WO2015141607A1 - 通信システム - Google Patents
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- WO2015141607A1 WO2015141607A1 PCT/JP2015/057611 JP2015057611W WO2015141607A1 WO 2015141607 A1 WO2015141607 A1 WO 2015141607A1 JP 2015057611 W JP2015057611 W JP 2015057611W WO 2015141607 A1 WO2015141607 A1 WO 2015141607A1
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- H04W36/08—Reselecting an access point
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- H—ELECTRICITY
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- H04W36/26—Reselection being triggered by specific parameters by agreed or negotiated communication parameters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Definitions
- the present invention relates to a communication system that performs wireless communication between a communication terminal device and a base station device.
- LTE Long Term Evolution
- SAE system architecture evolution
- SAE System Architecture Evolution
- OFDM Orthogonal Frequency Division Multiplexing
- SC-FDMA Single Carrier Frequency Division Multiple Access
- Non-Patent Document 1 (Chapter 5), 3GPP determination items related to the frame configuration in the LTE system will be described with reference to FIG.
- FIG. 1 is an explanatory diagram showing a configuration of a radio frame used in an LTE communication system.
- one radio frame (Radio frame) is 10 ms.
- the radio frame is divided into ten equally sized subframes.
- the subframe is divided into two equally sized slots.
- a downlink synchronization signal (Downlink Synchronization Signal: SS) is included in the first and sixth subframes for each radio frame.
- the synchronization signal includes a first synchronization signal (Primary Synchronization Signal: P-SS) and a second synchronization signal (Secondary Synchronization Signal: S-SS).
- Non-Patent Document 1 (Chapter 5) describes the decision items regarding the channel configuration in the LTE system in 3GPP. It is assumed that the same channel configuration as that of the non-CSG cell is used in a CSG (Closed Subscriber Group) cell.
- the physical broadcast channel (Physical channel PBCH) is a channel for downlink transmission from the base station to the mobile terminal.
- a BCH transport block (transport block) is mapped to four subframes in a 40 ms interval. There is no obvious signaling of 40ms timing.
- the physical control format indicator channel (Physical Control Format Indicator Channel: PCFICH) is a channel for downlink transmission from the base station to the mobile terminal.
- PCFICH notifies the number of OFDM (Orthogonal Frequency Division Multiplexing) symbols used for PDCCHs from the base station to the mobile terminal.
- PCFICH is transmitted for each subframe.
- the physical downlink control channel (Physical Downlink Control Channel: PDCCH) is a channel for downlink transmission from the base station to the mobile terminal.
- the PDCCH includes resource allocation (allocation) information of a downlink shared channel (DL-SCH), which is one of transport channels described later, and a paging channel (Paging channel: PCH, one of transport channels described later). ) Resource allocation (allocation) information and HARQ (Hybrid Automatic Repeat reQuest) information related to DL-SCH.
- the PDCCH carries an uplink scheduling grant (Uplink Scheduling Grant).
- the PDCCH carries Ack (Acknowledgement) / Nack (Negative Acknowledgment) which is a response signal for uplink transmission.
- the PDCCH is also called an L1 / L2 control signal.
- a physical downlink shared channel is a channel for downlink transmission from a base station to a mobile terminal.
- a downlink shared channel (DL-SCH) that is a transport channel and PCH that is a transport channel are mapped.
- the physical multicast channel is a channel for downlink transmission from the base station to the mobile terminal.
- a multicast channel (Multicast Channel: MCH) that is a transport channel is mapped to the PMCH.
- the physical uplink control channel (Physical Uplink Control Channel: PUCCH) is a channel for uplink transmission from the mobile terminal to the base station.
- the PUCCH carries Ack / Nack which is a response signal (response signal) for downlink transmission.
- the PUCCH carries a CQI (Channel Quality Indicator) report.
- CQI is quality information indicating the quality of received data or channel quality.
- the PUCCH carries a scheduling request (SR).
- SR scheduling request
- the physical uplink shared channel (Physical Uplink Shared Channel: PUSCH) is a channel for uplink transmission from the mobile terminal to the base station.
- An uplink shared channel (Uplink Shared Channel: UL-SCH), which is one of the transport channels, is mapped to the PUSCH.
- the physical HARQ indicator channel (Physical ARQ Indicator Channel: PHICH) is a channel for downlink transmission from the base station to the mobile terminal. PHICH carries Ack / Nack which is a response signal for uplink transmission.
- a physical random access channel (Physical Random Access Channel: PRACH) is a channel for uplink transmission from a mobile terminal to a base station. The PRACH carries a random access preamble.
- the downlink reference signal (Reference Signal: RS) is a symbol known as an LTE communication system.
- the following five types of downlink reference signals are defined.
- Data demodulation reference signals (Demodulation Reference Signals: DM-RSs) which are cell-specific reference signals (Cell-specific Reference Signals: CRSs), MBSFN reference signals (MBSFN reference signals), and UE-specific reference signals (UE-specific reference signals).
- Position determination reference signals Position determination reference signals (Positioning Reference Signals: PRSs), channel information reference signals (Channel-State Information Reference Signals: CSI-RSs).
- PRSs Position determination reference signals
- CSI-RSs Channel Information Reference Signals
- As a measurement of the physical layer of the mobile terminal there is a reference signal received power (RSRP) measurement.
- RSRP reference signal received power
- Non-Patent Document 1 (Chapter 5) will be described.
- a broadcast channel (Broadcast Channel: BCH) is broadcast to the entire coverage of the base station (cell).
- the BCH is mapped to the physical broadcast channel (PBCH).
- PBCH physical broadcast channel
- HARQ Hybrid ARQ
- DL-SCH downlink shared channel
- the DL-SCH can be broadcast to the entire coverage of the base station (cell).
- DL-SCH supports dynamic or semi-static resource allocation. Quasi-static resource allocation is also referred to as persistent scheduling.
- DL-SCH supports discontinuous reception (DRX) of a mobile terminal in order to reduce power consumption of the mobile terminal.
- the DL-SCH is mapped to the physical downlink shared channel (PDSCH).
- the Paging Channel supports DRX of the mobile terminal in order to enable low power consumption of the mobile terminal.
- the PCH is required to be broadcast to the entire coverage of the base station (cell).
- the PCH is mapped to a physical resource such as a physical downlink shared channel (PDSCH) that can be dynamically used for traffic.
- PDSCH physical downlink shared channel
- a multicast channel (Multicast Channel: MCH) is used for broadcasting to the entire coverage of a base station (cell).
- the MCH supports SFN combining of MBMS (Multimedia Broadcast Multicast Service) services (MTCH and MCCH) in multi-cell transmission.
- MTCH and MCCH Multimedia Broadcast Multicast Service
- the MCH supports quasi-static resource allocation.
- MCH is mapped to PMCH.
- HARQ Hybrid ARQ
- PUSCH physical uplink shared channel
- Random Access Channel is limited to control information. RACH is at risk of collision.
- the RACH is mapped to a physical random access channel (PRACH).
- PRACH physical random access channel
- HARQ is a technique for improving the communication quality of a transmission path by a combination of an automatic repeat request (Automatic Repeat reQuest: ARQ) and error correction (Forward Error Correction).
- ARQ Automatic Repeat reQuest
- error correction Forward Error Correction
- HARQ has an advantage that error correction functions effectively by retransmission even for a transmission path whose communication quality changes. In particular, further quality improvement can be obtained by combining the initial transmission reception result and the retransmission reception result upon retransmission.
- BCCH Broadcast Control Channel
- BCH Broadcast Control Channel
- DL-SCH downlink shared channel
- the paging control channel (Paging Control Channel: PCCH) is a downlink channel for transmitting changes in paging information (Paging Information) and system information (System Information).
- PCCH is used when the network does not know the cell location of the mobile terminal.
- the PCCH that is a logical channel is mapped to a paging channel (PCH) that is a transport channel.
- PCH paging channel
- the common control channel (Common Control Channel: CCCH) is a channel for transmission control information between the mobile terminal and the base station. CCCH is used when the mobile terminal does not have an RRC connection with the network.
- CCCH is mapped to a downlink shared channel (DL-SCH) that is a transport channel.
- DL-SCH downlink shared channel
- UL-SCH uplink shared channel
- the multicast control channel (Multicast Control Channel: MCCH) is a downlink channel for one-to-many transmission.
- the MCCH is used for transmission of MBMS control information for one or several MTCHs from the network to the mobile terminal.
- MCCH is used only for mobile terminals that are receiving MBMS.
- the MCCH is mapped to a multicast channel (MCH) that is a transport channel.
- the dedicated control channel (Dedicated Control Channel: DCCH) is a channel for transmitting individual control information between the mobile terminal and the network on a one-to-one basis.
- DCCH is used when the mobile terminal is in RRC connection.
- the DCCH is mapped to the uplink shared channel (UL-SCH) in the uplink, and is mapped to the downlink shared channel (DL-SCH) in the downlink.
- the dedicated traffic channel (Dedicated Traffic Channel: DTCH) is a channel for one-to-one communication to individual mobile terminals for transmitting user information.
- DTCH exists for both uplink and downlink.
- the DTCH is mapped to the uplink shared channel (UL-SCH) in the uplink, and is mapped to the downlink shared channel (DL-SCH) in the downlink.
- UL-SCH uplink shared channel
- DL-SCH downlink shared channel
- the multicast traffic channel is a downlink channel for transmitting traffic data from the network to the mobile terminal.
- MTCH is a channel used only for a mobile terminal that is receiving MBMS.
- the MTCH is mapped to a multicast channel (MCH).
- CGI is a Cell Global Identifier.
- ECGI is an E-UTRAN cell global identifier (E-UTRAN Cell Global Identifier).
- LTE Long Term Evolution Advanced
- UMTS Universal Mobile Telecommunication System
- a CSG (Closed Subscriber Group) cell is a cell in which an operator identifies an available subscriber (hereinafter, may be referred to as a “specific subscriber cell”).
- the identified subscribers are allowed to access one or more cells of the PLMN (Public Land Mobile Mobile Network).
- PLMN Public Land Mobile Mobile Network
- One or more cells to which the identified subscribers are allowed access are called “CSG cells (CSG cell (s))”.
- CSG cell (s) Public Land Mobile Mobile Network
- PLMN Public Land Mobile Mobile Network
- the CSG cell is a part of the PLMN that broadcasts a unique CSG identity (CSG identity: CSG ID; CSG-ID) and “TRUE” via CSG indication (CSG indication).
- CSG identity CSG ID; CSG-ID
- CSG indication CSG indication
- the CSG-ID is broadcast by the CSG cell or cell. There are a plurality of CSG-IDs in an LTE communication system. The CSG-ID is then used by the mobile terminal (UE) to facilitate access of CSG related members.
- UE mobile terminal
- the location tracking of the mobile terminal is performed in units of areas composed of one or more cells.
- the position tracking is performed to track the position of the mobile terminal and call the mobile terminal even in the standby state, in other words, to enable the mobile terminal to receive a call.
- This area for tracking the location of the mobile terminal is called a tracking area.
- Non-Patent Document 3 discloses three different modes of access to HeNB and HNB. Specifically, an open access mode (Open access mode), a closed access mode (Closed access mode), and a hybrid access mode (Hybrid access mode) are disclosed.
- Open access mode Open access mode
- closed access mode closed access mode
- Hybrid access mode Hybrid access mode
- Each mode has the following characteristics.
- the HeNB and HNB are operated as normal cells of a normal operator.
- the closed access mode the HeNB and HNB are operated as CSG cells.
- This CSG cell is a CSG cell accessible only to CSG members.
- the hybrid access mode the HeNB and HNB are operated as CSG cells in which non-CSG members are also allowed to access at the same time.
- a hybrid access mode cell (also referred to as a hybrid cell) is a cell that supports both an open access mode and a closed access mode.
- PCI range reserved by the network for use in the CSG cell among all physical cell identities (PCI) (see non-patent document 1, chapter 10.5.1.1). Dividing the PCI range may be referred to as PCI split.
- Information on the PCI split (also referred to as PCI split information) is reported from the base station to the mobile terminals being served by the system information. Being served by a base station means that the base station is a serving cell.
- Non-Patent Document 4 discloses the basic operation of a mobile terminal using PCI split.
- a mobile terminal that does not have PCI split information needs to perform cell search using all PCIs, for example, using all 504 codes.
- a mobile terminal having PCI split information can perform a cell search using the PCI split information.
- LTE-A Long Term Evolution Advanced
- Release 10 the Long Term Evolution Advanced (LTE-A) standard is being developed as Release 10 (see Non-Patent Document 5 and Non-Patent Document 6).
- LTE-A is based on the LTE wireless communication system, and is configured by adding several new technologies.
- CC component carriers
- transmission bandwidths up to 100 MHz
- CA Carrier aggregation
- the UE When CA is configured, the UE has a network (NW) and only one RRC connection (RRC connection). In the RRC connection, one serving cell provides NAS mobility information and security input. This cell is referred to as a primary cell (PCell).
- a carrier corresponding to PCell is a downlink primary component carrier (Downlink Primary Component Carrier: DL PCC).
- the carrier corresponding to the PCell in the uplink is an uplink primary component carrier (Uplink Primary Component Carrier: UL PCC).
- a secondary cell (Secondary Cell: SCell) is configured to form a set of a PCell and a serving cell.
- the carrier corresponding to the SCell in the downlink is a downlink secondary component carrier (Downlink Secondary Component Carrier: DL SCC).
- the carrier corresponding to the SCell in the uplink is an uplink secondary component carrier (Uplink Secondary Component Carrier: UL SCC).
- a set of one PCell and a serving cell composed of one or more SCells is configured for one UE.
- Non-Patent Document 7 describes CoMP being studied for LTE-A by 3GPP.
- the amount of mobile network traffic is increasing and the communication speed is increasing.
- LTE and LTE-A start full-scale operation, it is expected that the communication speed will be further increased and the traffic volume will increase.
- 3GPP is working on the formulation of the 12th release standard.
- use of a small eNB is considered in order to cope with a huge amount of traffic in the future.
- a technology for increasing frequency utilization efficiency and increasing communication capacity by installing a large number of small eNBs and configuring a large number of small cells has been studied.
- Non-Patent Document 11 dual connectivity is discussed as a technology for connecting a mobile terminal to both a macro cell and a small cell when the macro cell and the small cell overlap.
- Non-Patent Document 11 discloses dual connectivity as a technique for connecting a mobile terminal to both a macro cell and a small cell when the macro cell and the small cell overlap. Has been.
- Non-Patent Document 11 the handling when a mobile terminal in dual connectivity performs a handover is not disclosed in Non-Patent Document 11.
- the mobile terminal is connected to only one cell, and the connection between both the macro cell and the small cell in the dual connectivity is not considered.
- An object of the present invention is to provide a communication system in which a mobile terminal device connected to both a macro cell and a small cell can perform handover between macro cells.
- the communication system of the present invention is a communication system comprising a mobile terminal device and a base station device that constitutes a cell capable of wireless communication with the mobile terminal device, and the range in which the mobile terminal device can communicate as the cell
- a plurality of macro cells having a relatively large coverage and a small cell having a relatively small coverage, and when the mobile terminal device is connected to one of the plurality of macro cells and the small cell,
- a pre-handover process for canceling the connection with the small cell is performed before the handover process for switching the macro cell to which the mobile terminal apparatus is connected from the source macro cell to the destination macro cell.
- a post-handover process for re-establishing a connection with the small cell may be performed.
- the communication system of the present invention is a communication system comprising a mobile terminal device and a base station device that constitutes a cell capable of wireless communication with the mobile terminal device, and can communicate with the mobile terminal device as the cell.
- the mobile terminal device moves, when a handover process for switching the macro cell to which the mobile terminal device is connected from the source macro cell to the destination macro cell is started, the small cell is controlled to the small cell. It is notified that a macro cell is changed.
- a mobile terminal apparatus connected to both a macro cell and a small cell can perform handover between macro cells.
- FIG. 2 is an explanatory diagram showing a configuration of a radio frame used in an LTE communication system.
- 1 is a block diagram showing an overall configuration of an LTE communication system 700 discussed in 3GPP.
- FIG. It is a block diagram which shows the structure of the mobile terminal 71 shown in FIG. 2 which is a mobile terminal which concerns on this invention.
- 5 is a flowchart illustrating an outline from a cell search to a standby operation performed by a mobile terminal (UE) in an LTE communication system.
- UE mobile terminal
- FIG. FIG. 2 is a block diagram showing an overall configuration of an LTE communication system 700 discussed in 3GPP.
- the radio access network is referred to as an E-UTRAN (Evolved Universal Terrestrial Radio Access Network) 70.
- a mobile terminal device hereinafter referred to as “user equipment (UE)” which is a communication terminal device is capable of wireless communication with a base station device (hereinafter referred to as “base station (E-UTRAN NodeB: eNB)”) 72. Yes, signals are transmitted and received by wireless communication.
- UE Evolved Universal Terrestrial Radio Access Network
- Control protocols for the mobile terminal 71 such as RRC (Radio Resource Control) and user planes such as PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), MAC (Medium Access Control), PHY (Physical Layer) If terminated at station 72, the E-UTRAN is composed of one or more base stations 72.
- RRC Radio Resource Control
- PDCP Packet Data Convergence Protocol
- RLC Radio Link Control
- MAC Medium Access Control
- PHY Physical Layer
- the control protocol RRC Radio Resource Control
- RRC connection management RRC connection management
- RRC_IDLE PLMN (Public Land Mobile Mobile Network) selection, system information (System Information: SI) notification, paging, cell re-selection, mobility, and the like are performed.
- RRC_CONNECTED the mobile terminal has an RRC connection and can send and receive data to and from the network.
- handover Handover: HO
- measurement of neighbor cells neighborhbour cells
- the base station 72 is classified into an eNB 76 and a Home-eNB 75.
- the communication system 700 includes an eNB group 72-1 including a plurality of eNBs 76 and a Home-eNB group 72-2 including a plurality of Home-eNBs 75.
- a system composed of EPC (Evolved Packet Core) as a core network and E-UTRAN 70 as a radio access network is referred to as EPS (Evolved Packet System).
- EPS Evolved Packet System
- the EPC that is the core network and the E-UTRAN 70 that is the radio access network may be collectively referred to as a “network”.
- the eNB 76 includes a mobility management entity (MME), an S-GW (Serving Gateway), or an MME / S-GW unit (hereinafter also referred to as “MME unit”) 73 including the MME and the S-GW.
- MME mobility management entity
- S-GW Serving Gateway
- MME unit MME / S-GW unit
- the control information is communicated between the eNB 76 and the MME unit 73 connected by the S1 interface.
- a plurality of MME units 73 may be connected to one eNB 76.
- the eNBs 76 are connected by the X2 interface, and control information is communicated between the eNBs 76.
- the Home-eNB 75 is connected to the MME unit 73 via the S1 interface, and control information is communicated between the Home-eNB 75 and the MME unit 73.
- a plurality of Home-eNBs 75 are connected to one MME unit 73.
- the Home-eNB 75 is connected to the MME unit 73 via a HeNBGW (Home-eNB Gateway) 74.
- Home-eNB 75 and HeNBGW 74 are connected via an S1 interface, and HeNBGW 74 and MME unit 73 are connected via an S1 interface.
- One or more Home-eNBs 75 are connected to one HeNBGW 74, and information is communicated through the S1 interface.
- the HeNBGW 74 is connected to one or a plurality of MME units 73, and information is communicated through the S1 interface.
- the MME unit 73 and the HeNBGW 74 are higher-level devices, specifically higher-level nodes, and control connection between the eNBs 76 and Home-eNBs 75, which are base stations, and the mobile terminal (UE) 71.
- the MME unit 73 constitutes an EPC that is a core network.
- the base station 72 and the HeNBGW 74 constitute an E-UTRAN 70.
- the X2 interface between Home-eNB 75 is supported. That is, the Home-eNB 75 is connected by the X2 interface, and control information is communicated between the Home-eNB 75. From the MME unit 73, the HeNBGW 74 appears as a Home-eNB 75. From the Home-eNB 75, the HeNBGW 74 appears as the MME unit 73.
- the interface between the Home-eNB 75 and the MME unit 73 is an S1 interface. The same.
- the base station device 72 may constitute one cell or a plurality of cells. Each cell has a predetermined range as a coverage that is a range in which communication with the mobile terminal 71 is possible, and performs wireless communication with the mobile terminal 71 within the coverage. When one base station apparatus 72 comprises a some cell, each cell is comprised so that communication with the mobile terminal 71 is possible.
- FIG. 3 is a block diagram showing a configuration of the mobile terminal 71 shown in FIG. 2, which is a mobile terminal according to the present invention.
- a transmission process of the mobile terminal 71 shown in FIG. 3 will be described.
- control data from the protocol processing unit 801 and user data from the application unit 802 are stored in the transmission data buffer unit 803.
- the data stored in the transmission data buffer unit 803 is transferred to the encoder unit 804 and subjected to encoding processing such as error correction.
- the data encoded by the encoder unit 804 is modulated by the modulation unit 805.
- the modulated data is converted into a baseband signal, and then output to the frequency conversion unit 806, where it is converted into a radio transmission frequency.
- a transmission signal is transmitted from the antenna 807 to the base station 72.
- the reception process of the mobile terminal 71 is executed as follows.
- a radio signal from the base station 72 is received by the antenna 807.
- the reception signal is converted from a radio reception frequency to a baseband signal by the frequency conversion unit 806, and demodulated by the demodulation unit 808.
- the demodulated data is passed to the decoder unit 809 and subjected to decoding processing such as error correction.
- control data is passed to the protocol processing unit 801, and user data is passed to the application unit 802.
- a series of processing of the mobile terminal 71 is controlled by the control unit 810. Therefore, the control unit 810 is connected to the respective units 801 to 809, which is omitted in FIG.
- FIG. 4 is a block diagram showing a configuration of the base station 72 shown in FIG. 2, which is a base station according to the present invention.
- the transmission process of the base station 72 shown in FIG. 4 will be described.
- the EPC communication unit 901 transmits and receives data between the base station 72 and the EPC (such as the MME unit 73) and the HeNBGW 74.
- the other base station communication unit 902 transmits / receives data to / from other base stations.
- the EPC communication unit 901 and the other base station communication unit 902 exchange information with the protocol processing unit 903, respectively. Control data from the protocol processing unit 903 and user data and control data from the EPC communication unit 901 and the other base station communication unit 902 are stored in the transmission data buffer unit 904.
- the data stored in the transmission data buffer unit 904 is transferred to the encoder unit 905 and subjected to encoding processing such as error correction. There may exist data that is directly output from the transmission data buffer unit 904 to the modulation unit 906 without performing the encoding process.
- the encoded data is subjected to modulation processing by the modulation unit 906.
- the modulated data is converted into a baseband signal, and then output to the frequency conversion unit 907 to be converted into a radio transmission frequency. Thereafter, a transmission signal is transmitted from the antenna 908 to one or a plurality of mobile terminals 71.
- the reception process of the base station 72 is executed as follows. Radio signals from one or a plurality of mobile terminals 71 are received by the antenna 908. The reception signal is converted from a radio reception frequency to a baseband signal by the frequency conversion unit 907, and demodulated by the demodulation unit 909. The demodulated data is transferred to the decoder unit 910 and subjected to decoding processing such as error correction. Of the decoded data, the control data is passed to the protocol processing unit 903 or the EPC communication unit 901 and the other base station communication unit 902, and the user data is passed to the EPC communication unit 901 and the other base station communication unit 902. A series of processing of the base station 72 is controlled by the control unit 911. Therefore, although not shown in FIG. 4, the control unit 911 is connected to the units 901 to 910.
- FIG. 5 is a block diagram showing the configuration of the MME according to the present invention.
- FIG. 5 shows the configuration of the MME 73a included in the MME unit 73 shown in FIG.
- the PDN GW communication unit 1001 transmits and receives data between the MME 73a and the PDN GW.
- the base station communication unit 1002 performs data transmission / reception between the MME 73a and the base station 72 using the S1 interface. If the data received from the PDN GW is user data, the user data is passed from the PDN GW communication unit 1001 to the base station communication unit 1002 via the user plane communication unit 1003 to one or a plurality of base stations 72. Sent. When the data received from the base station 72 is user data, the user data is passed from the base station communication unit 1002 to the PDN GW communication unit 1001 via the user plane communication unit 1003 and transmitted to the PDN GW.
- control data is passed from the PDN GW communication unit 1001 to the control plane control unit 1005.
- control data is transferred from the base station communication unit 1002 to the control plane control unit 1005.
- the HeNBGW communication unit 1004 is provided when the HeNBGW 74 exists, and performs data transmission / reception through an interface (IF) between the MME 73a and the HeNBGW 74 according to the information type.
- the control data received from the HeNBGW communication unit 1004 is passed from the HeNBGW communication unit 1004 to the control plane control unit 1005.
- the result of processing in the control plane control unit 1005 is transmitted to the PDN GW via the PDN GW communication unit 1001. Further, the result processed by the control plane control unit 1005 is transmitted to one or a plurality of base stations 72 via the S1 interface via the base station communication unit 1002, and to one or a plurality of HeNBGWs 74 via the HeNBGW communication unit 1004. Sent.
- the control plane control unit 1005 includes a NAS security unit 1005-1, an SAE bearer control unit 1005-2, an idle state mobility management unit 1005-3, and the like, and performs overall processing for the control plane.
- the NAS security unit 1005-1 performs security of a NAS (Non-Access Stratum) message.
- the SAE bearer control unit 1005-2 performs management of SAE (System Architecture Evolution) bearers.
- the idle state mobility management unit 1005-3 manages mobility in a standby state (idle state; also referred to as LTE-IDLE state or simply idle), generation and control of a paging signal in the standby state,
- the tracking area of one or a plurality of mobile terminals 71 is added, deleted, updated, searched, and tracking area list is managed.
- the MME 73a distributes the paging signal to one or a plurality of base stations 72. Further, the MME 73a performs mobility control (Mobility control) in a standby state (Idle State). The MME 73a manages the tracking area (Tracking Area) list when the mobile terminal is in a standby state and in an active state (Active State). The MME 73a starts a paging protocol by transmitting a paging message to a cell belonging to a tracking area (tracking area: TrackingTrackArea) where the UE is registered.
- the idle state mobility management unit 1005-3 may perform CSG management, CSG-ID management, and white list management of the Home-eNB 75 connected to the MME 73a.
- FIG. 6 is a flowchart illustrating an outline from a cell search to a standby operation performed by a mobile terminal (UE) in an LTE communication system.
- the mobile terminal uses the first synchronization signal (P-SS) and the second synchronization signal (S-SS) transmitted from the neighboring base stations in step ST1, and uses the slot timing, frame, Synchronize timing.
- P-SS first synchronization signal
- S-SS second synchronization signal
- PP-SS and S-SS are collectively called synchronization signal (SS).
- SS synchronization signal
- a synchronization code corresponding to one-to-one is assigned to the PCI assigned to each cell.
- 504 patterns are under consideration. Synchronization is performed using the 504 PCIs, and the PCI of the synchronized cell is detected (specified).
- a cell-specific reference signal that is a reference signal (reference signal: RS) transmitted from the base station to each cell is detected.
- RS Reference Signal Received Power
- RSRP Reference Signal Received Power
- RS Reference Signal Received Power
- step ST3 the cell having the best RS reception quality, for example, the cell having the highest RS reception power, that is, the best cell is selected from one or more cells detected up to step ST2.
- step ST4 the PBCH of the best cell is received and the BCCH which is broadcast information is obtained.
- MIB Master Information Block
- the MIB information includes, for example, DL (downlink) system bandwidth (also called transmission bandwidth setting (transmission bandwidth configuration: dl-bandwidth)), the number of transmission antennas, SFN (System frame number), and the like.
- SIB1 includes information related to access to the cell, information related to cell selection, and scheduling information of other SIBs (SIBk; an integer of k ⁇ 2).
- SIB1 includes a tracking area code (TrackingTrackArea Code: TAC).
- the mobile terminal compares the TAC of SIB1 received in step ST5 with the TAC part of the tracking area identifier (Tracking Area Identity: TAI) in the tracking area list already owned by the mobile terminal.
- the tracking area list is also referred to as a TAI list (TAI list).
- TAI is identification information for identifying a tracking area, and is composed of MCC (Mobile Country Code), MNC (Mobile Network Code), and TAC (Tracking Area Code).
- MCC Mobile Country Code
- MNC Mobile Network Code
- TAC Track Area Code
- MCC Mobile Country Code
- MNC Mobile Network Code
- TAC Track Area Code
- step ST6 If the result of the comparison in step ST6 shows that the TAC received in step ST5 is the same as the TAC included in the tracking area list, the mobile terminal enters a standby operation in the cell. In comparison, if the TAC received in step ST5 is not included in the tracking area list, the mobile terminal passes through the cell to the core network (Core Network, EPC) including MME and the like, and TAU (Tracking Area Update) Request tracking area change to do
- core network Core Network, EPC
- MME Management Entity
- a device that constitutes a core network performs tracking based on the identification number (UE-ID, etc.) of the mobile terminal sent from the mobile terminal together with the TAU request signal. Update the area list.
- the core network side device transmits the updated tracking area list to the mobile terminal. Based on the received tracking area list, the mobile terminal rewrites (updates) the TAC list held by the mobile terminal. Thereafter, the mobile terminal enters a standby operation in the cell.
- a cell configured by an eNB has a relatively wide range of coverage.
- a cell is configured to cover a certain area with a relatively wide range of coverage of a plurality of cells configured by a plurality of eNBs.
- the cell configured by the eNB has a coverage that is narrower than the coverage of the cell configured by the conventional eNB. Therefore, in the same way as in the past, in order to cover a certain area, a larger number of eNBs having a smaller cell size are required as compared with the conventional eNB.
- a cell having a relatively large coverage such as a cell configured by a conventional eNB
- a macro cell an eNB that configures the macro cell
- a cell having a relatively small coverage such as a small cell
- an eNB configuring the small cell is referred to as a “small eNB”.
- the macro eNB may be a “wide area base station” described in Non-Patent Document 8, for example.
- the small eNB may be, for example, a low power node, a local area node, a hot spot, or the like.
- the small eNB is a pico eNB that constitutes a pico cell, a femto eNB that constitutes a femto cell, a HeNB, an RRH (Remote Radio Unit), an RRU (Remote Radio Unit), an RRE (Remote Radio Equipment), or an RN (Relay Node).
- the small eNB may be a “local area base station (Local Base Station)” or “Home base station (Home Base Station)” described in Non-Patent Document 8.
- FIG. 7 is a diagram illustrating a concept of a cell configuration when a macro eNB and a small eNB coexist.
- a macro cell configured by a macro eNB has a relatively wide range of coverage 1301.
- the small cell configured by the small eNB has a coverage 1302 having a smaller range than the coverage 1301 of the macro cell configured by the macro eNB.
- the coverage of a cell configured by a certain eNB may be included in the coverage of a cell configured by another eNB.
- the small cell coverage 1302 configured by the small eNB is included in the macro cell coverage 1301 configured by the macro eNB. May be.
- a plurality of, for example, two small cell coverages 1302 may be included in one macro cell coverage 1301.
- a mobile terminal (UE) 1303 is included in, for example, a small cell coverage 1302 and performs communication via the small cell.
- the macro cell coverage 1301 configured by the macro eNB and the small cell coverage 1302 configured by the small eNB overlap in a complicated manner. Cases arise.
- the macro cell coverage 1301 configured by the macro eNB may not overlap with the small cell coverage 1302 configured by the small eNB.
- a coverage 1302 of a large number of small cells configured by a large number of small eNBs is configured within a coverage 1301 of a macro cell configured by a single macro eNB. Sometimes it happens.
- FIG. 8 and 9 are diagrams illustrating an example of eNB coverage in the communication system according to Embodiment 1 of the present invention.
- FIG. 8 and FIG. 9 show a case where the UE 57 in dual connectivity performs HO between the macro cells 51 and 53.
- a macro cell that performs dual connectivity may be referred to as a “master cell”, and an eNB that configures the master cell may be referred to as a “master eNB (abbreviation: MeNB)”.
- MeNB master eNB
- the HO source MeNB may be referred to as “source MeNB (abbreviation: S-MeNB)”
- target MeNB abbreviation: T-MeNB
- a small cell that performs dual connectivity may be referred to as a “secondary cell”, and an eNB that configures the secondary cell may be referred to as a “secondary eNB (abbreviation: SeNB)”.
- the S-MeNB is indicated by a reference sign “51”, and the coverage of the S-MeNB 51 is indicated by a reference sign “52”.
- T-MeNB is denoted by reference numeral “53”, and the coverage of T-MeNB 53 is denoted by reference numeral “54”.
- SeNB is shown with the reference code “55”, and the coverage of the SeNB 55 is shown with the reference code “56”.
- SeNB 55 shown in FIG. 8 may be a source SeNB (hereinafter may be referred to as “source SeNB”) 55, and another SeNB may be referred to as a destination SeNB (hereinafter referred to as “target SeNB”). There is 58).
- source SeNB source SeNB
- target SeNB destination SeNB
- reference numeral “56” indicates the coverage of the movement source SeNB 55
- reference numeral “59” indicates the coverage of the movement destination SeNB 58.
- the measurement report that the reception quality of the S-MeNB 51 is deteriorated in the measurement of the neighboring cell of the UE 57 and the reception quality of the T-MeNB 53 is improved. The case where it is performed will be described.
- FIG. 10 is a diagram illustrating an example of a sequence of handover-related processing in the communication system according to Embodiment 1 of the present invention.
- FIG. 11 is a diagram illustrating an example of the HO preprocessing sequence in step ST908 of FIG.
- FIG. 12 is a diagram showing an exemplary sequence of the HO process in step ST928 in FIG.
- FIG. 13 is a diagram showing an exemplary sequence of post-HO processing in step ST949 in FIG.
- handover related processing refers to processing related to handover (HO), and includes HO pre-processing, HO processing, and post-HO processing.
- the UE in dual connectivity Discloses a method of performing HO between macrocells.
- a path for communication from the S-GW via the MeNB (hereinafter also referred to as “MeNB path”) and a path for communication from the S-GW via the small cell SeNB (Hereinafter also referred to as “SeNB route”).
- the MeNB via path is a path using the bearer 1, and is used for packet data communication in, for example, step ST902 and step ST903.
- the SeNB-routed path is a path that uses the bearer 2, and is used for packet data communication in, for example, step ST904 and step ST905.
- the S-MeNB notifies the UE of a measurement control (Measurement Control) message.
- Measurements of neighboring SeNBs may be set in the measurement control message.
- frequency measurement for SeNB may be set.
- an event at a frequency for SeNB or a frequency for SeNB or a criterion for an event may be set separately from MeNB.
- the Setting parameters include SeNB identifier, frequency, event number for reporting, reception quality threshold, measurement period, and the like.
- the reception quality includes RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), and the like.
- UE which received the measurement control message in step ST901 performs measurement of neighboring cells (MeNB and SeNB).
- Step ST906 the UE notifies the S-MeNB of a measurement report (Measurement Report) message.
- the S-MeNB that has received the measurement report message in step ST906 determines whether or not to hand over (HO) the UE to the T-MeNB using the result of the measurement report. In the example illustrated in FIG. 10, in step ST907, the S-MeNB determines to cause the UE to HO to the T-MeNB.
- step ST907 If the S-MeNB decides to cause the UE to HO to the T-MeNB in step ST907, the process moves to step ST908, and in step ST908, the SeNB release process, which is the pre-HO process shown in FIG. 11, is executed.
- the S-MeNB determines in step ST907 in FIG. 10 that the UE should be HOed to the T-MeNB, the S-MeNB moves to step ST909 in FIG.
- step ST909 the S-MeNB notifies the SeNB of a SeNB release request (SeNB Release Request) message.
- Step ST910 the SeNB that has received the SeNB release request message in Step ST909 notifies the S-MeNB of an SeNB release response (SeNB Release Response) message.
- step ST911 the S-MeNB notifies the UE of an RRC connection reconfiguration (RRC Connection Reconfiguration) message as information on RRC.
- RRC connection reconfiguration RRC Connection Reconfiguration
- Step ST912 the SeNB performs SN status transmission (SN Status Transfer) that transmits the status of the PDCP sequence number (Sequence Number: abbreviated as SN) to the S-MeNB. Specifically, the SeNB notifies the SN information of PDCP to the S-MeNB. Further, in Step ST913, the SeNB may perform data transfer (Data Forwarding) for transferring data that has not been transmitted to the S-MeNB to establish communication without loss.
- SN Status Transfer SN Status Transfer
- SN Sequence Number: abbreviated as SN
- the SeNB notifies the SN information of PDCP to the S-MeNB.
- Step ST913 the SeNB may perform data transfer (Data Forwarding) for transferring data that has not been transmitted to the S-MeNB to establish communication without loss.
- QoS quality of service
- delay time generated in the backhaul of the connection destination cell may be determined.
- transfer number retransfer of transferred data
- presence / absence of transfer may be determined.
- a service that does not cause a problem even if data loss occurs such as voice data such as VoIP (Voice over Internet Protocol)
- VoIP Voice over Internet Protocol
- no transfer is performed when transfer data is re-transferred by handover during handover.
- transfer is not performed when the delay time generated in the backhaul of the connection destination cell is large. As described above, resource release can be performed promptly and stable operation can be provided.
- step ST914 the S-MeNB stores the data transferred from the SeNB in a buffer.
- Step ST915 the UE notifies the S-MeNB of an RRC connection reconfiguration complete (RRC Connection Reconfiguration Complete) message.
- RRC connection reconfiguration complete RRC Connection Reconfiguration Complete
- step ST918 the S-MeNB notifies the MME of a path switch request (Path Switch Request) message for requesting path switching.
- Step ST919 the MME that has been notified of the path switch request message notifies the S-GW of a bearer change request (Modify Bearer Request) message for requesting a bearer change.
- step ST918 or step ST919 information indicating whether or not SeNB has been changed may be given. Or the information which shows that it is not the path switch request
- step ST920 the S-GW notified of the bearer change request message changes the transmission destination of the bearer 2 used for communication from SeNB to S-MeNB.
- the bearer may be changed for the path via the S-MeNB in consideration of the accommodation situation of the users of the S-MeNB.
- step ST924 the S-GW notifies the MME of a modify bearer response message indicating that the bearer change request has been accepted.
- Step ST925 the MME notified of the bearer change response message notifies the S-MeNB of a path switch request acceptance response (Path ⁇ ⁇ Switch Request Ack) message indicating acceptance of the path switching request.
- the S-MeNB transmits and receives two bearers, bearer 1 and bearer 2, to the same UE in step ST902, step ST903 in FIG. 10, step ST916 and step ST922 in FIG.
- the S-GW may add an end marker (End Marker) to the PDCP transmitted to the SeNB to notify the end of the transfer process.
- End Marker an end marker
- the SeNB may add an end marker and transfer it to the S-MeNB.
- the S-MeNB can release the transfer acceptance buffer at a lean timing.
- Step ST926 the S-MeNB notifies the SeNB of a UE context release (UE context release) message that instructs the UE to release (release) the UE context.
- the S-MeNB is notified of the end marker in step ST923, in addition to notifying the SeNB of the UE context release message in step ST926, the S-MeNB notifies the SeNB that the end marker has been received. In this way, by notifying the SeNB that the UE context release message or the end marker has been received, the SeNB can release the management information of the UE in step ST927.
- the end marker may be determined whether or not the end marker is attached according to the bearer type or QoS. For services that do not cause any problems even if data loss occurs, such as voice data such as VoIP, resources can be managed quickly by releasing resources without adding an end marker. It is possible to obtain the effect that the operation can be provided.
- the S-MeNB 51 determines that the T-MeNB 53 is based on the measurement report of the UE 57 in step ST907 of FIG. Decide to HO. At this time, the measurement value of the SeNB 55 during communication also becomes good.
- the S-MeNB 51 determines that the UE 57 exists in the coverage 56 of the SeNB 55 even after the HO when the measurement value of the SeNB 55 is good. And in step ST909 of FIG. 11, you may give and notify the resource reservation instruction
- the SeNB 55 does not release the setting or information related to RRC and the setting or information related to radio synchronization that has been set, and after HOing to the T-MeNB 53, when the dual connectivity is reset from the T-MeNB 53 to the SeNB 55 Resource reservation processing and resynchronization processing can be reduced.
- step ST927 After the UE management information is released by the SeNB in step ST927, a handover process from the S-MeNB to the T-MeNB is performed in step ST928 in FIG. As a result, the two bearers are both switched from the S-MeNB to the T-MeNB.
- Step ST928 the handover process in step ST928 is executed as shown in FIG.
- the S-MeNB notifies the handover request (Handover Request) message to the T-MeNB that is the HO destination.
- the HO request message includes E-RAB (E-UTRAN Radio Access Bearer) information for performing HO.
- E-RAB E-UTRAN Radio Access Bearer
- Step ST930 the T-MeNB performs admission control for confirming the accommodated capacity.
- the T-MeNB When determining that the HO can be accepted based on the result of the admission control, the T-MeNB notifies the S-MeNB of an HO request acceptance response (Handover Request Ack) message in step ST931.
- Handover Request Ack HO request acceptance response
- step ST932 upon receiving the HO request response possible message in step ST931, the S-MeNB notifies the UE of an RRC connection reconfiguration (RRC ⁇ ⁇ Connection ⁇ ⁇ ⁇ ⁇ Reconfiguration) message including mobility control information.
- RRC connection reconfiguration RRC ⁇ ⁇ Connection ⁇ ⁇ ⁇ ⁇ Reconfiguration
- step ST933 the S-MeNB performs SN status transmission (SN Status Transfer) to the T-MeNB. Specifically, the S-MeNB notifies the T-MeNB of the SN information of PDCP.
- the S-MeNB may perform data forwarding (Data Forwarding) for transferring data that has not been transmitted to the T-MeNB.
- the T-MeNB stores the data transferred from the S-MeNB in a buffer.
- Step ST936 the UE completes the radio setting and notifies the T-MeNB of an RRC connection reconfiguration complete (RRC Connection Reconfiguration Complete) message.
- RRC connection reconfiguration Complete RRC Connection Reconfiguration Complete
- step ST939 the T-MeNB notifies the MME of a path switch request (Path Switch Request) message.
- Step ST940 the MME that has been notified of the path switch request message notifies the S-GW of a change bearer request (Modify Bearer Request) message.
- step ST939 or step ST940 information indicating whether or not SeNB has been changed may be given.
- requirement by HO of UE may be provided.
- information identifying the HO target UE may be given to indicate a path switch request or bearer change request by the UE HO.
- a conventional path switch request or a bearer change request may be used to indicate the conventional UE HO.
- the MME, S-GW, or separately provided location registration management function unit performs UE location information update processing and radio resource management processing associated with location information update as normal HO processing. be able to.
- step ST941 the S-GW that has been notified of the bearer change request message changes the transmission destination of the bearer 2 used for communication to T-MeNB.
- the bearer may be changed for the T-MeNB route in consideration of the accommodation status of the T-MeNB user.
- bearer 1 and bearer 2 are set via T-MeNB, and in step ST937, communication is performed between the UE and T-MeNB. In step ST943, S-GW and T-MeNB Communication takes place between them.
- step ST945 the S-GW notifies the MME of a modify bearer response message.
- Step ST946 the MME notified of the bearer change response message notifies the T-MeNB of a path switch request acceptance response (Path ⁇ ⁇ Switch Request Ack) message.
- the S-GW may add an end marker to the final data to the S-MeNB in step ST942.
- the S-MeNB can release the transfer buffer at a lean timing.
- step ST944 the S-MeNB may add an end marker to the final transfer data.
- the T-MeNB can release the transfer acceptance buffer at a lean timing.
- Step ST947 the T-MeNB notifies the S-MeNB of a UE context release (UE context release) message.
- the S-MeNB notifies the S-MeNB that the end marker has been received in addition to notifying the UE context release message to the S-MeNB in step ST947. To do.
- the S-MeNB can release the management information of the UE in step ST948.
- an SeNB addition process which is a post-HO process, is performed in step ST949 in FIG. Specifically, the SeNB addition process in step ST949 is executed as shown in FIG.
- the T-MeNB After switching to the T-MeNB by the HO process in step ST928 in FIG. 10, the T-MeNB notifies the SeNB of a SeNB addition request (SeNB ⁇ Addition Request) message in step ST950 in FIG.
- SeNB ⁇ Addition Request SeNB addition request
- Step ST951 the SeNB notifies the T-MeNB of an SeNB addition response (SeNB Addition Response) message.
- SeNB Addition Response SeNB Addition Response
- Step ST952 the T-MeNB notifies the UE of an RRC connection reconfiguration (RRC Connection Reconfiguration) message as information on RRC.
- RRC connection reconfiguration RRC Connection Reconfiguration
- the T-MeNB transmits the SN status transmission ( (SNCPStatus Transfer), the PDCP SN information is notified to the SeNB.
- the T-MeNB may perform data transfer (Data Forwarding) for transferring data that has not been transmitted to the SeNB to establish communication without loss.
- Data Forwarding data transfer
- the T-MeNB may determine the presence or absence of data transfer or the presence or absence of SN reordering according to the bearer type or QoS. For bearers that do not have any problem even if data loss occurs like voice data such as VoIP, it is possible to quickly release resources and provide stable operation by omitting data transfer or SN reordering. The effect that it is possible can be obtained.
- step ST955 the SeNB stores the data transferred from the T-MeNB in a buffer.
- Step ST956 the UE completes radio synchronization and notifies the T-MeNB of an RRC connection reconfiguration complete (RRC Connection Reconfiguration Complete) message indicating that reconfiguration of the RRC connection between the SeNB and the UE is completed.
- RRC connection reconfiguration complete RRC Connection Reconfiguration Complete
- Step ST959 the SeNB notifies the T-MeNB of an SeNB addition completion message indicating completion of wireless setting, specifically, addition of SeNB.
- Step ST960 the T-MeNB notified of the SeNB addition completion message notifies the MME of a path switch request (Path ⁇ Switch Request) message.
- Step ST961 the MME that has been notified of the path switch request message notifies the S-GW of a change bearer request (Modify Bearer Request) message.
- step ST960 or step ST961 information indicating whether or not SeNB is changed (added) may be provided. Or the information which shows that it is not the path switch request
- step ST962 the S-GW notified of the bearer change request message changes the transmission destination of the bearer 2 used for communication to S-MeNB.
- the bearer may be changed for the path via the SeNB in consideration of the accommodation status of the SeNB user.
- Step ST966 the S-GW notifies the MME of a modify bearer response message.
- Step ST967 the MME that has been notified of the bearer change response message notifies the T-MeNB of a path switch request acceptance response (Path Switch Request Ack) message indicating completion of path switching.
- bearer 2 is set via SeNB, and in step ST957, communication is performed between the UE and SeNB, and in step ST964, communication is performed between S-GW and SeNB.
- Step ST968 the T-MeNB may release management information for the bearer 2 of the UE.
- the S-GW may add an end marker to the PDCP transmitted to the T-MeNB to notify the end of the transfer process.
- the T-MeNB can recognize the end of the transfer data, and thus can release the transfer buffer at a useless timing.
- the T-MeNB may add an end marker and transfer it to the SeNB.
- the SeNB can release the transfer buffer at a lean timing.
- the end marker may be determined whether or not the end marker is attached according to the bearer type or QoS. For services that do not cause any problems even if data loss occurs, such as voice data such as VoIP, resources can be managed quickly by releasing resources without adding an end marker. It is possible to obtain the effect that the operation can be provided.
- the T-MeNB 53 adds the movement direction information of the UE 57, the movement speed information of the UE 57, or the position information of the neighboring SeNB (GPS information of each SeNB).
- SeNB designation information for designating a SeNB to be added after HO may be added to the HO request message notified in step ST929 in FIG.
- the dual connectivity process can be reduced by adding the destination SeNB. That is, after adding a movement source SeNB, when the UE moves at a high speed, an increase in processing due to immediate release of the movement source SeNB and addition of a movement destination SeNB can be prevented.
- the source SeNB when communicating with the CSG, even if the destination SeNB is temporarily good due to shadowing of a human body or the like, it is communicating with the CSG or moving The source SeNB is added due to the low speed. Thereby, it is possible to continuously perform stable communication.
- the macro cell to which the UE is connected is moved along with the movement of the UE.
- Pre-HO processing is performed before the HO processing for switching from the S-MeNB that is the macro cell to the T-MeNB that is the destination macro cell, and post-HO processing is performed after the HO processing.
- the SeNB that is a small cell is released, and the connection with the SeNB is canceled.
- HO post-processing SeNB is added and the connection with SeNB is established again.
- a UE in dual connectivity can realize HO between macro cells.
- FIG. 14 is a diagram showing an exemplary sequence of handover-related processing in the communication system according to Modification 1 of Embodiment 1 of the present invention.
- FIG. 15 is a diagram showing an exemplary sequence of HO preprocessing in step ST1009 of FIG.
- FIG. 16 is a diagram showing an exemplary sequence of post-HO processing in step ST1010 of FIG. Since the handover related process of the present modification is similar to the handover related process of the first embodiment shown in FIGS. 10 to 13, the same steps are denoted by the same step numbers and the description thereof is omitted.
- Non-Patent Document 11 in the case of the option 3C (Alternative 3C) of the dual connectivity user plane architecture described in Non-Patent Document 11, the UE in dual connectivity is used (see Non-Patent Document 11 8.1.1.8). Discloses a method of performing HO between macrocells.
- the bearer (bearer 2) is divided by the MeNB into a path (bearer 1) for direct communication between the MeNB and the UE and a path for communication via the small cell.
- a bearer split is performed.
- an E-RAB corresponding to one EPS bearer is separated into two paths by the S-MeNB, and data is communicated between the S-GW and the UE.
- step ST1001 data is directly communicated between the S-MeNB and the UE.
- Step ST1003 and Step ST1004 data is communicated between the S-MeNB and the UE via the SeNB.
- step ST1002 data is communicated with one path between the S-MeNB and the S-GW. Communication between SeNB and MeNB is performed between different eNBs. When the communication quality of the communication path between different eNBs is poor, data loss or the like may occur. In order to solve such a problem, a delivery confirmation process may be introduced in communication between the SeNB and the MeNB. For example, retransmission processing may be introduced. By doing in this way, it becomes possible to reduce the lack of data in communication between SeNB and MeNB.
- the SeNB release process is performed as follows.
- the S-MeNB that has received the measurement report from the UE in Step ST906 of FIG. 14 determines to cause the UE to HO to the T-MeNB using the result of the measurement report in Step ST907 of FIG.
- the S-MeNB determines to cause the UE to HO to the T-MeNB, in step ST909, the S-MeNB transmits a SeNB release request (SeNB Release Request) message requesting the SeNB to be released.
- the S-MeNB transmits an RRC connection re-establishment request message to the UE as information related to RRC.
- the S-MeNB stops bearer splitting of the bearer 2 and directly transmits / receives the bearer 2 to / from the UE in Step ST916 and Step ST917.
- a handover (HO) process from S-MeNB to T-MeNB is performed in step ST928 of FIG.
- the HO process in step ST928 is executed in the same manner as the HO process shown in FIG.
- the two bearers are both switched from the S-MeNB to the T-MeNB.
- step ST1010 in FIG. 14 After switching to T-MeNB, post-HO processing in step ST1010 in FIG. 14 is executed. Specifically, in step ST950 of FIG. 16, the T-MeNB notifies the SeNB of an addition request message, and in step ST952, notifies the UE of information related to RRC for performing communication.
- the bearer 2 is split by the above.
- One bearer of bearers 2 that have been split into bearers is used when data is directly communicated between the T-MeNB and the UE in Step ST1005, and the other bearer is used in Step ST1007 and Step ST1008.
- the other bearer is used in Step ST1007 and Step ST1008.
- Step ST1006 Used when data is communicated between the T-MeNB and the UE via the SeNB.
- step ST1006 data is communicated between the T-MeNB and the S-GW through one path. In this way, the bearer split can be processed without sending a path switch request to the MME and S-GW.
- FIG. 17 to 19 are diagrams showing an example of a sequence of handover-related processing in the communication system according to the second embodiment of the present invention. 17 and 18 are connected by a boundary line BL1. 18 and 19 are connected by a boundary line BL2. Since the handover related process of the present embodiment is similar to the handover related process of the first embodiment shown in FIGS. 10 to 13, the same step number is assigned to the same step, and the description is omitted. .
- the connection with the SeNB is not released. That is, HO between MeNB is performed, maintaining UE dual connectivity.
- the S-MeNB notifies the UE of a measurement control message.
- Measurements of neighboring SeNBs may be set in the measurement control message.
- frequency measurement for SeNB may be set.
- an event or criteria for an event at a frequency for SeNB or SeNB may be set separately from MeNB.
- Setting parameters include SeNB identifier, frequency, event number for reporting, reception quality threshold, measurement period, and the like.
- reception quality there are RSRP, RSRQ, and the like.
- the UE that has received the measurement control message in Step ST901 performs MeNB and SeNB measurement.
- the reception quality of the S-MeNB due to measurement deteriorates due to movement of the UE
- the reception quality of the T-MeNB improves
- the measurement report is performed according to the event criteria.
- step ST906 the UE performs a measurement report to the S-MeNB.
- the identifier of the SeNB used for dual connectivity and the reception quality may be included in the measurement report from the UE.
- step ST907 the S-MeNB that has received the measurement report from the UE in step ST906 determines to cause the UE to HO to the T-MeNB using the result of the measurement report.
- the S-MeNB notifies the T-MeNB of the HO request message.
- This HO request message may be notified by including information on SeNB (hereinafter sometimes referred to as “SeNB information”).
- the SeNB information includes, for example, an SeNB identifier, SeNB reception quality at the UE, and the like.
- the SeNB bearer As information on the SeNB bearer (hereinafter also referred to as “bearer information”), there is an E-RAB identifier or the like.
- the MeNB may provide an identifier for each bearer when multiple bearers are set in the SeNB. It is preferable to notify each bearer by associating the identifier of the bearer with information on the bearer configuration. Also, the identifier of the SeNB and the identifier of the bearer may be associated and notified.
- QoS parameters specifically, quality of service class identifier (QoS Class Identifier; abbreviation: QCI), allocation and retention priority (Allocation and Retention Priority; abbreviation: ARP) ), And guaranteed bandwidth quality information (Guaranteed Bit Rate Rate QoS Information).
- the S-MeNB can notify the T-MeNB of the bearer setting used by the SeNB.
- the T-MeNB can acquire the bearer setting for each bearer of the SeNB, and can determine whether or not the change for each bearer is necessary.
- the bearer setting may be notified in association with information on the bearer information of the SeNB.
- RRC context As setting information regarding RRC, for example, there is an RRC context (RRC context).
- the RRC context includes, for example, an AS (Access Stratum) configuration (AS configuration) indicating a configuration of radio resources, an RRM configuration (RRM configuration) indicating radio resource management (Radio Resource Management; abbreviation: RRM) information, and the like.
- AS configuration Access Stratum
- RRM configuration radio resource management
- the information regarding RRC includes information regarding RRC for MeNB and information regarding RRC for SeNB.
- Information regarding each RRC may be identifiable. For example, the RRC context for the MeNB and the RRC context for the SeNB are created separately. Alternatively, information for MeNB and information for SeNB may be created separately in one RRC context.
- the information regarding the RRC for the SeNB and the information regarding the RRC for the MeNB can be individually configured, and the S-MeNB sends the information regarding the RRC of each of the MeNB and the SeNB to the T-MeNB. Notification can be made.
- the T-MeNB can acquire information about the RRC of each of the S-MeNB and the SeNB, and the T-MeNB can determine whether or not a setting change regarding the RRC of the SeNB is necessary.
- the T-MeNB determines whether to change the SeNB using information received from the S-MeNB in the HO request message. This process determines whether the T-eNB can take over in a state where the SeNB bearer is set in the S-eNB. For example, there is a limit to the number of S-eNBs that can be accommodated by a T-eNB, and there are cases where the acceptance is impossible due to the limitation. In addition, in the case of the option 3C of the user plane architecture in dual connectivity, it is also information for determining whether or not a bearer split by the S-MeNB can be accommodated.
- the mobile terminal makes a transition to step ST1102. Further, not only when it is determined to change the SeNB, but when the T-MeNB determines the release of the SeNB in the HO process, the process may move to step ST1102.
- Step ST1102 the T-MeNB executes the SeNB release process in Step ST908 shown in FIG. 10 described above to release the SeNB, and then executes the HO process in Step ST908. Specifically, the T-MeNB notifies the S-MeNB of information indicating an execution request for the SeNB release process (hereinafter also referred to as “SeNB release process execution request information”).
- the S-MeNB notified of the SeNB release process execution request information from the T-MeNB may apply the method disclosed in Embodiment 1, and the description thereof is omitted here.
- the HO request from the S-MeNB to the T-MeNB in step ST1100 may be omitted.
- the T-MeNB may perform admission control in Step ST930 after notifying the S-MeNB of SeNB release process execution request information.
- the notification of the SeNB release process execution request information from the T-MeNB to the S-MeNB may be performed using the HO request acceptance response message. For example, you may perform using the HO request
- the T-MeNB that has decided to release the SeNB in the HO process determines to perform HO only between the MeNBs, performs admission control accordingly, and for the S-MeNB including the SeNB release process execution request information, A HO request acceptance response message is notified.
- the HO request acceptance response message may indicate an execution request for SeNB release processing.
- the S-MeNB performing dual connectivity that has received the HO request acceptance response message from the T-MeNB performs the release process of the SeNB.
- the notification of the SeNB release process execution request information from the T-MeNB to the UE may be notified using an RRC connection reconfiguration message including MCI (Mobility Control Information).
- MCI Mobility Control Information
- an RRC connection reconfiguration message including the MCI in step ST1106 may be used.
- an RRC connection reconfiguration message including MCI may indicate an execution request for SeNB release processing.
- the UE configuring the SeNB that has received the RRC connection reconfiguration message including the MCI from the S-MeNB executes the SeNB release process.
- the T-MeNB determines to perform the HO process while maintaining the use of the SeNB in step ST1103. In other words, only the MeNB is changed.
- the change process of the bearer 2 using SeNB is not performed.
- Step ST930 the T-MeNB performs admission control for the HO request.
- This admission control may be performed before the above-described determination as to whether or not to change the SeNB. Alternatively, it may be performed together with the determination.
- the T-MeNB performs settings related to RRC for the T-MeNB.
- Settings related to RRC include an AS configuration (AS configuration) indicating a configuration of radio resources, an RRM configuration (RRM configuration) indicating RRM information, and the like.
- AS configuration AS configuration
- RRM configuration RRM configuration
- information included in the RRC connection reconfiguration message may be set.
- the UE-specific RACH preamble configuration used in the T-MeNB may be provided separately from the UE-specific RACH preamble configuration used in the SeNB.
- the C-RNTI Cell-Radio Network Temporary Identifier
- the SeNB supports other UEs that are not under the T-MeNB, it can be set individually for each UE, thereby enabling flexible control.
- the UE-specific RACH preamble configuration used in the T-MeNB may be set to be the same as the UE-specific RACH preamble configuration used in the SeNB.
- the C-RNTI used in the T-MeNB may be set to be the same as the C-RNTI used in the SeNB.
- the setting related to RRC for T-MeNB requires information that enables the UE to reconfigure RRC connection with T-MeNB.
- the T-MeNB determines to accept the HO request, in step ST1104, the T-MeNB notifies the S-MeNB of a HO request acceptance response message including a HO instruction message.
- the HO instruction message may include setting information regarding RRC for the T-MeNB described above.
- the T-MeNB may notify the S-MeNB that HO is possible while maintaining the configuration of the bearer 2 using the SeNB. Further, when maintaining the configuration of the bearer 2 using the SeNB, the T-MeNB may notify the S-MeNB that HO is possible while maintaining the settings related to RRC for the SeNB. These notifications may be performed using a HO request acceptance response message. You may notify with the HO request
- the S-MeNB In the HO request acceptance response message or the HO instruction message, information regarding whether or not there is a change in the SeNB RRC setting may be included.
- the S-MeNB may further acquire a setting related to the RRC of the SeNB. This makes it possible to simplify the process when there is no change.
- the setting information may not be included in the HO instruction message. As a result, the amount of information to be signaled can be reduced.
- setting information related to RRC for SeNB may be included in the HO instruction message.
- the S-MeNB can compare the setting information related to the RRC for the SeNB acquired from the T-MeNB with the setting information related to the RRC for the SeNB that the own cell has, and there is no change. It becomes possible to verify this.
- the S-MeNB that has received the HO request acceptance response message in step ST1104 can recognize to the T-MeNB that it is a HO that maintains the SeNB for the UE in dual connectivity.
- the S-MeNB that has recognized that HO is performed while maintaining the SeNB does not request the SeNB to change the bearer 2 configuration.
- the setting change request related to RRC for SeNB is not performed.
- a process of notifying the SeNB of information indicating that HO is activated is performed among the T-MeNB, S-MeNB, and SeNB.
- the T-MeNB notifies the SeNB of information indicating that HO is activated.
- This notification may be performed when the T-MeNB transmits a HO request acceptance response message to the S-MeNB.
- requirement acceptance response message from T-MeNB may notify the information which shows starting HO to SeNB.
- step ST1108 of FIG. 18 the S-MeNB transfers PDCP SN information and data that has not been transmitted to the T-MeNB, and establishes communication without loss.
- the UE in dual connectivity may not change the bearer 2 configuration by SeNB activation during HO between MeNBs. If there is a change in bearer configuration due to SeNB activation during HO, this processing is performed when the MeNB is changed from S-MeNB to T-MeNB, so that control becomes complicated and the possibility of malfunction increases. By not changing the configuration of the bearer 2 by starting SeNB at the time of HO, it becomes possible to reduce malfunctions.
- a method for preventing change of the configuration of the bearer 2 by SeNB activation during HO is disclosed below.
- T-MeNB notifies SeNB of information indicating that HO is activated. This notification may be performed when the T-MeNB transmits a HO request acceptance response message to the S-MeNB. Or S-MeNB which received the HO request
- the SeNB that has received the information indicating that the HO has been activated does not activate the bearer 2 configuration change request. It is good not to start until this HO is completed.
- the S-MeNB or T-MeNB may notify the SeNB of Nack (or rejection) in response to the bearer 2 configuration change request from the SeNB.
- Reason information may be included, and information indicating that the HO is being performed may be provided and set as the reason.
- the T-MeNB may notify the SeNB of information indicating completion of HO. This notification may be performed when the T-MeNB receives a path switch request acceptance response message from the MME in the HO process. Alternatively, completion of the MeNB change process, which will be described later, may be HO completion.
- the S-MeNB when performing HO while maintaining the above-mentioned SeNB, the S-MeNB does not request the SeNB to change the configuration of the bearer 2 and the setting change related to RRC for the SeNB.
- the S-MeNB may notify the SeNB that it is HO while maintaining the SeNB. Or you may notify that the request
- the SeNB can recognize whether or not the HO performs HO while maintaining the SeNB during the HO.
- the SeNB can be configured not to change the configuration of the bearer 2 for the UE activated by the SeNB during the HO. The same effect as described above can be obtained.
- the S-MeNB that has received the HO request acceptance response message performs RRC connection reconfiguration (RRC) including mobility control information (Mobility Control Information; abbreviation: MCI) to cause the UE to perform HO to the T-MeNB in step ST1106. Connection Reconfiguration) message. Further, the S-MeNB that has received the HO request acceptance response message may notify the UE that there is no bearer change using the SeNB.
- RRC RRC connection reconfiguration
- MCI mobility control information
- the S-MeNB notifies the UE that there is no change in the SeNB for E-RAB performing the bearer 2 at the time of the HO. Moreover, you may notify that there is no setting change regarding RRC for SeNB. It may be notified together with the RRC connection reconfiguration message including the MCI.
- the S-MeNB may notify the UE of the setting information when it recognizes the setting information related to RRC for the SeNB.
- the UE can compare the setting information related to RRC for the SeNB to which the UE is connected and the received setting information, and can verify that there is no change.
- Step ST1106 the UE that has received the RRC connection reconfiguration message including the MCI performs HO from the S-MeNB to the T-MeNB while maintaining synchronization and connection with the SeNB.
- the UE performs HO while maintaining radio resources with the SeNB. In this state, the UE can communicate with the SeNB.
- a method for handling uplink data from the UE to the SeNB will be disclosed below.
- the UE When the UE performs HO while maintaining connection with the SeNB, the UE can maintain transmission of uplink data of the bearer 2. Alternatively, until the HO from the S-MeNB to the T-MeNB is completed, the UE can stop transmission of uplink data during the HO and store it in the buffer. By doing so, it is possible to wait for the establishment of the control plane, and to reduce the buffering process of the control information of the SeNB and S-MeNB or the SeNB and T-MeNB when the control plane path is not established And SeNB processing can be simplified.
- Step ST1106 the UE that has received the MCI instructing HO from the S-MeNB to the T-MeNB stops transmission of the uplink data of the bearer 1 and stores it in the buffer in Step ST1107.
- step ST1109 the UE performs a connection change process from the S-MeNB to the T-MeNB according to the MCI. After receiving the MCI, the UE disconnects from the S-MeNB and connects to the T-MeNB. The UE reconfigures the RRC connection for the T-MeNB using the content received in the RRC connection reconfiguration message in Step ST1106, and connects to the T-MeNB.
- step ST1110 the UE performs RA processing with the T-MeNB.
- step ST1111 the UE notifies the T-MeNB of an RRC connection reconfiguration completion message.
- the UE can directly perform data communication with the T-MeNB after notifying the T-MeNB of the RRC connection reconfiguration completion message.
- the UE transmits the uplink data of the bearer 1 after notifying the RRC connection reconfiguration completion message with the T-MeNB.
- the SeNB can maintain transmission of downlink data of the bearer 2 when performing HO while maintaining connection with the UE.
- the SeNB can stop transmission of downlink data during the HO and store it in the buffer. By doing so, it is possible to wait for the establishment of the control plane, and to reduce the buffering process of the control information of the SeNB and S-MeNB or the SeNB and T-MeNB when the control plane path is not established And SeNB processing can be simplified.
- the SeNB is notified of the bearer configuration for dual connectivity to the UE by the MeNB. Moreover, the setting information regarding RRC with respect to this UE of SeNB is notified by this MeNB.
- the SeNB needs to recognize from which MeNB the configuration of the bearer has been notified, which MeNB should be notified of the setting information regarding the RRC set by the SeNB. That is, it is necessary to recognize the MeNB.
- SeNB performs the data communication for UE which performs dual connectivity between MeNB.
- the SeNB needs to recognize which MeNB should transmit data to the UE and which MeNB should transmit data from the UE. That is, it is necessary to recognize the MeNB.
- the former MeNB and the latter MeNB may be set separately, but here, a case where they are the same will be described.
- the MeNB is referred to as a SeNB control MeNB.
- the SeNB is not changed in the HO processing of the UE during dual connectivity, and the MeNB is changed from S-MeNB to T-MeNB, the method of recognizing which MeNB the control MeNB of the SeNB has changed to Is disclosed.
- the following two (1) and (2) are disclosed as specific examples of the method of recognizing which MeNB the control MeNB has changed to.
- the S-MeNB notifies the SeNB of the change of the control MeNB.
- the T-MeNB notifies the SeNB of the change of the control MeNB.
- the T-MeNB When the T-MeNB receives the RRC connection reconfiguration completion message from the UE, the T-MeNB notifies the SeNB of the control MeNB change request message so as to request the SeNB to change the control MeNB.
- the notification may be performed using X2 signaling. You may notify to this notification including the identifier of SeNB which changes control MeNB. Moreover, you may notify including the reason information of a change. Information indicating that the MeNB is changed by HO may be provided and notified.
- the S-MeNB that has received the notification notifies the SeNB that changes the control MeNB of a control MeNB change request message that requests the change of the control MeNB.
- the notification may be performed using X2 signaling. Or you may perform using the signaling on the interface provided between MeNB and SeNB.
- the following five (1) to (5) are disclosed as specific examples of information included in the signaling.
- an E-RAB identifier may be an E-RAB ID or the like
- an EPS bearer identifier may be an E-RAB ID or the like.
- the SeNB that has received the control MeNB change request message identifies a bearer that changes the MeNB from the information included in the control MeNB change request message.
- the SMeNB changes the control MeNB of the bearer to the changed MeNB.
- the management of bearers in the SeNB may be performed in association with the identifier of the control MeNB. That is, the bearer identifier and the control MeNB identifier may be associated with each other. By doing in this way, SeNB can change the control MeNB of the bearer for UE which performs dual connectivity.
- the SeNB accepts a request for correction and release of the bearer only from the changed control MeNB after the change of the control MeNB.
- the SeNB performs data communication with the changed MeNB.
- the SeNB can recognize to which MeNB the control MeNB has been changed, and the modification of the bearer for the UE, a release request, etc. with the control MeNB after the change, etc. Communication for control and data communication can be performed.
- the SeNB that has changed the control MeNB may notify the S-MeNB of a control MeNB change response message.
- the message may include information indicating that the control MeNB has been changed.
- the S-MeNB that has received the control MeNB change response message from the SeNB may notify the control MeNB after the change, here the T-MeNB, of a message indicating that the SeNB control MeNB change has been completed.
- the changed MeNB in this case the T-MeNB, can recognize that the SeNB's control MeNB has been changed, and the SeNB can modify and release the bearer for the UE. It is possible to start communication for control such as a request and data communication.
- the post-change MeNB may notify the SeNB of a message confirming that the bearer control MeNB for the UE has been changed.
- the SeNB may respond to the message.
- the T-MeNB Upon receiving the RRC connection reconfiguration completion message from the UE, the T-MeNB notifies the SeNB of a control MeNB change request message.
- the SeNB identifier may be SeNB information included in the HO request message received from the S-MeNB.
- the notification may be performed using X2 signaling. Or you may perform using the signaling on the interface provided between MeNB and SeNB.
- Information disclosed in the method of the specific example (1) can be applied to the information included in the signaling.
- the SeNB can recognize to which MeNB the control MeNB has been changed, and for the control of the bearer modification, release request, etc. for the UE with the control MeNB after the change. Communication and data communication can be performed.
- the SeNB that has changed the control MeNB may notify the T-MeNB of a control MeNB change response message.
- the message may include information indicating that the control MeNB has been changed.
- the T-MeNB that has received the control MeNB change response message from the SeNB may notify a message indicating that the control MeNB change of the SeNB has been completed to the control MeNB before the change, in this case, the S-MeNB.
- the MeNB before the change in this case, the S-MeNB, can recognize that the control MeNB of the SeNB has been changed, and the modification, release of the bearer for the UE is made to the SeNB. Communication for control such as a request for data and data communication can be terminated.
- the SeNB can perform communication for control related to the bearer configuration and data communication with the changed MeNB (T-MeNB). Become.
- Step ST1112 the T-MeNB that has received the RRC connection reconfiguration completion message from the UE in Step ST1111, notifies the S-MeNB of a control MeNB change request message that requests a change of the SeNB's control MeNB.
- the identifier of the SeNB that changes the control MeNB is included in the control MeNB change request message of the SeNB.
- the S-MeNB that has received the message notifies the SeNB that changes the control MeNB of the control MeNB change request message.
- the control MeNB change request message information indicating the change of the control MeNB, the identifier of the T-MeNB, the bearer identifier of the path using the SeNB, the identifier of the bearer that changes the control MeNB in the SeNB, the identifier of the S-MeNB, and the SeNB Include the identifier of the UE targeted for HO to be used for dual connectivity. By doing so, the SeNB can recognize which bearer set by which MeNB should change the control MeNB.
- the SeNB that has received the control MeNB change request message changes the control MeNB using the received information in step ST1114. Thereby, the SeNB thereafter performs communication and data communication for control related to the bearer with the T-MeNB that is the control MeNB after the change.
- the SeNB that has changed the control MeNB ends communication and data communication for control with the control MeNB before the change.
- step ST1115 the SeNB that has changed the control MeNB in step ST1114 notifies the S-MeNB of the control MeNB change response message in order to notify the S-MeNB that the control MeNB has been changed.
- step ST1116 the S-MeNB that has received the control MeNB change response message notifies the T-MeNB of the SeNB control MeNB change response message to notify the T-MeNB that the change of the SeNB control MeNB has been completed. .
- the T-MeNB can recognize that the control MeNB of the SeNB has been changed to the T-MeNB. Therefore, the T-MeNB can perform communication and data communication for control related to the bearer with the SeNB.
- the notification of the control MeNB change request message to the SeNB is executed via the S-MeNB.
- the T-MeNB and the SeNB directly without using the S-MeNB.
- control MeNB change request message and control MeNB change response message may be included in the control MeNB change request message and used in the SeNB control MeNB change process to determine that it is not an unauthorized control MeNB change request.
- Step ST1117 shows SeNB control MeNB change processing performed among T-MeNB, S-MeNB and SeNB.
- the subsequent path switching process in the S-GW for changing the MeNB is the same as that in FIG.
- the path switching process enables data communication via the T-MeNB between the S-GW and the UE that was the HO target.
- the control MeNB change process of the SeNB is performed after the T-MeNB receives an RRC connection reconfiguration completion message from the UE.
- the SeNB control MeNB change process may be performed.
- the above-described method may be applied to the SeNB control MeNB change process.
- the SeNB control MeNB change process may be performed.
- the T-MeNB receives the path switch request acceptance response message from the MME, the T-MeNB notifies the SeNB of the change of the MeNB.
- the S-MeNB may notify the SeNB of the MeNB change.
- the above-described method may be applied to the SeNB control MeNB change process.
- the SeNB that is a small cell is notified that the macro cell that controls the small cell is changed.
- the HO process can be executed while maintaining the path for communication from the S-GW via the small cell, so that the user plane data communication can be continued even during the HO process. Become.
- control sequence is simplified compared to the case where HO is executed after the SeNB is released as in the first embodiment, the amount of information to be signaled in the HO sequence from the dual connectivity can be reduced. It becomes possible.
- FIG. 20 to 22 are diagrams showing an exemplary sequence of handover-related processing in the communication system according to Embodiment 3 of the present invention.
- 20 and 21 are connected by a boundary line BL3.
- 21 and 22 are connected by a boundary line BL4.
- the handover related process of the present embodiment is similar to the handover related process of the first embodiment shown in FIGS. 10 to 13 and the second embodiment shown in FIGS. 17 to 19, and therefore the same steps are the same.
- the step number is attached and the description is omitted.
- SeNB is not released in the case of the option 3C (Alternative 3C) of the dual connectivity user plane architecture described in Non-Patent Document 11 (see Non-Patent Document 11 8.1.1.8).
- a method for performing HO is disclosed.
- the MeNB performs bearer split in which the bearer is divided between a path for direct communication between the MeNB and the UE and a path for communication via the small cell.
- a UE in dual connectivity by bearer split When a UE in dual connectivity by bearer split performs inter-MeNB HO, the connection with the SeNB is not released. That is, HO between MeNB is performed, maintaining UE dual connectivity.
- the E-RAB corresponding to one EPS bearer is separated into two paths by the S-MeNB, and between the S-GW and the UE.
- the data is communicated with.
- step ST1001 data is directly communicated between the S-MeNB and the UE.
- step ST1003 and step ST1004 data is communicated between the S-MeNB and the UE via the SeNB.
- step ST1002 data is communicated between the S-MeNB and the S-GW through one path.
- the method disclosed in the first embodiment can be applied to the method in which the MeNB notifies the UE in dual connectivity by bearer split to the measurement control message.
- the description is omitted here.
- the reception quality of the S-MeNB due to the measurement is deteriorated, the reception quality of the T-MeNB is improved, and the measurement report is performed according to the event criteria will be described.
- step ST906 the UE performs a measurement report to the S-MeNB.
- the identifier of the SeNB used for dual connectivity and the reception quality may be included in the measurement report from the UE.
- the S-MeNB that has received the measurement report from the UE determines to cause the UE to HO to the T-MeNB using the result of the report.
- the S-MeNB notifies the T-MeNB of a HO request message.
- This message may be notified including SeNB information.
- SeNB information includes, for example, SeNB identifier, SeNB reception quality at the UE, and the like.
- E-RAB identifier or the like as bearer information related to the bearer performing bearer splitting.
- the configuration of a bearer split into a direct path between the MeNB and the UE and a path between the MeNB and the UE via the SeNB (hereinafter sometimes referred to as “split bearer”) ( Hereinafter, there is information regarding “split bearer configuration”.
- the MeNB may set a split bearer for each split path.
- An identifier for each path may be provided.
- the identifier of each path and the information related to the split bearer configuration set for each path may be notified in association with each other.
- the SeNB identifier and the path identifier may be associated and notified.
- Examples of information related to the split bearer configuration set for each path include QoS parameters, specifically, QCI, ARP, and bandwidth guarantee service quality information.
- the S-MeNB can notify the T-MeNB of split bearer settings for each path.
- the T-MeNB can acquire the split bearer setting for each path, and can determine whether it is necessary to change the split bearer setting for each path.
- RRC context As setting information regarding RRC in bearer split, for example, there is an RRC context (RRC context).
- the RRC context includes, for example, an AS configuration (AS configuration) indicating a configuration of radio resources, an RRM configuration (RRM configuration) indicating RRM information, and the like.
- AS configuration AS configuration
- RRM configuration RRM configuration
- the information regarding RRC includes information regarding RRC for MeNB and information regarding RRC for SeNB.
- Information regarding each RRC may be identifiable. For example, the RRC context for the MeNB and the RRC context for the SeNB are created separately. Alternatively, information for MeNB and information for SeNB may be created separately in one RRC context.
- the information regarding the RRC for the SeNB and the information regarding the RRC for the MeNB can be individually configured, and the S-MeNB sends the information regarding the RRC of each of the MeNB and the SeNB to the T-MeNB. Notification can be made.
- the T-MeNB can acquire information regarding the RRC of each of the S-MeNB and the SeNB, and the T-MeNB can determine whether or not the setting regarding the RRC of the SeNB needs to be changed.
- step ST1101 the T-MeNB determines whether to change the SeNB using the information received in the HO request message from the S-MeNB.
- the process in step ST1101 is the same as the process in step ST1101 in FIG.
- the mobile terminal makes a transition to step ST1102.
- the method disclosed in Embodiment 2 may be applied to the process in step ST1102, and description thereof is omitted here.
- the T-MeNB determines to perform the HO process while maintaining the use of the SeNB in step ST1103. In other words, the T-MeNB determines to change only the MeNB.
- the split bearer configuration using SeNB is maintained. The split bearer configuration change process to the SeNB is not performed.
- the T-MeNB performs admission control for the HO request.
- This admission control may be performed before determining whether or not to change the aforementioned SeNB. Alternatively, it may be performed together with the determination.
- the T-MeNB performs settings related to RRC for the T-MeNB.
- Settings related to RRC include an AS configuration (AS configuration) indicating a configuration of radio resources, an RRM configuration (RRM configuration) indicating RRM information, and the like.
- AS configuration AS configuration
- RRM configuration RRM configuration
- information included in the RRC connection reconfiguration message may be set.
- the UE-specific RACH preamble configuration used in the T-MeNB may be provided separately from the UE-specific RACH preamble configuration used in the SeNB. Further, the C-RNTI used in the T-MeNB may be provided separately from the C-RNTI used in the SeNB. When the SeNB supports other UEs that are not under the T-MeNB, it can be set individually for each UE, thereby enabling flexible control.
- the UE-specific RACH preamble configuration used in the T-MeNB may be set to be the same as the UE-specific RACH preamble configuration used in the SeNB.
- the C-RNTI used in the T-MeNB may be set to be the same as the C-RNTI used in the SeNB.
- the setting related to RRC for T-MeNB requires information that enables the UE to reconfigure RRC connection with T-MeNB.
- the T-MeNB determines acceptance of the HO request, in step ST1203, the T-MeNB notifies the S-MeNB including the HO instruction message in the HO request acceptance response message.
- the HO instruction message may include setting information related to the RRC for the T-MeNB.
- the T-MeNB when maintaining the configuration of the split bearer using SeNB, notifies the S-MeNB of the identifier of the SeNB, the E-RAB identifier, information on the bearer split, information on RRC in the bearer split, and the like. .
- the T-MeNB may notify the S-MeNB that HO is possible while maintaining the configuration of the split bearer using the SeNB.
- the T-MeNB may notify the S-MeNB that HO is possible while maintaining the setting related to RRC for SeNB.
- These notifications may be performed using a HO request acceptance response message. You may notify with the HO request
- the S-MeNB In the HO request acceptance response message or the HO instruction message, information regarding whether or not there is a change in the SeNB RRC setting may be included.
- the S-MeNB may further acquire a setting related to the RRC of the SeNB. This makes it possible to simplify the process when there is no change.
- the setting information may not be included in the HO instruction message.
- the amount of information to be signaled can be reduced.
- setting information related to RRC for SeNB may be included in the HO instruction message.
- the S-MeNB can compare the setting information related to the RRC for the SeNB acquired from the T-MeNB with the setting information related to the RRC for the SeNB that the own cell has, and there is no change. It becomes possible to verify this.
- the S-MeNB that has received the HO request acceptance response message in step ST1203 can recognize that the T-MeNB is a HO that maintains the SeNB for the UE in dual connectivity.
- the S-MeNB that has recognized that HO is performed while maintaining the SeNB does not request the SeNB to change the split bearer configuration.
- the setting change request related to RRC for SeNB is not performed.
- the UE in dual connectivity may not change the bearer split configuration by SeNB activation during HO between MeNBs. If there is a change in the bearer split configuration due to SeNB activation during HO, the process is performed when the MeNB is changed from the S-MeNB to the T-MeNB, so that the control becomes complicated and the possibility of malfunctioning increases. By not changing the bearer split configuration due to SeNB activation at the time of HO, it is possible to reduce malfunctions.
- a method for preventing change of the bearer split configuration due to SeNB activation during HO is disclosed below.
- T-MeNB notifies SeNB of information indicating that HO is activated. This notification may be performed when the T-MeNB transmits a HO request acceptance response message to the S-MeNB. Or S-MeNB which received the HO request
- the SeNB that has received the information indicating that the HO has been activated does not activate the bearer split configuration change request. It is good not to start until this HO is completed.
- the S-MeNB or T-MeNB may notify the SeNB of Nack (or rejection) in response to a bearer split configuration change request from the SeNB.
- Reason information may be included, and information indicating that the HO is being performed may be provided and set as the reason.
- step ST1204 these processes are performed among the T-MeNB, S-MeNB, and SeNB.
- the T-MeNB may notify the SeNB of information indicating completion of HO. This notification may be performed when the T-MeNB receives a path switch request acceptance response message from the MME in the HO process. Alternatively, completion of the MeNB change process, which will be described later, may be HO completion.
- the S-MeNB when performing HO while maintaining the above-mentioned SeNB, does not request the SeNB to change the split bearer configuration or to change the setting related to RRC for the SeNB.
- the S-MeNB may notify the SeNB that it is HO while maintaining the SeNB. Or you may notify not performing the request
- the SeNB can recognize whether or not the HO performs HO while maintaining the SeNB during the HO.
- the SeNB can be prevented from changing the bearer split configuration for the UE activated by the SeNB during the HO. The same effect as described above can be obtained.
- the S-MeNB that has received the HO request acceptance response message notifies the UE of an RRC connection Reconfiguration (RRC connection Reconfiguration) message including MCI (Mobility Control Information) in order to cause the T-MeNB to perform HO.
- RRC connection Reconfiguration RRC connection Reconfiguration
- MCI Mobility Control Information
- the S-MeNB that has received the HO request acceptance response message may notify the UE that there is no change in the bearer split using the SeNB.
- the S-MeNB notifies the UE that there is no change in the SeNB for E-RAB that performs split bearer at the time of the HO. Moreover, you may notify that there is no setting change regarding RRC for SeNB. It may be notified together with the RRC connection reconfiguration message including the MCI.
- the S-MeNB may notify the UE of the setting information when it recognizes the setting information related to RRC for the SeNB.
- the UE can compare the setting information related to RRC for the SeNB to which the UE is connected and the received setting information, and can verify that there is no change.
- Step ST1205 the UE that has received the RRC connection reconfiguration message including the MCI performs HO from the S-MeNB to the T-MeNB while maintaining synchronization and connection with the SeNB.
- the UE performs HO while maintaining radio resources with the SeNB. For example, the UE does not reset the MAC setting for the SeNB. Alternatively, the RLC setting for SeNB is not reconfigured. In this state, the UE can communicate with the SeNB.
- the setting for the MeNB follows the setting information related to RRC for the MeNB of the RRC connection reconfiguration message including the MCI. Since PDCP is located in MeNB, the setting of PDCP should follow the setting for MeNB. For example, the setting for the S-MeNB is reset to the setting for the T-MeNB.
- the RRC connection reconfiguration message including the MCI it is preferable that setting information related to RRC for the MeNB and setting information related to RRC for the SeNB are individually provided and individually settable. As a result, the UE can reconfigure or maintain the settings for the SeNB and the settings for the MeNB individually or shift to the default settings. In this example, since the UE can reconfigure the settings for the MeNB while maintaining the settings for the SeNB, it is possible to change from the S-MeNB to the T-MeNB while maintaining the SeNB connection.
- a method for handling uplink data from the UE to the SeNB will be disclosed below. Even when the UE performs HO while maintaining the connection with the SeNB, the UE does not recognize whether the SeNB is connected to the S-MeNB or the T-MeNB. During the HO process, if the UE transmits uplink data to the SeNB when the SeNB is not yet connected to the T-MeNB, the SeNB cannot transmit the T-MeNB uplink data. It will cause loss.
- a method for solving such a problem is disclosed.
- the UE After receiving the MCI from the S-MeNB, the UE stops transmitting uplink data and stores it in the buffer. Further, the UE stops transmission of uplink data until the RRC connection reconfiguration with the T-MeNB is completed, and stores it in the buffer. The UE transmits the uplink data after notifying the RRC connection reconfiguration completion message with the T-MeNB. The UE may stop transmission of new uplink data after receiving MCI from the S-MeNB and store it in the buffer.
- the uplink data may be all the uplink data transmitted from the UE.
- the UE may stop and store the uplink data to be transmitted on the direct path to the T-MeNB and the uplink data to be transmitted on the path to the T-MeNB via the SeNB in a buffer.
- uplink data transmitted on the direct path to the T-MeNB and uplink data transmitted on the path to the T-MeNB via the SeNB are distributed within the UE, both are stopped, It may be stored in a buffer.
- PDCP SN numbering may be performed as uplink data processing in the UE. By doing so, it is possible to solve the problem of loss of uplink data.
- Step ST1205 the UE that has received MCI instructing HO from the S-MeNB to the T-MeNB stops transmission of uplink data and stores it in the buffer in Step ST1206.
- Step ST1207 the UE performs a connection change process from the S-MeNB to the T-MeNB according to the MCI.
- Step ST1207 after receiving the MCI, the UE disconnects from the S-MeNB and connects to the T-MeNB.
- the UE reconfigures the RRC connection for the T-MeNB using the content received in the RRC connection reconfiguration message in Step ST1205, and connects to the T-MeNB.
- UE performs RA processing with T-MeNB in step ST1212, and notifies RRC connection reconfiguration completion message to T-MeNB in step ST1213.
- the UE can perform direct data communication with the T-MeNB after notifying the T-MeNB of the RRC connection reconfiguration completion message.
- the UE sends uplink data after notifying RRC connection reconfiguration complete message with T-MeNB.
- the uplink data is divided into a path directly transmitted to the T-MeNB and a path transmitted to the T-MeNB via the SeNB in the UE, and the UE transmits uplink data to each of the T-MeNB and SeNB. .
- Step ST1219 the UE transmits uplink data through a path directly transmitted to the T-MeNB.
- Step ST1220 the UE transmits uplink data to the SeNB. Uplink data may be transmitted according to PDCP SN.
- the UE or SeNB may perform synchronization processing between the UE and SeNB as necessary while the UE is in HO from the S-MeNB to the T-MeNB. Or you may perform before UE starts uplink data transmission with respect to SeNB. RA processing may be used.
- the UE may continue the transmission process for uplink data to the S-MeNB that has been transmitted / received to / from the SeNB before reception of MCI, that is, before transmission of uplink data is stopped.
- the transmission process may be continued until the transmission of the uplink data directly performed with the S-MeNB is not achieved. These are performed using the overhead compression setting notified by the S-MeNB.
- the UE transmits data that failed to be transmitted among the uplink data transmitted / received to / from the S-MeNB directly or via the SeNB before receiving the MCI, that is, before the uplink data transmission is stopped. May start transmission to the T-MeNB.
- the UE may start transmission to the T-MeNB from data with the smallest PDCP SN among the data that failed to be transmitted. From the data, the UE may transmit to the T-MeNB directly or via the SeNB.
- this method makes it possible to minimize data loss. Also, this method requires a small amount of uplink data buffer in the SeNB, so that the buffer capacity of the SeNB can be reduced and the configuration can be simplified. SeNB can be made inexpensive.
- the transmission to the T-MeNB may use the header compression setting set by the T-MeNB in both cases of transmission to the T-MeNB directly and via the SeNB to the T-MeNB.
- the SeNB may not yet be connected to the T-MeNB.
- the SeNB may store the uplink data from the UE in the buffer until the change of the MeNB setting with the T-MeNB is completed.
- SeNB transmits the uplink data from UE to T-MeNB after completion of MeNB setting change with T-MeNB.
- the SeNB may reorder and transmit using the data PDCP SN.
- the MeNB setting change between the SeNB and the T-MeNB is delayed for some reason, and even when uplink data transmission from the UE to the SeNB has been performed, data loss in the SeNB occurs. Can solve the problem.
- the UE transmits uplink data to the SeNB without waiting for completion of connection with the T-MeNB.
- the SeNB stores uplink data from the UE in a buffer until the change of the MeNB setting with the T-MeNB is completed.
- SeNB transmits the uplink data from UE to T-MeNB after completion of MeNB setting change with T-MeNB.
- the SeNB may reorder and transmit using the data PDCP SN. This can solve the problem of data loss in the SeNB.
- the buffer amount required for the SeNB is larger than that of the above method, but when the MeNB setting is changed between the SeNB and the T-MeNB, the buffer is immediately buffered from the SeNB to the T-MeNB. Therefore, uplink data from the UE can be delivered to the T-MeNB at an early stage.
- new uplink data is transmitted to the T-MeNB via the SeNB.
- the T-MeNB notifies the UE of the header compression setting via the S-MeNB, and the UE uses the header compression setting for new uplink communication with the T-MeNB via the SeNB.
- the UE may stop transmitting uplink data to the S-MeNB that was performed with the SeNB before receiving the MCI.
- Data for which uplink data transmission to the S-MeNB has failed may also be transmitted to the SeNB with header compression setting by the T-MeNB.
- the UE may start transmission from the data with the smallest PDCP SN to the T-MeNB via the SeNB among the data that failed to be transmitted.
- the UE may transmit uplink data for both the S-MeNB and the T-MeNB with the SeNB.
- the SeNB may determine which is the uplink data by identifying which header compression is used.
- the PDCP format D / C bit may be set as the bit for the information.
- the SeNB buffers the uplink data from the UE until the change of the MeNB setting with the T-MeNB is completed, and transmits the uplink data from the UE to the T-MeNB after the MeNB setting change with the T-MeNB is completed. To do.
- the SeNB may reorder and transmit using the data PDCP SN.
- the uplink data received from the UE by the S-MeNB will be described.
- the uplink data received from the UE received by the S-MeNB may be managed by the PDCP SN together with the uplink data received directly from the UE and the uplink data received via the SeNB.
- the S-MeNB reorders according to PDCP SN and transmits to the S-GW.
- the uplink data being communicated directly with the UE when transmitting the MCI is transmitted from the S-MeNB to the S-GW after successful data delivery to the S-MeNB. May be.
- uplink data being communicated with the UE via the SeNB when transmitting MCI may be transmitted to the S-GW after successful data delivery to the S-MeNB.
- the order management of the data received from the S-MeNB and the data received from the T-MeNB may be performed by the S-GW.
- the UE Generated by the UE not transmitting the data to the T-MeNB if the data that the UE has determined to have completed transmission when receiving the MCI has not been successfully delivered to the S-MeNB for any reason. Data loss can be prevented. Further, instead of transmitting from the S-MeNB to the S-GW, forwarding to the T-MeNB (forwarding) may be performed. The T-MeNB may reorder according to PDCP SN and transmit to the S-GW. As a result, the same effect as the method of transmitting to the S-GW can be obtained.
- the subject to be set may be a node on the RAN side or the core network side.
- the setting information may be notified to the S-MeNB in advance. For example, the MME or S-GW notifies the setting information to the S-MeNB in advance.
- the S-MeNB transmits MCI to the UE
- the data that has been successfully delivered after the data that has failed to be delivered immediately before may be transmitted to the S-GW or forwarded (forwarded) to the T-MeNB.
- uplink transmission is performed by the T-MeNB from the failed data.
- the transferred data can be used.
- a method for handling downlink data notified from the MeNB to the UE via the SeNB will be disclosed below.
- the S-MeNB that has received the HO request acceptance response message in step ST1203 stops the transmission of new downlink data and stores it in the buffer.
- the downlink data may be all downlink data transmitted to the UE that performs HO.
- the S-MeNB may stop and store the downlink data to be transmitted on the direct path to the UE and the downlink data to be transmitted on the path to the UE via the SeNB in a buffer. Or, even if downlink data transmitted on the direct path to the UE and downlink data transmitted on the path to the UE via the SeNB are distributed in the S-MeNB, transmission of both data is stopped. And store it in the buffer.
- PDCP SN numbering may be performed as downlink data processing in the S-MeNB.
- the S-MeNB transmits downlink data after downlink data that has not been transmitted among downlink data transmitted / received to / from the UE before reception of the HO request acceptance response message, that is, before transmission of data is stopped. To the T-MeNB (forwarding).
- the downlink data transmitted by the direct path from the S-MeNB to the UE and the downlink data transmitted by the path via the SeNB may be combined (forwarded) from the data having the smallest PDCP SN to the T-MeNB.
- step ST1208 the S-MeNB starts forwarding (forwarding) to the T-MeNB.
- step ST1209 the S-MeNB performs SN status transmission (SN Status Transfer), and performs data forwarding (Data ⁇ Forwarding) in step ST1210. Do.
- the transfer is managed by the PDCP SN, and the end marker from the S-GW notified in step ST942 and step ST944 is transferred.
- step ST1211 the T-MeNB stores the data forwarded from the S-MeNB in the buffer.
- the T-MeNB stores the downlink data in the buffer until the direct RRC connection reconfiguration with the UE is completed and until the MeNB change process in the SeNB is completed.
- the T-MeNB may buffer the downlink data by the direct path with the UE and the downlink data by the path via the SeNB before or after separating by the bearer split. . Both can be managed by numbered PDCP SN.
- the UE can be reordered by PDCP SN.
- the data Allows scheduling for separation In the method of storing in the buffer before separation, when changing the bearer split configuration using SeNB, after the new bearer split configuration is set for both paths, the data Allows scheduling for separation. Therefore, efficient scheduling can be performed for the dual connectivity UE.
- the T-MeNB When the direct connection with the UE is completed and when the MeNB change process in the SeNB is completed, the T-MeNB performs downlink scheduling for downlink data for each path, and uses each path for downlink data to the UE. Send.
- the T-MeNB starts downlink data transmission to the UE on the earlier of the completion of the direct connection with the UE and the completion of the MeNB change notification with the SeNB.
- T-MeNB When the T-MeNB stores data in the buffer before separating the data, downlink data transmission is performed on the earlier path until both paths are established. After that, bearer split may be started when both paths are established.
- the T-MeNB separates data and stores it in the buffer, it is preferable to perform downlink data transmission according to the establishment of each path.
- downlink data can be transmitted to the UE as early as possible.
- the SeNB is notified by the MeNB of the bearer split configuration for dual connectivity to the UE. Moreover, the setting information regarding RRC with respect to this UE of SeNB is notified by this MeNB.
- the SeNB needs to recognize from which MeNB the configuration of the bearer split is notified, which MeNB should be notified of the setting information regarding the RRC set by the SeNB. That is, it is necessary to recognize the MeNB.
- SeNB performs the data communication for UE which performs dual connectivity between MeNB.
- the SeNB needs to recognize which MeNB should transmit data to the UE and which MeNB should transmit data from the UE. That is, it is necessary to recognize the MeNB.
- the former MeNB and the latter MeNB may be set separately, but here, a case where they are the same will be described.
- the MeNB is referred to as a SeNB control MeNB.
- a method of recognizing which MeNB has changed the control MeNB of the SeNB when the MeNB is changed from S-MeNB to T-MeNB without changing the SeNB in the HO processing of the UE in dual connectivity is disclosed below. As specific examples, the following two (1) and (2) are disclosed. (1) The S-MeNB notifies the SeNB of the change of the control MeNB. (2) The T-MeNB notifies the SeNB of the change of the control MeNB.
- the T-MeNB When receiving the RRC connection reconfiguration completion message from the UE, the T-MeNB notifies the S-MeNB of a control eNB change request message of the SeNB.
- the notification may be performed using X2 signaling. You may notify to this notification including the identifier of SeNB which changes control MeNB. Moreover, you may notify including the reason information of a change. Information indicating that the MeNB is changed by HO may be provided and notified.
- the S-MeNB that has received the notification notifies the SeNB that changes the control MeNB of the change of the control MeNB.
- the notification may be performed using X2 signaling. Or you may perform using the signaling on the interface provided between MeNB and SeNB.
- the following seven (1) to (7) are disclosed as specific examples of information included in the signaling.
- Information indicating the change of the control MeNB. (2) The identifier of the control MeNB after the change. Here, the identifier of the T-MeNB.
- an E-RAB identifier (may be an E-RAB ID or the like) or an EPS bearer identifier.
- the identifier of the S-MeNB. An identifier of a UE that performs dual connectivity using bearer splitting. (7) A combination of the above (1) to (6).
- the SeNB that has received the control MeNB change notification message identifies the split bearer that changes the MeNB from the information included in the change notification message.
- the SMeNB changes the control MeNB of the split bearer to the changed MeNB.
- the management of the split bearer in the SeNB may be performed in association with the identifier of the control MeNB. That is, it is good to associate the identifier of a split bearer with the identifier of a control MeNB. By doing in this way, SeNB can change the control MeNB of the split bearer for UE which performs dual connectivity.
- the SeNB accepts only the request for modification and release of the split bearer after the change of the control MeNB from the control MeNB after the change.
- the SeNB performs data communication with the changed MeNB.
- the SeNB can recognize to which MeNB the control MeNB has been changed, and control of the split bearer modification, release request, etc. for the UE with the control MeNB after the change. Communication and data communication can be performed.
- the SeNB that has changed the control MeNB may notify the S-MeNB of a control MeNB change response message.
- the message may include information indicating that the control MeNB has been changed.
- the S-MeNB that has received the control MeNB change response message from the SeNB may notify the control MeNB after the change, here the T-MeNB, of a message indicating that the SeNB control MeNB change has been completed.
- the changed MeNB here the T-MeNB can recognize that the control MeNB of the SeNB has been changed, and the modification of the split bearer for the UE to the SeNB, Communication for control such as a release request and data communication can be started.
- the changed MeNB may notify the SeNB of a message confirming that the control MeNB of the split bearer for the UE has been changed.
- the SeNB may respond to the message.
- the T-MeNB Upon receiving the RRC connection reconfiguration completion message from the UE, the T-MeNB notifies the SeNB of a control MeNB change request message.
- the SeNB identifier may be SeNB information included in the HO request message received from the S-MeNB.
- the notification may be performed using X2 signaling. Or you may perform using the signaling on the interface provided between MeNB and SeNB.
- Information disclosed in the method of the specific example (1) can be applied to the information included in the signaling.
- SeNB can recognize to which MeNB the control MeNB has been changed, such as modification of the split bearer for the UE, a request for release, etc. with the control MeNB after the change. Communication for control and data communication can be performed.
- the SeNB that has changed the control MeNB may notify the T-MeNB of a control MeNB change response message.
- the message may include information indicating that the control MeNB has been changed.
- the T-MeNB that has received the control MeNB change response message from the SeNB may notify a message indicating that the control MeNB change of the SeNB has been completed to the control MeNB before the change, in this case, the S-MeNB.
- the S-MeNB can recognize that the control MeNB of the SeNB has been changed, and for the SeNB, the modification of the split bearer for the UE, Communication for control such as a release request and data communication can be terminated.
- SeNB when HO of a UE in dual connectivity is performed using SeNB, SeNB can perform communication for control related to the split bearer configuration and data communication with the changed MeNB (T-MeNB). It becomes.
- step ST1214 the T-MeNB that has received the RRC connection reconfiguration completion message from the UE in step ST1213 in FIG. 21 notifies the S-MeNB of a change request message for the SeNB control MeNB.
- the identifier of the SeNB that changes the control MeNB is included in the message.
- the S-MeNB that has received the message notifies the SeNB that changes the control MeNB of a message requesting the change of the control MeNB.
- information indicating the change of the control MeNB, the identifier of the T-MeNB, the bearer identifier of the path using the SeNB, the identifier of the split bearer for changing the control MeNB in the SeNB, the identifier of the S-MeNB, and the dual using the SeNB Include the identifier of the UE targeted for HO for connectivity. By doing so, the SeNB can recognize which split bearer set by which MeNB should change the control MeNB.
- the SeNB that has received the message changes the control MeNB in step ST1216 using the information received in step ST1215. Accordingly, the SeNB subsequently performs communication and data communication for control related to the split bearer with the T-MeNB that is the changed MeNB.
- the SeNB that has changed the control MeNB ends communication and data communication for control with the control MeNB before the change.
- the SeNB that has changed the control MeNB notifies the control MeNB change response message to notify the S-MeNB that the control MeNB has been changed in step ST1217.
- the S-MeNB that has received the response message notifies the T-MeNB of the SeNB control MeNB change response message to notify the T-MeNB that the SeNB control MeNB change has ended. Accordingly, the T-MeNB can recognize that the SeNB MeNB has been changed to the T-MeNB. Therefore, the T-MeNB can perform communication and data communication for control related to the split bearer with the SeNB.
- step ST1220 and step ST1221 it becomes possible to communicate both the downlink data from the T-MeNB to the UE and the uplink data from the UE to the T-MeNB via the SeNB.
- Step ST1214 to step ST1218 shown in FIG. Step ST1222 shows SeNB MeNB change processing performed in T-MeNB, S-MeNB, and SeNB.
- Step ST1005 In the data communication between the S-GW and the UE, one of the data is directly communicated between the S-MeNB and the UE in Step ST1005, and the other is the S-MeNB in Step ST1007 and Step ST1008. Between the UE and the UE via the SeNB. In Step ST1006, data is communicated through one path between the S-MeNB and the S-GW.
- MeNB change process step ST1222 to SeNB Another method is disclosed about MeNB change process step ST1222 to SeNB.
- the MeNB change process to the SeNB is performed after the T-MeNB receives the RRC connection reconfiguration completion message from the UE.
- the MeNB change process to the SeNB may be performed.
- the above-described method may be applied to the MeNB change process to the SeNB.
- the SeNB can change the control MeNB to T-MeNB at an early stage, so that data communication can be performed between the SeNB and the T-MeNB at an early stage.
- the UE does not need to buffer and buffer uplink data until the reconfiguration of the RRC connection with the T-MeNB is completed. Alternatively, transmission may be stopped and not buffered in the SeNB. The UE can quickly communicate uplink data to the T-MeNB via the SeNB by the split bearer using the SeNB.
- T-MeNB does not have to buffer downlink data until it receives RRC connection reconfiguration completion from the UE.
- the T-MeNB can quickly communicate uplink data to the UE via the SeNB by the split bearer using the SeNB.
- the T-MeNB may perform the MeNB change process to the SeNB after completing the path switch process performed for the MME and the S-GW.
- the T-MeNB receives a path switch request acceptance response message from the MME, the T-MeNB notifies the SeNB of the change of the MeNB.
- the S-MeNB may notify the SeNB of the MeNB change when receiving a UE context release (UETcontext release) message from the T-MeNB.
- UE context release UE context release
- FIG. 23 to 25 are diagrams showing an exemplary sequence of handover-related processing in the communication system according to Embodiment 4 of the present invention.
- FIG. 23 and FIG. 24 are connected by a boundary line BL5.
- 24 and 25 are connected by a boundary line BL6.
- the handover related processing of the present embodiment is the same as that of the first embodiment shown in FIGS. 10 to 13, the second embodiment shown in FIGS. 17 to 19, and the third embodiment shown in FIGS. Since it is similar to the related process, the same step is given the same step number, and the description is omitted.
- This embodiment is different from the above-described third embodiment in the method of handling downlink data.
- it discloses below about the handling method of the downlink data notified to UE via MeNB from SeNB.
- the S-MeNB that has received the HO request acceptance response message in step ST1203 stops transmission of new downlink data and stores it in the buffer.
- the downlink data may be all downlink data transmitted to the UE that performs HO.
- the S-MeNB distributes the downlink data to be transmitted on the direct path to the UE and the downlink data to be transmitted on the path to the UE via the SeNB, stops after storing the data, and stores it in the buffer to the UE via the SeNB. It is preferable to continue the transmission without stopping the downlink data transmitted through the path.
- PDCP SN numbering may be performed as downlink data processing in the S-MeNB.
- the S-MeNB transmits downlink data after downlink data that has not been transmitted among downlink data transmitted / received to / from the UE before reception of the HO request acceptance response message, that is, before transmission of data is stopped.
- To the T-MeNB (forwarding).
- the data having the smallest PDCP SN may be forwarded to the T-MeNB (forwarding).
- the data having the smallest PDCP SN may be forwarded to the T-MeNB (forwarding).
- data having the smallest PDCP SN may be forwarded to the T-MeNB (forwarding).
- step ST1301 the S-MeNB starts forwarding (forwarding) to the T-MeNB.
- step ST1209 the S-MeNB performs SN status transmission (SN Status Transfer), and in step ST1210, data forwarding (Data Forwarding). I do.
- the transfer is managed by the PDCP SN, and the end marker from the S-GW notified in step ST942 and step ST944 is transferred.
- Step ST1211 the T-MeNB stores the data forwarded from the S-MeNB (forwarding) in a buffer.
- the T-MeNB stores the downlink data in the buffer until the direct RRC connection reconfiguration with the UE is completed and until the MeNB change process in the SeNB is completed.
- the T-MeNB may store the downlink data by the direct path with the UE and the downlink data by the path through the SeNB after separating them in the buffer by bearer splitting. It is possible to manage with the numbered PDCP SN.
- the UE can be reordered by PDCP SN.
- the data Allows scheduling for separation In the method of storing in the buffer before separation, when changing the bearer split configuration using SeNB, after the new bearer split configuration is set for both paths, the data Allows scheduling for separation. Therefore, efficient scheduling can be performed for the dual connectivity UE.
- the downlink data can be immediately transmitted to the UE using both paths. That is, an increase in delay amount can be prevented.
- the T-MeNB performs downlink scheduling for downlink data for each path, and uses each path for downlink data to the UE. Send.
- the T-MeNB starts downlink data transmission to the UE on the earlier of the completion of the direct connection with the UE and the completion of the MeNB change notification with the SeNB.
- downlink data can be transmitted to the UE as early as possible.
- FIG. 26 to 28 are diagrams showing an exemplary sequence of handover-related processing in the communication system according to Embodiment 5 of the present invention.
- FIG. 26 and FIG. 27 are connected by a boundary line BL7.
- 27 and FIG. 28 are connected by a boundary line BL8.
- bearer 2 (hereinafter referred to as “EPS bearer # 2”) is used as a bearer corresponding to EPS (hereinafter also referred to as “EPS bearer”).
- EPS bearer # 2 a bearer corresponding to EPS
- Both the SeNB and the S-MeNB transmit / receive data to / from the UE.
- only the SeNB transmits / receives data to / from the UE.
- both the SeNB and the T-MeNB perform data transmission / reception with the UE.
- a UE that transmits and receives data to and from both SeNB and S-MeNB using EPS bearer # 2 will be described.
- the EPS bearer # 2 does not go through the RLC / MAC of the S-MeNB, but only the RLC / MAC / PHY of the SeNB. Everything is migrated to go through.
- all EPS bearer # 2 including GTPu / PDCP are transferred so that all lower layers than S-GW do not go through S-MeNB, but go through only RLC / MAC / PHY of SeNB. .
- the EPS bearer # 2 is all transferred so as to pass through all of SeNB's GTPu / PDCP / RLC / MAC / PHY, instead of being transferred only through that of SeNB's RLC / MAC / PHY. To be migrated. In the following description, in this way, shifting all bearers so as to pass through the SeNB may be referred to as “all shifting to SeNB”.
- step ST2001 the S-MeNB, T-MeNB, MME, and S-GW grant area restrictions (AreaARestriction Provided).
- step ST2002 the S-MeNB notifies the UE of a measurement control (Measurement Control) message.
- Measurements of neighboring SeNBs may be set in the measurement control message.
- frequency measurement for SeNB may be set.
- an event at a frequency for SeNB or a frequency for SeNB or a criterion for an event may be set separately from MeNB.
- the Setting parameters include SeNB identifier, frequency, event number for reporting, reception quality threshold, measurement period, and the like.
- the reception quality includes RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), and the like.
- the UE that has received the measurement control message in Step ST2002 performs measurement of neighboring cells, that is, the MeNB and SeNB.
- step ST2003 packet data communication is performed between the UE and the S-MeNB
- step ST2004 packet data communication is performed between the S-MeNB and the S-GW.
- step ST2005 packet data is directly communicated between the UE and S-MeNB, and in step ST2006, packet data is directly transmitted between S-MeNB and S-GW. Communicated.
- step ST2007 and step ST2008 packet data is communicated between the UE and the S-MeNB via the SeNB. Specifically, in step ST2007, packet data is communicated between the UE and SeNB, and in step ST2008, packet data is communicated between SeNB and S-MeNB.
- step ST2009 the S-MeNB notifies the UE of uplink allocation (UL allocation) information.
- Step ST2010 the UE notifies the S-MeNB of a measurement report (Measurement Report) message.
- step ST2011 the S-MeNB that has received the measurement report message in step ST2010 determines whether or not to hand over (HO) the UE to the T-MeNB using the result of the measurement report. In the example illustrated in FIG. 26, the S-MeNB determines to cause the T-MeNB to HO in step ST2011.
- Step ST2012 whether or not the S-MeNB performs correction for the entire transfer of the EPS bearer # 2 to the SeNB (hereinafter may be referred to as “correction for the entire transfer of the EPS bearer # 2 to the SeNB”). To decide. In the example illustrated in FIG. 26, the S-MeNB determines to perform correction for the entire transition of the EPS bearer # 2 to the SeNB.
- the S-MeNB performs an EPS bearer # 2 full migration availability confirmation process for the SeNB.
- the EPS bearer # 2 all migration permission confirmation process for the SeNB is the SeNB that determines whether the EPS bearer # 2 can be completely migrated to the SeNB, that is, whether the EPS bearer # 2 can be completely migrated to the SeNB.
- the process to check Specifically, the S-MeNB confirms whether or not all transition to the SeNB of the EPS bearer # 2 is possible with respect to the SeNB as the EPS bearer # 2 all transition permission confirmation process for the SeNB. Notify the signal.
- the SeNB that has received the all migration permission confirmation signal notifies the S-MeNB of whether all migration to the SeNB of the EPS bearer # 2 is possible.
- step ST2014 the S-MeNB determines whether or not all transitions to the SeNB are possible based on whether or not all transitions notified from the SeNB are possible.
- the process proceeds to step ST2015, and when it is determined that all transition to SeNB is not possible, the process proceeds to step ST2016.
- Step ST2015 the UE, SeNB, and S-MeNB perform EPS bearer # 2 all transition correction processing on the S-MeNB. Specifically, in step ST2015, a process of fully transferring EPS bearer # 2 to SeNB is performed.
- step ST2016 the S-MeNB performs the HO process after releasing the SeNB in the same manner as in step ST1102 of FIG.
- step ST2017 packet data is communicated between the S-MeNB and the S-GW.
- step ST2018 packet data communication is performed between the UE and the SeNB.
- step ST2019 packet data is communicated between the SeNB and the S-MeNB.
- the S-MeNB notifies the handover request (Handover Request) message to the HO destination T-MeNB.
- the HO request message includes SeNB information and information on EPS bearer # 2 (hereinafter may be referred to as “EPS bearer # 2 information”). SeNB information and EPS bearer # 2 information may be notified using a message different from the HO request message.
- step ST2021 the T-MeNB determines whether the SeNB needs to be changed. When it is determined that SeNB change is necessary, the process proceeds to step ST2022, and when it is determined that SeNB change is not necessary, the process proceeds to step ST2023.
- Step ST2022 the T-MeNB performs the handover (HO) process after releasing the SeNB in the same manner as in Step ST1102 of FIG.
- step ST2023 the T-MeNB judges whether or not the bearer configuration needs to be changed. When it is determined that the bearer configuration needs to be changed, the process proceeds to step ST2025 in FIG. 28, and when it is determined that the bearer configuration does not need to be changed, the process proceeds to step ST2024.
- Step ST2024 the SeNB and T-MeNB performs a MeNB change confirmation process for the SeNB.
- the MeNB change confirmation process refers to a process of confirming whether or not to change the MeNB from the S-MeNB to the T-MeNB.
- the T-MeNB notifies the SeNB of a MeNB change confirmation signal for confirming whether or not to change the MeNB from the S-MeNB to the T-MeNB.
- the SeNB that has received the MeNB change confirmation signal notifies the T-MeNB whether or not to change the MeNB.
- S-MeNB is not involved in the process of step ST2024.
- Step ST2025 of FIG. 28 the MeNB HO process for EPS bearer # 1 is performed by the UE, SeNB, S-MeNB, T-MeNB, MME, and S-GW. Even when there is NAS signaling via the SeNB, it follows the MeNB HO process for EPS bearer # 1 in step ST2025. Details of the MeNB HO process for EPS bearer # 1 will be described later.
- Step ST2026 the SeNB, S-MeNB, and T-MeNB perform MeNB change processing on the SeNB.
- This is a process of notifying that the SeNB control plane (C-plane), for example, the macro eNB (MeNB) that performs signaling, has been changed after the MeNB handover is completed.
- C-plane SeNB control plane
- MeNB macro eNB
- This process is a process necessary for notifying that the MeNB of EPS bearer # 2 has been changed to T-MeNB and enabling data transmission / reception between the T-MeNB and SeNB.
- the S-MeNB notifies the SeNB of a signal indicating that the MeNB has been changed to T-MeNB.
- step ST2027 packet data is communicated between the UE and the SeNB.
- Step ST2028 packet data communication may be performed between the SeNB and the T-MeNB.
- Step ST2029 the T-MeNB determines whether or not the EPS bearer # 2 is to be corrected for the entire transition of the EPS bearer # 2 to the SeNB. In the example illustrated in FIG. 28, the T-MeNB determines to modify the EPS bearer # 2 for the entire transition of the EPS bearer # 2 to the SeNB.
- the EPS bearer # 2 is changed so as to be transmitted / received only from the SeNB that is not handed over during the handover process of the MeNB, so that it is not affected by the handover. Therefore, the handover process can be simplified, and handover failures can be reduced. Further, data loss can be reduced.
- Step ST2030 the UE, SeNB, and T-MeNB perform processing for confirming whether or not EPS bearer # 2 is fully migrated to SeNB and modification processing for all migration of EPS bearer # 2 to SeNB.
- the S-MeNB is not involved in the process of step ST2030.
- step ST203 communication of packet data is performed between the UE and the T-MeNB.
- Step ST2032 packet data communication is performed between the T-MeNB and the S-GW.
- step ST2033 packet data communication is performed between the UE and the SeNB.
- Step ST2034 communication of packet data is performed between the SeNB and the T-MeNB.
- 29 and 30 are diagrams illustrating an example of a sequence of the MeNB HO process for EPS bearer # 1 in step ST2025 of FIG.
- step ST2041 the T-MeNB performs admission control for confirming the accommodation capacity in the same manner as in step ST930 shown in FIG. If the T-MeNB determines that HO can be accepted based on the result of the admission control, the HO request acceptance response (Handover Request Ack) message is sent to the S-MeNB in step ST ⁇ b> 931 as in step ST ⁇ b> 931. To be notified.
- the HO request acceptance response (Handover Request Ack) message is sent to the S-MeNB in step ST ⁇ b> 931 as in step ST ⁇ b> 931. To be notified.
- the SeNB, S-MeNB, and T-MeNB Upon receiving the HO request acceptance response message in step ST2042, in step ST2043, the SeNB, S-MeNB, and T-MeNB perform MeNB change processing on the SeNB.
- the MeNB change process is a data flow from the T-MeNB to the S-MeNB, and further from the S-MeNB to the SeNB, or a data flow from the T-MeNB to the S-MeNB and from the T-MeNB to the SeNB.
- a process for notifying that a control plane (C-plane) of SeNB, for example, a macro eNB (MeNB) that performs signaling has been changed.
- the S-MeNB notifies the SeNB of a signal indicating that the MeNB has been changed to the T-MeNB.
- the change of MeNB may be notified using the HO request acceptance response (Handover Request Ack) message in step ST2042.
- step ST2044 packet data is communicated between the UE and the S-MeNB.
- Step ST2045 packet data communication is performed between the S-MeNB and the T-MeNB.
- step ST2046 the S-MeNB notifies the UE of downlink allocation (DL allocation) information.
- Step ST2047 the S-MeNB notifies the UE of an RRC connection reconfiguration (RRC Connection Reconfiguration) message including mobility control information.
- RRC Connection Reconfiguration RRC Connection Reconfiguration
- step ST2048 The processing from step ST2048 to step ST2055 is the same as 3GPP TS36.300. Specifically, in step ST2048, the UE detaches from the S-MeNB that is the old cell and starts synchronization with the T-MeNB that is the new cell.
- step ST2049 the S-MeNB transmits the packet stored in the buffer and the packet being transmitted to the T-MeNB that is the target eNB.
- step ST2050 the S-MeNB performs SN status transmission (SN Status Transfer) for transmitting the status of the sequence number (SN) of PDCP to the T-MeNB in the same manner as in step ST912 of FIG.
- the S-MeNB may perform data forwarding (Data ⁇ ⁇ Forwarding) for transferring data that has not been transmitted to the T-MeNB.
- the T-MeNB stores the packet transmitted from the S-MeNB in a buffer.
- Step ST2053 the UE synchronizes with the T-MeNB.
- the T-MeNB notifies the UE of uplink allocation (UL allocation) information and a UE tracking area (TA).
- the UE notifies the T-MeNB of an RRC connection reconfiguration complete (RRC Connection Reconfiguration Complete) message.
- Step ST2056 in FIG. 30 the SeNB, S-MeNB, and T-MeNB perform MeNB change processing on the SeNB in the same manner as in Step ST2026 in FIG.
- This is a process of notifying that the control plane (C-plane) of the SeNB, for example, a macro eNB (MeNB) that performs signaling has been changed.
- C-plane control plane
- MeNB macro eNB
- step ST2057 packet data communication may be performed between the UE and the T-MeNB.
- Step ST2058 packet data communication is performed between the UE and the SeNB.
- Step ST2059 packet data communication may be performed between the SeNB and the T-MeNB.
- Step ST2060 the T-MeNB may transmit packet data to the S-GW.
- step ST2671 the T-MeNB, MME, and S-GW make a path switch request for requesting to change the paths of the EPS bearer # 1 and the EPS bearer # 2 from the S-MeNB to the T-MeNB.
- step ST2061 the T-MeNB notifies the MME of a path switch request (Path Switch Request) message.
- Step ST2062 the MME that has been notified of the path switch request message notifies the S-GW of a change bearer request (Modify Bearer Request) message.
- step ST2063 the S-GW that has been notified of the bearer change request message changes the downlink path.
- the S-GW may give the end marker to the PDCP transmitted to the S-MeNB to notify the end of the transfer process.
- the S-MeNB may add an end marker and transfer it to the T-MeNB.
- packet data communication may be performed between the T-MeNB and the S-GW.
- step ST2067 the S-GW notifies the MME of a modify bearer response message (Modify Bearer Response).
- Step ST2068 the MME that has been notified of the bearer change response message notifies the T-MeNB of a path switch request acceptance response (Path Switch Request Ack) message indicating completion of path switching. In this way, the process of step ST2671 ends.
- Step ST2069 the T-MeNB notifies the S-MeNB of a UE context release (UE context release) message.
- Step ST2670 the S-MeNB notified of the UE context release message releases (releases) the resources allocated to the UE. After the resource release process in step ST2670, the MeNB change process for the SeNB in step ST2026 in FIG. 28 described above is performed.
- step ST2029 As described above, only the SeNB is set to perform data transmission / reception using the EPS bearer # 2 with the UE at the time of handover by the process of step ST2029 in FIG. How the process of step ST2029 is performed will be described with reference to FIG.
- FIG. 31 is a diagram illustrating an example of a state of data transmission / reception with the UE.
- the S-GW 601 includes a PDCP processing eNB switching unit 602.
- the S-MeNB 603 includes a first PDCP processing unit 604, an RLC processing unit 605, a MAC processing unit 606, a PHY processing unit 607, and a second PDCP processing unit 608.
- the SeNB 609 includes a PDCP processing unit 610, a PDCP path switching unit 611, an RLC processing unit 612, a MAC processing unit 613, and a PHY processing unit 614.
- the UE 615 Before handover switching, the UE 615 performs data transmission / reception with both the S-MeNB 603 and the SeNB 609 using the EPS bearer # 2. For example, in the case of downlink, data is provided from the S-GW 601 to the first PDCP processing unit 604 and the second PDCP processing unit 608 of the S-MeNB 603.
- First and second PDCP processing units (hereinafter sometimes collectively referred to as “PDCP processing units”) 604 and 608 perform PDCP processing in LTE or LTE-A.
- the data given to the second PDCP processing unit 608 is given to the PDCP path switching unit 611 of the SeNB 609.
- the PDCP path switching unit 611 switches the PDCP path.
- the PDCP path switching unit 611 determines that the PDCP from the second PDCP processing unit 608 is to be given to the RLC processing unit 612 because the handover is not in progress, and gives the data from the second PDCP processing unit 608 to the RLC processing unit 612.
- the RLC processing unit 612 performs RLC processing in LTE or LTE-A.
- the data given to the RLC processing unit 612 is then given to the MAC processing unit 613 and the PHY processing unit 614 in order, and then given to the UE 615 by wireless transmission.
- the MAC processing unit 613 performs MAC processing in LTE or LTE-A.
- the PHY processing unit 614 performs PHY processing in LTE or LTE-A.
- the SeNB 609 does not change the data transmission / reception as in the present embodiment, and only the MeNB handover is performed, the data using the EPS bearer # 2 is transmitted between the UE 615 and the S-MeNB 603 during the handover. Transmission / reception is not performed.
- the S-GW 601 switches the eNB that performs PDCP processing by the PDCP processing eNB switching unit 602.
- the PDCP processing eNB switching unit 602 transmits data using the EPS bearer # 2 to the PDCP processing unit 610 of the SeNB 609 instead of the second PDCP processing unit 608 of the S-MeNB 603.
- the PDCP processing unit 610 performs PDCP processing in LTE or LTE-A.
- the SeNB 609 that has received data from the S-GW 601 performs PDCP processing on the received data by the PDCP processing unit 610, and provides the processed data to the PDCP path switching unit 611.
- the SeNB 609 selects the PDCP data from the PDCP processing unit 610 of its own device instead of the PDCP data from the second PDCP processing unit 608 of the S-MeNB 603 by the PDCP path switching unit 611, and provides the PDCP data to the RLC processing unit 612.
- the PDCP data given to the RLC processing unit 612 is then given and processed in the order of the MAC processing unit 613 and the PHY processing unit 614, and finally transmitted to the UE 615 by wireless transmission.
- the processing flow is the same as in the case of downlink.
- the processing flow is the same as in the case of downlink.
- the process of performing data continuity only by the SeNB that is not handed over is performed. Can be realized.
- the process in the case where data transmission / reception using EPS bearer # 2 is performed in both SeNB and T-MeNB is performed as follows.
- the SeNB changes the connection from the S-MeNB to the T-MeNB.
- the T-MeNB changes the data transmission / reception path of the SeNB only to the data transmission / reception path of the SeNB and the T-MeNB.
- a method may be considered in which connection is performed using data transmission / reception paths of both SeNB and T-MeNB at the time of handover.
- the configuration of the radio resource (Configuration) is changed between (A) the setting of the split bearer configuration from the T-MeNB and (B) the case of changing the data transmission / reception path switching.
- a street is conceivable.
- SeNB identification information specifically, information related to the SeNB's destination address (address). This is because the PDCP-processed data is transmitted to the SeNB, and SeNB identification information is required at that time. Without the SeNB identification information, the T-MeNB does not know to which SeNB the data should be transmitted and from which SeNB the data should be received. Further, since the T-MeNB needs to know parameter information indicating which RRC connection parameter the SeNB is operating on, the information is also notified.
- A-2 Information that needs to be notified from the T-MeNB to the S-MeNB is information on whether the handover of the MeNB has succeeded or failed.
- information indicating an instruction to perform data transfer is also information that needs to be notified from the T-MeNB to the S-MeNB.
- (A-3) Information that needs to be notified to the UE is a notification indicating that the MeNB has been switched from the S-MeNB to the T-MeNB by the handover.
- the UE transmits / receives data to / from the T-MeNB instead of the S-MeNB.
- the SeNB transmits and receives data to and from the S-GW via the PDCP processing unit of either the S-MeNB or the T-MeNB. Therefore, the information that needs to be notified to the SeNB is information on which SeNB passes through the PDCP processing unit of the S-MeNB or T-MeNB.
- (B-1) Information that needs to be notified from the S-MeNB to the T-MeNB is the SeNB identification information. This is because if the S-MeNB does not know which SeNB was communicating at the same time before the handover, it does not know which SeNB may communicate at the same time after the handover. Further, since the T-MeNB needs to know parameter information indicating which RRC connection parameter the SeNB is operating on, the information is also notified. In this specific example (B-1), it is assumed that the SeNB only transmits and receives data, and the control information (signaling) is handled by the T-MeNB.
- Information that needs to be notified from the T-MeNB to the S-MeNB includes information on whether the MeNB handover has succeeded or failed, and the buffer of the S-MeNB, as in the specific example (A-2). This is a notification for instructing to perform data forwarding (Data Forwarding) when data is retained.
- (B-3) Information that needs to be notified to the UE is a notification indicating that the MeNB has been switched from the S-MeNB to the T-MeNB by handover, as in the specific example (A-3).
- the UE transmits / receives data to / from the T-MeNB instead of the S-MeNB.
- (B-4) Information that needs to be notified to the SeNB is information indicating that the MeNB has been switched from the S-MeNB to the T-MeNB due to the completion (success) of the handover. Since the SeNB is subordinate to the MeNB, it is necessary to know which MeNB out of the MeNB that is the subordinate is transmitting and receiving a control signal for its own device, for example, signaling, and to follow the control from the MeNB It is.
- the configuration of the radio resource is changed at three timings: (1) step ST2026, (2) step ST2056, and (3) step ST2043.
- the timings (1) to (3) will be specifically described below.
- the configuration of the radio resource is changed after the downlink path change timing in step ST2063. Therefore, since the MeNB is switched to the T-MeNB and the resources of the S-MeNB are released, it is possible to prevent erroneous processing with the resources before the handover. Further, the processing can be realized with simple processing, and the processing can be realized with a circuit having a relatively small scale.
- the processing is more complicated than the case where it is performed at the timing of (1), but the switching timing is earlier, so that the risk of data transmission / reception only by the SeNB, for example, multiple UEs to the SeNB Therefore, it is possible to avoid the concentration of accesses from becoming a congested state and to realize a stable operation.
- data can be transmitted / received only by transmission / reception of uplink data depending on the configuration of the radio resource.
- the transmission / reception of downlink data is after the T-MeNB receives data from the S-GW.
- FIG. 32 and 33 are diagrams showing an exemplary sequence of the MeNB HO process for EPS bearer # 1 in the communication system according to the sixth embodiment of the present invention. 32 and 33 are connected by a boundary line BL10.
- the S-MeNB performs reconfiguration, but in this embodiment, the T-MeNB performs reconfiguration.
- step ST2680 shown in FIGS. 32 and 33 is used in place of step ST2025 shown in FIGS. 29 and 30 in the sequence of the fifth embodiment shown in FIGS.
- the same processing as that of the fifth embodiment is performed except that the EPS bearer # 1 MeNB HO processing is performed.
- step ST2680 shown in FIG. 32 and FIG. 33 is similar to the EPS bearer # 1 MeNB HO process of step ST2025 shown in FIG. 29 and FIG. 30, and therefore the same step is denoted by the same step number.
- the common explanation is omitted.
- step ST2680 is the same as that in step ST2025 in the fifth embodiment shown in FIGS. 29 and 30 except that processing in step ST2681 and step ST2682 is performed in place of step ST2046 and step ST2047 in FIG. 5 is the same as the process in step ST2025.
- Step ST2681 the T-MeNB notifies the UE of downlink allocation (DL allocation) information.
- Step ST2682 the T-MeNB notifies the UE of an RRC connection reconfiguration (RRC Connection Reconfiguration) message.
- the RRC connection reconfiguration message does not include mobility control information.
- the S-MeNB notifies the UE of the RRC connection reconfiguration (RRC Connection Reconfiguration) message, but in this embodiment, the T-MeNB notifies the UE of the RRC connection reconfiguration ( RRC Connection Reconfiguration) message.
- the optimal RRC connection setting is performed not by the handover source S-MeNB but by the T-MeNB that is the handover destination that will perform the communication connection from now on, so that the communication between the UE and the MeNB is stabilized. Can do.
- FIG. 34 and 35 are diagrams showing an exemplary sequence of the MeNB HO process for EPS bearer # 1 in the communication system according to the seventh embodiment of the present invention. 34 and 35 are connected by a boundary line BL11.
- the EPS bearer # 1 in step ST2690 shown in FIGS. 34 and 35 is used in place of step ST2025 shown in FIGS. 29 and 30 in the sequence of the fifth embodiment shown in FIGS. A process similar to that of the fifth embodiment is performed except for performing the MeNB HO process.
- step ST2690 shown in FIGS. 34 and 35 is similar to the EPS bearer # 1 MeNB HO process of step ST2025 shown in FIGS. 29 and 30. Therefore, the same steps are denoted by the same step numbers. The common explanation is omitted.
- step ST2690 is the same as the process of step ST2025 of the fifth embodiment except that the process of step ST2691 is performed in addition to step ST2025 of the fifth embodiment shown in FIGS. 29 and 30.
- the T-MeNB before step ST2646 and step ST2647, in step ST2691, the T-MeNB notifies the S-MeNB of the RRC connection reconfiguration (RRC Connection Reconfiguration) message and downlink assignment (DL allocation) information. To do.
- RRC connection reconfiguration RRC Connection Reconfiguration
- DL allocation downlink assignment
- the UE does not notify the UE of the reconfiguration message notified from the T-MeNB, but notifies the UE of the content of the reconfiguration message notified from the T-MeNB. Will do.
- the optimal RRC connection setting is performed not by the S-MeNB that is the handover source but by the T-MeNB that is the handover destination that performs communication connection from now on, so that the UE and the MeNB Communication with can be stabilized.
- a set of serving cells configured by the SeNB may be referred to as SCG (secondary cell group), and a set of serving cells configured by the MeNB may be referred to as MCG (master cell group).
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Abstract
Description
図2は、3GPPにおいて議論されているLTE方式の通信システム700の全体的な構成を示すブロック図である。図2について説明する。無線アクセスネットワークは、E-UTRAN(Evolved Universal Terrestrial Radio Access Network)70と称される。通信端末装置である移動端末装置(以下「移動端末(User Equipment:UE)」という)71は、基地局装置(以下「基地局(E-UTRAN NodeB:eNB)」という)72と無線通信可能であり、無線通信で信号の送受信を行う。
図14は、本発明の実施の形態1の変形例1の通信システムにおけるハンドオーバ関連処理のシーケンスの一例を示す図である。図15は、図14のステップST1009のHO前処理のシーケンスの一例を示す図である。図16は、図14のステップST1010のHO後処理のシーケンスの一例を示す図である。本変形例のハンドオーバ関連処理は、前述の図10~図13に示す実施の形態1のハンドオーバ関連処理と類似するので、同一のステップについては同一のステップ番号を付して、説明を省略する。
図17~図19は、本発明の実施の形態2の通信システムにおけるハンドオーバ関連処理のシーケンスの一例を示す図である。図17と図18とは、境界線BL1で接続されている。図18と図19とは、境界線BL2で接続されている。本実施の形態のハンドオーバ関連処理は、前述の図10~図13に示す実施の形態1のハンドオーバ関連処理と類似するので、同一のステップについては同一のステップ番号を付して、説明を省略する。
(1)S-MeNBがSeNBに制御MeNBの変更を通知する。
(2)T-MeNBがSeNBに制御MeNBの変更を通知する。
(1)制御MeNBの変更を示す情報。
(2)変更後の制御MeNBの識別子。ここでは、T-MeNBの識別子。
(3)SeNBを用いたパスのベアラ識別子。ここでは、E-RAB識別子(E-RAB IDなどであってもよい)、あるいは、EPSベアラ識別子。
(4)ベアラを用いてデュアルコネクティビティを行うUEの識別子。
(5)前記(1)~(4)の組合せ。
図20~図22は、本発明の実施の形態3の通信システムにおけるハンドオーバ関連処理のシーケンスの一例を示す図である。図20と図21とは、境界線BL3で接続されている。図21と図22とは、境界線BL4で接続されている。本実施の形態のハンドオーバ関連処理は、前述の図10~図13に示す実施の形態1および図17~図19に示す実施の形態2のハンドオーバ関連処理と類似するので、同一のステップについては同一のステップ番号を付して、説明を省略する。
(1)S-MeNBがSeNBに制御MeNBの変更を通知する。
(2)T-MeNBがSeNBに制御MeNBの変更を通知する。
(1)制御MeNBの変更を示す情報。
(2)変更後の制御MeNBの識別子。ここでは、T-MeNBの識別子。
(3)SeNBを用いたパスのベアラ識別子。ここでは、E-RAB識別子(E-RAB IDなどであってもよい)、あるいは、EPSベアラ識別子。
(4)SeNBにおける制御MeNBを変更するスプリットベアラの識別子。
(5)ベアラスプリット構成の設定要求したMeNBの識別子。ここでは、S-MeNBの識別子。
(6)ベアラスプリットを用いてデュアルコネクティビティを行うUEの識別子。
(7)前記(1)~(6)の組合せ。
図23~図25は、本発明の実施の形態4の通信システムにおけるハンドオーバ関連処理のシーケンスの一例を示す図である。図23と図24とは、境界線BL5で接続されている。図24と図25とは、境界線BL6で接続されている。本実施の形態のハンドオーバ関連処理は、前述の図10~図13に示す実施の形態1、図17~図19に示す実施の形態2、および図20~図22に示す実施の形態3のハンドオーバ関連処理と類似するので、同一のステップについては同一のステップ番号を付して、説明を省略する。
図26~図28は、本発明の実施の形態5の通信システムにおけるハンドオーバ関連処理のシーケンスの一例を示す図である。図26と図27とは、境界線BL7で接続されている。図27と図28とは、境界線BL8で接続されている。
図32および図33は、本発明の実施の形態6の通信システムにおけるEPSベアラ#1用MeNB HO処理のシーケンスの一例を示す図である。図32と図33とは、境界線BL10で接続されている。
図34および図35は、本発明の実施の形態7の通信システムにおけるEPSベアラ#1用MeNB HO処理のシーケンスの一例を示す図である。図34と図35とは、境界線BL11で接続されている。
Claims (3)
- 移動端末装置と、前記移動端末装置と無線通信可能なセルを構成する基地局装置とを備える通信システムであって、
前記セルとして、前記移動端末装置と通信可能な範囲であるカバレッジが比較的大きい複数のマクロセルと、前記カバレッジが比較的小さいスモールセルとを備え、
前記移動端末装置は、
前記複数のマクロセルのうちの1つと前記スモールセルとに接続されるとき、
前記移動端末装置の移動に伴って、前記移動端末装置が接続されるマクロセルを移動元のマクロセルから移動先のマクロセルに切替えるハンドオーバ処理の前に、前記スモールセルとの接続を解消するハンドオーバ前処理を行い、
前記ハンドオーバ処理の後に、前記スモールセルとの接続を再度確立するハンドオーバ後処理を行うことを特徴とする通信システム。 - 移動端末装置と、前記移動端末装置と無線通信可能なセルを構成する基地局装置とを備える通信システムであって、
前記セルとして、前記移動端末装置と通信可能な範囲であるカバレッジが比較的大きい複数のマクロセルと、前記カバレッジが比較的小さいスモールセルとを備え、
前記移動端末装置が前記複数のマクロセルのうちの1つと前記スモールセルとに接続されるとき、
前記移動端末装置の移動に伴って、前記移動端末装置が接続されるマクロセルを移動元のマクロセルから移動先のマクロセルに切替えるハンドオーバ処理が起動されると、前記スモールセルに、前記スモールセルを制御する前記マクロセルが変更されることが通知されることを特徴とする通信システム。 - 前記マクロセルと前記移動端末装置との間、および前記スモールセルと前記移動端末装置との間では、ベアラスプリットされたベアラを用いて通信が行われることを特徴とする請求項1または2に記載の通信システム。
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US20240267813A1 (en) | 2024-08-08 |
JP2020162180A (ja) | 2020-10-01 |
JP6731844B2 (ja) | 2020-07-29 |
US10743227B2 (en) | 2020-08-11 |
US20200314715A1 (en) | 2020-10-01 |
JP2022106987A (ja) | 2022-07-20 |
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EP3122119A4 (en) | 2017-10-25 |
US20180176839A1 (en) | 2018-06-21 |
EP3474600A1 (en) | 2019-04-24 |
EP4266795A3 (en) | 2023-12-06 |
EP3122119A1 (en) | 2017-01-25 |
CN106134253B (zh) | 2019-11-29 |
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US20220353770A1 (en) | 2022-11-03 |
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