A method and device for switching between different MeNBs in a small cell system

Abstract

The present application discloses a secondary base station and a method thereof in a switching process from a source primary base station to a target primary base station in a wireless communication system supporting dual connectivity. The method comprises: the secondary base station receives a first message from a target primary base station that maintains the secondary base station, the first message including information indicating a key associated with the security of the secondary base station and a request for a secondary cell group SCG configuration related to the secondary base station; the secondary base station sends a second message including information about the SCG configuration to the target primary base station in response to the first message; and the secondary base station receives a third message from the target primary base station indicating that the radio resource control RRC configuration associated with the user equipment UE during the switching process is completed.

Description

[0001] This application is a divisional application of an invention patent application whose application date (international application date) is March 26, 2015, application number is 201510136863.6, and invention name is "A method and device for switching between different MeNBs in a small cell system". Technical Field

[0002] The present invention relates to wireless communication technology, and in particular to a method and device for switching between different MeNBs in a small cell system. Background Art

[0003] Modern mobile communications are increasingly tending to provide users with high-speed transmission of multimedia services, such as Figure 1 The following is a diagram of the system architecture of the System Architecture Evolution (SAE).

[0004] User equipment (UE) 101 is a terminal device used to receive data. Evolved Universal Terrestrial Radio Access Network (E-UTRAN) 102 is a wireless access network, which includes a macro base station (eNodeB / NodeB) that provides a wireless network interface for the UE to access. The mobile management entity (MME) 103 is responsible for managing the mobile context, session context and security information of the UE. The serving gateway (SGW) 104 mainly provides user plane functions, and the MME 103 and SGW 104 may be in the same physical entity. The packet data network gateway (PGW) 105 is responsible for functions such as billing and lawful interception, and may also be in the same physical entity as the SGW 104. The policy and charging rules function entity (PCRF) 106 provides quality of service (QoS) policies and charging criteria. The general packet radio service support node (SGSN) 108 is a network node device that provides routing for data transmission in the universal mobile telecommunications system (UMTS). The Home Subscriber Server (HSS) 109 is the home subsystem of the UE and is responsible for protecting user information including the current location of the user equipment, the address of the service node, user security information, and the packet data context of the user equipment.

[0005] 3GPP proposed the requirement of small cell enhancement in Release 12 (Rel-12). The target scenarios of small cell enhancement include scenarios with macro cell coverage and scenarios without macro cell coverage, indoor and outdoor, and enhancement of ideal and non-ideal backhaul, such as Figure 2 shown.

[0006] In the case of macro cell coverage, a technology for applying carrier aggregation between different base stations is proposed. Macro cells and small cells can operate in different frequency bands. There are two architectures for applying carrier aggregation between different base stations: an architecture in which user plane data is separated based on the radio access network (RAN) and an architecture in which user plane data is separated based on the core network (CN). The architecture separated based on CN means that for the bearer established on the pico cell (pico), the data is directly sent from the SGW in the core network to the Pico, and the user plane data is not forwarded through the macro cell (macro).

[0007] In the small cell architecture, the UE can send and receive data on two base stations at the same time, which is called dual-connectivity. Among the two base stations, only one base station is responsible for sending radio resource control (RRC) messages to the UE and interacting with the core network control plane entity MME. This base station is called the master base station (MeNB), and the other base station is called the secondary base station (SeNB). The UE has one cell in the master base station, which is the primary cell (Pcell) of the UE, and RRC messages are sent to the UE through this primary cell. The other cells are secondary cells (Scell). The UE has one cell in the Scell ​​of the secondary base station, which is the primary cell of the secondary base station pScell. There is an uplink physical layer control channel on the pScell, but not on other Scells. The cell group of the primary base station is MCG, and the cell group of the secondary base station is SCG. The resources of the secondary base station cell group on the UE side are configured by the secondary base station. The secondary base station sends the configuration of the UE to the primary base station through the RRC container, and the primary base station sends it to the UE. The primary base station does not parse the RRC container, or parses but does not change the configuration in the RRC container.

[0008] As the UE moves or the channel quality changes, when the master base station decides to switch the cell on the master base station to a new base station, the new base station is called the target master base station MeNB, and a handover between different MeNBs will occur. During the MeNB handover process, the current process is to switch all bearers (including bearers on the source MeNB and bearers on the SeNB) to the target MeNB. The disadvantage of this method is that the bearers are frequently reconfigured, and dual connectivity is not effectively used to increase the system capacity and data transmission speed provided to the UE. Summary of the invention

[0009] The present invention provides a method and device for switching between different MeNBs in a small cell system to improve system capacity and data transmission speed.

[0010] The present invention provides a method for switching between different master base stations MeNB in ​​a small cell system, including:

[0011] During the handover, the source primary base station and / or the target primary base station decides whether to keep the secondary base station;

[0012] Different handover processes are triggered according to the decision result of whether to keep the secondary base station.

[0013] Preferably, the source primary base station and / or the target primary base station decides whether to keep the secondary base station including:

[0014] The source primary base station decides whether to keep the secondary base station;

[0015] If the decision result of the source primary base station is to keep the secondary base station, a handover request message is sent to the target primary base station;

[0016] The source primary base station receives a handover request confirmation message from the target primary base station, where the handover request confirmation message includes a decision result on whether to keep the secondary base station.

[0017] Preferably, the source primary base station and / or the target primary base station decides whether to keep the secondary base station including:

[0018] The source primary base station sends a handover request message to the target primary base station;

[0019] The source primary base station receives a handover request confirmation message from the target primary base station, where the handover request confirmation message includes a decision result on whether to keep the secondary base station.

[0020] Preferably, the source primary base station and / or the target primary base station decides whether to keep the secondary base station including:

[0021] The source primary base station decides whether to keep the secondary base station, and obtains a decision result of whether to keep the secondary base station.

[0022] Preferably, the source primary base station and / or the target primary base station decides whether to keep the secondary base station including:

[0023] The source primary base station sends a handover request message to the target primary base station;

[0024] The source master base station receives a handover request confirmation message from the target master base station, where the handover request confirmation message includes information about whether there is an X2 interface between the target master base station and the secondary base station or whether the secondary base station remains feasible;

[0025] The source primary base station decides whether to keep the secondary base station according to the information in the handover request confirmation message, and obtains a decision result on whether to keep the secondary base station.

[0026] Preferably, the handover request message includes a combination of one or more of the following information:

[0027] a cell identifier of a secondary cell of the secondary base station and / or a base station identifier of the secondary base station;

[0028] UE bearer in the secondary base station;

[0029] Whether the bearer of the UE in the secondary base station is a split bearer or an SCG bearer;

[0030] UE measurement results;

[0031] The identifier of the UE in the secondary base station;

[0032] The TEID and transport layer address of the X2 interface downlink allocated by the secondary base station to the split bearer.

[0033] Preferably, triggering different handover processes according to the decision result of whether to keep the secondary base station includes:

[0034] If the decision result is not to keep the secondary base station, the bearer on the secondary base station is switched to the target primary base station during the switching process;

[0035] If the decision result is to keep the secondary base station, the bearer on the secondary base station is kept during the handover process.

[0036] Preferably, maintaining the bearer on the secondary base station includes:

[0037] The target primary base station allocates the TEID and transport layer address of the downlink interface between the target primary base station and the SGW for the split bearer on the secondary base station; the TEID and transport layer address are carried in a handover request confirmation message and sent to the source primary base station, and the source primary base station carries the TEID and transport layer address in a path switch request message and sends it to the MME;

[0038] For the SCG bearer on the secondary base station, the target primary base station does not allocate a downlink TEID and a transport layer address for the bearer, and sends an E-RAB modification indication or an enhanced path switching request message to the MME, which includes the TAI and / or ECGI of the primary cell of the target primary base station, and the TAI and / or ECGI of the secondary cell of the secondary base station;

[0039] For the bearer that is switched to the target primary base station and needs data forwarding, the target primary base station allocates the TEID and transport layer address of the X2 interface for data forwarding;

[0040] The RRC reconfiguration message sent by the source master base station to the UE does not include information instructing the UE to delete the SCG.

[0041] Preferably, when the decision result is to keep the secondary base station, the method further comprises:

[0042] The target main base station decides whether to modify the configuration of the UE's bearer on the secondary base station based on the target main base station's configuration of the UE bearer and / or the UE's capability information. If it decides to modify, the target main base station sends an SCG configuration request message to the secondary base station; the secondary base station sends an SCG configuration response message to the target main base station.

[0043] Preferably, the SCG configuration request message includes: an identifier of the UE in the secondary base station, a MeNB UE X2AP ID allocated by the target primary base station to the UE, which is used to identify the UE between the target primary base station and the secondary base station, or a new key in the secondary cell calculated by the target primary base station for the UE;

[0044] The SCG configuration response message includes: the configuration RRC container of the secondary cell air interface updated by the secondary base station and the SeNB UE X2AP ID allocated by the secondary base station for identifying the UE between the target primary base station and the secondary base station.

[0045] Preferably, when the decision result is to keep the secondary base station, the method further comprises:

[0046] The target master base station sends a UE configuration completion message to the secondary base station, where the message includes a MeNB UE X2AP ID between the target master base station and the secondary base station allocated by the target master base station for the UE. If the target master base station changes the configuration of the secondary base station before the target master base station sends the UE configuration completion message to the secondary base station, the message includes a SeNB UE X2AP ID allocated by the secondary base station to identify the UE between the target master base station and the secondary base station; otherwise, the message includes information used by the secondary base station to identify the UE, where the information used by the secondary base station to identify the UE is: an identifier of a secondary cell on the secondary base station and a C-RNTI of the UE in the secondary cell. If there are multiple secondary cells on the secondary base station, multiple secondary cell identifiers and C-RNTIs are included respectively; or, the information used by the secondary base station to identify the UE is the SeNB UE X2AP ID of the UE allocated by the secondary base station. When the SeNB UE X2AP ID of the UE allocated by the secondary base station is included, the UE configuration completion message also includes an identifier of the source master base station and / or a MeNB UE X2AP ID allocated by the source master base station.

[0047] Preferably, for a split bearer, the UE configuration completion message further includes a bearer identifier ERAB ID and a TEID and a transport layer address allocated by the destination primary base station;

[0048] In the case of SGW reselection, corresponding to the SCG bearer, the UE configuration completion message also includes the uplink TEID and transport layer address allocated by the new SGW.

[0049] The present application also provides a device for switching between different master base stations in a small cell system, including: a decision module and a switching module, wherein:

[0050] The decision module is used to decide whether to keep the secondary base station during switching;

[0051] The switching module is used to trigger different switching processes according to the decision result of whether to keep the secondary base station.

[0052] It can be seen from the above technical solution that the method and device for switching between different MeNBs in a small cell system provided by the present invention can reduce unnecessary deletion and re-establishment of UE bearers on the secondary base station, avoid erroneous deletion of bearers, reduce data forwarding, and decide to switch SeNB or keep SeNB unchanged according to the actual situation of network deployment, support SGW reselection, and improve system capacity and data transmission speed. More importantly, it can solve the following technical problems existing in the prior art:

[0053] Question 1: How to decide whether to keep SeNB?

[0054] Question 2: How does the target MeNB know which bearers are on the SeNB?

[0055] Question 3: How do the source MeNB and the target MeNB correctly configure resources for the UE's bearer?

[0056] Question 4: How does the target MeNB notify the SeNB which UE has been handed over?

[0057] Question 5: How can the target MeNB correctly notify the core network of bearer switching information to avoid the MME from mistakenly releasing certain bearers?

[0058] Question 6: How to handle the problem of SGW reselection during switching between different MeNBs?

[0059] The present application also provides a secondary base station and a method thereof in a switching process from a source primary base station to a target primary base station in a wireless communication system supporting dual connectivity. The method comprises: the secondary base station receives a first message from a target primary base station that maintains the secondary base station, the first message including information indicating a key associated with the security of the secondary base station and a request for a secondary cell group SCG configuration related to the secondary base station; the secondary base station sends a second message including information about the SCG configuration to the target primary base station in response to the first message; and the secondary base station receives a third message from the target primary base station indicating that the radio resource control RRC configuration associated with the user equipment UE during the switching process is completed.

[0060] The present application also provides a secondary base station in a switching process from a source main base station to a target main base station in a wireless communication system supporting dual connectivity, the secondary base station comprising: a transceiver; and at least one processor connected to the transceiver and configured to: receive a first message from a target main base station that maintains the secondary base station, the first message comprising information indicating a key associated with the security of the secondary base station and a request for a secondary cell group SCG configuration related to the secondary base station; in response to the first message, send a second message including information about the SCG configuration to the target main base station; and receive a third message from the target main base station indicating that the radio resource control RRC configuration associated with the user equipment UE during the switching process is completed.

[0061] The present application also provides a method for a target main base station during a switching process from a source main base station to a target main base station in a wireless communication system supporting dual connectivity, wherein the target main base station maintains a secondary base station, the method comprising: the target main base station sends a first message to the secondary base station, the first message comprising information indicating a key associated with the security of the secondary base station and a request for a secondary cell group SCG configuration related to the secondary base station; the target main base station receives a second message including information about the SCG configuration in response to the first message from the secondary base station; and the target main base station sends a third message to the secondary base station indicating that a radio resource control RRC configuration associated with a user equipment UE during the switching process is completed.

[0062] The present application also provides a method for a target main base station during a switching process from a source main base station to a target main base station in a wireless communication system supporting dual connectivity, wherein the target main base station maintains a secondary base station, and the target main base station includes: a transceiver; and at least one processor, which is connected to the transceiver and is configured to: send a first message to the secondary base station, the first message including information indicating a key associated with the security of the secondary base station and a request for a secondary cell group SCG configuration related to the secondary base station; receive a second message including information about the SCG configuration in response to the first message from the secondary base station; and send a third message to the secondary base station indicating that the radio resource control RRC configuration associated with the user equipment UE during the switching process is completed. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 This is the existing SAE system architecture diagram;

[0064] Figure 2 A schematic diagram of a deployment scenario for small cell enhancement;

[0065] Figure 3 Schematic diagram of a first switching method between different MeNBs in a small cell system of the present invention;

[0066] Figure 4 Schematic diagram of the second switching method between different MeNBs in the small cell system of the present invention;

[0067] Figure 5 Schematic diagram of the third handover method between different MeNBs in the small cell system of the present invention;

[0068] Figure 6 Schematic diagram of a fourth switching method between different MeNBs in a small cell system of the present invention;

[0069] Figure 7 This is a schematic diagram of the signaling process of Embodiment 1 of the present application;

[0070] Figure 8 This is a signaling flow diagram of Embodiment 2 of the present application;

[0071] Fig. 9 This is a schematic diagram of the signaling flow of Embodiment 3 of the present application;

[0072] Fig.10 A schematic diagram of the structure of a device for switching between different master base stations in a preferred small cell system of the present application. DETAILED DESCRIPTION

[0073] In order to make the objectives, technical means and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings.

[0074] Figure 3 It is a schematic diagram of a switching method 1 between different MeNBs in the small cell system of the present invention. The main process of the method is: the source main base station decides whether to keep the secondary base station, and triggers different processes according to the decision result. If the decision result of the source main base station is that the secondary base station can be kept unchanged, the destination main base station further decides whether to keep the secondary base station, and informs the source main base station of the decision result, and the source main base station sends a corresponding message to the UE. After receiving the RRC reconfiguration response message from the UE, the destination main base station sends a corresponding message to the core network, so that the bearer of the secondary base station is maintained on both the UE side and the core network without switching. In the above process, both the source main base station and the destination main base station make a decision on whether to switch the secondary base station. For the sake of distinction, the decision of the source main base station can be called an initial decision, and the decision of the destination main base station can be called a final decision. Specifically, Figure 3 The method shown comprises the steps of:

[0075] Step 301: The source primary base station decides to hand over the UE to the target primary base station.

[0076] In step 302 , the source primary base station initially decides whether to change the secondary base station. If the source primary base station decides to switch the bearer on the secondary base station to the target primary base station, step 307 is executed; if the source primary base station decides to keep the secondary base station unchanged, step 303 is executed.

[0077] In this step, the source main base station can decide whether the secondary base station can remain unchanged according to the measurement result of the UE. For example, if the signal quality of the UE's Scell ​​in the secondary base station is good enough in the measurement result of the UE, the source main base station can decide that the secondary base station can remain unchanged; if the signal quality of the UE's Scell ​​in the secondary base station is not good enough in the measurement result of the UE, the source main base station can decide to switch the bearer on the secondary base station.

[0078] Step 303: The source primary base station sends a handover request message to the target primary base station.

[0079] The handover request message includes the content in the existing 3GPP specification TS36.423, such as the E-RAB list to be established, the UE measurement report and UE capability information, etc. Each ERAB information to be established includes the E-RAB identifier, ERAB service quality assurance (QoS) information, and the uplink GTP channel end number.

[0080] The handover request message also includes a combination of one or more of the following information:

[0081] -The cell identifier of the UE in the Scell ​​of the SeNB and / or the base station identifier of the SeNB.

[0082] -UE's bearers on SeNB, that is, which of the UE's bearers are on SeNB; specifically, this can be represented by different ERAB lists, such as the ERAB list to be established when switching to the target master base station and the ERAB list on SeNB; or the ERAB list to be established contains all the E-RAB information of the UE, and an information element - Scell ​​identifier or indication on SeNB is added to the E-RAB information to be established, and this information element is included in the bearer information on the secondary base station, and the ERAB information to be switched to the target master base station does not contain this new information element. Both of the above methods can enable the target master base station to know which bearers of the UE are on the secondary base station. For split bearers, the latter method has obvious advantages, because the same bearer consumes resources both on the primary base station and on the secondary base station.

[0083] -Whether the bearer of the UE on the SeNB is a split bearer or an SCG bearer; through this new information element, the target primary base station can know whether the bearer on the secondary base station is a split bearer or an SCG bearer.

[0084] -UE measurement results;

[0085] -UE identification in the secondary base station. The UE identification in the secondary base station may be the Scell ​​identification of the UE in the secondary base station and the C-RNTI of the UE in the Scell. The UE identification in the secondary base station may also be the X2AP ID of the UE at the interface between the source primary base station and the secondary base station, including the SeNB UE X2 AP ID assigned by the secondary base station, and / or the MeNB UE X2AP ID assigned by the source primary base station, and / or the identification of the source MeNB.

[0086] -The TEID and transport layer address of the X2 interface downlink allocated by the secondary base station to the split bearer.

[0087] Step 304: The target primary base station decides whether to change the secondary base station.

[0088] In this step, the target master base station decides whether to change the secondary base station according to the measurement result of the UE received from the source master base station and the base station identifier of the secondary base station or the cell identifier of the secondary cell on the secondary base station. For example: the target master base station determines whether there is an X2 interface between the target master base station and the secondary base station according to the identifier of the secondary base station or the identifier of the secondary cell on the secondary base station. If there is an X2 interface and according to the UE measurement result received from the master base station (for example, the signal of the secondary base station Scell ​​is good enough), the target master base station can decide to keep the secondary base station unchanged; if the target master base station and the secondary base station do not have an X2 interface or the target master base station according to the UE measurement result received from the master base station (for example, the signal of the secondary base station Scell ​​is not good enough), the target master base station can decide not to keep the secondary base station. The target master base station can also consider other factors (for example, O&M configuration) when making a decision without affecting the main content of the present invention.

[0089] If the secondary base station does not change, the bearer originally established on the secondary base station will not be switched to the target primary base station, but will remain on the secondary base station. In this way, frequent bearer deletion and establishment processes are not required, and dual connections can continue to be used after the primary base station is switched, thereby increasing the speed of sending data to the UE.

[0090] While keeping the bearer on the SeNB unchanged, the target main base station may also decide to modify the configuration of the bearer of the UE on the SeNB according to the configuration of the bearer of the UE by the target main base station and / or the capability information or other information of the UE. If the target main base station decides to modify the configuration of the bearer on the SeNB, the target main base station sends an SCG configuration request message to the secondary base station. The target main base station obtains the secondary base station of the UE according to the cell identifier of the UE in the Scell ​​of the SeNB and / or the base station identifier of the SeNB contained in the switching request message in step 303. The SCG configuration request message contains the identifier of the UE in the secondary base station, and the identifier of the UE in the secondary base station is the same as that in step 303, which is not repeated here. The SCG configuration request message may also include the MeNB UEX2AP ID allocated by the target main base station to the UE, which is used to identify the UE between the target main base station and the secondary base station. The SCG configuration request may be an existing SeNB modification request or a new message. The SCG configuration request may also include a new key in the Scell ​​calculated by the target main base station for the UE. The secondary base station sends an SCG configuration response message to the target primary base station. The message may include the Scell ​​air interface configuration RRC container updated by the secondary base station (RRC container from the SeNB), and the message may also include the SeNB UE X2AP ID allocated by the secondary base station to identify the UE between the target primary base station and the secondary base station.

[0091] Step 305, the target master base station sends a handover request confirmation message to the source master base station. The message includes information on whether the secondary base station is retained. The target master base station allocates the downlink TEID and transport layer address of the S1 interface (the interface between the target master base station and the SGW) for the bearer switched to the target master base station.

[0092] According to the information about the bearers on SeNB (i.e., which bearers are on SeNB) and whether the bearers on SeNB are split bearers or SCG bearers contained in the switching request message received from the source main base station in step 303, the target main base station knows which bearers of the UE are on SeNB and whether the bearers on SeNB are split bearers or SCG bearers. The target main base station allocates the downlink TEID and transport layer address of the interface between the target main base station and SGW for the split bearer. For SCG bearers, if the target main base station decides to keep the SeNB unchanged, the target main base station does not need to allocate downlink TEID and transport layer address for the bearer. If the target main base station decides to switch the bearer on the secondary base station to the target main base station, the target main base station allocates the downlink TEID and transport layer address of the S1 interface for the bearer.

[0093] For the bearer that is switched to the target primary base station and requires data forwarding, the target primary base station allocates a TEID and a transport layer address of the X2 interface for data forwarding.

[0094] The target primary base station includes the TEID and transport layer address allocated for each bearer of the UE in a handover request confirmation message and sends it to the source primary base station.

[0095] The target primary base station allocates air interface resources for the bearer switched to the target primary base station, and sends the air interface configuration to the source primary base station (RRC container from the target MeNB) through the RRC container.

[0096] In the case where the bearer on the SeNB remains unhandled, if the target primary base station modifies the configuration on the SeNB and receives the RRC container from the SeNB, the target primary base station sends the RRC container from the SeNB to the source primary base station through a handover request confirmation.

[0097] Step 306: The source master base station sends a corresponding message to the UE. The source master base station sends an RRC reconfiguration message to the UE. The RRC reconfiguration message includes configuration information of the bearer switched to the target master base station, that is, includes the RRC container from the target MeNB.

[0098] If the source master base station receives information from the target master base station not to switch SeNB, the RRC reconfiguration message does not include information instructing the UE to delete SCG. In the case of SeNB not switching, the source master base station can also modify the configuration of SCG according to the information received from the target master base station, that is, send the RRC container from SeNB to UE.

[0099] If the source master base station receives information about switching SeNB from the target master base station, the source master base station instructs the UE to delete the SCG while reconfiguring the MCG, and establishes the bearer on the source SCG on the target master base station.

[0100] In the case of SeNB switching, the source master base station also sends a SeNB deletion request to the SeNB before sending the RRC reconfiguration to the UE. The process of notifying the SeNB of the TEID and transport layer address of data forwarding through the message is an existing process and is not the main content of the present invention. The detailed technical description is omitted here.

[0101] The UE sends an RRC reconfiguration response message to the target master base station.

[0102] The target master base station sends a corresponding message to the MME.

[0103] In the case of SeNB switching, the target primary base station sends a path switching request message to the MME. The path switching request includes the downlink TEID and transport layer address allocated by the target primary base station to each bearer.

[0104] When the SeNB remains unchanged but the bearer on the SeNB is a split bearer, the target master base station sends a path switching request message to the MME. The path switching request includes the downlink TEID and transport layer address allocated by the target master base station for each bearer.

[0105] When the SeNB remains unchanged and the bearer on the SeNB is an SCG bearer, the target main base station sends an E-RAB modification indication to the MME or sends an enhanced path switching request message to the MME. The enhanced path switching request message here does not refer to the name of the message, but includes new information elements in the existing path switching request message or the behavior of the MME after receiving the message is different from the existing one. The E-RAB modification indication or enhanced path switching request message may also include the TAI and / or ECGI of the main cell of the target main base station, and may also include the TAI and / or ECGI of the secondary base station Scell.

[0106] The E-RAB modification indication triggers the establishment of a UE-associated S1 signaling connection between the target main base station and the MME. The E-RAB modification indication includes the MME UE S1AP ID of the UE in the MME. The E-RAB modification indication includes the eNB UE S1AP ID assigned by the target main base station. The E-RAB modification indication includes information about the bearer to be switched. The bearer information maintained in the SeNB does not need to be included in the message. After receiving the E-RAB modification indication message, the MME establishes a UE-associated signaling connection between the target main base station and the MME. For the ERAB not included in the message, the MME remains unreleased. The MME sends a modify bearer request message to the SGW, requesting to modify the switched bearer. After receiving the modify bearer response message from the SGW, the MME sends an E-RAB modification indication confirmation message to the target main base station. The E-RAB modification indication confirmation message includes security context information, which is used to update the key between the target main base station and the UE. After receiving the E-RAB modification indication message, the MME can also determine whether it is necessary to reselect the SGW. When determining whether it is necessary to reselect the SGW, the MME may consider the TAI where the main cell of the target main base station is located, and may also consider the TAI where the main cell of the target main base station and the secondary base station Scell ​​are located. If it is necessary to reselect the SGW, the MME sends a create session request message to the target SGW, and the message includes all bearers of the UE, including bearer information that needs to be switched and bearer information that does not need to be switched received from the target main base station. The MME knows the information of the bearers that do not need to be switched based on the saved UE context. The target SGW allocates an uplink TEID and a transport layer address for each bearer. The target SGW sends a create session response message to the MME. The MME sends an ERAB modification indication confirmation message to the target main base station. If the SGW is reselected, the ERAB modification indication confirmation message includes not only the uplink TEID and transport layer address of the switched bearer, but also the uplink TEID and transport layer address information of the bearer that has not been switched. In the case where the SGW is not reselected, the E-RAB modification indication confirmation message includes security context information, which is used to update the key between the target main base station and the UE.

[0107] The enhanced path switching request may include all bearers, such as bearers that need to be switched and bearers that do not need to be switched. After receiving the message, for bearers that do not need to be switched (for example, the TEID and transport layer address of the bearer have not changed), the MME does not consider this to be an erroneous message, nor does it trigger the bearer deactivation process. If the TEID and transport layer address of a bearer have not changed, the MME thereby learns that the bearer has not been switched. Or the enhanced switching request includes indication information, which indicates that the bearer not included in the path switching request message will not be released. After receiving the enhanced path switching request message, the MME does not trigger the deactivation process for the bearer not included in the path switching request message according to the indication information. The MME sends a modify bearer request message to the SGW to request modification of the switched bearer. After receiving the modify bearer response message from the SGW, the MME sends a path switching request confirmation message to the destination master base station. After receiving the path switching request message, the MME may also determine whether it is necessary to reselect the SGW. When determining whether it is necessary to reselect the SGW, the MME may consider the TAI where the main cell of the target main base station is located, and may also consider the TAI where the main cell of the target main base station and the secondary base station Scell ​​are located. If it is necessary to reselect the SGW, the MME sends a create session request message to the target SGW, and the message includes all bearers of the UE, including the bearer information that needs to be switched and the bearer information that does not need to be switched received from the target main base station. The target SGW allocates an uplink TEID and a transport layer address to each bearer. The target SGW sends a create session response message to the MME. The MME sends a path switching request confirmation message to the target main base station. If the SGW is reselected, the path switching request confirmation message includes not only the uplink TEID and transport layer address of the switched bearer, but also the uplink TEID and transport layer address information of the bearer that has not been switched.

[0108] The target master base station sends a UE configuration completion message to the secondary base station. The message includes the MeNB UE X2AP ID between the target master base station and the secondary base station allocated by the target master base station for the UE. If before this step (for example, in step 304), the target master base station has made a configuration change to the secondary base station, the message includes the SeNB UE X2AP ID allocated by the secondary base station to identify the UE between the target master base station and the secondary base station.

[0109] If the configuration change process between the target master base station and the secondary base station is not performed before this step (for example, in step 304), the message contains information for the secondary base station to identify the UE, so that the secondary base station can know which master base station of the UE has been switched. The information for the secondary base station to identify the UE is received from the source master base station. It can be the identifier of the secondary cell on the secondary base station and the C-RNTI of the UE in the secondary cell. If there are multiple secondary cells on the secondary base station, multiple secondary cell identifiers and C-RNTIs are included respectively. The information for the secondary base station to identify the UE can also be the SeNB UE X2APID of the UE assigned by the secondary base station. When the SeNB UE X2AP ID of the UE assigned by the secondary base station is included, the identifier of the source master base station and / or the MeNB UE X2AP ID assigned by the source master base station can also be included. Through this process, a UE-associated X2 signaling connection between the target master base station and the secondary base station can be established.

[0110] For split bearers, the message also includes the bearer identifier ERAB ID and the TEID and transport layer address assigned by the destination master base station. In the case of SGW reselection, for the SCG bearer, the message also includes the uplink TEID and transport layer address assigned by the new SGW. The SeNB saves the information received from the destination master base station and deletes the relevant information of the source master base station. If the SeNB receives a new Key from the destination master base station, the SeNB updates the key used.

[0111] Through step 303, the source master base station informs the target master base station of the SeNB of the UE and the information identifying the UE on the SeNB. The target master base station sends a message to the correct secondary base station. The target master base station sends the information identifying the UE on the SeNB to the SeNB. The SeNB can know which UE's master base station has been switched, and the SeNB makes correct modifications and deletions, thereby solving the fourth problem raised by the present invention.

[0112] Optionally, the SeNB may also send a UE configuration completion confirmation message to the target primary base station.

[0113] The destination primary base station can obtain the X2 interface downlink TEID and transport layer address allocated by the secondary base station for the split bearer in two ways:

[0114] Method 1: In step 303, the source primary base station informs the target primary base station of the secondary base station of the X2 interface downlink TEID and transport layer address allocated for the split bearer.

[0115] Method 2: Through the UE configuration completion confirmation message, the secondary base station sends the X2 interface downlink TEID and transport layer address allocated for the split bearer to the target primary base station.

[0116] Therefore, the target primary base station can send downlink data to the secondary base station.

[0117] Step 307: The source master base station performs a handover process from the source master base station to the target master base station, and also switches the bearer on the SeNB to the target master base station. This process is the same as the existing handover process from MeNB to eNB, which is not the focus of the present invention, and the detailed technical description is omitted here.

[0118] Figure 3 The method shown, the source main base station initially decides whether to keep the SeNB, and the target main base station finally decides whether to keep the SeNB, so that when the SeNB is kept without switching, it can ensure that the bearers of the UE and the core network are also kept on the SeNB and are not released by mistake, avoiding the deletion and re-establishment of the bearers on the SeNB, and can also support SGW reselection, solving the six technical problems mentioned above.

[0119] Figure 4 It is a schematic diagram of the second switching method between different MeNBs in the small cell system of the present invention. The main process of this method is: the source main base station sends a switching request message to the target main base station, the target main base station decides whether to keep the secondary base station, and informs the source main base station of the decision result, the source main base station sends a corresponding message to the UE, and the target main base station sends a corresponding message to the core network after receiving the RRC reconfiguration response message of the UE, so that the bearer of the secondary base station is maintained on both the UE side and the core network without being released. The switching request and switching response are enhanced switching request and switching response messages. Enhancement does not refer to the name of the message, but adds new information elements to the existing switching request and switching response messages. Specifically, Figure 4 The method shown comprises the steps of:

[0120] Step 401: The source primary base station decides to hand over the UE to the target primary base station.

[0121] Steps 402 to 405 are the same as steps 303 to 306 and are not described again here.

[0122] Through the above Figure 4 The method is that the target master base station decides whether to keep the SeNB. When the SeNB is kept unchanged, it can ensure that the bearers of the UE and the core network are also kept on the SeNB and are not released by mistake, thereby avoiding the deletion and re-establishment of the bearers on the SeNB. It can also support SGW reselection, thereby solving the six technical problems found in the present invention.

[0123] Figure 5The schematic diagram of the switching method between different MeNBs in the small cell system of the present invention is as follows: the source master base station decides whether to keep the secondary base station. If it decides to keep the secondary base station, the corresponding process is executed to keep the bearers that are not switched between the UE and the network from being released, and the bearers that are not switched do not need to be deleted and re-established. Specifically, Figure 5 The method shown comprises the steps of:

[0124] Step 501: The source primary base station decides to hand over the UE to the target primary base station.

[0125] Step 502 , the source primary base station decides whether to keep the secondary base station. If the source primary base station decides to switch the bearer on the secondary base station to the target secondary base station, step 506 is executed; if the primary base station decides to keep the secondary base station unchanged, step 503 is executed.

[0126] In this step, the source main base station can decide whether to change the secondary base station according to the measurement result of the UE. For example, if the signal quality of the secondary base station Scell ​​in the measurement result of the UE is good enough, the source main base station can decide that the secondary base station can remain unchanged; if the signal quality of the secondary base station Scell ​​in the measurement result of the UE is not good enough, the source main base station can decide to switch the bearer on the secondary base station.

[0127] The source main base station can also determine whether to change the secondary base station based on the measurement results of the UE and whether there is an X2 interface between the target main base station and the secondary base station. For example: if the signal quality of the secondary base station Scell ​​in the measurement results of the UE is good enough and there is an X2 interface between the target main base station and the secondary base station, the source main base station can decide that the secondary base station can remain unchanged; if the signal quality of the secondary base station Scell ​​in the measurement results of the UE is not good enough or there is no X2 interface between the target main base station and the secondary base station, the source main base station can decide to switch the bearer on the secondary base station. The source main base station can know whether there is an X2 interface between the target main base station and the secondary base station according to the configuration. The source main base station can also know whether there is an X2 interface between the target main base station and the secondary base station in other ways without affecting the main content of the present invention.

[0128] The source master base station may also consider other factors (such as O&M configuration) when making a decision without affecting the main content of the present invention.

[0129] Step 503 is the same as step 303 and will not be described again here.

[0130] Step 504: The target primary base station sends a handover request confirmation message to the source primary base station.

[0131] The destination main base station allocates the downlink TEID and transport layer address of the S1 interface (the interface between the destination main base station and the SGW) for the bearer switched to the destination main base station. According to the information on the bearers on the SeNB (i.e., which bearers are on the SeNB) and whether the bearers on the SeNB are split bearers or SCG bearers contained in the switching request message received from the source main base station in step 503, the destination main base station knows which bearers of the UE are on the SeNB and whether the bearers on the SeNB are split bearers or SCG bearers. The destination main base station allocates the downlink TEID and transport layer address of the interface between the destination main base station and the SGW for the split bearer. For the SCG bearer, the destination secondary base station does not need to allocate a downlink TEID and transport layer address for the bearer. For the bearer switched to the destination main base station and requiring data forwarding, the destination main base station allocates the TEID and transport layer address of the X2 interface for data forwarding.

[0132] The target primary base station includes the TEID and transport layer address allocated for each bearer of the UE in a handover request confirmation message and sends it to the source primary base station.

[0133] Before the target master base station sends a handover request confirmation message to the source MeNB, for the bearer maintained on the SeNB, the target master base station may also decide to modify the configuration of the bearer of the UE on the SeNB according to the configuration of the UE bearer by the target master base station and / or the capability information or other information of the UE. If the target master base station decides to modify the configuration of the bearer on the SeNB, the target master base station sends an SCG configuration request message to the secondary base station. The target master base station learns the secondary base station of the UE according to the cell identifier of the UE in the Scell ​​of the SeNB and / or the base station identifier of the SeNB contained in the handover request message in step 503. The SCG configuration request message contains the identifier of the UE in the secondary base station, and the identifier of the UE in the secondary base station is the same as that in step 503, which is not repeated here. The SCG configuration request message may also include the MeNB UE X2AP ID allocated by the target master base station to the UE, which is used to identify the UE between the target master base station and the secondary base station. The SCG configuration request may be an existing SeNB modification request or a new message. The SCG configuration request may also include a new key in the Scell ​​calculated by the target master base station for the UE. The secondary base station sends an SCG configuration response message to the target master base station. The message may include the configuration RRC container of the Scell ​​air interface updated by the secondary base station (RRC container from the SeNB). The message may also include the SeNB UE X2APID allocated by the secondary base station to identify the UE between the target primary base station and the secondary base station.

[0134] The target MeNB allocates air interface resources for the bearer switched to the target MeNB, and sends the air interface configuration to the source MeNB through the RRC container (RRC container from the target MeNB).

[0135] In the case where the bearer on the SeNB remains unhandled, if the target primary base station modifies the configuration on the SeNB and receives the RRC container from the SeNB, the target primary base station sends the RRC container from the SeNB to the source primary base station through a handover request confirmation.

[0136] Step 505: The source master base station sends a corresponding message to the UE. The source master base station sends an RRC reconfiguration message to the UE. The RRC reconfiguration message includes configuration information of the bearer switched to the target master base station, that is, includes the RRC container from the target MeNB.

[0137] If the source master base station decides not to switch the bearer on the SeNB, the RRC reconfiguration message does not include information instructing the UE to delete the SCG. In the case where the SeNB does not switch, the source master base station can also modify the configuration of the SCG according to the information received from the target master base station, that is, send the RRC container from the SeNB to the UE.

[0138] If the source master base station decides to switch the bearer on the SeNB, the source master base station instructs the UE to delete the SCG while reconfiguring the MCG, and at the same time establishes the bearer on the source SCG on the target master base station.

[0139] In the case of SeNB switching, the source master base station also sends a SeNB deletion request to the SeNB before sending the RRC reconfiguration to the UE. The process of notifying the SeNB of the TEID and transport layer address of data forwarding through the message is an existing process and is not the main content of the present invention. The detailed technical description is omitted here.

[0140] The UE sends an RRC reconfiguration response message to the target master base station.

[0141] The target master base station sends a corresponding message to the MME. The specific process between the target master base station and the MME and the process between the MME and the SGW are the same as those described in step 306, and will not be repeated here.

[0142] The target master base station sends a UE configuration completion message to the secondary base station. The message includes the MeNB UE X2AP ID between the target master base station and the secondary base station allocated by the target master base station for the UE. If before this step (for example, in step 504), the target master base station has made a configuration change to the secondary base station, the message includes the SeNB UE X2AP ID allocated by the secondary base station to identify the UE between the target master base station and the secondary base station.

[0143] If the configuration change process between the target master base station and the secondary base station is not performed before this step (for example, in step 504), the message contains information for the secondary base station to identify the UE, so that the secondary base station can know which master base station of the UE has been switched. The information for the secondary base station to identify the UE is received from the source master base station. It can be the identifier of the secondary cell on the secondary base station and the C-RNTI of the UE in the secondary cell. If there are multiple secondary cells on the secondary base station, multiple secondary cell identifiers and C-RNTIs are included respectively. The information for the secondary base station to identify the UE can also be the SeNB UE X2APID of the UE assigned by the secondary base station. When the SeNB UE X2AP ID of the UE assigned by the secondary base station is included, the identifier of the source master base station and / or the MeNB UE X2AP ID assigned by the source master base station can also be included. Through this process, a UE-associated X2 signaling connection between the target master base station and the secondary base station can be established.

[0144] For split bearers, the message also includes the bearer identifier ERAB ID and the TEID and transport layer address assigned by the destination master base station. In the case of SGW reselection, for the SCG bearer, the message also includes the uplink TEID and transport layer address assigned by the new SGW. The SeNB saves the information received from the destination master base station and deletes the relevant information of the source master base station. If the SeNB receives a new Key from the destination master base station, the SeNB updates the key used.

[0145] Through step 503, the source master base station informs the target master base station of the SeNB of the UE and the information identifying the UE on the SeNB. The target master base station sends a message to the correct secondary base station. The target master base station sends the information identifying the UE on the SeNB to the SeNB. The SeNB can know which UE's master base station has been switched, and the SeNB makes correct modifications and deletions, thereby solving the fourth problem raised by the present invention.

[0146] Optionally, the SeNB may also send a UE configuration completion confirmation message to the target primary base station.

[0147] The destination primary base station can obtain the X2 interface downlink TEID and transport layer address allocated by the secondary base station for the split bearer in two ways:

[0148] Method 1: In step 503, the source primary base station informs the target primary base station of the secondary base station of the X2 interface downlink TEID and transport layer address allocated for the split bearer.

[0149] Method 2: Through the UE configuration completion confirmation message, the secondary base station sends the X2 interface downlink TEID and transport layer address allocated for the split bearer to the target primary base station.

[0150] Therefore, the target primary base station can send downlink data to the secondary base station.

[0151] Step 506 is the same as step 307 and will not be described again here.

[0152] Through the above Figure 5 The method is that the source master base station decides whether to keep the SeNB. When the SeNB is kept unchanged, it can ensure that the bearers of the UE and the core network are also kept on the SeNB and are not released by mistake, and avoid deletion and re-establishment of the bearers on the SeNB. It can also support SGW reselection, and solve the six technical problems found in the present invention.

[0153] Figure 6 The schematic diagram of the fourth switching method between different MeNBs in the small cell system of the present invention. The main process of the method is: the target master base station notifies the source master base station whether there is an X2 interface between the target master base station and the secondary base station, the source master base station decides whether to keep the secondary base station, and if it decides to keep the secondary base station, executes the corresponding process to keep the bearers that have not been switched between the UE and the network from being released. Specifically, Figure 6 The method shown comprises the steps of:

[0154] Step 601: The source primary base station decides to hand over the UE to the target primary base station.

[0155] Step 602 is the same as step 303 and will not be described again here.

[0156] Step 603: The target master base station sends a handover request confirmation message to the source master base station. The message includes information about whether the target master base station and the secondary base station have an X2 interface or whether the secondary base station is feasible. The target master base station determines whether the secondary base station is feasible, for example: if the target master base station and the secondary base station have an X2 interface, it is feasible; if there is no X2 interface, it is not feasible. When considering whether it is feasible, the target master base station may also consider other information, such as O&M configuration.

[0157] The destination main base station allocates the downlink TEID and transport layer address of the S1 interface (the interface between the destination main base station and the SGW) for the bearer switched to the destination main base station. According to the information on the bearer on the SeNB contained in the switching request message received from the source main base station in step 602, and whether the bearer on the SeNB is a split bearer or an SCG bearer, the destination main base station knows which bearers of the UE are on the SeNB and whether the bearer on the SeNB is a split bearer or an SCG bearer. The destination main base station allocates the downlink TEID and transport layer address of the interface between the destination main base station and the SGW for the split bearer. For the SCG bearer, the destination secondary base station does not need to allocate a downlink TEID and transport layer address for the bearer. For the bearer switched to the destination main base station and requiring data forwarding, the destination main base station allocates the TEID and transport layer address of the X2 interface for data forwarding.

[0158] The target primary base station includes the TEID and transport layer address allocated for each bearer of the UE in a handover request confirmation message and sends it to the source primary base station.

[0159] Step 604 , the source primary base station decides whether to keep the secondary base station. If the source primary base station decides to switch the bearer on the secondary base station to the target primary base station, step 606 is executed; if the primary base station decides to keep the secondary base station unchanged, step 605 is executed.

[0160] The source main base station can determine whether to change the secondary base station based on the measurement results of the UE and whether there is an X2 interface between the target main base station and the secondary base station or the information received from the target main base station whether the secondary base station remains feasible. For example: if the signal quality of the secondary base station Scell ​​in the measurement results of the UE is good enough and there is an X2 interface between the target main base station and the secondary base station or the secondary base station remains feasible, the source main base station can decide to keep the secondary base station unchanged; if the signal of the secondary base station Scell ​​in the measurement results of the UE is not good enough or there is no X2 interface between the target main base station and the secondary base station or the secondary base station remains unfeasible, the source main base station can decide to switch the bearer on the secondary base station. The source main base station can also consider other factors (such as O&M configuration) when making a decision without affecting the main content of the present invention.

[0161] If the source master base station decides to keep the secondary base station, the source master base station informs the target master base station to keep the secondary base station. The target master base station releases the S1 interface downlink TEID and transport layer address allocated for the SCG bearer and the air interface resources allocated for the SCG bearer.

[0162] For the bearer maintained on the SeNB, the target main base station may also decide to modify the configuration of the bearer of the UE on the SeNB according to the configuration of the bearer of the UE by the target main base station and / or the capability information or other information of the UE. If the target main base station decides to modify the configuration of the bearer on the SeNB, the target main base station sends an SCG configuration request message to the secondary base station. The target main base station obtains the secondary base station of the UE according to the cell identifier of the UE in the Scell ​​of the SeNB and / or the base station identifier of the SeNB contained in the handover request message in step 602. The SCG configuration request message contains the identifier of the UE in the secondary base station, and the identifier of the UE in the secondary base station is the same as that in step 602, which is not repeated here. The SCG configuration request message may also include the MeNB UE X2APID allocated by the target main base station to the UE, which is used to identify the UE between the target main base station and the secondary base station. The SCG configuration request may be an existing SeNB modification request or a new message. The SCG configuration request may also include a new key in the Scell ​​calculated by the target main base station for the UE. The secondary base station sends an SCG configuration response message to the target main base station. The message may include the configuration RRC container of the Scell ​​air interface updated by the secondary base station (RRC container from the SeNB), and the message may also include the SeNB UE X2AP ID assigned by the secondary base station to identify the UE between the target primary base station and the secondary base station. If the target primary base station receives the RRC container from the SeNB, the target primary base station sends the RRC container from the SeNB to the source primary base station.

[0163] Step 605 is the same as step 505 and will not be described again here.

[0164] Step 606, the source master base station performs other processes of switching from the source master base station to the target master base station, and also switches the bearer on the SeNB to the target master base station. This process is the same as the existing MeNB to eNB switching process, for example, the source master base station sends a SeNB release request to the secondary base station, the source master base station sends an RRC reconfiguration message to the UE, etc. This process is not the focus of the present invention, and the detailed technical description is omitted here.

[0165] Through the above Figure 6 The method is that the source master base station decides whether to keep the SeNB. When the SeNB is kept unchanged, it can ensure that the bearers of the UE and the core network are also kept on the SeNB and are not released by mistake, thereby avoiding the deletion and re-establishment of the bearers on the SeNB. It can also support SGW reselection, and solve the six technical problems found in the present invention.

[0166] The technical solution of the present application is further described in detail below through several embodiments.

[0167] Embodiment 1:

[0168] The signaling flow chart of the first embodiment of the present invention is as follows: Figure 7 As shown. Figures 3 to 6 Methods 1 to 4 have respectively described in detail how to decide whether to keep the secondary base station, so this embodiment will not describe in detail how to decide whether to keep the secondary base station. This embodiment focuses on how to solve problems 2 to 6 proposed by the present invention. Figure 7 The process shown includes the steps:

[0169] Step 701, the source primary base station sends a handover request to the target primary base station, and the handover request message may include: source secondary base station information, UE identification information in the secondary base station, UE bearers in the secondary base station, and whether these bearers are split bearers or SCG bearers, etc. This step is the same as step 303, and will not be repeated here.

[0170] In the case of handover between different MeNBs without SeNB change, the source SeNB is also the target SeNB. Therefore, the source SeNB, the target SeNB and the SeNB refer to the same base station, that is, the second base station that allocates resources to the UE on the air interface in addition to the MeNB that allocates air interface resources to the UE before and after the handover.

[0171] Step 702: The target primary base station sends a handover request confirmation message to the source primary base station.

[0172] Corresponding to the method in which the target primary base station determines whether the secondary base station remains unchanged, the message further includes information that the secondary base station remains unchanged.

[0173] The target primary base station allocates the downlink TEID and transport layer address of the S1 interface (the interface between the target primary base station and the SGW) for the bearer switched to the target primary base station.

[0174] According to the information contained in the switching request message received from the source main base station in step 701, which includes which bearers are on SeNB and whether the bearers on SeNB are split bearers or SCG bearers, the target main base station knows which bearers of the UE are on SeNB and whether the bearers on SeNB are split bearers or SCG bearers. The target main base station allocates the downlink TEID and transport layer address of the interface between the target main base station and SGW for the split bearer. For SCG bearers, if the target main base station decides to keep the SeNB unchanged, the target main base station does not need to allocate downlink TEID and transport layer address for the bearer. If the target main base station decides to switch the bearer on the secondary base station to the target main base station, the target main base station allocates the downlink TEID and transport layer address of the S1 interface for the bearer.

[0175] For the bearer that is switched to the target primary base station and requires data forwarding, the target primary base station allocates a TEID and a transport layer address of the X2 interface for data forwarding.

[0176] The target primary base station includes the TEID and transport layer address allocated for each bearer of the UE in a handover request confirmation message and sends it to the source primary base station.

[0177] The target MeNB allocates air interface resources for the bearer switched to the target MeNB, and sends the air interface configuration to the source MeNB through the RRC container (RRC container from the target MeNB).

[0178] Through step 701, the source main base station informs the target main base station which bearers of the UE are on the SeNB, and whether the bearers on the SeNB are split bearers or SCG bearers. The target main base station keeps the bearers on the SeNB unchanged according to its own decision, or informs the target main base station that the bearers on the SeNB will not be switched after the source main base station decides. Therefore, the target main base station knows which bearers are bearers on the SeNB, and the target main base station correctly configures resources for different bearers of the UE, thereby solving the second and third problems raised by the present invention.

[0179] Step 703: The source master base station sends an RRC reconfiguration message to the UE.

[0180] If the SeNB is not switched, the source master base station sends an RRC reconfiguration message to the UE, which does not include information instructing the UE to delete the SCG. In the case where the SeNB is not switched, the source master base station may also decide to modify the configuration of the SCG based on information received from the target master base station.

[0181] If the SeNB is switched, the source master base station instructs the UE to delete the SCG while reconfiguring the MCG, and at the same time establishes the bearer on the source SCG on the target master base station.

[0182] Step 704: The source master base station sends a sequence number (SN) status to the target master base station.

[0183] The source master base station can start data forwarding.

[0184] In the present invention, there is no absolute order between step 703 and step 704, that is, the source master base station may first send the sequence status to the target master base station and forward the data, and then send the RRC reconfiguration request message to the UE.

[0185] Step 705: The UE sends an RRC reconfiguration response message to the target master base station.

[0186] Step 706: The target master base station sends a path switching request or an E-RAB modification indication message to the MME.

[0187] In the case of SeNB switching, the target primary base station sends a path switching request message to the MME. The path switching request includes a downlink TEID and a transport layer address allocated by the target primary base station for each bearer switched to the target primary base station.

[0188] When the SeNB remains unchanged but the bearer on the SeNB is a split bearer, the target master base station sends a path switching request message to the MME. The path switching request includes the downlink TEID and transport layer address allocated by the target master base station for each bearer.

[0189] When the SeNB remains unchanged and the bearer on the SeNB is an SCG bearer, the target main base station sends an E-RAB modification indication to the MME or sends an enhanced path switching request message to the MME. The enhanced path switching request message here does not refer to the name of the message, but a new information element is included in the existing path switching request message or the behavior of the MME after receiving the message is different from the existing one. The E-RAB modification indication or enhanced path switching request message may also include the TAI and / or ECGI of the main cell of the target main base station, and may also include the TAI and / or ECGI of the secondary base station Scell. If the UE has multiple secondary cells in the secondary base station, the message may include multiple TAIs and / or ECGIs.

[0190] The E-RAB modification indication triggers the establishment of a UE-associated S1 signaling connection between the target main base station and the MME. The E-RAB modification indication includes the MME UE S1AP ID of the UE in the MME. The E-RAB modification indication includes the eNB UE S1AP ID assigned by the target main base station. The E-RAB modification indication includes information about the bearer to be switched. The bearer information maintained in the SeNB does not need to be included in the message. After receiving the E-RAB modification indication message, the MME establishes a UE-associated signaling connection between the target main base station and the MME. The ERAB not included in the message is kept by the MME without being released. The MME sends a modification bearer request message to the SGW to request modification of the downlink channel of the switched bearer. After receiving the modification bearer response message from the SGW, the MME sends an E-RAB modification indication confirmation message to the target main base station. The E-RAB modification indication confirmation message includes security context information, which is used to update the key between the target main base station and the UE. After receiving the E-RAB modification indication message, the MME can also determine whether it is necessary to reselect the SGW. When determining whether it is necessary to reselect the SGW, the MME may consider the TAI where the main cell of the target main base station is located, and may also consider the TAI where the main cell of the target main base station and the secondary base station Scell ​​are located. If it is necessary to reselect the SGW, the MME sends a create session request message to the target SGW. The message contains all the bearers of the UE, including the bearer information that needs to be switched and the bearer information that does not need to be switched received from the target main base station. The MME knows the information of the bearers that do not need to be switched based on the saved UE context. The target SGW allocates an uplink TEID and a transport layer address for each bearer. The target SGW sends a create session response message to the MME. The MME sends an ERAB modification indication confirmation message to the target main base station. If the SGW is reselected, the ERAB modification indication confirmation message contains not only the uplink TEID and transport layer address of the switched bearer, but also the uplink TEID and transport layer address information of the bearer that has not been switched. In the case where the SGW is not reselected, the E-RAB modification indication confirmation message contains security context information, which is used to update the key between the target main base station and the UE.

[0191] The enhanced path switching request may include all bearers, such as bearers that need to be switched and bearers that do not need to be switched. After receiving the message, the MME does not trigger the bearer deactivation process for the bearer that does not need to be switched (for example, the TEID of the bearer is the same as the transport layer address). Or the enhanced switching request includes indication information, and the indication information indicates that the bearer not included in the path switching request message is not released. After receiving the enhanced path switching request message, the MME does not trigger the deactivation process of the bearer not included in the path switching request message according to the indication information. The MME sends a modify bearer request message to the SGW to request modification of the switched bearer. After receiving the modify bearer response message from the SGW, the MME sends a path switching request confirmation message to the target main base station. After receiving the path switching request message, the MME can also determine whether it is necessary to reselect the SGW. When determining whether it is necessary to reselect the SGW, the MME can consider the TAI where the main cell of the target main base station is located, and can also consider the TAI where the main cell of the target main base station and the secondary base station Scell ​​are located at the same time. If the SGW needs to be reselected, the MME sends a create session request message to the target SGW, and the message contains all the bearers of the UE, including the bearer information that needs to be switched and the bearer information that does not need to be switched received from the target main base station. The target SGW allocates an uplink TEID and a transport layer address for each bearer. The target SGW sends a create session response message to the MME. The MME sends a path switch request confirmation message to the target main base station. If the SGW is reselected, the path switch request confirmation message contains not only the uplink TEID and transport layer address of the switched bearer, but also the uplink TEID and transport layer address information of the bearer that has not been switched.

[0192] Step 707: The MME sends an E-RAB modification indication confirmation message or a path switch request confirmation message to the target master base station.

[0193] If what is received in step 706 is an E-RAB modification indication, what is sent in this step is an E-RAB modification indication confirmation. If what is received in step 706 is a path switching request, what is sent in this step is a path switching request confirmation.

[0194] If the SGW is reselected, the ERAB modification indication confirmation or path switch request confirmation message also includes the uplink TEID and transport layer address information of the bearer that is not switched.

[0195] Through step 701, the source master base station lets the target master base station know which bearers of the UE are on the SeNB, whether the bearers on the SeNB are split bearers or SCG bearers, and the target master base station keeps the bearers on the SeNB unchanged according to its own decision, or informs the target master base station that the bearers on the SeNB will not be switched after the source master base station decides. Thus, the target master base station knows that it can notify the MME through appropriate messages which bearers need to be switched and which bearers do not need to be switched, thereby avoiding the MME from releasing some bearers incorrectly. When SGW reselection is required, the MME can also notify the SGW to allocate uplink TEID and transport layer address for bearers that do not need to be switched. Thereby solving the fifth and sixth problems raised by the present invention.

[0196] Step 708: The target primary base station sends a UE configuration completion message to the secondary base station. The message includes the MeNB UE X2AP ID between the target primary base station and the secondary base station allocated by the target primary base station to the UE.

[0197] The message includes information for the secondary base station to identify the UE, so that the secondary base station can know which UE's primary base station has switched. The information for the secondary base station to identify the UE is received from the source primary base station. It can be the identifier of the secondary cell on the secondary base station and the C-RNTI of the UE in the secondary cell. If there are multiple secondary cells in the secondary base station, multiple secondary cell identifiers and C-RNTIs are included respectively. The information for the secondary base station to identify the UE can also be the SeNB UE X2APID of the UE assigned by the secondary base station. When the SeNB UE X2AP ID of the UE assigned by the secondary base station is included, the identifier of the source primary base station and / or the MeNB UE X2AP ID assigned by the source primary base station can also be included.

[0198] For a split bearer, the message further includes a bearer identifier ERAB ID and a TEID and a transport layer address allocated by the destination primary base station to each bearer.

[0199] In the case of SGW reselection, corresponding to the SCG bearer, the message also includes the uplink TEID and transport layer address allocated by the new SGW.

[0200] The SeNB saves the information received from the target master base station and deletes the relevant information of the source master base station. If the SeNB receives a new Key from the target master base station, the SeNB updates the key used.

[0201] Through this process, a UE-associated X2 signaling connection may be established between the target primary base station and the secondary base station.

[0202] Optionally, the SeNB may also send a UE configuration completion confirmation message to the target primary base station.

[0203] The destination primary base station can obtain the X2 interface downlink TEID and transport layer address allocated by the secondary base station for the split bearer in two ways:

[0204] Method 1: In step 701, the source primary base station informs the target primary base station of the secondary base station of the X2 interface downlink TEID and transport layer address allocated for the split bearer.

[0205] Method 2: Through the UE configuration completion confirmation message, the secondary base station sends the X2 interface downlink TEID and transport layer address allocated for the split bearer to the target primary base station.

[0206] Through step 701, the source master base station informs the target master base station of the SeNB of the UE and the information identifying the UE on the SeNB, the target master base station sends a message to the correct secondary base station, the target master base station sends the information identifying the UE on the SeNB to the SeNB, the SeNB can know which UE's master base station has been switched, and the SeNB performs correct modification and deletion, thereby solving the fourth problem raised by the present invention.

[0207] Through this embodiment, various problems in the handover process between different MeNBs can be solved, so that the solution of keeping the SeNB from switching when switching between different MeNBs is feasible.

[0208] Embodiment 2:

[0209] The signaling flow chart of the second embodiment of the present invention is as follows: Figure 8 As shown. Figures 3 to 6 Methods 1 to 4 have respectively described in detail how to decide whether to keep the secondary base station, so this embodiment will not describe in detail how to decide whether to keep the secondary base station. This embodiment focuses on how to solve problems 2 to 6 proposed by the present invention. Figure 8 The process shown includes the steps:

[0210] Step 801, the source primary base station sends a handover request to the target primary base station, and the handover request message may include: source secondary base station information, UE identification information in the secondary base station, UE bearers in the secondary base station, and whether these bearers are split bearers or SCG bearers, etc. This step is the same as step 303, and will not be repeated here.

[0211] In the case of handover between different MeNBs without SeNB change, the source SeNB is also the target SeNB. Therefore, the source SeNB, the target SeNB and the SeNB refer to the same base station, that is, the second base station that allocates resources to the UE on the air interface in addition to the MeNB that allocates air interface resources to the UE before and after the handover.

[0212] Step 802: The target primary base station sends an SCG configuration request to the secondary base station. According to the secondary base station identifier or the secondary base station Scell ​​identifier received in step 801, the target primary base station knows the secondary base station of the UE.

[0213] The target primary base station can calculate a new key Key of the UE in the secondary base station, and the target primary base station sends a configuration request to the secondary base station through the SCG.

[0214] The message contains information for the secondary base station to identify the UE, so that the secondary base station can know which UE's primary base station has switched. The information for the secondary base station to identify the UE is received from the source primary base station. The specific information is the same as described in step 708, and will not be repeated here.

[0215] The target primary base station may also modify the configuration carried by the secondary base station through the SCG configuration request message.

[0216] The SCG configuration may be a new message or may be implemented by enhancing an existing SeNB modification request.

[0217] Through this message, a UE-associated X2 signaling connection may be established between the target primary base station and the secondary base station.

[0218] Through step 801, the source master base station informs the target master base station of the SeNB of the UE and the information identifying the UE on the SeNB, the target master base station sends a message to the correct secondary base station, the target master base station sends the information identifying the UE on the SeNB to the SeNB, the SeNB can know which UE's master base station has been switched, and the SeNB performs correct modification and deletion, thereby solving the fourth problem raised by the present invention.

[0219] Step 803: The secondary base station sends an SCG configuration response message to the target primary base station.

[0220] The message may also include the SeNB X2AP ID between the secondary base station and the target primary base station allocated by the secondary base station.

[0221] This embodiment may include this step or not include this step.

[0222] If step 802 is a SeNB modification request, this step is a SeNB modification request confirmation.

[0223] If the configuration of the bearer on the SeNB is modified, the SeNB sends the reconfiguration information of the air interface to the target master base station through the SCG configuration response including the RRC container (RRC container from the SeNB).

[0224] The message may also include indication information that the SeNB has retained the UE context. Retaining the UE context here does not exclude the possibility of updating the UE context information. When the SeNB receives the SCG configuration request message, the behavior of the SeNB may be different. For example, for the Rel-13 SeNB, the SeNB retains the UE context, updates some information, or updates the configuration information of the bearer. For the Rel-12 SeNB, the SeNB may establish a new UE context and configure the bearer based on the information in the SCG configuration request message. If the SeNB retains the UE context, the SeNB includes indication information that the UE context has been retained in the SCG configuration response message.

[0225] Step 804: The target primary base station sends a handover request confirmation message to the source primary base station.

[0226] Corresponding to the method in which the target primary base station determines that the secondary base station remains unchanged, the message further includes information that the secondary base station remains unchanged.

[0227] The source primary base station may decide not to initiate a SeNB release process and / or a UE context release process according to the information that the secondary base station remains unchanged.

[0228] The target primary base station allocates the downlink TEID and transport layer address of the S1 interface (the interface between the target primary base station and the SGW) for the bearer switched to the target primary base station.

[0229] According to the information contained in the switching request message received from the source main base station in step 801, which includes which bearers are on SeNB and whether the bearers on SeNB are split bearers or SCG bearers, the target main base station knows which bearers of the UE are on SeNB and whether the bearers on SeNB are split bearers or SCG bearers. The target main base station allocates the downlink TEID and transport layer address of the interface between the target main base station and SGW for the split bearer. For SCG bearers, if the target main base station decides to keep the SeNB unchanged, the target main base station does not need to allocate downlink TEID and transport layer address for the bearer. If the target main base station decides to switch the bearer on the secondary base station to the target main base station, the target main base station allocates the downlink TEID and transport layer address of the S1 interface for the bearer.

[0230] For the bearer that is switched to the target primary base station and requires data forwarding, the target primary base station allocates a TEID and a transport layer address of the X2 interface for data forwarding.

[0231] The target primary base station includes the TEID and transport layer address allocated for each bearer of the UE in a handover request confirmation message and sends it to the source primary base station.

[0232] The target MeNB allocates air interface resources for the bearer switched to the target MeNB, and sends the air interface configuration to the source MeNB through the RRC container (RRC container from the target MeNB).

[0233] If the bearer on the secondary base station is reconfigured, the target primary base station sends the RRC container received from the secondary base station (RRC container from the SeNB) to the source primary base station.

[0234] Through step 801, the source main base station lets the target main base station know which bearers of the UE are on the SeNB, and whether the bearers on the SeNB are split bearers or SCG bearers. The target main base station keeps the bearers on the SeNB unchanged according to its own decision, or informs the target main base station that the SeNB bearers will not be switched after the source main base station makes a decision. Thus, the target main base station knows which bearers are on the SeNB, and the target main base station correctly configures resources for different bearers of the UE, thereby solving the second and third problems raised by the present invention.

[0235] If the destination main base station receives the indication information that the UE context is retained from the secondary base station, the destination main base station sends the information to the source main base station. The destination main base station sends the indication information that the UE context is retained to the source main base station through the switching request confirmation. The source main base station decides whether to trigger the release of the UE context on the SeNB based on the received information. For example, if the source main base station receives the indication information that the UE context is retained, the source main base station may not initiate the SeNB release process and / or the UE context release process. If the source main base station does not receive the indication information that the UE context is retained and / or the information that the secondary base station remains unchanged, the source main base station may initiate the SeNB release process and / or the UE context release process.

[0236] Step 805: The source master base station sends an RRC reconfiguration message to the UE.

[0237] If the SeNB is not switched, the source master base station sends an RRC reconfiguration message to the UE, and the message does not contain information indicating that the UE deletes the SCG. In the case where the SeNB is not switched, the source master base station can also modify the configuration of the SCG based on the information received from the target master base station. The source master base station sends the RRC container from the SeNB received from the target master base station to the UE. At the same time, the RRC container from the target master base station received from the target master base station is sent to the UE. The former contains the reconfiguration information of the bearer on the SeNB, and the latter contains the configuration information of the bearer switched to the target MeNB.

[0238] If the SeNB is switched, the source master base station instructs the UE to delete the SCG while reconfiguring the MCG, and at the same time establishes the bearer on the source SCG on the target master base station.

[0239] Step 806: The source master base station sends the sequence number SN status to the destination master base station.

[0240] The source master base station can start data forwarding.

[0241] In the present invention, there is no absolute order between step 805 and step 806, that is, the source master base station may first send the sequence status to the target master base station and forward the data, and then send the RRC reconfiguration request message to the UE.

[0242] Steps 807 to 809 are the same as steps 705 to 707 and will not be repeated here.

[0243] Step 810: The target primary base station sends a UE configuration completion message to the secondary base station. The message includes the MeNB UE X2AP ID between the target primary base station and the secondary base station allocated by the target primary base station to the UE.

[0244] The message also includes the SeNB X2AP ID between the secondary base station and the target primary base station allocated by the secondary base station.

[0245] For a split bearer, the message further includes a bearer identifier ERAB ID and a TEID and a transport layer address allocated by the destination primary base station to each bearer.

[0246] In the case of SGW reselection, corresponding to the SCG bearer, the message also includes the SCG bearer identifier ERAB ID and the uplink TEID and transport layer address allocated by the new SGW.

[0247] The SeNB saves the information received from the target master base station and deletes the relevant information of the source master base station.

[0248] Optionally, the SeNB may also send a UE configuration completion confirmation message to the target primary base station.

[0249] The destination primary base station can obtain the X2 interface downlink TEID and transport layer address allocated by the secondary base station for the split bearer in two ways:

[0250] Method 1: In step 801, the source primary base station informs the target primary base station of the secondary base station of the X2 interface downlink TEID and transport layer address allocated for the split bearer.

[0251] Method 2: Through the UE configuration completion confirmation message, the secondary base station sends the X2 interface downlink TEID and transport layer address allocated for the split bearer to the target primary base station.

[0252] Through this embodiment, various problems in the handover process between different MeNBs can be solved, so that the solution of keeping the SeNB from switching when switching between different MeNBs is feasible.

[0253] Embodiment three:

[0254] The signaling flow chart of the third embodiment of the present invention is as follows: Fig. 9 As shown. Figures 3 to 6 Methods 1 to 4 of the present invention have respectively described in detail how to decide whether to keep the secondary base station. Therefore, this embodiment will not describe in detail how to decide whether to keep the secondary base station. This embodiment focuses on how to solve problems 2 to 6 proposed by the present invention. Fig. 9 The process shown includes the steps:

[0255] Step 901: The source master base station sends a handover request to the target master base station. This step is the same as step 303 and will not be described again.

[0256] In the case where there is no change in SeNB during handover between different MeNBs, the source SeNB is also the target SeNB. Therefore, the source SeNB, the target SeNB and the SeNB refer to the same base station, that is, the second base station that allocates resources to the UE on the air interface in addition to the MeNB that allocates air interface resources to the UE before and after the handover. Step 902: The target master base station sends an SCG configuration request to the secondary base station. This step is the same as step 802 and will not be repeated here.

[0257] Step 903: The secondary base station sends an SCG configuration response message to the target primary base station.

[0258] The message may also include the SeNB X2AP ID between the secondary base station and the target primary base station allocated by the secondary base station.

[0259] The secondary base station reallocates TEID and / or transport layer address for the bearer on the secondary base station, that is, allocates a new TEID and / or transport layer address, releases the original TEID and / or transport layer address, and sends the TEID and / or transport layer address corresponding to each ERAB ID to the target primary base station through the SCG configuration response message. The reallocation of TEID and / or transport layer address may be only for the SCG bearer on the secondary base station.

[0260] If step 802 is a SeNB modification request, this step is a SeNB modification request confirmation.

[0261] If the configuration of the bearer on the SeNB is modified, the SeNB sends the reconfiguration information of the air interface to the target master base station by including the RRC container (RRC container from the SeNB) in the SCG configuration response.

[0262] The message may also include indication information that the SeNB has retained the UE context. Retaining the UE context here does not exclude the possibility of updating the UE context information. When the SeNB receives the SCG configuration request message, the behavior of the SeNB may be different. For example, for the Rel-13 SeNB, the SeNB retains the UE context, updates some information, or updates the configuration information of the bearer. For the Rel-12 SeNB, the SeNB may establish a new UE context and configure the bearer based on the information in the SCG configuration request message. If the SeNB retains the UE context, the SeNB includes indication information that the UE context has been retained in the SCG configuration response message.

[0263] Step 904: The target primary base station sends a handover request confirmation message to the source primary base station.

[0264] Corresponding to the method in which the target primary base station determines that the secondary base station remains unchanged, the message further includes information that the secondary base station remains unchanged.

[0265] The source primary base station may decide not to initiate a SeNB release process and / or a UE context release process according to the information that the secondary base station remains unchanged.

[0266] The target primary base station allocates the downlink TEID and transport layer address of the S1 interface (the interface between the target primary base station and the SGW) for the bearer switched to the target primary base station.

[0267] According to the information contained in the switching request message received from the source main base station in step 901, which bearers are on SeNB and whether the bearers on SeNB are split bearers or SCG bearers, the target main base station knows which bearers of the UE are on SeNB and whether the bearers on SeNB are split bearers or SCG bearers. The target main base station allocates the downlink TEID and transport layer address of the interface between the target main base station and SGW for the split bearer. For the SCG bearer, if the target main base station decides to keep the SeNB unchanged, the target main base station does not need to allocate the downlink TEID and transport layer address for the bearer, and the target main base station sends the TEID and / or transport layer address reallocated by the secondary base station received from the secondary base station in step 903 to the source main base station. If the target main base station decides to switch the bearer on the secondary base station to the target main base station, the target main base station allocates the downlink TEID and transport layer address of the S1 interface for the bearer.

[0268] For the bearer that is switched to the target primary base station and requires data forwarding, the target primary base station allocates a TEID and a transport layer address of the X2 interface for data forwarding.

[0269] The target master base station includes the TEID and transport layer address allocated for each bearer of the UE in the handover request confirmation message and sends it to the source master base station. For SCG bearers, the target master base station includes the TEID and / or transport layer address reallocated by the secondary base station in the handover request confirmation message and sends it to the source master base station.

[0270] The target MeNB allocates air interface resources for the bearer switched to the target MeNB, and sends the air interface configuration to the source MeNB through the RRC container (RRC container from the target MeNB).

[0271] If the bearer on the secondary base station is reconfigured, the target primary base station sends the RRC container received from the secondary base station (RRC container from the SeNB) to the source primary base station.

[0272] Through step 901, the source main base station lets the target main base station know which bearers of the UE are on the SeNB, and whether the bearers on the SeNB are split bearers or SCG bearers. The target main base station keeps the bearers on the SeNB unchanged according to its own decision, or informs the target main base station that the SeNB bearers will not be switched after the source main base station makes a decision. Thus, the target main base station knows which bearers are on the SeNB, and the target main base station correctly configures resources for different bearers of the UE, thereby solving the second and third problems raised by the present invention.

[0273] If the destination main base station receives the indication information that the UE context is retained from the secondary base station, the destination main base station sends the information to the source main base station. The destination main base station sends the indication information that the UE context is retained to the source main base station through the switching request confirmation. The source main base station decides whether to trigger the release of the UE context on the SeNB based on the received information. For example, if the source main base station receives the indication information that the UE context is retained, the source main base station may not initiate the SeNB release process and / or the UE context release process. If the source main base station does not receive the indication information that the UE context is retained and / or the information that the secondary base station remains unchanged, the source main base station may initiate the SeNB release process and / or the UE context release process.

[0274] Steps 905 to 907 are the same as steps 805 to 807 and will not be repeated here.

[0275] Step 908: The destination master base station sends a path switching request message to the MME. The message includes information about the bearer switched from the source master base station to the destination master base station. For the SCG bearer, it also includes information about the bearer that remains unswitched in the SeNB, because the downlink TEID and / or transport layer address of the SCG bearer that remains unswitched in the SeNB is reallocated by the SeNB.

[0276] Step 909: The MME sends a path switching request confirmation message to the target master base station.

[0277] Step 910 is the same as step 810 and will not be described again here.

[0278] Through this embodiment, various problems in the handover process between different MeNBs can be solved, so that the solution of keeping the SeNB from switching when switching between different MeNBs is feasible.

[0279] Corresponding to the above method, the present application also provides a device for switching between different master base stations in a small cell system, such as Fig.10 As shown, the device includes: a decision module and a switching module, wherein:

[0280] The decision module is used to decide whether to keep the secondary base station during switching;

[0281] The switching module is used to trigger different switching processes according to the decision result of whether to keep the secondary base station.

[0282] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for switching from a source primary base station to a destination primary base station in a wireless communication system, the method include: The secondary base station receives a first message from the target primary base station, where the first message includes: an identification ID of a user equipment UE allocated by the secondary base station and an ID of the UE allocated by the target primary base station; The secondary base station sends a second message to the target primary base station in response to the first message, where the second message includes information about secondary cell configuration; and The secondary base station receives a third message from the target primary base station indicating that the reconfiguration of the radio resource control RRC connection associated with the UE during the handover process is completed, The first message is sent by the target primary base station to the secondary base station when the secondary base station is decided to be retained by the target primary base station. The UE ID allocated by the secondary base station is the application protocol ID of the UE on the interface between the source primary base station and the secondary base station. The UE ID allocated by the target primary base station is the application protocol ID of the UE on the interface between the target primary base station and the secondary base station, and The ID of the UE allocated at the secondary base station and the ID of the secondary base station are included in the handover request message received by the target primary base station from the source primary base station.

2. The method according to claim 1, in, The information about the secondary cell configuration is included in the RRC configuration information.

3. The method according to claim 1, in, The third message includes: the ID of the UE allocated by the secondary base station.

4. The method according to claim 3, in, The UE ID allocated by the secondary base station includes the secondary base station UE X2AP ID allocated by the secondary base station.

5. The method according to claim 1, in, The first message further includes: information indicating a key associated with security of the secondary base station, and a request for configuration of a secondary cell group SCG related to the secondary base station.

6. A secondary base station in a process of switching from a source primary base station to a target primary base station in a wireless communication system, the secondary base station include: Transceiver; as well as At least one processor, coupled to the transceiver, configured to: Receiving a first message from a target primary base station, where the first message includes: an identification ID of a user equipment UE allocated by the secondary base station and an ID of the UE allocated by the target primary base station; In response to the first message, sending a second message to a target primary base station, wherein the second message includes information about secondary cell configuration; and receiving, from the target primary base station, a third message indicating completion of reconfiguration of a radio resource control (RRC) connection associated with the UE during the handover process, The first message is sent by the target primary base station to the secondary base station when the secondary base station is decided to be retained by the target primary base station. The UE ID allocated by the secondary base station is the application protocol ID of the UE on the interface between the source primary base station and the secondary base station. The UE ID allocated by the target primary base station is the application protocol ID of the UE on the interface between the target primary base station and the secondary base station, and The ID of the UE allocated at the secondary base station and the ID of the secondary base station are included in the handover request message received by the target primary base station from the source primary base station.

7. The secondary base station according to claim 6, in, The information about the secondary cell configuration is included in the RRC configuration information.

8. The secondary base station according to claim 6, in, The third message includes: the ID of the UE allocated by the secondary base station.

9. The secondary base station according to claim 8, in, The UE ID allocated by the secondary base station includes the secondary base station UE X2AP ID allocated by the secondary base station.

10. The secondary base station according to claim 6, in, The first message further includes: information indicating a key associated with security of the secondary base station, and a request for configuration of a secondary cell group SCG related to the secondary base station.

11. A method for switching from a source primary base station to a destination primary base station in a wireless communication system, the method include: The target primary base station sends a first message to the secondary base station, where the first message includes: an ID of the UE allocated in the secondary base station and an ID of the UE allocated in the target primary base station; The target primary base station receives a second message in response to the first message from the secondary base station, where the second message includes information about secondary cell configuration; and The target primary base station sends a third message to the secondary base station indicating that the reconfiguration of the radio resource control RRC connection associated with the UE during the handover process is completed, The first message is sent by the target primary base station to the secondary base station when the target primary base station decides to keep the secondary base station. The UE ID allocated by the secondary base station is the application protocol ID of the UE on the interface between the source primary base station and the secondary base station. The UE ID allocated by the target primary base station is the application protocol ID of the UE on the interface between the target primary base station and the secondary base station, and The target master base station receives a handover request message including the ID of the UE allocated at the secondary base station and the ID of the secondary base station from the source master base station.

12. The method according to claim 11, in, The information about the secondary cell configuration is included in the RRC configuration information.

13. The method according to claim 11, in, The third message includes: the ID of the UE allocated by the secondary base station.

14. The method according to claim 13, in, The UE ID allocated by the secondary base station includes the secondary base station UE X2AP ID allocated by the secondary base station.

15. The method according to claim 11, in, The first message further includes: information indicating a key associated with security of the secondary base station, and a request for configuration of a secondary cell group SCG related to the secondary base station.

16. A target master base station in a process of switching from a source master base station to a target master base station in a wireless communication system include: Transceiver; as well as At least one processor, coupled to the transceiver, configured to: Sending a first message to the secondary base station, where the first message includes: an ID of the UE allocated by the secondary base station and an ID of the UE allocated by the target primary base station; receiving, from the secondary base station, a second message in response to the first message, the second message including information about secondary cell configuration; and sending a third message to the secondary base station indicating that the reconfiguration of the radio resource control (RRC) connection associated with the UE during the handover process is completed, The first message is sent by the target primary base station to the secondary base station when the target primary base station decides to keep the secondary base station. The UE ID allocated by the secondary base station is the application protocol ID of the UE on the interface between the source primary base station and the secondary base station. The UE ID allocated by the target primary base station is the application protocol ID of the UE on the interface between the target primary base station and the secondary base station, and The at least one processor is further configured to receive, from the source primary base station, a handover request message including an ID of the UE allocated at the secondary base station and an ID of the secondary base station.

17. The target master base station according to claim 16, in, The information about the secondary cell configuration is included in the RRC configuration information.

18. The target master base station according to claim 16, in, The third message includes: the ID of the UE allocated by the secondary base station.

19. The target master base station according to claim 18, in, The UE ID allocated by the secondary base station includes the secondary base station UE X2AP ID allocated by the secondary base station.

20. The target master base station according to claim 16, in, The first message further includes: information indicating a key associated with security of the secondary base station, and a request for configuration of a secondary cell group SCG related to the secondary base station.

21. A method for switching a source master node MN to a destination MN, the method include: The target MN receives a handover request message from the source MN, wherein the handover request message includes an identification ID of the user equipment UE allocated at the SN and an ID of the SN; The destination MN sends a configuration request message including the ID of the UE allocated at the SN to the SN; The destination MN receives a configuration request confirmation message from the SN; The target MN sends a handover request confirmation message to the source MN, wherein the handover request confirmation message includes information indicating that the UE context in the SN is retained; The destination MN sends a configuration completion message to the SN; The destination MN sends a path switch request message to the mobility management entity; and The destination MN receives a path switch request confirmation message from the mobility management entity; The UE ID allocated at the SN is the application protocol ID of the UE on the interface between the source MN and the SN.

22. The method according to claim 21, in, The configuration completion message includes: The ID of the UE assigned at the destination MN, and The ID of the UE assigned at the SN; The UE ID allocated at the target MN is the application protocol ID of the UE on the interface between the target MN and the SN.

23. The method according to claim 21, in, The configuration request message also includes the ID of the UE allocated at the target MN and a key related to security; The UE ID allocated at the target MN is the application protocol ID of the UE on the interface between the target MN and the SN.

24. The method according to claim 21, in, The handover request message includes an ID of a mobility management entity.

25. The method according to claim 21, in, Whether to retain the UE context in the SN is determined by the target MN.

26. The method according to claim 21, in, The configuration request message also includes the ID of the UE allocated at the target MN.

27. A master node MN, wherein the MN include: Transceiver; as well as At least one processor, coupled to the transceiver, configured to: receiving a handover request message from the source MN, wherein the handover request message includes an identification ID of the user equipment UE allocated at the SN and an ID of the SN; sending a configuration request message including the ID of the UE allocated at the SN to the SN; receiving a configuration request confirmation message from the SN; Sending a handover request confirmation message to the source MN, wherein the handover request confirmation message includes information indicating that the UE context in the SN is retained; Send a configuration completion message to the SN; sending a path switch request message to a mobility management entity; and receiving a path switch request confirm message from a mobility management entity; The UE ID allocated at the SN is the application protocol ID of the UE on the interface between the source MN and the SN.

28. The MN according to claim 27, in, The configuration completion message includes: The ID of the UE assigned at the destination MN, and The ID of the UE assigned at the SN; The UE ID allocated at the target MN is the application protocol ID of the UE on the interface between the target MN and the SN.

29. The MN according to claim 27, in, The configuration request message also includes the ID of the UE allocated at the target MN and a key related to security; The UE ID allocated at the target MN is the application protocol ID of the UE on the interface between the target MN and the SN.

30. The MN of claim 27, in, The handover request message includes an ID of a mobility management entity.

31. The MN of claim 27, in, Whether to retain the UE context in the SN is determined by the target MN.

32. The MN of claim 27, in, The configuration request message also includes the ID of the UE allocated at the target MN.

33. A method for switching from a source master node MN to a destination MN, the method include: The source MN sends a handover request message to the target MN, wherein the handover request message includes an identification ID of the user equipment UE allocated at the SN and an ID of the SN; and The source MN receives a handover request confirmation message from the target MN, wherein the handover request confirmation message includes information indicating that the UE context in the SN is retained; The UE ID allocated at the SN is the application protocol ID of the UE on the interface between the source MN and the SN.

34. The method of claim 33, in, The handover request message includes an ID of a mobility management entity.

35. The method of claim 33, in, Whether to retain the UE context in the SN is determined by the target MN.

36. The method of claim 33, in, The method further includes sending a radio resource control (RRC) reconfiguration message to the UE for handover to the target MN.

37. A master node MN, wherein the MN include: Transceiver; as well as At least one processor, coupled to the transceiver, configured to: Sending a handover request message to the target MN, wherein the handover request message includes an identification ID of the user equipment UE allocated at the SN and an ID of the SN; and receiving a handover request confirmation message from the target MN, which includes information indicating that the UE context in the SN is retained; The UE ID allocated at the SN is the application protocol ID of the UE on the interface between the source MN and the SN.

38. The MN of claim 37, in, The handover request message includes an ID of a mobility management entity.

39. The MN of claim 37, in, Whether to retain the UE context in the SN is determined by the target MN.

40. The MN of claim 37, in, The at least one processor is further configured to send a radio resource control (RRC) reconfiguration message to the UE for handover to a target MN.

41. A method for switching from a source master node MN to a destination MN, the method include: The SN receives, from the target MN, a configuration request message including an ID of the user equipment UE allocated at the SN; The SN sends a configuration request confirmation message to the target MN; as well as The SN receives a configuration completion message from the target MN; The ID of the UE allocated at the SN is the application protocol ID of the UE on the interface between the source MN and the SN. The handover request message is sent from the source MN to the target MN, and the handover request message includes the ID of the UE allocated at the SN and the ID of the SN. The handover request confirmation message is sent by the target MN to the source MN based on the configuration request confirmation message, wherein the handover request confirmation message includes information indicating that the UE context in the SN is retained.

42. The method of claim 41, in, The configuration completion message includes: The ID of the UE assigned at the destination MN, and The ID of the UE assigned at the SN; The UE ID allocated at the target MN is the application protocol ID of the UE on the interface between the target MN and the SN.

43. The method of claim 41, in, The configuration request message also includes the ID of the UE allocated at the target MN and a key related to security; The UE ID allocated at the target MN is the application protocol ID of the UE on the interface between the target MN and the SN.

44. A secondary node SN, the SN include: Transceiver; as well as At least one processor, coupled to the transceiver, configured to: receiving, from the destination master node MN, a configuration request message including an ID of the user equipment UE allocated at the SN; Send a configuration request confirmation message to the target MN; as well as Receive a configuration completion message from the destination MN; The ID of the UE allocated at the SN is the application protocol ID of the UE on the interface between the source MN and the SN. The handover request message is sent from the source MN to the target MN, and the handover request message includes the ID of the UE allocated at the SN and the ID of the SN. The handover request confirmation message is sent by the target MN to the source MN based on the configuration request confirmation message, wherein the handover request confirmation message includes information indicating that the UE context in the SN is retained.

45. The SN according to claim 44, in, The configuration completion message includes: The ID of the UE assigned at the destination MN, and The ID of the UE assigned at the SN; The UE ID allocated at the target MN is the application protocol ID of the UE on the interface between the target MN and the SN.

46. ​​The SN according to claim 44, in, The configuration request message also includes the ID of the UE allocated at the target MN and a key related to security; The UE ID allocated at the target MN is the application protocol ID of the UE on the interface between the target MN and the SN.

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