Terminal in wireless communication system and execution method thereof

Abstract

The present disclosure relates to a method performed by a terminal in a wireless communication system, the method comprising: receiving listen before talk (LBT) related configuration information, the configuration information comprising first information on a timer for LBT failure detection and second information on a maximum counter value for LBT failure detection; performing LBT for transmission; in the case that the transmission is not executed, identifying that the LBT fails; and starting the timer and incrementing the counter value, where the counter value is set to 0 if the timer expires before the counter value reaches a maximum counter value.

Description

[0001] This application is a divisional application of the following application: Application number: 202080024086.5; Application date: March 27, 2020; Invention name: "Method and device for detecting uplink LBT failure in a wireless communication system using unlicensed frequency bands". Technical Field

[0002] The present disclosure generally relates to a method for detecting uplink Listen-Before-Talk (LBT) failure, and more specifically, to detecting LBT failure when using 3rd Generation Partnership Project (3GPP) 5th Generation (5G) New Radio (NR) technology in a wireless communication system. Background Art

[0003] To meet the growing demand for wireless data services since the deployment of the 4th generation (4G) communication system, efforts have been made to develop improved 5G or pre-5G communication systems. 5G or pre-5G communication systems may also be referred to as "beyond 4G networks" or "post-Long Term Evolution (LTE) systems."

[0004] In order to achieve higher data rates, it is expected that 5G communication systems will be implemented in higher frequency (mmWave) bands (e.g., 60 GHz bands). In order to reduce the propagation loss of radio waves and increase the transmission distance, beamforming, massive multiple-input multiple-output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive antenna technologies are being discussed for use in 5G communication systems.

[0005] In addition, in the 5G communication system, system network improvements based on advanced small cells, cloud radio access network (RAN), ultra-dense network, device-to-device (D2D) communication, wireless backhaul, mobile network, cooperative communication, coordinated multi-point (CoMP), receiving-end interference elimination, etc. are being developed. In the 5G system, hybrid frequency shift keying (FSK) and quadrature amplitude modulation (QAM) (FQAM) and sliding window superposition coding (SWSC) have been developed for advanced coding modulation (ACM). Filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA) and sparse code multiple access (SCMA) have been developed as advanced access technologies.

[0006] The Internet is evolving towards the Internet of Things (IoT), where distributed entities (such as things) exchange and process information without human intervention. The Internet of Everything (IoE) has also emerged, which is a combination of IoT technology and big data processing technology through connection with cloud servers.

[0007] Since IoT implementation requires technical elements such as "sensing technology", "wired / wireless communication and network infrastructure", "service interface technology" and "security technology", sensor networks, machine-to-machine (M2M) communication, machine type communication (MTC), etc. are being studied.

[0008] The IoT environment can provide intelligent Internet technology services by collecting and analyzing data generated among connected things. Through the integration and combination of existing information technology (IT) and various industrial applications, IoT can be applied to various fields, including smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, healthcare, smart appliances and advanced medical services.

[0009] Therefore, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as sensor networks, MTC, and M2M communications can be implemented through beamforming, MIMO, and array antennas. Cloud radio access networks (RANs) as an application of the above-mentioned big data processing technologies can also be considered as an example of the fusion of 5G technology and IoT technology.

[0010] Recently, with the development of LTE and LTE-Advanced (LTE-A), research on technologies for operating mobile communication systems in unlicensed bands has been actively conducted. Specifically, channel sensing (or LBT) can be utilized in unlicensed bands. In this case, a method and apparatus for smoothly operating a mobile communication system in an unlicensed band is needed. Summary of the invention

[0011] Technical issues

[0012] According to the prior art, when an LBT failure occurs, a problem occurs in which the terminal cannot communicate effectively.

[0013] Problem Solution

[0014] An aspect of the present disclosure is to provide a method for detecting uplink transmission failure due to interference from another device in an unlicensed band.

[0015] Another aspect of the present disclosure is to provide a method for detecting uplink transmission failure due to interference from another device in an unlicensed frequency band and reestablishing a connection with a new base station.

[0016] According to one aspect of the present disclosure, a method for a terminal in a wireless communication system is provided. The method includes receiving system information including listen-before-talk (LBT) related parameters; performing LBT on a first bandwidth part (BWP) of a cell; determining whether LBT has succeeded for the first BWP based on the system information; in response to determining that LBT has not succeeded for the first BWP, announcing LBT failure for the first BWP; and switching from the first BWP to a second BWP for operation of the terminal.

[0017] According to another aspect of the present disclosure, a terminal for use in a wireless communication system is provided. The terminal includes a transceiver; and a controller configured to receive system information including listen-before-talk (LBT) related parameters from a base station via the transceiver, perform LBT on a first bandwidth part (BWP) of a cell, determine whether LBT has succeeded for the first BWP based on the system information, declare LBT failure for the first BWP in response to determining that LBT has not succeeded for the first BWP, and switch from the first BWP to a second BWP for operation of the terminal.

[0018] Advantageous Effects of the Invention

[0019] According to an embodiment of the present invention, if an uplink problem of an unlicensed band persists, the problem can be effectively solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0021] Figure 1 An LTE system according to an embodiment is shown;

[0022] Figure 2 A radio protocol structure in an LTE or NR system according to an embodiment is shown;

[0023] Figure 3 A downlink and uplink channel frame structure when communication is performed based on a beam in an NR system according to an embodiment is shown;

[0024] Figure 4 A process of contention-based 4-step random access performed by a terminal to a base station according to an embodiment is shown;

[0025] Figure 5 LBT Type 1 according to an embodiment is shown;

[0026] Figure 6 LBT Type 2 according to an embodiment is shown;

[0027] Figure 7shows a process between a terminal and a base station when the terminal identifies an uplink LBT problem according to an embodiment;

[0028] Fig. 8A is a flowchart showing an operation sequence of a terminal identifying an uplink LBT problem according to an embodiment;

[0029] Figure 8B is a flowchart showing an operation sequence of a terminal in the event of expiration of a timer;

[0030] Fig. 9 A terminal in a wireless communication system according to an embodiment is shown. DETAILED DESCRIPTION

[0031] Hereinafter, various embodiments of the present disclosure will be described in detail in conjunction with the accompanying drawings. In the following description of the present disclosure, a detailed description of known functions or configurations incorporated herein will be omitted when it may make the subject matter of the present disclosure quite unclear. The terms described below are defined in consideration of the functions in the present disclosure and may differ depending on the user, the user's intention or custom. Therefore, the definition of the terms should be made based on the content of the entire specification.

[0032] By referring to the embodiments described in detail below in conjunction with the accompanying drawings, the advantages and features of the present disclosure and the ways to achieve them will be apparent. However, the present disclosure is not limited to the embodiments set forth below and can be implemented in various forms. The following embodiments are provided only to fully disclose the present disclosure and inform those skilled in the art of the scope of the present disclosure, and the present disclosure is limited only by the scope of the appended claims.

[0033] Throughout the specification, the same or similar reference numerals designate the same or similar elements.

[0034] In the following description, for the sake of convenience, terms for identifying access nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, terms referring to various identification information, etc. are illustratively used. Therefore, the present disclosure is not limited to the terms used below, and other terms referring to subjects with equivalent technical meanings may be used.

[0035] The present disclosure also uses terms and names defined in the LTE and NR standards, which are standards defined by the 3GPP organization among existing communication standards. However, the present disclosure is not limited to the above terms and names, and can be applied to systems that comply with other standards. Specifically, the present disclosure is applicable to 3GPP NR (5G mobile communication standard).

[0036] Figure 1 The LTE system structure according to the embodiment is shown. The NR system has a similar structure.

[0037] refer to Figure 1 , the LTE wireless communication system includes a plurality of base stations 1-05, 1-10, 1-15 and 1-20, a mobility management entity (MME) 1-25 and a serving gateway (S-GW) 1-30. A user equipment (UE) or terminal 1-35 accesses an external network via the base stations 1-05, 1-10, 1-15 and 1-20 and the S-GW 1-30.

[0038] Base stations 1-05, 1-10, 1-15 and 1-20 are access nodes of the cellular network and provide wireless access to terminals accessing the network. That is, base stations 1-05, 1-10, 1-15 and 1-20 collect status information of the terminal (such as buffer status, available transmission power status, channel status, etc.) and perform scheduling to serve the user's business, and support the connection between the terminal and the core network (CN).

[0039] The MME 1-25 is responsible for various control functions and mobility management functions of the terminal 1-35. The MME 1-25 is connected to a plurality of base stations 1-05, 1-10, 1-15, and 1-20. The S-GW 1-30 provides data bearers. The MME 1-25 and the S-GW 1-30 may also perform authentication, bearer management, etc. of the terminal 1-35 accessing the network, and process packets received from the base stations 1-05, 1-10, 1-15, and 1-20 and packets to be delivered to the base stations 1-05, 1-10, 1-15, and 1-20.

[0040] Figure 2 A radio protocol structure in an LTE or NR system according to an embodiment is shown.

[0041] refer to Figure 2 , the radio protocol of the LTE system includes the packet data convergence protocol (PDCP) 2-05 and 2-40, the radio link control (RLC) 2-10 and 2-35, and the medium access control (MAC) 2-15 and 2-30 in the terminal (or UE) and the base station (or eNB or gNB), respectively. PDCP 2-05 and 2-40 are responsible for operations such as Internet Protocol (IP) header compression / recovery, and RLC 2-10 and 2-35 reconfigure the PDCP packet data unit (PDU) to an appropriate size. MAC 2-15 and 2-30 are connected to a plurality of RLC layer devices included in one terminal, and perform multiplexing of RLC PDU to MAC PDU and demultiplexing of RLC PDU from MAC PDU.

[0042] The physical (PHY) layers 2-20 and 2-25 perform channel coding and modulation of the upper layer data, configure the channel-coded and modulated upper layer data into orthogonal frequency division multiplexing (OFDM) symbols, and transmit the OFDM symbols via a wireless channel, or demodulate and channel-decode the OFDM symbols received via the wireless channel and pass them to the upper layer. The physical layer uses hybrid automatic repeat request (HARQ) for additional error correction, and the receiving end sends an indication of whether the packet sent by the transmitting end is received in 1 bit. This is called HARQ acknowledgement / negative acknowledgement (ACK / NACK) information. In the LTE system, downlink HARQ ACK / NACK information for uplink data transmission is transmitted via a physical hybrid ARQ indicator channel (PHICH) as a physical channel. In the NR system, because NR applies asynchronous HARQ, it can be determined whether retransmission is necessary or whether a new transmission can be performed in a physical dedicated control channel (PDCCH) according to the scheduling information of the corresponding terminal. PDCCH is a channel through which downlink / uplink resource allocation, etc. are transmitted.

[0043] Uplink HARQ ACK / NACK information for downlink data transmission can be sent via a physical channel such as a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH). PUCCH is usually sent in the uplink of the primary cell (PCell). However, if the terminal supports it, the base station can also send PUCCH to the terminal in the secondary cell (SCell). SCell can also be called PUCCH SCell.

[0044] Despite Figure 2 Although not shown in the figure, a radio resource control (RRC) layer exists above the PDCP layer of each of the terminal and the base station, and configuration control messages related to measurement and access may be exchanged in the RRC layer for radio resource control.

[0045] The PHY layer may include one or more frequencies / carriers, and the technology of configuring and using multiple frequencies at the same time is called carrier aggregation (CA) technology. In CA technology, the use of only one carrier for communication between the terminal and the base station is changed to further use a main carrier and one or more subcarriers, so that the transmission amount can be significantly increased with the number of subcarriers. In LTE, the cell of the base station using the main carrier is called the primary cell or PCell, and the cell of the base station using the subcarrier is called the subcell or SCell.

[0046] Figure 3 A downlink and uplink channel frame structure when beam-based communication is performed in an NR system according to an embodiment is shown.

[0047] refer to Figure 3 , the base station 3-01 sends signals in the form of beams 3-11, 3-13, 3-15 and 3-17 in order to send a strong signal or send the signal to a wider coverage area. Therefore, the terminal 3-03 in the cell should use a specific beam (e.g., beam #1 3-13) sent by the base station 3-01 to send or receive data.

[0048] The state of the terminal 3-03 is classified into a sleep mode (or RRC_IDLE) and a connected mode (or RRC_CONNECTED) according to whether the terminal 3-03 is connected to the base station 3-01. The base station 3-01 cannot identify the location of the terminal 3-03 in the sleep mode.

[0049] If the terminal 3-03 in the sleep mode is to be converted to the connection mode, the terminal 3-03 receives synchronization signal blocks (SSBs) 3-21, 3-23, 3-25 and 3-27 from the base station 3-01. The SSB is an SSB signal periodically transmitted according to a period configured by the base station 3-01, and is divided into a primary synchronization signal (PSS) 3-41, a secondary synchronization signal (SSS) 3-43 and a physical broadcast channel (PBCH) 3-45.

[0050] exist Figure 3 In , it is assumed that SSB is transmitted for each beam. Specifically, Figure 3 SSB#0 3-21 transmitted using beam #0 3-11, SSB#1 3-23 transmitted using beam #1 3-13, SSB#2 3-25 transmitted using beam #2 3-15, and SSB#3 3-27 transmitted using beam #3 3-17 are shown.

[0051] exist Figure 3 , it is assumed that the terminal 3-03 in the sleep mode is located in the beam #1 3-13. However, even when the terminal 3-03 is in the connected mode and performs random access, the terminal 3-03 selects the SSB received at the time point of performing the random access.

[0052] Therefore, in Figure 3 , SSB#1 3-23 transmitted via beam #1 3-13 is received by terminal 3-03. Upon receiving SSB#1 3-23, terminal 3-03 obtains the physical cell identifier (PCI) of base station 3-01 via PSS and SSS, and terminal 3-03 can determine the identifier of the currently received SSB (i.e., #1), the position of the current SSB received within the 10ms frame, and the position within the system frame number (SFN) with a period of 10.24 seconds by receiving PBCH.

[0053] A Master Information Block (MIB) is included in the PBCH. The MIB indicates a location where a System Information Block Type 1 (SIB1) configured to broadcast more detailed cell configuration information can be received.

[0054] Upon receiving SIB1, the terminal 3-03 can identify the total number of SSBs transmitted by the base station 3-01 and can determine the location of the physical random access channel (PRACH) opportunity for random access in order to transition to the connected mode. More specifically, the PRACH opportunity allows the transmission of a preamble that is a physical signal specifically designed to match uplink synchronization. Figure 3 In the figure, a scenario with allocation every 1ms has been assumed, from 3-30 to 3-39.

[0055] In addition, based on the reception of SIB1, the terminal 3-03 can identify which PRACH opportunity among the PRACH opportunities is mapped to which SSB index. Figure 3 In the present invention, a scenario of allocation every 1 ms has been assumed, and a scenario of allocating 1 / 2 SSB per PRACH opportunity (i.e., two PRACH opportunities per SSB) has been assumed. Therefore, from the beginning of the PRACH opportunity according to the SFN value, two PRACH opportunities are allocated to each SSB. More specifically, PRACH opportunities 3-30 and 3-31 are allocated to SSB#0, and PRACH opportunities 3-32 and 3-33 are allocated to SSB#1. After the configuration of all SSBs, PRACH opportunities 3-38 and 3-39 are reallocated to SSB#0.

[0056] The terminal 3-03 identifies the positions of the PRACH opportunities 3-32 and 3-33 of SSB#1, and transmits a random access preamble via the fastest PRACH opportunity (e.g., 3-32) at the current time point among the PRACH opportunities 3-32 and 3-33 corresponding to SSB#1. Because the base station 3-01 has received the preamble in the PRACH opportunity of 3-32, it can recognize that the terminal 3-03 has selected SSB#1 3-23 and transmitted the preamble, and therefore, when performing subsequent random access, transmits or receives data via the corresponding beam.

[0057] Even when the terminal 3-03 in the connected state moves from the current (source) base station to the target base station, for example due to switching, the terminal 3-03 performs random access at the target base station and selects the SSB to send the random access, as described above. In addition, during the switching, a switching command is sent to the terminal 3-03, so that the terminal 3-03 moves from the source base station to the target base station. The switching command can be assigned a random access preamble identifier dedicated to each SSB of the target base station, so that when random access is performed in the target base station, a dedicated random access preamble identifier can be used. The base station may not allocate dedicated random access preamble identifiers for all beams (depending on the current position of the terminal, etc.), so some SSBs may not be assigned dedicated random access preamble identifiers (for example, a dedicated random access preamble is only assigned to beam #2 and beam #3).

[0058] If a dedicated random access preamble is not allocated to the SSB selected for preamble transmission, the terminal 3-03 randomly selects a contention-based random access preamble and performs random access. Figure 3 In the example, terminal 3-03 is located in beam #13-13 and performs random access, but after failure, when the random access preamble is transmitted again, a scenario is possible in which terminal 3-03 is located in beam #3 3-17 and transmits a dedicated preamble. That is, even in one random access procedure, if preamble retransmission occurs, the contention-based random access procedure and the non-contention-based random access procedure can be mixed depending on whether a dedicated random access preamble is allocated to the selected SSB at each preamble transmission.

[0059] Figure 4 The process of contention-based 4-step random access performed by a terminal to a base station according to an embodiment is shown. Specifically, Figure 4 A 4-step contention-based random access procedure is shown performed by a terminal in various scenarios requiring initial access, reconnection, handover, and other random accesses to a base station.

[0060] refer to Figure 4 In order to access the base station 4-03, the terminal 4-01, for example, according to Figure 3To select PRACH, and in step 4-11, a random access preamble is sent to PRACH. One or more terminals can simultaneously send random access preambles via PRACH resources. PRACH resources can span a subframe, or can use only a portion of symbols in a subframe. Information about PRACH resources can be included in the system information broadcast by the base station 4-03, so that the time-frequency resources where the preamble should be sent can be identified. Even if the transmission is performed before synchronization with the base station is completed, the random access preamble corresponds to a specific sequence for reception. According to the standard, there can be multiple preamble identifiers (or indexes). If there are multiple preamble identifiers, the preamble sent by the terminal 4-01 can be randomly selected by the terminal 4-01, or it can be a specific preamble specified by the base station 4-03.

[0061] In response to receiving the preamble, the base station 4-03 sends a random access response (RAR) message to the terminal 4-01 in step 4-21. The RAR message includes identification information of the preamble used in step 4-11, uplink transmission timing correction information, temporary terminal identifier information, and uplink resource allocation information. For example, if multiple terminals attempt random access by sending different preambles in step 4-11, the identifier information of the preamble is sent to indicate the preamble, where the RAR message is a response message for the preamble. The uplink resource allocation information includes detailed information of the resources to be used by the terminal 4-01 in step 4-31, and includes the physical location and size of the resources, the modulation and coding scheme (MCS) used when performing the transmission, and the power adjustment information when performing the transmission. If the terminal 4-01 that has sent the preamble performs initial access and does not have an identifier for communication with the base station 4-03, the temporary terminal identifier information can be used.

[0062] The RAR message should be sent within a predetermined time period starting from a predetermined time after sending the preamble. This time period may be referred to as a RAR window 4-23. The RAR window 4-23 starts from a predetermined time after sending the first preamble. The predetermined time may have a value of a subframe unit (e.g., 4ms) or less. In the system information message broadcast by the base station 4-03, the length of the RAR window 4-23 may be a predetermined value configured by the base station 4-03 for each PRACH resource or one or more PRACH resource sets.

[0063] When sending a RAR message, the base station 4-03 schedules the RAR message via the PDCCH, and the scheduling information is encrypted using a random access radio network temporary identifier (RA-RNTI). In step 4-11, the RA-RNTI is mapped to the PRACH resource used to send the message, and the terminal 4-01 that has sent a preamble to a specific PRACH resource attempts to receive the PDCCH based on the RA-RNTI to determine whether there is a corresponding RAR message. If the RAR message is a response to the preamble sent by the terminal 4-01 in step 4-11, the RA-RNTI used in the RAR message scheduling information includes information about the transmission in step 4-11. The RA-RNTI can be calculated using the following equation (1).

[0064] RA-RNTI=1+s_id+14Xt_id+14X80Xf_id+14X80X8Xul_carrier_id...(1)

[0065] In equation (1), s_id is an index corresponding to the first OFDM symbol starting from the preamble transmission performed in step 4-11, and has a value of 0<=s_id<14 (i.e., the maximum number of OFDM in one slot). In addition, t_id is an index corresponding to the first slot starting from the preamble transmission performed in step 4-11, and has a value of 0<=t_id<80 (i.e., the maximum number of slots in one system frame (40ms)). In addition, f_id indicates the number of PRACH resources before the PRACH resources of the preamble transmitted in step 4-11 are transmitted, and has a value of 0 0<=f_id<8 (i.e., the maximum number of PRACHs on the frequency in the same time). If two carriers are used in the uplink of one cell, ul_carrier_id is a factor for distinguishing whether the preamble is transmitted in the normal uplink (NUL) (0 in this case) or in the supplementary uplink (SUL) (1 in this case).

[0066] In response to receiving the RAR message, in step 4-31, the terminal 4-01 sends different messages to the resources allocated to the RAR message according to the aforementioned various purposes. Figure 4In the embodiment of the present invention, the third message may be referred to as Msg3. Similarly, the preamble in step 4-11 may be referred to as Msg1, and the RAR in step 4-21 may be referred to as Msg2. Examples of Msg3 sent by the terminal 4-01 include an RRCConnectionRequest message as a message of the RRC layer sent in the case of an initial connection, an RRCConnectionReestablishmentRequest message sent in the case of a reconnection, and an RRCConnectionReconfigurationComplete message sent during a handover. Alternatively, a buffer status report (BSR) message of a resource request may be sent.

[0067] Thereafter, for initial transmission (i.e., when Msg3 does not include the base station identifier information previously assigned to the terminal 4-01), in step 4-41, the terminal 4-01 receives a contention resolution message from the base station 4-03. Since the content sent by the terminal 4-01 in Msg3 is included in the contention resolution message, even if there are a plurality of terminals that have selected the same preamble in step 4-11, the terminal that responds thereto can be notified.

[0068] When the uplink allocated for Msg3 transmission via RAR or PDCCH ends (e.g., the first OFDM symbol after the uplink), the contention resolution timer (ra-ContentionResolutionTimer) is started or restarted. Therefore, the terminal 4-01 attempts to receive Msg4 from the base station 4-03 until the timer expires, and if the Msg4 is not received until the timer expires, the terminal 4-01 determines that the contention resolution has failed and retransmits the preamble.

[0069] The above 5G system can consider the scenario of operating in an unlicensed band. An unlicensed band is a band that is freely available to anyone without a license within the regulatory permitted range of the corresponding frequency. For example, there is a 2.4 GHz band or a 5 GHz band, and wireless local area network (LAN), Bluetooth TM etc. perform communication using the corresponding frequency.

[0070] In order to perform communication in an unlicensed band, data must be sent or received according to regulations set for each country. According to the regulations, before a communication device performs transmission in an unlicensed band, the communication device should "listen" and determine whether the unlicensed band is occupied by another communication device, and then perform "transmission" if the unlicensed band is determined to be idle. This scheme of listening and performing transmission when idle is called LBT. Regulations requiring the performance of LBT by country and unlicensed band have been determined, and when performing communication in an unlicensed band according to these regulations, the communication device should perform LBT.

[0071] There are generally two types of LBT, Type 1 and Type 2.

[0072] Figure 5 An LBT type 1 according to an embodiment is shown.

[0073] refer to Figure 5 , LBT Type 1 includes randomly determining the time to monitor whether other peripheral devices are performing transmissions before performing transmissions, and performing transmissions when the channel is idle for a random period of time. The communication device first monitors whether the channel is idle for a fixed time (T d ), and when the channel is idle, determine whether the channel has been idle for a random period of time (N).

[0074] A method to determine T d The method of determining the value of N can be determined differently according to the priority, importance of the service, etc., and there are a total of four different classes. This class is called a channel access priority class (CAPC).

[0075] According to CAPC, the time length T is obtained d =16+m p *9(μs), and obtain N random(0,CW p )*9(μs), where the CW value is from CW min,p Initially, each time a transmission fails, the CW value doubles and has a maximum value of CW max,p .

[0076] For example, if LBT is performed using a CAPC of 3, then T d The length of is 16+3*9=43 μs, and N selects a random value between 0 and 15 for initial transmission. For example, if 7 is selected, N is 7*9=63 μs, and the communication device sends data when the channel is idle for 106 μs.

[0077] [Table 1]

[0078]

[0079]

[0080] In the example above (where 7 is chosen for N), if when determining whether the channel is idle

[0081] (For example, in the case of 4, after passing 3 of 7) it is determined that the channel is occupied by another device (i.e., the received signal strength indication (RSSI) is greater than or equal to a predetermined threshold), the terminal waits until the channel occupation ends, and waits again for T d, determine whether the channel is idle for the remaining time period of 4, and then perform transmission. As shown in Table 1 above, when sending a service with a high priority, the LBT scheme with a low CAPC is used.

[0082] Figure 6 An LBT type 2 according to an embodiment is shown.

[0083] refer to Figure 6 In LBT Type 2, before executing a transmission, the time to monitor whether other peripheral devices are performing transmission is fixed, so when the channel is idle for a fixed period of time, the transmission is performed immediately. Figure 6 As shown, in the LBT type 2 scheme, when a communication device needs to perform transmission, the communication device short (=T f +T s ) within a period of time, and if the channel is determined to be idle, data is sent immediately. When sending a signal with a very high priority, LBT type 2 can be used. Therefore, the above random access preamble ( Figure 4 4-11) and the described PUCCH are signals with high importance and can be transmitted using the LBT type 2 scheme.

[0084] Figure 7 A process between a terminal and a base station when the terminal identifies an uplink LBT problem according to an embodiment is shown.

[0085] refer to Figure 7 , it is assumed that the terminal (or user equipment) 7-01 accesses the base station 7-03 operating in the unlicensed band and is in the RRC connected (RRC_CONNECTED) state. In the RRC connected state, the terminal 7-01 can perform data transmission or reception with the base station 7-03.

[0086] In step 7-11, the terminal 7-01 receives the configuration of parameters related to uplink LBT problem detection from the base station 7-03 via an RRCReconfiguration message or a SIB message.

[0087] In step 7-13, the terminal 7-01 receives uplink resources scheduled from the base station 7-03 via the PDCCH, or may perform uplink transmission for performing random access, PUCCH transmission, data transmission to a configured uplink grant, and the like.

[0088] If data is sent in an unlicensed band, the terminal 7-01 should perform an LBT operation and configure the type of LBT to be performed for each logical channel within the RRC message or each corresponding uplink resource allocation in the PDCCH. The terminal 7-01 can perform LBT based on the configuration of the highest (or lowest) priority among the logical channels to which the sent data belongs.

[0089] If the terminal 7-01 cannot perform transmission due to LBT failure when performing uplink transmission (that is, if a signal is detected due to transmission of another device in the channel, so transmission cannot be performed), in step 7-15, the terminal 7-01 determines whether a predetermined timer is running. If the timer is not running, the terminal 7-01 drives the timer. The length of the timer can be configured according to the RRCReconfiguration or SIB message.

[0090] exist Figure 7 In the example, each time LBT fails in steps 7-17 and 7-19, a predetermined counter is increased, which allows the counter to recognize the severity of the UL LBT problem while the timer is running, and perform additional operations when the counter reaches a value configured by the base station 7-03 according to the RRCReconfiguration or SIB message.

[0091] exist Figure 7 In the example of , while the timer is running, the uplink transmission succeeds in steps 7-21 and 7-23 (by succeeding in LBT). Therefore, before reaching the value configured by the counter, when the uplink transmission succeeds in steps 7-21 and 7-23 for a preset number of times ( Figure 7 When the preset number of times is reached (twice in ), the terminal stops the timer and sets the counter to 0 7-25. The preset number of times can be configured by the base station 7-03. The process determines that smooth data transmission / reception is available because the uplink transmission has become smooth again.

[0092] As another example, when the terminal 7-01 cannot perform transmission due to LBT failure when the terminal 7-01 performs uplink transmission, the terminal 7-01 determines whether the timer is running, and in step 7-27, operates the timer when the timer is not running. Figure 7 In the example, the transmission fails in steps 7-29 and 7-31 due to LBT failure. However, if the failure does not occur a preset number of times (e.g., as configured by base station 7-03) before the timer expires, when the timer expires in step 7-33, terminal 7-01 determines that the uplink LBT problem no longer occurs and sets the counter to 0.

[0093] As another example, when the terminal 7-01 cannot perform transmission due to LBT failure when the terminal 7-01 performs uplink transmission, the terminal determines whether the timer is running, and in step 7-35, operates the timer when the timer is not running. Therefore, if the terminal 7-01 has further attempted to perform uplink transmission, has continuously failed to perform transmission due to UL LBT problems in steps 7-37 to 7-43, and the failure has occurred a preset number of times (for example, four times) as configured by the base station 7-03, then in step 7-45, the terminal 7-01 recognizes that an uplink LBT problem has occurred.

[0094] As another example, if the terminal cannot perform transmission due to LBT failure when the terminal performs uplink transmission, the terminal determines whether the timer is running, and if the timer is not running, the timer is operated. The terminal can restart the timer each time an LBT failure occurs, and if the counter value reaches a value configured by the base station while the timer is running, the terminal recognizes that an uplink LBT problem has occurred and performs an attach process.

[0095] Fig. 8A is a flowchart illustrating an operation sequence of a terminal when an uplink LBT problem is identified according to an embodiment.

[0096] refer to Fig. 8A , after the terminal accesses a base station operating in an unlicensed frequency band and is in an RRC connected state, the terminal can perform data transmission or reception with the base station.

[0097] In step 8a-03, the terminal receives configuration related to uplink LBT problem detection from the base station via an RRCReconfiguration message or a SIB message.

[0098] In step 8a-05, the terminal receives uplink resources scheduled from the base station via the PDCCH, and performs uplink transmission for performing random access, PUCCH transmission, data transmission to a configured uplink grant, and the like.

[0099] If data is sent in an unlicensed band, the terminal should perform an LBT operation and configure the type of LBT to be performed for each logical channel within the RRC message or each corresponding uplink resource allocation in the PDCCH, and the terminal can perform LBT based on the configuration of the highest (or lowest) priority among the logical channels to which the data actually sent belongs.

[0100] In step 8a-07, the terminal determines whether UL LBT has succeeded or failed.

[0101] If a UL LBT failure has occurred in step 8a-07, the terminal determines in step 8a-11 whether a predetermined timer is running.

[0102] If the timer is not running in step 8a-11, the terminal operates the timer in step 8a-13. The length of the timer can be configured according to the RRCReconfiguration or SIB message. In step 8a-15, each time the LBT fails, the terminal increases a predetermined counter. The counter is used to recognize the severity of the UL LBT problem and perform additional operations when the counter reaches a value configured by the base station according to the RRCReconfiguration or SIB message.

[0103] Therefore, while the timer is running, the terminal determines in step 8a-17 whether UL LBT failure has occurred a preset number of times.

[0104] If the UL LBT failure has occurred a preset number of times in step 8a-17, the terminal recognizes that an uplink LBT problem has occurred and performs an attach procedure in step 8a-19.

[0105] Examples of additional procedures include the following.

[0106] In the first example, the MAC layer of the terminal notifies the upper layer (e.g., RRC layer) that a UL LBT problem has occurred. The upper layer of the terminal then declares a radio link failure (RLF). If a radio link failure is declared, the terminal selects a cell with the strongest signal from among neighboring cells and attempts to reestablish a connection (connection reestablishment). If a cell that is the same as the previous cell or a cell that is at the same frequency as the cell used by the previous cell is selected, because the uplink LBT problem may continue to occur, the terminal can assume that the previous cell or the frequency of the previous cell has been prohibited (or the access priority of the cell / frequency is reduced), and a cell can be selected.

[0107] Alternatively, another frequency band of the corresponding cell can be used without announcing RLF as in the above example. The next generation communication system such as NR supports a wideband bandwidth (e.g., 100MHz) for one cell, and the base station can perform communication by configuring only a portion of the bandwidth of one cell bandwidth to the terminal. A portion of this bandwidth is called a bandwidth part (BWP). BWP can be configured for each terminal, and BWP can be configured via an RRCReconfiguration message from the base station. Therefore, if a BWP with a 20MHz width of multiple 100MHz cells is configured in the terminal, the terminal is operating in its specific BWP, and the channel condition of another BWP is good, a scenario of moving to the corresponding channel and performing the operation without announcing RLF can be considered. If the terminal recognizes that the described uplink LBT problem has occurred, the terminal determines the BWP (i.e., the BWP configured with PRACH resources) that allows random access from the BWP configured in the terminal. Therefore, by determining whether the channel is congested, a BWP is selected from the BWPs that allow random access.

[0108] Channel congestion can be determined based on a BWP-specific time occupancy rate in which the signal level of a predetermined time period exceeds a predetermined threshold. If the terminal selects a BWP that allows one random access, the terminal uses the BWP to perform random access. The network may have pre-allocated dedicated resources (e.g., dedicated preambles) for random access in advance, and if dedicated resources are available, the terminal can use the pre-allocated resources to perform random access, otherwise, the terminal uses the described contention-based random access to perform random access. If the terminal performs contention-based random access, the base station may not know why the terminal performs random access, and due to the occurrence of uplink LBT problems, Msg3 can be used to notify the terminal that random access has been performed. This can be notified using a MAC control element (CE) message, and the MAC CE can be 1 byte in size, where only a MAC subheader is present, or a MAC CE accompanied by a payload.

[0109] For a MAC CE in which only a 1-byte size of a MAC subheader is present, a notification that the terminal has performed random access due to the occurrence of an uplink LBT problem can be provided via a logical channel identifier included in the MAC subheader. For a MAC CE accompanied by a payload, the reason why the terminal performs random access can be separately notified via an additional field in the payload, and another reason can also be included in the additional field. For example, the terminal can also be notified that a random access is performed due to a transmission failure caused by a deviation of the communication beam. Therefore, the base station can know that the terminal has performed random access due to an uplink LBT problem, and can further perform operations such as allowing switching to another base station or switching the BWP for an operation to stop using, even for other terminals regarding the BWP in which the terminal used to operate.

[0110] Although the above example assumes a scenario where the terminal operates in the PCell, a scenario where an uplink LBT problem occurs in the SCell can also be considered. In this case, the terminal can report the SCell where the uplink LBT problem has occurred to the base station by using an RRC layer message. The base station can perform operations such as deactivating the SCell or cancelling the configuration of the SCell.

[0111] When the terminal determines in step 8a-07 that the UL LBT has succeeded, the terminal stops the timer and sets the counter to 0 8a-09.

[0112] For example, while the timer is running, the uplink transmission may be successful (by succeeding in LBT). If the uplink transmission succeeds a preset number N (e.g., as configured by the base station), the terminal stops the timer and sets the counter to 0 8a-09. Alternatively, the counter may be reduced by one instead of stopping the timer.

[0113] Figure 8B is a flowchart showing the operation sequence of the terminal in the case where the timer expires

[0114] When the timer expires before the current number of failures occurs in step 8b-21, the terminal determines that uplink LBT no longer occurs and sets the counter to 0 in step 8b-23.

[0115] Fig. 9 A terminal in a wireless communication system according to an embodiment is shown.

[0116] refer to Fig. 9 The terminal includes a radio frequency (RF) processor 9-10, a baseband processor 9-20, a memory 9-30 and a controller 9-40.

[0117] The RF processor 9-10 performs functions for transmitting or receiving signals via a wireless channel, such as frequency band conversion and amplification of the signal. The RF processor 9-10 up-converts the baseband signal provided by the baseband processor 9-20 into an RF band signal, transmits the converted RF band signal through an antenna, and then down-converts the RF band signal received through the antenna into a baseband signal. The RF processor 9-10 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), etc. Although Fig. 9 Only one antenna is shown in the figure, but the terminal may have multiple antennas. The RF processor 9-10 may include multiple RF chains. The RF processor 9-10 may perform beamforming. For beamforming, the RF processor 9-10 may adjust the phase and amplitude of each signal sent or received via multiple antennas or antenna elements.

[0118] The baseband processor 9-20 performs conversion between baseband signals and bit streams according to the physical layer specifications of the system. During data transmission, the baseband processor 9-20 generates complex symbols by encoding and modulating the transmitted bit stream. During data reception, the baseband processor 9-20 reconstructs the received bit stream via demodulation and decoding of the baseband signal provided from the RF processor 9-10. In the OFDM scheme, during data transmission, the baseband processor 9-20 generates complex symbols by encoding and modulating the transmitted bit stream, maps the complex symbols to subcarriers, and then configures OFDM symbols by performing an inverse fast Fourier transform (IFFT) operation and a cyclic prefix (CP) insertion. During data reception, the baseband processor 9-20 divides the baseband signal provided from the RF processor 9-10 into OFDM symbols, reconstructs the signal mapped to the subcarrier via a fast Fourier transform (FFT) operation, and then reconstructs the received bit stream via demodulation and decoding.

[0119] The baseband processor 9-20 and the RF processor 9-10 send and receive signals as described above. Therefore, the baseband processor 9-20 and the RF processor 9-10 can be collectively referred to as a transmitter, a receiver, a transceiver and / or a communication unit. At least one of the baseband processor 9-20 and the RF processor 9-10 may include a plurality of communication modules supporting a plurality of different radio access technologies. At least one of the baseband processor 9-20 and the RF processor 9-10 may include different communication modules to process signals of different frequency bands. Different radio access technologies may include wireless LANs (e.g., IEEE 802.11), cellular networks (e.g., LTE), etc. Different frequency bands may include ultra-high frequency (SHF) bands (e.g., 2.5 GHz and 5 GHz) and millimeter wave bands (e.g., 60 GHz).

[0120] The memory 9-30 stores data, such as default programs, applications, configuration information, etc., for the operation of the terminal. The memory 9-30 can store information related to wireless LAN nodes that perform wireless communication using wireless LAN access technology. The memory 9-30 provides the stored data in response to a request from the controller 9-40.

[0121] The controller 9-40 controls the overall operation of the terminal. The controller 9-40 sends or receives a signal via the baseband processor 9-20 and the RF processor 9-10. The controller 9-40 records and reads data in the memory 9-30. The controller 9-40 may include at least one processor. The controller 9-40 may include a communication processor (CP) configured to perform control for communication and an application processor (AP) configured to control an upper layer (such as an application).

[0122] exist Fig. 9 In the embodiment, the controller 9-40 includes a multi-connection processor 9-42 configured to perform processing for operating in the multi-connection mode. The controller 9-40 can control the terminal to perform Figure 5 The process shown in .

[0123] The controller 9-40 may detect the UL LBT procedure, for example by using the described method, and trigger a random access or instruct the RRC layer to perform an RLF operation.

[0124] The methods according to various embodiments described in the specification of the present disclosure may be implemented by hardware, software, or a combination of hardware and software.

[0125] When the method is implemented by software, a computer-readable storage medium for storing one or more programs (software modules) may be provided. One or more programs stored in the computer-readable storage medium may be configured to be executed by one or more processors in an electronic device. At least one program may include instructions that cause an electronic device to perform a method according to the various embodiments of the present disclosure defined by the attached claims and / or disclosed herein.

[0126] The program (software module or software) can be stored in a non-volatile memory, wherein the non-volatile memory includes random access memory and flash memory, read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), magnetic disk storage device, compact disk ROM (CD-ROM), digital versatile disk (DVD) or other types of optical storage devices or tapes. Alternatively, any combination of some or all of the memories can form a memory storing the program. In addition, multiple such memories may be included in the electronic device.

[0127] In addition, the program can be stored in an attachable storage device, which can access the electronic device through a communication network such as the Internet, an intranet, a LAN, a wide LAN (WLAN), and a storage area network (SAN) or a combination thereof. Such a storage device can access the electronic device via an external port. In addition, a separate storage device on a communication network can access the portable electronic device.

[0128] In the above-mentioned embodiment of the present disclosure, according to the detailed embodiment presented, the elements included in the present disclosure are expressed in the singular or plural. However, for ease of description, the singular form or the plural form is appropriately selected to the presented situation, and the present disclosure is not limited by the elements expressed in the singular or plural form. Therefore, the elements expressed in the plural may also include a single element, or the elements expressed in the singular may also include multiple elements.

[0129] While the invention has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.

Claims

1. A method performed by a terminal in a wireless communication system, the method comprising: receiving listen-before-talk LBT related configuration information, the configuration information comprising first information about a timer for LBT failure detection and second information about a maximum counter value for LBT failure detection; Perform LBT for transfer; In the event that the transfer is not performed, identifying an LBT failure; and Start the timer and increment the counter value, Therein, in the event that the timer expires before the counter value reaches the maximum counter value, the counter value is set to 0.

2. The method according to claim 1, wherein: In the event that a channel associated with the LBT is identified as occupied, transmission is not performed.

3. The method according to claim 1, further comprising: In a case where the counter value is greater than or equal to the maximum counter value before the timer expires, it is identified whether the serving cell on which the LBT is performed is a primary cell or a secondary cell.

4. The method according to claim 1, wherein: The LBT related configuration information is received via a radio resource control RRC reconfiguration message. 5 . The method according to claim 3 , further comprising, in a case where the serving cell is a primary cell, identifying a radio link failure (RLF) by a radio resource control (RRC) layer of the terminal.

6. The method according to claim 5, wherein: For all uplink UL bandwidth parts BWP configured with physical random access channel PRACH resources on the serving cell, LBT failure is identified.

7. The method of claim 6, further comprising performing an RRC re-establishment procedure.

8. The method according to claim 5, further comprising: When the serving cell is the primary cell and LBT failure is not identified for all uplink UL bandwidth parts BWP configured with physical random access channel PRACH resources on the serving cell, switching is performed from the first UL BWP on which LBT failure is identified to the second UL BWP configured with PRACH resources and for which LBT failure is not identified.

9. The method according to claim 8, further comprising: A random access procedure is performed for the second UL BWP.

10. The method according to claim 3, further comprising: In case the serving cell is a secondary cell, a control message associated with LBT failure is sent.

11. A terminal in a wireless communication system, the terminal comprising: Transceiver; and The controller is configured as: receiving, via the transceiver, listen-before-talk LBT related configuration information, the configuration information comprising first information about a timer for LBT failure detection and second information about a maximum counter value for LBT failure detection, Perform LBT for transfer, In the case where the transfer is not performed, the LBT failure is identified, and Start the timer and increment the counter value, Therein, in the event that the timer expires before the counter value reaches the maximum counter value, the counter value is set to 0.

12. The terminal according to claim 11, wherein: In the event that a channel associated with the LBT is identified as occupied, transmission is not performed.

13. The terminal according to claim 11, wherein: The controller is further configured to, in a case where the counter value is greater than or equal to the maximum counter value before the timer expires, identify whether the serving cell on which the LBT is performed is a primary cell or a secondary cell.

14. The terminal according to claim 11, wherein: The LBT related configuration information is received via a radio resource control RRC reconfiguration message.

15. The terminal according to claim 13, wherein: The controller is further configured to, in a case where the serving cell is a primary cell, identify a radio link failure (RLF) by a radio resource control (RRC) layer of the terminal.

16. The terminal according to claim 15, wherein: For all uplink UL bandwidth parts BWP configured with physical random access channel PRACH resources on the serving cell, LBT failure is identified.

17. The terminal according to claim 16, wherein: The controller is further configured to perform an RRC re-establishment procedure.

18. The terminal according to claim 15, wherein: The controller is also configured to: When the serving cell is the primary cell and LBT failure is not identified for all uplink UL bandwidth parts BWP configured with physical random access channel PRACH resources on the serving cell, switching is performed from the first UL BWP on which LBT failure is identified to the second UL BWP configured with PRACH resources and for which LBT failure is not identified.

19. The terminal according to claim 18, wherein: The controller is further configured to perform a random access procedure for the second UL BWP.

20. The terminal according to claim 13, wherein: The controller is further configured to, if the serving cell is a secondary cell, send a control message associated with LBT failure via the transceiver.

Images