[0001]The present disclosure relates to wireless communication networks, in particular to Dual Connectivity (DC).
Background technique
[0002]3GPP Release 12 defines a Dual Connectivity (DC) (e.g., see Non-Patent Documents 1 and 2). DC is similar to Coordinated Multipoint introduced in 3GPP Release 11 (CoMP) different. In particular, in DC, the different carrier frequencies out with macrocells and small cells (picocells) is used, the wireless terminal (User Equipment (UE)) to perform a two Medium Access Control (MAC) entity (i.e., UE utilizes radio resources provided by two independent scheduler of the master base station (master eNodeB (MeNB)) and the secondary base station (secondary eNB (SeNB))), and the UE simultaneous use of at least two UL carrier there is a need to support.
[0003]
　In DC of 3GPP Release 12, UE is connected to one MeNB and one SeNB. UE that is set to DC (DC UE) uses at least two Radio Link Control (RLC) entity and two MAC entities for data flow in each of the MeNB and SeNB. MeNB at DC is the eNB that terminates S1-MME for DC UE. SeNB in ​​DC provide additional radio resources to the DC UE. 1 or more serving cells is provided to the UE by the MeNB is called Master Cell Group (MCG), one or more serving cells is provided to the UE by the SeNB called Secondary Cell Group (SCG). MCG is 1 or more serving cell associated with the MeNB, including Primary Cell (PCell) optional one or more Secondary Cells (SCells). SCG is 1 or more serving cells associated with SeNB, including Primary Secondary Cell (PSCell) optional one or more Secondary Cells (SCells). In DC of 3GPP Release 12 is PSCell is a special cell in the SCG, different from the conventional SCell in that the uplink for UE (PUCCH) is set.
[0004]
　The control plane architecture for DC, the S1-MME only one exists for each one DC UE. The S1-MME is set between the MeNB and Mobility Management Entity (MME), MeNB terminates the S1-MME. Signaling between the MeNB and SeNB about DC UE is performed using the signaling interface between eNB (ie, X2-C).
[0005]
　Two user plane architecture for DC is allowed. In one architecture, S1-U is terminated only at MeNB, the user plane data are transferred using the X2-U to SeNB from MeNB. In another architecture, it is possible to S1-U is terminated even SeNB.
[0006]
　Thus, three kinds of radio bearers for DC, i.e. MCG bearer split bearer, and SCG bearer is defined. For the MCG bearer, MeNB is terminated S1-U connection with the Serving Gateway (S-GW), the wireless protocol is arranged only MeNB to use the MeNB resources. Therefore, SeNB is not involved in the transfer of user plane data in the Uu interface regarding MCG bearer.
[0007]
　With respect to the split bearer, MeNB is terminated S1-U connection to the S-GW, Packet Data Convergence Protocol (PDCP) data (PDCP Protocol Data Unit (PDCP PDU)) is transferred between the MeNB and SeNB. Thus, both the MeNB and SeNB the transfer of user plane data in the Uu interface regarding split bearers are involved.
[0008]
　For the SeNB bearer, SeNB is terminated S1-U connection to the S-GW, the wireless protocol is arranged only SeNB to use the SeNB resources. Therefore, MeNB is not involved in the transfer of user plane data in the Uu interface related SCG bearer.
[0009]
　Some whole procedure for DC is defined in Non-Patent Document 1 (e.g., see Non-Patent Document 1 section 10.1.2.8).
[0010]
SeNB Addition, steps (procedure):
　The procedure is initiated by the MeNB to establish a UE context in the SeNB. The procedure is used to add the first cell in the least SCG (ie, PSCell). In this case, at least one bearer (split bearer or SCG bearer) is set always in the SCG.
[0011]
SeNB Modification Procedure:
　The procedure is used to make changes in SCG in the SeNB, initiated by MeNB or SeNB. The procedure is used in the same SeNB, for then-or releasing establish and modify the bearer context, to send a bearer context to SeNB (or from SeNB), or to modify other properties of the UE context It is. MeNB is, SCG SCells, using the SCG bearer (s), and split the procedures to add or release the SCG portion bearer (s). MeNB further using the procedure in order to trigger PSCell changes with PSCell release.
[0012]
SeNB Release Procedure:
　The procedure is initiated by the MeNB or SeNB, is used to initiate the release of the UE context in SeNB.
[0013]
Intra-MeNB Change Procedure:
　The procedure is used in order to perform a handover in the same MeNB while maintaining the SCG in the same SeNB (keep).
[0014]
SeNB Change Procedure:
　The procedure is used to change the SCG between SeNB (Inter-SeNB) (Change ). The procedure is initiated by MeNB, transfers UE context from the source SeNB the target SeNB, is used to change from the SeNB that the SCG settings in UE (SCG configuration) to another SeNB. The procedure is basically realized by the combination of the SeNB Addition, procedures and SeNB Release procedure.
[0015]
MeNB-to eNB Change Procedure:
　The procedure is initiated by the MeNB. The procedure is used to transfer context data from the source MeNB and source SeNB to the target eNB.
[0016]
　Transfer of signaling and user plane data between the MeNB and SeNB in DC is performed in the X2 interface. Accordingly, X2 procedure for DC below are defined (e.g., see Section 8.6 and Section 9.1.3 of Non-Patent Document 2). Some of the whole procedure described above utilizes an X2 procedures for these DC.
· SeNB Addition Preparation procedure
· MeNB initiated SeNB Modification Preparation procedure
· SeNB initiated SeNB Modification procedure
· MeNB initiated SeNB Release procedure
· SeNB initiated SeNB Release procedure
[0017]
　In 3GPP Release 12, if the UE handover from the MeNB to another eNB (Target eNB), MeNB to eNB Change procedure described above is used. In this procedure, SeNB (SCG) is completely released (release). Therefore, if it is required SCG after the handover, a target eNB needs to perform again SeNB Addition, steps after completion of the handover. That is, the MeNB-to eNB Change procedure, in addition to the normal handover procedure, the same signaling and SeNB Change procedure, i.e. requiring a combination of SeNB Release procedure SeNB Addition, procedures. Further, with respect to SCG bearer, data forwarding to the source MeNB is made from SeNB, it is necessary to further data forwarding from the source MeNB to the target eNB is performed.
[0018]
　In 3GPP Release 13, it is considered to support the MeNB handover involving inter MeNB (Inter-MeNB) handover, or the SeNB Addition, steps from sources MeNB without SeNB change (change) the target MeNB. By these procedures are supported, may SeNB Addition, procedures for the target eNB sets anew SCG to SeNB becomes unnecessary. Further, the data forwarding related SCG bearer to the source MeNB, and data forwarding related to the SCG bearer from the source MeNB to the target eNB may become unnecessary from SeNB.
[0019]
　Incidentally, Patent Document 1 also wireless terminal discloses several procedures for handover to the second master base station from the first master base station during Dual Connectivity. In one procedure disclosed in Patent Document 1, when the wireless terminal performs a handover from the first master base station to the second master base station during Dual Connectivity, first master base station to the secondary base station requests to suspend service provision in SCell, secondary base station holds the communication status information in SCell with service interruption provided in SCell. Furthermore, in this procedure, the second master base station transmits an indication of communication restart the secondary base station after the handover, the communication condition at the SCell a secondary base station in response to the reception of the instruction is held in the secondary base station restart the service in the SCell based on the information. Communication status information in the SCell, for example, (a) transmission status or receiving status of the user data (User Plane (U-plane)), (b) the service information, (c) bearer information, and (d) radio resource configuration information comprising at least one of.
CITATION
Patent Literature
[0020]
Patent Document 1: International Publication No. WO 2014/103145
Non-Patent Document
[0021]
非特許文献1 : 3GPP TS 36.300 V12.6.0 (2015-06), “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 (Release 12)”, June 2015
非特許文献2 : 3GPP TS 36.423 V12.6.0 (2015-06), “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access Network (E-UTRAN); X2 application protocol (X2AP) (Release 12)”, June 2015
Summary of the Invention
Problems that the Invention is to Solve
[0022]
　MeNB change from first MeNB without SeNB changes to a second MeNB (or MeNB handover), or MeNB changes with SeNB Addition, (or MeNB handover), the existing related DC specified in 3GPP Release 12 it is realized by using X2 procedures and X2 messages that may be preferred. Furthermore, if in these MeNB changes, while maintaining the SeNB a part of the bearer of the plurality of bearers already set to SeNB for Dual Connectivity (keep), transferring the remaining bearer second MeNB or it may be preferable which can control that releases.
[0023]
　One objective to be achieved is the embodiment disclosed herein, the secondary base station while providing a Dual Connectivity to the wireless terminal (UE) (SeNB) master base station without the release of ( MeNB) change procedure or a master base station with the additional secondary base station (SeNB) a (MeNB) change procedure, using the existing inter-base station interface (X2 in interface) procedures and inter-base station signaling message (X2 message) It contributes to making the apparatus is to provide a method, and a program. Incidentally, this objective should embodiment disclosed herein is noted that only one of a plurality of objects to be achieved. Other objects or problems and novel features will become apparent from the description, or the accompanying drawings of this specification.
Means for Solving the Problems
[0024]
　In a first aspect, the secondary base station includes at least one processor coupled to at least one wireless transceiver, and the at least one wireless transceiver. Wherein the at least one processor, SeNB addition request message from the second master base station while providing secondary cell group for dual connectivity in conjunction with the first master base station (SCG) to the wireless terminal configured to receive. The SeNB addition request message indicates whether each of the at least one bearer is already set to the secondary base station for the dual connectivity is maintained by said secondary base station.
[0025]
　In a second aspect, the method of the secondary base station,
a while (a) providing a secondary cell group for dual connectivity in conjunction with the first master base station (SCG) to the wireless terminal 2 to the receive SeNB addition request message from the master base station maintenance, the SeNB addition request message, said each of the at least one bearer to the secondary base station has already been set for the dual connectivity is by the secondary base station indicating whether the, and
(b) in response to reception of the SeNB addition request message, even if one or more of the first bearer is maintained by the secondary base station not maintained by the secondary base station It is distinguished from good one or a plurality of the second bearer,
including.
[0026]
　In a third aspect, the second master base station includes at least one processor coupled to at least one wireless transceiver, and the at least one wireless transceiver. Wherein the at least one processor is said SeNB addition request message while the secondary base station is providing the secondary cell group (SCG) for cooperation with dual connectivity with the first master base station to the radio terminal secondary configured to transmit to the base station. The SeNB addition request message indicates whether each of the at least one bearer is already set to the secondary base station for the dual connectivity is maintained by said secondary base station.
[0027]
　In a fourth aspect, the method of the second master base station provides a secondary cell group (SCG) for dual connectivity to the wireless terminal secondary base station in conjunction with the first master base station It comprises transmitting the SeNB addition request message to the secondary base station during. The SeNB addition request message indicates whether each of the at least one bearer is already set to the secondary base station for the dual connectivity is maintained by said secondary base station.
[0028]
　In a fifth aspect, the first master base station includes at least one processor coupled to at least one wireless transceiver, and the at least one wireless transceiver. Wherein the at least one processor, while the secondary base station is providing the secondary cell group (SCG) for dual connectivity in conjunction with the first master base station to the radio terminal, the handover of the radio terminal It sends a request to the second master base station, configured to receive a response message to the handover request from the second master base station. Whether the response message is transferred to the expectorated or the second master base station maintaining said each of the at least one bearer is already set to the secondary base station by the secondary base station for the dual connectivity show.
[0029]
　In a sixth aspect, the method of the first master base station,
the (a) a secondary cell group for dual connectivity secondary base station in conjunction with the first master base station (SCG) to the wireless terminal while providing said sending a handover request of the wireless terminal to the second master base station, and
(b) a response message to the handover request that is received from the second master base station, the response message indicates the one each of the at least one bearer is already set to the secondary base station is transferred to the expectorated or the second master base station maintained by the secondary base station for the dual connectivity,
including.
[0030]
　In a seventh aspect, the program, when loaded into a computer, comprising a second above, fourth, or sixth instructions for causing the method to a computer in accordance with aspects of the (software code).
[0031]
　In an eighth aspect, the wireless terminal includes the first master base station, the second master base station, and at least one radio transceiver for communicating with the secondary base station, and at least one processor. The first master base station, the second master base station, and the secondary base station, the secondary cell group for dual connectivity the secondary base station in conjunction with the first master base station (SCG ) when the offering to the radio terminal, and is configured to perform a procedure for changing the master base station of the dual connectivity from the first master base station to the second master base station. Configuration wherein the at least one processor, during the procedure, to receive the SCG settings for the second master cell group on the master base station (MCG) setting and the secondary base station from the first master base station It is. Maintaining the at least one processor, in response to receiving the MCG setting and the SCG setting, wherein each of the at least one bearer to the secondary base station has already been set for the dual connectivity is by the secondary base station It is configured to recognize the transferred to whether or the second master base station is. Wherein the at least one processor is further at least one comprising said bearer while maintaining the connection to the SCG of secondary base station, the dual connectivity the master base station from the first master base station the second of It is configured to change the master base station.
Effect of the invention
[0032]
　According to the embodiments described above, additional a Dual Connectivity wireless terminal master base station without releasing the secondary base station (SeNB) while offering the (UE) (MeNB) change procedure or secondary base station (SeNB) the master base station (MeNB) change procedure involving contributes to be performed using the existing inter-base station interface (X2 in interface) procedures and inter-base station signaling message (X2 message) apparatus, a method, and a program It can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033]
It is a diagram illustrating a configuration example of a wireless communication network according to FIG. 1 with some embodiments.
Is a sequence diagram showing an example of the overall procedure of MeNB changes according to FIG. 2A] Some embodiments (MeNB handover).
It is a sequence diagram showing an example of the overall procedure of MeNB changes according to FIG. 2B] Some embodiments (MeNB handover).
3 is a sequence diagram for explaining the operation of the T-MeNB and SeNB according to the first embodiment.
4 is a flowchart showing an example of the operation of the SeNB according to the first embodiment.
It is a diagram showing an example of the change in [Figure 5A] SeNB Addition Request message (modification).
Is a diagram showing an example of the change in [Figure 5B] SeNB Addition Request message (modification).
6 is a sequence diagram for explaining the operation of the T-MeNB and S-MeNB according to the second embodiment.
7 is a flowchart showing an example of the operation of the T-MeNB according to the second embodiment.
8 is a diagram showing an example of the change of the Handover Request Acknowledge message (modification).
9 is a sequence diagram for explaining the operation of the S-MeNB and SeNB according to a third embodiment.
FIG. 10 is a flowchart showing an example of the operation of the S-MeNB according to the third embodiment.
Is a diagram showing an example of the change in [Figure 11A] SeNB Release Request message (modification).
It is a diagram showing an example of the change in [Figure 11B] SeNB Release Request message (modification).
Is a block diagram showing an exemplary configuration of a base station according to FIG. 12 with some embodiments.
13 is a block diagram showing a configuration example of a radio terminal according to some embodiments.
DESCRIPTION OF THE INVENTION
[0034]
　Hereinafter, specific embodiments will be described in detail with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same reference numerals, for clarity of description, repeated explanation is omitted as appropriate.
[0035]
　The following several embodiments shown in will be described an Evolved Packet System (EPS) that houses the LTE and SAE (System Architecture Evolution) as a main target. However, these embodiments are not intended to be limited to EPS, other mobile communication networks or systems, for example 3GPP UMTS, 3GPP2 CDMA2000 systems (1xRTT, HRPD (High Rate Packet Data)), global system for mobile communications ( GSM (TM)) / General packet radio service (GPRS) system, and may be applied to WiMAX systems.
[0036]
　Figure 1 shows a configuration example of a wireless communication network according to some embodiments. In the example of FIG. 1, a wireless communication network includes a base station (eNB) 1, base station (eNB) 2, a base station (eNB) 3, and the wireless terminal (UE) 4. eNB1 and eNB2 operate respectively as MeNB and SeNB for Dual Connectivity (DC) to UE4. UE4 is set to DC by MeNB1, simultaneously utilizing the SCG comprising a cell 21 provided by the MCG and SeNB2 including the cell 11 provided by MeNB1.
[0037]
　In some embodiments, as shown in FIG. 1, while the SeNB2 is providing SCG for DC in conjunction with eNB (MeNB) 1 to UE4, the MeNB of DC for UE4 eNB1 handling MeNB changes 101 to change eNB3 from. After MeNB changes, UE4 is set to DC by MeNB3, simultaneously utilizing the SCG comprising a cell 21 provided by the MCG and SeNB2 including the cell 31 provided by MeNB3. Such MeNB changes may also be referred to as MeNB handover. The referred to eNB1 is MeNB before MeNB change (MeNB handover) source MeNB (S-MeNB), the eNB3 a MeNB after MeNB changed (MeNB handover) is called a target MeNB (T-MeNB) below .
[0038]
　Each eNBs1 ~ 3 shown in FIG. 1 may be a Centralized Radio Access Network (C-RAN) Baseband Unit used in the architecture (BBU). In other words, each eNB shown in FIG. 1 may be a RAN node connected to one or more Remote Radio Head (RRH). In some implementations, each of eNBs1 ~ 3 as BBU is responsible for digital baseband signal processing control plane processing and user plane. Meanwhile, RRH is responsible for analog Radio Frequency (RF) signal processing (eg, frequency conversion and signal amplification). Incidentally, C-RAN may also be referred to as the Cloud RAN. Further, BBU may also be referred to as a Radio Equipment Controller (REC) or Data Unit (DU). The RRH, Radio Equipment (RE), Radio Unit (RU), or sometimes referred to as Remote Radio Unit (RRU).
[0039]
　2A and 2B, an example of the overall procedure of MeNB change according to some embodiments (MeNB handover) shows a (Step 200). Incidentally, as described later, MeNB handover procedure 200 encompasses a procedure corresponding to the SeNB Addition, the procedure of 3GPP Release 12 (steps 202 and 203). In other words, the procedure 200 is MeNB changed (MeNB handover) procedure with additional SeNB while offering Dual Connectivity to UE4. In other words, the procedure 200 is MeNB changed (MeNB handover) procedure without the release of SeNB2 while offering Dual Connectivity to UE4.
[0040]
　In step 201, S-MeNB1 requests MeNB handover of UE4 to T-MeNB3. Handover request message of step 201 may also be referred to as MeNB change request message.
[0041]
　In step 202, in response to receiving a handover request message in step 201, T-MeNB3 transmits SeNB add request (SeNB Addition, Request) message to SeNB2. SeNB additional request (SeNB Addition Request) message may be referred to as SCG additional request (SCG Addition Request) message. The SeNB Addition, Request message indicates the character of the radio access bearer (ie, E-UTRAN Radio Access Bearer (E-RAB)) (characteristics), for requesting allocation of the radio resources for a particular E-RAB to SeNB2 . Characteristics of E-RAB, for example, E-RAB identifier (E-RAB ID), and shows a bearer type (ie, SCG bearer or split bearer). Here, the bearer type is also referred to as a DRB type. The SeNB Addition, Request message further, information for SCG settings including MCG setting (MCG Configuration) and UE capability (UE capabilities) (SCG-ConfigInfo) may contain.
[0042]
　As described in detail in the following embodiments, SeNB Addition, Request message (step 202), a part of the bearer of the plurality of bearers configured to SeNB2 (ie, SCG bearer or split bearer or both) of maintained in SeNB2, it may instruct the SeNB2 that the remaining bearer is or released is transferred to the T-MeNB3.
[0043]
　SeNB2, in response to receipt of SeNB Addition, Request message from the T-MeNB3, radio resources and control plane (C-plane) resources was prepared, to prepare the transport network resources for SCG bearer. Then, SeNB2 transmits SCG configure (SCG-Config) encompassing response message (SeNB Addition Request Acknowledge) to the T-MeNB3 (step 203). SCG-Config, for example including PSCellToAddMod IE, may include RadioResourceConfigDedicatedSCG IE.
[0044]
　At step 204, T-MeNB3 transmits a response message indicating acceptance of the handover request (Handover Request Acknowledge) to the S-MeNB1. In step 205, in response to receiving the Handover Request Acknowledge message, S-MeNB1 transmits SeNB release request (SeNB Release Request) message to SeNB2. SeNB release request (SeNB Release Request) message may be referred to as SCG release request (SCG Release Request) message.
[0045]
　In step 206, S-MeNB1 requests PCell in MCG (eg, cell 11) radio resource control in the (Radio Resource Control (RRC)) reconfiguration of the connection (reconfiguration) to UE4. RRC Connection Reconfiguration message in step 206, the mobility control information on T-MeNB3 (Mobility Control Info) and MCG settings, and configuration information about SCG of SeNB2 (SCG Configuration, ie, scg-ConfigPartMCG (eg, scg-Counter), scg including the -ConfigPartSCG). Thus, UE4 is connected to SCG of SeNB2 (i.e., at least one bearer (SCG bearer or split bearer)) while maintaining the, the master base station of the DC switch from S-MeNB1 to T-MeNB3 Inter-eNB It recognizes that has been instructed to execute the Handover. Furthermore, among the SCG bearer, while retaining much, which it is possible to recognize whether the release. For example, UE4, upon receiving the RRC Connection Reconfiguration message, resets the MCG side MAC entity MAC of (MCG MAC) and SCG side entity (SCG MAC). Then, re-establish the PDCP entity (SCG PDCP) corresponding to SCG bearer holding of MCG side PDCP entity and (MCG PDCP) (case of SCG bearer only) SCG side (re-establish) to. Subsequently, the MCG side RLC entity (MCG RLC) and re-establish the SCG side of RLC entity (SCG RLC) corresponding to the SCG bearer the holding (re-establish).
[0046]
　In step 207 and 208, UE4, in order to synchronize the T-MeNB3, perform the random access procedure, notifying the completion of the RRC reconfiguration, including modification of the handover confirmation (confirm) and MCG setting and SCG set (or changed) the RRC Connection Reconfiguration Complete message to be transmitted to the T-MeNB3.
[0047]
　In step 209, UE4 according RRC Connection Reconfiguration message new SCG settings received in step 206 (including the Mobility Control InfoSCG), executes the random access procedure to synchronize with SeNB2.
[0048]
　In step 210, T-MeNB3 informs in response to the reception of RRC Connection Reconfiguration message (step 208) from UE4, the completion of the SeNB reconstituted SeNB2 (SeNB Reconfiguration Complete message).
[0049]
　In step 211, S-MeNB1 is reported data communication context for MCG, i.e. transmits the SN Status Transfer message to the T-MeNB3. The SN Status Transfer message, for example, the uplink PDCP sequence number for MCG bearer (Sequence Number (SN)), uplink hyper frame number (Hyper Frame Number (HFN)), downlink PDCP sequence number and downlink including the hyper frame number. The SN Status Transfer message may include the PDCP sequence number and a hyperframe number for the split bearer. In step 212, S-MeNB1 starts forwarding to the T-MeNB3 downlink user data unsent received from S-GW 5.
[0050]
　In step 213, SeNB2 the communication status report on one or more bearers transferred to the the or T-MeNB3 release of the at least one bearer for UE4 set in SeNB2, i.e. the SN Status Transfer message It is sent to the T-MeNB3. The SN Status Transfer message, for example, the uplink PDCP sequence number for SCG bearer (Sequence Number (SN)), uplink hyper frame number (Hyper Frame Number (HFN)), downlink PDCP sequence number and downlink including the hyper frame number. The SN Status Transfer message may include the PDCP sequence number and a hyperframe number for the split bearer.
[0051]
　In step 214, SeNB2 starts forwarding to the T-MeNB3 downlink user data unsent received from S-GW 5. Incidentally, SN Status Transfer (step 213) and the data forwarding (step 214) by SeNB2 may be initiated in response to receiving the SeNB Release Request message (step 205) from the S-MeNB1, to T-MeNB3 SeNB Addition, may be started after the transmission of Request Acknowledge message (step 203).
[0052]
　In step 215, T-MeNB3 starts S1 path switch procedure. The S1 path switch procedure of steps 215 to 219, with one or more S1 bearer between S-GW 5 and T-MeNB3 for MCG bearer (and split bearer options) (217), S for SCG bearer S1 bearer (218) is set between the -GW5 and SeNB2. Incidentally, if there is no correction of the SCG bearer (E-RAB), S1 set bearer (218) between the S-GW 5 and SeNB2 may be the same as before the start of the handover between the MeNB. For example, S1 path switch procedure may be omitted.
[0053]
　In step 220, T-MeNB3 is a UE Context Release message sent to S-MeNB1, starts UE Context Release procedure. In response to receiving the UE Context Release message (step 220) from the T-MeNB3, S-MeNB1 can release radio and C-plane resources associated with the UE context. In step 221, S-MeNB1 in response to the reception of the UE Context Release message from the T-MeNB3, sends a UE Context Release message to SeNB2.
[0054]
　In the following, some embodiments are described. These embodiments may be implemented independently, or may be implemented in appropriate combination. These embodiments are provided for purposes of illustration (illustration).
[0055]

　In the MeNB change procedure shown in FIGS. 2A and 2B, a plurality of bearers (ie, SCG bearer or split bearer, or both that are already set in SeNB2 for Dual Connectivity (DC) while maintaining the SeNB2 some bearer of), it may be preferable to be controlled that the rest of the bearer or released and transferred to T-MeNB3. In the present embodiment, improvement of the MeNB plurality of bearers that are configured to SeNB2 in the modified procedure partial release or partial maintenance allow the SeNB Addition, for Request message (step 202) is described.
[0056]
　Figure 3 is a SeNB2 is MeNB (S-MeNB) 1 SeNB2 is SeNB Addition, Request message to another eNB while in cooperation providing the SCG for a DC to specific UE4 and (T-MeNB) 3 an example of the reception procedures shows (Step 300). Step 301 and 302 shown in FIG. 3 corresponds to steps 201 and 202 shown in Figure 2A. That is, in step 301, S-MeNB1 sends a handover request message for requesting the MeNB handover of UE4 to T-MeNB3. The handover request message may include, for example, before the handover MCG setting and SCG settings.
[0057]
　The handover request message (step 301), further, SeNB (or SCG, or bearer (SCG bearer or split bearer) of SCG) explicit from S-MeNB1 the T-MeNB3 that the MeNB changes while maintaining the or for implicitly convey may include one or more additional information elements. Thus, T-MeNB3 is the handover request in response to receiving from the S-MeNB1, SeNB (or SCG, or bearer (SCG bearer or split bearer) of SCG) changes MeNB still maintaining the (MeNB during handover) it can recognize that it is requesting.
[0058]
　In some implementations, additional information elements included in the handover request message (step 301) (information element (s)) in order to indicate implicitly change the MeNB of DC for UE4, S-MeNB1 When SeNB2 between base stations interface between (ie, X2 interface) assigned by SeNB2 to uniquely identify the UE4 in the wireless terminal identifier (ie, SeNB UE X2AP ID) may include. The additional information element is one or more bearer identifiers (eg, network bearer identity (E-RAB ID or eps-Bearer Identity for UE4 already set in SeNB2 for DC in conjunction with S-MeNB1 ), the identifier (DRB Identity data radio bearer (data radio bearer (DRB))), or may further include the same bearer identifier and these combinations).
[0059]
　Additionally or alternatively, in some implementations, additional information elements included in the handover request message (step 301) (information element (s)) is implicitly change the MeNB of DC for UE4 to illustrate, the terminal identifier assigned to UE4 by SeNB2 to uniquely identify the UE4 in SCG (eg, Cell- Radio Network Temporary identifier (C-RNTI)) may include. In this case, the additional information element is one or more bearer identifiers (eg, E-RAB ID or eps-Bearer Identity for UE4 already set in SeNB2 for DC in conjunction with S-MeNB1, DRB Identity, or may further include the same bearer identifier and these combinations). Furthermore, E-RAB ID is transmitted as an information element of the X2 message, eps-Bearer Identity and DRB Identity is included as an information element of the RRC layer in the container included in the X2 message (MeNB to SeNB Container) transmission it may be.
[0060]
　Additionally or alternatively, in some implementations, the handover request message additional information element included in the (step 301) (information element (s)) is, MeNB of DC for UE4 is MeNB (S-MeNB ) it may be explicitly indicated to be changed from 1 to MeNB (T-MeNB) 3. In this case, the additional information element is one or more bearer identifiers for UE4 already set in SeNB2 for DC in conjunction with MeNB1 (eg, E-RAB ID or eps-Bearer Identity, DRB Identity , or it may indicate that these combinations) is not changed.
[0061]
　In step 302, in response to receiving a handover request message in step 301, T-MeNB3 transmits the SeNB Addition, Request message to SeNB2. The SeNB Addition, Request message indicates the character of the radio access bearer (ie, E-UTRAN Radio Access Bearer (E-RAB)) (characteristics), for requesting allocation of the radio resources for a particular E-RAB to SeNB2 . Characteristics of E-RAB, for example, E-RAB identifier (E-RAB ID), and shows a bearer type (ie, SCG bearer or split bearer). Here, the bearer type is also referred to as a DRB type. The SeNB Addition, Request message further, information for SCG settings including MCG setting (MCG Configuration) and UE capability (UE capabilities) (SCG-ConfigInfo) may contain. Moreover, T-MeNB3, in SCG-ConfigInfo, to that using network bearer identifier (eg, eps-Bearer Identity) and data radio bearer identifier (DRB Identity) in DC between the S-MeNB1 and SeNB2 it may be specified to be set to the same value. Similarly, T-MeNB3 logical identifier (sCellIndex, ServCellIndex) cell 21 may be specified to be set to the same value as the one used in DC between the S-MeNB1 and SeNB2.
[0062]
　The SeNB Addition, Request message (step 302), further, SeNB (or SCG, or SCG bearer (SCG bearer or split bearer)) while maintaining the MeNB is to be changed to T-MeNB3 from S-MeNB1 SeNB2 one or more additional information elements to convey explicitly or implicitly may contain a. The one or more additional information elements Information elements may be the same as the additional information element corresponding contained in the handover request message (step 301), may be directed from now.
[0063]
　That is, in some implementations, SeNB Addition, Request message additional information element included in the (step 302) (information element (s)) in order to indicate implicitly change the MeNB of DC for UE4, S-MeNB1 base station between the interfaces between the SeNB2 (ie, X2 interface) assigned by SeNB2 to uniquely identify the UE4 in the wireless terminal identifier (ie, SeNB UE X2AP ID) may include. In this case, the additional information element is one or more bearer identifiers (eg, E-RAB ID or eps-Bearer Identity for UE4 already set in SeNB2 for DC in conjunction with S-MeNB1, DRB Identity, or may further include the same bearer identifier and these combinations).
[0064]
　Additionally or alternatively, in some implementations, SeNB Addition, Request message additional information element included in the (step 302) (information element (s)), the implicit changes MeNB of DC for UE4 in order to indicate the terminal identifier (eg, C-RNTI) assigned to UE4 by SeNB2 to uniquely identify the UE4 in SCG it may contain. In this case, the additional information element is one or more bearer identifiers (eg, E-RAB ID or eps-Bearer Identity for UE4 already set in SeNB2 for DC in conjunction with S-MeNB1, DRB Identity, or may further include the same bearer identifier and these combinations).
[0065]
　Additionally or alternatively, in some implementations, additional information elements included in the SeNB Addition, Request message (step 302) (information element (s)) is, MeNB of DC for UE4 is MeNB (S- may be explicitly indicates to change from the MeNB) 1 to MeNB (T-MeNB) 3. For example, SeNB Addition, Request message, may be added to SCG Change Indication IE. Furthermore, the new Cause values ​​of SCG Change Indication IE (eg, Inter MeNB Handover, SeNB (SCG) Stored Handover) is defined, SeNB Addition, Request message may specify the Cause value. In this case, the additional information element, the bearer identifier (eg, E-RAB ID or eps-Bearer Identity for UE4 already set in SeNB2 for DC in conjunction with MeNB1, DRB Identity, or it may indicate that these combinations) is not changed.
[0066]
　The SeNB Addition, Request message (step 302), further, each of the at least one bearer is already set in SeNB2 for DC indicating whether maintained by SeNB2. In other words, the SeNB Addition, Request message indicates (or transferred as MCG bearer or T-MeNB3) already each bearer that is set either or released is maintained by SeNB2 be changed MeNB to SeNB2 . That is, the SeNB Addition, Request message, distinguished from one or more of the first bearer not be maintained by SeNB2 that (transferred or T-MeNB3) optionally one or more second bearer is maintained by SeNB2 to allow to SeNB2 to be.
[0067]
　In some implementations, the SeNB Addition, Request message, transferred to T-MeNB3 as at least one or bearers are or released is maintained by SeNB2 be changed MeNB (or MCG bearer is already set to SeNB2 are either) may indicate each bearer. More specifically, the SeNB Addition, Request message may include one or more first bearer (eg, SCG bearer # 1) is maintained by SeNB2 after MeNB changed first list indicating, and after MeNB change SeNB2 may include one or both of the second list indicating the second bearer may be 1 or more not be maintained (eg, SCG bearer # 2) by. The second list may indicate the one or more second bearer transferred as MCG bearer T-MeNB3 from SeNB2.
[0068]
　As shown in FIG. 3, in one example, the first list, "E-RAB To Be Added List" information element (Information Element (IE)) may be defined as. On the other hand, the second list, "E-RAB To Be Changed List" may be defined as an information element (IE). Alternatively, the second list, "E-RAB To Be Released List" information element (IE) or "E-RAB To Be Reconfigured List" may be defined as an information element (IE).
[0069]
　In step 303, SeNB2, while offering SCG for a DC to specific UE4 in conjunction with MeNB (S-MeNB) 1, SeNB Addition Request message including the additional information elements described above (step 302 ) in response to receiving, the SeNB Addition, request message, recognizes that the requesting modifying the (changing) the settings for already SCG that is set for the DC in conjunction with S-MeNB1 (consider) It is configured. Configuration modifications (changes) of about SCG, for example, (a) SCG MeNB settings associated with (eg, MeNB UE X2AP ID) modification (change), (b) associated with the SCG of MCG or MCG bearer configuration modifications (changes), including at least one of, modification of (c) SeNB security key (S-KeNB) (changed), and (d) SCG or SCG bearer or modify settings of the split bearer (change). As a more specific example, SeNB2 is, SeNB Addition Request E-RAB To Be Added List IE message, already same value that is set for UE4 doing a DC between S-MeNB1 If the wireless terminal identifier (eg, SeNB UE X2AP ID), and a E-RAB ID of the same value as that set for the UE4, modifications of setting the SeNB Addition, Request corresponds to the E-RAB (change), or recognizes that a reconfiguration of SCG including the E-RAB.
[0070]
　Further, in step 303, SeNB2 is, SeNB Addition, on the basis of the Request message (step 302), one or more first bearer (eg, SCG bearer # 1) is maintained by SeNB2 without maintained by the SeNB2 good (or be transferred to T-MeNB3) 1 or more second bearer (eg, SCG bearer # 2) is configured to distinguish from.
[0071]
　For example, SeNB Addition, Request message (step 302), include both first list mentioned above (eg, E-RAB To Be Added List) and a second list (eg, E-RAB To Be Changed List) good. In this case, SeNB2 is that the first in the list 1 or SeNB2 multiple bearers should maintain recognizes (Consider), 1 included in the second list or plurality of bearers may recognize that but transferred in or T-MeNB3 may be released.
[0072]
　In another example, SeNB Addition, Request message (step 302), the first list mentioned above (eg, E-RAB To Be Added List) including a second list (eg, E-RAB To Be Changed List ) may or may not contain. In this case, SeNB2 may recognize that is transferred to the first not included in the list of one or more possible bearers may be released or T-MeNB3.
[0073]
　In yet another example, SeNB Addition, Request message (step 302), which includes a second list described above (eg, E-RAB To Be Changed List), the first list (eg, E-RAB To Be Added List) may not include a. In this case, SeNB2 may recognize that it is not included in the second list one or a plurality of bearers SeNB2 should maintain.
[0074]
　In step 304, SeNB2, based on the information (eg, SCG-ConfigInfo) from T-MeNB3 contained SeNB Addition, Request message (step 302), generates a new SCG set (SCG-Config), the new response message (SeNB Addition Request Acknowledge) to send to the T-MeNB3 encompasses such SCG settings. The new SCG configuration, one or more first bearer (eg, SCG bearer # 1) which is instructed to SeNB2 from T-MeNB3 to maintain SeNB2 Oite about. The new SCG settings may include terminal identifier assigned to UE4 by SeNB2 to uniquely identify the UE4 in SCG (C-RNTI). SeNB2 is, SCG in addition to the case of SCG established (SCG establishment), SCG modifications accompanying MeNB change (change) · SCG reestablishment (SCG re-establishment) · or SCG relocation (SCG relocated, SCG relocation) in the case of the "MobilityControlInfoSCG" information element in the configuration may be always added to C-RNTI.
[0075]
　Incidentally, in the abnormality condition (Abnormal the Conditions) on the procedures shown in FIG. 3, SeNB2 and T-MeNB3 may operate as follows. If SeNB Addition, Request message wireless terminal identifier indicated by (step 302) (ie, SeNB UE X2AP ID) is S-MeNB1 and between base stations during SeNB2 interface (ie, X2 interface) uniquely specifying for the UE4 in If not used, SeNB2 may transmit the SeNB Addition, Request Reject message instead of SeNB Addition, Request Acknowledge message (step 304). The SeNB Addition, Request Reject message indicates that unacceptable the SeNB Addition, Request message (step 302). The SeNB Addition, Request Reject message may include a Cause value (eg, Inappropriate X2AP ID) indicating that the requested wireless terminal identifier (ie, SeNB UE X2AP ID) is inappropriate.
[0076]
　Alternatively, if the functions required for inter-eNB handover of DC UE it will always have the SCG SeNB2 does not support, SeNB Addition, Request Reject message, Cause value indicative thereof (eg, "Bearer Keeping Option Not Supported" , "Bearer Keeping Handover Not supported") may contain a.
[0077]
　Alternatively, functions required for DC UE of inter-eNB handover which involves the remaining bearer or released and transferred to T-MeNB3 while maintaining the SeNB2 part of the bearer of the plurality of bearers being set to SeNB2 If the SeNB2 does not support, SeNB Addition Request Reject message, Cause value indicative thereof (eg, "Bearer Keeping Option not supported", "Bearer Keeping Handover not supported") may contain.
[0078]
　T-MeNB3 in response to reception of the SeNB Addition, Request Reject message, the response message indicating that not accept handover (Handover Preparation Failure message) may be sent to the S-MeNB1. Alternatively, T-MeNB3 is the E-RABs Not Admitted List IE in Handover Request Acknowledge message may include the E-RAB ID bearer (SCG bearer or split bearer) of the SeNB. In this case, S-MeNB1 instructs the handover to UE4 (RRC Connection Reconfiguration including mobility Control Info) cancel or handover before sending the (interruption), may be released to SCG, MCG and SCG bearer it may be changed to the bearer.
[0079]
　Figure 4 is a flowchart showing an example of the operation of SeNB2 the (process 400). In block 401, SeNB2, while offering SCG for a DC to specific UE4 in conjunction with MeNB (S-MeNB) 1, the SeNB Addition, Request message to another eNB (T-MeNB) 3 It received. At block 402, SeNB2, in response to reception of the SeNB Addition, Request message, with respect to at least one bearer SeNB2 for DC in conjunction with S-MeNB1 already set, and the one or more maintained by SeNB2 first distinguish one bearer from the second bearer may not be maintained (or be transferred to T-MeNB3) 1 or more by SeNB2.
[0080]
　As understood from the above description, according to the example described with reference to FIGS. 3 and 4, T-MeNB3 at least one post-bearer MeNB changes that have already been set in SeNB2 for DC can also carry one or may be released is maintained in SeNB2 (or either transferred to T-MeNB3) for each bearer SeNB2. SeNB2, in response to receipt of SeNB Addition, Request message from the T-MeNB3, or at least one bearer is already set to SeNB2 may be or freed is maintained after changing MeNB for DC ( or transferred to T-MeNB3) can recognize for each bearer.
[0081]
　Then hereinafter be described with reference to FIGS. 5A and 5B specific example of changes SeNB Addition, Request message (modification). 5A and 5B show a modification for the SeNB Addition, Request message described in Non-Patent Document 2 sections 9.1.3.1. "E-RAB To Be Changed List" IE is (transferred or T-MeNB3) may already not be maintained by SeNB2 after MeNB change of the at least one bearer is set to SeNB2 for DC 1 or a plurality of bearers are used to inform the T-MeNB3 to SeNB2.
[0082]
　“E-RABs To Be Changed List”IEは、“E-RABs To Be Changed Item”IEを含む。“E-RABs To Be Changed Item”IEは、SCG Bearerに関して、“E-RAB ID”IE、“DL Forwarding GTP Tunnel Endpoint”IE、及び“UL Forwarding GTP Tunnel Endpoint”IEを含む。“DL Forwarding GTP Tunnel Endpoint”IEは、DLデータ（DL PDUs）フォワーディングのためのX2トランスポートベアラに関するT-MeNB３のEndpoint設定（つまり、Transport Network Layer（TNL）アドレス及びTunnel Endpoint Identifier（TEID））を示す。“UL Forwarding GTP Tunnel Endpoint”IEとのは、ULデータ（UL PDUs）フォワーディングのためのX2トランスポートベアラに関するT-MeNB３のEndpoint設定（つまり、TNLアドレス及びTEID）を示す。同様に、“E-RABs To Be Changed Item”IEは、Split Bearerに関して、E-RAB ID”IE、及び“DL Forwarding GTP Tunnel Endpoint”IEを含む。
[0083]
　As previously described, the name of the "E-RAB To Be Changed List" IE is an example. For example, instead of "E-RAB To Be Changed List" IE, "E-RAB To Be Released List" IE or "E-RAB To Be Reconfigured List" the name of the IE may be used.
[0084]

　In the present embodiment, Handover Request Acknowledge message for enabling a plurality of bearers partial release or partial maintenance of which is set to SeNB2 in MeNB change procedure of (Step 204) improvement is described.
[0085]
　6, T-MeNB3 is, after receiving the SeNB Addition, Request Acknowledge message from SeNB2, shows an example of a procedure of transmitting the Handover Request Acknowledge message to the S-MeNB1 a (Step 600). Step 601-604 shown in FIG. 6 are similar to steps 301-304 shown in FIG. Step shown in FIG. 6 605 corresponds to step 204 shown in Figure 2A. That is, in step 605, T-MeNB3 transmits a handover request response message indicating acceptance of (step 501) (Handover Request Acknowledge) to the S-MeNB1.
[0086]
　Handover Request Acknowledge message (step 605) indicates whether each of the at least one bearer SeNB2 for DC in conjunction with S-MeNB1 has already been set is maintained by SeNB2. In other words, the Handover Request Acknowledge message indicates whether each of the at least one bearer is already set to SeNB2 is transferred to the expectorated or T-MeNB3 maintained by SeNB2. That is, the Handover Request Acknowledge message, makes it possible to distinguish from one or more of the second bearer 1 or more first bearer are transferred to T-MeNB3 maintained by SeNB2 the S-MeNB1.
[0087]
　In some implementations, the Handover Request Acknowledge message, whether at least one bearer is already set to SeNB2 is transferred to T-MeNB3 or as MCG bearer is maintained by SeNB2 be changed MeNB each bearer it may indicate. Maintaining More specifically, the Handover Request Acknowledge message, which is allowed by T-MeNB3 (admitted) 1 or the third list indicative of a plurality of bearers, and each bearer included in the third list is by SeNB2 or transferred to or T-MeNB3 is can include explicitly shown bearer status information element.
[0088]
　As shown in FIG. 6, in one example, the third list is defined as "E-RAB Admitted List" information element (IE), bearer status information element, "E-RAB Status" information element ( IE) may be defined as. "E-RAB Status" IE explicitly or transferred to S-MeNB1 each bearer is set in SeNB2 for DC of (eg, SCG bearer) or T-MeNB3 is maintained in SeNB2 to show. Alternatively, bearer Status information element is set to at least one of indicates that it is maintained "E-RAB Kept" indicates that the transferred IE, and T-MeNB3 "E-RAB Relocated (Switched)" IE in SeNB2 it may be defined.
[0089]
　In another example, the Handover Request Acknowledge message indicates a third list above, and whether the bearer included in the third list is transferred to the expectorated or T-MeNB3 maintained by SeNB2 implicitly it may include a tunnel endpoint identifier (TEID). Tunnel Endpoint Identifier is the TEID of X2 transport bearer for data forwarding related to the bearer transferred to T-MeNB3 from SeNB2. That, S-MeNB1, when including a bearer identifier for the bearer there is a third list (E-RAB) does not contain a TEID to be associated with this, if it is the bearer to which the bearer is maintained by SeNB2 it may be recognized.
[0090]
　Figure 7 is a flow chart showing an example of the operation of the T-MeNB3 the (process 700). In block 701, T-MeNB3 receives SeNB Addition, Request Acknowledge message from SeNB2. In block 702, T-MeNB3 sends a Handover Request Acknowledge message to the S-MeNB1. The Handover Request Acknowledge message, explicitly or implicitly indicates the bearer is set to SeNB2 is transferred to SeNB2 Thus either maintained or T-MeNB3.
[0091]
　As understood from the above description, according to the example described with reference to FIGS. 6 and 7, T-MeNB3 at least one post-bearer MeNB changes that have already been set in SeNB2 for DC can be transmitted to S-MeNB1 whether also transferred to the expectorated or T-MeNB3 maintained in SeNB2 each bearer. S-MeNB1 in response to the reception of the Handover Request Acknowledge message from the T-MeNB3, or T-MeNB3 least one bearer that has already been set in SeNB2 for DC is maintained at SeNB2 be changed MeNB it can recognize whether the each bearer is transferred to.
[0092]
　Then hereinafter be described with reference to FIG. 8 specific example of changes in Handover Request Acknowledge message (modification). Figure 8 shows a modification for the Handover Request Acknowledge message described in Non-Patent Document 2 sections 9.1.1.2. "E-RAB Status" IE explicitly or transferred to S-MeNB1 each bearer is set in SeNB2 for DC of (eg, SCG bearer) or T-MeNB3 is maintained in SeNB2 to show.
[0093]

　In the present embodiment, SeNB Release Request message for enabling a plurality of bearers partial release or partial maintenance of which is set to SeNB2 in MeNB change procedure of (Step 205) improvement is described.
[0094]
　9, S-MeNB1 is, after receiving the Handover Request Acknowledge message from the T-MeNB3, shows an example of a procedure of transmitting the SeNB Release Request message to SeNB2 a (Step 900). Step 901-905 shown in FIG. 9 are the same as steps 601-605 shown in FIG. Step 906 shown in FIG. 9 corresponds to step 205 shown in Figure 2A. That is, in step 906, S-MeNB1 transmits the SeNB Release Request message to SeNB2. The SeNB Release Request message triggers resource (eg, UE context) as SeNB about UE4 for DC and S-MeNB1 release of the SeNB2.
[0095]
　SeNB Release Request message (step 906) indicates whether each of the at least one bearer SeNB2 for DC in conjunction with S-MeNB1 already set is maintained by SeNB2. In other words, the SeNB Release Request message indicates whether already each of the at least one bearer is set may be or released is maintained by SeNB2 (or either transferred to T-MeNB3) to SeNB2. That is, the SeNB Release Request message confirms one or more first bearer, and (transferred or T-MeNB3) may be released one or more second bearers to be maintained by SeNB2 it allows to the SeNB2.
[0096]
　In some implementations, the SeNB Release Request message may indicate whether at least one bearer is already set to SeNB2 may be or released is maintained by SeNB2 be changed MeNB each bearer . Each More specifically, the SeNB Release Request message contains a fourth list of illustrating one or more bearers are set to SeNB2 for DC and S-MeNB1, and the fourth list of bearer may include explicitly shown bearer status information element whether it may be or released is maintained (or either transferred to T-MeNB3) by SeNB2.
[0097]
　As shown in FIG. 9, in one example, the fourth listing is defined as "E-RAB Released List" information element (IE), bearer status information element, "E-RAB Status" information element ( IE) may be defined as. "E-RAB Status" IE is, S-MeNB1 each bearer is set in SeNB2 for DC of (eg, SCG bearer) is whether or be released is maintained in SeNB2 (or T- or transferred to MeNB3) explicitly shows the. Alternatively, bearer status information element indicates which is maintained indicates that "E-RAB Kept" IE, and may be released (or transferred to T-MeNB3) that in SeNB2 "E-RAB Released" IE it may be defined by at least one of.
[0098]
　In another example, the SeNB Release Request message may be freed of the at least one bearer is set to SeNB2 (i.e., transferred to T-MeNB3) 1 or more bearers only a fourth showing It includes a list may not include the bearer status information elements described above. In this case, SeNB2 can confirm that it should maintain the bearer that is not included in the fourth list.
[0099]
　Step 907 of FIG. 9 corresponds to step 206 of FIG. 2A. That is, in step 907, S-MeNB1 the transmission PCell in MCG (eg, cell 11) the RRC Connection Reconfiguration message to request radio resource control (RRC) connection reconfiguration in a (reconfiguration) to UE4 to UE4 to. The RRC Connection Reconfiguration message, the mobility control information on T-MeNB3 (Mobility Control Info) and MCG setting, as well as SCG settings for SeNB2. MCG settings for these T-MeNB3 and SCG settings related SeNB2 indicates whether each of the at least one bearer is already set to SeNB2 is maintained by SeNB2. In other words, these MCG settings and SCG setting indicates whether each bearers already set SeNB2 is transferred as MCG bearer or T-MeNB3 maintained by SeNB2 be changed MeNB. UE4, in response to reception of the RRC Connection Reconfiguration message (step 907), can be distinguished from one or more bearers transferred to one or more bearers maintained by SeNB2 after MeNB change T-MeNB3 .
[0100]
　Step 908 and 909 in FIG. 9 corresponds to the step 213 and 214 in Figure 2B. That is, in step 908, SeNB2 may include one or more bearers transferred to the the or T-MeNB3 release of the at least one bearer for UE4 set in SeNB2 SN related (eg, the bearer # 2 in SCG) to send a Status Transfer message to T-MeNB3.
[0101]
　In step 909, SeNB2 starts forwarding to the T-MeNB3 downlink user data unsent received from S-GW 5. Incidentally, SN Status Transfer (step 908) and the data forwarding (step 909) by SeNB2 may be initiated after sending the SeNB Addition, Request Acknowledge message to the T-MeNB3 (step 904), from the T-MeNB3 SeNB Reconfiguration Complete message may be initiated in response to receipt of (step 210).
[0102]
　Figure 10 is a flow chart showing an example of the operation of the S-MeNB1 the (processing 1000). In block 1001, S-MeNB1 receives Handover Request Acknowledge message from the T-MeNB3. In block 1002, S-MeNB1 transmits the SeNB Release Request message to SeNB2. The SeNB Release Request message, the bearer is set to SeNB2 is (or is transferred to or T-MeNB3) or may be or released SeNB2 Thus is maintained explicitly or implicitly indicate the.
[0103]
　As understood from the above description, according to the example described with reference to FIGS. 9 and 10, S-MeNB1 at least one post-bearer MeNB changes that have already been set in SeNB2 for DC can also carry one or may be released is maintained in SeNB2 (or either transferred to T-MeNB3) for each bearer SeNB2. SeNB2, in response to receipt of SeNB Release Request message from the S-MeNB1, at least one bearer is already set to SeNB2 may be or released is maintained in SeNB2 be changed MeNB for DC or (or either transferred to T-MeNB3) can be checked for each bearer.
[0104]
　Then hereinafter be described with reference to FIGS. 11A and 11B for a specific example of changes SeNB Release Request message (modification). 11A and 11B show the modifications to SeNB Release Request message described in Non-Patent Document 2 sections 9.1.3.11. "E-RAB Status" IE explicitly or transferred to S-MeNB1 each bearer is set in SeNB2 for DC of (eg, SCG bearer) or T-MeNB3 is maintained in SeNB2 to show.
[0105]
　Finally, eNB1 according to embodiments described above, eNB2, eNB 3, and configuration examples of UE4 is described. Figure 12 is a block diagram showing a configuration example of SeNB2. S-MeNB1 and T-MeNB3 also may have a configuration similar to that of FIG. 12. Referring to FIG. 12, SeNB2 includes an RF transceiver 1201, a network interface 1203, a processor 1204, and memory 1205. RF transceiver 1201 performs an analog RF signal processing to communicate with the UEs. RF transceiver 1201 may include a plurality of transceivers. RF transceiver 1201 is coupled to antenna 1202 and the processor 1204. RF transceiver 1201 receives the modulated symbol data (or OFDM symbol data) from the processor 1204, generates a transmission RF signal and provides a transmit RF signal to the antenna 1202. Also, RF transceiver 1201 to generate a baseband received signal based on the reception RF signal received by an antenna 1202, and supplies it to the processor 1204.
[0106]
　Network interface 1203 is used for communicating network nodes (eg, other eNBs, MME, and S-GW) and. Network interface 1203 may include, for example, a network interface card that complies with the IEEE 802.3 series (NIC).
[0107]
　The processor 1204, performs data plane processing and control plane processing including digital baseband signal processing for wireless communication. For instance, in the case of LTE and LTE-Advanced, digital base band signal processing by the processor 1204, PDCP layer, RLC layer may include a signal processing of the MAC layer, and the PHY layer. Further, the signal processing by the processor 1204 may include signal processing GTP-U · UDP / IP layer in the X2-U interface and S1-U interface. The control plane processing by the processor 1204, X2AP protocol may include a process of S1-MME protocol and the RRC protocol.
[0108]
　Processor 1204 may include multiple processors. For example, the processor 1204, a modem processor that performs digital baseband signal processing (eg, DSP), X2-U interface and S1-U interface of the GTP-U · UDP / IP layer processor for performing signal processing (eg, DSP), and a protocol stack processor for performing control plane processing (eg, may include a CPU or MPU).
[0109]
　Memory 1205 is constituted by a combination of volatile and nonvolatile memory. Memory 1205 may include a physically independent plurality of memory devices. Volatile memory may be, for example, Static Random Access Memory (SRAM) or Dynamic RAM (DRAM) or a combination thereof. The non-volatile memory, a mask Read Only Memory (MROM), Electrically Erasable Programmable ROM (EEPROM), flash memory, or hard disk drive, or any combination thereof. Memory 1205 may include a storage that is remotely located from the processor 1204. In this case, the processor 1204 may access the memory 1205 via the I / O interfaces that are not network interface 1203 or illustrated.
[0110]
　Memory 1205 may store software modules (computer program) including instructions and data for processing by SeNB2 described in several embodiments described above. In some implementations, the processor 1204, the software module that executes from the memory 1205 may be configured to perform processing of SeNB2 described in the above embodiments.
[0111]
　Figure 13 is a block diagram showing a configuration example of UE4. Radio Frequency (RF) transceiver 1301 performs an analog RF signal processing to communicate with the eNB2. Analog RF signal processing performed by the RF transceiver 1301 includes a frequency up-conversion, the frequency down-conversion, and amplification. RF transceiver 1301 is coupled to antenna 1302 and the base band processor 1303. That, RF transceiver 1301 receives the modulated symbol data (or OFDM symbol data) from the baseband processor 1303, generates a transmission RF signal and provides a transmit RF signal to the antenna 1302. Also, RF transceiver 1301 to generate a baseband received signal based on the reception RF signal received by an antenna 1302, and supplies it to the baseband processor 1303.
[0112]
　Baseband processor 1303 performs control plane processing and digital baseband signal processing for wireless communication (data plane processing). Digital baseband signal processing, (a) data compression / decompression, (b) segmentation / concatenation of data, generation / decomposition of (c) transmission format (transmission frame), (d) transmission channel coding / decoding , including generation of (e) modulation (symbol mapping) / demodulation, and OFDM symbol data by (f) Inverse Fast Fourier Transform (IFFT) (baseband OFDM signal). On the other hand, the control plane processing, layer 1 (eg, transmission power control), Layer 2 (eg, radio resource management, and hybrid automatic repeat request (HARQ) process), and layer 3 (eg, attach, mobility and call management including communication management signaling) related.
[0113]
　For example, in the case of LTE and LTE-Advanced, a digital baseband signal processing by a baseband processor 1303, Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC) layer, includes a signal processing of the MAC layer, and a PHY layer But good. Further, the control plane processing by baseband processor 1303, Non-Access Stratum (NAS) protocol, RRC protocol, and may include a process of MAC CE.
[0114]
　Baseband processor 1303, a modem processor that performs digital baseband signal processing (eg, Digital Signal Processor (DSP)) and protocol stack processor for performing control plane processing (eg, Central Processing Unit (CPU), or Micro Processing Unit it may include (MPU)). In this case, the protocol stack processor for performing control plane processing may be shared with an application processor 1304 which will be described later.
[0115]
　The application processor 1304, CPU, MPU, also referred to as a microprocessor or processor cores. The application processor 1304 may include a plurality of processors (multiple processor cores). The application processor 1304, a memory 1306 or illustrated which do not result system read from the memory a software program (Operating System (OS)) and various application programs (e.g., call application, WEB browser, a mailer, a camera operation application, music playback by running the application), to implement the various functions of UE4.
[0116]
　In some implementations, as indicated by the dashed line (1305) in FIG. 13, the baseband processor 1303 and an application processor 1304 may be integrated on a single chip. In other words, the baseband processor 1303 and an application processor 1304 may be implemented as a single System on Chip (SoC) device 1305. SoC devices, sometimes referred to as system Large Scale Integration (LSI) or chipset.
[0117]
　Memory 1306 is a volatile memory or nonvolatile memory, or a combination thereof. Memory 1306 may include a physically independent plurality of memory devices. Volatile memory may be, for example, Static Random Access Memory (SRAM) or Dynamic RAM (DRAM) or a combination thereof. The non-volatile memory, a mask Read Only Memory (MROM), Electrically Erasable Programmable ROM (EEPROM), flash memory, or hard disk drive, or any combination thereof. For example, memory 1306, a baseband processor 1303, an application processor 1304, and may contain accessible external memory device from SoC1305. Memory 1306, within baseband processor 1303, within the application processor 1304, or may include an integrated chip memory device within SoC1305. Furthermore, memory 1306 may include a memory in the Universal Integrated Circuit Card (UICC).
[0118]
　Memory 1306 may store software modules (computer program) including instructions and data for processing by the UE4 described in several embodiments described above. In some implementations, the baseband processor 1303 or the application processor 1304, the software module that executes from the memory 1306 may be configured to perform processing of UE4 described in the above embodiments.
[0119]
　As described with reference to FIGS. 12 and 13, each of the processors eNB1, eNB2, eNB 3, and UE4 have according to the above-described embodiments, instructions for performing the algorithm described with reference to the drawings in the computer perform one or more programs including the group. This program is stored using a non-transitory computer readable media of various types (non-transitory computer readable medium), it can be supplied to the computer. Non-transitory computer readable media include with various types of entities (tangible storage medium). Examples of non-transitory computer readable media include magnetic storage media (such as floppy disks, magnetic tape, hard disk drive), magneto-optical recording medium (e.g., magneto-optical disk), Compact Disc Read Only Memory (CD-ROM), CD- R, including CD-R / W, a semiconductor memory (e.g., a mask ROM, Programmable ROM (PROM), Erasable PROM (EPROM), flash ROM, Random Access memory (RAM)). The program may be provided to a computer using a temporary computer readable media of various types (transitory computer readable medium). Examples of transitory computer readable media include electric signals, optical signals, and electromagnetic waves. Transitory computer readable media, wired communication path such as electrical wires and optical fibers, or via a wireless communication path can provide the program to a computer.
[0120]

　The above-described embodiments have mainly described LTE / LTE-Advanced and improvements. However, the above-described embodiments may be applied to other wireless communication network or system. Each eNBs1 ~ 3 described in the above embodiments may also be referred to as a radio station. Radio station herein, the control node (eg, Radio Network Controller in the UMTS (RNC), or Base Station Controller in GSM system (BSC)), and a radio transmission node having a radio resource management functions (eg, NodeB in UMTS, or it may comprise a Base transceiver station (BTS)) in the GSM system.
[0121]
　Furthermore, the above-described embodiments are only examples for the application of technical ideas obtained by the present inventor. In other words, the technical idea is not limited to the embodiments described above, it is needless to say various modifications are possible.
[0122]
　For example, some or all of the above embodiments, can be described as the following notes, not limited to the following.
[0123]
(Supplementary Note 1)
　A secondary base station,
　and at least one wireless transceiver
　and at least one processor coupled to the at least one radio transceiver,
comprising a
　at least one processor includes a first master base station cooperation and is configured to receive the SeNB addition request message from the second master base station while providing secondary cell group for dual connectivity the (SCG) to the wireless terminal,
　the SeNB addition request message, wherein each of the at least one bearer is already set to the secondary base station indicating whether or not maintained by the secondary base station, for the dual connectivity
secondary base station.
[0124]
(Supplementary Note 2)
　wherein the at least one processor, in response to reception of the SeNB addition request message, the one or more first bearer is maintained by the secondary base station, even if it is not maintained by the secondary base station It is configured to distinguish from good one or a plurality of the second bearer,
the secondary base station according to Appendix 1.
[0125]
(Supplementary Note 3)
　the at least one processor, said one or more second said that from the secondary base station performs at least one of reporting and data forwarding of the data communication status to the second master base station related to the bearer It is configured,
the secondary base station according to Appendix 2.
[0126]
(Supplementary Note 4)
　The SeNB addition request message may be 1 or more is also be one or more of not maintained by the first of the first indicating the bearer list and the secondary base station is first maintained by the secondary base station including either or both of the second list indicating the second bearer,
the secondary base station according to Appendix 1.
[0127]
(Supplementary Note 5)
　The SeNB addition request message includes at least the first list,
　the at least one processor is not included in the first list 1 or more bearers may be released or It is configured to recognize that is transferred to the second master base station,
the secondary base station according to Appendix 4.
[0128]
(Supplementary Note 6)
　The SeNB addition request message includes at least the second list,
　the at least one processor may include one or more bearers not included in the second list is maintained by the secondary base station it is configured to recognize that it is a Rubeki,
secondary base station according to Appendix 4.
[0129]
(Supplementary Note 7)
　wherein the at least one processor, said after receiving the SeNB addition request message from the second master base station, the dual SeNB release request the message first to trigger a release of resources for the connectivity is configured to receive from the master base station,
　the SeNB release request message, the indicates whether each of the at least one bearer is maintained by the secondary base station,
any one of appendices 1 to 6 secondary base station as claimed.
[0130]
(Supplementary Note 8)
　wherein the at least one processor, in response to reception of the SeNB release request message, the one or more first bearer is maintained by a secondary base station, and even if it is not maintained by the secondary base station It is configured to check the good one or a plurality of the second bearer,
the secondary base station according to Appendix 7.
[0131]
(Supplementary Note 9)
　The SeNB release request message is a SCG release request message, or the context release message indicating the release of context for the wireless terminal indicating the release of the SCG,
secondary base station according to appendix 7 or 8.
[0132]
(Supplementary Note 10)
　A method in a secondary base station,
　a second master base while providing secondary cell group for dual connectivity in conjunction with the first master base station (SCG) to the wireless terminal receiving a SeNB addition request message from the station or the SeNB addition request message, wherein each of the at least one bearer is already set to the secondary base station for the dual connectivity is maintained by the secondary base station indicating as to whether or not, and
　in response to receiving the SeNB addition request message, the secondary base is the one or more of the first bearer is not to be 1 or more maintained by the secondary base station maintained by the station first , to distinguish from 2 bearers
method comprising.
[0133]
(Note 11)
　further comprising carrying out at least one of the one or more second bearer relating to the data communication status reporting and data forwarding from the secondary base station to the second master base station,
in appendage 10 the method described.
[0134]
(Supplementary Note 12)
　The SeNB addition request message includes either or both of the second list showing the one or more first first list and the one or more second bearer indicating the bearer ,
the method of statement 10 or 11.
[0135]
(Supplementary Note 13)
　After receiving the SeNB addition request message from the second master base station, receives the SeNB release request message that triggers the release of resources for the dual connectivity from the first master base station further comprising, that
　the SeNB release request message, the indicates whether each of the at least one bearer is maintained by the secondary base station,
the method according to any one of appendices 10-12.
[0136]
(Supplementary Note 14)
　A program for causing a process in the secondary base station to the computer,
　the method comprising
　a wireless terminal secondary cell group (SCG) for dual connectivity in conjunction with the first master base station second receiving a SeNB addition request message from the master base station, the SeNB addition request message, the at least one bearer that has already been set to the secondary base station for said dual connectivity while providing the indicating whether each of which is maintained by the secondary base station, and
　the SeNB according to reception of the addition request message, the secondary base station to one or a plurality of first bearer is maintained by the secondary base station , to distinguish from the second bearer may also be one or more not be maintained by
including a
program.
[0137]
(Appendix 15)
　and at least one wireless transceiver
　and at least one processor coupled to the at least one radio transceiver
includes a
　said at least one processor, the secondary base station in conjunction with a first master base station is configured to transmit the SeNB addition request message to the secondary base station while providing secondary cell group for dual connectivity the (SCG) to the wireless terminal,
　the SeNB addition request message, for said dual connectivity already it indicates whether each of the at least one bearer is set is maintained by the secondary base station, the secondary base station to the
second master base station.
[0138]
(Supplementary Note 16)
　The SeNB addition request message may be 1 or more is also be one or more of not maintained by the first of the first indicating the bearer list and the secondary base station is first maintained by the secondary base station including either or both of the second list indicating the second bearer,
the second master base station according to note 15.
[0139]
(Supplementary Note 17)
　the at least one processor is in response to said handover request received from the first master base station, the SeNB is configured to send the addition request message,
the according to Note 15 or 16 2 of the master base station.
[0140]
(Supplementary Note 18)
　the at least one processor, after receiving a response message to the SeNB addition request message from the secondary base station, configured to send a response message to the handover request to the first master base station,
　the response message to the handover request, the indicating at least one of each of the bearer is moved to be expectorated or the second master base station maintained by the secondary base station,
a second master according to note 17 base station.
[0141]
(Supplementary Note 19)
　the response message to the handover request, the third list showing one or more bearers allowed by the second master base station, and each bearer said secondary included in the third list including bearer status information element indicating transferred to or the second master base station is maintained by the base station,
the second master base station according to Appendix 18.
[0142]
(Supplementary Note 20)
　A method in a second master base station,
　provides a secondary cell group for dual connectivity secondary base station in conjunction with the first master base station (SCG) to the wireless terminal sending a SeNB addition request message to the secondary base station during the SeNB addition request message, at least one of each of the secondary base station bearers the already set to the secondary base station for the dual connectivity It indicates whether maintained by
the method comprising.
[0143]
(Supplementary Note 21)
　The SeNB addition request message may be 1 or more is also be one or more of not maintained by the first of the first indicating the bearer list and the secondary base station is first maintained by the secondary base station including either or both of the second list indicating the second bearer,
the method of statement 20.
[0144]
(Supplementary Note 22)
　to said transmission in response to receiving the handover request from the first master base station, comprises transmitting the SeNB addition request message,
the method of statement 20 or 21.
[0145]
(Supplementary Note 23)
　from the secondary base station after receiving a response message to the SeNB addition request message, further comprising sending a response message to the handover request to the first master base station,
　the response to the handover request message, the indicating at least one of each of the bearer is moved to be expectorated or the second master base station maintained by the secondary base station,
the method of statement 22.
[0146]
(Supplementary Note 24)
　A program for causing a process to the computer at the second master base station,
　the method comprising the secondary cell for dual connectivity secondary base station in conjunction with the first master base station, sending a SeNB addition request message to the secondary base station while providing the group (SCG) to the wireless terminal, the SeNB addition request message, the already set to the secondary base station for the dual connectivity each of the at least one bearer indicates whether maintained by the secondary base station are
provided with,
a program.
[0147]
(Supplementary Note 25)
　A first master base station,
　and at least one wireless transceiver
　and at least one processor coupled to the at least one radio transceiver,
comprising a
　at least one processor, the secondary base station while providing the secondary cell group (SCG) for dual connectivity in conjunction with the first master base station to the wireless terminal, it transmits a handover request of the wireless terminal to the second master base station the configured to receive a response message from the second master base station to the handover request,
　the response message, said each of the at least one bearer that has already been set to the secondary base station for the dual connectivity wherein either maintained by the secondary base station or the second master base station Indicating transferred to,
the first master base station.
[0148]
(Supplementary Note 26)
　said response message is maintained, said third list showing one or more bearers allowed by second master base station, and each bearer included in the third list is by the secondary base station bearer status including information element indicating whether transferred to or the second master base station is
the first master base station according to Appendix 25.
[0149]
(Supplementary Note 27)
　the at least one processor, after receiving the response message, is configured to transmit the SeNB release request message that triggers the release of resources for the dual connectivity to the secondary base station,
　the SeNB release request message, the indicates whether each of the at least one bearer is maintained by the secondary base station,
the first master base station according to note 25 or 26.
[0150]
(Supplementary Note 28)
　The release message, the at least one bearer status information element indicating whether each bearer is or released is maintained by the secondary base station,
a first master according to note 27 base station.
[0151]
(Supplementary Note 29)
　A method in a first master base station,
　to provide a secondary cell group for dual connectivity the (SCG) to the radio terminal secondary base station in conjunction with the first master base station during are, sending a handover request of the wireless terminal to the second master base station, and
　receiving a response message to the handover request from the second master base station, the response message, the dual connectivity wherein each of the at least one bearer is already set to the secondary base station, indicating transferred to be the or the second master base station maintained by the secondary base station for
a method comprising the.
[0152]
(Supplementary Note 30)
　said response message is maintained, said third list showing one or more bearers allowed by the second master base station, and each bearer included in the third list is by the secondary base station It is expectorated or including bearer status information element indicating transferred to the second master base station,
the method of statement 29.
[0153]
(Supplementary Note 31)
　after receiving the response message, further comprising a resource SeNB release request message that triggers the release of the for dual connectivity to be transmitted to the secondary base station,
　the SeNB release request message, said at least each one bearer indicating whether maintained by the secondary base station,
the method of statement 29 or 30.
[0154]
(Supplementary Note 32)
　The method of the first master base station a program for causing a computer,
　the method comprising
　the secondary cell for dual connectivity secondary base station in conjunction with the first master base station · group (SCG) while providing the wireless terminal, sending a handover request of said wireless terminal to the second master base station, and
　a response message for the handover request from the second master base station incoming, said response message indicates whether maintained by pre-set each of the at least one bearer is said secondary base station to the secondary base station for the dual connectivity
comprises,
program .
[0155]
(Supplementary Note 33)
　A wireless terminal,
　the first master base station, and at least one radio transceiver for communicating with the second master base station, and the secondary base station,
　and at least one processor,
comprising a
　said the first master base station, the second master base station, and the secondary base station, the secondary cell group for dual connectivity the secondary base station in conjunction with the first master base station (SCG) the while offering to the radio terminal, wherein being configured to perform the procedure for changing the dual connectivity of the master base station from the first master base station to the second master base station,
　the at least one processor,
　during the procedure, the second master cell group on the master base station (MCG) setting and the secondary base station Is configured to the SCG setting received from the first master base station relating,
　in response to said receipt of MCG setting and the SCG setting, the dual at least said already set to the secondary base station for connectivity one of each of the bearers is configured to recognize whether transferred to whether or the second master base station is maintained by the secondary base station,
　to the SCG of the secondary base station comprising at least one bearer while maintaining the connection, and is configured to change the master base station of the dual connectivity from the first master base station to the second master base station,
the wireless terminal.
[0156]
(Supplementary Note 34)
　the at least one processor is in response to said reception of MCG setting and the SCG set, transferred to one or more of the first bearer is maintained by the secondary base station to the second master base station 1 or is configured to distinguish the plurality of second bearers are
radio terminal according to supplementary note 33.
[0157]
　This application claims priority based on 2015 July 31, 2008 Japanese Patent Application No. 2015-152736, filed on, the entire disclosure of which is incorporated herein.
DESCRIPTION OF SYMBOLS
[0158]
1-3 Base station
(eNBs) 4 radio terminal
(UE) 1201 RF transceiver
1204 processor
1205 memory

claims

[Claim 1]A secondary base station,
　and at least one wireless transceiver
　and at least one processor coupled to the at least one radio transceiver,
comprising a
　at least one processor, in conjunction with the first master base station dual secondary cell group for connectivity the (SCG) from the second master base station while providing the wireless terminal is configured to receive the SeNB addition request message,
　the SeNB addition request message, the dual connectivity It said each of the at least one bearer is already set to the secondary base station indicating whether or not maintained by the secondary base station, for
the secondary base station.
[Claim 2]
　Wherein the at least one processor, the SeNB in response to receiving the additional request message, the one or more first bearer is maintained by a secondary base station, the plurality may 1 or may not be maintained by the secondary base station It is configured to distinguish from the second bearer,
the secondary base station according to claim 1.
[Claim 3]
　Wherein the at least one processor is configured to perform at least one of the one or more second bearer relating to the data communication status reporting and data forwarding from the secondary base station to the second master base station ,
the secondary base station according to claim 2.
[Claim 4]
　The SeNB addition request message, the one or more first second bearer may also be one or more not be maintained by the first list and the secondary base station indicating the bearer is maintained by the secondary base station including either or both of the second list shown,
the secondary base station according to claim 1.
[Claim 5]
　The SeNB addition request message includes at least the first list,
　the at least one processor, the not included in the first list one or more bearers may be released or the second It is configured to recognize that is transferred to the master base station,
the secondary base station according to claim 4.
[Claim 6]
　Wherein the at least one processor, said after accepting the SeNB addition request message from the second master base station, SeNB release request message said first master base station to trigger the release of resources for the dual connectivity is configured to receive from,
　the SeNB release request message, the indicates whether each of the at least one bearer is maintained by the secondary base station,
the secondary according to any one of claims 1 to 5 base station.
[Claim 7]
　A method in a secondary base station,
　SeNB added from the second master base station while providing secondary cell group for dual connectivity in conjunction with the first master base station (SCG) to the wireless terminal receiving a request message, the SeNB addition request message indicates whether each of the at least one bearer is already set to the secondary base station for the dual connectivity is maintained by the secondary base station and
　in response to receiving the SeNB addition request message, the second bearer may also be one or more not be maintained 1 or more first bearer is maintained by the secondary base station by the secondary base station , to distinguish
the method comprising.
[8.]
　The non-transitory computer readable medium storing a program for causing a process in the secondary base station to the computer,
　the method comprising
　the secondary cell group for dual connectivity in conjunction with the first master base station (SCG) to receive the SeNB addition request message from the second master base station while providing the wireless terminal, the SeNB addition request message is already set in the secondary base station for the dual connectivity each of the at least one bearer is indicating whether maintained by the secondary base station, and
　in response to receiving the SeNB addition request message, and the one or more first maintained by the secondary base station this distinguishes the bearer from the second bearer may also be one or more not be maintained by the secondary base station And
comprises,
non-transitory computer readable media.
[Claim 9]
　And at least one wireless transceiver
　and at least one processor coupled to the at least one radio transceiver,
comprising a
　at least one processor is for dual connectivity secondary base station in conjunction with the first master base station is configured to transmit the SeNB addition request message to the secondary base station while providing the secondary cell group (SCG) to the wireless terminal,
　the SeNB addition request message, the secondary base for said dual connectivity already it indicates whether each of the at least one bearer is set is maintained by the secondary base station, the station
the second master base station.
[Claim 10]
　Wherein the at least one processor is in response to said handover request received from the first master base station, the SeNB is configured to send the addition request message,
the second master base station according to claim 9 .
[Claim 11]
　Wherein the at least one processor, after receiving a response message to the SeNB addition request message from the secondary base station, configured to send a response message to the handover request to the first master base station,
　to said handover request the response message, the indicating at least one of each of the bearer is moved to be expectorated or the second master base station maintained by the secondary base station,
the second master base station according to claim 10.
[Claim 12]
　The response message to the handover request maintained, said third list showing one or more bearers allowed by the second master base station, and each bearer included in the third list is by the secondary base station including bearer status information element indicating transferred to or the second master base station is,
the second master base station according to claim 11.
[Claim 13]
　A method in a second master base station,
　SeNB added between the secondary base station is providing a secondary cell group for dual connectivity in conjunction with the first master base station (SCG) to the wireless terminal sending a request message to the secondary base station, the SeNB addition request message, wherein each of the at least one bearer is already set to the secondary base station is maintained by the secondary base station for the dual connectivity It indicates whether
the method comprising.
[Claim 14]
　The non-transitory computer readable medium storing a program for causing the method in the second master base station to the computer,
　the method, dual connectivity secondary base station in conjunction with the first master base station sending a SeNB addition request message to the secondary base station during the secondary cell group (SCG) is provided to the wireless terminal for the SeNB addition request message, the secondary base for said dual connectivity already each of the at least one bearer is set to the station indicates whether or not maintained by the secondary base station
comprises,
non-transitory computer readable media.
[Claim 15]
　A first master base station,
　and at least one wireless transceiver
　and at least one processor coupled to the at least one radio transceiver,
comprising a
　at least one processor, the secondary base station the first while in conjunction with the master base station provides a secondary cell group for dual connectivity the (SCG) to the wireless terminal, transmits a handover request of the wireless terminal to the second master base station, the handover request is configured to a response message received from the second master base station for,
　the response message, the dual each said secondary base station of the at least one bearer that has already been set to the secondary base station for connectivity is either or transferred to the second master base station maintained by the It is shown,
the first master base station.
[Claim 16]
　Wherein the at least one processor, after receiving the response message, the configured the resource SeNB release request message that triggers the release of for dual connectivity transmitted to the secondary base station,
　the SeNB release request message, wherein indicating whether at least one of each of the bearer is maintained by the secondary base station,
the first master base station according to claim 15.
[Claim 17]
　The SeNB release request message, comprising said bearer status information element indicating either or is released and maintained each of the at least one bearer by the secondary base station,
the first master base according to claim 16 station.
[Claim 18]
　A method in a first master base station,
　while the secondary base station is providing the secondary cell group (SCG) for dual connectivity in conjunction with the first master base station to the wireless terminal, wherein sending the handover request of the wireless terminal to the second master base station, and
　receiving a response message to the handover request from the second master base station, the response message, the order of the dual connectivity already indicate each of the at least one bearer is set is transferred to the expectorated or the second master base station maintained by the secondary base station to the secondary base station
method comprising.
[Claim 19]
　The non-transitory computer readable medium storing a program for causing a process in a computer in the first master base station,
　the method
　in the secondary base station in cooperation with the first master base station dual secondary cell group for connectivity the (SCG) while providing the wireless terminal, sending a handover request of the wireless terminal to the second master base station, and
　wherein a response message for the handover request first receiving from the second master base station, said response message, whether each of the at least one bearer is already set to the secondary base station for the dual connectivity is maintained by the secondary base station shows,
comprises,
non-transitory computer readable media.
[Claim 20]
　A wireless terminal,
　the first master base station, the second master base station, and at least one radio transceiver for communicating with the secondary base station,
　and at least one processor,
comprising a
　first master base station, the second master base station, and the secondary base station, the secondary cell group for dual connectivity the secondary base station in conjunction with the first master base station (SCG) wireless terminal when offering a is configured to perform the steps to change the second master base station master base station of the dual connectivity from the first master base station,
　the at least one processor,
　wherein during the procedure, the second master cell group on the master base station (MCG) SCG set on setting and the secondary base station It is configured to receive a constant from the first master base station,
　in response to said receipt of MCG setting and the SCG setting, the at least one bearer that has already been set to the secondary base station for the dual connectivity each is configured to recognize whether transferred to whether or the second master base station is maintained by the secondary base station,
　the connection to the SCG of secondary base stations including at least one bearer while it is holding, and is configured to change the master base station of the dual connectivity from the first master base station to the second master base station,
the wireless terminal.