Method and apparatus for a connection processing mechanism in an L2 U2N relay case

Abstract

Embodiments of the present disclosure relate to a method and apparatus for a connection processing mechanism in a layer 2 (L2) user equipment (UE)-to-network (U2N) relay case in a communication system. According to embodiments of the present application, a user equipment (UE) includes a transceiver and a processor coupled to the transceiver, and the processor is configured to access a network node via an indirect path associated with a source relay node, and in response to receiving a radio resource control (RRC) reconfiguration message for a path switch from the network node via the transceiver, execute a path switch procedure from the indirect path to a target path, where the target path is either a direct path between the UE and the network node or another indirect path between the UE and a network node associated with a target relay node, and during the path switch procedure, receive data from the source relay node via the transceiver via a source link between the UE and the source relay node.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to communication technologies, and more specifically, to a connection processing mechanism in a layer 2 (L2) user equipment (UE)-to-network (U2N) relay case in a communication system.

Background Art

[0002] Vehicle-to-everything (V2X) has been introduced into 5G wireless communication technology. From the perspective of the channel structure of V2X communication, a direct link between two user equipments (UEs) is called a sidelink. The sidelink is a long term evolution (LTE) function introduced in the 3rd Generation Partnership Project (3GPP (registered trademark)) Release 12, enabling direct communication between neighboring UEs without the need for data to go through a base station (BS) or a core network.

[0003] In 3GPP (registered trademark), the deployment of relay nodes (RNs) in a wireless communication system is underway. One purpose of deploying an RN is to expand the coverage area of a BS by improving the throughput of user equipments (UEs) located within a coverage area that may result in relatively low signal quality or away from the BS. An RN may sometimes be named a relay UE. A 3GPP (registered trademark) 5G sidelink system including a relay UE may be named a sidelink relay system. A U2N relay UE is a UE that provides functionality to support the connection of a U2N remote UE to a network.

[0004] Currently, in a wireless communication system or the like, details regarding the connection processing mechanism in the case of L2 U2N relay have not yet been specifically discussed.

Summary of the Invention

Means for Solving the Problems

[0005] Some embodiments of the present disclosure provide a user equipment (UE). The UE may include a transceiver and a processor coupled to the transceiver. The processor is configured to access a network node via a first indirect path associated with a source relay node, and in response to receiving a radio resource control (RRC) reconfiguration message for a path switch from the network node via the transceiver, perform a path switch procedure from the first indirect path to a target path, where the target path is either a direct path between the UE and the network node or a second indirect path between the UE and a network node associated with a target relay node, and during the path switch procedure, receive data from the source relay node via the transceiver via a source link between the UE and the source relay node.

[0006] In some embodiments of the present disclosure, the processor of the UE is configured to stop receiving at least one of user plane (UP) data or control plane (CP) data via the transceiver from the source relay node in response to receiving an RRC reconfiguration message for a path switch.

[0007] In some embodiments of the present disclosure, the processor of the UE is configured to perform at least one of receiving a first notification message or a PC5 unicast link release indication from the source relay node during the path switch procedure, ignoring the first notification message or the PC5 unicast link release indication in response to receiving the first notification message or the PC5 unicast link release indication and in response to a timer for the path switch being running, stopping receiving at least one of UP data or CP data from the source relay node, or releasing a source link between the UE and the source relay node.

[0008] In some embodiments of the present disclosure, the first notification message is received from a source relay node via a transceiver, and the PC5 unicast link release instruction is indicated by the upper layer of the UE or received from the source relay node via the transceiver.

[0009] In some embodiments of the present disclosure, in response to the path switch procedure being a dual active protocol stack (DAPS) path switch procedure, the processor of the UE is configured to receive a second notification message from the target relay node via the transceiver, receive a PC5 unicast link release instruction, where the PC5 unicast link release instruction is indicated by the upper layer of the UE or received from the target relay node via the transceiver, or detect a radio link failure (RLF) on the link between the UE and the target relay node, and perform at least one of these actions.

[0010] In some embodiments of the present disclosure, the processor of the UE is configured to return to the source link in response to the source link being available, or transmit fault-related information to the network node via the transceiver, and perform at least one of these actions.

[0011] In some embodiments of the present disclosure, the processor of the UE is configured to execute a re-establishment procedure in response to the source link not being available, receive a request from the network node via the transceiver after completing the re-establishment procedure, and transmit a response including fault-related information to the network node via the transceiver.

[0012] In some embodiments of the present disclosure, the fault-related information indicates at least one of receiving a second notification message from the target relay node, receiving a PC5 unicast link release instruction, or detecting an RLF on the link between the UE and the target relay node.

[0013] In some embodiments of the present disclosure, the processor of the UE is configured to receive a PC5 unicast link release indication before receiving an RRC reconfiguration message for a path switch, and in response to a timer for an RRC re-establishment request not being running and in response to the UE being in the RRC connected state, perform a re-establishment procedure.

[0014] In some embodiments of the present disclosure, the processor of the UE is configured to receive a PC5 unicast link release indication before receiving an RRC reconfiguration message for a path switch, and in response to a timer for an RRC re-establishment request being running, perform at least one of entering the RRC idle state or stopping the timer for the RRC re-establishment request.

[0015] In some embodiments of the present disclosure, in response to a timer for an RRC re-establishment request being running, the processor of the UE is further configured to perform an action when entering the RRC idle state.

[0016] In some embodiments of the present disclosure, the PC5 unicast link release indication is indicated by an upper layer of the UE or received from a source relay node via a transceiver.

[0017] In some embodiments of the present disclosure, the processor of the UE is configured to receive a third notification message from a source relay node via a transceiver before receiving an RRC reconfiguration message for a path switch, and in response to a timer for an RRC re-establishment request not being running, the UE being in the RRC connected state, or the UE not performing a re-establishment procedure and the UE being in the RRC connected state, perform a re-establishment procedure.

[0018] In some embodiments of the present disclosure, at least one of the first notification message, the second notification message, or the third notification message is triggered by at least one of the occurrence of Uu RLF, reception of an RRC reconfiguration message including a configuration by synchronization, reselection of a cell, occurrence of an RRC connection failure, RRC connection rejection, expiration of a timer for an RRC setup request, and occurrence of an RRC resume failure.

[0019] Some embodiments of the present disclosure provide a relay node. The relay node may include a transceiver and a processor coupled to the transceiver. The processor may be configured to transmit at least one of a notification message or a PC5 unicast link release instruction to a user equipment (UE) via the transceiver while the UE is performing a path switch procedure from a source path to a target path, where the source path is a first direct path between the UE and a network node or a first indirect path between the UE and a network node associated with a source relay node, the target path is a second direct path between the UE and a network node or a second indirect path between the UE and a network node associated with a target relay node, and the relay node functions as a source relay node or a target relay node.

[0020] In some embodiments of the present disclosure, in response to the relay node functioning as a source relay node, the processor of the relay node is configured to receive measurement results from the UE and transmit the measurement results to the network node via the transceiver via a first indirect path between the UE and the network node, and transmit data to the UE via the transceiver via a source link between the UE and the source relay node while the UE is performing a path switch procedure.

[0021] In some embodiments of the present disclosure, in response to a relay node functioning as a target relay node, the path switch procedure is a dual active protocol stack (DAPS) path switch procedure.

[0022] In some embodiments of the present disclosure, the notification message is triggered by at least one of the occurrence of Uu RLF at the relay node, the reception of an RRC reconfiguration message including a configuration by synchronization at the relay node, the reselection of a cell at the relay node, the occurrence of an RRC connection failure at the relay node, the rejection of an RRC connection at the relay node, the expiration of a timer for an RRC setup request at the relay node, and the occurrence of an RRC resume failure at the relay node.

[0023] Some embodiments of the present disclosure provide a network node (e.g., a BS). The network node may include a transceiver and a processor coupled to the transceiver. The processor is configured to send a request to a user equipment (UE) via the transceiver after the UE has completed a reestablishment procedure to the network node, where the reestablishment procedure is initiated by the UE in response to the occurrence of a failure while the UE is performing a path switch procedure from a source path to a target path and in response to the unavailability of a source link between the UE and a source relay node, the source path being a first direct path between the UE and the network node or a first indirect path between the UE and a network node associated with the source relay node, and the target path being a second direct path between the UE and the network node or a second indirect path between the UE and a network node associated with the target relay node, and to receive a response from the UE via the transceiver including failure-related information.

[0024] In some embodiments of the present disclosure, the fault-related information indicates at least one of: reception of a notification message by the UE from the target relay node; reception of a PC5 unicast link release indication, where the PC5 unicast link release indication is indicated by the upper layer of the UE or received by the UE from the target relay node; or detection of a radio link failure (RLF) on the link between the UE and the target relay node.

[0025] In some embodiments of the present disclosure, the path switch procedure is a dual active protocol stack (DAPS) path switch procedure.

[0026] Some embodiments of the present disclosure provide a method performed by a user equipment (UE). The method may include accessing a network node via a first indirect path associated with a source relay node; in response to receiving a radio resource control (RRC) reconfiguration message for a path switch from the network node, performing a path switch procedure from the first indirect path to a target path, where the target path is either a direct path between the UE and the network node or a second indirect path between the UE and a network node associated with a target relay node; and during the path switch procedure, receiving data from the source relay node via a source link between the UE and the source relay node.

[0027] Some embodiments of the present disclosure provide a method performed by a relay node. The method may include transmitting at least one of a notification message or a PC5 unicast link release indication to a user equipment (UE) while the UE is performing a path switch procedure from a source path to a target path, where the source path is a first direct path between the UE and a network node or a first indirect path between the UE and a network node associated with a source relay node, the target path is a second direct path between the UE and a network node or a second indirect path between the UE and a network node associated with a target relay node, and the relay node functions as a source relay node or a target relay node.

[0028] Some embodiments of the present disclosure provide a method performed by a network node. The method is a step of transmitting a request to a user equipment (UE) after the UE has completed a re-establishment procedure to the network node, where the re-establishment procedure is initiated by the UE in response to the occurrence of a failure while the UE is performing a path switch procedure from a source path to a target path and in response to the unavailability of a source link between the UE and a source relay node, the source path is a first direct path between the UE and a network node or a first indirect path between the UE and a network node associated with a source relay node, the target path is a second direct path between the UE and a network node or a second indirect path between the UE and a network node associated with a target relay node, and may include the step of receiving a response from the UE including failure-related information.

[0029] Some embodiments of the present disclosure provide a user equipment (UE). The UE may include a transceiver and a processor coupled to the transceiver. The processor may be configured to access a network node via an indirect path through a relay node, receive data from the relay node via the transceiver via a link between the UE and the relay node, and receive at least one of a notification message or a PC5 unicast link release indication.

[0030] In some embodiments of the present disclosure, the notification message is received from the relay node via the transceiver, and the PC5 unicast link release indication is indicated by an upper layer of the UE or received from the relay node via the transceiver.

[0031] In some embodiments of the present disclosure, in response to receiving the PC5 unicast link release indication, in response to a timer for an RRC reestablishment request not being running, and in response to the UE being in the RRC connected state, the processor of the UE is configured to execute a reestablishment procedure.

[0032] In some embodiments of the present disclosure, in response to receiving the PC5 unicast link release indication, in response to a timer for an RRC reestablishment request being running, the processor of the UE is configured to perform at least one of entering the RRC idle state or stopping the timer for the RRC reestablishment request.

[0033] In some embodiments of the present disclosure, the processor of the UE is further configured to perform an action when entering the RRC idle state.

[0034] In some embodiments of the present disclosure, in response to receiving a notification message, a processor of the UE is configured to execute a reestablishment procedure in response to the fact that a timer for an RRC reestablishment request is not running, the UE is in the RRC connected state, or the UE is not executing a reestablishment procedure and the UE is in the RRC connected state.

[0035] In some embodiments of the present disclosure, the notification message is associated with one or more conditions in the relay UE, and the one or more conditions include at least one of the occurrence of Uu RLF, reception of an RRC reconfiguration message including a configuration by synchronization, reselection of a cell, occurrence of an RRC connection failure, RRC connection rejection, expiration of a timer for an RRC setup request, and occurrence of an RRC resume failure.

[0036] Some embodiments of the present disclosure provide a method performed by a user equipment (UE). The method may include accessing a network node via an indirect path through a relay node, receiving data from the relay node via a transceiver via a link between the UE and the relay node, and receiving at least one of a notification message or a PC5 unicast link release indication.

[0037] Some embodiments of the present disclosure provide an apparatus. According to some embodiments of the present disclosure, the apparatus may include at least one non-transitory computer-readable medium storing computer-executable instructions, at least one receiving circuit, at least one transmitting circuit, and at least one processor coupled to the at least one non-transitory computer-readable medium, the at least one receiving circuit, and the at least one transmitting circuit, and the at least one non-transitory computer-readable medium and the computer-executable instructions may be configured to cause the apparatus to execute a method according to some embodiments of the present disclosure together with the at least one processor.

[0038] Embodiments of the present disclosure provide technical solutions for facilitating and improving the implementation of various communication technologies such as 5G NR.

[0039] To explain how the advantages and features of the present disclosure can be obtained, the description of the present disclosure is given with reference to specific embodiments shown in the accompanying drawings. These drawings show only exemplary embodiments of the present disclosure and should not be regarded as limiting its scope.

Brief Description of the Drawings

[0040]

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DETAILED DESCRIPTION OF THE INVENTION

[0041] The detailed description of the accompanying drawings is intended as a description of the preferred embodiments of the present disclosure and is not intended to represent the only form in which the present disclosure can be implemented. It should be understood that the same or equivalent functions can be achieved by different embodiments intended to be included within the gist and scope of the present disclosure.

[0042] Here, some embodiments of the present disclosure will be referred to in detail, and examples thereof are shown in the accompanying drawings. For ease of understanding, embodiments are provided under specific network architectures and new service scenarios such as the 3rd Generation Partnership Project (3GPP (registered trademark)) 5G (NR), 3GPP (registered trademark) Long Term Evolution (LTE) Release 8. With the development of network architectures and new service scenarios, it is assumed that all embodiments of the present disclosure are also applicable to similar technical problems. Furthermore, the terms described in the present disclosure may be changed, which should not affect the principles of the present disclosure.

[0043] FIG. 1 shows a schematic diagram of a wireless communication system 100 according to some embodiments of the present disclosure.

[0044] As shown in FIG. 1, the wireless communication system 100 may support sidelink communication. Sidelink communication supports direct UE-to-UE communication. In the context of the present disclosure, sidelink communication can be classified according to the adopted wireless communication technology. For example, sidelink communication may include NR sidelink communication and V2X sidelink communication.

[0045] NR side-link communication (e.g., as specified in 3GPP (R) TS38 series specifications) may refer to an access stratum (AS) functionality that enables at least vehicle-to-everything (V2X) communication between adjacent UEs without traversing any network nodes, while using NR technology. V2X side-link communication (e.g., as specified in 3GPP (R) TS36 series specifications) may refer to an AS functionality that enables V2X communication between adjacent UEs without traversing any network nodes, while using evolved universal mobile telecommunication system (UMTS) terrestrial radio access (UTRA) (E-UTRA) technology. However, when not specified, "side-link communication" may refer to NR side-link communication, V2X side-link communication, or any side-link communication employing other wireless communication technologies.

[0046] Referring to FIG. 1, wireless communication system 100 may include several base stations (e.g., BS102 and BS103) and several UEs (e.g., UE101A, UE101B, and UE101C). Although a specific number of UEs and BSs are shown in FIG. 1, it is assumed that any number of UEs and BSs may be included within wireless communication system 100.

[0047] The UE and the BS may support communication based on, for example, 3G, Long Term Evolution (LTE), LTE-Advanced (LTE-A), New Radio (NR), or other suitable protocols. In some embodiments of the present disclosure, the BS (e.g., BS102 or BS103) may be referred to as an access point, access terminal, base, base unit, microcell, Node B, evolved Node B (eNB), gNB, ng-eNB, home Node B, relay node, or device, or may be described using other terms used in the art. The UE (e.g., UE101A, UE101B, or UE101C) may include, for example, but not limited to, computing devices, wearable devices, mobile devices, IoT devices, vehicles, and the like. Those skilled in the art should understand that as technology develops and progresses, the terms described in the present disclosure may change, but should not affect or limit the principles and gist of the present disclosure.

[0048] In the example of FIG. 1, BS102 and BS103 may be included within a Next Generation Radio Access Network (NG-RAN). In some embodiments of the present disclosure, BS102 may be a gNB, and BS103 may be an ng-eNB.

[0049] UE101A and UE101B can be within coverage (e.g., inside the NG-RAN). For example, as shown in FIG. 1, UE101A can be within the coverage of BS102, and UE101B can be within the coverage of BS103. UE101C can be outside the coverage (e.g., outside the coverage of the NG-RAN). For example, as shown in FIG. 1, UE101C can be outside the coverage of any BS, e.g., outside the coverage of both BS102 and BS103. UE101A and UE101B can each be connected to BS102 and BS103 via a network interface, e.g., the Uu interface specified in the 3GPP (registered trademark) specifications. The control plane protocol stack within the Uu interface may include an RRC layer, which may be called Uu RRC. The link established between a UE (e.g., UE101A) and a BS (e.g., BS102) may be called a Uu link. BS102 and BS103 can be connected to each other via a network interface, e.g., the Xn interface specified in the 3GPP (registered trademark) standard documents. UE101A, UE101B, and UE101C can each be connected to each other via, for example, the PC5 interface specified in the 3GPP (registered trademark) standard documents. The control plane protocol stack within the PC5 interface may include an RRC layer, which may be called PC5 RRC. The link established between two UEs (e.g., UE101A and UE101B) may be called a PC5 link.

[0050] Support for V2X services via the PC5 interface can be provided, for example, by NR sidelink communication and / or V2X sidelink communication. NR sidelink communication can support one of the following three types of transmission modes, namely, unicast transmission, groupcast transmission, and broadcast transmission, for a pair of a source layer 2 ID and a destination layer 2 ID. Transmission and reception of sidelink communication via the PC5 interface are supported when the UE is either inside or outside the coverage. For example, UE101A inside the coverage of BS102 can perform sidelink transmission and reception (e.g., sidelink unicast transmission, sidelink groupcast transmission, or sidelink broadcast transmission) via the PC5 interface. UE101C outside the coverage of both BS102 and BS103 can also perform sidelink transmission and reception via the PC5 interface.

[0051] A UE that supports sidelink communication and / or V2X communication may be referred to as a V2X UE. According to some other embodiments of the present disclosure, the V2X UE can be a mobile phone, a vehicle, a roadmap device, a computer, a laptop, an IoT (Internet of Things) device, or other types of devices.

[0052] As described above, the sidelink-based relay function can be supported in a communication network. Sidelink relay can provide connectivity to the network for another UE (remote UE). In some embodiments of the present disclosure, UE-to-network relay is supported. For example, a coverage-in UE communicating with a remote UE (e.g., an out-of-coverage UE or an in-coverage UE) can function as a relay UE between the serving BS of the coverage-in UE and the remote UE. Thus, the remote UE can communicate with the BS via this relay UE. Data between the remote UE and the BS can be transferred by the relay UE. In this scenario, the relay UE may be referred to as the serving relay of the remote UE, and the serving BS or serving cell of the relay UE may be referred to as the serving BS or serving cell of the remote UE, respectively.

[0053] The remote UE may have RRC states such as the RRC_IDLE state, the RRC_INACTIVE state, and the RRC_CONNECTED state defined in the 3GPP (registered trademark) specifications. The RRC_IDLE state may also be named as the RRC idle state, etc. The RRC_INACTIVE state may also be named as the RRC inactive state, etc. The RRC_CONNECTED state may also be named as the RRC connected state, etc. The relay UE may be in the RRC_CONNECTED state to perform the relay of unicast data. In some embodiments, in the case of a path switch, a relay UE in the RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED state can be selected as the target relay UE.

[0054] In some embodiments, the following combinations of RRC states may be supported for L2 U2N relay operation, - For performing the transmission or reception of relayed unicast data, both the relay UE and the remote UE may be in the RRC_CONNECTED state, - As long as all remote UEs connected to the relay UE are in either the RRC_INACTIVE state or the RRC_IDLE state, the relay UE can be in the RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED state.

[0055] A single unicast link can be established between one relay UE and one remote UE. The traffic of the remote UEs via a given relay UE and the traffic of the relay UE can be separated into different Uu relay radio link control (RLC) channels. In some embodiments, for L2 U2N relays, the remote UE can be configured to use only resource allocation mode 2 for the data to be relayed.

[0056] FIG. 2 shows a schematic diagram of a relay-based wireless communication system 200 according to some embodiments of the present disclosure. The details described in all of the foregoing embodiments of the present disclosure are applicable to the embodiment shown in FIG. 2.

[0057] As shown in FIG. 2, the wireless communication system 200 may include a BS (e.g., BS 202) and several UEs (e.g., UE 201A and UE 201B). Although a specific number of UEs and BSs are shown in FIG. 2, it is assumed that any number of UEs and BSs may be included in the wireless communication system 200. In some examples, UE 201B may function as UE 101A or UE 101B shown in FIG. 1, and UE 201A may function as UE 101C shown in FIG. 1. UE 201B may be named relay UE 201B as shown in FIG. 2.

[0058] UE201B can be within the coverage of BS202. For example, UE201B and BS202 can establish an RRC connection between them. UE201A can be outside the coverage of BS202. The wireless communication system 200 can support sidelink communication. For example, UE201B can be in sidelink communication with UE201A. PC5 RRC communication can be established between UE201A and UE201B.

[0059] In some embodiments of the present disclosure, UE201A can initiate a procedure (i.e., UE-to-network relay) to establish a connection with BS202 via UE201B. For example, UE201A can send an RRC setup request to BS202 via UE201B. BS202 can send an RRC setup message including a response to UE201A via UE201B. After such a procedure, UE201A can access BS202 (e.g., a cell of BS202) via UE201B. This cell may be referred to as the serving cell of UE201A. UE201A and BS202 can establish an RRC connection between them. UE201A may also be referred to as a remote UE, and UE201B may also be referred to as a relay UE, a sidelink relay, or a serving relay of UE201A.

[0060] Although a single relay node (e.g., UE201B) is shown between UE201A and BS202 in FIG. 2, it should be understood by those skilled in the art that any number of relay nodes can be included. In FIG. 2, it is shown that UE201A is outside the coverage of BS202, but in some other embodiments of the present disclosure, it is assumed that UE201A can be within the coverage of BS202. In these embodiments, UE201A can connect directly to BS202 and / or connect to BS202 via UE201B.

[0061] FIG. 3 shows a flowchart of an exemplary procedure 300 for a notification message according to some embodiments of the present disclosure. The details described in all of the foregoing embodiments of the present disclosure are applicable to the embodiments shown in FIG. 3.

[0062] Referring to FIG. 3, in some embodiments, at operation 311, relay node 302 may send a notification message to UE 301. In some examples, relay node 302 may be a relay UE, such as a U2N relay UE. In this scenario, the notification message may sometimes be referred to as a "notification message for sidelink" or a "NotificationMessageSidelink message".

[0063] In some embodiments of the present disclosure, relay node 302 may, for example, start the exemplary procedure 300 when one of the following conditions is met, i.e., - in response to a Uu RLF as described below, or - in response to receiving an RRC reconfiguration message including a reconfigurationWithSync information element (IE) such as a handover command, or - in response to cell reselection at relay node 302, or - in response to an RRC connection failure at relay node 302, which may include, for example, RRC connection rejection, expiration of a timer for an RRC setup request (e.g., T300 specified in the 3GPP (registered trademark) specification), and RRC resume failure. The exemplary procedure 300 may be started.

[0064] The notification message may include a type indication (e.g., "indicationType") indicating that the notification message is due to one of relay Uu RLF, relay handover, relay cell reselection, and / or relay connection failure.

[0065] In some embodiments of the present disclosure, a relay node (e.g., relay node 302) may use the following criteria, i.e., - Expiration of a radio problem timer started after an indication of a radio problem from the physical layer (if the radio problem is recovered before the timer expires, the relay node stops the timer), or - Expiration of a timer started when a measurement report regarding the measurement ID for which the timer is set is triggered while another radio problem timer is running, or - Failure of a random access procedure, or - RLC failure Based on at least one of the above, Uu RLF (e.g., RLF between the relay node and the BS) can be declared.

[0066] In some other embodiments of the present disclosure, either the access stratum (AS) layer of the L2 U2N relay UE or the L2 U2N remote UE can indicate to the upper layer of the UE to release the PC5 RRC connection and release the PC5 unicast link, for example, after receiving an RRCReconfiguration message from the BS. The timing for performing the PC5 unicast link release depends on the implementation of the UE.

[0067] For example, referring back to FIG. 3, in operation 311, the relay node 302 can send a PC5 unicast link release instruction to the UE 301. In some examples, the relay node 302 can be a relay UE such as a U2N relay UE. In this scenario, the PC5 unicast link release instruction may be named, for example, a PC5 unicast link release message. The PC5 unicast link release instruction can be sent in a PC5-S message from the upper layer of the UE 301 to the AS layer of the UE 301.

[0068] Figure 4 shows an exemplary UE information procedure according to some embodiments of the present disclosure. All the details described in the foregoing embodiments of the present disclosure are applicable to the embodiment shown in FIG. 4. The embodiment of FIG. 4 shows the procedure by which a UE (e.g., UE 401) communicates with a BS (e.g., BS 402). In some examples, UE 401 may function as UE 201A in FIG. 2. BS 402 may function as BS 202 in FIG. 2.

[0069] As shown in FIG. 4, in operation 411, BS 402 transmits a UE information request message to UE 401. BS 402 may be the source BS that controls the serving cell of UE 401. In operation 412, UE 401 transmits a UE information request message (e.g., including an RLF report) to BS 402. BS 402 can optimize mobility problems based on the response transmitted from UE 401.

[0070] In some embodiments of the present disclosure, a remote UE can be switched (or handed over) from an indirect path (e.g., the UE indirectly accesses the source BS (or source cell) via a source relay node) to another indirect path (e.g., the UE indirectly accesses the target BS (or target cell) via a target relay node). In some embodiments of the present disclosure, a remote UE can be switched (or handed over) from a direct path (e.g., the UE directly accesses the target BS (or target cell) without any relay node) to an indirect path (e.g., the UE indirectly accesses the target BS (or target cell) via a target relay node).

[0071] For example, in the procedure for switching from an indirect path to a direct Uu cell, when the L2 U2N remote UE communicates with a network node (e.g., BS) via an indirect path through the L2 U2N relay UE, if the BS decides to switch the L2 U2N remote UE to the direct Uu path, the BS may send an RRCReconfiguration message to the L2 U2N remote UE. Then, the L2 U2N remote UE may synchronize with the BS and execute a random access (RA) procedure. The L2 U2N remote UE may send an RRCReconfigurationComplete message to the BS via the direct Uu path, for example, using the configuration provided in the RRCReconfiguration message. After this step, the L2 U2N remote UE may use the RRC connection via the direct Uu path to the BS.

[0072] Generally, a DAPS path switch (or DAPS handover) is introduced, and the UE maintains the source cell (or source BS) connection after receiving a handover command related to DAPS and releases the source cell connection only after successful access to the target cell (or target BS). This may also be referred to as "soft handover". In the case of DAPS handover, the UE continues to receive data (e.g., UP data and / or CP data) from the source until it releases the source cell, and may continue to send UL user data transmissions to the source BS until the random access procedure to the target BS is successful. In the context of the present disclosure, "handover" and "path switch" may be used interchangeably.

[0073] Currently, the details regarding the connection processing mechanism in different scenarios in the L2 U2N relay case have not yet been specifically discussed in a wireless communication system or the like. For example, some embodiments of the present disclosure provide a mechanism for a remote UE to receive a notification message or a PC5 unicast link release instruction from a source relay UE when the remote UE is executing a path switch procedure. Some embodiments of the present disclosure introduce a mechanism for receiving a notification message or a PC5 unicast link release instruction for a DAPS path switch procedure or transmitting failure-related information related to an RLF on a PC5 link. Some embodiments of the present disclosure consider conditions for triggering a re-establishment procedure and transitioning to the RRC_IDLE state when the remote UE receives a PC5 unicast link release instruction.

[0074] For further details, they will be described in the following document in combination with the accompanying drawings. Those skilled in the art should be well aware that expressions such as "first," "second," and "third" are used only for the purpose of clear description and should not be regarded as any substantial limitation, such as an order limitation.

[0075] FIG. 5 shows a flowchart of an exemplary procedure 500 for executing a path switch procedure according to some embodiments of the present disclosure. The details described in all other embodiments of the present disclosure are applicable to the embodiment shown in FIG. 5. The exemplary procedure 500 may be executed by a UE, for example, UE101c in FIG. 1 or UE201A in FIG. 2.

[0076] In the exemplary procedure 500, in operation 501, the UE (for example, UE201A in FIG. 2) may access a network node (for example, BS202 in FIG. 2) via an indirect path associated with a source relay node (for example, relay UE201B in FIG. 2).

[0077] In operation 502, in response to receiving an RRC reconfiguration message for a path switch from a network node, the UE may execute a path switch procedure from an indirect path to a target path. The target path may be "a direct path between the UE and the network node" or "another indirect path between the UE and a network node associated with the target relay node". In some embodiments, in response to receiving an RRC reconfiguration message for a path switch, the UE may stop receiving at least one of user plane (UP) data or control plane (CP) data from the source relay node. A specific example will be described as operation 714 in the embodiment of FIG. 7 as follows.

[0078] In operation 503, during the path switch procedure, the UE may receive data (e.g., UP data and / or CP data) from the source relay node via the "source link between the UE and the source relay node".

[0079] In some embodiments, during the path switch procedure, the UE may receive a notification message (simply denoted as notification message #1 for simplicity) or a PC5 unicast link release instruction from the source relay node. In response to receiving the notification message #1 or the PC5 unicast link release instruction, and in response to a timer for the path switch being running (e.g., T304 specified in the 3GPP (registered trademark) specification), the UE may (1) ignore the notification message #1, (2) ignore the PC5 unicast link release instruction, (3) stop receiving at least one of UP data or CP data from the source relay node, or (4) release the source link between the UE and the source relay node of which at least one may be executed. A specific example will be described as option 1, option 2, or option 3 of operation 717 in the embodiment of FIG. 7 as follows.

[0080] In some embodiments, the notification message #1 is received by the UE from the source relay node. In some embodiments, the PC5 unicast link release indication is indicated by the upper layer of the UE or received by the UE from the source relay node.

[0081] In some embodiments, in response to the path switch procedure being a DAPS path switch procedure, the UE may (1) receive a further notification message (referred to as notification message #2 for simplicity) from the target relay node (e.g., target relay UE 803), (2) receive a PC5 unicast link release indication that may be indicated by the upper layer of the UE or received from the target relay node, or (3) detect an RLF on the link between the UE and the target relay node and perform at least one of the above. For a specific example, it will be described in operations 817A and 817B in the embodiment of FIG. 8 as follows.

[0082] In some embodiments, the UE may perform at least one of returning to the source link in response to the source link being available or, for example, transmitting fault-related information to the network node in operation 817A in the embodiment of FIG. 8.

[0083] In some other embodiments, in response to the source link not being available, the UE may perform a re-establishment procedure, for example, in operation 817B in the embodiment of FIG. 8. After completing the re-establishment procedure, the UE may receive a request from the network node and transmit a response including fault-related information to the network node. In an embodiment, the fault-related information may be (1) receipt of notification message #2 from the target relay node, (2) receipt of a PC5 unicast link release indication, or (3) Detection of RLF on the link between the UE and the target relay node indicates at least one of them.

[0084] In some embodiments, the UE receives a PC5 unicast link release indication before receiving an RRC reconfiguration message for a path switch, and in response to the timer for the RRC re-establishment request (e.g., T301 specified in the 3GPP (registered trademark) specification) not being running and in response to the UE being in the RRC connected state, the UE may execute a re-establishment procedure. For a specific example, it will be described in the embodiment of FIG. 9 as follows.

[0085] In some embodiments, the UE may receive a PC5 unicast link release indication before receiving an RRC reconfiguration message for a path switch. In response to the timer for the RRC re-establishment request (e.g., T301) being running, the UE may execute at least one of entering the RRC idle state or stopping the timer for the RRC re-establishment request. For a specific example, it will be described in the embodiment of FIG. 10 as follows. In an embodiment, in response to the timer for the RRC re-establishment request (e.g., T301) being running, the UE may execute an action when entering the RRC idle state. For example, when entering the RRC idle state, the UE resets the MAC, stops all running timers except for timers T302, T320, T325, T330, T331, and T400, discards the UE non-active AS context if there is one, releases it if suspendConfig is configured, removes all of them if there are entries in VarConditionalReconfig, and K gNB key, S-K gNB key, S-K eNB key, K RRCenc key, K RRCint key, K UPint key, and K UPencIf keys exist, discard them, release all radio resources, including the release of the RLC entity, BAP entity, MAC configuration and related PDCP entities, and SDAP for all established RBs, indicate the release of the RRC connection to the upper layer along with the release reason, discard any segments of the stored segmented RRC messages, and / or enter the RRC idle state and perform cell selection.

[0086] In some embodiments, the PC5 unicast link release indication is indicated by the upper layer of the UE or received from the source relay node.

[0087] In some embodiments of the present disclosure, the UE receives another notification message (denoted as notification message #3 for simplicity) from the source relay node before receiving the RRC reconfiguration message for the path switch, the timer for the RRC re - establishment request (e.g., T301) is not running, the UE is in the RRC connected state, or the UE is not performing the re - establishment procedure and, in response to the UE being in the RRC connected state, may perform the re - establishment procedure. Specific examples will be described in the embodiment of FIG. 11 as follows.

[0088] In some embodiments of the present disclosure, at least one of notification message #1, notification message #2, or notification message #3 is (1) the occurrence of Uu RLF, (2) the reception of an RRC reconfiguration message including a configuration by synchronization, (3) cell reselection, (4) the occurrence of an RRC connection failure, (5) RRC connection rejection, (6) the expiration of the timer for the RRC setup request (e.g., T300), and (7) the occurrence of an RRC resume failure triggered by at least one of the above.

[0089] Those skilled in the art should understand that, without departing from the spirit and scope of the present disclosure, the order of operations in the exemplary procedure 500 can be changed, and some of the operations in the exemplary procedure 500 can be deleted or modified.

[0090] FIG. 6 shows a flowchart of an exemplary procedure 600 for initializing COT according to some embodiments of the present disclosure. Details described in all other embodiments of the present disclosure are applicable to the embodiment shown in FIG. 6. In some examples, the procedure can be performed by a network node (e.g., BS), such as BS 202 in FIG. 2.

[0091] In the exemplary procedure 600, in operation 601, the network node may send a request to the UE after the UE has completed the re-establishment procedure to the network node. The re-establishment procedure may be initiated by the UE in response to the occurrence of a failure while the UE is performing a path switch procedure from the source path to the target path, and in response to the source link between the UE and the source relay node not being available. The source path can be a "direct path between the UE and the network node" or an "indirect path between the UE and the network node associated with the source relay node". The target path can be "another direct path between the UE and the network node" or "another indirect path between the UE and the network node associated with the target relay node".

[0092] In operation 602, the UE may receive a response from the UE including failure-related information from the network node. In an embodiment, the failure-related information (1) receipt of a notification message from the target relay node by the UE, (2) receipt of a PC5 unicast link release instruction that may be indicated by the upper layer of the UE or received by the UE from the target relay node, or (3) detection of an RLF on the link between the UE and the target relay node indicates at least one of.

[0093] In some embodiments of the present disclosure, the path switching procedure is a DAPS path switching procedure. For a specific example, it will be described in the embodiment of FIG. 8 as follows.

[0094] It should be understood by those skilled in the art that, without departing from the spirit and scope of the present disclosure, the order of operations in the exemplary procedure 600 may be changed, and some of the operations in the exemplary procedure 600 may be deleted or modified.

[0095] In addition, some embodiments of the present disclosure provide an exemplary procedure executed by a relay node (e.g., a relay UE), e.g., UE101b in FIG. 1. Although described with respect to a relay node, it should be understood that other devices may be configured to perform similar procedures.

[0096] It should be understood by those skilled in the art that, without departing from the spirit and scope of the present disclosure, the order of operations in this exemplary procedure of the relay node may be changed, and some of the operations in this exemplary procedure may be deleted or modified. The details described in all other embodiments of this application, e.g., the embodiments of FIGS. 5 to 12, are applicable to this exemplary procedure. Further, the details described in this exemplary procedure are applicable to all embodiments of FIGS. 1 to 12.

[0097] In particular, in this exemplary procedure, the relay node may send at least one of a notification message or a PC5 unicast link release indication to the UE (e.g., UE201A in FIG. 2) while the UE is performing a path switch procedure from a source path to a target path. The source path may be a "direct path between the UE and the network node" or an "indirect path between the UE and the network node associated with the source relay node". The target path may be another "direct path between the UE and the network node" or another "indirect path between the UE and the network node associated with the target relay node". The relay node functions as a source relay node or a target relay node in different embodiments.

[0098] In some embodiments, the notification message is (1) the occurrence of Uu RLF at the relay node, (2) the reception of an RRC reconfiguration message including a configuration by synchronization at the relay node, (3) cell reselection of the relay node, (4) the occurrence of an RRC connection failure at the relay node, (5) RRC connection rejection for the relay node, (6) the expiration of a timer (e.g., T300) for an RRC setup request at the relay node, and (7) the occurrence of an RRC resume failure at the relay node triggered by at least one of.

[0099] In some embodiments, when the relay node functions as a source relay node, the relay node may receive measurement results from the UE and send the measurement results to the network node via an indirect path between the UE and the network node, and may send data (e.g., UP data and / or CP data) to the UE via a source link between the UE and the source relay node while the UE is performing a path switch procedure. For a specific example, it will be described in the embodiment of FIG. 7 as follows.

[0100] In some embodiments, when the relay node functions as the target relay node, the path switch procedure is a DAPS path switch procedure. For a specific example, it will be described in the embodiment of FIG. 8 as follows.

[0101] Some other embodiments of the present disclosure provide exemplary procedures executed by a UE, for example, UE101c in FIG. 1 or UE201A in FIG. 2. Although described with respect to the UE, it should be understood that other devices may be configured to execute similar procedures.

[0102] Those skilled in the art should understand that, without departing from the spirit and scope of the present disclosure, the order of operations in this exemplary procedure of the UE may be changed, and some of the operations in this exemplary procedure may be deleted or modified. The details described in all other embodiments of this application, for example, the embodiments of FIGS. 5 to 12, are applicable to this exemplary procedure. Further, the details described in this exemplary procedure are applicable to all embodiments of FIGS. 1 to 12.

[0103] In particular, in this exemplary procedure, the UE (for example, UE201A in FIG. 2) may access a network node (for example, BS202 in FIG. 2) via an indirect path through a relay node (for example, relay UE201B in FIG. 2). The UE may receive data (for example, UP data and / or CP data) from the relay node via the link between the UE and the relay node. The UE may receive a notification message (for example, notification message #1 described in the embodiment of FIG. 5) and / or a PC5 unicast link release instruction (for example, the PC5 unicast link release instruction described in the embodiment of FIG. 5).

[0104] In some embodiments, the notification message is received from the relay node. The PC5 unicast link release instruction is indicated by the upper layer of the UE or received from the relay node.

[0105] In some embodiments, in response to receiving a PC5 unicast link release indication, in response to a timer for an RRC re-establishment request not being running, and in response to the UE being in the RRC connected state, the UE may execute a re-establishment procedure.

[0106] In some embodiments, in response to receiving a PC5 unicast link release indication, in response to a timer (e.g., T301) for an RRC re-establishment request being running, the UE may enter the RRC idle state and / or may stop the timer for the RRC re-establishment request.

[0107] In some embodiments, when entering the RRC idle state, the UE may execute an action, e.g., as described in the embodiment of FIG. 5 or in option Y of operation 1014 in the embodiment of FIG. 11, the UE may execute an action that can be executed by the UE when entering the RRC idle state.

[0108] In some embodiments, in response to receiving a notification message, the UE (1) a timer (e.g., T301) for an RRC re-establishment request is not running and the UE is in the RRC connected state, or (2) the UE is not executing a re-establishment procedure and the UE is in the RRC connected state in response, may execute a re-establishment procedure.

[0109] In some embodiments, a notification message (e.g., a NotificationMessageSidelink message) is associated with one or more conditions in a relay UE. The one or more conditions are (1) the occurrence of a Uu RLF, (2) receiving an RRC reconfiguration message including a configuration by synchronization, (3) cell reselection, (4) the occurrence of an RRC connection failure, (5) RRC connection rejection, (6) Expiration of a timer for an RRC setup request (e.g., T300), and (7) Occurrence of an RRC resume failure may include at least one of the above.

[0110] FIG. 7 shows a flowchart of an exemplary procedure 700 for wireless communication according to some embodiments of the present disclosure. All the details described in the foregoing embodiments of the present disclosure are applicable to the embodiments shown in FIG. 7. The exemplary procedure 700 may be executed by a remote UE, a relay node (e.g., a relay UE), and a network node (e.g., a BS).

[0111] Referring to FIG. 7, in operation 711, a remote UE 701 (which may also be named as an L2 U2N remote UE, etc.) may access a serving network node, e.g., a BS 703, via an indirect path. The indirect path may be associated with a relay UE (which may also be named as an L2 U2N relay UE or a source relay UE, etc.), e.g., a relay UE 702A. In some embodiments, the remote UE 701 remains in the RRC connected state. In some embodiments, the remote UE 701 may report measurement results based on the configuration from the BS 703. The measurement results may include measurement results regarding a cell or a candidate relay UE, e.g., a relay UE 702B.

[0112] In operation 712, the BS 703 may determine to switch the remote UE 701 to a direct Uu path or another indirect path.

[0113] In operation 713, the BS 703 may send an RRC reconfiguration message to the remote UE 701. In some embodiments, after receiving the RRC reconfiguration message with a path switch configuration from the BS 703, the remote UE 701 may stop UP and / or CP transmission via the relay UE 702A.

[0114] In operation 714 (which is optional and marked with a dotted line as shown in FIG. 7), after receiving an RRC reconfiguration message having a path switch configuration from BS 703, the remote UE 701 may stop UP and / or CP reception via relay UE 702A. In some embodiments, the remote UE 701 may continue to maintain the PC5 link between the remote UE 701 and the relay UE 702A for data reception.

[0115] In operation 715, after the remote UE 701 receives an RRC reconfiguration message for a path switch, the remote UE 701 may start a timer for the path switch (e.g., T304 specified in the 3GPP (registered trademark) specification). In some embodiments, when the target node is one cell, the remote UE 701 starts a timer for the path switch (e.g., T304) and performs a random access (RA) procedure towards the target cell. In some other embodiments, when the target node is one relay UE, in operation 715A (which is optional and marked with a dotted line as shown in FIG. 7), the remote UE 701 starts a timer related to the path addition procedure (e.g., T420 specified in the 3GPP (registered trademark) specification) and establishes a PC5 RRC connection towards the target relay UE 702B.

[0116] In operation 716, the remote UE 701 receives a notification message (e.g., NotificationMessageSidelink message) or a PC5 unicast link release indication from the source relay UE 702A. For example, the notification message is (1) the occurrence of Uu RLF in relay UE 702A, (2) the reception of an RRC reconfiguration message including a configuration by synchronization in relay UE 702A, (3) the cell reselection of relay UE 702A, (4) the occurrence of an RRC connection failure in relay UE 702A, (5) the RRC connection rejection for relay UE 702A, (6) Expiration of a timer (e.g., T300) for an RRC setup request in relay UE 702A, and (7) Occurrence of an RRC resume failure in relay UE 702A can be triggered by at least one of the following.

[0117] In some embodiments, a notification message (e.g., a NotificationMessageSidelink message) may include a type indication (e.g., "indicationType") that may indicate that the notification message is due to one of relay Uu RLF, relay handover, relay cell reselection, and / or relay connection failure.

[0118] In operation 717 (which is optional and marked with a dotted line as shown in FIG. 7), in different embodiments, the following three options, namely, Option 1, Option 2, and Option 3, may exist. (1) Option 1: In some embodiments, remote UE 701 may ignore a notification message or a PC5 unicast link release indication from source relay UE 702A when a timer for path switch (e.g., T304) is running. (2) Option 2: In some further embodiments, when remote UE 701 receives a notification message or a PC5 unicast link release indication from source relay UE 702A when a timer for path switch (e.g., T304) is running, it may stop receiving CP and / or UP data. (3) Option 3: In some other embodiments, when remote UE 701 receives a notification message or a PC5 unicast link release indication from source relay UE 702A when a timer for path switch (e.g., T304) is running, it may release the PC5 RRC connection.

[0119] In operation 718, when the remote UE 701 successfully completes the RA procedure to the BS 703 or sends an RRC reconfiguration complete message to the BS 703, it may stop a timer (e.g., T304) for path switching.

[0120] In operation 719, the BS 703 may send an RRC reconfiguration message to the relay UE 702A to reconfigure the connection between the relay UE 702A and the BS 703. The RRC reconfiguration message to the relay UE 702A can be sent at any point after operation 713, based on the implementation of the BS 703 (e.g., to release the Uu and PC5 relay RLC channel configurations for relaying and the bearer mapping configuration related to the remote UE 701). For example, in some embodiments, operation 719 in which the RRC reconfiguration message is sent is after operation 713 and before operation 718.

[0121] In operation 720, either the relay UE 702A or the remote UE 701 may release the PC5 RRC connection between the remote UE 701 and the relay UE 702A and may instruct the upper layer of the remote UE 701 to release the PC5 RRC connection (i.e., the PC5 unicast link). Then, the data path between the remote UE 701 and the BS 703 is switched from the indirect path to a target relay node, e.g., the relay UE 702B.

[0122] FIG. 8 shows a flowchart of an exemplary procedure 800 for wireless communication according to some embodiments of the present disclosure. All of the details described in the foregoing embodiments of the present disclosure are applicable to the embodiments shown in FIG. 8. The exemplary procedure 800 may be performed by a remote UE, a relay node (e.g., a relay UE), and a network node (e.g., a BS).

[0123] Referring to FIG. 8, in operation 811, a remote UE 801 (which may also be named as an L2 U2N remote UE etc.) accesses a serving network node, e.g., BS 804, via an indirect path. The indirect path is associated with a relay UE (which may also be named as an L2 U2N relay UE or a source relay UE etc.), e.g., source relay UE 802. In some embodiments, the remote UE 801 remains in the RRC connected state. In some embodiments, the remote UE 801 reports measurement results based on the configuration from BS 804. The measurement results may include measurement results regarding a cell or a candidate relay UE, e.g., target relay UE 803.

[0124] In operation 812, BS 804 determines to switch the remote UE 801 to a direct Uu path or another indirect path.

[0125] In operation 813, BS 804 sends an RRC reconfiguration message for a path switch, which includes, e.g., a configuration related to the DAPS procedure, to the remote UE 801. In some embodiments, the remote UE 801 may continue to maintain the source PC5 link between the remote UE 801 and the source relay UE 802 for data reception or data transmission.

[0126] In operation 814, after the remote UE 801 receives the RRC reconfiguration message for the path switch, the remote UE 801 may start a timer (e.g., T304) for the path switch.

[0127] In operation 815, when the target node is a relay UE, e.g., target relay UE 803, the remote UE 801 starts a timer (e.g., T420) related to the path addition procedure and establishes a PC5 RRC connection towards the target relay UE 803.

[0128] In operation 816, in some embodiments, the remote UE 801 may receive a notification message (e.g., a NotificationMessageSidelink message) or a PC5 unicast link release indication from the target relay UE 803, or in some other embodiments, the remote UE 801 may detect an RLF on the target PC5 link between the remote UE 801 and the target relay UE 803. For example, the notification message may be (1) the occurrence of a Uu RLF in the target relay UE 803, (2) the reception of an RRC reconfiguration message including a configuration by synchronization in the target relay UE 803, (3) the cell reselection of the target relay UE 803, (4) the occurrence of an RRC connection failure in the target relay UE 803, (5) an RRC connection rejection for the target relay UE 803, (6) the expiration of a timer (e.g., T300) for an RRC setup request in the target relay UE 803, and (7) the occurrence of an RRC resume failure in the target relay UE 803 may be triggered by at least one of them.

[0129] In some embodiments, the notification message (e.g., a NotificationMessageSidelink message) may include a type indication (e.g., "indicationType") that may indicate that the notification message is due to one of a relay Uu RLF, a relay handover, a relay cell reselection, and / or a relay connection failure.

[0130] After operation 816, in different embodiments, there may be three options below, namely, Option A (operations 817A and 818A are executed), Option B (operations 817B, 818B, and 819B are executed), and Option C (operations 817A, 818B, and 819B are executed).

[0131] Option A: In operation 817A, if the source link between the remote UE 801 and the source relay UE 802 is still available, the remote UE 801 may return to (fall back to) the source link. In operation 818A, the remote UE 801 may initiate a failure information procedure to report failure-related information related to the DAPS path switch procedure. For example, the failure-related information may include at least one of reception of a notification message, reception of a PC5 unicast link release indication, or detection of an RLF on the PC5 link between the remote UE 801 and the target relay UE 803.

[0132] Option B: In operation 817B, if the source link is not available, the remote UE 801 executes a re-establishment procedure to the BS 804. In operation 818B, after successfully completing the re-establishment procedure, the remote UE 801 may receive a request (e.g., a UE information request message) from the BS 804. In operation 819B, the remote UE 801 may send a response (e.g., a UE information response message) including failure-related information to the BS 804 for the purpose of self-optimization (SON). For example, the failure-related information may include at least one of reception of a notification message, reception of a PC5 unicast link release indication, or detection of an RLF on the PC5 link between the remote UE 801 and the target relay UE 803.

[0133] Option C: In operation 817A, if the source link between the remote UE 801 and the source relay UE 802 is still available, the remote UE 801 can return to (fall back to) the source link. In operation 818B, after returning to the source link, the remote UE 801 can receive a request (e.g., a UE information request message) from the BS 804. In operation 819B, the remote UE 801 can send a response (e.g., a UE information response message) including fault-related information to the BS 804 for the purpose of self-optimization (SON). For example, the fault-related information can include at least one of the reception of a notification message, or the reception of a PC5 unicast link release indication, or the detection of an RLF on the PC5 link between the remote UE 801 and the target relay UE 803.

[0134] FIG. 9 shows a flowchart of an exemplary procedure 900 for wireless communication according to some embodiments of the present disclosure. The details described in all of the foregoing embodiments of the present disclosure are applicable to the embodiments shown in FIG. 9. The exemplary procedure 900 can be executed by a remote UE, a relay node (e.g., a relay UE), and a network node (e.g., a BS).

[0135] Referring to FIG. 9, in operation 911, a remote UE 901 (which may also be named, for example, an L2 U2N remote UE) accesses a serving network node, e.g., a BS 903, via an indirect path. The indirect path is associated with a relay UE (which may also be named, for example, an L2 U2N relay UE), e.g., a relay UE 902. In some embodiments, if the remote UE 901 remains in the RRC connected state, the remote UE 901 reports measurement results based on the configuration from the BS 903. The measurement results can include measurement results regarding cells or candidate relay UEs.

[0136] In operation 912, relay UE 902 sends a PC5 unicast link release indication to the connected remote UE 901. In some embodiments, relay UE 902 may send a PC5 unicast link release indication to remote UE 901 when relay UE 902 declares RLF on the Uu link. In some other embodiments, relay UE 902 may send a PC5 unicast link release indication to remote UE 901 when relay UE 902 receives an RRC reconfiguration message including a synchronization-based configuration from BS 903.

[0137] In some embodiments, in operation 912A (which is optional and marked with a dotted line as shown in FIG. 9), after the upper layer of remote UE 901 receives a PC5 unicast link release indication from relay UE 902, the upper layer indicates the PC5 unicast link release indication to the AS layer of remote UE 901. When the PC5 unicast link release indication is indicated by the upper layer in remote UE 901, remote UE 901 will start the re-establishment procedure to BS 903 if the timer for RRC re-establishment request (e.g., T301) is not running.

[0138] In operation 913, after remote UE 901 receives a PC5 unicast link release indication from the relay UE, remote UE 901 executes the re-establishment procedure to BS 903.

[0139] FIG. 10 shows a flowchart of an exemplary procedure 1000 for wireless communication according to some embodiments of the present disclosure. All the details described in all of the foregoing embodiments of the present disclosure are applicable to the embodiments shown in FIG. 10. The exemplary procedure 1000 may be executed by a remote UE, a relay node (e.g., relay UE), and a network node (e.g., BS).

[0140] Referring to FIG. 10, in operation 1011, a remote UE 1001 (which may also be named, for example, as an L2 U2N remote UE) accesses a serving network node, for example, BS 1003, via an indirect path. The indirect path is associated with a relay UE (which may also be named, for example, as an L2 U2N relay UE), for example, relay UE 1002. In some embodiments, when the remote UE 1001 remains in the RRC connected state, the remote UE 1001 reports measurement results based on the configuration from BS 1003. The measurement results may include measurement results regarding cells or candidate relay UEs.

[0141] In operation 1012, the remote UE 1001 sends a re-establishment request and starts a timer (e.g., T301) for the RRC re-establishment request when sending the re-establishment request.

[0142] In operation 1013, the relay UE 1002 sends a PC5 unicast link release indication to the connected remote UE 1001. In some embodiments, the relay UE 1002 may send a PC5 unicast link release indication to the remote UE 1001 when the relay UE 1002 declares an RLF on the Uu link. In some embodiments, the relay UE 1002 may send a PC5 unicast link release indication to the remote UE 1001 when the relay UE 1002 receives an RRC reconfiguration message including a configuration by synchronization from BS 1003. In some embodiments, the remote UE 1001 receives a PC5 unicast link release indication from the relay UE 1002 when the remote UE 1001 executes a re-establishment procedure.

[0143] In operation 1014, in different embodiments, there may be the following two options, namely, option X and option Y.

[0144] Option X: In some embodiments, when a PC5 unicast link release indication is indicated by the upper layer in the remote UE 1001, if the remote UE 1001 is in the RRC connected state while the timer for the RRC re-establishment request (e.g., T301) is running, the remote UE 1001 may enter the RRC idle state and / or the remote UE 1001 may stop the timer for the RRC re-establishment request (e.g., T301).

[0145] Option Y: In some embodiments, when a PC5 unicast link release indication is indicated by the upper layer in the remote UE 1001, if the remote UE 1001 is in the RRC connected state while the timer for the RRC re-establishment request (e.g., T301) is running, the remote UE 1001 performs an action when it enters the RRC idle state. For example, when entering the RRC idle state, the UE resets the MAC, stops all running timers except timers T302, T320, T325, T330, T331, and T400, discards the UE inactive AS context if there is one, releases suspendConfig if it is configured, removes all entries if they exist in VarConditionalReconfig, K gNB Key, S-K gNB Key, S-K eNB Key, K RRCenc Key, K RRCint Key, K UPint Key, and K UPenc discards them if they exist, releases all radio resources including the release of the RLC entity, BAP entity, MAC configuration and related PDCP entities, and SDAP for all established RBs, indicates the release of the RRC connection to the upper layer along with the release reason, discards any segments of the stored segmented RRC messages, and / or enters the RRC idle state and may perform cell selection.

[0146] FIG. 11 shows a flowchart of an exemplary procedure 1100 for wireless communication according to some embodiments of the present disclosure. The details described in all of the foregoing embodiments of the present disclosure are applicable to the embodiments shown in FIG. 11. The exemplary procedure 1100 may be performed by a remote UE, a relay node (e.g., a relay UE), and a network node (e.g., a BS).

[0147] Referring to FIG. 11, in operation 1111, a remote UE 1101 (which may be named, for example, as an L2 U2N remote UE) accesses a serving network node, e.g., a BS 1103, via an indirect path. The indirect path is associated with a relay UE (which may be named, for example, as an L2 U2N relay UE), e.g., a relay UE 1102. In some embodiments, when the remote UE 1101 remains in the RRC connected state, the remote UE 1101 reports measurement results based on the configuration from the BS 1103. The measurement results may include measurement results regarding a cell or a candidate relay UE.

[0148] In operation 1112, the relay UE 1102 may send a notification message (e.g., a NotificationMessageSidelink message) to the remote UE 1101 upon receiving an RRC reconfiguration message including Uu RLF or a configuration by synchronization. For example, the notification message may be (1) the occurrence of Uu RLF in the relay UE 1102, (2) the reception of an RRC reconfiguration message including a configuration by synchronization in the relay UE 1102, (3) the cell reselection of the relay UE 1102, (4) the occurrence of an RRC connection failure in the relay UE 1102, (5) the RRC connection rejection for the relay UE 1102, (6) the expiration of a timer (e.g., T300) for an RRC setup request in the relay UE 1102, and (7) the occurrence of an RRC resume failure in the relay UE 1102 triggered by at least one of the above.

[0149] In some embodiments, when relay UE 1102 declares RLF on the Uu link, relay UE 1102 sends a notification message due to the Uu RLF.

[0150] In some embodiments, when relay UE 1102 receives an RRC reconfiguration message including a configuration by synchronization, relay UE 1102 sends a notification message.

[0151] In some embodiments, the notification message (e.g., NotificationMessageSidelink message) may include a type indication (e.g., "indicationType") indicating that the notification message is due to one of relay Uu RLF, relay handover, relay cell reselection, and / or relay connection failure.

[0152] In operation 1113, in different embodiments, the following two options, i.e., Option I and Option II, may exist.

[0153] Option I: In some embodiments, after remote UE 1101 receives a notification message from relay UE 1102, if remote UE 1101 is in the RRC connected state and a timer (e.g., T301) for RRC re-establishment request is not running, remote UE 1101 will start the re-establishment procedure to BS 1103.

[0154] Option II: In some embodiments, after remote UE 1101 receives a notification message from the relay UE, if remote UE 1101 is in the RRC connected state and remote UE 1101 is not executing the re-establishment procedure, remote UE 1101 will start the re-establishment procedure to BS 1103.

[0155] The details described in all other embodiments of this application (e.g., details regarding how to handle connections in the L2 U2N relay case) are applicable to the embodiments of any of FIGS. 7 to 11. Further, the details described in any of the embodiments of FIGS. 7 to 11 are applicable to all embodiments of FIGS. 1 to 6 and FIG. 12. It should be understood by those skilled in the art that, without departing from the gist and scope of the present disclosure, the order of operations in the exemplary procedures in any of the embodiments of FIGS. 7 to 11 can be changed, and some of the operations in the exemplary procedures in any of the embodiments of FIGS. 7 to 11 can be deleted or modified.

[0156] FIG. 12 shows a block diagram of an exemplary apparatus 1200 according to some embodiments of the present disclosure.

[0157] As shown in FIG. 12, the apparatus 1200 may include at least one processor 1206 and at least one transceiver 1202 coupled to the processor 1206. The apparatus 1200 may be a UE, a relay node (e.g., a relay UE), or a network node (e.g., a BS).

[0158] In this figure, elements such as at least one transceiver 1202 and processor 1206 are described in the singular, but the plural is assumed unless a limitation to the singular is explicitly stated. In some embodiments of this application, the transceiver 1202 may be divided into two devices such as a receiving circuit and a transmitting circuit. In some embodiments of this application, the apparatus 1200 may further include an input device, a memory, and / or other components.

[0159] In some embodiments of the present application, the apparatus 1200 may be a UE. The transceiver 1202 and the processor 1206 may interact with each other to perform operations related to the UE described in FIGS. 1 to 11. In some embodiments of the present application, the apparatus 1200 may be a relay node (e.g., a relay UE). The transceiver 1202 and the processor 1206 may interact with each other to perform operations related to the relay node described in FIGS. 1 to 11. In some embodiments of the present application, the apparatus 1200 may be a network node (e.g., a BS). The transceiver 1202 and the processor 1206 may interact with each other to perform operations related to the network node described in FIGS. 1 to 11.

[0160] In some embodiments of the present application, the apparatus 1200 may further include at least one non-transitory computer-readable medium. For example, in some embodiments of the present disclosure, the non-transitory computer-readable medium may store computer-executable instructions for causing the processor 1206 to implement the methods related to the UE described above. For example, when the computer-executable instructions are executed, they cause the processor 1206 that interacts with the transceiver 1202 to perform the operations related to the UE described in FIGS. 1 to 11.

[0161] In some embodiments of the present disclosure, the non-transitory computer-readable medium may store computer-executable instructions for causing the processor 1206 to implement the methods related to the relay node (e.g., a relay UE) described above. For example, when the computer-executable instructions are executed, they cause the processor 1206 that interacts with the transceiver 1202 to perform the operations related to the relay node described in FIGS. 1 to 11.

[0162] In some embodiments of the present disclosure, the non-transitory computer-readable medium may store computer-executable instructions that cause the processor 1206 to perform the methods described above for the network nodes (e.g., BS). For example, when executed, the computer-executable instructions cause the processor 1206, which interacts with the transceiver 1202, to perform the operations related to the network nodes described in FIGS. 1-11.

[0163] Those skilled in the art will understand that the operations or steps of the methods described in connection with the aspects disclosed herein may be embodied directly in hardware, in software modules executed by a processor, or in a combination of the two. Software modules may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. Additionally, in some aspects, the operations or steps of the methods may exist as one or any combination or set of codes and / or instructions on a non-transitory computer-readable medium that may be incorporated into a computer program product.

[0164] Although the present disclosure has been described with reference to its specific embodiments, it will be apparent to those skilled in the art that many alternatives, modifications, and variations are possible. For example, the various components of the embodiments may be exchanged, added, or replaced in other embodiments. Also, not all elements of each figure are necessary for the operation of the disclosed embodiments. For example, those skilled in the art of the disclosed embodiments can create and use the teachings of the present disclosure by simply adopting the elements of the independent claims. Accordingly, the embodiments of the present disclosure as described herein are intended to be illustrative and not limiting. Various changes may be made without departing from the spirit and scope of the present disclosure.

[0165] In this document, the terms "handover" and "pass switch" may be used interchangeably. Terms such as "include", "including", or any other variant are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements does not include only those elements but may also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Elements preceded by "a", "an", etc. do not, without further limitation, preclude the existence of additional identical elements in a process, method, article, or apparatus that includes the element. Also, the term "another" is defined as at least second and later. Terms such as "having" used herein are defined as "including". Expressions such as "A and / or B" or "at least one of A and B" may include any combination of the words listed with the expression. For example, the expression "A and / or B" or "at least one of A and B" may include A, B, or both A and B. Expressions such as "first", "second", etc. are used only to clearly describe embodiments of this application and are not used to limit the content of this application.

Explanation of Signs

[0166] 100 Wireless communication system 101A UE 101B UE 101C UE 102 BS 103 BS 200 Wireless communication system 201A UE 201B UE 202 BS 300 Procedure 301 UE 302 Relay node 311 Operation 401 UE 402 BS 412 Operation 701 UE, Remote UE 702A UE, Relay UE, Source Relay UE 702B UE, Relay UE 703 BS 801 Remote UE 802 Source Relay UE 803 Target Relay UE 804 BS 901 Remote UE 902 Relay UE 903 BS 1001 Remote UE 1002 Relay UE 1003 BS 1101 Remote UE 1102 Relay UE 1103 BS 1200 Device 1202 Transceiver 1206 Processor

Claims

1. A user equipment (UE) comprising a transceiver and a processor coupled to the transceiver, wherein the processor is configured to: access a network node via a first indirect path associated with a source relay node; in response to receiving a radio resource control (RRC) reconfiguration message for a path switch from the network node via the transceiver, execute a path switch procedure from the first indirect path to a target path, where the target path is either a direct path between the UE and the network node or a second indirect path between the UE and the network node associated with a target relay node; and during the path switch procedure, receive data from the source relay node via the transceiver via a source link between the UE and the source relay node. The user equipment (UE) is configured as described above.

2. The UE according to claim 1, wherein the processor of the UE is configured to stop receiving at least one of user plane (UP) data or control plane (CP) data from the source relay node via the transceiver in response to receiving the RRC reconfiguration message for the path switch.

3. The UE according to claim 1, wherein the processor of the UE is configured to: receive a first notification message or a PC5 unicast link release indication from the source relay node during the path switch procedure; in response to receiving the first notification message or the PC5 unicast link release indication and in response to a timer for the path switch being running, ignore the first notification message or the PC5 unicast link release indication, stop receiving at least one of UP data or CP data from the source relay node, or release the source link between the UE and the source relay node, and execute at least one of the above.

4. ​ ​ ​ The UE according to claim 3, wherein the first notification message is received from the source relay node via the transceiver, and the PC5 unicast link release instruction is indicated by an upper layer of the UE or received from the source relay node via the transceiver.

5. In response to the path switch procedure being a dual active protocol stack (DAPS) path switch procedure, the processor of the UE receives a second notification message from the target relay node via the transceiver, receives a PC5 unicast link release instruction, wherein the PC5 unicast link release instruction is indicated by an upper layer of the UE or received from the target relay node via the transceiver, or detects a radio link failure (RLF) on a link between the UE and the target relay node The UE according to claim 1, configured to perform at least one of the above.

6. The processor of the UE returns to the source link in response to the source link being available, or transmits fault-related information to the network node via the transceiver The UE according to claim 5, configured to perform at least one of the above.

7. The processor of the UE performs a re-establishment procedure in response to the source link not being available, receives a request from the network node via the transceiver after completing the re-establishment procedure, and transmits a response including fault-related information to the network node via the transceiver The UE according to claim 5, configured to perform the above.

8. The fault-related information indicates at least one of receiving the second notification message from the target relay node, receiving the PC5 unicast link release instruction, or detecting the RLF on the link between the UE and the target relay node The UE according to claim 6 or 7.

9. The processor of the UE receives a PC5 unicast link release instruction before receiving the RRC reconfiguration message for the path switch, In response to the timer for the RRC re - establishment request not being running and in response to the UE being in the RRC connected state, execute the re - establishment procedure The UE according to claim 1, configured to perform the above.

10. The processor of the UE is configured to Receive a PC5 unicast link release indication before receiving the RRC re - configuration message for the path switch In response to the timer for the RRC re - establishment request being running Enter the RRC idle state, or Stop the timer for the RRC re - establishment request Perform at least one of the above The UE according to claim 1, configured to perform the above.

11. The UE according to claim 10, wherein the processor of the UE is further configured to perform an action when entering the RRC idle state in response to the timer for the RRC re - establishment request being running.

12. The UE according to any one of claims 9 to 11, wherein the PC5 unicast link release indication is indicated by the upper layer of the UE or received from the source relay node via the transceiver.

13. The processor of the UE is configured to Receive a third notification message from the source relay node via the transceiver before receiving the RRC re - configuration message for the path switch Execute the re - establishment procedure, which is In response to the timer for the RRC re - establishment request not being running and the UE being in the RRC connected state, or In response to the UE not executing the re - establishment procedure and the UE being in the RRC connected state Execute the re - establishment procedure The UE according to claim 1, configured to perform the above.

14. At least one of the first notification message, the second notification message, or the third notification message is Occurrence of Uu RLF Receiving an RRC re - configuration message including a configuration by synchronization Cell reselection Occurrence of an RRC connection failure RRC connection rejection Expiration of the timer for the RRC setup request, and Occurrence of an RRC resume failure The UE according to any one of claims 3 to 8 and 13, triggered by at least one of the above.

15. A transceiver, A processor coupled to the transceiver A relay node comprising, wherein the processor is configured to transmit at least one of a notification message or a PC5 unicast link release instruction to the UE via the transceiver while the UE is executing a path switch procedure from a source path to a target path, wherein the source path is a first direct path between the UE and a network node or a first indirect path between the UE and the network node associated with the source relay node, wherein the target path is a second direct path between the UE and a network node or a second indirect path between the UE and the network node associated with the target relay node, wherein the relay node functions as the source relay node or the target relay node, Relay node.

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