Methods, architectures, apparatuses, and systems relating to hybrid automatic repeat request (HARQ) operations for sidelink communications in unlicensed spectrum

Abstract

Provided are procedures, methods, architectures, apparatuses, systems, devices, and computer program products relating to hybrid automatic repeat request (HARQ) operations for sidelink communications in unlicensed spectrum. There is a method among the methods that may include performing a channel access procedure for a physical sidelink feedback channel (PSFCH) transmission at one or more of one or more transmission occasions that may occur within a HARQ delay boundary.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of (i) U.S. Provisional Patent Application No. 63 / 335,134 filed on April 26, 2022, (ii) U.S. Provisional Patent Application No. 63 / 395,620 filed on August 5, 2022, and (iii) U.S. Provisional Patent Application No. 63 / 421,632 filed on November 2, 2022, each of which is incorporated herein by reference. Background Art

[0003] The present application relates to wired and / or wireless communications, including, for example, methods, architectures, devices, and systems related to hybrid automatic repeat request (HARQ) operations for sidelink communications in unlicensed spectrum. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] A more detailed understanding can be obtained from the following detailed description, which is given by way of example in conjunction with its accompanying drawings. As with the detailed description, the figures in such drawings are examples. Therefore, the drawings and detailed description should not be considered limiting, and other equally effective examples are possible and expected. In addition, like reference numerals ("ref.") in the drawings indicate similar elements, and among them:

[0005] Figure 1A is a system diagram illustrating an example communication system;

[0006] Figure 1B is an example that can be Figure 1A A system diagram of an example wireless transmit / receive unit (WTRU) for use within the illustrated communication system;

[0007] Figure 1C is an example that can be Figure 1A a system diagram of an example radio access network (RAN) and an example core network (CN) used within the illustrated communication system;

[0008] Figure 1D is an example that can be Figure 1A A system diagram of another example RAN and another example CN used within the illustrated communication system;

[0009] Figure 2 An example physical sidelink feedback channel (PSFCH) slot format and PSFCH transmission opportunity configuration are illustrated;

[0010] Figure 3An example of a PSFCH transmission and an associated physical sidelink shared channel (PSSCH) transmission and / or a physical sidelink control channel (PSCCH) transmission ("PSSCH / PSCCH transmission") performed during the same channel occupancy time (COT) is illustrated;

[0011] Figure 4 A to Figure 4 B illustrates an example of an initial transmission and a blind retransmission and an associated PSFCH transmission during one or more COTs;

[0012] Figure 5 A to Figure 5 B illustrates an example of initial transmission and blind retransmission performed during COT, as well as associated PSFCH transmission and associated hybrid automatic repeat request (HARQ) state transmission;

[0013] Figure 6 A to Figure 6 B illustrates an example of initial transmission, blind retransmission and PSSCH / PSCCH transmission and associated PSFCH transmission during one or more COTs;

[0014] Figure 7 An example of PSFCH transmission in COT based on transmitting WTRU polling is illustrated;

[0015] Figure 8 An example of PSFCH transmission in a shared COT is illustrated;

[0016] Fig. 9 An example of HARQ feedback in COT initiated for PSFCH transmission is illustrated;

[0017] Fig.10 is a flow chart illustrating an example process for performing an initial transmission and a second transmission and an associated PSFCH transmission during one or more COTs;

[0018] Fig.11 is a flow chart illustrating an example process for performing non-continuous initial transmission and HARQ retransmission within a single COT; and

[0019] Fig.12 is a flow chart illustrating an example process for non-continuous initial transmission and HARQ retransmission within two or more COTs. DETAILED DESCRIPTION

[0020] In the following specific embodiments, many specific details are set forth to provide a thorough understanding of the embodiments and / or examples disclosed herein. However, it should be understood that such embodiments and examples can be practiced without some or all of the specific details set forth herein. In other cases, well-known methods, procedures, components and circuits are not described in detail to avoid blurring the following description. In addition, the embodiments and examples not specifically described herein can be practiced in place of the embodiments and other examples explicitly, implicitly and / or inherently described, disclosed or otherwise provided (collectively referred to as "provided") herein, or practiced in combination with these embodiments and examples. Although various embodiments are described and / or claimed herein, wherein devices, systems, equipment, etc. and / or any of their elements perform operations, processes, algorithms, functions, etc. and / or any part thereof, it should be understood that any embodiments described herein and / or protected by the claims assume that any device, system, equipment, etc. and / or any of its elements are configured to perform any operations, processes, algorithms, functions, etc. and / or any part thereof.

[0021] Example Communication System

[0022] The methods, devices, and systems provided herein are well suited for communications involving both wired and wireless networks. Wired networks are well known. Figures 1A to 1D An overview of various types of wireless devices and infrastructure is provided, wherein various elements of the network may utilize, perform, be arranged according to, and / or be adapted and / or configured for the methods, apparatus, and systems provided herein.

[0023] Figure 1A 1 is a diagram of an example communication system 100 in which one or more disclosed embodiments may be implemented. The example communication system 100 is provided for illustrative purposes only and does not limit the disclosed embodiments. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, broadcast, etc. to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content through sharing of system resources (including wireless bandwidth). For example, the communication system 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 (ZT) unique word (UW) discrete Fourier transform (DFT) spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, filter bank multi-carrier (FBMC), etc.

[0024] like Figure 1A As shown, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, a radio access network (RAN) 104 / 113, a core network (CN) 106 / 115, a public switched telephone network (PSTN) 108, the Internet 110 and other networks 112, but it should be understood 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” and / or “STA”) may be configured to send and / or receive wireless signals and may include (or be) a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a subscription-based unit, a pager, a cellular phone, a personal digital assistant (PDA), a smart phone, a laptop, a netbook, a personal computer, a wireless sensor, a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), a consumer electronic device, a device operating on a commercial and / or industrial wireless network, etc. Any of the WTRUs 102a, 102b, 102c, and 102d may be interchangeably referred to as a WTRU.

[0025] The communication 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, for example, facilitate access to one or more communication networks (such as the CN 106 / 115, the Internet 110, and / or the network 112). By way of example, the base stations 114a, 114b may be any of a base transceiver station (BTS), a Node B (NB), an evolved Node B (eNB), a Home Node B (HNB), a Home evolved Node B (HeNB), a gNode B (gNB), a NR Node B (NR NB), a site controller, an access point (AP), a wireless router, and the like. Although the base stations 114a, 114b are each depicted as a single element, it should be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and / or network elements.

[0026] The base station 114a may be part of the RAN 104 / 113, 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), a relay node, etc. The base station 114a and / or the base station 114b may be configured to send and / or receive wireless signals on one or more carrier frequencies, which may be referred to as cells (not shown). These frequencies may be in a licensed spectrum, an unlicensed spectrum, or a combination of licensed and unlicensed spectrums. A cell may provide coverage of wireless services to a specific geographic area, which may be relatively fixed or may change over time. The cell may be further divided into cell sectors. For example, a cell associated with the base station 114a may be divided into three sectors. Therefore, 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 or any sector of the cell. For example, beamforming may be used to send and / or receive signals in a desired spatial direction.

[0027] 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).

[0028] More specifically, as noted above, the communication 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, etc. For example, the base station 114a in the RAN 104 / 113 and the WTRUs 102a, 102b, 102c may implement a radio technology such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA), which may use Wideband CDMA (WCDMA) to establish the air interface 115 / 116 / 117. WCDMA may include communication 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 (HSUPA).

[0029] 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) that may establish the air interface 116 using Long Term Evolution (LTE) and / or Advanced LTE (LTE-A) and / or Advanced LTE Pro (LTE-A Pro).

[0030] In other embodiments, the base station 114a and the WTRUs 102a, 102b, 102c may implement radio technologies such as 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), GSM Enhanced Data Rates for Evolution (EDGE), GSM EDGE (GERAN), etc.

[0031] 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 New Radio (NR).

[0032] 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 together implement LTE radio access and NR radio access, for example 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 transmitted to / from multiple types of base stations (e.g., eNBs and gNBs).

[0033] 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 (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), GSM Enhanced Data Rates for Evolution (EDGE), GSM EDGE (GERAN), etc.

[0034] Figure 1AThe base station 114b in 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 local area, such as a business location, a home, a vehicle, a campus, an industrial facility, an air corridor (e.g., for use by drones), a road, 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 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 one embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.) to establish any of a microcell, a picocell, or a femtocell. As Figure 1A As shown, base station 114b may have a direct connection to Internet 110. Therefore, base station 114b may not need to access Internet 110 via CN 106 / 115.

[0035] The RAN 104 / 113 may be in communication with the CN 106 / 115, 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 different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calls, Internet connectivity, video distribution, etc., and / or perform advanced security functions, such as user authentication. Although not described in detail in the text and video above, the CN 106 / 115 may be 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 different quality of service (QoS) requirements, such as different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, mobility requirements, etc. The CN 106 / 115 may provide call control, billing services, mobile location-based services, prepaid calls, Internet connectivity, video distribution, etc., and / or perform advanced security functions, such as user authentication. Figure 1A Although not shown in the figure, it will be appreciated that the RAN 104 / 113 and / or the CN 106 / 115 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 / 113 or a different RAT. For example, in addition to being connected to the RAN 104 / 113, which may utilize NR radio technology, the CN 106 / 115 may also be in communication with another RAN (not shown) that employs any of GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or Wi-Fi radio technologies.

[0036] The CN 106 / 115 may also act 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 that provides 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 the Internet Protocol (IP) in the TCP / IP Internet protocol suite. The networks 112 may include wired 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, which may employ the same RAT as the RAN 104 / 114 or a different RAT.

[0037] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communication 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 via different wireless links). Figure 1A The illustrated WTRU 102c 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.

[0038] Figure 1B 1 is a system diagram of an example WTRU 102. The example WTRU 102 is provided for illustration purposes only and is not intended to limit the disclosed embodiments. Figure 1B As shown, 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 other peripherals 138. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0039] 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 associated with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), a state machine, etc. The processor 118 may perform signal decoding, 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 Figure 1B The processor 118 and the transceiver 120 are depicted as separate components, but it is understood that the processor 118 and the transceiver 120 may be integrated together, such as in an electronic package or chip.

[0040] The send / receive element 122 may be configured to send a signal to a base station (e.g., base station 114a) or receive a signal from the base station via an air interface 116. For example, in one embodiment, the send / receive element 122 may be an antenna configured to send and / or receive an RF signal. In one embodiment, the send / receive element 122 may be a transmitter / detector configured to send and / or receive, for example, IR, UV or visible light signals. In one embodiment, the send / receive element 122 may be configured to send and receive both RF signals and optical signals. It should be understood that the send / receive element 122 may be configured to send and / or receive any combination of wireless signals.

[0041] Furthermore, although the transmit / receive element 122 Figure 1B Although depicted as a single element in the figure, the WTRU 102 may include any number of transmit / receive elements 122. For example, 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.

[0042] The transceiver 120 may be configured to modulate signals to be transmitted by the transmit / receive element 122 and to demodulate signals received by the transmit / receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. For example, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0043] The processor 118 of the WTRU 102 may be coupled to and may receive user input 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 a non-removable memory 130 and / or a removable memory 132. The non-removable memory 130 may include a random access memory (RAM), a 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 a memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0044] The processor 118 may receive power from the power source 134, and may be configured to distribute and / or control power to 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, etc.

[0045] 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 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 received from two or more nearby base stations. It will be appreciated that the WTRU 102 may acquire location information by any suitable location-determination method while remaining consistent with an embodiment.

[0046] The processor 118 may also be coupled to other peripherals 138, which may include one or more software modules / units and / or hardware modules / units 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 (e.g., for photos or videos), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands-free headset, module, a frequency modulation (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, etc. Peripheral device 138 may include one or more sensors, which may be one or more of the following: 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, and / or a humidity sensor.

[0047] The WTRU 102 may include a full-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) and downlink (e.g., for reception)) may be concurrent and / or simultaneous. The full-duplex radio may include an interference management unit for reducing and / or substantially eliminating self-interference via hardware (e.g., choke) or via signal processing performed by a processor (e.g., a separate processor (not shown) or via the processor 118). In one embodiment, the WTRU 102 may include a half-duplex radio for which transmission and reception of some or all signals (e.g., associated with specific subframes for UL (e.g., for transmission) or downlink (e.g., for reception)) may be concurrent and / or simultaneous.

[0048] Figure 1C 1 is a system diagram of the RAN 104 and the CN 106 according to another embodiment. As noted above, the RAN 104 may employ E-UTRA radio technology to communicate with the WTRUs 102a, 102b, and 102c over the air interface 116. The RAN 104 may also be in communication with the CN 106.

[0049] The RAN 104 may include evolved Node-Bs 160a, 160b, 160c, though it will be appreciated that the RAN 104 may include any number of evolved Node-Bs while remaining consistent with an embodiment. The evolved Node-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 evolved Node-Bs 160a, 160b, 160c may implement MIMO technology. Thus, the evolved Node-B 160a, for example, may use multiple antennas to transmit wireless signals to, and receive wireless signals from, the WTRU 102a.

[0050] Each of the evolved Node Bs 160a, 160b, and 160c may be associated with a particular cell (not shown) and may be configured to manage radio resource management decisions, handover decisions, user scheduling in uplink (UL) and / or downlink (DL), etc. Figure 1C As shown, the eNode-Bs 160a, 160b, 160c may communicate with each other via an X2 interface.

[0051] Figure 1C The illustrated core network 106 may include a mobility management gateway (MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN) gateway 166. While each of the foregoing elements is depicted as being part of the CN 106, it should be understood that any of these elements may be owned and / or operated by an entity other than a CN operator.

[0052] The MME 162 may be connected to each of the evolved Node-Bs 160a, 160b, and 160c 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, etc. The MME 162 may also provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM or WCDMA.

[0053] The SGW 164 may be connected to each of the evolved Node-Bs 160a, 160b, 160c in the RAN 104 via an S1 interface. The SGW 164 may generally route and forward user data packets to / from the WTRUs 102a, 102b, 102c. The SGW 164 may also perform other functions, such as anchoring the user plane during inter-evolved Node-B handovers, triggering paging and / or mobile termination when DL data is available for the WTRUs 102a, 102b, 102c, managing and storing the context of the WTRUs 102a, 102b, 102c, and the like.

[0054] The SGW 164 may also be connected to a PDN Gateway 166, which may provide the WTRUs 102a, 102b, and 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.

[0055] 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 acts 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 or wireless networks owned and / or operated by other service providers.

[0056] Although the WTRU Figures 1A to 1D Although described as a wireless terminal, it is contemplated that in certain representative embodiments such a terminal may (eg, temporarily or permanently) employ a wired communications interface with a communications network.

[0057] In a representative embodiment, the other network 112 may be a WLAN.

[0058] The WLAN in the infrastructure basic service set mode may have an access point (AP) for the basic service set and one or more stations (STA) 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 entering and / or leaving the basic service set. Traffic originating from outside the basic service set and directed to the STA may be reached by the AP and may be delivered to the STA. Traffic originating from the STA and directed to a destination outside the basic service set may be sent to the AP to be delivered to the corresponding destination. Traffic between STAs within the basic service set may be sent by the AP, for example, where the source STA may send traffic to the AP, and the AP may deliver traffic to the destination STA. Traffic between STAs within the basic service set may be considered and / or referred to as point-to-point traffic. Direct link establishment (DLS) may be used to transmit point-to-point traffic between the source STA and the destination STA (e.g., directly between them). In certain representative embodiments, DLS may use 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using independent basic service set mode may not have an AP, and STAs (eg, all STAs) within or using an independent basic service set may communicate directly with each other. The independent basic service set communication mode may sometimes be referred to herein as an "ad hoc" communication mode.

[0059] When using the 802.11ac infrastructure operation mode or a similar operation mode, the AP may send beacons 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 width dynamically set via signaling. The primary channel may be an operating channel for a basic service set and may be used by a STA to establish a connection with the AP. In certain representative embodiments, carrier sense multiple access / collision avoidance (CSMA / CA) may be implemented, for example, in an 802.11 system. For CSMA / CA, a STA (e.g., each STA) (including an AP) may sense the primary channel. In the case where the primary channel is sensed / detected and / or determined to be busy by a specific STA, the specific STA may back off. One STA (e.g., only one station) may transmit at any given time in a given basic service set.

[0060] High throughput (HT) STAs may communicate using a 40 MHz wide channel, for example, via a combination of a primary 20 MHz channel and adjacent or non-adjacent 20 MHz channels to form a 40 MHz wide channel.

[0061] Very high throughput (VHT) STA can support 20MHz, 40MHz, 80MHz and / or 160MHz wide channels. 40MHz channels and / or 80MHz channels can be formed by combining continuous 20MHz channels. 160MHz channels can be formed by combining 8 continuous 20MHz channels, or by combining two non-continuous 80MHz channels (this can be called 80+80 configuration). For 80+80 configuration, after channel coding, the data can pass through a segment parser that can divide the data into two streams. Each stream can be processed by inverse fast Fourier transform (IFFT) and time domain processing separately. These streams can be mapped to two 80MHz channels, and data can be sent by the transmitting STA. At the receiver of the receiving STA, the above-mentioned operation for the 80+80 configuration can be reversed, and the combined data can be sent to the medium access control (MAC).

[0062] 802.11af and 802.11ah support operating modes below 1GHz. Channel operating bandwidths and carriers are reduced in 802.11af and 802.11ah relative to those used in 802.11n and 802.11ac. 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the TV White Space (TVWS) spectrum, and 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using non-TVWS spectrum. According to a representative embodiment, 802.11ah may support meter type control / machine type communication (MTC), such as MTC devices in macro coverage areas. MTC devices may have certain capabilities, such as limited capabilities, including support for (e.g., only support for) certain bandwidths and / or limited bandwidths. MTC devices may include batteries with battery life above a threshold (e.g., to maintain very long battery life).

[0063] WLAN systems that can support multiple channels and channel bandwidths (such as 802.11n, 802.11ac, 802.11af, and 802.11ah) include channels that can be designated as primary channels. The primary channel may have a bandwidth equal to the maximum common operating bandwidth supported by all STAs in the basic service set. The bandwidth of the primary channel may be set and / or limited by a STA (which supports the minimum bandwidth operating mode) from among all STAs operating in the basic service set. In the example of 802.11ah, for STAs (e.g., MTC-type devices) that support (e.g., only support) 1MHz mode, the primary channel may be 1MHz wide, even if the AP and other STAs in the basic service set support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes. Carrier sensing and / or network allocation vector (NAV) settings may depend on the state of the primary channel. If the primary channel is busy, for example, because a STA (supporting only 1MHz operating mode) is sending to the AP, the entire available frequency band may be considered busy even if most of the frequency bands remain idle and may be available.

[0064] In the United States, the available frequency band for 802.11ah is 902MHz to 928MHz. In South Korea, the available frequency band is 917.5MHz to 923.5MHz. In Japan, the available frequency band is 916.5MHz to 927.5MHz. The total bandwidth available for 802.11ah is 6MHz to 26MHz, depending on the country code.

[0065] Figure 1D1 is a system diagram illustrating the RAN 113 and the CN 115 in accordance with an embodiment. As noted above, the RAN 113 may employ NR radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 113 may also be in communication with the CN 115.

[0066] The RAN 113 may include gNBs 180a, 180b, 180c, though it will be appreciated that the RAN 113 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, the gNBs 180a, 180b may utilize beamforming to send signals to and / or receive signals from the gNBs 180a, 180b, 180c. Thus, the gNB 180a may, for example, use multiple antennas to send wireless signals to and / or receive wireless signals from the WTRU 102a. 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 gNB 180a and gNB 180b (and / or gNB 180c).

[0067] The WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using transmissions associated with parameter sets that may be scalable. For example, 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 transmit time intervals (TTIs) of varying or scalable lengths (e.g., containing different numbers of OFDM symbols and / or varying absolute time lengths over time).

[0068] 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 while not accessing other RANs (e.g., such as the eNodeBs 160a, 160b, 160c). In a standalone configuration, the WTRUs 102a, 102b, 102c may use one or more of the gNBs 180a, 180b, 180c as mobility anchors. In a standalone configuration, the WTRUs 102a, 102b, 102c may communicate with the gNBs 180a, 180b, 180c using signals in an unlicensed band. In a non-standalone configuration, the WTRUs 102a, 102b, 102c may communicate / connect with the gNBs 180a, 180b, 180c while also communicating / connecting with another RAN, such as the eNode-Bs 160a, 160b, 160c. For example, the WTRUs 102a, 102b, 102c may implement the DC principle to communicate with one or more gNBs 180a, 180b, 180c and one or more eNode-Bs 160a, 160b, 160c substantially simultaneously. In a non-standalone configuration, the eNode-Bs 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.

[0069] Each of the gNBs 180a, 180b, 180c may be associated with a specific cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in UL and / or DL, support of network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data towards a user plane function (UPF) 184a, 184b, routing of control plane information towards an access and mobility management function (AMF) 182a, 182b, etc. Figure 1D As shown, gNBs 180a, 180b, and 180c may communicate with each other via an Xn interface.

[0070] Figure 1DThe illustrated CN 115 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 at least one data network (DN) 185a, 185b. While each of the foregoing elements is depicted as part of the CN 115, it should be understood that any of these elements may be owned and / or operated by an entity other than the CN operator.

[0071] The AMF 182a, 182b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N2 interface and may act as a control node. For example, the AMF 182a, 182b may be responsible for authenticating users of the WTRU 102a, 102b, 102c, support of network slicing (e.g., handling of different protocol data unit (PDU) sessions with different requirements), selecting a specific SMF 183a, 183b, management of registration areas, termination of non-access stratum (NAS) signaling, mobility management, etc. The AMF 182a, 182b may use network slicing to customize CN support for the WTRU 102a, 102b, 102c, for example, based on the type of services used by the WTRU 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, and / or services for MTC access, etc. The AMF 162 may provide a control plane function for switching between the RAN 113 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.

[0072] The SMF 183a, 183b may be connected to the AMF 182a, 182b in the CN 115 via the N11 interface. The SMF 183a, 183b may also be connected to the UPF 184a, 184b in the CN 115 via the N4 interface. The SMF 183a, 183b may select and control the UPF 184a, 184b, and configure the traffic routing through the UPF 184a, 184b. The SMF 183a, 183b may perform other functions, such as managing and allocating UE IP addresses, managing PDU sessions, controlling policy implementation and QoS, providing downlink data notification, etc. The PDU session type may be IP-based, non-IP-based, Ethernet-based, etc.

[0073] The UPF 184a, 184b may be connected to one or more of the gNBs 180a, 180b, 180c in the RAN 113 via the N3 interface, which may provide the WTRUs 102a, 102b, 102c with access to packet-switched networks, such as the Internet 110, for example, 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 downlink packets, providing mobility anchoring, etc.

[0074] The CN 115 may facilitate communications with other networks. For example, the CN 115 may include or may communicate with an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between the CN 115 and the PSTN 108. In addition, the CN 115 may provide the WTRUs 102a, 102b, 102c with access to other networks 112, which may include other wired networks and / or wireless networks owned and / or operated by other service providers. In one embodiment, the WTRUs 102a, 102b, 102c may be connected to local data networks (DNs) 185a, 185b via the UPF 184a, 184b via an N3 interface to the UPF 184a, 184b and an N6 interface between the UPF 184a, 184b and the DN 185a, 185b.

[0075] Given that Figures 1A to 1D as well as Figures 1A to 1D Corresponding to the description of the present invention, one or more or all of the functions described herein with reference to any of the following may be performed by one or more simulation elements / devices (not shown): WTRU 102a-102d, base station 114a-114b, evolved Node B 160a-160c, MME 162, SGW 164, PGW 166, gNB 180a-180c, AMF 182a-182b, UPF 184a-184b, SMF 183a-183b, DN 185a-185b and / or any other element / device described herein. The simulation device may be one or more devices configured to mimic one or more or all of the functions described herein. For example, the simulation device may be used to test other devices and / or simulate network and / or WTRU functions.

[0076] The simulation device may be designed to implement one or more tests of other devices in a laboratory environment and / or in an operator network environment. For example, one or more simulation devices may perform one or more functions 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. One or more simulation devices may perform one or more functions or all functions while being temporarily implemented / deployed as part of a wired and / or wireless communication network. The simulation device may be directly coupled to another device for testing purposes and / or may use over-the-air wireless communications to perform testing.

[0077] One or more simulation devices can perform one or more (including all) functions without being implemented / deployed as part of a wired and / or wireless communication network. For example, the simulation device can be used in a test scenario in a test laboratory and / or a non-deployed (e.g., testing) wired and / or wireless communication network to implement testing of one or more components. One or more simulation devices can be test equipment. Direct RF coupling and / or wireless communication via RF circuits (e.g., which may include one or more antennas) can be used by the simulation device to send and / or receive data.

[0078] introduction

[0079] Sidelink operation in unlicensed spectrum

[0080] It was agreed in RAN#94 that the Sidelink Evolution work item for 3GPP Release 18 ("R18 SL Evolution WI") will include studies on sidelink operation supporting both Mode 1 and Mode 2 in unlicensed spectrum within Frequency Range 1 (FR1). The unlicensed sidelink bands are 5 GHz and 6 GHz, and Uu operations associated with Mode 1 are limited to licensed spectrum. The channel access design for the sidelink in unlicensed spectrum (SL U) will be based on regional regulatory requirements, with the existing channel access for NR in unlicensed spectrum (NR U) as a starting point.

[0081] The R16SL resource allocation mechanism specified for licensed spectrum may be reused. The scope of the R18 SL evolution work item may include determining, evaluating and / or specifying the required changes to the NR SL physical (PHY) channel structure and procedures to operate in unlicensed spectrum. Hybrid Automatic Repeat Request (HARQ) feedback support in NR V2X for unicast transmission and / or multicast transmission may be evaluated in the R18 SL evolution work item discussion.

[0082] NR U channel access

[0083] In NR U, the WTRU may access a channel for uplink transmission according to a Type 1 uplink channel access procedure or a Type 2 uplink channel access procedure. The Type 1 uplink channel access procedure and the Type 2 uplink channel access procedure are designed to comply with regulatory requirements related to, for example, sensing (e.g., listen-before-talk (LBT) sensing), maximum channel occupancy time (MCOT), occupied channel bandwidth (OCB), and power spectral density (PSD).

[0084] The Type 1 channel access procedure includes performing LBT sensing with random backoff and a variable extended clear channel assessment (CCA) period based on a contention window, the size of which is selected based on the channel access priority class (CAPC) configuration. The gNB or WTRU must perform the Type 1 channel access procedure to initiate COT. The Type 2 uplink channel access procedure can be one of the Type 2A uplink channel access procedure, the Type 2B uplink channel access procedure, and the Type 2C uplink channel access procedure. The Type 2A uplink channel access procedure and the Type 2B uplink channel access procedure are performed when the gaps in transmission ("transmission gaps") are 25 microseconds (μs) and 16μs, respectively. When the transmission gap is less than 16μs, the Type 2C uplink channel access procedure is applied with transmission immediately after the transmission gap without performing sensing.

[0085] For downlink transmissions, due to the uncertainty caused by LBT sensing, NR U adds COT structure indication, dynamic PDCCH monitoring, and flexible starting position for physical downlink shared channel (PDSCH) transmissions. For uplink control and data channel transmissions, in order to comply with OCB requirements, new block-interleaved based transmissions are used for PUCCH and PUSCH transmissions, and PUSCH transmissions have flexible starting positions. NR U SRS transmissions are also enhanced with additional flexibility in configuration and triggering. In addition, NR U supports frame structures with multiple downlink to uplink (DL to UL) switching points and uplink to downlink (UL to DL) switching points within the shared COT.

[0086] NR U supports additional HARQ transmission opportunities and immediate HARQ transmission for corresponding data in the same shared COT and subsequent COTs to ensure channel access for HARQ transmission.

[0087] In R17V2X, a set of frequency and code resources (e.g., physical resource blocks (PRBs) and sequence resources) are pre-configured in a resource pool dedicated to physical sidelink feedback channel (PSFCH) transmissions that carry sidelink HARQ feedback. A one-to-one association between a PSFCH transmission and an associated physical sidelink shared channel (PSSCH) transmission and / or physical sidelink control channel transmission ("PSSCH / PSCCH transmission") is implicitly indicated in the resources used for PSFCH transmission because it is determined based on the resource allocation information for PSSCH / PSSCH transmission. Such implicit association relies on a deterministic time-frequency relationship between the PSSCH / PSCCH transmission and the corresponding PSFCH transmission, and will not work in unlicensed spectrum because, due to LBT uncertainty, the PSFCH transmission may be sent in different COTs after random time periods. Therefore, a new mechanism for channel access for PSFCH transmission and related association with the corresponding PSSCH / PSCCH transmission is needed.

[0088] The continuity of transmissions within the COT is important because, in a shared spectrum, a device is not allowed to transmit after a gap in transmissions of a certain duration (e.g., a transmission gap of a given duration) and another channel access procedure must be performed to (re)acquire a channel for transmission. In NR U, the gNB schedules all transmissions within the COT shared by the gNB and one or more WTRUs. Coordination by a centralized node ensures the continuity of transmissions within the COT. In sidelink operation of Mode 2 in unlicensed spectrum ("Mode 2 SLU"), coordination of transmissions of different WTRUs within a COT (and / or in different COTs) is not or may not be performed by a centralized node. It is important in Mode 2 SLU that coordination of transmissions of different WTRUs achieve seamless connectivity so as to avoid transmission gaps within the COT (e.g., unintentional transmission gaps), for example, when the COT is shared between PSSCH / PSCCH and PSFCH transmissions of different WTRUs, where one or more transmit / receive (Tx / Rx) switching points of one or more of the WTRUs may occur within the COT.

[0089] Overview

[0090] Disclosed herein are methods, apparatus, systems, etc., relating to and / or for performing HARQ operations for sidelink communications, such as in unlicensed spectrum. Such methods, apparatus, systems, etc., for example, may address the involvement of apparatus and systems (methods and techniques configured therein, implemented therein, and / or performed thereby) for performing initial transmissions and subsequent transmissions (e.g., blind retransmissions) and associated PSFCH transmissions during one or more COTs.

[0091] For simplicity of explanation, the following disclosure is partially made from the perspective of a WTRU. A person of ordinary skill in the art will recognize that much of such disclosure may be equally applicable to network elements (e.g., base stations or other RAN elements), other network elements, and / or network functions, and therefore, such modifications and variations are intended to fall within the scope of the present disclosure and the appended claims.

[0092] In various embodiments, the first method may include any of the following:

[0093] During a first COT established for device-to-device communication, receiving an initial transmission of first control information and a transport block, the initial transmission being followed by a second transmission of second control information and the same transport block, wherein (i) at least the first control information may indicate a first transmission opportunity within the first COT, and (ii) at least the second control information may indicate a latency boundary for reporting HARQ feedback for the transport block; determining first HARQ feedback for the transport block, wherein the first HARQ feedback may be and / or may include a non-acknowledgement; performing a first channel access procedure during the first COT; sending a third transmission indicating the first HARQ feedback during the first transmission opportunity; determining a second HARQ feedback for the transport block; determining a second transmission opportunity that meets the latency boundary from one or more transmission opportunities; performing a second channel access procedure for device-to-device communication at the second transmission opportunity and establishing a second channel occupancy time; and sending a fourth transmission indicating the second HARQ feedback at the second transmission opportunity.

[0094] In various embodiments, any one of the initial transmission and the second transmission is a PSCCH transmission, a PSSCH transmission, or a combination of a PSCCH transmission and a PSSCH transmission. In various embodiments, the first control information may be and / or may include an SCI, and wherein the first transmission opportunity may be a transmission opportunity for a PSFCH transmission. In various embodiments, the transmission opportunity may be a time slot.

[0095] In various implementations, the second transmission opportunity may be based on PSSCH to PSFCH association between different COTs.

[0096] In various embodiments, the first method may include determining one or more resources for the fourth transmission according to a frequency allocation based on any one of a transmission opportunity index, a source identifier, a destination identifier, and a channel occupancy time index. In various embodiments, the frequency allocation may be and / or may include any one of an RB, an RB interlace, a subchannel, a CS, and a CS index.

[0097] In various embodiments, determining a first HARQ feedback for the transport block may include determining the first HARQ feedback for the transport block for the initial transmission. In various embodiments, determining a second HARQ feedback for the transport block may include determining the second HARQ feedback for the transport block jointly for the initial transmission and the second transmission.

[0098] In various embodiments, the transmission opportunities are configured (eg, to the WTRU or based on a pool).

[0099] In various embodiments, the second channel occupancy time may be initiated by the WTRU or another WTRU.In various embodiments, the WTRU may be a first WTRU, the first COT may be initiated by a second WTRU, and receiving the initial transmission and the second transmission may include receiving the initial transmission and the second transmission from the second WTRU.

[0100] In various embodiments, the second transmission may occur after the third control information and at least one fifth transmission of the same transmission block. In various embodiments, the third control information may indicate, may be and / or may include any one of the first transmission opportunity and the delay boundary.

[0101] In various implementations, determining the second HARQ feedback for the transport block may include determining the second HARQ feedback for the transport block jointly for the initial transmission, the at least one fifth transmission, and the second transmission.

[0102] In various embodiments, the first channel access procedure may be a type 1 channel access procedure. In various embodiments, the second channel access procedure may be a type 2 channel access procedure.

[0103] In various implementations, the first method may be implemented in a WTRU.

[0104] In various embodiments, the second method may include any of the following: performing a first transmission of first information during the COT; performing one or more blind retransmissions of the first information during the COT after the first transmission; and receiving a second transmission during the COT after the one or more blind transmissions. In various embodiments, the second transmission may be and / or may include second information indicating HARQ state information for the first information.

[0105] In various embodiments, the second information indicating the HARQ status information for the first information may indicate, may be and / or may include third information, wherein the third information indicates that the HARQ status information may be based on the decoding results of one or more of the first transmission and the one or more blind retransmissions.

[0106] In various embodiments, the second information may indicate, may be and / or may include fourth information, which indicates that the HARQ state information may be based on the decoding result of any one of the following: (i) one or some blind retransmissions in the first transmission and the blind retransmission, (ii) some blind retransmissions in the blind retransmission, (iii) all blind retransmissions in the first transmission and the blind retransmission, and (iv) all blind retransmissions in the blind retransmission.

[0107] In various embodiments, the HARQ state information may indicate an acknowledgement (eg, a HARQ acknowledgement). Alternatively, in various embodiments, the HARQ state information may indicate a non-acknowledgement (eg, a HARQ non-acknowledgement).

[0108] In various embodiments, the second transmission may be and / or may include a MAC control element (MAC CE). In various embodiments, the MAC CE may indicate and / or may include the second information.

[0109] In various embodiments, the second method may include performing HARQ retransmissions during the COT and after the second transmission.

[0110] In various embodiments, the COT may be a first COT, the HARQ state information is first HARQ state information, and the method may include receiving a third transmission during a second COT after the first COT. In various embodiments, the third transmission may be and / or may include fifth information indicating second HARQ state information for the first information.

[0111] In various embodiments, the second method may include performing HARQ retransmissions during the second COT.

[0112] In various embodiments, the HARQ retransmission may be a first HARQ retransmission, and the second method may include performing a second HARQ retransmission during the second COT.

[0113] In various embodiments, the second method may include performing a third HARQ retransmission during a third COT.

[0114] In various embodiments, the HARQ retransmission may be a first HARQ retransmission, and the second method may include performing the HARQ retransmission during a third COT.

[0115] In various embodiments, the HARQ retransmission may be a first HARQ retransmission, and the second method may include performing a second HARQ retransmission during a third COT.

[0116] In various embodiments, the third COT may occur after the first COT. In various embodiments, the third COT may occur before the second COT.

[0117] In various embodiments, the second HARQ state information may indicate, may be and / or may include an acknowledgement (e.g., a HARQ acknowledgement). In various embodiments, the second HARQ state information may indicate, may be and / or may include a non-acknowledgement (e.g., a HARQ non-acknowledgement).

[0118] In various embodiments, the fifth information may indicate, may be and / or may include second information, wherein the second information indicates that the second HARQ information may be based on a decoding result of one or more of the first transmission and the blind retransmission.

[0119] In various embodiments, the fifth information may indicate, may be and / or may include seventh information, which indicates that the second HARQ state information may be based on the decoding result of any one of the following: (i) one or some blind retransmissions in the first transmission and the blind retransmission, (ii) some blind retransmissions in the blind retransmission, (iii) all blind retransmissions in the first transmission and the blind retransmission, and (iv) all blind retransmissions in the blind retransmission.

[0120] In various embodiments, the MAC CE may be a first MAC CE, and / or the third transmission may be and / or may include a second MAC CE, and the second MAC CE may indicate and / or include the fifth information.

[0121] In various embodiments, the first transmission may be and / or may include any of an initial transmission and a HARQ retransmission. In various embodiments, the initial transmission may be and / or may include a PSFCH transmission.

[0122] In various embodiments, this second method may be implemented in a WTRU.

[0123] In various embodiments, the third method may include any of the following: receiving a first transmission of first information performed during the COT; and performing a second transmission during the COT after one or more third transmissions performed after the first transmission. In various embodiments, the third transmission may be and / or may include one or more blind retransmissions of the first information, and the second transmission may be and / or may include second information indicating HARQ state information for the first information. In various embodiments, the third method may include receiving one or more of the blind retransmissions.

[0124] In various embodiments, the second information may indicate, may be and / or may include third information, wherein the third information indicates that the HARQ state information is based on a decoding result of one or more of: the first transmission and one or more blind retransmissions in the blind retransmission.

[0125] In various embodiments, the second information may indicate, may be and / or may include fourth information, which indicates that the HARQ state information may be based on the decoding result of any one of the following: (i) one or some blind retransmissions in the first transmission and the blind retransmission, (ii) some blind retransmissions in the blind retransmission, (iii) all blind retransmissions in the first transmission and the blind retransmission, and (iv) all blind retransmissions in the blind retransmission.

[0126] In various embodiments, the HARQ state information may indicate, may be and / or may include an acknowledgement (e.g., a HARQ acknowledgement). Alternatively, in various embodiments, the HARQ state information may indicate, may be and / or may include a non-acknowledgement (e.g., a HARQ non-acknowledgement).

[0127] In various implementations, the second transmission may be and / or may include a MAC CE, and the MAC CE may indicate and / or may include the second information.

[0128] In various embodiments, the third method may include determining the HARQ state information (not shown).

[0129] In various embodiments, the third method may include receiving a HARQ retransmission (not shown) during the COT and after the second transmission.

[0130] In various embodiments, the COT may be a first COT, the HARQ state information may be and / or may include first HARQ state information, and the third method may include performing a fourth transmission during a second COT after the first COT. In various embodiments, the fourth transmission may be and / or may include fifth information indicating second HARQ state information for the first information.

[0131] In various embodiments, the HARQ retransmission may be a first HARQ retransmission, and the third method may include receiving a second HARQ retransmission during the second COT. In various embodiments, the third method may include receiving a HARQ retransmission during the second COT.

[0132] In various embodiments, the third method may include receiving a third HARQ retransmission during a third COT.

[0133] In various embodiments, the HARQ retransmission may be a first HARQ retransmission, and the third method may include receiving a second HARQ retransmission during a third COT. In various embodiments, the HARQ retransmission may be a first HARQ retransmission, and the third method may include receiving a second HARQ retransmission during a third COT. In various embodiments, the third COT occurs after the first COT. In various embodiments, the third COT occurs before the second COT.

[0134] In various implementations, the HARQ state information may indicate an acknowledgement (eg, a HARQ acknowledgement). In various implementations, the second HARQ state information may indicate a non-acknowledgement (eg, a HARQ non-acknowledgement).

[0135] In various embodiments, the fifth information may indicate, may be and / or may include sixth information, which indicates that the second HARQ state information may be based on a decoding result of one or more of the first transmission and the blind retransmission.

[0136] In various embodiments, the fifth information may indicate, may be and / or may include third information, wherein the third information indicates that the second HARQ state information may be based on a decoding result of any one of: (i) one or some blind retransmissions in the first transmission and the blind retransmission, (ii) some blind retransmissions in the blind retransmission, (iii) all blind retransmissions in the first transmission and the blind retransmission, and (iv) all blind retransmissions in the blind retransmission.

[0137] In various implementations, the MAC CE may be a first MAC CE, the fourth transmission may be a second MAC CE, and / or the second MAC CE may include the fifth information.

[0138] In various embodiments, the third method may include determining the second HARQ state information. In various embodiments, the first transmission may be and / or include any one of an initial transmission and a HARQ retransmission. In various embodiments, the initial transmission may be and / or include a PSFCH transmission.

[0139] In various embodiments, the third method may be implemented in a WTRU.

[0140] In various embodiments, the fourth method may include any of the following: performing channel access for a first transmission at one or more transmission opportunities of one or more transmission opportunities occurring within a HARQ delay boundary. In various embodiments, the first transmission may be and / or may include first information indicating HARQ state information associated with a second transmission performed during the COT.

[0141] In various embodiments, the fourth method may be implemented in a WTRU.

[0142] In various implementations, the fifth method may include performing channel access for PSFCH transmission at one or more of the one or more transmission opportunities that occur within a HARQ delay boundary.

[0143] In various embodiments, the fifth method may be implemented in a WTRU.

[0144] In various implementations, the sixth method may include any of: performing non-continuous initial transmission and HARQ request retransmission within the COT based on the associated channel being determined to be available within a time between the initial transmission and a transmission opportunity for performing HARQ retransmission.

[0145] In various implementations, the sixth method may be implemented in a WTRU.

[0146] In various embodiments, the seventh method may include any of the following: determining that the channel is available within the COT between the initial transmission and the transmission opportunity for performing HARQ retransmission; and based on determining that the channel is available, performing non-continuous initial transmission and HARQ retransmission within the channel occupancy time.

[0147] In various embodiments, the seventh method may be implemented in a WTRU.

[0148] In various embodiments, the eighth method may include any of the following: determining that the channel is unavailable within a first COT at a time after an initial transmission and a transmission opportunity for performing HARQ retransmission; and based on determining that the channel is unavailable, performing non-continuous initial transmission and HARQ retransmission within the first COT and the second COT.

[0149] In various implementations, the eighth method may be implemented in a WTRU.

[0150] In various embodiments, the thirteenth method may include performing a HARQ retransmission of an earlier transmission based on control information received during a COT initiated for the transmission. In various embodiments, the transmission may include information indicating HARQ state information associated with the earlier transmission.

[0151] In various implementations, the eighth method may be implemented in a WTRU.

[0152] In various embodiments, the ninth method may include performing HARQ retransmission based on information of an SCI received in a COT initiated for an associated PSFCH transmission.

[0153] In various implementations, the ninth method may be implemented in a WTRU.

[0154] In various embodiments, an apparatus includes a circuit including a transmitter, a receiver, a processor, and a memory, the apparatus being configured to perform at least one of the above methods.

[0155] In various embodiments, an apparatus may be, may be configured as, and / or may be configured with an element of a WTRU.

[0156] Representative SL U PSSCH / PSCCH transmission and PSFCH transmission

[0157] Channel access for PSSCH / PSCCH transmission and / or PSFCH transmission may be performed, used, defined, configured and / or determined. In various embodiments, the WTRU may perform channel access and resource selection procedures in the SL U. The SL U channel access and resource selection procedures may be an initiated COT and / or a shared ongoing COT. The WTRU may perform one or more sidelink continuous transmissions in an initiated COT and / or a shared COT.

[0158] The SLU channel access and resource selection procedures may include LBT sensing and SCI sensing. For example, channel access may be based on LBT sensing ("LBT sensing-based channel access"), and may be based on type 1 channel access procedures. The WTRU may perform LBT sensing, may determine the availability of the SLU channel based on and / or in response to LBT sensing, and / or may perform transmission on the SLU channel based on, in response to and / or conditional on the availability of the SLU channel. The SLU channel may refer to a resource pool and / or a set of resource blocks (RBs). The resource pool and / or the RB set may be (pre-)configured for side link transmissions in a shared spectrum. The WTRU may perform LBT sensing on a bandwidth. The bandwidth may be the bandwidth of the resource pool and / or the RB set. The WTRU may perform LBT sensing on a bandwidth and within an LBT sensing slot having a duration. The duration may be, for example, T sl =9us.

[0159] The WTRU may perform one or more sidelink transmissions within the COT after a successful SLU channel acquisition, for example, resulting from the WTRU performing an SLU channel access and resource selection procedure. The COT may be represented in various ways, such as, for example, the total amount of time for one or more WTRUs to perform one or more transmissions after a successful channel acquisition. Transmission gaps that are less than or equal to a certain value (e.g., 25 μs) may be counted as part of the total amount of time for one or more WTRUs to perform one or more transmissions. Alternatively, the COT may be the total amount of time for one or more WTRUs to perform one or more transmissions after a successful channel acquisition plus a budgeted amount of time for a certain number of transmission gaps, where the amount of time for each (or all) of the transmission gaps is less than or equal to a certain value (e.g., 25 μs). The WTRU may continue to transmit after a transmission gap in the same COT.

[0160] The WTRU may be (pre-)configured with all symbols of PSSCH / PSCCH transmissions within a timeslot ("sidelink timeslot") used for sidelink communications. Such sidelink timeslots may be referred to as PSSCH / PSCCH timeslots. The WTRU may perform PSSCH / PSCCH transmissions and / or associated DMRS transmissions in PSSCH / PSCCH timeslots within a COT. The COT may have been initiated by the WTRU ("initiated COT"), or may have been initiated by another WTRU and available to and / or shared by (at least) that WTRU ("shared COT").

[0161] A WTRU that performs a PSSCH / PSCCH transmission in a sidelink timeslot in a resource pool in an initiated COT and / or a shared COT may be referred to as a TX WTRU. A WTRU that performs a PSFCH transmission in an initiated COT and / or a shared COT in response to a PSSCH / PSCCH transmission received in a resource pool used by the TX WTRU may be referred to as a RX WTRU. A PSSCH / PSCCH transmission by a TX WTRU and a corresponding PSFCH transmission by a RX WTRU in a resource pool may be referred to as an associated PSSCH / PSCCH and PSFCH transmission and / or a corresponding PSSCH / PSCCH and PSFCH transmission.

[0162] The WTRU may perform PSSCH / PSCCH and / or PSFCH transmissions in an indexed sidelink logical timeslot and / or an indexed physical timeslot in the resource pool. A sidelink timeslot may refer to a sidelink logical timeslot and / or a physical timeslot, unless otherwise specified.

[0163] The RX WTRU may receive a PSSCH / PSCCH transmission in a sidelink timeslot during a COT (e.g., in a resource pool). The RX WTRU may receive information indicating a report of HARQ information for a received PSSCH / PSCCH transmission. Information indicating a report of HARQ information may be carried in sidelink control information (SCI) associated with a PSSCH / PSCCH transmission (e.g., an SCI that schedules a PSSCH / PSCCH transmission). The HARQ information may include HARQ ACK information or HARQ NACK information for an associated SL PSSCH / PSCCH transmission (e.g., a transport block (TB) received therein). Although "transport block" and "TB" are used in the embodiments / examples described herein (e.g., above and / or below), applications of the embodiments / examples may use other types / formats of information (e.g., instead of or in addition to a transmission block) and still be consistent with the disclosure herein.

[0164] One or more resource allocations and / or one or more formats for PSFCH communication (one or more PSFCH transmissions) may be used, defined, configured and / or determined. The WTRU may be (pre)configured with M RB interlaces for PSFCH transmission. The WTRU may be (pre)configured with M RB interlaces for PSFCH transmission over the bandwidth of a resource pool and / or RB set. For example, the M RB interlaces (each a "PSFCH RB interlace") for PSFCH transmission may be based on M=10 (for 15-kHz SCS) and M=5 (for 30-kHz). Each PSFCH RB interlace may be indicated by an index m. For example, the index m may be an integer from 0 to M-1. The PSFCH RB interlace represented by the index m may include RBs corresponding to indices (m, m+M, m+2xM, m+3xM...m+NxM), where N may be the total number of RBs in the RB interlace.

[0165] In various embodiments, the WTRU may be (pre)configured with a sequence-based format for PSFCH transmission. For example, the WTRU may be (pre)configured with multiple sequences ("PSFCH sequences") for PSFCH transmission. In various embodiments, the PSFCH sequence may include a first PSFCH sequence indicating a HARQ ACK and a second PSFCH sequence indicating a HARQ NACK. The WTRU may be (pre)configured to transmit any PSFCH sequence (e.g., any one of the first PSFCH sequence and the second PSFCH sequence) in one or more (e.g., each) PRBs of the PSFCH interlace. For example, the PSFCH interlace may be (pre)configured in a resource pool for associated PSSCH / PSCCH transmissions. The same PSFCH sequence may be repeated in two or more (e.g., each) PRBs of the PSFCH interlace.

[0166] In various embodiments, the PSFCH sequence may include one or more sets of PSFCH sequences. The PSFCH sequences in each set of PSFCH sequences may be different from each other. For example, the set of PSFCH sequences may include a first set of PSFCH sequences and a second set of PSFCH sequences. The first set of PSFCH sequences may indicate HARQ ACK, and the second set of PSFCH sequences may indicate HARQ NACK. In various embodiments, each PSFCH sequence in one or more sets of the set of PSFCH sequences may be a cyclic shift version of a Zadoff Chu (ZC) base sequence. Each sequence in one or more (e.g., each) set of PSFCH sequences for HARQ ACK (e.g., the first set of PSFCH sequences) in the set of PSFCH sequences may be represented by a cyclic shift index. Each sequence in one or more (e.g., each) set of PSFCH sequences for HARQ NACK (e.g., the second set of PSFCH sequences) may be represented by a cyclic shift index.

[0167] In various embodiments, the WTRU may be (pre)configured with a pre-selected option and / or a default option for a PSFCH sequence ("default PSFCH sequence") and a pre-selected option and / or a default option for a PSFCH RB interleaving ("default PSFCH RB interleaving"). The WTRU may be (pre)configured and / or may perform one or more transmissions of a default PSFCH sequence. For example, the WTRU may be (pre)configured and / or may perform a transmission of a default PSFCH sequence in one or more PRBs (e.g., each PRB) of a default PSFCH RB interleaving. In various embodiments, the WTRU may be (pre)configured and / or may receive one or more HARQ-enabled PSSCH / PSCCH transmissions. The WTRU may be (pre)configured and / or may perform a transmission of a default PSFCH sequence in conjunction with (e.g., after, at, at the time of, based on, in response to, conditional on, etc.) receiving a HARQ-enabled PSSCH / PSCCH transmission (e.g., in a PRB (e.g., each PRB) of a default PSFCH RB interleaving).

[0168] The WTRU may be (pre-)configured to and / or may perform one or more transmissions of a PSFCH sequence in one or more PRBs to indicate (e.g., and / or provide information indicating the following): any of a HARQ ACK and a HARQ NACK corresponding to a received PSSCH / PSCCH transmission (e.g., one or more of the HARQ-enabled PSSCH / PSCCH transmissions). For example, in addition to being (pre-)configured to perform and / or perform transmissions of a default PSFCH sequence in PRBs (e.g., each of the PRBs) of a default PSFCH RB interlace, the WTRU may also be (pre-)configured to and / or may perform transmissions of a PSFCH sequence in PRBs to indicate (e.g., and / or provide information indicating the following): any of a HARQ ACK and a HARQ NACK corresponding to a received PSSCH / PSCCH transmission.

[0169] The WTRU may be (pre-)configured and / or may receive an SCI of an associated PSSCH / PSCCH transmission (e.g., one or more of the HARQ-enabled PSSCH / PSCCH transmissions). The WTRU may be (pre-)configured and / or may receive a PSSCH / PSCCH transmission in one or more of the plurality of logical time slots. The SCI may indicate and / or may include information indicating any of a transmission index, an RB interlace assignment, a source ID of the WTRU, a destination ID of the WTRU, etc. One or more of the logical time slots (e.g., each logical time slot) may have an associated index.

[0170] The WTRU may be (pre-)configured and / or may determine the index of a PSFCH PRB in one or more of the PRBs that may be sent to indicate (e.g., and / or provide information indicating the following): any of a HARQ ACK and a HARQ NACK corresponding to a received PSSCH / PSCCH transmission. The WTRU may be (pre-)configured and / or may determine the index of the PSFCH PRB based on any of: a transmission index, an RB interlace assignment, a WTRU source ID, a WTRU destination ID, and one or more indices of one or more logical time slots in which the associated PSSCH / PSCCH transmission is received. In various embodiments, the WTRU is (pre-)configured and / or may determine that the determined PSFCH PRB and the PRBs included in the default PSFCH RB interlace may overlap (e.g., at least partially) in time and / or frequency. The WTRU may be (pre-)configured and / or may use a PSFCH sequence other than the default PSFCH sequence (e.g., a PSFCH sequence for / associated with a determined PSFCH PRB), for example in conjunction with (e.g., after, at, at, based on, in response to, conditional on, etc.) PRBs in which a determined PSFCH PRB and PRBs included in a default PSFCH RB interlace may overlap (e.g., at least partially) in time and / or frequency.

[0171] In various embodiments, the WTRU may be (pre-)configured with a PSFCH having an information payload of a (pre-)configured number of bits, e.g. Figure 2 PSFCH slot format 5 is shown in FIG. 5. The WTRU may include one or more HARQ feedback information in the PSFCH.

[0172] One or more transmission opportunities and / or one or more time slots for PSFCH communication (one or more PSFCH transmissions) may be used, defined, configured and / or determined. The WTRU may perform PSFCH transmission in a transmission opportunity ("PSFCH transmission opportunity") in a sidelink time slot. A sidelink time slot including a PSFCH transmission opportunity may be referred to as a PSFCH time slot. In various embodiments, the location (e.g., start (time) and duration) of the PSFCH transmission opportunity within the sidelink time slot may be (pre)configured, for example, in a resource pool. For example, the PSFCH transmission opportunity may be (pre)configured to include multiple consecutive symbols at the end of the PSFCH time slot. Alternatively and / or additionally, the PSFCH transmission opportunity may be (pre)configured at the beginning of the PSFCH time slot. Alternatively and / or additionally, the WTRU may be (pre)configured with the starting symbol and number of symbols of the PSFCH transmission opportunity within the PSFCH time slot. Alternatively and / or additionally, the PSFCH time slot may include symbols that are (pre)configured for PSSCH / PSCCH transmission.

[0173] The WTRU may be (pre-)configured with one or more PSFCH transmission opportunity configurations. In various embodiments, the WTRU may be (pre-)configured with either 2-symbol PSFCH transmission opportunities and 3-symbol PSFCH transmission opportunities.

[0174] A 2-symbol PSFCH transmission opportunity may include two symbols of a PSFCH slot. The two symbols may include a first symbol followed by a second symbol. The first symbol and the second symbol may be consecutive or non-consecutive. The second symbol may carry PSFCH content. The first symbol may be (pre-)configured as an AGC symbol and may carry a copy of the PSFCH content. The RX WTRU may copy the PSFCH content to the first (AGC) symbol, may send the first (AGC symbol and may send the PSFCH content at the second symbol. The first (AGC) symbol may enable convergence of the AGC for the TX WTRU to receive the PSFCH transmission.

[0175] A 3-symbol PSFCH transmission opportunity may include three symbols of a PSFCH slot. The three symbols may include a first symbol, followed by a second symbol, followed by a third symbol. The first symbol and the second symbol may be consecutive or non-consecutive, and the second symbol and the third symbol may be consecutive or non-consecutive. The second symbol may carry PSFCH content. The first symbol may be (pre)configured as an AGC symbol and may carry a copy of the PSFCH content. The third symbol may be (pre)configured as a protection symbol and may carry a copy of the PSFCH content. The RX WTRU may copy the PSFCH content to the first (AGC) symbol, may send the first (AGC) symbol, and may send the PSFCH at the second symbol. The first (AGC) symbol may enable convergence of the AGC for the TX WTRU to receive the PSFCH transmission. The RX WTRU may copy the 2nd PSFCH symbol to the third (protection) symbol, and may send the third (protection) symbol. The third (guard) symbol at the end of the PSFCH transmission opportunity may allow (e.g., provide a sufficient amount of time for) the TX WTRU to switch from a receive operation (e.g., for receiving a PSFCH transmission) to a transmit operation for sending (e.g., immediately sending) a PSSCH / PSCCH transmission in a subsequent (e.g., next) PSSCH / PSCCH time slot in the COT, for example, to maintain the COT.

[0176] In various embodiments, the WTRU may be (pre-)configured with one or more of a variety of PSFCH slot formats. Figure 2 Examples of various PSFCH time slot formats are shown. Figure 2 As shown, the various PSFCH time slot formats may include a first PSFCH time slot format, a second PSFCH time slot format, a third PSFCH time slot format, a fourth PSFCH time slot format, and a fifth PSFCH time slot format.

[0177] The first PSFCH slot format ("PSFCH slot format 1") may include one or more PSSCH / PSCCH symbols and a 2-symbol PSFCH transmission opportunity at the end of the PSFCH slot. PSFCH slot format 1 may be used and / or may be (pre-)configured for one or more PSFCH transmissions at the end of the COT.

[0178] A second PSFCH slot format ("PSFCH slot format 2") may include one or more PSSCH / PSCCH symbols and a 3-symbol PSFCH transmission opportunity at the end of the PSFCH slot. PSFCH slot format 2 may be used and / or may be (pre-)configured for one or more PSFCH transmissions within the COT.

[0179] A third PSFCH slot format ("PSFCH slot format 3") may include one or more 2-symbol PSFCH transmission opportunities. For example, PSFCH slot format 3 may include multiple consecutive 2-symbol PSFCH transmission opportunities. PSFCH slot format 3 may be used and / or may be (pre-)configured for one or more PSFCH transmissions at the beginning and / or end of the COT.

[0180] A fourth PSFCH slot format ("PSFCH slot format 4") may be used and / or may be (pre-)configured for one or more PSFCH transmissions in a PSFCH slot following a PSCCH transmission at the beginning of a PSFCH slot. One or more PSFCH transmissions may be immediately following a PSCCH transmission. PSFCH slot format 4 may include a PSCCH transmission opportunity followed by one or more 2-symbol PSFCH transmission opportunities. For example, PSFCH slot format 4 may include a PSCCH transmission opportunity followed by multiple consecutive 2-symbol PSFCH transmission opportunities. A PSCCH transmission opportunity may include one or more symbols. As shown, a PSCCH transmission opportunity may include a first symbol and a second symbol. The second symbol may be (pre-)configured as an AGC symbol and may carry a copy of the PSCCH content. The RX WTRU may copy the PSCCH content to a first (AGC) symbol, may send a first (AGC) symbol, may send a PSCCH at a second symbol, and may send multiple consecutive 2-symbol PSFCH transmission opportunities.

[0181] A fifth PSFCH slot format ("PSFCH slot format 5") may include a single slot PSFCH transmission opportunity.PSFCH slot format 5 may be used and / or may be (pre-)configured for one or more PSFCH transmissions at the beginning and / or end of a COT.

[0182] In various embodiments, a WTRU (pre)configured with PSFCH slot format 1 may be (pre)configured with a guard symbol prior to a 2-symbol PSFCH transmission opportunity in a PSFCH slot. In various embodiments, a WTRU (pre)configured with PSFCH slot format 2 may be (pre)configured with a guard symbol prior to a 3-symbol PSFCH transmission opportunity in a PSFCH slot. The TXWTRU may copy the contents of the symbol preceding (e.g., immediately preceding) the guard symbol to the guard symbol. For example, according to Figure 2In PSFCH slot formats 1 and 2 as shown, the TX WTRU may transmit a PSSCH / PSCCH transmission on one or more symbols preceding a PSFCH transmission opportunity followed by a guard symbol that includes a duplicate content of one of the symbols (e.g., the last transmitted symbol) that carries PSSCH / PSCCH content in the PSFCH slot, and in the same slot, the RX WTRU may transmit via one or more PSFCH transmissions during one or more PSFCH transmission opportunities. The guard symbol preceding the PSFCH transmission opportunity may allow (e.g., provide a sufficient amount of time for) the RX WTRU to switch from a receive operation (e.g., for receiving a PSSCH / PSCCH transmission) to a transmit operation for sending (e.g., immediately sending) a PSFCH transmission during the PSFCH transmission opportunity.

[0183] The purpose of sending duplicate content during the guard symbols may be to minimize the possibility of transmission gaps greater than a value in the COT (e.g., 25 μs) so that the TX WTRU may have an opportunity and / or may continue PSSCH / PSCCH transmission within the COT after receiving a PSFCH transmission.

[0184] The reception of PSSCH / PSCCH communications (e.g., one or more PSSCH / PSCCH transmissions) in a SLU in a COT by a WTRU may be performed, used, defined, configured, and / or determined. The RX WTRU may receive one or more PSSCH / PSCCH transmissions within a COT from one or more TX WTRUs. The RX WTRU may receive an SCI associated with a PSSCH / PSCCH transmission (e.g., an SCI for scheduling a PSSCH / PSCCH transmission). The SCI may include information indicating parameters associated and / or related to channel access and / or resource determination for an associated PSFCH transmission. The information may include, for example, any of the following.

[0185] • Layer 1 (L1) priority, which is assigned to TBs carried in PSSCH transmissions.

[0186] • The type of broadcast of the TB (eg, unicast, multicast, and / or broadcast).

[0187] • The WTRU source identifier (ID) associated with the PSSCH / PSCCH and associated PSFCH transmissions.

[0188] • The WTRU destination ID associated with the PSSCH / PSCCH and associated PSFCH transmissions.

[0189] WTRU geographic location. The TX WTRU may indicate its geographic location in this indication. For example, the value of this indication may be the region ID of the TX WTRU.

[0190] Minimum Communication Range (MCR) parameter or requirement for the TB sent in the PSSCH. The TX WTRU may include an index corresponding to the (pre-)configured MCR parameter or requirement in meters. When the determined geographical distance between the RX WTRU and the TX WTRU that may send the TB may be less than or equal to the indicated MCR parameter or requirement, the RX WTRU may be (pre-)configured to perform sidelink HARQ reporting for the received TB.

[0191] ·COT duration indication. For example, the TX WTRU may indicate the remaining time of the COT. The remaining time may be measured from the sidelink timeslot in which the SCI may be received and the end of the acquired COT. For example, the time unit of the COT duration indication may be milliseconds. Alternatively, the time unit may be a sidelink logical timeslot and / or physical timeslot of a resource pool used for PSSCH / PSCCH transmissions carrying the decoded SCI. The TX WTRU may determine the value of the indication based on: a (pre-) configured maximum COT (mCOT), for example, the maximum amount of time the TX WTRU is allowed to transmit upon a successful channel access. The TX WTRU may determine the mCOT based on and / or in response to the L1 priority of the TB used for PSSCH / PSCCH transmissions within the COT.

[0192] Remaining COT duration and / or transmit indication. For example, the TX WTRU may indicate the number of remaining sidelink time slots scheduled for PSCCH / PSSCH transmission. A time resource indication value (TRIV) may be used for the remaining COT duration and / or transmit indication. The TRIV may be based on and / or responsive to the number of consecutive sidelink time slots scheduled for PSCCH / PSSCH transmission in the remaining COT duration.

[0193] Alternatively and / or additionally, TRIV may be jointly calculated based on and / or in response to the COT duration and the number of transmissions scheduled in the COT.The applied sidelink timeslot may be a SL logical timeslot and / or a physical timeslot of a resource pool for PSSCH / PSCCH transmission.

[0194] HARQ transmission index. For example, the TX WTRU may indicate the index in ascending order of the PSSCH / PSCCH transmissions for which HARQ feedback is implemented in the COT. The TX WTRU may expect a HARQ feedback transmission for each PSSCH / PSCCH transmission in the COT. The HARQ transmission index may have n bits and indicate at most 2n HARQ-enabled PSSCH / PSCCH transmissions.

[0195] COT index. For example, the TX WTRU may indicate the index in ascending order of the COTs that include the PSSCH / PSCCH transmissions that implement HARQ feedback. The COT index may have n bits and indicate up to 2 n COT executed.

[0196] Frequency resource assignment. For example, the TX WTRU may indicate one or more RB interlaces and / or RB sets in the resource pool that are assigned for PSSCH transmission in the COT. The TX WTRU may perform transmission of one or more TBs within the COT using the same frequency resources and may indicate the frequency resource assignment in the SCI in each PSSCH / PSCCH transmission. Alternatively and / or additionally, the TX WTRU may perform transmission of one or more TBs within the COT using different frequency resources and may indicate the frequency resource assignment for the next n consecutive PSSCH / PSCCH transmissions. The value of n may be (pre-)configured in the resource pool.

[0197] A frequency resource indication value (FRIV) value may be used for this indication, for example, the TX WTRU may calculate the FRIV value based on the starting RB interlace and the number of RB interlaces used for PSSCH transmission in each slot within the COT.

[0198] · COT sharing indication for PSSCH / PSCCH. For example, the TX WTRU may indicate whether the COT may be shared by another WTRU to perform one or more PSSCH / PSCCH transmissions within the COT. The COT sharing indication for PSSCH / PSCCH may be, for example, a sharing enable / disable indication. When a shareable COT for PSSCH / PSCCH transmission may be indicated, unoccupied resources in the COT (e.g., sidelink time slots that are not scheduled for PSSCH / PSCCH transmissions and frequency resources (RBs and / or interlaces) that are not assigned for scheduled PSSCH / PSCCH transmissions) may be used by another WTRU for PSSCH / PSCCH transmissions.

[0199] · COT sharing indication for PSFCH. In various embodiments, for example, the TX WTRU may indicate whether the COT may be shared by the RX WTRU to perform one or more PSFCH transmissions associated with one or more PSSCH / PSCCH transmissions in the COT. The COT sharing indication for the PSFCH may be, for example, a sharing enable / disable indication. When the indication may be enabled, the RX WTRU may perform a PSFCH transmission in the same COT in which the RX WTRU may receive the associated PSSCH / PSCCH transmission. Alternatively and / or additionally, the TX WTRU may indicate whether the COT may be shared by the RX WTRU to send one or more PSFCH transmissions associated with one or more PSSCH / PSCCH transmissions performed in a previous COT by the same and / or different TX WTRU.

[0200] In various embodiments, the TX WTRU may indicate a HARQ feedback request in the indication to request the RX WTRU to perform one or more PSFCH transmissions associated with one or more PSCCH / PSSCH transmissions received from the same TX WTRU and / or a different TX WTRU in the current COT and / or one or more previous COTs. The RX WTRU may treat such a request as a poll for untransmitted HARQ information (feedback) and perform PSFCH transmissions of all (or at least some) of the untransmitted HARQ information (feedback).

[0201] ·PSFCH transmission opportunity indication. In various embodiments, for example, the TX WTRU may indicate that the (e.g., current) side link timeslot may be a PSFCH timeslot. The PSFCH transmission opportunity indication may indicate that there is a PSFCH transmission opportunity in the side link timeslot, such as, for example, at the end of the timeslot in which the SCI including the indication may be received. In various embodiments, the TX WTRU may indicate that another side link timeslot within the COT may be a PSFCH timeslot. For example, the TX WTRU may include a side link timeslot index and / or a timeslot offset (n) in the PSFCH transmission opportunity indication. A side link timeslot having an indicated timeslot index and / or being located n side link timeslots after the current side link timeslot may be a PSFCH timeslot. In various embodiments, the TX WTRU may indicate a PSFCH transmission opportunity configuration including a (pre-)configured PSSCH to PSFCH offset in the same COT, the last side link timeslot of the same COT, another COT, etc. The indication value may be (pre-)configured for each PSFCH transmission opportunity configuration.

[0202] In various embodiments, a resource pool may be (pre-)configured with one or more PSFCH slots ("resource pool PSFCH slots"), and the resource pool PSFCH slots may be used to (pre-)configure one or more PSFCH transmission opportunities. For example, the (pre-)configured PSFCH transmission opportunities ("pool PSFCH transmission opportunities") may be mapped to resource pool PSFCH slots in a bijective manner. Alternatively, the (pre-)configured pool PSFCH transmission opportunities are mapped to a corresponding plurality of resource pool PSFCH slots. For example, the (pre-)configured pool PSFCH transmission opportunities are mapped to a plurality of different and / or mutually exclusive resource pool PSFCH slots.

[0203] Some or all of the (pre-)configured pool PSFCH transmission opportunities may have the same duration as the corresponding PSFCH slot of the resource pool PSFCH slot. Alternatively, the duration of some or all of the (pre-)configured pool PSFCH transmission opportunities may be less than the duration of the corresponding PSFCH slot, and any of them may occur during a portion of the corresponding resource pool PSFCH slot.

[0204] In various embodiments, the PSFCH transmission timing indication may indicate (involve) any of the following: a resource pool, one or more of the resource pool PSFCH time slots, and one or more of the (pre-)configured pool PSFCH transmission opportunities. In various embodiments, the PSFCH transmission timing indication may include information indicating (involving) any of the following: a resource pool, one or more of the resource pool PSFCH time slots, and one or more of the (pre-)configured pool PSFCH transmission opportunities.

[0205] ·HARQ delay boundary. The TX WTRU may indicate a HARQ delay boundary, e.g., a time period during which the RX WTRU may perform one or more PFSCH transmissions associated with one or more PSSCH / PSCCH transmissions in a (e.g., current) sidelink timeslot. The TX WTRU may determine the HARQ delay boundary based on a remaining packet delay budget (PDB) for a TB carried in the PSSCH transmission. The HARQ delay boundary may be represented in various ways, such as, for example, a number of logical timeslots. The TX WTRU may monitor PSFCH transmissions (e.g., expected PSFCH transmissions) within the HARQ delay boundary. In various embodiments, the TX WTRU may monitor PSFCH transmissions in one or more (each) of the resource pool PSFCH timeslots that occur within the indicated HARQ delay boundary (e.g., after the start and before the end). As used herein, "monitor" and / or "monitor for"

[0206] It can refer to the detection of transmission, signal, etc., the attempt to receive, the reception, the attempt to decode,

[0207] Any of decoding, etc. The TX WTRU may flush any HARQ process buffers corresponding to one or more PSFCH transmissions that were not received during the delay boundary.

[0208] Representative channel access for PSFCH communications

[0209] Channel access for PSFCH communication in SL U (e.g., for one or more PSFCH transmissions) and / or one or more channel access procedures for performing channel access for PSFCH communication in SL U may be performed, used, defined, configured and / or determined. In various embodiments, the RX WTRU may perform channel access for PSFCH communication based on COT sharing (i.e., in a shared COT). The terms "channel access" and "channel access procedures", etc., may be used interchangeably herein. According to the channel access for PSFCH communication based on COT sharing, the RX WTRU may perform one or more PSFCH transmissions in one or more PSFCH transmission opportunities in one or more PSFCH time slots within the COT. The COT may be the same COT in which the RX WTRU may receive an associated PSSCH transmission from the TX WTRU (e.g., as disclosed below and / or above herein). Alternatively, the COT may be different from the COT in which the RX WTRU may receive an associated PSSCH / PSCCH transmission from the TX WTRU (e.g., as disclosed below and / or above herein).

[0210] The RX WTRU may detect a COT. The RX WTRU may determine that the COT may be used for a PSFCH transmission associated with a PSSCH / PSCCH transmission received in one or more previous COTs. The detection and determination may be based on and / or in response to an SCI (e.g., a decoded SCI). The COT may be initiated by the same TX WTRU and / or another TX WTRU for which the PSFCH transmission may be intended.

[0211] The RX WTRU may perform LBT sensing in channel access for PSFCH communication based on COT sharing. For example, the RX WTRU may perform LBT sensing when there may be a gap in the COT before one or more PSFCH transmissions are about to occur.

[0212] The WTRU may determine to perform LBT sensing after a gap of 25 μs (e.g., based on a Type 2A LBT channel access). Alternatively and / or additionally, the WTRU may determine to perform LBT sensing after a gap of 16 μs (e.g., based on a Type 2B LBT channel access). Alternatively and / or additionally, the WTRU may determine not to perform LBT sensing after a gap less than 16 μs (e.g., based on a Type 2C LBT channel access).

[0213] In various embodiments, when the RX WTRU may perform one or more PSFCH transmissions during a PSFCH transmission opportunity with a start symbol immediately following the last symbol of a PSSCH / PSCCH transmission, the RX WTRU may perform channel access based on a type 2C LBT channel access, wherein LBT sensing is not performed prior to the PSFCH transmission. In various embodiments, when the TX WTRU may perform a PSSCH / PSCCH transmission at a symbol immediately following the last symbol of a received PSFCH transmission at a PSFCH transmission opportunity (e.g., according to PSFCH slot format 2), the TX WTRU may perform channel access based on a type 2C LBT channel access, wherein LBT sensing is not performed prior to the PSSCH / PSCCH transmission.

[0214] In various embodiments, the WTRU may be (pre-)configured and / or may receive a PSFCH transmission at / during a PSFCH opportunity. The WTRU may be (pre-)configured and / or may perform a PSSCH / PSCCH transmission at a symbol after (e.g., immediately after) the last symbol of a received PSFCH transmission at a PSFCH opportunity. The WTRU may be (pre-)configured and / or may indicate a PSFCH slot format having unoccupied symbols at and / or near the end of a PSFCH opportunity. For example, the WTRU may be (pre-)configured and / or may indicate a PSFCH slot format having unoccupied symbols at and / or near the end of a PSFCH opportunity in conjunction with the WTRU performing a PSSCH / PSCCH transmission at a symbol after (e.g., immediately after) the last symbol of a received PSFCH transmission at (e.g., immediately after) the PSFCH (e.g., after, at, at the time of, based on, in response to, conditional on, etc.).

[0215] In various embodiments, the PSFCH slot format may be (pre)configured. The (pre)configured PSFCH slot format may enable the WTRU to perform a Type 2A / 2B LBT procedure, for example in conjunction with (e.g., prior to) a PSSCH / PSCCH transmission that shares a COT with a preceding (e.g., earlier in time) PSFCH transmission.

[0216] In various embodiments, the WTRU may be (pre)configured to and / or may use a (pre)configured PSFCH time slot format to perform PSFCH transmission, and / or may be (pre)configured to and / or may give up performing (e.g., may not perform) transmission at the last symbol.

[0217] In various embodiments, the WTRU may be (pre)configured and / or may perform PSSCH / PSCCH transmission after PSFCH transmission in the shared COT, and / or may be (pre)configured and / or may perform (pre)configured type 2A LBT channel access or type 2B LBT channel access, for example, at the beginning of the last symbol. In various embodiments, the TX WTRU may be (pre)configured and / or may perform transmission of a channel reservation signal and / or cyclic prefix extension (CPE), for example, in conjunction with successful (e.g., after, at, at, based on, in response to, conditional on, etc.) execution of type 2A LBT channel access or type 2B LBT channel access until the next slot boundary. The TX UE may perform PSSCH / PSCCH transmission at the next slot boundary in the COT.

[0218] The WTRU may perform LBT sensing on a bandwidth of a resource pool and / or a set of RBs (e.g., (pre-)configured for PSFCH transmission). The RX WTRU may determine not to use a transmit gap of a shared COT if the transmit gap may be less than a first value (e.g., 25 us). The RX WTRU may perform one or more PSFCH transmissions in a transmit gap of a shared COT if the transmit gap may be greater than a second value (e.g., 25 us). The first value and the second value may be the same or different.

[0219] In various embodiments, the RX WTRU may initiate (i.e., in an initiated COT) channel access for PSFCH communication. The RX WTRU may initiate a COT for one or more PSFCH transmissions associated with one or more PSSCH / PSCCH transmissions received from one or more TX WTRUs in one or more previous COTs. Alternatively and / or additionally, the RX WTRU may initiate a COT for one or more PSFCH transmissions and one or more PSSCH / PSCCH transmissions when the RX WTRU may have data for transmission in a buffer. Based on the channel access for PSFCH communication initiated based on the COT, the RX WTRU may perform one or more PSFCH transmissions in one or more PSFCH transmission opportunities in one or more PSFCH time slots within the COT. The COT may be a COT in which the RX WTRU may initiate one or more PSFCH transmissions and / or one or more PSSCH / PSCCH transmissions (e.g., as disclosed herein below and / or above).

[0220] The WTRU may perform LBT sensing for COT initiation, for example, based on type 1 channel access, in a set of logical time slots (e.g., a set of consecutive logical time slots), and on a bandwidth of a resource pool (e.g., (pre-) configured for PSFCH transmission). The WTRU may concurrently perform SCI decoding and may detect a sharable COT from the SCI on which COT-sharing-based channel access for PSFCH communication may be performed. If the WTRU may detect a sharable COT, the WTRU may stop COT initiation, and one or more PSFCH transmissions may be performed in the sharable COT (e.g., based on the COT-sharing-based channel access for PSFCH communication).

[0221] Representative procedures and mechanisms for PSFCH transmission

[0222] A PSFCH communication (e.g., one or more PSFCH transmissions) in a SLU in the same COT as an associated PSSCH / PSCCH communication (e.g., one or more PSSCH / PSCCH transmissions) may be performed, used, defined, configured, and / or determined. The RX WTRU may determine a PSFCH transmission timing for an associated PSSCH / PSCCH transmission in the same COT based on and / or in response to any of various criteria, factors, and / or other information. The criteria, factors, and / or other information may include, for example, any of the following:

[0223] Channel access (pre-)configuration for PSFCH communications;

[0224] PSSCH to PSFCH offset;

[0225] The L1 priority associated with the PSFCH transmission (e.g., the L1 priority indicated in the SCI of the associated PSSCH / PSCCH transmission);

[0226] PSFCH transmission timing (pre-) configuration;

[0227] COT duration;

[0228] The remaining transmissions scheduled in the COT; and

[0229] • TX WTRU indication.

[0230] Figure 3 An example of PSFCH transmission and associated PSSCH / PSCCH transmission during the same COT is illustrated.

[0231] A WTRU may be (pre-)configured in a resource pool with one or more PSFCH transmissions performed in the same COT, and a RX WTRU may receive one or more associated PSSCH transmissions from a TX WTRU in the same COT.

[0232] In various embodiments, the RX WTRU may determine the PSFCH transmission timing for associated PSSCH / PSCCH transmissions in the same COT based on and / or in response to any of various criteria, factors and / or other information. For example, the RX WTRU may determine the PSFCH transmission timing for associated PSSCH / PSCCH transmissions in the same COT based on a (pre-)configured PSSCH to PSFCH offset in units of logical time slots in a resource pool used by the PSSCH / PSCCH transmissions. The offset may be based on the minimum processing time period for the PSFCH transmission required to decode the TBs in the PSSCH and generate the HARQ feedback carried in the PSFCH transmission. The value of the minimum processing time may depend on the WTRU capabilities, the subcarrier spacing of the resource pool, the TB size, the MCS configuration, and the like.

[0233] In various embodiments, when such a PSSCH to PSFCH offset may be (pre-)configured to n sidelink time slots, the RX WTRU may determine that a PSFCH transmission opportunity may be included in a PSFCH time slot that may be n sidelink time slots later than the sidelink time slot in which the PSSCH / PSSCH transmission may be received. For an example of n=2, see Figure 3 A).

[0234] In various embodiments, the RX WTRU may be (pre-)configured with PSFCH transmission opportunities specific to a resource pool, such as a plurality of side link time slots in the resource pool for a period of the PSFCH transmission opportunity. The (pre-)configured period of the PSFCH transmission opportunity may be m side link time slots. There may be one PSFCH transmission opportunity (PSFCH time slot) for every m side link time slots in the resource pool. The RX WTRU may determine a PSFCH transmission opportunity in a first side link time slot in the COT, which may include the (pre-)configured PSFCH transmission opportunity and at least a PSSCH pair of PSFCH time slots after the associated PSSCH / PSCCH transmission.

[0235] In various embodiments, when the value of the L1 priority indicated in the associated PSSCH / PSCCH transmission may be below a (pre-)configured threshold, the RX WTRU may perform a determination of the PSFCH transmission timing based on the PSSCH to PSFCH offset and / or resource pool specific PSFCH transmission timing. A small L1 priority value may indicate a TB with high priority and / or low latency and may require rapid HARQ feedback.

[0236] In various embodiments, the RX WTRU may determine which of the various PSFCH slot formats to use based on and / or in response to any of various criteria, factors, and / or other information. For example, the RX WTRU may determine which of the various PSFCH slot formats to use based on the relative position of the determined PSFCH slot within the COT. The RX WTRU may determine the relative position based on the indicated COT duration and / or remaining transmissions, for example, as disclosed above. When the indicated value of the remaining transmissions may be greater than the PSSCH to PSFCH offset, the RX WTRU may determine that the PSFCH slot may be within the COT and / or that PSFCH slot format 2 may be applicable. When the indicated value of the remaining transmissions may be equal to the PSSCH to PSFCH offset, the RX WTRU may determine that the PSFCH slot may be the last sidelink slot of the scheduled transmission and / or that PSFCH slot format 1 may be applicable. When the indicated value of the remaining transmissions may be less than the PSSCH to PSFCH offset, the WTRU may determine that the PSFCH time slot may be outside the indicated COT duration and / or the scheduled PSSCH / PSCCH transmission, and may retain the HARQ ACK information (if any) for the PSFCH transmission in the subsequent COT.

[0237] In various embodiments, the WTRU may determine to use PSFCH slot format 5 in the determined PSFCH transmission opportunities at the beginning and / or end of the COT. The WTRU may determine to use PSFCH slot format 5 in the determined PSFCH transmission opportunities at the beginning and / or end of the COT, for example, based on, in response to, and / or conditional on a reference signal received power (RSRP) of an associated PSSCH / PSCCH transmission satisfying (e.g., being less than) a (pre-)configured threshold. Alternatively and / or additionally, the WTRU may determine to use PSFCH slot format 5 in the determined PSFCH transmission opportunities at the beginning and / or end of the COT based on, in response to, and / or conditional on a distance between the RX WTRU and the TX WTRU satisfying (e.g., being greater than) a (pre-)configured threshold. Alternatively and / or additionally, the WTRU may determine to use PSFCH time slot format 5 in the determined PSFCH transmission timing at the beginning and / or end of the COT based on, in response to and / or conditional on the number of HARQ feedback bits meeting (e.g., being greater than) a (pre-)configured threshold.

[0238] Single-slot PSFCH transmissions may provide a larger payload and improve PSFCH coverage and reception. The RX WTRU may determine the distance to the TX WTRU based on the RX WTRU's geographic location information and the region ID indicated in the SCI of the PSSCH / PSCCH transmission received from the TX WTRU. For example, the RX WTRU's geographic location information may be based on Global Navigation Satellite System (GNSS) information.

[0239] In various embodiments, the RX WTRU may determine a PSFCH transmission opportunity for an associated PSSCH / PSCCH transmission in a COT based on and / or in response to a (e.g., (pre-)configured) COT-specific PSFCH time slot within the same COT. Such a PSFCH transmission opportunity may be (e.g., (pre-)configured) at the end (e.g., the last one or more sidelink time slots) of the indicated COT and / or the scheduled transmission in the COT, such as Figure 3 Alternatively and / or additionally, the RX WTRU may receive an SCI including information (e.g., an information element, an indication, etc.) indicating that the PSFCH transmission opportunity for PSSCH / PSCCH transmission may be at the end of the same COT.

[0240] In various embodiments, when the value of the L1 priority indicated in the associated PSSCH / PSCCH transmission may exceed a (pre-)configured threshold, the RX WTRU may perform a determination of the PSFCH transmission opportunity at the end of the same COT. A larger value for the L1 priority may indicate a TB with low priority and / or large latency and may be transmitted at the end of the COT, for example, to reduce PSFCH transmission overhead.

[0241] The RX WTRU may determine the last sidelink timeslot of the COT based on and / or in response to any of various criteria, factors and / or other information. For example, the RX WTRU may determine the last sidelink timeslot of the COT based on and / or in response to the remaining COT / scheduled transmission information in and / or indicated by the SCI of one or more PSSCH / PSCCH transmissions received in the COT. For example, when the RX WTRU may receive such an indication of m in timeslot (n) within the COT, the RX WTRU may determine that the last sidelink timeslot of the remaining COT and / or scheduled transmissions in the COT may be sidelink timeslot (n+m). The RX WTRU may determine the PSFCH transmission timing in sidelink timeslot (n+m) for PSFCH timeslot format 1 and / or in sidelink timeslot (n+m+1) for PSFCH timeslot formats 3 and 4.

[0242] In various embodiments, the RX WTRU may determine the PSFCH transmission opportunity for the associated PSSCH / PSCCH transmission based on and / or in response to information in and / or indicated by the SCI from the TX WTRU. For example, the information about the location of the PSFCH transmission opportunity in and / or indicated by the SCI from the TX WTRU may include any of the following:

[0243] Information indicating that PSFCH transmission opportunities may be in the same COT (e.g., based on PSSCH to PSFCH offset);

[0244] Information indicating that the PSFCH transmission opportunity may be at the end of the same COT (e.g., one or more last sidelink time slots);

[0245] Information indicating that the PSFCH transmission opportunities may be in different COTs with the TX WTRU polling; and

[0246] • Information indicating that the PSFCH transmission opportunity may be in a different COT without the TX WTRU polling.

[0247] The RX WTRU may determine to multiplex multiple PSFCHs in the time domain in the same PSFCH transmission opportunity. For example, the RX WTRU may determine to multiplex multiple PSFCHs in the time domain in the same PSFCH transmission opportunity based on and / or in response to the RX WTRU determining a PSFCH transmission opportunity at the end of the same COT, such as Figure 3 The RX WTRU may determine the PFSCH transmission opportunities, e.g., symbol positions, in the PSFCH slots in ascending order of the transmission indexes of the associated PSCCH / PSSCH transmissions in the COT. The RX WTRU may send a sequence for HARQ NACK at the determined PSFCH transmission opportunities corresponding to the transmission indexes that were missed, e.g., due to an inability to receive and / or decode the SCI of the PSSCH / PSCCH transmissions.

[0248] In various embodiments, the RX WTRU may determine a combination, group, or set (collectively, a "set") of one or more PSFCH transmission opportunities for an associated PSSCH / PSCCH transmission. The RX WTRU may determine the set of PSFCH transmission opportunities, for example, based on one or more (pre-)configured pool PSFCH transmission opportunities, a PSSCH-to-PSFCH offset, and a HARQ delay boundary. By way of example, the RX WTRU may determine as a member (e.g., as an initial member) in a set of PSFCH transmission opportunities ("first PSFCH transmission opportunity") one of the (pre-)configured pool PSFCH transmission opportunities that occurs during a side link time slot after at least a PSSCH-to-PSFCH offset (e.g., in terms of time slots) after an associated PSSCH / PSCCH transmission. For example, the determined first PSFCH transmission opportunity may be one of the (pre-)configured pool PSFCH transmission opportunities, wherein the (pre-)configured pool PSFCH transmission opportunity may occur during a sidelink timeslot that may be later than an associated PSSCH / PSCCH transmission by at least a PSSCH-to-PSFCH offset. In various embodiments, the sidelink timeslot may be the next occurring sidelink timeslot after a PSSCH-to-PSFCH offset, wherein the PSSCH-to-PSFCH offset begins immediately after or otherwise after an associated PSSCH / PSCCH transmission (e.g., a timeslot). The RX WTRU may determine to include in the set of PSFCH transmission opportunities one or more of the (pre-)configured pool PSFCH transmission opportunities that occur between the first PSFCH transmission opportunity and the end of the HARQ delay boundary. For example, the RX WTRU may determine to include in the set of PSFCH transmission opportunities all (pre-)configured pool PSFCH transmission opportunities that occur between the first PSFCH transmission opportunity and the end of the HARQ delay boundary.

[0249] In various embodiments, the RX WTRU may determine that a PSFCH transmission opportunity and an associated PSSCH / PSCCH transmission may be within the same COT (or not within the same COT) based on whether the PSFCH transmission opportunity is located in a PSFCH timeslot that occurs during the COT. Alternatively, the RX WTRU may determine that a PSFCH transmission opportunity and an associated PSSCH / PSCCH transmission may be within the same COT (or not within the same COT) based on whether the PSFCH transmission opportunity is located in a PSFCH timeslot that occurs at a time other than during the COT ("outside the COT"). For example, the RX WTRU may determine that a PSFCH transmission opportunity may be within the same COT with an associated PSSCH / PSCCH transmission based on (e.g., when, conditionally, etc.) that the PSFCH timeslot that includes the PSFCH transmission opportunity may be within the remaining duration of the COT indicated in the SCI of the PSSCH / PSCCH transmission. Alternatively, the RX WTRU may determine that the PSFCH transmission opportunity may be outside the COT based on (e.g., when, conditionally, etc.) that the PSFCH transmission opportunity occurs during a PSFCH time slot that occurs outside the remaining duration of the COT indicated in the SCI for the PSSCH / PSCCH transmission or outside any other (e.g., earlier) portion of the COT. As another alternative, the RX WTRU may determine that the PSFCH transmission opportunity may be outside the COT based on (e.g., when, conditionally, etc.) that the PSFCH time slot including the PSFCH transmission opportunity occurs outside the remaining duration of the COT indicated in the SCI for the PSSCH / PSCCH transmission or outside any other (e.g., earlier) portion of the COT. The PSFCH transmission opportunity may be outside the COT during which PSSCH / PSCCH transmission occurs based on (e.g., when, conditionally, etc.) that the PSFCH time slot is outside the COT.

[0250] In various embodiments, the RX UE may perform channel access (e.g., LBT channel access) in conjunction with (e.g., after, at, at, based on, in response to, conditional on, etc.) a PSFCH transmission opportunity and an associated PSSCH / PSCCH transmission being within the same COT (may be, may be determined to be, determined to be within the same COT, etc.). For example, the RX WTRU may (i) determine that a PSFCH transmission opportunity and an associated PSSCH / PSCCH transmission are likely to be within the same COT based on the PSFCH transmission opportunity being within a PSFCH timeslot occurring during the COT, and (ii) perform channel access (e.g., LBT channel access) based on (e.g., in response to, conditional on, etc.) the determination.

[0251] In various embodiments, the RX UE may perform a Type 2 LBT channel access (e.g., any of a Type 2A channel access, a Type 2B channel access, and a Type 2C channel access ("Type 2A / 2B / 2C")) when (e.g., conditionally, etc.) a PSFCH transmission opportunity and an associated PSSCH / PSCCH transmission may be within the same COT. For example, the RX WTRU may (i) determine that the PSFCH transmission opportunity and the associated PSSCH / PSCCH transmission may be within the same COT based on the PSFCH transmission opportunity being in a PSFCH timeslot occurring during the COT, and (ii) perform a Type 2 LBT channel access (e.g., Type 2A / 2B / 2C) based on (e.g., in response to, conditionally, etc.) the determination.

[0252] In various embodiments, the RX WTRU may receive a PSSCH / PSCCH transmission in a first COT and may perform a Type 1 LBT channel access to initiate a second COT when (e.g., conditionally, etc.) a PSFCH transmission opportunity may occur after the first COT. For example, the RX WTRU may (i) determine that a PSFCH transmission opportunity may occur after the first COT, for example, based on the PSFCH transmission opportunity being in a PSFCH time slot that occurs after the first COT, (ii) perform a Type 1 LBT channel access based on (e.g., in response to, conditionally, etc.) determining to initiate a second COT, and / or (iii) perform a PSFCH transmission during the second COT and the PSFCH transmission opportunity (or other PSFCH transmission opportunities that may occur during the second COT).

[0253] In various embodiments, the RX WTRU may perform a Type 2 LBT channel access (e.g., Type 2A / 2B / 2C) when (e.g., conditional on, etc.) a PSFCH transmission opportunity may be within a new COT initiated by the TX WTRU that sent the associated PSSCH / PSCCH transmission. For example, the TX WTRU may request a PSFCH transmission at a PSFCH transmission opportunity within the new COT. For example, the TX WTRU may indicate a HARQ poll in the SCI to request a PSFCH transmission at a PSFCH transmission opportunity within the new COT. The RX UE WTRU may perform a Type 2 LBT channel access (e.g., Type 2A / 2B / 2C) based on (e.g., in response to, conditional on, etc.) a HARQ poll in the SCI.

[0254] In various embodiments, the RX WTRU may perform channel access prior to a PSFCH transmission opportunity (e.g., one or more PSFCH transmission opportunities that may be (may be determined to be, may be determined to be, etc.) members of a set of PSFCH transmission opportunities ("member PSFCH transmission opportunities"). For example, the RX UE WTRU may perform channel access prior to a first PSFCH transmission opportunity and / or any other member PSFCH transmission opportunities among the member PSFCH transmission opportunities that occur between the first PSFCH transmission opportunity and an end of a HARQ delay boundary.

[0255] In various embodiments, the RX WTRU may not be able to access the channel before one of a plurality of PSFCH transmission opportunities and may perform channel access before another (e.g., next in time) PSFCH transmission opportunity among the plurality of PSFCH transmission opportunities (e.g., between two PSFCH transmission opportunities among the plurality of PSFCH transmission opportunities). For example, the RX WTRU may not be able to access the channel before one of the PSFCH transmission opportunities that may be (may be determined to be, may be determined to be, etc.) a member of a set of PSFCH transmission opportunities (each, a "member PSFCH transmission opportunity") and may perform channel access before another (e.g., next in time) member PSFCH transmission opportunity among the member PSFCH transmission opportunities.

[0256] In various embodiments, the RX WTRU may attempt to access the channel in conjunction with at least one of the member PSFCH transmission opportunities and may be unable to access the channel at a time in the set of PSFCH transmission opportunities used (e.g., at any time before the end of the most recently occurring member PSFCH transmission opportunity).

[0257] In various embodiments, the RX WTRU may perform channel access and acquire the COT to perform PSSCH / PSCCH transmission in conjunction with the RX WTRU (e.g., its buffer) having data to transmit (may have data, may be determined to have data, is determined to have data, etc.) (e.g., data available for transmission) (e.g., after, at, at, based on, in response to, conditional on, etc.). The RX WTRU may perform PSFCH transmissions at member PSFCH transmission opportunities that occur within the COT.

[0258] In various embodiments, the RX WTRU may attempt to access the channel in conjunction with at least one of the member PSFCH transmission opportunities to transmit at least some of the data, and may be unable to access the channel at a time in the set of used PSFCH transmission opportunities (e.g., at any time before the end of the most recently occurring member PSFCH transmission opportunity). In various embodiments, the RX WTRU may discard HARQ state information and data (e.g., flush HARQ buffers) based on and / or in response to being unable to access the channel within a period of time (e.g., at a time in the set of used PSFCH transmission opportunities).

[0259] In various embodiments, the TX WTRU may monitor PSFCH transmissions during one or more (e.g., each) of the member PSFCH transmission opportunities (e.g., during a first PSFCH transmission opportunity and / or one or more of the member PSFCH transmission opportunities that occur between the first PSFCH transmission opportunity and the end of the HARQ delay boundary). In various embodiments, based on and / or in response to monitoring the PSFCH transmissions during the member PSFCH transmission opportunities, the TX UE may be unable to receive the PSFCH transmissions (e.g., may be unable to receive the PSFCH transmissions at any time before the end of the last occurring member PSFCH transmission opportunity). The TX UE may be unable to receive the PSFCH transmissions based on and / or in response to the RX WTRU being unable to access the channel to transmit data at a time using the set of PSFCH transmission opportunities or due to other reasons (such as channel conditions). In various embodiments, the TX WTRU may perform a retransmission of the associated PSSCH / PSCCH transmission based on and / or in response to not receiving the PSFCH transmissions during the monitored member PSFCH transmission opportunities.

[0260] In various embodiments, the RX WTRU may indicate / report channel access failure information, for example, to a higher layer. For example, the channel access failure information may include information (and / or a cause code, etc.) indicating that the RX WTRU was unable to access the channel, for example, based on and / or in response to performing an LBT channel access. The RX WTRU may indicate / report channel access failure information, for example, based on and / or in conjunction with an inability to access the channel after attempting channel access in conjunction with a PSFCH transmission opportunity. For example, the RX WTRU may indicate / report channel access failure information based on and / or in conjunction with an inability to access the channel after attempting channel access in conjunction with a single PSFCH transmission opportunity (e.g., a single PSFCH transmission opportunity in a set of PSFCH transmission opportunities). Alternatively and / or additionally, the RXUE WTRU may indicate / report channel access failure information based on and / or in conjunction with an inability to access the channel after attempting channel access in conjunction with more than one PSFCH transmission opportunities (e.g., two or more PSFCH transmission opportunities in a set of PSFCH transmission opportunities). The channel access failure information may include information indicating any one of an identification, context and / or details of a corresponding PSFCH transmission opportunity for at least one PSFCH transmission opportunity among more than one PSFCH transmission opportunities. Alternatively and / or additionally, the RX UE may indicate / report the channel access failure information based on and / or in conjunction with the time of any one of the multiple PSFCH transmission opportunities before the end of using the HARQ delay boundary (e.g., any time before the end of the last occurring member PSFCH transmission opportunity in the set of PSFCH transmission opportunities) being unable to access the channel. Alternatively and / or additionally, the RX UE may indicate / report the channel access failure information based on and / or in conjunction with the inability to perform PSFCH transmission within a time period due to the inability to access the channel after a single attempt or more than one attempt (e.g., as disclosed herein). For example, the RX UE may indicate / report channel access failure information based on and / or in combination with the inability to perform PSFCH transmission due to the inability to access the channel at any PSFCH transmission opportunity among multiple PSFCH transmission opportunities before the end of using the HARQ delay boundary (for example, any time before the end of the last occurring member PSFCH transmission opportunity in the set of PSFCH transmission opportunities).

[0261] The RX WTRU may determine the frequency resource for the PSFCH transmission in the determined PSFCH transmission opportunity. In various embodiments, the frequency resource for the PSFCH transmission may be a PSFCH RB interlace represented by index m, for example, as disclosed above. The RX WTRU may be (pre-)configured with M PSFCH RB interlaces in a resource pool. The RX WTRU may determine such a PSFCH RB interlace index for the PSFCH based on and / or in response to any of various criteria, factors, and / or other information. The criteria, factors, and / or other information may include, for example, one or more of the following:

[0262] (e.g., as indicated in the SCI transmitted by the associated PSSCH / PSCCH)

[0263] HARQ transmission index;

[0264] SL logical slot index of the associated PSSCH / PSCCH transmission;

[0265] One or more indices of one or more RB interlaces used by the associated PSSCH / PSCCH transmission;

[0266] The WTRU source ID of the TB carried in the associated PSSCH / PSCCH transmission; and

[0267] • The WTRU destination ID of the TB carried in the associated PSSCH / PSCCH transmission.

[0268] In various embodiments, the RX WTRU may determine the PSFCH RB interlace index by performing a modulo operation of (HARQ transmit index) MOD (total number of PSFCH RB interlaces). As an example, the SCI may include an n-bit HARQ transmit index indication, and the TX WTRU may include up to 2 bits in the COT. nHARQ-enabled PSSCH / PSCCH transmissions. In various embodiments, the RX WTRU may determine the PSFCH RB interlace index by performing a modulo operation of (index of the logical timeslot in which the associated PSSCH / PSCCH transmission may be received) MOD (total number of PSFCH RB interlaces). In various embodiments, the RX WTRU may determine the PSFCH RB interlace index based on a (pre-)configured mapping between PSSCH / PSCCH and PSFCH RB interlaces. When the RX WTRU may perform a PSFCH transmission associated with PSSCH / PSCCH transmissions from multiple TX WTRUs, the RX WTRU may determine the PSFCH RB interlace index by performing a modulo operation of (value of the TX WTRU source and / or destination ID) MOD (total number of PSFCH RB interlaces).

[0269] In various embodiments, the WTRU may be (pre-)configured with a sequence-based format for PSFCH communication. The WTRU may be (pre-)configured with one or more sets of PSFCH sequences, for example, a first set of one or more PSFCH sequences indicating HARQ ACK and a second set of one or more PSFCH sequences indicating HARQ NACK. The PSFCH sequences in each set of PSFCH sequences may be different from each other. The WTRU may determine, from one or more (different) PSFCH sequences in one of the first set and the second set, a sequence (i.e., a cyclic shift (CS) index) corresponding to an expected HARQ feedback to be sent in a PRB of a PSFCH interlace in a resource pool (e.g., (pre-)configured) for an associated PSSCH / PSCCH transmission.

[0270] The RX WTRU may determine to send a sequence corresponding to the HARQ reporting information at each RB of the determined PSFCH RB interlace in the determined PSFCH transmission opportunity. As disclosed above, in various embodiments, the RX WTRU may repeat the same sequence that is (pre-)configured as HARQ ACK or HARQ NACK in each RB of the PSFCH RB interlace. In various embodiments, the RX WTRU may send a different time-shifted version of the sequence that is (pre-)configured as HARQ ACK or HARQ NACK in one or more RBs (e.g., each of the RBs) of the PSFCH RB interlace.

[0271] The RX WTRU may determine to multiplex multiple PSFCHs in the frequency domain in the same PSFCH transmission opportunity. For example, the RX WTRU may determine to multiplex multiple PSFCHs in the frequency domain in the same PSFCH transmission opportunity based on and / or in response to the RX WTRU determining a PSFCH transmission opportunity at the end of the same COT, such as Figure 3 As shown in B).

[0272] The RX WTRU may use a different PFSCH RB interlace for each PSFCH transmission. The RX WTRU may allocate power (e.g., an equal amount of power) to each PSFCH transmission. The transmit power available for one or more PSFCH transmissions may be 1 / n of the total available power, where n may be the number of one or more PSFCH transmissions that are (wholly or partially) transmitted simultaneously. The RX WTRU may determine to perform such frequency domain multiplexing based on and / or in response to any of various criteria, factors, and / or other information. For example, the RX WTRU may determine to perform such frequency domain multiplexing based on, in response to, and / or conditional on the RSRP of the associated PSSCH / PSCCH transmissions satisfying (e.g., being greater than) a (pre-)configured threshold. Alternatively and / or additionally, the RX WTRU may determine to perform frequency domain multiplexing based on, in response to, and / or conditional on the distance between the RX WTRU and the TX WTRU satisfying (e.g., being less than) a (pre-)configured threshold. Alternatively and / or additionally, the RX WTRU may determine to perform frequency domain multiplexing based on, in response to and / or conditioned on the number of HARQ feedback bits satisfying a threshold (eg, being less than a (pre-)configured threshold).

[0273] The RX WTRU may use the same or different PFSCH RB interlaces for each PSFCH transmission. The power available for PSFCH transmission may be the same as the total available power and may provide better coverage. The RX WTRU may determine to perform such time domain multiplexing based on any of various criteria, factors and / or other information. For example, the RX WTRU may determine to perform time domain multiplexing based on, in response to, and / or conditional on the RSRP of the associated PSSCH / PSCCH transmission satisfying (e.g., less than) a (pre-)configured threshold. Alternatively and / or additionally, the RX WTRU may determine to perform time domain multiplexing based on, in response to, and / or conditional on the distance between the RX WTRU and the TX WTRU satisfying (e.g., greater than) a (pre-)configured threshold. Alternatively and / or additionally, the RX WTRU may determine to perform time domain multiplexing based on, in response to, and / or conditional on the number of HARQ feedback bits satisfying (e.g., greater than) a (pre-)configured threshold.

[0274] In various embodiments, the RX WTRU may determine to apply PSFCH slot format 4. For example, the RX WTRU may determine to apply PSFCH slot format 4 based on, in response to, and / or conditioned on the RX WTRU intending to perform one or more PSFCH transmissions at the end of the same COT and / or at the end of the same COT. In various embodiments, the RX WTRU may send a PSCCH transmission. The PSCCH transmission may include an SCI. The SCI may include information indicating and / or relating to PSFCH transmissions in the same PSFCH slot. For example, the information indicating and / or relating to the PSFCH transmissions may include information indicating a transmission index corresponding to each of the PSFCH transmissions.

[0275] In various embodiments, PSFCH communication (e.g., one or more PSFCH transmissions) in the same or different COT in which associated PSSCH / PSCCH communication (e.g., one or more PSSCH / PSCCH transmissions) and / or associated retransmission communication (e.g., one or more blind retransmissions) are performed may be performed, used, defined, configured, and / or determined. The WTRU may perform an initial transmission and / or HARQ retransmission of a HARQ-enabled TB. The WTRU may perform one or more retransmissions after the initial transmission and / or HARQ retransmission. The retransmission may be, for example, a set of one or more retransmissions and / or a plurality of consecutive retransmissions or a set of two or more consecutive retransmissions. The retransmission may not (or need not) be triggered by a non-acknowledgement of a previous transmission (e.g., by a HARQ NACK, receipt of a transmission reporting a HARQ NACK, etc.), and may be referred to as a blind retransmission.

[0276] The WTRU may determine to perform and / or may perform blind retransmissions for an initial transmission (e.g., a HARQ-enabled initial transmission) and / or a HARQ retransmission based on, according to, and / or under one or more of various information, conditions, criteria, parameters, etc. The information, conditions, criteria, parameters, etc. may include any of the following:

[0277] The WTRU may have one or more TBs in the buffer for transmission in the COT;

[0278] The WTRU may determine to enable PSFCH sharing in a COT, e.g., enabled PSFCH transmissions and associated initial PSSCH / PSCCH transmissions and / or HARQ retransmissions of a TB in the same COT; and

[0279] QoS, for example, the priority of a TB may meet (eg, may be greater than) a (pre-)configured threshold.

[0280] In various embodiments, the WTRU may determine the number (K) of blind retransmissions of a TB performed in / during the COT. For example, the WTRU may determine the number (K) of blind retransmissions corresponding to the initial transmission of the TB. Alternatively or additionally, the WTRU may determine the number (K) of blind retransmissions corresponding to HARQ retransmissions of the TB. The number (K) of blind retransmissions corresponding to the initial transmission of the TB and the number (K) of blind retransmissions corresponding to the HARQ retransmissions of the TB may be the same number or may be different numbers. Alternatively, the WTRU may determine the number (K) of blind retransmissions corresponding to both the initial transmission of the TB and the HARQ retransmissions of the TB.

[0281] In various embodiments, the WTRU may receive an SCI and a TB transmitted by a PSSCH / PSCCH in a COT. The SCI may indicate (e.g., may include information indicating the following): the availability of PSFCH sharing in the COT (e.g., may indicate that PSFCH sharing is available and / or enabled or not enabled in the same COT as the PSSCH / PSCCH transmission of the TB). The WTRU may determine the number (K) of blind retransmissions of the TB to be performed in / during the COT in conjunction with being notified that PSFCH sharing is available / enabled in the COT (e.g., after, at, at, based on, in response to, conditional on, etc.). The number (K) of blind retransmissions of the TB to be performed in / during the COT may be based on, in accordance with, and / or under one or more of various information, conditions, criteria, parameters, etc. For example, the WTRU may determine the number (K) of blind retransmissions of the TB to be performed in / during the COT based on, in accordance with, under one or more of the following:

[0282] Maximum COT (MCOT) duration;

[0283] PSFCH timing within COT;

[0284] The transmission gap between the PSSCH / PSCCH transmission and the associated PSFCH transmission in the COT (e.g., the (pre-)configured transmission gap); and

[0285] • The amount and / or availability of (e.g. (pre-)configured)) PSFCH time slots, e.g. the periodicity of PSFCH time slots in a resource pool.

[0286] A transmit gap may be (e.g., represented as) a duration (e.g., in μs), one or more logical time slots, a duration equal to one or more logical time slots, a fraction or percentage of the duration of the COT, etc. For example, a transmit gap may be a duration of 25 μs or less, 2 or 3 logical time slots, a duration equal to 2 or 3 logical time slots, two-fifths or three-fifths of the duration of the COT, etc. A transmit gap may be represented in various other ways, e.g., as disclosed below.

[0287] Figure 4 A to Figure 4 B illustrates an example of PSFCH transmission and associated initial transmission and / or blind retransmission during the same COT and / or different COTs. For example, Figure 4 A illustrates an example of an initial transmission and a blind retransmission performed during a COT and an associated PSFCH transmission performed during the same COT. Figure 4 B illustrates an example of an initial transmission and blind retransmission during a COT and an associated PSFCH transmission during the same COT and a different COT (eg, a COT occurring later).

[0288] like Figure 4 A to Figure 4As shown in FIG. 1B , a first WTRU (e.g., a Tx WTRU) may perform a PSSCH / PSCCH transmission of a TB (e.g., a HARQ-enabled TB), and a second WTRU (e.g., an Rx UE) may perform a PSFCH transmission associated with the PSSCH / PSCCH transmission in / during the COT. The first WTRU (e.g., a Tx WTRU) may perform one or more blind retransmissions between the PSSCH / PSCCH transmission and the associated PSFCH transmission. In addition to and / or in contrast to the conventional benefits and / or problems solved by using retransmissions, blind retransmissions have additional benefits and solve other problems. For example, one of the problems solved by retransmissions is the loss of the COT (and the cost involved in having to incur the process of initiating a new COT due to the loss), which will or may occur if the transmission gap between the PSSCH / PSCCH transmission and the associated PSFCH transmission meets a threshold (e.g., greater than 25 μs, such as in a shared spectrum where a new COT is required when there is a transmission gap greater than 25 μs). Retransmissions may prevent the COT from being abandoned or lost (and / or prevent another Tx WTRU from acquiring the channel), for example, by limiting any transmission gap after a PSSCH / PSCCH transmission and before an associated PSFCH transmission to a value that satisfies a threshold (e.g., less than or equal to 25 μs, such as in a shared spectrum where a new COT is required when there is a transmission gap greater than 25 μs). By preventing the abandonment or loss of the COT (or alternatively allowing the COT to be preserved), retransmissions may allow the RX WTRU to determine / process the HARQ ACK / NACK state information during the COT and send the HARQ ACK / NACK in the associated PSFCH transmission (where the benefit is that the PSCCH / PSSCH transmission and the associated PSFCH transmission share the COT).

[0289] In various embodiments, the WTRU may determine the number of blind retransmissions (K) for the initial transmission of a TB based on (according to, among others) a transmission gap (e.g., a (pre-)configured gap) between a PSSCH / PSCCH transmission and an associated PSFCH transmission in the COT. The transmission gap may be as disclosed above and / or may be a fixed value and / or may take into account or be based on the (e.g., assumed) RX WTRU process time of receiving a PSSCH / PSCCH transmission and performing a PSFCH transmission carrying HARQ ACK / NACK information.

[0290] In various embodiments, a PSFCH slot periodicity (e.g., 1 PSFCH slot every X slots in a resource pool) may be used to (pre) configure a PSFCH slot including PSFCH opportunities and resources in a resource pool. The number of logical slots between a PSSCH / PSCCH transmission and an associated PSFCH transmission in a COT may vary, for example, based on (and / or depending on) the PSFCH periodicity and / or the starting logical slot of the COT. The WTRU may determine the number (K) of blind retransmissions for an initial transmission of a TB based on (according to, etc.) the number of logical slots between the initial transmission and the PSFCH slot (e.g., a number equal to the total number of logical slots). The WTRU may determine (and / or be informed of) a PSFCH slot. The PSFCH slot may be, for example, the earliest PSFCH slot. The earliest PSFCH slot may be the PSFCH slot that occurs first in time after the initial transmission according to the PSFCH periodicity. Alternatively, the earliest PSFCH time slot may be the PSFCH time slot that occurs first in time according to the PSFCH periodicity after (i) initial transmission and / or (ii) an amount of time. The amount of time may be (pre)configured and may be based on a processing time (e.g., a minimum processing time, a (pre)configured minimum processing time, etc.). The PSFCH time slot may be a PSFCH time slot that occurs after the earliest PSFCH time slot, e.g., the next occurring PSFCH time slot.

[0291] In various embodiments, the WTRU may receive various transmissions (e.g., one or more blind retransmissions in addition to or in lieu of an initial transmission and / or a HARQ retransmission). The WTRU may determine that the various transmissions may include blind retransmissions based on (depending on, etc.) one or more of various information, conditions, criteria, parameters, etc. The various information, conditions, criteria, parameters, etc. may include, for example, any of a HARQ process ID, an NDI, and an RV indicated in an SCI. Alternatively, the various information, conditions, criteria, parameters, etc. may include information, conditions, criteria, parameters, etc. that may be indicated in an SCI of a current transmission related to an upcoming blind retransmission of the same TB in the same COT, such as, for example:

[0292] a transmission index corresponding to (eg, specific to) the COT of the retransmission;

[0293] The index of the logical time slot to retransmit; and

[0294] The gap between the current transmission and the retransmission in logical time slots.

[0295] In various embodiments, the TX WTRU may perform an initial transmission of a TB or a HARQ retransmission of a TB and then perform one or more blind retransmissions of the TB during the COT, e.g., Figure 4 A to Figure 4 B. The initial transmission may be, for example, an initial PSCCH / PSSCH transmission. Although the embodiments / examples described herein (e.g., above and / or below) may include the use of an initial transmission (e.g., an initial PSCCH / PSSCH transmission) or a HARQ retransmission, the application of the embodiments / examples may use another type of transmission (e.g., an initial blind retransmission) and still be consistent with the disclosure herein. It is also contemplated that other types of transmission may be used in place of the initial transmission, the initial PSCCH / PSSCH transmission and / or the HARQ retransmission or in addition to the initial transmission, the initial PSCCH / PSSCH transmission and / or the HARQ retransmission, and the other types of transmission may still be consistent with the disclosure herein. In addition, to simplify the description, the terms "initial transmission", "initial PSCCH / PSSCH transmission", "HARQ retransmission", etc. may be used interchangeably herein. For example, a HARQ retransmission may replace an initial transmission (and vice versa).

[0296] The RX WTRU may receive an initial transmission of a TB. The RX WTRU may determine a HARQ state (e.g., HARQ-ACK or HARQ-NACK) for the initial transmission of the TB, for example, based on decoding of the initial transmission. The RX WTRU may perform a PSFCH transmission corresponding to the initial transmission in / during the same COT as the initial transmission of the TB. The PSFCH transmission may report (e.g., indicate and / or include information indicating): a HARQ state.

[0297] In various embodiments, the HARQ state may be HARQ-ACK, e.g., Figure 4 A). The HARQ-ACK reported in the PSFCH transmission may indicate that the TB may have been correctly received and / or further action may not (or need to) be taken regarding the HARQ state of the TB. For example, further reporting of the HARQ state of the transmitted TB by the Rx WTRU and / or HARQ retransmission by the Tx WTRU may not be performed (or further reporting of the HARQ state of the transmitted TB by the Rx WTRU and / or HARQ retransmission by the Tx WTRU may not (or need to) be performed).

[0298] In various embodiments, the HARQ state may be HARQ-NACK, e.g. Figure 4B. The TX WTRU may not (or need not) perform a corresponding HARQ retransmission in conjunction with reporting a HARQ-NACK in / by a PSFCH transmission (e.g., after, at, at, based on, in response to, conditional on, etc.). In various embodiments, the RX WTRU may receive one or more of the blind retransmissions of the TB. The RX WTRU may determine the HARQ state (e.g., HARQ-ACK or HARQ-NACK) for the TB based on the decoding of the initial transmission of the TB and one or more of the blind retransmissions. For example, the RX WTRU may combine the decoding results of the received transmissions to improve the reception of the TB. The RX WTRU may perform a PSFCH transmission in the same COT in which the initial transmission and the blind retransmission are performed or in a COT that occurs after the COT in which the initial transmission and the blind retransmission are performed. For simplicity of explanation herein, the COT in which the initial transmission and blind retransmission are performed may be referred to as the “first COT”, the PSFCH transmission occurring during the first COT may be referred to as the “first PSFCH transmission”, the COT occurring after the first COT may be referred to as the “second COT”, and the PSFCH transmission occurring during the second COT may be referred to as the “second PSFCH transmission”. The second COT may be performed by the RX WTRU (e.g., Figure 4 B) or initiated and / or shared by the TX WTRU.

[0299] The second PSFCH transmission may report (e.g., indicate and / or include information indicating the following): a HARQ state. In various embodiments, the HARQ state may be a HARQ-ACK. The HARQ-ACK reported in / by the second PSFCH transmission may indicate that the TB may have been correctly received and / or that further action may not (or need not) be taken regarding the HARQ state of the TB. For example, further reporting of the HARQ state of the transmitted TB by the Rx WTRU and / or HARQ retransmissions by the Tx WTRU may not be performed (or further reporting of the HARQ state of the transmitted TB by the Rx WTRU and / or HARQ retransmissions by the Tx WTRU may not (or need not) be performed).

[0300] In various embodiments, the HARQ state may be HARQ-NACK, e.g. Figure 4B. The TX WTRU may perform corresponding HARQ retransmissions of the TB in conjunction with reporting the HARQ-NACK in / by the second PSFCH transmission (e.g., after, at, at, based on, in response to, conditional on, etc.). The TX WTRU may perform corresponding HARQ retransmissions in / during a second COT (the same COT in which the second PSFCH transmission occurs). Alternatively or additionally, the TX WTRU may perform corresponding HARQ retransmissions in / during a COT subsequent to the second COT. The COT subsequent to the second COT ("third COT") may be initiated and / or shared by the TX WTRU (or RX WTRU).

[0301] In various embodiments, the TX WTRU may receive a second PSFCH transmission. For example, the TX WTRU may receive a second PSFCH transmission that is performed during the first COT or that is performed during the second COT. If the second PSFCH transmission is performed during the first COT, the TX WTRU may receive the second PSFCH transmission during the first COT (e.g., as adjusted by timing advance, etc.). Alternatively, if the second PSFCH transmission is performed during the second COT, the TX WTRU may receive the second PSFCH transmission during the second COT (e.g., as adjusted by timing advance, etc.).

[0302] The TX WTRU may determine, for example, based on (according to, etc.) various information, conditions, criteria, parameters, etc. that the HARQ state information reported in / by the second PSFCH transmission (e.g., indicated by and / or included in the second PSFCH transmission) may correspond to the PSSCH / PSCCH transmission of the TB performed during the first COT. For example, the information, conditions, criteria, parameters, etc. may include information associated with the TB and indicated in the SCI of the PSSCH / PSCCH transmission, such as one or more of the following:

[0303] HARQ process ID

[0304] Source ID (e.g., ID of the source WTRU / ID associated with the source WTRU (WTRU Source ID));

[0305] • Destination ID (e.g., the ID of the destination WTRU / an ID associated with the destination WTRU (WTRU Destination ID));

[0306] One or more frequency resources (e.g., one or more RB interlace indices);

[0307] Send index;

[0308] COT index; and

[0309] • The index of the logical timeslot in which the transmission of the TB is performed.

[0310] In one example, the source ID (e.g., WTRU source ID), destination ID (e.g., WTRU destination ID), and / or HARQ process ID may be explicitly indicated in the SCI associated with the PSFCH transmission. In another example, the TX WTRU may perform such a determination based on an implicit association between the PSFCH resource and one or more of the information, conditions, criteria, parameters, etc. (e.g., one or more of the information associated with the TB and indicated in the SCI of the PSSCH / PSCCH transmission). The PSFCH resource may be an index of a PSFCH RB interlace and / or an index of a PRB within a PSFCH RB interlace.

[0311] In various embodiments, PSFCH communication (e.g., one or more PSFCH transmissions) and HARQ state communication (e.g., one or more HARQ state transmissions) in the same or different COTs in which associated initial communication (e.g., one or more initial transmissions) and / or associated retransmission communication (e.g., one or more blind retransmissions) are performed may be performed, used, defined, configured, and / or determined. Each HARQ state transmission (or one or more HARQ state transmissions) in the HARQ state transmissions may include a MAC control element (MAC CE). The MAC CE may include a bit field. The bit field may include entries corresponding to initial transmissions and blind retransmissions, for example, entries corresponding to initial transmissions of a TB in a COT and corresponding blind retransmissions of the TB.

[0312] Figure 5 A to Figure 5 B illustrates an example of initial transmission and blind retransmission during COT, as well as associated PSFCH transmission and associated hybrid automatic repeat request (HARQ) state transmission. Figure 5 A to Figure 5 B(and Figure 4 A to Figure 4 B), a first WTRU (e.g., a Tx WTRU) may perform an initial transmission of a TB (e.g., a HARQ-enabled TB). The first WTRU (e.g., a Tx WTRU) may perform one or more blind retransmissions between the initial transmission and the associated PSFCH transmission. Blind retransmissions have additional benefits and solve other problems in addition to and / or in contrast to conventional benefits and / or problems solved by using retransmissions. Benefits and / or problems solved by using blind retransmissions include those disclosed herein (e.g., disclosed below).

[0313] In various embodiments, the RX WTRU may receive an initial transmission of a TB. The RX WTRU may determine a HARQ state (e.g., HARQ-ACK or HARQ-NACK) for the initial transmission of the TB, for example, based on decoding the initial transmission. The RX WTRU may perform a PSFCH transmission to report (e.g., indicate and / or include information indicating the following): a HARQ state.

[0314] In various embodiments, the HARQ state may be a HARQ-ACK. The HARQ-ACK reported in the PSFCH transmission may indicate that the TB may have been correctly received and / or further action may not (or need not) be taken regarding the HARQ state of the TB. For example, further reporting of the HARQ state of the transmitted TB by the Rx WTRU and / or HARQ retransmissions by the Tx WTRU may not be performed (or further reporting of the HARQ state of the transmitted TB by the Rx WTRU and / or HARQ retransmissions by the Tx WTRU may not (or need not) be performed).

[0315] In various embodiments, the HARQ state may be HARQ-NACK, e.g. Figure 5 A to Figure 5 B. The TX WTRU may not (or need not) perform a corresponding HARQ retransmission in conjunction with reporting a HARQ-NACK in / by a PSFCH transmission (e.g., after, at, at, based on, in response to, conditional on, etc.). In various embodiments, the RX WTRU may receive one or more of the blind retransmissions of the TB. The RX WTRU may determine the HARQ state (e.g., HARQ-ACK or HARQ-NACK) for the TB based on decoding of the initial transmission of the TB and one or more of the blind retransmissions. For example, the RX WTRU may combine the decoding results of the received transmissions to improve reception of the TB.

[0316] The Rx WTRU may report the HARQ ACK / NACK status using one or more MAC CEs carried in / by one or more PSSCH / PSCCH transmissions performed during the same COT in which the initial transmission and blind retransmission are performed. In this solution, the PSSCH / PSCCH transmissions of the RX WTRU may preserve the COT, for example by performing PSSCH / PSCCH transmissions such that all transmission gaps after a PSFCH transmission reporting HARQ-ACK (e.g., indicating HARQ-ACK and / or including information indicating HARQ-ACK) and before (if any) a PSSCH / PSCCH transmission and / or between (if any) PSSCH / PSCCH transmissions are restricted to a value (duration) that satisfies a threshold (e.g., less than or equal to 25 μs, such as in a shared spectrum where a new COT is required when there is a transmission gap greater than 25 μs). The MAC CE for HARQ status information reporting may be enabled and / or disabled based on (pre-) configuration in a resource pool.

[0317] In various embodiments, the RX WTRU may include data (e.g., data intended for the TX WTRU (buffered and / or available data)) in one or more of the PSSCH / PSCCH transmissions along with the HARQ state information. For example, the RX WTRU may multiplex (piggyback or otherwise combine) the HARQ state information (e.g., one or more of the HARQ state MAC CEs) with the data (e.g., data intended for the TX WTRU (buffered and / or available data)) and may include the combination of the HARQ state information and the data in one or more of the PSSCH / PSCCH transmissions. Alternatively, the RX WTRU may include the HARQ state information in one or more of the PSSCH / PSCCH transmissions independently of (and together with) the data. The RX WTRU may perform one or more PSSCH / PSCCH transmissions carrying data (e.g., data (buffered and / or available data) intended for the TX WTRU) independently of a PSSCH / PSCCH transmission carrying HARQ state information (e.g., in the same COT or a different COT). The PSSCH / PSCCH transmissions may include HARQ state information without the data. The RX WTRU may not (or need not) include data in any of the PSSCH / PSCCH transmissions carrying HARQ state information (e.g., when all of the data (buffered and / or available data) intended for the TX WTRU is included in one or more PSSCH / PSCCH transmissions of a previously performed PSSCH / PSCCH transmission, when there is no data (buffered and / or available data) intended for the TX WTRU, and / or even if data (buffered data) intended for the TX WTRU may be transmitted). For simplicity of explanation, it is assumed herein that transmission carrying (including) HARQ state information may refer to transmission carrying (including) HARQ state information and data (and vice versa).

[0318] In various embodiments, the RX WTRU may include data (e.g., data intended for the TX WTRU (buffered and / or available data)) in one or more of the PSSCH / PSCCH transmissions together with one or more HARQ STATUS MAC CEs in the HARQ STATUS MAC CE. For example, the RX WTRU may multiplex (piggyback or otherwise combine) one or more of the HARQ STATUS MAC CEs with the data (e.g., data intended for the TX WTRU (buffered and / or available data)) and may include the combination of the one or more HARQ STATUS MAC CEs and the data in one or more of the PSSCH / PSCCH transmissions. Alternatively, the RX WTRU may include one or more HARQ STATUS MAC CEs independently of (and together with) the data in one or more of the PSSCH / PSCCH transmissions. The RX WTRU may perform one or more PSSCH / PSCCH transmissions carrying data (e.g., data intended for the TX WTRU (buffered and / or available data)) independently of the PSSCH / PSCCH transmission carrying the HARQ STATUS MAC CE (e.g., in the same COT or a different COT). The PSSCH / PSCCH transmission may include the HARQ STATUS MAC CE without the data. The RX WTRU may not (or need not) include data in any of the PSSCH / PSCCH transmissions carrying the HARQ STATUS MAC CE (e.g., when all of the data intended for the TX WTRU (buffered and / or available data) is included in one or more PSSCH / PSCCH transmissions in the previously performed PSSCH / PSCCH transmissions, when there is no data intended for the TX WTRU (buffered and / or available data), and / or even if data intended for the TX WTRU (buffered data) may be transmitted). To simplify the explanation, it is assumed herein that transmission carrying (including) one or more HARQ state MAC CEs may refer to transmission carrying (including) one or more HARQ state MAC CEs and data (and vice versa).

[0319] In various embodiments, the PSSCH / PSCCH transmission carrying the HARQ status MAC CE may be (or include) two or more PSSCH / PSCCH transmissions performed sequentially and / or continuously. The RX WTRU may perform sequential PSSCH / PSCCH transmissions such that all transmission gaps between sequential PSSCH / PSCCH transmissions (or sequential and consecutive PSSCH / PSCCH transmissions) are limited to a value (duration) that satisfies a threshold (e.g., less than or equal to 25 μs, such as in a shared spectrum where a new COT is required when there is a transmission gap greater than 25 μs).

[0320] In various embodiments, the RX WTRU may determine the HARQ state (e.g., HARQ-ACK or HARQ-NACK) for the TB based on the decoding (decoding result) of the initial transmission of the TB and one of the blind retransmissions. For example, the RX WTRU may determine the HARQ state for the TB based on the decoding result of the initial transmission and the blind retransmission that the RX WTRU receives first in time ("first blind retransmission") among the blind retransmissions. The first blind retransmission may be / correspond to the blind retransmission that the TX WTRU performs first in time among the blind retransmissions ("first blind retransmission in time"). Alternatively, the first blind retransmission may be / correspond to the blind retransmission that the TX WTRU performs after the first blind retransmission in time among the blind retransmissions.

[0321] In various embodiments, the RX WTRU may determine the HARQ state (e.g., HARQ-ACK or HARQ-NACK) for the TB based on the decoding (decoding results) of the initial transmission of the TB and some of the blind retransmissions in the blind retransmissions. For example, the RX WTRU may determine the HARQ state for the TB based on the decoding results of the initial transmission, the first blind retransmission, and / or (in the blind retransmissions) one or some of the blind retransmissions received by the RX WTRU after the first blind retransmission ("second blind retransmission"). The second blind retransmission may be / correspond to one or some of the blind retransmissions performed by the TX WTRU after the first blind retransmission in time in the blind retransmissions. For example, the second blind retransmission may be / correspond to one or some of the blind retransmissions performed by the TX WTRU in time after the first blind retransmission in time in the blind retransmissions.

[0322] In various embodiments, the RX WTRU may determine the HARQ state (e.g., HARQ-ACK or HARQ-NACK) for the TB based on the decoding (decoding results) of the initial transmission of the TB and all blind retransmissions received by the RX WTRU in the blind retransmissions. For example, the RX WTRU may determine the HARQ state for the TB based on the decoding results of the initial transmission, the first blind retransmission, and / or all second blind retransmissions in the second blind retransmission.

[0323] In various embodiments, the HARQ state MAC CE (in the HARQ state MAC CE) carried by (e.g., each) PSSCH / PSCCH transmission (in the PSSCH / PSCCH transmission) may include a single entry or two or more entries, which may indicate a HARQ state corresponding to any one of the following: (i) an initial transmission and one or more blind retransmissions in a blind retransmission or (ii) two or more blind retransmissions in a blind retransmission. For example, the HARQ state MAC CE carried by one PSSCH / PSCCH transmission in the PSSCH / PSCCH transmission may include a single entry or two or more entries, which may indicate a HARQ state corresponding to any one of the following: (i) an initial transmission and a first blind retransmission, (ii) a first blind retransmission and a second blind retransmission, or (iii) two second blind retransmissions. For example, the HARQ state MAC CE may include: a first entry, which may indicate a HARQ state corresponding to the initial transmission; and a second entry, which may indicate a HARQ state corresponding to the first blind retransmission. Alternatively, the HARQ state MAC CE may include: a first entry, which may indicate a HARQ state corresponding to a first blind retransmission; and a second entry, which may indicate a HARQ state corresponding to a second blind retransmission. Alternatively, the HARQ state MAC CE may include: a first entry, which may indicate a HARQ state corresponding to a first first blind retransmission of two second blind retransmissions; and a second entry, which may indicate a HARQ state corresponding to a second second blind retransmission of the second blind retransmission. The HARQ state MAC CE may include (e.g., may also include) one or more fields corresponding to transmissions (e.g., one or more of the initial transmission and / or blind retransmissions) for which the HARQ state is not determined and / or reported. Those fields may have empty or default entries. The one PSSCH / PSCCH transmission may be the PSSCH / PSCCH transmission of the PSSCH / PSCCH transmission that occurs first in time, or the PSSCH / PSCCH transmission that occurs thereafter.

[0324] For another example, the HARQ state MAC CE carried by one of the PSSCH / PSCCH transmissions may include a single entry or two or more entries, which may indicate HARQ states corresponding to three or more of the following: (i) initial transmission, (ii) first blind retransmission, and (iii) one or more second blind retransmissions. For example, the HARQ state MAC CE may include: a first entry, which may indicate the HARQ state corresponding to the initial transmission; a second entry, which may indicate the HARQ state corresponding to the first blind retransmission; and one or more third entries, which may indicate the HARQ state corresponding to the one or more second blind retransmissions. The HARQ state MAC CE carried by one of the PSSCH / PSCCH transmissions may include any of other permutations / combinations of single and multiple entries (including, for example, a single entry or multiple entries that may indicate the HARQ state corresponding to three or more of the initial transmission, the first blind retransmission, and the one or more second blind retransmissions) that may indicate the HARQ state corresponding to three or more of the initial transmission, the first blind retransmission, and the one or more second blind retransmissions. The HARQ state MAC CE may include (for example, may also include) one or more fields corresponding to transmissions for which the HARQ state is not determined and / or reported (for example, one or more of the initial transmission and / or the blind retransmission), and those fields may have empty or default entries. The one PSSCH / PSCCH transmission may be the PSSCH / PSCCH transmission that occurs first in time among the PSSCH / PSCCH transmissions, or the PSSCH / PSCCH transmission that occurs thereafter.

[0325] In various embodiments, the RX WTRU may determine the HARQ state of the TB based on (e.g., using) one, some, or all of the blind retransmissions that may occur N logical time slots earlier than the logical time slot in which one of the PSSCH / PSCCH transmissions carrying the associated HARQ state MAC CE may be performed. For example, the RX WTRU may determine multiple HARQ states for the TB (e.g., in conjunction with each of the PSSCH / PSCCH transmissions carrying the HARQ state MAC CE), where each successive HARQ state of the multiple HARQ states may be determined based on an initial transmission and an increasing number of blind retransmissions. The HARQ state MAC CE of the first PSSCH / PSCCH transmission in the PSSCH / PSCCH transmission may indicate the HARQ state corresponding to all blind retransmissions that occur N logical time slots earlier than the logical time slot in which the first PSSCH / PSCCH transmission in the PSSCH / PSCCH transmission can be performed, the HARQ state MAC CE of the second PSSCH / PSCCH transmission in the PSSCH / PSCCH transmission may indicate the HARQ state corresponding to all blind retransmissions that occur N+1 logical time slots earlier than the logical time slot in which the second PSSCH / PSCCH transmission in the PSSCH / PSCCH transmission can be performed, and so on.

[0326] refer to Figure 5 A, N may be equal to 2. The RX WTRU may determine a first HARQ state of the two HARQ states based on the combined decoding results of the initial transmission and the first blind retransmission. The RX WTRU may include the first HARQ state in the first PSSCH / PSCCH transmission in the PSSCH / PSCCH transmission. As shown, the first HARQ state may be HARQ-NACK. The RX WTRU may determine a second HARQ state of the two HARQ states based on the combined decoding results of the initial transmission and the first blind retransmission and the second blind retransmission. The RX WTRU may include the second HARQ state in the second PSSCH / PSCCH transmission in the PSSCH / PSCCH transmission. As shown, the second HARQ state may be HARQ-ACK. Figure 5In the example shown in A, the RX WTRU may perform reporting of HARQ state information derived from an initial transmission of a TB in / during the same COT and two blind retransmissions in the blind retransmission. The HARQ-ACK reported in / in the HARQ state MAC CE carried by / in the second PSSCH / PSCCH transmission may indicate that the TB may have been correctly received and / or further action may not (or may not) be taken regarding the HARQ state of the TB. For example, further reporting of the HARQ state of the transmitted TB by the Rx WTRU and / or HARQ retransmission by the Tx WTRU may not be performed (or further reporting of the HARQ state of the transmitted TB by the Rx WTRU and / or HARQ retransmission by the Tx WTRU may not (or may not) be performed).

[0327] Although in Figure 5 A(and / or Figure 5 B), but the RX WTRU may determine that the HARQ state based on the combined decoding results of the initial transmission and the first blind retransmission may be HARQ-ACK (e.g., instead of HARQ-NACK). The RX WTRU may indicate / include the HARQ-ACK in a PSSCH / PSCCH transmission performed (e.g., at the logical slot N+2 after the logical slot in which the first blind retransmission occurred). The HARQ-ACK reported in / by the HARQ Status MAC CE carried by / in the PSSCH / PSCCH transmission may indicate that the TB may have been received correctly and / or that no further action may (or need to) be taken regarding the HARQ state of the TB. For example, further reporting of the HARQ status of the transmitted TB by the Rx WTRU and / or HARQ retransmission by the Tx WTRU may not be performed (or further reporting of the HARQ status of the transmitted TB by the Rx WTRU and / or HARQ retransmission by the Tx WTRU may not be performed (or may not be required)).

[0328] Alternatively, the RX WTRU may determine that the first HARQ state based on the combined decoding results of the initial transmission and the first blind retransmission may be HARQ-ACK, and may continue to receive / process the second blind retransmission and / or determine the second HARQ state of the TB based on (i) the initial transmission and the second blind retransmission or (ii) the decoding results of the first blind retransmission and the second blind retransmission. The second HARQ state may be HARQ-ACK. The RX WTRU may indicate / include the second HARQ-ACK (instead of the first HARQ-ACK) in the PSSCH / PSCCH transmission performed (e.g., at the logical time slot N+2 after the logical time slot in which the first blind retransmission occurred). Alternatively, the RX WTRU may indicate / include a first HARQ-ACK in a first PSSCH / PSCCH transmission among PSSCH / PSCCH transmissions performed (e.g., at a logical time slot N+2 after a logical time slot in which a first blind retransmission occurs), and may indicate / include a second HARQ-ACK in a second PSSCH / PSCCH transmission among PSSCH / PSCCH transmissions performed (e.g., at a logical time slot N+3 after a logical time slot in which a first blind retransmission occurs). In various embodiments, the first PSSCH / PSCCH transmission may be performed to preserve the COT and / or the first HARQ-ACK in the first PSSCH / PSCCH transmission may be ignored by the TX WTRU.

[0329] exist Figure 5 In the example shown in B, the RX WTRU may perform reporting of HARQ state information derived from the initial transmission of a TB in the same COT and all blind retransmissions in the blind retransmission. As shown, the HARQ-NACK may be reported in each HARQ state MAC CE for all PSSCH / PSCCH transmissions. The TX WTRU may perform HARQ retransmissions in a new COT initiated or shared by the TX WTRU in conjunction with reporting the HARQ-NACK in each HARQ state MAC CE for all PSSCH / PSCCH transmissions (e.g., after, at, at the time of, based on, in response to, conditional on, etc.). Although Figure 5 B shows three PSSCH / PSCCH transmissions, but more or less than three PSSCH / PSCCH transmissions may be performed. In another solution, the TX WTRU may perform HARQ retransmissions during the time slot after the last of the PSSCH / PSCCH transmissions carrying the HARQ MAC CE.

[0330] In various embodiments, PSFCH communications (e.g., one or more PSFCH transmissions) in the same or different COTs in which associated initial communications (e.g., one or more initial transmissions), associated retransmission communications (e.g., one or more blind retransmissions), associated PSSCH / PSCCH communications (e.g., one or more associated PSSCH / PSCCH transmissions), and / or HARQ retransmission communications (e.g., one or more HARQ retransmissions) are performed may be performed, used, defined, configured, and / or determined. For example, multiple PSFCH transmissions carrying consecutive HARQ state information corresponding to a combination of initial transmissions, blind retransmissions, and / or HARQ retransmissions may be performed, used, defined, configured, and / or determined.

[0331] Figure 6 A to Figure 6 B illustrates an example of initial transmission, blind retransmission, and PSSCH / PSCCH transmission and associated PSFCH transmission during one or more COTs. Figure 6 A illustrates an example of an initial transmission, a blind retransmission, and a PSSCH / PSCCH transmission during a COT, and an associated PSFCH transmission during the same COT. Figure 6 B illustrates an example of initial transmission, blind retransmission, and PSSCH / PSCCH transmission during a COT, and associated PSFCH transmission during the same COT and a different COT (a COT occurring later).

[0332] In various embodiments, the WTRU may report the HARQ ACK / NACK status of a TB in multiple PSFCH transmissions performed within the same COT, where the associated PSSCH / PSCCH transmissions include initial transmissions, blind retransmissions, and / or HARQ retransmissions (e.g., Figure 6 A).

[0333] The TX WTRU may determine the number of blind retransmissions for a TB that was initially transmitted (e.g., as disclosed above) and / or may indicate to the RX WTRU, e.g., in the SCI, that a PSFCH transmission is performed at each PSFCH opportunity within the COT. The PSFCH slots, e.g., the slots comprising the PSFCH opportunities and resources may be (pre-)configured according to the PSFCH slots in the resource pool. In one example, the PSFCH slots may be (pre-)configured with a periodicity of one, i.e., each slot may comprise a PSFCH opportunity and resources in the resource pool. In another example, the TX WTRU may indicate, e.g., in the SCI, the PSFCH opportunities in each slot within the COT. Both examples are reflected in Figure 6 A to Figure 6 B. One of the two.

[0334] In various embodiments, the TX WTRU may perform another TB of PSSCH / PSCCH transmission in the next time slot after receiving the PSFCH transmission, for example, when the TX WTRU has data in the buffer. In various embodiments, the TX WTRU may perform blind retransmissions and / or HARQ retransmissions in the PSSCH / PSCCH transmission. The TX WTRU may stop blind retransmissions in conjunction with reaching the maximum COT duration and not receiving a HARQ-ACK (e.g., after, at, at, based on, in response to, conditional on, etc.). The TX WTRU may stop blind retransmissions and / or HARQ retransmissions in conjunction with decoding the HARQ-ACK status in the received PSFCH transmission (e.g., after, at, at, based on, in response to, conditional on, etc.).

[0335] When one or more blind retransmissions and / or HARQ retransmissions occur N (e.g., 2) logical time slots earlier than the PSFCH time slot, the RX WTRU may determine that these blind retransmissions and / or HARQ retransmissions may be associated with HARQ state information. The RX WTRU may combine (e.g., perform a combination of the decoding results) of the initial transmission and all the determined associated blind retransmissions and / or HARQ retransmissions and may generate a HARQ state for the TB.

[0336] The RX WTRU may transmit a first PSFCH including HARQ state information derived based on an initial transmission. In each successive PSFCH transmission, the RX WTRU may report HARQ state information derived based on the initial transmission and the combined decoding results of blind retransmissions and / or HARQ retransmissions associated with the PSFCH. The number of transmissions combined for HARQ state information may be incremented for each successive PSFCH transmission.

[0337] The RX WTRU may report a HARQ NACK in the last PSFCH of the COT. The RX WTRU may perform a PSFCH transmission in a second COT initiated and / or shared by the RX WTRU in conjunction with (e.g., after, at, at, based on, in response to, conditional on, etc.) reporting the HARQ NACK in the last PSFCH in the COT. The HARQ state information included in the PSFCH transmission in the second COT may be derived based on the initial transmission and all blind retransmissions and / or HARQ retransmissions performed in the first COT.

[0338] The TX WTRU may perform a blind retransmission and / or a HARQ retransmission in the next slot after the PSFCH transmission. The TX WTRU may, for example, perform a Type 2A LBT procedure or a Type 2B LBT procedure at the beginning of the last symbol of the PSFCH transmission in conjunction with performing a blind retransmission and / or a HARQ retransmission in the next slot after the PSFCH transmission (e.g., after, at, at, based on, in response to, conditional on, etc.). The RX WTRU may not perform a transmission at this symbol according to the PSFCH slot format indicated by the TX WTRU in the SCI of the associated PSSCH / PSCCH transmission in the COT.

[0339] The TX WTRU may perform a channel reservation signal and / or a cyclic prefix extension (CPE) between the end of a successful Type 2A LBT procedure or a Type 2B LBT procedure and the next slot boundary, for example, to preserve the COT. At the next slot boundary, the TX WTRU may perform a PSSCH / PSCCH blind retransmission and / or a HARQ retransmission.

[0340] Reception of PSFCH communications (e.g., one or more PSFCH transmissions) in a SLU in the same COT as associated PSSCH / PSCCH communications (e.g., one or more PSSCH / PSCCH transmissions) may be performed, used, defined, configured, and / or determined. As disclosed above in conjunction with the RX WTRU, the TX WTRU may perform determination of PSFCH transmission timing, PSFCH slot format, and PSFCH resources. The TX WTRU may switch from TX to RX during a guard symbol prior to the PSFCH transmission timing. The TX WTRU may perform PSFCH reception using the determined PSFCH resources in the determined PSFCH transmission timing. When the TX WTRU may receive a PSFCH transmission at a PSFCH transmission timing within the COT and / or a scheduled transmission, the TX WTRU may switch from RX to TX during a guard symbol at the end of the PSFCH transmission timing, and may perform channel access, such as channel access based on type 2C channel access, and / or may continue with the PSSCH / PSCCH transmission scheduled in the COT. When a PSFCH transmission may not be received, the TX WTRU may stop transmitting in the COT and / or may perform another channel access to obtain a new COT for PSSCH / PSCCH transmission.

[0341] In various embodiments, the TX WTRU may perform a Type 2A channel access or a Type 2B channel access during a gap in a PSFCH transmission opportunity (e.g., the end of a PSFCH transmission opportunity). The gap may be (pre-)configured and may have a duration, which may be fixed or variable. In various embodiments, the duration of the gap may be, for example, 16 μs or 25 μs. In various embodiments, based on and / or in response to the Type 2A channel access or the Type 2B channel access, the TX UE may continue to transmit in the same COT based on and / or in response to the channel being determined to be available.

[0342] In various embodiments, an initial transmission and its one or more HARQ retransmissions may be configured for, determined for, defined for, used at, and / or performed at the same COT. In various embodiments, one or more HARQ retransmissions may be configured for, determined for, defined for, used at, and / or performed at the same COT as the initial transmission. In various embodiments, one or more HARQ retransmissions of an initial transmission may be configured for, determined for, defined for, used at, and / or performed at the same COT as the initial transmission.

[0343] In various embodiments, the WTRU may perform an initial PSSCH / PSCCH transmission and one or more corresponding HARQ retransmissions in the same COT. For example, the WTRU may perform an initial PSSCH / PSCCH transmission and corresponding HARQ retransmissions in the same COT based on non-continuous transmissions in the same COT.

[0344] In various embodiments, the WTRU may perform an initial PSSCH / PSCCH transmission in the COT and may monitor the corresponding PSFCH in a PSFCH transmission opportunity. In various embodiments, the PSFCH transmission opportunity within the COT may be indicated in the SCI of the PSSCH / PSCCH transmission. In various embodiments, the PSFCH transmission opportunity may be (pre-)configured within the COT, for example, in a sidelink timeslot that is one or more timeslots (e.g., a (pre-)configured number, X timeslots) later than the PSSCH / PSCCH transmission.

[0345] In various embodiments, the WTRU may receive the PSFCH at a PSFCH transmission opportunity in a frequency allocation (e.g., PRB / PRB interlace / subchannel). In various embodiments, the WTRU may determine the frequency allocation ("PSFCH frequency allocation") based on any of a source ID carried in the PSSCH / PSCCH transmission (e.g., WTRU source ID), a destination ID carried in the PSSCH / PSCCH transmission (e.g., WTRU destination ID), the frequency allocation for the PSSCH / PSCCH transmission, and / or a timeslot index of the PSFCH transmission opportunity.

[0346] In various embodiments, the WTRU may, for example, perform a HARQ retransmission of an earlier transmission in the same COT based on and / or in response to any of various criteria, factors, and / or other information. For example, the WTRU may receive and decode a PSFCH transmission, obtain a HARQ NACK for an earlier transmission in the COT based on and / or in response to decoding the received PSFCH transmission, and perform a HARQ retransmission of the earlier transmission in the same COT based on and / or in response to the HARQ NACK. Alternatively and / or additionally, the WTRU may monitor PSFCH transmissions at one or more PSFCH opportunities, and perform a HARQ retransmission of the earlier transmission in the same COT based on and / or in response to not receiving the PSFCH transmission at the monitored PSFCH transmission opportunities. In various embodiments, the WTRU may perform a HARQ retransmission of the earlier transmission in the same COT based on and / or in response to (i) a HARQ NACK or not receiving a PSFCH transmission at the monitored PSFCH opportunity and (ii) availability of a channel for performing the HARQ retransmission.

[0347] For example, the WTRU may receive and decode a PSFCH transmission, may obtain an HARQ NACK for an earlier transmission in the COT, and determine that the channel may be available between the end of the received PSFCH transmission and the start of the HARQ retransmission. In various embodiments, the WTRU may perform LBT sensing after (e.g., immediately after) the received PSFCH transmission, and determine the availability of the channel ("channel availability") based on one or more results (e.g., combined results) of the LBT sensing within the period. For example, the WTRU may perform LBT sensing in each sensing time slot, and determine the channel availability based on the results of one or more (e.g., all) of the sensing time slots. In various embodiments, the WTRU determines that the channel may be available (e.g., determines that the channel availability indicates that the channel may be available) based on and / or in response to the results of all sensing time slots indicating that the channel is idle (e.g., the measured RSSI is below a (pre-)configured threshold). In various embodiments, the WTRU may (e.g., instead of or in addition to LBT sensing) perform a Type 2 LBT channel access (e.g., Type 2A LBT channel access) and determine that the channel may be available (immediately or at some time before a HARQ retransmission) (e.g., determine that channel availability indicates that the channel may be available). For example, the WTRU may perform a Type 2 LBT channel access (e.g., Type 2A LBT channel access) at a time when it is determined that the channel may be available (immediately or at some time before a HARQ retransmission) (e.g., determine that channel availability indicates that the channel may be available) (e.g., instead of or in addition to LBT sensing).

[0348] As another example, the WTRU may monitor PSFCH transmissions at one or more PSFCH transmission opportunities, fail to receive PSFCH transmissions at one or more monitored PSFCH opportunities, and determine that the channel may be available between the last PSFCH transmission opportunity and the start of HARQ retransmissions. In various embodiments, the WTRU may perform LBT sensing after (e.g., immediately after) the last PSFCH transmission opportunity, and determine channel availability based on one or more results (e.g., combined results) of the LBT sensing within the time period. For example, the WTRU may perform LBT sensing in each sensing time slot, and determine channel availability based on the results of one or more (e.g., all) of the sensing time slots. In various embodiments, the WTRU determines that the channel is available (e.g., determines that the channel availability indicates that the channel is available) based on and / or in response to the results of all sensing time slots indicating that the channel is idle (e.g., the measured RSSI is below a (pre-)configured threshold). In various embodiments, the WTRU may (e.g., instead of or in addition to LBT sensing) perform a Type 2 LBT channel access (e.g., Type 2A LBT channel access) and determine that the channel may be available (immediately or at some time before a HARQ retransmission) (e.g., determine that channel availability indicates that the channel may be available). For example, the WTRU may perform a Type 2 LBT channel access (e.g., Type 2A LBT channel access) at a time when it is determined that the channel may be available (immediately or at some time before a HARQ retransmission) (e.g., determine that channel availability indicates that the channel may be available) (e.g., instead of or in addition to LBT sensing).

[0349] In various embodiments, the WTRU may perform HARQ retransmissions in the side link timeslots indicated in the SCI of the initial / earlier transmission in the same COT. For example, the SCI of the initial / earlier transmission may include information (e.g., one or more information elements) indicating the side link timeslots. The information may be information indicating the time gap (e.g., amount of time) between the initial / earlier transmission and the HARQ retransmission. In various embodiments, for example, the time gap may be the number of logical side link timeslots, and the information indicating the time gap may be expressed, for example, in units of logical side link timeslots. In various embodiments, the information indicating the time gap may be an index of a side link timeslot within the COT. In various embodiments, the SCI of the HARQ retransmission may include a new data indication (NDI), a HARQ process ID, and a redundancy version (RV), and the WTRU may set the NDI, HARQ process ID, and RV of the HARQ retransmission accordingly.

[0350] In various embodiments, the WTRU may not perform, may not perform, or abandon performing HARQ retransmissions based on and / or in response to any of various criteria, factors, and / or other information. In various embodiments, the WTRU may not perform, may not perform, or abandon performing HARQ retransmissions of earlier transmissions in the same COT based on and / or in response to any of various criteria, factors, and / or other information. For example, based on and / or in response to (i) HARQ ACK or receipt of PSFCH transmissions at monitored PSFCH opportunities and / or (ii) lack of availability of a channel for performing HARQ retransmissions (e.g., contrary to the above), HARQ retransmissions of earlier transmissions in the same COT may not be performed, may not be performed, or abandon performing. In various embodiments, the WTRU may perform a Type 1 LBT channel access and / or a Type 2 LBT channel access to obtain a new COT and perform HARQ retransmissions in the new COT.

[0351] A PSFCH communication (e.g., one or more PSFCH transmissions) in a SLU may be performed, used, defined, configured, and / or determined to be in a COT different from a COT used for associated PSSCH / PSCCH communications (e.g., one or more PSSCH / PSCCH transmissions) (e.g., a different and shared COT). The RX WTRU may determine that one or more PSFCH transmissions associated with one or more PSSCH / PSCCH transmissions are performed in a COT different from a COT used for associated PSSCH / PSCCH transmissions (e.g., a different and shared COT). For example, when indicated by information indicated in one or more transmissions from the TX WTRU, and / or based on and / or in response to the information, the RX WTRU may determine that one or more PSFCH transmissions associated with one or more PSSCH / PSCCH transmissions are performed in a COT different from a COT used for associated PSSCH / PSCCH transmissions (e.g., a different and shared COT) and / or may be performed in the different COT. Information indicated in one or more transmissions from the TX WTRU may indicate, for example, that the duration and / or the remainder of the duration of the COT for the associated PSSCH / PSCCH transmission may be too short compared to the HARQ process time for one or more PSFCH transmissions (or one or more of the one or more PSFCH transmissions).

[0352] The RX WTRU may detect the COT. The RX WTRU may determine that the detected COT may be used for one or more PSFCH transmissions of untransmitted HARQ feedback information based on and / or in response to any of various criteria, factors, and / or other information. The criteria, factors, and / or other information may include any of the following. For example, the RX WTRU may determine that the detected COT may be used for one or more PSFCH transmissions of untransmitted HARQ feedback information based on and / or in response to information in the COT from one or more transmissions from the TX WTRU indicating that the transmission of HARQ feedback information intended for the TX WTRU (e.g., such as Figure 4 For example, a TX WTRU may initiate a COT for one or more PSSCH / PSCCH transmissions and include in the SCI HARQ requests and / or polls to one or more RX WTRUs for sending untransmitted HARQ feedback information corresponding to one or more previous PSSCH / PSCCH transmissions from the same TX WTRU.

[0353] Alternatively and / or additionally, the RX WTRU may determine that the detected COT may be used for one or more PSFCH transmissions of untransmitted HARQ feedback information based on, in response to, and / or conditioned on information in the COT from one or more transmissions from the TX WTRU indicating that the COT is shareable for one or more PSFCH transmissions (e.g., such as Figure 8 For example, a WTRU may perform PSSCH / PSCCH transmission with HARQ disabled in the initiated COT and may indicate that the remaining COT may be shared by another WTRU for PSFCH transmission.

[0354] When PSFCH sharing indication may be enabled in a COT, the WTRU may not perform PSSCH / PSCCH sharing with that COT. This may reduce conflicts between WTRUs sharing the same COT. The RX WTRU may be (pre-)configured to share the COT for PSFCH transmissions, e.g., at the end of the COT and / or scheduled transmissions. Alternatively and / or additionally, PSFCH transmission opportunities within and / or at the end of the COT and / or one or more scheduled transmissions may be explicitly indicated to the RX WTRU in the SCI.

[0355] The RX WTRU may determine to perform a PSFCH transmission for untransmitted HARQ feedback information in a shareable COT initiated by the TX WTRU and may perform the PSFCH transmission, which HARQ feedback information may not be intended for the TX WTRU, e.g. Figure 8In various embodiments, the RX WTRU may determine to share such COT for PSFCH transmission when, based on, in response to, and / or conditioned on: the priority associated with the PSFCH transmission may meet (e.g., be greater than) a (pre-)configured threshold condition.

[0356] PSFCH transmission opportunities and resources for PSFCH communications (e.g., one or more PSFCH transmissions) in the SLU may be used, defined, configured, and / or determined. The RX WTRU may be instructed in the SCI received in the COT to send all or some of the untransmitted HARQ feedback information to the TX WTRU initiating the COT. Figure 7 ). The RX WTRU may determine the PSFCH transmission timing and resources in the COT including the HARQ request based on and / or in response to any of various criteria, factors and / or other information. The criteria, factors and / or other information may include any of the following.

[0357] • Number and / or index of one or more associated COTs. The associated COTs may be one or more COTs in which the RX WTRU may receive associated one or more PSSCH / PSCCH transmissions with the COT index indicated in the SCI of the PSSCH / PSCCH transmissions.

[0358] • Associated WTRU source and / or destination ID. The associated WTRU source and / or destination ID may be the WTRU source and / or destination ID indicated in the SCI transmitted by the associated PSSCH / PSCCH(s).

[0359] • Associated transmission index. The associated transmission index may be the transmission index indicated in the SCI of the associated one or more PSSCH / PSCCH transmissions in the associated COT for the associated WTRU source ID and / or WTRU destination ID.

[0360] The WTRU may determine the end of the COT and / or scheduled transmissions based on and / or in response to any of a variety of criteria, factors and / or other information. For example, the WTRU may determine the end of the COT and / or scheduled transmissions based on and / or in response to an indicated COT duration and / or scheduled transmissions and / or transmission indexes. In various embodiments, the RX WTRU may determine the number of PSFCH transmission opportunities to be performed in the COT based on, in response to, and / or conditional on the following: untransmitted HARQ feedback corresponding to one or more previously received PSSCH / PSCCH transmissions associated with the WTRU source ID and / or WTRU destination ID is the same as or corresponds to the WTRU ID indicated in the SCI comprising the HARQ poll request.

[0361] The WTRU may determine a set of one or more PSFCH transmit opportunities for each associated COT from the TX WTRU in ascending order of the associated COT index. The RX WTRU may determine (e.g., set) one or more PSFCH transmit opportunities within each set of one or more PSFCH transmit opportunities (in ascending order) based on and / or in response to the associated transmit index within the associated COT.

[0362] When there may be a lost COT and / or transmission index, for example due to an inability to receive one or more SCIs of one or more PSSCH / PSCCH transmissions in the PSSCH / PSCCH transmissions, the RX WTRU may determine a sequence for sending a HARQ NACK in each PSFCH RB interlace at the PSFCH transmission timing corresponding to the lost COT and / or transmission index.

[0363] Figure 7 An example of PSFCH transmission in the COT based on and / or in response to TX WTRU polling is illustrated. Figure 7 , the RX WTRU may determine to send and / or may send PSFCH transmissions corresponding to four received PSSCH / PSCCH transmissions when requested by TX WTRU 1 in a COT initiated by TX WTRU 1. Based on the associated COT index and the transmission index within each COT, the RX WTRU may determine six PSFCH transmission opportunities for TX WTRU 1. In the 3rd PSFCH transmission opportunity and the 4th PSFCH transmission opportunity, the RX WTRU may send a PSFCH transmission of a HARQ NACK for the lost (missed) PSSCH / PSCCH transmission.

[0364] The RX WTRU may determine the index of the PSFCH RB interlace to be used for each PSFCH transmission based on the associated WTRU source and / or destination ID, for example by (value of WTRU ID) MOD (total number of pre-configured PSFCH RB interlaces). Alternatively and / or additionally, the RX WTRU may determine the index of the PSFCH RB interlace based on the (pre-)configuration for PSFCH COT sharing. The RX WTRU may determine the PSFCH sequence to be sent in each RB of the determined PSFCH RB interlace corresponding to the HARQ feedback information (i.e., from a (pre-)configured set of PSFCH sequences for HARQ ACK and another set of PSFCH sequences for HARQ NACK), for example according to the disclosure above and / or below in this document.

[0365] In various embodiments, the RX WTRU may determine one or more PSFCH transmission opportunities within the COT based on one or more PSFCH resources (such as one or more PSFCH resources that may be (pre-)configured in a resource pool). In various embodiments, the WTRU may determine the frequency allocation of the PSFCH transmission. The frequency allocation of the PSFCH transmission may be one or more RBs, one or more RB interlaces, one or more sub-channels, etc. In various embodiments, the WTRU may determine the frequency allocation of the PSFCH transmission based on the source ID indicated in the associated PSSCH / PSCCH transmission (e.g., WTRU source ID), the destination ID indicated in the associated PSSCH / PSCCH transmission (e.g., WTRU destination ID), the associated COT index, the transmit index of the associated PSSCH / PSCCH transmission and / or the frequency allocation of the associated PSSCH / PSCCH transmission (e.g., sub-channel / RB interlace).

[0366] In various embodiments, the RX WTRU may include HARQ feedback information in a PSSCH / PSCCH transmission (e.g., in a MAC CE carried in the PSSCH / PSCCH transmission). In various embodiments, the RX WTRU may include information in a PSSCH / PSCCH transmission (e.g., in a MAC CE) that identifies the PSSCH / PSCCH transmission associated with the HARQ feedback information. The information may include, for example, a source ID (e.g., a WTRU source ID) indicated in the associated PSSCH / PSCCH transmission, a destination ID (e.g., a WTRU destination ID) indicated in the associated PSSCH / PSCCH transmission, an associated COT index, a transmit index of the associated PSSCH / PSCCH transmission, and / or a frequency allocation (e.g., subchannel / RB interleaving) of the associated PSSCH / PSCCH transmission.

[0367] In various embodiments, the RX WTRU may determine to transmit using PSFCH slot format 5 and / or may transmit one or more PSFCH transmissions. The RX WTRU may include an indication of the corresponding HARQ feedback information for the requesting TX WTRU. The HARQ feedback information may include a plurality of HARQ feedbacks corresponding to one or more associated PSSCH / PSCCH transmissions in a (pre-)configured order. For example, the order may be based on the associated COT and transmission index. The RX WTRU may indicate a HARQ NACK for a PSSCH / PSCCH transmission corresponding to a missing COT and / or transmission index.

[0368] The TX WTRU may monitor the end of the COT in which the HARQ request may be transmitted. The TX WTRU may determine the PSFCH transmission opportunity corresponding to the expected PSFCH transmission based on the COT and / or the transmission index of the associated PSSCH / PSCCH transmission. The TX WTRU may receive a sequence in the PSFCH RB interlace based on its source and / or destination ID. The TX WTRU may decode the HARQ feedback information in the received PSFCH sequence (e.g., HARQ ACK or NACK sequence) at each PSFCH transmission opportunity corresponding to the PSSCH / PSCCH transmission performed in ascending order (first by the transmission index within the COT and second by the COT index).

[0369] When the RX WTRU performs a PSFCH transmission in a shared COT initiated by a TX WTRU (for which the PSFCH transmission may not be intended), the RX WTRU may follow the PSFCH transmission timing and resource determination according to the disclosure below.

[0370] A PSFCH communication (e.g., one or more PSFCH transmissions) in a SLU in a COT may be performed, used, defined, configured, and / or determined that is initiated by the RX WTRU and is different from a COT initiated by the TX WTRU and used for associated PSSCH / PSCCH communications (e.g., one or more PSSCH / PSCCH transmissions). The COT initiated by the RX WTRU may be based on LBT sensing. For example, the WTRU may perform an SLU channel access based on LBT sensing, such as a channel access based on a type 1 LBT channel access, to initiate a COT for one or more PSFCH transmissions. The WTRU may determine the configuration of the SLU channel access based on LBT sensing based on and / or in response to any of various criteria, factors, and / or other information, such as, for example, any of the following:

[0371] Resource pool;

[0372] One or more RB sets;

[0373] The priority associated with the PSFCH transmission;

[0374] HARQ delay bound;

[0375] The number of PSFCH transmissions to be performed in the COT;

[0376] · The priority of one or more TBs;

[0377] One or more TBs of remaining PDB;

[0378] The number of TBs sent;

[0379] one or more PSFCH resources, e.g. (pre-)configured in a resource pool; and

[0380] • Information indicating one or more PSFCH transmission opportunities, for example, information indicating one or more PSFCH transmission opportunities received in one or more SCIs of one or more of the associated PSSCH / PSCCH transmissions.

[0381] The WTRU may determine to use the bandwidth of a (pre-)configured resource pool and / or RB set as the bandwidth for LBT sensing. For example, the resource pool may be the same as the resource pool used by the associated PSSCH / PSCCH transmission.

[0382] The WTRU may determine the duration of the COT for initiation and the size of the contention window based on a priority associated with a PSFCH transmission, for example when, based on, in response to, and / or conditional on: the COT for initiation may be used by a PSFCH transmission. The priority associated with the PSFCH transmission may be the highest priority of the PSSCH / PSCCH transmissions associated with the PSFCH transmission.

[0383] In various embodiments, the WTRU may determine the maximum COT duration and the size of the contention window corresponding to the (pre-)configured priority. In various embodiments, the association between the priority and the corresponding maximum COT duration and the size of the contention window may be defined in the CAPC configuration. In one example, the (pre-)configured priority may be the highest priority, e.g., having a value of 1.

[0384] As another example, when the WTRU may have one or more TBs in the buffer for PSSCH / PSCCH transmissions and untransmitted HARQ feedback information, the WTRU may initiate a COT for PSSCH / PSCCH and PSFCH transmissions. The WTRU may determine the duration of such COT and the size of the contention window based on the highest priority of the PSFCH transmission and the one or more TBs. The WTRU may determine the COT duration based on the number of transmissions of the one or more TBs.

[0385] If during LBT sensing initiated for a COT, the WTRU may detect a shareable COT for one or more PSFCH transmissions, the WTRU may determine to stop LBT sensing and perform one or more PSFCH transmissions in the detected shareable COT.

[0386] A PSFCH transmission timing and / or resource determination may be performed, used, defined, configured and / or determined. For example, when a COT may be initiated, the RX WTRU may determine a PSFCH transmission timing and / or resource in an initiated COT for one or more PSFCH transmissions. The RX WTRU may determine a PSFCH transmission timing and / or resource in an initiated COT for one or more PSFCH transmissions based on and / or in response to any of various criteria, factors and / or other information, such as, for example, any of the following.

[0387] • Number and / or index of associated COTs. The associated COTs may be one or more COTs in which the RX WTRU may receive one or more associated PSSCH / PSCCH transmissions with the COT index indicated in the SCI of the PSSCH / PSCCH transmissions.

[0388] • Associated WTRU source and / or destination ID. The associated WTRU source and / or destination ID may be the WTRU source and / or destination ID indicated in the SCI transmitted in one or more associated PSSCH / PSCCHs.

[0389] • Associated transmit index. The associated transmit index may be the transmit index indicated in the SCI of one or more associated PSSCH / PSCCH transmissions in the associated COT for the associated WTRU source ID and / or the associated WTRU destination ID.

[0390] In various implementations, the RX WTRU may determine the number of PSFCH transmission opportunities to be performed in the COT initiated in the PSFCH slot based on the number of untransmitted HARQ feedbacks in the buffer.

[0391] The RX WTRU may group the PSFCH transmissions for different associated WTRU source and / or destination IDs. For each group, the WTRU may determine a set of PSFCH transmission opportunities for each associated COT in ascending order of the associated COT index. For each set, the RX WTRU may determine the PSFCH transmission opportunities on symbols in ascending order based on the associated transmission index within the associated COT.

[0392] When there may be a lost COT and / or a transmission index within the COT, for example due to the inability to receive the SCI of one or more PSSCH / PSCCH transmissions, the RX WTRU may determine to send a PSFCH sequence for HARQ NACK in each PSFCH RB interlace at the PSFCH transmission timing corresponding to the lost COT and / or transmission index.

[0393] Fig. 9 An example HARQ feedback in the initiated COT for PSFCH transmission is illustrated. Fig. 9 As shown, the RX WTRU may determine to send one or more PSFCH transmissions corresponding to six PSSCH / PSCCH transmissions received from two TX WTRUs in three different COTs. Based on the associated COT index and the transmission index within each COT, the RX WTRU may determine six PSFCH transmission opportunities for TX WTRU 1 and two PSFCH transmission opportunities for TX WTRU 2. In the 3rd PSFCH transmission opportunity and the 4th PSFCH transmission opportunity, the RX WTRU may send a PSFCH transmission (e.g., a PSFCH sequence) for the HARQ NACK for the missed PSSCH / PSCCH transmissions.

[0394] The RX WTRU may determine an index of a PSFCH RB interlace to be used for each PSFCH transmission based on an associated WTRU source and / or destination ID, e.g., by (value of WTRU ID) MOD (total number of pre-configured PSFCH RB interlaces). The RX WTRU may determine a PSFCH sequence to be sent in each RB of the determined PSFCH RB interlace corresponding to the HARQ feedback information. The PSFCH sequence may be obtained from a first (pre-)configured set of PSFCH sequences for HARQ ACK and a second (pre-)configured set of PSFCH sequences for HARQ NACK, e.g., according to the disclosure herein above and below.

[0395] In various embodiments, the RX WTRU may determine to transmit and / or may transmit a PSFCH transmission using PSFCH slot format 5. The RX WTRU may include information indicating a source ID and / or destination ID of the TX WTRU (e.g., an indication of the source ID and / or destination ID of the TX WTRU) and corresponding HARQ feedback information. Each HARQ feedback information for the indicated TX WTRU may include a plurality of HARQ feedbacks corresponding to the associated PSSCH / PSCCH transmissions in a (pre-)configured order based on the associated COT and transmission index. The RX WTRU may indicate a HARQ NACK for a PSSCH / PSCCH transmission corresponding to a missing COT and / or transmission index.

[0396] PSFCH communications (e.g., one or more PSFCH transmissions) in an initiated COT may be performed, used, defined, configured, and / or determined. In various embodiments, the RX WTRU may send a PSSCH transmission before sending one or more PSFCH transmissions. The PSSCH transmission may include an SCI. The SCI may include information about the PSFCH transmission, for example, a Tx monitoring behavior PSFCH transmission indication and identification information; associated WTRU source and destination IDs, an associated COT index, and / or an associated transmission index. The Tx monitoring behavior PSFCH transmission indication and identification information may indicate that a transmission included in a sidelink timeslot may be a PSFCH transmission, and a mapping may be defined between the WTRU source and / or destination IDs associated with the PSFCH transmission and the PSFCH transmission opportunity within the timeslot.

[0397] Due to LBT uncertainty, the RX WTRU may not have a channel to send the PSFCH for the untransmitted HARQ within the HARQ delay boundary indicated for the HARQ process. When the delay boundary may expire, the RX WTRU may flush the HARQ process buffer for the untransmitted HARQ.

[0398] When the RX WTRU may have data in the buffer, the RX WTRU may perform PSSCH / PSCCH and PSFCH transmissions in the initiated COT. For example, the RX WTRU may apply PSFCH slot format 1 and transmit the PSFCH corresponding to one COT in the PSFCH slot. The RX WTRU may indicate the associated WTRU source and / or destination ID and the associated COT index in the SCI in the PSCCH transmission. For another example, the RX WTRU may apply PSFCH slot format 5 and perform a PSFCH transmission at the end of the initiated COT.

[0399] In various embodiments, the WTRU may perform a Type 1 LBT channel access to initiate a COT so that its duration includes one or more (pre-)configured PSFCH transmission opportunities that may occur within the HARQ delay boundary. In various embodiments, the HARQ delay boundary may be indicated in the SCI transmitted by the PSSCH / PSCCH.

[0400] In various embodiments, the WTRU may perform one or more PSFCH transmissions that carry various (e.g., all) untransmitted HARQ feedback information associated with one or more PSSCH / PSCCH transmissions received in one or more of the same and / or different COTs. In various embodiments, the WTRU may determine a frequency allocation for the PSFCH transmissions. The frequency allocation for the PSFCH transmissions may be one or more RBs, one or more RB interlaces, one or more subchannels, and the like. In various embodiments, the WTRU may determine a frequency allocation for the PSFCH transmissions based on a source ID (e.g., WTRU source ID) indicated in the associated PSSCH / PSCCH transmission, a destination ID (e.g., WTRU destination ID) indicated in the associated PSSCH / PSCCH transmission, an associated COT index, a transmit index of the associated PSSCH / PSCCH transmission, and / or a frequency allocation (e.g., subchannel / RB interlace) for the associated PSSCH / PSCCH transmission.

[0401] In various embodiments, the WTRU may include various (e.g., all) untransmitted HARQ feedback information in a PSSCH / PSCCH transmission (e.g., in a MAC CE carried in the PSSCH / PSCCH transmission). In various embodiments, the WTRU may include in a PSSCH / PSCCH transmission (e.g., in a MAC CE) information identifying the PSSCH / PSCCH transmission associated with the HARQ feedback information. The information may include, for example, a source ID (e.g., a WTRU source ID) indicated in the associated PSSCH / PSCCH transmission, a destination ID (e.g., a WTRU destination ID) indicated in the associated PSSCH / PSCCH transmission, an associated COT index, a transmit index of the associated PSSCH / PSCCH transmission, and / or a frequency allocation (e.g., subchannel / RB interleaving) of the associated PSSCH / PSCCH transmission.

[0402] In various embodiments, the WTRU may construct (generate and / or determine, etc.) HARQ feedback information, for example, in a HARQ codebook. In various embodiments, the WTRU may construct (generate and / or determine, etc.) HARQ feedback information based on a COT index and / or a PSSCH / PSCCH transmission index.

[0403] The success and / or failure of PSFCH communications (e.g., one or more PFSCH transmissions) may be performed, used, defined, configured, and / or determined. The RX WTRU may perform one or more LBT sensing-based channel accesses to initiate a COT to send untransmitted HARQ feedback information. In various embodiments, the RX WTRU may determine (e.g., LBT) a PSFCH channel access failure based on and / or in response to any of various criteria, factors, and / or other information. For example, the RX WTRU may determine (e.g., LBT) a PSFCH channel access failure when, based on, in response to, and / or conditional on the following: the RX WTRU may not be able to access the channel within the HARQ delay boundary indicated in the SCI sent by the TX WTRU's PSSCH / PSCCH. Alternatively and / or additionally, the RX WTRU may determine (e.g., LBT) PSFCH channel access failure when, based on, in response to and / or conditioned on the following circumstances: the RX WTRU may be unable to access the channel at a determined PSFCH transmission timing corresponding to the WTRU's PSSCH / PSCCH transmission.

[0404] The RX WTRU may determine consecutive (e.g., LBT) PSFCH channel access failures when the number of individually determined (e.g., LBT) PSFCH channel access failures may meet (e.g., be greater than) a (pre-)configured threshold. The RX WTRU may report consecutive LBT PFSCH channel access failures to higher layers. The RX WTRU may receive an LBT sensing configuration in response to the reported consecutive LBT PSFCH channel access failures. In various embodiments, the CAPC configuration for received LBT sensing may have a longer contention window.

[0405] Monitoring of PSFCH communications (e.g., one or more transmissions) by the TX WTRU may be performed, used, defined, configured, and / or determined. The TX WTRU may monitor the PSFCH transmissions within the HARQ delay boundaries indicated in the associated PSSCH / PSCCH transmissions in each sidelink time slot. The TX WTRU may determine, for example, based on information in the SCI received by the TX WTRU, the PSFCH transmission timing associated with its source and / or destination ID corresponding to the expected PSFCH transmission. The TX WTRU may decode the PSFCH transmission at each determined PSFCH transmission timing within the PSFCH RB interlace based on the source and / or destination ID of the PSFCH transmission. The TX WTRU may determine the decoded PSFCH results (e.g., HARQ ACK or NACK sequence) as the expected HARQ feedback corresponding to the PSSCH / PSCCH transmissions performed in ascending order (first by the transmission index within the COT and second by the COT index).

[0406] Sharing of a COT initiated for a PSFCH transmission may be performed, used, defined, configured and / or determined.

[0407] In various embodiments, the WTRU may monitor a PSFCH transmission during one or more PSFCH transmission opportunities indicated in the SCI of the associated PSSCH / PSCCH transmission and may receive the PSFCH transmission. In various embodiments, the WTRU may associate HARQ feedback information in a received PSFCH transmission with the PSSCH / PSCCH transmission based on and / or in response to any of various criteria, factors and / or other information. For example, the WTRU may associate HARQ feedback information in a received PSFCH transmission with a PSSCH / PSCCH transmission based on and / or in response to any of the following: (i) a PSFCH transmission timing (e.g., any one of one or more PSFCH transmission timings indicated in the SCI of the associated PSSCH / PSCCH transmission); (ii) a PSFCH transmission timing during which the PSFCH transmission is received / transmitted; (iii) a frequency allocation for the PSFCH transmission (e.g., PRBs, RB interleaving and / or subchannels); (iv) a HARQ process ID, e.g., carried in an SCI associated with the PSFCH transmission; (v) a source ID (e.g., a WTRU source ID), e.g., indicated in an SCI associated with the PSFCH transmission; and (vi) a destination ID (e.g., a WTRU destination ID), e.g., indicated in an SCI associated with the PSFCH transmission.

[0408] In various embodiments, the HARQ feedback information received in (and / or obtained from) a PSFCH transmission may be a HARQ ACK, and the WTRU may flush the buffer of the associated HARQ process based on and / or in response to the HARQ ACK (and / or receiving a PSFCH transmission indicating a HARQ ACK). In various embodiments, the HARQ feedback information received in (and / or obtained from) a PSFCH transmission may be a HARQ NACK, and the WTRU may perform a HARQ retransmission based on and / or in response to the HARQ NACK (and / or receiving a PSFCH transmission indicating a HARQ NACK).

[0409] In various embodiments, the WTRU may not or may not receive a PSFCH transmission at a PSFCH transmission opportunity within the same COT as the associated PSSCH / PSCCH transmission, and the WTRU may perform HARQ retransmissions based on or in response thereto. In various embodiments, the WTRU may not or may not receive a PSFCH transmission at a PSFCH transmission opportunity after the COT during which the associated PSSCH / PSCCH transmission was received / transmitted, and the WTRU may not, may not, or may abstain from performing HARQ retransmissions, and may monitor the PSFCH transmission at the next PSFCH transmission opportunity within the HARQ delay boundary.

[0410] In various embodiments, the WTRU may receive a HARQ NACK in a PSFCH transmission at a PSFCH transmission opportunity in a COT initiated for the PSFCH transmission ("PSFCH COT"). In various embodiments, the WTRU may be (pre-)configured with a maximum COT duration for the PSFCH COT.

[0411] In various embodiments, the WTRU may perform HARQ retransmissions in the PSFCH COT, for example, based on COT sharing information indicated in an SCI associated with a received PSFCH transmission. In various embodiments, the WTRU may be instructed to perform HARQ retransmissions in a sidelink timeslot within the PSFCH COT. In various embodiments, the WTRU may perform a type 2 (e.g., type 2A or 2B) channel access prior to the start of a sidelink timeslot. In various embodiments, the channel may be sensed as available (e.g., determined to be available based on sensing), and the WTRU may perform one or more transmissions of a channel reservation signal and / or CPE, for example, until the start of a sidelink timeslot. In various embodiments, the WTRU may perform HARQ retransmissions in a sidelink timeslot.

[0412] In various embodiments, the WTRU may be indicated in the SCI to perform LBT sensing between the end of a received PSFCH transmission and the start of a sidelink timeslot for HARQ retransmissions (e.g., one or more times after the end of the received PSFCH transmission and before the start of the sidelink timeslot). In various embodiments, the WTRU may perform HARQ retransmissions in a sidelink timeslot based on and / or in response to performing LBT sensing in one or more (each of one or more) sensing timeslots between the end of the received PSFCH transmission and the start of the indicated HARQ retransmission, and the channel is sensed as idle in one or more (all) of the sensing timeslots. In various embodiments, the WTRU may (e.g., instead of or in addition to LBT sensing) perform a type 2 LBT channel access (e.g., a type 2A / 2B LBT channel access) and determine that the channel may be available (immediately or at some time before the HARQ retransmission) (e.g., determine that channel availability indicates that the channel may be available). For example, the WTRU may perform a Type 2 LBT channel access (e.g., Type 2A LBT channel access) at a time (e.g., instead of or in addition to LBT sensing) when it determines that the channel may be available (immediately or at some time prior to a HARQ retransmission) (e.g., determining that a channel availability indicates that the channel may be available).

[0413] Fig.10 is a flow chart illustrating an example process 1000 for performing an initial transmission and a second transmission (e.g., a blind retransmission) and an associated PSFCH transmission during one or more COTs. Process 1000 and the disclosure attached hereto may be considered a generalization of at least some of the disclosures above and may be considered to cover and / or include various embodiments of the disclosures above (e.g., various embodiments of initial transmission and second transmission (e.g., blind retransmission) and associated PSFCH transmissions during one or more COTs disclosed herein). Figures 1A to 1D The process 1000 may be performed using the architecture of the communication system 100. Other architectures may also be used to perform the process 1000.

[0414] refer to Fig.10 The WTRU may receive an initial transmission of first control information and a transport block during a first COT established for device-to-device communication, followed by a second transmission of second control information and the same transport block (1002). In various embodiments, at least the first control information indicates a first transmission opportunity within the first COT. In various embodiments, at least the second control information indicates a latency boundary for reporting HARQ feedback for the transport block.

[0415] The WTRU may determine 1004 a first HARQ feedback for the transport block. In various implementations, the first HARQ feedback may be and / or may include a non-acknowledgement.

[0416] The WTRU may perform a first channel access procedure during a first COT (1006). The WTRU may send a third transmission indicating a first HARQ feedback during the first transmission opportunity (1008). The WTRU may determine a second HARQ feedback for the transport block (1010). The WTRU may determine a second transmission opportunity that meets the latency bound from one or more transmission opportunities (1012). In various embodiments, the transmission opportunities may be configured (e.g., pre-configured).

[0417] The WTRU may perform a second channel access procedure for device-to-device communication at the second transmission opportunity and establish a second COT (1014). The WTRU may send a fourth transmission indicating a second HARQ feedback at the second transmission opportunity during the second COT (1016).

[0418] In various embodiments, either of the initial transmission and the second transmission may be and / or may include a PSCCH transmission, a PSSCH transmission, or a combination of PSCCH / PSSCH transmissions. In various embodiments, the second transmission opportunity may be based on PSSCH to PSFCH association between different COTs.

[0419] In various implementations, the first control information may be and / or may include an SCI. In various implementations, the first transmission opportunity may be and / or may include a transmission opportunity for PSFCH transmission.

[0420] In various embodiments, the WTRU may determine one or more resources for the fourth transmission based on a frequency allocation based on any of a transmission opportunity index, a source identifier, a destination identifier, and a COT index (not shown). In various embodiments, the frequency allocation may be and / or may include any of a resource block, a resource block interlace, a subchannel, a cyclic shift, and a cyclic shift index.

[0421] In various embodiments, the WTRU may determine a first HARQ feedback for the transport block for an initial transmission. In various embodiments, the WTRU may determine a second HARQ feedback for the transport block for both the initial transmission and the second transmission.

[0422] In various embodiments, the second COT is initiated by the WTRU or another WTRU.In various embodiments, the WTRU is a first WTRU, the first COT is initiated by a second WTRU, and the WTRU may receive the initial transmission and the second transmission from the second WTRU.

[0423] In various implementations, the second transmission occurs after the third control information and at least one fifth transmission of the same transport block. In various implementations, the third control information indicates any one of the first transmission opportunity and a delay boundary.

[0424] In various implementations, the WTRU may determine the second HARQ feedback for the transport block jointly for the initial transmission, the at least one fifth transmission, and the second transmission.

[0425] In various embodiments, the first channel access procedure may be and / or may include a Type 1 channel access procedure. In various embodiments, the second channel access procedure may be and / or may include a Type 2 channel access procedure.

[0426] Fig.11 1 is a flow chart illustrating an example process 1100 for performing non-continuous initial transmission and HARQ retransmission within a single COT. Process 1100 and the disclosure attached hereto may be considered a generalization of at least some of the disclosures above, and may be considered to cover and / or include various embodiments of the disclosures above (e.g., various embodiments disclosed herein for performing non-continuous initial transmission and HARQ retransmission within a single COT). Figures 1A to 1D The process 1100 may be performed using the architecture of the communication system 100. Other architectures may also be used to perform the process 1100.

[0427] refer to Fig.11 The WTRU may determine that a channel is available within the COT at a time between an initial transmission and a transmission opportunity for performing a HARQ retransmission (1102). The WTRU may perform non-continuous initial transmission and HARQ retransmission within the COT based on determining that the channel is available (1102).

[0428] Fig.12 1 is a flow chart illustrating an example process 1200 for performing non-continuous initial transmission and HARQ retransmission within two or more COTs. The process 1200 and the disclosure attached hereto may be considered as a generalization of at least some of the disclosures above, and may be considered to cover and / or include various embodiments of the disclosures above (e.g., various embodiments disclosed herein for non-continuous initial transmission and HARQ retransmission within two or more COTs). Figures 1A to 1D The process 1200 may be performed using the architecture of the communication system 100. Other architectures may also be used to perform the process 1200.

[0429] refer to Fig.12The WTRU may determine that a channel is not available within a first COT at a time after an initial transmission and a transmission opportunity for performing a HARQ retransmission (1202). The WTRU may perform non-continuous initial transmission and HARQ retransmission within the first COT and the second COT based on determining that the channel is not available (1204).

[0430] in conclusion

[0431] Although features and elements are provided above in specific combinations, it will be understood by those of ordinary skill in the art that each feature or element may be used alone or in any combination with other features and elements. The present disclosure is not limited to the specific embodiments described in the present application, which are intended to be illustrative of various aspects. Many modifications and variations can be made without departing from the essence and scope of the present invention, as they will be apparent to those skilled in the art. Unless explicitly provided as such, any element, action or description used in the present application specification should not be understood as being essential or necessary to the present invention. According to the foregoing description, in addition to those listed herein, functionally equivalent methods and devices within the scope of the present disclosure will be apparent to those skilled in the art. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is limited only to the terms of the appended claims and the full range of equivalent forms of such entitled claims. It should be understood that the present disclosure is not limited to a specific method or system.

[0432] For simplicity, the foregoing embodiments are discussed with reference to the terminology and structure of infrared capable devices (i.e., infrared transmitters and receivers). However, the embodiments discussed are not limited to these systems, but can be applied to other systems using other forms of electromagnetic waves or non-electromagnetic waves (such as sound waves).

[0433] It should also be understood that the terms used herein are used only for the purpose of describing specific embodiments and are not intended to be limiting. As used herein, the term "video" or the term "image" may mean any of a snapshot, a single image, and / or a plurality of images displayed on a time basis. For example, when referred to herein, the term "user equipment" and its abbreviation "UE", the term "remote" and / or the term "head-mounted display" or its abbreviation "HMD" may mean or include (i) a wireless transmit and / or receive unit (WTRU); (ii) any of a plurality of embodiments of the WTRU; (iii) a wireless and / or wired (e.g., tetherable) device configured with (in particular) some or all of the structure and functionality of the WTRU; (iii) a wireless and / or wired device configured with less than all of the structure and functionality of the WTRU; or (iv), etc. References herein Figures 1A to 1DDetails of an example WTRU are provided that may represent any WTRU described herein. As another example, various disclosed embodiments herein are described above and below as utilizing a head mounted display. Those skilled in the art will recognize that devices other than head mounted displays may be utilized and that some or all of the present disclosure and various disclosed embodiments may be modified accordingly without undue experimentation. Examples of such other devices may include drones or other devices configured to stream information to provide an adapted reality experience.

[0434] In addition, the methods provided herein may be implemented in a computer program, software, or firmware incorporated into a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (sent via 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 built-in hard disks and removable disks), magneto-optical media, and optical media (such as CD-ROM disks and digital versatile disks (DVDs)). A processor associated with the software may be used to implement a radio frequency transceiver for a WTRU, UE, terminal, base station, RNC, or any host computer.

[0435] Variations of the methods, devices, and systems provided above are possible without departing from the scope of the present invention. In view of the various embodiments that may be applied, it should be understood that the illustrated embodiments are merely examples and should not be considered to limit the scope of the following claims. For example, the embodiments provided herein include handheld devices that may include or be used with any suitable voltage source (such as a battery, etc.) that provides any suitable voltage.

[0436] In addition, in the embodiments provided above, processing platforms, computing systems, controllers and other devices comprising processors are indicated. These devices may include at least one central processing unit ("CPU") and memory. According to the practice of those skilled in the art of computer programming, references to the symbolic representations of actions and operations or instructions may be performed by various CPUs and memories. Such actions and operations or instructions may be referred to as being "executed", "computer executed" or "CPU executed".

[0437] Those of ordinary skill in the art will appreciate that the actions and symbolic representations of operations or instructions include manipulation of electrical signals by the CPU. The electrical system represents data bits, which may result in the ultimate transformation of electrical signals or reduction of electrical signals and the retention of data bits at memory locations in the memory system, thereby reconfiguring or otherwise changing the operation of the CPU and performing other processing of signals. The memory location that holds the data bits is a physical location that has specific electrical, magnetic, optical, or organic properties that correspond to or represent the data bits. It should be understood that the embodiments are not limited to the above-mentioned platforms or CPUs, and other platforms and CPUs may also support the provided methods.

[0438] The data bits may also be maintained on computer-readable media, including magnetic disks, optical disks, and any other volatile (e.g., random access memory ("RAM")) or non-volatile (e.g., read-only memory ("ROM")) mass storage system readable by the CPU. The computer-readable media may include cooperating or interconnected computer-readable media that reside solely on the processing system or distributed across multiple interconnected processing systems that may be local or remote relative to the processing system. It should be understood that the embodiments are not limited to the above-mentioned memories, and other platforms and memories may also support the provided methods.

[0439] In an exemplary embodiment, any of the operations, processes, etc. described herein may be implemented as computer-readable instructions stored on a computer-readable medium. The computer-readable instructions may be executed by a processor of a mobile unit, a network element, and / or any other computing device.

[0440] There is little difference between hardware implementation and software implementation of various aspects of the system. The use of hardware or software is usually (but not always, because in some contexts, the choice between hardware and software may become important) a design choice that represents a trade-off between cost and efficiency. There may be various media (e.g., hardware, software, and / or firmware) that can implement the processes and / or systems and / or other technologies described herein, and the preferred media may vary with the context of the deployment process and / or system and / or other technologies. For example, if the implementer determines that speed and accuracy are most important, the implementer may choose a media that is primarily hardware and / or firmware. If flexibility is most important, the implementer may choose a specific implementation that is primarily software. Alternatively, the implementer may choose some combination of hardware, software, and / or firmware.

[0441] The above specific embodiments have been listed various embodiments of devices and / or processes by using block diagrams, flow charts and / or examples. Where such block diagrams, flow charts and / or examples contain one or more functions and / or operations, it will be understood by those skilled in the art that each function and / or operation within such block diagrams, flow charts or examples may be implemented individually and / or collectively by a wide range of hardware, software, firmware or almost any combination thereof. In one embodiment, several parts of the subject matter described herein may be implemented via application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), digital signal processors (DSPs) and / or other integrated formats. However, those skilled in the art will recognize that some aspects of the embodiments disclosed herein may be equivalently implemented in integrated circuits as a whole or in part as one or more computer programs running on one or more computers (e.g., one or more programs running on one or more computer systems), one or more programs running on one or more processors (e.g., one or more programs running on one or more microprocessors), firmware or almost any combination thereof, and according to the present disclosure, designing circuits and / or writing software and / or firmware codes will be completely within the technical scope of those skilled in the art. Furthermore, those skilled in the art will appreciate that the mechanisms of the subject matter described herein can be distributed as a program product in a variety of forms, and that the illustrative embodiments of the subject matter described herein apply regardless of the specific type of signal-bearing medium used to actually perform the distribution. Examples of signal-bearing media include, but are not limited to, the following: recordable type media (such as floppy disks, hard drives, CDs, DVDs, digital tapes, computer memory, etc.); and transmission type media (such as digital and / or analog communication media (e.g., fiber optic cables, waveguides, wired communication links, wireless communication links, etc.)).

[0442] Those skilled in the art will recognize that it is common in the art to describe devices and / or processes in the manner set forth herein, and thereafter use engineering practices to integrate such described devices and / or processes into a data processing system. That is, at least a portion of the devices and / or processes described herein can be integrated into a data processing system via a reasonable amount of experimentation. Those skilled in the art will recognize that a typical data processing system generally may include one or more of the following: a system unit housing; a video display device; a memory, such as a volatile memory and a non-volatile memory; a processor, such as a microprocessor and a digital signal processor; a computing entity, such as an operating system, a driver, a graphical user interface, and an application; one or more interactive devices, such as a touch pad or a screen; and / or a control system, including a feedback loop and a control motor (e.g., a feedback for sensing position and / or velocity, a control motor for moving and / or adjusting components and / or quantities). A typical data processing system may be implemented using any suitable commercially available components, such as those typically found in data computing / communication and / or network computing / communication systems.

[0443] The subject matter described herein sometimes shows different parts contained in or connected to different other parts.It should be understood that such depicted architectures are merely examples, and in fact many other architectures that achieve the same function can be implemented.In a conceptual sense, any arrangement of parts that achieve the same function is effectively "associated" so that the desired function can be achieved.Therefore, any two components that are combined to achieve a specific functionality in this article can be considered to be "associated" with each other so that the desired functionality can be achieved, regardless of the architecture or intermediate components.Similarly, any two parts so associated can also be considered to be "operably connected" or "operably coupled" to each other to achieve the desired function, and any two parts that can be so associated can also be considered to be "operably coupled" to each other to achieve the desired function.Specific examples of operable coupling include, but are not limited to, components that can physically cooperate and / or physically interact and / or components that can wirelessly interact and / or wirelessly interact and / or components that can logically interact and / or components that can logically interact.

[0444] With respect to substantially any plural and / or singular terms used herein, those skilled in the art may translate from the plural to the singular and / or from the singular to the plural as appropriate, as appropriate to the context and / or application. For clarity, various singular / plural arrangements may be explicitly listed herein.

[0445] Those skilled in the art will understand that, in general, the terms used herein and in particular in the appended claims (e.g., the bodies of the appended claims) are generally intended to be “open-ended” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “comprising” should be interpreted as “including but not limited to, etc.”), and / or “permissive” terms (e.g., the term “is” and / or the term “are” can be interpreted as “can” and / or “may,” the term “refers to” can be interpreted as “can refer to” and / or “may refer to,” the term “receive” can be interpreted as “can receive” and / or “may receive,” the term “supports” can be interpreted as “can support” and / or “may support,” the term “interfacing” can be interpreted as “can” The term "docking" and / or "may dock", the term "send" may be interpreted as "can dock" and / or "may dock", "can send" and / or "may send", the term "transmit" may be interpreted as "can transmit" and / or "may transmit", the term "do not refer" (etc.) may be interpreted as "may not refer" and / or "may not refer", the term "do not receive" (etc.) may be interpreted as "may not receive" and / or "may not receive", the term "do not support" (etc.) may be interpreted as "may not support" and / or "may not support", the term "do not dock" (etc.) may be interpreted as "may not dock" and / or "may not dock", the term "do not send" (etc.) may be interpreted as "may not send" and / or "may not send", the term "do not transmit" (etc.) may be interpreted as "may not transmit" and / or "may not transmit", etc.). It should also be understood by those skilled in the art that if a specific number of an introduced claim recitation object is intended, such intent will be explicitly recited in the claim, and in the absence of such a recitation object, no such intent is present. For example, where only one item is contemplated, the term "single" or similar language may be used. To aid understanding, the following appended claims and / or the description herein may include the use of the introductory phrases "at least one" and "one or more" to introduce claim recitation objects. However, the use of such phrases should not be understood to imply that any particular claim containing such introduced claim recitation objects is limited to an embodiment containing only one such recitation object by the indefinite article "a" or "a kind" to introduce the claim recitation object. This is true even when the same claim includes the introductory phrases "one or more" or "at least one" and an indefinite article such as "a" or "a kind" (for example, "a" and / or "a kind" should be interpreted as meaning "at least one" or "one or more"). The same applies to the use of definite articles used to introduce claim recitation objects.Furthermore, even if a specific number of an introduced claim recitation is explicitly recited, one skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., a bare recitation of "two recitations" without other modifiers means at least two recitations or two or more recitations). Additionally, in those instances where a convention similar to "at least one of A, B, and C, etc." is used, generally speaking, the meaning of such construction is that one skilled in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include, but is not limited to, a system having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). In those instances where a convention similar to "at least one of A, B, or C, etc." is used, generally speaking, the meaning of such construction is that one skilled in the art will understand the convention (e.g., "a system having at least one of A, B, or C" will include, but is not limited to, systems having A alone, B alone, C alone, A and B at the same time, A and C at the same time, B and C at the same time, and / or A, B, and C at the same time, etc.). One skilled in the art will also understand that, in fact, any separate word and / or phrase presenting two or more alternative terms, whether in the specification, claims, or drawings, should be understood to contemplate the possibility of including one of the terms, any of the terms, or both of the terms. For example, the phrase "A or B" will be understood to include the possibility of "A" or "B" or "A and B". In addition, as used herein, the term "any of..." followed by a listing of multiple items and / or multiple categories of items is intended to include "any of," "any combination," "any multiples," and / or "any combination of multiples" of the items and / or categories of items, either alone or in combination with other items and / or other categories of items. Furthermore, as used herein, the term "set" is intended to include any number of items, including zero. Additionally, as used herein, the term "number" is intended to include any number, including zero.

[0446] In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also described in terms of any individual member or subgroup of members of the Markush group.

[0447] As will be understood by those skilled in the art, for any and all purposes (such as in terms of providing a written description), all ranges disclosed herein also encompass any and all possible sub-ranges and combinations of their sub-ranges. Any listed range can be easily identified as fully describing and enabling the same range to be divided into at least equal halves, one-third, one-quarter, one-fifth, one-tenth, etc. As a non-limiting example, each range discussed herein can be easily divided into a lower third, a middle third, and an upper third, etc. As will be understood by those skilled in the art, all languages ​​such as "up to", "at least", "greater than", "less than", etc. include the cited numbers and refer to the ranges that can be subsequently divided into sub-ranges as described above. Finally, as will be understood by those skilled in the art, the range includes each individual number. Therefore, for example, a group with 1 to 3 units refers to a group with 1, 2 or 3 units. Similarly, a group with 1 to 5 units refers to a group with 1, 2, 3, 4 or 5 units, etc.

[0448] Furthermore, the claims should not be read as limited to the order or elements presented unless otherwise stated. Furthermore, the use of the term "means for..." in any claim is intended to invoke 25 U.S.C. § 112, 6 or means-plus-function claim format, and any claim without the term “means for…” is not intended to be so.

Claims

1. A method implemented in a wireless transmitting / receiving unit, the method comprising: receiving, during a first channel occupancy time established for device-to-device communication, an initial transmission of first control information and a transport block, the initial transmission being followed by a second transmission of second control information and the same transport block, wherein (i) at least the first control information indicates a first transmission opportunity within the first channel occupancy time, and (ii) at least the second control information indicates a delay bound for reporting hybrid automatic repeat request (HARQ) feedback for the transport block; determining a first HARQ feedback for the transport block, wherein the first HARQ feedback comprises a non-acknowledgement; performing a first channel access procedure during the first channel occupancy time; sending, during the first transmission opportunity, a third transmission indicating the first HARQ feedback; determining a second HARQ feedback for the transport block; Determine a second sending opportunity that satisfies the delay boundary from one or more sending opportunities; performing a second channel access procedure for device-to-device communication at the second transmission opportunity and establishing a second channel occupancy time; as well as A fourth transmission indicating the second HARQ feedback is sent at the second transmission opportunity.

2. The method according to claim 1, wherein either the initial transmission and the second transmission is a physical sidelink control channel (PSCCH) transmission, a physical sidelink shared channel (PSSCH) transmission, or a combination of a PSCCH transmission and a PSSCH transmission.

3. The method according to at least one of claims 1 to 2, wherein the first control information is sidelink control information, and wherein the first transmission opportunity is a transmission opportunity for physical sidelink feedback channel (PSFCH) transmission.

4. The method according to at least one of claims 1 to 3, wherein the second transmission opportunity is based on PSSCH to PSFCH association between different channel occupancy times.

5. The method according to at least one of claims 1 to 4, comprising: One or more resources for the fourth transmission are determined according to the frequency allocation based on any one of a transmission opportunity index, a source identifier, a destination identifier, and a channel occupancy time index.

6. The method of claim 5, wherein the frequency allocation is any one of a resource block, a resource block interlace, a subchannel, a cyclic shift, and a cyclic shift index.

7. The method according to at least one of claims 1 to 6, wherein determining a first HARQ feedback for the transport block comprises: The first HARQ feedback for the transport block is determined for the initial transmission.

8. The method according to at least one of claims 1 to 7, wherein determining a second HARQ feedback for the transport block comprises: The second HARQ feedback for the transport block is determined jointly for the initial transmission and the second transmission.

9. The method according to at least one of claims 1 to 8, wherein the one or more transmission opportunities are configured.

10. The method of at least one of claims 1 to 9, wherein the second channel occupancy time is initiated by the WTRU or another WTRU.

11. The method of at least one of claims 1 to 10, wherein the WTRU is a first WTRU, wherein the first channel occupancy time is initiated by a second WTRU, and wherein receiving an initial transmission and a second transmission comprises receiving the initial transmission and the second transmission from the second WTRU.

12. The method according to at least one of claims 1 to 11, wherein the second transmission occurs after third control information and at least one fifth transmission of the same transport block, wherein the third control information indicates any one of the first transmission opportunity and the delay boundary.

13. The method of claim 12, wherein determining a second HARQ feedback for the transport block comprises: The second HARQ feedback for the transport block is determined jointly for the initial transmission, the at least one fifth transmission, and the second transmission.

14. The method according to at least one of claims 1 to 12, wherein the first channel access procedure is a type 1 channel access procedure.

15. The method according to at least one of claims 1 to 13, wherein the second channel access procedure is a type 2 channel access procedure.

16. An apparatus comprising a circuit comprising a first transmitter, a receiver, a processor and a memory, the apparatus being configured to perform the method according to at least one of the preceding claims.

17. The apparatus of claim 16, wherein the apparatus is a wireless transmit / receive unit (WTRU), configured as a wireless transmit / receive unit (WTRU), and / or a component configured with a wireless transmit / receive unit (WTRU).

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