WO2016121609A1

WO2016121609A1 - User terminal and base station

Info

Publication number: WO2016121609A1
Application number: PCT/JP2016/051648
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

Abstract

A user terminal according to an embodiment of the present invention can communicate in a licensed band and can communicate, in an unlicensed band, with a base station that periodically transmits a reference signal in the unlicensed band. The user terminal is provided with a control unit that makes a measurement regarding a reference signal from the base station in the unlicensed band, and reports measurement results regarding the reference signal. The control unit identifies a time when the user terminal received interference during the measurement, and excludes the measurement result corresponding to the identified time.

Description

User terminal and base station

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 level is low), a radio signal can be transmitted in the unlicensed band.

On the other hand, in some regions (for example, Europe), a radio signal that satisfies a predetermined condition can be exceptionally transmitted without measuring interference power in the unlicensed band.

The user terminal according to an embodiment can communicate in the licensed band, and can communicate in the unlicensed band with a base station that periodically transmits a reference signal in the unlicensed band. The user terminal includes a control unit that measures a reference signal from the base station in the unlicensed band and reports a measurement result of the reference signal. The control unit specifies a timing at which the user terminal receives interference during the measurement, and excludes the measurement result corresponding to the specified timing.

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 a listening failure before DRS transmission. FIG. 11 is a diagram for explaining LAA DRS RSRP measurement. FIG. 12 is a diagram for explaining an example (right) of existing channel mapping (left) and proposed channel mapping.

[Outline of Embodiment]
In some areas, since it is not necessary to measure interference power, it is assumed that the base station periodically transmits a reference signal (Discovery Reference signal) without measuring the interference power in the unlicensed band. . The user terminal can measure the reference signal transmitted periodically and report the measurement result to the base station. Based on the measurement result, the base station can determine whether communication with the user terminal in the unlicensed band is possible or the communication quality in the unlicensed band.

However, since the base station transmits the reference signal without measuring the interference power, the measurement result for the reference signal may be affected by interference. As a result, there is a possibility that an appropriate measurement result for the reference signal in the unlicensed band 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 user terminals according to the first to third embodiments can communicate in the licensed band, and can communicate in the unlicensed band with a base station that periodically transmits a reference signal in the unlicensed band. . The user terminal includes a control unit that measures a reference signal from the base station in the unlicensed band and reports a measurement result of the reference signal. The control unit specifies a timing at which the user terminal receives interference during the measurement, and excludes the measurement result corresponding to the specified timing.

The user terminal according to the first embodiment further includes a receiving unit that receives interference information related to timing at which the base station receives interference before transmitting the reference signal. The control unit identifies timing at which the user terminal receives interference based on the interference information.

In the second embodiment, the control unit measures interference power in the unlicensed band before the base station transmits the reference signal. Based on the measurement result of the interference power, the timing at which the user terminal receives interference during the measurement is specified.

In the third embodiment, the control unit measures the interference power in the unlicensed band at a timing different from the transmission timing of the reference signal. The control unit identifies a timing at which the user terminal receives interference during the measurement based on a measurement result at the different timing and a measurement result at the transmission timing.

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 identifies a timing at which interference does not occur in the unlicensed band, a first wireless communication unit that transmits measurement information to the user terminal in the licensed band, and in the unlicensed band A second wireless communication unit that transmits the reference signal at the timing. The measurement information is information for causing the user terminal to perform measurement on a reference signal in the unlicensed band at the timing.

In 4th Embodiment, the said control part allocates a radio | wireless resource in order to transmit user data at the said timing with respect to another user terminal. The reference signal is transmitted along with the user data.

In the fourth embodiment, the second wireless communication unit transmits another reference signal in the unlicensed band before transmitting the reference signal. The control unit is a predetermined unit for reporting the measurement result of the reference signal based on the measurement result of the other reference signal from the user terminal of the own station that has transmitted the measurement result of the other reference signal. A user terminal is determined.

In the fourth embodiment, the control unit measures interference power in the unlicensed band. The control unit specifies the timing based on the measurement result of the interference power.

[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, eNB 200 measures interference power to confirm whether or not a frequency (carrier) in the unlicensed band is available (CCA). 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). Note that 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).

On the other hand, in some areas (for example, Europe), a control signal (Short control signaling) that satisfies a predetermined condition can be transmitted without measuring interference power in the unlicensed band. For example, a control signal that satisfies a predetermined condition is a signal that satisfies a maximum duty cycle of 5% within an observation period of 50 ms.

Here, when the eNB 200 transmits a reference signal as control information, the reference signal can be periodically transmitted. The UE 100 performs measurement on the reference signal transmitted periodically, and the eNB 200 can report the measurement result to the management. Based on the measurement result, the eNB 200 can determine whether communication with the UE 100 in the unlicensed band is possible or the communication quality in the unlicensed band.

However, since the eNB 200 transmits the reference signal without measuring the interference power, the measurement result for the reference signal may be subject to interference. As a result, there is a possibility that an appropriate measurement result for the reference signal in the unlicensed band cannot be acquired.

Therefore, the above-described problem is solved by the following method.

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 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 at a specific frequency within the unlicensed band managed by the eNB 200. Alternatively, the UE 100 may perform communication at a specific frequency.

In this embodiment, as will be described later, the eNB 200 performs interference power measurement (CCA) at a specific frequency and then transmits a reference signal at the specific frequency. However, the eNB 200 periodically transmits the reference signal regardless of the measurement result of the interference power.

Near the UE 100 and the eNB 200, there is an AP 400 that transmits a radio signal (data: DATA) at a specific frequency in the unlicensed band. In FIG. 6, the AP 400 transmits data at t1 and t3.

As shown in FIG. 6, at t1, the eNB 200 measures interference power at a specific frequency in the unlicensed band. Here, based on the data transmission from AP400, it demonstrates on the assumption that interference electric power exceeded the threshold value. The eNB 200 determines that it has received interference and stores the transmission timing of the reference signal immediately after.

Next, the eNB 200 transmits a reference signal even when the interference power is larger than a threshold value (for example, a threshold value indicating that there is no empty channel in the LBT method).

Here, 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.

UE 100 performs a measurement on a reference signal at a specific frequency in the unlicensed band. When receiving setting information related to the transmission timing of the reference signal from the eNB 200, the UE 100 can perform measurement on the reference signal based on the setting information. 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).

The UE 100 stores the measurement result for the reference signal in association with the measurement timing. Since the AP 400 is transmitting data at t1, the measurement result is affected by interference.

At t2, the eNB 200 measures the interference power similarly to t1. Here, since there is no data transmission from AP400, it demonstrates supposing that interference power is less than a threshold value. The eNB 200 determines that no interference is received. The eNB 200 may not store the transmission timing of the reference signal immediately after. Thereafter, the eNB 200 transmits a reference signal.

UE100 performs the measurement for the reference signal in the same manner as t1. The UE 100 stores the measurement result in association with the measurement timing. Since the AP 400 transmits data at t2, the measurement result is not affected by interference.

At t3, each of the UE 100 and the eNB 200 operates similarly to t1, and at t4, each of the UE 100 and the eNB 200 operates similarly to t2.

Here, the eNB 200 transmits, to the UE 100, interference information regarding the timing at which the interference is received before transmitting the reference signal. The interference information is, for example, information (list) indicating the transmission timing of the reference signal transmitted after determining that the interference has been received. In the present embodiment, timings indicating t1 and t3 are shown. The interference information may be indicated by a subframe number. The interference information may be transmitted by a common signal (for example, SIB, PDCCH) or may be transmitted by an individual signal (for example, PDSCH). These signals may be transmitted to the UE 100 by a frequency (carrier) in the licensed band, or may be transmitted to the UE 100 by a specific frequency (carrier) in the unlicensed band. Further, the interference information may be included in a message requesting deletion of the measurement result corresponding to the timing indicated by the interference information. In addition, eNB200 may notify one transmission timing, whenever interference power exceeds a threshold value, without notifying several transmission timing collectively.

The UE 100 specifies the timing at which the UE 100 receives interference while performing the measurement on the reference signal based on the interference information. That is, the UE 100 specifies (estimates) the timing at which the UE 100 receives interference during measurement of the timing at which the eNB 200 receives interference. The UE 100 excludes (deletes) the measurement result corresponding to the identified timing (timing indicated by the interference information). Thereby, UE100 can exclude the measurement result estimated to have received interference from the calculation object or the report object to eNB200. Therefore, the UE 100 and the eNB 200 can acquire an appropriate measurement result.

[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. The operating environment of the second embodiment is the same as the operating environment of the first embodiment.

In the second embodiment, the UE 100 measures the interference power in the unlicensed band, and the UE 100 excludes the measurement result based on the measurement result of the interference power.

At t1, the eNB 200 measures the interference power as in the first embodiment, and periodically transmits the reference signal regardless of the measurement result of the interference power. Note that the eNB 200 may periodically transmit the reference signal without measuring the interference power.

On the other hand, before measuring the reference signal, the UE 100 measures the interference power (performs CCA). The UE 100 measures the interference power at the timing when the eNB 200 performs CCA to determine whether or not the reference signal can be transmitted in the LBT scheme. That is, the UE 100 measures the interference power at the timing when the eNB 200 measures the interference power. Note that the measurement for the reference signal and the measurement of the interference power may be different from each other, but are the same operation in terms of measurement for a radio signal at a specific frequency.

UE100 excludes the measurement result of the reference signal when the interference power exceeds the threshold value. Or UE100 does not need to memorize the measurement result of a reference signal, and does not need to perform the measurement to a reference signal, when interference power exceeds a threshold. Thereby, UE100 and eNB200 can acquire a suitable measurement result.

Note that, as in the first embodiment, the UE 100 may receive the interference information from the eNB 200 and exclude the measurement result based on the interference information as well as its own measurement result. Thereby, UE100 and eNB200 can acquire the appropriate measurement result in the timing when data is not transmitted in a specific frequency.

[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 performs interference power measurement (CCA) at a timing different from the transmission timing of the reference signal. UE100 specifies the timing which received interference based on the measurement result with respect to a reference signal, and the measurement result of interference electric power.

As shown in FIG. 8A, a first wireless communication device (WT 500-1) and a second wireless communication device (WT 500-2) exist in the vicinity of the UE 100. UE 100 is closer to WT 500-1 than WT 500-2. WT 500-1 and WT 500-2 transmit a radio signal at a specific frequency in the unlicensed band (see FIG. 8B).

Further, the eNB 200 periodically transmits a reference signal. 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 performs interference power measurement (CCA) at a specific frequency 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 the timing before (immediately before) and after (immediately) the scheduled transmission timing (see FIG. 8B). In addition, the UE 100 measures the interference power at an intermediate time (t4, t8) between the predetermined transmission scheduled timing and the next scheduled transmission timing. Therefore, the UE 100 intermittently measures the interference power.

As shown in FIG. 8B, at t2, t6, and t10, the eNB 200 transmits a reference signal at a specific frequency, and the UE 100 performs measurement on the reference signal. In addition, the UE 100 measures interference power at t1, t3, t4, t5, t7, t8, t9, and t10. The WT 500-1 transmits a radio signal at a specific frequency from t5 to t8. The WT 500-2 transmits a radio signal at a specific frequency from t1 to t3. As a result, the measurement results from t1 to t3 in the UE 100 are affected by interference due to the transmission of the radio signal from the WT 500-2. The measurement results from t5 to t7 in the UE 100 are more strongly affected by interference due to the transmission of a radio signal from the WT 500-1 that exists near the UE 100 than in the WT 500-2.

Next, the UE 100 determines whether or not the UE 100 is receiving interference during measurement of the reference signal.

The measurement value in FIG. 8 (B) indicates the measurement result (reception level) in the UE 100. The measurement values at t2, t6, and t10 are DRS measurement values that can include interference power, and the measurement values at t1, t3, t4, t5, t7, t8, t9, and t10 are interference measurement values. In the following, description will be made assuming that the measured value at t4 is the lowest value.

First, the UE 100 compares the measured value (DRS measured value) at the scheduled transmission timing with the measured value (interference measured value) at timings before and after the scheduled transmission timing (first timing). When the DRS measurement value is higher than the interference measurement value by a predetermined value or more (that is, the DRS measurement value−interference measurement value> predetermined value), the UE 100 may have received the interference, or the DRS interference It is determined that it has not received. In other words, when the difference between the DRS measurement value and the interference measurement value is less than the predetermined value, the UE 100 determines that interference has occurred (it is highly likely that the interference has been received).

Specifically, since the difference between the DRS measurement value at t6 and the interference measurement value at t5 (t7) is less than a predetermined value, the DRS measurement value at t6 is specified as the timing of the interference.

Second, the UE 100 compares the measurement value (interference measurement value) at the first timing with the lowest measurement value (minimum measurement value) among the interference measurement values. When the interference measurement value is higher than the minimum measurement value by a predetermined value or more (ie, interference measurement value−minimum measurement value> predetermined value), the UE 100 receives the DRS measurement value before or after the first interference measurement value due to interference. It is determined that there is a possibility. In other words, when the difference between the interference measurement value and the minimum measurement value is less than the predetermined value, the UE 100 determines that it is receiving interference (may be receiving interference).

Specifically, since the difference between the interference measurement value at t1 (t3) and the minimum measurement value at t4 is equal to or greater than a predetermined value, the UE 100 may have the interference of the DRS measurement value at t2. judge. On the other hand, since the difference between the interference measurement value at t9 (t11) and the minimum measurement value at t4 is less than a predetermined value, it is determined that the DRS measurement value at t10 is not subject to interference.

Thus, the UE 100 identifies the timing at which the UE 100 receives interference during the measurement by comparing the DRS measurement value and the interference measurement value or by comparing the interference measurement values. Thereby, UE100 and eNB200 can acquire an appropriate measurement result by excluding the measurement result (DRS measurement value) corresponding to the specified timing.

The U100 may determine whether or not to exclude the interference measurement value determined to be subject to interference from the calculation target or the report target depending on the accuracy and parameter of the measurement result.

Note that the UE 100 may report not only the measurement result for the reference signal but also the measurement result (interference measurement value) of the interference power to the eNB 200. In this case, the UE 100 reports the measurement result of the interference power associated with the measurement timing to the eNB 200. The eNB 200 may make the above determination based on the measurement report. Further, the eNB 200 may remove a predetermined measurement result in consideration of its own interference power measurement result.

[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 FIG. 9, each UE 100 (UE 100-1 to UE 100-3) is located in a licensed cell managed by the eNB 200. The UE 100-2 may not be located in the licensed cell. In the initial state, each UE 100 may be in the RRC idle state or in the RRC connected state. Each UE 100 does not start communication at a specific frequency within the unlicensed band managed by the eNB 200.

In the fourth embodiment, the eNB 200 identifies the timing at which no interference occurs, and the UE 100 performs the measurement for the reference signal at the identified timing.

As shown in FIG. 9, in step S101, the eNB 200 transmits a first reference signal (DRS) at a specific frequency in the unlicensed band. Each UE 100 performs a measurement on a reference signal. The DRS is transmitted for a period of 1 to 5 subframes, for example.

In step S102, each UE 100 determines whether or not the measurement result in step S101 exceeds a threshold value. Specifically, each UE 100 executes the process of step S103 when the reception level (RSRP) of the reference signal exceeds the threshold. Here, the description will be made on the assumption that the reception level in UE 100-1 and UE 100-3 exceeds the threshold.

In step S103, the UE 100-1 and the UE 100-3 perform a measurement report indicating that the reception level of the first reference signal exceeds the threshold to the eNB 200. Accordingly, the UE 100 reports (transmits) only the measurement result of the first reference signal once (for example, 1 to 5 subframes) to the eNB 200. UE100 can report the measurement result of a 1st reference signal to eNB200 via a licensed cell. Thereby, the eNB 200 receives the first measurement report (that is, the measurement result of the first reference signal) from the UE 100-1 and the UE 100-3.

In step S104, the eNB 200 performs scheduling based on the first measurement report.

The eNB 200 determines that the UE 100-1 and the UE 100-3 that transmitted the first measurement report exist in an unlicensed cell operated at a specific frequency. On the other hand, the eNB 200 determines that the UE 100-2 that has not transmitted the first measurement report does not exist in the unlicensed cell.

Further, the eNB 200 transmits user data at a specific frequency in the unlicensed band from the UE 100 of the own station (specifically, the UE 100-1 and the UE 100-3 existing in the unlicensed band). Allocate radio resources. For example, the eNB 200 allocates radio resources (radio resources at specific frequencies in the unlicensed band) to the UE 100 having a large RSRP value included in the first measurement report. Thereby, eNB200 determines UE100 used as the receiving object of user data. Here, the description will proceed assuming that the eNB 200 has assigned radio resources to the UE 100-1.

On the other hand, the eNB 200 causes other UEs 100-3 existing in the unlicensed state to perform measurement and report of measurement results for the second reference signal (CRS) within the radio resources allocated to the UE 100-1. UE 100 is determined. That is, eNB200 determines predetermined | prescribed UE100 (measurement report object) which reports the measurement result of a 2nd reference signal based on the measurement information mentioned later. The measurement information includes information indicating the transmission timing of the second reference signal in the radio resource allocated to the UE 100-1. The measurement information indicates, for example, a subframe number in which at least the second reference signal is transmitted. The measurement information may indicate a subframe number in which user data of the UE 100-1 is transmitted.

Here, the eNB 200 determines the UE 100-3 that is not the user data reception target as the measurement report target.

Note that the eNB 200 measures the interference power at the specific frequency before assigning the radio resource to the UE 100-1, and confirms that the interference power at the specific frequency is less than the threshold. Thereby, eNB200 specifies the timing when interference does not occur in an unlicensed band based on interference power. The eNB 200 assigns radio resources to the UE 100-1 at a timing at which no interference occurs.

In step S105, the eNB 200 transmits measurement information to the UE 100-3 using the frequency in the licensed band. The UE 100-3 receives the measurement information. The measurement information may be transmitted by a common signal (for example, SIB, PDCCH), or may be transmitted by an individual signal (for example, PDSCH).

In step S106, the eNB 200 transmits scheduling information indicating the radio resource allocated to the UE 100-1 using the frequency in the licensed band. The UE 100-1 receives the scheduling information. The scheduling information may be transmitted by a common signal (for example, SIB, PDCCH), or may be transmitted by an individual signal (for example, PDSCH).

In step S107, eNB200 transmits user data using the radio | wireless resource allocated in the specific frequency. The UE 100-1 receives user data. On the other hand, the eNB 200 transmits a second reference signal accompanying the user data.

In step S108, the UE 100-1 receives user data. The UE 100-1 may perform measurement on the second reference signal transmitted along with the user data. Here, it is assumed that UE 100-1 has performed measurement on the second reference signal.

In step S109, the UE 100-3 performs measurement on the second reference signal based on the measurement information. Here, the UE 100 can measure reception strength (RSRP), reception quality (RSRQ, SINR), and the like as the measurement for the second reference signal.

In step S110, the UE 100-1 and the UE 100-3 report the measurement result for the second reference signal to the eNB 200. The eNB 200 receives the second measurement report (that is, the measurement result of the second reference signal). The second measurement report may include a measurement report of reception strength (RSRP) and reception quality (RSRQ, SINR).

In step S111, the eNB 200 determines the UE 100 that is a user data reception target based on the second measurement report, similarly to step S104. Since the second measurement report may include a measurement report of reception strength (RSRP) and reception quality (RSRQ, SINR), the eNB 200 determines whether the UE 100 is receiving interference from a radio communication apparatus that the eNB 200 cannot detect. be able to.

Thus, in the fourth embodiment, measurement is performed based on the second reference signal instead of the first reference signal. Since the second reference signal is transmitted at a timing at which no interference occurs, an appropriate measurement result can be acquired.

Note that the eNB 200 may omit the transmission of the first reference signal after instructing the UE 100 to measure the second reference signal, or may perform the first reference based on the interference power measurement result in the eNB 200. The signal may be transmitted intermittently.

[Other Embodiments]
In the above-described embodiment, the LTE system has been described as an example of the mobile communication system. However, the embodiment is not limited to the LTE system, and the content of the present application may be applied to a system other than the LTE system.

Of course, the above-described embodiments can be appropriately combined.

[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. 62/109879 (filed on January 30, 2015) are incorporated herein by reference.

Claims

A user terminal capable of communicating in the licensed band and capable of communicating in the unlicensed band with a base station that periodically transmits a reference signal in the unlicensed band,
A controller that performs a measurement on a reference signal from the base station in the unlicensed band and reports a measurement result on the reference signal;
The said control part specifies the timing when the said user terminal received interference during the said measurement, and excludes the said measurement result corresponding to the said specified timing, The user terminal characterized by the above-mentioned.
A receiver that receives interference information related to timing at which the base station receives interference before transmitting the reference signal;
The said control part specifies the timing when the said user terminal received interference based on the said interference information, The user terminal of Claim 1 characterized by the above-mentioned.
The control unit measures interference power in the unlicensed band before the base station transmits the reference signal,
The user terminal according to claim 1, wherein a timing at which the user terminal receives interference during the measurement is specified based on a measurement result of the interference power.
The control unit measures interference power in the unlicensed band at a timing different from the transmission timing of the reference signal,
The said control part specifies the timing when the said user terminal received interference during the said measurement based on the measurement result in the said different timing, and the measurement result in the said transmission timing. The described user terminal.
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 that identifies a timing at which no interference occurs in the unlicensed band;
A first wireless communication unit for transmitting measurement information to the user terminal in the licensed band;
A second wireless communication unit that transmits the reference signal at the timing in the unlicensed band,
The base station characterized in that the measurement information is information for causing the user terminal to perform measurement on a reference signal in the unlicensed band at the timing.
The control unit allocates radio resources to other user terminals to transmit user data at the timing,
The base station according to claim 5, wherein the reference signal is transmitted along with the user data.
The second wireless communication unit transmits another reference signal in the unlicensed band before transmitting the reference signal,
The control unit is a predetermined unit that reports the measurement result of the reference signal based on the measurement result of the other reference signal from the user terminal of the own station that has transmitted the measurement result of the other reference signal. The base station according to claim 5, wherein a user terminal is determined.
The control unit measures interference power in the unlicensed band,
The base station according to claim 5, wherein the control unit specifies the timing based on a measurement result of the interference power.