Connection of relay node to network

Abstract

A method performed by a network control relay (NCR) is provided. The method includes determining whether a radio link failure (RLF) occurs between the NCR and a first base station. The method includes performing cell selection for a radio resource control (RRC) connection procedure in a case where RLF occurs between the NCR and a first base station. The method includes performing an RRC connection procedure with the selected base station based on a result of performing the cell selection procedure.

Description

Technical Field

[0001] The present disclosure relates to one or more techniques for handling the connection of a repeater node to a network. More specifically, the present disclosure relates to one or more techniques for handling the connection of a network control repeater (NCR) to a radio access network (RAN) node in a 3rd Generation Partnership Project (3GPP) 5th Generation (5G) New Radio (NR) network after a radio link failure (RLF). Background Art

[0002] 5G mobile communication technology defines wide frequency bands, enabling high transmission rates and new services, which can be achieved not only in the "Sub 6GHz" frequency band such as 3.5GHz, but also in the "Above 6GHz" frequency band called mmWave, which includes 28GHz and 39GHz. In addition, it has been considered to implement 6G mobile communication technology (referred to as Beyond 5G system) in the terahertz frequency band (e.g., 95GHz to 3THz frequency band) in order to achieve a transmission rate 50 times faster than 5G mobile communication technology and an ultra-low latency of one-tenth of 5G mobile communication technology.

[0003] At the beginning of the development of 5G mobile communication technology, in order to support services and meet the performance requirements related to enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and massive machine-type communication (mMTC), standardization has been carried out on the following technologies: beamforming and massive MIMO, which are used to mitigate radio wave path loss and increase the radio wave transmission distance in millimeter waves; parameter sets that support dynamic operations for the effective utilization of millimeter wave resources and time slot formats (e.g., operating multiple subcarrier spacings). Initial access technologies that support multi-beam transmission and broadband; the definition and operation of bandwidth parts (BWPs); new channel coding methods such as low-density parity-check (LDPC) codes for large data transmission and polar codes for highly reliable transmission of control information; L2 preprocessing; and network slicing for providing dedicated networks dedicated to specific services.

[0004] Currently, in terms of the services supported by 5G mobile communication technology, discussions are being held on the improvement and performance enhancement of the initial 5G mobile communication technology, and physical layer standardization has been carried out on technologies such as: vehicle-to-everything (V2X) that helps autonomous vehicle driving determination based on information about the position and status of vehicles transmitted by vehicles and enhances user convenience; new radio unlicensed (NR-U) aims to make system operations meet various regulatory requirements in unlicensed frequency bands; NR UE energy saving; non-terrestrial network (NTN), which is direct communication between a UE and a satellite, for providing coverage in areas where communication with a terrestrial network is not possible; and positioning.

[0005] In addition, the following technologies have been standardized in the air interface architecture / protocol: Internet of Things (IoT) for supporting new services through interoperability and convergence with other industries; integrated access and backhaul (IAB) for providing nodes for network service area expansion by supporting wireless backhaul links and access links in an integrated manner; mobility enhancements including conditional handover and dual active protocol stack (DAPS) handover; and two-step random access (two-step RACH for NR) for simplifying the random access process. Regarding the 5G baseline architecture for combining network function virtualization (NFV) and software-defined network (SDN) technologies (e.g., service-based architecture or service-based interface), and mobile edge computing (MEC) for receiving services based on UE location, standardization has also been carried out in the system architecture / services.

[0006] With the commercialization of 5G mobile communication systems, exponentially growing connected devices will be connected to the communication network, and thus enhanced functions and performance of 5G mobile communication systems and integrated operation of connected devices are expected to be required. For this purpose, new research on the following technologies has been put on the agenda: extended reality (XR) for effectively supporting augmented reality (AR), virtual reality (VR), mixed reality (MR), etc.; 5G performance improvement and complexity reduction by leveraging artificial intelligence (AI) and machine learning (ML); AI service support; metaverse service support; and drone communication.

[0007] In addition, this development of 5G mobile communication systems will not only serve as the basis for developing the following technologies: new waveforms for providing coverage in the terahertz band of 6G mobile communication technologies; full-duplex technologies for improving the frequency efficiency of 6G mobile communication; multi-antenna transmission technologies such as full-dimensional MIMO (FD-MIMO), array antennas, and massive antennas; metasurface-based lenses and antennas for improving the coverage of terahertz band signals; and high-dimensional spatial multiplexing technologies using orbital angular momentum (OAM) and reconfigurable intelligent surfaces (RIS), but also serve as the basis for developing the following technologies: full-duplex technologies for improving the frequency efficiency of 6G mobile communication technologies and enhancing system networks; AI-based communication technologies for achieving system optimization from the design phase by leveraging satellites and AI and internalizing end-to-end AI support functions; and a new generation of distributed computing technologies for realizing services with complexity exceeding the UE operation capacity limit by utilizing ultra-high-performance communication and computing resources.

[0008] To provide enhanced network coverage, various different types of network nodes have been developed. For example, radio frequency (RF) repeaters can be used to amplify and forward any signals they receive to supplement the coverage provided by conventional cells. An enhanced repeater node called a network control repeater (NCR) is currently under development and is part of Release 18 study item / work item (3GPP RP-213700).

[0009] Figure 1 Fig. shows the network architecture of NCR communication according to the related art.

[0010] Referring Figure 1 , the NCR receives signals from the base station (gNB) via the NCR-Fwd link and forwards them to the user equipment (UE). The NCR also receives control signals for configuring the NCR from the gNB via the NCR mobile terminal (MT) link. Once configured, the NCR provides an amplification and forwarding function that is transparent to the UE. Thus, the gNB can communicate with the UE directly or via the NCR.

[0011] To enable easy deployment of NCR nodes, the NCR is configured to be transparent to the UE regardless of whether it communicates via the NCR. For example, when deploying the NCR, to make the NCR transparent to the UE during the random access procedure, when the NCR registers with the network, the gNB can allocate a set of SSB indexes to the NCR (while other SSB indexes are retained at the gNB), as described in Section 5 of 3GPP R1-2203741 for example. Then, the UE can perform the random access procedure via the SSB transmitted by the SSB indexes allocated to the NCR as if the random access procedure was performed via the gNB.

[0012] It is expected that the NCR-MT part of the NCR will act almost like a normal UE, which means signaling the NCR configuration similar to a normal UE. This means that the NCR-MT will have a complete protocol stack, but some functions that are typically used by the UE may not apply and will not be implemented by the NCR-MT and / or configured by the network.

[0013] The radio link failure (RLF) procedure has been introduced to allow the UE to regain its radio link to the base station (or another base station) in case of its radio link failure. After triggering the RLF, the UE performs radio resource control (RRC) reconstruction. During this process, the UE performs cell selection to select a cell (a new cell or possibly the same cell) and connect to the selected cell.

[0014] RLF can be declared in many cases, including for example the following cases:

[0015] The UE is out of sync;

[0016] The UE measures the cell strength through radio link monitoring. If the cell strength is below a certain threshold for a certain number of times, the UE triggers a timer (T310) to cause the UE to recover. If it does not recover, the UE declares RLF.

[0017] The RLC PDU is retransmitted multiple times;

[0018] The network configuration can attempt to retransmit the RLC PDU a certain number of times (maxRetxThreshold).

[0019] Random access problems;

[0020] This can occur when the UE is in the connected mode and the UE attempts to resynchronize, for example, after losing uplink synchronization.

[0021] Backhaul (BH) RLF (IAB related);

[0022] Backhaul link failure.

[0023] Uplink listen-before-talk (LBT) failure;

[0024] This is the LBT failure when the UE is on an unlicensed band.

[0025] As part of the RLF procedure execution, the UE can be configured to collect an RLF report containing information about the RLF, and the RLF report can then be reported to the gNB where the RLF occurred or any other gNB.

[0026] Figure 2 The RRC reconstruction procedure after RLF according to the related art is shown.

[0027] Reference Figure 2 , the RRC reconstruction procedure (along with RLF). The steps are as follows:

[0028] In operation 201, the RLF between the UE and the gNB ('old' gNB) is declared. This may also be a handover failure.

[0029] In operation 202, the UE performs idle mode cell selection (selecting the 'new' gNB in this example).

[0030] In operation 203, the UE sends an RRC reconstruction request to the selected new gNB (after performing random access for the first time).

[0031] In operation 204, the new gNB requests the UE context from the old gNB (if the new gNB is different from the old gNB).

[0032] In operation 205, the old gNB provides the requested UE context to the new gNB.

[0033] In operation 206, the new gNB answers the RRC Reestablishment Request with an RRC Reestablishment message in step 3. If needed, the new gNB may potentially reconfigure the UE, or continue to use the same previous RRC configuration. If the UE is reconfigured, the new gNB answers with an RRCSetup message.

[0034] In operation 207, the UE responds with an RRC Reestablishment Complete message.

[0035] Figure 3 The fault indication process according to the related art, the accompanying RLF and RRC reestablishment processes, and the RLF report transmission are shown.

[0036] Reference Figure 3 , in operations 301, 302, 303, 304, and 305, in order to indicate to the old gNB that a UE previously associated / connected with it has failed, the new gNB may signal an RLF indication to the old gNB via the Xn interface. The RLF indication may include, for example, an RLF report compiled by the UE.

[0037] In some cases, such as when an RRC reestablishment fails, or if the UE has not yet activated AS security, the UE may have to leave the connected mode under the release cause "RRC connection failure". In this case, the release cause is relayed to the upper layer of the UE-NAS. The action of the NAS when entering the RRC idle mode with this release cause is to trigger a tracking area update for any cell according to the idle mode process.

[0038] The above information is presented only as background information to facilitate understanding of the present disclosure. No determination has been made, nor is any assertion made, as to whether any of the above can be applicable as prior art with respect to the present disclosure. Summary of the Invention

[0039] [Technical Solution]

[0040] Aspects of the present disclosure are to solve at least the above problems and / or disadvantages and provide at least the following advantages. Accordingly, one aspect of the present disclosure is to provide one or more techniques for handling the connection of a repeater node to a network.

[0041] The present disclosure is defined in the independent claims. Advantageous features are defined in the dependent claims.

[0042] Additional aspects will be set forth in part in the following description, and in part will be obvious from the description, or may be learned by practice of the presented embodiments.

[0043] According to one aspect of the present disclosure, a method performed by a network control repeater (NCR) in a wireless communication system is provided. The method includes determining whether a radio link failure (RLF) occurs between the NCR and a first base station. The method includes performing cell selection for a radio resource control (RRC) connection procedure in case of an RLF between the NCR and the first base station. The method includes performing an RRC connection procedure with the selected base station based on a result of performing the cell selection procedure.

[0044] According to one aspect of the present disclosure, a network control repeater (NCR) in a wireless communication system is provided. The NCR includes a transmitter, a receiver, and at least one processor coupled to the transmitter and the receiver. The at least one processor is configured to determine whether a radio link failure (RLF) occurs between the NCR and a first base station. The at least one processor is configured to perform cell selection for a radio resource control (RRC) connection procedure in case of an RLF between the NCR and the first base station. The at least one processor is configured to perform an RRC connection procedure with the selected base station based on a result of performing the cell selection procedure.

[0045] Other aspects, advantages, and salient features of the present disclosure will become apparent to those skilled in the art from the following detailed description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] From the following description taken in conjunction with the accompanying drawings, the above and other aspects, features, and advantages of certain embodiments of the present disclosure will become more apparent, in which:

[0047] Figure 1 A network control repeater (NCR) communication architecture is shown, where an NCR mobile terminal (MT) is a control link for controlling an NCR-Fwd link at the NCR according to the related art;

[0048] Figure 2 A radio resource control (RRC) reestablishment procedure after a radio link failure (RLF) according to the related art is shown;

[0049] Figure 3 A failure indication procedure according to the related art, an accompanying RLF and RRC reestablishment procedures, and an RLF report transmission are shown;

[0050] FIG. 4A shows an RLF procedure without performing cell reselection according to an embodiment of the present disclosure;

[0051] FIG. 4B shows an RLF procedure according to an embodiment of the present disclosure, where cell selection is performed for a fallback gNB;

[0052] Figure 5Illustrates sending an NCR indication to a user equipment (UE) according to an embodiment of the present disclosure and sending an NCR recovery indication to the UE once the NCR has been re-established to a new donor gNB;

[0053] Figure 6 Illustrates the transmission of an NCR indication in an RLF report according to an embodiment of the present disclosure;

[0054] Figure 7 Illustrates the transmission of an NCR failure indication to a core network or OAM according to an embodiment of the present disclosure;

[0055] Figure 8 Illustrates the transmission of an NCR-specific RLF report according to an embodiment of the present disclosure;

[0056] Figure 9 Illustrates an NCR return procedure according to an embodiment of the present disclosure; and

[0057] Figure 10 Is a block diagram of a network entity according to an embodiment of the present disclosure.

[0058] In all the figures, it should be noted that the same reference numerals are used to describe the same or similar elements, features, and structures. Detailed Description

[0059] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to facilitate understanding, but these are only considered exemplary. Thus, those of ordinary skill in the art will recognize that various changes and modifications can be made to the various embodiments described herein without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and structures may be omitted for clarity and conciseness.

[0060] The terms and words used in the following description and claims are not limited to their bibliographical meanings, but are used by the inventors only to enable a clear and consistent understanding of the present disclosure. Thus, those skilled in the art should clearly understand that the following description of the various embodiments of the present disclosure is provided for illustrative purposes only and not for limiting the disclosure defined by the appended claims and their equivalents.

[0061] It should be understood that the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes reference to one or more such surfaces.

[0062] The same or similar components may be denoted by the same or similar reference numerals, although they may be shown in different figures.

[0063] For clarity and conciseness, and to avoid obscuring the subject matter of the present disclosure, detailed descriptions of techniques, structures, configurations, functions, or processes known in the art may be omitted.

[0064] The terms and words used herein are not limited to their bibliographical or standard meanings, but are used only to enable a clear and consistent understanding of the present disclosure.

[0065] Throughout the specification and claims of the description, the words "comprising", "including", and "containing", and variations of the words, such as "containing" and "accommodating", mean "including but not limited to", and are not intended to (and do not) exclude other features, elements, components, wholes, steps, processes, operations, functions, characteristics, properties, and / or groups thereof.

[0066] Throughout the specification and claims of the description, singular forms, such as "a", "an", and "the", cover the plural, unless the context otherwise requires. For example, a reference to "an object" includes a reference to one or more such objects. Throughout the specification and claims of the description, language in the general form of "X of Y" (where Y is some action, process, operation, function, activity, or step, and X is some means for performing that action, process, operation, function, activity, or step) includes means X that are adapted to, configured for, or specifically but not exclusively for performing Y.

[0067] Features, elements, components, wholes, steps, processes, operations, functions, characteristics, properties, and / or groups thereof described in connection with a particular aspect, embodiment, or disclosure of the present disclosure, embodiment, or claim should be understood to be applicable to any other aspect, embodiment, of the disclosure, embodiment, or claim described herein, unless incompatible therewith.

[0068] Those skilled in the art will understand that the techniques described herein can be used in any suitable combination.

[0069] Certain examples of the present disclosure provide one or more techniques for handling the connection of a repeater node to a network. For example, certain examples of the present disclosure provide one or more techniques for handling the connection of NCR to a RAN node in a 3GPP 5G NR network after RLF. However, those skilled in the art will understand that the present disclosure is not limited to these examples and can be applied to any suitable system or standard, such as one or more existing and / or future generation wireless communication systems or standards, including any existing or future version of the same standard specification, such as 3GPP 5G.

[0070] The following examples may apply to and use terms associated with 3GPP 5G. However, those skilled in the art will understand that the techniques disclosed herein are not limited to 3GPP 5G. For example, the functions of the various network entities and other features disclosed herein may be applied to corresponding or equivalent entities or features in other communication systems or standards. Corresponding or equivalent entities or features may be considered entities or features that perform the same or similar roles, functions, or purposes within a network.

[0071] A particular network entity may be implemented as a network element on dedicated hardware, a software instance running on dedicated hardware, and / or a virtualized function instantiated on a suitable platform (e.g., on a cloud infrastructure).

[0072] Certain examples of the present disclosure may be provided in the form of a device / equipment / network entity configured to perform one or more defined network functions and / or its method. Certain examples of the present disclosure may be provided in the form of a system (e.g., a network or a wireless communication system) including one or more such devices / equipment / network entities and / or its method.

[0073] In view of the related art, there are at least the following problems:

[0074] When the NCR detects / declares an RLF, various behaviors / requirements are currently undefined compared to when the UE detects / declares an RLF, such as including:

[0075] How does the NCR perform cell selection during reconstruction? For example, can the NCR freely connect to any cell?

[0076] How is the NCR-MT RLF indication conveyed to the UE connected via the NCR?

[0077] How should the NCR failure be indicated to the network, new gNB, old gNB, core network, and / or OAM so that the network can perform appropriate operations?

[0078] What is reported in the NCR RLF report? What is reported to the gNB and what is reported to the UE attached to the NCR?

[0079] What actions should be taken when the NCR reconstruction procedure fails?

[0080] Certain examples of the present disclosure provide one or more techniques for performing RLF and RRC reconstruction for an NCR (e.g., NCR-MT) and / or a UE attached to the network via the NCR.

[0081] Those skilled in the art will understand that the technologies disclosed herein can be applied to a gNB, such as an NG-RAN gNB. Those skilled in the art will also recognize that the technologies disclosed herein can also be applied to an NCR-MT in EN-DC.

[0082] Various technologies will be described below. Those skilled in the art will understand that these technologies can be applied in any suitable combination.

[0083] 1. Fallback (donor-)gNB

[0084] FIG. 4A shows an RLF process without cell reselection according to an embodiment of the present disclosure.

[0085] Referring to FIG. 4A, in operation 401, when an NCR (e.g., NCR-MT) declares an RLF, the NCR selects, in operation 402, the cell with which it performs RRC reestablishment in operation 403. In some examples, the NCR may select the same cell that was previously connected to the NCR prior to the RLF. For example, in the cell selection mechanism, the NCR does not select a cell different from the previously connected cell. This is advantageous when the NCR is preconfigured with information about which donor gNB it should connect to, such that the NCR may not be permitted to attempt to connect to any cell. For example, in some cases, the donor gNB should have only a single NCR, e.g., due to the bandwidth usage of its connected NCR. An example of such a technique is shown in FIG. 4A.

[0086] FIG. 4B shows an RLF process according to an embodiment of the present disclosure, in which cell selection is performed for a fallback gNB.

[0087] Referring to FIG. 4B, in operations 404, 405, and 406, the NCR may be preconfigured with multiple potential fallback donor gNBs from which a cell can be selected. This is advantageous when the donor gNB can be either a macro cell or a small cell. An example of such a technique is shown in FIG. 4B. In some examples, the NCR may be preconfigured with multiple potential fallback donor gNBs, and when one or more criteria are met, the NCR may select a cell from these candidate gNBs. For example, if the frequency of occurrence of an RLF when connecting (and reconnecting) to a given cell is greater than a threshold, the NCR may select a (different) cell from a set of preconfigured cells.

[0088] In some examples, the candidate cells may be configured among multiple NCRs via a broadcast message, or may be configured in one or more specific NCRs via one or more NCR-specific messages (e.g., via dedicated RRC signaling). In some examples, the candidate cells may be preconfigured via OAM, or may be configured during the initial NCR connection and establishment.

[0089] In one example, the above technique can be implemented by configuring the NCR with one or more NCR-specific cell (re)-selection parameters to be used in the case of RLF or reconstruction. This can be achieved, for example, by sending a dedicated SIB2 (system information block containing one or more cell (re)-selection parameters) via RRC, where the SIB2 (only) relates to the parameters to be used for NCR when performing RLF and reconstruction.

[0090] Example 1

[0091] In the following example of the above technique, the NCR-MT reselects the same donor gNB and does not perform cell selection.

[0092] ---------------3GPP TS 38.331 V17.2.0---------------

[0093] 5.3.7 RRC connection reestablishment

[0094] 5.3.7.1 General ...

[0096] When initiating this procedure, the UE shall:

[0097] 1> Stop timer T310 (if running);

[0098] 1> Stop timer T312 (if running);

[0099] 1> Stop timer T304 (if running);

[0100] 1> Start timer T311;

[0101] 1> Stop timer T316 (if running); ...

[0103] 1> If Sl-L2RelayUE-Config is configured, release Sl-L2RelayUE-Config;

[0104] 1> If Sl-L2RemoteUE-Config is configured, release Sl-L2RemoteUE-Config;

[0105] 1> If an SRAP entity is configured, release the SRAP entity;

[0106] 1> If the UE acts as an L2 u2n remote UE:

[0107] 2> If the PC5-RRC connection with the U2N relay UE is determined to be released:

[0108] 3> Indicate to the upper layer to trigger the release of the PC5 unicast link;

[0109] 3> Perform cell selection according to the cell selection procedure specified in TS 38.304

[20] , or perform cell selection according to the relay selection specified in Clause 5.8.15.3, or both;

[0110] 2> Otherwise (i.e., maintain the PC5 RRC connection):

[0111] 3> Consider the connected L2 U2N relay UE as appropriate and perform actions as specified in Clause 5.3.7.3a;

[0112] Note 1: Whether to release or maintain the current PC5 unicast link depends on the remote UE implementation.

[0113] Otherwise:

[0114] 2 If the UE acts as an NCR-MT:

[0115] 3> Consider that the same cell has been selected and follow the procedure specified in 5.3.7.3

[0116] 2> Otherwise:

[0117] 3> Perform cell selection according to the cell selection procedure specified in TS 38.304

[20] .

[0118] ---------------3GPP TS 38.331 V17.2.0---------------

[0119] Example 2

[0120] In the following example of the above technology, the network configures NCR-specific cell reselection parameters via the dedicated delivery of SIB2.

[0121] ---------------3GPP TS 38.331 V17.2.0---------------

[0122] -RRCReconfiguration

[0123] The RRCReconfiguration message is a command to modify the RRC connection. It can carry information for measurement configuration, mobility control, radio resource configuration (including RBs, MAC primary configuration, and physical channel configuration), and AS security configuration.

[0124] Signaling radio bearer: SRB1 or SRB3

[0125] RLC-SAP: AM

[0126] Logical channel: DCCH

[0127] Direction: Network to UE

[0128] RRCReconfiguration message

[0129] --ASN1START

[0130] --TAG-RRCRECONFIGURATION-START

[0131] RRCReconfiguration ::= SEQUENCE {

[0132] rrc-TransactionIdentifier RRC-TransactionIdentifier,

[0133] criticalExtensions CHOICE {

[0134] rrcReconfiguration RRCReconfiguration-IEs,

[0135] criticalExtensionsFuture SEQUENCE {}

[0136] }

[0137] }

[0138] …

[0139] RRCReconfiguration-v1530-IEs ::= SEQUENCE {

[0140] masterCellGroup OCTET STRING(CONTAINING CellGroupConfig)

[0141] OPTIONAL, --Need M

[0142] fullConfig ENUMERATED {true} OPTIONAL, --Cond FullConfig

[0143] dedicatedNAS-MessageList SEQUENCE(SIZE(1..maxDRB)) OF

[0144] DedicatedNAS-Message

[0145] OPTIONAL,--Cond nonHO

[0146] masterKeyUpdate MasterKeyUpdate OPTIONAL,--Cond

[0147] MasterKeyChange

[0148] dedicatedSIB1-Delivery OCTET STRING(CONTAINING SIB1)

[0149] OPTIONAL,--Need N

[0150] dedicatedSystemInformationDelivery OCTET STRING

[0151] (CONTAINING SystemInformation)OPTIONAL,--Need N

[0152] otherConfig OtherConfig OPTIONAL,--Need M

[0153] nonCriticalExtension RRCReconfiguration-v1540-IEs OPTIONAL

[0154] }

[0155] --TAG-RRCRECONFIGURATION-STOP

[0156] --ASN1STOP

[0157]

[0158] ---------------3GPP TS 38.331V17.2.0---------------

[0159] 2. NCR indicates a failure to the UE

[0160] In some examples, the NCR may send an indication of detecting an RLF on the NCR-MT to gNB link to the connected UE, for example, via specific L1 / L2 signaling.

[0161] In some examples, the indication can be in a form such that from the perspective of the UE it appears to come from the donor gNB. For example, the indication can be in the form of existing gNB signaling, such as an indication for the UE to search for an alternative cell (e.g., an RRC release message). Then, the UE can take any appropriate action based on the RLF indication received from the gNB. This technique maintains NCR transparency such that the UE is unaware that it is connected to the network via NCR.

[0162] Figure 5 Illustrated is an example in accordance with an embodiment of the present disclosure of sending an NCR indication to a UE and, once the NCR has been re-established to a new donor gNB, sending an NCR resume indication to the UE.

[0163] Referring Figure 5 , when receiving an RLF indication in operation 501 from the NCR (or from the donor gNB where the RLF indication pertains to the NCR-to-gNB link), the UE may not actually treat it as an RLF indication with the donor gNB regarding what action to take in response, but instead may take an alternative action in operation 502. For example, as Figure 5 shown, when receiving an NCR failure indication from the NCR in operation 503, the UE may wait in operation 504 for the completion of the RRC re-establishment procedure between the NCR and the donor gNB and then perform an NCR resume procedure in operation 505. In some examples, when the NCR declares an RLF, the gNB may configure the NCR according to the techniques described above.

[0164] In some examples, an RLF detection indication (indicating that an RLF has been detected but not declared) and / or an RLF declaration indication can be sent to the UE.

[0165] In some examples, after the NCR has detected an RLF on the link between the NCR and the gNB, the NCR can send a message, such as an RRC release, to the UE associated with the NCR. The NCR can also provide an indication to the donor gNB, for example, during the re-establishment procedure. For example, this can be indicated in an NCR failure report.

[0166] In some examples, the RLF detection indication can be sent to the UE attached to the NCR. Once a new link is established between the NCR and the old donor gNB or the new donor gNB, an indication of RLF recovery can be sent to the UE. For example, if the NCR reconnects to the old gNB, the indication can be a random access of the PDCCH command to resynchronize all UEs. The random access of the PDCCH command can trigger the UE to perform random access, thereby regaining any lost synchronization. On the other hand, if the NCR reconnects to the new gNB, reconfiguration (handover) with a synchronization process can be performed to ensure that the UE is connected to the new donor gNB. Since it is the NCR that sends the reconfiguration (handover) with synchronization, this behavior can be configured by the donor gNB or other network elements.

[0167] 3. NCR RLF Indication and Reconstruction

[0168] Figure 6 Shows the transmission of the NCR indication in the RLF report according to an embodiment of the present disclosure.

[0169] Refer to Figure 6 , in some examples, if the NCR performs an RLF process in operation 601 and then connects to another donor gNB in operations 602 and 603, the new gNB can send an indication to the old donor gNB that the NCR has failed. For example, this can be achieved by sending an RLF report in the RLF indication for the NCR. In some examples, in operation 604, the NCR-MT can include a flag in the RLF report to indicate to the network that the "UE" is an NCR node. In other examples, the NCR-MT can be recognized as an NCR without this flag, for example, based on its C-RNTI or other radio / CN identifier. In some examples, in operation 605, the new donor gNB can include the NCR indication in the RLF indication itself. Figure 6 Shows an example of this technique.

[0170] Figure 7 Shows the transmission of the NCR failure indication to the core network or OAM according to an embodiment of the present disclosure.

[0171] Refer to Figure 7 , in operations 701 and 702, if the NCR cannot find a suitable NCR-capable donor gNB when performing a reconstruction process in operation 703, the NCR may be configured to connect to a gNB that does not have NCR capabilities. Thereafter, the NCR (acting as a UE for the gNB) can signal a failure in operation 704 to, for example, the core network or OAM. This allows the core network or OAM to reconfigure the NCR or allows reporting to the operator that there is a problem with the NCR setup, configuration, or deployment.Figure 7 An example of such a technique is shown.

[0172] In some examples, the above method of including a flag in the RLF report to indicate the NCR identity can be used. The report can then be sent to the previous gNB, which can then correctly interpret the sent flag.

[0173] 4. NCR RLF Report

[0174] Figure 8 The transmission of an NCR-specific RLF report according to an embodiment of the present disclosure is shown.

[0175] Referring to Figure 8 , in operations 801, 802, 803, and 804, the NCR report can provide NCR-specific fault information to the donor gNB. An example of such a technique is shown in Figure 8 .

[0176] The NCR report can include any suitable information, such as one or more of the following:

[0177] Whether the UE is in the NCR Fwd on / off mode.

[0178] The buffer data occupancy rate at NCR-Fwd, the amount of transmitted packets whose reception status is not acknowledged and / or is waiting for retransmission, or any other suitable indicator of data going to / from the UE that has not been successfully delivered.

[0179] Load indicators, such as how much NCR bandwidth is being used and / or how many UEs are attached to the NCR and / or channel condition / link state updates on the access link.

[0180] Any NCR-specific configuration configured for the NCR, such as the configuration of NCR-Fwd, such as whether NCR-Fwd is ON / OFF, the beam used, or any other NCR-Fwd configuration or status.

[0181] How many UEs are connected via the NCR.

[0182] 5. NCR Reconstruction Procedure

[0183] In some examples, when the NCR node performs an RLF or reconstruction failure, the NCR may not indicate to the upper layer that the release reason is "RRC connection failure". In this case, the NCR node will not be configured to perform a tracking area update. This can be important because the NCR node may not be configured to perform any tracking area updates, for example because it may be a fixed node, and / or the network may not be configured to handle tracking area updates from the NCR.

[0184] In some examples, if the NCR cannot find any suitable donor gNB with NCR support, the NCR can perform a tracking area update as a normal UE and can transparently indicate to, for example, the core network or OAM for the gNB.

[0185] 6. NCR Return Procedure

[0186] In some cases, if RLF occurs between the NCR and the first gNB, and then the NCR performs a reconstruction with the second gNB, problems may occur if the second gNB accepts and continues the connection with the NCR. For example, if the operator has configured the first gNB to operate the NCR (e.g., based on using OAM or manual configuration), it may be more desirable to provide a mechanism to regain the NCR connection with the first gNB or avoid the NCR connection with the second gNB.

[0187] In some examples, if RLF occurs, the first gNB can indicate that it requires the NCR to reconnect to the first gNB. For example, this can be achieved by the first gNB indicating to the second gNB that the NCR needs to be switched back to the first gNB.

[0188] In some examples, a suitable indication to the second gNB can be sent in any suitable message (e.g., a separate (e.g., newly defined) message) or any suitable pre - existing message (e.g., RETRIEVE UE CONTEXT FAILURE / RETRIEVE UE CONTEXT RESPONSE). In some examples, the indication can be provided in the form of a flag, e.g., returnNCR - Request.

[0189] In some examples, the return of the NCR can be switched by a synchronized RRC re - configuration (i.e., connection mode switch) or achieved by an RRC release with redirection.

[0190] The indication that the NCR of the first gNB has connected to the second gNB can be done by any suitable technique, such as any of the techniques disclosed above (e.g., item 3 above).

[0191] Examples of such techniques are in Figure 9 shown.

[0192] Figure 9 The NCR return procedure according to an embodiment of the present disclosure is shown.

[0193] Figure 10It is a block diagram of a network entity according to an embodiment of the present disclosure. Those skilled in the art will understand that a network entity can be implemented, for example, as a network element on dedicated hardware, a software instance running on dedicated hardware, and / or as a virtualized function instantiated on a suitable platform (e.g., on a cloud infrastructure).

[0194] Referring to Figure 9 and 10 in Figure 9 operations 901, 902, 903, 904, 905, and 906 of Figure 10 and the elements of

[0195] The techniques described herein can be implemented using any suitably configured device and / or system. Such a device and / or system can be configured to perform a method according to any aspect, embodiment, example, or claim disclosed herein. Such a device can include one or more elements, such as one or more of a receiver, a transmitter, a transceiver, a processor, a controller, a module, a unit, etc., each element being configured to perform one or more corresponding processes, operations, and / or method steps for implementing the techniques described herein. For example, the operation / function of X can be performed by a module (or X module) configured to perform X. One or more elements can be implemented in the form of hardware, software, or any combination of hardware and software.

[0196] It should be understood that the examples of the present disclosure can be implemented in the form of hardware, software, or any combination of hardware and software. Any such software can be stored in the form of volatile or non-volatile memory, for example, a storage device such as ROM, whether erasable or rewritable, or in the form of a memory, such as RAM, a memory chip, a device, or an integrated circuit, or stored on an optically or magnetically readable medium, such as a CD, a DVD, a disk, or a magnetic tape, etc.

[0197] It should be understood that the storage device and the storage medium are examples of machine-readable memories, which are adapted to store one or more programs including instructions that, when executed, implement certain examples of the present disclosure. Accordingly, certain examples provide a program that includes code for implementing a method, apparatus, or system according to any example, embodiment, aspect, and / or claim disclosed herein, and / or a machine-readable memory storing such a program. Further, such a program can be electronically transmitted via any medium, such as a communication signal transmitted via a wired or wireless connection.

[0198] Certain examples of the present disclosure provide a method for a Network Control Repeater (NCR), the method comprising: determining that a connection between the NCR and a first Radio Access Network (RAN) node has been terminated (e.g., due to RLF or handover); selecting a RAN node to perform an RRC connection procedure with the NCR; and performing a connection procedure with the selected RAN node.

[0199] In certain examples, selecting the RAN node may include selecting a first RAN node based on the configuration of the NCR.

[0200] In certain examples, selecting the RAN node may include selecting a RAN node different from the first RAN node.

[0201] In certain examples, if one or more specific criteria are met, a RAN node other than the first RAN node may be selected.

[0202] In certain examples, one or more criteria may include that the termination of the connection between the NCR and the first RAN node has occurred more than a certain threshold number of times within a certain time window.

[0203] In certain instances, the method may further include obtaining a list of RAN nodes, and wherein selecting the RAN node includes selecting a RAN node from the list of RAN nodes.

[0204] In certain examples, it is possible to: obtain a list of RAN nodes according to a configuration (e.g., via OAM / RRC / NAS signaling), according to a pre-configuration (e.g., via OAM), via SIB2 in an RRC message, and via one or more of broadcast signals.

[0205] In certain examples, the method may further include sending an indication to one or more UEs connected to the NCR that the connection between the NCR and the first RAN node has been terminated.

[0206] In certain examples, the indication may be sent in a message of a type (e.g., an RRC release message) sent by the first RAN node to the UE to indicate that the connection between the first RAN node and the UE has been terminated.

[0207] In some examples, the indication may indicate that the termination of the connection has been detected but not declared.

[0208] In some examples, the method may further include: when a connection between the NCR and the selected RAN node is established, sending an indication that the connection has been established to one or more UEs.

[0209] In some examples, the method may further include sending information related to the terminated connection (e.g., RLF report) to the selected RAN node.

[0210] In some examples, the method may further include the selected RAN node sending information related to the terminated connection (e.g., RLF report) to the first RAN node.

[0211] In some examples, the information sent by the selected RAN node may include an indication that the terminated connection is a connection to the NCR.

[0212] In some examples, the information related to the terminated connection may include information indicating one or more of the following: the number of UEs connected via the NCR, whether the NCR is in NCR Fwd on / off mode, the buffer data occupancy of the NCR, the amount of data unsuccessfully delivered to / from the UEs, a load indicator related to the NCR; and one or more NCR configurations configuring the NCR.

[0213] In some examples, when no RAN node capable of supporting the NCR is available, the selected RAN node may be a RAN node that cannot support the NCR, and the method may further include sending a message indicating that the connection has been terminated to a core network entity.

[0214] In some examples, when a connection cannot be established between the NCR and the RAN node, the NCR may not perform one or both of a tracking area update and a RAN-based notification area update.

[0215] In some examples, the method may further include: when no RAN node capable of supporting the NCR is available, performing a tracking area update as a UE.

[0216] Certain examples of the present disclosure provide an apparatus (e.g., a network control repeater) configured to perform a method according to any aspect, example, claim, or embodiment disclosed herein.

[0217] Certain examples of the present disclosure provide a network (or wireless communication system) including an apparatus according to any aspect, example, claim, or embodiment disclosed herein.

[0218] Certain examples of the present disclosure provide a computer program including instructions that, when the program is executed by a computer or a processor, cause the computer or the processor to perform a method according to any aspect, example, claim, or embodiment disclosed herein.

[0219] Certain examples of the present disclosure provide a computer or processor-readable data carrier having stored thereon a computer program according to any aspect, example, claim, or embodiment disclosed herein.

[0220] Although the present disclosure has been shown and described with reference to various embodiments thereof, those skilled in the art will understand that various changes may be made therein in form and detail without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

[0221] According to an aspect of the present disclosure, a method performed by a network control repeater (NCR) in a wireless communication system is provided. The method includes determining whether a radio link failure (RLF) occurs between the NCR and a first base station. The method includes, in the case where an RLF occurs between the NCR and the first base station, performing cell selection for a radio resource control (RRC) connection procedure. The method includes performing an RRC connection procedure with the selected base station based on a result of performing the cell selection procedure.

[0222] According to an embodiment of the present disclosure, performing cell selection includes selecting a first base station based on a configuration of the NCR.

[0223] According to an embodiment of the present disclosure, the method further includes obtaining a list of base stations. Performing cell selection includes selecting a second base station based on the list of base stations.

[0224] According to an embodiment of the present disclosure, the list of base stations includes at least one of a candidate base station or a prohibited base station. A candidate base station is allowed to connect to the NCR, and a prohibited base station is not allowed to connect to the NCR.

[0225] According to an embodiment of the present disclosure, the list of base stations is obtained from operation, administration, and maintenance (OAM).

[0226] According to an embodiment of the present disclosure, the method further includes, in the case where an RLF occurs between the NCR and the first base station, sending an indication that an RLF has occurred between the NCR and the first base station to a UE connected to the NCR.

[0227] According to an embodiment of the present disclosure, the method further includes: in the case where an RRC connection between the NCR and the selected base station is established, sending an indication indicating the recovery of the RLF to a UE connected to the NCR.

[0228] According to an embodiment of the present disclosure, the method further includes sending information related to the RLF to the selected base station.

[0229] According to one aspect of the present disclosure, a network control repeater (NCR) in a wireless communication system is provided. The NCR includes a transmitter, a receiver, and at least one processor coupled to the transmitter and the receiver. The at least one processor is configured to determine whether a radio link failure (RLF) occurs between the NCR and a first base station. The at least one processor is configured to perform cell selection for a radio resource control (RRC) connection procedure in the case where the RLF between the NCR and the first base station occurs. The at least one processor is configured to perform an RRC connection procedure with a selected base station based on a result of performing the cell selection procedure.

Claims

1. A method performed by a network control repeater (NCR) in a wireless communication system, the method comprising: Determining whether a radio link failure (RLF) has occurred between the NCR and a first base station; Performing cell selection for a radio resource control (RRC) connection procedure in case the RLF has occurred between the NCR and the first base station; And Performing an RRC connection procedure with the selected base station based on the result of performing the cell selection procedure.

2. The method according to claim 1, wherein, Performing cell selection includes: Selecting the first base station based on the configuration of the NCR.

3. The method according to claim 1, further comprising: Obtaining a list of base stations; And Wherein, performing cell selection includes: Selecting a second base station based on the list of base stations.

4. The method according to claim 3, wherein, The list of base stations includes at least one of candidate base stations or prohibited base stations, Wherein, the candidate base stations are allowed to be connected to the NCR, and Wherein, the prohibited base stations are not allowed to be connected to the NCR.

5. The method according to claim 1, further comprising: Sending an indication that the RLF has occurred between the NCR and the first base station to a user equipment (UE) connected to the NCR in case the RLF has occurred between the NCR and the first base station.

6. The method according to claim 1, further comprising: Sending an indication indicating RLF recovery to a UE connected to the NCR in case an RRC connection between the NCR and the selected base station is established.

7. The method according to claim 1, further comprising: Sending an NCR report related to the RLF to the selected base station.

8. The method according to claim 7, wherein, The NCR report includes information related to the NCR forwarding mode of a UE connected to the NCR.

9. A network control repeater (NCR) in a wireless communication system, the NCR comprising: A transmitter (1003); A receiver (1005); And At least one processor (1001) coupled to the transmitter and the receiver and configured to: Determine whether a radio link failure (RLF) has occurred between the NCR and a first base station; Perform cell selection for a radio resource control (RRC) connection procedure in case the RLF has occurred between the NCR and the first base station; And Perform an RRC connection procedure with the selected base station based on the result of performing the cell selection procedure.

10. The method according to claim 9, wherein The at least one processor is further configured to: Select the first base station based on the configuration of the NCR for the RRC connection procedure.

11. The method according to claim 9, wherein The at least one processor is further configured to: Obtain a list of base stations; and Select a second base station based on the list of base stations for the RRC connection procedure.

12. The method according to claim 9, wherein The at least one processor is further configured to: Send an indication that the RLF has occurred between the NCR and the first base station to a user equipment (UE) connected to the NCR in case the RLF has occurred between the NCR and the first base station.

13. The method according to claim 9, wherein The at least one processor is further configured to: Send an indication indicating RLF recovery to a UE connected to the NCR in case an RRC connection between the NCR and the selected base station is established.

14. The method according to claim 9, wherein, The at least one processor is further configured to: Send information related to the RLF to a selected base station.

15. The method according to claim 14, wherein, The NCR report includes information related to the NCR forwarding mode of the UE connected to the NCR.

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