Method for sidelink unlicensed channel access - Patents.com

Abstract

There may be approaches for sidelink unlicensed (SL U) channel access in Mode 2. For example, a wireless transmit / receive unit (WTRU) may perform SL U channel access and resource selection for channel occupation time (COT) sharing and COT initiation within a resource selection window (RSW). The WTRU may detect the COT and share based on control information such as remaining duration, number of scheduled transmissions within the COT, frequency resource allocation, priority, cast type, WTRU source and / or destination ID, COT / resource reservation, channel congestion, etc. The WTRU may determine SL COT initiation based on LBT and SCI sensing information including COT / resource reservation, priority, cast type, WTRU source and / or destination ID, channel congestion, etc. The WTRU may determine transmission resources in the SL COT to be shared and initiated based on the WTRU source and / or destination ID of the transmitting TB, the RB interlace allocation indicated in the decoded SCI associated with the overlapping reserved COT.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Application No. 63 / 308,341, filed February 9, 2022, U.S. Provisional Application No. 63 / 327,206, filed April 4, 2022, U.S. Provisional Application No. 63 / 395,220, filed August 4, 2022, U.S. Provisional Application No. 63 / 410,907, filed September 28, 2022, and U.S. Provisional Application No. 63 / 421,831, filed November 2, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] In unlicensed spectrum communications, a process known as listen-before-talk may be employed to ensure that each device operating in the unlicensed spectrum does not interfere with another device. However, there is a need to improve upon this basic concept to provide a more efficient and capable system for communicating in the unlicensed spectrum. Summary of the Invention

[0003] There may be approaches for sidelink unlicensed (SL U) channel access in Mode 2. For example, a wireless transmit receive unit (WTRU) may perform SL U channel access and resource selection for channel occupancy time (COT) sharing and COT initiation within a resource selection window (RSW). The WTRU may detect the COT and share based on control information such as remaining duration, number of scheduled transmissions in the COT, frequency resource allocation, priority, cast type, WTRU source and / or destination ID, COT / resource reservation, channel congestion, etc. The WTRU may determine SL COT initiation based on LBT and SCI sensing information including COT / resource reservation, priority, cast type, WTRU source and / or destination ID, channel congestion, etc. [Brief description of the drawings]

[0004] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings, in which like reference numbers indicate similar elements and in which: [Figure 1A] FIG. 1A is a system diagram illustrating an example communication system in which one or more disclosed embodiments may be implemented. [Figure 1B] FIG. 1B is a system diagram illustrating an example wireless transmit / receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1A, according to one embodiment. [Figure 1C] FIG. 1C is a system diagram illustrating an example radio access network (RAN) and an example core network (CN) that may be used within the communication system illustrated in FIG. 1A, according to one embodiment. [Figure 1D]FIG. 1D is a system diagram illustrating a further exemplary RAN and a further exemplary CN that may be used within the communications system illustrated in FIG. 1A, according to one embodiment. [Figure 2A] FIG. 2A shows an example of a SL U resource allocation unit. [Figure 2B] FIG. 2B shows an example of a SL U resource allocation unit. [Diagram 3] FIG. 3 shows an example of a sharing WTRU decision for Type 2 LBT for COT sharing. [Figure 4A] FIG. 4A shows an example of an SL U channel access and resource selection example. [Figure 4B] FIG. 4B shows an example of an SL U channel access and resource selection example. [Figure 4C] FIG. 4C shows an example of a SL U channel access and resource selection example. [Diagram 5] FIG. 5 shows an example of a WTRU determination of a COT starting position in a SL slot. [Figure 6] FIG. 6 shows an example of WTRU resource group / COT selection before Type 1 LBT for COT initiation. [Figure 7] FIG. 7 shows an example of a process for a WTRU to transmit in an unlicensed spectrum. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] As discussed herein, one or more abbreviations may be present, such as those shown in Table 1.

[0006] [Table 1-1]

[0007] [Table 1-2]

[0008] 1A is a diagram illustrating an example communications system 100 in which one or more disclosed embodiments may be implemented. Communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcasts, etc., to multiple wireless users. Communications system 100 may enable multiple wireless users to access such content through sharing of system resources, including wireless bandwidth. For example, the communications system 100 may use one or more channel access methods such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique-word discrete Fourier transform Spread OFDM (ZT-UW-DFT-S-OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multicarrier (FBMC), and the like.

[0009] 1A, communications system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104, a core network (CN) 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, although it will be understood that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and / or network elements. Each of WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d, any of which may be referred to as a station (STA), may be configured to transmit and / or receive wireless signals and may include user equipment (UE), mobile stations, landline or mobile subscriber units, subscription-based units, pagers, mobile phones, personal digital assistants (PDAs), smartphones, laptops, netbooks, personal computers, wireless sensors, hotspots or Mi-Fi devices, Internet of Things (IoT) devices, watches or other wearables, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in industrial and / or automated processing chain contexts), home electronic devices, devices operating in commercial and / or industrial wireless networks, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0010] The communications system 100 may also include a base station 114a and / or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communications networks, such as the CN 106, the Internet 110, and / or other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node B, an eNode B (eNode B, eNB), a Home Node B, a home eNode B, a next generation Node B (eNode B, gNB, etc.), a new radio (NR) Node B, a site controller, an access point (AP), a wireless router, etc. Although the base stations 114a, 114b are each illustrated as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0011] The base station 114a may be part of the RAN 104, which may also include other base stations, such as a base station controller (BSC), a radio network controller (RNC), relay nodes, and / or network elements (not shown). The base station 114a and / or the base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be referred to as cells (not shown). These frequencies may be licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide wireless service coverage for a particular geographic area, which may be relatively fixed or may change over time. A cell may be further divided into cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, i.e., one transceiver for each sector of the cell. In one embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and may utilize multiple transceivers for each sector of the cell, for example, using beamforming to transmit and / or receive signals in a desired spatial direction.

[0012] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d via an air interface 116, which may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0013] More specifically, as noted above, the communications system 100 may be a multiple access system, but may use one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, etc. For example, the base stations 114a and the WTRUs 102a, 102b, 102c of the RAN 104 may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may establish the air interface 116 using wideband CDMA (WCDMA). WCDMA may include communications protocols such as High-Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High-Speed ​​Downlink Packet Access (HSDPA) and / or High-Speed ​​Uplink Packet Access (UL)).

[0014] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as Evolved UMTS Terrestrial Radio Access (E-UTRA), which may establish the air interface 116 using Long Term Evolution (LTE) and / or LTE-Advanced (LTE-A) and / or LTE-Advanced Pro (LTE-A Pro).

[0015] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement a radio technology such as NR radio access, which may establish the air interface 116 using NR.

[0016] In one embodiment, the base station 114a and the WTRUs 102a, 102b, 102c may implement multiple radio access technologies. For example, the base station 114a and the WTRUs 102a, 102b, 102c may implement LTE radio access and NR radio access together, e.g., using dual connectivity (DC) principles. Thus, the air interface utilized by the WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and / or transmissions sent to and from multiple types of base stations (e.g., eNBs and gNBs).

[0017] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement a wireless technology such as IEEE 802.11 (i.e., Wireless Fidelity, Wi-Fi), IEEE 802.16 (i.e., Worldwide Interoperability for Microwave Access, WiMAX), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global System for Mobile communications (GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), or the like.

[0018] 1A may be, for example, a wireless router, a Home NodeB, a Home eNodeB, or an access point, and may utilize any suitable RAT to facilitate wireless connectivity in a localized area, such as an office, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, etc. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology, such as IEEE 802.11, to establish a wireless local area network (WLAN). In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology, such as IEEE 802.15, to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may establish a picocell or a femtocell using a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.). As shown in FIG. 1A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not need to access the Internet 110 through the CN 106.

[0019] The RAN 104 may communicate with the CN 106, which may be any type of network configured to provide voice, data, application, and / or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have various quality of service (QoS) requirements, such as, for example, different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 may provide call control, billing services, mobile location-based services, prepaid calling, Internet connectivity, video distribution, etc., and / or perform high-level security functions such as user authentication. Although not shown in FIG. 1A, it will be understood that the RAN 104 and / or the CN 106 may communicate directly or indirectly with other RANs that use the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may utilize NR radio technology, the CN 106 may also communicate with another RAN (not shown) employing GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or Wi-Fi radio technology.

[0020] The CN 106 may also serve as a gateway for the WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and / or other networks 112. The PSTN 108 may include a circuit-switched telephone network providing plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), the user datagram protocol (UDP), and / or the internet protocol (IP) of the TCP / IP Internet protocol suite. The networks 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs that may use the same RAT as the RAN 104 or a different RAT.

[0021] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities (e.g., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links). For example, the WTRU 102c shown in FIG. 1A may be configured to communicate with a base station 114a, which may employ a cellular-based wireless technology, and a base station 114b, which may employ an IEEE 802 wireless technology.

[0022] Figure 1B is a system diagram illustrating an example WTRU 102. As shown in Figure 1B, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, non-removable memory 130, removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and / or other peripherals 138. It will be understood that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0023] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit / receive element 122. Although FIG. 1B illustrates the processor 118 and the transceiver 120 as separate components, it will be understood that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0024] The transmit / receive element 122 may be configured to transmit or receive signals to or from a base station (e.g., base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In one embodiment, the transmit / receive element 122 may be an emitter / detector configured to transmit and / or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and light signals. It will be appreciated that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0025] 1B as a single element, the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0026] The transceiver 120 may be configured to modulate signals transmitted by the transmit / receive element 122 and demodulate signals received by the transmit / receive element 122. As mentioned above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as, for example, NR and IEEE 802.11.

[0027] The processor 118 of the WTRU 102 may be coupled to and may receive user-entered data from a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light-emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may access information from and store data in any type of suitable memory, such as non-removable memory 130 and / or removable memory 132. The non-removable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, etc. In other embodiments, the processor 118 may access information from and store data in memory that is not physically located on the WTRU 102, such as on a server or home computer (not shown).

[0028] The processor 118 may receive power from the power source 134 and may be configured to distribute and / or control the power to other components in the WTRU 102. The power source 134 may be any suitable device for providing power to the WTRU 102. For example, the power source 134 may include one or more dry batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, etc.

[0029] The processor 118 may also be coupled to a GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to, or in lieu of, information from the GPS chipset 136, the WTRU 102 may receive location information from a base station (e.g., base stations 114a, 114b) over the air interface 116 and / or determine its location based on the timing of signals being received from two or more nearby base stations. It will be appreciated that the WTRU 102 may obtain location information by way of any suitable location determination method while remaining consistent with an embodiment.

[0030] The processor 118 may further be coupled to other peripherals 138, which may include one or more software and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an electronic compass, a satellite transceiver, a digital camera (for photos and / or videos), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, a virtual reality and / or augmented reality (VR / AR) device, an activity tracker, and the like. The peripherals 138 may include one or more sensors. The sensor may be one or more of a gyroscope, an accelerometer, a Hall effect sensor, a magnetometer, an orientation sensor, a proximity sensor, a temperature sensor, a time sensor, a geolocation sensor, an altimeter, a light sensor, a touch sensor, a magnetometer, a barometer, a gesture sensor, a biometric sensor, a humidity sensor, and the like.

[0031] The WTRU 102 may include a full-duplex radio where the transmission and reception of some or all of the signals (e.g., associated with a particular subframe of both the UL (e.g., for transmission) and DL (e.g., for reception)) may be simultaneous and / or together. The full-duplex radio may include an interference management unit to reduce and or substantially eliminate self-interference via either hardware (e.g., a choke) or signal processing via a processor (e.g., via a separate processor (not shown) or via processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio where the transmission and reception of some or all of the signals (e.g., associated with a particular subframe of either the UL (e.g., for transmission) or DL ​​(e.g., for reception)) may be simultaneous and / or together.

[0032] 1C is a system diagram illustrating the RAN 104 and the CN 106, according to one embodiment. As mentioned above, the RAN 104 may employ E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also communicate with the CN 106.

[0033] The RAN 104 may include eNodeBs 160a, 160b, 160c, although it will be understood that the RAN 104 may include any number of eNodeBs while remaining consistent with an embodiment. The eNodeBs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In an embodiment, the eNodeBs 160a, 160b, 160c may implement MIMO technology. Thus, the eNodeB 160a may, for example, use multiple antennas to transmit wireless signals to and / or receive wireless signals from the WTRU 102a.

[0034] Each of the eNodeBs 160a, 160b, 160c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the UL and / or DL, etc. As shown in FIG 1C, the eNodeBs 160a, 160b, 160c may communicate with each other via an X2 interface.

[0035] 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (PGW) 166. Although the foregoing elements are illustrated as part of the CN 106, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0036] The MME 162 may be connected to each of the eNodeBs 162a, 162b, 162c in the RAN 104 via an S1 interface and may function as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, activating / deactivating bearers, selecting a particular serving gateway during initial attachment of the WTRUs 102a, 102b, 102c, etc. The MME 162 may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM and / or WCDMA.

[0037] The SGW 164 may be connected to each of the eNodeBs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to and from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring the user plane during inter-eNodeB handover, triggering paging when DL data is available to the WTRUs 102a, 102b, 102c, and managing and storing the context of the WTRUs 102a, 102b, 102c.

[0038] The SGW 164 may be connected to a PGW 166, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0039] The CN 106 may facilitate communications with other networks. For example, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to circuit-switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the CN 106 may include or communicate with an IP gateway (e.g., an IP multimedia subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0040] Although the WTRU is depicted in FIGS. 1A-1D as a wireless terminal, in certain representative embodiments, it is contemplated that such a terminal may use a wired communications interface (e.g., temporarily or permanently) with the communications network.

[0041] In an exemplary embodiment, the other network 112 may be a WLAN.

[0042] A WLAN in infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) of the BSS and one or more stations (STAs) associated with the AP. The AP may have access or interface to a Distribution System (DS) or another type of wired / wireless network that carries traffic within the BSS and / or outside the BSS. Traffic originating from outside the BSS to the STA may arrive through the AP and be delivered to the STA. Traffic originating from the STA to a destination outside the BSS may be sent to the AP to be delivered to the respective destination. Traffic between STAs within the BSS may be sent, for example, through the AP, where the source STA may send traffic to the AP, which may deliver the traffic to the destination STA. Traffic between STAs within the BSS may be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic may be sent between (e.g., directly between) the source STA and the destination STA using a direct link setup (DLS). In certain representative embodiments, the DLS may use 802.11e DLS or 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and STAs (e.g., all of the STAs) within or using the IBSS may communicate directly with each other. The IBSS mode of communication may be referred to herein as an "ad-hoc" communication mode.

[0043] When using an 802.11ac infrastructure mode of operation or a similar mode of operation, an AP may transmit a beacon on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., a 20 MHz wide bandwidth) or a dynamically set width. The primary channel may be the operating channel of the BSS, but may be used by STAs to establish a connection with the AP. In certain representative embodiments, Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. With CSMA / CA, STAs (e.g., all STAs), including the AP, may sense the primary channel. If the primary channel is sensed / detected and / or determined to be busy by a particular STA, the particular STA may back off. One STA (e.g., only one station) may transmit at any given time in a given BSS.

[0044] A High Throughput (HT) STA may use a 40 MHz wide channel for communication, which may be formed, for example, through a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels.

[0045] A Very High Throughput (VHT) STA may support 20 MHz, 40 MHz, 80 MHz, and / or 160 MHz wide channels. A 40 MHz and / or 80 MHz channel may be formed by combining multiple contiguous 20 MHz channels. A 160 MHz channel may be formed by combining eight contiguous 20 MHz channels or by combining two non-contiguous 80 MHz channels, which may be referred to as an 80+80 configuration. For the 80+80 configuration, after channel encoding, the data may pass through a segment parser that may split the data into two streams. Inverse Fast Fourier Transform (IFFT) processing and time domain processing may be performed separately on each stream. The streams may be mapped to two 80 MHz channels and the data may be transmitted by the transmitting STA. At the receiver of the receiving STA, the operations described above for the 80+80 configuration may be reversed and the combined data may be sent to the Medium Access Control (MAC).

[0046] Sub-1 GHz operation modes are supported by 802.11af and 802.11ah. The channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah compared to those used in 802.11n and 802.11ac. 802.11af supports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space (TVWS) spectrum, while 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support meter-type control / machine-type communications (MTC), such as MTC devices in macro coverage areas. MTC devices may have limited capabilities, including certain capabilities, for example, support for (e.g., support only for) certain and / or limited bandwidths. The MTC device may include a battery that has a battery life above a threshold (eg, to maintain a very long battery life).

[0047] WLAN systems that may support multiple channels and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include a channel that may be designated as a primary channel. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be configured and / or limited by the STAs among all STAs operating in the BSS that support the smallest bandwidth operating mode. In an 802.11ah embodiment, the primary channel may be 1 MHz wide for STAs (e.g., MTC-type devices) that support (e.g., only) the 1 MHz mode, even if the AP and other STAs in the BSS support 2 MHz, 4 MHz, 8 MHz, 16 MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or Network Allocation Vector (NAV) configuration may depend on the status of the primary channel. For example, if a STA transmitting to an AP (e.g., supporting only a 1 MHz mode of operation) has a busy primary channel, all of the available frequency bands may be considered busy even if most of the available frequency bands are idle.

[0048] In the United States, the available frequency bands that can be used by 802.11ah are 902MHz to 928MHz. In South Korea, the available frequency bands are 917.5MHz to 923.5MHz. In Japan, the available frequency bands are 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz depending on the country code.

[0049] 1D is a system diagram illustrating the RAN 104 and the CN 106, according to one embodiment. As mentioned above, the RAN 104 may use NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also communicate with the CN 106.

[0050] The RAN 104 may include gNBs 180a, 180b, 180c, although it will be understood that the RAN 104 may include any number of gNBs while remaining consistent with an embodiment. The gNBs 180a, 180b, 180c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In an embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, the gNBs 180a, 108b may utilize beamforming to transmit signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a may transmit and / or receive wireless signals to and from the WTRU 102a, for example, using multiple antennas. In one embodiment, the gNBs 180a, 180b, 180c may implement carrier aggregation technology. For example, the gNB 180a may transmit multiple component carriers to the WTRU 102a (not shown). A subset of these component carriers may be on an unlicensed spectrum, while the remaining component carriers may be on a licensed spectrum. In one embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, the WTRU 102a may receive coordinated transmissions from the gNBs 180a and 180b (and / or gNB 180c).

[0051] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with scalable numerology. For example, the OFDM symbol spacing and / or OFDM subcarrier spacing may vary for different transmissions, different cells, and / or different portions of the wireless transmission spectrum. The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using subframes or transmission time intervals (TTIs) of varying or scalable lengths (e.g., including varying numbers of OFDM symbols and / or varying lengths of absolute time durations).

[0052] The gNBs 180a, 180b, 180c may be configured to communicate with the WTRUs 102a, 102b, 102c in a standalone configuration and / or a non-standalone configuration. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c without accessing another RAN (e.g., eNodeBs 160a, 160b, 160c, etc.). In a standalone configuration, the WTRUs 102a, 102b, 102c may utilize one or more of the gNBs 180a, 180b, 180c as mobility anchor points. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in unlicensed bands. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate with and connect to a gNB 180a, 180b, 180c while also communicating with and connecting to another RAN, such as an eNodeB 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNodeBs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNodeBs 160a, 160b, 160c may act as mobility anchors for the WTRUs 102a, 102b, 102c, and the gNBs 180a, 180b, 180c may provide additional coverage and / or throughput for serving the WTRUs 102a, 102b, 102c.

[0053] Each of the gNBs 180a, 180b, 180c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and / or DL, support for network slicing, DC, interworking between NR and E-UTRA, routing of user plane data to User Plane Functions (UPFs) 184a, 184b, routing of control plane information to Access and Mobility Management Functions (AMFs) 182a, 182b, etc. As shown in FIG. 1D, the gNBs 180a, 180b, 180c may communicate with each other via an Xn interface.

[0054] 1D may include at least one AMF 182a, 182b, at least one UPF 184a, 184b, at least one Session Management Function (SMF) 183a, 183b, and possibly a Data Network (DN) 185a, 185b. Although the foregoing elements are illustrated as part of the CN 106, it will be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0055] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via an N2 interface and may function as a control node. For example, the AMF 182a, 182b may be responsible for user authentication of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling different protocol data unit (PDU) sessions having different requirements), selection of a particular SMF 183a, 183b, management of registration areas, termination of non-access stratum (NAS) signaling, mobility management, etc. The network slicing may be used by the AMF 182a, 182b to customize the CN support of the WTRUs 102a, 102b, 102c based on the type of service utilizing the WTRUs 102a, 102b, 102c. For example, different network slices may be established for different use cases, such as services relying on ultra-reliable low latency (URLLC) access, services relying on enhanced massive mobile broadband (eMBB) access, services for MTC access, etc. The AMF 182a, 182b may provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies, such as Wi-Fi.

[0056] The SMFs 183a, 183b may be connected to the AMFs 182a, 182b in the CN 106 via an N11 interface. The SMFs 183a, 183b may also be connected to the UPFs 184a, 184b in the CN 106 via an N4 interface. The SMFs 183a, 183b may select and control the UPFs 184a, 184b and configure the routing of traffic through the UPFs 184a, 184b. The SMFs 183a, 183b may perform other functions, such as managing and assigning UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notification, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0057] The UPFs 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 104 via an N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices. The UPFs 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policy, supporting multi-homed PDU sessions, handling user plane QoS, buffering DL packets, providing mobility anchoring, etc.

[0058] The CN 106 may facilitate communication with other networks. For example, the CN 106 may include or communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that serves as an interface between the CN 106 and the PSTN 108. In addition, the CN 106 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to the local DNs 185a, 185b through the UPFs 184a, 184b via an N3 interface to the UPFs 184a, 184b and an N6 interface between the UPFs 184a, 184b and the DNs 185a, 185b.

[0059] 1A-1D and the corresponding description thereof, one or more or all of the functions described herein with respect to one or more of the WTRUs 102a-102d, base stations 114a-114b, eNodeBs 160a-160c, MME 162, SGW 164, PGW 166, gNBs 180a-180c, AMFs 182a-182b, UPFs 184a-184b, SMFs 183a-183b, DNs 185a-185b, and / or any other devices described herein may be performed by one or more emulation devices (not shown). The emulation devices may be one or more devices configured to emulate one or more or all of the functions described herein. For example, the emulation devices may be used to test other devices and / or to simulate network and / or WTRU functions.

[0060] The emulation device may be designed to implement one or more tests of other devices in a lab environment and / or an operator network environment. For example, one or more emulation devices may perform one or more or all functions while fully or partially implemented and / or deployed as part of a wired and / or wireless communication network to test other devices in the communication network. One or more emulation devices may perform one or more or all functions while temporarily implemented / deployed as part of a wired and / or wireless communication network. The emulation device may be directly coupled to another device for the purpose of testing and / or performing tests using over-the-air wireless communication.

[0061] The one or more emulation devices may perform one or more functions, including but not limited to, while not implemented / deployed as part of a wired and / or wireless communication network. For example, the emulation devices may be utilized in test scenarios in a test lab and / or in an undeployed (e.g., test) wired and / or wireless communication network to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuitry (which may include, for example, one or more antennas) may be used by the emulation devices to transmit and / or receive data.

[0062] In some cases, the WTRU may operate in an unlicensed (U) spectrum. Additionally, the WTRU may communicate using sidelink (SL) communications. Thus, there may be sidelink operation for both Mode 1 and Mode 2 in an unlicensed spectrum, such as Frequency Range 1 (FR1), which may be referred to as Sidelink Unlicensed (SL U). For example, the unlicensed SL frequency bands may be 5 GHz and 6 GHz, and Uu operation related to Mode 1 may be limited to licensed spectrum only. The SL U channel access design may be based on regional regulatory requirements starting with New Radio Unlicensed (NR U) channel access.

[0063] The SL resource allocation mechanism for licensed spectrum may be (re)used in the SL U. The SL U may cover modifications to the NR SL PHY channel structure and procedures for operating in the unlicensed spectrum.

[0064] In some cases, the WTRU may operate in an unlicensed spectrum. Furthermore, the WTRU may communicate in an NR system. In New Radio Unlicensed (NR U), the WTRU may access a channel for uplink (UL) transmission according to one of Type 1 or Type 2 uplink (UL) channel access procedures. The procedures may be designed to comply with regulatory requirements related to, for example, sensing (e.g., Listen Before Talk (LBT), Maximum Channel Occupancy Time (MCOT), Occupied Channel Bandwidth (OCB), and / or Power Spectral Density (PSD).

[0065] The Type 1 channel access procedure may include LBT sensing with random backoff and a variable extended clear channel assessment (CCA) period based on a contention window, where the contention window size may be selected based on a channel access priority class (CAPC) configuration. A base station (e.g., a gNB, etc.) or a WTRU may perform a Type 1 channel access procedure to initiate a channel occupation time (COT). Type 2A and 2B channel access may be performed when the transmission gap is 25us and 16us, respectively. If the transmission gap is smaller than 16us, Type 2C channel access may be applied with immediate transmission after the gap without performing sensing.

[0066] For initial access, the NR U may use one or more Discovery Reference Signals (DRS) including a synchronization signal / Physical Broadcast Channel (SSB) block burst set, and the number of candidate SSB positions increases within the DRS window. Related designs may also include handling of reduced SSB blocks and Remaining Minimum System Information (RMSI) transmission opportunities due to LBT failure. Modifications to the random access procedure, such as Physical Random-Access Channel (PRACH) repetition in the frequency domain and extension of the random access response window, may be adopted to handle reduced message 1 / 2 / 3 / 4 transmission opportunities due to LBT failure. The PRACH preamble format may also be extended to meet the OCB requirements.

[0067] For downlink (DL) transmission, the NR U may address COT structure indication, dynamic PDCCH monitoring, and / or flexible PDSCH start position due to the uncertainty caused by LBT. For UL control and data channel transmission, a new block interlace-based transmission may be used for PUCCH and PUSCH with flexible start position for PUSCH to comply with one or more OCB requirements. NR U sounding reference signal (SRS) transmission may also be extended with additional flexibility in configuration and triggering. In addition, the NR U may support a frame structure with multiple DL-to-UL and UL-to-DL switching points within a shared COT.

[0068] The NR U may support additional HARQ transmission opportunities and immediate HARQ transmission for corresponding data in the same shared COT as well as subsequent COTs to ensure channel access for HARQ transmission.

[0069] One or more problems may arise for a WTRU operating in an unlicensed spectrum.

[0070] For example, the SL PHY layer structure and signals may not need to be modified to address the required parameters of occupied channel bandwidth (OCB) and power spectral density (PSD). In unlicensed spectrum, transmissions may be required to occupy at least a certain amount X%, 90%, etc. of the channel bandwidth. This OCB requirement may ensure that channel occupancy can be detected. Also, a maximum PSD may be required on transmissions in unlicensed spectrum to spread the resulting interference across the unlicensed carriers. The SL PHY layer structure and signal design may need to address these issues. For example, in some cases, an SL transmission may be spread across one or more subchannels and occupy only a portion of the SL carrier. The maximum PSD in such a transmission may be significantly higher than the maximum PSD requirement. Also, guard symbols may be used at the end of the SL slot and between the PSSCH and PSFCH symbols in the SL slot (e.g., the length of the guard symbols may be greater than 16us). Transmissions from a WTRU separated by such a gap may be considered to be separate transmission bursts, and new sensing for channel access may need to be performed after the gap, and thus a single-slot SL transmission may not be completed in one channel access. In addition, the SL resource pool may include logical slots that are not contiguous in the time domain, and an SL transmission burst spanning several such logical slots indicated by consecutive indices may have gaps in the transmission and therefore cannot be performed in one COT.

[0071] In another example of a potential problem, SL resource allocation and reservation may not be feasible in unlicensed spectrum due to regulatory requirements for fair coexistence. In some cases, in the case of unlicensed spectrum, all nodes must follow the channel access procedure specified for unlicensed spectrum to implement fair coexistence. SL resource allocation and reservation in Mode 1 and Mode 2 may not include LBT sensing-based channel access, and thus improved mechanisms may be needed for SL resource acquisition in unlicensed spectrum, especially considering one or more changes in the PHY layer structure and the resulting granularity of resources for SL transmission. Reservation of resources for aperiodic SL TB retransmission or another new SL TB transmission (e.g., semi-persistent transmission), etc., may be deterministic in SL design, with reserved future resources indicated in SL control information (SCI) in PSCCH. However, in unlicensed spectrum, due to the uncertainty of sensing and channel access results, resources may not be able to be reserved in the same way as SL, and new resource reservation design may be needed.

[0072] In another example of a potential problem, there may be no centralized base station (e.g., gNB) to coordinate and schedule COT sharing in Mode 2. In an NR U design, the WTRU may receive UL scheduling information including COT indication and sharing information, such as COT duration and channel access for COT sharing. As a central node, the base station may be able to coordinate a set of DL and UL transmissions to and from the WTRU to enable the WTRU to share the COT initiated by the base station. For example, the base station may schedule a UL transmission with a timing that may be aligned with the DL transmission, such that the WTRU can share the COT using Type 2C channel access without performing sensing. In SL Mode 2, when the WTRU acquires and reserves resources without the involvement of the base station, COT sharing between WTRUs may be performed by the WTRU in a distributed manner, and therefore one or more procedures are required to address this approach.

[0073] As discussed herein, there may be one or more approaches that address the above potential problems, as well as other problems not disclosed herein.

[0074] In some cases (e.g., in the time domain), the WTRU may determine the SL U resources that belong to the SL U resource pool. The minimum SL U time domain allocation unit for PSSCH / PSCCH transmission may be some time unit, such as a slot, a minislot, etc. The WTRU may be (pre-)configured with a time unit configuration for a (pre-)configured SL U resource pool. The time unit configuration may include a duration (e.g., of a minislot, such as 2 symbols, 5 symbols, or 7 symbols). As discussed herein, some examples herein may refer to a particular time unit for demonstration purposes, but any reference to a time unit, such as a slot, may refer to a slot and / or a minislot, and / or any other time unit as discussed herein).

[0075] The WTRU may perform a TB transmission on the PSSCH with an associated PSCCH in the slot. The associated PSCCH transmission may carry a first tier SCI (SCI-1) associated with the PSSCH transmission. A second tier SCI (SCI-2) may be multiplexed with the PSSCH in the resources allocated for the PSSCH transmission. In some instances, the WTRU may not switch between PSCCH transmission and reception in a slot. In another example, the PSCCH may carry all control information for the associated SL PSSCH transmission.

[0076] In one approach, the WTRU may be (pre-)configured with all symbols for PSSCH / PSCCH transmission in a slot, and the WTRU may perform PSSCH / PSCCH and associated DMRS transmissions in consecutive symbols within such PSSCH / PSCCH slot.

[0077] The WTRU may be (pre)configured with an automatic gain control (AGC) symbol as the first symbol of a slot. The WTRU may replicate the content of the second symbol into the AGC symbol. The AGC symbol may enable AGC convergence for PSSCH / PSCCH transmission reception. During the AGC symbol, the WTRU may adjust the RX front-end radio gain to achieve the desired baseband input power level. Due to variations in the received input signal, it may take some time for the gain to converge to the desired level.

[0078] The WTRU may be (pre-)configured with a set of PSSCH / PSCCH transmission DMRS configurations. Each configuration may include an index of the symbol used for DMRS transmission in a slot. The WTRU may determine the DMRS configuration and indicate the determined DMRS configuration in an SCI in the associated PSCCH transmission.

[0079] In some cases (e.g., in the frequency domain), the WTRU may be (pre-)configured with one or more SL U carriers. The WTRU may be (pre-)configured with one or more SL U bandwidth portions (BWPs) within the (pre-)configured SL U carriers.

[0080] The WTRU may be (pre-)configured with one or more RB sets in the SL U BWP. Each RB set may include several consecutive RBs, and the (pre-)configuration of an RB set may include an index of a starting RB and the number of RBs in the RB set. Within the SL U BWP, the RB sets may be indexed in ascending order. The WTRU may determine a frequency resource allocation for the RB set based on the RB set index.

[0081] The smallest SL U frequency domain allocation unit for PSSCH / PSCCH transmission may be an RB interlace. SL U transmission based on RB interlaces may meet the occupied channel bandwidth (OCB) requirement of the unlicensed spectrum. Across the frequency bandwidth of the RB set, the WTRU may be (pre-)configured with M RB interlaces. The value of M may be associated with a subcarrier spacing (SCS), such as 10 for 15 kHz, 5 for 30 kHz, etc. Each RB interlace in the RB set and / or resource pool may be denoted by index (m), where m may be an integer from 0 to M-1. The RB interlace (m) may include RBs with index (m, m+M, m+2×M, m+3×M,..., m+N×M), where N may be the (pre-)configured total number of RBs in the RB interlace.

[0082] In some cases, the WTRU may determine SL U resources that belong to a resource pool. Figure 2 may be referred to herein as referring to both Figures 2A and 2B. Figure 2 illustrates an example of SL U resources comprising RB interlaces within a time period (e.g., Figure 2A relates to an example slot and Figure 2B relates to an example minislot).

[0083] As shown in Figures 2A and 2B, both show a set of resource blocks, where time (202) is shown on the horizontal axis and frequency (201) is shown on the vertical axis. Below each graph of the RBs is an example of how the RBs can be used (e.g., for each symbol 203 in the RB, different types of transmissions can be reserved or scheduled in these time arrangements, such as AGC, DMRS, PSSCH, PSCCH, etc.). 205A is a slot for PSCCH / PSSCH transmissions with 14 symbols including an AGC symbol at the beginning of the slot, and 205B is a minislot for PSCCH / PSSH transmissions with 7 symbols including an AGC symbol at the beginning of the slot. For illustration purposes, a set of RBs 206 is shown in one SL U resource pool, but there can be more than one RB set in a given pool. For illustration purposes, only one slot / minislot is shown, but there can be more than one slot / minislot (e.g., one or more sets) in a resource pool. In one example, as shown, the AGC symbol may be used for convergence (as discussed herein) and therefore may not hold useful data, and therefore the data may be copied / replicated in the symbol next to the AGC symbol, thus replicating 204.

[0084] A WTRU may be (pre-)configured with one or more SL U resource pools. The WTRU may allocate and reserve one or more such SL resources belonging to the resource pools for SL U transmissions.

[0085] A frequency domain resource allocation for such a SL U resource pool may include one or more RB sets. For the resource pool and / or RB set, the WTRU may be (pre-)configured with M RB interlaces. Each RB interlace may include N RBs separated by M-1 RBs, where N may be (pre-)configured for the resource pool and / or RB set.

[0086] In the time domain, the WTRU may determine a set of slots that may belong to the SL resource pool based on a (pre-)configured bitmap associated with the resource pool and the S-SSB transmission (pre-)configuration. The WTRU may determine a set of slots in an SFN or DFN cycle as (t0, t1, ..., t max ) in ascending order, where max may be the maximum index (e.g., 10240 for an SCS of 15 kHz, 20480 for an SCS of 30 kHz, and 40960 for an SCS of 60 kHz) and t0 may indicate the first slot of a radio frame corresponding to SFN0 or DFN0 of the serving cell. The indexed slots in such a set may be referred to as physical slots, and the physical slots of the set may be contiguous in the time domain.

[0087] The WTRU may first exclude from the set slots that are (pre)configured for S-SS / PSBCH Block (S-SSB) transmission. The number of such slots (N S-SSB ) may be determined based on (pre-)configured S-SSB parameters such as the duration of the S-SSB transmission period, the number of S-SSB slots within the S-SSB transmission period, and / or the periodicity of the S-SSB transmission.

[0088] The WTRU allocates the remaining (NN S-SSB ) slots that can be allocated to the resource pool. The bitmap may include L bits, and the WTRU may determine which of the (NN S-SSB)MOD L may be expected to be equal to 0. The WTRU may apply a bitmap for each of the L slots in the set, with each bit corresponding to a slot. If the (pre-)configured bit value is 1, the WTRU may determine that the corresponding slot may belong to the resource pool. The WTRU may exclude slots or minislots that correspond to bit values ​​of 0 from the set. The WTRU may determine that all remaining slots may belong to the resource pool.

[0089] In another approach, the WTRU may determine the set of slots that may belong to the SL resource pool based on a (pre-)configured set of non-SL slots, a (pre-)configured bitmap associated with the resource pool, and / or an S-SSB transmission (pre-)configuration.

[0090] The WTRU may exclude a set of non-SL slots from the same physical slot set. Non-SL slots may be physical slots that are not available for SL transmission and / or reception, and thus the WTRU may not include the non-SL slots in the resource pool.

[0091] In one example, a WTRU may receive an SL symbol (pre-) configuration, which may include a start symbol index and a number of symbols following the start symbol. The WTRU may determine that a physical slot may be an SL slot when a symbol in the slot corresponding to the (pre-) configuration may be an UL symbol. The WTRU may be (pre-)configured to perform SL operations on UL symbols, and thus, the WTRU may determine that a physical slot may be a non-SL slot when one or more SL symbols corresponding to the SL symbol (pre-) configuration may not be an UL symbol.

[0092] In another example, the WTRU may receive an SL slot (pre)configuration, which may indicate which slots may be available for SL transmission and / or reception on a carrier. Such a (pre)configuration may include a pattern of physical slots assigned to Uu (DL / UL) and SL operation. The WTRU may determine that a physical slot may be a non-SL slot when the slot may be (pre)configured for Uu operation.

[0093] The WTRU may exclude the determined non-SL slots from the physical slot set, and the number of such non-SL slots may be N non-SL The WTRU may also use N S-SSB Slots can be excluded.

[0094] The WTRU allocates the remaining (NN S-SSB -N non-SL ) slots that can be allocated to the resource pool. The bitmap may include L bits, and the WTRU may determine which of the N reserved slots can be further excluded, where N reserved is (NN S-SSB -N non-SL ) MOD L. The WTRU may apply a bitmap for each of the L slots in the set, with each bit corresponding to a slot. If the (pre-)configured bit value is 1, the WTRU may determine that the corresponding physical slot may belong to the resource pool. The WTRU may exclude physical slots corresponding to bit values ​​of 0 from the set.

[0095] The WTRU may determine that all remaining physical slots may belong to a resource pool for which the associated bitmap is (pre-)configured. The WTRU may define the determined slots of the resource pool as (T0, T1, ..., T max), where T max is max -N S-SSB -N non-SL -N reserved The WTRU may apply these re-indexed slots of the resource pool as logical slots.

[0096] In some cases, the WTRU may determine the time continuity of logical slots in a resource pool.

[0097] In one example, the WTRU may determine that the resource pool may include all available physical slots when one or more of the following conditions are met: All slots may be (pre)configured for SL operation on the carrier (N non-SL =0); SSB transmission does not have to be (pre)configured (N S-SSB =0); the value of each bit in the (pre)configured bitmap associated with a resource pool may be equal to 1, such as all slots assigned to the associated resource pool (N non-allocated =0), and / or (NN S-SSB N non-SL ) MOD L may be equal to 0 (N reserv =0).

[0098] Alternatively, the WTRU may be (pre)configured with a resource pool that contains all available physical slots. If the resource pool contains all available physical slots, then the logical slots are i =T i (i is 0 to t max ), the logical slots of such a resource pool may correspond to physical slots indicated by the same index. The logical slots of such a resource pool may be contiguous in the time domain.

[0099] In another example, the WTRU may determine a resource pool that may contain a subset of all available physical slots when one or more of the following physical slots are excluded from the resource pool: non-SL >0); SSB transmission is (pre)configured for the physical slot (N S-SSB >0); physical slots (N non-allocated >0), e.g., physical slots that are not assigned to the associated resource pool; and / or physical slots that are identified as reserved slots, and the WTRU reserv slots (where N reserv =(NN S-SSB -N non-SL )MOD L and (N reserv >0)) are excluded from the resource pool to ensure that the indexes of the logical slots in the resource pool can be repeated at each SFN / DFN cycle.

[0100] In such a resource pool, logical slots may not correspond to physical slots with the same index, and the determined set of logical slots of the resource pool may not be contiguous in the time domain. In this case, the WTRU may determine a mapping between the indexes of the logical slots of the resource pool and the indexes of the corresponding physical slots. The WTRU may determine whether any two logical slots of the resource pool with consecutive indexes may be contiguous in the time domain.

[0101] In another case, the WTRU may not re-index the logical slots included in the resource pool and may not refer to the logical slots of the resource pool with their corresponding physical slot indices, in which case the WTRU may determine whether two logical slots may be consecutive in time based on the continuity of the slot indices.

[0102] In some cases, the WTRU may send / receive a PSSCH transmission and an associated PSCCH transmission. The WTRU may perform PSSCH and associated PSCCH transmissions in one or more RB interlaces within a slot. The WTRU may indicate the RB interlace allocation for the PSSCH in a "frequency resource allocation" bit field of the SCI in the associated PSCCH transmission. The indication may include one or more RB interlace indices and / or an RB set index.

[0103] The WTRU may be (pre-)configured with some symbols in a slot for PSCCH transmission, as shown in the example of Figure 2. For example, the second and third symbols of a slot may be (pre-)configured for PSCCH transmission for a resource pool. In addition, the WTRU may transmit a PSCCH transmission in (pre-)configured PSCCH RBs of the (pre-)configured PSCCH symbols. In one example, the WTRU may transmit a PSCCH transmission in (pre-)configured RBs starting from the lowest RB of the RB interlace with the lowest RB interlace index when one or more RB interlaces are allocated for PSSCH / PSCCH transmission.

[0104] The WTRU may perform a SL transmission burst in an initiated or shared COT in a resource pool. A SL transmission burst may include PSSCH / PSCCH transmissions on consecutive logical and / or physical slots of the resource pool applied in the time domain, with one PSSCH / PSCCH transmission in each slot.

[0105] In some cases, the WTRU may be in a particular mode (e.g., Mode 2) and there may be one or more procedures for determining SL U channel access and resource selection. In some cases, the SL U channel access and / or resource selection may be based on LBT and / or SCI sensing. The WTRU may perform LBT sensing to determine the availability of the SL U channel prior to transmission on the SL U channel. The SL U channel may refer to a (pre-)configured resource pool and / or RB set for SL transmission in a shared spectrum. The WTRU may, for example, determine the availability of the SL U channel in the T sl Within an LBT sensing slot having a duration of .times. ...

[0106] The WTRU may perform a SL U channel access and resource selection procedure to determine whether the WTRU can transmit on the sensed SL U channel and which resources to select and / or reserve for the SL transmission. In general, to reserve something for a SL transmission, the WTRU may send a reservation signal, transmission, and / or message to indicate to other devices that the WTRU is attempting to reserve the channel for use. In one example, one type of reservation signal may be a cyclic prefix extension (CPE), and the CPE and reservation signal may be interchangeable as disclosed herein. In another example, the reservation transmission may be any type of message disclosed herein (e.g., SCI, control information, reservation message, reservation signal, channel occupancy information, window information, etc.). In one example, the reservation signal may be transmitted continuously, once every desired period, periodically, and / or intermittently as needed by a given situation to reserve the channel. The WTRU may perform one or more SL transmissions in the channel occupation time (COT) upon successful completion of the SL U channel access and resource selection procedure.

[0107] The WTRU may perform a SL U channel access and resource selection procedure for COT initiation to initiate a COT. The WTRU may perform one or more SL continuous transmissions from the beginning of the initiated COT. The SL U channel access and resource selection procedure for COT initiation may include LBT sensing based channel access for COT initiation and SCI sensing based channel access and resource selection for COT initiation. For example, the LBT sensing based channel access for COT initiation may be based on Type 1 channel access.

[0108] A WTRU may perform transmissions in a COT initiated by another WTRU, such as sharing the COT, when the gap between the transmissions of the two WTRUs is up to a threshold (e.g., 25 us). The WTRU may perform SL transmissions in a determined set of slots and / or minislots in the shared COT. The WTRU may perform SL U channel access and resource selection procedures for COT sharing to share the detected and ongoing COT. The SL U channel access and resource selection procedures for COT sharing may include LBT sensing based channel access for COT sharing and SCI sensing based channel access and resource selection for COT sharing.

[0109] In one or more techniques disclosed herein, there may be a determination of a SL U LBT energy detection threshold (EDT). The WTRU may perform Type 1 and / or Type 2 LBT sensing based on power detection (e.g., RSSI measurement) performed in a sensing slot having a (pre-)configured (e.g., 9us) duration. The WTRU may determine whether the channel is available during the sensing slot when the detected power (e.g., measured RSSI) is below the energy detection threshold (EDT) for at least a specified amount of time (e.g., 4us) within the (e.g., 9us) sensing slot duration. If not, the WTRU may determine that the channel is busy during the sensing slot. It is recognized that a low EDT may make it more difficult to acquire a channel, but the acquired channel will have less interference (e.g., due to collisions) compared to a high EDT. Considering the distributed manner of channel access by SL WTRUs, it may be beneficial to allow the WTRU to adjust the EDT under real-time conditions so that the WTRU can more easily acquire the channel when channel congestion levels are low and when collision risk due to association is low.

[0110] In one approach, the WTRU may determine a default EDT for the LBT procedure based on one or more of the following: a (pre-)configured EDT (e.g., a maximum EDT (pre-)configured by higher layers); an EDT level required by regulations (e.g., an explicit level in dBm); a (pre-)configured channel access type (e.g., dynamic channel access such as Load Based Equipment (LBE) or semi-static channel access such as Frame Based Equipment (FBE)); a (pre-)configured SL U maximum transmit power on the LBT channel; and / or a (pre-)configured LBT bandwidth.

[0111] The WTRU may dynamically determine the EDT for the next LBT procedure based on the default EDT and one or more of the following: channel congestion level (e.g., SL CBR, CO, and / or RSSI); type of channel to transmit (e.g., PSSCH / PSCCH or PSFCH); priority of the SL TB to transmit; remaining PDB of the SL TB to transmit; remaining duration of resource selection window for the SL TB to transmit; received HARQ feedback status associated with transmissions performed on the LBT channel; received SL CSI report (e.g., CQI measurement); and / or Type 1 LBT (COT start) or Type 2 (COT sharing).

[0112] The WTRU may increase the default EDT by a (pre-)configured offset (e.g., X dBm) when one or more of the following conditions occur: the channel congestion level (e.g., SL CBR, CO, and / or RSSI) measured on the channel falls below a (pre-)configured threshold; the remaining PDB and / or remaining duration of the resource selection window of the transmitting SL TB falls below a (pre-)configured threshold; the number of HARQ ACKs received from transmissions performed on the channel may exceed a (pre-)configured threshold; the number of reported SL CSI (e.g., CQI measurements) above a (pre-)configured threshold may exceed a (pre-)configured threshold; and / or the WTRU performs Type-2 LBT for COT sharing for PSSCH / PSCCH and / or PSFCH transmissions.

[0113] The WTRU may decrease the default EDT by a (pre-)configured offset (e.g., X dBm) when one or more of the following conditions occur: the channel congestion level (e.g., SL CBR, CO, and / or RSSI) measured on the channel exceeds a (pre-)configured threshold; the priority of the transmitting TB is higher than a (pre-)configured threshold; the number of HARQ NACKs received from transmissions performed on the channel may exceed a (pre-)configured threshold; the number of reported SL CSI (e.g., CQI) measurements below a (pre-)configured threshold may exceed a (pre-)configured threshold; and / or the WTRU performs a Type 1 LBT for COT initiation for PSFCH transmission.

[0114] In some cases, the WTRU may perform SCI decoding for SCI sensing. The WTRU may monitor PSCCH transmissions in each slot belonging to one or more (pre-)configured resource pools, except for the resource pool in which the WTRU performs transmission. The WTRU may perform blind decoding on (pre-)configured PSCCH resources, such as the lowest RB of each RB interlace (pre-)configured for a resource pool, and / or the RB set in each monitored slot. The number of such blind decodings may depend on the number of (pre-)configured RB interlaces for each resource pool and / or RB set, the number of (pre-)configured RB sets for a resource pool, and / or the number of (pre-)configured resource pools for SCI monitoring.

[0115] When the WTRU successfully decodes the SCI in slot (t), the WTRU may receive information from the corresponding bit field included in the decoded SCI.

[0116] In an example, the WTRU may decode and receive SCI information associated with a TB carried in a PSSCH transmission: the level of priority assigned to the TB (e.g., L1), the cast type of the TB, and / or the source and destination IDs. The cast type of the TB may be indicated as unicast, groupcast, or broadcast.

[0117] In an example, the WTRU may decode and receive SCI information associated with the COT (e.g., current COT) on which the decoded SCI is transmitted, such as remaining COT duration, MCOT duration, COT start slot index, COT start / sharing indication, COT sharing for PSSCH / PSCCH indication, COT sharing for PFSCH indication, and / or channel congestion indication.

[0118] The remaining COT duration may be the remaining time of the COT used between the slot where the SCI is decoded and the end of the COT. The unit of such remaining COT duration indication may be a unit of time (e.g., ms) and / or a number of slots. For example, a remaining COT duration of 5 slots indicated in a SCI received in slot (t) may indicate that the current COT may include consecutive slots from slot (t+1) to slot (t+5). In one example, the unit of the remaining COT duration may be a logical slot of a resource pool used for PSSCH / PSCCH transmission carrying the decoded SCI. In another example, a physical slot may be applied to indicate the duration. The WTRU may determine the number of logical slots or time (e.g., ms) remaining in this COT with respect to the maximum COT. In some cases, based on this indicator and the remaining transmission indicator of the SCI, the WTRU may determine the period of time and / or the number of logical slots in the COT that may not be scheduled for transmission and therefore may be applied for COT sharing. In one example, the value may be indicated using a Time Resource Indication Value (TRIV).

[0119] For the MCOT duration, the WTRU may determine the maximum COT duration of the ongoing COT based on this SCI indication. The maximum COT value indicated in this SCI field may be determined by the initiating WTRU for the COT corresponding to the CAPC configuration of the performed Type-1 LBT procedure.

[0120] In the case of a COT start slot index, the WTRU may determine a logical slot index of the first slot of the COT. In another case, when the WTRU decodes an SCI in the COT, the WTRU may determine the period of time and / or the number of logical slots in the COT based on the indicated COT start slot index and the MCOT duration indicated in the same SCI.

[0121] For the COT start / sharing indication, the WTRU may determine that the received SCI may be transmitted by the WTRU initiating the COT when this SCI indicator indicates COT start. The WTRU may further identify the initiating WTRU by a WTRU source and / or destination ID indicated with the same SCI. Similarly, the WTRU may determine that the received SCI may be transmitted by the WTRU sharing the COT when this SCI indicator indicates COT sharing. The WTRU may further identify the sharing WTRU by a WTRU source and / or destination ID indicated with the same SCI. In one example, one value may correspond to COT start (e.g., 0) and the value may be incremented by each WTRU sharing the COT (e.g., 1 may indicate the first WTRU sharing the COT, 2 may indicate the second WTRU sharing the COT, etc.). The WTRU may determine the number of WTRUs sharing the current COT based on this indication. The WTRU may determine not to share the COT when the number of WTRUs sharing the COT may exceed a (pre-)configured threshold.

[0122] The COT sharing for PSSCH / PSCCH indication may indicate whether the current COT may be sharable, e.g., whether it may be shared by another WTRU to perform PSSCH / PSCCH transmission within the COT. When a sharable COT is indicated, the WTRU may perform SL U channel access and resource selection procedures for COT sharing to perform PSSCH / PSCCH transmission in the current COT.

[0123] The COT sharing for PSFCH indication may indicate whether one or more PSFCHs carrying HARQ feedback corresponding to one or more PSSCH / PSCCH transmissions in the current COT may be transmitted within the COT. When a shareable COT for the PSFCH is indicated, the WTRU may perform a SL U channel access and resource selection procedure for COT sharing to perform a PSFCH transmission in the current COT.

[0124] The channel congestion indication may be an indication of the congestion status of the SL U channel. In one example, a binary channel congestion indication may be (pre)configured, where a value of 1 may indicate a congested channel and a value of 0 may indicate that the channel may not be congested.

[0125] The indication of the SL slots for sharing in the COT may be an indication of which SL slots in the COT may be shared. In one example, the TRIV may be used to indicate a logical slot offset, such as the number of logical slots between the SL slot containing the SCI indication and the SL slot indicated for sharing. In another example, the logical slot index of the SL slot for sharing may be indicated.

[0126] In an example, the WTRU may decode and receive one or more of the following SCI information associated with resource allocation for PSSCH / PSCCH transmissions performed within the current COT, such as remaining transmission duration and / or frequency resource allocation for PSCCH transmissions:

[0127] The remaining transmission duration may be the number of consecutive slots scheduled for PSCCH / PSSCH transmission during the remaining COT duration. For example, a time resource indication value (TRIV) may be used to indicate the number of remaining scheduled slots. A TRIV of x for a SCI received in slot (t) may indicate that the WTRU transmitting the decoded SCI may continue PSCCH / PSSCH transmission in the next x consecutive slots from slot (t+1) to slot (t+x). In one example, the slots applied in this indication may be logical slots of a resource pool used for PSSCH / PSCCH transmission carrying the decoded SCI, e.g., the x consecutive slots may be x consecutive logical slots. In another example, physical slots may be applied. In one example, the value may be indicated using a TRIV.

[0128] The frequency resource allocation for the PSSCH may be an RB interlace index and / or an RB set index of the PSSCH transmission performed in the current COT. In one example, the WTRU may perform transmission of the TB and / or different TBs in the COT using the same frequency resource allocation. The WTRU may indicate a Frequency Resource Indication Value (FRIV) value in the SCI associated with each PSSCH transmission scheduled in the COT based on the frequency resource allocation, such as an index of the allocated starting RB interlace and the number of RB interlaces and / or RB sets allocated for the PSSCH transmission. In this example, the FRIV value may be calculated based on the starting RB interlace and the number of RB interlaces used for the PSSCH transmission in each slot in the COT. In another example, the WTRU may perform transmission of the TB and / or different TBs in the COT using different frequency resource allocations (e.g., different RB interlace indexes in one resource pool and / or RB set). In this example, the WTRU may indicate a frequency resource indication value (FRIV) for an SCI transmitted in slot (t) calculated based on the frequency resource allocation for PSSCH transmissions in each of consecutive slots from (t) to (t+a), where a may be a (pre-)configured value for the resource pool. For example, if a=2, the FRIV value indicated for an SCI transmitted in slot (t) may be calculated based on the start RB interlace and number of RB interlaces for PSSCH transmissions in slot (t), slot (t+1), and slot (t+2).

[0129] In an example, a WTRU may decode and receive SCI information associated with a reservation of a COT and / or resources for transmission by the WTRU transmitting the decoded SCI, such as a COT / resource reservation interval and / or a COT / resource reservation window. Such a reservation by the WTRU may indicate that the WTRU may perform channel access and resource selection for COT initiation to start a COT after the reservation interval or within the duration of the reservation window. A WTRU that performs channel access based on such decoded SCI information may exclude slots associated with the reserved COT and / or reservation window from its SL U channel access and resource selection procedure for COT initiation.

[0130] The COT and / or resource reservation interval may be the time period in ms or number of slots between the current COT and / or resources indicated in the decoded SCI and the COT and / or resources reserved for transmission of another TB by the same WTRU. The extent of the reservation interval may be (pre-)configured in a resource pool, and the WTRU may determine the length of the interval based on the traffic periodicity of the SL service and / or application. The WTRU may reserve the same frequency resources in the reserved COT as those used in the current COT. The WTRU may reserve a COT of the same length as the length of the current COT. For example, the reserved COT length may be determined based on an association with the L1 priority indicated for the TB transmitted in the current COT. In another example, the reservation window may be (pre-)configured in association with the reserved COT length. In another example, the reservation window associated with the indicated COT and / or resource reservation interval may be indicated in the same SCI. The WTRU may perform channel access and resource selection to start such reserved COT within the (pre-)configured window. In one example, the unit of the COT and / or resource reservation interval may be a logical slot of the resource pool used for the PSSCH / PSCCH transmission carrying the decoded SCI. In another example, a physical slot may be applied to indicate this interval time. In one example, the value may be indicated using TRIV.

[0131] The COT and / or resource reservation window may be a time period in ms or number of slots following the end of the current COT indicated in the decoded SCI. The length of the window may be (pre)configured in the resource pool. In one example, the WTRU may determine the length of the window based on the remaining packet delay budget (PDB) of the TBs transmitted in the current COT. In one example, the unit of the COT and / or resource reservation window may be logical slots of the resource pool used for the PSSCH / PSCCH transmission carrying the decoded SCI. In another example, physical slots may be applied to indicate this window length. In one example, the value may be indicated using TRIV.

[0132] In an example, the WTRU may decode and receive SCI information associated with the HARQ process of the PSSCH / PSCCH transmission in slot (t), such as a HARQ process number and / or a HARQ feedback enable / disable indication. The HARQ process number may be a new data indicator and / or a redundancy version. The HARQ feedback enable / disable indication may be an indication of whether HARQ feedback is enabled and a PSFCH carrying a HARQ ACK / NACK is expected for the PSSCH / PSCCH transmission.

[0133] In an example, the WTRU may decode and receive SCI information associated with a transmission configuration for a PSSCH / PSCCH transmission in slot (t), such as a transmission configuration including a number of DMRS ports, a DMRS pattern, an MCS value, and / or an MCS table indication.

[0134] In an example, the WTRU may decode and receive SCI information associated with an SCI-2 transmission multiplexed with a PSSCH transmission in slot (t), such as an indication of the SCI-2 format and a beta offset value.

[0135] In an example, the WTRU may decode and receive one or more of the following SCI information associated with the WTRU geographic location and range requirements of the TB transmitted in slot (t): the WTRU's zone ID, and / or an index corresponding to a (pre-)configured minimum communication range (MCR) requirement in meters.

[0136] In an example, the WTRU may decode and receive one or more of the following SCI information associated with the synchronization source of the WTRU performing the PSSCH transmission received in slot (t): Based on the synchronization source indication, the WTRU may determine that the transmission received in the COT is performed by a GNSS, gNB, SyncRef WTRU, or a WTRU that is synchronized with an internal WTRU clock, and / or the WTRU may determine the SLSS ID of the SL synchronization signal of the indicated SyncRef WTRU.

[0137] In some cases, the WTRU may perform SCI decoding within the detected SL COT. When the WTRU decodes the SCI in slot (t) and detects the COT indicated by the SCI, the WTRU may determine one or more COT-specific PSCCH resources on which the WTRU can perform SCI decoding during the remaining duration of the detected COT. The COT-specific PSCCH resources may include a (pre-)configured number of symbols in each slot included in the detected COT and / or a (pre-)configured number of RBs in one or more RB interlaces scheduled for PSSCH transmission within the detected COT.

[0138] In one example, the WTRU may determine one or more COT-specific PSCCH resources based on the time (TRIV) and frequency (FRIV) resource allocation indicated in the decoded SCI. The WTRU may determine the RB interlace that contains the PSCCH RB based on the indexed PSSCH interlace indicated in the FRIV. The WTRU may switch from blind decoding on each RB interlace (pre-)configured in the resource pool to performing COT-specific SCI decoding on the determined COT-specific PSCCH resource for the remaining duration of the detected COT. The WTRU may switch back to blind decoding of the SCI after the end of the detected COT.

[0139] In another example, the WTRU may determine to stop SCI decoding for the remaining COT duration indicated in the decoded SCI when the WTRU source and / or destination IDs indicated in the same SCI may not be (pre-)configured by higher layers. In this case, the WTRU may not be (pre-)configured to receive TB transmitted within the detected COT. The WTRU may enter an inactive state when SL DRX may be (pre-)configured and enabled. The WTRU may determine a microsleep, light sleep, and / or deep sleep inactive state based on the length of the remaining duration of the detected COT. The WTRU may wake up at the first SL slot after the end of the detected COT and resume SCI decoding (e.g., blind decoding).

[0140] In some cases, there may be a SL U channel access and resource selection procedure for COT sharing. In some cases, the WTRU may perform SCI sensing for access and resource selection. The WTRU may be triggered by higher layers to perform SL U channel access and resource selection for COT sharing in slot(n) for transmission of one or more TBs. The WTRU may perform SCI sensing for triggered SL U channel access and resource selection for COT sharing as discussed herein.

[0141] The WTRU may be provided with one or more of the following information by higher layers for SCI detection: Resource pool and / or RB set applicable for the SL channel and resource selection decision, such as an index indicating the resource pool and / or RB set; Priority of the TB; TX ), where the WTRU may determine this priority to be the highest priority (e.g., lowest L1 priority value) of a TB when SCI sensing may be triggered for transmission of a different TB; the number of RB interlaces to be used for PSSCH / PSCCH transmission carrying a TB in one slot (L RB_interlace ); remaining packet delay budget (PDB), where the WTRU may determine this remaining PDB value to be the smallest remaining PDB of a TB when SCI sensing may be triggered for transmission of a different TB; and / or COT and / or resource reservation interval (P ) when the traffic type of the TB is periodic and COT and / or resource reservation for another TB is enabled in the (pre-)configuration of the indicated resource pool and / or RB set. rsvp_TX ).

[0142] The WTRU may determine a resource selection window (RSW), such as the time interval between slots (n+T1) and (n+T2). The WTRU may determine T2 based on the indicated remaining PDB (e.g., T2 may be equal to the indicated remaining PDB value). The WTRU may determine T1 based on the processing time (e.g., T process,1 (T may be (pre)configured for the indicated resource pool and / or RB set). The (pre)configured processing time may indicate a time period for the WTRU to process the decoded SCI and measured RSRP within the SCI sensing window. In one example, the WTRU may process,1 The T1 value can be determined based on the ability to do so, with the upper limit being 1.

[0143] The WTRU determines the number of transmissions (N TX The determination may be based on the QoS requirements of the TB, such as priority, reliability, and / or latency. The WTRU may determine the corresponding total number of SL U resources in the RSW (N r_total ), for example, N r_total is N TX In another example, N r_total is the number of RB interlaces for transmission, N TX The SL_U resource available for transmission may be equal to the indicated number of RB interlaces in one slot, and may be referred to herein as a candidate resource.

[0144] The WTRU TX SCI sensing for SL U channel access and resource selection for COT sharing in each slot (i) starting from slot (n) may be performed until N transmissions can be performed within the RSW. The number of transmissions performed using the RSW is determined. TXIf the WTRU is less than 1, the WTRU starts from slot (n) and proc,1 ) may perform SCI sensing for SL U channel access and resource selection for COT sharing in each slot (i).

[0145] For each slot (i), the WTRU proc,0 ) for the indicated resource pool and / or RB set. The WTRU may be (pre)configured with a T0 value for the indicated resource pool and / or RB set. For example, when COT and / or resource reservation for another TB is enabled in the resource pool (pre)configuration, the WTRU may be (pre)configured with a T0 value corresponding to the maximum length of the (pre)configured reservation interval. When COT and / or resource reservation for another TB is disabled in the resource pool (pre)configuration, the WTRU may be (pre)configured with a T0 value corresponding to the maximum (pre)configured COT length. The WTRU may be (pre)configured with a T0 value for the resource pool associated with the SCS, such as 1 slot for a 15 kHz SCS. proc,0 The value can be (pre)configured.

[0146] The WTRU may monitor the SCI in the PSCCH in slots belonging to the indicated resource pool within the determined sensing window, except for the slot in which the WTRU performs transmission. The WTRU may perform blind decoding on the (pre-)configured lowest RBs of each RB interlace (pre-)configured for the indicated resource pool and / or RB set in each monitored slot. When the WTRU successfully decodes an SCI in a slot within the SCI sensing window, the WTRU may measure the RSRP of the DMRS associated with the detected PSSCH / PSCCH transmission. The WTRU may measure the RSRP of the DMRS associated with the detected PSSCH / PSCCH transmission in slots (i-T0) and (iT proc,0 ) the decoded SCI and measured RSRP data can be processed based on SCI sensing from an SCI sensing window between

[0147] In some cases, the WTRU may determine the COT sharing based on SCI sensing. The WTRU may be triggered by higher layers to perform SL U channel access and resource selection for COT sharing in slot(n) for transmission of one or more TBs. The WTRU may perform SCI sensing to determine whether the WTRU can perform COT sharing for the transmission of the TBs.

[0148] Based on the SCI sensing information, the WTRU may determine, for each slot in the RSW, proc,1 ), the WTRU may determine whether to perform COT sharing. The WTRU may detect the COT at slot(t) when the WTRU determines the remaining COT duration (e.g., TRIV) indicated in the decoded SCI in a sensing window (e.g., including slot(t)). The detected COT may be referred to herein as the current COT.

[0149] The WTRU determines the remaining number of available candidate resources for COT sharing within the current COT (N r_COT ) can be determined based on one or more of the following SCI sensing information: remaining_COT ); remaining transmission duration T remaining_TX ;Frequency resource allocation for scheduled PSSCH transmission in the current COT, such as RB interlace and / or RB set index; and / or candidate resource, etc. L in one slot for TB to transmit RB_interlace RB interlaces.

[0150] The WTRU determines that the last slot of the current COT is slot(t+T remaining_COT ), and slot(t) and slot(t+T remaining_COT ) the number of slots with no transmission between slot_no_tx ), but (T remaining_COT -T remaining_TXFor example, if the remaining COT duration and remaining transmission duration indicated for slot(t) are 5 slots and 2 slots, respectively, the WTRU may determine that the number of slots with no scheduled transmission in the current COT will be 3 slots.

[0151] The WTRU determines the number of available candidate resources for COT sharing within the current COT (N r_COT ) may be determined. This number may be the sum of one or more of the number of available candidate resources in the determined slots with no transmission in the current COT and / or the number of available candidate resources in slots scheduled for transmission in the current COT. For example, there may be only one COT, called the shared current COT, and there may be two types of slots in the shared current COT. The first type is the slots that are not occupied by the transmission by the WTRU initiating the COT, and the second type is the slots that are occupied by the transmission by the WTRU initiating the COT. In the unoccupied slots, the number of resources may be equal to the number of interlaces per slot multiplied by the number of unoccupied slots, and in the occupied slots, the number of resources may depend on how many interlaces are occupied by the WTRU initiating the COT, and thus the number may be calculated based on the number of unused interlaces multiplied by the number of occupied slots. The total resources may be the sum of these two types of numbers.

[0152] For the number of available candidate resources in the determined slots with no transmission in the current COT, the WTRU may set such number to N slot_no_tx ×floor(M / L RB_interlace ), where N slot_no_tx may be the number of slots with no transmission in the current COT, M may be the (pre-)configured number of RB interlaces for the indicated resource pool and / or RB set, and floor(M / LRB_interlace ) may be the number of available candidate resources in each such slot.

[0153] For the number of available candidate resources in a slot scheduled for transmission within the current COT, the WTRU may determine such number as T remaining_TX ×floor((MN assigned_interlace ) / L RB_interlace ) in which T remaining_TX is the number of slots with scheduled transmissions in the current COT, M is the (pre-)configured number of RB interlaces for the indicated resource pool and / or RB set, and N assigned_interlace is the number of allocated / occupied RB interlaces, and floor((MN assigned_interlace ) / L RB_interlace ) is the number of available candidate resources in such a slot.

[0154] For SCI sensing, the WTRU may also determine whether the current COT may overlap with the reserved COT and / or resources based on the decoded SCI information associated with the COT and / or resource reservation for the transmission. Such SCI information may include a COT and / or resource reservation interval (e.g., for semi-persistent reservation) and a COT and / or resource reservation window (e.g., for retransmission reservation). The WTRU may determine one or more slots in the RSW that are included in such COT and / or resource reservation. The WTRU may determine that the current COT may overlap with such reserved COT and / or resources when the slot is included in the current COT. The WTRU may associate an L1 priority (e.g., an L1 priority indicated on the SCI on which the COT and / or resource reservation may be decoded) and a measured RSRP value (e.g., measured on the DMRS of the PSCCH and / or PSSCH transmission that includes the SCI on which the COT and / or resource reservation may be decoded) with the determined overlap.

[0155] The WTRU may determine whether to share the current COT based on one or more of the following information: (pre)configured COT sharing enabled / disabled in the resource pool; COT sharing for a PSSCH / PSCCH indication associated with the current COT, such as an indication included in the SCI where the current COT information may be decoded; and the determined number of available candidate resources for COT sharing (N r_COT A channel congestion indication associated with the current COT, such as an indication included in the SCI where the current COT information can be decoded; L1 priority of the TB transmitted in the current COT. COT ), cast type, WTRU source and / or destination ID; L1 priority of the TB sent by the WTRU ( TX ), cast type, WTRU source and / or destination ID; current COT and reserved COT and / or resources and associated L1 priority resv ) and the RSRP value; distance to the WTRU that may have initiated the current COT; measured RSRP of the PSCCH DMRS and / or PSSCH DMRS associated with the SCI that carries the current COT information; measured congestion level (e.g., SL U CBR and RSSI); cast type of PSSCH / PSCCH transmission within the COT by the WTRU initiating the COT; WTRU source and / or destination ID of the WTRU initiating the COT; COT initiation and / or sharing indication for the SCI and / or SL slot indication for sharing within the COT.

[0156] The WTRU may determine whether to share the current COT based on one or more conditions.

[0157] In an example, the WTRU may determine to share the current COT when COT sharing is (pre-)configured to be enabled in the indicated resource pool.

[0158] In an example, the WTRU may determine to share the current COT when the COT sharing indication indicates that the current COT may be shared.

[0159] In the example, the WTRU selects the L1 priority of the TB to transmit. TX ) is higher than a (pre-)configured threshold for the resource pool. In another example, such a threshold may be associated with a channel congestion status with a higher threshold for a congested channel (e.g., when the channel congestion indication associated with the current COT may be 1). The WTRU may determine a threshold corresponding to the value of the channel congestion indication associated with the current COT. The association may prioritize WTRUs with higher priority TBs in COT sharing.

[0160] In the example, the WTRU selects the L1 priority of the TB to transmit. TX ) is the L1 priority associated with the TB to be sent in the current COT. COT ), it can be determined to share the current COT.

[0161] In the example, the WTRU may determine whether a COT start is indicated by a SCI decoded in the current COT and / or whether the priority of the TB to transmit in the COT is equal to or greater than the priority of the TB to transmit in the COT. TX ) is the priority value indicated by the decoded SCI in the current COT. COT ) may be met. Since the priority indicated in the COT by the initiating WTRU is used to set the LBT and resource selection parameters for obtaining and initiating the COT, it may not be fair to other non-3GPP systems in the unlicensed spectrum for another WTRU to be able to share the COT to transmit a TB with a lower priority.

[0162] In an example, a WTRU may determine to share the current COT when the cast type of the TB transmitted in the current COT is unicast and the WTRU source and destination ID pair of the unicast transmission and the WTRU source and destination ID pair of the transmitting TB are associated with the same unicast SL (e.g., the WTRUs may share the current COT for TBs associated with the same unicast link). When two WTRUs establish a unicast SL between each other, each WTRU may be (pre-)configured with an associated unidirectional WTRU source and destination ID pair for the transmission of the unicast SL. The two WTRUs may exchange WTRU source and destination ID information via RRC connection establishment and / or configuration signaling, and thus each WTRU may associate two pairs of WTRU source and destination IDs with the same unicast SL.

[0163] In an example, a WTRU may determine to share a current COT when the WTRU initiating the COT is a peer WTRU that has a (pre-)configured unicast link between the initiating WTRU and the WTRU that shares the COT. Each WTRU may indicate a pair of WTRU IDs to a peer WTRU in the SCI of a PSSCH / PSCCH transmission for unicast link traffic as discussed herein. Thus, when the COT initiation is indicated in the SCI, the WTRU may determine that the initiating WTRU may be a peer WTRU of a (pre-)configured unicast link when a pair of source and destination WTRU IDs indicated in the same SCI are (pre-)configured for a unicast link. In some cases, the WTRU may share a COT initiated by a peer WTRU of a (pre-)configured unicast link and perform a PSSCH / PSCCH transmission to a peer WTRU (e.g., the initiating WTRU) for traffic associated with the unicast link. In this case, COT sharing may be applied exclusively to unicast link traffic carried in a SL transmission between two WTRUs (pre-)configured for a unicast link. In another case, a WTRU may share a COT initiated by a peer WTRU of a (pre-)configured unicast link and perform PSCCH / PSCCH transmissions for traffic associated with the unicast, groupcast, and / or broadcast links operated by the WTRU.

[0164] In an example, the WTRU may determine to share the current COT when the cast type of the TB transmitted in the current COT is groupcast and the WTRU destination ID of the groupcast transmission is the same as the WTRU destination ID of the transmitting TB, e.g., the WTRU may share the current COT with a transmission of a TB associated with the same groupcast SL.

[0165] In an example, the WTRU may determine to share the current COT when the cast type of the TB transmitted in the current COT is broadcast and the WTRU destination ID of the broadcast transmission is the same as the WTRU destination ID of the transmitting TB, e.g., the WTRU may share the current COT with a transmission of a TB associated with the same broadcast SL.

[0166] In an example, the WTRU may determine not to share the COT when the SCI decoded in the current COT indicates COT sharing, such as the COT may already be shared by another WTRU. In this case, the COT initiated by the WTRU may be shared by one or less WTRUs. However, in groupcast and / or broadcast transmissions, it may be beneficial for multiple WTRUs to share a COT for SL traffic associated with the same groupcast and / or broadcast link. Thus, in another case, the WTRU may determine to share the COT when the SCI decoded in the current COT indicates COT sharing and the WTRU is a member of a group indicated by the WTRU destination ID of the SCI decoded in the current COT. The WTRU may share the COT and perform transmission of TBs associated with the same WTRU destination ID indicated in the SCI received in the COT, such as traffic belonging to the same groupcast and / or broadcast link.

[0167] In an example, COT sharing by one or more WTRUs as discussed herein may be enabled or disabled by a (pre-)configuration of a resource pool. In addition, when such sharing is enabled, there may be a (pre-)configured maximum number of sharing WTRUs in the resource pool. If the WTRU detects a WTRU capable of sharing and determines that the value of the COT sharing indication is below the (pre-)configured maximum number of sharing WTRUs for the COT, the WTRU may determine to share the COT. Otherwise, the WTRU may determine not to share the COT.

[0168] The WTRU may determine to share the COT when the synchronization source indicated in the decoded SCI in the current sharable COT is the same as and / or belongs to the same (pre-)configured synchronization source group with its own synchronization source. In another example, when both the indicated synchronization source and its own synchronization source are SyncRef WTRU, the WTRU may determine to share the COT when the indicated SLSS ID is also the same as that of its own SyncRef WTRU, e.g., the initiating WTRU and the sharing WTRU of the COT may synchronize with the same SyncRef WTRU. The WTRU may determine not to share the COT when the SLSS IDs are different.

[0169] In an example, the WTRU may determine the number of determined available candidate resources for COT sharing (N r_COT ) is equal to or greater than a (pre-)configured threshold. In one example, such threshold value may be associated with the L1 priority of the transmitting TB, with a larger threshold corresponding to a higher L1 priority. In another example, such threshold value may also be associated with a channel congestion status, with a larger value corresponding to a channel congestion indication of 1. The WTRU may determine such threshold value corresponding to the L1 priority of the transmitting TB and / or the value of the channel congestion indication associated with the current COT. When there is no such (pre-)configuration or the (pre-)configured value is 0, the WTRU may determine to share the current COT without considering the determined number of available candidate resources for COT sharing.

[0170] In an example, the WTRU may determine not to share the current COT when a determined available candidate resource overlaps with one reserved COT and / or resource and the RSRP (e.g., determined upon SCI detection) associated with the overlap is higher than a (pre-)configured threshold. In one example, the value of such threshold may be determined based on the L1 priority (Priority) associated with the overlap.resv ) and the L1 priority of the TB to be sent (Priority TX In another example, such a threshold value may be associated with channel congestion. The WTRU may determine the priority of the SCI of the current COT based on the priority of the SCI of the current COT. resv , Priority TX , and an RSRP threshold corresponding to channel congestion, which can ensure that WTRUs with TBs with higher priority share the same current COT, especially in a congested channel.

[0171] In an example, a WTRU may determine to share the current COT when the distance between itself and the WTRU initiating the current COT falls below a (pre-)configured threshold. The WTRU may determine such distance (e.g., in meters) based on its own location information, such as GNSS geographic coordinates and / or zone ID, indicated in the SCI carrying the current COT information. In one example, the (pre-)configured threshold may be an MCR requirement, indicated in the SCI carrying the current COT information.

[0172] In an example, the WTRU may determine to share the current COT when the RSRP measured on the PSCCH DMRS and / or PSSCH DMRS associated with the SCI carrying information of the current COT is higher than a (pre-)configured threshold. In one example, such a threshold may be determined based on the L1 priority of the transmitting TB. TX ) and / or the L1 priority associated with the TB to be transmitted in the current COT. COT ) of a TB to transmit, so that a WTRU with a TB with a higher priority may be prioritized to share the current COT. TX )

[0173] In an example, the WTRU may determine to share the current COT when a measured congestion level falls below a (pre-)configured threshold. The WTRU may determine such congestion level based on one or more (pre-)configured measurements performed in LBT sensing and / or SCI sensing. The measurements may include RSSI measured in sensing slots, RSSI measured in SL slots, RSRP measured on PSCCH DMRS, PSSCH DMRS associated with the decoded SCI, and / or the number of slots where the LBT sensing result of the channel may be busy, etc. The WTRU may perform such congestion level measurements within a (pre-)configured SL U channel congestion measurement window. The measurement-based channel congestion level may be expressed as a ratio of the number of slots where the measurement value (e.g., RSSI or number of busy sensing slots) exceeds a (pre-)configured level to the total number of measured sensing and / or SL slots in the resource pool. In one example, the (pre-)configured threshold may be determined based on the L1 priority (Priority) of the transmitting TB. TX ) and / or the L1 priority associated with the TB to be transmitted in the current COT. COT A higher threshold corresponds to a higher priority for the TB to be sent. TX ), and thus, at a given congestion level, a WTRU with a TB with higher priority may be allowed to share the current COT. The WTRU may determine to share the current COT when there is an indication of SL slot sharing in the COT.

[0174] In some cases, the WTRU may select resources within the COT to be shared. When the WTRU determines to perform COT sharing, the WTRU may select available candidate resources within the current COT to use for the transmission of TB as a fraction of the determined total number of resources for the transmission of TB (N r_total ); Determined available candidate resources in the current COT to be shared (N r_COT ); L1 priority of the TB to be sent (Prio TX), the determination may be based on one or more factors such as.

[0175] The WTRU is provided with the maximum number of available candidate resources for COT sharing in the resource pool (N r_max ) may be (pre)configured, and the WTRU determines the number of resources to use (N r_share ) to N r_share =Nr _max In another example, such a value may be associated with an L1 priority. The WTRU may determine that the L1 priority of the (pre)configured association and transmitting TB is TX ) based on N r_max The maximum resource determination may allow the current COT to be shared among the WTRUs.

[0176] In another approach, the WTRU may receive the determined available candidate resources (N r_COT ) can be (pre)configured. The WTRU determines the number of resources (N r_share ) to N r_share =Nr _COT ×P%, where P may be associated with an L1 priority, and the WTRU may determine the L1 priority of the TB to transmit. TX ) of the TB to transmit. In another example, the value of P may be associated with a channel congestion status. The WTRU may determine the value of P based on the L1 priority (Priority TX ) and / or a channel congestion indication associated with the current COT. Thus, more resources may be selected when the channel is not congested.

[0177] WTRU has such N r_max And / or when the P ratio is not (pre-)configured, the WTRU may select all determined available candidate resources in the current COT to be shared, N r_share =Nr _COT , it can be determined that the determined Nr_share is equal to or greater than the total number of determined resources for the transmission of TB (N r_share ≧N r_total ), WTRU is Nr _share =N r_total In this case, the WTRU may complete the determined transmission of TB in the shared current COT.

[0178] The WTRU selects N for COT sharing in ascending order with respect to the RB interlace index and slot index. r_COT The determined available candidate resources may be indexed. For example, the WTRU may index the first available candidate resource in a slot in ascending order of RB interlace index, and then continue indexing the candidate resources in the next slot until the last slot for sharing in the current COT. The WTRU may index each available candidate resource as r j where the index j is (0, 1, N r_COT -1).

[0179] The WTRU may be configured to receive the N r_COT From such resources, N for the transmission of TB r_share The WTRU may select available candidate resources from the available candidate resources. The WTRU may determine that it has one or more available candidate resources in each slot of the shared current COT that may not include a scheduled transmission.

[0180] The WTRU determines which N r_share The decision to use the available candidate resources may be based on one or more of the following: random selection, WTRU source and / or destination ID, slot index, cast type, and / or (pre)configured resource pattern.

[0181] The WTRU isr_COT -1) to N r_share The WTRU may randomly select indexes and determine to use the available candidate resources indicated by the selected indexes. The WTRU may determine N r_share The WTRU may determine the slot index in the seed selection. In one example, for a unicast transmission, the WTRU may determine the randomly selected initialization seed based on a WTRU source ID and / or a WTRU destination ID. In addition, the WTRU may also include the slot index in the seed initialization. In another example, for a groupcast transmission, the WTRU may determine the randomly selected initialization seed based on a WTRU destination ID and / or a (pre-)configured group member ID. For a broadcast transmission, the WTRU may determine the randomly selected initialization seed based on a WTRU destination ID.

[0182] The WTRU may be (pre)configured with a set of available candidate resource selection patterns. For example, the WTRU may be configured with a set of candidate resource selection patterns with indices (r0, r1, r Nr_sharing ) r_share A first group of N available candidate resources may be selected. r_share =N r_total When , the WTRU may perform all transmissions of TB in the first contiguous available candidate resource in the shared current COT.

[0183] In another example, the WTRU may offset ,r offset+1 ,r offset+Nr_sharing ) r_tx_sharingThe WTRU may select a group of available candidate resources. The WTRU may determine the available candidate resource group offset value based on the WTRU source and / or destination ID and the WTRU destination ID for unicast transmissions. The WTRU may determine the available candidate resource group offset value based on the WTRU destination ID and / or a (pre-)configured group cast member ID for groupcast transmissions. The WTRU may determine the available candidate resource group offset value based on the WTRU destination ID for broadcast transmissions. For example, the WTRU may determine the available candidate resource group offset value based on the numeric value of the WTRU ID and / or group cast member ID and floor(N r_COT / N r_share Such an offset can be determined by performing a modular function using the number of available candidate resource groups, which may be equal to (1 / 1).

[0184] In another approach, the WTRU determines frequency resources for PSSCH / PSCCH transmissions to share the COT based on the WTRU source and / or destination ID. The frequency resources may include one or more RBs, RB interlaces, subchannels, and / or RB sets. The WTRU may be (pre-)configured with a set of such frequency resources, each indicated by an index. The WTRU may perform a modulo operation of a numeric version of the total number of resources and the WTRU source and / or destination ID to determine the index of the start frequency resource for the PSSCH / PSCCH transmission. In another example, the WTRU may select frequency resources based on resource groups and / or COT reservation information. The WTRU may exclude reserved frequency resources from the (pre-)configured frequency resource set before performing the selection based on the WTRU ID, as described above.

[0185] In some cases, there may be a frequency multiplexing-based COT sharing COT, and the frequency multiplexing-based COT sharing scheme may be (pre)configured as enabled or disabled in the resource pool. When the scheme is (pre)configured as disabled in the resource pool, the WTRU may share the COT by performing SL transmissions in the remaining unused (e.g., no scheduled transmissions) SL slots of the shared COT after a Type-2 LBT procedure as described herein. When the scheme is (pre)configured as enabled in the resource pool, the WTRU may share the COT by performing SL transmissions in both the remaining unused slots and SL slots with existing SL transmissions using the available RB interlaces (e.g., as discussed herein).

[0186] The WTRU may determine the number of unused slots in the COT to be shared based on the received SCI indication, which includes the remaining COT duration, the remaining scheduled transmissions, the maximum COT duration, and / or the logical slot index of the start slot of the shared COT.

[0187] The WTRU may determine one or more available RB interlaces in an SL slot where there is an existing SL transmission in the shared COT based on the frequency allocation of the SCIs of the PSSCH / PSCCH transmissions in the COT. In some cases, the WTRU may randomly select one or more available RB interlaces for an SL transmission multiplexed with an existing SL transmission (e.g., by the initiating WTRU) in the shared COT.

[0188] In another case, the WTRU may determine which of the available RB interlaces to use for transmission to share the COT based on the synchronization source indicated in the decoded SCI in the COT. In one example, the WTRU may apply any available RB interlace for SL transmission when the indicated synchronization source is the same as and / or belongs to the same (pre-)configured synchronization source group (e.g., GNSS, same gNB, and / or same SyncRef WTRU) with its own synchronization source. A common synchronization source may mitigate inter-RB interference between transmissions from different WTRU multiplexing frequency domains.

[0189] When the indicated synchronization source is different from and / or does not belong to the same (pre-)configured synchronization source group as its own synchronization source, the WTRU may not perform frequency multiplexing-based COT sharing. In this case, the WTRU may select one or more RB interlaces for transmission from among the available RB interlaces based on the muting (pre-)configuration. In one example, the WTRU may mute (e.g., not select and transmit) RB interlaces adjacent to the RB interlace used for SL transmission in the COT (e.g., by the initiating WTRU).

[0190] Furthermore, when the WTRU determines to perform such frequency multiplexing based COT sharing, the WTRU may determine a maximum power of its SL transmission multiplexed with an existing SL transmission in an SL slot based on: the measured power level (e.g., RSSI) of the existing SL transmission in the SL slot in the shared COT; and / or the regulatory imposed power spectral density (PSD) requirement in the channel (e.g., a maximum of P0 dBm / MHz).

[0191] The WTRU may determine that the maximum power for an SL slot is the maximum PSD specified in the regulation P=P0(dBm / MHz)×total transmission bandwidth (MHz), where the total transmission bandwidth may be LBT BW. The WTRU may determine that the maximum power for an SL transmission that is performed in the same slot is PPS. measured where P measured may be the power level measured in the SL slot.

[0192] In one approach, a sharing WTRU may share the current COT by performing a PSSCH / PSCCH transmission in a slot that includes a PSSCH / PSCCH transmission by the WTRU initiating the current COT. The initiating WTRU may indicate a gap for Type-2 LBT in the SCI of each PSSCH / PSCCH transmission. In another example, the WTRU may be (pre-)configured with such a gap at the end of a PSSCH / PSCCH transmission.

[0193] The sharing WTRU may determine frequency resources scheduled for PSSCH / PSCCH transmission by the initiating WTRU based on the frequency allocation information of the decoded SCI. The sharing WTRU may select frequency resources, such as a set of RBs, RB interlaces, and / or subchannels, for PSSCH / PSCCH transmission. In one example, the sharing WTRU may determine such frequency resource allocation by excluding the decoded frequency resources from a (pre-)configured resource pool and selecting frequency resources from among the remaining frequency resources based on the WTRU source and / or destination ID.

[0194] The WTRU may perform a Type 2 LBT, such as a Type 2B LBT, in the indicated or (pre-)configured gap. When the channel is available, the WTRU may perform a PSSCH / PSCCH transmission using the determined frequency resource in the slot containing the PSSCH / PSCCH transmission by the initiating WTRU. When the channel is not available, the physical layer may indicate an LBT failure to higher layers.

[0195] In some cases, the WTRU may send a PSSCH / PSCCH transmission in the shared current COT. The WTRU may send a PSSCH / PSCCH transmission in the shared current COT. r_share A PSSCH / PSCCH transmission of one or more TBs may be sent on the available candidate resources. The WTRU may perform LBT sensing for SL U channel access and resource selection when there is a gap in the PSSCH / PSCCH transmission performed for COT sharing. The WTRU may determine to perform LBT sensing (e.g., Type 2A LBT channel access as discussed herein) following such a 25 us gap. The WTRU may determine to perform LBT sensing (e.g., Type 2B LBT channel access as discussed herein) following such a 16 us gap. The WTRU may determine to perform LBT sensing (e.g., Type 2C LBT channel access as discussed herein) following such a gap smaller than 16 us. The WTRU may perform LBT sensing on the bandwidth of the resource pool and / or RB set indicated for SCI sensing.

[0196] In some cases, the WTRU may select a Type 2 LBT procedure for COT sharing. The WTRU may enable COT sharing to be initiated and / or shared by the WTRU based on one or more scenarios (e.g., when the WTRU performs an action).

[0197] In one example scenario, a WTRU may set the value of COT sharing for a PSSCH / PSCCH indication in the SCI of a PSSCH / PSCCH transmission in the COT to “enabled” when the COT should be shared by a PSCCH / PSSCH transmission of another WTRU.

[0198] In one example scenario, a WTRU may set the value of COT sharing for a PSFCH indication in the SCI of a PSSCH / PSCCH transmission in the COT to “enabled” when the COT should be shared by another WTRU's PSFCH transmission.

[0199] In one example scenario, the WTRU may not transmit in a (pre-)configured Type 2 LBT opportunity (e.g., gap period) at the end of the last PSCCH / PSSCH transmission scheduled in the COT (e.g., COT end gap). The WTRU may perform rate matching for the shortened PSSCH / PSCCH transmission in the last PSCCH / PSSSCH slot. In one example, such a gap may be (pre-)configured as one symbol, such as in a 14 symbol SL slot, and the last PSCCH / PSSCH transmission may occupy 13 symbols in the COT, with the last symbol being empty.

[0200] A WTRU that detects a current COT available for sharing may perform a Type 2 LBT procedure at the beginning of a Type 2 LBT opportunity to acquire the channel before sharing the COT. The Type 2 LBT procedure may include a Type 2A, a Type 2B, and / or a Type 2C LBT procedure.

[0201] When performing a Type 2A LBT procedure, the WTRU may transmit immediately after sensing that the channel is available for a 25 us sensing period. Within the sensing period, the WTRU may perform LBT sensing over two sensing slots of 9 us, and when the channel is available in both sensing slots, the WTRU may determine that the channel is available.

[0202] When performing a Type 2B LBT procedure, the WTRU may perform transmission immediately after sensing that the channel is available for a 16 us sensing period. The WTRU may perform LBT in one sensing slot of 9 us, and the WTRU may determine that the channel is available when the channel is sensed as available for at least 4 us within the sensing slot for a total of at least 5 us.

[0203] When performing a Type 2C LBT procedure, the WTRU may perform a transmission without performing sensing. The duration of such a transmission without sensing may be up to 584 us.

[0204] When a WTRU performs a Type 2A or Type 2B LBT to obtain a channel for sharing a COT, the WTRU may transmit until the end of the maximum duration (MCOT) of the shared COT. The WTRU may determine this information based on the remaining COT duration, the MCOT, and / or an SCI indication that includes a logical slot index of the start slot of the COT received in the COT. The WTRU may stop transmission in the shared COT at the end of the MCOT duration of the shared COT.

[0205] When the WTRU performs a Type 2C LBT to acquire a channel for sharing the COT, the WTRU may perform an SL transmission within a duration that is the minimum between 584us and the remaining COT duration until the end of the maximum duration (e.g., MCOT).

[0206] In one approach, the WTRU may determine a Type 2 LBT opportunity in the COT based on one or more SCI indications received in the COT, such as the remaining scheduled transmission duration, the remaining COT duration, and / or an index of a logical slot in the COT. At the beginning of a Type 2 LBT opportunity in a detected sharable COT, the WTRU may perform one of the Type 2 LBT procedures described herein. The WTRU may determine which Type 2 LBT procedure (e.g., 2A, 2B, or 2C) to perform before sharing the COT based on one or more of the following: L1 priority of the TB transmitting in the shared COT. TX ); The L1 priority associated with the TB being sent in the current COT. COT ); remaining PDB of the TB transmitting in the shared COT; duration of transmission of the TB in the shared COT; remaining duration of resource selection window for the TB transmitting in the shared COT; cast type of the TB transmitting in the shared COT; type of SL channel sharing the COT (e.g., PSFCH or PSSCH / PSCCH transmission); measured channel congestion level (e.g., SL CBR, CO, RSSI); channel congestion indication of SCI transmitted by the initiating WTRU in the COT; measured RSRP of PSCCH and / or PSSCH received in the COT; and / or distance between the initiating WTRU and the sharing WTRU.

[0207] The WTRU determines the priority associated with that transmission. TX ) may be higher than a (pre-)configured threshold and the transmission duration may be less than 584 us (e.g., PSSCH / PSCCH transmission with 60 kHz SCS on one SL slot). In another case, the WTRU may perform a Type 2C LBT procedure when the remaining PDB of the TB and / or the remaining duration of the resource selection window may be less than a (pre-)configured threshold and the transmission duration may be less than 584 us.

[0208] When the WTRU transmits one or more PSFCHs in a shared COT, the WTRU may perform a Type 2C LBT procedure.

[0209] When the SL transmission duration exceeds 485 us, the WTRU may determine whether to use a Type 2B or Type 2A LBT procedure. In some cases, the WTRU may be (pre-)configured to perform Type 2A LBT for unicast and / or groupcast transmissions and Type 2B LBT for broadcast transmissions.

[0210] In some cases, the WTRU may TX ) is equal to or greater than a (pre-)configured threshold, and to perform a Type 2A LBT otherwise. In another case, the WTRU may perform a Type 2B LBT procedure if the remaining PDB of the TB is equal to or less than a (pre-)configured threshold, and to perform a Type 2A LBT procedure otherwise.

[0211] In another case, when the channel congestion level is equal to or greater than a (pre)configured threshold (e.g., the first criterion) and the TB priority TX There may be two criteria, such as when the LBT time t1 is greater than or equal to a (pre-)configured threshold (e.g., the second criterion), and the WTRU may decide to perform a Type 2A LBT procedure (e.g., in a busy channel for a high priority TB, a longer LBT is applied). The WTRU may decide to perform a Type 2B LBT procedure if one or both criteria are not met. When the channel is busy, the WTRU may perform longer sensing to reduce collisions for high priority TBs.

[0212] When the channel congestion level falls below a (pre)configured threshold, the WTRU may select the TB priority. TX) is equal to or greater than a (pre)configured threshold. The WTRU may determine to perform a Type 2B LBT procedure when the priority is lower than the threshold. When the channel is not busy, the WTRU may perform shorter sensing on high priority TBs to acquire the channel faster.

[0213] The WTRU may determine the channel congestion level based on measurements of the SL CBR, CO, and / or RSSI of the channel (pre-)configured for the LBT. In another example, the WTRU may determine the information based on the congestion level indicated in the COT by the initiating WTRU.

[0214] In one example, the (pre)configured priority threshold applied in the Type 2 LBT decision discussed above is the priority associated with the TB to be transmitted in the current COT. COT ) may be based on

[0215] 3 shows an example of a sharing WTRU decision of Type 2 LBT for COT sharing. As shown, there may be an initiating WTRU 310, a sharing WTRU 311 with priority 1, and a sharing WTRU 312 with priority 2. Time is shown on the horizontal axis, but frequency is not intended to be shown on the vertical axis. As shown, the WTRU 310 may initiate the COT, which may then be shared by WTRUs 311 and 312. In one instance, each WTRU may use the same, partially the same (i.e., overlapping), or different frequency resources, since the transmissions of one WTRU do not overlap in time.

[0216] Since the Type 2B LBT procedure takes less time to acquire the channel when it is available, the priority-based Type 2 LBT selection may allow a WTRU with a high priority TB to share the COT more easily when multiple WTRUs attempt to share the COT. This may be applicable to low congestion scenarios where collisions are not an issue. As shown in the example of FIG. 3, both WTRU 311 and WTRU 312 may detect an ongoing shareable COT (e.g., initiated by WTRU 310) and perform Type 2 LBT in the same Type 2 LBT opportunity. WTRU 311 may be associated with Type 2B LBT because its priority (Priority_1) is higher than a threshold and the measured CBR is below a (pre)configured threshold (e.g., where CBR is the SL measurement of the resource pool, which is an indication of congestion in the channel). The WTRU 312 may perform Type 2A LBT because its TB priority (Priority_2) is below a threshold and may be associated with a Type 2A LBT (e.g., the measured CBR is also below a threshold). The WTRU 311, which has a TB transmission with a higher priority, may share the COT with the WTRU 310, and the WTRU 312 may detect a busy channel due to the WTRU 311 transmission and continue to gain channel access (e.g., repeat one or more procedures referenced herein). In some cases, the WTRU 311 may transmit a reservation signal 303, such as a cyclic prefix extension (CPE), at the end of the COT so that it can begin transmitting the higher priority TB.

[0217] In a further example, the WTRU may determine to perform a Type 2A LBT if the distance between the WTRU and the intended target WTRU of the transmission may be greater than or equal to a (pre-)configured threshold, and may determine to perform a Type 2B LBT if this is not the case.

[0218] In another example, a WTRU sharing the COT may perform a Type-2 LBT procedure based on Type-2 channel access information indicated in the SCI of a PSSCH / PSCCH transmission in the COT. In this case, a WTRU initiating and / or sharing the COT may indicate the following information in the SCI of a PSSCH / PSCCH transmission in the COT: The value of COT sharing for the PSSCH / PSCCH indication is "valid" when the COT is to be shared by another WTRU's PSCCH / PSSCH transmission; the value of COT sharing for the PSFCH indication is "valid" when the COT is to be shared by another WTRU's PSFCH transmission; the start of the period for the Type 2 LBT procedure (e.g., logical slot index, symbol index with slot, (pre-)configured Type 2 LBT opportunity, etc.); the type of Type 2 LBT to perform to share the COT (2A, 2B or 2C); the length of the gap reserved for the Type 2 LBT preceding the start of the transmission to share the COT; an indication of the SL slots available for sharing in the COT; and / or the COT time, such as the MCOT, remaining COT duration, and / or COT start slot index.

[0219] In some cases, the WTRU may perform a channel reservation signal and / or CPE transmission following the end of the last PSCCH / PSSCH transmission scheduled in the COT (e.g., as in the example of FIG. 3). In some cases, the WTRU may not perform a PSSCH / PSSCH transmission in the last symbol of the last SL slot scheduled in the COT. Instead, the WTRU may transmit the channel reservation signal and / or CPE from the start of the last symbol to keep the COT started and / or shared. The WTRU may leave a gap of length Xus between the end of the channel reservation signal and / or CPE transmission and the end of the last symbol. In one example, the value of X may be explicitly indicated in an SCI bit field with log2(maximum(X)) bits, where maximum(X) is the maximum gap length (e.g., one symbol). In another example, the gap length may be indicated using an index in the SCI bit field. The set of indices may be (pre)configured to indicate gap lengths, for example, below 16us, 16us, greater than 16us and less than 25us, and / or greater than or equal to 25us.

[0220] A WTRU sharing an initiating and / or shared COT may determine to perform Type 2 LBT channel access according to a gap length indicated in the SCI received in the COT. For example, the WTRU may perform Type 2C LBT channel access when the indicated gap length is less than 16 us. The WTRU may perform Type 2B LBT channel access when the indicated gap length is 16 us.

[0221] The WTRU may perform Type 2B LBT channel access when the indicated gap length is greater than 16 us and less than 25 us. The WTRU may randomly select a 16 us period within the gap to perform Type 2B LBT. In another approach, the WTRU may select the start time Type 2B LBT based on the priority of the TB transmitting in the shared COT. For example, the WTRU may perform Type 2B LBT within the first 16 us period of the gap when the priority is higher than a (pre)configured threshold. Otherwise, the WTRU may perform Type 2B LBT within the last 16 us period of the gap.

[0222] In some cases, the WTRU may be (pre)configured with Type 2X (e.g., Type 2A, 2B, or 2C) LBT channel access when the indicated gap length is greater than 16 us and less than 25 us. With Type 2X LBT channel access, the WTRU may perform an SL transmission after sensing that the channel is idle within a duration equal to the gap length indicated in the SCI received in the COT. The Type 2X LBT duration may include a sensing slot (e.g., at the end of the duration).

[0223] The WTRU may perform reservation signaling and / or CPE transmission between the end of Type 2 LBT channel access (e.g., Type 2A LBT) and the start of PSSCH / PSCCH transmission to share the COT. In some cases, the WTRU may determine the duration of the channel reservation signaling and / or CPE based on the priority of the TB transmitting in the shared COT.

[0224] In one example, the reservation signal and / or the CPE may Reserve / CPE =N Reserv / CPE ×T unit etc., integer (N Reserv / CPE ) (pre)configured time units (T unit ) duration (T Reserve / CPE) The time unit can have an LBT sensing slot (T SL ), LBT contention period (T contention ), 16us, and / or 25us. Each SL priority has a corresponding N Reserv / CPE The value can be (pre)configured. Higher priority (lower priority value) means a larger N Reserv / CPE It may be associated with a value.

[0225] A WTRU (e.g., wanting to share a COT) may determine whether to start a PSSCH / PSCCH transmission (e.g., at the boundary of the first SL slot of the shared COT (t t )) to share the COT based at least in part on one or more of the MCOT, remaining COT duration, start slot index, indication of SL slot for sharing, and / or SCI indication, including the like as disclosed herein. sharing-start The WTRU can determine the determined start of PSSCH / PSCCH transmission (t sharing-start ) and / or the duration of the channel reservation signal and / or the CPE (T Reserve / CPE ) may be used to determine the start of Type 2 LBT channel access (e.g., Type 2A LBT). For example, the start of Type 2A LBT channel access may be determined based at least in part on (t sharing-start -T Reserve / CPE -25).

[0226] Thus, when multiple WTRUs attempt to share a detected COT starting from the same SL slot, a WTRU with a higher priority TB may perform a longer channel reservation signal and / or CPE transmission and accordingly start Type 2 LBT channel access earlier in the gap. The resulting channel reservation signal and / or CPE transmission may cause Type 2 LBT channel access failure of another WTRU with a lower priority TB (see, e.g., the example of FIG. 3).

[0227] In another example, the WTRU may be (pre-)configured with a set of Type 2 LBT procedures in addition to other Type 2A / 2B / 2C procedures (e.g., as discussed herein). Each Type 2 LTB may include N sensing slots, and the WTRU may determine that the channel is available before performing COT sharing. The number (N) may be associated with the priority of the TBs transmitting in the shared COT and / or the channel congestion level (e.g., CBR, Channel Occupancy (CO), and / or RSSI). In one example, when the congestion level exceeds a (pre-)configured threshold, the WTRU may determine a large number (N) of sensing slots for the high priority TB. When the congestion level falls below a (pre-)configured threshold, the WTRU may determine a small number (N) of sensing slots for the high priority TB.

[0228] In an example, if the WTRU determines that there is no SL transmission in the SL slot immediately preceding the first SL slot for sharing the COT, such as the last SL slot of the remaining transmissions indicated in the current shared COT, the WTRU may determine not to perform PSSCH / PSCCH transmissions of one or more TBs in the current shared COT. The WTRU may determine that there is no such transmission when the WTRU does not detect an SCI in SCI decoding in the SL slot (e.g., the slot immediately preceding the first SL slot for sharing the COT). In this example, the absence of SL transmission does not necessarily mean that there is no transmission, but rather that there is no transmission (e.g., a non-3GPP transmission) for which the SCI cannot be decoded, and therefore sharing is not possible. For example, the WTRU may only share the COT when the ongoing transmission is an SL transmission. In another example, the WTRU may determine that there is no such transmission when the WTRU can measure an RSSI level lower than a (pre-)configured threshold in LBT sensing in the SL slot.

[0229] In some cases, WTRUs sharing a COT may perform non-consecutive transmissions within the COT. The WTRU may determine to share a COT based on the SCI indication and / or conditions disclosed herein. For the first transmission on one or more symbols or one or more consecutive SL slots, the WTRU may perform Type 2 LBT channel access and transmission of channel reservation signals and / or CPEs based on the SCI indication or priority of the TB transmitting in the COT. The first transmission may be, for example, a PSFCH and / or a PSSCH. The second transmission depends on spectrum availability and may have one or more approaches.

[0230] If the first transmission ends before the end of the shareable COT length, the WTRU may perform a second transmission and continue sharing the COT when the following conditions are met: the WTRU may determine that the channel may be available until the start of the second transmission, the WTRU may perform LBT sensing immediately after the first transmission and determine channel availability based on the LBT results over this period (e.g., the WTRU may perform LBT at each sensing slot and determine that the channel is available when the results of all sensing slots indicate that the channel is idle, such as the measured RSSI being below a (pre-)configured threshold); and / or the WTRU may further perform Type 2 LBT channel access (e.g., Type 2A LBT channel access) and determine that the channel may be available immediately before the second transmission. The WTRU may determine the shareable COT length (e.g., the number of shareable slots in the COT) based on one or more of the following: The maximum COT (MCOT) associated with the priority indicated in the CAPC configuration; the remaining scheduled transmission duration and / or the remaining COT; the COT start slot index; and / or an indication of a shared slot.

[0231] If any of these conditions are met, the second transmission may be made. However, if these conditions are not met, the WTRU may not perform the second transmission and may not stop COT sharing. If the second transmission is not sent, the WTRU may perform Type 1 LBT channel access to start another COT for the transmission of the TB that would have been carried in the second transmission that was not sent.

[0232] In this approach of COT sharing for non-consecutive transmissions, channel reservation signals and / or CPE transmissions may not be performed between the first and second transmissions. A WTRU that shares the COT with the first transmission may continue with the second transmission to share the COT if it senses that the channel is available within the COT.

[0233] For each PSSCH / PSCCH transmission performed in the shared current COT, the WTRU may indicate one or more SCI information in the PSCCH, the transmitted TB, the transmission configuration, and so on, on the shared current COT.

[0234] The one or more SCI information may include an L1 priority, a cast type, a WTRU source ID, and / or a destination ID of the TB transmitted on the PSSCH.

[0235] The one or more pieces of SCI information may include a remaining COT duration, which may be the remaining time of the COT between the slot in which the SCI is transmitted and the end of the current COT that is shared.

[0236] The one or more SCI information may include an MCOT duration, and a maximum COT corresponding to the configuration used for the Type 1 LBT performed to start the current COT may be indicated by the initiating WTRU, which may be in ms or in logical SL slots. The sharing WTRU may duplicate (e.g., retransmit) this information in its transmission within the shared COT.

[0237] The one or more SCI information may include a COT start slot index, and the initiating WTRU may indicate a logical slot index of the first slot of the COT. When the WTRU decodes the SCI in the COT, it may determine the number of remaining slots available for SL transmission in the COT based on the indicated start slot index and MCOT duration. The sharing WTRU may replicate this information in its transmissions within the shared COT.

[0238] The one or more SCI information may include a COT sharing for PSSCH / PSCCH indication, where the value of this indication may be valid and may be the same as the indication associated with the current shared COT.

[0239] The one or more SCI information may include a COT sharing for PSFCH indication, which may be an indication that is enabled / disabled according to a (pre-)configured PSFCH resource configuration for a resource pool if HARQ feedback is enabled for a TB transmitted on the PSSCH, or the indication may be disabled if HARQ feedback is disabled for a TB transmitted on the PSSCH.

[0240] The one or more SCI information may include a COT initiation / sharing indication. A WTRU sharing a COT may indicate a value corresponding to COT sharing (e.g., a value of 1) in this SCI field of all transmissions performed to share the COT. In another example, when multiple WTRUs sharing a COT are enabled (e.g., in a resource pool (pre) configuration), the sharing WTRU may increment the value of this field to indicate the number of WTRUs sharing this COT.

[0241] The one or more SCI information may include a channel congestion indication, and the value of this indication may be the same as the value indicated in the SCI associated with the shared current COT.

[0242] The one or more SCI information may include a remaining transmission duration, which may be, for example, the number of consecutive slots scheduled for PSCCH / PSSCH transmission in the remaining shared current COT duration, indicated by TRIV.

[0243] The one or more SCI information may include a frequency resource allocation for the PSSCH, which may be, for example, an RB interlace index and / or an RB set index of a PSSCH transmission performed within the shared current COT, as indicated by a frequency resource indication value (FRIV).

[0244] The one or more SCI information may include a COT and / or a resource reservation window, where the WTRU may indicate a value of 0 when the COT and / or resource reservation for retransmissions for COT sharing may be disabled in the resource pool. r_total ) may be performed in the shared current COT. The WTRU may indicate a value of 0 when the time period following the end of the shared current COT and / or between the end of the current COT and the start of the next reserved COT and / or reservation period, in ms or number of slots. The WTRU may determine the length of the window based on the remaining packet delay budget (PDB) of the TBs transmitted in the shared current COT.

[0245] The one or more SCI information may include a HARQ process number, a new data indicator, and / or a redundancy version.

[0246] The one or more SCI information may include a HARQ feedback enable / disable indication, which may be an indication of whether HARQ feedback may be enabled and whether a PSFCH carrying a HARQ ACK / NACK may be expected for a PSSCH / PSCCH transmission. The WTRU may determine this indication based on the QoS requirements of the TBs transmitted in the shared current COT. In one example, the QoS may be associated with a priority as configured in a higher layer. In one example, the WTRU may use one or more QoS parameters (e.g., priority, or other parameters) to determine whether HARQ is enabled / disabled.

[0247] The one or more SCI information may include a transmission configuration including a number of DMRS ports, a DMRS pattern, an MCS value, and / or an MCS table indication.

[0248] The one or more pieces of SCI information may include an indication of an SCI-2 format and a beta offset value.

[0249] The one or more SCI information may include an indication of a synchronization source used by the sharing WTRU. In one example, the value may indicate one of the sources including GNSS, gNB, SyncRef WTRU, and WTRU internal clock. In another example, the additional indication may be (pre-)configured to indicate a SL SSID.

[0250] The one or more SCI information may include a COT and / or a resource reservation interval, where the WTRU may indicate a value of 0 when the COT and / or resource reservation for another TB for COT sharing may be disabled in the resource pool, and / or the WTRU may indicate a value of 0 when the TB transmitted on the PSSCH may be aperiodic.

[0251] When COT and / or resource reservation for another TB for COT sharing is enabled in the resource pool and the TB transmitted on the PSSCH is periodic, the WTRU may indicate the time period in ms or slots between the current COT and / or resources to be shared and the reserved COT and / or resources for transmission for another TB. This time period may be the COT and / or resource reservation interval (P) indicated by higher layers. rsvp_TX )

[0252] By reserving such COT and / or resources, the WTRU can perform SL channel access to start a reserved COT that corresponds to the priority indicated in the SCI of the transmission performed in the shared current COT. In addition, the reservation window may be (pre-)configured with a COT length (e.g., associated with a specific COT length). The WTRU can start the reserved COT within the reservation window.

[0253] In another example, the COT and / or resource reservation for transmissions performed in the shared COT may be enabled / disabled in the (pre-)configuration of the resource pool, and the WTRU may set the indication to 0 when this (pre-)configuration is disabled in the resource pool, regardless of the (pre-)configuration for the traffic type of the TB transmitted in the current shared COT and / or the COT and resource reservation for another TB.

[0254] FIG. 4 refers to FIG. 4A, FIG. 4B, and FIG. 4C (the end of one figure flows into the next and may be indicated using an indicator A in a circle indicating that FIG. 4B is an extension of FIG. 4A, and an indicator B in a circle indicating that FIG. 4C is an extension of FIG. 4B). FIG. 4 illustrates an example of SL U channel access and resource selection. In some cases, the WTRU may perform SL U channel access and resource selection for COT initiation following COT sharing. The WTRU may select N SL U channel access and resource selection for the current shared COT based on the SL U channel access and resource selection procedure for COT sharing. r_share When the number of transmissions to be performed in the shared current COT may be smaller than the number of determined transmissions for TB (N r_share <N r_total ), the WTRU may continue to perform SCI sensing for triggered SL U channel access and resource selection for COT sharing. When the WTRU cannot detect a sharable COT, the WTRU may perform SL U channel access and selection for COT initiation simultaneously with SL U channel access and resource selection for COT sharing, as shown in FIG.

[0255] As shown in FIG. 4A, at 401, the WTRU may be triggered in slot (n) to perform SL U LBT channel access and resource selection for one or more TB transmissions. At 402, the WTRU may determine the number of total transmissions based on the QoS of the TBs and / or the corresponding number of required resources (N). At 403, the WTRU may determine the number of total transmissions based on the QoS of the TBs and / or the corresponding number of required resources (N). 0_proc) and slot (n-T0), the WTRU may receive and process information from SCI sensing of decoded SCI and measured RSRP (e.g., process historical transmissions from which SCI information / measurements are obtained to see if there is a COT reservation). As a result of one or more pieces of information received and / or collected, the WTRU may determine: a resource selection window between slot (n+T1) and slot (n+T2); the presence of a SL COT that includes slot (n+T1+1); and / or a reserved COT within the resource selection window. At 404, the WTRU may determine SL U LBT channel access for COT start configuration based on CAPC parameters configured according to the TB's QoS (e.g., configured by higher layers for each TB for transmission). At 405, the WTRU may perform slot-by-slot processing starting at slot (n+T1+1) (e.g., all processing that may be performed in slots after time 405). At 406, the WTRU may perform per-slot SCI decoding (e.g., the initiating WTRU is performing SCI decoding, which in this example may be receiving / monitoring to see if there is a COT to share; since there is no transmission yet, the COT has not yet been obtained). At 407, the WTRU may determine whether a SL COT exists in the current slot based on the SCI decoded in one or more previous slots (e.g., decoding an ongoing transmission in the current COT). If yes (a SL COT exists in the current slot based on the SCI decoded in the previous slot), at 408, the WTRU may determine whether a SL COT is shareable based on one or more parameters such as information from the SCI (e.g., remaining duration, interlace block allocation, priority, cast type, source and / or destination ID) and / or TB information (e.g., priority, cast type, source and / or destination ID, periodicity, etc.). At 409, the WTRU determines that the COT is shareable (as described at 408).If no (COT is not sharable), at 410, the WTRU determines whether the current slot overlaps with a SL COT reserved by another WTRU from a previously decoded SCI. If yes (COT is sharable), the WTRU proceeds to 418, where the WTRU shares the SL. At 418, the WTRU shares the CL COT and determines resources (e.g., slots, minislots, interlace blocks, etc.) in the SL COT for the determined transmission of the TB based on one or more of the following: remaining COT duration; scheduled transmission; and / or RB interlace allocation indicated in the decoded SCI associated with the shared COT. At 419, the WTRU determines to perform SL U LBT channel access for COT sharing.

[0256] Returning to 407, if no (there is no SL COT in the current slot based on the SCI decoded in the previous slot), then at 410 the WTRU determines whether the current slot overlaps with a SL COT reserved by another WTRU from a previously decoded SCI. If yes (the current slot overlaps with a SL COT reserved by another WTRU from a previously decoded DCI), then at 422 the WTRU continues processing, where it checks whether the slot next =slot current +1, and then the WTRU may proceed to 425, where the WTRU may select the minimum channel access time n+T 2-(pre)(425 and the results of that determination are discussed further herein). If no (the current slot does not overlap with a SL COT reserved by another WTRU from a previously decoded DCI), then at 411, the WTRU performs SL U LBT channel access for COT initiation according to the determined configuration. At 412, if the channel access is completed and unsuccessful, the WTRU may return to 411 and repeat the channel access again (e.g., in some cases this may be repeated until the channel is acquired, or this may be repeated until the TB latency is reached (when the TB expires)). At 412, if the channel access is completed and successful, then at 413, the WTRU may determine whether the starting SL COT overlaps with a SL COT reserved by another WTRU from a previously decoded SCI. If yes (the starting SL COT will overlap with a SL COT reserved by another WTRU from a previously decoded SCI), at 420, the WTRU may evaluate whether to start a SL COT based on one or more of the following information (e.g., decoded from the SCI reserving the overlapping SL COT): resources reserved within the reserved SL COT; a priority associated with the reserved SL COT; and / or other information or parameters (e.g., as described herein). If no (the starting SL COT will not overlap with a SL COT reserved by another WTRU from a previously decoded SCI), the WTRU may proceed with starting the SL COT (e.g., at 414).

[0257] Based on the evaluation at 420, the WTRU may determine at 421 whether to start the SL COT. If yes, the WTRU may proceed with starting the SL COT (e.g., at 414). If no, the WTRU may continue processing to the next slot, where slot next =slot current+1, and then the WTRU may proceed to 425, where the WTRU determines whether the slot is equal to or smaller than the minimum channel access time n+T 2-(pre) (425 and the consequences of that determination are discussed further herein).

[0258] At 414, the WTRU may start a SL COT and determine resources (e.g., slots, minislots, interface blocks, etc.) in the SL COT for the determined transmission of the TB based on one or more of the WTRU source and / or destination ID of the transmitting TB and / or the RB interlace allocation indicated in the decoded SCI associated with the overlapping reserved COT. At 415, the WTRU may transmit a channel reservation signal (e.g., a set of AGC symbols, SL CSI-RS, etc.) until the beginning of the first slot of the started COT. At 416, the WTRU may perform transmission (as described further herein).

[0259] At 416, the WTRU TX M transmissions on the determined resources in the SL COT can be performed for the duration of the slot. Thus, as shown at 417, the next slot for processing is slot+T TX may be equal to N remaining may be equal to NM (e.g., the WTRU needs to transmit on N resources to start, so after each M transmission, the remaining resources are NM). At 423, the WTRU determines whether more resources are needed for one or more transmissions of TB (e.g., based on step 417, N remainingIf no (more resources are not needed for the transmission of TB), then channel access and resource selection for TB is completed at 424, and TB is transmitted. If yes (the WTRU needs more resources for the transmission of TB), then the WTRU determines at 425 whether the slot is configured for the minimum channel access time n+T 2-(pre) (e.g., configured as part of the channel access configuration). If no (the slot is greater than the configured minimum channel access time n+T 2-(pre) If yes (the slot is not greater than the configured minimum channel access time n+T 2-(pre) If , the TB's channel access and resource selection may fail at 426, which may be reported to higher layers.

[0260] In some cases, there may be one or more procedures for SL U channel access and resource selection procedures for COT initiation. In some cases, the WTRU may determine the COT sharing based on LBT sensing. In some cases, the number of transmissions performed within the shared or initiated COT is less than the total number of determined transmissions (N r_share <N r_total ) and / or if the WTRU may not detect an available current COT for sharing based on SCI sensing, the WTRU may determine to perform SL U channel access and resource selection for COT initiation. In some cases, the WTRU may be triggered by higher layers to perform SL U channel access and resource selection for COT initiation in slot(n) for transmission of one or more TBs when COT sharing is (pre-)configured as disabled in the resource pool.

[0261] The WTRU may perform LBT sensing based SL U channel access (e.g., Type 1 LBT channel access as discussed herein) for COT initiation. The WTRU may simultaneously perform SCI sensing for detection of the current COT for COT sharing, as described herein. The WTRU may determine a configuration for LBT sensing based SL U channel access based on one or more of the following SCI information (as described herein): Resource pool and / or RB set; TB priority; TX remaining packet delay budget (PDB); resource selection window (RSW); and / or number of transmissions including initial and retransmissions of TB (N TX ), and the corresponding total number of SL U resources in the RSW (N r_total ).

[0262] The WTRU may determine to use a bandwidth of a resource pool and / or an RB set as the bandwidth for LBT sensing. In another example, the WTRU may be (pre-)configured with several RB sets for LBT sensing. The WTRU may perform LBT sensing on the bandwidth of each RB set for LBT sensing-based channel access.

[0263] The WTRU may determine the duration of the COT and the size of the contention window for initiation based on the priority, the PDB, and / or the number of transmissions of the TB. In one example, the WTRU may select a short COT duration and a small contention window size for a TB with a high priority and a small PDB. With such an LBT sensing configuration, the WTRU may take less time to access the channel. In another example, the WTRU may select a long COT duration and a large contention window size for a TB with a low priority, a large PDB, and / or a large number of transmissions.

[0264] In one approach, the WTRU may determine a time within a determined resource selection window (RSW) to start LBT sensing for SL U channel access for COT initiation. For example, if a current sharable COT is not detected, the WTRU may start LBT sensing at the beginning of the RSW. In another example, the WTRU may randomly select an LBT sensing start time within the RSW.

[0265] In another approach, the WTRU may determine the time to start an LBT sensing channel access (e.g., type 1 LBT channel access for initiating a COT) based on a (pre-)configured LBT sensing start opportunity in a SL slot, subframe, and / or frame. A set of LBT sensing channel access start opportunities may be (pre-)configured, for example, in a SL slot, subframe, and / or frame. Each (pre-)configured LBT sensing channel access start opportunity may be associated with an SL priority. When the WTRU is triggered to perform an LBT sensing channel access (e.g., type 1 LBT channel access) for a TB transmission, the WTRU may start the triggered LBT sensing channel access at the earliest LBT sensing channel access time associated with the priority of the TB.

[0266] In another approach, the WTRU may determine to exclude one or more reserved COTs and / or resources from the determined RSW from LBT sensing. In one example, the WTRU may consider the LBT sensing slots included in the excluded period having the RSW to be busy. In another example, the WTRU may suspend LBT sensing during the LBT sensing slots, such as ignoring the LBT sensing results from the sensing slots. The WTRU may determine the priority indicated in the SCI for reserving the COTs and / or resources and / or the priority of the TB to transmit. TX Priority associated with the reserved COT and / or resources, such as resv) associated with the reserved COT and / or resources. resv ) is the priority of the TB to be sent. TX In another example, the WTRU may determine to perform the exclusion when the RSRP measured on a PSSCH / PSCCH transmission reserving the COT and / or resources exceeds a (pre)configured threshold. The WTRU may determine to perform the exclusion when the RSRP measured on a PSSCH / PSCCH transmission reserving the COT and / or resources exceeds a (pre)configured threshold. resv ), and / or the priority of the TB to be sent TX ) such a threshold can be selected based on

[0267] In one case, during LBT sensing for SL U channel access for COT initiation, when the WTRU detects a current COT that is sharable, the WTRU may switch from the ongoing SL U channel access and resource selection for COT initiation to performing SL U channel access and resource selection for COT sharing. In another case, the WTRU may adjust the LBT sensing-based channel access procedure based on SCI sensing and / or COT sharing. The WTRU may suspend and resume the LBT sensing-based SL U channel access by excluding one or more of the following slots from LBT sensing: slots where the current COT is detected based on SCI sensing; and / or slots where the WTRU performs transmission within the current COT that is shared.

[0268] In some instances, the WTRU may not perform LBT sensing in a slot during LBT sensing based SL U channel access.

[0269] The WTRU may perform LBT sensing for SL U channel access for COT initiation, such as Type 1 channel access, in a set of consecutive logical slots in the time domain of the determined SL resource pool. Such LBT sensing may be performed continuously over time to ensure fair access to the spectrum.

[0270] In one example, the WTRU may perform LBT sensing in physical slots to ensure time continuity of all sensing slots. Upon successful LBT channel access, the WTRU may perform LBT sensing in consecutive physical slot indexes (t i ) of each of the included physical slots based on a mapping between the physical slots and the logical slots belonging to the resource pool used for the PSSCH / PSCCH transmissions sent within the initiated COT. i ) for the logical slots in the resource pool. The WTRU determination of such mapping is discussed further herein (e.g., WTRU process for determining time continuity of logical slots in a resource pool). Thus, the WTRU may determine the logical slot index (T i The WTRU may initiate a COT that includes a set of logical slots having a COT duration, a remaining transmission duration, a COT and / or resource reservation interval, a COT and / or resource reservation window, etc., accordingly, and include in the SCI transmission.

[0271] In another example, the WTRU may perform LBT sensing in logical slots of a resource pool used for PSSCH / PSCCH transmission. The WTRU may determine to stop ongoing LBT sensing when LBT sensing is performed across logical slots (e.g., having consecutive logical slot indices) that may not be consecutive (e.g., having a gap in the time domain). The WTRU may resume LBT sensing for channel access after the gap in the time domain. Alternatively, the WTRU may continue ongoing LBT sensing and add some deferral period in LBT sensing corresponding to the length of the gap in the time domain. Thus, the WTRU may determine to stop ongoing LBT sensing when LBT sensing is performed across logical slots (e.g., having consecutive logical slot indices) that may not be consecutive (e.g., having a gap in the time domain). i ) may be initiated.

[0272] When the LBT sensing based channel access is successful, e.g., when the SL U channel is available, the WTRU may determine to start a COT and perform resource selection within the initiated COT. In another example, the WTRU may determine whether to start a COT and perform resource selection within the initiated COT based on the COT and resource reservation information based on the SCI sensing.

[0273] In one example, the WTRU may determine not to start a COT when the duration of the COT for initiation overlaps with a reserved COT and / or resources. The WTRU may perform another LBT sensing-based channel access after the slots reserved in the COT and / or resource reservation.

[0274] In another example, if the duration of the starting COT overlaps with a reserved COT and / or resources, the WTRU may use the priority associated with the overlapping reserved COT. resvPriority of the TB transmitting in the COT to start and / or resources (e.g., priority indicated in the COT and / or SCI reserving the resources) TX ) the WTRU may determine not to start the COT. The WTRU may determine to perform LBT sensing based SL U channel access for COT initiation after the end of the overlapping reserved COT.

[0275] In another example, the WTRU may determine to start a COT that overlaps with a reserved COT and / or resources when the RSRP associated with the overlap (determined in SCI sensing) is lower than a (pre-)configured threshold. For example, the value of such threshold may be determined based on the L1 priority associated with the overlapping reserved COT. resv ) and the L1 priority of the TB to be sent (Priority TX ) The value of such a threshold may be associated with channel congestion. resv , Priority TX , as well as an RSRP threshold corresponding to the channel congestion measured in the LBT sensing and / or SCI sensing.

[0276] In another example, the WTRU may determine to exclude frequency resources allocated to the reserved COT and / or resources from the resource selection in the initiated COT and initiate a COT that overlaps with the reserved COT and / or resources. In this case, the WTRU may initiate the COT with resource reservation in the frequency domain and / or resource multiplexing with the frequency resources allocated in the COT.

[0277] If the LBT sensing channel access is successful, the WTRU may determine to start the COT immediately after the end of the LBT sensing. The WTRU may determine whether to start the COT based on the time continuity of the logical slots included in the starting COT. In one example, the WTRU may determine that the logical slots included in the COT may not be contiguous in the time domain based on the mapping between the physical slots and the logical slots belonging to the resource pool used for the PSSCH / PSCCH transmission to be performed in the started COT. The WTRU may then determine not to start the COT following the performed LBT sensing channel access and start another LBT sensing channel access for the COT initiation.

[0278] Upon successful LBT sensing channel access, the WTRU may determine to start COT immediately after the end of LBT sensing based on a measured congestion level. In one example, the WTRU may determine to start COT when the measured congestion level falls below a (pre-)configured threshold. The WTRU may determine such congestion level based on one or more (pre-)configured measurements performed in LBT sensing and / or SCI sensing. The measurements may include, for example, RSSI measured in sensing slots, RSSI measured in SL slots, RSRP measured on PSCCH DMRS and / or PSSCH DMRS associated with the decoded SCI, number of slots in which the LBT sensing result of the channel may be busy, etc. The WTRU may perform such congestion level measurements within a (pre-)configured SL U channel congestion measurement window.

[0279] The measurement-based channel congestion level can be expressed as the ratio of the number of slots where the measurement (e.g., RSSI or number of busy sensing slots) exceeds a (pre)configured level to the total number of measured sensing and / or SL slots in the resource pool. In one example, the (pre)configured threshold is the L1 priority of the transmitting TB. TXA higher threshold may be associated with a higher priority of the TB to be transmitted. TX ), and thus, at a given congestion level, a WTRU with a TB with higher priority may be allowed to start COT upon successful LBT-sensing channel access.

[0280] In some cases, there may be a WTRU transmission after Type 1 LBT channel access success without a channel reservation signal and / or CPE transmission. In one approach for COT initiation, time instance t LBT-success If the LBT that senses channel access at is successful, the WTRU determines the start time (t PSSCH-COT-start The WTRU may not immediately perform a channel reservation signal and / or CPE transmission to hold the channel until the WTRU has received the channel reservation signal and / or CPE transmission. The WTRU may perform an initiated COT PSSCH / PSCCH transmission without a channel reservation signal and / or CPE transmission when one or more conditions are met.

[0281] For example, one condition is the time offset between the completion of Type 1 LBT channel access and the start of PSSCH / PSCCH transmission (i.e., t PSSCH-COT-start -t LBT-success ) may be smaller than a (pre)configured threshold and may be larger than a symbol.

[0282] For example, one condition may be when the WTRU may determine that the channel may be available in all N sensing slots before the start of the PSSCH / PSCCH transmission of the COT. The minimum N value may be (pre-)configured, such as one sensing slot. In one example, the WTRU may select N based on the measured SL U CBR. A larger value may be selected when the SL U CBR is high, such as when the channel is busy.

[0283] For example, one condition may be when the WTRU may determine that the channel may be available in all sensing slots included in an LBT contention period following N sensing slots. p The duration of consecutive sensing slots (T sl =9us) is immediately followed by a duration (T f = 16 us), where m p may be selected from the CAPC configuration based on the priority of the TB transmitting in the initiated COT.

[0284] If one of the conditions is not met, the WTRU may not perform a PSSCH / PSCCH transmission and may not start a COT. The WTRU may perform another Type 1 LBT channel access and start another COT.

[0285] Type 1 Time offset between LBT channel access completion and the start of PSSCH / PSCCH transmission (e.g., t PSSCH-COT-start -t LBT-success ) is less than a symbol, the WTRU may perform channel reservation signaling and / or CPE transmission immediately after successful Type 1 LBT sensing channel access.

[0286] In some cases, there may be one or more procedures for resource selection in the initiated COT. When the WTRU initiates the COT, the WTRU may perform resource selection within the initiated COT. The WTRU may select the number of available candidate resources (N r_COT ) can be determined based on one or more of the following information: initiated_COT ); L in one slot for TB to send RB_interlace Candidate resources such as RB interlaces; and / or frequency resource allocation of overlapping reserved COT and / or resources.

[0287] The WTRU determines the number of available candidate resources (N r_COT ) to T initiated_COT ×floor(M / L RB_interlace ), where N slot is the number of slots in the started COT, M is the (pre)configured number of RB interlaces for the indicated resource pool, and / or the RB set and floor(M / L RB_interlace ) is the number of available candidate resources in each such slot. When the WTRU starts a COT that overlaps with a reserved COT and / or resources, the WTRU must determine the number of available candidate resources (N r_COT ) is T initiated_COT ×floor(M / L RB_interlace )-N r_reserve where N r_reserve may be the number of reserved resources.

[0288] The WTRU is provided with the maximum number of available candidate resources for COT initiation in the resource pool (N r_max ) may be (pre)configured, and the WTRU determines the number of resources to use (N r_init ) to N r_init =Nr _max In another example, such a value may be determined to be the L1 priority. TX The WTRU may associate with a (pre)configured association and L1 priority of the transmitting TB. TX ) based on N r_max may be determined.

[0289] In another approach, the WTRU may receive the determined available candidate resources (N r_COT ) can be (pre)configured. The WTRU determines the ratio (P%) of the number of resources (N r_init ) to N r_init =Nr _COT ×P%, the value of P may be associated with an L1 priority, and the WTRU may determine the L1 priority (Prio) of the TB to transmit. TX) for the TB to transmit. In a further example, the value of P may be associated with a channel congestion status. The WTRU may determine the L1 priority of the TB to transmit, such as based on LBT sensing, resource pool, and / or RSSI over the bandwidth of the RB set. TX ), and / or channel congestion measured in LBT sensing and / or SCI sensing, may be used to determine the value of P.

[0290] WTRU has such N r_max And / or when the P ratio is not (pre-)configured, the WTRU may use all determined available candidate resources in the started COT, N r_init =Nr _COT , it can be determined that the determined N r_init is equal to or greater than the total number of determined resources for the transmission of TB (N r_init ≧N r_total ), WTRU is Nr _init =N r_total In this case, the WTRU may complete the determined transmission of TB in the initiated COT.

[0291] The WTRU selects, in ascending order with respect to RB interlace index and slot index, the N r_COT The determined available candidate resources may be indexed. For example, the WTRU may index the first available candidate resource in a slot in ascending order of RB interlace index, and then continue indexing the candidate resources in the next slot until the last slot for sharing in the current COT. The WTRU may index each available candidate resource as r j where the index j is (0,1,...N r_COT -1).

[0292] The WTRU may be configured to receive the N r_COTFrom such resources, N for the transmission of TB r_init The WTRU may select available candidate resources from the candidate resource pool. The WTRU may determine that it has one or more available candidate resources in each slot of the started COT.

[0293] The WTRU determines which N r_init The decision to use the available candidate resources may be based on one or more of the following: random selection, WTRU source and / or destination ID slot index, cast type, and / or (pre)configured resource pattern.

[0294] The WTRU is a (0,1,...N r_COT -1) to N r_init The WTRU may randomly select indexes and determine to use the available candidate resources indicated by the selected indexes. The WTRU may determine N r_init The WTRU may determine the slot index in the seed selection. In one example, for a unicast transmission, the WTRU may determine the randomly selected initialization seed based on a WTRU source ID and / or a WTRU destination ID. In addition, the WTRU may also include the slot index in the seed initialization. In another example, for a groupcast transmission, the WTRU may determine the randomly selected initialization seed based on a WTRU destination ID and / or a (pre-)configured group member ID. For a broadcast transmission, the WTRU may determine the randomly selected initialization seed based on a WTRU destination ID.

[0295] The WTRU may be (pre)configured with a set of available candidate resource selection patterns. For example, the WTRU may be configured with a set of candidate resource selection patterns with indices (r0, r1, ... r Nr_init ) r_init A first group of N available candidate resources may be selected. r_init =Nr_total When N , the WTRU may perform all transmissions of TB within the first contiguous available candidate resource within the initiated COT. r_init <N r_total , the WTRU determines N of the TB in the first contiguous available candidate resource in the started COT. r_init TB may then perform this transmission and perform a new SL U channel access procedure to perform the remaining transmissions of TB in the new started COT or another shared COT.

[0296] In another example, the WTRU may offset ,r offset+1 ,...r offset+Nr_init ) r_tx_init The WTRU may select a group of available candidate resources. The WTRU may determine the available candidate resource group offset value based on the WTRU source and / or destination ID and the WTRU destination ID for unicast transmissions. The WTRU may determine the available candidate resource group offset value based on the WTRU destination ID and / or a (pre-)configured group cast member ID for groupcast transmissions. The WTRU may determine the available candidate resource group offset value based on the WTRU destination ID for broadcast transmissions. For example, the WTRU may determine the available candidate resource group offset value based on the numeric value of the WTRU ID and / or group cast member ID and floor(N r_COT / N r_init Such an offset can be determined by performing a modular function using the number of available candidate resource groups, which may be equal to (1 / 1).

[0297] In some cases, there may be a PSSCH / PSCCH transmission in the initiated COT. The WTRU may r_initPSSCH / PSCCH transmission of one or more TBs may be performed on the available candidate resources. For each PSSCH / PSCCH transmission performed in the initiated COT, the WTRU may indicate one or more of SCI information in the PSCCH on the initiated COT, the transmitted TB, the transmission configuration, etc.

[0298] An example of SCI information may be the L1 priority, cast type, WTRU source ID and / or destination ID of the TB transmitted on the PSSCH.

[0299] An example of SCI information may be the remaining COT duration, which may be the remaining time of the COT between the slot in which the SCI is transmitted and the end of the started COT. In one example, the unit of the remaining COT duration may be a logical slot of the resource pool used for PSCCH / PSCCH transmission within the started COT. In another example, a physical slot may be applied to indicate the duration. The WTRU may determine the remaining COT duration of each SCI transmitted in the COT based on the maximum COT and the index of the slot containing the SCI transmission. The WTRU may not use all the remaining COT duration for SL transmission. The actual transmission scheduled within the COT may be indicated with a separate SCI indication of the remaining transmission duration.

[0300] An example of the SCI information may be the MCOT duration, which may indicate the maximum COT corresponding to the configuration of Type 1 LBT that the WTRU may perform to initiate the COT, which may be in ms or logical SL slots.

[0301] An example of SCI information may be a COT start slot index. The WTRU may indicate a logical slot index of the first slot of the COT. When the WTRU decodes the SCI in the COT, the WTRU may determine the number of remaining slots available for SL transmission in the COT based on the indicated start slot index and MCOT duration.

[0302] An example of SCI information may be a COT Start / Sharing Indication. A WTRU initiating a COT may indicate a value corresponding to COT start (e.g., a value of 1) in this SCI field of all SL transmissions performed by the WTRU in the initiated COT.

[0303] An example of SCI information may be COT sharing for PSSCH / PSCCH indication, where the WTRU may set the value of this indication based on the (pre)configuration of the resource pool (enabled / disabled). The WTRU may set the value as "enabled" when the COT transmitted by the WTRU may be shared by another WTRU. If set as "disabled", the COT may not be shared.

[0304] An example of SCI information may be a COT sharing for a PSFCH indication, where the WTRU may set the value of this indication based on a resource pool (pre-)configuration (enabled / disabled) when HARQ feedback is enabled for a TB transmitted on a PSSCH. When HARQ feedback is disabled for a TB transmitted on a PSSCH, the WTRU may set the indication to disabled. When this SCI indication is set to "enabled" and HARQ is enabled, the PSFCH may be transmitted in the same COT (e.g., sharing a COT) where the associated PSSCH / PSCCH transmission is received. When this SCI indication is set to "disabled" and HARQ is enabled, the PSFCH may not be transmitted in the same COT (e.g., sharing a COT) where the associated PSSCH / PSCCH transmission is received. In one example, when there is no (pre-)configured PSFCH opportunity in the COT, the WTRU may disable PSFCH sharing.

[0305] An example of SCI information may be a channel congestion indication, and the WTRU may determine such a value based on one or more (pre-)configured attributes of the LBT sensing and / or SCI sensing performed to initiate the COT. The attributes may include, for example, the length of time to complete the procedure, the number of slots in which the LBT sensing result of the channel may be busy, the number of deferred durations performed, etc. The WTRU may set the value to 1 when one or more such numbers exceed a (pre-)configured threshold. In another example, the WTRU may determine a channel congestion indication value based on the measured RSSI in a resource pool and / or RB set. The WTRU may set the indication to 1 when the measured RSSI may exceed a (pre-)configured threshold. The WTRU may also determine a channel congestion level, such as a SL U Channel Busy Ratio (CBR), using a ratio of the number of slots in which the measured RSSI for a resource pool and / or RB set may exceed a (pre-)configured level to the number of measured SL slots in the resource pool. The WTRU may set the indication when this channel congestion level may exceed a (pre-)configured threshold. The RSSI measurement may be based on LBT sensing and / or measurements on the PSCCH DMRS associated with the decoded SCI. The WTRU may perform such RSSI measurements within a (pre-)configured SL U CBR measurement window.

[0306] An example of SCI information may be the remaining transmission duration, which may be the number of consecutive slots scheduled for PSCCH / PSSCH transmission between the slot in which the SCI is transmitted and the end of the started COT, as indicated in the TRIV. In one example, the unit of the remaining transmission duration may be logical slots of the resource pool used for PSCCH / PSCCH transmission within the started COT. In another example, physical slots may be applied.

[0307] An example of SCI information may be a frequency resource allocation for the PSSCH, which may be an RB interlace index and / or an RB set index for the PSSCH transmission between the slot in which the SCI is transmitted and the end of the started COT, as indicated in the FRIV.

[0308] An example of SCI information may be the COT and / or resource reservation interval, where the WTRU may indicate a value of 0 when the COT and / or resource reservation for another TB may be disabled in the resource pool. The WTRU may indicate a value of 0 when the TB transmitted on the PSSCH may be aperiodic.

[0309] When COT and / or resource reservation for another TB is enabled in the resource pool and the TB transmitted on the PSSCH may be periodic, the WTRU may indicate the time period in ms or slots between the initiated COT and / or resources and the reserved COT and / or resources for transmission for another TB. This time period may be the COT and / or resource reservation interval (P) indicated by higher layers. rsvp_TX In one example, the unit of the COT and / or resource reservation interval may be a logical slot of the resource pool used for PSCCH / PSCCH transmission within the initiated COT. In another example, a physical slot may be applied to indicate this interval time.

[0310] By reserving such a COT and / or resources, the WTRU can perform SL channel access to initiate a reserved COT of the same length as the initiated COT. In addition, the reservation window may be (pre-)configured in association with the COT length. The WTRU can initiate the reserved COT within the reservation window. In another example, the reservation window associated with the indicated COT and / or resource reservation interval may be indicated in the same SCI.

[0311] In another example, the COT and / or resource reservation for a transmission performed in the initiated COT may be enabled / disabled in the (pre-)configuration of the resource pool, and the WTRU may set the indication to 0 when this (pre-)configuration is disabled in the resource pool, regardless of the (pre-)configuration for the traffic type of the TB transmitted in the shared current COT and / or the COT and resource reservation for another TB.

[0312] An example of SCI information may be a COT and / or resource reservation window, where the WTRU may indicate a value of 0 when COT and / or resource reservation for retransmissions for COT start may be disabled in the resource pool. r_total ) may be performed in the started COT. The WTRU may indicate a value of 0 when the end of the current COT is in ms or in number of slots. The WTRU may determine the window length based on the remaining packet delay budget (PDB) of the TBs transmitted in the shared current COT. The WTRU may also determine the window length based on the remaining packet delay budget (PDB) of the TBs transmitted in the started COT. In one example, the unit of the COT and / or resource reservation window may be logical slots of the resource pool used for PSCCH / PSCCH transmission in the started COT. In another example, physical slots may be applied to indicate this window length.

[0313] An example of SCI information may be a HARQ process number, a new data indicator, and / or a redundancy version.

[0314] An example of SCI information may be a HARQ feedback enable / disable indication, which may be an indication of whether HARQ feedback is enabled and a PSFCH carrying HARQ ACK / NACK is expected for a PSSCH / PSCCH transmission. The WTRU may determine this indication based on the QoS requirements of the TBs transmitted in the shared current COT.

[0315] An example of SCI information may be a transmission configuration including the number of DMRS ports, the DMRS pattern, the MCS value, and an MCS table indication.

[0316] An example of SCI information may be an indication of the SCI-2 format and a beta offset value.

[0317] One example of SCI information may be a zone ID of the WTRU determined based on geographic coordinates (eg, from GNSS).

[0318] An example of SCI information may be an indication of a (pre-)configured minimum communication range (MCR) requirement (e.g., in meters) for a TB transmitted in a PSSCH / PSCCH transmission, such as an index corresponding to the (pre-)configured MCR requirement.

[0319] An example of SCI information may be an indication of the synchronization source of the WTRU. The WTRU may set a set of values ​​in this SCI indicator that correspond to the source to which the WTRU synchronizes. The values ​​may be (pre-)configured to correspond to GNSS, gNB, SyncRef WTRU, and / or internal WTRU clock. In another case, an additional SCI indication may be applied to indicate the SL synchronization signal ID received from the SL synchronization signal (SLSS).

[0320] An example of SCI information may be an indication of SL slots for sharing within the COT. The WTRU may explicitly indicate which SL slots in the COT may be shared. In one example, the TRIV may be used to indicate a logical slot offset, such as the number of logical slots between the SL slot containing the SCI indication and the SL slot indicated for sharing. In another example, the logical slot index of the SL slot for sharing may be indicated.

[0321] In some cases, the WTRU may determine a COT start position for COT initiation and COT sharing. In some cases, the WTRU may be (pre)configured with a set of start positions of the COT within a (pre)configured period (e.g., time instances for starting SL transmission in the COT). The (pre)configured period may be an SL slot, an SL subframe, a radio frame (denoted as SFN), and / or a (pre)configured period within an SL resource pool. The (pre)configured set may include N COT start positions in each consecutive (pre)configured period within the resource pool. Each start position may be indicated by a COT start position index that is unique to the (pre)configured period. If the (pre)configured period is one SL slot, the COT start position may also be indicated by a symbol index. For example, if there are two (pre)configured COT start positions in an SL slot (N=2), the first COT start position may be located at symbol 0 and the second COT start position may be located at symbol 7 of the SL slot. In one example, the COT start position may be the start of a (pre-)configured SL slot and / or minislot.

[0322] In one approach, the COT start position may be one or more of the following transmission instances: the start of a PSSCH / PSCCH transmission included in the starting and / or shared COT, where such a COT start position may be (pre-)configured as the beginning of a slot, minislot and / or symbol in the SL resource pool; and / or the start of a reservation signal and / or CPE transmission preceding a PSSCH / PSCCH transmission included in the starting and / or shared COT, where the duration of the reservation signal and / or CPE may not be counted towards the length of the starting and / or shared COT.

[0323] Such a COT start position may be (pre)configured as the beginning of a time unit. Such a time unit may be (pre)configured as one of the following: SL slot, minislot, symbol, LBT sense slot (e.g., T of 9us). sl ) and / or LBT contention period (e.g., T d =T f +m p ×T sl , where T f may be 16us, T sl may be 9us, m p can be a value of 1, 3, or 7 selected from the CAPC configuration based on the priority of the TBs transmitting in the mimicked and / or shared COT.

[0324] The reservation signal and / or CPE may have a duration spanning an integer number of such (pre)configured time units. In one example, a set of LBT sensing slots and / or LBT contention periods may be (pre)configured in an SL slot, and the beginning of each LBT sensing slot and / or LBE contention period may be a COT start position. The WTRU may start transmission for the starting and / or shared COT by performing a channel reservation signal and / or CPE transmission at the earliest COT start position associated with the priority of the TB to be transmitted in the starting and / or shared COT.

[0325] In another example, the WTRU may determine the transmission start position based on a duration of a channel reservation signal and / or a CPE associated with a priority of a TB transmitting in the COT. The duration may include a number of time units, where such a time unit may be an LBT sensing slot (T SL ), LBT contention period (T contention ), 16us duration, 25us duration, symbol, SL minislot, and / or SL slot. Each such channel reservation and / or CPE duration may be (pre)configured with an association with an SL priority. The WTRU may select a channel reservation signal and / or CPE associated with a priority of the TB to transmit in the COT and determine the corresponding transmission start position based on the duration and start symbol / minislot / slot of the first PSSCH / PSCCH transmission of the COT, such as the start position of the channel reservation signal and / or CPE (start of PSSCH / PSCCH transmission - duration of channel reservation signal and / or CPE).

[0326] In some cases, the WTRU may be (pre-)configured with an association between a COT start position and a SL TB priority threshold. When the WTRU completes a Type-1 LBT and finds an available channel, the WTRU may determine whether to start a COT and perform a SL transmission at the earliest next COT start position after completing the Type-1 LBT based on the priority of the TB to transmit in the COT and the priority threshold associated with the earliest next COT start position.

[0327] Eight priority values ​​for SL TBs, from 1 to 8, may be defined and indicated in the 3-bit SCI field. In some cases, the higher the priority value indicated for a TB, the lower the priority of the TB, and vice versa in other cases.

[0328] If the priority of the TB is greater than or equal to the priority threshold associated with the earliest COT start position (e.g., the priority value of the TB is less than or equal to the priority threshold), the WTRU may determine to start a COT and perform a SL transmission at the earliest next COT start position.

[0329] If the priority of the TB is lower than the priority threshold associated with the earliest COT start position (e.g., the priority value of the TB is greater than the priority threshold), the WTRU may decide not to start the COT (e.g., abandon the available channel) and perform a SL transmission at the earliest next COT start position (e.g., abandon the available channel).

[0330] In one example, there are two (pre-)configured COT start positions in a SL slot (N=2), where COT start position 1 may be (pre-)configured to be associated with priority threshold 4 and COT position 2 may be (pre-)configured to be associated with priority threshold 8. In this example, both COT start positions 1 and 2 may be used by the COT for SL transmissions for TBs with priority values ​​1, 2, 3, and 4. However, for TBs with priority values ​​of 5, 6, 7, and 8, the WTRU may not use COT start position 1 and may have one start position (e.g., COT start position 2) in each SL slot.

[0331] In another approach, the (pre)configured set of COT start positions may be split into several subsets, and each subset of COT start positions may be associated with a range of SL TB priorities. When the TB priority is associated with the earliest next COT start position after Type 1 LBT completion, the WTRU may determine to start the COT and perform SL transmission of the TB at the earliest next COT start position. When the TB priority is not associated with the earliest next COT start position after Type 1 LBT completion, the WTRU may determine not to start the COT and perform SL transmission of the TB at the earliest next COT start position.

[0332] In the above example with two (pre)configured COT start positions in a set, a first subset may include both COT start positions and be associated with a range of priority values ​​from 1 to 4. A second subset may include a second COT start position in each SL slot and be associated with a range of priority values ​​from 1 to 8.

[0333] When the WTRU determines to start the COT at the earliest next COT start position, the WTRU may perform CPE (cyclic prefix extension) and / or channel reservation signaling transmission in the time gap between the completion of the Type 1 LBT and the earliest next COT start position. When the WTRU determines not to start the COT at the earliest next COT start position, the WTRU may start another Type 1 LBT and continue to acquire a channel for SL transmission of the TB.

[0334] FIG. 5 illustrates an example of a WTRU determining a COT start position within an SL slot. As illustrated, there are two WTRUs 501 and 502 that are about to transmit a message (e.g., a transport block), and time is shown on the horizontal axis 510. The vertical axis is only there to illustrate the two WTRUs, but each WTRU may be transmitting on the same channel / spectrum (e.g., therefore, competing transmissions need to be avoided by the system). This priority-based COT start position determination may allow a WTRU with a higher priority TB to access the channel more frequently when multiple SL WTRUs contend for a channel. As shown in the example of FIG. 5, two WTRUs (e.g., 501 and 502) contend for a channel for SL transmission of TBs with different priorities (e.g., priority 1 and priority 2, with priority 1 being lower). The result of this approach is that the WTRU 501 may complete a Type 1 LBT first, but may determine to forgo an available channel, and the WTRU 502 with the highest priority TB may acquire the channel and begin COT for the SL transmission. The WTRU may use CPE transmissions and / or channel reservation signaling (512) to accomplish this technique.

[0335] As shown in the example, a first set of (pre-)configured start positions 513 for SL slots may be associated with Priority 2 and / or associated with a priority threshold value equal to or greater than the value of Priority 2. A second set of (pre-)configured start positions 514 for SL slots may be associated with both Priority 1 and Priority 2 and / or associated with a priority threshold value equal to or greater than Priority 1.

[0336] At 521, the WTRU 501 may detect available channels and determine that the earliest next COT start position is not associated with the second set of start positions 514 for Priority 1 and / or the value of Priority 1 is greater than the associated priority threshold. Thus, the WTRU 501 may determine not to start a COT and not to perform another Type 1 LBT (e.g., at 522) to continue acquiring the channel.

[0337] At 531, the WTRU 502 may complete the Type 1 LBT and determine that the earliest next COT start position is associated with Priority 2 and / or the value of Priority 2 is less than an associated priority threshold. Thus, the WTRU 502 may determine to start a COT at the earliest next COT start position in the first set 513. The WTRU 502 may perform CPE transmissions and / or channel reservation signaling (e.g., 516) until the earliest next COT start position in the first set 513, at which point, at 532, the WTRU 502 may proceed with transmitting the TB.

[0338] The WTRU 501 may obtain available channels within the resource selection window and determine that the earliest next COT start position is associated with Priority 1 and / or the value of Priority 1 is less than the associated priority threshold. At 522, the WTRU 501 may perform another LBT Type 1 for Priority 1, where there may actually be two start positions (e.g., one in each slot) from the second set of start positions 514 applicable to the TB for Priority 1, but the WTRU 501 will detect a reservation signal 516 from the WTRU 502 before the first start position 514, and thus, the WTRU 501 may determine to start the COT at the second suitable start position 514. The WTRU 502 may perform a CPE transmission and / or a channel reservation signal transmission 515 until the earliest next COT start position of the first set 514. At 523, the WTRU may proceed with the transmission of the TB.

[0339] Assuming that the WTRU 501 fails to acquire an available channel within the resource selection window 511, the WTRU 501 may report an LBT and / or channel access failure to higher layers.

[0340] In one approach, the WTRU may apply a slot structure used for the COT start position for PSSCH / PSCCH transmission. For example, if the COT start position is symbol-based and the slot is (pre-)configured, each COT start position and the following symbols until the next COT start position may be a PSSCH / PSCCH mini-slot. When the WTRU starts the COT, the WTRU may determine to apply such a mini-slot structure to perform PSSCH / PSCCH transmission within the COT.

[0341] In another approach, the WTRU may switch from the slot structure used for the COT start position to another slot structure (pre-)configured for PSSCH / PSCCH transmission in the initiated COT. In one example, the WTRU may apply slot-based PSSCH / PSCCH transmission in the COT starting from the first SL slot boundary following one or more minislot-based transmissions in the COT. The WTRU may indicate the duration of the PSSCH / PSCCH transmission in the COT (e.g., number of symbols, minislots, and / or slots in the SCI).

[0342] Similarly, WTRU determination of COT start position based on TB priority may be applied to COT sharing to allow WTRUs with higher priority TBs to share the COT more easily. In some cases, the WTRU may determine whether to share the COT and start performing SL transmission at the earliest next COT start position in the ongoing shareable COT based on the TB priority and the priority range and / or priority threshold associated with the (pre-)configured COT start position.

[0343] Following a successful Type 2 LBT, the WTRU may determine not to share the COT when the earliest next COT start position in the COT is not associated with the TB priority and / or is associated with a higher priority threshold than the TB priority. The WTRU may determine to share an ongoing sharable COT when the earliest next COT start position in the COT is associated with the TB priority and / or is associated with a lower priority threshold than the TB priority.

[0344] In another case, the WTRU may apply a COT start position determination (e.g., as discussed herein) when the CBR and / or RSSI measured in Type 1 and / or Type 2 LBT exceeds a (pre-)configured threshold. When the CBR and / or RSSI measurements fall below a (pre-)configured threshold, the WTRU may start and / or share the COT at the earliest next COT start position without considering the priority of the TBs transmitting in the COT.

[0345] In some cases, the WTRU may perform SL U channel access for SL synchronization signal block (S-SSB) transmission based on a synchronization reference (SyncRef) WTRU priority level. The WTRU may become a SyncRef WTRU and perform SL synchronization signal block (S-SSB) transmission. The WTRU may be (pre-)configured with the periodicity (e.g., X frames) of the SL synchronization signal block (S-SSB) transmission. In each period, the number of S-SSB transmissions may be (pre-)configured. The S-SSB candidate opportunity, such as the time domain location of the S-SSB transmission within the period, may be (pre-)configured with a start slot offset and an S-SSB interval (e.g., in units of slots). The WTRU may determine the first S-SSB candidate opportunity within a slot, which may be N slots after the beginning of the period, where N is the (pre-)configured start slot offset. The WTRU may determine subsequent S-SSB candidate opportunities based on the determined first S-SSB candidate opportunity and the S-SSB interval.

[0346] The priority level of the SyncRef WTRU may be based on one or more of the following: the GNSS coverage of the SyncRef WTRU; the network coverage of the SyncRef WTRU; and / or the synchronization reference of the SyncRef WTRU.

[0347] The SyncRef WTRU may be synchronized with the GNSS (eg, when in coverage), a base station (eg, when in coverage), another SyncRef WTRU, or its own internal clock.

[0348] In one example, the priority levels of a SyncRef WTRU may be (pre-)configured in descending order as follows: a first priority level where the SyncRef WTRU is in-coverage and can synchronize directly with GNSS; a second priority level where the SyncRef WTRU is out-of-coverage and can synchronize with another SyncRef WTRU that can synchronize directly with GNSS (e.g., one hop away from GNSS); a third priority level where the SyncRef WTRU can synchronize directly with a base station; a fourth priority level where the SyncRef WTRU can synchronize with another SyncRef WTRU that synchronizes directly with a base station (e.g., one hop away from the base station); a fifth priority level where the SyncRef WTRU can synchronize with another SyncRef WTRU whose synchronization source may be more than one hop away from the base station or GNSS; and / or a sixth priority level where the SyncRef WTRU can synchronize with its own internal clock.

[0349] A SyncRef WTRU may perform Type 2 (e.g., Type 2A) channel access before an S-SSB candidate opportunity. If one S-SSB transmission (pre)configuration is applied, SyncRef WTRUs of different priority levels may contend for channel access before the same S-SSB candidate opportunity. Depending on the proximity and timing reference of the SyncRef WTRUs, a SyncRef WTRU of a lower priority level may access the channel first and block another SyncRef WTRU of a higher priority level. It may be beneficial to avoid such blocking.

[0350] In one approach, the WTRU may be (pre)configured with an association between each S-SSB candidate opportunity and a SyncRef WTRU priority level. In one example, one or more S-SSB candidate opportunities may be associated with a priority level equal to or greater than a (pre)configured threshold. In these opportunities, SyncRef WTRUs with a priority level equal to or greater than the (pre)configured threshold may avoid channel contention with SyncRef WTRUs with a priority level lower than the threshold. The remaining S-SSB candidate opportunities may be associated with all priority levels. Thus, SyncRef WTRUs with higher priority levels may contention for the channel in more S-SSB candidate opportunities.

[0351] In another approach, the WTRU may be (pre-)configured with a set of S-SSB transmission (pre-)configurations, each of which may include a different start slot offset and / or S-SSB interval and / or may have a different number of S-SSB candidate opportunities. The WTRU may be (pre-)configured with an association between the S-SSB transmission (pre-)configuration and the SyncRef WTRU priority level.

[0352] In one example, a SyncRef WTRU may apply an S-SSB transmission (pre-)configuration when its priority level is equal to or greater than a (pre-)configured threshold. The S-SSB transmission opportunities of such an S-SSB transmission (pre-)configuration may not overlap with S-SSB transmission opportunities of an S-SSB transmission (pre-)configuration associated with a priority level lower than the threshold. As a result, the SyncRef WTRU may avoid contention for the channel in the same S-SSB transmission opportunity. In another example, an S-SSB transmission (pre-)configuration associated with a priority level equal to or greater than a (pre-)configured threshold may have more S-SSB candidate opportunities. Thus, a SyncRef WTRU at a higher priority level may access the channel more frequently.

[0353] In another approach, the WTRU may be (pre)configured with multiple start positions associated with priority levels for one or more S-SSB candidate opportunities of an S-SSB transmission (pre)configuration. In one example, the start position may be indicated by a timing offset before a symbol boundary of the first symbol of the S-SSB candidate opportunity. The timing offset may be an integer number of (pre)configured time units of LBT sensing slots, contention periods, symbols, minislots, and / or slots. A start position with a large timing offset may indicate an early start position for the S-SSB candidate opportunity. The WTRU may perform reservation signaling and / or CPE transmission from the start position to the start of the S-SSB candidate opportunity. In another example, the start position may be indicated by a duration of CPE transmission performed before the symbol boundary of the first symbol of the S-SSB transmission. The WTRU may be (pre)configured with a set of CPE durations to indicate a start position for the S-SSB candidate opportunity.

[0354] Before an S-SSB candidate opportunity with multiple start positions associated with a priority level (pre-)configured, a SyncRef WTRU with a higher priority level may start a CPE transmission at an earlier start position and thus block channel access by another SyncRef WTRU with a lower priority level.

[0355] The WTRU may also be (pre-)configured for a single starting position for one or more S-SSB candidate opportunities of the S-SSB transmission (pre-)configuration, in which the SyncRef WTRU can access the channel regardless of priority level.

[0356] Possibly, the WTRU may perform a SL U channel access and resource selection procedure for the start of a reserved COT to perform a retransmission of a TB transmitted in a previous COT.

[0357] The WTRU determines whether the number of performed transmissions is equal to or smaller than the determined total number of transmissions, including initial transmissions and retransmissions, to be performed within the determined RSW of the TB (N TX ), it may be determined to perform LBT sensing based SL U channel access and resource selection for COT initiation after performing TB initial transmission and retransmission in a shared or initiated COT.

[0358] The WTRU may indicate a COT and / or a resource reservation window in the SCI of a PSSCH / PSCCH transmission performed in a shared or initiated COT. The WTRU may perform channel access and resource selection for a COT start within the indicated window. In one example, the WTRU may select the L of the resource pool used for the PSSCH / PSCCH transmission. w Such a reservation window has a length of L logical slots. w The WTRU may indicate the value of L based on the remaining PDB of the TB to transmit. w It is possible to determine:

[0359] The start of the reservation window may be (pre)configured with respect to the end of the COT in which the SCI containing the reservation window information may be transmitted. In one example, when a WTRU performs a TB transmission in a shared or started COT that ends in slot (t), the start slot of the reservation window may be set to slot (t+T ch ), and T ch can be the (pre)configured processing time, and the end slot of the window is slot (t+T ch +L w +1). In another example, the indicated window length and window start and end slots may use units of physical slots.

[0360] The WTRU may perform LBT sensing based SL U channel access and resource selection for COT initiation within the indicated window, and if the channel access is successful, the WTRU may determine available resources within the initiated COT according to the resource selection in the initiated COT. The WTRU may indicate failure to upper layers for the channel access and resource selection triggered for the transmitted (TB) when the LBT sensing based SL U channel access is not successful within the indicated reservation window.

[0361] Possibly, there may be a SL U channel access and resource selection procedure for the start of a reserved COT to perform the initial transmission and retransmissions of a new TB.

[0362] The WTRU may perform semi-static COT and / or resource reservation for initial transmission and retransmission of another TB when COT and / or resource reservation for another TB for COT sharing is enabled in the resource pool.

[0363] The reservation interval may be indicated in units of ms or number of logical or physical slots between the current COT and the reserved COT for transmission of another TB by the same WTRU. The WTRU may be (pre)configured to reserve a COT of the same length as the current COT. The WTRU may also be (pre)configured to reserve the same frequency resources as those used in the current COT.

[0364] In one example, a reservation window associated with an indicated reservation interval may be included in the same SCI (e.g., a reservation window is associated with a reservation interval and both pieces of information are included in the SCI). The WTRU may determine the length of such associated reservation window based on the remaining PDB of TBs transmitted in the current COT. The WTRU may assume that TBs transmitted in the current COT and TBs to be transmitted in the reserved COT have the same remaining PDB. In another example, such associated reservation window may have a (pre)configured length.

[0365] When the WTRU performs a TB transmission in the first SL slot (t) of the initiated or the first shared SL slot (t) in the shared COT, the WTRU may use a reserved interval (P rsvp_TX The indication may indicate that the WTRU should perform SL U channel access and resource selection for COT initiation in the SL slot (t+P rsvp_TX ) and / or SL slot (t+P rsvp_TX In another example, the WTRU may perform SL U channel access and resource selection for COT sharing to start a COT including SL slot (t+P rsvp_TX ) can be shared.

[0366] In another example, the WTRU may perform SL U channel access and resource selection for COT initiation to start COT within an associated reservation window. The associated reservation window may include an SL slot (t+P rsvp_TX ) The WTRU may initiate and / or share a COT within the associated reservation window.

[0367] In another approach, the reservation window may include a period reserved for Type 1 LBT channel access preceding the reserved COT. The WTRU may determine the duration of the period based on the duration of the LBT contention window indicated in the CAPC configuration according to the priority of the TB transmitting in the reserved COT. The WTRU may perform Type 1 LBT-sensing channel access within this period to start the reserved COT in the reservation window.

[0368] In another example, when a WTRU performs a TB transmission in slot (t) within a starting or shared COT, the WTRU may indicate a reservation range and / or latency bound in an SCI associated with the PSSCH / PSCCH transmission performed within the COT. The WTRU may perform LBT sensing based SL U channel access and resource selection for COT start to start a COT of the same length within the indicated range and / or before the latency bound. The WTRU may indicate the start and end slots of the range and latency bound in units of logical slots of the resource pool. In another example, physical slots may be applied for the indication. The WTRU may determine the range and / or latency bound based on one or more factors, such as the remaining PDB of the TB to transmit.

[0369] If channel access within the indicated associated window, range, and / or latency bound is successful, the WTRU may determine available resources within the initiated COT according to the resource selection in the initiated COT. The WTRU may indicate failure to upper layers for channel access and resource selection triggered for the transmitted TB when the LBT sensing based SL U channel access is not successful.

[0370] FIG. 6 illustrates an example of WTRU resource group / COT selection before Type 1 LBT for COT initiation. In some cases, the WTRU may select resource group / COT before LBT for COT initiation. As illustrated, time may be shown on the horizontal axis. The WTRU may determine a set of resource groups and / or COT based on sensing information (e.g., SCI, RSRP, etc.) before performing Type 1 LBT to initiate COT.

[0371] In one example, a resource group may include several slots with several RB interlaces selected in each slot for initial transmission or retransmission of the TB. The COT may be the duration of such a resource group, such as the number of consecutive slots. In one example, the duration of the resource group may be the maximum COT indicated in the CAPC configuration corresponding to the priority of the TB.

[0372] In another example, the duration of the resource group may include a period preceding the COT. The WTRU may determine the duration of the period based on the duration of the LBT contention window associated with the priority of the TB transmitting in the reserved COT and indicated in the CAPC configuration. The WTRU may reserve SL slots included in the determined period within the resource group. The reserved period may be intended for the WTRU to perform Type 1 LBT-sensing channel access before starting the reserved COT.

[0373] At 601, the WTRU may determine a Resource Selection Window (RSW) 606 between slots (n+T1) and (n+T2), where T1 and T2 may be values ​​based on the (pre-)configured WTRU processing time and the indicated remaining PDB (e.g., the sensing window means that the WTRU decodes all detected SCI and other related information and stores the information for processing and later use). At 602, the WTRU is triggered by higher layers to determine a Priority Selection Window (RSW) 606 between slots (n+T1) and (n+T2), where T1 and T2 may be values ​​based on the (pre-)configured WTRU processing time and the indicated remaining PDB (e.g., the sensing window means that the WTRU decodes all detected SCI and other related information and stores the information for processing and later use). TX) and the SL TB with the remaining PDB.

[0374] In some cases, the WTRU may determine the total number of initial transmissions and retransmissions of the TB based on the indicated priority of the TB. The WTRU may determine the total number of SL slots for the initial transmissions and retransmissions of the TB, which may be equal to the total number of transmissions of the TB. In one approach, if the priority of the TB corresponds to an MCOT of X slots and the total number of transmissions of the TB is Y, the WTRU may determine the number of resource groups needed (N required ) may be determined, and / or the COT for transmission may be Ceiling(Y / Z), such as the nearest integer greater than Y / Z.

[0375] In some cases, the WTRU may determine the number of resource groups and / or COTs in the RSW (N) to acquire using a Type 1 LBT. Due to the uncertainty of the LBT, the WTRU may determine a number that is larger than required (e.g., N=N required + offset). The offset may be a (pre)configured value. In one approach, the offset may be associated with a channel congestion level and / or priority of the TB. A larger offset may be associated with a higher congestion level and higher priority of the TB. An increase in the number of resource groups and / or COTs may enable the WTRU to perform more Type 1 LBTs to acquire the channel.

[0376] In some instances, the WTRU may determine the location of the N resource groups and / or COT in the RSW based on the reserved COT / resource information decoded in the sensing. The WTRU may exclude one or more of the following slots from the RSW: COT and / or slots reserved in the resource reservation, and / or RSRP measured in a PSSCH / PSCCH transmission reserving resources / COT that may exceed a (pre-)configured threshold, where the value of the threshold is determined based on the priority associated with the PSSCH / PSCCH transmission. resv ) and the priority of the TB to be sent (Priority TX ) may be based on

[0377] In the remaining SL slots in the RSW, the WTRU may determine the N selected resource groups and / or COTs (as shown in FIG. 6). Before each selected resource group and / or COT, the WTRU may determine an associated LBT period to perform a Type 1 LBT procedure. The duration of the LBT period may be (pre-)configured.

[0378] In some cases, the WTRU may determine frequency resources in the selected resource group and / or each slot of the COT. The frequency resources may be several RBs of several subchannels or interlaces. The determination of the subchannel or RB interlace may be based on one or more of the following: total number of (pre-)configured subchannels or RB interlaces in the resource pool; WTRU source and / or destination ID; random selection; logical slot index; and / or (pre-)configured pattern.

[0379] As shown in FIG. 6, the WTRU may perform a Type 1 LBT procedure in an LBT period associated with a selected resource group and / or COT. When the channel is sensed to be available, the WTRU may perform a channel reservation signal and / or CPE transmission before the earliest slot boundary (e.g., 605A and 605B). The WTRU may start the COT and perform a TB transmission at the slot boundary (e.g., 607A and 607B). When the channel is sensed to be busy at the end of the LBT period, the WTRU may stop LBT sensing (e.g., stop the LBT procedure for this period) and perform a Type 1 LBT procedure in an LBT period associated with the next selected resource group and / or COT.

[0380] As shown in the example of FIG. 6, during an LBT period 612 associated with a first selected resource group and / or COT 613 in the RSW 606, the WTRU fails to acquire a channel (e.g., the channel is not available at the start of the selected resource group / COT / time window) and stops the Type 1 LBT. The WTRU may perform a Type 1 LBT in an LBT period 615 associated with a second selected resource group and / or COT 616 (e.g., 604), the LBT is successful (e.g., the channel is available at the start of the selected resource group / COT / time window), and may start the COT for the SL transmission (e.g., 607A). The WTRU may send a reservation signal 605A before sending the TB 607A. The WTRU may then determine the number of COTs to be started (N required) is greater than the number of COTs already started, the WTRU may continue to perform the Type 1 LBT in the LBT period 618 associated with the next selected resource group and / or COT (e.g., the third selected resource group 619). In this example, the WTRU starts another COT in the third selected resource group and / or COT 619, and the LBT is successful and completes all transmissions determined for the TB (e.g., 607B). The WTRU may send a reservation signal 605B before transmitting TB 607B. Once the transmission is completed, the WTRU may not perform an LBT and acquire channels in the remaining selected resource groups and / or COTs in the RSW (e.g., an LBT may not need to be performed between 619 and 620).

[0381] In one example, the examples of Figures 5 and 6 can be read together, where the second selected resource group (COT) 616 encompasses instances where WTRU 501 and WTRU 502 perform LBT, and WTRU 502 sends a reservation signal and transmits its TBs (e.g., 521, 522, 531, and 532). Furthermore, the third selected resource group (COT) 619 can encompass instances where WTRU 501 can perform LBT, send a reservation signal, and transmit its TBs (e.g., 522 and 523). In this combined example, neither WTRU 501 nor WTRU 502 can access a channel during the first selected group (e.g., due to a busy channel). As a result, WTRU 501 and WTRU 502 can perform LBT at the next available opportunity (e.g., time) in the second selected resource group 616. The number of start positions associated with priority 1 (e.g., as referenced in Figure 5) is greater than priority 2. When the channel is idle, the WTRU 501 may finish the LBT first, but during the long gap to the WTRU 501's (pre-)configured start position, the WTRU 502 may access the channel first and transmit its TB. The WTRU 501 must then perform an LBT before its associated next start position and determine if the channel is idle.

[0382] In general, the WTRU may be configured to detect when the WTRU does not acquire channels in all selected resource groups and / or COTs and / or when the number of initiated COTs is greater than the determined number of COTs required (N required ), an LBT failure may be indicated to higher layers. In another case, the WTRU may trigger resource reselection when Type 1 LBT-sensing channel access fails before one or more selected resource groups and / or COT.

[0383] The WTRU may perform channel access (e.g., Type 1 LBT channel access) before the start of the selected resource group. When the channel is sensed to be available, the WTRU may start COT and perform PSSCH / PSCCH transmission on the selected resources. In one case, when the channel is sensed to be busy at the start of the selected resource group, the WTRU may stop channel access and perform a new channel access before the next selected resource group in the resource selection window. In another case, when the channel is sensed to be busy at the start of the selected resource group, the WTRU may continue to perform LBT channel access in the selected resource group. The WTRU may sense that the channel is idle in the selected resource group and may start COT with the remainder of the resource group. In another example, the WTRU may indicate COT with the remainder of the selected resource group when the number of remaining logical slots in the selected resource group exceeds a (pre-)configured threshold.

[0384] In some cases, the WTRU may initiate a COT with an MCOT that overlaps with the reserved resources / COT. When the WTRU is triggered to perform resource selection for a TB with priority (p), the WTRU may determine a transmission duration, such as the number of consecutive SL slots for transmission of the initial transmission and retransmissions of the TB. The WTRU may determine a maximum COT (MCOT) duration according to the priority from the CAPC configuration.

[0385] When the WTRU selects a resource group and / or COT for initiation that includes a period for Type 1 LBT-sensing channel access and a determined transmission duration (as discussed herein), the WTRU may initiate a COT with an MCOT duration that may overlap with the reserved resource group and / or COT. The WTRU may not transmit during the overlapping duration, such that the determined transmission duration may not overlap with any of the reserved resource group and / or COT. In addition, the WTRU may indicate in the SCI that the overlapping duration in the COT may not be shared by another WTRU. In one example, the WTRU may indicate "disabled" in the COT sharing SCI indication. In another example, the WTRU may explicitly indicate the index of the non-overlapping SL slot to share in the COT.

[0386] In some cases, the WTRU may initiate a COT based on frequency domain multiplexing. The WTRU may select a resource group to initiate a COT that may overlap in time with the reserved resource group and / or COT. The WTRU may select one or more frequency resources that may not be reserved in the resource group and / or COT reservation. For example, the frequency resources may include one or more RBs, one or more subchannels, one or more RB interlaces, and / or one or more RB sets.

[0387] The WTRU may determine to perform a Type 1 LBT before the selected resource group. The WTRU may determine to start a COT in the selected resource group when one of the following occurs: when the channel may be sensed as available as a result of the Type 1 LBT; and / or when the channel may be sensed as busy as a result of the Type 1 LBT and the decoded SCI may indicate that the selected frequency resource may not be used.

[0388] The WTRU may perform PSSCH / PSCCH transmission within the initiated COT on a resource group detected in the SCI sensing and / or on frequency resources different from those indicated in the COT reservation.

[0389] In another example, the WTRU may perform frequency reselection when the channel is sensed to be busy as a result of a Type 1 LBT and the decoded SCI may indicate that the selected frequency resource may be used, and the WTRU may perform PSSCH / PSCCH transmission within the initiated COT on a different frequency resource than that indicated in the SCI received during the Type 1 LBT.

[0390] Thus, the WTRU may initiate a COT that may be frequency domain multiplexed (FDM.ed) with reserved and / or ongoing resource groups and / or COTs. The WTRU may be (pre-)configured to perform such a frequency domain multiplexed COT initiation when one or more of the following occurs: when the number of candidate resource groups and / or COTs in the RSW falls below a (pre-)configured threshold; when a channel congestion metric (e.g., CBR and / or CO) exceeds a (pre-)configured threshold.

[0391] In some cases, the WTRU may determine the success or failure of the SL U channel access and resource selection. The WTRU may perform one or more SL U channel access and resource selections for the COT start in the determined RSW. The WTRU may determine the success or failure of the SL U channel access and resource selection for the COT start in the determined RSW. TX When the transmission of (TB) is performed, the WTRU may stop performing the LBT sensing based SL U channel access and resource selection for COT initiation in the determined RSW. The WTRU may indicate to upper layers the success of the channel access and resource selection triggered for the transmitted (TB).

[0392] The WTRU transmits the signal in slot (n+T process_min ), where slot (n+T2) is the determined end of the RSW, and the LBT sensing based SL U channel access and resource selection for the COT start in slot (n+T2) can be stopped. process_min is the (pre)configured minimum processing time and / or the number of transmissions performed within the initiated COT and / or the shared COT in the RSW (N tx_performed ) is the number of transmissions that are judged to be TB (N TX ) is smaller than (N tx_performed <N TX ), in this case, the WTRU may indicate to higher layers a failure to channel access and resource selection triggered for the transmitted (TB).

[0393] In another example, the WTRU may receive the number of determined transmissions (N TX ) that can indicate the minimum number of transmissions to be performed for TB. tx %) may be (pre)configured. The WTRU may process_min If the WTRU stops the LBT sensing based SL U channel access and resource selection for the COT initiation in (TB), the WTRU may indicate failure to upper layers for the triggered channel access and resource selection for the transmitted (TB). For example, the number of transmissions performed within the initiated COT and / or the shared COT in the RSW (N tx_performed ) is smaller than the number of TB transmissions (N tx_performed <Th tx %×N TX ). If not, the WTRU may indicate to higher layers about the success of the triggered channel access and resource selection for the transmitted (TB). In another example, such a threshold may be associated with the priority of the TB, and the WTRU may select the threshold based on the (pre)configuration and the priority of the transmitting (TB).

[0394] In one example, when the WTRU starts the COT, the WTRU may determine to apply a gap period at the end of the last PSSCH / PSCCH transmission scheduled in the COT. The WTRU may perform TX / RX switching during this gap period. In one example, the gap period may be (pre)configured with a duration greater than 16us, and a gap period of one symbol may be (pre)configured for resource pools with SCS of 15kHz, 30kHz, and 60kHz. In another example, the gap period may be (pre)configured with a duration greater than 25us. In this case, a gap period of one symbol may be (pre)configured for resource pools with SCS of 15kHz and 30kHz, and two symbols may be (pre)configured for resource pools with SCS of 60kHz.

[0395] In some cases, there may be a WTRU physical layer LBT failure indication based on channel access for PSSCH / PSCCH transmission. The WTRU may indicate an LBT failure to higher layers based on type 1 LBT channel access performed on one or more selected resource groups and / or COTs in the RSW for PSSCH / PSCCH transmission. Examples of such selected resource groups and / or COTs are shown in FIG. 6.

[0396] In some instances, the WTRU may indicate an LBT failure to higher layers according to one or more conditions.

[0397] For example, the WTRU may indicate an LBT failure when the WTRU performs a Type 1 LBT channel access, fails to access the channel, and fails to perform a PSSCH / PSCCH transmission during one selected resource group and / or COT in the RSW. The WTRU may evaluate the LBT failure indication for each selected resource group and / or COT in the RSW.

[0398] For example, the WTRU may indicate an LBT failure when the WTRU performs a Type 1 LBT channel access, fails to access the channel, and fails to perform a PSSCH / PSCCH transmission during a first selected resource group and / or COT in an RSW. The WTRU may not indicate an LBT failure in subsequent selected resource groups and / or COTs in an RSW regardless of the LBT channel access result. The WTRU may evaluate the LBT failure indication for each RSW.

[0399] For example, the WTRU may indicate an LBT failure when the WTRU performs a Type 1 LBT channel access, fails to access the channel, and fails to perform PSSCH / PSCCH transmission during all selected resource groups and / or COTs in an RSW. Thus, the WTRU may evaluate the LBT failure indication for each RSW.

[0400] For example, the WTRU may indicate an LBT failure when the WTRU performs a Type 1 LBT channel access and fails to access the channel and fails to perform a PSSCH / PSCCH transmission during each of several selected resource groups and / or COTs in the RSW. The WTRU may determine the number based on a (pre-)configured ratio to the total number of selected resource groups and / or COTs in the RSW. The WTRU may evaluate such an LBT failure indication for each RSW.

[0401] In some instances, the WTRU may indicate an LBT failure to higher layers based on the number of PSSCH / PSCCH transmissions performed within the RSW. The WTRU may indicate an LBT failure according to one or more conditions.

[0402] For example, the WTRU may perform one or more Type 1 LBT channel accesses and fail to access the channel and fail to perform a PSSCH / PSCCH transmission of the TB within the RSW.

[0403] For example, the WTRU may perform one or more Type 1 LBT channel accesses and fail to perform the required number of PSSCH / PSCCH transmissions for the TBs in the RSW. The WTRU may determine the required number of PSSCH / PSCCH transmissions, including initial transmissions and retransmissions, for one or more TBs when the WTRU is triggered for higher layer resource selection for COT initiation and LBT channel access.

[0404] In some instances, the WTRU may indicate an LBT failure to upper layers based on a type 1 LBT channel access performed for a PSSCH / PSCCH transmission scheduled by the base station. The WTRU may indicate an LBT failure according to one or more conditions.

[0405] For example, a WTRU may perform one or more Type 1 LBT channel accesses and fail to access the channel before the start of a PSSCH / PSCCH transmission scheduled in a dynamic grant (DG). The WTRU may determine the start of a PSSCH / PSCCH transmission based on SL transmission timing information received in a DCI that includes a dynamic grant. The SL timing information may be indicated as a time gap (e.g., in logical SL slots) between the DL slot in which the DCI is received and the SL slot in which the PSSCH / PSCCH transmission is scheduled.

[0406] For example, a WTRU may perform one or more Type 1 LBT channel accesses and fail to access the channel and fail to perform a PSSCH / PSCCH transmission within the scheduled transmission period / window indicated in the dynamic grant (DG). The WTRU may receive SL transmission period and / or window duration information (e.g., in units of logical slots) in the DCI that contains the dynamic grant. The period and / or window may start from the DL slot in which the DCI is received and end after the indicated duration.

[0407] For example, a WTRU may perform one or more type 1 LBT channel accesses and fail to access the channel before the start of periodic SL transmissions according to a configured grant (CG). The WTRU may determine the start of SL transmissions based on transmission timing information included in the RRC configuration of the configured grant. The timing information may include a transmission periodicity, a reference slot, and / or a slot offset.

[0408] In some instances, the WTRU may indicate an LBT failure to higher layers based on a Type 2 LBT channel access performed for PSSCH / PSCCH transmission. The WTRU may indicate an LBT failure when the following occurs: The WTRU may perform a Type 2 LBT channel access (e.g., Type 2A / 2B) and fail to access the channel before the start position associated with the priority of the TB to transmit in the current sharable COT. Thus, the WTRU may fail to share the current sharable COT (e.g., as shown in FIG. 3).

[0409] In some cases, there may be a WTRU physical layer LBT failure indication based on channel access for a PSFCH transmission. The WTRU can indicate an LBT failure to upper layers based on a type 1 LBT channel access performed for one or more PSFCH transmissions in one or more PSFCH opportunities within the HARQ latency. In one example, such a PSFCH opportunity may be in a PSFCH slot outside the COT that includes the PSSCH / PSCCH transmission associated with the PSFCH transmission.

[0410] The WTRU may determine the HARQ latency based on the QoS of the TB and indicate it in the SCI of the PSSCH / PSCCH transmission. In another example, the HARQ latency may be (pre-)configured with an association with a priority, and the WTRU may determine the HARQ latency accordingly based on such (pre-)configuration and the L1 priority indicated in the SCI of the associated PSSCH / PSCCH transmission.

[0411] In a further example, the WTRU may determine the HARQ latency to indicate in the SCI of the PSSCH / PSCCH transmission based on the received PUCCH resource configuration / scheduling. The WTRU may perform the PSSCH / PSCCH transmission according to the SL scheduling grant received in the DCI from the base station. The WTRU may receive the PUCCH resource configuration / scheduling in the same DCI to transmit a PUCCH carrying SL HARQ feedback information associated with the scheduled PSSCH / PSCCH transmission. Thus, the WTRU may indicate an LBT failure to upper layers based on the Type 1 LBT channel access performed for the PSFCH transmission to be included in the PUCCH scheduled by the base station.

[0412] The WTRU may determine one or more PSFCH slots, each of which includes a PSFCH opportunity within the determined HARQ latency. In one example, the PSFCH slots may be (pre-)configured in a resource pool. In another example, the PSFCH slots may be indicated in the SCI of the associated PSSCH / PSCCH transmission.

[0413] In some instances, the WTRU may indicate an LBT failure to higher layers under one or more circumstances.

[0414] For example, the WTRU may perform Type 1 LBT channel access and fail to access the channel before the start of each PSFCH opportunity within the HARQ latency. The WTRU may evaluate LBT failure for each PSFCH opportunity.

[0415] For example, the WTRU may perform Type 1 LBT channel access and fail to access the channel before the start of the first PSFCH opportunity within the determined HARQ latency. The WTRU may not be able to indicate LBT failure in subsequent PSFCH opportunities and therefore may be able to evaluate LBT failure for each HARQ latency.

[0416] In some instances, the WTRU may indicate an LBT failure to higher layers based on whether the PSFCH transmission can be performed within the HARQ latency. The WTRU may indicate an LBT failure under one or more circumstances.

[0417] For example, a WTRU may perform one or more Type 1 LBT channel accesses and fail to access the channel and fail to perform a PSFCH transmission within the HARQ latency. The WTRU may evaluate the LBT failure for each HARQ latency.

[0418] For example, a WTRU may perform one or more Type 1 LBT channel accesses and fail to access the channel and fail to perform a PSFCH transmission before a scheduled PUCCH transmission. The WTRU may evaluate LBT failure for each scheduled PUCCH transmission.

[0419] For example, a WTRU may perform one or more Type 1 LBT channel accesses and fail to access the channel in some PSFCH opportunities prior to a successful PSFCH transmission within the HARQ latency. The number of such PSFCH opportunities may be (pre-)configured with an association with a priority. A lower threshold may be (pre-)configured for high priority to allow the WTRU to more quickly adjust channel access parameters for HARQ feedback associated with high priority PSSCH / PSCCH transmissions.

[0420] For example, the WTRU may fail to receive a PSFCH transmission within the HARQ latency indicated in the performed PSSCH / PSCCH transmission. In another example, the WTRU may fail to receive a PSFCH transmission before a scheduled PUCCH transmission. The WTRU may report such an LBT failure to the base station.

[0421] The WTRU may indicate an LBT failure to upper layers based on a Type 2 LBT channel access performed for one or more PSFCH transmissions in one or more PSFCH opportunities within the HARQ latency. In one example, such a PSFCH opportunity may be in a PSFCH slot in a COT that includes a PSSCH / PSCCH transmission associated with the PSFCH transmission. The WTRU may indicate an LBT failure to upper layers under one or more circumstances. For example, the WTRU may perform a Type 2 LBT channel access (e.g., Type 2A / 2B) and fail to access a channel before the start of a PSFCH opportunity in the current COT that is shareable for the PSFCH transmission.

[0422] In some cases, there may be a WTRU physical layer failure indication based on channel access for S-SSB (SL synchronization signal block) transmission. The WTRU can indicate an LBT failure to upper layers based on Type 1 and / or Type 2 LBT channel access performed for one or more S-SSB transmissions in one or more S-SSB candidate opportunities within a (pre-)configured S-SSB period. The WTRU can determine one or more S-SSB candidate opportunities (e.g., SL slots and symbol positions) based on the (pre-)configured S-SSB period duration, S-SSB start slot offset, and / or spacing between S-SSBs within the period (e.g., all in logical SL slot units).

[0423] In some instances, the WTRU may indicate an LBT failure to higher layers according to one or more conditions.

[0424] For example, the WTRU may indicate an LBT failure when the WTRU performs Type 1 and / or Type 2 LBT (e.g., Type 2A / 2B) channel access and fails to access the channel before an S-SSB candidate opportunity and fails to perform an S-SSB transmission. The WTRU may evaluate the LBT failure indication for each S-SSB candidate opportunity.

[0425] For example, the WTRU may indicate an LBT failure when the WTRU performs a Type 1 and / or Type 2 LBT (e.g., Type 2A / 2B) channel access and fails to access the channel before the first S-SSB candidate opportunity in an S-SSB period. The WTRU may not indicate an LBT failure in the remaining S-SSB candidate opportunities in the S-SSB period. The WTRU may evaluate the LBT failure for each S-SSB period.

[0426] For example, the WTRU may indicate an LBT failure when the WTRU performs one or more Type 1 and / or Type 2 LBT (e.g., Type 2A / 2B) channel accesses and fails to access the channel before all S-SSB candidate opportunities within an S-SSB period. Thus, the WTRU may indicate an LBT failure when the WTRU fails to perform any S-SSB transmission within an S-SSB period.

[0427] For example, the WTRU may indicate an LBT failure when the WTRU performs one or more Type 1 and / or Type 2 LBT (e.g., Type 2A / 2B) channel accesses and fails to access the channel before a (pre-)configured number of S-SSB candidate opportunities within the S-SSB period.

[0428] The WTRU may adjust S-SSB transmission parameters when the indicated number of S-SSB LBT failures exceeds a (pre-)configured threshold. In one example, the WTRU may determine different S-SSB start slot offsets within the S-SSB period to access the channel at different time instances.

[0429] In some cases, there may be a WTRU physical layer indication of additional information accompanying the LBT failure. In addition to the LBT failure indication, the WTRU may provide one or more of the following information to upper layers: the type of LBT channel access performed, such as Type 1, Type 2A, Type 2B LBT; the type of SL channel to transmit on, such as PSSCH / PSCCH, PSFCH, S-SSB; the priority / CAPC configuration associated with the performed LBT channel access; and / or the mode of channel access, such as scheduled, base station or WTRU autonomous.

[0430] In another example, the WTRU may determine consecutive LBT sensing failures for SL U channel access and resource selection when the number of failures for SL U channel access and resource selection as discussed herein may exceed a (pre)configured threshold. In one example, the threshold may be a number of TBs that the WTRU may fail to transmit due to LBT sensing failures. The WTRU may report such consecutive LBT sensing failures to upper layers. The WTRU may receive an LBT sensing configuration in response to the reported consecutive LBT sensing failures. For example, the CAPC configuration for subsequent LBT sensing for SL U channel access and resource selection may have a longer contention window.

[0431] FIG. 7 illustrates an example process for a WTRU to transmit a message in an unlicensed spectrum. At some previous time, the WTRU may receive one or more configuration information in one or more messages. At 701, the WTRU may select a first channel occupation time (COT) period from a preconfigured number of candidate COT periods in a resource selection window (RSW). At 702, the WTRU may perform a first listen-before-talk (LBT) in the first COT period on a channel in the unlicensed spectrum. At 703, upon indication of success of the first LBT, the WTRU may determine a corresponding time gap to an earliest preconfigured transmission start time associated with a first priority of a sidelink transport block (SL-TB). At 704, the WTRU may transmit a channel reservation signal until the earliest preconfigured transmission start time associated with the first priority of the SL-TB. At 705, the WTRU may transmit the TB (e.g., transmit a physical sidelink shared channel transmission or a physical control channel transmission) at the earliest preconfigured transmission start time associated with the first priority of the SL-TB. At 706, in some cases, if the determined gap is greater than a symbol, the WTRU may perform a second LBT over a preconfigured number of slots and proceed with transmitting the PSSCH / PSCCH transmission based on the second LBT indicating that the channel is idle in all slots. At 707, in some cases, a channel reservation signal may be transmitted on the condition that the determined gap is less than or equal to a preconfigured time period, the preconfigured time period being a symbol. In some cases, the configuration information may include candidate COT periods within a number of RSWs. In some cases, the first LBT may be type 1. In some cases, selecting the first COT period may be based on COT reservation information from the sidelink control information (SCI). In some cases, the RSW may be determined based on a remaining packet delay budget (PDB) of the SL-TB.

[0432] Based on one or more techniques described herein, in one example, there may be one or more methods related to Mode 2 SL U channel access and resource selection based on LBT and SCI sensing based channel access for COT initiation and COT sharing performed within a resource selection window.

[0433] For example, a WTRU COT sharing method may include one or more steps. The WTRU may be triggered to perform a channel access and resource selection procedure for one or more TBs of slot (n). The WTRU may determine a channel access and resource selection window (RSW) between slot (n+T1) and slot (n+T2), where T1 is (pre)configured and T2 is based on the remaining PDB of the TB; and / or may determine a number of retransmissions based on the QoS of the TB and a total number of corresponding resources. The WTRU may determine that a COT is detected in a slot within the determined RSW based on the SCI sensing. The WTRU may determine to share the detected COT based on one or more of the following decoded SCIs from the SCI sensing: remaining duration of the detected COT; number of scheduled transmissions within the COT; frequency allocation of the scheduled transmission; cast type, WTRU source and / or destination ID associated with the TB transmitted in the COT; priority associated with the TB for transmitting by the WTRU; and / or channel congestion indication. The WTRU may perform transmissions within the determined shared COT using the following resources: One or more slots that are not scheduled for transmission; and / or one or more frequency resources, such as an RB interlace index, that are not allocated for scheduled transmission.

[0434] For example, a WTRU COT initiation method may include one or more steps. The WTRU may be triggered to perform a channel access and resource selection procedure for one or more TBs in slot (n). The WTRU may determine: a channel access and resource selection window (RSW) between slot (n+T1) and slot (n+T2), where T1 is (pre)configured and T2 is based on the remaining PDB of the TB; and / or the number of retransmissions based on the QoS of the TB and the total number of corresponding resources. The WTRU may determine to perform the SL U channel access procedure for COT initiation using the RSW. The WTRU may suspend the SL U channel access procedure for COT initiation in slots that overlap with the COT and / or resources reserved by another WTRU according to the SCI sensing information. Upon successful channel access, the WTRU may determine to start the COT and resources in the COT for transmission based on the following: WTRU source and / or destination ID, cast type, priority of the TB to transmit; and / or priority and scheduled resources of PSSCH / PSCCH transmission in overlapping reserved COT and / or resources. The WTRU may transmit channel reservation signals, such as AGC symbols and / or SL RS transmissions, until the beginning of the started COT. The WTRU may transmit PSSCH / PSCCH transmissions of the TB using the determined resources in the started COT with the following information indicated in the SCI: remaining duration of the detected COT; number of scheduled transmissions in the COT; frequency allocation of the scheduled transmissions; priority associated with the TB transmitted in the COT, cast type, WTRU source and / or destination ID; and / or channel congestion indication. The WTRU may repeat channel access and resource selection for COT start until all determined transmissions of the TB are performed within the RSW and / or until slot (n+T2-X), where X is a (pre-)configured minimum processing time and the number of performed transmissions is less than the determined number of transmissions of the TB.In some cases, the WTRU may drop the remaining transmissions of the TB. Additionally / alternatively, the WTRU may indicate a failure of the TB's SL U channel access and resource selection.

[0435] Based on one or more techniques described herein, in one example, there may be a WTRU decision to start a SL COT based on a measured congestion status, such as the SL U CBR and time continuity of logical slots in the SL COT according to a mapping between physical slots in a resource pool used for the SL COT and corresponding logical slots.

[0436] Based on one or more techniques described herein, in one example, there may be a WTRU switch between blind SCI decoding on each (pre-)configured PSCCH resource in a resource pool outside the detected COT and SCI decoding on COT-specific PSCCH resources within the remaining duration of the detected COT.

[0437] Based on one or more techniques described herein, in one example, there may be a WTRU decision of SL COT sharing based on the distance between the WTRU and the WTRU initiating the COT, the RSRP of the PSSCH / PSCCH DMRS, and a measured congestion status (e.g., SL U CBR).

[0438] Based on one or more techniques described herein, in one example, there may be a WTRU that performs LBT-sensing channel access according to the COT and / or resource reservation interval and associated reservation window, reservation range, latency bound indicated in the semi-persistent COT, and / or resource reservation in a previously transmitted SCI.

[0439] Based on one or more techniques described herein, in one example, there may be a WTRU dynamic determination of a COT start position for COT initiation based on a TB priority, a priority associated with the COT start position, and a channel congestion level.

[0440] Based on one or more techniques described herein, in one example, there may be a COT sharing condition based on the COT start / sharing indication start of the SCI of the initiating and sharing WTRUs, the WTRU source and / or destination ID, TB priority or synchronization source.

[0441] Based on one or more techniques described herein, in one example, there may be WTRU selection of Type 2A / 2B / 2C LBT procedures in COT sharing based on channel congestion, TB priority, cast and channel type, remaining PDB and transmission duration.

[0442] Based on one or more techniques described in this specification, in one example, there may be frequency multiplexing-based COT sharing with muting of interlace RBs to mitigate interference, as well as WTRU decision to set transmit power based on PSD restrictions, transmission bandwidth, and measured power in the shared COT.

[0443] Based on one or more techniques described herein, in one example, there may be WTRU dynamic adjustment of energy detection threshold (EDT) based on channel congestion, channel type, HARQ feedback status, CSI reporting, COT initiation / sharing, etc.

[0444] Based on one or more techniques described herein, in one example, there may be a WTRU COT initiation based on resource / COT selection prior to Type 1 LBT using resource / COT reservation information from sensing.

[0445] Based on one or more techniques described herein, there may be a method implemented by a WTRU. The WTRU may receive a trigger message prompting the execution of an LBT and resource selection to transmit the SL-TB. The WTRU may determine an RSW based on a remaining PDB, which is the remaining PDB of the SL-TB. The WTRU may select a frequency resource based on a WTRU source / destination ID. The WTRU may select a (pre-)configured number of candidate COT periods within the determined RSW based on COT reservation information from sidelink control information sensing. The WTRU may perform an LBT in the first determined candidate COT period to measure. If the LBT is successful, the WTRU may determine a corresponding time gap to the earliest preconfigured transmission start position associated with the L1 priority of the SL-TB. The WTRU may transmit a channel reservation signal to the earliest preconfigured transmission start position associated with the L1 priority of the SL-TB when the determined gap is less than or equal to the preconfigured time period. The WTRU may transmit a PSSCH / PSCCH at the earliest preconfigured transmission start position associated with the L1 priority of the SL-TB. The WTRU may perform LBT sensing over a (pre)configured number of sensing slots, provided that the determined gap is larger than a symbol, and may proceed with PSSCH / PSCCH transmission when the channel is idle in all sensed slots. The preconfigured time period may be a symbol. The frequency resource may be an index of a resource block interlace. The WTRU may perform sidelink control information (SCI) sensing. The LBT may be Type 1. The WTRU may receive configuration information at an initial time, the configuration information relating to performing one or more of the above actions.

[0446] In one or more embodiments disclosed herein, there may be a WTRU procedure that performs SLU channel access and resource selection simultaneously for COT sharing and COT initiation within the RSW.

[0447] In one or more embodiments disclosed herein, the WTRU decision of SL COT detection and sharing may be based on SCI sensing information including remaining duration, number of transmissions scheduled within the COT, frequency resource allocation, priority, cast type, WTRU source and / or destination ID, COT / resource reservation, channel congestion, etc.

[0448] In one or more embodiments disclosed herein, the WTRU decision to initiate SL COT may be based on LBT and SCI sensing information including COT / resource reservation, priority, cast type, WTRU source and / or destination ID, channel congestion, etc.

[0449] In one or more embodiments disclosed herein, there may be a WTRU determination of transmission resources within the shared and initiated SL COTs based on the WTRU source and / or destination ID of the transmitting TB and the RB interlace allocation indicated in the decoded SCI associated with the overlapping reserved COT.

[0450] As described herein, a higher layer may refer to one or more layers in a protocol stack or a particular sublayer within a protocol stack. The protocol stack may be comprised of one or more layers in a WTRU or a network node (e.g., eNB, gNB, other functional entity, etc.), where each layer may have one or more sublayers. Each layer / sublayer may be responsible for one or more functions. Each layer / sublayer may directly or indirectly communicate with one or more of the other layers / sublayers. In some cases, these layers may be numbered as Layer 1, Layer 2, and Layer 3. For example, Layer 3 may be comprised of one or more of the following: Non-Access Stratum (NAS), Internet Protocol (IP), and / or Radio Resource Control (RRC). For example, Layer 2 may be comprised of one or more of the following: Packet Data Convergence Control (PDCP), Radio Link Control (RLC), and / or Medium Access Control (MAC). For example, Layer 3 may consist of physical (PHY) layer type operations. The higher the layer number, the higher the layer is relative to other layers (e.g., Layer 3 is higher than Layer 1). In some cases, the above examples may be referred to as layers / sublayers themselves, regardless of the number of layers, and may be referred to as higher layers as described herein. For example, higher layers may refer to one or more of the following layers / sublayers, from highest to lowest: NAS layer, RRC layer, PDCP layer, RLC layer, MAC layer, and / or PHY layer. Any reference to higher layers herein in connection with a process, device, or system will refer to a layer that is higher than the layer of the process, device, or system. In some cases, reference to higher layers herein may refer to functions or operations performed by one or more layers described herein.In some cases, references herein to higher layers may refer to information sent or received by one or more layers described herein. In some cases, references herein to higher layers may refer to configurations sent and / or received by one or more layers described herein.

[0451] Although features and elements are described above in certain combinations (e.g., embodiments, methods, examples, etc.), those skilled in the art will understand that each feature or element can be used alone or in any combination with other features and elements. For example, as disclosed herein, there may be a method described in connection with a figure for illustrative purposes, and those skilled in the art will understand that one or more features or elements from the method can be used alone or in combination with one or more features from another method described elsewhere (e.g., in another figure, or in a separate part of the description). In addition, the methods described herein may be performed in a device executing a computer program, software, and / or firmware embodied in a computer-readable medium for execution by a computer and / or processor operatively connected to a transceiver (e.g., wireless or wired) of the device. Examples of computer-readable media include electronic signals (transmitted over a wired or wireless connection) and computer-readable storage media. Examples of computer readable storage media include, but are not limited to, read only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media and optical media such as CD-ROM disks and digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

1. 1. A method performed by a wireless transmit-receive unit (WTRU), comprising: selecting a first channel occupancy time (COT) period from a preconfigured number of candidate COT periods within a resource selection window (RSW); performing a first listen-before-talk (LBT) during the first COT period on a channel in an unlicensed spectrum; determining a corresponding time gap to an earliest preconfigured transmission start time associated with a first priority of a sidelink transport block (SL-TB) when success of the first LBT is indicated; transmitting a channel reservation signal until the earliest preconfigured transmission start time associated with the first priority of the SL-TB; transmitting a physical sidelink shared channel (PSSCH) transmission or a physical sidelink control channel (PSSCH) transmission at the earliest preconfigured transmission start time associated with the first priority of the SL-TB; A method comprising:

2. 2. The method of claim 1, further comprising: performing a second LBT over a preconfigured number of slots, on the condition that the determined gap is greater than a symbol; and proceeding with the transmission of the PSSCH or PSCCH based on the second LBT indicating that the channel is idle in all slots.

3. 2. The method of claim 1, wherein the channel reservation signal is transmitted on the condition that the determined gap is less than or equal to a preconfigured time period, the preconfigured time period being in symbols.

4. The method of claim 1 , further comprising receiving configuration information related to the pre-configured number of candidate COT periods in the RSW.

5. The method of claim 1 , wherein the first LBT is Type 1.

6. 2. The method of claim 1, wherein the selecting the first COT period is based on COT reservation information from a sidelink control information (SCI).

7. The method of claim 1 , wherein the RSW is determined based on a remaining packet delay budget (PDB) of the SL-TB.

8. The method of claim 1 , wherein the channel reservation signal is a cyclic prefix extension.

9. 1. A wireless transmit-receive unit (WTRU), comprising: means for selecting a first channel occupancy time (COT) period from a preconfigured number of candidate COT periods within a resource selection window (RSW); means for performing a first listen-before-talk (LBT) during the first COT period on a channel in an unlicensed spectrum; means for determining, when a success of the first LBT is indicated, a corresponding time gap to an earliest preconfigured transmission start time associated with a first priority of a Sidelink Transport Block (SL-TB); means for transmitting a channel reservation signal until the earliest preconfigured transmission start time associated with the first priority of the SL-TB; means for transmitting a Physical Sidelink Shared Channel (PSSCH) transmission or a Physical Sidelink Control Channel (PSSCH) transmission at the earliest preconfigured transmission start time associated with the first priority of the SL-TB; A WTRU comprising:

10. The WTRU of claim 9, further comprising: performing a second LBT over a preconfigured number of slots, provided that the determined gap is greater than a symbol; and proceeding with the transmission of the PSSCH or PSCCH based on the second LBT indicating that the channel is idle in all slots.

11. 10. The WTRU of claim 9, wherein the channel reservation signal is transmitted on the condition that the determined gap is less than or equal to a preconfigured time period, the preconfigured time period being in symbols.

12. The WTRU of claim 9 , further comprising: means for receiving configuration information relating to the pre-configured number of candidate COT periods within the RSW.

13. The WTRU of claim 9 , wherein the first LBT is Type 1.

14. The WTRU of claim 9, wherein selecting the first COT period is based on COT reservation information from sidelink control information (SCI).

15. The WTRU of claim 9, wherein the RSW is determined based on a remaining packet delay budget (PDB) of the SL-TB, and the channel reservation signal is a cyclic prefix extension.

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