Patent Description:
Vehicle-to-everything (V2X) communication is the passing of information from a vehicle to any entity that may affect the vehicle, and vice versa. It is a vehicular communication system that incorporates other more specific types of communication as vehicle-to-infrastructure (V2I), vehicle-to-network (V2N), vehicle-to-vehicle (V2V), vehicle-to-pedestrian (V2P), vehicle-to-device (V2D) and vehicle-to-grid (V2G).

<NPL>, proposes the following: L1 performs packet filtering at least for sidelink unicast and groupcast. With a given full source/destination ID, if a portion of it is used as L1 source/destination ID in SCI, the rest portion is conveyed in MAC subheader as L2 source/destination ID. In case of NR V2X broadcast, source and destination IDs are conveyed only in MAC subheader as in LTE V2X. In case of NR V2X unicast and groupcast, L2 determines L1 IDs based on given full L2 source/destination IDs from upper layers and link information. Upon RAN2/SA2 progress, for the same unicast UE pair, each UE uses one L1 source ID which may be associated to multiple links. RAN1/RAN2 investigates the support of using shortened local L1/L2 IDs in SCI for SL unicast after link establishment.

<CIT>, which was published after the priority date of the present application but claims a priority before the priority date of the present application, discloses a communication method and device. A second terminal device may receive data of a corresponding communication type based on a first target side identifier and the communication type that are included in SCI sent by a first terminal device, or the communication type included in the SCI sent by the first terminal device, to reduce a packet receiving error rate of the second terminal device, and further improve packet receiving efficiency of the second terminal device.

<CIT>, which was published after the priority date of the present application but claims a priority before the priority date of the present application, discloses a method and apparatus for transmitting sidelink control information in a wireless communication system. A wireless device determines that a sidelink (SL) resource has not been reserved within a time period related to transmission of sidelink control information (SCI), and triggers SL resource reservation for transmission of the SCI.

An aspect of the present disclosure is to provide a method and apparatus for allocating/providing a lower identifier (ID) associated with an upper ID, e.g., source/destination Layer-<NUM> ID, for sidelink transmission.

An aspect of the present disclosure is to provide a method and apparatus for monitoring/receiving sidelink control information (SCI) and/or sidelink data based on the lower ID.

Advantageous embodiments are indicated in the dependent claims.

The present disclosure can have various advantageous effects.

For example, one UE can allocate a lower ID associated with an upper ID to the other UE for a direct link, in particular when the UE performs sidelink transmissions with one or several UEs.

For example, the system can avoid collision of IDs with low overhead in sidelink control information transmissions for the direct link between UEs performing sidelink communication.

Advantageous effects which can be obtained through specific embodiments of the present disclosure are not limited to the advantageous effects listed above. For example, there may be a variety of technical effects that a person having ordinary skill in the related art can understand and/or derive from the present disclosure. Accordingly, the specific effects of the present disclosure are not limited to those explicitly described herein, but may include various effects that may be understood or derived from the technical features of the present disclosure.

For example, "A/ B" may mean "A and/or B".

Also, parentheses used in the present disclosure may mean "for example". In detail, when it is shown as "control information (PDCCH)", "PDCCH" may be proposed as an example of "control information". In other words, "control information" in the present disclosure is not limited to "PDCCH", and "PDDCH" may be proposed as an example of "control information". In addition, even when shown as "control information (i.e., PDCCH)", "PDCCH" may be proposed as an example of "control information".

In addition, one of the most expected <NUM> use cases relates a function capable of smoothly connecting embedded sensors in all fields, i.e., mMTC. It is expected that the number of potential Internet-of-things (IoT) devices will reach <NUM> hundred million up to the year of <NUM>. An industrial IoT is one of categories of performing a main role enabling a smart city, asset tracking, smart utility, agriculture, and security infrastructure through <NUM>.

Mission critical application (e.g., e-health) is one of <NUM> use scenarios. A health part contains many application programs capable of enjoying benefit of mobile communication. A communication system may support remote treatment that provides clinical treatment in a faraway place. Remote treatment may aid in reducing a barrier against distance and improve access to medical services that cannot be continuously available in a faraway rural area. Remote treatment is also used to perform important treatment and save lives in an emergency situation. The wireless sensor network based on mobile communication may provide remote monitoring and sensors for parameters such as heart rate and blood pressure.

The loT device (e.g., a sensor) may perform direct communication with other IoT devices (e.g., sensors) or other wireless devices 100a to 100f.

Referring to <FIG>, a first wireless device <NUM> and a second wireless device <NUM> may transmit/receive radio signals to/from an external device through a variety of RATs (e.g., LTE and NR). In <FIG>, {the first wireless device <NUM> and the second wireless device <NUM>} may correspond to at least one of {the wireless device 100a to 100f and the BS <NUM>}, {the wireless device 100a to 100f and the wireless device 100a to 100f} and/or {the BS <NUM> and the BS <NUM>} of <FIG>.

The first wireless device <NUM> may include one or more processors <NUM> and one or more memories <NUM> and additionally further include one or more transceivers <NUM> and/ or one or more antennas <NUM>. The processor(s) <NUM> may control the memory(s) <NUM> and/or the transceiver(s) <NUM> and may be configured to implement the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts described in the present disclosure. The processor(s) <NUM> may receive radio signals including second information/signals through the transceiver(s) <NUM> and then store information obtained by processing the second information/signals in the memory(s) <NUM>. For example, the memory(s) <NUM> may store software code including commands for performing a part or the entirety of processes controlled by the processor(s) <NUM> or for performing the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts described in the present disclosure. The transceiver(s) <NUM> may be interchangeably used with radio frequency (RF) unit(s). In the present disclosure, the first wireless device <NUM> may represent a communication modem/circuit/chip.

The second wireless device <NUM> may include one or more processors <NUM> and one or more memories <NUM> and additionally further include one or more transceivers <NUM> and/ or one or more antennas <NUM>. The processor(s) <NUM> may control the memory(s) <NUM> and/or the transceiver(s) <NUM> and may be configured to implement the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts described in the present disclosure. For example, the memory(s) <NUM> may store software code including commands for performing a part or the entirety of processes controlled by the processor(s) <NUM> or for performing the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts described in the present disclosure. In the present disclosure, the second wireless device <NUM> may represent a communication modem/circuit/chip.

As an example, one or more application specific integrated circuits (ASICs), one or more digital signal processors (DSPs), one or more digital signal processing devices (DSPDs), one or more programmable logic devices (PLDs), or one or more field programmable gate arrays (FPGAs) may be included in the one or more processors <NUM> and <NUM>. descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure may be implemented using firmware or software and the firmware or software may be configured to include the modules, procedures, or functions. Firmware or software configured to perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure may be included in the one or more processors <NUM> and <NUM> or stored in the one or more memories <NUM> and <NUM> so as to be driven by the one or more processors <NUM> and <NUM>. The descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure may be implemented using firmware or software in the form of code, commands, and/or a set of commands.

The one or more transceivers <NUM> and <NUM> may be connected to the one or more antennas <NUM> and <NUM> and the one or more transceivers <NUM> and <NUM> may be configured to transmit and receive user data, control information, and/or radio signals/channels, mentioned in the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure, through the one or more antennas <NUM> and <NUM>. In the present disclosure, the one or more antennas may be a plurality of physical antennas or a plurality of logical antennas (e.g., antenna ports).

The one or more transceivers <NUM> and <NUM> may convert received radio signals/ channels, etc., from RF band signals into baseband signals in order to process received user data, control information, radio signals/channels, etc., using the one or more processors <NUM> and <NUM>. The one or more transceivers <NUM> and <NUM> may convert the user data, control information, radio signals/channels, etc., processed using the one or more processors <NUM> and <NUM> from the base band signals into the RF band signals. For example, the transceivers <NUM> and <NUM> can up-convert OFDM baseband signals to a carrier frequency by their (analog) oscillators and/or filters under the control of the processors <NUM> and <NUM> and transmit the up-converted OFDM signals at the carrier frequency. The transceivers <NUM> and <NUM> may receive OFDM signals at a carrier frequency and down-convert the OFDM signals into OFDM baseband signals by their (analog) oscillators and/or filters under the control of the transceivers <NUM> and <NUM>.

In the implementations of the present disclosure, a UE may operate as a transmitting device in uplink (UL) and as a receiving device in downlink (DL). In the implementations of the present disclosure, a BS may operate as a receiving device in UL and as a transmitting device in DL. Hereinafter, for convenience of description, it is mainly assumed that the first wireless device <NUM> acts as the UE, and the second wireless device <NUM> acts as the BS. For example, the processor(s) <NUM> connected to, mounted on or launched in the first wireless device <NUM> may be configured to perform the UE behavior according to an implementation of the present disclosure or control the transceiver(s) <NUM> to perform the UE behavior according to an implementation of the present disclosure. The processor(s) <NUM> connected to, mounted on or launched in the second wireless device <NUM> may be configured to perform the BS behavior according to an implementation of the present disclosure or control the transceiver(s) <NUM> to perform the BS behavior according to an implementation of the present disclosure.

The communication unit <NUM> may include a communication circuit <NUM> and transceiver(s) <NUM>. For example, the communication circuit <NUM> may include the one or more processors <NUM> and <NUM> of <FIG> and/or the one or more memories <NUM> and <NUM> of <FIG>. For example, the transceiver(s) <NUM> may include the one or more transceivers <NUM> and <NUM> of <FIG> and/or the one or more antennas <NUM> and <NUM> of <FIG>. The control unit <NUM> is electrically connected to the communication unit <NUM>, the memory <NUM>, and the additional components <NUM> and controls overall operation of each of the wireless devices <NUM> and <NUM>. For example, the control unit <NUM> may control an electric/mechanical operation of each of the wireless devices <NUM> and <NUM> based on programs/code/commands/information stored in the memory unit <NUM>.

As an example, the control unit <NUM> may be configured by a set of a communication control processor, an application processor (AP), an electronic control unit (ECU), a graphical processing unit, and a memory control processor. As another example, the memory <NUM> may be configured by a RAM, a DRAM, a ROM, a flash memory, a volatile memory, a non-volatile memory, and/or a combination thereof.

<FIG> shows another example of wireless devices to which implementations of the present disclosure is applied.

The first wireless device <NUM> may include at least one transceiver, such as a transceiver <NUM>, and at least one processing chip, such as a processing chip <NUM>. The processing chip <NUM> may include at least one processor, such a processor <NUM>, and at least one memory, such as a memory <NUM>. The memory <NUM> may be operably connectable to the processor <NUM>. The memory <NUM> may store various types of information and/or instructions. The memory <NUM> may store a software code <NUM> which implements instructions that, when executed by the processor <NUM>, perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. For example, the software code <NUM> may implement instructions that, when executed by the processor <NUM>, perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. For example, the software code <NUM> may control the processor <NUM> to perform one or more protocols. For example, the software code <NUM> may control the processor <NUM> may perform one or more layers of the radio interface protocol.

The second wireless device <NUM> may include at least one transceiver, such as a transceiver <NUM>, and at least one processing chip, such as a processing chip <NUM>. The processing chip <NUM> may include at least one processor, such a processor <NUM>, and at least one memory, such as a memory <NUM>. The memory <NUM> may be operably connectable to the processor <NUM>. The memory <NUM> may store various types of information and/or instructions. The memory <NUM> may store a software code <NUM> which implements instructions that, when executed by the processor <NUM>, perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. For example, the software code <NUM> may implement instructions that, when executed by the processor <NUM>, perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. For example, the software code <NUM> may control the processor <NUM> to perform one or more protocols. For example, the software code <NUM> may control the processor <NUM> may perform one or more layers of the radio interface protocol.

Referring to <FIG>, a UE <NUM> may correspond to the first wireless device <NUM> of <FIG> and/or the first wireless device <NUM> of <FIG>.

The processor <NUM> may be configured to implement the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. The processor <NUM> may be configured to control one or more other components of the UE <NUM> to implement the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. Layers of the radio interface protocol may be implemented in the processor <NUM>. The processor <NUM> may include ASIC, other chipset, logic circuit and/or data processing device. The processor <NUM> may be an application processor. The processor <NUM> may include at least one of a digital signal processor (DSP), a central processing unit (CPU), a graphics processing unit (GPU), a modem (modulator and demodulator). An example of the processor <NUM> may be found in SNAPDRAGON™ series of processors made by Qualcomm®, EXYNOS™ series of processors made by Samsung®, A series of processors made by Apple®, HELIO™ series of processors made by MediaTek®, ATOM™ series of processors made by Intel® or a corresponding next generation processor.

The transceiver <NUM> is operatively coupled with the processor <NUM>, and transmits and/ or receives a radio signal.

<FIG> show an example of protocol stacks in a 3GPP based wireless communication system to which implementations of the present disclosure is applied.

In particular, <FIG> illustrates an example of a radio interface user plane protocol stack between a UE and a BS and <FIG> illustrates an example of a radio interface control plane protocol stack between a UE and a BS. The control plane refers to a path through which control messages used to manage call by a UE and a network are transported. The user plane refers to a path through which data generated in an application layer, for example, voice data or Internet packet data are transported. Referring to <FIG>, the user plane protocol stack may be divided into Layer <NUM> (i.e., a PHY layer) and Layer <NUM>. Referring to <FIG>, the control plane protocol stack may be divided into Layer <NUM> (i.e., a PHY layer), Layer <NUM>, Layer <NUM> (e.g., an RRC layer), and a non-access stratum (NAS) layer. Layer <NUM>, Layer <NUM> and Layer <NUM> are referred to as an access stratum (AS).

In the 3GPP LTE system, the Layer <NUM> is split into the following sublayers: MAC, RLC, and PDCP. In the 3GPP NR system, the Layer <NUM> is split into the following sublayers: MAC, RLC, PDCP and SDAP. The PHY layer offers to the MAC sublayer transport channels, the MAC sublayer offers to the RLC sublayer logical channels, the RLC sublayer offers to the PDCP sublayer RLC channels, the PDCP sublayer offers to the SDAP sublayer radio bearers. The SDAP sublayer offers to <NUM> core network quality of service (QoS) flows.

In the 3GPP NR system, the main services and functions of the MAC sublayer include: mapping between logical channels and transport channels; multiplexing/ de-multiplexing of MAC SDUs belonging to one or different logical channels into/ from transport blocks (TB) delivered to/from the physical layer on transport channels; scheduling information reporting; error correction through hybrid automatic repeat request (HARQ) (one HARQ entity per cell in case of carrier aggregation (CA)); priority handling between UEs by means of dynamic scheduling; priority handling between logical channels of one UE by means of logical channel prioritization; padding. A single MAC entity may support multiple numerologies, transmission timings and cells. Mapping restrictions in logical channel prioritization control which numerology(ies), cell(s), and transmission timing(s) a logical channel can use.

Different kinds of data transfer services are offered by MAC. To accommodate different kinds of data transfer services, multiple types of logical channels are defined, i.e., each supporting transfer of a particular type of information. Each logical channel type is defined by what type of information is transferred. Logical channels are classified into two groups: control channels and traffic channels. Control channels are used for the transfer of control plane information only, and traffic channels are used for the transfer of user plane information only. Broadcast control channel (BCCH) is a downlink logical channel for broadcasting system control information, paging control channel (PCCH) is a downlink logical channel that transfers paging information, system information change notifications and indications of ongoing public warning service (PWS) broadcasts, common control channel (CCCH) is a logical channel for transmitting control information between UEs and network and used for UEs having no RRC connection with the network, and dedicated control channel (DCCH) is a point-to-point bi-directional logical channel that transmits dedicated control information between a UE and the network and used by UEs having an RRC connection. Dedicated traffic channel (DTCH) is a point-to-point logical channel, dedicated to one UE, for the transfer of user information. A DTCH can exist in both uplink and downlink. In downlink, the following connections between logical channels and transport channels exist: BCCH can be mapped to broadcast channel (BCH); BCCH can be mapped to downlink shared channel (DL-SCH); PCCH can be mapped to paging channel (PCH); CCCH can be mapped to DL-SCH; DCCH can be mapped to DL-SCH; and DTCH can be mapped to DL-SCH. In uplink, the following connections between logical channels and transport channels exist: CCCH can be mapped to uplink shared channel (UL-SCH); DCCH can be mapped to UL-SCH; and DTCH can be mapped to UL-SCH.

The RLC sublayer supports three transmission modes: transparent mode (TM), unacknowledged mode (UM), and acknowledged node (AM). The RLC configuration is per logical channel with no dependency on numerologies and/or transmission durations. In the 3GPP NR system, the main services and functions of the RLC sublayer depend on the transmission mode and include: transfer of upper layer PDUs; sequence numbering independent of the one in PDCP (UM and AM); error correction through ARQ (AM only); segmentation (AM and UM) and re-segmentation (AM only) of RLC SDUs; reassembly of SDU (AM and UM); duplicate detection (AM only); RLC SDU discard (AM and UM); RLC re-establishment; protocol error detection (AM only).

In the 3GPP NR system, the main services and functions of the PDCP sublayer for the user plane include: sequence numbering; header compression and decompression using robust header compression (ROHC); transfer of user data; reordering and duplicate detection; in-order delivery; PDCP PDU routing (in case of split bearers); retransmission of PDCP SDUs; ciphering, deciphering and integrity protection; PDCP SDU discard; PDCP re-establishment and data recovery for RLC AM; PDCP status reporting for RLC AM; duplication of PDCP PDUs and duplicate discard indication to lower layers. The main services and functions of the PDCP sublayer for the control plane include: sequence numbering; ciphering, deciphering and integrity protection; transfer of control plane data; reordering and duplicate detection; in-order delivery; duplication of PDCP PDUs and duplicate discard indication to lower layers.

In the 3GPP NR system, the main services and functions of the RRC sublayer include: broadcast of system information related to AS and NAS; paging initiated by 5GC or NG-RAN; establishment, maintenance and release of an RRC connection between the UE and NG-RAN; security functions including key management; establishment, configuration, maintenance and release of signaling radio bearers (SRBs) and data radio bearers (DRBs); mobility functions (including: handover and context transfer, UE cell selection and reselection and control of cell selection and reselection, inter-RAT mobility); QoS management functions; UE measurement reporting and control of the reporting; detection of and recovery from radio link failure; NAS message transfer to/from NAS from/to UE.

<FIG> shows a frame structure in a 3GPP based wireless communication system to which implementations of the present disclosure is applied.

The frame structure shown in <FIG> is purely exemplary and the number of subframes, the number of slots, and/or the number of symbols in a frame may be variously changed. In the 3GPP based wireless communication system, OFDM numerologies (e.g., subcarrier spacing (SCS), transmission time interval (TTI) duration) may be differently configured between a plurality of cells aggregated for one UE. For example, if a UE is configured with different SCSs for cells aggregated for the cell, an (absolute time) duration of a time resource (e.g., a subframe, a slot, or a TTI) including the same number of symbols may be different among the aggregated cells. Herein, symbols may include OFDM symbols (or CP-OFDM symbols), SC-FDMA symbols (or discrete Fourier transform-spread-OFDM (DFT-s-OFDM) symbols).

Referring to <FIG>, downlink and uplink transmissions are organized into frames. Each frame has Tf = <NUM> duration. Each frame is divided into two half-frames, where each of the half-frames has <NUM> duration. Each half-frame consists of <NUM> subframes, where the duration Tsf per subframe is <NUM>. Each subframe is divided into slots and the number of slots in a subframe depends on a subcarrier spacing. Each slot includes <NUM> or <NUM> OFDM symbols based on a cyclic prefix (CP). In a normal CP, each slot includes <NUM> OFDM symbols and, in an extended CP, each slot includes <NUM> OFDM symbols. The numerology is based on exponentially scalable subcarrier spacing Δf = <NUM>u*<NUM>.

Table <NUM> shows the number of OFDM symbols per slot Nslotsymb, the number of slots per frame Nframe,uslot, and the number of slots per subframe Nsubframe,uslot for the normal CP, according to the subcarrier spacing Δf = <NUM>u* <NUM>.

Table <NUM> shows the number of OFDM symbols per slot Nslotsymb, the number of slots per frame Nframe,uslot, and the number of slots per subframe Nsubframe,uslot for the extended CP, according to the subcarrier spacing Δf = <NUM>u*<NUM>.

A slot includes plural symbols (e.g., <NUM> or <NUM> symbols) in the time domain. For each numerology (e.g., subcarrier spacing) and carrier, a resource grid of Nsize,ugrid,x*NRBsc subcarriers and Nsubframe,usymb OFDM symbols is defined, starting at common resource block (CRB) Nstart,ugrid indicated by higher-layer signaling (e.g., RRC signaling), where Nsize,ugrid,x is the number of resource blocks (RBs) in the resource grid and the subscript x is DL for downlink and UL for uplink. NRBsc is the number of subcarriers per RB. In the 3GPP based wireless communication system, NRBsc is <NUM> generally. There is one resource grid for a given antenna port p, subcarrier spacing configuration u, and transmission direction (DL or UL). The carrier bandwidth Nsize,ugrid for subcarrier spacing configuration u is given by the higher-layer parameter (e.g., RRC parameter). Each element in the resource grid for the antenna port p and the subcarrier spacing configuration u is referred to as a resource element (RE) and one complex symbol may be mapped to each RE. Each RE in the resource grid is uniquely identified by an index k in the frequency domain and an index l representing a symbol location relative to a reference point in the time domain. In the 3GPP based wireless communication system, an RB is defined by <NUM> consecutive subcarriers in the frequency domain.

In the 3GPP NR system, RBs are classified into CRBs and physical resource blocks (PRBs). CRBs are numbered from <NUM> and upwards in the frequency domain for subcarrier spacing configuration u. The center of subcarrier <NUM> of CRB <NUM> for subcarrier spacing configuration u coincides with 'point A' which serves as a common reference point for resource block grids. In the 3GPP NR system, PRBs are defined within a bandwidth part (BWP) and numbered from <NUM> to NsizeBWP,i-<NUM>, where i is the number of the bandwidth part. The relation between the physical resource block nPRB in the bandwidth part i and the common resource block nCRB is as follows: nPRB = nCRB + NsizeBWP,i, where NsizeBWP,i is the common resource block where bandwidth part starts relative to CRB <NUM>. The BWP includes a plurality of consecutive RBs. A carrier may include a maximum of N (e.g., <NUM>) BWPs. A UE may be configured with one or more BWPs on a given component carrier. Only one BWP among BWPs configured to the UE can active at a time. The active BWP defines the UE's operating bandwidth within the cell's operating bandwidth.

In the present disclosure, the term "cell" may refer to a geographic area to which one or more nodes provide a communication system, or refer to radio resources. A "cell" as a geographic area may be understood as coverage within which a node can provide service using a carrier and a "cell" as radio resources (e.g., time-frequency resources) is associated with bandwidth which is a frequency range configured by the carrier. The "cell" associated with the radio resources is defined by a combination of downlink resources and uplink resources, for example, a combination of a DL component carrier (CC) and a UL CC. The cell may be configured by downlink resources only, or may be configured by downlink resources and uplink resources. Since DL coverage, which is a range within which the node is capable of transmitting a valid signal, and UL coverage, which is a range within which the node is capable of receiving the valid signal from the UE, depends upon a carrier carrying the signal, the coverage of the node may be associated with coverage of the "cell" of radio resources used by the node. Accordingly, the term "cell" may be used to represent service coverage of the node sometimes, radio resources at other times, or a range that signals using the radio resources can reach with valid strength at other times.

In CA, two or more CCs are aggregated. A UE may simultaneously receive or transmit on one or multiple CCs depending on its capabilities. CA is supported for both contiguous and non-contiguous CCs. When CA is configured, the UE only has one RRC connection with the network. At RRC connection establishment/ re-establishment/handover, one serving cell provides the NAS mobility information, and at RRC connection re-establishment/handover, one serving cell provides the security input. This cell is referred to as the primary cell (PCell). The PCell is a cell, operating on the primary frequency, in which the UE either performs the initial connection establishment procedure or initiates the connection re-establishment procedure. Depending on UE capabilities, secondary cells (SCells) can be configured to form together with the PCell a set of serving cells. An SCell is a cell providing additional radio resources on top of special cell (SpCell). The configured set of serving cells for a UE therefore always consists of one PCell and one or more SCells. For dual connectivity (DC) operation, the term SpCell refers to the PCell of the master cell group (MCG) or the primary SCell (PSCell) of the secondary cell group (SCG). An SpCell supports PUCCH transmission and contention-based random access, and is always activated. The MCG is a group of serving cells associated with a master node, comprised of the SpCell (PCell) and optionally one or more SCells. The SCG is the subset of serving cells associated with a secondary node, comprised of the PSCell and zero or more SCells, for a UE configured with DC. For a UE in RRC_CONNECTED not configured with CA/DC, there is only one serving cell comprised of the PCell. For a UE in RRC_CONNECTED configured with CA/DC, the term "serving cells" is used to denote the set of cells comprised of the SpCell(s) and all SCells. In DC, two MAC entities are configured in a UE: one for the MCG and one for the SCG.

<FIG> shows a data flow example in the 3GPP NR system to which implementations of the present disclosure is applied.

Referring to <FIG>, "RB" denotes a radio bearer, and "H" denotes a header. Radio bearers are categorized into two groups: DRBs for user plane data and SRBs for control plane data. The MAC PDU is transmitted/received using radio resources through the PHY layer to/from an external device. The MAC PDU arrives to the PHY layer in the form of a transport block.

In the PHY layer, the uplink transport channels UL-SCH and RACH are mapped to their physical channels physical uplink shared channel (PUSCH) and physical random access channel (PRACH), respectively, and the downlink transport channels DL-SCH, BCH and PCH are mapped to physical downlink shared channel (PDSCH), physical broadcast channel (PBCH) and PDSCH, respectively. In the PHY layer, uplink control information (UCI) is mapped to physical uplink control channel (PUCCH), and downlink control information (DCI) is mapped to physical downlink control channel (PDCCH). A MAC PDU related to UL-SCH is transmitted by a UE via a PUSCH based on an UL grant, and a MAC PDU related to DL-SCH is transmitted by a BS via a PDSCH based on a DL assignment.

Vehicle-to-everything (V2X) communication in <NUM> NR is described. Sections <NUM> and <NUM> of 3GPP TS <NUM> V1. <NUM> can be referred.

For V2X communication, two types of PCS reference points exist: the LTE based PCS reference point, and the NR based PCS reference point. A UE may use either type of PCS or both for V2X communication depending on the services the UE supports. The V2X communication over PCS reference point supports roaming and inter-public land mobile network (PLMN) operations. V2X communication over PCS reference point is supported when UE is "served by NR or E-UTRA" or when the UE is "not served by NR or E-UTRA".

A UE is authorized to transmit and receive V2X messages when it has valid authorization and configuration.

The V2X communication over PCS reference point has the following characteristics:.

The identifiers used in the V2X communication over PCS reference point are described below in detail. UE decides on the type of PCS reference point and Tx Profile to use for the transmission of a particular packet based on the configuration.

If the UE has an ongoing emergency session via industrial scientific and medical (IMS), the ongoing emergency session via IMS shall be prioritized over V2X communication over PCS reference point.

Broadcast mode of communication is supported over both LTE based PCS reference point and NR based PCS reference point. Therefore, when broadcast mode is selected for transmission over PCS reference point, PCS RAT selection needs to be performed based on configuration.

For LTE based PCS reference point, broadcast mode is the only supported communication mode.

For NR based PCS reference point, the broadcast mode also supports enhanced QoS handling.

Groupcast mode of communication is only supported over NR based PCS reference point.

Unicast mode of communication is only supported over NR based PCS reference point. The following principles apply when the V2X communication is carried over PCS unicast link:.

When the Application Layer in the UE initiates data transfer for a V2X service which requires unicast mode of communication over PCS reference point:.

After successful PCS unicast link establishment, UE A and UE B use the same pair of Layer-<NUM> IDs for subsequent PCS-S signaling message exchange and V2X service data transmission. The V2X layer of the transmitting UE indicates to the AS layer whether a transmission is for a PCS-S signaling message (i.e., direct communication request/accept, link identifier update request/response, disconnect request/response, link modification request/accept) or V2X service data.

For every PCS unicast link, a UE self-assigns a distinct PCS link identifier that uniquely identifies the PCS unicast link in the UE for the lifetime of the PCS unicast link. Each PCS unicast link is associated with a unicast link profile which includes:.

For privacy reason, the Application Layer IDs and Layer-<NUM> IDs may change during the lifetime of the PCS unicast link and, if so, shall be updated in the unicast link profile accordingly. The UE uses PCS link identifier to indicate the PCS unicast link to V2X Application Layer, therefore V2X Application Layer identifies the corresponding PCS unicast link even if there are more than one unicast link associated with one service type (e.g., the UE establishes multiple unicast links with multiple UEs for a same service type).

The unicast link profile shall be updated accordingly after a Layer-<NUM> link modification for an established PCS unicast link.

Identifiers for V2X communication is described.

Each UE has one or more Layer-<NUM> IDs for V2X communication over PCS reference point, consisting of:.

Source and destination Layer-<NUM> IDs are included in layer-<NUM> frames sent on the layer-<NUM> link of the PCS reference point identifying the layer-<NUM> source and destination of these frames. Source Layer-<NUM> IDs are always self-assigned by the UE originating the corresponding layer-<NUM> frames.

The selection of the source and destination Layer-<NUM> ID(s) by a UE depends on the communication mode of V2X communication over PCS reference point for this layer-<NUM> link, as described below in detail. The source Layer-<NUM> IDs may differ between different communication modes.

When IP-based V2X communication is supported, the UE configures a link local IPv6 address to be used as the source IP address. The UE may use this IP address for V2X communication over PCS reference point without sending neighbor solicitation and neighbor advertisement message for duplicate address detection.

If the UE has an active V2X application that requires privacy support in the current geographical area, as identified by configuration, in order to ensure that a source UE (e.g., vehicle) cannot be tracked or identified by any other UEs (e.g., vehicles) beyond a certain short time-period required by the application, the source Layer-<NUM> ID shall be changed over time and shall be randomized. For IP-based V2X communication over PCS reference point, the source IP address shall also be changed over time and shall be randomized. The change of the identifiers of a source UE must be synchronized across layers used for PC5, e.g., when the application layer ID changes, the source Layer-<NUM> ID and the source IP address need to be changed.

For broadcast mode of V2X communication over PCS reference point, the UE is configured with the destination Layer-<NUM> ID(s) to be used for V2X services. The destination Layer-<NUM> ID for a V2X communication is selected based on the configuration.

The UE self-selects a source Layer-<NUM> ID. The UE may use different source Layer-<NUM> IDs for different types of PCS reference points, i.e., LTE based PCS and NR based PC5.

For groupcast mode of V2X communication over PCS reference point, the V2X application layer may provide group identifier information. When the group identifier information is provided by the V2X application layer, the UE converts the provided group identifier into a destination Layer-<NUM> ID. When the group identifier information is not provided by the V2X application layer, the UE determines the destination Layer-<NUM> ID based on configuration of the mapping between service type (e.g., PSID/ITS-AID) and Layer-<NUM> ID.

The UE self-selects a source Layer-<NUM> ID.

For unicast mode of V2X communication over PCS reference point, the destination Layer-<NUM> ID used depends on the communication peer, which is discovered during the establishment of the PCS unicast link. The initial signaling for the establishment of the PCS unicast link may use a default destination Layer-<NUM> ID associated with the service type (e.g., PSID/ITS-AID) configured for PCS unicast link establishment. During the PCS unicast link establishment procedure, Layer-<NUM> IDs are exchanged, and should be used for future communication between the two UEs.

The Application Layer ID is associated with one or more V2X applications within the UE. If UE has more than one Application Layer IDs, each Application Layer ID of the same UE may be seen as different UE's Application Layer ID from the peer UE's perspective.

The UE maintains a mapping between the Application Layer IDs and the source Layer-<NUM> IDs used for the PCS unicast links, as the V2X application layer does not use the Layer-<NUM> IDs. This allows the change of source Layer-<NUM> ID without interrupting the V2X applications.

When Application Layer IDs change, the source Layer-<NUM> ID(s) of the PCS unicast link(s) shall be changed if the link(s) was used for V2X communication with the changed Application Layer IDs.

A UE may establish multiple PCS unicast links with a peer UE and use the same or different source Layer-<NUM> IDs for these PCS unicast links.

Sidelink resource allocation is described in detail. If the TX UE is in RRC_CONNECTED and configured for gNB scheduled sidelink resource allocation (e.g., Mode <NUM>), the TX UE may transmit sidelink UE Information including traffic pattern of Service, TX carriers and/or RX carriers mapped to service, QoS information related to Service (e.g. SQI, ProSe-per-packet priority (PPPP), ProSe-per-packet reliability (PPPR), QoS class identifier (QCI) value), and destination related to Service.

After receiving the sidelink UE Information, gNB constructs sidelink configuration at least including one or more resource pools for service and sidelink buffer status reporting (BSR) configuration. gNB signals the sidelink configuration to the TX UE and then the TX UE configures lower layers with sidelink configuration.

If a message becomes available in L2 buffer for sidelink transmission, the TX UE triggers scheduling request (SR), so that the TX UE transmits PUCCH resource. If PUCCH resource is not configured, the TX UE performs random access procedure as the SR. If an uplink grant is given at a result of the SR, the TX UE transmits sidelink BSR to gNB. The sidelink BSR indicates at least a destination index, a logical channel group (LCG), and a buffer size corresponding to the destination.

After receiving the sidelink BSR, gNB transmits a sidelink grant to the TX UE, e.g., by sending downlink control information (DCI) in PDCCH. The DCI may include an allocated sidelink resource. If the TX UE receives the DCI, the TX UE uses the sidelink grant for transmission to the RX UE.

Alternatively, if the TX UE is configured for UE autonomous scheduling of sidelink resource allocation (e.g., Mode <NUM>) regardless of RRC state, the TX UE autonomously select or reselect sidelink resources to create a sidelink grant used for transmission to the RX UE.

For NR sidelink transmission, a transmitting UE (TX UE) transmits sidelink control information (SCI) to a receiving UE (RX UE) to indicate sidelink shared channel (SL-SCH) transmission. When HARQ operation is used for SL-SCH transmissions, the SCI may indicate to the RX UE which SL-SCH transmissions should be received and combined for the same HARQ process. Thus, the RX UE will combine differently received SL-SCH transmissions into the same HARQ buffer of the HARQ process.

Meanwhile, as mentioned above, source Layer-<NUM> ID and destination Layer-<NUM> ID are used to uniquely identify different SL-SCH transmissions. Since UE should identify combinable SL-SCH transmissions based on SCI before decoding a MAC PDU on SL-SCH, UE only should rely on the SCI to identify combinable SL-SCH transmissions. Thus, SCI may need to indicate both source Layer-<NUM> ID and destination Layer-<NUM> ID. However, if each ID is <NUM> bits long as in LTE V2X, NR SCI transmission should support more than <NUM> bits which will be too heavy to be carried in a SCI transmission.

The following drawings are created to explain specific embodiments of the present disclosure. The names of the specific devices or the names of the specific signals/ messages/fields shown in the drawings are provided by way of example, and thus the technical features of the present disclosure are not limited to the specific names used in the following drawings.

<FIG> shows an example of a method performed by a first wireless device (e.g., receiving (RX) wireless device) configured to operate in a wireless communication system to which implementations of the present disclosure is applied.

In step S1000, the first wireless device establishes a sidelink with a second wireless device. That is, the first wireless device establishes a direct link with the second wireless device for a service.

In some implementations, the direct link may be a unicast link. That is, the service may be a unicast service. In this case, the first wireless device may be a receiving wireless device of the unicast service, and the second wireless device may be a transmitting wireless device of the unicast service.

In some implementations, the direct link may be a groupcast link. That is, the service may be a groupcast service. In this case, the first wireless device may be one of a receiving wireless devices of the groupcast service to be provided to a group including the first wireless device, and the second wireless device may be a wireless device of the groupcast service.

In some implementations, the first wireless device may determine at least one upper identifier (e.g., Layer-<NUM> ID) for the direct link.

For example, the upper ID may be either a source Layer-<NUM> ID or a destination Layer-<NUM> IDs for the direct link.

For example, the upper ID may be ID of the first wireless device or ID of the second wireless device.

In step S1010, the first wireless device monitors a control channel, transmitted by the second wireless device, addressed to at least the upper ID, and receives, from the second wires device, a lower ID associated with the upper ID via a data channel scheduled by the control channel. The lower ID is received via upper layer signaling, e.g., PC5-RRC message.

In some implementations, the control channel may carry the SCI, and the data channel may be SL-SCH.

In step S1020, after receiving the lower ID from the second wireless device, the first wireless device monitors SCI based on the lower ID and the upper ID. That is, the first wireless device may monitor the control channel indicating both the lower ID and the upper ID.

In some implementations, for sidelink transmission of the unicast service, the SCI on the control channel may include the lower ID (e.g., destination Layer-<NUM> ID) allocated to the first wireless device and the upper ID (e.g., source Layer-<NUM> ID) of the second wireless device and.

In some implementations, for sidelink transmission of the groupcast service, the SCI on the control channel may include the upper ID (e.g., destination Layer-<NUM> ID) of a group including the first wireless device and the lower ID (e.g., source Layer-<NUM> ID) allocated to the second wireless device. The upper ID of the group may correspond to the groupcast service.

In step S1030, the first wireless device receives, from the second wireless device, a data unit scheduled by the SCI.

In some implementations, a header of the data unit may include a source Layer-<NUM> ID and/or a destination Layer-<NUM> ID.

In some implementations, the first wireless device may transmit, to the second wireless device, a feedback for the data unit based on the lower ID.

In some implementations, the first wireless device may be in communication with at least one of a mobile device, a network, and/or autonomous vehicles other than the first wireless device.

Furthermore, the method in perspective of the first wireless device described above in <FIG> may be performed by first wireless device <NUM> shown in <FIG>, the wireless device <NUM> shown in <FIG>, the first wireless device <NUM> shown in <FIG> and/or the UE <NUM> shown in <FIG>.

More specifically, the first wireless device comprises at least one transceiver, at least processor, and at least one computer memory operably connectable to the at least one processor and storing instructions that, based on being executed by the at least one processor, perform operations.

The operations comprise establishing a sidelink with a second wireless device, receiving, via upper layer signaling from the second wireless device, a lower ID associated with an upper ID, monitoring SCI based on the lower ID and the upper ID, and receiving, from the second wireless device, a data unit scheduled by the SCI.

In some implementations, for sidelink transmission of the unicast service, the SCI on the control channel may include the lower ID (e.g., destination Layer-<NUM> ID) allocate to the first wireless device and the upper ID (e.g., source Layer-<NUM> ID) of the second wireless device and.

Furthermore, the method in perspective of the first wireless device described above in <FIG> may be performed by control of the processor <NUM> included in the first wireless device <NUM> shown in <FIG>, by control of the communication unit <NUM> and/or the control unit <NUM> included in the wireless device <NUM> shown in <FIG>, by control of the processor <NUM> included in the first wireless device <NUM> shown in <FIG> and/or by control of the processor <NUM> included in the UE <NUM> shown in <FIG>.

More specifically, the first wireless device configured to operate in a wireless communication system (e.g., wireless device) comprises at least processor, and at least one computer memory operably connectable to the at least one processor. The at least one processor is configured to perform operations comprising establishing a sidelink with a second wireless device, receiving, via upper layer signaling from the second wireless device, a lower ID associated with an upper ID, monitoring SCI based on the lower ID and the upper ID, and receiving, from the second wireless device, a data unit scheduled by the SCI.

Furthermore, the method in perspective of the first wireless device described above in <FIG> may be performed by a software code <NUM> stored in the memory <NUM> included in the first wireless device <NUM> shown in <FIG>.

More specifically, at least one computer readable medium (CRM) stores instructions that, based on being executed by at least one processor, perform operations comprising establishing a sidelink with a second wireless device, receiving, via upper layer signaling from the second wireless device, a lower ID associated with an upper ID, monitoring SCI based on the lower ID and the upper ID, and receiving, from the second wireless device, a data unit scheduled by the SCI.

<FIG> shows an example of a method performed by a second wireless device (e.g., transmitting (TX) wireless device) configured to operate in a wireless communication system to which implementations of the present disclosure is applied.

In some implementations, the second wireless device may receive allocated sidelink resources (e.g., sidelink grant) from a network. Additionally and/or alternatively, the second wireless device may autonomously select sidelink resources from a pool of sidelink resources.

In step S1100, the second wireless device establishes a sidelink with a first wireless device. That is, the second wireless device establishes a direct link with the first wireless device for a service.

In some implementations, the direct link may be a unicast link. That is, the service may be a unicast service. In this case, the second wireless device may be a transmitting wireless device of the unicast service and the first wireless device may be a receiving wireless device of the unicast service.

In some implementations, the direct link may be a groupcast link. That is, the service may be a groupcast service. In this case, the second wireless device may be a wireless device of the groupcast service and the first wireless device may be one of a receiving wireless devices of the groupcast service to be provided to a group including the first wireless device.

In step S1110, the second wireless device creates at least one lower ID associated with the upper ID.

In step S1120, the second wireless device transmits, to the first wireless device, the lower ID via a data channel, e.g., SL-SCH, scheduled by a control channel, e. The lower ID is transmitted via upper layer signaling, e.g., PC5-RRC message.

In some implementations, the second wireless device may also transmit, to the first wireless device, the upper ID together with the lower ID. The lower ID may be carried in a MAC PDU on SL-SCH transmission, and the upper ID may be carried in SCI associated with the SL-SCH transmission.

In step S1130, the second wireless device transmits, to the first wireless device, a data unit scheduled by SCI indicating both the upper ID and the lower ID. That is, the second wireless device performs data transmission of the service scheduled by the control channel indicating both the upper ID and the lower ID to the first wireless device.

In some implementations, for sidelink transmission of the unicast service, the SCI on the control channel may include the lower ID (e.g., destination Layer-<NUM> ID) allocated to the first wireless device and the upper ID (e.g., source Layer-<NUM> ID) of the second wireless device and.

In some implementations, the data unit may be transmitted on a data channel, e.g., SL-SCH.

In some implementations, the upper ID and the lower ID may be associated with different wireless devices.

In some implementations, the second wireless device may receive, from the first wireless device, a feedback for the data unit based on the lower ID.

In some implementations, the second wireless device may be in communication with at least one of a mobile device, a network, and/or autonomous vehicles other than the second wireless device.

Furthermore, the method in perspective of the second wireless device described above in <FIG> may be performed by second wireless device <NUM> shown in <FIG>, the wireless device <NUM> shown in <FIG>, the second wireless device <NUM> shown in <FIG> and/or the UE <NUM> shown in <FIG>.

More specifically, the second wireless device comprises at least one transceiver, at least processor, and at least one computer memory operably connectable to the at least one processor and storing instructions that, based on being executed by the at least one processor, perform operations.

The operations comprise establishing a sidelink with a first wireless device, creating a lower ID associated with an upper ID, transmitting, to the first wireless device, the lower ID, and transmitting, to the first wireless device, a data unit scheduled by SCI indicating both the upper ID and the lower ID.

Furthermore, the method in perspective of the second wireless device described above in <FIG> may be performed by control of the processor <NUM> included in the second wireless device <NUM> shown in <FIG>, by control of the communication unit <NUM> and/or the control unit <NUM> included in the wireless device <NUM> shown in <FIG>, by control of the processor <NUM> included in the second wireless device <NUM> shown in <FIG> and/or by control of the processor <NUM> included in the UE <NUM> shown in <FIG>.

More specifically, the second wireless device configured to operate in a wireless communication system (e.g., wireless device) comprises at least processor, and at least one computer memory operably connectable to the at least one processor. The at least one processor is configured to perform operations comprising establishing a sidelink with a first wireless device, creating a lower ID associated with an upper ID, transmitting, to the first wireless device, the lower ID, and transmitting, to the first wireless device, a data unit scheduled by SCI indicating both the upper ID and the lower ID.

Furthermore, the method in perspective of the second wireless device described above in <FIG> may be performed by a software code <NUM> stored in the memory <NUM> included in the second wireless device <NUM> shown in <FIG>.

More specifically, at least one CRM stores instructions that, based on being executed by at least one processor, perform operations comprising establishing a sidelink with a first wireless device, creating a lower ID associated with an upper ID, transmitting, to the first wireless device, the lower ID, and transmitting, to the first wireless device, a data unit scheduled by SCI indicating both the upper ID and the lower ID.

<FIG> shows an example of PC5 procedures for a UE performing sidelink communication, according to an embodiment of the present invention.

In some implementations, RX UE1 and/or RX UE2 in <FIG> may correspond to a first wireless device described above in <FIG> and/or <FIG>. In some implementations, TX UE in <FIG> may correspond to a second wireless device described above in <FIG> and/or <FIG>.

In some implementations, if the TX UE is in RRC_CONNECTED and configured for gNB scheduled sidelink resource allocation, the TX UE receives a sidelink grant from a network, e.g., by DCI in PDCCH. The DCI may include an allocated sidelink resource. The TX UE may use the sidelink grant for transmission to the RX UE.

In some implementations, if the TX UE is configured for UE autonomous scheduling of sidelink resource allocation regardless of RRC state, the TX UE autonomously select and/or reselect sidelink resources to create a sidelink grant used for transmission to the RX UE.

In step S1200, the TX UE establishes a direct link with the RX UE1 for a unicast service. The TX UE determines at least one Layer-<NUM> ID (e.g., upper layer ID) for the direct link. The TX UE and the RX UE1 performs PC5-S direct link setup procedure for unicast service. The TX UE and the RX UE1 may exchange the determined at least one Layer-<NUM> ID.

The Layer-<NUM> ID includes a source Layer-<NUM> ID and a destination Layer-<NUM> ID for the direct link. The TX UE and the RX UE determine both source Layer-<NUM> ID and destination Layer-<NUM> ID for the direct link.

In some implementations, the Layer-<NUM> ID may include ID of the TX UE or ID of the RX UE1.

In step S1202, the TX UE establishes a direct link with the RX UE1 and the RX UE2 for a groupcast service (or a broadcast service). The TX UE determines at least one Layer-<NUM> ID for the direct link. The TX UE and the RX UE1/UE2 performs PC5-S direct link setup procedure for groupcast service. The TX UE and the RX UE1/UE2 may exchange the determined at least one Layer-<NUM> ID.

In some implementations, the Layer-<NUM> ID may include at least one of a source Layer-<NUM> ID and/or a destination Layer-<NUM> ID for the groupcast service. The TX UE may determine both source Layer-<NUM> ID and destination Layer-<NUM> ID for the groupcast service. The source Layer-<NUM> ID may correspond to the TX UE while the destination Layer-<NUM> ID may correspond to a group including the RX UE1 and RX UE2, or the groupcast service.

In step S1210, the TX UE creates at least one Layer-<NUM> ID (e.g., Layer-<NUM> ID #<NUM>) associated with the Layer-<NUM> ID for the unicast service. In step S1212, the TX UE allocates the Layer-<NUM> ID #<NUM> to the RX UE1 and transmits the Layer-<NUM> ID #<NUM> to the RX UE1 via a PC5-RRC message transmitted on SL-SCH scheduled by SCI.

In some implementations, the TX UE may also transmit the Layer-<NUM> ID associated with the Layer-<NUM> ID #<NUM> to the RX UE1 together with the Layer-<NUM> ID #<NUM>. In this case, the Layer-<NUM> ID #<NUM> may be carried in a MAC PDU on SL-SCH transmission while the Layer-<NUM> ID may be carried in the SCI which schedules the SL-SCH transmission carrying the Layer-<NUM> ID #<NUM>.

In some implementations, for unicast service, the Layer-<NUM> ID #<NUM> may be a destination Layer-<NUM> ID allocated to the RX UE1.

In step S1220, the TX UE creates at least one Layer-<NUM> ID (e.g., Layer-<NUM> ID #<NUM>) associated with the Layer-<NUM> ID for the groupcast service. In step S1222, the TX UE allocates the Layer-<NUM> ID #<NUM> to the RX UE1 and RX UE2 and transmits the Layer-<NUM> ID #<NUM> to the RX UE1 and RX UE2 via a PC5-RRC message transmitted on SL-SCH scheduled by SCI.

In some implementations, the TX UE may also transmit the Layer-<NUM> ID associated with the Layer-<NUM> ID #<NUM> to the RX UE1 and RX UE2 together with the Layer-<NUM> ID #<NUM>. In this case, the Layer-<NUM> ID #<NUM> may be carried in a MAC PDU on SL-SCH transmission while the Layer-<NUM> ID may be carried in the SCI which schedules the SL-SCH transmission carrying the Layer-<NUM> ID #<NUM>.

In some implementations, for groupcast service, the Layer-<NUM> ID #<NUM> may be a source Layer-<NUM> ID allocated to the TX UE. Alternatively, the Layer-<NUM> ID #<NUM> may be a destination Layer-<NUM> ID allocated to a group including the RX UE1 and RX UE2 or the groupcast service.

In step S1230, the TX UE transmits SCI indicating both the Layer-<NUM> ID #<NUM> and the Layer-<NUM> ID. In step S1232, the TX UE transmits a MAC PDU of the unicast service on SL-SCH scheduled by the SCI.

For unicast service, the Layer-<NUM> ID #<NUM> is the destination Layer-<NUM> ID allocated to RX UE1. The Layer-<NUM> ID is the source Layer-<NUM> ID allocated to the TX UE.

In some implementations, the header of the MAC PDU may or may not include at least of the source Layer-<NUM> ID and/or destination Layer-<NUM> ID.

In some implementations, after receiving the Layer-<NUM> ID #<NUM> in step S1212, the RX UE1 monitors SCI transmission indicating both the Layer-<NUM> ID #<NUM> and the Layer-<NUM> ID. If the received SCI indicates both the Layer-<NUM> ID #<NUM> and the Layer-<NUM> ID, the RX UE1 receives the SL-SCH transmission of the unicast service scheduled by the SCI in step S1232.

In step S1234, if HARQ feedback for SL-SCH transmission is indicated in the SCI or has been configured by the PC5-RRC message, the RX UE1 may transmit HARQ feedback such as HARQ ACK or NACK to the TX UE. The HARQ feedback may indicate the Layer-<NUM> ID #<NUM> and/or the Layer-<NUM> ID.

In some implementations, when HARQ feedback is indicated and/or configured, and if transmission of the MAC PDU is not positively acknowledged (e.g., HARQ NACK), the TX UE may perform HARQ retransmission of the MAC PDU for which SCI transmission indicates both the same Layer-<NUM> ID #<NUM> and the same Layer-<NUM> ID for retransmission.

In step S1240, the TX UE transmits SCI indicating both the Layer-<NUM> ID #<NUM> and the Layer-<NUM> ID. In step S1232, the TX UE transmits a MAC PDU of the groupcast service on SL-SCH scheduled by the SCI.

In some implementations, for groupcast service, the Layer-<NUM> ID #<NUM> may be the source Layer-<NUM> ID allocated to RX UE1. The Layer-<NUM> ID may be a destination Layer-<NUM> ID of the groupcast service used for both the RX UE1 and RX UE2.

In some implementations, after receiving the Layer-<NUM> ID #<NUM> in step S1222, the RX UEs (i.e., RX UE1/RX UE2) monitor SCI transmission indicating both the Layer-<NUM> ID #<NUM> and the Layer-<NUM> ID. If the received SCI indicates both the Layer-<NUM> ID #<NUM> and the Layer-<NUM> ID, the RX UEs receive the SL-SCH transmission of the groupcast service scheduled by the SCI in step S1242.

In step S1244, if HARQ feedback for SL-SCH transmission is indicated in the SCI or has been configured by the PC5-RRC message, each RX UE may transmit HARQ feedback such as HARQ ACK or NACK to the TX UE. The HARQ feedback may indicate the Layer-<NUM> ID #<NUM> and/or the Layer-<NUM> ID. Different RX UEs may use the same sidelink resource and/or different sidelink resources for transmission of the HARQ feedback.

In some implementations, when HARQ feedback is indicated and/or configured, and if transmission of the MAC PDU is not positively acknowledged (e.g., HARQ NACK) at least by one RX UE, the TX UE may perform HARQ retransmission of the MAC PDU for which SCI transmission indicates both the same Layer-<NUM> ID #<NUM> and the same Layer-<NUM> ID for retransmission.

In some implementations, each RX UE may perform measurements on transmissions from the TX UE. When the RX UE transmits measured results such as channel quality indicator (CQI) report, channel state information (CSI) report, reference signal received power (RSRP), reference signal received quality (RSRQ), etc., in a message, the RX UE may indicate at least one of the Layer-<NUM> ID and the Layer-<NUM> ID for transmission of the message.

Claim 1:
A method performed by a first wireless device (<NUM>) configured to operate in a wireless communication system, the method comprising:
establishing a direct link with a second wireless device (<NUM>) for a unicast service;
identifying a set of a source layer-<NUM> identifier, ID, and a destination layer-<NUM> ID based on establishing the direct link;
receiving sidelink control information, SCI, from the second wireless device (<NUM>); and
based on the SCI including i) information for a layer-<NUM> ID associated with the destination layer-<NUM> ID and ii) information for the source layer-<NUM> ID, receiving, from the second wireless device (<NUM>), a data on a data channel scheduled by the SCI.