Method and apparatus for transmitting and receiving a wireless signal in a wireless communication system

Abstract

In the present invention, a method for a first UE to transmit a signal includes performing a procedure for setting a split bearer including both a direct path between the first UE and a network and an indirect path between the first UE and the network. When setting the split bearer, it is determined that the direct path is set as the primary path of the split bearer. Based on the primary path of the split bearer, first upstream data is transmitted to the network via the direct path. A failure related to the direct path is detected. Based on the detection of the failure related to the direct path, the primary path of the split bearer is switched from the direct path to the indirect path, and second upstream data is transmitted to the network by a second UE operating as a relay UE for the indirect path to the network on the switched primary path of the split bearer.

Description

Technical Field

[0001] The present invention relates to a wireless communication system, and more particularly, to a method and apparatus for transmitting and receiving wireless signals.

Background Art

[0002] A wireless communication system is a multiple access system that shares available system resources (such as bandwidth, transmission power, etc.) to support communication with multiple users. Examples of multiple access systems include CDMA (code division multiple access) systems, FDMA (frequency division multiple access) systems, TDMA (time division multiple access) systems, OFDMA (orthogonal frequency division multiple access) systems, SC-FDMA (single carrier frequency division multiple access) systems, MC-FDMA (multi carrier frequency division multiple access) systems, and the like.

[0003] Sidelink (SL) refers to a communication method in which a direct link is established between terminals (User Equipment, UE) to directly exchange voice or data between the terminals without going through a base station (Base Station, BS). SL is one solution to solve the burden on the base station due to rapidly increasing data traffic.

[0004] V2X (vehicle-to-everything) refers to a communication technology that exchanges information with other vehicles, pedestrians, and infrastructure such as constructed things through wired and wireless communication. V2X is classified into four types such as V2V (vehicle-to-vehicle), V2I (vehicle-to-infrastructure), V2N (vehicle-to-network), and V2P (vehicle-to-pedestrian). V2X communication is provided by the PC5 interface and / or the Uu interface.

[0005] On the other hand, as more communication devices require larger communication capacities, the need for improved mobile broadband communication compared to existing radio access technologies (RATs) is emerging. As a result, the design of communication systems considering services or terminals sensitive to reliability and latency is being discussed. The next-generation radio access technology considering improved mobile broadband communication, massive MTC, URLLC (Ultra-Reliable and Low Latency Communication), etc. is called new radio access technology (new RAT) or NR (new radio). V2X (vehicle-to-everything) communication can also be supported in NR.

[0006] FIG. 1 is a diagram for explaining a comparison between V2X communication based on RAT before NR and V2X communication based on NR.

[0007] In relation to V2X communication, in RATs prior to NR, solutions for providing safety services based on V2X messages such as BSM (Basic Safety Message), CAM (Cooperative Awareness Message), and DENM (Decentralized Environmental Notification Message) were being discussed. V2X messages include location information, dynamic information, attribute information, etc. For example, a terminal can send a periodic message type CAM and / or an event triggered message type DENM to other terminals.

[0008] For example, CAM includes dynamic state information of a vehicle such as direction and speed, static vehicle data such as dimensions, basic vehicle information such as external lighting status, and route details. For example, a terminal can broadcast CAM, and the delay of CAM is less than 100 ms. For example, when an emergency situation such as a vehicle breakdown or accident occurs, the terminal can generate and send a DENM to other terminals. For example, all vehicles within the transmission range of the terminal can receive CAM and / or DENM. In this case, DENM has a higher priority than CAM.

[0009] Subsequently, various V2X scenarios have been defined in NR in relation to V2X communication. For example, various V2X scenarios include vehicle platooning, advanced driving, extended sensors, remote driving, etc.

[0010] For example, based on vehicle platooning, vehicles dynamically form groups and move together. For example, in order to perform platoon operations based on vehicle platooning, vehicles belonging to the above group receive periodic data from the leading vehicle. For example, vehicles belonging to the above group can use the periodic data to reduce or increase the inter-vehicle distance.

[0011] For example, based on improved driving, the vehicle is semi-automated or fully automated. Each vehicle can adjust its trajectories or maneuvers based on data obtained from local sensors of neighboring vehicles and / or neighboring logical entities. For example, each vehicle can share its driving intention with neighboring vehicles.

[0012] For example, based on extended sensors, raw data, processed data, or live video data obtained by local sensors can be exchanged between vehicles, logical entities, pedestrian terminals, and / or V2X application servers. Thus, for example, a vehicle can recognize an environment that is better than the environment it can sense using its own sensors.

[0013] For example, based on remote driving, for a person who cannot drive or a remote vehicle located in a dangerous environment, a remote driver or a V2X application can operate or control the remote vehicle. For example, when the route can be predicted, such as in public transportation, cloud computing-based driving is used for the operation or control of the remote vehicle. For example, a connection to a cloud-based back-end service platform is considered for remote driving.

[0014] On the other hand, solutions for specifying service requirements for various V2X scenarios such as platooning vehicles, improved driving, extended sensors, and remote driving are being discussed in NR-based V2X communication. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0015] An object of the present invention is to provide a method for accurately and efficiently performing a wireless signal transmission and reception procedure and an apparatus therefor.

[0016] The technical problems to be solved by the present invention are not limited to the above technical problems, and other technical problems not mentioned will be clearly understandable to those having ordinary knowledge in the technical field to which the present invention belongs from the following description.

Means for Solving the Problems

[0017] According to one aspect of the present invention, in a wireless communication system, a method for a first UE to transmit a signal includes performing a procedure for setting a split bearer including both a direct path between the first UE and a network and an indirect path between the first UE and the network, and when setting the split bearer, determining that the direct path is set as a primary path of the split bearer, transmitting first upstream data to the network via the direct path based on the primary path of the split bearer, detecting a failure related to the direct path, switching the primary path of the split bearer from the direct path to the indirect path based on the detection of the failure related to the direct path, and transmitting second upstream data to the network by a second UE operating as a relay UE for an indirect path to the network on the switched primary path of the split bearer.

[0018] Preferably, the indirect path is set based on a sidelink interface between the first UE and the relay UE.

[0019] Preferably, the second upstream data is transmitted to the network via a Uu interface between the second UE and the network.

[0020] Preferably, the failure related to the direct path is a Uu interface failure between the first UE and the network.

[0021] Preferably, the RRC (radio resource control) message in the split bearer is exchanged via the primary path.

[0022] Preferably, the RRC message exchanged via the primary path includes an RRC message for the secondary path of the split bearer.

[0023] Preferably, the failure related to the direct path includes at least one of an integrity protection failure, an RLC (radio link control) retransmission failure, an RLF (radio link failure), a bearer reconfiguration failure, and a beam failure.

[0024] Preferably, the first UE operates as a remote UE in the indirect path.

[0025] According to another aspect of the present invention, there is provided a computer-readable medium storing instructions that, when executed by a processor, cause the processor to perform the method described above.

[0026] According to another aspect of the present invention, there is provided a terminal configured to perform the method.

[0027] According to another aspect of the present invention, there is provided an apparatus configured to control a terminal configured to perform the method.

Advantages of the Invention

[0028] According to the present invention, the wireless signal transmission and reception procedure can be performed accurately and efficiently.

[0029] The effects that can be obtained from various examples of the present disclosure, and other effects not mentioned, will be clearly derived and understood by those having ordinary knowledge in the technical field to which the present invention pertains from the following description.

Brief Description of the Drawings

[0030]

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Embodiments for Carrying Out the Invention

[0031] A wireless communication system is a multiple access system that shares available system resources (e.g., bandwidth, transmission power, etc.) to support communication with multiple users. Examples of multiple access systems include CDMA (code division multiple access) systems, FDMA (frequency division multiple access) systems, TDMA (time division multiple access) systems, OFDMA (orthogonal frequency division multiple access) systems, SC-FDMA (single carrier frequency division multiple access) systems, MC-FDMA (multi carrier frequency division multiple access) systems, etc.

[0032] For background technology, terms, definitions, and abbreviations related to this invention, the following documents can be referred to.

[0033] 3GPP (Registered Trademark) LTE

[0034] - 3GPP TS 36.211: Physical channels and modulation

[0035] - 3GPP TS 36.212: Multiplexing and channel coding

[0036] - 3GPP TS 36.213: Physical layer procedures

[0037] - 3GPP TS 36.214: Physical layer; Measurements

[0038] - 3GPP TS 36.300: Overall description

[0039] - 3GPP TS 36.304: User Equipment (UE) procedures in idle mode

[0040] - 3GPP TS 36.314: Layer 2 - Measurements

[0041] - 3GPP TS 36.321: Medium Access Control (MAC) protocol

[0042] - 3GPP TS 36.322: Radio Link Control (RLC) protocol

[0043] - 3GPP TS 36.323: Packet Data Convergence Protocol (PDCP)

[0044] - 3GPP TS 36.331: Radio Resource Control (RRC) protocol

[0045] 3GPP NR

[0046] - 3GPP TS 38.211: Physical channels and modulation

[0047] - 3GPP TS 38.212: Multiplexing and channel coding

[0048] - 3GPP TS 38.213: Physical layer procedures for control

[0049] - 3GPP TS 38.214: Physical layer procedures for data

[0050] - 3GPP TS 38.215: Physical layer measurements

[0051] - 3GPP TS 38.300: Overall description

[0052] - 3GPP TS 38.304: User Equipment (UE) procedures in idle mode and in RRC inactive state

[0053] - 3GPP TS 38.321: Medium Access Control (MAC) protocol

[0054] - 3GPP TS 38.322: Radio Link Control (RLC) protocol

[0055] - 3GPP TS 38.323: Packet Data Convergence Protocol (PDCP)

[0056] - 3GPP TS 38.331: Radio Resource Control (RRC) protocol

[0057] - 3GPP TS 37.324: Service Data Adaptation Protocol (SDAP)

[0058] - 3GPP TS 37.340: Multi-connectivity; Overall description

[0059] Sidelink (SL) refers to a communication method that directly establishes a link between User Equipments (UEs) and enables direct exchange of voice or data between UEs without going through a Base Station (BS). Sidelink is a solution to relieve the burden on the base station caused by the rapidly increasing data traffic.

[0060] V2X (vehicle-to-everything) means a communication technology that exchanges information with other vehicles, pedestrians, infrastructure, etc. through wireless communication. V2X is classified into four types such as V2V (vehicle-to-vehicle), V2I (vehicle-to-infrastructure), V2N (vehicle-to-network), and V2P (vehicle-to-pedestrian). V2X communication is provided by the PC5 interface and / or the Uu interface.

[0061] On the one hand, as more communication devices demand greater communication capacity, the need for mobile broadband communication that is improved compared to existing radio access technologies (RATs) is emerging. Accordingly, communication systems that take into account services or terminals sensitive to reliability and latency are being discussed. Next-generation radio access technologies that consider enhanced mobile broadband communication, massive MTC, Ultra-Reliable and Low Latency Communication (URLLC), etc. are called new radio access technology (new RAT) or NR (new radio). V2X (vehicle-to-everything) communication can also be supported in NR.

[0062] The following technologies can be used in various wireless connection systems such as CDMA (Code Division Multiple Access), FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access), OFDMA (Orthogonal Frequency Division Multiple Access), SC-FDMA (Single Carrier Frequency Division Multiple Access), etc. CDMA can be implemented by radio technologies such as UTRA (Universal Terrestrial Radio Access) and CDMA2000. TDMA can be implemented by radio technologies such as GSM (Global System for Mobile communications) / GPRS (General Packet Radio Service) / EDGE (Enhanced Data Rates for GSM Evolution). OFDMA can be implemented by radio technologies such as IEEE802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE802-20, E-UTRA (Evolved UTRA), etc. IEEE 802.16m is an evolution of IEEE 802.16e and provides backward compatibility with systems based on IEEE 802.16e. UTRA is part of UMTS (Universal Mobile Telecommunications System). 3GPP (3rd Generation Partnership Project) LTE (long term evolution) is part of E-UMTS (Evolved UMTS) that uses E-UTRA, adopts OFDMA in the downlink, and adopts SC-FDMA in the uplink. LTE-A (Advanced) is an evolution of 3GPP LTE.

[0063] 5G NR is a technology that follows LTE-A and is a new clean-slate mobile communication system with characteristics such as high performance, low latency, and high availability. 5G NR can utilize all available spectrum resources, including low-frequency bands below 1 GHz, intermediate-frequency bands from 1 GHz to 10 GHz, and high-frequency (millimeter-wave) bands above 24 GHz.

[0064] For a clearer explanation, the description will be centered around LTE-A or 5G NR, but the technical idea according to an embodiment of the present invention is not limited to these.

[0065] Figure 2 shows the structure of an LTE system according to an embodiment of the present invention. This is also called E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) or an LTE (Long Term Evolution) / LTE-A system.

[0066] Referring to Figure 2, E-UTRAN includes a base station 20 that provides a control plane and a user plane to a terminal 10. The terminal 10 can be fixed or mobile and is also called by terms such as MS (mobile station), UT (user terminal), SS (Subscriber station), MT (mobile terminal), and wireless device. Generally, the base station 20 is a fixed station that communicates with the terminal 10 and is also called by applications such as eNB (evolved NodE-B), BTS (base transceiver system), and AP (access point).

[0067] The base stations 20 are connected to each other through an X2 interface. The base station 20 is connected to the EPC (evolved Packet core, 30) through an S1 interface, and more specifically, is connected to the MME (mobility management entity) through S1-MME and to the S-GW (Serving gateway) through S1-U.

[0068] EPC30 is composed of an MME, an S-GW, and a P-GW (Packet data network-gateway). The MME has connection information of a terminal and information regarding the capabilities of the terminal, and such information is mainly used for mobility management of the terminal. The S-GW is a gateway with the E-UTRAN as an end point, and the P-GW is a gateway with a PDN (Packet Date Network) as an end point.

[0069] The radio interface protocol layer between a terminal and a network is classified into a first layer (L1), a second layer (L2), and a third layer (L3) based on the lower three layers of the well-known Open System Interconnection (OSI) reference model in a communication system. Among them, the physical layer belonging to the first layer provides an information transmission service using a physical channel, and the RRC (Radio Resource Control) layer belonging to the third layer controls radio resources between the terminal and the network. For this purpose, the RRC layer exchanges RRC messages between the terminal and the base station.

[0070] Figure 3 shows the structure of the NR system.

[0071] Referring to Figure 3, the NG-RAN (Next Generation-Radio Access Network) includes a gNB (next generation-Node BF cell) and / or an eNB that provide user plane and control plane protocol termination to a terminal. The case where only a gNB is included is illustrated in Figure 7. The gNB and the eNB are connected to each other by an Xn interface. The gNB and the eNB are connected to a 5th generation core network (5G Core Network: 5GC) by an NG interface. More specifically, the AMF (access and mobility management function) is connected by an NG-C interface, and the UPF (user plane function) is connected by an NG-U interface.

[0072] FIG. 4 shows the structure of an NR radio frame.

[0073] Referring to FIG. 4, in NR, radio frames are used for uplink and downlink transmissions. The radio frame has a length of 10 ms and is defined by two 5-ms half-frames (HF). A half-frame contains five 1-ms subframes (SF). A subframe is divided into one or more slots, and the number of slots in a subframe depends on the subcarrier spacing (SCS). Each slot contains 12 or 14 OFDM(A) symbols by means of a cyclic prefix (CP).

[0074] When normal CP is used, each slot contains 14 symbols. When extended CP is used, each slot contains 12 symbols. Here, the symbols include OFDM symbols (or CP-OFDM symbols), SC-FDMA symbols (or DFT-s-OFDM symbols).

[0075] Table 1 exemplifies the number of symbols per slot (N slot symbol ), the number of slots per frame (N frame,u slot ), and the number of slots per subframe (N subframe,u slot ) according to the SCS setting (μ) when normal CP is used.

[0076]

Table 1

[0077] Table 2 exemplifies the number of symbols per slot, the number of slots per frame, and the number of slots per subframe according to the SCS when extended CP is used.

[0078]

Table 2

[0079] In the NR system, the OFDM(A) numerology (e.g., SCS, CP length, etc.) can be set to be different among a plurality of cells merged into one terminal. Thereby, the (absolute time) intervals of time resources (e.g., subframe, slot or TTI) (for convenience, commonly referred to as TU (Time Unit)) composed of the same number of symbols are set to be different among the merged cells.

[0080] In NR, a number of numerologies or SCSs are supported to support various 5G services. For example, when the SCS is 15 kHz, a wide area in a traditional cellular band is supported. When the SCS is 30 kHz / 60 kHz, a dense-urban area, lower latency and wider carrier bandwidth are supported. When the SCS is 60 kHz or higher, a bandwidth greater than 24.25 GHz is supported to overcome phase noise.

[0081] The NR frequency band is defined by two types of frequency ranges. The two types of frequency ranges are FR1 and FR2. The numerical values of the frequency ranges can be changed. For example, the two types of frequency ranges are as shown in Table 3 below. Among the frequency ranges used in the NR system, FR1 means "sub 6GHz range" and FR2 means "above 6GHz range", which is also called millimeter wave (mmW).

[0082] [Table 3]

[0083] As described above, the numerical values of the frequency range of the NR system can be changed. For example, FR1 includes a band from 410 MHz to 7125 MHz as shown in Table 4 below. That is, FR1 includes a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or higher. For example, the frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or higher included within FR1 includes an unlicensed band. The unlicensed band is used for various applications, for example, for communication for vehicles (e.g., autonomous driving).

[0084]

Table 4

[0085] FIG. 5 is a diagram showing the slot structure of an NR frame.

[0086] Referring to FIG. 5, a slot includes a plurality of symbols in the time domain. For example, in the case of normal CP, one slot includes 14 symbols, while in the case of extended CP, one slot includes 12 symbols. Or in the case of normal CP, one slot includes 7 symbols, while in the case of extended CP, one slot includes 6 symbols.

[0087] A carrier wave includes a plurality of subcarriers in the frequency domain. An RB (Resource Block) is defined as a plurality (e.g., 12) of consecutive subcarriers in the frequency domain. A BWP is defined as a plurality of consecutive (P)RBs ((Physical) Resource Blocks) in the frequency domain and corresponds to one numerology (e.g., SCS, CP length, etc.). A carrier wave includes a maximum of N (e.g., 5) BWPs. Data communication is performed on the activated BWP. Each element is referred to as a resource element (RE) in the resource grid, and one complex symbol can be mapped.

[0088] On one hand, the wireless interface between terminals or the wireless interface between a terminal and a network is composed of an L1 layer, an L2 layer, and an L3 layer. In various embodiments of the present invention, the L1 layer means the physical layer. The L2 layer means, for example, any one of the MAC layer, the RLC layer, the PDCP layer, and the SDAP layer. The L3 layer means, for example, the RRC layer.

[0089] Hereinafter, V2X or SL (sidelink) communication will be described.

[0090] FIG. 6 shows the radio protocol architecture for SL communication. More specifically, FIG. 6(a) shows the user plane protocol stack of NR, and FIG. 6(b) shows the control plane protocol stack of NR.

[0091] Hereinafter, the Sidelink Synchronization Signal (SLSS) and synchronization information will be described.

[0092] The SLSS includes a Primary Sidelink Synchronization Signal (PSSS) and a Secondary Sidelink Synchronization Signal (SSSS) as an SL-specific sequence. The PSSS is called the S-PSS (Sidelink Primary Synchronization Signal), and the SSSS is called the S-SSS (Sidelink Secondary Synchronization Signal). For example, length-127 M-sequences are used for the S-PSS, and length-127 Gold sequences are used for the S-SSS. For example, a terminal detects the first signal using the S-PSS and acquires synchronization. For example, a terminal acquires detailed synchronization using the S-PSS and the S-SSS and detects the synchronization signal ID.

[0093] The Physical Sidelink Broadcast Channel (PSBCH) is a (broadcast) channel on which the basic (system) information that a terminal should know first before SL signal transmission and reception is transmitted. For example, the basic information includes information about SLSS, Duplex Mode (DM), TDD UL / DL (Time Division Duplex Uplink / Downlink) configuration, information about resource pools, types of applications related to SLSS, subframe offset, broadcast information, etc. For example, in order to evaluate the performance of the PSBCH, in NR V2X, the payload size of the PSBCH is 56 bits including a 24-bit CRC.

[0094] S-PSS, S-SSS, and PSBCH are included in a block format (e.g., SL SS (Synchronization Signal) / PSBCH block, hereinafter referred to as S-SSB (Sidelink-Synchronization Signal Block)) that supports periodic transmission. The S-SSB has the same numerology (i.e., SCS and CP length) as the PSCCH (Physical Sidelink Control Channel) / PSSCH (Physical Sidelink Shared Channel) within the carrier, and the transmission bandwidth is within the (pre-set) SL BWP (Sidelink BWP). For example, the bandwidth of the S-SSB is 11 Resource Blocks (RB). For example, the PSBCH spans 11 RB. Also, the frequency position of the S-SSB is (pre-set). Therefore, the terminal does not need to perform hypothesis detection in terms of frequency to discover the S-SSB in the carrier.

[0095] On the one hand, in the NR SL system, a plurality of numerologies with different SCSs and / or CP lengths are supported. At this time, as the SCS increases, the length of the time resource for the transmitting terminal to transmit the S-SSB becomes shorter. As a result, the coverage of the S-SSB decreases. Therefore, in order to ensure the coverage of the S-SSB, the transmitting terminal transmits one or more S-SSBs to the receiving terminal within one S-SSB transmission period according to the SCS. For example, the number of S-SSBs transmitted by the transmitting terminal to the receiving terminal within one S-SSB transmission period is pre-configured or configured in the transmitting terminal. For example, the S-SSB transmission period is 160 ms. For example, a 160-ms S-SSB transmission period is supported for all SCSs.

[0096] For example, when the SCS is 15 kHz in FR1, the transmitting terminal transmits one or two S-SSBs to the receiving terminal within one S-SSB transmission period. For example, when the SCS is 30 kHz in FR1, the transmitting terminal transmits one or two S-SSBs to the receiving terminal within one S-SSB transmission period. For example, when the SCS is 60 kHz in FR1, the transmitting terminal transmits one, two, or four S-SSBs to the receiving terminal within one S-SSB transmission period.

[0097] For example, when the SCS is 60 kHz in FR2, the transmitting terminal transmits one, two, four, eight, sixteen, or thirty-two S-SSBs to the receiving terminal within one S-SSB transmission period. For example, when the SCS is 120 kHz in FR2, the transmitting terminal transmits one, two, four, eight, sixteen, thirty-two, or sixty-four S-SSBs to the receiving terminal within one S-SSB transmission period.

[0098] On one hand, when the SCS is 60 kHz, two types of CPs are supported. Also, depending on the CP type, the structure of the S-SSB transmitted by the transmitting terminal to the receiving terminal may be different. For example, the CP type is Normal CP (NCP) or Extended CP (ECP). Specifically, for example, when the CP type is NCP, the number of symbols for mapping the PSBCH in the S-SSB transmitted by the transmitting terminal is 9 or 8. On the other hand, for example, when the CP type is ECP, the number of symbols for mapping the PSBCH in the S-SSB transmitted by the transmitting terminal is 7 or 6. For example, the PSBCH is mapped to the first symbol in the S-SSB transmitted by the transmitting terminal. For example, the receiving terminal that receives the S-SSB performs an AGC (Automatic Gain Control) operation in the first symbol section of the S-SSB.

[0099] FIG. 7 shows a terminal for performing V2X or SL communication.

[0100] Referring to FIG. 7, in V2X or SL communication, the term "terminal" mainly means the user's terminal. However, when network equipment such as a base station transmits and receives signals according to the communication method between terminals, the base station may also be regarded as a kind of terminal. For example, terminal 1 is the first device 100, and terminal 2 is the second device 200.

[0101] For example, terminal 1 selects a resource unit corresponding to a specific resource in a resource pool that means a set of a series of resources. Also, terminal 1 transmits an SL signal using the resource unit. For example, terminal 2, which is a receiving terminal, has a resource pool set where it can transmit a signal to terminal 1, and detects the signal of terminal 1 within the resource pool.

[0102] Here, when the terminal 1 is within the connection range of the base station, the base station notifies the terminal 1 of the resource pool. On the other hand, when the terminal 1 is outside the connection range of the base station, another terminal notifies the terminal 1 of the resource pool, or the terminal 1 uses a preset resource pool.

[0103] Generally, a resource pool consists of a plurality of resource units, and each terminal selects one or more resource units to use for its own SL signal transmission.

[0104] Figure 8 shows resource units for V2X or SL communication.

[0105] Referring to Figure 8, the entire frequency resource of the resource pool is divided into NF, and the entire time resource of the resource pool is divided into NT. Therefore, a total of NF * NT resource units are defined within the resource pool. Figure 8 shows an example where the resource pool is repeated with a period of NT subframes.

[0106] As shown in Figure 8, one resource unit (for example, Unit #0) is periodically repeated. Alternatively, in order to obtain the effect of diversity in the time or frequency dimension, the index of the physical resource unit to which one logical resource unit is mapped may change in a pattern predetermined by time. In this resource unit structure, the resource pool means a set of resource units available for transmission by a terminal attempting to transmit an SL signal.

[0107] The resource pool can be subdivided into several types. For example, according to the content of the SL signal transmitted from each resource pool, the resource pool can be classified as follows.

[0108] (1) Scheduling Assignment (SA) is a signal that contains information such as the position of resources used by a transmitting terminal for transmitting on the SL data channel, the Modulation and Coding Scheme (MCS) or Multiple Input Multiple Output (MIMO) transmission method required for demodulating other data channels, and Timing Advance (TA). SA can also be multiplexed and transmitted with SL data on the same resource unit. In this case, the SA resource pool means the resource pool on which SA is multiplexed and transmitted with SL data. SA is also called the SL control channel.

[0109] (2) The Physical Sidelink Shared Channel (PSSCH) is the resource pool used by a transmitting terminal for transmitting user data. If SA is multiplexed and transmitted with SL data on the same resource unit, only the SL data channel in a form excluding SA information is transmitted from the resource pool for the SL data channel. In other words, the Resource Elements (REs) used for transmitting SA information on individual resource units within the SA resource pool can still be used for transmitting SL data in the resource pool of the SL data channel. For example, a transmitting terminal maps and transmits the PSSCH to consecutive Physical Resource Blocks (PRBs).

[0110] (3) The discovery channel is the resource pool for a transmitting terminal to transmit information such as its own ID. This enables the transmitting terminal to be discovered by adjacent terminals.

[0111] Even when the content of the aforementioned SL signal is the same, different resource pools can be used according to the attributes of the transmission and reception of the SL signal. As an example, even for the same SL data channel or discovery message, depending on the SL signal transmission timing determination method (for example, whether it is transmitted at the reception time of the synchronization reference signal, or transmitted by applying a certain timing advance to the reception time), resource allocation method (for example, whether the base station designates the transmission resources of individual signals to individual transmission terminals, or whether individual transmission terminals themselves select individual signal transmission resources within the resource pool), signal format (for example, the number of symbols occupied by each SL signal in one subframe, or the number of subframes used for the transmission of one SL signal), signal strength from the base station, transmission power strength of the SL terminal, etc., it may be divided into different resource pools.

[0112] SL DRX (sidelink discontinuous reception)

[0113] SL supports SL DRX for unicast, groupcast, and broadcast. Define similar parameters (on-duration, inactivity-timer, retransmission-timer, cycle) for Uu for SL to determine the SL active time for SL DRX. During the SL active time, the terminal performs SCI monitoring for data reception (for example: two-stage SCI of PSCCH and PSSCH). During the SL DRX inactivity time, the terminal may skip SCI monitoring for data reception.

[0114] The actual parameters supported for each cast type (unicast, groupcast, broadcast) are specified in the following subsections.

[0115] The SL active time of the RX terminal includes the time during which an applicable SL on-duration timer, SL inactivity timer, or SL retransmission timer is running (for one of unicast, groupcast, or broadcast). Also, the slots related to the known periodic transmissions of the TX terminal and the time when the terminal expects a CSI report associated with a CSI request (for unicast) are considered the SL active time of the RX terminal.

[0116] The TX terminal maintains a timer set corresponding to the SL DRX timer of the RX terminal for each source / destination L2 ID pair for unicast or each destination L2 ID for groupcast / broadcast. If there is data to be transmitted to one or more RX terminals with SL DRX set, the TX terminal selects resources considering the active time of the RX terminal determined by the timer maintained at itself.

[0117] For unicast, SL DRX is set for each pair of source L2 ID and destination L2 ID.

[0118] The terminal maintains an SL DRX timer set for each direction for each pair of source L2 ID and destination L2 ID. For the SL DRX setting in one direction for a source / destination L2 ID pair, it can be negotiated between terminals in the AS hierarchy. For the SL DRX setting in each direction where one terminal is the TX terminal and the other is the RX terminal:

[0119] - The RX terminal can send assistance information including the desired on-duration timer, SL DRX start offset, and SL DRX period to the TX terminal, and all 2TX terminals can use this to determine the SL DRX setting for the RX terminal.

[0120] Regardless of whether support information is provided or not, a TX terminal in RRC_IDLE / RRC_INACTIVE / OOC, or a TX terminal in RRC_CONNECTED that uses mode 2 resource allocation determines the SL DRX setting for the RX terminal. In the case of a TX terminal in RRC_CONNECTED that uses mode 1 resource allocation, the SL DRX setting for the RX terminal is determined by the serving base station of the TX terminal.

[0121] - The TX terminal sends the SL DRX setting used by the RX terminal to the RX terminal.

[0122] - The RX terminal accepts or rejects the SL DRX setting.

[0123] The basic SL DRX setting (default SL DRX configuration) for groupcast / broadcast is used in the DCR message.

[0124] When the TX terminal is in RRC_CONNECTED, the TX terminal reports the received support information to the serving base station, and when it receives the SL DRX setting in a dedicated RRC signal at the base station, it sends the SL DRX setting to the RX terminal. When the RX terminal is in RRC_CONNECTED, the RX terminal reports the received SL DRX setting to its serving base station, for example, for the alignment of the Uu setting and the SL DRX setting.

[0125] The SL on-duration timer, SL inactivity timer, SL HARQ RTT timer, and SL HARQ retransmission timer are supported in unicast. The SL HARQ RTT timer and SL HARQ retransmission timer are maintained for each SL process at the RX terminal. When the SCI indicates two or more transmission resources, in addition to the (pre-)set value for each of these timers, the SL HARQ RTT timer value is derived from the retransmission resource timing.

[0126] The SL DRX MAC CE is introduced only for unicast SL DRX operation.

[0127] For groupcast / broadcast, SL DRX is configured commonly among multiple terminals based on the QoS profile and the destination L2 ID. Multiple SL DRX configurations can be supported for each groupcast / broadcast.

[0128] For groupcast, an SL on-duration timer, an SL inactivity timer, an SL HARQ RTT timer, and an SL retransmission timer are supported. For broadcast, only the SL on-duration timer is supported. The SL DRX period, the SL on-duration, and the SL inactivity timer (only applicable to groupcast) are configured for each QoS profile. The start offset and the slot offset of the SL DRX period are determined according to the destination L2 ID. The SL HARQ RTT timer (only applicable to groupcast) and the SL HARQ retransmission timer (only applicable to groupcast) are not configured for each QoS profile or destination L2 ID. For groupcast, the RX terminal maintains an SL inactivity timer for each destination L2 ID, and selects the maximum SL inactivity timer value when multiple SL inactivity timer values associated with different QoS profiles are configured for that L2 ID. For groupcast and broadcast, when multiple QoS profiles are configured for each destination L2 ID, the RX terminal maintains a single SL DRX period (selected as the minimum SL DRX period of all QoS profiles of that L2 ID) and a single SL on-duration (selected as the maximum SL on-duration of all QoS profiles of that L2 ID) for that L2 ID.

[0129] In the case of groupcast, the SL HARQ RTT timer and the SL retransmission timer are maintained at the RX terminal for each SL process. The SL HARQ RTT timer may be set to different values from each other so as to support both HARQ enabled transmission and HARQ disabled transmission.

[0130] A common basic SL DRX setting between groupcast and broadcast is used for QoS profiles that are not mapped to non-default SL DRX settings.

[0131] TX terminals and RX terminals within the coverage of RRC_IDLE / RRC_INACTIVE acquire their SL DRX settings in the SIB. (TX or RX) terminals in RRC_CONNECTED acquire the SL DRX settings in the SIB or from dedicated RRC signals during handover. In the case of out-of-coverage, the SL DRX settings are acquired by pre-configuration.

[0132] In the case of groupcast, when a TX terminal receives new data having the same destination L2 ID, it resumes its timer corresponding to the SL inactivity timer for the destination L2 ID (used for determining the allowed transmission time).

[0133] The TX profile is introduced to ensure compatibility for groupcast and broadcast transmissions between terminals that support / do not support the SL DRX function. The TX profile is provided from the upper layer to the AS layer and identifies one or more SL function groups. The TX terminal assumes SL DRX for the RX terminal only when the relevant TX profile corresponds to SL DRX support. The RX terminal determines that SL DRX is used when there is a relevant TX profile corresponding to SL DRX support for all destination L2 IDs of interest.

[0134] For unicast, groupcast, and broadcast, alignment of Uu DRX and SL DRX for RRC_CONNECTED terminals is supported. Alignment of Uu DRX and SL DRX is supported for the same terminal. Also, in mode 1 scheduling, alignment of the Uu DRX of the TX terminal and the SL DRX of the RX terminal is supported.

[0135] Alignment is performed with overall or partial time overlap between Uu DRX and SL DRX. In the case of an RRC_CONNECTED SL RX terminal, alignment is performed at the base station.

[0136] The SL DRX function that controls the SCI (i.e., one-stage SCI and two-stage SCI) monitoring activities of the terminal for unicast, groupcast, and broadcast is set by RRC to the MAC entity. When using SL DRX operation, the MAC entity also needs to monitor the SCI (i.e., one-stage SCI and two-stage SCI) according to the requirements in other sections of the present invention.

[0137] RRC sets the following parameters to control SL DRX operation.

[0138] - sl-drx-onDurationTimer: Duration at the start of the SL DRX cycle

[0139] - sl-drx-SlotOffset: Delay time before the start of sl-drx-onDurationTimer

[0140] - sl-drx-InactivityTimer (except for broadcast transmissions): Period after the first slot of the SCI (i.e., one-stage SCI and two-stage SCI) reception indicating a new SL transmission to the MAC entity

[0141] - sl-drx-RetransmissionTimer (per SL process except for broadcast transmissions): Maximum period until an SL retransmission is received

[0142] - sl-drx-StartOffset: The slot at which the SL DRX cycle starts

[0143] - sl-drx-Cycle: SL DRX cycle

[0144] - sl-drx-HARQ-RTT-Timer (per SL process excluding broadcast transmission): The minimum period before the MAC entity anticipates an SL HARQ retransmission

[0145] When SL DRX is configured, the active time includes the following times.

[0146] - The time when the sl-drx-onDurationTimer or sl-drx-InactivityTimer is running, or

[0147] - The time when the sl-drx-RetransmissionTimer is running, or

[0148] - When the SL-CSI report MAC CE is not received, the sl-LatencyBoundCSI-Report interval set by RRC, or

[0149] - When the SL-CSI report MAC CE is received, the time between the SL-CSI report request transmission and the SL-SCI report MAC CE reception, or

[0150] - Slots related to the known periodic transmissions of the terminal transmitting SL-SCH data.

[0151] When one or more SL DRXs are configured, the MAC entity performs the following.

[0152] 1> When multiple SL DRX periods mapped to a plurality of SL - QoS - Profiles of a destination Layer - 2 ID and an interested cast type are related to group cast and broadcast:

[0153] 2> Among the multiple SL DRX periods mapped to a plurality of SL - QoS - Profiles related to a destination Layer - 2 ID, select the sl - drx - Cycle with the shortest length.

[0154] 2> Among the multiple SL DRX onduration timers mapped to a plurality of SL - QoS - Profiles related to a destination Layer - 2 ID, select the sl - drx - onDurationTimer with the longest length.

[0155] 1> When the sl - drx - HARQ - RTT - Timer expires:

[0156] 2> If the data of the SL process is not successfully decoded or HARQ feedback (i.e., negative acknowledgment) is not unicast according to the UL / SL priority:

[0157] 3> After the sl - drx - HARQ - RTT - Timer expires, start the sl - drx - RetransmissionTimer for the SL process in the first slot.

[0158] When the cast type is group cast or broadcast as instructed by the upper layer, sl - drx - StartOffset and sl - drx - SlotOffset are derived from the following formula.

[0159] sl - drx - StartOffset(ms) = Destination Layer - 2 ID modulo sl - drx - Cycle(ms).

[0160] sl-drx-SlotOffset (ms) = Destination Layer-2 ID modulo sl-drx-onDurationTimer (ms).

[0161] 1> When the SL DRX cycle is used and [(DFN Х 10) + subframe number] modulo (sl-drx-Cycle) = sl-drx-StartOffset:

[0162] 2> Start sl-drx-onDurationTimer after sl-drx-SlotOffset from the start of the subframe.

[0163] 1> When SL DRX is the active time:

[0164] 2> Monitor the SCI (i.e., one-stage SCI and two-stage SCI) in this SL DRX.

[0165] 2> When the SCI indicates a new SL transmission:

[0166] 3> When the source Layer-1 ID of the SCI is equal to the 8 LSBs of the intended destination Layer-2 ID, the destination Layer-1 ID of the SCI is equal to the 8 LSBs of the intended source Layer-2 ID, and the cast type indicator of the SCI is set to unicast:

[0167] 4> Start or restart sl-drx-InactivityTimer for the pair of its source Layer-2 ID and destination Layer-2 ID after the first slot of the SCI reception.

[0168] 3> When the destination Layer-1 ID of the SCI (i.e., two-stage SCI) is equal to the 8 LSBs of the intended destination Layer-1 ID and the cast type indicator of the SCI is set to groupcast:

[0169] 4> Select the sl-drx-InactivityTimer with the longest length among the multiple SL DRX inactivity timers mapped to the multiple SL-QoS-Profiles of the destination Layer-2 ID related to the destination Layer-1 ID of the SCI.

[0170] 4> After the first slot of the SCI reception, start or resume the sl-drx-InactivityTimer for its destination Layer-2 ID.

[0171] 2> When the SCI indicates an SL transmission:

[0172] 3> When no PSFCH resource is configured for the SL grant related to the SCI:

[0173] 4> Start the sl-drx-HARQ-RTT-Timer for that SL process in the slot after the transmission of the PSSCH (i.e., the currently received PSSCH) has ended.

[0174] 3> When a PSFCH resource is configured for the SL grant related to the SCI:

[0175] 4> When HARQ feedback is activated by the SCI and the cast type indicator of the SCI is set to unicast; or, 4> When HARQ feedback is activated by the SCI, the cast type indicator of the SCI is set to groupcast, and positive-negative acknowledgement is selected;

[0176] 5> After the transmission of the PSFCH for transmitting the SL HARQ feedback has ended, start the sl-drx-HARQ-RTT-Timer for that SL process in the first slot. Or

[0177] 5> When the SL HARQ feedback is not transmitted according to the UL / SL priority, after the PSFCH resource for the SL HARQ feedback ends, start the sl-drx-HARQ-RTT-Timer for that SL process in the first slot.

[0178] 4> When HARQ feedback is activated in the SCI, the cast type indicator of the SCI is set to group cast, and only negative-only acknowledgment is selected;

[0179] 5> After the PSFCH transmission for transmitting the SL HARQ feedback ends, start the sl-drx-HARQ-RTT-Timer for that SL process in the first slot. Or

[0180] 5> When the SL HARQ feedback is not transmitted according to the UL / SL priority, after the PSFCH resource for the SL HARQ feedback ends, start the sl-drx-HARQ-RTT-Timer for that SL process in the first slot. Or

[0181] 5> When the SL HARQ feedback is an affirmative acknowledgment, after the PSFCH resource for the SL HARQ feedback ends, start the sl-drx-HARQ-RTT-Timer for that SL process in the first slot.

[0182] 4> When the SCI deactivates the HARQ feedback and resources for one or more retransmission opportunities are not scheduled by the SCI:

[0183] 5> Start the sl-drx-HARQ-RTT-Timer for that SL process in the slot after the PSFCH resource ends.

[0184] 4> If HARQ feedback is deactivated in the SCI and resources for one or more retransmission opportunities are scheduled by the SCI:

[0185] 5> Start the sl-drx-HARQ-RTT-Timer for that SL process in the slot after the transmission of the PSSCH (i.e., the currently received PSSCH) has ended.

[0186] Reference: When the SCI indicates the next retransmission resource, the sl-drx-HARQ-RTT-Timer is derived from the retransmission resource timing (i.e., the next retransmission resource indicated by the SCI). The terminal uses the configured sl-drx-HARQ-RTT-Timer when the SCI does not indicate the next transmission resource.

[0187] 3> Abort the sl-drx-RetransmissionTimer for that SL process.

[0188] 1> If an SL DRX command MAC CE for a unicast source Layer-2 ID and destination Layer-2 ID pair is received:

[0189] 2> Abort the sl-drx-onDurationTimer for the unicast source Layer-2 ID and destination Layer-2 ID pair.

[0190] 2> Abort the sl-drx-InactivityTimer for the unicast source Layer-2 ID and destination Layer-2 ID pair.

[0191] Inter-UE Coordination (IUC)

[0192] The SL terminal supports inter-UE coordination (IUC) in mode 2. Here, terminal-A sends information about resources to terminal-B, and terminal-B uses this for resource (re)selection. The following inter-UE coordination methods are supported.

[0193] - In IUC mode 1, the adjustment information transmitted from terminal - A to terminal - B indicates the preferred and / or non - preferred resources for the transmission of terminal - B.

[0194] - In IUC mode 2, the adjustment information transmitted from terminal - A to terminal - B indicates the existence of predicted / potential resource collisions for the resources indicated by the SCI of terminal - B.

[0195] In mode 1, IUC can be triggered by an explicit request from terminal - B or the state of terminal - A. Terminal - A determines a set of resources reserved by other terminals or a set of slots that are not expected to receive SL from terminal - B when terminal - A is the intended receiver of terminal - B and terminal - A performs half - duplex operation. Terminal - A uses this resource as a set of non - preferred resources or excludes this resource to determine a set of preferred resources, and transmits the preferred / non - preferred resources to terminal - B. The resources of terminal - B for (re)selection may be based on the detection result of terminal - B (if available) and the adjustment information received at terminal - A, or may be based only on the adjustment information received at terminal - A. In the case of mode 1, IUC can be transmitted using MAC CE and two - stage SCI or MAC CE only. The explicit request and report for IUC are supported in unicast mode.

[0196] In mode 2, terminal - A determines the predicted / potential collision resources within the resources indicated by the SCI of terminal - B for the resources reserved by other terminals and identified as completely / partially overlapping with the resources indicated by the SCI of terminal - B at terminal - A, or for the slots that are not expected to receive SL in that slot by half - duplex operation when terminal - A is the intended receiver of terminal - B. Terminal - B determines the resources to re - select using the collision resources and excludes the collision resources from the re - selected resources. In the case of mode 2, PSFCH is used to transmit IUC.

[0197] The procedure for transmitting the adjustment request (SL-IUC Req) between SL terminals is used to trigger the transmission of adjustment information between SL terminals of the peer UE.

[0198] The procedure for reporting the adjustment information (SL-IUC Info) between SL terminals is used to provide the adjustment information between terminals to the peer UE.

[0199] - sl-LatencyBoundIUC-Report is maintained for each PC5-RRC connection.

[0200] The MAC entity maintains sl-IUC-ReportTimer for each pair of source Layer-2 ID and destination Layer-2 ID corresponding to the PC5-RRC connection. The sl-IUC-ReportTimer is used for the SL-IUC information reporting terminal to comply with the delay requirement notified by the IUC-Information triggering terminal. The value of the sl-IUC-ReportTimer is the same as the delay requirement for the SL-IUC information of sl-LatencyBoundIUC-Report set in RRC.

[0201] The MAC entity performs the following for each pair of source Layer-2 ID and destination Layer-2 ID corresponding to the PC5-RRC connection set in the upper layer.

[0202] 1> When the SL-IUC information report is triggered by the SL-IUC request MAC CE (and / or SCI) and has not been cancelled:

[0203] 2> When the sl-IUC-ReportTimer is not running for the triggered SL-IUC information report:

[0204] 3> Start the sl-IUC-ReportTimer.

[0205] 2> When the sl-IUC-ReportTimer has expired for the triggered SL-IUC information report:

[0206] 3> Cancel the triggered SL-IUC information report.

[0207] 2> Otherwise, if the MAC entity has the SL resources allocated for the new transmission and, as a result of the logical channel prioritization, the SL-SCH resources can accommodate the SL-IUC information MAC CE and its subheader:

[0208] 3> As defined in 6.1.3.35, instruct to generate the adjustment information MAC CE between SL terminals in the multiplexing and assembly procedures.

[0209] 3> Stop the sl-IUC-ReportTimer for the triggered SL-IUC information report.

[0210] 3> Cancel the triggered SL-IUC information report.

[0211] Figure 9 shows the adjustment information MAC CE between terminals.

[0212] The adjustment information MAC CE between terminals is identified by a MAC subheader having the LCID specified in Table 5.

[0213]

Table 5

[0214] The priority of the adjustment information MAC CE between terminals is fixed at "1". The adjustment information MAC CE between terminals has a variable size and includes the following fields.

[0215] - RT: This field is the code point value of the SCI format 2-C resourceSetType field and indicates the resource set type, i.e., the preferred resource set or the non-preferred resource set.

[0216] - RSL: This field is the code point value of the SCI format 2-C referenceSlotLocation field, indicating the position of the reference slot. The length of said field is 17 bits. If the length of the referenceSlotLocation field in SCI format 2-C is shorter than 17 bits, this field contains the referenceSlotLocation field using the LSB bits.

[0217] - LSIi: This field is the code point value of the SCI format 2-C lowestIndices field, indicating the lowest sub-channel index for the first resource position of each TRIV. LSI0 indicates the lowest sub-channel index for the first resource position of TRIV within the first resource combination, and LSI1 indicates the lowest sub-channel index for the first resource position of TRIV within the second resource combination. The length of said field is 5 bits. If the length of the lowestIndices field in SCI format 2-C is shorter than 5 bits, this field contains the lowestIndices field using the LSB bits.

[0218] - RCi: This field is the code point value of the SCI format 2-C resourceCombination field, indicating the resource combination. RC0 indicates the first resource combination, and RC1 indicates the second resource combination. [The maximum number of resource combinations included is 8.] The length of said field is 26 bits. If the length of the resourceCombination field in SCI format 2-C is shorter than 26 bits, this field contains the resourceCombination field using the LSB bits.

[0219] - First resource locationi-1: This field is the code point value of the SCI format 2-C firstResourceLocation field, indicating the first resource location. First Resource location0 indicates the first resource location of the second resource combination, and First Resource location1 indicates the first resource location of the third resource combination. The length of the field is 13 bits. If the length of the firstResourceLocation field in SCI format 2-C is shorter than 13 bits, this field contains the firstResourceLocation field using the LSB bit.

[0220] - R: Reserved bit, set to 0.

[0221] Figure 10 shows the adjustment request MAC CE between terminals.

[0222] The adjustment request MAC CE between terminals is identified by a MAC sub-header with the LCID specified in Table 5. The priority of the adjustment request MAC CE between terminals is fixed at "1". The adjustment request MAC CE between terminals has a variable size and includes the following fields.

[0223] - RT: This field is the code point value of the SCI format 2-C resourceSetType field, indicating the resource set type, i.e., the preferred resource set or the non-preferred resource set.

[0224] - RP: This field is the code point value of the SCI format 2-C resourceReservationPeriod field, indicating the resource reservation period. The length of the field is 4 bits. If the length of the resourceReservationPeriod field in SCI format 2-C is shorter than 4 bits, this field contains the resourceReservationPeriod field using the LSB bit.

[0225] - Priority: This field is the code point value of the SCI format 2-C priority field and indicates the priority. The length of the field is 3 bits.

[0226] - RSWL: This field is the code point value of the SCI format 2-C resourceSelectionWindowLocation field and indicates the position of the resource selection window. The length of the field is 34 bits. If the length of the resourceSelectionWindowLocation field in SCI format 2-C is shorter than 34 bits, this field contains the resourceSelectionWindowLocation field using the LSB bits.

[0227] - Number of Subchannel: This field is the code point value of the SCI format 2-C numberOfSubchannel field and indicates the number of subchannels. The length of the field is 5 bits. If the length of the numberOfSubchannel field in SCI format 2-C is shorter than 5 bits, this field contains the numberOfSubchannel field using the LSB bits.

[0228] - R: Reserved bit, set to 0.

[0229] SL relay

[0230] The SL relay is introduced to support the 5G ProSe terminal-network relay (U2N relay) function that provides network connection to the U2N remote terminal. Both L2 and L3 U2N relay architectures are supported. The L3 U2N relay architecture is transparent to the serving RAN of the U2N relay terminal except for SL resource control.

[0231] Relay Discovery: An AS function that activates UE-to-Network Relay Discovery using NR technology without going through network nodes.

[0232] U2N Relay Terminal: A terminal that provides a function to assist network connection to U2N remote terminals.

[0233] U2N Remote Terminal: A terminal that communicates with the network through a U2N relay terminal.

[0234] Upstream: The direction from the IAB topology towards the parent node.

[0235] Uu Relay RLC Channel: An RLC channel between the L2 U2N relay terminal and the base station, which is used to transmit packets via Uu for L2 terminal-network relay.

[0236] The U2N relay terminal needs to be in the RRC_CONNECTED state to relay unicast data.

[0237] For L2 U2N relay operation, the following RRC state combinations are supported.

[0238] - Only when both the U2N relay terminal and the U2N remote terminal are in the RRC CONNECTED state can they send / receive relayed unicast data.

[0239] - When all U2N remote terminals connected to the U2N relay terminal are in RRC_INACTIVE or RRC_IDLE, the U2N relay terminal can be in RRC_IDLE, RRC_INACTIVE or RRC_CONNECTED.

[0240] In the case of L2 U2N relay, the U2N remote terminal is set to use only resource allocation mode 2 for the data to be relayed.

[0241] A single unicast link is established between one L2 U2N relay terminal and one L2 U2N remote terminal. The traffic of the U2N remote terminal and the traffic of the U2N relay terminal via a given U2N relay terminal need to be separated into different Uu RLC channels on Uu.

[0242] Protocol stack of SL relay

[0243] FIG. 11 shows (a) the user plane protocol stack and (b) the control plane protocol stack of the L2 terminal - network relay.

[0244] The protocol stacks for the user plane and the control plane of the L2 U2N relay architecture are shown in FIGS. 11(a) and (b). The SRAP sub - array is placed on the RLC sub - layer for both CP and UP at both the PC5 interface and the Uu interface. Uu SDAP, PDCP, and RRC are terminated between the L2 U2N remote terminal and the base station, while SRAP, RLC, MAC, and PHY are terminated at each hop (i.e., the link between the L2 U2N remote terminal and the L2 U2N relay terminal and the link between the L2 U2N relay terminal and the base station).

[0245] In the case of the L2 U2N relay, the SRAP sub - layer for the PC5 hop is only for bearer mapping. The SRAP sub - layer does not exist on the PC5 hop for relaying the messages of the L2 U2N remote terminal in BCCH and PCCH. In the case of the L2 U2N remote terminal messages of SRB0, the SRAP sub - layer does not exist on the PC5 hop, but the SRAP sub - layer exists on the Uu hop for both DL and UL.

[0246] In the case of the L2 U2N relay, uplink:

[0247] - The Uu SRAP sublayer assists in the UL bearer mapping between the receiving PC5 relay RLC channel and the transmitting Uu relay RLC channel for relay via the L2 U2N relay terminal Uu interface. In the case of uplink relay traffic, other end-to-end RBs (SRB or DRB) of the same remote terminal and / or other terminals of other remote terminals are multiplexed via the same Uu relay RLC channel.

[0248] - The Uu SRAP sublayer assists in the identification of the L2 U2N remote terminal for UL traffic. The ID information of the L2 U2N remote terminal Uu radio bearer and the local remote terminal ID are included in the UL Uu SRAP header so that the base station can correlate the received packets with the specific PDCP entity associated with the correct Uu radio bearer of the remote terminal.

[0249] - The PC5 SRAP sublayer of the L2 U2N remote terminal assists in the UL bearer mapping between the remote terminal Uu radio bearer and the transmitting PC5 relay RLC channel.

[0250] For the L2 U2N relay, downlink:

[0251] - The Uu SRAP sublayer assists in the DL bearer mapping at the base station to map the radio bearers (SRB, DRB) between the terminals of the remote terminal to the Uu relay RLC channel via the relay terminal Uu interface. The Uu SRAP sublayer assists in the DL bearer mapping and data multiplexing between the radio bearers (SRB or DRB) of multiple terminals of the L2 U2N remote terminal and / or other L2 U2N remote terminals and one Uu Relay RLC channel via the relay terminal Uu interface.

[0252] - The Uu SRAP sublayer assists in identifying remote terminals for DL traffic. The ID information of the remote terminal Uu radio bearer and the local remote terminal ID are included in the Uu SRAP header by the base station in the DL so that the relay terminal maps the packets received in the remote terminal Uu radio bearer to the associated PC5 Relay RLC channel.

[0253] - The PC5 SRAP sublayer of the relay terminal assists in DL bearer mapping between the received Uu Relay RLC channel and the transmitted PC5 Relay RLC channel.

[0254] - The PC5 SRAP sublayer of the remote terminal correlates the received packets to the specific PDCP entity associated with the correct Uu radio bearer of the remote terminal based on the ID information included in the Uu SRAP header.

[0255] The local remote terminal ID is included in both the PC5 SRAP header and the Uu SRAP header. The local remote terminal ID used for the SRAP header by the base station is set in the L2 U2N relay terminal. The remote terminal obtains the local remote ID from the base station by Uu RRC messages including RRCSetup, RRCReconfiguration, RRCResume, and RRCReestablishment. Uu DRB and Uu SRB are mapped to other PC5 relay RLC channels and Uu relay RLC channels in both the PC5 hop and the Uu hop.

[0256] The base station is responsible for preventing collisions in the use of the local remote terminal ID. The base station can update the local remote terminal ID by transmitting the updated local remote ID to the relay terminal by the RRCReconfiguration message. The serving base station can perform local remote terminal ID update independently of the procedure for PC5 unicast link L2 ID update.

[0257] FIG. 12 shows the protocol stack of the discovery message for relay between the terminal and the network.

[0258] For U2N relay discovery, discovery models of Model A and Model B are supported. The protocol stack used for discovery is shown in FIG. 12.

[0259] The U2N remote terminal can send a relay discovery message and can monitor the SL for the relay discovery message while in RRC_IDLE, RRC_INACTIVE or RRC_CONNECTED. The network can broadcast a threshold value, which is used to determine whether the U2N remote terminal can send a Relay discovery solicitation message to the U2N relay terminal.

[0260] The U2N relay terminal can send a relay discovery message and can monitor the SL for the relay discovery message while in RRC_IDLE, RRC_INACTIVE or RRC_CONNECTED. The network can broadcast the maximum Uu RSRP threshold, the minimum Uu RSRP threshold or both, which are used to determine whether the U2N relay terminal can send a relay discovery message to the U2N remote terminal.

[0261] The network can provide relay discovery settings using broadcast or dedicated signaling for relay discovery. Also, the U2N remote terminal and the U2N relay terminal can use pre-configurations for relay discovery.

[0262] For relay discovery, a resource pool used for NR SL communication can be employed, or the network can configure a resource pool dedicated to relay discovery. The resource pool dedicated to relay discovery and the resource pool for NR SL communication can be configured simultaneously through system information, dedicated signaling, and / or pre-configuration. Whether a resource pool dedicated to relay discovery is configured depends on the implementation of the network. If a resource pool dedicated to relay discovery is configured, only the resource pool dedicated to relay discovery is used for relay discovery. If only the resource pool for NR SL communication is configured, all configured transmission resource pools can be used for relay discovery and SL communication.

[0263] In the case of a U2N remote terminal connected to the network by a U2N relay terminal (including both within and outside the coverage), only resource allocation mode 2 is used for transmitting discovery messages.

[0264] Relay discovery re-uses the NR SL resource allocation principle for U2N relay terminals within the coverage and the NR SL resource allocation principle for all U2N remote terminals within and outside the coverage.

[0265] SL power control for transmitting relay discovery messages is performed in the same way as NR SL communication.

[0266] PDCP layer encryption or integrity protection is not applied to relay discovery messages.

[0267] The terminal determines whether the base station supports relay discovery, non-relay discovery, or both through SIB12.

[0268] Relay selection / reselection

[0269] The U2N remote terminal performs radio measurements at the PC5 interface and uses this, together with upper layer criteria, for U2N relay selection and reselection. If there is no unicast PC5 connection between the U2N relay terminal and the U2N remote terminal, the U2N remote terminal evaluates whether the PC5 link quality to the U2N relay terminal meets the relay selection criteria using SD-RSRP measurements.

[0270] For relay reselection, if there is data transmission from the U2N relay terminal to the U2N remote terminal, the U2N remote terminal uses SL-RSRP measurements for the serving U2N relay terminal for relay reselection trigger evaluation. If there is no data transmission from the U2N relay terminal to the U2N remote terminal, whether to use SL-RSRP or SD-RSRP for relay reselection trigger evaluation depends on the implementation of the terminal.

[0271] If the PC5 link quality measured by the U2N remote terminal for the U2N relay terminal exceeds a set threshold (pre-set or provided by the base station), the U2N remote terminal considers the U2N relay terminal suitable from the radio criteria aspect. The U2N remote terminal searches for suitable U2N relay terminal candidates that meet all AS layer and upper layer criteria (see TS 23.304[xx]). If there are multiple suitable U2N relay terminals, the selection of one U2N relay terminal from among them depends on the implementation of the U2N remote terminal. For L2 U2N relay (re)selection, the PLMN ID and cell ID can be used as additional AS criteria.

[0272] The U2N remote terminal triggers U2N relay selection in the following cases.

[0273] - When the direct Uu signal strength of the current serving cell of the U2N remote terminal is lower than the set signal strength threshold.

[0274] - When instructed by the upper layer of the U2N remote terminal.

[0275] The U2N remote terminal triggers U2N relay reselection in the following cases.

[0276] - When the PC5 signal strength of the current U2N relay terminal is lower than the (pre-set) signal strength threshold.

[0277] - When the U2N relay terminal notifies cell (re)selection, handover, or Uu RLF by means of a PC5-RRC signal.

[0278] - When the remote terminal receives a PC5-S link release message from the U2N relay terminal.

[0279] - When the U2N remote terminal detects a PC5 RLF.

[0280] - When instructed at a higher layer.

[0281] For the L2 U2N remote terminal and the L3 U2N remote terminal in RRC_IDLE / INACTIVE, the cell (re)selection procedure and the relay (re)selection procedure are performed independently. When both a suitable cell and a suitable U2N relay terminal are available, the terminal implementation selects either the cell or the U2N relay terminal. The L3 U2N remote terminal can select a cell and a U2N relay terminal simultaneously, which varies depending on the implementation of the L3 U2N remote terminal.

[0282] In the case of the L2 and L3 U2N relay terminals in RRC_IDLE / INACTIVE, when the U2N relay terminal selects a new cell, a PC5-RRC message is used to notify the connected remote terminal. The PC5-RRC message is also used to notify the connected L2 or L3 U2N remote terminal when the L2 / L3 U2N relay terminal performs a handover or detects a Uu RLF. Upon receiving the PC5 RRC message for notification, whether to release or maintain the unicast PC5 link depends on the implementation of the U2N remote terminal. If the U2N remote terminal decides to release the unicast PC5 link, it triggers the L2 release procedure and can perform relay reselection.

[0283] Control plane procedures for L2 U2N relay

[0284] 1) RRC Connection Management

[0285] The U2N remote terminal needs to configure its PDU session / DRB with the network before transmitting user plane data.

[0286] Before the U2N remote terminal configures the Uu RRC connection with the network through the U2N relay terminal, the NR V2X PC5 unicast link setup procedure is reused to set up a secure unicast link between the U2N remote terminal and the U2N relay terminal.

[0287] The Uu configuration procedure for relay between the L2 terminal and the network is applied to the setup of the Uu SRB1 / SRB2 and DRB of the U2N remote terminal.

[0288] Figure 13 shows the L2 U2N remote terminal connection setup procedure. The following high-level connection setup procedure in Figure 13 is applicable to the L2 U2N relay.

[0289] 1. The U2N remote terminal and the U2N relay terminal perform a discovery procedure and configure the PC5-RRC connection using the NR V2X procedure.

[0290] 2. The U2N remote terminal uses the specified PC5 relay RLC channel settings to send the first RRC message (i.e., RRCSetupRequest) for its connection settings with the base station by the relay terminal. If the U2N relay terminal is not in RRC_CONNECTED, it needs to perform its connection settings when receiving a message on the specified PC5 relay RLC channel. During the RRC connection setup procedure of the relay terminal, the base station can set up the Uu relay RLC channel that relays SRB0 for the U2N relay terminal. The base station responds to the U2N remote terminal with an RRCSetup message. The RRCSetup message is sent to the U2N remote terminal using the SRB0 relay channel via Uu and the specified PC5 relay RLC channel via PC5.

[0291] 3. The base station and the U2N relay terminal perform the relay channel setup procedure via Uu. According to the settings from the base station, the U2N relay / remote terminal sets up the PC5 relay RLC channel for relaying SRB1 to the U2N remote / relay terminal via PC5.

[0292] 4. The RRCSetupComplete message is sent from the U2N remote terminal to the base station by the U2N relay terminal using the SRB1 relay channel via PC5 and the SRB1 relay channel set for the U2N relay terminal via Uu. Then, the U2N remote terminal is RRC-connected via Uu.

[0293] 5. The U2N remote terminal and the base station set up security through the Uu procedure, and the security message is relayed by the U2N relay terminal.

[0294] 6. The base station sends an RRCReconfiguration message to the U2N remote terminal via the U2N relay terminal to configure the SRB2 / DRB for relay purposes. The U2N remote terminal sends an RRCReconfigurationComplete message to the base station via the U2N relay terminal as a response. Also, the base station further configures the Uu relay RLC channel between the base station and the U2N relay terminal, and configures the PC5 relay RLC channel between the U2N relay terminal and the U2N remote terminal for relay traffic.

[0295] 2) Radio Link Failure

[0296] When the U2N remote terminal in RRC_CONNECTED is connected to the base station by the U2N relay terminal, it suspends the Uu RLM.

[0297] The U2N relay terminal declares a radio link failure (RLF) according to the same criteria.

[0298] After the RLF is declared, the U2N relay terminal performs the following operations.

[0299] - A PC5-RRC message is used to send an instruction to the U2N remote terminal connected to the U2N relay terminal, which triggers an RRC connection reconfiguration for the U2N remote terminal.

[0300] When detecting the PC5 RLF, the U2N remote terminal triggers a connection reconfiguration.

[0301] 3) RRC Connection Re-establishment

[0302] The U2N remote terminal performs the following operations during the RRC connection reconfiguration procedure.

[0303] - If only an appropriate cell is available, the U2N remote terminal starts the RRC reconfiguration procedure for the appropriate cell.

[0304] - If only a suitable U2N relay terminal is available, the U2N remote terminal starts an RRC reconfiguration procedure for the serving cell of the suitable relay terminal as appropriate.

[0305] - If both a suitable cell and a suitable relay are available, the U2N remote terminal selects one of the two to start the RRC reconfiguration procedure, depending on the implementation.

[0306] 4) RRC connection re-establishment

[0307] The RRC connection re-establishment mechanism is applied to the U2N remote terminal.

[0308] 5) System information

[0309] U2N remote terminals within coverage can obtain all necessary SIBs via the Uu interface, regardless of the PC5 connection with the relay terminal. After the PC5 connection with the U2N relay terminal is established, the U2N remote terminal may receive system information from the relay terminal.

[0310] U2N remote terminals in the RRC_CONNECTED state can request SIBs from the U2N relay terminal using the on-demand SIB framework. U2N remote terminals in the RRC_IDLE or RRC_INACTIVE state can notify the U2N relay terminal of the SIB types requested by the PC5-RRC message. Subsequently, the U2N relay terminal triggers the on-demand SI / SIB acquisition procedure according to its own RRC state (if necessary) and transmits the SI / SIBs obtained by PC5-RRC to the U2N remote terminal.

[0311] The SIBs used by an RRC_IDLE or RRC_INACTIVE U2N remote terminal (for example, for the purpose of a relay) can be requested at the U2N remote terminal (to the U2N relay terminal or the network). In the case of an SIB requested by the U2N remote terminal from the U2N relay terminal, the U2N relay terminal re-transmits it if there is an update for the requested SIB. In the case of an RRC_CONNECTED U2N remote terminal, it is the responsibility of the network to send the updated SIB to the U2N remote terminal during an update. When the U2N remote terminal enters the RRC_CONNECTED state, it releases the SI request with the U2N relay terminal.

[0312] In the case of SIB1 transmission, both the request-based transmission (i.e., the SIB1 request of the U2N remote terminal) and the unrequested transmission to the U2N remote terminal are supported by the U2N relay terminal, and its use is implemented by the U2N relay terminal. When SIB1 is changed, the U2N relay terminal always transmits SIB1 to the U2N remote terminal in the RRC_IDLE or RRC_INACTIVE state.

[0313] For an L2 U2N remote terminal in the RRC_IDLE or RRC_INACTIVE state, short messages via the Uu interface are not transmitted from the L2 U2N relay terminal to the L2 U2N remote terminal. The L2 U2N relay terminal can transmit the PWS SIB to the L2 U2N remote terminal connected to it.

[0314] RAN sharing is supported by the L2 U2N relay terminal. In particular, the L2 U2N relay terminal can transmit information regarding cell access by means of a discovery message before setting up a PC5-RRC connection.

[0315] 6) Paging

[0316] When both the U2N relay terminal and the U2N remote terminal are in the RRC IDLE or RRC INACTIVE state, the U2N relay terminal monitors the paging occasions of the U2N remote terminal connected to it. If the U2N relay terminal needs to monitor paging for the U2N remote terminal, the U2N relay terminal must monitor all the POs of the U2N remote terminal.

[0317] When the U2N relay terminal is in the RRC CONNECTED state and the U2N remote terminal is in the RRC_IDLE or RRC_INACTIVE state, there are two options for paging transmission.

[0318] - If a CORESET and a paging search space are configured in the active DL BWP of the U2N relay terminal, the U2N relay terminal monitors the POs of the U2N remote terminal connected to it.

[0319] - The paging transmission of the U2N remote terminal can be performed by a dedicated RRC message from the base station to the U2N relay terminal. The dedicated RRC message for transmitting remote terminal paging to the RRC_CONNECTED relay terminal contains one or more remote terminal IDs (5G-S-TMSI or I-RNTI).

[0320] Which of the two options described above is used depends on the implementation of the network. When a paging search space is configured for the RRC CONNECTED U2N relay terminal, it is possible to determine whether to monitor the POs for the U2N remote terminal based on the PC5-RRC signal received by the U2N remote terminal.

[0321] The U2N remote terminal in RRC_IDLE requests the U2N relay terminal to perform PO monitoring by providing the 5G-S-TMSI (configured at the upper layer) and the terminal-specific DRX cycle. The U2N remote terminal in RRC_INACTIVE provides the minimum value of the two terminal-specific DRX cycles (configured at the upper layer and set by the RAN), the 5G-S-TMSI, and the I-RNTI to the U2N relay terminal for PO monitoring. The L2 U2N relay terminal can notify the base station of the remote terminal information (i.e., 5G-S-TMSI / I-RNTI) by means of the SidelinkUEInformationNR message for the purpose of paging transmission. The U2N relay terminal receives the paging message, checks the 5G-S-TSMI / I-RNTI, and transmits the relevant paging record to the remote terminal accordingly.

[0322] The U2N relay terminal can send paging to the U2N remote terminal via PC5 using unicast signaling.

[0323] 7) Access control

[0324] The U2N remote terminal performs unified access control (UAC). The RRC-CONNECTED U2N relay terminal does not perform UAC on the data of the U2N remote terminal.

[0325] 8) Mobility Registration Update and RAN Area Update

[0326] When the L2 U2N remote terminal is connected to the L2 U2N relay terminal, it performs mobility registration update / RNAU based on the serving cell of the L2 U2N relay terminal. When the serving cell of the L2 U2N remote terminal in the RRC_IDLE or RRC_INACTIVE state is changed (due to cell change by the U2N relay terminal), and the new serving cell is outside the configured RNA / TA of the U2N remote terminal, it starts the mobility registration update / RNAU procedure.

[0327] Service continuity for L2 U2N relay

[0328] 1) Switching from an indirect path to a direct path

[0329] Figure 14 shows the procedure for the U2N remote terminal to switch directly to the Uu cell.

[0330] For the service continuity of the L2 U2N relay, when the U2N remote terminal switches to the direct path, the following procedure is performed.

[0331] 1. The Uu measurement setup and measurement reporting signaling procedures are performed to evaluate both relay link measurements and Uu link measurements. When the configured measurement reporting criteria are met, the measurement results of the U2N remote terminal are reported. The SL relay measurement report should include at least the source L2 ID of the U2N relay terminal, the serving cell ID (i.e., NCGI), and the SL measurement quantity information. The SL measurement quantity is the SL-RSRP of the serving U2N relay terminal, and if SL-RSRP is not available, SD-RSRP is used.

[0332] 2. The base station decides to switch the U2N remote terminal to the direct Uu path.

[0333] 3. The base station sends an RRCReconfiguration message to the U2N remote terminal. After receiving the RRCReconfiguration message from the base station, the U2N remote terminal aborts the UP and CP transmissions by the U2N relay terminal.

[0334] 4. The U2N remote terminal performs random access in synchronization with the base station.

[0335] 5. The terminal (i.e., the previous-stage U2N remote terminal) uses the settings provided in the RRCReconfiguration message to send RRCReconfigurationComplete to the base station via the direct path. From this stage onwards, the terminal (i.e., the previous-stage U2N remote terminal) uses the RRC connection via the direct path to the base station.

[0336] 6. The base station sends an RRCReconfiguration message to the U2N relay terminal to reconfigure the connection between the U2N relay terminal and the base station. The RRCReconfiguration message to the U2N relay terminal is sent at any time after three stages by the implementation of the base station (e.g., to release the Uu and PC5 relay RLC channel settings for relaying and the bearer mapping setting between the PC5 RLC and the Uu RLC).

[0337] 7. The U2N relay terminal or the U2N remote terminal initiates PC5 unicast link release (PC5-S). The timing of link release depends on the implementation of the terminal. When the base station receives RRC Reconfiguration in the sixth stage, the U2N relay terminal performs PC5 connection reconfiguration to release the PC5 relay RLC channel for relaying, or when the base station receives RRCReconfiguration in the third stage, the terminal (i.e., the previous U2N remote terminal) performs PC5 connection reconfiguration to release the PC5 relay RLC channel.

[0338] 8. The data path is switched from the indirect path to the direct path between the terminal (i.e., the previous U2N remote terminal) and the base station. During the path switch, DL / UL lossless transmission is performed according to the PDCP data recovery procedure.

[0339] Reference: The 8th step can be performed at any time after the 4th step. The 8th step is independent of the 6th and 7th steps.

[0340] 2) Switching from the direct path to the indirect path

[0341] FIG. 15 shows the procedure for the U2N remote terminal to switch to the indirect path.

[0342] The base station can select a U2N relay terminal in all RRC states such as RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED as the target U2N relay terminal for the direct-indirect path switch.

[0343] For the service continuity of the L2 U2N remote terminal, when the L2 U2N remote terminal switches to the indirect path by a U2N relay terminal in the RRC_CONNECTED state, the following procedure is performed.

[0344] 1. After the U2N remote terminal measures / discovers candidate U2N relay terminals, it reports one or more candidate U2N relay terminals and Uu measurement values.

[0345] - The terminal can appropriately filter a U2N relay terminal according to the relay selection criteria before reporting. The terminal needs to report only the U2N relay terminal candidates that meet the upper layer criteria.

[0346] - The report includes at least the U2N relay terminal ID, the serving cell ID of the U2N relay terminal, and the SL measurement quantity information. The SL measurement quantity is the SL-RSRP of the candidate U2N relay terminal, and when the SL-RSRP is not available, the SD-RSRP is used.

[0347] 2. The base station decides to switch the U2N remote terminal to the target U2N relay terminal. Thereafter, the base station sends an RRCReconfiguration message to the target U2N relay terminal. This includes at least the local ID and L2 ID of the remote terminal, Uu and PC5 relay RLC channel settings for relaying, and bearer mapping settings.

[0348] 3. The base station sends an RRCReconfiguration message to the U2N remote terminal. The content of the RRCReconfiguration message includes at least the U2N relay terminal ID, PC5 relay RLC channel settings for relay traffic, and the radio bearers between related endpoints. After receiving the RRCReconfiguration message from the base station, the U2N remote terminal aborts UP and CP transmissions via Uu.

[0349] 4. The U2N remote terminal sets up a PC5 connection with the target U2N relay terminal.

[0350] 5. The U2N remote terminal sends an RRCReconfigurationComplete message to the base station via the relay terminal to complete the path switching procedure.

[0351] 6. The data path is switched from a direct path to an indirect path between the U2N remote terminal and the base station.

[0352] When the U2N relay terminal selected for direct-indirect path switching is in RRC_IDLE or RRC_INACTIVE, after receiving the path switching command, the U2N remote terminal sets up a PC5 link with the U2N relay terminal and sends an RRCReconfigurationComplete message by the U2N relay terminal. In that case, the U2N relay terminal is switched to the RRC_CONNECTED state. In FIG. 15, the U2N remote terminal procedure for switching to the indirect path is also applicable when the U2N relay terminal selected for direct-indirect path switching is in RRC_IDLE or RRC_INACTIVE, but the four steps must be performed before the two steps.

[0353] SL discovery

[0354] The terminal can perform NR SL discovery while inside or outside coverage for non-relay operation.

[0355] The relay discovery mechanism (excluding the transmission of discovery messages based on a predetermined threshold of the U2N relay) is also applicable to SL discovery.

[0356] Selection and flow control of direct and indirect paths for multi-path operation

[0357] According to the prior art, when a relay function between the terminal and the network (U2N relay) is set for the relay terminal and the remote terminal, the relay terminal provides a network connection to the U2N remote terminal. In this case, the remote terminal is not directly connected to the network while maintaining an indirect connection based on the U2N relay function.

[0358] On the other hand, it is advantageous for the remote terminal to maintain not only an indirect connection based on both PC5 and Uu but also a direct connection only by Uu to support multi-path (MP) operation. The remote terminal with MP operation set can select one or both of the connections for data transmission to the network for more stable transmission and / or higher throughput.

[0359] For the MP operation, the remote terminal configures an indirect connection and a direct connection. It is not clear how the remote terminal selects one or both of the indirect connection and the direct connection for data transmission, and how the relay terminal controls the DL data reception for better buffer management.

[0360] The method by which the terminal performs data transmission includes the following steps.

[0361] When both a direct path and an indirect path via a relay terminal are configured between the base station and the remote terminal, the remote terminal determines whether to directly transmit to the base station from the UL or the SL so that specific upstream data is relayed to the base station by the relay terminal.

[0362] When the remote terminal configures a split bearer, the following operations are performed on the split bearer having a direct path and an indirect path.

[0363] If the primary path of a specific bearer is a direct path, the remote terminal can preferentially use UL resources for the data of the bearer, and when all UL resources are exhausted, the remaining data can be transmitted by SL resources.

[0364] If the primary path of a specific bearer is an indirect path, the remote terminal can preferentially use SL resources for the data of the bearer, and when all SL resources are exhausted, the remaining data can be transmitted by UL resources.

[0365] The remote terminal can switch the primary path of a specific bearer to an indirect path or maintain the primary path when any one or more of the following conditions are met.

[0366] When the measurement result of the serving cell of the remote terminal is less than a predetermined threshold, the primary path of a specific bearer can be switched to an indirect path.

[0367] When the measurement result of CBR for the SL resource is less than a predetermined threshold, the primary path of a specific bearer can be switched to an indirect path.

[0368] When the measurement result of the SL relay for the SL resource (for example: the measurement result of SL-RSRP or SD-RSRP of the relay terminal) exceeds a predetermined threshold, the primary path of a specific bearer can be switched to an indirect path.

[0369] When a Uu failure is detected in a specific bearer, the primary path of the specific bearer can be switched to an indirect path.

[0370] When integrity protection failure, RLC retransmission failure, RLF, bearer reconfiguration failure, beam failure, etc. are detected for a specific bearer, it can be switched to the direct path.

[0371] When one or more of the following conditions are met, the remote terminal can switch or maintain the primary path of a specific bearer to the direct path.

[0372] When the measurement result of the serving cell of the remote terminal exceeds a predetermined threshold, the primary path of a specific bearer can be switched to the direct path.

[0373] When the measurement result of CBR for the SL resource exceeds a predetermined threshold, the primary path of a specific bearer can be switched to the direct path.

[0374] When the SL relay measurement result for the SL resource (for example: the measurement result of SL-RSRP or SD-RSRP of the relay terminal) is less than a predetermined threshold, the primary path of a specific bearer can be switched to the direct path.

[0375] When an SL failure is detected in a specific bearer, the primary path of the specific bearer can be switched to the direct path.

[0376] When integrity protection failure, RLC retransmission failure, HARQ feedback-based SL failure, bearer reconfiguration failure, etc. are detected for a specific bearer, it is possible to switch to an indirect path.

[0377] On the other hand, the remote terminal can report the downlink data transmission state to the relay terminal, and the relay terminal can report the downlink data transmission state to the base station. The station or the remote terminal can have the relay terminal report the downlink data transmission state to the base station. At this time, the downlink data transmission state report can be reported by an RLC control PDU, by a MAC CE, by an RRC message, by a PDCP control PDU, or by other layer 2 control PDUs.

[0378] Figure 16 shows the simultaneous configuration of direct / indirect paths in the RRC connection establishment of the U2N infrastructure.

[0379] The method for the terminal to perform data transmission and reception includes the following steps.

[0380] 1. The U2N remote terminal and the U2N relay terminal perform a discovery procedure and configure a PC5-RRC connection using the NR V2X procedure.

[0381] 2. After the establishment of the PC5-RRC connection by PC5 unicast link configuration, the remote terminal and the relay terminal can trigger the sidelink terminal capability transmission procedure and exchange their terminal capabilities. Here, the remote terminal sends a UECapabilityEnquirySidelink message to the relay terminal to request the MP capability of the relay terminal, and the relay terminal sends a UECapabilityInformationSidelink message including its own MP capability to the remote terminal. After that, the relay terminal sends a UECapabilityEnquirySidelink message to request the MP capability of the remote terminal to the remote terminal, and the remote terminal sends a UECapabilityInformationSidelink message including its own MP capability to the relay terminal.

[0382] The MP capabilities of the UE include one or more of the following.

[0383] - Whether the terminal supports multi-path operation as a remote terminal and / or a relay terminal

[0384] - The SL / UL / DL frequency carriers / bands that the terminal supports for MP operation for transmission and / or reception

[0385] - The combination of the SL carrier / band and the UL carrier / band that the terminal supports for MP operation for its own transmission

[0386] - The combination of the SL carrier / band and the DL carrier / band that the terminal supports for MP operation for its own reception

[0387] 3. If the remote terminal and the relay terminal assist the MP operation in the DL / UL carrier of the serving cell, and the side - link transmission and / or side - link reception between the remote terminal and the relay terminal are performed in the SL carrier, or if the serving cell assists the side - link resources for side - link transmission / reception and / or MP operation (e.g., the resource pool configuration basis for system information or dedicated signals), the relay terminal can determine the requirement for multi - path operation and initiate the RRC connection establishment. The relay terminal can send the first side - link message to the remote terminal, and can inform the remote terminal of the requirement for multi - path operation, the RRC state of the relay terminal, or whether the relay terminal is in the RRC_CONNECTED state. When the relay terminal (and the remote terminal) determines the requirement for multi - path operation, the first RRC message (e.g., RRCSetupRequest or RRCResumeRequest) sent by the relay terminal at the time of RRC connection establishment can indicate the requirement for multi - path operation to the base station, for example, by means of EstablishmentCause or ResumeCause. When the above - mentioned conditions are met (and when the relay terminal requests multi - path operation), the remote terminal can also inform the relay terminal of the requirement for multi - path operation, the RRC state of the remote terminal, or whether the remote terminal is in the RRC_CONNECTED state by sending the second side - link message including the multi - path operation request to the relay terminal.

[0388] A. The first side - link message includes one or more of the following.

[0389] - The PCell cell ID of the relay terminal.

[0390] - The PLMN ID of the PLMN in which the relay terminal is registered.

[0391] - The tracking area code of the tracking area in which the relay terminal is registered for the PCell.

[0392] - The multi - path operation request

[0393] B. When receiving the first sidelink message, the remote terminal can perform one or more of the following steps, for example, cell reselection before or during RRC connection establishment at the remote terminal, or cell reselection during or after RRC connection establishment at the relay terminal.

[0394] - If the cell indicated by the relay terminal is different from the serving cell camped on by the remote terminal, the remote terminal can reselect the cell indicated according to the cell reselection process or abort the multi-path operation configuration with the relay terminal. If the remote terminal cannot reselect the cell indicated according to the cell reselection process, the remote terminal aborts the multi-path operation configuration with the relay terminal.

[0395] - If the tracking area indicated by the relay terminal is different from the registered tracking area of the remote terminal, the remote terminal triggers a tracking area update procedure to register in the tracking area indicated by the relay terminal or aborts the multi-path operation configuration with the relay terminal. For example, if the remote terminal cannot register in the tracking area indicated due to the failure of the tracking area update procedure or other related NAS procedures, the remote terminal aborts the multi-path operation configuration with the relay terminal.

[0396] - If the PLMN indicated by the relay terminal is different from the registered PLMN of the remote terminal, the remote terminal reselects the PLMN indicated by the relay terminal and registers in the indicated PLMN, or aborts the multi-path operation configuration with the relay terminal. For example, if the remote terminal cannot register in the PLNN indicated due to the failure of the PLMN registration procedure or other related NAS procedures, the remote terminal aborts the multi-path operation configuration with the relay terminal.

[0397] C. The first sidelink message is a RemoteUEInformationSidelink message, a UEAssistanceInformationSidelink message, an RRCReconfigurationSidelink message, or an RRCReconfigurationCompleteSidelink message.

[0398] 4. Based on the exchange of the sidelink terminal capabilities, the relay terminal identifies that both the relay terminal and the remote terminal support the MP capability. When the remote terminal is not in RRC_CONNECTED, the remote terminal determines a request for multi-path operation and, as follows, the relay terminal can initiate the RRC connection establishment procedure.

[0399] When there is no direct Uu RRC connection to the U2N remote terminal, the U2N remote terminal uses the PC5 relay RLC channel configuration specified by the relay terminal for connection establishment with the base station and transmits the first RRC message (i.e., RRCSetupRequest or RRCResumeRequest). When the remote terminal (and the relay terminal) determines a request for multi-path operation, the first RRC message of the remote terminal can indicate the request for multi-path operation to the base station by EstablishmentCause or ResumeCause. The remote terminal can also indicate the request for multi-path operation to the relay terminal by the SCI that schedules the SCI scheduling PSSCH including the first RRC message in SL, by the SL MAC CE of another SL MAC PDU or the SL MAC PDU including the first RRC message in SL, by the MAC (sub) header of the SL MAC PDU including the first RRC message in SL, or by another PC5-RRC message transmitted to the relay terminal.

[0400] 5. When the U2N relay terminal is not in the RRC_CONNECTED state, when receiving a message on the specified PC5 relay RLC channel, it is necessary to perform self-connection establishment. When the relay terminal (and the remote terminal) determines the multi-path operation request, in the RRC connection establishment, the first RRC message (e.g., RRCSetupRequest or RRCResumeRequest) of the relay terminal can indicate the multi-path operation request to the base station, for example, by means of EstablishmentCause or ResumeCause. During the RRC connection establishment procedure of the relay terminal, the base station can send the first RRC message (e.g., RRCSetup message or RRCResume message) to the U2N relay terminal and configure the Uu relay RLC channel for relaying SRB0.

[0401] A. If the relay terminal and the remote terminal are not configured in the same cell or not registered in the same tracking area and / or the same PLMN, the base station sends a handover command to the relay terminal by means of the second RRC message, so that both the relay terminal and the remote terminal are in the same cell, the same tracking area and / or the same PLMN.

[0402] 6. The base station responds to the U2N remote terminal by the U2N relay terminal in the second RRC message (e.g., RRCSetup message or RRCResume message). The second RRC message is sent to the U2N remote terminal using the SRB0 relay channel via Uu and the specified PC5 relay RLC channel via PC5.

[0403] A. If the relay terminal and the remote terminal are not configured in the same cell or not registered in the same tracking area and / or the same PLMN, the base station can send a handover command to the remote terminal by means of the second RRC message so that both the relay terminal and the remote terminal are in the same cell, the same tracking area and / or the same PLMN.

[0404] 7. When both the relay terminal and the remote terminal are in RRC_CONNECTED and the base station decides whether to add a direct path and an indirect path to the remote terminal according to the multi-path operation request of the relay terminal and / or the remote terminal, the base station configures a direct path for the remote terminal by, for example, a second RRC message sent to each of the relay terminal and the remote terminal.

[0405] To add not only an indirect path but also a direct path to the remote terminal, as an alternative message for adding the direct path or as a subsequent additional message to the second message for adding the direct path, after the RRC connection (re) establishment (and AS security activation) for the relay terminal or the remote terminal is completed, the base station can send an (first) RRCReconfiguration message to the relay terminal and / or the remote terminal. When the base station sends an RRCReconfiguration message to the remote terminal, this message can be sent indirectly to the remote terminal by the relay terminal or directly via only the Uu interface.

[0406] - When sl-L2RelayUEConfig is included in the second RRC message for the relay terminal, the relay terminal performs the L2 U2N relay terminal configuration procedure and (re) configures zero, one or more direct bearers, zero, one or more indirect bearers and zero, one or more split bearers for the upstream data from the remote terminal and / or the downstream data to the remote terminal.

[0407] - When sl-L2RemoteUEConfig is included in the second RRC message for the remote terminal, the remote terminal performs the L2 U2N remote terminal configuration procedure and (re) configures zero, one or more direct bearers, zero, one or more indirect bearers and zero, one or more split bearers for the upstream data from the remote terminal and / or the downstream data to the remote terminal for the remote terminal.

[0408] - If the direct path configuration of the direct bearer and / or split bearer is included in the second RRC message for the relay terminal, the remote terminal (re)configures the direct paths of zero, one or more direct bearers and zero, one or more split bearers for the upstream data from the remote terminal and / or the downstream data to the remote terminal.

[0409] - If the direct path configuration of the direct bearer and / or split bearer is included in the second RRC message for the remote terminal, the remote terminal (re)configures the direct paths of zero, one or more direct bearers and zero, one or more split bearers for the upstream data from the remote terminal and / or the downstream data to the remote terminal.

[0410] - The indirect bearer or split bearer includes the setting of the Uu relay RLC channel.

[0411] - The indirect bearer is composed of an indirect link including the Uu link and the sidelink.

[0412] - The direct bearer is composed solely of a direct link on the Uu.

[0413] - The split bearer is composed of the indirect path and the direct path of the split bearer. The base station can select one or both of the indirect path and the direct path for the downstream data transmission towards the remote terminal, and the remote terminal can select one or both of the indirect path and the direct path for the upstream data transmission towards the base station.

[0414] 8. The base station and the U2N relay terminal perform a relay channel setting procedure via the Uu. According to the setting of the base station, the U2N relay / remote terminal sets a PC5 relay RLC channel for relaying the SRB1 to the U2N remote / relay terminal via the PC5.

[0415] 9. The second message sent to the remote terminal (e.g., RRCSetup message or RRCResume message) can trigger the RACH of the remote terminal and can include the RACH configuration. In this case, the remote terminal triggers the RACH procedure and sends an RRCSetupComplete message.

[0416] - The RRC configuration may include a terminal-specific preamble. In this case, the remote terminal can transmit the RACH preamble with the terminal-specific preamble.

[0417] - The MAC PDU of MSG3 PUSCH or MSGA PUSCH includes a C-RNTI MAC CE indicating the C-RNTI assigned by the second message. If no C-RNTI is assigned by the second message, the remote terminal includes a C-RNTI MAC CE indicating the temporary C-RNTI determined in this RACH procedure. Alternatively, if no C-RNTI is assigned by the second message, the MAC PDU includes a MAC CE or an RRC message including another terminal ID of the remote terminal, e.g., s-TMSI or resumeID.

[0418] - The MAC PDU of MSG3 PUSCH or MSGA PUSCH can also include a buffer status report for reporting at least the UL buffer size for transmitting the RRCSetupComplete message at the remote terminal.

[0419] - When the remote terminal is configured with SL resource allocation mode 1, the remote terminal can also report the SL buffer size including the sidelink buffer status report and request SL resources to transmit SL data via the split bearer's indirect bearer or indirect path at the remote terminal.

[0420] If the RACH procedure can be successfully completed at the remote terminal, the remote terminal directly sends a third message (i.e., the RRCSetupComplete message or the RRCResumeComplete message) to the base station. Thereafter, the remote terminal enters the RRC_CONNECTED state on all of the indirect path via the relay terminal and the direct path to the base station.

[0421] If the RACH procedure of the remote terminal cannot be successfully completed (i.e., RACH fails), the remote terminal indirectly sends a third message (e.g., the RRCSetupFailure message or the RRCReumeFailure message) to the base station using the SRB1 relay channel via PC5 and the SRB1 relay channel configured in the U2N relay terminal via Uu. In this way, the remote terminal enters the RRC_CONNECTED state with the base station only on the indirect path via the relay terminal. When RACH fails, the third message can inform the base station of the RACH failure and / or the failure of direct path setup or multi-path operation.

[0422] Alternatively, if the RACH procedure of the remote terminal cannot be successfully completed (i.e., RACH fails), the remote terminal sends an RRCReestablishmentRequest message indirectly via the relay terminal or directly to the base station to initiate the RRC reestablishment procedure. When the RRCReestablishmentRequest message is sent directly to the base station, the remote terminal triggers the RACH procedure again and sends an RRCReestablishmentRequest message indicating the recovery or failure of multi-path operation. In this procedure, the remote terminal can perform cell reselection in the same cell as the relay terminal.

[0423] Alternatively, if the RACH procedure of the remote terminal cannot be successfully completed (i.e., RACH fails), the remote terminal sends an RRCResumeRequest message indirectly through the relay terminal or directly to the base station to initiate the RRC resume procedure. When the RRCResumeRequest message is sent directly to the base station, the remote terminal triggers the RACH procedure again and sends an RRCResumeRequest message indicating the recovery or failure of the multi-path operation. In this procedure, the remote terminal can perform cell reselection in the same cell as the relay terminal.

[0424] 10. If the RACH procedure of the remote terminal can be successfully completed, the U2N remote terminal and the base station set up AS security according to the Uu procedure via, for example, a direct path.

[0425] However, if the RACH procedure of the remote terminal cannot be successfully completed (i.e., RACH fails), the U2N remote terminal and the base station set up AS security via an indirect path, and the AS security message is transmitted by the U2N relay terminal.

[0426] 11. The third message of the remote terminal may include the initial NAS message of the remote terminal. The third message of the relay terminal may include the initial NAS message of the relay terminal. Upon receiving the third message, the base station transmits the initial NAS message (e.g., service request message) to the core network (CN) node (e.g., AMF or SMF). Upon receiving the initial NAS message, the CN node can provide multi-path configuration to the base station and the terminal as follows.

[0427] 1) Option 1:

[0428] - When a remote terminal establishes an RRC connection with a base station through a relay terminal, for example, the remote terminal sends an initial NAS message to the CN node. The initial NAS message can indicate the preference level of the remote terminal for multi-path operation. Upon receiving the initial NAS message from the remote terminal, the CN node provides the base station with the terminal capabilities related to multi-path operation and the NAS configuration related to multi-path. Upon receiving the terminal capabilities and / or the NAS configuration, the base station determines whether to configure multi-path operation as described above.

[0429] Also, when the relay terminal establishes an RRC connection with the base station, the relay terminal sends an initial NAS message to the CN node. The initial NAS message can indicate the preference level of the relay terminal for multi-path operation. Upon receiving the initial NAS message from the relay terminal and the initial NAS message from the remote terminal, the CN node provides the base station with the terminal capabilities related to multi-path operation and the NAS configuration related to multi-path. Upon receiving the terminal capabilities and / or the NAS configuration, the base station determines whether to configure multi-path operation as described above.

[0430] 2) Alternative 2:

[0431] - After the remote terminal establishes an RRC connection with the base station through the relay terminal, the base station determines whether to configure multi-path operation as described above. If the base station determines to perform multi-path operation, the base station instructs the CN node to perform multi-path operation.

[0432] Upon receiving the instruction from the base station, the CN node provides the base station with the terminal capabilities related to multi-path operation and the NAS configuration related to multi-path. Upon receiving the terminal capabilities and / or the NAS configuration, the base station configures multi-path operation as described above based on the received terminal capabilities and / or the NAS configuration.

[0433] Upon receiving the instruction from the base station, the CN node provides the NAS configuration related to the multi-path to the remote terminal and / or relay terminal. The remote terminal and / or relay terminal configures the multi-path operation based on the NAS configuration related to the multi-path on the RRC configuration provided by the base station as described above.

[0434] 3) Alternative 3:

[0435] - When the relay terminal establishes an RRC connection with the base station, the relay terminal transmits an initial NAS message to the CN node. The initial NAS message can indicate the preference level of the relay terminal for multi-path operation. Upon receiving the initial NAS message from the relay terminal, the CN node provides the terminal capabilities related to multi-path operation and the NAS configuration related to the multi-path to the base station. Upon receiving the terminal capabilities and / or NAS configuration, the base station determines whether to configure the multi-path operation as described above.

[0436] Also, when the relay terminal, for example, sets up an RRC connection with the base station by the relay terminal, the remote terminal can also transmit an initial NAS message to the CN node. The initial NAS message can indicate the preference level of the remote terminal for multi-path operation. Upon receiving the initial NAS message from the remote terminal and the initial NAS message from the relay terminal, the CN node provides the terminal capabilities related to multi-path operation and the NAS configuration related to the multi-path to the base station. Upon receiving the terminal capabilities and / or NAS configuration, the base station determines whether to configure the multi-path operation as described above.

[0437] The CN node (e.g., AMF or SMF) can notify the base station of the terminal capabilities and multi-path configuration, or the addition of multi-path configuration, based on the QoS profile for the remote terminal and / or relay terminal. The QoS profile is transmitted from the CN node to the base station.

[0438] - The information related to multi-path in the QoS profile can indicate whether the multi-path can be configured for any one of the following.

[0439] Each PDU session

[0440] Each QoS flow

[0441] Each remote terminal

[0442] Each relay terminal

[0443] Each frequency

[0444] Each cell

[0445] Each RAT

[0446] Each PLMN

[0447] Each tracking area

[0448] Each base station

[0449] 12. When the CN node does not provide the terminal capabilities of the remote terminal, the U2N remote terminal shall notify the base station of the terminal capabilities of the remote terminal according to the request of the base station. This includes whether the remote terminal supports U2N bearer / channel and / or MP operations.

[0450] When the CN node does not provide the terminal capabilities of the relay terminal, the U2N relay terminal shall notify the base station of the terminal capabilities of the relay terminal including whether the relay terminal supports U2N bearer / channel and / or MP operations according to the request of the base station.

[0451] 13. To add a direct path to the remote terminal in addition to the indirect path, as a subsequent additional message for the alternative message to add the direct path or the second message to add the direct path, after the base station completes the RRC connection (re)establishment (and AS security activation) for the relay terminal or the remote terminal, it can send an RRCReconfiguration message to the relay terminal and / or the remote terminal based on the terminal capabilities and multi-path settings of the CN node. The base station sends the RRCReconfiguration message indirectly by the U2N relay terminal or directly to the U2N remote terminal, and configures SRB2 / DRB for all of the direct path and the indirect path. Also, the base station sends the RRCReconfiguration message to the U2N relay terminal.

[0452] - If sl-L2RelayUEConfig is included in the RRCReconfiguration message for the relay terminal, the relay terminal performs the L2 U2N relay terminal configuration procedure and (re)configures zero, one or more direct bearers, zero, one or more indirect bearers, and zero, one or more split bearers for the upstream data from the remote terminal and / or the downstream data to the remote terminal.

[0453] - If sl-L2RemoteUEConfig is included in the RRCReconfiguration message for the remote terminal, the remote terminal performs the L2 U2N remote terminal configuration procedure and (re)configures zero, one or more direct bearers, zero, one or more indirect bearers, and zero, one or more split bearers for the remote terminal for the upstream data from the remote terminal and / or the downstream data to the remote terminal.

[0454] - If the direct path configuration of the bearer and / or split bearer is included directly in the second RRC message and / or the RRCReconfiguration message for the relay terminal, the remote terminal (re)configures the direct paths of zero, one or more direct bearers and zero, one or more split bearers for the upstream data from the remote terminal and / or the downstream data to the remote terminal.

[0455] - If the direct path configuration of the bearer and / or split bearer is included directly in the second RRC message and / or the RRCReconfiguration message for the remote terminal, the remote terminal (re)configures the direct paths of zero, one or more direct bearers and zero, one or more split bearers for the upstream data from the remote terminal and / or the downstream data to the remote terminal.

[0456] A. Option 1: Joint RRC Reconfiguration

[0457] - The base station transmits an RRCReconfiguration message to the relay terminal. The RRCReconfiguration message includes at least a first part and a second part. The first part includes the configuration for adding an indirect / split bearer applied to the relay terminal, and the second part includes the configuration for adding an indirect / split bearer applied to the remote terminal and adding a direct path of a direct bearer or split bearer.

[0458] (i) Option 1A: The relay terminal sends a Uu RRC message (e.g., an RRCReconfiguration message) to the remote terminal and transmits the second part to the remote terminal.

[0459] For example, the second part is included in the RRC container of the RRCReconfiguration message. The base station encrypts the first part with the first security key configured between the base station and the relay terminal, and at the same time encrypts the second part with the second security key configured between the base station and the remote terminal. When receiving the RRCReconfiguration message and the relay terminal can successfully apply the configuration of the first part, the layer of the relay terminal removes the first part from the RRCReconfiguration message, sends the RRCReconfiguration message with the first part removed to the remote terminal, and transmits the second part of the RRC container to the remote terminal. The layer of the relay terminal is any one of the PDCP layer, SRAP layer, and RRC layer of the relay terminal. On the other hand, when the relay terminal cannot successfully apply the configuration of the first part, the relay terminal may not be able to transmit the second part of the RRC container to the remote terminal.

[0460] When receiving the second part, the remote terminal decrypts the second part using the second security key. When the remote terminal can successfully apply the configuration of the second part, the remote terminal encrypts the RRCReconfigurationComplete message using the second security key and then directly sends it to the base station or indirectly sends it to the base station through the relay terminal. When the remote terminal cannot successfully apply the configuration of the second part, the remote terminal encrypts the RRCReconfigurationFailure or RRCReconfigurationComplete message indicating the failure of the U2N configuration or multi-path setting using the second security key and then directly sends it to the base station or indirectly sends it to the base station through the relay terminal. Alternatively, when the remote terminal fails to apply the configuration of the second part, the remote terminal starts an RRC re-establishment procedure to temporarily suspend its own direct bearer and temporarily suspend or release the indirect / split bearer. The remote terminal can also release the PC5-RRC connection with the relay terminal.

[0461] In the case of the RRC reestablishment procedure via the Uu interface, the remote terminal performs a random access to the base station and directly constitutes only the bearer as a result of the procedure. In the RRC reestablishment procedure, the relay terminal transmits an RRCReestablishmentComplete message indicating a U2N configuration or multi-path setting failure and the source or destination ID of the relay terminal and / or the remote terminal.

[0462] In the case of the RRC reestablishment procedure by the relay terminal, after the remote terminal uses SL-RLC1 for SRB1 to send an RRCReestablishmentComplete message to the relay terminal, the relay terminal transmits the RRCReestablishmentComplete message to the base station. The RRCReestablishmentComplete message indicates a U2N configuration or multi-path setting failure and the source or destination ID of the relay terminal and / or the remote terminal.

[0463] If the remote terminal fails to apply the configuration of the second part, the remote terminal can release the PC5-RRC connection with the relay terminal or notify the relay terminal of a sidelink relay reconfiguration failure or a multi-path setting failure.

[0464] When the PC5-RRC connection is released, or a sidelink relay reconfiguration failure or a multi-path configuration failure is received, the relay terminal sends an RRCReconfigurationFailure or RRCReconfigurationComplete message indicating a U2N configuration or a multi-path configuration failure to the base station. The RRC container of the RRCReconfigurationComplete message sent from the relay terminal to the base station can include the RRCReconfigurationComplete message received by the remote terminal. Alternatively, when the PC5-RRC connection is released, or a sidelink relay reconfiguration failure or a multi-path configuration failure is received or detected, or when the relay terminal cannot apply the configuration of the first part, the relay terminal starts an RRC re-establishment procedure, suspends or releases the bearers it directly manages, and suspends or releases the indirect / split bearers. The relay terminal can also release the PC5-RRC connection with the remote terminal or notify the remote terminal of a sidelink relay reconfiguration failure or a multi-path configuration failure. In the RRC re-establishment procedure, the relay terminal performs a random access to the base station and configures only the direct bearers as a result of the procedure. In the RRC re-establishment procedure, the relay terminal sends an RRCReestablishmentComplete message indicating a U2N configuration or a multi-path configuration failure, and the source or destination ID of the relay terminal and / or the remote terminal.

[0465] (ii) Option 1B: The relay terminal sends a PC5 RRC message (e.g., an RRCReconfigurationSidelink message or a UuMessageTransferSidelink message) to the remote terminal to transmit the second part to the remote terminal.

[0466] For example, the second part is included in the RRC container of the RRCReconfiguration message or the UuMessageTransferSidelink message. The base station encrypts the first part with the first security key configured between the base station and the relay terminal, and at the same time, encrypts the second part with the first security key (or the second security key configured between the base station and the remote terminal). When receiving the RRCReconfiguration message, the relay terminal decrypts the second part using the first security key (or the second security key). Thereafter, the relay terminal encrypts the second part using the third security key configured on the PC5 interface between the relay terminal and the remote terminal. The relay terminal includes the second part in the RRCReconfigurationSidelink message transmitted to the remote terminal and transmits the second part to the remote terminal. The second part is included in the RRC container of the RRCReconfigurationSidelink message or is reset to be included in the RRCReconfigurationSidelink message.

[0467] When receiving the second part, the remote terminal decrypts the second part using the third security key. If the remote terminal can successfully apply the configuration of the second part, the remote terminal encrypts the RRCReconfigurationCompleteSidelink message using the third security key and then transmits it to the relay terminal. If the remote terminal cannot successfully apply the configuration of the second part, the remote terminal encrypts the RRCReconfigurationFailureSidelink message indicating the failure of the U2N configuration or the multi-path setting using the third security key and then transmits it to the relay terminal. Alternatively, if the remote terminal fails to apply the configuration of the second part, the remote terminal starts the RRC re-establishment procedure to directly suspend its bearer and suspend or release its indirect / split bearer. The remote terminal can also release the PC5-RRC connection with the relay terminal.

[0468] In the case of an RRC re-establishment procedure via the Uu interface, the remote terminal performs a random access to the base station and directly configures only the bearer as a result of the procedure. In the RRC re-establishment procedure, the relay terminal transmits an RRCReestablishmentComplete message indicating the failure of the U2N configuration or the multi-path setting and the source or destination ID of the relay terminal and / or the remote terminal.

[0469] In the case of an RRC re-establishment procedure by the relay terminal, after the remote terminal transmits the RRCReestablishmentComplete message to the relay terminal using SL-RLC1 for SRB1, the relay terminal transmits the RRCReestablishmentComplete message to the base station. The RRCReestablishmentComplete message indicates the failure of the U2N configuration or the multi-path setting and the source or destination ID of the relay terminal and / or the remote terminal.

[0470] If the relay terminal fails to successfully apply the configuration of the first part when it receives an RRCReconfigurationFailureSidelink message, receives a sidelink relay reconfiguration failure or a multi-path configuration failure, or detects a sidelink failure (e.g., due to the expiration of timer T400), the relay terminal shall send an RRCReconfigurationFailure or RRCReconfigurationComplete message to notify the base station of the U2N configuration or multi-path configuration failure. Alternatively, if the relay terminal fails to successfully apply the configuration of the first part when it receives an RRCReconfigurationFailureSidelink message, receives a sidelink relay reconfiguration failure or a multi-path configuration failure, or detects a sidelink failure (e.g., due to the expiration of timer T400), the relay terminal shall initiate an RRC re-establishment procedure to directly release the bearer and to release or cancel the indirect / split bearer. The relay terminal may also release the PC5-RRC connection with the remote terminal or notify the remote terminal of the sidelink relay reconfiguration failure or multi-path configuration failure. In the RRC re-establishment procedure, the relay terminal shall perform a random access to the base station and configure only the direct bearer as a result of the procedure. In the RRC re-establishment procedure, the relay terminal shall send an RRCReestablishmentComplete message indicating the failure of the U2N configuration or multi-path configuration and the source or destination ID of the relay terminal and / or the remote terminal.

[0471] In Option 1, when the remote terminal or the relay terminal performs an RRC re-establishment procedure, it can also notify the base station which terminal failed to apply the U2N configuration or multi-path configuration, i.e., whether it is the remote terminal or the relay terminal.

[0472] B. Option 2: Separate Transmission of RRC Reconfiguration

[0473] - The base station transmits a first RRCReconfiguration message to the relay terminal. The first RRCReconfiguration message includes configurations for at least adding an indirect / split bearer applied to the relay terminal.

[0474] If the relay terminal receives the first RRCReconfiguration message and can successfully apply the configuration of the first message, the relay terminal transmits an RRCReconfigurationComplete message to the base station. However, if the relay terminal cannot successfully apply the configuration of the first message after receiving the first message, or if the PC5-RRC connection is released, or if it receives or detects a sidelink relay reconfiguration failure or a multi-path configuration failure, the relay terminal starts an RRC re-establishment procedure to temporarily suspend or release its direct bearer and indirect / split bearers. The relay terminal can also release the PC5-RRC connection with the remote terminal or notify the remote terminal of a sidelink relay reconfiguration failure or a multi-path configuration failure. In the RRC re-establishment procedure, the relay terminal performs a random access to the base station and, as a result of the procedure, configures only the direct bearer. In the RRC re-establishment procedure, the relay terminal transmits an RRCReestablishmentComplete message indicating the failure of the U2N configuration or multi-path configuration and the source or destination ID of the relay terminal and / or the remote terminal.

[0475] - The base station transmits a second RRCReconfiguration message to the remote terminal. The second RRCReconfiguration message includes configurations for adding an indirect / split bearer and adding a direct path for the direct bearer and split bearer applied to the remote terminal.

[0476] The base station can directly transmit the second RRCReconfiguration message from the Uu interface to the remote terminal using SRB1.

[0477] If the remote terminal receives the second message and can successfully apply the configuration of the second message, the remote terminal shall send an RRCReconfigurationComplete message to the base station. If the remote terminal cannot successfully apply the configuration of the second message, the remote terminal shall directly or indirectly send an RRCReconfigurationFailure or RRCReconfigurationComplete message to the base station to indicate the failure of U2N configuration or multi-path configuration.

[0478] The RRCReconfigurationComplete or RRCReconfigurationFailure message shall be sent directly to the base station using SRB1 or indirectly to the base station by the relay terminal using SL-RLC1 for SRB1.

[0479] If the remote terminal cannot successfully apply the configuration of the second message, the remote terminal may release the PC5-RRC connection with the relay terminal or notify the relay terminal of the sidelink relay reconfiguration failure or multi-path configuration failure.

[0480] Alternatively, if the remote terminal fails to apply the configuration of the second message, the remote terminal shall initiate an RRC re-establishment procedure to suspend or release the direct bearer and suspend or release the indirect / split bearer by itself. The remote terminal may also release the PC5-RRC connection with the relay terminal or notify the relay terminal of the sidelink relay reconfiguration failure or multi-path configuration failure.

[0481] When performing the RRC re-establishment procedure via the Uu interface, the remote terminal shall perform a random access to the base station and configure only the direct bearer as a result of the procedure. In the RRC re-establishment procedure, the relay terminal shall send an RRCReestablishmentComplete message indicating the failure of U2N configuration or multi-path configuration and the source or destination ID of the relay terminal and / or the remote terminal.

[0482] In the case of the RRC re-establishment procedure by the relay terminal, after the remote terminal transmits the RRCReestablishmentComplete message to the relay terminal using SL-RLC1 for SRB1, the relay terminal transmits the RRCReestablishmentComplete message to the base station. The RRCReestablishmentComplete message indicates a U2N configuration or multi-path setup failure and the source or destination ID of the relay terminal and / or the remote terminal.

[0483] When the PC5-RRC connection is released, or a sidelink relay reconfiguration failure or multi-path setup failure is received, the relay terminal transmits an RRCReconfigurationFailure or RRCReconfigurationComplete message to the base station to notify the U2N configuration or multi-path setup failure. When receiving an RRCReestablishmentRequest message from the remote terminal, the RRC container of the RRCReconfigurationComplete message transmitted from the relay terminal to the base station can include the RRCReestablishmentRequest message received from the remote terminal.

[0484] Alternatively, if the PC5-RRC connection is released, or a sidelink relay reconfiguration failure or a multi-path configuration failure is received or detected, or the relay terminal cannot successfully apply the configuration of the first message, the relay terminal starts the RRC re-establishment procedure, directly terminates its bearers, and terminates or releases the indirect / split bearers. The relay terminal can also release the PC5-RRC connection with the remote terminal or notify the remote terminal of a sidelink relay reconfiguration failure or a multi-path configuration failure. In the RRC re-establishment procedure, the relay terminal performs a random access to the base station and, as a result of the procedure, configures only the direct bearers. In the RRC re-establishment procedure, the relay terminal transmits an RRCReestablishmentComplete message indicating the failure of the U2N configuration or multi-path configuration and the source or destination ID of the relay terminal and / or the remote terminal. When receiving an RRCReestablishmentRequest message at the remote terminal, the RRC container of the RRCReestablishmentComplete message transmitted from the relay terminal to the base station can include the RRCReestablishmentRequest message received at the remote terminal.

[0485] Alternatively, the base station can indirectly transmit a second RRCReconfiguration message to the relay terminal using the PC5 relay RLC channel for SRB1, i.e., SL-RLC1.

[0486] If the relay terminal receives the first RRCReconfiguration message and can successfully apply the configuration of the first message, the relay terminal transmits the second RRCReconfiguration message received at the base station to the remote terminal. The relay terminal also sends an RRCReconfigurationComplete message to the base station. However, if the relay terminal fails to apply the configuration of the first message after receiving the first message, or if the PC5-RRC connection is released, or if it receives or detects a sidelink relay reconfiguration failure or a multi-path configuration failure, the relay terminal does not transmit the second RRCReconfiguration message received at the base station to the remote terminal, directly suspends its own bearers, and initiates an RRC re-establishment procedure to suspend or release the indirect / split bearers. The relay terminal can also release the PC5-RRC connection with the remote terminal or notify the remote terminal of a sidelink relay reconfiguration failure or a multi-path configuration failure. In the RRC re-establishment procedure, the relay terminal performs a random access to the base station and, as a result of the procedure, configures only the direct bearers. In the RRC re-establishment procedure, the relay terminal sends an RRCReestablishmentComplete message indicating the U2N configuration or multi-path configuration failure and the source or destination ID of the relay terminal and / or the remote terminal.

[0487] If the relay terminal notifies the remote terminal of a sidelink relay reconfiguration failure or a multi-path configuration failure, the remote terminal initiates an RRC re-establishment procedure to directly suspend its own bearers and suspend or release the indirect / split bearers. The remote terminal can also release the PC5-RRC connection with the relay terminal.

[0488] In the case of an RRC re-establishment procedure via the Uu interface, the remote terminal performs a random access to the base station and, as a result of the procedure, configures only the direct bearers. In the RRC re-establishment procedure, the relay terminal sends an RRCReestablishmentComplete message indicating the U2N configuration or multi-path configuration failure and the source or destination ID of the relay terminal and / or the remote terminal.

[0489] In the case of the RRC re-establishment procedure by the relay terminal, after the remote terminal uses SL-RLC1 for SRB1 to send an RRCReestablishmentComplete message to the relay terminal, the relay terminal transmits the RRCReestablishmentComplete message to the base station. The RRCReestablishmentComplete message indicates a U2N configuration or multi-path setup failure and the source or destination ID of the relay terminal and / or the remote terminal.

[0490] 14. The U2N remote terminal sends an RRCReconfigurationComplete message to the base station indirectly or directly by the U2N relay terminal as a response. Also, the base station configures an additional Uu relay RLC channel between the base station and the U2N relay terminal and a PC5 relay RLC channel between the U2N relay terminal and the U2N remote terminal for relay traffic.

[0491] 15. The remote terminal uses the Uu relay RLC channel and the PC5 relay RLC channel to send upstream data to the base station by the relay terminal. The base station uses the Uu relay RLC channel and the PC5 relay RLC channel to send downstream data to the remote terminal by the relay terminal.

[0492] 16. The remote terminal and / or the relay terminal can perform flow control as follows to control the amount of data passing through the indirect path.

[0493] For example, the remote terminal can report the downlink data transmission status to the relay terminal, the relay terminal can report the downlink data transmission status to the base station, and the remote terminal can report the downlink data transmission status to the base station through the relay terminal. The downlink data transmission status report can be reported by an RLC control PDU, by a MAC CE, by an RRC message, by a PDCP control PDU, or by another layer 2 control PDU.

[0494] For example, when the DL DATA DELIVERY STATUS is reported by a PDCP control PDU, it is reported as follows. For example, the remote terminal reports the DL DATA DELIVERY STATUS to the base station as follows.

[0495] The remote terminal can report the downlink data transmission status to the base station via a direct path or an indirect path.

[0496] In the case of data transmission without SL HARQ feedback or SL RLC feedback (for example: RLC UM or HARQ feedback deactivated channel), the remote terminal is configured to report to the base station via a direct path.

[0497] In the case of data transmission with SL HARQ feedback or SL RLC feedback (for example: RLC AM or HARQ feedback activated channel), the remote terminal is configured to report to the base station via a direct path.

[0498] The downlink data transmission status procedure is to provide feedback from a remote terminal or a relay terminal to the base station hosting the NR PDCP entity, enabling the base station hosting the NR PDCP entity to control the downlink user data flow for the data radio bearer by the relay terminal. The relay terminal can also transmit the uplink user data for the data radio bearer to the base station hosting the NR PDCP entity together with DL DATA DELIVERY STATUS in the same layer 2 PDU that transmits the uplink user data.

[0499]

Table 6-1

Table 6-2

[0500] For example, when DL DATA DELIVERY STATUS is reported by an RLC control PDU, it is reported as follows. For example, the relay UE reports DL DATA DELIVERY STATUS to the base station as follows.

[0501] For this purpose, the remote UE can provide the SL RLC status report to the relay UE. For example, before performing the downlink data transmission status procedure, the relay terminal triggers the SL RLC status report of the remote terminal by SL RLC polling.

[0502] The downlink data transmission status procedure is to provide feedback to the base station hosting the NR PDCP entity in the remote terminal or relay terminal, so that the base station hosting the NR PDCP entity can control the downlink user data flow by the relay terminal for the data radio bearer. The relay terminal can also transmit the uplink user data for the data radio bearer to the base station hosting the NR PDCP entity together with DL DATA DELIVERY STATUS by the same layer 2 PDU that transmits the uplink user data.

[0503]

Table 7-1

Table 7-2

[0504] For example, the DL DATA DELIVERY STATUS reported to the base station or relay terminal is configured as follows, and the PDCP SN of the DL DATA DELIVERY STATUS is replaced by the RLC SN for the DL DATA DELIVERY STATUS from the relay terminal.

[0505] Figure 17 shows an example of DL DATA DELIVERY STATUS.

[0506] - By the RRC reconfiguration message, the base station can set the SL resource allocation mode 1 and allocate the SL resources of the remote terminal. That is, the base station can allocate the SL grant transmitted by the remote terminal by DCI. In this case, the remote terminal performs the following operations.

[0507] (1) The remote terminal can directly report Uu BSR (Buffer Status Report MAC CE) and SL-BSR (Sidelink Buffer Status Report MAC CE) to the base station by any one of the following methods. For example, when PDCP duplication is set, the BSR is reported by Method 1, and if not, the BSR is reported by Method 2 or Method 3. Alternatively, the BSR is reported by any one of the following methods according to the settings of the base station.

[0508] 1) Method 1: The Uu BSR and SL-BSR for the remote terminal are configured to report the 100% buffer status redundantly for the same bearer. For example, when the SL RLC entity and the UL RLC entity are both connected to the same PDCP entity, if the PDCP buffer size of the bearer is 100 bytes:

[0509] - In the SL BSR, for the buffer size of the bearer, the PDCP buffer size of 100 bytes and the SL RLC buffer size can be reported together.

[0510] Here, in the SL-BSR, the buffer status for a specific destination can be set for the SL relay. When configuring the SL BSR MAC CE for multiple destinations, the buffer size of a specific destination for the SL relay can be preferentially included in the SL BSR MAC CE over the buffer sizes of other destinations.

[0511] - In the Uu BSR, for the buffer size of the bearer, the PDCP buffer size of 100 bytes and the UL RLC buffer size can be reported together.

[0512] - After receiving the SL BSR and Uu BSR, the base station can allocate UL BS (Buffer Size) and SL BS to allocate UL resources and SL resources.

[0513] 2) Method 2: When the SL RLC entity and the UL RLC entity are both connected to the same PDCP entity, the base station determines whether to include the PDCP buffer size in the Uu BSR or the SL BSR for each specific bearer, each specific logical channel group, or each specific destination. The remote terminal determines whether to include the PDCP buffer size in the Uu BSR or the SL BSR and report it for each specific bearer, each specific logical channel group, or each specific destination according to the settings of the base station.

[0514] 3) Method 3: When the SL RLC entity and the UL RLC entity are both connected to the same PDCP entity, the remote terminal reports whether to include the PDCP buffer size in the Uu BSR or the SL BSR according to whether the RLC entity determined for the primary path is UL or SL.

[0515] - The PDCP entity buffer size of the bearer having the direct path as the primary path is reported in the Uu BSR instead of the SL BSR.

[0516] - The PDCP entity buffer size of the bearer having the indirect path as the primary path is reported in the SL BSR instead of the Uu BSR.

[0517] 4) Method 4: When the remote terminal operates in SL mode 2, SL resources are reserved. At this time, the remote terminal can determine the Y% buffer state based on the reserved resources, and the Uu BSR is configured to report the (100 - Y)% buffer size. The SL-BSR is configured to report the remaining Y% buffer size, or the SL-BSR report may not be configured / sent.

[0518] 5) Method 5: The X% buffer state is determined by the UL resources allocated to the remote terminal, and the SL-BSR is configured to report (100 - X)% of the buffer size. The Uu BSR is configured to report or not report X% of the buffer size. The remote terminal is set to SL mode 1 or SL mode 2. When set to SL mode 2, the remote terminal can reserve SL resources by (100 - X)% of the buffer size even if it does not report (100 - X)% of the buffer size in the SL-BSR.

[0519] In the Uu BSR of the method described above, the remote terminal can report the BS (buffer size) of the split bearer, the BS of the indirect bearer, the BS of the direct bearer, and the BS of the bearer with PDCP replication set.

[0520] - For example, the BS (buffer size) of the split bearer, the BS of the indirect bearer, the BS of the direct bearer, and the BS of the bearer with PDCP replication set are reported as the BSs for different LCGs.

[0521] - Alternatively, the Uu BSR is configured to include another BS field for the BS (buffer size) of the split bearer, the BS of the indirect bearer, the BS of the direct bearer, and the BS of the bearer with PDCP replication set.

[0522] (2) BSR reporting method or resource allocation method of the relay terminal

[0523] When the remote terminal reports the SL-BSR or Uu BSR, the base station is set so that the relay terminal does not report the buffer state of the U2N bearer. Alternatively, the relay terminal is set to include a specific logical channel group or a specific destination for the U2N bearer in the Uu BSR with a low priority. Alternatively, the buffer state for the destination of a specific remote terminal is not reported or is set to be included in the BSR with a low priority.

[0524] The base station can allocate the SL resources of the remote terminal according to the SL BSR of the remote terminal, and allocate the UL resources of the relay terminal by the SL resources.

[0525] - The base station can allocate UL resources to the logical channel for a specific remote terminal or U2N relay by DCI. The DCI indicates the destination of the remote terminal, and the CRC is scrambled by the terminal-specific RNTI mapped to the remote terminal or the RNTI for U2N relay.

[0526] - Alternatively, when receiving the SL data of a specific PC5 RLC channel from the remote terminal, a specific UL resource within a predetermined time interval may be preferentially used for the uplink transmission of the SL data. For example, in the process of specifying the priority order of the UL logical channel, when constructing the UL MAC PDU, the data of the UL RLC channel mapped to a specific PC5 RLC channel is preferentially mapped to a specific UL resource within a predetermined time interval.

[0527] (3) The base station can set the SL resource allocation mode 2 and allocate the SL resources of the remote terminal. That is, the remote terminal can select and transmit SL resources within the resource pool allocated by the base station.

[0528] In such SL mode 2, the remote terminal can be configured to report the SL BSR only for the logical channel for the U2N relay. For example, methods 4 and 5 are applied as follows.

[0529] 4) Method 4: When the remote terminal operates in SL mode 2, it can reserve SL resources. The remote terminal can determine the Y% buffer state based on the reserved SL resources, and the Uu BSR is configured to report the buffer size of (100 - Y)%. The SL-BSR is configured to report the remaining Y% buffer size, or the SL-BSR report may not be configured / transmitted.

[0530] Alternatively, out of the overall 100% uplink data transmission rate, the remote terminal can determine a Y% uplink data transmission rate based on the reserved SL resources and transmit the remaining (100 - Y)% data transmission rate to the UL. Therefore, the UL buffer size for the remaining (100 - Y)% data transmission rate can be reported to the Uu BSR. The SL-BSR may be configured to report only the remaining Y% data transmission rate, or may not be configured / transmitted.

[0531] 5) Method 5: The X% buffer state is determined by the UL resources allocated to the remote terminal, and the SL-BSR can report the (100 - X)% buffer size. The Uu BSR may be configured to report the X% buffer size or may not be configured to report it. When set to SL mode 2, the remote terminal can reserve SL resources for only the (100 - X)% buffer size. The remote terminal may not report the SL-BSR for the bearer.

[0532] Alternatively, out of the overall 100% uplink data transmission rate, the remote terminal can determine an X% uplink data transmission rate based on the allocated UL resources and transmit the remaining (100 - X)% data transmission rate to the SL. Therefore, SL resources can be reserved for the (100 - X)% data transmission rate. The UL buffer size can be reported to the Uu BSR. The Uu BSR can be configured to report or not report the X% buffer size. The remote terminal may not report the SL-BSR for the bearer.

[0533] (4) When the SL BSR is not configured, the remote terminal can report only the Uu BSR.

[0534] Since the base station cannot control SL transmission, there is a problem that when the Uu BSR for the remote terminal always reports a 100% buffer state, UL or SL resources are allocated unnecessarily.

[0535] Uplink Resources of Remote Terminal

[0536] - The base station can allocate UL BS and SL BS and assign UL resources.

[0537] - Except for the amount of data transmitted on the UL resource, the remaining data is transmitted to the SL relay.

[0538] - The remote terminal can be set to allocate only Y% of the PDCP buffer to the SL resource.

[0539] The remote terminal can configure Y% for all destinations or each logical channel.

[0540] The remote terminal can determine Y% with the value indicated by the base station or relay terminal, or the minimum, maximum, or average value of Y1 and Y2 indicated by the base station / relay terminal.

[0541] - The remote terminal can specify the maximum, minimum, or average SL data transmission rate for all destinations or each logical channel. Therefore, SL data transmissions exceeding the SL data transmission rate are either dropped, the SL resources are allocated so as not to exceed the SL data transmission rate, or the SL resources exceeding the SL data transmission rate are canceled.

[0542] For example, the reserved SL resources per unit time are restricted according to the SL data transmission rate.

[0543] The remote terminal can set the SL data transmission rate for all destinations or each logical channel.

[0544] The remote terminal can determine the SL data transmission rate with the value indicated by the base station or relay terminal, or the minimum, maximum, or average value of the SL data transmission rate 1 and the SL data transmission rate 2 indicated by the base station / relay terminal.

[0545] - The base station or relay terminal can set the CR limit applied by the remote terminal. The remote terminal can limit the amount of data transmitted to the SL according to the CR limit. Therefore, SL data transmission exceeding the CR limit can be leaked.

[0546] The CR limit can be set for all targets or each logical channel.

[0547] The remote terminal can determine the CR limit with the value indicated by the base station or relay terminal, or determine the CR limit with the minimum, maximum, or average value of the CR limit 1 and CR limit 2 indicated by the base station / relay terminal.

[0548] - The base station or relay terminal can set a resource pool for all targets or each logical channel, and the remote terminal can reserve and transmit SL resources within the configured resource pool.

[0549] The base station can be set to limit the number of SL resources in the resource pool. Also, the relay terminal can further limit the number of SL resources in the resource pool set by the base station. Alternatively, the number of SL resources can be determined with the minimum value, maximum value, or average value of the number of SL resources 1 and the number of SL resources 2 limited by the base station / relay terminal.

[0550] (5) When the U2N relay is set, the remote terminal and the relay terminal can report the Uu BSR or SL BSR as follows.

[0551] 1) BSR reporting method of the remote terminal

[0552] - Uu BSR

[0553] In the case of a specific bearer or split bearer, for the bearer's PDCP entity and UL RLC entity:

[0554] The remote terminal can report only the PDCP buffer size excluding the RLC buffer size to the BSR.

[0555] Alternatively, the remote terminal can report both the RLC buffer size and the PDCP buffer size to the BSR.

[0556] Alternatively, the remote terminal can report only the RLC buffer size excluding the PDCP buffer size to the BSR.

[0557] For a specific indirect bearer, the remote terminal does not include the BS in the BSR.

[0558] - SL-BSR

[0559] For a specific bearer or split bearer, for the PDCP entity and the SL RLC entity of the bearer:

[0560] The remote terminal can report only the PDCP buffer size excluding the RLC buffer size to the SL BSR.

[0561] Alternatively, the remote terminal can report both the RLC buffer size and the PDCP buffer size to the SL BSR.

[0562] Alternatively, the remote terminal can report only the RLC buffer size excluding the PDCP buffer size to the SL BSR.

[0563] For a specific direct bearer, the remote terminal does not include the BS in the SL BSR.

[0564] 2) BSR reporting method for relay terminals

[0565] - Uu BSR

[0566] In the case of a specific bearer, split bearer, or indirect bearer, only the RLC buffer size of the U2N bearer can be reported.

[0567] - SL-BSR

[0568] The base station can allocate SL resources of the relay terminal according to the DL U2N bearer data transmission volume. However, the base station may not know about SL RLC AM retransmission, SL RLC control PDU, or SL MAC CE. Therefore, the relay terminal can be configured to include only the sizes of SL RLC AM retransmission, SL RLC control PDU, or SL MAC CE in the SL BSR.

[0569] To reduce unnecessary SL BSR transmissions,

[0570] the relay terminal can be configured not to report the SL BS for a specific destination.

[0571] The relay terminal can be configured to report only specific data (e.g., retransmission / control PDU / MAC CE) for a specific destination.

[0572] The remote terminal can report the TX SL buffer size waiting for transmission from the remote terminal to the relay terminal. In this case, the relay terminal can report a pre-emptive BSR to the base station. The pre-emptive BSR MAC CE can include the predicted PDCP and / or RLC buffer sizes calculated based on the TX SL buffer size reported by the remote terminal.

[0573] (6) When the remote terminal configures a split bearer, the following operations are performed for the split bearer having a direct path and an indirect path.

[0574] When the primary path of a specific bearer is a direct path, the remote terminal can preferentially use UL resources for the data of the bearer, and after consuming all UL resources, only the remaining data can be transmitted to the SL resources.

[0575] When the primary path of a specific bearer is an indirect path, the remote terminal can preferentially use SL resources for the data of the bearer, and after consuming all SL resources, only the remaining data can be transmitted to the UL resources.

[0576] The remote terminal can switch or maintain the primary path of a specific bearer to an indirect path when any one or more of the following conditions are met.

[0577] - When the measurement result of the serving cell of the remote terminal is less than a predetermined threshold, the primary path of a specific bearer can be switched to an indirect path.

[0578] - When the measurement result of the CBR for the SL resources is less than a predetermined threshold, the primary path of a specific bearer can be switched to an indirect path.

[0579] - When the SL relay measurement result for the SL resources (for example: the measurement result of the SL-RSRP or SD-RSRP of the relay terminal) exceeds a predetermined threshold, the primary path of a specific bearer can be switched to an indirect path.

[0580] - When a Uu failure is detected in a specific bearer, the primary path of the specific bearer can be switched to an indirect path.

[0581] When integrity protection failure, RLC retransmission failure, RLF, bearer reconfiguration failure, beam failure, etc. are detected for a specific bearer, it can be switched to an indirect path.

[0582] If any one or more of the following conditions are met, the remote terminal can switch or maintain the primary path of a specific bearer to the direct path.

[0583] - If the measurement result of the serving cell of the remote terminal is equal to or greater than a predetermined threshold, the primary path of a specific bearer can be switched to the direct path.

[0584] - If the measurement result of the CBR for the SL resource exceeds a predetermined threshold, the primary path of a specific bearer can be switched to the direct path.

[0585] - If the measurement result of the SL relay for the SL resource (e.g., the measurement result of the SL-RSRP or SD-RSRP of the relay terminal) is less than a predetermined threshold, the primary path of a specific bearer can be switched to the direct path.

[0586] - When an SL failure is detected in a specific bearer, the primary path of the bearer can be switched to the direct path.

[0587] When integrity protection failure, RLC retransmission failure, SL failure based on HARQ feedback, bearer reconfiguration failure, etc. are detected for a specific bearer, it can be switched to the direct path.

[0588] 17. The network configures the remote terminal to derive the NR SL measurement results of the serving L2 relay terminal or candidate L2 U2N relay terminal related to the measurement object set in measObjectRelay.

[0589] The remote terminal can receive the measurement configuration in the RRCReconfiguration message. When the terminal receives measConfig in the RRCReconfiguration message, the terminal performs measurements as follows for each measId included in measIdList in VarMeasConfig and starts the measurement reporting procedure.

[0590] When the A.measObject is related to the L2 U2N relay terminal, the remote terminal performs the measurement related to the candidate relay terminal at the frequency indicated by the related measObject. When performing the measurement, the terminal filters the measurement result based on layer 3 filtering before using it for the reporting criterion evaluation or the measurement report for the measured quantity of each candidate L2 U2N relay terminal.

[0591] B. For the measured quantity of each L2 U2N relay terminal derived, the remote terminal performs the following.

[0592] - Derive the measured quantity based on the DMRS as shown in TS 38.215 of the L2 U2N relay terminal related to the NR SL frequency indicated by the related measObjectRelay. Also,

[0593] - Apply layer 3 filtering.

[0594] C. When the measObject is related to the L2 U2N relay terminal:

[0595] - When eventY1-Relay is set in the reportConfig; or

[0596] - When the reportType set to periodical is included in the reportConfig:

[0597] The remote terminal needs to consider all L2 U2N relay terminals detected at the related frequency as applicable to this measId.

[0598] Table 8 describes the events for measurement report triggering.

[0599]

Table 8-1

Table 8-2

Table 8-3

Table 8-4

[0600] In the state where the D.VarMeasReportList does not contain the measurement report item for this measId (the first L2 U2N relay terminal triggers the event), when the reportType is set to eventTriggered and the item conditions applicable to this event, that is, the event corresponding to the eventId of the reportConfig in the VarMeasConfig, are satisfied for all the measurements after layer 3 filtering performed during the timeToTrigger defined for this event in the VarMeasConfig for one or more applicable L2 U2N relay terminals, the remote terminal performs the following.

[0601] - Include the measurement report item in the VarMeasReportList for this measId.

[0602] - Set the numberOfReportsSent defined in the VarMeasReportList for this measId to 0.

[0603] - Include the L2 U2N relay terminals related to the relaysTriggeredList defined in the VarMeasReportList for this measId.

[0604] - Start the measurement report procedure as follows.

[0605] Otherwise, if reportType is set to eventTriggered and the applicable item conditions for this event, i.e., the event corresponding to the eventId of the relevant reportConfig in VarMeasConfig, are met for all measurements after layer 3 filtering performed during the timeToTrigger defined for this event in VarMeasConfig for one or more applicable L2 U2N relay terminals not included in the relaysTriggeredList (subsequent L2 U2N relay terminals trigger the event), the remote terminal shall do the following.

[0606] - Set the numberOfReportsSent defined in VarMeasReportList for this measId to 0.

[0607] - Include the L2 U2N relay terminal in the relaysTriggeredList defined in VarMeasReportList for this measId.

[0608] - Start the measurement reporting procedure as follows.

[0609] E. Otherwise, if reportType is set to eventTriggered and the applicable detachment conditions for this event are met for one or more of the L2 U2N relay terminals included in the relaysTriggeredList defined in VarMeasReportList for this measId for all measurements after layer 3 filtering performed during the timeToTrigger defined for this event in VarMeasConfig, the remote terminal shall do the following.

[0610] - Remove the relevant L2 U2N relay terminal from the relaysTriggeredList defined in VarMeasReportList for this measId.

[0611] - When reportOnLeave is set to true for the report setting, start the measurement reporting procedure as follows.

[0612] - If the relaysTriggeredList defined in VarMeasReportList for this measId is empty: Remove the measurement report items in VarMeasReportList for this measId; If the periodic reporting timer for this measId is running, stop it.

[0613] If F.reportType is set to periodical and (the first) measurement results are available:

[0614] - If reportAmount exceeds 1: Immediately after the amount to be reported to the NR SpCell or, if the terminal is an L2 U2N remote terminal, to the serving L2 U2N relay terminal becomes available, start the measurement reporting procedure as shown in 5.5.5.

[0615] - Otherwise (i.e., if reportAmount is 1): Immediately after the amount to be reported to the NR SpCell and the strongest cell among the cells, or to the NR SpCell and the strongest L2 U2N relay terminal among the applicable L2 U2N relay terminals becomes available, start the measurement reporting procedure as shown in 5.5.5; or, immediately after the amount to be reported to the serving L2 U2N relay terminal and the strongest cell among the applicable cells (if the terminal is an L2 U2N remote terminal) becomes available, start the measurement reporting procedure as follows.

[0616] 18. In the previous stage, when starting the measurement reporting procedure, for the measId for which the measurement reporting procedure is triggered, the terminal sets the measResults in the MeasurementReport message as follows, and then the remote terminal sends the MeasurementReport message to the network via the SRB.

[0617] A. When the terminal is connected to the L2 U2N relay terminal by PC5 - RRC connection (i.e., when the terminal is an L2 U2N remote terminal), the terminal needs to set sl - MeasResultServingRelay to include the SL - RSRP of the serving L2 U2N relay terminal.

[0618] - When there is no data transmission from the L2 U2N relay terminal to the L2 U2N remote terminal, whether to use SL - RSRP or SD - RSRP when setting the sl - MeasResultServingRelay of the serving L2 U2N relay terminal depends on the implementation of the terminal.

[0619] B. When there is one or more applicable adjacent cells to report:

[0620] - When reportType is set to eventTriggered or periodical and the measurement report is related to the candidate L2 U2N relay terminal, the terminal needs to set sl - MeasResultCandRelay to include the best candidate L2 U2N relay terminal up to maxReportCells as follows.

[0621] When reportType is set to eventTriggered: The terminal needs to include the L2 U2N relay terminals included in relaysTriggeredList as defined in VarMeasReportList for this measId.

[0622] Otherwise, the terminal needs to include the applicable L2 U2N relay terminals for which new measurement results have become available after the last periodic report, or after the measurement is started or reset.

[0623] - For each L2 U2N relay terminal included in sl-MeasResultsCandRelay, the terminal shall include sl-RelayUEIdentity. For each included L2 U2N relay terminal, the terminal shall include layer 3 filtered measurement results according to the reportConfig for this measId.

[0624] If the measObject related to this measId is related to the L2 U2N relay terminal, the terminal shall set the measResult to include the quantity indicated from reportQuantityRelay within the related reportConfigRelay in descending order of the sorting quantity, with the best L2 U2N relay terminal included first.

[0625] For candidate L2 U2N relay terminals, the terminal shall consider yN-Threshold2-Relay as the sorting quantity.

[0626] For candidate L2 U2N relay terminals, the terminal shall consider reportQuantityRelay as the sorting quantity.

[0627] Table 9 describes the SL-MeasResultsSLRelay information element.

[0628]

Table 9

[0629] C. In the second message or RRCReconfiguration message, the base station can set the reportConfig related to the measId that triggered the measurement report to eventTriggered as follows, and set the eventID to one or more events for the event-triggered measurement report.

[0630] > In the case of the serving cell camped on by the remote terminal, the serving cell camped on by the relay terminal, or the cell with the highest suitability for the remote terminal, one or more of the following events can be set for the remote terminal.

[0631] Event A1 (serving / best cell quality is better than the threshold)

[0632] Event A2 (serving / best cell quality is worse than the threshold)

[0633] Event A3 (adjacent cell is offset better than the serving / best cell in terms of cell quality)

[0634] Event N1 (adjacent cell quality is better than the threshold)

[0635] The remote terminal can trigger this event only for the cell indicated by the base station in the RRCReconfiguration message.

[0636] Event N2 (adjacent cell quality is worse than the threshold)

[0637] The remote terminal can trigger this event only for the cell indicated by the base station in the RRCReconfiguration message.

[0638] Note that the cell with the highest suitability for the remote terminal or the serving cell camped on by the remote terminal may be the same as or different from the serving cell of the relay terminal.

[0639] Note that the remote terminal is set to trigger Event A3, N1, and / or N2 only for the cell indicated by the base station in the RRCReconfiguration message.

[0640] - For the serving cell on which the remote terminal camps or the serving frequency of the cell with the highest suitability for the remote terminal, the reselection priority of the cell with the highest priority, or the reselection priority of the cell with a priority higher than the priority threshold (for example: a priority higher than the threshold), or for the non-serving frequency of the remote terminal, the remote terminal can set any one or more of the following events for the remote terminal.

[0641] Event S1 (the fitness / best cell quality is better than the threshold at the said frequency)

[0642] Event S2 (the fitness / best cell quality is worse than the threshold at the said frequency)

[0643] Event S3 (the qualified neighboring cell is offset better than the best cell in terms of cell quality)

[0644] When the above-mentioned event is triggered for the fitness / best cell or the neighboring cell, the remote terminal reports the following information to the base station.

[0645] Measurement results for the fitness / best cell and / or the qualified neighboring cell

[0646] Whether the neighboring cell is suitable as a result of the suitability check based on the SIB1 reading of the neighboring cell

[0647] Global cell ID of the fitness / best cell

[0648] Global cell ID of the neighboring cell

[0649] D. In the second message or the RRCReconfiguration message, the base station can set the reportType of the reportConfig related to the measId that triggered the measurement report to periodical, and the remote terminal performs the following operations.

[0650] - The terminal performs the said measurements related to the serving cell of the remote terminal, the serving cell of the relay terminal (when the serving cell is indicated by the relay terminal), and / or the best (matched) cell of the remote terminal for the frequency indicated by the base station.

[0651] - If the received measObject contains cellsToAddModList of the RRCReconfiguration message, the terminal performs the said measurements related to each cell corresponding to the physCellId value included in cellsToAddModList or each cell detected at the frequency indicated by the base station.

[0652] - Thereafter, the terminal periodically reports the measurement results for each cell (measured by the remote terminal at the aforementioned stage) to the base station by the relay terminal.

[0653] In the measurement report transmitted to the base station, the terminal first includes the measurement results for the serving cell of the remote terminal and / or the serving cell of the relay terminal (or, the serving cell of the relay terminal and / or the serving cell of the remote terminal) in this order, and then includes the measurement results for each of the other cells in cellsToAddModList in descending order of the sorted quantity (for example: in descending order of the measured RSRP or RSRQ results).

[0654] 19. After the RRC connection establishment and the PC5 - RRC connection establishment, the relay terminal and / or the remote terminal performs the SL terminal information for the NR sidelink communication procedure in which the terminal transmits the SidelinkUEInformationNR message to the base station.

[0655] The terminal configures the content of the SidelinkUEInformationNR message as follows.

[0656] A. When sl-NonRelayDiscovery is included in a specific SIB (e.g., SIB12) and is set by the upper layer to receive NR SL non-relay discovery information, or when sl-L2U2N-Relay is included in a specific SIB (e.g., SIB12) and is set by the upper layer to receive NR SL L2 U2N relay discovery information, or when sl-L3U2N-RelayDiscovery is included in a specific SIB (e.g., SIB12) and is set by the upper layer to receive NR SL L3 U2N relay discovery information, or when an instruction for multi-path support is included in a specific SIB (e.g., SIB12) and is set by the upper layer to receive NR SL U2N relay discovery information:

[0657] - The terminal includes sl-RxInterestedFreqListDisc and sets it to the frequency for receiving NR SL relay discovery information.

[0658] - When the terminal can perform L2 U2N remote terminal operations or can perform multi-path operations as a remote terminal, the terminal includes sl-SourceIdentity-RemoteUE and sets it to the source ID set by the upper layer for NR SL L2 U2N relay communication transmission.

[0659] B. When sl-NonRelayDiscovery is included in a specific SIB (e.g., SIB12) and is set by the upper layer to transmit NR SL non-relay discovery information, or when sl-L2U2N-Relay is included in a specific SIB (e.g., SIB12) and is set by the upper layer to transmit NR SL L2 U2N relay discovery information, or when sl-L3U2N-RelayDiscovery is included in a specific SIB (e.g., SIB12) and is set by the upper layer to transmit NR SL L3 U2N relay discovery information, or when an instruction for multi-path support is included in a specific SIB (e.g., SIB12) and is set by the upper layer to transmit NR SL U2N relay discovery information, the terminal includes sl-TxResourceReqListDis and for each destination for which it requests the network to allocate NR SL discovery information resources, (if necessary) it sets this field as follows:

[0660] - Set sl-DestinationIdentityDisc to the destination ID set by the upper layer for NR SL discovery information transmission.

[0661] - When the terminal operates as an L2 U2N relay terminal, the terminal sets sl-SourceIdentity-RelayUE to the source ID set by the upper layer for NR SL L2 U2N relay discovery information transmission.

[0662] - Set sl-CastTypeDisc to the cast type of the related destination ID set by the upper layer for NR SL discovery information transmission.

[0663] - Set sl-InterestedFreqListDisc to indicate the frequencies of the related destinations for NR SL discovery information transmission.

[0664] - Set the sl-TypeTxSyncListDisc to the current synchronization reference type used in the related sl-InterestedFreqList for NR SL discovery known transmission.

[0665] - Set the sl-DiscoveryType to the current discovery type of the related destination ID set at the upper layer for NR SL discovery known transmission.

[0666] C. Set by the upper layer to transmit NR SL L2 U2N relay communication. When the terminal operates as an L2 U2N relay terminal for multi-path, the relay terminal shall perform the following.

[0667] - Include sl-TxResourceReqL2U2N-Relay in sl-TxResourceReqListCommRelay and set this field as follows for each destination that requests (if necessary) the network to allocate NR SL L2 U2N relay communication resources.

[0668] - Set the sl-DestinationIdentityL2U2N to the destination ID set at the upper layer for NR SL L2 U2N relay communication transmission.

[0669] - Set the sl-TxInterestedFreqListL2U2N to indicate the frequencies of the related destinations for NR SL L2 U2N relay communication transmission.

[0670] - Set the sl-TypeTxSyncListL2U2N to the current synchronization reference type used in the related sl-InterestedFreqListL2U2N for NR SL L2 U2N relay communication transmission.

[0671] - Set the sl-LocalID-Request to request the local ID for the L2 U2N remote terminal.

[0672] - Set the sl-PagingIdentity-RemoteUE to the paging terminal ID received at the peer L2 U2N remote terminal.

[0673] - Set the sl-CapabilityInformationSidelink to include the UECapabilityInformationSidelink message (if present) received at the peer terminal.

[0674] - Include the ue-Type and set this to the relay UE.

[0675] - Include the multi-path support / request indication.

[0676] - Include an indication of whether the remote terminal's RRC state or whether the remote terminal is in RRC_CONNECTED.

[0677] - Include the cell ID of the PCell for the remote terminal.

[0678] - Include the PLMN ID of the PLMN registered for the remote terminal.

[0679] - Include the tracking area code of the tracking area in which the remote terminal is registered to the PCell.

[0680] If the upper layer is configured to send NR sidelink L2 U2N relay communication and there is an L2 U2N relay terminal selected by the terminal for multi-path, the remote terminal shall perform the following.

[0681] - Include the sl-TxResourceReqL2U2N-Relay in the sl-TxResourceReqListCommRelay and (if necessary) configure this field as follows to request the network to allocate NR SL L2 U2N relay communication resources.

[0682] - Set sl-TxInterestedFreqListL2U2N to indicate the frequencies of the destinations relevant for NR SL L2 U2N relay communication transmission.

[0683] - Set sl-TypeTxSyncListL2U2N to the current synchronization reference type used in the relevant sl-InterestedFreqListL2U2N for NR SL L2 U2N relay communication transmission.

[0684] - If there is a terminal CapabilityInformationSidelink message received at the peer terminal, set sl-CapabilityInformationSidelink to include this.

[0685] - Include ue-Type and set it to remoteUE.

[0686] - Include multi-path support / request indication.

[0687] - Include an indication of the RRC state of the relay terminal or whether the relay terminal is in RRC_CONNECTED.

[0688] - Include the PCell cell ID of the relay terminal.

[0689] - Include the PLMN ID of the registered PLMN of the relay terminal.

[0690] - Include the tracking area code of the tracking area where the relay terminal is registered to the PCell.

[0691] When configured by the upper layer to transmit E.NR SL L3 U2N relay communication, the relay terminal or the remote terminal shall perform the following.

[0692] - Include sl-TxResourceReqL3U2N-Relay in sl-TxResourceReqListCommRelay and set this field as follows for each destination (if necessary) for which the network is requested to allocate NR SL L3 U2N relay communication resources:

[0693] - Set sl-DestinationIdentity to the destination ID set at a higher layer for NR SL L3 U2N relay communication transmission.

[0694] - Set sl-CastType to the cast type of the associated destination ID set at a higher layer for NR SL L3 U2N relay communication transmission.

[0695] - If the associated two-way SL DRB is set by the configuration by RRCReconfigurationSidelink, set sl-RLC-ModeIndication to include the RLC mode of the RLC mode of the associated SL QoS flow and optionally the QoS profile.

[0696] - Set sl-QoS-InfoList to include the QoS profile of the SL QoS flow of the associated destination set at a higher layer for NR SL L3 U2N relay communication transmission.

[0697] - Set sl-TxInterestedFreqList to indicate the frequencies of the associated destination for NR SL L3 U2N relay communication transmission.

[0698] - Set sl-TypeTxSyncList to the current synchronization reference type used in the associated sl-InterestedFreqList for NR SL L3 U2N relay communication transmission.

[0699] - When the UECapabilityInformationSidelink message is received from the peer terminal, set sl-CapabilityInformationSidelink to include this.

[0700] - Include ue-Type, and if the terminal is operating as an NR SL L3 U2N relay terminal, set it to relayUE; otherwise, set it to remoteUE.

[0701] - Include multi-path support / request indication.

[0702] - Include an indication of the RRC state of the relay terminal or whether the relay terminal is in RRC_CONNECTED.

[0703] - Include an indication of the RRC state of the remote terminal or whether the remote terminal is in RRC_CONNECTED.

[0704] - When the terminal is operating as an NR SL U2N remote terminal:

[0705] Include the cell ID of the PCell for the relay terminal.

[0706] Include the PLMN ID of the registered PLMN for the relay terminal.

[0707] Include the tracking area code of the tracking area registered by the relay terminal for the PCell.

[0708] - When the terminal is operating as an NR SL U2N relay terminal:

[0709] Include the cell ID of the PCell for the remote terminal.

[0710] Include the PLMN ID of the PLMN registered for the remote terminal.

[0711] Include the tracking area code of the tracking area registered by the remote terminal for the PCell.

[0712] 20. When receiving a report from a remote terminal and / or a relay terminal (e.g., MeasurementReport message and / or SidelinkUEInformationNR message from a remote terminal and / or SidelinkUEInformationNR message from a relay terminal and / or multi-path configuration from a base station), the base station determines whether to modify or release the direct path to the remote terminal with the base station.

[0713] 21. When the base station sends another RRCReconfiguration message, the relay terminal and the remote terminal can release one or more or all of the indirect bearers and / or split bearers that can be reconfigured to a direct bearer according to the RRCReconfiguration message of the base station. According to the RRCReconfiguration message of the base station, the remote terminal maintains both the direct link and the indirect link by the relay terminal.

[0714] To release the indirect path of an indirect bearer or a split bearer for the indirect path of a multi-path reconfigured to a direct bearer according to the RRCReconfiguration message of the base station, the remote terminal or the relay terminal performs one or more of the following.

[0715] A. The receiving PDCP entity of the bearer of the remote terminal can trigger a PDCP status report to be sent to the base station as described below.

[0716] - The PDCP status report is sent directly from the remote terminal to the base station or indirectly to the base station by the relay terminal.

[0717] - When receiving the PDCP status report, the transmitting PDCP entity of the bearer of the base station triggers "multi-path data switching" to retransmit or transmit PDCP SDUs in the direct path towards the remote terminal as follows.

[0718] - Before / after receiving the RRCReconfiguration message for bearer release, the SL RLC entity of the remote terminal or relay terminal performs one or more of the following.

[0719] Option 1: The remote terminal releases the Uu RLC entity and / or PC5 RLC entity for the bearer's downstream indirect path. As a result, the SL data buffered in the TX RLC entity is deleted / is deleted, or the DL data buffered in the RX RLC entity is deleted.

[0720] Option 2: In the case of the SL RLC entity of the PC5 RLC channel for the bearer's downstream indirect path, the AM RLC entity of the relay terminal polls the peer AM RLC entity to trigger an RLC status report at the peer AM RLC entity of the remote terminal. Based on the polling, the AM RLC entity of the remote terminal triggers an RLC status report to be sent to the peer AM RLC entity of the relay terminal.

[0721] Option 3: In the case of the SL RLC entity of the PC5 RLC channel for the bearer's downstream indirect path, the AM RLC entity of the remote terminal triggers an RLC status report to be sent to the peer AM RLC entity of the relay terminal.

[0722] - When receiving an RLC status report from the receiving RLC entity, the SL transmitting RLC entity of the relay terminal retransmits the RLC SDU or RLC SDU segment for which a negative acknowledgment was received by the RLC status report, as follows.

[0723] B. The receiving PDCP entity of the base station's bearer can trigger a PDCP status report to be sent to the remote terminal, as follows.

[0724] - The PDCP status report is sent directly from the base station to the remote terminal or indirectly to the remote terminal by the relay terminal.

[0725] - Upon receiving the PDCP status report, the transmitting PDCP entity of the bearer of the remote terminal triggers "multi-path data switching" to retransmit or transmit the PDCP SDU on the direct path towards the base station as follows.

[0726] - Before / after receiving the RRCReconfiguration message for bearer release, the SL RLC entity of the relay terminal or the remote terminal performs one or more of the following.

[0727] Option 1: The relay terminal releases the Uu RLC entity and / or the PC5 RLC entity for the upstream indirect path of the bearer. As a result, the SL data buffered in the RX RLC entity is deleted / is deleted, or the UL data buffered in the TX RLC entity is deleted.

[0728] Option 2: In the case of the SL RLC entity of the PC5 RLC channel for the upstream indirect path of the bearer, the AM RLC entity of the remote terminal polls the peer AM RLC entity and triggers an RLC status report at the peer AM RLC entity of the relay terminal. Based on the polling, the AM RLC entity of the relay terminal triggers an RLC status report to be sent to the peer AM RLC entity of the remote terminal.

[0729] Option 3: In the case of the SL RLC entity of the PC5 RLC channel for the upstream indirect path of the bearer, the AM RLC entity of the relay terminal triggers an RLC status report to be sent to the peer AM RLC entity of the remote terminal.

[0730] - When receiving an RLC status report from the receiving RLC entity, the SL transmission RLC entity of the remote terminal retransmits the SL RLC SDU or SL RLC SDU segment for which a negative acknowledgment has been received by the RLC status report over Uu / PC5 until the bearer is released.

[0731] When receiving an SL RLC SDU and / or SL RLC SDU segment from the remote terminal, the relay terminal retransmits the UL RLC SDU or UL RLC SDU segment corresponding to the SL RLC SDU and / or SL RLC SDU segment over the uplink until the bearer is released.

[0732] - Thereafter, the relay terminal and / or the remote terminal notifies the base station of the bearer release, for example, by transmitting a terminal information message to the base station.

[0733] Before / after receiving the terminal information message, the base station releases the PDCP / RLC entity corresponding to the bearer and / or the PC5-RRC connection.

[0734] Before / after transmitting the terminal information message, or when transmitting an RRCReconfiguration message for releasing the bearer to the remote terminal and / or the relay terminal, the relay terminal and / or the remote terminal releases the Uu / PC5 PDCP / RLC entity corresponding to the bearer and / or the PC5-RRC connection.

[0735] C. Before / after receiving the RRCReconfiguration message for releasing the bearer, with respect to the downstream indirect path of the bearer, the relay terminal aborts all RLC status reporting procedures in the DL receiving RLC entity and / or the SL transmission RLC entity, and releases the DL receiving RLC entity and / or the SL transmission RLC entity. The relay terminal can also transmit an RRCReconfigurationSidelink message to the remote terminal to release the peer SL receiving RLC entity at the remote terminal.

[0736] When a PDCP status report is triggered, the receiving PDCP entity shall do the following.

[0737] - Compile the PDCP status report as instructed below.

[0738] - Set the FMC field to RX_DELIV.

[0739] - If RX_DELIV < RX_NEXT:

[0740] - Start from the first missed PDCP SDU, excluding this one, and including the last out-of-sequence PDCP SDU, assign a bitmap field with a value rounded up to the next multiple of 8 as the COUNT value up to this last PDCP SDU, or including up to the PDCP SDU where the resulting PDCP control PDU size becomes 9000 bytes, with the same bit length as the COUNT value up to this PDCP SDU.

[0741] - Set to "0" in the bitmap field for all PDCP SDUs not received and for PDCP SDUs that selectively failed decompression.

[0742] - Set to "1" in the bitmap field for all received PDCP SDUs.

[0743] - Submit the PDCP status report to the lower layer as the first PDCP PDU to be transmitted by the transmitting PDCP entity for the Uu interface and for the PC5 interface.

[0744] For an AM DRB, when a PDCP status report is received on the downlink or sidelink, the transmitting PDCP entity shall do the following.

[0745] - For each PDCP SDU for which the bit in the bitmap is set to "1" or the associated COUNT value is less than the FMC field value, it is considered that the PDCP SDU has been successfully transmitted, and this PDCP SDU is deleted.

[0746] When multi-path data switching for a bearer (e.g., from an indirect bearer to a direct bearer) is triggered, the transmitting PDCP entity for DL, UL, or SL shall perform the following for the bearer.

[0747] - For an AM DRB, starting from the first PDCP SDU for which successful transmission of the PDCP data PDU cannot be confirmed by the RLC entity associated with the indirect path, re-transmit or transmit all PDCP SDUs already associated with the PDCP SN and the PDCP SDU in ascending order of the COUNT value associated with the PDCP SDU prior to multi-path data switching to the RLC entity associated with the direct path in DL, UL, or SL as follows.

[0748] - Perform header compression of the PDCP SDU using ROHC.

[0749] - Perform integrity protection and encryption of the PDCP SDU using the COUNT value associated with this PDCP SDU.

[0750] - Submit the resulting PDCP data PDU to the RLC entity of the direct path.

[0751] - For a UM DRB, for all PDCP SDUs that have been processed by PDCP but have not yet been submitted to the lower layer, transmit the PDCP SDUs to the RLC entity associated with the direct path in DL, UL, or SL in ascending order of the COUNT value as specified below.

[0752] - Perform header compression of the PDCP SDU using ROHC.

[0753] - Use the COUNT value associated with this PDCP SDU to perform integrity protection and encryption of the PDCP SDU.

[0754] - Submit the resulting PDCP data PDU directly to the RLC entity on the direct path in DL, UL, or SL.

[0755]

Table 10-1

Table 10-2

[0756] When the transmitting side of the AM RLC entity receives a STATUS report from the receiving RLC AM entity, it performs the following.

[0757] - If the STATUS report includes a positive or negative acknowledgment for an RLC SDU having the same sequence number as POLL_SN:

[0758] - If t-PollRetransmit is in progress:

[0759] - Stop and reset the timer t-PollRetransmit used by the transmitting side of the AM RLC entity to retransmit the poll.

[0760] - Consider retransmitting the RLC SDU or RLC SDU segment for which a negative acknowledgment was received.

[0761] On the other hand, when receiving an RRCReconfiguration message from the base station, for the bearer (e.g., split bearer), the remote terminal can reconfigure the direct path of the split bearer to the primary path as follows:

[0762] - If the RRCReconfiguration message does not configure the primary path of the bearer, the remote terminal reconfigures the direct path of the split bearer as the primary path.

[0763] Alternatively, if the RRCReconfiguration message does not configure the primary path of the bearer, the remote terminal maintains (or configures) the indirect path of the split bearer as the primary path.

[0764] Alternatively, if the RRCReconfiguration message does not configure the primary path of the bearer, the remote terminal configures the direct path or indirect path of the split bearer as the primary path according to the indicated configuration or basic configuration.

[0765] - If the RRCReconfiguration message configures the primary path of the bearer, the remote terminal configures the direct path or indirect path of the split bearer as the primary path according to the configuration of the RRCReconfiguration message.

[0766] - A specific type of Signalling RB can always set the direct path of the split bearer as the primary path (e.g., according to the indicated configuration or basic configuration).

[0767] 22. When the relay terminal requests / requests the modification or release of the indirect bearer and / or the indirect path of the split bearer to the base station, or when any one or more of the following conditions are met, it can notify the base station using the first terminal information message for the conditions (i.e., any one or more of the following conditions) that trigger the modification or release.

[0768] - When the relay terminal detects a buffer overflow for the relayed bearer / channel (e.g., TX or RX buffer overflow for SL transmission and reception between the relay terminal and the remote terminal, or buffer overflow for UL transmission and reception or DL reception for U2N relay)

[0769] - If the relay terminal cannot meet the QoS requirements of the relayed bearer / channel, for example, if it cannot meet the delay requirements or the data rate requirements of the relayed bearer / channel

[0770] - When the relay terminal sets up a PC5 unicast link with one or more remote terminals

[0771] - When the relay terminal releases the PC5 unicast link with the remote terminal

[0772] - When the relay terminal detects a side link failure of the PC5 unicast link with the remote terminal (e.g., side link radio link failure or side link reconfiguration failure or side link integrity protection failure)

[0773] - When the remote terminal and / or the relay terminal cannot map the newly configurable SL bearer to the established Uu / PC5 RLC channel for relaying the SL bearer

[0774] - When the SL bearer mapped to the established Uu / PC5 RLC channel is released by the remote terminal and / or the relay terminal

[0775] - When the NAS layer of the relay terminal requests the addition, modification, or release of the indirect path of the configurable indirect bearer and / or split bearer for multi-path operation

[0776] The first terminal information message includes one or more of the following.

[0777] - The identifier of the relayed bearer / channel to which the above-mentioned modification or modification condition applies, for example, the bearer ID, logical channel ID, source ID, or destination ID of the relayed bearer / channel

[0778] - Identifiers of the relayed bearer / channel to which the aforementioned release or release conditions apply, e.g., the bearer ID, logical channel ID, source ID, or destination ID of the relayed bearer / channel

[0779] - Reasons related to the aforementioned modification conditions

[0780] 23. The remote terminal can request the base station to modify or release the indirect bearer and / or the indirect path of the split bearer, or can notify the base station using a second terminal information message for the conditions (i.e., any one or more of the following conditions) that trigger the modification or release when any one or more of the following conditions are met.

[0781] - When the remote terminal detects a buffer overflow for the relayed bearer / channel (e.g., TX or RX buffer overflow for SL transmission and reception between the relay terminal and the remote terminal)

[0782] - When the remote terminal cannot meet the QoS requirements of the relayed bearer / channel, e.g., when it cannot meet the delay requirements or the speed requirements of the relayed bearer / channel

[0783] - When the remote terminal sets up a PC5 unicast link with one or more relay terminals

[0784] - When the remote terminal releases the PC5 unicast link with the relay terminal

[0785] - When the remote terminal detects a side link failure of the PC5 unicast link with the relay terminal (e.g., side link radio link failure, side link reconfiguration failure, or side link integrity protection failure)

[0786] - When the remote terminal and / or the relay terminal cannot map the newly configurable SL bearer to the previously configured Uu / PC5 RLC channel for relaying the SL bearer

[0787] - When releasing an SL bearer mapped to a Uu / PC5 RLC channel configured with a remote terminal and / or a relay terminal

[0788] - When the NAS layer of a remote terminal requests the addition, modification, or release of an indirect path of an indirect bearer and / or a split bearer whose multi-path operation can be configured

[0789] The second terminal information message includes one or more of the following.

[0790] - Identifiers of the relayed bearer / channel to which the above-mentioned modification or modification conditions apply, such as the bearer ID, logical channel ID, source ID, or destination ID of the relayed bearer / channel

[0791] - Identifiers of the relayed bearer / channel to which the above-mentioned release or release conditions apply, such as the bearer ID, logical channel ID, source ID, or destination ID of the relayed bearer / channel

[0792] - The cause related to the above-mentioned release condition

[0793] 24. When a remote terminal deems that the entry condition for one of the following events is satisfied based on the above-mentioned measurement configuration, the remote terminal starts the first measurement reporting procedure.

[0794] - Event X1 (The serving L2 U2N relay terminal deteriorates beyond threshold 1 and the NR cell improves beyond threshold 2)

[0795] - Event X3 (The serving L2 U2N relay terminal deteriorates beyond threshold 1 and the PCell (or PSCell or SCell) improves beyond threshold 2)

[0796] - Event X2 (The serving L2 U2N relay terminal deteriorates beyond the threshold)

[0797] - Event Y2 (Candidate L2 U2N relay terminal improves beyond the threshold)

[0798] - Event C1 (NR side link channel utilization rate exceeds the threshold)

[0799] If the remote terminal deems that the detachment condition for one of the following events is satisfied based on the aforementioned measurement configuration, the remote terminal starts the first measurement reporting procedure.

[0800] - Event C2 (NR side link channel utilization rate is less than the threshold)

[0801] - Event Y1 (PCell is worse than threshold 1, and candidate L2 U2N relay terminal is better than threshold 2)

[0802] If the relay terminal deems that the entry condition for one of the following events is satisfied according to the aforementioned measurement configuration, the relay terminal starts the second measurement reporting procedure.

[0803] - Event A2 (Serving cell deteriorates beyond the threshold)

[0804] - Event A3 (Adjacent cell is better than SpCell by the offset)

[0805] - Event B1 (Inter-RAT adjacent cell is better than the threshold)

[0806] - Event B2 (PCell is worse than threshold 1, and inter-RAT adjacent cell is better than threshold 2)

[0807] - Event C1 (NR side link channel utilization rate exceeds the threshold)

[0808] If the relay terminal deems that the detachment condition for one of the following events is satisfied according to the aforementioned measurement configuration, the relay terminal starts the second measurement reporting procedure.

[0809] - Event C2 (NR sidelink channel utilization rate is less than the threshold)

[0810] - Event A1 (serving is better than the threshold)

[0811] When the first measurement reporting procedure is started, the remote terminal uses the first measurement report to inform the base station of the measurement results of the relay terminal and the identifier of the relay terminal.

[0812] When the second measurement reporting procedure is started, the relay terminal uses the second measurement report to inform the base station of the measurement results of the remote terminal and the identifier of the remote terminal.

[0813] 25. The CN node (e.g., AMF or SMF) can inform the base station of the addition, modification, or release of the multi-path configuration in the QoS profile for the remote terminal and / or the relay terminal, for example. The QoS profile is transmitted from the CN node to the base station.

[0814] - Information regarding the multi-path of the QoS profile can indicate whether the multi-path can be configured for any one of the following.

[0815] Each PDU session

[0816] Each QoS flow

[0817] Each remote terminal

[0818] Each relay terminal

[0819] Each frequency

[0820] Each cell

[0821] Each RAT

[0822] Each PLMN

[0823] Each tracking area

[0824] Each base station

[0825] 26. Based on the first / second terminal information message and / or the first / second measurement report and / or the aforementioned multi-path configuration, the base station determines an addition, modification, or release of an indirect path of an indirect bearer and / or a split bearer for the relayed bearer / channel.

[0826] When the base station determines an addition, modification, or release of an indirect path of an indirect bearer and / or a split bearer for the relayed bearer / channel by the following Option 1 or Option 2, the base station transmits an RRCReconfiguration message to each of the relay terminal and the remote terminal, for example. The base station can transmit an RRCReconfiguration message by Option 1 as described below for the modification of the relayed bearer / channel, while transmitting an RRCReconfiguration message by Option 2 as described below for the release of the relayed bearer / channel.

[0827] - If the sl-L2RelayUEConfig of the RRCReconfiguration message contains the SL-DestinationIdentity corresponding to the remote terminal, the relay terminal releases the L2 U2N remote terminal and releases all indirect bearers and one or more split bearers for the remote terminal.

[0828] - If the SL-DestinationIdentity corresponding to the remote terminal in the sl-L2RelayUEConfig of the RRCReconfiguration message and the BearerIdentity or SL-DestinationIdentity corresponding to the indirect bearer or split bearer for the remote terminal are included, the relay terminal releases one or more L2 entities (for example, RLC entity) and the logical channel corresponding to the indirect bearer or split bearer for the remote terminal.

[0829] - If the l-L2RemoteUEConfig of the RRCReconfiguration message contains the SL-DestinationIdentity corresponding to the relay terminal and the BearerIdentity or SL-DestinationIdentity corresponding to the indirect bearer or split bearer for the remote terminal, the remote terminal shall release or modify one or more L2 entities (e.g., RLC entity) and the logical channel corresponding to the indirect bearer or split bearer for the relay terminal according to the message. The remote terminal can also add or modify the direct bearer to change the indirect / split bearer to a direct bearer.

[0830] - If the sl-L2RemoteUEConfi of the RRCReconfiguration message contains the SL-DestinationIdentity corresponding to the relay terminal, the remote terminal shall release all indirect bearers for the relay terminal and release or modify one or more split bearers according to the message. The remote terminal may add or modify the direct bearer to change the indirect / split bearer to a direct bearer.

[0831] At this stage, the following options for the aforementioned RRC reconfiguration can be considered.

[0832] A. Option 1: The joint RRC reconfiguration can be used for the remote terminal and the relay terminal to modify or release the indirect bearer and / or split bearer. Furthermore, the connection of the U2N infrastructure can also be released.

[0833] B. Option 2: The separate transmission of the RRC reconfiguration can be used for the remote terminal and the relay terminal to modify or release the indirect bearer and / or split bearer. Furthermore, the connection of the U2N infrastructure can also be released.

[0834] 27. At the above-described stage, the relay terminal and the remote terminal can release one or all of the indirect bearers and / or split bearers that can be directly reconfigured to the bearer. As a result of this stage, the remote terminal can maintain either the direct link and the indirect link by the relay terminal, or the remote terminal can release the PC5-RRC connection, if possible, with the indirect link by the relay terminal and maintain only the direct link.

[0835] To release the indirect path of the indirect bearer or split bearer for the multi-path indirect path, the remote terminal or the relay terminal performs one or more of the following.

[0836] A. The receiving PDCP entity of the bearer of the remote terminal can trigger a PDCP status report to be sent to the base station as described below.

[0837] - The PDCP status report is sent directly from the remote terminal to the base station or indirectly to the base station by the relay terminal.

[0838] - Upon receiving the PDCP status report, the transmitting PDCP entity of the bearer of the base station triggers "multi-path data switching" to retransmit or transmit the PDCP SDU on the direct path towards the remote terminal as described below.

[0839] - When receiving / before receiving the RRCReconfiguration message for bearer release, or when releasing / before releasing the PC5-RRC connection, the SL RLC entity of the remote terminal or the relay terminal performs one or more of the following.

[0840] Option 1: The remote terminal releases the Uu RLC entity and / or the PC5 RLC entity for the downstream indirect path of the bearer. As a result, the SL data buffered in the TX RLC entity is deleted / is deleted, or the DL data buffered in the RX RLC entity is deleted.

[0841] Option 2: For the SL RLC entity of the PC5 RLC channel for the downstream indirect path of the bearer, the AM RLC entity of the relay terminal polls the peer AM RLC entity and triggers an RLC status report at the peer AM RLC entity of the remote terminal. Based on the polling, the AM RLC entity of the remote terminal triggers an RLC status report to be sent to the peer AM RLC entity of the relay terminal.

[0842] Option 3: For the SL RLC entity of the PC5 RLC channel for the downstream indirect path of the bearer, the AM RLC entity of the remote terminal triggers an RLC status report to be sent to the peer AM RLC entity of the relay terminal.

[0843] - When receiving an RLC status report from the receiving RLC entity, the SL transmitting RLC entity of the relay terminal retransmits the RLC SDU or RLC SDU segment for which a negative acknowledgment has been received by the RLC status report, as described below.

[0844] B. The receiving PDCP entity of the bearer at the base station can trigger a PDCP status report to be sent to the remote terminal, as described below.

[0845] - The PDCP status report is sent directly from the base station to the remote terminal or indirectly to the remote terminal by the relay terminal.

[0846] - When receiving a PDCP status report, the transmitting PDCP entity of the bearer at the remote terminal triggers "multi-path data switching" to retransmit or transmit PDCP SDUs on the direct path towards the base station, as described below.

[0847] - When receiving / receiving before an RRCReconfiguration message for bearer release or when releasing / before releasing the PC5-RRC connection, the SL RLC entity of the relay terminal or the remote terminal performs one or more of the following.

[0848] Option 1: The relay terminal releases the Uu RLC entity and / or the PC5 RLC entity for the bearer's upstream indirect path. As a result, the SL data buffered in the RX RLC entity is deleted / is deleted, or the UL data buffered in the TX RLC entity is deleted.

[0849] Option 2: In the case of the SL RLC entity of the PC5 RLC channel for the bearer's upstream indirect path, the AM RLC entity of the remote terminal polls the peer AM RLC entity and triggers an RLC status report at the peer AM RLC entity of the relay terminal. Based on the polling, the AM RLC entity of the relay terminal triggers an RLC status report to be sent to the peer AM RLC entity of the remote terminal.

[0850] Option 3: In the case of the SL RLC entity of the PC5 RLC channel for the bearer's upstream indirect path, the AM RLC entity of the relay terminal triggers an RLC status report to be sent to the peer AM RLC entity of the remote terminal.

[0851] - When receiving an RLC status report from the receiving RLC entity, the SL transmitting RLC entity of the remote terminal retransmits the SL RLC SDU or SL RLC SDU segment for which a negative acknowledgment was received by the RLC status report as described below until a PC5-RRC release and / or a bearer release of Uu / PC5 is performed.

[0852] When receiving an SL RLC SDU and / or an SL RLC SDU segment from the remote terminal, the relay terminal performs an uplink retransmission of the UL RLC SDU or UL RLC SDU segment corresponding to the SL RLC SDU and / or the SL RLC SDU segment until the PC5-RRC connection or the bearer is released.

[0853] - Subsequently, the relay terminal and / or the remote terminal notify the release of the PC5-RRC connection and / or the bearer by transmitting a terminal information message to the base station.

[0854] Before / after receiving the terminal information message, the base station releases the PDCP / RLC entity corresponding to the bearer and / or the PC5-RRC connection.

[0855] The relay terminal and / or the remote terminal release the Uu / PC5 PDCP / RLC entity corresponding to the bearer and / or the PC5-RRC connection before / after transmitting the terminal information message, or when transmitting an RRCReconfiguration message for releasing the bearer to the remote terminal and / or the relay terminal.

[0856] C. When receiving / before receiving an RRCReconfiguration message for releasing the bearer, or when releasing / before releasing the PC5-RRC connection for the downstream indirect path of the bearer, the relay terminal aborts all RLC status reporting procedures in the DL receive RLC entity and / or the SL transmit RLC entity, and the relay terminal releases the DL receive RLC entity and / or the SL transmit RLC entity. The relay terminal can also transmit an RRCReconfigurationSidelink message to the remote terminal to release the peer SL receive RLC entity at the remote terminal.

[0857] According to the present invention described above, the network can simultaneously configure a direct path and an indirect path for multi-path operation, and use the flow control according to the present invention to select one or both of the paths, particularly when the terminal can support the U2N relay function via SL.

[0858] The present invention is advantageous in that the system can appropriately apply multi-path operation including a direct link and an indirect link via U2N relay. In the prior art, there was no mechanism for providing SL relay for multi-path operation.

[0859] FIG. 18 shows a method for a first UE (user equipment) to transmit a signal in an embodiment of the present invention.

[0860] Referring to FIG. 18, the first UE performs a procedure for setting up a split bearer that includes both a direct path between the first UE and the network and an indirect path between the first UE and the network (1805). When setting up the split bearer, the direct path is set as the primary path of the split bearer.

[0861] The first UE transmits first upstream data to the network via the direct path based on the primary path of the split bearer (1810).

[0862] The first UE detects a failure associated with the direct path (1815).

[0863] Based on the detection of the failure associated with the direct path, the first UE switches the primary path of the split bearer from the direct path to the indirect path (1820).

[0864] The first UE transmits second upstream data to the network through a second UE that operates as a relay UE for the indirect path to the network on the switched primary path of the split bearer (1825).

[0865] Preferably, the indirect path is set based on a sidelink interface between the first UE and the relay UE.

[0866] Preferably, the second upstream data is transmitted to the network via a Uu interface between the second UE and the network.

[0867] Preferably, the failure associated with the direct path is a Uu interface failure between the first UE and the network.

[0868] Preferably, the RRC (radio resource control) messages in the split bearer are exchanged via the primary path.

[0869] Preferably, the RRC messages exchanged via the primary path include RRC messages for the secondary path of the split bearer.

[0870] Preferably, the failures related to the direct path include at least one of integrity protection failure, RLC (radio link control) retransmission failure, RLF (radio link failure), bearer reconfiguration failure, and beam failure.

[0871] Preferably, the first UE operates as a remote UE in the indirect path.

[0872] Without limitation, the various descriptions, functions, procedures, proposals, methods, and / or flowcharts of the present invention disclosed in this specification can be applied to various fields that require wireless communication / connection between devices (e.g., 5G).

[0873] Hereinafter, it will be described more specifically with reference to the drawings. In the following figures / descriptions, the same reference numerals exemplify the same or corresponding hardware blocks, software blocks, or functional blocks unless otherwise specifically mentioned.

[0874] FIG. 19 illustrates a communication system applicable to the present invention.

[0875] Referring to FIG. 19, the communication system 1 applied to the present invention includes a wireless device, a base station, and a network. Here, the wireless device means a device that communicates using a wireless connection technology (for example, 5G NR (New RAT), LTE (Long Term Evolution)), and is also referred to as a communication / wireless / 5G device. Without being limited thereto, the wireless devices include a robot 100a, vehicles 100b-1, 100b-2, an XR (Extended Reality) device 100c, a hand-held device 100d, a home appliance 100e, an IoT (Internet of Thing) device 100f, and an AI device / server 400. For example, the vehicles include vehicles equipped with a wireless communication function, autonomous driving vehicles, vehicles capable of vehicle-to-vehicle communication, etc. Here, the vehicles include UAVs (Unmanned Aerial Vehicles) (for example, drones). The XR device includes an AR (Augmented Reality) / VR (Virtual Reality) / MR (Mixed Reality) device, and is embodied in the form of an HMD (Head-Mounted Device), an HUD (Head-Up Display) provided in a vehicle, a TV, a smartphone, a computer, a wearable device, a home appliance, a digital signage, a vehicle, a robot, etc. The hand-held devices include smartphones, smart pads, wearable devices (for example, smartwatches, smart glasses), computers (for example, notebook personal computers, etc.). The home appliances include TVs, refrigerators, washing machines, etc. The IoT devices include sensors, smart meters, etc. For example, the base station and the network are also embodied in the wireless device, and a specific wireless device 200a can also operate as a base station / network node for other wireless devices.

[0876] Wireless devices 100a to 100f are connected to network 300 via base station 200. AI (Artificial Intelligence) technology is applied to wireless devices 100a to 100f, and wireless devices 100a to 100f are connected to AI server 400 via network 300. Network 300 is configured using a 3G network, a 4G (e.g., LTE) network, a 5G (e.g., NR) network, or the like. Wireless devices 100a to 100f can communicate with each other via base station 200 / network 300, but can also communicate directly without going through the base station / network (e.g., sidelink communication). For example, vehicles 100b-1 and 100b-2 can communicate directly (e.g., V2V (Vehicle to Vehicle) / V2X (Vehicle to everything) communication). Also, IoT devices (e.g., sensors) can communicate directly with other IoT devices (e.g., sensors) or other wireless devices 100a to 100f.

[0877] Wireless communications / connections 150a, 150b, and 150c are performed between wireless devices 100a to 100f / base station 200 and between base stations 200 / 200. Here, the wireless communications / connections are uplink / downlink communications 150a, sidelink communications 150b (or D2D communications), and inter-base station communications 150c (e.g., performed by various wireless connection technologies such as relay and IAB (Integrated Access Backhaul) (e.g., 5G NR)). Through wireless communications / connections 150a, 150b, and 150c, wireless devices and base stations / wireless devices, and base stations and base stations can transmit / receive wireless signals to / from each other. For example, wireless communications / connections 150a, 150b, and 150c can transmit / receive signals via various physical channels. For this purpose, based on various proposals of the present invention, any one of the setting process of various configuration information for transmitting / receiving wireless signals, various signal processing processes (e.g., channel encoding / decoding, modulation / demodulation, resource mapping / demapping, etc.), and resource allocation process is performed.

[0878] FIG. 20 illustrates a wireless device applicable to the present invention.

[0879] Referring to FIG. 20, the first wireless device 100 and the second wireless device 200 transmit and receive wireless signals by various wireless connection technologies (e.g., LTE, NR). Here, {the first wireless device 100, the second wireless device 200} corresponds to {the wireless device 100x, the base station 200} in FIG. 19 and / or {the wireless device 100x, the wireless device 100x}.

[0880] The first wireless device 100 includes one or more processors 102 and one or more memories 104, and further includes one or more transceivers 106 and / or one or more antennas 108. The processor 102 controls the memory 104 and / or the transceiver 106, and is configured to implement the descriptions, functions, procedures, proposals, methods and / or flowcharts disclosed in this specification. For example, after the processor 102 processes the information in the memory 104 to generate a first information / signal, the transceiver 106 transmits a wireless signal including the first information / signal. Also, after the processor 102 receives a wireless signal including a second information / signal by the transceiver 106, the information obtained from the signal processing of the second information / signal is stored in the memory 104. The memory 104 is connected to the processor 102 and stores various information related to the operation of the processor 102. For example, the memory 104 stores software code that performs some or all of the processes controlled by the processor 102, or includes instructions for performing the descriptions, functions, procedures, proposals, methods and / or flowcharts disclosed in this specification. Here, the processor 102 and the memory 104 are part of a communication modem / circuit / chip designed to implement wireless communication technologies (e.g., LTE, NR). The transceiver 106 is connected to the processor 102 and transmits and / or receives wireless signals by one or more antennas 108. The transceiver 106 includes a transmitter and / or a receiver. The transceiver 106 can also be used interchangeably with an RF (radio Frequency) unit. In the present invention, the wireless device can also mean a communication modem / circuit / chip.

[0881] Specifically, the UE includes a processor 102 and a memory 104 that are coupled to the RF transceiver. The memory 104 includes at least one program capable of performing operations related to the embodiments shown in FIGS. 11 to 27.

[0882] Alternatively, a chipset including a processor 102 and a memory 104 is configured. In this case, the chipset includes at least one processor and at least one memory that is operably coupled to the at least one processor and causes the at least one processor to operate when executed.

[0883] The second wireless device 200 includes one or more processors 202 and one or more memories 204, and further includes one or more transceivers 206 and / or one or more antennas 208. The processor 202 controls the memory 204 and / or the transceiver 206 and is configured to implement the descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed in this specification. For example, after the processor 202 processes information in the memory 204 to generate third information / signals, the transceiver 206 transmits a wireless signal including the third information / signals. Also, after the processor 202 receives a wireless signal including fourth information / signals by the transceiver 206, the information obtained from the signal processing of the fourth information / signals is stored in the memory 204. The memory 204 is coupled to the processor 202 and stores various information related to the operation of the processor 202. For example, the memory 204 stores software code that performs some or all of the processes controlled by the processor 202 or includes instructions for performing the descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed in this specification. Here, the processor 202 and the memory 204 are part of a communication modem / circuit / chip designed to implement wireless communication technologies (e.g., LTE, NR). The transceiver 206 is coupled to the processor 202 and transmits and / or receives wireless signals via one or more antennas 208. The transceiver 206 includes a transmitter and / or a receiver. The transceiver 206 can also be used interchangeably with an RF unit. In the present invention, a wireless device also means a communication modem / circuit / chip.

[0884] Hereinafter, the hardware elements of the wireless devices 100 and 200 will be described more specifically. Although not limited thereto, one or more protocol layers are implemented by one or more processors 102 and 202. For example, one or more processors 102 and 202 implement one or more layers (for example, functional layers such as PHY, MAC, RLC, PDCP, RRC, and SDAP). One or more processors 102 and 202 generate one or more PDUs (Protocol Data Units) and / or one or more SDUs (Service Data Units) according to the descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed in this specification. One or more processors 102 and 202 generate messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed in this specification. One or more processors 102 and 202 generate a signal (for example, a baseband signal) including a PDU, an SDU, a message, control information, data, or information according to the functions, procedures, proposals, and / or methods disclosed in this specification, and provide it to one or more transceivers 106 and 206. One or more processors 102 and 202 receive a signal (for example, a baseband signal) from one or more transceivers 106 and 206, and can obtain PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed in this specification.

[0885] One or more processors 102, 202 are also referred to as a controller, a microcontroller, a microprocessor, or a microcomputer. The one or more processors 102, 202 are implemented by hardware, firmware, software, or a combination thereof. As an example, one or more ASICs (Application Specific Integrated Circuits), one or more DSPs (Digital Signal Processors), one or more DSPDs (Digital Signal Processing Devices), one or more PLDs (Programmable Logic Devices), or one or more FPGAs (Field Programmable Gate Arrays) are included in the one or more processors 102, 202. The descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed in this specification are implemented using firmware or software, and the firmware or software is implemented to include modules, procedures, functions, and the like. The firmware or software configured to perform the descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed in this specification is included in the one or more processors 102, 202, or stored in the one or more memories 104, 204 and driven by the one or more processors 102, 202. The descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed in this specification are implemented using firmware or software in the form of code, instructions, and / or sets of instructions.

[0886] One or more memories 104, 204 are connected to one or more processors 102, 202 and store various forms of data, signals, messages, information, programs, codes, instructions and / or commands. The one or more memories 104, 204 are constituted by a ROM, a RAM, an EPROM, a flash memory, a hard drive, a register, a cache memory, a computer-readable storage medium and / or a combination thereof. The one or more memories 104, 204 are located inside and / or outside the one or more processors 102, 202. Also, the one or more memories 104, 204 are connected to the one or more processors 102, 202 by various techniques such as wired or wireless connections.

[0887] One or more transceivers 106, 206 transmit user data, control information, radio signals / channels, etc. mentioned in this specification, such as in methods and / or flowcharts, to one or more other devices. One or more transceivers 106, 206 receive user data, control information, radio signals / channels, etc. mentioned in the descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed in this specification from one or more other devices. For example, one or more transceivers 106, 206 are connected to one or more processors 102, 202 and transmit and receive radio signals. For example, one or more processors 102, 202 control one or more transceivers 106, 206 to transmit user data, control information, or radio signals to one or more other devices. Also, one or more processors 102, 202 control one or more transceivers 106, 206 to receive user data, control information, or radio signals from one or more other devices. One or more transceivers 106, 206 are connected to one or more antennas 108, 208, and one or more transceivers 106, 206 are configured to transmit and receive user data, control information, radio signals / channels, etc. mentioned in the descriptions, functions, procedures, proposals, methods, and / or flowcharts disclosed in this specification by one or more antennas 108, 208. In this specification, one or more antennas are multiple physical antennas or multiple logical antennas (e.g., antenna ports). One or more transceivers 106, 206 convert received radio signals / channels, etc. from RF band signals to baseband signals (Convert) in order to process received user data, control information, radio signals / channels, etc. using one or more processors 102, 202. One or more transceivers 106, 206 convert user data, control information, radio signals / channels, etc. processed using one or more processors 102, 202 from baseband signals to RF band signals. For this purpose, one or more transceivers 106, 206 include (analog) oscillators and / or filters.

[0888] FIG. 21 illustrates another example of a wireless device to which this invention is applied. The wireless device can be embodied in various forms depending on usage examples / services (see FIG. 19).

[0889] Referring to FIG. 21, the wireless devices 100 and 200 correspond to the wireless devices 100 and 200 in FIG. 20 and are composed of various elements, components, units / parts, and / or modules. For example, the wireless devices 100 and 200 include a communication unit 110, a control unit 120, a memory unit 130, and additional elements 140. The communication unit includes a communication circuit 112 and a transceiver 114. For example, the communication circuit 112 includes one or more processors 102 and 202 and / or one or more memories 104 and 204 in FIG. 20. For example, the transceiver 114 includes one or more transceivers 106 and 206 and / or one or more antennas 108 and 208 in FIG. 20. The control unit 120 is electrically connected to the communication unit 110, the memory unit 130, and the additional elements 140 to control various operations of the wireless device. For example, the control unit 120 controls the electrical / mechanical operations of the wireless device based on programs / codes / instructions / information stored in the memory unit 130. The control unit 120 also transmits the information stored in the memory unit 130 to the outside (e.g., other communication devices) by the communication unit 110 via a wireless / wired interface, or stores the information received from the outside (e.g., other communication devices) by the communication unit 110 via a wireless / wired interface in the memory unit 130.

[0890] The additional elements 140 are variously configured depending on the type of the wireless device. For example, the additional elements 140 include any one of a power unit / battery, an input / output unit (I / O unit), a drive unit, and a computer unit. Without being limited thereto, the wireless device is embodied in the form of a robot (FIGS. 19, 100a), a vehicle (FIGS. 19, 100b-1, 100b-2), an XR device (FIGS. 19, 100c), a portable device (FIGS. 19, 100d), a home appliance (FIGS. 19, 100e), an IoT device (FIGS. 19, 100f), a digital broadcast terminal, a hologram device, a public safety device, an MTC device, a medical device, a fintech device (or financial device), a security device, a climate / environment device, an AI server / device (FIGS. 19, 400), a base station (FIGS. 19, 200), and a network node, etc. The wireless device is movable depending on the usage example / service or is used at a fixed location.

[0891] In FIG. 21, various elements, components, units / parts, and / or modules within the wireless devices 100 and 200 are all connected to each other by a wired interface, or at least some of them are wirelessly connected by the communication unit 110. For example, within the wireless devices 100 and 200, the control unit 120 and the communication unit 110 are wired-connected, and the control unit 120 and the first units (e.g., 130, 140) are wirelessly connected by the communication unit 110. Also, each element, component, unit / part, and / or module within the wireless devices 100 and 200 further includes one or more elements. For example, the control unit 120 is composed of one or more sets of processors. For example, the control unit 120 is composed of a set such as a communication control processor, an application processor, an ECU (Electronic Control Unit), a graphics processing processor, and a memory control processor. As another example, the memory unit 130 is composed of a RAM (Random Access Memory), a DRAM (Dynamic RAM), a ROM (Read Only Memory), a flash memory, a volatile memory, a non-volatile memory, and / or a combination thereof.

[0892] FIG. 22 illustrates a vehicle or an autonomous driving vehicle to which the present invention is applied. The vehicle or the autonomous driving vehicle is embodied as a mobile robot, a vehicle, a train, an aerial vehicle (AV), a ship, or the like.

[0893] Referring to FIG. 22, the vehicle or the autonomous driving vehicle 100 includes an antenna unit 108, a communication unit 110, a control unit 120, a driving unit 140a, a power supply unit 140b, a sensor unit 140c, and an autonomous driving unit 140d. The antenna unit 108 is composed of a part of the communication unit 110. Each of the blocks 110 / 130 / 140a to 140d corresponds to the blocks 110 / 130 / 140 in FIG. 21.

[0894] The communication unit 110 transmits and receives signals (such as data, control signals, etc.) with external devices such as other vehicles, base stations (for example, base stations, roadside units, etc.), and servers. The control unit 120 controls elements of the vehicle or the autonomous driving vehicle 100 to perform various operations. The control unit 120 includes an ECU (Electronic Control Unit). The driving unit 140a enables the vehicle or the autonomous driving vehicle 100 to travel on the ground. The driving unit 140a includes an engine, a motor, a power train, wheels, brakes, a steering device, and the like. The power supply unit 140b supplies power to the vehicle or the autonomous driving vehicle 100 and includes a wired / wireless charging circuit, a battery, and the like. The sensor unit 140c can obtain vehicle state, surrounding environment information, user information, and the like. The sensor unit 140c includes an IMU (Inertial Measurement Unit) sensor, a collision sensor, a wheel sensor, a speed sensor, an inclination sensor, a weight sensing sensor, a heading sensor, a position module, a vehicle forward / backward sensor, a battery sensor, a fuel sensor, a tire sensor, a steering sensor, a temperature sensor, a humidity sensor, an ultrasonic sensor, an illuminance sensor, a pedal position sensor, and the like. The autonomous driving unit 140d implements technologies such as maintaining the lane during driving, automatically adjusting the speed like an adaptive cruise control, automatically driving along a predetermined route, and automatically setting and driving along a route when a destination is set.

[0895] As an example, the communication unit 110 receives map data, traffic information data, etc. from an external server. The autonomous driving unit 140d generates an autonomous driving route and a drive plan based on the obtained data. The control unit 120 controls the drive unit 140a so that the vehicle or the autonomous driving vehicle 100 moves along the autonomous driving route according to the drive plan (e.g., speed / direction adjustment). The communication unit 110 periodically obtains the latest traffic information data from the external server during autonomous driving and also obtains traffic information data of surrounding vehicles from the surrounding vehicles. Further, the sensor unit 140c obtains vehicle state and surrounding environment information during autonomous driving. The autonomous driving unit 140d updates the autonomous driving route and the drive plan based on the newly obtained data / information. The communication unit 110 transmits information regarding the vehicle position, the autonomous driving route, the drive plan, etc. to the external server. The external server can predict traffic information data in advance using AI technology, etc. based on the information collected from the vehicle or the autonomous driving vehicle and provide the predicted traffic information data to the vehicle or the autonomous driving vehicle.

[0896] Here, the wireless communication technology implemented in the wireless devices (XXX, YYY) of this specification includes not only LTE, NR, and 6G, but also Narrowband Internet of Things for low-power communication. At this time, for example, NB-IoT technology is an example of LPWAN (Low Power Wide Area Network) technology, and is implemented in standards such as LTE Cat NB1 and / or LTE Cat NB2, and is not limited to the above-mentioned names. Further or alternatively, the wireless communication technology implemented in the wireless devices (XXX, YYY) of this specification communicates based on LTE-M technology. At this time, as an example, LTE-M technology is an example of LPWAN technology, and is also called by various names such as eMTC (enhanced Machine Type Communication). For example, LTE-M technology is implemented in any of various standards such as 1) LTE CAT0, 2) LTE Cat M1, 3) LTE Cat M2, 4) LTE non-BL (non-Bandwidth Limited), 5) LTE-MTC, 6) LTE Machine Type Communication, and / or 7) LTE M, and is not limited to the above-mentioned names. Further or alternatively, the wireless communication technology implemented in the wireless devices (XXX, YYY) of this specification includes any one of ZigBee (registered trademark), Bluetooth (registered trademark), and Low Power Wide Area Network (LPWAN) considering low-power communication, and is not limited to the above-mentioned names. As an example, ZigBee technology generates PAN (personal area networks) related to small / low-power digital communication based on various standards such as IEEE802.15.4, and is called by various names.

[0897] The embodiments described above combine the components and features of the present invention in a predetermined form. Each component or feature is considered optional unless otherwise explicitly stated. Each component or feature can be implemented in a form that does not combine with other components or features, or some components and / or features can be combined to form embodiments of the present invention. The order of operations described in the embodiments of the present invention may be changed. Some components and features of one embodiment may be included in other embodiments, or may replace the corresponding components or features of other embodiments. It is obvious that claims that do not have an explicit citation relationship in the claims can be combined to form embodiments, or included as new claims by amendment after filing.

[0898] In this specification, the embodiments of this invention are mainly described centering on the signal transmission and reception relationship between the terminal and the base station. Such a transmission and reception relationship can be similarly / identically extended to the signal transmission and reception between the terminal and the relay or between the base station and the relay. Specific operations assumed to be performed by the base station in this document may in some cases be performed by its upper node. That is, it is obvious that various operations performed for communication with the terminal in a network composed of a plurality of network nodes including the base station can be performed by the base station or other network nodes other than the base station. The base station may be referred to by terms such as fixed station, Node b, eNode b (eNB), access point, etc. Also, the terminal may be referred to by terms such as UE (User Equipment), MS (Mobile Station), MSS (Mobile Subscriber Station), etc.

[0899] Embodiments according to the present invention are implemented by various means such as hardware, firmware, software, or combinations thereof. In the case of implementation by hardware, an embodiment of the present invention is implemented by 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, microprocessors, etc.

[0900] In the case of implementation by firmware or software, an embodiment of the present invention is implemented in the form of modules, procedures, functions, etc. that perform the functions or operations described above. The software code is stored in a memory and driven by a processor. The memory unit is provided inside or outside the processor and exchanges data with the processor by various known means.

[0901] It is obvious to those skilled in the art that the present invention can be embodied in other specific forms without departing from the features of the present invention. Therefore, the above detailed description should not be construed restrictively in all aspects and should be considered as exemplary. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the present invention are included in the scope of the present invention.

Industrial Applicability

[0902] The present invention can be applied to terminals, base stations, or other devices in a wireless mobile communication system.

Claims

1. In a wireless communication system, a method for a first UE (user equipment) to transmit a signal, comprising: executing a procedure for setting a split bearer that includes both a direct path between the first UE and a network and an indirect path between the first UE and the network; when setting the split bearer, determining that the direct path is set as the primary path of the split bearer; transmitting first upstream data to the network via the direct path based on the primary path of the split bearer; detecting a failure related to the direct path; based on the detection of the failure related to the direct path, switching the primary path of the split bearer from the direct path to the indirect path, and transmitting second upstream data to the network by a second UE operating as a relay UE for the indirect path to the network via the switched primary path of the split bearer.

2. The method according to claim 1, wherein the indirect path is set based on a sidelink interface between the first UE and the relay UE.

3. The method according to claim 1, wherein the second upstream data is transmitted to the network via a Uu interface between the second UE and the network.

4. The method according to claim 1, wherein the failure related to the direct path is a Uu interface failure between the first UE and the network.

5. The method according to claim 1, wherein RRC (radio resource control) messages in the split bearer are exchanged via the primary path.

6. The method according to claim 5, wherein the RRC messages exchanged via the primary path include RRC messages for a secondary path of the split bearer.

7. The method according to claim 1, wherein the failure related to the direct path includes at least one of an integrity protection failure, an RLC (radio link control) retransmission failure, an RLF (radio link failure), a bearer reconfiguration failure, and a beam failure. Claim 8 The method according to claim 1, wherein the first UE operates as a remote UE in the indirect path. Claim 9 A computer-readable medium storing instructions which, when executed by a processor, cause the processor to perform the method according to claim 1. Claim 10 An apparatus for wireless communication, comprising a memory configured to store instructions, and a processor configured to execute the instructions to perform operations, wherein the operations performed by the processor include executing a procedure for setting up a split bearer including both a direct path and an indirect path between the apparatus and a network, determining that the direct path is set as the primary path of the split bearer when setting up the split bearer, transmitting first upstream data to the network via the direct path based on the primary path of the split bearer, detecting a failure associated with the direct path, switching the primary path of the split bearer from the direct path to the indirect path based on the detection of the failure associated with the direct path, and transmitting second upstream data to the network by operating as a relay UE for the indirect path to the network on the switched primary path of the split bearer. Claim 11 The apparatus according to claim 10, wherein the apparatus is an ASIC (application-specific integrated circuit) or a digital signal processor. Claim 12 The apparatus according to claim 10, wherein the apparatus is a UE (user equipment) operating in a 3GPP (registered trademark) (3rd generation partnership project)-based wireless communication system.

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