Method and apparatus for processing mobility configurations when a notification message is received - Patents.com

Abstract

The present application relates to a method and apparatus for processing mobility configurations when receiving a notification message in a Layer 2 (L2) UE-to-Network (U2N) relay case. According to the present application, a user equipment (UE) comprises a processor and a transceiver coupled to the processor, the processor is configured to access a serving cell via a direct path or an indirect path, the indirect path being associated with a relay UE, and receive a radio resource control (RRC) reconfiguration message from the serving cell via the transceiver, the RRC reconfiguration message including at least one of a measurement configuration, a conditional handover (CHO) configuration associated with a candidate cell, an indication indicating whether the UE is triggered to report measurement results of the candidate relay UE in response to identifying a cell change of the candidate relay UE, or an indication of a relay operation related configuration to be used by the remote UE in response to accessing the serving cell via the indirect path.

Description

[Technical field]

[0001] FIELD Embodiments of the present application generally relate to wireless communication technologies, and more particularly, to a method and apparatus for processing mobility configuration upon receiving a notification message in a Layer 2 (L2) UE-to-Network (U2N) relay case. [Background technology]

[0002] Vehicle-to-Everything (V2X) communication is being introduced into 5G wireless communication technology. From the perspective of the channel structure of V2X communication, the direct link between two User Equipments (UEs) is called sidelink. Sidelink is a feature of Long Term Evolution (LTE) introduced in 3GPP Release 12 that enables direct communication between nearby UEs, without the data having to go through a base station (BS) or core network.

[0003] The Third Generation Partnership Project (3GPP®) is promoting the introduction of relay nodes (RNs) in wireless communication systems. One purpose of the introduction of RNs is to enhance the coverage area of ​​a BS by improving the throughput of user equipment (UE) located in the coverage or far from the BS that may experience relatively poor signal quality. RNs may also be referred to as relay UEs in some cases. A 3GPP® 5G sidelink system that includes relay UEs may be referred to as a sidelink relay system. A U2N relay UE is a UE that provides functionality to support connectivity to the network for U2N remote UEs.

[0004] Currently, in wireless communication systems and the like, the details regarding the processing of mobility configuration when a notification message is received in the L2 U2N relay case have not yet been specifically discussed. Summary of the Invention [Means for solving the problem]

[0005] Some embodiments of the present application provide a user equipment (UE), comprising: a processor; and a transceiver coupled to the processor, the processor configured to: access a serving cell via a direct path or an indirect path, the indirect path being associated with a relay UE; and receive a radio resource control (RRC) reconfiguration message from the serving cell via the transceiver, the RRC reconfiguration message including at least one of a measurement configuration, a conditional handover (CHO) configuration associated with a candidate cell, an indication indicating whether the UE is triggered to report measurement results of the candidate relay UE in response to identifying a cell change of the candidate relay UE, or an indication of a relay operation related configuration to be used by the remote UE in response to accessing the serving cell via the indirect path.

[0006] In some embodiments, a processor of the UE is configured to receive a notification message from the relay UE via the transceiver, the notification message including at least one indication of a handover of the relay UE, a radio link failure (RLF) on a Uu link of the relay UE, a cell selection or cell reselection of the relay UE, a rejection of a radio resource control (RRC) connection establishment, or an RRC connection establishment failure.

[0007] In some embodiments, an RRC reconfiguration message including the CHO configuration is received from a serving cell via an indirect path, and a processor of the UE is configured to initiate evaluating at least one execution condition associated with the candidate cell in response to the RRC reconfiguration message including the CHO configuration.

[0008] In some embodiments, in response to receiving the notification message from the relay UE, the processor of the UE is configured to stop evaluating the at least one execution condition, or to continue evaluating the at least one execution condition and not perform the CHO even if the at least one execution condition is satisfied.

[0009] In some embodiments, a processor of the UE is configured to receive, from the relay UE via the transceiver, a message for releasing the PC5 RRC connection.

[0010] In some embodiments, a processor of the UE is configured to initiate an RRC re-establishment procedure in response to receiving a notification message including an indication of at least one of a handover of the relay UE, a radio link failure (RLF) on a Uu link of the relay UE, a cell selection or cell reselection of the relay UE, a failure of the RRC establishment procedure, or a rejection of the RRC establishment procedure, or receiving a message to release the PC5 RRC connection from the relay UE.

[0011] In some embodiments, a processor of the UE is configured to release the relay operation related configuration used by the remote UE in response to the RRC reconfiguration message including the relay operation related configuration used by the remote UE, the RRC re-establishment procedure being initiated, and the RRC reconfiguration message not including the CHO configuration.

[0012] In some embodiments, a processor of the UE is configured to perform cell selection in response to initiating an RRC re-establishment procedure, and to release the relay operation related configuration used by the remote UE in response to the RRC reconfiguration message including a relay operation related configuration used by the remote UE, in response to a CHO configuration being configured for the remote UE, and in response to the selected cell being not a CHO candidate cell.

[0013] In some embodiments, a processor of the UE is configured to report one or more measurement results of the one or more candidate relay UEs to a serving cell via an indirect path, the one or more measurement results of the one or more candidate relay UEs including a measurement result of the candidate relay UE, the measurement result of the candidate relay UE including at least one of a channel quality of a link between the UE and the candidate relay UE, identification (ID) information of the candidate relay UE, or ID information of a first serving cell of the candidate relay UE.

[0014] In some embodiments, a processor of the UE is configured to trigger reporting of the measurement results of the candidate relay UE in response to identifying a cell change of the candidate relay UE after reporting one or more measurement results including the measurement results of the candidate relay UE.

[0015] In some embodiments, a processor of the UE is configured to receive, from a candidate relay UE via the transceiver, a discovery message including identification (ID) information of a second serving cell of the candidate relay UE.

[0016] In some embodiments, the measurement result of the candidate relay UE includes ID information of the second serving cell, and a cell change of the candidate relay UE is identified after receiving the discovery message.

[0017] Some embodiments of the present application provide a relay UE, the relay UE comprising: a processor; and a transceiver coupled to the processor, the processor being configured to: receive a radio resource control (RRC) reconfiguration message from a serving cell via the transceiver, the RRC reconfiguration message including at least one of a conditional handover (CHO) configuration associated with a candidate cell or a relay operation related configuration used by the relay UE; and send a notification message via the transceiver to a remote UE via a PC5 link when at least one of the following conditions is met: when declaring a radio link failure (RLF) on a Uu link of the relay UE, when receiving a radio resource control (RRC) reconfiguration message including a reconfiguration synchronization information element (IE), when performing a handover, when performing a conditional handover (CHO), when cell selection or cell reselection of the relay UE, when being rejected by the serving cell for establishing an RRC connection between the relay UE and the serving cell, or when an RRC connection establishment failure occurs.

[0018] In some embodiments, the notification message includes at least one indication of a handover of the relay UE, an RLF on the Uu link of the relay UE, a cell selection or cell reselection of the relay UE, a rejection of the RRC connection establishment, or an RRC connection establishment failure.

[0019] In some embodiments, a processor of the relay UE is configured to send a message to the remote UE via the transceiver to release the PC5 RRC connection when the relay UE is rejected from the serving cell for establishing the RRC connection.

[0020] Some embodiments of the present application provide a network node (e.g., BS), comprising: a processor and a transceiver coupled to the processor, the processor configured to transmit a radio resource control (RRC) reconfiguration message to a user equipment (UE) via the transceiver via a direct path or an indirect path, the indirect path being associated with a relay UE, the RRC reconfiguration message including at least one of an indication of whether the UE is triggered to report measurement results of the candidate relay UE in response to identifying a measurement configuration, a conditional handover (CHO) configuration associated with a candidate cell, or a cell change of the candidate relay UE.

[0021] In some embodiments, a processor of the network node is configured to receive one or more measurement results of one or more candidate relay UEs from the UE via the transceiver via an indirect path, the one or more measurement results of the one or more candidate relay UEs including a measurement result of the candidate relay UE, the measurement result of the candidate relay UE including at least one of a channel quality of a link between the UE and the candidate relay UE, identification (ID) information of the candidate relay UE, or ID information of a first serving cell of the candidate relay UE.

[0022] In some embodiments, the processor of the network node is configured to receive, in response to the UE identifying a cell change of the candidate relay UE, measurement results for the candidate relay UE from the UE via the transceiver.

[0023] In some embodiments, the measurement result of the candidate relay UE includes identification (ID) information of a second serving cell of the candidate relay UE, and a cell change of the candidate relay UE is identified after the UE receives the discovery message.

[0024] Some embodiments of the present application provide a method that may be performed by a UE, the method comprising: accessing a serving cell via a direct or indirect path, the indirect path being associated with a relay UE; and receiving a radio resource control (RRC) reconfiguration message from the serving cell, the RRC reconfiguration message including at least one indication of a measurement configuration, a conditional handover (CHO) configuration associated with a candidate cell, an indication of whether the UE is triggered to report measurement results of the candidate relay UE in response to identifying a cell change of the candidate relay UE, or a relay operation related configuration to be used by the remote UE in response to accessing the serving cell via the indirect path.

[0025] In some embodiments, the method further comprises receiving a notification message from the relay UE, the notification message including at least one indication of a handover of the relay UE, a radio link failure (RLF) on a Uu link of the relay UE, a cell selection or cell reselection of the relay UE, a rejection of a Radio Resource Control (RRC) connection establishment, or an RRC connection establishment failure.

[0026] In some embodiments, an RRC reconfiguration message including the CHO configuration is received via an indirect path from the serving cell, and the method further comprises initiating, in response to the RRC reconfiguration message including the CHO configuration, evaluating at least one execution condition associated with the candidate cell.

[0027] In some embodiments, the method further comprises, in response to receiving the notification message from the relay UE, stopping evaluating the at least one execution condition or continuing to evaluate the at least one execution condition and not performing the CHO even if the at least one execution condition is satisfied.

[0028] In some embodiments, the method further comprises receiving a message to release the PC5 RRC connection from the relay UE.

[0029] In some embodiments, the method further comprises initiating an RRC re-establishment procedure in response to receiving a notification message including an indication of at least one of a handover of the relay UE, a Radio Link Failure (RLF) on the Uu link of the relay UE, a cell selection or cell reselection of the relay UE, a failure of the RRC establishment procedure, or a rejection of the RRC establishment procedure, or receiving a message to release the PC5 RRC connection from the relay UE.

[0030] In some embodiments, the method further comprises, in response to the RRC reconfiguration message including a relay operation related configuration used by the remote UE, the RRC re-establishment procedure being initiated, and the RRC reconfiguration message not including a CHO configuration, releasing the relay operation related configuration used by the remote UE.

[0031] In some embodiments, the method further comprises the steps of performing a cell selection in response to initiating an RRC re-establishment procedure, and releasing the relay operation related configuration used by the remote UE in response to the RRC reconfiguration message including a relay operation related configuration used by the remote UE, in response to a CHO configuration being configured for the remote UE, and in response to the selected cell being not a CHO candidate cell.

[0032] In some embodiments, the method further comprises reporting one or more measurement results of the one or more candidate relay UEs to a serving cell via an indirect path, the one or more measurement results of the one or more candidate relay UEs including a measurement result of the candidate relay UE, the measurement result of the candidate relay UE including at least one of a channel quality of a link between the UE and the candidate relay UE, identification (ID) information of the candidate relay UE, or ID information of a first serving cell of the candidate relay UE.

[0033] In some embodiments, the method further comprises triggering reporting of the measurement results for the candidate relay UE in response to identifying a cell change for the candidate relay UE after reporting one or more measurement results including the measurement results for the candidate relay UE.

[0034] In some embodiments, the method further comprises receiving, from the candidate relay UE, a discovery message including identification (ID) information of a second serving cell of the candidate relay UE.

[0035] In some embodiments, the measurement result of the candidate relay UE includes ID information of the second serving cell, and a cell change of the candidate relay UE is identified after receiving the discovery message.

[0036] Some embodiments of the present application provide a method that may be performed by a relay UE, comprising: receiving a radio resource control (RRC) reconfiguration message from a serving cell, where the RRC reconfiguration message includes at least one of a conditional handover (CHO) configuration associated with a candidate cell or a relay operation related configuration used by the relay UE; and sending a notification message to a remote UE via a PC5 link when at least one of the following conditions is met: when declaring a radio link failure (RLF) on the Uu link of the relay UE, when receiving a radio resource control (RRC) reconfiguration message including a reconfiguration synchronization information element (IE), when performing a handover, when performing a conditional handover (CHO), when cell selection or cell reselection of the relay UE, when being rejected by the serving cell for establishing an RRC connection between the relay UE and the serving cell, or when an RRC connection establishment failure occurs.

[0037] In some embodiments, the notification message includes at least one indication of a handover of the relay UE, an RLF on the Uu link of the relay UE, a cell selection or cell reselection of the relay UE, a rejection of the RRC connection establishment, or an RRC connection establishment failure.

[0038] In some embodiments, the method further comprises sending a message to the remote UE to release the PC5 RRC connection when the establishing of the RRC connection is rejected from the serving cell.

[0039] Some embodiments of the present application provide a method that may be performed by a network node (e.g., a BS), comprising: transmitting a radio resource control (RRC) reconfiguration message to a user equipment via a direct path or an indirect path, the indirect path being associated with a relay UE, and the RRC reconfiguration message including at least one indication of an indication indicating whether the UE is triggered to report measurement results for the candidate relay UE in response to identifying a measurement configuration, a conditional handover (CHO) configuration associated with a candidate cell, or a cell change for the candidate relay UE.

[0040] In some embodiments, the method further comprises receiving one or more measurement results of the one or more candidate relay UEs from the UE via an indirect path, the one or more measurement results of the one or more candidate relay UEs including a measurement result of the candidate relay UE, the measurement result of the candidate relay UE including at least one of a channel quality of a link between the UE and the candidate relay UE, identification (ID) information of the candidate relay UE, or ID information of a first serving cell of the candidate relay UE.

[0041] In some embodiments, the method further comprises receiving, from the UE, measurement results for the candidate relay UE in response to the UE identifying a cell change for the candidate relay UE.

[0042] In some embodiments, the measurement result of the candidate relay UE includes identification (ID) information of a second serving cell of the candidate relay UE, and a cell change of the candidate relay UE is identified after the UE receives the discovery message.

[0043] Some embodiments of the present application also provide an apparatus for wireless communication, the apparatus comprising: a non-transitory computer-readable medium having stored thereon computer-executable instructions, a receiving circuit, a transmitting circuit, and a processor coupled to the non-transitory computer-readable medium, the receiving circuit, and the transmitting circuit, the computer-executable instructions causing the processor to implement any of the above-mentioned methods performed by a UE, a relay UE, or a network node (e.g., a BS).

[0044] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will become apparent from the description and drawings, and from the claims.

[0045] To explain how the advantages and features of the present application can be obtained, the present application will be described with reference to specific embodiments that are illustrated in the accompanying drawings. These drawings depict only exemplary embodiments of the present disclosure and therefore should not be considered as limiting the scope of the present application. [Brief description of the drawings]

[0046] [Figure 1] 1 is a schematic diagram of a wireless communication system in accordance with some embodiments of the present application. [Diagram 2] 1 is an example flowchart of a sidelink RRC reconfiguration procedure according to some embodiments of the present application. [Diagram 3] 4 is a flowchart of an example procedure for wireless communication in accordance with some embodiments of the present disclosure. [Figure 4] 4 is a flowchart of an example procedure for wireless communication in accordance with some embodiments of the present disclosure. [Diagram 5] 4 is a flowchart of an example procedure for wireless communication in accordance with some embodiments of the present disclosure. [Figure 6] FIG. 1 is an example block diagram of an apparatus for a L2 U2N relay case according to some embodiments of the present application. [Figure 7]FIG. 13 is a further example block diagram of an apparatus for a L2 U2N relay case, according to some embodiments of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] The detailed description of the accompanying drawings is intended as an illustration of a preferred embodiment of the present application, and is not intended to represent the only form in which the present application may be practiced. It is to be understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the present application.

[0048] Reference will now be made in detail to some embodiments of the present application, examples of which are illustrated in the accompanying drawings. For ease of understanding, the embodiments are provided under specific network architectures and new service scenarios, such as 3rd Generation Partnership Project (3GPP) LTE and LTE advanced, 3GPP 5G NR, 5G-Advanced, 6G, etc. With the development of network architectures and new service scenarios, it is contemplated that all the embodiments in the present application are also applicable to similar technical challenges, and furthermore, the terms described in the present application may be changed, which should not affect the principles of the present application.

[0049] 1 illustrates a schematic diagram of a wireless communication system 100 in accordance with some embodiments of the present application. As illustrated in FIG. 1, the wireless communication system 100 includes, for illustrative purposes, a UE 101, a BS 102, and a relay UE 103. Although a particular number of UEs, relay UEs, and BSs are illustrated in FIG. 1, it is contemplated that any number of UEs, relay UEs, and BSs may be included in the wireless communication system 100.

[0050] Due to the distance between the UE 101 and the BS 102, they communicate with each other through the relay UE 103. The UE 101 may be connected to the relay UE 103 through a network interface, such as a PC5 interface defined in a 3GPP® standard document. The relay UE 103 may be connected to the BS 102 through a network interface, such as a Uu interface defined in a 3GPP® standard document. Referring to FIG. 1, the UE 101 is connected to the relay UE 103 through a PC5 link, and the relay UE 103 is connected to the BS 102 through a Uu link. The UE 101 may be a U2N remote UE. The relay UE 103 may be a U2N relay UE, which is a UE that provides functionality to support connectivity to a network for the U2N remote UE.

[0051] In some embodiments of the present application, the UE 101 or relay UE 103 may include computing devices such as desktop computers, laptop computers, personal digital assistants (PDAs), tablet computers, smart televisions (e.g., televisions connected to the Internet), set-top boxes, gaming consoles, security systems (including security cameras), in-vehicle computers, network devices (e.g., routers, switches, and modems), etc.

[0052] In some further embodiments of the present application, the UE 101 or relay UE 103 may include a portable wireless communications device, a smartphone, a cellular telephone, a flip phone, a device with a subscriber identity module, a personal computer, selective call receiving circuitry, or any other device capable of sending and receiving communication signals over a wireless network.

[0053] In some other embodiments of the present application, the UE 101 or relay UE 103 may include a wearable device such as a smart watch, a fitness band, an optical head mounted display, etc. Additionally, the UE 101 or relay UE 103 may be referred to as a subscriber unit, a mobile, 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, and may be described using other terms used in the art.

[0054] The BSs 102 may be distributed across a geographic region. In certain embodiments of the present application, each of the BSs 102 may be referred to as an access point, access terminal, base, base unit, macro cell, Node B, evolved Node B (eNB), gNB, home Node B, relay node, or device, or may be described using other terms used in the art. The BSs 102 are generally part of a radio access network, which may include one or more controllers communicatively coupled to one or more corresponding BSs 102.

[0055] The wireless communication system 100 is compatible with any type of network capable of transmitting and receiving wireless communication signals. For example, the wireless communication system 100 is compatible with a wireless communication network, a cellular telephone network, a time division multiple access (TDMA) based network, a code division multiple access (CDMA) based network, an orthogonal frequency division multiple access (OFDMA) based network, an LTE network, a 3GPP® based network, a 3GPP® 5G network, a satellite communication network, a stratospheric platform network, and / or other communication networks.

[0056] In some embodiments of the present application, the wireless communication system 100 is compatible with the 5G New Radio (NR) of 3GPP® protocol, where the BS 102 transmits data using an OFDM modulation scheme on the downlink (DL) and the UE 101 (e.g., the UE 101 or other similar UEs) transmits data on the uplink (UL) using a Discrete Fourier Transform Spread Orthogonal Frequency Division Multiplexing (DFT-S-OFDM) or Cyclic Prefix OFDM (CP-OFDM) scheme. However, more generally, the wireless communication system 100 may implement some other open or proprietary communication protocol, such as, for example, WiMAX, among others.

[0057] In some embodiments of the present application, the BS 102 may communicate using other communication protocols, such as the IEEE 802.11 family of wireless communication protocols. Additionally, in some embodiments of the present application, the BS 102 may communicate over a licensed spectrum, while in other embodiments, the BS 102 may communicate over an unlicensed spectrum. This application is not intended to be limited to any particular wireless communication system mechanism or protocol implementation. In further embodiments of the present application, the BS 102 may communicate with the UE 101 using 3GPP 5G protocols.

[0058] The UE 101 may access the BS 102 to receive data packets from the BS 102 via a downlink channel and / or transmit data packets to the BS 102 via an uplink channel. In normal operation, the UE 101 does not know when the BS 102 transmits data packets to the UE, so the UE 101 must always be awake and monitor a downlink channel (e.g., a physical downlink control channel (PDCCH)) to be ready to receive data packets from the BS 102. However, if the UE 101 keeps monitoring the downlink channel all the time even when there is no traffic between the BS 102 and the UE 101, it will result in significant power waste, which is problematic for power-limited or power-sensitive UEs.

[0059] The BS 102 may include one or more cells. The UE 101 may perform a cell selection procedure between different cells of different BSs. The UE 101 may handover from a serving cell of a source BS to a target cell of a target BS. For example, in the wireless communication system 100 illustrated in FIG. 1, the BS 102 illustrated in FIG. 1 may function as a source BS and a further BS 102 (not shown in FIG. 1) may function as a target BS. When the need for handover arises, the UE 101 illustrated in FIG. 1 may perform a handover procedure from a serving cell of the BS 102 to a target cell of the further BS depending on the measurement results. The handover procedure performed by the UE 101 may be a CHO procedure.

[0060] As specified in 3GPP standard documents, CHO is defined as a handover executed by a UE when one or more handover execution conditions are met. The UE starts evaluating the execution conditions when it receives a CHO configuration and stops evaluating the execution conditions during the CHO procedure once the execution conditions are met.

[0061] 2 illustrates an example flow chart of a sidelink RRC reconfiguration procedure according to some embodiments of the present application. As shown in FIG. 2, in step 201, UE(a) (e.g., UE 101 illustrated in FIG. 1) initiates a sidelink RRC reconfiguration procedure to UE(b) (e.g., relay UE 103 illustrated in FIG. 1) by sending an RRCReconfigurationSidelink message to UE(b).

[0062] If the sidelink RRC reconfiguration procedure is completed successfully, in step 202, UE(b) may send an "RRC reconfiguration complete sidelink message" to UE(a), such as, for example, an RRCReconfigurationCompleteSidelink message, as defined in 3GPP® standard documents. Alternatively, if the sidelink RRC reconfiguration procedure is not completed successfully, in step 202, UE(b) may send an "RRC reconfiguration failure sidelink message" to UE(a), such as, for example, an RRCReconfigurationFailureSidelink message, as defined in 3GPP® standard documents.

[0063] The purpose of the sidelink RRC reconfiguration procedure is to modify the PC5 RRC connection, e.g., to establish, modify, or release sidelink data radio bearers (DRBs), to configure NR sidelink measurements and reporting, and to configure sidelink channel state information (CSI) reference signal resources.

[0064] A UE (e.g., UE (a) shown in FIG. 2) may initiate a sidelink RRC reconfiguration procedure and perform operations for the corresponding PC5 RRC connection in the following cases: - release of a sidelink DRB associated with a peer UE (e.g., UE (b) shown in FIG. 2); - Establishment of a sidelink DRB associated with the peer UE; -Changes to parameters included in the Sidelink Radio Bearer (SLRB)-Config of a Sidelink DRB associated with a peer UE; - Configuration information of the peer UE for performing NR sidelink measurements and reporting; and - Configuration information for sidelink CSI reference signal resources.

[0065] A UE capable of NR sidelink communication initiates a sidelink UE information procedure for NR to report to the network or BS that a sidelink Radio Link Failure (RLF) (e.g., expiration of timer T400) or a sidelink RRC reconfiguration failure has been declared.

[0066] The embodiments of the present application aim to solve the problems in the L2 U2N relay case. For example, some embodiments of the present application consider a mechanism for the case where the CHO configuration is configured in the remote UE and / or the relay UE. Some embodiments of the present application consider a mechanism for the case where the relay UE selects (reselects) another cell after the remote UE reports the measurement result. Some embodiments of the present application consider new behaviors and / or instructions of the remote UE and the relay UE in the direct-to-indirect path switching case or the indirect-to-indirect path switching case where the relay UE fails to establish a Uu connection.

[0067] Details are described in the following description in conjunction with the accompanying drawings. Those skilled in the art should understand that descriptions such as "first", "second" and "third" are used for clarity of description only and should not be considered as any substantial limitation, such as sequence limitation.

[0068] 3 illustrates a flow chart of an example procedure 300 for a wireless communication system according to some embodiments of the present disclosure. Details described in all other embodiments of the present disclosure are applicable to the embodiment illustrated in FIG.

[0069] The exemplary procedure 300 refers to a scenario that addresses the case where the relay UE selects (reselects) another cell before performing CHO after the remote UE receives the CHO configuration, and introduces a new trigger condition for sending a notification message when the CHO configuration is configured for the relay UE. Referring to Figure 3, a remote UE 301, a relay UE 302, and a BS 303 may function as the UE 101, the relay UE 103, and the BS 102 shown in Figure 1, respectively. In particular, the exemplary procedure 300 includes the following steps.

[0070] In step 311, the remote UE 301 accesses the BS 303 via the relay UE 302, which is, for example, an L2 U2N relay UE. In other words, the remote UE 301 accesses the serving cell of the BS 303 via an indirect path. For example, the BS 303 may send an indication to indicate whether the L2 U2N relay UE is supported.

[0071] In step 312, the BS 303 sends an RRC reconfiguration message to the remote UE 301. In some embodiments, the RRC reconfiguration message may include at least one of the following configurations: (1) Relay operation related configuration used by remote UE 301. For example, an RRC reconfiguration message to remote UE 301 includes an sl-L2RemoteConfig information element (IE). The sl-L2RemoteConfig IE may include an L2 U2N relay operation related configuration used by an L2 U2N remote UE (e.g., remote UE 301). (2) Configuration related to paging messages. For example, an RRC reconfiguration message to a remote UE 301 includes a dedicated PagingDelivery IE. The dedicated PagingDelivery IE may be used to forward paging messages to a relay UE (e.g., a relay UE 302) that is in an RRC_CONNECTED state. (3) A CHO configuration associated with the candidate cell. For example, an RRC reconfiguration message including a reconfigurationWithSync IE including a conditionalReconfiguration IE is sent from the BS 303 to the remote UE 301. The CHO configuration is included in the conditionalReconfiguration IE.

[0072] In step 313, the BS 303 sends an RRC reconfiguration message to the relay UE 302. In some embodiments, the RRC reconfiguration message may include at least one of the following configurations: (1) A CHO configuration associated with a candidate cell. For example, an RRC reconfiguration message including a reconfigurationWithSync IE including a conditionalReconfiguration IE is sent from the BS 303 to the relay UE 302. The CHO configuration is included in the conditionalReconfiguration IE. (2) Relay operation related configuration used by the relay UE 302 For example, the RRC reconfiguration message to the relay UE 302 includes an sl-L2RelayConfig IE. The sl-L2RelayConfig IE may include an L2 U2N relay operation related configuration used by the L2 U2N relay UE (e.g., the relay UE 302).

[0073] In step 314, the relay UE 302 sends a notification message to the remote UE 301 when at least one of the following conditions is met: (1) upon receiving an RRC reconfiguration message that includes a reconfiguration synchronization IE, e.g., a reconfigurationWithSync IE; (2) When relay UE 302 declares RLF on the Uu link, (3) When the relay UE 302 selects (reselects) a cell, (4) When performing a handover, for example by performing an RRCReconfiguration including reconfigurationWithSync, or (5) When executing CHO It is.

[0074] In step 315, after the remote UE 301 receives the notification message from the relay UE 302, the remote UE 301 initiates an RRC re-establishment procedure. There are two options in different embodiments: option 1 and option 2. (1) In some embodiments, in option 1 of step 315, after the remote UE 301 receives the CHO configuration, the remote UE 301 starts evaluating the CHO execution condition. Upon receiving a notification message from the relay UE 302 (which may include at least one indication of cell (re)selection, handover, or Uu RLF of the relay UE 302), the remote UE 301 may stop evaluating the CHO execution condition. (2) In some embodiments, in option 2 of step 315, after the remote UE 301 receives the CHO configuration, the remote UE 301 starts evaluating the CHO execution condition. The remote UE 301 continues to evaluate the CHO execution condition even if it receives a notification message from the relay UE 302, which may include at least one indication of cell (re)selection, handover, or Uu RLF of the relay UE 302. However, the remote UE 301 does not perform CHO even if the CHO execution condition is met.

[0075] In step 315, in some embodiments, when the remote UE 301 initiates the RRC re-establishment procedure, it releases the sl-L2RemoteConfig IE received in step 312, for example if the remote UE 301 was not configured with a conditionalReconfiguration IE in step 312.

[0076] In some embodiments, after step 315, in response to initiating the RRC re-establishment procedure, the remote UE 301 performs cell selection (reselection). If the selected (reselected) cell is not a CHO candidate cell, and if a CHO configuration is configured for the remote UE 301, the remote UE 301 may release relay operation related configuration (e.g., sl-L2RemoteConfig) used by the remote UE 301 if configured in step 312. In some embodiments, the sl-L2RemoteConfig includes configuration associated with a Sidelink Relay Adaptation Protocol (SRAP), which is used to set configurable SRAP parameters used by the L2 U2N relay UE (e.g., relay UE 302) and the L2 U2N remote UE (e.g., remote UE 301). (1) For example, as specified in 3GPP standard document TS38.351, the configuration of an SRAP entity for a U2N remote UE may include at least one of the following: a) Mapping of radio bearer identified by BEARER ID to output PC5 RLC (Radio Link Control) channel via RRC. b) A local identifier via RRC. (2) For example, as specified in 3GPP standard document TS38.351, the configuration of the SRAP entity for a U2N relay UE may include at least one of the following: a) A local identifier for each U2N remote UE via RRC. b) Mapping from UE ID and BEARER ID to output Uu RLC channel for each U2N remote UE via RRC. c) Mapping from UE ID and BEARER ID to output PC5 RLC channel for each U2N remote UE via RRC.

[0077] In step 316, after the remote UE 301 initiates the RRC re-establishment procedure, the remote UE 301 sends an RRC re-establishment request message.

[0078] It will be apparent to one of ordinary skill in the art that the sequence of operations in the example procedure 300 of FIG. 3 may be changed and some of the operations in the example procedure 300 of FIG. 3 may be omitted or modified without departing from the scope of the present disclosure.

[0079] 4 illustrates a flow chart of an example procedure 400 for wireless communication according to some embodiments of the present disclosure. Details described in all other embodiments of the present disclosure are applicable to the embodiment illustrated in FIG.

[0080] The exemplary procedure 400 refers to a scenario dealing with a case where a remote UE selects (reselects) to another cell after the remote UE reports a measurement result. Referring to Figure 4, a remote UE 401, a relay UE 402, and a BS 403 may function as the UE 101, the relay UE 103, and the BS 102 shown in Figure 1, respectively. In particular, the exemplary procedure 400 includes the following steps:

[0081] In step 411, the remote UE 401 accesses the BS 403 via the relay UE 402, which is, for example, an L2 U2N relay UE. In other words, the remote UE 401 accesses the serving cell of the BS 403 via an indirect path. For example, the BS 403 may send an indication to indicate whether the L2 U2N relay UE is supported.

[0082] In step 412, the BS 403 sends an RRC reconfiguration message to the remote UE 401. In some embodiments, the RRC reconfiguration message may include at least one of the following configurations: (1) Measurement configuration. (2) Relay operation related configuration used by the remote UE 401. For example, an RRC reconfiguration message to the remote UE 401 includes an sl-L2RemoteConfig information element (IE). The sl-L2RemoteConfig IE may include an L2 U2N relay operation related configuration used by the L2 U2N remote UE (e.g., the remote UE 401). (3) Configuration related to paging messages. For example, an RRC reconfiguration message to the remote UE 401 includes a dedicatedPagingDelivery IE. The dedicatedPagingDelivery IE may be used to forward paging messages to a relay UE (e.g., the relay UE 402) that is in an RRC_CONNECTED state. (4) An indication for indicating whether the remote UE 401 is triggered to report measurement results of the candidate relay UE in response to identifying a cell change of the candidate relay UE. For example, the BS 403 configures an indication indicating whether the UE is triggered to report measurement results including ID information of the new serving cell of the candidate relay UE. For example, the indication may be included in the reporting configuration.

[0083] In step 413, the remote UE 401 performs measurements and reports the measurement results to the serving cell of the BS 403. In some embodiments, the measurement results may include at least one candidate relay UE and corresponding serving cell information. In an embodiment, the measurement results include (1) channel quality of the link between the remote UE 401 and the candidate relay UE, (2) identity information of the candidate relay UE, and / or (3) identity information of the serving cell of the candidate relay UE. For example, the identity information of the serving cell of the candidate relay UE includes at least one of a new radio cell identity (NCI), a cell ID, or a public land mobile network (PLMN) ID.

[0084] In step 414, after the remote UE 401 reports the measurement result including the at least one candidate relay UE and the corresponding serving cell information, the serving cell of the at least one candidate relay UE is changed. The remote UE 401 can identify the cell change of the at least one candidate relay UE after monitoring the discovery messages from the candidate relay UE. In some embodiments, the cell change of the candidate relay UE triggers the remote UE 401 to send the measurement result including ID information of the new serving cell of the candidate relay UE. For example, the ID information of the new serving cell of the candidate relay UE includes at least one of an NCI, a cell ID, or a PLMN ID.

[0085] In step 415, after the remote UE 401 receives a discovery message from at least one candidate relay UE, the remote UE 401 is triggered to report measurement results of the at least one candidate relay UE to a serving cell of the BS 403.

[0086] It will be apparent to one of ordinary skill in the art that the sequence of operations in the example procedure 400 of FIG. 4 may be changed and some of the operations in the example procedure 400 of FIG. 4 may be omitted or modified without departing from the scope of the present disclosure.

[0087] 5 illustrates a flow chart of an example procedure 500 for wireless communication according to some embodiments of the present disclosure. Details described in all other embodiments of the present disclosure are applicable to the embodiment illustrated in FIG.

[0088] The exemplary procedure 500 refers to a scenario in which the relay UE fails to establish a Uu connection, and considers new behaviors and / or instructions of the remote UE and relay UE in a direct-to-indirect path switching case or an indirect-to-indirect path switching case. Embodiments 1 and 2 of the exemplary procedure 500 are described below, in which the remote UE, the relay UE, and a network node (e.g., BS) perform the following operations:

[0089] EMBODIMENT 1 The first embodiment refers to a direct-to-indirect path switching case in which the target relay UE fails to establish a Uu connection. For example, in the first embodiment, the remote UE 501 and the BS 503 function as the UE 101 and the BS 102 shown in Fig. 1, respectively, and the target relay UE 502 (e.g., an L2 U2N relay UE) is a candidate relay UE not shown in Fig. 1. In particular, the following steps may be performed in the first embodiment: (1) In step 511, the remote UE 501 accesses the BS 503 via a direct path (i.e., a Uu interface). For example, the BS 503 may send an indication to indicate whether the L2 U2N relay UE is supported. (2) In step 512, the BS 503 sends an RRC reconfiguration message to the remote UE 501. In some embodiments, the RRC reconfiguration message may include the measurement configuration. (3) In step 513, the remote UE 501 performs measurements and reports the measurement results to the serving cell of the BS 503. In some embodiments, the measurement results include channel quality of the link between the remote UE 501 and the candidate relay UE (e.g., the target relay UE 502 shown in FIG. 5) and identity information of the candidate relay UE and / or identity information of the serving cell of the candidate relay UE. For example, the identity information of the serving cell of the candidate relay UE includes at least one of an NCI, a cell ID, or a PLMN ID. The target relay UE 502 may also be referred to as a "candidate target relay UE 502" or a "target candidate relay UE 502", etc. (4) In step 514, the serving cell of the BS 503 may send a path switch command to the remote UE 501, including the ID information of the target relay UE 502. (5) In step 515, the remote UE 501 establishes a PC5 RRC connection towards the target relay UE 502. In some embodiments, the remote UE 501 starts a timer associated with the path switch to the target relay UE 502. In an embodiment of the direct to indirect path switch case, the timer may be referred to as a "timer for path switch to the target relay UE" or a "timer for path switch from direct to indirect path", etc. In this embodiment, the source path of the path switch is the direct path and the target path of the path switch is the indirect path via the target relay UE 502. -In some embodiments, once a PC5 RRC connection towards the target relay UE 502 is established or a PC5 RRC connection establishment completion message is sent, the remote UE 501 stops a timer associated with the path switch to the target relay UE 502 (e.g., a timer for path switch from direct path to indirect path). (6) In step 516, if the target relay UE 502 is in an RRC_IDLE or RRC_INACTIVE state, the target relay UE 502 establishes a Uu connection. In some embodiments, the target relay UE 502 may receive a rejection message from the serving cell of the BS 503. (7) After step 516, there can be two cases in different embodiments: case 1 and case 2. In case 1, both steps 517a and 518a are executed. In case 2, both steps 517b and 518b are executed. 1)Case 1: Step 517a: When the target relay UE 502 in RC_IDLE or RRC_INACTIVE state is rejected by the serving cell of the BS 503, the target relay UE 502 sends a notification message to the remote UE 501. For example, the notification message includes at least one indication of an RRC connection establishment failure or a rejection of the RRC connection establishment. - Step 518a: When the remote UE 501 receives the notification message, the remote UE 501 initiates an RRC re-establishment procedure. 2)Case 2: Step 517b: When the target relay UE 502 in RC_IDLE or RRC_INACTIVE state is rejected by the serving cell of the BS 503, the target relay UE 502 is triggered to release the PC5 RRC connection between the remote UE 501 and the target relay UE 502. For example, the target relay UE 502 is triggered to send a message to release the RC5 RRC connection, for example a PC5-S release message. - Step 518b: When the remote UE 501 receives the message to release the PC5 RRC connection, the remote UE 501 initiates an RRC re-establishment procedure.

[0090] EMBODIMENT 2 Embodiment 2 refers to an indirect-to-indirect path switching case in which the target relay UE fails to establish a Uu connection. For example, in embodiment 1, the remote UE 501 and the BS 503 function as the UE 101 and the BS 102 shown in Fig. 1, respectively, and the target relay UE 502 (e.g., an L2 U2N relay UE) is a candidate relay UE not shown in Fig. 1. In particular, the following steps may be performed in embodiment 2: (1) In step 511, the remote UE 501 accesses the BS 503 via an indirect path via a relay UE (e.g., the relay UE 103 shown in FIG. 1, which may be an L2 U2N relay UE). For example, the BS 503 may send an indication to indicate whether the L2 U2N relay UE is supported. (2) In step 512, the BS 503 sends an RRC reconfiguration message to the remote UE 501. In some embodiments, the RRC reconfiguration message may include at least one of the following configurations: 1) Measurement configuration. 2) Relay operation related configuration used by remote UE 501. For example, an RRC reconfiguration message to remote UE 501 includes an sl-L2RemoteConfig information element (IE). The sl-L2RemoteConfig IE may include L2 U2N relay operation related configuration used by an L2 U2N remote UE (e.g., remote UE 501). 3) Configuration related to paging messages. For example, an RRC reconfiguration message to a remote UE 501 includes a dedicated PagingDelivery IE. The dedicated PagingDelivery IE can be used to forward paging messages to a relay UE (e.g., relay UE 402) that is in an RRC_CONNECTED state. 4) Secondary Cell Group (SCG) configuration: In case of Dual Connectivity (DC), a group of serving cells associated with a secondary node includes a SpCell (PSCell) and optionally one or more Scells. In case of DC, a secondary node refers to a radio access node that does not have a control plane connection to the core network and provides additional resources to a remote UE 501. (3) In step 513, the remote UE 501 performs measurements and reports the measurement results to the serving cell of the BS 503. In some embodiments, the measurement results include channel quality of the link between the remote UE 501 and the candidate relay UE (e.g., the target relay UE 502 shown in FIG. 5) and identity information of the candidate relay UE and / or identity information of the serving cell of the candidate relay UE. For example, the identity information of the serving cell of the candidate relay UE includes at least one of an NCI, a cell ID, or a PLMN ID. The target relay UE 502 may also be referred to as a "candidate target relay UE 502" or a "target candidate relay UE 502", etc. In case of Multi-Radio Dual Connectivity (MR-DC), if there is a random access problem indication from the SCG MAC (Medium Access Control) while the handover timer (e.g. timer T304) is not running, the remote UE 501 considers that a radio link failure is detected for the SCG, i.e. an SCG Radio Link Failure (RLF). The remote UE 501 then initiates an SCG Failure Information procedure. (4) In step 514, the serving cell of the BS 503 sends a path switch command to the remote UE 501, including the ID information of the target relay UE 502. (5) In step 515, the remote UE 501 establishes a PC5 RRC connection towards the target relay UE 502. In some embodiments, the remote UE 501 starts a timer associated with the path switch to the target relay UE 502. In an embodiment of the indirect-to-indirect path switch case, the timer may be referred to as "timer for path switch from source relay UE to target relay UE" or "timer for path switch from indirect path to indirect path", etc. In this embodiment, both the source path and the target path of the path switch are indirect paths. -In some embodiments, once a PC5 RRC connection towards the target relay UE 502 is established or a PC5 RRC connection establishment completion message is sent, the remote UE 501 stops a timer associated with the path switch to the target relay UE 502 (e.g., a timer for the path switch from an indirect path to an indirect path). (6) In step 516, if the target relay UE 502 is in an RRC_IDLE or RRC_INACTIVE state, the target relay UE 502 establishes a Uu connection. In some embodiments, the target relay UE 502 may receive a rejection message from the serving cell of the BS 503. (7) After step 516, there can be two cases in different embodiments: case 1 and case 2. In case 1, both steps 517a and 518a are executed. In case 2, both steps 517b and 518b are executed. 1)Case 1: Step 517a: When the target relay UE 502 in RC_IDLE or RRC_INACTIVE state is rejected by the serving cell of the BS 503, the target relay UE 502 sends a notification message to the remote UE 501. For example, the notification message includes at least one indication of an RRC connection establishment failure or a rejection of the RRC connection establishment. - Step 518a: When the remote UE 501 receives the notification message, the remote UE 501 initiates an RRC re-establishment procedure. 2)Case 2: Step 517b: When the target relay UE 502 in RC_IDLE or RRC_INACTIVE state is rejected by the serving cell of the BS 503, the target relay UE 502 is triggered to release the PC5 RRC connection between the remote UE 501 and the target relay UE 502. For example, the target relay UE 502 is triggered to send a message to release the RC5 RRC connection, for example a PC5-S release message. - Step 518b: When the remote UE 501 receives the message to release the PC5 RRC connection, the remote UE 501 initiates an RRC re-establishment procedure.

[0091] It will be apparent to one of ordinary skill in the art that the sequence of operations in the example procedure 500 of FIG. 5 may be changed and some of the operations in the example procedure 500 of FIG. 5 may be omitted or modified without departing from the scope of the present disclosure.

[0092] Some embodiments of the present disclosure provide a wireless communication device for a L2 U2N relay case. For example, FIG. 6 shows an example block diagram of an apparatus 600 for a L2 U2N relay case according to some embodiments of the present application.

[0093] 6, the apparatus 600 includes at least one non-transitory computer-readable medium 602, at least one receiving circuit 604, at least one transmitting circuit 606, and at least one processor 608 coupled to the non-transitory computer-readable medium 602, the receiving circuit 604, and the one transmitting circuit 606. The at least one processor 608 may be a CPU, a DSP, a microprocessor, etc. The apparatus 600 may be a network device (e.g., a BS) or a UE (e.g., a remote UE or a relay UE) configured to perform the methods illustrated above.

[0094] In this figure, elements such as at least one processor 608, receiving circuitry 604, and transmitting circuitry 606 are described in the singular, but the plural is contemplated unless expressly stated to be limited to the singular. In some embodiments of the present application, the receiving circuitry 604 and the transmitting circuitry 606 may be combined into a single device, such as a transceiver. In certain embodiments of the present application, the apparatus 600 may further include an input device, a memory, and / or other components.

[0095] In some embodiments of the present application, the non-transitory computer-readable medium 602 may store computer-executable instructions that cause a processor to perform a method with respect to a remote UE, a relay UE, or a network device (e.g., a BS), such as described or explained above in any of Figures 3-5. For example, the computer-executable instructions, when executed, cause a processor interacting with the receiving circuitry 604 and the transmitting circuitry 606 to perform steps with respect to a remote UE, a relay UE, or a network device (e.g., a BS), such as described or explained above in any of Figures 3-5.

[0096] FIG. 7 is a further example block diagram of an apparatus 700 for a L2 U2N relay case, according to some embodiments of the present application.

[0097] 7, an apparatus 700, such as a BS or a UE, may include at least one processor 702 and at least one transceiver 704 coupled to the at least one processor 702. The transceiver 704 may include at least one separate receiving circuit 706 and transmitting circuit 708, or at least one integrated receiving circuit 706 and transmitting circuit 708. The at least one processor 702 may be a CPU, DSP, microprocessor, etc.

[0098] According to some other embodiments of the present application, when the apparatus 700 is a remote UE, the processor 702 is configured to access a serving cell via a direct path or an indirect path, where the indirect path is associated with a relay UE, and receive a radio resource control (RRC) reconfiguration message from the serving cell via the transceiver 704, where the RRC reconfiguration message includes at least one of a measurement configuration, a conditional handover (CHO) configuration associated with a candidate cell, an indication of whether the UE is triggered to report measurement results for the candidate relay UE in response to identifying a cell change for the candidate relay UE, or an indication of a relay operation related configuration to be used by the remote UE in response to accessing the serving cell via the indirect path.

[0099] According to some embodiments of the present application, when the apparatus 700 is a relay UE, the processor 702 is configured to receive a radio resource control (RRC) reconfiguration message via the transceiver 704 from a serving cell, where the RRC reconfiguration message includes at least one of a conditional handover (CHO) configuration associated with a candidate cell or a relay operation related configuration used by the relay UE, and to send a notification message via the transceiver 704 to the remote UE via a PC5 link when at least one of the following conditions is met: when declaring a radio link failure (RLF) on a Uu link of the relay UE, when receiving a radio resource control (RRC) reconfiguration message including a reconfiguration synchronization information element (IE), when performing a handover, when performing a conditional handover (CHO), when cell selection or cell reselection of the relay UE, when being rejected by the serving cell for establishing an RRC connection between the relay UE and the serving cell, or when an RRC connection establishment failure occurs.

[0100] According to some embodiments of the present application, when the apparatus 700 is a BS, the processor 702 is configured to transmit a radio resource control (RRC) reconfiguration message to a user equipment via the transceiver 704 via a direct path or an indirect path, where the indirect path is associated with a relay UE, and the RRC reconfiguration message includes at least one of an indication of whether the UE is triggered to report measurement results for the candidate relay UE in response to identifying a measurement configuration, a conditional handover (CHO) configuration associated with a candidate cell, or a cell change for the candidate relay UE.

[0101] The methods of the present disclosure may also be performed on a programmed processor. However, the controllers, flowcharts, and modules may also be implemented in hardware electronic or logic circuits such as general purpose or special purpose computers, programmed microprocessors or microcontrollers and peripheral integrated circuit elements, integrated circuits, discrete element circuits, programmable logic devices, etc. In general, any device having a finite state machine capable of implementing the flowcharts shown in the figures may be used to implement the processing functions of the present disclosure.

[0102] Although the present disclosure has been described with its specific embodiments, it is clear that many alternatives, modifications, and variations will be apparent to those skilled in the art. For example, various components of the embodiments may be exchanged, added, or substituted in other embodiments. Also, not all elements of each figure are necessarily essential for the operation of the disclosed embodiments. For example, a person skilled in the art will be able to make and use the disclosed teachings by simply adopting the elements of the independent claims. Thus, the embodiments of the present disclosure described herein are intended to be illustrative, not limiting. Various modifications may be made without departing from the scope of the present disclosure.

[0103] As used herein, the terms "includes," "including," or any other variations thereof, are intended to cover a 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 include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by "a," "an," etc., does not, without more constraints, preclude the existence of additional equivalent elements in the process, method, article, or apparatus that includes that element. Also, the term "another" is defined as at least a second or more. As used herein, terms such as "having" are defined as "including." [Explanation of symbols]

[0104] 100 Wireless communication system 101UE 102, 303, 403, 503BS 103, 302, 402 Relay UE 301, 401, 501 Remote UE 502 Target Relay UE 600, 700 devices 602 Non-transitory computer-readable medium 604, 706 Receiver circuit 606, 708 Transmitting circuit 608, 702 processors 704 Transceiver

Claims

1. A processor; a transceiver coupled to the processor, The processor, accessing a serving cell via a direct path or an indirect path, the indirect path being associated with a relay UE; receiving a radio resource control (RRC) reconfiguration message from the serving cell via the transceiver; and the RRC reconfiguration message is configured to: Measurement configuration, a conditional handover (CHO) configuration associated with the candidate cell; an indication of whether the candidate relay UE is triggered to report measurement results for the candidate relay UE in response to identifying a cell change for the candidate relay UE; or A relay operation-related configuration used by a remote UE in response to accessing the serving cell via the indirect path. The UE includes at least one instruction of:

2. The processor of the UE is configured to receive a notification message from the relay UE via the transceiver, the notification message comprising: handover of the relay UE; A Radio Link Failure (RLF) on a Uu link of the relay UE; a cell selection or cell reselection of the relay UE; Rejection of Radio Resource Control (RRC) connection establishment, or RRC connection establishment failure The UE of claim 1 , further comprising at least one indication of:

3. 3. The UE of claim 1, wherein the RRC reconfiguration message including the CHO configuration is received from the serving cell via the indirect path, and the processor of the UE is configured to start evaluating at least one execution condition associated with the candidate cell in response to the RRC reconfiguration message including the CHO configuration.

4. In response to receiving a notification message from the relay UE, the processor of the UE: ceasing to evaluate said at least one execution condition; or continuing to evaluate the at least one execution condition and not executing the CHO even if the at least one execution condition is satisfied; The UE of claim 3 , configured to:

5. The UE of claim 1 , wherein the processor of the UE is configured to receive a message for releasing a PC5 RRC connection from the relay UE via the transceiver.

6. The processor of the UE, handover of the relay UE; A Radio Link Failure (RLF) on a Uu link of the relay UE; a cell selection or cell reselection of the relay UE; The RRC establishment procedure failed, or Rejection of the RRC establishment procedure, receiving a notification message including at least one indication of: receiving a message for releasing a PC5 RRC connection from the relay UE; The UE according to claim 2 or 5, configured to initiate an RRC re-establishment procedure in response to.

7. The processor of the UE, the RRC reconfiguration message includes the relay operation related configuration to be used by a remote UE; The RRC re-establishment procedure has been initiated, and the RRC reconfiguration message does not include the CHO configuration; 7. The UE of claim 6, configured to release the relay operation related configuration used by a remote UE in response to.

8. The processor of the UE, In response to initiating the RRC re-establishment procedure, perform a cell selection; 7. The UE of claim 6, configured to release the relay operation related configuration used by a remote UE in response to the RRC reconfiguration message including the relay operation related configuration used by a remote UE, in response to a CHO configuration being configured for the remote UE, and in response to a selected cell not being a CHO candidate cell.

9. the processor of the UE is configured to report one or more measurement results of one or more candidate relay UEs via the indirect path to the serving cell; The one or more measurement results of the one or more candidate relay UEs include a measurement result of the candidate relay UE, and the measurement result of the candidate relay UE comprises: a channel quality of a link between the UE and the candidate relay UE; Identification (ID) information of the candidate relay UE; or ID information of a first serving cell of the candidate relay UE The UE of claim 1 , comprising at least one of:

10. 10. The UE of claim 9, wherein the processor of the UE is configured to trigger reporting of the measurement results of the candidate relay UE in response to identifying a cell change of the candidate relay UE after reporting the one or more measurement results including the measurement result of the candidate relay UE.

11. 11. The UE of claim 10, wherein the processor of the UE is configured to receive, from the candidate relay UE via the transceiver, a discovery message including identification (ID) information of a second serving cell of the candidate relay UE.

12. 11. The UE of claim 10, wherein the measurement result of the candidate relay UE includes the ID information of a second serving cell, and the cell change of the candidate relay UE is identified after receiving a discovery message.

13. A processor; a transceiver coupled to the processor, The processor, receiving a radio resource control (RRC) reconfiguration message from a serving cell via the transceiver, the RRC reconfiguration message comprising: a conditional handover (CHO) configuration associated with the candidate cell, or Relay operation related configuration used by relay UE and and transmitting a notification message via the transceiver to a remote UE via a PC5 link when at least one of the following conditions is met: When declaring a Radio Link Failure (RLF) on the Uu link of the relay UE, Upon receiving a radio resource control (RRC) reconfiguration message that includes a reconfiguration synchronization information element (IE), When performing a handover, When performing a conditional handover (CHO), When the relay UE selects or reselects a cell, when a serving cell rejects establishing an RRC connection between the relay UE and the serving cell; or When RRC connection establishment fails That is, Relay UE.

14. The notification message is handover of the relay UE; an RLF on the Uu link of the relay UE; a cell selection or cell reselection of the relay UE; Rejection of RRC connection establishment, or RRC connection establishment failure The relay UE of claim 13, further comprising at least one indication of:

15. 14. The relay UE of claim 13, wherein the processor of the relay UE is configured to send a message to the remote UE via the transceiver to release a PC5 RRC connection when the relay UE is rejected by the serving cell for establishing the RRC connection.

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