WO2016121608A1

WO2016121608A1 - Base station and user terminal

Info

Publication number: WO2016121608A1
Application number: PCT/JP2016/051647
Authority: WO
Inventors: 宏行浦林; 空悟守田; 憲由福田; 直久松本
Original assignee: 京セラ株式会社
Priority date: 2015-01-30
Filing date: 2016-01-21
Publication date: 2016-08-04
Also published as: JP6619862B2; JP2019062542A; JPWO2016121608A1; JP6438052B2

Abstract

A base station according to an embodiment of the present invention is provided with: a transmission unit that transmits a reference signal in an unlicensed band; a reception unit that receives, from a user terminal, measurement results regarding a wireless signal in the unlicensed band; and a control unit that excludes, from the measurement results, a measurement value that was measured at a time when the reference signal was not sent in the unlicensed band.

Description

Base station and user terminal

This application relates to a user terminal capable of communicating in a licensed band and an unlicensed band and a base station capable of communicating with the user terminal.

In 3GPP (3rd Generation Partnership Project), which is a standardization project for mobile communication systems, specifications are being developed to improve LTE (Long Term Evolution) to meet the rapidly increasing traffic demand (see Non-Patent Document 1, for example). .

In addition, in order to respond to the rapidly increasing traffic demand, not only communication using a licensed frequency band (licensed band) but also a frequency band that does not require a license (Unlicensed Band / Unlicensed Spectrum) was used. Communication is attracting attention.

Here, according to the law (for example, the Radio Law in Japan), when a radio signal is transmitted using an unlicensed band, it is required to execute CCA (Clear channel Assessment) before transmitting the radio signal. . Specifically, the base station measures the interference power in the unlicensed band. When the measurement result is good (specifically, when the interference power is low), a radio signal can be transmitted in the unlicensed band.

The base station according to an embodiment includes: a transmission unit that transmits a reference signal in an unlicensed band; a reception unit that receives a measurement result of a radio signal in the unlicensed band from a user terminal; and A control unit that excludes measurement values measured at a timing when the reference signal is not transmitted in the unlicensed band.

FIG. 1 is a configuration diagram of an LTE system according to each embodiment. FIG. 2 is a block diagram of the UE according to each embodiment. FIG. 3 is a block diagram of the eNB according to each embodiment. FIG. 4 is a protocol stack diagram according to each embodiment. FIG. 5 is a configuration diagram of a radio frame according to each embodiment. FIG. 6 is a diagram for explaining an operation according to the first embodiment. FIG. 7 is a diagram for explaining an operation according to the second embodiment. FIG. 8 is a diagram for explaining an operation according to the third embodiment. FIG. 9 is a diagram for explaining an operation according to the fourth embodiment. FIG. 10 is a diagram for explaining an operation according to the modified example of the fourth embodiment. FIG. 11 is a diagram for explaining a listen failure before DRS transmission. FIG. 12 is a diagram for explaining LAA DRS RSRP measurement. FIG. 13 is a diagram for explaining an example (right) of existing channel mapping (left) and proposed channel mapping.

[Outline of Embodiment]
Here, it is assumed that the user terminal performs measurement on the reference signal transmitted from the base station in the unlicensed band. When the user terminal reports the measurement result to the base station, the base station can measure the availability of communication with the user terminal or the communication quality in the unlicensed band.

However, the base station cannot transmit the reference signal when the measurement result of the interference power is bad. For this reason, even if the user terminal knows the scheduled transmission timing of the reference signal, the user terminal cannot determine whether the reference signal is not transmitted or whether the reference signal is transmitted but cannot be received due to interference. As a result, there is a possibility that an appropriate measurement result for the reference signal cannot be acquired.

Therefore, an object of the present application is to make it possible to obtain an appropriate measurement result for a reference signal in an unlicensed band.

The base station according to the embodiment includes: a transmission unit that transmits a reference signal in an unlicensed band; a reception unit that receives a measurement result of a radio signal in the unlicensed band from a user terminal; and A control unit that excludes measurement values measured at a timing when the reference signal is not transmitted in the licensed band.

The reception unit may receive the measurement result from the user terminal that transmits one measurement result every time the base station transmits one reference signal.

The base station according to the fourth embodiment can communicate in the unlicensed band with user terminals that can communicate in the licensed band and the unlicensed band. The base station includes a control unit that measures interference power in the unlicensed band, a transmission unit that transmits a reference signal in the unlicensed band based on a measurement result of the interference power, and a measurement of the interference power. And a storage unit that holds a transmission record related to the timing at which the reference signal is not transmitted based on the result. The control unit, when a measurement result for the reference signal is reported from the user terminal, based on the transmission record, a predetermined result corresponding to a timing at which the reference signal is not transmitted from the measurement result for the reference signal. Exclude measurement results.

In the modification of the fourth embodiment, the transmission unit transmits setting information for causing the user terminal to perform measurement of interference power in the unlicensed band at the same timing as the base station. The control unit acquires the measurement result of the interference power in the user terminal, and transmits the measurement result of the interference power in the user terminal and the measurement result of the interference power in the user terminal to the user terminal. Determine data error tolerance.

In a modification of the fourth embodiment, the control unit measures interference power in the unlicensed band immediately before transmitting the data. The measurement result of the interference power in the local station includes not only the measurement result of the interference power measured immediately before the transmission of the reference signal but also the measurement result of the interference power measured immediately before the transmission of the data.

The user terminal according to each embodiment can communicate in the licensed band, and can communicate in the unlicensed band with a base station that transmits a radio signal based on the measurement result of interference power in the unlicensed band. It is. The user terminal includes a control unit that performs measurement on a predetermined radio signal in the unlicensed band and reports a measurement result on the predetermined radio signal. The control unit specifies a timing at which a reference signal is not transmitted from the base station in the unlicensed band, and excludes a predetermined measurement result corresponding to the specified timing.

The user terminal according to the first embodiment further includes a storage unit that stores signal sequence information for specifying a signal sequence related to the reference signal transmitted from the base station. When the correlation value between the signal sequence of the predetermined radio signal and the signal sequence specified based on the signal sequence information is less than a threshold, the control unit determines the timing at which the predetermined radio signal is transmitted, It is specified as the timing when the reference signal is not transmitted.

The user terminal according to the second embodiment further includes a receiving unit that receives transmission information related to the timing at which the reference signal is transmitted. The control unit identifies a timing at which the reference signal is not transmitted based on the transmission information.

The user terminal according to the third embodiment further includes a receiving unit that receives schedule information related to a scheduled transmission timing of the reference signal before measurement of the predetermined radio signal. The control unit measures the predetermined radio signal at the scheduled transmission timing based on the schedule information, and measures interference power in the unlicensed band at a timing different from the scheduled transmission timing. The control unit identifies a timing at which the reference signal is not transmitted based on a measurement result at the different timing and a measurement result at the scheduled transmission timing.

In the third embodiment, the different timing is at least one of the timing before and after the scheduled transmission timing. The control unit refers to the scheduled transmission timing when the first reception level, which is a measurement result at the different timing, is higher than a second reception level, which is the measurement result at the scheduled transmission timing, by a predetermined value or more. It is specified as the timing when the signal is transmitted.

[First Embodiment]
In the following, an embodiment in which the contents of the present application are applied to an LTE system will be described.

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

UE 100 corresponds to a user terminal. The UE 100 is a mobile communication device, and performs wireless communication with a connection destination cell (serving cell). The configuration of the UE 100 will be described later.

E-UTRAN 10 corresponds to a radio access network. The E-UTRAN 10 includes an eNB 200 (evolved Node-B). The eNB 200 corresponds to a base station. The eNB 200 is connected to each other via the X2 interface. The configuration of the eNB 200 will be described later.

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. The eNB 200 has a radio resource management (RRM) function, a user data routing function, a measurement control function for mobility control / scheduling, and the like. “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 EPC 20 corresponds to a core network. The E-UTRAN 10 and the EPC 20 constitute an LTE system network (LTE network). The EPC 20 includes an MME (Mobility Management Entity) / S-GW (Serving-Gateway) 300. The EPC 20 may include OAM (Operation and Maintenance).

The MME performs various mobility controls for the UE 100. The S-GW controls user data transfer. The MME / S-GW 300 is connected to the eNB 200 via the S1 interface.

The OAM is a server device managed by an operator and performs maintenance and monitoring of the E-UTRAN 10.

FIG. 2 is a block diagram of the UE 100. As shown in FIG. 2, the UE 100 includes a plurality of antennas 101, a radio transceiver 110, a user interface 120, a GNSS (Global Navigation Satellite System) receiver 130, a battery 140, a memory 150, and a processor 160. 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 'that constitutes the control unit.

The antenna 101 and the wireless transceiver 110 are used for transmitting and receiving wireless signals. The radio transceiver 110 converts the baseband signal (transmission signal) output from the processor 160 into a radio signal and transmits it from the antenna 101. Further, the radio transceiver 110 converts a radio signal received by the antenna 101 into a baseband signal (received signal) and outputs the baseband signal to the processor 160.

The wireless transceiver 110 includes a wireless transceiver 110A and a wireless transceiver 110B. The radio transmission / reception 110A transmits / receives a radio signal in the licensed band, and the radio transmission / reception 110B transmits / receives a radio signal in the unlicensed band.

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 operation from the user and outputs a signal indicating the content of the operation 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 location information indicating the geographical location of the UE 100. The battery 140 stores electric 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 modulates / demodulates and encodes / decodes a baseband signal, and a CPU (Central Processing Unit) 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 corresponds to a control unit, and 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 a plurality of antennas 201, a radio transceiver 210, a network interface 220, a memory 230, and a processor 240. 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 'that constitutes the control unit.

The antenna 201 and the wireless transceiver 210 are used for transmitting and receiving wireless signals. The radio transceiver 210 transmits and receives radio signals in the licensed band. Alternatively, the wireless transceiver 210 may be able to transmit and receive wireless signals not only in the licensed band but also in the unlicensed band. The radio transceiver 210 converts the baseband signal (transmission signal) output from the processor 240 into a radio signal and transmits it from the antenna 201. In addition, the radio transceiver 210 converts a radio signal received by the antenna 201 into a baseband signal (received signal) and outputs the baseband signal 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 300 via the S1 interface. The network interface 220 is used for communication performed on the X2 interface and communication performed on 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 a program stored in the memory 230 and performs various processes. The processor 240 corresponds to a control unit, and 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 (schedules) uplink / downlink transport formats (transport block size, modulation / coding scheme) and resource blocks allocated 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.

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

FIG. 5 is a configuration diagram of a radio frame used in the LTE system. In the LTE system, OFDMA (Orthogonal Frequency Division Multiple Access) is applied to the downlink (DL), and SC-FDMA (Single Carrier Frequency Multiple Access) is applied to the uplink (UL).

As shown in FIG. 5, 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. A resource element is composed of one subcarrier and one symbol. Among radio resources allocated to the UE 100, frequency resources are configured by resource blocks, and time resources are configured by subframes (or slots).

(Communication using unlicensed bandwidth)
Hereinafter, communication using an unlicensed band according to the present embodiment will be described.

The UE 100 may perform communication using not only a licensed band (licensed band / licensed spectrum) licensed to a cellular network operator but also an unlicensed band (unlicensed band / unlicensed spectrum) that can be used without a license. it can.

Specifically, first, the UE 100 can perform communication using an unlicensed band by carrier aggregation (CA).

In CA, the carrier (frequency band) in LTE is positioned as a component carrier in order to realize a wide band while ensuring backward compatibility with LTE, and UE 100 communicates using a plurality of component carriers (a plurality of serving cells) simultaneously. I do. In CA, a cell that provides predetermined information when a UE starts an RRC connection is called a primary cell (PCell). For example, the primary cell provides NAS mobility information (eg, TAI) during RRC connection establishment / re-establishment / handover, or provides security information during RRC connection re-establishment / handover. On the other hand, the auxiliary serving cell paired with the primary cell is called a secondary cell (SCell). The secondary cell is formed together with the primary cell.

When using CA for communication using an unlicensed band, there are cases where a predetermined frequency (carrier) in the unlicensed band is used as a secondary cell. In the following, when a predetermined frequency is used as a secondary cell, the secondary cell is referred to as a U-SCell.

Second, the UE 100 can perform communication using an unlicensed band by a dual connection method (Dual Connectivity: DC).

In DC, radio resources are assigned to the UE 100 from a plurality of eNBs 200. The DC may be referred to as inter-eNB carrier aggregation (inter-eNB CA).

In DC, only the master eNB (MeNB) among the plurality of eNBs 200 that establish a connection with the UE 100 establishes an RRC connection with the UE 100. On the other hand, a secondary eNB (SeNB) among the plurality of eNBs 200 provides the UE 100 with additional radio resources without establishing an RRC connection with the UE 100. An Xn interface is set between the MeNB and SeNB. The Xn interface is an X2 interface or a new interface.

In DC, the UE 100 can perform carrier aggregation using the N cells managed by the MeNB and the M cells managed by the SeNB at the same time. A group consisting of N cells managed by the MeNB is referred to as a master cell group (MCG). Moreover, the group which consists of M cells which SeNB manages is called a secondary cell group (SCG). Further, among cells managed by the SeNB, a cell having at least an uplink control signal (PUCCH) reception function is referred to as a PSCell. PSCell has some functions similar to PCell, but does not perform RRC connection with UE 100 and does not transmit an RRC message, for example. When a predetermined frequency (carrier) in the unlicensed band is used as an SCell, the SCell is referred to as a U-SCell. When used as a PSCell, the SCell is referred to as a U-PSCell. Called.

Here, it is assumed that LAA (LAA: Licensed-Assessed Access) is used as a form of communication using the unlicensed band. In LAA, the UE 100 communicates with a cell operated in a licensed band (hereinafter, licensed cell) and a cell operated in an unlicensed band (hereinafter, unlicensed cell). The licensed cell may be used as a PCell, and the unlicensed cell may be used as an SCell (or PSCell). When UE100 communicates with a licensed cell and an unlicensed cell, the said licensed cell and the said unlicensed cell may be managed by one node (for example, eNB200). When the licensed cell and the unlicensed cell are managed (controlled) by one eNB 200, the unlicensed cell (and licensed cell) is formed by an RRH (Remote Radio Head) having a radio transceiver. Also good. Alternatively, the license cell may be managed by the eNB 200, and the unlicensed cell may be managed by a radio communication apparatus different from the eNB 200. The eNB 200 and the wireless communication apparatus can exchange various types of information to be described later via a predetermined interface (X2 interface or S1 interface). The eNB 200 that manages the license cell may notify the information acquired from the UE 100 to the radio communication device, or may notify the UE 100 of the information acquired from the radio communication device.

In the unlicensed band, CCA (Clear channel Assessment) is executed before transmitting a radio signal in order to avoid interference with a system different from the LTE system (such as a wireless LAN) or another operator's LTE system. (So-called LBT (Listen Before Talk)) is required. Specifically, in CCA, the eNB 200 measures interference power to confirm whether or not a frequency (carrier) in the unlicensed band is available. The eNB 200 allocates, to the UE 100, radio resources included in the frequency (carrier) that is confirmed to be an empty channel based on the measurement result of the interference power (scheduling). The eNB 200 performs scheduling in the unlicensed cell via the unlicensed cell. Or eNB200 may perform the scheduling in an unlicensed cell via a licensed cell (namely, cross-carrier scheduling).

Hereinafter, the operation by the eNB 200 will be appropriately described as an operation by a cell managed by the eNB 200. In the following, a case where one eNB 200 communicates with the UE 100 using a frequency in the licensed band (licensed cell) and a frequency in the unlicensed band (unlicensed cell) will be mainly described, but the present invention is not limited thereto. Should be noted.

(Operation according to the first embodiment)
Next, the operation according to the first embodiment will be described with reference to FIG. FIG. 6 is a diagram for explaining an operation according to the first embodiment.

In FIG. 6, the UE 100 is located in a PCell (licensed cell) managed by the eNB 200. The UE 100 may be in an RRC idle state or an RRC connected state. In the initial state of FIG. 6, the UE 100 has not started communication with the U-SCell (unlicensed cell) managed by the eNB 200. Alternatively, the UE 100 may perform communication with the U-SCel.

As shown in FIG. 6, in step S101, the PCell (eNB 200) transmits signal sequence information. The signal sequence information may be transmitted by a common signal (for example, SIB, PDCCH), or may be transmitted by an individual signal (for example, PDSCH). The UE 100 stores the received signal sequence information in the memory 150.

The signal sequence information is information for specifying a signal sequence related to a reference signal transmitted from the U-SCell (eNB 200). The reference signal is, for example, a discovery reference signal (DRS: Discovery Reference signal). The DRS includes a synchronization signal (primary synchronization signal (PSS) and / or secondary synchronization signal (SSS)), cell reference signal, channel state information reference signal (CSI-RS), and downlink demodulation reference signal (DL-DMRS). Including at least one of the signals. Therefore, DRS is used for at least one of cell identification, synchronization, and channel state observation.

The signal sequence information includes a subframe number, a cell identifier (Cell ID), a CSI identifier (CSI ID), and the like. The UE 100 calculates the signal sequence of the reference signal transmitted from the U-SCell based on the signal sequence information.

In step S102, the U-SCell (eNB 200) transmits a reference signal (DRS). The reference signal is transmitted using a specific frequency (carrier) on which the U-SCell is operated. Here, the eNB 200 measures the interference power at a specific frequency before the reference signal is transmitted.

Note that the eNB 200 is set to transmit the reference signal periodically (for example, at intervals of Xms). However, when the interference power exceeds the threshold (when interference is detected) as a result of measuring the interference power at a predetermined frequency in the unlicensed band, the eNB 200 stops transmitting the radio signal. Therefore, there may be a period during which the eNB 200 cannot transmit a radio signal as set.

In the following, description will be made assuming that the interference power is less than the threshold.

UE 100 performs measurement (Measurement) on a radio signal in the unlicensed band. The UE 100 may receive information on the DRS transmission timing from the PCell and / or information indicating a specific frequency on which the U-SCell is operated, and perform measurement based on the information.

Here, UE100 confirms whether the acquired measurement result is a measurement result with respect to DRS. First, the UE 100 calculates a signal sequence of a radio signal received during measurement, and obtains a correlation value between the signal sequence and a signal sequence calculated based on the signal sequence information. Next, UE100 determines whether the calculated | required correlation value is less than a threshold value. When the correlation value is less than the threshold, the UE 100 determines that the radio signal received during the measurement is not a reference signal transmitted from the U-SCell. In this case, the UE 100 specifies the measured timing as the timing at which the reference signal is not transmitted. On the other hand, when the correlation value is equal to or greater than the threshold value, the UE 100 determines that the received radio signal is a reference signal transmitted from the U-SCell. In this case, the UE 100 specifies the measured timing as the timing at which the reference signal is transmitted. Note that the threshold may be stored in advance by the UE 100 or may be provided from the eNB 200.

UE100 does not need to memorize | store a measurement result, when specifying the measured timing as a timing in which the reference signal is not transmitted. Thereby, the measurement result corresponding to the timing when the reference signal is not transmitted can be excluded from the report target. Alternatively, the UE 100 stores the measurement value and the measurement time for the radio signal in association with each other, and the UE 100 performs the above determination before reporting the measurement result, and the measurement result corresponding to the timing at which the reference signal is not transmitted. You may exclude from report object.

In step S103, the UE 100 transmits the measurement result for the radio signal in the unlicensed band to the PCell. The measurement result may be a result regarding the reception level (RSRP / RSRQ) or a result regarding the channel state (specifically, CSI, PMI, RI, etc.).

Since the UE 100 excludes the measurement result corresponding to the timing when the reference signal is not transmitted from the report target, the measurement result does not include the measurement result measured at the timing when the reference signal is not transmitted. For this reason, eNB200 (PCell) can determine appropriately regarding UE100 and communication in an unlicensed band based on a measurement result. For example, the eNB 200 can determine whether or not communication (connection) with the PSCell is possible based on the measurement result, and can calculate communication quality in the PSCell.

[Second Embodiment]
Next, an operation according to the second embodiment will be described with reference to FIG. FIG. 7 is a diagram for explaining an operation according to the second embodiment. Description of the same parts as those in the above-described embodiment will be omitted as appropriate.

In the second embodiment, the UE 100 excludes the measurement result corresponding to the timing at which the reference signal is not transmitted, from the report target, based on the information received from the eNB 200.

As shown in FIG. 7, in step S201, the U-SCell (eNB 200) performs interference power measurement (CCA) at a specific frequency where the U-SCell is operated. Here, the description will be made assuming that the interference power is less than the threshold value.

In step S202, the U-SCell transmits a DRS on a specific frequency.

In step S203, the UE 100 performs measurement on a radio signal at a specific frequency. The UE 100 stores the measurement result (first measurement result). The measurement result is stored in association with the measurement time.

In step S204, the U-SCell measures the interference power after a predetermined time has elapsed after performing the CCA in step S201. Here, the description will be made assuming that the interference power is equal to or greater than the threshold value. In this case, the U-SCell stops the DRS transmission.

In step S205, the UE 100 performs measurement on the radio signal at the specific frequency, and stores the measurement result (second measurement result).

In step S206, the U-SCell measures the interference power after a predetermined time has elapsed after performing the CCA in step S204. Here, the description will be made assuming that the interference power is less than the threshold value.

In step S207, the U-SCell transmits a DRS on a specific frequency.

In step S208, the UE 100 performs the measurement on the radio signal at the specific frequency, and stores the measurement result (third measurement result).

In step S209, the PCell transmits transmission information related to the timing at which the reference signal is transmitted. UE100 receives transmission information. The transmission information may be transmitted by a common signal (for example, SIB, PDCCH) or may be transmitted by an individual signal (for example, PDSCH).

The transmission information may be information indicating the timing when the reference signal is transmitted, or may be information indicating the timing when the reference signal is not transmitted. For example, the transmission information may be a list of subframe numbers. The transmission information may be included in a message requesting deletion of the measurement result corresponding to the timing when the reference signal is not transmitted.

ENB 200 stores at least one of the timing at which the reference signal is transmitted and the timing at which the reference signal is not transmitted. Note that the timing at which the reference signal is not transmitted may be a timing at which the reference signal is scheduled to be transmitted and a timing at which the reference signal cannot be transmitted based on the measurement result of the interference power.

On the other hand, the UE 100 identifies the timing at which the reference signal is not transmitted based on the transmission information. The UE 100 excludes the measurement result corresponding to the identified timing from the report target. In the present embodiment, it is assumed that the transmission information indicates the timing at which the transmission of the reference signal after step S204 is scheduled. The UE 100 excludes the second measurement result corresponding to the timing indicated by the transmission information from the report target.

The UE 100 may perform an operation of excluding the measurement result from the report target by using the reception of the transmission information as a trigger, or excluding the measurement result from the report target by starting the operation for reporting the measurement result. May be performed.

In step S210, the UE 100 transmits the measurement result to the PCell. The measurement result includes the first measurement result and the third measurement result, and does not include the second measurement result that is not the measurement result for the reference signal. Thereby, eNB200 can acquire a suitable measurement result. Therefore, the eNB 200 can appropriately determine the communication in the unlicensed band based on the measurement result.

In the present embodiment, the transmission information indicates a plurality of timings related to the reference signal, but is not limited thereto. The transmission information may be transmitted to the UE 100 every time the DRS is not transmitted, or may be transmitted to the UE 100 every time the DRS is transmitted.

[Third Embodiment]
Next, an operation according to the third embodiment will be described with reference to FIG. FIG. 8 is a diagram for explaining an operation according to the third embodiment. Description of parts similar to those of the above-described embodiments is omitted as appropriate.

In the third embodiment, the UE 100 excludes the measurement result corresponding to the timing at which the reference signal is not transmitted, from the report target, based on the measurement result of the interference power.

As shown in FIG. 8A, the first radio communication device (WT 400-1) exists in the vicinity of the UE 100, and the second radio communication device (WT 400-2) exists in the vicinity of the eNB 200. To do. WT 400-1 and WT 400-2 transmit radio signals at a specific frequency in the unlicensed band (see FIG. 8B).

Also, the eNB 200 transmits setting information related to the scheduled transmission timing of the reference signal. UE100 receives the setting information regarding the transmission plan timing of a reference signal. The setting information may be information specifying measurement timing for a reference signal at a specific frequency. The setting information may be transmitted by a common signal (for example, SIB, PDCCH) or may be transmitted by an individual signal (for example, PDSCH). Based on the setting information, the UE 100 performs the measurement for the reference signal at the specific frequency at the reference signal transmission scheduled timing.

Furthermore, the UE 100 measures the interference power at a specific frequency (execution of CCA) at a timing different from the scheduled transmission timing of the reference signal. The different timing is at least one of the timing before and after the scheduled transmission timing. The different timing may be a timing before a predetermined time and / or a timing after a predetermined time with respect to the timing for performing the measurement on the reference signal. The different timing may be the same timing as the timing at which the eNB 200 measures the interference power. In the present embodiment, the UE 100 measures the interference power at timings before and after the scheduled transmission timing (see FIG. 8B).

As shown in FIG. 8B, from t1 to t3, the WT 400-1 transmits a radio signal at a specific frequency. From t4 to t6, WT 400-2 transmits a radio signal at a specific frequency.

At t1, the eNB 200 and the UE 100 measure the interference power. Since the eNB 200 is far from the WT 400-1, the interference power in the eNB 200 is less than the threshold value. As a result, the eNB 200 determines to transmit the reference signal at t2.

At t2, the eNB 200 transmits a reference signal at a specific frequency. The UE 100 performs measurement at a specific frequency.

At t3, the UE 100 measures the interference power.

At t4, the eNB 200 and the UE 100 measure the interference power. Since eNB 200 is close to WT 400-2, the interference power in eNB 200 is equal to or greater than the threshold. As a result, the eNB 200 determines not to transmit the reference signal at t5.

At t5, the eNB 200 does not transmit a reference signal, but the UE 100 performs measurement at a specific frequency.

At t6, measurement at a specific frequency is performed.

From t7 to t9, the eNB 200 and the UE 100 operate in the same manner as from t1 to t3.

The CCA result in FIG. 8 (B) shows the measurement result (measurement value: reception level) in the UE 100.

Next, the UE 100 measures the measurement results at different timings (specifically, t1, t3, t4, t6, t7, t9) and the measurement results at the scheduled transmission timings (specifically, t2, t5, t8). Based on the above, the timing at which the reference signal is not transmitted is specified.

Since the reception level at t2 is higher than the reception level at t1 (t3) by a predetermined value or more (ie, reception level at t2−reception level at t1 (t3)> predetermined value), the eNB 200 receives the reference signal. I guess it was sent. Therefore, the UE 100 specifies the timing of t2 and the timing at which the reference signal is transmitted.

Further, since the reception level at t5 is not higher than a predetermined value by the UE 100 than the reception level at t4 (t6) (ie, the reception level at t5−the reception level at t4 (t6) <the predetermined value), the eNB 200 It is assumed that the reference signal is not transmitted. Therefore, the UE 100 specifies the timing at t2 and the timing at which the reference signal is not transmitted.

Further, since the reception level at t8 is higher than the reception level at t7 (t9) by the UE 100 (that is, reception level at t8−reception level at t7 (t9)> predetermined value), the eNB 200 refers to Guess that a signal was sent. Therefore, the UE 100 specifies the timing of t2 and the timing at which the reference signal is transmitted.

From the above, the UE 100 excludes the measurement result at t5 from the report target, and reports the measurement results at t2 and t8 to the eNB 200. Therefore, the eNB 200 can appropriately determine the communication in the unlicensed band based on the measurement result.

[Fourth Embodiment]
(Operation according to the fourth embodiment)
Next, an operation according to the fourth embodiment will be described with reference to FIG. FIG. 9 is a diagram for explaining an operation according to the fourth embodiment. Description of parts similar to those of the above-described embodiments is omitted as appropriate.

In the fourth embodiment, the eNB 200 excludes the measurement result based on the transmission record of the reference signal.

The operating environment in FIG. 9 is the same as the operating environment in the first embodiment (FIG. 6).

Steps S301 to S308 correspond to Steps S201 to S208.

In step S309, the UE 100 transmits the measurement result to the PCell. The measurement result here includes not only the first measurement result and the third measurement result but also the second measurement result.

Here, in the present embodiment, the eNB 200 stores at least one of the timing at which the reference signal is transmitted and the timing at which the reference signal is not transmitted, as in the second embodiment. Specifically, the eNB 200 holds a transmission record related to the timing when the reference signal is not transmitted. Specifically, the eNB 200 leaves at least one of the timing at which the reference signal is transmitted and the timing at which the reference signal is not transmitted in the transmission record. In the present embodiment, the eNB 200 leaves the timing at which the reference signal was not transmitted according to the measurement result of step S304 in the transmission record.

In step S310, the PCell (eNB 200) excludes the measurement result corresponding to the timing at which the reference signal is not transmitted from the measurement result reported from the UE 100. In the present embodiment, the eNB 200 excludes the second measurement result corresponding to the timing at which the transmission of the reference signal after step S304 is scheduled. Thereby, eNB200 can acquire a suitable measurement result.

(Modification of the fourth embodiment)
Next, an operation according to a modified example of the fourth embodiment will be described with reference to FIG. FIG. 10 is a diagram for explaining an operation according to the modified example of the fourth embodiment. Description of parts similar to those of the above-described embodiments is omitted as appropriate.

In the modification of the fourth embodiment, the UE 100 reports not only the measurement result for the reference signal but also the measurement result of the interference power to the eNB 200. eNB200 determines MCS (transmission rate, error tolerance) of the data transmitted to UE100 based on the measurement result of interference power.

As shown in FIG. 10A, the first radio communication device (WT 400-1) exists in the vicinity of the UE 100-1, and the second radio communication device (WT 400-1) exists in the vicinity of the UE 100-2 and the eNB 200. WT 400-2) exists. WT 400-1 and WT 400-2 transmit radio signals at a specific frequency in the unlicensed band (see FIG. 10B).

Also, the eNB 200 transmits first setting information related to the scheduled transmission timing of the reference signal. Each UE 100 (UE 100-1 and UE 100-2) receives the first setting information regarding the scheduled transmission timing of the reference signal. Each UE 100 performs a measurement on a reference signal at a specific frequency at a scheduled transmission timing of the reference signal based on the first setting information.

Furthermore, the eNB 200 transmits second setting information for causing each UE 100 to perform measurement of interference power to each UE 100. This 2nd setting information contains the information for making UE100 perform the measurement of the interference power in the specific frequency in an unlicensed band at the same timing as eNB200. Each UE 100 measures the interference power at the same timing as the eNB 200 based on the second setting information. Note that each UE 100 may estimate the timing at which the eNB 200 measures the interference power based on the first setting information even when the UE 100 does not receive the second setting information.

As shown in FIG. 10B, at t1, WT 400-1 transmits a radio signal at a specific frequency. At t2, WT 400-2 transmits a radio signal at a specific frequency.

At t1, the eNB 200 and each UE 100 measure the interference power at the same timing. Since the eNB 200 is far from the WT 400-1, the interference power in the eNB 200 is less than the threshold value. As a result, the eNB 200 determines to transmit the reference signal.

Next, the eNB 200 transmits a reference signal at a specific frequency. Each UE 100 performs measurement at a specific frequency. The measurement result of UE 100-1 is a measurement result that has received interference from WT 400-1.

At t2, the eNB 200 and the UE 100 measure the interference power at the same timing. Since eNB 200 is close to WT 400-2, the interference power in eNB 200 is equal to or greater than the threshold. As a result, the eNB 200 determines not to transmit the reference signal. Although the eNB 200 does not transmit a reference signal, each UE 100 performs measurement at a specific frequency. The measurement result of UE 100-2 is a measurement result that has received interference from WT 400-2.

At t3, each UE 100 reports not only the measurement result (DRS result) with respect to the reference signal but also the measurement result (CCA result) of the interference power to the eNB 200. The eNB 200 receives (acquires) the first measurement result and the second measurement result.

At t4, the eNB 200 measures the interference power. The interference power in the eNB 200 is less than the threshold value. As a result, the eNB 200 determines that no interference is received in the eNB 200 similarly to t1. The eNB 200 determines to transmit data to the UE 100.

When the DRS result from the UE 100 is larger than the first threshold, the eNB 200 determines that there is an interference source near the UE 100 that is the transmission source of the DRS result. As a result, the eNB 200 increases error tolerance of transmission data to the UE 100. The first threshold may be a threshold used by the eNB 200 for detection of interference, or may be a threshold corresponding to the transmission power of the reference signal (DRS) transmitted by the eNB 200.

On the other hand, when the CCA result from the UE 100 is smaller than the second threshold (for example, a threshold lower than the first threshold), the eNB 200 determines that there is no interference source near the UE 100 that is the transmission source of the first measurement result. to decide. As a result, the eNB 200 reduces the error resistance of transmission data to the UE 100.

Further, the eNB 200 compares the CCA result in the local station immediately before transmitting data with the past CCA result in the local station (for example, the CCA result immediately before transmitting the reference signal), thereby improving the error tolerance of the transmission data. Can be determined. For example, the eNB 200 determines error tolerance (MCS) as follows.

The eNB 200 determines that the UE 100-1 has received interference at t1 based on the CCA result from the UE 100-1. In addition, the eNB 200 receives the interference of the UE 100-1 at t1, even though the eNB 200 is not receiving the interference. For this reason, the eNB 200 determines that there is a possibility that the UE 100-1 may receive interference at t4 although it has not received interference at t4. Therefore, the eNB 200 determines the MCS for the transmission data to the UE 100-1 to be an MCS with high error resistance based on the DRS result at t1 from the UE 100-1.

Alternatively, the eNB 200 determines error tolerance based on the CCA result (or DRS result) in which the UE 100-1 is not receiving interference. Here, the eNB 200 does not transmit the reference signal (DRS) at t2. For this reason, the eNB 200 does not normally determine error resilience (MCS) based on the DRS result at t2 from the UE 100-1. On the other hand, the CCA result from the UE 100-1 knows that the UE 100-1 is not receiving interference when the eNB 200 is receiving interference.

On the other hand, the eNB 200 determines from the CCA result at t1 that the UE 100-2 is not receiving interference at the t1, similarly to the eNB 200. For this reason, since the eNB 200 has not received interference at t4, the eNB 200 determines that the possibility that the UE 100-2 receives interference at t4 is low. Thereby, the eNB 200 determines MCS (for transmission data to the UE 100-2) as MCS with high transmission rate (MCS with low error tolerance) based on the DRS result at t1.

In this case, when the eNB 200 transmits data only to one of the UE 100-1 and the UE 100-2 at t4, for example, the eNB 200 transmits (priority) the data to the UE 100-2 that is unlikely to receive interference. Then you can decide.

In eNB 200, a case is assumed in which the CCA result at t4 is larger than the CCA result at t1 and smaller than the CCA result at t2 (t2 result> t4 result> t1 result). In this case, the eNB 200 determines that the UE 100-2 is receiving interference in the same manner as the eNB 200 based on the CCA result from the UE 100-2. Therefore, the eNB 200 determines that there is a high possibility that the UE 100-2 is receiving interference at t4 based on the CCA result of the eNB 200 at t4. The eNB 200 determines the MCS to be applied to the transmission data to the UE 100-2 at t4 as the MCS with high error tolerance.

Meanwhile, the eNB 200 determines that the UE 100-1 is not receiving interference in the same manner as the eNB 200 based on the CCA result at t2 from the UE 100-1. Therefore, the eNB 200 determines that the UE 100-1 is unlikely to receive interference at t4 based on the CCA result of the eNB 200 at t4. The eNB 200 determines an MCS to be applied to transmission data to the UE 100-2 as an MCS having a high transmission rate.

In this case, when the eNB 200 transmits data only to one of the UE 100-1 and the UE 100-2 at t4, for example, the eNB 200 transmits (priority) the data to the UE 100-1 that is unlikely to receive interference. Then you can decide.

As described above, the eNB 200 determines the UE 100 and the MCS that are data transmission destinations based on the CCA result in the eNB 200 (particularly, the CCA result immediately before the data transmission to the UE 100), the DRS result and the CCA result of each UE 100. Can be determined.

[Other Embodiments]
In each embodiment mentioned above, although UE100 demonstrated the case where a measurement result was reported to eNB200, it is not restricted to this. The UE 100 may make a predetermined determination based on a highly effective measurement result from which the measurement result corresponding to the timing at which the reference signal is not transmitted from the eNB 200 is excluded. For example, the UE 100 can make a determination regarding the communication environment of the unlicensed cell based on a highly effective measurement result.

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

[Appendix]
(1) Introduction This appendix describes the design of a reference signal for LAA RRM measurement. It also provides views on other functionality that takes into account the approach to reference signals.

(2) Design of reference signal for RRM measurement It was agreed that Rel-12 DRS is the starting point for the design of reference signal used in RRM measurement in the unlicensed band. Based on the Rel-12 DRS design, the eNB is required to transmit PSS / SSS / CRS (and CSI-RS) at regular intervals without exception. It can be achieved without problems because the eNB uses licensed band resources allocated to transmit DRS. However, in contrast to the licensed band, more than one wireless system / node could share the unlicensed band. In addition to sharing unlicensed bandwidth, each system uses LBT (Listen Before Talk) to avoid collisions required in some countries / regions. Therefore, DRS, in our view, requires LBT when DRS is transmitted in an unlicensed band.

One design perspective is to consider whether LBT should be an essential function. LBT is an indispensable function in EU and Japan, but EU regulation does not detect the frequency for the presence of signal, but transmits management and control frames, that is, short-time control signaling transmission (Short Control Signaling Transmission) ) According to EU regulations, adaptive device short-time control signaling transmissions should have a maximum duty cycle of 10% within a 50 millisecond observation period. Based on the above requirements, when the DRS transmission satisfies the condition, the LTE eNB can transmit the DRS in the unlicensed band without executing the LBT. However, LBT should be mandated as it helps to obtain fair coexistence with other systems and avoid collisions. The LBT mandate will also be considered a simple design and could provide one general solution for all regions where LAA is expected to be deployed.

Proposal 1: Recommendation 1: It should be agreed to apply LBT functionality to Rel-12 DRS based on LAA DRS transmission.

If Proposal 1 is accepted as an agreement, the LBT functionality does not allow the eNB to transmit its DRS in the unlicensed band if a busy channel is detected (see FIG. 10). As a result, the measurement accuracy requirement may not be met if the eNB has not transmitted a DRS during some of the DRS transmission opportunities. According to the current definition of RSRP measurement, the UE must measure RSRP in a subframe configured as a discovery signal opportunity. This is because the UE has to monitor the configured radio resources and the UE may include these resource results in the final measurement result regardless of whether DRS was actually transmitted on these resources. It means you can't. Furthermore, the number of resource elements in the measurement frequency band and in the measurement period used by the UE to determine RSRP is left to the implementation of the UE with constraints that the corresponding measurement accuracy requirements must be met. . Therefore, the reported RSRP can be very inaccurate. The combination of the UE implementation based on RSRP measurements and the unavailability of some DRS transmissions due to the eNB's LBT functionality provides the UE with accurate radio environment information for the exact unlicensed band to the eNB. The problem of not being able to do.

I think that the above-mentioned problems must be solved by RAN4. One approach is for RAN1 to send a request LS to RAN4 to perform a search to see if the current measurement accuracy requirements are satisfied by the existing specification. In cases where the current specification does not meet the exact requirements, new solutions can be considered. Below are some candidate options.

Option 1: The eNB broadcasts / unicasts a DRS measurement instruction in the licensed band.

In this option, the eNB notifies the UE via the licensed band about the condition under which the RSRP of the subframe is to be calculated. During the RSRP calculation, it is expected that the UE will adopt and modify the DRS measurement according to the information provided from the eNB about the RSRP measurement conditions in the unlicensed band. When and how the eNB can provide this information to the UE is a further challenge.

Option 2: Specify CRS (included in DRS) based on RSRP measurement for LAA.

In this option 2, some restrictions apply to the way the UE performs DRS measurements to determine RSRP. For example, the UE should send one measurement result per 1 DRS burst. Since the eNB knows which DRS is transmitted in the unlicensed band, the eNB can determine whether the measurement report received from the specific UE is reliable or not (see FIG. 11).

Proposal 2: If Proposal 1 is accepted as an agreement, RAN1 should send an LS requesting whether the current measurement accuracy requirements are satisfied by the existing specification to RAN4.

(3) Functionality analysis for LAA Unlike RRM measurements, reference signals to support other functionality were not treated. If Proposal 1 is accepted as an agreement, Rel-12 DRS with LBT should be the starting point for other functionality as well. It is assumed that AGC (Automatic Gain Control) setting, coarse synchronization and CSI measurement can be performed using the above DRS for LAA. This would be a baseline solution. However, further research is needed for the case where the eNB does not transmit DRS somewhere during some of the transmission opportunities of DRS. As explained earlier, this situation is similar to RRM measurements.

On the other hand, if the eNB cannot transmit the DRS beyond the currently specified maximum DRS interval, there is a possibility that at least fine frequency / time estimation for demodulation cannot be performed. Existing specifications cannot guarantee a DRS interval longer than 160 msec. This issue will be discussed in the next chapter.

Proposal 3: LAA DRS based on Rel-12 DRS with LBT should also be used for AGC configuration, coarse synchronization and CSI measurements.

(4) Synchronous signal design As mentioned above, LBT based on transmission is required in the unlicensed band in various countries / regions. Therefore, the eNB may not be able to transmit DRS in the unlicensed band for a long time due to the presence of other transmissions by neighboring nodes sharing the same band. One approach is to set a fixed upper limit for the period between two DRS transmissions, for example 160 msec. If the eNB is unable to transmit a DRS longer than the upper limit, it should be assumed that fine frequency / time estimation is not guaranteed. However, due to interference, the UE may not be able to detect / decode some of the correct DRS transmissions. This situation forces consideration to provide other synchronization signals during data transmission in addition to DRS transmission. In one solution, the eNB transmits a synchronization signal (LAA sync (LAA sync)) in a symbol located before the data region (for example, the first symbol of the subframe) (see FIG. 12). This approach is very similar to the D2D sync signal design. In that case, the UE achieves coarse synchronization using DRS and fine frequency / time estimation using the LAA sink. When this solution is applied, the AGC configuration is performed based on the LAA sink instead of the DRS because the LAA sink is located next to the data area in the first subframe received at the UE. .

It is proposed that the current physical control channel area should be replaced by LAA sink. The number of resource elements used to transmit the physical control channel is changed according to the number of UEs scheduled in the subframe, for example. In the case of low traffic situations, the physical control channel area may not be fully occupied, resulting in low resource element density and resulting low transmit power over OFDM symbols resulting in higher false positives by neighboring nodes . This leads to collisions because neighboring nodes may assume that a channel is available for each transmission. In order to avoid collisions, it is proposed that the physical control channel should be removed from unlicensed band transmissions and instead LAA sinks should be transmitted. Further research is needed on how the LAA sink is mapped just before the data region.

Proposal 4: The current physical control channel area should be replaced with this LAA sink.

Note that the entire contents of US Provisional Application No. 62/109850 (filed on January 30, 2015) are incorporated herein by reference.

Claims

A base station,
A transmitter for transmitting a reference signal in an unlicensed band;
A receiver that receives a measurement result of a radio signal in the unlicensed band from a user terminal;
And a control unit that excludes a measurement value measured at a timing when the reference signal is not transmitted in the unlicensed band from the measurement result.
The base station according to claim 1, wherein the reception unit receives the measurement result from the user terminal that transmits one measurement result every time the base station transmits one reference signal.
A user terminal capable of communicating in a licensed band and an unlicensed band and a base station capable of communicating in the unlicensed band,
A control unit for measuring interference power in the unlicensed band;
A transmitter that transmits a reference signal in the unlicensed band based on the measurement result of the interference power;
A storage unit that holds a transmission record related to the timing at which the reference signal was not transmitted based on the measurement result of the interference power, and
The control unit, when a measurement result for the reference signal is reported from the user terminal, based on the transmission record, a predetermined result corresponding to a timing at which the reference signal is not transmitted from the measurement result for the reference signal. A base station that excludes measurement results.
The transmitter transmits setting information for causing the user terminal to perform measurement of interference power in the unlicensed band at the same timing as the base station, and
The control unit acquires the measurement result of the interference power in the user terminal, and transmits the measurement result of the interference power in the user terminal and the measurement result of the interference power in the user terminal to the user terminal. 4. The base station according to claim 3, wherein error tolerance of data is determined.
The control unit measures the interference power in the unlicensed band immediately before transmitting the data,
The measurement result of the interference power in the local station includes not only the measurement result of the interference power measured immediately before the transmission of the reference signal but also the measurement result of the interference power measured immediately before the transmission of the data. The base station according to claim 4.
A user terminal capable of communicating in the licensed band and capable of communicating in the unlicensed band with a base station that transmits a radio signal based on a measurement result of interference power in the unlicensed band,
A control unit that performs measurement on a predetermined radio signal in the unlicensed band and reports a measurement result on the predetermined radio signal;
The user terminal characterized by specifying a timing at which a reference signal is not transmitted from the base station in the unlicensed band, and excluding a predetermined measurement result corresponding to the specified timing.
A storage unit for storing signal sequence information for specifying a signal sequence related to the reference signal transmitted from the base station;
When the correlation value between the signal sequence of the predetermined radio signal and the signal sequence specified based on the signal sequence information is less than a threshold, the control unit determines the timing at which the predetermined radio signal is transmitted, The user terminal according to claim 6, wherein the user terminal is specified as a timing at which the reference signal is not transmitted.
A receiver that receives transmission information related to the timing at which the reference signal is transmitted;
The user terminal according to claim 6, wherein the control unit specifies a timing at which the reference signal is not transmitted based on the transmission information.
A receiver for receiving schedule information related to a scheduled transmission timing of the reference signal before measuring the predetermined radio signal;
The control unit performs measurement on the predetermined radio signal at the scheduled transmission timing based on the schedule information, and measures interference power in the unlicensed band at a timing different from the scheduled transmission timing,
The user according to claim 6, wherein the control unit specifies a timing at which the reference signal is not transmitted based on a measurement result at the different timing and a measurement result at the scheduled transmission timing. Terminal.
The different timing is at least one of a timing before and after the scheduled transmission timing,
The control unit refers to the scheduled transmission timing when the first reception level, which is a measurement result at the different timing, is higher than a second reception level, which is the measurement result at the scheduled transmission timing, by a predetermined value or more. The user terminal according to claim 9, wherein the user terminal is specified as a timing at which a signal is transmitted.