Method for processing communication by using multiple paths and apparatus therefor

Abstract

The present disclosure relates to a technique by which a remote terminal connected to a base station transmits / receives data through a direct path and an indirect path by means of a relay terminal. The method in which a remote terminal performs communication through a plurality of paths may comprise the steps of: receiving configuration information for configuring a plurality of paths including a direct path and an indirect path from a base station; applying the configuration information to configure a plurality of paths; and transmitting an RRC message if a radio link failure is detected in at least one of the plurality of paths.

Description

Technical Field

[0001] The present disclosure relates to a technology in which a remote terminal connected to a base station through a relay terminal transmits and receives data through a direct path and an indirect path. Background Art

[0002] 3GPP is discussing and developing sidelink communication that can be used for vehicle-to-vehicle communication. Sidelink (SL) refers to a communication scheme that establishes a direct link between user equipment (UE) to exchange voice or data or other types of information directly between terminals without going through a base station (BS). SL is considered a solution to reduce the burden on base stations due to the rapid increase in data traffic.

[0003] Meanwhile, wireless communication technology includes relay technology, which provides an additional hop during the process of a terminal connecting to a base station. Generally, relay technology has been applied between a terminal and a base station, and research on applying relay technology to side link communication is ongoing.

[0004] The sidelink relay can support UE-to-Network (U2N) relay function, which provides the connection of U2N remote terminals. Both L2 and L3 U2N relay structures can be supported. U2N relay terminals should be in RRC connected state to perform relay of unicast data.

[0005] In the related art, for an L2 U2N remote terminal in an RRC idle / inactive state, a cell selection / reselection process and a relay selection / reselection process can be operated independently. If a suitable cell and a suitable U2N relay terminal are available, the selection of a cell or a U2N relay terminal depends on the implementation of the terminal. Therefore, data transmission by the U2N remote terminal can be performed by selecting one of the following: i) RRC / SRB / DRB connection with a base station in a corresponding cell through a Uu wireless interface, through a direct path (direct path: a type of transmission path from UE to network, in which data is sent between UE and network without side link relay), and ii) RRC / SRB / DRB connection through an indirect path (indirect path: a type of transmission path from UE to network, in which data is forwarded between U2N remote UE and network via U2N relay UE) through a corresponding U2N relay terminal.

[0006] Therefore, wireless reliability and throughput may be reduced compared to when multiple transmission paths are used. Summary of the invention

[0007] Technical issues

[0008] In the above background, the present disclosure provides a technology in which a remote terminal connected to a base station through a relay terminal transmits and receives data through a direct path and an indirect path.

[0009] Technical Solutions

[0010] According to an embodiment, a method of a remote terminal may be provided for performing communication through multiple paths. The method may include receiving configuration information for configuring multiple paths including direct paths and indirect paths from a base station, configuring the multiple paths by applying the configuration information, and sending an RRC message when a radio link failure is detected in at least one of the multiple paths.

[0011] According to another embodiment, a method of a base station for controlling communication through multiple paths of a remote terminal may be provided. The method may include sending an RRC reconfiguration message for configuring an indirect path to a relay terminal providing a connection with the remote terminal, sending configuration information for configuring multiple paths including a direct path and an indirect path in the remote terminal to the relay terminal, and receiving an RRC message when a radio link failure is detected in at least one of the multiple paths in the remote terminal.

[0012] According to another embodiment, a remote terminal for performing communication through multiple paths may be provided. The remote terminal may include a receiver that receives configuration information for configuring multiple paths including a direct path and an indirect path from a base station; a controller that configures the multiple paths by applying the configuration information; and a transmitter that sends an RRC message when a radio link failure is detected in at least one of the multiple paths.

[0013] According to another embodiment, a base station may be provided for controlling communication through multiple paths of a remote terminal, the base station comprising a transmitter that sends an RRC reconfiguration message for configuring an indirect path to a relay terminal that provides a connection with the remote terminal, and sends configuration information for configuring multiple paths including a direct path and an indirect path in the remote terminal to the relay terminal; and a receiver that receives the RRC message when a radio link failure is detected in at least one of the multiple paths in the remote terminal.

[0014] Beneficial Effects

[0015] According to an embodiment, a remote terminal connected to a base station through a relay terminal can transmit and receive data through both a direct path and an indirect path. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a view schematically showing the structure of an NR wireless communication system.

[0017] Figure 2 is a view showing the frame structure in the NR system.

[0018] Figure 3 is a diagram showing a resource grid supported by a radio access technology.

[0019] Figure 4 is a diagram showing bandwidth portions supported by radio access technologies.

[0020] Figure 5 is a view exemplarily showing a synchronization signal block in a radio access technology.

[0021] Figure 6 is a view showing a random access procedure in radio access technology.

[0022] Figure 7 is a view showing CORESET.

[0023] Figure 8 is a view showing a control plane protocol structure for L2 UE to network relay according to an embodiment.

[0024] Fig. 9 is a flowchart illustrating the operation of the remote terminal according to the embodiment.

[0025] Fig.10 is a flowchart for describing the operation of a base station according to an embodiment.

[0026] Fig.11 is a diagram showing an example of split radio bearer / SRB / DRB configuration through multiple paths.

[0027] Fig.12 is a block diagram illustrating a remote terminal according to an embodiment.

[0028] Fig.13 is a block diagram showing a base station according to an embodiment. DETAILED DESCRIPTION

[0029] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. When assigning reference numerals to the components of each of the accompanying drawings, the same numerals may be assigned to the components even when the same components are shown on different drawings. When it is determined that the subject matter including the present disclosure will make it unclear, the detailed description of known technologies or functions may be skipped. The terms "include" and / or "include", "have" and / or "have" or "include" and / or "include" used in this specification are intended to specify the presence of the features, regions, integers, steps, operations, elements, components and / or groups thereof, but do not exclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components and / or groups thereof. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "the" used herein are also intended to include plural forms.

[0030] When describing the components of the present invention, terms such as "first", "second", "A", "B", "(a)", and "(b)" may be used. These terms are provided only to distinguish one component from another, and the nature, order or number of the components are not limited by these terms.

[0031] When describing the positional relationship between components, when two or more components are described as being “connected,” “coupled,” or “linked,” the two or more components may be directly “connected,” “coupled,” or “linked,” or there may be intermediate components. In this case, the intermediate components may be included in one or more of the two or more components that are “connected,” “coupled,” or “linked” to each other.

[0032] When such terms as "after", "next", "before" and similar expressions are used to describe time-flow relationships related to components, methods of operation and methods of manufacture, they may include non-continuous relationships unless the terms "immediately" or "directly" are used.

[0033] When a component is specified by a value or its corresponding information (eg, a level), the value or the corresponding information may be interpreted as including tolerances caused by various factors (eg, process factors, internal or external influences, or noise).

[0034] In the present disclosure, a 'wireless communication system' refers to a system that provides various communication services such as voice and data packets using radio resources, and may include a terminal, a base station, or a core network.

[0035] The present embodiment disclosed below can be applied to wireless communication systems using various radio access technologies. For example, the present embodiment can be applied to various radio access technologies, such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA) or non-orthogonal multiple access (NOMA). In addition, radio access technology can refer not only to a specific access technology, but also to each generation of communication technology established by various communication organizations, such as 3GPP (3rd Generation Partnership Project), 3GPP2, Wi-Fi, Bluetooth, IEEE (Institute of Electrical and Electronics Engineers) and ITU (International Telecommunication Union). For example, CDMA can be implemented as a radio technology, such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA can be implemented as GSM (Global System for Mobile Communications) / GPRS (General Packet Radio Service) / EDGE (Enhanced Data Rates for GSM Evolution). OFDMA can be implemented with wireless technologies such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, Evolved UTRA (E-UTRA, evolved UTRA), etc. IEEE 802.16m is an evolution of IEEE802.16e and provides backward compatibility with systems based on IEEE 802.16e. UTRA is part of UMTS (Universal Mobile Telecommunications System). 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) is part of E-UMTS (Evolved UMTS) using Evolved-UMTS Terrestrial Radio Access (E-UTRA, evolved-UMTS terrestrial radio access), and adopts OFDMA for downlink and SC-FDMA for uplink. Therefore, this embodiment can be applied to currently disclosed or commercialized radio access technologies, and can also be applied to radio access technologies that are currently being developed or to be developed in the future.

[0036] Meanwhile, in the present disclosure, "terminal" is a comprehensive concept, which refers to a device including a wireless communication module that communicates with a base station in a wireless communication system, and should be interpreted as including not only UE (user equipment) in, for example, WCDMA, LTE, NR, HSPA, and IMT-2020 (5G or new radio), but also mobile stations (MS, mobilestation), user terminals (UT, user terminals), subscriber stations (SS, subscriber station) or wireless devices in GSM. In addition, depending on the type of use, the terminal may be a user portable device (such as a smartphone), and in a V2X communication system, the terminal may refer to a vehicle or a device including a wireless communication module in a vehicle. In addition, in the case of a machine type communication system, the terminal may refer to a machine type communication (MTC, machine type communication) terminal, a machine to machine (M2M, machine-to-machine) terminal, or an ultra reliable low latency communication (URLLC, ultra reliable low latency communication) terminal equipped with a communication module to perform machine type communication.

[0037] In the present disclosure, a "base station" or a "cell" refers to a terminal that communicates with a terminal according to a network, and conceptually includes various coverage areas, such as a node B, an evolved node B (eNB), a gNode-B (gNB), a low power node (LPN), a sector, a site, various types of antennas, a base transceiver system (BTS), an access point, a point (e.g., a transmission point, a reception point, or a transmission / reception point), a relay node, a macro cell, a macro cell, a micro cell, a pico cell, a femto cell, a remote radio head (RRH), a radio unit (RU), or a small cell. In addition, a "cell" may refer to a cell including a bandwidth part (BWP) in the frequency domain. For example, a "serving cell" may refer to an activated BWP of a terminal.

[0038] Since there is a base station that controls one or more of the various cells listed above, the base station can be interpreted as two meanings. The base station can be 1) a device itself that provides a giant cell, a macro cell, a micro cell, a pico cell, a femto cell or a small cell related to a radio area, or 2) the radio area itself. In 1), all devices that provide a predetermined radio area and are controlled by the same entity or interact via cooperative interaction to configure the radio area are represented as base stations. An embodiment of a base station is a transmission / reception point, a transmission point or a reception point depending on the scheme for configuring the radio area. In 2), the radio area itself that receives or sends a signal from the perspective of a terminal or a neighboring base station can be a base station.

[0039] In the present disclosure, a "cell" may refer to the coverage of a signal transmitted from a transmission / reception point, a component carrier having coverage of a signal transmitted from a transmission / reception point (transmission point or transmission / reception point), or the transmission / reception point itself.

[0040] An uplink (UL) refers to a scheme for sending data from a terminal to a base station or for receiving data at a terminal from a base station, and a downlink (DL) refers to a scheme for sending data from a base station to a terminal and / or receiving data at a base station from a terminal. A downlink may refer to a communication or communication path from a plurality of transmission / reception points to a terminal, and an uplink may refer to a communication or communication path from a terminal to a plurality of transmission / reception points. In this case, in the downlink, a transmitter may be part of a plurality of transmission / reception points, and a receiver may be part of a terminal. In addition, in the uplink, a transmitter may be part of a terminal, and a receiver may be part of a plurality of transmission / reception points.

[0041] The uplink and downlink configure control channels (such as physical downlink control channel (PDCCH) or physical uplink control channel (PUCCH)) and send and receive control information through the control channels. The uplink and downlink configure data channels (such as physical downlink shared channel (PDSCH) or physical uplink shared channel (PUSCH)) to send and receive data. In the following, the context of sending or receiving signals through channels (such as PUCCH, PUSCH, PDCCH and PDSCH) is expressed as "sending or receiving PUCCH, PUSCH, PDCCH and PDSCH".

[0042] Although, for the sake of clarity, the technical spirit is mainly described with respect to the 3GPP LTE / LTE-A / New Radio (NR) communication system, the technical features are not limited to this communication system.

[0043] After studying fourth-generation (4G) communication technologies, 3GPP developed fifth-generation (5G) communication technologies to meet the requirements of ITU-R for next-generation radio access technologies. Specifically, 3GPP developed new NR communication technologies separate from LTE-A Pro and 4G communication technologies as 5G communication technologies, which have enhanced LTE-Advanced technologies to meet the requirements of ITU-R. LTE-A Pro and NR both refer to 5G communication technologies. Hereinafter, unless specified as a specific communication technology, 5G communication technologies will be described focusing on NR.

[0044] The operation scenarios in NR define various operation scenarios by adding considerations for satellites, automobiles, and new vertical domains to the existing 4G LTE scenarios. From the perspective of services, NR supports i) the enhanced mobile broadband (eMBB) scenario, ii) the massive machine communication (mMTC) scenario characterized by high terminal density, wide deployment, low data rate, and asynchronous access, and iii) the ultra-reliability and low-latency (URLLC) scenario, which requires high reliability and also supports high-speed mobility.

[0045] To meet these scenarios, NR introduces a wireless communication system that employs new waveform and frame structure technologies, low-latency technologies, millimeter-wave (mmWave) support technologies, and forward compatibility provision technologies. In particular, the NR system proposes various technical changes focusing on flexibility to provide forward compatibility. The main technical features of NR will be described hereinafter with reference to the accompanying drawings.

[0046] <Overview of the NR System>

[0047] Figure 1 is a view schematically showing the structure of the NR system.

[0048] Refer to Figure 1, the NR system is divided into a 5G core network (5GC) and an NR-RAN part. The next generation radio access network (NG-RAN) includes gNBs and ng-eNBs, which provide user plane (SDAP / PDCP / RLC / MAC / PHY) and UE (user equipment) control plane (RRC) protocol terminations. The gNBs or the gNBs and ng-eNBs are interconnected via the Xn interface. The gNBs and ng-eNBs are connected to the 5G core network (5GC) via the NG interface. The 5GC may include i) an access and mobility management function (AMF) responsible for the control plane, including terminal access and mobility control functions, and ii) a user plane function (UPF) that processes user data control functions. NR supports frequency bands below 6 GHz (Frequency Range 1 (FR1)) and above 6 GHz (Frequency Range 2 (FR2)).

[0049] A gNB refers to a base station that provides NR user plane and control plane protocol terminations for terminals, and an ng-eNB refers to a base station that provides E-UTRA user plane and control plane protocol terminations for terminals. In the present disclosure, a base station should be understood to include gNBs and ng-eNBs and may be used to separately represent a gNB or an ng-eNB when necessary.

[0050] <NR Waveform, Numerology, and Frame Structure>

[0051] NR uses the CP-OFDM waveform with a cyclic prefix for downlink transmission and uses CP-OFDM or DFT-s-OFDM for uplink transmission. OFDM technology is easy to integrate with multiple input multiple output (MIMO) and provides advantages such as high spectral efficiency and the ability to use low-complexity receivers.

[0052] At the same time, since the above three scenarios in NR have different requirements for data rate, latency, and coverage, it is necessary to effectively meet the requirements of each scenario through the frequency bands that make up any NR system. To achieve this, techniques based on multiple different numerologies have been proposed for the effective reuse of radio resources.

[0053] Specifically, the NR transmission parameter set is determined based on the subcarrier spacing and the cyclic prefix (CP). As shown in Table 1 below, it changes exponentially, where the exponent value 2 is used as μ relative to 15kHz.

[0054] [Table 1]

[0055] μ Subcarrier spacing Cyclic prefix Supporting Data Support synchronization 0 15 normal yes yes 1 30 normal yes yes 2 60 Normal, Extended yes no 3 120 normal yes yes 4 240 normal no yes

[0056] As shown in Table 1 above, NR parameter sets can be divided into five types according to the subcarrier spacing. This is different from the fixed subcarrier spacing of 15kHz in LTE of 4G communication technology. Specifically, in NR, the subcarrier spacing for data transmission is 15, 30, 60 and 120kHz, and the subcarrier spacing for synchronization signal transmission is 15, 30, 120 and 240kHz. In addition, the extended CP is only applied to 60kHz subcarrier spacing. At the same time, as part of the frame structure in NR, a frame of length 10ms is defined, which consists of 10 subframes of equal length (each 1ms). Each frame can be divided into two half frames of 5ms, each half frame can include 5 subframes. For 15kHz subcarrier spacing, a subframe consists of a time slot, and each time slot consists of 14 OFDM symbols.

[0057] Figure 2 is a view showing the frame structure in the NR system.

[0058] Reference Figure 2 , in the case of normal CP, the time slot is fixedly composed of 14 OFDM symbols, but the length of the time slot in the time domain can vary according to the subcarrier spacing. For example, for a parameter set with a 15kHz subcarrier spacing, the length of the time slot is the same as the length of the subframe, which is 1ms. In contrast, for a parameter set with a 30kHz subcarrier spacing, the time slot consists of 14 OFDM symbols, but one subframe may include two time slots with a length of 0.5ms. In other words, subframes and frames are defined to have a fixed length, and the time slot is defined by the number of symbols, and the time length can vary according to the subcarrier spacing.

[0059] At the same time, NR defines the time slot as the basic unit of scheduling, and in order to reduce the transmission delay of the radio section, mini time slots (or also called sub-time slots or non-time slot based scheduling) are adopted. When a wide subcarrier spacing is used, the length of a time slot is inversely proportional to the subcarrier spacing, thereby allowing the transmission delay in the radio section to be reduced. Mini time slots are designed to effectively support URLLC scenarios and enable scheduling in units of 2, 4 or 7 symbols.

[0060] In addition, different from LTE, NR defines uplink and downlink resource allocation at the symbol level within a time slot. To reduce HARQ latency, a time slot structure is introduced to enable the direct transmission of HARQ ACK / NACK within the transmission time slot. In the description, this time slot structure is referred to as a self - contained structure.

[0061] NR is designed to support a total of 256 time slots, of which 62 time slot formats are used in 3GPP Rel - 15. In addition, a common frame structure for FDD or TDD frames is supported through various combinations of time slots. For example, NR supports i) a time slot structure where all symbols in the time slot are configured as downlink, ii) a time slot structure where all symbols are configured as uplink, and iii) a time slot structure where downlink symbols and uplink symbols are combined. In addition, NR supports distributed data transmission at both ends of one or more time slots and in the middle of the scheduled data transmission. Therefore, the base station can use a slot format indicator (SFI) to notify the terminal whether a given time slot is a downlink time slot, an uplink time slot, or a flexible time slot. The base station can indicate the time slot format by indicating (e.g., providing) the index of a table configured by UE - specific RRC signaling via SFI, and can indicate it dynamically through downlink control information (DCI), or indicate it statically or semi - statically through RRC.

[0062] <NR Physical Resources>

[0063] Regarding the physical resources in NR, factors such as antenna ports, resource grids, resource elements, resource blocks, and bandwidth parts are considered.

[0064] Antenna ports are defined such that the channel carried by a symbol on an antenna port can be inferred from the channel carried by another symbol on the same antenna port. When the large - scale characteristics of the channel carrying a symbol on one antenna port can be inferred from the channels carrying symbols on different antenna ports, the two antenna ports can be considered to have a QC / QCL (quasi - co - located) relationship. Here, the large - scale characteristics include one or more of delay spread, Doppler spread, frequency shift, average received power, and reception timing.

[0065] Figure 3 is a view showing the resource grid supported by a radio access technology.

[0066] Refer to Figure 3 Since NR supports multiple parameter sets on the same carrier, the resource grid can be defined for each parameter set. In addition, the resource grid can also vary according to antenna ports, sub - carrier spacing, or transmission direction.

[0067] A resource block consists of 12 subcarriers and is defined only in the frequency domain. In addition, a resource element consists of one OFDM symbol and one subcarrier. Therefore, as Figure 3 shown, the size of a resource block can vary according to the subcarrier spacing. In addition, in NR, "Point A" is defined as a common reference point for the resource block grid, common resource blocks, and virtual resource blocks.

[0068] Figure 4 is a view showing the bandwidth part supported by the radio access technology.

[0069] In NR, different from LTE where the carrier bandwidth is fixed at 20 MHz, the maximum carrier bandwidth ranges from 50 MHz to 400 MHz, depending on the subcarrier spacing. Therefore, it is not assumed that all terminals utilize all available carrier bandwidths. Thus, in NR, as Figure 4 shown, a bandwidth part (BWP) can be specified within the carrier bandwidth and allocated for use by a terminal. In addition, the bandwidth part is associated with a parameter set, which consists of a subset of consecutive common resource blocks and can be dynamically activated as time progresses. Up to four bandwidth parts (BWPs) can be configured for each of the uplink and downlink in a terminal. Data is sent / received using the bandwidth part (BWP) activated at a given time.

[0070] For paired spectra, the uplink and downlink bandwidth parts are configured independently, while for unpaired spectra, the uplink and downlink bandwidth parts are paired to share the center frequency, thus preventing unnecessary frequency retuning between downlink and uplink operations.

[0071] <NR Initial Access>

[0072] In NR, a terminal performs a cell search and random access procedure to connect to a base station and perform communication.

[0073] Cell search is a process in which a terminal synchronizes with a cell of a base station using a synchronization signal block (SSB) sent by the base station, retrieves the physical layer cell ID, and obtains system information.

[0074] Figure 5 is a view exemplarily showing the synchronization signal block in the radio access technology.

[0075] Refer to Figure 5The SSB consists of a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) (each occupying 1 symbol and 127 subcarriers respectively) and a PBCH spanning 3 OFDM symbols and 240 subcarriers.

[0076] The terminal monitors the SSB in the time domain and the frequency domain and receives the SSB.

[0077] SSB can be transmitted up to 64 times within 5ms. Multiple SSBs are transmitted using different transmission beams within 5ms, and it is assumed that SSB is transmitted once every 20ms period based on the specific beam used for transmission, and the terminal performs detection. As the frequency band increases, the number of beams available for SSB transmission within 5ms can increase. For example, up to 4 SSB beams can be transmitted at 3GHz, up to 8 different beams can be used to transmit SSB in the 3-6GHz frequency band, and up to 64 different beams can be used to transmit SSB in the 6GHz or higher frequency band.

[0078] Two SSBs are included in one slot, and the starting symbol position and the number of repetitions within the slot are determined based on the subcarrier spacing, as described below.

[0079] At the same time, unlike the SS of typical LTE, SSB is not sent at the center frequency of the carrier bandwidth. Instead, SSB can be sent at a location other than the center of the system frequency band, and multiple SSBs can be sent in the frequency domain when wideband operation is supported. Therefore, the terminal monitors SSB using a synchronization raster, which indicates a candidate frequency position for monitoring SSB. Carrier raster and synchronization raster are newly defined in NR, which provide center frequency position information for initial access. In addition, the synchronization raster is characterized by a wider frequency interval than the carrier raster, enabling the terminal to perform faster SSB search.

[0080] The terminal can obtain the master information block (MIB) through the PBCH of the SSB. The master information block (MIB) includes the minimum information required for the terminal to receive the remaining system information (remaining minimum system information (RMSI)) broadcast by the network. In addition, the PBCH may include information about the position of the first DM-RS symbol in the time domain, information required for the terminal to monitor SIB1 (for example, SIB1 parameter set information, information related to SIB1 CORESET, search space information, PDCCH-related parameter information, etc.), offset information between common resource blocks and SSBs (the absolute position of SSBs within the carrier is sent through SIB1), and similar information. Here, the SIB1 parameter set information is also applied to some messages used in the random access process that enables the terminal to access the base station after completing the cell search process. For example, parameter set information about SIB1 can be applied to at least one of messages 1 to 4 of the random access process.

[0081] The above-mentioned RMSI may refer to system information block 1 (SIB1, systeminformation block 1). SIB1 is broadcast periodically (for example, every 160ms) in the cell. SIB1 includes information required for the terminal to perform the initial random access process and is periodically sent through the PDSCH. In order to receive SIB1, the terminal must first obtain the parameter set information associated with the SIB1 transmission and the control resource set (CORESET) information for SIB1 scheduling through the PBCH. The terminal uses the SI-RNTI in the CORESET to identify the scheduling information of SIB1 and obtains SIB1 from the PDSCH according to the scheduling information. In addition to SIB1, the remaining SIBs may be sent periodically or upon request of the terminal.

[0082] Figure 6 : is a diagram showing a random access procedure in a radio access technology to which the present embodiment can be applied.

[0083] Reference Figure 6 , if the cell search is successfully completed, the terminal sends a random access preamble to the base station to initiate random access. The random access preamble is sent through PRACH. Specifically, the random access preamble is sent to the base station through PRACH consisting of continuous radio resources in a specific time slot that is repeated periodically. Generally, when the terminal initially accesses a cell, a contention-based random access procedure is performed, and when performing random access for beam failure recovery (BFR, beam failure recovery), a non-contention-based random access procedure is performed.

[0084] The terminal receives a random access response to the random access preamble sent. The random access response may include a random access preamble identifier (ID, identifier), uplink radio resources (UL authorization), a temporary cell-radio network temporary identifier (C-RNTI, cell-radio network temporary identifier) ​​and a time alignment command (TAC, time alignment command). Since a random access response may include random access response information of multiple terminals, a random access preamble identifier may be included to indicate which terminal the included UL authorization, temporary C-RNTI and TAC apply to. The random access preamble identifier may be an identifier of a random access preamble received by a base station. TAC may be included as information for the terminal to adjust uplink synchronization. The random access response may be indicated by a random access identifier (specifically, a random access-radio network temporary identifier (RA-RNTI, random access-radio network temporary identifier)) on a PDCCH.

[0085] After receiving a valid random access response, the terminal processes the information included in the random access response and performs scheduled transmission to the base station. For example, the terminal applies the TAC and stores the temporary C-RNTI. In addition, the terminal uses the UL grant to send the data stored in its buffer or the newly generated data to the base station. In this case, information that can identify the terminal should be included.

[0086] Finally, the terminal receives a downlink message for contention resolution.

[0087] <NR CORESET>

[0088] In NR, the downlink control channel is sent in a control resource set (CORESET) of length 1 to 3 symbols and carries uplink / downlink scheduling information, slot format index (SFI), transmit power control (TPC) information and other related information.

[0089] Therefore, NR introduces the concept of CORESET to ensure the flexibility of the system. The control resource set (CORESET) refers to the time-frequency resources used for downlink control signals. The terminal can use one or more search spaces in the CORESET time-frequency resources to decode the control channel candidates. A quasi co-location (QCL) assumption for each CORESET has been defined, which is used to indicate not only the characteristics of the simulated beam direction, but also the delay spread, Doppler spread, Doppler shift and average delay, all of which are assumed by typical QCL.

[0090] Figure 7 is a view showing CORESET.

[0091] Reference Figure 7 , a CORESET can exist in various forms within the carrier bandwidth and within a time slot. In the time domain, a CORESET can consist of up to 3 OFDM symbols. In addition, a CORESET is defined as a multiple of up to 6 resource blocks of the carrier bandwidth in the frequency domain.

[0092] The first CORESET is indicated as part of the initial bandwidth portion configuration through the MIB to enable the terminal to receive additional configuration and system information from the network. After establishing a connection with the base station, the terminal can receive and configure one or more CORESET information through RRC signaling.

[0093] As used herein, terms such as frequency, frame, subframe, resource, resource block, area, band, subband, control channel, data channel, synchronization signal, various reference signals, various signals, and various messages related to new radio (NR) may be interpreted with various meanings that are currently used or may be defined in the future.

[0094] Sidelink Relay

[0095] Sidelink relay has been introduced to support UE to Network (U2N) relay functionality, which provides connectivity to U2N remote terminals. Both L2 and L3 U2N relay structures can be supported. U2N relay terminals should be in RRC connected state to perform relaying of unicast data.

[0096] L2 U2N relay operation supports the following RRC state combinations:

[0097] - The U2N relay terminal and the U2N remote terminal should be in RRC connected state to send and receive relayed unicast data.

[0098] - A U2N relay user can be in RRC idle, RRC inactive or RRC connected state as long as all U2N remote terminals connected to the U2N relay terminal are in RRC inactive or RRC idle state.

[0099] Figure 8 is a diagram showing a control plane protocol structure for L2 UE to network relay according to an embodiment.

[0100] Reference Figure 8 , the remote terminal can be connected to the base station through the relay terminal. Between the remote terminal and the relay terminal, the physical, MAC and RLC channels can be connected through the PC5 interface. The relay terminal can be connected to the base station via the Uu interface. In addition, the remote terminal and the base station can be connected through the Uu interface at the PDCP and RRC layers.

[0101] In the related art, for an L2 U2N remote terminal in an RRC idle / inactive state, a cell selection / reselection process and a relay selection / reselection process can be operated independently. If a suitable cell and a suitable U2N relay terminal are available, the selection of a cell or a U2N relay terminal depends on the terminal. Therefore, data transmission by a U2N remote terminal can be performed by selecting one of the following: i) RRC / SRB / DRB connection with a base station in a corresponding cell through a Uu wireless interface, through a direct path (direct path: a type of transmission path from UE to network, in which data is sent between UE and network without side link relay), and ii) RRC / SRB / DRB connection through an indirect path (indirect path: a type of transmission path from UE to network, in which data is forwarded between U2N remote UE and network via U2N relay UE.) through a corresponding U2N relay terminal. Therefore, wireless reliability and throughput may be reduced compared to when multiple transmission paths are used. However, there is no specific method for using direct and indirect paths simultaneously for remote terminals.

[0102] In typical sidelink relay technologies, a remote terminal can select a direct path or an indirect path to send and receive data, which may result in reduced throughput and wireless reliability. However, there is no specific technology for remote terminals to use both direct and indirect paths at the same time.

[0103] As a solution to the above problems, the present disclosure proposes a method and device for a remote terminal to simultaneously send and receive data using a direct path and an indirect path, and also proposes a method for handling a radio link failure when it occurs in this case.

[0104] The following describes a data transmission / reception method and a radio link failure handling method based on 5GS / NR technology. However, this is for ease of description, and the present embodiment can be applied to any system / radio access technology (e.g., LTE, 6G). The embodiments described in the present disclosure include information elements specified in the NR / 5GS standard (e.g., TS38.321 as a MAC standard, TS 38.331 as an NR RRC standard, etc.) and operation contents. Although the present disclosure does not include details about terminal operations related to the definition of corresponding information elements, the corresponding contents set forth in the standards of known technologies may be incorporated or included in the present embodiment.

[0105] The following embodiments may be applied to side link communications performed between NR terminals and NR terminals through NR / LTE base stations. The following embodiments may also be applied to side link communications performed between NR terminals and LTE terminals (or terminals between any RAT) through NR / LTE base stations. In addition, the following embodiments may also be applied to side link communications performed between LTE terminals and LTE terminals through NR / LTE base stations. In addition, the following embodiments may also be applied to side link communications performed between LTE terminals and LTE terminals through LTE base stations (or base stations between any RAT). In other words, this embodiment may be applied regardless of the type of side link communication configuration.

[0106] At the same time, any function described below is defined as a single terminal capability (UE radio capability or UE core network capability), and can be sent by the terminal to the base station / core network entity (e.g., AMF / SMF) / corresponding terminal through corresponding signaling. Alternatively, any function can be combined / merged, which is defined as the corresponding terminal capability, and then sent by the terminal to the base station / core network entity / corresponding terminal through corresponding signaling. The base station can send / indicate information about the corresponding function / function combination that allows / supports / configured for any function or function combination described below to the terminal through an RRC message. For example, the corresponding RRC message can be indicated to the terminal before, after, or at the same time as the corresponding function / function combination is configured / applied. The RRC message can be broadcast through system information. Alternatively, the corresponding indication information can be delivered to the terminal through a dedicated RRC message or via the side link BCCH / DCCH.

[0107] The functions described below can be performed individually and independently. In addition, the functions described below can be combined / merged arbitrarily, and it is obvious that they are also included in the scope of this embodiment. For example, one or more functions can be applied simultaneously.

[0108] In the present disclosure, a remote terminal may refer to a terminal that is connected to a base station through a relay terminal to perform communication. A relay terminal refers to a terminal that performs a function of associating a remote terminal with a base station. A remote terminal may be associated with a base station through a direct path and an indirect path. Therefore, in the present disclosure, "remote terminal" and "relay terminal" refer to terms that provide a terminal with a corresponding function, but the present disclosure is not limited thereto. The operation of a remote terminal and a base station according to the present embodiment is described below with reference to the accompanying drawings.

[0109] Fig. 9 is a flowchart illustrating the operation of the remote terminal according to the embodiment.

[0110] Reference Fig. 9 , a remote terminal that performs communication through a plurality of paths may perform a step of receiving configuration information for configuring a plurality of paths including a direct path and an indirect path from a base station (S910).

[0111] According to an embodiment, the remote terminal may receive configuration information for configuring multiple paths including a direct path to the base station and an indirect path through a relay terminal. The configuration information may be received from the base station through higher layer signaling. For example, the configuration information may be received through an RRC message. As another example, the configuration information may be received through a relay terminal.

[0112] The configuration information may include at least one of the following: direct path addition configuration information, indirect path addition configuration message, direct path RLC bearer configuration message, indirect path RLC bearer configuration information, bearer mapping configuration information, direct path radio bearer configuration information, indirect path radio bearer configuration information, separate signaling radio bearer (SRB, signaling radio bearer) configuration information, separate data radio bearer (DRB, data radio bearer) configuration information and L2 relay terminal identification information. According to an embodiment, the configuration information may include direct path addition configuration information for additionally configuring a direct path in a remote terminal. In addition, the configuration information may include indirect path addition configuration information for additionally configuring an indirect path in a remote terminal. In addition, the configuration information may include direct path RLC bearer configuration information and / or indirect path RLC bearer configuration information for configuring a path for each bearer. Alternatively, the configuration information may include bearer mapping configuration information for mapping bearers and paths. In addition, the configuration information may include at least one of the following: direct path radio bearer configuration information, indirect path radio bearer configuration information, separate SRB configuration information and separate DRB configuration information. The configuration information may include L2 relay terminal identification information connected to the remote terminal.

[0113] The remote terminal may perform a step of configuring a plurality of paths by applying the configuration information (S920).

[0114] According to an embodiment, if the remote terminal receives configuration information from the base station, the remote terminal can configure multiple paths in the terminal based on the corresponding configuration information. For example, the remote terminal can configure the main path of the separate signaling radio bearer (SRB) as a direct path. As another example, the remote terminal can configure an indirect path by establishing a PC5 RRC connection with the relay terminal.

[0115] The remote terminal may be configured by adding a direct path and / or an indirect path using the information included in the configuration information. Alternatively, the remote terminal may configure a radio bearer indicated by the configuration information in the terminal to control communication using a direct path and / or an indirect path.

[0116] The remote terminal can perform communication with the base station through multiple configured paths. However, during communication, communication limitations may occur due to various factors. For example, a communication failure condition may be detected, such as a radio link failure.

[0117] If a radio link failure is detected in at least one of the plurality of paths, the remote terminal may perform the step of transmitting an RRC message (S930).

[0118] According to an embodiment, the remote terminal may monitor whether a radio link failure occurs in a plurality of paths. If a radio link failure is detected in one or more of the plurality of paths, the remote terminal may send information about the failure through an RRC message indicating the failure.

[0119] For example, when a path in which a radio link failure is detected is a direct path, the RRC message may be transmitted as a path failure report through an indirect path.

[0120] As another example, when a path in which a radio link failure is detected is an indirect path, an RRC message may be transmitted as a path failure report through a direct path.

[0121] According to an embodiment, the radio link failure detected on the indirect path may be due to a side link failure or a radio link failure between the relay terminal and the base station on the indirect path. In other words, when the side link failure is detected, a communication problem occurs between the remote terminal and the relay terminal, which causes the radio link failure to be detected on the indirect path. Alternatively, if a radio link failure occurs between the relay terminal and the base station, the remote terminal may detect the radio link failure on the indirect path. In this case, the radio link failure between the relay terminal and the base station may be reported.

[0122] According to another embodiment, if a radio link failure is detected in both the direct path and the indirect path, the remote terminal may perform a cell selection operation or a relay selection operation according to the RRC reconfiguration process. In addition, if a radio link failure is detected in both the direct path and the indirect path, the remote terminal may send an RRC reconfiguration request message to the base station. The cell selection or relay selection operation may be performed before or after the transmission of the RRC reconfiguration request message. Alternatively, the transmission of the RRC reconfiguration request message may be performed as part of the cell selection and relay selection operations.

[0123] Meanwhile, the RRC message transmitted through the path failure report may include the failure cause information.Alternatively, the RRC message may include information on the radio bearer in which the radio link failure is detected, failure type information or other relevant details.

[0124] Meanwhile, before step S910, the base station may also send an RRC reconfiguration message for indirect path configuration to the relay terminal providing a connection between the remote terminal and the base station.

[0125] According to the above-described embodiments, when a radio link failure is detected, a remote terminal that performs communications through a plurality of different paths of a direct path and an indirect path can take quick action to prevent degradation of a communication context.

[0126] Fig.10 is a flowchart for describing the operation of a base station according to an embodiment.

[0127] Reference Fig.10 , a base station controlling communication through a plurality of paths of a remote terminal may perform a step (S1010) of sending an RRC reconfiguration message for indirect path configuration to a relay terminal providing a connection with the remote terminal.

[0128] According to an embodiment, the base station may send an RRC reconfiguration message for configuring an indirect path for the remote terminal to the relay terminal. Therefore, the relay terminal may configure an indirect path with the indicated remote terminal to transmit the data of the remote terminal to the base station. In addition, the data received by the remote terminal from the base station may be transmitted to the remote terminal.

[0129] However, step S1010 may be performed only when an indirect path is added to the remote terminal. In other words, in the case where the remote terminal and the relay terminal configure an indirect path, if a direct path is added to the remote terminal, step S1020 may be performed without step S1010. Therefore, step S1010 may be optionally performed only when necessary.

[0130] The base station may perform a step of transmitting configuration information for configuring a plurality of paths including a direct path and an indirect path to the remote terminal (S1020).

[0131] According to an embodiment, the base station may send configuration information for configuring multiple paths, the multiple paths including a direct path to the remote terminal and an indirect path through a relay terminal. For example, the configuration information may be sent from the base station via higher layer signaling. For example, the configuration information may be sent via an RRC message. As another example, the configuration information may be transmitted to the remote terminal via a relay terminal.

[0132] The configuration information may include at least one of the following: i) direct path addition configuration information, ii) indirect path addition configuration information, iii) direct path RLC bearer configuration information, iv) indirect path RLC bearer configuration information, v) bearer mapping configuration information, vi) direct path radio bearer configuration information, vii) indirect path radio bearer configuration information, viii) separate signaling radio bearer (SRB) configuration information, ix) separate data radio bearer (DRB) configuration information, and x) L2 relay terminal identification information. For example, the configuration information may include direct path addition configuration information for additionally configuring a direct path in a remote terminal. In addition, the configuration information may include indirect path addition configuration information for additionally configuring an indirect path in a remote terminal. In addition, the configuration information may include direct path RLC bearer configuration information and / or indirect path RLC bearer configuration information for configuring a path for each bearer. Alternatively, the configuration information may include bearer mapping configuration information for mapping bearers and paths. In addition, the configuration information may include at least one of the following: a) direct path radio bearer configuration information, b) indirect path radio bearer configuration information, c) separate SRB configuration information, and d) separate DRB configuration information. The configuration information may include identification information of an L2 relay terminal connected to the remote terminal.

[0133] According to an embodiment, if the remote terminal receives configuration information from the base station, the remote terminal can configure multiple paths in the terminal based on the corresponding configuration information. For example, the remote terminal can configure the main path of the split signaling radio bearer (SRB) as a direct path. As another example, the remote terminal can configure an indirect path by establishing a PC5 RRC connection with a relay terminal.

[0134] The remote terminal may be configured by adding a direct path and / or an indirect path using the information included in the configuration information. Alternatively, the remote terminal may configure a radio bearer indicated by the configuration information in the terminal to control communication using a direct path and / or an indirect path.

[0135] The base station can perform communication with the remote terminal through multiple configured paths. However, during communication, communication restrictions may occur due to various factors. For example, a communication failure event may occur, such as a radio link failure. The remote terminal can monitor whether a radio link failure occurs.

[0136] The base station may perform the step of receiving an RRC message when a radio link failure is detected in at least one of the plurality of paths in the remote terminal (S1030).

[0137] According to an embodiment, the remote terminal may monitor whether a radio link failure occurs in a plurality of paths. If a radio link failure is detected in one or more of the plurality of paths, the base station may receive information about the occurrence of the failure through an RRC message.

[0138] For example, when a radio link failure is detected in a direct path, an RRC message may be received as a path failure report through an indirect path.

[0139] As another example, when a radio link failure is detected in an indirect path, an RRC message may be received as a path failure report through a direct path.

[0140] For example, a radio link failure detected on an indirect path may be caused by a side link failure or a radio link failure between a relay terminal and a base station on the indirect path. In other words, when a side link failure is detected, a communication problem occurs between the remote terminal and the relay terminal, which results in a radio link failure being detected on the indirect path. Alternatively, if a radio link failure occurs between the relay terminal and the base station, the remote terminal may detect a radio link failure on the indirect path. In this case, a radio link failure between the relay terminal and the base station may be reported.

[0141] As another example, if a radio link failure is detected in both the direct path and the indirect path, the remote terminal may perform a cell selection operation or a relay selection operation according to the RRC reconfiguration procedure. In addition, if a radio link failure is detected in both the direct path and the indirect path, the remote terminal may send an RRC reconfiguration request message to the base station, and the base station may then receive the request (e.g., the RRC reconfiguration request message). The cell selection or relay selection operation performed by the remote terminal may be performed before or after receiving the RRC reconfiguration request message. Alternatively, the reception of the RRC reconfiguration request message may be regarded as part of the cell selection and relay selection operation process.

[0142] Meanwhile, the RRC message transmitted through the path failure report may include the failure cause information.Alternatively, the RRC message may include information on the radio bearer in which the radio link failure is detected, failure type information or other relevant details.

[0143] According to the above-described embodiments, when a radio link failure is detected, a remote terminal that performs communications through a plurality of different paths including a direct path and an indirect path can take quick action to prevent degradation of a communication context.

[0144] In the following, more embodiments and various functions that can be performed by the above-mentioned remote terminal, relay terminal and base station will be described in more detail. The functions and embodiments described below can be arbitrarily combined and performed by the remote terminal, relay terminal and base station.

[0145] For ease of description, hereinafter, the term "L2 U2N remote terminal" will refer to the remote terminal. This is for ease of description only, and any terminal connected to the network through any relay terminal / node (such as an L3 U2N remote terminal, IAB, Mobile-IAB or similar entity) may be included under the definition of remote terminal. The interface between the remote terminal and the relay terminal may be connected through PC5, F1 or any non-3GPP technology.

[0146] Add / modify / release the path of the remote terminal

[0147] A remote terminal in an RRC idle / inactive state can establish an indirect path through a relay terminal (a process for terminal connection setup of a remote terminal or SRB / DRB setup for sending / receiving user plane data and / or RRC messages through an indirect path). Thereafter, the base station serving the remote terminal can add a direct path for the terminal.

[0148] For example, the remote terminal and the relay terminal may perform a side link discovery process and establish a PC5-RRC connection. The remote terminal may send an RRC message (e.g., an RRC setup request) for connection setup with the base station to the base station through the relay terminal. If the relay terminal is not in an RRC connected state, the relay terminal receiving the message on the corresponding PC5 relay RLC channel may perform (RRC) connection setup. During the RRC connection setup of the relay terminal, the base station may configure SRB0 to relay the Uu relay RLC channel to the relay terminal. The base station may respond to the remote terminal with an RRC setup message. The RRC setup message may be sent to the remote terminal using the SRB0 relay channel through Uu and the corresponding PC5 relay RLC channel through PC5. The base station and the relay terminal may perform a relay channel setup process through Uu. The relay / remote terminal may set up a PC5 relay RLC channel for SRB1 relay. The remote terminal sends an RRC setup completion message through the relay terminal. The remote terminal and the base station set up security. The base station may send an RRC reconfiguration message to the remote terminal through the relay terminal to set up SRB2 / DRB for relay purposes. The corresponding RRC reconfiguration message may include configuration information for adding / modifying / releasing the path of the remote terminal. For example, the configuration information may include one or more of the following: measurement configuration, report configuration, cell group configuration information (CellGroupConfig) about the direct path of the remote terminal, RLC bearer configuration information about the direct path, SRB0 / SRB1 / SRB2 / DRB configuration through the direct path, (side link) SRB0 / SRB1 / SRB2 / DRB configuration through the indirect path of the remote terminal, SRAP configuration for the side link L2 remote terminal, PC5 (relay) RLC channel configuration information between the relay terminal and the remote terminal, and separate SRB1 / SRB2 / DRB configuration using both indirect and direct paths.

[0149] The remote terminal may set up a direct path. Thereafter, the base station serving the remote terminal may add an indirect path through the relay terminal. For example, the remote terminal may perform an RRC setup procedure with the base station. The base station may send an RRC reconfiguration message to the remote terminal over the Uu interface to add SRB / DRB for relay purposes. The RRC reconfiguration message may include configuration information for adding / modifying / releasing the path of the remote terminal. For example, the configuration information may include one or more of the following: measurement configuration, report configuration, cell group configuration information (CellGroupConfig) about the direct path of the remote terminal, RLC bearer configuration information about the direct path, SRB0 / SRB1 / SRB2 / DRB configuration through the direct path, (side link) SRB0 / SRB1 / SRB2 / DRB configuration through the indirect path of the remote terminal, SRAP configuration for the side link L2 remote terminal, PC5 (relay) RLC channel configuration information between the relay terminal and the remote terminal, separate SRB1 / SRB2 / DRB configuration using both indirect and direct paths, source / destination L2ID for the relay terminal or the remote terminal, relay terminal ID, local ID of the remote terminal, L2 ID, C-RNTI, Uu and PC5 relay RLC channel configuration for relay, and bearer mapping configuration. In order to add / modify / release the indirect path, the remote terminal and the relay terminal may perform a side link discovery process. The remote terminal may set up a PC5-RRC connection with the relay terminal. The remote terminal or the relay terminal can indicate the PC5-RRC connection information corresponding to the base station.

[0150] Before, at the same time or after the base station sends the RRC reconfiguration message to the remote terminal through the Uu interface on the direct path, the base station may send the RRC reconfiguration message to the relay terminal. The RRC reconfiguration message may include one or more of the following: the source / destination L2 ID of the relay terminal or the remote terminal, the relay terminal ID, the local ID of the remote terminal, the L2ID, the C-RNTI, the Uu and PC5 relay RLC channel configurations for relaying, and the bearer mapping configuration. Alternatively, the RRC reconfiguration message sent by the base station to the remote terminal through the Uu interface on the direct path may include a container / IE / command in the RRC reconfiguration message for the relay terminal configuration. The remote terminal may send the corresponding container / IE / command to the relay terminal. The corresponding configuration may be applied to the relay terminal, and an RRC reconfiguration completion message confirming the update may be sent to the base station. Alternatively, the base station may send the RRC reconfiguration message to the remote terminal through an indirect path. In this case, the corresponding RRC reconfiguration message may be included in the RRC reconfiguration message for the relay terminal configuration through the container / IE / command. The base station and the relay terminal can perform the relay channel setup process via Uu. According to the configuration received from the base station, the relay terminal and the remote terminal can set up the PC5 relay RLC channel for SRB / DRB relay. The remote terminal can send an RRC reconfiguration completion message via the direct path.

[0151] When the remote terminal sets / configures / modifies the direct path and the indirect path to the terminal by path addition / modification (for example, when setting / configuring / modifying RRC / SRB / DRB by multiple paths including the direct path and the indirect path to the terminal), one of the multiple (or two) paths may be indicated / configured / set / considered as the primary path. For ease of description, the path for the default / priority transmission / reception of one or more of the RRC messages, PDCP control PDUs, and PDCP data PDUs (for example, user data) in the terminal is indicated as the primary path, which is configured simultaneously with the direct path and the indirect path. This designation is for ease of description only and may be replaced with any other name.

[0152] For example, among multiple paths, the initial path or the first path in which the remote terminal establishes an RRC connection can be regarded as the main path of the remote terminal. The base station can configure an auxiliary path for the corresponding remote terminal through the main path. Alternatively, the main path can be selected from a direct path or an indirect path. In another example, the main path can be selected from the RLC entity and the SRAP / PC5-RLC entity for uplink data transmission. In addition, the main path can be configured to indicate the main RLC entity / PC5-RLC entity for sending the PDCP control PDU. The corresponding RLC entity / PC5-RLC entity can be distinguished by PCell LCID / SL-LCID. In addition, the PDCP control PDU can be sent through the main path. Alternatively, the main path can be indicated / configured / specified with information different from that used to indicate the main RLC entity / PC5-RLC entity for sending the PDCP control PDU. For example, the PCDP control PDU can be sent through a non-main path.

[0153] In another example, the PCell of the remote terminal may be a cell serving the primary path. For example, if the direct path of the remote terminal is the primary path, the PCell serving the remote terminal serves as the PCell of the remote terminal. Conversely, if the indirect path of the remote terminal is the primary path, the PCell serving the relay terminal may be the PCell of the remote terminal.

[0154] In another example, the base station may configure information through an RRC reconfiguration message to indicate a primary path for the remote terminal.

[0155] In another example, the primary path may be a default path over which most or all RRC messages are sent. In addition, the RRC messages provided via a non-primary path (e.g., a secondary path) may be limited to specific RRC messages. For example, if an RLF is declared / detected on the primary path, a message notifying / indicating that information (e.g., failure information) may be sent to the base station via the secondary path. Alternatively, any terminal assistance information that helps determine an appropriate path may be sent to the base station via the secondary path.

[0156] In another example, if multiple paths are configured in the terminal, one or more of the following may be configured: i) radio bearer / SRB / DRB via a direct path, ii) radio bearer / SRB / DRB via an indirect path, and iii) separate radio bearers / SRB / DRBs using both direct and indirect paths.

[0157] In another example, if a radio link failure is detected on the primary path, the remote terminal can trigger an RRC reconfiguration on the primary path. In another example, if a radio link failure is detected on the primary path, and if the remote terminal is able to send and receive data through the secondary path, the remote terminal can switch the primary path to the secondary path, and then send and receive data through the secondary path. To this end, a conditional path change configuration can be set in the terminal. The configuration can be set by a candidate path configuration and an execution condition. The corresponding path configuration may include one or more configuration information (e.g., parameters) described in the present disclosure.

[0158] In another example, the remote terminal may trigger RRC reconfiguration only on the primary path. In addition, the remote terminal may perform cell selection or relay selection between the primary path and the secondary path. In addition, the (preferred) path through which the remote terminal is to trigger RRC reconfiguration may be configured in the terminal by the base station.

[0159] Fig.11 is a diagram showing an example of split radio bearer / SRB / DRB configuration through multiple paths.

[0160] Reference Fig.11 , the remote terminal can be connected to the base station via the relay terminal through an indirect path. Alternatively, the remote terminal can be directly connected to the base station through a direct path. When the remote terminal is connected to the base station through a direct path, the PDCP, RLC and MAC entities in the remote terminal and the base station can be configured to send and receive data. When the remote terminal is connected to the base station through an indirect path, the PC5-MAC, PC5-RLC and SRAP of the remote terminal and the relay terminal can be configured. The relay terminal is connected to the base station through the MAC, RLC and SRAP entities.

[0161] Radio link failure handled by a terminal with multiple paths configured

[0162] The remote terminal may perform radio link monitoring only on the primary path. Alternatively, the remote terminal may perform radio link monitoring on both the primary path and the secondary path.

[0163] For example, when the remote terminal establishes an initial RRC connection through a relay terminal and is connected to a base station (or when the remote terminal is connected to a base station using an indirect path as a main path), the remote terminal can suspend radio link monitoring (RLM) on the radio link (Uu) between the terminal and the base station (or on a direct path).

[0164] In another example, when the remote terminal establishes an initial RRC connection through a relay terminal and is connected to a base station (or when the remote terminal is connected to a base station using an indirect path as a main path), the remote terminal can perform RLM on the radio link (Uu) between the terminal and the base station (or on a direct path).

[0165] In another example, when the remote terminal establishes an initial RRC connection through a relay terminal and is connected to a base station (or when the remote terminal is connected to the base station using an indirect path as a main path), if the remote terminal is instructed to send uplink data through a direct path, the remote terminal can perform RLM on the radio link (Uu) between the terminal and the base station (or on the direct path).

[0166] Similarly, when the remote terminal establishes an initial RRC connection through the relay terminal and is connected to the base station (or when the remote terminal is connected to the base station using an indirect path as a main path), if the remote terminal detects a side link radio link failure, if the remote terminal receives a side link notification message according to a specific operation of the relay terminal in the RRC connected state, or if the remote terminal receives a PC5 unicast link release indicated by a higher layer in the RRC connected state, the remote terminal can perform / recover RLM on the radio link (Uu) between the terminal and the base station (or on a direct path).

[0167] In another example, when the remote terminal is connected to the base station using an auxiliary path through a relay terminal (or when the remote terminal is connected to the base station using an indirect path as an auxiliary path), the remote terminal can perform RLM on the radio link (Uu) between the terminal and the base station.

[0168] In another example, when the remote terminal establishes an initial RRC connection through the relay terminal and is connected to the base station (or when the remote terminal is connected to the base station using an indirect path as a main path), if the remote terminal detects a sidelink radio link failure in the RRC connected state (for example, when the sidelink RLC entity indicates that the maximum number of retransmissions for a specific destination has been reached; or when T400 (when transmitting RRCReconfigurationSidelink) of the specific destination expires; or when the MAC entity indicates that the maximum number of consecutive HARQ DTXs for the specific destination has been reached; or when an integrity check failure indication from the sidelink PDCP entity is related to SL-SRB2 or SL-SRB3 of the specific destination), or if the remote terminal receives a sidelink notification message according to a specific operation of the relay terminal in the RRC connected state (for example, at Uu RLF; when RRCReconfiguration including reconfigurationWithSync is received; at cell reselection; at L2 U2N relay UE's RRC connection failure including RRC connection rejection, and T300 expiration and RRC recovery failure), the remote terminal can suspend the transmission of SRBs and DRBs (all except SRB0 / broadcast-MRB) through indirect paths. If it is determined that the PC5-RRC connection with the relay terminal is released, the remote terminal can perform PC5-RRC connection release. The remote terminal can release the side link radio bearer with the relay terminal. The remote terminal can release the L2 entity through an indirect path for the separated bearer. Alternatively, if the remote terminal receives a PC5 unicast link release indicated by a higher layer in the RRC connected state, it is determined that the PC5-RRC connection with the relay terminal is released, the remote terminal can perform PC5-RRC connection release. The remote terminal can perform cell selection according to the cell selection process, or perform relay selection according to the relay selection process. The remote terminal can then initiate the transmission of an RRC reconfiguration request message. For example, the remote terminal can send an RRC reconfiguration request message through the selected cell. Alternatively, the remote terminal may send an RRC reconfiguration request message to the base station through the selected relay.

[0169] In another example, when the remote terminal establishes an initial RRC connection through a relay terminal and is connected to a base station (or when the remote terminal is connected to a base station using an indirect path as a primary path), if the remote terminal detects a sidelink radio link failure, if the remote terminal receives a sidelink notification message according to a specific operation of the relay terminal in an RRC connected state, or if the remote terminal receives a PC5 unicast link release indicated by a higher layer in an RRC connected state, the remote terminal may suspend transmission through an indirect path for SRBs and DRBs (all except SRB0 / broadcast-MRB). If it is determined that the PC5-RRC connection with the relay terminal is released, the remote terminal may perform a PC5-RRC connection release. The remote terminal may release the sidelink radio bearer with the relay terminal. The remote terminal may release the L2 entity through an indirect path for a separated bearer. If the direct path is maintained or the direct path satisfies a specific condition indicated (e.g., a threshold, a timing advance timer, or a specific timer operation), the remote terminal may send information to the base station indicating one or more (or corresponding causes) of the sidelink notification message reception and the PC5-RRC connection release. If the direct path is maintained or the direct path satisfies the indicated specific condition (e.g., a threshold, a timing advance timer, or a specific timer operation), the remote terminal can maintain the wireless connection with the corresponding cell. The remote terminal can maintain data communication through the corresponding cell. The base station can configure / modify / reconfigure the radio bearer / SRB / DRB through the direct path through an RRC reconfiguration message. The base station can release / modify / reconfigure the radio bearer / SRB / DRB and / or the split radio bearer / SRB / DRB through an indirect path through an RRC reconfiguration message (e.g., reconfigure the split radio bearer / SMB / DRB to a radio bearer / SRB / DRB through a direct path).

[0170] In another example, when the remote terminal establishes an initial RRC connection through the relay terminal and is connected to the base station (or when the remote terminal is connected to the base station using an indirect path as the main path), if the remote terminal detects a side link radio link failure, if the remote terminal receives a side link notification message according to a specific operation of the relay terminal in the RRC connection state, or if the remote terminal receives a PC5 unicast link release indicated by a higher layer in the RRC connection state, the remote terminal can suspend transmission of SRBs and DRBs (all except SRB0 / broadcast-MRB) through an indirect path. Alternatively, the remote terminal can suspend SRBs and DRBs (all through an indirect path, except SRB0 / broadcast-MRB). If it is determined that the PC5-RRC connection with the relay terminal is released, the remote terminal can perform a PC5-RRC connection release. (Simultaneously with, after, or before RLF on the main path) If the remote terminal detects a radio link failure on the direct path, the remote terminal can suspend transmission of SRBs and DRBs (all except SRB0 / broadcast-MRB) through a direct path / indirect path. Alternatively, the remote terminal may suspend SRBs and DRBs (all except SRB0 / Broadcast-MRB).

[0171] The remote terminal may perform cell selection according to a cell selection process, or perform relay selection according to a relay selection process. The remote terminal may initiate transmission of an RRC reconfiguration request message. For example, the remote terminal may send an RRC reconfiguration request message through a selected cell. Alternatively, the remote terminal may send an RRC reconfiguration request message to a base station through a selected relay.

[0172] In another example, when the remote terminal establishes an initial RRC connection through a direct path and is connected to the base station (or when the remote terminal is connected to the base station using the direct path as a primary path), if the remote terminal detects a radio link failure on the direct path (e.g., Uu) in the RRC connected state, the remote terminal may suspend transmission of SRBs and DRBs (all except SRB0 / Broadcast-MRB) through the direct path. Alternatively, the remote terminal may suspend SRBs and DRBs (all except SRB0 / Broadcast-MRB). The remote terminal may perform cell selection according to a cell selection procedure. The remote terminal may initiate transmission of an RRC reconfiguration request message. For example, the remote terminal may send an RRC reconfiguration request message through the selected cell.

[0173] In another example, when the remote terminal establishes an initial RRC connection through a direct path and is connected to the base station (or when the remote terminal is connected to the base station using the direct path as the main path), if the remote terminal detects a radio link failure on the direct path (e.g., Uu) in the RRC connected state, the remote terminal can suspend transmission through the direct path for SRBs and DRBs (all except SRB0 / Broadcast-MRBs). If the remote terminal does not detect a sidelink radio link failure in the RRC connected state, if the remote terminal does not receive a sidelink notification message according to a specific operation of the relay terminal in the RRC connected state, or if the remote terminal does not receive a PC5 unicast link release indicated by a higher layer in the RRC connected state, the remote terminal can maintain transmission through an indirect path for SRBs and DRBs. If it is determined that the PC5-RRC connection with the relay terminal is released, the remote terminal can perform a PC5-RRC connection release. The remote terminal can release the sidelink radio bearer with the relay terminal. The remote terminal can and / or suspend SRBs and DRBs (all except SRB0 / Broadcast-MRBs). In addition, the remote terminal may release the L2 entity via an indirect path for the split bearer. Otherwise, the remote terminal may maintain the PC5 RRC connection.

[0174] If the indirect path is maintained or the indirect path satisfies the indicated specific condition (e.g., an SD-RSRP / SL-RSRP threshold or a specific timer operation), the remote terminal may send information indicating a direct path radio link failure to the base station via the indirect path. If the indirect path is maintained or the indirect path satisfies the indicated specific condition (e.g., a threshold or a specific timer operation), the remote terminal may maintain the wireless connection via the corresponding path. Data communication may be maintained via the corresponding path. The base station may set / modify / reconfigure the radio bearer / SRB / DRB via the indirect path via an RRC reconfiguration message. The base station may release / modify / reconfigure the radio bearer / SRB / DRB and / or separate radio bearer / SRB / DRB via the direct path via an RRC reconfiguration message (e.g., reconfigure the separate radio bearer / SRB / DRB to a radio bearer / SRB / DRB via an indirect path).

[0175] In another example, when the remote terminal establishes an initial RRC connection through a direct path and is connected to the base station (or when the remote terminal is connected to the base station using the direct path as the main path), if the remote terminal detects a radio link failure on the direct path (e.g., Uu) in the RRC connected state, the remote terminal can suspend transmission through the direct path for SRBs and DRBs (all except SRB0 / Broadcast-MRBs). If the remote terminal detects a side link radio link failure in the RRC connected state, if the remote terminal receives a side link notification message according to a specific operation of the relay terminal in the RRC connected state, or if the remote terminal receives a PC5 unicast link release indicated by a higher layer in the RRC connected state, the remote terminal can suspend transmission through an indirect path for SRBs and DRBs (all except SRB0 / Broadcast-MRBs). Alternatively, the remote terminal can suspend SRBs and DRBs (all through indirect paths, except SRB0 / Broadcast-MRBs). In addition, the remote terminal can suspend transmission through direct paths / indirect paths for SRBs and DRBs. In addition, the remote terminal can suspend SRBs and DRBs (all except SRB0 / Broadcast-MRB).

[0176] The remote terminal may perform cell selection according to a cell selection process, or perform relay selection according to a relay selection process. The remote terminal may initiate transmission of an RRC reconfiguration request message. For example, the remote terminal may send an RRC reconfiguration request message through a selected cell. Alternatively, the remote terminal may send an RRC reconfiguration request message to a base station through a selected relay.

[0177] In another example, when the remote terminal establishes an initial RRC connection through a direct path and is connected to the base station (or when the remote terminal is connected to the base station using a direct path as the main path), if the remote terminal detects a side link radio link failure, or if the remote terminal receives a side link notification message due to a specific operation of the relay terminal in the RRC connection state, the remote terminal can suspend transmission through an indirect path for SRBs and DRBs (all except SRB0 / broadcast-MRB). If it is determined that the PC5-RRC connection with the relay terminal is released, the remote terminal can perform a PC5-RRC connection release. The remote terminal can also release the side link radio bearer with the relay terminal, and / or release the L2 entity through an indirect path for a separated bearer. Alternatively, if the PC5-RRC connection with the relay terminal is determined to be released when the remote terminal receives a PC5 unicast link release indicated by a higher layer in the RRC connection state, the remote terminal can perform a PC5-RRC connection release. The remote terminal may send information indicating one or more (or corresponding reasons) of a side link radio link failure, a side link notification message reception, and a PC5-RRC connection release to the base station via a direct path. If the direct path is maintained or a specific condition (e.g., a threshold, a timing advance timer, or a specific timer operation) is met, the remote terminal may maintain a wireless connection with the corresponding cell. The remote terminal may maintain data communication through the corresponding cell. The base station may set / modify / reconfigure a radio bearer / SRB / DRB via a direct path via an RRC reconfiguration message. The base station may release / modify / reconfigure a radio bearer / SRB / DRB and / or a separated radio bearer / SRB / DRB via an indirect path via an RRC reconfiguration message (e.g., reconfiguring a separated radio bearer / SRB / DRB to a radio bearer / SRB / DRB via a direct path).

[0178] According to an embodiment of the present disclosure, a remote terminal can stably send data through multiple paths and effectively handle radio link failures. Hereinafter, the configuration of a terminal and a base station capable of performing operations of a remote terminal, a relay terminal, and a base station according to the above-described embodiment will be described. For convenience, although not explicitly described, each entity can perform all or part of the above-described operations according to the embodiment.

[0179] Fig.12 is a block diagram illustrating a remote terminal according to an embodiment.

[0180] refer to Fig.12, a remote terminal 1200 that performs communication through multiple paths may include: a receiver 1230 that receives configuration information for configuring (e.g., establishing) multiple paths including a direct path and an indirect path from a base station; a controller that configures (e.g., establishes) the multiple paths by applying the configuration information; and a transmitter 1220 that sends an RRC message when a radio link failure is detected in at least one of the multiple paths.

[0181] According to an embodiment, the receiver 1230 may receive configuration information for configuring multiple paths, the multiple paths including a direct path to the base station and an indirect path through the relay terminal. For example, the configuration information may be received from the base station through higher layer signaling. For example, the configuration information may be received through an RRC message. In another example, the configuration information may be received through a relay terminal.

[0182] For example, the configuration information may include at least one of the following: i) direct path addition configuration information, ii) indirect path addition configuration information, iii) direct path RLC bearer configuration information, iv) indirect path RLC bearer configuration information, v) bearer mapping configuration information, vi) direct path radio bearer configuration information, vii) indirect path radio bearer configuration information, viii) separate signaling radio bearer (SRB) configuration information, ix) separate data radio bearer (DRB) configuration information, and x) L2 relay terminal identification information. For example, the configuration information may include direct path addition configuration information for additionally configuring a direct path in a remote terminal. In addition, the configuration information may include indirect path addition configuration information for additionally configuring an indirect path in a remote terminal. In addition, the configuration information may include direct path RLC bearer configuration information and / or indirect path RLC bearer configuration information for configuring a path for each bearer. Alternatively, the configuration information may include bearer mapping configuration information for mapping bearers and paths. In addition, the configuration information may include at least one of the following: a) direct path radio bearer configuration information, b) indirect path radio bearer configuration information, c) separate SRB configuration information, and d) separate DRB configuration information. The configuration information may include identification information of an L2 relay terminal connected to the remote terminal.

[0183] Meanwhile, if configuration information is received from the base station, the controller 1210 may configure multiple paths in the terminal based on the corresponding configuration information. For example, the controller 1210 may configure the primary path of the separate signaling radio bearer (SRB) as a direct path. In another example, the controller 1210 may configure an indirect path by establishing a PC5 RRC connection with the relay terminal.

[0184] The controller 1210 may configure by adding a direct path and / or an indirect path using the information included in the configuration information. Alternatively, the controller 1210 may configure the radio bearer indicated by the configuration information in the terminal to control communication using the direct path and / or the indirect path.

[0185] The controller 1210 may perform communication with the base station through a plurality of configured paths. However, during communication, communication limitations may occur due to various factors. For example, a communication failure event such as a radio link failure may be detected.

[0186] For example, the controller 1210 may monitor whether a radio link failure occurs in the plurality of paths. If a radio link failure is detected in one or more of the plurality of paths, the transmitter 1220 may transmit information on the occurrence of the failure through an RRC message.

[0187] For example, when a radio link failure is detected on a direct path, an RRC message may be sent as a path failure report through an indirect path.

[0188] As another example, when a radio link failure is detected on an indirect path, an RRC message may be sent over the direct path as a path failure report.

[0189] For example, a radio link failure detected on an indirect path may be caused by a side link failure or a radio link failure between a relay terminal and a base station on the indirect path. In other words, when a side link failure is detected, a communication problem occurs between the remote terminal and the relay terminal, which results in a radio link failure being detected on the indirect path. Alternatively, if a radio link failure occurs between the relay terminal and the base station, the controller 1210 may detect a radio link failure on the indirect path. In this case, a radio link failure between the relay terminal and the base station may be reported.

[0190] In another example, if a radio link failure is detected in both the direct path and the indirect path, the controller 1210 may perform a cell selection operation or a relay selection operation according to the RRC reconfiguration process. In addition, if a radio link failure is detected in both the direct path and the indirect path, the transmitter 1220 may send an RRC reconfiguration request message to the base station. The cell selection or relay selection operation may be performed before or after the transmission of the RRC reconfiguration request message. Alternatively, the transmission of the RRC reconfiguration request message may be regarded as part of the cell selection and relay selection operation.

[0191] Meanwhile, the RRC message transmitted through the path failure report may include the failure cause information.Alternatively, the RRC message may include information on the radio bearer in which the radio link failure is detected, failure type information or other relevant details.

[0192] In addition, the controller 1210 manages the overall operation of the remote terminal 1200 according to the radio link failure handling operation and the configuration of multiple paths required to perform the above disclosure.

[0193] The transmitter 1220 and the receiver 1230 are used to transmit / receive signals, messages or data required to perform the above disclosure together with the base station or the relay terminal.

[0194] Fig.13 is a block diagram showing a base station according to an embodiment.

[0195] refer to Fig.13 , a base station 1300 for controlling communication through multiple paths of a remote terminal may include: a transmitter 1320 that sends an RRC reconfiguration message for configuring an indirect path to a relay terminal that provides a connection with the remote terminal, and sends configuration information for configuring multiple paths including a direct path and an indirect path in the remote terminal to the relay terminal; and a receiver 1330 that receives the RRC message when a radio link failure is detected in at least one of the multiple paths in the remote terminal.

[0196] According to an embodiment, the transmitter 1320 may send an RRC reconfiguration message for configuring an indirect path for a remote terminal to the relay terminal. Therefore, the relay terminal may configure an indirect path with the indicated remote terminal to transmit the data of the remote terminal to the base station. In addition, the relay terminal may transmit the data of the remote terminal received from the base station to the remote terminal.

[0197] However, the above operation can be performed only when an indirect path is added to the remote terminal. In other words, if the remote terminal and the relay terminal have configured an indirect path, and then a directional path is added to the remote terminal, the transmission of the RRC reconfiguration message to the relay terminal can be omitted.

[0198] At the same time, transmitter 1320 can send configuration information to configure multiple paths including a direct path to the remote terminal and an indirect path through a relay terminal. For example, the configuration information can be sent from the base station via higher layer signaling. For example, the configuration information can be sent via an RRC message. In another example, the configuration information can be transmitted to the remote terminal via a relay terminal.

[0199] The configuration information may include at least one of the following: i) direct path addition configuration information; ii) indirect path addition configuration information; iii) direct path RLC bearer configuration information; iv) indirect path RLC bearer configuration information; v) bearer mapping configuration information; vi) direct path radio bearer configuration information; vii) indirect path radio bearer configuration information; viii) separate signaling radio bearer (SRB) configuration information; ix) separate data radio bearer (DRB) configuration information, and x) L2 relay terminal identification information. For example, the configuration information may include direct path addition configuration information for additionally configuring a direct path in a remote terminal. In addition, the configuration information may include indirect path addition configuration information for additionally configuring an indirect path in a remote terminal. In addition, the configuration information may include direct path RLC bearer configuration information and / or indirect path RLC bearer configuration information for configuring a path for each bearer. Alternatively, the configuration information may include bearer mapping configuration information for mapping bearers and paths. In addition, the configuration information may include at least one of the following: a) direct path radio bearer configuration information, b) indirect path radio bearer configuration information, c) separate SRB configuration information, and d) separate DRB configuration information. The configuration information may include identification information of an L2 relay terminal connected to the remote terminal.

[0200] According to an embodiment, if the remote terminal receives configuration information from the base station, the remote terminal can configure multiple paths in the terminal based on the corresponding configuration information. For example, the remote terminal can configure the main path of the separated signaling radio bearer (SRB) as a direct path. In another example, the remote terminal can configure an indirect path by establishing a PC5 RRC connection with the relay terminal.

[0201] The remote terminal may be configured by adding a direct path and / or an indirect path using the information included in the configuration information. Alternatively, the remote terminal may configure a radio bearer indicated by the configuration information in the terminal to control communication using a direct path and / or an indirect path.

[0202] Controller 1310 can perform communication with the remote terminal through multiple configured paths. However, during communication, communication restrictions may occur due to various factors. For example, communication failure events may occur, such as radio link failure. The remote terminal can monitor whether the radio link fails.

[0203] At the same time, the remote terminal may monitor whether a radio link failure occurs in the multiple paths. If a radio link failure is detected in one or more of the multiple paths, the receiver 1330 may receive information about the failure occurrence through an RRC message.

[0204] For example, when a radio link failure is detected in a direct path, an RRC message may be received as a path failure report through an indirect path.

[0205] As another example, when a radio link failure is detected in an indirect path, an RRC message may be received as a path failure report through a direct path.

[0206] For example, a radio link failure detected on an indirect path may be caused by a side link failure or a radio link failure between a relay terminal and a base station on the indirect path. In other words, when a side link failure is detected, a communication problem occurs between the remote terminal and the relay terminal, which results in a radio link failure being detected on the indirect path. Alternatively, if a radio link failure occurs between the relay terminal and the base station, the remote terminal may detect a radio link failure on the indirect path. In this case, a radio link failure between the relay terminal and the base station may be reported.

[0207] In another example, if a radio link failure is detected in both the direct path and the indirect path, the remote terminal may perform a cell selection operation or a relay selection operation according to the RRC reconfiguration process. In addition, if a radio link failure is detected in both the direct path and the indirect path, the remote terminal may send an RRC reconfiguration request message to the base station. Therefore, the receiver 1330 may receive the RRC reconfiguration request message. The cell selection or relay selection operation of the remote terminal may be performed before or after receiving the RRC reconfiguration request message. Alternatively, the reception of the RRC reconfiguration request message may be regarded as part of the cell selection and relay selection operation process.

[0208] Meanwhile, the RRC message transmitted through the path failure report may include the failure cause information.Alternatively, the RRC message may include information on the radio bearer in which the radio link failure is detected, failure type information or other relevant details.

[0209] In addition, the controller 1310 manages the overall operation of the base station 1300 according to a radio link failure handling operation and configuration of a plurality of paths required to implement the operation according to an embodiment of the present disclosure.

[0210] The transmitter 1320 and the receiver 1330 are used to transmit / receive signals or messages or data required to perform the above-mentioned operations according to the embodiments of the present disclosure together with the remote terminal and the relay terminal.

[0211] The above-mentioned embodiments may be supported by standard documents disclosed in IEEE 802, 3GPP, and 3GPP2 as radio access systems. In other words, the above-mentioned standard documents may support steps, components, and parts that are not described in the embodiments to clarify the technical spirit. In addition, all terms disclosed in the present disclosure may be described by the above-mentioned disclosed standard documents.

[0212] The above-mentioned embodiment can be implemented in various ways. For example, the embodiment can be implemented in various ways (for example, hardware, firmware, software or a combination thereof).

[0213] When implemented in hardware, the method according to the present embodiment can be implemented by, for example, one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers or microprocessors.

[0214] When implemented in firmware or hardware, the method according to the present embodiment can be implemented in the form of a device, program or function that performs the above-mentioned functions or operations. The software code can be stored in a memory unit and driven by a processor. The memory unit can be located inside or outside the processor to exchange data with the processor through various known means.

[0215] The above terms (such as "system", "processor", "controller", "component", "module", "interface", "model" or "unit") generally refer to computer-related physical hardware, a combination of hardware and software, software, or software being executed. For example, the above components can be but are not limited to processes driven by one or more processors, controllers, control processors, entities, execution threads, programs and / or computers. For example, both an application executed by a controller or processor and the controller or processor can be a component. One or more components can reside within a process and / or execution thread, and these components can be located in one device (e.g., a system, a computing device, etc.) or distributed among two or more devices.

[0216] The above embodiments are merely examples, and those of ordinary skill in the art will appreciate that various changes may be made thereto without departing from the scope of the invention. Therefore, the embodiments described herein are provided for illustrative purposes, but do not limit the scope of the invention, and it should be understood that the scope of the invention is not limited by the embodiments. The scope of the present disclosure shall be interpreted by the following claims, and all technical spirits within their equivalents shall be interpreted as belonging to the scope of the present disclosure.

[0217] CROSS-REFERENCE TO RELATED APPLICATIONS

[0218] This patent application claims the benefit of priority under 35 U.S.C. § 119(a) to Korean Patent Application Nos. 10-2022-0123587 and 10-2023-0121265 filed in the Korean Intellectual Property Office on September 28, 2022 and September 12, 2023, respectively, the disclosures of which are incorporated herein by reference in their entirety. This patent application claims the benefit of priority to other applications filed in other countries, the disclosures of which are also incorporated herein by reference in their entirety.

Claims

1. A method for performing communication by a remote terminal through multiple paths, the method comprising: receiving, from a base station, configuration information for configuring a plurality of paths including a direct path and an indirect path; configuring the plurality of paths by applying the configuration information; as well as Upon detecting a radio link failure in at least one of the plurality of paths, an RRC message is sent.

2. The method according to claim 1, wherein: The configuration information includes at least one of the following: direct path addition configuration information, indirect path addition configuration information, direct path RLC bearer configuration information, indirect path RLC bearer configuration information, bearer mapping configuration information, direct path radio bearer configuration information, indirect path radio bearer configuration information, separate signaling radio bearer (separate SRB) configuration information, separate data radio bearer (separate DRB) configuration information and L2 relay terminal identification information.

3. The method according to claim 1, wherein: Configuring the multiple paths is configuring a main path (main path) of a separate signaling radio bearer (separate SRB) as the direct path, and establishing a PC5 RRC connection with the relay terminal.

4. The method according to claim 1, wherein: When the path in which the radio link failure is detected is the direct path, the RRC message is sent as the path failure report through the indirect path, and when the path in which the radio link failure is detected is the indirect path, the RRC message is sent as the path failure report through the direct path.

5. The method according to claim 4, wherein: The radio link failure detected on the indirect path is a notification due to a side link failure or a radio link failure between the relay terminal and the base station on the indirect path.

6. The method according to claim 1, wherein: If a radio link failure is detected in both the direct path and the indirect path, sending the RRC message is to perform a cell selection or relay selection operation according to an RRC reconfiguration procedure, and to send an RRC reconfiguration request message to the base station.

7. A method for controlling communications by a base station through multiple paths of a remote terminal, the method comprising: sending an RRC reconfiguration message for configuring an indirect path to a relay terminal providing a connection with the remote terminal; Sending configuration information for configuring a plurality of paths including a direct path and the indirect path in the remote terminal to the relay terminal; as well as An RRC message is received when a radio link failure is detected in at least one of the plurality of paths in the remote terminal.

8. The method according to claim 7, wherein: The configuration information includes at least one of the following: direct path additional configuration information, indirect path additional configuration information, direct path RLC bearer configuration information, indirect path RLC bearer configuration information, bearer mapping configuration information, direct path radio bearer configuration information, indirect path radio bearer configuration information, separate signaling radio bearer (separate SRB) configuration information, separate data radio bearer (separate DRB) configuration information and L2 relay terminal identification information.

9. The method according to claim 7, wherein: When the path in which the radio link failure is detected is the direct path, the RRC message is received as the path failure report through the indirect path, and when the path in which the radio link failure is detected is the indirect path, the RRC message is received as the path failure report through the direct path.

10. The method according to claim 9, wherein: The radio link failure detected on the indirect path is a notification due to a side link failure or a radio link failure between the relay terminal and the base station on the indirect path.

11. The method according to claim 7, wherein: If a radio link failure is detected in both the direct path and the indirect path, the RRC message is an RRC reconfiguration request message according to an RRC reconfiguration procedure.

12. A remote terminal for performing communication via multiple paths, comprising: a receiver receiving, from a base station, configuration information for configuring a plurality of paths including a direct path and an indirect path; a controller, the controller configuring the plurality of paths by applying the configuration information; as well as A transmitter transmits an RRC message when a radio link failure is detected in at least one of the plurality of paths.

13. The remote terminal according to claim 12, wherein: The configuration information includes at least one of the following: direct path addition configuration information, indirect path addition configuration message, direct path RLC bearer configuration information, indirect path RLC bearer configuration information, bearer mapping configuration information, direct path radio bearer configuration information, indirect path radio bearer configuration information, separate signaling radio bearer (separate SRB) configuration information, separate data radio bearer (separate DRB) configuration information and L2 relay terminal identification information.

14. The remote terminal according to claim 12, wherein: The controller configures a primary path (primary path) of a split signaling radio bearer (split SRB) as the direct path, and configures a PC5 RRC connection with a relay terminal to configure the plurality of paths.

15. The remote terminal according to claim 12, wherein: When the path in which the radio link failure is detected is the direct path, the RRC message is sent as the path failure report through the indirect path, and when the path in which the radio link failure is detected is the indirect path, the RRC message is sent as the path failure report through the direct path.

16. The remote terminal according to claim 15, wherein: The radio link failure detected on the indirect path is a notification due to a side link failure or a radio link failure between the relay terminal and the base station on the indirect path.

17. The remote terminal according to claim 12, wherein: If a radio link failure is detected in both the direct path and the indirect path, the controller performs a cell selection or a relay selection operation according to an RRC reconfiguration procedure, and the transmitter transmits an RRC reconfiguration request message to the base station.

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