Method and apparatus for relay link change and path switching to relay UE

Abstract

The embodiment of the invention relates to a method and equipment for relay link change and path switching to relay UE (User Equipment). In accordance with an embodiment of the present application, a user equipment (UE) includes a transceiver and a processor coupled to the transceiver; and the processor is configured to: receive a radio resource control (RRC) reconfiguration message from a network node, wherein the RRC reconfiguration message includes one of: a relay link change indication if the UE accesses the network node via both a direct path between the UE and the network node and a first indirect path between the UE and the network node associated with a source relay UE; and a path switching indication to a candidate relay UE in the event that the UE accesses the network node via the direct path, the first indirect path, or both the direct path and the first indirect path; and performing a relay link change or path switch based on the RRC reconfiguration message. According to another embodiment of the present application, a source network node comprises: a transceiver; and a processor coupled to the transceiver; and the processor is configured to: transmit a handover request for a path switching operation to one or more candidate network nodes, wherein the handover request includes ID information of a requested target UE served by a target network node; receiving a response message from the one or more candidate network nodes, wherein the response message comprises ID information of at least one candidate relay UE; and transmitting an RRC reconfiguration message associated with the at least one candidate relay UE to a remote UE.

Description

Technical Field

[0001] Embodiments of the present application generally relate to wireless communication technology, and more particularly, to methods and apparatus for relay link change and path switching to a relay UE. Background Art

[0002] Vehicle-to-everything (V2X) has been introduced into 5G wireless communication technology. In terms of the channel structure of V2X communication, the direct link between two user equipments (UEs) is called a sidelink. Sidelink is a long-term evolution (LTE) feature introduced in 3GPP Release 12, and enables direct communication between nearby UEs without the data passing through a base station (BS) or core network.

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

[0004] Currently, in 3GPP 5G wireless systems, etc., details regarding how to design solutions regarding relay link changes and path switching to relay UEs have not been specifically discussed. Summary of the invention

[0005] Some embodiments of the present disclosure provide a user equipment (UE). The UE may include: a transceiver; and a processor coupled to the transceiver. The processor may be configured to: receive a radio resource control (RRC) reconfiguration message from a network node, wherein the RRC reconfiguration message includes one of the following: a relay link change indication in the case where the UE accesses the network node via both a direct path between the UE and the network node and a first indirect path between the UE and the network node and associated with a source relay UE; and a path switching indication to a candidate relay UE in the case where the UE accesses the network node via the direct path, the first indirect path, or both the direct path and the first indirect path; and perform a relay link change or a path switching based on the RRC reconfiguration message.

[0006] In some embodiments of the present disclosure, if the RRC reconfiguration message includes the relay link change indication, then the processor of the UE is configured to perform at least one of the following: starting a timer for the relay link change immediately after receiving the RRC reconfiguration message; receiving a first notification message or a first PC5 unicast link release message from the source relay UE during a path switch from the first indirect path to a second indirect path between the UE and the network node and associated with a target relay UE; or receiving a second notification message or a second PC5 unicast link release message from the target relay UE during a path switch from the first indirect path to the second indirect path.

[0007] In some embodiments of the present disclosure, the RRC reconfiguration message includes configuration information related to at least one candidate relay UE.

[0008] In some embodiments of the present disclosure, the first notification message or the second notification message indicates at least one of the following: Uu radio link failure (RLF); relay UE cell reselection; relay UE handover; Uu RRC connection failure; reception of an RRC connection reject message; expiration of a timer for an RRC setup request; or Uu RRC recovery failure.

[0009] In some embodiments of the present disclosure, in response to receiving the first notification message or the first PC5 unicast link release message during a path switch from the first indirect path to the second indirect path, the processor of the UE is configured to perform at least one of the following: if the UE has not released the PC5 link between the UE and the source relay UE, then ignore the first notification message or the first PC5 unicast link release message; stop receiving data from the source relay UE; or stop receiving the data from the source relay UE and release the PC5 link between the UE and the source relay UE.

[0010] In some embodiments of the present disclosure, the processor of the UE is configured to transmit a first message associated with a relay link change failure to the network node in response to at least one of the following: expiration of the timer for the relay link change; or receipt of the second notification message or the second PC5 unicast link release message.

[0011] In some embodiments of the present disclosure, the first message includes at least one of the following: the expiration of the timer for the relay link change; the receipt of the second notification message or the second PC5 unicast link release message from the target relay UE; or a set of measurement results associated with at least one candidate relay UE.

[0012] In some embodiments of the present disclosure, the processor of the UE is configured to: maintain the first indirect path until the UE receives an indication to release the source relay link; and if the UE fails to access the target relay UE, perform a fallback operation to communicate with the network node via the first indirect path.

[0013] In some embodiments of the present disclosure, the processor of the UE is configured to transmit information related to the fallback operation to the network node.

[0014] In some embodiments of the present disclosure, if the RRC reconfiguration message includes the path switch indication, then the RRC reconfiguration message further includes one or more sets of conditions associated with one or more candidate relay UEs.

[0015] In some embodiments of the present disclosure, the processor of the UE is configured to start a timer for path switching immediately after at least one of the following occurs: path switching to one candidate relay UE within the one or more candidate relay UEs; applying the RRC reconfiguration message when the RRC reconfiguration message includes a reconfigurationWithSync information element (IE) for path switching to the one candidate relay UE; or applying the RRC reconfiguration message when the path switching indication in the RRC reconfiguration message is related to the one candidate relay UE.

[0016] Some embodiments of the present application provide a source network node (e.g., a source BS). The source network node may include: a transceiver; and a processor coupled to the transceiver. The processor may be configured to: transmit a switching request for a path switching operation to one or more candidate network nodes, wherein the switching request includes identity (ID) information of a requested target relay user equipment (UE) served by a target network node; receive a response message from the one or more candidate network nodes, wherein the response message includes ID information of at least one candidate relay UE; and transmit a radio resource control (RRC) reconfiguration message associated with the at least one candidate relay UE to a remote UE.

[0017] In some embodiments of the present disclosure, the processor of the source network node is configured to communicate with the remote UE via at least one of a direct path or an indirect path between the remote UE and the source network node and associated with a source relay UE.

[0018] In some embodiments of the present disclosure, the RRC reconfiguration message includes at least one of the following: the ID information of the at least one candidate relay UE; or one or more sets of conditions associated with the at least one candidate relay UE.

[0019] In some embodiments of the present disclosure, the processor of the source network node is configured to receive a first message from a first candidate network node among the one or more candidate network nodes, and the first message instructs the source network node to cancel the path switching operation to a first candidate relay UE associated with the first candidate network node.

[0020] In some embodiments of the present disclosure, the first message includes at least one of the following: ID information of the first candidate relay UE; or a reason for canceling the path switching operation to the first candidate relay UE.

[0021] In some embodiments of the present disclosure, the processor of the source network node is configured to receive a second message from a second candidate network node within the one or more candidate network nodes, and the second message indicates that the remote UE has successfully accessed a target relay UE associated with the second candidate network node.

[0022] In some embodiments of the present disclosure, the second message includes at least one of the following: the ID information of the requested target relay UE; the ID information of the target relay UE; or the ID information of the target cell of the target relay UE.

[0023] In some embodiments of the present disclosure, the ID information of the target relay UE is added to the second message in the following form: independent of the ID information of the requested target relay UE; or sub-level information of the ID information of the requested target relay UE.

[0024] In some embodiments of the present disclosure, the second message includes the ID information of the requested target relay UE, and wherein the processor of the source network node is configured to deem that the remote UE has successfully accessed the candidate relay UE corresponding to the ID information of the requested target relay UE.

[0025] In some embodiments of the present disclosure, the processor of the source network node is configured to transmit a third message to other candidate network nodes within the one or more candidate network nodes.

[0026] In some embodiments of the present disclosure, the third message indicates at least one of the following: an ongoing path switching preparation operation or a prepared path switching operation to a group of candidate relay UEs associated with the other candidate network nodes is to be canceled; or the remote UE has successfully accessed the target relay UE.

[0027] In some embodiments of the present disclosure, the third message includes at least one of the following: ID information of a group of candidate cells associated with the other candidate network nodes; or ID information of a group of candidate relay UEs associated with the other candidate network nodes.

[0028] In some embodiments of the present disclosure, the ID information of the group of candidate relay UEs is added to the third message as sub-level information of the ID information of the target cell.

[0029] In some embodiments of the present disclosure, the third message includes the ID information of a set of candidate cells associated with the other candidate network nodes, and the other candidate network nodes believe that the source network node is only canceling the handover associated with the set of candidate cells and one or more candidate relay UEs served by the set of candidate cells.

[0030] In some embodiments of the present disclosure, the processor of the source network node is configured to receive at least one of the following from the remote UE: a message associated with a relay link change failure during a path switch from a first indirect path between the UE and the source network node and associated with a source relay UE to a second indirect path between the remote UE and the source network node and associated with a target relay UE; or information related to a fallback operation performed by the remote UE to communicate with the source network node via the first indirect path.

[0031] Some embodiments of the present application provide a candidate network node (e.g., a candidate BS). The candidate network node may include: a transceiver; and a processor coupled to the transceiver. The processor may be configured to: receive a switching request for a path switching operation from a source network node, wherein the switching request includes identity (ID) information of a requested target relay user equipment (UE) of a target network node, and the source network node is configured to communicate with the UE via at least one of a direct path or an indirect path between the UE and the source network node and associated with the source relay UE; and transmit a response message to the source network node, wherein the response message includes ID information of the candidate relay UE associated with the candidate network node.

[0032] In some embodiments of the present disclosure, the processor of the candidate network node is configured to transmit a first message to the source network node, and the first message instructs the source network node to cancel the path switching operation to the candidate relay UE.

[0033] In some embodiments of the present disclosure, the first message includes at least one of the following: ID information of the candidate relay UE; or a reason for canceling the path switching operation to the candidate relay UE.

[0034] In some embodiments of the present disclosure, the processor of the candidate network node is configured to transmit a second message to the source network node, the second message indicating that the UE has successfully accessed the candidate relay UE and the candidate relay UE serves as a target relay UE.

[0035] In some embodiments of the present disclosure, the second message includes at least one of the following: the ID information of the requested target relay UE; the ID information of the target relay UE; or the ID information of the target cell of the target relay UE.

[0036] In some embodiments of the present disclosure, at least one of the ID information of the target relay UE or the ID information of the target cell is added to the second message in the following form: independent of the ID information of the requested target relay UE; or sub-layer information of the ID information of the requested target relay UE.

[0037] In some embodiments of the present disclosure, the second message includes the ID information of the requested target relay UE, and the source network node considers that the UE has successfully accessed the candidate relay UE corresponding to the ID information of the requested target relay UE.

[0038] In some embodiments of the present disclosure, the processor of the candidate network node is configured to receive a third message from the source network node, and the third message indicates at least one of the following: an ongoing path switching preparation operation or a prepared path switching operation to a group of candidate relay UEs including the candidate relay UE is to be canceled; or the UE has successfully accessed the target relay UE.

[0039] In some embodiments of the present disclosure, the third message includes at least one of the following: ID information of a group of candidate cells associated with a group of candidate network nodes including the candidate network node; or ID information of the group of candidate relay UEs including the candidate network node.

[0040] In some embodiments of the present disclosure, the ID information of the group of candidate relay UEs is added to the third message as sub-level information of the ID information of the target cell.

[0041] In some embodiments of the present disclosure, the third message includes the ID information of a set of candidate cells associated with a set of candidate network nodes including the candidate network node, and the candidate network node is configured to consider that the source network node is canceling only the handover associated with the set of candidate cells and one or more candidate relay UEs served by the set of candidate cells.

[0042] 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 from a network node, wherein the RRC reconfiguration message includes one of the following: a relay link change indication when the UE accesses the network node via both a direct path between the UE and the network node and a first indirect path between the UE and the network node and associated with a source relay UE; and a path switching indication to a candidate relay UE when the UE accesses the network node via the direct path, the first indirect path, or both the direct path and the first indirect path; and performing a relay link change or a path switching based on the RRC reconfiguration message.

[0043] Some embodiments of the present disclosure provide a method performed by a source network node (e.g., a source BS). The method may include: transmitting a switching request for a path switching operation to one or more candidate network nodes, wherein the switching request includes identity (ID) information of a requested target relay user equipment (UE) served by the target network node; receiving a response message from the one or more candidate network nodes, wherein the response message includes ID information of at least one candidate relay UE; and transmitting a radio resource control (RRC) reconfiguration message associated with the at least one candidate relay UE to a remote UE.

[0044] Some embodiments of the present disclosure provide a method performed by a candidate network node (e.g., a candidate BS). The method may include: receiving a switching request for a path switching operation from a source network node, wherein the switching request includes identity (ID) information of a requested target relay user equipment (UE) of a target network node, and the source network node is configured to communicate with the UE via at least one of a direct path or an indirect path between the UE and the source network node and associated with the source relay UE; and transmitting a response message to the source network node, wherein the response message includes ID information of a candidate relay UE associated with the candidate network node.

[0045] Some embodiments of the present application also provide an apparatus for wireless communication. The apparatus includes: a non-transitory computer-readable medium having computer-executable instructions stored thereon; a receiving circuit system; a transmitting circuit system; and a processor coupled to the non-transitory computer-readable medium, the receiving circuit system, and the transmitting circuit system, wherein the computer-executable instructions cause the processor to implement any of the above-mentioned methods performed by a UE, a source network node (e.g., a source BS), or a candidate network node (e.g., a candidate BS).

[0046] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to describe the manner in which the advantages and features of the present application can be obtained, the description of the present application is presented by reference to specific embodiments of the present application illustrated in the accompanying drawings. These drawings depict only example embodiments of the present application and therefore should not be considered to limit the scope of the present application.

[0048] Figure 1 A schematic diagram illustrating a wireless communication system according to some embodiments of the present application is illustrated.

[0049] Figure 2 An exemplary wireless communication system according to some embodiments of the present application is illustrated.

[0050] Figure 3 A flow chart illustrating a method of performing a relay link change or path switch according to some embodiments of the present application.

[0051] Figure 4 A flow chart illustrating a method of transmitting a handover request according to some embodiments of the present application.

[0052] Figure 5 A flow chart illustrating a method of receiving a handover request according to some embodiments of the present application is shown.

[0053] Figure 6 A flow chart illustrating a relay link change operation according to some embodiments of the present application.

[0054] Figure 7 A flow chart illustrating a relay link change operation according to some embodiments of the present application.

[0055] Figure 8 A flow chart illustrating a path switching operation to a relay UE according to some embodiments of the present application is shown.

[0056] Fig. 9A block diagram illustrating an exemplary apparatus according to some embodiments of the present application is shown. DETAILED DESCRIPTION

[0057] The detailed description is intended to describe the preferred embodiments of the present application, but is not intended to represent the only form in which the present application can be practiced. It should be understood that the same or equivalent functions can be achieved by different embodiments that are intended to be included in the spirit and scope of the present application.

[0058] Reference will now be made in detail to some embodiments of the present application, examples of which are illustrated in the accompanying drawings. To facilitate understanding, the embodiments are provided in a specific network architecture and new service context, such as 3GPP 5G, 3GPP LTE Release 8, etc. Please consider that, as network architectures and new service contexts evolve, all embodiments in the present application are also applicable to similar technical issues; and in addition, the terms recorded in the present application may be changed, which will not affect the principles of the present application.

[0059] Figure 1 The diagram illustrates a schematic diagram of a wireless communication system according to some embodiments of the present application. Figure 1 As illustrated and shown in , for illustrative purposes, a wireless communication system 100 includes at least two UEs (ie, UE 101 and relay UE 102) and at least one BS (eg, BS 103). Figure 1 Although a specific number of UEs and BSs are depicted in FIG. 1 , please consider that any number of UEs and BSs may be included in the wireless communication system 100. Figure 1 , UE 101 may communicate with BS 103 via a direct path between UE 101 and BS 103 or via an indirect path between UE 101 and BS 103 through relay UE 102. That is, UE 101 may communicate with BS 103 via multiple paths. The multiple paths may also be named "multipath" or the like.

[0060] The UE in the wireless communication system 100 may include a computing device, such as a desktop computer, a laptop computer, a personal digital assistant (PDA), a tablet computer, a smart TV (e.g., a TV connected to the Internet), a set-top box, a game console, a security system (including a security camera), a vehicle-mounted computer, a network device (e.g., a router, a switch, and a modem), an Internet of Things (IoT) device, etc. According to some embodiments of the present application, the UE may include a portable wireless communication device, a smart phone, a cellular phone, a flip phone, a device with a subscriber identity module, a personal computer, a selective call receiver, or any other device capable of sending and receiving communication signals on a wireless network. In some embodiments of the present application, the UE includes a wearable device, such as a smart watch, a fitness band, an optical head-mounted display, etc. In addition, the UE may be referred to as a subscriber unit, a mobile device, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a subscriber station, a user terminal or a device, or described using other terms used in the art. The UE may communicate directly with the BS via a UL communication signal.

[0061] In some embodiments of the present application, each of the UEs may be deployed with IoT applications, enhanced mobile broadband (eMBB) applications, and / or ultra-reliable and low latency communications (URLLC) applications. Please consider that the specific types of applications deployed in the UEs may be changed and are not limited.

[0062] The BSs in the wireless communication system 100 may be distributed throughout a geographic area. In certain embodiments of the present application, each of the BSs may also be referred to as an access point, an access terminal, a base, a base unit, a macro cell, a node B, an evolved node B (eNB), a gNB, an NG-RAN (next generation radio access network) node, a home node B, a relay node or a device, or described using other terms used in the art. A BS is typically part of a radio access network, which may include one or more controllers that can be communicatively coupled to one or more corresponding BSs. Each of the BSs may include one or more cells. Each UE may perform a cell selection process between different cells of different BSs.

[0063] The wireless communication system 100 may be compatible with any type of network capable of sending and receiving wireless communication signals. For example, the wireless communication system 100 may be 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 high altitude platform network, and / or other communication networks.

[0064] In some embodiments of the present application, the wireless communication system 100 may be compatible with the 5G New Radio (NR) of the 3GPP protocol, wherein the BS transmits data using an OFDM modulation scheme on the DL and the UE 101 transmits data using a single carrier frequency division multiple access (SC-FDMA) or OFDM scheme on the UL. However, more generally, the wireless communication system 100 may implement some other open or proprietary communication protocols, such as WiMAX and other protocols.

[0065] In some embodiments of the present application, the BS in the wireless communication system 100 may communicate using other communication protocols (e.g., IEEE 802.11 series wireless communication protocols). In addition, in some embodiments of the present application, the BS may communicate via a licensed spectrum, while in other embodiments, the BS may communicate via an unlicensed spectrum. The present application is not intended to be limited to implementations of any particular wireless communication system architecture or protocol. In other embodiments of the present application, the BS may communicate with the UE using the 3GPP 5G protocol.

[0066] Figure 2 The diagram illustrates an exemplary wireless communication system according to some embodiments of the present application. Figure 2 As shown in FIG. 1 , the wireless communication system includes a gNB 202, an ng-eNB 203, and some V2X UEs, namely, UE 201-A, UE 201-B, and UE 201-C. Each of these UEs may refer to Figure 1 UE 101a, UE 101b or relay UE 103 shown and illustrated in .

[0067] Specifically, UE 201-A is within the coverage of gNB 202, UE 201-B is within the coverage of ng-eNB 203, and UE 201-C is outside the coverage of gNB 202 and ng-eNB 203. Support for V2X services via the PC5 interface may be provided by NR sidelink communication and / or V2X sidelink communication. NR sidelink communication may support one of three types of transmission modes for a pair of source layer-2 (L2) identity (ID) and destination L2 ID: unicast transmission; multicast transmission; and broadcast transmission. Sidelink transmission and reception via the PC5 interface is supported when the UE is within the NG-RAN coverage or outside the NG-RAN coverage.

[0068] UE 201-A within the coverage of gNB 202 may perform sidelink unicast transmission, sidelink multicast transmission, or sidelink broadcast transmission via the PC5 interface. UE 201-C outside the coverage may also perform sidelink transmission and reception via the PC5 interface. Please consider that, according to some other embodiments of the present application, the V2X communication system may include more or fewer BSs and more or fewer V2X UEs. In addition, please consider that Figure 2 The names of the V2X UEs (which represent Tx UE, Rx UE, etc.) illustrated and shown in FIG. 2 may be different, for example, UE 201c, UE 204f, UE 208g, etc.

[0069] In addition, although Figure 2 Each V2X UE shown in the figure is illustrated in the shape of a mobile phone, but please consider that according to some other embodiments of the present application, the V2X communication system may include any type of UE (e.g., a roadmap device, a mobile phone, a computer, a laptop, an IoT (Internet of Things) device, or other type of device).

[0070] according to Figure 2 In some embodiments, UE 201-A is used as a Tx UE, and UE 201-B and UE 201-C are used as Rx UEs. UE 201-A can exchange V2X messages with UE 201-B or UE 201-C via a sidelink (e.g., a PC5 interface defined in 3GPP TS23.303). UE 201-A can transmit information or data to other UEs within the V2X communication system via sidelink unicast, sidelink multicast, or sidelink broadcast. Sidelink communications include NR sidelink communications and V2X sidelink communications. For example, UE 201-A can transmit data to UE 201-C in an NR sidelink unicast session, and UE 201-B can transmit data to UE 201-C in a V2X sidelink unicast session. UE 201-A may transmit data to UE 201-B and UE 201-C in the multicast group via the sidelink multicast transmission session.

[0071] Sidelink communication includes NR sidelink communication and V2X sidelink communication. Figure 2 Demonstration of NR sidelink communications as specified in 3GPP TS 38.311. V2X sidelink communications as specified in 3GPP TS 36.311.

[0072] Currently, details on how to design relay link changes and path switching to relay UEs have not been specifically discussed. Embodiments of the present application are intended to address these issues. In embodiments of the present application, a multipath scenario refers to a direct path between a UE and a BS and / or an indirect path between a UE and a BS via a relay UE. Multipath may also be named "multiple paths" or the like.

[0073] Specifically, in some embodiments, in a multipath scenario, a mechanism is studied to handle the situation where a remote UE receives a notification message or a PC5 unicast link release message from a source relay link in a relay link change scenario. In some embodiments, if the timer for the relay link change expires, a fallback mechanism for the source relay UE is studied. In some embodiments, after a successful fallback operation of the UE, a report from the UE to the source direct path is required. In some embodiments, during a conditional path switch to a target relay UE, a condition is introduced to stop the timer for the path switch to the target relay UE. In some embodiments, for some Xn messages for path switching to a target relay UE, information (e.g., cause and / or relay UE ID) is required. More details will be illustrated in the following text in conjunction with the accompanying drawings.

[0074] Figure 3 The flowchart of the method for performing a relay link change or path switching according to some embodiments of the present application is illustrated. The method may be performed by a UE or a remote UE (e.g., Figure 1 , 2 6-8) is performed by UE101, UE 201-C, UE 601, UE 701 or UE 801 as illustrated and shown in any one of UEs 6-8. Although described with respect to a UE or a remote UE, it should be understood that other devices may be configured to perform the same as Figure 3 A similar approach to the one used in this paper.

[0075] exist Figure 3 In the exemplary method 300 shown in FIG. 1 , in operation 301 , a UE (eg, Figure 1 1 and 101) may receive a message from a network node (e.g., Figure 1 BS 103 as illustrated and shown in FIG. 1 receives an RRC reconfiguration message. The RRC reconfiguration message may include one of the following:

[0076] (1) The UE is connected to the network node via a “direct path between the UE and the network node” and a “path between the UE and the network node and the source relay UE (e.g. Figure 1 In the case where both access network nodes are associated with the relay BS 102) illustrated and shown in the figure, the relay link change indication is given. For simplicity, this indirect path is labeled as "indirect path #1".

[0077] (2) When the UE accesses the network node via the direct path, the indirect path #1, or both the direct path and the indirect path #1, a path switching instruction is issued to the candidate relay UE.

[0078] In operation 302, the UE may perform a relay link change or a path switch based on the RRC reconfiguration message.

[0079] In some embodiments, if the RRC reconfiguration message includes a relay link change indication, the UE may perform at least one of the following:

[0080] (1) The timer for relay link change is started immediately after receiving the RRC reconfiguration message.

[0081] (2) Between the UE and the network node and the target relay UE (e.g., Figure 1 During a path switch of an indirect path (labeled as “indirect path #2”) associated with a relay UE (not shown in the figure), a notification message (labeled as “Notification message #1”) or a PC5 unicast link release message (labeled as “PC5 unicast link release message #1”) is received from a source relay UE. In some embodiments, the notification message #1 indicates at least one of the following: UuRLF between the source relay UE and the network node; cell reselection of the source relay UE; handover of the source relay UE; Uu RRC connection failure of the source relay UE; RRC connection rejection message received by the source relay UE; expiration of a timer for RRC setup request at the source relay UE (e.g., timer T300 specified in the 3GPP standard document); or Uu RRC recovery failure of the source relay UE.

[0082] (3) During the path switch from the indirect path #1 to the indirect path #2, a notification message (labeled as "Notification message #2") or a PC5 unicast link release message (labeled as "PC5 unicast link release message #2") is received from the target relay UE. In some embodiments, the notification message #2 indicates at least one of the following: UuRLF between the target relay UE and the network node; cell reselection of the target relay UE; handover of the target relay UE; Uu RRC connection failure of the target relay UE; RRC connection rejection message received by the target relay UE; expiration of a timer for RRC setup request (e.g., timer T300) at the target relay UE; or Uu RRC recovery failure of the target relay UE.

[0083] In some embodiments, the RRC reconfiguration message includes configuration information related to at least one candidate relay UE.

[0084] In some embodiments, in response to receiving a notification message #1 or a PC5 unicast link release message #1 from a source relay UE during a path switch from an indirect path #1 to an indirect path #2, the UE may perform one of the following:

[0085] (1) If the UE has not released the PC5 link between the UE and the source relay UE, then ignore the notification message #1 or the PC5 unicast link release message #1;

[0086] (2) stop receiving data from the source relay UE; and

[0087] (3) Stop receiving data from the source relay UE and release the PC5 link between the UE and the source relay UE. Figure 6 Specific examples are described in the Examples below.

[0088] In some embodiments, the UE may transmit a message associated with the relay link change failure to the network node in response to: expiration of a timer for the relay link change; and / or receipt of a notification message #2 or a PC5 unicast link release message #2 from the target relay UE. In one embodiment, the message associated with the relay link change failure may include or indicate at least one of the following:

[0089] (1) Expiration of a timer for relay link change (e.g., timer T420 specified in the 3GPP standard document);

[0090] (2) receiving notification message #2 or PC5 unicast link release message #2; or

[0091] (3) A set of measurement results associated with at least one candidate relay UE.

[0092] In some embodiments, the UE may maintain the indirect path #1 until the UE receives an indication to release the source relay link, and if the UE fails to access the target relay UE, the UE may perform a fallback operation to communicate with the network node via the indirect path #1. For example, after the timer for the relay link change (e.g., timer T420) expires, the UE may immediately determine that it has failed to access the target relay UE, and then may perform a fallback operation.

[0093] In an embodiment of the present application, when a remote UE communicating with a BS via a target relay UE performs a fallback operation, the remote UE may release the PC5 link between the remote UE and the target relay UE and communicate with the BS via an indirect PC5 link between the remote UE and the source relay UE. That is, by performing the fallback operation, the remote UE may switch back from the target relay link to the source relay link.

[0094] Back reference Figure 3In some embodiments, after performing the fallback operation, the UE may transmit information related to the fallback operation to the network node. Figure 7 Specific examples are described in the Examples below.

[0095] In some embodiments, if the RRC reconfiguration message includes a path switch indication, the RRC reconfiguration message further includes one or more sets of conditions associated with one or more candidate relay UEs, for example, one or more sets of path switch conditions.

[0096] In some embodiments, the UE may start a timer for path switching upon occurrence of at least one of the following:

[0097] (1) Path switching to a candidate relay UE among one or more candidate relay UEs;

[0098] (2) In the case where the RRC reconfiguration message includes a reconfigurationWithSync IE for path switching to a candidate relay UE, the RRC reconfiguration message is applied; or

[0099] (3) In the case where the path switch indication in the RRC reconfiguration message is related to a candidate relay UE, the RRC reconfiguration message is applied. For example, during the application of the RRC Reconfiguration message, the UE may apply the parameters included in the RRC Reconfiguration message. Figure 8 Specific examples are described in the Examples below.

[0100] In one embodiment, after receiving the RRC reconfiguration message, the UE may evaluate the one or more sets of conditions.Once a set of conditions associated with a candidate relay UE is met, the UE may perform a path switch to the candidate relay UE.

[0101] In some embodiments of the present application, new events related to the conditions for triggering measurement reports or path switching conditions are defined as follows, namely, event Z1 and event Z2. For example, event Z1 and / or event Z2 may be defined in the RRC specification. Parameters such as offsets will be configured for the UE, and the UE may determine whether the measurement report is triggered based on the configured event Z1 or event Z2. Event Z1 and event Z2 may be used in the case of indirect to indirect path switching.

[0102] In some cases, the UE may evaluate whether event Z1 and / or event Z2 are achieved before reporting the measurement results associated with the candidate relay UE to the BS. When event Z1 and / or event Z2 are achieved, the UE may report the measurement results. In some other cases, the UE may evaluate whether event Z1 and / or event Z2 are achieved before performing a path switch. When event Z1 and / or event Z2 are achieved, the UE may perform a path switch to the candidate relay UE.

[0103] - Event Z1: (the serving relay UE becomes worse than threshold 1 and the candidate relay UE becomes better than threshold 2)

[0104] - When both conditions Z1-1 and Z1-2 specified below are fulfilled, the UE shall consider the entry conditions of this event to be met;

[0105] - When the condition Z1-3 or condition Z1-4 specified below (i.e. at least one of the two) is fulfilled, the UE shall consider the exit condition of this event to be met;

[0106] Inequality Z1-1 (entry condition 1)

[0107] Mp+Hys <Thresh1

[0108] Inequality Z1-2 (entry condition 2)

[0109] Mr–Hys>Thresh2

[0110] Inequality Z1-3 (leaving condition 1)

[0111] Mp–Hys>Thresh1

[0112] Inequality Z1-4 (leaving condition 2)

[0113] Mr+Hys <Thresh2

[0114] The variables in the formula are defined as follows:

[0115] Mp is the measurement result of the serving relay UE without taking any offset into account.

[0116] Mr is the measurement result of the candidate L2 U2N relay UE without taking any offset into account.

[0117] Hys is the hysteresis parameter for this event (ie, the hysteresis defined in reportConfigInterRAT for this event).

[0118] Thresh1 is the threshold parameter for this event (ie, y1-Threshold1 defined in reportConfigInterRAT for this event).

[0119] Thresh2 is the threshold parameter for this event (ie, y1-Threshold2-Relay defined in reportConfigInterRAT for this event).

[0120] Mp is expressed in dBm in the case of RSRP, or in dB in the case of RSRQ and SINR.

[0121] Mr is expressed in dBm or dB, depending on the measurement quantity of the candidate L2 U2N relay UE.

[0122] Hys is expressed in dB.

[0123] Thresh1 is expressed in the same units as Mp.

[0124] Thresh2 is expressed in the same units as Mr.

[0125] - Event Z2 (the offset of the serving L2 U2N relay UE is better than the offset of the candidate L2 U2N relay UE)

[0126] Figure 4 The flowchart of the method for transmitting a switching request according to some embodiments of the present application is illustrated. The method may be performed by a source network node (e.g., Figure 1 , 2 8 and any of the BS 103, gNB 202 or source BS 803) performed. Although described with respect to a source network node (e.g., a source BS), it should be understood that other devices may be configured to perform the same as Figure 4 A similar approach to the one used in this paper. Figure 8 The embodiments described in Figure 4 Specific examples of embodiments are as follows.

[0127] exist Figure 4 In the exemplary method 400 shown in FIG. 4 , in operation 401, a source network node (eg, Figure 8 803) may provide one or more candidate network nodes (e.g., Figure 8 The candidate BS 805 illustrated and shown in FIG. 8 transmits a switching request for a path switching operation. The switching request may include ID information of a requested target relay UE served by the target network node, which may be a target relay UE selected by the source network node.

[0128] In operation 402, the source network node may receive one or more response messages from one or more candidate network nodes. The one or more response messages may include ID information of at least one candidate relay UE. For example, if there are three candidate network nodes (e.g., Figure 8 In the embodiment of the present invention, if the source network node includes candidate gNB#1, candidate gNB#2 and candidate gNB#3), the source network node may receive three response messages, each of which includes the ID information of a candidate relay UE associated with the corresponding candidate network node.

[0129] In operation 403, the source network node may send a message to a remote UE (eg, Figure 8 UE 801) illustrated and shown in FIG. 8 transmits an RRC reconfiguration message associated with at least one candidate relay UE.

[0130] In some embodiments, the network node may communicate with the remote UE via at least one of a "direct path" or an "indirect path between the remote UE and the source network node and associated with the source relay UE" (ie, via multiple paths).

[0131] In some embodiments, the RRC reconfiguration message includes at least one of the following: ID information of at least one candidate relay UE; and / or one or more sets of conditions (eg, several sets of path switching conditions) associated with at least one candidate relay UE.

[0132] In some embodiments, the source network node may receive a message (labeled as "Message #1") from a candidate network node (labeled as "Candidate Network Node #1") within one or more candidate network nodes. Message #1 may indicate that the source network node cancels a path switching operation to a candidate relay UE (labeled as "Candidate Relay UE #1") associated with the candidate network node #1. In one embodiment, Message #1 may include: ID information of the candidate relay UE #1; and / or a reason for canceling the path switching operation to the candidate relay UE #1. In one embodiment, Message #1 may be a conditional handover cancel message, such as a CONDITIONAL HANDOVER CANCEL message, or a conditional path switching cancel message.

[0133] In general, the target NG-RAN node initiates the procedure by sending an Xn message, such as a Conditional Handover Cancel message, to the source NG-RAN node. The target NG-RAN node shall indicate the reason for cancelling the conditional path switch by an appropriate cause value. Upon receipt of the Xn message, the source NG-RAN node shall assume that the target NG-RAN node is about to remove any reference to candidate cells and release any resources previously reserved for candidate cells associated with UE associated signalling identified by the source NG-RAN node UE XnAP ID IE and the target NG-RAN node UE XnAP ID IE. If a List of Candidate Cells to be Cancelled IE is included in the Xn message, the source NG-RAN node shall assume that only the resources reserved for the cells identified by the included NG-RAN CGI are about to be released.

[0134] Back reference Figure 4 In some embodiments, the source network node may receive a message (labeled as "Message #2") from a candidate network node (labeled as "Candidate Network Node #2") within the one or more candidate network nodes. Message #2 may indicate that the UE has successfully accessed a target relay UE associated with Candidate Network Node #2 (e.g., Figure 8 804). Candidate network node #2 may be the same as or different from candidate network node #1.

[0135] In one embodiment, message #2 may include: the ID information of the requested target relay UE; the ID information of the target relay UE; and / or the ID information of the target cell of the target relay UE. For example, in some embodiments, the ID information of the target relay UE may be added to message #2 in a form independent of the ID information of the requested target relay UE, for example, as shown in Table 1 below. In some other embodiments, the ID information of the target relay UE may be added to message #2 as sub-level information of the ID information of the requested target relay UE, for example, as shown in Table 2 below. In one embodiment, message #2 may be a handover success message, for example, a HANDOVER SUCCESS message.

[0136] In general, the target NG-RAN node may initiate the procedure by sending an Xn message, such as a Handover Success message, to the source NG-RAN node. If deferred data forwarding is configured for this UE, the source NG-RAN node shall start data forwarding using the tunnel information associated with the global target cell ID provided in the Xn message. When the source NG-RAN node receives the Xn message, it shall consider that all other CHO preparations accepted for this UE under the same UE-associated signaling connection in the target NG-RAN node have been cancelled.

[0137] exist Figure 4 In some embodiments, the ID information of the target relay UE may be added to an Xn message such as a handover success message, for example, the “target relay UE ID” shown in Table 1 below.

[0138] Table 1

[0139]

[0140] exist Figure 4 In some other embodiments, the ID information of the target relay UE may be added to an Xn message such as a switching success message as sub-level information of the requested target relay UE ID information, for example, "target relay UE ID" is sub-level information of "requested target cell ID", as shown in Table 2 below.

[0141] Table 2

[0142]

[0143]

[0144] Back reference Figure 4 In some embodiments, message #2 may include the ID information of the requested target relay UE. The source network node may consider that the UE has successfully accessed the candidate relay UE corresponding to the ID information of the requested target relay UE.

[0145] In some embodiments, the source network node may transmit a message (labeled as "Message #3") to other candidate network nodes within the one or more candidate network nodes to indicate at least one of the following:

[0146] (1) To cancel an ongoing path switching preparation operation or a prepared path switching operation to a group of candidate relay UEs associated with other candidate network nodes.

[0147] (2) The UE has successfully accessed the target relay UE.

[0148] In some embodiments, message #3 may include at least one of the following:

[0149] (1) ID information of a group of candidate cells associated with other candidate network nodes.

[0150] (2) ID information of a group of candidate relay UEs associated with other candidate network nodes.

[0151] In some embodiments, the ID information of the set of candidate relay UEs is added to message #3, for example, as shown in Table 3 below, “Candidate relay UE ID”. For example, the ID information of the set of candidate relay UEs is the “Candidate relay UE List to be Cancelled” IE in message #3, for example, as shown in Table 4 below. If the “Candidate relay UE List to be Cancelled” IE is included in message #3, the target network node may consider that the source network node is canceling the handover associated with the candidate relay UE. Without departing from the spirit and scope of the present disclosure, the “Candidate Relay UE List To Be Cancelled” may also be named as the “Candidate Relay UE To Be Cancelled List” or the like.

[0152] In some other embodiments, the ID information of the group of candidate relay UEs is added to message #3 as sub-level information of the ID information of the target cell (e.g., "target cell ID"), for example, "candidate relay UE ID" is sub-level information of "target cell ID", as shown in Table 5, or "candidate relay UE list to be cancelled" is sub-level information of "target cell ID", as shown in Table 6 below.

[0153] In one embodiment, message #3 may be a handover cancel message, such as a HANDOVER CANCEL message.

[0154] In general, the source NG-RAN node may initiate the procedure by sending an Xn message, such as a Handover Cancel message, to the target NG-RAN node. The source NG-RAN node shall indicate the reason for cancelling the handover by an appropriate cause value. If the "List of candidate cells to be cancelled" IE is included in the Xn message, the target NG-RAN node shall assume that the source NG-RAN node is only cancelling handovers associated with candidate cells identified by the included NG-RAN CGI and associated with the same UE-associated signalling connection identified by the source NG-RAN node UE XnAP ID IE and, if included, by the target NG-RAN node UE XnAP ID IE as well.

[0155] exist Figure 4 In some embodiments, the ID information of the group of candidate relay UEs may be added to an Xn message such as a switching cancellation message, for example, the "Candidate relay UE ID" shown in Table 3 or the "Candidate relay UE list to be cancelled" shown in Table 4 below.

[0156] Table 3

[0157]

[0158]

[0159] Table 4

[0160]

[0161] exist Figure 4 In some other embodiments, the ID information of the group of candidate relay UEs can be added to an Xn message such as a handover cancellation message as sub-level information of the ID information of the target relay UE. For example, "candidate relay UE ID" is sub-level information of "target cell ID", as shown in Table 5 below, or "list of candidate relay UEs to be canceled" is sub-level information of "target cell ID", as shown in Table 6 below.

[0162] Table 5 Table 6

[0163]

[0164]

[0165] Back reference Figure 4 In some embodiments, message #3 may include ID information of a set of candidate cells associated with other candidate network nodes. Other candidate network nodes may assume that the source network node is only canceling the handover associated with the set of candidate cells and one or more candidate relay UEs served by the set of candidate cells.

[0166] In some embodiments, the source network node may receive from the UE at least one of:

[0167] (1) Indirect paths between the slave UE and the source network node and associated with the source relay UE (e.g. Figure 3 Indirect path #1 in the embodiment of the present invention) to another indirect path (eg, Figure 3 A message associated with a relay link change failure during a path switch of an indirect path #2) in an embodiment of the present invention; or

[0168] (2) Information related to a fallback operation performed by the UE to obtain a message via an indirect path between the UE and the source network node and associated with the source relay UE (e.g., Figure 3 Indirect path #1) in the embodiment of communicates with the source network node.

[0169] Figure 5The flowchart of the method for receiving a handover request according to some embodiments of the present application is illustrated. The method may be performed by a candidate network node (e.g., Figure 2 or Figure 8 805). Although described with respect to a candidate network node (e.g., a candidate BS), it should be understood that other devices may be configured to perform the same as Figure 5 A similar approach to the one used in this paper. Figure 8 The embodiments described in Figure 5 Specific examples of embodiments are as follows.

[0170] exist Figure 5 In the exemplary method 500 shown in FIG. 5 , in operation 501, a candidate network node (eg, Figure 8 805) may be from a source network node (e.g., Figure 8 The source BS 803 illustrated and shown in FIG. 8 receives a handover request for a path switch operation. The handover request may include the ID information of the requested target relay UE of the target network node. The source network node may communicate with the source relay UE (e.g., via a direct path or between the UE and the source network node and the source relay UE) via a direct path or between the UE and the source network node and the source relay UE (e.g., Figure 8 802) to communicate with a UE (e.g., Figure 8 UE 801) communications as illustrated and shown in FIG.

[0171] In operation 502, the candidate network node may transmit a response message to the source network node. The response message includes ID information of a candidate relay UE associated with the candidate network node.

[0172] In some embodiments, the candidate network node may transmit a message to the source network node (eg, Figure 4 In some embodiments, the message includes at least one of the following: ID information of the candidate relay UE; or a reason for canceling the path switching operation to the candidate relay UE. In one embodiment, the message may be a conditional switching cancellation message or a conditional path switching cancellation message.

[0173] In some embodiments, the candidate network node may transmit a message to the source network node (eg, Figure 4 This message may indicate that the UE has successfully accessed the candidate relay UE and that the candidate relay UE serves as the target relay UE (e.g., Figure 8804 as illustrated and shown in FIG. 804). In one embodiment, this message may be a handover success message. In some embodiments, this message includes at least one of the following: ID information of the requested target relay UE; ID information of the target relay UE; or ID information of the target cell of the target relay UE.

[0174] In some embodiments, at least one of the target relay UE's ID information or the target cell's ID information is added to message #2 as: independent of the requested target relay UE's ID information; or sub-level information of the requested target relay UE's ID information.

[0175] In some embodiments, message #2 may include the ID information of the requested target relay UE. The source network node may consider that the UE has successfully accessed the candidate relay UE corresponding to the ID information of the requested target relay UE.

[0176] In some embodiments, the candidate network node may receive a message from the source network node (e.g., Figure 4 This message may indicate at least one of the following: to cancel an ongoing path switching preparation operation or a prepared path switching operation to a group of candidate relay UEs including the candidate relay UE; or the UE has successfully accessed the target relay UE.

[0177] In some embodiments, message #3 may include at least one of the following: ID information of a group of candidate cells associated with a group of candidate network nodes including the candidate network node; or ID information of a group of candidate relay UEs including the candidate network node. In some embodiments, the ID information of the group of candidate relay UEs is added to message #3 as sub-level information of the ID information of the target cell. In one embodiment, message #3 may be a handover cancellation message.

[0178] In some embodiments, message #3 may include ID information of a set of candidate cells associated with a set of candidate network nodes including the candidate network node. The candidate network node may assume that the source network node is only canceling the handover associated with the set of candidate cells and one or more candidate relay UEs served by the set of candidate cells.

[0179] The details described in all other embodiments of this application apply to Figures 3 to 5 In any embodiment of the present invention. In addition, Figures 3 to 5 The details described in any of the embodiments apply to Figure 1 , 2 And all embodiments 6 to 9. Those skilled in the art will appreciate that without departing from the spirit and scope of the present disclosure, Figures 3 to 5The order of operations in the flowcharts of any of the embodiments may be changed, and Figures 3 to 5 Some of the operations in the flowcharts in any of the embodiments may be eliminated or modified.

[0180] The following text describes Figures 3 to 5 A specific embodiment of the method shown and illustrated in any of the.

[0181] Figure 6 A flowchart illustrating a relay link change operation according to some embodiments of the present application is shown. Figure 6 According to the flowchart 600 of the embodiment, UE 601, source relay UE 602, BS 603 and target relay UE 604 perform the following operations.

[0182] In operation 611, UE 601 may access a serving BS, such as BS 603, via multiple paths. The multiple paths may include direct paths and / or indirect paths. The indirect paths may be associated with a relay UE (e.g., a L2 U2N relay UE) (e.g., Figure 6 ) is associated with the source relay UE 602 shown in . The indirect path between UE 601 and the source relay UE 602 may also be named as a “relay link” or a “source relay link”, a “source indirect link”, etc. UE 601 may be named as a “remote UE 601”, a “L2U2N remote UE 601”, etc. UE 601 may remain in the RRC connected state.

[0183] In some embodiments, UE 601 may report measurement results to serving BS 603 based on configuration information received from BS 603. The measurement results may include measurement results associated with candidate cells or candidate relay UEs.

[0184] In operation 612 , the BS 603 may decide to switch from the source relay UE 602 to the candidate relay UE, for example, based on the measurement result from the UE 601 .

[0185] In operation 613, BS 603 may send a relay link change indication to UE 601. The relay link change indication may also be named "relay change indication" or the like. In some embodiments, the relay link change indication may be included in the RRCReconfiguration message transmitted in operation 613. In one embodiment, identity (ID) information of the candidate relay UE may also be included in the RRCReconfiguration message.

[0186] In operation 614, after UE 601 receives the relay link change indication, UE 601 may perform a relay link change procedure, which may also be named a "relay change procedure", etc. In some embodiments, UE 601 may start a timer for relay link change (e.g., timer T420 specified in the 3GPP standard document) immediately after receiving the relay link change indication. In some embodiments, UE 601 may not release the PC5 unicast link between UE 601 and the source relay UE 602 during the relay link change procedure.

[0187] In operation 615 , the source relay UE 602 may transmit a notification message (eg, a notification message sidelink message) and / or a PC5 unicast link release message to the UE 601 during the relay link change procedure performed by the UE 601 .

[0188] In some embodiments, the source relay UE 602 may transmit the notification message or the PC5 unicast link release message due to at least one of the following: Uu RLF between the source relay UE 602 and the BS 603, cell reselection of the source relay UE 602, handover of the source relay UE 602, RRC connection reject message received by the source relay UE 602, expiration of a timer (e.g., timer T300) for RRC setup request at the source relay UE 602, failure of Uu RRC connection establishment of the source relay UE 602, and / or failure of Uu RRC connection recovery of the source relay UE 602.

[0189] In operation 616, after UE 601 receives a notification message and / or a PC5 unicast link release message from source relay UE 602 during the relay link change procedure, the following different embodiments may exist in different situations.

[0190] In some embodiments, if UE 601 has not released the PC5 unicast link between UE 601 and source relay UE 602 during the indirect to indirect path switching process (e.g., while timer T420 is running), then UE 601 may ignore the notification message and / or PC5 unicast link release message from source relay UE 602.

[0191] In some other embodiments, when a timer for path switching (e.g., timer T304 specified in the 3GPP standard document) is running, UE 601 may stop receiving data (e.g., control plane (CP) data and / or user plane (UP) data) immediately after receiving a notification message and / or a PC5 unicast link release message from the source relay UE 602.

[0192] In some other embodiments, when the timer for path switching (e.g., timer T304) is running, UE 601 may stop receiving data (e.g., CP and / or UP data) and release the PC5 RRC connection immediately after receiving a notification message or a PC5 unicast link release message from the source relay UE 602.

[0193] In operation 617 (optional), the UE 601 may stop a timer for relay link change (eg, timer T420 ) upon successfully completing a random access (RA) procedure to the target relay UE 604 or upon sending an RRCReconfigurationComplete message to the BS 603 .

[0194] In some embodiments, BS 603 may send an RRCReconfiguration message to source relay UE 602 to reconfigure the connection between relay UE 602 and BS 603 .

[0195] In some embodiments, the source relay UE 602 or UE 601 may release the PC5 RRC connection between the source relay UE 602 and UE 601 , and may instruct an upper layer to release the PC5 unicast link between the source relay UE 602 and UE 601 .

[0196] In operation 618 , the data path is switched from the indirect path between the UE 601 and the source relay UE 602 to another indirect path between the UE 601 and the target relay UE 604 .

[0197] Figure 7 A flowchart illustrating a relay link change operation according to some embodiments of the present application is shown. Figure 7 According to the flowchart 700 of the embodiment of the present invention, UE 701, source relay UE 702, BS 703 and target relay UE 704 perform the following operations.

[0198] In operation 711, UE 701 accesses a serving BS, such as BS 703, via multiple paths. The multiple paths may include direct paths and / or indirect paths. The indirect paths may be associated with a relay UE (e.g., a L2 U2N relay UE) (e.g., Figure 7 ) is associated with the source relay UE 702 shown in . The indirect path between UE 701 and the source relay UE 702 may also be named as a “relay link”, “source relay link”, “source indirect link”, etc. UE 701 may also be named as a “remote UE 701”, “L2U2N remote UE 701”, etc. UE 701 may remain in the RRC connected state.

[0199] In some embodiments, UE 701 may report measurement results to serving BS 703 based on configuration information from BS 703. The measurement results may include measurement results associated with candidate cells or candidate relay UEs.

[0200] In operation 712 , the BS 703 may decide to switch from the source relay UE 702 to the candidate relay UE, for example, based on the measurement result from the UE 701 .

[0201] In operation 713, BS 703 may send a relay link change indication, which may also be named "relay change indication", etc. to UE 701. In some embodiments, the relay link change indication may be included in the RRCReconfiguration message transmitted in operation 713. ID information of the candidate relay UE may be included in the RRCReconfiguration message.

[0202] In operation 714, after UE 701 receives the relay link change indication, UE 701 may perform a relay link change procedure, which may also be named as a “relay change procedure” or the like. In some embodiments, UE 701 may start a timer (e.g., timer T420) for relay link change immediately after receiving the relay link change indication. In some embodiments, UE 701 may maintain a source relay link between UE 701 and source relay UE 702 during the relay link change procedure. UE 701 may continue to receive and transmit data via the source relay link before a target relay link between UE 701 and a target relay UE (e.g., target relay UE 704) is available.

[0203] After operation 714, a relay link change failure may occur. For example, in some embodiments, in operation 715A (optional), a timer (e.g., timer T420) for relay link change may expire. In some other embodiments, in operation 715B (optional), the remote UE 701 may receive a notification message (e.g., a notification message sidelink message) or a PC5 unicast link release message from the target relay UE 704.

[0204] In operation 716, once the relay link change failure occurs, the UE 701 may transmit a message associated with the relay link change failure to the BS 703. For example, the message may include an indication of the relay link change failure. The relay link change failure may also be named "relay change failure" or the like.

[0205] In some embodiments, in operation 716, UE 701 may transmit a message including failure-related information to source serving BS 703. The failure-related information reported in operation 716 may include at least one of the following:

[0206] (1) The timer for relay link change (eg, timer T420) expires.

[0207] (2) UE 701 receives a notification message (e.g., a notification message sidelink message) or a PC5 unicast link release message from the target relay UE 704, for example, in operation 715B. In one embodiment, the notification message may indicate at least one of the following: Uu RLF between the source relay UE 702 and the BS 703; cell reselection of the source relay UE 702; handover of the source relay UE 702; RRC connection failure of the source relay UE 702; RRC connection rejection message received by the source relay UE 702; expiration of a timer for an RRC setup request at the source relay UE 702; or RRC recovery failure of the source relay UE 702.

[0208] (3) Measurement results associated with candidate cells and candidate relay UEs.

[0209] After operation 716, UE 701 may switch back to the source indirect path between UE 701 and source relay UE 702. In some embodiments, in operation 717 (optional), UE 701 may continue to maintain the source indirect path between UE 701 and source relay UE 702 until UE 701 receives an indication to release the source relay link, and if UE 701 fails to access target relay UE 704, a fallback operation may be performed to communicate with BS 703 via the source indirect path. In one embodiment, after the timer for relay link change (e.g., timer T420) expires, UE 701 may immediately determine that UE 701 fails to access target relay UE 704 and then perform a fallback operation. In another embodiment, after receiving a notification message or a PC5 unicast link release message from target relay UE 704 in operation 715B (optional), UE 701 may perform a fallback operation. For example, UE 701 may restore a source relay UE link between UE 701 and source relay UE 702 by performing a fallback operation.

[0210] In an embodiment of the present application, when a remote UE (e.g., UE 701) communicating with a BS (e.g., BS 703) via a target relay UE (e.g., target relay UE 704) performs a fallback operation, the remote UE may release a PC5 link between the remote UE and the target relay UE and communicate with the BS via an indirect PC5 link between the remote UE and a source relay UE (e.g., target relay UE 702). That is, by performing the fallback operation, the remote UE may switch back from the target relay link to the source relay link.

[0211] In operation 718 (optional), the remote UE 701 may report information related to the fallback operation to the BS 703.

[0212] Figure 8 The diagram illustrates a flow chart of a path switching operation to a relay UE according to some embodiments of the present application. Figure 8 According to the flowchart 800 of the embodiment of the present invention, the UE 701, the source relay UE 802, the source BS 803, the target relay UE 804 and the candidate BS 805 perform the following operations.

[0213] In operation 811, UE 801 accesses a serving gNB, such as BS 803, via a direct or indirect path or multiple paths. The indirect path is with a relay UE (e.g., L2 U2N relay UE) (e.g., Figure 8 801 is associated with the source relay UE 802 shown in . The indirect path between UE 801 and the source relay UE 802 may also be named as a “relay link”, “source relay link”, “source indirect link”, etc. UE 801 may also be named as a “remote UE 801”, “L2 U2N remote UE 801”, etc. UE 801 may remain in the RRC connected state.

[0214] In some embodiments, UE 801 may report measurement results to serving BS 803 based on configuration information from BS 803. The measurement results may include measurement results associated with candidate cells or candidate relay UEs.

[0215] In some embodiments, UE 801 may evaluate whether some events (eg, event Z1 and / or event Z2 described above) are achieved. When such events are achieved, UE 801 may report the measurement results.

[0216] In operation 812, BS 803 may decide to switch to a candidate relay UE based on a measurement report from UE 801 (eg, based on a measurement result from UE 801).

[0217] In operation 813, BS 803 may send a signal to one or more candidate BSs (e.g., Figure 8 804) sends a handover request message. For example, candidate BS 804 includes candidate gNB#1, candidate gNB#2, and candidate gNB#3. BS 803 may also be named “source BS 803”, “source NG-RAN node 803”, etc. Candidate BS 804 may also be named “candidate NG-RAN node 804”, etc.

[0218] In some embodiments, PC5 resources should be added in the handover request message. The target BS can then use the information to avoid resource overlap. For example, the resource pools used for transmission and / or reception of each candidate BS 804 do not overlap with each other.

[0219] In some embodiments, the handover request message includes ID information of one or more candidate relay UEs. The handover request message may include corresponding measurement results of these candidate relay UEs. The preferred RRC state of the candidate relay UE may also be included, because an idle or inactive state may be selected as the target relay UE. The handover request message may include resources configured for the source PC5 link.

[0220] In operation 814, after receiving the handover request message from the source BS 803, the candidate BS 804 may determine its associated candidate relay UE. For example:

[0221] (1) Candidate gNB#1 may determine the ID of a candidate relay UE (e.g., candidate relay UE#1).

[0222] (2) Candidate gNB#2 may determine the ID of a candidate relay UE (e.g., candidate relay UE#2).

[0223] (3) Candidate gNB#3 may determine the ID of a candidate relay UE (e.g., candidate relay UE#3).

[0224] In operation 815, the candidate BS 804 (e.g., candidate gNB#1, candidate gNB#2, and candidate gNB#3) may transmit a handover request confirmation message to the source BS 803. In some embodiments, the handover request confirmation message may include at least the following information:

[0225] (1) ID information of a single target relay UE. This target relay UE may be outside the container containing the RRC reconfiguration message.

[0226] (2) RRC status of the candidate relay UE.

[0227] In operation 816 , the source BS 803 may transmit an RRC reconfiguration message associated with the candidate relay UEs (eg, candidate relay UE #1, candidate relay UE #2, and candidate relay UE #3) to the remote UE 801 .

[0228] In some embodiments, the RRC reconfiguration message may include a separate set of conditions for each of the candidate relay UEs for conditional path switching. Different candidate relay UEs may be configured with different sets of conditions for conditional path switching.

[0229] In operation 817, UE 801 may begin to evaluate the conditions of candidate relay UE #1, candidate relay UE #2, and candidate relay UE #3. In some embodiments, UE 801 may evaluate whether some events (e.g., event Z1 and / or event Z2 described above) are achieved. When such events of any candidate relay UE are achieved, UE 801 may perform a path switching operation to this candidate relay UE. For example, if remote UE 801 determines that event Z1 and / or event Z2 of candidate relay UE #1 are achieved, remote UE 801 may perform a path switching operation to candidate relay UE #1.

[0230] In operation 818 (optional), the candidate network node (e.g., candidate gNB#2) may transmit a message via an Xn interface to cancel a conditional path switch to a candidate relay UE (e.g., candidate relay UE#2) associated with the candidate network node. In some embodiments, the message via the Xn interface may be a conditional switch cancel message or a conditional path switch cancel message. For example, the message includes at least one of the following:

[0231] (1) the ID of a candidate relay UE (e.g., candidate relay UE #2); or

[0232] (2) A new reason for canceling the path switching operation to the candidate relay UE, for example, the candidate relay UE is unreachable.

[0233] In operation 819 (optional), once the source BS 803 receives the message to cancel the conditional path switch, the source BS 803 may transmit to the UE 801 a corresponding configuration for removing the conditional path switch to the candidate relay UE (eg, candidate relay UE#2).

[0234] In some embodiments, the source BS 803 may assume that the target network node is about to remove any reference to the candidate relay UE and release any resources previously reserved for the candidate relay UE.

[0235] In some embodiments, the source BS 803 may transmit an Xn message to cancel the prepared target relay UE. For example, the source BS 803 may transmit an Xn message to cancel the ongoing path switch to other candidate network nodes (e.g., candidate gNB#1 and / or candidate gNB#3). For example, the message may be a switch cancel message. The Xn message may include ID information of the candidate relay UE, for example, the ID of the candidate relay UE#3.

[0236] In one embodiment, only the cell ID is added to the handover cancellation message without adding the candidate relay UE ID. The candidate network node should assume that the source NG-RAN node is only canceling the handover associated with the candidate cell and the candidate relay UE served by the candidate cell.

[0237] In another embodiment, the ID information of the candidate relay UE is added to the handover cancellation message. If the handover cancellation message contains the candidate relay UE list IE to be cancelled, the target network node should consider that the source network node is canceling the handover associated with the candidate relay UE. In another embodiment, the ID information of the candidate relay UE is added as a sub-level of the ID information of the target cell, for example, in Table 5, "Candidate relay UE ID" is added as a sub-level of "target cell ID", or in Table 6 shown above, "Candidate relay UE list to be cancelled" is a sub-level information of "target cell ID".

[0238] In operation 820, once the path switching condition is met, UE 801 may apply a configuration for path switching to a candidate relay UE (eg, candidate relay UE#1). The candidate relay UE serves as target relay UE#1.

[0239] In some embodiments, UE 801 may start a timer (e.g., timer T420) for conditional path switching to target relay UE#1 when one of the following occurs:

[0240] (1) When a path switch to a target relay UE is executed.

[0241] (2) When applying a stored RRCReconfiguration message including “RRCReconfigurationWithSync for path switching to target relay UE”. For example, during application of the stored RRCReconfiguration message, UE 801 may apply parameters included in the stored RRCReconfiguration message.

[0242] (3) When the stored RRCReconfiguration message including "indication of path switching to target relay UE" is applied.

[0243] In operation 821, after the remote UE 801 successfully accesses the target relay UE 804 (e.g., candidate relay UE#1, which acts as target relay UE#1), the relevant target network node (e.g., target gNB#1) transmits a message to the source BS 803 indicating that UE 801 has successfully completed the path switch.

[0244] In some embodiments, the message indicating the successful path switching includes the ID information of the target relay UE (eg, target relay UE#1). The message may be a switching success message.

[0245] In operation 822, after receiving the message (eg, the switching success message), source BS 803 may release the context of UE 801. In some embodiments, source BS 803 may inform other candidate network nodes (eg, candidate relay UE#2 and / or candidate relay UE#3) of the successful path switching.

[0246] Fig. 9 A block diagram of an exemplary device 900 is illustrated according to some embodiments of the present application. 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 UE, a source network node (eg, a source BS), or a candidate network node (eg, a candidate BS).

[0247] Although in this figure, elements such as at least one transceiver 902 and processor 906 are described in the singular, please consider the plural unless explicitly stated as limited to the singular. In some embodiments of the present application, the transceiver 902 can be divided into two devices, such as a receiving circuit system and a transmitting circuit system. In some embodiments of the present application, the device 900 may further include an input device, a memory and / or other components.

[0248] 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 perform Figures 1 to 8 In some embodiments of the present application, the device 900 may be a source network node (eg, a source BS). The transceiver 902 and the processor 906 may interact with each other to perform Figures 1 to 8 In some embodiments of the present application, the device 900 may be a candidate network node (eg, a candidate BS). The transceiver 902 and the processor 906 may interact with each other to perform Figures 1 to 8 The operations described in regarding candidate network nodes.

[0249] In some embodiments of the present application, the device 900 may further include at least one non-transitory computer-readable medium. For example, in some embodiments of the present disclosure, the non-transitory computer-readable medium may store thereon computer-executable instructions to cause the processor 906 to implement the method described above with respect to the UE. 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 the UE are described in .

[0250] 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 described above with respect to a source network node (e.g., a source BS). 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 the source network node are described in .

[0251] 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 described above with respect to a candidate network node (e.g., a candidate BS). 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 described in regarding candidate network nodes.

[0252] It should be understood by those skilled in the art that the operations or steps of the methods described in conjunction with the various 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, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art. In addition, in some aspects, the operations or steps of the methods may reside as one or any combination or a set of codes and / or instructions on a non-transitory computer-readable medium that can be incorporated into a computer program product.

[0253] Although the present disclosure is described with respect to specific embodiments of the present disclosure, it is apparent that many substitutions, modifications and variations may be apparent to those skilled in the art. For example, the various components of the embodiments may be interchanged, added or replaced in other embodiments. Moreover, all elements in 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 elements of independent technical solutions. 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.

[0254] In this document, the term "switching" and "path switching" can be used interchangeably. The term "includes", "including" or any other variation thereof is intended to cover non-exclusive inclusion, so that the process steps, methods, objects or equipment comprising a series of elements do not only include those elements, but may include other elements that are not explicitly listed or inherent to this process step, method, object or equipment. The "a, an" in front of the element, etc., do not exclude the presence of additional identical elements in the process steps, methods, objects or equipment comprising the element without more constraints. And, the term "another" is defined as at least the second or more. The term "having" used herein, etc., is defined as "including". For example, expressions such as "A and / or B" or "at least one of A and B" may include any and all combinations of words listed together with the expression. For example, expressions "A and / or B" or "at least one of A and B" may include A, B or both A and B. The terms “first”, “second”, etc. are only used to clearly illustrate the embodiments of the present application but are 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: A radio resource control (RRC) reconfiguration message is received from a network node, wherein the RRC reconfiguration message includes one of: a relay link change indication in the event that the UE accesses the network node via both a direct path between the UE and the network node and a first indirect path between the UE and the network node and associated with a source relay UE; and if the UE accesses the network node via the direct path, the first indirect path, or both the direct path and the first indirect path, a path switching indication to a candidate relay UE; and A relay link change or a path switch is performed based on the RRC reconfiguration message.

2. A source network node, comprising: Transceiver; and a processor coupled to the transceiver, wherein the processor is configured to: transmitting a handover request for a path switch operation to one or more candidate network nodes, wherein the handover request includes identity ID information of a requested target relay user equipment UE served by the target network node; receiving a response message from the one or more candidate network nodes, wherein the response message includes ID information of at least one candidate relay UE; and A radio resource control (RRC) reconfiguration message associated with the at least one candidate relay UE is transmitted to the remote UE.

3. The source network node of claim 2, wherein the processor of the source network node is configured to communicate with the remote UE via at least one of a direct path or an indirect path between the remote UE and the source network node and associated with a source relay UE.

4. The source network node of claim 2, wherein the RRC reconfiguration message comprises at least one of: The ID information of the at least one candidate relay UE; or One or more sets of conditions associated with the at least one candidate relay UE.

5. The source network node of claim 2, wherein the processor of the source network node is configured to receive a first message from a first candidate network node within the one or more candidate network nodes, and the first message instructs the source network node to cancel the path switching operation to a first candidate relay UE associated with the first candidate network node.

6. The source network node of claim 5, wherein the first message comprises at least one of: ID information of the first candidate relay UE; or The reason for canceling the path switching operation to the first candidate relay UE.

7. The source network node of claim 2, wherein the processor of the source network node is configured to receive a second message from a second candidate network node within the one or more candidate network nodes, and the second message indicates that the remote UE has successfully accessed a target relay UE associated with the second candidate network node.

8. The source network node of claim 7, wherein the second message comprises at least one of: The ID information of the requested target relay UE; ID information of the target relay UE; or The ID information of the target cell of the target relay UE.

9. The source network node according to claim 8, wherein the ID information of the target relay UE is added to the second message in the following form: Independent of the ID information of the requested target relay UE; or The sub-level information of the ID information of the requested target relay UE.

10. The source network node according to claim 7, wherein the second message includes the ID information of the requested target relay UE, and wherein the processor of the source network node is configured to consider that the remote UE has successfully accessed the candidate relay UE corresponding to the ID information of the requested target relay UE.

11. The source network node of claim 7, wherein the processor of the source network node is configured to transmit a third message to other candidate network nodes within the one or more candidate network nodes.

12. The source network node of claim 11, wherein the third message indicates at least one of: to cancel an ongoing path switch preparation operation or a prepared path switch operation towards a group of candidate relay UEs associated with the other candidate network nodes; or The remote UE has successfully accessed the target relay UE.

13. The source network node of claim 11, wherein the third message includes at least one of: ID information of a group of candidate cells associated with the other candidate network nodes; or ID information of a group of candidate relay UEs associated with the other candidate network nodes.

14. The source network node according to claim 13, wherein the ID information of the group of candidate relay UEs is added to the third message as sub-level information of ID information of a target cell.

15. The source network node of claim 11, wherein the third message includes the ID information of a set of candidate cells associated with the other candidate network nodes, and the other candidate network nodes believe that the source network node is canceling only handovers associated with the set of candidate cells and one or more candidate relay UEs served by the set of candidate cells.

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