JP2018007267A - User terminal, method, and processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable appropriate selection of a user terminal of an offload object.SOLUTION: A UE 100 transmits and receives traffic to/from an eNB 200 in a cellular communication system capable of cooperation with a WLAN system. The UE 100 determines whether or not to perform offload on the basis of a decision parameter related to a state of the UE 100, when the UE 100 is selected as an offload object to transfer traffic to the WLAN system. The UE 100, on determining that the offload is not to be performed, transmits to the eNB 200 a rejection notification related to offload rejection.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a user terminal, a cellular base station, and a processor used in a cellular communication system capable of cooperating with a wireless LAN system.

  In recent years, user terminals (so-called dual terminals) having a cellular communication unit and a wireless LAN communication unit have become widespread. 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 the cellular communication system and the wireless LAN system.

  For example, the traffic load of the cellular base station can be reduced (offload) by shifting traffic transmitted and received between the user terminal and the cellular base station to the wireless LAN system.

  As a method for performing such offloading, the cellular base station sets up WLAN measurement for the user terminal to be offloaded, the user terminal reports the WLAN measurement result to the cellular base station, and the cellular base station A method for transmitting an offload instruction to a user terminal based on a report has been proposed (see Non-Patent Document 1).

3GPP Technical Report “TR 37.834 V0.33.0” 2 May 013

  As a method of selecting user terminals to be offloaded, from the viewpoint of a cellular base station, a method of selecting user terminals that use a large amount of radio resources can be considered.

  However, when selecting a user terminal to be offloaded only with such selection criteria, there is a possibility that an unfavorable selection may be performed from the viewpoint of the user terminal. For example, a user terminal that does not have a wireless LAN access point in the vicinity, a user terminal that is moving, or a user terminal that has a low remaining battery level should not be offloaded.

  Therefore, an object of the present invention is to provide a user terminal, a cellular base station, and a processor that can appropriately select user terminals to be offloaded.

  A user terminal according to the first feature transmits and receives traffic to and from a cellular base station in a cellular communication system capable of cooperating with a wireless LAN system. Whether the user terminal should perform the offload based on a determination parameter related to the status of the user terminal when the user terminal is selected as an offload target for transferring the traffic to the wireless LAN system The control part which judges whether is provided. When the control unit determines that the offload should not be performed, the control unit transmits a rejection notification regarding the rejection of the offload to the cellular base station.

  A cellular base station according to the second feature transmits and receives traffic to and from user terminals in a cellular communication system that can cooperate with a wireless LAN system. The cellular base station, when the user terminal is selected as an offload target for transferring the traffic to the wireless LAN system, and when a rejection notification about the offload rejection is received from the user terminal, A control unit that excludes the user terminal from the offload target.

  A processor according to a third feature is provided in a user terminal that transmits / receives traffic to / from a cellular base station in a cellular communication system capable of cooperating with a wireless LAN system. Whether the processor should perform the offload based on a determination parameter related to the status of the user terminal when the user terminal is selected as an offload target for transferring the traffic to the wireless LAN system And a process of transmitting a rejection notification regarding the rejection of the offload to the cellular base station when it is determined that the offload should not be performed.

  According to the present invention, it is possible to provide a user terminal, a cellular base station, and a processor that can appropriately select user terminals to be offloaded.

It is a system configuration figure concerning a 1st embodiment and a 2nd embodiment. It is a block diagram of UE (user terminal) concerning a 1st embodiment and a 2nd embodiment. It is a block diagram of eNB (cellular base station) which concerns on 1st Embodiment and 2nd Embodiment. It is a block diagram of AP (wireless LAN access point) concerning 1st Embodiment and 2nd Embodiment. It is a protocol stack figure of the radio | wireless interface in a LTE system. It is a block diagram of the radio | wireless frame used with a LTE system. It is a sequence diagram which shows the basic operation | movement which concerns on 1st Embodiment. It is a sequence diagram of the operation | movement pattern 1 which concerns on 1st Embodiment. It is a sequence diagram of the operation | movement pattern 2 which concerns on 1st Embodiment. It is a sequence diagram of the operation | movement pattern 3 which concerns on 1st Embodiment. It is a sequence diagram concerning a 2nd embodiment.

[Outline of Embodiment]
User terminals according to the first embodiment and the second embodiment transmit and receive traffic to and from a cellular base station in a cellular communication system capable of cooperating with a wireless LAN system. Whether the user terminal should perform the offload based on a determination parameter related to the status of the user terminal when the user terminal is selected as an offload target for transferring the traffic to the wireless LAN system The control part which judges whether is provided. When the control unit determines that the offload should not be performed, the control unit transmits a rejection notification regarding the rejection of the offload to the cellular base station.

  In the first embodiment, the determination parameter is information indicating whether or not a wireless LAN access point exists around the user terminal. The control unit determines that the offload should not be performed when there is no wireless LAN access point around the user terminal.

  In the first embodiment, the determination parameter is information indicating whether or not the user terminal is moving. The control unit determines that the offload should not be performed when the user terminal is moving.

  In the first embodiment, the determination parameter is information indicating a remaining battery level of the user terminal. The control unit determines that the offload should not be performed when the remaining battery level is below a threshold value.

  In the first embodiment, the determination parameter is information indicating a power consumption level of the user terminal. The control unit determines that the offload should not be performed when the power consumption level exceeds a threshold value.

  In the operation pattern 1 according to the first embodiment, the user terminal further includes a reception unit that receives a wireless LAN measurement instruction indicating that the user terminal has been selected as the offload target from the cellular base station. When determining that the offload should not be performed, the control unit transmits the rejection notification to the cellular base station as a response to the wireless LAN measurement instruction.

  In the operation pattern 2 according to the first embodiment, the user terminal further includes a reception unit that receives a wireless LAN measurement instruction indicating that the user terminal has been selected as the target of the offload from the cellular base station. When it is determined that the offload should not be performed, the control unit transmits the rejection notification to the cellular base station together with a wireless LAN measurement report for reporting the result of the wireless LAN measurement.

  In the operation pattern 3 according to the first embodiment, the user terminal further includes a receiving unit that receives an offload instruction for instructing execution of the offload from the cellular base station. When determining that the offload should not be performed, the control unit transmits the rejection notification to the cellular base station as a response to the offload instruction.

  In the first embodiment, the control unit includes, in the rejection notification, rejection reason information indicating a reason for rejection when the rejection notification is transmitted to the cellular base station.

  In the second embodiment, the user terminal further includes a transmission unit that transmits a terminal information notification including the determination parameter to the cellular base station before the user terminal is selected as the offload target. Prepare.

  The cellular base stations according to the first embodiment and the second embodiment transmit and receive traffic to and from user terminals in a cellular communication system capable of cooperating with a wireless LAN system. The cellular base station, when the user terminal is selected as an offload target for transferring the traffic to the wireless LAN system, and when a rejection notification about the offload rejection is received from the user terminal, A control unit that excludes the user terminal from the offload target.

  In the second embodiment, the cellular base station receives, from the user terminal, a terminal information notification including a determination parameter regarding the status of the user terminal before selecting the user terminal as the offload target. A receiving unit is further provided. The control unit selects a user terminal to be offloaded based on the determination parameter.

  In the second embodiment, the determination parameter is information indicating whether or not a wireless LAN access point exists in the vicinity of the user terminal. The control unit excludes user terminals having no wireless LAN access point in the vicinity from the offload targets.

  In the second embodiment, the determination parameter is information indicating whether or not the user terminal is moving. The control unit excludes a moving user terminal from the offload target.

  In the second embodiment, the determination parameter is information indicating a remaining battery level of the user terminal. The control unit excludes, from the offload target, user terminals whose remaining battery capacity is below a threshold value.

  In the second embodiment, the determination parameter is information indicating a power consumption level of the user terminal. The control unit excludes user terminals whose power consumption level exceeds a threshold from the offload targets.

  The processor according to the first embodiment and the second embodiment is provided in a user terminal that transmits / receives traffic to / from a cellular base station in a cellular communication system capable of cooperating with a wireless LAN system. Whether the processor should perform the offload based on a determination parameter related to the status of the user terminal when the user terminal is selected as an offload target for transferring the traffic to the wireless LAN system And a process of transmitting a rejection notification regarding the rejection of the offload to the cellular base station when it is determined that the offload should not be performed.

[First Embodiment]
Hereinafter, an embodiment in the case where a cellular communication system (LTE system) configured in conformity 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 first embodiment. As shown in FIG. 1, the cellular communication 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 radio access network (RAN). The EPC 20 corresponds to a core 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. Moreover, eNB200 is connected with MME / S-GW500 contained in EPC20 via S1 interface.

  The EPC 20 includes a plurality of MME (Mobility Management Entity) / S-GW (Serving-Gateway) 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 system includes a WLAN access point (WLAN AP) 300. The WLAN system is configured in accordance with, for example, IEEE 802.11 standards. The WLAN AP 300 communicates with the UE 100 in a frequency band (WLAN frequency band) different from the cellular frequency band. The WLAN AP 300 is connected to the EPC 20 via a router or the like.

  Further, the eNB 200 and the WLAN AP 300 are not limited to being individually arranged, and the eNB 200 and the WLAN AP 300 may be arranged at the same place (Collocated). As one form of Collated, the eNB 200 and the WLAN AP 300 may be directly connected by an arbitrary interface of the operator.

  Next, configurations of the UE 100, the eNB 200, and the WLAN AP 300 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.

  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 network interface 220 is used for communication with the WLAN AP 300 via the EPC 20.

  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 a program 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 block diagram of the WLAN AP 300. As illustrated in FIG. 4, the WLAN AP 300 includes an antenna 301, a WLAN communication unit 311, a network interface 320, a memory 330, and a processor 340.

  The antenna 301 and the WLAN communication unit 311 are used for transmission / reception of WLAN radio signals. The WLAN communication unit 311 converts the baseband signal output from the processor 340 into a WLAN radio signal and transmits it from the antenna 301. In addition, the WLAN communication unit 311 converts the WLAN radio signal received by the antenna 301 into a baseband signal and outputs the baseband signal to the processor 340.

  The network interface 320 is connected to the EPC 20 via a router or the like. The network interface 320 is used for communication with the eNB 200 via the EPC 20.

  The memory 330 stores a program executed by the processor 340 and information used for processing by the processor 340. The processor 340 includes a baseband processor that performs modulation / demodulation and encoding / decoding of the baseband signal, and a CPU that executes programs stored in the memory 330 and performs various processes.

  FIG. 5 is a protocol stack diagram of a radio interface in the cellular communication system. As shown in FIG. 5, the radio interface protocol is divided into layers 1 to 3 of the OSI reference model, and layer 1 is a physical (PHY) layer. Layer 2 includes a MAC (Media Access Control) layer, an RLC (Radio Link Control) layer, and a PDCP (Packet Data Convergence Protocol) layer. Layer 3 includes an RRC (Radio Resource Control) layer.

  The physical layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data is transmitted between the physical layer of the UE 100 and the physical layer of the eNB 200 via a physical channel.

The MAC layer performs data priority control, retransmission processing by hybrid ARQ (HARQ), and the like. Data is transmitted via the transport channel between the MAC layer of the UE 100 and the MAC layer of the eNB 200. The MAC layer of eNB 200 is
It includes a scheduler for selecting uplink / downlink transport formats (transport block size, modulation / coding scheme, etc.) and allocated resource blocks.

  The RLC layer transmits data to the RLC layer on the receiving side using functions of the MAC layer and the physical layer. Data is transmitted between the RLC layer of the UE 100 and the RLC layer of the eNB 200 via a logical channel.

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

The RRC layer is defined only in the control plane. Control messages (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. If 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 a connected state (RRC connected state), and otherwise, the UE 100 is in an idle state (RRC idle state).

  A NAS (Non-Access Stratum) layer located above the RRC layer performs session management, mobility management, and the like.

  FIG. 6 is a configuration diagram of a radio frame used in the LTE system. 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.

  As shown in FIG. 6, the radio frame is composed of 10 subframes arranged in the time direction, and 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. The resource block includes a plurality of subcarriers in the frequency direction.

  Among radio resources allocated to the UE 100, a frequency resource can be specified by a resource block, and a time resource can be specified by a subframe (or slot).

  In the downlink, the section of the first few symbols of each subframe is a control region mainly used as a physical downlink control channel (PDCCH). The remaining section of each subframe is an area that can be used mainly as a physical downlink shared channel (PDSCH). Also, in the downlink, reference signals such as cell-specific reference signals are distributed and arranged in each subframe.

  In the uplink, both ends in the frequency direction in each subframe are control regions mainly used as a physical uplink control channel (PUCCH). Further, the central portion in the frequency direction in each subframe is an area that can be used mainly as a physical uplink shared channel (PUSCH).

(Operation according to the first embodiment)
Next, an operation according to the first embodiment will be described.

(1) Outline of Operation In the first embodiment, an operation environment in which the WLAN AP 300 is provided in the coverage area of the eNB 200 is assumed. The WLAN AP 300 is an AP (Operator controlled AP) managed by an operator. When eNB200 establishes connection with many UE100, the traffic load of eNB200 will become high. Therefore, the traffic load of the eNB 200 can be reduced (offload) by shifting traffic (user data) transmitted and received between the UE 100 and the eNB 200 to the WLAN system.

  In the first embodiment, in order to perform such offloading, the eNB 200 sets WLAN measurement for the UE 100 to be offloaded, the UE 100 reports the WLAN measurement result to the eNB 200, and the eNB 200 is based on the report. An offload instruction is transmitted to the UE 100.

  FIG. 7 is a sequence diagram showing a basic operation according to the first embodiment. In the initial state of this sequence, the UE 100 is in a state (connection state) in which an RRC connection with the eNB 200 is established.

  As illustrated in FIG. 7, in step S1, the eNB 200 transmits a WLAN measurement instruction for controlling WLAN measurement to the UE 100 that is an offload target. The WLAN measurement instruction includes an identifier (WLAN identifier) of the WLAN AP 300 that the UE 100 is to be measured. Further, the WLAN measurement instruction includes trigger information indicating a trigger for transmitting a WLAN measurement report for reporting a WLAN measurement result to the eNB 200.

  The UE 100 that has received the WLAN measurement instruction performs WLAN measurement according to the WLAN measurement instruction. For example, the UE 100 measures the reception power of the beacon signal from the WLAN AP 300, etc., targeting the WLAN identifier included in the WLAN measurement instruction.

  In step S2, UE100 detects the event used as the transmission trigger of a WLAN measurement report based on the trigger information contained in a WLAN measurement instruction | indication. Here, if the UE 100 has transitioned to the idle state, the UE 100 establishes an RRC connection with the eNB 200 again in order to transmit a WLAN measurement report to the eNB 200 (step S3).

  In step S4, UE100 transmits the WLAN measurement report for reporting the result of WLAN measurement to eNB200. The WLAN measurement report includes, for example, a WLAN identifier and a WLAN measurement result (such as received power of a beacon signal).

  In step S5, the eNB 200 that has received the WLAN measurement report transmits a Steering command (offload instruction) that instructs execution of offload to the UE 100 based on the WLAN measurement report and the load of the RAN. The steering command is not limited to a command that instructs traffic shift (offload) from the eNB 200 to the WLAN, but may be a command that instructs traffic shift (offload cancellation) from the WLAN to the eNB 200.

  In step S6, the UE 100 that has received the offload instruction executes offload. That is, UE100 switches the traffic transmitted / received with eNB200 so that it may transmit / receive with the WLAN AP300. If the UE 100 has not established a connection with the WLAN AP 300 when receiving the offload instruction, the UE 100 establishes a connection with the WLAN AP 300 prior to the offload.

  In step S7, the UE 100 transmits a response corresponding to the offload instruction to the eNB 200.

  In such a sequence, when the eNB 200 selects the UE 100 to be offloaded, the selection of the UE 100 to be offloaded may be inappropriate. For example, the UE 100 that does not have the WLAN AP 300 in the vicinity, the UE 100 that is moving, or the UE 100 that has a low remaining battery level should not be offloaded.

  In 1st Embodiment, when UE100 is selected as the object of the offload which transfers a traffic to a WLAN system, UE100 judges whether it should perform offload based on the judgment parameter regarding the condition of UE100. . Details of the determination parameter (determination parameter 1 to determination parameter 4) will be described later.

  If the UE 100 determines that the offload should not be performed based on the determination parameter, the UE 100 transmits a rejection notification regarding the rejection of the offload to the eNB 200. The timing (operation pattern 1 to operation pattern 3) for transmitting the rejection notification to the eNB 200 will be described later.

  The eNB 200 excludes the UE 100 from the offload target when the UE 100 is selected as an offload target for transferring the traffic to the WLAN system, and when a rejection notification related to the offload rejection is received from the UE 100. Therefore, it becomes possible to appropriately select the offload target UE 100.

(2) Determination parameter As the determination parameter described above, at least one of the following determination parameters 1 to 4 can be used.

  The determination parameter 1 is information indicating whether or not the WLAN AP 300 exists around the UE 100. For example, if the UE 100 receives a beacon signal from the WLAN AP 300, it can be considered that the WLAN AP 300 exists around the UE 100. Alternatively, in the case where the UE 100 holds the location information (AP location information) of the WLAN AP 300, if the difference (that is, the distance) between the GNSS location information of the UE 100 and the AP location information is small, the WLAN is located around the UE 100. It can be considered that the AP 300 exists. Based on the determination parameter 1, when there is no WLAN AP 300 in the vicinity of the UE 100, the UE 100 determines that the offload should not be performed, and transmits a rejection notification. Thereby, it can avoid selecting UE100 in the state which cannot be offloaded as an offload object.

  The determination parameter 2 is information indicating whether or not the UE 100 is moving. For example, if the change per unit time of the GNSS position information of the UE 100 is larger than a predetermined amount, it can be considered that the UE 100 is moving. Alternatively, if the number of handovers or cell reselection times per unit time of the UE 100 is larger than a predetermined number, it can be considered that the UE 100 is moving. Based on the determination parameter 2, the UE 100 determines that the offload should not be performed when the UE 100 is moving, and transmits a rejection notification. The moving UE 100 passes through the coverage area of the AP 300 in a short time. Therefore, by making it possible to exclude the moving UE 100 from the offload target, it is possible to avoid inefficient offloading.

  The determination parameter 3 is information indicating the remaining battery level of the UE 100. The information indicating the remaining battery level may be the voltage value of the battery 140 or an index indicating the voltage level of the battery 140. Based on the determination parameter 3, the UE 100 determines that the offload should not be performed when the remaining battery level is below the threshold, and transmits a rejection notification. When offloading is performed, there is a problem in that power consumption of the UE 100 increases, the battery of the UE 100 runs out, or a call (including an emergency call) becomes impossible. Therefore, such a problem can be avoided by making it possible to exclude the UE 100 having a small remaining battery level from the offload target.

  The determination parameter 4 is information indicating the power consumption level of the UE 100. For example, if the UE 100 is set to the power saving mode, the power consumption level of the UE 100 is small. If the UE 100 is set to the high performance mode, the power consumption level of the UE 100 is large. Based on the determination parameter 4, the UE 100 determines that the offload should not be performed when the power consumption level exceeds the threshold, and transmits a rejection notification. When offloading is performed, the power consumption of the UE 100 increases, and there is a problem that the power consumption exceeds a permissible value for the UE 100 with a high power consumption level due to offloading. Accordingly, such a problem can be avoided by making it possible to exclude the UE 100 having a high power consumption level from the offload target.

(3) Operation pattern 1
FIG. 8 is a sequence diagram of the operation pattern 1 according to the first embodiment. Here, differences from the basic operation described above will be mainly described.

  As illustrated in FIG. 8, in step S1, the UE 100 receives a WLAN measurement instruction indicating that the UE 100 has been selected as an offload target from the eNB 200.

  In step S10, the UE 100 determines whether or not to perform offload based on the determination parameter.

  When it is determined that the offload should not be performed (step S10: No), in step S11, the UE 100 transmits a rejection notification to the eNB 200 as a response to the WLAN measurement instruction. The UE 100 may include rejection reason information indicating the reason for rejection in the rejection notification. Reasons for refusal include, for example, “no WLAN AP 300 in the vicinity”, “moving”, “low battery level”, “high power consumption level”, and the like. The eNB 200 that has received the rejection notification excludes the UE 100 from the offload target.

  On the other hand, if it is determined that offloading should be performed (step S10: Yes), in step S2, the UE 100 uses the trigger information included in the WLAN measurement instruction as an event to be a WLAN measurement report transmission trigger. Is detected. The subsequent operations are the same as the basic operations described above.

(4) Operation pattern 2
FIG. 9 is a sequence diagram of an operation pattern 2 according to the first embodiment. Here, differences from the basic operation described above will be mainly described.

  As shown in FIG. 9, steps S1 to S3 are the same as the basic operation described above.

  In step S20, the UE 100 determines whether or not to perform offload based on the determination parameter.

  When it is determined that the offload should not be performed (step S20: No), in step S4 ', the UE 100 transmits a rejection notification to the eNB 200 together with the WLAN measurement report for reporting the result of the WLAN measurement. The UE 100 may transmit the rejection notification included in the WLAN measurement report, or may transmit the WLAN measurement report and the rejection notification by individual messages. The UE 100 may include rejection reason information in the rejection notification. The eNB 200 that has received the rejection notification excludes the UE 100 from the offload target.

  On the other hand, if it is determined that offloading should be performed, the UE 100 transmits a WLAN measurement report to the eNB 200 without transmitting a rejection notification. The subsequent operations are the same as the basic operations described above.

(5) Operation pattern 3
FIG. 10 is a sequence diagram of the operation pattern 3 according to the first embodiment. Here, differences from the basic operation described above will be mainly described.

  As shown in FIG. 10, steps S1 to S5 are the same as the basic operation described above. Specifically, in step S5, the UE 100 receives an offload instruction for instructing execution of offload from the eNB 200.

  In step S30, the UE 100 determines whether or not to perform offload based on the determination parameter.

  When it is determined that the offload should not be performed (step S30: No), in step S31, the UE 100 transmits a rejection notification to the eNB 200 as a response to the offload instruction. Note that the UE 100 may include rejection reason information in the rejection notification. The eNB 200 that has received the rejection notification excludes the UE 100 from the offload target.

  On the other hand, when it is determined that the offload should be performed (step S30: Yes), in step S6, the UE 100 executes the offload. The subsequent operations are the same as the basic operations described above.

(Summary of the first embodiment)
As described above, when the UE 100 is selected as an offload target, the UE 100 determines whether or not to perform offload based on the determination parameter regarding the status of the UE 100. If the UE 100 determines that the offload should not be performed based on the determination parameter, the UE 100 transmits a rejection notification regarding the rejection of the offload to the eNB 200. The eNB 200 excludes the UE 100 from the offload target when the UE 100 is selected as the offload target and when the rejection notification related to the offload rejection is received from the UE 100. Therefore, it becomes possible to appropriately select the offload target UE 100.

  In the operation pattern 1 according to the first embodiment, since the rejection notification is transmitted to the eNB 200 without transmitting the WLAN measurement report to the eNB 200, the processing load of the UE 100 can be reduced, and the radio resource associated with the WLAN measurement report can be reduced. Consumption can be reduced. On the other hand, in the operation pattern 3 according to the first embodiment, since the UE 100 makes the determination immediately before the timing at which the offload is to be performed, the determination can be appropriately made based on the latest situation of the UE 100. The operation pattern 2 according to the first embodiment has an intermediate property between the operation pattern 1 and the operation pattern 2.

[Second Embodiment]
The second embodiment will be described mainly with respect to differences from the first embodiment. In the second embodiment, the system configuration and basic operation are the same as those in the first embodiment.

(Operation according to the second embodiment)
The operation according to the second embodiment is performed prior to the basic operation described above. Specifically, the UE 100 transmits, to the eNB 200, the terminal information notification including the above-described determination parameter (at least one of the determination parameters 1 to 4) before the UE 100 is selected as an offload target. . The terminal information notification may be “UE Capability Information” which is one of RRC messages.

  The eNB 200 receives a terminal information notification including a determination parameter from the UE 100 before selecting the UE 100 as an offload target. And eNB200 selects UE100 made into the object of an offload based on a determination parameter. For example, based on the determination parameter 1, the eNB 200 excludes the UE 100 that does not have the WLAN AP 300 in the vicinity from the offload target. Based on the determination parameter 2, the eNB 200 excludes the moving UE 100 from the offload target. Based on the determination parameter 3, the eNB 200 excludes the UE 100 whose remaining battery level is lower than the threshold from the offload target. Based on the determination parameter 3, the eNB 200 excludes the UE 100 whose power consumption level exceeds the threshold from the offload target.

  FIG. 11 is a sequence diagram according to the second embodiment.

  As illustrated in FIG. 11, in step S101, the eNB 200 transmits, to the UE 100, UE Capability Enquiry that requests transmission of terminal information notification (UE Capability Information).

  In step S102, the UE 100 that has received UE Capability Enquiry transmits a terminal information notification (UE Capability Information) including a determination parameter to the eNB 200.

(Summary of the second embodiment)
As described above, the UE 100 transmits a terminal information notification including a determination parameter to the eNB 200 before the UE 100 is selected as an offload target. The eNB 200 receives a terminal information notification including a determination parameter from the UE 100 before selecting the UE 100 as an offload target. eNB200 selects UE100 made into the object of an offload based on a determination parameter. Thereby, it becomes possible to appropriately select the UE 100 to be offloaded.

[Other Embodiments]
In 2nd Embodiment mentioned above, eNB200 selected UE100 made into the object of an offload based on the determination parameter received from UE100. However, the eNB 200 may select the UE 100 to be offloaded without being based on the determination parameter received from the UE 100. For example, the eNB 200 measures the elapsed time after the UE 100 has handed over to its own cell, and excludes the UE 100 whose elapsed time is shorter than a certain time from being subject to offloading. Thereby, UE100 which exists in a self-cell for a long term can be made into the object of offload, and UE100 which only passes through the own cell temporarily can be excluded from the object of offload.

  The second embodiment described above is assumed to be used together with the first embodiment. However, the second embodiment can be implemented separately from the first embodiment, and may be implemented by the second embodiment alone.

  In each embodiment mentioned above, although the LTE system was demonstrated as an example of a cellular communication system, it is not limited to a LTE system, You may apply this invention to systems other than a LTE system.

  In each operation sequence described above, the operation performed by the eNB 200 (base station) may be performed by another network device (for example, RNC) instead of the base station.

DESCRIPTION OF SYMBOLS 10 ... E-UTRAN, 20 ... EPC, 100 ... UE, 101, 102 ... Antenna, 111 ... Cellular communication part, 112 ... WLAN communication part, 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 ... WLAN AP, 301 ... antenna, 311 ... WLAN communication unit, 320 ... network interface, 330 ... memory, 340 ... Processor, 500 ... MME / S-GW

Claims (6)

A user terminal comprising a control unit,
The controller is
An offload instruction for instructing an offload is received from a cellular base station, and the offload is an operation in which the user terminal moves traffic from the cellular base station to a WLAN access point while maintaining a connection with the cellular base station. And
In response to receiving the offload instruction, whether or not connection with the WLAN access point is possible is determined based on the situation in the user terminal in addition to the situation of the WLAN signal,
In response to determining that the connection with the WLAN access point is impossible, the reason why the connection with the WLAN access point is impossible is as follows: a reason regarding the state of the WLAN signal and a reason regarding the state within the user terminal Notify one of them to the cellular base station,
User terminal. Before receiving the offload instruction, the control unit performs a process of transmitting a measurement report including a WLAN identifier and a reception power measurement result of a WLAN signal to the cellular base station.
The user terminal according to claim 1. A method for executing on a user terminal,
An offload instruction for instructing an offload is received from a cellular base station, and the offload is an operation in which the user terminal moves traffic from the cellular base station to a WLAN access point while maintaining a connection with the cellular base station. And
In response to receiving the offload instruction, whether or not connection with the WLAN access point is possible is determined based on the situation in the user terminal in addition to the situation of the WLAN signal,
In response to determining that the connection with the WLAN access point is impossible, the reason why the connection with the WLAN access point is impossible is as follows: a reason regarding the state of the WLAN signal and a reason regarding the state within the user terminal Notify one of them to the cellular base station,
Method. Before receiving the offload instruction, a measurement report including a WLAN identifier and a reception power measurement result of a WLAN signal is transmitted to the cellular base station.
The method of claim 3. A processor for controlling a user terminal,
An offload instruction for instructing an offload is received from a cellular base station, and the offload is an operation in which the user terminal moves traffic from the cellular base station to a WLAN access point while maintaining a connection with the cellular base station. And
In response to receiving the offload instruction, whether or not connection with the WLAN access point is possible is determined based on the situation in the user terminal in addition to the situation of the WLAN signal,
In response to determining that the connection with the WLAN access point is impossible, the reason why the connection with the WLAN access point is impossible is as follows: a reason regarding the state of the WLAN signal and a reason regarding the state within the user terminal Notify one of them to the cellular base station,
Processor. Before receiving the offload instruction, a process of transmitting a measurement report including a WLAN identifier and a reception power measurement result of a WLAN signal to the cellular base station is performed.
The processor according to claim 5.

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