In the implementation process, the processor may be a processor specifically configured to execute these methods, or a processor that executes computer instructions in the memory to execute these methods, such as a general-purpose processor. The memory may be a non-transitory memory, such as a read-only memory (ROM). The memory and the processor may be integrated on the same chip, or may be located separately on different chips. The type of memory and the manner in which the memory and the processor are configured are not limited to the embodiments of the present application.

[0121] According to a thirteenth aspect, there is provided a computer readable storage medium storing program code for execution by a device, the program code being for performing the methods provided in the first to ninth aspects.

[0122] According to a fourteenth aspect there is provided a computer program product comprising instructions which, when executed on a computer, enable the computer to carry out the methods provided in the first to ninth aspects.

[0123] According to a fifteenth aspect, there is provided a chip, the chip comprising a processor and a communication interface, the processor reading instructions stored in a memory through the communication interface and executing the methods provided in the first to ninth aspects.

[0124] Optionally, in the implementation, the chip may further include a memory, the memory storing instructions, and the processor configured to execute the instructions stored in the memory, the instructions, when executed, causing the processor to perform the methods provided in the first to ninth aspects.

[0125] According to a sixteenth aspect, there is provided a communication system, including the master network device and candidate network devices as described above.

[0126] According to a 17th aspect, there is provided a communication system, comprising: a source network device and a target network device as described above; a source network device and a second network device as described above; a target network device and a second network device as described above; or a source network device, a target network device, and a second network device as described above. [Brief description of the drawings]

[0127] [Figure 1] FIG. 1 is a schematic diagram of the CU-DU architecture.

[0128] [Diagram 2] FIG. 2 is a schematic diagram of a wireless communication system 200 usable in embodiments of the present application.

[0129] [Diagram 3] 1 is a schematic diagram of a wireless communication system 300 that can be used in embodiments of the present application.

[0130] [Figure 4] FIG. 2 is a schematic diagram of a DC control plane architecture applicable in embodiments of the present application;

[0131] [Diagram 5] A schematic diagram of the network side protocol stack in EN-DC for MCG bearer, SCG bearer and split bearer.

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

[0133] [Figure 7] 1 is a schematic diagram of a data transmission method according to an embodiment of the present application;

[0134] [Figure 8] FIG. 2 is a schematic diagram of a data transmission method according to another embodiment of the present application;

[0135] [Figure 9] FIG. 1 is a schematic diagram of a CPA procedure applicable to embodiments of the present application.

[0136] [Figure 10] FIG. 2 is a schematic diagram of a CPC procedure triggered by a MN, which is applicable to an embodiment of the present application;

[0137] [Figure 11] FIG. 1 is a schematic diagram of a CPC procedure triggered by an SN, which is applicable to embodiments of the present application.

[0138] [Figure 12] 1 is a schematic flow chart of a scenario applicable to another embodiment of the present application, in which CPAC is configured before handover and then MN handover occurs;

[0139] [Figure 13] 1 is a schematic flow chart of a scenario applicable to another embodiment of the present application, in which a CPC is configured before handover and then an SN handover occurs;

[0140] [Figure 14] 13 is a schematic flow chart of a scenario applicable to another embodiment of the present application, in which CPAC is not configured before handover and then a MN handover occurs;

[0141] [Figure 15] 1 is a schematic block diagram of a data transmission device according to an embodiment of the present application;

[0142] [Figure 16] FIG. 2 is another schematic block diagram of a data transmission device according to an embodiment of the present application;

[0143] [Figure 17] FIG. 2 is a schematic diagram of the structure of a network device according to an embodiment of the present application; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0144] The technical solutions of the present application are described below with reference to the accompanying drawings.

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

[0146] The terminal device in the embodiment of the present application may also be referred to as user equipment (UE), access terminal, subscriber unit, subscriber station, mobile station (MS), mobile terminal (MT), remote station, remote terminal, mobile device, user terminal, terminal, wireless communication device, user agent, or user equipment. The terminal device in the embodiment of the present application may be a device that provides voice and / or data connection to a user, and may be configured to connect people, objects, and machines, and may be, for example, a handheld device or a vehicle-mounted device with wireless connection capabilities. The terminal device in the embodiment of the present application may be a mobile phone, a tablet computer, a notebook computer, a palmtop computer, a mobile Internet device (MID), a wearable device, a virtual reality (VR) device, an augmented reality (AR) device, a wireless terminal in industrial control, a wireless terminal in self-driving, a wireless terminal in remote medical surgery, a wireless terminal in a smart grid, a wireless terminal in transportation safety, a wireless terminal in a smart city, a wireless terminal in a smart home, and the like. Optionally, the UE may function as a base station. For example, the UE may function as a scheduling entity that provides a sidelink signal between UEs in V2X or D2D communication. For example, a mobile phone and an automobile communicate with each other by using a sidelink signal. The base station does not need to relay a communication signal for communication between a mobile phone and a smart home device.

[0147] The network device in the embodiment of the present application may be a device configured to communicate with a terminal device. The network device may also be referred to as an access network device or a radio access network device. For example, the network device may be a base station. The network device in the embodiment of the present application may be a radio access network (RAN) node (or device) that enables the terminal device to access a radio network. The base station may broadly cover or be interchangeable with the following names, such as NodeB, evolved NodeB (eNB), next generation NodeB (gNB), relay station, access point, transmission reception point (TRP), transmission point (TP), master eNodeB MeNB, secondary eNodeB SeNB, multi-standard radio (MSR) node, home base station, network controller, access node, radio node, access point (AP), transmission node, transceiver node, baseband unit (BBU), remote radio unit (RRU), active antenna unit (AAU), remote radio head (RRH), central unit (CU), distributed unit (DU), and positioning node. The base station may be a macro base station, a micro base station, a relay node, a donor node, a similar device, or a combination thereof. The base station may alternatively be a communication module, modem, or chip located in the above mentioned device or apparatus.Alternatively, the base station may be a mobile switching center, a device performing base station functions in device-to-device (D2D), vehicle-to-everything (V2X), and machine-to-machine (M2M) communications, a network side device in a 6G network, a device performing base station functions in future communication systems, and the like. The base station may support a network using the same access technology or different access technologies. The particular technology used by the network device and the particular device form are not limited in the embodiments of this application.

[0148] A base station may be fixed or mobile. For example, a helicopter or unmanned aerial vehicle may be configured to function as a mobile base station, and one or more cells may move with the location of the mobile base station. In another example, a helicopter or unmanned aerial vehicle may be configured as a device that communicates with another base station.

[0149] In some deployments, the network device in the embodiment of the present application may be a CU or a DU, or includes a CU and a DU. The gNB may further include an active antenna unit (AAU). As an illustrative example, FIG. 1 is a schematic diagram of a CU-DU architecture. The CU performs part of the functions of the gNB, and the DU performs part of the functions of the gNB. For example, the CU is responsible for processing non-real-time protocols and services, and implements functions of the radio resource control (RRC) layer and the packet data convergence protocol (PDCP) layer. The DU is responsible for processing physical layer protocols and real-time services, and implements functions of the radio link control (RLC) layer, the media access control (MAC) layer, and the physical (PHY) layer. The AAU implements some of the physical layer processing functions, radio frequency processing, and functions related to active antennas. Information at the RRC layer is finally converted to or from information at the PHY layer. Therefore, in this architecture, higher layer signaling such as RRC layer signaling may be considered as being transmitted by the DU or transmitted by the DU and the AAU. It may be understood that a network device may be a device including one or more of a CU node, a DU node, and an AAU node. In addition, a CU may be classified as a network device in a radio access network (RAN) or may be classified as a network device in a core network (CN). This is not limited in this application.

[0150] Further, the CU may be divided into a central unit-control plane (CU-CP) and a central unit-user plane (CU-UP). The CU-CP and the CU-UP may also be deployed in different physical devices. The CU-CP is responsible for the control plane function, and mainly includes an RRC layer and a PDCP-C layer. The PDCP-C layer is mainly responsible for data encryption and decryption, integrity protection, data transmission, etc. in the control plane. The CU-UP is responsible for the user plane function, and mainly includes a service data adaptation protocol (SDAP) layer and a PDCP-U layer. The SDAP layer is mainly responsible for processing data of the core network and mapping flows to bearers. The PDCP-U layer is mainly responsible for at least one function in encryption and decryption, integrity protection, header compression, serial number maintenance, data transmission, and the like for the data plane. Specifically, the CU-CP and the CU-UP are connected through a communication interface (e.g., an E1 interface). Instead of a network device, the CU-CP is connected to a core network device through a communication interface (e.g., an Ng interface). The CU-CP is connected to a DU through a communication interface (e.g., an F1-C (control plane) interface). The CU-UP is connected to a DU through a communication interface (e.g., an F1-U (user plane) interface).

[0151] In another possible implementation, the PDCP-C layer is also included in the CU-UP.

[0152] It can be understood that the above protocol layer division between CU and DU, and the protocol layer division between CU-CP and CU-UP are merely examples, and there may be other division methods. The embodiment of the present application is not limited thereto.

[0153] A network device in an embodiment of the present application may be a device including a CU, a DU, or a CU and a DU, or may be a device including a CU control plane node (CU-CP node), a CU user plane node (CU-UP node), and a DU node.

[0154] The network devices and terminal devices include indoor devices, outdoor devices, handheld devices, or vehicle-mounted devices, and may be deployed on the ground; on water; or on airborne aircraft, balloons, and satellites. The scenarios of the network devices and terminal devices are not limited in the embodiments of the present application.

[0155] Some embodiments of the present application further relate to a core network device. Specifically, a core network device is a device in a core network (CN) that provides service support to a terminal device. Currently, some examples of a core network device are an access and mobility management function (AMF) entity, a session management function (SMF) entity, a user plane function (UPF) entity, and the like. Examples are not listed one by one here. The AMF entity may be responsible for access management and mobility management of a terminal device. The SMF entity may be responsible for session management, e.g., session establishment, of a terminal device. The UPF entity may be a user plane function entity, and is mainly responsible for connecting to an external network. It should be noted that entities in the present application may also be referred to as network elements or function entities. For example, an AMF entity may also be referred to as an AMF network element or an AMF function entity. In another example, an SMF entity may also be referred to as an SMF network element or an SMF function entity.

[0156] It should be understood that the above names are defined only to facilitate distinguishing different functions, and do not constitute any limitation to the present application. The present application does not exclude the possibility of using other names in 5G networks and other future networks. For example, in a 6G network, some or all of the above network elements may still use the terminology in 5G, or may use other names.

[0157] To facilitate understanding of the embodiments of the present application, a communication system usable in the embodiments of the present application will first be described in detail with reference to FIGS.

[0158] As an illustrative example, Fig. 2 is a schematic diagram of a wireless communication system 200 that can be used in an embodiment of the present application. As shown in Fig. 2, the wireless communication system 200 may include at least one network device, for example, the network device 210 shown in Fig. 2. The wireless communication system 200 may further include at least one terminal device, for example, the terminal device 220 shown in Fig. 2. Multiple antennas may be configured for each of the network device and the terminal device. The network device and the terminal device may communicate with each other by using multi-antenna technology.

[0159] When a network device communicates with a terminal device, the network device may manage one or more cells, and there may be an integer number of terminal devices in one cell. Optionally, the single-cell communication system includes a network device 210 and a terminal device 220. Without loss of generality, the cell is described as cell #1. The network device 210 may be a network device in cell #1, in other words, the network device 210 may function as a terminal device (e.g., terminal device 220) in cell #1.

[0160] It should be noted that a cell may be understood as an area within the coverage of a radio signal of a network device.

[0161] It should be understood that Fig. 2 is merely a simplified schematic diagram used as an example for ease of understanding. The wireless communication system 200 may further include other network devices or other terminal devices not shown in Fig. 2.

[0162] The method provided in the present application may further be applied to a dual connectivity (DC) scenario. For ease of understanding, the DC scenario is described with reference to Figure 3 by using an example in which the terminal device is a UE and the network device is a base station.

[0163] In a wireless network, one UE may communicate with multiple base stations. This is dual connectivity (DC), also called multi-radio dual connectivity (MR-DC). For uniformity, DC is used below for denotation. The multiple base stations may be base stations belonging to the same radio access technology (RAT) (where, for example, all the base stations are 4G base stations or 5G base stations) or may be base stations belonging to different RATs (where, for example, one is a 4th generation 4G base station and one is a 5th generation 5G base station).

[0164] As an illustrative example, Fig. 3 is another schematic diagram of a wireless communication system 300 that can be used in the embodiments of the present application. Please refer to Fig. 3. The UE 320 can communicate with the base station 311 and the base station 312 by using DC technology, and the base station 311 and the base station 312 both access the core network 330. The core network 330 can be a 4G core network or a 5G core network.

[0165] The network side can provide communication services to the UE by using resources of multiple base stations, and provide high-speed transmission to the UE. In the DC scenario, for a particular UE, a base station exchanging control plane signaling with the core network is called a master node (MN), and another base station is called a secondary node (SN). The MN may also be called a master base station in some cases, and the SN may also be called a secondary base station in some cases. The base stations have different RLC entities and different MAC entities. In the DC scenario, data radio bearers (DRB) may be classified into three types: master cell group bearer (MCG bearer), secondary cell group bearer (SCG bearer), and split bearer. The MCG bearer means that the RLC entity and MAC entity of the DRB are on the master base station, the SCG bearer means that the RLC entity and MAC entity of the DRB are on the secondary base station, and the split bearer means that the RLC entity and MAC entity of the DRB are on both the master base station and the secondary base station. Similarly, a bearer whose PDCP is terminated on the MN may be referred to as an MN terminated bearer. Specifically, downlink (DL) data arrives directly from the core network to the MN, is processed by the MN's PDCP / SDAP, and then is sent to the UE through the MN's or SN's RLC / MAC; uplink (UL) data is processed by the MN's PDCP / SDAP, and then is sent to the core network. A bearer whose PDCP is terminated on the SN may be referred to as an SN terminated bearer.Specifically, DL data arrives directly from the core network to the SN, is processed by the PDCP / SDAP of the SN, and then is sent to the UE through the RLC / MAC of the MN or the SN; UL data is processed by the PDCP / SDAP of the SN, and then is sent to the core network. In some cases, for example, when a terminal device is connected to a 5G core network, it can be understood that there is an SDAP layer.

[0166] In addition, in the dual connection, the master base station and the secondary base station each have an RRC entity that can generate an RRC message (i.e., a control message, e.g., a measurement message). As an illustrative example, FIG. 4 is a schematic diagram of a DC control plane architecture that is applicable to an embodiment of the present application. The master base station and the core network communicate with each other through a communication interface (e.g., an NG-C interface), the master base station and the secondary base station communicate with each other through a communication interface (e.g., an Xn-C interface), the master base station and the UE communicate with each other through a communication interface (e.g., a Uu interface), and the secondary base station and the UE communicate with each other through a communication interface (e.g., a Uu interface).

[0167] The secondary base station may directly transmit the RRC message generated by the secondary base station to the UE. In this case, the RRC message sent by the UE to the secondary base station is also directly transmitted to the secondary base station. The RRC message directly exchanged between the secondary base station and the UE is referred to as signaling radio bearer 3 (SRB3). Alternatively, the secondary base station may notify the master base station of the generated RRC message, and the master base station transmits the RRC message to the UE. In this case, the master base station forwards the RRC message sent by the UE to the secondary base station to the secondary base station. For the UE in the DC scenario, the user plane of the secondary base station may be connected to a core network connected to the master base station. In other words, the core network may directly transmit data to the UE through the secondary base station.

[0168] It should be understood that the interfaces between devices in the present application (where, for example, a master base station and a secondary base station may communicate with each other through an Xn-C interface) are merely examples for explanation and do not limit the scope of protection of the embodiments of the present application.

[0169] Scenarios in which the present application is applicable may include the following DC types: Evolved Universal Terrestrial Radio Access-New Radio Dual Connectivity (E-UTRA-NR dual connectivity, EN-DC), Next Generation Radio Access Network Evolved Universal Terrestrial Radio Access-New Radio Dual Connectivity (NG-RAN E-UTRA-NR dual connectivity, NGEN-DC), New Radio-Evolved Universal Terrestrial Radio Access Dual Connectivity (NR-E-UTRA dual connectivity, NE-DC), and New Radio-New Radio Dual Connectivity (NR-NR dual connectivity, NR-DC).

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

[0171] In NGEN-DC, the master 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 master 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 also sometimes referred to as NSA because in the initial phase of 5G, UEs on the EN-DC network cannot camp on NR cells. The NR base station on which the UE camps may also be sometimes referred to as SA NR base station.

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

[0174] As an illustrative example, Figure 5 is a schematic diagram of network side protocol stacks in EN-DC for MCG bearer, SCG bearer and split bearer. As an illustrative example, Figure 6 is a schematic diagram of network side protocol stacks in NGEN-DC / NE-DC / NR-DC for MCG bearer, SCG bearer and split bearer. From Figure 5 and Figure 6, it can be seen that the transmission of each bearer needs to be performed through RLC / MAC and PDCP / SDAP.

[0175] A UE may be served by multiple cells of one base station. A serving cell group provided by an MN for a UE may be referred to as a master cell group (MCG), where the MCG includes one or more cells. A serving cell group provided by an SN for a UE may be referred to as a secondary cell group (SCG), where the SCG includes one or more cells. When an MCG includes only one cell, the cell is a primary cell (PCell) of the UE. When an SCG includes only one cell, the cell is a primary secondary cell group cell (PSCell) of the UE. To standardize various terms, in NR, PCell and PSCell are collectively referred to as special cells (SpCells). When an MCG or SCG includes multiple cells, cells other than SpCell may be referred to as secondary cells (SCells). Carrier aggregation may be performed on SCells or SpCells in an MCG or SCG to jointly provide transmission resources for the UEs.

[0176] It should be understood that the application scenario of the present application is not limited to the above DC scenario. The present application can also be applied to DC scenarios of other systems, such as DC scenarios including 5G base stations and Wi-Fi (registered trademark), or DC scenarios including base stations deployed as licensed spectrum and base stations deployed as unlicensed spectrum.

[0177] In order to facilitate understanding of the embodiments of the present application, several basic concepts in the embodiments of the present application are briefly described. The basic concepts described below are briefly described by using the basic concepts specified in the current protocol as an example, but it should be understood that the embodiments of the present application are not limited to be applied only to the existing communication system. Therefore, all standard names that appear when the existing communication system is used as an example for explanation are functional descriptions, and the specific names are not limited.

[0178] 1. Carrier aggregation (CA) is a technology in which multiple component carriers (cells) are configured for a single terminal device to jointly perform data transmission.

[0179] 2. Primary cell PCell is a cell deployed on a primary frequency (in other words, a cell operating on a primary component carrier). PCell is the corresponding cell where a terminal device initiates an initial connection establishment process or a connection re-establishment process. Specifically, when a terminal device initiates an initial connection establishment process or a connection re-establishment process in a specific cell, the cell is referred to as a PCell. In a handover process, a cell may be designated as a PCell.

[0180] 3. A primary secondary cell group cell PSCell is a cell in an SCG from which a terminal device performs random access or initial physical uplink shared channel (PUSCH) transmission in the SCG (where, for example, the UE initiates initial PUSCH transmission when an SCG change is performed and no random access process is required), or a cell in an SCG from which a terminal device performs random access in a synchronous reconfiguration process.

[0181] 4. A secondary cell (SCell) is a cell that operates on a secondary component carrier. When an RRC connection is established, the SCell may be configured to provide additional radio resources. In a dual connection system, all cells other than the PCell and PSCell in the MCG and SCG may be referred to as SCells.

[0182] A PSCell is also referred to as an SCell in some descriptions, in other words, it should be understood that a SCell also includes a PSCell.

[0183] 5. Serving cell: If carrier aggregation or dual connectivity is not configured for a terminal device in RRC_CONNECTED mode, there is only one serving cell, i.e., PCell. If carrier aggregation or dual connectivity is configured, the serving cell of the terminal device may be considered to include the PCell, PSCell, and all SCells.

[0184] It should be understood that the above PCell, PSCell, and all SCells are merely examples. Any meaning indicating the same function in a future protocol is applicable to the embodiments of the present application.

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

[0186] In dual connectivity, generally, due to the mobility of the terminal device, the network side triggers a PSCell change (specifically, the network side notifies the terminal device that it is handed over from a PSCell to another PSCell, and notifies the configuration information corresponding to the PSCell obtained after the change). For example, the network side recognizes that the signal quality of the PSCell becomes worse and the signal quality of another PSCell becomes better based on the measurement result of the terminal device, and as a result, the network side notifies the terminal device to perform a PSCell change. It should be understood that the PSCell change may be that the terminal device is handed over from a cell of an SN to a cell of another SN, or that the terminal device is handed over from a cell of an SN to another cell of an SN. In addition, the PSCell change may be triggered by the MN, in other words, the MN decides (or initiates) the handover from the PSCell to another PSCell, or may be triggered by the SN, in other words, the SN decides (or initiates) the handover from the PSCell to another PSCell.

[0187] The conditional PSCell addition / change (CPAC) method is as follows: the network side pre-configures multiple candidate PSCells and notifies the terminal device of the configurations of multiple candidate PSCells and the conditions corresponding to each candidate PSCell. Then, when it is determined that there is a candidate PSCell that satisfies the condition corresponding to the candidate PSCell, the terminal device may directly access the candidate PSCell that satisfies the condition. In this way, the network side does not need to wait until the terminal device reports a measurement report before delivering a new PSCell configuration to the terminal device, thereby reducing the delay of the PSCell addition or change. In addition, in the scenario in which the SN triggers the PSCell change, the failure of reporting the measurement report and delivering the reconfiguration message through the SRB3 can be avoided when the signal quality of the PSCell changes rapidly. Therefore, the robustness of the PSCell change is improved.

[0188] It may be understood that CPAC in this application is a general term, and may refer to a conditional PSCell addition and / or modification configuration.

[0189] In CPAC, when there is a candidate PSCell that satisfies the conditions corresponding to the candidate PSCell, the terminal device can directly access the candidate PSCell that satisfies the conditions, thereby shortening the delay for PSCell addition or modification. However, after the terminal device accesses the candidate PSCell, the candidate PSCell cannot immediately transmit data to the terminal device, and needs to transmit data to the terminal device only after the device before the terminal device accesses the candidate PSCell transmits a data packet to the candidate PSCell. This increases the transmission delay of these data packets.

[0190] The embodiments of the present application provide a solution to reduce data transmission delay.

[0191] It should be noted that in the embodiment of the present application, the handover process mainly includes CPAC-related procedures, such as PSCell addition or modification.

[0192] With reference to the accompanying drawings, the following describes in detail the embodiments provided in the present application.

[0193] 7 is a schematic diagram of a data transmission method 700 according to an embodiment of the present application. The method 700 may include the following steps.

[0194] 710: The master network device performs a conditional candidate PSCell addition or modification procedure with the candidate network device.

[0195] The master network device may be, for example, an MN, and the candidate network devices and the secondary network devices may be, for example, SNs.

[0196] In step 710, the master network device or the secondary network device may trigger a conditional candidate PSCell addition or change configured for the terminal device. Specifically, the master network device or the secondary access network device triggers the candidate network device to pre-configure multiple candidate PSCells. Then, the master access network device may notify the terminal device of the configuration of multiple candidate PSCells and the trigger condition corresponding to each candidate PSCell. Then, when it is determined that there is a candidate PSCell that satisfies the condition corresponding to the candidate PSCell, the terminal device may directly access the candidate PSCell that satisfies the trigger condition. When there are multiple candidate PSCells that satisfy the trigger condition corresponding to the candidate PSCell, a corresponding design may be made for a specific candidate PSCell that satisfies the condition and that the terminal device accesses based on the requirements of the system to which the terminal device belongs. For example, the terminal device performs the determination of selecting any candidate PSCell that satisfies the condition, or selecting a candidate PSCell that the terminal device has previously accessed. This is not limited in the present specification.

[0197] It should be understood that, mainly for ease of understanding, Fig. 7 uses a master network device and one candidate network device as an example for illustration purposes. The number of candidate network devices is not limited in this embodiment of the present application. For example, in practice, more candidate network devices may be included.

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

[0199] In other words, in step 720, the master network device may transmit 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 may be a candidate network device, for example a candidate SN.

[0200] In a possible manner, in step 720, the master network device performs early data transmission directed to the network device to which the candidate PSCell belongs. The early data transmission is to transmit 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 format of the one or more data packets transmitted by the master network device to the candidate network devices may be a Packet Data Convergence Protocol protocol data unit (PDU) (PDCP PDU).

[0202] In this embodiment of the present application, the master network device may perform early data transmission on data packets on an MN terminated SCG bearer directed to a candidate network device, and may further perform early data transmission on data packets on an MN terminated split bearer directed to a candidate network device.

[0203] A data packet on an MN terminated SCG bearer indicates that the RLC entity and MAC entity of the DRB corresponding to the data packet are on the SN, and that the PDCP entity is on the MN. Similarly, a data packet on an MN terminated split bearer indicates that the RLC entity and MAC entity of the DRB corresponding to the data packet are on the SN and MN, and that the PDCP entity is on the MN. Specifically, in early data transmission, a data packet on an MN terminated SCG bearer or an MN terminated split bearer is processed by the PDCP / SDAP of the MN.

[0204] It should be understood that in the embodiments of the present application, whether a PDCP layer is deployed on a candidate network device (e.g., a candidate SN) or whether the candidate network device supports the functionality of the PDCP layer is not limited.

[0205] In this application, for an MN terminated SCG bearer or an MN terminated split bearer, early data transmission may also be referred to as early data forwarding, or may have another name. The name of early data transmission does not limit the scope of protection of the embodiments of this application. In the following, for uniformity, data forwarding between a master network device or a secondary network device and a candidate network device in CPAC is described as early data forwarding.

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

[0207] 730: After the terminal device accesses the candidate network device, the candidate network device transmits a part or all of the one or more data packets to the terminal device.

[0208] In other words, after the terminal device accesses the candidate network device, the candidate network device may transmit the data forwarded to the candidate network device to the terminal device, so as to reduce the data transmission delay.

[0209] According to this embodiment of the present application, early data forwarding may be performed between a master network device and a candidate network device (e.g., a MN and a candidate SN). In this way, after the terminal device accesses the candidate network device, the candidate network device may transmit data forwarded to the candidate network device to the terminal device, reducing data transmission delay. In addition, for MN terminated SCG bearers and / or MN terminated split bearers, the master network device may also perform early data forwarding directed to the candidate network device, for example, in the form of PDCP PDUs. Thus, this embodiment of the present application may support early data forwarding of data packets on MN terminated SCG bearers and / or data packets on MN terminated split bearers, thereby reducing the transmission delay of data on these bearers.

[0210] Optionally, the master network device may further send instruction information #1 to the candidate network device (i.e., the network device to which the candidate PSCell belongs) to instruct it to discard or ignore part or all of one or more data packets. For example, the MN may send instruction information #1 to the candidate SN to instruct it to discard or ignore part or all of the data packets in the early data transfer. In this way, the candidate network device may transmit data to the terminal device based on the data in the early data transfer and the instruction information #1. In this case, the candidate network device may transmit part of 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 instructed to be discarded or directly ignore these data packets. For example, after the master network device transmits the CPAC configuration to the terminal device, the master network device or the secondary network device may continue to transmit data to the terminal device, so that the master network device or the secondary network device may successfully transmit part of the data packets to the terminal device during the period from transmitting the CPAC configuration to the terminal device to accessing the candidate PSCell by the terminal device. In order to prevent the candidate network device from retransmitting data packets that were successfully transmitted to the terminal device after the terminal device accesses the candidate PSCell, the master network device or the secondary network device notifies the candidate network device to discard or ignore some data packets that were successfully transmitted to the terminal device.

[0211] This scheme can avoid the case where the candidate network device holds back or repeatedly transmits some data packets that have been successfully received by the terminal device to the terminal device, thereby reducing resource waste.

[0212] For the sake of distinction, in this embodiment of the present application, instruction information #1 represents information instructing to discard or ignore some or all of the data packets in the early data transfer.

[0213] The transmission opportunity of the indication information #1 is not limited. For example, the indication information #1 may be transmitted when a preset condition is satisfied. The preset condition may be a time restriction (e.g., periodic transmission), a data amount restriction (e.g., a comparison between the data amount and a threshold or a threshold range), or a restriction in another respect.

[0214] In addition, the format of the indication information #1 is not limited. In a possible format, the indication information #1 may be in the form of one or more sequence numbers (SN). In this application, the sequence number is mentioned several times, and the specific format of the sequence number is not limited. For example, the sequence number may be a packet data convergence protocol sequence number (PDCP SN), a new radio user plane sequence number (NR-U SN), or another sequence number. This is not limited and will not be described again below.

[0215] The transmission method of the indication information #1 is also not limited. For example, the indication information #1 can be transmitted between the master network device and the candidate network device through a user plane, or can be transmitted between the master network device and the candidate network device through a control plane (where, for example, the master network device transmits a message to the candidate network device, and, for example, the master network device includes the indication information #1 in an early status transfer message).

[0216] An example is used in which the indication information #1 is transmitted between the master network device and the candidate network device through the user plane. For example, the data transmitted by the master network device to the candidate network device through the user plane carries a sequence number corresponding to a data packet that needs to be discarded or ignored. For example, the data carries one PDCP SN and instructs to discard or ignore all data packets having a sequence number before the sequence number, where the data packets include the data packets corresponding to the sequence number. In another example, the data carries indication information for indicating data packets corresponding to a number of blocks. For example, the indication information includes the number of blocks, the PDCP SN corresponding to the first data packet in each block that needs to be discarded or ignored, and the number of data packets corresponding to the block, where each block corresponds to data packets corresponding to several consecutive PDCP SNs.

[0217] The specific content of the instruction information #1 will be described in detail below with reference to the method 900 shown in FIG.

[0218] Optionally, the master network device may further send indication information #2 to the candidate network device (i.e., the network device to which the PSCell belongs), where the indication information #2 instructs to perform early data transmission on the MN terminated SCG bearer and / or the MN terminated split bearer. For example, the MN may send indication information #2 to the candidate SN to instruct to perform early data transmission on the MN terminated SCG bearer and / or the MN terminated split bearer. After sending indication information #2 to the candidate network device, the master network device may perform early data transmission on the MN terminated SCG bearer and / or the MN terminated split bearer with the candidate network device.

[0219] For the sake of distinction, in this embodiment of the present application, the indication information #2 represents information for instructing to perform early data transmission on the MN terminated SCG bearer and / or the MN terminated split bearer.

[0220] The indication information #2 may be transmitted between the master network device and the candidate network device through a control plane interface, or may be transmitted between the master network device and the candidate network device through a user plane interface, but is not limited thereto.

[0221] In addition, the indication manner may be to give an indication by using specific content in the indication information #2, or to give an indication through the action of sending the indication information #2, without being limited thereto. For example, the indication is given through the action of sending the indication information #2. By way of example and not limitation, a specific field may be pre-agreed or pre-configured. When the field is sent, it indicates that early data transmission is to be performed on the MN terminated SCG bearer and / or the MN terminated split bearer.

[0222] Particular procedures applicable to the method 700 are described below with reference to the embodiments shown in FIGS.

[0223] 8 is a schematic diagram of a data transmission method 800 according to an embodiment of the present application. The method 800 may include the following steps.

[0224] 810: The target network device determines to configure N first network devices for the terminal device, where the N first network devices include a second network device.

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

[0226] In this embodiment of the present application, for the sake of distinction, the target network device refers to the network device after the handover, and the source network device refers to the network device before the handover. The network device may be, for example, an MN or an SN. For example, the handover is performed from a source MN to a target MN. In another example, the handover is performed from a source SN to a target SN. In another example, the handover is performed from a source MN to a target MN and from a source SN to a target SN.

[0227] The target network device determines to configure N first network devices for the terminal device, where the N first network devices may include a network device serving the terminal device and / or a candidate network device. After the handover, if the N first network devices include a second network device, the second network device may be a network device serving the terminal device or a candidate network device.

[0228] In this application, before handover means before the terminal device is handed over from the source network device to the target network device, specifically before the network device serving 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 serving the terminal device or the candidate network device configured for the terminal device changes. After handover means after the terminal device is handed over from the source network device to the target network device, specifically after the network device serving 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 serving the terminal device or the candidate network device configured for the terminal device changes. For simplicity, in the following, before handover and after handover are used for description.

[0229] The second network device before and after the handover may be in the following cases:

[0230] In a possible case, the second network device after the handover is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device.

[0231] For example, in a scenario where a conditional primary secondary cell group cell (PSCell) addition (CPA) / conditional primary secondary cell group cell (PSCell) change (CPC) is configured after handover, the candidate network device that the target network device decides to configure is partially or completely the same as the network device before handover (where, for example, before handover, the network device is the network device providing service to the terminal device or is the candidate network device configured for the terminal device). In other words, the candidate network device that the target network device decides to configure includes the network device configured for the terminal device before handover, i.e., the second network device.

[0232] Before the handover, the second network device may be a network device that serves the terminal device. For example, before the handover, the second network device is a network device in a DC scenario, such as a secondary network device. Alternatively, before the handover, the second network device may be a candidate network device configured for the terminal device. For example, before the handover, the second network device is a network device in a CPA / CPC scenario.

[0233] In another possible case, the second network device before the handover is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device.

[0234] For example, in a CPA / CPC scenario before handover, the second network device is a candidate network device configured for the terminal device, and after handover, the second network device may be a candidate network device or may be a network device serving the terminal device.

[0235] In an example, in a scenario where the CPA / CPC is configured after handover, the candidate network devices that the target network device decides to configure are partially or completely identical to the candidate network devices that were configured for the terminal device before handover. In other words, the candidate network devices that the target network device decides to configure include the candidate network devices that were configured for the terminal device before handover, i.e., the second network devices.

[0236] In another example, in a scenario in which a DC is configured after handover, the network device (e.g., secondary network device) that the target network device (e.g., master network device) decides to configure is partially or completely identical to the candidate network device that was configured for the terminal device before handover. In other words, the network device that the target network device decides to configure includes the candidate network device, i.e., the second network device, that was configured for the terminal device before handover.

[0237] In another possible case, before and after handover, the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device.

[0238] For example, in a CPA / CPC scenario before handover, the second network device is a candidate network device configured for the terminal device, and in a CPA / CPC configured after handover scenario, the candidate network device for which the target network device determines the configuration is partially or completely the same as the candidate network device configured for the terminal device before handover.

[0239] It should be understood that the above three possible cases are merely illustrative examples, and any one of the variations of the above cases can be applied to the embodiments of the present application. For example, the N first network devices include a plurality of second network devices, and specifically, the target network device may decide to maintain the plurality of second network devices configured for the terminal device before handover.

[0240] After the handover, when the target network device determines that the N first network devices configured for the terminal device include a network device configured for the terminal device before the handover, the data transferred in the previous early data transfer may be used, in other words, some unnecessary data transfer may be reduced. For example, the target network device may send instruction information, for example described as instruction information #3, to instruct the second network device to use or maintain information about the terminal device.

[0241] The information about the terminal device in the second network device may include, for example, one or more of the following: a context of the terminal device in the second network device, a data packet of the terminal device transmitted to the second network device, and information about a data packet that can be discarded or ignored by the second network device. The data packet that can be discarded by the second network device represents a discardable data packet in a data packet in a previous early data forwarding in the second network device. By way of example and not limitation, the instruction information #3 may instruct to maintain the context of the terminal device in the second network device. Alternatively, the instruction information #3 may instruct to use or maintain the early data forwarding information of the second network device. The early data forwarding information of the second network device includes information about a data packet in a previous early data forwarding in the second network device (i.e., a data packet of the terminal device transmitted to the second network device) and / or a data packet that can be discarded or ignored by the second network device.

[0242] In this embodiment of the present application, for the sake of distinction, the instruction information #3 represents information for instructing to use or maintain information about the terminal device in some network devices configured for the terminal device before handover. A specific instruction manner may be to give an instruction by using specific content in the instruction information #3, or to give an instruction through an action of sending the instruction information #3. The embodiment of the present application is not limited thereto.

[0243] In the example, the specific content in the instruction information #3 may instruct to use or maintain information about the terminal device in some network devices configured for the terminal device before the handover.

[0244] For example, it is assumed that the function of the indication information #3 is predefined in the protocol as using or maintaining information about the terminal device in some network devices configured for the terminal device before handover. For example, a 1-bit field may indicate using or maintaining information about the terminal device in some network devices configured for the terminal device before handover. 0 corresponds to using or maintaining information about the terminal device in some network devices configured for the terminal device before handover, and 1 corresponds to not using or not needing to maintain information about the terminal device in some network devices configured for the terminal device before handover, or releasing information about the terminal device in some network devices configured for the terminal device before handover.

[0245] In another example, the 1-bit field may indicate that the instruction information #3 indicates whether to maintain the context of the terminal device in the second network device or to use or maintain the early data forwarding information of the second network device, where 0 corresponds to the instruction information #3 indicating to maintain the context of the terminal device in the second network device, and 1 corresponds to the instruction information #3 indicating to use or maintain the early data forwarding information of the second network device.

[0246] In another example, the action of sending the instruction information #3 may instruct to use or maintain information about the terminal device in some network devices configured for the terminal device before the handover. For example, the instruction information #3 may be designed specifically to instruct to use or maintain information about the terminal device in some network devices configured for the terminal device before the handover. When the information is received, it is determined that information about the terminal device in some network devices configured for the terminal device before the handover needs to be used or maintained. When the information is not received, it is determined that information about the terminal device in some network devices configured for the terminal device before the handover is not used or does not need to be maintained, or information about the terminal device in some network devices configured for the terminal device before the handover is released.

[0247] The 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 transmits the indication information #3 to the second network device. After the second network device receives the indication information #3, the second network device may determine that the data packets forwarded in the previous early data forwarding do not need to be released based on the indication information #3. The second network device's use of the information on the terminal device may instruct the second network device to keep or hold the data packets forwarded in the previous early data forwarding. Alternatively, if the second network device receives the indication information #1 before the second network device receives the indication information #3, for example, the second network device receives the indication information #1 from the source network device, i.e., the indication information instructing to discard or ignore some or all of the data packets, the second network device may determine which data packets are to be kept or held, or which data packets are to be sent to the terminal device, based on the data packets forwarded in the early data forwarding and the indication information #1.

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

[0251] In step 8202, the target network device sends instruction information #3 to the source network device. After receiving the instruction information #3, the source network device may determine that the second network device does not need to release the data packet forwarded in the previous early data forwarding. For example, the source network device may continue to forward the data packet to the second network device, and the second network device may then transmit the forwarded data packet to the terminal device. The source network device may further send instruction information #1 to the second network device to instruct it to discard or ignore some or all of the data packet.

[0252] In addition, the source network device may further forward the instruction information #3 to the second network device. Based on the instruction information #3, the second network device may determine that the second network device does not need to release the data packet forwarded in the previous early data forwarding. The instruction information #3 sent by the source network device to the second network device may be the same as or different from the instruction information #3 received by the source network device from the target network device. This is not limited. In an example, the instruction information #3 sent by the source network device to the second network device is different from the instruction information #3 received by the source network device from the target network device. For example, the instruction information #3 received by the source network device from the target network device instructs to use or maintain the early data forwarding information of the second network device, and the instruction information #3 sent by the source network device to the second network device instructs to maintain the context of the terminal device in the second network device. In another example, the instruction information #3 sent by the source network device to the second network device is the same as the instruction information #3 received by the source network device from the target network device. For example, instruction information #3 received by the source network device from the target network device instructs the second network device to use or maintain the early data forwarding information, and instruction information #3 sent by the source network device to the second network device also instructs the second network device to use or maintain the early data forwarding information.

[0253] The above is just a brief description. Specific procedures applicable to the method 800 are described below with reference to the embodiments shown in FIGS.

[0254] According to this embodiment of the present application, data transferred in a previous early data forwarding may be used when the network devices determined after a handover configured for the terminal device include network devices configured for the terminal device before the handover, avoiding forwarding these data packets anew in the early data forwarding and reducing the transmission delay of these data packets.

[0255] Optionally, the method 800 may further comprise step 830 .

[0256] 830: The source network device determines that the network devices configured for the terminal device after the handover include the second network device.

[0257] In a possible manner, the target network device sends the identification information of the second network device to the source network device, and the source network device determines that the network devices configured for the terminal device after the handover include the second network device based on the identification information of the second network device, in other words, determines that the network devices of the data packets in the early data forwarding need to be maintained or suspended. The manner using the identifier is simple and accurate. In addition, when multiple second network devices are involved, in other words, when the N first network devices after the handover include multiple candidate network devices (i.e., multiple second network devices) before the handover, a small number of resources are used in the identifier indication manner.

[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, where the handover request response message carries the identification information of the second network device. In another example, the identification information of the second network device and the indication information #3 can be carried in the same signaling.

[0259] In the following, an example of a solution is described in which the identification information of the second network device and the indication information #3 are carried in the same signaling.

[0260] For example, when the network devices configured for the terminal device after the handover include one second network device, the source network device receives one signaling sent by the target network device, where the signaling includes indication information #3 and an identifier of the second network device, and the indication information #3 instructs to use information about the terminal device in the second network device. The source network device determines that the network devices configured for the terminal device after the handover include the second network device based on the signaling. Furthermore, the signaling may include indication information indicating whether the second network device configured by the target network device for the terminal device functions as a candidate network device or a secondary network device.

[0261] In another example, when the network devices configured for the terminal device after the handover include multiple second network devices, the source network device receives one signaling sent by the target network device, where the signaling includes indication information #3 and identifiers of the multiple second network devices, and the indication information #3 instructs to use information about the terminal device in the multiple second network devices. The source network device determines that the network devices configured for the terminal device after the handover include multiple second network devices based on the identifiers of the multiple second network devices included in the signaling. Furthermore, the signaling may include indication information indicating whether the second network devices configured by the target network device for the terminal device function as candidate network devices or secondary network devices.

[0262] In another example, when the network devices configured for the terminal device after the handover include multiple second network devices, the source network device receives multiple signalings sent by the target network device, where each of the signalings includes one indication information #3 and an identifier of one second network device, and the indication information #3 instructs to use information about the terminal device in the second network device. The source network device determines that the network devices configured for the terminal device after the handover include multiple second network devices based on the identifiers of the multiple second network devices included in the multiple signalings. Furthermore, each of the signalings may include indication information indicating whether the second network device configured by the target network device for the terminal device functions as a candidate network device or a secondary network device.

[0263] It should be understood that the above is merely an example for explanation. This is not limited. Any solution that allows the source network device to determine whether the network device configured for the terminal device after handover includes the network device before handover is applicable to the embodiment of the present application. For example, the target network device can send the identification information of the N first network devices to the source network device, and the source network device determines whether the network device configured for the terminal device after handover includes the network device before handover based on the identification information of the N first network devices.

[0264] Optionally, the target network device may receive information about the terminal device in the second network device. For example, as shown in FIG.

[0265] 840: The target network device may receive early data forwarding information from the source network device.

[0266] In this way, the target network device may determine which data packets sent to the terminal device to subsequently forward to the second network device based on early data forwarding information, e.g., information about data packets forwarded in a previous early data forwarding at the second network device and / or data packets that can be discarded or ignored by the second network device.

[0267] In addition, the target network device may further inform the second network device of the data packets in the early data transmission that may be discarded. For example, the target network device may further send indication information #1 to the second network device.

[0268] Optionally, the target network device may further recognize information about the network devices configured for the terminal device before the handover. The second network device is used as an example. The information about the second network devices 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. The information about the network devices configured for the terminal device before the handover may be held, for example, in a handover request message. Specifically, the source network device sends a handover request message to the target network device, where the handover request message may include information about the network devices configured for the terminal device before the handover.

[0269] In addition, the target network device may further determine whether the configured N first network devices include a network device configured for the terminal device before the handover based on the identification information of the network device configured for the terminal device before the handover. For example, the target network device may recognize whether the network device before the handover is the same as the network device after the handover based on the identifier of the network device.

[0270] In addition, after recognizing the information about the network devices configured for the terminal device before the handover, the target network device may determine which network device is selected to serve the terminal device based on the information, or may determine which candidate network device is selected based on the information. In this way, the previous early transmission data may be reused as much as possible to reduce the transmission delay and improve the user experience.

[0271] Optionally, the target network device may further transmit identification information of the terminal device at the second network device to the second network device.

[0272] The data transmission method provided in the embodiment of the present application is described above with reference to Figures 7 and 8 separately. It should be understood that the method 700 and the method 800 can be used separately or in combination. This is not limited. For example, the method 700 and the method 800 can be used in combination. Before handover, early data transfer can be performed according to the solution described in the method 700; when it is determined that a network device handover needs to be performed, the handover can be performed according to the solution described in the method 800.

[0273] For ease of understanding, examples are provided for illustration with reference to different procedures.

[0274] First, with reference to FIGS. 9 through 11, possible procedures applicable to the embodiment described in method 700 are described.

[0275] Figure 9 is a schematic diagram of a conditional PSCell addition (CPA) procedure applicable to an embodiment of the present application. As shown in Figure 9, the method 900 is mainly described by using interactions between a terminal device, a MN, a candidate SN1, and a candidate SN2 as an example. The method 900 shown in Figure 9 may include the following steps:

[0276] 910: The MN performs a conditional PSCell addition procedure with the candidate SN.

[0277] As shown in FIG. 9, the MN performs a conditional PSCell addition procedure (ie, a CPA procedure) between candidate SN1 and candidate SN2.

[0278] For example, the MN sends an SN addition request message to each candidate SN. For example, the SN addition request message may carry indication information indicating that the current SN addition request message is for a conditional SN addition. Alternatively, for example, regardless of whether it is a conditional SN addition or a conditional SN change, the SN addition request message indicates that the current SN addition request message is for a conditional SN addition.

[0279] The candidate SN may send a response message for the SN addition request message to the MN. For example, the candidate SN may feed back an SN addition request acknowledgement message to the MN. For example, the SN addition request acknowledgement message may carry indication information indicating that the current SN addition request acknowledgement message is a response for a conditional SN addition. For example, the SN addition request acknowledgement message may further carry radio configuration information corresponding to the candidate PSCell and configured by the candidate SN for the terminal device.

[0280] The above is just an example for illustration purposes. Step 910 is not limited to this embodiment of the present application. For example, please refer to the prior art or future schemes for step 910.

[0281] In this embodiment of the present application, it should be understood that one conditional SN addition procedure may correspond to one candidate PSCell, specifically, one SN addition request message and one SN addition request acknowledgement message are specific to one candidate PSCell. Alternatively, one conditional SN addition procedure may correspond to multiple candidate PSCells, specifically, one SN addition request message and one SN addition request acknowledgement message are specific to multiple candidate PSCells.

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

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

[0284] The CPA configuration information may include, for example, one or more of the following: a trigger condition configured by the MN for each candidate PSCell; radio configuration information configured by the candidate SN for the terminal device corresponding to the candidate PSCell; and radio configuration information of an MCG configured by the MN for the terminal device corresponding to each candidate PSCell when the terminal device accesses the candidate PSCell. The trigger condition indicates that the terminal device can access the candidate PSCell cell when the candidate PSCell satisfies a certain condition. For example, the trigger condition may be that the signal quality of the candidate PSCell satisfies a certain condition, for example, the signal quality of the candidate PSCell is better than a certain threshold, the signal quality of the candidate PSCell is better than the signal quality of the PCell by a certain threshold, or the signal quality of the PCell is worse than a certain threshold and the signal quality of the candidate PSCell is better than a certain threshold.

[0285] In addition, when the terminal device selects a particular candidate PSCell that satisfies the conditions as a final PSCell, the terminal device may use radio configuration information corresponding to the candidate PSCell. If the CPA configuration information includes radio configuration information of the MCG configured by the MN for the terminal device corresponding to each candidate PSCell, the terminal device also uses the radio configuration information of the MCG corresponding to the candidate PSCell.

[0286] The above is just an example for illustration purposes. Step 920 is not limited in this embodiment of the present application. For example, for step 920, please refer to the prior art or future schemes.

[0287] 930: The terminal device determines whether the candidate PSCell satisfies a trigger condition in the CPA corresponding to the candidate PSCell.

[0288] For example, the terminal device receives CPA configuration information from the MN, and the terminal device determines whether a trigger condition corresponding to a PSCell is satisfied based on the candidate PSCell and the corresponding trigger condition in the CPA configuration information.

[0289] The above is just an example for illustration purposes. Step 930 is not limited to this embodiment of the present application. For example, for step 930, please refer to the prior art or future schemes.

[0290] 940: The MN transmits instruction information #1 to the candidate SN, instructing it to discard or ignore some or all of the data packets in the early data transfer.

[0291] As shown in FIG. 9, the MN transmits instruction information #1 to the candidate SN1, instructing it to discard or ignore part or all of the data packets in the early data transfer.

[0292] In other words, in step 940, the MN sends indication information #1 to the candidate SN, where the indication information #1 indicates which data packets on the MN terminated SCG bearer and / or the MN terminated split bearer are to be discarded or ignored in the early data transfer.

[0293] For the sake of distinction, in this embodiment of the present application, instruction information #1 represents information instructing to discard or ignore some or all of the data packets in the early data transfer.

[0294] In an example, before step 940, the MN may perform early data forwarding on the MN terminated SCG bearer towards a candidate SN (e.g., candidate SN1). In step 940, the MN sends indication information #1 to the candidate SN (e.g., candidate SN1) to indicate which data packets on the MN terminated SCG bearer in the early data forwarding are to be discarded or ignored.

[0295] In another example, prior to step 940, the MN may perform an early data transfer on the MN terminated split bearer directed to a candidate SN (e.g., candidate SN1). In step 940, the MN sends indication information #1 to the candidate SN (e.g., candidate SN1) to indicate which data packets on the MN terminated split bearer in the early data transfer are to be discarded or ignored.

[0296] As described above, for MN terminated SCG bearer or MN terminated split bearer, early data forwarding may also be referred to as early data transmission, or may have another name. The name of early data forwarding does not limit the scope of protection of the embodiments of this application. In this application, early data forwarding is mainly used as an example for explanation.

[0297] The MN performs an early data forwarding directed to the candidate SN on the MN terminated SCG bearer or the MN terminated split bearer. For these bearers (i.e., MN terminated SCG bearer or MN terminated split bearer), in a possible implementation, the early data forwarding performed by the MN may be the transmission of data packets in the form of PDCP PDUs to the SN.

[0298] In a possible implementation, the MN transmits these PDCP PDUs to the candidate SN through a user plane interface between the MN and the candidate SN, for example, the MN transmits these data packets to the candidate SN according to the general packet radio service (GPRS) tunneling protocol user plane (GTP-U) protocol.

[0299] In addition, the sequence number (SN) corresponding to the data packet may further be retained in the early data forwarding. For example, the GTP-U extension header may retain the new radio user plane (NR-U) sequence number corresponding to the data packet. In general, the MN may assign consecutive NR-U sequence numbers to all forwarded data packets and recognize the data packets for which early data forwarding is performed by using the retained NR-U sequence number corresponding to the data packet.

[0300] After the early data transfer is performed, the MN may send indication information #1 to the candidate SN based on the current status of transmitting data to the terminal device, instructing which data packets on the MN terminated SCG bearer and / or MN terminated split bearer in the early data transfer to be discarded or ignored.

[0301] The transmission opportunity of the indication information #1 is not limited. For example, the indication information #1 may be transmitted when a preset condition is satisfied. The preset condition may be a time restriction (e.g., periodic transmission), a data amount restriction (e.g., a comparison between the data amount and a threshold or a threshold range), or a restriction in another respect.

[0302] For example, in a possible case, the MN may periodically transmit the indication information #1. For another example, in another possible case, the MN transmits the indication information #1 to the candidate SN when the amount of downlink data transmitted by the MN to the terminal device reaches a certain threshold. In another example, in another possible case, the MN transmits the indication information #1 to the candidate SN after the downlink data transmitted by the MN to the terminal device is correctly received by the terminal device.

[0303] In addition, the format of the indication information #1 is not limited. In a possible format, the indication information #1 can be in the form of one or more sequence numbers.

[0304] In a possible manner, the indication information #1 may be, for example, one sequence number described as sequence number #A. For example, the sequence number #A may indicate that the candidate SN needs to discard data packets whose corresponding sequence numbers are lower than the sequence number #A and that are in a previously forwarded data packet (for example, a PDCP PDU) (where the data packets corresponding to the sequence number #A may also be discarded). In other words, if the MN needs to indicate to discard or ignore data packets whose corresponding sequence numbers are lower than the sequence number #A (and further indicate that the data packets corresponding to the sequence number #A may be discarded), the MN may indicate the sequence number #A to the candidate SN. If the candidate SN has not transmitted data packets whose corresponding sequence numbers are lower than the sequence number #A (and further data packets corresponding to the sequence number #A) to the terminal device, the candidate SN will not transmit these data packets (i.e. data packets whose corresponding sequence numbers are lower than the sequence number #A and further data packets corresponding to the sequence number #A) to the terminal device. By way of example and not limitation, the candidate SN may discard these data packets (i.e., data packets whose corresponding sequence numbers are lower than sequence number #A) and even data packets corresponding to sequence number #A, or may directly ignore these data packets.

[0305] In another possible manner, the indication information #1 may be a number of sequence numbers, for example in the form of a sequence number list. For example, the sequence number list may indicate that the candidate SN should discard data packets in the previously forwarded data packet (e.g., PDCP PDU) that correspond to the sequence numbers in the sequence number list. In other words, the MN may indicate that the sequence numbers corresponding to the data packets are to be discarded or ignored. If the candidate SN has not transmitted data packets corresponding to the sequence numbers in the sequence number list to the terminal device, the candidate SN will not transmit these data packets (i.e., data packets corresponding to the sequence numbers in the sequence number list) to the terminal device. By way of example and not limitation, the candidate SN may discard these data packets (i.e., data packets corresponding to the sequence numbers in the sequence number list) or may directly ignore these data packets.

[0306] In another possible manner, the indication information #1 may be a block corresponding to a number of data packets, a starting sequence number of the block corresponding to each data packet, and the number of data packets in the block. The data packets corresponding to each block are data packets corresponding to a number of consecutive sequence numbers starting from the starting sequence number. For example, the number of downlink blocks to be discarded (DL discard number of blocks), the starting SN of the data packet (e.g., NR PDCP PDU) corresponding to each block (DL discard NR PDCP PDU SN start), and the size corresponding to each block (discarded block size) are maintained. The information may indicate that the candidate SN needs to discard data packets in the previously forwarded data packets (e.g., PDCP PDU) that correspond to the sequence numbers in these blocks. In other words, the MN may indicate that the sequence numbers corresponding to the data packets are to be discarded or ignored. If the candidate SN has not transmitted data packets corresponding to these sequence numbers to the terminal device, the candidate SN will not transmit these data packets (i.e., data packets corresponding to these sequence numbers) to the terminal device. By way of example and not limitation, the candidate SN may discard these data packets (ie, the data packets corresponding to these sequence numbers) or may directly ignore these data packets.

[0307] It should be understood that the above two methods are merely illustrative examples, and are not limited thereto. For example, the MN may alternatively indicate to the candidate SN the sequence numbers corresponding to the data packets to be reserved, and the candidate SN may discard or ignore data packets other than these data packets (i.e., the sequence numbers corresponding to the data packets that the MN indicates to be reserved).

[0308] It should be further understood that in future protocols, names indicating the same functions as the indication information #1 may be applicable to the embodiments of the present application, for example, the indication information #1 may alternatively be early data transfer information.

[0309] Optionally, the MN may further indicate to the candidate SN the DRB corresponding to the indication information #1. For example, the information sent by the MN to the candidate SN may hold a DRB list of the MN terminated SCG bearer and / or the MN terminated split bearer. The DRB list may include a DRB ID of each DRB and may further include information about the forwarded downlink data packet, where the indication information #1 indicates that the candidate SN may discard the forwarded downlink data packet.

[0310] It should be understood that the above information (e.g., indication information #1 and / or DRB corresponding to indication information #1) may be transmitted between the MN and the candidate SN via the user plane (e.g., maintained in the GTP-U protocol) or may be transmitted between the MN and the candidate SN via the control plane (where, for example, the MN sends a message to the candidate SN, e.g., the MN includes the above information in an early status transfer message).

[0311] Optionally, when information is transmitted between the MN and the candidate SN through the user plane, since the GTP-U protocol tunnel established on the user plane is for each bearer, not all indication information #1 may need to carry the DRB ID.

[0312] Optionally, the MN may further send indication information #2 to the candidate SN, indicating that the MN performs or supports performing early data forwarding on the MN terminated SCG bearer and the MN terminated split bearer. For example, before the MN performs early data forwarding directed to the candidate SN, the MN may send indication information to the candidate SN, indicating that the MN may perform or supports performing early data forwarding on one or both of the MN terminated SCG bearer and the MN terminated split bearer. For example, the indication information #2 may be sent between the MN and the candidate SN through a control plane interface, or may be sent between the MN and the candidate SN through a user plane interface. This is not limited thereto.

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

[0314] It should be further understood that the MN may transmit the instruction information #1 to the candidate SN multiple times. For example, the MN may transmit the instruction information #1 to the candidate SN periodically. In this manner, the candidate SN may determine, based on the multiple received instruction information #1, to discard or ignore the data packets that each piece of the instruction information #1 instructs to discard or ignore. Alternatively, the candidate SN may determine, based on the most recently received instruction information #1, which data packets are to be discarded or ignored. For example, if the instruction information #1 is one sequence number, e.g., sequence number #A, the candidate SN may determine, based on the last received instruction information #1, to discard or ignore the data packets whose corresponding sequence numbers are lower than sequence number #A.

[0315] It should be further understood that in the example shown in Fig. 9, the interaction between the MN and the candidate SN1 is mainly used as an example for explanation, and is not limited thereto. For example, early data transfer may also be performed between the MN and the candidate SN2, and the MN may also send the indication information #1 to the candidate SN2 one or more times. In another example, after the MN determines that the terminal device accesses a candidate SN that satisfies the condition, the MN may perform early data transfer with the candidate SN that satisfies the condition, and may further send the indication information #1 to the candidate SN that satisfies the condition.

[0316] 950: The terminal device accesses a candidate SN that satisfies the condition.

[0317] When the terminal device determines that the trigger condition of the candidate PSCell is satisfied, the terminal device accesses the candidate PSCell. For example, the terminal device performs a random access process with the candidate PSCell. As shown in Figure 9, assuming that the trigger condition of the candidate PSCell in the candidate SN1 is satisfied, the terminal device accesses the candidate SN1.

[0318] The above is just an example for illustration purposes. Step 950 is not limited in this embodiment of the present application. For example, please refer to the prior art or future schemes for step 950.

[0319] 960: The candidate SN transmits downlink data to the terminal device.

[0320] After the terminal device accesses the candidate SN, the candidate SN may transmit downlink data to the terminal device. For example, the candidate SN may transmit downlink data to the terminal device based on the status of early data transfer. In another example, the candidate SN may transmit downlink data to the terminal device based on the status of early data transfer and the indication information #1.

[0321] In the following, MN terminated SCG bearer or MN terminated split bearer is used as an example to illustrate the following possible cases.

[0322] In possible cases, after the terminal device accesses a candidate SN, for an MN terminated SCG bearer or an MN terminated split bearer, the candidate SN may send downlink data to the terminal device based on data in an early data transfer performed by the MN.

[0323] Alternatively, in another possible case, after the terminal device accesses the candidate SN, for the MN terminated SCG bearer or MN terminated split bearer, the candidate SN may transmit downlink data to the terminal device based on the data in the early data transfer performed by the MN and the indication information #1 (e.g., the last received indication information #1). For example, the candidate SN may not transmit to the terminal device the data packets (e.g., PDCP PDUs) that the indication information #1 (e.g., the last received indication information #1) instructs to discard, and the candidate SN may discard or directly ignore these data packets that need to be discarded.

[0324] Alternatively, in another possible case, after the MN recognizes that the terminal device accesses the candidate SN (where, for example, the MN receives an indication from the terminal device indicating that the terminal device satisfies the trigger condition of the candidate PSCell; or, after the terminal device successfully accesses the candidate SN, the candidate SN sends an indication to the MN indicating the access of the terminal device), the MN sends indication information #1 to the candidate SN, and the candidate SN transmits downlink data to the terminal device based on the data in the early data transfer performed early by the MN and the indication information #1. For example, for the MN terminated SCG bearer and / or the MN terminated split bearer, after the MN recognizes that the terminal device accesses the candidate SN, the MN may send indication information #1 to the candidate SN to instruct which data packets on the MN terminated SCG bearer and / or the MN terminated split bearer in the early data transfer are to be discarded or ignored (same as the content of step 940).

[0325] With reference to steps 910 to 960 shown in Fig. 9, the above describes an example of a CPA procedure. It should be understood that the above steps are merely illustrative examples. This is not strictly limited. In addition, the sequence numbers of the above processes do not imply an execution order. The execution order of the processes should be determined according to the functions and internal logic of the processes, and should not be construed as any limitation on the implementation process of the embodiments of the present application.

[0326] FIG. 10 is a schematic diagram of a conditional PSCell change (CPC) procedure triggered by an MN that is applicable to an embodiment of the present application.

[0327] As shown in Fig. 10, the method 1000 is mainly described by using interactions between a terminal device, a MN, a candidate SN1, a candidate SN2, and a source SN as an example. For distinction, the source SN represents the SN currently configured for the terminal device. It should be understood that the source SN is a name for distinction. For example, the source SN may alternatively be described as a current SN. The specific naming scheme of the source SN does not limit the protection scope of the embodiment of the present application. The method 1000 shown in Fig. 10 may include the following steps.

[0328] 1010: The MN performs a CPC procedure with the candidate SN.

[0329] In other words, the MN performs a conditional PSCell change procedure between the candidate SNs. As shown in Fig. 10, the MN performs a conditional PSCell change procedure (i.e., a CPC procedure) between the candidate SN1 and the candidate SN2.

[0330] For example, the MN sends an SN addition request message to each candidate SN. For example, the SN addition request message may carry indication information indicating that the current SN addition request message is for a conditional SN change. Alternatively, for example, regardless of whether it is a conditional SN addition or a conditional SN change, the SN addition request message indicates that the current SN addition request message is for a conditional SN change.

[0331] The candidate SN may send a response message for the SN addition request message to the MN. For example, the candidate SN may feed back an SN addition request acknowledgement message to the MN. For example, the SN addition request acknowledgement message may carry indication information indicating that the current SN addition request acknowledgement message is a response for a conditional SN change. For example, the SN addition request acknowledgement message may further carry radio configuration information corresponding to the candidate PSCell and configured by the candidate SN for the terminal device. For example, the radio configuration information corresponding to the candidate PSCell and configured by the candidate SN for the terminal device is carried in the SN addition request acknowledgement message in the form of an RRC reconfiguration message configured by the candidate SN for the terminal device.

[0332] The above is just an example for illustration purposes. Step 1010 is not limited in this embodiment of the present application. For example, for step 1010, please refer to the prior art or future schemes.

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

[0334] 1001: The MN may instruct the source SN that the source SN may perform early data transfer on an SN terminated bearer.

[0335] In other words, after step 1010, the MN may send indication information to the source SN, indicating that the source SN may perform early data forwarding on SN terminated bearers (where the SN terminated bearers are in front of the CPC, in other words, these bearers are SN terminated bearers in front of the CPC), and forward data packets to be transmitted to the terminal device at the source SN. Alternatively, the MN may send indication information to the source SN, indicating that the MN triggers the CPC. In this way, the source SN may determine whether to perform early data forwarding on the SN terminated bearers, in other words, whether to perform early data forwarding on the SN terminated bearers is determined by the source SN.

[0336] It should be understood that step 1001 is merely an example, and is not limited thereto. For example, the source SN may send indication information to the MN to indicate that early data transfer may be performed on the SN terminated bearer.

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

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

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

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

[0341] When the terminal device selects a particular candidate PSCell that satisfies the conditions as a final PSCell, the terminal device may use the radio configuration information corresponding to the candidate PSCell. If the CPC configuration includes radio configuration information of the MCG configured by the MN for the terminal device corresponding to each candidate PSCell, the terminal device also uses the radio configuration information of the MCG corresponding to the candidate PSCell.

[0342] The above is just an example for illustration purposes. Step 1020 is not limited in this embodiment of the present application. For example, for step 1020, please refer to the prior art or future schemes.

[0343] 1030: The terminal device determines whether the candidate cell satisfies a condition.

[0344] In other words, the terminal device determines whether the candidate PSCell satisfies a trigger condition corresponding to a conditional PSCell change.

[0345] For example, the terminal device receives CPC configuration information from the MN, and the terminal device determines whether the trigger condition corresponding to the PSCell is satisfied based on the candidate PSCell and the corresponding trigger condition in the CPC configuration information.

[0346] The above is just an example for illustration purposes. Step 1030 is not limited in this embodiment of the present application. For example, for step 1030, please refer to the prior art or future schemes.

[0347] 1040: The MN transmits instruction information #1 to the candidate SN, instructing it to discard or ignore some or all of the data packets in the early data transfer.

[0348] As shown in FIG. 10, the MN transmits instruction information #1 to the candidate SN1, instructing it to discard or ignore part or all of the data packets in the early data transfer.

[0349] In other words, in step 1040, the MN sends indication information #1 to the candidate SN, where the indication information #1 indicates which data packets on the MN terminated SCG bearer and / or the MN terminated split bearer in the early data transfer are to be discarded or ignored.

[0350] In an example, prior to step 1040, the MN may perform early data forwarding on the MN terminated SCG bearer directed to a candidate SN (e.g., candidate SN1). In step 1040, the MN sends indication information #1 to the candidate SN (e.g., candidate SN1) to indicate which data packets on the MN terminated SCG bearer in the early data forwarding are to be discarded or ignored.

[0351] In another example, prior to step 1040, the MN may perform early data forwarding on the MN terminated split bearer directed to a candidate SN (e.g., candidate SN1). In step 1040, the MN transmits indication information #1 to the candidate SN (e.g., candidate SN1) to indicate which data packets on the MN terminated split bearer in the early data forwarding are to be discarded or ignored.

[0352] Optionally, for bearers that are SN terminated bearers before CPC, in the CPC procedure, these bearers become MN terminated split bearers or MN terminated SCG bearers, and the source SN may perform early data forwarding for data packets directed to the MN through step 1001. Then, according to the description in step 1040, the MN may perform early data forwarding and instruct which data packets on the MN terminated split bearers in the early data forwarding are to be discarded or ignored. In this case, the MN may determine which data packets on the SN terminated bearers in the early data forwarding are to be discarded or ignored based on the instruction sent by the source SN to the MN. For example, the source SN sends some instruction information to the MN to instruct which data packets on the SN terminated bearers in the early data forwarding are to be discarded or ignored. The specific instruction information is the same as the instruction information #1. The format of the data packets in the early data forwarding between the source SN and the MN may be PDCP SDU. The MN may generate instruction information #1 to be sent to the candidate SN based on the instruction of the source SN.

[0353] Optionally, for bearers that are MN terminated bearers before CPC, in the CPC procedure, these MN terminated bearers become MN terminated split bearers or MN terminated SCG bearers. In this case, the MN may generate indication information #1.

[0354] Step 1040 is identical to step 940 in the CPA procedure above, and details will not be repeated here.

[0355] It should be understood that in the example shown in Figure 10, the MN terminated SCG bearer is a MN terminated SCG bearer in a CPC configured by the network side for the terminal device. In the example shown in Figure 10, the MN terminated split bearer is a MN terminated split bearer in a CPC configured by the network side for the terminal device. Before the CPC triggered by the MN, these bearers can be SN terminated MCG / SCG / split bearers or MN terminated MCG / SCG / split bearers.

[0356] 1050: The terminal device accesses a candidate SN that satisfies the condition.

[0357] When the terminal device determines that the trigger condition of the candidate PSCell is satisfied, the terminal device accesses the candidate PSCell. For example, the terminal device performs a random access process with the candidate PSCell. As shown in Figure 10, assuming that the trigger condition of the candidate PSCell in the candidate SN1 is satisfied, the terminal device accesses the candidate SN1.

[0358] Step 1050 is identical to step 950 in the CPA procedure above, and the details will not be repeated here.

[0359] 1060: The candidate SN transmits downlink data to the terminal device.

[0360] After the terminal device accesses the candidate SN, the candidate SN may transmit downlink data to the terminal device. For example, the candidate SN may transmit downlink data to the terminal device based on the status of early data transfer. In another example, the candidate SN may transmit downlink data to the terminal device based on the status of early data transfer and the indication information #1.

[0361] Step 1060 is identical to step 960 in the CPA procedure above, and the details will not be repeated here.

[0362] With reference to steps 1010 to 1060 shown in Fig. 10, the above describes an example of a MN triggered CPC procedure. It should be understood that the above steps are merely illustrative examples. This is not strictly limited. In addition, the sequence numbers of the above processes do not imply an execution order. The execution order of the processes should be determined according to the functions and internal logic of the processes, and should not be construed as any limitation on the implementation process of the embodiments of the present application.

[0363] FIG. 11 is a schematic diagram of a CPC procedure triggered by an SN that is applicable to an embodiment of the present application.

[0364] As shown in FIG. 11, the method 1100 is mainly described by using interactions between a terminal device, a MN, a candidate SN1, a candidate SN2, and a source SN as an example. For distinction, the source SN represents the SN currently configured for the terminal device. It should be understood that the source SN is a name for distinction. For example, the source SN may alternatively be described as a current SN. The specific naming scheme of the source SN does not limit the scope of protection of the embodiments of the present application. The method 1100 shown in FIG. 11 may include the following steps.

[0365] 1110: The source SN performs a CPC procedure with the candidate SN.

[0366] In other words, the source SN performs a conditional PSCell change procedure among the candidate SNs. As shown in Figure 11, the MN performs a conditional PSCell change procedure (i.e., a CPC procedure) among the candidate SN1, the candidate SN2, and the source SN.

[0367] For example, the source SN sends a SN change required message to the MN. For example, the SN change required message may carry indication information indicating that the current SN change required message is for a conditional SN change. The SN change required message may carry identifiers of candidate SNs.

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

[0369] The candidate SN may send a response message for the SN addition request message to the MN. For example, the candidate SN may feed back an SN addition request acknowledgement message to the MN. For example, the SN addition request acknowledgement message may carry indication information indicating that the current SN addition request acknowledgement message is a response for a conditional SN change. For example, the SN addition request acknowledgement message may further carry radio configuration information corresponding to the candidate PSCell and configured by the candidate SN for the terminal device. For example, the radio configuration information corresponding to the candidate PSCell and configured by the candidate SN for the terminal device may be carried in the SN addition request acknowledgement message in the form of an RRC reconfiguration message configured by the candidate SN for the terminal device.

[0370] The above is just an example for illustration purposes. Step 1110 is not limited to this embodiment of the present application. For example, for step 1110, please refer to the prior art or future schemes.

[0371] For example, the method 1100 may further comprise step 1101 .

[0372] 1101: The MN may instruct the source SN that the source SN may perform early data transfer on an SN terminated bearer.

[0373] In other words, after step 1110, the MN may send indication information to the source SN, indicating that the source SN may perform early data forwarding on SN terminated bearers (where the SN terminated bearers are in front of the CPC, in other words, these bearers are SN terminated bearers in front of the CPC), and forward data packets to be transmitted to the terminal device at the source SN. Alternatively, the MN may send indication information to the source SN, indicating that the MN triggers the CPC. In this way, the source SN may determine whether to perform early data forwarding on the SN terminated bearers, in other words, whether to perform early data forwarding on the SN terminated bearers is determined by the source SN.

[0374] It should be understood that step 1101 is merely an example, and is not limited thereto. For example, the source SN may send indication information to the MN to indicate that early data transfer may be performed on the SN terminated bearer.

[0375] Before step 1101 , the method 1100 may further comprise step 1120 .

[0376] 1120: The MN sends the CPC configuration information to the terminal device.

[0377] Step 1120 is the same as step 1020 in the MN-triggered CPC above, and will not be described in detail again here.

[0378] 1130: The terminal device determines whether the candidate cell satisfies a condition.

[0379] In other words, the terminal device determines whether the candidate PSCell satisfies a trigger condition corresponding to a conditional PSCell change.

[0380] Step 1130 is the same as step 1030 in the MN-triggered CPC above, and will not be described in detail again here.

[0381] 1140: The MN transmits instruction information #1 to the candidate SN, instructing it to discard or ignore some or all of the data packets in the early data transfer.

[0382] In other words, in step 1140, the MN sends indication information #1 to the candidate SN, where the indication information #1 indicates which data packets on the MN terminated SCG bearer and / or the MN terminated split bearer in the early data transfer are to be discarded or ignored.

[0383] In an example, prior to step 1140, the MN may perform early data forwarding on the MN terminated SCG bearer directed to a candidate SN (e.g., candidate SN1). In step 1140, the MN sends indication information #1 to the candidate SN (e.g., candidate SN1) to indicate which data packets on the MN terminated SCG bearer in the early data forwarding are to be discarded or ignored.

[0384] In another example, prior to step 1140, the MN may perform early data forwarding on the MN terminated split bearer directed to a candidate SN (e.g., candidate SN1). In step 1140, the MN transmits indication information #1 to the candidate SN (e.g., candidate SN1) to indicate which data packets on the MN terminated split bearer in the early data forwarding are to be discarded or ignored.

[0385] Optionally, for bearers that are SN terminated bearers before CPC, in the CPC procedure, these bearers become MN terminated split bearers or MN terminated SCG bearers, and the source SN performs early data forwarding for data packets directed to the MN through step 1101. Then, according to the description in step 1140, the MN may perform early data forwarding and instruct which data packets on the MN terminated split bearers in the early data forwarding are to be discarded or ignored. In this case, the MN may determine which data packets on the SN terminated bearers in the early data forwarding are to be discarded or ignored based on the instruction sent by the source SN to the MN. For example, the source SN sends some instruction information to the MN to instruct which data packets on the SN terminated bearers in the early data forwarding are to be discarded or ignored. The specific instruction information is the same as the instruction information #1. The format of the data packets in the early data forwarding between the source SN and the MN may be PDCP SDU. The MN may generate instruction information #1 to be sent to the candidate SN based on the instruction of the source SN.

[0386] Optionally, for bearers that are MN terminated bearers before CPC, in the CPC procedure, these MN terminated bearers become MN terminated split bearers or MN terminated SCG bearers. In this case, the MN may generate indication information #1.

[0387] Step 1140 is the same as step 1040 in the MN-triggered CPC above, and will not be described again in detail here.

[0388] 1150: The terminal device accesses a candidate SN that satisfies the condition.

[0389] When the terminal device determines that the trigger condition of the candidate PSCell is satisfied, the terminal device accesses the candidate PSCell. For example, the terminal device performs a random access process with the candidate PSCell. As shown in Figure 11, assuming that the trigger condition of the candidate PSCell in the candidate SN1 is satisfied, the terminal device accesses the candidate SN1.

[0390] Step 1150 is the same as step 1050 in the MN-triggered CPC described above, and will not be described in detail again here.

[0391] 1160: The candidate SN transmits downlink data to the terminal device.

[0392] Step 1160 is the same as step 1060 in the MN-triggered CPC described above, and will not be described again in detail here.

[0393] With reference to steps 1110 to 1160 shown in FIG. 11, the above describes an example of a CPC procedure triggered by an SN. It should be understood that the above steps are merely illustrative examples. This is not strictly limited. In addition, the sequence numbers of the above processes do not imply an execution order. The execution order of the processes should be determined according to the functions and internal logic of the processes, and should not be construed as any limitation on the implementation process of the embodiments of the present application.

[0394] With reference to Figures 9-11, the above provides possible procedures that are applicable to the embodiment shown in method 700. According to the above solutions, for MN terminated SCG bearers and / or MN terminated split bearers, the MN may perform early data forwarding directed to the SN. In addition, the MN may further send indication information #1 to the SN to indicate which data packets in the early data forwarding are to be discarded or ignored. Thus, after the terminal device accesses the candidate PSCells, the candidate PSCells may transmit downlink data on these bearers to the terminal device, reducing the transmission delay of the downlink data on these bearers.

[0395] 12-14, possible procedures applicable to the embodiment shown in method 800 are described below.

[0396] FIG. 12 is a schematic flow chart of a scenario applicable to an embodiment of the present application in which CPAC is configured before handover and then MN handover occurs.

[0397] As shown in Fig. 12, the method 1200 is mainly described by using interactions between a terminal device, a source MN, a candidate SN1, a candidate SN2, and a target MN as an example. For distinction, the source MN represents the MN before handover, and the target MN represents the MN after handover. It should be understood that the source MN and the target MN are names for distinction, and the specific naming scheme of the source MN and the target MN does not constitute a limitation to the protection scope of the embodiments of the present application. The method 1200 shown in Fig. 12 may include the following steps.

[0398] 1210: The network side configures a CPAC for the terminal device.

[0399] Step 1210 is not limited to this embodiment of the present application. For example, please refer to the description of steps 910 and 920, the description of steps 1010 and 1020, or the description of steps 1110 and 1120. For step 1210, please refer to the prior art or future schemes. Details 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 handover the terminal device to the target MN, and the source MN sends a handover request message to the target MN. The handover request message may include one or more of the identifiers of the candidate SNs and the identifiers of the terminal devices in the candidate SNs. For example, the identifiers of the terminal devices in the candidate SNs may be identifiers assigned to the terminal devices by the candidate SNs via a control plane interface established between the MN and the candidate SNs for the terminal devices, such as XnAP ID or X2AP ID. Optionally, the above information (i.e., the identifiers of the candidate SNs and the identifiers of the terminal devices in the candidate SNs) may be referred to as context reference information of the terminal devices in the candidate SNs. It should be noted that the information is for each candidate SN, in other words, the handover request message holds the above information of the terminal devices in each candidate SN.

[0402] It should be understood that the above provides an explanation by using an example in which the context reference information of the terminal device in the candidate SN is carried in the handover request message, which is not limited thereto. For example, the context reference information of the terminal device in the candidate SN can alternatively be sent separately to the target MN.

[0403] 1230: The target MN sends an SN addition request message to the SN.

[0404] As shown in FIG. 12, the target MN may send an SN Add Request message to candidate SN1 and candidate SN2.

[0405] In the following, an explanation is provided with reference to several scenarios.

[0406] Scenario 1: A scenario in which CPA is configured both before and after handover

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

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

[0409] For example, the target MN may recognize whether the candidate SN before the handover is the same as the candidate SN after the handover based on the candidate SN identifier sent by the source MN (e.g., the candidate SN identifier carried in the handover request message sent by the source MN).

[0410] It should be understood that when there are multiple candidate SNs, the target MN may perform the determination independently.

[0411] Scenario 2: CPA is configured before handover and DC is configured after handover

[0412] The target MN determines to configure a DC for the terminal device, specifically, to configure one SN (in this case, not referred to as a candidate SN, but may be referred to, for example, as an SN or a target SN) for the terminal device.

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

[0414] For example, the target MN may recognize whether the SN before the handover is the same as the SN after the handover based on the identifier of the candidate SN sent by the source MN (e.g., 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 may perform the determination independently.

[0416] Scenario 3: CPC is configured both before and after handover

[0417] (1) Scenario in which MN-triggered CPC is configured both before and after handover

[0418] The target MN decides to configure an MN-triggered CPC for the terminal device.

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

[0420] For example, the target MN may recognize whether the candidate SN before the handover is the same as the candidate SN after the handover based on the candidate SN identifier sent by the source MN (e.g., the candidate SN identifier carried in the handover request message sent by the source MN).

[0421] It should be understood that when there are multiple candidate SNs, the target MN may perform the determination independently.

[0422] (2) A scenario in which SN-triggered CPC is configured both before and after handover

[0423] The target MN sends an SN establishment request message to the target SN after handover (i.e., the SN that triggers CPC after handover). The SN establishment request message may carry the identifiers of the candidate SNs before handover. In addition, the SN establishment request message may further carry the identifiers of the terminal device in each candidate SN (one or more candidate SNs). For SN-triggered CPC, if the candidate SN determined by the target SN is the same as the candidate SN before handover, there may be two cases:

[0424] In a possible case, when the target SN obtains the identifier of the terminal device in each candidate SN (one or more candidate SNs) from the target MN, using one of the candidate SNs as an example, the target SN transmits the identifier of the terminal device in the candidate SN to the candidate SN. For example, the target SN transmits the identifier of the terminal device in the candidate SN directly to the candidate SN. Alternatively, the target MN may transmit the identifier of the terminal device in the candidate SN to the candidate SN (where, for example, the target SN first transmits the identifier to the target MN, and then the target MN transmits the identifier to the candidate SN).

[0425] In another possible case, 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, using one of the candidate SNs as an example, the target SN sends the identifier of the candidate SN to the target MN, and the target MN obtains the identifier of the terminal device before handover in the candidate SN based on the identifier of the candidate SN, and then the target MN sends the identifier of the terminal device in the candidate SN to the candidate SN.

[0426] It should be understood that when there are multiple candidate SNs, the target MN may perform the determination independently.

[0427] (3) A scenario in which the SN-triggered CPC is configured before handover and the MN-triggered CPC is configured after handover.

[0428] The target MN decides to configure an MN-triggered CPC for the terminal device.

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

[0430] For example, the target MN may recognize whether the candidate SN before the handover is the same as the candidate SN after the handover based on the candidate SN identifier sent by the source MN (e.g., the candidate SN identifier carried in the handover request message sent by the source MN).

[0431] It should be understood that when there are multiple candidate SNs, the target MN may perform the determination independently.

[0432] (4) A scenario in which the MN-triggered CPC is configured before handover and the SN-triggered CPC is configured after handover.

[0433] The target MN sends an SN establishment request message to the target SN after handover (i.e., the SN that triggers CPC after handover). The SN establishment request message may carry the identifiers of the candidate SNs before handover. In addition, the SN establishment request message may further carry the identifiers of the terminal device in each candidate SN (one or more candidate SNs). For SN-triggered CPC, if the candidate SN determined by the target SN is the same as the candidate SN before handover, there may be two cases:

[0434] In a possible case, when the target SN obtains the identifier of the terminal device in each candidate SN (one or more candidate SNs) from the target MN, using one of the candidate SNs as an example, the target SN transmits the identifier of the terminal device in the candidate SN to the candidate SN. For example, the target SN transmits the identifier of the terminal device in the candidate SN directly to the candidate SN. Alternatively, the target MN may transmit the identifier of the terminal device in the candidate SN to the candidate SN (where, for example, the target SN first transmits the identifier to the target MN, and then the target MN transmits the identifier to the candidate SN).

[0435] In another possible case, 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, using one of the candidate SNs as an example, the target SN sends the identifier of the candidate SN to the target MN, and the target MN obtains the identifier of the terminal device before handover in the candidate SN based on the identifier of the candidate SN, and then the target MN sends the identifier of the terminal device in the candidate SN to the candidate SN.

[0436] It should be understood that the above uses one candidate SN as an example for illustration purposes. When there are multiple candidate SNs, the target MN may perform the determination separately.

[0437] Scenario 4: CPC is configured before handover and CPA is configured after handover

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

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

[0440] For example, the target MN may recognize whether the candidate SN before the handover is the same as the candidate SN after the handover based on the candidate SN identifier sent by the source MN (e.g., the candidate SN identifier carried in the handover request message sent by the source MN).

[0441] It should be understood that when there are multiple candidate SNs, the target MN may perform the determination independently.

[0442] For example, the above solution may be applicable to a scenario in which a CPC triggered by an MN is configured before a handover and a CPA is configured after a handover, or may be applicable to a scenario in which a CPC triggered by an SN is configured before a handover and a CPA is configured after a handover.

[0443] Scenario 5: CPC is configured before handover and DC is configured after handover

[0444] The target MN determines to configure a DC for the terminal device, specifically, to configure one SN (in this case, not referred to as a candidate SN, but may be referred to, for example, as an SN or a target SN) for the terminal device.

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

[0446] For example, the target MN may recognize whether the SN before the handover is the same as the SN after the handover based on the identifier of the candidate SN sent by the source MN (e.g., 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 may perform the determination independently.

[0448] For example, the above solution may be applicable to a scenario in which a MN-triggered CPC is configured before handover and a DC is configured after handover, or may be applicable to a scenario in which a SN-triggered CPC is configured before handover and a DC is configured after handover.

[0449] With reference to the five scenarios, the above describes the case where the target MN sends an SN addition request message to the SN. It should be understood that in different scenarios, adaptive adjustments can be performed based on the case of each scenario.

[0450] 1240: The target MN sends a handover request response message to the source MN.

[0451] In addition, the target MN may further send instruction information #3 to the source MN to instruct it to use or maintain information regarding the terminal device in the candidate SN.

[0452] The information about the terminal device at the candidate SN may include, for example, one or more of a context of the terminal device at the candidate SN and information about an early data transfer previously performed by the candidate SN.

[0453] Optionally, the target MN may further send an instruction to the source MN to indicate candidate SNs, where the context of the terminal device in the candidate SNs may be maintained or the early data transfer previously performed by the candidate SNs may be suspended. For example, the identifiers of the candidate SNs may be retained for the instruction. For example, the instruction information #3 or the handover request response message may retain the identifiers of one or more candidate SNs. In this manner, it is instructed to maintain the context of the terminal device in one or more candidate SNs or to suspend the early data transfer previously performed by one or more candidate SNs.

[0454] The indication information #3 can be carried in the handover request response message or can be sent separately, but is not limited thereto.

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

[0456] As shown in FIG. 12, the source MN may send an SN release request message to candidate SN1 and candidate SN2.

[0457] In addition, the source MN may further send instruction information #3 to the candidate SN to instruct the candidate SN to use or maintain information regarding the terminal device.

[0458] The indication information #3 may be carried in the SN release request message or may be sent separately, but is not limited thereto.

[0459] 1260: The source MN indicates information about the candidate SN's early data transfer to the target MN.

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

[0461] The information about the early data forwarding of the candidate SN may include, for example, one or more of the data packets for which the early data forwarding was performed from the source MN to the candidate SN (e.g., indicated by the PDCP SN or NR-U sequence number) and the data packets in the early data forwarding that can be discarded by the candidate SN. Optionally, the target MN may then inform the candidate SN of the data packets in the early data forwarding that can be discarded. It should be understood that the early data forwarding of the SN terminated bearer may be included here.

[0462] In the following, an explanation is provided with reference to several scenarios.

[0463] Scenario 1: A scenario in which CPA is configured both before and after handover

[0464] In this scenario, the source MN may send information about the candidate SN's early data forwarding to the target MN.

[0465] In this scenario, the source MN may forward data on the bearer to the target MN, for example, downlink data packets that are not correctly received by the terminal device are forwarded to the target MN, or, as another example, uplink data packets that are received out of order from the terminal device are forwarded to the target MN.

[0466] Scenario 2: CPA is configured before handover and DC is configured after handover

[0467] In this scenario, at least two implementation solutions may be involved.

[0468] Solution 1: The source MN continues to perform early data forwarding towards the candidate SN.

[0469] In this solution, the source MN does not need to send information about the candidate SN's early data forwarding to the target MN. After the source MN forwards all data packets corresponding to the bearer before the end marker received from the core network to the candidate SN, the source MN may send indication information #4 to the candidate SN to indicate that all data packets corresponding to the bearer have been forwarded to the candidate SN. For example, the indication information #4 may be a user plane indication, such as an end marker. Alternatively, the indication information #4 may be a control plane indication, in other words, the indication information #4 is sent to the candidate SN on the control plane. In this solution, the candidate SN before the handover is the SN after the handover.

[0470] In this embodiment of the present application, for the sake of distinction, the indication information #4 represents information indicating that all data packets corresponding to the bearer have been forwarded to the candidate SN. The indication manner may be to give an indication by using specific content in the indication information #4, or to give an indication through the action of sending the indication information #4. This is not limited.

[0471] In addition, the source MN may send the indication information #4 directly to the candidate SN, or may send the indication information #4 to the candidate SN through the target MN. After receiving the indication information #4, the candidate SN (where, in this scenario, the candidate SN is also the SN after the handover) may start to send new data packets corresponding to the bearer directly received from the core network to the terminal device. In this solution, the candidate SN may use the data packets in the early data transfer previously received from the source MN as the data that needs to be sent to the terminal device after the handover, to avoid the delay that occurs when the source MN forwards the data packets to the target MN and then the target MN sends the data packets to the SN.

[0472] Solution 2: The source MN stops performing data transfers directed to the candidate SN.

[0473] In this solution, the source MN may send information about the candidate SN's early data forwarding to the target MN.

[0474] In this solution, the source MN may forward data packets corresponding to the bearer received from the core network to the target MN. For example, for a bearer that is an SN terminated bearer after the handover, the source MN may forward data packets corresponding to the bearer received from the core network to the target MN, and then the target MN forwards the data packets to the SN. In another example, for a bearer that is an MN terminated SCG bearer terminated or MN terminated split bearer after the handover, the source MN may forward data packets corresponding to the bearer received from the core network to the target MN. Then, the target MN processes the data packets (e.g., modifies the data packets from PDCP SDUs to PDCP PDUs) and sends the processed data packets to the SN. In this solution, the candidate SN before the handover is the SN after the handover.

[0475] It should be understood that the above two solutions are merely illustrative examples, and are not limiting. For example, the source MN may continue to forward some of the data packets to the candidate SN, and continue to send the remaining data packets to the SN through the target MN.

[0476] Scenario 3: CPC is configured both before and after handover

[0477] Scenario 3 is similar to scenario 1 (i.e., the scenario where CPA is configured both before and after handover). For example, in scenario 3, the source MN may forward data on the bearer to the target MN. For example, downlink data packets that are not correctly received by the terminal device are forwarded to the target MN. As another example, uplink data packets that are received out of order from the terminal device side are forwarded to the target MN.

[0478] In addition, in scenario 3, the device that triggers the CPC is not limited. For example, scenario 3 may be a scenario in which the MN-triggered CPC is configured both before and after handover. Alternatively, scenario 3 may be a scenario in which the SN-triggered CPC is configured both before and after handover. Alternatively, scenario 3 may be a scenario in which the MN-triggered CPC is configured before handover and the SN-triggered CPC is configured after handover. Alternatively, scenario 3 may be a scenario in which the SN-triggered CPC is configured before handover and the MN-triggered CPC is configured after handover.

[0479] Scenario 4: CPC is configured before handover and CPA is configured after handover

[0480] In this scenario, the source MN may send information about the candidate SN's early data forwarding to the target MN.

[0481] In this scenario, the source MN may forward data on the bearer to the target MN, for example, downlink data packets that are not correctly received by the terminal device are forwarded to the target MN, or, as another example, uplink data packets that are received out of order from the terminal device are forwarded to the target MN.

[0482] In scenario 4, the device that triggers the CPC is not limited. For example, scenario 4 may be a scenario in which the CPC triggered by the MN is configured before the handover and the CPA is configured after the handover. Alternatively, scenario 4 may be a scenario in which the CPC triggered by the SN is configured before the handover and the CPA is configured after the handover.

[0483] Scenario 5: CPC is configured before handover and DC is configured after handover

[0484] (1) For early data forwarding performed between a candidate SN and a source MN before handover, e.g., early data forwarding between a source MN and a candidate SN, and between an MN terminated bearer in a source MN and an SN terminated bearer in a candidate SN in a CPC (specifically, early data forwarding is performed for data packets on an MN terminated bearer in front of a CPC before handover, forwarding the data packets to an SN terminated bearer in a CPC), in a possible solution, the solution 1 in the above scenario 2 may be used. In another possible solution, the solution 2 in the above scenario 2 may be used.

[0485] (2) For early data forwarding performed between the source SN and the candidate SN before handover, for example, early data forwarding between the source SN and the candidate SN and between an SN terminated bearer in the source SN and an SN terminated bearer in the candidate SN in the CPC (specifically, early data forwarding is performed for data packets on an SN terminated bearer in the source SN before the CPC before handover, and forwards the data packets to an SN terminated bearer in the candidate SN in the CPC), in a possible solution, the source SN may continue to forward data to the candidate SN. In this solution, the source MN does not need to send information about the early data forwarding of the candidate SN to the target MN. After the source SN forwards all data packets corresponding to the bearer before the end marker received from the core network to the candidate SN, the source SN may send indication information #4 to the candidate SN to indicate that all data packets corresponding to the bearer have been forwarded to the candidate SN. For example, the indication information #4 may be a user plane indication, for example, an end marker. Alternatively, the indication information #4 may be a control plane indication, in other words, the indication information #4 is sent to the candidate SN on the control plane. In addition, the source SN may send the indication information #4 directly to the candidate SN, or may send the indication information #4 to the candidate SN through the target MN. After receiving the indication information #4, the candidate SN may send new data packets corresponding to the bearer received from the core network to the terminal device.

[0486] In another possible solution, the source SN stops forwarding data to the candidate SN. In this solution, the source MN can send information about the candidate SN's early data forwarding to the target MN. In addition, the source SN can forward data packets received from the core network corresponding to the bearer to the target MN, and the target MN then forwards the data packets to the SN.

[0487] It should be understood that the device that triggers the CPC in scenario 5 is not limited. For example, scenario 5 may be a scenario in which the CPC triggered by the MN is configured before handover and the DC is configured after handover. Alternatively, scenario 5 may be a scenario in which the CPC triggered by the SN is configured before handover and the DC is configured after handover.

[0488] According to the above solution, the target MN may recognize the relevant information of the candidate SN configured by the network side before handover (e.g., the identifier of the candidate SN configured by the network side before handover and the identifier of the terminal device in the candidate SN). The target MN may send the identifier of the terminal device in the candidate SN to the candidate SN. Thus, the early data forwarding in CPAC is performed before the handover, and after the handover, the network side may continue to use the data forwarded in the previous early data forwarding. If the CPAC is further configured after the handover, the early data forwarding does not need to be performed for the data. If the DC is configured after the handover, the normal data forwarding (i.e., the conventional data forwarding between the MN terminated bearer and the SN terminated bearer) may not need to be performed for the data.

[0489] With reference to steps 1210 to 1260 shown in FIG. 12, the above describes an example of a scenario in which CPAC is configured before handover and then MN handover occurs. It should be understood that the above steps are merely illustrative examples. This is not strictly limited. In addition, the sequence numbers of the above processes do not imply an execution order. The execution order of the processes should be determined according to the functions and internal logic of the processes, and should not be construed as any limitation on the implementation process of the embodiments of the present application.

[0490] FIG. 13 is a schematic flow chart of a scenario applicable to an embodiment of the present application in which a CPC is configured before handover and then a SN handover occurs.

[0491] As shown in Fig. 13, the method 1300 is mainly described by using interactions between a terminal device, a MN, a source SN, a candidate SN1, a candidate SN2, and a target SN as an example. For distinction, the source SN represents the SN before handover, and the target SN represents the SN after handover. It should be understood that the source SN and the target SN are names for distinction, and the specific naming scheme of the source SN and the target SN does not constitute a limitation to the protection scope of the embodiments of the present application. The method 1300 shown in Fig. 13 may include the following steps.

[0492] 1310: The network side configures a CPC for the terminal device.

[0493] Step 1310 is not limited to this embodiment of the present application. For example, please refer to the description of steps 910 and 920, the description of steps 1010 and 1020, or the description of steps 1110 and 1120. For step 1310, please refer to the prior art or future schemes. Details will not be described here.

[0494] 1320: The source SN or MN sends relevant information of the candidate SNs, which is configured by the network side before the handover, to the target SN.

[0495] The relevant information of the candidate SN may include, for example, one or more of an identifier of the candidate SN configured by the network device before the handover and an identifier of a terminal device in the candidate SN.

[0496] It should be understood that any manner in which the target SN can recognize the relevant information of the candidate SN configured by the network side before handover belongs to the scope of protection of the embodiment of the present application. For example, as shown in Figure 13, the relevant information can be sent by the source SN, or the relevant information can be sent in another manner (for example, forwarded by the source MN). This is not limited.

[0497] In the following, an explanation is provided with reference to several scenarios.

[0498] Scenario A: The scenario in which the MN triggers the CPC is configured before the handover, and the CPC triggered by the SN is configured after the handover.

[0499] When the source SN triggers a SN handover, for example when the source SN sends a SN change required message to the MN, the SN change required message may carry an identifier of the target SN.

[0500] After receiving the SN CHANGE REQUIRED message sent by the source SN, the MN may send relevant information of the candidate SN (e.g., the identifier of the candidate SN before handover and the identifier of the terminal device at the candidate SN) to the target SN. For example, after receiving the SN CHANGE REQUIRED message sent by the source SN, the MN may send an SN ADD REQUEST message to the target SN, where the SN ADD REQUEST message may carry relevant information of the candidate SN.

[0501] The MN triggers the SN handover. For example, the MN sends an SN addition request message to the target SN, where the SN addition request message may carry relevant information of the candidate SN.

[0502] Scenario B: The scenario in which the SN triggers the CPC is configured both before and after the handover.

[0503] When the source SN triggers a SN handover, for example, the source SN may send a SN CHANGE REQUIRED message to the MN, where the SN CHANGE REQUIRED message may carry information (e.g., relevant information of the candidate SN) to be sent by the source SN to the target SN. After receiving the SN CHANGE REQUIRED message sent by the source SN, the MN may send the relevant information of the candidate SN (e.g., an identifier of the candidate SN before the handover and an identifier of the terminal device at the candidate SN) to the target SN. For example, after receiving the SN CHANGE REQUIRED message sent by the source SN, the MN may send a SN ADD REQUEST message to the target SN, where the SN ADD REQUEST message may carry the relevant information of the candidate SN.

[0504] In other words, in scenario B, the source SN may first send relevant information of the candidate SN (e.g., an identifier of the candidate SN before handover and an identifier of the terminal device at the candidate SN) to the MN, and then the MN sends the relevant information of the candidate SN to the target SN (where, for example, the relevant information is carried in an SN addition request message).

[0505] The MN triggers the SN handover. For example, the MN sends an SN addition request message to the target SN, where the SN addition request message may carry relevant information of the candidate SN.

[0506] Scenario C: A scenario in which the MN-triggered CPC is configured before handover and the DC is configured after handover.

[0507] When the source MN triggers a SN handover, for example, the source MN sends relevant information of the candidate SN (e.g., an identifier of the candidate SN before the handover and an identifier of a terminal device in the candidate SN) to the target SN. For example, the MN sends an SN Addition Request message to the target SN, where the SN Addition Request message may carry relevant information of the candidate SN.

[0508] Scenario D: A scenario in which SN-triggered CPC is configured before handover and DC is configured after handover.

[0509] When a source SN triggers a SN handover, for example, when the source SN sends a SN change required message to the MN, the SN change required message may carry an identifier of the target SN and related information of the candidate SNs.

[0510] After receiving the SN CHANGE REQUIRED message sent by the source SN, the MN may send an SN ADD REQUEST message to the target SN, where the SN ADD REQUEST message may carry relevant information of the candidate SN.

[0511] When the source MN triggers the SN handover, the solution is similar to that in scenario C. The details will not be described again here.

[0512] With reference to the four scenarios, the above describes the case where the target SN obtains the relevant information of the candidate SNs configured by the network side before handover. It should be understood that in different scenarios, adaptive adjustment can be performed based on the case of each scenario. Any solution that can finally allow the target SN to obtain the relevant information of the candidate SNs configured by the network side before handover is applicable to the embodiments of the present application.

[0513] 1330: The target SN sends identification information of the terminal device in the candidate SN to the candidate SN.

[0514] As shown in FIG. 13, the target SN may transmit identification information of the terminal device in the candidate SN to candidate SN1 and candidate SN2.

[0515] In the following, an explanation is provided with reference to several scenarios.

[0516] Scenario A: The scenario in which the MN triggers the CPC is configured before the handover, and the CPC triggered by the SN is configured after the handover.

[0517] The target SN receives the relevant information of the candidate SN sent by the MN. When the target SN decides to trigger the CPC and the candidate SN is the same as the candidate SN before the handover (where, for example, based on the relevant information of 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 may send information to the candidate SN, where the information may hold an identifier of the terminal device in the candidate SN.

[0518] Optionally, the target SN may further send instruction information #3 to the MN, where the instruction information #3 instructs the MN to use or maintain information about the terminal device in the candidate SN (where, for example, the information may include one or more of the context of the terminal device in the candidate SN and the early data transfer previously performed by the candidate SN). The instruction information #3 and the identifier of the terminal device in the candidate SN may be carried in the same message or may be sent separately. This is not limited.

[0519] After receiving the indication information #3, the MN may send the indication information #3 to the candidate SN. For example, the MN sends an SN release request message to the candidate SN, where the SN release request message carries the indication information #3.

[0520] Scenario B: SN-triggered CPC is configured both before and after handover

[0521] The target SN receives the relevant information of the candidate SN sent by the source SN. When the target SN decides to trigger the CPC and the candidate SN is the same as the candidate SN before the handover (where, for example, based on the relevant information of the candidate SN sent by the MN, the candidate SN is determined to be the same as the candidate SN before the handover), the target SN may send information to the candidate SN, where the information may hold an identifier of the terminal device in the candidate SN.

[0522] Optionally, the target SN may further send instruction information #3 to the MN, where the instruction information #3 instructs the MN to use or maintain information about the terminal device in the candidate SN (where, for example, the information may include one or more of the context of the terminal device in the candidate SN and the early data transfer previously performed by the candidate SN). The instruction information #3 and the identifier of the terminal device in the candidate SN may be carried in the same message or may be sent separately. This is not limited.

[0523] After receiving the indication information #3, the MN may send the indication information #3 to the candidate SN. For example, the MN sends an SN release request message to the candidate SN, where the SN release request message carries the indication information #3.

[0524] Optionally, after step 1330, the MN may send configuration information to the terminal device, where the configuration information may be the configuration information of the DC, or may be the configuration information of the CPC.

[0525] 1340: The target SN receives information about the candidate SN's early data transfer.

[0526] The MN or the source SN may transmit information about the candidate SN's early data transfer to the target SN. For example, the MN may transmit information about the candidate SN's early data transfer directly to the target SN. In another example, the MN may first transmit information about the candidate SN's early data transfer to the source SN, and then the source SN transmits information about the candidate SN's early data transfer to the target SN. Figure 13 only shows the case where the source SN transmits information about the candidate SN's early data transfer to the target SN. It should be understood that Figure 13 is merely an example for explanation and does not limit the scope of the present application.

[0527] The information about the early data forwarding of the candidate SN may include, for example, data packets for which early data forwarding was performed from the source MN to the candidate SN (e.g., indicated by a PDCP SN or NR-U sequence number) and one or more of data packets in the early data forwarding that can be discarded by the candidate SN.

[0528] In the following, an explanation is provided with reference to several scenarios.

[0529] Scenario A: The scenario in which the MN triggers the CPC is configured before the handover, and the CPC triggered by the SN is configured after the handover.

[0530] In this scenario, the MN may send information about the candidate SN's early data forwarding to the target SN.

[0531] After receiving information about the candidate SN's early data transfer, the target SN may notify the candidate SN of the data packets in the early data transfer that can be discarded, specifically, the target SN may send indication information #1 to the candidate SN.

[0532] In addition, the target SN may determine data packets for which early data forwarding directed to the candidate SN needs to be performed based on the data packets for which the MN has performed early data forwarding directed to the candidate SN.

[0533] In addition, after step 1340, the target SN may further send multiple indication information #1 to the candidate SN based on the status of downlink data packets sent by the target SN to the terminal device, indicating which data packets in the early data transfer can be discarded by the candidate SN.

[0534] For the contents of the instruction information #1, please refer to the above description of the method 900. Here, the details will not be described again.

[0535] Scenario B: SN-triggered CPC is configured both before and after handover

[0536] In this scenario, the MN or source SN may send information about the candidate SN's early data forwarding to the target SN. After receiving information about the candidate SN's early data transfer, the target SN may notify the candidate SN of the data packets in the early data transfer that can be discarded, specifically, the target SN may send indication information #1 to the candidate SN.

[0537] In addition, the target SN may determine the data packets for which early data forwarding directed to the candidate SN needs to be performed based on the data packets for which the MN has performed early data forwarding directed to the candidate SN and the data packets for which the source SN has performed early data forwarding directed to the candidate SN, so that the forwarding of repeated data packets can be avoided as much as possible.

[0538] In addition, after step 1340, the target SN may further send multiple indication information #1 to the candidate SN based on the status of downlink data packets sent by the target SN to the terminal device, indicating which data packets in the early data transfer can be discarded by the candidate SN.

[0539] Scenario C: A scenario in which the MN-triggered CPC is configured before handover and the DC is configured after handover.

[0540] In this scenario, the MN may send information about the candidate SN's early data forwarding to the target SN.

[0541] Scenario D: A scenario in which SN-triggered CPC is configured before handover and DC is configured after handover.

[0542] In this scenario, the MN or source SN may send information about the candidate SN's early data forwarding to the target SN.

[0543] With reference to the four scenarios, the above describes the case where the target SN receives the information about the early data transfer of the candidate SN. It should be understood that in different scenarios, adaptive adjustment can be performed based on the case of each scenario. Any solution that can make the target SN aware of the information about the early data transfer of the candidate SN is applicable to the embodiments of the present application.

[0544] 1350: The target SN sends downlink data to the terminal device.

[0545] In the following, an explanation is provided with reference to several scenarios.

[0546] Scenario A: The scenario in which the MN triggers the CPC is configured before the handover, and the CPC triggered by the SN is configured after the handover.

[0547] After the terminal device determines that the trigger condition of the candidate PSCell is satisfied and the terminal device accesses the candidate PSCell, the candidate SN may transmit downlink data to the terminal device based on the information about the most recent early data transfer and the early transfer data. For example, the candidate SN may transmit downlink data to the terminal device based on the most recent instruction information #1 and the early transfer data, for example, discard the data packet that the instruction information #1 instructs to discard, and transmit the remaining data packets in the early transfer data packet to the terminal device.

[0548] Scenario B: SN-triggered CPC is configured both before and after handover

[0549] The solution is similar to that in Scenario A. The details will not be explained again here.

[0550] Scenario C: A scenario in which the MN-triggered CPC is configured before handover and the DC is configured after handover.

[0551] After the terminal device determines that the trigger condition of the candidate PSCell is satisfied and the terminal device accesses the candidate PSCell, the SN may transmit the data in the previous early data transfer to the terminal device.

[0552] Scenario D: A scenario in which SN-triggered CPC is configured before handover and MR-DC is configured after handover.

[0553] The solution is similar to that in Scenario C. The details will not be explained again here.

[0554] According to the above solution, the target SN knows the relevant information of the candidate SN configured by the network side before handover (e.g., the identifier of the candidate SN configured by the network side before handover and the identifier of the terminal device in the candidate SN), and the target SN can send the identifier of the terminal device in the candidate SN before handover to the candidate SN. In addition, the target SN can receive information about the early data forwarding of the candidate SN before handover. In this way, after the handover, the network side can continue to use the data forwarded in the previous early data forwarding. In addition, if the CPC is further configured after the handover, the early data forwarding does not need to be performed for the data. If the DC is configured after the handover, normal data forwarding (i.e., conventional data forwarding between the MN terminated bearer and the SN terminated bearer) may not need to be performed for the data.

[0555] With reference to steps 1310 to 1350 shown in Figure 13, the above describes an example of a scenario in which a CPC is configured before handover and then an SN handover occurs. It should be understood that the above steps are merely illustrative examples. This is not strictly limited. In addition, the sequence numbers of the above processes do not imply an execution order. The execution order of the processes should be determined according to the functions and internal logic of the processes, and should not be construed as any limitation on the implementation process of the embodiments of the present application.

[0556] FIG. 14 is a schematic flow chart of a scenario applicable to an embodiment of the present application where CPAC is not configured before handover and then MN handover occurs.

[0557] As shown in Fig. 14, the method 1400 is mainly described by using interactions between a terminal device, a source MN, a source SN, a candidate SN1, a target SN, and a target MN as an example. For distinction, the source SN represents an SN before handover, the target SN represents an SN after handover, the source MN represents an MN before handover, and the target MN represents an MN after handover. It should be understood that the source SN, the target SN, the source MN, and the target MN are all names for distinction, and the specific naming schemes of the source SN, the target SN, the source MN, and the target MN do not constitute limitations on the scope of protection of the embodiments of the present application. The method 1400 shown in Fig. 14 may include the following steps.

[0558] 1410: The network side configures a DC for the terminal device.

[0559] For example, the MN sends an SN addition request message to the SN, and the SN feeds back an SN addition request response to the MN. The MN may notify the terminal device to configure a DC. For example, the MN sends an RRC reconfiguration message to the terminal device, where the RRC reconfiguration message instructs the terminal device to configure a DC.

[0560] The above is just an example for illustration purposes. Step 1410 is not limited to this embodiment of the present application. For example, for step 1410, please refer to the prior art or future schemes.

[0561] 1420: The source MN sends a handover request message to the target MN.

[0562] Optionally, the source MN may further transmit an identifier of the SN before the handover and an identifier of the terminal device in the SN to the target MN, for example, the handover request message carries an identifier of the SN before the handover and an identifier of the terminal device in the SN.

[0563] 1430: The target MN sends an SN addition request message to the target SN or the candidate SN.

[0564] Optionally, the target MN may further send an identifier of the terminal device in the SN before the handover to the target SN or the candidate SN. For example, the SN addition request message carries an identifier of the terminal device in the SN before the handover.

[0565] It should be understood that the target SN may or may not be the SN before the handover, and there is no limitation in this regard.

[0566] In the following, an explanation is provided with reference to three cases.

[0567] In possible cases, the CPA is configured after the handover.

[0568] In this case, in step 1430, the target MN sends an SN Add Request message to the candidate SN.

[0569] In this case, the source SN may forward the data to the target MN. For example, the source SN forwards the data directly to the target MN. In another example, the source SN may first forward the data packet to the source MN, and then the source MN transmits the forwarded data packet to the target MN.

[0570] The target MN may know which data packets have been previously received by the candidate SN based on the data packets forwarded by the source SN. In this way, data forwarding does not need to be performed for these data packets in the earlier data transfer between the target MN and the candidate SN. In a possible manner, the target MN knows which data packets have been previously received by the candidate SN based on the downlink sequence number carried in the SN status transfer sent by the source MN, which needs to be assigned by the target MN, and the data packets received by the source MN.

[0571] In another possible case, the CPC triggered by the MN is configured after handover.

[0572] In this case, in step 1430, the target MN sends an SN Add Request message to the candidate SN.

[0573] In this case, the source SN may forward the data to the target SN. For example, the source SN forwards the data directly to the target SN. In another example, the source SN may first forward the data packet to the source MN, which then forwards the data packet to the target MN, and the target MN sends the forwarded data packet to the target SN.

[0574] The target SN may recognize which data packets have been previously received by the candidate SN based on the data packets forwarded by the source SN. For a specific scheme, please refer to the scheme in the first case.

[0575] In another possible case, the SN-triggered CPC is configured after handover.

[0576] In this case, the target MN sends an SN Addition Request message to the target SN in step 1430. The target SN may then send an identifier of the terminal device in the SN before the handover to the candidate SN.

[0577] In addition, the source SN may forward data to the target SN. In addition, the target SN may recognize which data packets have been previously received by the candidate SN based on the data packets forwarded by the source SN. For details, please refer to the second case above. Details will not be repeated here.

[0578] The above uses three cases as examples for illustration, which are not strictly limited.

[0579] Optionally, after step 1430, the target MN may further send configuration information to the terminal device, where the configuration information includes the configuration information of the CPAC.

[0580] 1440: The candidate SN receives instruction information #3, instructing it to use or maintain information regarding the terminal device at the candidate SN.

[0581] The information about the terminal device at the candidate SN may include, for example, one or more of a context of the terminal device at the candidate SN and an early data transfer previously performed by the candidate SN.

[0582] For example, as shown in FIG. 14, in step 1440, candidate SN1 receives indication #3 instructing it to continue to use data packets received before the handover as data packets in the early data transfer.

[0583] In addition, when the CPA or the MN-triggered CPC is configured after the handover, the target MN sends the indication information #3 to the candidate SN in step 1440. When the SN-triggered CPC is configured after the handover, the target SN sends the indication information #3 to the candidate SN in step 1440; or the target SN first sends the indication information #3 to the MN, and then the MN sends the indication information #3 to the candidate SN.

[0584] For the instruction information #3, please refer to the above explanation, and the details will not be explained here.

[0585] 1450: The candidate SN transmits downlink data to the terminal device.

[0586] Optionally, before this stage, the candidate SN may receive indication information #1, where indication information #1 informs the candidate SN which data packets in the early data transfer can be discarded. The candidate SN may receive indication information #1 from the MN or may receive indication information #1 from the target SN.

[0587] When the terminal device determines that the trigger condition of the candidate PSCell is satisfied, the terminal device accesses the candidate PSCell, for example, the terminal device performs a random access process with the candidate PSCell.

[0588] The terminal device accesses the candidate SN, and the candidate SN can transmit data packets in the early data transfer (including data packets received before handover) to the terminal device based on the indication information #1 and the information about the early data transfer. Alternatively, if the candidate SN recognizes that the SN before the handover and the candidate SN after the handover are the same SN, the candidate SN can transmit data packets in the early data transfer (including data packets received before handover) to the terminal device based on the most recently received indication information #1.

[0589] According to the above solution, in a scenario where CPAC is not configured before handover and then MN handover occurs, the target MN configures early data forwarding of CPAC for the terminal device. For SN terminated bearers in CPAC configured after MN handover, data packets received by the candidate SN before handover can be used as data packets in early data forwarding, avoiding re-forwarding these data packets in early data forwarding and reducing the transmission delay of these data packets.

[0590] With reference to steps 1410 to 1450 shown in FIG. 14, the above describes an example of a scenario in which CPAC is not configured before handover and then MN handover occurs. It should be understood that the above steps are merely illustrative examples. This is not strictly limited. In addition, the sequence numbers of the above processes do not imply an execution order. The execution order of the processes should be determined according to the functions and internal logic of the processes, and should not be construed as any limitation on the implementation process of the embodiments of the present application.

[0591] It should be understood that some message names, such as early data transfer (or early data transmission), SN addition request message, indication information #1, and indication information #2, are related to some of the above embodiments. It should be understood that the names do not limit the scope of protection of the embodiments of the present application.

[0592] It should be further understood that in some of the above embodiments, a base station (e.g., MN or SN) is mainly used as an example for explanation. It should be understood that network devices in other forms can be used in the embodiments of the present application.

[0593] In some of the above embodiments, the SN addition request message is referred to multiple times and may also be described as a request message for SN addition, and it should be further understood that the name of the SN addition request message does not limit the scope of protection of the embodiments of the present application.

[0594] It should be further understood that in some of the above embodiments, in the case of PSCell addition, a SN addition request message is sent, where the SN addition request message is for conditional SN addition; in the case of PSCell change, a SN addition request message is sent, where the SN addition request message is for conditional SN change. The above is merely an example for explanation. The content specifically indicated by the SN addition request message is not strictly limited. For example, regardless of whether it is PSCell addition or PSCell change, a SN addition request message is sent, where the SN addition request message is for conditional SN addition. In other words, the SN addition request message may be defined as being for conditional SN addition, and SN change and SN addition are not specifically distinguished.

[0595] It should be further understood that in some of the above embodiments, the forwarded data packet is mentioned multiple times, mainly indicating forwarding of a data packet that is not transmitted and / or a data packet that has failed to be transmitted. Here, the data packet may be an uplink data packet or a downlink data packet, without being limited thereto. For example, the source network device may forward a downlink data packet transmitted to a terminal device to a target network device. In another example, the source network device may forward an uplink data packet received out-of-order from the terminal device to the target network device.

[0596] It should be further understood that in Figures 12 to 14, the early data transfer between the MN and the SN includes early data transfer of SN terminated SCG / MCG / split bearer at the candidate SN in the CPAC, and may further include early data transfer between the MN and the SN that is of MN terminated SCG / split bearer at the MN. Unless otherwise specified, the format of the data packet in the early data transfer is not limited in this application.

[0597] Each embodiment described in this specification may be an independent solution or may be combined based on internal logic, all of which are included in the protection scope of this application.

[0598] In the above method embodiments, it may be understood that the methods and operations implemented by a terminal device may alternatively be implemented by components (e.g., chips or circuits) that may be used in a terminal device, and the methods and operations implemented by a network device (e.g., MN or SN) may alternatively be implemented by components (e.g., chips or circuits) that may be used in a network device.

[0599] The method provided in the embodiment of the present application is described in detail above with reference to Figures 7 to 14. With reference to Figures 15 to 17, the data transmission device provided in the embodiment of the present application is described in detail below. It should be understood that the description of the embodiment of the device corresponds to the description of the embodiment of the method. Therefore, for the contents not described in detail, please refer to the above embodiment of the method. For the sake of brevity, the details will not be described again in this specification.

[0600] 15 is a schematic block diagram of a data transmission device according to an embodiment of the present application. The device 1500 includes a transceiver unit 1510 and a processing unit 1520. The transceiver unit 1510 may implement corresponding communication functions, and the processing unit 1520 is configured to process data. The transceiver unit 1510 may also be referred to as a communication interface or a communication unit.

[0601] Optionally, the apparatus 1500 may further include a storage unit. The storage unit may be configured to store instructions and / or data. The processing unit 1520 may read the instructions and / or data in the storage unit, such that the apparatus implements the above method embodiments.

[0602] The apparatus 1500 may be configured to perform the actions performed by the network device in the above method embodiments. In this case, the apparatus 1500 may be a network device or a component that may be configured on the network device. The transceiver unit 1510 is configured to perform transceiver-related operations at the network device side in the above method embodiments. The processing unit 1520 is configured to perform processing-related operations at the network device side in the above method embodiments.

[0603] In design, the apparatus 1500 is configured to perform the actions performed by a master network device (eg, MN) in the method embodiments described above.

[0604] In a possible implementation, the processing unit 1520 is configured to configure a conditional candidate PSCell addition or modification for the terminal device. The transceiver unit 1510 is configured to perform early data transmission directed to a network device to which the candidate PSCell belongs, where the early data transmission is to transmit one or more data packets to the network device to which the candidate PSCell belongs before the terminal device accesses the candidate PSCell, where the format of the data packets is a protocol data unit of a Packet Data Convergence Protocol, where the one or more data packets include data packets on a MN terminated secondary cell group bearer configured for the terminal device and / or data packets on a MN terminated split bearer configured for the terminal device.

[0605] In an example, the transceiver unit 1510 is further configured to send first indication information to a network device to which the candidate PSCell belongs, where the first indication information instructs performing early data transmission on the MN terminated secondary cell group bearer and / or the MN terminated split bearer.

[0606] In another example, the transceiver unit 1510 is further configured to transmit second instruction information to a network device to which the candidate PSCell belongs, the second instruction information instructing the network device to discard or ignore some or all of the one or more data packets.

[0607] In another example, the second instruction information includes information about one or more sequence numbers, where the information about the one or more sequence numbers instructs discarding or ignoring some or all of the one or more data packets.

[0608] In another example, the sequence number is a Packet Data Convergence Protocol sequence number or a new wireless user plane sequence number.

[0609] In another example, the transceiver unit 1510 is specifically configured to send second indication information to the network device to which the candidate PSCell belongs when a preset condition is met.

[0610] The apparatus 1500 may implement corresponding steps or procedures performed by a master network device (e.g., MN) in the embodiment of the method according to the embodiment of the present application. The apparatus 1500 may include units configured to perform the methods performed by the master network device (e.g., MN) in Figures 7 and 9-11. In addition, the units in the apparatus 1500 and other operations and / or functions described above are each intended to implement corresponding procedures in the embodiment of the method of the master network device (e.g., MN) in Figures 7 and 9-11.

[0611] When the apparatus 1500 is configured to perform the method 700 in FIG. 7, the transceiver unit 1510 may be configured to perform stage 720 in the method 700, and the processing unit 1520 may be configured to perform a processing stage in the method 700, such as stage 710.

[0612] When the apparatus 1500 is configured to perform the method 900 in FIG. 9, the transceiver unit 1510 may be configured to perform steps 920 and 940 in the method 900, and the processing unit 1520 may be configured to perform a processing step in the method 900, such as step 910.

[0613] When the apparatus 1500 is configured to perform the method 1000 in FIG. 10, the transceiver unit 1510 may be configured to perform steps 1020 and 1040 in the method 1000, and the processing unit 1520 may be configured to perform a processing step in the method 1000, such as step 1010.

[0614] When the apparatus 1500 is configured to perform the method 1100 in FIG. 11, the transceiver unit 1510 may be configured to perform steps 1120 and 1140 in the method 1100, and the processing unit 1520 may be configured to perform a processing step in the method 1100, such as step 1110.

[0615] It should be understood that the specific process in which each unit performs the above corresponding step is described in detail in the above method embodiments, and for the sake of brevity, the details will not be described again in this specification.

[0616] In another design, apparatus 1500 is configured to perform actions performed by a candidate network device (eg, a candidate SN) in the method embodiments described above.

[0617] In a possible implementation, the transceiver unit 1510 is configured to receive one or more data packets from the MN, where the format of the data packets is a protocol data unit of the Packet Data Convergence Protocol, and the one or more data packets include data packets on a MN terminated secondary cell group bearer configured for the terminal device and / or data packets on a MN terminated split bearer configured for the terminal device. The processing unit 1520 is configured to access the terminal device. The transceiver unit 1510 is further configured to transmit a part or a whole of the one or more data packets to the terminal device, where a conditional candidate primary secondary cell group cell PSCell addition or change is configured for the terminal device.

[0618] In an example, the transceiver unit 1510 is further configured to receive second instruction information, where the second instruction information instructs to discard or ignore some or all of the one or more data packets. The transceiver unit 1510 is specifically configured to transmit data to the terminal device based on the one or more data packets and the second instruction information.

[0619] In another example, the second instruction information includes information about one or more sequence numbers, where the information about the one or more sequence numbers instructs discarding or ignoring some or all of the one or more data packets.

[0620] In another example, the sequence number is a Packet Data Convergence Protocol sequence number or a new wireless user plane sequence number.

[0621] In another example, the transceiver unit 1510 is specifically configured to receive the second indication information periodically.

[0622] The apparatus 1500 may implement corresponding steps or procedures performed by a candidate network device (e.g., a candidate SN) in the embodiment of the method according to the embodiment of the present application. The apparatus 1500 may include units configured to perform the method performed by the candidate network device (e.g., a candidate SN) in Figures 7 and 9-11. In addition, the units in the apparatus 1500 and other operations and / or functions described above are each intended to implement corresponding procedures in the embodiment of the method of the candidate network device (e.g., a candidate SN) in the SN in Figures 7 and 9-11.

[0623] When the apparatus 1500 is configured to perform the method 700 in FIG. 7, the transceiver unit 1510 may be configured to perform steps 720 and 730 in the method 700, and the processing unit 1520 may be configured to perform a processing step in the method 700, such as step 710.

[0624] When the apparatus 1500 is configured to perform the method 900 in FIG. 9, the transceiver unit 1510 may be configured to perform steps 940, 950 and 960 in the method 900, and the processing unit 1520 may be configured to perform a processing step in the method 900, such as step 910.

[0625] When the apparatus 1500 is configured to perform the method 1000 in FIG. 10, the transceiver unit 1510 may be configured to perform steps 1040, 1050 and 1060 in the method 1000, and the processing unit 1520 may be configured to perform a processing step in the method 1000, such as step 1010.

[0626] When the apparatus 1500 is configured to perform the method 1100 in FIG. 11, the transceiver unit 1510 may be configured to perform steps 1140, 1150 and 1160 in the method 1100, and the processing unit 1520 may be configured to perform a processing step in the method 1100, such as step 1110.

[0627] It should be understood that the specific process in which each unit performs the above corresponding steps is described in detail in the above method embodiments, and for the sake of brevity, the details will not be described again here.

[0628] In another design, apparatus 1500 is configured to perform actions performed by a source network device (eg, a source MN or a source SN) in the above method embodiments.

[0629] In a possible implementation, the processing unit 1520 is configured to determine that the network devices configured for the terminal device after the handover include a second network device, where before the terminal device is handed over from the apparatus 1500 to the target network device, the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device, and after the terminal device is handed over from the apparatus 1500 to the target network device, the second network device is a candidate network device in a conditional candidate PSCell addition or modification scenario configured for the terminal device, or or when the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device after the terminal device is handed over from the apparatus 1500 to the target network device, the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device before the terminal device is handed over from the apparatus 1500 to the target network device, or the second network device is a network device serving the terminal device. The transceiver unit 1510 is configured to send third indication information to the second network device, where the third indication information instructs using information about the terminal device in the second network device.

[0630] In an example, the information about the terminal device includes one or more of context information about the terminal device, data packets of the terminal device transmitted to the second network device, and information about data packets of the terminal device that can be discarded by the second network device.

[0631] In another example, the transceiver unit 1510 is further configured to receive the identification information of the second network device sent by 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 devices configured for the terminal device after the handover include the second network device.

[0632] In another example, the transceiver unit 1510 is further configured to transmit early data transmission information of the second network device to the target network device.

[0633] In another example, the transceiver unit 1510 is further configured to transmit information about the one or more network devices to the target network device, where the one or more network devices include a second network device, the one or more network devices are candidate network devices in a conditional candidate PSCell addition or modification scenario configured for the terminal device before the terminal device is handed over from the source network device to the target network device, or are network devices that serve the terminal device; the information about the one or more network devices includes one or more of identification information of the one or more network devices and identification information of the terminal device in the one or more network devices.

[0634] In another example, the transceiver unit 1510 is specifically configured to send a handover request message to the target network device, where the handover request message includes information about the one or more network devices.

[0635] In another example, the transceiver unit 1510 is further configured to transmit the data packets to be transmitted to the terminal device to the target network device or the second network device.

[0636] In another example, the target network device is a network device in a conditional candidate PSCell addition or modification scenario, and the apparatus 1500 is a network device in a conditional candidate PSCell addition or modification scenario. Alternatively, the target network device is a network device in a conditional candidate PSCell addition or modification scenario, and the apparatus 1500 is a network device in a carrier aggregation scenario. Alternatively, the target network device is a network device in a carrier aggregation scenario, and the apparatus 1500 is a network device in a conditional candidate PSCell addition or modification scenario.

[0637] The apparatus 1500 may implement corresponding steps or procedures performed by a source network device (e.g., source MN or source SN) in the method embodiments according to the present application. The apparatus 1500 may include units configured to perform the methods performed by the source network device (e.g., source MN or source SN) in Figures 8 and 12-14. In addition, the units in the apparatus 1500 and other operations and / or functions described above are each intended to implement corresponding procedures in the method embodiments in Figures 8 and 12-14.

[0638] When the apparatus 1500 is configured to perform the method 800 in FIG. 8, the transceiver unit 1510 may be configured to perform steps 8202 and 840 in the method 800, and the processing unit 1520 may be configured to perform a processing step in the method 800, such as step 830.

[0639] When the apparatus 1500 is configured to perform the method 1200 in FIG. 12, the transceiver unit 1510 may be configured to perform steps 1220, 1240, 1250 and 1260 in the method 1200, and the processing unit 1520 may be configured to perform a processing step in the method 1200, such as step 1210.

[0640] When the apparatus 1500 is configured to perform the method 1300 in FIG. 13, the transceiver unit 1510 may be configured to perform steps 1320 and 1340 in the method 1300, and the processing unit 1520 may be configured to perform a processing step in the method 1300, such as step 1310.

[0641] When the apparatus 1500 is configured to perform the method 1400 in FIG. 14, the transceiver unit 1510 may be configured to perform stage 1420 in the method 1400, and the processing unit 1520 may be configured to perform a processing stage in the method 1400, such as stage 1410.

[0642] It should be understood that the specific process in which each unit performs the above corresponding steps is described in detail in the above method embodiments, and for the sake of brevity, the details will not be described again here.

[0643] In another design, apparatus 1500 is configured to perform actions performed by a target network device (eg, a target MN or a target SN) in the method embodiments described above.

[0644] In a possible implementation, the processing unit 1520 is configured to determine to configure N first network devices for the terminal device, where the N first network devices include a second network device, N is an integer equal to or greater than 1, where before the terminal device is handed over from the source network device to the apparatus 1500, the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device, and after the terminal device is handed over from the source network device to the apparatus 1500, the second network device is a candidate network device in a conditional candidate PSCell addition or modification scenario configured for the terminal device. or the second network device is a complementary network device, or the second network device is a network device serving the terminal device; or before the terminal device is handed over from the source network device to the apparatus 1500, the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device, when the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device after the terminal device is handed over from the source network device to the apparatus 1500. The transceiver unit 1510 is configured to transmit third instruction information, where the third instruction information instructs using information about the terminal device in the second network device.

[0645] In an example, the information about the terminal device includes one or more of context information about the terminal device, data packets of the terminal device transmitted to the second network device, and information about data packets of the terminal device that can be discarded by the second network device.

[0646] In another example, the transceiver unit 1510 is specifically configured to send the third indication information to the second network device, or send the third indication information to the source network device.

[0647] In another example, the transceiver unit 1510 is further configured to receive early data transmission information of the second network device sent by the source network device.

[0648] In another example, the transceiver unit 1510 is further configured to perform early data transmission to and from the second network device based on the early data transmission information of the second network device.

[0649] In another example, the transceiver unit 1510 is further configured to transmit the identification information of the second network device to the source network device.

[0650] In another example, the transceiver unit 1510 is further configured to receive information about the one or more network devices from the source network device, where the one or more network devices include a second network device, and the one or more network devices are candidate network devices in a conditional candidate PSCell addition or modification scenario configured for the terminal device before the terminal device is handed over from the source network device to the target network device, or are network devices that serve the terminal device; the information about the one or more network devices includes one or more of identification information of the one or more network devices and identification information of the terminal device in the one or more network devices.

[0651] In another example, the information about the one or more network devices includes identification information of the one or more network devices. The processing unit 1520 is further configured to determine that the N first network devices include the second network device based on the identification information of the one or more network devices.

[0652] In another example, the transceiver unit 1510 is specifically configured to receive a handover request message, where the handover request message includes information about one or more network devices.

[0653] In another example, the apparatus 1500 is a network device in a conditional candidate PSCell addition or modification scenario, and the source network device is a network device in a conditional candidate PSCell addition or modification scenario. Alternatively, the apparatus 1500 is a network device in a conditional candidate PSCell addition or modification scenario, and the source network device is a network device in a carrier aggregation scenario. Alternatively, the apparatus 1500 is a network device in a carrier aggregation scenario, and the source network device is a network device in a conditional candidate PSCell addition or modification scenario.

[0654] The apparatus 1500 may implement corresponding steps or procedures performed by a target network device (e.g., a target MN or a target SN) in the method embodiments according to the present application. The apparatus 1500 may include units configured to perform the methods performed by the target network devices (e.g., a target MN or a target SN) in Figures 8 and 12-14. In addition, the units in the apparatus 1500 and other operations and / or functions described above are each intended to implement the corresponding procedures in the method embodiments in Figures 8 and 12-14.

[0655] When the apparatus 1500 is configured to perform the method 800 in FIG. 8, the transceiver unit 1510 may be configured to perform steps 8201, 8201 and 840 in the method 800, and the processing unit 1520 may be configured to perform a processing step in the method 800, such as step 810.

[0656] When the apparatus 1500 is configured to perform the method 1200 in FIG. 12, the transceiver unit 1510 may be configured to perform steps 1220, 1230, 1240 and 1260 in the method 1200, and the processing unit 1520 may be configured to perform the processing steps in the method 1200.

[0657] When the apparatus 1500 is configured to perform the method 1300 in FIG. 13, the transceiver unit 1510 may be configured to perform steps 1320, 1330 and 1340 in the method 1300, and the processing unit 1520 may be configured to perform the processing steps in the method 1300.

[0658] When the apparatus 1500 is configured to perform the method 1400 in FIG. 14 , the transceiver unit 1510 may be configured to perform steps 1420, 1430 and 1440 in the method 1400, and the processing unit 1520 may be configured to perform the processing steps in the method 1400.

[0659] It should be understood that the specific process in which each unit performs the above corresponding steps is described in detail in the above method embodiments, and for the sake of brevity, the details will not be described again here.

[0660] The processing unit 1520 in the above embodiments may be implemented by at least one processor or processor-related circuitry. The transceiver unit 1510 may be implemented by a transceiver or transceiver-related circuitry. The storage unit may be implemented by at least one memory.

[0661] As shown in Fig. 16, an embodiment of the present application further provides a data transmission device 1600. The device 1600 includes a processor 1610. The processor 1610 is coupled to a memory 1620. The memory 1620 is configured to store computer programs or instructions and / or data. The processor 1610 is configured to execute the computer programs or instructions and / or data stored in the memory 1620, so that the method in the above method embodiment is performed.

[0662] Optionally, the apparatus 1600 includes one or more processors 1610 .

[0663] Optionally, as shown in FIG. 16, the apparatus 1600 may further include a memory 1620.

[0664] Optionally, the device 1600 may include one or more memories 1620.

[0665] Optionally, the memory 1620 and the processor 1610 may be integrated or located separately.

[0666] Optionally, as shown in Figure 16, the device 1600 may further include a transceiver 1630. The transceiver 1630 is configured to receive and / or transmit signals. For example, the processor 1610 is configured to control the transceiver 1630 to receive and / or transmit signals.

[0667] In the solution, the apparatus 1600 is configured to implement the operations performed by the network device in the above method embodiments.

[0668] For example, the processor 1610 is configured to implement processing-related operations performed by a master network device (e.g., an MN) in the above method embodiments, and the transceiver 1630 is configured to implement transceiver-related operations performed by a master network device in the above method embodiments.

[0669] In another example, the processor 1610 is configured to implement processing-related operations performed by a candidate network device (e.g., a candidate SN) in an embodiment of the method described above, and the transceiver 1630 is configured to implement transceiver-related operations performed by a candidate network device in an embodiment of the method described above.

[0670] In another example, the processor 1610 is configured to implement processing-related operations performed by a source network device (e.g., a source MN or a source SN) in an embodiment of the method described above, and the transceiver 1630 is configured to implement transceiver-related operations performed by a source network device in an embodiment of the method described above.

[0671] In another example, the processor 1610 is configured to implement processing-related operations performed by a target network device (e.g., a target MN or a target SN) in an embodiment of the above method, and the transceiver 1630 is configured to implement transceiver-related operations performed by a target network device in an embodiment of the above method.

[0672] The embodiment of the present application further provides a communication device 1700, which may be a network device or a chip. The communication device 1700 may be configured to perform the operations performed by the network device in the above method embodiments.

[0673] When the communication device 1700 is a network device, for example, a base station, FIG. 17 is a simplified schematic diagram of the structure of the base station. The base station includes a part 1710 and a part 1720. The part 1710 is mainly configured to receive and transmit radio frequency signals, and perform conversion between radio frequency signals and baseband signals. The part 1720 is mainly configured to perform baseband processing, control the base station, and so on. The part 1710 can be generally referred to as a transceiver unit, a transceiver, a transceiver circuit, or the like. The part 1720 is generally the control center of the base station, and can be generally referred to as a processing unit, and is configured to control the base station and perform processing operations at the receiving end device side in the above method embodiment.

[0674] The transceiver unit of the portion 1710 may also be referred to as a transceiver or the like, and includes an antenna and a radio frequency circuit. The radio frequency circuit is mainly configured to perform radio frequency processing. Optionally, a component in the portion 1710 configured to implement a receiving function may be considered as a receiving unit, and a component configured to implement a transmitting function may be considered as a transmitting unit. In other words, the portion 1710 includes a receiving unit and a transmitting unit. The receiving unit may also be referred to as a receiver, a receiver circuit, or the like. The transmitting unit may be referred to as a transmitter, a transmitter circuit, or the like.

[0675] Portion 1720 may include one or more boards, each of which may include one or more processors and one or more memories. The processors are configured to load and execute programs in the memories to implement baseband processing functions and control the base station. When there are multiple boards, the boards may be interconnected with each other to enhance processing capabilities. In an optional implementation, multiple boards may share one or more processors, may share one or more memories, or may share one or more processors simultaneously.

[0676] It should be understood that Figure 17 is merely an example, not a limitation, and the above network device including the transceiver unit and the processing unit may not depend on the structure shown in Figure 17.

[0677] When the device 1700 is a chip, the chip includes a transceiver unit and a processing unit. The transceiver unit may be an input / output circuit or a communication interface. The processing unit may be a processor, a microprocessor, or an integrated circuit integrated on a chip. Of course, the device 1700 may alternatively be a chip system or a processing system, so that the device in which the device 1700 is mounted may implement the methods and functions in the embodiments of the present application. For example, the processing unit 1720 may be a processing circuit in the chip system or the processing system for controlling the chip system or the device in which the processing system is mounted, and may be coupled to the storage unit to call instructions in the storage unit, so that the device may implement the methods and functions in the embodiments of the present application. The transceiver unit 1710 may be an input / output circuit in the chip system or the processing system for outputting information processed by the chip system or for inputting data or signaling information to be processed to the chip system for processing.

[0678] An embodiment of the present application further provides a computer-readable storage medium, where the computer-readable storage medium stores computer instructions for implementing the method performed by the network device in the above method embodiment.

[0679] For example, the computer instructions, when executed by a computer, may cause the computer to implement the methods performed by the network device in the method embodiments described above.

[0680] An embodiment of the present application further provides a computer program product including instructions, which, when executed by a computer, enable the computer to implement the method performed by the network device in the method embodiments described above.

[0681] An embodiment of the present application further provides a communication system, which includes the network devices in the above embodiments, such as a master network device and a candidate network device; a source network device and a target network device; or a source network device, a target network device, and a candidate network device.

[0682] For the description of the relevant contents and beneficial effects of any one of the devices provided above, please refer to the corresponding method embodiments provided above, and the details will not be described again here.

[0683] It should be understood that the processor in the embodiments of the present application may be a central processing unit (CPU), or may be another general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or another programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, or the like. A general-purpose processor may be a microprocessor, or the processor may be any conventional processor, etc.

[0684] It should be further understood that the memory in the embodiments of the present application may be volatile memory and / or non-volatile memory. The non-volatile memory may 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. The volatile memory may be random access memory (RAM). For example, the RAM may be used as an external cache. By way of example and not limitation, RAM may include several forms of the following: static random access memory (static RAM, SRAM), dynamic random access memory (dynamic RAM, DRAM), synchronous dynamic random access memory (synchronous DRAM, SDRAM), double data rate synchronous dynamic random access memory (double data rate SDRAM, DDR SDRAM), enhanced synchronous dynamic random access memory (enhanced SDRAM, ESDRAM), synchlink dynamic random access memory (synchlink DRAM, SLDRAM), and direct rambus random access memory (direct rambus RAM, DR RAM).

[0685] It should be noted that when the processor is a general-purpose processor, a DSP, an ASIC, an FPGA, or another programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component, the memory (storage module) may be integrated into the processor.

[0686] It should be further noted that memory as described herein is intended to include, without being limited to, these and any other suitable types of memory.

[0687] Those skilled in the art may find that, in combination with the examples described in the embodiments disclosed herein, the units and steps may be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented by hardware or software is determined by the specific application and design constraints of the technical solution. Those skilled in the art may use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the protection scope of the present application.

[0688] In some embodiments provided in the present application, it should be understood that the disclosed apparatus and method can be implemented in other ways. For example, the embodiment of the described apparatus is merely an example. For example, the division into multiple units is merely a logical division of functions, and other divisions may be possible in actual implementation. For example, multiple units or components may be combined or integrated into another system, or some functions may be ignored or not performed. Furthermore, the shown or described mutual couplings or direct couplings or communication connections may be implemented through some interfaces. Indirect couplings or communication connections between devices or units may be implemented in electrical, mechanical, or other forms.

[0689] The units described as separate parts may or may not be physically separate, and the parts shown as units may or may not be physical units, specifically located in one place or distributed over multiple network units. To implement the solutions provided herein, some or all of the units may be selected based on actual requirements.

[0690] In addition, the functional units in the embodiments of the present application may be integrated into one unit, and each of the units may exist physically alone, or two or more units may be integrated into one unit.

[0691] All or part of the above embodiments may be implemented by software, hardware, firmware, or any combination thereof. When software is used to implement the embodiments, all or part of the embodiments may be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the procedures or functions according to the embodiments of the present application are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. For example, the computer may be a personal computer, a server, a network device, or the like. The computer instructions may be stored in a computer-readable storage medium or transmitted from a computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website, computer, server, or data center to another website, computer, server, or data center in a wired (e.g., coaxial cable, optical fiber, or digital subscriber line (DSL)) or wireless (e.g., infrared, radio wave, or microwave) manner. The computer-readable storage medium may be any available medium accessible by a computer, or a data storage device (e.g., a server or a data center) that integrates one or more available media. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, or a magnetic tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid state disk, SSD), etc. For example, the available medium may include, but is not limited to, any medium that can store program code, such as a USB flash drive, a removable hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0692] The above description is merely a specific implementation of the present application, and is not intended to limit the scope of protection of the present application. Any modifications or replacements that are easily conceived by those skilled in the art within the technical scope disclosed in this application shall be included in the scope of protection of the present application. Therefore, the scope of protection of the present application shall be subject to the scope of protection of the claims. Other possible items (Item 1) Configuring a conditional candidate primary secondary cell group cell PSCell addition or modification for a terminal device; and performing an early data transmission directed to a network device to which a candidate PSCell belongs, where the early data transmission is to transmit one or more data packets to the network device to which the candidate PSCell belongs before the terminal device accesses the candidate PSCell, and the format of the one or more data packets is a protocol data unit of a Packet Data Convergence Protocol; wherein the one or more data packets include a data packet on a master base station MN terminated secondary cell group bearer configured for the terminal device, and / or a data packet on a MN terminated split bearer configured for the terminal device; Data transmission method. (Item 2) The method further comprises: sending first indication information to the network device to which the candidate PSCell belongs, where the first indication information indicates to perform early data transmission on the MN terminated secondary cell group bearer and / or the MN terminated split bearer; The method of claim 1, comprising: (Item 3) The method further comprises: sending second instruction information to the network device to which the candidate PSCell belongs, where the second instruction information instructs the network device to discard or ignore a part or all of the one or more data packets; 3. The method according to item 1 or 2, comprising: (Item 4) 4. The method of claim 3, wherein the second instruction information includes information about one or more sequence numbers, the information about the one or more sequence numbers instructing the discarding or ignoring of the part or all of the one or more data packets. (Item 5) 5. The method of claim 4, wherein the sequence number is a Packet Data Convergence Protocol sequence number or a New Wireless User Plane sequence number. (Item 6) The step of transmitting second indication information to the network device to which the candidate PSCell belongs includes: transmitting the second indication information to the network device to which the candidate PSCell belongs when a preset condition is satisfied. 6. The method according to any one of items 3 to 5, comprising: (Item 7) receiving one or more data packets from a master base station MN prior to access of the terminal device, where the format of the one or more data packets is a protocol data unit of a Packet Data Convergence Protocol, the one or more data packets including data packets on a MN terminated secondary cell group bearer configured for the terminal device and / or data packets on a MN terminated split bearer configured for the terminal device; and transmitting a part or all of the one or more data packets to the terminal device after said access of the terminal device. A conditional candidate primary secondary cell group cell PSCell addition or change is configured for the terminal device. Data transmission method. (Item 8) The method further comprises: receiving second instruction information, wherein the second instruction information instructs the user to discard or ignore some or all of the one or more data packets; The step of transmitting the one or more data packets to the terminal device includes transmitting data to the terminal device based on the one or more data packets and the second indication information. The method according to item 7. (Item 9) 9. The method of claim 8, wherein the second instruction information includes information about one or more sequence numbers, the information about the one or more sequence numbers instructing the discarding or ignoring of the part or all of the one or more data packets. (Item 10) 10. The method of claim 9, wherein the sequence number is a Packet Data Convergence Protocol sequence number or a New Wireless User Plane sequence number. (Item 11) 11. The method according to any one of claims 8 to 10, wherein the step of receiving the second instruction information comprises the step of periodically receiving the second instruction information. (Item 12) determining, by the target network device, to configure N first network devices for the terminal device, where the N first network devices include a second network device, N being an integer equal to or greater than 1; When the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device before the terminal device is handed over from the source network device to the target network device, after the terminal device is handed over from the source network device to the target network device, the second network device is the candidate network device in the conditional candidate PSCell addition or modification scenario configured for the terminal device, or the second network device is a network device serving the terminal device; or When the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device after the terminal device is handed over from a source network device to the target network device, before the terminal device is handed over from the source network device to the target network device, the second network device is the candidate network device in the conditional candidate PSCell addition or modification scenario configured for the terminal device, or the second network device is a network device serving the terminal device; and sending, by the target network device, third instruction information, where the third instruction information instructs the second network device to use information about the terminal device; A data transmission method comprising: (Item 13) Item 13. The method of item 12, wherein the information regarding the terminal device includes one or more of context information of the terminal device, data packets of the terminal device transmitted to the second network device, and information about data packets of the terminal device that can be discarded by the second network device. (Item 14) The step of transmitting third indication information by the target network device further comprises: sending, by the target network device, the third indication information to the second network device; or sending, by the target network device, the third indication information to the source network device; 14. The method according to item 12 or 13, comprising: (Item 15) The method further comprises: receiving, by the target network device, information of an early data transmission of the second network device from the source network device; 15. The method according to any one of items 12 to 14, comprising: (Item 16) The method further comprises: performing early data transmission between the target network device and the second network device based on the early data transmission information of the second network device by the target network device; Item 16. The method of item 15, comprising: (Item 17) The method further comprises: transmitting, by the target network device, an identification of the second network device to the source network device. 17. The method according to any one of items 12 to 16, comprising: (Item 18) The method further comprises: receiving, by the target network device, information about one or more network devices from the source network device, where the one or more network devices include the second network device, and the one or more network devices are candidate network devices in the conditional candidate PSCell addition or modification scenario that are configured for the terminal device before the terminal device is handed over from the source network device to the target network device, or are network devices that serve the terminal device; and wherein the information about the one or more network devices comprises: Identification information of the one or more network devices, and identification information of the terminal device in the one or more network devices including one or more of 18. The method according to any one of items 12 to 17. (Item 19) the information about the one or more network devices includes the identification information of the one or more network devices; The method further includes determining, based on the identification information of the one or more network devices, that the N first network devices include the second network device. 20. The method of claim 18, comprising: (Item 20) The step of receiving, by the target network device, information about one or more network devices from the source network device, further comprising: receiving, by the target network device, a handover request message from the source network device, where the handover request message includes the information about the one or more network devices; 20. The method according to item 18 or 19, comprising: (Item 21) the target network device is a network device in the conditional candidate PSCell addition or modification scenario, and the source network device is a network device in the conditional candidate PSCell addition or modification scenario; The target network device is a network device in the conditional candidate PSCell addition or modification scenario, and the source network device is a network device in a carrier aggregation scenario; or The target network device is a network device in a carrier aggregation scenario, and the source network device is a network device in the conditional candidate PSCell addition or modification scenario. 21. The method according to any one of items 12 to 20. (Item 22) determining, by the source network device, that network devices configured for the terminal device after the handover include a second network device, where: When the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device before the terminal device is handed over from the source network device to the target network device, after the terminal device is handed over from the source network device to the target network device, the second network device is the candidate network device in the conditional candidate PSCell addition or modification scenario configured for the terminal device, or the second network device is a network device serving the terminal device; or When the second network device is a candidate network device in a conditional candidate primary secondary cell group cell PSCell addition or modification scenario configured for the terminal device after the terminal device is handed over from the source network device to the target network device, before the terminal device is handed over from the source network device to the target network device, the second network device is a candidate network device in the conditional candidate PSCell addition or modification scenario configured for the terminal device, or the second network device is a network device serving the terminal device; and sending, by the source network device, third instruction information to the second network device, where the third instruction information instructs the second network device to use information about the terminal device; A data transmission method comprising: (Item 23) 23. The method of claim 22, wherein the information regarding the terminal device includes one or more of context information of the terminal device, data packets of the terminal device transmitted to the second network device, and information about data packets of the terminal device that can be discarded by the second network device. (Item 24) The step of determining, by the source network device, that the network devices configured for the terminal device after the handover include a second network device, receiving, by the source network device, an identity of the second network device from the target network device; and determining, by the source network device based on the identification information of the second network device, that the network devices configured for the terminal device after the handover include the second network device; 24. The method according to item 22 or 23, comprising: (Item 25) The method further comprises: transmitting early data transmission information of the second network device to the target network device by the source network device; 25. The method according to any one of items 22 to 24, comprising: (Item 26) The method further comprises: transmitting, by the source network device, information about one or more network devices to the target network device, where the one or more network devices include the second network device, and the one or more network devices are candidate network devices in the conditional candidate PSCell addition or modification scenario that are configured for the terminal device before the terminal device is handed over from the source network device to the target network device, or are network devices that serve the terminal device. and wherein the information about the one or more network devices comprises: Identification information of the one or more network devices, and identification information of the terminal device in the one or more network devices including one or more of 26. The method according to any one of items 22 to 25. (Item 27) The step of transmitting, by the source network device, information about one or more network devices to the target network device, further comprising: sending, by the source network device, a handover request message to the target network device, where the handover request message includes the information about the one or more network devices; 27. The method according to item 26, comprising: (Item 28) The method further comprises: transmitting, by the source network device, data packets to be transmitted to the terminal device to the target network device or to the second network device; 28. The method according to any one of items 22 to 27, comprising: (Item 29) the target network device is a network device in the conditional candidate PSCell addition or modification scenario, and the source network device is a network device in the conditional candidate PSCell addition or modification scenario; The target network device is a network device in the conditional candidate PSCell addition or modification scenario, and the source network device is a network device in a carrier aggregation scenario; or The target network device is a network device in a carrier aggregation scenario, and the source network device is a network device in the conditional candidate PSCell addition or modification scenario. 29. The method according to any one of items 22 to 28. (Item 30) 30. A computer-readable storage medium storing a computer program, the computer program being capable of, when executed by one or more processors, causing an apparatus including the processors to perform the method according to any one of items 1 to 29. (Item 31) 30. A computer program product comprising computer program code, which, when said computer program code is executed on a computer, implements the method according to any one of items 1 to 29. (Item 32) The target network device and the source network device according to any one of items 12 to 29, or 30. The target network device, the source network device, and the second network device according to any one of claims 12 to 29. A communication system comprising:

Claims

1. 1. A data transmission method, comprising: A master node (MN) configuring a conditional candidate primary secondary cell group cell (PSCell) addition or change for a terminal device; and a step of the MN performing an early data transmission directed to a network device to which a candidate PSCell belongs, where the early data transmission is to transmit one or more data packets to the network device to which the candidate PSCell belongs before the terminal device accesses the candidate PSCell, and the format of the one or more data packets is a Protocol Data Unit (PDU) of a Packet Data Convergence Protocol (PDCP); wherein the one or more data packets include at least one of a data packet on a master node (MN) terminated secondary cell group (SCG) bearer configured for the terminal device or a data packet on a MN terminated split bearer configured for the terminal device; The data transmission method further comprises: the MN sending second indication information to the network device to which the candidate PSCell belongs, where the second indication information instructs the MN to discard or ignore a part or all of the one or more data packets; A method comprising:

2. The method further comprises: the MN sending first indication information to the network device to which the candidate PSCell belongs, where the first indication information indicates to perform early data transmission on at least one of the MN-terminated secondary cell group bearer or the MN-terminated split bearer; The method of claim 1 , comprising:

3. 3. The method of claim 1 or 2, wherein the second instruction information includes information about one or more sequence numbers, the information about the one or more sequence numbers instructing to discard or ignore the part or all of the one or more data packets.

4. The method of claim 3 , wherein the sequence number is a Packet Data Convergence Protocol sequence number or a New Wireless User Plane sequence number.

5. The method described in claim 3 or 4, wherein the second instruction information is a sequence number that indicates that the network device to which the candidate PSCell belongs should discard or ignore data packets in previously forwarded data packets whose corresponding sequence numbers are lower than the sequence number.

6. The step of transmitting second indication information to the network device to which the candidate PSCell belongs includes: and when a preset condition is satisfied, the MN transmits the second indication information to the network device to which the candidate PSCell belongs. The method of any one of claims 1 to 5, comprising:

7. 1. A data transmission method, comprising: A step in which a candidate network device receives one or more data packets from a master node (MN) before access of a terminal device, where the format of the one or more data packets is a Packet Data Convergence Protocol (PDCP) Protocol Data Unit (PDU), and the one or more data packets include at least one of a data packet on a MN-terminated Secondary Cell Group (SCG) bearer configured for the terminal device, or a data packet on a MN-terminated split bearer configured for the terminal device; and transmitting, after the access of the terminal device, a part or all of the one or more data packets to the terminal device by the candidate network device. A conditional candidate primary secondary cell group cell (PSCell) addition or modification is configured for the terminal device; The data transmission method further comprises: receiving, by the candidate network device, second instruction information, wherein the second instruction information instructs the candidate network device to discard or ignore some or all of the one or more data packets; The method, wherein the step of transmitting some or all of the one or more data packets to the terminal device includes transmitting data to the terminal device based on the one or more data packets and the second indication information.

8. 8. The method of claim 7, wherein the second instruction information includes information about one or more sequence numbers, the information about the one or more sequence numbers instructing to discard or ignore the part or all of the one or more data packets.

9. The method of claim 8 , wherein the sequence number is a Packet Data Convergence Protocol sequence number or a New Wireless User Plane sequence number.

10. The method described in claim 8 or 9, wherein the second instruction information is a sequence number that indicates that the candidate network device should discard or ignore data packets in previously forwarded data packets whose corresponding sequence numbers are lower than the sequence number.

11. The method of claim 7 , wherein the step of receiving second indication information comprises the candidate network device receiving the second indication information periodically.

12. A data transmission device comprising means for carrying out the method according to any one of claims 1 to 6.

13. A data transmission device comprising means for carrying out the method according to any one of claims 7 to 11.

14. A computer program product causing a processor to carry out a method according to any one of claims 1 to 6 or any one of claims 7 to 11.

15. A data transmission device according to claim 12. A communication system comprising the data transmission device according to claim 13.

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