WO2011099509A1 - Mobile communication system - Google Patents

Abstract

Provided is a mobile communication system wherein it is possible to operate a plurality of local area range nodes and to flexibly arrange same. A value in which the communication quality of the backhaul link of a serving cell is considered is used as the measurement start threshold value (S_intrasearch_total) for cell reselection. In step (ST1401), a mobile terminal (71) compares the measurement start threshold value (S_intrasearch_total) with the reception power measurement value (Sx) of the serving cell. If Sx is equal to or less than S_intrasearch_total, it is determined that the reception quality of the serving cell including the communication quality of the backhaul link is bad, and in step (ST1302), the measurement for cell reselection is started.

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. In addition, by adding a packet transmission channel (High-Speed-Downlink Shared Channel: HS-DSCH) to the downlink (dedicated data channel, dedicated control channel), further speeding up data transmission using the downlink 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.

Further, in 3GPP, as a communication method different from W-CDMA, the entire system configuration including a long term evolution (LTE) and a core network (also simply referred to as a network) is used for the radio section. A new communication method called Evolution (System Architecture Evolution: SAE) is being studied.

In LTE, the access method, wireless channel configuration, and protocol are completely different from the current W-CDMA (HSDPA / HSUPA). For example, W-CDMA uses code division multiple access (Code-Division-Multiple-Access), whereas LTE uses 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 5 MHz for W-CDMA, whereas the bandwidth can be selected for each base station from 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz in LTE. 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 (General Packet Radio Service: GPRS). Is done. Therefore, in order to distinguish from the W-CDMA communication system, in the LTE communication system, a base station (Base station) that communicates with a mobile terminal (User Equipment: UE) is referred to as an eNB (E-UTRAN NodeB). A base station controller (Radio Network Controller) that exchanges control data and user data with the base station is called EPC (Evolved Packet Core) or aGW (Access Gateway). In this 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 (Chapter 4.6.1) describes the current decisions regarding the overall architecture of the LTE system in 3GPP. The overall architecture 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 the mobile terminal 101 such as RRC (Radio Resource Control) and a user plane such as PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), MAC (Medium Access Control), PHY (Physical Layer) E-UTRAN (Evolved１０２Universal Terrestrial Radio Access) is composed of one or more base stations 102.

The base station 102 performs scheduling and transmission of a paging signal (also called paging signaling or paging message) notified from an MME (Mobility Management Entity) 103. 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, the base station 102 is connected to an MME (Mobility Management Entity) 103 via an S1_MME interface, and is connected to an S-GW (Serving Gateway) 104 via an S1_U interface.

The MME 103 distributes a paging signal to a plurality or a single base station 102. Further, the MME 103 performs mobility control (Mobility control) in a standby state (Idle State). The MME 103 manages a tracking area (Tracking Area) list when the mobile terminal is in a standby state and an active state (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 (Mobility Anchor Point) during handover between base stations. The EPC further includes 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, a mobile terminal has an RRC connection (connection), can transmit and receive data to and from the network, and performs handover (Handover: HO), measurement of a neighbor cell (Neighbour cell), and the like.

Non-Patent Document 1 (Chapter 5) describes the current decisions regarding the frame configuration in the LTE system in 3GPP, 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 (Chapter 5) describes the current decisions regarding the channel configuration in the LTE system in 3GPP. It is assumed that the CSG cell (ClosedｎSubscriber Group に お い て cell) uses the same channel configuration as the non-CSG cell. A physical channel 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 (PBCH) 401 is a downlink channel transmitted from the base station 102 to the mobile terminal 101. A 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 (Physical-Control-Format-Indicator-Channel: PCFICH) 402 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 (Physical Downlink Control Channel: PDCCH) 403 is a downlink channel transmitted from the base station 102 to the mobile terminal 101. The PDCCH is resource allocation, HARQ information regarding DL-SCH (a downlink shared channel that is one of the transport channels shown in FIG. 5 described later), and PCH (one of the transport channels shown in FIG. 5). A certain paging channel). The PDCCH carries an uplink scheduling grant (Uplink Scheduling Grant). The PDCCH carries Ack (Acknowledgement) / Nack (Negative Acknowledgment) which is a response signal for uplink transmission. The PDCCH is also called an L1 / L2 control signal.

A physical downlink shared channel (PDSCH) 404 is a downlink channel transmitted from the base station 102 to the mobile terminal 101. In PDSCH, DL-SCH (downlink shared channel) which is a transport channel and PCH which is a transport channel are mapped. A physical multicast channel (Physical Multicast Channel: PMCH) 405 is a downlink channel transmitted from the base station 102 to the mobile terminal 101. The PMCH is mapped with an MCH (multicast channel) which is a transport channel.

A physical uplink control channel (Physical Uplink Control Channel: PUCCH) 406 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 (SR). A physical uplink shared channel (Physical Uplink Shared Channel: PUSCH) 407 is an uplink channel transmitted from the mobile terminal 101 to the base station 102. The 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 (Physical Hybrid ARQ Indicator Channel: PHICH) 408 is a downlink channel transmitted from the base station 102 to the mobile terminal 101. PHICH carries Ack / Nack which is a response to uplink transmission. A physical random access channel (Physical Random Access Channel: PRACH) 409 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 received power of a reference symbol (Reference Symbol Received Power: RSRP).

The transport channel described in Non-Patent Document 1 (Chapter 5) will be described with reference to FIG. FIG. 5 is an explanatory diagram for explaining a transport channel used in an LTE communication system. FIG. 5A shows the 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. The broadcast channel (Broadcast Channel: BCH) is broadcast to the entire base station (cell) regarding the downlink transport channel. The BCH is mapped to the physical broadcast channel (PBCH).

Retransmission control by HARQ (Hybrid ARQ) is applied to the downlink shared channel (DL-SCH). The DL-SCH can be broadcast to the entire base station (cell). DL-SCH supports dynamic or semi-static resource allocation. Quasi-static resource allocation is also referred to as persistent scheduling. DL-SCH supports DRX (Discontinuous reception) of a mobile terminal in order to reduce power consumption of the mobile terminal. The DL-SCH is mapped to the physical downlink shared channel (PDSCH).

The Paging Channel (PCH) supports DRX of the mobile terminal in order to enable low power consumption of the mobile terminal. The PCH is required to be broadcast to the entire base station (cell). The PCH is mapped to a physical resource such as a physical downlink shared channel (PDSCH) that can be dynamically used for traffic, 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 broadcast to the entire base station (cell). The MCH supports SFN combining of MBMS services (MTCH and MCCH) in multi-cell transmission. The MCH 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). UL-SCH supports dynamic or semi-static resource allocation. UL-SCH is mapped to a physical uplink shared channel (PUSCH). The random access channel (Random Access Channel: RACH) shown in FIG. 5B is limited to control information. RACH is at risk of collision. The RACH is mapped to a physical random access channel (PRACH).

HARQ will be described. HARQ is a technique for improving the communication quality of a transmission path by combining automatic retransmission (AutomaticAutoRepeat reQuest) and error correction (Forward Error Correction). There is also an advantage that error correction functions effectively by retransmission even for transmission paths in which communication quality changes. In particular, further quality improvement can be obtained by combining the initial transmission reception result and the retransmission reception result upon retransmission.

An example of the retransmission method will be described. When the reception side cannot decode the received data correctly, in other words, when a CRC (Cyclic Redundancy Check) error occurs (CRC = NG), “Nack” is transmitted from the reception side to the transmission side. The transmitting side that has received “Nack” retransmits the data. When the reception side can correctly decode the received data, in other words, 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.

As an example of the HARQ method, there 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. This means that even if there is an error in the initial transmission data, the data is partially accurate, and the data is transmitted with higher accuracy by combining the correct initial transmission data and the retransmission data. It is based on the idea that it can be done. Another example of the HARQ method is IR (Incremental Redundancy). IR is to increase redundancy, and by transmitting parity bits in retransmission, the redundancy is increased in combination with initial transmission, and the quality is improved by an error correction function.

The logical channel described in Non-Patent Document 1 (Chapter 6) 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: BCCH) 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).

The 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 common control channel (Common Control Channel: CCCH) is a channel for transmission control information between the mobile terminal and the base station. CCCH is used when the mobile terminal does not have an RRC connection with the network. In the downlink direction, 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. The MCCH is used for transmission of MBMS control information for one or several MTCHs from the network to the mobile terminal. MCCH is used only for mobile terminals that are receiving MBMS. The MCCH is mapped to the 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 for transmitting 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 individual mobile terminals for transmitting user information. DTCH exists for both uplink and downlink. The DTCH is mapped to the uplink shared channel (UL-SCH) in the uplink, and is mapped to the downlink shared channel (DL-SCH) in the downlink.

The multicast traffic channel (MTCH) is a downlink channel for transmitting traffic data from the network to the mobile terminal. MTCH is a channel used only for a mobile terminal that is receiving MBMS. The MTCH is mapped to a downlink shared channel (DL-SCH) or a multicast channel (MCH).

GCI is a global cell identifier (Global Cell Identity). In LTE and UMTS (Universal Mobile Telecommunication System), CSG cells (Closed Subscriber Group Cell) are introduced. CSG will be described below (see Non-Patent Document 3, Chapter 3.1). CSG (Closed Subscriber Group) is a cell in which an operator identifies an available subscriber (a cell for a specific subscriber). The identified subscribers are allowed to access one or more E-UTRAN cells of the PLMN (Public Land Mobile Mobile Network). 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 in advance and permitted access the CSG cell using the CSG-ID as access permission information.

The CSG-ID is broadcast by the CSG cell or 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. 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 (CSG white list) is a list stored in a USIM (Universal Subscriber Identity Module) in which all CSG IDs of CSG cells to which the subscriber belongs are recorded. The CSG white list may be referred to as an allowed CSG list (Allowed CSG ID List).

“Suitable cell” will be described below (see Non-Patent Document 3, Chapter 4.3). A “suitable cell” is a cell that the UE camps on to receive normal service. Such a cell shall satisfy the following conditions:

(1) The cell is a selected PLMN or a registered PLMN, or a part of the PLMN in the “Equivalent PLMN list”.

(2) In the latest information provided by NAS (Non-Access Stratum), the following conditions must be satisfied. (A) The cell is not a barred cell. (B) And not a part of the “Forbidden LAs” list, but a part of at least one 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 CSG cell according to system information (SI). For the identified cell, the CSG-ID shall be part of the UE's “CSG WhiteList” (included in the UE's CSG WhiteList).

“Acceptable cell” will be described below (see Non-Patent Document 3, Chapter 4.3). This is a cell where the UE camps on in order to receive a limited service (emergency call). Such a cell shall satisfy 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 means that 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. The HNB in UTRAN or the HeNB in E-UTRAN is a base station for, for example, home, corporate, and commercial access services. Non-Patent Document 4 discloses three different modes of access to HeNB and HNB. Specifically, an open access mode (Open access mode), a closed access mode (Closed access mode), and a hybrid access mode (Hybrid access mode).

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, a cell in hybrid access mode (also referred to as a hybrid cell) is a cell that supports both an open access mode and a closed access mode.

3GPP discusses dividing all PCI (Physical Cell Identity) into a CSG cell and a non-CSG cell (referred to as PCI split) (see 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. Non-Patent Document 5 discloses a basic operation of a mobile terminal using PCI split. 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.

In 3GPP, the Long Term Evolution Advanced (LTE-A) standard is being developed as Release 10 (see Non-Patent Document 6 and Non-Patent Document 7).

In the LTE-A system, in order to obtain a high communication speed, a high throughput at the cell edge, a new coverage area, etc., it is considered to support a relay (Relay: relay node (RN)). The relay node is wirelessly connected to the radio access network via a donor cell (Donor cell; Donor eNB; DeNB). Within the donor cell, the network (NW) to relay link shares the same frequency band as the network to UE link. In this case, a Release 8 UE can also be connected to the donor cell. A link between the donor cell and the relay node is referred to as a backhaul link, and a link between the relay node and the UE is referred to as an access link.

As a backhaul link multiplexing method in FDD (Frequency Division Duplex), transmission from DeNB to RN is performed in a downlink (DL) frequency band, and transmission from RN to DeNB is performed in an uplink (UL) frequency band. As a resource division method in the relay, a link from DeNB to RN and a link from RN to UE are time-division multiplexed in one frequency band, and a link from RN to DeNB and a link from UE to RN are also one frequency band. Is time-division multiplexed. By doing so, it is possible to prevent the relay transmission from interfering with the reception of the own relay in the relay.

Heterogeneous Networks (HetNets) has been added as one of the technologies studied in LTE-A (see Non-Patent Document 8). Heterogeneous networks are networks in which one or more local area range nodes such as HeNBs and relay nodes are incorporated in a normal eNB (macro cell).

In heterogeneous networks, there is a problem that cell selection to the cell with the strongest reception power is not always optimal. Further, although it may be better not to connect to a cell with poor communication quality of the backhaul link, the conventional cell selection has a problem that the communication quality of the backhaul link is not taken into consideration. Further, in the heterogeneous network, there is a problem that the optimum cell in the downlink is different from the optimum cell in the uplink. In the conventional cell selection, since cell selection to the optimum cell is performed in the downlink, no consideration is given to the uplink. These problems occur not only in cell selection but also in selection or change of a serving cell such as cell reselection or handover.

These problems lead to problems such as increased interference between UEs or nodes in a heterogeneous network and reduced capacity of each node. In order to enable the operation of a huge number of local area range nodes in the future and their flexible arrangement, it is important to solve these problems.

Non-Patent Document 8 proposes that cell selection considering the quality of the backhaul link, measurement of a cell with weak received power, and a trigger mechanism are necessary to solve these problems. Non-Patent Document 9 discloses a cell selection method considering the communication quality of a relay node backhaul link. Non-Patent Document 10 discloses that an uplink and a downlink are independently connected to different cells.

Non-Patent Document 8 proposes that cell selection taking into account the quality of the backhaul link, measurement of a cell with weak reception power, and a trigger mechanism are necessary to solve the above-described problems. However, these specific methods are not described at all.

Non-Patent Document 9 describes that the relay node broadcasts the quality of the backhaul link, and the UE performs cell selection in consideration thereof. However, there is no disclosure of a specific method by which the quality of the backhaul link is taken into consideration.

Non-Patent Document 10 discloses that an uplink and a downlink are connected independently to different cells, but this specific method is not described at all. In addition, connecting to different cells in the uplink and the downlink is considered to make communication control very complicated because the UE has a plurality of serving cells.

An object of the present invention is to provide a mobile communication system that enables operation of a huge number of local area range nodes and their flexible arrangement.

The mobile communication system of the present invention includes a plurality of base station devices connected to a core network and mobile terminal devices capable of wireless communication with each of the base station devices, and a communicable range of the plurality of base station devices A mobile communication system in which at least a part of a plurality of cells overlap, wherein the mobile terminal apparatus receives a signal reception quality from a base station apparatus in each cell, and between the base station apparatus and the core network. The cell of the base station apparatus to be communicated is selected from the plurality of cells based on selection information including the communication quality of the communication line.

The mobile communication system of the present invention includes a plurality of base station devices, a mobile terminal device capable of wireless communication with each of the base station devices, at least one base station device of the plurality of base station devices, and the mobile A mobile communication system in which at least a part of a plurality of cells that are communicable ranges of the plurality of base station devices overlap each other, including a relay device that relays wireless communication with the terminal device The apparatus is configured to select from among the plurality of cells based on selection information including reception quality of a signal from the base station apparatus in each cell and communication quality of a communication line between the base station apparatus and the relay apparatus. The base station apparatus cell to be communicated is selected.

The mobile communication system of the present invention includes a plurality of base station devices and a mobile terminal device capable of wireless communication with each of the base station devices, and a plurality of cells that are communicable ranges of the plurality of base station devices. In which at least a portion of the mobile terminal apparatus overlaps the reception quality of the signal from the base station apparatus in each cell and the uplink communication line from the mobile terminal apparatus to the base station apparatus in each cell. A cell of a base station apparatus to be a communication target is selected from the plurality of cells based on selection information including a state.

Further, according to the mobile communication system of the present invention, the mobile terminal apparatus selects the reception quality of the signal from the base station apparatus in each cell and the communication quality of the communication line between the base station apparatus and the core network. Based on the information, a cell of the base station apparatus to be communicated is selected from a plurality of cells. Thereby, in addition to the reception quality of each cell, the communication quality of the communication line between the base station apparatus and the core network can be taken into consideration, and the cell of the base station apparatus to be communicated can be selected. Therefore, for example, since it is possible to improve the interference problem and the capacity problem in heterogeneous networks, it is possible to operate a large number of local area range nodes and flexibly arrange them.

According to the mobile communication system of the present invention, the mobile terminal apparatus selects information including the reception quality of the signal from the base station apparatus in each cell and the communication quality of the communication line between the base station apparatus and the relay apparatus. Based on the above, a cell of a base station apparatus to be a communication target is selected from a plurality of cells. Thereby, in addition to the reception quality of each cell, the communication quality of the communication line between the base station apparatus and the relay apparatus can be taken into consideration, and the cell of the base station apparatus to be communicated can be selected. Therefore, for example, since it is possible to improve the interference problem and the capacity problem in heterogeneous networks, it is possible to operate a large number of local area range nodes and flexibly arrange them.

Further, according to the mobile communication system of the present invention, the mobile terminal apparatus determines the reception quality of the signal from the base station apparatus in each cell and the state of the uplink communication line from the mobile terminal apparatus to the base station apparatus in each cell. Based on the selection information included, a cell of a base station apparatus to be communicated is selected from a plurality of cells. Thereby, in addition to the reception quality of each cell, the state of the uplink communication line of each cell can be taken into consideration, and the cell of the base station apparatus to be communicated can be selected. Therefore, for example, since it is possible to improve the interference problem and the capacity problem in heterogeneous networks, it is possible to operate a large number of local area range nodes and flexibly arrange them.

The objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

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 of the LTE system currently discussed in 3GPP. It is a block diagram which shows the structure of the mobile terminal (mobile terminal 71 of FIG. 7) which concerns on this invention. It is a block diagram which shows the structure of the base station (base station 72 of FIG. 7) based on this invention. It is a block diagram which shows the structure of MME which concerns on this invention (MME part 73 of FIG. 7). It is a block diagram which shows the structure of HeNBGW74 shown in FIG. 7 which is HeNBGW which concerns on this invention. 5 is a flowchart illustrating an outline from a cell search to a standby operation performed by a mobile terminal (UE) in an LTE communication system. It is a flowchart which shows the process sequence of the celery selection of UE by the technique of a nonpatent literature 3. It is a flowchart which shows the process sequence of the celery selection which put the communication quality of the backhaul link of a serving cell in the threshold value for a measurement start for celery selection. It is a flowchart which shows the process procedure of the cell reselection which put the communication quality of the backhaul link of a serving cell in the measured value of the serving cell. It is a flowchart which shows the process sequence of the celery selection which provided the backhaul threshold value (start) as a threshold value for a measurement start for celery selection. It is a flowchart which shows the processing procedure of the cell reselection which put the communication quality of the backhaul link of each cell into the measured value of the cell at the time of cell ranking. It is a flowchart which shows the processing procedure of the cell reselection which performs a cell ranking in consideration of the reception quality of a backhaul link when there exists a cell whose reception quality is a certain value or more. It is a flowchart which shows the process sequence of the cell reselection which performs cell ranking in consideration of the reception quality of a cell, when the communication quality of a backhaul link has a certain value or more. It is a flowchart which shows the processing procedure of the celery selection which also considered the state of the uplink. It is a flowchart which shows the processing procedure of the celery selection which performs a cell ranking in consideration of a path loss, when there exists a cell whose reception quality is a certain value or more. It is an example of the flowchart which shows the processing procedure of the celery selection which combined the method disclosed in the modification 1 of Embodiment 1 of this invention. It is a flowchart which shows the process procedure of the cell selection of UE by the technique of a nonpatent literature 3. It is a flowchart which shows the process procedure of the cell selection which considered the communication quality and uplink state of the cell backhaul link which are disclosed by this Embodiment. FIG. 10 is a sequence diagram illustrating a normal HO processing procedure according to the technique of Non-Patent Document 1. It is a flowchart which shows an example of the selection procedure of the target cell by a serving cell. It is a flowchart which shows the communication procedure of the cell backhaul link disclosed in this Embodiment, and the process procedure of HO which considered the state of the uplink.

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), and GERAN BSS) are being studied, and a configuration as shown in FIG. 7 has been proposed for E-UTRAN (non-patent document). Reference 1 see Chapter 4.6.1.).

Referring to FIG. A mobile terminal device (hereinafter referred to as “mobile terminal” or “UE”) 71 is capable of wireless communication with a base station device (hereinafter referred to as “base station”) 72, and transmits and receives signals by wireless communication. The base station 72 is classified into an eNB 72-1 and a Home-eNB 72-2. The eNB 72-1 is connected to the MME, S-GW, or the MME / S-GW unit (hereinafter referred to as “MME unit”) 73 including the MME and the S-GW via the S1 interface. Control information is communicated between the two. The eNB 72-1 is connected to the core network via the MME unit 73. A plurality of MME units 73 may be connected to one eNB 72-1. The eNBs 72-1 are connected by the X2 interface, and control information is communicated between the eNBs 72-1.

The Home-eNB 72-2 is connected to the MME unit 73 via the S1 interface, and control information is communicated between the Home-eNB 72-2 and the MME unit 73. A plurality of Home-eNBs 72-2 are connected to one MME unit 73. Alternatively, the Home-eNB 72-2 is connected to the MME unit 73 via a HeNBGW (Home-eNB GateWay) 74. Home-eNB 72-2 and HeNBGW 74 are connected via an S1 interface, and HeNBGW 74 and MME unit 73 are connected via an S1 interface. The Home-eNB 72-2 is connected to the core network via the MME unit 73 or the MME unit 73 and the HeNBGW 74. One or a plurality of Home-eNBs 72-2 are connected to one HeNBGW 74, and information is communicated through the S1 interface. The HeNBGW 74 is connected to one or a plurality of MME units 73, and information is communicated through the S1 interface.

Furthermore, the following configurations are currently being studied in 3GPP. The X2 interface between Home-eNB 72-2 is not supported. From the MME unit 73, the HeNBGW 74 appears as an eNB 72-1. From the Home-eNB 72-2, the HeNBGW 74 appears as the MME unit 73. Regardless of whether or not the Home-eNB 72-2 is connected to the MME unit 73 via the HeNBGW 74, the interface between the Home-eNB 72-2 and the MME unit 73 is the same in the S1 interface. Mobility to the Home-eNB 72-2 or mobility from the Home-eNB 72-2 that spans a plurality of MME units 73 is not supported. Home-eNB 72-2 supports only one cell.

FIG. 8 is a block diagram showing a configuration of a mobile terminal (mobile terminal 71 in FIG. 7) according to the present invention. A transmission process of the mobile terminal 71 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 directly output from the transmission data buffer unit 803 to the modulation unit 805 without performing the encoding process. The data encoded by the encoder unit 804 is modulated by the modulation unit 805. The modulated data is converted into a baseband signal, and then output to the frequency conversion unit 806, where it is converted into a radio transmission frequency. Thereafter, a transmission signal is transmitted from the antenna 807 to the base station 72.

Also, the reception process of the mobile terminal 71 is executed as follows. A radio signal from the base station 72 is received by the antenna 807. The reception signal is converted from a radio reception frequency to a baseband signal by the frequency conversion unit 806, and demodulated by the demodulation unit 808. The demodulated data is passed to the decoder unit 809 and subjected to decoding processing such as error correction. 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 71 is controlled by the control unit 810. Therefore, the control unit 810 is connected to the respective units 801 to 809, which is omitted in FIG.

FIG. 9 is a block diagram showing the configuration of the base station (base station 72 in FIG. 7) according to the present invention. The transmission process of the base station 72 shown in FIG. 9 will be described. The EPC communication unit 901 transmits and receives data between the base station 72 and the EPC (MME unit 73, HeNBGW 74, etc.). The other base station communication unit 902 transmits / receives data to / from other base stations. Since the X2 interface between the Home-eNB 72-2 is a direction that is not supported, the Home-eNB 72-2 may not include the other base station communication unit 902. The EPC communication unit 901 and the other base station communication unit 902 exchange information with the protocol processing unit 903, respectively. Control data from the protocol processing unit 903 and user data and control data from the EPC communication unit 901 and the other base station communication unit 902 are stored in the transmission data buffer unit 904.

The data stored in the transmission data buffer unit 904 is transferred to the encoder unit 905 and subjected to encoding processing such as error correction. There may exist data that is directly output from the transmission data buffer unit 904 to the modulation unit 906 without performing the encoding process. The encoded data is subjected to modulation processing by the modulation unit 906. The modulated data is converted into a baseband signal, and then output to the frequency conversion unit 907 to be converted into a radio transmission frequency. Thereafter, a transmission signal is transmitted from the antenna 908 to one or a plurality of mobile terminals 71.

Further, the reception process of the base station 72 is executed as follows. Radio signals from one or a plurality of mobile terminals 71 are received by the antenna 908. The reception signal is converted from a radio reception frequency to a baseband signal by the frequency conversion unit 907, and demodulated by the demodulation unit 909. The demodulated data is transferred to the decoder unit 910 and subjected to decoding processing such as error correction. Of the decoded data, the control data is passed to the protocol processing unit 903 or the EPC communication unit 901 and the other base station communication unit 902, and the user data is passed to the EPC communication unit 901 and the other base station communication unit 902. A series of processing of the base station 72 is controlled by the control unit 911. Therefore, although not shown in FIG. 9, the control unit 911 is connected to the units 901 to 910.

The functions of Home-eNB 72-2 currently being discussed in 3GPP are shown below (see Non-Patent Document 1, Chapter 4.6.2). The Home-eNB 72-2 has the same function as the eNB 72-1. In addition, when connecting to the HeNBGW 74, the Home-eNB 72-2 has a function of finding an appropriate serving HeNBGW 74. The Home-eNB 72-2 is only connected to one HeNBGW 74. That is, in the case of connection with the HeNBGW 74, the Home-eNB 72-2 does not use the Flex function in the S1 interface. When the Home-eNB 72-2 is connected to one HeNBGW 74, the Home-eNB 72-2 is not simultaneously connected to another HeNBGW 74 or another MME unit 73.

The TAC and PLMN ID of the Home-eNB 72-2 are supported by the HeNBGW 74. When the Home-eNB 72-2 is connected to the HeNBGW 74, the selection of the MME unit 73 in “UE attachment” is performed by the HeNBGW 74 instead of the Home-eNB 72-2. Home-eNB 72-2 may be deployed without network planning. In this case, Home-eNB 72-2 is moved from one geographic region to another. Therefore, the Home-eNB 72-2 in this case needs to be connected to different HeNBGW 74 depending on the position.

FIG. 10 is a block diagram showing the configuration of the MME (MME unit 73 in FIG. 7) according to the present invention. The PDN GW communication unit 1001 transmits and receives data between the MME unit 73 and the PDN GW. The base station communication unit 1002 performs data transmission / reception between the MME unit 73 and the base station 72 through the S1 interface. If the data received from the PDN GW is user data, the user data is passed from the PDN GW communication unit 1001 to the base station communication unit 1002 via the user plane communication unit 1003 to one or a plurality of base stations 72. Sent. When the data received from the base station 72 is user data, the user data is passed from the base station communication unit 1002 to the PDN GW communication unit 1001 via the user plane communication unit 1003 and transmitted to the PDN GW.

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 transmits and receives data through an interface (IF) between the MME unit 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 a bearer of SAE (System Architecture) Evolution. The idle state mobility management unit 1005-3 manages mobility 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 Add, delete, update, search, and track area list (TA エ リ ア List) management.

The MME unit 73 initiates the paging protocol by transmitting a paging message to a cell belonging to a tracking area (tracking area: Tracking Area: TA) in which 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 unit 73.

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. Management related to these CSGs may be performed in other parts of the MME unit 73. A series of processing of the MME unit 73 is controlled by the control unit 1006. Therefore, although not shown in FIG. 10, the control unit 1006 is connected to the units 1001 to 1005.

The functions of MME currently being discussed in 3GPP are shown below (refer to Chapter 4.6.2 of Non-Patent Document 1). The MME performs access control of one or a plurality of mobile terminals of CSG (Closed Subscriber Groups). The MME accepts paging optimization as an option.

FIG. 11 is a block diagram showing a configuration of the HeNBGW 74 shown in FIG. 7 which is the HeNBGW according to the present invention. The EPC communication unit 1101 performs data transmission / reception between the HeNBGW 74 and the MME unit 73 through the S1 interface. The base station communication unit 1102 performs data transmission / reception between the HeNBGW 74 and the Home-eNB 72-2 via the S1 interface. The location processing unit 1103 performs a process of transmitting registration information and the like among the data from the MME unit 73 delivered via the EPC communication unit 1101 to the plurality of Home-eNBs 72-2. 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 FIG. 11, the control unit 1104 is connected to the units 1101 to 1103.

The functions of HeNBGW74 currently being discussed in 3GPP are shown below (see Non-Patent Document 1, Chapter 4.6.2). The HeNBGW 74 relays for the S1 application. Although part of the procedure of the MME unit 73 to the Home-eNB 72-2, the HeNBGW 74 terminates the S1 application not related to the mobile terminal 71. When the HeNBGW 74 is arranged, procedures unrelated to the mobile terminal 71 are communicated between the Home-eNB 72-2 and the HeNBGW 74, and between the HeNBGW 74 and the MME unit 73. The X2 interface is not set between the HeNBGW 74 and other nodes. The HeNBGW 74 recognizes execution of paging optimization (Paging optimization) as an option.

Next, an example of a general cell search method in a mobile communication system is shown. FIG. 12 is a flowchart showing an outline from a cell search to a standby operation performed by a mobile terminal (UE) in an LTE communication system. When starting the cell search, the mobile terminal uses the first synchronization signal (P-SS) and the second synchronization signal (S-SS) transmitted from the neighboring base stations in step ST1201, and the slot timing, frame Synchronize timing. In combination with P-SS and S-SS, the synchronization signal (SS) is assigned a synchronization code corresponding to one-to-one PCI (Physical Cell Identity) assigned to 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).

For the next 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 the PCI one-to-one, and can be separated from other cells by taking a correlation with the code. By deriving the RS code of the cell from the PCI specified in step ST1201, it is possible to detect the RS and measure the RS received power.

Next, in step 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 step ST1202.

Next, in step ST1204, the PBCH of the best cell is received and the BCCH that is broadcast information is obtained. MIB (Master Information Block) including cell configuration information is carried on BCCH on PBCH. Therefore, the MIB is obtained by receiving the PBCH and obtaining the BCCH. 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, in step ST1205, the DL-SCH of the cell is received based on the MIB cell configuration information to obtain SIB (System Information Block) 1 in the broadcast information BCCH. SIB1 includes information related to access to the cell, information related to cell selection, and scheduling information of other SIBs (SIBk; an integer of k ≧ 2). Also, SIB1 includes TAC (Tracking Area Code).

Next, in step ST1206, the mobile terminal compares the TAC of SIB1 received in step 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 (Tracking Area 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 receipt 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. A CSG cell and one or more registered mobile terminals 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 any one CSG cell, it can access another CSG cell to which the CSG cell belongs.

In addition, Home-eNB in LTE and Home-NB in UMTS may be used as CSG cells. The mobile terminal registered in the CSG cell has a white list. Specifically, the white list is stored in SIM (Subscriber Identity Module) / USIM. The white list stores CSG information of CSG cells registered by the mobile terminal. Specifically, CSG-ID, TAI (Tracking Area Identity), TAC, etc. can be considered as the CSG information. Either of the CSG-ID and the TAC may be used as long as they are associated with each other. 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 a CSG cell and a non-CSG cell (referred to as PCI split) (see 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. Non-Patent Document 5 discloses a basic operation of a mobile terminal using PCI split. 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.

In 3GPP, it has been determined that PCI for hybrid cells is not included in the PCI range for CSG cells (see Non-Patent Document 1, Chapter 10.7).

The HeNB and HNB are required to support various services. For example, an operator increases a radio resource that can be used by a mobile terminal by allowing the mobile terminal to be registered in a certain HeNB and HNB and allowing only the registered mobile terminal to access the HeNB and HNB cells. To enable high-speed communication. Accordingly, the service is such that the operator sets the charging fee higher than usual.

In order to realize such a service, a CSG (Closed Subscriber Group Cell) cell that can be accessed only by registered (subscribed, member) mobile terminals has been introduced. Many CSG (Closed Subscriber Group Cell) cells are required to be installed in shopping streets, condominiums, schools, companies, and the like. For example, a CSG cell is installed for each store in a shopping street, each room in a condominium, each classroom in a school, and each section in a company, and only a user registered in each CSG cell can use the CSG cell. Is required. HeNB / HNB is required not only to complement communication outside the coverage of the macro cell, but also to support various services as described above. For this reason, a case where the HeNB / HNB is installed in the coverage of the macro cell may occur.

Heterogeneous networks (HetNets) was added as one of the technologies to be studied in LTE-A. In 3GPP, a low output power local area range such as a pico eNB (pico cell), a node for a hot zone cell, a HeNB / HNB / CSG cell, a relay node, a remote radio head (RRH) range) network nodes (local area range node (local area node), local area node (local area node), local node (local node)). Therefore, it is required to operate a network in which one or more such local area range nodes are incorporated in a normal eNB (macro cell). A network in which one or more such local area range nodes are incorporated in a normal eNB (macro cell) is called heterogeneous networks, and an interference reduction method, a capacity improvement method, and the like are studied.

Non-patent document 8 describes the technology of heterogeneous networks. In the conventional cell selection algorithm, after the neighboring cells are measured, the cell selection is performed to the cell having the strongest reception power (strongest cell, best cell). However, in the case of HeNB, there is a problem that the best cell cannot be selected due to the limitation by CSG. Further, in a network in which macro cells and pico cells exist, there is a problem that the best cell is not necessarily the optimal cell for communication.

Furthermore, there are cases where the UE should not connect to a cell with poor backhaul link communication quality. This applies not only to a backhaul link of a relay node that is a relay device, but also to a node having a wired backhaul link such as a pico cell or a femto cell (HeNB). In particular, the femtocell (HeNB) is assumed to be home use, and is connected to the core network side through a general broadband line. Therefore, the use band is limited and the reliability is deteriorated in the backhaul link. The backhaul link of the relay node is a communication line between the relay node and the base station device. A backhaul link of a base station apparatus such as a pico cell and a femto cell (HeNB) is a communication line between the base station apparatus and the core network.

Non-Patent Document 8 proposes that cell selection considering the quality of the backhaul link, measurement of a cell with weak received power, and a trigger mechanism are necessary to solve these problems. However, these specific methods are not described at all.

These problems occur not only in cell selection but also in selection or change of a serving cell such as cell reselection or handover (HO).

Non-Patent Document 9 discloses a cell selection method considering a backhaul link of a relay node. It is described that the relay node broadcasts the quality of the backhaul link and the UE performs cell selection in consideration thereof. However, there is no disclosure of a specific method by which the quality of the backhaul link is taken into consideration.

Further, Non-Patent Document 9 describes that the donor eNB reports the quality of the backhaul link of all the relay nodes, and that the link quality between the relay node and the donor eNB is inserted into Qoffset. However, as shown in Non-Patent Document 3, Qoffset is an offset value added to the received power measurement value of the adjacent cell at the time of cell reselection. Therefore, in the method disclosed here, the communication quality of the backhaul link is not included in the cell selection. Further, since Qoffset is an offset value given to the received power measurement value of the adjacent cell, the communication quality of the serving cell backhaul link cannot be incorporated into the received power of the serving cell.

FIG. 13 is a flowchart showing a celery selection processing procedure of the UE according to the technique of Non-Patent Document 3. The UE measures the received power of the serving cell for cell reselection. The received power measurement value of the serving cell is Sx.

In step ST1301, the UE compares Sx with a measurement start threshold (S_intrasearch) for celery selection. S_intrasearch is notified in advance from the serving cell. The UE compares Sx and S_intrasearch, and when Sx is equal to or less than S_intrasearch, the UE determines that the reception power of the serving cell is low and starts measurement for celery selection (step ST1302). If Sx is larger than S_intrasearch, the UE determines that the received power of the serving cell is sufficient, does not start measurement for cell reselection, measures Sx, returns to step ST1301, and again returns to Sx and S_intrasearch. And compare.

In step ST1302, the UE measures received power of neighboring cells. At this time, the reception power of the serving cell may be measured. In Step ST1303, the UE calculates a value (Srxlev) in which a correction value in the received power is inserted from the measured value for each cell. This correction value and calculation method are described in Non-Patent Document 3.

The UE that has calculated Srxlev determines whether or not the Srxlev is greater than 0 in step ST1304. If the Srxlev is greater than 0, the process of step ST1306 described later is performed with the cell as a candidate for best cell selection. When the Srxlev is 0 or less, the cell is not regarded as a best cell selection candidate.

UE performs the process of above-mentioned step ST1303 and step ST1304 with respect to the one or some cell obtained by the measurement for the cell reselection of step ST1302. As a result, when no cell having Srxlev greater than 0 is obtained, the process moves to step ST1305 and becomes out of range. If a cell having Srxlev greater than 0 is obtained, the process proceeds to step ST1306.

For a cell in which Srxlev is greater than 0, in step ST1306, the UE calculates Rs and Rn using the following equations (see Non-Patent Document 3).

Rs = Qmeas, s + Qhyst
Rn = Qmeas, n-Qoffset
Qmeas, s is a received power measurement value of a serving cell for celery selection, and Qmeas, n is a received power measurement value of an adjacent cell for celery selection (a cell that is not a serving cell). Qhyst is an offset value giving a hysteresis. Qoffset is an offset value for correction between cells in cell reselection within the same frequency carrier, and is an offset value for correction between cells and correction between frequencies in reselection to a different frequency carrier or another system.

The UE uses the calculated Rs and Rn to select the cell (best cell) with the highest received power. Then, the UE performs celery selection on the best cell selected in step ST1306.

Since the cell reselection is performed as described above, the method disclosed in Non-Patent Document 9 has a problem in that the communication quality of the serving cell backhaul link cannot be included in the received power of the serving cell.

Furthermore, in the cell reselection disclosed in Non-Patent Document 3, the reception power of the serving cell is measured before the reception power measurement of the neighboring cell, and it is determined whether or not the measurement for the cell reselection is performed according to the measured value. However, Non-Patent Document 9 does not describe this at all. In the method disclosed in Non-Patent Document 9, the communication quality of the backhaul link of the serving cell cannot be considered at all in determining whether or not to perform the measurement of the neighboring cell for celery selection shown in step ST1301. .

For example, when the serving cell is a relay, the reception quality of the access link is good, but the communication quality of the backhaul link may be bad. If the communication quality of the backhaul link of the serving cell is not taken into consideration in the determination of whether to perform the measurement of the neighboring cell for cell reselection in step ST1301, the communication quality of the backhaul link is poor. , Celery selection will not be performed. As a result, the communication speed is reduced, and in the worst case, communication is interrupted.

This occurs not only at the relay but also at other local nodes. For example, in the HeNB, the backhaul link is a broadband line that connects the HeNB and the core network. The same problem occurs when communication quality deteriorates due to congestion of this broadband line.

In order to solve these problems, this embodiment discloses a method in which the communication quality of the backhaul link of at least one of the serving cell and the neighboring cell is taken into consideration for cell reselection.

In the present embodiment, as a method of taking into account the communication quality of the serving cell backhaul link in the cell reselection, the communication quality of the backhaul link is taken into account in the criteria for starting measurement for the cell reselection, that is, the reference value. .

As an example of taking the backhaul link communication quality into consideration in the measurement start criteria for celery selection, the communication quality of the serving cell backhaul link is inserted into the measurement start threshold for celery selection.

FIG. 14 is a flowchart showing the processing procedure of celery selection in which the communication quality of the backhaul link of the serving cell is inserted in the measurement start threshold for celery selection. The process of the flowchart shown in FIG. 14 is similar to the process of the flowchart shown in FIG. 13, so only the different processes will be described, the corresponding parts will be denoted by the same step numbers, and the description of the processes will be omitted. .

UE measures the received power of the serving cell for celery selection. Here, a measurement start threshold (S_intrasearch_total) for celery selection considering the communication quality of the backhaul link of the serving cell is newly provided.

In step ST1401, the UE compares the received power measurement value (Sx) of the serving cell with a measurement start threshold value (S_intrasearch_total) for cell reselection considering the communication quality of the backhaul link of the serving cell. The reception quality of the serving cell and the communication quality of the backhaul link correspond to selection information.

The UE compares Sx and S_intrasearch_total, and when Sx is equal to or less than S_intrasearch_total, the UE determines that the reception quality of the serving cell including the communication quality of the backhaul link is poor and starts measurement for celery selection ( Step ST1302). If Sx is larger than S_intrasearch_total, the UE determines that the reception quality of the serving cell including the communication quality of the backhaul link is sufficient, does not start measurement for cell reselection, measures Sx, Returning to ST1401, Sx is again compared with S_intrasearch_total.

In this way, the communication quality of the backhaul link of the serving cell is included in the measurement start threshold for celery selection, so that the communication quality of the backhaul link is taken into consideration for the measurement start criteria for celery selection.

The serving cell measures the communication quality of the backhaul link and determines a measurement start threshold (S_intrasearch_total) for new cell reselection in consideration of the measurement result. The serving cell notifies the S_intrasearch_total in advance. The UE receives the S_intrasearch_total broadcast from the serving cell in advance and uses it as a measurement start threshold for cell reselection in step ST1401.

In FIG. 14, S_intrasearch_total is newly provided separately from S_intrasearch of FIG. This makes it possible to use different threshold values depending on whether or not the backhaul link is considered.

On the other hand, instead of newly providing S_intrasearch_total, a measurement start threshold for cell reselection considering the communication quality of the backhaul link derived by the serving cell may be set in S_intrasearch. In the case of a cell that always considers the backhaul link, the communication quality of the backhaul link can always be inserted into S_intrasearch, and the number of parameters to be notified can be reduced.

The communication quality of the backhaul link may be received power (RSRP, RSRQ: Reference Signal Received Quality), communication speed, communication capacity, line quality, and the like. In the relay, as the communication quality of the backhaul link, the received power (RSRP, RSRQ) and the like are aligned with the conventional threshold (S_intrasearch), and S_intrasearch_total can be directly calculated by a certain function. This makes it easy to derive S_intrasearch_total in the serving cell. Instead of calculating and deriving with a certain function, it may be derived using a correspondence table between the communication quality of the backhaul link and the corresponding threshold value S_intrasearch_total.

If the backhaul link is wired, the communication quality of the backhaul link should be the communication speed, communication capacity, line quality, etc. In this case, the unit is different from the conventional threshold (S_intrasearch). In that case, a function having the communication quality of the backhaul link as a variable may be provided, and S_intrasearch_total may be derived by the function. Or you may make it derive | lead-out using the correspondence table of the communication quality of a backhaul link, and the threshold value S_intrasearch_total corresponding to it. These functions or correspondence tables may be determined statically in advance.

The serving cell may be notified by including a measurement start threshold value (S_intrasearch_total) for new cell reselection in SIB3, or may be included in SIB1. In the case of SIB3, since the cell reselection parameter is included, the UE can receive it together with other cell reselection parameters. For this reason, the reception operation of the UE can be simplified, and the control malfunction can be reduced. In the case of SIB1, since the timing to be notified in advance is determined, the UE can receive at an early stage during measurement. For this reason, it becomes possible to reduce the control delay in the measurement operation of the UE.

In the method disclosed above, the serving cell derives a measurement start threshold (S_intrasearch_total) for a new cell reselection. However, the present invention is not limited to this, and the UE may derive a measurement start threshold value (S_intrasearch_total) for a new celery selection. In this case, the serving cell may notify the UE of the communication quality of the backhaul link of the serving cell. The UE derives the threshold S_intrasearch_total using the notified communication quality of the backhaul link of the serving cell.

The communication quality of the backhaul link varies. Therefore, when the communication quality of the backhaul link is changed and notified, the notification information may be corrected. The serving cell may report the average value or the value after filtering by averaging or filtering the communication quality of the backhaul link for a certain period. You may make it match this certain period with the timing when alerting | reporting information is corrected.

The serving cell may notify the communication quality of the backhaul link of the serving cell by including it in SIB3 or may be notified by including it in SIB1. In each case, the same effect as when S_intrasearch_total is notified can be obtained.

As a method for the UE to derive the threshold S_intrasearch_total using the communication quality of the backhaul link of the serving cell broadcast from the serving cell, a method similar to the method derived by the serving cell can be applied.

Here, celery selection within the same frequency carrier has been described, but the same method can be applied to celery selection to cells in other frequency carriers and celery selection to other systems such as W-CDMA. Instead of the measurement start threshold (S_intrasearch) for celery selection, the communication quality of the backhaul link may be considered in the measurement start threshold (S_nonintrasearch) for celery selection for other frequency carriers or other systems. A similar method may be used by separately providing a measurement start threshold (S_nonintrasearch_total) for cell reselection for a new other frequency carrier or another system considering the communication quality of the backhaul link.

By adopting the method disclosed in the present embodiment, cell reselection can be performed in consideration of the communication quality of the backhaul link in addition to the reception quality of each cell. As a result, even if the reception quality of the serving cell is good, cell reselection is started depending on the communication quality of the backhaul link of the serving cell, so the communication speed due to the deterioration of the communication quality of the backhaul link of the serving cell. And the occurrence of communication interruption can be suppressed. Therefore, since it is possible to improve the interference problem and capacity problem in heterogeneous networks, it is possible to operate a large number of local area range nodes and to arrange them flexibly.

Embodiment 1 Modification 1
As another example of taking the communication quality of the backhaul link into consideration for the measurement start criteria for celery selection, a case will be described in which the communication quality of the backhaul link of the serving cell is included in the measurement value of the serving cell.

FIG. 15 is a flowchart showing a processing procedure of cell reselection in which the communication quality of the serving cell backhaul link is inserted into the measured value of the serving cell. The processing of the flowchart shown in FIG. 15 is similar to the processing of the flowchart shown in FIG. 13, so only the different processing will be described, the corresponding steps will be given the same step numbers, and the description of the processing will be omitted. .

UE measures the received power of the serving cell for celery selection. The UE derives a value (Sx_total) obtained by inserting the communication quality of the backhaul link of the serving cell into the received power measurement value (Sx) of the serving cell.

The serving cell measures the communication quality of the backhaul link and informs the UE. The UE receives the communication quality broadcast from the serving cell in advance and uses it when deriving the above-described Sx_total.

In step ST1501, the UE compares Sx_total with a measurement start threshold (S_intrasearch) for celery selection. The UE compares Sx_total and S_intrasearch, and when Sx_total is equal to or lower than S_intrasearch, the UE determines that the reception quality of the serving cell including the communication quality of the backhaul link is poor and starts measurement for celery selection ( Step ST1302). When Sx_total is larger than S_intrasearch, the UE determines that the reception quality of the serving cell including the communication quality of the backhaul link is sufficient, does not start measurement for cell reselection, and returns to step ST1501. Sx is measured again, Sx_total is derived and compared with S_intrasearch.

In this way, a value (Sx_total) in which the communication quality of the backhaul link of the serving cell is inserted into the received power measurement value (Sx) of the serving cell measured by the UE is derived, and Sx_total is measured for cell reselection. The communication quality of the serving cell backhaul link is taken into account.

The communication quality of the backhaul link may be received power (RSRP, RSRQ), communication speed, communication capacity, line quality, and the like. In the relay, as the communication quality of the backhaul link, the received power (RSRP, RSRQ) or the like is aligned with the measured value (Sx) of the access link, and Sx_total can be directly calculated by a certain function. This makes it easy to derive Sx_total at the UE. Further, it may be derived using a correspondence table instead of being calculated using a certain function.

If the backhaul link is wired, the communication quality of the backhaul link may be the communication speed, communication capacity, line quality, etc. In this case, although the unit is different from the received power measurement value (Sx) of the conventional serving cell, in that case, a certain function with the communication quality of the backhaul link as a variable is provided, and Sx_total is derived by the function. It may be. Alternatively, it may be derived using a correspondence table between the communication quality of the backhaul link and the corresponding measurement value Sx_total. These functions or correspondence tables may be determined statically in advance.

The serving cell reports the communication quality of the backhaul link, but the communication quality of the backhaul link varies. Therefore, when the communication quality of the backhaul link is changed and notified, the notification information may be corrected. The serving cell may report the average value or the value after filtering by averaging or filtering the communication quality of the backhaul link for a certain period. You may make it match this certain period with the timing when alerting | reporting information is corrected.

The UE may average or filter the communication quality of the backhaul link for a certain period. The serving cell may notify the UE of the communication quality measurement value of the backhaul link without averaging, and may average or filter the communication quality measurement value of the backhaul link notified by the UE.

The serving cell may be notified by including the communication quality of the backhaul link in SIB3 or may be included in SIB1. In the case of SIB3, since the cell reselection parameter is included, the UE can receive it together with other cell reselection parameters. For this reason, the reception operation of the UE can be simplified, and the control malfunction can be reduced. In the case of SIB1, since the timing to be notified in advance is determined, the UE can receive early at the time of measurement. For this reason, it becomes possible to reduce the control delay in the measurement operation of the UE.

In addition to the effects described in the first embodiment, the following effects can be obtained by adopting the method of the present modification. By inserting the communication quality of the backhaul link of the serving cell into the reception power measurement value of the serving cell, the UE can derive the total reception quality from the network to the UE via the serving cell. For this reason, it becomes possible to appropriately consider the effect of the communication quality of the backhaul link, and even when the communication quality of the backhaul link becomes dominant, the measurement for celery selection is started with high accuracy. It becomes possible.

Embodiment 1 Modification 2
As another example of taking into account the communication quality of the backhaul link in the measurement start criteria for celery selection, the communication quality threshold of the serving cell backhaul link (hereinafter, “ A backhaul threshold (start) ”).

FIG. 16 is a flowchart showing a processing procedure of celery selection in which a backhaul threshold value (start) is provided as a measurement start threshold value for celery selection. The process of the flowchart shown in FIG. 16 is similar to the process of the flowchart shown in FIG. 13, so only the different processes will be described, the corresponding parts will be denoted by the same step numbers, and the description of the processes will be omitted. .

UE measures the received power of the serving cell for celery selection. In Step ST1301, the UE compares the received power measurement value (Sx) of the serving cell with a measurement start threshold value (S_intrasearch) for cell reselection. S_intrasearch is notified in advance from the serving cell.

The UE compares Sx and S_intrasearch, and when Sx is equal to or lower than S_intrasearch, the UE determines that the reception power of the serving cell is low, and starts measurement for cell reselection (step ST1302). If Sx is larger than S_intrasearch, the UE compares the communication quality of the backhaul link of the serving cell with the communication quality threshold (backhaul threshold (start)) of the backhaul link of the serving cell in step ST1601. The communication quality of the backhaul link of the serving cell and the communication quality threshold of the backhaul link of the serving cell are each notified beforehand from the serving cell.

In step ST1601, when the communication quality of the backhaul link of the serving cell is equal to or lower than the backhaul threshold (start), the UE determines that the communication quality of the backhaul link is low and performs measurement for cell reselection. Start (step ST1302). If the communication quality of the serving cell backhaul link is greater than the backhaul threshold (start), the UE determines that the communication quality of the backhaul link is sufficient and does not start the measurement for celery selection, Returning to step ST1301, Sx is measured, and Sx and S_intrasearch are compared.

The comparison of the communication quality of the backhaul link of the serving cell and the backhaul threshold (start) in step ST1601 is a comparison between the received power measurement value (Sx) of the normal serving cell and the threshold of received power (S_intrasearch) in step ST1301. It should be done under or conditions. Thereby, when any of the conditions becomes insufficient for communication, measurement for celery selection can be started.

In this way, a communication quality threshold for the backhaul link of the serving cell is provided, and used to determine whether or not to start measurement for celery selection, and the determination is put into measurement start conditions for celery selection. Thus, the communication quality of the serving cell backhaul link is taken into account.

Although the communication quality of the backhaul link varies, the coping method may be the same as that disclosed in the first modification of the first embodiment.

The backhaul link communication quality and the backhaul link communication quality threshold may be received power (RSRP, RSRQ), communication speed, communication capacity, line quality, and the like. The communication quality of the backhaul link and the communication quality threshold value of the backhaul link may be different indicators, but may be the same. In the case of the same, the unit becomes the same, so that direct comparison is possible, and thus the control at the UE is simplified.

The serving cell may notify the communication quality of the backhaul link and the communication quality threshold of the backhaul link together or separately in the SIB3, or may be notified in the SIB1. In the case of SIB3, since the cell reselection parameter is included, the UE can receive it together with other cell reselection parameters. For this reason, the reception operation of the UE can be simplified, and the control malfunction can be reduced. In the case of SIB1, since the timing to be notified in advance is determined, the UE can receive early at the time of measurement. For this reason, it becomes possible to reduce the control delay in the measurement operation of the UE.

The communication quality threshold value of the serving cell backhaul link may be determined in advance as a static value instead of being notified. In this case, the UE can use a predetermined value. Thereby, broadcast information can be reduced and signaling load can be reduced.

In addition, when the communication quality threshold of the backhaul link is notified as the initial value by using a predetermined value as the communication quality threshold of the backhaul link, instead of the initial value, the notified backhaul link A communication quality threshold may be used. In this case, the serving cell may notify the backhaul link communication quality threshold as necessary.

In addition to the effects described in the first embodiment, the following effects can be obtained by adopting the method of the present modification. Since the reception quality of the serving cell and the communication quality of the backhaul link can be individually set, it is possible to make a highly flexible and precise setting. Therefore, even when the number of cells that need to consider the communication quality of the backhaul link increases, cell reselection that suppresses the decrease in communication speed and the occurrence of communication disconnection is possible.

Embodiment 2. FIG.
The aforementioned non-patent document 9 discloses that the link quality between the relay node and the donor eNB is inserted into Qoffset. However, in the method disclosed in Non-Patent Document 9, the communication quality of the backhaul link of the serving cell cannot be inserted at the time of cell ranking in celery selection. In the cell ranking, if the communication quality of the backhaul link of the serving cell is not taken into consideration, when the reception power of the serving cell is good, the possibility of selecting the serving cell as the best cell increases. When the communication quality of the backhaul link of the serving cell is poor, the communication speed is lowered and the communication is interrupted even after the best cell is selected.

In the present embodiment, as a method for taking into account the communication quality of the backhaul link of at least one of the serving cell and the neighboring cell in the cell reselection, at the time of cell ranking, the backhaul link of at least one of the serving cell and the neighboring cell is selected. Incorporate communication quality.

Here, as an example of incorporating the communication quality of the backhaul link of at least one of the serving cell and the neighboring cell at the time of cell ranking, the communication quality of the backhaul link of each cell is inserted into the measured value of the cell at the time of cell ranking.

FIG. 17 is a flowchart showing a processing procedure of cell reselection in which the communication quality of the backhaul link of each cell is included in the cell measurement value at the time of cell ranking. The processing of the flowchart shown in FIG. 17 is similar to the processing of the flowchart shown in FIG. 13 and FIG. 16, so only the different processing will be described, and the corresponding steps will be denoted by the same step numbers and the description of the processing. Is omitted. The operation until the measurement for celery selection is started uses the method disclosed in the second modification of the first embodiment, but is not limited thereto. The method disclosed in the first embodiment or the first modification of the first embodiment may be used.

In this embodiment, the UE performs the process of step ST1701 for the cell in which Srxlev is greater than 0 in step ST1304. In Step ST1701, the UE derives a reception quality obtained by inserting the communication quality of the backhaul link of the serving cell into the reception power measurement value of the serving cell. The reception quality including the communication quality of the backhaul link of the serving cell is Rs_total.

Further, in step ST1701, the UE derives reception quality obtained by inserting the communication quality of the backhaul link of the adjacent cell into the reception power measurement value of the adjacent cell. Rn_total is the reception quality including the communication quality of the backhaul link of the adjacent cell.

The UE uses the derived Rs_total and Rn_total to select the cell (best cell) with the best reception quality including the communication quality of the backhaul link. Then, the UE performs celery selection on the best cell selected in step ST1701.

The serving cell notifies the UE of the communication quality of the backhaul link of the own cell, and the UE receives the information notified from the serving cell and uses it for derivation of Rs_total in step ST1701. As a method for the serving cell to notify the information, the method disclosed in the first modification of the first embodiment may be used.

The serving cell notifies the UE of the communication quality of the backhaul link of the neighboring cell, and the UE receives the information notified from the serving cell and uses it for derivation of Rn_total in step ST1701.

Since the serving cell broadcasts the information, the serving cell needs to recognize the communication quality of the backhaul link of the neighboring cell. As this method, each cell measures the communication quality of the backhaul link of its own cell, and notifies the neighbor cell of the result together with or in association with the identity (PCI, GCI) of the cell. An X2 interface or an S1 interface may be used as the notification interface.

In the case of a relay, the donor eNB (DeNB) may be notified using an uplink backhaul link (link from the relay to the DeNB). The DeNB may notify the relays being served thereby. By doing so, the relay can recognize the communication quality of the backhaul link of the adjacent relay. As a notification method, you may notify separately to a subordinate relay from DeNB, and you may alert | report from DeNB. In the case of a relay, the DeNB may measure the communication quality of the uplink backhaul link and use the result as the communication quality of the backhaul link of the relay. This eliminates the need to notify the DeNB from the relay. In this way, the serving cell can recognize the communication quality of the backhaul link of the adjacent cell.

In the case of the HeNB connected to the HeNBGW, the HeNBGW may measure the communication quality of the backhaul link of the HeNB being served, and the HeNBGW may notify the measurement value to the HeNB being served.

The method in which the serving cell reports the communication quality of the backhaul link of the neighboring cell may be the same as the method of reporting the communication quality of the backhaul link of the serving cell disclosed in the first modification of the first embodiment.

The derivation of the average value of the communication quality of the backhaul link or the value after filtering may be performed by the serving cell, the UE, or may be performed for each cell. Each cell should be performed in its own cell. As a result, the information after averaging or filtering may be notified every certain period. You may make it match this certain period with the timing when alerting | reporting information is corrected. By doing so, it is possible to reduce the amount of information that each cell notifies the serving cell and the amount of information that the serving cell notifies the UE.

The serving cell may be notified by including the communication quality of the backhaul link of the adjacent cell in the SIB4. Since SIB4 includes information on neighboring cells, the UE can receive information associated with other neighboring cells, for example, PCI. For this reason, the reception operation of the UE can be simplified, and the control malfunction can be reduced.

The index used for the communication quality of the backhaul link, the derivation method using the index, and the derivation method when the units of the received power measurement values of the cells are different are the same as those disclosed in the first modification of the first embodiment. Use it.

The method disclosed in the present embodiment enables cell reselection in consideration of the communication quality of the backhaul link of the neighboring cell and the communication quality of the backhaul link of the serving cell. Even if the reception quality of the serving cell is good, if the communication quality of the backhaul link of the serving cell is bad, cell reselection to another cell can be performed. For this reason, it becomes possible to suppress the reduction in communication speed and the occurrence of communication disconnection due to the deterioration of the communication quality of the backhaul link of the serving cell.

In addition, cell reselection is not performed on cells with poor communication quality on the backhaul link, so that it is possible to suppress a decrease in communication speed and occurrence of communication disconnection after reselection.

In addition, since it is not necessary to perform cell selection and cell reselection operations again due to a radio link failure after reselection and further communication disconnection, it is possible to reduce UE power consumption and make the system unstable. It can be eliminated.

In addition, taking into account the communication quality of the backhaul link of the serving cell and the communication quality of the backhaul link for each neighboring cell individually, and deriving the total cell communication quality, it varies depending on the cell. The communication quality of the backhaul link can be individually entered. A cell having no change in the communication quality of the backhaul link does not need to notify the changed communication quality, so the number of notifications using the X2 interface or the S1 interface can be reduced. Therefore, it is possible to reduce the signaling load and the power consumption of the UE.

The communication quality of the backhaul link may be an offset value that can be expressed in units of received power of the serving cell. For example, the offset value taking into account the communication quality of the backhaul link of the serving cell may be Qoffset, s, and the offset value taking into account the communication quality of the backhaul link of the neighboring cell may be set to Qoffset, n. The serving cell notifies the UE of the offset value. In Step ST1701, the UE calculates Rs_total and Rn_total using the following equations.

Rs_total = Qmeas, s-Qoffset, s + Qhyst
Rn_total = Qmeas, n-Qoffset, n
The UE uses the calculated Rs_total and Rn_total to select the cell (best cell) with the highest received power. Then, celery selection is performed on the best cell selected by the UE.

By doing so, it becomes possible to take into account the communication quality of the backhaul link in almost the same manner as conventional celery selection.

In this embodiment, since the serving cell recognizes the communication quality of the backhaul link of the neighboring cell, each cell measures the communication quality of the backhaul link of its own cell, and the result is obtained as an X2 interface or an S1 interface. Is used to notify neighboring cells. As another method, each cell may broadcast the communication quality of its own backhaul link on a plurality of frequency carriers. Each cell receives broadcast information of an adjacent cell on a frequency carrier different from the frequency carrier used by the own cell among the plurality of frequency carriers. A dedicated frequency carrier for broadcasting the broadcast information may be statically determined in advance. Each cell measures a neighboring cell with respect to a frequency carrier to which the broadcast information is transmitted periodically or at any time, and receives broadcast information of a cell whose received power is larger than a certain threshold. In this way, each cell can recognize the broadcast information of neighboring cells.

In the LTE-A system, it is considered to support a frequency bandwidth larger than the frequency bandwidth (transmission シ ス テ ム bandwidths) of the LTE system. Therefore, it is considered that an LTE-A compatible mobile terminal receives one or a plurality of component carriers (Component ： Carrier: CC) at the same time. You may make it perform the above-mentioned method using this component carrier. Each cell broadcasts the communication quality of its own backhaul link on a plurality of component carriers, and each cell reports broadcast information on neighboring cells on the component carrier used by the own cell among the plurality of component carriers. What is necessary is just to make it receive. The component carrier to which the broadcast information is transmitted can also be used for communication with the UE.

In 3GPP, the HeNB currently does not have an X2 interface. Therefore, by using this method in a heterogeneous network in which a HeNB is present, it is possible to obtain information on neighboring cells through an air interface without an X2 interface. For example, when the HeNB exists in the macro cell range, the communication quality of the backhaul link of the own cell is increased from the macro cell to the HeNB or from the HeNB to the macro cell using the above-described method. You may make it notify. As a result, notification can be made earlier than notification via the S1 interface. The communication quality of the backhaul link that varies with time can be notified to the neighboring cell with a delay time smaller than that of the S1 interface.

Embodiment 2 Modification 1
In Embodiment 2, the serving cell notifies the UE of the communication quality of the backhaul link of the adjacent cell. However, if the serving cell notifies the UE of the communication quality for all neighboring cells, the notification information becomes enormous. Furthermore, the signaling load increases and the power consumption of the UE also increases. In addition, it is assumed that a general user installs the HeNB in home use, and a large amount of HeNB is installed in an arbitrary place. Therefore, configuring neighboring cell information in a network including these HeNBs becomes very complicated. Therefore, it is complicated as a system for the serving cell to notify the UE of the communication quality of the backhaul link of the adjacent cell. This is a problem that occurs even when the serving cell broadcasts an offset value that takes into account the communication quality of the backhaul link of the neighboring cell, or when it broadcasts Qoffset disclosed in Non-Patent Document 9.

In order to solve these problems, in this modified example, the serving cell does not report the communication quality of the backhaul link of the neighboring cell, but the cell notifies the communication quality of the backhaul link of its own cell, and the UE The communication quality is used for cell ranking in celery selection.

UE which starts the measurement of the cell for celery selection starts the measurement of a cell in step ST1302 shown in FIG. At this time, the UE not only measures the reception power of each cell, but also receives the communication quality of the backhaul link of the own cell broadcast by each cell.

In step ST1701, the UE derives Rs_total and Rn_total of each cell using the communication quality of the backhaul link of each cell received in step ST1302. The backhaul link communication quality index and the derivation method, and the derivation method when the unit of the cell received power measurement value is different may be performed in the same manner as in the second embodiment.

Each cell reports the communication quality of its own backhaul link, but the communication quality of the backhaul link varies. Therefore, when the communication quality of the backhaul link is changed and notified, the notification information may be corrected. The derivation of the average value of the communication quality of the backhaul link or the value after filtering may be performed by the UE or may be performed for each cell, but each cell is preferably performed in its own cell. By doing so, it is only necessary to notify the information after averaging or after filtering every certain period. Therefore, it is possible to reduce the amount of information that each cell notifies the serving cell and the amount of information that the serving cell notifies the UE. You may make it match this certain period with the timing when alerting | reporting information is corrected.

Each cell reports the communication quality of the backhaul link of its own cell, but at this time, it may be reported in SIB1. In the case of SIB1, since the timing to be notified in advance is determined, the UE can receive early at the time of measurement. For this reason, it becomes possible to reduce the control delay in the measurement operation of the UE. In this case, in the above-described cell search procedure shown in FIG. 12, the best cell selection in step ST1203 may be performed after receiving SIB1 in step ST1205.

In addition to the effects described in the second embodiment, the following effects can be obtained by adopting the method of the present modification. Neighboring cell information can be reduced from information broadcast by the serving cell. In addition, each cell does not need to notify the neighboring cell of the communication quality of the backhaul link of the own cell and the identity (PCI, GCI) of the cell. Accordingly, it is possible to reduce the signaling load on the air interface, the X2 interface, and the S1 interface. For this reason, it is possible to construct a system with a simple configuration even in a network including a large amount of HeNBs installed in an arbitrary place.

Also, each cell may broadcast an offset value taking into account the communication quality of the backhaul link of its own cell or Qoffset disclosed in Non-Patent Document 9. Even if it does in this way, the effect equivalent to this modification is acquired.

Embodiment 2 Modification 2
In this modification, an indicator is provided that indicates whether or not to be subject to celery selection. The serving cell broadcasts an indicator that indicates whether or not the own cell is allowed to be subject to celery selection, and an indicator that indicates whether or not neighboring cells are allowed to be subject to celery selection. The indicator of the adjacent cell may be provided for each cell and notified.

The operation of the UE at the time of celery selection is made possible by changing a part of the flowchart shown in FIG. The UE receives the indicator broadcast from the serving cell in advance, and at the time of cell reselection, in step ST1303 of FIG. 17, only the cell that is allowed to be subject to cell reselection by the indicator is Srxlev. Is calculated.

Then, in step ST1303, the UE performs cell ranking in step ST1701 from the cells in which Srxlev is greater than 0 in step ST1304, and selects the best cell. Good. By doing so, it is possible to select the best cell from the cells that are permitted to be subject to celery selection.

As the cell ranking and best cell selection method, it is not necessary to perform the process of step ST1701 in FIG. 17, and the process of step ST1306 in FIGS. 13 to 16 may be performed. In this case, the UE performs cell ranking and best cell selection in Step ST1306 from among cells in which Srxlev is greater than 0 in Step ST1304. By doing so, it is possible to select the best cell from the cells that are permitted to be subject to celery selection.

If the indicator is a cell that is not permitted to be subject to celery selection, the indicator is excluded from the targets for calculating Srxlev in step ST1303. As a result, in selecting the best cell, a cell that is not permitted to be subject to celery selection is not selected.

In this modification, Srxlev is calculated only for the cells permitted to be subject to celery selection by the indicator in step ST1303, but the present invention is not limited to this. For example, when measuring the received power of a cell for celery selection shown in step ST1302, only the cell permitted to be subject to celery selection by the indicator may be measured. Further, for example, when performing the process of step ST1306 in FIG. 13 to FIG. 16 as the cell ranking and best cell selection method, in step ST1306, only the cells that are permitted to be subject to cell reselection by the indicator. , Rs, Rn may be calculated. When performing the processing of step ST1701 in FIG. 17, Rs_total and Rn_total may be calculated only for the cells that are permitted to be subject to cell reselection by the indicator in step ST1701. The best cell may be selected from the cells permitted to be subject to celery selection by the indicator.

The serving cell needs to recognize the indicator of the neighboring cell. This method may be the same as the method disclosed in Embodiment 2 in which the serving cell recognizes the communication quality of the backhaul link of the neighboring cell.

Also, the method of notifying the indicator by the serving cell may be the same as the method of notifying the communication quality of the backhaul link of the adjacent cell disclosed by the second embodiment.

Each cell measures the communication quality of its own backhaul link and sets the value of the indicator according to the measurement result. In this way, when the backhaul link communication quality is poor and the backhaul link communication is not sufficient, the indicator can be used to prevent the cell reselection from being permitted. In addition, it is possible to prevent the UE from selecting the cell.

In addition to the effects described in the second embodiment, the following effects can be obtained by using the method disclosed in the present modification. When there is a cell with extremely poor communication quality of the backhaul link, the cell can be removed from the cell reselection target, so that the cell reselection control can be simplified. In addition, the power consumption of the UE can be reduced.

In addition, since the indicator can have a smaller amount of information than the communication quality of the backhaul link of each cell described in Embodiment 2, the amount of information notified from each cell to the serving cell and the amount of information broadcast from the serving cell can be reduced. It becomes possible.

The indicator may be 1 bit. 1 (or 0) indicates that it is permitted to become a celery selection target, and 0 (or 1) indicates that it is not permitted to be a celery selection target. As a result, it can be realized with a minimum amount of information.

In this modification, the serving cell broadcasts an indicator that indicates whether the own cell is permitted to be subject to celery selection, and an indicator that indicates whether neighboring cells are allowed to be subject to celery selection. However, each cell may notify an indicator indicating whether or not each cell is permitted to be subject to celery selection. In this case, as in the method disclosed in the first modification of the second embodiment, the UE that starts measuring the cell for celery selection performs each cell measurement in step ST1302 illustrated in FIG. The indicator broadcast by the cell may be received. This eliminates the need for the serving cell to report the indicator of the neighboring cell. The method for notifying each cell of the indicator may be the same as the method of the first modification of the second embodiment.

The following effects can be further obtained by notifying each cell of an indicator indicating whether or not each cell is permitted to be subject to celery selection. Neighboring cell information can be reduced from information broadcast by the serving cell. In addition, each cell does not need to notify the neighboring cell of the communication quality of the backhaul link of the own cell and the identity (PCI, GCI) of the cell. Accordingly, it is possible to reduce the signaling load on the air interface, the X2 interface, and the S1 interface. For this reason, it is possible to construct a system having a simple configuration even in a network including a large amount of HeNBs installed at an arbitrary place.

Embodiment 2 Modification 3
In this modified example, another method of incorporating the communication quality of the backhaul link of at least one of the serving cell and the neighboring cell at the time of cell ranking is disclosed. In this modification, when there is a cell whose reception quality exceeds a certain value, cell ranking is performed in consideration of the reception quality of the backhaul link. A reception quality threshold value (reference value) is provided as the certain value.

FIG. 18 is a flowchart showing a processing procedure of cell reselection in which cell ranking is performed in consideration of the reception quality of the backhaul link when there is a cell whose reception quality is a certain value or more. The process of the flowchart shown in FIG. 18 is similar to the process of the flowcharts shown in FIGS. 13 and 16, so only the different processes will be described, and the corresponding parts will be denoted by the same step numbers and the description of the processes Is omitted. The operation until the measurement for celery selection is started uses the method disclosed in the second modification of the first embodiment, but is not limited thereto. The method disclosed in the first embodiment or the first modification of the first embodiment may be used.

In this modification, the UE performs the process of step ST1801 for the cell in which Srxlev is greater than 0 in step ST1304. In Step ST1801, the UE determines whether the reception quality of the cell is equal to or higher than the reception quality threshold (reference value), specifically, whether the received power measurement value indicating the reception quality of the cell is equal to or higher than the reception quality threshold (reference value). Determine whether. When the received power measurement value is greater than or equal to the reception quality threshold (reference value), the mobile terminal makes a transition to step ST1803. When the received power measurement value is smaller than the reception quality threshold value (reference value), the mobile terminal makes a transition to step ST1802.

Among the cells in which Srxlev is greater than 0 in step ST1304, if there is a cell whose received power measurement value is equal to or greater than the reception quality threshold (reference value) in step ST1801, in step ST1803, the UE Cell ranking is performed based on the communication quality of the backhaul link, and the cell with the best communication quality of the backhaul link is selected as the best cell. Then, the UE performs celery selection on the best cell selected in step ST1803. By setting the reception quality threshold (reference value) to the reception quality required for the UE to perform cell reselection, the cell backhaul is received from the cells whose reception quality measurement values satisfy the required reception quality. The best cell can be selected according to the communication quality of the link.

Among the cells in which Srxlev is greater than 0 in step ST1304, if there is no cell whose received power measurement value is equal to or greater than the reception quality threshold (reference value) in step ST1801, in step ST1802, the UE Cell ranking is performed based on the reception quality, specifically, the received power measurement value. This cell ranking method can be the same as the conventional cell ranking method. In step ST1802, the UE selects the cell with the best received power measurement value as the best cell. Then, the UE performs celery selection on the best cell selected in step ST1802.

The reception quality threshold value (reference value) may be one or plural, for example, for each cell. For example, when a reception quality threshold (reference value) is provided for each cell, the reception quality threshold (reference value) may be used for each cell to be determined in step ST1801. When the reception quality threshold value (reference value) is provided for each cell, it may be associated with the cell identity (PCI, GCI). By doing so, since the situation for each cell can be taken into consideration, more precise celery selection becomes possible.

The serving cell may notify the reception quality threshold (reference value), or each cell may notify. When the serving cell notifies, it may be included in SIB3, notified in SIB1, or included in SIB4. In the case of broadcasting by SIB3, since the celery selection parameter is included, it can be received together with other celery selection parameters. For this reason, the reception operation of the UE can be simplified, and the control malfunction can be reduced. In the case of SIB1, since the timing to be notified in advance is determined, the UE can receive early at the time of measurement. For this reason, it becomes possible to reduce the control delay in the measurement operation of the UE. When broadcasting by SIB4, since information on neighboring cells is included, it is possible to receive information in association with information on other neighboring cells, for example, PCI. Broadcasting by SIB4 is suitable when the reception quality threshold value (reference value) is provided for each cell, and has an advantage that the reception operation of the UE can be simplified and the control malfunction can be reduced.

When each cell broadcasts the reception quality threshold (reference value), it may be broadcast by including it in SIB1. In the case of SIB1, since the timing to be notified in advance is determined, the UE can receive early at the time of measurement. For this reason, it becomes possible to reduce the control delay in the measurement operation of the UE.

The reception quality threshold (reference value) may be determined in advance as a static value instead of being notified. In this case, the UE can use a predetermined value. Since the UE does not need to be notified of the reception quality threshold (reference value), the signaling load can be reduced and the power consumption of the UE can be reduced.

In addition, when a predetermined value is used as the initial value for the reception quality threshold (reference value), and the reception quality threshold (reference value) is reported from the serving cell or each cell, it is notified instead of the initial value. Alternatively, the reception quality threshold value (reference value) of each cell may be used. In this case, the serving cell or each cell may notify the reception quality threshold (reference value) as necessary.

In step ST1803, the UE selects the best cell based on the communication quality of the backhaul link. Therefore, the UE needs to recognize the communication quality of the serving cell and the backhaul link of each cell. For this method, Embodiment 2, Modification 1 of Embodiment 2, or the like may be used.

By using the method disclosed in this modification, the following effects can be obtained in addition to the effects described in the second embodiment and the first modification of the second embodiment. When sufficient reception quality is obtained for communication, the best cell can be selected depending on the communication quality of the backhaul link. Since the cell to be selected with priority on the reception quality can be determined, the cell can be easily found. Further, it is not necessary for the UE to derive the total reception quality using the communication quality of the backhaul link. Therefore, the celery selection control of the UE becomes easy, and the power consumption of the UE can be reduced.

In this modified example, in FIG. 18, apart from the determination by Srxlev in step ST1304, it is determined in step ST1801 whether or not the reception quality is equal to or higher than the reception quality threshold (reference value). By making these two judgments as one, the processing of step ST1801 and step ST1802 may be eliminated. In this case, the following is performed.

In step ST1304, it was described that Srxlev was derived in consideration of a certain offset value for the received power measurement value for each cell. In addition to this offset, a new offset may be provided, and a value considering the reception quality threshold (reference value) may be used as the new offset value. By using the new offset when deriving Srxlev, the reception quality threshold value (reference value) can be taken into consideration. Instead of providing the new offset, a value considering the reception quality threshold value (reference value) may be inserted into the existing offset.

In this way, the determination by Srxlev in step ST1304 and the determination of whether the reception quality in step ST1801 is equal to or higher than the reception quality threshold (reference value) are performed in one step, thereby simplifying the determination in the UE. It becomes possible. Further, it can be performed in the same manner as the conventional cell ranking method.

Embodiment 2 Modification 4
In this modified example, another method of incorporating the communication quality of the backhaul link of at least one of the serving cell and the neighboring cell at the time of cell ranking is disclosed. In this modification, when there is a cell whose backhaul link communication quality exceeds a certain value, cell ranking is performed in consideration of the reception quality of the cell. As the certain value, a backhaul threshold value (reference value) is provided.

FIG. 19 is a flowchart showing a processing procedure of cell reselection in which cell ranking is performed in consideration of the reception quality of a cell when the communication quality of the backhaul link exceeds a certain value. The processing of the flowchart shown in FIG. 19 is similar to the processing of the flowcharts shown in FIGS. 13 and 16, so only the different processing will be described, and the corresponding steps will be denoted by the same step numbers and the description of the processing. Is omitted. The operation until the measurement for celery selection is started uses the method disclosed in the second modification of the first embodiment, but is not limited thereto. The method disclosed in the first embodiment or the first modification of the first embodiment may be used.

In this modification, the UE performs the process of step ST1901 for the cell in which Srxlev is greater than 0 in step ST1304. In Step ST1901, the UE determines whether or not the communication quality of the cell backhaul link is equal to or higher than a backhaul threshold (reference value). When the communication quality of a backhaul link is more than a backhaul threshold value (reference value), it transfers to step ST1903. When the communication quality of a backhaul link is smaller than a backhaul threshold value (reference value), it transfers to step ST1902.

If there is a cell in which the communication quality of the backhaul link is greater than or equal to the backhaul threshold (reference value) in step ST1901 among the cells in which Srxlev is greater than 0 in step ST1304, in step ST1903, the UE Then, cell ranking is performed based on the reception quality, specifically, the received power measurement value, and the cell having the best reception quality, specifically, the received power measurement value, is selected as the best cell. This cell ranking method can be the same as the conventional cell ranking method. And UE performs celery selection to the best cell selected by step ST1903. By setting the backhaul threshold (reference value) to the communication quality of the backhaul link necessary for the UE to perform cell reselection, the communication quality of the backhaul link satisfies the required communication quality of the backhaul link. The best cell can be selected from the received cells according to the reception quality of the cell, specifically, the received power measurement value.

If there is no cell whose backhaul link communication quality is equal to or higher than the backhaul threshold (reference value) in step ST1901 among the cells in which Srxlev is greater than 0 in step ST1304, in step ST1902, the UE Cell ranking is performed according to the communication quality of the backhaul link. In step ST1902, the UE selects the cell with the best communication quality of the backhaul link as the best cell. And UE performs celery selection to the best cell selected by step ST1902.

The setting method of the backhaul threshold value (reference value), the notification method to the UE, and the like may be set similarly to the reception quality threshold value (reference value) described in the third modification of the second embodiment. The communication quality of the backhaul link between the serving cell and each cell may be the same as the method described in the third modification of the second embodiment.

By using the method disclosed in this modification, the following effects can be obtained in addition to the effects described in the second embodiment and the first modification of the second embodiment. When the communication quality of the backhaul link sufficient for communication is obtained, it is possible to select the best cell according to the reception quality of the cell, specifically, the received power measurement value. Since it is possible to determine a cell to be selected with priority on the communication quality of the backhaul link, it is possible to easily find a cell in which a reliable link can be set.

Also, it is not necessary for the UE to derive the total reception quality using the communication quality of the backhaul link. Therefore, the celery selection control of the UE becomes easy, and the power consumption of the UE can be reduced.

Embodiment 3 FIG.
In the present embodiment, another method is disclosed in which the communication quality of the backhaul link of at least one of the serving cell and the neighboring cell is taken into consideration for cell reselection. In the present embodiment, the communication quality of the backhaul link according to the communication speed of the UE is taken into consideration.

As an example, the UE performs cell ranking among cells satisfying the required communication quality of the backhaul link according to the desired communication speed of the own UE. The communication quality of the desired backhaul link varies depending on the communication speed. For example, high backhaul communication quality is required for high speed and large capacity communication, and low backhaul link communication quality may be used for low speed and small capacity communication. Therefore, cell ranking is performed among cells satisfying the required communication quality of the backhaul link according to the desired communication speed of the UE.

As a method of providing desired backhaul link communication quality according to the desired communication speed of the UE, for example, a threshold value of required backhaul link communication quality according to the communication speed of the UE may be provided. The UE derives a threshold value of the backhaul link communication quality corresponding to the communication speed from the desired communication speed of the own UE, and selects a cell by cell ranking from cells having a communication quality of the backhaul link higher than the threshold value. To do.

The correspondence relationship between the UE communication speed and the backhaul link communication quality threshold value may be determined in advance as a static value, or may be reported from the serving cell or each cell. Alternatively, a static value may be set as the initial value, and then notified from the serving cell or each cell, and the notified value may be used instead of the initial value.

The correspondence relationship between the communication speed of the UE and the threshold value of the communication quality of the backhaul link may be provided with a correspondence table, or may be derived from the communication speed of the UE using an appropriate function. When an appropriate function is used, the function may be determined in advance.

Although the desired communication speed of the UE has been described, the present invention is not limited thereto, and the UE's transmission buffer state and the UE's capability indicating how much communication speed the UE can support may be taken into consideration. . In this case, what is necessary is just to make it match | combine with the threshold value of the communication quality of a backhaul link according to the transmission buffer state of UE, or the capability of UE.

By adopting the method disclosed in the present embodiment, in addition to the effects described in the second embodiment and the first modification of the second embodiment, it is possible to enable celery selection in consideration of the desired communication speed of the UE. it can.

Embodiment 4 FIG.
As described above, as an interference reduction method and capacity improvement method in heterogeneous networks, Non-Patent Document 8 proposes that measurement of a cell with a weak reception power and a trigger mechanism are necessary. There is no mention of a practical method.

Non-Patent Document 10 describes that in heterogeneous networks, there is a problem that the optimum cell in the downlink is different from the optimum cell in the uplink.

As a situation where such a problem occurs, for example, there is a case where a HeNB is arranged in the coverage of a macro cell. The macro cell coverage is large compared to the HeNB coverage. Therefore, the downlink transmission power of the macro cell is larger than the downlink transmission power of the HeNB. Even when the UE is located closer to the HeNB than the macro cell, the macro cell may be better than the HeNB as downlink reception quality. However, since the UE is located closer to the HeNB than the macro cell, the HeNB is better than the macro cell as uplink communication quality.

In order to solve such a problem, Non-Patent Document 10 discloses that the uplink and the downlink are independently connected to different cells, but this specific method is not described at all. Absent. In addition, connecting to different cells in the uplink and the downlink is considered to make communication control very complicated because the UE has a plurality of serving cells.

In order to solve these problems, the present embodiment discloses a method that enables reselection to a cell with weak received power by taking the uplink state into consideration in cell reselection. The uplink state corresponds to selection information, and the uplink corresponds to an uplink communication line.

Since the optimal cell in the downlink is different from the optimal cell in the uplink, the optimal cell in the uplink may be a cell with weak received power in the downlink. In conventional cell reselection, cell ranking is performed based on downlink received power, and in such a case, cell reselection to an optimal cell in the uplink cannot be performed. Therefore, in the present embodiment, the uplink state is also taken into consideration in celery selection.

In this embodiment, in order to take the uplink state into consideration in celery selection, the cell loss threshold of the measurement start serving cell for celery selection (hereinafter also referred to as “path loss threshold (start)”), the cell A path loss threshold value for each cell for ranking (hereinafter sometimes referred to as “path loss threshold value (reference value)”) is newly provided.

This is because the smaller the path loss, the more optimal the cell can be determined on the uplink. This is because if the path loss is small, the cell can obtain reception power necessary for demodulating the uplink signal with a small UE transmission power. Therefore, the UE can operate with low power consumption, and the uplink interference can be reduced as a system.

As the path loss, an uplink path loss may be used, but since it is complicated for the UE to recognize the uplink path loss, a downlink path loss may be used. Since the relative value of the path loss mainly depends on the route (path) of the link caused by the positions of the cell and the UE, it can also be determined using the downlink path loss. Therefore, in order to take the uplink state into consideration, downlink path loss is used here.

FIG. 20 is a flowchart showing the processing procedure of celery selection taking into account the uplink state. The processing of the flowchart shown in FIG. 20 is similar to the processing of the flowchart shown in FIG. 13, so only the different processing will be described, the corresponding steps will be denoted by the same step numbers, and the description of the processing will be omitted. .

UE measures the received power of the serving cell for celery selection. In step ST1301, the UE compares Sx and S_intrasearch, and when Sx is equal to or lower than S_intrasearch, the UE determines that the reception power of the serving cell is low and starts measurement for celery selection (step ST1302). When Sx is larger than S_intrasearch, the UE compares the path loss of the serving cell with the path loss threshold (start) in step ST2001. The UE measures the path loss of the serving cell. The path loss may be measured when measuring the received power of the serving cell for cell reselection.

In step ST2001, when the path loss of the serving cell is equal to or greater than the path loss threshold (start), the UE determines that the uplink state is bad and starts measurement for cell reselection (step ST1302). If the serving cell path loss is smaller than the path loss threshold (start), the UE determines that the uplink state is sufficient for communication, does not start measurement for cell reselection, returns to step ST1301, and sets Sx Measure and compare Sx and S_intrasearch.

The comparison between the path loss of the serving cell in step ST2001 and the path loss threshold (start) is based on the comparison between the received power measurement value (Sx) of the normal serving cell in step ST1301 and the threshold (S_intrasearch) of the received power, and the OR condition. It should be done. Thereby, when any of the conditions becomes insufficient for communication, measurement for celery selection can be started.

Thus, by setting a path loss threshold for the serving cell, it is used to determine whether or not to start measurement for celery selection, and by inserting this determination into the measurement start condition for celery selection, Uplink conditions can be taken into account.

The UE that has started measurement for cell reselection in step ST1302 calculates Srxlev from the received power measurement value of each cell in step ST1303. For the cell in which Srxlev is greater than 0 in step ST1304, the UE performs step ST2002. Perform the process. When there is no cell in which Srxlev is greater than 0 in Step ST1304, the UE moves to Step ST1305 and enters an out-of-service state.

In step ST2002, the UE determines whether or not the cell path loss measurement value is equal to or less than the path loss threshold (reference value). The UE measures the path loss of each cell. The path loss may be measured when the UE performs measurement for celery selection in step ST1302. When the path loss measurement value of the cell is equal to or less than the path loss threshold value (reference value), the process proceeds to step ST2004. When the path loss measurement value of the cell is larger than the path loss threshold value (reference value), the process proceeds to step ST2003.

Among the cells in which Srxlev is greater than 0 in Step ST1304, if there is a cell whose path loss measurement value is equal to or less than the path loss threshold (reference value) in Step ST2002, in Step ST2004, the UE determines reception quality among the cells. Based on cell ranking, the cell with the best reception quality is selected as the best cell. This cell ranking method can be the same as the conventional cell ranking method. And UE performs celery selection to the best cell selected by step ST2004. By setting the path loss threshold (reference value) to the uplink state of the cell necessary for the UE to perform cell reselection, the reception quality of the cell can be selected from the cells that satisfy the required uplink state. The best cell can be selected accordingly.

If there is no cell whose path loss measurement value is equal to or smaller than the path loss threshold value (reference value) in step ST2002 among the cells in which Srxlev is greater than 0 in step ST1304, in step ST2003, the UE determines the path loss measurement value from the cells. Perform cell ranking with. In step ST2003, the UE selects the cell with the smallest path loss measurement value as the best cell. Then, the UE performs celery selection on the best cell selected in step ST2003.

Since the path loss fluctuates, the UE may average or filter the path loss measurement result for a certain period. The average value or the value after filtering may be compared with a path loss threshold value (reference value) in step ST2002.

The serving cell notifies the path loss threshold (start). The notification may be included in SIB3 or may be notified in SIB1. In the case of SIB3, since the cell reselection parameter is included, the UE can receive it together with other cell reselection parameters. For this reason, the reception operation of the UE can be simplified, and the control malfunction can be reduced. In the case of SIB1, since the timing to be notified in advance is determined, the UE can receive at an early stage during measurement. For this reason, it becomes possible to reduce the control delay in the measurement operation of the UE.

The path loss threshold (start) may not be notified but may be determined in advance as a static value. In this case, the UE can use a predetermined value. Thereby, broadcast information can be reduced and signaling load can be reduced.

In addition, when a predetermined value is used as an initial value for the path loss threshold (start) and the path loss threshold (start) is notified, the notified path loss threshold (start) is used instead of the initial value. May be. In this case, the serving cell may notify the path loss threshold (start) as necessary.

The path loss threshold value (reference value) may be one or plural, for example, for each cell. For example, when a path loss threshold value (reference value) is provided for each cell, the path loss threshold value (reference value) may be used for each cell to be determined in step ST2002. When the path loss threshold value (reference value) is provided for each cell, it may be associated with the cell identity (PCI, GCI). By doing so, since the uplink situation for each cell can be taken into account, more precise cell reselection is possible.

The serving cell may notify the path loss threshold (reference value), or each cell may notify. When the serving cell notifies, it may be notified by being included in SIB3, may be notified by being included in SIB1, or may be notified by being included in SIB4. When broadcasting with SIB3, since the celery selection parameter is included, the UE can receive it together with other celery selection parameters. For this reason, the reception operation of the UE can be simplified, and the control malfunction can be reduced.

In the case of SIB1, since the timing to be notified in advance is determined, the UE can receive early at the time of measurement. For this reason, it becomes possible to reduce the control delay in the measurement operation of the UE. In the case of SIB4, since information on neighboring cells is included, it is possible to receive information in association with information on other neighboring cells, for example, PCI. Broadcasting with SIB4 is suitable when the path loss threshold value (reference value) is provided for each cell, and can simplify the reception operation of the UE and reduce control malfunctions.

When each cell notifies the path loss threshold (reference value), it may be included in SIB1 and notified. In the case of SIB1, since the timing to be notified in advance is determined, the UE can receive early at the time of measurement. For this reason, it becomes possible to reduce the control delay in the measurement operation of the UE.

The path loss threshold (reference value) may not be notified but may be determined in advance as a static value. In this case, the UE can use a predetermined value. Since the UE does not need to be notified of the path loss threshold (reference value), the signaling load can be reduced and the power consumption of the UE can be reduced.

In addition, when a predetermined value is used as the initial value for the path loss threshold (reference value), and the path loss threshold (reference value) is notified from the serving cell or each cell, The path loss threshold value (reference value) of the cell may be used. In this case, the serving cell or each cell may notify the path loss threshold (reference value) as necessary.

In this embodiment, the path loss threshold (start) and the path loss threshold (reference value) are provided, but either one may be used. Either the determination in step ST2001 or step ST2002 may be performed.

In the present embodiment, it is disclosed that a path loss is used as an index indicating the uplink state between the cell and the UE, but an actual distance may be used as an index indicating the uplink state. However, the present invention is not limited to these, and any index that represents the uplink state may be used. When using the distance, it is determined that the uplink state is better as the distance between the cell and the UE is smaller. The actual distance may be derived by, for example, the following method. The cell measures the position of its own cell by GPS (Global Positioning System) or the like, and notifies the position information. The UE measures the position of its own cell by GPS or the like. Moreover, UE receives the positional information on the cell alert | reported from a serving cell or each cell. The UE derives the distance between each cell and the UE based on the measured location information of the own UE and the received location information of each cell. This makes it possible to use the actual distance between each cell and the UE as an index representing the uplink state.

By using the method disclosed in this embodiment, cell reselection can be performed in consideration of uplink communication quality in addition to reception quality of each cell. Thereby, even if the reception quality of the serving cell is good, depending on the path loss of the serving cell, cell reselection is started, so the communication speed decreases due to the increase of the serving cell path loss, the occurrence of communication disconnection, the UE An increase in power consumption can be suppressed. Furthermore, since the uplink transmission power of the UE can be suppressed, uplink interference can be avoided as a system. Therefore, since it is possible to improve the interference problem and capacity problem in heterogeneous networks, it is possible to operate a large number of local area range nodes and to arrange them flexibly.

Also, by using the method disclosed in the present embodiment, it is possible to take into account the path loss of the serving cell and the path loss of the neighboring cell in cell ranking. As a result, even if the reception quality of the serving cell is good, if the path loss of the serving cell is large, it is possible to perform cell reselection to another cell. For this reason, it becomes possible to suppress a decrease in communication speed due to an increase in path loss of the serving cell, occurrence of communication disconnection, and an increase in power consumption of the UE.

In addition, since cell reselection is not performed on a cell with a large path loss, it is possible to suppress a decrease in communication speed after reselection, occurrence of communication disconnection, and an increase in power consumption of the UE.

In addition, since the uplink transmission power of the UE can be suppressed, uplink interference can be avoided as a system.

In addition, by using the method disclosed in the present embodiment, it is possible to select the best cell according to the reception quality of the cell when a sufficient path loss for uplink communication is obtained. Since a cell to be selected with priority given to path loss can be determined, it is easy to find a cell that can set a reliable uplink.

Embodiment 4 Modification 1
In this modification, another method that takes the uplink state into consideration in celery selection is disclosed. When there is a cell whose reception quality is a certain value or higher, cell ranking is performed in consideration of the uplink state. A reception quality threshold value (reference value) is provided as the certain value. The reception quality threshold (reference value) may be different from the reception quality threshold (reference value) disclosed in the third modification of the second embodiment, but the reception quality of the cell obtains reception quality sufficient for communication. Since it is a threshold value that is an index of whether or not it is set, it may be the same. In the case of the same, the parameter indicating the reception quality threshold value (reference value) can be made one.

FIG. 21 is a flowchart showing a processing procedure of cell reselection in which cell ranking is performed in consideration of path loss when there is a cell whose reception quality exceeds a certain value. The process of the flowchart shown in FIG. 21 is similar to the process of the flowcharts shown in FIGS. 13 and 20, so only the different processes will be described, and the corresponding parts will be denoted by the same step numbers and the description of the processes Is omitted. The operation until the measurement for celery selection is started is the method disclosed in the fourth embodiment.

The UE performs the process of step ST2101 for the cell where Srxlev is greater than 0 in step ST1304. In Step ST2101, the UE determines whether or not the reception quality of the cell, specifically, the received power measurement value is equal to or higher than the reception quality threshold (reference value). When the received power measurement value is greater than or equal to the reception quality threshold (reference value), the mobile terminal makes a transition to step ST2103. When the received power measurement value is smaller than the reception quality threshold value (reference value), the mobile terminal makes a transition to step ST2102.

Among the cells in which Srxlev is greater than 0 in step ST1304, if there is a cell whose received power measurement value is equal to or higher than the reception quality threshold (reference value) in step ST2101, the UE in step ST2103 Cell ranking is performed by path loss, and the cell with the smallest path loss is selected as the best cell. Then, the UE performs celery selection on the best cell selected in step ST2103. By setting the reception quality threshold (reference value) to the reception quality necessary for the UE to perform cell reselection, the reception quality measurement value is changed from the cell that satisfies the required reception quality to the path loss of the cell. The best cell can be selected accordingly.

If there is no cell whose received power measurement value is equal to or greater than the reception quality threshold value (reference value) in step ST2101 among the cells whose Srxlev is greater than 0 in step ST1304, the UE receives the received cell from the cell in step ST2102. Cell ranking is performed using the measured power value. This cell ranking method can be the same as the conventional cell ranking method. In step ST2102, the cell with the best received power measurement value is selected as the best cell. Then, the UE performs celery selection on the best cell selected in Step ST2102. The reception quality threshold (reference value) may be the same as the method disclosed in the third modification of the second embodiment.

The determination by Srxlev in step ST1304 and the determination in step ST2101 whether or not the reception quality is equal to or higher than the reception quality threshold (reference value) may be combined. This method may be the same as the method disclosed in the third modification of the second embodiment. This makes it possible to simplify the determination at the UE.

UE selects the best cell based on the path loss in step ST2103. Therefore, the UE needs to recognize the serving cell and the path loss of each cell. For this method, the method disclosed in Embodiment 4 may be used.

In addition to the effects described in the fourth embodiment, the following effects can be obtained by using the method disclosed in the present modification. If reception quality sufficient for communication is obtained, the best cell can be selected by path loss. Since the cell to be selected with priority on the reception quality can be determined, the cell can be easily found.

Embodiment 5 FIG.
In order to solve the problem in the heterogeneous networks, the methods disclosed in the first modification of the first to fourth embodiments may be combined.

FIG. 22 is an example of a flowchart showing a processing procedure of celery selection combining the methods disclosed in the first modification of the first to fourth embodiments of the present invention. The processing of the flowchart shown in FIG. 22 is similar to the processing of the flowcharts shown in FIGS. 13, 16, 18, 19, and 20, so only the different processing will be described, and the corresponding steps will be the same step. A number is attached and explanation of processing is omitted.

The UE takes into consideration the communication quality of the backhaul link of the serving cell and the path loss of the serving cell, as shown in Step ST1601 and Step ST2001, as a determination of whether to start measurement for celery selection. Together with the serving cell reception power shown in step ST1301, these determinations are set to an OR condition so that measurement for cell reselection is started when any of the conditions becomes insufficient for communication. it can.

In cell ranking, as shown in step ST1801, the UE takes into account the reception quality of the cell, takes into account the cell path loss in step ST2002, takes into account the communication quality of the cell backhaul link in step ST1901, In step ST2201, the desired communication speed of the UE is taken into consideration.

If a cell that satisfies the communication quality threshold of the backhaul link corresponding to the desired communication speed of the UE cannot be obtained in step ST2201, the mobile station moves to step ST2202, performs cell ranking based on the reception quality of the cell, and performs the best reception. Select the quality cell (best cell). Alternatively, cell ranking may be performed based on the cell path loss, and the cell with the smallest path loss (best cell) may be selected.

Also, in step ST2201, the method of associating the desired communication speed of the UE and the communication quality of the backhaul link disclosed in Embodiment 3 is not limited to the communication quality of the backhaul, but is associated with the uplink state. You may do it. Both may be performed. As an index indicating the uplink state, for example, the path loss or distance disclosed in the fourth embodiment may be used. When path loss is used, a path loss threshold value corresponding to the desired communication speed of the UE is provided, and it is determined in step ST2201 whether the path loss threshold value corresponding to the desired communication speed of the UE is satisfied. The correspondence between the UE communication speed and the uplink path loss threshold may be the same as the method disclosed in the third embodiment. This makes it possible to consider the desired communication speed of the UE when taking the uplink state into consideration.

If a cell that satisfies the communication quality threshold of the backhaul link corresponding to the desired communication speed of the UE is obtained in step ST2201, the mobile terminal moves to step ST2203 and performs cell ranking based on the communication quality of the cell backhaul link. The cell with the best communication quality of the backhaul link (best cell) is selected. The UE performs celery selection on the best cell selected in step ST1802, step ST2003, step ST1902, step ST2202 or step ST2203.

By doing in this way, it becomes possible to have the effects described in the first modification of the first to fourth embodiments in the cell ranking.

As disclosed in the present embodiment, the quality of the backhaul link of at least one of the serving cell and the neighboring cell is considered by combining the methods disclosed in the first modification of the first to fourth embodiments. Cell reselection and cell reselection to a cell with weak received power are possible, and it is possible to improve interference problems and capacity problems in heterogeneous networks.

Furthermore, by combining the necessary methods according to the arrangement status of the macro cell and the local node, it becomes possible to optimize interference and capacity even in a heterogeneous network of a vast and complicated situation. .

Embodiment 6 FIG.
As described above, heterogeneous networks are required to reduce interference and improve capacity. As the method, Non-Patent Document 8 proposes that measurement of a cell with weak received power and a trigger mechanism are necessary, but no specific method is described. Non-Patent Document 9 discloses a cell selection method that considers the backhaul link of the relay node, but what kind of mechanism is taken into consideration the quality of the backhaul link, for a specific method, Nothing is disclosed. Further, in the method disclosed in Non-Patent Document 10, communication control becomes very complicated.

In order to solve these problems, this embodiment discloses a specific method for taking into account at least one of the communication quality of the cell backhaul link and the uplink state in the cell selection. In this embodiment, a case will be described in which both the communication quality of the cell backhaul link and the uplink state are taken into consideration.

FIG. 23 is a flowchart showing a UE cell selection processing procedure according to the technique of Non-Patent Document 3. In Step ST2301, the UE measures received power of neighboring cells for cell selection. In Step ST2302, the UE calculates a value (Srxlev) obtained by inserting a certain correction value into the received power from the measurement value for each cell. This correction value and its calculation method are described in Non-Patent Document 3.

The UE that has calculated Srxlev determines whether or not the Srxlev is greater than 0 in step ST2303. If the Srxlev is greater than 0, the cell is determined as a best cell selection candidate, and the process moves to step ST2305. When the Srxlev is 0 or less, the cell is not regarded as a best cell selection candidate.

UE performs each process of step ST2302 and step ST2303 with respect to the one or some cell obtained by the measurement for cell selection. As a result, when no cell having Srxlev greater than 0 is obtained, the mobile terminal shifts to step ST2304 to enter an out-of-service state. If a cell having Srxlev greater than 0 is obtained, the process of step ST2305 is performed. In Step ST2305, the UE selects a cell (best cell) having the highest received power from the cells having Srxlev greater than 0. Then, the UE camps on the selected best cell.

FIG. 24 is a flowchart showing a cell selection processing procedure that takes into consideration the communication quality of the cell backhaul link and the uplink state, disclosed in the present embodiment. The processing of the flowchart shown in FIG. 24 is similar to the processing of the flowchart shown in FIG. 18, FIG. 19, FIG. 20, FIG. 22 and FIG. A number is attached and explanation of processing is omitted.

In this embodiment, when a cell having Srxlev greater than 0 is obtained in step ST2303, the UE takes into account the reception quality of the cell in step ST1801 when selecting the best cell, and in step ST2002, the cell In step ST1901, the communication quality of the cell backhaul link is taken into consideration, and in step ST2201, the desired communication speed of the UE is taken into consideration.

If a cell that satisfies the communication quality threshold of the backhaul link corresponding to the desired communication speed of the UE cannot be obtained in Step ST2201, the process proceeds to Step ST2202, and the cell with the best cell reception quality (best cell) Make a selection. Alternatively, the cell with the smallest cell path loss (best cell) may be selected.

If a cell satisfying the communication quality threshold of the backhaul link corresponding to the desired communication speed of the UE is obtained in step ST2201, the cell moves to step ST2203 and the cell with the best communication quality of the cell backhaul link is obtained. Select (Best Cell). The UE selects the best cell selected in Step ST1802, Step ST2003, Step ST1902, Step ST2202 or Step ST2203 as a cell to camp on.

As can be seen from FIG. 24, in the present embodiment, the cell ranking method of the cell reselection disclosed in the second embodiment to the fifth embodiment after the start of measurement for cell reselection can be applied.

By adopting the method disclosed in the present embodiment, it is possible to take into consideration at least one of the communication quality of the cell backhaul link and the uplink state even in the cell selection. For this reason, it becomes possible to improve the interference problem and capacity problem in heterogeneous networks.

Furthermore, by combining the necessary methods according to the arrangement status of the macro cell and the local node, it becomes possible to optimize interference and capacity even in a heterogeneous network of a vast and complicated situation. .

Also, by applying the method disclosed in the second to fifth embodiments in selecting the best cell, it is possible to have each effect.

Embodiment 7 FIG.
In the first to sixth embodiments, the method of taking into account at least one of the communication quality of the cell backhaul link and the uplink state in celery selection and cell selection has been disclosed. Now, a method of taking into account at least one of the communication quality of the cell backhaul link and the uplink state in handover (HO) is disclosed.

In the heterogeneous networks, the above-described problems occur not only in cell selection and cell reselection, but also in the case of handover (HO). This is because the aforementioned problem occurs when the serving cell is selected or changed. In HO, a target cell to be a HO destination must be selected. Therefore, the selection of the target cell becomes a problem.

FIG. 25 is a sequence diagram showing a normal HO processing procedure according to the technique of Non-Patent Document 1. The serving cell becomes the source cell. Here, a case where communication between the source cell and the target cell is performed using the X2 interface is shown.

In step ST2501, the source cell notifies the UE of a measurement control message, and causes the UE to perform measurement, that is, measurement. Specifically, reception power representing reception quality is measured. In Step ST2502, the UE notifies the source cell of the measurement result, that is, the measurement result, as a measurement report (Measurement report). Specifically, the reception quality measurement result, more specifically, the received power measurement value is notified as a measurement report.

In step ST2503, the source cell determines a target cell using a measurement report from the UE. In this way, in normal HO, each cell determines whether the UE needs HO and to which cell to make HO mainly based on the reception quality measurement result of the UE. That is, the source cell activates the HO procedure using the measurement report received from the UE in step ST2502 as a trigger.

In step ST2504, the source cell that has determined the target cell notifies the target cell of a HO request message. The HO request message includes UE context (UE context) information, which is information related to the UE to be HOed. In Step ST2505, the target cell determines whether to permit HO to the UE in consideration of the state of the own cell and information on the UE. FIG. 25 shows a case where the target cell permits HO to the UE.

In the case of HO permission, the target cell notifies the source cell of a permission message (HO request Ack) for the HO request in step ST2506. In Step ST2507, the source cell that has received the permission message notifies the UE of Mobility (HO) control information. In step ST2509, the source cell notifies the target cell of data necessary for continuing communication with HO and PDCP SN status (SN （status) information related thereto.

The UE that has received the HO control information in step ST2507 performs detachment from the source cell in step ST2508, and synchronizes with the target cell in step ST2510 based on the target cell information included in the HO control information. Process. In step ST2511, the target cell notifies the UE of uplink resource allocation information and TA (Timing Advance) information that is transmission timing information.

In Step ST2512, the UE that has received the uplink resource allocation information and TA information notifies the target cell of an RRC connection reconfiguration complete (RRC connection reconfiguration complete) message. Thereby, data communication between the UE and the target cell is started. In Step ST2513, the target cell that has received the RRC connection reconfiguration completion message in Step ST2512 completes HO (HO ソ ー ス completion) with the source cell via the MME and serving GW (S-GW) that are higher-level devices. Process for. Along with the process for completing HO in step ST2513, the source cell releases the resources used for the control associated with the information on the UE in step ST2514.

In celery selection and cell selection, the UE selects the best cell. However, in HO, as shown in step ST2503 in FIG. 25, the serving cell that is the source cell selects the target cell. FIG. 26 is a flowchart illustrating an example of a target cell selection procedure by the serving cell. In Step ST2601, the serving cell receives the measurement report (Measurement Report) notified from the UE.

In step ST2602, the serving cell that has received the measurement report notified from the UE in step ST2601 selects a cell having the best reception quality as a target cell based on the reception quality of the UE from the result of the measurement report.

Therefore, in the present embodiment, at the time of selection of a target cell by the serving cell, at least one of the communication quality of the cell backhaul link and the uplink state is taken into account in the HO. In this embodiment, a case will be described in which both the communication quality of the cell backhaul link and the uplink state are taken into consideration.

FIG. 27 is a flowchart showing the processing procedure of HO taking into consideration the communication quality of the cell backhaul link and the uplink state, disclosed in the present embodiment. The processing of the flowchart shown in FIG. 27 is similar to the processing of the flowcharts shown in FIGS. 18, 19, 20, 22, and 26, so only the different processing will be described, and the corresponding steps will be the same step. A number is attached and explanation of processing is omitted.

In step ST2601, the serving cell that has received the measurement report notified from the UE takes the cell reception quality into consideration in step ST1801 and the cell path loss in step ST2002 when selecting the target cell. In step ST2201, the desired communication speed of the UE is taken into consideration in step ST2201.

If a cell that satisfies the communication quality threshold of the backhaul link corresponding to the desired communication speed of the UE cannot be obtained in step ST2201, the process proceeds to step ST2704, and the cell with the best cell reception quality is selected as the target cell. To do. Alternatively, the cell with the smallest cell path loss may be selected as the target cell.

When a cell that satisfies the communication quality threshold of the backhaul link corresponding to the desired communication speed of the UE is obtained in step ST2201, the cell moves to step ST2705, and the cell having the best communication quality of the cell backhaul link As the target cell. The serving cell selects, as a target cell, the cell selected in step ST2701, step ST2702, step ST2703, step ST2704, and step ST2705.

As can be seen from FIG. 27, in the present embodiment, the cell ranking method after the start of measurement for celery selection in the celery selection disclosed in the second to fifth embodiments is the target cell by the serving cell in HO. Can be applied to the choice of.

In the selection of the target cell disclosed in the present embodiment, the serving cell needs to recognize the communication quality of the backhaul link of the neighboring cell. As this method, the method disclosed in the second embodiment may be used.

In the selection of the target cell disclosed in the present embodiment, the serving cell needs to recognize a path loss between the UE and the cell. It is necessary to recognize not only the serving cell path loss but also the neighboring cell path loss. As this method, a measurement configuration for path loss is provided. The serving cell notifies the UE to measure the path loss of the adjacent cell using the measurement configuration for path loss as the measurement control shown in Step ST2501 of FIG. For a cell whose measured path loss satisfies a certain condition, the UE notifies the serving cell of the path loss value together with the identity (PCI, GCI) of the cell in the measurement report corresponding to the measurement configuration.

As a certain condition, for example, the serving cell notifies the UE of the threshold for path loss in the measurement configuration. The UE that has received the measurement configuration measures the path loss of at least one of the serving cell and the neighboring cell, and notifies the serving cell of the measurement report for the cell whose path loss measurement result is greater than the threshold. As another example, the UE measures the path loss of at least one of the serving cell and the neighboring cell, and notifies the serving cell of the measurement report for the cell with the smallest path loss. These methods are set by the serving cell separately or simultaneously in the measurement configuration. Thereby, the serving cell can recognize a path loss between the serving cell and the UE or between the neighboring cell and the UE.

As for the path loss between the serving cell and the UE, the serving cell may measure the uplink received power from the UE and derive it using the transmission power of the UE and the received power measurement value. When the serving cell sets the transmission power of the UE, the serving cell recognizes the transmission power of the UE. When the UE sets transmission power, the UE may notify the serving cell of the transmission power information together with the transmission data. Thereby, the serving cell can recognize the transmission power information.

As described in the fourth embodiment, an actual distance may be used as the uplink state instead of a path loss. In this case, a measurement configuration for position measurement is provided. The UE that has received the measurement configuration measures the position of the own UE by GPS or the like. The UE notifies the serving cell of the measured position through a measurement report corresponding to the measurement configuration.

The serving cell needs to recognize not only the UE but also the location of its own cell and neighboring cells. Each cell may measure the position of its own cell by GPS or the like, and notify the neighboring cell of the position information in advance. The notification may be performed when each cell is installed or initialized, that is, at initialization. As a result, the serving cell can recognize the position of the neighboring cell, and therefore, the actual distance between each cell and the UE can be derived using the position of the UE described above. .

In the selection of the target cell disclosed in the present embodiment, the serving cell needs to recognize the desired communication speed of the UE. When using the desired communication speed of the UE, the amount of transmission data of the UE, and the capability of the UE, not only the desired communication speed of the UE, it is necessary for the serving cell to recognize these pieces of information. Here, the UE notifies the serving cell of such information in advance. The UE may notify the serving cell of these pieces of information when requesting the RRC connection or when in the RRC_connected state. Alternatively, the serving cell may be notified together with the measurement report shown in step ST2502 of FIG. 25 or included in the measurement report message. RRC signaling may be used, or MAC signaling may be used. These pieces of information may be notified individually, or a plurality of pieces of information may be combined and notified as necessary.

By adopting the method disclosed in the present embodiment, even in HO, it becomes possible to take into consideration at least one of the communication quality of the cell backhaul link and the uplink state. For this reason, it becomes possible to improve the interference problem and capacity problem in heterogeneous networks.

Further, the methods disclosed in the first embodiment to the present embodiment may be combined, and in this case, when the serving cell is selected or changed regardless of the UE state (RRC_Idle state and RRC_Connected state), the cell back It becomes possible to take into consideration at least one of the communication quality of the hall link and the uplink state, and it becomes possible to improve the interference problem and the capacity problem in the heterogeneous network.

In addition, by combining the required methods according to the arrangement status of the macro cell and the local node, it becomes possible to optimize interference and capacity even in a heterogeneous network in a vast and complicated situation. .

The method disclosed in the present invention is not limited to a network in which one or more local nodes are incorporated in a normal eNB (macro cell), but also in a macro cell only network or a local node only network. It is possible to apply for For example, in a macro cell, a dedicated line is used for many of the backhaul links, but the communication quality of the dedicated line varies from cell to cell. When an event is being performed in a certain cell, the communication load of the cell increases, and the communication quality of the backhaul dedicated line of the cell may deteriorate accordingly. Even in such a case, by selecting the serving cell in consideration of the communication quality of the backhaul link, it is possible to select a different cell while avoiding the cell. Therefore, it is possible to distribute the capacity among the cells, and it is possible to prevent the communication speed from being lowered and the communication interruption that occurs in the worst case.

In the above embodiment, the LTE system (E-UTRAN) has been mainly described. However, the mobile communication system of the present invention can be applied to any communication system using one or a plurality of types of nodes. . For example, the present invention can be applied to a W-CDMA system (UTRAN, UMTS) or LTE-Advanced.

Although the present invention has been described in detail, the above description is illustrative in all aspects, and the present invention is not limited thereto. It is understood that countless variations that are not illustrated can be envisaged without departing from the scope of the present invention.

71 mobile terminals, 72 base stations, 72-1 eNB, 72-2 Home-eNB, 73 MME / S-GW unit, 74 HeNBGW.

Claims (4)

1. A plurality of base station devices connected to a core network; and mobile terminal devices capable of wireless communication with each of the base station devices, wherein at least a part of a plurality of cells that are communicable ranges of the plurality of base station devices An overlapping mobile communication system,
   The mobile terminal device
   Based on selection information including reception quality of a signal from a base station apparatus in each cell and communication quality of a communication line between the base station apparatus and the core network, a communication target is selected from the plurality of cells. A mobile communication system, wherein a cell of a base station device to be selected is selected.
2. Relaying wireless communication between a plurality of base station devices, a mobile terminal device capable of wireless communication with each of the base station devices, and at least one of the plurality of base station devices and the mobile terminal device A mobile communication system in which at least a part of a plurality of cells that are communicable ranges of the plurality of base station devices overlap each other,
   The mobile terminal device
   Based on selection information including the reception quality of the signal from the base station apparatus in each cell and the communication quality of the communication line between the base station apparatus and the relay apparatus, a communication target is selected from the plurality of cells. A mobile communication system, wherein a cell of a base station device to be selected is selected.
3. The mobile communication system according to claim 1 or 2, wherein the selection information includes a state of an uplink communication line from the mobile terminal apparatus to the base station apparatus in each cell.
4. A mobile communication system including a plurality of base station devices and mobile terminal devices capable of wireless communication with each of the base station devices, wherein at least a part of a plurality of cells that are communicable ranges of the plurality of base station devices overlap Because
   The mobile terminal device
   Based on selection information including the reception quality of the signal from the base station apparatus in each cell and the state of the uplink communication line from the mobile terminal apparatus to the base station apparatus in each cell, the communication target is selected from the plurality of cells. A mobile communication system, wherein a cell of a base station device to be selected is selected.

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