CN117296354A - Method and apparatus for remote UE operation and relay UE recovery in wireless communication system related to RLF - Google Patents

Abstract

Embodiments relate to a method of operation of a remote User Equipment (UE) in a wireless communication system, the method comprising the steps of: the remote UE establishes connection with a first relay UE; the remote UE receiving information informing of Uu Radio Link Failure (RLF) from the first relay UE; and performing a relay reselection or cell selection procedure based on having received the information informing the Uu RLF, wherein the remote UE transmits information informing a fallback to a previous link to a reselected second relay UE or a base station associated with cell selection based on having received the information informing that Uu link recovery has succeeded from the first relay UE.

Description

Method and apparatus for remote UE operation and relay UE recovery in wireless communication system related to RLF

Technical Field

The following description relates to wireless communication systems, and more particularly, to methods and apparatus related to operation of a relay User Equipment (UE) when Uu Radio Link Failure (RLF) occurs and Uu link recovery is successful.

Background

Wireless communication systems are being widely deployed to provide various types of communication services such as voice and data. In general, a wireless communication system is a multiple access system capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of multiple-access systems include Code Division Multiple Access (CDMA) systems, frequency Division Multiple Access (FDMA) systems, time Division Multiple Access (TDMA) systems, orthogonal Frequency Division Multiple Access (OFDMA) systems, single carrier frequency division multiple access (SC-FDMA) systems, and multiple carrier frequency division multiple access (MC-FDMA) systems.

Wireless communication systems employ various Radio Access Technologies (RATs) such as Long Term Evolution (LTE), LTE-advanced (LTE-a), and wireless fidelity (WiFi). Generation 5 (5G) is also included in the RAT. Three key areas of demand for 5G are (1) enhanced mobile broadband (emmbb), (2) large machine type communication (mctc), and (3) Ultra Reliable Low Latency Communication (URLLC). Some use cases may require multiple sizes for optimization, while other use cases may focus on only one Key Performance Indicator (KPI). The 5G supports these various use cases in a flexible and reliable manner.

The eMBB far exceeds basic mobile internet access and encompasses rich interactive work, media and entertainment applications in the cloud or Augmented Reality (AR). Data is one of the key drivers for 5G, and in the 5G era, dedicated voice services may not be seen for the first time. In 5G, speech is expected to be treated as an application using only the data connectivity provided by the communication system. The main driving force for traffic increases is the number of applications requiring high data rates and the increase in content size. Streaming services (audio and video), interactive video and mobile internet connections will continue to be widely used as more and more devices are connected to the internet. Many of these applications require an always-on connection to push real-time information and notifications to the user. Cloud storage and applications for mobile communication platforms are rapidly increasing. This applies both to work and entertainment. Cloud storage is one particular use case that drives the increase in uplink data rates. 5G will also be used for tele-work in the cloud, which when done with a haptic interface requires much lower end-to-end latency to maintain a good user experience. Entertainment (e.g., cloud gaming and video streaming) is another key driving force to increase the demand for mobile broadband capabilities. Entertainment will be critical for smartphones and tablets wherever high mobility environments are involved, such as trains, automobiles and airplanes. Another use case is Augmented Reality (AR) for entertainment and information searching, which requires very little latency and a large amount of instant data.

One of the most promising 5G use cases is the active connection of embedded sensor functionality in each field (i.e., mctc). It is expected that there will be 204 million potential internet of things (IoT) devices before 2020. In industrial IoT, 5G is one of the areas of key role in implementing smart cities, asset tracking, smart utilities, agriculture, and security infrastructure.

URLLC includes services that will make use of ultra-reliable/available low latency links for industry reform, such as key infrastructure and remote control of autonomous vehicles. The level of reliability and latency is critical to smart grid control, industrial automation, robotics, drone control and coordination, etc.

Now, a plurality of use cases will be described in detail.

5G may supplement Fiber To The Home (FTTH) and cable-based broadband (or Data Over Cable Service Interface Specification (DOCSIS)) as a means of providing streams at data rates of hundreds of megabits per second to gigabits per second. Such high speeds are required for Virtual Reality (VR) and AR as well as TV broadcasting with a resolution of 4K or higher (6K, 8K or higher). VR and AR applications mainly include immersive sporting events. A particular application may require a particular network configuration. For example, for VR games, the gaming establishment may have to integrate the core server with the network operator's edge network server in order to minimize latency.

The automotive industry is expected to become a very important new driving force for 5G, with many use cases for mobile communication of vehicles. For example, entertainment for passengers requires both high capacity and high mobility mobile broadband, as future users will want to keep their high quality connections all the time, independent of their location and speed. Other examples of uses in the automotive industry are AR dashboards. These dashboards display overlay information on what the driver is looking through the front window, identify objects in the dark, and inform the driver of the distance and movement of the objects. In the future, the wireless module will be able to effect communication between the vehicles themselves, information exchange between the vehicles and the supporting infrastructure, and information exchange between the vehicles and other connected devices (e.g., devices carried by pedestrians). The safety system may guide the driver to take alternative courses of action to enable them to drive more safely and with reduced risk of accident. The next stage will be a remotely controlled or automatically driven vehicle. This requires very reliable, very fast communication between different autonomous vehicles and between the vehicle and the infrastructure. In the future, an autonomous vehicle will perform all driving activities while the driver will focus on traffic anomalies where the vehicle itself is elusive. The technical requirements of autonomous vehicles require ultra low waiting times and ultra high reliability, increasing traffic safety to levels that cannot be achieved by humans.

Smart cities and smart households, often referred to as smart society, will be embedded in dense wireless sensor networks. The distributed network of intelligent sensors will confirm the cost and energy efficient maintenance conditions of the city or home. A similar arrangement can be made for each household, wherein the temperature sensor, the window and heating controller, the burglar alarm and the household appliance are all connected in a wireless manner. Many of these sensors are typically characterized by low data rates, low power and low cost, but for example, real-time High Definition (HD) video may be required in certain types of monitoring devices.

The consumption and distribution of energy, including heat or gas, is becoming highly decentralized, creating the need for automatic control of very decentralized sensor networks. The smart grid interconnects these sensors using digital information and communication technology to collect and take action on the information. The information may include information about the behavior of suppliers and consumers, enabling the smart grid to improve efficiency, reliability, economic feasibility and sustainability of production of the distribution of fuel such as electricity in an automated manner. The smart grid may be considered as another sensor network with little delay.

The hygiene field has many applications that can benefit from mobile communications. The communication system enables telemedicine providing clinical medical services at a remote distance. It helps to eliminate distance obstructions and improve access to medical services that will often not be available continuously in remote rural communities. It can also be used to save lives in intensive care and emergency situations. Wireless sensor networks based on mobile communications may provide remote monitoring and sensors for parameters such as heart rate and blood pressure.

Wireless and mobile communications are becoming increasingly important for industrial applications. The installation and maintenance costs of the wires are high and the possibility of replacing the cable with a reconfigurable wireless link is an attractive opportunity for many industries. However, to achieve this, wireless connections are required to operate with similar delay, reliability and capacity to the cable, and to simplify its management. Low latency and very low error probability are new requirements that 5G needs to cope with.

Finally, logistics and shipping tracking are important uses of mobile communications to enable tracking of inventory and packages anywhere they are located using a location-based information system. Logistical and shipment tracking use cases typically require lower data rates, but require broad coverage and reliable location information.

A wireless communication system is a multiple access system that supports communication for multiple users by sharing available system resources (bandwidth, transmit power, etc.). Examples of multiple-access systems include CDMA systems, FDMA systems, TDMA systems, OFDMA systems, SC-FDMA systems, and MC-FDMA systems.

The Sidelink (SL) refers to a communication scheme in which a direct link is established between User Equipments (UEs) and the UEs directly exchange voice or data without intervention of a Base Station (BS). SL is considered as a solution to mitigate the rapidly growing data traffic constraints of BSs.

Vehicle-to-everything (V2X) is a communication technology in which a vehicle exchanges information with another vehicle, pedestrians, and infrastructure through wired/wireless communication. V2X can be divided into four types: vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), vehicle-to-network (V2N), and vehicle-to-pedestrian (V2P). V2X communication may be provided via a PC5 interface and/or Uu interface.

As more and more communication devices require greater communication capacity, enhanced mobile broadband communication relative to existing RATs is required. Thus, a communication system that considers reliability and latency sensitive services or UEs is being discussed. The next generation RAT considering eMBB, MTC and URLLC is called new RAT or NR. In NR, V2X communication may also be supported.

Fig. 1 is a diagram illustrating comparison of V2X communication based on RAT before NR and V2X communication based on NR.

For V2X communication, technologies for providing security services based on V2X messages such as Basic Security Messages (BSM), collaboration Awareness Messages (CAM), and distributed environment notification messages (denom) are mainly discussed in the previous NR RATs. The V2X message may include location information, dynamic information, and attribute information. For example, the UE may send CAM of periodic message type and/or DENM of event triggered type to another UE.

For example, the CAM may include basic vehicle information including dynamic state information such as direction and speed, vehicle static data such as size, external lighting status, path details, and the like. For example, the UE may broadcast a CAM, which may have a latency of less than 100ms. For example, when an unexpected event such as a breakage of a vehicle or an accident occurs, the UE may generate and transmit the denom to another UE. For example, all vehicles within the transmission range of the UE may receive CAM and/or denom. In this case, denom may have a higher priority than CAM.

Regarding V2X communication, various V2X scenarios are proposed in NR. For example, V2X scenes include vehicle queuing, advanced driving, extension sensors, and remote driving.

For example, vehicles may be dynamically grouped and driven together based on vehicle queuing. For example, to perform a queuing operation based on vehicle queuing, vehicles in a group may receive periodic data from a leading vehicle. For example, vehicles in a group may widen or narrow their gap based on periodic data.

For example, the vehicle may be semi-automatic or fully automatic based on advanced driving. For example, each vehicle may adjust the trajectory or maneuver based on data obtained from nearby vehicles and/or nearby logical entities. For example, each vehicle may also share driving intent with nearby vehicles.

For example, based on the extended sensors, raw or processed data or real-time video data obtained by the local sensors may be exchanged between the vehicle, the logical entity, the pedestrian's terminal and/or the V2X application server. Thus, the vehicle may perceive a high-level environment relative to the environment perceived by the vehicle's sensors.

For example, based on remote driving, a remote driver or V2X application may operate or control a remote vehicle on behalf of a person who is unable to drive or is in a dangerous environment. For example, cloud computing based driving may be used to operate or control a remote vehicle when a path may be predicted as in public transportation. For example, access to a cloud-based backend service platform may also be used for remote driving.

In NR-based V2X communications, schemes are discussed that specify service requirements for various V2X scenarios including vehicle queuing, advanced driving, extension sensors, and remote driving.

Disclosure of Invention

Technical solution

An object of an embodiment relates to a method of operation of a remote User Equipment (UE) when Uu Radio Link Failure (RLF) of the UE occurs and Uu link recovery is successful. An object of the embodiments relates to operations of a relay UE and a remote UE performed in an AS layer when the remote UE and the relay UE belong to different TAU/RNAU areas.

Technical solution

According to an embodiment, a method of operating a remote User Equipment (UE) in a wireless communication system includes the steps of: establishing a connection with a first relay UE by the remote UE; receiving, by the remote UE, information indicating Uu Radio Link Failure (RLF) from the first relay UE; and performing a relay reselection or cell selection procedure based on receiving information indicating the Uu RLF, wherein the remote UE transmits information to return to a previous link to a reselected second relay UE or a Base Station (BS) related to cell selection based on receiving information indicating that Uu link recovery is successful from the first relay UE.

According to an embodiment, a remote User Equipment (UE) apparatus in a wireless communication system includes: at least one processor; and at least one computer memory operably connected to the at least one processor and configured to store instructions that, when executed, cause the at least one processor to perform operations comprising: establishing connection with a first relay UE; receiving information indicating Uu radio link failure, RLF, from the first relay UE; and performing a relay reselection or cell selection procedure based on receiving information indicating the Uu RLF, wherein the remote UE transmits information to fall back to a previous link to a reselected second relay UE or a BS related to cell selection based on receiving information indicating that Uu link recovery is successful from the first relay UE.

According to an embodiment, there is provided a processor for performing operations for a remote User Equipment (UE) in a wireless communication system, the operations comprising: establishing connection with a first relay UE; receiving information indicating Uu Radio Link Failure (RLF) from the first relay UE; and performing a relay reselection or cell selection procedure based on receiving information indicating the Uu RLF, wherein the remote UE transmits information to fall back to a previous link to a reselected second relay UE or a BS related to cell selection based on receiving information indicating that Uu link recovery is successful from the first relay UE.

According to an embodiment, there is provided a non-transitory computer-readable storage medium storing at least one computer program comprising instructions that, when executed by at least one processor, cause the at least one processor to perform operations for a Base Station (BS), the operations comprising the steps of: establishing connection with a first relay UE; receiving information indicating Uu Radio Link Failure (RLF) from the first relay UE; and performing a relay reselection or cell selection procedure based on receiving information indicating the Uu RLF, wherein the remote UE transmits information to fall back to a previous link to a reselected second relay UE or a BS related to cell selection based on receiving information indicating that Uu link recovery is successful from the first relay UE.

The information indicating that the Uu link recovery is successful may be received before the connection with the second relay UE is completed or before the connection with the BS is completed.

The remote UE may stop a connection procedure with the second relay UE or a connection procedure with a BS after receiving the information indicating that the Uu link recovery is successful.

The remote UE may skip transmitting a Radio Resource Control (RRC) setup request or an RRC connection complete message to the BS after receiving the information indicating that the Uu link recovery is successful.

The remote UE may maintain a connection with the first relay UE until the connection with the second relay UE or BS is completed.

The remote UE may release the connection with the first relay UE based on the connection completion with the second relay UE or BS.

The remote UE may prefer relay UEs belonging to the same Tracking Area (TA)/RAN based notification area (RNA) as the remote UE.

The remote UE may identify the TA/RNA of the relay UE by information included in the discovery message.

The remote UE may notify the relay UE of the updated TA/RNA information.

The remote UE transmits the TA/RNA information to the relay UE based on an updated TA/RNA that is different from an existing TA/RNA.

Advantageous effects

According to the embodiment, when Uu Radio Link Failure (RLF) of the relay UE occurs and then Uu link recovery is successful, unnecessary connection procedures can be shortened. In addition, the remote UE can maintain the same TA/RNA as the relay UE, and thus paging can be efficiently performed.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate embodiments of the disclosure and together with the description serve to explain the principles of the disclosure. In the drawings:

FIG. 1 is a diagram comparing pre-new radio access technology (pre-NR) based Internet of vehicles (V2X) communications with NR based V2X communications;

fig. 2 is a diagram illustrating a structure of a Long Term Evolution (LTE) system according to an embodiment of the present disclosure;

fig. 3 is a diagram illustrating a user plane and control plane radio protocol architecture according to an embodiment of the present disclosure;

fig. 4 is a diagram showing the structure of an NR system according to an embodiment of the present disclosure;

fig. 5 is a diagram showing functional division between a next generation radio access network (NG-RAN) and a fifth generation core network (5 GC) according to an embodiment of the present disclosure;

fig. 6 is a diagram showing a structure of an NR radio frame suitable for use according to an embodiment of the present disclosure;

fig. 7 is a diagram showing a slot structure of an NR frame according to an embodiment of the present disclosure;

fig. 8 is a diagram illustrating a radio protocol architecture for Sidelink (SL) communication according to an embodiment of the present disclosure;

fig. 9 is a diagram illustrating a radio protocol architecture for SL communication according to an embodiment of the present disclosure;

fig. 10 is a diagram showing a procedure of performing V2X or SL communication by a UE according to a transmission mode;

fig. 11 and 12 are diagrams for describing embodiments; and is also provided with

Fig. 13, 14, 15, 16, 17, 18, and 19 are diagrams showing various devices to which the embodiments are applied.

Detailed Description

In various embodiments of the present disclosure, "/" and "," should be interpreted as "and/or". For example, "A/B" may mean "A and/or B". In addition, "A, B" may mean "a and/or B". In addition, "a/B/C" may mean "at least one of A, B and/or C". In addition, "A, B, C" may mean at least one of "A, B and/or C.

In various embodiments of the present disclosure, "or" should be construed as "and/or". For example, "a or B" may include "a only", "B only", or "both a and B". In other words, "or" should be interpreted as "additionally or alternatively".

The techniques described herein may be used for various wireless access systems such as Code Division Multiple Access (CDMA), frequency Division Multiple Access (FDMA), time Division Multiple Access (TDMA), orthogonal Frequency Division Multiple Access (OFDMA), single carrier frequency division multiple access (SC-FDMA), etc. CDMA may be implemented as a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA 2000. TDMA may be implemented as a radio technology such as global system for mobile communications (GSM)/General Packet Radio Service (GPRS)/enhanced data rates for GSM evolution (EDGE). OFDMA may be implemented as a radio technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, evolved UTRA (E-UTRA), and so on. IEEE 802.16m is an evolution of IEEE 802.16e that provides backward compatibility with IRRR 802.16 e-based systems. UTRA is part of Universal Mobile Telecommunications System (UMTS). The third generation partnership project (3 GPP) Long Term Evolution (LTE) is part of evolved UMTS (E-UMTS) that uses evolved UTRA (E-UTRA). 3GPP LTE employs OFDMA for the Downlink (DL) and SC-FDMA for the Uplink (UL). LTE-advanced (LTE-a) is an evolution of 3GPP LTE.

The successor to LTE-a, the 5 th generation (5G) new radio access technology (NR), is a new clean state mobile communication system characterized by high performance, low latency, and high availability. The 5G NR may use all available spectrum resources including a low frequency band of 1GHz or less, a middle frequency band between 1GHz and 10GHz, and a high frequency (millimeter) band of 24GHz or more.

Although the following description is mainly given in the context of LTE-a or 5G NR for clarity of description, the technical ideas of the embodiments of the present disclosure are not limited thereto.

Fig. 2 illustrates a structure of an LTE system according to an embodiment of the present disclosure. This may also be referred to as an evolved UMTS terrestrial radio access network (E-UTRAN) or LTE/LTE-a system.

Referring to fig. 2, the e-UTRAN includes an evolved Node B (eNB) 20 providing a control plane and a user plane to the UE 10. The UE 10 may be fixed or mobile and may also be referred to as a Mobile Station (MS), a User Terminal (UT), a Subscriber Station (SS), a Mobile Terminal (MT), or a wireless device. The eNB 20 is a fixed station that communicates with the UE 10 and may also be referred to as a Base Station (BS), a Base Transceiver System (BTS), or an access point.

The enbs 20 may be connected to each other via an X2 interface. The eNB 20 is connected to an Evolved Packet Core (EPC) 39 via an S1 interface. More specifically, the eNB 20 is connected to a Mobility Management Entity (MME) via an S1-MME interface and to a serving gateway (S-GW) via an S1-U interface.

EPC 30 includes an MME, an S-GW, and a packet data network gateway (P-GW). The MME has access information or capability information about the UE, which is mainly used for mobility management of the UE. The S-GW is a gateway with the E-UTRAN as an endpoint and the P-GW is a gateway with a Packet Data Network (PDN) as an endpoint.

The radio protocol stack between the UE and the network can be divided into layer 1 (L1), layer 2 (L2) and layer 3 (L3) based on the lowest three layers of the Open System Interconnection (OSI) reference model known in the communication system. These layers are defined in pairs between the UE and the evolved UTRAN (E-UTRAN) for data transmission via the Uu interface. The Physical (PHY) layer at L1 provides information transfer services on a physical channel. The Radio Resource Control (RRC) layer at L3 is used to control radio resources between the UE and the network. For this purpose, the RRC layer exchanges RRC messages between the UE and the eNB.

Fig. 3 (a) illustrates a user plane radio protocol architecture according to an embodiment of the present disclosure.

Fig. 3 (b) illustrates a control plane radio protocol architecture according to an embodiment of the present disclosure. The user plane is a protocol stack for user data transmission, and the control plane is a protocol stack for control signal transmission.

Referring to (a) in fig. 3 and (b) in fig. 3, the PHY layer provides an information transfer service to its higher layers on a physical channel. The PHY layer is connected to a Medium Access Control (MAC) layer through a transport channel, and data is transferred between the MAC layer and the PHY layer over the transport channel. The transmission channels are divided according to the characteristics with which data is transmitted via the radio interface.

Data is transmitted on a physical channel between different PHY layers (i.e., PHY layers of a transmitter and a receiver). The physical channel may be modulated in Orthogonal Frequency Division Multiplexing (OFDM) and uses time and frequency as radio resources.

The MAC layer provides services to a higher layer, radio Link Control (RLC), on a logical channel. The MAC layer provides a function of mapping from a plurality of logical channels to a plurality of transport channels. In addition, the MAC layer provides a logical channel multiplexing function by mapping a plurality of logical channels to a single transport channel. The MAC sublayer provides data transmission services on logical channels.

The RLC layer performs concatenation, segmentation and reassembly on RLC Service Data Units (SDUs). To guarantee various quality of service (QoS) requirements for each Radio Bearer (RB), the RLC layer provides three modes of operation, transparent Mode (TM), unacknowledged Mode (UM), and Acknowledged Mode (AM). The AM RLC provides error correction through automatic repeat request (ARQ).

The RRC layer is defined only in the control plane and controls logical channels, transport channels, and physical channels in relation to configuration, reconfiguration, and release of RBs. The RB refers to a logical path for data transmission between the UE and the network provided by L1 (PHY layer) and L2 (MAC layer, RLC layer, and Packet Data Convergence Protocol (PDCP) layer).

The user plane functions of the PDCP layer include user data transmission, header compression, and ciphering. The control plane functions of the PDCP layer include control plane data transmission and ciphering/integrity protection.

RB set-up corresponds to a process of defining radio protocol layers and channel characteristics and configuring specific parameters and operation methods in order to provide a specific service. RBs can be divided into two types, signaling Radio Bearers (SRBs) and Data Radio Bearers (DRBs). The SRB is used as a path for transmitting RRC messages on the control plane, and the DRB is used as a path for transmitting user data on the user plane.

Once an RRC connection is established between the RRC layer of the UE and the RRC layer of the E-UTRAN, the UE is in an rrc_connected state, otherwise the UE is in an rrc_idle state. In NR, an rrc_inactive state is additionally defined. The UE in rrc_inactive state may maintain a connection with the core network while releasing the connection from the eNB.

DL transport channels that transport data from the network to the UE include a Broadcast Channel (BCH) on which system information is transmitted and a DL shared channel (DL SCH) on which user traffic or control messages are transmitted. Traffic or control messages of a DL multicast or broadcast service may be transmitted on a DL-SCH or DL multicast channel (DL MCH). The UL transport channels that carry data from the UE to the network include a Random Access Channel (RACH) on which an initial control message is transmitted and a UL shared channel (UL SCH) on which user traffic or control messages are transmitted.

Logical channels above and mapped to the transport channels include a Broadcast Control Channel (BCCH), a Paging Control Channel (PCCH), a Common Control Channel (CCCH), a Multicast Control Channel (MCCH), and a Multicast Traffic Channel (MTCH).

The physical channel includes a plurality of OFDM symbols in the time domain multiplied by a plurality of subcarriers in the frequency domain. One subframe includes a plurality of OFDM symbols in the time domain. An RB is a resource allocation unit defined by a plurality of OFDM symbols multiplied by a plurality of subcarriers. In addition, each subframe may use a specific subcarrier of a specific OFDM symbol (e.g., a first OFDM symbol) in a corresponding subframe for a Physical DL Control Channel (PDCCH), i.e., an L1/L2 control channel. A Transmission Time Interval (TTI) is a unit time of a subframe transmission.

Fig. 4 illustrates a structure of an NR system according to an embodiment of the present disclosure.

Referring to fig. 4, a next generation radio access network (NG-RAN) may include a next generation Node B (gNB) and/or eNB providing user plane and control plane protocol termination to a UE. In fig. 4, for example, the NG-RAN is shown to include only the gNB. The gNB and the eNB are connected to each other via an Xn interface. The gNB and eNB are connected to a 5G core network (5 GC) via an NG interface. More specifically, the gNB and eNB are connected to an access and mobility management function (AMF) via an NG-C interface and to a User Plane Function (UPF) via an NG-U interface.

Fig. 5 illustrates functional partitioning between NG-RAN and 5GC according to an embodiment of the present disclosure.

Referring to fig. 5, the gnb may provide functions including inter-cell Radio Resource Management (RRM), radio admission control, measurement configuration and provisioning, and dynamic resource allocation. The AMF may provide functions such as non-access stratum (NAS) security and idle state mobility handling. The UPF may provide functions including mobility anchoring and Protocol Data Unit (PDU) processing. Session Management Functions (SMFs) may provide functions including UE Internet Protocol (IP) address allocation and PDU session control.

Fig. 6 illustrates a radio frame structure in NR to which the embodiments of the present disclosure are applied.

Referring to fig. 6, a radio frame may be used for UL transmission and DL transmission in NR. The radio frame is 10ms in length and may be defined by two 5ms half frames. HF may comprise five 1ms subframes. The subframe may be divided into one or more slots, and the number of slots in the SF may be determined according to a subcarrier spacing (SCS). Each slot may include 12 or 14 OFDM (a) symbols according to a Cyclic Prefix (CP).

In the case of Normal CP (NCP), each slot may include 14 symbols, and in the case of Extended CP (ECP), each slot may include 12 symbols. Herein, the symbol may be an OFDM symbol (or CP-OFDM symbol) or an SC-FDMA symbol (or DFT-s-OFDM symbol).

Table 1 below lists the number N of symbols per slot for a SCS configuration μ in the case of NCP ^{Time slots} _(symbol) Number of slots per frame N ^{Frame u} _{Time slots} And the number of slots per subframe, N ^{Frame u} _{Time slots} 。

TABLE 1

SCS(15×2 u )	N Time slots (symbol)	N Frame(s) , u Time slots	N Sub-frames , u Time slots
				15KHz(u＝0)	14	10	1
30KHz(u＝1)	14	20	2
				60KHz(u＝2)	14	40	4
120KHz(u＝3)	14	80	8
				240KHz(u＝4)	14	160	16

Table 2 below lists the number of symbols per slot, the number of slots per frame, and the number of slots per subframe according to SCS in the case of ECP.

TABLE 2

SCS(15×2^u)	N Time slots (symbol)	N Frame u Time slots	N Subframe, u Time slots
				60KHz(u＝2)	12	40	4

In an NR system, different OFDM (a) parameter sets (e.g., SCS, CP length, etc.) may be configured for a plurality of cells aggregated for one UE. Thus, the (absolute time) duration of a time resource (e.g., a subframe, a slot, or a TTI) comprising the same number of symbols, collectively referred to as a Time Unit (TU) for convenience, may be configured to be different for aggregated cells.

In the NR, various parameter sets or SCS may be supported to support various 5G services. For example, with a 15 kHz SCS, a wide area in the traditional cellular band can be supported, while with a 30 kHz/60 kHz SCS, dense urban areas, lower latency and wide carrier bandwidths can be supported. With SCS of 60 kHz or higher, bandwidths greater than 24.25 GHz can be supported to overcome phase noise.

The NR frequency band may be defined by two types of frequency ranges FR1 and FR 2. The values in each frequency range may vary. For example, two types of frequency ranges may be given in table 3. In an NR system, FR1 may be "the range below 6 GHz" and FR2 may be "the range above 6 GHz" referred to as millimeter wave (mmW).

TABLE 3

Frequency range assignment	Corresponding frequency range	Sub-carriersSpacing (SCS)
			FR1	450MHz–6000MHz	15、30、60kHz
FR2	24250MHz–52600MHz	60、120、240kHz

As mentioned above, in an NR system, values in the frequency range can be changed. For example, as listed in table 4, FR1 may range from 410 MHz to 7125 MHz. That is, FR1 may include a frequency band of 6 GHz (or 5850, 5900, and 5925 MHz) or more. For example, the frequency bands of 6 GHz (or 5850, 5900, and 5925 MHz) or above may include unlicensed frequency bands. The unlicensed frequency band may be used for various purposes, such as vehicle communication (e.g., autonomous driving).

TABLE 4

Frequency range assignment	Corresponding frequency range	Subcarrier spacing (SCS)
			FR1	410MHz–7125MHz	15、30、60kHz
FR2	24250MHz–52600MHz	60、120、240kHz

Fig. 7 illustrates a slot structure in an NR frame according to an embodiment of the present disclosure.

Referring to fig. 7, a slot includes a plurality of symbols in a time domain. For example, one slot may include 14 symbols in the case of NCP and 12 symbols in the case of ECP. Alternatively, one slot may include 7 symbols in the case of NCP and 6 symbols in the case of ECP.

The carrier includes a plurality of subcarriers in the frequency domain. An RB may be defined by a plurality (e.g., 12) of consecutive subcarriers in the frequency domain. The bandwidth part (BWP) may be defined by a plurality of consecutive (physical) RBs ((P) RBs) in the frequency domain, and corresponds to one parameter set (e.g., SCS, CP length, etc.). The carrier may include up to N (e.g., 5) BWPs. Data communication may be performed in the activated BWP. Each element may be referred to as a Resource Element (RE) in the resource grid, and one complex symbol may be mapped to the RE.

The radio interface between UEs or between a UE and a network may include L1, L2, and L3. In various embodiments of the present disclosure, L1 may refer to a PHY layer. For example, L2 may refer to at least one of a MAC layer, an RLC layer, a PDCH layer, or an SDAP layer. For example, L3 may refer to the RRC layer.

Now, a description will be given of sub-link (SL) communication.

Fig. 8 illustrates a radio protocol architecture for SL communication according to an embodiment of the present disclosure. Specifically, (a) in fig. 8 illustrates a user plane protocol stack in LTE, and (b) in fig. 8 illustrates a control plane protocol stack in LTE.

Fig. 9 illustrates a radio protocol architecture for SL communication according to an embodiment of the present disclosure. Specifically, (a) in fig. 9 illustrates a user plane protocol stack in NR, and (b) in fig. 9 illustrates a control plane protocol stack in NR.

Fig. 10 illustrates a procedure of performing V2X or SL communication by a UE according to a transmission mode according to an embodiment of the present disclosure. The embodiment of fig. 10 may be combined with various embodiments of the present disclosure. In various embodiments of the present disclosure, the transmission mode may be referred to as a mode or a resource allocation mode. For convenience of the following description, a transmission mode in LTE may be referred to as an LTE transmission mode, and a transmission mode in NR may be referred to as an NR resource allocation mode.

For example, (a) in fig. 10 illustrates UE operations related to LTE transmission mode 1 or LTE transmission mode 3. Alternatively, for example, (a) in fig. 10 illustrates the UE operation related to NR resource allocation pattern 1. For example, LTE transmission mode 1 may be applied to common SL communication, and LTE transmission mode 3 may be applied to V2X communication.

For example, (b) in fig. 10 illustrates UE operations related to LTE transmission mode 2 or LTE transmission mode 4. Alternatively, for example, (b) in fig. 10 illustrates the UE operation related to NR resource allocation pattern 2.

Referring to (a) in fig. 10, in LTE transmission mode 1, LTE transmission mode 3, or NR resource allocation mode 1, the BS may schedule SL resources to be used for SL transmission by the UE. For example, in step S8000, the BS may transmit information related to SL resources and/or information related to UE resources to the first UE. For example, UL resources may include Physical Uplink Control Channel (PUCCH) resources and/or Physical Uplink Shared Channel (PUSCH) resources. For example, the UL resource may be a resource for reporting SL HARQ feedback to the BS.

For example, the first UE may receive information related to Dynamic Grant (DG) resources and/or information related to Configuring Grant (CG) resources from the BS. For example, CG resources may include CG type 1 resources or CG type 2 resources. In this specification, DG resources may be resources configured/allocated by the BS in Downlink Control Information (DCI) to the first UE. In this specification, CG resources may be (periodic) resources configured/allocated by the BS in DCI and/or RRC messages to the first UE. For example, for CG type 1 resources, the BS may send an RRC message to the first UE that includes information related to the CG resources. For example, for CG type 2 resources, the BS may transmit an RRC message including information related to CG resources to the first UE, and the BS may transmit DCI related to activation or release of CG resources to the first UE.

In step S8010, the first UE may transmit a physical secondary link control channel (PSCCH) (e.g., secondary link control information (SCI) or first level SCI) to the second UE based on the resource schedule. In step S8020, the first UE may transmit a Physical Sidelink Shared Channel (PSSCH) associated with the PSCCH (e.g., a second-stage SCI, a MAC PDU, data, etc.) to the second UE. In step S8030, the first UE may receive a Physical Sidelink Feedback Channel (PSFCH) associated with the PSCCH/PSSCH from the second UE. For example, HARQ feedback information (e.g., NACK information or ACK information) may be received from the second UE through the PSFCH. In step S8040, the first UE may transmit/report HARQ feedback information to the BS through the PUCCH or PUSCH. For example, the HARQ feedback information reported to the BS may include information generated by the first UE based on HARQ feedback information received from the second UE. For example, the HARQ feedback information reported to the BS may include information generated by the first UE according to a predetermined rule. For example, the DCI may be DCI for scheduling SL. For example, the format of the DCI may include DCI format 3_0 or DCI format 3_1. Table 5 shows one example of DCI for scheduling SL.

TABLE 5

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Referring to (b) of fig. 10, for LTE transmission mode 2, LTE transmission mode 4, or NR resource allocation mode 2, the ue may determine SL transmission resources among SL resources configured by the BS/network or pre-configured SL resources. For example, the configured SL resources or pre-configured SL resources may be a pool of resources. For example, the UE may autonomously select or schedule resources for SL transmission. For example, the UE may perform SL communication by selecting resources within the configured resource pool by itself. For example, the UE may perform sensing and resource (re) selection procedures to select resources by itself within a selection window. For example, sensing may be performed in units of subchannels. For example, in step S8010, a first UE that has self-selected resources in the resource pool may use the resources to transmit a PSCCH (e.g., a secondary link control information (SCI) or a first level SCI) to a second UE. In step S8020, the first UE may transmit a pscsch (e.g., second-level SCI, MAC PDU, data, etc.) related to the PSCCH to the second UE. In step S8030, the first UE may receive a PSCCH related to a PSCCH/PSCCH from the second UE.

Referring to (a) in fig. 10 or (b) in fig. 10, for example, the first UE may transmit the SCI to the second UE on the PSCCH. Alternatively, for example, the first UE may transmit two consecutive SCIs (e.g., two-stage SCIs) to the second UE on the PSCCH and/or PSSCH. In this case, the second UE may decode two consecutive SCIs (e.g., two-stage SCIs) to receive the PSSCH from the first UE. In this specification, an SCI transmitted on a PSCCH may be referred to as a first SCI, a first level SCI, or a first level SCI format, and an SCI transmitted on a PSSCH may be referred to as a second SCI, a second level SCI, or a second level SCI format. For example, the first level SCI format may include SCI format 1-A, and the second level SCI format may include SCI format 2-A and/or SCI format 2-B. Table 6 shows one example of the first stage SCI format.

TABLE 6

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Table 7 shows one example of a second level SCI format.

TABLE 7

Referring to (a) in fig. 10 or (b) in fig. 10, the first UE may receive the PSFCH based on table 8 in step S8030. For example, the first UE and the second UE may determine PSFCH resources based on table 8, and the second UE may transmit HARQ feedback to the first UE using the PSFCH resources.

TABLE 8

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Referring to (a) in fig. 10, in step S8040, the first UE may transmit SL HARQ feedback to the BS through PUCCH and/or PUSCH based on table 9.

TABLE 9

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Fig. 11 illustrates a procedure in which a remote UE selects a relay UE in a NE-to-network relay. The relay UE and the gNB are in a connected state (S1101), and a remote UE broadcast discovery message of the relay UE is searched. At this time, as a scheme for transmitting the discovery message, there are a model a and a model B, and in this regard, the model a is a method in which the remote UE finds the relay UE by periodically broadcasting the discovery message (S1102 a), and the model B is a method in which when the relay UE broadcasts the discovery solicitation message, the broadcasted nearby remote UE is heard to respond with the discovery message (S1102 sb). At this time, a UE that becomes a relay UE may be selected as a UE whose measurement signal (e.g., RSRP or RSRQ) value with the gNB falls within a certain threshold range.

Sidelink relay and Tracking Area (TA)/RAN based notification area (RNA)

When the UE is in an active state (communication state), the network core network knows the location of the UE cell by cell. In other words, it is possible to know which gNB and which cell the UE is located in. However, when the UE is in an IDLE/INACTIVE (INACTIVE) state, the location of the UE is known in units of Tracking Areas (TAs) instead of in units of cells. In other words, the network groups several nearby gnbs and defines them as one TA. This is a value that has been determined when the telecommunications provider initially deployed the network. That is, each gNB may be preconfigured with which TA the gNB belongs to. The TA is required because the network needs to page the UE when traffic to idle/inactive UEs that do not communicate with the UE occurs, and in this case, when the core network knows that the location of the UE in the idle/inactive state belongs to the TA3 area and needs to transmit data to the corresponding location to wake up the UE, the network can transmit paging messages to all the gnbs belonging to TA3, and the gNB that receives the paging messages transmits each paging message and wakes up the UE.

In order for the core network to perform paging, the core network needs to always have the latest location information on which TA the UE in idle/inactive state is located. Thus, every time the TA changes, the UE should report the fact of the TA change to the core network through a Tracking Area Update (TAU). In other words, the UE receives the TA list while connected to the core network, and reports the location information to the BS (or core network) (TAU) when the UE moves and its location no longer belongs to the received TA list. In this case, the corresponding BS (or core network) assigns a new TA value to the UE.

The agreement on L2 relay shown in table 10 below was derived at 3gpp RAN2 113bis-e conference.

TABLE 10

When performing L2 relay, the relay UE and the remote UE may independently perform TAU/RNAU procedures. However, problems in paging performance may occur when the relay UE and the remote UE belong to different TAU/RNAU areas. The relay UE needs to receive and forward pages of the remote UE on behalf of the remote UE, but when the remote UE and the relay UE belong to different TAU/RNAU areas, the relay UE cannot receive and forward pages of the remote UE on behalf of the remote UE. Thus, alignment operations of TAU/RNAU areas of the relay UE and the remote UE are required.

Alignment of the TAU area may be performed by the AMF and alignment of the RNAU may be performed by the BS. However, for this alignment operation, the BS and the core network need to know whether the relay UE and the remote UE are connected or released from each other. It is necessary to inform at the NAS/RRC layer whether the relay UE and the remote UE are connected/released to each other, which has not yet been specified in SA 2.

Table 10 below shows disclosure related to selection and reselection of sidelink relay UEs in 3gpp TS 36.331. The disclosure in table 11 is used as a related art of the present disclosure, and as for necessary details, reference is made to 3gpp TS 36.331, and as for a specific architecture of the relay UE, reference is made to 3gpp TR 38.836.

TABLE 11

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According to the determination on the 3GPP RAN2 relay WI 113bis-e conference, when a Uu Radio Link Failure (RLF) occurs between the remote UE and the relay UE, the relay UE notifies the remote UE of this, and the remote UE receiving this triggers relay reselection.

TABLE 12

However, when Uu RLF occurs, the relay UE may perform a resume operation, and the relay UE may inform the remote UE of success/failure of the resume operation. In response, the remote UE receiving this may indicate whether to continue to connect to the current relay UE or release.

In this regard, according to an embodiment related to the present disclosure, an operation in which the remote UE receives notification of Uu RLF from the relay UE will be described.

The remote UE according to the embodiment may establish a connection with the first relay UE (S1201 in fig. 12), and the remote UE may receive information indicating Uu Radio Link Failure (RLF) from the first relay UE (S1202). The remote UE may perform a relay reselection or cell selection procedure based on receiving information indicating Uu RLF (S1203). In other words, the remote UE receiving notification of Uu link RLF from the relay UE triggers relay reselection.

Here, the remote UE may transmit information indicating that the remote UE is backed off to the previous link to the reselected second relay UE or the BS related to cell selection based on receiving information indicating that Uu link recovery is successful from the first relay UE. When the remote UE identifies the Uu RLF of the relay UE, the remote UE may search for a new relay UE or search for a new cell to establish a Uu direct link. However, the remote UE may receive notification of Uu link restoration success from the currently connected relay UE before finding a new relay UE and completing a connection with the network or before finding a Uu direct link and completing a connection. In this case, the remote UE stops all operations for establishing a new connection and maintains the connection through the current relay UE.

Accordingly, the remote UE may reduce signaling effort required to establish a new connection.

The information indicating that the Uu link recovery is successful may be received before the connection with the second relay UE is completed or before the connection with the BS is completed. The remote UE may stop the connection procedure with the second relay UE or the connection procedure with the BS after receiving the information indicating that the Uu link recovery is successful. For example, the remote UE may not transmit an RRC setup request or an RRC connection complete message to the BS after receiving the information indicating that Uu link recovery is successful. That is, when receiving a resume success message from a relay UE currently maintaining PC5-S/PC5-RRC before transmitting an RRC setup request or an RRC connection completion message to the gNB, the remote UE may not transmit the RRC setup request or the RRC connection completion message to the gNB. Alternatively, the remote UE may respond to include the content of the fallback to the previous link in an RRC setup request or RRC connection complete message.

In the process of establishing the PC5-S/PC5-RRC connection with the new relay UE, the remote UE may no longer respond when receiving a Uu link restoration success message from the relay UE currently maintaining the PC5-S/PC5-RRC, or may respond to the new relay UE with information about fallback to the previous link.

The remote UE may disconnect from the first relay UE based on completing the connection with the second relay UE or the BS. In other words, when the remote UE finds a new relay UE and completes the connection with the network, or finds a Uu direct link and completes the connection, the remote UE may release the link with the currently connected relay UE. When the link with the currently connected relay UE is released, the remote UE may notify the relay UE of this or perform disconnection without notification. For example, when the remote UE completes the PC5-S/PC5-RRC connection through the new relay UE, the remote UE may release the link with the currently connected relay UE.

Alternatively, the remote UE may complete the PC5-S/PC5-RRC connection through the new relay UE, complete sending an RRC connection complete message to the gNB, and then release the link with the currently connected relay UE. Alternatively, after completion of transmission of the RRC connection complete message through the new cell, the relay UE releases the link with the currently connected relay UE.

Regarding the above description, the process of the UE establishing a connection with the gNB may refer to fig. 12.

In the above description, the remote UE may maintain the connection with the first relay UE until the connection with the second relay UE or the BS is completed. Although it is known that the link through the currently connected relay UE remains connected to the network in a failure state, the remote UE remains connected to the PC5 of the relay UE. In other words, the remote UE may maintain a connection (RLF link) with the current relay UE until a new relay UE is found and a connection with the network is completed or Uu direct link is found and a connection is completed.

With respect to the above description or as a separate embodiment, the remote UE may prefer to select a relay UE belonging to the same Tracking Area (TA)/RAN based notification area (RNA) as the remote UE. The remote UE may identify the TA/RNA of the relay UE by information included in the discovery message. In more detail, this may help the remote UE select the relay UE when the relay UE and the remote UE are able to know from an initial stage of establishing a connection whether the relay UE and the remote UE belong to the same TA/RNA region. For example, when TA/RNA region information is included in a discovery message and transmitted, in case of L2 relay operation, the information may be referred to when a relay UE is selected. Because the remote UE can receive pages through the relay UE only when selecting relay UEs belonging to the same TA/RNA, the remote UE may prefer to select relay UEs belonging to the same TA/RNA. At this point, the same TA/RNA may mean that at least one TA/RNA in the TA/RNA list is replicated.

The remote UE may notify the relay UE of the updated TA/RNA information. Here, the remote UE may send TA/RNA information to the relay UE based on the updated TA/RNA being different from the existing TA/RNA. In order to know whether the relay UE and the remote UE belong to different TA/RNA areas, when the remote UE updates the TA/RNA to the BS (or core network), the remote UE may also notify the relay UE of updated TA/RNA area information. Alternatively, the remote UE may forward the (newly) configured latest TA/RNAU value from the BS (or core network) to the relay UE. At this time, the remote UE may include corresponding information in the adaptation layer or notify the relay UE through a PC5-S/PC5-RRC/NAS message or the like. Alternatively, when forwarding the TAU/RNAU value received from the remote/relay UE to the core network, the gNB may forward the TAU/RNAU value including (displaying) information indicating that the corresponding remote UE and relay UE are connected to each other for relaying communication. These operations may be for the case where the remote UE and the relay UE identify each other's TA/RNA region and belong to different TA/RNA regions.

When the TA/RNA region information of the remote UE is different from the latest TA/RNA region information of the remote UE, the relay UE receiving the latest TA/RNA region (list) information from the remote UE may notify the remote UE of this. When the TA/RNA region information of the remote UE is partially different from the latest TA/RNA region information of the remote UE, the relay UE may notify only the remote UE of the different information or may notify the remote UE of the entire TA/RRNA (list) information of the relay UE. The method of the relay UE informing the remote UE that the relay UE and the remote UE belong to different TA/RNA areas may be performed by including corresponding information in the adaptation layer or by a PC5-S/PC5-RRC/NAS message or the like.

The relay UE may perform paging monitoring for the remote UE when the cell ID on which the relay UE resides is included in the TA/RNA list of the remote UE. A relay UE receiving a page for a remote UE may forward the page to the remote UE.

Alternatively, when the cell ID on which the relay UE camps is not included in the TA/RNA cell list of the remote UE, the relay UE may monitor paging to the remote UE only for signal strengths greater than or equal to a certain threshold among signal strengths of the cell IDs included in the TA/RNA of the remote UE (even though the corresponding cell ID is not a camping cell, e.g., a neighbor cell).

The remote UE that receives an indication from the relay UE that the remote UE and the remote UE belong to different TA/RNA regions may connect to a direct link (disconnect a sidelink with the currently connected relay UE), may find a relay UE belonging to the same TA/RNA region and may connect to the relay UE to indirectly receive the page, or may directly receive the page through a cell belonging to the TA/RNA region of the remote UE. The operation may be limited to a case where the TA/RNA lists of the relay UE and the remote UE do not overlap or a case where the camping cell of the relay UE is not included in the TA/RNA list of the remote UE.

When TAU/RNAU region values to which the remote UE and the relay UE belong are included in the adaptation layer of the Uu link, the gNB may determine whether the remote UE and the relay UE belong to the same TAU/RNAU region. When the gNB detects that the remote UE and the relay UE do not belong to the same TAU/RNAU region, the gNB can notify the NAS layer of this information along with the ID of the remote UE. Alternatively, (to support TAU/RNAU region alignment in the NAS layer), the gNB may inform that the remote UE to which the remote UE corresponds belongs to a different TAU/RNAU region than the relay UE, or trigger relay reselection/path switching, etc.

With regard to the above description, a remote UE device includes at least one processor and at least one computer memory operably connected to the at least one processor and configured to store instructions that, when executed, cause the at least one processor to perform operations comprising: establishing a connection with a first relay UE, receiving information indicating a Uu Radio Link Failure (RLF) from the first relay UE, and performing a relay reselection or cell selection procedure based on the received information indicating the Uu RLF, and in this case, the remote UE transmits information to fall back to a previous link to a reselected second relay UE or a BS related to cell selection based on the received information indicating a Uu link recovery success from the first relay UE.

In a processor that performs operations for a remote UE, the operations include establishing a connection with a first relay UE, receiving information indicating a Uu Radio Link Failure (RLF) from the first relay UE, and performing a relay reselection or cell selection procedure based on receiving the information indicating the Uu RLF, and in this case, based on receiving information indicating that Uu link recovery was successful from the first relay UE, the remote UE transmits information to fall back to a previous link to a reselected second relay UE or a BS related to cell selection.

There is provided a non-transitory computer readable storage medium for storing at least one computer program comprising instructions for causing at least one processor to perform operations for a Base Station (BS) when executed by the at least one processor, the operations comprising the steps of: a connection is established with a first relay UE, information indicating a Uu Radio Link Failure (RLF) is received from the first relay UE and a relay reselection or cell selection procedure is performed based on the received information indicating a Uu RLF, and in this case, a remote UE transmits information to return to a previous link to a reselected second relay UE or a BS related to cell selection based on the received information indicating a Uu link recovery success from the first relay UE.

Examples of communication systems suitable for use in the present disclosure

The various descriptions, functions, procedures, suggestions, methods and/or operational flowcharts of the present disclosure described in this document may be applied to, but are not limited to, various fields in which wireless communication/connection (e.g., 5G) between devices is required.

Hereinafter, a description will be given in more detail with reference to the accompanying drawings. In the following figures/description, like reference numerals may refer to like or corresponding hardware, software, or functional blocks unless otherwise specified.

Fig. 13 illustrates a communication system 1 applied to the present disclosure.

Referring to fig. 13, a communication system 1 applied to the present disclosure includes a wireless device, a BS, and a network. Herein, a wireless device means a device that performs communication using a RAT (e.g., 5G NR or LTE), and may be referred to as a communication/radio/5G device. Wireless devices may include, but are not limited to, robots 100a, vehicles 100b-1 and 100b-2, augmented reality (XR) devices 100c, handheld devices 100d, home appliances 100e, internet of things (IoT) devices 100f, and Artificial Intelligence (AI) devices/servers 400. For example, the vehicles may include vehicles having wireless communication functions, autonomous driving vehicles, and vehicles capable of performing inter-vehicle communication. Herein, the vehicle may include an Unmanned Aerial Vehicle (UAV) (e.g., an unmanned aerial vehicle). XR devices may include Augmented Reality (AR)/Virtual Reality (VR)/Mixed Reality (MR) devices and may be implemented in the form of head-mounted devices (HMDs), head-up displays (HUDs) installed in vehicles, televisions, smartphones, computers, wearable devices, home appliance devices, digital signage, vehicles, robots, and the like. Handheld devices may include smart phones, smart boards, wearable devices (e.g., smart watches or smart glasses), and computers (e.g., notebooks). Home appliances may include TVs, refrigerators, and washing machines. IoT devices may include sensors and smart meters. For example, the BS and network may be implemented as wireless devices, and a particular wireless device 200a may operate as a BS/network node with respect to other wireless devices.

The wireless devices 100a to 100f may be connected to the network 300 via the BS 200. AI technology may be applied to the wireless devices 100a to 100f, and the wireless devices 100a to 100f may be connected to the AI server 400 via the network 300. The network 300 may be configured using a 3G network, a 4G (e.g., LTE) network, or a 5G (e.g., NR) network. Although the wireless devices 100a to 100f may communicate with each other through the BS 200/network 300, the wireless devices 100a to 100f may perform direct communication (e.g., sidelink communication) with each other without going through the BS/network. For example, vehicles 100b-1 and 100b-2 may perform direct communication (e.g., V2V/V2X communication). The IoT devices (e.g., sensors) may perform direct communication with other IoT devices (e.g., sensors) or other wireless devices 100 a-100 f.

Wireless communication/connection 150a, 150b, or 150c may be established between wireless devices 100 a-100 f/BS200 or BS200/BS 200. Herein, wireless communication/connection may be established through various RATs (e.g., 5G NR) such as UL/DL communication 150a, sidelink communication 150b (or D2D communication), or inter-BS communication (e.g., relay, integrated Access Backhaul (IAB)). The wireless device and BS/wireless device can transmit/receive radio signals to/from each other through wireless communication/connections 150a and 150 b. For example, the wireless communication/connections 150a and 150b may transmit/receive signals over various physical channels. To this end, at least a part of various configuration information configuration procedures, various signal processing procedures (e.g., channel coding/decoding, modulation/demodulation, and resource mapping/demapping) and resource allocation procedures for transmitting/receiving radio signals may be performed based on various proposals of the present disclosure.

Examples of wireless devices suitable for use in the present disclosure

Fig. 14 illustrates a wireless device suitable for use in the present disclosure.

Referring to fig. 14, the first wireless device 100 and the second wireless device 200 may transmit radio signals through various RATs (e.g., LTE and NR). Herein, { first wireless device 100 and second wireless device 200} may correspond to { wireless device 100x and BS200} and/or { wireless device 100x and wireless device 100x } in fig. 13.

The first wireless device 100 may include one or more processors 102 and one or more memories 104, and additionally include one or more transceivers 106 and/or one or more antennas 108. The processor 102 may control the memory 104 and/or the transceiver 106 and may be configured to implement the descriptions, functions, procedures, suggestions, methods, and/or operational flowcharts disclosed herein. For example, the processor 102 may process the information within the memory 104 to generate first information/signals and then transmit radio signals including the first information/signals through the transceiver 106. The processor 102 may receive a radio signal including the second information/signal through the transceiver 106 and then store information obtained by processing the second information/signal in the memory 104. The memory 104 may be connected to the processor 102 and may store various information related to the operation of the processor 102. For example, the memory 104 may store software code including commands for performing some or all of the processes controlled by the processor 102 or for performing the descriptions, functions, procedures, suggestions, methods, and/or operational flowcharts disclosed herein. Herein, the processor 102 and the memory 104 may be part of a communication modem/circuit/chip designed to implement a RAT (e.g., LTE or NR). The transceiver 106 may be connected to the processor 102 and transmit and/or receive radio signals through one or more antennas 108. Each of the transceivers 106 may include a transmitter and/or a receiver. Transceiver 106 may be used interchangeably with Radio Frequency (RF) unit(s). In this disclosure, a wireless device may represent a communication modem/circuit/chip.

The second wireless device 200 may include one or more processors 202 and one or more memories 204, and additionally include one or more transceivers 206 and/or one or more antennas 208. The processor 202 may control the memory 204 and/or the transceiver 206 and may be configured to implement the descriptions, functions, processes, suggestions, methods, and/or operational flowcharts disclosed herein. For example, the processor 202 may process the information within the memory 204 to generate a third information/signal and then transmit a radio signal including the third information/signal through the transceiver 206. The processor 202 may receive a radio signal including the fourth information/signal through the transceiver 106 and then store information obtained by processing the fourth information/signal in the memory 204. The memory 204 may be connected to the processor 202 and may store various information related to the operation of the processor 202. For example, memory 204 may store software code including commands for performing part or all of the processes controlled by processor 202 or for performing the descriptions, functions, procedures, suggestions, methods, and/or operational flowcharts disclosed herein. Herein, the processor 202 and the memory 204 may be part of a communication modem/circuit/chip designed to implement a RAT (e.g., LTE or NR). The transceiver 206 may be connected to the processor 202 and transmit and/or receive radio signals through one or more antennas 208. Each of the transceivers 206 may include a transmitter and/or a receiver. The transceiver 206 may be used interchangeably with RF units. In this disclosure, a wireless device may represent a communication modem/circuit/chip.

Hereinafter, hardware elements of the wireless devices 100 and 200 will be described in more detail. One or more protocol layers may be implemented by, but are not limited to, one or more processors 102 and 202. For example, one or more of processors 102 and 202 may implement one or more layers (e.g., functional layers such as PHY, MAC, RLC, PDCP, RRC and SDAP). The one or more processors 102 and 202 may generate one or more Protocol Data Units (PDUs) and/or one or more Service Data Units (SDUs) according to the descriptions, functions, procedures, proposals, methods and/or operational flowcharts disclosed herein. One or more processors 102 and 202 may generate messages, control information, data, or information in accordance with the descriptions, functions, procedures, suggestions, methods, and/or operational flows disclosed herein. The one or more processors 102 and 202 may generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed herein, and provide the generated signals to the one or more transceivers 106 and 206. The one or more processors 102 and 202 may receive signals (e.g., baseband signals) from the one or more transceivers 106 and 206 and obtain PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and/or operational procedures disclosed herein.

One or more of the processors 102 and 202 may be referred to as a controller, microcontroller, microprocessor, or microcomputer. One or more of the processors 102 and 202 may be implemented in hardware, firmware, software, or a combination thereof. As an example, one or more Application Specific Integrated Circuits (ASICs), one or more Digital Signal Processors (DSPs), one or more Digital Signal Processing Devices (DSPDs), one or more Programmable Logic Devices (PLDs), or one or more Field Programmable Gate Arrays (FPGAs) may be included in the one or more processors 102 and 202. The descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed herein may be implemented using firmware or software, and the firmware or software may be configured to include modules, procedures or functions. Firmware or software configured to perform the descriptions, functions, procedures, suggestions, methods and/or operational flow diagrams disclosed herein may be included in one or more processors 102 and 202 or stored in one or more memories 104 and 204 so as to be driven by one or more processors 102 and 202. The descriptions, functions, procedures, suggestions, methods and/or operational flows disclosed herein may be implemented using firmware or software in the form of codes, commands and/or sets of commands.

One or more memories 104 and 204 may be coupled to one or more processors 102 and 202 and store various types of data, signals, messages, information, programs, code, instructions, and/or commands. One or more of the memories 104 and 204 may be comprised of read-only memory (ROM), random Access Memory (RAM), electrically erasable programmable read-only memory (EPROM), flash memory, a hard drive, registers, cache memory, a computer-readable storage medium, and/or combinations thereof. The one or more memories 104 and 204 may be located internal and/or external to the one or more processors 102 and 202. The one or more memories 104 and 204 may be connected to the one or more processors 102 and 202 by respective techniques such as wired or wireless connections.

One or more transceivers 106 and 206 may transmit the user data, control information, and/or radio signals/channels referred to in the methods and/or operational flow diagrams herein to one or more other devices. One or more transceivers 106 and 206 may receive the user data, control information, and/or radio signals/channels mentioned in the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed herein from one or more other devices. For example, one or more transceivers 106 and 206 may be connected to one or more processors 102 and 202 and transmit and receive radio signals. For example, the one or more processors 102 and 202 may perform control such that the one or more transceivers 106 and 206 may transmit user data, control information, or radio signals to one or more other devices. The one or more processors 102 and 202 may perform control such that the one or more transceivers 106 and 206 may receive user data, control information, or radio signals from one or more other devices. One or more transceivers 106 and 206 may be connected to one or more antennas 108 and 208, and one or more transceivers 106 and 206 may be configured to transmit and receive the user data, control information, and/or radio signals/channels mentioned in the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed herein through one or more antennas 108 and 208. Herein, the one or more antennas may be a plurality of physical antennas or a plurality of logical antennas (e.g., antenna ports). The one or more transceivers 106 and 206 may convert received radio signals/channels, etc. from RF band signals to baseband signals for processing received user data, control information, radio signals/channels, etc. using the one or more processors 102 and 202. The one or more transceivers 106 and 206 may convert user data, control information, radio signals/channels, etc., processed using the one or more processors 102 and 202 from baseband signals to RF band signals. To this end, one or more of the transceivers 106 and 206 may comprise (analog) oscillators and/or filters.

Examples of vehicles or autonomous vehicles suitable for use in the present disclosure

Fig. 15 illustrates a vehicle or autonomous driving vehicle applied to the present disclosure. The vehicle or autonomous driving vehicle may be implemented by a mobile robot, a car, a train, a manned/unmanned Aircraft (AV), a ship, or the like.

Referring to fig. 15, the vehicle or autonomous driving vehicle 100 may include 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 may be configured as part of the communication unit 110.

The communication unit 110 may transmit and receive signals (e.g., data and control signals) to and from external devices such as other vehicles, BSs (e.g., gNB and roadside units), and servers. The control unit 120 may perform various operations by controlling elements of the vehicle or the autonomously driven vehicle 100. The control unit 120 may include an ECU. The driving unit 140a may cause the vehicle or the autonomous driving vehicle 100 to travel on a road. The drive unit 140a may include an engine, a powertrain, wheels, brakes, steering, and the like. The power supply unit 140b may supply power to the vehicle or the autonomous driving vehicle 100 and include a wired/wireless charging circuit, a battery, and the like. The sensor unit 140c may acquire a vehicle state, surrounding information, user information, and the like. The sensor unit 140c may include an Inertial Measurement Unit (IMU) sensor, a collision sensor, a wheel sensor, a speed sensor, a gradient sensor, a weight 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 may implement a technique for keeping a lane on which the vehicle is driven, a technique for automatically adjusting a speed such as adaptive cruise control, a technique for autonomously driving along a determined path, a technique for driving by automatically setting a path when a destination is set, and the like.

For example, the communication unit 110 may receive map data, traffic information data, and the like from an external server. The autonomous driving unit 140d may generate an autonomous driving path and a driving plan from the obtained data. The control unit 120 may control the drive unit 140a such that the vehicle or the autonomous driving vehicle 100 may move along the autonomous driving path according to a driving plan (e.g., speed/direction control). In autonomous driving, the communication unit 110 may acquire latest traffic information data from an external server aperiodically/periodically, and may acquire surrounding traffic information data from a neighboring vehicle. In autonomous driving, the sensor unit 140c may obtain vehicle state and/or ambient information. The autonomous driving unit 140d may update the autonomous driving path and the driving plan based on the newly obtained data/information. The communication unit 110 may transmit information about the vehicle position, the autonomous driving path, and/or the driving plan to an external server. The external server may predict traffic information data using AI technology or the like based on 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.

Examples of vehicles and AR/VR suitable for use in the present disclosure

Fig. 16 illustrates a vehicle applied to the present disclosure. The vehicle may be implemented as a vehicle, an aircraft, a ship, or the like.

Referring to fig. 16, the vehicle 100 may include a communication unit 110, a control unit 120, a storage unit 130, an I/O unit 140a, and a positioning unit 140b.

The communication unit 110 may transmit and receive signals (e.g., data and control signals) to and from external devices such as other vehicles or BSs. The control unit 120 may perform various operations by controlling constituent elements of the vehicle 100. The storage unit 130 may store data/parameters/programs/codes/commands for supporting various functions of the vehicle 100. The I/O unit 140a may output the AR/VR object based on information within the storage unit 130. The I/O unit 140a may include a HUD. The positioning unit 140b may acquire information about the position of the vehicle 100. The position information may include information about the absolute position of the vehicle 100, information about the position of the vehicle 100 within a driving lane, acceleration information, and information about the position of the vehicle 100 relative to neighboring vehicles. The positioning unit 140b may include a GPS and various sensors.

As an example, the communication unit 110 of the vehicle 100 may receive map information and traffic information from an external server and store the received information in the storage unit 130. The positioning unit 140b may obtain vehicle position information through GPS and various sensors, and store the obtained information in the storage unit 130. The control unit 120 may generate a virtual object based on the map information, the traffic information, and the vehicle position information, and the I/O unit 140a may display the generated virtual object in a window in the vehicle (1410 and 1420). The control unit 120 may determine whether the vehicle 100 is normally driven in the driving lane based on the vehicle position information. If the vehicle 100 abnormally leaves the driving lane, the control unit 120 may display a warning on a window in the vehicle through the I/O unit 140 a. In addition, the control unit 120 may broadcast a warning message about driving abnormality to the neighboring vehicle through the communication unit 110. According to circumstances, the control unit 120 may transmit the vehicle position information and the information about driving/vehicle abnormality to the relevant organization.

Examples of XR devices suitable for use in the present disclosure

Fig. 17 illustrates an XR device applied to the present disclosure. The XR device may be implemented by an HMD, HUD mounted in a vehicle, television, smart phone, computer, wearable device, household appliance, digital signage, vehicle, robot, or the like.

Referring to fig. 17, xr device 100a may include a communication unit 110, a control unit 120, a storage unit 130, an I/O unit 140a, a sensor unit 140b, and a power supply unit 140c.

The communication unit 110 may transmit and receive signals (e.g., media data and control signals) to and from external devices such as other wireless devices, handheld devices, or media servers. The media data may include video, images, and sound. Control unit 120 may perform various operations by controlling the constituent elements of XR device 100 a. For example, the control unit 120 may be configured to control and/or perform processes such as video/image acquisition, (video/image) encoding, and metadata generation and processing. Memory unit 130 may store data/parameters/programs/codes/commands needed to drive XR device 100 a/generate XR objects. The I/O unit 140a may obtain control information and data from the outside and output the generated XR object. The I/O unit 140a may include a camera, a microphone, a user input unit, a display unit, a speaker, and/or a haptic module. Sensor unit 140b may obtain XR device status, ambient information, user information, etc. The sensor unit 140b may include a proximity sensor, an illuminance sensor, an acceleration sensor, a magnetic sensor, a gyro sensor, an inertial sensor, an RGB sensor, an IR sensor, a fingerprint recognition sensor, an ultrasonic sensor, a light sensor, a microphone, and/or a radar. The power supply unit 140c may supply power to the XR device 100a and include wired/wireless charging circuitry, batteries, and the like.

For example, storage unit 130 of XR device 100a may include information (e.g., data) required to generate an XR object (e.g., an AR/VR/MR object). I/O unit 140a may receive commands from a user for manipulating XR device 100a, and control unit 120 may drive XR device 100a in accordance with the user's drive commands. For example, when a user desires to watch a movie or news through the XR device 100a, the control unit 120 transmits content request information to another device (e.g., the handheld device 100 b) or a media server through the communication unit 110. The communication unit 110 may download/stream content such as movies or news from another device (e.g., the handheld device 100 b) or a media server to the storage unit 130. The control unit 120 may control and/or perform processes such as video/image acquisition, (video/image) encoding and metadata generation/processing for content, and generate/output XR objects based on information about surrounding space or real objects obtained through the I/O unit 140 a/sensor unit 140 b.

XR device 100a may be wirelessly connected to handheld device 100b via communication unit 110, and operation of XR device 100a may be controlled by handheld device 100 b. For example, handheld device 100b may operate as a controller for XR device 100a. To this end, XR device 100a may obtain information regarding the 3D position of handheld device 100b, generate and output an XR object corresponding to handheld device 100 b.

Examples of robots suitable for use in the present disclosure

Fig. 18 illustrates a robot applied to the present disclosure. Robots can be classified into industrial robots, medical robots, home robots, military robots, etc., according to the purpose or field of use.

Referring to fig. 18, the robot 100 may include a communication unit 110, a control unit 120, a storage unit 130, an I/O unit 140a, a sensor unit 140b, and a driving unit 140c.

The communication unit 110 may transmit and receive signals (e.g., driving information and control signals) to and from external devices such as other wireless devices, other robots, or a control server. The control unit 120 may perform various operations by controlling constituent elements of the robot 100. The storage unit 130 may store data/parameters/programs/codes/commands for supporting various functions of the robot 100. The I/O unit 140a may obtain information from the outside of the robot 100 and output the information to the outside of the robot 100. The I/O unit 140a may include a camera, a microphone, a user input unit, a display unit, a speaker, and/or a haptic module. The sensor unit 140b may obtain internal information, surrounding information, user information, etc. of the robot 100. The sensor unit 140b may include a proximity sensor, an illuminance sensor, an acceleration sensor, a magnetic sensor, a gyro sensor, an inertial sensor, an IR sensor, a fingerprint recognition sensor, an ultrasonic sensor, a light sensor, a microphone, a radar, and the like. The driving unit 140c may perform various physical operations such as moving a robot joint. In addition, the driving unit 140c may cause the robot 100 to travel or fly on a road. The driving unit 140c may include an actuator, an engine, wheels, a brake, a propeller, and the like.

Examples of AI devices to which the present disclosure is applied

Fig. 19 illustrates an AI apparatus applied to the present disclosure. The AI device may be implemented by a fixed device or a mobile device such as a TV, projector, smart phone, PC, notebook, digital broadcast terminal, tablet PC, wearable device, set-top box (STB), radio, washing machine, refrigerator, digital signage, robot, vehicle, etc.

Referring to fig. 19, the ai apparatus 100 may include a communication unit 110, a control unit 120, a storage unit 130, I/O units 140a/140b, a learning processor unit 140c, and a sensor unit 140d. Blocks 110 through 130/140a correspond to blocks 110 through 130/140, respectively, of fig. 14.

The communication unit 110 may transmit/receive wired/radio signals (e.g., sensor information, user input, learning model, or control signals) to/from other AI devices (e.g., 100x, 200, or 400 of fig. 13) or AI servers (e.g., 400 of fig. 13) using wired/wireless communication techniques. For this, the communication unit 110 may transmit information within the storage unit 130 to an external device and transmit a signal received from the external device to the storage unit 130.

The control unit 120 may determine at least one feasible operation of the AI device 100 based on information determined or generated using a data analysis algorithm or a machine learning algorithm. The control unit 120 may perform an operation determined by controlling the constituent elements of the AI apparatus 100. For example, the control unit 120 may request, search, receive, or use data of the learning processor unit 140c or the storage unit 130, and control constituent elements of the AI apparatus 100 to perform a predicted operation or a determined preferred operation among at least one possible operation. The control unit 120 may collect history information including the operation content of the AI device 100 and the operation feedback of the user, and store the collected information in the storage unit 130 or the learning processor unit 140c, or transmit the collected information to an external device such as an AI server (400 of fig. 13). The collected historical information may be used to update the learning model.

The storage unit 130 may store data for supporting various functions of the AI device 100. For example, the storage unit 130 may store data obtained from the input unit 140a, data obtained from the communication unit 110, output data of the learning processor unit 140c, and data obtained from the sensor unit 140. The storage unit 130 may store control information and/or software codes required for operating/driving the control unit 120.

The input unit 140a may acquire various types of data from outside the AI device 100. For example, the input unit 140a may acquire learning data for model learning and input data to which a learning model is to be applied. The input unit 140a may include a camera, a microphone, and/or a user input unit. The output unit 140b may generate an output related to a visual, auditory, or tactile sensation. The output unit 140b may include a display unit, a speaker, and/or a haptic module. The sensor unit 140 may use various sensors to obtain at least one of the internal information of the AI device 100, the surrounding environment information of the AI device 100, and the user information. The sensor unit 140 may include a proximity sensor, an illuminance sensor, an acceleration sensor, a magnetic sensor, a gyroscope sensor, an inertial sensor, an RGB sensor, an IR sensor, a fingerprint recognition sensor, an ultrasonic sensor, a light sensor, a microphone, and/or a radar.

The learning processor unit 140c may use the learning data to learn a model including an artificial neural network. The learning processor unit 140c may perform AI processing together with the learning processor unit of the AI server (400 of fig. 13). The learning processor unit 140c may process information received from an external device through the communication unit 110 and/or information stored in the storage unit 130. In addition, the output value of the learning processor unit 140c may be transmitted to an external device through the communication unit 110, and may be stored in the storage unit 130.

Industrial applicability

The above embodiments of the present disclosure are applicable to various mobile communication systems.

Claims (13)

1. A method of operation of a remote user equipment, UE, in a wireless communication system, the method comprising the steps of:

establishing a connection with a first relay UE by the remote UE;

receiving, by the remote UE, information from the first relay UE indicating Uu radio link failure, RLF; and

a relay reselection or cell selection procedure is performed based on receiving the information indicative of the Uu RLF,

wherein the remote UE sends information to the reselected second relay UE or the base station BS associated with cell selection to back to the previous link based on receiving information from the first relay UE indicating that Uu link recovery was successful.

2. The method of claim 1, wherein the information indicating that the Uu link recovery was successful is received before connection with the second relay UE is completed or before connection with the BS is completed.

3. The method of claim 1, wherein the remote UE stops a connection procedure with the second relay UE or a connection procedure with the BS after receiving the information indicating that the Uu link recovery is successful.

4. The method of claim 1, wherein the remote UE skips sending a radio resource control, RRC, setup request or RRC connection complete message to the BS after receiving the information indicating that the Uu link recovery was successful.

5. The method of claim 1, wherein the remote UE remains connected to the first relay UE until the connection to the second relay UE or the BS is completed.

6. The method of claim 5, wherein the remote UE releases the connection with the first relay UE based on completion of the connection with the second relay UE or the BS.

7. The method of claim 1, wherein the remote UE preferentially selects relay UEs belonging to the same tracking area TA/RAN based notification area RNA as the remote UE.

8. The method of claim 7, wherein the remote UE identifies the TA/RNA of the relay UE by information included in a discovery message.

9. The method of claim 1, wherein the remote UE informs the relay UE of updated TA/RNA information.

10. The method of claim 9, wherein the remote UE transmits the TA/RNA information to the relay UE based on the updated TA/RNA being different from an existing TA/RNA.

11. A remote user equipment, UE, apparatus in a wireless communication system, the remote UE apparatus comprising:

at least one processor; and

at least one computer memory operatively connected to the at least one processor and configured to store instructions that, when executed, cause the at least one processor to perform operations comprising:

establishing connection with a first relay UE;

receiving information indicating Uu radio link failure, RLF, from the first relay UE; and

a relay reselection or cell selection procedure is performed based on receiving the information indicative of the Uu RLF,

wherein the remote UE transmits information of fallback to a previous link to a reselected second relay UE or a BS related to cell selection based on receiving information indicating that Uu link recovery is successful from the first relay UE.

12. A processor for performing operations in a wireless communication system for a remote user equipment, UE, the operations comprising:

establishing connection with a first relay UE;

receiving information indicating Uu radio link failure, RLF, from the first relay UE; and

a relay reselection or cell selection procedure is performed based on receiving the information indicative of the Uu RLF,

wherein the remote UE transmits information of fallback to a previous link to a reselected second relay UE or a BS related to cell selection based on receiving information indicating that Uu link recovery is successful from the first relay UE.

13. A non-transitory computer-readable storage medium storing at least one computer program comprising instructions that, when executed by at least one processor, cause the at least one processor to perform operations for a base station BS, the operations comprising:

establishing connection with a first relay UE;

receiving information indicating Uu radio link failure, RLF, from the first relay UE; and

a relay reselection or cell selection procedure is performed based on receiving the information indicative of the Uu RLF,

wherein the remote UE transmits information of fallback to the previous link to the reselected second relay UE or the BS related to cell selection based on receiving information indicating that Uu link recovery is successful from the first relay UE.