Method executed by relay user equipment, and user equipment

Abstract

A method executed by a relay user equipment, i.e., a relay UE, and a UE. The method comprises: a relay UE triggering or starting a radio resource control (RRC) connection re-establishment procedure; and in the RRC connection re-establishment procedure, when the relay UE determines that the relay UE is executing an operation of an intermediate relay UE, the relay UE executing relay selection and not executing cell selection, and when the relay UE determines that the relay UE is executing an operation of a last relay UE, the relay UE executing cell selection and not executing relay selection.

Description

Methods performed by relay user equipment and user equipment Technical Field

[0001] This disclosure relates to the field of wireless communication technology, and more specifically, to methods performed by relay user equipment and 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) sidelink relay architecture. In a U2N relay architecture, communication between the remote UE and the network is conducted through a relay UE. This scenario can be described as a single-hop relay-based scenario, where at most one relay UE serves the remote UE.

[0003] In June 2024, at the RAN#104 plenary meeting, a work project on NR Sidelink multi-hop relay for 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. Unlike single-hop relay-based scenarios, in multi-hop relay-based scenarios, a remote UE can communicate with the network (or base station) through more than one relay UE; that is, at least two relay UEs provide services to the remote UE, enabling communication with the network.

[0004] Each UE on a multi-hop trunk link can be in RRC connected state, RRC idle state, or RRC inactive state. For UEs in RRC connected state, an RRC connection re-establishment procedure may be initiated under certain circumstances, which may cause services on the multi-hop trunk link to be suspended or fail. To ensure service continuity, how to manage UEs undergoing connection re-establishment is a problem that needs to be solved. Summary of the Invention

[0005] To address the aforementioned problems, the present invention provides a method and a user equipment executed by a relay user equipment.

[0006] According to one aspect of the present invention, a method performed by a relay user equipment (UE) is provided, comprising the following steps: the UE triggers or initiates a Radio Resource Control (RRC) connection re-establishment procedure; during the RRC connection re-establishment procedure, if the UE determines that it is performing an operation as an intermediate relay UE, the UE performs relay selection but not cell selection; if the UE determines that it is performing an operation as a last relay UE, the UE performs cell selection but not relay selection; if the UE determines that it has the capability to perform an intermediate relay UE operation, and if the UE determines that it is not performing an operation as a user equipment to network U2N relay UE, then the UE performs either cell selection or relay selection; if the UE determines that it is performing an operation as a U2N relay UE, then the UE performs cell selection but not relay selection.

[0007] In the above method, preferably, when the relay UE determines that it is performing the operation of an intermediate relay UE, it further determines whether there is at least one remote UE in RRC connection state connected to it. If there is at least one remote UE in RRC connection state connected to the relay UE, the relay UE performs relay selection and does not perform cell selection. If there is no remote UE in RRC connection state connected to the relay UE, the relay UE performs relay selection or performs cell selection.

[0008] In the above method, preferably, when the relay UE determines that it is performing the operation of the last relay UE, it further determines whether there is at least one remote UE in RRC connection state connected to it. If there is at least one remote UE in RRC connection state connected to the relay UE, the relay UE performs cell selection but does not perform relay selection. If there is no remote UE in RRC connection state connected to the relay UE, the relay UE performs cell selection or performs relay selection.

[0009] In the above method, preferably, after the relay UE performs cell selection, if the UE is an intermediate relay UE, the relay UE performs one or more of the following operations: triggers the upper layer to release the PC5 connection between itself and the remote UE; initiates a notification process and sets the indication type to cell selection in the side link notification message.

[0010] In the above method, preferably, after the relay UE performs relay selection, if the relay UE is a U2N relay UE, the relay UE performs one or more of the following operations: triggers the upper layer to release the PC5 connection between itself and the remote UE; initiates a notification process and sets the indication type to relay selection in the side link notification message.

[0011] In the above method, preferably, the relay UE receives configuration information from the network side, which may indicate that the relay UE does not need to perform cell selection, or does not need to perform relay selection, or only needs to perform cell selection, or only needs to perform relay selection in the RRC connection re-establishment process.

[0012] According to one aspect of the present invention, a user equipment is provided, comprising: a processor; and a memory storing instructions, wherein the instructions, when executed by the processor, perform the method according to any one of claims 1 to 6.

[0013] Invention Effects

[0014] According to the present invention, it is possible to effectively switch between multi-hop relay scenarios and single-hop relay scenarios. Attached Figure Description

[0015] The above and other features of this disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, wherein:

[0016] Figure 1 is a schematic diagram illustrating a single-hop U2N relay.

[0017] Figure 2 is a schematic diagram illustrating a multi-hop U2N relay.

[0018] Figure 3 is a simplified structural block diagram of the user equipment (UE) involved in this invention. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should be noted that the present invention 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 invention have been omitted to prevent confusion in understanding the present invention.

[0020] The following describes some of the terms involved in this invention. For the specific meanings of these terms, please refer to the latest 3GPP standard specifications.

[0021] UE: User Equipment

[0022] NR: New Radio, next-generation wireless technology

[0023] PHY: physical layer

[0024] MAC: Medium Access Control (Multimedia Access Control Layer)

[0025] RLC: Radio Link Control (layer)

[0026] SDAP: Service Data Adaptation Protocol (Layer)

[0027] PDCP: Packet Data Convergence Protocol (Layer)

[0028] SRAP: Sidelink Relay Adaptation Protocol (Layer)

[0029] RRC: Radio Resource Control (layer)

[0030] RRC_CONNECTED: RRC connection state

[0031] RRC_INACTIVE: RRC inactive state

[0032] RRC_IDLE: RRC idle state

[0033] RAN: Radio Access Network

[0034] NG-RAN: NG Radio Access Network, a next-generation radio access network

[0035] gNB: the next generation Node B, next-generation base station

[0036] Sidelink: Side-link communication, side-link

[0037] SL: Sidelink, side-to-side communication, side-to-side link

[0038] SCI: Sidelink Control Information

[0039] AS: Access Stratum

[0040] IE: Information Element

[0041] CE: Control Element

[0042] MIB: Master Information Block

[0043] SIB: System Information Block

[0044] DCI: Downlink Control Information

[0045] RB: radio bearer

[0046] DRB: Data Radio Bearer

[0047] SRB: Signaling Radio Bearer

[0048] Uu: Open air

[0049] ProSe: Proximity-based Services

[0050] V2X: Vehicle-to-Everything.

[0051] NAS: Non-Access Stratum

[0052] PC5-S: PC5 signalling

[0053] SL-SRB: Sidelink Signalling Radio Bearer

[0054] SL-DRB: Sidelink Data Radio Bearer

[0055] U2U: UE-to-UE, UE to UE

[0056] U2N: UE-to-Network

[0057] L2: Layer 2, a two-layer architecture

[0058] RSRP: Reference Signal Received Power

[0059] SL-RSRP: Sidelink RSRP, the received power of the sidelink communication reference signal.

[0060] SD-RSRP: Sidelink Discovery RSRP, a reference signal received by sidelink communication.

[0061] SpCell: Special Cell, including PCCell and PSCell.

[0062] PCell: Primary Cell

[0063] PSCell: Primary SCG Cell, SCG main cell

[0064] L2-ID: Layer-2 ID (identity), the identifier for the second layer.

[0065] 3GPP: 3rd Generation Partnership Project

[0066] RLF: Radio link failure.

[0067] TMSI: Temporary Mobile Subscriber Identity

[0068] RNTI: Radio Network Temporary Identifier

[0069] In this invention, 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 invention 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, home 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-CU) or distributed unit (gNB-DU) that makes up the base station.

[0070] In this invention, 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.

[0071] In this invention, Sidelink, SL, and PC5 can be used interchangeably.

[0072] In this invention, "change" and "update" can be used interchangeably.

[0073] In this invention, "configure", "set", and "present" can be used interchangeably.

[0074] In this invention, the terms "used", "available", "active", "applied", "performed", and "enabled" can be used interchangeably.

[0075] In this disclosure, the terms "use", "be available", "apply", "implement", "enable", "activate", "perform", and "do" can be used interchangeably.

[0076] In this disclosure, "associate", "correspond", and "map" can be used interchangeably.

[0077] In this disclosure, receive, detect, monitor, acquire, and derive are interchangeable.

[0078] In this invention, the terms "feedback", "submit", "report", "send", "transmit or transport", "inform", "indicate", "provide", and "forward" can be used interchangeably.

[0079] In this invention, "trigger" and "initiate" can be used interchangeably.

[0080] In this invention, the upper layer can refer to the ProSe layer, the V2X layer, the NAS layer, or the PC5-S protocol layer. The ProSe layer, V2X layer, NAS layer, and PC5-S protocol layer can be used interchangeably in this invention.

[0081] In this invention, "channel" can refer to one channel or multiple channels.

[0082] In this invention, "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.

[0083] In this invention, “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.

[0084] In this invention, "relay" can be used as a noun as an abbreviation for "relay UE", and as a verb, it refers to the relay operation.

[0085] In this invention, “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.

[0086] 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.

[0087] The related technologies of the present invention are described below.

[0088] PC5 interface

[0089] 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; each PC5 unicast link establishment corresponds to a PC5-RRC connection establishment. For sidelink unicast, the PC5-RRC connection is an AS layer logical connection between a source L2 ID and a destination L2 ID.

[0090] Uu interface

[0091] The Uu interface is the wireless communication interface between the UE and the base station. The UE can use NR technology and gNB communication on the Uu interface.

[0092] L2 architecture

[0093] 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.

[0094] U2N (UE-to-Network) relay

[0095] 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 establish a direct connection via the PC5 interface, while the relay UE and the network connect directly via the 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.

[0096] For U2N trunk architecture, a U2N remote UE refers to a UE that communicates with the network through a U2N trunk UE. An L2 U2N remote UE refers to a U2N remote UE in an L2 architecture. A U2N trunk UE refers to a UE that provides functionality to support U2N remote UE connections to the network. An L2 U2N trunk UE refers to a U2N trunk UE in an L2 architecture.

[0097] After a remote UE selects a relay UE to provide relay services, it establishes a PC5 connection with the relay UE, including the PC5 upper-layer connection and the PC5-RRC connection, so that the remote UE can communicate with the network through the relay UE. The remote UE can also establish an air interface RRC connection with the network through the relay UE for data transmission between the remote UE and the network.

[0098] As shown in Figure 1, the L2 U2N structure is a single-hop U2N relay, meaning that the remote UE communicates with the network through a relay UE. It can also be called a single-hop relay to distinguish it from subsequent multi-hop relays.

[0099] Multi-hop U2N relay

[0100] A single-hop U2N relay has only one U2N relay UE, and its coverage is limited. The multi-hop U2N relay structure is shown in Figure 2. The remote U2N UE connects to the network and communicates through multiple U2N relay UEs. Multi-hop U2N relay can extend the coverage of wireless communication.

[0101] In a multi-hop U2N trunk structure, there can be more than one trunk UE. These trunk UEs can all be called U2N trunk UEs, but to distinguish them from U2N trunk UEs in a single-hop U2N trunk structure, they can be differentiated based on their position within the structure. For example, as shown in Figure 2, the U2N trunk UE directly connected to the network can be called the "last U2N trunk UE," or simply "the last trunk UE." All trunk UEs other than the last U2N trunk UE can be called "intermediate trunk UEs."

[0102] Among these intermediate relay UEs, the intermediate UE that is directly connected to the remote UE can be referred to as the "first relay UE" or the "first intermediate relay UE", or simply the "first relay".

[0103] As can be seen, in a multi-hop U2N trunk structure, the trunk type of a trunk UE can be the first trunk UE, an intermediate trunk UE that is not the first trunk, an intermediate trunk UE (including the first trunk and other intermediate trunks), the last trunk UE, etc.

[0104] In a single-hop U2N trunk structure, the trunk type of a trunk UE can only be the last trunk UE.

[0105] Alternatively, a relay UE in a single-hop U2N relay structure can be called a U2N relay UE. For a relay UE that knows it is performing the operation of a U2N relay UE, it can be implied that the relay UE is working in a single-hop U2N relay structure.

[0106] For a relay UE that determines that it is performing the last relay UE operation, it can be implied that the relay UE is operating in a multi-hop U2N relay structure.

[0107] For a relay UE that determines that it is performing an intermediate relay UE operation, it can also imply that the relay UE is working in a multi-hop U2N relay structure.

[0108] For a relay UE that determines that it is performing the first intermediate relay UE operation, it can also imply that the relay UE is working in a multi-hop U2N relay structure.

[0109] In addition, the relay type can also be represented or determined in other ways. For example, it can indicate the connection method between the relay UE and the network or base station. For example, if the connection method between the relay UE and the network is direct connection, then the relay type of the relay UE can be determined as the last relay UE; if the connection method between the relay UE and the network is indirect connection, then the relay type of the relay UE can be determined as an intermediate relay UE; or, for example, it can indicate the connection method between the relay UE and the remote UE. If the connection method between the relay UE and the remote UE is direct connection, then the relay type of the relay UE can be determined as the first relay UE.

[0110] In this invention, the method of directly indicating the relay type is used as an example where "relay type" is involved, but it is equally applicable to cases where the relay type is determined indirectly by other means.

[0111] In a multi-hop U2N relay structure, the number of intermediate relay UEs can be one or more.

[0112] For example, in a multi-hop U2N trunk structure with an intermediate trunk UE, this intermediate trunk UE is the first trunk UE. It can connect to the remote UE through the PC5 interface, and it can also connect to the last U2N trunk UE through the PC5 interface. The last U2N trunk UE can connect to the network through the Uu interface.

[0113] For example, in a multi-hop U2N trunk structure with two intermediate trunk UEs, the U2N remote UE is connected to the first trunk UE via the PC5 interface, the first intermediate trunk UE is connected to the second intermediate trunk UE via the PC5 interface, the second trunk UE is connected to the last U2N trunk UE via the PC5 interface, and the last U2N trunk UE is connected to the network via the Uu interface.

[0114] The U2N remote UE establishes a (Uu)RRC connection with the network, a Uu SRB for transmitting signaling, and a Uu DRB for transmitting data.

[0115] Notification procedure

[0116] During the notification process, a relay UE sends a message called NotificationMessageSidelink to UEs with which it has a PC5 connection. A UE connected to a relay UE can be a remote UE, or another relay UE, such as an intermediate relay UE, or the last relay UE.

[0117] Relay UEs typically initiate the notification process under the following circumstances:

[0118] The relay UE detected a radio link failure (RLF) on the Uu interface;

[0119] The relay UE receives an RRC reconfiguration message containing synchronization information (ReconfigurationwithSync);

[0120] When a relay UE experiences cell reselection.

[0121] When a relay UE detects an RLF on the Uu interface and transmits a NotificationMessageSidelink message, the relay UE will set the indication type to Relay UE Uu RLF.

[0122] When a relay UE receives an RRC reconfiguration message containing synchronization information (ReconfigurationwithSync) and transmits a NotificationMessageSidelink message, the relay UE will set the indication type to Relay UE handover (HO).

[0123] When a relay UE transmits a NotificationMessageSidelink message during a cell reselection, the relay UE will set the indication type to Relay UE Cell Reselection.

[0124] These indication types are included in the NotificationMessageSidelink message. The relay UE delivers the NotificationMessageSidelink message to the lower layer for transmission, thereby sending it to the target UE.

[0125] Discovery process

[0126] 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 "I am here." The relay UE broadcasts a Relay Discovery Announcement message, or Discovery message for short. 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 format, first asking "Who is 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.

[0127] Timer T300,

[0128] After transmitting an RRC Setup Request message, the UE starts timer T300. Upon receiving an RRC Setup message, the timer stops running. When T300 times out, the UE enters the RRC idle state.

[0129] Timer T301

[0130] After transmitting an RRC re-establishment request message, the UE starts timer T301. When it receives an RRC re-establishment message or an RRC setup message, it stops running this timer. When T301 times out, the UE enters the RRC idle state.

[0131] Timer T302

[0132] When the UE receives an RRC Reject message, it starts timer T302. The timer stops running after the UE enters the RRC connected state. When timer T302 times out, the UE notifies its upper layers, such as the RRC layer, of a barring alleviation.

[0133] Timer T319

[0134] After transmitting an RRC resume request message, the UE starts timer T319. When it receives an RRC resume or RRC setup message, it stops running this timer. When T319 times out, the UE enters the RRC idle state.

[0135] Timer T420

[0136] When the UE receives an RRC reconfiguration message containing the SL path switch configuration, it starts timer T420. Upon successfully sending an RRC reconfiguration complete message, the timer stops running. When T420 times out, the UE initiates the RRC connection re-establishment procedure.

[0137] In the following embodiments, the same nouns may represent the same meaning, and the same parameter names may represent the same meaning.

[0138] The present invention also includes other embodiments not mentioned herein, which may achieve other effects not mentioned herein, which is self-evident.

[0139] The following describes in detail embodiments of the present invention that address the above-mentioned problems.

[0140] Example

[0141] The relay UE triggers or initiates the RRC Re-establishment procedure. During this procedure, the UE can perform the following operations:

[0142] In one scenario, the UE determines that it is acting as an intermediate relay UE, for example, as a relay UE in Figure 2. In this case, the UE performs relay selection, and preferably, the UE does not perform cell selection.

[0143] Furthermore, after determining that it is performing the operation of an intermediate relay UE, the UE can further determine whether there is at least one remote UE in RRC connection state connected to it (or determine whether it is serving at least one remote UE in RRC connection state):

[0144] If there is at least one remote UE in RRC connected state connected to this UE (or serving at least one remote UE in RRC connected state), then the UE performs relay selection. Preferably, the UE does not perform cell selection.

[0145] If there is no remote UE in RRC connection state connected to this UE (or there is no remote UE serving in RRC connection state), then the UE can perform relay selection or cell selection.

[0146] In another scenario, if the UE determines that it is acting as a last relay UE (as shown in Figure 2), then the UE performs cell selection. Preferably, the UE does not perform relay selection.

[0147] Furthermore, after determining that it is performing the last relay UE operation, the UE can further determine whether there is at least one remote UE in RRC connection state connected to it (or determine whether it is serving at least one remote UE in RRC connection state):

[0148] If there is at least one remote UE in RRC connection state connected to this UE (or serving at least one remote UE in RRC connection state), then the UE performs cell selection. Preferably, the UE does not perform relay selection.

[0149] If there is no remote UE in RRC connection state connected to this UE (or there is no remote UE serving in RRC connection state), then the UE can perform cell selection or relay selection.

[0150] In another scenario, if the UE determines that it has the capability to act as an intermediate relay UE, or the capability to act as a multi-hop relay, or the capability to select a relay, and if the UE determines that it is not acting as a U2N relay UE (as shown in Figure 1), the UE can perform cell selection or relay selection. If the UE determines that it is acting as a U2N relay UE, as shown in Figure 1, then the UE performs cell selection; preferably, the UE does not perform relay selection. Preferably, "U2N relay UE" here refers to a relay UE in a single-hop U2N structure. "Acting" as a relay UE can also be understood as determining the role or type of that relay UE in a single-hop or multi-hop relay structure.

[0151] Furthermore, after determining that it possesses the aforementioned capabilities and is performing U2N relay UE operations, the UE can further determine whether there is at least one remote UE in RRC connection state connected to it (or whether it is serving at least one remote UE in RRC connection state):

[0152] If there is at least one remote UE in RRC connection state connected to this UE (or serving at least one remote UE in RRC connection state), then the UE performs relay selection. Preferably, the UE does not perform relay selection.

[0153] If there is no remote UE in RRC connection state connected to this UE (or there is no remote UE serving in RRC connection state), then the UE can perform relay selection or cell selection.

[0154] In this paper, when a UE has multiple conditions that it needs to determine, it is not necessary to distinguish the order in which the conditions are determined. That is, which condition is determined first and which condition is determined next. This paper only provides one determination order, but other determination orders are not excluded. For example, the UE can first determine whether there is a remote UE in a connected state, and then determine whether it is performing a relay operation.

[0155] In this article, "UE can perform cell selection or relay selection" means that if a suitable cell exists, the UE selects that cell; if a suitable relay exists, the UE selects that relay. If both exist, the UE can preferentially select a suitable cell or prioritize a suitable relay.

[0156] In one scenario, the UE can perform cell selection during the RRC connection re-establishment procedure. Once the UE has selected a suitable cell, it can make the following judgments:

[0157] If the UE is an intermediate relay UE, or is performing the operation of an intermediate UE as shown in Figure 2, preferably, the UE is an intermediate relay UE before cell selection (i.e., a relay UE performing intermediate relay operation), or is an intermediate relay UE or performing the operation of an intermediate UE at or before initiating the RRC connection re-establishment procedure, then the UE can perform one or more of the following operations:

[0158] - Trigger the upper layer to release the PC5 connection between itself and the remote UE, preferably, this or these remote UEs are UEs in RRC connected state.

[0159] - Initiate the Notification process by setting the indication type to cell selection in the NotificationMessageSidelink message; a further implementation method is as follows: the UE can determine whether the selected cell is the same as the UE's previous serving cell, i.e., whether the cell identifiers are the same:

[0160] ■ If they are the same, then the UE does not need to initiate the Notification process.

[0161] ■ Alternatively, if they are the same, the UE can initiate a Notification procedure, and the NotificationMessageSidelink message sent in that procedure contains information indicating cell selection and / or indicating whether the cell has changed. For example, the indication type can be set to cell selection with the cell unchanged, thus indicating that the cell has not changed.

[0162] ■ If the UE determines that the selected cell is different from the UE's previous serving cell, the UE can initiate a Notification procedure, and the NotificationMessageSidelink message sent in this procedure contains information indicating the cell selection and / or whether the cell has changed. For example, the UE can set the indication type to cell selection with cell change in this message, or set the indication type to cell reselection, thereby indicating that the cell has changed.

[0163] As a supplement, if the UE is not an intermediate relay UE, or performs the operations of an intermediate UE, such as a U2N relay UE as shown in Figure 1 or Figure 2, then the above operations are not required.

[0164] In one scenario, the UE can perform relay selection during the RRC connection re-establishment procedure. Once the UE selects a suitable relay, the following checks can be performed:

[0165] If the UE is a U2N relay UE, or is acting as a U2N relay UE, preferably, "U2N relay UE" refers to a relay UE in a single-hop U2N structure, as shown in Figure 1. Preferably, the UE is a U2N relay UE before relay selection, or is a U2N relay UE or is acting as a U2N relay UE at or before initiating the RRC connection re-establishment procedure. Then the UE can perform one or more of the following operations:

[0166] - Trigger the upper layer to release the PC5 connection between itself and the remote UE, preferably, this or these remote UEs are remote UEs in RRC connected state.

[0167] - Initiate the Notification process by setting the indication type to relay selection in the NotificationMessageSidelink message; Alternatively, the UE can determine whether the serving cell of the selected relay is the same as the UE's previous serving cell, i.e., whether the cell identifiers are the same.

[0168] ■ If they are the same, then the UE does not need to initiate the Notification process;

[0169] ■ Alternatively, if they are the same, the UE can initiate a Notification procedure. The NotificationMessageSidelink message sent in this procedure contains information indicating that a relay selection or reselection has occurred, and / or indicating whether the cell has changed. For example, the UE can set the indication type to relay selection (or relay reselection), or preferably, it can set the indication type to relay selection (or reselection) with the cell unchanged, thus indicating that the cell has not changed.

[0170] ■ If the UE determines that the serving cell of the selected relay is different from the UE's previous serving cell, the UE can initiate a Notification procedure, and the NotificationMessageSidelink sent in this procedure contains information indicating that a relay selection or reselection has occurred, and / or indicating whether the cell has changed. For example, the UE can set the indication type to relay selection with cell change, or set the indication type to cell reselection to indicate that the cell has changed.

[0171] As a supplement, if the UE is not a U2N relay UE, or is performing U2N relay UE operations, and / or the UE does not have the ability to perform intermediate UE operations (or relay selection capabilities, or multi-hop relay capabilities), then the above operations are not required.

[0172] In another scenario, the UE can receive configuration information from the network side. This information may indicate whether the UE does not need to perform cell selection, relay selection, or only cell selection during the RRC connection re-establishment procedure. Based on this execution information, the UE can perform the corresponding operation during the RRC connection reconstruction procedure. Alternatively, if the UE does not receive the aforementioned configuration information, it can perform cell selection or relay selection according to the aforementioned scheme during the RRC connection re-establishment procedure.

[0173] The aforementioned UE operates as a relay UE. As a remote UE, upon receiving the aforementioned NotificationMessageSidelink message containing indication information, it can perform the following operations:

[0174] In one scenario, a NotificationMessageSidelink message sent from the relay UE indicates that cell selection, relay selection (or reselection), and / or a cell change has occurred. For example, it may contain an indication of relay selection (or relay reselection), preferably an indication of a cell change, or a cell selection indicating a cell change. Upon receiving this message, the remote UE may perform one or more of the following operations, depending on its own circumstances:

[0175] The -remote UE determines whether its timer T300, T319, T302, or T301 is running. If at least one of the four timers is running, the remote UE can enter the RRC idle state.

[0176] When a remote UE receives the above message, it can assume that a cell reselection has occurred.

[0177] When the remote UE receives the above message, it determines whether its timer T420 is running. If T420 is running, the remote UE can initiate the RRC connection re-establishment procedure.

[0178] Furthermore, since other relay UEs can also be connected to the relay UE, these other relay UEs can also perform one or more of the operations performed by the remote UE when they receive the aforementioned NotificationMessageSidelink message containing indication information.

[0179] Figure 3 is a simplified structural block diagram of the user equipment (UE) involved in this invention. As shown in Figure 3, the UE 300 includes a processor 301 and a memory 302. The processor 301 may include, for example, a microprocessor, a microcontroller, an embedded processor, etc. The memory 302 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 302. When executed by the processor 301, these instructions can perform the methods described in detail in this invention, which are executed by the user equipment.

[0180] Additionally, the computer-executable instructions or program running on the device according to this disclosure may be a program that enables the computer to perform the functions of the embodiments of this disclosure by controlling the 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.

[0181] Computer-executable instructions or programs for implementing the functions of the embodiments of this disclosure can be recorded on a computer-readable storage 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" herein can refer to a computer system embedded in the device, and may include an operating system or hardware (such as peripheral devices). "Computer-readable storage medium" can be a semiconductor recording medium, an optical recording medium, a magnetic recording medium, a short-time dynamic program storage medium, or any other computer-readable recording medium.

[0182] 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.

[0183] 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.

[0184] 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 relay user equipment (UE), comprising the following steps: The relay UE triggers or initiates the Radio Resource Control (RRC) connection re-establishment procedure. In the RRC connection re-establishment process, If the relay UE determines that it has the capability to act as an intermediate relay UE, it performs cell selection or relay selection. The intermediate relay UE refers to a relay UE that has a first PC5 connection with a remote UE and a second PC5 connection with another relay UE in a multi-hop relay communication from the user equipment UE to the network. If the relay UE determines that it is performing the operation of the last relay UE, then cell selection is performed. The last relay UE refers to a relay UE that has a Uu connection with the network. If the relay UE performs cell selection... Initiate the notification process, set the indication type to cell selection in the sidelink notification message, and deliver the sidelink notification message to the lower layer for transmission.

2. A user equipment, comprising: processor; as well as Memory, which stores instructions The instructions are executed by the processor according to the method of claim 1.

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