WO2010146834A1 - Mobile communication system - Google Patents

Abstract

In the provided mobile communication system, a base station uses a plurality of partial carriers individually, or uses an aggregate carrier that aggregates a plurality of partial carriers, to communicate wirelessly with a partial-carrier-compliant mobile terminal or an aggregate-carrier-compliant mobile terminal. In particular, when the base station uses an aggregate carrier to wirelessly communicate with an aggregate-carrier-compliant mobile terminal, the mobile terminal camps on one of the partial carriers included in the aggregate carrier. This allows communication speed to be increased via support of aggregate carriers, while at the same time allowing efficient camping on partial carriers included in aggregate carriers.

Description

Mobile communication system

The present invention relates to a mobile communication system that performs wireless communication between a plurality of mobile terminals and a base station.

Among the communication systems called third generation, the W-CDMA (Wideband Code Division Multiple Access) system has been commercialized in Japan since 2001. Also, by adding a packet transmission channel (HS-DSCH: High Speed-Downlink Shared Channel) to the downlink (individual data channel, individual control channel), data transmission using the downlink is further accelerated. Realized HSDPA (High Speed Down Link Link Packet Access) services have been started. Furthermore, in order to further increase the speed of data transmission in the uplink direction, a service has also been started for the HSUPA (High Speed Up Link Link Packet Access) system. W-CDMA is a communication system defined by 3GPP (3rd Generation Partnership Project), which is a standardization organization for mobile communication systems, and standardized release 8 editions are compiled.

In 3GPP, as a communication method different from W-CDMA, “Long Term Evolution” (Long Term Evolution LTE) is used for the radio section, and the entire system configuration including the core network (also simply referred to as network) is “System”. A new communication method called “Architecture Evolution (SAE)” is being studied. In LTE, the access scheme, radio channel configuration, and protocol are completely different from those of the current W-CDMA (HSDPA / HSUPA). For example, W-CDMA uses code division multiple access (Code Division Multiple Access), whereas LTE has OFDM (Orthogonal Frequency Division Multiplexing) in the downlink direction and SC-FDMA (Single in the uplink direction). Career Frequency Division Multiple Access). The bandwidth is selectable for each base station within 1.4 / 3/5/10/15/20 MHz in LTE, whereas W-CDMA is 5 MHz. Also, LTE does not include circuit switching as in W-CDMA, and only packet communication is used.

LTE is defined as an independent radio access network separate from the W-CDMA network because the communication system is configured using a new core network different from the W-CDMA core network (GPRS). Therefore, in order to distinguish from a W-CDMA communication system, in an LTE communication system, a base station (Base station) that communicates with a mobile terminal (UE: User Equipment) is an eNB (E-UTRAN NodeB), and a plurality of base stations A base station controller (Radio Network Controller) that exchanges control data and user data is referred to as EPC (Evolved Packet Core) (sometimes referred to as aGW: Access Gateway). In the LTE communication system, a unicast service and an E-MBMS service (Evolved Multimedia Broadcast Multicast Service) are provided. The E-MBMS service is a broadcast-type multimedia service and may be simply referred to as MBMS. Mass broadcast contents such as news, weather forecasts, and mobile broadcasts are transmitted to a plurality of mobile terminals. This is also called a point-to-multipoint service.

Non-Patent Document 1 describes the current decisions regarding the overall architecture of the LTE system in 3GPP. The overall architecture (Chapter 4 of Non-Patent Document 1) will be described with reference to FIG. FIG. 1 is an explanatory diagram illustrating a configuration of an LTE communication system. In FIG. 1, a control protocol (for example, RRC (Radio Resource Management)) and a user plane (for example, PDCP: Packet Data Convergence Protocol, RLC: Radio Link Control, MAC: Medium Access Control, PHY: Physical layer) for the mobile terminal 101 are based. If terminated at station 102, Evolved Universal Terrestrial Radio Access (E-UTRAN) is composed of one or more base stations 102.
The base station 102 performs scheduling (Scheduling) and transmission of a paging signal (also referred to as a paging message or paging message) notified from the MME 103 (Mobility Management Entity). Base stations 102 are connected to each other via an X2 interface. The base station 102 is connected to an EPC (Evolved Packet Core) via an S1 interface, more specifically, connected to an MME 103 (Mobility Management Entity) via an S1_MME interface, and connected to an S-GW 104 (Serving Gateway) via an S1_U interface. The The MME 103 distributes the paging signal to a plurality or a single base station 102. Further, the MME 103 performs mobility control (Mobility control) in an idle state. The MME 103 manages a tracking area list when the mobile terminal is in a standby state and an active state. The S-GW 104 transmits / receives user data to / from one or a plurality of base stations 102. The S-GW 104 becomes a local mobility anchor point at the time of handover between base stations. Further, there is a P-GW (PDN Gateway), which performs packet filtering and UE-ID address allocation for each user.

The control protocol RRC between the mobile terminal 101 and the base station 102 performs broadcast, paging, RRC connection management (RRC connection management), and the like.

There are RRC_Idle and RRC_CONNECTED as states of the base station and the mobile terminal in RRC.

In 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.

In RRC_CONNECTED, the UE has an RRC connection (connection), can transmit and receive data to and from the network, and performs handover (Handover, HO), neighbor cell measurement, and the like.

Non-Patent Document 1 (Chapter 5) describes the current decisions regarding the frame configuration in the LTE system in 3GPP. This will be described with reference to FIG. FIG. 2 is an explanatory diagram showing a configuration of a radio frame used in the LTE communication system. In FIG. 2, one radio frame (Radio frame) is 10 ms. The radio frame is divided into 10 equally sized sub-frames. 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). Channels other than MBSFN (Multimedia （Broadcast multicast service Single Frequency Network) and channels other than MBSFN are performed on a subframe basis. Hereinafter, a subframe for MBSFN transmission is referred to as an MBSFN subframe (MBSFN sub-frame). Non-Patent Document 2 describes a signaling example at the time of MBSFN subframe allocation. FIG. 3 is an explanatory diagram showing the configuration of the MBSFN frame. In FIG. 3, an MBSFN subframe is allocated for each MBSFN frame (MBSFN frame). A set of MBSFN frames (MBSFN frame Cluster) is scheduled. A repetition period (Repetition Period) of a set of MBSFN frames is assigned.

Non-Patent Document 1 describes the current decisions regarding the channel configuration in the LTE system in 3GPP. It is assumed that the same channel configuration as a non-CSG cell is used in a CSG (Closed 構成 Subscriber－Group cell) cell. A physical channel (Non-Patent Document 1, Chapter 5) will be described with reference to FIG. FIG. 4 is an explanatory diagram illustrating physical channels used in the LTE communication system. In FIG. 4, a physical broadcast channel 401 (PhysicalPhysBroadcast channel: PBCH) is a downlink channel transmitted from the base station 102 to the mobile terminal 101. The BCH transport block (transport block) is mapped to four subframes in a 40 ms interval. There is no obvious signaling of 40ms timing. A physical control channel format indicator channel 402 (Physical Control indicator channel: PCFICH) is transmitted from the base station 102 to the mobile terminal 101. PCFICH notifies base station 102 to mobile terminal 101 about the number of OFDM symbols used for PDCCHs. PCFICH is transmitted for each subframe. A physical downlink control channel 403 (Physical downlink control channel: PDCCH) is a downlink channel transmitted from the base station 102 to the mobile terminal 101. PDCCH includes resource allocation, HARQ information regarding DL-SCH (downlink shared channel which is one of the transport channels shown in FIG. 5), and PCH (paging which is one of the transport channels shown in FIG. 5). Channel). The PDCCH carries an uplink scheduling grant (Uplink Scheduling Grant). The PDCCH carries ACK / Nack that is a response signal for uplink transmission. PDCCH is also called an L1 / L2 control signal. A physical downlink shared channel 404 (Physical downlink shared channel: PDSCH) is a downlink channel transmitted from the base station 102 to the mobile terminal 101. PDSCH is mapped with DL-SCH (downlink shared channel) which is a transport channel and PCH which is a transport channel. A physical multicast channel 405 (Physical multicast channel: PMCH) is a downlink channel transmitted from the base station 102 to the mobile terminal 101. PMCH is mapped with MCH (multicast channel) which is a transport channel.

A physical uplink control channel 406 (Physical Uplink control channel: PUCCH) is an uplink channel transmitted from the mobile terminal 101 to the base station 102. The PUCCH carries ACK / Nack which is a response signal (response) to 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 (Scheduling Request: SR). A physical uplink shared channel 407 (Physical Uplink shared channel: PUSCH) is an uplink channel transmitted from the mobile terminal 101 to the base station 102. PUSCH is mapped with UL-SCH (uplink shared channel which is one of the transport channels shown in FIG. 5). A physical HARQ indicator channel 408 (Physical Hybrid ARQ indicator: PHICH) is a downlink channel transmitted from the base station 102 to the mobile terminal 101. The PHICH carries ACK / Nack that is a response to uplink transmission. A physical random access channel 409 (Physical random access channel: PRACH) is an uplink channel transmitted from the mobile terminal 101 to the base station 102. The PRACH carries a random access preamble.

As a downlink reference signal (Reference signal), a symbol known as a mobile communication system is inserted into the first, third and last OFDM symbols of each slot. As a measurement of the physical layer of the mobile terminal, there is a reference symbol received power (RSRP).

The transport channel will be described with reference to FIG. 5 (Chapter 5 of Non-Patent Document 1). FIG. 5 is an explanatory diagram for explaining a transport channel used in an LTE communication system. FIG. 5A shows mapping between the downlink transport channel and the downlink physical channel. FIG. 5B shows mapping between the uplink transport channel and the uplink physical channel. As for the downlink transport channel, a broadcast channel (Broadcast channel: BCH) is broadcast to the entire base station (cell). BCH is mapped to the physical broadcast channel (PBCH). Retransmission control by HARQ (Hybrid ARQ) is applied to the downlink shared channel (Downlink Shared channel: DL-SCH). Broadcasting to the entire base station (cell) is possible. Supports dynamic or semi-static resource allocation. Quasi-static resource allocation is also called Persistent Scheduling. In order to reduce the power consumption of the mobile terminal, DRX (Discontinuous reception) of the mobile terminal is supported. The DL-SCH is mapped to the physical downlink shared channel (PDSCH). A paging channel (Paging channel: PCH) supports DRX of the mobile terminal in order to enable low power consumption of the mobile terminal. Notification to the entire base station (cell) is required. It is mapped to a physical resource such as a physical downlink shared channel (PDSCH) that can be dynamically used for traffic, or a physical resource such as a physical downlink control channel (PDCCH) of another control channel. A multicast channel (Multicast channel: MCH) is used for broadcasting to the entire base station (cell). Supports SFN combining of MBMS services (MTCH and MCCH) in multi-cell transmission. Supports quasi-static resource allocation. MCH is mapped to PMCH.

Retransmission control by HARQ (Hybrid ARQ) is applied to the uplink shared channel (Uplink Shared channel: UL-SCH). Supports dynamic or semi-static resource allocation. The UL-SCH is mapped to the physical uplink shared channel (PUSCH). The random access channel (Random access channel: RACH) shown in FIG. 5B is limited to control information. There is a risk of collision. The RACH is mapped to a physical random access channel (PRACH). HARQ will be described.

HARQ is a technology for improving the communication quality of a transmission path by combining automatic retransmission (Automatic Repeat request) and error correction (Forward Error Correction). There is also an advantage that error correction functions effectively by retransmission even for a transmission path in which communication quality changes. In particular, further quality improvement can be obtained by combining the reception result of the initial transmission and the reception result of the retransmission upon retransmission. An example of the retransmission method will be described. If the reception data cannot be decoded correctly on the reception side (CRC Cyclic Redundancy Check error has occurred (CRC = NG)), "Nack" is transmitted from the reception side to the transmission side. The transmission side that has received “Nack” retransmits the data. When the reception data can be correctly decoded on the reception side (when no CRC error occurs (CRC = OK)), “Ack” is transmitted from the reception side to the transmission side. The transmitting side that has received “Ack” transmits the next data. An example of the HARQ system is “Chase Combining”. Chase combining is a method in which the same data sequence is transmitted for initial transmission and retransmission, and the gain is improved by combining the initial transmission data sequence and the retransmission data sequence in retransmission. The idea is that even if there is an error in the initial transmission data, it is partially accurate, and it is possible to transmit data with higher accuracy by combining the initial transmission data and the retransmission data of the correct part. Based on. Another example of the HARQ scheme is IR (Incremental Redundancy). IR is to increase redundancy. By transmitting parity bits in retransmission, the redundancy is increased in combination with the initial transmission, and the quality is improved by the error correction function.

A logical channel (Chapter 6 of Non-Patent Document 1) will be described with reference to FIG. FIG. 6 is an explanatory diagram illustrating logical channels used in the LTE communication system. FIG. 6A shows mapping between the downlink logical channel and the downlink transport channel. FIG. 6B shows mapping between the uplink logical channel and the uplink transport channel. The broadcast control channel (Broadcast control channel: CHBCCH) is a downlink channel for broadcast system control information. The BCCH that is a logical channel is mapped to a broadcast channel (BCH) that is a transport channel or a downlink shared channel (DL-SCH). A paging control channel (Paging control channel: PCCH) is a downlink channel for transmitting a paging signal. 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. The shared control channel (Common control channel: CCCC) 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. In the downlink method, the CCCH is mapped to a downlink shared channel (DL-SCH) that is a transport channel. In the uplink direction, the CCCH is mapped to an uplink shared channel (UL-SCH) that is a transport channel.

The multicast control channel (Multicast control channel: MCCH) is a downlink channel for one-to-many transmission. This is a channel used for transmission of MBMS control information for one or several MTCHs from the network to the mobile terminal. MCCH is a channel used only for a mobile terminal receiving MBMS. MCCH is mapped to a downlink shared channel (DL-SCH) or multicast channel (MCH) which is a transport channel. The dedicated control channel (Dedicated control channel: DCCH) is a channel that transmits dedicated control information between the mobile terminal and the network. 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 (Dedicate Traffic channel: DTCH) is a channel for one-to-one communication to an individual mobile terminal 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. A multicast traffic channel (Multicast Traffic channel: MTCH) is a downlink channel for transmitting traffic data from a network to a mobile terminal. MTCH is a channel used only for a mobile terminal that is receiving MBMS. The MTCH is mapped to the downlink shared channel (DL-SCH) or multicast channel (MCH).

GCI is a global cell identity. A CSG cell (Closed Subscriber Group cell) is introduced in LTE and UMTS (Universal Mobile Telecommunication System). CSG will be described below (Chapter 3.1 of Non-Patent Document 4). A CSG (Closed Subscriber Group) is a cell in which an operator identifies an available subscriber (a cell for a specific subscriber). The identified subscriber is allowed to access one or more E-UTRAN cells of the Public Land Mobile Network (PLMN). One or more E-UTRAN cells to which the identified subscribers are allowed access are referred to as “CSG cell (s)”. However, PLMN has access restrictions. A CSG cell is a part of a PLMN that broadcasts a unique CSG identity (CSG identity: CSG ID, CSG-ID). Members of the subscriber group who have been registered for use in advance and access the CSG cell using the CSG-ID as access permission information.
The CSG-ID is broadcast by the CSG cell or the cell. There are a plurality of CSG-IDs in a mobile communication system. The CSG-ID is then used by the mobile terminal (UE) to facilitate access of CSG related members. It has been discussed at the 3GPP meeting that the CSG cell or information broadcast by the cell is set to a tracking area code (TAC) instead of a CSG-ID. The location tracking of a mobile terminal is performed in units of areas composed of one or more cells. The position tracking is to enable tracking of the position of the mobile terminal and calling (the mobile terminal receives a call) even in the standby state. This area for tracking the location of the mobile terminal is called a tracking area. The CSG white list is a list stored in a USIM (Universal Subscriber Identity Module) in which all CSG IDs of CSG cells to which a subscriber belongs are recorded. The white list in the mobile terminal is given by the upper layer. Thereby, the base station of the CSG cell allocates radio resources to the mobile terminal.

“Suitable cell” will be described below (Non-Patent Document 4, Chapter 4.3). A “suitable cell” is a cell that the UE camps on to receive normal service. Such a cell was provided by (1) the selected PLMN or registered PLMN, or part of a PLMN in the “Equivalent PLMN list”, (2) NAS (non-access stratum) The latest information must satisfy the following conditions: (a) The cell is not a barred cell. (B) The cell is not part of the “Prohibited LAs for roaming” list, but part of at least one tracking area (Tracking Area: TA). In that case, the cell needs to satisfy the above (1), (c) the cell satisfies the cell selection evaluation criteria, (d) the cell is a system information (System Information: SI) as a CSG cell. ), The CSG-ID is part of the UE's “CSG White List” (CSG White List) (included in the UE's CSG White List).

An “acceptable cell” will be described below (Chapter 4.3 of Non-Patent Document 4). This is a cell where a UE camps on in order to receive a limited service (emergency call). Such a cell shall meet all the following requirements: That is, the minimum set of requirements for initiating an emergency call in an E-UTRAN network is shown below. (1) The cell is not a barred cell. (2) The cell satisfies the cell selection evaluation criteria.
Camping on a cell is a state in which the UE has completed cell selection / reselection processing and the UE has selected a cell for monitoring system information and paging information.

In 3GPP, base stations called Home-NodeB (Home-NB, HNB) and Home-eNodeB (Home-eNB, HeNB) are being studied. HNB / HeNB is a base station for UTRAN / E-UTRAN, for example, home, corporate, and commercial access services. Non-Patent Document 6 discloses three different modes of access to HeNB and HNB. An open access mode (Open access mode), a closed access mode (Closed access mode), and a hybrid access mode (Hybrid access mode). Each mode has the following characteristics. In the open access mode, the HeNB or HNB is operated as a normal cell of a normal operator. In the closed access mode, the HeNB or HNB is operated as a CSG cell. This is a CSG cell accessible only to CSG members. In the hybrid access mode, a non-CSG member is a CSG cell to which access is permitted at the same time. In other words, the cell in the hybrid access mode is a cell that supports both the open access mode and the closed access mode.

The Long Term Evolution Advanced (LTE-A) system is considered to support a frequency bandwidth that is larger than the frequency bandwidth of the LTE system. This is to improve the communication speed. In the current 3GPP, it is discussed that the frequency bandwidth of the LTE-A system is 100 MHz or less.

The frequency usage situation in each region varies. Therefore, there may be a region where the frequency bandwidth cannot be continuously secured at 100 MHz. Also, compatible operation of LTE-compatible mobile terminals is considered in the LTE-A system. Accordingly, in the current 3GPP, it is considered to divide the frequency band (carrier) into units called component carriers (partial carriers). In the current 3GPP, LTE-compatible mobile terminals are operable on this component carrier. Further, it is considered that the communication speed improvement as the LTE-A system is realized by using an aggregate carrier created by aggregating (collecting) component carriers. Hereinafter, the component carrier may be abbreviated as CC and the carrier aggregation may be abbreviated as CA.

An object of the present invention is to provide a mobile communication system that can efficiently camp on a partial carrier included in an aggregate carrier while realizing an improvement in communication speed corresponding to the aggregate carrier.

The present invention relates to a mobile terminal corresponding to the partial carrier or a mobile terminal and a base station corresponding to the aggregate carrier using a plurality of partial carriers individually or using an aggregate carrier obtained by collecting the plurality of partial carriers. Is a mobile communication system for wireless communication,
The mobile terminal camps on any one of the partial carriers included in the aggregate carrier when the mobile terminal and the base station corresponding to the aggregate carrier perform radio communication using the aggregate carrier. A mobile communication system.

According to the present invention, when a mobile terminal corresponding to an aggregate carrier and a base station perform radio communication using the aggregate carrier, the mobile terminal camps on any one partial carrier included in the aggregate carrier. It is possible to efficiently camp on the partial carriers included in the aggregate carrier while realizing the communication speed improvement corresponding to the aggregate carrier.

It is explanatory drawing which shows the structure of the communication system of a LTE system. It is explanatory drawing which shows the structure of the communication system of a LTE system. FIG. 2 is an explanatory diagram showing a configuration of a radio frame used in an LTE communication system. It is explanatory drawing which shows the structure of a MBSFN frame. It is explanatory drawing explaining the physical channel used with the communication system of a LTE system. It is explanatory drawing explaining the transport channel used with the communication system of a LTE system. It is explanatory drawing explaining the logical channel used with the communication system of a LTE system. It is a block diagram which shows the whole structure of the mobile communication system currently discussed by 3GPP. It is a block diagram which shows the structure of the mobile terminal 311 which concerns on this invention. It is a block diagram which shows the structure of the base station 312 which concerns on this invention. It is a block diagram which shows the structure of MME which concerns on this invention. It is a block diagram which shows the structure of HeNBGW which concerns on this invention. 3 is a flowchart illustrating an outline of cell search performed by a mobile terminal in an LTE communication system. It is a conceptual diagram about the RRC_IDLE state and RRC_CONNECTED state when the base station is CA-compliant. It is a conceptual diagram in the case of camping on any one CC of CC which can transmit / receive data. It is a conceptual diagram in the case of camping on any one CC among CCs belonging to the same frequency band. It is a conceptual diagram in the case of camping on any one CC among CC which can camp on at the time of RRC_IDLE. It is a sequence diagram of RA procedure. It is explanatory drawing explaining the downlink CC / uplink CC asymmetric operation at the time of CA. It is a sequence diagram at the time of state transition between RRC_IDLE and RRC_CONNECTED. It is a sequence diagram in case a base station notifies UE which is going to camp on and / or CC. It is a conceptual diagram in the case of camping on any one CC of CC except the CC of RA procedure failure. It is a conceptual diagram of CC which camps on at the time of RA procedure failure in downlink CC / uplink CC asymmetric operation. It is a flowchart of CC search in one cell. It is a flowchart about the determination method of the cell and CC which try camp on based on this invention. It is a sequence diagram at the time of RA procedure failure. It is a flowchart about the determination method of the cell and CC which try camp on based on this invention.

Embodiment 1 FIG.
FIG. 7 is a block diagram showing the overall configuration of an LTE mobile communication system currently under discussion in 3GPP. Currently, in 3GPP, CSG (Closed Subscriber Group) cells (e-UTRAN Home-eNodeB (Home-eNB, HeNB), UTRAN Home-NB (HNB)) and non-CSG cells (e-UTRAN eNodeB (eNB) ), UTRAN NodeB (NB), GERAN BSS) and other systems are being studied. For e-UTRAN, configurations such as (a) and (b) in FIG. It has been proposed (Non-Patent Document 1, Non-Patent Document 3). FIG. 7A will be described. A mobile terminal (UE) 71 performs transmission / reception with the base station 72. The base station 72 is classified into an eNB (non-CSG cell) 72-1 and a Home-eNB (CSG cell) 72-2.
The eNB 72-1 is connected to the MME 73 via the interface S1, and control information is communicated between the eNB and the MME. A plurality of MMEs are connected to one eNB. The Home-eNB 72-2 is connected to the MME 73 via the interface S1, and control information is communicated between the Home-eNB and the MME. A plurality of Home-eNBs are connected to one MME.

Next, FIG. 7B will be described. A mobile terminal (UE) 71 performs transmission / reception with the base station 72. The base station 72 is classified into an eNB (non-CSG cell) 72-1 and a Home-eNB (CSG cell) 72-2. As in FIG. 7A, the eNB 72-1 is connected to the MME 73 via the interface S1, and control information is communicated between the eNB and the MME. A plurality of MMEs are connected to one eNB. On the other hand, the Home-eNB 72-2 is connected to the MME 73 via a HeNBGW (Home-eNB Gateway) 74. Home-eNB and HeGW are connected by an interface S1, and HeNBGW 74 and MME 73 are connected through an interface S1_flex. One or a plurality of Home-eNBs 72-2 are connected to one HeNBGW 74, and information is communicated through S1. The HeNBGW 74 is connected to one or a plurality of MMEs 73, and information is communicated through S1_flex.

By connecting one HeNBGW 74 to a Home-eNB belonging to the same CSG-ID using the configuration of FIG. 7B, a plurality of information belonging to the same CSG-ID, such as registration information, can be obtained from the MME 73. When transmitting to the Home-eNB 72-2, it is transmitted to the HeNBGW 74 once, and then transmitted to the plurality of Home-eNBs 7-2, thereby signaling efficiency more directly than the plurality of Home-eNBs 72-2 respectively. Can be enhanced. On the other hand, when each Home-eNB 72-2 communicates individual information with the MME 73, the Home-eNB 72-2 passes through the HeNBGW 74 but only passes (transmits) the information without processing. And MME 73 can communicate with each other as if they were directly connected.

FIG. 8 is a block diagram showing a configuration of a mobile terminal (terminal 71 in FIG. 7) according to the present invention. Transmission processing of the mobile terminal shown in FIG. 8 will be described. First, 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. There may exist data that is directly output from the transmission data buffer unit 803 to the modulation unit 805 without being encoded. The data encoded by the encoder unit 804 is subjected to modulation processing 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. Thereafter, a transmission signal is transmitted from the antenna 807 to the base station 312. In addition, the reception process of the mobile terminal 311 is executed as follows. A radio signal from the base station 312 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 transferred to the decoder unit 809 and subjected to decoding processing such as error correction. Of the decoded data, 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 is controlled by the control unit 810. Therefore, the control unit 810 is connected to each unit (801 to 809), which is omitted in the drawing.

FIG. 9 is a block diagram showing the configuration of the base station (base station 72 in FIG. 7) according to the present invention. A transmission process of the base station shown in FIG. 9 will be described. The EPC communication unit 901 transmits and receives data between the base station 72 and EPC (MME73, HeNBGW74, etc.). 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. 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 being encoded. 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. Further, the reception process of the base station 72 is executed as follows. Radio signals from one or a plurality of mobile terminals 311 are received by the antenna 908. The received 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 decoding processing such as error correction is performed. 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, the control unit 911 is connected to each unit (901 to 910), which is omitted in the drawing.

FIG. 10 is a block diagram showing a configuration of MME (Mobility Management Entity) according to the present invention. The PDN GW communication unit 1001 transmits and receives data between the MME 73 and the PDN GW. The base station communication unit 1002 transmits and receives data between the MME 73 and the base station 72 using the S1 interface. When 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 processing unit 1003 and transmitted to one or a plurality of base stations 72. The When the data received from the base station 72 is user data, the user data is transferred from the base station communication unit 1002 to the PDN GW communication unit 1001 via the user plane processing unit 1003 and transmitted to the PDN GW.

When the data received from the PDN GW is control data, the control data is passed from the PDN GW communication unit 1001 to the control plane control unit 1005. When the data received from the base station 72 is control data, the 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 73 and the HeNBGW 74 depending on 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 manages the bearer of SAE (System Architecture Evolution). The idle state mobility management unit 1005-3 performs mobility management in a standby state (LTE-IDLE state, also simply referred to as idle), generation and control of a paging signal in the standby state, and one or more mobile terminals 71 being served thereby Tracking area (TA) addition, deletion, update, search, tracking area list (TA List) management and so on. The MME initiates the paging protocol by transmitting a paging message to a cell belonging to a tracking area (tracking area: tracking TA) 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 72-2 connected to the MME. In the management of CSG-ID, the relationship between the mobile terminal corresponding to the CSG-ID and the CSG cell is managed (added, deleted, updated, searched). For example, it may be a relationship between one or a plurality of mobile terminals registered for user access with a certain CSG-ID and a CSG cell belonging to the CSG-ID. In white list management, the relationship between a mobile terminal and a CSG-ID is managed (added, deleted, updated, searched). For example, one or a plurality of CSG-IDs registered by a certain mobile terminal as a user may be stored in the white list. Although these CSG-related management may be performed in other parts of the MME 73, tracking by the idle state mobility management unit 1005-3 instead of the CSG-ID currently being discussed at the 3GPP meeting A method using an area code (Tracking Area Code) can be performed efficiently. A series of processing of the MME 313 is controlled by the control unit 1006. Therefore, although not shown in the drawing, the control unit 1006 is connected to each unit (1001 to 1005).

FIG. 11 is a block diagram showing a configuration of the HeNBGW according to the present invention. The EPC communication unit 1101 transmits and receives data between the HeNBGW 74 and the MME 73 using the S1_flex interface. The base station communication unit 1102 transmits and receives data between the HeNBGW 74 and the Home-eNB 72-2 using the S1 interface. The location processing unit 1103 performs processing for transmitting registration information and the like to a plurality of Home-eNBs among data from the MME 73 passed via the EPC communication unit 1101. The data processed by the location processing unit 1103 is passed to the base station communication unit 1102 and transmitted to one or more Home-eNBs 72-2 via the S1 interface. Data that does not require processing in the location processing unit 1103 and is simply passed (transmitted) is passed from the EPC communication unit 1101 to the base station communication unit 1102 and sent to one or more Home-eNBs 72-2 via the S1 interface. Sent. A series of processing of the HeNBGW 74 is controlled by the control unit 1104. Therefore, although not shown in the drawing, the control unit 1104 is connected to each unit (1101 to 1103).

Next, an example of a general cell search method in a mobile communication system is shown. FIG. 12 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. When cell search is started in the mobile terminal, slot timing and frame timing using the first synchronization signal (P-SS) and the second synchronization signal (S-SS) transmitted from the neighboring base stations in step ST1201. Synchronize. In combination with P-SS and S-SS, a synchronization code (SS) is assigned a synchronization code corresponding to a PCI (Physical Cell Identity) allocated for each cell. Currently, 504 PCIs are being studied, and the 504 PCIs are used for synchronization, and the PCI of the synchronized cell is detected (specified). Next, for a synchronized cell, in step ST1202, a reference signal RS (Reference （Signal) transmitted from the base station for each cell is detected, and the received power is measured. The reference signal RS uses a code corresponding to PCI one-to-one, and can be separated from other cells by correlating with the code. By deriving the RS code of the cell from the PCI specified in ST1201, it becomes possible to detect the RS and measure the RS received power. Next, in ST1203, a cell having the best RS reception quality (for example, a cell having the highest RS reception power, that is, the best cell) is selected from one or more cells detected up to ST1202. Next, in ST 1204, PBCH of the best cell is received, and BCCH which is broadcast information is obtained. MIB (Master Information Block) including cell configuration information is carried on BCCH on PBCH. 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.

Next, at 1205, the DL-SCH of the cell is received based on the MIB cell configuration information, and SIB (System Information Block) 1 in the broadcast information BCCH is obtained. SIB1 includes information about access to the cell, information about cell selection, and scheduling information of other SIBs (SIBk; integer of k ≧ 2). SIB1 includes TAC (Tracking Area Code). Next, in ST1206, the mobile terminal compares the TAC received in ST1205 with the TAC already held by the mobile terminal. If the result of the comparison is the same, a standby operation is started in the cell. If they are different from each other, the mobile terminal requests a change of TA to perform TAU (TrackingTrackArea Update) to the core network (Core Network, EPC) (including MME) through the cell. The core network updates the TA based on the identification number (UE-ID or the like) of the mobile terminal sent from the mobile terminal together with the TAU request signal. After updating the TA, the core network transmits a TAU acceptance signal to the mobile terminal. The mobile terminal rewrites (updates) the TAC (or TAC list) held by the mobile terminal with the TAC of the cell. Thereafter, the mobile terminal enters a standby operation in the cell.

In LTE and UMTS (Universal Mobile Telecommunication System), introduction of CSG (Closed Subscriber Group) cells is being studied. As described above, access is permitted only to one or a plurality of mobile terminals registered in the CSG cell. One or a plurality of mobile terminals registered with the CSG cell constitute one CSG. A CSG configured in this way is given a unique identification number called CSG-ID. A single CSG may have a plurality of CSG cells. If a mobile terminal registers in one of the CSG cells, it can access other CSG cells to which the CSG cell belongs. In addition, Home-eNB in LTE and Home-NB in UMTS may be used as a CSG cell. The mobile terminal registered in the CSG cell has a white list. Specifically, the white list is stored in the SIM / USIM. The white list carries CSG information of the CSG cell registered by the mobile terminal. Specifically, CSG-ID, TAI (Tracking Area Identity), TAC, etc. can be considered as the CSG information. If CSG-ID and TAC are associated with each other, either one is sufficient. Further, GCI may be used as long as CSG-ID and TAC are associated with GCI (Global Cell Identity). From the above, a mobile terminal that does not have a white list (including a case where the white list is empty in the present invention) cannot access a CSG cell, and only accesses a non-CSG cell. Can not. On the other hand, a mobile terminal having a white list can access both a CSG cell of a registered CSG-ID and a non-CSG cell.

3GPP discusses dividing all PCI (Physical Cell Identity) into CSG cells and non-CSG cells (referred to as PCI split) (Non-patent Document 5). Further, it is discussed that the PCI split information is reported from the base station to the mobile terminals being served by the system information. A basic operation of a mobile terminal using PCI split is disclosed. A mobile terminal that does not have PCI split information needs to perform a cell search using all PCIs (for example, using all 504 codes). On the other hand, a mobile terminal having PCI split information can perform a cell search using the PCI split information.

As disclosed in Non-Patent Document 7 and Non-Patent Document 8, 3GPP is proceeding with the formulation of “Long Term Evolution Advanced” (LTE-A) as Release 10.

It is considered that the LTE-A system supports a frequency bandwidth larger than the frequency bandwidth (transmission bandwidth) of the LTE system.

Therefore, it is considered that LTE-A compatible mobile terminals receive one or more component carriers (CC) simultaneously.

It is considered that a mobile terminal supporting LTE-A has the capability to perform carrier aggregation on reception and transmission on a plurality of component carriers, or only reception or only transmission.

If the component carrier structure conforms to the current 3GPP (Release 8) specification, an LTE-compatible mobile terminal can receive and transmit only on a single component carrier.
An LTE compatible mobile terminal can also be referred to as a 3GPP Release 8 compatible mobile terminal. That is, it is considered that LTE-compatible mobile terminals can operate on the LTE-A system and can be compatible.

Non-Patent Document 8 describes a system information notification method in the LTE-A system. Further, a single carrier anchor (Multi carrier anchor) and a multicarrier anchor (Multi carrier anchor) in a base station supporting carrier aggregation are disclosed.

In the single carrier anchor, reception and transmission of LTE-compatible mobile terminals are possible. In the single carrier anchor, information indicating the carrier of the multicarrier anchor is notified. In the single carrier anchor, the current 3GPP (Release 8) system information (System information: SI) is reported.

On the other hand, even in a multicarrier anchor, reception and transmission of an LTE compatible mobile terminal is possible. Also in the multi-carrier anchor, the current 3GPP (Release 8) system information (System information: SI) is broadcast. In the multi-carrier anchor, multi-carrier system information is broadcast.

In Non-Patent Document 10, one or a plurality of components capable of transmitting / receiving data to / from a UE in an RRC connection state (RRC_CONNECTED state, also simply referred to as RRC_CONNECTED) in a carrier aggregation compatible base station (may be a cell) It has been proposed that the carrier set be a candy date component carrier set (Candidate Component Carrier Set).

It has also been proposed to use one or more component carriers on which actual data transmission / reception is performed as a scheduling component carrier.
Systems such as UTRA, LTE, and LTE-A are designed to operate in a frequency band composed of several continuous frequencies, both upstream and downstream. Each of these frequency bands is hereinafter referred to as a frequency band.

In UTRA, LTE, and LTE-A FDD systems, one upstream frequency band and a different downstream frequency band operate in pairs. Hereinafter, the upstream frequency band and the downstream frequency band are referred to as a paired band.

Also, in the LTE-A FDD system, one uplink CC and one different downlink CC operate in a pair in a carrier aggregation compatible base station. Similarly, the uplink CC and the downlink CC are hereinafter referred to as a paired band.

In the LTE-A FDD system, it is considered that one upstream frequency band and a plurality of different downstream frequency bands operate in pairs. That is, a plurality of downstream frequency bands are paired with respect to one upstream frequency band. In addition, in a base station supporting carrier aggregation, it is considered that a plurality of downlink CCs operate in pairs with respect to one uplink CC. That is, a plurality of downlink CCs become a pair band for one uplink CC. These operations are referred to as asymmetric operations.

When the UE ends data transmission / reception with the network through the base station (cell), the UE and the base station (cell) shift from the RRC_CONNECTED state (connection state) to the RRC_IDLE state (standby state). Thus, when the UE moves out of the RRC_CONNECTED state and moves to the RRC_IDLE state, conventionally, the UE attempts to camp on the last cell that was in the RRC_CONNECTED state.

However, when the base station (cell) is a carrier aggregation-compatible base station (cell) and the UE is transmitting and receiving data using one or more CCs in the RRC_CONNECTED state, the RRC_CONNECTED state is not used. When shifting to the RRC_IDLE state, it is unclear which component carrier of which base station (cell) should try camp-on by applying the conventional method.

FIG. 13 shows a conceptual diagram of the RRC_IDLE state and the RRC_CONNECTED state when the base station (cell) is a base station (cell) that supports carrier aggregation. (A) is an RRC_IDLE state, and (b) is an RRC_CONNECTED state. Reference numerals 1301 to 1303 denote cells, and a cell 1303 corresponds to carrier aggregation. Reference numerals 1304 to 1310 denote CCs on which the cell 1303 performs carrier aggregation, which are CC # 1 to CC # 7 in order. The horizontal axis indicates the frequency. In FDD, the DL frequency and the UL frequency are different, but for simplicity, the DL frequency and the UL frequency are described on the same axis. Similarly, for simplification, the number of the downlink component carrier (downlink CC, DL 、 CC) and the number of the uplink component carrier (uplink CC, UL CC) corresponding to each DL CC are the same, Both are shown as CC # n (n is a positive integer). Not limited to this, the numbers may be different between the downlink CC and the corresponding uplink CC, and the numbers may be the same or the arrangement order on the frequency axis may be different.

In the present specification, unless otherwise specified, the downlink CC and the corresponding uplink CC (which is a pair band) are collectively referred to as CC. In addition, although the UE camps on the downlink CC, for simplicity, it is described here that the camp is on the CC. It means to camp on the downlink CC of the CC.

1311 is a UE. The UE that has selected the cell 1303 after cell selection / reselection is camping on CC # 3 (1306) in the RRC_IDLE state, for example. The UE that has performed RRC connection with the base station (cell) enters the RRC_CONNECTED state, and transmits and receives data to and from the core network. At this time, since the base station (cell) is a base station (cell) that supports carrier aggregation, the UE transmits and receives data to and from the core network via the base station (cell) on one or a plurality of CCs.

One or a plurality of CCs that transmit and receive data may be dynamically changed according to the communication quality (for example, CQI, RSRP, etc.) of each CC. This is because by performing data transmission / reception with a CC having good communication quality, throughput can be improved and high-speed communication becomes possible.

In FIG. 13B, data is transmitted and received on CC # 2 (1305), CC # 4 (1307), and CC # 6 (1309). In this way, it is conceivable that the CC (CC # 3) that was camping on at the time of RRC_IDLE before entering RRC_CONNECTED may differ from the CC that performs data transmission / reception at the time of RRC_CONNECTED.

When the UE transmits / receives data to / from one or a plurality of CCs in the RRC_CONNECTED state as described above with the base station (cell) corresponding to the aggregation, the UE may move away from the RRC_CONNECTED state and shift to RRC_IDLE.

When moving from RRC_CONNECTED state to RRC_IDLE, the aggregation-capable base station (cell) supports multiple CCs, so the UE attempts to camp on the same base station (cell) as before Even in this case, the base station (cell) can be specified, but it becomes unclear which CC of the base station (cell) should camp on.

In such a situation, as a method of camping on any CC of the base station (cell), a method of searching all CCs in the base station (cell), selecting the best CC, and camping on can be considered. . FIG. 23 shows a flowchart example of CC search within one cell. As shown in the drawing, in ST2301, each CC in the base station (cell) is synchronized to detect PCI. This step can be omitted if the base station (cell) is synchronized and the PCI is known. In ST2302, RS detection and RS reception power of each CC are performed, and the best CC is selected as the best CC in ST2303. In ST2304, PBCH transmitted by the CC is received and MIB is received. In ST2305, DL-SCH transmitted in the CC is received and SIB1 is received. In ST2306, camp-on is performed on the CC of the base station (cell), and system information and paging information are monitored.

When the CC selection / reselection method in one base station (cell) that supports carrier aggregation is shifted from RRC_CONNECTED state to RRC_IDLE as described above, the method disclosed here is used. Thus, it is possible to camp on one of the CCs of the base station (cell). As a result, it is possible to specify which CC should be camp-on, and communication between the UE, the base station (cell), and the network can be enabled.

However, in the method disclosed here, the best CC must be searched for all CCs in one base station (cell) to perform CC selection / reselection processing, and the control delay time increases. The problem that the power consumption of UE increases will arise. Another possible method is to change the camp-on cell. In this case, too, the UE must perform a cell search and perform a cell selection / reselection process, which increases the control delay time, There arises a problem that power consumption increases.

Therefore, when the base station (cell) corresponding to carrier aggregation moves away from the RRC_CONNECTED state and shifts to the RRC_IDLE state, a new effective method is required in determining the cell and CC in which the UE camps on.

In order to solve the above-described problem, in this embodiment, the UE camps on one of the CCs that can transmit and receive data of the last base station (cell) that was in RRC_CONNECTED. Try to try.

FIG. 14 shows a conceptual diagram when camping on any one of the CCs capable of transmitting and receiving data. (A) is an RRC_CONNECTED state, and (b) is an RRC_IDLE state. In FIG. 14, the same reference numerals as those in FIG. 13 denote the same or corresponding parts, and the description of the same reference numerals will be omitted.

As shown in (a), since the base station (cell) (1303) supports carrier aggregation, the UE in the RRC_CONNECTED state has a plurality of CCs, CC # 2 (1305), CC # 4 (1307), CC # 6 (1309). ) Data transmission / reception above. In such a situation, when moving away from the RRC_CONNECTED state and moving to RRC_IDLE, as shown in (b), the UE can transmit / receive data of the last base station (cell) (1303) that was at the time of RRC_CONNECTED. Try to camp on any one of the CCs. Here, camp-on is attempted at CC # 2 (1305).

A CC capable of transmitting and receiving data between a UE and a base station (cell) in the RRC_CONNECTED state is considered to be a CC with good communication quality. Communication quality that enables at least data transmission and reception is obtained. Therefore, by trying to camp on any one of the CCs that can send and receive data, it is possible to camp on the CC of the cell when moving to RRC_IDLE away from the RRC_CONNECTED state. become. By making it possible to camp on reliably, it is not necessary to perform cell search, cell selection / reselection processing, or search of all CCs, CC selection / reselection processing that occurs when camp-on is not possible. Therefore, the control delay time can be reduced, and further, the power consumption of the UE can be reduced.

The specific operation of the state transition between RRC_IDLE and RRC_CONNECTED in the base station (cell) that supports carrier aggregation has not yet been examined and clarified in 3GPP. Accordingly, here, a specific operation that enables a state transition between RRC_IDLE and RRC_CONNECTED is disclosed.

FIG. 19 shows a sequence example at the time of state transition between RRC_IDLE and RRC_CONNECTED.

The figure will be explained. The UE in the RRC_IDLE state searches for a cell and / or CC (downlink CC) in ST1901, and camps on one CC (downlink CC) of one cell in ST1902. In Step ST1903, the UE that camps on a certain CC uses the CC (uplink CC (uplink CC corresponding to the downlink CC (uplink CC corresponding to the downlink CC)) to send an RRC connection request to a base station (cell) (eNB ). The base station (cell) that has received the RRC connection request transmits an RRC connection setup to the UE using the CC (downlink CC) in ST1904. The UE that has received the RRC connection setup transmits an RRC connection setup completion to the base station (cell) using the CC (uplink CC) in ST1905. As a result, the establishment of the RRC connection is successful and the state transits to the RRC_CONNECTED state. In ST1906, data transmission / reception is performed between the UE, the base station (cell), and the core network (CN) in the RRC_CONNECTED state.

In the base station (cell) that supports aggregation, addition / deletion / replacement of CCs that can transmit and receive data is performed in order to perform carrier aggregation using CCs with good communication quality in the RRC_CONNECTED state. The CC to be added / deleted / replaced is a downlink CC and / or an uplink CC.

At this time, addition / deletion / replacement may be performed with a pair of uplink CCs (pair bands) corresponding to the downlink CCs. This makes it possible to reduce the amount of signaling information required between the UE, the base station (cell), and the core network.

The CC to be added / deleted / replaced is set by the base station (cell). The setting may be set by the core network. In this case, the addition / deletion / replacement information of the set CC may be notified to the base station (cell). A base station (cell) that sets a CC to be added / deleted / replaced adds / deletes / replaces a CC. At this time, the base station (cell) notifies the UE of CC addition / deletion / replacement information in ST1907. The UE can recognize the CC that can be transmitted and received at the time of RRC_CONNECTED using the information. By receiving scheduling information of CCs that can be transmitted and received (downlink CC), UE enables data transmission / reception with a base station (cell) in CC after addition / deletion / replacement of CC in ST1908, and the base station in ST1909 Data can be transmitted / received to / from the core network via a station (cell).

Next, state transition from RRC_CONNECTED to RRC_IDLE will be described. When the data transmission / reception between the UE and the core network is completed and the RRC_CONNECTED state is no longer necessary between the UE and the base station (cell), the base station (cell) transmits an RRC connection release to the UE in ST1910. To do. UE which received this performs the procedure which leaves | separates from RRC_CONNECTED state and transfers to RRC_IDLE in ST1911. The UE that has executed the procedure leaves the CONNECTED state, moves to RRC_IDLE, and camps on one CC of one cell in ST1912.

In ST1911, the method disclosed in the present embodiment is executed. The UE tries to camp on any one of the CCs capable of transmitting and receiving data of the last base station (cell) that was at the time of RRC_CONNECTED. By so doing, when leaving the RRC_CONNECTED state and moving to RRC_IDLE, the UE can reliably camp on the selected CC of the selected cell in ST1912. Therefore, since it is not necessary to perform cell search, cell selection / reselection processing, or search of all CCs and CC selection / reselection processing that occur when camp-on cannot be performed, control delay time can be reduced. In addition, the power consumption of the UE can be reduced.

FIG. 24 shows a specific example of a flowchart regarding a method of determining a cell and CC for attempting camp-on according to the present invention.

In ST2401, the UE receives parameters used for each CC reselection. The method for notifying the UE of these parameters is individually notified to the UE from the base station (cell) together with (or included in the information of the message) the RRC connection release message of ST1910 shown in FIG. Not limited to this, the UE may be notified individually from the base station (cell) or the core network at the time of RRC_CONNECTED. For example, notification may be made in ST1909. As a result, even if the CC that can transmit and receive data during RRC_CONNECTED is dynamically changed for each UE, it is possible to transmit and receive parameters used for each CC reselection in the CC after the change. In addition, in this notification method, parameters used for CC reselection of necessary CCs can be dynamically notified to individual UEs. Therefore, when shifting to RRC_IDLE, optimal parameters as a system can be notified to UEs. It becomes possible.

As another notification method, when the base station (cell) camps on in ST1902, it may be included in the system information and broadcast from the base station (cell). In this case, the base station (cell) may be a parameter used for each CC reselection of all CCs to which it corresponds. This allows the UE to execute ST1911 using the parameter received at the RRC_IDLE even if the parameter is not received by RRC_CONNECTED.

As a specific example of a parameter used for each CC reselection, a parameter used for cell reselection of a base station (cell) to which the CC belongs may be used. For example, a threshold value for determining whether or not to perform CC reselection. Specifically, there are S_intrasearch, Q_Hyst, Q_offset, T_reselection, S_nonintrasearch, cellReselectionPriority, and the like. Further, only S_intrasearch may be used. In this case, the same parameters may be used in common for all CCs, and each parameter may be as follows.

S_intrasearch is a threshold for measurement at the same frequency.

Q_Hyst is the hysteresis value based on the ranking criteria.

Q_offset is the offset value between two cells.

T_reselection is the cell reselection timer value.

S_nonintrasearch is a threshold for measurement at different frequencies and different systems.

CellReselectionPriority is the absolute priority of the carrier frequency.

This makes it possible to reduce the amount of information and signaling capacity that must be notified to the UE from the base station (cell) or core network.

Alternatively, the above parameters may be provided for each CC. A value can be set for each CC.

As another method, an identifier of each CC may be provided and notified together with the parameter. The parameter is set to a value for the CC indicated by the identifier of the CC notified together. By doing so, the value for each CC can be set also in this method.

In ST2402, the UE selects the last cell that was in RRC_CONNECTED. In ST2403, the UE determines whether there is a CC that has not yet attempted camp-on in this procedure (ST1911) among CCs that can transmit and receive the data of the cell. If there is a CC that has not attempted camp-on, the UE selects one of the CCs that has not attempted camp-on in ST2404, and attempts to camp-on the selected CC in ST2405. In ST 2405 (or ST 2406 may be used), the UE measures the reception level (RSRP or the like) of the CC attempting to camp on. In ST2406, the UE determines whether or not to reselect CC. Further, as a specific example of determining whether or not to perform CC reselection, when the measured reception level of the CC is larger than the parameter (S_intrasearch), it is determined that CC reselection is not further performed. If it is determined that CC reselection is not performed, the UE moves to ST2407 and camps on the selected CC. If the reception level of the CC measured in ST2406 is equal to or less than the parameter (S_intrasearch), it is determined that CC reselection is performed, and the UE moves to ST2403 and tries to camp on again in this procedure (ST1911). It is determined whether or not there is a CC that is not present. If there is a CC that has not attempted camp-on, the process proceeds to ST2404 and the above-described processing is performed. When there is no CC that has not attempted camp-on, the mobile terminal makes a transition to ST 2408 and performs a process of searching for another cell or / and CC and reselecting another cell or / and CC. The other cell or / and CC search and the other cell or / and CC reselection process may use the method disclosed in FIG. After the search and reselection process of another cell or / and CC in ST2408, the UE camps on the selected cell or / and CC in ST2409. ST2407 and ST2409 correspond to ST1912 shown in FIG.

As disclosed in the present embodiment, in ST2402 to ST2405, the UE attempts to camp on any one of the CCs capable of transmitting and receiving data of the last base station (cell) at the time of RRC_CONNECTED. By doing so, the possibility of camping on the CC increases. This is because the reception level of the CC is likely to be larger than the reselection threshold (S_intrasearch) in the determination process of ST2406. As described above, a CC capable of transmitting / receiving data between the UE and the base station (cell) in the RRC_CONNECTED state is considered to be a CC having a good communication quality, so that at least a communication quality capable of transmitting / receiving data is obtained. Because.

Therefore, it is unlikely that the mobile station again shifts to the CC reselection process in ST2406, and further, the mobile station may move to another cell or / and CC search and another cell or / and CC reselection process in ST2408. Is even lower. Therefore, cell search, cell selection / reselection processing, or search of all CCs that occurs when camp-on cannot be ensured by ensuring camp-on to the selected cell and CC when moving from RRC_CONNECTED state to RRC_IDLE Since it is not necessary to perform the CC selection / reselection process, the control delay time can be reduced, and further, the power consumption of the UE can be reduced.

As a CC capable of transmitting and receiving data, for example, a CC in a candy component carrier set shown in Non-Patent Document 10 may be used. Similar effects can be obtained.

In the above-described method, the camp-on is attempted to any one of the CCs capable of transmitting and receiving data, but the UE actually transmits and receives data when leaving RRC_CONNECTED. You may make it try camping on any one of CC.

In this way, the UE can recognize the communication quality of each CC immediately before moving to RRC_IDLE. When leaving RRC_CONNECTED and moving to RRC_IDLE, it becomes possible to camp on more reliably. Therefore, a further reduction effect of the control delay time and a further reduction effect of the power consumption of the UE can be obtained.

As a CC that has been transmitting and receiving data, for example, a scheduling component carrier shown in Non-Patent Document 10 may be used. Similar effects can be obtained.

The CC that can transmit and receive data or the CC that actually transmits and receives data depends on the load status of the base station (cell) and the radio wave propagation environment of each CC depending on the network or base station (cell). It can be set accordingly. For this reason, it becomes possible to perform load distribution among CCs in consideration of the communication quality of each CC, and it is possible to improve the throughput of the entire base station (cell).

Also, the CC capable of transmitting / receiving data or the CC that actually transmits / receives data may be set for each individual UE. By doing so, it becomes possible to set the CC according to the radio wave propagation environment between the base station (cell) and the individual UE, and thus there is an effect that good reception quality can be obtained for each UE.

Any one CC described above may be a CC having PBCH. In this way, when the UE leaves RRC_CONNECTED, shifts to RRC_IDLE and camps on the CC, the UE can receive broadcast information newly transmitted by the PBCH. When the broadcast information is changed due to a change in cell configuration or the like, the network or the base station (cell) may notify the UE of an instruction to shift to RRC_IDLE and newly receive the broadcast information. . Since the UE can receive new broadcast information, it is possible to eliminate a communication abnormality due to a mismatch in cell configuration, and to supply a stable communication system.

Any one CC described above may be a CC having an SS. In this way, when the UE leaves RRC_CONNECTED, shifts to RRC_IDLE, and camps on the CC, it becomes possible to newly synchronize. Thereby, for example, when the CC is a CC that is not actually scheduled among CCs that can transmit and receive data, or when the CC performs a DRX operation at the time of RRC_CONNECTED, the UE When the period in which data is not received is long, it is possible to prevent the UE from receiving a long period of data when RRC_IDLE transitions and becoming out of synchronization. Therefore, it is possible to supply a stable communication system.

Any one of the CCs described above may be a CC that is always measured or monitored during RRC_CONNECTED. The UE will be in a state where it can monitor the CC when leaving RRC_CONNECTED. For this reason, even when shifting to RRC_IDLE and attempting to camp on the cell, it is possible to camp on reliably. Therefore, the effect of reducing the control delay time and the effect of reducing the power consumption of the UE are obtained.

The CC that is always measured or monitored at the time of RRC_CONNECTED may be, for example, an anchor carrier shown in Non-Patent Document 10. Similar effects can be obtained.

As any one of the CCs described above, the CC having the best recent reception quality at the time of leaving RRC_CONNECTED may be used. By doing so, it is possible to camp on the CC having the best reception quality, and the possibility of being unable to camp on is the lowest. For this reason, it becomes more effective in the reduction of control delay time and the reduction of the power consumption of UE.

The reception quality of each CC may be measured when leaving RRC_CONNECTED. This makes it possible to determine the CC that is optimal for the UE to camp on when leaving RRC_CONNECTED. Therefore, it is most effective in reducing the control delay time and the power consumption of the UE.

As a CC to be measured when leaving RRC_CONNECTED, it may be a CC that can transmit and receive data instead of all the CCs of the cell that was last in RRC_CONNECTED, or a CC that is actually transmitting and receiving data. By doing so, it is not necessary to measure all CCs, and it is possible to reduce the power consumption of the UE.

The base station (cell) or core network may notify the UE of the CC for measuring the reception quality. As a notification method, a method for notifying the UE of parameters used for each CC reselection can be applied. The base station (cell) or the core network determines the CC for measuring the reception quality in consideration of the connection load status of each CC, the capability of the UE, the communication quality between the UE and each CC, and the like. Thereby, the throughput of the entire base station (cell) and the entire system can be improved.

First Embodiment Modification 1
In this modified example, as another method for solving the problem described in the first embodiment, the UE uses the same frequency band as the CC that can transmit and receive data at the time of RRC_CONNECTED of the last base station (cell) that was at the time of RRC_CONNECTED. Try to camp on any one of the CCs to which it belongs.

FIG. 15 shows a conceptual diagram when camping on any one of the CCs belonging to the same frequency band. (A) is an RRC_CONNECTED state, and (b) is an RRC_IDLE state. In FIG. 15, the same reference numerals as those in FIG. 13 indicate the same or corresponding parts, and the description of the same reference numerals is omitted.

In FIG. 15, CC # 1 (1304) and CC # 2 (1305) belong to frequency band I, CC # 3 (1306) belongs to frequency band II, CC # 4 (1307) belongs to frequency band III, CC # 5 (1308), CC # 6 (1309), and CC # 7 (1310) belong to the frequency band IV. The frequency band here indicates a set of CCs having common physical characteristics or radio characteristics.

As shown in (a), since the base station (cell) (1303) supports carrier aggregation, the UE in the RRC_CONNECTED state has a plurality of CCs, CC # 2 (1305), CC # 4 (1307), CC # 6 (1309). ) Data transmission / reception above. In such a situation, when moving away from the RRC_CONNECTED state and moving to RRC_IDLE, as shown in (b), the UE can transmit and receive data of the last base station (cell) (1303) that was in RRC_CONNECTED. And try to camp on any one of the CCs belonging to the same frequency band. Here, a camp-on is tried to CC # 5 (1308). As shown in (a), CC # 6 (1309) is one of CCs that can transmit and receive data in the RRC_CONNECTED state. This CC # 6 (1309) belongs to the frequency band IV. Similarly, CCs belonging to the frequency band IV include CC # 5 (1308) and CC # 7 (1310). Therefore, the UE attempts to camp on CC # 5 (1308).

The sequence at the time of state transition between RRC_IDLE and RRC_CONNECTED may be the same as in FIG. In addition, the determination method of the cell and CC to attempt camp-on is based on whether or not there is a CC that does not attempt camp-on among CCs belonging to the same frequency band as the CC capable of transmitting and receiving data in ST2403 of FIG. It is sufficient to change so that it is judged by.

A CC capable of transmitting and receiving data between a UE and a base station (cell) in the RRC_CONNECTED state is considered to be a CC with good communication quality. Communication quality that enables at least data transmission and reception is obtained.

On the other hand, in CCs belonging to the same frequency band, the radio wave propagation environment is considered to be almost the same because the frequencies are close to each other. Therefore, the reception quality in CCs belonging to the same frequency band is considered to be almost the same.

Therefore, by trying to camp on any one of the CCs belonging to the same frequency band as the CC capable of transmitting and receiving data, the cell of the cell is changed when moving from the RRC_CONNECTED state to the RRC_IDLE. It will be possible to camp on the CC. Thereby, it is possible to obtain the same effect as in the first embodiment.

Furthermore, flexible control is possible in the UE by increasing the number of CCs to which camp-on is attempted.

Furthermore, an effect that load distribution among CCs in the base station (cell) becomes possible is obtained.

First Modification Example 2
In the first embodiment, the UE selects any one of the CCs capable of transmitting and receiving data of the last base station (cell) that was in RRC_CONNECTED. This is because the CC can be selected according to the communication status of the UE (for example, the communication quality of each CC (downlink CC and / or uplink CC)).

In this modification, as another method, a method in which a base station (cell) or a core network selects and notifies the UE is disclosed. In this case, the method for notifying which CC to select can be applied to the method for notifying the UE of the parameters used for each CC reselection disclosed in the first embodiment. In addition, the CC may be notified along with the parameter.

As an example, FIG. 20 shows a sequence diagram in the case where the base station (cell) notifies the UE of a cell and / or CC for which camp-on is attempted. In FIG. 20, the same reference numerals as those in FIG. 19 denote the same or corresponding parts, and the description of the same reference numerals is omitted. This is a case where the UE notifies the UE from the base station (cell) in the state of RRC_CONNECTED. Before notifying the UE of the RRC connection release message, the base station (cell) determines the communication status with the UE and determines the cell and CC to try to camp on when moving to RRC_IDLE. The CC information is notified. Information that can identify the cell and the CC, such as cell identifier (PCI, cell-ID), CC identifier (CC number, carrier frequency, CC carrier UARFCN (UTRA Absolute) Radio Frequency Channel Number) etc.

As CC information, information on only downlink CCs may be used instead of information on downlink CCs and uplink CCs that are pair bands. In this case, information on the corresponding uplink CC may be obtained from the downlink CC after camping on the downlink CC. For example, it may be reported as system information in the downlink CC. Thereby, the control signal with respect to individual UE can be reduced, and the effect of effective utilization of radio resources can be obtained.

The cell information may be omitted, and it may be determined in advance as the last cell at the time of RRC_CONNECTED. Thereby, the control signal with respect to individual UE can be reduced, and the effect of effective utilization of radio resources can be obtained.

When a base station (cell) or a core network determines a cell and a CC in which the UE attempts to camp on, determine the connection load status of each CC, UE capability, communication quality between the UE and each CC, and the like. .

By adopting the method disclosed in the present modification, in addition to the effects described in the first embodiment, a UE and a cell to be camped on are determined from the outside such as a base station (cell) or a core network. Therefore, it is possible to improve the communication quality and the throughput of the entire cell and the entire system.

Modification 1 of Embodiment 1
In the present modification, as another method for solving the problem described in the first embodiment, the UE may use any one of CCs that can camp on at the time of RRC_IDLE of the last base station (cell) that was at the time of RRC_CONNECTED. Try to camp on CC.

FIG. 16 shows a conceptual diagram when camping on any one of CCs that can be camp-on at the time of RRC_IDLE. (A) is an RRC_CONNECTED state, and (b) is an RRC_IDLE state. In FIG. 16, the same reference numerals as those in FIG. 13 indicate the same or corresponding parts, and the description of the same reference numerals will be omitted.

(B), CC # 1 (1304), CC # 3 (1306), CC # 4 (1307), and CC # 6 (1309) are CCs that can be camp-on at the time of RRC_IDLE.

In the present invention, a CC that can be camp-on at the time of RRC_IDLE is a CC that is not CC (for example, barred) where camp-on is prohibited at the time of RRC_IDLE.

As shown in (a), since the base station (cell) (1303) supports carrier aggregation, the UE in the RRC_CONNECTED state has a plurality of CCs, CC # 2 (1305), CC # 4 (1307), CC # 6 (1309). ) Data transmission / reception above. In this situation, when the UE moves away from the RRC_CONNECTED state and moves to RRC_IDLE, as shown in (b), the UE is able to camp on at the time of RRC_IDLE of the last base station (cell) (1303) that was at the time of RRC_CONNECTED. Try to camp on one of the CCs. Here, camp-on is attempted at CC # 3 (1306).

The sequence at the time of state transition between RRC_IDLE and RRC_CONNECTED may be the same as in FIG. In addition, the determination method of cells and CCs that attempt camp-on is changed from ST2403 in FIG. 24 to determine whether there is a CC that does not attempt camp-on among CCs that can be camp-on at the time of RRC_IDLE. It ’s fine.

CC information that can be camp-on at the time of RRC_IDLE may be determined in advance. By doing so, special signaling is not required for the notification of the information, so that the signaling load can be reduced.

In addition, the UE may be individually notified on the CC that is transmitting and receiving data at the time of RRC_CONNECTED, or may be notified through the CC that is transmitting and receiving data at the time of RRC_CONNECTED or other CCs. . As a notification method, a method of notifying the UE from the base station (cell) on a message or header of RRC signaling or MAC signaling, a method of notifying the UE from the base station (cell) on system information, and PDCCH There is a method of reporting from the base station (cell) to the UE.

The CC information that can be camp-on is notified before or together with the RRC_CONNECTION_RELEASE message from the base station to the UE. As a method for notifying CC information that can be camp-on at the time of RRC_IDLE, the method for notifying the UE of parameters used for each CC reselection disclosed in the first embodiment can be applied. Further, it may be notified together with the parameter.

When notifying by broadcast information, before notifying an RRC_CONNECTION_RELEASE message from the base station to the UE, the base station notifies the UE of correction information of the broadcast information, and the UE receives the corrected broadcast information. May be.

By adopting the method as described above, it is possible to change the CC that can be camp-on at the time of RRC_IDLE from semi-static or dynamic, and this CC is transferred from the base station to the UE. Notification or notification can be performed.

In the present invention, the CC that can camp on at the time of RRC_IDLE is a CC that is not a CC that is camp-on prohibited at the time of RRC_IDLE (for example, a barred CC), but among the CCs among them, the first cell selection / reselection As a result of measuring the received power by the UE at the time of CC selection / reselection, it may be a CC that has exceeded the threshold for CC reselection.

It suffices for the UE to store the CC. Specific examples of the CC information to be stored include the identifier of the CC. Further, the present invention is not limited thereto, and may be information necessary for reselection of the CC. This eliminates the need to report CC information that can be camp-on from the base station (cell) to the UE at the time of RRC_IDLE, thereby reducing the signaling load.

Also, the order of the CC may be stored together with information such as the identifier of the CC. The order of the CCs may be assigned, for example, from the higher one based on the measurement result of the received power, and camp-on may be attempted from the CC having a higher order. As a result, it is possible to camp on the CC having the highest received power, and the possibility that camp-on is impossible becomes the lowest. For this reason, it becomes more effective in the reduction of control delay time and the reduction of the power consumption of UE.

As described above, with the method disclosed in this modification, it is not necessary for the base station (cell) to perform cell selection / reselection processing for all CCs to be subjected to carrier aggregation, or all the CCs are selected. It is no longer necessary to perform the measurement. Therefore, the control delay time can be reduced, and further, the power consumption of the UE can be reduced.

Also, as one of the CCs that can be camp-on at the time of RRC_IDLE, camp-on may be attempted to the CC when camp-on is performed to the last base station (cell) that was at the time of RRC_CONNECTED. The camp-on of the cell to the CC will have a track record. Accordingly, since the camp-on can be reliably performed in this way, it is not necessary to perform the cell selection / reselection process or the CC selection / reselection process that occurs when the camp-on cannot be performed. Therefore, the control delay time can be reduced, and further, the power consumption of the UE can be reduced.

The UE may receive and store information broadcast from the CC of the cell when camping on the CC of the cell. It may be stored in the protocol control unit (801), application unit (802), control unit (810), etc. of the UE shown in FIG. Alternatively, it may be stored in the SIM.

Information received by the base station (cell) for the UE to receive and store includes system information, cell identifier (PCI, cell-ID), CC identifier, CC carrier frequency, CC carrier UARFCN (UTRAＮAbsolute Radio Frequency) (Channel Number) etc.

By storing these pieces of information, the UE does not need to receive these pieces of information when performing camp-on at the time of transition to RRC_IDLE, and further to operate after camp-on. In addition, it is possible to reduce the control delay time in the UE, and it is also possible to reduce the power consumption of the UE.

In addition, when there are a plurality of CCs that are camped on in the cell, the UE may select one of the plurality of CCs, or the reception quality (reception of the plurality of CCs) The UE may select the CC having the best reception quality.

Due to movement in the RRC_CONNECTED state, that is, handover (HO) or the like, the base station (cell) camping on at the time of RRC_IDLE and the last base station (cell) at the time of RRC_CONNECTED may be different. In such a case, if the UE has experience of camping on the last base station (cell) that was at the time of RRC_CONNECTED, the UE attempts to camp on the CC at the time of camping and receives when camping on the cell. Thus, the stored cell and the CC-related information may be used. On the other hand, if the UE has no experience of camping on the last base station (cell) at the time of RRC_CONNECTED, the information may be received after newly camping on, or the base station before HO at the time of RRC_CONNECTED (Cell) or the base station (cell) after HO may receive the information, or the UE issues a notification request for the information to the base station (cell) after HO during RRC_CONNECTED, and the base station accordingly A station (cell) may notify the UE. As the notification method, the above-described method can be used.

Also, camp-on may be attempted to a CC that monitors paging information or system information as one of the CCs that can be camp-on at the time of RRC_IDLE. A CC that monitors paging information or system information at the time of RRC_IDLE is referred to as an anchor carrier at the time of RRC_IDLE.

Since the system information is reported from the anchor carrier at the time of RRC_IDLE, the system information is not obtained after camp-on, and the process of reselecting / selecting another CC is not entered. Accordingly, it is possible to reduce the control delay time and the power consumption of the UE.

The anchor carrier may be a multicarrier anchor or a single carrier anchor.

The anchor carrier at the time of RRC_IDLE and the anchor carrier at the time of RRC_CONNECTED described in the first embodiment may be the same. In this way, since the same CC is monitored at both RRC_IDLE and RRC_CONNECTED, the state transition between RRC_IDLE and RRC_CONNECTED can be executed on the same CC first. Therefore, since the communication quality in RRC_IDLE and RRC_CONNECTED is maintained, if it is possible to camp on the CC with RRC_IDLE, it is possible to communicate with the CC even when transitioning to RRC_CONNECTED, and conversely, if communication with the CC is possible with RRC_CONNECTED, Camping can be performed on the CC at the time of transition to RRC_IDLE. Therefore, the effect that state transition can be executed reliably is obtained.

In addition, a base station (cell) may configure a subset with CCs that can be camp-on at the time of RRC_IDLE among CCs to be subjected to carrier aggregation, and the UE may attempt to camp on any one CC in the subset. .

In this way, similarly, it is not necessary for the base station (cell) to perform selection / reselection processing for all CCs to be subjected to carrier aggregation, or it is not necessary to perform measurement for all the CCs. Therefore, the control delay time can be reduced, and further, the power consumption of the UE can be reduced.

In order for the UE to recognize which CC of the cell is included in the subset, a synchronization signal (Synchronization 信号 Signal, SS) or PBCH is transmitted from the CC included in the subset. good. By doing so, the UE can select / reselect the CC. In addition, it is not necessary to notify the mobile terminal from the base station which CC of the cell is included in the subset, and the effect of effective use of radio resources can be obtained.

As another method, information on the subset (for example, CC information included in the subset) may be notified from all CCs. By doing so, the UE can select / reselect a certain CC and receive the broadcast information from the CC to obtain the subset information. The UE re-selects a CC that can be camp-on based on CC information that can be camp-on at the time of RRC_IDLE included in the received subset information, and camps on. As a result, the UE can select / reselect CCs included in the subset. Moreover, the effect that a flexible mobile communication system can be constructed can be obtained.

In the above description, a subset is composed of CCs that can be camp-on at the time of RRC_IDLE among CCs that are subject to carrier aggregation by the base station (cell). May be.

As described in the second modification of the present embodiment, the CCs belonging to the same frequency band are considered to have almost the same radio wave propagation environment because the frequencies are close to each other. Therefore, the reception quality in CCs belonging to the same frequency band is considered to be almost the same. Therefore, by providing one representative CC in the frequency band that can be camp-on at the time of RRC_IDLE, the base station (cell) selects / selects only some CCs instead of all CCs that are subject to carrier aggregation. Reselection processing or measurement can be performed.

In addition, since one CC is provided for each frequency band, a subset composed of the CCs has radio wave propagation characteristics of all frequency bands, so the UE is in the RRC_IDLE state. Sometimes the cell can maintain various radio wave propagation characteristics, and the UE can select a better cell or CC at the time of cell selection / reselection, which can improve the communication quality. It becomes.

A subset may be configured by providing one or more CCs that can be camp-on at the time of RRC_IDLE in the frequency band, and the above-described effects can be obtained. By configuring a subset by providing CCs that can be camp-on at the time of RRC_IDLE one by one in the frequency band, it is possible to configure a subset having the radio wave propagation characteristics of all frequency bands with the minimum number of CCs. It is possible to have the effect of improving the communication quality while obtaining the effect of reducing the control delay and power consumption by minimizing the number of CCs at the time of reselection.

Embodiment 2. FIG.
The UE in the RRC_IDLE state executes an RA (Random Access) procedure with the base station (cell) in order to shift to the RRC_CONNECTED state first when it becomes necessary to transmit / receive data to / from the network. The RA procedure is used to connect a random access channel.

Fig. 17 shows the sequence diagram of RA procedure.

The UE in the RRC_IDLE state transmits information (identifier) for identifying its own UE to the random access preamble to the base station (cell) (eNB) and transmits it (1701). This random access preamble is also called a message (Msg) 1.

The eNB that has received Msg1 sends a random access response including the UE identification information and uplink radio resource scheduling information (uplink grant, UL grant) on the PDCCH to which the random access identifier (RA-RNTI) is applied. Transmit (1702). This signal is also called Msg2.

The UE that has detected Msg2 by receiving a downlink signal from the eNB and detecting (also referred to as blind detection) using a random access identifier (RA-RNTI) on the PDCCH, It is determined whether or not it is addressed to the own UE by the information for UE identification.

If the information for UE identification of the own UE is included, the UE transmits a message according to the uplink scheduling information received by Msg2 (1703). This signal is also called Msg3. At this time, the UE also transmits its own UE identifier (C-RNTI) or contention resolution identification information (identifier).

The eNB that has received Msg3 transmits information including identification information for contention resolution and uplink radio resource scheduling information (uplink grant, UL grant) on the PDCCH to which the UE identifier (C-RNTI) is applied. Transmit (1704). This signal is also called Msg4.

The UE receives the downlink signal from the eNB, and performs detection (also called blind detection) using its own identifier (C-RNTI) on the PDCCH, thereby recognizing that it is Msg4 addressed to itself. , Receive uplink scheduling information addressed to the own UE included in Msg4, and transmit uplink data according to the scheduling.

This transmission / reception from Msg1 to Msg4 is called an RA procedure.

Further, in the Msg3, the UE may transmit an RRC CONNECTION REQUEST message to the eNB.

The eNB that has received the message may transmit an RRC CONNECTION SETUP message to the UE in the Msg4.

The UE that has received the message transmits an RRC CONNECTION SETUP COMPLETE message to the eNB according to the uplink scheduling information received in Msg4, and shifts to the RRC_CONNECTED state.

If the RA procedure is successful, the UE can transition from the RRC_IDLE state to the RRC_CONNECTED state. However, there are cases in which failure occurs during the RA procedure.

If it fails in the middle of the RA procedure, it is determined that RLF (Radio Link Failure) has been detected, and the UE stores the carrier frequency and cell parameters of the previously detected cell in order to search for a cell to camp on again. Then, a cell is searched from the stored information by the carrier frequency and cell parameter to select a cell. As a result, when a cell to be camp-on is not found yet, a cell is searched with all possible carrier frequencies of the system, and initial cell selection is executed.

However, the UE in the RRC_IDLE state is camping on one CC of the base station (cell) corresponding to the aggregation, starts the RA procedure with the base station (cell) using the CC, and in the middle of the RA procedure Think about the failure.

In such a case, when the conventional method is applied, the base station (cell) has a plurality of CCs and is likely to be able to camp on other CCs, but is stored in the UE. If a different cell is searched and selected, a situation occurs in which it is impossible to camp on another CC in the same base station (cell). Further, in this case, the UE must perform a cell search to perform cell selection / reselection processing, which causes a problem that the control delay time increases and the power consumption of the UE increases.

Therefore, in a base station (cell) that supports carrier aggregation, when an RA procedure fails, a new and effective method is required in determining the cell and downlink CC in which the UE camps on.

In order to solve the above-described problem, in the present embodiment, the UE is any one of CCs except for the CC that failed the RA procedure of the base station (cell) that was camping on when the RA procedure was started. To one CC among CCs that can camp on at the time of RRC_IDLE of the base station (cell) that was camping on at the start of the RA procedure, except the CC that failed the RA procedure Try to camp on.

Hereinafter, among the CCs that can be camp-on at the time of RRC_IDLE of the base station (cell) in which the UE is camping on when the RA procedure is started, the UE can camp on any one of the CCs except the CC that failed the RA procedure. The case of trying to turn on will be described.

FIG. 21 shows a conceptual diagram when camping on any one of the CCs excluding the CC that failed the RA procedure. (A) shows a CC that is camping on at the start of the RA procedure in the RRC_IDLE state, and (b) shows a CC that camps on after the RA procedure fails in the RRC_IDLE state. In FIG. 21, the same reference numerals as those in FIG. 13 denote the same or corresponding parts, and the description of the same reference numerals will be omitted.

As shown in (a), the base station (cell) (1303) supports carrier aggregation, and the UE (1311) that has selected the cell 1303 is camping on CC # 3 (1306) in the RRC_IDLE state. On the CC # 3 (1306), the UE starts the RA procedure. Here, in order to simplify the description, an uplink CC corresponding to downlink CC #n (n = 1 to 7) is assumed to be CC #n. Therefore, the RA procedure is performed on the downlink CC # 3 and the corresponding uplink CC # 3. Also, as shown in (b), CC # 1 (1304), CC # 3 (1306), CC # 4 (1307), and CC # 6 (1309) are CCs that can camp on at the time of RRC_IDLE.

If the failure occurs during the RA procedure, as shown in (b), the UE camps on any one of the CCs that can camp on at the time of RRC_IDLE, excluding the CC that failed the RA procedure. Try. Here, among CC # 1 (1304), CC # 3 (1306), CC # 4 (1307), and CC # 6 (1309) that can camp on at the time of RRC_IDLE, CC # 3 (1306) that failed during the RA procedure ), Except for CC # 4 (1307).

The specific operation in the case of RA procedure failure in a base station (cell) that supports carrier aggregation has not yet been studied in 3GPP and is not clear. Here, a specific operation when the RA procedure fails is disclosed.

FIG. 25 shows a sequence example when the RA procedure fails.

The figure will be explained. The UE in the RRC_IDLE state performs a cell or / and CC (downlink CC) search in ST2501, and camps on one CC (downlink CC) of one cell in ST2502. A UE that camps on a certain CC performs an RA procedure with a base station (cell) (eNB) using the CC (a downlink CC and an uplink CC as a pair band) in ST2503. Specifically, transmission / reception of Msg1 to Msg4 shown in FIG. 17 is performed. In ST2504, the UE that has executed the RA procedure determines whether the RA procedure has succeeded or failed. If successful, an RRC connection has been established between the UE and the eNB, and therefore enters the state of RRC_CONNECTED. Since the RRC connection is established, in ST2505, the UE can transmit and receive data between the base station (cell) and the core network.

On the other hand, if it is determined in ST2504 that the RA procedure has failed, it is determined that RLF (Radio Link Failure) has been detected, the process proceeds to ST2506, and a process of determining a cell and CC that attempt to camp on again is performed. The UE performs camp-on again in ST2502 on the cell and CC selected by the determination process.

In ST2506, the method disclosed in the present embodiment is executed. The base station (cell) that was camping on at the start of the RA procedure may try to camp on any one of the CCs that can camp on at the RRC_IDLE except the CC that failed the RA procedure. To do. It is possible to camp on the selected CC of the cell selected in ST2506 when the RA procedure fails. Therefore, since it is not necessary to perform cell search, cell selection / reselection processing, or search of all CCs and CC selection / reselection processing that occur when camp-on cannot be performed, control delay time can be reduced. In addition, the power consumption of the UE can be reduced.

FIG. 26 shows a specific example of a flowchart of a method for determining a cell and CC for attempting camp-on according to the present invention.

In ST2601, the UE receives parameters used for each CC reselection. These parameters may be included in the system information of the CC camped on in ST2502 shown in FIG. 25 and notified from the base station (cell) to the UE. The base station (cell) may be a parameter used for each CC reselection of all CCs to which it corresponds. As a result, the UE can execute the processing of ST2506.

Specific examples of parameters used for each CC reselection can be the same as the parameters used for each CC reselection disclosed in the first embodiment. For example, it is a threshold value of received power for determining whether or not to reselect CC. Since the parameters have been described in the first embodiment, description thereof is omitted here. Moreover, you may provide separately the parameter used for each CC reselection used in Embodiment 1, and the parameter used for each CC reselection used in this Embodiment. This makes it possible to set the parameter according to the situation (from RRC_CONNECTED to RRC_IDLE, RA procedure failure, etc.), and flexible UE access control can be performed. For this reason, it is possible to improve the throughput of the system.

In ST2602, the UE selects the cell that was present when the RA procedure was started. In ST2603, among the CCs that can be camp-on at the time of RRC_IDLE of the cell, CCs that have not yet attempted camp-on in this procedure (ST2506) exist except for CCs that failed the RA procedure. It is determined whether or not. If there is a CC that has not attempted camp-on, in ST 2604, the UE selects one of the CCs that has not attempted camp-on, and in ST 2605, attempts to camp on the selected CC. In ST2605 (or ST2606 may be used), the UE measures the reception level (RSRP or the like) of the CC that attempted to camp on. In ST2606, the UE determines whether or not to reselect CC. Further, as a specific example of determining whether or not to perform CC reselection, when the measured reception level of the CC is larger than the parameter (S_intrasearch), it is determined that CC reselection is not further performed. If it is determined that CC reselection is not performed, the UE moves to ST2607 and camps on the selected CC. When the reception level of the CC measured in ST2606 is equal to or less than the parameter (S_intrasearch), it is determined that CC reselection is performed, and the UE moves to ST2603 and tries to camp on again in this procedure (ST2506). It is determined whether or not there is a CC that is not present. If there is a CC that has not attempted camp-on, the process proceeds to ST2604 and the above-described processing is performed. If there is no CC that has not attempted to camp on, the mobile terminal makes a transition to ST2608 and performs a process of searching for another cell or / and CC and reselecting another cell or / and CC. The other cell or / and CC search and the other cell or / and CC reselection process may use the method disclosed in FIG. After a search and reselection process of another cell or / and CC in ST2608, the UE camps on the selected cell or / and CC in ST2609. ST2607 and ST2609 correspond to ST2502 shown in FIG.

As disclosed in the present embodiment, in ST2602 to ST2605, the UE excludes CCs that have failed in the RA procedure from among the CCs that can camp on at the RRC_IDLE of the base station (cell) that has executed the RA procedure. Try to camp on any one of the CCs. By selecting a cell attempting camp-on from CCs that can camp on at the time of RRC_IDLE of the base station (cell) that has executed the RA procedure, the possibility of camping on the CC increases. This is because the reception level of the CC is likely to be higher than the reselection threshold (S_intrasearch) in the determination process of ST2606. This is because it is considered that CCs used by the same base station (cell) are often operated so that the area coverage in each CC is substantially the same. In addition, even when other aggregation-compatible cells are adjacent, by making the area coverage for each CC almost the same, there are many cases where it is operated so that a dead zone does not occur only for a certain CC. This is because it is considered. Accordingly, a UE that can camp on one CC of a base station (cell) at the time of RRC_IDLE is more likely to camp on another CC of the base station (cell).

Therefore, it is unlikely to shift to the CC reselection process again in ST2606, and further to ST2608 to shift to another cell or / and CC search and another cell or / and CC reselection process. Is even lower. Therefore, cell search, cell selection / reselection processing, or search of all CCs that occurs when camp-on cannot be ensured by ensuring camp-on to the selected cell and CC when moving from RRC_CONNECTED state to RRC_IDLE Since it is not necessary to perform the CC selection / reselection process, the control delay time can be reduced, and further, the power consumption of the UE can be reduced.

Furthermore, the UE can avoid a failure caused by some factor in the downlink CC and / or the uplink CC by excluding the CC that failed the RA procedure as a CC that attempts to camp on after failing the RA procedure. That is, it is possible to prevent a failure during the RA procedure from occurring when the RA procedure is performed again with a newly camp-on CC. Therefore, the delay time of the transition control to the RRC_CONNECTED state is reduced, the power consumption of the UE is reduced, the contention of the RA procedure with another UE is reduced, the signaling capacity as a system is reduced, and the interference to other cells and other UEs Can be suppressed.

As described above, the UE can select any one of the CCs except the CC that failed the RA procedure from among the CCs that can camp on at the RRC_IDLE of the base station (cell) that was camping on at the start of the RA procedure. By trying to camp on the CC, it is possible to camp on reliably, so the carrier frequency and cell parameters of the previously detected cell are stored, and the carry frequency is determined from the stored information. A process of searching for a cell by cell parameters and performing cell selection is not required. For this reason, the control delay time can be reduced, and further, the power consumption of the UE can be reduced.

Even when the UE attempts to camp on any one of the CCs except the CC that failed the RA procedure of the base station (cell) that was camping on at the start of the RA procedure, the above-mentioned As a CC that attempts to camp on after failing the RA procedure, the effect of removing the CC that failed the RA procedure can be obtained.

In the above description, the downlink CC number (#n) and the uplink CC number (#n) corresponding to the CC number (#n) are the same. However, the present invention is not limited to this, and the downlink CC number, Corresponding uplink CC numbers (which are pair bands) may be different, and the method disclosed in this embodiment can be applied.

Any one CC described above may be a CC having PBCH. In this way, when the UE camps on the CC, the UE can receive broadcast information newly transmitted by the PBCH. When the broadcast information is changed due to a change in the cell configuration or the like, since the UE can receive new broadcast information, it is possible to eliminate a communication abnormality due to a mismatch in the cell configuration, etc. It becomes possible to supply.

Any one CC described above may be a CC having an SS. By doing so, the UE can newly re-synchronize when it camps on the CC. Thereby, it becomes possible to camp on the CC reliably even when the period during which the UE has not received data is long due to the DRX operation.

As another method, the UE attempts to camp on any one of the CCs belonging to the same frequency band as the CC at the start of the RA procedure among the CCs excluding the CC at the time of the RA procedure failure. You may do it.

In CCs belonging to the same frequency band, the radio wave propagation environment is considered to be almost the same because the frequencies are close to each other. Therefore, the reception quality in CCs belonging to the same frequency band is considered to be almost the same. Also, the area coverage of CCs belonging to the same frequency band is considered to be almost the same.

Therefore, it is possible to reliably camp on by trying to camp on another CC belonging to the same frequency band as the CC where the UE was camping on. For this reason, the control delay time can be reduced, and further, the power consumption of the UE can be reduced. Moreover, even if the area coverage differs for each frequency band, by applying this method, it is possible to reliably camp on when the RA procedure fails.

As another method, a base station (cell) disclosed in the first modification 3 configures a subset with CCs that can be camp-on at the time of RRC_IDLE among CCs targeted for carrier aggregation, and the UE You may make it try camping on any one of the CCs.

By doing so, in addition to the above-described effects, it is possible to obtain the effects described in the third modification of the first embodiment.

Similarly, as disclosed in the first modification 3 of the first embodiment, a subset is composed of CCs that can be camp-on at the time of RRC_IDLE among CCs to be subjected to carrier aggregation by the base station (cell). A subset may be configured by providing one CC in each frequency band.

By doing so, in addition to the above-described effects, it is possible to obtain the effects described in the third modification of the first embodiment.

In the above example, it has been shown that Msg1 to Msg4 are performed on one downlink CC and one uplink CC corresponding to it (pair band) in the RA procedure. For example, in FIG. 21, when the downlink CC that is camping on is CC # 3, Msg1 and Msg3 are performed on the uplink CC # 3 corresponding to the downlink CC # 3, and Msg2 and Msg4 are performed on the downlink CC # 3. . Also, it has been described that the downlink CC number and the corresponding uplink CC number may be different.

However, the RA procedure in the aggregation-compatible base station (cell) may be performed on a plurality of uplink CCs and a plurality of downlink CCs instead of being performed only on one downlink CC and uplink CC.

For example, Msg1 is transmitted by UL CC # 3 corresponding to downlink CC # 3 where the UE is camping on. The eNB that has received Msg1 transmits Msg2 using downlink CC # 3. Here, the scheduling information for Msg3 put on Msg2 is transmitted including information indicating that uplink CC # 4 is allocated. The UE that has received Msg2 transmits Msg3 using uplink CC # 4 based on the scheduling information. The eNB that has received Msg3 transmits Msg4 using downlink CC # 4. In this way, the RA procedure may be performed on a plurality of uplink CCs and a plurality of downlink CCs. The eNB can perform flexible control in consideration of the radio wave propagation environment of each CC and the load status of each CC, and can improve the throughput of the RA procedure and thus the throughput of the entire cell.

Further, the base station may use a pair band with the uplink CC used for transmission of Msg1 transmitted from the mobile terminal before the message for transmission of Msg2. As a result, it is possible to determine the CC to which Msg2 is transmitted in the mobile terminal without a new control signal, and the effect of effective utilization of radio resources can be obtained. In addition, since it is not necessary for the mobile terminal to blindly detect a plurality of CCs in order to receive Msg2, it is possible to obtain an effect of reducing the power consumption of the mobile terminal. The base station may use a pair band with the uplink CC used for transmission of Msg3 transmitted from the mobile terminal before the message for transmission of Msg4, and the same effect can be obtained.

Even in such a case, the CC that camps on when the RA procedure fails is disclosed in this embodiment, and the UE can camp on at the time of RRC_IDLE of the base station (cell) that was camping on at the start of the RA procedure. A method of trying to camp on any one of the CCs excluding the CC that failed the RA procedure among the CCs can be applied. As CCs for which the RA procedure has failed, one or a plurality of downlink CCs used until the RA procedure fails and one or a plurality of uplink CCs used until the RA procedure fails (downlink CCs corresponding to a pair band) And these CCs may be used.

For example, in the above example, the UE that failed to receive Msg4 and failed in the RA procedure is a CC excluding downlink CC # 3 and downlink CC # 4 corresponding to uplink CC # 4, and camp-on at RRC_IDLE. Try camp-on on any one of the possible CCs (CC # 1 or CC # 6).

This ensures that the UE can camp on other CCs in the cell when the RA procedure fails, and that the RA procedure can be reliably executed even if the RA procedure is performed after camp-on. . For this reason, the base station (cell) can perform flexible CC scheduling control, and further, can reduce control delay time and power consumption of the UE.

Modification 2 of Embodiment 2
In the second embodiment, the UE can select any one of the CCs that can camp on at the time of RRC_IDLE of the base station (cell) that was camped on at the start of the RA procedure, except the CC that failed the RA procedure. Although a method of trying to camp on two CCs has been disclosed, the RA procedure may not be excluded from CCs that have failed. That is, the UE may try to camp on any one of the CCs that can camp on at the time of RRC_IDLE of the base station (cell) that was camping on at the start of the RA procedure.

UE performs RA procedure after camping on a certain downlink CC. That is, it can be said that the reception quality of the downlink CC is good. Therefore, it is considered that failure in the RA procedure occurs mainly in the upstream. Then, UE is good also as a method of trying camp-on to any one CC among CC which can be camp-on at the time of RRC_IDLE of the base station (cell) which was camping on at the time of RA procedure start. By doing so, the UE can camp on the CC even if the CC that attempted to camp on was the CC that was camping on when the RA procedure failed. Therefore, after this, the radio wave propagation situation of the uplink CC changes, and when performing the RA procedure, it is considered that the radio wave propagation environment of the uplink CC becomes favorable and the RA procedure may be successful. Thus, first of all, by ensuring the camp-on when the RA procedure fails, it becomes possible to reduce the control delay time at the time of the camp-on and the power consumption of the UE. Then, it becomes possible to perform subsequent RA procedures.

Furthermore, in order to increase the possibility that the RA procedure after camp-on when the RA procedure fails can be executed reliably, in the uplink CC different from the uplink CC used for Msg1 and / or Msg3 when the RA procedure fails, Msg1 or / And Msg3 may be performed. In this way, even if the RA procedure fails, even if the RA procedure is performed again immediately after camp-on, the uplink CC different from the uplink CC used for the failed Msg1 and / or Msg3 is used. The radio wave propagation environment in communication is improved, and the possibility that the RA procedure can be reliably executed can be increased. Therefore, by using the method disclosed herein, it is possible to reduce the control delay time at the time of camp-on, reduce the power consumption of the UE, and to ensure that the subsequent RA procedure can be executed. , RRC_CONNECTED state transition control delay suppression, UE power consumption reduction, RA procedure contention reduction with other UEs, signaling capacity reduction as a system, interference with other cells and other UEs It becomes possible.

Also, the method disclosed in the second embodiment may be used as any one of the CCs that can be camp-on at the time of RRC_IDLE.

Further, as another method, camp-on may be attempted for the anchor carrier disclosed in the first modification 3 of the first embodiment. Since the system information is reported from the anchor carrier, the system information is not obtained after the camp-on, and the process of reselecting / selecting another CC is not entered. Accordingly, it is possible to reduce the control delay time and the power consumption of the UE.

In this way, in addition to the effects of the present modification, the effects described in the second embodiment and the first modification 3 can be obtained.

In this modification, the same effect as described above can be obtained by camping on a CC that can be camping on in the past.

Embodiment 3 FIG.
In 3GPP, an operation in which a downlink CC and an uplink CC are asymmetric when a carrier aggregation is performed in a base station (cell) that supports carrier aggregation is being studied. In such a case, it is considered that the UE that camps on one of the plurality of downlink CCs executes the RA procedure on the corresponding one uplink CC.

FIG. 18 shows an example of downlink CC / uplink CC asymmetric operation at the time of carrier aggregation. Reference numeral 1801 denotes a cell that supports carrier aggregation. Here, unlike FIG. 13, downlink CC and uplink CC are shown separately. Reference numerals 1802 to 1808 denote downlink CCs that perform carrier aggregation, and are sequentially referred to as CC # 1 to CC # 7. The horizontal axis indicates the downstream frequency. Reference numerals 1809 to 1812 denote uplink CCs for performing carrier aggregation, which are sequentially designated CC # A to CC # D. The horizontal axis indicates the uplink frequency. Reference numeral 1813 denotes a UE.

The uplink CC corresponding to downlink CC # 1 and downlink CC # 2 is uplink CC #A, the uplink CC corresponding to downlink CC # 3 is uplink CC #B, and the uplink CC corresponding to downlink CC # 4 is uplink An uplink CC corresponding to CC #C and corresponding to downlink CC # 5, downlink CC # 6, and downlink CC # 7 is uplink CC #D. Downlink CC # 1, downlink CC # 2 and uplink CC # A corresponding to them are asymmetrical. Similarly, downlink CC # 5, downlink CC # 6, downlink CC # 7, and uplink CC # D corresponding to them are asymmetrical operations. Thus, in asymmetric operation, one uplink CC corresponds to one or a plurality of downlink CCs (becomes a pair band).

When the RA procedure is executed in the asymmetric operation, the signaling shown in FIG. 17 is performed. The uplink signaling Msg1 and Msg3 correspond to the downlink CC with respect to one or a plurality of downlink CCs. In one uplink CC that performs (pair band), it is transmitted from the UE to the eNB using radio resources.

For example, the UE camping on the downlink CC # 1 transmits Msg1 and Msg3 using the radio resource (RB # 1 (1814)) of the uplink CC # A. The UE camping on the downlink CC # 2 transmits Msg1 and Msg3 using the radio resource (RB # 2 (1815)) of the uplink CC #A. Msg1 and Msg3 are multiplexed for each UE on the uplink CC # A.

Msg2 and Msg4 are transmitted from the eNB to the UE on the downlink CC # 1 for the UE camping on the downlink CC # 1 and on the downlink CC # 2 for the UE camping on the downlink CC # 2, respectively. The In transmission of Msg1 and Msg3, time division multiplexing, frequency division multiplexing, code division multiplexing, and the like are conceivable as multiplexing methods for each UE on the uplink CC # A.

As described above, in the asymmetric operation, when the RA procedure is performed and fails in the middle, application of the conventional method causes the problem described in the second embodiment.

Therefore, in a base station (cell) that supports carrier aggregation, a new effective method is required for determining a cell where the UE camps on when the RA procedure fails.

In order to solve these problems, the method disclosed in the second embodiment may be applied.

However, in the asymmetric operation, when the method disclosed in the second embodiment is applied as a method of determining a downlink CC to camp on when an RA procedure is performed and fails in the middle, the following problem occurs.

For example, as a method disclosed in the second embodiment, the UE is a CC that excludes CCs that failed the RA procedure from among CCs that can be camped on at the RRC_IDLE of the base station (cell) that was camping on at the start of the RA procedure. Try to camp on any one of the CCs.

For example, as shown in FIG. 18, it is assumed that the UE (1813) camps on the downlink CC # 2 (1803). Downlink CC # 1 (1802), downlink CC # 2 (1803) and the corresponding uplink CC # A (1809) are asymmetrical operations. When the UE executes the RA procedure, in the radio resource (RB # 2 (1815)) of the uplink CC # A (1809) corresponding to the downlink CC # 2 (1803) that is camping on, the UE is a base station (cell ) Msg1 is transmitted. Thereafter, Msg2 to Msg4 are communicated between the UE (1813) and the base station (cell) (1801) by the downlink CC # 2 (1803) and the corresponding uplink CC # A (1815). If the UE receives Msg4, the RA procedure is successful. However, if the RA procedure (Msg1 to Mag4) fails in the middle of the RA procedure, the UE can download a downlink CC (for example, downlink CC) that can be camp-on at the time of RRC_IDLE of the base station (cell) (1801) that was camping on at the start of the RA procedure. # 1 (1802) to downlink CC # 7 (1808)), and attempts to camp on any one of the downlink CCs except the downlink CC # 2 (1803) that failed the RA procedure. Like that. Here, downlink CC # 1 (1802) and downlink CC # 3 (1804) to downlink CC # 7 (1808) correspond. At this time, it is assumed that the UE attempts to camp on downlink CC # 1 (1802). Since the CC is in the same cell as the base station (cell) (1801) selected when executing the RA procedure, it is determined that the UE is likely to camp on CC # 1 (1802). Therefore, the UE camps on the downlink CC # 1 (1802) when the RA procedure fails.

However, in this case, there is a higher possibility that another RA procedure will fail. For example, when the RA procedure is executed again, the UE uses Msg1 as a base station (cell) (cell) (in radio resources (RB # 1 (1814)) of uplink CC # A (1809) corresponding to downlink CC # 1 (1802). 1801). Since the UE has failed the RA procedure in uplink CC # A (1809), there is a high possibility that this transmission will also fail. Furthermore, even if the base station (cell) has successfully received Msg1, the UE also receives Msg3 after receiving Mag2 in the uplink CC # A (1809) corresponding to downlink CC # 1 (1802). ) Must be sent to. Since the RA procedure has failed in the uplink CC # A (1809), there is a high possibility that this transmission will also fail. Thus, the possibility of failure in the middle of another RA procedure becomes higher.

The UE that has failed the RA procedure again must search for a CC to camp on again according to the method disclosed in the second embodiment. Since camping on CC # 1 (1802) has been performed once, when the RA procedure fails again, there is a case where camping on CC # 2 (1803) is attempted again. In such a case, when performing another RA procedure, the uplink CC # A (1809) is used. Therefore, there is a high possibility that this RA procedure also fails. Further, when the number of downlink CCs corresponding to the uplink CCs becomes large, the possibility that the failure of the RA procedure is repeated increases.

As described above, simply applying the method disclosed in the second embodiment may cause a situation where the RA procedure fails repeatedly. As a result, it takes a long time to start data communication between the UE, the base station (cell), and the network, and in some cases, communication becomes impossible. In addition, since the UE has to repeat the RA procedure many times, the power consumption increases.

Therefore, a new and effective method is required in determining the cell and CC to camp on when the RA procedure fails.

In order to solve the above-described problems, in this embodiment, the UE has failed in the RA procedure among the CCs that can be camp-on at the time of RRC_IDLE of the base station (cell) that was camp-on at the start of the RA procedure. Camp-on is attempted to any one of the CCs excluding the downlink CC corresponding to the CC.

FIG. 22 shows a conceptual diagram of a CC that camps on when an RA procedure fails in downlink CC / uplink CC asymmetric operation. In FIG. 22, the same reference numerals as those in FIG. 18 indicate the same or corresponding parts, and the description of the same reference numerals will be omitted.

For example, as shown in FIG. 18, it is assumed that the UE (1813) camps on the downlink CC # 2 (1803). In the uplink CC # A (1809) corresponding to the downlink CC # 2 (1803) in which the UE executes the RA procedure, the UE transmits Msg1 to the base station (cell), and Msg2 to Msg4 Communication is performed between the UE and the base station (cell) by downlink CC # 2 (1803) and uplink CC # A (1809) corresponding thereto. When the RA procedure (Msg1 to Mag4) fails in the middle of the procedure, as shown in FIG. 22, the UE can download a downlink CC that can be camp-on at the time of RRC_IDLE of the base station (cell) (1801) that has been camp-on at the start of the RA procedure. Among downlink CCs # 1 (1802) to downlink CCs # 7 (1808), for example, corresponding to downlink CC # 2 (1803) that failed in the RA procedure, and uplink CC #A (1809) The camp-on is attempted on any one of the downlink CCs other than the CCs excluding the downlink CC # 1 (1802) here. Here, downlink CC # 3 (1804) to downlink CC # 7 (1808) correspond. Here, for example, it is assumed that the UE attempts to camp on downlink CC # 3 (1804).

Since it is a CC in the same cell as the base station (cell) (1801) selected when executing the RA procedure, there is a high possibility that the UE can camp on CC # 3 (1804). Therefore, the UE can reliably execute camp-on when the RA procedure fails.

Also, when the UE camp-on to the downlink CC # 3 (1804) executes the RA procedure again, the uplink CC different from the uplink CC #A (1809) used at the time of the failure of the RA procedure earlier, here the uplink CC Since the RA procedure is performed again at CC # B (1810), there is no failure during the RA procedure. This is because the uplink CC # A and the uplink CC # B have different carrier frequencies, so that the radio wave propagation environment may be different. Thereby, it is possible to avoid the failure of the RA procedure. Therefore, the delay time of the transition control to the RRC_CONNECTED state is reduced, the power consumption of the UE is reduced, the contention of the RA procedure with another UE is reduced, the signaling capacity as a system is reduced, and the interference to other cells and other UEs Can be suppressed. Also, when the RA procedure execution permission limit time is set by a timer or the like, when the RA procedure is repeated for a long time and the timer is exceeded, communication between the UE and the base station (cell) and the network becomes impossible. However, this situation can be avoided. Therefore, the throughput of the base station or the entire system can be improved.

The sequence example when the RA procedure fails may be the same as in FIG. In addition, the determination method of the cell and CC to attempt camp on is as follows. ST2603 in FIG. 26 is a downlink CC excluding the downlink CC corresponding to the uplink CC that can camp on at the time of RRC_IDLE and the RA procedure failed. Of these, a change may be made so as to determine whether there is a downlink CC that has not attempted camp-on. More specifically, the CCs of ST2601, ST2604 to ST2609 may be changed to downlink CCs.

In ST2603, the UE needs information on which downlink CC corresponds to the uplink CC that failed the RA procedure. Information about which downlink CC corresponds to the uplink CC (downlink CC / uplink CC pair band information) may be reported from the base station (cell) to the UE as system information. In ST2502 after ST2501 in FIG. 25, the UE may receive the system information broadcasted on the downlink CC that first camps on the base station (cell).

Also, the method disclosed in the second embodiment may be used as any one of the CCs that can be camp-on at the time of RRC_IDLE.

Further, as another method, camp-on may be attempted for the anchor carrier disclosed in the first modification 3 of the first embodiment. Since the system information is reported from the anchor carrier, the system information is not obtained after the camp-on, and the process of reselecting / selecting another CC is not entered. Accordingly, it is possible to reduce the control delay time and the power consumption of the UE.

By doing so, in addition to the effects of the present embodiment, it is possible to obtain the effects described in the second embodiment and the first modification 3 of the first embodiment.

As one of the methods disclosed in the second embodiment described above, a subset is composed of CCs that can be camp-on at the time of RRC_IDLE among CCs to be subjected to carrier aggregation by the base station (cell). It was shown that a subset may be configured by providing one for each frequency band.

As another method, a subset may be configured by providing one CC that can be camp-on from one or a plurality of downlink CCs corresponding to the uplink CC of the base station (cell).

When the RA procedure fails, try to camp on other downlink CCs in the subset.

As described above, when the RA procedure fails, a cell attempting to camp on can be selected from the downlink CC in the subset, so that it is possible to reduce the control delay time and the power consumption of the UE.

In the above-described method, the UE receives the downlink CC information corresponding to the uplink CC at the time of RA procedure failure (paired band) by the broadcast information of the downlink CC of the base station (cell) that first camps on the UE. It was decided.

As another method, the UE stores uplink CC information at the time of RA procedure execution, and when the RA procedure fails, once selects one of the downlink CCs that can be camp-on at the time of RRC_IDLE, and then selects the downlink CC. To receive corresponding uplink CC information. If the uplink CC information is the same as the stored uplink CC information at the time of RA procedure failure, another downlink CC is selected and the corresponding uplink CC information is obtained by receiving the downlink CC broadcast information again. . If the uplink CC information is different from the stored uplink CC information at the time of RA procedure failure, camp on is performed on the downlink CC.

By doing so, in addition to the effect of the present embodiment, the effect of reducing the amount of information broadcast from each CC can be obtained.

Also, if the base station (cell) that was camping on at the time of executing the RA procedure has one downlink CC that can be camping on at the time of RRC_IDLE, it may be configured to try camping on another cell.

Also, if the base station (cell) that was camping on when performing the RA procedure is linked to all the same uplink CCs that can be camped on at the time of RRC_IDLE, try to camp on another cell. It ’s good if you keep it.

By doing this, even if there is no other downlink CC that can be camp-on when the RA procedure fails, or there is only an uplink CC that is highly likely to fail again, another base station (cell) Camping can be enabled, and the possibility of performing another RA procedure can be increased.

In the present embodiment, the case of asymmetric operation in which one uplink CC corresponds to one or a plurality of downlink CCs (becomes a pair band) has been described. The method disclosed in the present embodiment is not limited to this, and can also be applied to the case of asymmetric operation in which one or a plurality of uplink CCs correspond to one downlink CC (becomes a pair band). When there is an uplink CC that has not failed the RA procedure in one or a plurality of uplink CCs that are pair-band with one downlink CC, when the RA procedure fails, the uplink CC and the pair band that have failed the RA procedure, Try to camp on the downstream CC. This makes it possible to ensure camp-on. The UE performs the RA procedure after camping on a certain downlink CC. That is, it can be said that the reception quality of the downlink CC is good. Therefore, the failure in the RA procedure is considered to occur mainly in the upstream.

When the RA procedure is executed again, the RA procedure is executed on any one of the CCs on the uplink CC that has not failed the RA procedure among the uplink CCs paired with the camp-on downlink CC. Just keep it. As a result, it is possible to avoid the occurrence of repeated RA procedure failures, and to obtain the same effect as in the present embodiment.

In the second embodiment and the third embodiment, the case where Msg1 to Msg4 are executed as the RA procedure has been described. However, the present invention is not limited to this, as long as message transmission / reception is performed using the downlink CC and the uplink CC. The methods disclosed in Embodiment 2 and Embodiment 3 can be applied.

In the present invention, the first embodiment, the first modification of the first embodiment, the second modification of the first embodiment, the third modification of the first embodiment, the second embodiment, the first modification of the second embodiment, Although Embodiment 3 has been described individually, these may be used in combination.

In the present invention, the CC that the UE camps on at the time of RRC_IDLE is one, but the UE may camp on a plurality of CCs simultaneously. A plurality of CCs may be used instead of any one CC. Also in this case, the present invention can be applied and the same effect can be obtained.

If the UE is camping on multiple CCs at the time of RRC_IDLE, the RA procedure when transitioning to RRC_CONNECTED is performed on any one of the multiple CCs on which the UE is camping on. good. Since the UE can select a CC with good reception quality, it is possible to reduce failures during the RA procedure.

In the present invention, the LTE system (E-UTRAN) and the LTE advanced (LTE-Advanced) system are mainly described, but the present invention can also be applied to a W-CDMA system (UTRAN, UMTS).

Claims (11)

1. Wireless communication between a mobile terminal corresponding to the partial carrier or a mobile terminal corresponding to the aggregated carrier and a base station using a plurality of partial carriers individually or using an aggregate carrier obtained by collecting the plurality of partial carriers A mobile communication system
   The mobile terminal camps on any one of the partial carriers included in the aggregate carrier when the mobile terminal and the base station corresponding to the aggregate carrier perform radio communication using the aggregate carrier. Mobile communication system.
2. When the wireless communication between the mobile terminal and the base station transitions from a connected state to a standby state, the mobile terminal camps on any one of the partial carriers included in the aggregated carrier. The mobile communication system according to claim 1.
3. The mobile communication system according to claim 1, wherein the mobile terminal camps on any one of the partial carriers included in a set of partial carriers having common physical characteristics.
4. The mobile communication system according to claim 1, wherein the mobile terminal camps on one partial carrier designated from outside.
5. The mobile communication system according to claim 2, wherein the mobile terminal camps on a partial carrier that was camp-onable in a previous standby state.
6. 2. The mobile communication system according to claim 1, wherein a partial carrier to be monitored when the mobile terminal monitors the system information transmitted by the base station is common in the connected state and the standby state.
7. The mobile communication system according to claim 1, wherein, when connection of a random access channel fails, the mobile terminal camps on any one of the partial carriers included in the aggregate carrier.
8. 8. The mobile communication system according to claim 7, wherein the mobile terminal camps on one partial carrier excluding the partial carrier that is included in the aggregated carrier and failed to be connected.
9. 8. The mobile communication system according to claim 7, wherein the mobile terminal camps on a partial carrier that was camp-onable in a previous standby state.
10. The mobile communication system according to claim 1, wherein the mobile terminal camps on a partial carrier that can be camped on in the past.
11. When performing up / down asymmetric communication using one partial carrier in one communication direction in the uplink or downlink direction of wireless communication and using two or more partial carriers in the other communication direction corresponding to this, one communication When a random access channel connection fails in one direction and camps on one partial carrier in the other communication direction, the one partial carrier to be camped on is a partial carrier that fails to connect in one communication direction. 2. The mobile communication system according to claim 1, wherein the mobile communication system is selected from ones excluding two or more partial carriers in the other corresponding communication direction.

Images