Method and apparatus for relay path establishment and change in multi-path case

Abstract

The embodiment of the invention relates to a method and equipment for relay path establishment and relay change under the condition of multiple paths. In accordance with an embodiment of the present application, a user equipment (UE) includes a processor and a transceiver coupled to the processor; and the processor is configured to: receive, via the transceiver, a radio resource control (RRC) reconfiguration message for path addition from a network, wherein the RRC reconfiguration message for path addition includes an identifier (ID) of a relay UE; upon receiving the RRC reconfiguration message, starting a timer for a path addition procedure; and receiving a message associated with a link between the relay UE and the network.

Description

Technical Field

[0001] Embodiments of the present application generally relate to wireless communication technology, and more particularly to methods and apparatus for relay path establishment and relay change in multi-path situations. Background Art

[0002] Vehicle-to-everything (V2X) has been introduced into 5G wireless communication technology. In terms of the channel structure of V2X communication, the direct link between two user equipments (UEs) is called a side link. Side link is a long-term evolution (LTE) feature introduced in 3GPP Release 12, and enables direct communication between UEs that are close to each other, and data does not need to pass through a base station (BS) or a core network.

[0003] In the 3rd Generation Partnership Project (3GPP), the deployment of relay nodes (RN) in wireless communication systems is promoted. One goal of deploying RN is to enhance the coverage area of ​​the BS by improving the throughput of user equipment (UE) located within the coverage area or far away from the BS (which may result in relatively low signal quality). In some cases, RN may also be named as relay UE. A 3GPP 5G sidelink system including a relay UE may be named as a sidelink relay system.

[0004] Currently, in 3GPP 5G New Radio (NR) systems or the like, details on relay path establishment and relay change in a multipath situation have not been specifically discussed. A multipath situation refers to a diameter path and / or an indirect path via a relay UE. Multipath may also be named "multiple paths" or the like. Summary of the invention

[0005] Some embodiments of the present application provide a user equipment (UE). The UE includes a processor and a transceiver coupled to the processor; and the processor is configured to: receive a first radio resource control (RRC) reconfiguration message for path addition from a network via the transceiver, wherein the first RRC reconfiguration message for path addition includes an identifier (ID) of a relay UE; start a timer for a path addition procedure upon receiving the first RRC reconfiguration message; and receive a first message associated with a link between the relay UE and the network.

[0006] In some embodiments, the first message is one of: a notification message received by the UE from the relay UE via the transceiver; and a PC5 unicast link release message.

[0007] In some embodiments, the notification message indicates at least one of: Uu radio link failure (RLF) between the relay UE and the network; cell reselection of the relay UE; handover of the relay UE; RRC connection failure of the relay UE; RRC connection reject message received by the relay UE; expiration of a timer for RRC setup request at the relay UE; or RRC recovery failure of the relay UE.

[0008] In some embodiments, the processor of the UE is configured to stop the timer associated with the path addition procedure upon receiving the first message.

[0009] In some embodiments, the processor of the UE is configured to: determine whether a cell change or a base station (BS) change of the relay UE occurs; in response to determining that the cell change or the BS change of the relay UE occurs, release the PC5 link between the relay UE and the UE; or in response to determining that the cell change or the BS change of the relay UE does not occur, continue to establish and maintain the PC5 link.

[0010] In some embodiments, the processor of the UE is configured to transmit an indication to the network via the transceiver indicating that the PC5 link has been released or not released. In an embodiment, the indication is transmitted upon receiving the first message. In another embodiment, the indication is transmitted upon stopping the timer for the path addition procedure.

[0011] In some embodiments, the processor of the UE is configured to: start a fault information program upon receiving the first message; and transmit a fault message including a fault cause to the network via the transceiver, wherein the fault cause is one of the following: receiving a notification message due to Uu RLF between the relay UE and the network; receiving a notification message due to cell reselection of the relay UE; receiving a notification message due to switching of the relay UE; receiving a notification message due to RRC connection failure of the relay UE; receiving a notification message due to an RRC connection rejection message received by the relay UE; receiving a notification message due to expiration of a timer for an RRC setup request at the relay UE; receiving a notification message due to an RRC recovery failure of the relay UE; or receiving a PC5 unicast link release message indicated by an upper layer of the UE.

[0012] In some embodiments, the processor of the UE is configured to: store configuration information including the ID of the relay UE in response to the UE maintaining the PC5 link between the relay UE and the UE after receiving the first message; receive a second RRC reconfiguration message including the ID of the relay UE for the path addition procedure; and use the stored configuration information to re-add the path between the relay UE and the network.

[0013] In some embodiments, the processor of the UE is configured to transmit information about intra-cell path addition or intra-BS path addition to the relay UE via the transceiver.

[0014] In some embodiments, the processor of the UE is configured to receive, from the relay UE via the transceiver, a PC5 unicast link release message or a rejection message generated due to occurrence of a cell change or a BS change of the relay UE.

[0015] Some embodiments of the present application also provide a UE. The UE includes a processor and a transceiver coupled to the processor; and the processor is configured to: access a serving cell of a network via multiple paths, wherein the multiple paths include at least one of a direct path and a first indirect path via a source relay UE; receive from the serving cell via the transceiver one of the following: a radio resource control (RRC) reconfiguration message for a path switching procedure from the first indirect path to a second indirect path via a target relay UE; a release message without a suspension configuration; and a release message including the suspension configuration; and release the first indirect path upon receiving the release message without the suspension configuration.

[0016] In some embodiments, upon receiving the RRC reconfiguration message, the processor of the UE is configured to: initiate the path switching procedure to the second indirect path via the target relay UE; and start a timer for the path switching procedure.

[0017] In some embodiments, the processor of the UE is configured to: transmit an RRC reconfiguration complete message; and stop the timer for the path switch procedure when transmitting the RRC reconfiguration complete message.

[0018] In some embodiments, the processor of the UE is configured to transmit failure information to the network in response to expiration of the timer for the path switch procedure.

[0019] In some embodiments, the processor of the UE is configured to fall back to access the serving cell via the first indirect path in response to expiration of the timer for the path switch procedure and the first indirect path being available.

[0020] In some embodiments, the processor of the UE is configured to: maintain the first indirect path in response to receiving the RRC reconfiguration message for the path switching procedure; receive a first message or detect a radio link failure (RLF) on the PC5 link between the UE and the source relay UE in response to the timer for the path switching procedure being running; and release the first indirect path.

[0021] In some embodiments, the first message is one of: a notification message received by the UE from the source relay UE via the transceiver; and a PC5 unicast link release message.

[0022] In some embodiments, the notification message indicates at least one of: Uu radio link failure (RLF) between the source relay UE and the network; cell reselection of the source relay UE; handover of the source relay UE; RRC connection failure of the source relay UE; RRC connection reject message received by the source relay UE; expiration of a timer for RRC setup request at the source relay UE; or RRC recovery failure of the source relay UE.

[0023] In some embodiments, upon receiving the release message including the suspension configuration, the processor of the UE is configured to: release the first indirect path; and transition to an RRC inactive state.

[0024] In some embodiments, upon receiving the release message including the suspension configuration, the processor of the UE is configured to: store configuration information related to the first indirect path; and release the first indirect path in response to initiating resumption of connection between the UE and the source relay UE.

[0025] Some embodiments of the present application also provide a relay UE. The relay UE includes a processor and a transceiver coupled to the processor; and the processor is configured to transmit a first message associated with a link between the relay UE and a network to a remote UE via the transceiver, wherein the first message is one of the following: a notification message; a PC5 unicast link release message; and a rejection message generated due to the occurrence of a cell change or a base station (BS) change.

[0026] In some embodiments, the relay UE is a target relay UE during a path addition procedure.

[0027] In some embodiments, the notification message indicates at least one of: Uu radio link failure (RLF) between the target relay UE and the network; cell reselection of the target relay UE; handover of the target relay UE; RRC connection failure of the target relay UE; RRC connection reject message received by the target relay UE; expiration of a timer for RRC setup request at the target relay UE; or RRC recovery failure of the target relay UE.

[0028] In some embodiments, the processor of the target relay UE is configured to receive information about intra-cell path addition or intra-BS path addition from the remote UE via the transceiver.

[0029] In some embodiments, during the path addition procedure, the processor of the target relay UE is configured to: in response to the target relay UE being in an RRC idle state or an inactive state, not change from a first cell to a second cell or from a first BS to a second BS during a cell selection or reselection operation, or in response to the target relay UE changing to the second cell or the second BS, not enter an RRC connected state.

[0030] In some embodiments, in response to the target relay UE changing to the second cell or the second BS, the PC5 unicast link release message or the rejection message is transmitted by the target relay UE.

[0031] In some embodiments, the relay UE is a source relay UE during a path switching procedure from a first indirect path to a second indirect path, wherein the first indirect path is between the remote UE and the network via the source relay UE, and wherein the second indirect path is between the remote UE and the network via a second target relay UE.

[0032] In some embodiments, the notification message indicates at least one of: Uu radio link failure (RLF) between the source relay UE and the network; cell reselection of the source relay UE; handover of the source relay UE; RRC connection failure of the source relay UE; RRC connection reject message received by the source relay UE; expiration of a timer for RRC setup request at the source relay UE; or RRC recovery failure of the source relay UE.

[0033] Some embodiments of the present application provide a method that can be performed by a UE. The method includes: receiving a first radio resource control (RRC) reconfiguration message for path addition from a network, wherein the first RRC reconfiguration message for path addition includes an identifier (ID) of a relay UE; starting a timer for a path addition procedure upon receiving the first RRC reconfiguration message; and receiving a first message associated with a link between the relay UE and the network.

[0034] Some embodiments of the present application provide a method that can be performed by a relay UE. The method includes: accessing a serving cell of a network via multiple paths, wherein the multiple paths include at least one of a direct path and a first indirect path via a source relay UE; receiving from the serving cell one of: a radio resource control (RRC) reconfiguration message for a path switching procedure from the first indirect path to a second indirect path via a target relay UE; a release message without a suspension configuration; and a release message including the suspension configuration; and releasing the first indirect path upon receiving the release message without the suspension configuration.

[0035] Some embodiments of the present application provide a method that can be performed by a UE. The method includes: transmitting a first message associated with a link between the relay UE and a network to a remote UE, wherein the first message is one of: a notification message; a PC5 unicast link release message; and a rejection message generated due to the occurrence of a cell change or a base station (BS) change.

[0036] Some embodiments of the present application also provide an apparatus for wireless communication. The apparatus includes: a non-transitory computer-readable medium having computer-executable instructions stored thereon; a receiving circuit system; a transmitting circuit system; and a processor coupled to the non-transitory computer-readable medium, the receiving circuit system, and the transmitting circuit system, wherein the computer-executable instructions cause the processor to implement any of the above-mentioned methods performed by a remote UE or a relay UE.

[0037] The details of one or more examples are set forth in the accompanying drawings and the description below.Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to describe the manner in which the advantages and features of the present application can be obtained, the description of the present application is presented by reference to specific embodiments of the present application illustrated in the accompanying drawings. These drawings depict only example embodiments of the present application and are therefore not to be considered as limiting the scope of the present application.

[0039] Figure 1A schematic diagram illustrating a wireless communication system according to some embodiments of the present application.

[0040] Figure 2 An exemplary flow chart illustrating a sidelink RRC reconfiguration procedure according to some embodiments of the present application.

[0041] Figure 3 An exemplary flow chart illustrating a path adding procedure according to some embodiments of the present application.

[0042] Figure 4 An exemplary flow chart of a path switching procedure according to some embodiments of the present application is illustrated.

[0043] Figure 5 An exemplary flow chart illustrating a path adding or switching procedure according to some embodiments of the present application.

[0044] Figure 6 An exemplary flow chart illustrating a path adding procedure according to some embodiments of the present application.

[0045] Figure 7 An exemplary flow chart illustrating a path switching procedure in a multi-path situation according to some embodiments of the present application.

[0046] Figure 8 An exemplary block diagram illustrating an apparatus for multipath situations according to some embodiments of the present application.

[0047] Fig. 9 Another exemplary block diagram illustrating an apparatus for multipath situations according to some embodiments of the present application. DETAILED DESCRIPTION

[0048] The detailed description of the accompanying drawings is intended as a description of the preferred embodiments of the present application, and is not intended to represent the only form in which the present application can be practiced. It should be understood that the same or equivalent functions can be implemented by different embodiments that are intended to be included in the spirit and scope of the present application.

[0049] Reference will now be made in detail to some embodiments of the present application, examples of which are illustrated in the accompanying drawings. To facilitate understanding, embodiments are provided under specific network architectures and new service scenarios, such as the Third Generation Partnership Project (3GPP) LTE and LTE Advanced, 3GPP 5G NR, 5G-Advanced, 6G, etc. It is considered that with the development of network architectures and new service scenarios, all embodiments in the present application are also applicable to similar technical problems; and in addition, the terms cited in the present application may change, which should not affect the principles of the present application.

[0050] Figure 1A schematic diagram illustrating a wireless communication system according to some embodiments of the present application. Figure 1 , for illustrative purposes, a wireless communication system 100 includes at least two UEs (ie, UE 101 and relay UE 102) and at least one BS (eg, BS 103). Figure 1 A specific number of UEs and BSs are depicted in FIG. 1 , but it is contemplated that any number of UEs and BSs may be included in the wireless communication system 100. Figure 1 As shown in , UE 101 may communicate with BS 103 via a direct path between UE 101 and BS 103 or via an indirect path between UE 101 and BS 103 through relay UE 102.

[0051] The UE in the wireless communication system 100 may include a computing device, such as a desktop computer, a laptop computer, a personal digital assistant (PDA), a tablet computer, a smart TV (e.g., a TV connected to the Internet), a set-top box, a game console, a security system (including a security camera), a car computer, a network device (e.g., a router, a switch and a modem), an Internet of Things (IoT) device, or the like. According to some embodiments of the present application, the UE may include a portable wireless communication device, a smart phone, a cellular phone, a flip phone, a device with a subscriber identification module, a personal computer, a selective call receiver, or any other device capable of sending and receiving communication signals on a wireless network. In some embodiments of the present application, the UE includes a wearable device, such as a smart watch, a fitness bracelet, an optical head-mounted display, or the like. In addition, the UE may be referred to as a subscriber unit, a mobile device, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a subscriber station, a user terminal or a device, or described using other terms used in the art. The UE may communicate directly with the BS via a UL communication signal.

[0052] In some embodiments of the present application, each of the UEs may deploy IoT applications, enhanced mobile broadband (eMBB) applications, and / or ultra-reliable and low-latency communication (URLLC) applications. It is contemplated that the specific type of application deployed in the UE may vary and is not limited.

[0053] The BSs in the wireless communication system 100 may be distributed throughout a geographic area. In certain embodiments of the present application, each of the BSs may also be referred to as an access point, an access terminal, a base, a base unit, a macro cell, a Node B, an evolved Node B (eNB), a gNB, an NG-RAN (Next Generation Radio Access Network) node, a home Node B, a relay node or a device, or described using other terms used in the art. A BS is typically part of a radio access network that may include one or more controllers communicatively coupled to one or more corresponding BSs. Each of the BSs may include one or more cells. Each UE may perform a cell segmentation procedure between different cells of different BSs.

[0054] The wireless communication system 100 may be compatible with any type of network capable of sending and receiving wireless communication signals. For example, the wireless communication system 100 is compatible with a wireless communication network, a cellular telephone network, a network based on time division multiple access (TDMA), a network based on code division multiple access (CDMA), a network based on orthogonal frequency division multiple access (OFDMA), an LTE network, a network based on 3GPP, a 3GPP 5G network, a satellite communication network, a high altitude platform network, and / or other communication networks.

[0055] In some embodiments of the present application, the wireless communication system 100 is compatible with the 5G New Radio (NR) of the 3GPP protocol, in which the BS uses an OFDM modulation scheme to transmit data on the DL and the UE 101 uses a single carrier frequency division multiple access (SC-FDMA) or OFDM scheme to transmit data on the UL. However, more generally, the wireless communication system 100 may implement some other open or proprietary communication protocols, for example, WiMAX and other protocols.

[0056] In some embodiments of the present application, the BS in the wireless communication system 100 may communicate using other communication protocols, such as the IEEE 802.11 series of wireless communication protocols. In addition, in some embodiments of the present application, the BS may communicate via a licensed spectrum, while in other embodiments, the BS may communicate via an unlicensed spectrum. The present application is not intended to be limited to any particular wireless communication system architecture or protocol implementation. In some further embodiments of the present application, the BS may communicate with the UE using the 3GPP 5G protocol.

[0057] Figure 2 An exemplary flow chart illustrating a sidelink RRC reconfiguration procedure according to some embodiments of the present application. Figure 2 As shown in FIG. 2 , in step 201, UE (a) (e.g., Figure 1 101) by sending a signal to UE(b) (e.g., Figure 1The relay UE 102) illustrated and shown in FIG. 1 transmits an RRCReconfigurationSidelink message to initiate the sidelink RRC reconfiguration procedure to UE(b).

[0058] If the sidelink RRC reconfiguration procedure is successfully completed, then in step 202, UE (b) may transmit an "RRC reconfiguration complete sidelink message" to UE (a), for example, an RRCReconfigurationCompleteSidelink message as specified in the 3GPP standard document. Alternatively, if the sidelink RRC reconfiguration procedure is not successfully completed, then in step 202, UE (b) may transmit an "RRC reconfiguration failure sidelink message" to UE (a), for example, an RRCReconfigurationFailureSidelink message as specified in the 3GPP standard document.

[0059] The purpose of the sidelink RRC reconfiguration procedure is to modify the PC5 RRC connection, for example, to establish, modify or release sidelink data radio bearers (DRBs), configure NR sidelink measurements and reporting, and configure sidelink channel state information (CSI) reference signal resources.

[0060] In the following cases, the UE (for example, Figure 2 The UE (a) described and shown in FIG. 1 may initiate a sidelink RRC reconfiguration procedure and perform operations on the corresponding PC5 RRC connection:

[0061] - With a peer UE (e.g. Figure 2 Release of the sidelink DRB associated with the UE (b)) as described and shown in FIG.

[0062] - Establishment of a sidelink DRB associated with a peer UE;

[0063] - modification of parameters contained in the Sidelink Radio Bearer (SLRB)-Config of a sidelink DRB associated with a peer UE;

[0064] - Configuration information of peer UEs to perform NR sidelink measurements and reporting; and

[0065] - Configuration information of sidelink CSI reference signal resources.

[0066] A UE capable of NR sidelink communication may initiate a procedure for sidelink UE information for NR to report to the network or BS that a sidelink radio link failure (RLF) has been declared (e.g., timer T400 expires) or a sidelink RRC reconfiguration failure.

[0067] Embodiments of the present application are directed to solving the problems associated with multiple paths in the case of L2 UE to Network (U2N) relay. Some embodiments of the present application provide a mechanism for handling an ongoing path addition procedure when a remote UE receives a notification message or a PC5 unicast link release message (e.g., PC5-S message) during the path addition procedure. For example, the receipt of the notification message may be a triggering condition for transmitting a fault information report and / or stopping a timer for path addition.

[0068] Some embodiments of the present application study a mechanism for releasing or maintaining a PC5 link when a remote UE receives a PC5 unicast link release message (e.g., a PC5-S message) or a notification message during a path addition procedure. For example, if the remote UE maintains a PC5 link, some embodiments introduce an optimization solution. Some embodiments of the present application provide a solution for re-adding an indirect path via a relay UE. Some other embodiments of the present application provide a solution for avoiding a cell change or a BS change of a relay UE during relay path addition.

[0069] Some embodiments of the present application study the case where a failure occurs during the relay change procedure. For example, in some embodiments, if the source relay link is not released when the relay UE change procedure is performed, the remote UE can fall back to the source relay UE link if the source relay path is still available. In some embodiments, if the remote UE receives a PC5 unicast link release message (e.g., PC5-S message) or notification message due to UuRLF, handover of the source relay UE, or detection of RLF on the source PC5 link by the remote UE, the remote UE can release the source indirect path.

[0070] More details will be described below in conjunction with the accompanying drawings. It should be clear to those skilled in the art that the terms "first / the first", "second / the second" and "third / the third" are only used for clear description and should not be regarded as any substantial limitation, such as an order limitation.

[0071] Figure 3 An exemplary flow chart illustrating a path adding procedure according to some embodiments of the present application. Figure 3 The exemplary method 300 in Figure 1 , 2 101, UE(a) or UE601) shown in any of 6. Figure 6 Specific examples are described in the embodiments of the present invention and in Embodiment 1 as shown below. Although described with respect to a UE, it should be understood that other devices may be configured to perform similar Figure 3 method of method of method.

[0072] exist Figure 3 In the exemplary method 300 in FIG. 1 , in operation 301, the UE receives a request from a network (e.g., Figure 1 BS103 as shown in Figure 6 BS 603 shown in FIG. 6 receives an RRC reconfiguration message for path addition. The RRC reconfiguration message for path addition includes a relay UE (e.g., Figure 1 The relay UE 102 shown in Figure 6 The ID of the relay UE 602) shown in FIG.

[0073] In operation 302, the UE starts a timer for a path addition procedure upon receiving the RRC reconfiguration message.

[0074] In operation 303, the UE receives a message associated with relaying a link between the UE and the network. For simplicity, this message is represented as a "first message." In some embodiments, the UE may stop a timer associated with a path addition procedure upon receiving the first message.

[0075] In some embodiments, the first message may be one of the following: a notification message received by the UE from the relay UE; and a PC5 unicast link release message (e.g., a PC5-S message). In an embodiment, the notification message indicates at least one of the following:

[0076] (1) Relay Uu RLF between UE and network;

[0077] (2) Relay UE cell reselection;

[0078] (3) Handover of relay UE;

[0079] (4) RRC connection failure of the relay UE;

[0080] (5) RRC connection rejection message received by the relay UE;

[0081] (6) expiration of a timer for the RRC setup request at the relay UE; or

[0082] (7) RRC recovery failure of relay UE.

[0083] In some embodiments, the UE may determine whether a cell change or BS change of the relay UE occurs. In response to determining that a cell change or BS change of the relay UE occurs, the UE may release the PC5 link between the relay UE and the UE. Alternatively, in response to determining that a cell change or BS change of the relay UE does not occur, the UE may continue to establish and maintain the PC5 link.

[0084] In some embodiments, the UE may transmit an indication to the network indicating that the PC5 link has been released or not released. In an embodiment, the indication is transmitted upon receiving the first message. In another embodiment, the indication is transmitted upon stopping the timer for the path addition procedure.

[0085] In some embodiments, the UE may initiate a fault information procedure upon receiving the first message, and transmit a fault message including a fault cause to the network. For example, the fault cause may be one of the following:

[0086] (1) receiving a notification message due to a Uu RLF between a relay UE and a network; receiving a notification message due to a cell reselection of a relay UE;

[0087] (2) receiving a notification message due to a handover of a relay UE;

[0088] (3) receiving a notification message due to an RRC connection failure of the relay UE;

[0089] (4) receiving a notification message due to an RRC connection reject message received by the relay UE;

[0090] (5) receiving a notification message due to expiration of a timer for an RRC setup request at the relay UE;

[0091] (6) receiving a notification message due to an RRC recovery failure of the relay UE; or

[0092] (7) Receive the PC5 unicast link release message indicated by the upper layer of the UE.

[0093] In some embodiments, the UE may store configuration information including the ID of the relay UE in response to the UE maintaining the PC5 link between the relay UE and the UE after receiving the first message. The UE may receive another RRC reconfiguration message including the ID of the relay UE for the path addition procedure. The UE may then use the stored configuration information to re-add the path between the relay UE and the network.

[0094] In some embodiments, the UE may transmit information about intra-cell path addition or intra-BS path addition to the relay UE.

[0095] In some embodiments, the UE may receive a PC5 unicast link release message or a rejection message from the relay UE due to the occurrence of a cell change or a BS change of the relay UE. For example, the rejection message is a rejection message in response to a direct communication request (DCR), as described below in Embodiment 1.

[0096] Figure 4An exemplary flow chart of a path switching procedure according to some embodiments of the present application is illustrated. Figure 4 The exemplary method 400 in Figure 1 , 2 UE 101, UE(a) or UE 701) shown in any of 7 is executed. Figure 7 Specific examples are described in the embodiments of and embodiments 2 and 3 as shown below. Although described with respect to a UE, it should be understood that other devices may be configured to perform similar Figure 4 method of method of method.

[0097] exist Figure 4 In the exemplary method 400 in FIG. 4 , in operation 401, the UE may access a serving cell of a network via multiple paths (e.g., Figure 1 BS103 as shown in Figure 7 ). The multiple paths include direct paths and / or via a source relay UE (e.g., Figure 1 The relay UE 102 shown in Figure 7 For simplicity, the indirect path is represented as the "first indirect path".

[0098] In operation 402, the UE may receive one of the following from a serving cell:

[0099] (1) For a first indirect path to a UE via a target relay (e.g. Figure 7 The RRC reconfiguration message of the path switching procedure of another indirect path (for simplicity, represented as “second indirect path”) of the target relay UE703 shown in FIG.

[0100] (2) a release message without a pause configuration, and

[0101] (3) A release message containing a pause configuration.

[0102] In operation 403, the UE may release the first indirect path upon receiving a release message having no suspension configuration.

[0103] In some embodiments, upon receiving the RRC reconfiguration message, the UE may initiate a path switching procedure to a second indirect path via the target relay UE and start a timer for the path switching procedure. In an embodiment, the UE may transmit an RRC reconfiguration complete message and stop the timer for the path switching procedure when transmitting the RRC reconfiguration complete message.

[0104] In some embodiments, the UE may transmit failure information to the network in response to expiration of a timer for the path switch procedure.

[0105] In some embodiments, the UE may fall back to access the serving cell via the first indirect path in response to expiration of a timer for the path switching procedure and the first indirect path being available.

[0106] In some embodiments, the UE may maintain the first indirect path in response to receiving an RRC reconfiguration message for a path switching procedure, receive a message or detect RLF on a PC5 link between the UE and the source relay UE in response to a timer for the path switching procedure being running, and release the first indirect path. In an embodiment, the first message is one of the following: a notification message received by the UE from the source relay UE; and a PC5 unicast link release message (e.g., a PC5-S message). For example, the notification message indicates at least one of the following:

[0107] (1) Uu RLF between the source relay UE and the network;

[0108] (2) Cell reselection of the source relay UE;

[0109] (3) Handover of source relay UE;

[0110] (4) RRC connection failure of the source relay UE;

[0111] (5) RRC connection rejection message received by the source relay UE;

[0112] (6) expiration of a timer for the RRC setup request at the source relay UE; or

[0113] (7) RRC recovery failure of the source relay UE.

[0114] In some embodiments, upon receiving the release message including the suspension configuration, the UE may release the first indirect path and transition to the RRC inactive state.

[0115] In some embodiments, upon receiving a release message including a suspension configuration, the UE may store configuration information associated with the first indirect path, and release the first indirect path in response to initiating resumption of the connection between the UE and the source relay UE.

[0116] Figure 5 An exemplary flow chart illustrating a path adding or switching procedure according to some embodiments of the present application. Figure 5 The exemplary method 500 in Figure 1 , 2 , UE101, UE(a), UE 601 or UE 701) shown in any of , 6 and 7 are executed. Figure 6 and 7Specific examples are described in the embodiments of and embodiments 1 to 3 as shown below. Although described with respect to a relay UE, it should be understood that other devices may be configured to perform similar Figure 5 method of method of method.

[0117] exist Figure 5 In the exemplary method 500 in FIG. 5 , in operation 501, the relay UE sends a message to a remote UE (eg, Figure 1 UE 101 shown in Figure 6 UE 601 as shown in Figure 7 UE 701 shown in FIG. transmits a message associated with relaying a link between the UE and the network. The message may be one of: a notification message; a PC5 unicast link release message; and a rejection message generated due to the occurrence of a cell change or a base station (BS) change.

[0118] In some embodiments, the relay UE is a target relay UE during a path addition procedure. In an embodiment, the notification message transmitted in operation 501 indicates at least one of the following:

[0119] (1) Uu RLF between the target relay UE and the network;

[0120] (2) Cell reselection of the target relay UE;

[0121] (3) Handover of target relay UE;

[0122] (4) RRC connection failure of the target relay UE;

[0123] (5) RRC connection rejection message received by the target relay UE;

[0124] (6) expiration of a timer for the RRC setup request at the target relay UE; or

[0125] (7) RRC recovery failure of the target relay UE.

[0126] In some embodiments, the target relay UE may receive information about intra-cell path addition or intra-BS path addition from the remote UE.

[0127] In some embodiments, during the path addition procedure, in response to the target relay UE being in an RRC idle state or an inactive state, the target relay UE may not change from one cell to another cell or from one BS to another BS during a cell selection or reselection operation. In some other embodiments, during the path addition procedure, in response to the target relay UE changing to another cell or another BS, the target relay UE may not enter an RRC connected state. In an embodiment, in response to the target relay UE changing to a second cell or a second BS, a PC5 unicast link release message (e.g., a PC5-S message) or a rejection message is transmitted by the target relay UE. Figure 6 A specific example is described in the embodiments of and in Embodiment 1 as shown below. For example, the rejection message is a rejection message in response to a direct communication request (DCR), as described in Embodiment 1 below.

[0128] In some embodiments, the relay UE is a source relay UE during a path switching procedure from a first indirect path to a second indirect path, wherein the first indirect path is between the remote UE and the network via the source relay UE, and wherein the second indirect path is between the remote UE and the network via a second target relay UE.

[0129] In some embodiments, the notification message indicates at least one of: UuRLF between the source relay UE and the network; cell reselection of the source relay UE; handover of the source relay UE; RRC connection failure of the source relay UE; RRC connection rejection message received by the source relay UE; expiration of a timer for an RRC setup request at the source relay UE; or RRC recovery failure of the source relay UE. Figure 7 Specific examples are described in Example 1 and Examples 2 and 3 shown below.

[0130] Those skilled in the art will appreciate that the order of operations in exemplary flowcharts 300, 400, and 500 may be changed, and some operations in exemplary flowcharts 300, 400, and 500 may be eliminated or modified without departing from the spirit and scope of the present disclosure. Figures 3 to 5 The details described in the exemplary flow chart are applicable to the embodiments of Figure 1 , 2 and all embodiments of 6 to 9.

[0131] Figure 6 An exemplary flow chart illustrating a path adding procedure according to some embodiments of the present application. Figure 6 In the embodiment of the present invention, UE 601 (for example, Figure 1 or Figure 2The UE 101 or UE (a) shown and described in FIG. 1 may also be referred to as a remote UE. The relay UE 602 may be a Figure 1 BS 603 may be a relay UE 102 as shown and described in FIG. Figure 1 BS103 as shown and described in.

[0132] like Figure 6 As shown in FIG. 6 , in operation 611, UE 601 accesses a serving BS (ie, BS 603) via a Uu link (eg, a direct path). UE 601 may report a measurement result based on a configuration from BS 603.

[0133] In operation 612, the serving BS 603 decides to add another indirect path based on the measurement result.

[0134] In operation 613, the BS 603 transmits an RRC reconfiguration message to the remote UE.

[0135] In operation 614, once UE 601 receives the RRC reconfiguration message for path addition, UE 601 starts a timer for path addition. The timer for path addition may be timer T420 (see 3GPP standard document TS38.331). In some embodiments, the ID of the relay UE (i.e., L2 U2N relay UE, e.g., relay UE 602) is included in the RRC reconfiguration message for path addition.

[0136] In operation 615, after UE 601 receives the RRC reconfiguration message for path addition, UE 601 transmits request signaling for establishing a PC5 connection to relay UE 602. If relay UE 602 is in an RRC connected state, relay UE 602 may detect the RLF and transmit a PC5 unicast link release (e.g., PC5-S message) or a notification message including an indication type set to Uu RLF to UE 601 (i.e., remote UE).

[0137] In some embodiments, in operation 615A (which is optional and marked with a dotted line), if the relay UE 602 is in an RRC idle or inactive state, the relay UE 602 will request to establish an RRC connection. Before the relay UE 602 transmits a request to the network (e.g., BS 603), the relay UE 602 may perform cell reselection in operation 615B (which is optional and marked with a dotted line). The relay UE 602 may transmit a PC5 unicast link release (e.g., a PC5-S message) or a notification message due to cell reselection, an RRC connection failure of the relay UE 602, and / or an RRC recovery failure. For example, an RRC connection failure may include an RRC connection rejection and / or an expiration of a timer (e.g., T300) for an RRC setup request at the relay UE 602.

[0138] In operation 616, UE 601 may receive a PC5 unicast link release (PC5-S message) or notification message due to Uu RLF, an RRC reconfiguration message including reconfiguration with synchronization, cell reselection, RRC connection failure (which may include RRC connection rejection and / or expiration of a timer for RRC setup request), and / or RRC recovery failure.

[0139] In some embodiments, when the PC5 unicast link release is indicated by the upper layer (PC5-S layer) of UE 601 (e.g., PC5-S layer message) or when a notification message due to Uu RLF, an RRC reconfiguration message including reconfiguration with synchronization, cell reselection, RRC connection failure and / or RRC recovery failure is received, UE 601 may stop the timer for path addition.

[0140] In some embodiments, when the PC5 unicast link release is indicated by the upper layer of UE 601 (e.g., PC5-S message) or when a notification message attributed to Uu RLF is received, an RRC reconfiguration message including a reconfiguration with synchronization, cell reselection, RRC connection failure and / or RRC recovery failure, UE 601 may trigger reporting of failure information including the cause of the failure to BS 603.

[0141] For example, the cause of the failure may be: receiving a PC5 unicast link release (e.g., a PC5-S message); or receiving a notification message due to Uu RLF, an RRC reconfiguration message including reconfiguration with synchronization, cell reselection, RRC connection failure, and / or RRC recovery failure.

[0142] In operation 617 , the UE 601 may transmit a failure information report to the BS 603 after receiving a PC5 unicast link release (eg, a PC5-S message) or a notification message or detecting an RLF on a PC5 link between the UE 601 and the relay UE 602 .

[0143] In some embodiments, if UE 601 recognizes the BS change (or cell change) of relay UE 602, UE 601 may directly release the PC5 link between UE 601 and relay UE 602. Otherwise, UE 601 may continue to establish and maintain the PC5 connection.

[0144] In some embodiments, an indication that the PC5 connection was or was not released may be included in the fault information report.

[0145] In some embodiments, if UE 601 has not received a response from BS 603, an indication of "cell or BS change" may be transmitted to BS 603 after the notification message has been transmitted.

[0146] In operation 618, UE 601 may receive a response from BS 603. In some embodiments, if PC5 is not released and relay UE 602 is connected to the same serving cell or the same BS (i.e., BS 603), the serving cell may instruct UE 601 to reconnect the indirect path. In operation 619, UE 601 will establish the indirect path based on the response from BS 603 in operation 618.

[0147] In some embodiments, UE 601 stores the original RRC reconfiguration associated with relay UE 602. Then, in operation 618, UE 601 receives another RRC reconfiguration message including only one indication from BS 603. Once UE 601 receives only one indication, UE 601 may or may not start the timer for path addition, and UE 601 may directly transmit another RRC reconfiguration message to relay UE 602. In operation 619, the stored original RRC configuration information associated with relay UE 602 may be used to re-add the path between relay UE 602 and BS 603.

[0148] In some other embodiments, in operation 618, BS 603 may transmit an indication of releasing the PC5 link to UE 601. If the PC5 link is released, BS 603 will transmit an RRC reconfiguration message including a configuration with a synchronization IE to UE 601. UE 601 may perform a normal path adding procedure in operation 619.

[0149] Figure 7An exemplary flow chart illustrating a path switching procedure in a multi-path situation according to some embodiments of the present application. Figure 7 In the embodiment of the present invention, UE 701 (for example, Figure 1 or Figure 2 The UE 101 or UE(a) shown and described in FIG. 1 may also be referred to as a remote UE. The BS 704 may be a Figure 1 The source relay UE 702 may be a BS 103 as shown and described in FIG. Figure 1 The target relay UE 702 may be the relay UE 102 shown and described in FIG. Figure 1 Another relay UE not shown.

[0150] like Figure 7 As shown in FIG. 7 , in operation 711, UE 701 accesses a serving BS (i.e., BS 704) via multiple paths (e.g., one direct path and one indirect path). UE 701 remains in an RRC connected state. The indirect path is associated with a relay UE (e.g., source relay UE 702).

[0151] In operation 712 , the BS 704 decides to switch from the source relay UE 702 to another relay UE (eg, the target relay UE 703 ) based on the measurement report from the UE 701 .

[0152] In operation 713, the BS 704 may transmit an RRC reconfiguration message associated with the indirect path switch to the UE 701. For example, the RRC reconfiguration message may include a configuration with synchronization.

[0153] In operation 714, once UE 701 receives the reconfiguration message for indirect path switching, UE 701 starts the timer for path switching. In some embodiments, after UE 701 receives the RRC reconfiguration message for indirect path switching, UE 701 may release the source PC5 RRC connection between UE 701 and source relay UE 702, i.e., the source PC5 link. In some other embodiments, UE 701 may maintain the source PC5 RRC connection. In the embodiment where UE 701 decides to maintain the source PC5 RRC connection, the following operations 715A to 718 may be performed.

[0154] In operation 715A (which is optional and marked with a dotted line), UE 701 may receive a PC5 unicast link release message (e.g., a PC5-S message) or a notification message from source relay UE 702. Alternatively, in operation 715B (which is optional and marked with a dotted line), UE 701 may detect RLF on the PC5 link between UE 701 and source relay UE 702 during a timer for path switching. After operation 715A or 715B, UE 701 may release the source indirect path associated with source relay UE 702 in operation 716.

[0155] In operation 717, once the PC5 link associated with the target relay UE 703 is established, the UE 701 may transmit an RRC reconfiguration complete message to the target relay UE 703. The target relay UE 703 may transmit the RRC reconfiguration complete message to the BS 704. In some embodiments, when the UE 701 transmits the RRC reconfiguration complete message to the BS 704 via the target relay UE 703, the UE 701 may stop a timer for path switching.

[0156] In operation 718 , the UE 701 may transmit or receive data to or from the BS 704 via the target relay UE 703 .

[0157] The details described in all other embodiments of this application (for example, details on how to handle setup and failure in multipath situations) apply to Figure 6 or Figure 7 In addition, Figure 6 or Figure 7 The details described in the embodiments apply to Figures 1 to 5 , 8 and 9. Those skilled in the art will appreciate that Figure 6 or Figure 7 The order of operations in the exemplary procedures of the embodiments may be changed and Figure 6 or Figure 7 Some operations in the exemplary procedures in the embodiments may be eliminated or modified without departing from the spirit and scope of the present disclosure.

[0158] The following describes Figures 3 to 7 Specific embodiments 1 to 3 of the method shown and described in the embodiment. According to embodiments 1 to 3, a UE (e.g., Figure 1 or Figure 2 101 or UE (a) shown and described in the figure), a relay UE (e.g., Figure 1 102) and a network node (e.g., as shown and described in Figure 1 BS103) shown and described in the text performs the following operations.

[0159] Embodiment 1 aims to solve the problem of how to avoid the cell or BS change of the relay UE during the indirect path addition procedure. In embodiment 1, the following operations (1) to (7) are performed.

[0160] In operation (1), the UE accesses the serving BS via the Uu link. The UE remains in the RRC connected state. The UE may report measurement results based on the configuration from the serving BS. The UE may also be named as a remote UE.

[0161] In operation (2), the serving BS decides to add an indirect path based on the measurement result. The serving BS transmits an RRC reconfiguration message to the remote UE.

[0162] In operation (3), once the remote UE receives the RRC reconfiguration message for path addition, the remote UE starts a timer for path addition. For example, the timer for path addition may be timer T420.

[0163] In operation (4), after the remote UE receives the RRC reconfiguration message for path addition, the remote UE transmits a request signaling for establishing a PC5 connection between the remote UE and the relay UE to the relay UE.

[0164] In some embodiments, if the relay UE is in the RRC connected state, the relay UE may detect the RLF and transmit a notification message (eg, including an indication type set to Uu RLF) to the remote UE.

[0165] In some other embodiments, if the relay UE is in RRC idle or inactive state, the relay UE may request to establish an RRC connection. In some other embodiments, before the relay UE transmits a request to the network (i.e., serving BS), the relay UE may perform cell reselection. The relay UE may transmit a notification message due to cell reselection, an RRC connection failure of the L2 U2N relay UE including RRC connection rejection and / or T300 expiration, and / or an RRC recovery failure.

[0166] In some embodiments, information about the addition of an intra-cell or intra-BS indirect path may be indicated to the relay UE, for example, in a request for a PC5 setup message. In an embodiment, if the relay UE is in an RRC idle or inactive state, the relay UE will not change to another cell or another BS during cell selection or cell reselection. In another embodiment, if the relay UE must change to another cell or another BS, the relay UE will not enter the RRC connected state and will inform the remote UE. Then, the relay UE may transmit a PC5-S release message or may reject in response to a direct communication request (DCR).

[0167] In operation (5), the remote UE may receive a response from the relay UE, that is, a PC5 connection is established.

[0168] In operation (6), the remote UE may transmit an RRC reconfiguration complete message to the serving BS via the relay UE. Then, the remote UE stops the timer for path addition.

[0169] In operation (7), the remote UE may establish an indirect path based on a response from the serving BS.

[0170] Embodiment 2 is intended to solve the problem regarding the case where a failure occurs during a relay change. In Embodiment 2, the following operations (A) to (D) are performed.

[0171] In operation (A), the UE accesses the serving BS via multiple paths (eg, direct path and / or indirect path). The UE remains in the RRC connected state. The UE may also be named as a remote UE.

[0172] In operation (B), the serving BS decides to release the connected remote UE to the RRC idle state.

[0173] In operation (C), the remote UE receives a release message from the serving BS. In some embodiments, if the remote UE configured with multipath receives the release message, the remote UE needs to release the configuration associated with the indirect path (ie, relay link path) when transitioning to the RRC idle state.

[0174] In operation (D), the remote UE enters the RRC idle state.

[0175] Embodiment 3 also aims to solve the problem regarding the case where a failure occurs during a relay change. In embodiment 3, the following operations (a) to (e) are performed.

[0176] In operation (a), the UE accesses the serving BS via multiple paths (eg, direct path and / or indirect path). The UE remains in the RRC connected state. The UE may also be named as a remote UE.

[0177] In operation (b), the serving BS decides to release the connected remote UE to the RRC inactive state.

[0178] In operation (c), the remote UE receives a release message including a suspension configuration from the serving BS. In some embodiments, if the UE configured with multipath receives a release message including a suspension configuration, the remote UE needs to release the configuration associated with the indirect path (i.e., the relay link path) when transitioning to the RRC inactive state. In some other embodiments, if the UE configured with multipath receives a release message including a suspension configuration, the remote UE needs to store the configuration associated with the relay link path when transitioning to the RRC inactive state.

[0179] In operation (d), the remote UE resumes the connection, for example, UL data arrives or a radio access network (RAN) paging message is received. In some embodiments, if the UE configured with multipath receives a release message containing a suspension configuration, the remote UE needs to store the configuration associated with the relay link path when transitioning to the RRC inactive state. When the remote UE resumes the connection, the remote UE may release the configuration associated with the relay link path.

[0180] In operation (e), the remote UE enters an RRC connected state.

[0181] Figure 8 An exemplary block diagram illustrating an apparatus for multipath situations according to some embodiments of the present application. Figure 8 , the apparatus 800 may include at least one non-transitory computer-readable medium 802, at least one receiving circuit system 804, at least one transmitting circuit system 806, and at least one processor 808 coupled to the non-transitory computer-readable medium 802, the receiving circuit system 804, and the transmitting circuit system 806. The at least one processor 808 may be a CPU, a DSP, a microprocessor, etc. The apparatus 800 may be a remote UE, a relay UE, or a network node (e.g., a BS) configured to perform the method described above or the like.

[0182] Although in this figure, elements such as at least one processor 808, receive circuitry 804, and transmit circuitry 806 are described in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. In some embodiments of the present application, receive circuitry 804 and transmit circuitry 806 may be combined into a single device, such as a transceiver. In certain embodiments of the present application, apparatus 800 may further include an input device, a memory, and / or other components.

[0183] In some embodiments of the present application, a non-transitory computer-readable medium 802 may store thereon computer-executable instructions to enable a processor to implement the method described or illustrated above with respect to a remote UE, a relay UE, or a network node (e.g., a BS). For example, when the computer-executable instructions are executed, the processor 808 interacts with the receiving circuit system 804 and the transmitting circuit system 806 to perform the steps described or illustrated above with respect to a remote UE, a relay UE, or a network node (e.g., a BS).

[0184] Fig. 9 Another exemplary block diagram illustrating an apparatus for multipath situations according to some embodiments of the present application. Fig. 9 , the apparatus 900 (for example, a BS or a UE) may include at least one processor 902 and at least one transceiver 904 coupled to the at least one processor 902. The transceiver 904 may include at least one separate receive circuit system 906 and transmit circuit system 908, or at least one integrated receive circuit system 906 and transmit circuit system 908. The at least one processor 902 may be a CPU, a DSP, a microprocessor, etc.

[0185] According to some other embodiments of the present application, when the device 900 is a UE, the processor 902 may be configured to: receive an RRC reconfiguration message for path addition from the network via the transceiver 904, wherein the RRC reconfiguration message for path addition includes an identifier (ID) of the relay UE; start a timer for a path addition procedure upon receiving the RRC reconfiguration message; and receive a message associated with a link between the relay UE and the network.

[0186] According to some embodiments of the present application, when the device 900 is a UE, the processor 902 may be configured to: access a serving cell of a network via multiple paths, wherein the multiple paths include at least one of a direct path and an indirect path via a source relay UE; receive one of the following from the serving cell via the transceiver 904: a radio resource control (RRC) reconfiguration message for a path switching procedure from the indirect path to another indirect path via a target relay UE; a release message without a suspension configuration; and a release message including the suspension configuration; and release the indirect path when the release message without the suspension configuration is received.

[0187] According to some embodiments of the present application, when the device 900 is a relay UE, the processor 902 may be configured to transmit a message associated with a link between the relay UE and the network to a remote UE via the transceiver 904, wherein the message is one of: a notification message; a PC5 unicast link release message; and a rejection message generated due to the occurrence of a cell change or a base station (BS) change.

[0188] The methods of the present disclosure may be implemented on a programmed processor. However, the controller, flow charts, and modules may also be implemented on a general or special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit components, an integrated circuit, a hardware electronic or logic circuit (e.g., a discrete element circuit), a programmable logic device, or the like. In general, any device having a finite state machine capable of implementing the flow charts shown in the figures may be used to implement the processing functions of the present disclosure.

[0189] Although the present disclosure has been described with reference to specific embodiments of the present disclosure, it is apparent that many substitutions, modifications, and variations may be apparent to those skilled in the art. For example, the various components of the embodiments may be interchanged, added, or substituted in other embodiments. Moreover, all elements of each figure are not necessary for the operation of the disclosed embodiments. For example, it will enable a person of ordinary skill in the art to make and use the teachings of the present disclosure by simply adopting the elements of the independent claims. Therefore, the embodiments of the present disclosure as described herein are intended to be illustrative rather than restrictive. Various changes may be made without departing from the spirit and scope of the present disclosure.

[0190] In this document, the term "includes / including" or any other variation thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment containing a series of elements not only contains those elements, but also may contain other elements that are not explicitly listed or inherent to this process, method, article or equipment. Elements starting with "one", "one" or the like do not exclude the presence of additional identical elements in the process, method, article or equipment containing the elements without more constraints. Moreover, the term "another" is defined as at least the second or more. The term "having" and the like as used herein are defined as "including". For example, the expression of "A and / or B" or "at least one of A and B" may include any and all combinations of the words enumerated together 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. The wording "first", "second" or the like is only used to clearly illustrate the embodiments of the present application, and is not used to limit the essence of the present application.

Claims

1. A user equipment UE, comprising: Transceiver; and a processor coupled to the transceiver, wherein the processor is configured to: receiving, via the transceiver, a first radio resource control (RRC) reconfiguration message for path addition from a network, wherein the first RRC reconfiguration message for path addition includes an identifier (ID) of a relay UE; starting a timer for a path addition procedure upon receiving the first RRC reconfiguration message; and A first message associated with a link between the relay UE and the network is received.

2. The UE according to claim 1, wherein the first message is one of the following: a notification message received by the UE from the relay UE via the transceiver; and PC5 unicasts link release message.

3. The UE according to claim 2, wherein the notification message indicates at least one of the following: A Uu radio link failure RLF between the relay UE and the network; Reselection of a cell of the relay UE; Handover of the relay UE; An RRC connection failure of the relay UE; an RRC connection reject message received by the relay UE; expiry of a timer for an RRC setup request at the relay UE; or The RRC recovery failure of the relay UE. 4 . The UE of claim 1 , wherein the processor of the UE is configured to stop the timer associated with the path adding procedure upon receiving the first message.

5. The UE of claim 1, wherein the processor of the UE is configured to: Determine whether a cell change or a base station BS change of the relay UE occurs; In response to determining that the cell change or the BS change of the relay UE occurs, releasing the PC5 link between the relay UE and the UE; or In response to determining that the cell change or the BS change of the relay UE has not occurred, continuing to establish and maintain the PC5 link.

6. The UE according to claim 1 or claim 4, wherein the processor of the UE is configured to transmit an indication to the network via the transceiver indicating that the PC5 link has been released or has not been released.

7. The UE according to claim 1 or claim 6, wherein the processor of the UE is configured to: Initiating a fault information procedure upon receipt of the first message; and transmitting a fault message including a fault cause to the network via the transceiver, wherein the fault cause is one of: receiving a notification message due to a Uu RLF between the relay UE and the network; receiving a notification message due to cell reselection of the relay UE; receiving a notification message due to a handover of the relay UE; receiving a notification message due to an RRC connection failure of the relay UE; receiving a notification message resulting from an RRC connection reject message received by the relay UE; receiving a notification message due to expiration of a timer for an RRC setup request at the relay UE; receiving a notification message due to an RRC recovery failure of the relay UE; or Receive a PC5 unicast link release message indicated by an upper layer of the UE.

8. The UE of claim 1, wherein the processor of the UE is configured to: storing the configuration information including the ID of the relay UE in response to the UE maintaining the PC5 link between the relay UE and the UE after receiving the first message; receiving a second RRC reconfiguration message for the path adding procedure including the ID of the relay UE; and The stored configuration information is used to re-add the path between the relay UE and the network. 9 . The UE of claim 1 , wherein the processor of the UE is configured to transmit information about intra-cell path addition or intra-BS path addition to the relay UE via the transceiver.

10. The UE of claim 9, wherein the processor of the UE is configured to receive, from the relay UE via the transceiver, a PC5 unicast link release message or a rejection message generated due to occurrence of a cell change or a BS change of the relay UE.

11. A user equipment UE, comprising: Transceiver; and a processor coupled to the transceiver, wherein the processor is configured to: Accessing a serving cell of a network via multiple paths, wherein the multiple paths include at least one of a direct path and a first indirect path via a source relay UE; receiving, via the transceiver, from the serving cell one of: a radio resource control (RRC) reconfiguration message for a path switching procedure from the first indirect path to a second indirect path via a target relay UE; a release message without a suspension configuration; and a release message including the suspension configuration; and The first indirect path is released upon receiving the release message without the pause configuration.

12. The UE of claim 11, wherein upon receiving the RRC reconfiguration message, the processor of the UE is configured to: Initiating the path switching procedure to the second indirect path via the target relay UE; and A timer for the path switching procedure is started.

13. The UE of claim 12, wherein the processor of the UE is configured to: Transmitting an RRC reconfiguration complete message; and The timer for the path switch procedure is stopped when the RRC reconfiguration complete message is transmitted.

14. The UE according to claim 12, wherein: The processor of the UE is configured to transmit failure information to the network in response to expiration of the timer for the path switching procedure. 15 . The UE of claim 12 , wherein the processor of the UE is configured to fall back to access the serving cell via the first indirect path in response to expiration of the timer for the path switching procedure and the first indirect path being available.

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