Patent Description:
Abbreviations used in this disclosure include:.

Various efforts have been made to improve different aspects of wireless communication for cellular wireless communication systems, such as <NUM> NR by improving data rate, latency, reliability, and mobility. The <NUM> NR system is designed to provide flexibility and configurability to optimize the network services and types, accommodating various use cases such as enhanced Mobile Broadband (eMBB), massive Machine-Type Communication (mMTC), and Ultra-Reliable and Low-Latency Communication (URLLC). However, as the demand for radio access continues to increase, there exists a need for further improvements in the art.

<CIT> describes that a radio network node associated with a source cell provides sidelink configuration information to a wireless device to be handed over to a target cell. The information indicates the sidelink synchronization and resource configurations associated with the target cell, and the wireless device performs sidelink communications based on the sidelink synchronization and resource configurations of the target cell. Receiving the sidelink resource and timing information associated with the target cell enables the wireless device to perform sidelink communications using the target-cell resources and timing, even while still being served in a cellular sense from the source cell. The wireless device may begin or resume sidelink communications using the sidelink timing and resources associated with the target cell, irrespective of whether cellular handover of the wireless device from the source cell to the target cell has completed.

<NPL>, discusses the failure cases including RLF and configuration failure for NR sidelink unicast, proposing inter alia that a RRC_CONNECTED UE should inform the network of the sidelink capability of the peer UE in a unicast link, upon receiving it from it peer UE via PC5 RRC.

<CIT>, as state of the art under Art. <NUM>(<NUM>) EPC, hods and apparatuses for path switch in a wireless communication system. According to some embodiments of the disclosure, a method may include: establishing, at a first user equipment (UE), a radio resource control (RRC) connection with a base station (BS) via a second UE, wherein a PC5 RRC connection between the first UE and the second UE has been established and an RRC connection between the second UE and the BS has been established; receiving an RRC reconfiguration message including a path switching indication from the BS, wherein the path switching indication indicates a switch to a target cell of the BS using a Uu interface; in response to the path switch indication, performing a random access (RA) with the BS; and in response to accessing a target cell, transmitting an RRC reconfiguration complete message to the BS. Furthermore, the second UE may receive an indication from the BS to release the first UE. The second UE may forward the buffered data from the first UE to the BS after receiving the release indication.

The present disclosure is related to a method performed by a user equipment (UE) for sidelink failure management and a UE for sidelink failure management, as defined in the independent claims, respectively.

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying drawings. Various features are not drawn to scale. Dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.

The following description contains specific information related to implementations of the present disclosure. The drawings and their accompanying detailed description are merely directed to implementations. However, the present disclosure is not limited to these implementations. Other variations and implementations of the present disclosure will be obvious to those skilled in the art.

For the purpose of consistency and ease of understanding, like features may be identified (although, in some examples, not illustrated) by the same numerals in the drawings. However, the features in different implementations may be differed in other respects and shall not be narrowly confined to what is illustrated in the drawings.

The phrases "in one implementation," or "in some implementations," may each refer to one or more of the same or different implementations. The term "coupled" is defined as connected whether directly or indirectly through intervening components and is not necessarily limited to physical connections. The term "comprising" means "including, but not necessarily limited to" and specifically indicates open-ended inclusion or membership in the so-described combination, group, series or equivalent. The expression "at least one of A, B and C" or "at least one of the following: A, B and C" means "only A, or only B, or only C, or any combination of A, B and C.

The terms "system" and "network" may be used interchangeably. The term "and/or" is only an association relationship for describing associated objects and represents that three relationships may exist such that A and/or B may indicate that A exists alone, A and B exist at the same time, or B exists alone. The character "/" generally represents that the associated objects are in an "or" relationship.

For the purposes of explanation and non-limitation, specific details such as functional entities, techniques, protocols, and standards are set forth for providing an understanding of the disclosed technology. In other examples, detailed description of well-known methods, technologies, systems, and architectures are omitted so as not to obscure the description with unnecessary details.

Persons skilled in the art will immediately recognize that any network function(s) or algorithm(s) disclosed may be implemented by hardware, software or a combination of software and hardware. Disclosed functions may correspond to modules which may be software, hardware, firmware, or any combination thereof.

A software implementation may include computer executable instructions stored on a computer readable medium such as memory or other type of storage devices. One or more microprocessors or general-purpose computers with communication processing capability may be programmed with corresponding executable instructions and perform the disclosed network function(s) or algorithm(s).

The microprocessors or general-purpose computers may include Applications Specific Integrated Circuitry (ASIC), programmable logic arrays, and/or using one or more Digital Signal Processor (DSPs). Although some of the disclosed implementations are oriented to software installed and executing on computer hardware, alternative implementations implemented as firmware or as hardware or combination of hardware and software are well within the scope of the present disclosure. The computer readable medium includes but is not limited to Random Access Memory (RAM), Read Only Memory (ROM), Erasable Programmable Read-Only Memory (EPROM), Electrically Erasable Programmable Read-Only Memory (EEPROM), flash memory, Compact Disc Read-Only Memory (CD-ROM), magnetic cassettes, magnetic tape, magnetic disk storage, or any other equivalent medium capable of storing computer-readable instructions.

A radio communication network architecture such as a Long Term Evolution (LTE) system, an LTE-Advanced (LTE-A) system, an LTE-Advanced Pro system, or a <NUM> NR Radio Access Network (RAN) typically includes at least one BS, at least one UE, and one or more optional network elements that provide connection within a network. The UE communicates with the network such as a Core Network (CN), an Evolved Packet Core (EPC) network, an Evolved Universal Terrestrial RAN (E-UTRA), a <NUM> Core (5GC), or an internet via a RAN established by one or more BSs.

A UE may include but is not limited to a mobile station, a mobile terminal or device, or a user communication radio terminal. The UE may be portable radio equipment that includes but is not limited to a mobile phone, a tablet, a wearable device, a sensor, a vehicle, or a Personal Digital Assistant (PDA) with wireless communication capability. The UE is configured to receive and transmit signals over an air interface to one or more cells in a RAN.

A BS may be configured to provide communication services according to at least a Radio Access Technology (RAT) such as Worldwide Interoperability for Microwave Access (WiMAX), Global System for Mobile communications (GSM) that is often referred to as <NUM>, GSM Enhanced Data rates for GSM Evolution (EDGE) RAN (GERAN), General Packet Radio Service (GPRS), Universal Mobile Telecommunication System (UMTS) that is often referred to as <NUM> based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), LTE, LTE-A, evolved LTE (eLTE) that is LTE connected to 5GC, NR (often referred to as <NUM>), and/or LTE-A Pro. However, the present disclosure is not limited to these protocols.

A BS may include but is not limited to a node B (NB) in the UMTS, an evolved node B (eNB) in LTE or LTE-A, a radio network controller (RNC) in UMTS, a BS controller (BSC) in the GSM/GERAN, a ng-eNB in an E-UTRA BS in connection with 5GC, a next generation Node B (gNB) in the <NUM>-RAN, or any other apparatus capable of controlling radio communication and managing radio resources within a cell. The BS may serve one or more UEs via one or more radio interface.

Each cell (often referred to as a serving cell) provides services to serve one or more UEs within its radio coverage such that each cell schedules the downlink (DL) and optionally uplink (UL) resources to at least one UE within its radio coverage for DL and optionally UL packet transmissions. The BS can communicate with one or more UEs in the radio communication system via the plurality of cells.

A cell may allocate sidelink (SL) resources for supporting Proximity Service (ProSe) (e.g., (ProSe) direct communication services and (ProSe) direct discovery services) or V2X services (e.g., E-UTRA V2X sidelink communication services) or sidelink service (e.g., NR sidelink communication services). Each cell may have overlapped coverage areas with other cells.

As discussed previously, the frame structure for NR supports flexible configurations for accommodating various next generation (e.g., <NUM>) communication requirements such as Enhanced Mobile Broadband (eMBB), Massive Machine Type Communication (mMTC), and Ultra-Reliable and Low-Latency Communication (URLLC), while fulfilling high reliability, high data rate and low latency requirements. The Orthogonal Frequency-Division Multiplexing (OFDM) technology in the 3rd Generation Partnership Project (3GPP) may serve as a baseline for an NR waveform. The scalable OFDM numerology such as adaptive sub-carrier spacing, channel bandwidth, and Cyclic Prefix (CP) may also be used.

At least DL transmission data, a guard period, and UL transmission data should be included in a transmission time interval (TTI) of a single NR frame. The respective portions of the DL transmission data, the guard period, and the UL transmission data should also be configurable based on, for example, the network dynamics of NR. Sidelink resources may also be provided in an NR frame to support ProSe services, V2X services (e.g., E-UTRA V2X sidelink communication services) or sidelink services (e.g., NR sidelink communication services). In contrast, sidelink resources may also be provided in an E-UTRA frame to support ProSe services, V2X services (e.g., E-UTRA V2X sidelink communication services) or sidelink services (e.g., NR sidelink communication services).

V2X (Vehicle-to-Everything) services are provided to support the information exchange between vehicles. In LTE protocols, V2X services may be supported in the air interface by Uu interface and PC5 interface. The PC5 interface covers the designs in Layer <NUM> and Layer <NUM>. The airlink interface on the PC5 interface is also called sidelink in LTE protocols. The LTE network supports sidelink operations since Rel.

<FIG> illustrates a sidelink operation scenario <NUM> within a cell according to an implementation of the present disclosure. With sidelink (SL) operations, UEs <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> in the radio coverage <NUM> of BS <NUM> may exchange data and control signaling directly without the relaying of BS <NUM>. The BS <NUM> may be an eNB in an LTE network or a gNB in an NR network. For the convenience of description, all the the UEs in the present disclosure may be capable and authorized to access V2X services and the PC5 interface with neighbor UEs and RAN.

The V2X services may be further categorized based on different cast-types in sidelink, such as:.

Unicast: Only two UEs are in one sidelink group. Formulation of the sidelink group may be achieved in the NAS layer.

Multi-cast (Groupcast): More than two UEs are grouped in one sidelink group to exchange sidelink packets with all other members in the sidelink group.

In some implementations, sidelink groups may be formulated in the NAS layer (e.g., V2X application layer or PC5-S protocols) signaling, AS layer signaling in PC5 interface, (e.g., Sidelink RRC Layer signaling, PC5-RRC signaling), or AS layer signaling in Uu interface (e.g., RRC signaling, RRCReconfiguration message).

Broadcast: There may be no limitation to the sidelink group. A UE may be able to broadcast message(s) and its neighbor UE(s) within a sidelink communication range may receive and decode the broadcast message(s) successfully. In some implementations, the sidelink communication range may depend on transmission (Tx) power, hardware sensitivity, etc..

To enable sidelink operation under the coverage of RANs (e.g., E-UTRAN or NR-RAN), (LTE/NR) cells may provide SL (radio) configurations and SL (radio) resource allocation to UEs. UEs under the coverage of cellular networks may need to perform sidelink operations based on the (radio) configurations of serving RANs. To enable sidelink operation under the coverage of a RAN, the serving cell (or camped-on cells) may need to provide an SL (AS) configuration and SL resource allocation to UEs. To enable sidelink operation (e.g., E-UTRA V2X sidelink communication services or NR sidelink communication services), the UE may obtain sidelink (radio) configurations and/or sidelink (radio) resource allocation from a serving/camped cell(s) operating on one sidelink frequency carrier. In some additional implementations, the UE may obtain sidelink (radio) configurations and sidelink (radio) resource allocation from a non-serving cell in one sidelink frequency carrier. The sidelink frequency carriers are the frequency carriers which are defined/configured/enabled/allowed by network operators or service providers for UEs to implement sidelink data exchange with neighbor UEs directly.

In some implementations, the UE may obtain the locations of sidelink frequency carrier(s) in the frequency domain (e.g., Absolute Radio-Frequency Channel Number, ARFCN) based on sidelink pre-configuration (which may be pre-installed in USIM), broadcasting system information (e.g., SIB <NUM>, SIB <NUM> in NR protocols) from the serving/camped/non-serving cell, sidelink control signaling exchange between UEs (e.g., PC5-RRC signaling or Sidelink-Master Information Blocks), or UE specific dedicated control signaling from the serving cell.

Two basic approaches are provided for SL resource allocation in the LTE V2X services:.

The UE needs to be in the (LTE/NR) RRC_CONNECTED state to transmit data.

The UE requests SL resources from the eNB (by sending a sidelink buffer status report to the serving cell). The eNB schedules dedicated sidelink resource for the UE to transmit sidelink control information and sidelink data. To achieve this, the eNB may request the UE to report a sidelink buffer status report (SL-BSR) through the Uu interface. In addition, the UE may also trigger a Scheduling Request (SR) on an uplink physical resource (e.g., a PUCCH) or initiate a random access procedure while the UE wants to transmit an SL-BSR to the eNB, but a valid uplink resource is absent. The SR resource (or configurations) and the SR procedure may be common for both sidelink operations and uplink traffic.

UE autonomous resource selection may be applied to both UEs in the RRC connected state (e.g., through dedicated RRC signaling or system information broadcast) and UEs in the RRC inactive/idle state (e.g., through system information broadcast).

A resource pool is a set of (virtually continuous) resource blocks and the UE may determine which physical (radio) resource blocks the UE wants to access for SL packet transmission autonomously.

The UE on its own selects resources from the (sidelink) resource pools and performs transport format selection to transmit sidelink control information and data.

The UE may perform (partial) sensing for (re)selection of sidelink resources before SL packet delivery. Based on (partial) sensing results, the UE (re)selects some specific sidelink resources and reserves multiple sidelink resources. Up to <NUM> parallel (independent) resource reservation processes are allowed to be performed by the UE. The UE is also allowed to perform a single resource selection for its V2X sidelink transmission.

When the UE is out of coverage on the frequency used for V2X sidelink communication and if the eNB does not provide a V2X sidelink configuration for the frequency, the UE may use a set of transmission and reception resource pools preconfigured in the UE (e.g., sidelink pre-configuration, which may be pre-installed in the memory module of the UE). V2X sidelink communication resources may not be shared with other non-V2X data transmitted over the sidelink. In some implementations, the UE may obtain the pre-configuration through an installed USIM, stored memory, or through RAN which the UE has previously accessed. Moreover, the UE may implement a (LTE/NR) PC5 interface by synchronizing with a Global Navigation Satellite System (GNSS) and applying a pre-configuration. In this condition, the PC5 interface may be independent of the RAN and (LTE/NR) Uu interface.

<FIG> illustrates a V2X platooning scenario <NUM> according to an implementation of the present disclosure. In the platooning scenario, platoon X may include several vehicles (or UEs) <NUM>, <NUM>, <NUM> and <NUM>, where there may be (at least) one scheduler (e.g., vehicle <NUM>) in platoon X. In addition, vehicle <NUM> may be a UE that is not included in platoon X. In platoon X, the scheduler (e.g., vehicle <NUM>) may configure SL resources to members (e.g., vehicles <NUM>, <NUM> and <NUM>) in the same platoon X through the following approaches:.

Mode <NUM> approach: the scheduler may configure dynamic sidelink grants to members in the same platoon (e.g., dynamic sidelink grant through sidelink control information). In addition, the scheduler may also configure a semi-periodic sidelink grant (e.g., configured sidelink grant) to the UE through sidelink control signals (e.g., through a Physical Sidelink Broadcast Channel, or sidelink PC5-RRC signaling). To achieve Mode <NUM>-like approach, the scheduler may need UEs to provide feedback information through the (LTE/NR) PC5 interface.

Mode <NUM> approach: the scheduler may configure sidelink resource pools to members in the same platoon. The UEs may select sidelink grant by themselves automatically (e.g., sidelink grant selection with or without sensing). The platooning scenario may be applied when the vehicles of the platoon are in-coverage (i.e., all of the vehicles in the platoon are under the coverage of a cellular radio access network), out-of-coverage (i.e., all of the vehicles in the platoon are out of the coverage of a cellular radio access network), or partial in-coverage (i.e., some of the UEs in the platoon are in-coverage and the other UEs in the platoon are out-of-coverage of a cellular radio access network).

To support the scheduler, the members in the platoon, in the present disclosure, may need to support the following processes to report their own statuses to the scheduler through the PC5 interface:.

<FIG> illustrates PC5-RRC connections <NUM> between a pair of UEs according to an implementation of the present disclosure. A pair of UEs may construct multiple PC5-RRC connections, where each PC5-RRC connection may support different sets of V2X service(s) with different (Layer-<NUM>/Layer-<NUM>) UE IDs and different QoS requirements.

The concept of PC5-RRC connection may be different from RRC Connection in the Uu interface. In the NR PC5 interface, one SL-unicast group (e.g., UE#<NUM> and UE#<NUM> in <FIG>) may first need to build (at least) one PC5-S connection and each PC5-S connection may be associated with one PC5-RRC connection in the AS layer independently. In other words, the PC5-S connection and PC5-RRC connection may be a one-to-one mapping. Each PC5 RRC connection is a logical connection between a pair of source and destination (Layer-<NUM>) UE IDs. In the service level, one PC5-S connection (and so the associated PC5-RRC connection) may be built to serve one or more than one V2X service. For example, the PC5-S connection#<NUM> at the UE#<NUM> and UE#<NUM> are constructed to serve V2X service#<NUM>/#<NUM> and the PC5-S connection#<NUM> are constructed to serve V2X service #a/#b. However, there may be multiple active PC5-S connections/PC5-RRC connections in the paired UEs to support different sets of V2X services that have different QoS requirements. In some implementations, the UE may report the status of PC5-RRC connections to the serving cell (e.g., a PCell in a master cell group or a PSCell in a secondary cell group) and the serving RAN may also know the conditions of PC5-RRC connections in the UE side. In addition, the UE may also report the sidelink radio link failure event (to at least one PC5-RRC connection) to the serving RAN (e.g., for sidelink resource management such as a Mode <NUM> sidelink resource configuration approach). In one implementation, one UE may join multiple SL-unicast groups with different target UEs and, therefore, one UE may have PC5-RRC connections associated with different UEs.

In Release-<NUM>, for a UE performing (LTE/NR) sidelink operation, sidelink AS configuration (e.g., SL-ConfigDedicatedNR/SL-ConfigDedicatedEUTRA in NR protocols or sl-ConfigDedicatedForNR/sl-V2X-ConfigDedicated in E-UTRA protocols) may be configured by a serving cell based on the received dedicated control signaling (e.g., RRC(Connection)Reconfiguration message of LTE/NR RRC protocols). In addition, an NR cell may configure a sidelink AS configuration for an LTE/NR PC5 interface (e.g., sl-ConfigDedicatedNR / sl-ConfigDedicatedEUTRA for the AS configuration of an NR PC5 interface/LTE PC5 interface respectively) in the RRC(Connection)Reconfiguration message. Similarly, one E-UTRA cell may also configure a sidelink AS configuration for an LTE/NR PC5 interface through the RRC(Connection)Reconfiguration message (e.g., by transmitting sl-Conf gDedicatedForNR/sl-V2X-ConfigDedicated in E-UTRA protocols to the UE). To the UE, the sidelink AS configuration includes the AS layer configuration for an LTE PC5 interface and/or an NR PC5 interface. The sidelink AS configuration transmitted via RRC signaling may also be referred to as a sidelink RRC configuration in the present disclosure.

Table <NUM> lists an example RRC(Connection)Reconfiguration message including a sidelink AS configuration.

The UE may receive the sidelink AS configuration of (LTE/NR) PC5 interface through the RRC(Connection)Reconfiguration message. After receiving the (LTE/NR) sidelink AS configuration from the serving cell, the UE may configure the AS layers of (LTE/NR) PC5 interface accordingly.

In some of the implementations, the UE may obtain the sidelink AS configuration for a (LTE/NR) PC5 interface by receiving broadcast control signaling from the serving cell (or from a non-serving cell while the cell is operating on a sidelink component carrier in which the UE has interest to operate a sidelink data exchange). In some implementations, the UE may obtain the sidelink AS configuration through an SI on-demand procedure.

In comparison, in sidelink unicast service, the UE may obtain the sidelink AS configuration from a paired UE. <FIG> illustrates a procedure 400A for obtaining the sidelink AS configuration through PC5 RRC signaling according to an implementation of the present disclosure. {UE#<NUM><NUM>, UE#<NUM><NUM>} are formulated as a sidelink unicast group (e.g., by the V2X application layer). In addition, UE#<NUM><NUM> and UE#<NUM><NUM> may exchange PC5 RRC signaling. In action <NUM>, UE#<NUM><NUM> may provide a sidelink AS configuration to UE#<NUM><NUM> by transmitting an RRCReconfigurationSidelink message to the UE#<NUM><NUM>. Then, UE#<NUM><NUM> may configure its sidelink AS configuration (associated with UE#<NUM><NUM>) based on the received RRCReconfigurationSidelink message. UE#<NUM><NUM> may reply by transmitting an RRCReconfigurationCompleteSidelink message to the UE#<NUM><NUM> in action <NUM>.

A sidelink AS configuration failure event (or sidelink RRC configuration failure event) may happen when UE#<NUM><NUM> is unable to comply with (part of) the configuration included in the RRCReconfigurationSidelink message. <FIG> illustrates a procedure 400B for handling a sidelink AS configuration failure event according to an implementation of the present disclosure. In action <NUM>, UE#<NUM><NUM> may provide a sidelink AS configuration to UE#<NUM><NUM> by transmitting an RRCReconfigurationSidelink message to the UE#<NUM><NUM>. UE #<NUM><NUM> may perform at least one of the following actions when a sidelink AS configuration failure event occurs: continue using the stored sidelink AS configuration (associated with UE#<NUM><NUM>) used prior to the reception of the RRCReconfigurationSidelink message; and transmit an RRCReconfigurationFailureSidelink message to UE#<NUM><NUM> in action <NUM>.

The sidelink AS configuration may cover the following settings:.

The sl-AssistanceConfigEUTRA & sl-AssistanceConfigNR may be transmitted by a serving (NR/LTE) cell through the RRC(Connection)Reconfiguration message.

In some implementations, one sidelink AS configuration may be associated with one specific destination (Layer-<NUM>) UE ID in the AS layer of a (LTE/NR) PC5 interface. In some other implementations, one sidelink AS configuration may be associated with more than one specific destination ID in the AS layer. In some implementations, one sidelink AS configuration may be associated with all of the associated destination (UE) ID(s) at the UE side. For example, one common sidelink AS configuration may be transmitted through broadcast system information. Then, the UE may apply the common sidelink AS configuration to all of the associated destination ID(s).

In some implementations, the combination of sidelink AS configurations associated with one destination (UE) ID may depend on the case types (e.g., broadcast, groupcast, and uni-cast) associated with the destination ID. For example, one sidelink AS configuration may be associated with all associated destination ID(s) for a broadcast type. In some other conditions (e.g., for sidelink uni-cast type), each destination ID may be associated with one corresponding sidelink AS configuration.

The UE may derive the destination (Layer-<NUM>) ID through the input of upper layers. For example, when a UE is building the PC5 RRC connection with one target UE, the V2X layer of the UE side may generate a service-level destination (UE) ID associated with the target UE. Then, the service-level destination ID may be transmitted to the AS layer of the UE and the destination (Layer-<NUM>) ID may be generated in the AS layer to identify the target UE in the AS layer of the UE side.

The present disclosure is based on V2X services. However, the proposals and proposed implementations may also be applied to other services implemented on the (LTE/NR) sidelink services implemented on the (LTE/NR) PC5 interface and (LTE/NR) sidelink operation.

As illustrated in <FIG>, a sidelink AS configuration failure event may occur when UE#<NUM><NUM> receives the sidelink AS configuration through PC5 RRC signaling. In the NR PC5 interface, UE#<NUM><NUM> may release the PC5 RRC connection with UE#<NUM><NUM> if the sidelink AS configuration failure event occurs after receiving the RRCReconfigurationSidelink message from UE#<NUM><NUM> (or UE#<NUM><NUM> may just release the 'failed' sidelink radio bearers indicated in the RRCReconfigurationSidelink message).

Observation#<NUM>: However, , more UE behavior may be needed to address a sidelink RRC reconfiguration failure event between the Tx UE and Rx UE of the RRCReconfigurationFailureSidelink message.

Table <NUM> illustrates an example UE behavior upon a sidelink RRC reconfiguration failure event.

Observation#<NUM>: In addition, in the latest specification, the signaling content is still absent, with further signaling needed to resolve the reconfiguration failure event.

Table <NUM> illustrates an example RRCReconfigurationFailureSidelink message.

In the present disclosure, implementations that further enhance the sidelink AS configuration failure event and the signaling design in the PC5 interface are disclosed. In addition, a sidelink AS configuration failure event may also happen when the UE receives the sidelink AS configuration through dedicated control signaling (e.g., an RRC(connection)Reconfiguration message) through the Uu interface. This event may be considered as one sub-case of re-configuration failure in the associated Uu interface (e.g., LTE Uu interface and NR Uu interface). In addition, the UE may be instructed to perform at least one of the following actions when a reconfiguration failure event occurs in the Uu interface:.

Table <NUM> illustrates example UE behavior upon an RRC reconfiguration failure.

Observation#<NUM>: Different UE behavior may be applied to sidelink AS configuration failure event. The specific UE behavior to be applied may depend on whether the sidelink AS configuration comes from the serving cell (through the Uu interface) or the paired UE (through the PC5 interface via one or more PC5 RRC signalings).

Moreover, since an RRC connected UE (e.g., UE#<NUM><NUM> in <FIG>) may report 'sidelink RRC configuration failure event' (associated with UE#<NUM><NUM> in <FIG>) to the serving cell if the 'failed' sidelink AS configuration problem is generated by the PC5 interface, as illustrated in <FIG>, the same sidelink AS configuration failure report may also be applicable when the failed sidelink AS configuration is obtained through the Uu interface.

In some implementations, the noun 'sidelink AS configuration' may be equivalent to 'sidelink RRC configuration' (since the RRC layer manages all the AS layer sidelink configuration) or may be equivalent to 'sidelink radio configurations'. In this condition, both of the 'Sidelink AS Configuration Failure Report' and 'Sidelink RRC Configuration Failure Report' may be the same to the UE and serving RAN for the sidelink unicast/groupcast/broadcast services. However, in some other implementations, the sidelink RRC configuration may be limited by the PC5 RRC connection, which is supported only for the 'sidelink unicast service' in Rel-<NUM> specs. In this condition, the 'PC5 RRC configuration failure report' may be supported only in the sidelink unicast service. In comparison, the UE may transmit a 'Sidelink AS Configuration Failure Report' to the serving cell when the AS configuration failure event occurs to sidelink groupcast/broadcast services.

Observation#<NUM>: for a UE, the same Sidelink AS Configuration Failure Report caused by the failed sidelink AS configuration in the PC5 interface may also be applicable when the failed sidelink AS configuration is obtained through the (LTE/NR) Uu interface.

In addition, the conventional Reconfiguration Failure approach in the Uu interface may increase the vulnerability of the RRC connection.

Observation#<NUM>: One RRCReconfiguration message may contain sidelink AS configurations for as many as <NUM> destination IDs. A failed sidelink AS configuration to any of the destination IDs may cause the UE to initiate an RRC re-establishment procedure or to move to RRC idle state. Moreover, the RRC re-establishment procedure or RRC state transitions may also impact the sidelink packet exchange of other destination ID(s), whose associated sidelink AS configuration(s) are not changed/modified in the RRCReconfiguration message.

Therefore, to prevent the (unnecessary) impact from the PC5 interface to the Uu interface and the unnecessary impact to other destination ID(s), implementations are disclosed to enhance the Sidelink AS Configuration Failure Report when only part of the sidelink AS configuration fails at the UE side. Implementations of a partial failure design are disclosed to decrease the impact from the PC5 interface on the Uu interface. Then, management of the sidelink AS configuration may also be simplified.

Observation#<NUM>: Partial failure design may be applied to an (Uu) RRC Reconfiguration Failure event when the cause of failure is a sidelink RRC configuration failure event.

In addition, the Sidelink RRC Configuration Failure Report when the sidelink AS configuration is derived through a broadcast control message (e.g., system information) is also in the present disclosure.

Moreover, a full configuration approach similar to the Uu interface may also be implemented on the PC5 RRC connection. In one implementation, the UE handles new NR SL configurations using full configuration operations as in the Uu interface, in case the new configuration for SL cannot be performed by delta configuration (e.g., RRC state transition, change of SIB used for NR/E-UTRA SL and fullconfig present in dedicated signaling).

However, the details of a full configuration on sidelink is still absent. Therefore, how to implement a sidelink full configuration is also in the present disclosure.

Implementation#<NUM>: RRCReconfigurationFailureSidelink signaling design.

Table <NUM> summarizes implementations of the RRCReconfigurationFailureSidelink message, which is transmitted from the Rx UE to the Tx UE.

<FIG> illustrates signal flow 500A of sidelink full reconfiguration according to an implementation of the present disclosure. In some implementations, the Tx UE <NUM> may further indicate whether 'sidelink full configuration for the corresponding sidelink RRC Reconfiguration' is configured or not (e.g., one specific information element 'SL-fullconfig=true' is provided to the Rx UE <NUM> in the RRCReconfigurationSidelink message. ) If the sidelink reconfiguration failure event occurs, the Rx UE <NUM> may perform the sidelink full configuration procedure accordingly (while SL-fullconfig=true). The Tx UE <NUM> may also implement sidelink full configuration after receiving the RRCReconfigurationFailureSidelink message from the Rx UE <NUM>. Table <NUM> illustrates an example of UE behavior upon a sidelink RRC reconfiguration failure event.

<FIG> illustrates signal flow 500B of sidelink full reconfiguration according to another implementation of the present disclosure. In some implementations, when the sidelink reconfiguration failure event occurs, the Rx UE <NUM> may start the sidelink full configuration procedure by itself (the Tx UE <NUM> may not deliver the SL-fullconfig IE in the RRCReconfigurationSidelink message to the Rx UE <NUM>). In action <NUM>, the Rx UE <NUM> may provide the information element 'SL-fullconfig=true' in the RRCReconfigurationFailureSidelink message to the Tx UE <NUM>. After receiving the RRCReconfigurationFailureSidelink message, the Tx UE <NUM> may also implement the sidelink full configuration to the corresponding PC5 RRC connection. Table <NUM> illustrates an example UE behavior upon a sidelink RRC reconfiguration failure event.

In some implementations, the Rx UE <NUM> may implement sidelink full configuration implicitly if reconfiguration failure happens to the Rx UE <NUM> after receiving the RRCReconfigurationSidelink message. Then, after implementing sidelink full configuration, the Rx UE <NUM> may also reply with the RRCReconfigurationFailureSidelink message to the Tx UE <NUM>.

In some implementations, the Tx UE <NUM> may initiate sidelink full configuration implicitly after receiving the RRCReconfigurationFailureSidelink message (e.g., without further information about the failed sidelink configuration information or SL-fullconfig=true) from the Rx UE <NUM>.

In some implementations, one UE (e.g., the Rx UE <NUM>) may obtain the SL-fullconfig information element from one cell in an RAN through the relaying of another UE (e.g., the Tx UE <NUM>). So, the Tx UE <NUM> may receive the SL-fullconfig (e.g., associated with one or more than one (Layer-<NUM>) Destination ID which has PC5 RRC connection with the Tx UE <NUM>) from its serving cell through dedicated control signaling or broadcast system information.

The sidelink full configuration may include all or part of the following proposed UE implementations.

Table <NUM> illustrates an example method for sidelink full configuration.

In some implementations, the Tx UE <NUM> may also instruct the Rx UE <NUM> to implement the sidelink full configuration procedure directly (e.g., the RRCReconfigurationSidelink message contains another IE 'SL-fullconfig_direct=true' to trigger the Rx UE to implement the sidelink full configuration procedure directly, as illustrated in the <FIG>. In action <NUM>, the Tx UE <NUM> may transmit SL-fullconfigdirect or SL-fullconfig_direct via the RRCReconfigurationSidelink message. In some implementations, it is possible that no other sidelink RRC reconfiguration IE (which conveys sidelink (radio) configurations for the Rx UE <NUM>) is provided in the same signaling (e.g., the RRCReconfigurationSidelink message) to the Rx UE <NUM>. So, the Rx UE <NUM> may initiate the sidelink full configuration procedure directly after receiving the RRCReconfigurationSidelink message. Then, after the sidelink full configuration message procedure is finished successfully at the Rx UE <NUM>, the Rx UE <NUM> may also reply with the RRCReconfigurationCompleteSidelink message to the Tx UE <NUM>. In some other implementations, other sidelink RRC reconfiguration IE (which conveys sidelink RRC configurations for the Rx UE <NUM>) may be provided in the same signaling by the Tx UE <NUM> (e.g., RRCReconfigurationSidelink message in action <NUM>) to the Rx UE <NUM>. So, the Rx UE <NUM> may initiate the sidelink full configuration procedure directly after receiving the RRCReconfigurationSidelink message with 'SL-fullconfig_direct=true'. Then, after the sidelink full configuration message procedure is finished successfully at the Rx UE <NUM>, the Rx UE <NUM> may re-configure the sidelink AS layer configuration associated with the Tx UE <NUM> based on the sidleink radio configurations received in the same RRCReconfigurationSidelink message in action <NUM>. After re-configuring the sidelink radio configuration with Tx UE <NUM>, the Rx UE <NUM> may also reply the RRCReconfigurationCompleteSidelink message to the Tx UE <NUM>. Please note: during the sidelink full configuration, the Rx UE <NUM> may release or clear all current sidelink radio configurations associated with the Tx UE <NUM>. In some implementations, the Rx UE <NUM> may also release the sidelink radio bearers (SL-DRBs) associated with the Tx UE <NUM>. In some additional implementations, the UE may also apply the default MAC configuration for the sidelink specific MAC functions (or MAC entity) associated with the Tx UE <NUM>. For the sidelink specific MAC associated with the Tx UE <NUM>, in some implementations, the original sidelink specific MAC associated with the Tx UE <NUM> (before the Rx UE <NUM> receives the RRCReconfigurationSidelink message in action <NUM> from the Tx UE <NUM>) may be configured as part of one MAC entity, which may be shared with the sidelink specific MAC (functions) associated with other Layer-<NUM> destination IDs in (LTE/NR) PC5 interface and/or the (non-sidelink specific) MAC (functions) associated with the serving RAN in the (LTE/NR) Uu interface). However, in some other implementations, the sidelink specific MAC (functions) associated with the Tx UE <NUM> may be configured as one independent MAC entity at the Rx UE <NUM> side. In addition, for default MAC application, the original sidelink specific MAC associated with the Tx UE <NUM> may be reset firstly when the Rx UE <NUM> is implementing sidelink full configuration (based on the instruction from the Tx UE510). Please also note, the sidelink radio configuration may not be limited to the sidelink radio resource configuration (e.g., sidelink Tx/Rx resource pool configuration or exceptional resource pool configuration) but may also include other configurations about the (LTE/NR) PC5 interface, such as sidelink measurement configuration and/or sidelink CSI-RS configuration.

<FIG> illustrates signal flow 500C of sidelink full reconfiguration according to still another implementation of the present disclosure. In some implementations, the base station <NUM> (e.g., the E-UTRA eNB or NR gNB) may configure the UE <NUM> (which has a PC5 RRC connection(s) with one or more than one Rx UE(s)) to implement the sidelink full configuration procedure (e.g., by configuring SL-fullconfig=true). In some implementations, SL-fullconfig=true may be associated with all the (active) PC5 RRC connections of the corresponding UE <NUM> (so, the UE <NUM> may apply sidelink full configurations to all the associated Rx UEs). In some other implementations, SL-fullconfig=true may be associated with a subset of the (active) PC5 RRC connections. For example, the (Layer-<NUM>) Destination IDs of some Rx UEs may be configured by the base station along with the 'SL-fullconfig=true' IE in the RRCReconfiguration message. After receiving the RRCReconfiguration message, the UE <NUM> may implement the sidelink full configuration to the PC5 RRC connections associated with those indicated (Layer-<NUM>) Destination IDs. In contrast, the PC5 RRC Connections of other UEs (whose (Layer-<NUM>) Destinations IDs are not indicated in the RRCReconfiguration message) may not be impacted by the 'SL-fullconfig=true' IE. In some implementations, the SL-fullconfig IE may apply to all the destinations associated with the (Rx) UE, which may also include destinations associated with sidelink unicast/group-cast/broadcast services.

As illustrated in <FIG>, in some implementations, the subset of (active) PC5 RRC connections associated with the SL-fullconfig=true may already be signaled by the serving base station <NUM> via (at least) one previous RRCReconfiguration message(s) before the action <NUM> (e.g., the base station <NUM> has configured the sidelink radio configurations associated with the subset of (active) PC5 RRC connections in the (at least one) previous RRCReconfiguration message(s) before the action <NUM>). Then, in action <NUM>, the base station <NUM> may configure 'SL-fullconfig=true' in the RRCReconfiguration message directly without re-indicating the (Layer-<NUM>) Destination (UE) IDs of the subset of (active) PC5 RRC connections in the RRCReconfiguration message. After receiving 'SL-fullconfig=true' in action <NUM>, the UE <NUM> may implement sidelink full configuration for the subset (active) PC5 RRC connections associated with these (Layer-<NUM>) Destination (UE) IDs if the sidelink RRC configuration associated with the (Layer-<NUM>) Destination (UE) ID is configured by the serving base station <NUM> via the (at least one) previous RRCReconfiguration message(s). In contrast, after action <NUM>, the UE <NUM> may not implement sidelink full configuration for the (active) PC5 RRC connection associated with one (Layer-<NUM>) Destination ID if the sidelink RRC configuration associated with the same (Layer-<NUM>) Destination ID is not configured by the base station <NUM> via the (at least one) previous RRCReconfiguration message(s).

In some implementations, there may not be a SL-fullconfig IE in the RRCReconfiguration message. Instead, there may be a fullconfig IE configured in the control signaling dedicated to NR sidelink operation (e.g., in the sl-ConfigDedicatedNR message) such that the UE knows that the sidelink full configuration is to be initiated rather than the conventional full configuration procedure in the Uu interface.

In some implementations, the original fullconfig IE, which is originally defined the full configuration of the RRC connection in the Uu interface (such that the fullconfig IE is configured out of the sl-ConfigDedicatedNR IE), may be configured to have the functionalities of SL-fullconfig in the present disclosure. The UE may initiate the sidelink full configuration procedures on one (or more than one) active PC5 RRC connections and the active RRC connection (in the Uu interface) if fullconfig is configured to the UE via the RRCReconfiguration message.

The disclosed RRC signaling (and the disclosed information elements) may not be limited to the NR RRC signaling protocols (they may be realized in the LTE RRC protocols to implement sidelink full configuration on the LTE/NR PC5 interface).

In one implementation, the UE may also initiate the sidelink full configuration if the UE is re-configuring its own sidelink AS configuration based on the received sidelink configuration, which is received from the serving cell (e.g., through dedicated control signaling or broadcast system information, which may or may not be through the system information on-demand procedure). The serving cell may or may not deliver the SL-fullconfig to the in-coverage UEs through dedicated control signaling (e.g., RRC signaling) or system information (e.g., the system information specified for NR sidelink or V2X services).

All or part of the information elements in the present disclosure related to the Uu interface may be delivered through RRC signaling, such as an RRC Setup message, an RRC Reconfiguration message, an RRC Release message with/without a suspend configuration, an RRCReconfiguration message with a reconfigurationwithsync IE (e.g., for inter-RAT/intra-RAT handover procedure or special cell change) or an RRCReconfiguration message without a reconfigurationwithsync IE, or an RRC Resume message. In the uplink direction, (part of) the disclosed implementations may be transmitted through an RRC establishment request message, an RRC Re-establishment message, or an RRC Resume Request message. In addition, the disclosed implementations may not be limited to NR sidelink protocols. For example, the disclosed implementations may also be applicable to LTE (ProSe) sidelink operation or LTE V2X sidelink communication services.

Table <NUM> lists implementations of UE behaviors upon reconfiguration failure events. In Table <NUM>, the UE may initiate the conventional (RRC) Reconfiguration Failure event if the failed RRC configurations are provided for the (LTE/NR) Uu interface (e.g., case#<NUM>/#<NUM> in Table <NUM>).

In comparison, the UE may not initiate the conventional (RRC) Reconfiguration Failure event if the failed configurations are provided for the (LTE/NR) PC5 interface of one or more than one Destination IDs (e.g., case#<NUM>). Instead, the UE may just implement 'partial failure design'. For example, only sidelink radio link failure may be implemented or only 'failed' sidelink radio bearers (of those corresponding Destination IDs) may be released/ cleared. In addition, the UE may also report a 'sidelink RRC configuration failure' event to the serving cell. Moreover, in some implementations, the UE may not initiate a Reconfiguration Failure event (or part of the UE implementations in the Reconfiguration Failure event). In other words, the RRC connection in the Uu interface may not be impacted or the impact on the RRC connection may be limited. Details of the implementations in Table <NUM> are disclosed in Implementation#<NUM>-<NUM>.

Implementation#<NUM>-<NUM> addresses the case in which the failure event indication of the sidelink AS configuration is obtained through broadcast system information.

Implementation#<NUM>-<NUM> addresses the sidelink RRC configuration failure when the UE receives the sidelink RRC configuration through dedicated control signaling (e.g., RRC signaling) in the Uu interface. Table <NUM> lists detailed implementations of Implementation#<NUM>-<NUM>, which may correspond to Case#<NUM> in Table <NUM>.

<FIG> illustrates a process <NUM> for handling a sidelink failure event according to an implementation of the present disclosure. In action <NUM>, the UE <NUM> receives a first message including a sidelink RRC configuration associated with a target cell <NUM> from a source cell <NUM>. The source cell <NUM> may be the current serving cell of the UE <NUM>. In action <NUM>, the UE <NUM> may determine that a sidelink failure event associated with an associated sidelink destination UE <NUM> occurs. In action <NUM>, the UE <NUM> may perform a handover procedure to switch from the source cell <NUM> to the target cell <NUM>. In action <NUM>, the UE <NUM> may transmit a sidelink failure report indicating the sidelink failure event to the target cell <NUM>.

In one implementation, during the handover procedure, the source cell <NUM> may communicate with the target cell <NUM>. For example, the source cell <NUM> may provide information of the UE <NUM> to the target cell <NUM>. The target cell <NUM> may transmit configuration parameters (e.g., parameters related to sidelink radio configurations) to the source cell <NUM>, and the source cell <NUM> may transmit the configuration parameters to the UE <NUM> via the first message. Please note the SL RRC configuration message in action <NUM> may be transmitted via one UE-specific DL RRC signaling (e.g., RRCReconfiguraion message with 'reconfiguration with sync' IE, which is provided for connected UE mobility event). Please also note, in some implementations, the UE <NUM> may also have provided the information/configuration related to the sidelink destination UE <NUM> (e.g., the (Layer-<NUM>) Destination ID, cast types, QoS information, or other AS layer configurations associated with the sidelink destination UE <NUM>) to the source cell <NUM> before action <NUM> (e.g., via the sidelinkUEInformationNR or sidelinkUEInformationEUTRA transmitted in a UL UE-specific RRC signaling from UE <NUM> to the source cell <NUM>). Moreover, after receiving the sidelinkUEInformationNR/ sidelinkUEInformationEUTRA from the UE <NUM>, the source cell <NUM> may forward the sidelinkUEInformationNR/sidelinkUEInformationEUTRA to the target cell <NUM> through backhaul connection (e.g., via a handoverpreparationInformation message delivery procedure before the action <NUM>). Therefore, the target cell <NUM> could provide sidelink radio configurations (e.g., sidelink radio configurations associated with the sidelink destination UE <NUM>) to the UE <NUM> through the forwarding of the source cell <NUM>. In addition, after the handover procedure in action <NUM>, the target cell <NUM> could also identify the SL failure report transmitted by the UE <NUM> in action <NUM>.

During the process <NUM>, in some implementations, the UE <NUM> may act as a relay UE, and the sidelink destination UE <NUM> may act as a remote UE. The base station (e.g., the base station which configures the source cell <NUM>) may control the sidelink radio configuration and sidelink resource allocation of the remote UE (the sidelink destination UE <NUM>) via the relay UE (the UE <NUM>). In one implementation, after receiving the first message in action <NUM>, the UE <NUM> may transmit a second message including the sidelink RRC configuration associated with the target cell <NUM> to the sidelink destination UE <NUM>. The second message may be transmitted via a PC5 RRC connection between the UE <NUM> and the sidelink destination UE <NUM>.

There may be a sidelink failure event regarding the transmission of the second message from the UE <NUM> to the sidelink destination UE <NUM>. The sidelink failure event may be a sidelink RRC reconfiguration failure event for a PC5 RRC connection between the UE <NUM> and the associated sidelink destination UE <NUM>. For example, the sidelink destination UE <NUM> may successfully receive the sidelink RRC configuration but fail to apply the sidelink RRC reconfiguration. In one implementation, the sidelink destination UE <NUM> may transmit a sidelink failure indication to the UE <NUM> to indicate the sidelink RRC reconfiguration failure. The UE <NUM> may determine that the sidelink failure event associated with the sidelink destination UE <NUM> occurs in action <NUM> based on the sidelink failure indication received from the sidelink destination UE <NUM>. Then, the UE <NUM> may report this sidelink failure event to the target cell <NUM> via the SL failure report in action <NUM> (e.g., by attaching the (Layer-<NUM>) Destination ID of the UE <NUM> and a failure cause of '(sidelink) reconfiguration failure' in the SL failure report in action <NUM>).

The sidelink failure event may be a sidelink radio link failure event for a PC5 RRC connection between the UE <NUM> and the associated sidelink destination UE <NUM>. For example, the UE <NUM> may consider sidelink radio link failure event with the sidelink destination UE <NUM> to be detected when (at least) one of the following events happens:.

Based on the triggering events above, the UE <NUM> may determine that the sidelink failure event associated with the sidelink destination UE <NUM> occurs in action <NUM> by the UE <NUM> itself.

Please note, in some scenarios, the UE <NUM> may release the PC5 RRC connection with the sidelink destination UE <NUM> (and release/discard/remove the sidelink radio configurations associated with the sidelink destination UE <NUM>) when the UE <NUM> considers the sidelink radio link failure event for the sidelink destination UE <NUM> has been detected. However, please also note, the UE <NUM> may also receive (sidelink) full configuration instruction from the serving cell (e.g., the <NUM>st message in action <NUM>) (before or after) the sidelink radio link failure event happens. Under such condition, in some implementations, the UE <NUM> may just release the PC5-RRC connection with the sidelink destination UE <NUM> without being impacted by the (sidelink) full configuration (and so the UE <NUM> may still provide the SL failure report to the target cell <NUM> in action <NUM>). In addition, the UE <NUM> may ignore the (sidelink) full configuration instruction in the <NUM>st message even if there are any new sidelink radio configurations (associated with the sidelink destination UE <NUM>) provided in the <NUM>st message in action <NUM>.

In one implementation, the handover procedure in action <NUM> may be an intra-RAT handover procedure. Both the source cell <NUM> and the target cell <NUM> may belong to either an E-UTRAN or an NR-RAN.

In one implementation, the handover procedure in action <NUM> may be an inter-RAT handover procedure. One of the source cell <NUM> and the target cell <NUM> may belong to an E-UTRAN, and the other of the source cell <NUM> and the target cell <NUM> may belong to an NR-RAN. For example, the target cell <NUM> may belong to the E-UTRAN, and signaling to the target cell <NUM> may follow the E-UTRAN protocol. On the other hand, the sidelink failure report in action <NUM> may follow the NR protocol. An inter-RAT transceiver or an inter-RAT (signlaing) container may be provided such that the target cell <NUM> can accommodate the sidelink failure report.

In one implementation, the sidelink failure report in action <NUM> may include a failure cause and an ID of the sidelink destination UE <NUM> (also referred to as destination UE ID). The failure cause may indicate one of 'sidelink RRC reconfiguration failure' and 'sidelink radio link failure'. For example, the failure cause indicates 'sidelink (RRC) reconfiguration failure' when the sidelink failure event is a sidelink RRC reconfiguration failure event, whereas the failure cause indicates 'sidelink radio link failure' when the sidelink failure event is a sidelink radio link failure event.

In one implementation, the sidelink failure report in action <NUM> may be transmitted via an RRC reconfiguration complete message, which may be the last step of the handover procedure in action <NUM>. In some other implementations, the sidelink failure report in action <NUM> may be transmitted to the target cell <NUM> after the transmission of the RRC reconfiguration complete message.

In one implementation, the sidelink failure report in action <NUM> may be transmitted via NR RRC signaling to the target cell <NUM> in a case that the target cell <NUM> is an NR cell, whereas the sidelink failure report in action <NUM> may be transmitted via E-UTRA RRC signaling in a case that the target cell <NUM> is an E-UTRA cell.

In one implementation, in action <NUM>, the UE <NUM> may receive a full configuration indicator in the first message (e.g., the full configuration instructed by the target cell <NUM>). The UE <NUM> may determine to release a dedicated sidelink radio configuration associated with the sidelink destination UE <NUM> in a case that the dedicated sidelink radio configuration is configured by a serving RAN (which may be the source cell <NUM>) through UE-specific dedicated control signaling before the reception of the first message. The UE <NUM> may determine not to release the dedicated sidelink radio configuration associated with the sidelink destination UE <NUM> in a case that the dedicated sidelink radio configuration is not configured by the serving RAN (e.g., through UE-specific dedicated control signaling and/or broadcast system information) before the reception of the first message. The dedicated sidelink radio configuration includes a sidelink radio configuration for the UE <NUM> to implement at least one of an NR sidelink communication service and an LTE V2X sidelink communication service. However, in some implementations, the UE <NUM> may still transmit the SL failure report associated with the sidelink destination UE <NUM> no matter whether full configuration is instructed by the target cell <NUM> in action <NUM> and no matter whether any new sidelink radio configuration (associated with the sidelink destination UE <NUM>) is provided by the target cell <NUM>. In other words, the UE <NUM> may not release the SL failure report while the UE <NUM> is implementing full configuration (on Uu interface / PC5 interface). In contrast, in some additional implementations, the UE <NUM> may not implement the SL failure report associated with the sidelink destination UE <NUM> to the target cell <NUM> if the PC5 RRC connection associated with the sidelink destination UE <NUM> would be released by the (sidelink) full configuration instruction in the <NUM>st message in action <NUM> (e.g., when the (sidelink) full configuration is instructed by the target cell <NUM> in the action <NUM>) and new sidelink radio configurations associated with the sidelink destination UE <NUM> may or may not be transmitted jointly in the <NUM>st message in action <NUM>.

<FIG> illustrates a method <NUM> performed by a UE for sidelink failure management according to an implementation of the present disclosure. In action <NUM>, the UE receives a first message including a sidelink RRC configuration (e.g., SIB <NUM>/SIB <NUM> of the target cell or SL-ConfigDedicatedNR/SL-ConfigDedicatedEUTRA configured by the target cell for the UE) associated with a target cell from a source cell. In action <NUM>, the UE determines that a sidelink failure event associated with an associated sidelink destination UE occurs. In action <NUM>, the UE transmits a sidelink failure report indicating the sidelink failure event to the target cell after performing a handover procedure to switch from the source cell to the target cell. Actions <NUM>, <NUM>, and <NUM> may correspond to actions <NUM>, <NUM>, and <NUM> illustrated in <FIG>.

<FIG> illustrates a method <NUM> performed by a UE for sidelink failure management according to another implementation of the present disclosure. Actions <NUM>, <NUM>, and <NUM> may correspond to actions <NUM>, <NUM>, and <NUM> illustrated in <FIG>. In action <NUM>, the UE receives a full configuration indicator in the first message. In action <NUM>, the UE determines whether to release a dedicated sidelink radio configuration associated with the sidelink destination UE. In one implementation, the UE may determine to release a dedicated sidelink radio configuration associated with the sidelink destination UE in a case that the dedicated sidelink radio configuration is configured by a serving RAN (e.g., through UE-specific dedicated control signaling before the reception of the first message). In one implementation, the UE may determine not to release the dedicated sidelink radio configuration (associated with the sidelink destination UE) in a case that the dedicated sidelink radio configuration is not configured by the serving RAN (e.g., through UE-specific dedicated control signaling before the reception of the first message). In this condition, the dedicated sidelink radio configuration may be provided by the paired UE (e.g., the sidelink destination UE) in the PC5-RRC connection via PC5-RRC signaling(s), may be decided by sidelink pre-configuration stored by the UE itself, or may be decided by broadcast sidelink system information (e.g., SIB <NUM>/SIB <NUM>) from the serving RAN.

Implementation#<NUM>-<NUM> addresses the sidelink AS configuration failure when the UE receives the sidelink AS configuration through broadcast control signaling (e.g., system information specific to LTE or NR V2X services). Table <NUM> lists detailed implementations of Implementation#<NUM>-<NUM>, which is related to sidelink AS configuration failure when the sidelink AS configuration is obtained by reading the system information from the corresponding cell.

<FIG> is a block diagram illustrating a node <NUM> for wireless communication according to an implementation of the present disclosure. As illustrated in <FIG>, a node <NUM> may include a transceiver <NUM>, a processor <NUM>, a memory <NUM>, one or more presentation components <NUM>, and at least one antenna <NUM>. The node <NUM> may also include a Radio Frequency (RF) spectrum band module, a BS communications module, a network communications module, and a system communications management module, Input / Output (I/O) ports, I/O components, and a power supply (not illustrated in <FIG>).

The node <NUM> may include a variety of computer-readable media. Computer-readable media may be any available media that may be accessed by the node <NUM> and include both volatile and non-volatile media, removable and non-removable media.

The computer-readable media may include computer storage media and communication media. Computer storage media include both volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules or data.

Computer storage media include RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, Digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices. Computer storage media do not include a propagated data signal. Communication media typically embody computer-readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and include any information delivery media.

Communication media include wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. Combinations of any of the previously listed components should also be included within the scope of computer-readable media.

The memory <NUM> may include computer-storage media in the form of volatile and/or non-volatile memory. The memory <NUM> may be removable, non-removable, or a combination thereof. Example memory includes solid-state memory, hard drives, optical-disc drives, etc. As illustrated in <FIG>, the memory <NUM> may store computer-readable, computer-executable instructions <NUM> (e.g., software codes) that are configured to cause the processor <NUM> to perform various disclosed functions, for example, with reference to <FIG>. Alternatively, the instructions <NUM> may not be directly executable by the processor <NUM> but be configured to cause the node <NUM> (e.g., when compiled and executed) to perform various disclosed functions.

The processor <NUM> (e.g., having processing circuitry) may include an intelligent hardware device, e.g., a Central Processing Unit (CPU), a microcontroller, an ASIC, etc. The processor <NUM> may include memory. The processor <NUM> may process data <NUM> and the instructions <NUM> received from the memory <NUM>, and information transmitted and received via the transceiver <NUM>, the base band communications module, and/or the network communications module. The processor <NUM> may also process information to be sent to the transceiver <NUM> for transmission via the antenna <NUM> to the network communications module for transmission to a core network.

One or more presentation components <NUM> present data indications to a person or another device. Examples of presentation components <NUM> include a display device, a speaker, a printing component, and a vibrating component, etc..

Claim 1:
A method performed by a user equipment, UE (<NUM>), for sidelink failure management, the method comprising:
receiving (<NUM>, <NUM>), from a source cell, a first message including a sidelink Radio Resource Control, RRC, configuration associated with a target cell;
determining (<NUM>, <NUM>) that a sidelink failure event associated with an associated sidelink destination UE occurs; and
transmitting (<NUM>, <NUM>) a sidelink failure report indicating the sidelink failure event to the target cell after performing a handover procedure to switch from the source cell to the target cell, wherein:
a type of the sidelink failure event comprises a sidelink RRC reconfiguration failure event for a PC5-RRC connection between the UE and the associated sidelink destination UE or a sidelink radio link failure event for the PC5-RRC connection between the UE and the associated sidelink destination UE.