WO2017061723A1 - Method and apparatus for terminal to carry out measurements - Google Patents

Abstract

Provided are a method for a terminal to carry out measurements in a wireless communication system and an apparatus for the method. The terminal measures an unlicensed frequency during a first time duration and measures a received signal strength indicator (RSSI) for the unlicensed frequency during a second time duration, wherein the first time duration may not overlap with the second time duration.

Description

Method and apparatus for performing measurement by a terminal

The present invention relates to a wireless communication system, and more particularly, to a method for a terminal to perform measurement for an unlicensed band in a wireless communication system and an apparatus supporting the same.

The 3rd Generation Partnership Project (3GPP) long term evolution (LTE), an enhancement to the Universal Mobile Telecommunications System (UMTS), is being introduced as a 3GPP release 8. 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in downlink and single carrier-frequency division multiple access (SC-FDMA) in uplink. A multiple input multiple output (MIMO) with up to four antennas is employed. Recently, a discussion on 3GPP LTE-Advanced (LTE-A), an evolution of 3GPP LTE, is underway.

In a wireless communication system, it is necessary to estimate an uplink channel or a downlink channel for data transmission / reception, system synchronization acquisition, channel information feedback, and the like. In a wireless communication system environment, fading occurs due to a multipath time delay. The process of restoring the transmission signal by compensating for the distortion of the signal caused by a sudden environmental change due to fading is called channel estimation. In addition, it is necessary to measure the channel state (channel state) for the cell to which the terminal belongs or other cells. For channel estimation or channel state measurement, channel estimation is generally performed by using a reference signal (RS) that the transceiver knows from each other.

The terminal may perform the measurement in the following three ways.

1) RSRP (reference signal received power): Represents the average received power of all REs carrying the CRS transmitted over the entire band. In this case, the average received power of all REs carrying the CSI RS instead of the CRS may be measured.

2) Received signal strength indicator (RSSI): Received power measured in the entire band. RSSI includes signal, interference, and thermal noise.

3) reference symbol received quality (RSRQ): Represents a CQI and may be determined by RSRP / RSSI according to a measurement bandwidth or a subband. In other words, RSRQ means signal-to-noise interference ratio (SINR). Since RSRP does not provide sufficient mobility information, RSRQ may be used instead of RSRP during handover or cell reselection.

RSRQ = can be calculated as RSSI / RSSP. Or it may be calculated as RSRQ = N * RSSI / RSSP. Here, N may be a variable (eg, the number of PRBs) or a function related to the bandwidth for measuring the RSSI.

LTE-U (LTE in Unlicensed spectrum) or LAA (Licensed-Assisted Access using LTE) uses an LTE licensed band as an anchor and binds the licensed and unlicensed bands using carrier aggregation (CA). Technology. The terminal first accesses the network in the licensed band. The base station may offload the traffic of the licensed band to the unlicensed band by combining the licensed band and the unlicensed band according to the situation.

LTE-U can extend the advantages of LTE to unlicensed bands to provide improved mobility, security, and communication quality. LTE-U is more efficient in frequency than existing radio access technologies, resulting in increased throughput. Can be.

Unlike licensed bands, which are guaranteed for exclusive use, unlicensed bands are shared with various radio access technologies such as WLANs. Accordingly, each communication node acquires channel usage in the unlicensed band based on competition, which is called carrier sense multiple access with collision avoidance (CSMA / CA). Each communication node needs to perform channel sensing before transmitting a signal to check whether the channel is idle. This is called clear channel assessment (CCA).

The terminal may perform RSSI measurement on the frequency indicated by the base station. However, the RSSI measurement for the indicated frequency may also be performed on the reference signal transmitted from the serving cell existing in the unlicensed band. The reference signal may be at least one of DRS and CRS. Due to the reference signal transmitted from the serving cell, the RSSI measured by the terminal may be overestimated. In order to solve the problem that the RSSI measurement result is overestimated, a method for performing measurement by the terminal and a device supporting the same need to be newly proposed.

According to an embodiment, a method of performing measurement by a terminal in a wireless communication system is provided. The terminal measures unlicensed frequency in a first time duration and measures a received signal strength indicator (RSSI) for the unlicensed frequency in a second time duration. Including performing, the second time interval may not overlap with the first time interval.

The measurement for the unlicensed frequency may be a DRS based measurement. The first time interval may be a subframe in which the DRS is detected by the terminal. The first time period may be a subframe in which the DRS indicated by the base station is transmitted.

The measurement for the unlicensed frequency may be a CRS based measurement.

The first time interval may be a first measurement gap, and the second time interval may be a second measurement gap. The repetition period of the second measurement gap may be set by the base station. The duration of the second measurement gap may be set by the base station.

The terminal may further include receiving frequency information from a base station including a frequency at which the RSSI measurement should be performed. The RSSI measurement for the unlicensed frequency may be performed for the frequency included in the frequency information.

The terminal may further include receiving a quality threshold (s-Measure) of a primary cell (PCell). The RSSI measurement for the unlicensed frequency may be performed on the frequency included in the frequency information regardless of the reference signal received power (RSRP) of the PCell.

Provided is a terminal for performing a measurement in a wireless communication system. The terminal includes a memory; Transceiver; And a processor that connects the memory and the transceiver, wherein the processor performs a measurement on an unlicensed frequency in a first time duration, and in a second time duration. Received signal strength indicator (RSSI) measurement for the unlicensed frequency, wherein the second time interval may not overlap the first time interval.

More accurate RSSI measurement in the unlicensed band may be performed by the terminal.

1 shows a structure of an LTE system.

2 shows an air interface protocol of an LTE system for a control plane.

3 shows an air interface protocol of an LTE system for a user plane.

4 shows a conventional method of performing measurements.

5 shows a conventional single carrier system and a carrier aggregation system.

6 shows an example of an LTE service using an unlicensed band.

7 illustrates an example of a measurement gap set by the first method, according to an embodiment of the present invention.

8 illustrates an example of a measurement gap set by the second method, according to an embodiment of the present invention.

9 is a block diagram illustrating a method of performing measurement by a terminal according to an embodiment of the present invention.

10 is a block diagram of a wireless communication system in which an embodiment of the present invention is implemented.

The following techniques include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and the like. It can be used in various wireless communication systems. CDMA may be implemented with a radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as global system for mobile communications (GSM) / general packet radio service (GPRS) / enhanced data rates for GSM evolution (EDGE). OFDMA may be implemented by wireless technologies such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), and the like. IEEE 802.16m is an evolution of IEEE 802.16e and provides backward compatibility with systems based on IEEE 802.16e. UTRA is part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is part of evolved UMTS (E-UMTS) using evolved-UMTS terrestrial radio access (E-UTRA), which employs OFDMA in downlink and SC in uplink -FDMA is adopted. LTE-A (advanced) is the evolution of 3GPP LTE.

For clarity, the following description focuses on LTE-A, but the technical spirit of the present invention is not limited thereto.

1 shows a structure of an LTE system. Communication networks are widely deployed to provide various communication services such as IMS and Voice over internet protocol (VoIP) over packet data.

Referring to FIG. 1, an LTE system structure includes one or more UEs 10, an evolved-UMTS terrestrial radio access network (E-UTRAN), and an evolved packet core (EPC). The terminal 10 is a communication device moved by a user. The terminal 10 may be fixed or mobile and may be called by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), and a wireless device.

The E-UTRAN may include one or more evolved node-eB (eNB) 20, and a plurality of terminals may exist in one cell. The eNB 20 provides an end point of a control plane and a user plane to the terminal. The eNB 20 generally refers to a fixed station communicating with the terminal 10, and may be referred to in other terms such as a base station (BS), a base transceiver system (BTS), an access point, and the like. . One eNB 20 may be arranged per cell. There may be one or more cells within the coverage of the eNB 20. One cell may be configured to have one of bandwidths such as 1.25, 2.5, 5, 10, and 20 MHz to provide downlink (DL) or uplink (UL) transmission service to various terminals. In this case, different cells may be configured to provide different bandwidths.

Hereinafter, DL means communication from the eNB 20 to the terminal 10, and UL means communication from the terminal 10 to the eNB 20. In the DL, the transmitter may be part of the eNB 20 and the receiver may be part of the terminal 10. In the UL, the transmitter may be part of the terminal 10 and the receiver may be part of the eNB 20.

The EPC may include a mobility management entity (MME) that serves as a control plane, and a system architecture evolution (SAE) gateway (S-GW) that serves as a user plane. The MME / S-GW 30 may be located at the end of the network and is connected to an external network. The MME has information about the access information of the terminal or the capability of the terminal, and this information may be mainly used for mobility management of the terminal. S-GW is a gateway having an E-UTRAN as an endpoint. The MME / S-GW 30 provides the terminal 10 with the endpoint of the session and the mobility management function. The EPC may further include a packet data network (PDN) -gateway (GW). PDN-GW is a gateway with PDN as an endpoint.

The MME includes non-access stratum (NAS) signaling to the eNB 20, NAS signaling security, access stratum (AS) security control, inter CN (node network) signaling for mobility between 3GPP access networks, idle mode terminal reachability ( Control and execution of paging retransmission), tracking area list management (for terminals in idle mode and active mode), P-GW and S-GW selection, MME selection for handover with MME change, 2G or 3G 3GPP access Bearer management, including roaming, authentication, and dedicated bearer settings, SGSN (serving GPRS support node) for handover to the network, public warning system (ETWS) and commercial mobile alarm system (PWS) It provides various functions such as CMAS) and message transmission support. S-GW hosts can be based on per-user packet filtering (eg, through deep packet inspection), legal blocking, terminal IP (Internet protocol) address assignment, transport level packing marking in DL, UL / DL service level charging, gating and It provides various functions of class enforcement, DL class enforcement based on APN-AMBR. For clarity, the MME / S-GW 30 is simply represented as a "gateway", which may include both MME and S-GW.

An interface for user traffic transmission or control traffic transmission may be used. The terminal 10 and the eNB 20 may be connected by the Uu interface. The eNBs 20 may be interconnected by an X2 interface. Neighboring eNBs 20 may have a mesh network structure by the X2 interface. The eNBs 20 may be connected with the EPC by the S1 interface. The eNBs 20 may be connected to the EPC by the S1-MME interface and may be connected to the S-GW by the S1-U interface. The S1 interface supports a many-to-many-relation between eNB 20 and MME / S-GW 30.

The eNB 20 may select for the gateway 30, routing to the gateway 30 during radio resource control (RRC) activation, scheduling and transmission of paging messages, scheduling channel information (BCH), and the like. Perform connection mobility control in transmission, dynamic allocation of resources from the UL and DL to the terminals 10, configuration and provisioning of eNB measurements, radio bearer control, radio admission control (RAC) and LTE activation can do. As mentioned above, the gateway 30 may perform paging initiation, LTE idle state management, user plane encryption, SAE bearer control, and encryption and integrity protection functions of NAS signaling in the EPC.

2 shows an air interface protocol of an LTE system for a control plane. 3 shows an air interface protocol of an LTE system for a user plane.

The layer of the air interface protocol between the UE and the E-UTRAN is based on the lower three layers of the open system interconnection (OSI) model, which is well known in communication systems, and includes L1 (first layer), L2 (second layer), and L3 (third layer). Hierarchical). The air interface protocol between the UE and the E-UTRAN may be horizontally divided into a physical layer, a data link layer, and a network layer, and vertically a protocol stack for transmitting control signals. ) Can be divided into a control plane and a user plane which is a protocol stack for transmitting data information. Layers of the radio interface protocol may exist in pairs in the UE and the E-UTRAN, which may be responsible for data transmission of the Uu interface.

The physical layer (PHY) belongs to L1. The physical layer provides an information transmission service to a higher layer through a physical channel. The physical layer is connected to a higher layer of a media access control (MAC) layer through a transport channel. Physical channels are mapped to transport channels. Data may be transmitted between the MAC layer and the physical layer through a transport channel. Data between different physical layers, that is, between the physical layer of the transmitter and the physical layer of the receiver may be transmitted using radio resources through a physical channel. The physical layer may be modulated using an orthogonal frequency division multiplexing (OFDM) scheme, and utilizes time and frequency as radio resources.

The physical layer uses several physical control channels. A physical downlink control channel (PDCCH) reports resource allocation of a paging channel (PCH) and a downlink shared channel (DL-SCH), and hybrid automatic repeat request (HARQ) information related to the DL-SCH to the UE. The PDCCH may carry an uplink grant to report to the UE regarding resource allocation of uplink transmission. The physical control format indicator channel (PCFICH) informs the UE of the number of OFDM symbols used for the PDCCH and is transmitted every subframe. A physical hybrid ARQ indicator channel (PHICH) carries a HARQ ACK (non-acknowledgement) / NACK (non-acknowledgement) signal for UL-SCH transmission. A physical uplink control channel (PUCCH) carries UL control information such as HARQ ACK / NACK, a scheduling request, and a CQI for downlink transmission. The physical uplink shared channel (PUSCH) carries an uplink shared channel (UL-SCH).

The physical channel includes a plurality of subframes in the time domain and a plurality of subcarriers in the frequency domain. One subframe consists of a plurality of symbols in the time domain. One subframe consists of a plurality of resource blocks (RBs). One resource block is composed of a plurality of symbols and a plurality of subcarriers. In addition, each subframe may use specific subcarriers of specific symbols of the corresponding subframe for the PDCCH. For example, the first symbol of the subframe may be used for the PDCCH. The PDCCH may carry dynamically allocated resources, such as a physical resource block (PRB) and modulation and coding schemes (MCS). A transmission time interval (TTI), which is a unit time at which data is transmitted, may be equal to the length of one subframe. One subframe may have a length of 1 ms.

The transport channel is classified into a common transport channel and a dedicated transport channel depending on whether the channel is shared or not. A DL transport channel for transmitting data from a network to a UE includes a broadcast channel (BCH) for transmitting system information, a paging channel (PCH) for transmitting a paging message, and a DL-SCH for transmitting user traffic or control signals. And the like. The DL-SCH supports dynamic link adaptation and dynamic / semi-static resource allocation by varying HARQ, modulation, coding and transmit power. In addition, the DL-SCH may enable the use of broadcast and beamforming throughout the cell. System information carries one or more system information blocks. All system information blocks can be transmitted in the same period. Traffic or control signals of a multimedia broadcast / multicast service (MBMS) are transmitted through a multicast channel (MCH).

The UL transport channel for transmitting data from the terminal to the network includes a random access channel (RAC) for transmitting an initial control message, a UL-SCH for transmitting user traffic or a control signal, and the like. The UL-SCH can support dynamic link adaptation due to HARQ and transmit power and potential changes in modulation and coding. In addition, the UL-SCH may enable the use of beamforming. RACH is generally used for initial connection to a cell.

The MAC layer belonging to L2 provides a service to a radio link control (RLC) layer, which is a higher layer, through a logical channel. The MAC layer provides a mapping function from a plurality of logical channels to a plurality of transport channels. The MAC layer also provides a logical channel multiplexing function by mapping from multiple logical channels to a single transport channel. The MAC sublayer provides data transfer services on logical channels.

The logical channel may be divided into a control channel for information transmission in the control plane and a traffic channel for information transmission in the user plane according to the type of information to be transmitted. That is, a set of logical channel types is defined for other data transfer services provided by the MAC layer. The logical channel is located above the transport channel and mapped to the transport channel.

The control channel is used only for conveying information in the control plane. The control channel provided by the MAC layer includes a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a dedicated control channel (DCCH). BCCH is a downlink channel for broadcasting system control information. PCCH is a downlink channel used for transmitting paging information and paging a terminal whose cell-level location is not known to the network. CCCH is used by the terminal when there is no RRC connection with the network. MCCH is a one-to-many downlink channel used to transmit MBMS control information from the network to the terminal. DCCH is a one-to-one bidirectional channel used by the terminal for transmitting dedicated control information between the terminal and the network in an RRC connection state.

The traffic channel is used only for conveying information in the user plane. The traffic channel provided by the MAC layer includes a dedicated traffic channel (DTCH) and a multicast traffic channel (MTCH). DTCH is used for transmission of user information of one UE in a one-to-one channel and may exist in both uplink and downlink. MTCH is a one-to-many downlink channel for transmitting traffic data from the network to the terminal.

The uplink connection between the logical channel and the transport channel includes a DCCH that can be mapped to the UL-SCH, a DTCH that can be mapped to the UL-SCH, and a CCCH that can be mapped to the UL-SCH. The downlink connection between the logical channel and the transport channel is a BCCH that can be mapped to a BCH or DL-SCH, a PCCH that can be mapped to a PCH, a DCCH that can be mapped to a DL-SCH, a DTCH that can be mapped to a DL-SCH, MCCH that can be mapped to MCH and MTCH that can be mapped to MCH.

The RLC layer belongs to L2. The function of the RLC layer includes adjusting the size of the data by segmentation / concatenation of the data received from the upper layer in the radio section such that the lower layer is suitable for transmitting data. In order to guarantee the various QoS required by the radio bearer (RB), the RLC layer is divided into three modes: transparent mode (TM), unacknowledged mode (UM) and acknowledged mode (AM). Provides three modes of operation. AM RLC provides retransmission through automatic repeat request (ARQ) for reliable data transmission. Meanwhile, the function of the RLC layer may be implemented as a functional block inside the MAC layer, in which case the RLC layer may not exist.

The packet data convergence protocol (PDCP) layer belongs to L2. The PDCP layer introduces an IP packet, such as IPv4 or IPv6, over a relatively low bandwidth air interface to provide header compression that reduces unnecessary control information so that the transmitted data is transmitted efficiently. Header compression improves transmission efficiency in the wireless section by transmitting only the information necessary for the header of the data. In addition, the PDCP layer provides security. Security functions include encryption to prevent third party inspection and integrity protection to prevent third party data manipulation.

The radio resource control (RRC) layer belongs to L3. The RRC layer at the bottom of L3 is defined only in the control plane. The RRC layer serves to control radio resources between the terminal and the network. To this end, the UE and the network exchange RRC messages through the RRC layer. The RRC layer is responsible for the control of logical channels, transport channels and physical channels in connection with the configuration, re-configuration and release of RBs. RB is a logical path provided by L1 and L2 for data transmission between the terminal and the network. That is, RB means a service provided by L2 for data transmission between the UE and the E-UTRAN. Setting up an RB means defining the characteristics of the radio protocol layer and channel to provide a particular service, and determining each specific parameter and method of operation. RBs may be classified into two types: signaling RBs (SRBs) and data RBs (DRBs). The SRB is used as a path for transmitting RRC messages in the control plane, and the DRB is used as a path for transmitting user data in the user plane.

The non-access stratum (NAS) layer located above the RRC layer performs functions such as session management and mobility management.

Referring to FIG. 2, the RLC and MAC layers (end at the eNB at the network side) may perform functions such as scheduling, ARQ and HARQ. The RRC layer (ended at the eNB at the network side) may perform functions such as broadcast, paging, RRC connection management, RB control, mobility function, and UE measurement report / control. The NAS control protocol (terminated at the gateway's MME at the network side) may perform functions such as SAE bearer management, authentication, LTE_IDLE mobility handling, paging initiation at LTE_IDLE, and security control for signaling between the terminal and the gateway.

Referring to FIG. 3, the RLC and MAC layer (end at the eNB at the network side) may perform the same function as the function in the control plane. The PDCP layer (terminating at the eNB at the network side) may perform user plane functions such as header compression, integrity protection and encryption.

Hereinafter, the RRC state and the RRC connection method of the UE will be described.

The RRC state indicates whether the RRC layer of the UE is logically connected with the RRC layer of the E-UTRAN. The RRC state may be divided into two types, such as an RRC connected state (RRC_CONNECTED) and an RRC idle state (RRC_IDLE). When the RRC connection between the RRC layer of the terminal and the RRC layer of the E-UTRAN is established, the terminal is in the RRC connection state, otherwise the terminal is in the RRC idle state. Since the terminal of the RRC_CONNECTED has an RRC connection with the E-UTRAN, the E-UTRAN can grasp the existence of the terminal of the RRC_CONNECTED and can effectively control the terminal. Meanwhile, the E-UTRAN cannot grasp the terminal of the RRC_IDLE, and manages the terminal in units of a tracking area in which a core network (CN) is larger than a cell. That is, the terminal of the RRC_IDLE is only identified as a unit of a larger area, and in order to receive a normal mobile communication service such as voice or data communication, the terminal must transition to RRC_CONNECTED.

In the RRC_IDLE state, while the terminal designates a discontinuous reception (DRX) set by the NAS, the terminal may receive a broadcast of system information and paging information. In addition, the terminal may be assigned an identification (ID) that uniquely designates the terminal in the tracking area, and perform public land mobile network (PLMN) selection and cell reselection. In addition, in the RRC_IDLE state, no RRC context is stored in the eNB.

In the RRC_CONNECTED state, the UE may have an E-UTRAN RRC connection and an RRC context in the E-UTRAN to transmit data to the eNB and / or receive data from the eNB. In addition, the terminal may report channel quality information and feedback information to the eNB. In the RRC_CONNECTED state, the E-UTRAN may know the cell to which the UE belongs. Therefore, the network may transmit data to the terminal and / or receive data from the terminal, and the network may inter-RAT with a GSM EDGE radio access network (GERAN) through mobility of the terminal (handover and network assisted cell change (NACC)). radio access technology (cell change indication), and the network may perform cell measurement for a neighboring cell.

In the RRC_IDLE state, the UE designates a paging DRX cycle. In more detail, the UE monitors a paging signal at a specific paging occasion for each UE specific paging DRX cycle. Paging opportunity is the time interval during which the paging signal is transmitted. The terminal has its own paging opportunity.

The paging message is sent across all cells belonging to the same tracking area. If the terminal moves from one tracking area to another tracking area, the terminal sends a tracking area update (TAU) message to the network to update the location.

When the user first turns on the power of the terminal, the terminal first searches for an appropriate cell and then stays in RRC_IDLE in that cell. When it is necessary to establish an RRC connection, the terminal staying in the RRC_IDLE may make an RRC connection with the RRC of the E-UTRAN through the RRC connection procedure and may transition to the RRC_CONNECTED. The UE staying in RRC_IDLE needs to establish an RRC connection with the E-UTRAN when uplink data transmission is necessary due to a user's call attempt or when a paging message is received from the E-UTRAN and a response message is required. Can be.

In order to manage mobility of the UE in the NAS layer, two states of EMM-REGISTERED (EPS Mobility Management-REGISTERED) and EMM-DEREGISTERED are defined, and these two states are applied to the UE and the MME. The initial terminal is in the EMM-DEREGISTERED state, and the terminal performs a process of registering with the corresponding network through an initial attach procedure to access the network. If the attach procedure is successfully performed, the UE and the MME are in the EMM-REGISTERED state.

In order to manage a signaling connection between the UE and the EPC, two states are defined, an EPS Connection Management (ECM) -IDLE state and an ECM-CONNECTED state, and these two states are applied to the UE and the MME. When the UE in the ECM-IDLE state establishes an RRC connection with the E-UTRAN, the UE is in the ECM-CONNECTED state. The MME in the ECM-IDLE state becomes the ECM-CONNECTED state when it establishes an S1 connection with the E-UTRAN. When the terminal is in the ECM-IDLE state, the E-UTRAN does not have the context information of the terminal. Accordingly, the UE in the ECM-IDLE state performs a terminal-based mobility related procedure such as cell selection or cell reselection without receiving a command from the network. On the other hand, when the terminal is in the ECM-CONNECTED state, the mobility of the terminal is managed by the command of the network. In the ECM-IDLE state, if the position of the terminal is different from the position known by the network, the terminal informs the network of the corresponding position of the terminal through a tracking area update procedure.

4 shows a conventional method of performing measurements.

The terminal receives measurement configuration information from the base station (S410). A message including measurement setting information is called a measurement setting message. The terminal performs the measurement based on the measurement setting information (S420). If the measurement result satisfies the reporting condition in the measurement configuration information, and reports the measurement result to the base station (S430). A message containing a measurement result is called a measurement report message.

The measurement setting information may include the following information.

(1) Measurement object information: Information about an object to be measured by the terminal. The measurement object includes at least one of an intra-frequency measurement object that is an object for intra-cell measurement, an inter-frequency measurement object that is an object for inter-cell measurement, and an inter-RAT measurement object that is an object for inter-RAT measurement. For example, the intra-frequency measurement object indicates a neighboring cell having the same frequency band as the serving cell, the inter-frequency measurement object indicates a neighboring cell having a different frequency band from the serving cell, and the inter-RAT measurement object is The RAT of the serving cell may indicate a neighboring cell of another RAT.

(2) Reporting configuration information: Information on a reporting condition and a report type regarding when the terminal reports transmission of a measurement result. The report setting information may consist of a list of report settings. Each reporting setup may include a reporting criterion and a reporting format. The reporting criterion is a criterion that triggers the terminal to transmit the measurement result. The reporting criteria may be a single event for the measurement reporting period or the measurement report. The report format is information on what type the terminal configures the measurement result.

(3) Measurement identity information: This is information about a measurement identifier that associates a measurement object with a report configuration, and allows the terminal to determine what type and when to report to which measurement object. The measurement identifier information may be included in the measurement report message to indicate which measurement object the measurement result is and in which reporting condition the measurement report occurs.

(4) Quantitative configuration information: information on a parameter for setting filtering of a measurement unit, a reporting unit, and / or a measurement result value.

(5) Measurement gap information: Information about a measurement gap, which is a section in which a UE can only use measurement without considering data transmission with a serving cell because downlink transmission or uplink transmission is not scheduled. .

The terminal has a measurement target list, a measurement report configuration list, and a measurement identifier list to perform a measurement procedure.

In 3GPP LTE, the base station may set only one measurement target for one frequency band to the terminal. Table 1 lists the events that result in measurement reporting. If the measurement result of the terminal satisfies the set event, the terminal transmits a measurement report message to the base station.

Table 1

event	Report condition
Event A1	Serving becomes better than threshold
Event A2	Serving becomes worse than threshold
Event A3	Neighbor becomes offset better than PCell / PSCell
Event A4	Neighbor becomes better than threshold
Event A5	PCell / PSCell becomes worse than threshold1 and neighbor becomes better than threshold2
Event A6	Neighbor becomes offset better than SCell
Event B1	Inter RAT neighbor becomes better than threshold
Event B2	PCell becomes worse than threshold 1 and inter RAT neighbor becomes better than threshold 2
Event C1	CSI-RS resource becomes better than threshold
Event C2	CSI-RS resource becomes offset better than reference CSI-RS resource

The measurement report may include a measurement identifier, a measured quality of the serving cell, and a measurement result of a neighboring cell. The measurement identifier identifies the measurement object for which the measurement report is triggered. The measurement result of the neighbor cell may include the cell identifier of the neighbor cell and the measured quality. The measured quality may include at least one of Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ).

Hereinafter, a carrier aggregation (CA) system will be described.

5 shows a conventional single carrier system and a carrier aggregation system.

Referring to FIG. 5, in a single carrier system, only one carrier is supported to the UE in uplink and downlink. The bandwidth of the carrier may vary, but only one carrier is allocated to the terminal. On the other hand, in a carrier aggregation system, a plurality of component carriers (DL CC A to C, UL CC A to C) may be allocated to a terminal. For example, three 20 MHz component carriers may be allocated to allocate a 60 MHz bandwidth to the terminal.

The carrier aggregation system may be classified into a continuous carrier aggregation system in which each carrier is aggregated and a non-contiguous carrier aggregation system in which each carrier is separated from each other. Hereinafter, simply referred to as a carrier aggregation system, it should be understood to include both the case where the component carrier is continuous and the case where it is discontinuous.

When collecting one or more component carriers, the target component carrier may use the bandwidth used by the existing system as it is for backward compatibility with the existing system. For example, the 3GPP LTE system supports bandwidths of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz, and the 3GPP LTE-A system may configure a bandwidth of 20 MHz or more using only the bandwidth of the 3GPP LTE system. Alternatively, broadband can be configured by defining new bandwidth without using the bandwidth of the existing system.

The system band of a wireless communication system is divided into a plurality of carrier frequencies. Here, the carrier frequency means a center frequency of a cell. Hereinafter, a cell may mean a downlink frequency resource and an uplink frequency resource. Alternatively, the cell may mean a combination of a downlink frequency resource and an optional uplink frequency resource. In addition, in general, when a carrier aggregation (CA) is not considered, one cell may always have uplink and downlink frequency resources in pairs. In order to transmit and receive packet data through a specific cell, the terminal must first complete configuration for a specific cell. In this case, the configuration refers to a state in which reception of system information necessary for data transmission and reception for a corresponding cell is completed. For example, the configuration may include an overall process of receiving common physical layer parameters required for data transmission and reception, or MAC layer parameters, or parameters required for a specific operation in the RRC layer. When the set cell receives only the information that the packet data can be transmitted, the cell can be immediately transmitted and received.

The cell in the configuration complete state may exist in an activation or deactivation state. Here, activation means that data is transmitted or received or is in a ready state. The UE may monitor or receive a control channel (PDCCH) and a data channel (PDSCH) of an activated cell in order to identify resources (which may be frequency, time, etc.) allocated thereto.

Deactivation means that transmission or reception of traffic data is impossible, and measurement or transmission of minimum information is possible. The terminal may receive system information (SI) required for packet reception from the deactivated cell. On the other hand, the terminal does not monitor or receive the control channel (PDCCH) and data channel (PDSCH) of the deactivated cell in order to check the resources (may be frequency, time, etc.) allocated to them.

The cell may be divided into a primary cell, a secondary cell, and a serving cell.

The primary cell refers to a cell operating at a primary frequency, and is a cell in which the terminal performs an initial connection establishment procedure or connection reestablishment with the base station, or is indicated as a primary cell in a handover process. It means a cell. The secondary cell refers to a cell operating at the secondary frequency and is set up once the RRC connection is established and used to provide additional radio resources.

The serving cell is configured as a primary cell when the carrier aggregation (CA) is not configured or the terminal cannot provide the CA. When CA is set, the term serving cell is used to indicate a set of primary cells + one of a plurality of secondary cells or a plurality of secondary cells. That is, the primary cell refers to one serving cell that provides security input and NAS mobility information in an RRC connection or re-establishment state. According to the capabilities of the terminal, at least one cell may be configured to form a serving cell set together with a primary cell, wherein the at least one cell is called a secondary cell. Therefore, the set of serving cells configured for one terminal may consist of only one primary cell or one primary cell and at least one secondary cell.

A primary component carrier (PCC) refers to a component carrier (CC) corresponding to a primary cell. The PCC is a CC in which the terminal initially makes a connection (connection or RRC connection) with the base station among several CCs. The PCC is a special CC that manages a connection (Connection or RRC Connection) for signaling regarding a plurality of CCs and manages UE context, which is connection information related to a terminal. In addition, the PCC is connected to the terminal and always exists in the active state in the RRC connected mode.

Secondary component carrier (SCC) refers to a CC corresponding to the secondary cell. That is, the SCC is a CC allocated to the terminal other than the PCC, and the SCC is an extended carrier for the additional resource allocation other than the PCC and may be divided into an activated or deactivated state.

The downlink component carrier corresponding to the primary cell is called a downlink primary component carrier (DL PCC), and the uplink component carrier corresponding to the primary cell is called an uplink major component carrier (UL PCC). In addition, the component carrier corresponding to the secondary cell in downlink is called DL Secondary CC (DL SCC), and the component carrier corresponding to the secondary cell in uplink is called UL SCC (UL SCC). do.

The primary cell and the secondary cell have the following characteristics.

First, the primary cell is used for transmission of the PUCCH. Second, the primary cell is always activated, while the secondary cell is a carrier that is activated / deactivated according to specific conditions. Third, when the primary cell experiences a Radio Link Failure (RLF), RRC reconnection is triggered. Fourth, the primary cell may be changed by a security key change or a handover procedure accompanying a RACH (Random Access Channel) procedure. Fifth, non-access stratum (NAS) information is received through the primary cell. Sixth, the primary cell always consists of a pair of DL PCC and UL PCC. Seventh, a different CC may be configured as a primary cell for each UE. Eighth, procedures such as reconfiguration, adding, and removal of the secondary cell may be performed by the RRC layer. In the addition of a new secondary cell, RRC signaling may be used to transmit system information of a dedicated secondary cell.

The downlink component carrier may configure one serving cell, or the downlink component carrier and the uplink component carrier may be configured to configure one serving cell. However, the serving cell is not configured with only one uplink component carrier. The activation / deactivation of the component carrier is equivalent to the concept of activation / deactivation of the serving cell. For example, assuming that serving cell 1 is configured of DL CC1, activation of serving cell 1 means activation of DL CC1. If the serving cell 2 assumes that DL CC2 and UL CC2 are configured to be configured, activation of serving cell 2 means activation of DL CC2 and UL CC2. In this sense, each component carrier may correspond to a cell.

The number of component carriers aggregated between the downlink and the uplink may be set differently. The case where the number of downlink CCs and the number of uplink CCs are the same is called symmetric aggregation, and when the number is different, it is called asymmetric aggregation. In addition, the size (ie bandwidth) of the CCs may be different. For example, assuming that 5 CCs are used for a 70 MHz band configuration, 5 MHz CC (carrier # 0) + 20 MHz CC (carrier # 1) + 20 MHz CC (carrier # 2) + 20 MHz CC (carrier # 3) It may be configured as + 5MHz CC (carrier # 4).

Hereinafter, a reference signal (RS) will be described.

Since data / signals in a wireless communication system are transmitted over wireless channels, data / signals may be distorted over the air during transmission. In order to accurately receive the distorted signal at the receiving end, the distorted signal is preferably corrected using the channel information. In this case, the transmitting end and / or the receiving end may use a reference signal RS that is known to both sides to detect channel information. The reference signal may be called a pilot signal. When transmitting and receiving data using multiple input / output antennas at the transmitting end, it is preferable that a channel state between the transmitting antenna and the receiving antenna is detected in order to receive the data accurately at the receiving end. In this case, in order to detect a channel state at the receiving end, each transmitting antenna of the transmitting end preferably has a separate reference signal.

The downlink reference signal refers to a common reference signal (CRS: Common RS) shared by all terminals in a cell, a UE-specific RS (UE-specific RS) only for a specific terminal, and a multimedia broadcast and multicast single frequency network (MBSFN). Signal, positioning reference signal (PRS) and channel state information (CSI) reference signal (CSI RS).

The transmitter may provide the receiver with information for demodulation and channel measurement using the reference signals. The receiving end (for example, the terminal) measures the channel state using the CRS, and according to the measured channel state, channel quality such as a channel quality indicator (CQI), a precoding matrix index (PMI), and / or a rank indicator (RI) May be fed back to the transmitter (eg, the base station). In the present specification, the CRS may be referred to as a cell-specific RS. The CRS is transmitted in every downlink subframe in a cell supporting PDSCH transmission. The CRS may be transmitted on antenna ports 0 through 3, and the CRS may be defined only for Δf = 15 kHz. The CRS may refer to section 6.10.1 of 3GPP TS 36.211 V10.1.0 (2011-03).

On the other hand, the reference signal associated with the feedback of the channel state information (CSI) may be defined as CSI-RS. The CSI RS may be relatively sparse in the frequency domain or the time domain and may be punctured in the data region of the general subframe or the MBSFN subframe. If necessary through the estimation of the CSI, CQI, PMI and RI may be reported from the terminal.

The UE-specific reference signal may be transmitted to the terminals through the resource elements when data demodulation on the PDSCH is needed. The terminal may receive the presence of a terminal specific reference signal through higher layer signaling. The UE specific reference signal is valid only when a corresponding PDSCH signal is mapped.

The MBSFN reference signal may be transmitted in a subframe allocated for MBSFN transmission. The PRS may be used for position estimation of the terminal. The CSI RS is used for channel estimation for the PDSCH of the LTE-A terminal.

Reference signal (RS) is generally transmitted in sequence. As the reference signal sequence, any sequence may be used without particular limitation. The reference signal sequence may use a PSK-based computer generated sequence. Examples of PSK include binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK). Alternatively, the reference signal sequence may use a constant amplitude zero auto-correlation (CAZAC) sequence. Examples of CAZAC sequences are ZC-based sequences, ZC sequences with cyclic extensions, ZC sequences with truncation, etc. There is this. Alternatively, the reference signal sequence may use a pseudo-random (PN) sequence. Examples of PN sequences include m-sequences, computer generated sequences, Gold sequences, and Kasami sequences. In addition, the reference signal sequence may use a cyclically shifted sequence.

Hereinafter, DRS (Discovery RS) will be described.

A micro cell, a femto cell, a pico cell, etc., which have a small service coverage, may be installed at a specific location within the coverage of a macro cell having a wide coverage. Such a cell may be referred to as a small cell. A small cell cluster is a collection of small geographically adjacent cells. In most cases, one or two clusters may be located in one macro cell (or sector) to provide a high transmission amount to a terminal.

In order to control inter-cell interference, some small cells belonging to the small cell cluster are switched on / off for the appropriate time unit (~ several tens of ms), and traffic load balancing between cells is performed. Can be done. In order to reduce the time required for state transition of the small cell, the turned off small cell also transmits some signals (for example, CRS and CSI RS) at low periods (for example, 40 ms), so that the UE is in a state of the small cell. RRM can be measured regardless. That is, in order to increase downlink transmission amount, on / off state conversion of small cells belonging to the small cell cluster may be performed. The small cell in the off state in which the traffic load is increased needs to be quickly converted to the on state, and the small cell in the on state in which the traffic load is lightly needs to be converted to the off state. When the small cell is in an on state, the serving terminals may be transferred to a neighboring small cell with a traffic load, and the corresponding small cell may be considered to be turned off. Since the small cell is in the off state, the amount of interference in the adjacent small cell may be reduced, thereby indirectly increasing the amount of downlink transmission.

The small cell in the on state may transmit a control channel (eg, PDCCH), a pilot (eg, CRS, UE-specific reference signal), and data every subframe. The small cell in the off state preferably transmits no signal in terms of interference management. However, if the state change of the small cell is fast enough to respond to the traffic load change quickly, the amount of downlink transmission may increase when no signal is transmitted. Therefore, the small cell in the off state can transmit a minimum signal so that the transition to the on state can occur quickly. The minimum signal is newly introduced in Rel-12, which may be referred to as a discovery reference signal (DRS).

The DRS introduced in Rel-12 consists of a combination of Rel-8 primary synchronization signal (PSS), Rel-8 secondary synchronization signal (SSS), and Rel-8 CRS port 0. Rel-10 CSI-RS port 15 can be additionally configured. The UE may obtain rough time synchronization and frequency synchronization with the small cell from the small cell through the PSS and the SSS. By using CRS port 0, accurate time synchronization and frequency synchronization can be obtained. If DRS is set using only CRS, RRM (Radio Resource Management) can be measured using only CRS. If DRS is additionally set for CSI-RS, synchronization obtained using PSS / SSS / CRS can be used. Based on the CSI-RS can be used to measure RRM (Radio Resource Management).

The small cell may transmit the DRS regardless of the on state or the off state. DRS transmits for the state transition of the small cell, and fast state transition of the small cell is very helpful in terms of interference management in the small cell cluster. If adjacent small cells transmit DRS in synchronization, the terminal receiving the DRS has an advantage of performing intra-frequency / inter-frequency RRM measurement through low battery consumption.

DRS measurement timing configuration (DMTC) is a time when the UE may perform cell detection and RRM (radio resource measurement) measurement based on the DRS, and detects a plurality of DMTC-based cells for one frequency. Can be. Accordingly, the UE can anticipate the location of the DRS from the DMTC and the DMTC can include at least a period, an offset from the serving cell timing, and a use width, where the period is at least for the UE to perform handover or RRM measurement. 40 ms, 80 ms, or 160 ms.

Below, Unlicensed  The unlicensed band will be described.

6 shows an example of an LTE service using an unlicensed band.

Referring to FIG. 6, the wireless device 630 establishes a connection with the first base station 610 and receives a service through a licensed band. For offloading traffic, the wireless device 630 may be provided with a service through an unlicensed band with the second base station 620.

Although the first base station 610 is a base station supporting an LTE system, the second base station 620 may support other communication protocols such as a wireless local area network (WLAN) in addition to the LTE. The first base station 610 and the second base station 620 may be combined in a carrier aggregation (CA) environment so that a specific cell of the first base station 610 may be a primary cell. Alternatively, the first base station 610 and the second base station 620 may be combined in a dual connectivity environment so that a specific cell of the first base station 610 may be a primary cell. In general, a first base station 610 with a primary cell has wider coverage than a second base station 620. The first base station 610 may be referred to as a macro cell. The second base station 620 may be referred to as a small cell, femto cell or micro cell. The first base station 610 may operate a primary cell and zero or more secondary cells. The second base station 620 may operate one or more secondary cells. The secondary cell may be activated / deactivated by the indication of the primary cell. The above-described example is merely an example, and the first base station 610 may correspond to the primary cell and the second base station 620 may correspond to the secondary cell and may be managed by one base station.

The licensed band is a band that guarantees exclusive use for a specific communication protocol or a specific operator. The unlicensed band is a band in which various communication protocols coexist and guarantee shared use. The unlicensed band may include the 2.5 GHz and / or 5 GHz bands used by the WLAN.

Basically, in the unlicensed band, it is assumed that channel is secured through competition between communication nodes. Therefore, communication in the unlicensed band requires channel sensing to confirm that no other communication node is transmitting a signal. This is called listen before talk (LBT) for convenience and defines that a clear channel assessment (CCA) has been confirmed when the other communication node determines that no signal is being transmitted.

The UE may perform RSSI measurement to determine in which unlicensed band it is preferable to generate the SCell. Unlicensed bands with high RSSI can be evaluated as bands with high interference due to heterogeneous-RAT. For example, the hetero-RAT may be a wireless local area network (WLAN). Currently, the terminal can measure the RSSI for the frequency indicated by the base station. The RSSI measurement result may be an average value of RSSI measured during the measurement period. Alternatively, the RSSI measurement result may be the percentage of RSSI above the threshold during the measurement period.

Channel occupancy of the unlicensed frequency may be estimated as the rate of RSSIs exceeding a predefined threshold during the measurement period. For example, if there are three RSSI measurement results exceeding a threshold value among ten RSSIs measured during the measurement period, the channel occupancy of the unlicensed frequency may be evaluated as 30%. However, because the RSSI is measured from all sources received by the terminal including the serving cell, channel occupancy may be overestimated. For example, since the Discovery Reference Signal (DRS) transmitted in the serving cell belonging to the unlicensed frequency is used for RSSI measurement, channel occupancy may be overestimated. Therefore, for accurate RSSI measurement, a new RSSI measurement method needs to be proposed. That is, for accurate RSSI measurement in the unlicensed band, the RSSI measured from the serving cell needs to be excluded. The measurement gap for CRS / DRS based measurement and the measurement gap for RSSI measurement need to be separated. Or, RSSI measurement for frequency needs to be performed outside the DRS transmission interval. Hereinafter, according to an embodiment of the present invention, a method of performing measurement by the terminal and a device supporting the same will be described in detail.

One. First  How to: Perform RSSI Measurements Outside the DRS Transmission Cycle

(1) The UE may perform RSSI measurement outside the DRS transmission period. The RSSI measurement can be performed within the measurement gap. That is, the terminal may perform RSSI measurement for a specific frequency in the remaining sections except for the section in which the DRS for a specific frequency is transmitted.

(2) The UE can know the DRS transmission cycle in the following way. The terminal may detect whether the DRS is transmitted or not. Alternatively, the base station may explicitly indicate to the terminal a subframe used for DRS transmission.

(3) The base station may indicate a carrier frequency to which the terminal should report the RSSI measurement result. Alternatively, the base station may indicate a carrier frequency for which the terminal should perform RSSI measurement. For example, the base station may transmit frequency information including a frequency at which RSSI measurement should be performed to the terminal. For example, the base station may transmit frequency information including the frequency to which the RSSI measurement result should be reported to the terminal. If the RSSI measurement is set as a related measurement object, even if the threshold value (s-Measure) of the PCell is set and the quality (RSRP) of the PCell is larger than the threshold value (ie, s-Measure) set by the network, the terminal RSSI measurement may be performed on the frequency indicated by the related measurement object.

Conventionally, when the base station notifies the serving cell of the quality threshold (s-Measure), when the quality of the serving cell is lower than the quality threshold of the serving cell, the terminal performs the evaluation of the measurement and reporting criteria of the neighboring cell. Perform. That is, if the quality of the serving cell is higher than the quality threshold of the serving cell, the measurement and reporting conditions of the neighboring cell are not performed.

On the other hand, according to an embodiment of the present invention, if the base station notifies the quality threshold of the PCell, even if the quality of the PCell is higher than the quality threshold of the PCell, if the base station indicates the frequency to which the RSSI measurement results should be reported, the terminal May perform RSSI measurement and RSSI measurement result report on the indicated frequency.

7 illustrates an example of a measurement gap set by the first method, according to an embodiment of the present invention.

Referring to FIG. 7, it is assumed that the measurement gap is composed of six subframes. It is assumed that the DRS is transmitted in the fourth, fifth and sixth subframes on the first unlicensed frequency. It is assumed that the DRS is transmitted in the third and fourth subframes on the second unlicensed frequency. It is assumed that the DRS is not transmitted in a subframe on the third unlicensed frequency.

The UE may perform RSSI measurement on the first unlicensed frequency during the first, second and third subframes within the measurement gap. The UE may perform RSSI measurement on the second unlicensed frequency during the first, second, fifth, and sixth subframes within the measurement gap. The UE may perform RSSI measurement on the third unlicensed frequency during the first to sixth subframes (ie, during the entire measurement gap).

As shown in the embodiment of FIG. 7, the UE may perform RSSI measurement in the remaining subframes except for the subframe in which the DRS is transmitted in the measurement gap. In addition, the subframe in which the DRS is transmitted and the subframe in which the RSSI measurement is performed may be determined for each frequency. By performing RSSI measurement in a subframe other than the subframe in which the DRS is transmitted, the RSSI measurement result can be prevented from being overestimated.

2. 2nd  How to: Use Separate Measurement Gap

(1) Separate measurement gaps may be used for CRS / DRS based measurements and RSSI measurements. According to the second method, there may be two separate measurement gaps. In this specification, the first measurement gap may mean a measurement gap in which CRS based measurement and / or DRS based measurement is performed, and the second measurement gap may mean a measurement gap in which RSSI measurement is performed.

(2) The UE may perform CRS based measurement in the first measurement gap. Alternatively, the terminal may perform DRS-based measurement in the first measurement gap. Alternatively, the terminal may perform CRS based measurement and DRS based measurement in the first measurement gap. The first measurement gap may be an existing measurement gap.

(3) The terminal may perform RSSI measurement in the second measurement gap. The duration of the second measurement gap may be set by the base station. Alternatively, a repetition period of the second measurement gap may be set by the base station. Alternatively, the interval of the second measurement gap and the repetition period of the second measurement gap may be set by the base station. The second measurement gap may not be applied to an RF chain associated with an existing LTE band. That is, the second measurement gap can only be applied to the RF chain associated with the unlicensed band (eg 2.4 GHz or 5 GHz). The terminal may apply the second measurement gap to the RF chain associated with the unlicensed band.

(4) The first measurement gap and the second measurement gap may not overlap. The second measurement gap may be set by the network so as not to overlap the first measurement gap.

(5) The base station may indicate a carrier frequency to which the terminal should report the RSSI measurement result. Alternatively, the base station may indicate a carrier frequency for which the terminal should perform RSSI measurement. For example, the base station may transmit frequency information including a frequency at which RSSI measurement should be performed to the terminal. For example, the base station may transmit frequency information including the frequency to which the RSSI measurement result should be reported to the terminal. If the RSSI measurement is set as a related measurement object, even if the threshold value (s-Measure) of the PCell is set and the quality (RSRP) of the PCell is larger than the threshold value (ie, s-Measure) set by the network, the terminal RSSI measurement may be performed on the frequency indicated by the related measurement object.

8 illustrates an example of a measurement gap set by the second method, according to an embodiment of the present invention.

Referring to FIG. 8A, a first measurement gap and a second measurement gap may be set. The first measurement gap may be a measurement gap in which CRS based measurement and / or DRS based measurement is performed, and the second measurement gap may be a measurement gap in which RSSI measurement is performed. The second measurement gap may be set by the network so as not to overlap the first measurement gap. For example, the measurement gap period and the repetition period of the second measurement gap may be set by the network such that they do not overlap the first measurement gap. Since the second measurement gap and the first measurement gap are set so as not to overlap, the terminal may perform RSSI measurement outside the section in which the DRS is transmitted. Therefore, the RSSI measurement result can be prevented from being overvalued.

Referring to FIG. 8B, it is assumed that the terminal is configured to perform DRS measurement on the first frequency and the second frequency, and is configured to perform RSSI measurement on the second frequency and the third frequency. It is assumed that the first frequency is an LTE frequency, the second frequency is an unlicensed frequency, and the third frequency is an unlicensed frequency. Assume that RF chain A is an RF chain associated with an LTE frequency and RF chain B is an RF chain associated with an unlicensed frequency.

In the embodiment of FIG. 8 (b), the UE may perform DRS measurement in the interval of the first measurement gap with respect to the first frequency using the RF chain A. FIG. The UE may perform DRS measurement in the interval of the first measurement gap for the second frequency using the RF chain B. The terminal may perform RSSI measurement in the interval of the second measurement gap for the second frequency using the RF chain B. The terminal may perform RSSI measurement in the interval of the second measurement gap for the third frequency using the RF chain B.

In the case of the second frequency configured to perform the DRS measurement and the RSSI measurement, the UE may perform the DRS measurement in the interval of the first measurement gap and the RSSI measurement in the interval of the second measurement gap. Accordingly, the terminal may perform RSSI measurement outside the section in which the DRS is transmitted and prevent the RSSI measurement result from being overestimated.

9 is a block diagram illustrating a method of performing measurement by a terminal according to an embodiment of the present invention.

Referring to FIG. 9, in step S910, the terminal may perform measurement on an unlicensed frequency in a first time duration.

The measurement for the unlicensed frequency may be a DRS based measurement. The first time interval may be a subframe in which the DRS is detected by the terminal. The first time period may be a subframe in which the DRS indicated by the base station is transmitted.

The measurement for the unlicensed frequency may be a CRS based measurement.

In step S920, the terminal may perform RSSI (Received Signal Strength Indicator) measurement for the unlicensed frequency in a second time duration. The second time interval may not overlap the first time interval.

The first time interval may be a first measurement gap, and the second time interval may be a second measurement gap. The repetition period of the second measurement gap may be set by the base station. The duration of the second measurement gap may be set by the base station.

The terminal may receive frequency information including a frequency at which the RSSI measurement should be performed from a base station. The RSSI measurement for the unlicensed frequency may be performed for the frequency included in the frequency information.

The terminal may receive a quality threshold (s-Measure) of a primary cell (PCell). The RSSI measurement for the unlicensed frequency may be performed on the frequency included in the frequency information regardless of the reference signal received power (RSRP) of the PCell.

10 is a block diagram of a wireless communication system in which an embodiment of the present invention is implemented.

The base station 1000 includes a processor 1001, a memory 1002, and a transceiver 1003. The memory 1002 is connected to the processor 1001 and stores various information for driving the processor 1001. The transceiver 1003 is connected to the processor 1001 to transmit and / or receive a radio signal. Processor 1001 implements the proposed functions, processes and / or methods. In the above-described embodiment, the operation of the base station may be implemented by the processor 1001.

The terminal 1010 includes a processor 1011, a memory 1012, and a transceiver 1013. The memory 1012 is connected to the processor 1011 and stores various information for driving the processor 1011. The transceiver 1013 is connected to the processor 1011 to transmit and / or receive a radio signal. The processor 1011 implements the proposed functions, processes and / or methods. In the above-described embodiment, the operation of the terminal may be implemented by the processor 1011.

The processor may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and / or other storage device. The transceiver may include baseband circuitry for processing wireless signals. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in memory and executed by a processor. The memory may be internal or external to the processor and may be coupled to the processor by various well known means.

Based on the examples described above, various techniques in accordance with the present disclosure have been described with reference to the drawings and reference numerals. For convenience of description, each technique described a number of steps or blocks in a specific order, but the specific order of these steps or blocks does not limit the invention described in the claims, and each step or block may be implemented in a different order, or In other words, it is possible to be performed simultaneously with other steps or blocks. In addition, it will be apparent to those skilled in the art that the steps or blocks have not been described in detail, and that at least one other step may be added or deleted without departing from the scope of the invention.

The above-described embodiments include various examples. Those skilled in the art will appreciate that not all possible combinations of examples of the inventions can be described, and that various combinations can be derived from the description herein. Therefore, the protection scope of the invention should be judged by combining various examples described in the detailed description within the scope of the claims described below.

Claims (15)

1. In the method for the user equipment (Measurement) in a wireless communication system,

   Perform a measurement on an unlicensed frequency in a first time duration,

   Including a measurement of the received signal strength indicator (RSSI) for the unlicensed frequency in a second time duration (Second Time Duration),

   And the second time interval does not overlap the first time interval.
2. The method of claim 1,

   The measurement for the unlicensed frequency is a DRS based measurement.
3. The method of claim 2,

   Wherein the first time interval is a subframe in which DRS is detected by the terminal.
4. The method of claim 2,

   The first time period is a subframe in which the DRS indicated by the base station is transmitted.
5. The method of claim 1,

   The measurement for the unlicensed frequency is a CRS based measurement.
6. The method of claim 1,

   The first time interval is a first measurement gap (First Measurement Gap),

   The second time interval is a second measurement gap (Second Measurement Gap).
7. The method of claim 6,

   The repetition period of the second measurement gap is set by the base station.
8. The method of claim 6,

   The duration of the second measurement gap is set by the base station.
9. The method of claim 1,

   The terminal further comprises receiving frequency information from a base station including a frequency at which the RSSI measurement should be performed.
10. The method of claim 9,

    RSSI measurement for the unlicensed frequency is performed on the frequency included in the frequency information.
11. The method of claim 9,

    The terminal further comprises receiving a quality threshold (s-Measure) of the PCell (Primary Cell).
12. The method of claim 11,

    The RSSI measurement for the unlicensed frequency is performed on the frequency included in the frequency information irrespective of the RSRP (Reference Signal Received Power) of the PCell.
13. In the terminal for performing the measurement (Measurement) in a wireless communication system,

    Memory; Transceiver; And a processor connecting the memory and the transceiver, wherein the processor

    Perform a measurement on an unlicensed frequency in a first time duration,

    Configured to perform a received signal strength indicator (RSSI) measurement on the unlicensed frequency in a second time duration,

    The second time interval is characterized in that the terminal does not overlap the first time interval.
14. The method of claim 13,

    The UE is characterized in that the measurement for the unlicensed frequency is a DRS-based measurement.
15. The method of claim 13,

    The first time interval is a first measurement gap (First Measurement Gap),

    The second time interval is a terminal, characterized in that the second measurement gap (Second Measurement Gap).

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