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`US 20160029376Al
`
`c19) United States
`c12) Patent Application Publication
`FUKUTA et al.
`
`c10) Pub. No.: US 2016/0029376 Al
`Jan. 28, 2016
`(43) Pub. Date:
`
`(54) MOBILE COMMUNICATION SYSTEM AND
`USER TERMINAL
`
`(71) Applicant: KYOCERA CORPORATION, Kyoto
`(JP)
`
`(72)
`
`Inventors: Noriyoshi FUKUTA, Yokohama-shi
`(JP); Kugo MORITA, Yokohama-shi
`(JP); Chiharu YAMAZAKI, Ota-ku
`(JP); Henry CHANG, San Diego, CA
`(US); Amit KALHAN, San Diego, CA
`(US); Yushi NAGASAKA,
`Yokohama-shi (JP); Masato
`FUJISHIRO, Yokohama-shi (JP);
`Susumu KASHIWASE, Machida-shi
`(JP)
`
`(73)
`
`Assignee: KYOCERA CORPORATION, Kyoto
`(JP)
`
`(21) Appl. No.: 14/874,062
`
`(22)
`
`Filed:
`
`Oct. 2, 2015
`
`Related U.S. Application Data
`
`(63)
`
`Continuation of application No. PCT/JP2014/059839,
`filed on Apr. 3, 2014.
`
`(60) Provisional application No. 61/808,794, filed on Apr.
`5, 2013, provisional application No. 61/864,186, filed
`on Aug. 9, 2013, provisional application No. 61/934,
`241, filed on Jan. 31, 2014.
`
`Publication Classification
`
`(51)
`
`(52)
`
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`
`Int. Cl.
`H04W72/04
`H04B 7106
`H04W8/24
`H04W74/00
`U.S. Cl.
`CPC ........ H04W 7210426 (2013.01); H04W 741002
`(2013.01); H04B 710632 (2013.01); H04W 8124
`(2013.01); H04W 88/10 (2013.01)
`
`(57)
`
`ABSTRACT
`
`A base station is used for a mobile communication system
`that supports a dual connectivity. The base station includes a
`controller configured to establish an RRC connection with a
`user terminal, and to perform a mobility control in the dual
`connectivity.
`
`- - - -
`
`I
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`
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`
`10
`E-UTRAN
`
`s;
`X2~ y/2
`
`eNB " ' \ \ (~x~ ,/ / : eNB
`
`eNB
`
`200-2
`
`100-2
`
`I
`
`UE
`
`100-3
`
`I
`
`UE
`
`100-1
`
`I
`
`UE
`
`Ex.1020
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`

`Patent Application Publication
`
`Jan. 28, 2016 Sheet 1 of 17
`
`US 2016/0029376 Al
`
`FIG.1
`
`20 EPC
`
`300-2
`
`~
`
`300-1
`
`~
`
`/
`/
`/
`/
`/
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`E-UTRAN
`
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`,
`,'
`
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`~ j/
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`
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`
`100-2
`
`I
`
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`
`100-3
`
`I
`
`UE
`
`100-1
`
`I
`
`UE
`
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`

`Patent Application Publication
`
`Jan. 28, 2016 Sheet 2 of 17
`
`US 2016/0029376 Al
`
`FIG. 2
`
`120
`,J
`
`r-------------------
`160
`,J
`
`100
`;
`
`UE
`
`110
`\
`RADIO
`--,---- TRANSCEIVER
`
`01
`1
`c
`
`'
`..,
`"
`
`'
`I
`
`--'--
`
`I
`I
`
`USER
`INTERFACE
`✓- ✓130
`1-------J ___ ,
`GNSS
`RECEIVER :
`-----------·
`140
`I BATTER~ I
`
`PROCESSOR
`
`150
`
`_)
`
`I
`MEMORY
`
`160'
`..... -.... ..,·
`
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`
`- - - - - - - - - - - - - - - - - - - I
`
`220
`r1
`NETWORK
`INTERFACE
`
`FIG. 3
`
`/240
`
`-
`
`PROCESSOR
`
`-
`
`I
`I MEMORY
`
`230
`
`200
`~
`
`eNB
`2)0
`RADIO
`TRANSCEIVER
`
`
`2 01
`{
`
`'
`I
`
`'
`•
`"
`
`Ex.1020
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`

`Patent Application Publication
`
`Jan. 28, 2016 Sheet 3 of 17
`
`US 2016/0029376 Al
`
`r--------------1
`: MME
`:
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`.
`
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`
`ll>
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`
`r---------------,
`: UE
`:
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`
`FIG. 4
`
`feNB
`
`I
`
`1
`
`I
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`
`IE!
`NAS
`rt- BEARER --t--1 .... _R_R_C __
`.-------. :
`·--------
`RRC
`,..___P_D_CP_ ..... H
`!lt .... l _P_D_CP _ __,
`-------.'
`,,..__ __ _,
`,..__ __ _.,
`Li_: LOGICAL ~
`RLC
`I I CHANNEL ----..
`RLC
`MAC
`LLTRANSPORTJJ
`MAC
`·--------
`,___ _ _ ____,r-;- CHANNEL----:-, .... ____ __,
`....__P_HY _ __,rf- ~~\~2~t -ti .... _P_HY _
`-------.'
`--------------•
`
`RADIO
`
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`
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`L--------------
`
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`
`FIG. 5
`
`1 RADIO FRAME
`
`:1 SLOT ,
`IE
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`
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`!E 1 SUBFRAME lt!
`
`I
`
`I
`
`-TIME
`
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`Patent Application Publication
`
`Jan. 28, 2016 Sheet 4 of 17
`
`US 2016/0029376 Al
`
`_J
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`

`Patent Application Publication
`
`Jan. 28, 2016 Sheet 5 of 17
`
`US 2016/0029376 Al
`
`200-2~
`
`200-1
`
`FIG. 7
`
`100 i
`
`CONNECTION
`
`RRM
`
`MEASUREMENT REPORT
`
`S104
`
`S101
`
`S102
`
`S103
`
`S105
`DUAL CONNECTIVITY REQUEST
`)
`------------·r·----------L---
`AcK, RACH INFORMATION
`- - - - - - - - - - - - - 7 - - - - - - - - - - - - -
`--- UE ~ON~EXT,_ MA~RO qELL'S AS CONFIGURATION _ __,:_
`RRC RECONFIGURATION
`RACH INITIATION
`(TO SMALL CELL)
`
`S108
`
`RACH
`
`PHY CONNECTION
`
`MEASUREMENT REPORT
`
`S111
`
`S112
`
`S113
`,
`DUAL CONNECTIVITY RELEASE
`_..,J
`- - - - - - - - - - - - · - r - · - - - - - - - - - -~ - S114
`RELEASE COMPLETE, REMAINING DATA TRANSFER
`_..,J
`
`RRC RECONFIGURATION
`
`S115
`
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`Patent Application Publication
`
`Jan. 28, 2016 Sheet 6 of 17
`
`US 2016/0029376 Al
`
`200·2i
`
`200-1
`
`FIG. 8
`
`100 i
`
`CONNECTION
`
`MEASUREMENT REPORT
`S204
`
`S201
`
`S202
`S203
`
`S205
`DUAL CONNECTIVITY REQUEST
`)
`----------·7·----------___J_-
`ACK, RACH INFORMATION
`- - - - - - - - - - - 7 - - - - - - - - - - - - -
`____________ l ___________ _
`UE CONTEXT, MACRO CELL'S AS CONFIGURATION
`RACH INITIATION TO SMAL
`ELL)
`
`RACH
`CONNECTION
`
`S212
`
`MEASUREMENT REPORT
`
`MEASUREMENT REPORT
`
`MEASUREMENT REPORT
`
`DUAL CONNECTIVITY RELEASE
`- - - - - - - - - - -~ - - - - - - - - - - - - - -
`~ - - - - - - - - - RELEASEACK ________ _
`
`S213
`
`S216
`S217
`
`4 --------·-;r20 ·--------
`
`RELEASE COMPLETE, REMAINING DATA TRANSFER
`
`CONNECTION RELEASE
`
`.
`
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`Patent Application Publication
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`Jan. 28, 2016 Sheet 7 of 17
`
`US 2016/0029376 Al
`
`FIG. 9
`
`100 i
`
`200-2 ~
`
`CONNECTION
`
`MEASUREMENT REPORT
`S304
`
`S301
`
`S302
`S303
`
`S305
`.J
`DUAL CONNECTIVITY REQUEST
`- - - - - - - - - - -7 - - - - - - - - - - - - - - -L -
`ACK, RACH INFORMATION
`- - - - - - - - - - - 7 - - - - - - - - - - - - -
`UE CONTEXT, MACRO CELL'S AS CONFIGURATION
`- RRC RECONFIGURATION 1-----------(cid:173)
`RACH INITIATION (TO SMALL CELL)
`RACH
`CONNECTION
`
`S312
`
`MEASUREMENT REPORT
`
`MEASUREMENT REPORT
`
`MEASUREMENT REPORT
`
`DUAL CONNECTIVITY RELEASE
`- - - - - - - - - - · - · t - · - - - - - - - - - - -
`~ - - - - - - - - - RELEASEACK ________ _
`
`RRC RECONFIGURATION
`
`S313
`
`S316
`S317
`S318
`
`S321
`
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`Patent Application Publication
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`Jan. 28, 2016 Sheet 8 of 17
`
`US 2016/0029376 Al
`
`200-1
`
`FIG. 10
`
`100 i
`
`) <x)
`200-2 1J
`
`connection
`
`S403
`
`measurement report
`
`RACH
`
`RRC reconfiguration
`
`UE Context, Remaining data transfer
`
`connection
`
`S411
`
`S413
`
`Dual connectivity request
`- - - - - - - - - - - - - - - ; - - - - - - - - - - - - -
`ACK, RACH information
`- - - - - - - - · - · - - - - - t - · - - - - - - - - - - - -
`UE Context, Macro cell's AS configuration
`
`S417
`
`RRC reconfiguration
`RACH initiation (to small cell)
`
`RACH
`
`Phy connection
`
`measurement report
`
`S421
`
`Dual connectivity release
`- - - - - - - - - - - - - - - - i - - - - - - - - - - - - -
`
`Release complete, Remaining data transfer
`S424
`
`RRC reconfiguration
`
`S422
`S423
`
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`Jan. 28, 2016 Sheet 9 of 17
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`US 2016/0029376 Al
`
`200-1
`
`FIG. 11
`
`100 i
`
`200-2~
`
`CONNECTION
`
`S503
`
`MEASUREMENT REPORT
`
`- S506 ----·7----------
`
`MEASUREMENT REPORT TRANSFER
`
`DUAL CONNECTIVITY AVAILABLE
`---------
`-----------
`RACH INITIATION
`RACH
`
`UE CONTEXT TRANSFER
`CONNECTION
`
`S512
`
`MEASUREMENT REPORT
`
`S513
`
`S514
`
`MEASUREMENT REPORT
`
`MEASUREMENT REPORT
`
`DUAL CONNECTIVITY RELEASE
`- - - - - - - - - - - - r - - - - - - - - - - - - -
`RELEASEACK
`
`CONNECTION RELEASE
`
`RELEASE COMPLETE, REMAINING DATA TRANSFER
`
`-----------7·------------
`
`.
`
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`Patent Application Publication
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`Jan. 28, 2016 Sheet 10 of 17
`
`US 2016/0029376 Al
`
`200-1
`
`FIG.12
`
`100 i
`
`200-2~
`
`CONNECTION
`
`S603
`
`MEASUREMENT REPORT
`
`RACH
`
`UE CONTEXT TRANSFER
`CONNECTION
`
`S612
`
`MEASUREMENT REPORT
`
`S613
`
`S614
`
`MEASUREMENT REPORT
`
`MEASUREMENT REPORT
`
`DUAL CONNECTIVITY RELEASE
`- - - - - - - - · - · - - - - - t · - - - - - - - - - - - -
`RELEASEACK
`- - - - - - - - - - -
`- - - - - - - - - - - - -
`S619
`RRC RECONFIGURATION
`___ RELEASE COMPLETE(EMAINING DATA TRANSFER_ -
`CONNECTION
`CONNECTION
`
`S622
`
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`Patent Application Publication
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`Jan. 28, 2016 Sheet 11 of 17
`
`US 2016/0029376 Al
`
`FIG. 13
`
`MACRO CELL
`(FREQUENCY 1)
`
`<x)~
`{s-200-1
`
`eNB
`
`UE100
`
`SMALL CELL
`(FREQUENCY 2)
`_...+-_-.Lr
`
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`Patent Application Publication
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`Jan. 28, 2016 Sheet 12 of 17
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`US 2016/0029376 Al
`
`FIG.14
`
`eNB 200-1
`(MACRO CELL)
`
`UE100
`
`S1101
`
`RRC
`CONNECTED
`
`UE CAPABILITY INFORMATION
`
`S1102
`
`DEDICATED CONTROL INFORMATION
`
`S1103
`
`S1104
`
`RRCIDLE
`
`S1105
`
`CELL
`RESELECTION
`CONTROL
`
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`Patent Application Publication
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`Jan. 28, 2016 Sheet 13 of 17
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`US 2016/0029376 Al
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`FIG. 15
`
`eNB 200-1
`(MACRO CELL)
`
`UE100 I ~1201
`I RRC IDLE I
`
`BROADCAST CONTROL INFORMATION _
`(ACCESS RESTRICTION)
`)
`S1202
`
`S)203
`
`CELL
`RESELECTION
`CONTROL
`
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`Patent Application Publication
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`Jan. 28, 2016 Sheet 14 of 17
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`US 2016/0029376 Al
`
`FIG.16
`
`E-UTRAN10
`OR
`EPC20
`
`UE100 S1301
`
`RRC
`S1302 CONNECTED
`SMALL CELL LIST
`
`S1303
`
`RRC IDLE
`
`S1304
`
`CELL
`RESELECTION
`CONTROL
`
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`Patent Application Publication
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`Jan. 28, 2016 Sheet 15 of 17
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`US 2016/0029376 Al
`
`FIG.17
`
`eNB 200-2
`(SMALL CELL)
`
`UE100
`
`I S1401
`I RRC IDLE I
`
`,,J
`
`BROADCAST CONTROL INFORMATION
`(CELL TYPE= SMALL CELL) )
`S1402
`
`:::
`
`S1403
`/
`
`CELL
`RESELECTION
`CONTROL
`
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`Patent Application Publication
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`Jan. 28, 2016 Sheet 16 of 17
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`US 2016/0029376 Al
`
`_J
`_J
`
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`Patent Application Publication
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`Jan. 28, 2016 Sheet 17 of 17
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`US 2016/0029376 Al
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`FIG. 19
`
`MeNB
`
`~CQlofMeNB
`
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`US 2016/0029376 Al
`
`Jan. 28, 2016
`
`1
`
`MOBILE COMMUNICATION SYSTEM AND
`USER TERMINAL
`
`CROSS REFERENCE
`
`[0001] The entire contents of U.S. Provisional Application
`No. 61/808,794 (filed on Apr. 5, 2013), U.S. Provisional
`Application No. 61/864,186 (filedonAug. 9, 2013), and U.S.
`Provisional Application No. 61/934,241 (filed on Jan. 31,
`2014) are incorporated herein by reference.
`
`TECHNICAL FIELD
`
`[0002] The present disclosure relates to a mobile commu(cid:173)
`nication system that supports a dual connectivity.
`
`BACKGROUND ART
`
`[0003]
`In 3GPP (3rd Generation Partnership Project) which
`is a project aiming to standardize a mobile communication
`system, introduction of a dual connectivity has been dis(cid:173)
`cussed (see Non-patent document 1).
`[0004] The dual connectivity is a scheme in which a user
`terminal establishes a pair of connections with a pair of cells
`which is a combination of cells managed by different base
`stations.
`
`PRIOR ART DOCUMENT
`
`Non-Patent Document
`
`[0005] Non-patent document 1: 3GPP Contribution
`RP-122033
`
`SUMMARY
`
`[0006] However, in the current situation, there is a problem
`that there is no mechanism for appropriately controlling the
`dual connectivity.
`[0007] Therefore, the present disclosure provides a mobile
`communication system capable of appropriately controlling
`the dual connectivity.
`
`BRIEF DESCRIPTION OF DRAWINGS
`
`[0008] FIG. 1 is a configuration diagram of an LTE system
`according to a first embodiment and a second embodiment.
`[0009] FIG. 2 is a block diagram ofUE according to the first
`embodiment and the second embodiment.
`[0010] FIG. 3 is a block diagram of eNB according to the
`first embodiment and the second embodiment.
`[0011] FIG. 4 is a protocol stack diagram of a radio inter(cid:173)
`face in the LTE system.
`[0012] FIG. 5 is a configuration diagram of a radio frame
`used in the LTE system.
`[0013] FIG. 6 is a diagram illustrating an operation envi(cid:173)
`ronment according to the first embodiment and the second
`embodiment.
`[0014] FIG. 7 is a sequence diagram of an operation pattern
`1-1 according to the first embodiment.
`[0015] FIG. 8 is a sequence diagram of an operation pattern
`1-2 according to the first embodiment.
`[0016] FIG. 9 is a sequence diagramofa modification of the
`operation pattern 1-2 according to the first embodiment.
`[0017] FIG. 10 is a sequence diagram of an operation pat(cid:173)
`tern 2-1 according to the first embodiment.
`[0018] FIG. 11 is a sequence diagram of an operation pat(cid:173)
`tern 2-2 according to the first embodiment.
`
`[0019] FIG. 12 is a sequence diagram of a modification of
`the operation pattern 2-2 according to the first embodiment.
`[0020] FIG. 13 is a diagram illustrating an operation envi(cid:173)
`ronment according to a first modification of the second
`embodiment.
`[0021] FIG. 14 is a sequence diagram illustrating an opera(cid:173)
`tion sequence according to the first modification of the second
`embodiment.
`[0022] FIG. 15 is a sequence diagram illustrating an opera(cid:173)
`tion sequence according to a second modification of the sec(cid:173)
`ond embodiment.
`[0023] FIG. 16 is a sequence diagram illustrating an opera(cid:173)
`tion sequence according to a third modification of the second
`embodiment.
`[0024] FIG. 17 is a sequence diagram illustrating an opera(cid:173)
`tion sequence according to a fourth modification of the sec(cid:173)
`ond embodiment.
`[0025] FIG. 18 is a diagram illustrating an operation envi(cid:173)
`ronment according to other embodiments.
`[0026] FIG. 19 is a diagram according to an additional
`statement 3 of embodiments.
`
`DESCRIPTION OF EMBODIMENTS
`
`Overview of Embodiments
`
`[0027] A mobile communication system according to
`embodiments supports a dual connectivity. The mobile com(cid:173)
`munication system comprises: a first base station that estab(cid:173)
`lishes an RRC connection with a user terminal, and performs
`a mobility control in the dual connectivity; and a second base
`station that is adjacent to the first base station. The first base
`station transmits, to the second base station, an allocation
`request requesting additional radio resources for the user
`terminal when the first base station decides to start the dual
`connectivity.
`[0028]
`In the embodiments, the second base station trans(cid:173)
`mits a response to the first base station in accordance with a
`reception of the establishment request, the response including
`information on a random access channel to be used for per(cid:173)
`forming a random access to the second base station by the
`user terminal.
`[0029]
`In the embodiments, upon receiving the response,
`the first base station transmits, to the second base station,
`context information on the user terminal and configuration
`parameters in the first base station.
`[0030] A mobile communication system according to
`embodiments supports a dual connectivity. The mobile com(cid:173)
`munication system comprises: a first base station that estab(cid:173)
`lishes an RRC connection with a user terminal, and performs
`a mobility control in the dual connectivity; and a second base
`station that is adjacent to the first base station, and allocates
`additional radio resources to the user terminal during the dual
`connectivity. The first base station transmits, to the second
`base station, a release request requesting a release of the
`additional radio resources when the first base station decides
`to end the dual connectivity.
`[0031]
`In the embodiments, upon receiving the release
`request, the second base station transmits, to the first base
`station, a release notification for notifying release of the addi(cid:173)
`tional radio resources. After a transmission of the release
`notification, the second base station transmits, to the first base
`station, data that the second base station has not transmitted to
`the user terminal.
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`[0032] A mobile communication system according to
`embodiments supports a dual connectivity. The mobile com(cid:173)
`munication system comprises: a first base station that estab(cid:173)
`lishes an RRC connection with a user terminal, and performs
`a mobility control in the dual connectivity; and a second base
`station that is adjacent to the first base station, and allocates
`additional radio resources to the user terminal during the dual
`connectivity. The second base station queries the first base
`station regarding a feasibility of release of the additional radio
`resources when the second base station decides to end the
`dual connectivity.
`In the embodiments, the second base station trans(cid:173)
`[0033]
`mits, to the first base station, a release notification for the
`additional radio resources when the first base station allows
`the release of the additional radio resources. After a transmis(cid:173)
`sion of the release notification, the second base station trans(cid:173)
`mits, to the first base station, data that the second base station
`has not transmitted to the user terminal.
`[0034] A mobile communication system according to
`embodiments supports a dual connectivity. The mobile com(cid:173)
`munication system comprises: a first base station that estab(cid:173)
`lishes an RRC connection with a user terminal, and performs
`a mobility control in the dual connectivity; and a second base
`station that is adjacent to the first base station, and allocates
`additional radio resources to the user terminal during the dual
`connectivity. The second base station releases the additional
`radio resources and transmits, to the first base station, a noti(cid:173)
`fication indicating that an allocation of the additional radio
`resources can't be maintained, when the second base station
`decides that the allocation of the additional radio resources
`has to be ended.
`In the embodiments, after a transmission of the noti(cid:173)
`[0035]
`fication, the second base station transmits, to the first base
`station, data that the second base station has not transmitted to
`the user terminal.
`[0036] A mobile communication system according to
`embodiments supports a dual connectivity. The mobile com(cid:173)
`munication system comprises: a first base station that estab(cid:173)
`lishes an RRC connection with a user terminal, and performs
`a mobility control in the dual connectivity; and a second base
`station that is adjacent to the first base station, and allocates
`additional radio resources to the user terminal during the dual
`connectivity. The second base station transmits, to the first
`base station, a release notification indicating a release of the
`additional radio resources when the second base station
`decides to end the dual connectivity based on a measurement
`report from the user terminal.
`[0037] A mobile communication system according to
`embodiments supports a dual connectivity. The mobile com(cid:173)
`munication system comprises: a first base station that estab(cid:173)
`lishes an RRC connection with a user terminal, and performs
`a mobility control in the dual connectivity; and a second base
`station that is adjacent to the first base station, and allocates
`additional radio resources to the user terminal during the dual
`connectivity. The user terminal transmits a first CQI report to
`the first base station and a second CQI report to the second
`base station during the dual connectivity.
`[0038] A mobile communication system according to
`embodiments supports a dual connectivity. The mobile com(cid:173)
`munication system comprises: a first base station that per(cid:173)
`forms a mobility control in the dual connectivity; and a sec(cid:173)
`ond base station that is adjacent to the first base station. The
`second base station transmits broadcast information for pro(cid:173)
`hibiting the user terminal that supports the dual connectivity
`
`from camping on a cell of the second base station. The user
`terminal that is in an idle state camps on a cell of the first base
`station without camping on the cell of the second base station,
`based on the broadcast information.
`In the embodiments, the broadcast information is
`[0039]
`information indicating a specific access class. The user ter(cid:173)
`minal decides that camping on the cell of the second base
`station is prohibited when an access class of the user terminal
`is the specific access class.
`In the embodiments, the broadcast information is
`[0040]
`information indicating an access regulation for a user termi(cid:173)
`nal conforming to a specific release that supports the dual
`connectivity. The user terminal decides that camping on the
`cell of the second base station is prohibited when the release
`to which the user terminal conforms is the specific release and
`when the user terminal supports the dual connectivity.
`[0041] A mobile communication system according to
`embodiments supports a dual connectivity. The mobile com(cid:173)
`munication system comprises: a first base station that per(cid:173)
`forms a mobility control in the dual connectivity; and a sec(cid:173)
`ond base station that is adjacent to the first base station. The
`user terminal that is camping on a cell of the second base
`station in an idle state establishes a connection with the first
`base station after re-selecting a cell of the first base station,
`when starting communication in which the dual connectivity
`should be applied.
`[0042] A mobile communication system according to
`embodiments comprises: a base station that manages a cell;
`and a user terminal that support a dual connectivity with cells
`belonging to different frequencies. The user terminal trans(cid:173)
`mits capability information indicating a frequency band for
`which the user terminal can use in the dual connectivity. The
`base station determines whether to apply the dual connectiv(cid:173)
`ity to the user terminal based on the capability information.
`[0043] A mobile communication system according to
`embodiments supports a dual connectivity. The mobile com(cid:173)
`munication system comprises: a first base station that estab(cid:173)
`lishes an RRC connection with a user terminal, and performs
`a mobility control in the dual connectivity; and a second base
`station that is adjacent to the first base station, and allocates
`additional radio resources to the user terminal during the dual
`connectivity. The first base station decides a splitting mode of
`traffic of the user terminal, before starting the dual connec(cid:173)
`tivity or during an execution of the dual connectivity.
`[0044] A mobile communication system according to
`embodiments supports a dual connectivity. The mobile com(cid:173)
`munication system comprises: a first base station that estab(cid:173)
`lishes an RRC connection with a user terminal, and performs
`a mobility control in the dual connectivity; and a second base
`station that is adjacent to the first base station, and allocates
`additional radio resources to the user terminal during the dual
`connectivity. The first base station instruct a start of the dual
`connectivity to the user terminal when starting the dual con(cid:173)
`nectivity.
`[0045] A user terminal according to embodiments supports
`a dual connectivity scheme in which connections with a plu(cid:173)
`rality of cells managed by different base stations are estab(cid:173)
`lished simultaneously. The user terminal comprises: a con(cid:173)
`troller configured to perform a cell reselection for selecting a
`serving cell of the user terminal in an idle state. The plurality
`of cells include a first cell and a second cell, the second cell
`having a coverage narrower than a coverage of the first cell.
`The controller performs a cell reselection control for select-
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`ing the first cell as the serving cell without selecting the
`second cell as the serving cell.
`[0046]
`In the embodiments, the user terminal further com(cid:173)
`prises: a receiver configured to receive control information
`used for the cell reselection control, from the first cell or the
`second cell. The first cell belongs to a first frequency, and the
`second cell belongs to a second frequency. The control infor(cid:173)
`mation is information for relatively lowering a priority of the
`second frequency than a priority of the first frequency in the
`cell reselection. The controller performs the cell reselection
`control on the basis of the control information.
`[0047]
`In the embodiments, the controller notifies the first
`cell of capability information indicating that the user terminal
`supports the dual connectivity scheme, in a case where the
`RRC connection is established with the first cell. The receiver
`receives the control information transmitted in unicast from
`the first cell to the user terminal.
`[0048]
`In the embodiments, the user terminal comprises: a
`receiver that receives broadcast information used for the cell
`reselection control from the second cell. The broadcast infor(cid:173)
`mation is information indicating an access restriction on a
`user terminal that supports the dual connectivity scheme. The
`controller performs the cell reselection control based on the
`broadcast information.
`[0049]
`In the embodiments, the controller performs a pro(cid:173)
`cess for establishing a connection with the second cell irre(cid:173)
`spective of the access restriction, when the user terminal is
`controlled to establish the connection with the second cell
`from the first cell after establishing the RRC connection with
`the first cell.
`[0050]
`In the embodiments, the controller acquires a list
`that includes an identifier of the second cell, from a network
`including the plurality of cells. The controller performs the
`cell reselection control based on the list.
`[0051]
`In the embodiments, the cell reselection control is a
`control that prohibits a selection of the second cell as the
`serving cell.
`[0052]
`In the embodiments, the cell reselection control is a
`control that relatively lowers a priority of the second cell than
`a priority of the first cell in the cell reselection.
`[0053]
`In the embodiments, the user terminal comprises: a
`receiver that receives broadcast information used for the cell
`reselection control from the second cell. The broadcast infor(cid:173)
`mation is information indicating a cell type of a cell from
`which the broadcast information is transmitted. The control(cid:173)
`ler performs the cell reselection control on the basis of the
`broadcast information.
`[0054]
`In the embodiments, the cell reselection control is a
`control that prohibits a selection of the second cell as the
`serving cell.
`[0055]
`In the embodiments, the cell reselection control is a
`control that relatively lowers a priority of the second cell than
`a priority of the first cell in the cell reselection.
`[0056] A communication control method according to
`embodiments comprises a step of performing, by a user ter(cid:173)
`minal supporting a dual connectivity scheme in which con(cid:173)
`nections with a plurality of cells managed by different base
`stations are established simultaneously, a cell reselection for
`selecting a serving cell of the user terminal in an idle state.
`The plurality of cells include a first cell and a second cell, the
`second cell having a coverage narrower than a coverage of the
`first cell. The step of performing the cell reselection com(cid:173)
`prises a step of performing a cell reselection control for
`
`selecting the first cell as the serving cell without selecting the
`second cell as the serving cell.
`[0057] A processor according to embodiments is provided
`with a user terminal supporting a dual connectivity scheme in
`which connections with a plurality of cells managed by dif(cid:173)
`ferent base stations are established simultaneously. The pro(cid:173)
`cessor executes a step of performing a cell reselection for
`selecting a serving cell of the user terminal in an idle state.
`The plurality of cells include a first cell and a second cell, the
`second cell having a coverage narrower than a coverage of the
`first cell. The step of performing the cell reselection com(cid:173)
`prises a step of performing a cell reselection control for
`selecting the first cell as the serving cell without selecting the
`second cell as the serving cell.
`
`First Embodiment
`
`[0058] Hereinafter, with reference to the accompanying
`drawings, an embodiment will be described in a case where
`the present disclosure is applied to LTE (Long Term Evolu(cid:173)
`tion) standardized by 3GPP.
`[0059]
`(Configuration ofLTE System)
`[0060] FIG. 1 is a configuration diagram of an LTE system
`according to a first embodiment. As illustrated in FIG. 1, the
`LTE system includes a plurality ofUEs (User Equipments)
`100, E-UTRAN (Evolved-UMTS Terrestrial Radio Access
`Network) 10, andEPC (Evolved Packet Core) 20. The E-UT(cid:173)
`RAN 10 corresponds to a radio access network and the EPC
`20 corresponds to a core network. The E-UTRAN 10 and the
`EPC 20 constitute a network of the LTE system.
`[0061] The UE 100 is a mobile communication device and
`performs radio communication with a cell (a serving cell)
`with which a connection is established. The UE 100 corre(cid:173)
`sponds to the user terminal.
`[0062] The E-UTRAN 10 includes a plurality of eNBs 200
`(evolved Node-Bs). The eNB 200 corresponds to the base
`station. The eNB 200 manages one or a plurality of cells and
`performs radio communication with the UE 100 which estab(cid:173)
`lishes a connection with the cell of the eNB 200. It is noted
`that the "cell" is used as a term indicating a minimum unit of
`a radio communication area, and is also used as a term indi(cid:173)
`cating a function of performing radio communication with
`the UE 100.
`[0063] The eNB 200, for example, has a radio resource
`management (RRM) function, a routing function for user
`data, and a measurement control function for mobility control
`and scheduling.
`[0064] The EPC 20 includes a plurality of MME (Mobility
`Management Entity)/S-GWs (Serving-Gateways) 300. The
`MME is a network node that performs various mobility con(cid:173)
`trols and the like for the UE 100 and corresponds to a con(cid:173)
`troller. The S-GW is a network node that performs control to
`transfer user data and corresponds to a mobile switching
`center. The EPC 20 including the MME/S-GW 300 accom(cid:173)
`modates the eNB 200.
`[0065] The eNBs 200 are connected mutually via an X2
`interface. Furthermore, the eNB 200 is connected to the
`MME/S-GW 300 via an Sl interface.
`[0066] Next, the configurations of the UE 100 and the eNB
`200 will be described.
`[0067] FIG. 2 is a block diagram of the UE 100. As illus(cid:173)
`trated in FIG. 2, the UE 100 includes an antenna 101, a radio
`transceiver 110, a user interface 120, a GNSS (Global Navi(cid:173)
`gation Satellite System) receiver 130, a battery 140, a
`memory 150, and a processor 160. The memory 150 and the
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`processor 160 constitute a controller. The UE 100 may not
`have the GNSS receiver 130. Furthermore, the memory 150
`may be integrally formed with the processor 160, and this set
`(that is, a chip set) may be called a processor 160'.
`[0068] The antenna 101 and the radio transceiver 110 are
`used to transmit and receive a radio signal. The radio trans(cid:173)
`ceiver 110 converts a baseband signal (a transmission signal)
`output from the processor 160 into the radio signal and trans(cid:173)
`mits the radio signal from the antenna 101. Furthermore, the
`radio transceiver 110 converts a radio signal received by the
`antenna 101 into a baseband signal (a received signal), and
`outputs the baseband signal to the processor 160.
`[0069] The user interface 120 is an interface with a user
`carrying the UE 100, and includes, for example, a display, a
`microphone, a speaker, various buttons and the like. The user
`interface 120 accepts an operation from a user and outputs a
`signal indicating the content of the operation to the processor
`160. The GNSS receiver 130 receives a GNSS signal in order
`to obtain location informat