WO2020045861A1 - Method and apparatus for controlling random access operation in unlicensed band - Google Patents

Abstract

Disclosed is a technique by which a terminal accesses a base station by performing a random access operation in an unlicensed band. According to one aspect, the present embodiments can provide a method by which a terminal performs a random access procedure in an unlicensed band, and an apparatus, the method comprising the steps of: transmitting a random access preamble to a base station in the unlicensed band; receiving, from the base station, a random access response message in response to the transmission of the random access preamble in the unlicensed band; and transmitting an uplink message through at least one unlicensed band uplink radio resource indicated by the random access response message.

Description

Method and apparatus for controlling random access operation in unlicensed band

The present disclosure relates to a technology in which a terminal performs a random access operation in an unlicensed band and accesses a base station.

With the increase in the spread of smart phones and the like and the various uses of wireless communication devices, the amount of data transmission and reception using wireless communication technology is increasing rapidly. In addition, with the importance of low latency, development of the next generation wireless communication technology (New RAT) after LTE technology is in progress.

Meanwhile, technology development for providing a wireless communication service using an unlicensed band instead of a licensed band previously used exclusively by each operator is being progressed. In particular, in the case of the unlicensed band, since a short range wireless communication protocol can also be used at the same time, various technologies have been developed for coexistence of a mobile communication protocol and a short range wireless communication protocol. In view of this, the conventional mobile communication technology provides a communication service to a user by using an unlicensed band as an auxiliary cell. However, as the next generation wireless communication technology is developed, research into a technology for providing a mobile communication service using only an unlicensed band is in progress.

However, when providing a mobile communication service using only an unlicensed band, due to coexistence with other wireless communication protocols, it may be difficult to provide a communication service that satisfies user requirements.

In particular, when the terminal performs a random access operation with the base station, there is a possibility that the messages transmitted and received for performing the random access also fail as the unlicensed band is used. Therefore, there is a need for a study on a technique related to a random access procedure in the unlicensed band.

The embodiments may provide a technique for efficiently allowing a terminal to perform a random access operation in an unlicensed band.

In one aspect, the present embodiment provides a method for a UE performing a random access procedure in an unlicensed band, the method comprising: transmitting a random access preamble to an eNB in an unlicensed band and unlicensed a random access response message for random access preamble transmission from the base station The method may include receiving in a band and transmitting an uplink message through at least one unlicensed band uplink radio resource indicated by a random access response message.

In another aspect, the embodiments of the present invention provide a method for a base station to perform a random access procedure in an unlicensed band, the method comprising: receiving a random access preamble from a terminal in an unlicensed band and unlicensed a random access response message for transmitting a random access preamble to a terminal. The method may include transmitting in a band and receiving an uplink message through at least one unlicensed band uplink radio resource indicated by a random access response message.

In another aspect, the present embodiment, in the terminal performing a random access procedure in the unlicensed band, the unlicensed band for the random access response message for the random access preamble transmission from the base station and the base station for transmitting the random access preamble in the unlicensed band Including a receiving unit for receiving, the transmitting unit may provide a terminal device for transmitting an uplink message through at least one unlicensed band uplink radio resource indicated by a random access response message.

In another aspect, the present embodiment, in the base station performing a random access procedure in the unlicensed band, the unlicensed band for the random access preamble transmission for the random access preamble transmission to the terminal and the terminal receiving the random access preamble from the terminal in the unlicensed band Including a transmitting unit for transmitting, the receiving unit may provide a base station apparatus for receiving an uplink message through at least one unlicensed band uplink radio resource indicated by a random access response message.

According to the present embodiments, a technique for performing an efficient random access operation even in an unlicensed band can be provided.

1 is a diagram schematically illustrating a structure of an NR wireless communication system to which an embodiment of the present invention may be applied.

2 is a view for explaining a frame structure in an NR system to which the present embodiment can be applied.

3 is a diagram for describing a resource grid supported by a radio access technology to which an embodiment of the present invention can be applied.

4 is a diagram for describing a bandwidth part supported by a radio access technology to which an embodiment of the present invention can be applied.

5 is a diagram exemplarily illustrating a synchronization signal block in a radio access technology to which the present embodiment can be applied.

FIG. 6 is a diagram for explaining a random access procedure in a radio access technology to which the present embodiment can be applied.

7 is a diagram for explaining CORESET.

8 is a diagram for explaining a contention-free random access procedure in a radio access technology to which the present embodiment can be applied.

9 is a diagram for describing an operation of a terminal, according to an exemplary embodiment.

10 is a diagram illustrating an operation of a base station according to an embodiment.

11 illustrates a structure of a MAC subheader for random access response (RAR) according to an embodiment.

12 is a diagram illustrating a structure of a MAC payload for a random access response (RAR) according to an embodiment.

13 is a diagram for describing a terminal configuration, according to an exemplary embodiment.

14 is a diagram illustrating a configuration of a base station according to an embodiment.

Hereinafter, some embodiments of the present disclosure will be described in detail with reference to exemplary drawings. In adding reference numerals to components of each drawing, the same components may have the same reference numerals as much as possible even though they are shown in different drawings. In addition, in describing the present embodiments, when it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description may be omitted. When "include", "have", "consist", or the like, as used herein, other parts may be added unless "only" is used. In the singular form, the plural may include the plural unless specifically stated otherwise.

In addition, in describing the components of the present disclosure, terms such as first, second, A, B, (a), and (b) may be used. These terms are only to distinguish the components from other components, and the terms are not limited in nature, order, order or number of the components.

In the description of the positional relationship of components, when two or more components are described as being "connected", "coupled" or "connected", the two or more components are directly "connected", "coupled" or "connected". It may be understood, however, that two or more components and other components may be further “interposed” and “connected”, “coupled” or “connected”. Here, the other components may be included in one or more of two or more components that are "connected", "coupled" or "connected" to each other.

In the description of the temporal flow relations with respect to the components, the operation method, the fabrication method, and the like, for example, the temporal relationship between the temporal relationship of " after, ", " after, " Or where flow-benefit relationships are described, they may also include cases where they are not continuous unless "right" or "direct" is used.

On the other hand, when numerical values or corresponding information (e.g., levels) for the component are mentioned, the numerical values or corresponding information may be various factors (e.g., process factors, internal or external shocks, It may be interpreted as including an error range that may be caused by noise).

The wireless communication system in the present specification means a system for providing various communication services such as voice and data packets using radio resources, and may include a terminal, a base station, or a core network.

The embodiments disclosed below can be applied to a wireless communication system using various radio access technologies. For example, the embodiments of the present invention may include code division multiple access (CDMA), frequency division multiple access (FDMA), timedivision multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), and single carrier frequency division multiple access (SC-FDMA). Alternatively, the present invention may be applied to various radio access technologies such as non-orthogonal multiple access (NOMA). In addition, the wireless access technology may mean not only a specific access technology but also a communication technology for each generation established by various communication consultation organizations such as 3GPP, 3GPP2, WiFi, Bluetooth, IEEE, and ITU. For example, 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 in a wireless technology such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA). 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), employing OFDMA in downlink and SC- in uplink FDMA is adopted. As such, the embodiments may be applied to a wireless access technology that is currently disclosed or commercialized, and may be applied to a wireless access technology that is currently under development or will be developed in the future.

Meanwhile, the terminal in the present specification is a comprehensive concept of a device including a wireless communication module for performing communication with a base station in a wireless communication system, and in WCDMA, LTE, NR, HSPA, and IMT-2020 (5G or New Radio), etc. In addition to the user equipment (UE), as well as MS (Mobile Station), User Interface (UT), Subscriber Station (SS), a wireless device (wireless device) and the like in GSM should be interpreted. In addition, the terminal may be a user portable device such as a smart phone according to a usage form, and in the V2X communication system, it may mean a vehicle, a device including a wireless communication module in the vehicle, and the like. In addition, in the case of a machine type communication system, it may mean an MTC terminal, an M2M terminal, a URLLC terminal, etc. equipped with a communication module to perform machine type communication.

A base station or a cell of the present specification refers to an end point that communicates with a terminal in terms of a network, and includes a Node-B, an evolved Node-B, an eNB, a gNode-B, a Low Power Node, and an LPN. Sector, site, various types of antenna, base transceiver system (BTS), access point, point (for example, transmission point, reception point, transmission / reception point), relay node ), A mega cell, a macro cell, a micro cell, a pico cell, a femto cell, a remote radio head (RRH), a radio unit (RU), and a small cell. In addition, the cell may mean a bandwidth part (BWP) in the frequency domain. For example, the serving cell may mean an activation BWP of the terminal.

Since the above-described various cells have a base station that controls one or more cells, the base station may be interpreted in two meanings. 1) the device providing the mega cell, the macro cell, the micro cell, the pico cell, the femto cell, the small cell in relation to the radio area, or 2) the radio area itself. In 1) all devices that provide a given wireless area are controlled by the same entity or interact with each other to cooperatively configure the wireless area to the base station. According to the configuration of the wireless area, a point, a transmission point, a transmission point, a reception point, and the like become one embodiment of a base station. In 2), the base station may indicate the radio area itself that receives or transmits a signal from the viewpoint of the user terminal or the position of a neighboring base station.

In the present specification, a cell refers to a component carrier having coverage of a signal transmitted from a transmission / reception point or a signal transmitted from a transmission point or a transmission / reception point, and the transmission / reception point itself. Can be.

Uplink (UL, or uplink) means a method for transmitting and receiving data to the base station by the terminal, downlink (Downlink, DL, or downlink) means a method for transmitting and receiving data to the terminal by the base station do. Downlink (downlink) may mean a communication or communication path from the multiple transmission and reception points to the terminal, uplink (uplink) may mean a communication or communication path from the terminal to the multiple transmission and reception points. In this case, in the downlink, the transmitter may be part of multiple transmission / reception points, and the receiver may be part of the terminal. In addition, in uplink, a transmitter may be part of a terminal, and a receiver may be part of multiple transmission / reception points.

The uplink and the downlink transmit and receive control information through a control channel such as a physical downlink control channel (PDCCH), a physical uplink control channel (PUCCH), a physical downlink shared channel (PDSCH), a physical uplink shared channel (PUSCH), and the like. Configure the same data channel to send and receive data. Hereinafter, a situation in which a signal is transmitted and received through a channel such as a PUCCH, a PUSCH, a PDCCH, and a PDSCH may be described in the form of 'sending and receiving a PUCCH, a PUSCH, a PDCCH, and a PDSCH.'

For clarity, the following description focuses on the 3GPP LTE / LTE-A / NR (New RAT) communication system, but the present technical features are not limited to the communication system.

After researching 4G (4th-Generation) communication technology, 3GPP develops 5G (5th-Generation) communication technology to meet the requirements of ITU-R's next generation wireless access technology. Specifically, 3GPP develops a new NR communication technology separate from LTE-A pro and 4G communication technology, which is an enhancement of LTE-Advanced technology to the requirements of ITU-R with 5G communication technology. Both LTE-A pro and NR mean 5G communication technology. Hereinafter, 5G communication technology will be described based on NR when a specific communication technology is not specified.

Operational scenarios in NR defined various operational scenarios by adding considerations to satellites, automobiles, and new verticals in the existing 4G LTE scenarios.In terms of service, they have an eMBB (Enhanced Mobile Broadband) scenario and a high terminal density. Supports a range of mass machine communication (MMTC) scenarios that require low data rates and asynchronous connections, and Ultra Reliability and Low Latency (URLLC) scenarios that require high responsiveness and reliability and support high-speed mobility. .

In order to satisfy this scenario, NR discloses a wireless communication system using a new waveform and frame structure technology, low latency technology, mmWave support technology, and forward compatible technology. In particular, the NR system proposes various technological changes in terms of flexibility to provide forward compatibility. The main technical features of the NR will be described with reference to the drawings below.

<NR system general>

1 is a diagram briefly showing a structure of an NR system to which the present embodiment may be applied.

Referring to FIG. 1, an NR system is divided into a 5G core network (5GC) and an NR-RAN part, and the NG-RAN controls a user plane (SDAP / PDCP / RLC / MAC / PHY) and a user equipment (UE). It consists of gNB and ng-eNBs that provide planar (RRC) protocol termination. The gNB interconnects or gNBs and ng-eNBs are interconnected via an Xn interface. gNB and ng-eNB are each connected to 5GC through the NG interface. The 5GC may be configured to include an access and mobility management function (AMF) for controlling a control plane such as a terminal access and mobility control function, and a user plane function (UPF) for controlling a user data. NR includes support for sub-6 GHz frequency bands (FR1, Frequency Range 1) and 6 GHz and higher frequency bands (FR2, Frequency Range 2).

gNB means a base station that provides NR user plane and control plane protocol termination to the terminal, and ng-eNB means a base station that provides E-UTRA user plane and control plane protocol termination to the terminal. The base station described in the present specification should be understood to mean gNB and ng-eNB, and may be used to mean gNB or ng-eNB separately.

<NR waveform, pneumatic and frame structure>

In NR, a CP-OFDM waveform using a cyclic prefix is used for downlink transmission, and a CP-OFDM or DFT-s-OFDM is used for uplink transmission. OFDM technology is easy to combine with Multiple Input Multiple Output (MIMO), and has the advantage of using a low complexity receiver with high frequency efficiency.

On the other hand, in NR, since the requirements for data rate, delay rate, and coverage are different for each of the three scenarios described above, it is necessary to efficiently satisfy the requirements for each scenario through a frequency band constituting an arbitrary NR system. . To this end, a technique for efficiently multiplexing a plurality of different numerology-based radio resources has been proposed.

Specifically, the NR transmission neuron is determined based on sub-carrier spacing and cyclic prefix (CP), and μ is used as an exponential value of 2 based on 15khz as shown in Table 1 below. Is changed to

μ	Subcarrier spacing	Cyclic prefix	Supported for data	Supported for synch
0	15	Normal	Yes	Yes
One	30	Normal	Yes	Yes
2	60	Normal, Extended	Yes	No
3	120	Normal	Yes		Yes
4	240	Normal	No	Yes

As shown in Table 1 above, the NR's neuronality may be classified into five types according to the subcarrier spacing. This is different from the fixed subcarrier spacing of LTE, which is one of 4G communication technologies, to be 15 kHz. Specifically, the subcarrier spacing used for data transmission in NR is 15, 30, 60, 120khz, and the subcarrier spacing used for synchronization signal transmission is 15, 30, 12, 240khz. In addition, the extended CP is applied only to 60khz subcarrier spacing. On the other hand, the frame structure (frame) in NR is a frame having a length of 10ms consisting of 10 subframes having the same length of 1ms is defined. One frame may be divided into half frames of 5 ms, and each half frame includes five subframes. In the case of a 15khz subcarrier interval, one subframe consists of one slot, and each slot consists of 14 OFDM symbols. 2 is a view for explaining a frame structure in an NR system to which the present embodiment can be applied. Referring to FIG. 2, the slot is fixedly configured with 14 OFDM symbols in the case of a normal CP, but the length of the slot may vary according to the subcarrier spacing. For example, in the case of a newerology with a 15khz subcarrier spacing, the slot has a length of 1 ms and the same length as the subframe. On the contrary, in the case of a numerology having a 30khz subcarrier spacing, the slot includes 14 OFDM symbols, but two slots may be included in one subframe with a length of 0.5 ms. That is, the subframe and the frame are defined with a fixed time length, the slot is defined by the number of symbols, the time length may vary according to the subcarrier interval.

Meanwhile, NR defines a basic unit of scheduling as a slot and also introduces a mini slot (or subslot or non-slot based schedule) to reduce transmission delay of a radio section. The use of a wide subcarrier spacing shortens the length of one slot inversely, thus reducing the transmission delay in the radio section. The mini slot (or sub slot) is for efficient support for the URLLC scenario and can be scheduled in units of 2, 4, and 7 symbols.

In addition, unlike LTE, NR defines uplink and downlink resource allocation at a symbol level in one slot. In order to reduce the HARQ delay, a slot structure capable of transmitting HARQ ACK / NACK in a transmission slot is defined, and this slot structure is described as a self-contained structure.

NR is designed to support a total of 256 slot formats, of which 62 slot formats are used in 3GPP Rel-15. In addition, the combination of various slots supports a common frame structure constituting an FDD or TDD frame. For example, a slot structure in which all symbols of a slot are set to downlink, a slot structure in which all symbols are set to uplink, and a slot structure in which downlink symbol and uplink symbol are combined are supported. NR also supports that data transmission is distributed and scheduled in one or more slots. Accordingly, the base station can inform the terminal whether the slot is a downlink slot, an uplink slot, or a flexible slot by using a slot format indicator (SFI). The base station may indicate the slot format by indicating an index of a table configured through UE-specific RRC signaling using SFI, and may indicate the slot format dynamically through DCI (Downlink Control Information) or statically through RRC. You can also specify quasi-statically.

<NR Physical Resource>

With regard to physical resources in NR, antenna ports, resource grids, resource elements, resource blocks, bandwidth parts, etc. are considered do.

The antenna port is defined so that the channel on which the symbol is carried on the antenna port can be inferred from the channel on which another symbol on the same antenna port is carried. If the large-scale property of a channel carrying a symbol on one antenna port can be deduced from the channel carrying the symbol on another antenna port, the two antenna ports are quasi co-located or QC / QCL. quasi co-location relationship. Here, the broad characteristics include one or more of delay spread, Doppler spread, frequency shift, average received power, and received timing.

3 is a diagram for describing a resource grid supported by a radio access technology to which an embodiment of the present invention can be applied.

Referring to FIG. 3, since the Resource Grid supports a plurality of numerologies in the same carrier, a resource grid may exist according to each neuralology. In addition, the resource grid may exist according to antenna ports, subcarrier spacing, and transmission direction.

The resource block consists of 12 subcarriers and is defined only in the frequency domain. In addition, a resource element is composed of one OFDM symbol and one subcarrier. Accordingly, as shown in FIG. 3, one resource block may vary in size depending on the subcarrier spacing. In addition, the NR defines "Point A" serving as a common reference point for the resource block grid, a common resource block, a virtual resource block, and the like.

4 is a diagram for describing a bandwidth part supported by a radio access technology to which an embodiment of the present invention can be applied.

In NR, unlike LTE, which has a fixed carrier bandwidth of 20 MHz, the maximum carrier bandwidth is set from 50 MHz to 400 MHz per subcarrier interval. Therefore, it is not assumed that all terminals use all of these carrier bandwidths. Accordingly, in the NR, as shown in FIG. 4, the UE designates a bandwidth part (BWP) within the carrier bandwidth. In addition, the bandwidth part is associated with one neuralology and consists of a subset of consecutive common resource blocks and can be dynamically activated over time. The UE is configured with up to four bandwidth parts, respectively, for uplink and downlink, and data is transmitted and received using the bandwidth part activated at a given time.

In the case of paired spectrum, uplink and downlink bandwidth parts are set independently, and in the case of unpaired spectrum, to prevent unnecessary frequency re-tunning between downlink and uplink operation. For this purpose, the bandwidth parts of the downlink and the uplink are configured in pairs so as to share the center frequency.

<NR initial connection>

In NR, the UE performs a cell search and random access procedure to access and communicate with a base station.

Cell search is a procedure in which a terminal synchronizes with a cell of a corresponding base station, acquires a physical layer cell ID, and obtains system information by using a synchronization signal block (SSB) transmitted by a base station.

5 is a diagram exemplarily illustrating a synchronization signal block in a radio access technology to which the present embodiment can be applied.

Referring to FIG. 5, the SSB is composed of a primary synchronization signal (PSS) and a secondary synchronization signal (SSS), which occupy one symbol and 127 subcarriers, respectively, three OFDM symbols, and a PBCH spanning 240 subcarriers.

The terminal monitors the SSB in time and frequency domain and receives the SSB.

SSB can be transmitted up to 64 times in 5ms. A plurality of SSBs are transmitted in different transmission beams within 5 ms time, and the UE performs detection assuming that the SSB is transmitted every 20 ms period based on a specific beam used for transmission. The number of beams that can be used for SSB transmission within 5 ms time may increase as the frequency band increases. For example, up to 4 SSB beams may be transmitted at 3 GHz or less, and up to 8 different SSBs may be transmitted using a maximum of 8 different frequencies in a frequency band of 3 to 6 GHz and a maximum of 64 different beams in a frequency band of 6 GHz or more.

Two SSBs are included in one slot, and the start symbol and the number of repetitions in the slot are determined according to the subcarrier spacing.

On the other hand, the SSB is not transmitted at the center frequency of the carrier bandwidth, unlike the SS of the conventional LTE. That is, the SSB may be transmitted even where the center of the system band is not, and when supporting broadband operation, a plurality of SSBs may be transmitted in the frequency domain. Accordingly, the terminal monitors the SSB using a synchronization raster, which is a candidate frequency position for monitoring the SSB. The carrier raster and the synchronization raster, which are the center frequency position information of the channel for initial access, are newly defined in the NR, and the synchronization raster has a wider frequency interval than the carrier raster, and thus supports fast SSB search of the terminal. Can be.

The UE may acquire the MIB through the PBCH of the SSB. The Master Information Block (MIB) includes minimum information for the UE to receive the remaining system information (RMSI) that the network broadcasts. In addition, the PBCH is information on the position of the first DM-RS symbol in the time domain, information for the UE to monitor SIB1 (for example, SIB1 neuronological information, information related to SIB1 CORESET, search space information, PDCCH Related parameter information, etc.), offset information between the common resource block and the SSB (the position of the absolute SSB in the carrier is transmitted through SIB1), and the like. Here, the SIB1 neuronological information is equally applied to some messages used in a random access procedure for accessing a base station after the terminal completes a cell search procedure. For example, the neuralology information of SIB1 may be applied to at least one of messages 1 to 4 for the random access procedure.

The aforementioned RMSI may refer to System Information Block 1 (SIB1), which is broadcast periodically (ex, 160ms) in the cell. SIB1 includes information necessary for the UE to perform an initial random access procedure and is periodically transmitted through the PDSCH. In order to receive the SIB1, the UE needs to receive the information on the neuterology used for the SIB1 transmission and the control resource set (CORESET) information used for the scheduling of the SIB1 through the PBCH. The UE checks scheduling information on SIB1 using SI-RNTI in CORESET and obtains SIB1 on PDSCH according to the scheduling information. The remaining SIBs except for SIB1 may be periodically transmitted or may be transmitted at the request of the UE.

FIG. 6 is a diagram for explaining a random access procedure in a radio access technology to which the present embodiment can be applied.

Referring to FIG. 6, when the cell search is completed, the terminal transmits a random access preamble for random access to the base station. The random access preamble is transmitted on the PRACH. Specifically, the random access preamble is transmitted to the base station through a PRACH composed of consecutive radio resources in a specific slot that is periodically repeated. In general, when a UE initially accesses a cell, a contention-based random access procedure is performed, and when a UE performs random access for beam failure recovery (BFR), a contention-free random access procedure is performed.

The terminal receives a random access response to the transmitted random access preamble. The random access response may include a random access preamble identifier (ID), an UL grant (uplink radio resource), a temporary C-RNTI (Temporary Cell-Radio Network Temporary Identifier), and a time alignment command (TAC). Since one random access response may include random access response information for one or more terminals, a random access preamble identifier may be included to indicate to which UE the included UL Grant, temporary C-RNTI, and TAC are valid. The random access preamble identifier may be an identifier for the random access preamble received by the base station. The TAC may be included as information for the UE to adjust uplink synchronization. The random access response may be indicated by a random access identifier on the PDCCH, that is, a random access-radio network temporary identifier (RA-RNTI).

The terminal receiving the valid random access response processes the information included in the random access response and performs the scheduled transmission to the base station. For example, the terminal applies TAC and stores a temporary C-RNTI. In addition, by using the UL Grant, data or newly generated data stored in the buffer of the terminal is transmitted to the base station. In this case, information that can identify the terminal should be included.

Finally, the terminal receives a downlink message for contention resolution.

<NR CORESET>

The downlink control channel in NR is transmitted in a control resource set (CORESET) having a length of 1 to 3 symbols, and transmits up / down scheduling information, slot format index (SFI), and transmit power control (TPC) information. .

As such, the NR introduced the concept of CORESET in order to secure the flexibility of the system. CORESET (Control Resource Set) means a time-frequency resource for the downlink control signal. The terminal may decode the control channel candidate using one or more search spaces in the CORESET time-frequency resource. The QCL (Quasi CoLocation) assumption for each CORESET has been set, which is used to inform the analog beam direction in addition to the delay spread, Doppler spread, Doppler shift, and average delay, which are assumed by conventional QCL.

7 is a diagram for explaining CORESET.

Referring to FIG. 7, CORESET may exist in various forms within a carrier bandwidth in one slot, and CORESET may be configured with up to three OFDM symbols in the time domain. In addition, CORESET is defined as a multiple of six resource blocks up to the carrier bandwidth in the frequency domain.

The first CORESET is indicated through the MIB as part of the initial bandwidth part configuration to receive additional configuration information and system information from the network. After establishing the connection with the base station, the terminal may receive and configure one or more CORESET information through RRC signaling.

In this specification, frequency, frame, subframe, resource, resource block, region, band, subband, control channel, data channel, synchronization signal, various reference signals, various signals or various messages related to NR (New Radio) May be interpreted as meaning used in the past or present, or various meanings used in the future.

Meanwhile, the following description will be given for the technical idea based on two nodes of the terminal and the base station, but this is only for convenience of understanding, and the same technical idea may be applied between the terminal and the terminal. For example, the base station described below has been described and described by way of example to disclose a single node for communicating with the terminal, it may be replaced with other terminals or infrastructure devices for communicating with the terminal as needed.

That is, the present technical concept may be applied to not only communication between the terminal and the base station, but also device to device, side link communication, and vehicle communication (V2X). In particular, the present invention may be applied to the terminal-to-terminal communication in the next-generation radio access technology, and the terms such as a signal and a channel of the present specification may be variously modified and applied according to the type of communication between terminals.

For example, the terms PSS and SSS may be changed and applied to a primary D2D synchronization signal (PSSS) and a secondary D2D synchronization signal (SSSS) in terminal-to-device communication, respectively. In addition, the channel for transmitting broadcast information such as the above-described PBCH is changed to PSBCH, the channel for transmitting data in sidelinks such as PUSCH and PDSCH is converted into PSSCH, and the channel for transmitting control information such as PDCCH and PUCCH is changed to PSCCH. Can be applied. On the other hand, in the terminal-to-terminal communication, a discovery signal is required, which is transmitted and received through the PSDCH. However, it is not limited to these terms.

Hereinafter, the technical concept will be described as an example of communication between the terminal and the base station, but the base station node may be replaced with another terminal as necessary, and thus the technical concept may be applied.

In addition, in the present specification, a bandwidth consisting of a predetermined frequency section within a carrier bandwidth is described and described as a bandwidth part, a band whistle part, or a BWP, and the term is not limited thereto. In addition, although a bandwidth consisting of a predetermined frequency section in the bandwidth part is described as a subband, it is not limited to the term.

In addition, hereinafter, for convenience of description, a description of LBT (Listen Before Talk) as a technology for coexistence between each wireless communication technology in the unlicensed band, but the present disclosure may be applied to various coexistence technologies. Of course, the present disclosure may be applied not only to 5G or NR technology, which is a next generation wireless communication technology, but also to various wireless communication technologies such as 4G and Wifi.

NR (New Radio)

NR, a next-generation wireless technology that is being standardized in 3GPP, is a radio access technology that can provide improved data rates compared to LTE and satisfy various QoS requirements required for each detailed and detailed usage scenario. . In particular, representative usage scenarios of NR have been defined, such as enhancement Mobile BroadBand (eMBB), massive MTC (MMTC), and Ultra Reliable and Low Latency Communications (URLLC). As a method for satisfying each scenario requirement, a flexible frame structure compared to LTE is provided. For example, each usage scenario has different requirements for data rates, latency, reliability, coverage, and the like. Therefore, as a method for efficiently satisfying requirements for each use scenario through a frequency band constituting an arbitrary NR system, based on different numerology (eg subcarrier spacing, subframe, TTI, etc.) It is designed to efficiently multiplex the radio resource units of.

For example, a method for multiplexing and supporting a newerology with different subcarrier spacing values based on TDM, FDM, or TDM / FDM through one or more NR component carrier (s) and scheduling in time domain Discussion on how to support more than one time unit in constructing units has been discussed. In this regard, in NR, a subframe has been defined as a kind of time domain structure, and a 15 kHz SCS (Sub-S), which is the same as that of LTE, is defined as a reference numerology for defining a corresponding subframe duration. Carrier Spacing) is set. Thus, a single subframe duration consisting of 14 OFDM symbols of 15kHz SCS-based normal CP overhead is defined. That is, in NR, the subframe has a time duration of 1 ms. However, unlike LTE, a subframe of NR is an absolute reference time duration, and slot and mini-slot may be defined as time units based on actual uplink / downlink data scheduling. In this case, the number of OFDM symbols and the y value of the corresponding slot are determined to have a value of y = 14 regardless of the SCS value in the case of normal CP.

Accordingly, any slot consists of 14 symbols. In addition, according to the transmission direction of the slot, all symbols may be used for DL transmission, or all symbols may be used for UL transmission, or may be used in the form of DL portion + (gap) + UL portion. have.

In addition, in any numerology (or SCS), a mini-slot consisting of fewer symbols than the aforementioned slot is defined. A short time-domain scheduling interval for transmitting / receiving mini-slot based uplink / downlink data may be set, or a long time-domain scheduling interval for transmitting / receiving uplink / downlink data through slot aggregation may be configured. have. In particular, in case of transmitting / receiving latency-sensitive data such as URLLC, it is difficult to meet latency requirement when 1ms (14 symbols) based slot unit scheduling is defined in numerology-based frame structure with small SCS value such as 15kHz. Can be. Therefore, by defining a mini-slot consisting of fewer OFDM symbols than a slot consisting of 14 symbols, scheduling can be performed to satisfy the requirements of URLLC.

Alternatively, as described above, a neuron having different SCS values in one NR carrier may be multiplexed and supported by TDM and / or FDM. Therefore, a method of scheduling data according to latency requirements based on slots (or mini-slot) lengths defined for each neuron may be considered. For example, when the SCS is 60 kHz, since the symbol length is reduced to about 1/4 compared to the SCS 15 kHz, when one slot is configured with the same 14 OFDM symbols, the slot length based on the corresponding 15 kHz becomes 1 ms. As a result, the slot length based on 60kHz is reduced to about 0.25ms.

NR-U (Unlicensed spectrum)

Unlike licensed bands, unlicensed bands are available for the provision of wireless communications services by any operator or individual within the regulation of each country, rather than a wireless channel exclusively used by any operator. Accordingly, when providing NR service through an unlicensed band, there is a need to solve a co-existence problem with various short range wireless communication protocols, such as WiFi, Bluetooth, and NFC, which are already provided through the unlicensed band. In addition, there is a need to solve the problem of co-existence between respective NR operators or LTE operators.

Accordingly, when providing NR service through an unlicensed band, coexistence technology is required to avoid interference or collision between respective wireless communication services. For example, before transmitting a radio signal, a wireless channel access based on List Before Talk (LBT), which senses a power level of a radio channel or carrier to be used and determines whether the radio channel or carrier is available. It is necessary to support the method. In this case, if a specific radio channel or carrier of the unlicensed band is in use by another wireless communication protocol or another operator, there is a possibility that it is restricted from providing NR service through the corresponding band. Therefore, unlike the wireless communication service through the unlicensed band, the wireless communication service through the unlicensed band is difficult to guarantee the QoS required by the user.

In particular, NR-U can support a stand-alone scenario in which the unlicensed band is a PCell, unlike the existing LTE, which always supported the unlicensed band only by the SCell through a CA with the licensed band. In this case, the UE in the RRC idle state should perform a random access procedure for initial access to the cell using the unlicensed band. At this time, there is a problem that the access delay may be increased according to the LBT failure.

Random access procedure

Random access procedures take two forms. As shown in FIG. 6, in the contention based random access procedure, a random access preamble transmission of a terminal is transmitted to MSG1 (Message 1), a random access response transmission (RAR) by the base station is set to MSG2, and the uplink included in the RAR. A four-step procedure is performed with MSG3 as the link grant and MSG4 as the contention resolution. As such, in the 4-step random access procedure, the terminal or the base station may need to perform LBT for each step. Therefore, if LBT failure occurs frequently in each step, the time for performing the random access procedure may be delayed or random access procedure failure may be caused.

8 is a diagram for explaining a contention-free random access procedure in a radio access technology to which the present embodiment can be applied.

Similarly, in the contention free random access procedure as shown in FIG. 8, the base station allocates the random access preamble to the terminal, the step of transmitting the random access preamble assigned to the terminal to the base station, and the base station random access response to the terminal. The LBT is required to be performed in all the steps of transmitting the. Therefore, if LBT failure occurs frequently in each step, the time for performing the random access procedure may be delayed or random access procedure failure may be caused.

To solve this problem, we can think of ways to provide more transmission opportunities considering LBT failure, but no specific method is provided.

As described above, unlike the conventional LTE LAA technology using the unlicensed band through the SCell, when the unlicensed band is used as the PCell, a problem due to the LBT failure may occur in the random access procedure.

The present disclosure discloses an effective random access procedure to solve this problem. For example, it is intended to provide a technique for effectively providing multiple transmission opportunities for MSG3 transmission.

  For convenience of explanation, the present embodiment will be described below with reference to NR. However, this is only for convenience of description and the present disclosure may be applied to LTE or another wireless access network, which is also included in the scope of the present disclosure. In addition, the present disclosure may be applied to general NR access technology using a licensed band. In addition, the present disclosure may be used in one or more of the following unlicensed band implementation environments.

NR-U LAA: NR-U in "license assisted access" mode where primary cell is NR licensed

NR-U SA: NR-U stand-alone mode

ENU-DC: EN-DC where Secondary Node (SN) is NR-U

NNU-DC: DC between NR licensed (MN: Master Node) and NR-U (SN)

The embodiments described below may include the content of information elements and procedures specified in 3GPP TS 38.331, which is an NR RRC standard. Although the definition of the information element and the related procedure are not included in the present specification, the contents specified in the standard may be used in connection with the present embodiment or may be included in the scope of the right.

As described above, since NR-U must support LBT, it may be difficult to guarantee access to a wireless channel. Accordingly, data transmission and reception satisfying an appropriate QoS level may be difficult.

Unlike the existing LTE frame, the conventional LTE LAA defines frame type 3, a new frame structure consisting of a non-empty subframe in which data is transmitted and an empty subframe in which data is not transmitted, thereby supporting LTE operation in an unlicensed band. did. In order to configure a non-empty subframe, access / occupancy of the channel is determined through CCA (Clear Channel Assessment) in an empty subframe (section in which data is not transmitted), and channel occupancy and use are performed according to the CCA result. The data transmission time composed of non-empty subframes cannot exceed the maximum allowable time. It is only possible to transmit additional bursts of data within the maximum channel time allowed. LTE transmission is performed in a subframe unit (1ms), but CCA is performed in a time unit (a few μs) smaller than a subframe (1ms). Therefore, the channel occupancy can be configured at any point in the subframe other than the start point of the subframe, and the last point in time may be any point in the subframe due to the maximum allowable channel occupancy time constraint.

As described above, in the NR-U SA (Standalone) scenario, the PCell may use an unlicensed band. In ENU-DC or NNU-DC, unlicensed band can be used in PSCell. In the NR-U SA scenario, the RRC IDLE terminal should perform a random access procedure for initial access or the RRC connected state terminal during handover or reconfiguration. In the ENU-DC or NNU-DC, the UE must perform a random access procedure in the PSCell addition / change process. In addition, the random access procedure may be used for various events specified in Section 9.2.6 of 3GPP TS38.300. When performing the random access procedure in the above-described NR-U scenario, the terminal or the base station must perform LBT before transmitting the MSG of each step. However, the operation of performing LBT may reduce the transmission opportunity of the terminal and the base station and increase the time delay required for the random access procedure. Hereinafter, a method for solving this problem will be described. The embodiments described below may be implemented by combining / combining the respective contents individually or arbitrarily selecting each.

9 is a diagram for describing an operation of a terminal, according to an exemplary embodiment.

Referring to FIG. 9, a terminal performing a random access procedure in an unlicensed band may perform a step of transmitting a random access preamble to a base station in an unlicensed band (S900).

For example, the terminal may transmit a random access preamble to access the base station. As described above, the transmission of the random access preamble may be transmitted in a contention based random access procedure or may be transmitted in a non-competition based random access procedure. In order to transmit the random access preamble, the UE may perform the transmission after confirming a related channel by performing an LBT operation in an unlicensed band.

Meanwhile, in order to reduce the probability of transmission failure in the unlicensed band, the UE selects a plurality of PRACH Occasions by increasing the transmission opportunity of the random access preamble, and random access in the PRACH OCC that succeeds in LBT among the plurality of PRACH Occasions. The preamble may be transmitted to the base station.

The terminal may perform a step of receiving a random access response message for the random access preamble transmission from the base station in the unlicensed band (S910).

If the UE succeeds in transmitting the random access preamble, it may receive a random access response message from the base station. Even in this case, the base station may perform an LBT operation in the unlicensed band in order to transmit the random access response message. Accordingly, a random access response message transmission failure or delay may occur due to the LBT failure.

To solve this problem, the base station may perform a plurality of LBT operations within the random access response window, and if the LBT succeeds, the base station may transmit a random access response message at the corresponding time. Accordingly, the UE may monitor the reception of the random access response message within the random access response window that may be determined by at least one of a random access preamble, a random access preamble message transmission time, and a random access preamble transmission resource. In addition, since the random access response message is transmitted in the unlicensed band, the random access response window may be extended to guarantee transmission.

The terminal may perform the step of transmitting an uplink message through at least one unlicensed band uplink radio resource indicated by the random access response message (S920).

The random access response message may include uplink radio resource allocation information so that the terminal can transmit an uplink message. For example, in the contention-based random access procedure, the allocation information on the uplink radio resource for transmitting the MSG3 by the UE may be included in the random access response message. As another example, in a contention free random access procedure, allocation information on an uplink radio resource for transmitting an uplink message to be transmitted to a base station by a terminal may be included in the random access response message. The terminal transmits an uplink message to the base station using time / frequency resources indicated by uplink radio resource allocation information.

In this case, since the uplink message is transmitted on the unlicensed band, the terminal must perform an LBT operation. Therefore, when an LBT fails on an uplink radio resource allocated by a base station, an uplink message may not be transmitted or an uplink message transmission delay may occur.

To solve this problem, various embodiments below may be applied.

For example, the random access response message may include a plurality of uplink grant fields for indicating a plurality of unlicensed band uplink radio resources. That is, the random access response message may include a plurality of uplink radio resource allocation information. Through this, the UE may perform LBT on each uplink radio resource and transmit an uplink message through the uplink radio resource that succeeds in the LBT operation. In addition, the random access response message may include information for indicating the number of the plurality of uplink grant field. In this case, when the LBT succeeds in the plurality of uplink radio resources, the UE does not perform the LBT operation on the remaining uplink radio resources. Alternatively, the terminal performs an LBT operation on each of a plurality of uplink radio resources, and transmits an uplink message on the selected LBT successful uplink radio resource according to an arbitrary criterion.

As another example, the random access response message may include a repetitive transmission indication field for indicating repetitive transmission of the uplink message. The uplink message may be repeatedly transmitted in consecutive time intervals when the repetitive transmission indication field is a value indicating repetitive transmission. For example, the repetitive transmission indication field may be configured through one or more bits of the R field of the MAC RAR. Alternatively, the repeated transmission indication field may be configured as a specific field by changing the MAC RAR format. The UE performs the LBT operation in each slot, subframe, or mini slot of each successive time period indicated by the repetitive transmission indication field, and transmits an uplink message in the time period in which the LBT succeeds. The uplink message may be repeatedly transmitted from the time period in which the LBT succeeds.

As another example, the random access response message may include a field for indicating one or more subbands in which an uplink message is transmitted. One or more subbands are configured on the frequency axis, separated by at least two, within the bandwidth part of the unlicensed band. That is, one bandwidth part may be composed of N (natural numbers) subbands. When a plurality of subbands is indicated, the UE may sequentially perform LBT operations in each subband, and transmit an uplink message in a subband having succeeded in LBT. In this case, the LBT operation is not performed in the remaining subbands in which the LBT operation is to be performed after the subband in which the LBT succeeds. Alternatively, the UE performs an LBT operation in each of the plurality of subbands, selects one subband according to a specific condition, and transmits an uplink message in the selected subband. The field for indicating a subband may indicate an individual subband in the form of a bitmap or may be configured to indicate a specific subband and provide frequency offset information in the corresponding subband.

Meanwhile, the aforementioned random access response message may include a random access response format field for distinguishing from a random access response message using a licensed band. That is, it may include a separate indication field for indicating that the random access response message used in the unlicensed band. The format of the random access response message used in the unlicensed band and the random access response message used in the licensed band may be different. That is, the format of the random access response message used in the unlicensed band for the plurality of uplink radio resource allocation information, repetitive transmission, subband indication, etc. may be configured differently. Accordingly, the terminal may identify the random access response message by checking the random access response format field.

Alternatively, the aforementioned uplink radio resource allocation information, repetitive transmission, subband indication, and the like may be received by the terminal through system information. For example, information applied to at least one of the above-described embodiments may be broadcast through SIB1.

Through the operation described above, the UE in the unlicensed band can prevent the delay or failure of the random access procedure.

10 is a diagram illustrating an operation of a base station according to an embodiment.

Referring to FIG. 10, a base station performing a random access procedure in an unlicensed band may perform a step of receiving a random access preamble from a terminal in an unlicensed band (S1000).

As described above, the reception of the random access preamble may be received in a contention based random access procedure or may be received in a non-competition based random access procedure. In order to transmit the random access preamble, the UE may perform the transmission after confirming a related channel by performing an LBT operation in an unlicensed band.

Meanwhile, the base station may configure a plurality of PRACH occlusions in the terminal to prevent the random access preamble transmission failure of the terminal. The UE may increase a transmission opportunity of the random access preamble, select a plurality of PRACH occlusions, and transmit a random access preamble to the base station in a PRACH occlusion that succeeds in LBT among the plurality of PRACH occlusions. The base station may receive a random access preamble in an orc of the plurality of PRACH orcs the terminal succeeded in LBT.

The base station may perform the step of transmitting a random access response message for the random access preamble transmission in the unlicensed band to the terminal (S1010).

When the random access preamble of the terminal is received, the base station may transmit a random access response message. Even in this case, the base station may perform an LBT operation in the unlicensed band in order to transmit the random access response message. Accordingly, a random access response message transmission failure or delay may occur due to the LBT failure.

To solve this problem, the base station may perform a plurality of LBT operations within the random access response window, and if the LBT succeeds, the base station may transmit a random access response message at the corresponding time. The UE may monitor the reception of the random access response message within a random access response window that may be determined by at least one of a random access preamble, a random access preamble message transmission time, and a random access preamble transmission resource. In addition, since the random access response message is transmitted in the unlicensed band, the random access response window may be extended to guarantee transmission. The base station may be configured in the terminal for the extended random access response window.

The base station may perform the step of receiving an uplink message through at least one unlicensed band uplink radio resource indicated by the random access response message (S1020).

The random access response message may include uplink radio resource allocation information so that the terminal can transmit an uplink message. For example, in the contention-based random access procedure, the allocation information on the uplink radio resource for transmitting the MSG3 by the UE may be included in the random access response message. As another example, in a contention free random access procedure, allocation information on an uplink radio resource for transmitting an uplink message to be transmitted to a base station by a terminal may be included in the random access response message. The terminal transmits an uplink message to the base station using time / frequency resources indicated by uplink radio resource allocation information.

In this case, since the uplink message is transmitted on the unlicensed band, the terminal must perform an LBT operation. Therefore, when an LBT fails on an uplink radio resource allocated by a base station, an uplink message may not be transmitted or an uplink message transmission delay may occur.

To solve this problem, various embodiments below may be applied.

For example, the random access response message may include a plurality of uplink grant fields for indicating a plurality of unlicensed band uplink radio resources. That is, the random access response message may include a plurality of uplink radio resource allocation information. In this manner, the terminal may perform LBT on each uplink radio resource, and the base station may receive an uplink message through the uplink radio resource that succeeds in the LBT operation. In addition, the random access response message may include information for indicating the number of the plurality of uplink grant field. In this case, when the LBT succeeds in the plurality of uplink radio resources, the UE does not perform the LBT operation on the remaining uplink radio resources. Alternatively, the terminal performs an LBT operation on each of a plurality of uplink radio resources, and transmits an uplink message on the selected LBT successful uplink radio resource according to an arbitrary criterion.

As another example, the random access response message may include a repetitive transmission indication field for indicating repetitive transmission of the uplink message. The uplink message may be repeatedly transmitted in consecutive time intervals when the repetitive transmission indication field is a value indicating repetitive transmission. For example, the repetitive transmission indication field may be configured through one or more bits of the R field of the MAC RAR. Alternatively, the repeated transmission indication field may be configured as a specific field by changing the MAC RAR format. The UE performs the LBT operation in each slot, subframe, or mini slot of each successive time period indicated by the repetitive transmission indication field, and transmits an uplink message in the time period in which the LBT succeeds. The base station may repeatedly receive the uplink message from the time period in which the terminal succeeds in the LBT.

As another example, the random access response message may include a field for indicating one or more subbands in which an uplink message is transmitted. One or more subbands are configured on the frequency axis, separated by at least two, within the bandwidth part of the unlicensed band. That is, one bandwidth part may be composed of N (natural numbers) subbands. When a plurality of subbands is indicated, the terminal sequentially performs LBT operations in each subband, and the base station may receive an uplink message in the subband in which the terminal succeeds in LBT. In this case, the LBT operation is not performed in the remaining subbands in which the LBT operation is to be performed after the subband in which the LBT succeeds. Alternatively, the UE performs an LBT operation in each of the plurality of subbands, selects one subband according to a specific condition, and transmits an uplink message in the selected subband. The field for indicating a subband may indicate an individual subband in the form of a bitmap or may be configured to indicate a specific subband and provide frequency offset information in the corresponding subband.

Meanwhile, the aforementioned random access response message may include a random access response format field for distinguishing from a random access response message using a licensed band. That is, it may include a separate indication field for indicating that the random access response message used in the unlicensed band. The format of the random access response message used in the unlicensed band and the random access response message used in the licensed band may be different. That is, the format of the random access response message used in the unlicensed band for the plurality of uplink radio resource allocation information, repetitive transmission, subband indication, etc. may be configured differently. Accordingly, the base station allocates a random access response format field to the random access response message to distinguish which random access response message.

Alternatively, the above-described information such as uplink radio resource allocation information, repetitive transmission, subband indication, and the like may be transmitted through system information. For example, the base station may broadcast information applied to at least one of the above-described embodiments through SIB1.

As described above, in order to perform a random access procedure in the unlicensed band, the terminal and the base station can prevent transmission delay or failure in various ways.

That is, in order to effectively transmit random access in NR-U, the transmission opportunity may be increased and provided at each step of the random access procedure. Based on contention-based random access, by increasing the transmission opportunity for the MSG1, the UE may select a plurality of PRACH occasions, and transmit a preamble to one PRACH occasion in which LBT succeeds. Transmission opportunities can also be increased for MSG2 or MSG4 transmitted by the base station. For example, the base station may increase the transmission opportunity for MSG2 and transmit MSG2 if the LBT succeeds in the RAR window. Alternatively, the base station may increase the transmission opportunity for the MSG4 and transmit the MSG4 if the LBT succeeds in the contention resolution timer. On the other hand, the transmission opportunity for the MSG3 transmitted by the terminal should be increased. For example, a plurality of uplink radio resource allocations, repetitive transmissions, a plurality of subband indications, and the like may be used.

Hereinafter, an embodiment for expanding the uplink message transmission opportunity in the aforementioned unlicensed band will be described in more detail. The individual embodiments described below can be applied independently or through any combination. For convenience of understanding, the present specification will be described based on the contention-based random access procedure, but the same may be applied to the random access response message used in the contention-free random access procedure. In addition, below, the uplink radio resource allocation information is described as an uplink grand or uplink allocation information as necessary.

First embodiment: a method of instructing a terminal by including a plurality of uplink grants (UL grant) in a MAC PDU format

The RAR is transmitted through the downlink MAC PDU. One MAC PDU consists of one or more MAC subPDUs and optionally padding. Each MAC subPDUs consists of one of the following:

a MAC subheader with Backoff Indicator only;

a MAC subheader with RAPID only (i.e. acknowledgment for SI request);

a MAC subheader with RAPID and MAC RAR.

11 is a diagram illustrating a structure of a MAC subheader for RAR according to an embodiment.

Referring to FIG. 11, a MAC subheader having a RAPID (Random Access Preamble ID) is configured with three header fields. Description of each field is as follows.

E: The extended field indicates whether the MAC subPDU containing this MAC subheader is the last MAC subPDU in the MAC PDU. If the E field is set to 1, it indicates that there is at least another MAC subPDU. If the E field is set to 0, it indicates that the MAC subPDU including the MAC subheader is the last MAC subPDU in the MAC PDU. (The Extension field is a flag indicating if the MAC subPDU including this MAC subheader is the last MAC subPDU or not in the MAC PDU.The E field is set to "1" to indicate at least another MAC subPDU follows.The E field is set to "0" to indicate that the MAC subPDU including this MAC subheader is the last MAC subPDU in the MAC PDU)

The T: type field is a flag indicating whether a random access preamble ID or a backoff indicator is included in the MAC subheader. The T field is set to "0" to indicate that the backoff indicator field exists in the subheader BI. The Type field is a flag indicating whether the MAC subheader contains a Random Access Preamble ID or a Backoff Indicator.The T field The T field is set to "1" to indicate that the subheader (RAPID) has a random access preamble ID field. is set to "0" to indicate the presence of a Backoff Indicator field in the subheader (BI) .The T field is set to "1" to indicate the presence of a Random Access Preamble ID field in the subheader (RAPID)).

RAPID: The Random Access Preamble IDifier field identifies the transmitted Random Access Preamble. The size of the RAPID field is 6 bits. If the RAPID in the MAC subheader of the MAC subPDU corresponds to one of the random access preambles configured for an SI request, the MAC RAR is not included in the MAC subPDU. (The Random Access Preamble IDentifier field identifies the transmitted Random Access Preamble (see subclause 5.1.3) .The size of the RAPID field is 6 bits.If the RAPID in the MAC subheader of a MAC subPDU corresponds to one of the Random Access Preambles configured for SI request, MAC RAR is not included in the MAC subPDU.)

12 is a diagram illustrating a structure of a MAC payload for RAR according to an embodiment.

Referring to FIG. 12, the MAC RAR format may include the following fields.

R: Reserved bit, set to 0 (Reserved bit, set to "0")

Timing Advance Command: The Timing Advance Command field indicates the index value TA used in 3GPPTS 38.213 to control the amount of timing adjustment the MAC entity should apply. The Timing Advance Command field indicates the index value TA used to control the amount of timing adjustment that the MAC entity has to apply in TS 38.213.The size of the Timing Advance Command field is 12 bits;)

The UL Grant: Uplink Grant field indicates a resource to be used in the uplink of TS 38.213. The Uplink Grant field indicates the resources to be used on the uplink in TS 38.213.The size of the UL Grant field is 25 bits;

Temporary C-RNTI: The Temporary C-RNTI field indicates a temporary ID used by the MAC entity during random access. (The Temporary C-RNTI field indicates the temporary identity that is used by the MAC entity during Random Access.The size of the Temporary C-RNTI field is 16 bits.)

As mentioned above, an uplink grant for transmission to MSG3 is provided over MSG2. If the transmission fails for the MSG3 due to the LBT failure, the terminal should receive the uplink grant scrambled by the Temporary C-RNTI from the base station and perform MSG3 retransmission. To this end, the base station may need to perform LBT again for uplink grant transmission used for retransmission. That is, in the conventional NR technology, the UE transmits a UL-SCH in the MSG3 PUSCH scheduled by the uplink grant in the RAR message. Retransmission of that UL-SCH in the MSG3 PUSCH, if present, is scheduled by the DCI format scrambled into CRC by the Temporary C-RNTI provided in the corresponding RAR message. (A UE transmits an UL-SCH in an Msg3 PUSCH scheduled by a RAR grant in a corresponding RAR message using redundancy version number 0.Retransmissions, if any, of the UL-SCH in an Msg3 PUSCH are scheduled by a DCI format 0_0 with CRC scrambled by a TC-RNTI provided in the corresponding RAR message.)

Therefore, if the MSG3 fails to transmit due to the LBT failure, when the uplink grant is transmitted from the base station for retransmission, the LBT needs to be performed once more, thereby increasing the delay. Thus, the base station may include a plurality of uplink grants in the MSG2 RAR. The MAC RAR format may be changed to include a plurality of uplink grants in the MAC RAR format.

For example, a field for indicating the number of uplink grant fields included in the MAC RAR may be included in the MAC RAR. This field may be provided through one or more bits of the above-described R field. Alternatively, this field may be provided by adding a field in a new MAC RAR format. For example, if the field indicating the number of uplink grant fields included in the MAC RAR consists of 1 bit, the number of uplink grants may be indicated by one or two uplink values through zero and one values provided in one bit. have. If the field indicating the number of uplink grant fields included in the MAC RAR is composed of 2 bits, the number of uplink grants is set to 1, 2, 3 through 00, 01, 10, and 11 values provided by 2 bits. You can tell by separating it with, 4. If a field indicating the number of uplink grant fields included in the MAC RAR is provided, uplink grand fields may be configured in the MAC RAR by the number of uplink grant fields indicated in the corresponding field. For example, each uplink grant field may include an uplink grant having different uplink radio resource allocation information.

When a plurality of uplink grant fields are indicated, the UE performs LBT on the uplink radio resource indicated by each uplink grant, and if the LBT succeeds, transmits an uplink message (ex, MSG3) to the base station. have. Or, when a plurality of uplink grant fields are indicated, the terminal performs LBT on the uplink radio resources indicated by each uplink grant, respectively, and performs a specific criterion (for example, time, default subband if the same time, etc.). In the uplink radio resource for which LBT is successful, an uplink message (ex, MSG3) may be transmitted to a base station through a PUSCH. If necessary, if transmission of an uplink message (ex, MSG3) is successful, the LBT operation may not be performed on the uplink radio resource indicated by the remaining uplink grant field. Alternatively, if transmission of the uplink message (ex, MSG3) is successful, the uplink radio resource indicated by the remaining uplink grant field may not perform an uplink message transmission operation. Alternatively, if transmission of an uplink message (ex, MSG3) is successful, the uplink radio resource indicated by the remaining uplink grant field may be used for another uplink data transmission.

As another example, a new extension field (denoted E2 below for convenience of description) may be added. This extension field E2 indicates whether the included uplink grant is the last uplink grant in the MAC PDU / subPDU. If this extension field E2 is set to 1, it indicates that there is at least another additional uplink grant. If this extension field E2 is set to 0, it indicates that it is the last uplink grant. For example, there is no additional uplink grant.

As another example, two or one uplink grant fields included in the RAR may be indicated by indicating one of the above-described R fields. If two uplink grants are included, 25 bits are added to the existing format. Therefore, seven bits (e.g. R fields) may be added unnecessarily for byte-aling. Therefore, one R field of the existing three R fields can be removed. As a result, only one R field remains, the other R field is replaced by a field to distinguish between two or one uplink grant, and the other R field is included in the uplink grant field to be used for byte alignment. Can be.

As another example, the RAR MAC PDU may include one or more MAC payloads for the conventional RAR as shown in FIG. 12. Alternatively, the RAR MAC PDU may include the number of uplink grants included on the RAR MAC PDU / subPDU on the MAC subheader format for RAR of FIG. 11.

For convenience of description, an embodiment in which a plurality of uplink grants are indicated to a UE through some fields on the RAR MAC PDU has been described. However, the RAR MAC PDU is a MAC subheader format for RAR or a MAC payload for RAR. It is a known technique to be configured in a format. Therefore, it is also included in the scope of the present invention to indicate to the terminal including a plurality of uplink grants by modifying or adding any field on the RAR MAC PDU format. For example, it is within the scope of the present invention to modify or add any field on the MAC subheader format for the RAR or the MAC payload format for the RAR to include a plurality of uplink grants to indicate to the terminal.

As such, a plurality of uplink grants may be provided through a random access response message to prevent the MSG3 transmission failure of the terminal.

Second Embodiment: Method for Instructing UE by Including Information for Instructing Repeated Transmission of Uplink Message in RAR MAU PDU Format

The MAC RAR may include a repetitive transmission indication field for indicating to perform repetitive transmission using an uplink grant. The repetitive transmission indication field may be configured through one or more bits of the above-described R field. Or, it may consist of a field additionally set in the new random access response message format. For example, if the repetitive transmission indication field included in the MAC RAR consists of 1 bit, a single transmission or repetitive transmission may be indicated through 0 values and 1 values provided in 1 bit. If the repetitive transmission indication field included in the MAC RAR consists of 2 bits, single transmission, twice repetitive transmission, 4 repetitive transmissions, 8 times through 00, 01, 10, and 11 values provided by 2 bits It can be indicated by repeating transmission. Here, the matching between the number of repetitive transmissions and the value of the field may be variously modified.

For example, a terminal receiving information for indicating repetitive transmission through MAC RAR repeatedly transmits an uplink message (ex, MSG3) through consecutive slots / subframes / mini-slots. For example, an uplink message is repeatedly transmitted through a slot / subframe / mini-slot sequence indicated by a time interval slot / subframe / mini-slot indicated by an uplink radio resource received through an uplink grant of a MAC RAR. The same symbol allocation may be applied to each slot / subframe / mini-slot.

As another example, the terminal receiving information for instructing repetitive transmission through MAC RAR repeatedly transmits an uplink message (eg, MSG3) through slot / subframe / mini-slot of the indicated interval. For example, an uplink message is repeatedly transmitted through slot / subframe / mini-slot at an interval indicated by a time interval slot / subframe / mini-slot indicated by an uplink radio resource received through an uplink grant of a MAC RAR. do. The same symbol allocation may be applied to each slot / subframe / mini-slot.

Meanwhile, the terminal may perform LBT in each of consecutive slots / subframes / mini-slots, and may transmit an uplink message (eg, MSG3) to the base station if the LBT succeeds. In addition, the terminal may repeatedly transmit the same uplink message according to the repeat transmission indication field without waiting for feedback according to the uplink message transmission. The HARQ entity for uplink message (ex, MSG3) transmission processing may use the HARQ process for transmission in consecutive slot / subframe / mini-slot respectively as the same HARQ process. For example, a specific single HARQ process (i.e. HARQ process 0) may be used.

The terminal performs LBT in each of consecutive slots / subframes / mini-slots. If the UE succeeds in LBT in a specific slot / subframe / mini-slot, the UE may not perform LBT operation in the remaining consecutive slots / subframes / mini-slots. Or, if the UE succeeds in LBT in a specific slot / subframe / mini-slot and transmits MSG3 in the PUSCH, the UE may not perform the LBT operation in the remaining consecutive slots / subframes / mini-slots. Or, if the UE receives confirmation information on the MSG3 that successfully transmits the LBT in a specific slot / subframe / mini-slot, the UE may not perform the LBT operation in the remaining consecutive slots / subframes / mini-slots. .

For convenience of description, an embodiment in which the UE includes information for indicating repetitive transmission of an uplink message through some fields on the RAR MAC PDU has been described. However, the RAR MAC PDU is a MAC subheader format or RAR for RAR. It is a known technique to configure the MAC payload format for the. Therefore, it is also included in the scope of the present invention to indicate to the terminal including information for indicating the repeated transmission of the uplink message by modifying or adding any field on the RAR MAC PDU format. For example, by modifying or adding an arbitrary field on the MAC subheader format for RAR or MAC payload format for RAR, the terminal includes information for indicating repetitive transmission of an uplink message. Included in the category.

Third Embodiment: Method for Including Information for Indicating Opportunity of Uplink Message Transmission in RAR MAU PDU Format

The MAC RAR may include information for indicating a plurality of transmission opportunities on the frequency axis. For example, the MAC RAR may include a subband indication field including information for indicating a plurality of transmission opportunities on the frequency axis. The subband indication field may be provided through one or more bits of the above-described R field. Or it may be configured as a separate field in the new MAC RAR format. The subband indication field may include information indicating a subband for transmitting an uplink message or may include information indicating the number of subbands.

For example, if the subband indication field included in the MAC RAR is configured through one bit, a single subband or two subbands may be assigned within the UL BWP through zero values and one values provided in one bit. By dividing by, you can tell to try sending. If the subband indication field included in the MAC RAR is provided through 2 bits, the subbands in the UL BWP can be divided into two subbands in the UL BWP through 00 values, 01 values, 10 values, and 11 values. Subdivided into four subbands, four subbands, and eight subbands, the transmission attempt may be distinguished and indicated. For example, if the bandwidth of the UL BWP configured in any UE is 80MHz, if it is instructed to attempt transmission by dividing into 4 subbands, the UE performs LBT in each of 4 subbands having a bandwidth of 20MHz and performs MSG3. Can be transmitted. As such, the subband indication field may indicate the number of subbands and may indicate a subband for which the UE should perform LBT.

For another example, when the bandwidth of the UL BWP configured for any terminal is 80MHz, the UL BWP may be divided into four subbands having a bandwidth of 20MHz, and resource allocation in corresponding subband units and MSG3 transmission may be performed accordingly. have. If the subband indication field included in the MAC RAR consists of 1 bit, the transmission attempt in one subband and the transmission attempt in four subbands are distinguished through 0 and 1 values provided in 1 bit. Can be.

As another example, the subband indication field included in the MAC RAR may be configured in the form of a bitmap indicating whether a transmission attempt is made for each subband configured in the terminal. For example, if the UE configures four subbands on the UL BWP, the subband indication field may have 4-bit bitmap information to indicate an uplink grant in each of the four subbands.

On the other hand, the terminal receiving the information for instructing a plurality of transmissions per subband in the MAC RAR is a sub-reference that is a reference to the uplink radio resources (specific RB allocation information or a plurality of transmissions per subband received through the uplink grant field MSG3 transmission may be attempted in a resource block (RB) within a subband to which transmission is indicated based on RB allocation information of a band).

Alternatively, the MAC RAR is a frequency offset information for indicating a plurality of transmissions based on the RB included in the received uplink grant and / or a multiple of applying the frequency offset in the reference RB (eg, -1 * frequency offset, 1 * frequency offset, other for example -1 * frequency offset, 1 * frequency offset, 2 * frequency offset, other for example 1 * frequency offset, 2 * frequency offset, 3 * frequency offset, etc. Can be. For example, the multiple information for applying the frequency offset may include a multiple value applied to the frequency offset, such as -1 * frequency offset and 1 * frequency offset. In the case of three multiples, the frequency offset can be calculated as -1 * frequency offset, 1 * frequency offset, 2 * frequency offset. Alternatively, when the multiple value is three, the frequency offset may be calculated as 1 * frequency offset, 2 * frequency offset, 3 * frequency offset. The multiple values are for illustrative purposes only and are not limited to the values described above.

The UE may perform LBT in each subband or subband / band corresponding to the RB indicated for transmission, and may transmit MSG3 to the base station if the LBT succeeds. Alternatively, the terminal may select one or more of the subbands for which LBT succeeds and transmit MSG3. For example, the terminal may preferentially select a subband including the radio resource indicated in the uplink grant field.

For convenience of description, an embodiment of instructing a terminal including information for indicating a plurality of uplink message transmission opportunities through some fields on the RAR MAC PDU has been described, but the RAR MAC PDU is a MAC subheader format for RAR. Or it is known technology that is configured in the MAC payload format for RAR. Therefore, it is also included in the scope of the present invention to indicate to the terminal including information for indicating a plurality of uplink message transmission opportunities by modifying or adding any field on the RAR MAC PDU format. For example, modifying or adding any field on the MAC subheader format for the RAR or the MAC payload format for the RAR to indicate to the terminal including a plurality of uplink message transmission opportunities is included in the scope of the present invention. do.

The MAC RAR format includes information for distinguishing between a generic MAC RAR and a newly defined RAR for an unlicensed band.

As described above, in the conventional NR, only one MAC RAR format as shown in FIG. 12 is used. However, as described above, an arbitrary MAC RAR format for NR-U may be newly defined. However, there may be a problem that the NR terminal cannot recognize or process the new MAC RAR format. In order to solve this problem, only a newly defined RAR MAC PDU format may be applied to an NR-U capable terminal, but in this case, the RAR MAC PDU format provided for the conventional NR cannot be processed. In other words, there is a possibility that the NR-U capable terminal cannot access the NR of the licensed band.

Therefore, if a RAR MAC PDU format for NR-U that is different from the existing RAR MAC PDU format is defined, the terminal should be able to distinguish and process it. The RAR MAC PDU format for any NR-U may be a RAR MAC PDU format including the fields described in the above embodiments, or may be any RAR MAC PDU format not disclosed in the above embodiments.

For example, a terminal may distinguish a licensed band RAR MAC PDU format from an unlicensed band RAR MAC PDU format. For example, a field for distinguishing a MAC payload format for RAR may be included in a MAC subheader format for RAR. As another example, a field for identifying a corresponding format may be included in a MAC payload format for RAR.

For example, the RAR MAC PDU format may be distinguished through a version field or a field indicating an on / off value. The terminal may distinguish and process a conventional RAR MAC PDU format and a newly defined RAR MAC PDU format through a field for identifying a RAR MAC PDU format. As another example, the RAR MAC PDU format may be distinguished using the R field in the RAR MAC PDU format.

On the other hand, the transmission opportunity expansion method of the various embodiments was described through the MAC RAR message. However, information for indicating the above-described embodiment may be transmitted through a message other than the MAC RAR message.

For example, the information of each of the above-described embodiments, which are indicated to increase transmission opportunities in the unlicensed band, may be transmitted through system information. In order to support the NR-U Stand alone scenario, the LBT operation may be performed even when the UE performs initial access to the unlicensed band cell. Therefore, configuration information for the LBT operation is delivered to the terminal through MIB or remaning system information (RSI) (ex, SIB1). The LBT configuration information may include an energy detection threshold value indicating an absolute maximum energy detection threshold value and energy detection threshold offset information indicating an offset value in a default maximum energy detection threshold value.

Therefore, the information transmitted to the terminal may be included in the system information (ex, SIB1) in order to increase the transmission opportunity of each embodiment described above.

For example, information for instructing transmission of an uplink message (eg, MSG3) in a plurality of transmission opportunities may be included in the system information. Upon receiving the system information, the UE may attempt transmission by applying the operation of the above-described embodiments to the uplink message ex, MSG3.

For another example, in order to attempt to transmit an uplink message (ex, MSG3) in a plurality of transmission opportunities, at least one of the information included in the above embodiments (RAR MAC PDU, etc.) is broadcast through the system information can do. Upon receiving the system information, the UE may attempt transmission by applying the operation of the above-described embodiments to the uplink message ex, MSG3.

For another example, in order to attempt to transmit an uplink message (ex, MSG3) in a plurality of transmission opportunities, preconfiguration information, profile information, cell common configuration information, and PUSCH common configuration information necessary for applying the above-described embodiment are used. Broadcast through system information. For example, PUSCH time domain resource allocation information may be indicated. The corresponding information may include a slot offset K ₂ , a start and length indicator SLIV or a start symbol S and an allocated length L, and PUSCH mapping table information applied to PUSCH transmission.

As described above, the present disclosure provides an effect of effectively performing a random access procedure by expanding a transmission opportunity reduced according to LBT in an NR-U environment. In the following description, a terminal and a base station capable of implementing some or all of the above-described embodiments are described in terms of configuration.

13 is a diagram for describing a terminal configuration, according to an exemplary embodiment.

Referring to FIG. 13, a terminal 1300 performing a random access procedure in an unlicensed band may receive a random access response message for transmitting a random access preamble from a base station 1320 and a base station transmitting a random access preamble to an base station in an unlicensed band. And a receiver 1330 for receiving in the unlicensed band. The transmitter 1320 may transmit an uplink message through at least one unlicensed band uplink radio resource indicated by a random access response message.

In addition, the transmitter 1320 may transmit a random access preamble to access the base station. The controller 1310 may control to perform an LBT operation in the unlicensed band in order to transmit the random access preamble.

Meanwhile, in order to reduce the probability of transmission failure in the unlicensed band, the control unit 1310 selects a plurality of PRACH Occasions by increasing the transmission opportunity of the random access preamble, and PRACH Occupation that succeeds in LBT among the plurality of PRACH Occasions. In this case, the random access preamble may be controlled to be transmitted.

When the terminal 1300 transmits the random access preamble successfully, the receiver 1330 may receive a random access response message from the base station. Even in this case, the base station may perform an LBT operation in the unlicensed band in order to transmit the random access response message. Accordingly, a random access response message transmission failure or delay may occur due to the LBT failure.

To solve this problem, the base station may perform a plurality of LBT operations within the random access response window, and if the LBT succeeds, the base station may transmit a random access response message at the corresponding time. Accordingly, the controller 1310 may monitor the reception of the random access response message in the random access response window that may be determined by at least one of a random access preamble, a random access preamble message transmission time, and a random access preamble transmission resource. In addition, since the random access response message is transmitted in the unlicensed band, the random access response window may be extended to guarantee transmission.

The random access response message may include uplink radio resource allocation information so that the terminal can transmit an uplink message. For example, in the contention-based random access procedure, the allocation information on the uplink radio resource for transmitting the MSG3 by the UE may be included in the random access response message. As another example, in a contention free random access procedure, allocation information on an uplink radio resource for transmitting an uplink message to be transmitted to a base station by a terminal may be included in the random access response message. The transmitter 1320 transmits an uplink message to a base station using a time / frequency resource indicated by uplink radio resource allocation information.

For example, the random access response message may include a plurality of uplink grant fields for indicating a plurality of unlicensed band uplink radio resources. That is, the random access response message may include a plurality of uplink radio resource allocation information. Through this, the terminal 1300 may perform LBT on each uplink radio resource, and transmit an uplink message through the uplink radio resource that succeeds in the LBT operation. In addition, the random access response message may include information for indicating the number of the plurality of uplink grant field. Herein, when the LBT succeeds in the plurality of uplink radio resources, the controller 1310 does not perform the LBT operation on the remaining uplink radio resources. Alternatively, the controller 1310 performs an LBT operation on each of a plurality of uplink radio resources, and controls the uplink message to be transmitted in the LBT successful uplink radio resource selected according to an arbitrary criterion.

As another example, the random access response message may include a repetitive transmission indication field for indicating repetitive transmission of the uplink message. The uplink message may be repeatedly transmitted in consecutive time intervals when the repetitive transmission indication field is a value indicating repetitive transmission. The controller 1310 performs an LBT operation in each slot, subframe, or mini slot of each successive time period indicated by the repetitive transmission indication field, and the transmitter 1320 transmits an uplink message in a time period in which the LBT succeeds. do. The uplink message may be repeatedly transmitted from the time period in which the LBT succeeds.

As another example, the random access response message may include a field for indicating one or more subbands in which an uplink message is transmitted. One or more subbands are configured on the frequency axis, separated by at least two, within the bandwidth part of the unlicensed band. That is, one bandwidth part may be composed of N (natural numbers) subbands. When a plurality of subbands are indicated, the controller 1310 may sequentially perform LBT operations in each subband, and the transmitter 1320 may transmit an uplink message in the subband in which LBT is successful. In this case, the controller 1310 does not perform the LBT operation on the remaining subbands in which the LBT operation is to be performed after the successful subband of the LBT. Alternatively, the controller 1310 performs an LBT operation on each of the plurality of subbands, selects one subband according to a specific condition, and the transmitter 1320 transmits an uplink message in the selected subband. The field for indicating a subband may indicate an individual subband in the form of a bitmap or may be configured to indicate a specific subband and provide frequency offset information in the corresponding subband.

Meanwhile, the aforementioned random access response message may include a random access response format field for distinguishing from a random access response message using a licensed band. That is, it may include a separate indication field for indicating that the random access response message used in the unlicensed band.

Alternatively, the receiver 1330 may receive the above-described information such as uplink radio resource allocation information, repetitive transmission, and subband indication through system information. For example, information applied to at least one of the foregoing embodiments may be received through SIB1.

In addition, the controller 1310 controls the overall operation of the terminal 1300 according to performing the random access procedure through the transmission opportunity extension necessary to perform the above-described embodiments.

In addition, the transmitter 1320 and the receiver 1330 are used to transmit and receive a signal, a message, and data necessary for performing the above-described embodiment with the base station.

14 is a diagram illustrating a configuration of a base station according to an embodiment.

Referring to FIG. 14, the base station 1400 performing a random access procedure in an unlicensed band may receive a random access response message for transmitting a random access preamble to a receiver 1430 and a terminal that receive a random access preamble from a terminal in an unlicensed band. It may include a transmitter 1420 for transmitting in the unlicensed band. The receiver 1430 may receive an uplink message through at least one unlicensed band uplink radio resource indicated by a random access response message.

As described above, the random access preamble may be received in a contention based random access procedure or may be received in a non-competition based random access procedure. In order to transmit the random access preamble, the controller 1410 may perform the LBT operation in the unlicensed band and check the related channel before performing the transmission.

Meanwhile, the controller 1410 may configure a plurality of PRACH occlusions in the terminal in order to prevent the UE from failing to transmit the random access preamble. The UE may increase a transmission opportunity of the random access preamble, select a plurality of PRACH occlusions, and transmit a random access preamble to the base station in a PRACH occlusion that succeeds in LBT among the plurality of PRACH occlusions. The reception unit 1430 may receive a random access preamble in an orcation in which the terminal succeeds in LBT among the plurality of PRACH orcions.

When the random access preamble of the terminal is received, the transmitter 1420 may transmit a random access response message. Even in this case, the controller 1410 may perform an LBT operation in the unlicensed band in order to transmit the random access response message. Accordingly, a random access response message transmission failure or delay may occur due to the LBT failure.

To solve this problem, the controller 1410 may perform a plurality of LBT operations within the random access response window, and when the LBT succeeds, the controller 1420 may transmit a random access response message at a corresponding time point. The UE may monitor the reception of the random access response message within a random access response window that may be determined by at least one of a random access preamble, a random access preamble message transmission time, and a random access preamble transmission resource. In addition, since the random access response message is transmitted in the unlicensed band, the random access response window may be extended to guarantee transmission. The controller 1410 may configure the terminal for the extended random access response window.

The random access response message may include uplink radio resource allocation information so that the terminal can transmit an uplink message. In this case, since the uplink message is transmitted on the unlicensed band, the terminal must perform an LBT operation. Therefore, when the LBT fails on the uplink radio resource allocated by the base station 1400, the uplink message may not be transmitted or an uplink message transmission delay may occur.

To solve this problem, various embodiments below may be applied.

For example, the random access response message may include a plurality of uplink grant fields for indicating a plurality of unlicensed band uplink radio resources. That is, the random access response message may include a plurality of uplink radio resource allocation information. Through this, the terminal may perform LBT on each uplink radio resource, and the reception unit 1430 may receive an uplink message through the uplink radio resource that succeeds in the LBT operation. In addition, the random access response message may include information for indicating the number of the plurality of uplink grant field.

As another example, the random access response message may include a repetitive transmission indication field for indicating repetitive transmission of the uplink message. The uplink message may be repeatedly transmitted in consecutive time intervals when the repetitive transmission indication field is a value indicating repetitive transmission. The receiver 1430 may repeatedly receive an uplink message from a time period in which the terminal succeeds in the LBT.

As another example, the random access response message may include a field for indicating one or more subbands in which an uplink message is transmitted. One or more subbands are configured on the frequency axis, separated by at least two, within the bandwidth part of the unlicensed band. When a plurality of subbands is indicated, the UE sequentially performs LBT operations in each subband, and the receiver 1430 may receive an uplink message in a subband in which the UE has succeeded in LBT. In this case, the terminal does not perform the LBT operation in the remaining subbands in which the LBT operation is to be performed after the subband in which the LBT succeeds. Alternatively, the UE performs an LBT operation in each of the plurality of subbands, selects one subband according to a specific condition, and transmits an uplink message in the selected subband. The field for indicating a subband may indicate an individual subband in the form of a bitmap or may be configured to indicate a specific subband and provide frequency offset information in the corresponding subband.

Meanwhile, the aforementioned random access response message may include a random access response format field for distinguishing from a random access response message using a licensed band. That is, it may include a separate indication field for indicating that the random access response message used in the unlicensed band.

Alternatively, the above-described information such as uplink radio resource allocation information, repetitive transmission, subband indication, and the like may be transmitted through system information. For example, the transmitter 1420 may broadcast information applied to at least one of the above-described embodiments through SIB1.

In addition, the controller 1410 controls the overall operation of the base station 1400 according to performing the random access procedure in the unlicensed band by extending the transmission opportunity necessary to perform the above-described embodiments.

In addition, the transmitter 1420 and the receiver 1430 are used to transmit and receive a signal, a message, and data necessary for carrying out the above-described embodiment.

The above-described embodiments may be supported by standard documents disclosed in at least one of the wireless access systems IEEE 802, 3GPP and 3GPP2. That is, steps, components, and parts which are not described in order to clearly reveal the present technical spirit of the embodiments may be supported by the aforementioned standard documents. In addition, all terms disclosed herein may be described by the standard documents disclosed above.

The above-described embodiments may be implemented through various means. For example, the embodiments may be implemented by hardware, firmware, software, or a combination thereof.

For implementation in hardware, the method according to the embodiments may include one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), FPGAs. (Field Programmable Gate Arrays), a processor, a controller, a microcontroller or a microprocessor may be implemented.

In the case of an implementation by firmware or software, the method according to the embodiments may be implemented in the form of an apparatus, procedure, or function for performing the functions or operations described above. The software code may be stored in a memory unit and driven by a processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various known means.

In addition, the terms "system", "processor", "controller", "component", "module", "interface", "model", or "unit" described above generally refer to computer-related entity hardware, hardware and software. May mean a combination of, software or running software. For example, the foregoing components may be, but are not limited to, a process driven by a processor, a processor, a controller, a control processor, an object, an execution thread, a program, and / or a computer. For example, both an application running on a controller or processor and a controller or processor can be components. One or more components may be within a process and / or thread of execution, and the components may be located on one device (eg, system, computing device, etc.) or distributed across two or more devices.

The above description is merely illustrative of the technical idea of the present disclosure, and various modifications and variations may be made by those skilled in the art without departing from the essential characteristics of the present disclosure. In addition, the present embodiments are not intended to limit the technical spirit of the present disclosure but to describe the scope of the present inventive concept. The scope of protection of the present disclosure should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto shall be construed as being included in the scope of the present disclosure.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is related to the patent application No. 10-2018-0103870 filed in Korea on August 31, 2018 and the patent application No. 10-2019-0097915 filed in Korea on August 12, 2019. Priority is claimed under section (a) (35 USC § 119 (a)), all of which is incorporated by reference in this patent application. In addition, if this patent application claims priority over the same reason for countries other than the United States, all its contents are incorporated into this patent application by reference.

Claims (15)

1. A method for performing a random access procedure in an unlicensed band by a terminal,

   Transmitting a random access preamble to a base station in an unlicensed band;

   Receiving a random access response message for the random access preamble transmission from the base station in the unlicensed band; And

   Transmitting an uplink message on at least one unlicensed band uplink radio resource indicated by the random access response message.
2. The method of claim 1,

   The random access response message,

   A plurality of uplink grant fields for indicating the plurality of unlicensed band uplink radio resources,

   And information for indicating the number of the plurality of uplink grant fields.
3. The method of claim 1,

   The random access response message,

   A repetitive transmission indication field for indicating repetitive transmission of the uplink message;

   The uplink message is,

   And if the repetitive transmission indication field is a value indicating repetitive transmission, the repetitive transmission is repeatedly transmitted in consecutive time periods.
4. The method of claim 1,

   The random access response message,

   A field for indicating one or more subbands in which the uplink message is transmitted;

   The one or more subbands,

   And divided into at least two within the bandwidth part of the unlicensed band.
5. The method of claim 1,

   The random access response message,

   And a random access response format field for distinguishing from a random access response message using a licensed band.
6. A method for a base station performing a random access procedure in an unlicensed band,

   Receiving a random access preamble from a terminal in an unlicensed band;

   Transmitting a random access response message for the random access preamble transmission to the terminal in the unlicensed band; And

   Receiving an uplink message via at least one unlicensed band uplink radio resource indicated by the random access response message.
7. The method of claim 6,

   The random access response message,

   A plurality of uplink grant fields for indicating the plurality of unlicensed band uplink radio resources,

   And information for indicating the number of the plurality of uplink grant fields.
8. The method of claim 6,

   The random access response message,

   A repetitive transmission indication field for indicating repetitive transmission of the uplink message;

   The uplink message is,

   And if the repetitive transmission indication field is a value indicating repetitive transmission, it is repeatedly received in consecutive time periods.
9. The method of claim 6,

   The random access response message,

   A field for indicating one or more subbands in which the uplink message is transmitted;

   The one or more subbands,

   And divided into at least two within the bandwidth part of the unlicensed band.
10. The method of claim 6,

    The random access response message,

    And a random access response format field for distinguishing from a random access response message using a licensed band.
11. A terminal performing a random access procedure in an unlicensed band,

    A transmitter for transmitting a random access preamble to an eNB in an unlicensed band; And

    A receiver configured to receive a random access response message for the random access preamble transmission from the base station in the unlicensed band,

    The transmitting unit,

    A terminal for transmitting an uplink message through at least one unlicensed band uplink radio resource indicated by the random access response message.
12. The method of claim 11,

    The random access response message,

    A plurality of uplink grant fields for indicating the plurality of unlicensed band uplink radio resources,

    And a terminal for indicating the number of the plurality of uplink grant fields.
13. The method of claim 11,

    The random access response message,

    A repetitive transmission indication field for indicating repetitive transmission of the uplink message;

    The uplink message is,

    And if the repetitive transmission indication field is a value indicating repetitive transmission, the terminal is repeatedly transmitted in consecutive time periods.
14. The method of claim 11,

    The random access response message,

    A field for indicating one or more subbands in which the uplink message is transmitted;

    The one or more subbands,

    And a terminal configured to be divided into at least two or more in the bandwidth part of the unlicensed band.
15. The method of claim 11,

    The random access response message,

    And a random access response format field for distinguishing from a random access response message using a licensed band.

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