Method and device for path switching

Abstract

The embodiment of the invention relates to a method and equipment for path switching in a communication system. According to some embodiments of the present disclosure, a UE may: receive, from a BS, an RRC reconfiguration message for DAPS path switching from a source connection to a target connection, where the RRC reconfiguration message indicates an ID of a target relay node; and starting a timer for path switching in response to receiving the RRC reconfiguration message.

Description

Technical Field

[0001] Embodiments of the present disclosure relate generally to communication technology, and more particularly, to path switching in a communication system. Background Art

[0002] Wireless communication systems are widely used to provide various telecommunication services, such as telephony, video, data, messaging, broadcast, etc. Wireless communication systems may employ multiple access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., time, frequency, and power). Examples of wireless communication systems may include fourth generation (4G) systems, such as long term evolution (LTE) systems, advanced LTE (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems, which may also be referred to as new radio (NR) systems.

[0003] In the above wireless communication system, a user equipment (UE) can communicate with another UE via a data path supported by an operator network (eg, a cellular or Wi-Fi network infrastructure). The data path supported by the operator network may include a base station (BS) and multiple gateways.

[0004] Some wireless communication systems may support sidelink communication, in which devices (e.g., UEs) that are relatively close to each other may communicate directly with each other via sidelinks, rather than being linked through a BS. A sidelink-based relay function may be supported in a communication network. For example, a UE that supports sidelink communication may be used as a relay node to extend the coverage of a BS. A UE outside or within the coverage may communicate with the BS via a relay node (e.g., a relay UE). In the context of the present disclosure, a UE that serves as a relay between another UE and a BS is referred to as a UE-to-network (U2N) relay.

[0005] There is a need to efficiently perform communication in a communication system supporting U2N relay. Summary of the invention

[0006] Some embodiments of the present disclosure provide a user equipment (UE). The UE may include: a transceiver; and a processor coupled to the transceiver. The processor may be configured to: receive a radio resource control (RRC) reconfiguration message for a dual active protocol stack (DAPS) path switch from a source connection to a target connection from a base station (BS), wherein the RRC reconfiguration message indicates an ID of a target relay node; and start a timer for the path switch in response to receiving the RRC reconfiguration message.

[0007] Some embodiments of the present disclosure provide a base station (BS). The BS may include: a transceiver; and a processor coupled to the transceiver. The processor may be configured to: receive capability information associated with a dual active protocol stack (DAPS) path switch from a user equipment (UE); and transmit a radio resource control (RRC) reconfiguration message for the DAPS path switch to the UE, wherein the RRC reconfiguration message indicates an ID of a target relay node.

[0008] In some embodiments of the present disclosure, the processor may be further configured to receive fault information associated with the DAPS path switch from the UE. The fault information may indicate at least one of the following: receiving a notification message from the target relay node; receiving a PC5 unicast link release indication; or detecting an RLF of the side link between the UE and the target relay node.

[0009] In some embodiments of the present disclosure, the PC5 unicast link release indication may be indicated by an upper layer of the UE, or may be received at the UE from the target relay node.

[0010] In some embodiments of the present disclosure, the notification message may be received in response to one of the following conditions: RLF between the target relay node and the target cell of the DAPS path switching; reception of an RRC reconfiguration message containing a configuration with synchronization at the target relay node; cell reselection at the target relay node; RRC connection establishment failure or RRC recovery failure at the target relay node; a successful switching procedure at the target relay node; a failed switching procedure at the target relay node; initiation of a reconstruction procedure at the target relay node; a successful reconstruction procedure at the target relay node; a failed reconstruction procedure at the target relay node; and a failed listen-before-talk (LBT) procedure at the target relay node.

[0011] In some embodiments of the present disclosure, the capability information may indicate whether the UE supports DAPS path switching associated with a relay node. In some embodiments of the present disclosure, the capability information may indicate at least one of: whether the UE supports path switching from an indirect path to another indirect path; or whether the UE supports path switching from a direct path to an indirect path.

[0012] Some embodiments of the present disclosure provide a method performed by a user equipment (UE). The method may include: receiving a radio resource control (RRC) reconfiguration message for a dual active protocol stack (DAPS) path switch from a source connection to a target connection from a base station (BS), wherein the RRC reconfiguration message indicates an ID of a target relay node; and starting a timer for the path switch in response to receiving the RRC reconfiguration message.

[0013] Some embodiments of the present disclosure provide a method performed by a relay node. The method may include: receiving capability information associated with a dual active protocol stack (DAPS) path switch from a user equipment (UE); and transmitting a radio resource control (RRC) reconfiguration message for the DAPS path switch to the UE, wherein the RRC reconfiguration message indicates an ID of a target relay node.

[0014] Some embodiments of the present disclosure provide a device. According to some embodiments of the present disclosure, the device may include: at least one non-transitory computer-readable medium having computer-executable instructions stored thereon; at least one receiving circuit system; at least one transmitting circuit system; and at least one processor coupled to the at least one non-transitory computer-readable medium, the at least one receiving circuit system, and the at least one transmitting circuit system, wherein the at least one non-transitory computer-readable medium and the computer-executable instructions may be configured to cause the device to perform the method according to some embodiments of the present disclosure together with the at least one processor.

[0015] Embodiments of the present disclosure provide technical solutions for facilitating and improving the implementation of various communication technologies (e.g., 5G NR). BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to describe the manner in which the advantages and features of the present disclosure can be obtained, the description of the present disclosure is presented by reference to specific embodiments of the present disclosure illustrated in the accompanying drawings. These drawings depict only exemplary embodiments of the present disclosure and therefore should not be considered to limit its scope.

[0017] Figure 1 A schematic diagram illustrating a wireless communication system according to some embodiments of the present disclosure;

[0018] Figure 2 A schematic diagram illustrating a relay-based wireless communication system according to some embodiments of the present disclosure;

[0019] Figure 3 A flowchart illustrating an exemplary notification message procedure according to some embodiments of the present disclosure;

[0020] Figure 4A schematic diagram illustrating a wireless communication system according to some embodiments of the present disclosure;

[0021] Figures 5 to 8 A flowchart illustrating an exemplary procedure for wireless communication according to some embodiments of the present disclosure; and

[0022] Fig. 9 A block diagram illustrating an exemplary apparatus according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0023] The detailed description of the accompanying drawings is intended as a description of the preferred embodiments of the present disclosure, and is not intended to represent the only form in which the present disclosure can be practiced. It should be understood that the same or equivalent functions can be achieved by different embodiments that are intended to be included in the spirit and scope of the present disclosure.

[0024] Reference will now be made in detail to some embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. To facilitate understanding, embodiments are provided under specific network architectures and new service scenarios (e.g., 3rd Generation Partnership Project (3GPP) 5G (NR), 3GPP Long Term Evolution (LTE) Release 8, etc.). It is contemplated that, with the development of network architectures and new service scenarios, all embodiments in the present disclosure are also applicable to similar technical issues; and in addition, the terms listed in the present disclosure may be changed, which should not affect the principles of the present disclosure.

[0025] Figure 1 A schematic diagram illustrating a wireless communication system 100 according to some embodiments of the present disclosure.

[0026] As in Figure 1 As shown in , the wireless communication system 100 can support sidelink communication. The sidelink communication supports UE-to-UE direct communication. In the context of the present disclosure, the sidelink communication can be classified according to the wireless communication technology adopted. For example, the sidelink communication can include NR sidelink communication and V2X sidelink communication.

[0027] For example, NR sidelink communication (e.g., specified in 3GPP TS 38 series specifications) may refer to access layer (AS) functionality that uses NR technology to enable at least vehicle-to-everything (V2X) communication between neighboring UEs without traversing any network nodes. V2X sidelink communication (e.g., specified in 3GPP TS 36 series specifications) may refer to AS functionality that uses Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA) (E-UTRA) technology to enable V2X communication between neighboring UEs without traversing any network nodes. However, if not specified, "sidelink communication" may refer to NR sidelink communication, V2X sidelink communication, or any sidelink communication that employs other wireless communication technologies.

[0028] refer to Figure 1 , the wireless communication system 100 may include some base stations (eg, BS 102 and BS 103) and some UEs (eg, UE 101A, UE 101B, and UE 101C). 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 .

[0029] UE and BS may support communication based on, for example, 3G, long term evolution (LTE), advanced LTE (LTE-A), new radio (NR), or other suitable protocols. In some embodiments of the present disclosure, a BS (e.g., BS102 or BS103) may 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-eNB, a home node B, a relay node or a device, or described using other terms used in the art. A UE (e.g., UE 101A, UE 101B, or UE 101C) may include, for example, but not limited to, a computing device, a wearable device, a mobile device, an IoT device, a vehicle, etc. Those skilled in the art should understand that, with the development and advancement of technology, the terms described in the present disclosure may change, but should not affect or limit the principles and spirit of the present disclosure.

[0030] exist Figure 1 In the example of, BS102 and BS103 may be included in a next generation radio access network (NG-RAN). In some embodiments of the present disclosure, BS102 may be a gNB, and BS103 may be an ng-eNB.

[0031] UE 101A and UE 101B may be within coverage (e.g., within the NG-RAN). Figure 1 , UE 101A may be within the coverage of BS 102, and UE 101B may be within the coverage of BS 103. UE 101C may be out of coverage (e.g., outside the coverage of the NG-RAN). Figure 1, UE 101C may be outside the coverage of any BS, such as BS 102 and BS 103. UE 101A and UE 101B may be connected to BS 102 and BS 103, respectively, via a network interface, such as a Uu interface specified in a 3GPP standard document. The control plane protocol stack in the Uu interface may include a radio resource control (RRC) layer, which may be referred to as Uu RRC. The link established between a UE (e.g., UE 101A) and a BS (e.g., BS 102) may be referred to as a Uu link. BS 102 and BS 103 may be connected to each other via a network interface, such as an Xn interface specified in a 3GPP standard document. UE 101A, UE 101B, and UE 101C may be connected to each other via a PC5 interface, such as specified in a 3GPP standard document, respectively. The control plane protocol stack in the PC5 interface may include a radio resource control (RRC) layer, which may be referred to as PC5RRC. A link established between two UEs (eg, UE 101A and UE 101B) may be referred to as a PC5 link.

[0032] Support for V2X services via the PC5 interface may be provided, for example, through NR sidelink communication and / or V2X sidelink communication. NR sidelink communication may support one of the following three types of transmission modes for a pair of source layer 2 identifiers and destination layer 2 identifiers: unicast transmission, multicast transmission, and broadcast transmission. When the UE is within coverage or outside coverage, sidelink communication transmission and reception via the PC5 interface are supported. For example, UE 101A within the coverage of BS102 may perform sidelink transmission and reception (e.g., sidelink unicast transmission, sidelink multicast transmission, or sidelink broadcast transmission) via the PC5 interface. UE 101C outside the coverage of both BS102 and BS103 may also perform sidelink transmission and reception via the PC5 interface.

[0033] A UE supporting sidelink communication and / or V2X communication may be referred to as a V2X UE. According to some other embodiments of the present disclosure, the V2X UE may be a mobile phone, a vehicle, a road map device, a computer, a laptop, an IoT (Internet of Things) device, or other types of devices.

[0034] As mentioned above, a sidelink-based relay function may be supported in a communication network. Sidelink relay may provide connectivity to the network for another UE (remote UE). In some embodiments of the present disclosure, UE-to-network relay is supported. For example, a UE within coverage that communicates with a remote UE (UE outside coverage or UE within coverage) may be used as a relay UE between a serving BS of the UE within coverage and the remote UE. Therefore, the remote UE may communicate with the BS via this relay UE. Data between the remote UE and the BS may be transmitted by the relay UE. In this scenario, the relay UE may be referred to as a serving relay for the remote UE, and the serving BS or serving cell of the relay UE may be referred to as a serving BS or serving cell of the remote UE, respectively.

[0035] The remote UE may have an RRC state, such as an RRC_IDLE state, an RRC_INACTIVE state, and an RRC_CONNECTED state as defined in the 3GPP specification. The relay UE may be in the RRC_CONNECTED state to perform relaying of unicast data. In some embodiments, in the case of a path switch, a relay UE in the RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED state may be selected as a target relay UE.

[0036] In some embodiments, for Layer 2 (L2) U2N relay operation, the following RRC state combinations may be supported:

[0037] - Both the relay UE and the remote UE may be in the RRC_CONNECTED state to perform transmission or reception of relayed unicast data; and

[0038] - The relay UE may be in RRC_IDLE, RRC_INACTIVE or RRC_CONNECTED state as long as each remote UE connected to the relay UE is in RRC_INAACTIVE state or in RRC_IDLE state.

[0039] A single unicast link may be established between one relay UE and one remote UE. Traffic of the remote UE via a given relay UE may be separated from traffic of the relay UE in different Uu relay radio link control (RLC) channels. In some embodiments, for L2 U2N relay, the remote UE may be configured to use resource allocation mode 2 only for data to be relayed.

[0040] Figure 2 A schematic diagram illustrating a relay-based wireless communication system 200 according to some embodiments of the present disclosure. Figure 2 The embodiments shown in .

[0041] As in Figure 2 As shown in FIG. 2 , a wireless communication system 200 may include a BS (eg, BS 202) and some UEs (eg, UE 201A and UE 201B). Figure 2 Although a specific number of UEs and BSs are depicted in FIG. 2 , it is contemplated that any number of UEs and BSs may be included in wireless communication system 200. In some examples, UE 201B may be used as Figure 1 1A or UE 101B shown in FIG. 1 , and UE 201A can be used as Figure 1 UE 101C shown in FIG.

[0042] UE 201B may be within the coverage of BS 202. For example, UE 201B and BS 202 may establish an RRC connection between them. UE 201A may be outside the coverage of BS 202. Wireless communication system 200 may support sidelink communications. For example, UE 201B may be in sidelink communications with UE 201A. A PC5 RRC connection may be established between UE 201A and UE 201B.

[0043] In some embodiments of the present disclosure, UE 201A may initiate a procedure for establishing a connection with BS 202 via UE 201B (i.e., UE to network relay). For example, UE 201A may transmit an RRC setup request to BS 202 via UE 201B. BS 202 may transmit an RRC setup message including a response to UE 201A via UE 201B. After this procedure, UE 201A may access BS 202 (e.g., a cell of BS 202) via UE 201B. This cell may be referred to as a serving cell of UE 201A. UE 201A and BS 202 may establish an RRC connection between them. UE 201A may also be referred to as a remote UE, and UE 201B may also be referred to as a relay UE, a sidelink relay, or a serving relay of UE 201A.

[0044] It should be understood by those skilled in the art that although Figure 2 A single relay node (eg, UE 201B) is depicted between UE 201A and BS 202, but it is contemplated that any number of relay nodes may be included. Figure 2 UE 201A is shown outside the coverage of BS 202, but in some other embodiments of the present disclosure, it may be considered that UE 201A may be within the coverage of BS 202. In these embodiments, UE 201A may be directly connected to BS 202 and / or connected to BS 202 via UE 201B.

[0045] Figure 3A flowchart illustrating an exemplary notification message procedure 300 according to some embodiments of the present disclosure. Figure 3 The embodiments shown in .

[0046] refer to Figure 3 In operation 311, the relay node 302 may transmit a notification message to the UE 301. In some examples, the relay node 302 may be a relay UE, such as a U2N relay UE. In this scenario, the notification message may also be referred to as a "notification message for a side link".

[0047] In some embodiments of the present disclosure, for example, when one of the following conditions is met, the relay node 302 may initiate the exemplary procedure 300:

[0048] - in response to a Uu RLF, as described below;

[0049] - in response to receiving an RRC reconfiguration message including a reconfigurationWithSync information element (IE),

[0050] For example, switch command;

[0051] - in response to cell reselection at the relay node 302; or

[0052] - In response to an RRC connection failure at the relay node 302, which may include, for example, an RRC connection reject, expiration of a timer for an RRC setup request (eg, T300 as specified in 3GPP specifications), and an RRC recovery failure.

[0053] The notification message may include a type indication (eg, "indicationType"), which may indicate that the notification message is due to one of relay Uu RLF, relay handover, relay cell reselection, and / or relay connection failure.

[0054] In some embodiments of the present disclosure, a relay node (e.g., relay node 302) may declare a Uu RLF (e.g., RLF between the relay node and the BS) based on at least one of the following criteria:

[0055] - expiry of a radio problem timer started after indication of a radio problem from the physical layer (if the radio problem is recovered before the timer expires, the relay node stops the timer); or

[0056] - expiry of a timer that was started when a measurement report for a measurement identity whose timer has been configured was triggered while another radio problem timer is running; or

[0057] - Random Access procedure failure; or

[0058] -RLC failure.

[0059] In some embodiments of the present disclosure, the remote UE may switch (or hand over) from an indirect path (e.g., the UE indirectly accesses the source BS (or source cell) via a source relay node) to another indirect path (e.g., the UE indirectly accesses the target BS (or target cell) via a target relay node). In some embodiments of the present disclosure, the remote UE may switch (or hand over) from a direct path (e.g., the UE directly accesses the target BS (or target cell) without any relay node) to an indirect path (e.g., the UE indirectly accesses the target BS (or target cell) via a target relay node).

[0060] In some embodiments of the present disclosure, during a path switch (or handover), the UE may release the connection with the source cell (e.g., source BS) before establishing a connection with the target cell (e.g., target BS). This may also be referred to as a "hard handover". Therefore, data transmission is stopped at the source cell before the UE starts communicating with the target cell. This will cause an interruption, which may be severe for services that are sensitive to latency or continuity.

[0061] In order to overcome the above problems, DAPS path switching (or DAPS switching) is introduced, in which the UE maintains the source cell (or source BS) connection after receiving a switching command associated with DAPS, and releases the source cell connection only after successfully accessing the target cell (or target BS). This may also be referred to as "soft switching". In the case of DAPS switching, the UE may continue to receive DL user data from the source until the source cell is released, and continue to transmit UL user data to the source BS until a successful random access procedure is performed on the target BS. Therefore, DAPS switching can be used to reduce or avoid service interruption and ensure service continuity during switching. This may require the UE to simultaneously receive and transmit data at both the source cell and the target cell within a short period of time during the switching procedure. In the context of the present disclosure, "switching" and "path switching" may be used interchangeably.

[0062] Figure 4 Schematic diagram of a wireless communication system 400 according to some embodiments of the present disclosure. Figure 4 The embodiments shown in .

[0063] refer to Figure 4 , the wireless communication system 400 may include some base stations (eg, BS 402A and BS 402B) and some UEs (eg, UE 401A and UE 401B). Figure 4Although a specific number of UEs and BSs are depicted in FIG. 4 , it is contemplated that any number of UEs and BSs may be included in wireless communication system 400. In some examples, UE 401A may be used as Figure 2 The UE 201A and UE 401B shown in FIG. 4 can be used as Figure 2 UE 201B shown in FIG. 1 , and BS 402A and BS 402B may be used as Figure 2 BS202 shown in the.

[0064] UE 401A may communicate with BS 402A. In some examples, UE 401A may communicate with BS 402A via a relay node (e.g., a relay UE, Figure 4 UE 401A may communicate with BS 402A directly without any relay nodes.

[0065] BS 402A may decide to handover UE 401A to a target relay node (eg, UE 401B). UE 401B may communicate with BS 402B. Figure 4 As shown in , DAPS handover can be performed. During DAPS handover, UE 401A maintains both the source connection and the target connection for a certain period of time.

[0066] It should be understood by those skilled in the art that although some embodiments of the present disclosure (e.g., Figure 2 and 4 ) is described with respect to a relay UE, but it may be considered that other types of relay nodes may be used to replace the relay UE.

[0067] Various issues need to be addressed during a DAPS handover of a remote UE. For example, a solution is needed for handling a target relay node during a DAPS handover of a remote UE. For example, during a DAPS handover, the remote UE may receive various messages from the target relay node. Solutions for handling these messages are needed. For example, solutions are needed for handling RLF between the remote UE and the target relay node during a DAPS handover. For example, solutions are needed for handling UL transmissions. More details about embodiments of the present disclosure will be described in the text below in conjunction with the accompanying drawings.

[0068] Figure 5 A flowchart illustrating an exemplary procedure 500 for wireless communication according to some embodiments of the present disclosure. The details described in all the above embodiments of the present disclosure apply to Figure 5 The embodiments shown in .

[0069] refer to Figure 5In operation 511, UE 501A may communicate with BS 502A. In some examples, UE 501A may communicate with BS 502A via a relay node ( Figure 5 1A may communicate with BS 502A directly without any relay node.

[0070] In some examples, UE 501A may be used as Figure 4 UE 401A shown in FIG. 4 , and BS 502A and BS 502B may be used as Figure 4 BS 402A and BS 402B shown in.

[0071] In some embodiments, UE 501A may report measurement results to BS 502A based on the configuration from BS 502A. The measurement results may include measurement results of a cell or a candidate relay node (eg, a relay UE).

[0072] In some embodiments, UE 501A may report capability information to BS 502A. In some embodiments, the capability information may be associated with DAPS path switching. For example, the capability information may indicate whether UE 501A supports DAPS path switching associated with a relay node (e.g., a relay UE). The path switching may be from an indirect path to another indirect path, or from a direct path to an indirect path. For example, the capability information may indicate at least one of the following: whether UE 501A supports a path switching from an indirect path to another indirect path; or whether UE 501A supports a path switching from a direct path to an indirect path.

[0073] In operation 513, BS 502A (source BS) may determine to switch UE 501A to a target relay node (e.g., to an indirect path) via a DAPS path switch. In some embodiments, the target relay node may be a relay UE. In operation 515, BS 502A may transmit a handover request message to a target BS (e.g., BS 502B). In some embodiments, the handover request message may include information about UE 501A (e.g., UE context and UE ID).

[0074] In response to receiving the handover request message, BS 502B may allow the path switch and may transmit a handover request confirmation message to BS 502A via, for example, an Xn interface in operation 517. The handover request confirmation message may include an RRC reconfiguration message. The RRC reconfiguration message (also referred to as an RRC reconfiguration message for path switching) may include a target relay node ( Figure 5(not shown).

[0075] In response to receiving the handover request confirm message, BS 502A may transmit an RRC reconfiguration message including (re)configuration with synchronization to UE 501A in operation 519. In the case of DAPS path switching, the RRC reconfiguration message may also be referred to as "RRC reconfiguration message for DAPS path switching".

[0076] In response to receiving the RRC reconfiguration message, UE 501A may perform a path switching procedure. For example, in operation 521, UE 501A may start a timer for path switching in response to receiving the RRC reconfiguration message. The timer may be T304 as specified in the 3GPP specification in the case of switching to a target cell (e.g., a direct path), or the timer may be T420 as specified in the 3GPP specification for switching to a target relay (e.g., an indirect path). For example, UE 501A may establish a PC5 connection with the target relay node.

[0077] In some embodiments of the present disclosure, UE 501A may indicate the ID of the target cell to the target relay node. This may be advantageous because it may avoid cell reselection at the target relay node.

[0078] In some embodiments of the present disclosure, when a timer for path switching (e.g., T420 as specified in the 3GPP specification) is running, UE 501A may receive a notification message from the target relay node. In some embodiments, the target relay node may transmit a notification message in response to one of the following conditions: RLF occurs between the target relay node and the target cell of the DAPS path switching (or between the target relay node and BS 502A); the target relay node receives an RRC reconfiguration message (e.g., a handover command) containing a reconfiguration with synchronization; the target relay node (re)selects a cell; an RRC connection establishment failure or an RRC recovery failure occurs at the target relay node; the target relay node successfully performs a handover procedure; the handover fails at the target relay node; the target relay node initiates a reestablishment procedure; the target relay node performs a successful reestablishment procedure; the reestablishment procedure fails at the target relay node; or a listen-before-talk (LBT) procedure fails at the target relay node. The RRC connection establishment failure may include, for example, an RRC connection reject or expiration of a timer for an RRC setup request (eg, T300 as specified in 3GPP specifications).

[0079] In some embodiments of the present disclosure, in response to receiving a notification message while the timer for path switching is running, UE 501A may restore to the source connection (e.g., the connection to BS 502A) if the source connection is available. In some embodiments of the present disclosure, in response to receiving a notification message while the timer for path switching is running, UE 501A may perform a reestablishment procedure if the source connection is unavailable.

[0080] In some embodiments of the present disclosure, in response to receiving a notification message while a timer for path switching is running, UE 501A may wait for restoration of the target relay node and may not fall back to the source connection. During the process, UE 501A may transmit or receive data via the source connection.

[0081] For example, in response to receiving a notification message while a timer for path switching is running, UE 501A may suspend the target connection (e.g., the connection to BS 502B). For example, in response to receiving a notification message while a timer for path switching is running, UE 501A may suspend the DAPS path switch.

[0082] In some embodiments, when, for example, the target relay node performs a successful connection establishment or restoration, the target relay node may transmit a restoration indication to the UE 501A (e.g., via a notification message). In some instances, in response to receiving the restoration indication, the UE 501A may restore the suspended target connection. In some instances, in response to receiving the restoration indication, the UE 501A may restore the suspended DAPS path switch.

[0083] In some embodiments, a timer (e.g., a timer for restoration) may be used to determine the waiting time. The value of the timer may be configured by the BS, or, for example, predefined in a standard. For example, in response to receiving a notification message, UE 501A may start a timer for restoration. In response to receiving a restoration indication from the target relay node, UE 501A may stop the timer for restoration. In some embodiments, in response to the expiration of the timer for restoration, UE 501A may restore to the source connection if the source connection is available. In some embodiments, in response to the expiration of the timer for restoration, UE 501A may perform a reestablishment procedure if the source connection is unavailable.

[0084] In some embodiments of the present disclosure, UE 501A may receive a PC5 unicast link release indication while a timer for path switching is running. In some embodiments of the present disclosure, in response to receiving a PC5 unicast link release indication while a timer for path switching is running, UE 501A may revert to a source connection (e.g., a connection to BS 502A) if the source connection is available. In some embodiments of the present disclosure, in response to receiving a PC5 unicast link release indication while a timer for path switching is running, UE 501A may perform a reestablishment procedure if the source connection is unavailable.

[0085] In some examples, the PC5 unicast link release indication may be transmitted from an upper layer (e.g., PC5-S layer) of UE 501A to a lower layer (e.g., AS layer) of UE 501A. In some examples, the PC5 unicast link release indication may be transmitted by the target relay node. For example, the upper layer (e.g., PC5-S layer) of the target relay node may transmit the PC5 unicast link release indication to the upper layer (e.g., PC5-S layer) of UE 501A.

[0086] In some embodiments of the present disclosure, while the timer for path switching is running, UE 501A may detect RLF of the side link between UE 501A and the target relay node. In some embodiments of the present disclosure, in response to detecting RLF while the timer for path switching is running, UE 501A may recover to the source connection (e.g., the connection to BS 502A) if the source connection is available. In some embodiments of the present disclosure, in response to detecting RLF while the timer for path switching is running, UE 501A may perform a reestablishment procedure if the source connection is unavailable.

[0087] In some embodiments as described above, in some cases, such as when UE 501A receives a notification message or a PC5 unicast link release indication, or when UE 501A detects the RLF of the side link between UE 501A and the target relay node when the timer for path switching is running, UE 501A may fall back to the source connection. In these cases, in response to resuming the source connection, UE 501A may transmit failure information associated with the DAPS path switch to the source BS (e.g., BS 502A) in operation 523 (indicated as an option by a dotted arrow). The failure information may indicate the reason why UE 501A reverts to the source connection. For example, the failure information may indicate at least one of the following: receiving a notification message from the target relay node; receiving a PC5 unicast link release indication; or detecting the RLF of the side link between UE 501A and the target relay node. The above description of the notification message and the PC5 unicast link release indication may also apply here. After falling back to the source connection, UE 501A may communicate with BS 502A via the source connection (eg, an indirect path or a direct path).

[0088] In some embodiments as described above, in some cases, such as when UE 501A receives a notification message or a PC5 unicast link release indication, or when UE 501A detects RLF of a side link between UE 501A and a target relay node when a timer for path switching is running, UE 501A may perform a reestablishment procedure. In these cases, after successful reestablishment, UE 501A may transmit a report on a failure occurring during DAPS to the BS, which may facilitate mobility robustness optimization (MRO) in the network. For example, UE 501A may transmit a radio link failure related report (e.g., RLF-report) to the BS.

[0089] In some embodiments of the present disclosure, UE 501A may receive an RRC release message from BS 502A. The RRC release message may include redirected carrier information for redirecting the UE to an NR or inter-radio access technology (RAT) carrier frequency by means of, for example, cell selection when transitioning to an RRC_IDLE or RRC_INACTIVE state. For example, BS 502A may use NR, and the redirected carrier information may indicate redirection to an LTE network (e.g., an Evolved Universal Terrestrial Radio Access (E-UTRA) network).

[0090] In some embodiments, when the core network (CN) type is indicated in the RRC release message, the AS layer of the UE 501A may indicate the available CN type and the received CN type to its upper layer after cell selection, relay selection or relay reselection.

[0091] In some embodiments, in the event that the RRC release message includes a suspension configuration, the UE 501A may enter an inactive state (eg, RRC_INACTIVE) and perform cell selection, relay selection, or relay reselection.

[0092] In some embodiments, in the event that the RRC release message does not include a suspension configuration, the UE 501A may enter an idle state (eg, RRC_IDLE) and perform cell selection, relay selection, or relay reselection.

[0093] Those skilled in the art will appreciate that the sequence of operations in the exemplary process 500 may be changed, and some operations in the exemplary process 500 may be eliminated or modified without departing from the spirit and scope of the present disclosure.

[0094] Figure 6 A flowchart illustrating an exemplary procedure 600 for wireless communication according to some embodiments of the present disclosure. The details described in all the above embodiments of the present disclosure apply to Figure 6 The embodiments shown in .

[0095] refer to Figure 6 In operation 611, UE 601A may communicate with BS 602A. In some examples, UE 601A may communicate with BS 602A via a relay node ( Figure 6 1A may communicate with BS 602A directly without any relay node.

[0096] In some embodiments, UE 601A may report measurement results to BS 602A based on the configuration from BS 602A. The measurement results may include measurement results of a cell or a candidate relay node (eg, a relay UE).

[0097] In some embodiments, UE 601A may report capability information to BS 602A. In some embodiments, the capability information may be associated with DAPS path switching. For example, the capability information may indicate whether UE 601A supports DAPS path switching associated with a relay node (e.g., a relay UE). The path switching may be from an indirect path to another indirect path, or from a direct path to an indirect path. For example, the capability information may indicate at least one of the following: whether UE 601A supports a path switching from an indirect path to another indirect path; or whether UE 601A supports a path switching from a direct path to an indirect path.

[0098] In operation 613, BS 602A (source BS) may determine to switch UE 601A to a target relay node (e.g., relay node 601B) via DAPS path switching. Relay node 601B may be connected to BS 602B. In some embodiments, relay node 601B may be a relay UE. In some examples, UE 601A and relay node 601B may serve as Figure 4 UE 401A and UE 401B shown in FIG. 4 , and BS 602A and BS 602B may be used as Figure 4 BS 402A and BS 402B shown in.

[0099] In operation 615, BS 602A may transmit a handover request message to a target BS (eg, BS 602B). In some embodiments, the handover request message may include information about UE 601A (eg, UE context and UE ID).

[0100] In response to receiving the handover request message, BS 602B may allow the path switch and may transmit a handover request confirmation message to BS 602A via, for example, an Xn interface in operation 617. The handover request confirmation message may include an RRC reconfiguration message. The RRC reconfiguration message (also referred to as an RRC reconfiguration message for path switching) may include the ID of the relay node 601B.

[0101] In response to receiving the handover request confirm message, BS 602A may transmit an RRC reconfiguration message including (re)configuration with synchronization to UE 601A in operation 619. In the case of DAPS path switching, the RRC reconfiguration message may also be referred to as "RRC reconfiguration message for DAPS path switching".

[0102] In response to receiving the RRC reconfiguration message, UE 601A may perform a path switching procedure. For example, in operation 621, UE 601A may start a timer for path switching in response to receiving the RRC reconfiguration message. The timer may be T304 as specified in the 3GPP specification in the case of switching to a target cell (e.g., a direct path), or the timer may be T420 as specified in the 3GPP specification for switching to a target relay (e.g., an indirect path). For example, UE 601A may establish a PC5 connection with relay node 601B.

[0103] In some embodiments of the present disclosure, the UE 601A may indicate the ID of the target cell to the relay node 601 B. This may be advantageous because it may avoid cell reselection at the relay node 601B.

[0104] In operations 623 and 623', UE 601A may transmit an RRC reconfiguration complete message to BS 602B via relay node 601B. In operation 625, in response to transmitting the RRC reconfiguration complete message, UE 601A may stop a timer for path switching (eg, T420 as specified in 3GPP specifications).

[0105] In some embodiments of the present disclosure, the notification message may be received from the relay node 601B after the timer for the path switch stops (eg, before the source connection is released). The triggering conditions for the notification message as described above may also apply here.

[0106] In some embodiments of the present disclosure, in response to receiving a notification message after a timer for path switching stops, the UE 601A may perform a re-establishment procedure.

[0107] In some embodiments of the present disclosure, in response to receiving a notification message after the timer for path switching stops, UE 601A may not perform a reestablishment procedure, especially when the source connection (e.g., the connection to BS 602A) is still available. For example, UE 601A may wait for the recovery of relay node 601B and may not perform a reestablishment procedure. For example, in the case where the source connection is available, UE 601A may prohibit the execution of the reestablishment procedure. In this scenario, due to the failure of the target connection, UE 601A may not receive an RRC reconfiguration message (e.g., for BS 602B) containing an indication to release the source connection.

[0108] For example, in some embodiments, in response to receiving a notification message after the timer for path switching stops, UE 601A may suspend the target connection (e.g., the connection to BS 602B). In some embodiments, when, for example, relay node 601B performs a successful connection establishment or restoration, relay node 601A may transmit a restoration indication to UE 601A (e.g., via a notification message). In some examples, in response to receiving the restoration indication, UE 601A may resume the suspended target connection.

[0109] In some embodiments, a timer (e.g., a timer for restoration) may be used to determine the waiting time. The value of the timer may be configured by the BS, or may be predefined, for example, in a standard. For example, in response to receiving a notification message after the timer for path switching stops, the UE 601A may start a timer for restoration. In response to receiving a restoration indication from the relay node 601B, the UE 601A may stop the timer for restoration. In some embodiments, in response to the expiration of the timer for restoration, the UE 601A may restore to the source connection if the source connection is available. In some embodiments, in response to the expiration of the timer for restoration, the UE 601A may perform a reestablishment procedure if the source connection is unavailable.

[0110] In some embodiments of the present disclosure, UE 601A may receive a PC5 unicast link release indication after a timer for path switching stops (e.g., before the source connection is released). The description of the PC5 unicast link release indication as described above may also apply here. In some embodiments of the present disclosure, in response to receiving a PC5 unicast link release indication after a timer for path switching stops, UE 601A may perform a reestablishment procedure.

[0111] In some embodiments of the present disclosure, UE 601A may detect RLF of the side link between UE 601A and relay node 601B after the timer for path switching stops (e.g., before the source connection is released). In some embodiments of the present disclosure, in response to detecting RLF after the timer for path switching stops, UE 601A may perform a reestablishment procedure.

[0112] In some embodiments of the present disclosure, in response to transmitting an RRC reconfiguration complete message (e.g., transmitted to BS 602B via relay node 601B in operations 623 and 623'), or stopping a timer for path switching (e.g., in operation 625), UE 601A may perform uplink switching of DAPS switching. For example, UE 601A may switch UL transmission to a target connection (e.g., a connection to BS 602B). In some examples, the UL transmission may include UL Packet Data Convergence Protocol (PDCP) data transmission.

[0113] In some embodiments of the present disclosure, the UE 601A may perform uplink switching of the DAPS switching in response to receiving an indication for uplink switching from the relay node 601B.

[0114] In some embodiments of the present disclosure, UE 601A may receive an RRC reconfiguration message from BS 602B in response to an RRC reconfiguration complete message. In some embodiments, the RRC reconfiguration message may include an indication of releasing the source connection. In response to receiving the RRC reconfiguration message, UE 601A may release the source connection (e.g., if the source connection is not released). For example, in the case where the source connection to BS 602A is via a direct path, UE 601A may release the UuRRC configuration from the source cell (e.g., BS 602A). For example, in the case where the source connection to BS 602A is via an indirect path, UE 601A may release the Uu RRC configuration and the PC5 RRC connection between UE 601A and the source relay node.

[0115] Those skilled in the art will appreciate that the sequence of operations in the exemplary process 600 may be changed, and some operations in the exemplary process 600 may be eliminated or modified without departing from the spirit and scope of the present disclosure.

[0116] Figure 7 A flowchart illustrating an exemplary procedure 700 for wireless communication according to some embodiments of the present disclosure. The details described in all the above embodiments of the present disclosure apply to Figure 7 In some examples, the process may be performed by a UE (eg, a remote UE).

[0117] refer to Figure 7 In operation 711, the UE may receive an RRC reconfiguration message from the BS for DAPS path switching from a source connection to a target connection, wherein the RRC reconfiguration message indicates an ID of a target relay node. In operation 713, the UE may start a timer for path switching (e.g., T420 as specified in the 3GPP specification) in response to receiving the RRC reconfiguration message.

[0118] In some embodiments of the present disclosure, the UE may perform at least one of the following: restore to the source connection if the source connection is available in response to receiving a notification message from the target relay node while the timer for path switching is running; restore to the source connection if the source connection is available in response to receiving a PC5 unicast link release indication while the timer for path switching is running; or restore to the source connection if the source connection is available in response to detecting a radio link failure (RLF) of a side link between the UE and the target relay node while the timer for path switching is running.

[0119] In some embodiments of the present disclosure, the UE may perform at least one of the following: performing a re-establishment procedure when the source connection is unavailable in response to receiving a notification message from the target relay node while the timer for path switching is running; performing a re-establishment procedure when the source connection is unavailable in response to receiving a PC5 unicast link release indication while the timer for path switching is running; or performing a re-establishment procedure when the source connection is unavailable in response to detecting a radio link failure (RLF) of a side link between the UE and the target relay node while the timer for path switching is running.

[0120] In some embodiments of the present disclosure, the UE may perform at least one of the following: in response to receiving a notification message from the target relay node while the timer for path switching is running, suspending the target connection; in response to receiving a notification message from the target relay node while the timer for path switching is running, suspending the DAPS path switching; in response to receiving a notification message from the target relay node while the timer for path switching is running, starting the timer for recovery; in response to receiving a recovery indication from the target relay node, resuming the suspended target connection; in response to receiving a recovery indication from the target relay node, resuming the suspended DAPS path switching; in response to receiving a recovery indication from the target relay node, stopping the timer for recovery; in response to expiration of the timer for recovery, resuming to the source connection if the source connection is available; or in response to expiration of the timer for recovery, performing a reestablishment procedure if the source connection is unavailable.

[0121] In some embodiments of the present disclosure, the UE may stop a timer for path switching in response to transmitting an RRC reconfiguration complete message.

[0122] In some embodiments of the present disclosure, the UE may perform at least one of the following after stopping the timer for path switching: performing a re-establishment procedure in response to receiving a notification message from a target relay node; performing a re-establishment procedure in response to receiving a PC5 unicast link release indication; performing a re-establishment procedure in response to detecting a radio link failure (RLF) of a side link between the UE and the target relay node; or prohibiting the execution of the re-establishment procedure in response to receiving a notification message from the target relay node if the source connection is available.

[0123] In some embodiments of the present disclosure, the UE may perform at least one of the following after stopping the timer for path switching: suspending the target connection in response to receiving a notification message from the target relay node; starting a timer for recovery in response to receiving a notification message from the target relay node; resuming the suspended target connection in response to receiving a recovery indication from the target relay node; stopping the timer for recovery in response to receiving a recovery indication from the target relay node; resuming to the source connection if the source connection is available in response to expiration of the timer for recovery; and performing a reconstruction procedure if the source connection is unavailable in response to expiration of the timer for recovery.

[0124] In some embodiments of the present disclosure, the UE may transmit failure information associated with the DAPS path switch to the BS in response to resuming the source connection. The failure information may indicate at least one of the following: receiving a notification message from the target relay node; receiving a PC5 unicast link release indication; or detecting RLF of the side link between the UE and the target relay node.

[0125] In some embodiments of the present disclosure, the PC5 unicast link release indication may be indicated by an upper layer of the UE. In some embodiments of the present disclosure, the PC5 unicast link release indication may be received from a target relay node.

[0126] In some embodiments of the present disclosure, a notification message may be received in response to one of the following conditions: RLF between a target relay node and a target cell of a DAPS path switch; reception of an RRC reconfiguration message containing a configuration with synchronization at the target relay node; cell reselection at the target relay node; RRC connection establishment failure or RRC recovery failure at the target relay node; a successful switching procedure at the target relay node; a failed switching procedure at the target relay node; initiation of a reconstruction procedure at the target relay node; a successful reconstruction procedure at the target relay node; a failed reconstruction procedure at the target relay node; or a failed LBT procedure at the target relay node.

[0127] In some embodiments of the present disclosure, the UE may perform uplink switching in response to one of: transmitting an RRC reconfiguration complete message; stopping a timer for path switching; and receiving an indication for uplink switching from a target relay node.

[0128] In some embodiments of the present disclosure, the UE may transmit the ID of the target cell of the DAPS path switching to the target relay node.

[0129] In some embodiments of the present disclosure, the UE may transmit capability information indicating whether the UE supports DAPS path switching associated with the relay node. The capability information may indicate at least one of the following: whether the UE supports path switching from an indirect path to another indirect path; or whether the UE supports path switching from a direct path to an indirect path.

[0130] Those skilled in the art should understand that the sequence of operations in the exemplary process 700 may be changed, and some operations in the exemplary process 700 may be eliminated or modified without departing from the spirit and scope of the present disclosure.

[0131] Figure 8 A flowchart illustrating an exemplary procedure 800 for wireless communication according to some embodiments of the present disclosure. The details described in all the above embodiments of the present disclosure apply to Figure 8 In some examples, the process may be performed by a UE.

[0132] refer to Figure 8 In operation 811, the BS may receive capability information associated with DAPS path switching from the UE. In operation 813, the BS may transmit an RRC reconfiguration message for DAPS path switching to the UE, wherein the RRC reconfiguration message indicates an ID of a target relay node.

[0133] In some embodiments of the present disclosure, the BS may receive failure information associated with DAPS path switching from the UE. The failure information may indicate at least one of the following: receiving a notification message from the target relay node; receiving a PC5 unicast link release indication; or detecting RLF of the side link between the UE and the target relay node.

[0134] In some embodiments of the present disclosure, the PC5 unicast link release indication may be indicated by an upper layer of the UE. In some embodiments of the present disclosure, the PC5 unicast link release indication may be received at the UE from the target relay node.

[0135] In some embodiments of the present disclosure, a notification message may be received in response to one of the following conditions: RLF between a target relay node and a target cell of a DAPS path switch; reception of an RRC reconfiguration message containing a configuration with synchronization at the target relay node; cell reselection at the target relay node; RRC connection establishment failure or RRC recovery failure at the target relay node; a successful switching procedure at the target relay node; a failed switching procedure at the target relay node; initiation of a reconstruction procedure at the target relay node; a successful reconstruction procedure at the target relay node; a failed reconstruction procedure at the target relay node; or a failed LBT procedure at the target relay node.

[0136] In some embodiments of the present disclosure, the capability information may indicate whether the UE supports DAPS path switching associated with the relay node. For example, the capability information may indicate at least one of the following: whether the UE supports path switching from an indirect path to another indirect path; or whether the UE supports path switching from a direct path to an indirect path.

[0137] Those skilled in the art will appreciate that the sequence of operations in the exemplary process 800 may be changed, and some operations in the exemplary process 800 may be eliminated or modified without departing from the spirit and scope of the present disclosure.

[0138] Fig. 9 A block diagram illustrating an exemplary apparatus 900 according to some embodiments of the present disclosure.

[0139] As in Fig. 9 , the apparatus 900 may include at least one processor 906 and at least one transceiver 902 coupled to the processor 906. The apparatus 900 may be a BS, a relay node, or a UE.

[0140] Although in this figure, elements such as at least one transceiver 902 and processor 906 are described in the singular, the plural may be contemplated unless explicitly limited to the singular. In some embodiments of the present application, the transceiver 902 may be divided into two devices, such as a receiving circuit system and a transmitting circuit system. In some embodiments of the present application, the apparatus 900 may further include an input device, a memory, and / or other components.

[0141] In some embodiments of the present application, the device 900 may be a UE. The transceiver 902 and the processor 906 may interact with each other to facilitate execution of the Figures 1 to 8 In some embodiments of the present application, the device 900 may be a relay node. The transceiver 902 and the processor 906 may interact with each other to facilitate execution of Figures 1 to 8 In some embodiments of the present application, the device 900 may be a BS. The transceiver 902 and the processor 906 may interact with each other to perform Figures 1 to 8 The operations of BS are described in .

[0142] In some embodiments of the present application, the apparatus 900 may further include at least one non-transitory computer-readable medium.

[0143] For example, in some embodiments of the present disclosure, a non-transitory computer-readable medium may store computer-executable instructions thereon to cause the processor 906 to implement the method for the UE as described above. For example, when the computer-executable instructions are executed, the processor 906 interacts with the transceiver 902 to perform Figures 1 to 8The operations of the UE are described in .

[0144] In some embodiments of the present disclosure, a non-transitory computer-readable medium may store thereon computer-executable instructions to cause the processor 906 to implement the method for the relay node as described above. For example, when the computer-executable instructions are executed, the processor 906 interacts with the transceiver 902 to perform Figures 1 to 8 The operations of relay nodes are described in .

[0145] In some embodiments of the present disclosure, a non-transitory computer-readable medium may store computer-executable instructions thereon to cause the processor 906 to implement the method for the BS as described above. For example, when the computer-executable instructions are executed, the processor 906 interacts with the transceiver 902 to perform Figures 1 to 8 The operation of BS is described in .

[0146] Those of ordinary skill in the art will appreciate that the operations or steps of the methods described in conjunction with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. Additionally, in some aspects, the operations or steps of the methods may reside as one or any combination or group of codes and / or instructions on a non-transitory computer-readable medium that may be incorporated into a computer program product.

[0147] Although the present disclosure has been described using specific embodiments of the present disclosure, it is apparent that many alternatives, modifications, and variations may be apparent to those skilled in the art. For example, in other embodiments, the various components of the embodiments may be interchangeable, added, or replaced. In addition, all elements of each figure are not necessary for the operation of the disclosed embodiments. For example, a person of ordinary skill in the art of the disclosed embodiments will be able 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 set forth 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.

[0148] In this document, the terms "switching" and "path switching" are used interchangeably. The term "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment comprising a series of elements not only comprises the elements, but also comprises other elements that are not explicitly listed or inherent to the process, method, article or equipment. In the absence of more constraints, elements starting with "one" or the like do not exclude the presence of additional equivalent elements in the process, method, article or equipment comprising the elements. In addition, the term "another" is defined as at least the second or more. The term "having" and the like as used herein are defined as "comprising". For example, the expression of "A and / or B" or "at least one of A and B" may include any and all combinations of 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, but 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 a radio resource control RRC reconfiguration message for a dual active protocol stack DAPS path switch from a source connection to a target connection from a base station BS, wherein the RRC reconfiguration message indicates an ID of a target relay node; and A timer for path switching is started in response to receiving the RRC reconfiguration message.

2. The UE of claim 1, wherein the processor is further configured to perform at least one of the following: reverting to the source connection if the source connection is available in response to receiving a notification message from the target relay node while the timer for path switching is running; In response to receiving a PC5 unicast link release indication while the timer for path switching is running, reverting to the source connection if the source connection is available; or In response to detecting a radio link failure (RLF) of a side link between the UE and the target relay node while the timer for path switching is running, restoring to the source connection if the source connection is available.

3. The UE of claim 1, wherein the processor is further configured to perform at least one of the following: performing a reestablishment procedure if the source connection is unavailable in response to receiving a notification message from the target relay node while the timer for path switching is running; In response to receiving a PC5 unicast link release indication while the timer for path switching is running, performing a reestablishment procedure if the source connection is unavailable; or In response to detecting a radio link failure (RLF) of a side link between the UE and the target relay node while the timer for path switching is running, a re-establishment procedure is performed if the source connection is unavailable.

4. The UE of claim 1, wherein the processor is further configured to perform at least one of the following: suspending the target connection in response to receiving a notification message from the target relay node while the timer for path switching is running; suspending the DAPS path switch in response to receiving a notification message from the target relay node while the timer for the path switch is running; in response to receiving a notification message from the target relay node while the timer for path switching is running, starting a timer for restoration; in response to receiving a restoration indication from the target relay node, resuming the suspended target connection; in response to receiving a restoration indication from the target relay node, resuming the suspended DAPS path switch; in response to receiving a restoration indication from the target relay node, stopping the timer for restoration; in response to expiry of the timer for restoration, reverting to the source connection if the source connection is available; or In response to expiration of the timer for restoration, a reestablishment procedure is performed if the source connection is unavailable.

5. The UE of claim 1, wherein the processor is further configured to: stopping the timer for path switching in response to transmitting an RRC reconfiguration complete message; and After stopping the timer for path switching, performing at least one of the following: performing a reestablishment procedure in response to receiving a notification message from the target relay node; executing a reestablishment procedure in response to receiving a PC5 unicast link release indication; In response to detecting a radio link failure (RLF) of a side link between the UE and the target relay node, performing a reestablishment procedure; or In response to receiving a notification message from the target relay node, performing a reestablishment procedure is prohibited if the source connection is available.

6. The UE of claim 1, wherein the processor is further configured to: stopping the timer for path switching in response to transmitting an RRC reconfiguration complete message; and After stopping the timer for path switching, performing at least one of the following: suspending the target connection in response to receiving a notification message from the target relay node; In response to receiving a notification message from the target relay node, starting a timer for recovery; in response to receiving a restoration indication from the target relay node, resuming the suspended target connection; in response to receiving a restoration indication from the target relay node, stopping the timer for restoration; In response to expiration of the timer for restoration, reverting to the source connection if the source connection is available; In response to expiration of the timer for restoration, a reestablishment procedure is performed if the source connection is unavailable.

7. The UE of any one of claims 2, 4, and 6, wherein the processor is further configured to transmit failure information associated with the DAPS path switch to the BS in response to resuming to the source connection.

8. The UE according to claim 7, wherein the failure information indicates at least one of the following: receiving a notification message from the target relay node; A PC5 unicast link release indication is received; or A RLF of the side link between the UE and the target relay node is detected.

9. The UE according to any one of claims 2, 3, 5 and 8, wherein the PC5 unicast link release indication is indicated by an upper layer of the UE or received from the target relay node.

10. The UE of any one of claims 2 to 6 and 8, wherein the notification message is received in response to one of the following conditions: RLF between the target relay node and the target cell of the DAPS path switching; receiving, at the target relay node, an RRC reconfiguration message including a configuration with synchronization; cell reselection at the target relay node; an RRC connection establishment failure or an RRC recovery failure at the target relay node; a successful handover procedure at said target relay node; a failover procedure at the target relay node; Initiating a reestablishment procedure at the target relay node; a successful re-establishment procedure at said target relay node; a failure re-establishment procedure at the target relay node; and Failed Listen-Before-Talk (LBT) procedure at the target relay node.

11. The UE of claim 1 , wherein the processor is further configured to perform uplink switching in response to one of: Transmitting an RRC reconfiguration complete message; stopping the timer for path switching; and An indication for uplink switching is received from the target relay node.

12. The UE of claim 1, wherein the processor is further configured to transmit an ID of a target cell of the DAPS path switch to the target relay node.

13. The UE of claim 1, wherein the processor is further configured to transmit capability information indicating whether the UE supports DAPS path switching associated with a relay node.

14. The UE according to claim 13, wherein the capability information indicates at least one of the following: whether the UE supports path switching from an indirect path to another indirect path; or Whether the UE supports path switching from a direct path to an indirect path.

15. A base station BS, comprising: Transceiver; and a processor coupled to the transceiver, wherein the processor is configured to: receiving capability information associated with dual active protocol stack DAPS path switching from a user equipment UE; as well as A radio resource control (RRC) reconfiguration message for the DAPS path switch is transmitted to the UE, wherein the RRC reconfiguration message indicates an ID of a target relay node.

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