Method executed by user equipment and user equipment

Abstract

Provided in the present disclosure are a method executed by a user equipment (UE) and a UE. In the method of one aspect of the present disclosure, a UE is the last U2N relay UE in a multi-hop UE-to-network relay, i.e., a multi-hop U2N relay. The method comprises: when a UE detects an anomaly, setting a PC5-RRC message for notifying the occurrence of the anomaly, wherein the PC5-RRC message comprises at least one of identification information of the last U2N relay UE and identification information of a U2N remote UE in a multi-hop U2N relay; and sending the PC5-RRC message to a previous-hop UE directly connected to the UE. The anomaly comprises any one of the following: a radio link failure has occurred on a Uu interface between the UE and a network; the UE has performed cell reselection; and an RRC connection establishment procedure initiated in the UE has been terminated by an upper layer, and the UE has not yet entered an RRC connected state.

Description

Methods executed by user equipment and user equipment Technical Field

[0001] This disclosure relates to the field of wireless communication technology, and more specifically, to a communication method based on a multi-hop U2N relay architecture performed by a user equipment and the corresponding user equipment. Background Technology

[0002] In March 2020, at RAN#91 plenary session, a work item on NR sidelink relaying (version 17) was proposed (see non-patent literature: RP-210904 New Study Item on NR Sidelink Relaying) and approved. The latest version of this work item is found in non-patent literature: RP-212601 reivised WID NR sidelink relay. One of the goals of this work item is to standardize the process of U2N (UE-to-Network) relay architecture. In U2N relay architecture, communication between the remote UE and the network occurs through a relay UE.

[0003] In December 2021, at the RAN#94 plenary meeting, a work project on NR sidelink relay enhancements for version 18 was proposed (see non-patent literature: RP-213585 New WID on NR sidelink relay enhancements) and approved. The latest version of this work project can be found in non-patent literature: RP-221262 Revised WID on NR sidelink relay enhancements. One of the goals of this work project is to standardize the control plane procedures for U2U (UE-to-UE) relay architectures. In a U2U relay architecture, two remote UEs communicate sidelink through a relay UE.

[0004] In June 2024, at RAN#104 plenary session, a work project for NR sidelink multi-hop relay version 19 was proposed (see non-patent literature: RP-241609 NR sidelink multi-hop relay) and approved. The goal of this work project is to standardize multi-hop L2 U2N relays. Summary of the Invention

[0005] The purpose of this disclosure is to provide a method for appropriately performing message forwarding related to multi-hop U2N relays.

[0006] Another objective of this disclosure is to provide a method for appropriately performing a relay discovery process in multi-hop U2N relays.

[0007] According to one aspect of this disclosure, a method is provided performed by a user equipment (UE), the UE being the last U2N relay UE in a multi-hop U2N relay, the method comprising: when the UE detects an anomaly, setting a PC5-RRC message to notify of the anomaly, the PC5-RRC message including at least one of identification information of the last U2N relay UE and identification information of the U2N remote UE in the multi-hop U2N relay; and sending the PC5-RRC message to the previous hop UE directly connected to the UE. The anomaly includes any of the following: a radio link failure occurred on the Uu interface between the UE and the network; the UE underwent cell reselection; the RRC connection establishment procedure initiated by the UE was terminated by an upper layer, and the UE had not yet entered an RRC connected state.

[0008] According to one aspect of this disclosure, another method is provided performed by a user equipment (UE), the UE being an intermediate U2N relay UE in a multi-hop U2N relay network, the method comprising: when the UE detects an anomaly, setting up a PC5-RRC message to notify of the anomaly, the PC5-RRC message including at least one of an identification of the U2N relay UE that caused the anomaly and an identification of the remote U2N UE in the multi-hop U2N relay; and sending the PC5-RRC message to the previous hop UE directly connected to the UE in the multi-hop U2N relay. The anomaly includes at least one of the following: a radio link failure occurred on the PC5 interface between the UE and the next-hop UE; a reselection of the next-hop UE occurred; the serving cell of the UE changed; a serving cell change occurred due to the reselection of the next-hop UE; an RRC connection establishment procedure initiated by the UE was terminated by an upper layer, and the UE had not yet entered an RRC connection state.

[0009] Optionally, the PC5-RRC message may also include the identification information of the last U2N relay in the multi-hop U2N relay.

[0010] Optionally, the PC5-RRC message may further include an indication type, which indicates the type of exception that triggered the PC5-RRC message.

[0011] According to another aspect of this disclosure, another method is provided performed by a user equipment (UE), the UE being an intermediate U2N relay UE or a U2N remote UE in a multi-hop U2N relay, the method comprising: receiving a PC5-RRC message from the next-hop UE of the UE, the PC5-RRC message indicating an anomaly has occurred at the network-side UE of the UE, and including at least one of identification information of the U2N remote UE and identification information of the U2N relay UE that has experienced the anomaly; and forwarding the PC5-RRC message to the previous-hop UE directly connected to the UE or the U2N remote UE indicated in the PC5-RRC message.

[0012] Optionally, when forwarding the PC5-RRC message, information indicating that the UE itself has not experienced any abnormalities may also be carried.

[0013] Optionally, the PC5-RRC message may also include an indication type representing the type of the anomaly, with information indicating that the UE itself has not experienced an anomaly being carried through the indication type.

[0014] Optionally, the method further includes: when the received PC5-RRC message does not include information indicating that the next-hop UE of the UE that sent the PC5-RRC message has not experienced an anomaly: if the UE is in an RRC connected state, an RRC connection reconstruction procedure is initiated; if the UE is in an RRC idle state or an RRC inactive state, the PC5 unicast link with the next-hop UE that sent the PC5-RRC message is released; and / or if the UE is in an RRC idle state or an RRC inactive state, and the UE decides not to release the PC5 unicast link with the next-hop UE that sent the PC5-RRC message, then corresponding processing is performed according to the type of anomaly indicated by the indication type.

[0015] Optionally, the method further includes at least one of the following: when the UE acting as an intermediate U2N relay UE receives a relay discovery notification message, if it can obtain the SD-RSRP at the time of receiving the relay discovery notification message and the SD-RSRP is higher than a discovery threshold, it forwards the relay discovery notification message; when the intermediate U2N relay UE receives a relay discovery response from a next-hop UE, if it can obtain the SD-RSRP at the time of receiving the relay discovery response and the obtained SD-RSRP is higher than a discovery threshold, it forwards the relay discovery response to the upstream UE directly connected to the UE; when the UE acting as the last U2N relay UE receives a relay discovery request, if it can obtain the SD-RSRP at the time of receiving the relay discovery request and the obtained SD-RSRP is higher than a discovery threshold, it sends a relay discovery response to the upstream UE directly connected to the UE.

[0016] According to another aspect of this disclosure, a user equipment is provided, comprising: a processor; and a memory storing instructions, wherein the instructions, when executed by the processor, perform the method as described above.

[0017] According to this disclosure, message forwarding related to multi-hop U2N relays can be appropriately performed in multi-hop U2N relays. Furthermore, according to this disclosure, relay discovery procedures can be appropriately performed in multi-hop U2N relays. Attached Figure Description

[0018] Figure 1 is a schematic diagram of the U2N relay architecture.

[0019] Figure 2 is a schematic diagram of a multi-hop U2N relay architecture.

[0020] Figure 3 is a flowchart illustrating a method in one or more embodiments of this disclosure.

[0021] Figure 4 is a flowchart illustrating a method in another embodiment of this disclosure.

[0022] Figure 5 is a flowchart schematically illustrating a method in one or more embodiments of the present disclosure.

[0023] Figure 6 is a flowchart schematically illustrating a method in one or more embodiments of the present disclosure.

[0024] Figure 7 is a flowchart schematically illustrating a method in one or more embodiments of the present disclosure.

[0025] Figure 8 is a flowchart schematically illustrating a method in one or more embodiments of the present disclosure.

[0026] Figure 9 is a simplified structural block diagram of the user equipment (UE) involved in this disclosure. Detailed Implementation

[0027] The present disclosure will now be described in detail with reference to the accompanying drawings and specific embodiments. It should be noted that the present disclosure should not be limited to the specific embodiments described below. Furthermore, for the sake of simplicity, detailed descriptions of well-known technologies not directly related to the present disclosure have been omitted to prevent confusion in understanding the present disclosure.

[0028] The following describes some of the terms used in this disclosure. For the specific meanings of these terms, please refer to the latest 3GPP standard specifications.

[0029] UE: User Equipment

[0030] NR: New Radio, next-generation wireless technology

[0031] PHY: physical layer

[0032] MAC: Medium Access Control

[0033] RLC: Radio Link Control

[0034] SDAP: Service Data Adaptation Protocol

[0035] PDCP: Packet Data Convergence Protocol

[0036] SRAP: Sidelink Relay Adaptation Protocol

[0037] RRC: Radio Resource Control

[0038] RRC_CONNECTED: RRC connection state

[0039] RRC_INACTIVE: RRC inactive state

[0040] RRC_IDLE: RRC idle state

[0041] RAN: Radio Access Network

[0042] NG-RAN: NG Radio Access Network, a next-generation radio access network

[0043] gNB: the next generation Node B, next-generation base station

[0044] Sidelink: Side-link communication, side-link

[0045] SL: Sidelink, side-to-side communication, side-to-side link

[0046] SCI: Sidelink Control Information

[0047] AS: Access Stratum

[0048] IE: Information Element

[0049] CE: Control Element

[0050] MIB: Master Information Block

[0051] SIB: System Information Block

[0052] DCI: Downlink Control Information

[0053] RB: radio bearer

[0054] DRB: Data Radio Bearer

[0055] SRB: Signaling Radio Bearer

[0056] Uu: Open air

[0057] ProSe: Proximity-based Services

[0058] V2X: Vehicle-to-Everything.

[0059] NAS: Non-Access Stratum

[0060] PC5-S: PC5 signalling

[0061] SL-SRB: Sidelink Signalling Radio Bearer

[0062] SL-DRB: Sidelink Data Radio Bearer

[0063] U2U: UE-to-UE, UE to UE

[0064] U2N: UE-to-Network

[0065] L2: Layer 2, a two-layer architecture

[0066] RSRP: Reference Signal Received Power

[0067] SL-RSRP: Sidelink RSRP, the received power of the sidelink communication reference signal.

[0068] SD-RSRP: Sidelink Discovery RSRP, a reference signal received by sidelink communication.

[0069] SpCell: Special Cell, including PCCell and PSCell.

[0070] PCell: Primary Cell

[0071] PSCell: Primary SCG Cell, SCG main cell

[0072] L2-ID: Layer-2 ID (identity), the identifier for the second layer.

[0073] 3GPP: 3rd Generation Partnership Project

[0074] RLF: Radio link failure.

[0075] In this disclosure, the network (or NW), base station (or gNB or eNB), and RAN are interchangeable. The network can be a Long Term Evolution (LTE) network, a New Radio Access Technology (New RAT, NR) network, an enhanced Long Term Evolution (eLTE) network, or other networks defined in subsequent 3GPP evolution versions. The base station in this disclosure can be any type of base station, including Node B, enhanced base station (eNB), 5G communication system base station (gNB); or micro base station, pico base station, macro base station, femto base station, etc.; the network generally refers to a base station or cell. The cell can also be a cell under any of the above-mentioned types of base stations. Unless otherwise specified, cell, beam, and transmission point (TRP) are interchangeable. The base station can also be the central unit (gNB-Central Unit, gNB-CU) or distributed unit (gNB-Distributed Unit, gNB-DU) that makes up the base station.

[0076] In this disclosure, the User Equipment (UE) may refer to the NR device that supports NR Sidelink relay function as described in the background art, or the NR device that supports L2 U2N relay function, or the NR device that supports multi-hop L2 U2N relay function, or other types of NR devices or LTE devices.

[0077] In this disclosure, sidelink, SL, and PC5 can be used interchangeably.

[0078] In this disclosure, "change" and "update" can be used interchangeably.

[0079] In this disclosure, "configure", "set", and "present" can be used interchangeably.

[0080] In this disclosure, the terms “used,” “available,” “active,” “applied,” “performed,” and “enabled” can be used interchangeably.

[0081] In this disclosure, the terms "use", "be available", "apply", "implement", "enable", "activate", "perform", and "do" can be used interchangeably.

[0082] In this disclosure, "associate", "correspond", and "map" can be used interchangeably.

[0083] In this disclosure, receive, detect, monitor, acquire, and derive are interchangeable.

[0084] In this disclosure, the terms "feedback", "submit", "report", "send", "transmit or transport", "inform", "indicate", "provide", and "forward" can be used interchangeably.

[0085] In this disclosure, "trigger" and "initiate" can be used interchangeably.

[0086] In this disclosure, the upper layer can refer to the ProSe layer, the V2X layer, the NAS layer, or the PC5-S protocol layer. In this disclosure, the ProSe layer, V2X layer, NAS layer, and PC5-S protocol layer can be used interchangeably.

[0087] In this disclosure, "channel" can refer to one channel or multiple channels.

[0088] In this disclosure, "first hop", "second hop" and "third hop" can all be modified by "PC5", that is, "first hop", "second hop" and "third hop" are all based on the PC5 interface.

[0089] In this disclosure, “relay UE”, “U2N relay UE” and “L2 U2N relay UE” can be used interchangeably, and “NR sidelink” can be added as a prefix to these names.

[0090] In this disclosure, “remote UE”, “U2N remote UE” and “L2 U2N remote UE” can be used interchangeably, and “NR sidelink” can be added as a prefix to these names.

[0091] In this disclosure, "higher than" and "greater than" can be used interchangeably, as can "lower than" and "less than".

[0092] It should be noted that in this specification, the two terms connected by "and", "or", or "and / or" may represent different ways of expressing the same meaning in different application scenarios. There may be a relationship of inclusion between the two terms, and they do not necessarily refer to completely different content.

[0093] The following describes the relevant technologies disclosed herein.

[0094] PC5 interface

[0095] The PC5 interface is the interface for control plane and user plane sidelink communication between UEs. The Upper layer(s) establishes PC5 unicast links for sidelink unicast communication, and the establishment of one PC5 unicast link corresponds to the establishment of one PC5-RRC connection. For sidelink unicast, the PC5-RRC connection is an AS layer logical connection between a source L2 ID and a destination L2 ID.

[0096] Uu interface

[0097] The Uu interface is the wireless communication interface between the UE and the base station. The UE can communicate using NR and gNB on the Uu interface.

[0098] L2 architecture

[0099] L2 architecture is relative to L3 architecture. In L2 architecture, the selection and reselection of relays, as well as communication between the UE and the network or another UE via relays, need to be controlled or controlled by the access layer. In contrast, in L3 architecture, the access layer is basically unaware of the existence of relays, or in other words, relays are transparent to the access layer.

[0100] U2N (UE-to-Network) relay

[0101] Figure 1 illustrates a UE-to-Network relay configuration. The left side represents the remote UE, the middle side represents the relay UE, and the right side represents the network. The remote UE and the relay UE are connected via a PC5 interface, while the relay UE and the network are connected via a Uu interface. Because the remote UE is far from the network or the communication environment is poor, the relay UE is needed to relay and forward signaling and data between the two.

[0102] For U2N relay architecture, U2N Remote UE refers to a UE that communicates with the network via a U2N Relay UE. L2 U2N Remote UE refers to a U2N Remote UE in the L2 architecture. U2N Relay UE refers to a UE that provides functionality to support U2N Remote UE connections to the network. L2 U2N Relay UE refers to a U2N Relay UE in the L2 architecture.

[0103] After a remote UE selects a relay UE to provide relay services, it establishes a PC5-RRC connection with the relay UE to enable communication between the remote UE and the network. The remote UE can also establish an air interface RRC connection with the network via the relay UE for data transmission between the remote UE and the network.

[0104] As shown in Figure 1, the L2 U2N architecture is a one-hop U2N relay, meaning that the remote UE communicates with the network through a relay UE.

[0105] Multi-hop U2N relay

[0106] A single-hop U2N relay has only one U2N Relay UE, and its coverage is limited. Multi-hop U2N relay, as shown in Figure 2, allows the U2N Remote UE to connect and communicate with the network through multiple U2N Relay UEs, thus extending coverage. The U2N Relay UE directly connected to the network is called the "last U2N Relay UE." As shown in Figure 2, both the first and second U2N Relay UEs can be called "intermediate U2N Relay UEs." In a multi-hop U2N relay architecture, the number of intermediate U2N Relay UEs can be one or more. For example, in a multi-hop U2N relay architecture with two intermediate U2N Relay UEs, the U2N Remote UE is connected to the first U2N Relay UE via the PC5 interface, the first U2N Relay UE is connected to the second U2N Relay UE via the PC5 interface, the second U2N Relay UE is connected to the last U2N Relay UE via the PC5 interface, and the last U2N Relay UE is connected to the network via the Uu interface.

[0107] Discovery process

[0108] The discovery process is used to detect and identify other UEs near a given UE. It helps a remote UE select or reselect a suitable relay UE. There are two models for the discovery process: Model A and Model B. Model A is a declaration-of-being-here approach. The relay UE broadcasts a Relay Discovery Announcement message. Upon receiving this message, a nearby remote UE can determine whether to select the relay UE for U2N relay communication. Model B is a question-and-answer approach, first asking "Who's there? Or are you there?". The remote UE broadcasts a Relay Discovery Solicitation message. Upon receiving this message, the relay UE sends a Relay Discovery Response message. The remote UE then determines whether to select the relay UE for U2N relay communication based on the received response message.

[0109] In multi-hop U2N relay, in Model A, the last relay UE sends a Relay Discovery Announcement message, and the intermediate relay UE forwards the Relay Discovery Announcement message; in Model B, the remote UE sends a Relay Discovery Solicitation message, and the intermediate relay UE forwards the Relay Discovery Solicitation message.

[0110] Relay selection / reselection

[0111] When the Relay UE detects a radio link failure (RLF) on the Uu interface, or when the Relay UE undergoes handover or cell reselection, the Relay UE sends a NotificationMessageSidelink message to notify the Remote UE. Upon receiving this message, the Remote UE, if in RRC connected state (RRC_CONNECED), initiates an RRC connection reconstruction procedure. If in RRC idle state (RRC_IDLE) or RRC inactive state (RRC_INACTIVE), it can determine whether to release or retain the PC5-RRC connection with the Relay UE, and may trigger Relay reselection. Generally, during Relay selection / reselection, the UE executes a discovery procedure.

[0112] Sidelink resource allocation mode

[0113] Sidelink resource allocation modes include two types: Mode 1 and Mode 2. In Mode 1, sidelink resource allocation is provided by the network. In Mode 2, the UE determines the SL transmission resources from the resource pool.

[0114] This disclosure discusses the conditions under which a relay UE sends a discovery message in a multi-hop U2N relay architecture, and the related handling when a radio link anomaly occurs after a relay UE has been selected. This disclosure enables a UE to select or reselect a suitable relay UE, and ensures that the UE can correctly handle link anomalies after selecting a relay UE, thereby avoiding impact on services.

[0115] First, the general outline of the implementation method of this disclosure will be described with reference to Figures 3 and 4.

[0116] Figure 3 is a flowchart illustrating a method in one or more embodiments of this disclosure.

[0117] As shown in Figure 3, in S301, when the UE detects an anomaly, it sets up a PC5-RRC message to notify that the anomaly has occurred. Then, in S302, the set PC5-RRC message is sent to the upstream UE directly connected to the UE.

[0118] The UE can be the last U2N relay UE in a multi-hop U2N relay, or it can be an intermediate U2N relay UE in a multi-hop U2N relay.

[0119] When the UE is the last U2N relay UE in a multi-hop U2N relay, the aforementioned anomaly includes any of the following: a radio link failure occurred on the Uu interface between the UE and the network; the UE underwent cell reselection; the RRC connection establishment procedure initiated by the UE was terminated by the upper layer, and the UE has not yet entered the RRC connected state. Furthermore, the PC5-RRC message may include at least one of the identification information of the last U2N relay UE and the identification information of the U2N remote UE in the multi-hop U2N relay.

[0120] When the UE is an intermediate U2N relay UE in a multi-hop U2N relay, the aforementioned anomaly includes at least one of the following: a radio link failure occurred on the PC5 interface between the UE and the next-hop UE; a reselection of the UE's next-hop UE occurred; the UE's serving cell changed; a serving cell change occurred due to the reselection of the next-hop UE; or the RRC connection establishment procedure initiated by the UE was terminated by the upper layer, and the UE has not yet entered the RRC connected state. Furthermore, the PC5-RRC message includes at least one of the identification information of the U2N relay UE that experienced the aforementioned anomaly and the identification of the U2N remote UE in the multi-hop U2N relay. In this case, the PC5-RRC message may further include the identification information of the last U2N relay.

[0121] The PCS-RRC message may also include an indication type, which indicates the type of anomaly that triggered the PCS-RRC message. After receiving the PC5-RRC message, the U2N remote UE or intermediate U2N relay UE can perform corresponding operations based on the type of anomaly indicated by the indication type.

[0122] Figure 4 is a flowchart illustrating a method in another embodiment of this disclosure. The UE performing the method shown in Figure 4 is an intermediate U2N relay UE or a U2N remote UE in a multi-hop U2N relay.

[0123] As shown in Figure 4, in S401, a PCS-RRC message is received from the next-hop UE of the UE. This PCS-RRC message indicates that an anomaly has occurred at the network-side UE of the UE, and includes at least one of the identification information of the U2N remote UE and the identification information of the U2N relay UE that has experienced the anomaly. Here, the so-called "network-side UE of the UE" can be any one or more relay UEs located between the UE and the network in a multi-hop U2N relay.

[0124] In S402, the PC5-RRC message is forwarded to the previous hop UE directly connected to the UE or the U2N remote UE indicated in the PC5-RRC message. If the PC5-RRC message includes the identification information of the U2N remote UE, the "U2N remote UE indicated in the PC5-RRC message" is the U2N remote UE corresponding to the identification information of the U2N remote UE. If the PC5-RRC message does not include the identification information of the U2N remote UE, but includes the identification information of a U2N relay UE that has experienced an anomaly (e.g., the last U2N relay UE or an intermediate U2N relay UE), then the "U2N remote UE indicated in the PC5-RRC message" can be all U2N remote UEs associated with the U2N relay UE that experienced the anomaly.

[0125] The following describes in detail several embodiments of this disclosure that address the above-mentioned problems.

[0126] In the following embodiments, the same nouns may represent the same meaning, and the same parameter names may represent the same meaning.

[0127] This disclosure also includes other implementation methods not mentioned herein, which may achieve other effects not mentioned herein, which is self-evident.

[0128] First, the descriptions in the embodiments will be explained.

[0129] "Last U2N Relay UE" refers to a UE (or U2N Relay UE) that is directly connected to the network via the Uu interface and provides functionality to support U2N Remote UE connections to the network. In this disclosure, "Last U2N Relay UE", "Root U2N Relay UE", "Parent U2N Relay UE", "Father U2N Relay UE", "Last L2 U2N Relay UE", "Root L2 U2N Relay UE", "Parent L2 U2N Relay UE" and "Father L2 U2N Relay UE" can be used interchangeably.

[0130] "Intermediate U2N Relay UE" refers to a UE that is not directly connected to the network but is directly connected to the last U2N Relay UE or another (or other) intermediate U2N Relay UE via a PC5 interface, providing functionality to support U2N Remote UE connections to the network. In a multi-hop U2N architecture, the number of intermediate U2N Relay UEs can be one or more. In this disclosure, "intermediate (or middle, etc.) U2N Relay UE", "child U2N Relay UE", "son U2N Relay UE", "leaf U2N Relay UE", "intermediate L2 U2N Relay UE", "child L2 U2N Relay UE", "son L2 U2N Relay UE", and "leaf L2 U2N Relay UE" can be used interchangeably.

[0131] Both "last U2N Relay UE" and "intermediate U2N Relay UE" are U2N Relay UEs, meaning that a U2N Relay UE includes both "last U2N Relay UE" and "intermediate U2N Relay UE".

[0132] The first U2N Relay UE refers to the UE (or U2N Relay UE, or intermediate U2N Relay UE) that is (directly) connected to the U2N Remote UE via the PC5 interface, and (directly) connected to the last U2N Relay UE or (other) intermediate U2N Relay UE via the PC5 interface, providing functionality to support the U2N Remote UE's connection to the network. Alternatively, the first U2N Relay UE refers to the intermediate U2N Relay UE (or U2N Relay UE) that is (directly) connected to the U2N Remote UE via the PC5 interface.

[0133] The second U2N Relay UE refers to a UE (or U2N Relay UE, or intermediate U2N Relay UE) that is (directly) connected to the first U2N Relay UE via a PC5 interface, and (directly) connected to the last U2N Relay UE or (other) intermediate U2N Relay UE via a PC5 interface, providing functionality to support U2N Remote UE connections to the network. Alternatively, the second U2N Relay UE refers to an intermediate U2N Relay UE (or U2N Relay UE) that is (directly) connected to the first U2N Relay UE via a PC5 interface.

[0134] Similarly, the nth U2N Relay UE refers to the UE (or U2N Relay UE, or intermediate U2N Relay UE) that is directly connected to the (n-1)th U2N Relay UE via the PC5 interface, and is also directly connected to the last U2N Relay UE via the PC5 interface, providing functionality to support the U2N Remote UE's connection to the network. Alternatively, the nth U2N Relay UE refers to the intermediate U2N Relay UE (or U2N Relay UE) that is directly connected to the (n-1)th U2N Relay UE via the PC5 interface.

[0135] The first U2N Relay UE, the second U2N Relay UE, and so on up to the nth U2N Relay UE are all intermediate U2N Relay UEs. "First U2N Relay UE" and "First L2 U2N Relay UE" can be used interchangeably, as can "Second U2N Relay UE" and "Second L2 U2N Relay UE".

[0136] "PC5-RRC message" refers to the side-link communication notification NotificationMessageSidelink message, the side-link communication Uu message transfer (UuMessageTransferSidelink) message, or other PC5-RRC messages.

[0137] "Previous hop UE" refers to the UE that is closer to the current UE (for a specific U2N Remote UE or for a specific multi-hop indirect path) in a multi-hop L2N relay architecture. "Previous hop UE" can be the (intermediate) U2N Relay UE, U2N Remote UE, or the first / second U2N Relay UE.

[0138] "Next-hop UE" refers to the UE that is closer to the network than the current UE in a multi-hop L2N relay architecture (for a specific U2N Remote UE or for a specific multi-hop indirect path). "Next-hop UE" can be the (intermediate) U2N Relay UE, the last U2N Relay UE, or the first / second U2N Relay UE.

[0139] Example 1

[0140] Figure 5 is a schematic diagram of the steps performed by the UE according to one or more embodiments. In Embodiment 1, the UE can perform one or more steps in Figure 5. As shown in Figure 5, Embodiment 1 includes steps S501 to S505.

[0141] Optionally, the UE is a UE with NR sidelink discovery capability, and / or the UE is an intermediate U2N Relay UE, and / or the UE is currently acting as an intermediate U2N Relay UE, and / or the UE is a UE that supports intermediate U2N Relay UE operation, and / or the UE is a first U2N Relay UE, and / or the UE is a second U2N Relay UE. Optionally, if it is determined that the UE has the above characteristics, steps S501 to S505 and the determination and operation in each step may be performed.

[0142] Optionally, in step S501, the UE receives a Discovery threshold and / or hysteresis sent by the network. The Discovery threshold and / or hysteresis are contained in a system message, a proprietary RRC message (e.g., an RRC Reconfiguration message), a MAC CE, or a pre-configuration. Optionally, the Discovery threshold is an SD-RSRP threshold indicated by the intermediate U2N Relay UE for evaluating AS layer conditions during discovery. The intermediate U2N Relay UE applies the value of the Discovery threshold to evaluate AS layer conditions and determine whether to forward or transmit a (Model A) Relay Discovery Announcement message. Optionally, the hysteresis indicates the hysteresis relative to the Discovery threshold.

[0143] Optionally, in step S502, the UE is configured by the upper layer to transmit or forward NR sidelink discovery messages, and the UE receives a (Model A) Relay Discovery Announcement message sent by the U2N Relay UE (or the next-hop UE). Optionally, the NR sidelink discovery message includes, but is not limited to, the Relay Discovery Announcement message.

[0144] Optionally, in step S503, the UE evaluates AS layer conditions for forwarding or transmitting (Model A) Relay Discovery Announcement messages.

[0145] Optionally, the UE considers the condition to be satisfied if at least one of the following conditions is met:

[0146] - The condition was not previously met;

[0147] - The conditions for forwarding or transmitting (Model A) Relay Discovery Announcement messages were not previously met;

[0148] - The Discovery threshold is not configured;

[0149] - The SD-RSRP of the Relay Discovery Announcement message (Model A) received from the U2N Relay UE is available;

[0150] - The SD-RSRP for U2N Relay UE is available;

[0151] - The SD-RSRP of the Relay Discovery Announcement message (Model A) received from the U2N Relay UE is higher than (or higher than or equal to) the Discovery threshold;

[0152] - The SD-RSRP of the U2N Relay UE is higher than (or equal to) the Discovery threshold.

[0153] Optionally, the UE considers the condition not to be met if at least one of the following conditions is met:

[0154] - The condition was previously met;

[0155] - The conditions for forwarding or transmitting (Model A) Relay Discovery Announcement messages have been met previously;

[0156] - The SD-RSRP of the Relay Discovery Announcement message (Model A) received from the U2N Relay UE is available;

[0157] - The SD-RSRP for U2N Relay UE is available;

[0158] - The SD-RSRP of the Relay Discovery Announcement message (Model A) received from the U2N Relay UE is lower than (or lower than or equal to) the Discovery threshold minus the hysteresis;

[0159] - The SD-RSRP of the U2N Relay UE is lower than (or equal to) the Discovery threshold minus the hysteresis.

[0160] Optionally, "U2N RelayUE" can be the last U2N RelayUE, or (other) intermediate U2N Relay UE, or the next-hop UE. For example, the next-hop UE of the first U2N Relay UE is the second U2N Relay UE, and the next-hop UE of the second U2N Relay UE is the third U2N Relay UE. The UE and the "U2N Relay UE" are directly connected.

[0161] Optionally, in step S504, if the condition described in step S503 is met, the UE initiates the transmission of an NR sidelink communication UE information (SidelinkUEInformationNR) message to instruct the network that the UE requests resources for an NR sidelink relay discovery message.

[0162] Optionally, in step S505, the UE determines whether to forward or transmit the (Model A) Relay Discovery Announcement message based on whether the conditions in step S503 are met. Optionally, if the conditions are met, the UE forwards or transmits the (Model A) Relay Discovery Announcement message.

[0163] Alternatively, in another implementation of step S505, when the UE is forwarding or transmitting a (Model A) Relay Discovery Announcement message, or when the UE is performing (multi-hop) U2N Relay discovery for Model A, a resource allocation mode is determined for forwarding or transmitting the (Model A) Relay Discovery Announcement message based on whether the conditions in step S503 are met. Optionally, if the conditions are met, the UE configures the lower layer(s) to perform sidelink resource allocation mode 2 for discovery transmission, or the UE configures the lower layer(s) to perform sidelink resource allocation mode 2 for (Model A) Relay Discovery Announcement message transmission.

[0164] Example 2

[0165] The general flow of Embodiment 2 is similar to that of Embodiment 1, with differences only in details. Therefore, FIG. 5 is also used to illustrate Embodiment 2. In Embodiment 2, the UE can perform one or more steps as shown in FIG. 5. As shown in FIG. 5, Embodiment 2 may include steps S501 to S505.

[0166] Optionally, the UE is a UE with NR sidelink discovery capability, and / or the UE is the last U2N Relay UE, and / or the UE is currently acting as the last U2N Relay UE, and / or the UE supports last U2N Relay UE operation. Optionally, if it is determined that the UE has the above characteristics, steps S501 to S505 and the determination and operation in each step may be executed.

[0167] Optionally, in step S501, the UE receives a Discovery threshold and / or hysteresis sent by the network. The Discovery threshold and / or hysteresis are contained in a system message, a proprietary RRC message (e.g., an RRC reconfiguration message), a MAC CE, or a pre-configuration. Optionally, the Discovery threshold is an SD-RSRP threshold indicated by the last U2N Relay UE for evaluating AS layer conditions during discovery. The last U2N Relay UE applies the value of the Discovery threshold to evaluate AS layer conditions and determine whether to send or transmit a (Model B) Relay Discovery Response message. Optionally, the hysteresis indicates the hysteresis relative to the Discovery threshold. Optionally, the Discovery threshold and the hysteresis may be the same as or different from the Discovery threshold described in Figure 3.

[0168] Optionally, in step S502, the UE is configured by the upper layer to transmit an NR sidelink discovery message, and the UE receives a (Model B) Relay Discovery Solicitation message sent by the U2N Remote UE (or the previous hop UE). Optionally, the NR sidelink discovery message includes, but is not limited to, a Relay Discovery Response message.

[0169] Optionally, in step S503, the UE evaluates AS layer conditions for sending or transmitting (Model B) Relay Discovery Response messages.

[0170] Optionally, the UE considers the condition to be satisfied if at least one of the following conditions is met:

[0171] - The condition was not previously met;

[0172] - The conditions for sending or transmitting the (Model B) Relay Discovery Response message were not previously met;

[0173] - The Discovery threshold is not configured;

[0174] - The SD-RSRP of the (Model B) Relay Discovery Solicitation message received from the intermediate U2N Relay UE is available;

[0175] SD-RSRP for the -intermediate U2N Relay UE is available;

[0176] - The SD-RSRP of the (Model B) Relay Discovery Solicitation message received from the intermediate U2N Relay UE is higher than (or equal to) the Discovery threshold;

[0177] -The SD-RSRP of the intermediate U2N Relay UE is higher than (or equal to) the Discovery threshold.

[0178] Optionally, the UE considers the condition not to be met if at least one of the following conditions is met:

[0179] - The condition was previously met;

[0180] - The conditions for sending or transmitting the (Model B) Relay Discovery Solicitation message have been met previously;

[0181] - The SD-RSRP of the (Model B) Relay Discovery Solicitation message received from the intermediate U2N Relay UE is available;

[0182] SD-RSRP for the -intermediate U2N Relay UE is available;

[0183] - The SD-RSRP of the (Model B) Relay Discovery Solicitation message received from the intermediate U2N Relay UE is lower than (or lower than or equal to) the Discovery threshold minus the hysteresis;

[0184] The SD-RSRP of the -intermediate U2N Relay UE is lower than (or equal to) the Discovery threshold minus the hysteresis.

[0185] Optionally, in step S504, if the condition described in step S503 is met, the UE initiates the transmission of an NR sidelink communication UE information (SidelinkUEInformationNR) message, instructing the UE to request NR sidelink relay discovery message resources.

[0186] Optionally, in step S505, the UE determines whether to send or transmit a (Model B) Relay Discovery Response message based on whether the conditions in step S503 are met. Optionally, if the conditions are met, the (Model B) Relay Discovery Response message is sent or transmitted.

[0187] Alternatively, in another implementation of step S505, when the UE is sending or transmitting a (Model B) Relay Discovery Response message, or when the UE is performing (multi-hop) U2N Relay discovery of Model B, a resource allocation mode is determined for sending or transmitting the (Model B) Relay Discovery Response message based on the satisfaction of the conditions in step S503. Optionally, if the conditions are satisfied, the UE configures the lower layer(s) to perform sidelink resource allocation mode 2 for discovery transmission, or the UE configures the lower layer(s) to perform sidelink resource allocation mode 2 for (Model B) Relay Discovery Response message transmission.

[0188] Example 3

[0189] Figure 6 is a schematic diagram of the steps performed by the UE according to one or more embodiments. In embodiment 3, the UE can perform one or more steps of Figure 6. As shown in Figure 6, embodiment 3 may include steps S601 to S603.

[0190] Optionally, the UE is a UE with NR sidelink discovery capability, and / or the UE is the last U2N Relay UE, and / or the UE is currently acting as the last U2N Relay UE, and / or the UE supports last U2N Relay UE operation. Optionally, if it is determined that the UE has the above characteristics, steps S601 to S603 and the determination and operation in each step may be executed.

[0191] Optionally, in step S601, when an RLF occurs on the Uu interface (or when a cell reselection occurs, or when the RRC connection establishment procedure is terminated by the upper layer), the UE initiates a procedure to send a PC5-RRC message (e.g., a Sidelink Notification Message). Optionally, if the UE is (or is currently acting as) the last U2N Relay UE, the PC5-RRC message is sent to the intermediate U2N Relay UE, or the PC5-RRC message is sent to the previous hop UE.

[0192] Optionally, the intermediate U2N Relay UE and the UE are directly connected. Optionally, the intermediate U2N Relay UE is a first U2N Relay UE, a second U2N Relay UE, or other intermediate U2N Relay UE directly connected to the UE. For a multi-hop U2N relay architecture with one intermediate U2N Relay UE, the intermediate U2N Relay UE is the first U2N Relay UE; for a multi-hop U2N relay architecture with two intermediate U2N Relay UEs, the intermediate U2N Relay UE is the second U2N Relay UE; and so on.

[0193] Optionally, in step S602, the UE sets the content of the PC5-RRC message.

[0194] Optionally, if the UE is (or is acting as) the last U2N Relay UE, the PC5-RRC message includes at least one of the following information, and the UE sets at least one of the following information:

[0195] - Identifier of the U2N Remote UE (identifier such as: L2 ID, or source L2 ID, or destination L2 ID);

[0196] -The identifier of the last U2N Relay UE (identifier such as: L2 ID, or source L2 ID, or destination L2 ID).

[0197] There may be one or more identifiers for the U2N Remote UE, or a list of identifiers for the U2N Remote UE if there are multiple identifiers. The identifier for the U2N Remote UE is used to indicate the U2N Remote UE, and the identifier for the last U2N Relay UE is used to indicate the last U2N Relay UE.

[0198] Optionally, in step S603, the UE submits the PC5-RRC message to the lower layer(s) for transmission.

[0199] Example 4

[0200] The general process of Embodiment 4 is the same as that of Embodiment 3, therefore, FIG. 6 is also used to illustrate Embodiment 4. In Embodiment 4, the UE can perform one or more steps of FIG. 6. As shown in FIG. 6, Embodiment 4 may include steps S601 to S603.

[0201] Optionally, the UE is a UE with NR sidelink discovery capability, and / or the UE is an intermediate U2N Relay UE, and / or the UE is currently acting as an intermediate U2N Relay UE, and / or the UE is a UE that supports intermediate U2N Relay UE operation, and / or the UE is a first U2N Relay UE, and / or the UE is a second U2N Relay UE. Optionally, if it is determined that the UE has the above characteristics, steps S601 to S603 and the determination and operation in each step may be executed.

[0202] Optionally, in step S601, when the first condition is met, the UE initiates a process of sending a PC5-RRC message (e.g., a sidelink notification message) to send an anomaly notification. Optionally, the PC5-RRC message is sent to a U2N Remote UE, or to an intermediate U2N Relay UE, or to the previous hop UE.

[0203] Optionally, the first condition includes at least one of the following:

[0204] - When PC5 RLF is detected;

[0205] -When relay reselection occurs;

[0206] -When the community changes;

[0207] -When a cell change occurs due to relay reselection;

[0208] - When the RRC connection establishment process is terminated by the upper layer, and the UE has not yet entered the RRC_CONNECTED state;

[0209] - When a path switch occurs.

[0210] Optionally, "relay reselection" refers to reselecting the last U2N Relay UE or reselecting the intermediate U2N Relay UE. Optionally, "cell change due to relay reselection" means that the cell corresponding to the last U2N Relay UE (or intermediate U2N Relay UE) reselected by the UE is different from the cell of the last U2N Relay UE (or intermediate U2N Relay UE) previously selected by the UE.

[0211] Optionally, the intermediate U2N Relay UE and the UE are directly connected, and / or the intermediate U2N Relay UE is the previous hop UE of the UE. In a multi-hop U2N relay architecture with two intermediate U2N Relay UEs, the UE is the second U2N Relay UE, the intermediate U2N Relay UE is the first U2N Relay UE, and so on.

[0212] Optionally, the PC5 RLF refers to at least one of the following meanings:

[0213] - The PC5 connection (or PC5-RRC connection) between the UE and the connected last U2N Relay UE experiences an RLF (or the PC5-RRC connection experiences an RLF).

[0214] - The PC5 connection (or PC5-RRC connection) between the UE and the connected next-hop UE experiences an RLF (or the PC5-RRC connection experiences an RLF).

[0215] - The PC5 RLF (or PC5-RRC connection RLF) occurs between the UE and the second U2N Relay UE (or: hop).

[0216] Optionally, in step S602, the UE sets the content of the PC5-RRC message.

[0217] Optionally, the PC5-RRC message includes at least one of the following information:

[0218] - Identifier of the U2N Remote UE (identifier such as: L2 ID, or source L2 ID, or destination L2 ID);

[0219] -The identifier of the last U2N Relay UE (identifier such as: L2 ID, or source L2 ID, or destination L2 ID);

[0220] - The identifier of the U2N relay UE that experienced the aforementioned anomaly (identifier, for example: L2 ID, or source L2 ID, or destination L2 ID);

[0221] -Indicator type.

[0222] Optionally, there may be one or more identifiers for the U2N Remote UE; if there are multiple identifiers, it may be a list of identifiers for the U2N Remote UE. The identifier of the U2N Remote UE is used to indicate the U2N Remote UE, and the identifier of the last U2N Relay UE is used to indicate the last U2N Relay UE.

[0223] The UE is configured with at least one of the above information. Alternatively, if the UE initiates the transmission of a PC5-RRC message due to the fulfillment of a first condition, the UE is configured with at least one of the above information.

[0224] Optionally, the UE setting indication type is at least one of the following:

[0225] PC5 RLF for -U2N Relay UE (or intermediate U2N Relay UE);

[0226] - Reselect U2N Relay UE (or intermediate U2N Relay UE);

[0227] - Reselect the relay (or relay UE) of the U2N Relay UE (or intermediate U2N Relay UE);

[0228] -U2N Relay UE (or intermediate U2N Relay UE) cell change;

[0229] -U2N Relay UE (or intermediate U2N Relay UE) path switching.

[0230] Optionally, the UE performs at least one of the following operations:

[0231] - When sending a PC5-RRC message is initiated due to the detection of the PC5 RLF, the PC5 RLF of the indication type is set to U2N Relay UE (or intermediate U2N Relay UE);

[0232] - When relay reselection occurs, set the reselection indicator type U2N Relay UE (or intermediate U2N Relay UE), or set the reselection indicator type U2N Relay UE (or intermediate U2N Relay UE) of the relay (or Relay UE) to be reselected;

[0233] - When the cell changes or when the cell changes due to relay reselection, set the indication type to U2N Relay UE (or intermediate U2N Relay UE) cell change;

[0234] - When a path switch occurs, set the indication type to U2N Relay UE (or intermediate U2N Relay UE) path switch.

[0235] Optionally, in step S603, the UE submits the PC5-RRC message to the lower layer(s) for transmission.

[0236] Example 5

[0237] Figure 7 is a schematic diagram of the steps performed by the UE according to one or more embodiments. In embodiment 5, the UE can perform one or more steps of Figure 7. As shown in Figure 7, embodiment 5 may include steps S701 to S703.

[0238] Optionally, the UE is a UE with NR sidelink discovery capability, and / or the UE is an intermediate U2N Relay UE, and / or the UE is currently acting as an intermediate U2N Relay UE, and / or the UE is a UE that supports intermediate U2N Relay UE operation, and / or the UE is a first U2N Relay UE, and / or the UE is a second U2N Relay UE. Optionally, if it is determined that the UE has the above characteristics, steps S701 to S703 and the determination and operation in each step may be executed.

[0239] Optionally, in step S701, the UE receives a PC5-RRC message (e.g., a NotificationMessageSidelink message). Optionally, the PC5-RRC message is received from the last U2N Relay UE, or from the intermediate U2N Relay UE, or from the next-hop UE. Optionally, the PC5-RRC message is used to send an anomaly notification, the PC5-RRC message contains an indication type, and the content of the PC5-RRC message is the same as that described in step S602 of Embodiment 3 and / or step S602 of Embodiment 4.

[0240] Optionally, in step S702, the UE initiates the process of forwarding / sending PC5-RRC messages.

[0241] Optionally, the UE performs at least one of the following operations:

[0242] - Forward / send PC5-RRC messages (e.g., NotificationMessageSidelink messages) to U2N Remote UE(s);

[0243] - Forward / send PC5-RRC messages (e.g., NotificationMessageSidelink messages) to intermediate U2N Relay UE(s);

[0244] - Forward / send PC5-RRC messages (e.g., NotificationMessageSidelink messages) to the previous UE(s);

[0245] - The same operation as when the U2N Remote UE receives the NotificationMessageSidelink message;

[0246] - (In the RRC_CONNECTED state) Initiate the RRC connection reconstruction process;

[0247] - (In RRC_IDLE or RRC_INACTIVE state, if it is decided to release the PC5-RRC connection with the last U2N Relay UE) Instructs the upper layer to trigger the release of the PC5 unicast link (with the last U2N Relay UE);

[0248] -(Optionally, in the RRC_IDLE or RRC_INACTIVE state, if it is decided not to release)

[0249] (Preserve the PC5-RRC connection with the last U2N Relay UE).

[0250] Optionally, the U2N Remote UE is the U2N Remote UE indicated in the PC5-RRC message received by the UE, specifically the U2N Remote UE indicated by the identifier of the U2N Remote UE in the received PC5-RRC message. If the received PC5-RRC message does not contain the identifier of the U2N Remote UE, then the UE forwards / sends the PC5-RRC message (e.g., a NotificationMessageSidelink message) to all associated U2N Remote UE(s), or the UE forwards / sends the PC5-RRC message (e.g., a NotificationMessageSidelink message) to all intermediate U2N Relay UE(s) (or to all previous hop UE(s)).

[0251] Optionally, an intermediate U2N Relay UE refers to an intermediate U2N Relay UE that includes at least one of the following characteristics:

[0252] - is the intermediate U2N Relay UE directly connected to the UE;

[0253] -Previous UE jump;

[0254] - For the intermediate U2N Relay UE associated with the U2N Remote UE.

[0255] Optionally, the PC5-RRC message forwarded / transmitted by the UE includes at least one of the following information:

[0256] - Identifier of the U2N Remote UE (identifier such as: L2 ID, or source L2 ID, or destination L2 ID);

[0257] -last U2N Relay UE identifier (identifier such as: L2 ID, or source L2 ID, or destination L2 ID);

[0258] - The identifier of the U2N relay UE that experienced the anomaly (identifier such as: L2 ID, or source L2 ID, or destination L2 ID);

[0259] -Indicator type;

[0260] - Message forwarding container.

[0261] Optionally, there may be one or more identifiers for the U2N Remote UE; if there are multiple identifiers, it may be a list of identifiers for the U2N Remote UE. The identifier of the U2N Remote UE is used to indicate the U2N Remote UE, and the identifier of the last U2N Relay UE is used to indicate the last U2N Relay UE.

[0262] The UE is configured with at least one of the above information. Alternatively, if the UE initiates PC5-RRC message transmission because it has received a PC5-RRC message sent by the last U2N Relay UE or the intermediate U2N Relay UE, the UE is configured with at least one of the above information.

[0263] Optionally, when the UE is configured with at least one of the above information, at least one of the following operations is performed:

[0264] - Set the indication type to the indication type carried in the PC5-RRC message received in step S701;

[0265] - Set the indicator type to empty;

[0266] - Set the identifier of the U2N Remote UE to the identifier of the U2N Remote UE carried in the PC5-RRC message received in step S701;

[0267] - Set the identifier of the last U2N Relay UE to the identifier of the last U2N Relay UE carried in the PC5-RRC message received in step S701;

[0268] - Set the identifier of the abnormal U2N relay UE to the identifier of the abnormal U2N relay UE carried in the PC5-RRC message received in step S701;

[0269] - The PC5-RRC message received in step S701 is packaged and carried in the message forwarding container.

[0270] Optionally, "empty" indicates that the UE itself has not experienced any abnormality but is forwarding an abnormality from another UE. Specifically, "empty" can be NULL, other, NONE, forward, or any value that indicates that the UE itself has not experienced any abnormality but is forwarding an abnormality from another UE.

[0271] Optionally, in step S703, the UE submits a PC5-RRC message to the lower layer(s) for transmission.

[0272] Example 6

[0273] Figure 8 is a schematic diagram of the steps performed by the UE according to one or more embodiments. In embodiment 6, the UE can perform one or more steps in Figure 8. As shown in Figure 8, embodiment 6 may include steps S801 to S802.

[0274] Optionally, the UE is a UE with NR sidelink discovery capability, and / or the UE is a U2N Remote UE, and / or the UE is currently acting as a U2N Remote UE, and / or the UE supports U2N Remote UE operation. Optionally, if it is determined that the UE has the above characteristics, steps S801 to S802 and the determination and operation in each step may be performed.

[0275] Optionally, in step S801, the UE receives a PC5-RRC message (e.g., a NotificationMessageSidelink message). Optionally, the PC5-RRC message is received from an intermediate U2N Relay UE or from a next-hop UE. Optionally, the PC5-RRC message is used to send an anomaly notification, and the PC5-RRC message contains an indication type.

[0276] Optionally, in step S802, different operations are performed based on the content of the PC5-RRC message.

[0277] Optionally, the UE determines at least one of the following conditions:

[0278] - The UE is (or is currently acting as) a U2N Remote UE;

[0279] - The PC5-RRC message contains an indication type, and the indication type is not empty;

[0280] -(If the indication type in the PC5-RRC message is empty or does not contain an indication type) The message forwarding container in the PC5-RRC message contains an indication type, and the indication type is not empty;

[0281] -UE is in RRC_CONNECTED state;

[0282] - The PC5-RRC message is received from the intermediate U2N Relay UE or from the next-hop UE.

[0283] Optionally, if at least one of the above conditions is met, the UE initiates an RRC connection reconstruction procedure.

[0284] Optionally, the UE determines at least one of the following conditions:

[0285] - The UE is (or is currently acting as) a U2N Remote UE;

[0286] - The PC5-RRC message contains an indication type, and / or the indication type is not empty;

[0287] -(If the indication type in the PC5-RRC message is empty or does not contain an indication type) The message forwarding container in the PC5-RRC message contains an indication type, and the indication type is not empty;

[0288] -UE is in RRC_IDLE or RRC_INACTIVE state;

[0289] - The PC5-RRC message is received from the intermediate U2N Relay UE.

[0290] Optionally, if at least one of the above conditions is met, the UE performs at least one of the following operations:

[0291] -(If it is decided not to release / retain the PC5-RRC connection with the intermediate U2N Relay UE) If the indication type in the PC5-RRC message is U2N Relay UE (or intermediate U2N Relay UE) relay (or Relay UE) reselection, then a relay reselection is considered to have occurred.

[0292] - (If it is decided not to release / retain the PC5-RRC connection with the intermediate U2N Relay UE) If the indication type in the PC5-RRC message is U2N Relay UE (or intermediate U2N Relay UE) cell change, then cell reselection is considered to have occurred;

[0293] - (If a decision is made to release the PC5-RRC connection with the intermediate U2N Relay UE) Instructs the upper layer to trigger the release of the PC5 unicast link (with the intermediate U2N Relay UE).

[0294] Unless otherwise specified, the judgments and operations in each step of the embodiment are independent of the execution order, that is, the execution order of judgments and operations can be interchanged.

[0295] Figure 9 is a simplified structural block diagram of the user equipment (UE) involved in this disclosure. As shown in Figure 9, the UE 900 includes a processor 901 and a memory 902. The processor 901 may include, for example, a microprocessor, a microcontroller, an embedded processor, etc. The memory 902 may include, for example, volatile memory (such as random access memory, RAM), a hard disk drive (HDD), non-volatile memory (such as flash memory), or other memory. Program instructions are stored on the memory 902. When executed by the processor 901, these instructions can perform the methods described in detail in this disclosure performed by the user equipment.

[0296] A program running on a device according to this disclosure may be a program that enables a computer to perform the functions of embodiments of this disclosure by controlling a central processing unit (CPU). The program or the information processed by the program may be temporarily stored in volatile memory (such as random access memory RAM), hard disk drive (HDD), non-volatile memory (such as flash memory), or other memory systems.

[0297] Programs used to implement the functions of the embodiments of this disclosure can be recorded on a computer-readable recording medium. The corresponding functions can be implemented by causing a computer system to read and execute the programs recorded on the recording medium. The term "computer system" here can refer to a computer system embedded in the device, and may include an operating system or hardware (such as peripheral devices). "Computer-readable recording medium" can be a semiconductor recording medium, an optical recording medium, a magnetic recording medium, a short-time dynamic storage program recording medium, or any other computer-readable recording medium.

[0298] Various features or functional modules of the devices used in the above embodiments can be implemented or executed by circuits (e.g., monolithic or multi-chip integrated circuits). Circuits designed to perform the functions described in this specification may include general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or any combination of the above devices. A general-purpose processor may be a microprocessor, or any existing processor, controller, microcontroller, or state machine. The circuits described above may be digital circuits or analog circuits. In cases where advancements in semiconductor technology have led to new integrated circuit technologies that replace existing integrated circuits, one or more embodiments of this disclosure may also be implemented using these new integrated circuit technologies.

[0299] Furthermore, this disclosure is not limited to the embodiments described above. Although various examples of the embodiments have been described, this disclosure is not limited thereto. Fixed or non-mobile electronic devices installed indoors or outdoors can be used as terminal devices or communication devices, such as AV equipment, kitchen equipment, cleaning equipment, air conditioners, office equipment, vending machines, and other household appliances.

[0300] As described above, embodiments of this disclosure have been described in detail with reference to the accompanying drawings. However, the specific structure is not limited to the above embodiments, and this disclosure also includes any design modifications that do not depart from the spirit of this disclosure. Furthermore, various modifications can be made to this disclosure within the scope of the claims, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included within the technical scope of this disclosure. In addition, components with the same effects described in the above embodiments can be substituted for each other.

Claims

1. A method performed by a user equipment, UE, which is a last U2N relay UE in a multi-hop user equipment-to-network relay, multi-hop U2N relay, the method comprising: setting, when the UE detects an abnormality, a PC5-RRC message for notifying that the abnormality has occurred, the PC5-RRC message including at least one of identification information of the last U2N relay UE and identification information of a U2N remote UE in the multi-hop U2N relay; and sending the PC5-RRC message to a previous hop UE directly connected with the UE, the abnormality including any one of: a radio link failure of a Uu interface between the UE and a network; a cell reselection of the UE; an RRC connection establishment procedure in the UE being terminated by an upper layer, and the UE not having entered an RRC connected state. 2.A method performed by a user equipment, UE, which is an intermediate U2N relay UE in a multi-hop user equipment-to-network relay, multi-hop U2N relay, the method comprising: setting, when the UE detects an abnormality, a PC5-RRC message for notifying that the abnormality has occurred, the PC5-RRC message including at least one of identification information of a U2N relay UE in which the abnormality has occurred and identification information of a U2N remote UE in the multi-hop U2N relay; and sending the PC5-RRC message to a previous hop UE in the multi-hop U2N relay directly connected with the UE, the abnormality including at least one of: a radio link failure of a PC5 interface between the UE and a next hop UE; a reselection of the next hop UE of the UE; a serving cell change of the UE; a serving cell change due to a reselection of the next hop UE; an RRC connection establishment procedure initiated in the UE being terminated by an upper layer, and the UE not having entered an RRC connected state. the PC5-RRC message further including identification information of a last U2N relay in the multi-hop U2N relay.

3. The method of claim 2, wherein, the PC5-RRC message further including an indication type indicating a type of the abnormality triggering the PC5-RRC message.

4. The method of claim 1 or 2, wherein, 5.A method performed by a user equipment, UE, which is an intermediate U2N relay UE or a U2N remote UE in a multi-hop user equipment-to-network relay, multi-hop U2N relay, the method comprising: receiving, from a next hop UE of the UE, a PC5-RRC message indicating that an abnormality has occurred at a network side UE of the UE, and including at least one of identification information of a U2N remote UE and identification information of a U2N relay UE in which the abnormality has occurred; and forwarding the PC5-RRC message to a previous hop UE directly connected with the UE or the U2N remote UE indicated in the PC5-RRC message. when forwarding the PC5-RRC message, further carrying information indicating that no abnormality has occurred in the UE itself. ​ 6. The method of claim 5, wherein, ​ 7. The method of claim 6, wherein, The PC5-RRC message further comprises an indication type representing a type of the exception, and information representing that no exception occurs in the UE itself is carried by the indication type.

8. The method of claim 6 or 7, further comprising: when the information representing that no exception occurs in the next-hop UE of the UE sending the PC5-RRC message is not included in the received PC5-RRC message: if the UE is in an RRC connected state, initiating an RRC connection reestablishment procedure; if the UE is in an RRC idle state or an RRC inactive state, releasing a PC5 unicast link between the UE and the next-hop UE sending the PC5-RRC message; and / or if the UE is in an RRC idle state or an RRC inactive state, and the UE decides not to release the PC5 unicast link between the UE and the next-hop UE sending the PC5-RRC message, performing a corresponding processing according to the type of the exception indicated by the indication type.

9. The method of any of claims 5-7, further comprising at least one of: the UE as an intermediate U2N relay UE forwards the relay discovery notification message upon reception of the relay discovery notification message, if an SD-RSRP at the time of reception of the relay discovery notification message is obtainable and the SD-RSRP is higher than a discovery threshold value; the UE as an intermediate U2N relay UE forwards the relay discovery response to a previous-hop UE directly connected to the UE upon reception of the relay discovery response from a next-hop UE, if an SD-RSRP at the time of reception of the relay discovery response is obtainable and the obtainable SD-RSRP is higher than a discovery threshold value; the UE as a last U2N relay UE sends a relay discovery response to a previous-hop UE directly connected to the UE upon reception of a relay discovery request, if an SD-RSRP at the time of reception of the relay discovery request is obtainable and the obtainable SD-RSRP is higher than a discovery threshold value.

10. A user equipment comprising: a processor; and a memory storing instructions, wherein the instructions, when executed by the processor, perform the method of any of claims 1-9.

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