Abstract: A method and device are disclosed from the perspective of a first device handling radio link failure. In one method, the method includes the first device performing or establishing sidelink unicast communication with a second device. The method also includes the first device performing or establishing sidelink unicast communication with a third device. The method also includes the first device detecting a radio link failure associated with the second device. The method further includes the first device performing a Sidelink MAC reset associated with the second device in response to the radio link failure, and not performing a Sidelink MAC reset associated with the third device.

Abstract: A method and device are disclosed from the perspective of a relay UE. In one embodiment, the relay UE establishes a Radio Resource Control (RRC) connection with a network node. The relay UE also transmits a Layer 2. Identity (L2ID) of the relay UE to the network node. Furthermore, the relay UE receives a local UE Identity (ID) for a remote UE and a L2ID of the remote UE from the network node. In addition, the relay UE establishes a PC5 connection with the remote UE. The relay UE further receives a first RRC Reconfiguration Complete message from the remote UE. The relay UE also transmits the first RRC Reconfiguration Complete message to the network node, wherein the first RRC Reconfiguration Complete message is included in an adaptation layer Protocol Data Unit (PDU) for transmission and the local UE ID for the remote UE is included in a header of the adaptation layer PDU.

Abstract: A method and apparatus are disclosed from the perspective of a first UE (User Equipment) to indicate a network node for releasing SLRB (Sidelink Radio Bearer) or SL-DRB (Sidelink-Data Radio Bearer). In one embodiment, the method includes transmitting a first RRC (Radio Resource Control) message to a network node for requesting sidelink resource, wherein the first RRC message includes a PFI (PC5 QoS Flow Identifier) of a PC5 QoS (Quality of Service) flow in a first list of PC5 QoS flows. The method also includes receiving a second RRC message from the network node, wherein the second RRC message configures a SLRB and maps the PC5 QoS flow to the SLRB. The method further includes transmitting a third RRC message to the network node if the PC5 QoS flow is deactivated or released, wherein the PFI of the PC5 QoS flow is removed from a second list of PC5 QoS flows included in the third RRC message.

Abstract: A method and apparatus are disclosed from the perspective of a network node. In one embodiment, the method includes receiving a resource request to allocate SPS resource from a UE, wherein the resource request indicates a first logical channel. The method also allocating the UE with a first SPS resource and a second SPS resource for the first logical channel and a second logical channel associated with the first logical channel based on the resource request.

Abstract: A method and device are disclosed for a relay User Equipment (UE). In one embodiment, the relay UE establishes a first layer-2 link with a first remote UE. The relay UE also establishes a Protocol Data Unit (PDU) session with a network, wherein the relay UE forwards traffic of the first remote UE on the PDU session. The relay UE further establishes a second layer-2 link with a second remote UE. In addition, the relay UE forwards traffic of the second remote UE on the PDU session. Furthermore, the relay UE receives a network control signaling from the network, wherein the network control signaling is associated with the first remote UE and is used for modifying the PDU session. The relay UE also initiates a layer-2 link modification procedure toward the first remote UE in response to reception of the network control signaling.

Abstract: A method and apparatus are disclosed. In an example from the perspective of a first device, a grant is received from a network node. The grant allocates a set of sidelink data resources. One or more sidelink data transmissions are performed on the set of sidelink data resources. A second feedback information associated with the one or more sidelink data transmissions is received and/or detected. An uplink resource is derived. A first feedback information is transmitted on the uplink resource to the network node. The first feedback information is set based upon the second feedback information.

Abstract: A method and device are disclosed from the perspective of a first User Equipment (UE) to support Sidelink (SL) Discontinuous Reception (DRX). In one embodiment, the method includes the first UE establishing a unicast link with a second UE. The method further includes the first UE receiving a SL DRX configuration associated with the second UE from the second UE. The method also includes the first UE transmitting the SL DRX configuration to a network node. In addition, the method includes the first UE receiving a sidelink grant from the network node, wherein the sidelink grant indicates sidelink resources. Furthermore, the method includes the first UE performing a sidelink transmission to the second UE based on the sidelink resources.

Abstract: A method and device are disclosed from the perspective of a first User Equipment (UE) to establish one-to-one connection between the first UE and a second UE. In one embodiment, the method includes the first UE initiating a first procedure of establishing the one-to-one connection with the second UE for a unicast communication between the first UE and the second UE or for a UE-to-UE communication between the first UE and a third UE via the second UE or a second procedure of establishing the one-to-one connection with the second UE for a UE-to-Network communication between the first UE and a network node via the second UE.

Abstract: A method and apparatus are disclosed from the perspective of a first UE (User Equipment) to support multiple services on a one-to-one sidelink communication link between the first UE and a second UE. In one embodiment, the first UE initiates a first service. The first UE also establishes the one-to-one sidelink communication link for the first service. Furthermore, the first UE negotiates a security configuration with the second UE for encrypting or decrypting data from the first service. In addition, the first UE initiates a second service. The first UE also encrypts or decrypts data from the second service with the security configuration used by the first service.

Abstract: A method and apparatus are disclosed from the perspective of a network node. In one embodiment, the method includes the network node transmitting a first message with a DRB (Data Radio Bearer) configuration to a UE (User Equipment) for establishing a default DRB for a PDU (Packet Data Unit) session, wherein the DRB configuration includes a QFI (QoS Flow Id) configuration used to indicate whether a QFI field is present or not in uplink for the default DRB and the QFI configuration is always set to a value indicating the QFI field is present in uplink for the default DRB. The method further includes the network node establishing the default DRB with a presence of the QFI field in uplink. The method also includes the network node receiving a SDAP (Service Data Adaptation Protocol) PDU with the QFI field via the default DRB from the UE.

Abstract: A method and device are disclosed from the perspective of a first UE. The first UE initiates a first procedure of establishing the one-to-one connection with the second UE for a unicast communication between the first UE and the second UE or for a UE-to-UE communication between the first UE and a third UE via the second UE or a second procedure of establishing the one-to-one connection with the second UE for a UE-to-Network communication between the first UE and a network node via the second UE. The first UE transmits a first PC5-S message to the second UE for completing establishment of a first security context in the first procedure of establishing the one-to-one connection with the second UE for the unicast communication or the UE-to-UE communication if the first procedure is initiated, wherein the first PC5-S message includes QoS information for the unicast communication or the UE-to-UE communication.

Abstract: A method and apparatus are disclosed from the perspective of an initiating UE (User Equipment) for establishing a one-to-one sidelink communication with a target UE. In one embodiment, the method includes transmitting a first PC5 signaling used for establishing the one-to-one sidelink communication, wherein the first PC5 signaling includes an identity of the target UE and an identity of a V2X (Vehicle-to-Everything) service.

Abstract: A method and apparatus are disclosed. In an example, a first user equipment (UE) may be configured with a first number of carriers corresponding to a maximum number of carriers that the first UE is able to use concurrently and/or transmit on concurrently. The first UE may receive a plurality of sidelink transmissions on a plurality of carriers. The first UE may derive a plurality of slots for transmitting Physical Sidelink Feedback Channels (PSFCHs) based upon resources associated with the plurality of sidelink transmissions. Responsive to determining that a number of carriers of a second plurality of carriers associated with derived transmissions of the PSFCHs exceeds the first number of carriers, the first UE may prioritize one or more PSFCHs of the PSFCHs based upon a rule. The plurality of slots for transmitting the PSFCHs may be at least partially overlapped in the time domain.

Abstract: A method and device are disclosed for a relay User Equipment (UE). The relay UE connects with a remote UE or serving the remote UE for a relay communication with a network node. The relay UE receives a message on a PC5 RLC channel from the remote UE, wherein the PC5 RLC channel is associated with a Uu SRB1 for the remote UE or a Uu SRB on which the remote UE transmitting RRC signalling in RRC_CONNECTED. The relay UE initiates or performs a RRC connection resume procedure with the network node in response to reception of the message on the PC5 RLC channel or when data is available for transmission from the relay UE to the network node on a Uu RLC channel associated with the Uu SRB1 for the remote UE or the Uu SRB on which the remote UE transmitting RRC signalling in RRC_CONNECTED.

Abstract: A method and device are disclosed for a User Equipment (UE) to sidelink discontinuous reception (DRX) for sidelink groupcast communication associated with a group. In one embodiment, the method includes the UE assuming or considering a sidelink DRX configuration applied for the sidelink groupcast communication associated with the group, wherein the sidelink DRX configuration comprises at least one of an on-duration timer length used for determining an on-duration at the beginning of each sidelink DRX cycle and/or a cycle length used for determining a length of each sidelink DRX cycle. The method also includes the UE deriving or determining a time to start of on-duration for each sidelink DRX cycle or start of each sidelink DRX cycle based on at least an identifier associated with the group.

Abstract: A method and device are disclosed for a User Equipment (UE) to configure sidelink discontinuous reception (DRX) for sidelink groupcast communication associated with a group are disclosed. In one embodiment, the method includes the UE applying a sidelink DRX configuration for the sidelink groupcast communication associated with the group, wherein the sidelink DRX configuration comprises at least one of an on-duration timer length used for determining an on-duration for each sidelink DRX cycle and/or a cycle length used for determining a length of each sidelink DRX cycle. The method further includes the UE deriving or determining a time to start of on-duration for each sidelink DRX cycle or start of each sidelink DRX cycle based on at least an identifier associated with the group.

Abstract: A method and device are disclosed for a relay User Equipment (UE) to support UE-to-Network relay communication with a remote UE. In one embodiment, the method includes the relay UE connecting with a network node. The method further includes the relay UE receiving a first paging message or information for the remote UE from the network node on a dedicated downlink channel or a paging channel. The method also includes the relay UE transmitting a second paging message or information to the remote UE in response to reception of the first paging message or information for the remote UE, wherein the second paging message or information is generated based on the first paging message or information.

Abstract: A method and apparatus are disclosed from the perspective of an initiating UE (User Equipment) for establishing a one-to-one sidelink communication with a target UE. In one embodiment, the method includes transmitting a first PC5 signalling used for establishing the one-to-one sidelink communication, wherein the first PC5 signalling includes an identity of the target UE and an identity of a V2X (Vehicle-to-Everything) service.

Abstract: A method and device are disclosed for a remote User Equipment (UE) to support UE-to-Network relay communication. In one embodiment, the method includes the remote UE connecting with a relay UE. The method also includes the remote UE connecting with a first network node via the relay UE. The method further includes the remote UE receiving a first Radio Resource Control (RRC) message from the first network node via the relay UE, wherein the first RRC message includes a Cell Radio Network Temporary Identifier (C-RNTI) of the remote UE used for constructing authentication information.

Abstract: A method and device are disclosed for a remote User Equipment (UE) to support UE-to-Network relay communication. The remote UE establishes a PC5 connection with a first relay UE for a relay communication with a first network node. The remote UE also performs a Radio Resource Control (RRC) connection establishment procedure with the first network node via the first relay UE. Furthermore, the remote UE transmits a first RRC message to a second network node via a second relay UE for requesting RRC connection re-establishment, wherein the first RRC message includes a first Cell Radio Network Temporary Identifier (C-RNTI) of the remote UE. Also, the remote UE receives a second RRC message from the second network node via the second relay UE for re-establishing a RRC connection between the second network node and the remote UE, wherein the second RRC message includes a second C-RNTI of the remote UE.