CN106941733B

CN106941733B - Method for realizing reconfiguration in dual connection, main service base station and auxiliary service base station

Info

Publication number: CN106941733B
Application number: CN201610006280.6A
Authority: CN
Inventors: 刘星; 施小娟; 黄河
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2016-01-04
Filing date: 2016-01-04
Publication date: 2022-05-13
Anticipated expiration: 2036-01-04
Also published as: CN106941733A; WO2017118225A1

Abstract

The invention discloses a method for realizing reconfiguration in double connection, a main service base station and an auxiliary service base station.A user plane interface for providing uplink data service and downlink data service for UE is established between a source SeNB and a target SeNB in the process of transferring the user plane bearing of the UE from the source SeNB to the target SeNB under the same MeNB; in the reconfiguration process, the target SeNB forwards the uplink RLC data PDU to the source SeNB, and the source SeNB shunts the downlink PDCP data PDU to the target SeNB and keeps data transmission with the UE until the reconfiguration is successful. In the process of establishing connection with the target SeNB, the UE establishes a user plane interface between the source SeNB and the target SeNB for providing uplink/downlink data service for the UE, so that the problem that the UE cannot transmit data with a network side on a micro base station or a low-power node layer when performing uplink and downlink synchronization with the target SeNB and establishing connection is solved, the rapid reduction of the user plane data throughput is avoided, and the user experience of the UE during user plane reconfiguration is ensured.

Description

Method for realizing reconfiguration in dual connection, main service base station and auxiliary service base station

Technical Field

The present invention relates to mobile communication technology, and in particular, to a method, a primary serving base station, and a secondary serving base station for implementing reconfiguration in dual connectivity.

Background

Fig. 1 is a schematic diagram of a network architecture of Dual Connectivity (DC) in the related art, and as shown in fig. 1, for each User Equipment (UE), in a control plane, a Master serving base station (MeNB, Master eNB), such as a macro base station node, is connected to a Mobility Management Entity (MME) through S1-MME, and the MeNB and a Secondary serving base station (SeNB, serving eNB), such as a micro base station or a low power node, are connected through X2-C. On the user plane, for a Master cell group bearer (MCG bearer), the MeNB is connected to a Serving Gateway (S-GW) through S1-U, and the SeNB does not participate in data transmission on the user plane. For split bearer (split bearer), the MeNB is connected to the S-GW through S1-U and the MeNB is connected to the SeNB through X2-U. For Secondary cell group bearer (SCG bearer), SeNB is connected to S-GW through S1-U, and MeNB does not participate in data transmission of user plane.

Fig. 2 is a User Plane Data Protocol stack of Long-term evolution (LTE) in the related art, and as shown in fig. 2, downlink Data received from a core network via a User Plane GPRS tunneling Protocol (GTP-U) is unpacked and then processed by a Packet Data Convergence Protocol (PDCP) sublayer, a Radio Link Control (RLC) Protocol sublayer, a Medium Access Control (MAC) Protocol sublayer and a physical layer (PHY) and then sent to a UE; the transmission of the upstream data is opposite to that of the downstream data. The third Generation Partnership Project (3GPP, 3rd Generation Partnership Project) mentioned two ways of offloading the user plane when discussing Release 12 dual connectivity: one is 1A, that is, the UE bearer user plane on the MeNB and SeNB is directly connected to the S-GW, as shown in fig. 3; one is 3C, that is, the MeNB is used as a offloading anchor point, and data is offloaded in the PDCP layer and the RLC layer and sent to the MeNB and the SeNB, respectively, for delivery, as shown in fig. 4.

The purpose of dual connectivity is that when the user plane bearer of the UE is transferred between senbs under the same MeNB, signaling impact on the core network can be reduced, and the data throughput and user experience of the UE are ensured. However, for the SCG bearer, the user plane still has a large interruption due to the re-establishment of the PDCP layer during the reconfiguration. Even considering the split bearer that does not require PDCP layer re-establishment, the UE still performs a break-before-make operation, i.e., the UE disconnects from the source SeNB and then establishes a connection with the target SeNB. Typically, the SeNB role is assumed by the micro base station or the low power node, and the MeNB role is assumed by the macro base station node. Since the micro base station or the low power node is closer to the UE and has a smaller coverage area, the SeNB may carry more user plane offload data than the MeNB, and therefore, even if the UE is disconnected from the SeNB for a short time, the throughput of the user may be reduced sharply.

Disclosure of Invention

The invention provides a method for realizing reconfiguration in dual connectivity, a main service base station and an auxiliary service base station, which can avoid the rapid reduction of user plane data throughput.

In order to achieve the object of the present invention, the present invention provides a method for implementing reconfiguration in dual connectivity, in a reconfiguration process of transferring a user plane bearer of a UE from a source SeNB to a target SeNB under the same MeNB, the method includes:

establishing a user plane interface between a source SeNB and a target SeNB for providing uplink data service and downlink data service for UE;

in the reconfiguration process, the target SeNB forwards the uplink radio link control RLC data protocol data unit PDU to the source SeNB, and the source SeNB shunts the downlink packet data convergence protocol PDCP data PDU to the target SeNB.

Optionally, the method further comprises: the source SeNB keeps data transmission with the UE until the reconfiguration is successful.

Optionally, before the establishing the user plane interface, the method further includes:

and the MeNB instructs the target SeNB to establish a corresponding split bearer protocol entity for one or more secondary cell group bearers SCG bearer to be transferred to the target SeNB on the source SeNB.

Optionally, the establishing a user plane interface between the source SeNB and the target SeNB for providing the UE with the uplink data service and the downlink data service includes:

the MeNB sends the transport layer address distributed from the target SeNB to a source SeNB, so that a user plane interface for providing downlink data distribution service for UE is established between the source SeNB and the target SeNB;

and the MeNB receives the distributed transport layer address from the source SeNB and then sends the transport layer address to the target SeNB, so that a user plane interface for providing uplink data distribution service for the UE is established between the source SeNB and the target SeNB.

Optionally, the indicating, by the MeNB, the target SeNB to establish a corresponding split bearer protocol entity for one or more SCG bearers to be transferred to the target SeNB on the source SeNB includes:

the MeNB sends an admission request message to the target SeNB, and the admission request message carries split bearer configuration information or indication information for establishing the split bearer;

the split bearer configuration information or the indication information for establishing the split bearer is used to establish a corresponding split bearer protocol entity on the target SeNB for one or more SCG bearers to be transferred to the target SeNB on the source SeNB.

Optionally, the MeNB sends the transport layer address allocated from the target SeNB to the source SeNB, so that the establishing, between the source SeNB and the target SeNB, a user plane interface for providing the UE with the downlink data offloading service includes:

after the target SeNB completes the resource configuration of the UE, replying an admission confirmation message to the MeNB, wherein the admission confirmation message carries a transport layer address allocated for receiving the established downlink PDCP data PDU of the split bearer;

and after receiving the admission confirmation message, the MeNB sends a modification request message to the source SeNB, wherein the modification request message carries the transport layer address allocated by the target SeNB, and the purpose is to establish a user plane interface between the source SeNB and the target SeNB for providing downlink data offloading service for the UE.

Optionally, the MeNB receives the allocated transport layer address from the source SeNB and then sends the transport layer address to the target SeNB, so that the establishing of the user plane interface between the source SeNB and the target SeNB for providing the UE with the uplink data offloading service includes:

the source SeNB sends a modification request confirmation message to the MeNB, wherein the modification request confirmation message carries a transport layer address distributed for receiving the established uplink RLC data PDU of the split bearer;

after receiving the modification request acknowledgement message of the source SeNB, the MeNB sends an X2 notification message to the target SeNB, where the X2 notification message carries a transport layer address allocated by the source SeNB, and is intended to establish a user plane interface between the source SeNB and the target SeNB for providing uplink data offloading service for the UE.

Optionally, the method further comprises:

after receiving the modification request confirmation message of the source SeNB, the MeNB forms a Radio Resource Control (RRC) signaling facing the UE according to the information carried in the received admission confirmation message and sends the RRC signaling to the UE; after receiving the RRC signaling indicating from the MeNB to transfer the first or the plurality of SCG bearer from the source SeNB to the target SeNB, the UE synchronizes with the target SeNB according to the information carried in the obtained RRC signaling, initiates random access to the target SeNB, establishes SCG bearers according to the new configuration, and establishes a corresponding split bearer protocol entity.

Optionally, the forwarding, by the target SeNB, the uplink RLC data PDU to the source SeNB includes: forwarding uplink RLC data PDUs to the source SeNB by a transport layer address allocated for receiving the established uplink RLC data PDUs of the split bearer;

the source SeNB shunting downlink PDCP data PDUs to the target SeNB includes: and shunting part or all downlink PDCP data PDUs to the target SeNB for transmission through a transmission layer address allocated for receiving the established downlink PDCP PDUs of the split bearer.

Optionally, for the created split bearer,

on a downlink, data are shunted between a PDCP layer and an RLC layer of the source SeNB and are respectively sent to the source SeNB and the target SeNB for transmission, and the target SeNB only establishes a protocol entity below the PDCP layer; after receiving the two paths of downlink data from the air interface, the UE merges the downlink data at a PDCP layer;

on an uplink, data is shunted between an RLC layer and an MAC of the UE and is respectively sent to the source SeNB and the target SeNB through air interfaces, and only a protocol entity below the RLC layer is established on the target SeNB; and after receiving the uplink data, the target SeNB sends the uplink data to the source SeNB and merges the uplink data in an RLC layer of the source SeNB.

Optionally, after the user plane interface providing the uplink data service and the downlink data service for the UE is established between the source SeNB and the target SeNB, the method further includes:

after the UE accesses the target SeNB and completes configuration updating, if the target SeNB receives the shunted downlink PDCP data PDU from the source SeNB through X2-U, the target SeNB starts to send the downlink PDCP data PDU to the UE after processing by a lower layer protocol entity of the split bearer.

and after the UE accesses the target SeNB and finishes configuration updating, sending an uplink data packet to the target SeNB through a split bearer and/or SCG bearer protocol entity corresponding to the target SeNB.

Optionally, when the source SeNB receives the end identifier from the S-GW, the method further includes:

after the source SeNB distributes SN numbers of a PDCP sublayer for all downlink data packets, the source SeNB sends an SN state transmission message to the target SeNB, and the target SeNB starts to distribute the SN numbers of the PDCP sublayer for the downlink data packets received from the S-GW according to the SN state transmission message; requesting the source SeNB to release after the source SeNB completes sending and/or forwarding of all downlink data; accordingly, the number of the first and second electrodes,

the target SeNB successfully sends all downlink forwarding data, or has received uplink data packets from the UE from the SCG bearer protocol entity and has completed the sequencing of all forwarding uplink data packets, and requests the MeNB to delete the split bearer protocol entity;

after receiving the messages from the source SeNB and the target SeNB for releasing the source SeNB and deleting the split bearer protocol entity, the MeNB sends an SeNB release confirmation message to the source SeNB, sends an SeNB modification confirmation message to the target SeNB, and sends an RRC connection reconfiguration message to the UE to request the UE to delete the corresponding split bearer.

The invention also provides a main service base station which comprises a first processing unit used for establishing a user plane interface between the source SeNB and the target SeNB for providing uplink data service and downlink data service for the UE.

Optionally, the first processing unit includes a first establishing module and a second establishing module; wherein the content of the first and second substances,

a first establishing module, configured to send a transport layer address allocated by the target SeNB to a source SeNB, so as to establish a user plane interface between the source SeNB and the target SeNB, where the user plane interface provides a downlink data offloading service for the UE;

a second establishing module, configured to receive the allocated transport layer address from the source SeNB, and then send the transport layer address to the target SeNB, so as to establish a user plane interface between the source SeNB and the target SeNB, where the user plane interface provides an uplink data offloading service for the UE; and forming RRC signaling facing the UE and sending the RRC signaling to the UE.

Optionally, the first establishing module is further configured to: and indicating the target SeNB to establish a corresponding split bearer protocol entity for one or more SCG bearers to be transferred to the target SeNB on the source SeNB.

Optionally, the first establishing module is specifically configured to:

sending an admission request message carrying split bearer configuration information or indication information for establishing the split bearer to the target SeNB; wherein the split bearer configuration information or the indication information for establishing the split bearer is used for establishing a corresponding split bearer protocol entity on the target SeNB for one or more SCG bearers to be transferred to the target SeNB on the source SeNB;

receiving an admission confirmation message from the target SeNB, wherein the admission confirmation message carries a transport layer address allocated for receiving the established downlink PDCP data PDU of the split bearer, and sending a modification request message carrying the transport layer address allocated by the target SeNB to the source SeNB.

Optionally, the second establishing module is specifically configured to:

receiving a modification request confirmation message from the source SeNB, wherein the modification request confirmation message carries a transport layer address distributed for receiving the established uplink RLC data PDU of the split bearer; sending an X2 notification message carrying a transport layer address allocated by the source SeNB for receiving the established uplink RLC data PDU to the target SeNB; and forming RRC signaling facing the UE according to the information carried in the received admission confirmation message and sending the RRC signaling to the UE.

Optionally, the second establishing module is further configured to:

and receiving messages from the source SeNB and the target SeNB for releasing the source SeNB and deleting the split bearer protocol entity, sending a SeNB release confirmation message to the source SeNB, sending a SeNB modification confirmation message to the target SeNB, and sending an RRC connection reconfiguration message to the UE to request the UE to delete the corresponding split bearer.

The present invention also provides an auxiliary serving base station, including: a second processing unit, and/or a third processing unit; wherein the content of the first and second substances,

the second processing unit is used for establishing a corresponding split bearer protocol entity for one or more SCG bearers to be transferred to the target SeNB on the source SeNB according to the instruction from the MeNB; allocating a transport layer address for receiving the established downlink PDCP data PDU of the split bearer; receiving a transport layer address distributed by a source SeNB from the MeNB, and establishing a user plane interface for providing uplink data distribution service for the UE between the source SeNB and a target SeNB;

a third processing unit for allocating a transport layer address for receiving an uplink RLC data PDU of the established split bearer; receiving an allocated transport layer address of a target SeNB from the MeNB; and establishing a user plane interface for providing downlink data distribution service for the UE between the source SeNB and the target SeNB.

Optionally, the second processing unit is specifically configured to:

receiving an admission request message carrying split bearer configuration information or split bearer establishment indication information from the MeNB, and establishing a corresponding split bearer protocol entity on a target SeNB for one or more SCG bearers to be transferred to the target SeNB on the source SeNB;

sending an admission confirmation message carrying a transport layer address allocated for receiving downlink PDCP data PDUs of the established split bearer to the MeNB;

receiving a modification request confirmation message from the MeNB carrying a transport layer address allocated by the source SeNB for receiving the established uplink RLC data PDU of the split bearer; establishing a user plane interface between the source SeNB and the target SeNB for providing uplink data distribution service for the UE;

and forwarding the uplink RLC data PDU to the source SeNB in the reconfiguration process.

Optionally, the third processing unit is specifically configured to:

receiving a modification request message carrying a transport layer address allocated by the target SeNB from the MeNB; establishing a user plane interface between the source SeNB and the target SeNB for providing downlink data distribution service for the UE;

sending a modification request confirmation message carrying a transport layer address allocated for receiving the established uplink RLC data PDU of the split bearer to the MeNB;

and shunting the downlink PDCP data PDU to the target SeNB in the reconfiguration process.

Optionally, the third processing unit is further configured to: maintaining data transmission with the UE until reconfiguration is successful.

Optionally, the third processing unit is further configured to: after SN numbers of a PDCP sublayer are distributed to all downlink data packets when an end identifier from an S-GW is received, an SN state transmission message is sent to the target SeNB, and after the sending and/or forwarding of all downlink data are completed, the source SeNB is requested to be released from the MeNB; accordingly, the number of the first and second electrodes,

the second processing unit is further configured to: according to the SN state transmission message, starting to distribute SN numbers of PDCP sublayers for downlink data packets received from the S-GW; and requesting the MeNB to delete the split bearer protocol entity when all downlink forwarding data have been successfully sent or uplink data packets from the UE have been received from the SCG bearer protocol entity and sequencing of all forwarding uplink data packets has been completed.

Compared with the prior art, the technical scheme of the application comprises the following steps: during the reconfiguration process of transferring the user plane bearer of the UE from the source SeNB to the target SeNB under the same MeNB, establishing a user plane interface between the source SeNB and the target SeNB for providing uplink data service and downlink data service for the UE; in the reconfiguration process, the target SeNB forwards the uplink RLC data PDU to the source SeNB, and the source SeNB shunts the downlink PDCP data PDU to the target SeNB. In the process of establishing connection with the target SeNB, the UE establishes a user plane interface between the source SeNB and the target SeNB for providing uplink/downlink data service for the UE, so that the problem that the UE cannot transmit data with a network side on a micro base station or a low-power node layer when performing uplink and downlink synchronization with the target SeNB and establishing connection is solved, the rapid reduction of the user plane data throughput is avoided, and the user experience of the UE during user plane reconfiguration is ensured.

Meanwhile, the target SeNB does not need to transmit the downlink data which is already transmitted to the source SeNB to the UE after being repackaged by the PDCP layer before the reconfiguration, that is, the downlink data which is already transmitted to the source SeNB is not needed to be forwarded to the target SeNB by data forwarding, and is not needed to be transmitted to the UE after being repackaged by the PDCP layer of the target SeNB, thereby reducing the waste of repeated processing.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:

fig. 1 is a schematic diagram of a network architecture of a DC in the related art;

fig. 2 is a user plane data protocol stack of LTE in the related art;

fig. 3 is a diagram illustrating a dual connectivity user plane 1A in the related art;

fig. 4 is a diagram illustrating a dual connectivity user plane 3C in the related art;

FIG. 5 is a flow chart of a method for implementing reconfiguration in dual connectivity according to the present invention;

FIG. 6 is a flowchart illustrating an embodiment of implementing reconfiguration in dual connectivity according to the present invention;

fig. 7 is a diagram illustrating a user plane protocol entity and a first embodiment of downlink data transmission according to the present invention;

fig. 8 is a diagram illustrating a user plane protocol entity and downlink data transmission according to a second embodiment of the present invention;

fig. 9 is a diagram of a user plane protocol entity and uplink data transmission according to a third embodiment of the present invention;

FIG. 10 is a diagram of a user plane protocol entity and a fourth embodiment of uplink data transmission according to the present invention

FIG. 11 is a schematic diagram of the structure of a primary serving base station according to the present invention;

fig. 12 is a schematic structural diagram of an auxiliary serving base station according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments and features of the embodiments in the present application may be arbitrarily combined with each other without conflict.

In the related art of the dual-connection 1A architecture, the user plane bearer of the UE is transferred from the source SeNB to the target SeNB under the same MeNB, and although the MeNB performs a procedure of adding the target SeNB first and then deleting the source SeNB, the UE actually needs to disconnect from the source SeNB first and then establish a connection with the target SeNB, so that there is also a problem of a rapid drop in user throughput due to the UE disconnecting from the SeNB briefly.

In the technical scheme provided by the embodiment of the invention, in the process of establishing connection with the target SeNB, the UE establishes the user plane interface which provides uplink/downlink data service for the UE between the source SeNB and the target SeNB, thereby solving the problem that the UE cannot transmit data with a network side on a micro base station or a low-power node level when performing uplink and downlink synchronization with the target SeNB and establishing connection, avoiding the rapid reduction of the user plane data throughput and ensuring the user experience of the UE during user plane reconfiguration.

Fig. 5 is a flowchart of a method for implementing reconfiguration in dual connectivity according to the present invention, and in a reconfiguration process of transferring a user plane bearer of a UE from a source SeNB to a target SeNB under the same MeNB, as shown in fig. 5, the method includes:

step 500: and establishing a user plane interface between the source SeNB and the target SeNB for providing uplink data service and downlink data service for the UE.

The method also comprises the following steps: the MeNB instructs the target SeNB to establish a corresponding split bearer protocol entity for one or more SCG bearers on the source SeNB to be transferred to the target SeNB. The method specifically comprises the following steps: the MeNB sends an admission request message to the target SeNB, and the admission request message carries at least split bearer configuration information or indication information for establishing the split bearer in addition to key information, UE security capability information, SCG bearer configuration information and the like with reference to an X2-AP message (SeNB allocation request) in a related protocol. The split bearer configuration information or the indication information for establishing the split bearer is used to establish a corresponding split bearer protocol entity on the target SeNB for one or more SCG bearers to be transferred to the target SeNB on the source SeNB.

The implementation of this step includes: the MeNB sends a transport layer address, such as a GPRS Tunneling Protocol (GTP) Tunnel Endpoint Identifier (TEID), and the like, allocated from the target SeNB to the source SeNB, so that a user plane interface providing downlink data offloading service for the UE is established between the source SeNB and the target SeNB. The method specifically comprises the following steps:

the target SeNB determines whether there are sufficient resources to allow access of the UE according to the received information. If the access is allowed, after the target SeNB completes the resource configuration of the UE, replying an admission confirmation message to the MeNB, wherein the admission confirmation message carries at least a transport layer address such as GTP TEID allocated for receiving a downlink PDCP Data Protocol Data Unit (PDU) of the established split bearer in addition to SCG bearer configuration information agreed to be admitted by the target SeNB by referring to an X2-AP message (SeNB allocation request acknowledgement) in a related Protocol;

and after receiving the admission confirmation message, the MeNB sends a modification request message to the source SeNB. The modification request message carries a transport layer address such as GTP TEID allocated by the target SeNB, and the purpose of the modification request message is to establish a user plane interface between the source SeNB and the target SeNB for providing the UE with downlink data offloading service. The bearer type on the source SeNB is changed from SCG bearer to split bearer.

The MeNB receives the distributed transport layer address such as GTP TEID from the source SeNB and then sends the transport layer address to the target SeNB, so that a user plane interface for providing uplink data distribution service for the UE is established between the source SeNB and the target SeNB. The method specifically comprises the following steps:

the source SeNB sends a modification request acknowledge message to the MeNB. Carrying a transport layer address such as GTP TEID allocated for receiving the established uplink RLC data PDU of the split bearer in the modification request confirmation message;

after receiving the modification request acknowledgement message of the source SeNB, the MeNB sends an X2 notification message to the target SeNB. The X2 notification message carries a transport layer address such as GTP TEID allocated by the source SeNB, which is intended to establish a user plane interface between the source SeNB and the target SeNB for providing the UE with the uplink data offloading service.

Simultaneously, this step still includes: after receiving the modification request acknowledgement message of the source SeNB, the MeNB forms a Radio Resource Control (RRC) signaling facing the UE according to the information carried in the received admission acknowledgement message, and sends the signaling to the UE. After receiving an RRC signaling indicating that one or more SCG bearer is transferred from a source SeNB to a target SeNB by the MeNB, the UE synchronizes with the target SeNB according to information carried in the RRC signaling, initiates random access to the target SeNB, establishes the SCG bearer according to new configuration, and establishes a corresponding split bearer protocol entity.

Step 501: in the reconfiguration process, the target SeNB forwards the uplink RLC data PDUs to the source SeNB, and the source SeNB shunts the downlink PDCP data PDUs to the target SeNB and keeps data transmission with the UE until the reconfiguration is successful.

The source SeNB can shunt part or all downlink PDCP data PDUs to the target SeNB for transmission through a transmission layer address such as GTP TEID distributed for receiving the established downlink PDCP PDUs of the split bearer;

the target SeNB may forward the uplink RLC data PDUs to the source SeNB by a transport layer address, e.g., GTP TEID, allocated for receiving the established uplink RLC data PDUs of the split bearer.

It should be noted that the RLC control PDU corresponding to the uplink RLC data PDU may be directly fed back by the source SeNB; the target SeNB may also be notified by the source SeNB and fed back by the target SeNB.

For split bearer, in particular,

on a downlink, data are shunted between a PDCP layer and an RLC layer of a source SeNB and are respectively sent to the source SeNB and a target SeNB for transmission, and only a protocol entity below the PDCP layer is established on the target SeNB; after receiving the two paths of downlink data from the air interface, the UE merges the downlink data in a PDCP layer;

on an uplink, data are shunted between an RLC layer and an MAC of the UE and are respectively sent to a source SeNB and a target SeNB through air interfaces, and the target SeNB only establishes a protocol entity below the RLC layer; and after receiving the uplink data, the target SeNB sends the uplink data to the source SeNB and merges the uplink data in an RLC layer of the source SeNB.

The source SeNB may shunt part of the downlink PDCP data PDUs to the target SeNB for transmission, or may shunt all the downlink PDCP data PDUs to the target SeNB for transmission, where:

when the signal quality of the source SeNB is still good, the source SeNB may only shunt a part of downlink PDCP data PDUs to the target SeNB, and maintain data transmission with the UE; when the signal quality of the source SeNB is already poor, the source SeNB may shunt most or even all downlink PDCP data PDCUs to the target SeNB, but at this time, since the UE has not yet accessed the target SeNB, the data transmission throughput of the UE will be slightly reduced. As can be seen from this, the method of the present invention selectively disconnects or maintains data transmission with the source SeNB according to the signal quality of the source SeNB, so that the UE maintains signal transmission with the source SeNB in the case that the signal quality of the source SeNB is still good.

After step 500, the method further comprises:

on the one hand, after the UE accesses the target SeNB and completes configuration update, if the target SeNB has received the shunted downlink PDCP data PDU from the source SeNB through X2-U, the target SeNB starts to process the downlink PDCP data PDU through a lower protocol entity of the split bearer, and then sends the processed downlink PDCP data PDU to the UE.

On the other hand, after the UE accesses the target SeNB and completes configuration update, the UE may start to send an uplink data packet to the target SeNB through a split bearer and/or SCG bearer protocol entity corresponding to the target SeNB.

After receiving the RRC connection reconfiguration complete message from the UE, the method further includes: the MeNB initiates a path switching program to the core network to request the change of all or part of the downlink tunnel end points carried by the downlink data.

When the source SeNB receives the end identity from the S-GW,

after allocating SN numbers of a PDCP sublayer to all downlink data packets, a source SeNB sends an SN state transmission message to a target SeNB, and the target SeNB can start allocating the SN numbers of the PDCP sublayer to the downlink data packets received from an S-GW according to the SN state transmission message;

and after the source SeNB completes the sending and/or forwarding of all downlink data, requesting the MeNB for releasing the source SeNB.

And the target SeNB will also request the MeNB to delete the split bearer protocol entity. Before requesting the MeNB to delete the split bearer protocol entity, the target SeNB has successfully sent all downlink forwarding data, or, before requesting the MeNB to delete the split bearer protocol entity, the target SeNB has received an uplink data packet from the UE from the SCG bearer protocol entity, and has completed the sequencing of all forwarding uplink data packets.

After receiving the messages of releasing the source SeNB and deleting the split bearer protocol entities from the source SeNB and the target SeNB, the MeNB sends a SeNB release confirmation message (SeNB release confirmation) to the source SeNB, sends a SeNB modification confirmation message (SeNB modification confirmation) to the target SeNB, and sends an RRC connection reconfiguration message to the UE to request the UE to delete the corresponding split bearer.

Fig. 6 is a flowchart illustrating an embodiment of implementing reconfiguration in dual connectivity according to the present invention, and as shown in fig. 6, this embodiment describes a procedure of transferring a user plane bearer of a UE after a MeNB receives a UE measurement report in the present invention. In the transfer execution phase, the MeNB needs the target SeNB to establish a corresponding split bearer protocol entity for the SCG bearer allowed to be admitted, in addition to requesting the target SeNB to execute admission decision for the SCG bearer of the UE on the source SeNB. The method specifically comprises the following steps:

step 601: the MeNB makes a decision that the user plane needs to be reconfigured according to measurement reports (or results obtained by other radio resource management functions, such as overload) of the UE, and assumes that the decision is to transfer the user plane bearer of the UE from the source SeNB to a target SeNB under the same MeNB to allow the UE to continue to obtain communication services from the auxiliary serving base station.

Step 602: the MeNB sends an admission request message to the target SeNB.

The admission request message carries key information, UE security capability information, SCG bearer configuration information, and the like with reference to a related protocol X2-AP message (SeNB allocation request), and also carries at least split bearer configuration information or indication information for establishing split bearer. The split bearer configuration information or the indication information for establishing the split bearer is used for establishing a corresponding split bearer protocol entity on the target SeNB for one or more SCG bearers to be transferred to the target SeNB on the source SeNB.

In the case of the split bearer,

on the downlink, data is shunted between a PDCP layer and an RLC layer of the source SeNB, and is respectively sent to the source SeNB and the target SeNB for transfer, and only a protocol entity below the PDCP layer is established on the target SeNB. After receiving the two downlink data paths from the air interface, the UE merges the two downlink data paths in the PDCP layer'

On the uplink, data is shunted between the RLC layer and the MAC of the UE, and is sent to the source SeNB and the target SeNB through air interfaces, respectively, and only a protocol entity below the RLC layer is established on the target SeNB. And after receiving the uplink data, the target SeNB sends the uplink data to the source SeNB and merges the uplink data in an RLC layer of the source SeNB.

Step 603: and after receiving the admission request message, the target SeNB judges whether the UE can be admitted or not by combining the resource condition of the target SeNB. The specific implementation of this step is well known to those skilled in the art, and is not used to limit the scope of the present invention, and will not be described herein.

Step 604: and if the target SeNB judges that the access of the UE can be admitted, replying an admission confirmation message to the MeNB, wherein the admission confirmation message carries at least a transport layer address such as GTP TEID (transport layer address) allocated for receiving downlink PDCP (packet data protocol) data PDU of the split bearer in addition to the SCG bearer list admitted by the target SeNB by referring to a related protocol X2-AP message (SeNB allocation request acknowledgement).

Step 605: and after receiving the admission confirmation message, the MeNB sends a modification request message to the source SeNB. The modification request message informs the source SeNB of a GTP TEID received from the target SeNB through the admission confirmation message, so as to establish a user plane interface between the source SeNB and the target SeNB for providing the UE with the downlink data offloading service. In this way, the source SeNB may shunt part or all of the downlink PDCP data PDUs to the target SeNB for transmission through X2-U by using the GTP TEID. The bearer type on the source SeNB is changed from SCG bearer to split bearer.

Step 606: the source SeNB sends a modification request acknowledgement message to the MeNB, informing the MeNB that the configuration modification is successful. Wherein, the modification request acknowledgement message also carries the GTP TEID allocated for receiving the uplink RLC data PDU of the split bearer.

In this step, the source SeNB starts to offload part or all of the downlink PDCP data PDUs to the target SeNB through the GTP TEID provided by the target SeNB while or after the source SeNB sends the modification request acknowledgement message to the MeNB.

If the signal quality of the source SeNB is still good, the source SeNB may only offload a part of downlink PDCP data PDUs to the target SeNB, and maintain data transmission with the UE. If the signal quality of the source SeNB is already poor, the source SeNB can shunt most or even all downlink PDCP data PDCUs to the target SeNB, but in this case, since the UE has not yet accessed the target SeNB, the data transmission throughput of the UE will be slightly reduced.

In this step, the source SeNB starts to send the uplink data packet, which has not been sequenced yet, to the target SeNB while or after the source SeNB sends the modification request acknowledgement message to the MeNB. Meanwhile, the sequencing function of the PDCP layer of the source SeNB stops working; and the source SeNB decrypts all the subsequently received uplink PDCP data PDUs, sends the target SeNB, and finishes sequencing by the PDCP layer of the target SeNB.

Step 607: after receiving the modification request acknowledgement message of the source SeNB, the MeNB sends an X2 notification message to the target SeNB. The X2 notification message is used to notify the target SeNB of the GTP TEID received from the source SeNB through the modification request acknowledgement message, and is intended to establish a user plane interface between the source SeNB and the target SeNB for providing the UE with the uplink data offloading service. In this way, the target SeNB can forward the uplink RLC data PDU received by the target SeNB from the UE to the source SeNB through the GTP TEID.

Step 608: after receiving the modification request acknowledgement message of the source SeNB, the MeNB forms a Radio Resource Control (RRC) signaling facing the UE according to the information carried in the received admission acknowledgement message and sends the signaling to the UE.

Step 609: after receiving the RRC signaling from the MeNB instructing to transfer the first one or more SCG bearer from the source SeNB to the target SeNB, the UE determines whether the RRC connection reconfiguration request can be executed according to the requirements in the RRC signaling. If so, the UE sends an RRC Connection Reconfiguration Complete (RRC Connection Reconfiguration Complete) message to the MeNB, indicating that the UE has enabled the new radio resource configuration.

Step 610: and the UE synchronizes with the target SeNB according to the information carried in the signaling, initiates random access to the target SeNB, establishes SCG bearer according to the new configuration and establishes a corresponding split bearer protocol entity.

After the UE accesses the target SeNB and completes configuration updating, if the target SeNB receives the shunted downlink PDCP data PDU from the source SeNB through X2-U at the moment, the target SeNB starts to send the downlink PDCP data PDU to the UE after processing the downlink PDCP data PDU through a lower protocol entity of the split bearer;

after the UE accesses the target SeNB and completes configuration update, the UE may start to send an uplink data packet to the target SeNB through a split bearer or SCG bearer protocol entity corresponding to the target SeNB.

Step 611: after receiving the RRC connection reconfiguration complete message of the UE, the MeNB initiates a path switching procedure to the core network, and requests a change of a downlink tunnel endpoint of all or part of the downlink data bearers.

Step 612: and the source SeNB receives the ending identification from the S-GW, and after distributing the SN numbers of the PDCP sublayer for all downlink data packets, sends an SN state transmission message to the target SeNB, and the target SeNB can start distributing the SN numbers of the PDCP sublayer for the downlink data packets received from the S-GW according to the SN state transmission message.

Step 613: and the source SeNB receives the end identification from the S-GW, and requests the MeNB to release the source SeNB after finishing sending and/or forwarding all downlink data.

Step 614: the target SeNB requests the MeNB to delete the split bearer protocol entity.

The target SeNB has successfully sent all downstream forwarding data before requesting the MeNB to delete the split bearer protocol entity. And the number of the first and second groups,

before requesting the MeNB to delete the split bearer protocol entity, the target SeNB has already received the uplink data packets from the UE from the SCG bearer protocol entity and has completed the ordering of all forwarded uplink data packets.

Step 615: after receiving the messages in step 613 and step 614, the MeNB sends a SeNB release confirm (SeNB release confirm) message to the source SeNB; sending a SeNB modification confirmation (SeNB modification confirmation) message to the target SeNB; sending the RRC connection reconfiguration message to the UE requires the UE to delete the corresponding split bearer.

Fig. 7 is a schematic diagram of a user plane protocol entity and a first embodiment of downlink data transmission according to the present invention, where the first embodiment describes user plane protocol entities on a source SeNB, a target SeNB, and a UE after path switching is completed, and a schematic diagram of downlink data transmission. As shown in fig. 7, assuming that the source SeNB has already transmitted PDCP data PDUs with SN numbers 1 to 5, when reconfiguration occurs, the UE receives only PDCP data PDUs with

SN numbers

1,2, and 4 and acknowledges to the source SeNB. For PDCP data PDUs with

SN numbers

3 and 5, the UE has received only partial RLC data PDUs. At this time, if the signal quality of the source SeNB is not enough to support the continuous data transmission to the UE, the source SeNB may forward PDCP data PDUs with

SN numbers

3 and 5 to the target SeNB, and the PDCP data PDUs are processed and transmitted by the split bearer protocol entity of the target SeNB. All downlink data which are received from the S-GW before the end identifier is received and have not started to be transmitted, such as PDCP data SDUs with SN numbers 6 to 9, are processed by the PDCP layer, forwarded to the target SeNB, processed by the split bearer protocol entity of the target SeNB, and transmitted.

For downlink data, after the UE and the PDCP entity corresponding to the source SeNB complete all data delivery operations to the upper layer, the PDCP entity corresponding to the target SeNB starts to deliver data to the upper layer, so as to avoid the upper layer from receiving out-of-order data packets.

Fig. 8 is a schematic diagram of a user plane protocol entity and downlink data transmission in a second embodiment of the present invention, where the second embodiment describes user plane protocol entities on a source SeNB, a target SeNB, and a UE after path switching is completed, and a schematic diagram of downlink data transmission. As shown in fig. 8, assuming that the source SeNB has already transmitted PDCP data PDUs with SN numbers 1 to 5, when reconfiguration occurs, the UE receives only PDCP data PDUs with

SN numbers

1,2, and 4 and acknowledges to the source SeNB. For PDCP data PDUs with

SN numbers

3 and 5, the UE has received only partial RLC data PDUs. At this time, at least for a while, the source SeNB may further continue to maintain data transmission with the UE, and the source SeNB may continue to transmit at least RLC data PDUs corresponding to PDCP data PDUs with

SN numbers

3 and 5 that have not received a UE acknowledgement reply or RLC data PDU segments. All downlink data which are received from the S-GW before the end identifier is received and have not started to be transmitted, such as PDCP data SDUs with SN numbers of 6 to 9, are processed by the PDCP layer and then shunted to the source SeNB or the target SeNB for transmission. As shown in fig. 7, before receiving the end identifier, the source SeNB also receives PDCP data SDUs with

SN numbers

6, 7, 8, and 9, and after processing by the PDCP layer, the source SeNB shunts the PDCP data PDUs with

SN numbers

8 and 9 to the target SeNB for transmission, and leaves the PDCP data PDUs with

SN numbers

6 and 7 in the source SeNB for transmission, thereby ensuring that certain data transmission is still maintained between the UE and the source SeNB when the UE synchronizes and accesses the target SeNB.

Fig. 9 is a schematic diagram of a user plane protocol entity and uplink data transmission in a third embodiment of the present invention, where the third embodiment describes user plane protocol entities and uplink data transmission on a source SeNB, a target SeNB, and a UE after path switching is completed. As shown in fig. 9, assuming that the UE has transmitted PDCP data PDUs with SN numbers 1 to 5, when reconfiguration occurs, the source SeNB receives only PDCP data PDUs with

SN numbers

1,2, and 4 and acknowledges to the UE. For PDCP data PDUs with

SN numbers

3 and 5, only a partial RLC data PDU is received by the source SeNB.

At this time, if the signal quality between the source SeNB and the UE cannot support the UE to transmit data to the source SeNB, for the PDCP data PDUs with

SN numbers

3 and 5, the UE may segment the RLC data PDU or RLC data PDU which is not transmitted or has not been successfully transmitted, and transmit the segmented RLC data PDU or RLC data PDU to the target SeNB through the split bearer protocol entity. And after receiving the RLC data PDU or the RLC data PDU segment, the target SeNB forwards the RLC data PDU or the RLC data PDU segment to the source SeNB, and the source SeNB combines the RLC data PDUs into PDCP data PDUs with SN numbers of 3 and 5. And the subsequent uplink data packets, such as the data packets with the SN number of 6 and the subsequent data packets, are sent to the target SeNB after being processed by the SCG bearer protocol entity corresponding to the target SeNB by the UE.

For uplink data, the target SeNB starts to deliver data to the S-GW after the source SeNB delivers the data to the S-GW, so that the upper layer is prevented from receiving out-of-order data packets.

Fig. 10 is a schematic diagram of a user plane protocol entity and uplink data transmission in a fourth embodiment of the present invention, where the fourth embodiment describes user plane protocol entities and uplink data transmission on a source SeNB, a target SeNB, and a UE after path switching is completed. As shown in fig. 10, assuming that the UE has transmitted PDCP data PDUs with SN numbers 1 to 5, when reconfiguration occurs, the source SeNB receives only PDCP data PDUs with

SN numbers

1,2, and 4 and acknowledges to the UE. For PDCP data PDUs with

SN numbers

3 and 5, only a partial RLC data PDU is received by the source SeNB.

At this time, if the signal quality between the source SeNB and the UE is still good enough, at least, for the PDCP data PDUs with

SN numbers

3 and 5, the UE will send RLC data PDUs or RLC data PDU segments that have not been sent or that have not been sent successfully, to the source SeNB through the split bearer protocol entity, and combine them with the RLC data PDUs or RLC data PDU segments that have been received into PDCP data PDUs with

SN numbers

3 and 5. Subsequent uplink data packets, such as data packets with SN number 6 and beyond, may be sent to the target SeNB after being processed by the UE using the SCG bearer protocol entity corresponding to the target SeNB.

Fig. 11 is a schematic structural diagram of the main serving base station of the present invention, and as shown in fig. 11, the main serving base station at least includes a first processing unit, which is configured to establish a user plane interface between a source SeNB and a target SeNB for providing uplink data service and downlink data service for a UE. Wherein the content of the first and second substances,

the first processing unit includes: the system comprises a first establishing module and a second establishing module; wherein the content of the first and second substances,

a first establishing module, configured to send a transport layer address allocated from a target SeNB to a source SeNB, so as to establish a user plane interface between the source SeNB and the target SeNB, where the user plane interface provides a downlink data offloading service for a UE;

a second establishing module, configured to receive the allocated transport layer address from the source SeNB, and send the transport layer address to the target SeNB, so as to establish a user plane interface between the source SeNB and the target SeNB, where the user plane interface provides an uplink data offloading service for the UE; and forming RRC signaling facing the UE and sending the RRC signaling to the UE.

Wherein the first establishing module is further configured to: and indicating the target SeNB to establish corresponding split bearer protocol entities for one or more SCG bearers to be transferred to the target SeNB on the source SeNB.

Wherein the content of the first and second substances,

the first establishing module is specifically configured to: and sending an admission request message carrying the split bearer configuration information or the indication information for establishing the split bearer to the target SeNB. The split bearer configuration information or the split bearer establishment indication information is used for establishing a corresponding split bearer protocol entity on the target SeNB for one or more SCG bearers to be transferred to the target SeNB on the source SeNB;

The second establishing module is specifically configured to: receiving a modification request confirmation message from a source SeNB, wherein the modification request confirmation message carries a transport layer address distributed for receiving uplink RLC data PDU of the built split bearer; sending an X2 notification message carrying a transport layer address allocated by the active SeNB for receiving the established uplink RLC data PDU of the split bearer to the target SeNB; and forming RRC signaling facing the UE according to the information carried in the received admission confirmation message and sending the RRC signaling to the UE.

Further, the air conditioner is provided with a fan,

the second establishing module is further configured to: when receiving the RRC connection reconfiguration complete message from the UE, initiating a path switching program to the core network to request the change of the downlink tunnel endpoint of all or part of downlink data bearers.

Fig. 12 is a schematic structural diagram of a secondary serving base station according to the present invention, as shown in fig. 12, the structural diagram at least includes: a second processing unit, and/or a third processing unit; wherein the content of the first and second substances,

the second processing unit is used for establishing a corresponding split bearer protocol entity for one or more SCG bearers to be transferred to the target SeNB on the source SeNB according to the instruction from the MeNB; allocating a transport layer address for receiving the established downlink PDCP data PDU of the split bearer; and receiving a transport layer address distributed by a source SeNB from the MeNB, and establishing a user plane interface for providing uplink data distribution service for the UE between the source SeNB and a target SeNB. The method is specifically used for:

receiving an admission request message carrying split bearer configuration information or split bearer establishment indication information from the MeNB, and establishing a corresponding split bearer protocol entity on the target SeNB for one or more SCG bearers to be transferred to the target SeNB on the source SeNB;

sending an admission confirmation message carrying a transport layer address allocated for receiving the downlink PDCP data PDU of the established split bearer to the MeNB;

receiving a transmission layer address modification request confirmation message which is from the MeNB and carries uplink RLC data PDU which is distributed by the active SeNB and is distributed for receiving the built split bearer; establishing a user plane interface between a source SeNB and a target SeNB for providing uplink data distribution service for UE;

in the reconfiguration process, the uplink RLC data PDU is forwarded to the source SeNB.

A third processing unit for allocating a transport layer address for receiving an uplink RLC data PDU of the established split bearer; receiving an allocated transport layer address of a target SeNB from the MeNB; and establishing a user plane interface between the source SeNB and the target SeNB for providing downlink data distribution service for the UE. The method is specifically used for:

receiving a modification request message from the MeNB carrying a transport layer address allocated by the target SeNB; establishing a user plane interface between a source SeNB and a target SeNB for providing downlink data distribution service for UE;

The third processing unit is further configured to: data transmission with the UE is maintained until the reconfiguration is successful.

Further, the air conditioner is provided with a fan,

the third processing unit is further configured to: after SN numbers of a PDCP sublayer are distributed to all downlink data packets when an end identifier from an S-GW is received, an SN state transmission message is sent to a target SeNB, and after the sending and/or forwarding of all downlink data are completed, a source SeNB release is requested to an MeNB; accordingly, the number of the first and second electrodes,

the second processing unit is further configured to: according to the SN state transmission message, starting to distribute SN numbers of PDCP sublayers for downlink data packets received from the S-GW; after all downlink forwarding data have been successfully sent or uplink data packets from the UE have been received from the SCG bearer protocol entity and the ordering of all forwarding uplink data packets has been completed, requesting the MeNB to delete the split bearer protocol entity;

at this time, the process of the present invention,

the second establishing module in the primary serving base station is further configured to: and receiving messages for releasing the source SeNB and deleting the split bearer protocol entity from the source SeNB and the target SeNB, sending a SeNB release confirmation message to the source SeNB, sending a SeNB modification confirmation message to the target SeNB, and sending an RRC connection reconfiguration message to the UE to request the UE to delete the corresponding split bearer.

The above description is only a preferred example of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for implementing reconfiguration in dual connectivity, in a reconfiguration process of transferring a user plane bearer of a UE from a source SeNB to a target SeNB under the same MeNB, the method comprising:

in the reconfiguration process, the target SeNB forwards an uplink Radio Link Control (RLC) data Protocol Data Unit (PDU) to the source SeNB, and the source SeNB shunts a downlink Packet Data Convergence Protocol (PDCP) data PDU to the target SeNB;

the source SeNB maintains data transmission with the UE until reconfiguration is successful.

2. The method of claim 1, wherein the establishing a user plane interface further comprises, prior to:

3. The method of claim 2, wherein establishing the user plane interface between the source SeNB and the target SeNB for providing the UE with uplink data service and downlink data service comprises:

4. The method of claim 2, wherein the MeNB instructs the target SeNB to establish corresponding split bearer protocol entities for one or more SCG bearers on the source SeNB to be transferred to the target SeNB, comprising:

5. The method of claim 3, wherein the MeNB sends the transport layer address allocated from the target SeNB to the source SeNB, so that establishing a user plane interface between the source SeNB and the target SeNB for providing the UE with the downlink data offloading service comprises:

and after receiving the admission confirmation message, the MeNB sends a modification request message to the source SeNB, wherein the modification request message carries the transport layer address allocated by the target SeNB, and the purpose of the modification request message is to establish a user plane interface between the source SeNB and the target SeNB for providing downlink data offloading service for the UE.

6. The method of claim 3, wherein the MeNB receives the allocated transport layer address from the source SeNB and then sends the allocated transport layer address to the target SeNB, so that establishing the user plane interface between the source SeNB and the target SeNB for providing the UE with the uplink data offloading service comprises:

7. The method according to any one of claims 2 to 6, further comprising:

8. The method of claim 1, wherein the target SeNB forwarding uplink RLC data PDUs to the source SeNB comprises: forwarding uplink RLC data PDUs to the source SeNB by a transport layer address allocated for receiving the established uplink RLC data PDUs of the split bearer;

9. The method of claim 1, wherein for the established split bearer,

on an uplink, data is distributed between an RLC layer and an MAC of the UE and is respectively sent to the source SeNB and the target SeNB through air interfaces, and only a protocol entity below the RLC layer is established on the target SeNB; and after receiving the uplink data, the target SeNB sends the uplink data to the source SeNB and merges the uplink data in an RLC layer of the source SeNB.

10. The method of claim 3, wherein after establishing a user plane interface between the source SeNB and the target SeNB for providing the UE with uplink data services and downlink data services, the method further comprises:

11. The method of claim 3, wherein after establishing a user plane interface between the source SeNB and the target SeNB for providing the UE with uplink data services and downlink data services, the method further comprises:

12. Method according to claim 2, 3, 10 or 11, characterized in that when the source SeNB receives the end identity from the S-GW, the method further comprises:

after the source SeNB distributes SN numbers of a PDCP sublayer for all downlink data packets, the source SeNB sends an SN state transmission message to the target SeNB, and the target SeNB starts to distribute the SN numbers of the PDCP sublayer for the downlink data packets received from the S-GW according to the SN state transmission message; after the source SeNB completes the sending and/or forwarding of all downlink data, requesting the MeNB to release the source SeNB; accordingly, the number of the first and second electrodes,

13. A secondary serving base station, comprising: a second processing unit, and/or a third processing unit; wherein the content of the first and second substances,

a third processing unit, configured to receive a modification request message from the MeNB and carrying the transport layer address allocated by the target SeNB; establishing a user plane interface between the source SeNB and the target SeNB for providing downlink data distribution service for the UE;

in the reconfiguration process, shunting downlink PDCP data PDU to the target SeNB;

maintaining data transmission with the UE until reconfiguration is successful.

14. The secondary serving base station according to claim 13, wherein the second processing unit is specifically configured to:

15. The secondary serving base station of any one of claims 13 to 14,

the third processing unit is further configured to: after SN numbers of a PDCP sublayer are distributed to all downlink data packets when an end identifier from an S-GW is received, an SN state transmission message is sent to the target SeNB, and after the sending and/or forwarding of all downlink data are completed, the source SeNB is requested to be released from the MeNB; accordingly, the number of the first and second electrodes,