JP2015159491A - Network selection control method, user terminal and cellular base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately control off-road related processing.SOLUTION: A network selection control method for selecting, from among E-UTRAN and WLAN, an access network for transmission and reception of the traffic of a UE 100 is provided. The network selection control method includes the steps of: transmitting, from an eNB 200 connected to the UE 100, off-road control information to request to change an access network for traffic transmission and reception to a WLAN; and controlling the UE 100, which receives the off-road control information is in a predetermined state, not to change the access network for traffic transmission and reception to a WLAN 30, when the self-UE 100 is in a predetermined condition.

Description

  The present invention relates to a network selection control method, a user terminal, and a cellular base station for selecting an access network that transmits and receives user terminal traffic from a cellular RAN and a wireless LAN.

  In recent years, user terminals (so-called dual terminals) having both functions of cellular communication and wireless LAN (Local Area Network) communication have been spreading. In addition, the number of wireless LAN access points managed by operators of cellular communication systems is increasing. In view of this, 3GPP (3rd Generation Partnership Project), which is a standardization project for cellular communication systems, is studying a technology that can enhance cooperation between cellular RAN (Radio Access Network) and wireless LAN.

  For example, the traffic load of the cellular RAN can be reduced (offload) by switching the traffic of the user terminal accommodated by the cellular RAN to be accommodated by the wireless LAN. In addition, a plurality of methods have been proposed as a network selection method for selecting an access network that transmits and receives user terminal traffic from the cellular RAN and the wireless LAN (see Non-Patent Document 1).

3GPP Technical Report “TR37.834 V12.0.0” December 2013

  Among the network selection methods described above, there is a method in which a user terminal performs offload-related processing for switching an access network that transmits and receives its own traffic to a wireless LAN, based on offload control information transmitted from the cellular RAN. is there.

  In such a system, when providing offload control information to a user terminal without considering the state of the user terminal, the user terminal that should not perform offload related processing, that is, the one accommodated by the cellular RAN There is a possibility that a user terminal that is preferable performs offload-related processing.

  Therefore, an object of the present invention is to provide a network selection control method, a user terminal, and a cellular base station that can appropriately control offload-related processing.

  The network selection control method according to the first feature is a method for selecting an access network that transmits and receives user terminal traffic from the cellular RAN and the wireless LAN. The network selection control method includes a step of transmitting offload control information for requesting a cellular base station connected to the user terminal to switch an access network that transmits and receives the traffic to the wireless LAN; and The user terminal that has received the control information has a step of controlling the access network for transmitting and receiving the traffic not to be switched to the wireless LAN when the state of the user terminal is in a predetermined state.

  The user terminal which concerns on a 2nd characteristic can select the access network which transmits / receives its traffic from cellular RAN and wireless LAN. The user terminal receives from the cellular base station connected to the user terminal, offload control information for requesting to switch the access network that transmits and receives the traffic to the wireless LAN, and the offload control A control unit that controls not to switch the access network that transmits and receives the traffic to the wireless LAN when the state of the user terminal is in a predetermined state even when the information is received.

  A cellular base station according to the third feature is connected to a user terminal. The cellular base station includes a transmitter that transmits offload control information for requesting switching of an access network that transmits and receives traffic of the user terminal to a wireless LAN, and a state of the user terminal is a predetermined state. A control unit that controls not to transmit the offload control information to the user terminal when it is determined that

  According to the present invention, it is possible to appropriately control offload-related processing.

It is a system configuration figure concerning an embodiment. It is a block diagram of UE which concerns on embodiment. It is a block diagram of eNB which concerns on embodiment. It is a protocol stack figure of a radio | wireless interface. It is a figure for demonstrating a MBMS interest notification. It is a figure for demonstrating proximity notification. It is a figure which shows the operating environment which concerns on embodiment. It is a figure which shows the operation | movement pattern 1 which concerns on embodiment. It is a figure which shows the operation | movement pattern 2 which concerns on embodiment.

[Outline of Embodiment]
The network selection control method according to the embodiment is a method for selecting an access network that transmits and receives user terminal traffic from the cellular RAN and the wireless LAN. The network selection control method includes a step of transmitting offload control information for requesting a cellular base station connected to the user terminal to switch an access network that transmits and receives the traffic to the wireless LAN; and The user terminal that has received the control information has a step of controlling the access network for transmitting and receiving the traffic not to be switched to the wireless LAN when the state of the user terminal is in a predetermined state.

  In the embodiment, the predetermined state is an MBMS interest notification indicating that an MBMS service provided by broadcast or multicast is received or interested in reception, and an interest related to the MBMS service. Is not changed compared with the time when the MBMS interest notification is transmitted.

  In the embodiment, the predetermined state is a transmission of a first proximity notification indicating entry into the vicinity of a CSG member cell registered in the white list of the own user terminal, and from the vicinity of the CSG member cell. This is a state where the second proximity notification indicating that the user is leaving has not been transmitted yet.

  In the embodiment, the predetermined state is a state in which radio resources are allocated to the user terminal by quasi-static scheduling (SPS) from the cellular RAN.

  In the operation pattern 1 according to the embodiment, in the step of transmitting the offload control information, the cellular base station transmits RAN auxiliary information including the offload control information by a broadcast signal. In the network selection control method, the user terminal that has received the RAN auxiliary information holds the RAN auxiliary information when the state of the own user terminal is the predetermined state, and the user terminal And a step of operating according to the held RAN auxiliary information when the terminal state is no longer the predetermined state.

  In the operation pattern 1 according to the embodiment, the network selection control method further includes a step of holding the updated RAN auxiliary information when the RAN auxiliary information transmitted from the cellular base station is updated.

  In the operation pattern 1 according to the embodiment, in the controlling step, the user terminal omits offload related processing for switching the access network that transmits and receives the traffic to the wireless LAN.

  In the operation pattern 1 according to the embodiment, the offload related processing is at least one of scanning of a wireless LAN access point, selection of the access network, transmission of a wireless LAN measurement report, and switching of the traffic.

  In the operation pattern 2 according to the embodiment, in the step of transmitting the offload control information, the cellular base station transmits the offload control information by a unicast signal. In the controlling step, the user terminal ignores the received offload control information.

  In the operation pattern 2 according to the embodiment, in the step of transmitting the offload control information, the cellular base station transmits the offload control information by a unicast signal. In the controlling step, the user terminal notifies the cellular base station that the user terminal is in the predetermined state.

  In the operation pattern 2 according to the embodiment, the notification is registered in the white list of the own user terminal, retransmission of the MBMS interest notification indicating that the MBMS distributed by broadcast or multicast is received or interested in reception. At least one of retransmission of the first proximity notification indicating entry into the vicinity of the CSG member cell and rejection notification for the offload control information.

  In the operation pattern 2 according to the embodiment, in the step of transmitting the offload control information, the cellular base station transmits the offload control information by a unicast signal. The network selection control method further includes a step of controlling the cellular base station that has determined that the state of the user terminal is a predetermined state not to transmit the offload control information to the user terminal.

  The user terminal according to the embodiment can select an access network that transmits and receives its own traffic from the cellular RAN and the wireless LAN. The user terminal receives from the cellular base station connected to the user terminal, offload control information for requesting to switch the access network that transmits and receives the traffic to the wireless LAN, and the offload control A control unit that controls not to switch the access network that transmits and receives the traffic to the wireless LAN when the state of the user terminal is in a predetermined state even when the information is received.

  The cellular base station which concerns on embodiment connects with a user terminal. The cellular base station includes a transmitter that transmits offload control information for requesting switching of an access network that transmits and receives traffic of the user terminal to a wireless LAN, and a state of the user terminal is a predetermined state. A control unit that controls not to transmit the offload control information to the user terminal when it is determined that

[Embodiment]
Hereinafter, an embodiment in which an LTE system, which is a cellular communication system configured in accordance with the 3GPP standard, is linked with a wireless LAN (WLAN) system will be described with reference to the drawings.

(System configuration)
FIG. 1 is a system configuration diagram according to the embodiment. As shown in FIG. 1, the LTE system includes a plurality of UEs (User Equipment) 100, an E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) 10, and an EPC (Evolved Packet Core) 20.

  The E-UTRAN 10 corresponds to a cellular RAN. The EPC 20 corresponds to a core network. The E-UTRAN 10 and the EPC 20 constitute an LTE system network.

  The UE 100 is a mobile radio communication device, and performs radio communication with a cell that has established a connection. UE100 is corresponded to a user terminal. The UE 100 is a terminal (dual terminal) that supports both cellular communication and WLAN communication methods.

  The E-UTRAN 10 includes a plurality of eNBs 200 (evolved Node-B). The eNB 200 corresponds to a cellular base station. The eNB 200 manages one or a plurality of cells, and performs radio communication with the UE 100 that has established a connection with the own cell. Note that “cell” is used as a term indicating a minimum unit of a radio communication area, and is also used as a term indicating a function of performing radio communication with the UE 100. The eNB 200 has, for example, a radio resource management (RRM) function, a user data routing function, and a measurement control function for mobility control and scheduling.

  The eNB 200 is connected to each other via the X2 interface. Further, the eNB 200 is connected to an MME (Mobility Management Entity) / S-GW (Serving-Gateway) 500 included in the EPC 20 via the S1 interface.

  The EPC 20 includes a plurality of MME / S-GWs 500. The MME is a network node that performs various types of mobility control for the UE 100, and corresponds to a control station. The S-GW is a network node that performs transfer control of user data, and corresponds to an exchange.

  The WLAN 30 includes a WLAN access point (hereinafter referred to as “AP”) 300. The AP 300 is an AP (Operator controlled AP) managed by a network operator of the LTE system, for example.

  The WLAN 30 is configured in accordance with, for example, IEEE 802.11 standards. The AP 300 communicates with the UE 100 in a frequency band (WLAN frequency band) different from the cellular frequency band. The AP 300 is connected to the EPC 20 via a router or the like.

  Moreover, not only when eNB200 and AP300 are arrange | positioned separately, eNB200 and AP300 may be arrange | positioned (Collocated) in the same place. As one form of Collated, the eNB 200 and the AP 300 may be directly connected by an arbitrary interface of the operator.

  The EPC 20 may further include an ANDSF (Access Network Discovery and Selection Function) server. The ANDSF server manages ANDSF information related to the WLAN 30. The ANDSF server provides ANDSF information related to the WLAN 30 to the UE 100 by a NAS (Non Access Stratum) message.

  Next, configurations of the UE 100 and the eNB 200 will be described.

  FIG. 2 is a block diagram of the UE 100. As shown in FIG. 2, the UE 100 includes antennas 101 and 102, a cellular communication unit 111, a WLAN communication unit 112, a user interface 120, a GNSS (Global Navigation Satellite System) receiver 130, a battery 140, and a memory. 150 and a processor 160. The memory 150 and the processor 160 constitute a control unit. The UE 100 may not have the GNSS receiver 130. Further, the memory 150 may be integrated with the processor 160, and this set (that is, a chip set) may be used as the processor 160 '.

  The antenna 101 and the cellular communication unit 111 are used for transmitting and receiving cellular radio signals. The cellular communication unit 111 converts the baseband signal output from the processor 160 into a cellular radio signal and transmits it from the antenna 101. In addition, the cellular communication unit 111 converts a cellular radio signal received by the antenna 101 into a baseband signal and outputs it to the processor 160.

  The antenna 102 and the WLAN communication unit 112 are used for transmission / reception of a WLAN radio signal. The WLAN communication unit 112 converts the baseband signal output from the processor 160 into a WLAN radio signal and transmits it from the antenna 102. In addition, the WLAN communication unit 112 converts the WLAN radio signal received by the antenna 102 into a baseband signal and outputs the baseband signal to the processor 160.

  The user interface 120 is an interface with a user who owns the UE 100, and includes, for example, a display, a microphone, a speaker, and various buttons. The user interface 120 receives an input from the user and outputs a signal indicating the content of the input to the processor 160. The GNSS receiver 130 receives a GNSS signal and outputs the received signal to the processor 160 in order to obtain position information indicating the geographical position of the UE 100. The battery 140 stores power to be supplied to each block of the UE 100.

  The memory 150 stores a program executed by the processor 160 and information used for processing by the processor 160. The processor 160 includes a baseband processor that performs modulation / demodulation and encoding / decoding of a baseband signal, and a CPU that executes programs stored in the memory 150 and performs various processes. The processor 160 may further include a codec that performs encoding / decoding of an audio / video signal. The processor 160 executes various processes and various communication protocols described later.

  FIG. 3 is a block diagram of the eNB 200. As illustrated in FIG. 3, the eNB 200 includes an antenna 201, a cellular communication unit 210, a network interface 220, a memory 230, and a processor 240. The memory 230 and the processor 240 constitute a control unit. Further, the memory 230 may be integrated with the processor 240, and this set (that is, a chip set) may be used as the processor 240 '.

  The antenna 201 and the cellular communication unit 210 are used for transmitting and receiving cellular radio signals. The cellular communication unit 210 converts the baseband signal output from the processor 240 into a cellular radio signal and transmits it from the antenna 201. In addition, the cellular communication unit 210 converts a cellular radio signal received by the antenna 201 into a baseband signal and outputs it to the processor 240.

  The network interface 220 is connected to the neighboring eNB 200 via the X2 interface, and is connected to the MME / S-GW 500 via the S1 interface.

  The memory 230 stores a program executed by the processor 240 and information used for processing by the processor 240. The processor 240 includes a baseband processor that performs modulation / demodulation and encoding / decoding of a baseband signal, and a CPU that executes programs stored in the memory 230 and performs various processes. The processor 240 executes various processes and various communication protocols described later.

  FIG. 4 is a protocol stack diagram of a radio interface in the LTE system. As shown in FIG. 4, the radio interface protocol is divided into the first to third layers of the OSI reference model, and the first layer is a physical (PHY) layer. The second layer includes a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, and a PDCP (Packet Data Convergence Protocol) layer. The third layer includes an RRC (Radio Resource Control) layer.

  The physical layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Between the physical layer of UE100 and the physical layer of eNB200, user data and a control signal are transmitted via a physical channel.

  The MAC layer performs data priority control, retransmission processing by hybrid ARQ (HARQ), and the like. Between the MAC layer of the UE 100 and the MAC layer of the eNB 200, user data and control signals are transmitted via a transport channel. The MAC layer of the eNB 200 includes a scheduler that determines an uplink / downlink transport format (transport block size, modulation / coding scheme) and an allocation resource block to the UE 100.

  The RLC layer transmits data to the RLC layer on the receiving side using the functions of the MAC layer and the physical layer. Between the RLC layer of the UE 100 and the RLC layer of the eNB 200, user data and control signals are transmitted via a logical channel.

  The PDCP layer performs header compression / decompression and encryption / decryption.

  The RRC layer is defined only in the control plane that handles control signals. Control signals (RRC messages) for various settings are transmitted between the RRC layer of the UE 100 and the RRC layer of the eNB 200. The RRC layer controls the logical channel, the transport channel, and the physical channel according to establishment, re-establishment, and release of the radio bearer. When there is a connection (RRC connection) between the RRC of the UE 100 and the RRC of the eNB 200, the UE 100 is in the RRC connected state, and otherwise, the UE 100 is in the RRC idle state.

  A NAS (Non-Access Stratum) layer located above the RRC layer performs session management, mobility management, and the like. The MME 500 and the ANDSF server transmit / receive a NAS message to / from the UE 100.

  In the LTE system, OFDMA (Orthogonal Frequency Division Multiplexing Access) is applied to the downlink, and SC-FDMA (Single Carrier Frequency Multiple Access) is applied to the uplink.

  The radio frame is composed of 10 subframes arranged in the time direction. Each subframe is composed of two slots arranged in the time direction. The length of each subframe is 1 ms, and the length of each slot is 0.5 ms. Each subframe includes a plurality of resource blocks (RB) in the frequency direction and includes a plurality of symbols in the time direction. Each resource block includes a plurality of subcarriers in the frequency direction. Among radio resources (time / frequency resources) allocated to the UE 100, frequency resources can be specified by resource blocks, and time resources can be specified by subframes (or slots).

  In the downlink, the section of the first few symbols of each subframe is an area mainly used as a physical downlink control channel (PDCCH) for transmitting a control signal. The remaining section of each subframe is an area that can be used as a physical downlink shared channel (PDSCH) mainly for transmitting user data.

  In the uplink, both ends in the frequency direction in each subframe are regions used mainly as physical uplink control channels (PUCCH) for transmitting control signals. The other part in each subframe is an area that can be used mainly as a physical uplink shared channel (PUSCH) for transmitting user data.

(MBMS)
MBMS is introduced in the LTE system according to the embodiment. In the following, an overview of MBMS (Multimedia Broadcast Multicast Service) will be described.

  In MBMS, the UE 100 receives an MBMS service provided by multicast or broadcast from the network. The UE 100 can receive the MBMS service not only in the RRC connected state but also in the RRC idle state.

  A plurality of cells constitute one MBSFN (Multicast-Broadcast Single-Frequency Network) area, and a plurality of MBSFN areas constitute an MBMS service area. In addition to the network entity shown in FIG. 1, the network includes a BMSC (broadcast multiservice service center) that provides an MBMS service distribution function, and an MBMS-GW (MBMS gateway) that broadcasts the MBMS service to each eNB 200. MCE (Multi-cell Coordination Entity) that controls radio resources used by each eNB 200 in the same MBSFN area is provided.

  In order to support the reception continuity of the MBMS service, MBMS Interest Indication (MBMS Interest Indication) has been introduced. FIG. 5 is a diagram for explaining the MBMS interest notification.

  As shown in FIG. 5, the MBMS interest notification is transmitted from the UE 100 in the RRC connected state to the E-UTRAN 10, and the UE 100 is receiving / not interested in receiving the MBMS service or is no longer receiving the MBMS service. Information to the E-UTRAN 10 regarding no / not interested in receiving is provided. Specifically, when the UE 100 establishes the RRC connection, and when the interest in the MBMS service (that is, interest in the MBMS frequency) changes compared to the time when the MBMS interest notification was last transmitted, the MBMS An interest notice is transmitted to E-UTRAN10. Note that the UE 100 can transmit the MBMS interest notification to the cell only when receiving the SIB 15 from the cell providing the system information block type 15 (SIB 15).

  For the MBMS interest notification, the UE 100 receives frequency information indicating an MBMS frequency received by MRB (MBMS Point-to-Multipoint Radio Bearer) or interested in reception, and prioritizes MBMS reception over unicast reception. MBMS priority information shown. Based on the MBMS interest notification, the E-UTRAN 10 performs control (handover, etc.) for guaranteeing MBMS reception to the UE 100 that is receiving or interested in receiving the MBMS service.

(Specific cell)
In the LTE system according to the embodiment, a specific cell whose access right is restricted is introduced. Below, the outline | summary of a specific cell is demonstrated.

  The specific cell is a CSG (Closed Subscriber Group) cell or a hybrid cell. The specific cell is a cell that broadcasts the CSG ID. The UE 100 stores a white list that is a list of CSG IDs to which the own UE 100 has access rights. UE100 collates CSG ID broadcast from a specific cell with a white list, and when the said CSG ID is contained in a white list, it judges that it is an accessible cell (CSG member cell).

  Moreover, proximity notification (Proximity Indication) is introduced in order to perform an efficient handover to the CSG member cell by the UE 100 measuring the frequency of the CSG member cell. FIG. 6 is a diagram for explaining proximity notification.

  As shown in FIG. 6, the proximity notification is transmitted from the UE 100 in the RRC connected state to the E-UTRAN 10, and notifies the E-UTRAN 10 whether the UE 100 enters or leaves the vicinity of the CSG member cell. Specifically, the UE 100 determines whether a CSG member cell exists in the vicinity by an autonomous search process, and transmits a proximity notification to the E-UTRAN 10 based on the determination result.

  The proximity notification can include frequency information indicating the frequency of the CSG member cell and type information indicating whether the UE 100 enters (Entering) or leaves (Leaving) the vicinity of the CSG member cell.

  The E-UTRAN 10 transmits a measurement configuration (Measurement configuration) for measurement to the CSG member cell to the UE 100 based on the proximity notification. Based on the measurement setting, the UE 100 transmits a measurement report including a measurement cell identifier (PCI: Physical Cell Identifier) to the E-UTRAN 10. The E-UTRAN 10 starts a handover procedure to the CSG member cell based on the measurement report.

(Quasi-static scheduling)
Semi-static scheduling (SPS: Semi Persistent Scheduling) is introduced in the LTE system according to the embodiment. In the following, an outline of quasi-static scheduling will be described.

  Basically, dynamic scheduling in units of one subframe is applied to uplink and downlink scheduling. On the other hand, services such as VoLTE (Voice over LTE), which is packet-based voice communication, intermittently transmits and receives a small amount of user data. Therefore, if dynamic scheduling is applied, control signals for PDCCH are wasted. Become more. For this reason, a service such as VoLTE (Voice over LTE) is applied with quasi-static scheduling that continuously assigns radio resources to the UE 100, thereby realizing reduction of control signals, that is, reduction of overhead.

(Operating environment according to the embodiment)
Hereinafter, an operating environment according to the embodiment will be described. FIG. 7 is a diagram illustrating an operating environment according to the embodiment. As shown in FIG. 7, a plurality of APs 300 (AP 300-1 to 300-3) are provided in the cell of the eNB 200. In addition, a plurality of UEs 100 (UEs 100-1 to 100-4) are present in the cell of the eNB 200. Furthermore, one or a plurality of specific cells may be provided in the cell of the eNB 200.

  UE100-1 thru | or UE100-3 are connected to eNB200, and are transmitting / receiving the traffic (user data) with eNB200. The UE 100-4 is connected to the AP 300-3 and transmits and receives traffic (user data) to and from the AP 300-3.

  In such an operating environment, the traffic load of the eNB 200 can be reduced by switching (traffic steering) so that the traffic of the UE 100 accommodated in the eNB 200 (E-UTRAN 10) is directed to the AP 300 (WLAN 30). Yes (ie off-road). For traffic steering, when the connection destination of the UE 100 is switched between the eNB 200 and the AP 300, and at least a part of the data path is switched between the eNB 200 and the AP 300 while the UE 100 is connected to both the eNB 200 and the AP 300. There are cases.

  Each UE 100 performs network selection for selecting an access network that transmits and receives traffic of the UE 100 from the E-UTRAN 10 and the WLAN 30 based on a network selection rule defined in advance. For example, the network selection rule is a rule that performs traffic steering for the WLAN 30 when “RAN measurement value <A & WLAN measurement value> B” and “offload is required”. Network selection rules may be provided from the ANDSF server.

  The eNB 200 transmits RAN auxiliary information applied to the network selection rule to the UE 100. The RAN auxiliary information includes, for example, load information related to the load level of the E-UTRAN 10 and thresholds (such as “A” and “B” described above) compared with the RAN measurement value and / or the WLAN measurement value. .

  The load information is information indicating the load level of the E-UTRAN 10 or information indicating requesting offload. That is, the load information is information for requesting the UE 100 to offload (that is, to switch the access network that transmits and receives traffic to the WLAN 30) directly or indirectly. Hereinafter, information (load information) requesting such offload is referred to as “offload control information”.

(Network selection control method)
Hereinafter, a network selection control method according to the embodiment will be described.

  The network selection control method according to the embodiment is a method for controlling network selection for selecting an access network for transmitting and receiving the traffic of the UE 100 from the E-UTRAN 10 and the WLAN 30. In the network selection control method, the eNB 200 connected to the UE 100 transmits the offload control information for requesting that the access network that transmits and receives traffic is switched to the WLAN 30 (offload), and the offload control information is received. And the UE 100 controlling not to switch the access network for transmitting and receiving traffic to the WLAN 30 when the UE 100 is in a predetermined state.

  In the embodiment, the predetermined state means that an MBMS interest notification indicating that the MBMS service provided by broadcast or multicast is received or interested in reception is transmitted to the eNB 200, and the interest related to the MBMS service. Is not changed compared to the point in time when the MBMS interest notification is transmitted.

  That is, even if the UE 100 receiving or interested in receiving the MBMS service in the RRC connected state maintains the connection with the eNB 200 without following the request even if the UE 100 is requested to perform offloading. Thereby, the reception continuity of the MBMS service for the UE 100 receiving or interested in receiving the MBMS service can be guaranteed.

  Alternatively, the predetermined state means that the first proximity notification indicating that the UE enters the vicinity of the CSG member cell registered in the white list of the UE 100 is transmitted to the eNB 200 and that the CSG member cell is separated from the vicinity. This is a state in which the second proximity notification shown is not yet transmitted to the eNB 200. The first proximity notification is a proximity notification including type information indicating Entering. The second proximity notification is a proximity notification including type information indicating Leaving. Alternatively, in addition to transmitting the first proximity notification, it may be added to the condition that the measurement setting of the CSG member cell is received.

  That is, UE 100 in which a CSG member cell is present in the vicinity in the RRC connected state maintains the connection with eNB 200 without following the request even if the off load is requested from eNB 200 in the RRC connected state. Thereby, it becomes possible to hand over UE100 in which a CSG member cell exists in the vicinity to the CSG member cell. In addition, by handing over UE100 to a CSG member cell, the offload of eNB200 is also implement | achieved.

  Alternatively, in the embodiment, the predetermined state is a state in which radio resources are allocated from the E-UTRAN 10 to the own UE 100 by quasi-static scheduling (SPS).

  That is, even if the UE 100 performing VoLTE or the like in the RRC connected state is requested to be offloaded from the eNB 200, the UE 100 maintains the connection with the eNB 200 without following the request. In WLAN 30, it is doubtful whether voice communication can be continued. Even if Voice over WLAN is possible, there may be a large delay and the quality may not be ensured. Therefore, even when an offload is requested from the eNB 200, disconnection of the voice communication can be avoided and the quality of the voice communication can be ensured by maintaining the connection with the eNB 200 without following the request.

(Operation pattern 1)
Hereinafter, the operation pattern 1 according to the embodiment will be described. In the operation pattern 1 according to the embodiment, the eNB 200 transmits RAN auxiliary information including offload control information for requesting offload using a broadcast signal. The broadcast signal is, for example, a system information block (SIB) that is a kind of common RRC message.

  The UE 100 that has received the RAN auxiliary information holds the RAN auxiliary information when the UE 100 is in a predetermined state. In addition, when the RAN auxiliary information transmitted from the eNB 200 is updated, the UE 100 holds the updated RAN auxiliary information. Then, when the UE 100 is no longer in a predetermined state, the UE 100 operates according to the retained RAN auxiliary information.

  In the operation pattern 1 according to the embodiment, the UE 100 that has received the offload control information transmitted by the broadcast signal is turned off to switch the access network that transmits and receives traffic to the WLAN 30 when the UE 100 is in a predetermined state. Omit load-related processing. The offload related processing is at least one of scanning of the AP 300, selection of an access network (network selection), transmission of a WLAN measurement report, and switching of traffic (traffic steering).

  FIG. 8 is a diagram illustrating an operation pattern 1 according to the embodiment. In FIG. 8, UE100 is the state (RRC connected state) which established the connection with eNB200. Further, it is assumed that the eNB 200 is in a congestion state.

  As illustrated in FIG. 8, in step S101, the eNB 200 transmits RAN auxiliary information including offload control information for requesting offload by a broadcast signal. The UE 100 receives RAN auxiliary information including offload control information.

  In step S102, the UE 100 determines whether or not the state of the own UE 100 is a predetermined state. When it is determined that the state of the own UE 100 is not the predetermined state (step S102; NO), in step S103, the UE 100 performs offload related processing according to the received RAN auxiliary information.

  On the other hand, when it is determined that the state of the own UE 100 is a predetermined state (step S102; YES), in step S104, the UE 100 holds the received RAN auxiliary information.

  In step S105, the UE 100 determines whether or not the state of the own UE 100 is a predetermined state. When it is determined that the state of the own UE 100 is the predetermined state (step S105; YES), the process returns to step S104 and continues to hold the RAN auxiliary information. Further, when the updated RAN auxiliary information is received from the eNB 200, the held RAN auxiliary information is also updated.

  Note that, when the UE 100 performs a handover, the UE 100 updates the held RAN auxiliary information with the received RAN auxiliary information in order to receive the RAN auxiliary information transmitted from the handover destination eNB 200. However, when the handover destination eNB 200 does not support the transmission of the RAN auxiliary information, it is considered that the WLAN interworking is not supported, and thus the held RAN auxiliary information may be discarded. In addition, when the UE 100 transitions to the RRC idle state, if the RAN auxiliary information is distributed by broadcast, the RAN auxiliary information is considered valid even in the RRC idle state, and thus the retained RAN auxiliary information is discarded. Hold without.

  When it is determined that the state of the own UE 100 is not the predetermined state (step S105; NO), in step S106, the UE 100 operates according to the stored RAN auxiliary information. Specifically, the UE 100 performs offload-related processing when the held RAN auxiliary information includes offload control information for requesting offload.

(Operation pattern 2)
Hereinafter, the operation pattern 2 according to the embodiment will be described. In the operation pattern 2 according to the embodiment, the eNB 200 transmits offload control information using a unicast signal. The unicast signal is, for example, an individual RRC message.

  eNB200 judges whether the state of UE100 is a predetermined state. Specifically, the eNB 200 determines whether the UE 100 is in a predetermined state from the reception status of the MBMS interest notification, the reception status of the proximity notification, the scheduling status, and the like. When the eNB 200 determines that the state of the UE 100 is the predetermined state, the eNB 200 controls the UE 100 not to transmit the offload control information requesting the offload.

  In the operation pattern 2 according to the embodiment, the UE 100 that has received the offload control information requesting the offload ignores the received offload control information when the state of the own UE 100 is a predetermined state. Further, the UE 100 notifies the eNB 200 that the own UE 100 is in a predetermined state.

  The notification is a re-transmission of the MBMS interest notification indicating that the MBMS distributed by broadcast or multicast is received or interested in reception, and enters the vicinity of the CSG member cell registered in the white list of the own UE 100. At least one of retransmission of the first proximity notification shown and rejection notification for the offload control information. Note that the MBMS interest notification is normally sent when the interest in the MBMS service changes, but even if the interest in the MBMS service has not changed, the MBMS interest notification is allowed to be retransmitted. Yes.

  FIG. 9 is a diagram illustrating an operation pattern 2 according to the embodiment. In FIG. 9, UE100 is the state (RRC connected state) which established the connection with eNB200. Further, it is assumed that the eNB 200 is in a congestion state.

  As illustrated in FIG. 9, in step S201, the eNB 200 determines whether or not the state of the UE 100 is a predetermined state. When it is determined that the state of the UE 100 is the predetermined state (step S201; YES), in step S202, the eNB 200 performs control so as not to transmit the offload control information requesting offload to the UE 100.

  On the other hand, when it is determined that the state of the UE 100 is not the predetermined state (step S201; NO), in step S203, the eNB 200 transmits offload control information for requesting offload to the UE 100 using a unicast signal. The UE 100 receives offload control information.

  In step S204, the UE 100 determines whether or not the state of the own UE 100 is a predetermined state. When it is determined that the state of the own UE 100 is not the predetermined state (step S204; NO), in step S205, the UE 100 performs offload related processing according to the received offload control information.

  On the other hand, when it is determined that the state of the own UE 100 is the predetermined state (step S204; YES), in step S206, the UE 100 notifies the eNB 200 that the own UE 100 is in the predetermined state.

[Other Embodiments]
In the above-described embodiment, as an example of the predetermined state, a state in which radio resources are allocated by quasi-static scheduling (SPS) has been described. However, the predetermined state may be a state where it is determined that voice communication is being performed. For example, QCI (QoS Class Identifier) that is a parameter for processing QoS (Quality of Service) is assigned to the UE 100. Here, since the QCI “1” is associated with the VoIP application, the state where the QCI is “1” may be set as the predetermined state. That is, even if the UE 100 whose QCI is “1” in the RRC connected state is requested to be offloaded from the eNB 200, the UE 100 maintains the connection with the eNB 200 without following the request.

  In the embodiment described above, load information is used as offload control information. However, a case is also assumed in which the UE 100 is indirectly requested to offload by adjusting a threshold value to be compared with the RAN measurement value and / or the WLAN measurement value. In such a case, the threshold value also corresponds to offload control information.

  In the above-described embodiment, the LTE system has been described as an example of the cellular communication system. However, the present invention is not limited to the LTE system, and the present invention may be applied to a system other than the LTE system.

  DESCRIPTION OF SYMBOLS 10 ... E-UTRAN, 20 ... EPC, 30 ... WLAN, 100 ... UE, 101, 102 ... Antenna, 111 ... Cellular communication unit, 112 ... WLAN communication unit, 120 ... User interface, 130 ... GNSS receiver, 140 ... Battery , 150 ... memory, 160 ... processor, 200 ... eNB, 201 ... antenna, 210 ... cellular communication unit, 220 ... network interface, 230 ... memory, 240 ... processor, 300 ... AP, 500 ... MME / S-GW

Claims (14)

A network selection control method for selecting an access network for transmitting and receiving user terminal traffic from a cellular RAN and a wireless LAN,
Transmitting offload control information for requesting a cellular base station connected to the user terminal to switch an access network for transmitting and receiving the traffic to the wireless LAN;
The user terminal that has received the offload control information controls to not switch the access network that transmits and receives the traffic to the wireless LAN when the state of the user terminal is a predetermined state;
A network selection control method comprising:   The predetermined state means that an MBMS interest notification indicating that the MBMS service provided by broadcast or multicast is being received or interested in reception is transmitted, and the interest related to the MBMS service is the MBMS interest. The network selection control method according to claim 1, wherein the network selection control method is in a state that does not change compared to the time when the notification is transmitted.   The predetermined state refers to transmitting a first proximity notification indicating entering the vicinity of the CSG member cell registered in the white list of the own user terminal and leaving the vicinity of the CSG member cell. The network selection control method according to claim 1, wherein the second proximity notification is not yet transmitted.   The network selection control method according to claim 1, wherein the predetermined state is a state in which radio resources are allocated to the user terminal by quasi-static scheduling (SPS) from the cellular RAN. In the step of transmitting the offload control information, the cellular base station transmits RAN auxiliary information including the offload control information by a broadcast signal,
The network selection control method includes:
The user terminal that has received the RAN auxiliary information holds the RAN auxiliary information when the state of the user terminal is the predetermined state;
The user terminal operating according to the retained RAN auxiliary information when the state of the user terminal is no longer the predetermined state;
The network selection control method according to any one of claims 1 to 4, further comprising:   The network selection control method according to claim 5, further comprising a step of holding the updated RAN auxiliary information when the RAN auxiliary information transmitted from the cellular base station is updated.   The network selection control method according to claim 5 or 6, wherein, in the controlling step, the user terminal omits an offload related process for switching an access network that transmits and receives the traffic to the wireless LAN. .   8. The offload-related processing is at least one of scanning of a wireless LAN access point, selection of the access network, transmission of a wireless LAN measurement report, and switching of the traffic. Network selection control method. In the step of transmitting the offload control information, the cellular base station transmits the offload control information by a unicast signal,
The network selection control method according to any one of claims 1 to 4, wherein, in the controlling step, the user terminal ignores the received offload control information. In the step of transmitting the offload control information, the cellular base station transmits the offload control information by a unicast signal,
The said control step WHEREIN: The said user terminal performs the notification which shows that the own user terminal is the said predetermined state with respect to the said cellular base station, The Claim 1 thru | or 4 characterized by the above-mentioned. Network selection control method.   The notification is a re-transmission of the MBMS interest notification indicating that the MBMS distributed by broadcast or multicast is received or interested in reception, and enters the vicinity of the CSG member cell registered in the white list of the own user terminal. 11. The network selection control method according to claim 10, wherein the network selection control method is at least one of a retransmission of a first proximity notification indicating a rejection notification and a rejection notification for the offload control information. In the step of transmitting the offload control information, the cellular base station transmits the offload control information by a unicast signal,
The network selection control method includes:
The cellular base station that has determined that the state of the user terminal is in a predetermined state further includes a step of controlling not to transmit the offload control information to the user terminal. The network selection control method according to claim 1. A user terminal capable of selecting an access network for transmitting and receiving own traffic from a cellular RAN and a wireless LAN,
A receiving unit that receives offload control information for requesting to switch the access network that transmits and receives the traffic to the wireless LAN from a cellular base station that is connected to the user terminal;
A control unit that controls not to switch the access network that transmits and receives the traffic to the wireless LAN when the state of the user terminal is a predetermined state even when the offload control information is received;
A user terminal characterized by comprising: A cellular base station connected to a user terminal,
A transmission unit that transmits offload control information for requesting to switch the access network that transmits and receives the traffic of the user terminal to a wireless LAN by a unicast signal;
A control unit that controls not to transmit the offload control information to the user terminal when it is determined that the state of the user terminal is a predetermined state;
A cellular base station characterized by comprising:

Images