KR102495208B1 - Method and apparatus for transmitting and receiving reference signal using unlicensed band - Google Patents

Abstract

Transmitting a DRS to user equipment through a channel of an unlicensed band, receiving a measurement report on a measurement performed based on the DRS from the user equipment, and scheduling a cell of the unlicensed band based on the measurement report, and Provided is a method and apparatus for transmitting a DRS through a step of providing a service to a user equipment through a cell of.

Description

Reference signal transmission and reception method and apparatus using unlicensed band {Method and apparatus for transmitting and receiving reference signal using unlicensed band}

The present disclosure relates to a method and apparatus for transmitting and receiving a reference signal using an unlicensed band in a mobile communication system.

3GPP LTE (3 ^rd Generation Partnership Project Long Term Evolution) was commercialized in 2009, and has expanded to 251 commercial networks in 93 countries worldwide over a period of about 4 years. Recently, the number of subscribers worldwide reached 120 million. has exceeded As a result, as the number of pad-type terminals supporting large screens and high resolutions increases, data usage through LTE services is increasing even more rapidly. An explosion is expected to occur.

In order to accommodate such an explosive increase in data, wireless communication service providers are expanding the data capacity that their networks can provide without large-scale facility investment or massive increase in communication rates while sufficiently meeting the demand for data usage of customers. I am researching a plan. One of the solutions introduced by a number of wireless communication operators to respond to data explosion in cellular networks utilizes a wireless LAN communication method operated in unlicensed bands such as ISM (Industrial, Scientific and Medical) bands. Thus, the wireless data traffic concentrated on the 3G or LTE network is distributed (ie, off-loading). Since the unlicensed band is not a band in which a communication service provider can secure an exclusive right to use a frequency, a considerable level of traffic capacity can be distributed at a low cost when using the unlicensed band. However, since a large number of communication devices can be used without restriction in the unlicensed band as long as the in-band interference-related regulations are complied with, it is difficult to secure a level of communication quality provided through a communication service through a licensed band with exclusive rights to use.

In 3GPP, standardization for interworking with Wi-Fi, an IEEE standard technology, has been in progress since 2002, along with High Speed Packet Access (HSPA) or LTE systems. this was enacted However, integrating the two systems into one network to ensure efficient mobility and service quality was not easy due to structural differences between cellular networks and wireless LANs. To solve these difficulties, a technology that is being actively discussed recently is LTE technology (LTE-U: LTE on Unlicensed spectrum or U-LTE) in unlicensed bands. 3GPP recently held a workshop for standardization of cellular technology in unlicensed bands, and discussed requirements based on the opinions of each vendor. And in 3GPP, under the name of "Study on Licensed-Assisted Access to Unlicensed Spectrum", it is approved as a study item (SI, Study Item) for providing LTE service in unlicensed bands, and standardization is in progress.

One embodiment provides an apparatus for transmitting a discovery reference signal through a channel of an unlicensed band.

Another embodiment provides a method of transmitting a discovery reference signal through a channel of an unlicensed band.

According to one embodiment, as a method for transmitting a discovery reference signal (DRS) from a base station, transmitting the DRS to user equipment through a channel of an unlicensed band, performing based on the DRS from the user equipment Receiving a measurement report on the measured measurement, and scheduling a cell of the unlicensed band based on the measurement report, and providing a service to the user equipment through the cell of the unlicensed band.

In the DRS transmission method, the measurement report may include measurement information of a physical layer between a base station and user equipment or measurement information of a radio resource control (RRC) layer.

In the DRS transmission method, the step of transmitting the DRS may include acquiring access rights to a channel of the unlicensed band, and when the access rights are obtained, transmitting the DRS to the user equipment through the channel of the unlicensed band. can

In the DRS transmission method, when access rights are acquired, the step of transmitting the DRS to the user equipment through the channel of the unlicensed band may further include transmitting a DRS indication including information about the DRS to the user equipment. there is.

The DRS transmission method may further include, prior to transmitting the DRS, a step of informing the user equipment of a delivery time point of the DRS through a licensed band cell.

The DRS transmission method may further include transmitting DRS Measurement Timing Configuration (DMTC) information, which is information related to transmission of the DRS, to the user equipment before transmitting the DRS.

In the DRS transmission method, the DMTC information may include at least one of a DRS transmission period, a subframe offset, a duration of a DRS occasion, and parameters for measurement. there is.

Transmitting the DRS in the DRS transmission method may include transmitting the DRS through a transmission period of a short control channel (SCS).

In the DRS transmission method, the transmission interval of the SCS may be set to a time interval corresponding to 10% of the 50 ms time interval or a time interval corresponding to 10% of the observation time interval equal to the dwell time. there is.

In the DRS transmission method, providing a service to user equipment may include turning on/off a cell of an unlicensed band based on physical layer signaling or physical layer scheduling.

According to another embodiment, it includes at least one processor, a memory, and a wireless communication unit, and the at least one processor executes at least one program stored in the memory to generate a discovery reference signal (DRS) in an unlicensed band. Transmitting to user equipment through a channel, receiving a measurement report for measurement performed based on DRS from the user equipment, and scheduling a cell of the unlicensed band based on the measurement report, and using the cell of the unlicensed band as the user A base station is provided that performs the step of providing service to the equipment.

The measurement report from the base station may include measurement information of a physical layer between the base station and user equipment or measurement information of a radio resource control (RRC) layer.

When the at least one processor in the base station performs the step of transmitting the DRS, the step of acquiring the access right to the channel of the unlicensed band, and when the access right is obtained, the DRS to the user equipment through the channel of the unlicensed band. The sending step can be performed.

At least one processor in the base station transmits a DRS indication containing information about the DRS to the user equipment when performing the step of transmitting the DRS to the user equipment through the channel of the unlicensed band when the access right is obtained More steps can be taken.

At least one processor in the base station may further perform, prior to the step of transmitting the DRS, a step of informing the user equipment of a delivery time point of the RS through a licensed band cell.

At least one processor in the base station may further perform a step of delivering DRS Measurement Timing Configuration (DMTC) information, which is information related to DRS transmission, to user equipment before the step of transmitting the DRS. .

In the base station, the DMTC information may include at least one of a DRS transmission period, a subframe offset, a duration of a DRS occasion, and parameters for measurement.

When performing the transmitting of the DRS, at least one processor in the base station may perform the transmitting of the DRS through a transmission period of a short control channel (SCS).

The transmission interval of the SCS in the base station may be set to a time interval corresponding to 10% of a 50 ms time interval or a time interval corresponding to 10% of an observation time interval equal to a dwell time.

At least one processor in the base station, when performing the step of providing a service to user equipment, performing on / off of a cell of an unlicensed band based on physical layer signaling or physical layer scheduling can be performed.

According to another embodiment, a method for a UE to receive a discovery reference signal (DRS) is provided. The DRS reception method includes the steps of searching for a DRS in a search window determined based on DRS measurement timing configuration (DMTC) information related to transmission of the DRS, and if the DRS received as a result of the search is not valid, the next reception point It includes the step of resetting.

In the DRS reception method, the search window may be determined based on the size and direction of the search window included in the DMTC information.

In the DRS reception method, if the direction is a negative value, the search window may be located on the left based on the DRS transmission period, and if the direction is a positive value, the search window may be located on the right based on the DRS transmission period.

The step of searching in the DRS reception method may include searching for the DRS at each point calculated by dividing the search window by the number of transmissions of the DRS.

A discovery reference signal used to search for a cell in an unlicensed band may be transmitted so that a frequency of the unlicensed band can be used in a mobile communication system.

1 is a conceptual diagram illustrating a secondary carrier aggregation method for LAA according to an embodiment.
2 is a conceptual diagram illustrating a deployment scenario for LAA according to an embodiment.
3 and 4 are state transition diagrams of LAA UEs according to an embodiment.
5 is a state transition diagram of a LAA base station according to an embodiment.
6 is a flowchart illustrating a cell search method according to an exemplary embodiment.
7 is a diagram illustrating information transmitted in explicit signaling for DRS transmission according to an embodiment.
8 is a conceptual diagram illustrating an aperiodic transmission method of DRS according to an embodiment.
9 is a conceptual diagram illustrating an aperiodic transmission method of DRS according to another embodiment.
10 is a diagram illustrating DMTC parameters for reconstructing a measurement point according to an embodiment.
11 is a flowchart illustrating an operating procedure of a LAA cell according to an embodiment.
12 is a conceptual diagram illustrating a method for controlling On/Off of a LAA cell using an implicit scheme according to an embodiment.
13 is a conceptual diagram illustrating a method for controlling On/Off of a LAA cell using an implicit scheme according to another embodiment.
14 is a conceptual diagram illustrating a method for controlling On/Off of a LAA cell using an explicit scheme according to an embodiment.
15 is a conceptual diagram illustrating a dynamic carrier setting method according to an embodiment.
16 is a conceptual diagram illustrating the hidden node problem in LTE LAA.
17 is a conceptual diagram illustrating a method for solving a hidden node problem based on RTS/CTS according to an embodiment.
18 is a conceptual diagram illustrating an eNB-based CTS scheme according to an embodiment.
19 is a conceptual diagram illustrating a UE-based CTS scheme according to an embodiment.
20 is a conceptual diagram illustrating an RTS/CTS listening and channel sensing scheme according to an embodiment.
21 is a conceptual diagram illustrating a method for solving a hidden node problem based on LTE measurement according to an embodiment.
22 is a block diagram illustrating a wireless communication system according to an embodiment.

Hereinafter, with reference to the accompanying drawings, embodiments of the present disclosure will be described in detail so that those skilled in the art can easily carry out the present invention. However, the present disclosure may be implemented in many different forms and is not limited to the embodiments described herein. In addition, in order to clearly explain the present description in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, user equipment (UE) includes a terminal mobile station (MS), a mobile terminal (MT), an advanced mobile station (AMS), and a high reliability mobile station ( high reliability mobile station (HR-MS), subscriber station (SS), portable subscriber station (PSS), access terminal (AT), machine type communication device (MTC) device), etc., and may include all or some functions of MT, MS, AMS, HR-MS, SS, PSS, AT, UE, etc.

In addition, a base station (BS) includes an advanced base station (ABS), a high reliability base station (HR-BS), a node B, an evolved node B, eNodeB), access point (AP), radio access station (RAS), base transceiver station (BTS), mobile multihop relay (MMR)-BS, relay that serves as a base station station (RS), relay node (RN) that serves as a base station, advanced relay station (ARS) that serves as a base station, and high reliability relay station (HR) that serves as a base station -RS), small base station [femto base station (femoto BS), home node B (home node B, HNB), home eNodeB (HeNB), pico base station (pico BS), macro base station (macro BS), micro base station (micro BS ), etc.], and may include all or some functions of ABS, NodeB, eNodeB, AP, RAS, BTS, MMR-BS, RS, RN, ARS, HR-RS, small base station, etc. there is.

1 is a conceptual diagram illustrating a secondary carrier aggregation method for LAA according to an embodiment.

Referring to FIG. 1, a cell in an unlicensed band on the left performs only downlink transmission, and an unlicensed cell on the right partially performs both uplink and downlink transmission.

In order to provide services through unlicensed bands in mobile communication systems such as LTE, small cells in unlicensed bands with low reliability are used for the purpose of traffic distribution based on highly reliable mobile communication macro cells. It can be. That is, highly reliable licensed bands are used for transmission/reception of system control information for which reliability must be guaranteed, such as configuration of radio resources and control of mobility of terminals, and user traffic considers network conditions and service requirements. It can be transmitted/received through the licensed band and the unlicensed band. In general, since downlink traffic is more than uplink traffic due to service traffic characteristics of a mobile communication network, cells in unlicensed bands can be mainly used for downlink traffic transmission in consideration of this. That is, an unlicensed cell can be used to supplementally improve cell capacity and user data speed through the support of a cell of a licensed band, and in the present description, the use of such an unlicensed cell is described as a licensed band assisted access (LTE-Licensed Assisted Access, LAA).

Meanwhile, in order to improve a user's transmission rate by efficiently using a cell operating in a plurality of component carriers (CC), carrier aggregation (CA) technology may be applied to the LAA. In one embodiment, a CC operating in a licensed band cell performs a Primary Component Carrier (PCC) function for reliable transmission/reception of system control information, and a component carrier operating in an unlicensed band cell performs a secondary A secondary component carrier (SCC) function may be performed. In addition, as a duplex method of each cell, a frequency division duplex (FDD) or a time division duplex (TDD) method may be considered.

2 is a conceptual diagram illustrating a deployment scenario for LAA according to an embodiment.

Each deployment scenario shown in FIG. 2 may be defined as shown in Table 1 below.

Justice Scenario 1 CA between licensed band macro cell (F1) and unlicensed band small cell (F3) Scenario 2 CA without macro cell coverage between the licensed band small cell (F2) and the unlicensed band small cell (F3) Scenario 3 CA under macro cell coverage between the licensed band small cell (F2) and the unlicensed band small cell (F3) Scenario 4 - Licensed band macro cell (F1), licensed band small cell (F2) and unlicensed band small cell (F3)
- CA between licensed band small cell (F2) and unlicensed band small cell (F3)
- When there is an ideal backhaul between the macro cell and the small cell, the carrier aggregation group (CAG) between the macro cell (F1), the licensed band small cell (F2) and the unlicensed band small cell (F3) ) existence
- When dual connectivity is possible, there is dual connectivity between the macro cell and the small cell.

In LAA, one or more small cells of unlicensed band can be operated based on CA. The small cell of the unlicensed band may be disposed overlapping with the macro cell or may be disposed only of the small cell of the licensed band, and may be disposed in indoor and outdoor environments. In addition, according to the small cell arrangement of the licensed band, the small cell of the unlicensed band is co-located with the cell of the licensed band or non-co-located through an ideal backhaul. can And, according to the frequencies used in the macro cell and the small cell of the licensed band, the same frequency scenario and the non-identical frequency scenario may be considered, respectively.

3 and 4 are state transition diagrams of an LAA UE according to an embodiment, and FIG. 5 is a state transition diagram of an LAA base station according to an embodiment.

In the present description, the LAA cell is a small cell of an unlicensed band, and the LAA UE is a UE that can access the LAA cell and receive service. From the perspective of the LAA UE, the LAA operating state varies depending on the configuration of the LAA cell operating in the unlicensed band and the activation of the configured LAA cell. That is, the state of the LAA UE for setting the LAA cell is a state according to the radio resource control (RRC) protocol operation procedure, and the state according to the activation of the LAA cell is a state according to the Media Access Control (MAC) It is a state according to the operating procedure of the protocol.

Referring to FIG. 3, when a LAA cell is added (LAA-SCell addition), the LAA UE in L-Mode transitions to U/L-Mode, and then the LAA UE in U/L-Mode uses the LAA cell or licensed band. It maintains the U/L-Mode state during cell addition, change, and release. And, when all LAA cells are released (LAA-SCell release), the LAA UE transitions from U/L-Mode to L-Mode again.

Configuration of the LAA cell for CA may be performed by an RRC protocol procedure such as secondary cell (SCell) addition (SCell addition), SCell modification (SCell modification), or SCell release (SCell release). The state of the LAA UE for setting the LAA cell is a state in which a cell of the licensed band is set according to the type of the set cell (L-Mode) and a state in which the cell of the licensed band and the unlicensed band are simultaneously set (U/L-Mode) divided into In addition, the state of the LAA UE may be transitioned by an RRC reset procedure such as cell configuration, change, and release.

Referring to FIG. 4, an LAA UE in an inactive state may transition to an active state through an activation request, and an LAA UE in an active state may transition to an inactive state through a deactivation request or a timer operation. state can be transitioned.

The LAA UE in the U/L-mode state after adding the LAA cell of the unlicensed band through the configuration of the LAA cell may be located in the Activation/Deactivation state by the control procedure of the MAC. The active state means a state in which traffic can be scheduled through the LAA cell, and the inactive state is a state in which an LAA cell of an unlicensed band is configured but traffic scheduling is impossible. When there is temporarily no data to be transmitted, the LAA UE can be located. An LAA UE located in an active state may provide a service using a LAA cell according to a physical layer signaling procedure.

When a LAA cell accesses a shared channel in an unlicensed band, it checks the channel occupancy through Clear Channel Assessment (CCA) and uses the channel when it is not being used by other devices or other LAA cells. do. Therefore, since the access right to the shared channel of the unlicensed band can be changed variably, if the LAA base station (LAA eNB) providing service using the LAA cell has the ability to determine the channel occupancy status and the access right to the channel A discontinuous transmission function that transmits a signal only is required.

In terms of the LAA cell, the LAA operating state may exist in three states according to data transmission through the LAA cell.

The On state is a state in which data to be transmitted in the LAA cell exists, and when the LAA cell has access to a channel of an unlicensed band through CCA, a signal and user data transmission is possible. Off state is a state in which data to be transmitted in the LAA cell does not exist, and only a discovery reference signal (DRS) is transmitted. In order for the LAA cell to transmit DRS in the off state, the LAA cell acquires access rights to channels in the unlicensed band through CCA and then transmits DRS or uses a short control signal (SCS) transmission period. It is possible to use a method of transmitting without acquiring access rights to channels in unlicensed bands. The CCA state is a state for obtaining access to a channel in an unlicensed band and can be used as a preliminary state for an On state or an Off state.

Referring to FIG. 5, when the LAA cell in the CCA state completes channel reservation (Channel reservation complete), it transitions to the On state. Thereafter, when all transmission through the LAA cell is completed (Packet transmission complete), the LAA cell then transitions to an Off state. An LAA cell in an OFF state maintains an OFF state while transmitting an SCS. Then, when a transmission opportunity is requested (TX opportunity request), the LAA cell transitions to the CCA state. The LAA cell transitions to the CCA state when there is a transmission opportunity request even in the on state. The LAA cell in the Off state may transition to the On state when there is a command from the serving cell (Serving cell order). In FIG. 5 , the CCA states respectively interlocked with the On state and the Off state are the same state.

6 is a flowchart illustrating a cell search method according to an exemplary embodiment.

The LAA cell may be located in an On/Off state depending on whether data to be transmitted exists in the corresponding cell. The LAA cell located in the Off state transitions to the On state under the control of the LAA eNB and provides service when data to be transmitted occurs in the corresponding cell. To this end, the LAA cell recognizes the LAA cell and transmits a signal (DRS) capable of detecting a channel state of the LAA cell through downlink. Then, the LAA UE monitors and measures the DRS transmitted through the downlink. When the discovery signal is discovered, the LAA UE delivers the discovery result and measurement information to the LAA eNB through the cell of the licensed band. Upon receiving the LAA cell discovery result and measurement information from the LAA UE, the LAA eNB performs a procedure for configuring and activating the LAA cell, and schedules the corresponding LAA cell to provide services to the LAA UE.

At this time, the need for a physical layer signaling procedure may be determined according to the previously described DRS transmission method (a method of transmitting a channel in an unlicensed band after acquiring access rights or a method of transmitting using SCS).

That is, when DRS is transmitted after obtaining access to a channel in an unlicensed band from the LAA eNB (channel sensing based DRS transmission) (S603), since DRS may be transmitted aperiodically, such as a DRS indication A procedure in which the LAA eNB transmits information indicating whether to transmit DRS to the LAA UE through a physical layer signaling procedure is required. On the other hand, when the LAA cell transmits the DRS using the SCS, since there is no need to acquire access rights to channels in the unlicensed band, the LAA eNB transmits the DRS according to a preset operation period (S604) and the LAA UE DRS signals can be measured. In this description, DRS is used for the purpose of synchronization for the LAA cell and measurement for the channel.

The LAA eNB may instruct the LAA UE to perform DRS measurement through measurement configuration (S602), which is an RRC protocol procedure. After measuring the DRS of the LAA cell (S605), the LAA UE may report the measurement result to the LAA eNB through a measurement report (S606), an RRC protocol procedure, or a CSI report, a signaling procedure of the physical layer. can Upon receiving the LAA cell measurement report or CSI report from the LAA UE, the LAA eNB may perform LAA cell configuration and LAA cell activation procedures for the LAA UE, and provide services to the LAA UE through the LAA cell.

Meanwhile, the DRS for LAA cell search may be transmitted periodically (periodic DRS transmission scheme) or aperiodically (DRS aperiodic transmission scheme).

According to the DRS periodic transmission method, the LAA cell periodically transmits a discovery signal for cell search, and the LAA UE measures the discovery signal based on the discovery signal transmission period set by the LAA eNB and reports the measurement result to the LAA eNB. do.

In order to periodically transmit the DRS for LAA cell search, an SCS used for transmission of a short control message in a Listen Before Talk (LBT) scheme may be used. That is, DRS can be transmitted periodically through SCS without channel sensing for unlicensed bands. The transmission duration of the SCS (i.e., the SCS duration) may be set to a time interval within 10% of the 50msec time interval or a time interval within 10% of the observation time interval equal to the dwell time. can Therefore, in the case of a DRS having a maximum length of 5 msec, it can be transmitted through SCS. However, since SCS is not included in regulations in each country (it is included in European regulations but not in Japanese regulations), and devices in other unlicensed bands can transmit signals during the SCS period, The accuracy of measurement results may be lowered. In addition, since the SCS in the Wi-Fi system is used to transmit control signals such as Ack/Nack, interference may occur between the LAA system and Wi-Fi, which may degrade system performance.

Therefore, transmitting DRS using SCS has the advantage that the previously discussed DRS transmission method and setting method can be used as it is because periodic transmission of DRS is possible, and when using regional information, a specific region (ie, Europe) ) can be useful. However, using SCS for DRS transmission cannot be used as a single solution without regional restrictions, has low reliability of measured results, and has disadvantages in terms of coexistence with Wi-Fi systems.

7 is a diagram illustrating information transmitted in explicit signaling for DRS transmission according to an embodiment, and FIG. 8 is a conceptual diagram illustrating an aperiodic transmission method of DRS according to an embodiment.

In the aperiodic DRS transmission scheme, when an LAA cell has access to a shared channel in an unlicensed band, it may opportunistically transmit a discovery signal for cell search. Therefore, the LAA UE detects a discovery signal aperiodically and reports it to the LAA eNB. When aperiodic DRS transmission is performed, an explicit signaling procedure (alt.1) or an implicit method (alt.2) may be used to recognize DRS in the LAA UE.

First, alt.1 indicating DRS delivery timing with explicit notification will be described. In alt. 1, the LAA eNB may inform the LAA UE of the timing of transmitting the DRS through the LAA cell using a signaling procedure through a cell of a highly reliable licensed band. In addition, the LAA UE detects the LAA cell and performs measurement based on the signaling received through the cell of the licensed band.

The DRS transmission time point may be indicated using various layer operation procedures such as RRC, MAC, and PHY through a signaling procedure between the LAA eNB and the LAA UE. When a MAC layer or RRC layer procedure is used, it may take tens of milliseconds to several seconds to transmit/receive and process signaling. In contrast, when using the signaling procedure of the physical layer, signaling may be performed in sub-frame units (1msec). Therefore, considering the channel occupancy time and signaling processing time according to LBT, the DRS delivery time point can be appropriately indicated when using the physical layer procedure. Methods for indicating the DRS transmission timing with physical layer signaling include a method using new downlink control information (DCI) (alt. 1-1) and a method using a new physical channel or extending an existing physical channel (alt. 1-2).

In the method (alt. 1-1) for indicating the DRS delivery time using the new DCI, when the LAA cell transmits the DRS, the LAA eNB transmits a physical downlink control channel (Physical Downlink Control Channel) transmitted for scheduling of the licensed band. Channel, PDCCH) (or enhanced physical downlink control channel (Enhanced PDCCH, EPDCCH)) DCI is loaded with information indicating that the DRS is transmitted at the time when the LAA cell is configured and delivered to the LAA UE. At this time, the timing at which the DRS is transmitted at the frequency of the LAA cell is n, n+1, or n+2 subframes ((E) PDCCH transmission subframe = n based on the subframe to which the information indicating DRS transmission is delivered). ) can be used, which is defined in advance according to the processing capabilities of the LAA eNB and the LAA UE.

This method can be divided into an LAA cell search setting step through an RRC protocol and a step of indicating a DRS transmission time point for each subframe through (E) PDCCH.

The LAA cell discovery and setup step through the RRC protocol is a step in which the identifier of the LAA cell, information on the frequency at which the LAA cell operates, and CSI-RS configuration information for measurement are transmitted to the LAA UE. The LAA cell search setting step through the RRC protocol may be performed through a system information transmission procedure or an RRC measurement setting procedure. The step of indicating the DRS transmission time is a step of transmitting signaling indicating whether to transmit the DRS to the LAA UE through a subframe of the LAA cell. For this step, a new LAA DCI having a common search space similar to the previously proposed DCI format 1C may be used, and a new Radio Network Temporary Identifier (RNTI) for DCI may be used. The LAA DCI introduced to indicate the DRS transmission time includes bitmap-type information indicating whether to transmit the DRS for each LAA cell presented in the RRC protocol procedure. For example, in the LAA cell discovery and configuration step, the LAA eNB transfers four pieces of LAA cell configuration information through an RRC procedure as shown on the left of FIG. can be done with At this time, since the bitmap of the new DCI information is “1, 0, 0, 1”, the LAA UE receives the DRS for the LAA cell corresponding to Cell index#1 and Cell index#4, searches for the LAA cell, and take measurements

Referring to FIG. 8, first, the LAA cell performs CCA (or Enhanced CCA, ECCA) on the LAA-Scell and reports the CCA (ECCA) result to the LAA eNB (S801). At this time, CCA is performed for the LAA eNB using LBT based on the Frame Based Equipment (FBE) algorithm, and ECCA is performed for the LAA eNB using LBT based on the Load Based Equipment (LBE) algorithm. It can be.

Thereafter, the LAA eNB generates DCI (or new physical channel) indicating DRS transmission (S802) and transmits (e) PDCCH (or new physical channel) and DRS (S803). Then, the LAA UE receiving the (e)PDCCH from the LAA eNB may receive the DRS by decoding the (e)PDCCH (S804).

Alternatively, when the DRS transmission timing is indicated by physical layer signaling, a new physical channel may be used or a function of an existing physical channel may be extended and used (alt. 1-2). However, designing a new physical channel to indicate the DRS transmission timing of the LAA cell is not desirable in terms of a change in specifications and functionality of the physical channel. In addition, in the method of indicating the DRS delivery time by changing the existing physical channel, a Physical Control Format Indicator Channel (PCFICH) or a Physical HARQ Indicator Channel (PHICH) may be considered. Since PCFICH is used to indicate the number of Orthogonal Frequency Division Multiplexing (OFDM) symbols used for PDCCH transmission in a subframe, Control Format Indicator (CFI) information and DRS transmission time information there is no correlation between In addition, PHICH is used to deliver Ack/Nack information for Physical Uplink Shared Channel (PUSCH) transmission and is transmitted only when there is PUSCH transmission, so these information are also not related to DRS transmission time information. does not exist. Therefore, a method of extending the existing physical channel and transmitting aperiodically transmitted DRS delivery time information is also undesirable.

9 is a conceptual diagram illustrating an aperiodic transmission method of DRS according to another embodiment.

In order to receive DRS transmitted aperiodically, the LAA UE continuously monitors the LAA cell. At this time, the LAA UE searches for the LAA cell at a preset period regardless of whether the LAA cell transmits DRS. To this end, the LAA eNB sets DRS measurement timing configuration (DMTC) information, which is information related to DRS transmission, to the LAA UE, and the LAA UE searches for the LAA cell based on the DMTC information. And the LAA eNB obtains access to the shared channel of the unlicensed band according to the result of (E) CCA, and transmits DRS according to a preset period. At this time, when the LAA eNB uses FBE-based LBT, the LAA eNB performs CCA in a fixed frame prior to DRS transmission and determines whether to transmit DRS in a DRS transmission period based on the CCA result. When the LAA eNB uses LBE-based LBT, the LAA eNB performs ECCA at any time prior to the DRS transmission period, obtains access to an unlicensed band shared channel, and transmits DRS. In addition, the LAA eNB stops ECCA and stops DRS transmission at the transmission time point when a preset transmission time point elapses while performing ECCA.

For aperiodic DRS reception using Alt.2, the LAA eNB delivers DMTC information including the following information to the LAA UE, and based on this, performs DRS transmission, LAA cell discovery and measurement procedures. The DMTC information includes at least one of a DRS transmission period, a sub-frame offset, a duration of a DRS occasion, and parameters for measurement (CRS based, CSI-RS based). may contain one.

Referring to FIG. 9, first, the LAA eNB performs CCA on the LAA-SCell using DMTC information (S901). Thereafter, the LAA eNB does not transmit DRS in downlink if the channel is busy or transmits DRS in downlink if the channel is not congested according to the CCA result (S902). Meanwhile, the LAA UE always monitors the LAA-SCell based on the DRS transmission period (not shown). At this time, when the LAA UE receives the DRS, the LAA UE performs synchronization and measurement (S903).

When DRS is received aperiodically through continuous LAA cell monitoring, aperiodic DRS transmission (Transmission of DRS without periodicity) problem (Issue 1) and DRS measurement (Measurement on other operator DRS) problem (Issue 2) may occur. The aperiodic DRS transmission presented in Issue 1 can be caused by LBT, and the LAA UE can solve it through no measurement or reconfiguration of measurement point.

In the case of non-measurement, since the DRS is not transmitted from the LAA cell, the LAA UE does not perform measurement. On the other hand, measurement time reconfiguration may occur when DRS is not transmitted depending on the result of LBT at the time of DRS transmission according to the transmission period. Therefore, a variable window is set based on the measurement period and DRS is It is a form of transmission/reception.

As a method for non-measurement, an explicit signaling procedure may be used or an implicit method may be used. Non-measurement using explicit signaling is a form of notifying whether or not to transmit DRS through physical layer signaling (LAA DCI or physical channel) using a cell of a licensed band. That is, the LAA UE performs measurement only when the DRS from the LAA cell is transmitted. Non-measurement using the implicit method can be performed as follows on the LAA eNB side and the LAA UE side.

On the LAA eNB side, if the (E)CCA result is congestion, the LAA eNB does not transmit DRS for the LAA cell. And, on the LAA UE side, the LAA UE monitors the LAA-SCell based on DMTC, and if the received DRS is valid, the LAA UE performs a measurement procedure.

Meanwhile, measurement time reconstruction is a form of setting a range for DRS transmission based on a measurement period and transmitting/receiving DRS within this range, and this method can be operated without an explicit signaling procedure. The DRS transmission/reception method through measurement point reconfiguration can be performed as follows from the LAA eNB side and the LAA UE side.

On the LAA eNB side, the LAA eNB sets a DRS searching window using DMTC, and if the CCA result is congested and the current time point (ie, the time point when the channel is congested after performing CCA) is located within the search window, the LAA eNB The eNB selects a new transmission point within the search window. However, if the current time point is not located within the search window, the LAA eNB does not transmit DRS for the LAA cell.

From the LAA UE side, the LAA UE monitors the LAA SCell based on DMTC. If the received signal is a valid signal, the LAA UE starts the measurement procedure. However, if the received signal (ie, DRS) is not valid, the LAA UE determines whether the current time point is located within the search window, and if it is within the search window, the LAA UE resets the next reception point.

10 is a diagram illustrating DMTC parameters for reconstructing a measurement point according to an embodiment.

Meanwhile, for measurement point reconstruction, the DMTC includes at least one of a search window size, a direction, and a number of DRS opportunities within a search window. The search window size means the size of an operation window for DRS transmission/reception, and the direction means the direction of the start point (DMTC periodicity - offset) of the search window based on the DRS transmission period. For example, if the offset is a minus value, the search window for measuring the DRS based on the DMTC cycle is located on the left side, and if the offset is a plus value, the search window for measuring the DRS based on the DMTC cycle is searched for. Indicates that the window is located on the right. As a method for searching for DRS within the search window, the UE searches for DRS at each time point calculated by dividing the search window by the number of DRS transmissions in the search window, and a method for continuously searching for DRS in all sections within the search window. can be used

A DRS measurement problem (Issue 2) of heterogeneous operators may occur when different operators transmit DRS through the same DMTC in the same geographical service area. In this case, signaling overhead due to unnecessary measurement reporting procedures may increase. Therefore, from the viewpoint of the LAA eNB, it is necessary to check whether the DRS measurement report transmitted from the LAA UE corresponds to the LAA cell indicated in the measurement configuration.

To this end, the LAA eNB receives a measurement report on the LAA cell from the LAA UE, and then compares the Physical Cell Identifier (PCI) of the LAA cell that has been measured and reported and the PCI set by the LAA eNB to compare other It can be recognized that a conflict between the service provider and the DMTC setting occurs. In addition, when a collision occurs, the LAA eNB may resolve the collision through a set DMTC change. Therefore, the measurement reporting procedure for LAA includes the PCI of the discovered LAA cell. The aperiodic DRS transmission/reception procedure described above may operate in conjunction with an FBE or LBE-based LBT procedure.

11 is a flowchart illustrating an operating procedure of a LAA cell according to an embodiment.

When a service is provided using the LAA cell under the control of the LAA eNB after the LAA cell is discovered, procedures such as setting and activating the cell are required. Hereinafter, a procedure for providing a service using a LAA cell will be described in detail.

The LAA cell may be configured for LAA UEs in the RRC Connected state (S1101). And, the LAA cell configuration procedure may be performed by a measurement report from the LAA UE (S1102) or a determination of the LAA eNB (S1103). Considering the CA operation procedure, the LAA cell can be configured/controlled through the operation of the RRC layer and the MAC layer. The RRC layer performs LAA cell setting control such as adding, changing, and canceling the LAA cell (S1104). The MAC layer performs activation and deactivation procedures of the configured LAA cell (S1105). And, in the physical layer, on/off control of the LAA cell is performed in units of subframes or in units of a plurality of subframes based on physical layer procedures (scheduling or signaling) (S1106).

Since the LAA cell does not continuously operate and transmits discontinuously depending on the presence or absence of user traffic, access rights to unlicensed band channels, etc., transmission control through On/Off of the LAA cell is required. On/Off of the LAA cell can be performed through the following procedure.

Handover-based on/off: 3-layer operation procedure

- DC (Dual Connectivity)-based on/off: 3-layer operation procedure

- CA (Carrier Aggregation)-based on/off: 2-layer operation procedure

- L1 (Layer1) -based on/off: 1st layer operation procedure

However, since the maximum channel occupancy time and LBT operation presented in the regulations require an on/off operation in milliseconds or tens of milliseconds, it is necessary to control the On/Off of the LAA cell using the existing 3-layer or 2-layer operation procedure. that is not suitable Therefore, in order to transmit opportunistically through the On/Off of the LAA cell, the LAA cell must be controlled in units of subframes or a plurality of subframes (ie, 10 msec or less). Can be On/Off.

Since the LAA cell reserves a channel in the unlicensed band based on LBT and transmits using it, in one embodiment, the On / Off information of the LAA cell is implicitly scheme (Implicit scheme: alt.1) or explicit scheme ( It is delivered to the LAA UE with Explicit scheme: alt.2).

First, a method of conveying On/Off information of a LAA cell to a LAA UE in an implicit manner will be described. An On/Off control method using an implicit scheme is a method capable of controlling On/Off of a LAA cell through scheduling without additional physical layer signaling, and will be described in detail with reference to FIGS. 12 and 13 .

12 is a conceptual diagram illustrating a method for controlling On/Off of a LAA cell using an implicit scheme according to an embodiment.

The LAA cell On/Off control method shown in FIG. 12 may be referred to as cross-carrier scheduling with licensed cell (alt.1-1) of a licensed cell. In this form, since the LAA cell operates in an auxiliary form to the cell of the licensed band, the cell of the unlicensed band is scheduled through cross-carrier scheduling and instructs the LAA UE to turn on/off the LAA cell. At this time, the LAA UE continuously monitors the (E)PDCCH of the PCell (S1201), and if the (E)PDCCH includes scheduling of the LAA cell (S1202), the LAA cell physical downlink shared channel (PDSCH) / PUSCH ( Data may be transmitted/received through a physical uplink shared channel).

13 is a conceptual diagram illustrating a method for controlling On/Off of a LAA cell using an implicit scheme according to another embodiment.

The LAA cell On/Off control method shown in FIG. 13 may be called same carrier scheduling (alt.1-2). In this form, the LAA UE continuously receives scheduling information of the LAA cell to recognize On/Off of the corresponding cell. At this time, the LAA UE continuously monitors the (E) PDCCH of the LAA cell (S1301), and when the (E) PDCCH includes scheduling of the LAA cell (S1302), data is transmitted/transmitted through the PDSCH/PUSCH of the LAA cell. can receive

When cell On/Off of the LAA cell is performed through the above method, alt.1-1 has an advantage in terms of battery touch consumption of the LAA UE compared to alt.1-2, but the (E)PDCCH of the licensed band cell Since scheduling is performed using a portion, congestion may occur in (E)PDCCH. Since alt.1-2 is scheduled through the (E)PDCCH of the LAA cell, there is no effect on the (E)PDCCH resource in the licensed band. It can consume more battery compared to alt.1-1.

14 is a conceptual diagram illustrating a method for controlling On/Off of a LAA cell using an explicit scheme according to an embodiment.

The LAA cell On/Off control method using an explicit scheme is a method of controlling the LAA cell On/Off through additional physical layer signaling, and has similar characteristics to the previously described aperiodic DRS transmission. According to this method, a new DCI or a new physical channel for On/Off control of the LAA cell can be transmitted using a cell of a highly reliable licensed band, and the LAA UE receiving the new DCI or the new physical channel can transmit the LAA cell It is possible to decode the transmitted physical channel and receive data. That is, the LAA cell acquires access rights by performing (E)CCA on the shared channel of the unlicensed band (S1401), and transfers control information indicating On of the LAA cell to the LAA UE through the cell of the licensed band ( S1402). Thereafter, the LAA UE receiving the control information indicating that the LAA cell is On may decode the PDCCH of the LAA cell and receive data (S1403). In the case of the implicit scheme, congestion of licensed band resources may increase due to cross-carrier scheduling, and battery consumption of the LAA UE may increase due to continuous monitoring of the (E)PDCCH of the LAA cell. However, since the implicit scheme does not introduce new signaling of the physical layer, it has the advantage of lowering the complexity of the physical layer procedure and the impact on the standard. On the other hand, in the case of the explicit scheme, the complexity due to the introduction of a new signaling procedure in the physical layer increases and the delay for (E)PDCCH processing increases, but the battery consumption of the LAA UE can be reduced.

15 is a conceptual diagram illustrating a dynamic carrier setting method according to an embodiment.

Since the unlicensed band may be composed of a plurality of usable carriers, a plurality of carriers in the unlicensed band must be dynamically selected and efficiently distributed and used for efficient communication. If the number of unlicensed band equipment operating in a specific carrier or interference from the unlicensed band equipment is large, the utilization efficiency of the LAA cell operating in the unlicensed band carrier is lowered. Accordingly, the LAA cell can dynamically select a plurality of carriers in the unlicensed band according to the communication state and perform communication through movement between carriers, thereby increasing the efficiency of using unlicensed frequencies on the side of the LAA cell.

In one embodiment, a carrier pool including a plurality of carriers in an unlicensed band is introduced. The LAA cell selects one carrier suitable for the communication environment from the carrier pool, communicates with the LAA UE using it, and performs communication while dynamically changing the carrier according to the state of the carrier.

15 shows an example of a dynamic carrier configuration method. Referring to FIG. 15 , LAA cell #1 may perform a service while dynamically changing a channel using a carrier pool composed of carrier #1 and carrier #2. That is, the LAA cell performs service using carrier #1 until time T1 and performs service using carrier #2 through a dynamic carrier configuration procedure between time T1 and T2. After time T2, LAA cell #1 may perform service using carrier #1 again through a dynamic carrier configuration procedure.

A dynamic carrier change method of a LAA cell according to an embodiment is as follows.

First, when performing an RRC connection setup procedure using a cell of a licensed band, the LAA eNB checks the capability of the LAA UE (ie, RF capability, ...). Subsequently, when the LAA cell is configured as a secondary cell through carrier aggregation, the LAA eNB exchanges a message including information on a plurality of operating frequencies at which the LAA cell can operate with the LAA UE (performed using an RRC procedure). )do.

Thereafter, the LAA eNB instructs the LAA UE, which has set the LAA cell as a secondary cell, to the previously set measurement configuration including frequency information operable in the LAA cell.

Then, the LAA UE performs measurement and reports the measurement result to the LAA eNB. The LAA eNB activates the LAA cell as a secondary cell through carrier aggregation based on the received measurement report, and designates an actual operating frequency on which communication is performed among a plurality of operating frequencies (using a MAC procedure). and perform). The measurement report received by the LAA eNB may include physical layer measurement information or RRC layer measurement information.

In this case, when the operating frequency is changed while communication is in progress, the LAA eNB and the LAA UE do not transmit/receive for a predetermined time to configure the new frequency. In addition, the LAA eNB instructing the LAA UE to configure the measurement, the LAA UE performing measurement and reporting the measurement result to the LAA eNB, and the LAA eNB performing carrier aggregation and specifying the actual operating frequency are all steps. It can be continuously performed through communication between the LAA eNB and the LAA UE.

16 is a conceptual diagram illustrating the hidden node problem in LTE LAA.

In the case of an IEEE 802.11 Wireless Local Area Network (WLAN) system, a wireless node detects a channel condition through frequency detection in order to communicate. And the wireless node can use the channel only when the channel is empty. If the channel is in use, the wireless node performs frequency detection again after waiting for a random back-off time. At this time, a node that is not found even if a channel is searched through channel sensing is referred to as a hidden node, and the hidden node may cause interference during wireless communication between two nodes.

Similar to WLAN, the hidden node problem can occur in the LTE LAA of unlicensed bands, and the hidden node problem can occur between cells operated by different LTE LAA operators or between LAA cells and Wi-Fi cells.

Referring to FIG. 16, UE#01-A and UE#02-A are subscribed to the LAA service provided by LAA operator #1, and each UE is a hidden node according to signal transmission from LAA operator #2 or WLAN devices. You may run into problems.

The hidden node problem may occur between cells within the same operator, between cells of different operators, or between an LAA cell and a Wi-Fi cell, and a solution may be considered in terms of coordination. That is, cells within the same operator can be configured to prevent hidden node problems from occurring by exchanging information on frequencies and channels used through an interface between base stations such as an X2 interface. Unlike this, the hidden node problem between cells of different operators or between LAA cells and Wi-Fi cells cannot be cooperated, so it is necessary to introduce a new mechanism to solve the problem. In order to solve the hidden node problem between cells of different operators or between LAA cells and Wi-Fi cells, a request to send (RTS)/clear to send (CTS) based method and an LTE measurement based method may be considered. .

17 is a conceptual diagram illustrating a method for solving a hidden node problem based on RTS/CTS according to an embodiment.

RTS/CTS-based hidden node problem solving method enables Wi-Fi function between LAA eNB and LAA UE, and LAA eNB and LAA UE transmit/receive RTS/CTS frames using Wi-Fi module during LAA service. It can operate in an environment where reception is possible.

In RTS/CTS-based operation, when a LAA cell accesses a shared channel in an unlicensed band, the LAA cell obtains access to the channel through (E)CCA and exchanges RTS/CTS, which is a Wi-Fi control frame. By reserving channels through , the hidden node problem can be solved. The RTS/CTS-based method is applicable to FBE-based LBT or LBE-based LBT and includes RTS/CTS-based mechanism, CTS-based mechanism, and RTS/CTS listening and channel sensing mechanism.

First, the RTS/CTS-based mechanism can be performed through the following procedure. First, the LAA eNB having channel access rights through (E)CCA delivers the RTS frame to the UE of the LAA cell. In addition, the LAA UE that has received the RTS frame from the LAA eNB transmits the CTS frame. Thus, channel reservation and hidden node problems can be solved. Thereafter, scheduling may be performed through (E) PDCCH and PDSCH may be transmitted.

Meanwhile, the eNB of the LTE system may perform scheduling for a plurality of UEs in a subframe of 1 msec interval, which is different from the 1:1 Wi-Fi communication method. That is, while the RTS/CTS scheme in existing Wi-Fi basically assumes 1:1 operation, LTE assumes 1:n operation. Therefore, in order to solve the hidden node problem through RTS/CTS transmission in LTE LAA, the following form can be considered.

First, RTS/CTS transmission (Alt.1) through setting the receiving address of the RTS frame may be considered. For RTS/CTS transmission through RTS frame reception address configuration, the LAA eNB maintains a mapping table between the WLAN identifier and the identifier used in LTE, and performs the RTS/CTS procedure only for LAA UEs to be scheduled in the LAA cell. As a method for performing, the following Receiver Address (RA) setting method may be used.

- Alt.1-1: How to use multicast address

In this method, the RA of the RTS frame is delivered using a preset multicast address, and the LAA UE that receives the RA of the RTS frame transmits the CTS message. However, it can be used when multicast-related functions such as multicast group management are supported in the WLAN standard.

- Alt.1-2: How to use multiple unicast addresses

This is a method of performing a plurality of RTS/CTS procedures for each LAA UE scheduled within a subframe. This method can perform the RTS / CTS procedure in consideration of the time domain scheduling time, but has the disadvantage of high operational complexity and high usage of radio resources due to multiple RTS / CTS transmission / reception. there is.

- Alt.1-3: A method using the unicast address of the representative UE.

This is a method of selecting a representative LAA UE from among all LAA UEs scheduled in a subframe and performing an RTS/CTS procedure between the selected LAA UE and the LAA eNB. For this method, it is necessary to locate LAA UEs and select representative LAA UEs, and when LAA UEs are distributed, they have the same characteristics as Alt.1-2.

Alternatively, scheduling (Alt.2) may be considered for only one UE per transmission time interval (TTI). This is a method in which only one LAA UE is scheduled in a specific subframe of the LAA cell, and a 1:1 communication structure of transmission and reception is established in the subframe to perform RTS/CTS operations similar to Wi-Fi. However, waste of radio resources may occur according to the traffic volume of the scheduled LAA UE.

18 is a conceptual diagram illustrating an eNB-based CTS method according to an embodiment, and FIG. 19 is a conceptual diagram illustrating a UE-based CTS method according to an embodiment.

According to the CTS-based mechanism, the LAA cell can occupy the shared channel of the unlicensed band only through CTS transmission without using RTS. The CTS-based mechanism can be divided into an eNB-based CTS method and a UE-based CTS method.

Referring to FIG. 18, according to the eNB-based CTS method, the LAA eNB having channel access rights through (E) CCA transmits the CTS frame (S1801), and then, cross-scheduling is performed through (E) PDCCH and PDSCH may be transmitted (S1802). At this time, the eNB-based CTS method cannot solve the hidden node problem on the UE side because transmission deferring for nodes that can affect the LAA UE is not possible.

Referring to FIG. 19, according to the UE-based CTS method, the LAA eNB having channel access rights through (E)CCA transmits a CTS frame transmission request to the LAA UE through the Pcell of the licensed band (S1901), and the LAA eNB Upon receiving the CTS frame transfer request from LAA, the UE transfers the CTS frame (S1902). Thereafter, scheduling may be performed through the (E) PDCCH and the PDSCH may be transmitted (S1903). In this case, since the UE-based CTS scheme requires all LAA UEs configured in the LAA eNB to transmit the CTS frame, a problem may occur due to 1:n scheduling. If CTS frames are transmitted between adjacent LAA UEs without channel sensing for the channel, interference between adjacent LAA UEs may occur, and transmission times between CTS frames transmitted to solve the interference problem are coordinated. In this case, the use of additional radio resources is required.

20 is a conceptual diagram illustrating an RTS/CTS listening and channel sensing scheme according to an embodiment.

Referring to FIG. 20, in the RTS/CTS listening and channel sensing mechanism, first, the LAA UE in RRC Connected mode activates the Wi-Fi module, and senses the channel for a shared channel in an unlicensed band and RTS/CTS transmitted by unlicensed devices. It starts by performing frame reception. Thereafter, the LAA UE transmits the reservation state for the shared channel of the unlicensed band of the Wi-Fi device obtained through channel sensing and RTS/CTS frame reception to the LAA eNB (S2001). Thereafter, the LAA eNB utilizes the channel reservation information received from the LAA UE for channel (re)selection and scheduling (S2002). However, since RTS/CTS is selectively used for frames shorter than a specific length (shorter than 2437Btyes) in the WLAN standard, all hidden node problems cannot be solved through the RTS/CTS listening and channel sensing mechanism, and even in this case, LAA Continuous channel sensing of the UE is required. In addition, for the RTS/CTS listening and channel sensing mechanism, an RRC level setting procedure and a physical layer level reporting procedure are additionally required.

Next, a method for solving the hidden node problem based on LTE measurement is described.

21 is a conceptual diagram illustrating a method for solving a hidden node problem based on LTE measurement according to an embodiment.

The LTE measurement-based method uses a measurement procedure provided in LTE to solve the hidden node problem of LTE LAA. That is, through LTE measurement, SNR (signal to noise ratio) or SINR (signal to interference plus noise ratio) is found, and by using this, the state of the shared channel in the unlicensed band and whether LAA transmission or Wi-Fi activation of other operators is detected You can check. At this time, since it is important to know the instantaneous state of the channel, an instantaneous channel stage indication (CSI) measurement is more suitable than the channel state for a long time. According to the hidden node problem solving method based on LTE measurement, the LAA eNB configures the LAA UE for CSI measurement, and after the LAA UE performs CSI measurement on the shared channel of the unlicensed band, the measurement result is sent to the LAA eNB. report. The order is as follows.

- The LAA eNB performs measurement configuration for the LAA UE.

In the case of periodic measurement, it is set by RRC configuration (cqi-ReportPeriodic of cqi-ReportConfig in PhysicalConfigDedicated). And, in the case of aperiodic measurement, it is set by RRC configuration (cqi-ReportModeAperiodic of cqi-ReportConfig in PhysicalConfigDedicated).

- Next, the LAA UE performs measurement in the form indicated by the LAA eNB and reports a periodic or event driven form of aperiodic measurement report to the LAA eNB.

At this time, wideband measurement is considered rather than sub-band measurement. In periodic measurement, measurement based on configured periodicity and reporting is performed (Measurement based on configured periodicity and reporting).

And, in aperiodic measurement, measurement is initiated in DCI format 0/4, and a measurement report is reported in an n+kth sub-frame (Initiated by DCI format 0/4, measurement report on n + k sub-frame). And, in the n-k sub-frame in which scheduling through the LAA cell is considered, CSI measurement reporting may be indicated through DCI.

And, as measurement reporting, enhanced legacy L1 feedback is required.

- Next, the LAA eNB performs channel selection and scheduling based on the measurement information received from the LAA UE.

22 is a block diagram illustrating a wireless communication system according to an embodiment.

Referring to FIG. 22 , a wireless communication system according to an embodiment includes a base station 2210 and a user equipment 2220.

The base station 2210 includes a processor 2211, a memory 2212, and a radio frequency unit (RF unit) 2213. The memory 2212 is connected to the processor 2211 and may store various information for driving the processor 2211 or at least one program executed by the processor 2211 . The wireless communication unit 2213 may be connected to the processor 2211 to transmit and receive wireless signals. The processor 2211 may implement a function, process, or method proposed in an embodiment of the present disclosure. In this case, in the wireless communication system according to an embodiment of the present disclosure, the air interface protocol layer may be implemented by the processor 2211. An operation of the base station 2210 according to an embodiment may be implemented by the processor 2211.

The user equipment 2220 includes a processor 2221, a memory 2222, and a wireless communication unit 2223. The memory 2222 is connected to the processor 2221 and may store various information for driving the processor 2221 or at least one program executed by the processor 2221 . The wireless communication unit 2223 may be connected to the processor 2221 to transmit and receive wireless signals. The processor 2221 may implement functions, steps, or methods proposed in the embodiments of the present disclosure. In this case, in the wireless communication system according to an embodiment of the present disclosure, the air interface protocol layer may be implemented by the processor 2221. Operations of user equipment 2220 according to an embodiment may be implemented by processor 2221 .

In an embodiment of the present description, the memory may be located inside or outside the processor, and the memory may be connected to the processor through various known means. Memory is a volatile or non-volatile storage medium in various forms, and may include, for example, read-only memory (ROM) or random access memory (RAM).

Although the embodiments have been described in detail above, the scope of rights is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts defined in the following claims also fall within the scope of rights.

Claims (20)

A method for transmitting a discovery reference signal (DRS) in a base station,
Transmitting DRS measurement timing configuration (DMTC) information as information related to transmission of the DRS for monitoring of user equipment;
Transmitting the DRS to the user equipment through the channel of the unlicensed band after obtaining access to the channel of the unlicensed band, and
Receiving, by the user equipment, a measurement report generated by measuring the channel based on the DRS
A DRS transmission method comprising a. In paragraph 1,
The measurement report includes measurement information of a physical layer between the base station and the user equipment or measurement information of a radio resource control (RRC) layer. In paragraph 1,
The DRS includes a synchronization signal and a cell specific reference signal (CRS). In paragraph 3,
The DRS further comprises a channel state information-reference signal (CSI-RS). In paragraph 1,
Prior to transmitting the DRS,
Notifying the user equipment of the DRS delivery time through a licensed band cell
DRS transmission method further comprising. delete In paragraph 1,
The DMTC information,
A DRS transmission method comprising at least one of a transmission period of the DRS, a subframe offset, a duration of a DRS occasion, and a parameter for measurement. delete As a base station,
at least one processor;
memory, and
radio communications department
including,
The at least one processor executes at least one program stored in the memory,
Transmitting DRS measurement timing configuration (DMTC) information as information related to transmission of a discovery reference signal (DRS) for monitoring of user equipment;
Transmitting the DRS to the user equipment through the channel of the unlicensed band after obtaining access to the channel of the unlicensed band, and
Receiving, by the user equipment, a measurement report generated by measuring the channel based on the DRS
To perform, the base station. In paragraph 9,
The measurement report includes measurement information of a physical layer between the base station and the user equipment or measurement information of a Radio Resource Control (RRC) layer. In paragraph 9,
The DRS includes a synchronization signal and a cell specific reference signal (CRS). In paragraph 11,
The DRS further includes a channel state information-reference signal (CSI-RS). In paragraph 11,
The at least one processor, prior to transmitting the DRS,
Notifying the user equipment of the DRS delivery time through a licensed band cell
Further performing, the base station. delete In paragraph 9,
The DMTC information,
A base station including at least one of a transmission period of the DRS, a subframe offset, a duration of a DRS occasion, and a parameter for measurement. delete As a method for a terminal to receive a discovery reference signal (DRS),
Receiving DRS measurement timing configuration (DMTC) information as information related to transmission of the DRS;
Searching for the DRS in a search window determined based on the DMTC information -The DRS is transmitted from the base station through the channel of the unlicensed band after the base station acquires access rights to the channel of the unlicensed band -, and
Generating a measurement report by measuring the channel of the unlicensed band based on the DRS
A DRS receiving method comprising a. In paragraph 17,
Wherein the search window is determined based on a search window size and direction included in the DMTC information. In paragraph 18,
If the direction is a negative value, the search window is located on the left based on the DRS transmission period, and when the direction is a positive value, the search window is located on the right based on the DRS transmission period. . In paragraph 17,
The searching step is
Searching for the DRS at each point calculated by dividing the search window by the number of transmissions of the DRS
Including, DRS receiving method.

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