WO2025034324A1 - Carrier-specific sl rlf based on harq counting - Google Patents

Abstract

A method of determining carrier-specific SL RLF for multicarrier with licensed and unlicensed carriers may generally include a SL WTRU resetting carrier-specific SL RLF HARQ DTX counters upon reception of a message (e.g., reset MAC CE) received from an RX WTRU. The TX WTRU is configured to perform independent (i.e., separate counters per carrier) counting of HARQ DTX on each carrier (licensed and unlicensed). When a message is received on a licensed carrier from the RX WTRU indicating one or more unlicensed carrier(s), the consecutive number of HARQ DTX may be reset or modified. If the number of consecutive HARQ DTX on a carrier reaches a threshold, the WTRU may indicate carrier specific SL RLF to the network for that carrier. Additional embodiments are disclosed.

Description

CARRIER-SPECIFIC SL RLF BASED ON HARQ COUNTING

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63/531 ,231 , filed August 7, 2023, the contents of which are incorporated herein by reference.

BACKGROUND

[0002] Multicarrier has been specified for new radio (NR) sidelink (SL) in 3^rd generation partnership (3GPP) Release 18. Multicarrier is expected to use long term evolution (LTE) as a baseline, while potentially considering some differences to account for unicast transmission in NR In addition, unlicensed operation for SL is also being specified and there are no expectations to have these two features interact Specifically, multicarrier operation is considered for licensed carriers in the case of Rel18 user equipment (UE). Furthermore, unlicensed operation is being considered for a single carrier only. It is expected, however, that future releases will need to support UEs which operate over a combination of licensed and unlicensed carriers.

[0003] A number of areas specific to sidelink (SL) communication are being considered for operating licensed and unlicensed carriers in a multicarrier fashion, including carrier selection, discontinuous reception (DRX) and hybrid automatic repeat request (HARQ) radio link failure (RLF). Carrier selection based on priority and channel busy ratio (CBR) may not be appropriate when a mix of licensed and unlicensed carriers are present. Specifically, licensed and unlicensed carriers cannot be considered equal from the perspective of resource usage, maintenance of QoS, and access. DRX for SL is currently designed for single carrier only. Multicarrier DRX exists for uplink and downlink (i.e , Uu interface) based on DRX groups. However, defining DRX groups has the limitations, in the context of multicarrier licensed/unlicensed in SL, that a receive (RX) UE would need to monitor all carriers configured for transmission by a transmit (TX) UE, which may not be ideal from a power consumption perspective, particularly if some of these carriers are in an unlicensed band. Hybrid automatic repeat request (HARQ)-based RLF determination is also designed for single carrier only. In SL multicarrier, whether issues on one carrier warrant determination of SL RLF of the entire link or not may vary on the carriers themselves and/or potentially on whether they are licensed/unlicensed.

[0004] Legacy SL RLF is designed for a single carrier. One issue with HARQ-based counting in unlicensed is there is no way to determine whether the HARQ DTX is due to decoding failure or LBT failure at the RX UE. Solutions for multicarrier sidelink using licensed and/or unlicensed carriers are needed.

SUMMARY

[0005] According to one aspect of the disclosure, a method is disclosed where a UE, also referred to herein as a wireless transmit receive unit (WTRU) resets carrier-specific SL-RLF HARQ DRX counters upon reception of a message (e.g., reset MAC CE) from the RX WTRU.

[0006] In one example, a SL TX WTRU establishes a unicast link with a peer WTRU (i.e., RX WTRU) and selects multiple licensed and/or unlicensed carriers for communication. The TX WTRU performs independent (i.e., separate counters per carrier) counting of hybrid automatic repeat request (HARQ) discontinuous transmission (DTX) on each carrier (licensed and unlicensed). The TX WTRU receives a message (e.g., MAC CE) on a licensed carrier from the RX WTRU that indicates one or more unlicensed carrier(s). The TX WTRU modifies the consecutive number of HARQ DTX on the indicated carrier(s). For example, the TX WTRU resets the consecutive number of HARQ DTX counts or subtracts a value (e g., indicated in the MAC CE) from the current consecutive HARQ DTX count. If the number of consecutive HARQ DTX on a carrier reaches a threshold, the WTRU may indicate carrier-specific SL radio link failure (RLE) to the network for that carrier. Additional embodiments are disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings, wherein like reference numerals in the figures indicate like elements, and wherein:

[0008] FIG. 1A is a system diagram illustrating an example communications system in which one or more disclosed embodiments may be implemented;

[0009] FIG. 1 B 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 an embodiment;

[0010] 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 communications system illustrated in FIG. 1A according to an embodiment;

[0011] FIG. 1D is a system diagram illustrating a further example RAN and a further example CN that may be used within the communications system illustrated in FIG. 1A according to an embodiment; and

[0012] FIG. 2 is a flow diagram illustrating a method of carrier-specific sidelink radio link failure (RLF) based on HARQ counting for multicarrier with licensed and unlicensed carriers according to an embodiment.

DETAILED DESCRIPTION

[0013] FIG. 1A is a diagram illustrating an example communications system 100 in which one or more disclosed embodiments may be implemented. The communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, etc., to multiple wireless users. The communications system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communications systems 100 may employ 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.

[0014] As shown in FIG. 1A, the 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, though it will be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and/or network elements. Each of the 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 a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Pi device, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e g., remote surgery), an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and/or industrial wireless networks, and the like. Any of the WTRUs 102a, 102b, 102c and 102d may be interchangeably referred to as a UE.

[0015] The communications systems 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 communication networks, such as the CN 106, the Internet 110, and/or the other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a NodeB, an eNode B (eNB), a Home Node B, a Home eNode B, a next generation NodeB, such as a gNode B (gNB), a new radio (NR) NodeB, a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted 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.

[0016] The base station 114a may be part of the RAN 104, which may also include other base stations and/or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, and the like. 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 a cell (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for a wireless service to a specific geographical area that may be relatively fixed or that may change over time. The cell may further be 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 for each sector of the cell. In an 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, beamforming may be used to transmit and/or receive signals in desired spatial directions.

[0017] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over 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). [0018] More specifically, as noted above, the communications system 100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a in the RAN 104 and the WTRUs 102a, 102b, 102c 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 communication protocols such as High-Speed Packet Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink (DL) Packet Access (HSDPA) and/or High-Speed Uplink (UL) Packet Access (HSUPA).

[0019] In an 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).

[0020] In an 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.

[0021] In an 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, for instance using dual connectivity (DC) principles. Thus, the air interface utilized by WTRUs 102a, 102b, 102c may be characterized by multiple types of radio access technologies and/or transmissions sent to/from multiple types of base stations (e g., an eNB and a gNB).

[0022] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi), 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), and the like.

[0023] The base station 114b in FIG. 1A may be a wireless router, Home Node B, Home eNode B, or access point, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a roadway, and the like. 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 an 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 utilize a cellularbased RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. 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 be required to access the Internet 110 via the CN 106.

[0024] The RAN 104 may be in communication with the CN 106, which may be any type of network configured to provide voice, data, applications, and/or voice over internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. The data may have varying quality of service (QoS) requirements, such as differing throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, and the like. The CN 106 may provide call control, billing services, mobile location-based services, pre-paid 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 appreciated that the RAN 104 and/or the CN 106 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may be utilizing a NR radio technology, the CN 106 may also be in communication with another RAN (not shown) employing a GSM, UMTS, CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

[0025] 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 the other networks 112. The PSTN 108 may include circuit-switched telephone networks that provide 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), user datagram protocol (UDP) and/or the internet protocol (IP) in the TCP/IP internet protocol suite. The networks 112 may include wired and/or wireless communications networks owned and/or operated by other service providers. For example, the networks 112 may include another CN connected to one or more RANs, which may employ the same RAT as the RAN 104 or a different RAT.

[0026] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multimode 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 the base station 114a, which may employ a cellular-based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0027] FIG. 1 B is a system diagram illustrating an example WTRU 102. As shown in FIG. 1 B, the WTRU 102 may include 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, among others. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0028] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), any other type of integrated circuit (IC), a state machine, and the like. 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. While FIG. 1 B depicts the processor 118 and the transceiver 120 as separate components, it will be appreciated that the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip. [0029] The transmit/receive element 122 may be configured to transmit signals to, or receive signals from, a base station (e.g., the 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 an 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.

[0030] Although the transmit/receive element 122 is depicted in FIG 1B as a single element, the WTRU 102 may include any number of transmit/receive elements 122. More specifically, the WTRU 102 may employ Ml MO 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.

[0031] The transceiver 120 may be configured to modulate the signals that are to be transmitted by the transmit/receive element 122 and to demodulate the signals that are received by the transmit/receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RAT s, such as NR and IEEE 802.11 , for example. [0032] The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker/microphone 124, the keypad 126, and/or the display/touchpad 128 (e.g., a liquid crystal display (LCD) display unit or 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 the non-removable memory 130 and/or the 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, and the like. 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 a home computer (not shown).

[0033] The processor 118 may receive power from the power source 134, and may be configured to distribute and/or control the power to the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g , nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and the like.

[0034] The processor 118 may also be coupled to the 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, the information from the GPS chipset 136, the WTRU 102 may receive location information over the air interface 116 from a base station (e.g., base stations 114a, 114b) and/or determine its location based on the timing of the signals being received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by way of any suitable location-determination method while remaining consistent with an embodiment. [0035] 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 e-compass, a satellite transceiver, a digital camera (for photographs and/or video), 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 sensors 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.

[0036] The WTRU 102 may include a full duplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for both the UL (e.g., for transmission) and DL (e.g , for reception) may be concurrent and/or simultaneous. 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., a separate processor (not shown) or via processor 118). In an embodiment, the WTRU 102 may include a halfduplex radio for which transmission and reception of some or all of the signals (e.g., associated with particular subframes for either the UL (e.g , for transmission) or the DL (e.g., for reception))

[0037] FIG. 1C is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0038] The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of eNode-Bs while remaining consistent with an embodiment. The eNode-Bs 160a, 160b, 160c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the eNode-B 160a, for example, may use multiple antennas to transmit wireless signals to, and/or receive wireless signals from, the WTRU 102a.

[0039] Each of the eNode-Bs 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, and the like. As shown in FIG. 1C, the eNode-Bs 160a, 160b, 160c may communicate with one another over an X2 interface.

[0040] The CN 106 shown in FIG. 1C may include a mobility management entity (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway (PGW) 166. While the foregoing elements are depicted as part of the CN 106, it will be appreciated that any of these elements may be owned and/or operated by an entity other than the CN operator.

[0041] The MME 162 may be connected to each of the eNode-Bs 162a, 162b, 162c in the RAN 104 via an S1 interface and may serve as a control node. For example, the MME 162 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation/deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. 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

[0042] The SGW 164 may be connected to each of the eNode Bs 160a, 160b, 160c in the RAN 104 via the S1 interface The SGW 164 may generally route and forward user data packets to/from the WTRUs 102a, 102b, 102c. The SGW 164 may perform other functions, such as anchoring user planes during inter-eNode B handovers, triggering paging when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like.

[0043] The SGW 164 may be connected to the 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.

[0044] 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 may 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 the other networks 112, which may include other wired and/or wireless networks that are owned and/or operated by other service providers.

[0045] Although the WTRU is described in FIGS. 1A-1 D as a wireless terminal, it is contemplated that in certain representative embodiments that such a terminal may use (e.g., temporarily or permanently) wired communication interfaces with the communication network.

[0046] In representative embodiments, the other network 112 may be a WLAN.

[0047] A WLAN in Infrastructure Basic Service Set (BSS) mode may have an Access Point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP may have access or an interface to a Distribution System (DS) or another type of wired/wireless network that carries traffic in to and/or out of the BSS. Traffic to STAs that originates from outside the BSS may arrive through the AP and may be delivered to the STAs. Traffic originating from STAs to destinations outside the BSS may be sent to the AP to be delivered to respective destinations. T raffic between STAs within the BSS may be sent through the AP, for example, where the source STA may send traffic to the AP and the AP may deliver the traffic to the destination STA. The traffic between STAs within a BSS may be considered and/or referred to as peer-to-peer traffic. The peer-to-peer traffic may be sent between (e g., directly between) the source and destination STAs with a direct link setup (DLS). In certain representative embodiments, the DLS may use an 802.11e DLS or an 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may not have an AP, and the STAs (e.g., all of the STAs) within or using the IBSS may communicate directly with each other. The IBSS mode of communication may sometimes be referred to herein as an “ad-hoc” mode of communication. [0048] When using the 802.11ac infrastructure mode of operation or a similar mode of operations, the AP may transmit a beacon on a fixed channel, such as a primary channel. The primary channel may be a fixed width (e.g., 20 MHz wide bandwidth) or a dynamically set width. The primary channel may be the operating channel of the BSS and may be used by the 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 802 11 systems. For CSMA/CA, the STAs (e.g., every STA), 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.

[0049] High Throughput (HT) STAs may use a 40 MHz wide channel for communication, for example, via a combination of the primary 20 MHz channel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHz wide channel.

[0050] Very High Throughput (VHT) STAs may support 20MHz, 40 MHz, 80 MHz, and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may be formed by combining contiguous 20 MHz channels. A 160 MHz channel may be formed by combining 8 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, the data, after channel encoding, may be passed through a segment parser that may divide the data into two streams. Inverse Fast Fourier Transform (IFFT) processing, and time domain processing, may be done on each stream separately. The streams may be mapped on to the two 80 MHz channels, and the data may be transmitted by a transmitting STA. At the receiver of the receiving STA, the above described operation for the 80+80 configuration may be reversed, and the combined data may be sent to the Medium Access Control (MAC).

[0051] Sub 1 GHz modes of operation are supported by 802.11 af and 802 11 ah. The channel operating bandwidths, and carriers, are reduced in 802.11 af and 802.11 ah relative 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, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and 16 MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11 ah may support Meter Type Control/Machine-Type Communications (MTC), such as MTC devices in a macro coverage area. MTC devices may have certain capabilities, for example, limited capabilities including support for (e.g., only support for) certain and/or limited bandwidths The MTC devices may include a battery with a battery life above a threshold (e.g., to maintain a very long battery life).

[0052] WLAN systems, which may support multiple channels, and channel bandwidths, such as 802.11 n, 802.11ac, 802.11 af, and 802.11 ah, include a channel which may be designated as the primary channel. The primary channel may have a bandwidth equal to the largest common operating bandwidth supported by all STAs in the BSS. The bandwidth of the primary channel may be set and/or limited by a STA, from among all STAs in operating in a BSS, which supports the smallest bandwidth operating mode. In the example of 802.11 ah, the primary channel may be 1 MHz wide for STAs (e.g., MTC type devices) that support (e.g., only support) a 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) settings may depend on the status of the primary channel. If the primary channel is busy, for example, due to a STA (which supports only a 1 MHz operating mode) transmitting to the AP, all available frequency bands may be considered busy even though a majority of the available frequency bands remains idle.

[0053] In the United States, the available frequency bands, which may be used by 802.11 ah, are from 902 MHz to 928 MHz. In Korea, the available frequency bands are from 917.5 MHz to 923 5 MHz In Japan, the available frequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11 ah is 6 MHz to 26 MHz depending on the country code.

[0054] FIG. 1 D is a system diagram illustrating the RAN 104 and the CN 106 according to an embodiment. As noted above, the RAN 104 may employ an NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116 The RAN 104 may also be in communication with the CN 106.

[0055] The RAN 104 may include gNBs 180a, 180b, 180c, though it will be appreciated 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 one embodiment, the gNBs 180a, 180b, 180c may implement MIMO technology. For example, gNBs 180a, 108b may utilize beamforming to transmit signals to and/or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a, for example, may use multiple antennas to transmit wireless signals to, and/or receive wireless signals from, the WTRU 102a. In an 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 unlicensed spectrum while the remaining component carriers may be on licensed spectrum. In an embodiment, the gNBs 180a, 180b, 180c may implement Coordinated Multi-Point (CoMP) technology. For example, WTRU 102a may receive coordinated transmissions from gNB 180a and gNB 180b (and/or gNB 180c).

[0056] The WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using transmissions associated with a 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 gNBs 180a, 180b, 180c using subframe or transmission time intervals (TTIs) of various or scalable lengths (e.g., containing a varying number of OFDM symbols and/or lasting varying lengths of absolute time).

[0057] 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 the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c without also accessing other RANs (e.g., such as eNode-Bs 160a, 160b, 160c). In the standalone configuration, WTRUs 102a, 102b, 102c may utilize one or more of gNBs 180a, 180b, 180c as a mobility anchor point. In the standalone configuration, WTRUs 102a, 102b, 102c may communicate with gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration WTRUs 102a, 102b, 102c may communicate with/connect to gNBs 180a, 180b, 180c while also communicating with/connecting to another RAN such as eNode-Bs 160a, 160b, 160c. For example, WTRUs 102a, 102b, 102c may implement DC principles to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In the non-standalone configuration, eNode-Bs 160a, 160b, 160c may serve as a mobility anchor for WTRUs 102a, 102b, 102c and gNBs 180a, 180b, 180c may provide additional coverage and/or throughput for servicing WTRUs 102a, 102b, 102c.

[0058] 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 the UL and/or DL, support of network slicing, DC, interworking between NR and E-UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184b, routing of control plane information towards Access and Mobility Management Function (AMF) 182a, 182b and the like. As shown in FIG. 1 D, the gNBs 180a, 180b, 180c may communicate with one another over an Xn interface.

[0059] The CN 106 shown in FIG. 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 While the foregoing elements are depicted as part of the CN 106, it will be appreciated that any of these elements may be owned and/or operated by an entity other than the CN operator.

[0060] 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 serve as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, support for network slicing (e.g., handling of different protocol data unit (PDU) sessions with different requirements), selecting a particular SMF 183a, 183b, management of the registration area, termination of non-access stratum (NAS) signaling, mobility management, and the like. Network slicing may be used by the AMF 182a, 182b in order to customize CN support for WTRUs 102a, 102b, 102c based on the types of services being utilized 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, and the like. 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 WiFi.

[0061] The SMF 183a, 183b may be connected to an AMF 182a, 182b in the CN 106 via an N11 interface. The SMF 183a, 183b may also be connected to a UPF 184a, 184b in the CN 106 via an N4 interface The SMF 183a, 183b may select and control the UPF 184a, 184b and configure the routing of traffic through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating UE IP address, managing PDU sessions, controlling policy enforcement and QoS, providing DL data notifications, and the like. A PDU session type may be IPbased, non-IP based, Ethernet-based, and the like.

[0062] The UPF 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 UPF 184, 184b may perform other functions, such as routing and forwarding packets, enforcing user plane policies, supporting multi-homed PDU sessions, handling user plane QoS, buffering DL packets, providing mobility anchoring, and the like. [0063] The CN 106 may facilitate communications with other networks. For example, the CN 106 may include, or may 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 the other networks 112, which may include other wired and/or wireless networks that are owned and/or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to a local DN 185a, 185b through the UPF 184a, 184b via the N3 interface to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0064] In view of FIGs. 1A-1 D, and the corresponding description of FIGs. 1A-1D, one or more, or all, of the functions described herein with regard to one or more of: WTRU 102a-d, Base Station 114a-b, eNode-B 160a-c, MME 162, SGW 164, PGW 166, gNB 180a-c, AMF 182a-b, UPF 184a-b, SMF 183a-b, DN 185a-b, and/or any other device(s) 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.

[0065] The emulation devices may be designed to implement one or more tests of other devices in a lab environment and/or in an operator network environment. For example, the one or more emulation devices may perform the one or more, or all, functions while being fully or partially implemented and/or deployed as part of a wired and/or wireless communication network in order to test other devices within the communication network. The one or more emulation devices may perform the one or more, or all, functions while being temporarily implemented/deployed as part of a wired and/or wireless communication network. The emulation device may be directly coupled to another device for purposes of testing and/or performing testing using over-the-air wireless communications.

[0066] The one or more emulation devices may perform the one or more, including all, functions while not being implemented/deployed as part of a wired and/or wireless communication network. For example, the emulation devices may be utilized in a testing scenario in a testing laboratory and/or a non-deployed (e.g., testing) wired and/or wireless communication network in order to implement testing of one or more components. The one or more emulation devices may be test equipment. Direct RF coupling and/or wireless communications via RF circuitry (e g., which may include one or more antennas) may be used by the emulation devices to transmit and/or receive data.

[0067] Solutions herein are disclosed for multicarrier operation by a SL WTRU where carriers can be licensed (i.e , access is via legacy SL) or unlicensed (i.e., access requires LBT-like operation). However, solutions can be extended to consider carriers having different properties apart from the access mechanism. In many cases, solutions can similarly be applied to multicarrier over multiple licensed carriers, where there may be some difference in the configuration or properties of such carriers. Finally, solutions are applicable also to operation over multiple bandwidth parts, multiple RB sets, etc., instead of consideration of multiple carriers.

[0068] Embodiments for Carrier-Specific SL radio link failure (RLF) based on HARQ counting will now be described. Legacy SL radio link failure (RLF) is designed for a single carrier. One issue with HARQ-based counting in unlicensed, is that existing mechanisms are unable to distinguish whether an HARQ DTX is due to decoding failure or a LBT failure at the RX WTRU. Use of a licensed carrier for information regarding HARQ DTX counting of unlicensed carrier(s) may help resolve this issue. According to one example embodiment, a WTRU resets/updates carrier-specific SL-RLF HARQ DRX counters upon reception of a message (e.g., reset MAC CE) received from the RX WTRU.

[0069] Referring to FIG. 2, an example method 200 is shown for determining carrier-specific SL RLF of unlicensed carrier(s) based on feedback information in a licensed carrier is shown. A SL TX WTRU may establish 205 a unicast link with a peer WTRU and select multiple licensed and/or unlicensed carriers for communication. Independent (i.e , separate counters per carrier) counting of HARQ DTX is performed 210 on each carrier (licensed and unlicensed). A message (e.g., a MAC CE) is received 215 on a licensed carrierfrom the RX WTRU that indicates reception information on one or more unlicensed carrier(s), e.g., whether a TB was received or not for an unlicensed carrier. Upon reception of the message, the WTRU may modify 220 the consecutive number of HARQ DTX on the indicated carrier(s). For example, the TX WTRU may reset the consecutive number of HARQ DTX or subtract a value (e.g., indicated in the MAC CE) from the current count of consecutive HARQ DTX, based on information in the received message. If 225 the number of consecutive HARQ DTX on a carrier reaches a threshold, the WTRU may indicate 230 carrier-specific SL RLF to the network for that carrier.

[0070] In various embodiments, a WTRU transmits/receives unlicensed carrier information on a licensed carrier. In one family of solutions, a WTRU may receive/transmit LBT-related or channel access-related information about a SL unlicensed carrier on a SL licensed carrier. Specifically, a WTRU may receive information about LBT failure, buffer status, channel occupancy time (COT) information, etc. on a licensed carrier, which represents information about access or transmission related to an unlicensed carrier. Similarly, based on certain triggers related to channel access on the unlicensed carrier, a WTRU may transmit information about the access on the unlicensed carrier in a SL message on the licensed carrier. A WTRU receiving such information may use the information to update counters, timers, resource allocation, and/or modify channel access on the unlicensed or licensed spectrum.

[0071 ] Information related to the unlicensed spectrum mentioned above may include one, or a combination, of any of the following:

[0072] (1) LBT status. As an example, a WTRU may transmit a message on the licensed carrier indicating LBT failure, consistent LBT failure, or similar information related to one or more unlicensed carriers.

[0073] (2) HARQ feedback failure status. In various examples, a WTRU may transmit a message on the licensed carrier indicating the failure to transmit HARQ ACK/NACK on the unlicensed spectrum due to LBT failure. By way of example, a WTRU may transmit a message on the licensed carrier upon failure to access the channel to send HARQ feedback on the unlicensed spectrum. In another example, a WTRU may transmit a message on the licensed carrier following “X” number (a configured value) of consecutive LBT failures associated with transmission of HARQ feedback. In an example, a WTRU may indicate in the message the number of consecutive LBT failures associated with HARQ feedback.

[0074] (3) Buffer status information. According to one example, a WTRU may transmit a message on the licensed carrier indicating the priority/CAPC/amount/L2 destination IDs of data available for transmission that can be sent (and is yet to be transmitted) on the unlicensed carrier. [0075] (4) Channel occupancy measurements. In some examples, a WTRU may transmit a message containing measurements of the channel occupancy of the unlicensed spectrum such as RSSI (possibly per RB set), CR, CBR, ratio of time period where SCI from other WTRUs can be detected, etc. In one example, a WTRU may perform a measurement of the channel indicating the ratio of time in which the RSSI is above a threshold without detection of SCI (i.e., an indication that the channel is occupied by WiFi transmissions).

[0076] (5) Channel occupancy time (COT) information. In an example, a WTRU may transmit a message upon reception/detection of COT information received on an unlicensed carrier, and the contents of the COT information (e.g., the length of the COT, the CAPC, the L2 destination IDs, etc.).

[0077] According to various embodiments, a WTRU may use received LBT failure information to manage SL RLF detection. In one solution, a WTRU may use a message from a peer WTRU on the licensed spectrum to update the counting of HARQ DTX for SL RLF on the unlicensed spectrum. For example, upon reception of a message on the licensed carrier indicating an unlicensed carrier, the TX WTRU may reset the number of consecutive HARQ DTX counter for SL RLF for that carrier. In an example, upon reception of a message on the licensed carrier indicating an unlicensed carrier, the WTRU may subtract, at most, a (pre)configured amount from the number of consecutive HARQ DTX counter for SL RLF forthat carrier. In one example, upon reception of a message on the licensed carrier indicating an unlicensed carrier and a value, the WTRU may subtract, at most, the received value from the number of consecutive HARQ DTX counter for SL RLF for that carrier. In an example, upon reception of a message on the licensed carrier indicating to enable/disable/suspend/resume HARQ DTX counting for SL RLF, a WTRU may enable/disable/suspend/resume HARQ DTX counting for SL RLF on the indicated unlicensed carrier.

[0078] In certain embodiments, a WTRU uses received COT/BSR information for scheduling. In one family of solutions, a WTRU may use received COT/BSR information for scheduling transmission on the unlicensed spectrum. In one solution, a WTRU may use COT information received on the licensed carrier from the peer WTRU to perform resource selection. Specifically, the WTRU may use information about the COT duration to select a resource which falls within the COT.

[0079] In another solution, a WTRU may use buffer status information received on the licensed carrier from the peer WTRU to determine COT information Specifically, the WTRU may determine a COT duration based on the amount of data indicated in buffer status from the peer WTRU. Specifically, if the buffer status is above a threshold, the WTRU may use a corresponding maximum COT duration. In another example, the WTRU may determine a set of L2 destination IDs (e.g., allowable COT sharing destinations) based on the L2 IDs associated with pending data in the buffer status information received from the peer WTRU on the licensed spectrum. Specifically, if the received message has SL RSRP above a threshold, the WTRU can include the L2 IDs associated with buffer status provided by the peer WTRU in the message

[0080] In another solution, a WTRU may use buffer status information received on the licensed carrier to determine the logical channel prioritization (LCP) behavior during transmission on the unlicensed spectrum. For example, if the BSR information indicates data associated with a specific priority, the WTRU receiving the BSR may include data in logical channels associated with the same/higher/lower priority than the specific priority. [0081] In yet another solution, a WTRU may use buffer status information received on the licensed carrier to determine the CAPC used to access the channel for creating a shared COT Specifically, the WTRU may use either the priority of the data in its own buffers, or the priority of the data in the peer WTRU’s BSR (i.e. , received in a message on the licensed spectrum) to determine the CAPC for channel access. For example, if the BSR information indicates data associated with a specific priority (potentially larger than the priority associated with any data in the transmitting WTRU’s buffers), the WTRU may use a CAPC associated with the peer WTRU’s BSR information rather than the WTRU’s own information

[0082] Although features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element can be used alone or in any combination with the other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer- readable storage media. Examples of computer-readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, 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

CLAIMS What is Claimed:

1 . A method for a wireless transmit and receive unit (WTRU), the method comprising: establishing a unicast link with a receive (RX) WTRU and selecting at least one licensed carrier and at least one unlicensed carrier for sidelink (SL) multicarrier communication with the RX WTRU; counting hybrid automatic repeat request (HARQ) discontinuous transmissions (DTXs) on each licensed and unlicensed carrier used for sidelink (SL) data transmissions; receiving a message on a licensed carrier from the RX WTRU indicating information of the at least one unlicensed carrier; modifying or resetting counted HARQ DTXs on the at least one unlicensed carrier based on the received message; and on a condition that a number of consecutive HARQ DTXs on any carrier reaches a threshold, reporting the respective carrier to a network as having SL radio link failure (RLF)

2. The method of claim 1, wherein the message comprises a medium access control (MAC) control element (CE).

3. The method of claims 1 or 2, wherein modifying the counted HARQ DTXs on the at least one unlicensed carrier comprises subtracting a value indicated by the information from a current count of consecutive HARQ DTXs for the at least one unlicensed carrier.

4. The method of any of claims 1 to 3, wherein the information comprises an indication of any one or more of RX WTRU buffer status, listen-before-talk (LBT) information of the at least one unlicensed carrier, or channel occupancy time (COT) information of the at least one unlicensed carrier

5. The method of any of claims 1 to 4, wherein the information comprises an indication to enable, disable, suspend or resume HARQ DTX counting for detecting SL RLF of the at least one unlicensed carrier

6. The method of claim 4, further comprising: scheduling transmission on the at least one unlicensed carrier, based on the indication.

7. A wireless transmit and receive unit (WTRU) comprising: a transceiver and a processor in communication with the transceiver, the transceiver and processor configured to: establish a unicast link with a receive (RX) WTRU and select at least one licensed carrier and at least one unlicensed carrier for sidelink (SL) multicarrier communication with the RX WTRU; count hybrid automatic repeat request (HARQ) discontinuous transmissions (DTXs) on each licensed and unlicensed carriers used for sidelink (SL) data transmissions; receive a message on a licensed carrier from the RX WTRU indicating information of the at least one unlicensed carrier; modify or reset counted HARQ DTXs on the at least one unlicensed carrier based on the received message; and on a condition that a number of consecutive HARQ DTXs on any carrier reaches a threshold, report the respective carrier to a network as having SL radio link failure (RLF)

8. The WTRU of claim 7, wherein the message comprises a medium access control (MAC) control element (CE).

9. The WTRU of claims 7 or 8, wherein modifying the counted HARQ DTXs on the at least one unlicensed carrier comprises subtracting a value indicated by the information from a current count of consecutive HARQ DTXs for the at least one unlicensed carrier.

10. The WTRU of any of claims 7 to 9, wherein the information comprises an indication of any one or more of RX WTRU buffer status, listen-before-talk (LBT) information of the at least one unlicensed carrier, or channel occupancy time (COT) information of the at least one unlicensed carrier

11. The WTRU of any of claims 7 to 10, wherein the information comprises an indication to enable, disable, suspend or resume HARQ DTX counting for detecting SL RLF of the at least one unlicensed carrier.

12. The WTRU of any of claims 7 to 11 , wherein the transceiver and processor are further configured to: schedule transmission on the at least one unlicensed carrier, based on the indication.

13. A method for a receive (RX) wireless transmit receive unit (WTRU), the method comprising: communicating, via a unicast link with a transmit (TX) WTRU, and receiving a configuration of at least one licensed carrier and at least one unlicensed carrier for sidelink (SL) multicarrier communication with the TX WTRU; sending, to the TX WTRU via a licensed carrier, an indication of the at least one unlicensed carrier, the indication including information relating to scheduling transmissions on the at least one unlicensed carrier and information associated with hybrid automatic repeat request (HARQ) feedback on the at least one unlicensed carrier used for sidelink (SL) data transmissions by the TX WTRU; and receiving, from the TX WTRU, at least one of scheduling information of data transmission on the at least one unlicensed carrier or a configuration update to remove the at least one unlicensed carrier from use.

14. The method of claim 13, wherein the information relating to scheduling transmissions comprises an indication of any one or more of RX WTRU buffer status, listen-before-talk (LBT) information of the at least one unlicensed carrier, or channel occupancy time (COT) information of the at least one unlicensed carrier.

15. The method of claim 13 or 14, wherein the information associated with HARQ DTXs on the at least one unlicensed carrier comprises a value to adjust a current count of consecutive HARQ DTXs for the at least one unlicensed carrier.

16. The method of any of claims 13 to 15, wherein the information associated with HARQ feedback on the at least one unlicensed carrier comprises an indication to enable, disable, suspend or resume HARQ DTX counting for detecting SL RLF of the at least one unlicensed carrier.

17. A receive (RX) wireless transmit and receive unit (WTRU) comprising: a transceiver and a processor in communication with the transceiver, the transceiver and processor configured to: communicate, via a unicast link with a transmit (TX) WTRU, and receive a configuration of at least one licensed carrier and at least one unlicensed carrier for sidelink (SL) multicarrier communication with the TX WTRU; send, to the TX WTRU via a licensed carrier, an indication of the at least one unlicensed carrier, the indication including information relating to scheduling transmissions on the at least one unlicensed carrier and information associated with hybrid automatic repeat request (HARQ) feedback on the at least one unlicensed carrier used for sidelink (SL) data transmissions by the TX WTRU; and receive, from the TX WTRU, at least one of scheduling information of data transmission on the at least one unlicensed carrier or a configuration update to remove the at least one unlicensed carrier from use.

18. The RX WTRU of claim 17, wherein the information relating to scheduling transmissions comprises an indication of any one or more of RX WTRU buffer status, listen-before-talk (LBT) information of the at least one unlicensed carrier, or channel occupancy time (COT) information of the at least one unlicensed carrier

19. The RX WTRU of claim 17 or 18, wherein the information associated with HARQ feedback on the at least one unlicensed carrier comprises a value to adjust a current count of consecutive HARQ DTXs for the at least one unlicensed carrier.

20. The RX WTRU of any of claims 17 to 19, wherein the information associated with HARQ feedback on the at least one unlicensed carrier comprises an indication to enable, disable, suspend or resume HARQ DTX counting for detecting SL RLF of the at least one unlicensed carrier.